Base station, communication method and computer readable medium

Abstract

The present invention relates to a base station, a communication method and a computer-readable medium, and also to a wireless network including an access point and a non-AP station. The station has a service queue and associated backoff counters, which decrease over time when the medium is continuously sensed as idle during a period exceeding the corresponding AIFS duration. In order to compensate for the additional opportunities provided by the OFDMA RU, the queue switches to MU mode when the data of the queue is transmitted in the RU provided by the AP. In order to restore the dynamics of the backoff counters frozen in MU mode in the known technology, an embodiment provides the following at each expiration of one of the queue backoff counters: determining the current mode of the expired service queue; in the case of the traditional mode, the station accesses the channel to transmit data from the queue; and in the case of the MU mode, in the absence of data transmitted from the queue, extracting a new backoff value to reset the expired backoff counter.

Description

[0001] (This application is a divisional application of an application filed on October 27, 2017, with application number 201780066921X, and invention name “QoS Management for Multi-User EDCA Transmission Mode in 802.11ax Networks”.) Technical Field

[0002] The present invention generally relates to communication networks, and more particularly to wireless communication methods and corresponding devices in a wireless network including an access point (AP) and a plurality of non-AP stations. The present invention relates to communication networks that provide channel access to non-AP stations through contention such as EDCA, and provide secondary access to the non-AP stations to subchannels (or resource units) that divide a transmission opportunity TXOP granted to an access point, thereby transmitting data.

[0003] The present invention may be applied in wireless communication networks, in particular in 802.11ax networks, thereby providing stations with access to 802.11ax composite channels and / or OFDMA resource units forming an 802.11ax composite channel, such as a grant access point, and enabling uplink communication. Background Art

[0004] The IEEE 802.11 MAC family of standards (a / b / g / n / ac, etc.) defines the way a wireless local area network (WLAN) must operate at the physical layer and the medium access control (MAC) layer. Typically, the 802.11 MAC (medium access control) operating mode implements the well-known distributed coordination function (DCF), which relies on a contention-based mechanism based on the so-called "Carrier Sense Multiple Access / Collision Avoidance" (CSMA / CA) technology.

[0005] The original DCF method of access has been improved into the well-known Enhanced Distributed Channel Access (EDCA) method to consider priority data traffic when accessing the communication channels of the network.

[0006] EDCA defines traffic classes, and four corresponding access categories that allow high priority traffic to be treated differently than low priority traffic.

[0007] EDCA may be implemented in a site using multiple service queues (known as "access categories") for serving data traffic at different priorities, wherein each service queue is associated with a corresponding queue backoff counter. The queue backoff counter is initialized with a backoff value randomly drawn from each queue contention parameter (e.g., EDCA parameter) and is used to contend for access to a communication channel in order to transmit data stored in the service queue.

[0008] Traditional EDCA parameters include CW for each service queue min , CW max and AIFSN, among which CW min and CW max The lower and upper boundaries of the selected range of the EDCA contention window CW are selected for a given traffic queue. AIFSN stands for Arbitration Interframe Space Number and defines the number of time slots (usually 9 μs) that a station must sense the medium as idle before decrementing the queue backoff value associated with the traffic queue under consideration, excluding the DIFS interval (which defines the sum of the AIFS time periods). This means that, with EDCA, the station decrements the queue backoff counter over time as long as the communication channel is continuously sensed as idle for a period exceeding the corresponding arbitration interframe space duration.

[0009] Traditional EDCA parameters may be defined in beacon frames sent by APs in the network to broadcast network information.

[0010] Contention window CW and queue backoff value are EDCA variables.

[0011] The conventional EDCA backoff process includes: the station randomly selects a backoff value for the service queue backoff counter from each contention window CW, and then decrements the backoff value when the medium is sensed as idle after the AIFS period. Once the backoff value reaches zero, the station is allowed to access the medium.

[0012] Thus, the EDCA queue backoff counters play two roles for the station. First, these counters drive the station to access the medium efficiently by reducing the risk of collisions; second, these counters provide management of the quality of service, i.e., QoS, by reflecting the aging of the data contained in the service queues (the older the data, the lower the backoff value), and thereby providing different priorities to the service queues through different values ​​of EDCA parameters (particularly the AIFSN parameters that delay the start of decrementing the EDCA queue backoff counters).

[0013] The EDCA backoff procedure is used by stations to access the communication network through backoff-based contention.

[0014] Recently, the Institute of Electrical and Electronics Engineers (IEEE) formally approved the 802.11ax task group as the successor to 802.11ac. The main goal of the 802.11ax task group involves trying to increase the data speed of wireless communication devices used in dense deployment scenarios.

[0015] In particular, the recent development of the 802.11ax standard attempts to optimize the use of communication channels by multiple stations in a wireless network with access points (APs). In fact, typical content has a significant amount of data, such as high-definition audio-visual real-time interactive content; and these contents should be transmitted with the required quality of service QoS.

[0016] 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 stations and traffic increases (ie, in a dense WLAN scenario).

[0017] In this context, multi-user (MU) transmission has been considered to allow multiple simultaneous transmissions relative to different users in the downlink (DL) and uplink (UL) directions relative to the AP and during a transmission opportunity granted to the AP. In the uplink, multi-user transmission can be used to reduce the probability of collisions by allowing multiple non-AP stations to transmit simultaneously.

[0018] In order to actually carry out such multi-user transmission, it is proposed to divide the granted communication channel into sub-channels (also called resource units (RUs)), where multiple users (non-AP stations) share these sub-channels in the frequency domain, for example based on orthogonal frequency division multiple access (OFDMA) technology. Each RU can be defined by multiple tones, where an 80MHz channel contains up to 996 available tones.

[0019] OFDMA is a multi-user variant of OFDM that emerged as a new key technology to improve the efficiency of wireless networks based on advanced architectures. OFDMA combines OFDM on the physical layer with frequency division multiple access (FDMA) on the MAC layer, enabling different subcarriers to be assigned to different sites to improve concurrency. Adjacent subcarriers often experience the same channel conditions and are therefore grouped into subchannels: an OFDMA subchannel or RU is therefore a collection of subcarriers.

[0020] The multi-user feature of OFDMA allows the AP to assign different RUs to different non-AP stations to increase contention. This can help reduce contention and collisions within the 802.11 network.

[0021] In OFDMA, different subsets of subcarriers in the channel bandwidth can be used simultaneously by different frame transmissions. In the downlink direction, the AP is allowed to transmit parallel transmissions to different receiving non-AP sites. These transmissions are called multi-user downlink transmissions (MU DL). In addition, the AP can provide uplink transmission scheduling to non-AP sites; this transmission scheme is called multi-user uplink (MU UL).

[0022] To support multi-user uplink (i.e., uplink transmissions to an 802.11ax access point (AP) during a granted TXOP), an 802.11ax AP must provide signaling information for legacy stations (non-802.11ax stations) to set their NAVs and for 802.11ax client stations to determine allocations of resource units RUs provided by the AP.

[0023] The 802.11ax standard defines a new control frame (ie, a trigger frame (TF)) sent by an AP to a station to trigger multi-user uplink communication.

[0024] Document IEEE 802.11-15 / 0365 proposes that a "trigger frame" (TF) is sent by the AP to request the transmission of a multi-user uplink (MU UL) OFDMA PPDU from multiple stations. The TF defines the resource units provided by the AP to these non-AP stations. In response, the station sends a MU UL (OFDMA) PPDU as an immediate response to the trigger frame. All transmitters can send data at the same time, but use a set of disjoint RUs (i.e., frequencies in the OFDMA scheme), resulting in less interference transmission.

[0025] The AP may reserve a resource unit RU for a specific station, in which case the AP indicates the station that has reserved the RU in the TF. Such a RU is called a scheduled RU. The indicated station does not need to compete for access to such a RU.

[0026] On the other hand, the AP can propose one or more resource units to the 802.11ax station through contention-based access. These RUs are called random RUs and help improve the efficiency of the network with respect to unmanaged traffic to the AP.

[0027] In the case where an AP preempts multiple communication channels (of typically 20 MHz width), all control frames including the trigger frame are replicated on each preempted channel. This is to allow legacy stations operating on any of these channels to set their NAVs.

[0028] The 802.11ax standard contemplates multiple types of trigger frames to trigger various information items to a station. For example, a trigger frame may be used to retrieve uplink data traffic stored in a station's traffic queue. In another example, a trigger frame may be used to request a buffer status report (BSR) from a station to determine which 802.11ax stations hold uplink packets waiting to be transmitted and the associated sizes of those uplink packets (the amount of data in the station's traffic queue).

[0029] From the above, it is easy to see that the multi-user uplink medium access scheme (or OFDMA or RU access scheme) allows reducing the number of conflicts generated by simultaneous medium access attempts, while also reducing the overhead caused by medium access (because the medium access cost is shared among several stations). Therefore, OFDMA or RU access schemes appear to be more efficient (in terms of medium usage) than traditional EDCA contention-based medium access schemes (in the environment of high-density 802.11 cells).

[0030] Although the OFDMA or RU access scheme seems to be more efficient, the EDCA access scheme must also survive and thus coexist with the OFDMA or RU access scheme.

[0031] This is mainly due to the presence of legacy 802.11 stations, which must still have a chance to access the medium, without being aware of OFDMA or the RU access scheme. In addition, overall fairness of access to the medium must be ensured.

[0032] It is also desirable that 802.11ax stations should also have the opportunity to access the medium via traditional EDCA contention-based medium access, for example to send data directly to another station (i.e., peer-to-peer [P2P] traffic as opposed to uplink traffic to the AP).

[0033] Therefore, two medium access schemes, EDCA and OFDMA / RU access scheme, must coexist.

[0034] This coexistence has disadvantages.

[0035] For example, 802.11ax stations and legacy stations have the same medium access probability using EDCA access scheme. However, 802.11ax stations have additional medium access opportunities using MU uplink or OFDMA or RU access schemes.

[0036] This results in access to the medium not being completely fair between 802.11ax stations and legacy stations.

[0037] In order to restore some fairness between the stations, the following solution is proposed: when data is successfully transmitted via the accessed resource unit (i.e., through MU UL OFDMA transmission), the current value of at least one EDCA parameter is modified to a penalty or degradation value to reduce the probability that the station will access the communication channel again through EDCA contention. For example, the penalty or degradation value to be used for the EDCA parameter is more restrictive than the original (or traditional) value.

[0038] For example, it is proposed that when the AP successfully transmits data (MU ULOFDMA) in the resource unit (RU) reserved for the 802.11ax station, the 802.11ax station switches to the MU EDCA mode and continues for a predetermined duration obtained by counting down using a timer (hereinafter referred to as HEMUEDCATimer, which stands for High Efficiency Multi-User EDCA Timer). In this MU EDCA mode, the set of EDCA parameters of the station has been modified (specifically, a penalty) to reduce the probability of the station accessing the communication channel again through the EDCA access scheme.

[0039] The penalty or degradation values ​​for a set of MU EDCA parameters are provided by the AP in a dedicated information element (usually in a beacon or association frame).

[0040] The method disclosed in the document suggests increasing only the value of AIFSN for each service queue transmitted in the visited RU, while maintaining CW min and CW max With the increase of the corresponding AIFS period, the service queue in MU EDCA mode is substantially delayed in decrementing its queue backoff counter when sensing the medium as idle. This is particularly noticeable in high-density environments where the medium does not remain idle for a long time.

[0041] When switching to MU EDCA mode, the station starts its HEMUEDCATimer countdown. HEMUEDCATimer is reinitialized each time the station successfully transmits data (MU UL OFDMA) in a newly reserved RU, regardless of the traffic queue from which the transmitted data comes. It is recommended that the initialization value of HEMUEDCATimer be high (e.g., tens of milliseconds) to include several new opportunities for MU UL transmissions.

[0042] The HEMUEDCAimer mechanism means that the station remains in the MUEDCA state as long as the AP provides the reserved RUs to the station.

[0043] When the HEMUEDCATimer expires, the service queue in MU EDCA mode switches back to the traditional EDCA mode with traditional EDCA parameters, thereby causing the queue to exit from MU EDCA mode.

[0044] Therefore, this dual working mode (legacy EDCA mode and MU EDCA mode) mechanism promotes the use of the MU UL mechanism by reducing the probability that a station in the MU EDCA mode uses the legacy EDCA mechanism to access the medium.

[0045] In addition, the document proposes to provide a specific value to the AIFSN parameter in the set of degradation / penalty parameters provided by the AP. The specific value indicates to the station that the specific value should use a very high value for the AIFSN of the concerned traffic queue.

[0046] As described in the document, a very high value of AIFSN is proposed equal to the HEMUEDCATimer value also provided by the AP. Typically, the HEMUEDCATimer timer value is of the order of tens of milliseconds, compared to less than 0.1 milliseconds for the worst AIFS[i] in conventional EDCA mode.

[0047] It is proposed to use "0" for a specific value of the AIFSN parameter. Since this value is generally not allowed for AIFSN (since AIFSN must be at least equal to DIFS), this value is directly detected by the station as a code to set the AIFSN using HEMUEDCATimer.

[0048] The result of this scheme is that the traffic queues in MU EDCA mode are granted transmission opportunities less frequently through EDCA contention. It is thus clear that the use of code values ​​(which have been "0" so far) is intended to make EDCA access to these traffic queues less frequent. On the other hand, this simplifies the processing at the AP, making it no longer necessary to calculate the associated penalty AIFSN value.

[0049] However, by preventing the backoff counters from evolving when a station uses the penalty MU EDCA parameters, the mechanism causes the queue backoff counters to no longer reflect which traffic queue should have the highest transmission priority in the sense of conventional EDCA (e.g., having the oldest data stored internally). For example, in the event that a station receives a trigger frame with a scheduled RU dedicated to that station, the station with the backoff counters frozen can no longer use these backoff counters to process the QoS for that station and send data with the highest priority (not only with respect to the station's access category, but also with respect to the corresponding age of the data in the AC[] queue).

