KR20080007088A - Apparatus and method of multi-channel media access control for wireless local area network devices with single radio interface - Google Patents

Abstract

A multi-channel MAC(Medium Access Control) device for a single wireless interface wireless LAN(Local Area Network) device and a method are provided to sense a common channel when channel interface window is initiated from window start time repeated at predetermined periods, and to store a non-unicast frame to be transmitted if the common channel is used, thereby preventing frame loss. When channel interface window is initiated from window start time repeated at predetermined periods, a common channel is sensed(S500,S502). At least more than two devices are allocated to a target channel by using a channel usage vector indicating whether to use each of plural channels during the initiated channel interface window(S504,S506). Frames are transmitted to the target channel allocated with the devices(S508).

Description

Apparatus and method for multi-channel media access control for single air interface wireless LAN device {APPARATUS AND METHOD OF MULTI-CHANNEL MEDIA ACCESS CONTROL FOR WIRELESS LOCAL AREA NETWORK DEVICES WITH SINGLE RADIO INTERFACE}

1 schematically illustrates a WLAN network element.

Figure 2 is a block diagram showing a single air interface wireless LAN device according to an embodiment of the present invention.

3 illustrates the distribution and synchronization of related parameters within a common channel framework in accordance with an embodiment of the present invention.

4 illustrates a channel matching mechanism on a common channel framework according to an embodiment of the present invention.

5 is a flowchart illustrating a multi-channel media access control method in a single air interface wireless LAN apparatus according to an embodiment of the present invention.

6 is a diagram showing total yield and channel utilization as the number of MP pairs increases in accordance with an embodiment of the present invention.

7 is a diagram showing the total yield by different control options as the number of MP pairs increases in accordance with an embodiment of the present invention.

8 is a diagram illustrating channel utilization by different control options as the number of MP pairs increases in accordance with an embodiment of the present invention.

9 illustrates a topology used in a BBS-heavy traffic scenario according to an embodiment of the present invention.

The present invention relates to a media access control (MAC) apparatus and method of a wireless LAN device, and more particularly, to a multi-channel media access control apparatus and method of a single wireless interface wireless LAN device.

In recent decades, the Institute for Electrical and Electronics Engineers (“IEEE”) 802.11 standards have provided the basis for the interworking of wireless LAN devices. Desirable outcomes are being made to reflect appropriate changes to standards (e.g., 802.11a, 802.11g, 802.11e, 802.11i, and 802.11n).

The main part of the WLAN standard is to address a link between an access point (hereinafter referred to as "AP") and stations of the AP (Stations, referred to as "STAs"). A well known topology for networking between APs and STAs is the Basic Service Set (hereinafter referred to as 'BBS'), where the STAs set is controlled by a single arbiter AP. A system and a local area network (LAN) used to connect a BBS set to each other are called a distribution system (hereinafter, referred to as a 'DS'). The DS is today mainly composed of wires. The primary purpose of IEEE 802.11s is to characterize the ability of APs to communicate wirelessly with each other and to form a Wireless Distribution System (WDS) that allows 802.11s nodes to carry traffic on behalf of each other. .

1 is a diagram schematically illustrating a WLAN network element.

Referring to FIG. 1, unlike the STA of the BSS, a basic element of an IEEE 802.11s mesh network is a mesh point 100 (hereinafter, referred to as an 'MP'). MPs forward frames on behalf of other MPs in a hop by hop like a router in a wired network. Mesh Access Point (hereinafter referred to as 'MAP') provides a wireless link between APs. Since the wireless link does not require a wired infrastructure, it is aimed at enabling such a device to be set in a difficult-to-control manner. It is hoped that the installation of a WLAN mesh network will quickly cover a wider coverage area. You can do it.

