Extended AC management in multi-user EDCA transmission mode in wireless networks

Abstract

To overcome loss of QoS handling resulting from introduction of MU UL OFDMA transmission.SOLUTION: A device according to the present invention has: first communication means that performs communication conforming to EDCA on the basis of a first contention parameter and transmits at least one of an RTS signal and a CTS signal; transmission means that transmits data to the other device with a resource unit (RU) conforming to the IEEE802.11 series standard; second communication means that, when the transmission means transmits data of a first access category (AC) to the other device with the RU, performs communication conforming to a first period EDCA corresponding to the first AC on the basis of a second contention parameter, and when the transmission means transmits data of a second AC to the other device with the RU, performs communication conforming to a second period EDCA corresponding to the second AC on the basis of a third contention parameter; and switching means that, in response to lapse of a first period from when the second communication means transmits the data of the first AC with the RU or in response to lapse of a second period from when the communication means transmits the data of the second AC with the RU, switches from the communication performed by the second communication means to the communication performed by the first communication means.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention broadly relates to a communication network, and more specifically to a communication network that provides nodes with channel access through competition for transmitting data, and provides nodes with secondary access to subchannels (or resource units) that divide the transmit opportunity TXOP permitted to the access point.

[0002] The present invention is applicable to wireless communication networks, and in particular to 802.11ax networks that provide nodes with access to OFDMA resource units that enable the formation of 802.11ax composite channels and / or, for example, 802.11ax composite channels authorized to access points, and enable uplink communication. [Background technology]

[0003] The IEEE 802.11MAC standard specifies how wireless local area networks (WLANs) must operate at the physical and media access control (MAC) levels. Typically, the 802.11MAC (media access control) operating mode implements a well-known distributed coordination function (DCF) that relies on a competition-based mechanism based on the so-called "collision-avoiding carrier detection multiple access" (CSMA / CA) technique.

[0004] The 802.11 media access protocol standard or mode of operation primarily concerns the management of communication nodes waiting for wireless media to become idle in order to attempt to access it.

[0005] The network operating modes defined by the IEEE 802.11ac standard provide very high throughput (VHT) by, among other things, shifting from the 2.4 GHz band, which is considered highly susceptible to interference, to the 5 GHz band, thereby enabling the use of a wider 80 MHz continuous frequency channel. Two of these channels can be optionally combined to form a 160 MHz channel as the operating bandwidth for the wireless network.

[0006] The 802.11ac standard also fine-tunes control frames such as the Request to Transmit (RTS) frame and Ready to Transmit (CTS) frame to enable composite channels with variable bandwidths of 20 MHz, 40 MHz, or 80 MHz, as well as fixed bandwidths. These composite channels consist of one or more consecutive communication channels within the operating bandwidth. A 160 MHz composite channel is possible by combining two 80 MHz composite channels within a 160 MHz operating bandwidth. The control frame specifies the channel width (bandwidth) of the composite channel in question.

[0007] Therefore, the composite channel consists of a primary channel in which a given node performs the EDCA backoff procedure to access the medium, and at least one secondary channel. These primary and secondary channels are, for example, 20 MHz each.

[0008] EDCA (Enhanced Distributed Channel Access) defines traffic categories and four corresponding access categories that allow for different handling of high-priority traffic compared to low-priority traffic.

[0009] The implementation of EDCA at a node can be performed using a plurality of traffic queues (known as "access categories") that serve data traffic at various priorities. Each traffic queue is associated with a respective queue backoff value. The queue backoff value is calculated from respective queue contention parameters, such as EDCA parameters, and is used to compete for access to the communication channel to transmit the data stored in the traffic queue.

[0010] Conventional EDCA parameters include the CW min of each traffic queue, max CW min and AIFSN. CW max and CW

[0011] are the lower and upper boundaries of the selection range from which the EDCA contention window CW is selected for a given traffic queue. AIFSN represents the number of arbitration inter-frame space numbers, and is the number of time slots (usually 9 μs) added to the DIFS interval (the total number defining the AIFS period) that a node must detect the medium as idle before decrementing the queue backoff value associated with the traffic queue under consideration.

[0012] The contention window CW and the queue backoff value are EDCA variables.

[0013] The conventional EDCA backoff procedure consists of the node selecting the queue backoff value of a traffic queue from the respective contention window CW, and then decrementing the queue backoff value when it detects the medium as idle after the AIFS period. When the backoff value reaches 0, the node is permitted to access the medium.

[0014] The EDCA queue backoff value or counter thus serves two roles. First, the EDCA queue backoff value puts the node in a state where it can efficiently access the medium by reducing the risk of collisions. Second, the EDCA queue backoff value mirrors the aging of data in the traffic queue (the older the data, the smaller the backoff value), and thus provides quality of service (QoS) management by providing different priorities to traffic queues through different values of EDCA parameters (especially the AIFSN parameter that delays the start of decrementing the EDCA queue backoff value).

[0015] By means of the EDCA backoff procedure, a node can thus access a communication network using a contention-based access mechanism based on queue contention parameters, usually based on a calculated queue backoff counter or value.

[0016] The primary channel is used by a communication node to detect whether the channel is idle, and the primary channel can be extended using one or more secondary channels to form a composite channel. The primary channel can also be used alone.

[0017] When the operating band is tree decomposed into basic 20 MHz channels, some secondary channels are called tertiary or quaternary channels.

[0018] In 802.11ac, all transmissions include a primary channel, and therefore, any possible composite channel includes a primary channel. This is because a node performs full carrier detection multiple access / collision avoidance (CSMA / CA) and network allocation vector (NAV) tracking only for the primary channel. Other channels are assigned as secondary channels, and for secondary channels, a node only has the ability of CCA (Clear Channel Evaluation), i.e., the ability to detect the idle or busy state / status of that secondary channel.

[0019] The problem with using composite channels, as defined in 802.11n or 802.11ac (or 802.11ax), is that nodes compliant with the use of composite channels (i.e., "HT nodes" representing 802.11n-compliant nodes and 802.11ac-compliant nodes or high-throughput nodes) must coexist with legacy nodes in the same wireless network that cannot use composite channels and rely only on the conventional 20MHz channel (i.e., non-HT nodes that only comply with 802.11a / b / g), and therefore must share the same 20MHz channel.

[0020] To address this issue, the 802.11n, 802.11ac, and 802.11ax standards provide the possibility of establishing the required TXOP protection across the entire composite channel by duplicating control frames (e.g., RTS / CTS frames or self-CTS (CTS-to-Self) frames, or ACK frames acknowledging the correct or erroneous reception of transmitted data) in the 802.11a legacy format (referred to as "non-HT") across each 20 MHz channel.

[0021] This ensures that any legacy 802.11a node using any of the 20MHz channels involved in the composite channel is aware that communication is underway on that 20MHz channel. As a result, legacy nodes are prevented from initiating new transmissions until the current composite channel TXOP permitted to the 802.11n / ac / ax node has finished.

[0022] As originally proposed by 802.11n, a replica of the conventional 802.11a transmission or "non-HT" transmission is provided to allow the simultaneous transmission of two identical 20 MHz non-HT control frames on both the primary and secondary channels forming the composite channel used.

[0023] This technique is an extension of 802.11ac to enable replication across channels forming a composite channel of 80 MHz or 160 MHz. In this specification, “replicated non-HT frame” or “replicated non-HT control frame” or “replicated control frame” means that a node device replicates a given control frame’s conventional or “non-HT” transmission across a secondary 20 MHz channel (which may be more than one) in the operating bandwidth (40 MHz, 80 MHz, or 160 MHz).

[0024] In practice, to request a new TXOP composite channel (40MHz or higher), the 802.11n / ac node performs the EDCA backoff procedure on the primary 20MHz channel, as described above. In parallel with this, during the PIFS interval before the start of the new TXOP (i.e., before any queue backoff counter expires), the node performs channel detection mechanisms, such as Clear Channel Evaluation (CCA) signal detection, on the secondary channels to detect one or more idle secondary channels (channel state / status is "idle").

[0025] More recently, the Institute of Electrical and Electronics Engineers (IEEE) officially recognized the 802.11ax Task Group as the successor to 802.11ac. The primary goal of the 802.11ax Task Group is to explore ways to improve data rates for wireless communication devices used in high-density deployment scenarios.

[0026] Recent developments in the 802.11ax standard have focused on optimizing the use of composite channels by multiple nodes in wireless networks with access points (APs). Indeed, typical content, such as high-definition audiovisual real-time / interactive content, involves large amounts of data. Furthermore, it is well known that the performance of the CSMA / CA protocol used in the IEEE 802.11 standard deteriorates rapidly as the number of nodes and the volume of traffic increase, i.e., in high-density WLAN scenarios.

[0027] In this context, multi-user (MU) transmission has been considered to enable multiple simultaneous transmissions in both the downlink (DL) direction from the AP to various users and the uplink (UL) direction from various users to the AP during the transmission opportunities permitted to the AP. On the uplink, multi-user transmission can be used to reduce the probability of collisions by enabling multiple non-AP stations or nodes to transmit simultaneously.

[0028] To actually perform such multi-user transmissions, it has been proposed to divide the permitted communication channel into subchannels, also called resource units (RUs), which are shared by multiple users (non-AP stations / nodes) in the frequency domain, for example, based on the orthogonal frequency division multiplexing access (OFDMA) technique. Each RU can be defined by multiple tones, i.e., an 80 MHz channel containing up to 996 usable tones.

[0029] OFDMA is a multi-user variation of OFDM that has emerged as a new key technology to improve efficiency in advanced infrastructure-based wireless networks. OFDMA combines OFDM on the physical layer with Frequency Division Multiple Access (FDMA) on the MAC layer to enhance simultaneity, allowing different subcarriers to be assigned to different stations / nodes. Consecutive subcarriers often receive similar channel states and are therefore grouped into subchannels. Thus, an OFDMA subchannel, or RU, is a set of subcarriers.

[0030] As is currently assumed, the granularity of such OFDMA subchannels is finer than the original 20MHz channel bandwidth. Typically, a subchannel of 2MHz or 5MHz can be considered as the minimum width, and therefore, within a single 20MHz channel, for example, nine subchannels or resource units can be defined.

[0031] OFDMA's multi-user characteristics allow APs to allocate / provide different RUs to different non-AP stations / nodes to increase competition. This can help reduce contention and conflicts within an 802.11 network.

[0032] Unlike downlink OFDMA (supported by a specific indication within the PLCP header), which allows an AP to send multiple data directly to multiple stations, a trigger mechanism is employed that allows an AP to trigger multi-user uplink (MU UL) OFDMA communication from various nodes.

[0033] During a pre-empted TXOP, in order to support multi-user uplink transmission, i.e., uplink transmission to an 802.11ax access point (AP), the 802.11ax AP must provide signaling information for the legacy nodes (non-802.11ax nodes) to configure their NAVs and for the 802.11ax nodes to determine the allocation of resource units (RUs) provided by the AP.

[0034] The 802.11ax standard defines the trigger frame (TF) that an AP sends to an 802.11ax node to trigger multi-user uplink communication.

[0035] The IEEE 802.11-15 / 0365 document proposes that an AP (Application Platform) (AP) sends a "trigger" frame (TF) to request the transmission of uplink (UL) multi-user (OFDMA) PPDUs from multiple nodes. The TF specifies the resource units provided to the nodes by the AP. In response, the nodes transmit an UL MU (OFDMA) PPDU as an immediate response to the trigger frame. All transmitters can transmit data simultaneously using dissimilar sets of RUs (i.e., frequencies in the OFDMA scheme), resulting in less interference transmission.

[0036] The bandwidth or width of the target composite channel is signaled in the TF frame, meaning that a value of 20MHz, 40MHz, 80MHz, or 160MHz is added. The TF frame is transmitted over the primary 20MHz channel and, where appropriate, duplicated (copied) onto the other 20MHz channels that form the target composite channel. As described above regarding the duplication of control frames, any consecutive legacy nodes (non-HT nodes or 802.11ac nodes) receiving the TF on their primary channel are expected to set their NAV to the value specified in the TF. This prevents these legacy nodes from accessing the channels of the target composite channel during TXOP.

