Patent Publication Number: US-2003227912-A1

Title: Voice packet preferential control equipment and control method thereof

Description:
CROSS REFERENCE TO THE RELATED APPLICATION  
       [0001] The present application has been filed with claiming priority based on Japanese Patent Application No. 2002-164113, filed on Jun. 5, 2002. Disclosure of the above-identified Japanese Patent Application is herein incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] The present invention relates generally to a preference control in a voice packet control. More particularly, the invention relates to a voice packet preference control equipment and control method thereof to be added in the conventional transmission path, such as wireless LAN and so forth.  
       [0004] 2. Description of the Related Art  
       [0005] In the recent years, it has been developed VoIP (Voice over IP) technology using IP (Internet Protocol) which is originally a standard protocol of data communication, and transmits voice by IP packet, and has been put into practice.  
       [0006] An application enabling telephone call from a personal computer, a telephone machine or so forth via Internet or LAN (Local Area Network), is an IP telephone. Such IP telephone is attracting attention as a method for establishing a telephone network at low cost.  
       [0007] However, since LAN has been grown for data communication by computers in history, it employs a simple control equipment as “data arriving earlier is processed earlier”. Therefore, upon transmitting voice packet on LAN, it becomes necessary to preferentially process voice packet relative to data packet so as not to cause delay in transmission of voice packet.  
       [0008] On the other hand, hot spot service using wireless LAN has been provided. In such service, in addition to demand for data communication, there is not small demand for voice communication using the foregoing VoIP technology. A problem arisen at this time is how to realize QoS (Quality of Service), such as preferential control or band control.  
       [0009] Namely, in the voice packet communication employing the wireless LAN, since transmission speed of a wired LAN is 100 Mbps to 1 Gbps whereas transmission speed of the wireless LAN is about 10 Mbps, retention of packet in a conversion device (access point of wireless LAN) for conversion from the wired LAN to the wireless LAN is inherently caused. For this reason, it becomes necessary to provide a buffer for voice packet and a buffer for data packet separately in the wireless LAN access point and to ensure real-time transmission ability of voice packet by processing voice packet preferentially.  
       [0010] As set forth above, in the voice packet communication using the wireless LAN, inexpensive LAN devices currently marketed do not support QoS, such as preferential control, band control and so forth.  
       SUMMARY OF THE INVENTION  
       [0011] The present invention has been worked out in view of the drawback in the conventional wireless LAN devices. It is therefore an object of the present invention to provide a wireless LAN system which enables voice packet communication in a wireless LAN utilizing inexpensive LAN equipment not supporting QoS, such as preferential control, band control and so forth, and can realize preferential control of voice packet without modifying an existing wireless LAN access point not supporting QoS.  
       [0012] In order to accomplish the above-mentioned object, according to the first aspect of the present invention, a voice packet preferential control equipment added a media conversion equipment connecting a high speed communication circuit and a low speed communication circuit,  
       [0013] when a voice packet is detected from packet information on a communication circuit, the control equipment preferentially transmits a voice packet and interrupting transmission of data packet from the high speed circuit and buffering data packet,  
       [0014] subsequently, the control equipment. checks traffic of the low speed circuit, continues the buffering when the traffic is in congestion state and terminates buffering to resume data packet transmission when the traffic is in non-congestion state.  
       [0015] In the preferred construction of the voice packet preferential control equipment, a wireless LAN access point as the media conversion equipment, connects a high speed wired LAN circuit as high speed communication circuit and a low speed wireless LAN circuit as low speed communication circuit. In practical operation, when a voice packet is detected from packet information on a communication circuit, the control equipment preferentially transmits a voice packet and interrupts transmission of data packet from the high speed wired LAN circuit and buffering data packet, and subsequently, the control equipment checks traffic of the low speed wireless LAN circuit, continues the buffering when the traffic is in congestion state and terminates buffering to resume data packet transmission when the traffic becomes non-congestion state.  
       [0016] The control equipment may include means for checking traffic in the low speed circuit, the means feeding a ping packet to a voice packet terminal of the low speed circuit, receiving a ping response from the voice packet terminal, and making judgment of traffic condition by measuring a round trip period between feeding of the ping packet and reception of the ping response.  
       [0017] The means for checking traffic may make judgment that traffic is in congestion state when the round trip period is larger than or equal to a preset value and that traffic is not in congestion state when the round trip period is smaller than the preset value.  
       [0018] According to the second aspect of the present invention, a voice packet preferential control method added medium conversion equipment connecting a high speed communication circuit and a low speed communication circuit,  
       [0019] when a voice packet is detected from packet information on a communication circuit, a voice packet is preferentially transmitted and transmission data packet from the high speed circuit being interrupted and data packet is buffered,  
       [0020] subsequently, traffic of the low speed circuit is checked, buffering is continued when the traffic is in congestion state and buffering is terminated to resume data packet transmission when the traffic becomes non-congestion state.  
