Initiating transmission opportunity in a WLAN using primary and secondary channels

Abstract

A first communication device configured to communicate with a second communication device, both communication devices belonging to a first basic service set (BSS), comprising circuitry configured to monitor a primary channel of the first BSS; either initiate a transmission opportunity (TXOP) for transmission on a non-primary channel of the first BSS or listen for a TXOP being initiated on a non-primary channel of the first BSS by the second communication device if a data unit received on the primary channel has not been transmitted by a communication device within the first BSS; and control the timing of initiating or listening for the initiation of the TXOP.

Description

INITIATING TRANSMISSION OPPORTUNITY IN A WLAN USING PRIMARY AND SECONDARY CHANNELSBACKGROUNDFIELD OF THE DISCLOSURE

[0001] The present disclosure relates to a first communication device and a corresponding method that are configured to communicate with a second communication device.DESCRIPTION OF RELATED ART

[0002] Wireless LAN uses the concept of primary and secondary channels. An access point (AP) communication defines a primary channel for its basic service set (BSS) or its cell. The bandwidth of such a primary channel is often 20 MHz. Any information flow that is important for a station (STA) communication device can be retrieved from the primarychannel. The primary channel is the channel where the backoff procedure for any STA of the basic service set (BSS) is performed on. Secondary channels may be used additionally to increase bandwidth and throughput. To initiate a transmission on secondary channels, a STA may listen to those secondary channels a short period in time (e.g. for priority interframe spacing (PiFS)) before the backoff procedure on the primary channel ends. If, during this time, the secondary channels were sensed as idle, a transmission on the primary and the secondary channel(s) may start. If the primary channel is busy or occupied, no transmission can take place although other neighboring channels would be empty.

[0003] The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor(s), to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.SUMMARY

[0004] It is an object to enable a communication device to use a non-primary (secondary) channel to communicate with its peer communication device. It is a further object to provide a communication device, a corresponding communication method as well as a corresponding computer program and a non-transitory computer-readable recording medium for implementing the communication method.

[0005] According to an aspect there is provided a first communication device configured to communicate with a second communication device, both communication devices belonging to a first basic service set (BSS), the first communication device comprising circuitry configured to: monitor a primary channel of the first BSS; either initiate a transmission opportunity (TXOP) for transmission on a non-primary channel of the first BSS or listen for a TXOP being initiated on a non-primary channel of the first BSS by the second communication device if a data unit received on the primary channel has not been transmitted by a communication device within the first BSS; andcontrol the timing of initiating or listening for the initiation of the TXOP.

[0006] According to further aspects a corresponding communication method, a computer program comprising program means for causing a computer to carry out the steps of the method disclosed herein, when said computer program is carried out on a computer, as well as a non-transitory computer-readable recording medium that stores therein a computer program product, which, when executed by a processor, causes the method disclosed herein to be performed are provided.

[0007] Embodiments are defined in the dependent claims. It shall be understood that the disclosed communication method, the disclosed computer program and the disclosed computer-readable recording medium have similar and / or identical further embodiments as the claimed communication device and as defined in the dependent claims and / or disclosed herein.

[0008] One of the aspects of the disclosure is to enable non-primary channel access in which channel access on a non-primary channel may take place by the first communication device, which may preferably operate as a non-AP STA but may also operate as an AP. For this purpose, it is detected if a primary channel (PC) is occupied by a transmission in its own basic service set (IBSS), herein also called first BSS. If this is not the case, this qualifies to transition to a non-primary channel (NPC). Furthermore, the timing of initiating a transmission opportunity (TXOP) or listening for the initiation of a TXOP after switching to the non-primary channel is controlled to avoid loss of time and ensure that the second communication device (herein also called peer communication device), which may preferably operate as an AP but may also operate as a non-AP STA, is available on the non-primary channel with high likelihood.

[0009] According to the present disclosure the non-primary channel of the first BSS can thus be used as an alternate primary channel if the data unit received on the primary channel has not been transmitted by a communication device within the first BSS. The first communication device hence uses a primary channel or an alternate primary channel to initiate aTXOP for transmission to the second communication device or for listing for a TXOP being initiated by the second communication device.

[0010] The foregoing paragraphs have been provided by way of general introduction and are not intended to limit the scope of the following claims. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWING

[0011] A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:Fig. 1 shows a diagram illustrating three typical examples of using a primary channel and zero, one or multiple secondary channels.Fig. 2 shows a diagram illustrating the same examples as shown in Fig. 1 with indications of the primary channel as busy.Fig. 3 shows a diagram illustrating the use of one secondary channel or two of the secondary channels as NPC(s).Fig. 4 shows a flowchart of a first embodiment of a communication method of the first communication device according to the present disclosure.Fig. 5 shows a flowchart of a second embodiment of a communication method of the first communication device according to the present disclosure.Fig. 6 shows a diagram of different embodiments of the step of determining when to start a TXOP based on an RTS-CTS procedure.Fig. 7 shows a diagram of different embodiments of the step of determining when to start a TXOP based on a special data unit format.Fig. 8 shows a diagram of different embodiments of the step of determining when to start a TXOP based on a trigger frame.Fig. 9 shows an embodiment of a flowchart of an embodiment of a method of determining if a switch from PC to NPC should be done according to the present disclosure.Fig. 10 shows a diagram illustrating an example of the evaluation of net duration.Fig. 11 shows a diagram illustrating a first embodiment of considering switching delay.Fig. 12 shows a diagram illustrating a second embodiment of considering switching delay.Fig. 13 shows a flowchart of a method of determining waiting time for TXOP initialization on an NPC.Fig. 14 shows a flowchart of a method for favorable parameter setting according to the present disclosure.Fig. 15 shows a flowchart of a method for enabling / disabling NPC channel access.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] Wireless LAN uses the concept of primary and secondary channels. Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, Fig. 1 shows a diagram illustrating three typical examples using either a primary channel only (example a), or a primary channel and a singlesecondary channel (example b), or a primary channel and three secondary channels (example c). Typically, an AP defines a primary channel for its BSS (herein also called first BSS). The bandwidth of such a primary channel is often 20 MHz. Any information flow that is important for a STA can be retrieved from the primary channel such as beacon transmissions. The primary channel is the channel where the backoff procedure for any STA of the BSS is performed on. Secondary channels may be used additionally to increase bandwidth and throughput. To initiate a transmission on secondary channels, a STA may listen to those secondary channels a short period in time (PiFS) before the backoff procedure on the primary channel ends. If, during this time, the secondary channels were sensed as idle, a transmission on the primary and the secondary channel(s) may start.