[0037] Resource units (RUs) can be reserved for specific nodes, in which case the application platform (AP) will display the nodes on which the RUs are reserved in the resource platform (TF). Such RUs are called scheduled RUs. The displayed nodes do not need to experience conflicts when accessing the scheduled RUs reserved for that node.

[0038] The types of data that a node is permitted to transmit in a scheduled RU can be specified by the AP in the TF. For example, the TF includes a 2-bit "Priority AC" field that indicates the AP is using one of four EDCA traffic queues. On the other hand, the AP can open up a scheduled RU to any type of data. To activate or deactivate the "Priority AC," the TF includes another 1-bit field, namely the "AC Priority Level."

[0039] To better improve the system's efficiency with respect to unmanaged traffic to an AP (e.g., uplink-managed frames from associated nodes or unassociated nodes intended to reach the AP, or simply unmanaged data traffic), an AP can propose resource units (RUs) to 802.11ax nodes through contention-based access. In other words, a resource unit (RU) can be randomly accessed by two or more nodes (of a group of nodes registered with the AP). Such an RU is called a random RU and is shown as a random RU in the TF. A random RU can serve as a fundamental element for contention among nodes intending to access the communication medium to transmit data.

[0040] An exemplary random resource selection procedure is described in the IEEE 802.11-15 / 1105 document. According to this procedure, each 802.11ax node maintains a dedicated backoff engine that competes for access to one of the random RUs using RU contention parameters, including an RU backoff value. This dedicated backoff engine is hereafter referred to as the OFDMA backoff engine or the RU (representing resource units) backoff engine. When the node's OFDMA backoff value or RU backoff value reaches 0 (this backoff value is decremented, for example, in each new TF-R frame by the number of random RUs specified in that frame), it becomes eligible for RU access and therefore randomly selects one RU from all the random RUs specified in the received trigger frame. The node then uses the selected RU to transmit data from at least one of the traffic queues.

[0041] As is immediately apparent from the above, the multi-user uplink media access method (or OFDMA access method or RU access method) makes it possible to reduce the number of collisions that occur due to simultaneous media access attempts, and also reduces the overhead caused by media access because the media access cost is shared among several nodes. The OFDMA access method or RU access method therefore appears to be considerably more efficient (in terms of media usage) than the conventional EDCA competition-based media access method (for high-density 802.11 cells).

[0042] While OFDMA or RU access methods appear more efficient, EDCA access methods must also be retained and therefore must coexist with OFDMA or RU access methods.

[0043] This is primarily due to the existence of legacy 802.11 nodes that still need access to media, but these nodes are unaware of OFDMA or RU access methods. Furthermore, overall fairness regarding media access must be ensured.

[0044] 802.11ax nodes also increasingly need to have the opportunity to access media through traditional EDCA competition-based media access, for example, to send data to other nodes (i.e., to obtain traffic different from uplink traffic to APs).

[0045] Therefore, the two media access methods, EDCA access and OFDMA / RU access, must coexist.

[0046] This coexistence has its disadvantages.

[0047] For example, 802.11ax nodes and legacy nodes have the same media access probability when using the EDCA access method. However, 802.11ax nodes have additional media access opportunities using MU uplinks, OFDMA access methods, or RU access methods.

[0048] As a result, access to media is not entirely fair between 802.11ax nodes and legacy nodes.

[0049] To restore some degree of fairness among these nodes, a solution has been proposed in which, upon successful transmission of data through an accessed resource unit (i.e., via UL OFDMA transmission), the current value of at least one queue contention parameter is changed to a penalty value or degraded value, thereby reducing the probability that a node will access the communication channel through (EDCA) contention. For example, the penalty value or degraded value is more restrictive than the original value (i.e., the legacy value).

[0050] For example, the IEEE 802.11-16 / 1180 document titled "Proposed text changes for MU EDCA parameters" proposes that, upon successful transmission of data (MU UL OFDMA) in a resource unit RU reserved by an AP, the node will be set to MU EDCA mode for a predetermined duration counted down by a timer (indicated by HEMUEDCATimer, representing a High Efficiency Multi-User EDCA Timer). In this MU EDCA mode, the EDCA parameters are set to values ​​called MU EDCA parameter values ​​or MU values, which are different from the legacy values ​​used in legacy EDCA mode. The MU parameter values ​​are set to more restrictive values ​​than the legacy values. More restrictive values ​​for the EDCA parameters mean that the probability of a node accessing a communication channel through the EDCA access method using MU values ​​is reduced compared to access using legacy values.

[0051] In other words, as soon as a node sends some data from one or more traffic queues using a scheduled RU assigned to it by the AP, it will modify the EDCA parameters associated with the transmission traffic queue(s) (hereinafter referred to as "degraded," "penalized," or "blocked" traffic queue(s)(s)) using several special and more restrictive ("MU" or "degraded") values. These values ​​may be provided by the AP in a dedicated information element of the beacon frame, including the values ​​used by the node for their HEMUEDCATimer.

[0052] Therefore, AP can note that when a node successfully transmits data through an accessed resource unit, it sends a more restrictive value to the node that drives it to change the current values ​​of those EDCA parameters to MU values. This also reduces the probability that a node will access the communication channel through the EDCA access method.

[0053] In addition, the AP can determine more specific values ​​based on the history of data received from the node (for example, through the RU).

[0054] The disclosed method increases only the AIFSN value of each transmit traffic queue, while CW min and CW max It is proposed to maintain this without change. As the corresponding AIFS period increases, especially in high-density environments where media are not left vacant for extended periods, traffic queues in MU EDCA mode will not have their queue backoff value or counter decremented (or at least significantly delayed) when it is detected that the media is not in use. New access to media using the EDCA access method will be statistically significantly reduced or may even become impossible.

[0055] When a node switches to MU EDCA mode, it begins counting down its HEMUEDCATimer. Each time a node successfully sends data (MU UL OFDMA) on a newly reserved RU, the HEMUEDCATimer is reinitialized. A large value (e.g., tens of milliseconds) is proposed for the HEMUEDCATimer's initialization to accommodate several new opportunities for MU UL transmissions.

[0056] Once HEMUEDCATimer has elapsed, the traffic queue in MU EDCA mode switches back to legacy EDCA mode with legacy EDCA parameters, thereby ending the queue's MU EDCA mode.

[0057] Therefore, this dual-operation mechanism of the conventional EDCA mode and MU EDCA mode promotes the use of the MU UL mechanism by reducing the probability that the MU UL transmit node accesses the medium using the EDCA mechanism.

[0058] The HEMUEDCATimer mechanism, which reinitializes the HEMUEDCATimer each time a node successfully sends new data via an accessed reserved RU, means that as long as the AP provides the node with (scheduled or random) RUs, the node will remain in the MU EDCA state.

[0059] This method has the following main drawbacks.

[0060] When a node transmits data from two or more traffic queues in one or more resource units provided by an AP (for example, if a dedicated traffic queue becomes empty, the node selects other data to be transmitted from a traffic queue with a higher priority), these two or more traffic queues are set to MU mode and a more limited EDCA mode. These traffic queues are primarily prevented from accessing the medium through the EDCA access method, for example, because their respective AIFSNs are very limited.

[0061] It is possible that an AP may periodically provide resource units to a node (in such a situation) using a display of the priority traffic queue from which data is selected.

[0062] As long as this polling using the priority traffic queue continues, when a node accesses the provided resource unit, it will empty the corresponding traffic queue while keeping two or more traffic queues in MU EDCA mode. This means that one or more other traffic queues remain locked in MU mode and / or more limited EDCA mode and cannot be purged by accessing the medium.

[0063] Therefore, QoS in the network deteriorates severely. [Overview of the project] [Problems that the invention aims to solve]

[0064] This invention aims to overcome the above limitations. In particular, this invention aims to overcome the loss of QoS handling caused by the introduction of MU UL OFDMA transmission. [Means for solving the problem]

[0065] The inventors have found that locking other traffic queues in MU competition modes such as the MU EDCA mode is due to having a HEMUEDCATimer that is reinitialized each time data from the same priority traffic queue is transmitted (periodically) to the resource unit. Therefore, the unity of HEMUEDCATimer that simultaneously manages all traffic queues in MU competition mode is considerably detrimental to QoS.

[0066] Therefore, the present invention aims to restore QoS by breaking the unity of HEMUEDCATimer.

[0067] In this context, the present invention relates to a communication method in a communication network comprising multiple nodes, wherein at least one node comprises multiple traffic queues serving data traffic with different priorities, each traffic queue is associated with a respective queue backoff value calculated from its respective queue conflict parameter having a legacy value in legacy conflict mode and used to compete for access to a communication channel to transmit data stored in the traffic queue, and the method comprises, at the node, We propose a method comprising: transmitting data stored in two or more traffic queues in one or more accessed resource units provided by another node within one or more transmission opportunities permitted to another node on the communication channel; and, upon transmitting data in each accessed resource unit, setting each transmit traffic queue to a different MU conflict mode (i.e., transmitting in the accessed resource unit) for a predetermined duration counted down by a timer associated with the transmit traffic queue, wherein in the MU conflict mode, the respective queue conflict parameters are set to MU values ​​different from the legacy values; and, upon the expiration of either timer, switching the associated (degenerate) traffic queue back to the legacy conflict mode, where the respective queue conflict parameters are set back to the legacy values.

[0068] Therefore, the present invention proposes using a dedicated HEMUEDCATimer for each AC queue so that each AC queue can exit MU competition mode independently of other AC queues.

[0069] You can use either a hardware-implemented timer or a software-implemented timer.

[0070] Therefore, fairness is restored between the two race modes of the 802.11ax node.

[0071] A traffic queue's MU value differing from its legacy value means that the MU value and legacy value of at least one identical conflict parameter are different from each other, regardless of whether the MU values ​​and legacy values ​​of other conflict parameters are equal or different.

[0072] Accordingly, the present invention also provides a communication device node in a communication network comprising multiple nodes, comprising multiple traffic queues serving data traffic in different priorities, each traffic queue associated with a queue backoff value calculated from a respective queue conflict parameter having a legacy value in legacy conflict mode and used to compete for access to a communication channel to transmit data stored in the traffic queue, and a plurality of timers, each associated with one of the traffic queues, and the following steps, i.e., within one or more transmission opportunities permitted to another node on the communication channel, one or more accessed A microprocessor configured to perform the following steps in a resource unit: sending data stored in two or more traffic queues; setting each transmit traffic queue to a different MU race mode from the legacy race mode for a predetermined duration counted down by an associated timer, wherein each queue race parameter in the MU race mode is set to an MU value different from the legacy value; and switching back to the legacy race mode when either timer expires, the associated (degenerate) traffic queue is set back to the legacy value. This also relates to communication device nodes that are equipped with such features.

[0073] This device node has the same advantages as the method described above.

[0074] Optional features of the present invention are defined in the appended claims. Some of these features are described below in relation to the method, but these features can be replaced with features of a system dedicated to any device node according to the present invention.

[0075] In this embodiment, the predetermined durations used to initialize the timers associated with each of the two traffic queues are different from each other. This configuration improves QoS management.

[0076] In other embodiments, the predetermined (preferably degraded) duration used to initialize the timer associated with each traffic queue is calculated from a common initialization value received from the other node and adjustment parameters specific to each traffic queue. Therefore, by combining the common initialization value and adjustment parameters of the AC queues, it becomes easy to adjust the duration for which each AC queue should remain in MU competition mode. This configuration also improves QoS management.

[0077] In the modified configuration, the predetermined duration used to initialize the timer associated with each traffic queue is set to the respective initialization value received directly from the other node. In other words, the other node, such as the AP, directly drives the duration for which each AC queue should remain in MU competition mode.

[0078] Therefore, other nodes, such as APs, can have a complete overview of the network (including conflict statistics and the number of nodes), enabling efficient management of QoS. Consequently, prioritizing such AC queues becomes easier, and the network becomes more efficient as a result.

[0079] In some embodiments, the timer associated with each traffic queue is reinitialized for the corresponding predetermined duration each time data from the associated traffic queue is transmitted to an accessed resource unit provided by another node within any subsequent transmission opportunity permitted to that node on the communication channel.

[0080] This means that the AC queue timer expires only if no data from this AC queue is sent to any resource unit provided by another node during the predetermined duration that initialized the timer. Otherwise, the timer is reinitialized.

