The present disclosure relates generally to wireless local area network (WLAN) communication, and more particularly relates to communication apparatuses and communication methods for enhanced random access within WLAN communication systems.
Communication apparatuses are prevalent in today's world in the form of phones, tablets, computers, cameras, digital audio/video players, wearable devices, game consoles, telehealth/telemedicine devices, and vehicles providing communication functionality, and various combinations thereof. The communication may include exchanging data through, for example, a wireless local area network (LAN) system, a cellular system, a satellite system, and various combinations thereof.
The 802.11 communication protocol uses a carrier sense multiple access (CSMA) method in which the communication apparatuses, such as wireless stations (STA), first sense the channel and attempt to avoid collisions by transmitting only when they sense the channel to be idle (i.e., when 802.11 signals are not detected). When a first STA hears a second STA, the first STA waits for a random amount of time for the second STA to stop transmitting before listening again for the channel to be free. When the first STA is able to transmit, the first STA transmits its whole packet data.
Wi-Fi STAs may use Request to Send/Clear to Send (RTS/CTS) to mediate access to the shared medium. The Access Point (AP) issues a CTS packet to one STA at a time, which in turn sends its entire frame to the AP. The STA then waits for an acknowledgement packet (ACK) from the AP indicating that the AP received the packet correctly. If the STA does not receive the ACK in time, the STA assumes the packet collided with some other transmission, moving the STA into a period of binary exponential backoff. The STA will then try to access the medium and re-transmit its packet after the backoff counter expires.
Although this Clear Channel Assessment and Collision Avoidance protocol serves well to divide the channel somewhat equally among all participants within the collision domain, its efficiency decreases when the number of participants grows very large such as in airport, stadium, mall and other high-density WiFi usage environments. Another factor that contributes to network inefficiency is having many APs with overlapping areas of service.
Thus, there is a need for communication apparatuses and communication methods for enhanced random access of AP controlled resources to alleviate the aforementioned issues, particularly in high density WLAN environments. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.
One non-limiting and exemplary embodiment facilitates providing multiple structures and methods to enable enhanced random access of access point (AP) controlled resources in a wireless local area network (WLAN) to reduce collisions and increase throughput and efficiency, particularly in high density WLAN environments.
In an exemplary embodiment, a communication apparatus including a transceiver and circuitry. The transceiver, in operation, receives signals from and transmits signals to at least one access point in a wireless local area network (WLAN). The circuitry, in operation, demodulates and decodes the signals from the at least one access point, the decoded signals comprising a WLAN transmission including a trigger frame, wherein the circuitry, in operation, prepares a trigger-based WLAN transmission and contends for one or more spatial streams in one of one or more random access resource units (RA-RUs) in response to enhanced uplink OFDMA-based random access (enhanced UORA) being enabled for the communication apparatus.
It should be noted that general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof.
Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. The benefits and/or advantages may be individually obtained by the various embodiments and features of the specification and drawings, which need not all be provided in order to obtain one or more of such benefits and/or advantages.
In the following, exemplary embodiments are described in more detail with reference to the attached figures and drawings.
And
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been depicted to scale.
The following detailed description is merely exemplary in nature and is not intended to limit the exemplary embodiments or the application and uses of the exemplary embodiments. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. It is the intent of the present disclosure to present exemplary embodiments of communication apparatuses and communication methods for enhanced random access in wireless local area network (WLAN) systems, including enhancement of uplink orthogonal frequency division multiple access (OFDMA)-based random access (UORA).
The wireless stations (STAs) are communication apparatuses operating in a WLAN system.
The STAs 120 communicate with the access points (APs) 110 in the WLAN system 100 to access resource units (RU) for exchanging data with the internet, other communication apparatuses or other systems.