[0013] Any transmission requires the primary channel to be idle. Fig. 2 shows a diagram illustrating the same examples as shown in Fig. 1 with indications of the primary channel as busy for the three example a-c shown in Fig. 1 . Since the primary channel is busy, no transmission on a secondary channel can occur. This can be a problem, especially since bandwidths of up to 320 MHz are supported of which the primary channel contributes 20 MHz only. If the primary channel of 20 MHz channel is busy, the remaining 300 MHz cannot be used. The idea in Ultra High Reliability (UHR) as defined in IEEE 802.11 bn is to define a non-primary channel (NPC) as an alternative primary channel (also called secondary primary channel) that can be used when the primary channel (PC) is detected as busy. Fig. 3 shows a diagram illustrating the use of no secondary channel (in example a), one secondary channel (in example b) or two of the secondary channels (in the third example c) as NPC(s).

[0014] The detection of the primary channel being busy and switching from the PC to the NPC is a complicated process because a STA should be able to identify that a transmission on the PC is present which originates from an overlapping BSS (OBSS; herein also called another BSS or neighboring BSS). Further, a STA should be able to identify the duration of such a transmission in order to decide if a switching to NPC makes sense, and a STA should not initiate a transmission on the NPC while its peer STA has not yet switched to the NPC, too. On top, there is the issue of hidden nodes, meaning that some STA cannot hear an OBSS transmission and may consequently wrongly assume that the PC is idle and therefore not initiate a switch to NPC.

[0015] For the following discussion, it is assumed that either the STA or the peer STA is an AP STA communication device, and the other STA is a non-AP STA communication device. However, other uses of the communication devices are possible as well. However, there is generally no non-AP STA to non-AP STA connectivity, i.e. no P2P connectivity, assumed in here.

[0016] According to the present disclosure a STA does not detect an OBSS transmission as such but identifies that a transmission is not from the internal BSS (IBSS) or first BSS to trigger transitioning to the NPC, which may be very beneficial in terms of the a priori knowledge a STA needs to judge if a transmission is from IBSS or OBSS. Since the detection times are different depending on the received PPDll, a PPDU-specific comparison to a threshold level may be used for the duration information included in the received PPDlls. The detection of an IBSS transmission depends on the received PPDll or frame type. It is further suggested in an embodiment that a STA waits for a certain period of time after switching to the NPC to maximize the likelihood that its peer STA is available. The waiting time depends on the PPDll or frame that triggered the NPC switch. Furthermore, the NPC may be disabled for certain STAs that fail to identify OBSS traffic due to a hidden node issue.

[0017] Fig. 4 shows a flowchart of a first embodiment of a communication method 100 of the STA (first communication device) according to the present disclosure. The STA is configured to communicate with an AP, both the STA and the AP belonging to a first basic service set (BSS, also called IBSS). In a first step 101 , the STA monitors a primary channel of the first BSS. In a second step 102, the STA either initiates a transmission opportunity (TXOP) for transmission on a non-primary channel of the first BSS or listens for a TXOP being initiated on a non-primary channel of the first BSS by the AP if a data unit received on the primary channel has not been transmitted by another STA or AP within the first BSS. In a third step 103, the STA controls the timing of initiating or listening for the initiation of the TXOP.

[0018] Fig. 5 shows a schematic diagram illustrating a second embodiment of a communication method 200 of the STA according to the present disclosure. Blocks with dashed outline are optional. According to this embodiment, a STA participating in non-primary channelaccess (NPCA) shall classify received PPDlls and determine the switching to non-primary channel (NPC) according to the proposed scheme.

[0019] In a first step 201 , the STA monitors the primary channel (PC) and inspects the PPDlls being received. When a PPDll is just received, the STA may in one embodiment check in step 202 whether it has data to transmit. If it has data to transmit it continues the NPC switching process. If it has no data to transmit it stays on the PC (step 203), waiting for another PPDll. This step 202 may be optionally introduced for power saving reasons: When a STA has no data to transmit, it does not change to NPC, which on one hand saves power but implies on the other hand that it cannot receive data from a peer STA; hence, it is non-reachable on NPC. Therefore, an AP may change always to NPC to receive uplink data from non-AP STAs (i.e. the AP does not check if it has data to transmit), whereas a non-AP STA only changes to NPC, when it has data to transmit (i.e. the non- AP STA checks if it has data to transmit). If power saving is not desired, both AP and non- AP STA should not implement this check; hence data can be transmitted to / from any STA on the NPC.

[0020] While a PPDll is being received, the STA determines if the PPDU transmission is from its own BSS (IBSS) in step 204. To accomplish this operation, the assumption is that each STA is aware of the MAC address and the BSS color (also called BSS identifier) of the AP to which it is associated. This information is known to any STA, at the latest after the association process with its AP.

