JP2007180687A - Wireless communication apparatus and wireless communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for decreasing an increase in a delay time due to repeating caused by using of a block ACK. <P>SOLUTION: The wireless communication apparatus includes: a propagation environment discrimination means for discriminating the propagation environment of a wireless interval; a block ACK request transmission period determining means for determining a period when a block ACK request is transmitted on the basis of a result of the discrimination by the propagation environment discrimination means; and a baseband processing means for carrying out baseband processing for transmitting the block ACK request in response to the transmission period of the block ACK request determined by the block ACK request transmission period determining means. When the wireless propagation environment is excellent, the transmission period of the block ACK request is extended and when the wireless propagation environment is deteriorated, the transmission period of the block ACK request is shortened so as to decrease the delay time required for retransmission of video data packets. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication method between a wireless base station and a wireless terminal in a wireless network such as a wireless LAN, and more specifically, wireless that reduces a delay time in a wireless section required for retransmission of a TCP / IP packet. It relates to a communication method.

  There is IEEE 802.11e as a wireless LAN standard. IEEE 802.11e includes EDCA (Enhanced Distributed Channel Access), which is a best-effort communication form, and HCCA (HCF Controlled Channel Access), which is a form of communication that guarantees a transmission band. HCCA is suitable for video transmission because it guarantees a transmission band.

  The HCCA packet delivery confirmation method includes a method of returning a block ACK, which is different from the conventional ACK (ACKnowledgement) return method. The block ACK return method is a method in which the receiving station collectively returns one ACK (block ACK) to a plurality of packets transmitted by the transmitting station (see Non-Patent Document 1).

  FIG. 1 is a diagram illustrating a configuration example of a wireless network using IEEE802.11e. Here, a video server 103 and a video display device 104 are connected to the radio base station 101 and the radio terminal 102, respectively. A video data packet transmitted from the video server 103 to the video display device 104 is transmitted wirelessly between the wireless base station 101 and the wireless terminal 102.

  FIG. 6 is a diagram showing a procedure for returning an HCCA block ACK when a video data packet is transmitted from the wireless base station 101 to the wireless terminal 102.

  The radio base station 101 determines a cycle for transmitting a block ACK request when establishing a radio link with the radio terminal 102. Thereafter, the radio base station 101 continuously transmits video data packets until the timing of transmitting a block ACK request. Here, a case is shown in which the wireless base station 101 transmits a block ACK request after continuously transmitting five video data packets. The wireless terminal 102 that has received the block ACK request returns a block ACK to the wireless base station 101. In the block ACK, the sequence number of the video data packet that could not be normally received by the wireless terminal 102 is clearly indicated in the bitmap format. Here, when the wireless terminal 102 cannot normally receive the third packet, the wireless base station 101 retransmits only the third video data packet.

As described above, the block ACK return method does not need to return one ACK for one data packet unlike the conventional ACK return method, and thus can improve the throughput accordingly.
IEEE P802.11e / D13.0, January 2005 “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) speci fi cation: Amen

  However, in the method using the above block ACK, as shown in FIG. 7, for example, a packet with a lower sequence number (for example, a packet with a sequence number of 1 in FIG. 7) is not normally received due to deterioration of the radio propagation environment. As a result, the delay time required for retransmission increases.

  By the way, when a TCP / IP video data packet is transmitted, an increase in delay time causes a large deterioration in throughput in the TCP layer. FIG. 9 is a diagram showing the relationship between delay time and throughput in TCP / IP. Here, assuming that the throughput is y [Mbps], the delay time is x [ms], and the transmission data size in TCP / IP is a [KB Byte], the relationship y = 8a / x holds. Thus, an increase in delay time leads to a deterioration in throughput.

  Therefore, when the upper layer of HCCA using block ACK is TCP / IP, if the delay time of the wireless section increases due to retransmission, the throughput in the TCP layer deteriorates, and the video display such as video disturbance is hindered. Had problems.

  An object of the present invention is to solve the conventional problems.

