JP4029670B2 - Congestion control method and system for wireless access - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a congestion control method for wireless access. In particular, the present invention relates to a congestion control method and a congestion control system for radio access that can control a transmission data rate from a radio base station to a terminal during congestion to avoid missing real-time signal packets during congestion.
[0002]
[Prior art]
FIG. 13 shows a conventional content distribution configuration via the Internet and wireless access. The terminal 11 accesses the Web via the wireless LAN access point AP12 and selects desired streaming content from the Web. Streaming content is distributed from the content server 13 storing the selected content via the wireless LAN.
[0003]
Currently, in IEEE 802.11b, which is the mainstream standard for wireless LAN, the maximum downlink transfer rate is 11 Mbps, so the number of terminals accessing a certain AP increases, and from that AP to each terminal. If the total downlink transfer rate exceeds 11 Mbps, the transmission rate is lowered. The effect of this decrease in transmission rate is that if the delivery information to the terminal is a mail or web browsing or storage type image, there will be problems such as a long transfer time or a long screen display on the web. become.
On the other hand, if the distribution information to the terminal is data that requires real-time performance, such as streaming live video, the image data must be played back at regular intervals. Packet loss occurs and the image deteriorates. Therefore, for delivery information that requires real-time performance such as live video delivery, a means for compensating for the delay when the AP being accessed is congested is required.
In addition, in the case of VoIP and TVoIP (two-way communication between voice and image over IP is referred to as TVoIP in this specification), the allowable delay on one side of voice is said to be approximately 200 msec, and a delay beyond that is If it happens, it will cause trouble in the conversation. Furthermore, when receiving a real-time signal and a non-real-time signal at the same time, for example, when browsing the Web in the middle of a VoIP conversation, the bandwidth is used to reduce the delay of the real-time signal even when the wireless LAN is congested. It is necessary to secure non-real time signal bandwidth.
[0004]
[Problems to be solved by the invention]
However, IEEE 802.11b or 802.11a, which is currently mainstream, does not have the functions of congestion control and QoS control as described above. The present invention has been made in view of such a conventional problem. The object of the present invention is to control the amount of flow into a radio base station, to detect congestion in a radio section, to control congestion and to transcoder (function). It is an object of the present invention to provide a wireless access congestion control method and system capable of suppressing a delay of a real-time signal even when wireless LAN is congested.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the congestion control method in wireless access of the present invention is a data signal that requires real-time property and a data signal that does not require real-time property through wireless access from a wireless base station to a wireless terminal. In the congestion control method in the information distribution system for simultaneously transferring both of the first and the second , the radio base station detects the first congestion, and the radio base station limits the transfer of the data signal that does not require the real-time property. After performing the first congestion control, the wireless terminal detects the second congestion and transmits the second congestion to the wireless base station, and the wireless base station performs the first congestion control. When the second congestion notification is received, the wireless base station executes second congestion control that restricts transfer of the data signal that requires the real-time property. The
The first congestion control is flow control for limiting the amount of data flowing into the radio base station, and the second congestion control is control for converting a bit rate transferred to the radio terminal.
[0006]
The congestion control system for wireless access according to the present invention simultaneously transfers both a data signal that requires real-time property and a data signal that does not require real-time property from the wireless base station to the wireless terminal via wireless access. In the information distribution system , the wireless base station includes a first congestion detection unit that detects first congestion, and when the wireless terminal detects the second congestion, the second congestion detection notification is sent to the wireless base station. A first congestion control unit configured to perform a first congestion control that restricts transfer of a data signal that does not require real-time performance when the first congestion is detected; And when the second congestion detection notification is received from the radio base station after the execution of the first congestion control, the data signal for which the real-time property is required is transferred. Performing a second congestion control for limiting those having a second congestion control unit.
The first congestion control is flow control for limiting the amount of data flowing into the radio base station, and the second congestion control is control for converting a bit rate transferred to the radio terminal.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
In this embodiment, considering the case of a wireless LAN which is one of wireless access, (1) a streaming distribution service using a wireless LAN and (2) a wireless LAN as an information distribution service for real-time signals via the wireless LAN. A case of using a VoIP service and (3) a TVVoIP service using a wireless LAN will be described. Further, as a service for simultaneous delivery of real-time signals and non-real-time signals, (4) a case of a simultaneous delivery service for VoIP and Web browsing using a wireless LAN will be given.