Since the MAC layer routing and management framework for the mesh network is a key element of the WLAN mesh network, the present invention focuses on the aspect of dealing with the multichannel operation of the MAC. In general, the WLAN access control scheme defines a mechanism by which two or more WLAN devices can communicate with each other on one channel. Multichannel access based on a single air interface means an independent IEEE 802.11 wireless device. In addition, even if one wireless device supports multiple radio bands but only one band at a time, it is regarded as a single air interface. This single air interface is based on a connection scheme using one channel. As such, this channel commonly used by all devices is called a common channel.

For multichannel operation of MPs with a single interface, when the common channel is changed to another channel, the state of the common channel is no longer sensed. In other words, the MP cannot communicate with any MP on the common channel. Although the sender MP selects the data channel used for data transmission by exchanging Request to Switch (RTX) and Clear to Switch (CTX) frames on the common channel with the receiver MP, the sender MP selects the RTX and CTX frames on the other channel. Can't hear In addition, since RTX and CTX frames are designed to identify hidden node problems, such MPs have the problem of destroying ongoing data transmissions after channel switching.

Accordingly, the present invention provides an apparatus and method for multi-channel medium access control in accordance with the current IEEE 802.11 standard.

In addition, the present invention provides a multi-channel medium access control apparatus and method that does not require a device having multiple air interfaces.

The present invention also provides an apparatus and method for multi-channel media access control in which a simple and extended framework is supported in different traffic scenarios.

The present invention also provides a multi-channel media access control apparatus and method for detecting a common channel when the channel matching window starts, and buffering a non-unicast frame to be transmitted if the common channel is in use.

In addition, the present invention starts buffering when the channel usage vector is updated or an RTX / CTX exchange is detected, and frames until all MPs located in one hop can use the common channel, i.e. until a new channel matching window is started. An apparatus and method for buffering a multi-channel medium access control are provided.

Hereinafter, the operation principle of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals refer to the same elements as shown in the drawings, even though they may be shown on different drawings, and in the following description, detailed descriptions of related well-known functions or configurations are not required in the following description. If it is determined that it can be blurred, the detailed description thereof will be omitted. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

In the following detailed description of the present invention, a multi-channel medium access control apparatus and method for a single air interface wireless LAN apparatus proposed by the present invention will be described. Also, a simple and extended framework is supported in different traffic scenarios. An apparatus and method for multi-channel medium access control will be described.

In the multi-channel medium access control method according to the present invention for achieving the above, in the medium access control method of a single wireless interface WLAN device, if the channel matching window is started from the start of the window repeated in a predetermined period, the common channel Allocating at least two or more devices to a destination channel using a channel usage vector indicating whether to use each of a plurality of channels during the started channel matching window, and transmitting and receiving a frame to the assigned destination channel. It includes the process of doing.

In addition, the multi-channel medium access control method according to the present invention for achieving the above, in the medium access control method of a single air interface wireless LAN apparatus, if the channel matching window is started from the start time of the window repeated in a predetermined period, Detecting a common channel; buffering a frame if the common channel is in use; and transmitting and receiving the buffered frame to the common channel when a new channel matching window starts.

In addition, the multi-channel medium access control apparatus according to the present invention for achieving the above, in the medium access control apparatus of a single air interface wireless LAN device, if the channel matching window starts from the start time of the window repeated in a predetermined period, A controller for allocating at least two or more devices to a destination channel using a channel detector for detecting a common channel, a channel use vector indicating whether each of the plurality of channels is used during the started channel matching window, and the allocated destination channel It includes a transceiver for transmitting and receiving a frame using.

In addition, the present invention provides a common channel framework (hereinafter referred to as 'CCF') designed to enable the operation of the device only a single air interface to overcome the limitations of the device by a plurality of air interfaces. In addition, each MP according to the present invention buffers a frame generated in an application layer at each cycle of the CCF or every repeated window. At the heart of this CCF is a common channel. In conventional devices (STAs and APs do not implement the standard functions of 802.11s), the common channel is the same as the other channels and does not affect the operation of the conventional device.

