Abstract:
A high-speed wireless LAN system is disclosed. The system includes a mobile station for transmitting/receiving data encrypted by a predetermined encryption method, communicating the data to associated access points by an ultra wide-band (UWB) communication method, and communicating an encryption key according to the encryption method to said associated access points by an optical or infra-red (IR) communication method; the plurality of access points, installed in a plurality of predetermined service areas, for relaying between the mobile station and a gateway of a remote place by communicating the data and the encryption key with the mobile station located in the corresponding service area by the UWB and the optical or IR communication methods and transmitting/receiving the data and the encryption key to/from the gateway by an optical communication method; and the gateway for providing an optical interface between an internal network and an external network, being provided with a plurality of gateway sub-modules for transmitting/receiving the data and the encryption key by communicating with the plurality of access points by the optical communication method, and transmitting a subscriber service transmitted from the external network to the corresponding access point.

Description:
This application claims priority pursuant to 35 USC §119 to that patent application entitled “High-speed wireless LAN system,” filed in the Korean Intellectual Property Office on Dec. 22, 2003 and assigned Serial No. 2003-94583, the contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a wireless LAN system, and more particularly to a high-speed wireless LAN system using a combined UWB (Ultra Wide Band) communication method and an optical communication method. 
   2. Description of the Related Art 
   Superior mobility and lack of cable connection represent significant advantages of wireless LAN systems over comparable wire-ed LAN systems and wireless LAN systems are becoming more widely used by the general population. Current wireless LAN systems operate in the radio frequency (RF) band of 2.4 GHz or 5 GHz as a carrier, e.g., IEEE 802.11a, b and g, and the selected carrier is modulated to carry the data content. These wireless LAN systems provide a transmission speed of 22 Mbps in the 2.4 GHz band, or a transmission speed of 54 Mbps in the 5 GHz band, respectively. 
   Under such transmission speeds, however, it is difficult to provide a high-capacity and high-speed service through the existing wireless LAN system due to the bottlenecks that may occur in the home or office. To solve this problem, there has recently been proposed a method that uses an UWB (Ultra Wide Broadband) connection instead of the RF band as a transmission medium. The transmission speed of high-speed wireless LAN systems that uses UWB connection as the transmission medium can be 100 Mbps (Mega bits/sec) or more. 
   An UWB-based wireless LAN system has the advantage in that it can provide a high-speed and large-capacity service, but its serviceable area is limited typically to less than 10 meters (m). Accordingly, conventional UWB-based wireless LAN systems use one gateway and a plurality of DAP (Dummy Access Point) properly arranged at important points within the network to increase the operating range. The gateway and the DAPs are typically connected together through an optical fiber. 
     FIG. 1  is a block diagram illustrating an example of the main parts of an UWB-based high-speed optical wireless LAN system. Referring to  FIG. 1 , the optical wireless LAN system shown includes a gateway sub-module  130 , a plurality of access points (APs/DAPs)  120  and a plurality of mobile stations (STAs)  110 , e.g., notebook computers. This system configuration may be referred to as a ‘UWB over fiber’ transmission, as the UWB connection is established using an optical fiber connection. In  FIG. 1 , one AP  120  and one mobile station  110  are illustrated for the convenience of explanation. However, it would be recognized by those skilled in the art that a plurality of APs  120  and stations  110  may be included within a wireless LAN system. 
   Referring to  FIG. 1 , the mobile station  110  transmits data modulated in a format according to the UWB communication method, or demodulates data received in the UWB format to the original data. Station  110  includes a UWB module  112  for transmitting/receiving UWB signal through UWB antenna  113 . AP  120  also includes UWB antenna  123  through which the AP  120  transmits/receives, wirelessly, the UWB signal to/from the mobile station  110 . AP  120  also includes WB optical transmitter/receiver  124  which transmits/receives a UWB signal to/from the gateway sub-module  130  through optical fibers  140 ,  150 . The gateway sub-module  130  includes UWB optical transmitter/receiver  134 , which transmits/receives the UWB signal to/from the AP  120  through the optical fiber  150 ,  140 , respectively. UWB module  132  modulates data to be transmitted through the optical transmitter/receiver  134  to a UWB format, or demodulates the data received in the UWB format to the original data. A large-capacity subscriber service can be provided through a Fiber-To-The House (FTTH) connection, wherein gateway sub-module  130  serves to provide services such as multimedia, VOD (Video On Demand), EOD (Education On Demand), AOD (Audio On Demand), etc., to the respective AP (DAP)  120  or directly to terminal, e.g., mobile station  110 , without occurring a service collision. 
