Communication device and method

Abstract

A first communication device configured to communicate with one or more second communication devices, the first communication device comprising circuitry configured to perform the following operations: detecting one or more data units having a preamble transmitted by one or more second communication devices and / or other communication devices; detecting a collision detection indication within or after the preamble of the detected one or more data units in accordance with a predetermined configuration of the collision detection indication, wherein the configuration comprises a sequence of tones mapped to tones of an OFDM symbol of the collision detection indication and / or a sequence of time / symbols applied to the OFDM symbol of the collision detection indication; and identifying at least one second communication device that transmitted the one or more data units based on the detected collision detection indication.

Description

Technical Field

[0001] This disclosure relates to a first communication device and a second communication device, specifically for conflict detection and resolution. Background Technology

[0002] Enhanced Distributed Channel Access (EDCA) is the primary channel access protocol used in WLANs. This protocol is efficient when the number of stations (STAs) contending for channel access is small, but it can introduce very long channel access delays as the number of STAs increases. Conversely, Triggered-Based (TB) channel access is more efficient when the number of STAs is large; however, it can also introduce long delays when the access point (AP) is unaware of the arrival of data traffic at the STA. Despite using this protocol and implementing a backoff process, channel access conflicts and delays can still occur when multiple STAs access the same channel.

[0003] The “Background Art” description provided herein is for the purpose of presenting the general context of this disclosure. The work of the currently named inventors, within the scope described in this Background Art section and in aspects that may not be described as prior art at the time of application, is neither explicitly nor implicitly acknowledged as prior art relative to this disclosure. Summary of the Invention

[0004] One objective is to reduce the probability of collisions and / or channel access delays, specifically in WLAN systems. Another objective is to provide a corresponding method and a corresponding computer program and a non-transitory computer-readable recording medium storing a computer program product for implementing the method.

[0005] According to one aspect, a first communication device is provided, the first communication device being configured to communicate with one or more second communication devices, the first communication device including circuitry configured to: - Detect one or more data units with preambles transmitted by one or more second communication devices and / or other communication devices; - According to a predetermined configuration of the collision detection indication, the collision detection indication is detected within or after the preamble of one or more detected data units, wherein the configuration includes a tone sequence mapped to the tone of the OFDM symbol of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbol of the collision detection indication; and - Based on the detected collision detection indication, identify at least one second communication device that has transmitted one or more data units.

[0006] According to another aspect, a second communication device is provided, the second communication device being configured to communicate with a first communication device, the first communication device being configured to communicate with one or more second communication devices, the second communication device including circuitry configured to perform the following operations: - Generate one or more data units with a preamble; - According to a predetermined configuration of the collision detection indication, a collision detection indication is provided within or after the preamble of one or more data units, wherein the configuration includes a tone sequence mapped to the tone of the OFDM symbol of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbol of the collision detection indication; and - Transmit one or more data units containing collision detection indications.

[0007] According to another aspect, a corresponding method, a computer program including program units, and a non-transitory computer-readable recording medium are provided, the program units being used to cause the computer to perform the steps of the method disclosed herein when the computer program is executed on a computer, the non-transitory computer-readable recording medium storing a computer program product therein, the computer program product causing the method disclosed herein to be performed when executed by a processor.

[0008] The embodiments are defined in the dependent claims. It should be understood that the disclosed method, the disclosed computer program, and the disclosed computer-readable recording medium have similar and / or identical embodiments to the claimed device and as defined in the dependent claims and / or disclosed herein.

[0009] One aspect of this disclosure is the use of a collision detection indication transmitted from a second communication device (which may be a STA in an embodiment) to a first communication device (which may be an AP in an embodiment). The collision detection indication is transmitted in the preamble of a data unit, for example, in the form of a collision detection field (such as a physical layer (PHY) field) in a data unit (e.g., a physical layer protocol data unit (PPDU)). If a collision or reception failure occurs, the first communication device can identify the second communication device that caused the collision or reception failure from the collision detection indication and can transmit a collision resolution indication to the second communication device, indicating that a collision or reception failure has occurred. This enables the second communication device to detect the collision and, optionally, take measures for collision resolution, which may be indicated by the first communication device.

[0010] Here, the term "collision" should be understood as an event in which two or more transmissions between different second communication devices or between a second communication device and another communication device (e.g., a conventional device that does not use collision detection indication or an interfering device) completely or partially overlap in the time and / or frequency domains. For example, an event in which two or more STA transmissions of PPDUs completely or partially overlap in time represents a collision. This can occur, for example, when devices simultaneously access the wireless medium after performing contention-based channel access or after receiving an indication from the AP that simultaneous transmission is permitted. Reception failure may be caused not only by the transmitting device but also by external factors such as interference and channel conditions that affect the reception of data units.

[0011] Collision detection indication should be broadly understood as an indication used within a wireless medium where collisions or packet reception failures may occur. Some exemplary applications of collision detection indication include one or more of the following: detecting collisions and identifying colliding STAs during distributed channel access and preemption scenarios, and identifying transmitters of data units that have failed to receive packets. Collision detection indication can be a signal inserted as a PHY field and composed of one or more OFDM symbols. These OFDM symbols can be truncated to form other periodic signals.

[0012] Contention-based channel access refers to a distributed channel access mechanism such as EDCA, in which a STA requiring access to the channel (or radio medium) performs Carrier Sense (CS) and / or Clear Channel Assessment (CCA) before transmission to determine if the channel is busy. If the channel is busy, a backoff procedure is invoked, and channel access is performed when the backoff counter reaches zero.

[0013] The foregoing paragraphs have been provided by way of general description and are not intended to limit the scope of the appended claims. The described embodiments and other advantages will be best understood by referring to the following detailed description taken in conjunction with the accompanying drawings. Attached Figure Description

[0014] Because a more comprehensive understanding of this disclosure and its many accompanying advantages becomes better understood when considered in conjunction with the accompanying drawings and the following detailed description, and thus they will be readily available: Figure 1 A diagram is shown illustrating a communication scheme for conflict resolution using traditional EDCA behavior.

[0015] Figure 2 A diagram illustrating a communication scheme that demonstrates an example of a conflict in frame-based preemption in a downlink scenario.

[0016] Figure 3A diagram illustrating a first embodiment of a communication scheme according to the present disclosure is shown, illustrating conflict resolution in the uplink via a conflict detection indication through trigger-based channel access.

[0017] Figure 4 A flowchart illustrating an implementation of a general process for conflict detection and resolution via a conflict detection field (CoF) at the AP is shown.

[0018] Figure 5 A diagram illustrating a second embodiment of the communication scheme according to this disclosure is shown, illustrating conflict resolution in the uplink via CoF through shared TXOP operations.

[0019] Figure 6 A diagram illustrating a third embodiment of a communication scheme according to the present disclosure is shown, illustrating conflict resolution in the uplink via CoF through delayed channel access.

[0020] Figure 7 A diagram illustrating a fourth embodiment of the communication scheme according to the present disclosure is shown, illustrating a response indication to a CRF to confirm CoF detection.

[0021] Figure 8 A flowchart illustrating an implementation of the general operation of a conflict STA is shown.

[0022] Figure 9 A diagram illustrating a fifth embodiment of a communication scheme according to the present disclosure is shown, illustrating conflict resolution with CoF for frame-based preemption.

[0023] Figure 10 A diagram illustrating a sixth embodiment of a communication scheme according to the present disclosure is shown, illustrating AP contention before the transmission collision resolution field (CRF).

[0024] Figure 11 A diagram illustrating an implementation method for setting up the CoF operation is shown.

[0025] Figure 12A An implementation based on the standard PPDU format is shown.

[0026] Figure 12B A first embodiment of the PPDU format according to this disclosure is shown.

[0027] Figure 12C A second embodiment of the PPDU format according to this disclosure is shown.

[0028] Figure 13 A diagram illustrating another embodiment of the process for generating and distributing CoF signals is shown.

[0029] Figure 14A schematic diagram illustrating an embodiment of the layout for transmitting STAs according to this disclosure is shown.

[0030] Figure 15 A diagram illustrating a first example of tone scheme and tone sequence generation is shown.

[0031] Figure 16 A diagram illustrating the generation of the same pitch scheme and pitch sequence is shown.

[0032] Figure 17 Instructions for use are shown. Figure 15 The diagram shown illustrates how the tone sequence generates the first part of the CoF.

[0033] Figure 18 Instructions for use are shown. Figure 15 The diagram shown illustrates how the tone sequence generates the second part of the CoF.

[0034] Figure 19 Instructions for use are shown. Figure 16 The diagram shown illustrates how the tone sequence generates the first part of the CoF.

[0035] Figure 20 Instructions for use are shown. Figure 16 The diagram shown illustrates how the tone sequence generates the second part of the CoF.

[0036] Figure 21 A diagram illustrating the generation of CoF using OFDM symbol sequence masks for synchronization scenarios is shown.

[0037] Figure 22 An example of an extended tone scheme is shown.

[0038] Figure 23 A diagram illustrating the generation of CoF using OFDM symbol sequence masks for synchronization cases involving pitch shifting using an extended pitch scheme is shown.

[0039] Figure 24 A flowchart illustrating an embodiment of receiver operation for detecting CoF according to the present disclosure is shown.

[0040] Figure 25 A diagram illustrating an implementation of receiver operation in the time domain is shown.

[0041] Figure 26 A flowchart illustrating an embodiment of the first communication method according to this disclosure is shown.

[0042] Figure 27 A flowchart illustrating an embodiment of the second communication method according to this disclosure is shown. Detailed Implementation

[0043] Referring now to the accompanying drawings, in which the same reference numerals designate the same or corresponding parts in all the views. Figure 1 A diagram illustrating a communication scheme using conflict resolution with traditional EDCA behavior is shown. A first communication device (AP in this embodiment) communicates with two second communication devices (stations STA1 and STA2 in this embodiment). EDCA is advantageous for low-latency applications because each STA can begin competing for channel access as soon as it has data to transmit, avoiding potential delays caused by waiting to be triggered by the AP. To avoid conflicts, STAs using EDCA need to invoke a backoff procedure when the channel is busy. Therefore, before transmission, the STA needs to detect that the channel is idle for the duration of the Arbitration Inter-Frame Interval (AIFS) and draw a random backoff counter from the interval [0, nCW], where nCW is an integer defining the size of the contention window (CW). The STA decrements its backoff counter for each specific time slot duration. When the backoff counter reaches zero, the STA is allowed to transmit. If the STA fails to transmit, for example due to a conflict or temporary coverage loss, the STA needs to invoke the backoff procedure again, but this time its CW needs to be doubled, meaning a new backoff counter is drawn from the interval [0, 2×nCW-1]. This is done to reduce the probability of conflict, but it may lead to longer delays, such as... Figure 1 As shown.

[0044] Conflicts may also occur in special scenarios based on frame preemption, in which protocol changes have been introduced to provide channel access for low-latency applications. Figure 2 A diagram illustrating a communication scheme demonstrating an example of conflict in frame-based preemption in a downlink scenario is shown. The AP initiates a transmission opportunity (TXOP) and adds an IFS gap (in the frame interval) with a longer duration than the usual Short Interframe Spacing (SIFS) between specific frames. Figure 2 This is represented as a preemptive IFS (pIFS). During these pIFS gaps, other STAs can send preemptive PPDUs (pPPDUs) carrying preemption indications or data. Typically, an indication exists in the previous PPDU, announcing the upcoming pIFS gap to the STA with preemptive service. When more than one STA sends a pPPDU in the same pIFS gap, a collision may occur, such as... Figure 2 The diagram shows STA2 and STA3.

[0045] Because of the specific pIFS gaps that allow STAs to send pPPDUs, collisions may occur more frequently than in regular contention scenarios. This can introduce unwanted latency and reduce the efficiency of TXOPs. The inherent inefficiency of frame-based preemption mechanisms stems from the fact that PPDUs need a finite duration to provide regular preemption gaps and support low-latency service constraints.

