KR100621133B1 - Method of wirelessly communicating in wireless network including MIMO station - Google Patents

Abstract

The present invention proposes a new MAC frame format for a standard management frame of 802.11a in wireless communication, and relates to a method for improving the efficiency of transmission between stations using the same.

In a wireless network communication method according to the present invention, a multi-input / multi-output transmission station secures a transmission medium through a predetermined channel acquisition procedure to configure BSS-related information and multiple input / multiple output support rate-related information, and the multiplexing. And sending, by an input / multiple output transmitting station, the BSS related information and the multiple input / multiple output support rate related information in a management frame to a receiving station through the transmission medium.

According to the present invention, a MIMO-supported rate information element consisting of a set of data rates that a MIMO station can support in an IBSS network including stations having different transmission capacities is transmitted in a beacon frame, thereby transmitting a maximum rate or It is effective to ensure efficient transmission rate selection.

WiFi, IBSS, MLME, MIMO

Description

Method of wirelessly communicating in wireless network including MIMO station

1 schematically illustrates a configuration in an IBSS communication network.

Figure 2 shows the beacon frame body frame in detail according to an embodiment of the present invention.

3A illustrates the MIMO parameter set information element field in detail according to an embodiment of the present invention.

3B illustrates the MIMO transmission capability information element field in detail according to an embodiment of the present invention.

4 schematically illustrates a process of setting a transmission rate between stations in an IBSS according to an embodiment of the present invention.

5 illustrates in detail the backoff procedure according to one embodiment of the invention.

The present invention relates to a method for increasing the transmission rate between stations in a BSS. More specifically, the present invention relates to a method of suggesting a new MAC frame format for a standard management frame of 802.11a in wireless network communication and using the same to increase the efficiency of transmission between stations.

A wireless LAN is a network that can transmit and receive data between stations within a certain distance without wiring to a floor as in a general LAN, and allows movement of stations within a WLAN.

In general, the basic configuration of an IEEE 802.11 WLAN network is a basic service set (BSS), and the BSS includes an independent basic service set (IBSS) and an infrastructure network (Infrastructure BSS).

In the infrastructure network, an access point (AP) is responsible for transmitting a beacon frame. The area in which the beacon frame appears defines the basic service area. The IBSS network is an 802.11 network that does not use an AP, and refers to an ad hoc network that directly communicates with another station in a BSS.

The process of configuring one IBSS network is as follows. First, a system management entity (SME) of a station that wants to create a new BSS starts BSS by generating a MAC Layer Management Entity (MLME) -START.request. At this time, the MLME-START.request primitive includes a BSS Basic Rate Set parameter and an OperationalRateSet, which are basically supported by all stations participating in the BSS. The data rate set to be performed, and the operation data rate set is a superset including the BSS basic data rate set and means a data rate set that can be used for communication between stations in the BSS.

The physical layer (PHY) supports the 5 GHz Orthogonal Frequency Division Multiplexing (OFDM) scheme, and the data payload transmits at a maximum speed of 54 Mbps. In the IEEE 802.11a standard, the BSS basic rate set and the operation rate set are {6, 12, respectively. , 24} Mbps and {6, 9, 12, 18, 24, 36, 48, 54} Mbps.

One BSS is formed through the above-described process, and the station that initializes the BSS transmits a beacon to another station in the BSS. The supported rate information element included in the beacon frame body is transmitted by carrying an operation rate set, and thus becomes a starting point of a transmission rate used in the BSS. Each station receiving the beacon matches its transmission capability and the set of operation rates of the BSS, sets a common part as the operation rate set, and when the stations are in the order of transmitting beacons, the beacon supported rate information element (beacon supported). The value is sent in a rate information element. This area includes data rates that all stations can use in common in the BSS. In other words, communication between stations in the BSS operates at the transmission rate.

As mentioned above, the support rate information element carried in the beacon informs each station of a set of operation rate to be used for the BSS, which transmits data that can be commonly handled by each station in the BSS. Contains a set of rates. That is, even if a station capable of processing a high data rate of 108, 216 Mbps or higher participates, if there is another station providing a low data rate (e.g., 54 Mbps) to the BSS, the data rate higher than the station can handle. Can not be put on the operation rate set.

