# Patent

## Title
Authentication system for terminal identification information

## Abstract

An authentication system receives encrypted terminal identification information and terminal identification information, from a transmission terminal, and determines whether decrypted identification information decrypted using a terminal public key obtained by the authentication system matches the terminal identification information received from the transmission terminal.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This patent application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application Nos. 2010-028781, filed on Feb. 12, 2010, 2010-028783, filed on Feb. 12, 2010, 2011-010032, filed on Jan. 20, 2011, and 2011-010025, filed on Jan. 20, 2011, in the Japanese Patent Office, the entire disclosure of which is hereby incorporated herein by reference.
FIELD OF THE INVENTION
The present invention generally relates to an apparatus, system, and method of authenticating a terminal that transmits or receives image data and/or voice data to or from another terminal through a network.
BACKGROUND
With the need for reducing costs or times associated with business trips, more companies are moving towards transmission systems to have teleconference or videoconference among remotely located offices via a communication network. The transmission systems allow transmission of image data or voice data among a plurality of transmission terminals that are remotely located from one another through a communication network such as the Internet to facilitate communication among the plurality of transmission terminals. Before initiating communication among the plurality of transmission terminals, the transmission systems usually authenticate the transmission terminal, for example, by using an authentication system that authenticates the transmission terminal based on identification information received from the transmission terminal.
For example, the recent transmission systems encrypt the identification information of the transmission terminal with a terminal private key, and send the encrypted identification information to the authentication system together with information for identifying a terminal public key that is paired with the terminal private key. The authentication system extracts a terminal public key using the information for identifying the terminal public key, and decrypts the encrypted identification information using the extracted terminal public key. While this suppresses the possibility of identity theft, the authentication system needs to manage the association between the identification information of the transmission terminal and the information for identifying the terminal public key. Especially when there are a large number of transmission terminals, or information of the transmission terminal is frequently updated, it has been cumbersome for the authentication system to keep updated the identification information and the public key information of each of the transmission terminals.
SUMMARY
Example embodiments of the present invention include a transmission system including a transmission terminal to log in the transmission system and an authentication system to authenticate the transmission terminal before the transmission terminal logs in the transmission system. The transmission terminal encrypts terminal identification information of the transmission terminal using a terminal private key assigned to the transmission terminal to generate encrypted terminal identification information, and transmits the encrypted terminal identification information and the terminal identification information to the authentication system. The authentication system obtains a terminal public key that corresponds to the terminal identification information received from the transmission terminal, decrypts the encrypted identification information using the terminal public key to obtain decrypted identification information, and determines whether the decrypted identification information obtained by the authentication system matches the terminal identification information received from the transmission terminal to generate a determination result.
Example embodiments of the present invention include an authentication apparatus for authenticating a transmission terminal before the transmission terminal logs in a transmission system. The authentication apparatus receives encrypted terminal identification information and terminal identification information from the transmission terminal, obtains a terminal public key that corresponds to the terminal identification information received from the transmission terminal, decrypts the encrypted identification information using the terminal public key to obtain decrypted identification information, and determines whether the decrypted identification information obtained by the authentication apparatus matches the terminal identification information received from the transmission terminal to generate a determination result.
In addition to the above-described example embodiments, the present invention may be practiced in various other ways, for example, in the form of a method of authenticating a transmission terminal and a recording medium storing a plurality of instructions which cause a processor to perform the method of authenticating a transmission terminal.



BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:
FIG. 1 is a schematic block diagram illustrating a transmission system according to an example embodiment of the present invention;
FIG. 2 is an illustration for explaining transmission or reception of data such as image data, voice data, or management data, performed by the transmission system of FIG. 1;
FIGS. 3A to 3C are illustrations for explaining image quality of image data transmitted or received by the transmission system of FIG. 1;
FIG. 4 is a perspective view illustrating the outer appearance of a terminal of the transmission system of FIG. 1, according to an example embodiment of the present invention;
FIG. 5 is a schematic block diagram illustrating a hardware structure of the terminal of the transmission system of FIG. 1;
FIG. 6 is a schematic block diagram illustrating a hardware structure of any one of a transmission management system, a relay terminal, an authentication system, and a program providing system of FIG. 1;
FIG. 7 is a schematic block diagram illustrating functional structures of the transmission management system, the terminal, and the relay terminal, of the transmission system of FIG. 1;
FIG. 8 is a schematic block diagram illustrating a functional structure of a secondary relay terminal selection unit of the terminal of FIG. 7;
FIG. 9 is a schematic block diagram illustrating a primary relay terminal selection unit of the transmission management system of FIG. 7;
FIG. 10 is an example data structure of a data quality management table, managed by the relay terminal of FIG. 7;
FIG. 11 is an example data structure of a relay terminal management table, managed by the transmission management system of FIG. 7;
FIG. 12 is an example data structure of a terminal authentication management table, managed by the transmission management system of FIG. 7;
FIG. 13 is an example data structure of a terminal management table, managed by the transmission management system of FIG. 7;
FIG. 14 is an example data structure of a candidate list management table, managed by the transmission management system of FIG. 7;
FIG. 15 is an example data structure of a session management table, managed by the transmission management system of FIG. 7;
FIG. 16 is an example data structure of an address priority management table, managed by the transmission management system of FIG. 7;
FIG. 17 is an example data structure of a transmission speed priority management table, managed by the transmission management system of FIG. 7;
FIG. 18 is an example data structure of a quality management table, managed by the transmission management system of FIG. 7;
FIG. 19 is a data sequence diagram illustrating operation of managing state information indicating an operation state of the relay terminal of the transmission system of FIG. 1, according to an example embodiment of the present invention;
FIGS. 20A and 20B are a data sequence diagram illustrating operation of establishing communication among two or more transmission terminals of the transmission system of FIG. 1, according to an example embodiment of the present invention;
FIG. 21 is a data sequence diagram illustrating operation of limiting a number of candidate relay terminals, performed by the transmission system of FIG. 1;
FIG. 22 is a flowchart illustrating operation of limiting a number of candidate relay terminals, performed by the transmission management system of FIG. 1;
FIG. 23 is a table storing priority points of the relay terminals that are respectively calculated by the transmission management system of FIG. 1 during the operation of limiting a number of candidate relay terminals;
FIGS. 24A and 24B are a data sequence diagram illustrating operation of selecting a relay terminal, performed by the transmission system of FIG. 1;
FIG. 25 is a flowchart illustrating operation of selecting a relay terminal, performed by the transmission terminal of FIG. 1;
FIG. 26 is a data sequence diagram illustrating operation of transmitting or receiving data such as image data and voice data, performed by two or more transmission terminals of the transmission system of FIG. 1;
FIG. 27 is a schematic block diagram illustrating a functional structure of a terminal authentication request of the transmission terminal of FIG. 7;
FIG. 28 is a schematic block diagram illustrating a functional structure of an authentication system of the transmission system of FIG. 1;
FIG. 29 is an example data structure of a terminal public key management table, managed by the authentication system of FIG. 1;
FIG. 30 is an example data structure of a login data management table, managed by the authentication system of FIG. 1;
FIG. 31 is an illustration for explaining encryption and decryption of data, performed by the transmission system of FIG. 1;
FIG. 32 is a flowchart illustrating operation of encrypting data for authentication, performed by the transmission terminal of FIG. 1; and
FIG. 33 is a flowchart illustrating operation of authenticating the transmission terminal of FIG. 1, performed by the transmission management system of FIG. 1.



