JP2006014103A - Radio communication control apparatus and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent radio communication apparatus and radio communication method in which a frame for which a confirmaiton response is not required, such as a broadcast frame or multicast frame can be appropriately transmitted. <P>SOLUTION: The present invention includes: acquiring radio transmission line information indicating the quality of a transmission line with a receiving side radio terminal; selecting a receiving side radio terminal having the lowest quality as a target terminal based on the radio transmission line terminal; setting the target terminal to redirect a reception confirmation frame in response to reception of a frame for which a confirmation response is not required; and re-transmitting the same frame if no reception confirmation frame is received from the target terminal after the frame for which the confirmation response is not required, is transmitted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radio communication technique, and more particularly, to a radio communication control apparatus and a control method therefor provided in an access point (AP) or a station (terminal).

Coupled with dramatic progress in technologies such as information processing and information communication, there is an increasing demand for network computing technology for interconnecting computers. In a network environment such as a LAN (Local Area Network) where multiple computers are interconnected, collaborative work such as sharing computer resources and sharing, distributing, distributing, and exchanging information among multiple users Can be performed smoothly.

Recently, wireless LANs using transmission lines other than wired cables, such as radio waves and infrared rays, have been spreading. According to this type of wireless LAN, since most of the wired cables can be omitted in a work space such as an office, a terminal such as a personal computer (PC) can be moved relatively easily.

In general, in a wireless communication system in which a plurality of wireless stations such as a wireless LAN communicate with each other, a transmitting wireless station transmits a data frame to a receiving wireless station, and the corresponding receiving wireless station is correctly received. In the case of confirmation, an acknowledgment frame (ACK frame) is returned. Then, the transmitting-side radio station checks the confirmation response frame and performs a process of retransmitting the data frame as necessary. Such retransmission control is defined, for example, in the MAC (Medium Access Control) layer of the data link layer of the OSI (Open Systems Interconnection) basic reference model.

On the other hand, in the case of broadcast or multicast data, there is a possibility that the ACK frame may collide when there are multiple transmission destinations such as broadcast compatible with all radio stations and multicast for a specific group. In the MAC layer, the transmitting wireless station only transmits a frame to the receiving wireless station, and does not know whether or not the frame is correctly received. In addition, if the receiving side radio station correctly receives the frame from the transmitting side radio station, the receiving side radio station captures it as it is, but if an error is detected, it only discards the frame and returns the ACK frame to the transmitting side radio station. I do not.

For this reason, the problem that data cannot be received correctly on the receiving side frequently occurs. In order to avoid such problems, a method has been proposed in which a transmitting radio station performs individual communication with each receiving radio station in turn and performs retransmission control using an ACK frame even for broadcast or multicast data. Has been. However, according to this retransmission control method, there is a problem that the time delay increases in proportion to the number of reception-side radio stations.

For example, Japanese Patent Laid-Open No. 2003-37606 proposes a method for suitably transmitting an acknowledgment-free frame such as a broadcast frame or a multicast frame. Specifically, in a situation where the quality of the transmission path is good and there is a very high probability that data can be correctly received on the receiving side, the number of repeated transmissions of the same frame is set to a low value to increase the throughput, while transmission In a situation where the channel quality is inferior and the probability of receiving data correctly on the receiving side is extremely low, high quality communication can be maintained by setting the number of repeated transmissions of the same frame large.

JP 2003-37606 A

  However, according to the communication method described in Patent Document 1, it is possible to increase the probability of correctly receiving data on the receiving side by repeatedly transmitting the same frame multiple times, but on the other hand, the same frame is repeatedly transmitted. The same number of times must be transmitted, and the communication efficiency is not good.

Also, in broadcast data and multicast data, there is a priority in data such as data that must be received correctly depending on services of the upper communication protocol layer, or data that has less adverse effects if not received correctly. Even in such a case, the communication method described in Patent Document 1 repeatedly transmits the same frame a predetermined number of times, so that processing according to the priority of data cannot be performed.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an excellent wireless communication apparatus and wireless communication method capable of suitably transmitting an acknowledgment response unnecessary frame such as a broadcast frame or a multicast frame.