       [0021] According to the third aspect of the present invention, a voice packet preferential control equipment adding a wireless LAN access point connecting a high speed wired LAN circuit and a low speed wireless LAN circuit, comprises:  
       [0022] voice packet detecting and separating block separating packets received from a VoIP terminal on a wired LAN side into voice packets and data packets;  
       [0023] data packet buffer buffering data packet separated by the voice packet detecting and separating block;  
       [0024] ping generating block generating a ping packet for measuring traffic condition of the wireless LAN;  
       [0025] ping measuring block measuring a period from transmission of the ping packet from the ping generating block to reception of a response to the ping packet;  
       [0026] a valve determining whether data in data buffer is to be transmitted to the wireless LAN side; and  
       [0027] voice packet detection block detecting the voice packets from packets received from the wireless LAN access point.  
       [0028] The voice packet detecting and separating block may transmit the separated voice packet to the wireless LAN access point.  
       [0029] The valve may interrupt transmission of data packet to the wireless LAN side when the period from transmission of the ping packet from the ping generating block to reception of a response to the ping packet is longer in comparison with a period in good condition of the circuit.  
       [0030] The voice packet preferential control equipment may further comprise an ftp terminal transmitting and receiving data packet on the wired LAN side and the wireless LAN side, and similar process as that for data packet transmitted from VoIP terminal, is performed for data packet transmitted from the ftp terminal. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0031] The present invention will be understood more fully from the detailed description given hereinafter and from the accompanying drawings of the preferred embodiment of the present invention, which, however, should not be taken to be limitative to the invention, but are for explanation and understanding only.  
     [0032] In the drawings:  
     [0033]FIG. 1 is a block diagram showing overall construction of a voice packet communication system according to the present invention;  
     [0034]FIG. 2 is a basic sequence chart showing a relationship of voice packet transmission and reception and ping packet transmission and reception for measuring circuit congestion condition on a wireless LAN;  
     [0035]FIG. 3 is a sequence chart in the case where communication between ftp terminals transmitting and receiving data packet and communication between VoIP terminal transmitting and receiving voice packet are performed simultaneously; and  
     [0036]FIG. 4 is a process flowchart relating to buffering start (data packet transmission interruption) in voice packet preferential control equipment  104  and buffering termination (data packet transmission resumption). 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0037] The present invention will be discussed hereinafter in detail in terms of the preferred embodiment of a wireless LAN system according to the present invention with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be obvious, however, to those skilled in the art that the present invention may be practiced without these specific details. In other instance, well-known structures are not shown in detail in order to avoid unnecessary obscurity of the present invention.  
     [0038]FIG. 1 is a block diagram showing an overall construction of a wireless LAN system with a voice packet preferential control equipment in accordance with the present invention. As shown in FIG. 1, VoIP (Voice over IP) terminal  101  is connected to a wired LAN side interface of a voice packet preferential control equipment  104  via a wired LAN. A wireless LAN side interface of the voice packet preferential control equipment  104  is connected to a wireless LAN access point  103 . A VoIP terminal  102  is connected to the wireless LAN access point  103  via a wireless medium in communicatable condition. The voice packet preferential control equipment  104  is inserted between the wired LAN side VoIP terminal  101  and the wireless LAN access point  103 .  
     [0039] The voice packet preferential control equipment  104  is constructed with a voice packet detection and separation block  111  separating packets received from the VoIP terminal on the wired LAN side into voice packets and data packets, a data packet buffer  112  buffering data packet separated by the voice packet detection block  111 , a ping generation block  113  generating aping packet for measurement for measuring traffic of the circuit on the wireless LAN, a ping measurement block  114  for measuring a period up to reception of a response to a ping packet transmitted by the pin generation block  113 , a valve  115  determining whether data of the data packet buffer  112  is to be transmitted to the wireless LAN side, and a voice packet detection block  116  detecting a voice packet from the packet received from the wireless LAN access point  103 .  
     [0040] It should be noted that the foregoing ping packet is a command to be used for verifying connection ability between terminals on an IP network including the wired LAN or the wireless LAN and checks how crowed of traffic in a route to a counterpart by measuring the period up to reception of the response.  
     [0041]FIG. 2 is a basic sequence chart showing a relationship of voice packet transmission and reception and ping packet transmission and reception for measuring circuit congestion condition on a wireless LAN. As shown in FIGS. 1 and 2, when the voice packet preferential control equipment  104  receives a voice packet  201  from the VoIP terminal lol on wired LAN side, a voice packet  202  is separated by the voice packet detection and separation block  111  and transmitted to the wireless LAN access point  103 . In conjunction therewith, in the ping generation block  113 , ping packet  204  is generated and transmitted to the wireless LAN access point  103 .  