[0050] As a result, the QoS in the network is severely degraded and there is a need to reintroduce proper QoS operations for traffic prioritization, which will accommodate the medium access penalty scheme envisioned in the 802.11ax standard. Summary of the invention

[0051] The present invention seeks to overcome the above concerns. In particular, the present invention seeks to overcome the loss of QoS treatment caused by the introduction of MU UL OFDMA transmission.

[0052] With the introduction of 802.11e, the priority of data is handled together with the four access category traffic queues via the EDCA backoff mechanism. Since the EDCA backoff counter does not evolve when transmitting data on the MU UL OFDMA resource units, the introduction of MU UL OFDMA communications destroys the ability of the EDCA backoff counter to reflect the relative priorities of the four AC traffic queues.

[0053] Thus, the present invention aims to restore some EDCA-like behavior to the queue backoff counters for the purpose of restoring relevant reflection of the relative priorities of the AC queues.

[0054] In this context, the present invention provides a communication device comprising:

[0055] A receiving component, configured to receive a signal transmitted from a base station constructing a wireless network compliant with the IEEE 802.11 series of standards, wherein the signal includes information related to the AIFSN value; and

[0056] The control component is used to control so that when the AIFSN value included in the signal received by the receiving component is zero, the data of the access category of enhanced distributed channel access (EDCA) access to the wireless network is not transmitted via the wireless network.

[0057] In turn, a communication method is also proposed, wherein the station performs the following:

[0058] receiving a signal transmitted from a base station constructing a wireless network compliant with the IEEE 802.11 series of standards, the signal including information related to the AIFSN value; and

[0059] Control is performed so that, when the AIFSN value included in the signal received by the receiving part is zero, data of the access category for obtaining enhanced distributed channel access (EDCA) access to the wireless network is not transmitted via the wireless network.

[0060] Other embodiments of the present invention provide a communication method in a communication network, the communication network comprising a plurality of sites, at least one site comprising a plurality of service queues for serving data services at different priorities, each service queue being associated with a corresponding queue backoff counter to compete for access to a communication channel to transmit data stored in the service queue,

[0061] The communication method comprises:

[0062] At the site,

[0063] The queue backoff counter is decremented over time as long as the communication channel is (usually continuously) sensed as idle (free or available) for more than the corresponding arbitration inter-frame space duration, i.e., AIFS duration. This means that each service queue detects the medium as idle during the corresponding AIFS period before decrementing its backoff counter at each new consecutive time slot during which the network is still sensed as idle;

[0064] When data stored in any service queue is transmitted (preferably successfully) in an accessed resource unit provided by the access point within a transmission opportunity granted to the access point on the communication channel, switching the service queue from the traditional contention mode to the MU contention mode; and

[0065] When one of the queue backoff counters expires (i.e., expires, such as reaching zero), a determination is made based on the current (i.e., at the time of expiration) mode of the associated service queue whether to access the communication channel to transmit data stored in the associated service queue, or to extract a new backoff value to reset the expired queue backoff counter without transmitting data from the associated service queue in the communication channel.

[0066] These embodiments can restore the decrement of the backoff counter while still maintaining the penalty scheme envisioned in the 802.11ax standard. Thus, the aging of data in the service queue can be restored, and thus QoS can be restored.

[0067] This is achieved by the proposed control of the medium access once the backoff counter expires. In contrast to the prior art preventive measures to avoid the backoff counter expiration, the proposed solution is a reactive countermeasure to such a backoff counter reaching zero. Thus a dynamic behavior of the backoff counter can be achieved again.

[0068] Consequences of these embodiments include the fact that the backoff counter may again reflect the aging of the data in the AC, but also the fact that restrictive AIFSN values ​​are no longer needed.

[0069] Accordingly, these embodiments further provide a communication site in a communication network, wherein the communication network includes a plurality of sites, and the communication site includes:

[0070] A plurality of service queues for servicing data services at different priorities, each service queue being associated with a corresponding queue backoff counter to compete for access to a communication channel to transmit data stored in the service queue; and

[0071] At least one microprocessor configured to perform the following steps:

[0072] decrementing the queue backoff counter over time as long as the communication channel is sensed as idle for a period exceeding a corresponding arbitration interframe gap duration;

[0073] When data stored in any service queue is transmitted in an accessed resource unit provided by the access point within a transmission opportunity granted to the access point on the communication channel, switching the service queue from the traditional contention mode to the MU contention mode; and

[0074] When one of the queue backoff counters expires, a determination is made based on the current mode of the associated service queue whether to access the communication channel to transmit data stored in the associated service queue, or to extract a new backoff value to reset the expired queue backoff counter without transmitting data from the associated service queue in the communication channel.

[0075] This site has the same advantages as the method defined above.

[0076] Optional features of the invention are defined in the appended claims. Some of these features are explained below with reference to methods, while these features can be converted into system features specific to any communication station according to the invention.

[0077] In an embodiment, if the current mode is the traditional contention mode, the station accesses the communication channel to transmit data stored in the associated service queue,

[0078] If the current mode is the MU contention mode, then a new backoff value is extracted to reset the expired queue backoff counter without transmitting data from the associated service queue in the communication channel.

[0079] This ensures that the penalty scheme envisioned in the 802.11ax standard is maintained: the EDCA scheme still works even after the association backoff counter expires with restored dynamism, while medium access to the traffic queue is not allowed in MU EDCA. This is the control provided by the present invention.

[0080] In some embodiments, the decision whether to access the communication channel or to extract a new backoff value is further based on data currently stored in the associated traffic queue. In particular, for the purpose of maintaining QoS fairness for data not related to MU UL transmission, the method enables the penalty scheme to be adjusted to some types of data.

[0081] According to a particular feature, if the current mode is a conventional contention mode or if the data stored in the associated service queue includes data to be addressed to another station different from the access point (i.e., the data is P2P data), the station accesses the communication channel to transmit the data stored in the associated service queue,

[0082] If the current mode is MU contention mode and the data stored in the associated service queue does not include data addressed to another station different from the access point, a new backoff value is extracted to reset the expired queue backoff counter without transmitting data from the associated service queue in the communication channel.

[0083] In this configuration, QoS fairness is maintained for P2P traffic since it does not involve MU UL transmission to the AP. In other words, the present invention allows EDCA access to the medium for P2P data even if the stations are in MU EDCA mode for the same AC.

[0084] In this context, it can be provided that in the case of access to a communication channel, only data stored in the associated service queue in MU contention mode and addressed to another station different from the access point is transmitted in the accessed communication channel. This means that only P2P data is allowed in conventional EDCA access while the station (or the corresponding AC) is in MU EDCA mode.

[0085] In some embodiments, the MU contention mode uses the same arbitration interframe gap duration as the conventional contention mode. Due to the reactive approach of the present invention, the control of medium access in the penalty scheme no longer depends on the contention parameters, but mainly relies on additional testing of the current mode when any backoff counter expires. As a result, the AIFSN no longer needs to be modified, and thus the AP no longer needs to transmit the modified value of the AIFSN. As a result, processing at the station and AP is reduced, while the use of bandwidth to transmit the penalty EDCA parameters is also reduced.

[0086] In a particular embodiment, each queue backoff counter is reset using an associated backoff value extracted from a corresponding contention window, and

[0087] MU competition mode uses the same lower boundary CW as traditional competition mode min and / or the same upper boundary CW max , where the lower boundary CW min and upper boundary CW max These two define the range of options for choosing the size of the contention window.

[0088] This configuration simplifies entry into and exit from MU contention mode (eg, MU EDCA mode) because the contention window can be left unchanged. However, variations may consider having different boundaries between the legacy contention mode and the MU contention mode.

[0089] In some embodiments, the method further includes: at the site, when the MU mode timer (referred to as HEMUEDCATimer in the standard) that is initialized when the service queue switches to the MU contention mode expires, switching the service queue back to the traditional contention mode. According to a specific feature, the MU mode timer is shared by all service queues and is reinitialized to a predetermined duration whenever data from any service queue is transmitted in an accessed resource unit provided by the access point in any subsequent transmission opportunity granted to the access point on the communication channel. This means that, when the predetermined duration expires, all service queues in MU contention mode exit the MU contention mode without transmitting any data from the site in any RU provided by the AP in subsequent transmission opportunities.

[0090] In some embodiments, data transmitted in resource units provided by an access point within a transmission opportunity granted to the access point is retrieved from at least one traffic queue selected based on a current (ie, when accessing the medium) backoff value of an associated queue backoff counter.

[0091] Thus, when implementing the present invention, fair management of QoS is maintained.

[0092] According to a specific feature, the service queue selects the service queue with the lowest current backoff value, thereby maintaining the EDCA-like behavior of the AC queue.

[0093] In an alternative embodiment, data transmitted in resource units provided by an access point within a transmission opportunity granted to the access point is retrieved from a preferred traffic queue indicated by the access point.

[0094] According to a particular feature, the preferred traffic queue indication is comprised in a trigger frame received from the access point, which trigger frame reserves a transmission opportunity granted to the access point on the communication channel and defines resource units, RUs, forming the communication channel comprising the accessed resource units.

[0095] This approach enables the AP to drive QoS management.

[0096] In other embodiments, a reset flag is associated with each service queue, wherein the reset flag is enabled whenever a new backoff value is drawn to reset the associated queue backoff counter without transmitting data from the service queue, and the reset flag is disabled whenever data from the service queue is transmitted, and

[0097] Data transmitted in resource units provided by the access point within a transmission opportunity granted to the access point is retrieved from at least one traffic queue selected based on an enabled or disabled state of a reset flag associated with the traffic queue.

[0098] Preferably, data transmitted in resource units provided by the access point within a transmission opportunity granted to the access point is retrieved from a traffic queue having a reset flag enabled.

[0099] These configured reset flags save the QoS information related to the service queues. In fact, due to the extraction of the new backoff value, the priority of the service queue compared to other service queues may be lost (because for this case, no data is transmitted in MU EDCA mode at the re-extraction timing of the new backoff value). Therefore, the reset flag is used to indicate which service queues have priority data that should be transmitted urgently when accessing the RU.

[0100] In some embodiments, the method further comprises: at the station, for at least one traffic queue transmitted in the accessed resource unit, calculating a new backoff value to reset an associated queue backoff counter.

[0101] This approach restores a fairer QoS management since the same behavior as conventional EDCA is applied here (a new backoff value for the traffic queue every time it is transmitted).

[0102] In a particular embodiment, a new backoff value is calculated only for the transmission service queues from which the data transmitted at the beginning of the accessed resource unit comes. Generally, it is assumed that the first transmission queue transmits most of the data in the accessed resource unit. The other transmission queues only send small amounts of data to fill the bandwidth available in the accessed resource unit (assumed to be a TXOP). In this regard, extracting new backoff values ​​for these "auxiliary" queues can be very disruptive to the remaining data of these queues, and thus a longer wait time must be made compared to direct OFDMA access. As a result, the proposed implementation maintains fairness with respect to these auxiliary queues by maintaining the same future transmission probability for these auxiliary queues.

[0103] In the modified example, a new queue backoff value is calculated for each transmission service queue. In this way, since the application is completely the same as the traditional EDCA behavior, fair QoS management is achieved.

[0104] In some embodiments, backoff values ​​for resetting queue backoff counters are calculated based on contention parameter sets each associated with a corresponding service queue, and

[0105] The method further comprises, at the site, resetting a contention parameter set associated with a (preferably each) traffic queue that remains in MU contention mode for at least a parameter lifetime duration to a default parameter set. For example, the parameter lifetime duration may correspond to at least two times a predetermined duration for initializing a MU mode timer (HEMUEDCATimer).

[0106] This helps improve network efficiency. In fact, since the service queue of interest remains in MU contention mode for a long time, the contention parameters (usually EDCA parameters) of the service queue no longer reflect the actual network conditions. Therefore, resetting these contention parameters erases any old network constraints that these contention parameters may be embedded in. Without any knowledge about the network conditions, it is as if the service queue is a new service queue in the network.

[0107] In other embodiments, the method further comprises: at the station, after transmitting the data stored in the associated service queue in the visited communication channel, extracting a new backoff value to reset the expired queue backoff counter. Thus, in the case where the station or service queue is in the traditional EDCA contention mode, the traditional EDCA scheme is maintained.

[0108] In yet other embodiments, the method includes: receiving, at the station, a trigger frame from an access point, the trigger frame reserving a transmission opportunity granted to the access point on a communication channel and defining at least one resource unit RU (preferably a plurality) forming a communication channel including the accessed resource unit. This complies with standard requirements for declaring RUs.

[0109] In other embodiments, the transmission service queue switches to MU contention mode only when data is successfully transmitted in the accessed resource unit. This structure ensures fairness. In fact, in the system of contention mode switching, only the penalty MU contention mode should be implemented to compensate for the existence of other transmission opportunities (here by RU), which means that data is successfully transmitted.

[0110] In yet other embodiments, the accessed resource unit via which the data is transmitted is a random resource unit that is accessed via contention using a set of RU contention parameters that is separate from a set of contention parameters used to extract a backoff value to reset a queue backoff counter.

[0111] In yet other embodiments, the accessed resource units via which the data is transmitted are scheduled resource units, wherein the scheduled resources are assigned to the station by the access point.

[0112] Of course, some stations may access scheduled RUs while other stations may access random RUs at the same time, which enables (for one or more AC queues) to have various stations in MU contention mode at the same time.

[0113] Another aspect of the invention relates to a non-transitory computer-readable medium storing a program which, when executed by a microprocessor or a computer system in a device, causes the device to perform any method as defined above.