[0046] In many cases, when a collision occurs, frames are lost because they cannot be decoded, and it is not known later which entity caused the collision. In the case of EDCA, the STAs involved in the collision need to wait for a predetermined timeout, such as... Figure 1 As shown, no response was received before the STA could realize its transmission failure. Afterwards, the colliding STA competed again with a new backoff counter that doubled its CW (in...). Figure 1 (AIFS is included in the timeout). A collision can only be detected at the AP after one of the STAs has successfully transmitted a frame containing a retransmission indication.

[0047] exist Figure 2 In the frame-based preemption scenario shown, the AP needs to initiate a Buffer Status Report (BSR) procedure to identify which STAs have experienced collisions. Furthermore, during TXOP, collisions can occur across multiple pIFS intervals. Therefore, using the BSR procedure to resolve collisions in frame-based preemption introduces additional latency and reduces the efficiency of data exchange during TXOP.

[0048] Figure 3 A diagram illustrating a first embodiment of the communication scheme according to this disclosure illustrates collision resolution in the uplink via collision detection indication through trigger-based (TB) channel access. According to this embodiment, collision detection fields (CoF) 10, 20, representing the collision detection indication, are added as PHY fields to PPDUs 11, 21 that identify the STA transmitting the PPDU. This enables the receiver STA (i.e., AP in this embodiment) to detect collisions. CoF 10, 20 may, for example, be located in the preamble of PPDUs 11, 21, after the legacy portion and at least one signaling field. In one example, CoF may be added to the first PPDU used to obtain the TXOP, which avoids further delays due to the exponential backoff process. CoF further enables the receiver STA (AP) to identify which STAs have collided, even if it cannot decode any other information (including SIG and data fields) from the colliding PPDUs 11, 21.

[0049] It should be noted that the AP is assumed to be the expected receiver of the CoF. If the AP identifies at least one of the STAs (STA1, STA2) where a collision has occurred, the AP can modify the channel access to (at least partially) resolve the collision and reduce channel access delay. To this end, the AP can transmit a collision resolution indication indicating that a collision or reception failure has occurred, and / or an indication that at least one of the STAs transmitted a PPDU that caused the collision or reception failure. In this embodiment, the Collision Resolution Field (CRF) 30 represents the collision resolution indication. When the likelihood value of the detection test does not reach a specific threshold within the selected detection window, the receiver can generally determine that a detection failure has occurred. This does not mean that CoF is present or absent, but only that the detection test did not detect CoF. When this occurs, a second, lower threshold can be used to trigger the start of detection window adjustment or the use of a continuous interference cancellation method.

[0050] To support the conflict resolution mechanism via CoF, the following can be considered. This can be done as part of the initialization or (re)configuration phase of each STA or during the association process: Generate and distribute CoFs for all STAs: The AP should know all CoFs and their allocation to each STA. CoFs can be assigned to a single STA or a group of STAs. CoFs can also be used to indicate a simplified service priority of the service buffer status. For example, each STA can have two CoFs, each CoF indicating whether the service buffer is below or above a certain level.

[0051] Configure the CoF to be used for each STA: CoF duration, CoF modulation parameters, and CoF sequence type.

[0052] Define the duration of TB-PPDU or TXOP that the AP can set after collision detection.

[0053] In one implementation, an operating mode is provided in which STAs that include a CoF in their PPDUs to request channel access are also configured to have equal durations. This ensures that the legacy signaling field (L-SIG) has identical content and improves the reliability of decoding the legacy signaling field. In the event of a conflict, if the AP can extract the duration information from the L-SIG, the AP can adjust the duration of the scheduled TB-PPDU or TXOP.

[0054] Figure 4 A flowchart illustrating an implementation of a general process 100 for conflict detection and resolution at the AP via CoF is shown. The proposed mechanism for conflict detection and resolution using CoF will be explained below.

[0055] In one implementation, there are two main assumptions regarding the format of the PPDU carrying the CoF: the PPDU may or may not contain a data field. In the first case, the PPDU with a data field carries an MPDU in its header containing Media Access Control (MAC) information such as a Transport Address (TA) and Network Allocation Vector (NAV) setting indication. Therefore, in the context of MAC information entries explained below, it is assumed that the PPDU contains a data field. In the second case, the PPDU carrying the CoF contains only physical layer (PHY) information, and the resulting behavior is independent of the MAC information.

[0056] First, refer to Figure 4 Explain the potential AP behavior. When energy is detected (L-STF detection) (energy detection can be part of a carrier sense (CS) or free channel assessment (CCA) process (step 101)), the AP processes the PPDU as usual (decoding the preamble and data field; steps 102 and 105, respectively). Additionally, the AP can run (step 103) a CoF detection process (based on the AP's configuration) in one or more of the following situations: for the first PPDU of an unestablished TXOP, for a PPDU transmitted during a service period allowing transmission by a specific STA, and for a PPDU within a TXOP that allows preemption (specifically, for a PPDU carrying a preemption indication or preemption data). Furthermore, the AP transmits (step 104) an indication of whether CoF was detected in subsequent frames. This indication can be a Contention Resolution / Recovery Frame (CRF) (…). Figure 3 This is part of 30), which will be explained in more detail below. The absence of such a transmission can also be an indication. If a CoF is detected, the STA ID or ID group is preferably also identified by the CoF. If the PPDU with the CoF also has a data field carrying a successfully decoded MPDU, the frame can also be included in the response PPDU.

[0057] The assessment of whether a collision has occurred can be performed as follows. A collision or packet decoding failure is detected via CoF in the following situations (AP actions are described below). Typically, CoF can be detected sequentially after preamble decoding and before data field decoding, or in parallel based on the results from the CS or CCA process. If a CoF is detected, one of the following may occur.

[0058] In the first case, a PPDU containing a data field is correctly decoded (step 105). This data field contains at least one MPDU with a transmitter address (TA) that identifies a transmitter STA that does not match an STA identified by the CoF or included in a group of STAs identified by the CoF, as checked in step 106. In this case, a collision is detected (step 107), but a TXOP can be established for the STA that sent the correctly decoded MPDU. The AP can send a response frame to the STA that initiated the TXOP (step 104) and allow the TXOP to be established. In the response frame, the AP may include channel access information for the STA identified by the CoF. Further mechanisms are explained below.

[0059] In the second case, the PHY preamble decoding fails (step 108), or, if the PPDU contains a data field, all MPDUs in the PPDU fail to be successfully decoded (step 105). This situation does not necessarily mean a collision has occurred, as decoding failure could also be due to an interruption within the coverage area. However, since the CoF is detected, the transmitting STA can be identified (step 109), and the AP can decide whether to provide channel access (step 104) (the AP can use a collision resolution mechanism to provide channel access).

[0060] If at least two CoFs are detected in step 103, this is interpreted as a conflict, and the following mechanisms for conflict resolution (steps 109, 104, 110) explained below can be applied.

[0061] In the absence of a collision, it is assumed that the PPDU can be successfully decoded. The AP can determine whether a CoF has been added via an indication in the PPDU preamble or through a previous negotiation phase (where it was determined which STAs will use the CoF) (detected in step 111). If no CoF is detected in step 111, and if a CoF has been added to the PPDU, the AP can request (step 110) a CoF configuration change for all STAs in the STA that sent the PPDU, or in a group of STAs sharing the same CoF configuration, or in the BSS (step 110). Furthermore, the AP can send a CoF report (step 110) to the STA identified by the TA in the decoded PPDU, which, in a separate frame, contains information about the detection value of the CoF (e.g., the likelihood ratio of the detection test, the detection probability, and / or the false alarm probability). It should be noted that the CoF is designed to be as robust as or more robust than the PHY preamble to ensure that the probability of a correctly decoded PPDU failing to detect a CoF is very low. Assuming the PPDU contains a data field, if a CoF is detected and if the CoF identifies the same STA as the STA identified by the TA of the MPDU carried in the PPDU, no further action is required for CoF processing except (optionally) sending a CoF report to the sending STA to collect statistics on CoF detection performance. PPDU processing should continue as normal.

[0062] If at least one MPDU has been successfully decoded in step 105, and if the MPDU is addressed to the STA and the acknowledgment policy requires it, then transmit an acknowledgment (step 112).

[0063] The following will explain the implementation of the conflict resolution method according to this disclosure. If a conflict or packet failure is detected via CoF, the AP predetermines an inter-frame interval (IFS) after the medium becomes idle (e.g., after a conflict occurs). Figure 3 The value is represented as IFS1, which sends a Contention Resolution / Resumption Frame (CRF) to resolve a conflict or to attempt to restore channel access if the attempt fails.

[0064] like Figure 3As shown, CRF can enable uplink TB channel access. The AP triggers (using CRF itself 30 and / or trigger frame TF 31) the STA identified in CoF 10, 20 to transmit data in TB-PPDU 12, 12a, 22, 22a, wherein the TB-PPDU duration can be determined by one of the following: the duration of the collision (which can be estimated as the difference between the point at which the radio medium is perceived as idle (as the end of the collision) and the start of collision PPDU detection (e.g., from CS / CCA), or a predetermined fixed value set by the AP or previously negotiated, or, in the case of collision PPDUs of equal length, the duration information from the successfully decoded L-SIG. Furthermore, the AP triggers the STA to collect BSR and continue uplink TB channel access.

[0065] like Figure 3 As shown, CRF 30 can act as a trigger frame for scheduling the first two PPDUs 12 and 22. Since the AP doesn't fully know how much traffic STA1 and STA2 need to transmit, the length of the first PPDUs 12 and 22 may be insufficient. Therefore, a second trigger 31 can be used to allow STA1 and STA2 to complete or continue their data transmission. Alternatively, CRF 30 can act as a trigger frame, but it first collects the buffer status from the STAs, i.e., the first PPDUs 12 and 22, and then triggers the uplink data, i.e., the second PPDUs 12a and 22a.

[0066] In another implementation, the CRF can initiate a shared TXOP operation with one or more conflicting STAs or other STAs that need to transmit. Figure 5 A diagram illustrating a second embodiment of the communication scheme according to this disclosure demonstrates conflict resolution in the uplink via CoF through shared TXOP operations. Furthermore, TXOPs can be shared between downlink and / or point-to-point (P2P) services. APs can assign priorities to one or more specific STAs, for example, based on Access Class (AC) or Service Identifier (TID).

[0067] In another implementation, the CRF can delay channel access for a specific STA group (e.g., a STA group with low-priority services). Figure 6 A diagram illustrating a third embodiment of the communication scheme according to this disclosure is shown, illustrating collision resolution in the uplink via CoF through delayed channel access. The AP may request STA2 not to repeat CW 24, 25 compared to the original CW 23 to avoid additional delays caused by increased exponential backoff.

[0068] exist Figure 6In the example shown, STA2 is delayed to support STA1, which gives STA1 priority. The next TXOP32 is initiated by the AP because it typically has a short backoff counter. At this point, STA2 begins to compete for channel access with a new, undoubled backoff counter of 24. This modification allows STA2 to avoid long waiting times before transmission. For example, in this case, STA1 has data arriving during the AP's TXOP 32. Without this modification to the CW 24 length, STA1 would likely win the contention before STA2.

[0069] In another implementation, the AP can move frame switching to another link.

[0070] In addition, a CRF can also indicate one or more of the following: Assuming the conflicting PPDU contains a data field carrying the MPDU, reset the NAV for all other STAs to prevent all other STAs from being able to extract the NAV information from the conflicting PPDU; Extract the STAs involved in the collision (or transmission failure) from the detected CoF, and also indicate whether these STAs are allowed to draw new backoff counters without doubling the CW, indicate whether one or more of these STAs can use other EDCA parameters (e.g., reduced AIFS), and / or indicate whether one or more of these STAs will be triggered in the upcoming TXOP; Instructing STAs that are not detected by the CoF (which the AP does not know who they are) to draw a new backoff counter without doubling the CW, which is only allowed if the collision is resolved (at least partially), means that the CRF grants channel access to at least one STA that is in conflict; For delayed and / or unscheduled STAs, only short frames are used to initiate their TXOPs with a mandatory CoF, and a more robust CoF configuration is also used.