  In order to solve the above-described conventional problems, a wireless communication device according to the present invention transmits a TCP / IP data packet to another wireless communication device in a wireless communication system including a plurality of wireless communication devices. In the wireless communication device, the block ACK request transmission period determining means for determining the number of data packets to be transmitted continuously, and after transmitting the data packets of the number of data packets determined by the block ACK request transmission period determining means, A baseband processing means for transmitting a block ACK request; and a propagation environment determining means for determining a propagation environment in a radio section, wherein the block ACK request transmission period determining means is based on a determination result of the propagation environment determining means, The number of data packets to be continuously transmitted is determined.

  The wireless communication method of the present invention is a wireless communication method in which a transmission-side wireless communication device in a wireless communication system including a plurality of wireless communication devices transmits a TCP / IP data packet to a reception-side wireless communication device. A first step of transmitting a confirmation response request after transmitting a predetermined number of continuous transmission packet data packets addressed to the reception side wireless communication device; and the confirmation response request transmitted by the reception side wireless communication device. Receiving a confirmation response that is a response to the data packet, and transmitting the data packet by repeating the first step and the second step. It is determined based on the number of transmitted packets and the number of packets retransmitted based on the previous acknowledgment.

  According to the radio packet transmission apparatus of the present invention, when the upper layer of HCCA using block ACK is TCP / IP, the delay time due to retransmission in the radio section is reduced, thereby reducing the degradation of throughput in the TCP layer. can do.

  Embodiments of the present invention will be described below with reference to the drawings.

  The configuration of the wireless network in the embodiment of the present invention is the same as that in FIG.

(Embodiment 1)
FIG. 2 is a block diagram showing an internal configuration of radio base station 101 according to Embodiment 1 of the present invention. When the wireless base station 101 transmits a video data packet to the wireless terminal 102, a solid thick arrow indicates the flow of the video data packet. On the other hand, thin solid arrows indicate the flow of data received by the radio base station. A broken arrow indicates a parameter flow.

  When transmitting a video data packet from the wireless base station to the wireless terminal, the CPU 201 passes the video data packet input from the Ethernet (registered trademark) 202 to the baseband processing unit 203. The baseband processing unit 203 has an access control function for avoiding packet collisions in a wireless section, a bandwidth allocation function, and a modulation / demodulation function. The video data packet modulated by the baseband processing unit 203 is transmitted to the radio section by the high frequency unit (RF) 204.

  When the wireless base station 101 receives a video data packet, the CPU 201 passes the video data packet demodulated by the baseband processing unit 203 to the Ethernet (registered trademark) 202.

  FIG. 3 is a flowchart showing the operation of the radio base station 101 in the present embodiment.

  The operation of the radio base station will be described with reference to FIG. 2 and FIG.

  In IEEE 802.11e HCCA, a radio base station assigns a transmission permission time (period) based on a band requested in advance from a radio terminal.

  If it is confirmed in S101 that it is a transmission permission time, the wireless base station 101 starts transmission of a video data packet.

  In S102, one video data packet is transmitted to the wireless terminal.

  In S103, the value of the counter 205 is incremented by one. The value of the counter 205 is set to an initial value 0 at the start of transmission.

  In S104, the value of the counter 205 is compared with the block ACK request cycle at that time. When the value of the counter 205 is equal to the block ACK request cycle, the process proceeds to S105, and when the value of the counter 105 is different from the block ACK request cycle (the value of the counter 205 is smaller than the block ACK request cycle), the process returns to S102. .

  In S105, a block ACK request is transmitted to the wireless terminal 102.

  In S106, a block ACK is received from the wireless terminal 102.

  In S107, the radio wave reception intensity (RSSI) of the block ACK is measured.

  In S108, the propagation environment determination unit 206 compares the RSSI value measured in S107 with the RSSI value of the previous block ACK. Here, when it is determined that the radio propagation environment is better than the previous time, that is, the RSSI value has increased, the process proceeds to S109, where the previous time and the radio propagation environment are equivalent, that is, the RSSI value has changed. If it is determined that the radio propagation environment has deteriorated compared to the previous time, that is, if it is determined that the RSSI value has decreased, the process proceeds to S111.