[0081] As a result, this traffic queue can exit MU contention mode by restoring its respective queue contention parameters to legacy values ​​only if no data from the AC queue under consideration is sent via OFDMA within a specified duration.

[0082] In an embodiment, the method further includes the node competing for access to the communication channel using the queue competition parameters in the MU competition mode. This means that the MU competition mode follows the same competition scheme as a legacy competition mode, such as conventional EDCA, but has MU competition parameters, preferably degenerate (i.e., more restrictive) competition parameters, in order to penalize AC queues polled by APs for transmission at the RU.

[0083] In this embodiment, the method further includes the node periodically receiving beacon frames from an access point, and each beacon frame broadcasts network information about the communication network to the plurality of nodes. At least one received beacon frame includes the legacy value and the MU value of the queue contention parameter of the plurality of traffic queues, and at least one initialization value that initializes the timer to the predetermined duration associated with the traffic queue.

[0084] In the embodiment, one or more of the transmit traffic queues are set to the MU competition mode only when the transmission of the data in the corresponding accessed resource unit is successful. This configuration ensures fairness. In fact, the basic idea of ​​switching the competition mode is that the MU mode should only be implemented to compensate for the existence of other transmission opportunities (in this case, through RUs), which means that the transmission of data is successful.

[0085] In some embodiments, the MU value includes a degraded number of arbitration interframe spaces (AIFSN) compared to the legacy value. This configuration is easy to implement to directly reduce (to a desired level) the opportunity for a particular traffic queue to access the medium through EDCA.

[0086] In particular, each queue backoff value can be initially selected from its respective conflict window, and the queue backoff value is decreased over time by the node to access the communication channel once it reaches 0. The MU value of the queue contention parameter is the same as the lower boundary CW value as the legacy value. min and / or upper boundary CW max This may include the two boundaries which define the selection range from which the size of the conflict window is selected.

[0087] This configuration eliminates the need to modify the conflict window, thus simplifying entry and exit to and from MU conflict mode (MU EDCA mode). However, in variant forms, it is possible to consider having different boundaries between legacy values ​​and MU values.

[0088] In some embodiments, the method further includes, when the node accesses a resource unit provided by the other node within a subsequent transmission opportunity permitted to the other node, selecting data from the traffic queue in both MU competition mode and legacy competition mode based on the associated current queue backoff value, and transmitting the selected data in the accessed resource unit within the new transmission opportunity.

[0089] Therefore, when implementing the present invention, fair management of QoS is maintained.

[0090] According to certain characteristics, selecting data involves selecting data from the traffic queue associated with the smallest current queue backoff value. Thus, behavior similar to EDCA of AC queues is maintained.

[0091] In an alternative embodiment, the method further includes, at the node, accessing a resource unit provided by the other node within a subsequent transmission opportunity permitted to the other node, selecting data from a preferred traffic queue indicated by the other node, and transmitting the selected data at the accessed resource unit within the new transmission opportunity.

[0092] According to certain features, the priority traffic queue indicator is included in a trigger frame received from the other node, which reserves the transmission opportunity permitted to the other node on the communication channel and defines the resource unit RU that forms the communication channel, including the accessed resource unit.

[0093] This method allows another node, which is normally an access point (AP), to drive QoS management.

[0094] In some embodiments of the present invention, the accessed resource unit on which the data is transmitted is a random resource unit whose access is performed through competition using separate RU competition parameters (separate from the queue competition parameters described above).

[0095] In another embodiment, the accessed resource unit from which the data is transmitted is a scheduled resource unit, and the scheduled resource is allocated to the node by the other node.

[0096] Of course, some nodes can access scheduled RUs while others can access random RUs, resulting in various nodes being in MU competition mode (for one or more AC queues) at the same time.

[0097] In some embodiments, the other node is an access point of the communication network to which the node is registered. This configuration takes advantage of the central location of the access point.

[0098] From the perspective of an access point, the present invention relates to a communication method in a communication network comprising a plurality of nodes and an access point, wherein each node comprises a plurality of traffic queues serving data traffic with different priorities, and each traffic queue is associated with a respective queue backoff value calculated from its respective queue conflict parameter having a legacy value in legacy conflict mode and used to compete for access to a communication channel to transmit data stored in the traffic queue. The proposed method includes the access point accessing the communication channel to reserve a transmission opportunity on the communication channel and transmitting a trigger frame that defines resource units RU that form the communication channel on which the node transmits data to the access point; transmitting to the node a set of legacy values ​​for the queue contention parameters, a set of MU values ​​for the queue contention parameters that are different from the set of legacy values, and a set of initialization values ​​for a node timer associated with the traffic queue, so that each of the two or more traffic queues of the node is configured to switch between an MU contention mode in which each of the queue contention parameters is set to an MU value and a legacy contention mode in which each is initialized based on the associated initialization value and maintained for a predetermined duration counted down by the associated timer, wherein each of the queue contention parameters in the MU contention mode is set to its respective MU value.

[0099] Accordingly, the present invention relates to an access point in a communication network also comprising a plurality of nodes, each node comprising a plurality of traffic queues serving data traffic with different priorities, each traffic queue associated with a respective queue backoff value calculated from its respective queue conflict parameter having a legacy value in legacy conflict mode and used to compete for access to a communication channel to transmit data stored in the traffic queue, the access point comprising the following steps: accessing the communication channel to reserve a transmission opportunity on the communication channel and transmitting a trigger frame that defines resource units RU that form the communication channel from which the node transmits data to the access point, and the queue conflict parameter We also propose an access point comprising at least one microprocessor configured to perform the steps of configuring each node when each of two or more traffic queues on the node switches between a legacy conflict mode in which each of the queue conflict parameters is set to a legacy value and an MU conflict mode in which the queue conflict parameters are initialized based on the associated initialization value and maintained for a predetermined duration counted down by the associated timer, wherein in the MU conflict mode, each of the queue conflict parameters is set to its respective MU value.

[0100] Therefore, access points can efficiently control fairness within the network. In fact, through MU values ​​and timer values, access points can drive nodes to coordinate their EDCA access schemes under MU competition modes, which differ from the traditional legacy mode.

[0101] Preferably, the legacy value, the MU value, and the timer value can be evaluated based on, in particular, the history of past transmissions from the node in the RU (random RU or scheduled RU) provided by the access point.

[0102] Optional features of the present invention are defined in the appended claims. Some of these features are described below with respect to methods, but those features can be replaced with features of a system specialized for any device node according to the present invention.

[0103] In some embodiments, the set of legacy values, the set of MU values, and the set of initialization values are transmitted within one or more beacon frames that are periodically transmitted by the access point that broadcasts network information about the communication network to the plurality of nodes.

[0104] In still other embodiments, the set of legacy values and the set of MU values differ depending on different arbitration interframe space numbers AIFSN.

[0105] In particular, each queue backoff value of the node can be selected first from the respective contention window, and the queue backoff value is decreased over time by the node to access the communication channel when it reaches 0. The set of legacy values and the set of MU values have the same lower bound CW min and / or upper bound CW max and can include both, and both boundaries together define a selection range in which the size of the contention window associated with the traffic queue is selected respectively.

[0106] Another aspect of the present invention relates to a non - transient computer - readable medium that stores a program that causes a device to execute any method as defined above when executed by a microprocessor or computer system within the device.

[0107] This non-temporary computer-readable medium may have features and advantages similar to those presented above and below with respect to the above method and device.

[0108] Another aspect of the present invention relates substantially to methods described herein with respect to and shown in the accompanying drawings, specifically Figure 5b, or Figure 11, or Figures 11 and 12, or Figures 11, 12 and 14b, or Figures 11, 12 and 14c.

[0109] At least some parts of the methods according to the present invention can be implemented by computer. Therefore, the present invention may take the form of a completely hardware embodiment, a completely software embodiment (including firmware, resident software, microcode, etc.), or a combination of software and hardware embodiments. All of these hardware and software are collectively referred to herein as “circuits,” “modules,” or “systems.” Furthermore, the present invention may take the form of a computer program product embodied in any tangible medium of expression in which computer-usable program code is realized.

[0110] Since the present invention can be implemented in software, it can be embodied as computer-readable code provided to a programmable device on any suitable carrier medium. The tangible carrier medium may include storage media such as hard disk drives, magnetic tape devices, or solid memory devices. The temporary carrier medium may include signals such as electrical signals, electronic signals, optical signals, acoustic signals, magnetic signals, or electromagnetic signals, such as microwave or RF signals.

[0111] Further advantages of the present invention will become apparent to those skilled in the art by examining the drawings and the detailed description. Embodiments of the present invention are described below as mere examples with respect to the following drawings. [Brief explanation of the drawing]

[0112] [Figure 1] This figure shows a typical wireless communication system that can implement embodiments of the present invention. [Figure 2a] This diagram shows the IEEE 802.11e EDCA with access categories. [Figure 2b] This diagram shows the IEEE 802.11e EDCA with access categories. [Figure 2c] This figure shows an example of values ​​for the degenerate EDCA parameter set. [Figure 3a] This diagram shows the 802.11ac mechanism for backoff counter countdown. [Figure 3b] This figure shows an example of the mapping between the eight priority levels of traffic classes and the four EDCA AC levels. [Figure 4] This figure shows an example of an 802.11ax uplink OFDMA transmission scheme, as known in the technology, in which the AP issues a trigger frame to reserve a transmission opportunity for an OFDMA subchannel (resource unit) on an 80MHz channel. [Figure 4a] This figure shows 802.11ac channel allocations that support channel bandwidths of 20 MHz, 40 MHz, 80 MHz, or 160 MHz, as known in the technology. [Figure 5a] This diagram shows the state of the transmit traffic queue that can be switched in MU EDCA mode, as known in conventional technology. [Figure 5b] This figure shows the state of the transmit traffic queue that can be switched in MU EDCA mode according to an embodiment of the present invention. [Figure 6] This figure shows a schematic representation of a communication device or communication station according to an embodiment of the present invention. [Figure 7] This figure shows a schematic representation of a wireless communication device according to an embodiment of the present invention. [Figure 8] This figure shows an exemplary transmission block of a communication node according to an embodiment of the present invention. [Figure 9] In an embodiment of the present invention, the flowchart shows the main steps performed by the MAC layer of a node when it receives new data to be transmitted. [Figure 10] This flowchart shows the steps for accessing a medium based on an EDCA medium access scheme in both situations having non-degenerate EDCA parameters or degenerate EDCA parameters, according to embodiments of the present invention. [Figure 11] This flowchart shows the steps of accessing a resource unit based on a RU or OFDMA access method upon receiving a trigger frame defining a RU, according to an embodiment of the present invention. [Figure 12] This flowchart shows the node management switching back to the non-degraded mode according to an embodiment of the present invention. [Figure 13] This diagram shows the structure of the trigger frame as defined in the 802.11ax standard. [Figure 14a] This diagram shows the structure of standardized information elements used to describe EDCA parameters in a beacon frame. [Figure 14b] This figure shows an exemplary structure of a dedicated information element for transmitting degenerate EDCA parameter values ​​and HEMUEDCATimer values ​​according to an embodiment of the present invention. [Figure 14c] This figure shows an exemplary structure of a dedicated information element for transmitting degenerate EDCA parameter values ​​and HEMUEDCATimer values ​​according to an embodiment of the present invention. [Modes for carrying out the invention]

[0113] Next, the present invention will be described by certain non-limiting exemplary embodiments with reference to the figures.

[0114] Figure 1 shows a communication system in which several communication nodes (or communication stations) 101-107 exchange data frames over a wireless transmission channel 100 of a wireless local area network (WLAN) under the management of a central station or access point (AP) 110 to which the nodes are registered. The wireless transmission channel 100 is defined by an operating frequency band consisting of a single channel or multiple channels forming a composite channel.

[0115] Access to a shared wireless medium for transmitting data frames is based on CSMA / CA techniques, which detect carriers and avoid collisions by separating simultaneous transmissions in space and time.

[0116] In CSMA / CA, carrier detection is performed through both physical and virtual mechanisms. Virtual carrier detection is achieved by sending a control frame that reserves the medium before transmitting the data frame.