To address dense environments, WLAN uses the IEEE 802.11ac or IEEE 802.11ax protocol as a communication method. To improve spectrum efficient utilization, a next-generation radio access technology referred to as Extremely High Throughput (EHT) introduces better power-control methods to avoid interference with neighboring networks, orthogonal frequency-division multiple access (OFDMA), higher order 1024-QAM, and up-link MU-MIMO within OFDMA added to the down link of MIMO and MU-MIMO to further increase throughput, as well as dependability improvements of power consumption and security protocols. EHT will be backward compatible with IEEE 802.11a/b/g/n/ac/ax technologies. Also, in IEEE 802.11ax High Efficiency (HE) WLAN, uplink OFDMA-based random access (UORA) is a mechanism for STAs to randomly select RUs assigned by an AP in a Trigger frame. However, there has not been much discussion on enhancement of UORA.
The STA 120 with pending frames for the AP 110 that is not the intended receiver of the User Info field 200 may contend for random access RUs (RA-RUs) if it can transmit a HE trigger-based (TB) physical layer protocol data unit (PPDU) in the RA-RU according to the parameters indicated in the Common Info field and in the User Info field 205. A SS Allocation/RA-RU Information field 220 in the User Info field 205 may indicate RA-RU allocated for UORA. When the value of the AID12 subfield 210 is ‘0’ or ‘2045’, only RA-RU Information is contained in this field. The RA-RU Information in the SS Allocation/RA-RU Information field 220 indicates the number of contiguous RUs allocated for UORA. There is no indication for Spatial Stream (SS) Allocation in the User Info field 205 for random access.
Upon the reception of a Trigger frame containing at least one eligible RA-RU, the STA 120 decrements its OFDMA Backoff (OBO) counter by the number of eligible RA-RUs (e.g., as indicated by the SS Allocation/RA-RU Information field 220). A non-AP STA may consider an RU as an eligible RA-RU if it supports all the transmit parameters indicated in the Common Info field and in the User Info field 205 that allocates that RU. If the result is not greater than zero, then the STA 120 sets its OBO counter to zero and randomly select one of the eligible RA-RUs to be considered for transmission. Otherwise, the STA 120 maintains the new OBO value until a next UORA.
In IEEE 802.11ax, a single spatial stream is used for transmission in a RA-RU. If a different STA randomly selects a same RA-RU, a collision is caused and transmission in the RA-RU fails. This is a problem as the maximal efficiency of RA-RU usage (i.e., acceptance rate of RA-RU) in IEEE 802.11ax is 37%. Thus, there is a need for a UORA procedure with more efficiency and higher throughput.
In accordance with the present disclosure an enhanced UORA procedure is carried out to address the problem set out above and provide for increased efficiency and higher throughput. The enhanced UORA procedure in accordance with the present disclosure includes the following steps:
When each STA selects only one SS, the AP lacks knowledge of whether the signal exists in each RU plus which STA transmits the signal, if any. This similarity to conventional UORA is advantageous for the enhanced UORA procedure. Also, in accordance with the enhanced UORA procedure of the present disclosure, the UL MU-MIMO within OFDMA is enabled in the RA-RUs and different STAs that select a same RA-RU are likely to select different SSs to transmit. Thus, the collision rate is advantageously decreased and throughput and overall efficiency is increased.
Whether the enhanced UORA is enabled may be indicated in different ways: there can be an explicit indication in a Trigger frame, there can be an explicit indication in the elements, or there can be an implicit indication by parameters in the Trigger frame.
In another possible option, the explicit indication of whether enhanced UORA is enabled may be indicated in the Common Info field 570 in the Trigger frame 510. When the Enhanced UORA Indication field 540 is indicated as “1”, enhanced UORA is enabled for the RA-RUs.
The enhanced UORA may also be enabled implicitly. There are three options for a receiver STA to tell whether enhanced UORA is enabled for an RA-RU. First, the receiver STA can tell from parameters indicated in the Trigger frame, including but not limited to RA-RU size or number of HE/EHT-LTF symbols. Secondly, the receiving STA can tell from capabilities broadcasted by the AP, such as Partial Bandwidth UL MU-MIMO. Finally, when Partial Bandwidth UL MU-MIMO is enabled at the EHT-AP, it also implicitly means the AP is capable of enhanced UORA. In this last option, it is defined that the EHT-AP with that capability supports the reception of TB PPDU by enhanced UORA.
