Random access based on orthogonal frequency division multiplexing (OFDM)

Abstract

A method, system and apparatus are disclosed. According to some embodiments, a method implemented in a station, STA (16), that is configured to communicate with an access point, AP (14) is provided. An indication of at least a first random access sequence of a plurality of random access sequences for random access is received where the plurality of random access sequences are configured for transmission in the frequency domain. A random access procedure is performed at least by transmitting, in the frequency domain, the first random access sequence of the plurality of random access sequences.

Description

[0001] RANDOM ACCESS BASED ON ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING (OFDM)

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to wireless communications, and in particular, to random access (RA) based on RA sequences distributed in the frequency domain.

[0004] BACKGROUND

[0005] Wi-Fi, also known as Wireless Local Area Network (WLAN), is a technology that currently mainly operates in the 2.4 GHz, the 5 GHz band, and the 6 GHz band. There are specifications regulating access points' or mobile terminals' physical (PHY) layer, medium access layer (MAC) layer, and other aspects in order to secure compatibility and interoperability between different WLAN entities, e.g., between an access point and mobile terminals, both of which may be referred to as stations (STAs) herein. Wi-Fi is generally operated in license-exempt bands, and as such, communication over Wi-Fi may be subject to interference sources from any number of known and unknown devices. Wi-Fi is commonly used as wireless extensions to fixed broadband access, e.g., in domestic environments and wireless hotspots, like airports, train stations and restaurants.

[0006] One goal of the next-generation Wi-Fi standards is to improve the performance of low-latency services such as automation, cloud gaming, and XR. In the project authorization request (PAR) of IEEE 802.11 Ultra High Reliability (UHR), the group has indicated that a goal is for at least one mode of operation that is capable of reducing latency by 25% for the 95th percentile of the latency distribution compared to the IEEE 802.11 Extremely High Throughput medium access control (MAC) / physical layer (PHY) operation.

[0007] One essential component for achieving low latency in Wi-Fi is to be able to obtain channel access. For a Wi-Fi STA to access the channel, the STA either determines that the channel is idle, which is performed using listen before talk (LBT) or the STA can transmit in response to a received packet, in which case it can be assumed that before this received packet was sent, the channel was determined to be idle using LBT at the access point (AP).

[0008] Traditionally, Wi-Fi has been based on distributed channel access, i.e., the wireless device that has something to send performs LBT. Distributed channel access has a low complexity level for implementation in a system, but such distributed channel access comes with at least two shortcomings. The first shortcoming is that the time it takes until a STA gets channel access can vary considerably. The time that it takes to gain channel access may depend largely on how many other STAs are contending with each other and the total load of the system. Further, even with a fixed number of STAs and a fixed load, the waiting time still suffers from large fluctuations due to the working procedure of LBT, which is based on waiting a random time and only being allowed to transmit in case the channel is still idle.

[0009] The second shortcoming is that there is a non-negligible risk that two STAs will wait the same random time in LBT and, therefore, initiate a transmission at the same time such that a collision will take place at the AP. A collision may mean that both transmissions are lost, and thus, the channel will effectively be unused for the duration of the longest packet transmitted by either of the two STAs. Moreover, due to the exponential back-off, a collision may severely impact the time it takes for a STA to eventually obtain channel access. Details about how LBT works, including exponential back-off, are well- known and will not be further discussed herein.

[0010] In order to help support low latency access by using distributed channel access, the shortcomings discussed above should be addressed.

[0011] Some proposals have been made within the task group 802.1 Ibn (IEEE 802.11 TGbn) to try to address one or more of these shortcomings, where the TGbn is developing the standard specification for the next Wi-Fi generation. In some proposals, the approach was taken to introduce a “deferral signal”, which a high-priority STA can send once the channel access is gained. The idea with the deferral signal is that a high-priority STA, in this way, can try to ensure that non-high-priority STAs will find the channel to be busy (due to the deferral signal) and thus defer from channel access. This approach works with legacy STAs. However, when more than one high-priority STA is trying to gain access to the channel, there is still a risk that there will be a collision at the AP.

[0012] In another proposal, a high-priority STA sends a short signal to the AP, indicating that it has data to send. Once the AP has identified that a high-priority STA has data to send, the AP can reserve the channel and schedule this high-priority STA or alternatively allocate resources for more efficient UL access, i.e., UL OFDMA-based Random Access (UORA). A feature of this proposal is that the high-priority STA should not send data but instead just send a very short (4 us) signal that can be detected by the AP. However, the high-priority STA may be a hidden node for some STAs, and therefore, it is not sufficient that the high-priority STA gains access to the channel. The AP should, in response to the signal sent from the high-priority STA, send a clear-to-send (CTS) like signal to ensure that no other STA initiates a transmission and causes interference to the high-priority STAs transmission. However, this approach may not be feasible in practice as legacy devices would not recognize this very short signal and thus not defer from transmitting.

[0013] As such, existing proposals suffer from one or more problematic issues.

[0014] SUMMARY

[0015] Some embodiments advantageously provide methods, systems, and apparatuses for random access (RA) based on RA sequences distributed in the frequency domain.

[0016] One or more embodiments relate to performing random access based on OFDMA in a manner that allows at least some and potentially all STAs to be able to perform contention-free access by allocating dedicated and potentially even orthogonal resources. In addition, other STAs can be allocated to use resources for channel access which may result in contention. To support a potentially large number of devices (e.g., STAs) doing channel access in an effective way, one or more embodiments described herein are based on exploring that the different devices performing RA can be assumed to be sufficiently time and frequency synchronized to properly allocate the RA resources to the different devices. Preferably, if the proposed solution is applied to IEEE 802.11 technology, the principles of UORA are reused as the proposed solution can be made to work with UORA in a way that is transparent to legacy devices.

[0017] The RA can be performed such that all devices performing RA are using the proposed approach or the proposed approach may be introduced such that it is done together with a legacy approach for RA. In the latter case, the RA in the legacy RA may suffer in case some device using the proposed approach actually would be performing RA, whereas the device using the proposed approach may be successful.

[0018] According to one aspect of the present disclosure, a method implemented in a station, STA, that is configured to communicate with an access point, AP is provided. An indication of at least a first random access sequence of a plurality of random access sequences for random access is received where the plurality of random access sequences are configured for transmission in the frequency domain. A random access procedure is performed at least by transmitting, in the frequency domain, the first random access sequence of the plurality of random access sequences. According to one or more embodiments of this aspect, the plurality of random access sequences are selected such that the cross-correlation between any two of the plurality of random access sequences is below a predefined threshold.

[0019] According to one or more embodiments of this aspect, the plurality of random access sequences are a plurality of Zadoff-Chu sequences.

[0020] According to one or more embodiments of this aspect, the indication of at least the first random access sequence indicates information associated with the random access.

[0021] According to one or more embodiments of this aspect, the indicated information comprises at least one of: a type of pending data associated with the random access; a type of priority associated with the pending data; an amount the pending data; or a buffer size.

[0022] According to one or more embodiments of this aspect, the first random access sequence is allocated to the STA.

[0023] According to one or more embodiments of this aspect, one of a plurality of random access sequences for random access is randomly selected where the selected random access sequence corresponds to the first random access sequence that is selectable by at least one other STA.

[0024] According to one or more embodiments of this aspect, a first subset of the plurality of random access sequences are selectable by a plurality of STAs, and each random access sequence of a second subset of the plurality of random access sequences is assigned to a respective STA, the first subset being different from the second subset.

[0025] According to one or more embodiments of this aspect, the indication of at least the first random access sequence is provided by a trigger frame for uplink request, TF-ULR.

[0026] According to one or more embodiments of this aspect, the radio access is at least one of: performed in a system compliant with Institute of Electrical and Electronics Engineers, IEEE, 802.11 Standard; and based on orthogonal frequency division multiplexing, OFDM.

[0027] According to another aspect of the present disclosure, the STA is configured to communicate with an access point, AP. The STA is configured to: receive an indication of at least a first random access sequence of a plurality of random access sequences for random access where the plurality of random access sequences are configured for transmission in the frequency domain, and perform a random access procedure at least by transmitting, in the frequency domain, the first random access sequence of the plurality of random access sequences. According to one or more embodiments of this aspect, the plurality of random access sequences are selected such that the cross-correlation between any two of the plurality of random access sequences are below a predefined threshold.

[0028] According to one or more embodiments of this aspect, the plurality of random access sequences are a plurality of Zadoff-Chu sequences.

[0029] According to one or more embodiments of this aspect, the indication of at least the first random access sequence indicates information associated with the random access.

[0030] According to one or more embodiments of this aspect, the indicated information comprises at least one of: a type of pending data associated with the random access; a type of priority associated with the pending data; an amount the pending data; or a buffer size.

[0031] According to one or more embodiments of this aspect, the first random access sequence is allocated to the STA.

[0032] According to one or more embodiments of this aspect, the STA is further configured to: randomly select one of a plurality of random access sequences for random access, the selected random access sequence corresponding to the first random access sequence that is selectable by at least one other STA.

[0033] According to one or more embodiments of this aspect, a first subset of the plurality of random access sequences are selectable by a plurality of STAs, and each random access sequence of a second subset of the plurality of random access sequences is assigned to a respective STA, where the first subset is different from the second subset.