A basic configuration of the present invention is shown in FIG. The present invention is shown in FIG. 1 as congestion monitoring means in the wireless section between the wireless base station a and the terminal c in the content distribution from the content server h via the wireless section of the Internet g, the wireless base station a, and the terminal c. It has a congestion detection unit d. A flow control unit f is provided as means for controlling the amount of data flowing into the radio base station when congestion is detected. Also, a transcoder e is provided as means for changing the data flow band between the radio base station and the terminal.
[0008]
The configuration of the embodiment will be described.
(1) In the case of streaming distribution FIG. 2 shows a configuration in the case of streaming distribution according to the present invention. In the present invention, compared to the conventional configuration of FIG. 13, the AP 1 has a congestion control unit 2, the terminal 4 has a congestion detection unit 5, and a transcoder 3 is connected to the AP 1. . The congestion control unit 2 and the congestion detection unit 5 may be added with functions by adding hardware inside the AP and inside the terminal, and may be added by software. The flow control unit 6 controls the congestion at the AP by changing the bandwidth of the signal flowing from the Internet network to the AP 1.
(2) In the case of VoIP FIG. 3 shows a configuration when a VoIP terminal is used via an AP. The call partner of the VoIP terminal may be a fixed telephone or a portable terminal. A transcoder 23 is arranged next to the AP 21. The terminal 24 has a congestion detection unit 25. The congestion control unit 22 included in the AP 21 receives a notification from the congestion detection unit 25 included in the terminal 24 and instructs the transcoder 23 to convert the bit rate. In response to an instruction from the AP, the transcoder 23 converts a bit rate of a voice codec (for example, AMR: Adaptive Multi Rate), and adjusts a bit rate of a voice call use band according to a traffic state in a wireless section. In the case of AMR, the bit rate can be varied in 8 steps between 12.2 kbps and 4.75 kbps. The flow control unit 26 controls the congestion at the AP by changing the band of the signal flowing into the AP 21.
(3) In the case of TVoIP The configuration when a TVoIP terminal is used via an AP is the same as that in FIG. The call partner of the TVoIP terminal may be a fixed telephone or a mobile terminal. A transcoder 23 is arranged next to the AP 21. The difference from the case of VoIP is the function of the transcoder 23. The transcoder 23, in addition to the function of converting the bit rate [bps] of the voice codec (for example, AMR) in accordance with an instruction from the AP 21, is the same as VoIP. The image bit rate and the image frame rate [fps] are converted or the screen size is changed, and the band used for the TV phone is adjusted according to the traffic state of the wireless section.
(4) When Real-Time Signal and Non-Real-Time Signal are Transferred Simultaneously FIG. 4 shows a configuration when a real-time signal and a non-real-time signal are used via an AP. In FIG. 4, the flow control unit 76 performs speed control of the non-real time signal flowing into the AP. The transcoder 73 converts the bit rate [bps] of an audio codec (for example, AMR) in accordance with an instruction from the AP (in addition to conversion of the bit rate of the image and the frame rate [fps] of the image), Or change the screen size.
[0009]
Next, the operation of the embodiment will be described.
(1) In the case of streaming distribution The operation in the case of streaming distribution will be described with reference to the congestion control flow of FIG.
In the streaming distribution service, image data must be reproduced at regular intervals so that streaming can be normally reproduced at the receiving terminal. When the next data to be reproduced does not arrive due to delay due to congestion in the wireless section, the distribution video is disturbed.
The congestion detection unit 5 of the terminal 4 checks the sequence number of the header of the RTP packet based on the protocol (RTP: Real-time Transport Protocol) for transmitting and receiving voice and video in real time, and the sequence number n and the sequence number When the interval of n + 1 RTP packets is delayed from a certain interval, it is determined that congestion has occurred (S1). When receiving the congestion notification (S2), the AP congestion control unit instructs the transcoder 3 to convert the bit rate (S3), and keeps the rate low.
When the bandwidth used by the congested AP decreases and the congestion state is resolved, the AP transmission rate detection unit detects the resolution of the congestion (S4), and returns the bit rate to the transcoder. (S5).
(2) In the case of VoIP The operation in the case of VoIP will be described with reference to the congestion control flow of FIG.
In the case of VoIP, a voice delay of up to 200 msec on one side is allowed, but if a delay of more than that occurs, the conversation is troubled. When voice is transferred on an RTP packet, the congestion detection unit of the terminal checks the sequence number of the RTP packet header, and the interval between the sequence numbers n and n + 1 (n is an arbitrary integer) has a constant threshold. If the value is, for example, the frame length of the voice codec × N (N is an arbitrary integer) msec or more, it is determined that congestion has occurred (S11). Alternatively, when the packet loss rate exceeds a certain threshold, it is determined that congestion has occurred. When congestion is detected at the terminal, the AP, when notified of congestion (S12), instructs the transcoder to suppress the bit rate of the voice codec (for example, AMR) (S13).