[0021] If the transmission is detected as being from IBSS, the STA stays on the primary channel (step 203) and performs regular IEEE 802.11 reception operation such as determining NAV (network allocation vector) or participating in a frame exchange. If the transmission is detected as not being from IBSS, the STA optionally checks (step 205) if the NPC is occupied by an OBSS transmission, i.e., a transmission from another BSS (OBSS) meaning a transmission from one or more devices belonging to another BSS. Such a check may be based on bandwidth information that is present in some received PPDUs. For example, if the received PPDU indicates that the bandwidth occupied by a non-IBSS transmission is the same as the bandwidth of the receiving STA’s BSS, it does not make sense to change to NPC because the NPC will be non-idle (i.e. busy), too.

[0022] If the NPC is not occupied by an OBSS transmission, the STA determines the waiting time for a TXOP to be initiated with its peer STA (step 206). If there is data to transmit and after this waiting time or even earlier (see below), the STA initiates a TXOP on the NPC (step 207), preferably according to conventional IEEE 802.11 rules for unlicensed bands, i.e. , if the NPC is getting busy during this time, it defers the TXOP initiation, for example. The length of such a TXOP depends on the transmission duration on the PC. If there is no data to transmit and after the waiting time or even earlier (see below), the STA shall listen for PPDlls received on the NPC (step 207). The listening time depends on the transmission duration on the PC. If the switch to NPC is only started when a STA has data to transmit, the step of listening is obsolete.

[0023] Fig. 5 also shows the phase in which the STA can switch to the NPC. As soon as a PPDll is determined not to be from IBSS, the STA may switch to NPC. No later than at the point in time of TXOP initiation, the STA should have completed the NPC switch. More details on switching time will be provided below.

[0024] In the following, step 204 of the embodiment shown in Fig. 5 is discussed in more detail. The underlying issue is that the point in time, when such a determination can be done, is different among STAs, in particular depending on the transmitted PPDll and / or frame type as well as the STA’s location (i.e. reception conditions). Fig. 6 shows a diagram of different embodiments of the step of determining when to start a TXOP based on an RTS / CTS procedure. An RTS / CTS procedure may happen in-between two OBSS STAs, STA 1 and STA 2 (i.e. communication devices not belonging to a first BSS, which may also be referred to as third communication devices according to the present disclosure), e.g., an AP STA and a non-AP STA. The determination if the received PPDll is from IBSS is based on another STA (STA A, i.e. the first communication device according to the present disclosure) listening to those frames or a subset of those frames. The different scenarios described in Fig. 6 may be due to different reception conditions. For example, in scenario C every frame is received whereas in scenarios A and B just a subset of frames is received. Depending on the location and / or selected MCS (modulation coding scheme) it may even happen that the other STA A does not hear any of those PPDUs i.e., the subset is empty.

[0025] In scenario A of Fig. 6, STA A receives the (MU-)RTS 10 and obtains parameters of this PPDll once the PPDll ended. Such parameters include the transmitter (TA) and intended receiver address (RA) as well as an indication of the planned TXOP length. STA A may compare if either the TA or RA is same as AP’s MAC address to which it is associated. If there is an address match, the PPDll is IBSS. If not, it is OBSS. Since STA 1 initiated the TXOP by an (MU-)RTS 10, it may happen that STA 2 does not respond. This may be observed by a CTS 11 or the first PPDU 12 not being received at STA A. Thus, STA A can only be sure that a TXOP is successfully initiated if it receives another (matching) PPDU within a timeout (= NAV timeout) interval. If such a PPDU is received, the STA may initiate the NPC switch. In scenario A, because the CTS 11 is assumed not to be received, the beginning of the first PPDU 12 is the earliest point in time when STA A can reliably determine if an OBSS TXOP was initiated. This point in time is marked by the solid arrow. An opportunistic (less reliable) determination may be already possible at the end of the RTS 10 (dashed arrow).

[0026] In scenario B of Fig. 6, it is assumed that the CTS 11 and the (B)Ack frame 13 are received only. Once the CTS frame 11 is received, STA A can reliably determine that an OBSS TXOP was initiated (solid arrow). However, the CTS frame 11 holds information about the TXOP length, but there may be ambiguities regarding the address as explained below. In such a case, STA A can only reliably determine that an OBSS TXOP was initiated once a (B)Ack (Block Acknowledgement) frame 13 has been received, which can be rather late within the TXOP (dashed arrow).

[0027] In scenario C of Fig. 6, all PPDUs 10-13 can be received by STA A, which can reliably determine that an OBSS TXOP was initiated right after the CTS frame 11 was received (solid arrow).

[0028] Fig. 7 shows a diagram of different embodiments of the step of determining when to start a TXOP based on a special frame format, such as a PPDU 20 of format High Efficiency HE (as described in IEEE 802.11ax), Extremely High Throughput EHT (as described in IEEE 802.11be), Ultra High Reliability UHR (as described in IEEE 802.11bn), or a newer amendment of the standard, indicated by HE+ PPDU in Fig. 7. Such a PPDU has the advantage that from the PPDU header 21 (indicated as signaling field SIG in Fig. 7), theIBSS / OBSS origin as well as the TXOP duration can be readily determined. In scenarios A and C, the determination can be reliably done by STA A after the PPDll header 21 was decoded. In scenario B, where only the response frame (B)Ack 22 is received, the determination can happen not earlier than at the end of the response frame 22.

[0029] Fig. 8 shows a diagram of different embodiments of the step of determining when to start a TXOP based on a trigger frame 30. Such a trigger frame 30 holds similar information as a (MU-)RTS frame 10 and triggers the transmission of a TB (trigger-based) PPDll 31. In scenario A, the determination can be reliably done by STA A after the trigger frame 30 or the response frame 33 was detected. Typically, various STAs are triggered; hence, the likelihood that at least one STA responds is higher compared to the RTS case. Therefore, awaiting a response frame may not be needed. In scenarios B and C, the determination can be reliably done by STA A after the SIG field 32 of the TB PPDll 31 was detected.