[0034] According to one or more embodiments of this aspect, the indication of at least the first random access sequence is provided by a trigger frame for uplink request, TF-ULR.

[0035] According to one or more embodiments of this aspect, the radio access is at least one of: performed in a system compliant with Institute of Electrical and Electronics Engineers, IEEE, 802.11 Standard; and based on orthogonal frequency division multiplexing, OFDM.

[0036] According to another aspect of the present disclosure, a method implemented in an access point, AP, that is configured to communicate with a station, STA is provided. An indication of at least a first random access sequence of a plurality of random access sequences for random access is transmitted to the STA, where the plurality of random access sequences are configured for transmission in the frequency domain. A random access sequence from the STA is received in the frequency domain as part of a random access procedure. The random access sequence is correlated with the first random access sequence as part of the random access procedure. According to one or more embodiments of this aspect, the plurality of random access sequences are selected such that the cross-correlation between any two of the plurality of random access sequences are below a predefined threshold.

[0037] According to one or more embodiments of this aspect, the plurality of random access sequences are a plurality of Zadoff-Chu sequences.

[0038] According to one or more embodiments of this aspect, the indication of at least the first random access sequence indicates information associated with the random access.

[0039] According to one or more embodiments of this aspect, the indicated information comprises at least one of: a type of pending data associated with the random access; a type of priority associated with the pending data; an amount the pending data; or a buffer size.

[0040] According to one or more embodiments of this aspect, the first random access sequence is allocated to the STA.

[0041] According to one or more embodiments of this aspect, the plurality of random access sequences are configured to be randomly selected for random access.

[0042] According to one or more embodiments of this aspect, a first subset of the plurality of random access sequences are selectable by a plurality of STAs, and each random access sequence of a second subset of the plurality of random access sequences is assigned to a respective STA, where the first subset is different from the second subset.

[0043] According to one or more embodiments of this aspect, the indication of at least the first random access sequence is provided by a trigger frame for uplink request, TF-ULR.

[0044] According to one or more embodiments of this aspect, the radio access is at least one of: performed in a system compliant with Institute of Electrical and Electronics Engineers, IEEE, 802.11 Standard; and based on orthogonal frequency division multiplexing, OFDM.

[0045] According to one or more embodiments of this aspect, the first random access sequence is received on random access resources that have been multiplexed with uplink data from another STA, where the multiplexing of the uplink data and the first random access sequence is configured to provide the AP with additional processing time for processing the first random access sequence.

[0046] According to one or more embodiments of this aspect, as part of coordinating channel resources with another AP, share at least a portion of the plurality of random access sequences with the other AP.

[0047] According to another aspect of the present disclosure, an access point, AP, is configured to communicate with a station, and the AP is configured to: transmit, to the STA, an indication of at least a first random access sequence of a plurality of random access sequences for random access, where the plurality of random access sequences are configured for transmission in the frequency domain. The AP is further configured to receive, from the STA, a random access sequence in the frequency domain as part of a random access procedure and correlate the random access sequence with the first random access sequence as part of the random access procedure.

[0048] According to one or more embodiments of this aspect, the plurality of random access sequences are selected such that the cross-correlation between any two of the plurality of random access sequences are below a predefined threshold.

[0049] According to one or more embodiments of this aspect, the plurality of random access sequences are a plurality of Zadoff-Chu sequences.

[0050] According to one or more embodiments of this aspect, the indication of at least the first random access sequence indicates information associated with the random access.

[0051] According to one or more embodiments of this aspect, the indicated information comprises at least one of: a type of pending data associated with the random access; a type of priority associated with the pending data; an amount the pending data; or a buffer size.

[0052] According to one or more embodiments of this aspect, the AP is further configured to allocate the first random access sequence to the STA.

[0053] According to one or more embodiments of this aspect, the plurality of random access sequences are configured to be randomly selected for random access.

[0054] According to one or more embodiments of this aspect, a first subset of the plurality of random access sequences are selectable by a plurality of STAs, where the AP is further configured to assign each random access sequence of a second subset of the plurality of random access sequences to a respective STA, where the first subset is different from the second subset.

[0055] According to one or more embodiments of this aspect, the indication of at least the first random access sequence is provided by a trigger frame for uplink request, TF-ULR.

[0056] According to one or more embodiments of this aspect, the first random access sequence is received on random access resources that have been multiplexed with uplink data from another STA, where the multiplexing of the uplink data and the first random access sequence is configured to provide the AP with additional processing time for processing the first random access sequence. According to one or more embodiments of this aspect, the AP is further configured to: as part of coordinating channel resources with another AP, share at least a portion of the plurality of random access sequences with the other AP.

[0057] According to one or more embodiments of this aspect, the radio access is at least one of: performed in a system compliant with Institute of Electrical and Electronics Engineers, IEEE, 802.11 Standard; and based on orthogonal frequency division multiplexing, OFDM.

[0058] BRIEF DESCRIPTION OF THE DRAWINGS

[0059] A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

[0060] FIG. l is a schematic diagram of an example network architecture illustrating a communication system according to the principles in the present disclosure;

[0061] FIG. 2 is a block diagram of an AP communicating with a non-AP STA over an at least partially wireless connection according to some embodiments of the present disclosure;

[0062] FIG. 3 is a schematic diagram of another example network architecture according to the principles in the present disclosure;

[0063] FIG. 4 is a flowchart of an example process in a non-AP STA according to some embodiments of the present disclosure; and

[0064] FIG. 5 is a flowchart of an example process in an AP STA according to some embodiments of the present disclosure.

[0065] DETAILED DESCRIPTION

[0066] As discussed above, the solutions proposed within the IEEE 802.11 TGbn suffer from one or more issues. It may be preferable that a STA that has data to send should just indicate this to the AP rather than sending the actual data. This is an approach taken in 3GPP, where a device that has data to send sends an UL transmission request. The network node may then send an UL transmission grant to the device to allow the device to send UL data in a dedicated UL resource.

[0067] In a cellular network based on, e.g., LTE, the approach of sending a UL request must be performed by each device separately as each device is only coarsely time- synchronized to the network (e.g., base station) since the radius of a cell is relatively large. Instead in Wi-Fi, where the coverage area of an AP is quite small, typically 20-30 meters, the AP can broadcast a signal that several STAs may respond to, and as long as the RX- TX turn-around times at the STAs are the same, the signals sent by the different STAs will be received in a synchronized fashion at the AP. Specifically, the signals received from the different STAs can be sufficiently synchronized so that if OFDM is used, a single FFT can be used to receive the different signals, which typically are sent on non-overlapping sub-carriers using OFDMA.

[0068] The notion that the STAs in Wi-Fi can be assumed to be synchronized is exploited in, e.g., the way the UL OFDMA-based Random Access (UORA) operates. In UORA, the bandwidth available for RA may be divided into several orthogonal parts, so that effectively more than one STA can get access to the channel at the same time. However, the approach is based on the notion that each STA draws a random back-off (BO) value that decreases as a function of the number of resources allocated to RA in UORA, and selects one of the resources randomly when the BO counter reaches zero. If two or more STAs select the same resource, a collision at the AP will occur in this particular resource. This approach has a built-in trade-off between delay and probability of collision. The BO is drawn uniformly in the range 0 to CW-1, where CW is the Contention Window size. The larger the CW, the smaller the probability of collision, but the expected delay is larger.

[0069] Historically, IEEE 802.11 has been based on distributed channel access, i.e., a device that has data to send performs channel access based on listen before talk (LBT). If the channel is found to be idle, the device may initiate a transmission procedure, whereas if the channel is found to be busy, the device must defer from transmission and perform channel access procedures until the channel is found to be idle. This approach works reasonably well as long as there are not too many devices trying to access the channel at the same time and, in particular, when not too many of the devices have low latency requirements. When many devices with low latency requirements are trying to access the channel at the same time, the distributed approach is not suitable. First, there is a nonsignificant risk that there will be a collision because two or more devices are transmitting at the same time. Second, even if there is no collision, a device that does not win the channel contention and, therefore, does not get channel access may suffer an access delay that is too large for the application to be supported. Therefore, distributed channel access (e.g., IEEE 802.11 based access) comes with various limitations when there are strict requirements on low latency, in particular when two or more devices have these strict requirements.

[0070] Further, in the development of IEEE 802.1 lax, also commonly referred to as Wi-Fi 6, one of the design goals was to improve the ability to support many devices. The approach for achieving this was to introduce orthogonal frequency division multiple access (OFDMA). Using OFDMA allows for a low complexity way to transmit to multiple devices in the downlink (DL) or to receive from multiple devices in the UL. The transmission in the UL is scheduled by the AP. The AP sends a Trigger Frame (TF) to the STAs that are scheduled for UL transmission, informing them of what frequency resources to use. The transmissions from the different STAs need to be synchronized in both time and frequency so as not to cause too much interference between the users at the AP. For the AP to be able to schedule an UL transmission it must know what STAs have UL data to send. To allow STAs whose statuses are not known by the AP to send UL data, the IEEE 802.1 lax standard also introduces another way of performing random access which is based on the OFDMA concept. It is still possible for STAs to perform LBT and, in this way, access the channel, but the goal is that the new RA concept should be used instead as this will allow for more effective channel access, and, in particular, the probability of collision will be reduced.