[0114] The non-transitory computer readable medium may have similar features and advantages as those set forth above and below in connection with the method and apparatus.

[0115] At least a portion of the method according to the present invention may be implemented by a computer. Thus, the present invention may take the form of an all-hardware embodiment, an all-software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects that may all be generally referred to herein as "circuits," "modules," or "systems." In addition, the present invention may take the form of a computer program product, wherein the computer program product may take the form of a computer program product embodied in any tangible medium having a representation of a computer-usable program code embodied in the medium.

[0116] Since the present invention can be implemented in software, the present invention can be embodied as computer readable code for provision to a programmable device on any suitable carrier medium. Tangible carrier media may include storage media such as hard drives, magnetic tape devices, or solid-state memory devices. Transient carrier media may include signals such as electrical signals, electronic signals, optical signals, acoustic signals, magnetic signals, or electromagnetic signals (e.g., microwave or RF signals). BRIEF DESCRIPTION OF THE DRAWINGS

[0117] Other advantages of the present invention will become apparent to those skilled in the art upon examination of the drawings and detailed description.Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings.

[0118] Figure 1 A typical wireless communication system in which embodiments of the present invention may be implemented is shown;

[0119] Figure 2a IEEE 802.11e EDCA is shown involving access categories;

[0120] Figure 2b An example of mapping between eight priority levels of a traffic class and four EDCA ACs is shown;

[0121] Figure 2c 802.11e mechanism showing backoff counter countdown;

[0122] Figure 2d Shows the structure of the MAC data frame header;

[0123] Figure 3 802.11ac channel allocations are shown to support composite channel bandwidths of 20 MHz, 40 MHz, 80 MHz, or 160 MHz as known in the prior art;

[0124] Figure 4An example of an 802.11ax uplink OFDMA transmission scheme is shown using a timeline, where an AP issues a trigger frame for reserving a transmission opportunity of an OFDMA resource unit on an 80 MHz channel as known in the prior art;

[0125] Figure 5a An exemplary scenario of conventional transmission of a trigger frame using an EDCA mechanism is shown, in which a penalty scheme known in the prior art may be applied;

[0126] Figure 5b shows an exemplary evolution of a backoff counter and associated data selection known in the prior art;

[0127] Figure 5c illustrates the evolution of a backoff counter and associated data selection according to an embodiment of the present invention;

[0128] Figure 6 shows a schematic representation of a communication device or station according to an embodiment of the present invention;

[0129] Figure 7 A block diagram schematically illustrating the architecture of a wireless communication device according to an embodiment of the present invention;

[0130] Figure 8 An exemplary transmission block of a communication station according to an embodiment of the present invention is shown;

[0131] Fig. 9 A flow chart is used to illustrate the main steps performed by the MAC layer of a station when receiving new data to be transmitted in an embodiment of the present invention;

[0132] Fig.10 A flow chart is used to illustrate steps of accessing a medium based on an EDCA medium access scheme according to an embodiment of the present invention;

[0133] Fig.11 A flow chart is used to illustrate the steps of accessing a resource unit based on an RU or an OFDMA access scheme when a trigger frame defining an RU is received according to an embodiment of the present invention;

[0134] Fig.12 A flow chart is used to illustrate station management for switching back (or retreating) from the MU contention mode to the traditional contention mode according to an embodiment of the present invention;

[0135] Fig.13 shows the structure of a trigger frame as defined in the 802.11ax standard;

[0136] Fig.14a shows the structure of a standardized information element used to describe parameters of EDCA in a beacon frame; and

[0137] Fig.14b An exemplary structure of a dedicated information element for transmitting a degraded EDCA parameter value and a HEMUEDCATimer value according to an embodiment of the present invention are shown. DETAILED DESCRIPTION

[0138] The invention will now be described using specific non-limiting exemplary embodiments and by reference to the accompanying drawings.

[0139] Figure 1 A communication system is shown in which a plurality of communication stations (or nodes) 101 to 107 exchange data frames via a wireless transmission channel 100 of a wireless local area network (WLAN) under the management of a central station or access point (AP) 110, which is also regarded as a station of the network. The wireless transmission channel 100 is defined by an operating frequency band, wherein the operating frequency band is composed of a single channel or a plurality of channels forming a composite channel.

[0140] Hereinafter, the word "station" refers to any type of station. The term "access point station" or simply "access point" (AP) refers to a station that plays the role of access point 110. The term "non-access point station" or simply "non-AP station" or client station (STA) refers to other stations 101-107.

[0141] Accessing the shared wireless medium to send data frames is mainly based on CSMA / CA technology to sense the carrier and avoid collisions by separating concurrent transmissions in space and time.

[0142] Carrier sensing in CSMA / CA is performed by both physical and virtual mechanisms. Virtual carrier sensing is achieved by transmitting a control frame to reserve the medium before transmitting a data frame.

[0143] Next, the source station or the transmitting station including the AP first attempts to sense the medium that has been idle for at least a DIFS (standing for DCF Inter-Frame Space) period through a physical mechanism before transmitting a data frame.

[0144] However, if the shared wireless medium is sensed to be busy for a DIFS period, the source station continues to wait until the wireless medium becomes idle.

[0145] Figure 1 The wireless communication system of the invention comprises a physical access point 110, which is configured to manage a WLAN BSS (Basic Service Set), i.e., a group of non-AP stations that have previously registered with the AP. Such a BSS managed by the AP is called an infrastructure BSS. Hereinafter, the term BSS will be used as an equivalent of the infrastructure BSS.

[0146] Once a BSS is established, access points can bridge traffic within the BSS or from other networks (e.g., wired networks) to the BSS (or vice versa). Thus, stations of the BSS should only talk to the AP that is responsible for relaying data frames if they are intended for another station of the BSS.

[0147] To access the medium, any station including the AP starts counting down a backoff counter designed to expire after a number of time slots randomly selected in the so-called contention window [0, CW], where CW is an integer. This backoff mechanism or process (also known as a channel access scheme) is the basis of a collision avoidance mechanism that postpones the transmission time by a random interval, thereby reducing the probability of collision on the shared channel. After the backoff time expires (i.e., the backoff counter reaches zero), the source station can send data or control frames if the medium is idle.

[0148] Management of Quality of Service (QoS) at the station level has been introduced in wireless networks through the well-known EDCA mechanism defined in the IEEE 802.11e standard.

[0149] In fact, in the original DCF standard, the communication station includes only one transmission queue / buffer. However, since the subsequent data frame cannot be transmitted until the transmission / retransmission of the previous frame is completed, the delay in transmitting / retransmitting the previous frame prevents the communication from having QoS.

[0150] Figure 2a The IEEE 802.11e EDCA mechanism involving access categories is shown to improve the quality of service (QoS) for more efficient use of the wireless medium.

[0151] The 802.11e standard relies on a coordination function, referred to as the Hybrid Coordination Function (HCF), with two modes of operation: Enhanced Distributed Channel Access (EDCA) and HCF Controlled Channel Access (HCCA).

[0152] EDCA enhances or extends the functionality of the original access DCF method: EDCA is designed to support priority services similar to DiffServ (Differentiated Services), which is a protocol for specifying and controlling network services by class so that specific types of services are prioritized.

[0153] EDCA is an important channel access scheme or mechanism in WLAN because it is a distributed and easily deployable mechanism. The scheme competes for access to at least one communication channel of the communication network using EDCA competition parameters so that the station transmits locally stored data on the accessed communication channel.

[0154] The above-mentioned inadequacy of having satisfactory QoS due to delays in frame retransmissions has been addressed by utilizing multiple transmission queues / buffers.

[0155] QoS support in EDCA is achieved by introducing four access categories (ACs) and thereby four corresponding transmission / traffic queues or buffers (210). Typically, the four ACs are as follows in descending priority order: voice (or "AC_VO"), video (or "AC_VI"), best effort (or "AC_BE"), and background (or "AC_BG").

[0156] Of course, another number of service queues may also be considered.

[0157] Each AC has its own service queue / buffer for storing corresponding data frames to be transmitted on the network. Data frames (i.e., MSDUs) incoming from the upper layers of the protocol stack are mapped to one of the four AC queues / buffers and are thereby input into the mapped AC buffer.

[0158] Each AC also has its own set of queue contention parameters and is associated with a priority value, thereby defining services with higher or lower priority in the MSDU. Thus, there are multiple service queues for servicing data services at different priorities. The queue contention parameters typically include a CW for each service queue. min , CW max , AIFSN and TXOP_Limit parameters. CW min and CW max The lower and upper boundaries of the selection range for selecting the EDCA contention window CW for a given service queue. AIFSN stands for arbitration inter-frame gap number and defines the sum of the AIFS time periods except for the SIFS interval (defined as the sum of the AIFS time periods - see Figure 2b ) must sense the medium as idle before decrementing the queue backoff counter associated with the traffic queue in question. TXOP_Limit defines the maximum size of a TXOP that a station can request.

[0159] This means that each AC (and corresponding buffer) acts as an independent DCF contention entity including a respective queue backoff engine 211. Thus, each queue backoff engine 211 is associated with each service queue to use queue contention parameters and extract a backoff value (from the CW) to initialize a respective queue backoff counter for contention access to at least one communication channel for transmission of data stored in each service queue on the accessed communication channel.

[0160] The contention window CW and the backoff value are called EDCA variables.

[0161] This causes ACs within the same communication site to compete with each other to access the wireless medium and obtain transmission opportunities using, for example, the conventional EDCA access scheme described above.

[0162] By setting different queue backoff parameters between ACs (such as different CW min , CW max , AIFS, and different transmission opportunity duration limits (TXOP_Limit), etc.) to achieve service differentiation between ACs. This helps to adjust QoS.

[0163] Using different AIFSN values ​​in addition to using an average lower CW (to postpone the decrement of the backoff counter) gives high priority traffic in EDCA a higher chance of being transmitted compared to low priority traffic: stations with high priority traffic wait statistically less on average before sending a packet than stations with low priority traffic.

[0164] refer to Figure 2a Of the four AC buffers (210) shown, buffers AC3 and AC2 are typically reserved for real-time applications (eg, voice AC_VO or video transmission AC_VI). These buffers have the highest priority and the second-to-last highest priority, respectively.

[0165] Buffers AC1 and AC0 are reserved for best effort (AC_BE) traffic and background (AC_BG) traffic. Buffers AC1 and AC0 have the second lowest priority and the lowest priority, respectively.

[0166] Each data unit MSDU arriving at the MAC layer from an upper layer (eg, link layer) having a priority is mapped into the AC according to a mapping rule. Figure 2b An example of mapping between eight priority traffic classes (user priority or UP between 0 and 7 according to IEEE 802.1d) and four ACs is shown. The data frame is then stored in a buffer corresponding to the mapped AC.

[0167] For example, Figure 2c The impact of different AIFSNs is shown in FIG.

[0168] Each station must wait a fixed amount of time to ensure that the medium is idle before attempting to transmit. With DCF, DIFS is constant for all types of traffic. However, with 802.11e, the fixed amount of time a station must wait will depend on the access category and is called the Arbitration Interframe Space (AIFS).

[0169] With AIFS, each service queue "i" waiting to transmit must wait until the medium is declared available via a clear channel assessment (CCA) and a network allocation vector (NAV) (neither of which is discussed here for brevity). Once the medium is available, each service queue "i" must wait for a corresponding AIFS[i] period (including a SIFS period to defer access to the medium) before decrementing its associated queue backoff counter.

[0170] Thus, each of the four traffic queues has a defined interframe gap value corresponding to the priority assigned to that queue. For example, the AC_VO queue is the highest priority and therefore has the lowest interframe gap timer. The AIFS timers (250) assigned by IEEE 802.11e are all defined as 1 Short Interframe Gap (SIFS) value + a variable number of slot times (AIFSN) defined by the physical layer coding method in use (CCK, DSSS, OFDM). The value of the EDCA parameter AIFS Number (AIFSN) is administrator configurable, with the default value defined as follows:

[0171]

[0172] The AIFSN value may be provided by the AP in a so-called EDCA parameter set information element (eg, in a beacon frame sent by the AP). The AIFSN field in this information element is four bits long, with a minimum value of 2 defined in the standard and a maximum value of 15 based on field length limitations.

[0173] In this manner, arbitrating the interframe gap allows statistical dominance of frames in higher priority traffic queues because these frames do not need to wait as long before having their random backoff counters decremented relative to other queues.

[0174] The figure shows two AIFS[i] corresponding to two different traffic queues. It can be seen that due to the priority difference, one prioritized traffic queue starts decrementing its backoff value earlier than the other less prioritized traffic queue. This situation is repeated after each new medium access by any station in the network (i.e., when the medium is again sensed as idle).

[0175] To initiate the transmission of data, a service queue in a station first randomly selects a backoff value for its backoff counter. As already explained above, the backoff value must be within the contention window value defined for that service queue. As with the AIFS parameter, the difference between the contention windows of the various service queues is used to prioritize services in these queues by allowing higher priority queues to wait for a shorter time interval before being allowed to transmit over the air.

[0176] Once the appropriate AIFS[i] period expires, each traffic queue may begin decrementing its queue backoff counter (251) by one for each time slot that passes.

[0177] Next, when the EDCA backoff process for the service queue (or AC) ends (at least one backoff counter reaches zero), the MAC controller (hereinafter referred to as Figure 7 704 in the figure) transmits the data frame from the service queue to the physical layer for transmission to the wireless communication network.

[0178] Since the service queues operate concurrently when accessing the wireless medium, it is possible that two service queues of the same communication station end their backoff at the same time. In this case, the virtual conflict handling procedure (212) of the MAC controller operates between the conflicting ACs (such as Figure 2b As shown in the figure, the AC with the highest priority is selected, and the transmission of data frames from the AC with a lower priority is abandoned.