For example, the receiver STA may decide that the enhanced UORA is enabled if the following conditions are satisfied: (a) The RA-RU size indicated in the User Info field supports UL MU-MIMO within OFDMA and (b) The number of HE/EHT-LTF symbols in the Common Info field supports multiple SSs. If either of these conditions are not met, the receiver STA may decide the RA-RU is for conventional UORA (i.e., IEEE 802.11ax-like UORA).
In accordance with the present disclosure, a contention procedure when enhanced UORA is indicated as enabled is carried out by first decrementing the OBO counter. Options for decrementing the OBO counter in accordance with the present disclosure include using the same contention procedure as in conventional UORA, using a contention procedure based on conventional counter decrement (i.e., only based on the number of eligible RA-RUs), and adopting a new OBO counter decrement value. The new OBO counter decrement value in accordance with the present disclosure corresponds to a number of eligible choices. In accordance with the enhanced UORA according to the present disclosure, the number of eligible choices could be a result of the number of eligible RA-RUs multiplied by the number of eligible SSs (e.g., if there are two RA-RUs in which four SSs may be used, then the number of eligible choices would be eight) or could be the result of the number of eligible RA-RUs multiplied by the number of eligible SSs groups (e.g., if there are two RA-RUs in which four SSs may be used and each STA may choose two SSs, then the number of eligible choices is four). Upon reception of a Trigger frame containing at least one eligible RA-RU, the STA decrements its OBO counter by the number of eligible choices. If the result is not greater than zero, then the STA sets its OBO counter to zero and randomly select one of the eligible RA-RUs and select one or more SSs in it to be considered for transmission. Otherwise, the STA maintains the new OBO value until the next UORA or enhanced UORA.
Since there are STAs that are not able to contend for enhanced UORA (e.g., HE STAs or post-HE STAs not supporting enhanced UORA), and if the new OBO counter decrement value is applied, a fairness issue may be caused. STAs that are not able to contend for enhanced UORA may have fewer eligible resources to contend and, thus, have less chance to win the contention.
To reduce the unfairness, two options are presented in accordance with the present disclosure.
In accordance with the present disclosure, a STA may randomly select a single SS in a RA-RU subject to the capabilities of the STA (i.e., whether the STA supports enhanced UORA or not) and the SS range indicated in the Trigger frame. When an HE trigger-based (TB) physical layer protocol data unit (PPDU) is solicited, a HE STA shall select the first SS. An EHT STA or post-EHT STA, on the other hand, shall select from SSs other than the first SS subject to the SS range.
When an EHT TB PPDU is solicited, the EHT STA or EHT+STA may select any SS subject to the SS range. STAs not supporting UL MU-MIMO within OFDMA may also contend for enhanced UORA.
In accordance with the present disclosure, if the enhanced UORA is indicated as enabled 1320, blind decoding on the indicated SS range is performed 1340. The AP 110 does not know which SS carries data or which STA is transmitting. So, the AP performs 1340 the blind decoding on all possible SSs in each RA-RU. Advantageously, the process is similar to conventional UORA where the AP 110 does not know which RA-RU carries data, so no change is needed for at the AP 110 side. After the blind decoding on the indicated SS range is performed 1340, the TB PPDU reception procedure ends 1350.
If the enhanced UORA is indicated as enabled 1420, the EHT TB PPDU transmission procedure determines 1450 whether the OBO counter is greater than the number of eligible choices. If the OBO counter is greater than the number of eligible choices 1450, the OBO counter is decremented 1460 by the number of eligible choices and the OBO counter value is maintained until a next UORA. Then the EHT TB PPDU transmission procedure ends 1440.
If the OBO counter is not greater than the number of eligible choices 1450, a RU is randomly selected from the RA-RUs and a spatial stream (SS) is randomly selected in the RU subject to the STA 120 capability and SS range 1470. A TB PPDU is then prepared 1480 according to the selected RA-RU and spatial stream and the EHT TB PPDU transmission procedure ends 1440 by transmitting the TB PPDU.