[0030] Fig. 9 shows a flowchart of an embodiment of a method 300 of determining if a switch from PC to NPC should be done according to the present disclosure. In a first step 301 , the PPDU or frame type is determined. In particular, it is checked if an RTS, a MU-RTS, a HE+ PPDU, a CTS, a trigger frame, or a response frame has been received. Since each frame or PPDU type has different content, a first check is performed depending on each frame or PPDU type: For RTS or MU-RTS (step 310), a STA checks if either the TA or RA equals the IBSS’s AP’s MAC address (step 311). For HE+ PPDU (step 320), a STA checks if the PPDU header contains the BSS color equal to the IBSS’s AP’s color (step 321). For CTS (step 330), a STA checks (step 331) if the RA equals the IBSS’s AP’s MAC address. This will only detect transmissions initiated by an AP, because the RA always equals the initiating STA’s MAC address; hence another mechanism is needed to clearly identify the switching to NPC, as will be explained below. For basic trigger frame or response frames (step 340 or 350), a STA checks if the TA equals the IBSS’s AP’s MAC address (step 341 or 351).

[0031] Since in each case the point in time of detection may be different, a duration information contained in the received PPDU is evaluated differently such that, regardless which frame or PPDU a STA detected, the net duration information is the same. A comparison to the net duration information is important for two reasons: i) A STA compares the net durationto a predefined threshold after which it makes sense to switch from PC to NPC. This is because the switching from PC to NPC takes time (switching delay) and when tuned to the NPC, a STA senses the medium for a while before it may initiate a TXOP (medium sync delay timer, also called medium synchronization time herein), on top it is a preferred operation that a STA returns to PC, before the OBSS TXOP on PC ends, ii) A STA can identify when it received a CTS that was not transmitted by an AP STA, if the CTS was from IBSS.

[0032] Fig. 10 shows a diagram illustrating an example of the evaluation of net duration. It is assumed that STA 1 and STA 2 initiate a TXOP via an RTS / CTS procedure 10, 11. Two IBSS STAs STA A and STA B have different views of the RTS / CTS exchange because of their location in the radio environment. STA A obtains the duration information of the RTS 10, durlnfo(RTS), which gives the time span as indicated until the end of the TXOP. At the point in time when STA A can do decision making, it subtracts 2xSIFS+duration(CTS) from durlnfo(RTS) in order to obtain the remaining TXOP duration which is then compared to a threshold in second step. STA B obtains the duration information of the CTS dur- Info(CTS) given as indicated. At the point in time when STA B can do decision making, it subtracts SIFS from durlnfo(CTS) to obtain the remaining TXOP duration which is then compared to same threshold as in STA A case in a second step.

[0033] For this reason, the threshold, to which a duration information is compared to as well as the comparison value, varies depending on the received PPDll or frame as shown in Fig. 9. Different frames or PPDlls contain different duration information, for which reason different duration information field names are given if Fig. 9. Furthermore, the equal signs for comparison in Fig. 9 should be interpreted as a PPDll containing a certain frame or a PPDll equaling to a certain PPDll type. In this context a multi-step process can be envisioned too, meaning that a first check is done for e.g. RTS / CTS and trigger frame and in a second check, the PPDU type is compared to HE+ formats.

[0034] It is assumed that T is the minimum duration of the remaining TXOP according to which a switch to NPC may be considered. Thus, if the remaining TXOP duration is shorter than T, a switch to NPC does not make sense (e.g. because of overhead reasons, or because notsufficient time would be left for a frame exchange). The following relations among the thresholds used in steps 312, 322, 332, 342 and 352 in Fig. 9 hold:• thresh_1 = T + 2x aSIFStime + duration(CTS); hereby, duration(CTS) refers to the duration of the CTS frame including PHY overhead but not the duration information within the CTS frame.• thresh_2 = T - SIG_detectionDelay• thresh_3 = T + aSIFStime• thresh_4 = T + aSIFStime• thresh_5 = equivalent(thresh_4) - Trigger_detection Delay• thresh_6 = T + aSIFStime

[0035] The “SI G_detection Delay” and “Trigger_detectionDelay” account for the delay caused by demodulation, decoding, parsing and FCS check of the respective frame. For thresh_5 an equivalent number of OFDM symbols based on thresh_4 is used. In general, if the remaining duration is sufficient, the switch to NPC is initiated, unless in case of RTS or Mll-RTS, where a check is done (step 313) to see if a PPDll is detected within a certain time span of NAVtimeout. If a PPDll is detected, the switch to NPC can be initiated, otherwise a STA shall stay on the primary channel.

[0036] Once a STA decided to switch to NPC and it has data to transmit, it determines a waiting time 206 after which it may start initiation process of a TXOP. The underlying concept is to design a waiting time such that the peer STA is available on the NPC in case it decided to switch to NPC.

[0037] The assumption is that any STA is aware of its channel switching time, i.e. , the time it takes to switch from PC to NPC. Furthermore, any STA is aware of the channel switching time of its peer STA. Since communication happens solely between AP STA and non-AP STA, this implies that each non-AP STA should have information about AP’s switching time and AP STA should have information about each STA’s switching time. This information can be transferred in an initial setup phase such as association.

[0038] Fig. 11 shows a diagram illustrating a first embodiment of considering switching delay. It is assumed that an OBSS STA pair (STA 1 , STA 2) initiates a TXOP by RTS / CTS mechanism 10, 11. IBSS STA A has data to transmit to IBSS STA B. STA A detects the (MU- )RTS 10 and the first PPDll 12. After detecting the first PPDll 12, it transitions to NPC, but waits until STA B is available before initiation the backoff procedure to initiate a TXOP on NPC. When IBSS STA B detects that an OBSS transmission is ongoing PC is unknown to STA A. Fig. 11 gives a possible range of detection times (either the (MU-)RTS 10 or the CTS 11).