In addition, an 802.11a-based multi-input multi-output (MIMO) communication system includes having one or more transmit antennas on the transmitting side and the receiving side also having one or more receiving antennas. The transmission data is divided into a plurality of sub data according to the number of transmission antennas, and then processed, respectively, and transmitted through the transmission antennas. The receiver finds and decodes sub data from the received signal and processes the sub data.

As described above, the throughput that can be processed by the station increases linearly with the number of antennas.

As shown in FIG. 1, the data rate supported by each station depends on the number of antennas. In the case of a conventional 802.11a system, when communicating with a station having one antenna, a maximum of 54 Mbps or more may be supported. It becomes impossible. In the BSS, there is a problem in that the data rate provided by the station having the smallest number of antennas is used to communicate at a low data rate even in communication between other stations capable of supporting a higher data rate.

In other words, when a station with multiple antennas (MIMO station) in addition to a station with one antenna in an IBSS composed of multiple stations communicates together, in the conventional case, the operation rate set in the BSS is determined by Stations are tuned to a rate that can be supported in common, and there is a problem that communication between stations that support a high data rate also fails to utilize all resources by operating at that rate.

Therefore, there is a need to devise a method that can guarantee communication between stations with multiple antennas, i.e., supporting high data rates, while guaranteeing an operation rate in the BSS.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a rate recognition algorithm that obtains maximum transmission efficiency between stations when a station configuring one BSS communicates with each other. It is done.

In a wireless network communication method according to the present invention, a multi-input / multi-output transmission station secures a transmission medium through a predetermined channel acquisition procedure to configure BSS-related information and multiple input / multiple output support rate-related information, and the multiplexing. And sending, by an input / multiple output transmitting station, the BSS related information and the multiple input / multiple output support rate related information in a management frame to a receiving station through the transmission medium.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In addition, the 802.11a standard management frame refers to a beacon frame, a probe request and response frame, and the combined request and response frame, the following description will be described by taking a beacon frame as an example.

Figure 2 shows the beacon frame body frame in detail according to an embodiment of the present invention. Beacon frame consists of MAC header, frame body and FCS. The beacon frame announces the existence of the network and plays an important role in network maintenance. The beacon frame is transmitted periodically to search and recognize the network as well as to match parameters for the mobile station to join the network.

The frame body field has a variable length as a data field. The Frame Check Sequence (FCS) field is used by the station to check the integrity of a received frame.

The supported data rate field 210 included in the frame body field in 802.11a is a BSS basic data rate set (6, 12, 24 Mbps) and an operating data rate set (6, 9, 12, 18, 24, 36, 48, 54 Mbps) is a field for recording information. The length of the supported data rate field 210 is 8 bytes and is used to indicate one data rate per byte. The value of the Most Significant Bit (MSB) of the byte representing each rate of the basic rate set is 1, and the value of the MSB of the byte representing each rate of the operating rate set is 0.

The MIMO Supported Rate field 220 has a variable length of 8 bytes and is added to the 802.11a standard frame format. Stations conforming to the 802.11a standard do not recognize the MIMO Supported Rate field 220 but are based on 802.11a. The MIMO station will recognize the MIMO supported rate field 220.

As described above, an 802.11a based MIMO communication system includes having one or more transmit antennas on the transmitting side and the receiving side also having one or more receiving antennas. The transmission data is divided into a plurality of sub data according to the number of transmission antennas, and then processed, respectively, and transmitted through the transmission antennas. The receiver finds and decodes sub data from the received signal and processes the sub data.

Therefore, the throughput that can be processed at the station increases linearly with the number of antennas. That is, a transmission rate that can be supported by the MIMO station supports 108Mbps, 216Mbps, 432Mbps, or more according to the number of antennas that the MIMO station has. As such, the set of data rates supported by the MIMO station is recorded in the MIMO supported data rate field 220.

The length of the MIMO supported rate field 210 is used to indicate one rate per byte if it has a variable length of 8 bytes.

3A and 3B illustrate a MIMO parameter set information element and a MIMO transmission capability information element according to an embodiment of the present invention.