[0071] Thus, a more centralized approach may be needed. However, the approach applied in 3GPP does not fully take advantage of the situation in an IEEE 802.11 network where the STAs are tightly synchronized to the AP (e.g., due to the smaller coverage area), and therefore, a more efficient approach can be taken. In addition, since the IEEE 802.11 standard supports UORA, UL OFDMA-based Random Access, it may be advantageous if this, to some extent could be reused and if the improved channel access could work with legacy devices supporting UORA as UORA does not meet the requirements on efficient low latency channel access.

[0072] IEEE 802.1 lax provides a random access concept called UORA, UL OFDMA- based Random Access. For example, in UORA, the AP allocates a number of frequency resources for RA in a UL transmission. The resources allocated for RA are multiplexed with resources that are allocated for UL data from other STAs. The amount of resources allocated to RA can be selected by the AP depending on the expected number of STAs that will perform RA and, in this way, somewhat control both the delay and success of the RA. The cost of allocating many resources for RA is that the amount of resources allocated for UL data may be reduced.

[0073] The RA itself is fundamentally different from existing systems and / or proposals in that no LBT is used by the STAs. Instead, the probability of collision between STAs performing RA is kept sufficiently low by allocating a sufficiently large number of resources for RA so that the probability of two STAs selecting the same resource is small enough. Although no LBT is performed by the STAs, the AP has performed LBT to ensure that the channel is idle. One advantage of this approach is that if none of the STAs are trying to access the channel using an existing RA approach such that no other devices, other than the AP, are contending for the channel, the AP will find the channel idle and will thus be able to transmit. In practice, the AP may find the channel to be busy because of ongoing transmissions in other overlapping basic service sets (OBSSs), but this specific scenario will not be further described herein.

[0074] A STA that is allowed to transmit in the UL during the UORA procedure may transmit data. This is in contrast to, e.g., cellular systems like LTE, where the RA procedure may be viewed as consisting of additional steps. Specifically, the user equipment (UE) that has UL data may perform RA, but not for directly sending the data but to notify the base station (BS) that it has data to send, i.e., the RA message is a request to send data in the UL. If the RA is successful, i.e., the request from the UE is received by the BS, then the BS will send a UL grant to the UE granting it resources to be used for UL data transmission.

[0075] There is also a possibility for a non-AP STA to deliver buffer status reports (BSRs) to assist the AP in allocating UL resources. The BSR may be delivered implicitly in any frame sent to the AP or explicitly as a response to the BSRP (e.g., BSR procedure) Trigger frame sent by the AP.

[0076] The difference between RA and implicit BSR is that the STA, in the latter case, has already gained access to the channel for sending data.

[0077] The difference between RA and explicit BSR is that in the latter case, the non-AP STA is polled, i.e., dedicated resources are allocated for this non-AP STA. RA based on the UORA procedure means that some resources are allocated, and there may or may not be a transmission; in addition, the allocated resources are, in general, to be shared by a number of non-AP STAs such that a collision may occur. It may be that using an explicit BSR together with the UORA procedure may not be feasible when the number of non-AP STAs becomes large. However, one or more embodiments described herein for RA may be used in combination with the explicit B SR in that, once the AP has received a RA request and has gained knowledge about which STAs want to be scheduled, the AP may send a request for a BSR for determining how much resources to allocate in the actual data scheduling.

[0078] Although sending a request for sending data rather than sending the data directly requires some extra steps, it comes with several advantages. One advantage is that it is feasible to allocate dedicated resources to at least some of the STAs. Therefore, if a STA that has been allocated a dedicated resource has UL data to send, it can send a request to the AP without any risk of a collision at the AP. Provided the AP can grant resources in the next UL transmission, the maximum delay for being able to send UL data will be very short and the delay will be very predictable. Another advantage is that the number of STAs that can successfully perform RA is orders of magnitude larger if no data is sent directly. As an example, in UORA, a reasonable number of resources allocated for RA is, for example, 1-5. Suppose, e.g., that 3 resources are allocated to UORA. This means that, at most 3, users can successfully transmit in the UL. If instead only an indication is sent, 30 STAs may send such an indication successfully. Once the AP has received such an indication, the AP can schedule the requesting STAs. Since OFDMA is supported, the AP may schedule up to 37 STAs concurrently in case the AP and the involved STAs support 80 MHz transmission bandwidth.

[0079] The procedure where a STA sends a request to the AP such that the AP, upon reception of this request, can send an UL grant relies on the notion that the requests sent by the STAs can be correctly received at the AP. This may, e.g., be achieved by a STA that is sending a specific sequence to the AP to represent an UL request. If the AP is able to determine which STA sent this specific sequence, the corresponding STA may be scheduled in an upcoming UL transmission, and the AP may send a TF in which the STA is scheduled for UL transmission.

[0080] Before describing in detail exemplary embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to random access (RA) based on RA sequences configured to be transmitted in the frequency domain, e.g., distributed in the frequency domain, spread across the frequency domain, etc.. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0081] As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and / or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0082] In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication.

[0083] In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and / or wireless connections.

[0084] Some embodiments of the present disclosure may be supported by an IEEE 802.11 standard. IEEE 802.11 has developed a set of Wireless Local Area Network (WLAN) air interface standards. Some embodiments may also be supported by systems and / or devices associated with the Third Generation Partnership Project (3GPP). The 3GPP has developed and is developing standards for Fourth Generation (4G) (also referred to as Long Term Evolution (LTE)) and Fifth Generation (5G) (also referred to as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile wireless devices (WD) or user equipment (UE), as well as communication between network nodes and between WDs or UEs. The 3GPP is also developing standards for Sixth Generation (6G) wireless communication networks. That is, some embodiments of the description can be supported by the above documents (e.g., standard documents). In addition, all the terms disclosed in the present document may be described by the above standard documents.

[0085] For example, one or more embodiments described herein provide for a system based on IEEE 802.11, and where at least one problem addressed by one or more embodiments is the following. The access point (AP) supports a number of STAs for both uplink (UL) and downlink (DL) communication and ensures that a STA should be able to transmit UL data with low enough delay such that low latency applications can be efficiently supported.

[0086] In some embodiments, the term “access point” or “AP” is used interchangeably and may comprise, or be, a network node. The AP may include any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node such as MSR BS, multi-cell / multicast coordination entity (MCE), relay node, integrated access and backhaul (IAB), donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The AP may also comprise test equipment. The AP may comprise a radio router, a radio transceiver, WiFi access point, wireless local area network (WLAN) access point, a network controller, etc.

[0087] In some embodiments, the non-limiting term “device” is used to describe a wireless device (WD) and / or user equipment (UE) that may be used to implement some embodiments of the present disclosure. In some embodiments, the device may be and / or comprise an access point (AP) station (STA). In some embodiments, the device may be and / or comprise a non-access point station (non-AP STA). In some embodiments, the device may be any type of device capable of communicating with a network node, such as an AP, over radio signals. The device may be any radio communication device, target device, a portable device, device-to-device (D2D) device, machine type device or device capable of machine to machine communication (M2M), low-cost and / or low-complexity device, a sensor equipped with a device, a computer, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (loT) device, or a Narrowband loT (NB-IOT) device, Reduced Capability (RedCap) device, etc.

[0088] A device may be considered a network node and may include physical components, such as processors, allocated processing elements, or other computing hardware, computer memory, communication interfaces, and other supporting computing hardware. The network node may use dedicated physical components, or the node may be allocated use of the physical components of another device, such as a computing device or resources of a datacenter, in which case the network node is said to be virtualized. A network node may be associated with multiple physical components that may be located either in one location or may be distributed across multiple locations.

[0089] Even though the descriptions herein may be explained in the context of one of a Downlink (DL) and an Uplink (UL) communication, it should be understood that the basic principles disclosed may also be applicable to the other of the one of the DL and the UL communication. In some embodiments in this disclosure, the principles may be considered applicable to, e.g., a first STA and, e.g., a second STA. For DL communication, the first STA may be the transmitter, and the second STA may be the receiver. For UL communication, the transmitter may be the second STA, and the receiver may be the first STA. In some embodiments, the first STA may be an AP or non-AP STA, and the second STA may be an AP or a non-AP STA.

[0090] Note that although terminology from one particular wireless system, such as, for example, IEEE 802.11, 3rd Generation Partnership Project (3GPP), Long Term Evolution (LTE), 5th Generation (5G) and / or New Radio (NR), may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. Other wireless systems, including without limitation Wideband Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure.

[0091] Note further, that functions described herein as being performed by one or more of a first STA, second STA, transmitting STA, receiving STA, AP, non-AP STA, wireless device, network node, etc., may be distributed over a plurality of STAs, APs, non-AP STAs, wireless devices, network nodes, etc. In other words, it is contemplated that the functions of the devices described herein are not limited to performance by a single physical device and, in fact, can be distributed among several physical devices. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0092] Some embodiments are directed to RA based on RA sequences transmitted in the frequency domain.