[0039] When STA A determines the waiting time, it makes the worst-case assumption that STA B detects the OBSS transmission at the end of the possible period (i.e., the end of the CTS 11). Based on this value, STA A adds the known channel switch delay of STA B. This point in time is then the earliest time when STA A may start contention on NPC for TXOP initiation. The channel switch delay of STA A is assumed to be significantly shorter than the one by STA B. A longer channel switch delay of STA A could result in no waiting time for STA A.

[0040] Fig. 12 shows a diagram illustrating a second embodiment of considering switching delay, which is rather similar to the embodiment illustrated in Fig. 11. However, STA A starts contention for channel access earlier than the predicted switching time of STA B. This is possible as long as STA A is not going to initiate the TXOP before STA B’s waiting time is over. Such an operation may be feasible when the random parameters of channel contention are already determined by STA A before the predicted switching time of STA B is over.

[0041] Fig. 13 shows a flowchart of a method 400 of determining waiting time for TXOP initialization of TXOP on NPC (step 206 in Fig. 5). Depending on the PPDll that triggered the NPC switch (step 401), a different waiting time is determined. In particular, the computations include a difference between the switching time of the peer STA (“swDelayPeer”) and the detecting STA (“swDelayOwn”) and an optional correction term Dtwhich is different depending on the detected PPDU that triggered the NPC switch. The following values hold• D = duration(CTS) + aSIFStime or D = 0. This is because when a STA detects an RTS (step 410), a STA expects that the peer STA can detect CTS only. This correction term is applied when the “PPDll detect before NAVtimeout” step 313 in Fig. 9 detects CTS as the PPDll. When it detects the first PPDll instead, D = 0 holds. Furthermore, if the option in Fig. 6, scenario B with detection of response frame (dashed arrow) is considered, it holds that D = duration(CTS) + 2x aSIFStime + duration(first PPDll) + duration(response frame) or D4= aSIFStime + du rati on (first PPDU) + duration(re- sponse frame), respectively. This special case is to be avoided by a specific parameter setting (see below), because D4is rather long.• D2= duration(HE+PPDU) - SIG_detectionDelay + aSIFStime + duration(response frame). This is because when a STA detects a HE+PPDU (step 420), it expects that the peer device can receive the related response frame only.• D3= TB_PPDU_SIG_detectionDelay + aSIFStime. This is because the peer STA may receive the TB PPDU only which follows SIFS after the basic trigger frame was detected (step 440) and the peer STA needs to parse the SIG field of the TB PPDU.• D4= aSIFStime. This is because the peer STA may wait for a PPDU to start SIFS after the CTS frame was detected (step 430).• In case a response frame was detected (step 450), there is correction term is zero; hence there is no D parameter considered in step 451 similar as in step 422 or step 442.

[0042] If the above computation (in steps 411 , 422, 423, 431 , 442, 443, 451) returns a positive result, the detecting STA shall wait for that time before it starts to initiate a TXOP. If the result is negative, it may start to initiate a TXOP immediately. As explained above, the CW count down may start before the waiting time has passed.

[0043] In the flow chart 400, there are two conditional settings (step 421 and step 441) of the switching delay that foresee a different waiting time if the decision policy indicates that a response frame shall be awaited before the switch to NPC should be done. The decision may be set by a policy i.e. , the AP STA indicates to the STAs in its BSS how to draw this decision all the time (e.g. always wait for a response frame). As an alternative, the policy may be set based on the length of the HE+ PPDU or the length of the TB PPDU solicited by the basic trigger frame. If the length is short (e.g. in comparison to the TXOP length), itcan be tolerated to detect the response frame. If the length is long lasting, it may be beneficial not to detect the response frame, because after the response frame not much time of the OBSS TXOP is left; hence switching to the NPC does not make sense.

[0044] Favorable parameters and settings for IBSS may be as follows. In the scenarios outlined in Figs. 6 to 8 and in the flowcharts in Figs. 9 and 13, it is apparent that the longest duration to determine if a PPDll is from IBSS is in case when the response frame provides final certainty in the determination. Therefore, it is suggested to adapt parameter settings of the IBSS such that the duration until a response frame arrives is relatively short. The AP may set such parameters and / or settings during a setup phase (e.g. association), and the parameters may be contained within one or more information elements. Fig. 14 shows a flowchart of a method 500 for favorable parameter settings according to the present disclosure. In step 501 the AP sets favorable settings and / or parameters. In step 502 the STA uses favorable settings and / or parameters for channel access.

[0045] Such favorable settings include:■ CTS-to-self (i.e. , CTS without RTS before) is disabled for non-AP STA, because the CTS in such cases includes the MAC address of the non-AP STA only. Thus, as long as IBSS STAs are not aware of the MAC address of all other IBSS STAs, the determination can only be done based on subsequent PPDlls and related response frames.■ CTS-to-self can be enabled for non-AP STAs, when TXOP duration is short compared to a threshold (the threshold is related to T, the minimum TXOP duration when a switch to NPC can be considered).■ CTS-to-self for an AP STA is fine for any parameters.■ When a TXOP is initiated via a HE+ PPDll for non-AP STA, the HE+ PPDll should not exceed a certain limit, because the response frame to that PPDll may otherwise be late.■ Any length of a HE+ PPDU is fine for an AP STA.■ When a response frame is transmitted, it should be preferably a response frame including a TA, for example BAck instead of Ack, if possible. This is to guarantee that the response frame is detected as IBSS when transmitted from an AP STA.■ The rate of RTS and CTS should be set such that any STA of the IBSS can demodulate the PPDU (this is probably already fulfilled within a BSS).■ Multiple protection should be used by IBSS, especially for trigger frames and response frames. This implies that the setting of the duration / ID field in any MAC header points towards the end of the TXOP and not towards the end of the frame as it would be the case of the single protection mode.