[0117] Next, the source node, i.e., the transmitting node, including the AP, first attempts to detect, through a physical mechanism, any medium that has been idle for at least one DIFS (representing DCF interframe spacing) time period before sending the data frame.

[0118] On the other hand, if the shared wireless medium is detected to be busy during the DIFS period, the source node will continue to wait until the wireless medium becomes idle.

[0119] To access the medium, the node starts a countdown backoff counter designed to expire after a randomly selected number of CW (integer) time slots within the so-called conflict window [0, CW]. This backoff mechanism or procedure, also called the channel access scheme, is the fundamental principle of collision avoidance mechanisms, delaying transmission time by a random interval and thus reducing the probability of collisions on a shared channel. After the backoff time period (i.e., after the backoff counter reaches 0), the source node can transmit a data frame or control frame if the medium is idle.

[0120] One problem with wireless data communication is that the source node cannot listen while transmitting, and therefore is unable to detect data corruption caused by channel fading, channel interference, or collision phenomena. The source node continues to transmit frames unnecessarily without realizing that the transmitted data frames are corrupted, and thus wastes access time.

[0121] Therefore, the CSMA / CA collision avoidance mechanism, upon successful reception of a frame, provides an acknowledgment (ACK) from the receiving node to the source node, notifying it that the transmitted data frame has not been corrupted.

[0122] An ACK is sent at the end of receiving a data frame immediately following a time period called a short interframe space (SIFS).

[0123] If the source node does not receive an ACK within the specified ACK timeout, or if it detects the transmission of a different frame on the channel, it can infer data frame loss. In that case, the source node generally reschedules the frame transmission according to the backoff procedure described above.

[0124] To improve the collision avoidance efficiency of CSMA / CA, a four-way handshake mechanism is optionally implemented. One embodiment is known as the RTS / CTS replacement as specified in the 802.11 standard.

[0125] The RTS / CTS exchange, during a transmission opportunity called TXOP in the 802.11 standard, involves exchanging control frames before transmitting data frames to reserve the radio medium and thus protect data transmission from further collisions. The four-way CTS / RTS handshake mechanism is well known and therefore will not be described further here. For further details, please refer to the standard.

[0126] The RTS / CTS four-way handshake mechanism is highly efficient from a system performance standpoint, especially for large frames, because it reduces the length of messages involved in competing processes.

[0127] In detail, assuming complete channel detection by each communication node, collisions can only occur when two (or more) frames are transmitted within the same time slot after DIFS (DCF Interframe Space), or when the backoff counters of two (or more) source nodes reach zero almost simultaneously. If both source nodes are using the RTS / CTS mechanism, this collision can only occur with RTS frames. Fortunately, such collisions are detected early by the source node if no CTS response is received.

[0128] Quality of Service (QoS) management is implemented at the node level in such wireless networks through the well-known EDCA mechanism specified in the IEEE 802.11e standard.

[0129] In fact, the original DCF standard only allowed a communication node to have one transmit queue / buffer. However, because subsequent data frames could not be transmitted until the transmission / retransmission of the preceding frame was complete, the delay caused by the transmission / retransmission of the preceding frame prevented the communication from having QoS.

[0130] Figures 2a and 2b illustrate the IEEE 802.11e EDCA mechanism with access categories to improve quality of service (QoS).

[0131] The 802.11e standard relies on a control function called Hybrid Control Function (HCF), which has two operating modes: Extended Distributed Channel Access (EDCA) and HCF-Controlled Channel Access (HCCA).

[0132] EDCA enhances or extends the functionality of the original access DCF method. Specifically, EDCA is designed to support prioritized traffic, similar to DiffServ (Differentiated Service), a protocol that specifies and controls network traffic by class so that certain types of traffic are given priority.

[0133] EDCA is a dominant channel access method or mechanism in WLANs because it features a distributed and easily deployable mechanism. This method involves a node competing for access to at least one communication channel in the communication network using a conflict parameter in order to transmit locally stored data over the accessed communication channel.

[0134] The aforementioned deficiency, which prevents satisfactory QoS due to frame retransmission delays, is resolved by using multiple transmission queues / buffers.

[0135] QoS support in EDCA is achieved by introducing four access categories (ACs), thereby introducing four corresponding transmit / traffic queues or buffers (210). Typically, the four ACs are, in descending order of priority, voice (or "AC_VO"), video (or "AC_VI"), best effort (or "AC_BE"), and background (or "AC_BG").

[0136] Of course, we can also consider a different number of traffic queues.

[0137] Each AC has its own traffic queue / buffer that stores the corresponding data frames transmitted over the network. Data frames arriving from higher layers of the protocol stack, i.e., MSDUs, are mapped to one of the four AC queues / buffers and are therefore fed into the mapped AC buffer.

[0138] Each AC also has its own set of queue contention parameters, associated with priority values, and thus defining the traffic of high-priority or low-priority MSDUs. Therefore, there are multiple traffic queues, each serving data traffic at a different priority. Queue contention parameters are typically per traffic queue CW min Parameters, CW max Includes parameters, AIFSN parameters, and TXOP_Limit parameters. CW min and CW maxThese are the lower and upper boundaries of the selection range that the EDCA conflict window CW selects for a given traffic queue. AIFSN represents the number of inter-frame arbitration spaces and specifies the number of time slots (usually 9μs) that are added to the DIFS interval (the total number that defines the AIFS period) that a node must detect as idle before decrementing the queue backoff value / counter associated with the traffic queue under consideration. TXOP_Limit specifies the maximum size of a TXOP that a node can request.

[0139] In other words, each AC (and its corresponding buffer) operates as an independent DCF contention entity with its own queue backoff engine 211. Thus, each queue backoff engine 211 is associated with its own traffic queue 210 for using queue contention parameters and setting its own queue backoff value / counter (randomly selected from CW) which is used to cause access contention to at least one communication channel in order to transmit the data stored in its respective traffic queue over the accessed communication channel.

[0140] The conflict window (CW) and queue backoff value / counter are known as EDCA variables.

[0141] As a result, ACs within the same communication node compete with each other to access the wireless medium and obtain transmission opportunities, for example, using conventional EDCA access methods as described above.

[0142] Service differentiation between ACs is different CWs min , CW max This is achieved by setting different queue back-off parameters between ACs, such as AIFSN and / or different transmit opportunity duration limits (TXOP_Limit). This contributes to adjusting QoS.

[0143] Access to the medium using the AIFSN parameter and queue back-off value in the EDCA mechanism is described below with reference to Figure 3a.

[0144] Figure 2b shows CW min Parameters, CW max The default values ​​for the parameters and AIFSN parameters are shown.

[0145] In this table, the typical values ​​for aCWmin and aCWmax are defined as 15 and 1023, respectively, in the aforementioned standard. Other values ​​can be set by nodes (usually access points) within the network and shared among nodes. This information can be broadcast in beacon frames.

[0146] To determine the delay AIFS[i] between detecting that the medium is not in use and the start of the queue backoff value decrement for traffic queue "i", the node multiplies the value indicated in the AIFSN parameter of traffic queue "i", i.e., AIFSN[i], by the time slot duration (typically 9 microseconds) and adds this value to the DIFS duration.

[0147] As shown in Figure 3a, each traffic queue consequently waits for an AIFS[i] period (including a DIFS period that delays access to the medium) before decrementing its associated queue backoff value / counter. This figure shows two AIFS[i] corresponding to two different ACs. It can be seen that one prioritized traffic queue begins decrementing its backoff value earlier than the other lower-priority traffic queue. This situation is repeated after each new medium access by any node in the network.

[0148] In addition to generally lower CW usage, this decrement deferral mechanism gives high-priority traffic a greater chance of being transmitted within EDCA than low-priority traffic. In other words, nodes with high-priority traffic will, on average, wait slightly less before transmitting their packets than nodes with low-priority traffic.

[0149] The EDCA queue backoff value, or counter, therefore serves two purposes. Firstly, the EDCA queue backoff value ensures that nodes can efficiently access the medium by reducing the risk of collisions. Secondly, the EDCA queue backoff value mirrors the aging of data contained in the traffic queue (the older the data, the smaller the backoff value), and therefore provides quality of service (QoS) management by offering different priorities to the traffic queue through different values ​​of EDCA parameters (particularly the AIFSN parameter, which delays the start of the decrement of the EDCA queue backoff value).

[0150] Referring to Figure 2a, buffers AC3 and AC2 are typically reserved for real-time applications (e.g., transmission of audio AC_VO or video AC_VI). These buffers have the highest and second highest priority, respectively.

[0151] Buffers AC1 and AC0 are reserved for best-effort (AC_BE) traffic and background (AC_BG) traffic, respectively. These buffers have the second lowest priority and the lowest priority, respectively.

[0152] Each data unit (MSDU) that reaches the MAC layer from a higher layer with a certain priority (e.g., the link layer) is mapped to an AC according to a mapping rule. Figure 3b shows an example of mapping between eight traffic class priorities (user priorities according to IEEE 802.1d, i.e., UP0-7) and four ACs. The data frame is then stored in a buffer corresponding to the mapped AC.

[0153] Once the traffic queue (or AC) backoff procedure is complete, the MAC controller of the transmitting node (reference numeral 704 in Figure 7 below) sends data frames from this traffic queue to the physical layer for transmission over the wireless communication network.

[0154] Since ACs operate simultaneously when accessing the wireless medium, it is possible for two ACs on the same communication node to terminate their backoff at the same time. In such a situation, the MAC controller's virtual collision handler (212) selects the AC with the highest priority among the colliding ACs (as shown in Figure 3b) and abandons the transmission of data frames from the ACs with lower priority.

[0155] Subsequently, the virtual collision handler instructs the AC with lower priority to restart the backoff operation using the increased CW value.

[0156] The QoS obtained as a result of using AC can be signaled in the QoS control field included in the header of a MAC data frame, for example, an IEEE 802.11e MAC frame.

[0157] To meet the growing demand for faster wireless networks that support applications using a lot of bandwidth, 802.11ac aims for greater bandwidth transmission through multi-channel operation. Figure 4a shows the 802.11ac channel allocation supporting combined channel bandwidths of 20 MHz, 40 MHz, 80 MHz, or 160 MHz.

[0158] IEEE 802.11ac introduces support for a limited number of default subsets of 20MHz channels that form their own default composite channel configuration, which are available for reservation by any 802.11ac node on a wireless network transmitting data.

[0159] These default subsets are shown in the diagram and correspond to channel bandwidths of 20MHz, 40MHz, 80MHz, and 160MHz, compared to only 20MHz and 40MHz supported by 802.11n. In fact, the 20MHz component channels 300-1 to 300-8 are concatenated to form a wider communication composite channel.

[0160] In the 802.11ac standard, the channels in each of the specified 40MHz, 80MHz, or 160MHz subsets are contiguous within the operating frequency band. That is, no holes (missing channels) are permitted in the ordered composite channels within the operating frequency band.

[0161] The 160MHz channel bandwidth consists of two 80MHz channels, which may or may not have consecutive frequencies. The 80MHz channel and the 40MHz channel each consist of two adjacent or consecutive 40MHz and 20MHz channels, respectively. On the other hand, the present invention may have embodiments having a channel bandwidth composition that includes only consecutive channels or a composition formed from discontinuous channels within the operating bandwidth.

[0162] Nodes are permitted to use TXOP via the Extended Distributed Channel Access (EDCA) mechanism on the “primary channel” (400-3). In fact, for each composite channel with a certain bandwidth, 802.11ac designates one channel as “primary,” meaning it is used for access contention to the composite channel. The primary 20MHz channel is common to all nodes (STAs) belonging to the same basic set, i.e., all nodes managed by or registered with the same local access point (AP).

[0163] On the other hand, to ensure that other legacy nodes (i.e., nodes not belonging to the same set) do not use the secondary channel, it is provided that control frames (e.g., RTS frames / CTS frames) reserving the composite channel are duplicated through each 20MHz channel of such composite channel.

[0164] As discussed above, the IEEE 802.11ac standard allows for the combination of up to four 20MHz channels, and even up to eight 20MHz channels. Due to the limited number of channels (19 in the 5GHz band in Europe), channel saturation becomes a problem. In fact, in densely populated areas, the 5GHz band tends to saturate even when each wireless LAN cell uses a bandwidth of 20MHz or 40MHz.

