Method and apparatus for priority transmission of WLAN frames

Abstract

Various aspects of the present disclosure provide mechanisms for minimizing latency in real-time application (RTA) traffic over wireless LANs. A wireless electronic device identifies real-time application network packets in the application layer, assigns them a new MPDU frame type and subtype, and maps them to a high-priority access category, such as AC_VO. Upon receiving a TXOP, the device prioritizes transmitting RTA frames over frames mapped to the access category granted the TXOP. Other aspects enable preemptive priority transmission of RTA frames.

Description

[0001] Cross-references

[0002] This application claims the benefit of and priority to U.S. non-provisional patent application serial number 16 / 818,975, filed on March 13, 2020, and entitled “Method and Apparatus for Priority Transmission of WLAN Frames,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates generally to wireless communications and, in a specific embodiment, to low-latency scheduling of real-time application frame traffic over a Wireless Local Area Network (WLAN). Background Art

[0004] The IEEE 802.11 Wireless Local Area Network (WLAN) standard defines one of the world's most widely deployed wireless technologies. The ubiquity of portable mobile handsets and the convenience of wireless communication have driven the growth of wireless networks. With the increasing deployment of multimedia content over the Internet (such as digital video, voice over IP (VoIP), video conferencing, and real-time applications such as multiplayer gaming), as well as the deployment of time-sensitive and critical applications, there is a strong need to develop QoS features to meet more stringent performance requirements.

[0005] Regarding QoS configuration, the legacy IEEE 802.11a / b / g standards only have basic distributed coordination functions (DCF) and optional point coordination functions (PCF) enhancements, such as collision avoidance and first-in-first-out (FIFO) schedulers. In DCF-based schemes, access to the medium is provided using a carrier sense multiple access (CSMA) scheme. Although statistically fair, not all sessions are created equally for expected network performance. Under heavy network load, DCF+CSMA could potentially result in sessions being deprived of their required bandwidth share. In a DCF-based environment, there is no suitable mechanism to differentiate sessions based on priority. Legacy IEEE 802.11a / b / g / standards do not have a standard mechanism to guarantee QoS. Since these standards do not include admission control, performance degradation occurs under heavy traffic load.

[0006] The IEEE 802.11e amendment introduces the Hybrid Coordination Function (HCF), a new coordination function proposed to enhance DCF. HCF introduces the concept of a transmission opportunity (TXOP) and uses two methods to obtain a TXOP: the first is contention-based, called enhanced distributed channel access (EDCA); the second is contention-free, called HCF-controlled channel access (HCCA). Both schemes facilitate QoS configuration to support delay-sensitive voice and video applications.

[0007] EDCA uses timing information based on the contention window size to distinguish between high-priority access categories and low-priority access categories. The central coordinator assigns shorter contention windows to high-priority access categories to help high-priority access categories obtain access to the medium and transmission opportunities (TXOPs) before low-priority access categories. To further distinguish, the interframe spacing (IFS) can vary for different access categories. For DCF services, a distributed interframe spacing (DIFS) is not used, but a new interframe spacing called arbitration interframe spacing (AIFS) is used. AIFS is the number of time slots that the EDCA function (EDCAF) waits before competing for the medium. Therefore, the smaller the AIFS of a service category, the higher the priority obtained.

[0008] Table 1 shows the default OFDMA parameters aCW min =15μs, aCW max =1023 μs and slot duration = 9 μs for the four access categories in EDCA.

[0009] Table 1: Contention window and TXOP duration for EDCA access categories

[0010]

[0011] Under these conditions, the contention window for the lowest-latency access category, AC_VO (voice), ranges from 3 to 8 milliseconds. Even with this relatively short backoff period, in the worst-case scenario, where the density of voice traffic mapped simultaneously with real-time application traffic to AC_VO is high, the latency of real-time application traffic mapped to AC_VO can result in an unsatisfactory user experience. It is desirable to provide a shorter maximum latency for real-time application traffic in wireless LANs. Summary of the Invention

[0012] Exemplary embodiments of the present invention provide methods and apparatus for priority transmission of WLAN frames.