Device pairs or clusters use CCF to select channels other than the common channel and then return to the common channel. During this time, the device exchanges one or more data frames or buffers the data frames if the data frame cannot be exchanged. Channel matching itself is performed on a common channel by exchanging control frames or management frames that convey information about the destination channel. Through this process, synchronized transmission is performed on multiple channels.

Single wireless MPs switching to other channels are unaware of the network state on the common channel (e.g., modifying network Allocation Vectors (NAVs) and the operating state of neighboring nodes, etc.). Therefore, the multichannel MAC protocol has been developed for single wireless MPs that must address the following issues. First, the multichannel MAC protocol facilitates the connectivity of any MPs that can be occupied on different channels. Second, the multi-channel MAC protocol facilitates the destruction of MPs in transit due to loss of network state information.

To identify these two issues, the following considerations should be considered. First, the concept of channel coordination window (hereinafter referred to as 'CCW') presented in the framework should be introduced. At the CCW start point, all MPs are tuned on a common channel. This allows any MPs to establish communication with each other. Secondly, at the CCW start point, the channel occupancy state is reset, and the MPs select the available channel. Once a channel is selected by one MP, the channel selected by the other MPs is marked as unavailable. The CCW is repeated in period P, and the CCW duration generally corresponds to a portion of P. Third, MPs located in every one hop buffer the frame to be transmitted until all MPs can use the common channel. That is, when all the MPs can use the common channel or when all the MPs exchange Request / Switch / Clear to Switch (RTX / CTX), the frame to be transmitted is buffered. The RTX / CTX is a request message for transmitting a frame and a response message in response thereto. Then, buffering is performed until the CCW which repeats every period P starts. The frame may be a non-unicast frame, and may correspond to a multicasting frame or a broadcasting frame.

2 is a block diagram showing a single air interface wireless LAN device according to an embodiment of the present invention.

Referring to FIG. 2, in the single wireless interface WLAN device according to an embodiment of the present invention, when the CCW starts from a start point of a window repeated at a predetermined period, the channel detector 200 detects a common channel, and the detected If the common channel is not available, the controller 210 stores and controls the data of the application layer 220 in the buffer 230, and the transceiver 240 transmits and receives the stored data when the common channel becomes available. It is configured to include).

The controller 210 is responsible for the overall control of the MP. In addition, periodically or when the data of the application layer 220 is generated, the channel detector 200 is controlled to detect the common channel. This detection is also common to MPs located in one hop. Each of the MPs located in the one hop periodically exchanges a detection result, and buffers a frame generated from an application layer until the MPs can use the common channel, or when a new CCW repeated every period P starts. Buffer until. This buffering begins when an RTX / CTX exchange is detected or a change or update of the channel usage vector is made. Such a buffered frame may be a multicasting frame or a broadcasting frame as a non-unicast frame.

In addition, the channel detector 200 detects a common channel when a beacon frame is received from periodic or adjacent MPs under the control of the controller 210. The beacon frame includes window P and CCW values of respective MPs. As such, each MP transmits a beacon frame to adjacent MPs, allowing adjacent MPs to know P and CCW. As such, when the common channel is detected, not only which MPs are currently transmitting or receiving data through the detected common channel but also the RTX / CTX frames exchanged between adjacent MPs can be identified. This data and / or RTX / CTX frame is repeated per window P.

When the common channel is detected as described above, the controller 210 determines whether the common channel is available. If the common channel is not available, the controller 210 generates a non-unicast frame to be transmitted from the application layer 220 to other MPs, and then, if the non-unicast frame is generated, the controller 210 stores the non-unicast frame. Save it. This buffering begins when an RTX / CTX exchange is detected or the channel usage vector is updated, and ends at the beginning of a new CCW. When the neighboring MPs can use the common channel through the beacon frame received from the periodic or neighboring MPs, the controller 210 transmits the non-unicast frame stored in the buffer through the transceiver 240. Transmit to adjacent MPs. Such transmissions include multicasting or broadcasting.