     [0042] The wireless LAN access point  103  delivers a voice packet  203  to the VoIP terminal  102 . In conjunction therewith, the ping packet  205  is also transmitted. Upon reception of the ping packet  205 , the VoIP terminal  102  generates a ping response  206  as response packet and feeds the same to the wireless LAN access point  103 . The wireless LAN access point  103  feeds a ping response  207  to the voice packet preferential control equipment  104 .  
     [0043] As a result, the voice packet preferential control equipment  104  measures the period up to reception of the ping response  207  from transmission of the ping packet  204  by the ping measurement block  114  to know a round trip period between the voice packet preferential control equipment  104  and the VoIP terminal  102 . This round trip period is a transmission period transmitted and returned through a high speed wired circuit between the voice packet preferential control equipment  104  and the wireless LAN access point  103  and a low speed wireless circuit between the wireless LAN access point  103  and the VoIP terminal  102 . Most of the round trip period is occupied by the transmission period in the low speed wireless LAN zone.  
     [0044] On the other hand, since the wireless LAN access point  103  performs conversion between the high speed wired LAN and the low speed wireless LAN, delay according to increase of the packet received from the wired LAN becomes greater. When traffic in the circuit of the wireless LAN increases (congestion condition), round trip period between the voice packet preferential control equipment  104  and the VoIP terminal  102  prolongs.  
     [0045] Accordingly, in the case where the voice packet is mixed in packet communication via the wireless LAN, when round trip period becomes large, the voice packet preferential control equipment  104  performs preferential control in which transmission of data packet to the wireless LAN access point  103  is interrupted at the valve  115  and the voice packet is preferentially transmitted in order to prevent deterioration of communication quality of the voice packet. While transmission of data packet is interrupted, data packet is buffered by the data packet buffer  112 .  
     [0046]FIG. 3 is a sequence chart in the case where communication between ftp terminals transmitting and receiving data packet and communication between VoIP terminal transmitting and receiving voice packet are performed simultaneously. Here, the ftp terminal is a terminal implementing FTP (File Transfer Protocol) as standard protocol for file transfer on Internet. The ftp terminal is normal data terminal, such as personal computer or the like, and can perform data transfer by executing an FTP application. It should be noted that detail of FTP is defined by RFC (Request For Comment)  959 .  
     [0047] As shown in FIG. 3, the ftp terminal  121  and the VoIP terminal  101  are connected to the voice packet preferential control equipment  103  via the wired circuit in communicatable condition. The ftp terminal  122  and the VoIP terminal  102  are connected to the wireless LAN access point  103  via the wireless circuit in communicatable condition. On the other hand, the voice packet preferential control equipment  104  performs detection and preferential control of data packet and voice packet. The wireless LAN access point  103  transmits the packet received from the wired LAN side to the wireless LAN side, and transmits the packet received from the wireless LAN side to the wired LAN side, in sequential order.  
     [0048] At first, when 100 Kbytes data is transmitted from the ftp terminal  121  on the wired LAN side to the ftp terminal  122  on the wireless LAN side, the ftp terminal  121  transmits sixty-seven ftp packets  301  (ftp packet group  1 ) to the voice packet preferential control equipment  104 , since 100 Kbytes data are transmitted per about 1500 bytes in IP communication. In the voice packet preferential control equipment  104 , since the voice packet is not transmitted and received at this time, the ftp packet  301  is transmitted to the wireless LAN access point  103  as is. Since the wireless zone is lower speed than the wired zone, the wireless LAN access point  103  transmits a ftp packet  305  to the ftp terminal  122  with longer period.  
     [0049] Next, it is assumed that while the wireless LAN access point  103  transmits the ftp packet  305 , the VoIP terminal  101  transmits the voice packet  1  ( 302 ). Then, the voice packet preferential control equipment  104  feeds the voice packet to the wireless LAN access point  103  and in conjunction therewith transmits the ping packet  303  to the VoIP terminal  102 . On the other hand, the voice packet preferential control equipment  104  interrupts transmission of data packet until congestion condition of the wireless circuit is known by the ping response and buffers data packet (step  304 ).  
     [0050] In the wireless LAN access point  103 , the voice packet  1  ( 302 ) and the ping packet  303  are received. However, since transmission of ftp packet  305  is not yet completed, the received voice packet and the pin packet are placed in waiting state until wireless circuit becomes vacant. After completion of transmission of the ftp packet  305 , the wireless LAN access point  103  transmits the voice packet ( 308 ) and the ping packet  309  to the VoIP terminal  102 .  
     [0051] Next, the voice packet preferential control equipment  104  receives new ftp packet  306  (ftp packet group  2 ) from the ftp terminal  121  and new voice packet  2  ( 307 ) from the VoIP terminal  101 . However, since transmission of data packet is already interrupted, the ftp packet  306  is buffered in the data packet buffer  112  of the voice packet preferential control equipment  104  and the voice packet preferential control equipment  104  feeds only voice packet  2  ( 307 ) to the wireless LAN access point  103 .  