[0013] According to an exemplary aspect of the present invention, the apparatus is a wireless electronic device for communicating via a wireless LAN. The wireless electronic device includes one or more processors coupled to a network interface and a computer-readable storage medium, wherein the storage medium stores instructions that can be executed by the processor to perform a method for communicating via a wireless LAN. The method includes: obtaining a transmission opportunity for a first access category through enhanced distributed channel access; and transmitting a first service frame including a frame header. The frame header includes a frame type subfield and a frame subtype subfield, and the values ​​of the frame type subfield and the frame subtype subfield identify the first service frame as a real-time application frame. Such a frame header advantageously enables each layer of the network protocol to quickly identify the real-time application frame so as to give priority access to the transmission medium.

[0014] In some embodiments, although the first traffic frame is mapped to a second access category different from the first access category granted a TXOP, the first traffic frame is the first frame transmitted within the transmission opportunity. Being transmitted first regardless of the access category granted a TXOP gives real-time application traffic an advantage in transmission priority over currently available traffic of the AC_VO category, thereby alleviating many delays experienced by real-time application traffic attempting to transmit over a WLAN.

[0015] According to any or all of the above aspects of the present invention, the second access category to which the first traffic frame is mapped is a voice (AC_VO) category. This advantageously gives RTA traffic access to the shortest average contention window and a multi-frame TXOP, during which any queued RTA traffic is quickly moved.

[0016] According to other or any of the above exemplary aspects of the present invention, the Frame Type subfield takes a 2-bit value of "11." This enables the use of frame subtypes not yet assigned by the IEEE, such as subtypes 1000 to 1111 of Type 11. Setting the MSB (bit 7) to 1 is logically consistent with the QoS frame subtype established by IEEE 802.11e in frame type 10 (data).

[0017] According to an alternative aspect of the present invention, a method for communicating over a wireless LAN includes obtaining a TXOP for a first AC via EDCA, then transmitting a portion of a first non-RTA traffic frame. Subsequently, transmission of the first traffic frame is suspended to make room for transmission of a second traffic frame. The second traffic frame is a real-time application frame, identified by its frame type and subtype in its frame header, and is transmitted within the TXOP, despite being mapped to a different AC. This suspension of transmission of the first frame to allow transmission of the second frame prevents real-time application traffic from having to wait for a long frame transmission to complete before being transmitted, as is done in the prior art, or worse, from having to wait for its station to contend for the TXOP again after the long frame transmission. In some aspects, transmission of the first traffic frame is resumed after the second traffic frame is fully transmitted. This resumption has the advantage of avoiding the need to expend additional airtime retransmitting the portion of the first non-RTA frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For a more complete understanding of the embodiments of the present invention and its advantages, reference is made to the following description in conjunction with the accompanying drawings by way of example, in which:

[0019] Figure 1A is a block diagram of a wireless local area network according to an embodiment of the present invention.

[0020] Figure 1B is a block diagram of a wireless electronic device according to an embodiment of the present invention.

[0021] FIG2 shows access category mapping and contention functionality for enhanced distributed channel access.

[0022] Figure 3 The diagram shows the path and processing of a service frame according to an embodiment of the present invention.

[0023] Figure 4 The figure shows the frame structure of the MPDU and possible positions of the real-time application service identifier according to an embodiment of the present invention.

[0024] Figure 5 is a flowchart illustrating the operation of a WLAN basic service set according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] For illustrative purposes, specific exemplary embodiments are described in more detail below with reference to the accompanying drawings.

[0026] The embodiments presented herein provide information sufficient to practice the claimed subject matter and illustrate methods for practicing such subject matter. After reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the claimed subject matter and will recognize applications of these concepts not specifically mentioned herein. It should be understood that these concepts and applications are within the scope of the present invention and the claims.

[0027] Furthermore, it should be understood that any module, component, or device disclosed herein that executes instructions may include or otherwise access one or more non-transitory computer / processor readable storage media for storing information, such as computer / processor readable instructions, data structures, program modules, and / or other data. A non-exhaustive list of examples of non-transitory computer / processor readable storage media includes magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, compact disc read-only memory (CD-ROM), digital video discs or digital versatile discs (i.e., DVDs), Blu-ray discs, TM Optical discs, or other optical storage, volatile and non-volatile, removable and non-removable media implemented by any method or technology, random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other storage technology. Any of these non-transitory computer / processor storage media can be part of the device, accessible by the device, or connected to the device. Computer / processor readable / executable instructions for implementing the applications or modules described herein can be stored or otherwise maintained by such non-transitory computer / processor readable storage media.