[0093] Referring to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in FIG. 1 a schematic diagram of the communication system 10, according to one embodiment, constructed in accordance with the principles of the present disclosure. The communication system 10 in FIG. 1 is a non-limiting example and other embodiments of the present disclosure may be implemented by one or more other systems and / or networks. Referring to FIG. 1, system 10 may comprise a wireless local area network (WLAN). The devices in the system 10 may communicate over one or more spectrums, such as, for example, a license-exempt spectrum, which may include frequency bands typically used by Wi-Fi technology. One or more of the devices may be further configured to communicate over other frequency bands, such as shared licensed frequency bands, etc. The system 10 may include one or more service areas 12a, 12b, etc. (collectively referred to herein as “service area 12”), which may be defined by corresponding access points (APs) 14a, 14b, etc. (collectively referred to herein as “AP STA 14” or “AP 14”). A service area 12 may also correspond to and / or be associated with a coverage area, and / or a cell.

[0094] The AP STAs 14 may or may not be connectable to another network, such as a core network over a wired or wireless connection. The system 10 includes a plurality of non-AP devices, such as, for example, non-AP STAs 16a, 16b (collectively referred to as “non-AP STA 16” or “STA 16”). Each of the non-AP STAs 16 may be located in one or more service areas 12 and may be configured to wirelessly connect to one or more AP STA 14. Note that although two AP STAs 14a and 14b and two non-AP STAs 16a and 16b are shown for convenience, the communication system may include many more non- AP STAs 16 and AP STAs 14. Each AP STA 14 may connect to serve / configure / schedule / etc., one or more non-AP STAs 16.

[0095] It should be understood that the system 10 may include additional nodes and / or devices not shown in FIG. 1. In addition, the system 10 may include many more connections and / or interfaces than those shown in FIG. 1. Thus, the elements shown in FIG. 1 are presented for ease of understanding.

[0096] Also, it is contemplated that a non-AP STA 16 can be in communication and / or configured to separately communicate with more than one AP STA 14 and / or more than one type of AP STA 14. Furthermore, an AP STA 14 may be in communication and / or configured to separately communicate with other AP STAs 14, as described herein, which may be via wired and / or wireless communication channels.

[0097] A non-AP STA 16 is configured to include a random access (RA) unit 18, which is configured to perform one or more non-AP STA 16 functions described herein. An AP STA 14 is configured to include management unit 20, which is configured to perform one or more AP STA 14 functions described herein.

[0098] Example implementations, in accordance with an embodiment, of the AP STA 14 and non-AP STA 16 discussed in the preceding paragraphs will now be described with reference to FIG. 2.

[0099] An AP STA 14 or a non-AP STA 16 may be generally referred to as a STA 22. For example, a first STA 22a may be an AP STA 14, and a second STA 22b may be a non-AP STA 16. System 10 may include one or more additional STAs 22n (which include AP STAs 14 and / or non-AP STAs 16), which may be in communication with STA 22a and / or STA 22b.

[0100] The AP STA 14 includes hardware 30 including a communication interface 32, processing circuitry 34, a processor 36, and memory 38. The communication interface 32 may be configured to communicate with any of the nodes / devices in the system 10 according to some embodiments of the present disclosure, such as with one or more other AP STAs 14 and / or one or more non-AP STAs 16. In some embodiments, the communication interface 32 may be formed as or may include, for example, one or more radio frequency (RF) transmitters, one or more RF receivers, and / or one or more RF transceivers, and / or may be considered a radio interface. In some embodiments, the communication interface 32 may also include a wired interface.

[0101] The processing circuitry 34 may include one or more processors 26 and memory, e.g., memory 38. In addition to a processor 36 and memory 38, the processing circuitry 34 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 36 may be configured to access (e.g., write to and / or read from) the memory 38, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0102] The AP STA 14 may further include software 40 stored internally in, for example, memory 38, or stored in external memory (e.g., database) accessible by the AP STA 14 via an external connection. The software 40 may be executable by the processing circuitry 34. The processing circuitry 34 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by AP STA 14. The memory 38 is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 40 may include instructions stored in memory 38 that, when executed by the processor 36 and / or management unit 20 causes the processing circuitry 34 and / or configures the AP STA 14 to perform the processes described herein with respect to the AP STA 14.

[0103] Still referring to FIG. 2, the non-AP STA 16 includes hardware 50, which may include a communication interface 52, processing circuitry 54, a processor 56, and memory 58. The communication interface 52 may be configured to communicate with one or more AP STA 14 and / or other STA 22n, such as via wireless connection 35, and / or with other elements in the system 10, according to some embodiments of the present disclosure. In some embodiments, the communication interface 52 may be formed as or may include, for example, one or more radio frequency (RF) transmitters, one or more RF receivers, and / or one or more RF transceivers, and / or may be considered a radio interface. In some embodiments, the communication interface 52 may also include a wired interface. In some embodiments, AP STA 14 may be configured to communicate with another AP STA 14, non-AP STA 16, and / or STA 22n via wireless connection 35 and / or via a wired connection (not shown).

[0104] The processing circuitry 54 may include one or more processors 56 and memory, such as, the memory 58. Furthermore, in addition to a traditional processor and memory, the processing circuitry 54 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 56 may be configured to access (e.g., write to and / or read from) the memory 58, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0105] Thus, the non-AP STA 16 may further include software 60 stored internally in, for example, memory 58, or stored in external memory (e.g., database) accessible by the non- AP STA 16 via an external connection. The software 60 may be executable by the processing circuitry 54. The processing circuitry 54 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by the non-AP STA 16. The memory 58 is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software may include instructions stored in memory 58 that, when executed by the processor 56 and / or RA unit 18, causes the processing circuitry 54 and / or configures the non-AP STA 16 to perform the processes described herein with respect to the non-AP STA 16.

[0106] In FIG. 2, the connection between the STAs 22 (i.e., AP STA 14, the non-AP STA 16, and STA 22n) is shown without explicit reference to any intermediary devices or connections. However, it should be understood that intermediary devices and / or connections may exist between these devices, although not explicitly shown.

[0107] Although FIG. 2 shows RA unit 18 and management unit 20, as being within a processor, it is contemplated that this element may be implemented such that a portion of the element is stored in a corresponding memory within the processing circuitry. In other words, the element may be implemented in hardware or in a combination of hardware and software within the processing circuitry.

[0108] FIG. 3 is a schematic diagram of an example communication system 10, according to another embodiment of the present disclosure. In the example of FIG. 3, the access point STA 14 and non-AP STAs 16 may be similar to those of the example of FIG. 2, described herein. Additionally, in the example of FIG. 3, one or more AP STAs 14 and / or non-AP STAs 16 may form and / or be part of a network 70 (e.g., network associated with grouping of AP STAs 14 and non-AP STAs 16). The communication system 10 and / or network 70. The connection 72 between the communication system 10 and / or the network 70 may extend via an optional intermediate network 76. The intermediate network 76 may be one of, or a combination of more than one of, a public, private or hosted network. The intermediate network 76, if any, may be a backbone network or the Internet. In some embodiments, the intermediate network 76 may comprise two or more sub-networks (not shown).

[0109] The communication system of FIG. 3 as a whole enables connectivity between one or more elements in FIG. 3.

[0110] FIG. 4 is a flowchart of an example process in a first STA 22, according to one or more embodiments of the present disclosure. One or more blocks and / or functions and / or methods performed by the first STA 22 may be performed by one or more elements of the first STA 22 (e.g., non-AP STA 16 / STA 16) such as by one or more of RA unit 18, processor 56, processing circuitry 54, communication interface 52, etc. First STA 22 is configured to receive (Block SI 00) an indication of at least a first random access sequence of a plurality of random access sequences for random access where the plurality of random access sequences are configured for transmission in the frequency domain, as described herein. First STA 22 is configured to perform (Block SI 02) a random access procedure at least by transmitting, in the frequency domain, the first random access sequence of the plurality of random access sequences, as described herein.

[0111] According to one or more embodiments, the plurality of random access sequences are selected such that the cross-correlation between any two of the plurality of random access sequences are below a predefined threshold.

[0112] According to one or more embodiments, the plurality of random access sequences are a plurality of Zadoff-Chu sequences.

[0113] According to one or more embodiments, the indication of at least the first random access sequence indicates information associated with the random access.

[0114] According to one or more embodiments, the indicated information comprises at least one of: a type of pending data associated with the random access, a type of priority associated with the pending data, an amount the pending data, or a buffer size.

[0115] According to one or more embodiments, the first random access sequence is configured to indicate one of a higher priority or a lower priority than at least one other random access sequence in the subset.

[0116] According to one or more embodiments, the first random access sequence is allocated to the first STA 22.

[0117] According to one or more embodiments, the first STA 22 is further configured to: randomly select one of a plurality of random access sequences for random access where the selected random access sequence corresponding to the first random access sequence that is selectable by at least one other STA 22. According to one or more embodiments, a first subset of the plurality of random access sequences are selectable by a plurality of STAs 22, and each random access sequence of a second subset of the plurality of random access sequences is assigned to a respective ST A 22 where the first subset is different from the second subset.

[0118] According to one or more embodiments, the indication of at least the first random access sequence is provided by a trigger frame for uplink request, TF-ULR.

[0119] According to one or more embodiments, the radio access is at least one of performed in a system compliant with Institute of Electrical and Electronics Engineers, IEEE, 802.11 Standard; and based on orthogonal frequency division multiplexing, OFDM.