3 illustrates the distribution and synchronization of related parameters within a common channel framework according to an embodiment of the invention.

Referring to FIG. 3, the MP detects beacon frames 300, 310, 320, and 330 through an association process of the WLAN. If the beacon frame is not detected, the MP transmits a beacon frame with its own window P and CCW values. The window P and CCW values are transmitted to the WLAN information element of the beacon. This, P and CCW values should be known to all MPs in the mesh network. Each MP transmits an offset D together with window P and CCW values when transmitting a beacon frame. The offset (D) is the time elapsed since the start of the current window P and corresponds to the remainder divided by P without synchronizing the hardware timer value. That is, the time elapsed since the start of P (modulo P). In practice, the MPs simply carry the values of P and CCW included in the beacon frames received from the other MPs. Each MP calculates its offset (D) before sending a beacon frame. As described above, in the case of calculating the offset D, when the MP having received the beacon is different from the current value of the new window P and CCW, the offset D may be calculated through Equation 1 below.

New offset (△ _new ) = (received offset (△ _rcvd ) + hardware timer value) modulo P

Equation 1 may be used to calculate the offset Δ or simply update the offset because the MPs may copy the window P and CCW values from beacons received from other MPs. The optimal values of the windows P and CCW may vary depending on the topology or the requirements of the application.

In addition, CCF enables channel formation between BBS and WDS (Wireless Distribution Service) traffic when MAP can switch to BBS channel after CCW, thereby enabling MAP to operate WDS with BBS traffic. . In addition, the framework may support channelization in the WDS, for example by allowing the formation of an ad-hoc cluster to switch to the agreed channel after CCW.

channel coordination  mechanism

4 illustrates a channel matching mechanism on a common channel framework according to an embodiment of the present invention.

Referring to FIG. 4, any MP pair on a common channel may initiate transmission by transmitting a Request to Switch (RTX) frame on the common channel. The transmitted RTX frame is transmitted to an adjacent multiple MP. The predetermined MP receiving the RTX frame accepts the frame transmission by transmitting a CTX (Clear to Switch) frame carrying the same destination channel information. Such frame transmission and reception may also be rejected by setting the destination channel index to the common channel.

MPs located in every one-hop buffer the frame until all MPs can use the common channel. That is, it buffers the non unicast frame transmitted when all MPs can use the common channel. And, when two frames are newly generated between MPs to which a frame is to be transmitted / received, normal STAs update only the NAV according to the value described in the duration ID field. The duration specified in the RTX / CTX frame does not include the occupancy time on the destination channel so that the common channel does not need to be left idle.

The MP selects the destination channel to switch the transmission frame. In order to facilitate channel selection, the MPs use a channel usage vector U of N channels, and the channel usage vector U can be expressed by Equation 2 below.

U = [ u ₁ , u ₂ , ..., u _N ]

Here, u _i ∈ {0,1}, u _i = 0 indicates that u _i channel is available, and u _i = 1 indicates that u _i channel is in use. At the CCW start point, U is reset according to the list of available channels. For example, the bits of U corresponding to the channel which are unavailable due to DFS (Dynamic Frequency Selection) conditions are kept at '1'. The other bits are set to '0'. Each MP updates U as the request succeeds. When the MP switches back to the common channel after switching to another channel, it is no longer assumed that the channels are in a usable state labeled u _i = 0. MPs returning to the common channel after data exchange limit the RTX signaling only to the previously successful destination channel since the channel usage status is not known.

If the receiving MP approves the RTX request, the MP pair sends the switching delay time T _s. Switch to the destination channel in less than a microsecond. Completion of the CTX frame T _s After (less than 100 microseconds), the transmitting MP performs a Clear Channel Assessment (CCA) during the Distributed Coordination Function (DCF) Interframe Space (DIFS) after a switching delay. The transmitting MP transmits data when the channel is found to be empty and returns to the common channel when the channel is not empty. If the receiving MP does not receive a data frame for the sum of the slot interframe space (SIFS) and the slot time after channel switching or transmitting the ACK, the transmitting MP returns to the common channel. After returning to the common channel, the transmitting MP starts the backoff process. Retransmission may occur in a common channel or destination channel.