  In S109, the block ACK request transmission cycle determination unit 207 increases the cycle of the block ACK request by one video data packet, and returns to S101.

  In S110, the block ACK request transmission cycle determination unit 207 maintains the block ACK request cycle and returns to S101.

  In S111, the block ACK request transmission cycle determination unit 207 reduces the cycle of the block ACK request by one video data packet, and returns to S101.

  Note that the propagation environment determining unit 206 excludes the block ACK at the time of retransmission of the video data packet from the wireless propagation environment determination target.

  The baseband processing unit 203 transmits a block ACK request at the cycle determined by the block ACK request transmission cycle determining unit 207.

  In order to compare the RSSI, the measured RSSI value is stored in the memory 208 as a reference value.

  According to the above configuration, since the cycle for transmitting the block ACK request can be dynamically changed according to the radio propagation environment, the delay time in packet retransmission can be reduced.

  In this embodiment, the increment / decrement unit of the cycle for transmitting the block ACK request is set to 1. However, for example, when the RSSI value fluctuates greatly (several dBm or more), 2, 3,... You may increase / decrease by a unit.

(Embodiment 2)
FIG. 4 is a block diagram showing an internal configuration of radio base station 101 according to Embodiment 2 of the present invention. In FIG. 4, the same symbols are used for the same components as in FIG. When the wireless base station 101 transmits a video data packet to the wireless terminal 102, a solid thick arrow indicates the flow of the video data packet. On the other hand, thin solid arrows indicate the flow of data received by the radio base station 101. A broken arrow indicates a parameter flow.

  When transmitting a video data packet from the wireless base station 101 to the wireless terminal 102, the CPU passes the video data packet input from the Ethernet (registered trademark) 202 to the baseband processing unit 203. The baseband processing unit 203 has an access control function for avoiding packet collisions in a wireless section, a bandwidth allocation function, and a modulation / demodulation function. The video data packet modulated by the baseband processing unit 203 is transmitted to the radio section by the high frequency unit (RF) 204.

  When the wireless base station 101 receives a video data packet, the CPU 201 passes the video data packet demodulated by the baseband processing unit 203 to the Ethernet (registered trademark) 202.

  FIG. 5 is a flowchart showing the operation of the radio base station 101 in the present embodiment. The operation of radio base station 101 in the present embodiment will be described with reference to FIG. 4 and FIG. In FIG. 5, steps S201 to S206 are the same as those in the first embodiment, and thus the description thereof is omitted.

  In S207, the packet reception success rate calculation unit 401 receives the packet reception from the number of continuous packet transmissions and the number of video data packets that could not be normally received (number of packet reception failures) specified in the bitmap format in the block ACK. Calculate the success rate.

  In S208, the packet reception success rate calculation unit 401 compares the value of the packet reception success rate calculated in S207 with the value of the packet reception success rate at the previous block ACK reception. Here, if it is determined that the packet reception success rate is higher than the previous time, the process proceeds to S209, and if it is determined that the packet reception success rate is the same as the previous time, the process proceeds to S210, where the packet reception success is successful. When it is determined that the rate has decreased, the process proceeds to S211.

  In S209, the block ACK request transmission cycle determination unit 207 increases the cycle of the block ACK request by one video data packet, and the process returns to S201.

  In S210, the block ACK request transmission cycle determining unit 207 maintains the cycle of the block ACK request and returns to S201.

  In S211, the block ACK request transmission cycle determination unit 207 reduces the cycle of the block ACK request by one video data packet, and returns to S201.

  The baseband processing unit 203 transmits a block ACK request at the cycle determined by the block ACK request transmission cycle determining unit 207.

  Note that the packet reception success rate calculation unit 401 does not calculate the packet reception success rate for block ACK at the time of video data packet retransmission.

  In order to compare the packet reception success rates, the calculated packet reception success rates are stored in the memory as reference values.

  According to the above configuration, since the cycle for transmitting the block ACK request can be dynamically changed according to the radio propagation environment, the delay time in packet retransmission can be reduced.