   Although not shown in  FIG. 1 , a UWB signal can be transferred to a plurality of APs  120  arranged at proper points of the LAN controlled by gateway sub-module  130  through the optical fiber. In this case, in order to transmit the UWB formatted signal through the optical fiber, the UWB formatted signal is directly modulated and transmitted, and this method is called the ‘UWB over fiber’. Using the ‘UWB over fiber’ technique, the limited service area can be expanded using the APs  120  arranged at proper points. 
   The UWB-based high-speed wireless LAN system as described above can perform a high-speed data transmission of 100 Mbps or more by using the UWB formatted signal instead of the RF signal. However, since the UWB formatted signal can easily pass through obstacles, according to the property of the medium, it is potentially in danger of being intercepted and subject to access by unauthorized persons. Hence the security of such UWB systems is considered weak. In order to improve the protection and security characteristic of the UWB system diverse encryption techniques and authentication methods such as WEP (Wired Equivalent Privacy), AES (Advanced Encryption Standard), and WPA (WI-FI Protected Access) are applied to the UWB-based high-speed wireless LAN system. However, such an application of encryption techniques and the authentication methods increases the cost of the UWB system and occupies valuable bandwidth. 
   Systems using an optical signal, e.g., IR (Infra-Red), have been shown to have a superior security characteristic as the optical or IR signal cannot pass through an obstacle, and thus it is more difficult to intercept. Hence the security of such a system is significantly increased.  FIG. 2  represents a block diagram illustrating an example of the main parts of an optical or IR-based wireless LAN system that exhibits a superior security characteristic. The IR wireless LAN system includes a gateway sub-module  230 , a plurality of access points (APs)  220 , and a plurality of mobile stations  210 . Again, as with regard to  FIG. 1 , only one element of each type is shown for purposes of explanation. 
   As shown, mobile station  210  is provided with an IR module  226  for transmitting/receiving an IR signal, and AP  220  is provided with an IR optical transmitter/receiver for transmitting/receiving an IR signal to/from the mobile station  210 . AP  220  further transmits/receives the IR signal to/from the gateway sub-module  230  through optical fibers  240 ,  250 , respectively. The gateway sub-module  230  includes IR module  236  provided with an IR optical transmitter/receiver  234  for transmitting/receiving the IR signal to/from the AP  220  through the optical fibers  240 ,  250 . Although not shown, it would be recognized that gateway sub-module  230  and the mobile station  210  may directly communicate with each other without passing through the AP  220 . 
   The gateway sub-module  230  modulates a signal inputted from an external network (not shown) onto an IR carrier signal, and transmits the IR carrier signal to the AP  220  through IR optical transmitter/receiver  234 . AP  220  receives the IR signal transmitted from the gateway sub-module  230  through IR optical transmitter/receiver  224 , and retransmits the IR signal, wirelessly, through optical antenna  221 . The IR signal transmitted wirelessly is received in the IR module  216  of the mobile station  210 , and then restored to the original signal. 
   According to the above-described construction, if any one intercepts the IR signal while the IR communication between the AP  220  and the mobile station  210  is performed the IR signal is not received by the mobile station  210 , and, thus, by grasping this lack of communication, the user can confirm that interception has occurred. 
   However, the conventional optical or IR signal has an imposed output power limitation in accordance with an eye-safety regulation. For example, in the case of the IR signal having a wavelength of 650 nm, its output power is limited to less than 0.2 mW. The limit of the output power causes the transmission speed to be limited to less than several Mega bits/second (Mbps), and thus significant limitations in the use of high-speed wireless LAN system using optical or IR communications exist. 