[0071] The expected response to a CRF frame can be configured as follows. Depending on the collision resolution mechanism triggered by the CRF, the STA can reply with a PPDU containing data, or as follows: Figure 6 No response will be given as indicated, or as shown in the image. Figure 7 The example shows a response using a short response. Figure 7 A diagram illustrating a fourth embodiment of the communication scheme according to the present disclosure is shown, illustrating a response indication to the CRF to confirm CoF detection.

[0072] In rare cases, the CoF detected by the AP may be incorrect, and an incorrect STA may be identified as a conflicting STA. For example, in Figure 7 In the example shown, STA3 is identified as a conflicting STA, but in reality only STA1 and STA2 are conflicting. To address this situation, the AP can request that STAs identified as conflicting in CRF 30 always respond with an indication indicating whether they are involved in the conflict. This request can take the form of an additional response field 36 included in or added to CRF 30. This response indication can be in a separate short PPDU, such as... Figure 7 The response frames R16 and R46 are shown in the middle.

[0073] Collision STAs not identified in CRF 30 can be allowed to be re-pumped with the backoff counter without doubling the CW or optionally using a shorter AIFS. Figure 7 In the example, this mechanism allows STA2 to have shorter contention (compared to double CW), avoiding further delays (e.g., otherwise STA3 would gain channel access before STA2).

[0074] If there is no response to the CRF, the AP should fall back to standard EDCA rules, for example, initiating a new backoff procedure to schedule the conflicting STA. For example, if the STA addressed in CRF 30 suffers a transient interruption (e.g., shadowing effect or external interference prevents them from decoding the CRF), no response may occur.

[0075] Now refer to Figure 8 Explain the behavior of conflicting STAs. Figure 8 A flowchart illustrating an implementation of a general operation 200 for a conflicting STA is shown. Initially, the STA and AP agree on the use and configuration of the CoF. First, the STA obtains channel access via EDCA contention (step 201) or during a preemptive pIFS gap (step 202). In step 203, the STA adds the CoF to the PPDU in one or more of the following cases: for the first PPDU of an unestablished TXOP, for a PPDU transmitted during a service period that allows transmission by a specific STA, or for a PPDU within a TXOP that allows preemptive operation (e.g., ...). Figure 9 As shown, Figure 9 A diagram illustrating a fifth embodiment of a communication scheme according to the present disclosure is shown, illustrating conflict resolution with CoF for frame-based preemption, particularly for PPDUs carrying preemption indications or preemption data.

[0076] If the STA receiving the response frame as usual (checked in step 204) and receiving an indication that the CoF was successfully detected (step 205), this means that no collision occurred and CoF detection worked as expected, therefore no further action is needed; that is, frame exchange can continue within the TXOP (step 206). If the STA receiving an indication of CoF failure (or missing CoF information) means that the PPDU was correctly decoded at the receiver, but the CoF was not detected. The STA can then modify the CoF configuration according to the AP's request (step 207).

[0077] If a CRF is received (step 208) and the CRF transmits an action addressing the conflicting STA, the conflicting STA follows the instructions of the AP (step 209), such as: responding to the TF, responding to a frame scheduling a shared TXOP operation (e.g., MU-RTS), delaying channel access by extracting a new backoff counter, and (if permitted) not doubling the CW before competing again and optionally modifying the AIF (this can be done on the same channel after the current TXOP ends, or on a separate link if indicated in the CRF), or modifying the EDCA parameters, such as not doubling the CW or changing the AIFS duration.

[0078] If a CRF is received but does not contain any action or information regarding the conflicting STA (step 210), it means the AP is unaware that the STA is also part of the conflict. If permitted (indicated in the CRF), the STA may not increment its CW, extract a new backoff counter, and optionally change its EDCA parameters according to the indication in the CRF. If indicated in the CRF, a short frame with a forced CoF and a more robust CoF configuration can be used in the next channel access attempt.

[0079] If no response frame is received within the predetermined timeout, the STA should fall back to standard backoff (2×CW-1) operation (step 201 or 202). The timeout value is set based on the duration required to receive the expected response. This can include AIFS, receiver PHY delay, and the length of the response frame.

[0080] For frame-based preemption scenarios, Figure 9 An example of conflict resolution is shown, where STA2 and STA3 are conflicting STAs. In this case, the STAs with preemptive services (STA2, STA3) should include CoF 20, 40 in PPDU 27, 47 carrying preemption instructions or data. This allows the AP to identify which STAs are involved in the conflict and initiate the conflict resolution mechanism from the mechanisms defined above (as explained for conflict resolution). Figure 9In the example shown, CRF 30 triggers a conflict STA to reduce the latency caused by the additional BSR process.

[0081] Normally, if a conflict occurs on CRF, all STAs should fall back to conventional behavior, doubling the CW before decrementing the backoff counter and waiting for AIFS.

[0082] In the IEEE 802.11 standard, a TXOP is typically established through the successful exchange of two PPDUs, where the STA initiating the exchange obtains channel access via EDCA. To comply with standard operation, one of the following rules can be implemented: In cases where collisions are detected via CoF detection, the AP can perform a backoff procedure before sending the CRF, such as... Figure 10 As shown, Figure 10 A diagram illustrating a sixth embodiment of the communication scheme according to this disclosure is shown, illustrating AP contention 33 prior to the transmission of CRF 30. In the case where the AP detects a collision via CoF detection, the AP can initiate TXOP without performing a backoff procedure, for example, as... Figure 5 As shown. Furthermore, at least one frame in the TXOP should be scheduled to resolve collisions and allow at least one conflicting STA to transmit data (e.g., the TF and / or CRF should schedule the conflicting STA). The duration of the TXOP containing the conflicting STA transmission can be set to a predetermined duration.

[0083] As explained above, the AP should determine the STA ID based on CoF detection. To achieve this, the AP can correlate the received signal with all possible CoF signals and select those with a likelihood value higher than a predetermined threshold. If the number of possible CoFs is too large (e.g., more than hundreds), this operation can become highly complex. To reduce complexity, multiple STAs can be grouped into a single CoF signal, and after detection, the AP can trigger the STA corresponding to that group to identify the sending STA.

[0084] In one embodiment of this operation, each CoF signal can identify a different transmitting STA, thus requiring the generation of multiple different CoF signals. The cross-correlation between the CoF signals determines the detection performance at the receiver; lower cross-correlation means higher detection reliability. Furthermore, conflicting transmissions are typically not synchronous, so the cross-correlation between the CoF signals should also be low in the presence of time and frequency offsets.

[0085] There are two main design parameters for generating CoF signals: the duration of the CoF signal and the number of different CoF signals to be generated (denoted as Ncof).

[0086] The duration of the CoF signal determines the number of CoF samples it has (e.g., based on PPDU bandwidth). More CoF samples result in higher detection reliability. Furthermore, a larger number of CoF samples makes it easier to separate the Ncof signal; specifically, it is desirable that the number of CoF samples is greater than or equal to Ncof.

[0087] Figure 11 A diagram illustrating an implementation of the process 300 for establishing CoF operation is shown. This process involves defining key parameters (e.g., the number of STAs), CoF configuration, signal generation, and distribution.

[0088] The general process for generating and distributing CoF signals can be as follows. In block 302, the duration of the CoF signal within the PPDU is defined. Multiple durations can be defined to map to multiple CoF configurations. Therefore, it is advantageous to define the duration with a predetermined step size. For example, for a bandwidth of 20 MHz, 4 μs is a practical step size size containing 80 samples, which would correspond to one OFDM symbol of FFT size NFFT=64 plus a guard interval (GI) of 16 samples.

[0089] In box 301, the number of different CoF signals to be generated (denoted as Ncof) is defined. They can be calculated as follows: Ncof=(ceil(N_contending_STAs / N_STA_groups)×N_ind_per_STA) Here, `ceil()` represents rounding down to the nearest largest integer value. `N_contending_STAs` is the number of STAs competing for channel access. `N_ind_per_STA` is the number of indications per STA in case the CoF needs to provide more information than just the STA identifier, such as: buffer status indications for each STA (each STA can have, for example, two CoFs, one indicating short packets below a certain threshold and the other indicating larger packets above that threshold) and the priority of the data to be transmitted, which can be defined based on TID, AC, or Flow Classification Service (SCS) characteristics. `N_STA_groups` is the number of groups that group multiple STAs together for a common CoF allocation.

[0090] In box 303, a CoF signal is generated. Specifically, a complex-valued sequence is generated by one of the following: A binary sequence is created and modulated using PSK modulation (e.g., BPSK or QPSK) to obtain a complex-valued sequence with low cross-correlation. The binary sequence can be a common sequence with low cross-correlation, such as the Gold sequence, or a randomly generated sequence, wherein the cross-correlation of the PSK-modulated complex-valued sequence is below a predetermined threshold.

[0091] Create complex-valued sequences based on DFT or Hadamard matrices.

[0092] The bits corresponding to each STA ID are encoded using robust channel coding operations (e.g., BCC with a code rate of 1 / 2 or 1 / 3), and the encoded bits are modulated using robust modulation (e.g., BPSK) to create a complex-valued sequence.

[0093] In block 304, the complex-valued sequence is modulated into the waveform to be transmitted. This can be accomplished using a time-domain waveform, where the complex-valued sequence can be phase-shifted and transmitted using pulse amplitude modulation (PAM). Alternatively, this can be accomplished using an OFDM waveform, where the complex-valued sequence can be phase-shifted and mapped to tones in an OFDM grid, which are then modulated into OFDM symbols and transmitted.

[0094] In block 305, CoF signals are assigned to STAs. In cases where multiple different CoF signals are assigned to each STA (e.g., each CoF signal has an additional indication), the signal with a greater cross-correlation than the CoF signals assigned to other STAs is selected. In cases where more than one STA is identified by different CoF signals, STAs unlikely to simultaneously compete for channel access (e.g., if the STAs have non-overlapping regular activity intervals) are grouped together.

[0095] In block 306, information is exchanged between the AP and all STAs in the BSS, so that each STA knows which CoF signal to use (and what additional instructions can be transmitted), and the AP knows all CoFs corresponding to each STA. The AP should be aware of all CoF signals, their STA assignments, and any additional instructions. CoF signal generation can be performed centrally at the AP, which then sends instructions to each STA containing information about how to generate its own CoF signal or the CoF signal itself.

[0096] Based on the general process of creating a CoF signal as explained above, it may be desirable to have multiple available CoF configurations to dynamically balance reliability, signaling overhead, and complexity. Different CoF configurations can be obtained by changing one or more of the following parameters: the duration and / or length of the CoF signal, the modulation parameters (modulation and coding scheme when using coded STA IDs to generate the CoF signal; FFT size, guard interval, and tone mapping to use in the case of OFDM modulation), and the sequence type, such as a low cross-correlation pseudo-random sequence type (e.g., Gold, Kasami, JPL) and an orthogonal sequence DTF, or Hadamard.

[0097] In many cases, when a collision occurs, frames are lost because they cannot be decoded, and information about which STAs collided is not available. Figure 12A The basic PPDU format in a WLAN, consisting of a PHY preamble and a data field, is shown. A more robust part of the PPDU is the traditional short training field (L-STF), used for packet detection and initial synchronization. However, this field does not carry any information. Signaling fields (such as L-SIG, RL-SIG, and SIG) carry basic information about the PPDU's duration, format, etc., and are modulated using a modulation and coding scheme (MCS) robust to channel variations and fading. However, decoding of these fields often fails in the event of a collision. Furthermore, the identity of the sending STA is typically contained in the MAC header of the MAC Protocol Data Unit (MPDU) carried in the data field, and its MCS is generally less robust than the MCS used in the PHY preamble.