[0179] The virtual conflict handler then commands the AC with the lower priority to start the backoff operation again using the increased CW value.

[0180] Figure 2d 2 shows the structure of the QoS control field 200 included in the header of the MAC data frame and the IEEE 802.11e MAC frame. In addition to other fields, the MAC data frame includes a frame control header 201 and a frame body 202. As shown in the figure, the QoS control field 200 is composed of two bytes, wherein the two bytes include the following information items:

[0181] - Bits B0 to B3 are used to store a service identifier (TID) 204 that identifies the service flow. The service identifier uses the transmission priority value (user priority UP, a value between 0 and 9 - see Figure 2b ) or the value of the service stream identifier (TSID) used for other data streams (a value between 8 and 15);

[0182] - Bit B4 is used by non-AP stations to distinguish the meaning of bits B8 to B15 and is described in detail below;

[0183] - Bits B5 and B6 define the ACK Policy subfield that specifies the acknowledgement policy associated with the data frame. This subfield is used to determine how the receiving station must acknowledge the data frame; Normal ACK, No ACK, or Block ACK.

[0184] - Bit B7 is reserved, meaning it is not used by the current 802.11 standard; and

[0185] - If bit B4 is set to 1, bits B8-B15 represent the "Queue Size" subfield 203 to indicate the amount of buffered traffic for a given TID at the non-AP station sending the frame. The queue size is the total size of all packets buffered for the specified TID rounded up to the nearest multiple of 256 octets and expressed in units of 256 octets. An access point receiving the frame can use this information to determine the next TXOP duration that the access point will grant to the station. A queue size of 0 indicates that there is no buffered traffic for the TID. A queue size of 255 indicates an unspecified or unknown size for the TID 204.

[0186] - As an alternative to the use of "Queue Size", if bit B4 is set to 0, bits B8-B15 represent the "Requested TXOP Duration" subfield. This indicates the duration in 32 μs required for the sending station to determine the next TXOP for the specified TID. Of course, the "Requested TXOP Duration" provides an equivalent request to the "Queue Size" because both take into account all packets buffered for the specified TID.

[0187] The 802.11e MAC frame format, and more particularly the QoS Control field 200, has been maintained for the latest version of the standard as now described.

[0188] To meet the growing demand for faster wireless networks to support bandwidth-intensive applications, 802.11ac targets higher bandwidth transmission via multi-channel operation. Figure 3 802.11ac channel allocations are shown supporting composite channel bandwidths of 20 MHz, 40 MHz, 80 MHz, or 160 MHz.

[0189] IEEE 802.11ac introduces support for a restricted number of predefined subsets of 20 MHz channels to form a dedicated predefined composite channel configuration that can be reserved by any 802.11ac station on the wireless network for the purpose of transmitting data.

[0190] The predefined subsets are shown in the figure and correspond to 20 MHz, 40 MHz, 80 MHz and 160 MHz channel bandwidths, compared to only 20 MHz and 40 MHz supported by 802.11n. In practice, the 20 MHz component channels 300-1 to 300-8 are cascaded to form a wider communication composite channel.

[0191] In the 802.11ac standard, the channels in each predefined 40 MHz, 80 MHz or 160 MHz subset are contiguous within the operating band, ie, no holes (missing channels) are allowed in the composite channels that are sequenced in the operating band.

[0192] The 160MHz channel bandwidth includes two 80MHz channels, wherein the two 80MHz channels may or may not be frequency continuous. The 80MHz channel and the 40MHz channel include two frequency adjacent or continuous 40MHz channels and a 20MHz channel, respectively. However, the present invention may include embodiments having any composition of channel bandwidth (i.e., only including continuous channels in the operating frequency band, or including non-continuous channels in the operating frequency band).

[0193] TXOPs are granted to stations via the Enhanced Distributed Channel Access (EDCA) mechanism on the "primary channel" (300-3). In practice, for each composite channel having bandwidth, 802.11ac designates one channel as "primary," meaning that the channel is used to contend for access to the composite channel. The 20 MHz primary channel is common to all client stations (STAs) belonging to the same basic set, i.e., managed by or registered to the same local access point (AP).

[0194] However, in order to ensure that other legacy stations (ie, legacy stations not belonging to the same set) do not use the secondary channel, it is proposed to replicate the control frames (eg, RTS frames / CTS frames) reserving such a composite channel on each 20 MHz channel in the composite channel.

[0195] As previously addressed, the IEEE 802.11ac standard enables the bonding of up to 4 or even 8 20 MHz channels. Due to the limited number of channels (19 in the 5 GHz band in Europe), channel saturation becomes a problem. In fact, in densely populated areas, the 5 GHz band will undoubtedly tend to be saturated even with 20 MHz or 40 MHz bandwidth usage for each wireless LAN cell.

[0196] The development of the 802.11ax standard seeks to enhance the efficiency and use of wireless channels in dense environments.

[0197] From this perspective, the multi-user (MU) transmission feature can be considered, allowing the utilization of multiple simultaneous transmissions of the access point to different users in both the downlink (DL) direction and the uplink (UL) direction. In the uplink, multi-user transmission can be used to reduce the probability of collision by allowing multiple non-AP stations to transmit to the AP simultaneously.

[0198] In order to actually carry out such multi-user transmission, it has been proposed to split the granted 20MHz channel (400-1 to 400-4) into at least one subchannel, but preferably multiple subchannels 410 (basic subchannels) (also called subcarriers or resource units (RUs) or "traffic channels"), where multiple users share these subchannels 410 in the frequency domain, for example based on orthogonal frequency division multiple access (OFDMA) technology.

[0199] refer to Figure 4 This situation is shown.

[0200] In this example, each 20 MHz channel (400-1, 400-2, 400-3 or 400-4) is subdivided in the frequency domain into four OFDMA subchannels or RUs 410 of size 5 MHz. Of course, the number of RUs that divide the 20 MHz channel can be different from four. For example, 2 to 9 RUs can be provided (thus each having a size of 10 MHz to about 2 MHz). The RU width can also be made larger than 20 MHz when the RU is included in a wider composite channel (e.g., 80 MHz).

[0201] In contrast to MU downlink OFDMA, where the AP can directly send multiple data to multiple stations (supported by specific indications in the PLCP header), a trigger mechanism has been adopted for the AP to trigger MU uplink communications from various non-AP stations.

[0202] To support MU uplink transmissions (during an AP-preempted TXOP), an 802.11ax AP must provide signaling information used by both legacy stations (i.e., non-802.11ax stations) to set their NAVs and by 802.11ax client stations to determine resource unit allocations.

[0203] In the following description, the term “legacy” refers to a non-802.11ax station, which means a prior art 802.11 station that does not support OFDMA communications.

[0204] like Figure 4 As shown in the example of , the AP sends a trigger frame (TF) 430 to the target 802.11ax station. The bandwidth or width of the target composite channel is notified in the TF frame, which means notifying a value of 20MHz, 40MHz, 80MHz or 160MHz. The TF frame is sent on the primary channel of 20MHz and is replicated (repeated) on each other channel of 20MHz to form the target composite channel. Due to the replication of control frames, it can be expected that each nearby traditional station that receives the TF frame (or its replication) on the primary channel will then set its NAV to the value specified in the TF frame. This prevents these traditional stations from accessing channels in the target composite channel during the TXOP.

[0205] Based on the AP's decision, the trigger frame TF may define multiple resource units (RUs) 410. The multi-user feature of OFDMA allows the AP to assign different RUs to different client stations to increase contention. This can help reduce contention and collisions within the 802.11 network.

[0206] As already discussed, RUs with widths greater than 20 MHz may be defined: as an example, an AP may provide a RU of 996 tones to cover an 80 MHz communication channel, thus being equivalent in capacity to a single-user 80 MHz communication. Thus, it may be noted that such an 80 MHz communication maintains the MU UL communication within the RU in the sense of being triggered by a trigger frame sent by the AP.

[0207] The trigger frame 430 may specify "scheduled" RUs that may be reserved by the AP for certain sites, in which case no contention for access to these RUs is required for these sites. These RUs and their corresponding scheduled sites are indicated in the trigger frame. For example, a site identifier (such as an association ID (AID) assigned to each site upon registration, etc.) is added in a manner associated with each scheduled RU to explicitly indicate the sites that are allowed to use each scheduled RU. This transmission mode is concurrent with the traditional EDCA mechanism and retrieves uplink data to be sent to the AP from the EDCA queue 210.

[0208] In addition to or instead of the "scheduled" RU, the trigger frame TF may also specify a "random" RU. A random RU may be randomly accessed by a station of the BSS. In other words, a random RU in the TF, designated or allocated by the AP, may be used as a basis for contention between stations that intend to access the communication medium to send data. In the event that two or more stations attempt to transmit simultaneously on the same RU, a conflict occurs. A random RU may be identified using an AID equal to 0.

[0209] Based on the additional backoff counters (OFDMA backoff counters, or OBO counters or RU counters) used by 802.11ax non-AP stations for RU contention, a random allocation process can be considered for the 802.11ax standard, i.e., to allow these 802.11ax non-AP stations to compete among themselves to access and send data on random RUs. The RU backoff counter is different from the EDCA backoff counter. However, it is assumed that the data transmitted in the accessed OFDMA RU 410 is provided from the same EDCA service queue 210.

[0210] The RU random allocation process includes the following steps for a station with a positive RU backoff value (initially drawn within the RU contention window range) among multiple 802.11ax stations: a first step for determining a subchannel or RU (so-called "random RU") of a communication medium that competes for an available communication medium based on a received trigger frame; a second step for verifying whether the value of the RU backoff value local to the considered station is not greater than the number of random RUs detected as available; and then in the case of successful verification, a third step for randomly selecting an RU from the RUs detected as available and then sending data. In the case of not verifying the second step, a fourth step is performed (instead of the third step) to decrement the RU backoff counter by the number of random RUs detected as available.

[0211] It can be noted that for each TF received, the station is not guaranteed to perform OFDMA transmission on a random RU. This is because at least the RU backoff counter is decremented by the number of proposed random RUs at each reception of a trigger frame, thereby making the data transmission to subsequent trigger frames different (depending on the current value of the RU backoff number and the number of random RUs provided by each further received TF)

[0212] return Figure 4 , from the various possible accesses to the RUs, it is obtained that some of these RUs will not be used (410u), because the stations whose RU backoff value OBO is less than the number of available random RUs do not randomly select one of these random RUs, while some other RUs collide (such as example 410c) (this is because at least two of these stations have randomly selected the same random RU). This shows that due to the random determination of the random RU to be accessed, conflicts may occur on some RUs, while other RUs can remain idle.

[0213] Once a station transmits data to the AP using scheduled and / or random RUs, the AP responds with a multi-user acknowledgement (not shown) to confirm the data on each RU.

[0214] Especially in the dense environments envisioned by the 802.11ax standard, the MU uplink (UL) medium access scheme including both scheduled RUs and random RUs is proven to be very efficient compared to the traditional EDCA access scheme. This is because both the number of collisions generated by simultaneous medium access attempts and the overhead caused by medium access are reduced.

[0215] However, the EDCA access scheme and the MU UL OFDMA / RU access scheme must coexist, especially allowing legacy 802.11 stations to access the medium and even allowing 802.11ax stations to initiate communications with other non-AP stations.

[0216] While the EDCA access scheme employed alone provides fair access to the medium among all stations, its association with the MUUL OFDMA / RU access scheme introduces a drift in fairness because, compared to legacy stations, 802.11ax stations have additional opportunities to transmit data through resource units provided in the transmission opportunities granted to the AP.

[0217] To restore some fairness between sites, solutions have been proposed.

[0218] For example, in co-pending UK application 1612151.9 filed on 13 July 2016, upon successful transmission of data via the accessed resource unit (i.e. via UL OFDMA transmission), the current value of at least one EDCA parameter is modified to a different value (MU EDCA parameter). This is to reduce the probability of a station competing for access to the communication channel via (legacy EDCA).

[0219] In this framework, a method is proposed to reduce the probability of a station's EDCA-based transmission (i.e., using the EDCA medium access scheme) immediately when the station successfully uses the MU UL mechanism to transmit its data. This reduction is achieved by modifying the well-known EDCA parameter set (which consists of AIFSN, CW min and CW max Composition) to carry out.

[0220] The proposed mechanism sets each transmission traffic queue to MU EDCA mode (or "MU mode") in response to successful transmission of data in the accessed MU UL OFDMA resource unit. The setting is performed for a predetermined duration known as HEMUEDCATimer. MU EDCA mode is a mode in which each EDCA parameter set is modified to a MU parameter set that is different from the legacy EDCA parameter set used in different legacy EDCA modes.

[0221] To switch from the traditional EDCA contention access mode to the MU EDCA mode, the station can modify its EDCA parameter set (AIFSN, CW min and / or CW max ). Switching back to legacy EDCA mode can occur when HEMUEDCATimer expires. Note: This timer is reset to its initial value every time the station transmits new data (from any AC) again during a newly accessed resource unit provided by the AP. It is recommended that the initialization value of HEMUEDCATimer be high (e.g., tens of milliseconds) in order to include several new opportunities for MU UL transmissions.

[0222] The modified values ​​of the EDCA parameter set (ie, the MU parameter set for the four traffic queues) may be transmitted by the access point in a dedicated information element (typically sent within a beacon frame that broadcasts network information to the stations).

[0223] The document provides the following specific configuration: For the transmission service queue in MU EDCA mode, EDCA access to the medium tends to be less frequent. The AP specifies the specific working mode by indicating a specific value (usually 0) of the AIFSN parameter in the set of MU EDCA parameters. This specific value means to the station that the station should use a very high value for its AIFSN in MU EDCA mode, which should be equal to the HEMUEDCATimer transmitted by the AP (hint: compared with the worst AIFS[i] of less than 0.1 milliseconds in the traditional EDCA mode, the value of HEMUEDCATimer should be high, i.e., about tens of milliseconds).