The accompanying drawings are intended to depict example embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
In describing example embodiments shown in the drawings, specific terminology is employed for the sake of clarity. However, the present disclosure is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner.
<Configuration of Transmission System>
FIG. 1 is a schematic block diagram illustrating a configuration of a transmission system 1 according to an example embodiment of the present invention. FIG. 2 is an illustration for explaining transmission or reception of various data such as image data, voice data, and management data, performed by the transmission system 1 of FIG. 1. FIGS. 3A to 3C are illustrations for explaining quality of image data transmitted by the transmission system 1 of FIG. 1.
Referring to FIG. 1, the transmission system 1 mainly includes a transmission management system 50, and a plurality of transmission terminals 10aa, 10ab, 10ac, 10ba, 10bb, 10bc, 10ca, 10cb, 10cc, 10da, 10db, and 10dc. Any one of the terminals 10 transmits or receives contents data such as image data and/or voice data to or from any other one of the terminals 10.
In one example, the transmission system 1 functions as a data providing system that transmits contents data from one transmission terminal to another transmission terminal in one direction through the transmission management system 50. In another example, the transmission system 1 functions as a two-way communication system that exchanges various information including image data and/or voice data that is used to convey human's feelings between or among two or more of the plurality of transmission terminals 10 each of which functioning as a communication terminal, through the transmission management system 50 that functions as a communication management system. When functioning as the communication system, the transmission system 1 may be implemented as a videoconference system or video teleconference system.
In the following examples, it is assumed that the transmission system 1 of FIG. 1 is implemented as the videoconference system, which is one example structure of the communication system. Based on this assumption, the transmission management system 50 is implemented as the videoconference communication management system, which is one example structure of the communication management system. Further, the transmission terminal 10 is implemented as the videoconference communication terminal, which is one example structure of the communication terminal. However, the use of transmission system 1 is not limited to the following examples such that the transmission system 1 may be implemented as the transmission system or the communication system as described above. Examples of the transmission system 1 include, but not limited to, videoconference system, teleconference system, voice conference system, voice teleconference system, and image data sharing system that shares an image being displayed onto a screen.
Referring to FIG. 1, the transmission system 1 further includes a plurality of displays 120aa, 120ab, 120ac, 120ba, 120bb, 120bc, 120ca, 120cb, 120cc, 120da, 120db, and 120dc, a plurality of relay terminals 30a, 30b, 30c, and 30d, an authentication system 80, a program providing system 90, and a maintenance system 100, which are connected through a communication network 2 including the Internet 2i. FIG. 1 also shows a plurality of routers 70a, 70b, 70c, 70d, 70ab, and 70cd. 
For the descriptive purposes, in this example, the transmission management system 50 may be referred to as the “management system” 50. Any number of the plurality of terminals 10aa to 10dc may be collectively or each referred to as the terminal 10. Any number of the plurality of displays 120aa to 120dc may be collectively or each referred to as the display 120. Any one of the plurality of relay terminals 30a, 30b, 30c, and 30d may be collectively or each referred to as the relay terminal 30. The terminal 10 that transmits data to another terminal 10 to carry out videoconference is referred to as the request terminal 10A. The terminal 10 that receives data from another terminal 10 to carry out videoconference is referred to as the counterpart terminal 10B. For example, the request terminal 10A includes any terminal 10 that requests another terminal 10 to start videoconference, and the counterpart terminal 10B includes any terminal 10 that is requested by the request terminal 10A to start videoconference.
As illustrated in FIG. 2, in the transmission system 1, the request terminal 10A and the counterpart terminal 10B first establish a management data session sei to start transmission and reception of various types of management data through the management system 50. Further, in this example, the request terminal 10A and the counterpart terminal 10B establish four contents data sessions sed to transmit or receive contents data through the relay terminal 30. The four contents data sessions, which may be referred to as image and/or voice data sessions, include a session “HL” to transmit high-level resolution image data HL, a session “ML” to transmit medium-level resolution image data ML, a session “LL” to transmit low-level resolution image data LL, and a session “V” to transmit voice data V.
Referring now to FIGS. 3A to 3C, various image data having different resolution levels, which are respectively transmitted by the terminal 10 of the transmission system 1, are explained. Referring to FIG. 3A, the low-level resolution image data, which functions as a base image, has 160 pixels in the horizontal direction and 120 pixels in the vertical direction. Referring to FIG. 3B, the medium-level resolution image data has 320 pixels in the horizontal direction and 240 pixels in the vertical direction. Referring to FIG. 3C, the high-level resolution image data has 640 pixels in the horizontal direction and 480 pixels in the vertical direction. In case of communicating with a narrowband signal line, low-quality image data that is generated based on the low-level resolution image data, which is the base image, is transmitted. In case of communicating with a wideband signal line, medium-quality image data that is generated based on the low-level resolution image data and the medium-level resolution image data is transmitted. In case of communicating with a broadband signal line, high-quality image data that is generated based on the low-level resolution image data, the medium-level resolution image data, and the high-level resolution image data is transmitted. Any one of the above-described types of image data may be transmitted together with voice data.
The relay terminal 30 of FIG. 1 relays contents data that is transmitted between the plurality of terminals 10. The management system 50 controls operation of the transmission system 1, for example, by performing authentication of a user at the terminal 10 through the login process, management of operation state of the terminal 10, management of a candidate list, management of operation state of the relay terminal 30, etc. In this example, the image data may be any desired data such as a moving picture and/or a still image.
The plurality of routers 70a to 70cd, which may be collectively or each referred to as the router 70, selects a route that is most suitable for transmitting contents data such as image data and voice data.
The authentication system 80, which includes a hard disk device (HD) 204 (FIG. 6), authenticates the transmission terminal 10 based on data received from the transmission terminal 10.
The program providing system 90 includes a hard disk device (HD) 204 (FIG. 6), which stores a terminal control program that causes the terminal 10 to perform various functions or operations. For example, the program providing system 90 sends the terminal control program to the terminal 10 through the Internet 2i to cause the terminal 10 to install the terminal control program. Further, the HD 204 of the program providing system 90 may store a relay control program that causes the relay terminal 30 to perform various functions or operations. For example, the program providing system 90 sends the relay control program to the relay terminal 30 through the Internet 2i to cause the relay terminal 30 to install the relay control program. Further, the HD 204 of the program providing system 90 may store a transmission management program that causes the management system 50 to perform various functions or operations. For example, the program providing system 90 sends the transmission management program to the management system 50 to cause the management system 50 to install the transmission management program. Further, the HD 204 of the program providing system 90 may store an authentication management program that causes the authentication system 80 to perform various functions or operations. For example, the program providing system 90 sends the authentication management program to the authentication system 80 to cause the authentication system 80 to install the authentication management program.
The maintenance system 100 is implemented as a computer capable of maintaining, managing, fixing, or upgrading at least one of the terminal 10, relay terminal 30, management system 50, authentication system 80, and program providing system 90. Assuming that the maintenance system 100 is provided within a country, and the terminal 10, the relay terminal 30, the management system 50, the authentication system 80, and the program providing system 90 are each installed outside the country, the maintenance system 100 maintains, manages, fixes, or upgrades at least one of the terminal 10, relay terminal 30, management system 50, authentication system 80, and program providing system 90, remotely through the communication network 2. The maintenance system 100 may manage maintenance of at least one of the terminal 10, relay terminal 30, management system 50, authentication system 80, and program providing system 90 without using the communication network 2. For example, a machine type number, a manufacturing number, customer information, maintenance and repair information, and failure log information may be maintained at the maintenance system 100 without using the communication network 2.
Still referring to FIG. 1, the terminals 10aa, 10ab, and 10ac, the relay terminal 30a, and the router 70a are connected to a local area network (LAN) 2a. The terminals 10ba, 10bb, and 10bc, the relay terminal 30b, and the router 70b are connected to a LAN 2b. The LAN 2a and the LAN 2b are connected to a leased line tab in which the router 70ab is provided. It is assumed that these devices including the terminals 10aa to 10bc are located in an area A. For example, assuming that the area A is any area in Japan, the LAN 2a could be located within an office in a city such as Tokyo, and the LAN 2b could be located within an office in another city such as Osaka.
The terminals 10ca, 10cb, and 10cc, the relay terminal 30c, and the router 70c are connected to a LAN 2c. The terminals 10da, 10db, and 10dc, the relay terminal 30d, and the router 70d are connected to a LAN 2d. The LAN 2c and the LAN 2d are connected to a leased line 2cd in which the router 70cd is provided. It is assumed that these devices including the terminals 10ca to 10dc are located in an area B apart from the area A. For example, assuming that the area is any area in the United States, the LAN 2c could be located within an office in a city such as New York, and the LAN 2d could be located within an office in another city such as Washington, D.C. The area A and the area B are connected through the Internet 2i, via the routers 70ab and 70cd. 
The management system 50, the authentication system 80, and the program providing system 90 are connected through the Internet 2i to the terminal 10 and the relay terminal 30. Any one of the management system 50, the authentication system 80, and the program providing system 90 may be located at any location within or outside any one of the area A and the area B.
In this example, the communication network 2 includes the LAN 2a, LAN 2b, leased line tab, Internet 2i, leased line 2cd, LAN 2c, and LAN 2d. Any one or any portion of these lines or any other lines that may be included in the communication network 2 may be implemented as wired network or wireless network such as Wireless Fidelity (WiFi) network or Bluetooth network.
As shown in FIG. 1, the terminal 10, the relay terminal 30, the management system 50, the router 70, the authentication system 80, and the program providing system 90 are each provided with four digit numbers. These four digit numbers separated by dots are the simple expressions of IP addresses respectively assigned to any one of the devices shown in FIG. 1, each of which has a function of communication device. For example, the IP address of the terminal 10aa is “1.2.1.3”. For simplicity, it is assumed that the IP address is expressed in IPv4. Alternatively, the IP address may be expressed in IPv6.
Further, in this example, the terminal 10 may be communicated in various ways. For example, at least two different terminals 10 that are located at different rooms in the same office, or at least two different terminals 10 that are located at different offices that are remotely located from one another, may communicate with one another. In another example, at least two different terminals 10 that are located in the same room may communicate with one another. In another example, one terminal 10 that is located indoor and another terminal 10 that is located outdoor, or at least two different terminals 10 that are both located outdoor, may communicate with one another. When the terminal 10 is located outdoor, the terminal 10 communicates with the other terminal 10 through a wireless network such as a wireless network designed for a mobile phone.
<Hardware Structure of Transmission System>
Next, a hardware structure of the transmission system 1 is explained according to an example embodiment of the present invention. In this example, when any delay in data reception is observed at the counterpart terminal 10B or the relay terminal 30, the relay terminal 30 changes resolution of image data to obtain converted image data and sends the converted image data to the counterpart terminal 10B or the request terminal 10A.
FIG. 4 is a perspective view illustrating the outer appearance of the terminal 10 of the transmission system 1. As illustrated in FIG. 4, the terminal 10 includes a body 1021, an arm 1074, and a camera housing 1075. The body 1021 includes a front side wall 1021a having a plurality of air intake holes 1021e that are formed over the nearly entire surface of the front side wall 1021a. The body 1021 further includes a back side wall 1021b having a plurality of exhaust holes over the nearly entire surface of the back side wall 1021b. When a cooling fan that is provided within the body 1021 is driven, air flows in through the intake holes 1021e of the front side wall 1021a and out through the exhaust holes of the back side wall 1021b. The front side wall 1021a is further provided with a sound pickup hole 1021f, which is formed at a central portion of the front side wall 1021a. Through the sound pickup hole 1021f, a microphone 114 (FIG. 5) of the terminal 10 is able to catch sounds such as human voice or any sound including noise. The body 1021 further includes a connection port 1021g that is formed on a lower side surface of the body 1021. The connection port 1021g is a hardware interface (I/F) that connects the terminal 10 with a cable terminal of any desired outside device such as an outside camera, microphone, speaker, etc.
The body 1021 has an operation panel 1022, which is provided at the left portion when viewed from the top. The operation panel 1022 includes a plurality of operation buttons 108 (“the operation button 108”), a power switch 109, and a plurality of sound output holes 1022f. Through the sound output holes 1022f, a speaker 115 (FIG. 5) of the terminal 10 is able to output sounds such as sounds generated based on human voice. The body 1021 further includes a holder 1021p, which is provided at the right portion when viewed from the top. The holder 1021p, which has a concave shape, accommodates therein the arm 1074 and the camera housing 1075.
The arm 1074 is fixed to the body 1021 via a torque hinge 1073. With the torque hinge 1073, the arm 1074 can be rotated in all directions of up, down, right, and left, with respect to the top surface of the body 1021, while making a pan angle θ1 that ranges from −180 degrees to +180 degrees and a tilt angle θ2 that ranges from 0 to 90 degrees with the top surface of the body 1021. When the arm 1074 is tilted at a relative tilt angle of 45 degrees, a click sound is generated.
The camera housing 1075 incorporates therein a camera 112 that takes an image of an object. The object may be a part of a user or a room where the terminal 10 is located. The camera housing 1075 is fixed to the arm 1074 through a torque hinge 1075a. With the torque hinge 1075a, the camera housing 1075 can be rotated with respect to the arm 1074, while making a tilt angle θ3 that ranges from about +100 degrees to −90 degrees in the direction toward the front side wall 1021a of the body 1021. The camera housing 1075 makes a tilt angle of 0 degree with respect to the arm 1074 when the camera housing 1075 and the arm 1074 are on the same plane.
Further, as illustrated in FIG. 4, the terminal 10 is connected to the display 120 through a cable 120c. 
The relay terminal 30, management system 50, authentication system 80, and program providing system 90 are each implemented by a general-purpose computer such as a personal computer or a server computer. For simplicity, explanation of the outer appearance of the computer is omitted.
FIG. 5 illustrates a hardware structure of the terminal 10 according to an example embodiment of the present invention. The terminal 10 includes a central processing unit (CPU) 101, a read only memory (ROM) 102, a random access memory (RAM) 103, a flash memory 104, a solid state drive (SSD) 105, a medium drive 107, the operation button 108, the power switch 109, a network interface (I/F) 111, the camera 112, an imaging element interface (I/F) 113, the microphone 114, the speaker 115, a voice input/output interface (I/O I/F) 116, a display interface (I/F) 117, and an outside device connection interface (I/F) 118, which are electrically connected through a bus 110 such as an address bus or data bus.
The CPU 101 controls entire operation of the terminal 10. The ROM 102 stores therein a control program for execution by the CPU 101, such as an initial program loader (IPL). The RAM 103 functions as a work area of the CPU 101. The flash memory 104 stores therein various data such as the terminal control program, image data, or voice data. The SSD 105 controls reading or writing of various data with respect to the flash memory 104 under control of the CPU 101. The medium drive 107 controls reading or writing of various data with respect to a removable recording medium 106 such as a flash memory. The operation button 108 allows the user to input a user instruction, for example, by allowing the user to select a communication destination such as the counterpart terminal 10B. The power switch 109 allows the user to switch on or off the power of the terminal 10. The network I/F 111 allows the terminal 10 to transmit data through the communication network 2.
The camera 112 takes an image of an object to obtain image data under control of the CPU 101. The imaging element I/F 113 controls operation of the camera 112. The microphone 114 catches sounds such as voice. The speaker 115 outputs sounds such as sounds generated based on voice. The voice I/O I/F 116 controls input or output of sound signals such as voice signals with respect to the microphone 114 and the speaker 115 under control of the CPU 101. The display I/F 117 transmits image data to the display 120 under control of the CPU 101. The outside device connection I/F 118 controls connection of the terminal 10 to various types of outside device.
The display 120 may be implemented by a liquid crystal display (LCD) or an organic light emitting display, which displays various data such as an image of an object or an operation icon. As illustrated in FIGS. 4 and 5, the display 120 is connected to the display I/F 117 through the cable 120c. The cable 120c may be implemented by an analog RCB (VGA) signal cable, a component video cable, a high-definition multimedia interface (HDMI) signal cable, or a digital video interactive (DVI) signal cable.
The camera 112 includes a plurality of devices such as a lens system, and a solid-state image sensing device that photo-electrically converts a light to generate an image of an object. For example, the solid-state image sensing device includes a complementary metal oxide semiconductor (CMOS) or a charge coupled device (CCD).
The outside device connection I/F 118 may be connected to an outside device such as a camera, microphone, or speaker through a universal serial bus (USB) cable. When the outside camera is connected to the terminal 10, the CPU 101 causes the terminal 10 to capture an image using the outside camera, rather than the camera 112 that is incorporated in the terminal 10. When the outside microphone or the outside speaker is connected to the terminal 10, the CPU 101 causes the terminal 10 to use the outside microphone or the outside speaker in replace of the incorporated microphone 114 or the incorporated speaker 115.
The recording medium 106, which can be freely attached to or detached from the terminal 10, includes any desired type of recording medium. In alternative to the flash memory 104, any nonvolatile memory that is readable and writable under control of the CUP 101 may be used such as Electrically Erasable and Programmable ROM (EEPROM).
The terminal control program may be written onto a recording medium that is readable by a general-purpose computer such as the recording medium 106 in any format that is installable or executable by a general-purpose computer. Once the terminal control program is written onto the recording medium, the recording medium may be distributed. Further, the terminal control program may be stored in any desired memory other than the flash memory 104, such as the ROM 102.
FIG. 6 illustrates a hardware structure of the management system 50 of FIG. 1. The management system 50 includes a CPU 201, a ROM 202, a RAM 203, the HD 204, a hard disk drive (HDD) 205, a medium drive 207, a display 208, a network interface (I/F) 209, a keyboard 211, a mouse 212, and a CD-ROM drive 214, which are electrically connected through a bus 210 such as an address bus or a data bus.