[0120] FIG. 5 is a flowchart of an example process in a second STA 22. One or more blocks and / or functions and / or methods performed by the second STA 22 may be performed by one or more elements of the second STA 22 (e.g., AP STA 14 / AP 14) such as by one or more of management unit 20, processor 36, processing circuitry 34, communication interface 32, etc. Second STA 22 is configured to transmit (Block SI 04), to the first STA 22, an indication of at least a first random access sequence of a plurality of random access sequences for random access where the plurality of random access sequences are configured for transmission in the a frequency domain, as described herein. Second STA 22 is configured to receive (Block SI 06), from the first STA 22, a random access sequence in the frequency domain as part of a random access procedure, as described herein. Second STA 22 is configured to correlate (Block SI 08) the random access sequence with the first random access sequence as part of the random access procedure, as described herein.

[0121] According to one or more embodiments, the plurality of random access sequences are selected such that the cross-correlation between any two of the plurality of random access sequences are below a predefined threshold.

[0122] According to one or more embodiments, the plurality of random access sequences are a plurality of Zadoff-Chu sequences.

[0123] According to one or more embodiments, the indication of at least the first random access sequence indicates information associated with the random access.

[0124] According to one or more embodiments, the indicated information comprises at least one of a type of pending data associated with the random access, a type of priority associated with the pending data, an amount the pending data, or a buffer size.

[0125] According to one or more embodiments, the first random access sequence is configured to indicate one of a higher priority or a lower priority than at least one other random access sequence in the subset.

[0126] According to one or more embodiments, the second STA 22 allocates the first random access sequence to the first STA 22.

[0127] According to one or more embodiments, the plurality of random access sequences are configured to be randomly selected for random access.

[0128] According to one or more embodiments, a first subset of the plurality of random access sequences are selectable by a plurality of STAs, and the second STA 22 is further configured to assign each random access sequence of a second subset of the plurality of random access sequences to a respective STA 22 w here the first subset is different from the second subset.

[0129] According to one or more embodiments, the indication of at least the first random access sequence is provided by a trigger frame for uplink request, TF-ULR.

[0130] According to one or more embodiments, the first random access sequence is received on random access resources that have been multiplexed with uplink data from another STA, where the multiplexing of the uplink data and the first random access sequence is configured to provide the AP with additional processing time for processing the first random access sequence.

[0131] According to one or more embodiments, the second STA 22 is further configured to, as part of coordinating channel resources with another AP 14 (e.g., another STA 22), share at least a portion of the plurality of random access sequences with the other AP 14.

[0132] According to one or more embodiments, the radio access is at least one of performed in a system compliant with Institute of Electrical and Electronics Engineers, IEEE, 802.11 Standard; and based on orthogonal frequency division multiplexing, OFDM.

[0133] Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide details and examples of arrangements for RA based on RA sequences transmitted or configured for transmission in the frequency domain.

[0134] Some embodiments provide RA based on RA sequences transmitted in the frequency domain. One or more AP 14 / AP STA 14 functions described below may be performed by one or more of processor 36, management unit 20, processing circuitry 34, communication interface 32, etc. One or more STA 16 / non-AP STA 16 functions described below may be performed by one or more of processing circuitry 54, processor 56, RA unit 18, communication interface 52, etc.

[0135] Example 1: Synchronized RA Request based on OFDM

[0136] According to one or more embodiments, it is assumed that a STA 16 that performs RA sends a UL request to the AP 14 and that this UL request is time and frequency synchronized to a signal sent from the AP 14. Specifically, the synchronization is at such a level that the UL signal can be based on OFDM to create an OFDM signal and this OFDM signal can be multiplexed with other OFDM signals such that OFDM access (OFDMA) is feasible. A signal sent from AP 14 to, for example, initiate or cause the UL request (if needed by STA 16) is referred to as a trigger frame for UL request, TF-ULR. The procedure with TF-ULR is similar to the UORA procedure in that resources for UL requests can be multiplexed with resources for UL data. For example, suppose that the resource allocated for UL requests corresponds to the smallest resource unit (RU) size, i.e., 26 sub-carriers and a duration of 30 symbols. This means that in the time-frequency grid there are in total 26x30 = 780 symbols. Normally, 2 of the 26 sub-carriers are used as pilots, and thus, only 24 sub-carriers are used for data. In what follows it is assumed that no pilots are used, although one or more embodiments described herein are not limited to this assumption. Also, the case with pilots is considered covered by one or more embodiments described herein. One reason why pilots are not used is because several different TF-ULR sequences may be sent concurrently where the reception at the AP 14 is based on correlating with the different sequences and considering the magnitude of the correlation, i.e., disregarding the phase.

[0137] Now, suitable sequences to be used for RA have the properties that different STAs 16 can be assigned different sequences, and still, it would be possible to identify what STA 16 has transmitted the sequence. This implies that it may be desirable to find a set of sequences with low cross-correlation between any two sequences within the set. Typically, in a RA access situation, the device transmitting the RA sequence and the intended receiver of the RA sequences are not time-synchronized. This implies that the intended receiver needs to correlate the received signal with the different sequences during a time corresponding to the timing uncertainty. In one or more embodiments described herein, it is assumed that the timing is such that the intended receiver may correlate only once with the sequence it is looking for to determine whether the sequence is present or absent. The fact that the intended receiver does not need to search in time, means that it is easier (e.g., less complex, requires fewer computing resources, etc.) to determine whether the sequence is present.

[0138] Example 2: RA Request sequences based on Zadoff-Chu (ZC) -sequences sent on multiple OFDM symbols

[0139] Although any set of sequences with the above-discussed properties may be used, in one or more embodiments, the set of sequences that are used is based on Zadoff-Chu (ZC)-sequences. The theory of ZC-sequences is assumed to be known and will not be further discussed. At least some of the properties of ZC-sequences that are used herein are those related to cross-correlation and autocorrelation. For the example above, assuming one wants to have a ZC-sequence whose length is a prime number, a ZC-sequence of length 773 may be chosen as 773 is the largest prime number less than 780, and thus this is the longest ZC-sequence that can be sent using the 780 symbols. From the theory of ZC- sequences, it is known that there will be 772 ZC-sequences of length 773 (N-l, where N is the length of the ZC-sequence) and that the cross-correlation between any of these will be l / sqrt(N) = 0.036.

[0140] Thus, by just allocating 30 symbols of the smallest size RU, the AP 14 can assign unique ZC-sequences to up to 772 STAs 16 where a STA 16 that has UL data to send will first send the ZC-sequence it has been assigned. That is, the STA 16 transmitted the assigned ZC-sequence to the AP 14 indicates, for example, that the STA 16 has data to send such that this transmission may correspond to sending a UL request. To detect what STA has sent an UL request, the AP 14 would typically correlate against the different ZC- sequences that have been assigned to the associated STAs 16 to determine whether any of them has sent an UL request. Further, because of the low cross-correlation among ZC- sequences, the reception of the different ZC-sequences is very robust, e.g., the AP can look for specific ZC-sequences even when a plurality of ZC-sequences are received by the AP 14.

[0141] Now, if the number of potential STAs 16 that can send a UL request is large, this implies that the number of correlations that need to be performed by AP 14 will be large. Since the AP 14 needs to finalize the correlations in due time (e.g., within a predetermined time period or time window) in order to properly schedule the STAs 16 that have requested to be scheduled, this may be computationally intense. For this reason, additional details are provided below with respect to computation or processing at the AP 14.

[0142] Example 3: Increasing the processing time for processing the RA Request sequences First, a receiver (e.g., AP 14) typically only has the switching time between receiving to transmitting modes for finalizing the receiver processing of the received data. However, in one or more embodiments, the available processing time may be significantly larger. Specifically, AP 14 may schedule UL data of a duration of, e.g., 1 ms, whereas the duration of the ZC-sequence is only 30 OFDM symbols, which amounts to approximately 400 us, depending on the duration of the cyclic prefix. Thus, compared to the above- mentioned switching time between receiving to transmitting modes, which may be on the order of 20 us, the processing time in one or more embodiments may be on the order of 600 us, i.e., 30 times longer.

[0143] Second, in cases where AP 14 would not be able to perform the correlation for STA 16 that sends an UL request, this has the same effect as if the correlation was unsuccessful in that the STA 16 would have to try again, e.g., resend the UL request. During and / or after attempting the correlation, AP 14 will know if it has not been able to perform all correlations, and thus, it may decide to trigger a new UL RA request event as soon as possible.

[0144] Thus, according to one or more embodiments, AP 14 may effectively increase the amount of time available for processing the RA requests by deliberately multiplexing the RA resources with data where the duration of the data is sufficiently much longer in duration, thereby allowing for the additional processing time.

[0145] According to the description above, the ZC-sequence may be transmitted such that the first 26 symbols are sent in the first OFDM symbol, the next 26 symbols are sent in the second OFDM symbol, and so on. In the 30th OFDM symbol, only the first 19 subcarriers may be used.

[0146] At the receiver side, i.e., in AP 14, the ZC-sequence is formed by taking the first 26 symbols from the first OFDM symbol, the next 26 symbols from the second symbol, and so on. Then, once the 773 symbols of the ZC-sequence are received, this sequence is correlated with all possible ZC-sequences AP 14 is looking for to determine if an expected ZC-sequence is present.

[0147] Further, because the STAs 16 are time synchronized with AP 14, AP 14 will know in which OFDM symbol and in which sub-carrier to find the corresponding symbol in the ZC-sequence.