  In order to achieve the above object, the invention according to claim 1 shows the quality of the transmission path between the frame transmitting means for transmitting a frame without an acknowledgment to the receiving wireless terminal and the receiving wireless terminal. Wireless transmission path information acquisition means for acquiring wireless transmission path information, target terminal selection means for selecting a receiving-side wireless terminal with the worst quality as the target terminal based on the wireless transmission path information, and confirmation response not required for the target terminal Confirmation response setting means for setting a reception confirmation frame in response to the reception of the frame, and retransmit the same frame when the reception confirmation frame is not received from the target terminal after transmitting the frame without the confirmation response And a retransmission control unit.

  Further, in the invention according to claim 7, when a confirmation-required frame is received from the transmitting-side wireless terminal, a reception confirmation frame is returned to the transmitting-side wireless terminal, and a confirmation-response unnecessary frame is received When receiving a setting request for returning a reception confirmation frame in response to reception of a frame without an acknowledgment response from a frame reception control means that does not send back an acknowledgment frame and a transmission-side wireless terminal, A confirmation response setting unit configured to send a reception confirmation frame in response to reception, and when a frame without a confirmation response is received from the wireless terminal on the transmission side, the presence / absence of confirmation response setting is determined, and the confirmation response setting is performed. When the wireless communication apparatus is set, a wireless communication apparatus is provided that returns a reception confirmation frame to the transmitting wireless terminal.

  ADVANTAGE OF THE INVENTION According to this invention, the outstanding radio | wireless communication apparatus and radio | wireless communication method which transmit an acknowledgment response unnecessary frame, such as a broadcast frame and a multicast frame suitably, can be provided.

A first embodiment of a wireless communication system of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of an infrastructure mode that is one form of a wireless network. A wireless control station (hereinafter referred to as AP: access point) 101 and wireless terminals (hereinafter referred to as STA: stations) 102, 103, 104 are formed, and the AP 101 and the STAs 102 to 104 form a wireless zone 105 (hereinafter referred to as BSS: Basic Service Set). The AP 101 can be wired to the STAs 102 to 104 and can be connected to a wide area network 106 (WAN: Wide Area Network), and each STA 102 to 104 performs wireless communication transmission via the AP 101.

FIG. 2 shows an example of an ad hoc mode which is another form of the wireless network. The STAs 201, 202, and 203 form a wireless zone 204 (hereinafter referred to as an IBSS: Independent Basic Service Set). The STAs 201, 202, and 203 are connected to each other and perform wireless communication transmission.

FIG. 3 is a functional block diagram of the AP 101 of the wireless communication system in the first embodiment. The AP 101 includes an antenna 301 that transmits and receives data, a transmission / reception unit 302 that performs channel (frequency) selection and conversion between an RF frequency and an IF frequency, a modulation / demodulation unit 303 that performs signal modulation / demodulation, error detection / correction, and the like, A transmission / reception control unit 306 that has a buffer and determines whether or not reception confirmation for a broadcast / multicast frame is necessary based on an acknowledgment setting program; a radio wave reception intensity measurement unit 304 that acquires a radio wave reception intensity obtained from the transmission / reception unit 302; A retransmission processing control unit 305 that performs control for retransmitting a transmission frame according to the presence or absence of a reception confirmation response, a MAC processing unit 307 having a frame identification function such as confirmation of an address of the reception frame, an internal bus 308, and a confirmation An internal memory 309 for storing a response setting program and its setting data, A node control unit 310 for overall control of the control function block, and an external interface 311 for performing data transfer between the upper layer 312.

FIG. 4 is a functional block diagram of the STAs 102, 103, 104, 201, 202, and 203 of the wireless communication system in the first embodiment. Each STA basically has the same configuration as that of the AP 101, and each STA has an antenna 313 for transmitting / receiving data, a transmission / reception unit 314 for selecting a channel (frequency) and converting between an RF frequency and an IF frequency, From a modulation / demodulation unit 315 that performs modulation / demodulation, error detection / correction, etc., a transmission / reception control unit 318 that has a frame buffer and determines whether or not a reception confirmation response to a broadcast / multicast frame is necessary based on an acknowledgment setting program, and a transmission / reception unit 314 A radio wave reception intensity measuring unit 316 that acquires the radio wave reception intensity obtained, a retransmission processing control unit 317 that performs control for retransmitting a transmission frame as necessary, and a MAC having a frame identification function such as address confirmation of the reception frame Processing unit 319, internal bus 320, confirmation response setting program, setting data thereof, etc. An internal memory 321 for storing, and a node control unit 322 for overall control of the respective control function block, and an external interface 323 for performing data transfer between the upper layer 324.