[0224] Unfortunately, by significantly modifying the EDCA parameters and in particular the AIFSN value, the known mechanisms for controlling the drift of fairness reduce the chances of the queue backoff counters of each service queue in MU EDCA mode evolving (decrementing), thereby reducing the efficient use of these queue backoff counters in determining the relative priority of the queues. In fact, the queue backoff values ​​thus no longer reflect which service queue should have the highest transmission priority in the sense of EDCA (e.g., having the oldest data stored internally).

[0225] It is then no longer possible for the station to comply with the QoS principles described in the 802.11e standard.

[0226] Reference now Figure 5a Describe the situation, where Figure 5a An exemplary scenario of an 802.11ax network implementing MU EDCA mode as described in the above document is described. In this scenario, the AP sends a completely random first trigger frame (which means that the AP only defines random RUs), followed by a completely scheduled second trigger frame (the AP only defines scheduled RUs) so that the AP polls stations with uplink data.

[0227] Since the receiver (access point) competes on behalf of non-AP stations in uplink OFDMA, the access point should know two indications, which non-AP stations have uplink packets and what the size of their buffers 210 is. In fact, if non-AP stations without uplink packets are polled for uplink OFDMA transmission, the allocated resource units for MUUL OFDMA transmission are wasted, thereby resulting in degradation of wireless medium usage.

[0228] The standard proposes that buffer status reports from 802.11ax stations can be used to support efficient MU UL operation of access points. To this end, upon receiving a trigger frame 430-BSR containing a request indication for a buffer status report, the 802.11ax station responds with a frame including a queue size subfield 203 in the QoS control field 200. The indication of the buffer status report can be, for example, a "trigger type" provided in the trigger frame, and a specific value indicates such a buffer status request. The trigger frame 430-BSR is regarded as a trigger frame for the buffer status report (BSR) of the station.

[0229] Preferably, the trigger frame 430-BSR is broadcast by the AP to reach all stations of the BSS, and most or even all resource units are of random type to allow all stations to have a random chance to provide a queue size report. In addition, in order to reach the most stations, the trigger frame 430-+BSR provides the maximum number of resource units, that is, to request the widest communication channel with the narrowest resource unit size.

[0230] In order to minimize the duration of TXOP 490 to obtain buffer status reports, the frames sent within resource unit 410-BSR should be constrained and of the same size to avoid inefficient filling. For example, the QoS_Null frame seems suitable to provide such a constraint. This particular QoS data frame contains a QoS control field with queue size information but no data payload.

[0231] The current version of IEEE 802.11ax extends the use of queue size information 203 in a new QoS Control field (i.e., HE Control) (and possibly in a replacement of the QoS Control field of an 802.11ax frame) to inform a station of an approximate number of, and preferably all, traffic queues 210 (rather than just one as proposed in the 802.11e standard).

[0232] Once the access point has buffer reports for a set of stations of its BSS, the access point can specifically poll these stations with scheduled resource unit allocations. This allocation is transmitted using a trigger frame 430-D for data transmission. The stations with the allocated resource units then transmit in a longer TXOP_TF data The buffered data is transmitted during 491 and within the allocated resource units 410-D of these stations. Since MU UL / DL OFDMA transmissions on all resource units of a composite channel should be aligned in time, a station may provide a filler payload 411-D if more data cannot be sent within the assigned resource units. This may occur, for example, if no more data is buffered for transmission or if the transmitting station does not want to fragment any remaining data frames.

[0233] The access point can manage resource unit size based on the reported station needs.The access point can schedule resource units during the TXOP period to any station that sent a report.

[0234] Once a station has used resource units 410-D to transmit data to the access point, the access point responds to acknowledge the data on each resource unit with a multi-user acknowledgment 440. The ACK ends the granted TXOP period.

[0235] Due to the AP's polling of a given traffic queue and subsequent OFDMA transmission of data from that traffic queue, subsequent OFDMA transmissions may switch to MU EDCA mode with AIFSN set to HEMUEDCATimer. Only other traffic queues (not transmitting) are still able to access the communication channel using the EDCA scheme.

[0236] In the case where the AIFSN value provided by the AP (eg, in the EDCA parameter set information of the beacon frame) is zero, data of the access category implementing EDCA access to the wireless network is not transmitted over the wireless network. This prevents the service queue of the station in MUEDCA mode from accessing the medium.

[0237] In the example shown in the figure, the AP polls the station STA4 for transmission of data from the service queue AC_VI (time slot 410-D4). Due to the switch to MU EDCA mode, the service queue AC_VI can no longer request EDCA access as long as the HEMUEDCATimer has not expired. However, the station STA4 can still request EDCA access to other service queues (until these service queues are provided in the next MU UL transmission when the next MU UL transmission occurs). This is why the service queue AC_VO in the traditional EDCA mode can use EDCA access to actually access the communication channel and then clear itself via single-user transmission 495-SU (this is TXOP 492).

[0238] Figure 5b The above penalty mechanism is further elaborated.

[0239] In the figure, four values ​​530 represent queue backoff counters BC[AC] (and their backoff values) associated with four service queues 210. Graphical codes are used to distinguish the different states that the queue backoff counters can be in. The graphical codes are provided directly in the figure as a legend.

[0240] In the first stage shown (each stage corresponds to a time period from when the network becomes available until the end of the granted TXOP), when BC[VI] reaches zero (the counter in the dashed box), station 502 accesses the medium via EDCA, while the best queue backoff value of AP 501 has only reached 4. The black portion 540 before decrementing the queue backoff value corresponds to AIFS[AC] (the different sizes of these black portions 540 are not shown).

[0241] Video data from AC[2] (ie, the traffic queue of AC_VI) is then transmitted during the grant TXOP 550. A new queue backoff value is extracted for AC_VI (white graph in black box).

[0242] In the second phase, AP 501 first accesses the network after its AIFS 540 and the countdown of its backoff value 710, and then sends a trigger frame 1300. TF 1300 provides station 502 with at least one scheduled RU.

[0243] TF 1300 does not indicate any preferred AC in the corresponding field ( Fig.13 The preferred AC level field 1330 is shown set to 0). Therefore, the station 502 needs to determine which AC queue has the highest priority for selecting corresponding data for MU UL OFDMA transmission.

[0244] To do this, station 502 selects the AC queue with the lowest current backoff counter value. In this example, the first AC queue (corresponding to the VO queue) is selected because its associated queue backoff value is equal to 1 (compared to 4, 6, and 12 for the other AC queues).

[0245] Thus, data from AC_VO may be transmitted (560) in the accessed resource unit.

[0246] After a successful MU UL OFDMA transmission 560 of data, the corresponding traffic queue enters MU EDCA mode, where the EDCA parameter set of the transmitting traffic queue (here AC_VO) is modified with a set of MU values. Traffic queues in MU EDCA mode are shown in the figure using bold boxes.

[0247] During this second phase, the queue backoff counter 531 associated with the transmission traffic queue AC_VO is frozen, which means that the queue backoff counter 531 is not updated and maintains its previous value (here "1").

[0248] Thus, the third phase begins with the station 502 entering the Defer Transmit state by waiting for the AIFS[i] timer (565) to expire before decrementing the queue backoff value BC[i] 530.

[0249] For traffic queues in MU EDCA mode with more restrictive EDCA parameters (such as very high AIFSN, etc.), the modified value of AIFS 565 causes the corresponding queue backoff value BC[AC] to be decremented less frequently. Therefore, in the event that AP 501 sends a new trigger frame 1300-2 when making EDCA-based access to the medium, the station 502 provided with the new scheduled RU determines which traffic queue has the lowest current queue backoff value.

[0250] Again, this is BC[3] with a backoff value of 1. This means that station 502 again transmits (570) data from AC_VO in the visited RU.

[0251] After a while, if several traffic queues, especially if all traffic queues enter MU EDCA mode, the associated queue backoff value is blocked. Thus, the same traffic queues used for MU UL OFDMA transmissions are always prioritized. The backoff-based QoS requirements are no longer met.

[0252] The lack of dynamism of the backoff counters due to freezing in case of MU UL OFDMA transmissions should be restored so that they still efficiently reflect the relative priorities of the AC queues. Advantageously, the restoration should maintain the penalty scheme to reduce the probability of EDCA-based transmissions for AC queues in MU EDCA mode, and should also keep the evolution principle of the backoff counters.

[0253] Within this framework, the present invention proposes to keep the queue backoff counter decrementing while introducing reactive countermeasures when the backoff counter expires, in particular by not penalizing the AIFSN of the AC queue.

[0254] It should be reiterated that the queue backoff counter decrements over time as long as the communication channel is sensed by a station as idle for a period exceeding the corresponding arbitration interframe gap duration; when data stored in any service queue is transmitted in an accessed resource unit provided by the access point within a transmission opportunity granted to the access point on the communication channel, the service queue switches from the traditional contention mode to the MU contention mode.

[0255] In order to efficiently restore the dynamics of the backoff counter while maintaining the penalty scheme, the present invention proposes that: when one of the queue backoff counters expires, the site determines whether to access the communication channel to transmit the data stored in the associated business queue based on the current mode of the associated business queue, or to extract a new backoff value to reset the expired queue backoff counter without transmitting data from the associated business queue in the communication channel.

[0256] In fact, if the current mode is the traditional contention mode, the station accesses the communication channel to transmit the data stored in the associated service queue. This is the traditional EDCA scheme. Otherwise, if the current mode is the MU contention mode, a new backoff value is extracted to reset the expired queue backoff counter without transmitting data from the associated service queue in the communication channel.

[0257] Slight variations can be envisioned, such as also basing the decision on whether to access the communication channel or to extract a new backoff value on data currently stored in the associated service queue. For example, the penalty for not transmitting data is applied even if the backoff counter expires only if no data intended for a non-AP site is stored in the associated AC queue in MU EDCA mode.

[0258] The resumption of decrementing the backoff counter of the non-transmitting AC queue in MU mode ensures the restoration of the aging characteristic of the EDCA backoff counter and thereby the restoration of QoS. Thus, the dual functionality of EDCA backoff is restored and allows the application of relative QoS priorities between the AC queues of a station.

[0259] Additionally, the reactive countermeasure of resetting the expired backoff counter without transmitting data in case of MU mode ensures that penalties are still applied to the AC queues in such MU mode to reduce EDCA accesses.

[0260] Thus, the present invention works in a manner opposite to known techniques, which are essentially precautionary measures to avoid the backoff counter reaching zero to ensure reduced EDCA accesses.

[0261] As will further become apparent, the method of the present invention is easier to implement in a standard environment, and in particular in the transmit state machine of an 802.11 device.

[0262] Reference now Figure 5c To illustrate the results of one implementation of the present invention, Figure 5c Use and Figure 5b The same sequence illustrates restoring QoS through relative EDCA based priorities between ACs.

[0263] The first phase remains unchanged.

[0264] During the second phase, station 502 receives TF 1300 from AP 501. The AC queue selection algorithm in the station determines that service queue AC_VO has the highest priority due to the lowest queue backoff value (eg, Figure 5b ). Data from AC_VO (AC[3]) undergoes MU UL OFDMA transmission.

[0265] After successful transmission 560 of the data in the accessed RU, AC_VO enters MU EDCA mode (backoff value in the bold box), and an embodiment of the present invention proposes selecting a new backoff value 531 (white number in the black box, here with the value "15") for the transmission service queue AC_VO from the current and unchanged associated contention window.

[0266] In addition, AIFS[AC_VO] does not change when entering MU EDCA mode. This means that the penalty caused by MU mode is not taken care of by degradation of EDCA parameters.

[0267] Next, in the third phase, the backoff counters are decremented taking into account their respective AIFS. Here, even if AC_VO is in MU mode, the backoff counter 531 of AC_VO is decremented by 1 for each time slot in which the medium is sensed as idle. This is achieved due to the unmodified (or in some embodiments very lightly penalized) value AIFS[AC_VO].

[0268] Again, station 502 receives TF 1300-2 from AP 501. The AC queue selection algorithm in this station determines that traffic queue AC_VI has the highest priority due to the lowest queue backoff value (because BC[VO] now has a value of 14). Therefore, data from AC_VO undergoes MU UL OFDMA transmission in the visited RU.

[0269] It can be noted that Figure 5b In contrast, another traffic queue is requested for MU UL OFDMA transmission in the third phase due to the new backoff value 532 extracted to reset the backoff counter of AC_VO. Thus, the relative priority between the traffic queues is restored for the OFDMA transmission traffic queues.

[0270] After successful transmission 570 of the data in the accessed RU, AC_VI also enters MU EDCA mode (backoff value in the bold box; while AC_VO is already in MU EDCA mode), and a new backoff value 532 (white number in the black box, here with value "9") is extracted from the contention window for the transmission service queue AC_VI.

[0271] Next, in the fourth phase, the medium is sensed as idle and the backoff counters are decremented in consideration of their respective AIFS. Here, even though both AC queues are in MU mode, the backoff counter 531 of AC_VO changes from 14 to 7, while the backoff counter 532 of AC_VI changes from 9 to 2.

[0272] At the same time, the backoff counter of AC_BE expires, thereby causing the data from AC_BE to be transmitted (580). For the expired backoff counter 533, a new backoff value "15" is extracted.

[0273] Next, in the fourth phase, the medium is sensed as idle and the backoff counters are decremented taking into account their respective AIFS. Here, during the first two time slots after the SIFS period, the backoff counter 531 of AC_VO changes from 7 to 5, while the backoff counter 532 of AC_VI expires.