[0148] As described above, a larger number of unique sequences can be obtained and / or used, and for most use cases, it is likely that this larger number of unique sequences will suffice as the number of associated STAs 16 will be less than this larger number of unique sequences. However, in case the number of STAs 16 exceeds the number of unique sequences, Example 4 provides one or more solutions to this scenario.

[0149] Example 4: RA with non-unique sequences

[0150] In one or more embodiments, the set of ZC-sequences are still used by STAs 16, but rather than having a specific sequence assigned for each one of STAs 16 (e.g., RA with unique sequences), STA 16 that wants to send an UL request selects one of the ZC- sequences randomly (or according to some predefined criterion) and then transmits the selected ZC-sequence. AP 14 correlates against the ZC-sequences just as in the case when each STA 16 was assigned a unique sequence. In this case, however, AP 14 does not know which STA 16 has sent the specific ZC-sequence, as AP 14 just knows which ZC- sequence was sent. Therefore, when AP 14 schedules the UL transmission, it cannot explicitly give the UL grant to a specific STA 16 but instead implicitly gives the UL grant to the specific STA 16 by indicating what ZC-sequence has been received and that the corresponding STA 16 is scheduled for UL transmission.

[0151] Some observations with respect to the RA procedure with non-unique sequences are as follows. First, there is a risk (e.g., small risk) that more than one STA 16 will select the same ZC-sequence. If this situation occurs, there is a chance that AP 14 will not detect the ZC-sequence because of the collision. In this case, the RA is unsuccessful and STAs 16 will re-attempt RA as STAs 16 will not receive an UL grant in response to the ZC- sequence. In cases where AP 14 detects the ZC-sequence and grants the corresponding STAs 16 UL grants, this means that all STAs 16 that randomly selected this ZC-sequence will send UL data using the same resources. This may end up being the same situation as when two STAs 16 performs LBT and collide due to their back-off counters reaching zero at the same time, and can be resolved in the same manner. That is, STAs 16 determine their transmissions (ZC-sequence transmissions) were unsuccessful and they perform RA again.

[0152] Example 5: RA with both unique and non-unique sequences

[0153] In another example, the two or more approaches described above are combined. Specifically, in a situation where some of STAs 16 have higher priority for channel access, e.g., due to more time-critical applications, these STAs 16 (e.g., high-priority STAs 16) may be allocated unique sequences, whereas STAs 16 that have lower-priority (e.g., low- priority STAs 16) may select a sequence randomly, as described above. The sequences that can be selected randomly are from a set of sequences that does not contain the sequences that may be allocated uniquely. In this way, effective RA can be supported, where both an arbitrarily large number of STAs 16 can be supported as well as a reasonably large number of STAs 16 with high requirements (e.g., lower latency requirements, etc.) on channel access time can be supported as well.

[0154] Example 6: RA with multiple sequences per STA 16

[0155] In another example, a plurality of sequences (e.g., different sequences) are assigned to the same STA 16 such that STA 16 may selectively use them for sharing different information with the AP 14 during its RA attempts. Each assigned sequence may be used to indicate, for example, one or more of the following -

[0156] • Different types of pending data (e.g., data that is pending transmission by STA 16), for example, based on different traffic identifiers (TIDs) or access categories (ACs),

[0157] • Different priorities for the pending data,

[0158] • Different amounts of pending data, i.e., different buffer sizes, o Different sequences may indicate different buffer sizes in a relative manner, o Different sequences may indicate different buffer sizes based on corresponding different thresholds,

[0159] Based on Example 6, the selective usage of multiple assigned sequences by the same STA 16 may help its serving AP 14 to prioritize and schedule that STA 16’s UL operations appropriately. It could also help AP 14, for example, to avoid potential additional steps of identifying how much data and / or what type of data is pending at STA 16 that transmitted the RA sequence.

[0160] Example 7: RA with coordination between APs 14

[0161] Example 7 addresses the situation where coordination is performed between APs 14. One way of coordination that is covered by Example 7 is when APs 14 are coordinated as currently described in, for example, IEEE 802.11TGbn. Specifically, a set of APs 14, e.g., 2 APs 14, are coordinating the channel resources such that when one of APs 14 wins the channel contention, it invites the other AP(s) 14 to share the transmission opportunity (TXOP). The sharing may, for example, be in time, such that APs 14 sharing the channel use the channel one after the other. Alternatively, the sharing may also be in frequency using OFDMA, i.e., the different APs 14 sharing the TXOP are using different subcarriers. Further, there may be more advanced ways of sharing the channel between APs 14 where the spatial dimension is exploited such that the same time and frequency resources may be used by more than one AP 14, provided the APs 14 are sufficiently far from one another. According to Example 7, when APs 14 are coordinating their transmission, APs 14 use disjunct subsets from the set of available sequences for RA requests. Taking the example with 772 different ZC-sequences of length 773, two APs 14 may agree that API uses the first 772 / 2 = 386 ZC-sequences whereas AP2 uses the last 386 sequences. Since the different ZC-sequences are defined by their root-index, 1,2,3,. . .,772, the different ZC-sequences can be described in terms of the first and the last half of sequences or, for example, sequences 1-100, providing a low complexity way to allowing involved APs 14 to agree on what AP 14 should use what sequences.

[0162] Example 8: RA based on assigning different time-shifts of the same ZC- sequence

[0163] Returning to the properties of ZC-sequences, another property of a specific ZC- sequence is that its autocorrelation for any cyclic shift is zero. In one or more embodiments described herein, this property is exploited as follows. The RA is based on using a single ZC-sequence but with different time-shifts. This gives in total N different sequences, so 773 sequences in the example above.

[0164] If this approach is used directly in the time-domain, i.e., if the ZC-sequence is not transmitted using OFDM, a time delay corresponding to one symbol in the ZC-sequence means that it could easily be mistaken for the ZC-sequence obtained by performing a one symbol cyclic shift. When the ZC-sequence is transmitted in the frequency domain, a delay in the reception will result in that the Fast Fourier Transform (FFT)-window is effectively being shifted so that the corresponding ZC-sequence after the FFT will be phase-rotated. Although this will result in the autocorrelation between different sequences no longer being zero, such a time shift will not cause a ZC-sequence to appear as another shifted version of the same ZC-sequence, thereby still allowing AP 14 to perform correlation to determine if one or more sequences are present.

[0165] Similar to the situation when the set of sequences used for RA are based on a set of ZC-sequences of the same length, as described herein, the different shifts of the selected ZC-sequence can be uniquely allocated to different STAs 16 as long as the number of STAs 16 does not exceed the number of available sequences.

[0166] In the event the number of STAs 16 exceeds the number of available sequences, the same approach described herein can be taken when a set of different sequences is used, e.g., where STAs 16 could select from the set of different sequences. In this way, an arbitrary large number of STAs 16 can be supported using a fixed set of sequences. The probability of two STAs 16 selecting the same sequence may still be low even if the number of STAs 16 are very large as long as the probability of a STA 16 performing RA is sufficiently low.

[0167] In one or more of the above embodiments, the focus has been on the sequences and how to allocate these to the different STAs 16. Specifically, one goal has been to provide configuration(s), process(es) and / or procedure(s) to support STAs 16 with low latency requirements. Since one or more embodiments described herein are based on AP 14 sending a TF-ULR frame, the latency may also depend on how often such a TF-ULR frame is sent. Hence, one or more of the following may apply:

[0168] • The higher the requirements in terms of latency, the more often a TF-ULR frame may have to be sent.

[0169] • The more resources allocated to UL request(s) in a TF-ULR frame, the more STAs 16 can be supported as more resources means that longer sequences can be supported and thus also a larger number of sequences.

[0170] Example 9: Grouped RA

[0171] In yet another embodiment, which is applicable to UL random access in general and not only to the embodiments described herein that are based on OFDM, the following approach is provided.

[0172] To enable channel access with sufficiently low latency that also takes into account that different STAs 16 have different requirements, a set of different TF-ULR frames is used.

[0173] As an example, suppose the requirements on channel access for a first type of STAs 16 are 2 ms, i.e., STA 16 should have the opportunity to send an UL request within 2 ms from when the packet arrived in the buffer, whereas the requirements for a second type of STAs 16 is 50 ms.

[0174] Moreover, assume that there are 10 STAs 16 of the first type and 500 STAs 16 of the second type. AP 14 may then send a TF-ULR every 2 ms and allocate unique sequences to 10 STAs 16 that have a 2 ms requirement to ensure that these 10 STAs 16 will have the opportunity to send an UL request. For the other 500 STAs 16, it may not be necessary to provide UL request opportunities in every TF-ULR frame. Instead, the 500 STAs 16 are split into, for example, 50 / 2=25 groups, each with 500 / 25 = 20 STAs 16. Each group of STAs 16 is allocated to one of the 25 TF-ULR frames every 50 ms, and STA 16 belonging to a specific group is expected to only send an UL request as a response to the corresponding TF-ULR. In this way, the expected channel access delay for the different STA 16 can be matched to the actual requirements such that less resources can be used. In the example above, the same sequence can be used for STAs 16 not belonging to the same group, thus ensuring contention-free channel access with a much smaller number of sequences. Alternatively, if the sequence used for RA is selected randomly as described in one or more embodiments, the probability of two STAs 16 randomly selecting the same sequence is reduced as the number of STAs 16 at each moment of time is reduced from 500 to 20.