[0165] The developments in the 802.11ax standard aim to improve the efficiency and utilization of wireless channels in high-density environments.

[0166] From this perspective, we can consider multi-user (MU) transmission characteristics that enable multiple simultaneous transmissions in both the downlink (DL) and uplink (UL) directions between various users and the main node, which is typically an AP. In the uplink, multi-user transmission can be used to reduce the probability of collisions by enabling multiple nodes to transmit to the AP simultaneously.

[0167] To actually perform such multi-user transmissions, it has been proposed to divide the permitted 20MHz channels (400-1 to 400-4) into subchannels 410 (basic subchannels), also called subcarriers or resource units (RUs). These subchannels are shared in the frequency domain by multiple users, for example, based on the orthogonal frequency division multiple access (OFDMA) technique.

[0168] This will be explained with reference to Figure 4.

[0169] OFDMA's multi-user characteristics allow nodes, which are typically access point APs, to assign different RUs to different nodes to encourage competition. This can help reduce contention and conflicts within an 802.11 network.

[0170] Unlike MU downlink OFDMA (supported by specific indications within the PLCP header), which allows an AP to directly send multiple data to multiple nodes, a trigger mechanism is employed where the AP triggers MU uplink communication from various nodes.

[0171] To support MU uplink transmission (during TxOP pre-acquired by the AP), the 802.11ax AP must provide signaling information for both legacy nodes (non-802.11ax nodes) to configure their NAVs and for 802.11ax nodes to determine resource unit allocation.

[0172] In the following explanation, the term "legacy" refers to a non-802.11ax node, meaning an 802.11 node using older technologies that do not support OFDMA communication.

[0173] As shown in the example in Figure 4, the AP transmits a trigger frame (TF) 430 to the target 802.11ax node. The bandwidth or width of the target composite channel is signaled in the TF frame, meaning that a value of 20MHz, 40MHz, 80MHz, or 160MHz is signaled. The TF frame is transmitted over the primary 20MHz channel and duplicated (copied) onto each other's 20MHz channels that form the target composite channel. As described above regarding the duplication of control frames, any consecutive legacy nodes (non-HT nodes or 802.11ac nodes) that receive the TF frame (or its duplicate) on their primary channel are expected to set their NAV to the value specified in the TF frame. This prevents these legacy nodes from accessing the channels of the target composite channel during the TXOP.

[0174] Based on the AP's decision, the trigger frame TF can define a number of resource units (RUs) 410, or "random RUs," that network nodes can randomly access. In other words, the random RUs designated or allocated by the AP in the TF can function as a fundamental element of competition between nodes intending to access the communication medium to transmit data. A collision occurs when two or more nodes attempt to transmit simultaneously through the same RU.

[0175] In that case, the trigger frame is called a random access trigger frame (TF-R). An AP can emit a TF-R so that multiple nodes can perform MU UL (Multi-User Uplink) random access and obtain RUs for their UL transmissions.

[0176] A trigger frame (TF) can specify scheduled resource units (RUs) in addition to, or instead of, random RUs. Scheduled RUs can be reserved by an AP for certain nodes, in which case no contention is required for access to those RUs. Such RUs and their corresponding scheduled nodes are indicated within the trigger frame. For example, to explicitly indicate which nodes can use each scheduled RU, a node identifier, such as an Association ID (AID) assigned to each node during registration, is added to the TF frame in association with each scheduled RU.

[0177] An AID equal to 0 can be used to identify a random RU.

[0178] OFDMA's multi-user characteristics allow access points (APs) to assign different RUs (Resource Units) to different nodes to encourage competition. This can help reduce contention and conflicts within an 802.11 network.

[0179] In the example in Figure 4, each 20 MHz channel (400-1, 400-2, 400-3, or 400-4) is subdivided in the frequency domain into four subchannels, or RU410, each typically 5 MHz in size.

[0180] Of course, the number of RUs dividing the 20MHz channel can be different from four. For example, two to nine RUs can be provided (so each has a size of 10MHz to approximately 2MHz).

[0181] When a node sends data to an AP using a RU, the AP responds with an acknowledgment (ACK) (not shown) to indicate that it has received the data on each RU. This allows each node to know whether the data transmission was successful (received an ACK) or unsuccessful (no ACK received after the time limit expires).

[0182] The IEEE 802.11-15 / 1105 document provides an exemplary random allocation procedure that a node can use to access a random RU indicated in a TF. This random allocation procedure, called the RU competition scheme, is managed by a dedicated RU access module separate from the channel access module described above, and is configured to manage access to at least one resource unit provided by another node (usually an AP) within a transmission opportunity permitted to that node on the communication channel for transmitting locally stored data through the accessed resource unit. Preferably, the RU access module includes a separate RU backoff engine from the queue backoff engine. This RU backoff engine competes for access to the random RU using RU competition parameters, which include a calculated RU backoff value.

[0183] In other words, the RU competition scheme is based on a new backoff counter called an OFDMA backoff counter / value or RU backoff counter / value (i.e., OBO) inside the 802.11ax node that allows dedicated competition when accessing random RUs to transmit data.

[0184] Each node STA1 to STAn is a transmitting node to a receiving AP, and as a result, each node has an active RU backoff engine separate from the queue backoff engine for calculating an RU backoff value (OBO) used to cause contention for access to at least one random resource unit that divides the permitted transmit opportunities on the communication channel in order to transmit data stored in any of the traffic queue ACs.

[0185] The random assignment procedure described herein includes a first step of determining from the trigger frame a random subchannel or RU of the communication medium available for competition for a node among a plurality of nodes having an active RU backoff value OBO; a second step of checking whether the value of the active RU backoff value OBO local to the node under consideration is less than or equal to the number of random RUs detected as available; and a third step of randomly selecting a random RU from the random RUs detected as available for transmitting data if it is confirmed to be less than or equal to the number of random RUs. If the second step is not confirmed, a fourth step (instead of the third step) is performed to decrement the RU backoff value OBO by the number of RUs detected as available.

[0186] As illustrated, within a resource unit, there are unused resource units (410u) where nodes with an RU backoff value (OBO) smaller than the number of available random RUs have not randomly selected one of these random RUs, while other resource units (e.g., 410c) experience collisions because two of these nodes randomly selected the same RU.

[0187] The MU Uplink (UL) media access scheme, which includes both scheduled and random RUs, is significantly more efficient than the conventional EDCA access scheme. This is because it reduces both the number of collisions caused by simultaneous media access attempts and the overhead associated with media access.

[0188] On the other hand, the EDCA access method and the MU UL OFDMA / RU access method must coexist, particularly in order to enable legacy 802.11 nodes to access the media and to enable 802.11ax nodes to initiate communication with nodes other than APs.

[0189] While the EDCA access scheme alone provides equitable access to the medium across all nodes, when this scheme is combined with the MU UL OFDMA / RU access scheme, equitable access is subject to drift. This is because, compared to legacy nodes, 802.11ax nodes have additional opportunities to transmit data through other nodes, particularly resource units provided during authorized transmission opportunities to APs.

[0190] Solutions have been proposed to restore some degree of fairness between nodes.

[0191] For example, in concurrently pending UK application No. 1612151.9, filed on July 13, 2016, if data transmission is successful through an accessed resource unit (i.e., via UL OFDMA transmission), the current value of at least one EDCA parameter is changed to a different value (MU EDCA parameter). This is to reduce the probability that a node will access the communication channel through (conventional EDCA) contention.

[0192] Within this framework, a mechanism has been proposed to reduce the probability that a node will perform an EDCA-based transmission (i.e., one using an EDCA medium access scheme) immediately after it successfully transmits its data using the MU UL mechanism. This reduction is achieved by modifying well-known EDCA parameters.

[0193] The proposed mechanism, as described in the IEEE 802.11-16 / 1180 document titled "Proposed text changes for MU EDCA parameters," sets each transmit traffic queue to MU EDCA mode in response to the successful transmission of data in the accessed MU UL OFDMA resource unit. This setting is performed for a predetermined duration known as HEMUEDCATimer. MU EDCA mode is a mode in which each EDCA parameter is set to a different MU value than the legacy value used in different legacy EDCA modes.

[0194] To switch from legacy EDCA conflict access mode to MU EDCA mode, the node sets the EDCA parameters (AIFSN, CW) of that node for all traffic queues that have successfully transmitted some data in the accessed resource unit. min , and / or CW max ) can be changed. Switching back to legacy EDCA mode can be done when HEMUEDCATimer expires. Note that this timer is reset to its initial value each time a node sends new data again (from any AC) between newly accessed resource units provided by the AP. A large value (e.g., tens of milliseconds) is proposed for the initialization value of HEMUEDCATimer to accommodate several new opportunities for MU UL transmission.

[0195] The MU value of the EDCA parameter can be transmitted by the AP in a dedicated information element. This information element is typically transmitted within a beacon frame that broadcasts network information to nodes.

[0196] The disclosed method increases only the AIFSN value of each transmit traffic queue, while CW min and CW maxIt is proposed to maintain this without change. As the corresponding AIFS period increases, when it is detected that the medium is no longer in use, each traffic queue in MU EDCA mode will not have its queue backoff value or counter decremented (or at least will be significantly delayed). New access to the medium using the EDCA access method will be statistically significantly reduced or even impossible for the aforementioned predetermined duration.

[0197] The MU mode AIFSN value can be very limited. Therefore, in high-density environments where the media is busy most of the time (and thus only available for very short periods), nodes in MU EDCA mode must wait for the corresponding very limited AIFS period, and thus, in MU EDCA mode, the AC queue backoff value is not decremented very often. As a result, nodes cannot experience EDCA access contention to the media very often.

[0198] Note that certain configurations in published documentation tend to completely prevent the transmission traffic queue from accessing the medium via EDCA while in MU EDCA mode (except when the network is not being used at all). The AP specifies this particular mode of operation by indicating a specific value (usually 0) for the AIFSN parameter in the set of MU EDCA parameters. Such a specific value means that for a node, that node uses a very large value for its AIFSN. This value is equal to the HEMUEDCATimer transmitted by the AP (recall that this value should be large, compared to the minimum AIFS[i] of less than 0.1 milliseconds in legacy EDCA mode, and should be around several tens of milliseconds).

[0199] Unfortunately, as long as a node periodically accesses an OFDMA RU and sends data, that traffic queue in MU EDCA mode will remain in the same MU mode. This is especially true for traffic queues in MU mode that do not uniformly send data on the accessed OFDMA RU over what can be very long periods of periodic OFDMA access. This contradicts the QoS principles described in the 802.11e standard.

[0200] Next, this situation will be explained with reference to Figure 5a. Figure 5a shows an example of an application using MU EDCA parameters as described in the publication mentioned above.

[0201] In the scenario shown in this diagram, AP501 polls node 502 by sending a standardized trigger frame 1300 requesting the node to send some QoS data from the AC_VI access category. This can be done by providing that node with one or more scheduled RUs. The category can be shown in the “Preferred AC” field 1330 shown in Figure 13.

[0202] After the SIFS time, node 502 initiates a MU UL OFDMA transmit 510 by picking up some QoS data (511) from the requested traffic queue AC_VI. In this exemplary scenario, the requested traffic queue AC_VI does not contain enough QoS data ready for transmit. In this situation, node 502 is allowed to retrieve other QoS data (512) from a higher priority traffic queue, for example, the AC_VO access category in this example. This data retrieval rule makes it possible to maximize bandwidth utilization as specified in the 802.11 standard.

[0203] Therefore, node 502 sends AC_VI data 511 and AC_VO data 512 to the AP using the scheduled RU. The two corresponding transmit traffic queues AC_VI and AC_VO then switch to MU EDCA mode (symbolized by white letters (figures) in black boxes), and node 502 then uses the MU EDCA parameter for each of these transmit traffic queues. In particular, a larger value for the AIFSN parameter can be used, and CW is optional. min Parameters and CW min Larger values ​​for the parameters can be used.

[0204] In parallel with this, when node 502 becomes capable of switching back to legacy EDCA mode with legacy EDCA parameters, HEMUEDCATimer 590 is started and counts down. This switching back can be performed after a predetermined duration has expired, i.e., when HEMUEDCATimer reaches 0.