[0098] In the event of a collision, the receiver is unable to extract highly reliable information to identify the situation or transmit a STA, preventing it from taking actions that could mitigate further delays. According to this disclosure, a PPDU format is defined to indicate a reliable channel access request. This PPDU format... Figure 12B and Figure 12C As shown in the diagram, it includes a Collision Detection Field (CoF), which can be detected with high reliability even in the event of a collision. The CoF contains a signal (denoted as the CoF signal) that identifies the transmitting STA, enabling the receiver to implement a collision resolution mechanism and reduce channel access delay.

[0099] The proposed PPDU format includes the same legacy preamble as the standard PPDU for backward compatibility. Traditional STAs use these fields to understand channel busy. The SIG field can be modified to indicate the new PPDU format, as well as the presence of the CoF field, which simplifies receiver operation in the absence of collisions.

[0100] The proposed PPDU format has two main variants: one without a data field (such as...). Figure 12B (as shown) and a data field (such as) Figure 12C (As shown). Figure 12B The first type shown is intended to be a PHY-only indication, with the purpose of issuing a channel access request. In this case, an optional STF can be added to support hardware functions such as automatic gain control settings. Optionally, a packet extension (PE) field can also be added in case the receiver requires additional processing time to detect the CoF signal. Figure 12C The second variant shown includes a data field with an MPDU, and the purpose of the CoF is to increase the reliability of PPDU transmission in the event of a collision. The CoF position can also be placed after the LTF in case a different FFT size is required than the traditional field.

[0101] The implementation of the general framework for creating and distributing CoF signals will first be explained. In its most basic form, each CoF signal identifies a different transmitting STA. However, multiple STAs can also be grouped to use a common CoF to reduce receiver complexity. Furthermore, each STA or group of STAs can use multiple CoFs to indicate further information, such as the buffer status or priority of queued traffic. For example, an STA can have two CoFs to indicate whether the buffer length of queued traffic is above or below a predetermined threshold. Similarly, it can be used to indicate whether queued traffic is above or below a predetermined priority. Priorities can be defined based on Access Class (AC), Traffic Identifier (TID), or Flow Classification Service (SCS) characteristics. Therefore, multiple different CoF signals can be generated. The cross-correlation between CoF signals determines the detection performance at the receiver; lower cross-correlation means higher detection reliability.

[0102] Figure 13 A diagram illustrating another embodiment of the process 400 for generating and distributing CoF signals is shown. This process is similar to... Figure 11 The process shown is 300, but there are some key differences that will be explained. The general process for generating and distributing CoF signals can be as follows.

[0103] Box 401 corresponds to box 301. Box 402 is similar to box 302. It defines the CoF configuration based on different durations, modulation parameters, tone schemes, and sequence types of the CoF signal. Further details regarding the CoF configuration are explained below.

[0104] In box 403, generating the CoF signal involves three main steps (details will be explained below): determining the number of periods or OFDM symbols, generating a tone map and tone sequence, and generating a time or symbol sequence. The generated CoF signal can be identified by two main parameters: the tone set index indicating the tones required to form the CoF, and the time / symbol sequence index indicating the time / symbol sequence used.

[0105] In box 404, similar to box 305, CoF signals are assigned to STAs. CoF signals can be assigned by distributing a tone set index and a time / symbol sequence index to each STA. This can be done statically or dynamically based on STA identifiers (IDs) (e.g., association identifiers (AIDs)). The AP can assign each index to each STA individually during the association or configuration phase, or the AP can transmit a range of AIDs with starting AID values ​​from which each STA can identify each index based on its AID number. A matrix known to all STAs can be created as the basis for sequence generation, which can be a low-complexity method for generating and assigning CoF signals, as the AP will only need to indicate the row (or column) indices to which the STAs want to use. Row (or column) indices can also be selected based on STA IDs to minimize signaling overhead. In cases where multiple different CoF signals are assigned to each STA (e.g., each CoF signal has an additional indication), signals with greater cross-correlation compared to the CoF signals assigned to other STAs can be selected. In cases where more than one STA is identified by different CoF signals, STAs that are unlikely to simultaneously compete for channel access (e.g., if the STAs have non-overlapping regular activity intervals) can be grouped together. Box 405 corresponds to box 306.

[0106] The following section will explain the generation of CoF signals based on OFDM for synchronous and asynchronous collision detection. First, the synchronization aspect will be discussed.

[0107] Collision transmissions in EDCA are typically asynchronous; therefore, even with time and frequency offsets, the cross-correlation between CoF signals should be low. However, in scenarios where the STA anticipates accessing or transmitting PPDUs on a time-contentious channel, such as in frame-based preemptive applications, synchronous operation can be assumed. The design of CoF signals varies depending on whether synchronous collisions can be assumed. For synchronous collisions, different CoF signals can be detected in the frequency domain after OFDM demodulation, while for asynchronous collisions, time detection without OFDM demodulation may be more reliable. The following sections categorize CoF design into two cases: time-detection (asynchronous) and frequency-detection (synchronous).

[0108] A CoF design for asynchronous collision scenarios can be implemented as follows. This case considers a periodic OFDM-based signal without a guard interval, where the signal period is less than the FFT size. This approach does not require generating complete OFDM symbols; instead, it generates complete periods. Therefore, the duration of the CoF signal can be adjusted by increasing or decreasing the number of periods in the signal. Periodic signals may be easier to generate because the fundamental signal is repeated multiple times, and may also be easier to detect because the receiver can find repetitions equal to the signal period. Furthermore, OFDM signals with periods shorter than the OFDM symbol duration can have low PAPR, making them less susceptible to hardware distortion. The proposed CoF design separates CoF signal generation in the frequency and time domains to simplify the generation, distribution, and allocation of CoF signals to STAs.

[0109] The proposed CoF design can be as follows. First, the number of CoF samples, denoted as Lcof, is determined based on the CoF duration and bandwidth. For example, for a CoF duration of 8 μs and a bandwidth of 20 MHz, Lcof = 160 samples. Then, a suitable period is determined. This period, denoted as Pcof, should be divisible by the number of CoF samples (e.g., for Lcof = 160, Pcof ∈ {2, 4, 5, 8, 10, 16, 20, 32, 40}), and the FFT size, denoted as NFFT, should be divisible by an integer (e.g., for Lcof = 160 and NFFT = 64, Pcof ∈ {2, 4, 8, 16, 32}). For this example, possible Pcof values ​​are {2, 4, 8, 16, 32}. Alternatively, a fixed predetermined period can be used, divisible by an integer from the NFFT size, and then Lcof and / or the CoF duration are determined by parameters indicating the number of periods in the CoF.

[0110] The tone scheme is then generated as follows. Suppose that the set of NFFT pitches consists of k∈{0, 1, ..., ... NFFT-1 If the index is used, then it is within the set. n ∈{0, 1, ..., Pcof-1 Select a tone (e.g., for Pcof=16 and NFFT=64, a tone can be selected from the set kp∈{0, 4, 8, 12, ..., 60}). Set the tone corresponding to the guard, DC, or empty subcarrier in the tone map to zero. The number of tones selected in the tone map is denoted as N_settones. N_settones tones can be divided into multiple tone groups, where each group is assigned to one or more different CoF signals.

[0111] Then, the number of complex tone sequences of length N_settones, denoted as N_toneseq, can be determined to map to the generated tone scheme as one of the following: N_toneseq equals 1; in this case, all CoFs share the same complex tone sequence, and CoFs are distinguished by tone assignment (when tones are grouped) and / or by an applied time mask (described below).

[0112] N_toneseq equals Ncof; in this case, each CoF will have a different complex tone sequence.

[0113] N_toneseq equals the number of indicators for each STA or STA group.

[0114] N_toneseq equals the number of STAs in each STA group.

[0115] Then, N_toneseq complex tone sequences are generated to be mapped to selected tones of the generated tone map by one of the following methods: Generating complex value sequences.

[0116] PSK modulation (e.g., BPSK or QPSK) is performed on pseudo-random binary sequences with low cross-correlation (e.g., well-known sequences such as Gold sequences, Kasami sequences, or JPL sequences can be used).

[0117] Orthogonal sequences can be generated by taking rows (or columns) of a Hadamard matrix or a DTF matrix.

[0118] A complex-valued tone sequence and tone assignment are distributed to each CoF signal, and the assigned complex-valued tone sequence is modulated into ceil(Lcof / NFFT) OFDM symbols to generate a time-domain CoF signal. If necessary, the time-domain CoF signal is truncated to Lcof samples.

[0119] Determine the number of time mask sequences, denoted as N_timeseq, to ​​be applied to the CoF time-domain signal, as one of the following: N_timeseq equals Ncof.

[0120] N_timeseq equals the number of STAs; in this case, if there are multiple CoFs assigned to each STA to transmit other indications, these CoFs will share the same time mask and be distinguished by tone mapping and / or complex tone sequences.

[0121] N_timeseq equals the number of STA groups; in this case, each group will have the same time mask.

[0122] N_timeseq complex-valued time series are generated from a pseudo-random or orthogonal sequence of length Lcof / Pcof (as described above for generating complex-valued sequences) to create a time mask for the time-domain CoF signal. The time mask is applied by multiplying all samples of each period by one element of the time mask. The purpose of the time mask is to further reduce the cross-correlation between CoF signals. Specifically, using a DTF matrix as the basis for generating the time mask is advantageous because the resulting sequences are orthogonal.

[0123] The CoF design for synchronization conflict scenarios can be as follows. This scenario considers OFDM-based signals, where each CoF signal consists of an integer number of OFDM symbols, and each OFDM symbol contains a cyclic prefix as a guard interval. This method assumes that the receiver performs OFDM demodulation and detects the CoF signal modulated into a specific tone. This scenario shares steps with the CoF signal for the asynchronous scenario explained above; therefore, the following steps focus on the differences.

[0124] The proposed CoF design can be as follows. Initially, the number of OFDM symbols, denoted as N_ofdmsym, is determined based on the CoF duration. N_ofdmsym can also be a design parameter, and the CoF duration can be extracted from N_ofdmsym and OFDM parameters (e.g., FFT size, guard interval, bandwidth, subcarrier spacing).

[0125] Subsequently, the pitch scheme is determined. Pitches are selected with an integer step size (denoted as N_step), which is a power of two and less than half the NFFT value. That is, for n∈{0, 1, log2( NFFT )-1},N_step=2 n The number of samples per OFDM symbol (excluding GI) is given by NFFT / N_step. This design provides flexibility to obtain different CoF durations. For example, for n =0, using all tones, and the symbol length is NFFT samples. If n =1, then use every other tone and halve the symbol length. n=2 uses every four tones, with a length of NFFT / 4, and so on. The tones corresponding to the guard, DC, or empty subcarrier in the tone map are set to zero. The number of tones selected in the tone map is denoted as N_settones. N_settones tones can be divided into multiple tone groups, where each group is assigned to one or more different CoF signals.

[0126] The following three steps are performed in the asynchronous case: determining N_toneseq complex-valued tone sequences, generating complex-valued tone sequences, and assigning the complex-valued tone sequences and tones to each CoF signal. Subsequently, the number of symbol sequences, denoted as N_symseq, is determined to be applied to the OFDM symbols for each CoF signal. The number N_symseq is determined in the same way as the number of time masks, “N_timeseq,” in the asynchronous case. N_symseq complex-valued symbol sequences of length N_ofdmsym are generated, derived from pseudo-random or orthogonal sequences (as explained above regarding complex-valued sequence generation). These sequences are applied to the tones assigned to the CoF signals by multiplying all assigned tones of each OFDM symbol by an element of the complex-valued symbol sequences. The resulting assigned tones, with the complex-valued symbol sequences applied, are modulated in the time domain into N_ofdmsym OFDM symbols. Each OFDM symbol can be truncated to a portion of size 1 / N_step (i.e., NFFT / N_step samples) and can be interpolated with GI.