  In the present embodiment, the increment / decrement unit of the cycle for transmitting the block ACK request is set to 1. However, for example, when the value of the packet reception success rate fluctuates greatly (several percent or more), 2, 3,. You may increase or decrease in units such as.

  In all the embodiments described above, the initial value of the transmission period of the burst ACK request may be arbitrary, but is set within a range not exceeding 64 which is the maximum value in the standard.

  In all the embodiments described above, the cycle for transmitting the block ACK request is changed according to the change of the radio propagation environment, but the value is directly determined according to the radio propagation environment. Also good. In such a case, the transmission period of the burst ACK request according to the value of RSSI or the packet reception success rate may be prepared in advance in a table, or the transmission period of the burst ACK request may be obtained by a function.

  Note that all the embodiments described above can also be applied when transmitting a video data packet from the wireless terminal 102 to the wireless base station 101. In that case, the propagation environment determination unit 206 and the block ACK request transmission cycle determination unit 207 shown in FIG. 2 or the packet reception success rate calculation unit 401 and the block ACK request transmission cycle determination unit 207 shown in FIG. You just have to implement it.

  Note that all the embodiments described above can also be realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include all or part of the structure.

  The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology.

  The wireless packet transmission apparatus according to the present invention is useful in a wireless LAN system that transmits video. The present invention can also be applied to other wireless communication systems and the like in which an ACK request is made and one ACK is returned for a plurality of transmission packets.

The figure which shows the structure of wireless networks, such as wireless LAN The figure which shows the internal block structure of the wireless base station in Embodiment 1 of this invention. The flowchart which shows operation | movement of the radio base station in Embodiment 1 of this invention. The figure which shows the internal block structure of the wireless base station in Embodiment 2 of this invention. The flowchart which shows operation | movement of the wireless base station in Embodiment 2 of this invention. The figure which shows the reply procedure of the block ACK in IEEE802.11e HCF mode The figure which shows the resending procedure of the unreceived packet in the block ACK reply method Diagram showing the relationship between delay and throughput in TCP / IP

Explanation of symbols

101 wireless base station 102 wireless terminal 103 video server 104 video display device 201 CPU
202 Ethernet (registered trademark)
203 Baseband processing unit 204 RF
205 Counter 206 Propagation Environment Determination Unit 207 Block ACK Request Transmission Period Determination Unit 208 Memory 401 Packet Reception Success Rate Calculation Unit

Claims (4)

A wireless communication apparatus configured to transmit a TCP / IP data packet to another wireless communication apparatus in a wireless communication system including a plurality of wireless communication apparatuses,
Block ACK request transmission period determining means for determining the number of data packets to be transmitted continuously;
Baseband processing means for transmitting a block ACK request after transmitting the number of data packets determined by the block ACK request transmission period determining means;
Propagation environment determination means for determining the propagation environment of the radio section,
The block ACK request transmission period determining means is a wireless communication apparatus that determines the number of data packets to be continuously transmitted based on a determination result of the propagation environment determining means. The propagation environment determining means measures a radio wave reception intensity of a block ACK transmitted from the other radio communication apparatus as a response to the block ACK request, and determines a propagation environment of a radio section based on the radio wave reception intensity. Item 2. The wireless communication device according to Item 1. The propagation environment determining unit calculates a packet reception success rate from the number of data packets transmitted continuously and information included in the block ACK transmitted from the other wireless communication device as a response to the block ACK request. The wireless communication device according to claim 1, wherein a propagation environment in a wireless section is determined based on the packet reception success rate. A wireless communication method in which a transmission-side wireless communication device in a wireless communication system including a plurality of wireless communication devices transmits a TCP / IP data packet to a reception-side wireless communication device,
A first step of transmitting an acknowledgment request after transmitting a predetermined number of continuous transmission packet data packets addressed to the receiving side wireless communication device;
Receiving a confirmation response that is a response to the confirmation response request transmitted by the reception-side wireless communication device; and
Transmitting the data packet by repeating the first step and the second step;
The wireless communication method, wherein the number of continuous transmission packets is determined based on the past number of continuous transmission packets and the number of packets retransmitted based on the past confirmation response.

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