   In spite of the good mobility and convenience of the wireless LAN system, security concerns limit the use of a UWB wireless LANs in most companies. Since a wireless LAN system, without guaranteed security, causes problems in a company&#39;s large-scale introduction of such a wireless LAN system, it is a priority to introduce a wireless LAN system with guaranteed security. 
   In order to guarantee the security of the wireless LAN system, optical or IR signals may be used instead of the RF signal. However, as described above, in the case of constructing a wireless LAN using the optical or IR signal, the transmission speed is limited to less than several Mbps due to the limit of the output power according to the eye-safety regulation. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a high-speed wireless LAN system which has superior security characteristics and a high transmission speed. 
   Another object of the present invention is to provide a high-speed wireless LAN system which has superior security characteristics at a low cost. 
   In order to accomplish these objects, there is provided a high-speed wireless LAN system characterized in that it encrypts the original data according to a predetermined encryption method through a UWB medium to transmit the encrypted data, and then it transmits the corresponding encryption key through an optical or IR medium that guarantees the security. Accordingly, while the encryption key is secured through the IR medium, a high-speed wireless data communication is performed through the UWB medium. The high-speed wireless LAN system according to the present invention can guarantee the security by transmitting the encryption key for security through the optical or IR signal having a superior security characteristic, and transmitting a high-speed data signal through the UWB connection. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a block diagram illustrating an example of the main parts of a UWB-based high-speed wireless LAN system; 
       FIG. 2  is a block diagram illustrating an example of the main parts of an optical or IR-based wireless LAN system; 
       FIG. 3  is block diagram illustrating an example of the main parts of a high-speed wireless LAN system according to a first embodiment of the present invention; 
       FIG. 4  is block diagram illustrating an example of the main parts of a high-speed wireless LAN system according to a second embodiment of the present invention; 
       FIG. 5  is block diagram illustrating an example of the main parts of a high-speed wireless LAN system according to a third embodiment of the present invention; and 
       FIG. 6  is block diagram illustrating a high-speed wireless LAN system according to a fourth embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, a high-speed wireless LAN system according to preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention unclear. 
     FIG. 3  is block diagram illustrating an example of the main parts of a high-speed wireless LAN system according to an embodiment of the present invention. 
   Referring to  FIG. 3 , the high-speed wireless LAN system according to an embodiment of the present invention is provided with a UWB/IR-combined gateway sub-module  330 , a UWB/IR-combined access point (AP)  320 , and a UWB/IR-combined mobile station  310 . The high-speed wireless LAN system is also provided with function blocks for transmitting/receiving encryption keys for security as optical or IR signals, i.e., optical or IR modules  316  and  336  and optical or IR optical transmitters/receivers  324   b  and  334   b , and UWB modules  312  and  332  and UWB transmitters/receivers  324   a  and  334   a  for transmitting a high-speed data signal of greater than 100 Mbps through a UWB connection. 
   In this embodiment, the UWB/IR-combined gateway sub-module  330  and the UWB/IR-combined AP  320  are connected together through optical fibers  340 ,  350 . The UWB/IR-combined gateway sub-module  330  and/or the UWB/IR-combined AP  320  modulates/demodulates a UWB signal to an signal suitable for transmission/reception through the UWB transmitter/receiver  324   a  or  324   b  using a ‘UWB over fiber’ method, and transmits the signal through the appropriate optical fiber  340 ,  350 . Between the UWB/IR-combined gateway sub-module  330  and the UWB/IR-combined AP  320 , the ‘UWB over fiber’ type signal used for a high-speed data transmission and the IR optical signal used as a security encryption key may be transmitted through different optical fibers (not shown) or through the same optical fiber,  340 , or  350  . In the exemplary embodiment shown in  FIG. 3 , optical fibers for transmission and for reception are separately provided between the UWB/IR-combined gateway sub-module  330  and the UWB/IR-combined AP  320 , and both the UWB signal and the IR signal are transmitted/received through the optical fibers for transmission and for reception, respectively. The UWB signal and the IR signal, which are transmitted to, or outputted from, the corresponding UWB optical transmitters/receivers  324   a  and  334   a  and IR optical transmitters/receivers  324   b  and  334   b  through the same optical fiber, are combined and divided by proper optical signal combiners/dividers  326   a  to  326   d . The construction and operation of the respective function blocks will now be explained in detail. 