[0205] On the other hand, HEMUEDCATimer is reinitialized to its initial value (a predetermined duration) each time node 502 transmits data on an accessed resource unit provided by the AP within any subsequent transmission opportunity permitted by the AP on the communication channel. In other words, the timer is reinitialized each time node 502 is polled again by the AP.

[0206] This occurs in the example in Figure 5a when AP501 sends a new trigger frame 1300-2 using a new RU from node 502 while HEMUEDCATimer590 has not yet expired. The AP then polls node 502 again to send QoS data from the AC_VI access category.

[0207] Node 502 again transmits QoS data 520 from the AC_VI access category, and HEMUEDCATimer 590 is reinitialized to its initial value, which is a predetermined duration. The same thing happens when AP 501 polls Node 502 again to transmit new QoS data from the AC_VI access category by sending a new trigger frame 1300-3.

[0208] In this scenario, node 502 is periodically polled by the AP to obtain OFDMA transmissions of QoS data from AC_VI. Ultimately, as long as sufficient data is provided by the AC_VI category, the AC_VO category will never be involved in any new OFDMA transmissions and will remain blocked in MU EDCA mode.

[0209] In addition, due to its MU mode AIFSN value (usually a more restrictive value, i.e., a large value), the traffic queue AC_VO is prevented (or severely delayed) from decrementing the associated backoff value for EDCA contention of the medium.

[0210] As a result, the AC_VO category, which essentially has the highest QoS priority, remains locked in MU EDCA mode without having a new EDCA opportunity to transmit its data. Therefore, the QoS requirements for 802.11ax remain severely degraded.

[0211] Within this framework, the present invention proposes restoring QoS fairness by breaking the unity of HEMUEDCATimer, which is locked in the event of periodic node polling by an AP in a traffic queue in MU mode.

[0212] In particular, if, within one or more transmission opportunities permitted to another node on a communication channel, data stored in two or more traffic queues is transmitted (preferably successfully transmitted) at each of the one or more accessed resource units provided by that other node, node 502 may set each transmission traffic queue (i.e., the traffic queue to be transmitted at the accessed resource unit) to a different MU EDCA mode from legacy EDCA mode for a predetermined duration counted down by the respective timers associated with that transmission traffic queue. Then, when either timer expires, node 502 may switch the associated traffic queue back to legacy EDCA mode, where the respective EDCA parameters are reset to legacy values.

[0213] The present invention thus provides a node having multiple timers, each timer associated with one of the traffic queues. Since a specific HEMUEDCATimer is dedicated to each AC queue, each AC queue can terminate MU EDCA mode independently of other AC queues. Thus, QoS at the AC queue level is restored.

[0214] Next, the results of one embodiment of the present invention will be described with reference to Figure 5b. Figure 5b describes the recovery of QoS through independent HEMUEDCATimer handling using the same sequence as in Figure 5a.

[0215] After the initial TF1300, both transmit traffic queues AC_VI and AC_VO are in MU EDCA mode. Their respective HEMUEDCATimer, namely HEMUEDCATimer591 for AC_VI and HEMUEDCATimer592 for AC_VO, are started and count down simultaneously when each traffic queue becomes capable of switching back to legacy EDCA mode with legacy EDCA parameters.

[0216] According to the present invention, the progress of these individual timers is independent of each other.

[0217] As explained below, different predetermined durations can be used to initialize these two timers associated with AC_VI and AC_VO. This is to improve QoS management.

[0218] Therefore, when the next TF1300-2 is received and AC_VI data is transmitted in the accessed OFDMA RU at the request of the AP, the HEMUEDCATimer591 associated with AC_VI is reinitialized with its corresponding predetermined initial duration, while the HEMUEDCATimer592 associated with AC_VO continues to elapse (because the VO data has not been transmitted in the accessed RU after TF1300-2).

[0219] As a result, HEMUEDCATimer592 associated with AC_VO expires before HEMUEDCATimer591 associated with AC_VI, and the MU EDCA constraint on traffic queue AC_VO is released. In fact, traffic queue AC_VO switches back to legacy EDCA mode, where legacy EDCA parameters are used. Therefore, the backoff value of the AC_VO traffic queue can be reduced as usual, allowing the AC_VO queue to efficiently compete for the medium.

[0220] Figure 6 schematically shows a communication device 600 of a wireless network 100 configured to carry out at least one embodiment of the present invention. The communication device 600 may preferably be a device such as a microcomputer, a workstation, or a lightweight portable device. The communication device 600 includes a communication bus 613. Preferably, the following are connected to this communication bus: • Central processing unit 611, represented by a CPU such as a microprocessor; • A read-only memory 607, indicated by ROM, for storing a computer program that implements the present invention; Random access memory 612, represented as RAM, for storing executable code for the method according to an embodiment of the present invention and registers adapted to record variables and parameters necessary for carrying out the method according to an embodiment of the present invention; and A wireless communication network 100, for example, at least one communication interface 602 connected to a wireless communication network compliant with the 802.11ax protocol, on which digital data packets or digital data frames or control frames are transmitted. The frame is either written from the FIFO transmit memory in RAM612 to the transmit network interface, or read from the receive network interface and written to the FIFO receive memory in RAM612, under the control of a software application running on CPU611.

[0221] The communication device 600 may optionally also include the following components: • Data storage means 604 such as a hard disk for storing a computer program that implements a method according to one or more embodiments of the present invention; Disk drive 605 of disk 606, adapted for reading data from or writing data to disk 606; Screen 609, which displays the decoded data and / or functions as a graphical interface with the user via the keyboard 610 or any other pointing means.

[0222] The communication device 600 can optionally be connected to various peripheral devices, such as a digital camera 608. Each peripheral device is connected to an input / output card (not shown) to supply data to the communication device 600.

[0223] Preferably, the communication bus provides communication and interoperability between various elements included in or connected to the communication device 600. The term "bus" is not limiting, and in particular, the central processing unit can be operated to communicate instructions directly to any element of the communication device 600 or through another element of the communication device 600.

[0224] Disk 606 can optionally be replaced with any information medium, such as a rewritable or non-rewritable compact disk (CD-ROM), ZIP disk, USB key, or memory card, and more broadly, with any information storage means. This information storage means can be read by a microcomputer or microprocessor, may or may not be built into the device, may be detachable, and is adapted to store one or more programs that, when executed, enable the implementation of the method according to the present invention.

[0225] The executable code can optionally be stored in read-only memory 607, hard disk 604, or a removable digital medium such as disk 606 as described above. In an optional variant, the program's executable code can be received via interface 602 using the communication network 603 for storage in one of the storage means of the communication device 600, such as hard disk 604, before execution.

[0226] The central processing unit 611 is preferably adapted to control and direct the execution of instructions or portions of the software code of one or more programs according to the present invention. These instructions are stored in one of the aforementioned storage means. When power is applied, one or more programs stored in non-volatile memory, for example, the hard disk 604 or the read-only memory 607, are transferred into the random access memory 612, which then includes the executable code of one or more programs and registers for storing variables and parameters necessary to carry out the present invention.

[0227] In a preferred embodiment, the device is a programmable device that implements the present invention using software. Alternatively, the present invention may be implemented in hardware (for example, in the form of an application-specific integrated circuit, i.e., an ASIC).

[0228] Figure 7 is a schematic block diagram illustrating one architecture of a communication device or node 600, particularly nodes 100-107, adapted to at least partially implement the present invention. As shown, node 600 comprises a physical (PHY) layer block 703, a MAC layer block 702, and an application layer block 701.

[0229] The PHY layer block 703 (here, the 802.11 standardized PHY layer) has the tasks of formatting a frame, modulating a frame onto any 20 MHz channel or composite channel, demodulating from any 20 MHz channel or composite channel, and transmitting and receiving the frame over the radio medium 100 used. The frame can be an 802.11 frame, for example, a medium access trigger frame TF430 defining resource units in an authorized transmission opportunity, a 20 MHz width MAC data management frame interacting with a legacy 802.11 station, and a MAC data management frame of OFDMA type with a width smaller than the 20 MHz legacy (typically 2 MHz or 5 MHz) between it and the radio medium.

[0230] The MAC layer block or controller 702 preferably comprises a MAC802.11 layer 704 that performs conventional 802.11ax MAC operation and an additional block 705 that at least partially performs the present invention. The MAC layer block 702 may optionally be implemented in software. This software is loaded into RAM 512 and executed by CPU 511.

[0231] Preferably, an additional block called the MU EDCA mode management module 705 performs the part of the invention relating to node 600, namely, managing the switching between the two modes, legacy mode and MU EDCA mode, and handling the various timers used to control each traffic queue in MU EDCA mode.

[0232] From the AP's perspective, the MU EDCA mode management module 705 can provide nodes with a set of legacy values ​​for the EDCA parameters, a set of MU values ​​for the EDCA parameters that differ from this set of legacy values, and a set of HEMUEDCATimer initialization values ​​that cause a node to enter MU EDCA mode to remain in such mode for at least a corresponding duration. These values ​​then drive each node to configure itself when one of the traffic queues of each node switches between legacy EDCA mode, where each EDCA parameter is set to a legacy value, and MU EDCA mode, where each EDCA parameter is set to a MU value, which is maintained for a predetermined duration initialized based on the associated initialization values ​​and counted down by an associated timer.

[0233] MAC802.11 layer 704 and the MU EDCA mode management module 705 interact with each other to provide management of the channel access module that handles the queue backoff engine and the RU access module that handles the RU backoff engine as described below.

[0234] At the top of the diagram, the application layer block 701 runs an application that generates and receives data packets, such as data packets for a video stream. The application layer block 701 represents all stack layers above the MAC layer according to ISO standards.

[0235] Next, embodiments of the present invention will be described using various exemplary embodiments. The proposed example uses a trigger frame 430 (see Figure 4) transmitted by the AP for multi-user uplink transmission, but an equivalent mechanism can be used in a centralized environment or an ad-hoc environment (i.e., without an AP). This means that any node in an ad-hoc environment can perform the operations described below with respect to the AP.

[0236] These embodiments are described primarily with respect to IEEE 802.11ax by considering OFDMA resource units. However, the applications of the present invention are not limited to those related to IEEE 802.11ax.

[0237] Furthermore, the present invention does not necessarily rely on the use of MU access schemes as described in 802.11ax. Any other RU access scheme that specifies an alternative media access scheme enabling simultaneous access by nodes to the same medium may also be used.

[0238] The set of MU values ​​can be more restrictive than the set of legacy values, resulting in fewer instances where traffic queues in MU EDCA mode access the media using the EDCA conflict access method.

[0239] On the other hand, the set of MU values ​​can be made more tolerant in some embodiments.

[0240] For clarity, the following explanation focuses on a more limited set of MU values. In this context, the MU EDCA mode is referred to as the “degenerate” mode, while the legacy EDCA mode is referred to as the “non-degenerate” mode.

[0241] Figure 8 shows an exemplary transmission block of a communication node 600 according to an embodiment of the present invention.

[0242] As described above, the node includes a channel access module and, in some cases, an RU access module. Both of these modules are implemented in MAC layer block 702. The channel access module includes the following: Multiple traffic queues 210 serving data traffic with different priorities; Multiple queue backoff engines 211. Each queue backoff engine is associated with a traffic queue that uses EDCA parameters, and in particular, with a traffic queue that calculates its respective queue backoff value, which is used to cause access conflicts on at least one communication channel in order to transmit the data stored in that traffic queue. This is the EDCA access scheme.

[0243] According to embodiments of the present invention, each queue backoff engine 211 has its own HEMUEDCATimer 2110. This means that a node has multiple timers, each timer associated with one of the traffic queues.

[0244] Furthermore, an EDCA mode switch 213 is provided within the node to handle switching between degenerate MU EDCA mode and legacy EDCA mode by updating EDCA parameters in accordance with the teachings of the present invention. This EDCA mode switch operates in response to each OFDMA transmission in the RU by the node.