     [0052] Subsequently, the voice packet preferential control equipment  104  receives the ping response  311  to the first ping packet and measures a period. However, since the ping packet  305  is transmitted by the wireless LAN access point  103 , the round trip period becomes larger in comparison with the condition where the circuit condition is good. Therefore, at this timing, interruption of transmission of data packet is not terminated, and the ping packet  313  is transmitted again to perform period measurement  2 .  
     [0053] At the timing where the ping packet  313  is transmitted, condition of the wireless circuit is resumed from congestion condition. Therefore, the wireless LAN access point  103  immediately feeds the ping packet  314  to the VoIP terminal  102 . Also, the VoIP terminal  102  immediately responds to the ping packet  314  to feed the ping response  315 . The ping response  316  reaches the voice packet preferential control equipment  104  via the wireless LAN access point  103 .  
     [0054] As a result, the round trip period in time measurement  2  becomes small to permit recognition that the congestion condition in the wireless circuit is resolved, in the voice packet preferential control equipment  104 . The voice packet preferential control equipment  104  recognizing that the congestion condition is resolved, resumes transmission of the ftp packet  306  (ftp packet group  2 ) as buffered (step  317 ).  
     [0055] As set forth above, the voice packet preferential control equipment  104  realizes preferential control of the voice packet in order to prevent deterioration of communication quality of the voice packet in the case where the voice packet is mixed in packet communication via the wireless LAN.  
     [0056]FIG. 4 is a process flowchart relating to buffering start (data packet transmission interruption) in voice packet preferential control equipment  104  and buffering termination (data packet transmission resumption). In the voice packet preferential control equipment  104 , packet information containing data packet and voice packet in admixing manner is received from the wired LAN side (step  401 ). Then, judgment is made whether the received packet is voice packet or not (step  402 ). When the received packet is the voice packet, the voice packet is preferentially fed to the wireless LAN side, and buffering of the subsequently transmitted data packet is started (step  403 ). Thereafter, the pin packet is generated and fed to the counterpart VoIP terminal, and then the ping response is received for ping measurement in order to measure the round trip period (step  404 ). As a result of measurement, when the round period is large and congestion is judged, the ping measurement is performed again. On the other hand, when judgment is made that the traffic is not in congestion, buffering is terminated (step  406 ).  
     [0057] It should be appreciated that while the particular numerical relationship between actual period up to reception of the ping response and data packet transmission interruption/resumption judgment is not recited in the shown embodiment, in consideration that the typical allowable delay period is about 200 ms (voice delay upon use of satellite circuit), interruption/resumption of buffering of data packet may be performed with taking 200 ms as criterion. However, the particular value, i.e. 200 ms should not be taken as limitative to the present invention. In practice, the practical criterion may be determined utilizing actually measured data as being influenced by buffer capacity of the wireless LAN access point, speed difference between the wireless circuit and the wired circuit.  
     [0058] On the other hand, while the shown embodiment has been discussed in terms of the network system employing the wireless LAN, the voice packet preferential control equipment utilizing the VoIP technology is applicable not only for wireless LAN but also for media converting equipment (e.g. ADSL modem) having communication speed difference. The present invention is further applicable in general for speed conversion equipment connecting the high speed circuit and the low speed circuit.  
     [0059] Namely, in place of the wireless LAN access point in FIG. 1, an ADSL modem is arranged. The VoIP terminal  101 , the voice packet preferential control equipment  104  and the ADSL modem are connected. The ADSL modem is connected to the VoIP terminal  102  via a metallic circuit provided transmission speed limit. Thus, the voice packet preferential transmission control in packet communication where voice packet is mixed, can be realized between the VoIP terminal  101  and the VoIP terminal  102 .  
     [0060] As set forth above, the present invention is effective in providing voice packet communication in the wireless LAN utilizing inexpensive LAN equipment not supporting QoS, such as preferential control, band control or so forth.  
     [0061] Also, since the voice packet preferential control is realized utilizing pin packet as general purpose command, the present invention is advantageous in that the voice packet preferential control will not be influenced by variation of system of wireless LAN in the future.  
     [0062] Furthermore, the present invention is advantageously applicable not only for the wireless LAN but also for media converting equipments (for example, ADSL modem having speed difference).  
     [0063] Although the present invention has been illustrated and described with respect to exemplary embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omission and additions may be made therein and thereto, without departing from the spirit and scope of the present invention. Therefore, the present invention should not be understood as limited to the specific embodiment set out above but to include all possible embodiments which can be embodied within a scope encompassed and equivalent thereof with respect to the feature set out in the appended claims.