[0274] When the service queue AC_VO is currently in MU mode, without transmitting data from the associated service queue in the communication channel, a new backoff value (in this example, "8") is extracted to reset the expired queue backoff counter 532. As a result, the decrement of the backoff counter continues (actually the decrement never stops), especially the backoff counter of the AP that expires in sequence. Thus, the station 502 receives the new TF 1300-3 from the AP 501, and the AC queue selection algorithm in the station can be executed.

[0275] For example, the station determines that the service queue AC_VO has the highest priority due to the lowest queue backoff value (because BC[VI] has been reset at the same time). Therefore, the data from AC_VO undergoes MU UL OFDMA transmission 590 in the accessed RU.

[0276] However, in an embodiment, the reset of any AC queue in MU mode may be saved, and this information may be used to select data to be transmitted. For example, a reset flag (not shown in the figure) may be associated with each service queue, wherein the reset flag is enabled (i.e., set to TRUE) whenever a new backoff value is drawn to reset the associated queue backoff counter without transmitting data from the service queue (i.e., when the AC queue is in MU mode). This is, for example, the case for service queue AC_VI during phase 5 (which is reset with a new backoff value of "8").

[0277] In this case, upon receiving TF 1300-3, the station determines that the service queue AC_VI has a reset flag set to true. Therefore, data from AC_VI (such as AC[2] shown in the example of the figure) undergoes MU UL OFDMA transmission in the accessed RU. This means that data transmitted in a resource unit provided by the access point within a transmission opportunity granted to the access point is retrieved from at least one service queue selected based on the enabled or disabled status of the reset flag associated with the service queue. In particular, data transmitted in a resource unit 590 provided by the access point within a transmission opportunity granted to the access point is retrieved from a service queue with an enabled reset flag.

[0278] On the other hand, whenever data from the service queue is transmitted, the reset flag is disabled (ie, set to FALSE). In this example, the reset flag of AC_VI is reset after a successful transmission 590 .

[0279] According to the embodiment shown in the figure, a new backoff value (the white number in the black box, here having the value "11") is extracted for the backoff counter 531 associated with the transmission service queue AC_VI.

[0280] This exemplary scenario clearly illustrates the full functional behavior of EDCA backoff, thereby restoring QoS and, in particular, restoring dynamic relative EDCA based priorities between traffic queues.

[0281] Figure 6 A communication device 600 of a wireless network is schematically shown, wherein the communication device 600 is configured to implement 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 to which the following components are preferably connected:

[0282] A central processing unit 611 , denoted as CPU, such as a microprocessor;

[0283] A read-only memory 607, denoted as ROM, for storing computer programs used to implement the present invention;

[0284] A random access memory 612 represented as a RAM for storing executable code of the method according to the embodiment of the present invention and registers, wherein the registers are configured to record variables and parameters required to implement the method according to the embodiment of the present invention; and

[0285] At least one communication interface 602 connected to a communication network 603 via which digital data packets or frames or control frames are transmitted, for example a wireless communication network according to the 802.11ax protocol. Under the control of a software application running in the CPU 611, frames are written from a FIFO transmit memory in the RAM 612 to the transmitting network interface, or frames are read from a receiving network interface and written to a FIFO receive memory in the RAM 612.

[0286] Optionally, the communication device 600 may further include the following components:

[0287] A data storage component 604, such as a hard disk, for storing a computer program used to implement the method according to one or more embodiments of the present invention;

[0288] a disk drive 605 for a disk 606, the disk drive being configured to read data from the disk 606 or to write data to the disk;

[0289] A screen 609 for displaying decoded data and / or for use as a graphical interface with the user via a keyboard 610 or any other indicating means.

[0290] The communication device 600 may optionally be connected to various peripheral devices such as a digital camera 608 , wherein each peripheral device is connected to an input / output card (not shown) to supply data to the communication device 600 .

[0291] Preferably, the communication bus provides communication and interoperability between the various elements included in or connected to the communication device 600. The representation of a bus is not limiting, in particular, the central processing unit is operable to communicate instructions to any element of the communication device 600 directly or through another element of the communication device 600.

[0292] Disk 606 can optionally be replaced by any information medium such as a compact disk (CD-ROM) (rewritable or non-rewritable), a ZIP disk, a USB key or a memory card, and is generally replaced by an information storage component, wherein the information storage component can be read by a microcomputer or a microprocessor, integrated or not integrated into the device, possibly removable and configured to store one or more programs, wherein the execution of these one or more programs enables the implementation of the method according to an embodiment of the present invention.

[0293] As previously mentioned, the executable code may optionally be stored in the read-only memory 607, on the hard disk 604, or on a removable digital medium such as a disk 606. According to an optional variant, the executable code of the program may be received via the interface 602 over the communication network 603 to be stored in one of the storage components of the communication device 600, such as the hard disk 604, before being executed.

[0294] The central processing unit 611 is preferably configured to control and direct the execution of a portion of the instructions or software code of the program according to the present invention, wherein these instructions are stored in one of the above-mentioned storage components. When powered on, the program stored in the non-volatile memory (e.g., stored on the hard disk 604 or stored in the read-only memory 607) is transferred to the random access memory 612 containing the executable code of the program and the registers for storing the variables and parameters required to implement the present invention.

[0295] In a preferred embodiment, the device is a programmable device that implements the invention using software.Alternatively, however, the invention may be implemented in hardware (for example in the form of an application specific integrated circuit or ASIC).

[0296] Figure 7 The block diagram schematically shows the architecture of a communication device or node 600 (particularly one of the stations 101-107) configured to at least partially implement the present invention. As shown in the figure, the station 600 includes a physical (PHY) layer block 703, a MAC layer block 702 and an application layer block 701.

[0297] The PHY layer block 703 (e.g., 802.11 standardized PHY layer) has the following tasks: formatting, modulating on or demodulating from any 20 MHz channel or composite channel, and thus sending or receiving frames via the wireless transmission channel 100 used, which are 802.11 frames (e.g., single user frames) such as: control frames (RTS / CTS / ACK / trigger frames), MAC data and management frames based on 20 MHz width for interaction with legacy 802.11 stations or with 802.11ax in legacy mode (such as for trigger frames, etc.), and OFDMA type MAC data frames preferably having a width smaller than the 20 MHz legacy (typically 2 MHz or 5 MHz) relative to the wireless medium.

[0298] The MAC layer block or controller 702 preferably includes a MAC 802.11 layer 704 that implements the conventional 802.11ax MAC operation and an additional block 705 for at least partially performing an embodiment of the present invention. The MAC layer block 702 may optionally be implemented in software, which is loaded into the RAM 612 and executed by the CPU 611.

[0299] Preferably, this additional block (referred to as EDCA medium access module 705) implements the portion of the invention relating to site 600, namely remembering that once a successful transmission in resource units is provided to a given AC, "MU mode" is established for that AC, thereby continuing to decrement the backoff counters of the AC regardless of the contention pattern of the associated service queues (in particular, whether or not it is in MU mode), optionally remembering when the backoff counters in MU mode are reset, and also preventing EDCA medium access once the backoff of the AC in MU mode drops to zero.

[0300] The MAC 802.11 layer 704 and the EDCA medium access module 705 interact with each other to provide management of the dual mode (single-user EDCA and multi-user UL OFDMA) as described below.

[0301] In the upper part of the figure, an application layer block 701 runs an application for generating and receiving data packets (eg, data packets of a video stream). The application layer block 701 represents all stacked layers above the MAC layer according to ISO standardization.

[0302] Various exemplary embodiments are now used to illustrate embodiments of the present invention. Although the examples presented use a trigger frame 430 sent by an AP (see Figure 4 ) for multi-user uplink transmission, but equivalent mechanisms can be used in centralized or ad hoc environments (i.e., without APs). This means that the operations described below with reference to an AP can be performed by any station in an ad hoc environment.

[0303] These embodiments are mainly described in the context of IEEE 802.11ax by considering OFDMA resource units. However, the application of the present invention is not limited to the IEEE 802.11ax context.

[0304] Furthermore, the present invention does not necessarily rely on the use of the MU access scheme as described in 802.11ax. Any other RU access scheme that defines an alternative medium access scheme that allows stations to access the same medium simultaneously may also be used.

[0305] Figure 8 A typical transmission block of the communication station 600 according to an embodiment of the present invention is shown.

[0306] As described above, the station includes a channel access module and possibly an RU access module, both of which are implemented in the MAC layer block 702. The channel access module includes:

[0307] A plurality of service queues 210 for serving data services according to different priorities;

[0308] A plurality of queue backoff engines 211, each associated with each service queue, are used to transmit data stored in each service queue using a set of EDCA parameters, in particular, calculating each queue backoff value to be used by the associated backoff counter to compete for access to at least one communication channel. This is an EDCA access scheme.

[0309] The RU access module includes a RU backoff engine 800 separate from the queue backoff engine for using RU contention parameters, in particular calculating a RU backoff value to be used by the RU backoff counter to contend for access to an OFDMA random resource unit defined in a received TF (e.g., sent by an AP), to transmit data stored in any service queue in an OFDMA RU. The RU backoff engine 800 is associated with a transmission module called an OFDMA multiplexer 801. For example, when the RU backoff value described below reaches zero, the OFDMA multiplexer 801 is responsible for selecting data to be transmitted from the AC queue 210.

[0310] The conventional AC queue backoff register drives the medium access request along the EDCA protocol (channel contention access scheme), while in parallel, the RU backoff engine 800 drives the medium access request onto the OFDMA multi-user protocol (RU contention access scheme).

[0311] When these two competing access schemes coexist, the station implements a medium access mechanism with conflict avoidance based on the calculation of the backoff value:

[0312] - Queue backoff counter value, which corresponds to the number of time slots (in addition to the AIFS period) that a station waits after the communication medium has been detected as idle before accessing the medium. This is EDCA regardless of whether in degraded or non-degraded state;

[0313] - RU backoff counter value, which corresponds to the number of idle random RUs detected by the station before accessing the medium after a TXOP has been granted to the AP or any other station on a composite channel composed of RUs. This is OFDMA. A variant to count down the RU backoff counter based on the number of idle random RUs may be based on a time-dependent countdown.

[0314] Fig. 9 The flowchart is used to illustrate the main steps performed by the MAC layer 702 of the station 600 when receiving new data to be transmitted (MSDU packet from the upper layer (eg, the application layer 701)). Fig. 9 Traditional FIFO feeding in the 802.11 context is shown.

[0315] Initially, no service queue 210 stores data to be transmitted. As a result, no queue backoff value is calculated. The corresponding queue backoff engine or the corresponding AC (access category) is considered inactive. When data is stored in a service queue, the queue backoff value is calculated immediately (according to the corresponding queue backoff parameters) and the associated queue backoff engine or AC is considered active.

[0316] When a station has data ready for transmission on the medium, the data is stored in one of the AC queues 210 and the associated backoff should be updated.

[0317] Now for the details.

[0318] In step 901, new data is received from an application running locally on the device (eg, from application layer 601), from another network interface, or from any other data source. The new data is ready to be sent by the station.

[0319] In step 902, the station determines in which of the AC queues 210 the data should be stored. This operation is usually performed (according to Figure 2bThis is done by checking the TID (Traffic Identifier) ​​value attached to the data (match shown).

[0320] Next, step 903 stores the data in the determined AC queue, which means that the data is stored in an AC queue having the same data type as the data.

[0321] In step 904, a conventional 802.11 AC backoff calculation is performed using a queue backoff engine associated with the determined AC queue.

[0322] If the determined AC queue is empty (ie, the AC is originally inactive) immediately before the storage in step 903 , a new queue backoff value of the corresponding backoff counter needs to be calculated.

[0323] Thus, the station calculates the queue backoff value to be equal to a random value selected in the range [0, CW], where: CW is the current value of the CW for the access category under consideration (as defined in the 802.11 standard and updated, for example, in accordance with some embodiments of the present invention as described below in step 1080). It should be reiterated that the queue backoff value will be added to the AIFS in order to achieve the relative priority of different access categories. CW is selected from the range [CW min ,CW max ], where the two boundary CW min and CW max Depends on the category of access considered.

[0324] As a result, AC becomes active.

[0325] The above parameters CW, CW min , CW max , AIFSN and backoff value form EDCA contention parameters and variables associated with each AC. These values ​​are used to set the relative priority of accessing the medium for different classes of data.

[0326] EDCA parameters usually have fixed values ​​(e.g., CW min , CW max and AIFSN), while the EDCA variables (CW and backoff value) evolve with time and medium availability. As is readily apparent from the above, due to the present invention, it is no longer necessary to downgrade EDCA parameters when applying the penalty MU mode. Of course, these EDCA parameters can still be modified, but this is not necessary.

[0327] Additionally, the random access procedure of UL RU OFDMA (as described above) may be supported by the station; in that case, if necessary, step 904 may include calculating the RU backoff value. If the RU backoff engine 800 is inactive (e.g., because there was no data in the traffic queue before the previous step 903), and if new data addressed to the AP has been received, then the RU backoff value needs to be calculated.

[0328] The RU backoff value can be used in a similar manner to the EDCA backoff value, i.e., using dedicated RU contention parameters such as a dedicated contention window [0, CWO] and a selection range [CWO min ,CWO max ] etc.) to calculate.

[0329] Note that some embodiments may provide for a distinction between data that may be sent via a resource unit (ie, compatible with MU UL OFDMA transmission) and data that may not be sent via a resource unit. Such a decision may be made during step 902, and a corresponding marking entry may be added to the stored data.

[0330] In this case, the RU backoff value is calculated only if the newly stored data is marked as compatible with MU UL OFDMA transmission (scheduled or random).

[0331] After step 904, Fig. 9 The processing is finished.