[0127] CoF configurations can be designed as follows. It is desirable for each STA to have multiple available CoF configurations to balance reliability, time overhead, and complexity. The AP can share multiple CoF configurations with each STA at once, or these configurations can be fixed and specified in a standard. The AP can instruct each STA which configuration should be used, for example, based on its STA ID value. CoF configurations differ in one or more of the following ways: Tone set index: Different tone maps can have different tone positions and non-zero tone counts; the tone set index can indicate the tone set assigned to each CoF.

[0128] Tone sequence index: Indicates which tone sequence is assigned to each CoF; in this case, CoFs share the same sequence (N_toneseq = 1), which can be indicated as part of the tone set index.

[0129] Time / symbol sequence index: It indicates the time / symbol sequence assigned to each CoF; it can be indicated as a row of a matrix containing the generated sequence (e.g., Figure 15and Figure 16 (As shown); the sequence can be modified to accommodate changes in CoF duration and pitch scheme by truncating or copying a fixed-size sequence with additional phase shift.

[0130] The duration of the CoF signal can be selected based on the period or the number of OFDM symbols. Defining the duration with a predetermined step size is advantageous. For example, 4 μs is a practical step size, which contains 80 samples for a 20 MHz bandwidth. This would correspond to one OFDM symbol of FFT size NFFT=64 plus a guard interval of 16 samples, or alternatively, 5 periods of 16 samples each.

[0131] Modulation parameters: FFT size, GI length, bandwidth.

[0132] The general design of CoF signals has been introduced in previous chapters. The following sections will explain how signals are generated at each STA once a CoF configuration is selected, and provide several examples. Figure 14 A schematic diagram illustrating an embodiment of the layout of a transmitting STA 500 for generating CoF signals according to this disclosure is shown. Components that have been modified or added compared to a WLAN transmitter according to IEEE 802.11 are labeled. Figure 14 As shown, based on the selected tone scheme, the tone sequence is modulated onto the tone (box 501), and for the synchronization design, it is also multiplied with the symbol sequence (box 502). Then, cyclic offset diversity (CSD; box 503), spatial mapping (box 504), and IDFT (box 505) are applied to obtain the time-domain signal.

[0133] According to this disclosure, the following three steps are implemented as follows. For the asynchronous case, only the last OFDM symbol can be truncated, such that the number of samples in the total CoF field is Lcof (box 506). Then, the samples in each period are multiplied by the time mask sequence (box 507). No GI is inserted, or if a GI is present, the length of the GI must be the same as the period, and the time truncation should correspond to Lcof-Pcof samples. Furthermore, for the asynchronous case, each OFDM symbol is truncated by 1 / N_step, no time series is applied, and a GI is inserted as in normal operation (box 508). Finally, windowing and simulated RF operations are performed (box 509), and a signal is transmitted.

[0134] Figure 15 and Figure 16An example of a tone scheme generated based on L-STF is shown, which has N_settones=12 selected tones and a minimum tone interval of 4 tones. The tone sequence can be determined by a DTF matrix, where some columns are multiplied by -1 to increase the diversity of the first row, otherwise the first row is all one. Figure 15 and Figure 16 Two examples are given on how to generate tone sequences, namely tone sequence A ( Figure 15 ) and B ( Figure 16 Case A is achieved by simply taking rows of a DFT matrix of size N_settones (e.g., ...). Figure 17 and Figure 18 As shown, it depicts the CoF generation using a time-series mask for the asynchronous case (tone sequence A). Case B assumes a DFT matrix of half the size and maps them to interleaved selected tones (e.g., Figure 19 and Figure 20 As shown, it depicts the CoF generation using a time-series mask for the asynchronous case (tone sequence B).

[0135] Assuming OFDM modulation with NFFT=64 is used, the time-domain signals of tone sequences A and B are respectively in Figure 17 , Figure 18 and Figure 19 , Figure 20 As shown, both have a period of Pcof = 16 samples. The duration of CoF is set to 4 μs, so at a bandwidth of 20 MHz, Lcof = 160 samples, and each CoF signal contains Lcof / Pcof = 10 periods. Then, by using a method similar to Figure 15 , Figure 16 The DTF matrix shown (but of size Lcof / Pcof) is multiplied by -1 in the even-numbered columns to generate Ncof time masks.

[0136] In these examples, the total number of different CoF signals that can be generated is N_settones×(Lcof / Pcof) = 120, which takes into account all possible combinations of tone sequences and DTF lines in the time series.

[0137] Figures 21 to 23 This demonstrates how to handle synchronization conflict situations using... Figure 16 The tone sequence shown is used to generate a CoF signal based on OFDM symbols with GI. In this case, the symbol sequence is multiplied by the modulated tone in the frequency domain before the IDFT operation. The length of the symbol sequence is Nsym = 4, which means that 4 OFDM symbols are modulated. Assuming NFFT = 64, GI = 16, and a bandwidth of 20 MHz, the total number of samples will be 320, which means that the CoF duration is 16 μs.

[0138] Figure 21 A diagram illustrating the generation of the CoF using an OFDM symbol sequence mask for synchronization is shown. Due to the selected tone scheme, each OFDM symbol contains a periodic signal with a period equal to 16 samples. Therefore, the CoF duration can be reduced by truncating an integer number of periods from each symbol. For example, truncating to 2 periods (32 samples) plus a GI of 16 samples results in a total of 48 × 4 = 192 samples, corresponding to a CoF duration of 9.6 μs at a 20 MHz bandwidth. Furthermore, by choosing a GI equal to one period length, the resulting time-domain signal will be a cascade of four periodic signals, each with four periods.

[0139] Figure 22 An example of an extended tone scheme is shown. Figure 23 A diagram illustrating the generation of CoF using OFDM symbol sequence masks for synchronization cases involving pitch shifting using an extended pitch scheme is shown. According to... Figure 22 The pitch mapping is expanded to cover 24 selected pitches with a minimum interval of 2 pitches, resulting in a periodic signal with a period of 32 samples. Using the same pitch sequence (e.g.... Figure 16 (as shown), but different pitch mapping operations are introduced, such as Figure 23 As shown, four allocations are available instead of two. This provides two additional degrees of freedom in the frequency domain to separate the CoF, which simplifies detection. If a periodic signal is desired, the GI can be selected as 32 samples.

[0140] Figure 24 A flowchart illustrating an embodiment of receiver operation 600 for detecting CoF according to this disclosure is shown. The receiver performs (step 601) a carrier sense (CS) or free channel assessment (CCA) procedure to detect the presence of PPDUs arriving at the PHY layer. These procedures identify the start point of the PPDU, from which a detection window can be identified based on the duration of the conventional preamble and SIG (optionally STF) fields (step 606). The detection window identifies the time interval from which all CoF signals are expected to occur, and the detection window should have margins at the beginning and end to account for possible time offset differences between conflicting PPDUs.

[0141] Next, decoding of the conventional field and the SIG field is performed (step 602). If decoding is successful, it can be assumed that no collision occurred, or that one of the colliding PPDUs was received with significantly higher power than the other. Successful preamble decoding indicates that at least one CoF should be correctly detected with high reliability (step 603). In this case, frequency domain detection may be easier to implement, and the detection window can be reduced to accommodate the CoF size. If preamble decoding fails, it can be assumed that a collision or interruption occurred, and therefore the detection window should remain the same. Decoding of the data field (step 605) (if present) proceeds as usual if the SIG field is correctly decoded. Before detecting CoFs (steps 603 or 607), a detection set should be defined, which includes the CoF signals that the receiver will attempt to detect. This can be the total number of defined CoFs, or a subset excluding STAs known not to participate in contention at a given time.

[0142] For cases where collisions are expected to synchronize within a certain tolerance margin (e.g., within the GI), it is advantageous to detect CoF in the frequency domain. Therefore, OFDM demodulation is performed, and CoF is detected by correlating the tone and the received values ​​in the OFDM symbols with each CoF signal in the detection set (step 603 or 607). A resulting likelihood value above a detection threshold indicates successful CoF detection.

[0143] In the time-domain CoF detection (step 603 or 607), the CoF signals in the detection set are correlated with the received samples in the detection window. A sliding window method can be used to correlate the CoF with different delays until a likelihood value above a threshold is identified.

[0144] Once CoF detection is performed, an indication is sent to the MAC layer (step 604 or 609) indicating whether the CoF detection was successful, which CoFs were identified, and optionally, the likelihood value of the detector for sharing with other devices. The MAC layer then maps the identified CoFs to the STA ID of the corresponding STA and any additional indications present.

[0145] Assuming the receiver has memory to process received samples over multiple iterations, the detection window can be adjusted after a detection failure (step 614), and / or successive interference cancellation (SIC) (steps 610, 611, and 612) can be employed to improve detection of more than one CoF in the event of a collision. These functions can be triggered, for example, when preamble decoding fails. The iterative receiver process can begin by performing CoF detection (step 607), and if detection fails (e.g., the likelihood value is below a set detection threshold), the number of CoF detection attempts is compared to a set limit (step 613), and the detection window is adjusted by increasing the number of samples and / or their time position. This process can be performed iteratively until CoF detection is successful, or the attempt limit is reached, in which case an indication of detection failure is sent to the MAC layer (step 609). If a CoF is successfully detected, it can be determined whether SIC should be performed based on the likelihood value (step 608). As an example, if the CoF signal with the maximum likelihood value is much higher than the detection threshold, and there is another CoF signal with a significant likelihood value but not higher than the detection threshold (e.g., higher than the second SIC threshold), then it can be determined (step 608) that the SIC will increase the detection probability of the potential second CoF signal.

[0146] The SIC process includes first identifying the successfully detected CoF signal with the highest likelihood value in the CoF set (step 610), modifying the CoF set by removing the CoF signal (step 611), and subtracting the CoF signal weighted by the channel estimation (and the STF, if present) from the received samples (step 612). Since the CoF signal is designed to be reliable, there are additional degrees of freedom to detect at least one strongest channel path component, which is sufficient to improve detection performance through SIC.

[0147] When there are no collisions, CoF detection can be performed as part of regular receiver processing. Basically, CoF detection can be performed in two ways: a) as part of sequential PPDU reception (after preamble detection and before data decoding) and b) as parallel CoF reception (based on a detection window that runs in parallel with PPDU receiver operation).

[0148] exist Figure 24The diagram illustrates receiver operation of a PPDU with a CoF, following two operating modes. The first mode corresponds to the following scenario: CoF detection (step 603) is performed as part of sequential PPDU reception, after preamble decoding (step 602) and before data field decoding (step 605). This mode simplifies CoF detection in the event of successful preamble decoding (e.g., collision-free), as the receiver already knows of the CoF's presence based on the indication contained in the SIG field. The second operating mode involves CoF reception in parallel with regular PPDU processing to address situations where preamble decoding fails or where there are conflicting PPDUs with low power or time offsets. In this case, a CoF detection window (step 607) is determined after the CS / CCA procedure (step 601), indicating the receiver sample for which CoF detection will be performed. These two operating modes can operate in parallel and independently of each other. Furthermore, after both CoF detection processes have completed, CoF detection indication from PHY to MAC can be performed separately or jointly.

[0149] Figure 25 A diagram illustrating an implementation of receiver operation 700 in the time domain is shown. Sequential PPDU reception begins with a CS or CCA procedure (step 701), in which a data packet sent by STA 1 is detected and the start of the PPDU is identified. The receiver then synchronizes with the L-STF and L-LTF and decodes L-SIG, RL-SIG, and SIG (steps 702, 703), followed by CoF detection (step 704), regardless of whether the SIG field is successfully decoded. If the SIG field is successfully decoded, fine synchronization (step 705) and automatic gain control settings can be performed based on the STF, followed by channel estimation using the LTF (step 706). Finally, the data field is decoded (step 707).