[0028] The present invention relates to communication between components of a basic service set (BSS) in a wireless LAN (WLAN). Referring to Figure 1, a BSS 100 includes one or more access points (APs) 104 that provide connectivity between client STAs 102 and a wide area network (WAN) (e.g., the Internet, a core network, a radio access network, or other network) via a wireless medium 106. Access points can include wireless routers, mobile phone personal hotspots, Wi-Fi-equipped PCs, Wi-Fi-equipped cable modems, or any other electronic device capable of hosting an IEEE 802.11 connection. The wireless medium 106 can include frequency channels in various spectrum bands, including bands around 900 MHz, 2.4 GHz, 5 GHz, 60 GHz, and any other portion of the unlicensed spectrum used for scientific and industrial purposes. Where a frequency is referenced, the actual frequency band includes a range of frequencies surrounding the referenced frequency. The AP 104 communicates with one or more of the STAs 102 over one or more air interfaces using a wireless medium 106 (e.g., radio frequency (RF), microwave, infrared (IR), etc.). The air interface may use any suitable radio access technology. For example, the BSS 100 may implement one or more orthogonal or non-orthogonal channel access methods in the air interface, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), or single-carrier FDMA (SC-FDMA).

[0029] STA 102 may include a cellular phone, tablet computer, computer, consumer entertainment device, appliance, Internet of Things (IoT) client, smartwatch, or any other device capable of connecting to a Wi-Fi basic service set. Communication may occur in the uplink (STA to AP) direction or the downlink (AP to STA) direction. In some cases, direct STA to STA communication (sidelink communication) may occur. Although FIG1 illustrates a certain number of these components or elements, any suitable number of these components or elements may be included in system 100.

[0030] refer to Figure 1BThe wireless communication device 102 acting as a STA in the BSS may be in the form of a smartphone, a portable computer, a consumer electronic device, or other component supporting Wi-Fi technology, and includes one or more processors 122 coupled to a computer-readable storage medium 106 and a network interface 124. The storage medium stores operating software for the wireless communication device 102, including instructions 128 for processing real-time application services according to the present invention. The processor 122 may include an integrated circuit, such as a central processing unit (CPU), an application processor (AP), a field programmable gate array (FPGA), or an application-specific integrated circuit (ASIC). The network interface 124 may include a baseband processor or other circuitry for implementing a media access controller, a physical layer, a transmit amplifier, and one or more RF antennas required for communication over a wireless medium. The network interface 124 may use any suitable radio access technology. For example, the communication system 102 may implement one or more orthogonal or non-orthogonal channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), or single carrier FDMA (SC-FDMA) in the network interface 124. The storage medium 106 may include non-volatile memory (such as EEPROM, NOR flash, and NAND flash) for powerless storage of software and volatile memory (such as DRAM and SRAM) for application processor work area.

[0031] STA devices 102 (e.g., personal computers, tablets, smartphones, thin-client notebooks, and interactive smart TVs) are capable of running high-performance, real-time applications such as live action games, music collaboration, augmented reality, vehicle navigation, and other applications that require low-latency interaction with other electronic devices to provide a satisfactory and (in some cases) secure user experience. When many STAs 102 share an AP 104, bandwidth is shared and devices must compete for access to the wireless medium 106. IEEE 802.11 currently includes Quality of Service (QoS) protocols to allow certain traffic classes (e.g., voice and video) to compete with other less time-sensitive traffic classes (e.g., file transfers, email, software updates, and other interruption-tolerant communication sessions).

[0032] refer to Figure 1Aand FIG2 describe contention-based enhanced distributed channel access. FIG2 shows a block diagram 200 of the EDCA process. The application (APP) layer 201 in the protocol stack generates data packets for transmission through the network connection 110 of the electronic device, which is established through an 802.11-compatible access point (AP) 104. The data packets must first be sent to the MAC layer 202 and packaged into MAC Protocol Data Units (MPDUs), also known as MAC frames. The User Priority (UP) field, which can take values ​​from 0 to 7, is stored in the frame header and is used by the hybrid coordination function 204 to map the MAC frame to one of four access categories (ACs) based on the UP of the MAC frame. Each access category has its own contention parameters, which determine which AC successfully accesses the wireless medium during each contention.