The CPU 201 controls entire operation of the management system 50. The ROM 202 stores a control program for execution by the CPU 201, such as the IPL. The RAM 203 functions as a work area of the CPU 201. The HD 204 stores therein various data such as a transmission management program. The HDD 205 controls reading or writing of various data with respect to the HD 204 under control of the CPU 201. The medium drive 207 controls reading or writing of various data with respect to a removable recording medium 206 such as a flash memory. The display 208 displays various data such as a cursor, menu, window, character, or image. The network I/F 209 allows the management system 50 to transmit data through the communication network 2. The keyboard 211 includes a plurality of keys, each of which is used for inputting a user instruction through a character, a numeral, or a symbol. The mouse 212 allows the user to input a user instruction including, for example, selection or execution of a specific instruction, selection of an area to be processed, and instruction of cursor movement. The CD-ROM drive 214 controls reading or writing of various data with respect to a CD-ROM 213. In alternative to the CD-ROM 213, any removable recording medium may be used.
The transmission management program may be written onto a recording medium that is readable by a general-purpose computer such as the recording medium 206 or the CD-ROM 213 in any format that is installable or executable by the general-purpose computer. Once the transmission management program is written onto the recording medium, the recording medium may be distributed. Further, the transmission management program may be stored in any desired memory other than the HD 204, such as the ROM 202.
The relay terminal 30 is substantially similar in hardware structure to the management system 50 of FIG. 6, except for replacement of the transmission management program with a relay terminal control program that is used for controlling the relay terminal 30. The relay terminal control program may be written onto a recording medium that is readable by a general-purpose computer such as the recording medium 206 or the CD-ROM 213 in any format that is installable or executable by the general-purpose computer. Once the relay terminal control program is written onto the recording medium, the recording medium may be distributed. Further, the relay terminal control program may be stored in any desired memory other than the HD 204, such as the ROM 202.
The authentication system 80 is substantially similar in hardware structure to the management system 50 of FIG. 6, except for replacement of the transmission management program with an authentication management program that is used for controlling the authentication system 80. The authentication management program may be written onto a recording medium that is readable by a general-purpose computer such as the recording medium 206 or the CD-ROM 213 in any format that is installable or executable by the general-purpose computer. Once the authentication management program is written onto the recording medium, the recording medium may be distributed. Further, the authentication management program may be stored in any desired memory other than the I-ID 204, such as the ROM 202.
The program providing system 90 is substantially similar in hardware structure to the management system 50 of FIG. 6, except for replacement of the transmission management program with a program providing program that is used for controlling the program providing system 90. The program providing program may be written onto a recording medium that is readable by a general-purpose computer such as the recording medium 206 or the CD-ROM 213 in any format that is installable or executable by the general-purpose computer. Once the program providing program is written onto the recording medium, the recording medium may be distributed. Further, the program providing program may be stored in any desired memory other than the HD 204, such as the ROM 202.
The maintenance system 100 is substantially similar in hardware structure to the management system 50 of FIG. 6.
Other examples of removable recording medium, which may be used in replace of the CD-ROM 213, include, but not limited to, compact disc recordable (CD-R), digital versatile disk (DVD), and blue ray disc.
<Functional Structure of Transmission System>
Referring now to FIG. 7, a functional structure of the transmission system 1 of FIG. 1 is explained according to an example embodiment of the present invention. More specifically, FIG. 7 illustrates a functional structure of the management system 50, a functional structure of the terminal 10, and a functional structure of the relay terminal 30. As illustrated in FIG. 1, the terminal 10, the relay terminal 30, and the management system 50 exchange data with one another through the communication network 2. For simplicity, the program providing system 90 and the authentication system 80 of FIG. 1 is not shown in FIG. 7.
<Functional Structure of Terminal>
The terminal 10 includes a data transmit/receive 11, an operation input 12, a login request 13, an imaging unit 14, a voice input 15a, a voice output 15b, a secondary relay terminal selection unit 16, a display control 17, a delay detector 18, a memory control 19, and a terminal authentication request 20. These units that are shown in FIG. 7 correspond to a plurality of functions or functional modules, which are executed according to an instruction of the CPU 101 (FIG. 5) that is generated according to the terminal control program being loaded from the flash memory 104 onto the RAM 103.
The terminal 10 further includes a memory 1000 that may be implemented by, for example, the RAM 103 (FIG. 5) and the flash memory 104 (FIG. 5).
Referring now to FIGS. 5 and 7, a functional structure of the terminal 10 is explained according to an example embodiment of the present invention. More specifically, in this example, the operations or functions that are performed by the terminal 10, which include the operations or functions performed by the units shown in FIG. 7, are performed in relation to one or more hardware devices of the terminal 10 that are shown in FIG. 5.
The operations or functions of the data transmit/receive 11 of the terminal 10 of FIG. 7 are performed by the network I/F 111 of FIG. 5 according to an instruction received from the CPU 101. The data transmit/receive 11 transmits or receives various data or information to or from another terminal, device, or system, through the communication network 2. In this example, the data transmit/receive 11 starts receiving state information that indicates the state of each candidate counterpart terminal 10 from the management system 50, before starting communication with any counterpart terminal 10B. With the state information of the candidate terminal 10, the user at the request terminal 10A is able to know the operation state of the candidate terminal 10. The operation state of the candidate terminal 10 indicates whether the candidate terminal 10 is on-line or off-line, whether the user at the candidate terminal 10 is having a session, or whether the user at the candidate terminal 10 is available or not available. The state information of the candidate terminal 10 further indicates various other types of information regarding the candidate terminal 10, such as whether the cable 120c is disconnected from the candidate terminal 10, whether the candidate terminal 10 is capable of outputting voice data but not to capable of outputting image data, or whether the candidate terminal 10 operates in MUTE mode in which no sounds are output. For the descriptive purposes, in the following examples, it is assumed that the state information of the candidate terminal 10 at least indicates the operation state of the candidate terminal 10.
The operations or functions of the operation input 12 of the terminal 10 of FIG. 7 are performed by the operation button 108 and the power switch 109 (FIG. 5) according to an instruction received from the CPU 101. The operation input 12 receives a user instruction input by the user through the operation button 108 or the power switch 109. For example, when the user selects “ON” using the power switch 109, the operation input 12 receives a user instruction for turning the power on, and causes the terminal 10 to turn on the power.
The operations or functions of the login request 13 are performed according to an instruction received from the CPU 101. When the power of the terminal 10 is turned on, the login request 13 automatically causes the data transmit/receive 11 to send login request information that requests the login process, and a current IP address of the terminal 10, to the management system 50 through the communication network 2. When the power of the terminal 10 is turned off according to a user instruction received from the user through the power switch 109, the login request 13 causes the data transmit/receive 11 to send current state information of the terminal 10 to the management system 50, which indicates that the power of the terminal 10 is turned off. After the state information is sent, the operation input 12 turns off the power of the terminal 10. As the state information of the terminal 10 is sent every time the power is turned off, the management system 50 is able to know that the terminal 10 is off-line in realtime.
The operations or functions of the imaging unit 14 of the terminal 10 of FIG. 7 are performed by the camera 112 and the imaging element I/F 113 according to an instruction received from the CPU 101. The imaging unit 14 takes an image of an object to output image data of the object.
The operations or functions of the voice input 15a of the terminal 10 of FIG. 7 are performed by the voice input/output I/F 116 according to an instruction received from the CPU 101. After the microphone 114 converts voice of the user at the terminal 10 to a voice signal, the voice input 15a inputs the voice signal in the form of voice data.
The operations or functions of the voice output 15b of the terminal 10 of FIG. 7 are performed by the voice input/output I/F 116 according to an instruction received from the CPU 101. The voice output 15b outputs a voice signal of voice data that is received from another terminal 10 through the speaker 115.
The secondary relay terminal selection unit 16 selects one of the relay terminals 30 that is suitable for communication to start videoconference. More specifically, according to an instruction received from the CPU 101 (FIG. 5), the secondary relay terminal selection unit 16 performs selection of the relay terminal 30 using a counter 16a, a calculator 16b, and a secondary selector 16c as illustrated in FIG. 8.
The counter 16a obtains date and time information indicating the date and time at which the data transmit/receive 11 of the terminal 10 receives preparatory transmit information when the preparatory transmit information is transmitted from another terminal 10. The calculator 16b calculates a time period T between the time when the preparatory information is transmitted by another terminal 10 and the time when the preparatory information is received at the terminal 10, based on the difference between the time and date information obtained by the counter 16a and time and date information included in the preparatory transmit information.
The secondary selector 16c selects one of the relay terminals 30 having the minimum value of the time period T calculated by the calculator 16b. 
The operations or functions of the display control 17 of the terminal 10 of FIG. 7 are performed by the display I/F 117 according to an instruction received from the CPU 101. The display control 17 controls transmit of image data to the display 120. The image data is generated by combining image data of different resolutions. Further, the display control 17 transmits candidate list information received from the transmission management system 50 to the display 120 to cause the display 120 to display a candidate list based on the candidate list information.
The delay detector 18 detects a delay time ms indicating a time period in which contents data such as image data or voice data sent through the relay terminal 30 from another terminal 10 is delayed, according to an instruction received from the CPU 101 (FIG. 5).
The memory control 19 is implemented by the SSD 105 (FIG. 5) according to an instruction received from the CPU 101. The memory control 19 stores various data in the memory 1000, or read out various data from the memory 1000. The memory 1000 stores therein various data such as terminal identification (ID) information for identifying the terminal 10, a password for authenticating the terminal 10 or a user at the terminal 10, a secret key assigned to the terminal 10, and a public key assigned to the authentication system 80. The memory control 19 further overwrites a memory space in the memory 1000 to store image data and/or voice data every time the terminal 10 communicates with another terminal 10. Before overwriting image data with new image data, the memory control 19 reads out the image data for display on the display 120, and the voice data for output through the speaker 150.
As the power is turned on, the terminal authentication request 20 is executed according to instructions received from the CPU 101 (FIG. 5) to function as a first encryption processor 20a and a second encryption processor 20b (FIG. 27). The first encryption processor 20a reads out identification information for identifying the terminal 10, such as the terminal ID of the terminal 10, from the memory 1000 via memory control 19. The first encryption processor 20a encrypts the terminal ID of the terminal 10 using a secret key for the terminal 10 to generate the encrypted terminal ID. For descriptive purposes, the encrypted terminal ID is referred to as first encrypted data. The second encryption processor 20b encrypts data containing the first encrypted data generated by the first encryption processor 20a and the terminal ID, using a public key assigned to the authentication system 80, to generate second encrypted data. In order to decrypt the secret key of the terminal 10, a public key that is paired with the secret key is needed. The data encrypted with the public key of the authentication system 80 can be decrypted only with a secret key that is paired with the authentication system's public key. The second decrypted data is transmitted to the authentication system 80 by the data transmit/receive 11 through the communication network.
In this example, any one of the terminal ID of the terminal 10, the login ID of the terminal 10, and the relay terminal ID of the relay terminal 30 includes any type of identification information that can be expressed by any language, character, symbol, mark, or any combination of language, character, symbol, and mark.
<Functional Structure of Relay Terminal>
Referring to FIG. 7, the relay terminal 30 includes a data transmit/receive 31, a state detector 32, a data quality checker 33, a data quality manager 34, a data quality changer 35, and a memory control 39. Upon execution, the CPU 201 (FIG. 6) loads the relay terminal control program from the HD 204 onto the RAM 203 to cause one or more of the units illustrated in FIG. 6 to perform functions or operations shown in FIG. 7. The relay terminal 30 further includes a memory 3000 that may be implemented by the RAM 203 and/or the HD 204 (FIG. 6).
The memory 3000 includes a data quality management database (DB) 3001, which stores a data quality management table illustrated in FIG. 10. The data quality management table of FIG. 10 stores an Internet protocol (IP) address of the counterpart terminal 10B to which image data is transmitted through the relay terminal 30, in association with quality of image data to be transmitted through the relay terminal 30 to the counterpart terminal 10B.
(Functional Structure of Relay Terminal)
Next, a functional structure of the relay terminal 30 is explained according to an example embodiment of the present invention. More specifically, in this example, the operations or functions that are performed by the relay terminal 30, which include the operations or functions performed by the units shown in FIG. 7, are performed in relation to one or more hardware devices of the relay terminal 10 that are shown in FIG. 6.
The data transmit/receive 31 of FIG. 7 is implemented by the network I/F 209 of FIG. 6 according to an instruction received from the CPU 201. The data transmit/receive 31 transmits or receives various data to or from another terminal, device, or system through the communication network 2.
The state detector 32, which is implemented by the CPU 201 of FIG. 6, detects an operation state of the relay terminal 30. The operation state includes the on-line state (“ON LINE”), the off-line state (“OFF LINE”), the communicating state, and the holding state. The on-line state is a state in which the relay terminal 30 is turned on and available for data transmission/reception. The off-line state is a state in which the relay terminal 30 is not available for data transmission/reception, for example, as the power is not turned on. The communicating state is a state in which the relay terminal 30 is on-line, but is communicating with another terminal. The holding state is a state in which the relay terminal 30 is on-line, but is not available at least for temporarily.
The data quality checker 33, which is implemented by the CPU 201 of FIG. 6, searches the data quality management DB 3001 (FIG. 11) using the IP address of the counterpart terminal 10B as a search key to extract information regarding the quality of image data suitable to communication with the counterpart terminal 10B. Based on the extracted information regarding the quality of image data, the relay terminal 30 determines the quality of image data to be transmitted to the counterpart terminal 10B.
The data quality manager 34, which may be implemented by the CPU 201 of FIG. 6, changes the contents of the data quality management DB 3001 based on the quality information that is received from the management system 50. For example, assuming that the request terminal 10aa having the terminal ID “01aa” communicates with the counterpart terminal 10db having the terminal ID “01db” to transmit or receive high quality image data during videoconference, transmission of image data may delay for various reasons. For example, if a request terminal 10bb and a counterpart terminal 10ca start videoconference over the communication network 2, transmission of image data from the request terminal 10aa to the counterpart terminal 10db tends to slow down due to the increase in traffic. In such case, the relay terminal 30 changes the quality of image data to be transmitted from high image quality to lower image quality. More specifically, the contents in the data quality management DB 3001 is changed from high-level image quality to medium-level image quality, based on the quality information indicating the use of medium-level image quality.
The data quality changer 35, which may be implemented by the CPU 201 of FIG. 6, changes the quality of image data received from the request terminal 10 to the quality of image data according to the contents of the data quality management DB 3001. The memory control 39 is implemented by the HDD 205 according to an instruction received from the CPU 201. The memory control 39 stores various data in the memory 3000, or reads out various data from the memory 3000.
<Functional Structure of Management System>
The management system 50 includes a data transmit/receive 51, a terminal authenticator 52, a state manager 53, a terminal extractor 54, a terminal state obtainer 55, a primary relay terminal selection unit 56, a session manager 57, a quality determiner 58, a memory control 59, and a delay time manager 60. Upon execution, the CPU 201 (FIG. 6) loads the transmission management program from the HD 204 onto the RAM 203 to cause the units shown in FIG. 6 to perform operations or functions as illustrated in FIG. 7. The management system 50 further includes a memory 5000, which may be implemented by the HD 204 of FIG. 6.
The memory 5000 includes a relay terminal management database (DB) 5001, which stores therein a relay terminal management table of FIG. 11. The relay terminal management table of FIG. 11 stores, for each relay terminal ID of the terminal 30, the operation state of the relay terminal 30, the received date and time at which the management system 50 receives the state information indicating the operation state of the relay terminal 30 from the relay terminal 30, the IP address of the relay terminal 30, and the maximum data transmission speed of the relay terminal 30 in Mbps. For example, for the relay terminal 30a having the relay terminal ID “111a”, the relay terminal management table indicates that the operation state is “ON LINE”, the received date and time at which the management system 50 receives the state information is “13:00 PM of Nov. 10, 2009”, the IP address of the relay terminal 30a is “1.2.1.2”, and the maximum data transmission speed of the relay terminal 30a is 100 Mbps.
The memory 5000 further includes a terminal authentication management database (DB) 5002, which stores a terminal authentication management table of FIG. 12. The terminal authentication management table of FIG. 12 stores a plurality of Login IDs respectively assigned to the terminals 10 that are managed by the management system 50, in association with a plurality of passwords that are previously determined for the respective terminals 10. For example, referring to the terminal authentication management table of FIG. 12, the terminal 10aa having the Login ID “aaLogin” is assigned with the password “aaaa”.
The memory 5000 further includes a terminal management database (DB) 5003, which stores a terminal management table of FIG. 13. The terminal management table of FIG. 13 stores, for each one of the terminal IDs assigned to the terminals 10, the terminal name to be used for communication with the terminal 10, the operation state of the terminal 10, the received date and time at which the management system 50 receives the login request information from the terminal 10, and the IP address of the terminal 10. For example, for the terminal 10aa having the terminal ID “01as”, the terminal management table of FIG. 13 indicates that the terminal name is “Japan Tokyo Office AA terminal”, the operation state is on-line (“ON LINE”) and is available for communication (“OK”), the received date and time is “13:40 PM, Nov. 10, 2009”, and the IP address of the terminal 10aa is “1.2.1.3”.