[0150] If the receiver can synchronize with the PPDU sent by STA 1, the above process can detect the CoF from STA 1 even if the preamble decoding fails. However, if synchronization fails due to a collision with STA 2, CoF detection may also fail. Furthermore, if... Figure 25 As shown, if the corresponding PPDU is time-shifted, it is impossible to detect the CoF sent by STA 2.

[0151] Therefore, parallel CoF reception is performed to reliably detect collisions and identify colliding STAs, without relying on the results of synchronization or preamble decoding. In this case, CoF detection is triggered by the results of CS / CCA, in which the start of the PPDU is identified. Then, a detection window is determined based on the duration of the signaling field plus / minus some margin (to account for the durations of different signaling fields or the time offset between colliding PPDUs) (step 710). The conventional fields (L-STF, L-LTF, L-SIG, and RL-SIG) have known fixed normalized durations, and the SIG field can have different durations, but they have normalization constraints. Finally, the CoF detection operation is performed within the selected window by cross-correlating the received samples with the CoF signals in the CoF set following a sliding window operation (step 711).

[0152] Figure 26 A flowchart illustrating an embodiment of a first communication method 800 according to a first communication device (AP) of the present disclosure is shown. This method can be executed by a programmed computer of a circuit or individual unit or processor of the first communication device. In a first step 801, one or more data units with preambles transmitted by one or more second communication devices and / or other communication devices are detected. In a second step 802, a collision detection indication is detected within or after the preamble of the detected one or more data units, according to a predetermined configuration of the collision detection indication, wherein the configuration includes a tone sequence mapped to the tone of the OFDM symbols of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbols of the collision detection indication. In a third step 803, at least one second communication device that transmitted one or more data units is identified based on the detected collision detection indication.

[0153] Figure 27 A flowchart illustrating an embodiment of a second communication method 900 according to the present disclosure for a second communication device (any of the STAs) is shown. This method can be executed by a programming computer of a circuit or individual unit or processor of the second communication device. In a first step 901, one or more data units having a preamble are generated. In a second step 902, a collision detection indication is set within or after the preamble of the one or more data units according to a predetermined configuration of the collision detection indication, wherein the configuration includes a tone sequence mapped to the tone of the OFDM symbol of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbol of the collision detection indication. In a third step 903, the one or more data units containing the collision detection indication are transmitted.

[0154] In summary, according to aspects of this disclosure, a communication device (such as an AP) can: detect a PHY indication in a received PPDU and extract information identifying the transmitting device of each transmission PPDU; determine whether a collision or packet reception failure has occurred between PPDUs; and, if a collision or packet reception failure has occurred, send an indication to the transmitting STA and other STAs indicating that a collision or packet reception failure has occurred and / or which STAs are identified in the detected PHY indication.

[0155] Transmit / collision communication devices such as STAs may include a PHY indication, at least in the first PPDU transmitted to establish a TXOP, or during a service period that allows a specific STA to transmit, or in a predetermined IFS gap within an established TXOP that allows preemption of data transmission. The PHY indication includes information identifying the STA as a transmitter and receiving an indication from the AP to determine whether a collision or packet failure occurred when transmitting the PPDU.

[0156] According to a further aspect of this disclosure, the transmitting STA can generate a PPDU with a preamble, which includes, in addition to the CoF (a training field for identifying the transmitting STA), traditional fields and signaling fields. Furthermore, the transmitting STA can derive the CoF configuration from an instruction transmitted by the AP (not necessarily immediately preceding it), which includes a tone set index and a time / symbol sequence index. Further, the transmitting STA can modulate the tone indicated by the tone set index by mapping the tone sequence to OFDM symbols, and map the time / symbol sequence by multiplying the time / symbol sequence indicated by the time / symbol sequence index with the tone of the corresponding OFDM symbol, and then modulating them into OFDM symbols to generate a time signal, or by multiplying OFDM symbols with a time / symbol sequence to generate a time signal. Additionally, the transmitting STA can insert the generated time signal into the CoF and transmit the PPDU.

[0157] The receiving STA or AP can: perform CS or CCA to detect PPDU arrival; determine the detection window based on the start point of PPDU detection, the preamble, and the duration of CoF (starting from the PPDU detection point plus the length of the preamble (traditional and SIG) minus the margin, and the duration equal to CoF plus the margin); and detect the CoF signal contained in the CoF and identify the transmitting STA.

[0158] The generation of CoF signals can be performed offline and may include one or more of the following: determining the number of CoF signals Ncof to be generated based on the number of competing STAs and the number of indications per STA; selecting a CoF duration that is contained within a set bandwidth and has a sample number greater than or equal to the number of CoF signals; determining the number of periods or OFDM symbols suitable for the selected CoF duration; generating a time series with the same length as the period or OFDM symbol; generating a tone scheme with a predetermined number of modulated tones; generating a tone sequence with the same length as the modulated tones; generating CoF signals by mapping the tone sequence to the generated tone scheme and applying the time series to OFDM symbols before OFDM modulation or to time periods after OFDM modulation; and assigning the generated CoF signals to a group of STAs.

[0159] This disclosure proposes a Protocol Data Unit (PPDU) format that includes a Collision Detection PHY Field (CoF) to implement collision detection in the PHY layer of a WLAN receiver. The proposed PPDU format is designed for use as a fast channel access request, reliably identifying the transmitting station (STA) even in the event of a collision.

[0160] The device can be implemented by corresponding units or circuits (e.g., processors, processing circuits, computers, dedicated hardware, etc.) that perform the functions of the device. Alternatively, a common unit or circuit (e.g., a common processor or computer) can implement various functions of the device, or separate units or elements that together represent the circuit can be used.

[0161] Therefore, the foregoing discussion has only disclosed and described exemplary embodiments of this disclosure. As those skilled in the art will understand, this disclosure may be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the disclosure of this disclosure is intended to be illustrative and not to limit the scope of this disclosure and the other claims. This disclosure (including any readily identifiable variations of the teachings herein) partially defines the scope of the foregoing claims so that no inventive subject matter is offered to the public.

[0162] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. A single element or other unit can perform the functions of several items listed in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to provide an advantage.

[0163] Since embodiments of this disclosure have been described as being implemented at least in part by a data processing apparatus controlled by software, it will be understood that non-transitory machine-readable media (such as optical discs, magnetic disks, semiconductor memories, etc.) carrying such software are also considered to represent embodiments of this disclosure. Furthermore, such software may be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0164] The components of the disclosed devices, apparatuses, and systems can be implemented by corresponding hardware and / or software components (e.g., suitable circuits or circuit systems). A circuit is a structural assembly of electronic components including conventional circuit elements, integrated circuits including application-specific integrated circuits (ASICs), standard integrated circuits, application-specific standard products, and field-programmable gate arrays (FPGAs). Furthermore, the circuit includes a central processing unit, graphics processing unit, and microprocessor programmed or configured according to software code. The circuit does not include pure software, although it includes the hardware that executes the aforementioned software. A circuit or circuit system can be implemented by a single device or unit, multiple devices or units, one or more chipsets, or one or more processors.

[0165] Below is a list of other implementations of the disclosed subject matter: 1. A first communication device configured to communicate with one or more second communication devices, the first communication device including circuitry configured to perform the following operations: - Detect one or more data units with preambles transmitted by one or more second communication devices and / or other communication devices; - According to a predetermined configuration of the collision detection indication, the collision detection indication is detected within or after the preamble of one or more detected data units, wherein the configuration includes a tone sequence mapped to the tone of the OFDM symbol of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbol of the collision detection indication; and - Based on the detected collision detection indication, identify at least one second communication device that has transmitted one or more data units.

[0166] 2. According to the first communication device of Embodiment 1, The circuit is configured to determine a detection window for detecting a collision detection indication based on the starting point of detecting one or more data units and the duration of a preamble, the preamble containing the collision detection indication or being placed before the collision detection indication.

[0167] 3. The first communication device according to any one of embodiments 1 to 2, The circuit is configured to generate and / or indicate a collision detection indication to one or more second communication devices via one or more of the following configurations: - Defines the duration of the collision detection indication within the data unit; - Define the number of different collision detection indicators; - Determine the number of cycles or OFDM symbols suitable for the duration of the collision detection indication; - Generate a time / symbol sequence with the same period or OFDM symbol length; - Define the time / symbol sequence index that identifies each time / symbol sequence; - Defines a bandwidth index that identifies the bandwidth occupied by the collision detection indicator; - Generate a pitch scheme with a predetermined number of modifiable pitches; - Generate a pitch scheme with a predetermined number of pitches, which are divided into continuous or non-contiguous pitch sets, wherein each pitch set is assigned a different collision detection indication; - Generate a tone sequence with a length equal to or less than the modifiable pitch and / or a length equal to the number of pitches in each pitch set; - Define the tone set index within the tone set that corresponds to the tone sequence and / or the tone assigned to one or more second communication devices; - Generate collision detection indications by mapping tone sequences to the generated tone scheme; - Create a sequence of complex values ​​representing a collision detection indicator or contained within a collision detection indicator; - Truncate one or more OFDM symbols contained in the collision detection instruction; - Apply the time / symbol sequence to the OFDM symbol before OFDM modulation, or apply the time / symbol sequence to the time period after OFDM modulation; - Modulate the complex-valued sequence into a waveform to be transmitted as a collision detection indication; - Assign one or more collision detection indications to one or more second communication devices; and - Notify the second communication device associated with the first communication device to assign one or more collision detection instructions to one or more second communication devices.

[0168] 4. A first communication device according to any one of embodiments 1 to 3, wherein the circuit is configured as follows: - Detect a collision detection indication in a data unit received from one or more data units in a second communication device configured to transmit a data unit containing a collision detection indication; - Determine whether a collision has occurred or reception has failed based on one or more received collision detection indications; and - If it is determined that a collision or reception failure has occurred, a collision resolution indication is transmitted, which indicates that a collision or reception failure has occurred and / or indicates that at least one of one or more second communication devices has transmitted the data unit that caused the collision or reception failure.

[0169] 5. A first communication device according to any one of embodiments 1 to 4, The circuit is configured to detect a collision detection indication in one or more received data units from a second communication device configured to transmit a data unit containing a collision detection indication after performing contention-based channel access, during a predetermined service period or during a predetermined time interval within an established transmission opportunity.

[0170] 6. A first communication device according to any one of embodiments 1 to 5, The circuitry is configured to receive and / or indicate and / or exchange information with one or more second communication devices, the information indicating one or more of the following: - Assign a collision detection indication to one or more second communication devices; - Whether a collision detection indication should be included in subsequent data units transmitted by one or more second communication devices; - Whether subsequent data units will be able to initiate a transmission opportunity; - Whether the collision detection indicator indicates the service priority and / or buffer status of the corresponding second communication device; - Configuration of conflict detection indication; and - The maximum length of the data unit containing the collision detection indication.

[0171] 7. A first communication device according to any one of embodiments 1 to 6, The circuit is configured to generate and / or indicate to one or more second communication devices one or more different collision detection indications in one or more of the following aspects: - Tone set index; - Pitch sequence index; - Time / symbol sequence index; - Bandwidth index; - The duration of the collision detection indication; and - One or more modulation parameters.

[0172] 8. A first communication device according to any one of embodiments 1 to 7, The circuit is configured to transmit information indicating one or more of the following to the MAC layer circuit if a collision detection indication has been detected: - Detection successful; - Which collision detection indicators have been detected; and / or - The likelihood value of the detection; and The MAC layer circuitry is configured to map one or more detected collision detection indications to the identifier of the second communication device.

[0173] 9. The first communication device according to Embodiment 2, The circuit is configured to adjust the detection window and / or employ continuous interference cancellation after a collision detection indication fails.

[0174] 10. A second communication device configured to communicate with a first communication device, the first communication device being configured to communicate with one or more second communication devices, the second communication device including circuitry configured to perform the following operations: - Generate one or more data units with a preamble; - According to a predetermined collision detection indication configuration, a collision detection indication is set within or after the preamble of one or more data units, wherein the configuration includes a tone sequence mapped to the tone of the OFDM symbol of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbol of the collision detection indication; and - Transmit one or more data units containing collision detection indications.