[0033] Table 2, reproduced from Table 10-1 in IEEE P802.11-REVmd / D3.0, October 2019, shows how UPs are mapped to ACs in EDCA.

[0034] Table 2: Mapping of user priority to access category

[0035]

[0036] Referring to Figure 2, the most popular priority services, which require approximately 10ms of latency, are mapped to AC VO 210. Services that can achieve approximately 100ms of latency are mapped to AC VI 220. A large amount of network traffic is mapped to AC BE 230, while low-priority service frames, which are allocated to wait for remaining network bandwidth, are mapped to AC BK 240. Each of queues 210, 220, 230, and 240 competes for the wireless medium through its corresponding EDCA function (EDCAF) 211, 221, 231, and 241, respectively. These EDCAFs take the parameters listed in Table 1 as input and calculate a contention window (CW) for each EDCAF. This contention window determines the amount of time each EDCAF must wait before requesting a TXOP. A TXOP has a duration, during which a STA can send as many MAC frames as possible from the AC queue to which the TXOP belongs to the physical layer before the duration expires. The MAC frame is sent to the PHY 203 for addition of a PHY preamble, encoding and modulation into a PHY Protocol Data Unit (PPDU) (or WLAN traffic frame), and finally transmission. High-priority ACs have small contention windows and tend to receive TXOPs first. Low-priority ACs tend to receive TXOPs when there are no frames in the high-priority queue or when the randomly assigned backoff time (part of the CW calculation) is shorter than the randomly assigned backoff time. Without a random backoff timer, low-priority traffic is almost completely deferred as long as there is any high-priority traffic in the queue.

[0037] Despite the current QoS configurations in 802.11, simulations and real-world observations have shown that even when traffic frames are mapped to AC_VO, latency for most performance-intensive real-time applications (such as high-frame-rate gaming and vehicle control) is a limiting factor in their practicality. This latency manifests as a noticeable lag between control inputs from the network and the resulting responses. This is due to several factors. First, when one of a STA's EDCAFs successfully contends for a TXOP, only frames in that EDCAF's queue are allowed to be transmitted within the TXOP. Second, each AC's queue is a FIFO queue, so RTA traffic frames mapped to AC_VO must wait for other AC_VO traffic before they can be transmitted. Third, if an RTA traffic frame is to be transmitted next, it may still need to wait for a long frame from another access category (such as a bulk file transfer in AC_BE) to complete before it can be transmitted. A mechanism is needed to enable low-latency traffic frames, such as real-time application frames, to address these limitations, thereby enabling higher priority transmission than is currently possible in WLAN traffic scheduling.

[0038] Various aspects of the present invention provide a method for communicating over a wireless LAN, the method comprising: transmitting a first traffic frame, wherein the first traffic frame includes a first frame header including a frame type and a frame subtype; and mapping the traffic frame to a first enhanced distributed channel access (EDCA) access category (AC). The method further comprises: obtaining a transmission opportunity (TXOP) for a second EDCA AC to transmit the traffic frame over a wireless medium; and transmitting the first traffic frame within the TXOP before any other traffic frames mapped to the second EDCA AC based on values ​​of the frame type and the frame subtype.

[0039] The following combination Figure 3 and Figure 4 Exemplary embodiments of the method of the present invention are described. Figure 5 The operation of the basic service set according to an embodiment of the present invention is shown.