In accordance with the present disclosure, the STA 120 may select a single SS in the RA-RU subject to capabilities and the SS range indicated in the Trigger frame following specific decision criteria. When HE TB PPDU is solicited, a HE STA shall select the first SS. The EHT STA or a post-EHT STA selects from SSs other than the first SS subject to the SS range. When EHT TB PPDU is solicited, an EHT STA or a post-EHT STA may select any SS subject to the SS range. The possible specific decision criteria may be an Index of SS selected based on the result of the STA's AID mod or the maximal number of SSs that may be used in RA-RU.
For example, assume a target STA1 is with AID 2 and a target STA2 is with AID 5, where STA1 and STA 2 are associated STAs. The STA1 and the STA2 randomly select a same RA-RU and there are four SSs that may be used in the RA-RU. For STA1, NAID mod NSS=2 mod 4=2, so STA1 selects SS 2 to transmit in the RA-RU. For STA2, NAID mod NSS=5 mod 4=1, so STA2 selects SS 1 to transmit in the RA-RU. Thus, in some scenarios where AIDs of target STAs are contiguous, the collision rate may be further decreased than the EHT TB PPDU transmission procedure of the flowchart 1400 by the avoidance of collision in the SS. Note that this is only applicable for associated STAs.
If the enhanced UORA is indicated as enabled 1520, the TB PPDU transmission procedure determines 1550 whether the OBO counter is greater than the number of eligible choices. If the OBO counter is greater than the number of eligible choices 1550, the OBO counter is decremented 1560 by the number of eligible choices and the OBO counter value is maintained until a next UORA. Then the TB PPDU transmission procedure ends 1540.
If the OBO counter is not greater than the number of eligible choices 1550, a RU is randomly selected from the RA-RUs and a spatial stream (SS) is selected in the RU according to the specific criteria 1570. A TB PPDU is then prepared 1580 according to the selected RA-RU and spatial stream and the TB PPDU reception procedure ends 1540 by transmitting the TB PPDU.
The STA 120 may randomly select one or more SSs in the RA-RU subject to capabilities (e.g., the maximal number of SSs the STA supports) and the SS range indicated in the Trigger frame. The number and index of SS(s) are decided by the STA 120 itself based on its requirements. For example, if the pending frames held by the STA 120 can only be transmitted with at least two SSs in the RA-RU according to the indicated parameters, then the STA may select two SSs to transmit. For simplicity, the index of multiple SSs selected by STA are contiguous. When HE TB PPDU is solicited, a HE STA shall select the first SS. An EHT STA or a post-EHT STA selects from SSs other than the first SS subject to the SS range. In addition, an EHT STA or a post-EHT STA may select two or more SSs if the AP 110 is capable of blind decoding. These procedures are applicable for both associated and unassociated STAs 120. While the random selection of multiple SSs provides higher throughput than non-random selection of a single SS (i.e., non-random selection being subject to the STAs capability and SS range or being subject to the specific criteria), the trade-off is the higher complexity required by the random selection of multiple SSs.
The illustration 1700 depicts a new User Info field format 1720 for the User Info field 1710 to indicate SS range and limitations of SS. The SS range is indicated by a SS Starting Index subfield 1730 and a SS End Index subfield 1735. The limitations of the SS are indicated by a Limitation of SS subfield 1740.
The illustration 1750 depicts a User Info field format 1770 for the User info field 1760 for RA-RU assignment. A UL DCM subfield 1780 is used for random access and for indication of SS limitations.
The STA 120 may also select one SS or more than one SS in the RA-RU subject to capabilities and the SS range and limitation of SS indicated in the Trigger frame in accordance with the present disclosure following specific decision criteria. The possible redefined decision criteria may be an Index of SS which is selected based on the result of the STA's AID mod and the number of SS groups.
If a Target STA1 is with AID 2 and a target STA2 is with AID 5, the STA1 and the STA2 are associated STAs, the STA1 and the STA2 randomly select a same RA-RU, there are eight SSs which may be used in the RA-RU and the maximal number of SS a STA may select is 2, the selection of SS is governed by Equation (1).