The MP that fails to acquire a channel during CCW may select a channel based on the channel usage vector U even after CCW. The MPs may continue to exchange RTX and CTX even after CCW, and may indicate a destination channel marked as available.

In order to prevent transmission of STAs in a common channel during CCW, MAP, like all MPs, may transmit MPs by transmitting a CTX frame whose destination address is a specific mesh address, and selectively stop the STAs. The pause duration can be as long as the CCW duration.

As described above, multichannel operation during CCW is described with reference to the example of FIG. 5. When MP A has data for MP B, MP A checks whether the following two conditions are true.

Condition 1: The presence of at least one available data channel

Condition 2: Transfer completed within cycle P

If both conditions are true, MP A selects any channel based on the channel usage vector (U). MP A transmits RTX 400 to MP B, and MP B transmits CTX 410 to MP A. If the channel is available, MP B uses the same channel index. If the channel is unavailable, MP B uses channel index 0 (common channel). When MP A receives the CTX 410 through the channel index, MP A updates the channel use vector U and performs backoff. If MP A does not receive CTX 410, MP A updates U and allocates NAV. Then, MP A and MP B switch channels. MP A waits for DIFS for the network connection process. MP A then transmits data 420 to MP B. When TXOP (transmission opportunity) is valid, MP A sets the duration to extended interframe space (EIFS), and if TXOP is not valid, MP A sets the duration to Short Inter Frame Space (SIFS) + Set to ACK.

MP B transmits ACK 430. MP B does not switch channels if the duration is greater than SIFS + ACK; otherwise it switches to the common channel. When TXOP ends, MP A switches to the common channel. MP A and MP B are regarded as selected channels only in the free channel, and update the channel usage vector (U) accordingly. If an error occurs, MP A and MP B are tuned back to the common channel.

In operation after CCW, the MP does not reverse the selection of data channels that are approved during CCW. If the use of the data channel is available, the MPs can use the data channel by using the rules during CCW. If the data channel is unavailable and Tx completes within the period P, the MPs may begin transmission on the common channel according to conventional 802.11 rules. As described above, while the MPs A and B are transmitting and receiving data, the remaining MPs except for the MPs A and B buffer data or frames to be transmitted. This buffering is done until MPs located in every one hop can use the common channel. The frame is a non-unicast frame to be transmitted in multicasting or broadcasting, and occurs within period P and buffers this frame.

Different traffic  Scenario operation

In addition to supporting one-to-one communication between MPs, the framework supports traffic scenarios in which a large amount of BSS traffic is generated. If enough channels are available, each MAP places the BBS in a separate channel. MAPs can switch their BSS channel to the end of the CCW. The remaining MPs remain tuned to the common channel. Through this process, MAPs enable WDS traffic during CCW. MAP may also allow APs to use a common channel for BSS traffic within the framework.

STAs are not affected by the CCF. The main agents that switch channels are MPs and MAPs. Each MAP selects a BSS channel according to a procedure known in 802.11. Thus, accessing multiple BSS channels does not require new control or management frames. Selecting a longer delay time P minimizes scheduling and channel switching overhead. The detailed configuration for managing the scheduling of the parameters varies depending on the traffic pattern or network topology.

5 is a flowchart illustrating a multi-channel media access control method in a single air interface wireless LAN apparatus according to an embodiment of the present invention.