The memory 5000 further includes a candidate list management database (DB) 5004, which stores a candidate list management table of FIG. 14. The candidate list management table of FIG. 14 stores, for each one of a plurality of request terminals 10A capable of requesting for videoconference communication, the terminal ID of the request terminal 10A, and one or more terminal IDs that are respectively assigned to candidate terminals 10 that are previously registered for the request terminal 10A. In this example, for the request terminal 10A, one or more terminals 10 of the transmission system 1 of FIG. 1 are previously registered as the candidate terminal 10. For example, the candidate list management table of FIG. 14 indicates that the request terminal 10aa having the terminal ID “01aa” is most likely to request for videoconference with respect to the terminal 10ab having the terminal ID “01ab”, the terminal 10ba having the terminal ID “01ba”, the terminal 10bb having the terminal ID “01bb”, etc. The management system 50 manages the candidate list management table of FIG. 14, for example, according to a user instruction received from any one of the terminals 10. For example, in response to a user instruction received from the terminal 10aa, the management system 50 may add or delete the contents of the candidate list management table.
The memory 5000 further includes a session management database (DB) 5005, which stores a session management table of FIG. 15. The session management table of FIG. 15 stores information regarding each of the sessions that are carried out by at least two terminals 10 of the transmission system 1 for the purpose of selecting the relay terminal 30 that is most suitable for communication between at least two terminals 10. More specifically, for each session ID that uniquely identifies each session, the session management table of FIG. 15 stores a relay terminal ID of the relay terminal 30 to be used for transmitting or receiving contents data such as image data and voice data, a terminal ID of the request terminal 10A, a terminal ID of the counterpart terminal 10B, a delay time ms indicating a time period required for receiving contents data at the counterpart terminal 10B, the date and time information indicating the time at which the management system 50 receives delay information from the counterpart terminal 10B. For example, referring to the session management table of FIG. 15, for the session having the session ID “se1”, the relay terminal 30a having the relay terminal ID “111a” is selected to relay contents data between the request terminal 10aa having the terminal ID “01aa” and the counterpart terminal 10db having the terminal ID “01db”. Further, the management system 50 receives the delay information from the counterpart terminal 10db at 14:00 PM, Nov. 10, 2009. Based on this date and time information, the delay time ms of 200 milliseconds (ms) is obtained. In case of having videoconference between only two terminals 10, the delay time may be determined based on the time when the management system 50 receives the delay information transmitted from the request terminal 10A rather than based on the time when the management system 50 receives the delay information transmitted from the counterpart terminal 10B. In case of having videoconference with more than two terminals 10, the delay information transmitted from the counterpart terminal 10B that receives the contents data is used to manage the date and time at which the delay information is received.
The memory 5000 further includes a priority management database (DB) 5006, which stores an address priority management table of FIG. 16. The address priority management table of FIG. 16 defines a number of address priority points to be assigned to an arbitrary set of terminal 10 and relay terminal 30 based on the degree of similarity between the IP address of the terminal 10 and the IP address of the relay terminal 30. Assuming that the IP address of the terminal 10 and the IP address of the relay terminal 30 are each expressed in the form of four digital numbers as described above referring to FIG. 1, as the degree of similarity between the terminal IP address and the relay terminal IP address increases, a larger number of address priority points is assigned. In FIG. 16, the “S” indicates that one digit of the IP address, which may be referred to as the dot address, is the same for both of the terminal 10 and the relay terminal 30. The “D” indicates that one digit of the IP address, or the dot address, is different between the terminal 10 and the relay terminal 30. More specifically, in this example, when the first to third digits or dot addresses are the same between the terminal 10 and the relay terminal 30, the address priority point is 5. When the first and second digits or dot addresses are the same between the terminal 10 and the relay terminal 30, the address priority point is 3. In such case, the fourth digit or dot address does not affect the address priority point. When the first digit or dot address is the same between the terminal 10 and the relay terminal 30, the address priority point is 1. In such case, the third and fourth digits or dot addresses do not affect the address priority point. When the first digit or dot address is different between the terminal 10 and the relay terminal 30, the address priority point is 0. In such case, the second to fourth digits or dot addresses do not affect the address priority point.
The priority management DB 5006 of the memory 5000 further includes a transmission speed priority management table of FIG. 17. The transmission speed priority management table of FIG. 17 stores a range of the maximum data transmission speeds in association with a transmission speed priority point. More specifically, the transmission speed priority management table of FIG. 17 indicates that the transmission speed priority point increases with the increase in value of the maximum data transmission speeds at the relay terminal 30. For example, referring to FIG. 17, when the maximum data transmission speed at the relay terminal 30 is equal to or greater than 1000 Mbps, the transmission speed priority point of 5 is assigned. For example, when the maximum data transmission speed at the relay terminal 30 is equal to or greater than 100 Mbps but less than 1000 Mbps, the transmission speed priority point of 3 is assigned. When the maximum data transmission speed at the relay terminal 30 is equal to or greater than 10 Mbps but less than 100 Mbps, the transmission speed priority point of 1 is assigned. When the maximum data transmission speed at the relay terminal 30 is less than 10 Mbps, the transmission speed priority point of 0 is assigned.
The memory 5000 further includes a quality management database (DB) 5007, which stores a quality management table of FIG. 18. The quality management table of FIG. 18 stores the delay time ms of image data in association with the quality of image data. More specifically, the quality management table of FIG. 18 indicates that the quality of image data to be processed by the relay terminal 30 is lowered, as the delay time of the image data at the request terminal 10A or the counterpart terminal 10B increases. For example, when the delay time ms is equal to or greater than 0 milliseconds (ms), but less than 100 ms, the image data quality is high. When the delay time ms is equal to or greater than 100 ms but less than 300 ms, the image data quality is medium. When the delay time ms is equal to or greater than 300 but less than 500 ms, the image data quality is low. When the delay time ms is equal to or greater than 500 ms, the management system 50 interrupts operation of transmitting data.
Next, a functional structure of the management system 50 is explained according to an example embodiment of the present invention. In this example, the operations or functions that are performed by the management system 50, which include the operations or functions performed by the units shown in FIG. 7, are performed in relation to one or more hardware devices of the management system 50 that are shown in FIG. 6.
The data transmit/receive 51, which may be implemented by the network I/F 209 (FIG. 6) according to an instruction received from the CPU 201, transmits or receives various data or information to or from another terminal, device, or system through the communication network 2.
Under control of the CPU 201 (FIG. 6), the terminal authenticator 52 obtains a login ID and a password from the login request information that is received from the data transmit/receive 51. Using the login ID and the password as a search key, the terminal authenticator 52 searches the terminal authentication management DB 5002 to determine whether the obtained set of login ID and password is registered. Based on the search result, the terminal authenticator 52 determines whether the user at the terminal 10 or the terminal 10 is allowed for access.
The state manager 53, which operates according to an instruction received from the CPU 201 (FIG. 6), manages the operation state of the request terminal 10A that sends the login request information using the terminal management DB 5003 (FIG. 13). More specifically, the state manager 503 stores the terminal ID of the request terminal 10A, the operation state of the request terminal 10A, the date and time at which the management system 50 receives the login request information from the request terminal 10A, and the IP address of the request terminal 10A. When the power of the terminal 10 is switched from the ON state to the OFF state according to a user instruction received through the power switch 109, the state manager 53 receives the state information of the terminal 10 indicating that the terminal 10 is turned off, from the terminal 10. Based on the state information of the terminal 10, the state manager 53 changes the state information of the terminal 10 that is stored in the terminal management DB 5003 from the on-line state to the off-line state.
The terminal extractor 54, which operates according to an instruction received from the CPU 201 (FIG. 6), searches the candidate list management DB 5004 (FIG. 14) using the terminal ID of the request terminal 10A as a key to obtain a list of terminal IDs each being assigned to a plurality of candidate terminals 10. Additionally, the terminal extractor 54 searches the candidate list management DB 5004 (FIG. 14) using the terminal ID of the request terminal 10A as a key to obtain a terminal ID of another request terminal 10A that registers the request terminal 10A as a candidate terminal for another request terminal 10A.
The terminal state obtainer 55, which operates under control of the CPU 201 (FIG. 6), searches the terminal management DB 5003 (FIG. 13) using the terminal ID of each candidate terminal 10 that is extracted by the terminal extractor 54 as a key to obtain the state information of each candidate terminal 10. Accordingly, the terminal state obtainer 55 obtains the operation state of each of the candidate terminal 10 that is previously determined for the request terminal 10A that sends the login request information. Further, the terminal state obtainer 55 searches the terminal management DB 5003 using the terminal ID extracted by the terminal extractor 54 as a key to obtain the state information of the request terminal 10A that sends the login request information.
The primary relay terminal selection unit 56, which operates according to an instruction received from the CPU 201 (FIG. 6), limits a number of relay terminals 30 each of which is a candidate relay terminal 30 that may be used for relaying contents data between at least two terminals 10. Based on the result obtained by the primary relay terminal selection unit 56, the secondary relay terminal selection unit 17 of the terminal 10 selects one terminal 30 that is most suitable for communication between at least two terminals 10. As illustrated in FIG. 9, the primary relay terminal selection unit 56 includes a session ID generator 56a, a terminal IP address extractor 56b, a primary selector 56c, and a priority determiner 56d. 
The session ID generator 56a of the primary relay terminal selection unit 56 generates a session ID for identifying a session that is used for selecting the relay terminal 30. The terminal IP address extractor 56b extracts the terminal ID of the request terminal 10A and the terminal ID of the counterpart terminal 10B respectively from the session request information received from the request terminal 10A, and searches the terminal management DB 5003 (FIG. 13) to obtain the IP address of the request terminal 10A and the IP address of the counterpart terminal 10B. The primary selector 56c selects one or more relay terminals 30 having the online state from the relay terminal management DB 5001 (FIG. 11) to obtain the relay terminal ID of the selected relay terminal 30. In this example, it is assumed that more than two relay terminals 30 are selected as having the on-line state.
Further, the primary selector 56c obtains the IP address of each of the selected relay terminals 30. Once the IP address of the relay terminal 30 is obtained for each relay terminal 30, the primary selector 56c compares the IP address of the relay terminal 30 with at least one of the IP address of the request terminal 10A and the IP address of the counterpart terminal 10B that are respectively obtained by the terminal IP address extractor 56b to analyze the degree of similarity between the IP address of the terminal 10 and the IP address of the relay terminal 30. More specifically, the primary selector 56c compares between the IP address of the terminal 10 and the IP address of the relay terminal 30, digit by digit, or dot address by dot address, to determine the degree of similarity. Using the address priority management table of FIG. 16, the primary selector 56c obtains the address priority point for each one of the relay terminals 30. Assuming that the primary selector 56c compares the IP address of the terminal 10 with the IP address of the relay terminal 30, respectively for the request terminal 10A and the counterpart terminal 10B, the primary selector 56c obtains two address priority points for each one of the relay terminals 30. In such case, the primary selector 56c selects the highest one of the address priority points as the address priority point for the relay terminal 30.
Additionally, for each of the selected relay terminals 30 having the on-line state, the primary selector 56c obtains the maximum data transmission speed of the relay terminal 30 from the relay terminal management table of FIG. 11. Using the transmission speed priority management table of FIG. 17, the primary selector 56c obtains the transmission speed priority point that corresponds to the maximum data transmission speed of the selected relay terminal 30, for each of the selected relay terminals 30.
For each of the relay terminals 30, the primary selector 56c obtains a total priority point by adding the address priority point and the transmission speed priority point together. In this example, the primary selector 56c selects two relay terminals 30 including the relay terminal 30 having the highest total priority point and the relay terminal 30 having the second highest total priority point.
In this example, a number of relay terminals 30 that is finally selected by the primary selector 56c is not limited to two such that more than two relay terminals 30 may be finally selected for further processing as long as a number of relay terminals 30 is sufficiently reduced.
The priority determiner 56d refers to the priority management DB 5006 (FIG. 16) to determine the address priority point for each one of the relay terminals 30 that is selected by the primary selector 56c. The priority determiner 56d obtains the maximum data transmission speed of the relay terminal 30 from the relay terminal management DB 5001 (FIG. 11), and refers to the priority management DB 5006 (FIG. 17) to obtain the transmission speed priority point of the relay terminal 30 that is selected by the primary selector 56c. 
Referring back to FIG. 7, the session manager 57, which operates according to an instruction received from the CPU 201, stores the session ID generated by the session ID generator 56a, the terminal ID of the request terminal 10A, and the terminal ID of the counterpart terminal 10B, in a corresponding manner, in the session management DB 5005 (FIG. 15) of the memory 5000. The session manager 57 further stores the relay terminal ID of the relay terminal 30 that is finally selected by the secondary selector 17c of the terminal 10 for each session ID, in the session management DB 5005 (FIG. 15).
The quality determiner 58, which operates according to an instruction received from the CPU 201 (FIG. 6), searches the quality management DB 5007 (FIG. 18) using the delay time ms obtained for the selected relay terminal 30 to obtain the image data quality that is desirable for communication using the relay terminal 30.
The memory control 59, which operates according to an instruction received from the CPU 201 (FIG. 6) in relation with the HDD 205 (FIG. 6), stores various data in the memory 5000 or read out various data from the memory 5000.
The delay time manager 60 searches the terminal management DB 5003 (FIG. 13) using the IP address of the counterpart terminal 10B to obtain the terminal ID of the counterpart terminal 10B. The delay time manager 60 further manages the session management table of FIG. 15 stored in the session management DB 5005 so as to keep updated the value stored in the “delay time” field for the obtained terminal ID of the counterpart terminal 10B.
<Functional Structure of Authentication System>
Referring now to FIG. 28, a functional structure of the authentication system 80 is explained according to an example embodiment of the present invention. The authentication system 80 includes a data transmit/receive 81, a second decryption processor 82, a public key extractor 83, a first decryption processor 84, a comparator 85, a login data extractor 86, and a memory control 89. These units illustrated in FIG. 28 correspond to a plurality of functions or functional modules, which are executed according to an instruction of the CPU 201 (FIG. 6) that is generated according to the authentication management program being loaded from the ROM 202 onto the RAM 203. The authentication system 80 further includes a memory 8000, which may be implemented by the HD 204 (FIG. 3).
The memory 8000 stores therein a terminal public key management DB 8001, which includes a terminal public key management table of FIG. 29. Using the terminal public key management table of FIG. 29, the management system 50 manages various information used for authenticating the terminal 10. More specifically, referring to FIG. 29, the terminal public key management table stores, for each terminal 10, a terminal public key in association with the terminal ID. In FIG. 29, the public key “PBKaa” is stored with respect to the terminal ID “01aa” for the terminal 10aa. Only with the public key “PBKaa”, encrypted data that is encrypted with a paired secret key “PVKaa” can be decrypted. Alternatively, the terminal public key management table of FIG. 28 may further store the login ID of the terminal 10 and the password of the terminal 10 with respect to the terminal ID of the terminal 10, in addition to the terminal public key.
The memory 8000 further stores therein a login data management DB 8002, which includes a login data management table of FIG. 30. Using the login data management table of FIG. 30, the management system 50 manages the login ID and the password of the terminal 10 with respect to the terminal ID of the terminal 10, for each of the terminals 10 that are registered in the transmission system 1. Referring to FIG. 30, the login ID “aaLogin” and the password “aaaa” are stored with respect to the terminal ID “01aa” of the terminal 10aa. 
Referring back to FIG. 28, a functional structure of the authentication system 80 is explained according to an example embodiment of the present invention. In this example, the operations or functions that are performed by the authentication system 80, which include the operations or functions performed by the units shown in FIG. 28, are performed in relation to one or more hardware devices of the authentication system 80 that are shown in FIG. 6.
The data transmit/receive 81, which may be implemented by the network I/F 209 (FIG. 6) according to an instruction received from the CPU 201, transmits or receives various data or information to or from another terminal, device, or system through the communication network 2.
The second decryption processor 82 decrypts the second encrypted data with a secret key of the authentication system 80 to obtain the first encrypted data that is encrypted by the first encrypted processor 20a of the terminal 10 and the terminal ID of the terminal 10.
The public key extractor 83 searches the terminal public key management DB 8001 using the terminal ID that is obtained by the second decryption processor 82 to obtain a public key of the terminal 10.
The first decryption processor 84 decrypts the first encrypted data that is obtained from the second decryption processor 82, using the public key of the terminal 10 that is extracted by the public key extractor 83, to obtain the terminal ID of the terminal 10.
Referring now to FIG. 31, encryption and decryption, performed by the transmission system 1 of FIG. 1, is explained according to an example embodiment of the present invention. As illustrated in FIG. 31, the terminal 10 includes a terminal private key PVKt assigned to the terminal 10, and a system public key PBKs that is assigned to the authentication system 80. The authentication system 80 includes a system private key PVKs assigned to the authentication system 80, and a terminal public key PBKt assigned to the terminal 10. The terminal 10 encrypts the terminal ID “ID” of the terminal 10 with the terminal private key PVKt to generate the encrypted terminal ID “PVKt(ID)”, which may be referred to as the first encrypted data. The terminal 10 encrypts the terminal ID “ID” and the first encrypted data “PVKt(ID)” with the system public key PBKs to generate the second encrypted data “PBKs (ID+PVKt(ID))”. The terminal 10 transmits the second encrypted data “PBKs (ID+PVKt(ID))” to the authentication system 80. The authentication system 80 decrypts the second encrypted data “PBKs (ID+PVKt(ID))” with the system private key PVKs to obtain the data “ID+PVKt(ID)”, that is the terminal ID “ID” and the first encrypted data “PVKt(ID)”. The authentication system 80 decrypts the first encrypted data PVKt(ID) with the terminal public key PBKt to obtain the terminal ID of the terminal 10.
Referring back to FIG. 28, the comparator 85 compares between the terminal ID obtained by the first decryption processor 84 and the terminal ID obtained by the second encryption processor 82 to determine whether they are identical to verify the terminal ID of the terminal 10.