The confirmation response setting program includes a terminal that transmits a broadcast (BC) / multicast frame (MC) (AP 101 in the wireless network of FIG. 1, STA 201, 202, or 203 in the wireless network of FIG. 2), broadcast This is executed with a terminal that receives a multicast frame (any one of the STAs 102, 103, and 104 in FIG. 1), and a reception confirmation frame when the terminal that receives the broadcast / multicast frame receives the frame. (ACK frame) is set to be returned. As a result, for example, when the AP 101 sets an acknowledgment response with the STA 102, when the STA 102 receives a broadcast / multicast frame, the AP 101 replies with an acknowledgment frame (ACK frame). When the AP 101 does not receive it, the AP 101 retransmits the same frame to the STA 102. Of course, if the confirmation response is not set between the AP 101 and the STA 102, even if the STA 102 receives the broadcast / multicast frame, the reception confirmation frame (ACK frame) is not returned as usual.

In this confirmation response program, a terminal that transmits a broadcast (BC) / multicast frame (MC), for example, the AP 101, sets one receiving terminal that performs confirmation response setting as a target STA, and the target STA and Acknowledgment processing is executed between.

Next, an operation for setting an acknowledgment in the wireless communication system according to the first embodiment configured as described above will be described.
FIG. 5 is a sequence diagram for explaining the operation of the confirmation response setting program.
For example, it is assumed that the AP 101 is a terminal that transmits a broadcast / multicast frame, and the STA 102 is selected as a target STA. The AP 101 (BC / MC transmission terminal) performs confirmation response setting notification to the target STA (STA 102) using the unicast frame, and assumes that the setting is completed when the frame reception is confirmed from the STA 102. Conversely, when canceling the confirmation response setting, a confirmation response setting cancellation notification is sent, and it is considered that the setting cancellation is completed when it is confirmed that this frame has been received. The AP 101 and the STA 102 set and store in the internal memories 309 and 321 that the confirmation response has been set.

Prior to the broadcast / multicast frame transmission, the AP 101 determines the target STA for executing the reception confirmation sequence based on the confirmation response setting program based on the wireless transmission path information indicating the quality of the wireless transmission path. . The wireless transmission path information regarding each STA 102, 103, 104 in the BSS is information based on the number of retransmissions by the retransmission processing control unit 305 or the number of retransmissions executed by software of the upper layer 312, or in the radio wave reception intensity measuring unit 304 There is radio wave reception intensity information. These pieces of information are obtained by unicast frame transmission / reception with each of the STAs 102 to 104. For example, information as shown in FIG. 6 is obtained. This is a case of a general wireless LAN (IEEE802.11a / g) module with a transmission power of 14 dbm as a reference. In this example, the STA 104 is determined as the target STA because it has the weakest radio wave intensity. Of course, when the radio field intensity of all the STAs 102, 103, and 104 is good, for example, −40 dbm or more, the target STA is not selected.

Even when the radio field strengths of all the STAs 102 to 104 are determined to be good, the upper layer 312 allows a specific application (for example, those requiring real-time performance such as video stream distribution or those with a strict frame loss tolerance). Is used, the STA having the lowest received radio wave intensity among the good ones is forcibly selected as the target STA. Therefore, when a specific application is not used by the upper layer and the received radio wave intensity at each STA is all good, the target STA is not selected.