[0040] Figure 3 3 is a block diagram illustrating the journey of data packets 305, 306 as they pass through the layers of the protocol stack 300 (from the application layer 301 executing the program on the wireless device 200 to the physical layer 303 of the network interface) for transmission over the medium 315. In the Open Systems Interconnection (OSI) model, there are seven layers of functionality in the order visible to the end user. Layer 7 is the application layer ( Figure 3 301 in ), is the domain of applications that deal with human-compatible input and output. The next layer is Layer 6, the Presentation Layer, which in one example is responsible for encrypting and decrypting data for secure transmission. Layer 5, the Session Layer, manages persistent connections between machines (sessions), such as telnet, ftp, or http sessions. The next layer is Layer 4, the Transport Layer, which establishes numbered ports over which protocols such as TCP and UDP can operate. The next layer is Layer 3, the Network Layer, where DNS, routers, and IP addresses ensure that data is transmitted to the right place anywhere in the world. Layer 2, the Data Link Layer, is responsible for maintaining logical LAN connections and includes the Logical Link Control Layer and a lower sublayer, the Medium Access Control (MAC) layer ( Figure 3 302 in ). Components on a LAN reference each other by their MAC addresses. Finally, Layer 1, the physical layer ( Figure 3The physical layer (303 in Figure 3) controls the actual bit transmission over the physical medium (e.g., radio waves and cables). The physical layer modulates, scrambles, and encodes the signal to provide a robust and dedicated transmission. For clarity, some layers in the protocol stack are omitted here because they do not perform any steps in the present invention.

[0041] refer to Figure 3 A generic network packet 306 generated by application layer 301 is marked by an icon representing a series of information fields indicated by blank squares. If the application generating the network packet requires low-latency, real-time communication, the application may identify the network packet as a real-time application (RTA) packet. An RTA network packet 305 is marked by a similar icon, except for an RTA identifier 307, which is represented by the first pattern of squares filling the icon of network packet 305. The exact format of RTA identifier 307 is outside the scope of this invention, but may take the form of, for example, a packet type field or subfield in a packet header. This advantageously allows RTA packets to be processed differently from other packets upon reaching the MAC layer. Network packets 306, 305, whether generic or RTA, generated by application layer 301, may arrive at MAC layer 302 in any order or, in alternative embodiments, be received by PHY layer 303 as traffic frames and decoded to have a final destination different from the wireless device 200 that received them. In this case, the MAC layer hardware 302 repackages the network data packets into new traffic frames for retransmission to their final destination.

[0042] To prepare network packets for transmission to other network nodes, MAC layer hardware 302 adds a MAC header to each network packet, thereby generating a MAC protocol data unit (MPDU) for each network packet. The MAC header of an RTAMPDU 308 includes an identifier (e.g., frame type and frame subtype) represented by a patterned filled square 310, the value of which identifies the frame as an RTA frame. Similarly positioned blank squares 313 in MPDU icon 309 represent identifiers of different values, indicating that these are not generic MPDUs from real-time applications.

[0043] Figure 4The detailed structure of the MAC header, adapted from IEEE 802.11-REVmd / D3.0, is shown. MAC header 410 includes several fields, of particular note: frame control field 411 and quality of service (QoS) control field 418. Frame control field 411 includes bit positions B2 and B3 432, which indicate the frame type, and bit positions B4 through B7 433, which indicate the frame subtype. The possible values ​​of these subfields distinguish between various possible management frames, control frames, data frames, and extended frames. The frame type (denoted as B3B2) can take the following values: 00 for management, 01 for control, 10 for data, and 11 for extended. The first three frame types have all their subtypes assigned to specific uses. According to one embodiment of the present invention, identifier 310, 450 includes a new combination of frame type 432 and frame subtype 433 values, which, in combination 450, identifies the MPDU as an RTAMPDU for any device capable of decoding the MAC header. New subtype values ​​ranging from 1000 (B7B6B5B4) to 1111 are proposed for Frame Type 11 representing extended frames to indicate that the traffic frame is QoS RTA data. Setting B7 to 1 preserves backward compatibility with the previously defined QoS Data frame subtype for Frame Type 10 data.

[0044] Therefore, according to one embodiment of the present invention, MAC hardware 302 adds a MAC header 410 including a frame type of 11 and a subtype in the range of 1000 to 1111 to RTA data packet 305, thereby generating an RTA MPDU 308. MAC hardware 302 adds a MAC header 410 including a different combination of frame type and subtype 313 to non-RTA data packet 306, thereby generating a generic MPDU 309.

[0045] The other part of the MAC header associated with the RTA MPDU is the Quality of Service (QoS) control field. The QoS control field format 420 includes a subfield TID 421 that identifies a 3-bit user priority level UP in the range of 0 to 7 corresponding to the UP in Table 2. In one embodiment of the present invention, real-time application MPDUs 308 are assigned a UP of 6 or 7 to ensure that they are mapped to the AC_VO access category 380.