[0175] Example 10: Overlayed RA sequences and legacy RA

[0176] As described herein, UORA is a procedure for performing coordinated channel access, where some resources are allocated for RA and may be multiplexed using OFDMA with ordinary UL data. One or more embodiments described herein provided for sending suitable sequences on these RA resources to request to be scheduled, rather than sending the data directly as can be the case in UORA. However, according to one or more embodiments, it is also possible to combine the two, i.e., to use the allocated RA resources for both sending RA data, i.e., legacy RA without RA sequences, and for sending RA sequences.

[0177] Additional details of Example 10 are as follows. First, the RA RUs are very often not used i.e., there is no RA sent from any STA 16. The reason for this is to ensure that the probability of collision is sufficiently low. Second, if a RA RU is used, most often it is only used by a single STA 16, i.e., most of the time collisions do not happen. In this case, i.e., when there is no collision, it does not matter that two different RA schemes are used. Either RA scheme will not be impacted by the other scheme. Third, in case there is a collision where RA data is sent concurrently with a RA sequence, the data will typically be lost, but this is not worse than if there would have been a collision between two RA data packets. However, since the RA sequence is very robust, there is a chance that the RA based on RA sequences will be successful in the case of collision. Hence, one or more embodiments that provide for RA sequences for performing RA may be a means to enable low latency channel access (since it can be performed with much lower probability of collision) in a way that is backward compatible with one or more existing standards and also transparent for legacy devices / STAs 16.

[0178] Some Additional Non-Limiting Examples

[0179] 1 A. A method for performing RA in the UL of a wireless system, where the network node (e.g., AP 14, network, etc.) allocates resources to the devices potentially wanting to perform RA which a device (e.g., STAs 16) uses for sending a sequence to indicate that it wants to be scheduled, where the RA is based on OFDM, i.e., the RA sequence is sent, in the frequency domain, from the device performing channel access and that is synchronized to the network node, where, in response to the sequence, the network node identifies that a device has performed RA and schedules that device in an upcoming UL transmission.

[0180] 2 A. The method of Example 1A, where some of the resources are uniquely allocated to specific devices.

[0181] 3 A. The method of Example 2A, where the uniquely allocated resources are allocated to devices that have requirements on low latency channel access.

[0182] 4 A. The method of Example 1 A, where some of the resources are not uniquely allocated to the devices but instead are selected randomly by devices wanting to perform RA.

[0183] 5 A. The method of any one of Examples 1A-4A, where the uniquely allocated resources and the non-uniquely allocated resources are sent in a way that the interference they cause to one another is designed to be below a threshold value.

[0184] 6 A. The method of any one of Examples 1 A-5A, where the uniquely allocated resources are orthogonal to one another.

[0185] 7 A. The method of any one of Examples 1A-6A, where the resources are sequences of length N.

[0186] 8 A. The method of Example 7 A, where the sequences are Zadoff-Chu sequences.

[0187] 9 A. The method of any one of Examples 1A-8A, where the RA is performed in a system compliant with IEEE 802.11.

[0188] 10 A. The method of any one of Examples 1A-9A, where the frequency resources allocated for RA are multiplexed with UL data using OFDMA.

[0189] 11 A. The method of any one of Examples 1 A-10A, where two different RA sequences may indicate different priorities.

[0190] 12 A. The method of any one of Examples 1 A-10A, where two different RA sequences may indicate different buffer status.

[0191] 13A. The method of any one of Examples 1A-12A, where multiple RA sequences are assigned to the same device.

[0192] 14 A. A method for performing RA in a system where two or more APs 14 are coordinating their transmissions, the two or more APs 14 share a transmission opportunity (TXOP) either in time or in frequency, and the two or more APs 14 allocate overlapping time and frequency resources for RA where the two and more different APs 14 are allocating RA sequences to their associated STAs 16 from non-overlapping sets. 15 A. The method of any one of Examples 1A-14A, where at least one sequence used for RA is allocated for STAs 16 not associated with the AP 14. This is useful for STAs that are not (yet) associated with an AP, i.e., STAs for potential association.

[0193] 16A. The method of any one of Examples 1A-15A, where the RA sequence is sent in a RA resource that also may be used to perform RA without using a RA sequence. This RA resource can apply for legacy RA where RA is made without using the herein proposed plurality of RA sequences. The legacy RA procedure includes for example transmission of UL data or buffer status reports (BSR) by non-AP STAs to their serving AP during the RA attempts. Such a legacy RA procedure is for example defined in the IEEE 802.1 lax amendment.

[0194] Accordingly, one or more embodiments described herein allows for efficient channel access in a way that supports low latency applications as well as numerous devices. In addition, one or more embodiments described herein may be used also when more advanced AP coordination schemes are employed. Finally, one or more embodiments described herein may be introduced in IEEE 802.11 as an enhancement of UORA which may reuse some of the UORA properties and may also be transparent to legacy devices supporting UORA.

[0195] As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, computer program product and / or computer storage media storing an executable computer program. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Any process, step, action and / or functionality described herein may be performed by, and / or associated to, a corresponding module, which may be implemented in software and / or firmware and / or hardware. Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that can be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

[0196] Some embodiments are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0197] These computer program instructions may also be stored in a computer readable memory or storage medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0198] The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0199] It is to be understood that the functions / acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality / acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

[0200] Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Python, Java® or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the "C" programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0201] Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments can be combined in any way and / or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.

[0202] Abbreviations that may be used in the preceding description include:

[0203] Abbreviations Explanation

[0204] ACK Acknowledgement

[0205] AP Access Point

[0206] CSMA / CA Carrier Sense Multiple Access with Collision Avoidance

[0207] DL Down-Link

[0208] LBT Listen Before Talk

[0209] MAC Medium Access Control

[0210] OFDM Orthogonal Frequency Division Multiplexing

[0211] OFDMA Orthogonal Frequency Division Multiple Access

[0212] PHY PHYsical Layer

[0213] ST A Station

[0214] TDMA Time Division Multiple Access

[0215] TXOP Transmission Opportunity

[0216] UL Up-Link

[0217] It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings.

Claims

CLAIMS:

1. A method implemented in a station, STA (16), that is configured to communicate with an access point, AP (14), the method comprising: receiving (SI 00) an indication of at least a first random access sequence of a plurality of random access sequences for random access, the plurality of random access sequences being configured for transmission in the frequency domain; and performing (SI 02) a random access procedure at least by transmitting, in the frequency domain, the first random access sequence of the plurality of random access sequences.

2. The method of Claim 1, wherein the plurality of random access sequences are selected such that the cross-correlation between any two of the plurality of random access sequences is below a predefined threshold.

3. The method of any one of Claims 1-2, wherein the plurality of random access sequences are a plurality of Zadoff-Chu sequences.

4. The method of any one of Claims 1-3, wherein the indication of at least the first random access sequence indicates information associated with the random access.

5. The method of Claim 4, wherein the indicated information comprises at least one of: a type of pending data associated with the random access; a type of priority associated with the pending data; an amount the pending data; or a buffer size.

6. The method of any one of Claims 1-5, wherein the first random access sequence is allocated to the STA (16).

7. The method of any one of Claims 1-5, further comprising randomly selecting one of a plurality of random access sequences for random access, the selected35random access sequence corresponding to the first random access sequence that is selectable by at least one other STA (16).

8. The method of any one of Claims 1-5, wherein a first subset of the plurality of random access sequences are selectable by a plurality of STAs (16); and each random access sequence of a second subset of the plurality of random access sequences being assigned to a respective STA (16), the first subset being different from the second subset.

9. The method of any one of Claims 1-8, wherein the indication of at least the first random access sequence is provided by a trigger frame for uplink request, TF-ULR.

10. The method of any one of Claims 1-9, wherein the radio access is at least one of performed in a system compliant with Institute of Electrical and Electronics Engineers, IEEE, 802.11 Standard; and based on orthogonal frequency division multiplexing, OFDM.

11. The method of any one of Claims 1-10, where at least one sequence of the plurality of random access sequences is allocated for STAs (16) not associated with the AP (14).

12. The method of any one of Claims 1-11, where the first random access sequence is sent in a random access resource in frequency domain used in a legacy random access procedure.

13. The method of any one of Claims 1-12, where random access resources in frequency domain are multiplexed with uplink data using orthogonal frequency division multiple access, OFDMA.

14. The method of any one of Claims 1-13, where two or more of the plurality of random access sequences are assigned to one STA.3615. The method of Claim 14, wherein the STA selectively uses the two or more of the plurality of random access sequences for sharing different information with the AP during random access attempts, wherein each selected random access sequence is associated by the STA with one or more of: a type of pending data associated with the random access; a type of priority associated with pending data; an amount the pending data; and a buffer size.

16. The method of any one of Claims 1-15, wherein, for a STA having a low- latency requirement, the first random access sequence is selected from a first sub-set of the plurality of random access sequences.

17. A station, STA (16), configured to communicate with an access point, AP (14), the STA configured to: receive an indication of at least a first random access sequence of a plurality of random access sequences for random access, the plurality of random access sequences being configured for transmission in the frequency domain; and perform a random access procedure at least by transmitting, in the frequency domain, the first random access sequence of the plurality of random access sequences.