Next, the operation of the wireless communication system according to the first embodiment of the present invention will be described.
FIG. 7 is a flowchart of a frame sequence in the AP 101. When a broadcast / multicast frame transmission request is generated (step 1), the AP 101 sequentially transmits a unicast frame to each STA and acquires wireless transmission path information as shown in FIG. 6 (step 2). Next, it is determined whether or not the received radio wave strength of each of the STAs 102 to 104 in this wireless transmission path information is good (step 3). If there is an STA that is not good, for example, does not reach −40 dbm, the received radio wave strength is weakest Only one STA is selected as a target STA (step 5). If it is determined in step 3 that the received radio wave strengths of all the STAs 102 to 104 are good, it is determined whether or not the application is a specific application from the upper layer 312 (step 4). Normal MC / BC frame transmission is executed (step 6). If it is determined in step 4 that the application is a specific application, the process proceeds to step 5 and only one STA having the weakest received radio wave intensity is selected as the target STA. When the target STA is selected, the confirmation response setting is executed between the AP 101 and the target STA based on the confirmation response setting sequence shown in FIG. 5 (step 7). After confirming the setting, broadcast / multicast frame transmission is executed (step 8), and it is confirmed whether or not a reception confirmation frame from the target STA has been received (step 9). If the reception confirmation with the target STA cannot be confirmed in step 9, the comparison is made with the predetermined number of retransmissions (step 10), and if it is within the predetermined number of times, the retransmission process is executed (step 11). If the predetermined number of times is exceeded in step 10, the process is terminated without performing the retransmission process.

FIG. 8 is a flowchart showing the operation of the STAs 102 to 104 that have received the broadcast / multicast frame.
When the STA receives the broadcast / multicast frame, the STA confirms whether or not an acknowledgment response is set (step 501). If the STA is not set, the STA confirms whether the received frame is duplicated (step 502). Discard (step 503), if not duplicated, execute frame reception processing (step 505). The determination of duplication is made by confirming a sequence control field in a frame format (FIG. 9) described later. In step 501, the target STA for which an acknowledgment response is set sends an acknowledgment frame to the transmission source (AP 101) for normal frame reception (step 504), and performs frame reception processing (step 505).

  The AP 101 can set / cancel the confirmation response by the confirmation response sequence at any time. Even during the execution of the confirmation response sequence, the AP 101 updates the wireless transmission path information at a predetermined timing and becomes subject to the change in the wireless transmission path status. It is possible to change the STA. This setting / cancellation determination may be performed in the AP wireless function or may be performed by the upper layer 312 in accordance with the use of a specific application.

The above has been described in the embodiment in the wireless network in the infrastructure mode in FIG. 1, but the same applies to the wireless network in the ad hoc mode in FIG. 2, and any one of the STAs 201, 202, 203 is broadcasted instead of the AP 101. The multicast frame is transmitted, and the other terminal becomes the receiving terminal. In such an ad hoc mode wireless network, it is assumed that a plurality of STAs simultaneously perform broadcast / multicast frame transmission.

For example, when the STA 201 sets an acknowledgment response to the STA 203 and starts broadcast / multicast frame transmission, and the STA 202 performs broadcast / multicast frame transmission almost simultaneously, if the acknowledgment response is set between the STA 201 and the STA 203, the STA 203 Does not acknowledge the frame from the STA 202 as usual, but acknowledges only the frame from the STA 201.

FIG. 9 shows an example of a frame format used for wireless transmission. FC 701 is a frame control field in which information about the frame itself, such as a protocol version and a frame type, is stored. DA 702 is a transmission destination address, SA 703 is a transmission source address, and BSSID 704 is a field for storing ID information indicating IBSS. A sequence control 705 is a sequence number assigned to the transmission frame, and a payload 706 is a variable-length field in which actual data is stored. FCS 707 is a field for storing a code for performing error detection for the entire frame.

In STA 203, the transmission source of the frame can be confirmed by SA703, and based on this, the presence / absence of confirmation response setting can be determined, and the necessity of returning the reception confirmation frame can be determined.

As described above, according to the wireless communication system according to the first embodiment of the present invention, the terminal (the wireless in FIG. 1) that transmits the broadcast (BC) / multicast frame (MC) by the confirmation response setting program. AP 101 in the network, or any one of STAs 201, 202, and 203 in the wireless network in FIG. 2) receives a broadcast / multicast frame from a terminal that receives the broadcast / multicast frame. Is set to respond to the reception confirmation frame (ACK frame), and the setting target STA is set by selecting one STA having the weakest received radio wave intensity. MC / BC transmission was executed only by receiving confirmation. , It can be extremely high possibility of receiving the MC / BC frame for all STA while eliminating unnecessary retransmissions.

In addition, even when the received radio field strength of the STA is good, the target STA is selected and the acknowledgment response is set when the specific application is used. The degree can be set.