[0175] 11. The second communication device according to embodiment 10, The circuit is configured as follows: - Obtain the collision detection indication configuration, which includes a tone set index and / or a time / symbol sequence index and / or a tone sequence index and / or a bandwidth index; - By mapping tone sequences to OFDM symbols and mapping time / symbol sequences indicated by time / symbol sequence indices to generate time signals, a collision detection indication indicated by a tone set index is generated; and - The generated time signal is included in the collision detection indication.

[0176] 12. The second communication device according to embodiment 11, The circuit is configured to generate a collision detection indication in the following manner: - Before modulating the tone corresponding to the OFDM symbol into an OFDM symbol, the tone is multiplied by the time / symbol sequence to generate a time signal, or - Multiply OFDM symbols with a time / symbol sequence to generate a time signal.

[0177] 13. A second communication device according to any one of embodiments 10 to 12, The circuit is configured as follows: - Transmit data units containing collision detection indications; and / or - Receive a response or conflict resolution indication for the transmitted data unit from a first communication device, the conflict resolution indication indicating that a conflict or reception failure has occurred and / or indicating at least one of one or more second communication devices that caused the conflict or reception failure.

[0178] 14. A second communication device according to any one of embodiments 10 to 13, The circuit is configured to include one or more of the following in the collision detection indication: - The first data unit transmitted after performing contention-based channel access; - Data units transmitted during service periods that allow one or more second communication devices to transmit; and - A data unit carrying a preemption instruction and / or preemption data.

[0179] 15. A second communication device according to any one of embodiments 10 to 14, The circuit is configured to: include an indication of the format of the data unit and / or an indication of the presence of a collision detection indication in the data unit in the signaling field of the preamble; and / or include a collision detection indication in the training field located within or after the preamble, or replace the training field with a collision detection indication.

[0180] 16. A second communication device according to any one of embodiments 10 to 15, The circuit is configured to use the collision detection indication design based on synchronous or asynchronous detection of the collision detection indication.

[0181] 17. A second communication device according to any one of embodiments 10 to 16, The circuit is configured to generate a collision detection indication by truncating one or more OFDM symbols and multiplying the truncated OFDM symbols by a time series.

[0182] 18. A second communication device according to any one of embodiments 10 to 17, The circuit is configured to generate one or more of the following configurations based on an indication received from a first communication device: - Defines the duration of the collision detection indication within the data unit; - Define the number of different collision detection indicators; - Determine the number of cycles or OFDM symbols suitable for the duration of the collision detection indication; - Generate a time / symbol sequence with the same period or OFDM symbol length; - Define the time / symbol sequence index that identifies each time / symbol sequence; - Defines a bandwidth index that identifies the bandwidth used by the collision detection indicator; - Generate a pitch scheme with a predetermined number of modifiable pitches; - Generate a pitch scheme with a predetermined number of pitches, which are divided into continuous or non-contiguous pitch sets, wherein each pitch set is assigned a different collision detection indication; - Generate a tone sequence with a length equal to or less than the modifiable pitch and / or a length equal to the number of pitches in each pitch set; - Define the tone set index within the tone set that corresponds to the tone sequence and / or the tone assigned to one or more second communication devices; - Generate collision detection indications by mapping tone sequences to the generated tone scheme; - Create a sequence of complex values ​​representing a collision detection indicator or contained within a collision detection indicator; - Truncate one or more OFDM symbols contained in the collision detection instruction; - Apply the time / symbol sequence to the OFDM symbol before OFDM modulation, or apply the time / symbol sequence to the time period after OFDM modulation; - Modulate the complex-valued sequence into a waveform that is transmitted as a collision detection indicator; - Assign one or more collision detection indications to one or more second communication devices; and - Notify the second communication device associated with the first communication device to assign one or more collision detection instructions to one or more second communication devices.

[0183] 19. A first communication method for a first communication device, the first communication device being configured to communicate with one or more second communication devices, the first communication method comprising: - Detect one or more data units with preambles transmitted by one or more second communication devices and / or other communication devices; - According to a predetermined configuration of the collision detection indication, the collision detection indication is detected within or after the preamble of one or more detected data units, wherein the configuration includes a tone sequence mapped to the tone of the OFDM symbol of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbol of the collision detection indication; and - Based on the detected collision detection indication, identify at least one second communication device that has transmitted one or more data units.

[0184] 20. A second communication method for a second communication device, the second communication device being configured to communicate with a first communication device, the first communication device being configured to communicate with one or more second communication devices, the second communication method comprising: - Generate one or more data units with a preamble; - According to a predetermined configuration of the collision detection indication, a collision detection indication is provided within or after the preamble of one or more data units, wherein the configuration includes a tone sequence mapped to the tone of the OFDM symbol of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbol of the collision detection indication; and - Transmit one or more data units containing collision detection indications.

[0185] 21. A non-transitory computer-readable recording medium storing a computer program product, which, when executed by a processor, causes the method according to embodiment 19 or 20 to be performed.

[0186] 22. A computer program including program code units, which, when executed on a computer, cause the computer to perform the steps of the method according to embodiment 19 or 20.

[0187] A1. A first communication device configured to communicate with one or more second communication devices, the first communication device including circuitry configured to perform the following operations: - Detect a collision detection indication in a data unit received from one or more data units in a second communication device configured to transmit a data unit containing a collision detection indication; - Determine whether a collision has occurred or reception has failed based on one or more received collision detection indications; and - If it is determined that a collision or reception failure has occurred, a collision resolution indication is transmitted, which indicates that a collision or reception failure has occurred and / or indicates that at least one of one or more second communication devices has transmitted data units that caused the collision or reception failure.

[0188] A2. The first communication device according to embodiment A1 The circuit is configured to detect a collision detection indication in one or more received data units from a second communication device configured to transmit data units containing a collision detection indication after performing contention-based channel access, during a predetermined service period, or during a predetermined time interval within an established transmission opportunity.

[0189] A3. A first communication device according to any one of embodiments A1 to A2 The circuit is configured to obtain and / or indicate and / or exchange with one or more second communication devices information indicating one or more of the following: - Collision detection indication to one or more second communication devices; - Whether a collision detection indication should be included in subsequent data units transmitted by one or more second communication devices; - Whether the subsequent data unit is able to initiate a transmission opportunity; - Whether the collision detection indicator indicates the service priority and / or buffer status of the corresponding second communication device; - Configuration of conflict detection indication; and - The maximum length of the data unit including the collision detection indication.

[0190] A4. The first communication device according to embodiment A3 The circuit is configured to acquire and / or indicate and / or exchange information with one or more second communication devices, the information indicating a configuration of a collision detection indication, the configuration including one or more of the following: duration, modulation parameters, sequence type, tone index assignment, time / symbol sequence index assignment, definition of trigger-based data units, and / or a transmission opportunity duration that the first communication device can set after detecting a collision or receiving failure.

[0191] A5. A first communication device according to any one of embodiments A1 to A4 The circuit is configured to determine whether a collision has occurred or a reception failure has occurred based on one or more received collision detection indications by detecting one or more of the following: - The transmission information included in the collision detection indication, which instructs the second communication device to act as the transmitter of the collision detection indication, does not match the transmission information included in the data unit received and correctly decoded by the first communication device; - At least one collision detection indication has been detected, and decoding of the preamble and / or data field of one or more data units has failed; - At least two collision detection indications have been received from different second communication devices.

[0192] A6. A first communication device according to any one of embodiments A1 to A5 The circuit is configured to perform one or more of the following if no collision detection indication is detected from the second communication device, but the first communication device is aware that the second communication device should have transmitted a collision detection indication: - Transmitting a request to one or more second communication devices to change the configuration of the collision detection indication; and - Send a collision detection report to one or more second communication devices, the collision detection report including information about the detection value of the collision detection indication.

[0193] A7. A first communication device according to any one of embodiments A1 to A6 The circuit is configured to transmit a collision resolution indication if a collision has occurred or reception has failed. This collision resolution indication is configured to notify at least one or more of the following to one or more second communication devices indicated by the received collision detection indication: - Enable trigger-based channel access; - Schedule the transmission of one or more second communication devices; - Initiate a shared TXOP operation with the first communication device; - Delayed channel access; - Move data exchange to another link; - Modify network vector assignment settings; - Whether the second communication device participated in the collision response; - Indicates whether the second communication device is allowed to draw a new backoff counter and / or whether the second communication device is allowed to draw a new backoff counter without increasing the contention window; - Indicates whether the second communication device can use other channel access parameters; - Indicate whether the second communication device will be triggered in the upcoming transmission opportunity; and - Indicates whether the second communication device can initiate a transmission opportunity with mandatory collision detection indication using only short frames and / or use a more robust configuration with collision detection indication.

[0194] A8. A first communication device according to any one of embodiments A1 to A7 The circuit is configured to transmit a collision resolution instruction in a broadcast data unit if a collision has occurred or reception has failed. This broadcast data unit is configured to notify the second communication device that previously transmitted the data unit of one or more of the following: - Modify network vector assignment settings; - Delayed channel access; - Whether the second communication device is allowed to extract a new backoff counter and / or whether the second communication device is allowed to extract a new backoff counter without increasing the contention window; - Indicates whether the second communication device can use other channel access parameters; and - Indicates whether the second communication device can initiate a transmission opportunity with mandatory collision detection indication using only short frames and / or use a more robust configuration with collision detection indication.

[0195] A9. A first communication device according to any one of embodiments A1 to A8, wherein the circuit is configured as follows: - Perform the backoff procedure before the transmission conflict resolution instruction; or - After determining that a collision or packet error has occurred and identifying the radio medium as idle, a transmission opportunity is initiated by transmitting a data unit carrying a collision resolution instruction that schedules a second communication device to transmit the data unit without performing a backoff procedure; or - After the first communication device transmits a conflict resolution instruction, it preempts the existing transmission opportunity to schedule the second communication device to transmit data units.

[0196] A10. A first communication device according to any one of embodiments A1 to A9 The circuit is configured to generate and / or indicate a collision detection indication to one or more second communication devices via one or more of the following configurations: - Defines the duration of the collision detection indication within the data unit; - Define the number of different collision detection indicators; - Create a sequence of complex values ​​representing a collision detection indicator or contained within a collision detection indicator; - Modulate the complex-valued sequence into a waveform that is transmitted as a collision detection indicator; - Assign one or more collision detection indications to one or more second communication devices; and - Notify the second communication device associated with the first communication device to assign one or more collision detection instructions to one or more second communication devices.

[0197] A11. A second communication device configured to communicate with a first communication device, the first communication device being configured to communicate with one or more second communication devices, the second communication device including circuitry configured to perform the following operations: - Transmit data units containing collision detection indications; and - Receive a response or conflict resolution indication from a first communication device for the transmitted data unit, the conflict resolution indication indicating that a conflict or reception failure has occurred and / or indicating at least one of one or more second communication devices that transmitted the data unit that caused the conflict or reception failure.

[0198] A12. The second communication device according to embodiment A11 The circuit is configured to receive a conflict resolution instruction from a first communication device, which identifies a second communication device as a participant in the conflict determined by the first communication device by detecting a conflict detection instruction.

[0199] A13. A second communication device according to any one of embodiments A11 to A12 The circuit is configured to include a collision detection indication in the preamble of the data unit, specifically in the physical layer preamble of the physical layer protocol data unit.

[0200] A14. A second communication device according to any one of embodiments A11 to A13 The circuit is configured to transmit data units containing a collision detection indication after performing contention-based channel access, or during a predetermined service period, or during a predetermined time interval within an established transmission opportunity, and / or to include the collision detection indication in one or more of the following: - The first data unit transmitted after performing contention-based channel access; - Data units transmitted during service periods that allow transmission by one or more second communication devices; and - A data unit carrying a preemption instruction and / or preemption data.