   The UWB/IR-combined gateway sub-module  330  serves to provide an optical interface between an internal network and an external network, and is provided with UWB optical transmitter/receiver  334   a , UWM module  332 , IR optical transmitter/receiver  334   b , and IR module  336 . UWB optical transmitter/receiver  334   a  is an optical transmitter/receiver suitable to transmit/receive a high-speed data signal of more than 100 Mbps, which is transmitted from a physical (PHY) layer of the UWB module  332 , through the optical fiber  350 , and the optical or IR optical transmitter/receiver  334   b  is a transmitter/receiver for security that is required to transmit/receive the encryption key for security to/from the mobile station  310  through the UWB/IR-combined AP  320 . In this case, a MAC (Media Access Control) layer serves to interface the high-speed data signal and the security signal with an upper layer in a manner that it transmits/receives the high-speed data signal through the UWB PHY layer, and transmits/receives the encryption signal for security to/from the IR optical transmitter/receiver  334   b.    
   The UWB/IR-combined AP  320  is provided with the UWB optical transmitter/receiver  324   a  connected to UWB antenna  323 , and the IR optical transmitter/receiver  324   b  connected to optical or IR antenna  321 . In this case, the optical transmitter/receiver  324   a  and the UWB antenna  323  of the UWB/IR-combined AP  320  transmit, wirelessly, the high-speed data signal to the mobile station  310 , or transmits the UWB signal received from the mobile station  310  to the UWB/IR-combined gateway sub-module  330  through optical fiber  340 . Also, optical or IR transmitter/receiver  324   b  and optical antenna  321  of the UWB/IR-combined AP  320  transmit/receive the encryption key between the mobile station  310  and the UWB/IR-combined gateway sub-module  330 . In this case, optical antenna  321  is designed to have a sufficient acceptance angle to receive and send the optical or IR signal. The optical or IR signal is designed to have a sufficiently low power to satisfy the eye-safety regulation when the communication is performed. 
   The UWB/IR-combined mobile station  310  is provided with the UWB module  312  connected to UWB antenna  313  and the IR module  316  connected to optical, e.g., IR, antenna  311 . The UWB module  312  is used to transmit/receive the high-speed data signal between the UWB/IR-combined mobile station  310  and the UWB/IR-combined AP  320 . Similarly, the IR module  316  is used to transmit/receive the encryption key to/from the UWB/IR-combined mobile station  310  and the UWB/IR-combined AP  320 . The UWB PHY layer of the UWB module  312  serves to transfer the high-speed data signal to the UWB MAC layer. In this case, the encryption key, referred to as “Key ID” in the figure, which is transmitted/received through the IR optical antenna  311 , is also provided from the IR module  316  to the UWB MAC layer and vice versa. Also, the MAC layer of the UWB module  312  transmits/receives the high-speed data signal through the UWB PHY layer, transmits/receives the encryption signal from/to the IR module  316  and interfaces the high-speed data signal and the encryption signal with the upper layer by performing an encapsulation or de-capsulation of the encryption signal. 
     FIG. 4  is block diagram illustrating an example of the main parts of a high-speed wireless LAN system according a second embodiment of the present invention. In this illustrated embodiment, the high-speed wireless LAN system uses a single optical fiber  440  for communication between the UWB/IR-combined AP  420  and the UWB/IR-combined gateway sub-module  430 . In this embodiment, the UWB signal for transmitting the high-speed data signal and the optical or IR signal for transmitting the encryption key are CWDM (Coarse Wavelength Division Multiplexing)-multiplexed by modules  428  and  438  in AP  420  and gateway  430 , respectively and then transferred via optical fiber  440 . 