N
SSgroups
=N
SS
/N
SS,u,max (1)
where, NSSgroups is the number of SS groups, and NSS,u,max is the maximal number of SSs which may be selected by a STA. For STA1, NAID mod NSSgroups=2 mod 4=2; so STA1 selects a SS from SS group 2, which contains SS 3 and SS 4. For STA2, NAID mod NSSgroups=5 mod 4=1; so STA2 selects a SS from SS group 1, which contains SS 1 and SS 2. STA1 and STA2 transmits TB PPDU in the RA-RU using SS 3/SS 4 and SS 1/SS 2, respectively. The other SSs in the RA-RU are empty. Note that this nonrandom selection of multiple SS procedure is only applicable for associated STAs.
If the enhanced UORA is indicated as enabled 1820, the TB PPDU transmission procedure determines 1850 whether the OBO counter is greater than the number of eligible choices. If the OBO counter is greater than the number of eligible choices 1850, the OBO counter is decremented 1860 by the number of eligible choices and the OBO counter value is maintained until a next UORA. Then the TB PPDU transmission procedure ends 1840.
If the OBO counter is not greater than the number of eligible choices 1850, a RU is randomly selected from the RA-RUs and one or more spatial streams (SSs) are randomly or nonrandomly selected in the RU subject to the STA 120 capability and the SS range 1870. A TB PPDU is then prepared 1880 according to the selected RA-RU and spatial stream and the EHT TB PPDU transmission procedure ends 1840 by transmitting the TB PPDU.
Enhanced UORA and conventional UORA may be enabled simultaneously in a same trigger-based transmission.
The AP may indicate whether there is any spatial resource in any of the allocated RUs which can be used for random access in the RA-SS Flag subfield 2025 in the Common Info field 2020 or indicate it in a UORA Parameter Set element. When the RA-SS Flag subfield 2025 is indicated as “1”, the AP may indicate whether the SS in an allocated RU can be used for random access in the RA-SS Indication subfield 2035 in the corresponding User Info field 2030. When the RA-SS Flag subfield 2025 is indicated as “1”, the STA checks the RA-SS Indication subfield 2035 in each User Info field 2030 until the end of the User Info fields or until the STA finds the matching AID.
The User Info field 2030 in which RA-SS Indication subfield 2035 is indicated as “1” carries the last allocated SS information and the STA may decide the index of the RA-SS by the SS range information (e.g., number of LTF symbols) and the SS information indicated in the User Info field 2030.
The number of eligible choices is determined in accordance with the present disclosure according to Equation 2.
N
SS,RA-RU,total
+N
RA-SS,total (2)
where NSS,RA-RU,total is the total number of spatial streams that may be used in the RA-RUs and NRA_SS,total is the total number of RA-SS.
If the RA-SS procedure is indicated as enabled 2220, the TB PPDU transmission procedure determines 2250 whether the OBO counter is greater than the number of eligible choices. If the OBO counter is greater than the number of eligible choices 2250, the OBO counter is decremented 2260 by the number of eligible choices and the OBO counter value is maintained until a next UORA. Then the TB PPDU transmission procedure ends 2240.
If the OBO counter is not greater than the number of eligible choices 2250, one or more eligible spatial streams (SSs) are randomly selected from the RA-RUs or form an allocated RU 2270. A TB PPDU is then prepared 2280 according to the selected spatial stream and the TB PPDU transmission procedure ends 2240 by transmitting the TB PPDU.
If the enhanced UORA procedure is indicated as enabled 2320, the TB PPDU reception procedure performs blind decoding on the indicated SS range of RA-RU and RA-SS of allocated RUs 2350. Then the TB PPDU reception procedure at the AP 110 ends 2340.
A variant of the TB PPDU reception process discussed above includes nonrandom selection of the RU. When post-HE TB PPDU are solicited, a post-HE STA may select a RA-RU subject to capabilities indicated in the Trigger frame, following specific decision criteria. The possible specific decision criteria may be an Index of the RA-RU is selected based on the result of the STA's AID mod and the number of RA-RUs. In some scenarios where the AIDs of target STAs are contiguous, the collision rate may be decreased as compared to conventional UORA. Note that this variant is only applicable to associated STAs.