In the first embodiment, the selection condition for the target STA is determined based on whether the received radio wave intensity is good and whether a specific application is used. Alternatively, the target STA may be selected based on the frame error rate instead of the received radio wave intensity. In addition, when a broadcast / multicast frame transmission request is generated, unicast frames are sequentially transmitted to each STA to acquire wireless transmission path information as shown in FIG. Instead, it goes without saying that data transmission / reception information by past unicast with each STA may be used as wireless transmission path information.

It is a figure which shows the example of the infrastructure mode which is one form of the wireless network concerning this invention. It is a figure which shows the example of the ad hoc mode which is another form of the wireless network concerning this invention. It is a functional block diagram of the access point of the radio | wireless communications system which is 1st embodiment of this invention. It is a functional block diagram of the station of the radio | wireless communications system which is 1st embodiment of this invention. It is a sequence diagram explaining operation | movement of the confirmation response setting program in 1st embodiment of this invention. It is a figure which shows the radio | wireless transmission path information in BSS or IBSS in 1st embodiment of this invention. It is a flowchart figure of the frame sequence in the access point of 1st embodiment of this invention. It is a flowchart figure of the frame sequence in the station of 1st embodiment of this invention. It is the figure which showed an example of the frame format used by the wireless transmission in 1st embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... AP (access point), 1a ... terminal, 5 ... BSA (basic service area), 6 ... Wireless communication control apparatus, 7 ... Wireless antenna, 8 ... RF part, DESCRIPTION OF SYMBOLS 9 ... Baseband process part, 10 ... CPU, 11 ... Electric power measurement part, 12 ... Control calculating part, 13 ... Statistical data table.

Claims (9)

Frame transmitting means for transmitting a frame that does not require an acknowledgment to the receiving wireless terminal;
Wireless transmission path information acquisition means for acquiring wireless transmission path information indicating the quality of the transmission path with the receiving wireless terminal;
A target terminal selecting means for selecting a wireless terminal on the receiving side having the lowest quality as a target terminal by the wireless transmission path information;
Confirmation response setting means for setting the target terminal to send back a reception confirmation frame in response to reception of the frame without the confirmation response;
A retransmission control means for retransmitting the same frame when a reception confirmation frame is not received from the target terminal after transmitting the confirmation response unnecessary frame;
A wireless communication apparatus comprising:   2. The wireless communication apparatus according to claim 1, wherein the target terminal setting unit does not specify the target terminal and does not set the confirmation response when it is determined that the wireless transmission path information is higher than a predetermined quality. .   3. The wireless communication apparatus according to claim 2, further comprising means for detecting whether or not a predetermined application by an upper layer is being used with a receiving-side wireless terminal, wherein the target terminal selecting means includes the wireless transmission A wireless communication apparatus, wherein the target terminal is selected when the predetermined application is used even when it is determined that the route information is higher than the predetermined quality.   4. The wireless communication apparatus according to claim 1, wherein the frame that does not require an acknowledgment is a multicast frame or a broadcast frame.   The wireless communication apparatus according to claim 1, wherein the wireless transmission path information is a received radio wave intensity in a transmission path with a receiving-side wireless terminal.   4. The wireless communication apparatus according to claim 1, further comprising confirmation response canceling means for canceling a setting for causing the target terminal to send back a reception confirmation frame in response to reception of the frame that does not require a confirmation response. . When a frame requiring confirmation response is received from the transmitting wireless terminal, a reception confirmation frame is returned to the transmitting wireless terminal. Control means;
When a setting request for returning a reception confirmation frame is received from the wireless terminal on the transmission side in response to the reception of the frame without the confirmation response, the reception confirmation frame is set to be returned for the reception of the frame without the confirmation response. Confirmation response setting means;
And determining whether or not a confirmation response is set when a frame that does not require an acknowledgment is received from the transmitting wireless terminal, and confirming the reception to the transmitting wireless terminal when the confirming response is set. A wireless communication apparatus characterized in that a frame is returned.   8. The wireless communication terminal according to claim 7, wherein when a confirmation response setting cancel request is received from the transmitting wireless terminal, the confirmation response for canceling the setting of returning a reception confirmation frame in response to reception of a confirmation response unnecessary frame A wireless communication apparatus comprising: release means.   The wireless communication apparatus according to claim 7 or 8, wherein the frame that does not require an acknowledgment is a multicast frame or a broadcast frame.

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