   In the same manner as the high-speed wireless LAN system described with regard to  FIG. 3 , the high-speed wireless LAN system of  FIG. 4  is provided with a UWB/IR-combined gateway sub-module  430 , a UWB/IR-combined access point (AP)  420 , and a UWB/IR-combined mobile station  310 . The high-speed wireless LAN system is provided with function blocks for transmitting/receiving encryption keys as IR signals, i.e., IR modules  316  and  436  and optical or IR optical transmitters/receivers  424   b  and  434   b , and UWB modules  312  and  432  and UWB optical transmitters/receivers  424   a  and  434   a  for transmitting/receiving a high-speed data signal through a UWB connection. 
   In this case, the construction and operation of the UWB/IR-combined mobile station  310  are the same as that of the system of  FIG. 3 , except that CWDMs (Coarse Wavelength Division Multiplexers)  428  and  438  are provided in the UWB/IR-combined gateway sub-module  430  and the UWB/IR-combined AP  420 , respectively, for multiplexing and transmitting/receiving the UWB signal and the IR signal through optical fiber  440 . CWDM  438  included in the UWB/IR-combined gateway sub-module  430 . multiplexes a signal transmitted from the UWB optical transmitter/receiver  434   a  and a signal transmitted from the IR optical transmitter/receiver  434   b , and transmits the multiplexed signal to the CWDM  428  of the UWB/IR-combined AP  420  through optical fiber  440 . CWDM  438  of the UWB/IR-combined gateway sub-module  430  also de-multiplexes the multiplexed optical signal transmitted from the CWDM  428  of the UWB/IR-combined AP  420 , and transmits the de-multiplexed optical signals to the corresponding UWB optical transmitter/receiver  434   a  and IR optical transmitter/receiver  434   b . In the same manner, CWDM  428  of the UWB/IR-combined AP  420  multiplexes/de-multiplexes the transmitted/received signals received from or destined to the UWB optical transmitter/receiver  424   a  and the IR optical transmitter/receiver  424   b.    
   In the high-speed wireless LAN systems as shown in  FIGS. 3 and 4 , the IR optical transmitters/receivers and the UWB optical transmitters/receivers are provided in the UWB/IR-combined gateway sub-modules  330  and  430  and the UWB/IR-combined APs  320  and  420 , respectively, in order to transmit the encryption keys using the optical or IR method and the high-speed data UWB signals using the ‘UWB over fiber’ method. 
     FIG. 5  is block diagram illustrating an example of main parts of a high-speed wireless LAN system according to still another embodiment of the present invention. 
   In this illustrated embodiment the high-speed wireless LAN system is provided with a UWB/IR-combined gateway sub-module  530 , a UWB/IR-combined access point (AP)  520 , and a UWB/IR-combined mobile station  310 . In order to transmit/receive the encryption key for security through the optical or IR port and to transmit/receive the high-speed data through the UWB, the UWB/IR-combined gateway sub-module  530  uses a 2-channel array optical transmitter/receiver module  535  employing center wavelengths as data carriers. In one aspect, a BI-DI (bi-directional) module may be used as such a 2-channel array optical transmitter/receiver module  535 . CWDM  538  of the UWB/IR-combined gateway sub-module  535  is operable to multiplex the UWB signal and the IR signal outputted from the 2-channel array optical transmitter/receiver module  535 , and transmit the multiplexed signal to a corresponding CWDM  528  within the UWB/IR-combined AP  520  through optical fiber  540 . CWDM  538  is also operable to de-multiplex the multiplexed optical signal transmitted from CWDM  528 , and provide the de-multiplexed signals to the 2-channel array optical transmitter/receiver module  535 . 
   In this embodiment, the UWB/IR-combined AP  520  uses an SOA (semiconductor optical amplifier)  525  rather than the UWB and IR optical transmitters/receivers as illustrated in  FIGS. 3 and 4 . The SOA  525 , which is imposed between the CWDM  528  and the UWB antenna  523 , converts an optical signal corresponding to the UWB signal received from the UWB/IR-combined gateway sub-module  530  through the CWDM  528  into a wireless signal to be transmitted through the UWB antenna  523 . The optical or IR signal, on the other hand, is transferred directly to optical or IR antenna  521 . Similarly, SOA  525  is operable to output an optical signal, with its gain amplified according to the UWB signal received through the UWB antenna  523 , to provide an optical signal to the CWDM  528  and the IR signal, inputted through the IR optical antenna  521 , is provided to the CWDM  528 . CWDM  528  then multiplexes the provided UWB signal and optical or IR signals and transmits the multiplexed signal to the CWDM  538  of the UWB/IR-combined gateway sub-module  530  through optical fiber  540 . In a similar manner, CWDM  528  is operable to de-multiplex the multiplexed optical signal transmitted from the CWDM  538  of the UWB/IR-combined gateway sub-module  530 , and provide the de-multiplexed signals to the SOA  525  and the IR antenna  521 , appropriately. 