When the comparator 85 determines that the terminal ID obtained by the first decryption processor 84 and the terminal ID obtained by the second encryption processor 82 are identical with each other, i.e., when the terminal ID of the terminal 10 is verified, the login data extractor 86 searches the login data management DB 8002 using the terminal ID, which is verified, as a search key to obtain the login ID and the password that corresponds to the terminal ID. Once the login ID and the password are extracted, the data transmit/receive 81 sends the login ID and the password to the terminal 10 that has sent the request for authentication as the login information.
The memory control 89, which may be implemented by the SSD 105 (FIG. 5), stores various data in the memory 8000 or read out various data from the memory 8000. In addition to the terminal public key management DB 8001 and the login data management DB 8002, the memory 8000 may store various data such as image data and/or voice data.
<Operation of Transmission System>
Referring now to FIGS. 19 to 33, operation performed by the transmission system 1 is explained according to an example embodiment of the present invention. FIG. 19 is a data sequence diagram illustrating operation of managing state information indicating the operation state of the relay terminal 30, which is sent from the relay terminal 30 to the management system 50, according to an example embodiment of the present invention. FIGS. 20A and 20B are a data sequence diagram illustrating operation of preparing for communication to be established between or among two or more of terminals 10. FIG. 21 is a data sequence diagram illustrating operation of selecting the relay terminal 30. FIG. 22 is a flowchart illustrating operation of selecting the relay terminal 30. FIG. 23 is a table for explaining operation of calculating a total priority point to be used for operation of selecting the relay terminal 30. FIGS. 24A and 24B are a data sequence diagram illustrating operation of selecting the relay terminal 30. FIG. 25 is a flowchart illustrating operation of selecting the relay terminal 30, performed by the terminal 10. FIG. 26 is a data sequence diagram illustrating operation of transmitting or receiving contents data such as image data and/or voice data to or from one terminal to another terminal.
FIG. 27 is a schematic block diagram illustrating a functional structure of the terminal authentication request 20 of the transmission terminal 10. FIG. 28 is a schematic block diagram illustrating a functional structure of the authentication system 80. FIG. 29 is an example data structure of the terminal public key management table. FIG. 30 is an example data structure of the login data management table. FIG. 31 is an illustration for explaining encryption and decryption of data, performed by the transmission system 1. FIG. 32 is a flowchart illustrating operation of encrypting terminal ID, performed by the terminal 10. FIG. 33 is a flowchart illustrating operation of authenticating the terminal 10, performed by the authentication system 80.
Referring now to FIG. 19, operation of managing state information of the terminal 30, which is sent from each terminal 30 to the management system 50, performed by the transmission system 1 is explained according to an example embodiment of the present invention. In this example, it is assumed that the relay terminals 30a, 30b, 30c, and 30d, which may be each or collectively referred to as the relay terminal 30, exit in the transmission system 1.
At S1-1, S1-2, S1-3, and S1-4, the relay terminals 30a, 30b, 30c, and 30d each periodically monitors the operation state of the relay terminal 30. This monitoring is performed by the state detector 32 (FIG. 7) of the relay terminal 30.
At S2-1, S2-2, S2-3, and S2-4, the data transmit/receive 31 of the relay terminal 30 periodically transmits state information of the relay terminal 30 to the management system 50 through the communication network 2. With the state information of the relay terminal 30 that is periodically received, the management system 50 is able to manage the operation state of the relay terminal 30 in realtime. The state information of the relay terminal 30 includes an operation state of the relay terminal 30 that is detected by the state detector 32 of the relay terminal 30, which is sent together with a relay terminal ID that uniquely identifies each relay terminal 30. For the descriptive purposes, in this example, it is assumed that the relay terminals 30a, 30b, and 30d each have the on-line state, and the relay terminal 30c has the off-line state due to the failure in relay control program of the relay terminal 30c. 
At S3-1, S3-2, S3-3, and S3-4, the management system 50 receives the state information from the relay terminal 30 at the data transmit/receive 51, and stores the received state information of the relay terminal 30 in the memory 5000 through the memory control 59. More specifically, the memory control 59 stores the state information of each relay terminal 30 in association with the relay terminal ID of the corresponding relay terminal 30 in the relay terminal management DB 5001 (FIG. 11).
For example, referring to FIG. 11, the management system 50 stores the state information of the relay terminal 30 indicating whether the relay terminal 30 is on-line, off-line, or in trouble, etc., in association with the relay terminal ID of the relay terminal 30. Additionally, the management system 50 stores the date and time information indicating the time when the management system 50 receives the state information of the relay terminal 30 in association with the relay terminal ID of the relay terminal 30. When the management system 50 does not receive any state information from the relay terminal 30, the relay terminal management table of FIG. 11 has an empty value for the “operation state” field and the “date and time” field for the subjected relay terminal 30. Alternatively, the value of the “operation state” field and the value of the “date and time” field may reflect the state information that is previously sent by the subjected relay terminal 30 to the management system 50 it the relay terminal management table of FIG. 11 retains such value.
Referring to FIGS. 20A and 20B, operation of transmitting and receiving various management data before starting videoconference between the request terminal 10aa and the counterpart terminal 10db is explained, according to an example embodiment of the present invention. More specifically, the operation of FIGS. 20A and 20B is performed during a management data session sei in which various management data is exchanged.
At S20, the user at the request terminal 10aa turns on the power of the request terminal 10aa through the power switch 109 (FIG. 5). The operation input 12 of the request terminal 10aa (FIG. 7) turns on the power of the request terminal 10aa. 
At S21-1, as the power is turned on, the terminal authentication request 20 causes the data transmit/receive 11 to send an authentication request to the authentication system 80 through the communication network 2.
Referring now to FIG. 32, operation of requesting the authentication system 80 for authentication, performed by the terminal 10aa at S21-1, is explained according to an example embodiment of the present invention.
At S21-11, the memory control 19 of the terminal 10aa reads out the terminal ID “01aa” from the memory 1000.
At S21-12, the first encryption processor 20a of the terminal authentication request 20 of the terminal 10aa encrypts the terminal ID “01aa”, using a private key “PVKaa” that is assigned to the terminal 10aa, to generate the first encrypted data “PVKaa(01aa)”.
At S21-13, the second encryption processor 20b of the terminal authentication request 20 of the terminal 10aa encrypts the first encrypted data and the terminal ID “PVKaa(01aa)+01aa”, with a public key PBKsys that is assigned to the authentication system 80, to generate the second encrypted data “PBKsys(PVKaa(01aa)+01aa)”. In this example, the memory control 19 reads out the public key PBKsys from the memory 1000.
Referring back to FIG. 20A, at S21-2, the data transmit/receive 11 of the terminal 10aa sends the second encryption data to the authentication system 80, as the authentication request information.
At S21-3, the authentication system 80 determines whether the terminal 10aa is an authenticated terminal based on the authentication request information that is received by the data transmit/receive 81 from the terminal 10aa. 
Referring now to FIG. 33, operation of determining whether the terminal 10aa is an authenticated terminal, performed by the authentication system 80, is explained according to an example embodiment of the present invention. The operation of FIG. 33 is performed when the data transmit/receive 81 receives the second encrypted data “PBKsys(PVKaa(01aa)+01aa)”, which is sent from the terminal 10aa as the authentication request information.
At S21-31, the second decryption processor 82 decrypts the second encrypted data “PBKsys(PVKaa(01aa)+01aa)” that is received at the data transmit/receive 81, with the private key PVKsys read out from the memory 8000 through the memory control 89, to obtain the first encrypted data “PVKaa(01aa)” and the terminal ID “01aa”.
At S21-32, the public key extractor 83 searches the terminal public key management DB 8001 using the terminal ID “01 aa” as a key to extract the public key “PBKaa” that corresponds to the terminal ID “01aa”.
At S21-33, the first decryption processor 84 decrypts the first encrypted data obtained by the second decryption processor 82 using the public key “PBKaa” that is extracted by the public key extractor 83 to obtain the terminal ID “01aa”.
At S21-34, the comparator 85 compares between the terminal ID obtained by the first decryption processor 84 and the terminal ID obtained by the second decryption processor 82 to determine whether they are identical. When it is determined that they are identical (“YES” at S21-34), the comparator 85 determines that the terminal 10aa, which sends the authentication request information, is an authenticated terminal, and the operation proceeds to S21-35. When it is determined that they are not identical (“NO” at S21-34), the comparator 85 determines that the terminal 10aa, which sends the authentication request information, is not an authenticated terminal, and the operation ends.
At S21-35, the login data extractor 86 searches the login data management DB 8002 using the verified terminal ID as a key to obtain the login ID and the password of the terminal 10aa. 
Referring back to FIG. 20A, at S21-4, the data transmit/receive 81 of the authentication system 80 sends the login information, which includes the login ID and the password that corresponds to the verified terminal ID, to the terminal 10aa. The login ID and the password are stored in the memory 1000 through the memory control 19.
As described above, only when it is determined that the terminal 10aa is an authenticated terminal based on the verified terminal ID, the authentication system 80 sends the login information that is needed for the terminal 10aa to login the management system 50. Accordingly, the login information, which includes the login ID and the password, is not most likely to be stolen by the third party, thus suppressing the identity theft. Further, after the terminal 10aa is authenticated by the authentication system 80 at S21-3, the management system 50 determines whether the terminal 10aa is an authorized terminal by checking the login ID and the password at S23. In this manner, even when the terminal 10aa updates its own login ID and password, the management system 50 is able to manage various information regarding the terminal 10aa using the same login ID assigned to the terminal 10aa. 
In the above-described example, the terminal 10 reads out the login ID from the memory 1000. Alternatively, the terminal 10 may read out the terminal ID from a removable memory such as the medium 106 (FIG. 5).
Further, in the above-described example, the terminal 10aa encrypts the first encrypted data using the public key of the authentication system 80. Alternatively, the first encrypted data and the terminal ID may be sent to the authentication system 80 without encrypting the first encrypted data and the terminal ID. In such case, the authentication system 80 does not perform S21-31 (FIG. 33) of second decryption process. The authentication system 80 perform S21-33 (FIG. 33) of first decryption process using the public key extracted from the terminal public key management DB 8001 using the received terminal ID.
Further, assuming that the transmission terminal 10 sends the first encrypted data and the identification information to the authentication system 80, without performing second encryption processing, the transmission terminal 10 may send the first encrypted data and the identification information at different times.
For the descriptive purposes, it is assumed that a third party, who has stolen the terminal ID “01aa” of the terminal 10aa, sends the authentication request information to the authentication system 80 through another terminal 10bb with is assigned with a private key PVKxx or another personal computer that is similar in structure to the terminal 10. More specifically, in this example, the third party at another terminal 10bb or another PC sends the second encrypted data “PBKsys(PVKxx(01aa)+01aa)” to the authentication system 80.
In such case, referring to FIG. 33, at S21-31, the second decryption processor 81 of the authentication system 80 decrypts the second decrypted data “PBKsys(PVKxx(01aa)+01aa)” that is received at the data transmit/receive 81 with a private key PVKsys read out from the memory 8000 through the memory control 89 to obtain the first encrypted data “PVKxx(01aa)” and the terminal ID “01aa”.
At S21-32, the public key extractor 83 searches the public key management DB 8001 using the terminal ID “01aa” as a key to obtain the public key “PBKaa” that corresponds to the terminal ID “01aa”.
At S21-33, the first decryption processor 84 tries to decrypt the first encrypted data obtained by the second decryption processor 82 using the public key “PBKaa” extracted by the public key extractor 83. Since the encrypted data that is encrypted using the private key “PVKxx” cannot be decrypted using the public key “PBKaa” that is not paired with the private key “PVKxx”, the first decryption processor 84 may obtain data such as “XYZABC123 . . . ” that is different from the decrypted terminal ID.
At S21-34, the comparator 85 determines that the terminal ID “01aa” obtained by the second decryption processor 81 differs from the terminal ID “XYZABC123 . . . ” obtained by the first decryption processor 84 (“NO” at S21-34), and the operation ends without performing S21-35. In such case, the comparator 85 may output the comparison result indicating that they are different.
Referring back to FIG. 20A, when the data transmit/receive 11 of the terminal 10aa receives the login information, the memory control 19 stores the login information including the login ID and the password in the memory 1000. At S22, the login request 13 of the request terminal 10aa automatically causes the data transmit/receive 11 to send the login request information that requests the login process to the management system 50 through the communication network 2. The login request information includes the login ID and the password that are received from the authentication system 80 as the login information at S21-4, and the terminal ID of the request terminal 10aa. More specifically, the memory control 19 reads out the login ID and the password from the memory 1000, and sends the read data to the data transmit/receive 11. The data transmit/receive 11 of the request terminal 10aa sends the login request information including the login ID, the terminal ID, and the password to the management system 50. At the time of sending the login request information from the request terminal 10aa to the management system 50, the request terminal 10aa sends an IP address of the request terminal 10aa such that the management system 50 knows the IP address of the request terminal 10aa. 
At S23, the terminal authenticator 52 of the management system 50 searches the terminal authentication management DB 5002 (FIG. 12) stored in the memory 5000 using the login ID and the password of the login request information received through the data transmit/receive 51. When it is determined that the login ID and the password of the login request information is stored in the terminal authentication management DB 5002, the terminal authenticator 52 determines that the terminal 10aa is a registered terminal that is authorized to use the transmission system 1.
At S24, when the terminal authenticator 52 determines that the login request information is received from the authorized terminal 10, the state manager 53 of the management system 50 stores the operation state, the date and time at which the login request information is received, and the IP address of the terminal 10aa, with respect to the terminal ID and the terminal name of the terminal 10aa in the terminal management DB 5003 (FIG. 13) to create a record of the terminal 10aa. Using the terminal management table of FIG. 13, which stores the operations state of online, the date and time of “13:40, Nov. 10, 2009”, and the terminal IP address of “1.2.1.3” in association with the terminal ID “01aa”, various information regarding the terminal 10aa can be managed.
Referring to FIG. 20B, at S25, the data transmit/receive 51 of the management system 50 sends the authorization result obtained by the terminal authenticator 52 to the request terminal 10aa that has sent the login request information through the communication network 2. As described above, in this example, it is assumed that the terminal authenticator 52 determines that the terminal 10aa is an authorized terminal.
When the request terminal 10aa receives the authorization result indicating that the terminal 10aa is authorized, at S26, the data transmit/receive 11 sends the candidate list request information that requests for a candidate list to the management system 50 through the communication network 2. The data transmit/receive 51 of the management system 50 receives the candidate list request information.
At S27, the terminal extractor 54 of the management system 50 searches the candidate list management DB 5004 (FIG. 14) using the terminal ID “01aa” of the request terminal 10aa that has sent the login request information to extract a terminal ID for each of candidate terminals 10 that are previously registered for the request terminal 10aa. More specifically, referring to FIG. 14, the terminal extractor 54 extracts terminal IDs including “01ab”, “01ba”, “01db”, etc. of terminals 10ab, 10ba, 10db, etc. to obtain information regarding candidate terminals for the request terminal 10aa. 
At S27, the terminal state obtainer 55 searches the terminal management table stored in the terminal management DB 5003 (FIG. 13) using the candidate terminal ID of the candidate terminal that is extracted by the terminal extractor 54 as a search key to obtain the operation state of the candidate terminal having the extracted candidate terminal ID. More specifically, in this example, referring to FIG. 13, the terminal state obtainer 55 obtains the operation states “off-line”, “on-line”, and “on-line” respectively for the terminal IDs “10ab”, “10ba”, and “10db”. 
At S28, the data transmit/receive 51 of the management system 50 sends the candidate state information including the terminal ID and the operation state of the candidate terminal obtained at S26 and S27, to the request terminal 10aa through the communication network 2. More specifically, in this example, the terminal IDs “01ab”, “01ba”, and “01db” and the operation states “off-line”, “on-line” and “on-line” that are obtained respectively for the candidate terminals 10ab, 10ba, and 10db are sent. With this candidate state information, the request terminal 10aa is able to know the current operation state of each of the candidate terminals 10.
At S29, the terminal extractor 54 of the management system 50 searches the candidate list management table stored in the candidate list management DB 5004 (FIG. 14) using the terminal ID “01aa” of the request terminal 10aa that has sent the login request information as a search key to obtain the terminal ID of another request terminal 10 that has registered the request terminal 10aa as a candidate terminal. More specifically, referring to FIG. 14, the request terminal 10aa is listed as a candidate terminal for the request terminal 10ab, 10ba, and 10db. Accordingly, the terminal extractor 54 extracts the terminal IDs “01ab”, “01ba”, and “01db”.
At S30, the terminal state obtainer 55 of the management system 50 searches the terminal state management table stored in the terminal state management DB 5003 (FIG. 13) using the terminal ID “01aa” of the request terminal 10aa that has sent the login request information as a search key to obtain the operation state of the request terminal 10aa. 
At S31-1 and S31-2, the data transmit/receive 51 of the management system 50 sends the terminal state information including the terminal ID “01aa” and the operation state of the request terminal 10aa, that are respectively obtained at S30, to the terminals 10ab, 10ba, and 10db each having the request terminal 10aa as a candidate terminal that is obtained at S29. In this example, the management system 50 sends the terminal state information of the request terminal 10aa to only the terminals 10ba and 10db each having the on-line state as shown in FIG. 13.
More specifically, in this example, the data transmit/receive 51 refers to the terminal management table of FIG. 13 to obtain the IP address of each of the terminals 10ba and 10db. Using the obtained IP addresses, the management system 50 is able to send the terminal state information of the request terminal 10aa to the terminals 10ba and 10db each of which lists the request terminal 10aa as a candidate terminal.
The above-described operation of S21 to S31 is performed by any desired terminal 10 as the power of the terminal 10 is turned on through the power switch 109 (FIG. 5) at S20.
Referring now to FIG. 21, operation of limiting a number of candidate relay terminals 30 is explained according to an example embodiment of the present invention. The operation of FIG. 21 is performed during a management data session sei (FIG. 2), which transmits or receives various management data in the transmission system 1. Further, in this example, the request terminal 10aa can start communication with at least one of the terminals 10ba and 10db each having the on-line state as indicated by the terminal state information received at S28 of FIG. 20B. For the descriptive purposes, it is assumed that the user at the request terminal 10aa starts communication with the counterpart terminal 10db. 