[0332] Once the data is stored in the AC queue, the site can refer to it as follows Fig.10 As shown in the EDCA access scheme, or as shown in the following reference Fig.11 The medium is shown to be directly accessed through resource units provided by the AP via one or more trigger frames.

[0333] Fig.10 The flowchart is used to illustrate the steps of accessing the medium based on the conventional EDCA medium access scheme to handle both the conventional contention mode and the MU contention mode according to an embodiment of the present invention. In particular, in this example, the reactive countermeasure of the present invention is implemented by the non-AP station 600 in step 999 .

[0334] For clarity, the Fig. 9 This is because data storage in the AC[] queue is a prerequisite for any tentative EDCA medium access.

[0335] Steps 1000-1020 describe the traditional waiting introduced in the EDCA mechanism to reduce the conflict on the shared wireless medium based on the backoff countdown. In step 1000, the station 600 senses the medium to wait for the medium to become available (ie, the detected energy is lower than a given threshold on the primary channel).

[0336] The medium is in (AIFS[i] time period (at least DIFS time period, see Figure 2d )+one time slot) becomes idle, step 1010 is executed, wherein in step 1010, station 600 starts to decrement all active (non-zero) AC[] queue backoff counters by 1. In other words, the station decrements the queue backoff value for each basic time unit in which the communication channel is detected as idle.

[0337] Next, in step 1020 , the station 600 determines whether at least one of the AC backoff counters reaches zero.

[0338] If no AC queue backoff reaches zero, the station 600 waits for another backoff slot (typically 9 μs) and thereby loops back to step 1000 to sense the medium again during the next backoff slot. This allows the AC backoff counters to be decremented at each new backoff slot as soon as their respective AIFS[i] has expired when the medium is sensed as idle.

[0339] If at least one AC queue backoff reaches 0 (in Figure 5c If it occurs three times in the scenario described above), the conventional step 1030 for starting the EDCA transmission phase will not be automatically reached.

[0340] According to the present invention, the station should determine whether to access the communication channel to transmit data stored in the associated service queue (through the traditional EDCA process starting from step 1030) based on the current mode of the service queue associated with the expired queue backoff counter, or to extract a new backoff value to reset the expired queue backoff counter without transmitting data from the associated service queue in the communication channel (this is an improvement of the present invention, thereby restoring the dynamics of the backoff counter in MU mode).

[0341] In the proposed embodiment, this determination step is implemented by step 1099, which thus modifies the normal behavior of the EDCA state machine so as to apply a penalty for EDCA medium access to the non-AP station 600 in MU mode.

[0342] Thus, new test 1099 determines whether the traffic queue associated with the expired queue backoff counter is in penalty MU mode. The traffic queue may have been marked with "MU mode" set to 1 (performed by step 1140 as further described below) to make it easy for station 600 to know that the traffic queue is in penalty mode for EDCA medium access.

[0343] A major advantage of this approach is that the hardware / state machine of the standard backoff decrement mechanism can still be reused, in particular the basic mechanism that is eventually enabled to initiate a medium access request when the backoff counter reaches zero. With the present invention, this request is only conditioned on the usage mode (MU mode on or off). The new test 1099 can be easily implemented in hardware.

[0344] In the case of a positive determination in test 1099 (the current mode is in MU mode), the station will postpone any EDCA medium attempts. As a result, without having to transmit data via EDCA access, a new backoff value is extracted by looping back to step 904 to reset the expired backoff counter. Therefore, regardless of the "MU mode", this step reintroduces EDCA backoff management.

[0345] In the case of a reset, a reset flag associated with the service queue involved may be enabled (as described above in Figure 5c ), to remember the fact that the service queue had the highest QoS before the reset. This flag will be used in step 1030 to select the highest priority data for OFDMA transmission.

[0346] Note that when test 1099 results in re-extraction of the backoff value without EDCA transmission, no modification of the EDCA parameters / variables CW is required min , CW max and current CW. This is because, since EDCA transmissions are not allowed, nothing is known about the EDCA medium conditions (basically, these values ​​evolve based on the correct behavior of EDCA transmissions). Hence, any updates to these values ​​are meaningless and useless.

[0347] Optionally, these EDCA parameters / variables may be updated only if the corresponding service queue has spent a significant amount of time (e.g., at least several times the HEMUEDCATimer value of 1425) in "MU mode". This is because these frozen values ​​established in the past no longer reflect actual network conditions. Thus, the EDCA mode may start with standardized initial values, as if this were an initial (first) transmission using EDCA. In other words, the site may reset the contention parameter set associated with the (preferably individual) service queues that remain in MU contention mode during at least the parameter lifetime duration to a default parameter set. For example, the parameter lifetime duration may correspond to at least two times (or more) the predetermined duration for initializing the MU mode timer (i.e., the value of HEMUEDCATimer).

[0348] On the other hand, in case of a negative judgment in step 1099 (the current mode is in the conventional EDCA mode), step 1030 is executed, wherein in this step 1030, the station 600 (more precisely, the virtual conflict handling program 212) selects the active AC queue with a zero queue backoff counter and the highest priority. Figure 5c The first and fourth stages of the situation.

[0349] In step 1040, an appropriate amount of data is selected from the selected AC for transmission.

[0350] Next, in step 1050, if, for example, the RTS / CTS exchange is successful to grant the EDCA TXOP, the station 600 initiates EDCA transmission. Thus, the station 600 transmits the selected data on the medium during the granted EDCA TXOP.

[0351] Next, at step 1060 , the station 600 determines whether the EDCA transmission is completed. If completed, step 1070 is executed.

[0352] At step 1070, the station 600 updates the EDCA contention window CW of the selected traffic queue based on the status of the transmission (positive or negative ack, or no ack received). Typically, in the event of a transmission failure, the station 600 doubles the value of CW until CW reaches a maximum value CW that depends on the AC type of the data. max On the other hand, if the EDCA transmission is successful, the contention window CW is set to the minimum value CW which also depends on the AC type of the data. min .

[0353] Again, it should be reiterated that, due to the present invention, CW min and CW maxThe values ​​of the MU EDCA parameter set element 1420 may be the same in both the traditional contention mode and the MU contention mode, which means that the two are not degraded during step 1170 described below. Of course, the present invention does not prohibit the degradation of these values ​​(step 1170) when switching to MU mode, for example based on the "MU EDCA parameter set" element 1420 received in the management frame (usually the beacon frame) sent by the AP. In this case, if the traffic queue under consideration is in MU mode, the referenced CW min and CW max To proceed to step 1070.

[0354] Note that if the data being transmitted comes from a service queue for which the reset flag is enabled, then this flag is disabled. In effect, the new backoff value to be drawn will reflect its new relative priority.

[0355] Next, if the selected service queue is not empty after the EDCA data transmission, a new associated queue backoff counter is randomly selected from [0, CW] by looping back to step 904. This means that after the data stored in the associated service queue is transmitted in the accessed communication channel, the station extracts a new backoff value to reset the expired queue backoff counter.

[0356] This is the end Fig.10 processing.

[0357] In a slight variation of the proposed test 1099 already described above, the test 1099 to determine whether to access the communication channel or to extract a new backoff value may also be based on data currently stored in a traffic queue associated with the expired traffic queue. This is to tailor the penalty scheme to certain types of data, in particular to maintain QoS fairness for data not related to the MU UL transmission (which triggered the penalty scheme).

[0358] Focuses on peer-to-peer (P2P or site-to-site) data transmission between non-AP stations.

[0359] The Direct Link Setup (DLS) announced in the 802.11e standard allows direct site-to-site frame transfer within the basic service set.

[0360] Subsequently, the 802.11z standard released Tunneled Direct Link Setup (TDLS), allowing devices to perform more efficient direct site-to-site frame transmission without support from access points. The Wi-Fi Alliance added a certification program for TDLS in 2012 and describes the feature as a technology that enables sites to link directly to another site when connected to a traditional infrastructure network.

[0361] More generally, transmissions to independent BSS (IBSS) stations (that is, the destination is not registered with any BSS) may be considered P2P communications.

[0362] Both DLS and TLDS require stations to be associated with the same access point. As a result, communications within the P2P group can be considered to occur concurrently with communications in the infrastructure network (including communications of access point 110). That is, the transmission queues 210 of stations involved in both P2P communications and the BSS network provide data from both traffic modes.

[0363] As a result, while the penalty scheme envisioned by the 802.11ax standard penalizes uplink traffic to the AP, the penalty scheme also prevents any traditional EDCA access for P2P communications.

[0364] To face this situation, the above test 1099 may be slightly modified as proposed above.

[0365] In particular, according to the changed test 1099, if the current mode is the traditional contention mode or if the data included in the associated service queue includes data to be addressed to another station different from the access point (i.e., the data is P2P data), the processing enters step 1030, through which the station accesses the communication channel to transmit the data stored in the associated service queue.

[0366] On the contrary, if the current mode is the MU contention mode and the data stored in the associated service queue does not include data to be addressed to another station different from the access point (i.e., the data is P2P data), the processing loop returns to step 904, which means that a new backoff value is extracted to reset the expired queue backoff counter without transmitting data from the associated service queue in the communication channel.

[0367] In other words, modify the 1099 test as follows:

[0368] -If (MU mode is active) and (AC queue with backoff expiration does not hold P2P traffic), the test result is positive (yes);

[0369] Otherwise, the test result is false and proceed to step 930 .

[0370] If the result of test 1099 is false due to the presence of P2P data when the AC queue is in MU mode, so that the communication channel is accessed to transmit data, it seems appropriate to prioritize the transmission of such P2P data as opposed to the data intended for the AP that can be sent in the next visited RU. This means that during the step 1040 of selecting data, the P2P criterion is implemented: in the case of access to the communication channel, only data stored in the associated service queue in MU contention mode and addressed to another station different from the access point are transmitted in the accessed communication channel.

[0371] Various ways to distinguish P2P data from UL data intended for the AP may be implemented by a station. For example, the distinction between these two types of data may be made using a destination address (receiver address or information about the AP). Figure 2d The UPLINK_FLAG parameter is set to 0. The UPLINK_FLAG parameter is set to 1 to indicate data in the uplink direction only toward the AP.

[0372] Thanks to this variant of the invention, P2P traffic can still be transmitted by the stations.

[0373] Fig.11 The flowchart is used to illustrate the steps of accessing a resource unit (random RU or scheduled RU) based on the RU access scheme when a trigger frame 430 for defining RU is received. For example, this shows that the station 502 Figure 5b Behavior in stage 2 or 3 or 5.

[0374] In step 1110, the station determines whether a trigger frame 430 is received from an access point in the communication network, wherein the trigger frame reserves a transmission opportunity granted to the access point on the communication channel and defines a resource unit RU forming the communication channel. If a trigger frame is received, the station analyzes the content of the received trigger frame.

[0375] In step 1120, the station determines whether the station can transmit data on one of the RUs defined in the received trigger frame. The determination may involve one or both of two conditions, in particular regarding the type of RU.

[0376] By analyzing the contents of the received TF, the station determines whether the defined RU is a scheduled resource unit assigned to the station by the access point. This can be done by looking up its own AID in the received TF, which will be associated with the specific scheduled RU to be used for transmission.

[0377] In addition, by analyzing the content of the received TF, the station determines whether one or more random RUs are defined in the TF, i.e., RUs being accessed through competition using dedicated RU competition parameters (including the above-mentioned RU backoff value 800). In this case, the station also determines (especially when the RU backoff value 800 is less than the number of random RUs available in the current TF) whether its current RU backoff value allows the selection of a random RU.

[0378] If a scheduled RU is assigned to the station or the station is allowed to access a random RU, the station determines the size of the random / scheduled RU to be used and performs step 1130. Otherwise, the station decrements the RU backoff value 800 based on the number of random resource units defined in the received trigger frame, and the process ends when the station cannot access any RU (scheduled or random) defined by the received TF.

[0379] In step 1130, the station selects at least one of the service queues 210 from which data to be transmitted is selected, and adds the data of the selected queue to the transmission buffer until the amount of data reaches the size of the resource unit selected to be used.

[0380] Due to the restoration of the EDCA backoff counter countdown according to the invention and thus due to the dynamic nature of the individual backoff values, the backoff values ​​can then be used as a means for application priority selection. This can be done, for example, by selecting the service queue 210 (or queues) with the lowest associated queue backoff value. Thus, the selection of the service queue depends on the value of the EDCA backoff (this approach ensures that the station complies with the EDCA principles and then ensures the correct QoS for the data for that station).

[0381] In a variation, the AP may indicate a preferred AC within the trigger frame parameters. Thus, the station may instead select a non-empty traffic queue associated with a data type that matches the data type associated with the resource unit to transmit the selected data. This specified data type may be used by the AP, for example, when the AC preference level field is set to 1. Fig.13 The preferred AC field 1340 in the trigger frame indicates the service queue.

[0382] In this variant, data transmitted in resource units provided by the access point within a transmission opportunity granted to the access point is retrieved from a preferred service queue indicated by the access point, and the preferred service queue indication is included in a trigger frame received from the access point, the trigger frame reserving a transmission opportunity granted to the access point on the communication channel and defining a resource unit RU, thereby forming a communication channel including the accessed resource unit.

[0383] In another variation of the reset flag described above (in the description Figure 5c 904), the station may prefer to select data from the service queues that were reset at the same time (i.e., in the absence of any transmissions from the service queues since the last OFDMA transmission). This is to prioritize those data that have the highest priority at a given time due to the backoff value, before the relative priority is slightly degraded due to the backoff counter reset.

[0384] If data is selected from a service queue with the reset flag enabled, the same reset flag should be disabled so that the relative priority of that service queue is given only by the associated backoff value.

[0385] Note also that in the case of handling P2P traffic, step 1130 may be limited to the selection of UL data (ie, data intended for the AP).