[0201] A15. A second communication device according to any one of embodiments A11 to A14 The circuit is configured to include transmission information indicating a second communication device as a transmitter in the collision detection indication.

[0202] A16. A second communication device according to any one of embodiments A11 to A15 The circuit is configured to perform one or more of the following in response to a received conflict resolution instruction: - A data unit that transmits a response and / or contains data; - Triggered channel access is performed by transmitting triggered data units; - Based on the received scheduled transmission service; - Initiate a shared TXOP operation with the first communication device; - Delayed channel access; - Move data exchange to another link; - Modify network vector assignment settings; - Whether the second communication device is involved in the collision response; - Extract a new backoff counter; - If the second communication device is not indicated or its channel access is delayed in the collision detection indication, a new backoff counter is drawn without increasing the contention window; - Use other channel access parameters; - Use only short frames to initiate transmission opportunities with mandatory collision detection indication; and - A more robust configuration using conflict detection indicators.

[0203] A17. A second communication device according to any one of embodiments A11 to A16 The circuit is configured to modulate one or more complex-valued sequences into waveforms to be transmitted as collision detection indications.

[0204] A18. A first communication method for a first communication device, the first communication device being configured to communicate with one or more second communication devices, the first communication method comprising: - Detect a collision detection indication from one or more data units received from a second communication device configured to transmit data units containing a collision detection indication; - Determine whether a collision has occurred or reception has failed based on one or more received collision detection indications; and - If it is determined that a collision or reception failure has occurred, a collision resolution indication is transmitted, which indicates that a collision or reception failure has occurred and / or indicates that at least one of one or more second communication devices has transmitted data units that caused the collision or reception failure.

[0205] A19. A second communication method for a second communication device, the second communication device being configured to communicate with a first communication device, the first communication device being configured to communicate with one or more second communication devices, the second communication method comprising: - Transmit data units containing collision detection indications; and - Receive a response or conflict resolution indication from a first communication device for the transmitted data unit, the conflict resolution indication indicating that a conflict or reception failure has occurred and / or indicating at least one of one or more second communication devices that transmitted the data unit that caused the conflict or reception failure.

[0206] A20. A non-transitory computer-readable recording medium storing a computer program product, which, when executed by a processor, causes the execution of the method according to embodiment A18 or A19.

[0207] A21. A computer program including program code units, which, when executed on a computer, cause the computer to perform the steps of the method according to embodiment A18 or A19.

Claims

1. A first communication device configured to communicate with one or more second communication devices, the first communication device including circuitry configured to perform the following operations: - Detect one or more data units with preambles transmitted by one or more second communication devices and / or other communication devices; - According to a predetermined configuration of the collision detection indication, a collision detection indication is detected within or after the preamble of the detected one or more data units, wherein, The configuration includes a tone sequence mapped to the tone of the OFDM symbols of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbols of the collision detection indication; and - Based on the detected collision detection indication, identify at least one second communication device that has transmitted the one or more data units.

2. The first communication device according to claim 1, in, The circuit is configured to determine a detection window for detecting the collision detection indication based on the starting point of detecting the one or more data units and the duration of the preamble, the preamble containing the collision detection indication or being placed before the collision detection indication.

3. The first communication device according to claim 1, in, The circuit is configured to generate and / or indicate a collision detection indication to one or more second communication devices via one or more of the following configurations: - Defines the duration of the collision detection indication within the data unit; - Define the number of different collision detection indicators; - Determine the number of cycles or OFDM symbols suitable for the duration of the collision detection indication; - Generate a time / symbol sequence with the same period or OFDM symbol length; - Define the time / symbol sequence index that identifies each time / symbol sequence; - Define a bandwidth index that identifies the bandwidth occupied by the conflict detection indication; - Generate a pitch scheme with a predetermined number of modifiable pitches; - Generate a pitch scheme with a predetermined number of pitches, the pitches being divided into continuous or discontinuous pitch sets, wherein each pitch set is assigned a different collision detection indication; - Generate a tone sequence with a length equal to or less than the modifiable pitch and / or a length equal to the number of pitches in each pitch set; - Define the tone set index within the tone set that corresponds to the tone sequence and / or the tone assigned to one or more second communication devices; - Generate collision detection indications by mapping tone sequences to the generated tone scheme; - Create a sequence of complex values ​​representing a collision detection indicator or contained within a collision detection indicator; - Truncate one or more OFDM symbols contained in the collision detection instruction; - Apply the time / symbol sequence to the OFDM symbol before OFDM modulation, or apply the time / symbol sequence to the time period after OFDM modulation; - Modulate the complex-valued sequence into a waveform to be transmitted as a collision detection indication; - Assign one or more collision detection indications to one or more second communication devices; and - Notify the second communication device associated with the first communication device to assign one or more conflict detection indications to one or more second communication devices.

4. The first communication device according to claim 1, in, The circuit is configured as follows: - Detect the collision detection indication in one or more data units received from a second communication device configured to transmit data units containing a collision detection indication; - Determine whether a collision has occurred or reception has failed based on one or more received collision detection indications; as well as - If it is determined that a conflict or reception failure has occurred, a conflict resolution indication is transmitted, which indicates that a conflict or reception failure has occurred and / or indicates that at least one of the one or more second communication devices has transmitted the data unit that caused the conflict or reception failure.

5. The first communication device according to claim 1, in, The circuit is configured to detect a collision detection indication in one or more data units received from a second communication device that is configured to transmit data units containing a collision detection indication after performing contention-based channel access, during a predetermined service period or during a predetermined time interval within an established transmission opportunity.

6. The first communication device according to claim 1, in, The circuit is configured to receive and / or indicate and / or exchange information with one or more second communication devices, the information indicating one or more of the following: - Assign a collision detection indication to the one or more second communication devices; - Whether a collision detection indication should be included in subsequent data units transmitted by one or more second communication devices; - Whether the subsequent data unit is able to initiate a transmission opportunity; - Whether the collision detection indicator indicates the service priority and / or buffer status of the corresponding second communication device; - Configuration of conflict detection indication; as well as - The maximum length of the data unit containing the collision detection indication.

7. The first communication device according to claim 1, in, The circuit is configured to generate and / or indicate to one or more second communication devices one or more different collision detection indications in one or more of the following aspects: - Tone set index; - Pitch sequence index; - Time / symbol sequence index; - Bandwidth index; - The duration of the collision detection indication; as well as - One or more modulation parameters.

8. The first communication device according to claim 1, in, The circuit is configured to transmit information indicating one or more of the following to the MAC layer circuit if a collision detection indication has been detected: - Detection successful; - Which collision detection indicators have been detected; and / or - The likelihood value of the detection; and The MAC layer circuitry is configured to map one or more detected collision detection indications to the identifier of a second communication device.

9. The first communication device according to claim 2, in, The circuit is configured to adjust the detection window and / or employ continuous interference cancellation after a collision detection indication fails.

10. A second communication device configured to communicate with a first communication device, the first communication device being configured to communicate with one or more second communication devices, the second communication device including circuitry configured to perform the following operations: - Generate one or more data units with a preamble; - According to a predetermined collision detection indication configuration, a collision detection indication is set within or after the preamble of the one or more data units, wherein, The configuration includes a tone sequence mapped to the tone of the OFDM symbols of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbols of the collision detection indication; and - Transmit the one or more data units containing the collision detection indication.

11. The second communication device according to claim 10, in, The circuit is configured as follows: - Obtain the collision detection indication configuration, which includes a tone set index and / or a time / symbol sequence index and / or a tone sequence index and / or a bandwidth index; - The collision detection indication indicated by the tone set index is generated by mapping the tone sequence to OFDM symbols and mapping the time / symbol sequence indicated by the time / symbol sequence index to generate a time signal; as well as - The generated time signal is included in the collision detection indication.

12. The second communication device according to claim 11, in, The circuit is configured to generate the collision detection indication in the following manner: - Before modulating the tone corresponding to the OFDM symbol into an OFDM symbol, the tone is multiplied by the time / symbol sequence to generate the time signal, or - The OFDM symbol is multiplied by the time / symbol sequence to generate the time signal.

13. The second communication device according to claim 10, in, The circuit is configured as follows: - Transmit data units containing the collision detection indication; and / or - Receive a response or conflict resolution indication for the transmitted data unit from the first communication device, the conflict resolution indication indicating that a conflict or reception failure has occurred, and / or indicating at least one of one or more second communication devices that caused the conflict or reception failure.

14. The second communication device according to claim 10, in, The circuit is configured to include a collision detection indication in one or more of the following: - The first data unit transmitted after performing contention-based channel access; - Data units transmitted during service periods that allow one or more second communication devices to transmit; as well as - A data unit carrying a preemption instruction and / or preemption data.

15. The second communication device according to claim 10, in, The circuit is configured to: include an indication of the format of the data unit and / or an indication of the presence of a collision detection indication in the data unit in the signaling field of the preamble; and / or include a collision detection indication in a training field located within or after the preamble, or replace the training field with a collision detection indication.

16. The second communication device according to claim 10, in, The circuit is configured to generate the collision detection indication by truncating one or more OFDM symbols and multiplying the truncated OFDM symbols by a time series.

17. The second communication device according to claim 10, in, The circuit is configured to generate one or more of the following configurations based on an indication received from the first communication device: - Defines the duration of the collision detection indication within the data unit; - Define the number of different collision detection indicators; - Determine the number of cycles or OFDM symbols suitable for the duration of the collision detection indication; - Generate a time / symbol sequence with the same period or OFDM symbol length; - Define the time / symbol sequence index that identifies each time / symbol sequence; - Define a bandwidth index that identifies the bandwidth occupied by the conflict detection indication; - Generate a pitch scheme with a predetermined number of modifiable pitches; - Generate a pitch scheme with a predetermined number of pitches, the pitches being divided into continuous or discontinuous pitch sets, wherein each pitch set is assigned a different collision detection indication; - Generate a tone sequence with a length equal to or less than the modifiable pitch and / or a length equal to the number of pitches in each pitch set; - Define the tone set index within the tone set that corresponds to the tone sequence and / or the tone assigned to one or more second communication devices; - Generate collision detection indications by mapping tone sequences to the generated tone scheme; - Create a sequence of complex values ​​representing a collision detection indicator or contained within a collision detection indicator; - Truncate one or more OFDM symbols contained in the collision detection instruction; - Apply the time / symbol sequence to the OFDM symbol before OFDM modulation, or apply the time / symbol sequence to the time period after OFDM modulation; - Modulate the complex-valued sequence into a waveform that is transmitted as a collision detection indicator; - Assign one or more collision detection indications to one or more second communication devices; and - Notify the second communication device associated with the first communication device to assign one or more conflict detection indications to one or more second communication devices.

18. A first communication method for a first communication device, the first communication device being configured to communicate with one or more second communication devices, the first communication method comprising: - Detect one or more data units with preambles transmitted by one or more second communication devices and / or other communication devices; - According to a predetermined configuration of the collision detection indication, a collision detection indication is detected within or after the preamble of the detected one or more data units, wherein the configuration includes a tone sequence mapped to the tone of the OFDM symbol of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbol of the collision detection indication; and - Based on the detected collision detection indication, identify at least one second communication device that has transmitted the one or more data units.

19. A second communication method for a second communication device, the second communication device being configured to communicate with a first communication device, the first communication device being configured to communicate with one or more second communication devices, the second communication method comprising: - Generate one or more data units with a preamble; - According to a predetermined configuration of the collision detection indication, a collision detection indication is provided within or after the preamble of the one or more data units, wherein the configuration includes a tone sequence mapped to the tone of the OFDM symbol of the collision detection indication and / or a time / symbol sequence applied to the OFDM symbol of the collision detection indication; and - Transmit the one or more data units containing the collision detection indication.

20. A non-transitory computer-readable recording medium storing a computer program product, which, when executed by a processor, causes to perform the method according to claim 18 or 19.

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