At S41, the user at the request terminal 10aa operates the operation button 108 to select the terminal 10db as a counterpart terminal. Upon selection, the operation input 12 (FIG. 7) of the request terminal 10aa receives a user instruction for starting communication with the counterpart terminal 10db. 
At S42, the data transmit/receive 11 of the request terminal 10aa sends the communication start request information that requests the management system 50 to start communication with the counterpart terminal 10db to the management system 50. The communication start request information at least includes identification information such as the terminal ID “01aa” of the request terminal 10aa and the terminal ID “01db” of the counterpart terminal 10db. 
At the time of receiving the communication start request information, the data transmit/receive 51 of the management system 50 obtains the IP address “1.2.1.3” of the request terminal 10aa. 
At S43, the state manager 53 looks for records in the terminal management DB 5003 (FIG. 13) based on the terminal ID “01aa” of the request terminal 10aa and the terminal ID “01db” of the counterpart terminal 10db, which are included in the communication start request information. The state manager 53 changes each of the operation states of the request terminal 10aa and the counterpart terminal 10db in the records, from the online state to the communicating state.
At this time, the request terminal 10aa and the counterpart terminal 10db has not started communication, but the request terminal 10aa and the counterpart terminal 10db each have the communicating state. In case another terminal 10 tries to communicate with the request terminal 10aa or the counterpart terminal 10db, the management system 50 causes the another terminal 10 to output voice or display indicating that the request terminal 10aa or the counterpart terminal 10db is in the communicating state.
At S44, the management system 50 prepares for a session that is performed for selecting the relay terminal 30 for communication between the request terminal 10aa and the counterpart terminal 10db. More specifically, at S44, the session ID generator 56a (FIG. 9) of the management system 50 generates a session ID for a session that is to be performed for selection of the relay terminal 30.
At S45, the session manager 57 stores the session ID “se1” generated at S44, the terminal ID “01aa” of the request terminal 10aa, and the terminal ID “01db” of the counterpart terminal 10db, in the session management DB 5005 (FIG. 15) stored in the memory 5000.
At S46, the primary relay terminal selection unit 56 of the management system 50 limits a number of candidate relay terminals 30 from which one relay terminal 30 to be used for communication between the request terminal 10aa and the counterpart terminal 10db is selected, using the relay terminal management DB 5001, the terminal management DB 5003, and the priority management DB 5006.
Referring now to FIG. 9 and FIG. 22, operation performed at S46 of FIG. 21 is explained in detail.
At S46-1 of FIG. 22, the terminal IP address extractor 56b of the management system 50 searches the terminal management DB 5003 (FIG. 13) using the terminal ID “01aa” of the request terminal 10aa and the terminal ID “01db” of the counterpart terminal 10db included in the communication start request information sent from the request terminal 10aa as a key to obtain the IP addresses of the terminals 10aa and 10db, i.e., the IP address “1.2.1.3” and the IP address “1.3.2.4”.
At S46-2, the primary selector 56c refers to the relay terminal management DB 5001 (FIG. 11) to select one or more relay terminals 30 having the on-line operation state, and obtains the relay terminal ID of the selected relay terminal 30. More specifically, in this example, the primary selector 56c obtains the relay terminal IDs 111a, 111b, and 111d of the relay terminals 30a, 30b, and 30d. 
At S46-3, the primary selector 56c searches the relay terminal management DB 5001 (FIG. 11) to obtain the IP address of each of the relay terminals 30a, 30b, and 30d, using the relay terminal IDs 111a, 111b, and 111d obtained at S46-2. Further, the primary selector 56c compares each one of the IP addresses “1.2.1.2”, “1.2.2.2”, and “1.3.2.2” of the relay terminals 30a, 30b, and 30d, with each one of the IP addresses “1.2.1.3” and “1.3.2.4” obtained at S46-1, dot address by dot address, to determine the degree of similarity between the relay terminal IP address and the terminal IP address.
At S46-4, the priority determiner 56d refers to the priority management DB 5006 (FIG. 16) to determine a value of address priority point for each one of the relay terminals 30a, 30b, and 30d. In this example, as illustrated in FIG. 23, for each one of the relay terminals 30a, 30b, and 30d, the priority determiner 56d obtains an address priority point with respect to the request terminal 10aa and an address priority point with respect to the counterpart terminal 10db. 
FIG. 23 illustrates a table storing a calculation result of a priority point, which is used for limiting a number of candidate relay terminals 30. The table of FIG. 23 stores an address priority point, a transmission speed priority point, and a total priority point, for each one of the relay terminals IDs of the relay terminals 30. The address priority point includes a first address priority point with respect to the request terminal 10aa, and a second address priority point with respect to the counterpart terminal 10db. The total priority point is obtained by adding the highest one of the first and second address priority points with the transmission speed priority point.
In this example, based on comparison between the IP address “1.2.1.2” of the relay terminal 30a and the IP address “1.2.1.3” of the request terminal 10aa, the degree of similarity is “S.S.S.D” such that the address priority point of 5 is obtained. Similarly, based on comparison between the IP address “1.2.1.2” of the relay terminal 30a and the IP address “1.3.2.4” of the counterpart terminal 10db, the degree of similarity is “S.D.D.D” such that the address priority point of 1 is obtained.
Based on comparison between the IP address “1.2.2.2” of the relay terminal 30b and the IP address “1.2.1.3” of the request terminal 10aa, the degree of similarity is “S.S.D.D” such that the address priority point of 3 is obtained. Similarly, based on comparison between the IP address “1.2.2.2” of the relay terminal 30b and the IP address “1.3.2.4” of the counterpart terminal 10db, the degree of similarity is “S.D.S.D” such that the address priority point of 1 is obtained.
Based on comparison between the IP address “1.3.2.2” of the relay terminal 30d and the IP address “1.2.1.3” of the request terminal 10aa, the degree of similarity is “S.D.D.D” such that the address priority point of 1 is obtained. Similarly, based on comparison between the IP address “1.3.2.2” of the relay terminal 30a and the IP address “1.3.2.4” of the counterpart terminal 10db, the degree of similarity is “S.S.S.D” such that the address priority point of 5 is obtained.
Referring back to FIG. 22, at S46-5, the priority determiner 56d searches the priority management DB 5006 (FIG. 17) using the maximum data transmission speed of the relay terminal 30 that is stored in the relay terminal management DB 5001 (FIG. 11) to determine a transmission priority point for each one of the relay terminals 30a, 30b, and 30d that are selected at S46-2.
In this example, referring to FIG. 11 and FIG. 17, the relay terminal 30a having the maximum data transmission speed of 100 Mbps is assigned with the transmission priority point of 3. Similarly, the relay terminal 30b having the maximum data transmission speed of 1000 Mbps is assigned with the transmission priority point of 5. Similarly, the relay terminal 30d having the maximum data transmission speed of 10 Mbps is assigned with the transmission priority point of 1. Accordingly, the priority determiner 56d stores the transmission priority point for each one of the relay terminals 30a, 30b, and 30d in the table of FIG. 23.
At S46-6, for each one of the relay terminals 30a, 30b, and 30d, the primary selector 56c adds the highest one of the first and second address priority points with the transmission speed priority point to obtain a total priority point. The primary selector 56c selects the total of two relay terminals 30 having the highest priority point. For example, the primary selector 56c selects the relay terminal 30 having the highest total priority point and the relay terminal 30 having the second highest total priority point as a candidate relay terminal 30 for further processing. In this example, referring to FIG. 23, the relay terminals 30a, 30b, and 30d having the relay terminal IDs 111a, 111b, and 111d respectively have the total priority points of 8, 8, and 6. Accordingly, the primary selector 56c selects the relay terminal 30a having the relay terminal ID 111a, and the relay terminal 30b having the relay terminal ID 111b. 
After the operation of S46 illustrated in FIG. 21 completes, at S47 of FIG. 21, the data transmit/receive 51 (FIG. 7) of the management system 50 sends the relay terminal selection information to the counterpart terminal 10db through the communication network 2. The relay terminal selection information includes a number of candidate relay terminals 30, which is “2”, the terminal ID “01aa” of the request terminal 10aa, and the session ID “se1” for relay terminal selection. With this relay terminal selection information, the counterpart terminal 10db is able to obtain information including the number of candidate relay terminals 30, the request terminal 10aa that requests for videoconference, and the session ID “se1” of the session for relay terminal selection. In addition, the counterpart terminal 10db obtains the IP address “1.1.1.2” of the management system 50 that has sent the relay terminal selection information.
At S48, the data transmit/receive 11 of the counterpart terminal 10db sends confirmation information indicating that the relay terminal selection information is received, to the management system 50 through the communication network 2, with the IP address of the counterpart terminal 10db. The confirmation information includes the session ID “se1”. With this confirmation information, the management system 50 is able to know that the counterpart terminal 10db is notified with the number of candidate relay terminals 30 obtained during the session se1, and the IP address “1.3.2.4” of the counterpart terminal 10db. 
Referring now to FIGS. 24A, 24B, and 25, operation of selecting the relay terminal 30, performed by the counterpart terminal 10db, is explained according to an example embodiment of the present invention. The operation of FIGS. 24A and 24B is performed during the management data session sei of FIG. 2, which transmits or receives various management data in the transmission system 1.
Before starting videoconference, at S61-1 and S61-2, the management system 50 sends preparatory relay request information, respectively, to the relay terminals 30a and 30b, which are selected by the management system 50 at S46 as candidate relay terminals. The preparatory relay request information requests the relay terminal 30 to perform relay processing before starting the videoconference. More specifically, the preparatory relay request information includes the session ID “se1”, the IP address “1.2.1.3” of the request terminal 10aa, and the IP address “1.3.2.4” of the counterpart terminal 10db, and is transmitted with the IP address of the management system 50. With this preparatory relay request information, the relay terminals 30a and 30b are each able to obtain information including the session, the request terminal, the counterpart terminal, and the IP address “1.1.1.2” of the management system 50 that has sent the preparatory relay request information.
At S62-1 and S62-2, the relay terminals 30a and 30b each cause the data transmit/receive 31 to send preparatory transmit request information to the request terminal 10aa through the communication network 2. The preparatory transmit request information requests the request terminal 10aa to send preparatory transmit information including the Packet Internet Grouper (PING) to each one of the relay terminals 30a and 30b before starting the videoconference. More specifically, the preparatory transmit request information includes the session ID “se1”, and is transmitted with the IP addresses of the relay terminals 30a and 30b. With this preparatory transmit request information, the request terminal 10aa is able to know that the preparatory transmit information is to be sent during the session with the session ID “se1”, as well as the IP addresses “1.2.1.2” and “1.2.2.2” of the relay terminals 30a and 30b. 
As described above, the management system 50 does not directly send the IP address of the counterpart terminal 10db to the request terminal 10aa. Instead, as described above referring to S61-1 and S61-2, the management system 50 sends the IP address of the counterpart terminal 10db respectively to the relay terminal 30a and the relay terminal 30b. As described above referring to S62-1, the relay terminal 30aa requests the request terminal 10aa to send the preparatory transmit information to the relay terminal 30aa. In this manner, the management system 50 prevents the terminal 10 from obtaining the IP address of another terminal 10, thus improving the security.
At S63-1 and S63-2, the request terminal 10aa causes the data transmit/receive 11 to send the preparatory transmit information, respectively, to the relay terminals 30a and 30b through the communication network 2. The preparatory transmit information is sent to the counterpart terminal 10db through each one of the relay terminals 30a and 30b before the contents data such as the image data and the voice data is transmitted. By sending the preparatory transmit information in replace of the contents data, the management system 50 is able to calculate a time period required for transmitting the contents data from the request terminal 10aa to the counterpart terminal 10db through each one of the relay terminals 30a and 30b. Further, the preparatory transmit information includes PING information used for checking whether the request terminal 10aa, the relay terminal 30a or 30b, and the counterpart terminal 10db are each connected to allow communication, the date and time of which the request terminal 10aa sends the preparatory transmit information, and the session ID “se1”. With this preparatory transmit information, each of the relay terminals 30a and 30b knows that the preparatory transmit information is transmitted in the session with the session ID “se1”, and the IP address “1.2.1.3” of the request terminal 10aa that has sent the preparatory transmit information.
At S64-1 and S64-2, the relay terminals 30a and 30b each transmit the preparatory transmit information to the counterpart terminal 10db having the IP address “1.3.2.4”, which is obtained from the preparatory transmit information. With the preparatory transmit information, the counterpart terminal 10db is able to know that the preparatory transmit information is transmitted during the session with the session ID “se1”, and the IP addresses “1.2.1.2” and “1.2.2.2” of the relay terminals 30a and 30b that respectively send the preparatory transmit information.
At S65, the secondary relay terminal selection unit 17 of the counterpart terminal 10db selects one of the relay terminals 30a and 30b to be used for videoconference, based on the preparatory transmit information.
Referring now to FIG. 8 and FIG. 25, operation of selecting the relay terminal 30 for videoconference, which is performed at S65 of FIG. 24B, is explained.
At S65-1, the counter 16a of the secondary relay terminal selection unit 16 (FIG. 8) obtains the date and time at which the data transmit/receive 11 of the counterpart terminal 10db receives the preparatory transmit information for each one of the relay terminals 30a and 30b. 
At S65-2, the calculator 16b calculates, for each one of the relay terminals 30a and 30b, a time period between the time when the preparatory transmit information is transmitted by the request terminal 10aa and the time when the preparatory transmit information is received by the counterpart terminal 10db. The date and time at which the preparatory information is transmitted by the request terminal 10aa is obtainable from the preparatory transmit information. The date and time of which the preparatory transmit information is received at the counterpart terminal 10db is obtained by the counter 16a. 
At S65-3, the secondary selector 16c determines whether all items of preparatory transmit information is received for all of candidate relay terminals, during the session with the session ID “se1”. In this example, the secondary selector 16c counts a total number of items of preparatory transmit information that have been received, and compares with the total number of candidate relay terminals 30 of “2”.
When it is determined that the preparatory transmit information has not been received for at least one relay terminal 30 (“NO” at S65-3), the operation proceeds to S65-4. When it is determined that the preparatory transmit information has been received for all of the candidate relay terminals 30 (“YES” at S65-3), the operation proceeds to S65-5.
At S65-4, the secondary selector 16c determines whether a predetermined time period passes after the preparatory transmit information is received at the counterpart terminal 10db. In this example, the predetermined time period is set to one minute. When it is determined that the predetermined time period has not passed (“NO” at S65-4), the operation returns to S65-1. When it is determined that the predetermined time period has passed (“YES” at S65-4), the operation proceeds to S65-5.
At S65-5, the secondary selector 16c selects one of the relay terminals 30, which has the least value of the time period required for transmitting the preparatory transmit information based on the calculation of the calculator 16b. 
In this example, it is assumed that the relay terminal 30a is selected as a time period for transmitting the preparatory transmit information that is relayed through the relay terminal 30a has a value less than the value of the time period for transmitting the preparatory transmit information that is relayed through the relay terminal 30b. 
Referring back to FIG. 24B, at S66, the data transmit/receive 11 of the counterpart terminal 10db sends the relay terminal selection information to the management system 50 through the communication network 2. In this example, the relay terminal selection information indicates that the relay terminal 30a is selected. More specifically, the relay terminal selection information includes the session ID “se1”, and the relay terminal ID “111a” of the selected relay terminal 30a, and is transmitted with the terminal IP address of the counterpart terminal 10db. With the relay terminal selection information, the management system 50 is able to know that the relay terminal 30a has been selected during the session with the session ID “se1”, and the IP address “1.3.2.4” of the counterpart terminal 10db that has sent the relay terminal selection information.
At S67, the session manager 57 of the management system 50 stores, in the session management table of FIG. 15 stored in the session management DB 5005, the relay terminal ID “111a” of the relay terminal 30a, which is finally selected for communication, in the “relay terminal ID” field of a record provided for the session with the session ID “se1”.
At S68, the data transmit/receive 51 of the management system 50 sends the relay start request information to the relay terminal 30a through the communication network 2. The relay start request information requests the relay terminal 30a to start relay operation. More specifically, the relay start request information includes the IP address “1.2.1.3” of the request terminal 10aa, and the IP address “1.3.2.4” of the counterpart terminal 10db. 
At S69, the relay terminal 30a establishes four sessions between the request terminal 10aa and the counterpart terminal 10db including a session for transmission of low-level resolution image data, a session for transmission of medium-level resolution image data, a session for transmission of high-level resolution image data, and a session for transmission of voice data. Once these sessions are established, the request terminal 10aa is able to start videoconference with the counterpart terminal 10db. 
In the above-described example, the management system 50 sends the relay terminal selection information to the counterpart terminal 10db at S47 (FIG. 21), and the counterpart terminal 10db performs operation of S48, S64-1 (FIG. 24A), S64-2 (FIG. 24B), and S65 (FIG. 24B) to select the relay terminal 30. In alternative to this example, the management system 50 may send the relay terminal selection information to the request terminal 10aa to cause the request terminal 10aa to perform selection of the relay terminal 30. In such case, the request terminal 10aa performs operation of S48, S64-1 (FIG. 24A), S64-2 (FIG. 24B), and S65 (FIG. 24B) in a substantially similar manner as described above. Further, at S66, the request terminal 10aa sends the relay terminal selection information to the management system 50.
Referring now to FIG. 7 and FIG. 26, operation of transmitting and receiving contents data such as image data and voice data between the request terminal and the counterpart terminal to carry out videoconference, performed by the transmission system 1, is explained according to an example embodiment of the present invention.
In this example, the contents data such as the image data and the voice data flows in a direction from the request terminal 10aa to the counterpart terminal 10db, or in another direction from the counterpart terminal 10db to the request terminal 10aa. Since operation such as transmission and reception of the contents data or detection of delay time is the same for both of the directions, the following example focuses on communication in which data flows from the request terminal 10aa to the counterpart terminal 10db. 
Referring to FIG. 26, at S81, the data transmit/receive 11 of the request terminal 10aa sends the contents data to the relay terminal 30a through the communication network 2 in the contents data session “sed”. The contents data includes image data such as image data of an object captured by the imaging unit 14a and voice data that is input through the voice input 15a. In this example, it is assumed that the high-quality image data based on the low-level resolution image data, the medium-level resolution image data, and the high-level resolution image data, and the voice data, are transmitted. Accordingly, the data transmit/receive 31 of the relay terminal 30a receives the image data of three different resolution levels, and the voice data.