[0010]
If the AP detects congestion elimination (S14), it instructs the transcoder to restore the voice codec bit rate (S15).
(3) In the case of TVoIP The operation in the case of TVoIP will be described with reference to the congestion control flow of FIG. In the case of TVoIP, as in the case of VoIP, if a delay of 200 msec or more occurs in a voice call, a problem occurs in the conversation. Similarly to the above, when the sequence number of the RTP packet header is checked by the congestion detection unit of the terminal and the interval between the RTP packets of the sequence numbers n and n + 1 is equal to or greater than a certain threshold, congestion is occurring. Judgment is made (S21). Upon receiving notification of congestion (S22), the AP instructs the transcoder to keep the bit rate of the audio codec and the transmission rate of the image data low (S23). For audio, the transcoder converts the bit rate of the audio codec from 12.2 kbps to a low rate of 7.95 kbps, and the image is thinned out from the frame rate per second by the transcoder (in FIG. 6, from 10 fps to 5 fps). (S24), and the number of frames remains unchanged, and the transcoder converts the image size display to a smaller one (CIF → QSIF), thereby reducing the transfer rate.
[0011]
When congestion elimination is detected at the AP (S25), the transcoder is instructed to restore the bit rate of the audio codec and the number of frames or the image size (S26).
(4) In the case of simultaneous transfer of real-time signal and non-real-time signal The operation in the case of simultaneous transfer of real-time signal and non-real-time signal will be described with reference to the congestion control flow of FIG.
In the operations (2) and (3), a real-time signal and a non-real-time signal may be simultaneously transferred during a call, such as file transfer or Web browsing. In this case, if there is no measure against congestion, the transfer rate of the real-time signal and the non-real-time signal is similarly reduced. Even if it takes a little time to transfer non-real-time signals such as web browsing, it is necessary to secure the bandwidth for real-time signals as much as possible and keep the delay small. Is reduced to ½, the real-time signal and the non-real-time signal are not halved, but the non-real-time signal is significantly suppressed, and the communication speed reduction of the real-time signal is alleviated.
[0012]
If congestion occurs even when the bandwidth of the non-real-time signal is reduced and the real-time signal is prioritized, the rate of the audio codec or the image codec is suppressed using a transcoder. For this reason, in FIG. 8, congestion control is performed in two stages, and congestion detection is also performed in two stages. The first congestion detection is performed by detecting congestion of a non-real-time signal at the AP, and the next congestion control is performed by detecting the congestion of the real-time signal at the terminal.
In FIG. 8, the Web is browsed while having a conversation with VoIP. The total downlink speed of VoIP and Web browsing is 64 kbps, the voice band is 12.2 kbps, and the Web data band is 51.8 kbps. In the first congestion detection, the congestion control unit 72 of the AP 71 detects congestion of the non-real-time signal (S31), and notifies the flow control unit 76 of the congestion (S32). The flow control unit 76 monitors the amount of inflow to the AP 71 so that there is no inflow exceeding the downlink speed from the AP (for example, 11 Mbps for IEEE802.11b, 54 Mbps for 802.11a) (S33). If the data arrives at a higher speed, first, the Web transfer speed is controlled from 51.8 kbps to 24 kbps so as not to affect the voice bandwidth (S34).
However, if a large delay in the voice data is detected by the congestion detection unit of the terminal 74 even if the Web data transfer band is suppressed (S35), the AP 71 is notified of the congestion (S36), and the AP 71 transmits the transcoder 73. Is instructed to convert the bit rate (S37). Upon receiving the bit rate conversion instruction, the transcoder converts the audio codec from 12.2 kbps to 7.95 kbps and transmits it to the terminal (S38), thereby minimizing the audio delay.
[0013]
The functions and configurations of congestion detection and signal speed control in the above embodiment can be modified.
In FIG. 2, which is a configuration in the case of streaming distribution, congestion detection is not performed by the congestion detection unit 5 of the terminal 4, but a decrease in the transfer rate to the terminal 4 is detected by the congestion control unit 2 of the AP1, A method for instructing the coder 3 to perform rate conversion is conceivable. In addition, in the control flow of FIG. 5, there may be a method of narrowing the service bandwidth that can tolerate other delay without reducing the communication speed for streaming delivery by priority control instead of suppressing the streaming rate.