As illustrated in FIG. 3A, the MIMO parameter set information element is composed of an element ID field, a length field, a minimum transmission capability field 310, a CA level field 320, and a CA type field 330. Here, the minimum transmission capability field 310 means the minimum number of antennas that a station has in the BSS. For example, if the field value is 1, it means that an existing SISO station exists in the BSS. 2 or more refers to a system having a system with a different number of antennas. In the CA (Collision Avoidance) level field 320, three choices are given. Forced as a first choice allows each station to use a collision avoidance mechanism. Recommended as a second option is to recommend a collision avoidance mechanism for each station. The third choice, don't care, is to ignore whether each station uses a collision avoidance mechanism. The CA type field 330 is a field specifying a collision avoidance mechanism to be used, and is composed of an RTS-CTS mechanism and a self-CTS mechanism.

As described above, the BSS information is collected and used through the MIMO parameter set information element. That is, it is possible to know the minimum number of antennas in the BSS, the existence of the SISO station, and the use of the collision avoidance mechanism due to the presence of the SISO station.

The information element is a variable length field of a management frame. The MIMO transmission capability information element as illustrated in FIG. 3B includes an element ID field, a length field and an antenna field 340, a reservation field, and a MIMO supported transmission rate set field 350.

Information Element Element id SSID 0 Support transfer rate One FH parameter set 2 DS parameter set 3 CF parameter set 4 TIM 5 IBSS parameter set 6 reservation 7-15 Challenge text 16 Reserve for Challenge Syntax Expansion 17-31 MIMO parameter set 32 reservation 33-39 MIMO Capability Information 40 reservation 41-255

The element ID field has a standardized value as shown in Table 1. The length field indicates the byte length of the following MIMO capability information element field. The antenna field 340 indicates the maximum number of eight antennas that the MIMO station can support. The 3-bit antenna number field 341 may represent a MIMO station having up to eight antennas. The MIMO supported bit rate set field 350 is encoded into 32 octets capable of supporting up to 32 bit rates, with one octet representing one bit rate each. In addition, one octet corresponds to a data rate from 500kb / s to 5 * 255 Mb / s in an increment of 500 kb / s. MIMO stations with four antennas support the set of supported data rates {27, 72, 96, 108, 144, 162, 192, 216}.

As described above, the information of each MIMO station is collected and used through the MIMO transmission capability information element, and this information element informs the supported transmission rate and the number of antennas of each station.

4 is a flowchart illustrating the formation of an infrastructure mode network and communication between stations in accordance with an embodiment of the present invention.

First, the access point selects an available channel through channel scanning (S410). Here, the detailed scanning process for each channel is as follows. First, scanning is started by performing MLME-SCAN.request in a MAC sublayer management entity (MLME), and MLME-SCAN.request includes a scan type, a channel list, and the like. Thereafter, the SSID (Service Set Identifier) and the MIMO transmission capability information element for the next channel are carried in the probe request frame. Next, in response, the receiving station receives a probe response frame including the capability information, the SSID, the MIMO capability information (extended support rate), the CF parameter set, the IBSS parameter set, and the like. After receiving the probe response frame, the MLME-SCAN including a BSSDescriptionSet (PHY parameter set, CF parameter set, IBSS parameter set, transmission capability information, BSS basic transmission rate set, etc.) and a result code (ResultCode). The scan procedure is terminated by notifying the MLME.

Second, if the BSS is formed of the selected channel, each station is combined to this channel (S420).

Third, the stations inform their transmission capability through the MIMO transmission capability information element when combined (S430), and the access point knows information of all stations of the BSS. For example, the information on the station may include the existence of an 802.11a station, a supported transmission rate of each station, and the like.

Fourth, one superframe includes a contention free period and a contention period, and determines whether the contention period is a non-competition period or a competition period (S440). During the non-competition period, the access point enables transmission by polling each station (S451). Only stations that receive polling can communicate. During the contention period, communication is performed using the existing backoff mechanism (S452). That is, in the IBSS, the transmitting MIMO station secures a transmission medium through a backoff process. The MIMO station configures the MIMO supported rate information element 300 and loads it in a beacon frame through the transmission medium to transmit to the receiving station (S460). The receiving station receiving the beacon frame collects the MIMO supported rate information element 300 (S470). Finally, the receiving station reads the MIMO supported rate information element 300 to set an efficient data rate with the MIMO station (S480).

5 illustrates in detail the backoff procedure according to one embodiment of the invention. Access to a transmission medium of IEEE 802.11 uses a DCF (Distributed Coordination Function) and a PCF (Point Coordination Function). DCF provides competition-based services, while PCF provides services without competition. DCF uses Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) as the access protocol. To avoid collisions, we use a looping backoff window mechanism. The criterion for determining whether the medium is used in the DCF is DIFS (DCF InterFrame Space; about 34 μs).