At S82, the data quality checker 33 searches the data quality management DB 3001 (FIG. 11) using the IP address “1.3.2.4” of the counterpart terminal 10db as a key to obtain the quality of the image data to be transmitted to the relay terminal 30a. 
In this example, the quality of image data to be transmitted to the relay terminal 30a is the high-quality image data. Since the image data that is received at the data transmit/receive 31 has the quality that is the same as the quality of the image data obtained from the data quality management DB 3001, at S83, the relay terminal 30a sends the high-quality image data and the voice data to the counterpart terminal 10db in the contents data session “sed”, without applying further image processing.
The counterpart terminal 10db receives the high quality image data that is generated based on the low-level resolution image data, medium-level resolution image data, and high-level resolution image data, and the voice data, at the data transmit/receive 11. The display control 17 combines the image data of three different resolution levels into the high quality image data for display onto the display 120. Further, the voice output 15b outputs the voice sound based on the voice data.
At S84, the delay detector 18 of the counterpart terminal 10db periodically detects a delay time indicating the time at which the image data is received at the data transmit/receive 11, for example, every one second. In this example, it is assumed that the delay time of 200 ms is obtained.
At S85, the data transmit/receive 11 of the counterpart terminal 10db sends the delay time information indicating the delay time of 200 ms to the management system 50 through the communication network 2, during the management data session “sei”. With the delay time information, the management system 50 is notified of the delay time, and the IP address “1.3.2.4” of the counterpart terminal 10db that has sent the delay time information.
At S86, the delay time manager 60 of the management system 50 searches the terminal management DB 5003 (FIG. 13) using the IP address “1.3.2.4” of the counterpart terminal 10db as a search key to extract the terminal ID “01db” of the counterpart terminal 10db. The delay time manager 60 stores the delay time of 200 ms obtained from the delay time information in a “delay time” field of the record of the terminal ID “01db” of the session management table stored in the session management DB 5005 (FIG. 15).
At S87, the quality determiner 58 searches the quality management DB 5007 (FIG. 18) using the delay time of 200 ms to extract the image data quality of “MEDIUM”. Based on the extracted image data quality, the quality determiner 58 determines that the quality of image data suitable for the delay time of 200 ms is medium.
At S88, the data transmit/receive 51 searches the relay terminal management DB 5001 (FIG. 11) using the relay terminal ID “111a”, which is stored in the session management DB (FIG. 15) in association with the counterpart terminal ID “01db”, to extract the IP address “1.2.1.2” of the relay terminal 30a. 
At S89, the data transmit/receive 51 sends the quality information indicating that the image data quality that has been determined at S87 is medium-level, to the relay terminal 30a through the communication network 2 during the management data session “sei”. The image quality information is transmitted with the IP address “1.3.2.4” of the counterpart terminal 10db, which was used as a search key at S86.
At S90, the change quality manager 34 of the relay terminal 30a stores the IP address “1.3.2.4” of the counterpart terminal 10db in association with the “medium-level” quality image data to be relayed by the counterpart terminal 10db, in the data quality management DB 3001 (FIG. 10).
At S91, the request terminal 10aa transmits the high quality image data including the low-level resolution image data, the medium-level resolution image data, and the high-level resolution image data, and the voice data, to the relay terminal 30a during the contents data session “sed”, in a substantially similar manner as described above referring to S81.
At S92, the data quality checker 33 of the relay terminal 30a searches the data quality management DB 3001 (FIG. 10) using the IP address “1.3.2.4” of the counterpart terminal 10db as a search key to extract the quality of the image data suitable for the counterpart terminal 10db, in a substantially similar manner as described above referring to S82.
At S93, since the image data quality that is stored for the counterpart terminal 10db is the medium-level, which is lower than the quality of the image data that is received at the data transmit/receive 31, the data quality changer 35 changes the quality of the image data from the high-level to the medium level. In this example, the quality of the voice data remains the same.
At S94, the data transmit/receive 31 of the relay terminal 30 sends the image data having the quality that is lowered to the medium-level, and the voice data, to the counterpart terminal 10db through the communication network 2, during the contents data session “sed”. The data transmit/receive 11 of the counterpart terminal 10db receives the medium-quality image data that is generated based on the low-level resolution image data and the medium-level resolution image data, and the voice data. The display control 17 of the counterpart terminal 10db combines the image data of two different resolution levels to generate the medium-level image data for display on the display 120. Further, the voice output 15db outputs the voice sound generated based on the voice data.
As described above, when any delay in receiving the image data at the counterpart terminal 10db is observed, the relay terminal 30a changes the quality of image data by lowering the quality of image data. Accordingly, the users participating the videoconference are able to carry out communication more smoothly.
Further, as describe above, in this example, the terminal 10 sends the first encrypted data that is generated by encrypting the identification information of the terminal 10, and the identification information of the terminal 10, to the authentication system 80. The authentication system 80 determines whether the decrypted data, which is obtained by decrypting the first encrypted data, matches the identification information of the terminal 10 received from the terminal 10, to generate a determination result. The authentication system 80 is able to determine whether the terminal 10 is an authenticated terminal based on only the information provided by the terminal 10. Accordingly, the authentication system 80 does not have to be previously provided with information indicating the association between the identification information of the terminal and the information for identifying the public key that is used for encryption by the terminal. As there is no need to use such association information, the authentication system 80 does not have to keep the association information updated, thus reducing the load required for maintaining the association information.
Further, as described above, the terminal 10 is assigned with the login information that is required for logging into the transmission system only when the authentication system 80 determines that the terminal 10 is the authenticated terminal based on information transmitted from the terminal 10. This suppresses the identity theft, as the login information is only sent to the terminal 10 that has been authenticated. Further, since the login information, which is used for logging in through the management system 50, is assigned by the authentication system 80, the authentication system 80 or the management system 50 does not have to keep updated identification information of the terminal 10 even when such identification information, such as the ID or the password, is changed by the user at the terminal 10.
The relay terminal 30, the management system 50, the authentication system 80, the program providing system 90, and the maintenance system 100 may be each implemented by a single computer. Alternatively, any number of parts, functions, or modules of the relay terminal 30, the management system 50, the authentication system 80, the program providing system 90, and the maintenance system 100 may be classified into a desired number of groups to be carried out by a plurality of computers. In case the program providing system 90 is implemented by the single computer, the program to be provided by the program providing system 90 may be transmitted, one module by one module, after dividing into a plurality of modules, or may be transmitted at once. In case the program providing system 90 is implemented as a plurality of computers, each computer may transmit each module that is stored in its memory, after the program is divided into a plurality of modules.
A recording medium storing any one of the terminal control program, relay control program, authentication management program, and transmission management program, or a storage device such as the HDD 204 that stores any one of the terminal control program, relay control program, authentication management program, and transmission management program, or the program providing system 90 provided with the HD 204 storing any one of the terminal control program, relay control program, authentication management program, and transmission management program, may be distributed within the country or to another country as a computer program product.
In the above-described examples, the quality of image data to be processed by the relay terminal 30, which is determined based on information obtainable from any one of the data quality management table of FIG. 10 and the quality management table of FIG. 18 is analyzed in terms of image resolution. Alternatively, any other criteria may be used to analyze quality of image data including, for example, depth of image, sampling frequency in case of voice data, and bit length in case of voice data.
Further, the date and time information stored in the relay terminal management table of FIG. 11 or the terminal management table of FIG. 13, or the delay time information stored in the session management table of FIG. 15, is expressed in terms of date and time. Alternatively, the date and time information or the delay time information may be expressed only in terms of time such as the time at which information is received.
Further, in the above-described examples, the relay terminal IP address of the relay terminal 30 and the terminal IP address of the terminal 10 are respectively managed using the relay terminal management table of FIG. 11 and the terminal management table of FIG. 13. Alternatively, the relay terminal 30 and the terminal 10 may each be managed using any other identification information or using any other tables. For example, when the relay terminal 30 or the terminal 10 needs to be identified on the communication network 2, the relay terminal 30 or the terminal 10 may be managed using Fully Qualified Domain Name (FQDN). In such case, the transmission system 10 is provided with a domain name system (DNS) server that obtains the IP address that corresponds to the FQDN of the relay terminal 30 or the terminal 10. In view of this, identification information for identifying the relay terminal 30 on the communication network 2 may not only include the identification information that identifies the relay terminal 30 on the communication network 2, but also identification information that identifies a node on the communication network 2 to which the relay terminal 30 is connected, or identification information that identifies a node on the communication network 2 from which the relay terminal 30 is connected. Similarly, identification information for identifying the terminal 10 on the communication network 2 may not only include the identification information that identifies the terminal 10 on the communication network 2, but also identification information that identifies a node on the communication network 2 to which the terminal 10 is connected, or identification information that identifies a node on the communication network 2 from which the terminal 10 is connected.
In the above-described examples, the transmission system 1 of FIG. 1 is treated as a videoconference system. Alternatively, the transmission system 1 of FIG. 1 may be implemented as a teleconference system such as the IP teleconference system or the Internet teleconference system. Alternatively, the transmission system 1 of FIG. 1 may be implemented as a car navigation system. For example, the request terminal 10 may be implemented as a car navigation system that is installed onto an automobile. The counterpart terminal 10 may be implemented as a management terminal or server at a management center that manages the car navigation system or a car navigation system that is installed onto another automobile. In another example, the transmission system 1 of FIG. 1 may be implemented as a communication system having a portable phone. In such case, the terminal 10 is implemented as the portable phone.
In the above-described examples, the contents data is assumed to include image data and voice data. Alternatively, the contents data may include any other type of data that affects human senses of sight in alternative to image data, or any other type of data that affects human senses of hearing in alternative to voice data. Alternatively, the contents data may include any other type of data that affects human senses of sight, smell, taste, touch, and hearing. In case the contents data that affects human senses of touch, the terminal 10 may convey the contents data that reflects senses of touch that is felt by a user at the terminal 10 to another terminal 10 through the communication network 2. In case the contents data that affects human senses of smell, the terminal 10 may convey the contents data that affects senses of smell felt by a user at the terminal 10 to another terminal 10 through the communication network 2. In case the contents data that affects human senses of taste, the terminal 10 may convey the contents data that affects senses of taste felt by a user at the terminal 10 to another terminal 10 through the communication network 2.
Further, the contents data may only include one type of contents data selected from sight data such as image data, hearing data such as voice data, touch data, smell data, and taste data.
Further, in the above-described examples, the transmissions system 1 is implemented as a videoconference system for use at offices. Other examples of use of the transmission system I include, but not limited to, meetings, casual conversation among family members or friends, and distribution of information in one direction.
Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of the present invention may be practiced otherwise than as specifically described herein.
With some embodiments of the present invention having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications are intended to be included within the scope of the present invention.
For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.
Further, as described above, any one of the above-described and other methods of the present invention may be embodied in the form of a computer program stored in any kind of storage medium. Examples of storage mediums include, but are not limited to, flexible disk, hard disk, optical discs, magneto-optical discs, magnetic tapes, involatile memory cards, ROM (read-only-memory), etc.
Alternatively, any one of the above-described and other methods of the present invention may be implemented by ASIC, prepared by interconnecting an appropriate network of conventional component circuits or by a combination thereof with one or more conventional general purpose microprocessors and/or signal processors programmed accordingly.
In one example, the present invention may reside in: an authentication system for authenticating a transmission terminal that transmits or receives image data or voice data to or from another transmission terminal. The authentication system includes: means for storing identification information for identifying the transmission terminal and a public key of the transmission terminal in a memory; means for receiving first encrypted data that is obtained by encrypting the identification information of the transmission terminal with a terminal private key that is paired with the terminal public key together with the identification information of the transmission terminal, from the transmission terminal; means for searching the memory to obtain a terminal public key that corresponds to the identification information that is received by the means for receiving; and means for decrypting the first encrypted data received by the means for receiving with the extracted public key to obtain decrypted identification information from the first encrypted data; and means for determining whether the decrypted identification information obtained by the means for decrypting is identical with the identification information of the transmission terminal received by the means for receiving to generate a determination result.
In another example, the authentication system further includes means for transmitting login information to the transmission terminal based on the determination result, wherein the transmission terminal uses the login information when requesting a transmission management system to login.
In another example, the means for receiving receives second encrypted data from the transmission terminal. The second encrypted data is obtained by encrypting the first encrypted data and the identification information of the transmission terminal with a system public key assigned to the authentication system. The authentication system further includes means for decrypting the second encrypted data received by the means for receiving with a system private key that is paired with the system public key of the authentication system to obtain the decrypted first encrypted data and the decrypted identification information of the transmission terminal. The means for searching searches the memory to obtain a terminal public key that corresponds to the decrypted identification information of the transmission terminal.
In another example, the present invention may reside in a transmission terminal that transmits or receives image data or voice data to or from another transmission terminal after being authenticated by an authentication system. The transmission terminal includes: means for storing a private key of the transmission terminal and identification information for identifying the transmission terminal in a memory; first encryption means for encrypting the identification information for identifying the transmission terminal with the private key to obtain first encrypted data; and means for transmitting the first encrypted data and the identification information of the transmission terminal to the authentication system.
In another example, the transmission terminal further includes means for receiving login information from the authentication system when the authentication system determines that the transmission terminal is an authenticated terminal based on the first encrypted data sent by the transmission terminal.
In another example, the means for string further stores a system public key assigned to the authentication system. The transmission terminal further includes means for encrypting the first encrypted data and the identification information of the transmission terminal with the system public key of the authentication system to obtain second encrypted data. The means for transmitting transmits the second encrypted data to the authentication system.
In another example, the present invention may reside in a method of authenticating a transmission terminal before the transmission terminal logs in a transmission system. The method includes: encrypting terminal identification information of the transmission terminal using a terminal private key assigned to the transmission terminal to generate encrypted terminal identification information; transmitting the encrypted terminal identification information and the terminal identification information from the transmission terminal to an authentication system; obtaining, by the authentication system, a terminal public key that corresponds to the terminal identification information transmitted from the transmission terminal; decrypting, at the authentication system, the encrypted identification information using the terminal public key to obtain decrypted identification information; and determining whether the decrypted identification information obtained by the authentication system matches the terminal identification information transmitted from the transmission terminal to generate a determination result.
In another example, the above-described method further includes: storing, in a memory, a plurality of items of identification information each identifying a specific transmission terminal of the transmission system in association with a plurality of terminal public keys each assigned to the specific transmission terminal of the transmission system. The obtaining includes: extracting one of the plurality of items of identification information stored in the memory using the terminal identification information received from the transmission terminal to obtain the terminal public key.
In another example, the above-described method further includes: encrypting information containing the encrypted terminal identification information and the terminal identification information, using a system public key assigned to the authentication system, to generate encrypted information containing the encrypted terminal identification information and the terminal identification information; transmitting the encrypted information containing the encrypted terminal identification information and the terminal identification information from the transmission terminal to the authentication system; and decrypting, at the authentication system, the encrypted information containing the encrypted terminal identification information and the terminal identification information, using a system private key that is paired with the system public key, to obtain the encrypted terminal identification information and the terminal identification.
In another example, the above-described method further includes: transmitting login information to the transmission terminal when the determination result indicates that the decrypted identification information matches the terminal identification information received from the transmission terminal; and causing the transmission terinal to log in the transmission system using the login information received from the authentication system.