[0014]
In addition, a method of adding a transcoder function to the AP in a soft manner instead of adding a transcoder for bit rate conversion as hardware next to the AP is also conceivable.
The function of the congestion control unit 2 in the streaming delivery of FIG. 1 can be implemented as a congestion control unit 32 outside the AP as shown in FIG. In addition, the function of the congestion control unit 22 in VoIP and TVoIP in FIG. 3 can be implemented as a congestion control unit 42 outside the AP as shown in FIG.
Further, the transcoder shown at 3 in FIG. 1 can be mounted as a transcoder function 53 inside the AP as shown in FIG. Similarly, the transcoder 23 shown in FIG. 3 can be mounted as a transcoder function 63 inside the AP as shown in FIG.
[0015]
【The invention's effect】
By using the present invention, even when the connection to one AP is concentrated and congestion occurs, the delay of the real-time signal is minimized, and the streaming is not disturbed, and the VoIP or TVoIP is used. In this way, it is possible to solve the problem of the call due to delay.
[Brief description of the drawings]
FIG. 1 is a diagram showing a principle configuration of the present invention.
FIG. 2 is a diagram showing a network configuration for implementing a congestion control method in streaming delivery according to the first embodiment of this invention.
FIG. 3 is a diagram showing a network configuration for implementing a congestion control method in VoIP according to the second embodiment of the present invention and TVoIP according to the third embodiment.
FIG. 4 is a diagram showing a network configuration for implementing a congestion control method in real-time signal / non-real-time signal simultaneous transfer according to a fourth embodiment of the present invention.
FIG. 5 is a diagram illustrating a congestion control flow in streaming delivery according to the first embodiment of this invention.
FIG. 6 is a diagram illustrating a congestion control flow in VoIP according to the second embodiment of this invention.
FIG. 7 is a diagram showing a congestion control flow in TVoIP according to the third embodiment of the present invention.
FIG. 8 is a diagram showing a congestion control flow in real-time signal / non-real-time signal simultaneous transfer according to the fourth embodiment of the present invention;
FIG. 9 is a diagram showing another embodiment of FIG. 2;
10 is a diagram showing another embodiment of FIG. 4;
FIG. 11 is a view showing still another embodiment of FIG. 2;
FIG. 12 is a diagram showing still another embodiment of FIG. 4;
FIG. 13 is a diagram showing a network configuration for implementing a conventional congestion control method.
[Explanation of symbols]
1 AP
2 Congestion control unit 3 Transcoder 4 Terminal 5 Congestion detection unit 6 Flow control unit 21 AP
22 Congestion Control Unit 23 Transcoder 24 Terminal 25 Congestion Detection Unit 26 Flow Control Unit 11 Terminal 12 AP
13 Content server 21 AP
22 Congestion Control Unit 23 Transcoder 24 Terminal 25 Congestion Detection Unit 26 Flow Control Unit 71 AP
76 Flow control unit 74 terminal

Claims (4)

In a congestion control method in an information distribution system for simultaneously transferring both a data signal that requires real-time property and a data signal that does not require real-time property via wireless access from a wireless base station to a wireless terminal,
The radio base station detects a first congestion, perform the first congestion control for limiting the transfer of the said real time is not required in the radio base station data signals,
After the execution of the first congestion control, the wireless terminal detects the second congestion and transmits the second congestion to the wireless base station,
When the radio base station receives the second congestion notification, the radio base station executes second congestion control that restricts transfer of a data signal that requires the real-time property. Congestion control method for wireless access. The first congestion control is flow control for limiting a data amount flowing into the radio base station, and the second congestion control is control for converting a bit rate transferred to the radio terminal. The congestion control method according to claim 1. In an information distribution system that simultaneously transfers both a data signal that requires real-time property and a data signal that does not require real-time property via wireless access from a wireless base station to a wireless terminal,
The radio base station includes a first congestion detection unit that detects first congestion, and the radio terminal transmits a second congestion detection notification to the radio base station when the second congestion is detected. Congestion detector
The radio base station is
A first congestion control unit that executes first congestion control that restricts transfer of a data signal that does not require the real-time property when detecting the first congestion;
After the execution of the first congestion control, the second congestion control is executed to limit the transfer of the data signal that requires the real-time property upon receiving the second congestion detection notification from the radio base station. Congestion control unit and
A congestion control system for wireless access, comprising: The first congestion control is flow control for limiting a data amount flowing into the radio base station, and the second congestion control is control for converting a bit rate transferred to the radio terminal. The congestion control system for wireless access according to claim 3.

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