[0046] Fig. 15 show a flowchart of a method 600 for enabling / disabling NPC channel access. Since some STAs may receive OBSS PPDlls which are however not received by their peer STA (e.g. AP STA), transition to NPC is therefore unnecessary. To avoid such issues, it is suggested that the NPC channel access may be disabled for some STAs in step 601. However, as soon as there is at least one non-AP STA that performs NPC channel access, the AP STA performs NPC channel access, too. The disabling of NPC channel access may be due to various failed TXOP initiations on NPC for example. Such a disabling may be even OBSS PPDll specific in which case a STA filters PPDlls e.g. regarding their MAC address before entering the method 600 illustrated in Fig. 15. In step 601 STA is enabling / disabling NPC channel access. In step 602 peer STA is enabling / disabling NPC channel access. In step 601, a STA (either AP or non-AP) decides to enable or disable NPC channel access. The decision is forwarded to its peer STA in step 602 such that both STAs operate synchronously.

[0047] Thus, the foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. As will be understood by those skilled in the art, the present disclosure may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosure of the present disclosure is intended to be illustrative, but not limiting of the scope of the disclosure, as well as other claims. The disclosure, including any readily discernible variants of the teachings herein, defines, in part, the scope of the foregoing claim terminology such that no inventive subject matter is dedicated to the public.

[0048] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certainmeasures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0049] In so far as embodiments of the disclosure have been described as being implemented, at least in part, by software-controlled data processing apparatus, it will be appreciated that a non-transitory machine-readable medium carrying such software, such as an optical disk, a magnetic disk, semiconductor memory or the like, is also considered to represent an embodiment of the present disclosure. Further, such a software may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0050] The elements of the disclosed devices, apparatus and systems may be implemented by corresponding hardware and / or software elements, for instance appropriated circuits. A circuit is a structural assemblage of electronic components including conventional circuit elements, integrated circuits including application specific integrated circuits, standard integrated circuits, application specific standard products, and field programmable gate arrays. Further a circuit includes central processing units, graphics processing units, and microprocessors which are programmed or configured according to software code. A circuit does not include pure software, although a circuit includes the above-described hardware executing software.