Thus, it can be seen that the exemplary embodiments provide multiple structures and methods to enable enhanced random access of AP controlled resources to reduce collisions and increase throughput and efficiency, particularly in high density WLAN environments.
The present disclosure can be realized by software, hardware, or software in cooperation with hardware. Each functional block used in the description of each embodiment described above can be partly or entirely realized by a large-scale integration (LSI) such as an integrated circuit, and each process described in each embodiment may be controlled partly or entirely by the same LSI or a combination of LSIs. The LSI may be individually formed as integrated circuit chips, or one chip may be formed so as to include a part or all of the functional blocks. The LSI may include a data input and output coupled thereto. The LSI may be referred to as an integrated circuit (IC), a system LSI, a super LSI, or an ultra-LSI depending on a difference in the degree of integration. However, the technique of implementing an integrated circuit is not limited to the LSI and may be realized by using a dedicated circuit, a general purpose processor, or a special purpose processor. In addition, a Field Programmable Gate Array (FPGA) that can be programmed after the manufacture of the LSI or a reconfigurable processor in which the connections and the settings of circuit cells disposed inside the LSI can be reconfigured may be used. The present disclosure can be realized as digital processing or analogue processing. If future integrate circuit technology replaces LSIs as a result of the advancement of semiconductor technology or other derivative technology, the functional blocks could be integrated using the future integrated circuit technology. Biotechnology can also be applied.
The present disclosure can be realized by any kind of apparatus, device or system having a function of communication, which is referred to as a communication apparatus. The communication apparatus may comprise a transceiver and processing/control circuitry. The transceiver may comprise and/or function as a receiver and a transmitter. The transceiver, as the transmitter and receiver, may include a radio frequency (RF) module including amplifiers, RF modulators/demodulators and the like, and one or more amplifiers, RF modulators/demodulators and the like, and one or more antennas. The processing/control circuitry may include power management circuitry which may comprise dedicated circuitry, a processor and instructions for power management control as either firmware or instructions stored in a memory coupled to the processor.
Some non-limiting examples of such a communication apparatus include a phone (e.g., cellular (cell) phone, smart phone), a tablet, a personal computer (PC) (e.g., laptop, desktop, netbook), a camera (e.g., digital still/video camera), a digital player (e.g., digital audio/video player), a wearable device (e.g., wearable camera, smart watch, tracking device), a game console, a digital book reader, a telehealth/telemedicine (remote health and medicine) device, and a vehicle providing communication functionality (e.g., automotive, airplane, ship), and various combinations thereof.
The communication apparatus is not limited to be portable or movable, and may also include any kind of apparatus, device or system being non-portable or stationary, such as a smart home device (e.g., an appliance, lighting, smart meter, control panel), a vending machine, and any other “things” in a network of an “Internet of Things (IoT)”. The communication may include exchanging data through, for example, a cellular system, a wireless LAN system, a satellite system, etc., and various combinations thereof.
The communication apparatus may comprise a device such as a controller or a sensor which is coupled to a communication device performing a function of communication described in the present disclosure. For example, the communication apparatus may comprise a controller or a sensor that generates control signals or data signals which are used by a communication device performing a communication function of the communication apparatus.
The communication apparatus may also include an infrastructure facility, such an access point, and any other apparatus, device or system that communicates with or controls apparatuses such as those in the non-limiting examples provided herein.
While exemplary embodiments have been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should further be appreciated that the exemplary embodiments are only examples, and are not intended to limit the scope, applicability, operation, or configuration of the present disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing exemplary embodiments, it being understood that various changes may be made in the function and arrangement of the STA communication apparatus and/or the AP communication apparatus described in the exemplary embodiments without departing from the scope of the present disclosure as set forth in the appended claims.
Number | Date | Country | Kind |
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10202102561V | Mar 2021 | SG | national |
Filing Document | Filing Date | Country | Kind |
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PCT/SG2021/050822 | 12/23/2021 | WO |