18. The STA (16) of Claim 17, wherein the plurality of random access sequences are selected such that the cross-correlation between any two of the plurality of random access sequences is below a predefined threshold.

19. The STA (16) of any one of Claims 17-18, wherein the plurality of random access sequences are a plurality of Zadoff-Chu sequences.

20. The STA (16) of any one of Claims 17-19, wherein the indication of at least the first random access sequence indicates information associated with the random access.

21. The STA (16) of Claim 20, wherein the indicated information comprises at least one of:a type of pending data associated with the random access; a type of priority associated with the pending data; an amount the pending data; or a buffer size.

22. The STA (16) of any one of Claims 17-21, wherein the first random access sequence is allocated to the STA (16).

23. The STA (16) of any one of Claims 17-21, wherein the STA (16) is further configured to: randomly select one of a plurality of random access sequences for random access, the selected random access sequence corresponding to the first random access sequence that is selectable by at least one other STA (16).

24. The STA (16) of any one of Claims 17-23, wherein a first subset of the plurality of random access sequences are selectable by a plurality of STAs (16); and each random access sequence of a second subset of the plurality of random access sequences being assigned to a respective STA (16), the first subset being different from the second subset.

25. The STA (16) of any one of Claims 17-24, wherein the indication of at least the first random access sequence is provided by a trigger frame for uplink request, TF-ULR.

26. The STA (16) of any one of Claims 17-25, wherein the radio access is at least one of: performed in a system compliant with Institute of Electrical and Electronics Engineers, IEEE, 802.11 Standard; and based on orthogonal frequency division multiplexing, OFDM.

27. The STA (16) of any one of Claims 17-26, where at least one sequence of the plurality of random access sequences is allocated for STAs (16) not associated with the AP (14).

28. The STA (16) of any one of Claims 17-27, where the first random access sequence is sent in a random access resource in frequency domain used in a legacy random access procedure.

29. The STA (16) of any one of Claims 17-28, where random access resources in frequency domain are multiplexed with uplink data using orthogonal frequency division multiple access, OFDMA.

30. The STA (16) of any one of Claims 17-29, where two or more of the plurality of random access sequences are assigned to one STA.

31. The STA (16) of Claim 30, wherein the STA selectively uses the two or more of the plurality of random access sequences for sharing different information with the AP during random access attempts, wherein each selected random access sequence is associated by the STA with one or more of: a type of pending data associated with the random access; a type of priority associated with pending data; an amount the pending data; and a buffer size.

32. The STA (16) of any one of Claims 17-31, wherein, for a STA having a low- latency requirement, the first random access sequence is selected from a first sub-set of the plurality of random access sequences.

33. A method implemented in an access point, AP (14), that is configured to communicate with a station, STA (16), the method comprising: transmitting (SI 04), to the STA (16), an indication of at least a first random access sequence of a plurality of random access sequences for random access, the plurality of random access sequences being configured for transmission in the frequency domain; receiving (S106), from the STA (16), a random access sequence in the frequency domain as part of a random access procedure; and correlating (SI 08) the random access sequence with the first random access sequence as part of the random access procedure.3934. The method of Claim 33, wherein the plurality of random access sequences are selected such that the cross-correlation between any two of the plurality of random access sequences are below a predefined threshold.

35. The method of any one of Claims 33-34, wherein the plurality of random access sequences are a plurality of Zadoff-Chu sequences.

36. The method of any one of Claims 33-35, wherein the indication of at least the first random access sequence indicates information associated with the random access.

37. The method of Claim 36, wherein the indicated information comprises at least one of: a type of pending data associated with the random access; a type of priority associated with the pending data; an amount the pending data; or a buffer size.

38. The method of any one of Claims 33-37, further comprising allocating the first random access sequence to the STA (16).

39. The method of any one of Claims 33-38, wherein the plurality of random access sequences are configured to be randomly selected for random access.

40. The method of any one of Claims 33-39, wherein a first subset of the plurality of random access sequences are selectable by a plurality of STAs (16); and the method further comprises assigning each random access sequence of a second subset of the plurality of random access sequences to a respective STA (16), the first subset being different from the second subset.

41. The method of any one of Claims 33-40, wherein the indication of at least the first random access sequence is provided by a trigger frame for uplink request, TF- ULR.4042. The method of any one of Claims 33-41, wherein the first random access sequence is received on random access resources that have been multiplexed with uplink data from another STA (16), the multiplexing of the uplink data and the first random access sequence being configured to provide the AP (14) with additional processing time for processing the first random access sequence.

43. The method of any one of Claims 33-42, further comprising: as part of coordinating channel resources with another AP (14), share at least a portion of the plurality of random access sequences with the other AP (14).

44. The method of any one of Claims 33-43, wherein the radio access is at least one of: performed in a system compliant with Institute of Electrical and Electronics Engineers, IEEE, 802.11 Standard; and based on orthogonal frequency division multiplexing, OFDM.

45. The method of any one of Claims 33-44, where at least one sequence of the plurality of random access sequences is allocated for STAs (16) not associated with the AP (14).

46. The method of any one of Claims 33-45, where the first random access sequence is received in a random access resource in frequency domain used in a legacy random access procedure.

47. The method of any one of Claims 33-46, where random access resources in frequency domain are multiplexed with uplink data using orthogonal frequency division multiple access, OFDMA.

48. The method of any one of Claims 33-47, where two or more of the plurality of random access sequences are assigned to one STA.

49. The method of Claim 48, wherein the STA (16) uses the two or more of the plurality of random access sequences for sharing different information with the AP during41random access attempts, wherein each of the used random access sequences is associated with one or more of: a type of pending data associated with the random access; a type of priority associated with pending data; an amount the pending data; and a buffer size.

50. The method of any one of Claims 33-49, wherein, for a STA having a low- latency requirement, the first random access sequence is assigned from a first sub-set of the plurality of random access sequences.

51. An access point, AP (14), configured to communicate with a station, AP (14) is configured to: transmit, to the STA (16), an indication of at least a first random access sequence of a plurality of random access sequences for random access, the plurality of random access sequences being configured for transmission in the frequency domain; receive, from the STA (16), a random access sequence in the frequency domain as part of a random access procedure; and correlate the random access sequence with the first random access sequence as part of the random access procedure.

52. The AP (14) of Claim 51, wherein the plurality of random access sequences are selected such that the cross-correlation between any two of the plurality of random access sequences are below a predefined threshold.

53. The AP (14) of any one of Claims 51-52, wherein the plurality of random access sequences are a plurality of Zadoff-Chu sequences.

54. The AP (14) of any one of Claims 51-53, wherein the indication of at least the first random access sequence indicates information associated with the random access.

55. The AP (14) of Claim 54, wherein the indicated information comprises at least one of: a type of pending data associated with the random access;42a type of priority associated with the pending data; an amount the pending data; or a buffer size.

56. The AP (14) of any one of Claims 51-55, wherein the AP (14) is further configured to allocate the first random access sequence to the STA (16).

57. The AP (14) of any one of Claims 51-56, wherein the plurality of random access sequences are configured to be randomly selected for random access.

58. The AP (14) of any one of Claims 51-57, wherein a first subset of the plurality of random access sequences are selectable by a plurality of STAs (16); and the AP (14) is further configured to assign each random access sequence of a second subset of the plurality of random access sequences to a respective STA (16), the first subset being different from the second subset.

59. The AP (14) of any one of Claims 51-58, wherein the indication of at least the first random access sequence is provided by a trigger frame for uplink request, TF- ULR.

60. The AP (14) of any one of Claims 51-59, wherein the first random access sequence is received on random access resources that have been multiplexed with uplink data from another STA (16), the multiplexing of the uplink data and the first random access sequence being configured to provide the AP (14) with additional processing time for processing the first random access sequence.

61. The AP (14) of any one of Claims 51-60, wherein the AP (14) is further configured to: as part of coordinating channel resources with another AP (14), share at least a portion of the plurality of random access sequences with the other AP (14).

62. The AP (14) of any one of Claims 51-61, wherein the radio access is at least one of:43performed in a system compliant with Institute of Electrical and Electronics Engineers, IEEE, 802.11 Standard; and based on orthogonal frequency division multiplexing, OFDM.

63. The AP (14) of any one of Claims 51-62, where at least one sequence of the plurality of random access sequences is allocated for STAs (16) not associated with the AP (14).

64. The AP (14) of any one of Claims 51-63, where the first random access sequence is received in a random access resource in frequency domain used in a legacy random access procedure.

65. The AP (14) of any one of Claims 51-64, where random access resources in frequency domain are multiplexed with uplink data using orthogonal frequency division multiple access, OFDMA.

66. The AP (14) of any one of Claims 61-65, where two or more of the plurality of random access sequences are assigned to one STA.

67. The AP (14) of Claim 66, wherein the STA (16) uses the two or more of the plurality of random access sequences for sharing different information with the AP during random access attempts, wherein each of the used random access sequences is associated with one or more of: a type of pending data associated with the random access; a type of priority associated with pending data; an amount the pending data; and a buffer size.

68. The AP (14) of any one of Claims 51-67, wherein, for a STA having a low- latency requirement, the first random access sequence is assigned from a first sub-set of the plurality of random access sequences.44

Images