   The operation of the SOA  525  is determined by a current controller  526  for controlling an injection current of the SOA  525 . Specifically, in the case of a downward communication for transmitting data from the UWB/IR-combined gateway sub-module  530  to the UWB/IR-combined mobile station  310 , the current controller  526  causes SOA  525  to operate as an optical detector by applying current to the SOA  525  less than SOA  525  threshold current. In the case of an upward communication for transmitting data from the UWB/IR-combined mobile station  310  to the UWB/IR-combined gateway sub-module  530 , current controller  526  causes SOA  525  to apply a gain factor by applying a current to the SOA  525  greater than SOA  525  threshold current. 
   In the system illustrated in  FIG. 5 , the UWB/IR-combined AP  520  is constructed so that it serves only to transfer the signal between the UWB/IR-combined gateway sub-module  530  and the UWB/IR-combined mobile station  310 . In the illustrated embodiment, the UWB/IR-combined AP  520  uses a light source in the band of 1300 nm or 1500 nm. Transmission in this range can be used to supplement a signal loss that may occur as compared to the UWB/IR-combined AP provided with the IR optical transmitters/receivers. 
     FIG. 6  is block diagram illustrating the construction of a high-speed wireless LAN system according to an embodiment of the present invention. 
   The high-speed wireless LAN system of  FIG. 6  may be installed in the home, company, building, or a plurality of adjacent buildings, and is includes a gateway, a plurality of associated UWB/IR-combined gateway sub-modules  330 - 1  to  330 -n, and UWB/IR-combined APs  320 - 1  to  320 -n connected to the UWB/IR-combined gateway sub-modules  330 - 1  to  330 -n of the gateway  620 , respectively. The UWB/IR-combined APs  320 - 1  to  320 -n form sub-networks  610 - 1  to  610 -n with respect to their serviceable areas. The respective sub-network includes a plurality of UWB/IR-combined mobile terminals  310 - 1  to  310 -n that communicate with the corresponding UWB/IR-combined APs, respectively. 
   The respective UWB/IR-combined mobile stations  310 - 1  to  310 -n transmit/receive the encryption key to/from the corresponding UWB/IR-combined APs using the IR signal and transmit the high-speed data signal using the UWB connection. The UWB/IR-combined APs  320 - 1  to  320 -n transmit/receive the IR signal to/from the corresponding UWB/IR-combined gateway sub-modules through the optical fibers. The gateway  620  divides services, such as multimedia, VOD, EOD, AOD, etc., provided through the FTTH, among the corresponding UWB/IR-combined gateway sub-modules using an NI (Network Interface) module  340 , and provides the services to the respective UWB/IR-combined APs or the mobile stations without occurring a service collision. 
   As described above, the high-speed wireless LAN system according to the present invention has a superior security characteristic and a high transmission speed of more than 100 Mbps at a low cost. Accordingly, using the high-speed wireless LAN system according to the present invention, it is expected that the installation of an ultrahigh-speed wireless LAN system in national organizations, company research institutes, financial institutions, etc., can be expedited, and the optical system can even be introduced into general homes. 
   While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. For example, while the optical system has been referred to herein as an infra-red (IR) system, one skilled in the art would recognized at the optical system may also include frequencies in the visible or ultra-violet or higher ranges with suitable alterations in the components selected. Additionally, while the transmitter and receiver functions have been referred to separately, one skilled in the art would recognize that these functions may be performed by individual units or combined in a single unit. Hence, the commonly referred to term “transceiver” shall be used to define both configurations.