[0051] It follows a list of further embodiments of the disclosed subject matter:1 . First communication device configured to communicate with a second communication device, both communication devices belonging to a first basic service set (BSS), the first communication device comprising circuitry configured to: monitor a primary channel of the first BSS; either initiate a transmission opportunity (TXOP) for transmission on a non-primary channel of the first BSS or listen for a TXOP being initiated on a non-primary channel of the first BSS by the second communication device if a data unit received on the primary channel has not been transmitted by a communication device within the first BSS; and control the timing of initiating or listening for the initiation of the TXOP.2. First communication device according to embodiment 1 , wherein the circuitry is configured to: check if a data unit received on the primary channel has been transmitted by a communication device within the first BSS; and / or check if a data unit received on the primary channel has been transmitted by a communication device within another BSS.3. First communication device according to any preceding embodiment, wherein the circuitry is configured to switch to a non-primary channel of the first BSS before initiating a TXOP for transmission on the non-primary channel or before listening for a TXOP being initiated on the non-primary channel by the second communication device.4. First communication device according to any preceding embodiment, wherein the circuitry is configured to perform, only if the first communication device has data to transmit, one or more of the steps of checking if a data unit received on the primary channel has been transmitted by a communication device within the first BSS, checking if a data unit received on the primary channel has been transmitted by a communication device within another BSS, switching to the non-primary channel of the first BSS, and initiating the TXOP.5. First communication device according to any preceding embodiment, wherein the circuitry is configured to determine if the non-primary channel is occupied by a transmission from another BSS, in particular based on bandwidth information included in a data unit received on the primary channel; and switch to the non-primary channel of the first BSS and / or initiate the TXOP or listen for a TXOP being initiated if the data unit received on the primary channel has not been transmitted by a communication device within the first BSS and the non-primary channel is not occupied by a transmission from another BSS.6. First communication device according to any preceding embodiment, wherein the circuitry is configured to control the timing of initiating the TXOP or listening for a TXOP being initiated by determining a waiting time, for which the first communication device shall wait before initiating the TXOP or after which the first communication device shall be available on the non-primary channel for listening for a TXOP being initiated, based on one or more of a switching delay of the first communication device, a switching delay of the second communication device, a medium synchronization time, and a predetermined or set correction time.7. First communication device according to any preceding embodiment, wherein the length of the TXOP initiated by the first communication device on the non-pri- mary channel is set depending on the transmission duration on the primary channel, in particular does not extend beyond the end of the transmission duration on the primary channel.8. First communication device according to any preceding embodiment, wherein the circuitry is configured to stay on the primary channel and continue monitoring the primary channel if the first communication device has no data to transmit and / or if the data unit received on the primary channel has been transmitted by a communication device within the first BSS and / or if the non-primary channel is occupied by a transmission within another BSS.9. First communication device according to any preceding embodiment, wherein the circuitry is configured to check if a data unit received on the primary channel has been transmitted by a communication device within the first BSS or within another BSS based on one more of: which communication device transmitted the data unit; which communication device was addressed by the data unit; to which BSS the communication device belongs to; and the type and / or content of the data unit.10. First communication device according to any preceding embodiment,wherein the circuitry is configured to determine that the data unit received on the primary channel has not been transmitted by a communication device within the first BSS or that the data unit received on the primary channel has been transmitted by a communication device within another BSS based on reception and / or evaluation of parameters of one or more of a ready-to send (RTS) frame; a clear-to-send (CTS) frame; a response frame to a data unit; a data frame; a signaling field of a data unit; a trigger frame; and a response frame to a trigger frame.11. First communication device according to claim 10, wherein the circuitry is configured to initiate checking if the data unit received on the primary channel has not been transmitted by a communication device within the first BSS or if the data unit received on the primary channel has been transmitted by a communication device within another BSS upon reception of one of said frames or the signaling field of a data unit, in particular immediately after the end of reception of one of said frames or the signaling field of a data unit.12. First communication device according to claim 10 or 11 , wherein the circuitry is configured to check if the data unit received on the primary channel has not been transmitted by a communication device within the first BSS or if the data unit received on the primary channel has been transmitted by a communication device within another BSS by comparing address information and / or BSS information contained in one of said frames or the signaling field of a data unit to a MAC address of the second communication device and / or the BSS identifier of the first BSS or another BSS.13. First communication device according to any preceding embodiment, wherein the circuitry is configured to determine if a TXOP shall be initiated on the non-pri- mary channel of the first BSS or if listening for a TXOP shall be initiated on a non-primary channel of the first BSS or if switching to the non-primary channel of the first BSS shall beinitiated and / or to determine the timing of switching to the non-primary channel of the first BSS based on duration information included in the data unit received on the primary channel and a predetermined duration threshold.14. First communication device according to claim 11 , wherein the circuitry is configured to use a predetermined duration threshold depending on the kind of frame or data unit received on the primary channel.15. First communication device according to claim 6, wherein the circuitry is configured to determine the waiting time as the difference between the switching delay of the second communication device and the switching delay of the first communication device, optionally plus a predetermined or set correction time and / or a medium synchronization time.16. First communication device according to claim 15, wherein the circuitry is configured to use a predetermined or set correction time depending on the kind of frame or data unit received on the primary channel.17. First communication device according to claim 15 or 16, wherein the circuitry is configured to wait for the waiting time before initiating the TXOP if the determined waiting time has a positive value and to initiate the TXOP immediately if the determining waiting time is zero or has a negative value.18. First communication device according to claim 14, 15 or 16, wherein the circuitry is configured to be available on the non-primary channel after the waiting time passed for listening for a TXOP being initiated if the determined waiting time has a positive value and to be available immediately or as soon as possible on the non- primary channel if the determined waiting time is zero or has a negative value.19. First communication device according to any preceding embodiment, wherein the circuitry is configured to use one or more parameters set by the second communication device according to which one or more of the following applies: clear-to-send (CTS) to self is disabled;CTS to self is enabled for short TXOP duration only; the length of a data unit, in particular a high-efficiency data units containing a BSS identifier and / or TXOP duration information in one or more signaling fields, is limited; a response frame includes transmitter address information; a rate of ready-to-send (RTS) and CTS is set to enable demodulation by any communication device within the first BSS; multiple protection is used for transmissions within the first BSS; the primary channel of the first BSS is defined; the non-primary channel of the first BSS is defined; the MAC address of the second communication device is defined; the switching delay of the second communication device is defined; the medium synchronization time of the first BSS is defined; the BSS identifier of the first BSS is defined.20. First communication device according to any preceding embodiment, wherein the circuitry is configured to check if initiating a TXOP on a non-primary channel of the first BSS or listening for a TXOP to be initiated on a non-primary channel of the first BSS is disabled by the second communication device for the first communication device, preferably for a defined MAC address of a communication device within another BSS; and not access the non-primary channel if initiating a TXOP or listening for a TXOP is disabled.21. Communication method of a first communication device configured to communicate with a second communication devices, both communication devices belonging to a first basic service set (BSS), the communication method comprising: monitoring a primary channel of the first BSS; either initiating a transmission opportunity (TXOP) for transmission on a non-primary channel of the first BSS or listening for a TXOP being initiated on a non-primary channel of the first BSS by the second communication device if a data unit received on the primary channel has not been transmitted by a communication device within the first BSS; and controlling the timing of initiating or listening for the initiation of the TXOP.22. A non-transitory computer-readable recording medium that stores therein a computer program product, which, when executed by a processor, causes the method according to embodiment 21 to be performed.23. A computer program comprising program code means for causing a computer to perform the steps of said method according to embodiment 21 when said computer program is carried out on a computer.

Claims

CLAIMS1. First communication device configured to communicate with a second communication device, both communication devices belonging to a first basic service set (BSS), the first communication device comprising circuitry configured to: monitor a primary channel of the first BSS; either initiate a transmission opportunity (TXOP) for transmission on a non-primary channel of the first BSS or listen for a TXOP being initiated on a non-primary channel of the first BSS by the second communication device if a data unit received on the primary channel has not been transmitted by a communication device within the first BSS; and control the timing of initiating or listening for the initiation of the TXOP.

2. First communication device according to claim 1 , wherein the circuitry is configured to: check if a data unit received on the primary channel has been transmitted by a communication device within the first BSS; and / or check if a data unit received on the primary channel has been transmitted by a communication device within another BSS.

3. First communication device according to claim 1 , wherein the circuitry is configured to switch to a non-primary channel of the first BSS before initiating a TXOP for transmission on the non-primary channel or before listening for a TXOP being initiated on the non-primary channel by the second communication device.

4. First communication device according to claim 1 , wherein the circuitry is configured to perform, only if the first communication device has data to transmit, one or more of the steps of checking if a data unit received on the primary channel has been transmitted by a communication device within the first BSS, checking if a data unit received on the primary channel has been transmitted by a communication device within another BSS, switching to the non-primary channel of the first BSS, and initiating the TXOP.