## Claims

1. A transmission system, comprising:
a management system that manages communication between a plurality of transmission terminals;
the plurality of transmission terminals each to log in to the transmission system to communicate with a counterpart transmission terminal; and
an authentication system that authenticates at least one of the transmission terminals before the transmission terminal logs in the transmission system, wherein:
the management system includes:
a first memory that stores terminal identification information of each one of the plurality of transmission terminals each capable of establishing communication with a counterpart communication terminal via the management system; and
a communication manager that manages the communication between the plurality of transmission terminals based on the terminal identification information stored in the first memory, and

the plurality of transmission terminals each includes:
a second memory that stores a terminal private key assigned to the transmission terminal;
a first encryption processor that encrypts terminal identification information of the transmission terminal using the terminal private key stored in the second memory to generate encrypted terminal identification information; and
a first transmitter the transmits the encrypted terminal identification information and the terminal identification information of the transmission terminal to the authentication system, and

the authentication system includes:
a third memory that stores the terminal identification information stored in the memory of the management system, and terminal public keys respectively corresponding to terminal private keys stored in the second memory of the transmission terminal, the terminal public key identified by the terminal identification information, in association with each other;
a receiver that receives the encrypted terminal identification information and the terminal identification information, from the transmission terminal;
a key extractor that obtains a terminal public key that corresponds to the terminal identification information received from the transmission terminal, from the third memory, the terminal public key being a public key of the transmission terminal to be authenticated by the authentication system;
a first decryption processor that decrypts the encrypted terminal identification information using the terminal public key extracted by the key extractor to obtain decrypted identification information;
a determiner that determines whether the decrypted terminal identification information obtained by the first decryption processor matches the terminal identification information received from the transmission terminal; and
a second transmitter that transmits login information to be used for logging in to the management system to the transmission terminal when the determiner determines that the decrypted terminal identification information matches the terminal identification information, and not to transmit login information to be used for logging in to the management system to the transmission terminal when the determiner determines that the decrypted terminal identification information does not match the terminal identification information,

wherein when the transmission terminal receives the login information from the authentication system, the transmission terminal logs in the management system based on the received login information to establish communication with the counterpart transmission terminal.

2. The transmission system of claim 1, wherein:
the transmission terminal further includes a second encryption processor that encrypts information containing the encrypted terminal identification information and the terminal identification information, using a system public key assigned to the authentication system, in order to generate encrypted information containing the encrypted terminal identification information and the terminal identification information, the transmitter transmits the encrypted information containing the encrypted terminal identification information and the terminal identification information,
the authentication system further includes a second decryption processor that decrypts the encrypted information containing the encrypted terminal identification information and the terminal identification information, using a system private key that is paired with the system public key, in order to obtain the encrypted terminal identification information and the terminal identification information, and
the determiner determines whether the decrypted identification information obtained by the first decryption processor matches the terminal identification information obtained by the second decryption processor in order to generate the determination result.

3. The transmission system of claim 1, wherein the authentication system further includes:
a login data extractor that obtains login identification information of the transmission terminal that corresponds to the terminal identification information, wherein the login information includes the login identification information obtained by the login data extractor.

4. An authentication apparatus for authenticating a transmission terminal before the transmission terminal logs in to a transmission system which includes a management system, the apparatus comprising:
a memory that stores terminal identification information stored in a memory of the management system, and terminal public keys respectively corresponding to terminal private keys stored in a memory of the transmission terminal, the terminal public key identified by the terminal identification information, in association with each other;

a receiver that receives encrypted terminal identification information and terminal identification information from the transmission terminal, wherein the encrypted terminal identification information is encrypted with a terminal private key assigned to the transmission terminal;
a key extractor that obtains a terminal public key that corresponds to the terminal identification information received from the transmission terminal, from the memory;
a first decryption processor that decrypts the encrypted identification information using the terminal public key to obtain decrypted identification information;
a determiner that determines whether the decrypted identification information obtained by the first decryption processor matches the terminal identification information received from the transmission terminal; and
a transmitter that transmits login information to be used for logging in to the management system to the transmission terminal when the determiner determines that the decrypted terminal identification information matches the terminal identification information, and not to transmit login information to be used for logging in to the management system to the transmission terminal when the determiner determines that the decrypted terminal identification information does not match the terminal identification information,
wherein when the transmission terminal receives the login information from the authentication system, the transmission terminal logs in the management system based on the received login information to establish communication with the counterpart transmission terminal.

5. The authentication apparatus of claim 4, further comprising:
a second decryption processor that:
receives encrypted information containing the encrypted terminal identification information and the terminal identification information from the transmission terminal via the receive unit; and
decrypts the encrypted information containing the encrypted terminal identification information and the terminal identification information, using a system private key that is paired with the system public key, in order to obtain the encrypted terminal identification information and the terminal identification information, wherein the determiner determines whether the decrypted identification information obtained by the first decryption processor matches the terminal identification information obtained by the second decryption processor in order to generate the determination result.

6. The authentication apparatus of claim 4, further comprising:
a login data extractor that obtains login identification information of the transmission terminal that corresponds to the terminal identification information, wherein the login information includes the login identification information obtained by the login data extractor.

7. A non-transitory computer readable recording medium which stores a plurality of instructions which, when executed, cause a processor to perform a method of authenticating a transmission terminal before the transmission terminal logs in a transmission system, the method comprising:
encrypting terminal identification information of the transmission terminal using a terminal private key assigned to the transmission terminal to generate encrypted terminal identification information;
transmitting the encrypted terminal identification information and the terminal identification information from the transmission terminal to an authentication system;
obtaining, by the authentication system from a memory of the authentication system which stores the terminal identification information which is also stored in a memory of a management system, and terminal public keys respectively corresponding to terminal private keys stored in a memory of the transmission terminal, the terminal public key identified by the terminal identification information, in association with each other, the terminal public key that corresponds to the terminal identification information transmitted from the transmission terminal based on the terminal identification information, the terminal public key being a public key of the transmission terminal to be authenticated;
decrypting, at the authentication system, the encrypted identification information using the terminal public key to obtain decrypted identification information;
determining whether the decrypted identification information obtained by the authentication system matches the terminal identification information transmitted from the transmission terminal; and
transmitting login information to be used for logging in to the management system to the transmission terminal when the determining determines that the decrypted identification information matches the terminal identification information, and not to transmit login information to be used for logging in to the management system to the transmission terminal when the determining determines that the decrypted identification information does not match the terminal identification information, wherein when the transmission terminal receives the login information from the authentication system, the transmission terminal logs in to the management system based on the received login information to establish communication with a counterpart transmission terminal.

8. The non-transitory computer readable medium of claim 7, wherein the method further comprises:
encrypting information containing the encrypted terminal identification information and the terminal identification information, using a system public key assigned to the authentication system, in order to generate encrypted information containing the encrypted terminal identification information and the terminal identification information;
transmitting the encrypted information containing the encrypted terminal identification information and the terminal identification information from the transmission terminal in order to the authentication system; and
decrypting, at the authentication system, the encrypted information containing the encrypted terminal identification information and the terminal identification information, using a system private key that is paired with the system public key, in order to obtain the encrypted terminal identification information and the terminal identification.

9. A method, implemented by an authentication apparatus, for authenticating a transmission terminal before the transmission terminal logs in a transmission system, the method comprising:
receiving encrypted terminal identification information and terminal identification information from the transmission terminal, wherein the encrypted terminal identification information is encrypted with a terminal private key assigned to the transmission terminal;
obtaining from a memory of the authentication apparatus which stores the terminal identification information which is also stored in a memory of a management system, and terminal public keys respectively corresponding to terminal private keys stored in a memory of the transmission terminal, the terminal public key identified by the terminal identification information, in association with each other, the terminal public key that corresponds to the terminal identification information received from the transmission terminal based on the terminal identification information, the terminal public key being a public key of the transmission terminal to be authenticated;
decrypting, using a decryption processor of the authentication apparatus, the encrypted identification information using the terminal public key to obtain decrypted identification information;
determining whether the decrypted identification information obtained by the decryption processor matches the terminal identification information received from the transmission terminal to generate a determination result in order to authenticate the transmission terminal; and
transmitting login information to be used for logging in to the management system to the transmission terminal when the determining determines that the decrypted identification information matches the terminal identification information, and not to transmit login information to be used for logging in to the management system to the transmission terminal when the determining determines that the decrypted identification information does not match the terminal identification information, wherein when the transmission terminal receives the login information from the authentication system, the transmission terminal logs in to the management system based on the received login information to establish communication with a counterpart transmission terminal.

10. The method of claim 9, further comprising:
receiving encrypted information containing the encrypted terminal identification information and the terminal identification information from the transmission terminal;
second decrypting the encrypted information containing the encrypted terminal identification information and the terminal identification information, using a system private key that is paired with the system public key, in order to obtain the encrypted terminal identification information and the terminal identification information; and
determining whether the decrypted identification information obtained by the decrypting matches the terminal identification information obtained by the second decrypting in order to generate the determination result.