[0245] The RU access module includes a separate RU backoff engine 800 from the queue backoff engine. This RU backoff engine 800 uses RU contention parameters to calculate an RU backoff value used to cause contention for access to an OFDMA random resource unit specified in a received TF (e.g., one sent by an AP) in order to transmit data stored in any traffic queue in an OFDMA RU. The RU backoff engine 800 is associated with a transmit module called an OFDMA maxer 801. For example, the OFDMA maxer 801 is responsible for selecting data to be transmitted from the AC queue 210 when the RU backoff value OBO, as described below, reaches 0.

[0246] The conventional AC queue backoff register 211 drives media access requests according to the EDCA protocol (channel contention access method), while the RU backoff engine 800 drives media access requests on the OFDMA multi-user protocol (RU contention access method).

[0247] Since these two competing access methods coexist, the source node implements a media access mechanism with collision avoidance based on the calculation of the following backoff value. - A queue back-off counter value corresponding to the number of time slots the node waits for (in addition to the DIFS period) after the communication medium is detected as idle and before accessing the medium. This is EDCA, whether in a degenerate or non-degenerate state. - A RU backoff counter value (OBO) corresponding to the number of idle random RUs detected by the node after TXOP has authorized the AP or any other node for a composite channel formed from RUs, but before accessing the medium. This is OFDMA. One variation of the OBO countdown based on the number of idle random RUs can be based on a time-based countdown.

[0248] Figure 9 shows, using a flowchart, the main steps performed by MAC layer 702 on node 600 when it receives new data to transmit. This figure illustrates conventional FIFO feeding related to 802.11.

[0249] Initially, at the start, none of the traffic queues 210 have data to send. As a result, the queue backoff value 211 is not calculated. The corresponding queue backoff engine or corresponding AC (Access Category) is said to be inactive. As soon as data is stored in the traffic queue, the queue backoff value is calculated (from the corresponding queue backoff parameters), and the associated queue backoff engine or AC is said to be active.

[0250] When a node has data ready to be transmitted on the medium, this data is stored in one of the AC queues 210, and the associated backoff 211 is updated.

[0251] In step 901, new data is received from an application running on the device (e.g., application layer 701), another network interface, or any other data source. This new data is then prepared for transmission by the node.

[0252] In step 902, the node determines which AC queue 210 the data should be stored in. This is typically done by examining the TID (Traffic Identifier) ​​value attached to the data (according to the matching shown in Figure 3b).

[0253] Next, step 903 stores the data in the determined AC queue. This means that the data is stored in an AC queue that has the same data type as the data in question.

[0254] In step 904, the conventional 802.11 AC backoff calculation is performed by the queue backoff engine associated with the determined AC queue.

[0255] If the determined AC queue was empty immediately before the memory in step 903 (i.e., the AC was initially inactive), a new queue backoff value must be calculated for the corresponding backoff counter.

[0256] The node then calculates the queue backoff value to be equal to a random value selected within the range [0, CW], where CW is the current value of the CW of the access category under consideration (as specified in the 802.11 standard). Note that the queue backoff value is added to the AIFSN (which may be degenerate in MU EDCA mode) to implement the relative priority of different access categories. CW is selected within the range [CW min ,CW max The congestion window value selected from ], and the boundary CW of both sides min and CW max (It may be degraded in some cases) depends on the access category being considered.

[0257] As a result, AC is activated.

[0258] The above parameters CW, CW min , CW max The AIFSN and backoff values ​​form the EDCA parameters and variables associated with each AC. They are used to set relative priorities for accessing media of different data categories.

[0259] EDCA parameters (for example, CW min , CW maxAnd AIFSN), while usually having a fixed value, the EDCA variables (CW and backoff values) change with time and medium availability. As is immediately apparent from the above, the present invention provides a gradual change through switching between the degenerate parameter value and the non-degenerate parameter value of the EDCA parameter.

[0260] Also, step 904 can also include calculating the RU backoff value OBO if necessary. When the RU backoff engine 800 is inactive (for example, because there was no data in the traffic queue until the previous step 903) and new data destined for the AP is received, it is necessary to calculate the RU backoff value OBO.

[0261] The RU backoff value OBO can be calculated in a similar manner to the EDCA backoff value, that is, using dedicated contention windows [0, CWO] and selection ranges [CWO min , CWO max , etc., of dedicated RU contention parameters.

[0262] Note that some embodiments can provide a distinction between data that can be transmitted through a resource unit (i.e., is compatible with MU UL OFDMA transmission) and data that cannot be transmitted. Such a determination can be made during step 902, and the corresponding marking item can be added to the stored data.

[0263] In such a case, the RU backoff value OBO is calculated only when the newly stored data is marked as being compatible with MU UL OFDMA transmission.

[0264] After step 904, the process of FIG. 9 ends.

[0265] Once data is stored in the AC queue, the node can access the medium directly through an EDCA access method (either legacy EDCA mode or degenerate MU EDCA mode), as described below with reference to Figure 10, or through resource units provided by the AP via one or more trigger frames, as described below with reference to Figure 11.

[0266] Figure 10 shows the steps for accessing a medium based on the (legacy or degenerate MU) EDCA medium access method, using a flowchart.

[0267] Steps 1000–1020 demonstrate conventional waiting introduced into the EDCA mechanism to reduce collisions on a shared radio medium. In step 1000, node 600 detects the medium and waits for the medium to become available (i.e., the detected energy falls below a given threshold on the primary channel).

[0268] When the medium becomes unused during the AIFS[i] period (including the DIFS period and the AIFSN[i] period; see Figure 3a), step 1010 is executed, in which node 600 decrements all active (non-zero) AC[] queue back-off counters 211 by one. In other words, the node decrements the queue back-off value for each basic time unit in which the communication channel is detected as idle.

[0269] Next, in step 1020, node 600 determines whether at least one of the AC backoff counters has reached 0.

[0270] If the AC queue backoff has not reached 0, node 600 waits for another backoff time slot (typically 9 μs) and therefore loops back to step 1000 to detect the medium again during the next backoff time slot. This makes it possible to decrement the AC backoff counter as soon as their respective AIFS[i] expire in each new backoff time slot in which the medium is detected as idle.

[0271] If at least one AC queue backoff reaches 0, step 1030 is executed, in which node 600 (more precisely, virtual collision handler 212) selects an active AC queue with a queue backoff counter of 0 and the highest priority.

[0272] In step 1040, an appropriate amount of data for transmission is selected from this selected AC to match the bandwidth of the TXOP.

[0273] Next, in step 1050, node 600 initiates EDCA transmission, for example, if it has successfully performed the RTS / CTS exchange and TXOP is permitted. Node 600 then transmits the selected data on the medium during the permitted TXOP.

[0274] Next, in step 1060, node 600 determines whether or not the EDCA transmission has finished, and if it has finished, step 1070 is executed.

[0275] In step 1070, node 600 updates the conflict window CW of the selected traffic queue based on the transmission status (positive ack, negative ack, or no ack received). Typically, node 600 sets the CW to the maximum value CW that depends on the data's AC type. maxIf transmission fails, the CW value is doubled until either degenerate or non-degenerate is reached. On the other hand, if EDCA transmission is successful, the conflict window CW is the minimum CW, which also depends on the AC type of the data. min It is set to either degenerate or non-degenerate.

[0276] Next, if the selected traffic queue is not empty after the EDCA data has been sent, a new associated queue backoff counter is randomly selected from [0, CW], similar to step 904.

[0277] This completes the process shown in Figure 10.

[0278] Figure 11 shows, using a flowchart, the steps taken to access a resource unit based on the RU access method or OFDMA access method upon receiving a trigger frame defining a RU. For example, this illustrates the behavior of node 502 in Figure 5b.

[0279] In step 1110, the node determines whether a trigger frame has been received from an access point in the communication network. This trigger frame reserves a transmission opportunity permitted to the access point on the communication channel and defines the resource unit RU that forms the communication channel. If received, the node analyzes the contents of the received trigger frame.

[0280] In step 1120, the node determines whether it can transmit data through one of the RUs specified in the received trigger frame. This determination may involve one or both of two conditions, particularly regarding the type of RU.

[0281] By analyzing the content of the received TF, the node determines whether the specified RU is the scheduled resource unit assigned to the node by the access point. This can be done by looking for its own AID within the received TF. This AID is associated with a specific scheduled RU used for MU UL OFDMA transmission.

[0282] Also, by analyzing the content of the received TF, the node determines whether one or more random RUs, i.e., RUs whose access is performed through contention using dedicated RU contention parameters (including the above OBO value 800), are defined within the TF. In that case, the node also determines whether it is possible to select one random RU according to its current OBO value 800 (e.g., OBO800 is less than the number of random RUs within the TF).

[0283] If one scheduled RU is assigned to the node, i.e., the node is permitted (after contention) to access one random RU, this node determines the size of the random / scheduled single or multiple RUs to be used, and step 1130 is executed. Otherwise, the node decrements the RU backoff value OBO800 based on the number of random resource units defined in the received trigger frame, and since the node cannot access the RUs defined by the received TF, the process ends.

[0284] In step 1130, the node selects at least one of the traffic queues 210 from which the data to be transmitted is selected, and adds the data of the selected single or multiple queues to the transmission buffer until the amount of data reaches the size of the selected resource unit used.

[0285] Various criteria for selecting the current traffic queue can be involved.

[0286] For example, this can be done as follows: Select the traffic queue 210 with the smallest associated queue backoff value. The selection of the traffic queue depends on the value of EDCA backoff 211, as described above, thereby ensuring that the node adheres to the EDCA principle and that correct QoS is performed on its data. Randomly selecting one non-empty traffic queue from the traffic queues; Select the traffic queue that stores the largest amount of data (i.e., the one that gets the most load); (Given the AC categories shown in Figure 3b) Select the non-empty traffic queue with the highest associated traffic priority; Select a non-empty traffic queue associated with a data type that matches the data type associated with the resource unit from which the selected data is sent. Such a specified data type can be the traffic queue indicated by the AP in the trigger frame, for example, when the AC priority level field is set to 1, using the priority AC field 1340 in Figure 13. This is the selection criterion used in the example in Figure 5b.

[0287] Following step 1130, step 1140 provides that a node configure or update the list of outgoing / transmitting queues by inserting the current traffic queue from which the data selected in step 1130 will be obtained. This list maintains the order in which the outgoing / transmitting queues are inserted, making it easy to identify, for example, the first outgoing / transmitting queue (the first queue selected in step 1030) and subsequent outgoing / transmitting queues.

[0288] In addition, during step 1140, the node can store an information item representing the amount of data to be sent to the RU, which is selected from the current traffic queue as described above. For example, the node updates the list of discharge queues by also inserting the amount of data to be selected from the current traffic queue.

[0289] This list of release / transmit queues can be implemented using a table that includes the rank of the transmit queue (which can be simplified to "primary" or "secondary" queues) and the amount of data placed in the transmit buffer for each traffic queue.

[0290] In step 1150, the node determines whether the amount of data stored in the transmit buffer is sufficient to fill the selected resource unit.

[0291] If insufficient, the resource unit still has room to add data. Therefore, the process loops back to step 1130, during which another traffic queue can be selected using the same selection criteria. In this way, the send buffer is gradually filled until it reaches the size of the selected resource unit.

[0292] Therefore, it can be seen that multiple outgoing traffic queues on the same node can be involved during MU UL OFDMA transmission, thereby allowing multiple queues to enter MU EDCA mode.

[0293] In one variant, to avoid mixing data from two or more traffic queues (i.e., data for a selected RU is selected from a single traffic queue), padding data can be added to fully fill the selected RU. This is to ensure that the entire duration of the RU has energy that can be detected by legacy nodes.

[0294] In another variant that implements specific data aggregation rules, if the initially selected traffic queue does not have enough data to fully fill the accessed resource unit, data can be selected from a higher-priority traffic queue.

[0295] When the transmit buffer of the selected RU is filled, step 1160 initiates a MU UL OFDMA transmission of the data stored in the transmit buffer to the AP. This OFDMA transmission is based on an OFDMA subchannel and the received trigger frame, in particular with the modulation specified in the RU definition.

[0296] Next, once the transmission is performed and preferably successful (i.e., an acknowledgment is received from the AP), step 1170 determines one or more new values ​​to apply to one or more EDCA parameters in order to change the values ​​of one or more EDCA parameters in one or more traffic queues to one or more penalty values.