5. First communication device according to claim 1 , wherein the circuitry is configured to determine if the non-primary channel is occupied by a transmission from another BSS, in particular based on bandwidth information included in a data unit received on the primary channel; and switch to the non-primary channel of the first BSS and / or initiate the TXOP or listen for a TXOP being initiated if the data unit received on the primary channel has not been transmitted by a communication device within the first BSS and the non-primary channel is not occupied by a transmission from another BSS.

6. First communication device according to claim 1 , wherein the circuitry is configured to control the timing of initiating the TXOP or listening for a TXOP being initiated by determining a waiting time, for which the first communication device shall wait before initiating the TXOP or after which the first communication device shall be available on the non-primary channel for listening for a TXOP being initiated, based on one or more of a switching delay of the first communication device, a switching delay of the second communication device, a medium synchronization time, and a predetermined or set correction time.

7. First communication device according to claim 1 , wherein the length of the TXOP initiated by the first communication device on the non-primary channel is set depending on the transmission duration on the primary channel, in particular does not extend beyond the end of the transmission duration on the primary channel.

8. First communication device according to claim 1 , wherein the circuitry is configured to stay on the primary channel and continue monitoring the primary channel if the first communication device has no data to transmit and / or if the data unit received on the primary channel has been transmitted by a communication device within the first BSS and / or if the non-primary channel is occupied by a transmission within another BSS.

9. First communication device according to claim 1 , wherein the circuitry is configured to check if a data unit received on the primary channel has been transmitted by a communication device within the first BSS or within another BSS based on one more of: which communication device transmitted the data unit; which communication device was addressed by the data unit; to which BSS the communication device belongs to; and the type and / or content of the data unit.

10. First communication device according to claim 1 , wherein the circuitry is configured to determine that the data unit received on the primary channel has not been transmitted by a communication device within the first BSS or that the data unit received on the primary channel has been transmitted by a communication device within another BSS based on reception and / or evaluation of parameters of one or more of a ready-to send (RTS) frame; a clear-to-send (CTS) frame; a response frame to a data unit; a data frame; a signaling field of a data unit; a trigger frame; and a response frame to a trigger frame.

11. First communication device according to claim 10, wherein the circuitry is configured to initiate checking if the data unit received on the primary channel has not been transmitted by a communication device within the first BSS or if the data unit received on the primary channel has been transmitted by a communication device within another BSS upon reception of one of said frames or the signaling field of a data unit, in particular immediately after the end of reception of one of said frames or the signaling field of a data unit.

12. First communication device according to claim 10,wherein the circuitry is configured to check if the data unit received on the primary channel has not been transmitted by a communication device within the first BSS or if the data unit received on the primary channel has been transmitted by a communication device within another BSS by comparing address information and / or BSS information contained in one of said frames or the signaling field of a data unit to a MAC address of the second communication device and / or the BSS identifier of the first BSS or another BSS.

13. First communication device according to claim 1 , wherein the circuitry is configured to determine if a TXOP shall be initiated on the non-pri- mary channel of the first BSS or if listening for a TXOP shall be initiated on a non-primary channel of the first BSS or if switching to the non-primary channel of the first BSS shall be initiated and / or to determine the timing of switching to the non-primary channel of the first BSS based on duration information included in the data unit received on the primary channel and a predetermined duration threshold, in particular a predetermined duration threshold depending on the kind of frame or data unit received on the primary channel.

14. First communication device according to claim 6, wherein the circuitry is configured to determine the waiting time as the difference between the switching delay of the second communication device and the switching delay of the first communication device, optionally plus a predetermined or set correction time and / or a medium synchronization time.

15. First communication device according to claim 14, wherein the circuitry is configured to use a predetermined or set correction time depending on the kind of frame or data unit received on the primary channel.

16. First communication device according to claim 14, wherein the circuitry is configured to wait for the waiting time before initiating the TXOP if the determined waiting time has a positive value and to initiate the TXOP immediately if the determining waiting time is zero or has a negative value, and / or be available on the non-primary channel after the waiting time passed for listening for a TXOP being initiated if the determined waiting time has a positive value and to beavailable immediately or as soon as possible on the non-primary channel if the determined waiting time is zero or has a negative value.

17. First communication device according to claim 1 , wherein the circuitry is configured to use one or more parameters set by the second communication device according to which one or more of the following applies: clear-to-send (CTS) to self is disabled;CTS to self is enabled for short TXOP duration only; the length of a data unit, in particular a high-efficiency data units containing a BSS identifier and / or TXOP duration information in one or more signaling fields, is limited; a response frame includes transmitter address information; a rate of ready-to-send (RTS) and CTS is set to enable demodulation by any communication device within the first BSS; multiple protection is used for transmissions within the first BSS; the primary channel of the first BSS is defined; the non-primary channel of the first BSS is defined; the MAC address of the second communication device is defined; the switching delay of the second communication device is defined; the medium synchronization time of the first BSS is defined; the BSS identifier of the first BSS is defined.

18. First communication device according to claim 1 , wherein the circuitry is configured to check if initiating a TXOP on a non-primary channel of the first BSS or listening for a TXOP to be initiated on a non-primary channel of the first BSS is disabled by the second communication device for the first communication device, preferably for a defined MAC address of a communication device within another BSS; and not access the non-primary channel if initiating a TXOP or listening for a TXOP is disabled.

19. Communication method of a first communication device configured to communicate with a second communication devices, both communication devices belonging to a first basic service set (BSS), the communication method comprising:monitoring a primary channel of the first BSS; either initiating a transmission opportunity (TXOP) for transmission on a non-pri- mary channel of the first BSS or listening for a TXOP being initiated on a non-primary channel of the first BSS by the second communication device if a data unit received on the primary channel has not been transmitted by a communication device within the first BSS; and controlling the timing of initiating or listening for the initiation of the TXOP.

20. A non-transitory computer-readable recording medium that stores therein a computer program product, which, when executed by a processor, causes the method according to claim 19 to be performed.

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