Referring to FIG. 5, when a frame (eg, a non-unicast frame) to be transmitted to adjacent MPs is generated from an application layer of the MP, a common channel commonly used in common with the adjacent MPs is sensed (S500 and S502). ). As a technique for detecting the common channel, the transceiver may be periodically detected between the MPs through a beacon frame. The beacon frame includes window P and CCW values of respective MPs. This detection is common to all MPs located in one hop. As a result of the detection, if the common channel is not available, the generated non unicast frame is buffered (S504 and S506). Using the common channel in step S504 means that all MPs located in one hop may use the common channel. As such, the reason why a predetermined MP can determine whether adjacent MPs can use a common channel can be determined through a beacon frame periodically transmitting and receiving between MPs. In addition, the frame buffered in step S504 is performed until all MPs located in one hop can use a common channel. In addition, the frame is buffered until a point at which transmission of a multicasting frame or a broadcasting frame is restarted. That is, such buffering starts when an update of a channel usage vector or an RTX / CTX exchange is detected, and until a new CCW starts. When the neighboring MPs become available in the process (S506), the buffered non-unicast frame is multicasted or broadcasted to the neighboring MPs (S508).

Hereinafter, a simulation result according to an embodiment of the present invention will be described.

The simulation tool of the present invention was performed via OPNET.

Nodes were configured to use the PHYs Physical Model of 802.11a. A bandwidth of 24 Mbit / s was used for data transmission and a bandwidth of 6 Mbit / s was used for control frames. The switching delay time was set to 100 microseconds. All devices are assumed to be in the radio band. Additional parameter settings are described in Table 1 below.

parameter value meaning T _slot 9㎲ Length of slot time T _DIFS 34㎲ Length of distributed interface area T _SIFS 16㎲ Short interface area length Payload 1500 Size of payload used for data frame T _SW 100㎲ Latency spent switching channels T _P 163 yen Cycle to repeat CCW T _CCW 16㎲ CCW duration

Two traffic scenarios were considered in detail. The first scenario, named the distributed WDS traffic scenario, is a scenario in which communication between a node in a network and any other node occurs. The second traffic scenario is a BSS-heavy traffic scenario, in which the MAPs have a certain amount of WDS traffic in addition to the BSS traffic.

Dispersion WDS traffic  scenario

For the purposes of the simulation, it is assumed that the source and destination pairs do not change during the period P (eg 10 milliseconds). Five examples are shown with 1, 2, 3, 4, and 8 MP pairs. Of each MP pair, if one MP is the source, the remaining MPs are assumed to sink.

6 is a diagram showing the aggregate yield and channel utilization as the number of MP pairs increases according to an embodiment of the present invention.

Referring to FIG. 6, when the maximum MP pair has eight pairs, orthogonal channels independent of each other are provided to each communication MP pair along with a common channel. The aggregate yield is linearly proportional to the number of channels. 6 also displays channel utilization along with aggregate yield. The channel utilization rate is defined by the following Equations 3 and 4.

U _DC = ∑ (2T _SW + T _DIFS + T _DATA + T _SIFS + T _ACK ) / T _sim

U _CC = ∑ (T _DIFS + T _RTX + T _CTX + T _SIFS ) / T _sim

In Equation 3, U _DC means channel utilization rate of the target channel, and in Equation 4, U _CC means channel utilization rate of the common channel. T _RTX , T _CTX , T _DATA and T _ACK refer to propagation occupancy times of the respective RTX, CTX, DATA and ACK frames. T _sim is the simulation time.

Until four MP pairs are on the channel, the use of the destination channel remains 85% on all channels, and the use of the common channel increases by about 20%. With eight MP pairs, the use of common channels goes up to 40% and the use of data channels goes down to 70%. The use of the data channel decreases rapidly when the MP pairs return to the common channel because the MP pairs wait for transmission because of the probability that the exchange of RTX / CTX frames rapidly increases. The wait time depends on the loss of the target channel utilization.

7 is a diagram showing the total yield by different control options as the number of MP pairs increases according to an embodiment of the present invention.