[0386] Next, at step 1140, the site may store the fact that the selected service queue is a transmission service queue. For example, the selected first service queue (i.e., selected when step 1130 occurs for the first time) may be memorized as the primary service queue, and the other selected service queues may be memorized as secondary service queues.

[0387] In step 1150, the station determines whether the amount of data stored in the transmission buffer is sufficient to fill the selected resource unit.

[0388] If not, there is still room in the resource unit for additional data to serve another AC queue. The second AC queue (referred to as the secondary AC) may be determined using the same criteria as defined above for the remaining service queues. Thus, the process loops back to step 1130, during which another service queue is selected. In this way, the transmit buffer is progressively filled to reach the selected resource unit size.

[0389] Thus, it can be noted that multiple transmission traffic queues of the same site may be involved during MU UL OFDMA transmission, causing the multiple queues to enter MU EDCA mode.

[0390] In a variation to avoid mixing data from two or more traffic queues (ie, selecting data for a selected RU from a single traffic queue), padding data may be added to completely fill the selected RU. This is to ensure that the entire RU duration has energy detectable by a conventional station.

[0391] According to another variant implementing a specific data aggregation rule, if the first selected service queue does not have enough data to completely fill the accessed resource unit, data from a higher priority service queue may be selected.

[0392] Once the transmit buffer is full for the selected RU, step 1160 initiates MU UL OFDMA transmission of the data stored in the transmit buffer to the AP. The MU UL OFDMA transmission is based on the OFDMA subchannels and modulation defined in the received trigger frame and specifically in the RU definition.

[0393] Next, once the transmission has occurred, and preferably upon successful transmission (ie, acknowledgment received from the AP), the transmit queue identified in step 1140 enters MU mode. One or more transmit queues may already be in MU mode.

[0394] The MU mode timer may be initialized with HEMUEDCATimer, where the MU mode timer gradually elapses over time. Note that if the MU mode timer has elapsed (which means the station is already in MU EDCA mode) when the new transmission 1160 ends successively, the MU mode timer is reinitialized to HEMUEDCATimer again to keep the station in MU EDCA mode for the next HEMUEDCATimer period.

[0395] Thus, step 1170 may be performed to determine one or more new values ​​for one or more EDCA parameters to be applied to one or more traffic queues in order to modify the new value or values ​​to penalty values ​​where appropriate.

[0396] As described above, since in an embodiment the penalty scheme is now fully implemented by the new step 1099 of the EDCA state machine, step 1170 is now optional (compared to the prior art document).

[0397] Not modifying EDCA parameters means: MU contention mode uses the same arbitration interframe gap duration as the traditional contention mode, and in addition MU contention mode uses the same lower boundary CW as the traditional contention mode min and / or the same upper boundary CW max , among which CW min and CW max These two define the range of options for choosing the size of the contention window.

[0398] Using the same value advantageously reduces the bandwidth used by the AP to transmit parameters in the beacon frame. In practice, the "MU EDCA parameter set" element 1420 can be greatly reduced to only signal the HEMUEDCA Timer value. In other words, fields 1421-1424 can be removed from 1420.

[0399] Additionally, it may be noted that, as the EDCA backoff value now evolves again over time, regular polling of several traffic queues is performed, and thus a single MU mode timer to exit MU mode is sufficient to drive the station efficiently.

[0400] Next, optional step 1180 is implemented so that the QoS features supported by the backoff counter are also restored, which causes the backoff value to be recalculated more frequently.

[0401] In this optional step, for each transmission service queue, a new EDCA backoff value may be extracted even if its current backoff value has not dropped to zero. This is to maintain the relative priority between service queues (the re-extracted value is likely to serve as the upper limit of the pending queue on other service queues, so for the next transmission, other queues are given priority).

[0402] For example, the station calculates or extracts a new backoff value for at least one service queue transmitted in the accessed resource unit to reset the associated queue backoff counter. Figure 5c The situation of backoff counters 531 and 532 at the end of the second and third stages of the scenario.

[0403] In the first embodiment, the new queue backoff value is calculated only for the transmission service queue that transmits data at the beginning of the accessed resource unit.Preferably, only the primary service queue identified in step 1140 is involved in the reset with the new queue backoff value.

[0404] In a second embodiment, for each transmission service queue identified in step 1140 , a new queue backoff value is calculated.

[0405] It may be noted that even if some backoff values ​​are re-drawn (and thus the corresponding backoff counters are reset), these values ​​will still be decremented again and thereby provide a new chance of reaching zero, in which case the test 1099 will be performed again to work according to the current contention mode.

[0406] Although the above embodiments of the present invention provide penalty schemes for the case where both scheduled access and random access are used on UL MU resource units, it is contemplated that the penalty scheme is applied only in response to successful transmissions in scheduled RUs. This is motivated in the sense that the penalty MU EDCA parameters (1150) will be applied with respect to AP behavior (if the AP in fact decides to grant (schedule) UL access for a given site). For random accessed RUs, the AP does not specify any particular site (i.e., does not explicitly confirm that one site is being prioritized, etc.), so the penalty is not considered to apply to the EDCA access mode.

[0407] Fig.12 The flow chart is used to illustrate the station management for switching back to the conventional EDCA mode in the above example. The management is based on the HEMUEDCATimer described above. In fact, as long as the MU mode timer has not expired, the station remains in the MUEDCA mode.

[0408] Thus, in step 1210, it is checked whether HEMUEDCATimer has expired / expired, ie reached the value 0.

[0409] In the affirmative, in step 1220, the station switches back to EDCA mode, for example, by setting the "MU mode" flag to 0 for all traffic queues.

[0410] In this embodiment, all degraded service queues share the same predetermined degrade duration HEMUEDCATimer, so that all degraded service queues exit the degraded MU EDCA mode at the same time. The exit may mean restoring the traditional EDCA parameters when the MU mode includes the degraded EDCA parameters.

[0411] Note that since the MU mode timer is reinitialized for each new MU UL OFDMA successful transmission of the station, expiration of the MU mode timer occurs only when no data is transmitted from the station in any RU provided by the AP in a subsequent TXOP granted to the AP within the predetermined downgrade duration HEMUEDCATimer.

[0412] The process then ends in step 1230 .

[0413] Fig.13 2 shows the structure of a trigger frame as defined in the 802.11ax draft standard.

[0414] The trigger frame 1300 includes a dedicated field 1310 called a user information field. This field contains a “trigger dependent common information” field 1320, which contains an “AC preference level” field 1330 and a “preferred AC” field 1340.

[0415] The Preferred AC field 1330 is a 2-bit field that indicates the AC queue (value of 0-3) from which data should be sent by the station on the RU assigned to the station in the trigger frame.

[0416] AC preference level field 1330 is a bit indicating whether the value of preferred AC field 1340 is significant. If field 1340 is set to 1, the station should consider preferred AC field 1340 when selecting data in step 1130. If field 1330 is set to 0, the station is allowed to send data from any AC queue regardless of the value of preferred AC field 1340.

[0417] Other fields of the trigger frame are defined in the 802.11ax standard.

[0418] The AP may also be responsible for broadcasting EDCA parameters for both EDCA mode and MU mode (in the case where the MU mode has degraded parameter values). The AP preferably broadcasts using the well-known beacon frame dedicated to configuring all stations in an 802.11 cell. Note that if the AP is unable to broadcast EDCA parameters, stations are configured to fall back to default values ​​as defined in the 802.11ax standard.

[0419] Fig.14a The structure of a standardized information element 1410 for describing legacy EDCA parameters in a beacon frame is shown.

[0420] Fields 1411, 1412, 1413, 1414 describe parameters associated with each traffic queue 210. For each traffic queue, subfield 1415 includes EDCA parameters: AIFSN as the delay before starting to decrease the associated backoff value, min and maximum CW max The values ​​of the contention window, ECWmin and ECWmax, and finally the TXOP limit which is the maximum transmission time of an 802.11 device.

[0421] All other fields of the information element are fields described in the 802.11 standard.

[0422] This standardized information element 1410 is used by a station to configure itself in legacy EDCA mode.

[0423] Fig.14bAn exemplary structure of a dedicated information element 1420 for transmitting parameter values ​​of MU mode according to the present invention is shown, wherein the dedicated information element 1420 includes possible degraded EDCA parameters (if present) and HEMUEDCATimer value (always present). The dedicated information element 1420 may be included in a beacon frame sent by the AP.

[0424] The dedicated information element 1420 includes, for each AC queue, degraded EDCA parameters (1421, 1422, 1423, 1424) to be used by stations in MU mode. The dedicated information element 1420 also includes a subfield 1425 that specifies the value of HEMUEDCATimer.

[0425] Each subfield 1421, 1422, 1423, 1424 includes the downgraded AIFSN value (if present) of the corresponding service queue, as well as the downgraded ECWmin value and the downgraded ECWmax value (which may be the same as the legacy EDCA values). A value of 0 in the AIFSN field indicates that the AIFS is equal to the HEMUEDCATimer value set in the MU EDCA timer subfield 1425.

[0426] Of course, if the MU mode uses conventional EDCA parameters, fields 1421, 1422, 1423, 1424 may be omitted, thereby reducing bandwidth usage.

[0427] The MU EDCA timer subfield 1425 indicates the HEMU EDCA timer value in units of 8 TUs (a time unit is a measurement of time equal to 1024 μs).

[0428] In this example, a set of non-degradation values ​​and degradation values ​​(if present), as well as the HEMUEDCATimer value, are transmitted in a beacon frame periodically transmitted by an access point for broadcasting network information related to the communication network to a plurality of stations. In a variant, these values ​​may be included in a probe response frame or a (re)association response frame.

[0429] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to these specific embodiments, and those skilled in the art will appreciate that modifications exist within the scope of the present invention.

[0430] Many other modifications and variations will be apparent to those skilled in the art when referring to the foregoing exemplary embodiments which are given by way of example only and are not intended to limit the scope of the invention, and which are determined solely by the appended claims. In particular, different features from different embodiments may be interchanged where appropriate.

[0431] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.

Claims

1. A base station for building a wireless network that complies with the IEEE 802.11 series of standards, the base station comprising: a sending component, configured to send a signal, wherein the signal includes information related to the AIFSN value, wherein a first station receiving the signal sent by the sending component is controlled so that, in a case where the AIFSN value indicated by the information in the signal is zero, enhanced distributed channel access transmission (EDCA transmission) of data of an access category to be addressed to the base station is disabled, while EDCA transmission of data of the same access category to be addressed to a second station different from the base station remains enabled, The access category is the same as the access category of data that has been successfully transmitted by the first station via a resource unit that complies with the IEEE 802.11 series standards.

2. The base station according to claim 1, wherein: The EDCA transmission of data addressed to the second station is peer to peer traffic distinct from uplink traffic to the base station.

3. The base station according to claim 1, wherein: EDCA transmission of data addressed to the second station is performed without support from the base station.

4. The base station according to claim 1, wherein: A peer group for EDCA transmission of data addressed to the second station is maintained in parallel with the wireless network constructed by the base station.

5. The base station according to claim 1, wherein: The communication device and the second station are associated with the same base station.

6. The base station according to claim 1, wherein: An AIFSN value equal to zero prevents the first station from performing EDCA transmissions within the value specified by the HEMUEDCATimer timer.

7. The base station according to claim 1, wherein: The first station is controlled to switch the access category from a traditional contention mode to an MU contention mode when transmitting data of the access category in an accessed uplink OFDMA resource unit provided by the base station, and the MU contention mode does not transmit data of the access category to be addressed to the base station for the wireless network.

8. The base station according to claim 7, wherein: The first station is controlled to switch to the MU contention mode only if the AIFSN value is zero.

9. The base station according to claim 7, wherein: The first station is controlled to switch the access category back to the conventional contention mode when an MU mode timer that is initialized when the access category is switched to the MU contention mode expires.

10. A communication method, comprising: At a base station used to build a wireless network compliant with the IEEE 802.11 series standards, sending a signal, the signal comprising information related to the AIFSN value, wherein the first station receiving the transmitted signal is controlled so that, in the case where the AIFSN value indicated by the information in the signal is zero, enhanced distributed channel access transmission, i.e., EDCA transmission, of data of an access category to be addressed to the base station is disabled, while EDCA transmission of data of the same access category to be addressed to other stations different from the base station remains enabled, The access category is the same as the access category of data that has been successfully transmitted by the first station via a resource unit that complies with the IEEE 802.11 series standards.

11. The communication method according to claim 10, wherein: The EDCA transmission of data addressed to the other stations is peer to peer traffic distinct from uplink traffic to the base station.

12. The communication method according to claim 10, wherein: EDCA transmission of data addressed to the other stations is performed without support from the base station.

13. The communication method according to claim 10, wherein: A peer group for EDCA transmission of data addressed to the other stations is maintained in parallel with the wireless network constructed by the base station.

14. The communication method according to claim 10, wherein: The communication device and the other station are associated with the same base station.

15. The communication method according to claim 10, wherein: An AIFSN value equal to zero prevents the first station from performing EDCA transmissions within the value specified by the HEMUEDCATimer timer.

16. The communication method according to claim 10, wherein: The first station is controlled to switch the access category from a traditional contention mode to an MU contention mode when transmitting data of the access category in an accessed uplink OFDMA resource unit provided by the base station, and the MU contention mode does not transmit data of the access category to be addressed to the base station for the wireless network.

17. The communication method according to claim 16, wherein: The first station is controlled to switch to the MU contention mode only if the AIFSN value is zero.

18. The communication method according to claim 16, wherein: The first station is controlled to switch the access category back to the conventional contention mode when an MU mode timer that is initialized when the access category is switched to the MU contention mode expires.

19. A non-transitory computer-readable medium storing a program which, when executed by a microprocessor or a computer system in a device, causes the device to perform the communication method according to claim 10.

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