[0297] Transmit queues added to the list in step 1140 therefore enter MU EDCA mode, which means their EDCA parameter set or “queue contention” parameter set should be changed, in particular, to the required degenerate parameter values. One or more transmit queues may already be in MU EDCA mode; however, their degenerate parameter values ​​will be determined as well (these degenerate parameter values ​​can be changed by recently received beacon frames with new degenerate values).

[0298] During step 1170, the degeneracy parameter value is determined.

[0299] In this embodiment, the degenerate value of the EDCA parameters includes the degenerate number of inter-frame arbitration spaces (AIFSN) compared to the non-degenerate value of the EDCA parameters used for traffic queues that are not set to MU EDCA mode. In other words, the AIFSN of the transmit queue is set to the degenerate value.

[0300] In some embodiments, AIFSN is the only parameter that changes when switching to MU EDCA mode. This is because the degenerate value of the EDCA parameter is the same as the non-degenerate value used in legacy EDCA mode, under lower boundary CW. min and / or upper boundary CW max This means including CW. min and CW max Both define the selection range in which the size of the competing window is selected.

[0301] The degenerate value used in this step is preferably selected in the last received dedicated information element, which typically forms part of the beacon frame transmitted by the AP. Thus, if each beacon frame broadcasts network information about the communication network to multiple nodes, and the nodes periodically receive this beacon frame from the access point, the received beacon frame typically includes, as described above, degenerate values ​​of the EDCA parameters of multiple traffic queues that switch to MU EDCA mode, in addition to the non-degenerate (or legacy EDCA) values.

[0302] If such degraded values ​​are not received from the AP, the default settings described in the standard can be used.

[0303] Step 1170 also includes determining a predetermined degraded duration HEMUEDCATimer[AC] value for each transmit traffic queue AC. This duration defines the period during which a node must remain in the MU EDCA mode for the associated degraded traffic queue. This information can also be obtained from the AP, for example, from specific dedicated information elements of the received beacon frame as shown in Figure 14b or Figure 14c below.

[0304] Following step 1170, step 1180 actually replaces the current values ​​of the EDCA parameters associated with the transmit traffic queue(s) with the degraded values ​​determined in step 1170.

[0305] Parameter CW min and / or CW max If it has a new value, the current CW for one or more traffic queues may have expired. In that case, the newly defined range [CW min ,CW max You can select a new CW from [ ].

[0306] Next, in step 1190, the timer 2110 associated with each transmit traffic queue 210 is initialized by the respective predetermined degradation duration HEMUEDCATimer[AC] determined in step 1170. The timer 2110 is then started and elapses continuously as time progresses.

[0307] Note that if the timer has already elapsed when step 1180 is executed (meaning the associated traffic queue was already in MU EDCA mode), the timer will be reinitialized (i.e., reset) to the HEMUEDCATimer[AC] value again in order to keep the node in MU EDCA mode for the next HEMUEDCATimer[AC] period. This is the case for timer 591 in the example in Figure 5b.

[0308] Figure 12 illustrates the node management at the queue level when switching back to non-degraded legacy mode in the above example, using a flowchart. This management is based on a dedicated HEMUEDCATimer[AC] for the relevant traffic queue AC. In fact, a traffic queue AC can remain in MU EDCA mode as long as this timer HEMUEDCATimer[AC] has not elapsed.

[0309] Therefore, in step 1210, it is confirmed whether HEMUEDCATimer[AC] has elapsed / completed, that is, whether it has reached a value of 0.

[0310] If the time has elapsed / expired, the traffic queue AC is switched back to EDCA mode in step 1220. This may include resetting the EDCA parameters to non-degraded values, such as those provided to the node by the AP using the beacon frame shown in Figure 14a below.

[0311] It should be noted that, due to the reinitialization of the timer in each new step 1190, HEMUEDCATimer[AC] expires only when no data from the traffic queue AC is sent from the node to an OFDMA resource unit provided by the AP within a subsequent TXOP authorized by the AP during a predetermined degraded duration.

[0312] Next, the process ends in step 1230.

[0313] The process in Figure 12 is executed independently and in parallel for each traffic queue in degenerate MU EDCA mode (i.e., the mode in which the timer has elapsed). This is because the timers 2110 are separate according to the teachings of the present invention.

[0314] Figure 13 shows the structure of a trigger frame as defined in the 802.11ax draft standard.

[0315] The trigger frame 1300 consists of a dedicated field 1310 called the User Info Field. This field includes a Trigger-dependent Common info field 1320, which contains the AC Preference Level field 1330 and the Preferred AC field 1340.

[0316] The priority AC field 1340 is a 2-bit field (values ​​between 0 and 3) that indicates the AC queue to which data should be sent by the node in the RU assigned to that node within the trigger frame.

[0317] The AC priority level field 1330 is a bit that indicates whether the value of the priority AC field 1340 is meaningful. If field 1340 is set to 1, the node should consider the priority AC field 1340 when selecting data in step 1130. If field 1330 is set to 0, the node is allowed to send data from any AC queue regardless of the value of the priority AC field 1340.

[0318] Other fields in the trigger frame are specified in the 802.11ax standard.

[0319] The AP may also be responsible for broadcasting the EDCA parameters for both EDCA mode and MU EDCA mode, as well as one or more initialization values ​​used to initialize or reset the timer 2110 associated with the traffic queue 210. The AP preferably performs the broadcast using a well-known beacon frame dedicated to configuring all nodes in the 802.11 cell. Note that if the AP is unable to broadcast the EDCA parameters, the node is configured to fall back to default settings as specified in the 802.11ax standard.

[0320] Figure 14a shows the structure of a standardized information element 1410 used to describe EDCA parameters in a beacon frame.

[0321] Fields 1411, 1412, 1413, and 1414 describe the parameters associated with each traffic queue 210. For each traffic queue, subfield 1415 describes the EDCA parameters, namely AIFSN as the delay before the associated backoff value begins to decrease, and minimum CW. min and maximum CW max This includes ECWmin and ECWmax as the values ​​for the conflict window, and finally, the TXOP limit as the maximum transmit data time for an 802.11 device.

[0322] All other fields of the information element are as specified in the 802.11 standard.

[0323] Figure 14b shows an exemplary structure of a dedicated information element 1420 that transmits the degraded EDCA parameter value according to the present invention and a common initialization value for the timer HEMUEDCATimer[AC] of all traffic queues. The dedicated information element 1420 can be included in a beacon frame transmitted by the AP.

[0324] The dedicated information element 1420 contains the degenerate EDCA parameters (1421, 1422, 1423, 1424) used by nodes in MU EDCA mode for each AC queue. This dedicated information element also includes a subfield 1425 that specifies common initialization values ​​for HEMUEDCATimer.

[0325] Each subfield 1421, 1422, 1423, and 1424 contains the degraded AIFSN value, degraded ECWmin value, and degraded ECWmax value (which may be the same as the legacy EDCA value) of the corresponding traffic queue.

[0326] In this embodiment, a predetermined degraded duration used to initialize the timer HEMUEDCATimer[AC] associated with each traffic queue AC is calculated from a common initialization value 1425 received from the AP and adjustment parameters specific to each traffic queue.

[0327] By using different tuning parameters, it is possible to obtain different predetermined degraded durations used to initialize the timers associated with each of the two traffic queues.

[0328] In one embodiment, a common initialization value, such as one provided by the AP, can be multiplied by a constant value (adjustment parameter) based on the priority of each traffic queue AC. For example, the constant value may be equal to 1 for the AC_VO and AC_VI access categories, and equal to 3 for the AC_BE and AC_BG access categories.

[0329] Figure 14c shows another exemplary structure of a dedicated information element 1430 that transmits a degenerate EDCA parameter value according to the present invention and one initialization value for each timer HEMUEDCATimer[AC] performed by the node. The dedicated information element 1430 can be included in a beacon frame transmitted by the AP.

[0330] The dedicated information element 1430 includes, for each AC queue, the degenerate parameters (1431, 1432, 1433, 1434) used by the node in MU EDCA mode. This dedicated information element also includes a subfield 1425 that specifies common initialization values ​​for HEMUEDCATimer.

[0331] Each subfield 1431, 1432, 1433, and 1434 contains the degenerate AIFSN value, the degenerate ECWmin value and the degenerate ECWmax value (which can be the same as the legacy EDCA value), and finally, the initialization value used for the HEMUEDCATimer of the relevant traffic queue.

[0332] This means that the AP is responsible for calculating and then transmitting a dedicated initialization value for each traffic queue. In this embodiment, the predetermined degraded duration used to initialize the timer HEMUEDCATimer[AC] associated with each traffic queue is set to the respective initialization value received directly from the AP.

[0333] To improve QoS management, the initialization values ​​calculated by the AP are preferably based on the priority of each AC.

[0334] Although the present invention has been described above with respect to specific embodiments, the present invention is not limited to these specific embodiments, and modifications within the scope of the present invention will be obvious to those skilled in the art.

[0335] For example, while the EDCA parameters and degenerate MU EDCA parameters are broadcast in a dedicated information element of the same beacon frame in the above description, a variation can be considered in which a beacon frame transmitting the EDCA parameters is alternated with another beacon frame broadcasting the degenerate MU EDCA parameters.

[0336] Referring to the exemplary embodiments described above, many further modifications and variations will be conceivable to those skilled in the art. The exemplary embodiments described above are provided solely as examples and are not intended to limit the scope of the invention, which is defined solely by the appended claims. In particular, different features from different embodiments may be substituted as needed.

[0337] In the claims, the term “equips / includes” does not exclude other elements or steps, and unless otherwise specified, it includes both singular and plural elements. The mere fact that different features are listed in different dependent claims does not imply that combinations of these features cannot be used to their advantage.

Claims

1. A transmission means for transmitting data, A receiving means for receiving multiple Timer values ​​from an access point, corresponding to each of the multiple access categories defined in the IEEE 802.11 series standard, The system includes a control means that, when the transmission of data by the transmission means is successful, uses a first parameter as a conflict parameter when transmitting data according to EDCA until a predetermined period has elapsed, and updates the conflict parameter to a second parameter different from the first parameter once the predetermined period has elapsed. The predetermined period is determined based on the Timer value among the plurality of Timer values ​​received by the receiving means that corresponds to the access category of the data successfully transmitted by the transmitting means. A communication device characterized by the following features.

2. The communication device according to claim 1, characterized in that the transmitting means transmits data using a resource unit allocated by the access point.

3. The communication device according to claim 2, characterized in that the resource unit is allocated by a trigger frame transmitted from the access point.

4. In communication using the second parameter as the conflict parameter, the communication device A communication device according to any one of claims 1 to 3, characterized in that it transmits at least one of an RTS signal and a CTS signal.

5. The communication device according to any one of claims 1 to 4, characterized in that the plurality of Timer values ​​are included in the beacon frame transmitted from the access point.

6. The communication device according to any one of claims 1 to 5, characterized in that the probability of the communication device accessing the communication channel is lower when using the first parameter than when using the second parameter.

7. The communication device according to any one of claims 1 to 6, characterized in that the first parameter is included in the beacon frame transmitted from the access point.

8. The communication device according to any one of claims 1 to 7, characterized in that the first parameter is a parameter corresponding to the access category of data successfully transmitted by the transmission means.

9. The communication device according to any one of claims 1 to 8, characterized in that the aforementioned conflict parameter includes at least CWmin, which is the minimum value of the contention window, and CWmax, which is the maximum value of the contention window.

10. The communication device according to any one of claims 1 to 9, characterized in that the aforementioned data is video stream data.

11. A transmission step of transmitting data, A receiving step that receives multiple Timer values ​​from an access point, each corresponding to one of the multiple access categories defined in the IEEE 802.11 series standard, The system includes a control step in which, if the transmission of data is successful in the transmission step, a first parameter is used as a conflict parameter when transmitting data according to EDCA until a predetermined period has elapsed, and when the predetermined period has elapsed, the conflict parameter is updated to a second parameter different from the first parameter. The predetermined period is determined based on the Timer value among the plurality of Timer values ​​received in the receiving step that corresponds to the access category of the data that was successfully transmitted in the transmitting step. A communication method characterized by the following features.

12. A program for operating a computer as a communication device according to any one of claims 1 to 10.

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