Referring to FIG. 7, the effect of the number of available channels is also simulated. In other words, the number of MP pairs was fixed at 4 and the number of available channels was increased from 1 to 4. Three different control options apply. 1) Tx on DC exclusive indicates that data frame transmission can occur only on the target channel and not on the common channel. 2) Tx on CC except CCW indicates that data frame transmission can occur in common channel only after CCW. 3) Tx on CC incl. CCW indicates that the transmission of data frames can always occur on a common channel.

As shown in FIG. 7, it can be seen that when two channels are available and transmission of data frames on the CC is not allowed, the total yield decreases. When there are three or more channels available, the aggregate yield increases linearly. Since CCW is part of period P, the contribution of CCW is Tx on CC except CCW and Tx on CC incl. In the case of CCW it is very minimal.

8 is a diagram illustrating channel utilization rates by different control options as the number of MP pairs increases according to an embodiment of the present invention.

Referring to FIG. 8, if data frames can be transmitted on a common channel, the channel utilization rate of the common channel defined in Equation 4 increases as shown in FIG. 8. As the utilization rate of the common channel increases, the probability that the destination channel diverges decreases. Therefore, the total yield of three or four channels is smaller than the total yield of 'Tx on DC exclusive'.

BSS - heavy traffic  scenario

9 is a diagram illustrating a topology used in a BBS-heavy traffic scenario according to an embodiment of the present invention.

Referring to FIG. 9, MAPs include BSS traffic as well as WDS traffic. In this scenario, it is assumed that the BSS traffic of the MAP is more concentrated than the WDS traffic. WDS traffic is only applied during CCW. If the BSS network is located on another channel (ie, not common channel), the MAPs switch to the BSS channel after CCW.

The number of MAPs is 1 or 2, and each MAP includes two or four STAs. The simulation results of the scenario are summarized in Table 2 (yield of single channel MAC ≒ 16.05 Mbit / s).

# MAPs # STAs per MAP Yield (Mbit / s) Use channel WDS BSS1 BBS2 One 2 31.170 0.967 0.828 N / A 4 31.978 0.964 0.875 N / A 2 2 46.476 0.963 0.827 0.827 4 48.099 0.948 0.875 0.875

In the case of 1 MAP, two channels (common channel and another channel) are used, and in the case of 2 MAP, three channels are used. In the case of a single channel, the increase in yield is noticeable when the maximum yield is 16.05 Mbit / s. As we have seen, the CCF allows BSS traffic located on other channels while providing the possibility to handle WDS traffic as well.

The present invention has been described in detail so far, but the embodiments mentioned in the process are only illustrative, and are not intended to be limiting, and the present invention is provided by the following claims. Within the scope not departing from the scope of the present invention, component changes to the extent that they can be equivalently substituted from the present invention will fall within the scope of the present invention.

As described above, the multi-channel medium access control apparatus and method for a single air interface wireless LAN device according to the present invention conforms to the IEEE 802.11 standard, and does not require a device with multiple air interface multi-channel medium access control method In addition, the present invention also provides a multi-channel medium access control method in which a simple and extended framework is supported in different traffic scenarios.

In addition, when the channel matching window starts from the start of the window repeated in a predetermined period, the common channel is detected. As a result, when the common channel is in use, the frame loss is prevented by buffering a non-unicast frame to be transmitted. .

Claims (29)