As illustrated in this figure, after a DIFS period, a contention window section of a predetermined size is set and a random slot size having the same probability of being selected by the backoff algorithm is assigned to each participating station in the IBSS. The size of the contention window section is one smaller than the square of two. For example, it has a value of 31, 63, 127, 255 and the like and is limited to 1023 due to the limitation of the physical layer.

When frame transmission of station A, which is currently using a channel, is terminated, stations B, C, and D, which are postponing frame transmission, participate in a competition for channel acquisition after DIFS. First, when the backoff timer of the station C which selected the minimum backoff time in the first contention window period becomes 0, frame transmission starts. After the next DIFS section, in the second contention window section, the stations B, D, and E participate in the contention and perform the same process as above, and the station D secures a transmission medium and starts frame transmission. In the third contention window section, stations B and E participate in a contention and perform the same process as above, so that station E secures a transmission medium and transmits a frame. In the fourth contention window section, only station B participates in contention and performs the same process as above, so station B secures a transmission medium and transmits a frame.

As described above, when a station in the IBSS network uses a wireless medium through a backoff procedure, the MIMO supported rate information element 300 including data rate set information that the MIMO station can support is configured to be included in the beacon frame. Send it. A MIMO station or single input / single output (SISO) station communicating with a MIMO station in an IBSS network recognizes the support rate of the MIMO station that transmitted the beacon from the beacon and selects a predetermined support rate among the recognized support rates. To communicate at an efficient data rate.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains (ie, those skilled in the art) should know that the present invention may be embodied in other specific forms without changing its technical spirit or essential features. It will be appreciated that it may be practiced.

Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

It is intended that the scope of the invention be indicated by the following claims rather than the foregoing description, and that all changes or modifications derived from the claims and their equivalents shall be included within the scope of the invention. Should be.

According to the present invention, a MIMO supported rate information element consisting of a set of data rates that can be supported by a MIMO station in an IBSS network including stations having different transmission capacities is transmitted in a management frame, thereby providing a maximum rate or It is effective to ensure efficient transmission rate selection.

In addition, there is an effect of enabling various collision avoidance mechanisms by providing a base for collision avoidance when 802.11a and MIMO stations coexist.

Claims (13)

Acquiring, by a multi-input multi-output (MIMO) station, a right to transmit data over a channel in a contention-free or competitive manner; Generating first information indicating a minimum number of antennas among the number of antennas included in a basic service set (BSS), and second information indicating a number of antennas of the MIMO station and a transmission rate set supported by the MIMO station; And And transmitting the generated first information and the second information in a management frame to a receiving station through the channel. 2. The method of claim 1, wherein acquiring the data transfer right comprises the MIMO station receiving polling from an access point. The method of claim 1, wherein the competition scheme is And a backoff algorithm for acquiring the transmission right by the station where the timer becomes zero. 2. The method of claim 1, wherein said management frame complies with the IEEE 802.11a standard. The method of claim 1, wherein the management frame is a beacon frame. The method of claim 1, wherein the management frame is a probe request and response frame. The method of claim 1, wherein the management frame is a join request and response frame. 2. The method of claim 1, wherein the first information includes a minimum transmission capability field representing the minimum number of antennas, a collision avoidance level field representing three levels of enforcement and recommendation and disregard, and at least an RTS-CTS mechanism (RTS (Request to Send) frame means a collision avoidance type field representing the acquisition of the data transmission right for the duration included in the RTS frame or the CTS frame when the station transmitting the CTS (Clear to Send) frame; And a MIMO parameter set information element. The method of claim 1, wherein the second information is And a MIMO transmission capability information element field comprising an antenna field representing the number of antennas, and a MIMO supported transmission rate field comprising a set of transmission rates that the MIMO station can support. 6. The method of claim 5, wherein the set of rates supported by the MIMO station comprises at least one of 108 Mbps, 216 Mbps, and 432 Mbps. 10. The method of claim 9, wherein the MIMO capability information element field is added to an 802.11a standard management frame. The method of claim 1, wherein the receiving station is a MIMO station (Multi-input Multi-output) or SISO (Single-input Single-output) station. 6. The method of claim 5, further comprising the step of the receiving station reading the second information and selecting one of the rate sets for communication with the MIMO station. .

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