In the medium access control method of a single air interface wireless LAN device, Detecting a common channel when the channel matching window starts from a start point of a window repeated at a predetermined period; Allocating at least two or more devices to a destination channel using a channel usage vector indicating whether each of the plurality of channels is used during the started channel matching window; And transmitting and receiving a frame to the allocated destination channel. The method of claim 1, wherein the transmission and reception process is And returning to the common channel when the frame transmission and reception is successful. The method of claim 1, further comprising: buffering the frame to be transmitted when an update of a channel usage vector and / or a message exchanged between adjacent devices is detected; And transmitting the buffered frame if the neighboring devices are able to use the common channel. The method of claim 3, wherein the message exchanged And updating the channel usage vector and / or request to switch (RTX) and clearing to switch (CTX) frames. The method of claim 3, wherein the buffering is The multi-channel medium access control method made up to the time when the channel matching window is repeated every predetermined period. The method of claim 1, The channel usage vector is U = [ u ₁ , u ₂ , .., u _N ], u _i ∈ {0,1}, u _i = 0 is u _i Multi-channel media access control method indicating that this is available, and u _i = 1 indicates that u _i is in use. The method of claim 1, The channel usage vector is And resetting according to a list of available channels at the start of the channel matching window. The method of claim 1, Each of the devices And updating the channel usage vector according to whether a switching request is successful. The method of claim 1, Among the devices, a device having a connection point function And transmitting a Clear Response Switch (CTX) frame such that STAs (STAs) are inactive before starting the channel matching window. The method of claim 1, Among the devices, a device having a connection point function A multi-channel medium access control method for setting a duration field covering a period deviating from a common channel. The method of claim 1, And the devices that do not succeed in allocating a channel during the channel matching window can allocate a channel based on their channel usage vector even after the channel matching window. The method of claim 1, wherein the frame A multichannel media access control method comprising a non-unicast frame. In the medium access control method of a single air interface wireless LAN device, Detecting a common channel when a channel matching window starts from a start point of a window repeated at a predetermined period; If the common channel is in use, buffering a frame; And when the new channel matching window starts, transmitting and receiving the buffered frame through the common channel. The method of claim 13, wherein the frame is A method of controlling a multi-channel media access, wherein an update of a channel usage vector and / or a message exchanged between adjacent devices is detected or a channel usage vector is updated. 15. The method of claim 14, wherein said message is And a request and response message of the frame transmission. 15. The method of claim 14, wherein the channel usage vector is U = [ u ₁ , u ₂ , .., u _N ], u _i ∈ {0,1}, u _i = 0 is u _i A multichannel media access control method indicating that this is available and u _i = 1 indicates that u _i is in use. 15. The method of claim 14, wherein the channel usage vector is And resetting according to a list of available channels at the start of the channel matching window. 15. The method of claim 14, wherein a device having an access point function among the adjacent devices transmits a clear response signal (CTX) frame so that its stations are inactive before the channel matching window starts. . 14. The method of claim 13, wherein the device that is not successful in allocating a channel during the channel matching window allocates a channel based on its channel usage vector even after the channel matching window. In a single air interface wireless LAN device, A channel detector for detecting a common channel when a channel matching window starts from a start point of a window repeated at a predetermined period; A controller for allocating at least two or more devices to a destination channel using a channel usage vector indicating whether each of the plurality of channels is used during the started channel matching window; And a transmitter / receiver for transmitting and receiving a frame by using the allocated destination channel. The method of claim 20, wherein the control unit And if a device located on one hop occupies the common channel, buffering the frame to be transmitted until all devices can use the common channel. The method of claim 21, wherein the buffering is And updating a channel usage vector and / or a request to switch (RTX) and a response to a clear to switch (CTX) frame. The method of claim 21, wherein the buffering is And a multi-channel medium access control device starting for each channel matching window repeated every predetermined period. The method of claim 20, The channel use vector is represented by U = [ u ₁ , u ₂ , .., u _N ], u _i ∈ {0,1}, and u _i = 0 is u _i A multi-channel media access control device indicating that this is available, and u _i = 1 indicating that u _i is in use. The method of claim 20, And each device updates the channel usage vector according to whether a switching request is successful. The method of claim 20, And a device having an access point function of the devices transmits a clear response signal (CTX) frame so that their stations (STAs) are inactive before the channel matching window starts. The method of claim 20, And a device having an access point function of the devices sets a duration field covering a period away from a common channel. The method of claim 20, And any pair of devices that did not succeed in allocating a channel during the channel matching window may assign a channel based on its channel usage vector even after the channel matching window. The method of claim 20, wherein the frame is Multi-channel media access control device comprising a non-unicast frame (non-unicast frame).

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