[0046] The MAC layer hardware 302 maps the non-RTA service frame 309 to any of the four access categories (ACs) AC_BK 350, AC_BE 360, AC_VI 370, and AC_VO 380 according to Table 2 based on the user priority value of the non-RTA service frame 309. Generally speaking, a FIFO queue is maintained for each AC so that the first MPDU queued in the same AC is usually transmitted before other MPDUs queued later. Note that Figure 3The information flow in FIG is shown as proceeding from top to bottom of the diagram, with frames at the bottom of the access category queue at the front of the queue. Advantageously, according to the present invention, MAC hardware 302 identifies RTA MPDUs 308 and similar content and queues them first, overriding FIFO ordering. Thus, once a TXOP 304 is received for that queue, RTA traffic frames are transmitted before any other traffic in AC_VO 380.

[0047] TXOP is used as a threshold for the PHY layer to process the MPDU into physical medium service frames and transmission service frames. In EDCA, contention for TXOP is performed by the EDCA function (EDCAF). The EDCAF of each AC achieves this by first checking the idle channel indication and setting the network allocation vector to 0. Then, the EDCAF of each AC waits for a time equal to its contention window, which is the sum of the arbitration inter-frame interval (the arbitration inter-frame interval of each AC is different) and the random backoff time. If the channel is still idle, the EDCAF attempts to access the medium. The conflict arbitration function in the MAC layer 302 resolves any conflicts (connections, simultaneous transmission attempts) between EDCAFs within a single STA. The winning EDCAF causes the STA to send MPDUs 308 and 309 to the PHY 303 in an attempt to transmit them as service frames. At this point, in the prior art, the MPDUs in the queue of the winning AC are sent to the PHY for transmission. However, embodiments of the present invention provide a technical advantage in that, regardless of which EDCAF wins the contention, the first frame sent for transmission by the PHY layer 303 will be an RTA frame 308 marked with the RTA frame type and subtype 450. Only after all RTA frames 308 have been transmitted can the remaining frames 309 from the contention-winning AC be transmitted in FIFO order within the time limit defined by the TXOP 304. If the TXOP is exhausted before all RTA traffic is transmitted, the STA must contend again for another TXOP before transmitting the remaining RTA traffic frames and non-RTA frames.

[0048] If no RTA MPDU 308 is queued in AC_VO 380, and STA 102, which maintains queues 350, 360, 370, and 380, wins TXOP 304 for the first AC (which can be, for example, AC_BK 350 or any other access category), then the leader MAC frame 309 in queue 350 for the first AC is sent to PHY 303 for transmission. At some point during the transmission of the non-RTA frame 309, an RTA frame 308 may be placed in queue AC_VO 380 at the transmitting STA 102. According to the present invention, this RTA frame 308 becomes the next frame to be transmitted as long as there is sufficient time remaining in the TXOP. In one embodiment of the present invention, the RTA frame 308 is assigned non-preemptive priority, meaning that it is transmitted as soon as the non-RTA frame 309 completes transmission, as long as the TXOP length allows. In another embodiment, the RTA frame 308 is given preemptive priority, which means that the transmission of the non-RTA frame 309 is immediately stopped to free up the wireless medium 315 for the transmission of the RTA frame 308. If the transmitting STA 102 notifies the receiving STA of a transmission pause, then once the transmission of the RTA frame 308 is completed, the transmission of the non-RTA frame 309 can be resumed from where it was interrupted, again as long as the TXOP length allows. If the transmitting STA 102 does not notify the receiving STA of a transmission pause, the frame fragments are discarded at the receiving end, and the transmission must start from the frame header.

[0049] refer to Figure 5 , shows a flowchart describing the operation of a Wi-Fi Basic Service Set (BSS) according to an embodiment of the present invention. BSS 500 includes, for example, at least AP 570, STA A 510, and STA B 540. Each component of BSS 500 is associated with a vertical timeline on the flowchart, which progresses chronologically from top to bottom. Events within each component are marked with boxes, and transmission / reception / carrier sense events between components are marked with arrows indicating the direction of information communication.

[0050] At the beginning of the flowchart, AP 570 manages communications on the wireless link medium. For example, if the AP is sending management frames to other STAs (not shown), the medium is characterized by a busy state 571. Simultaneously, STA A 510 is preparing data for network transmission by first generating an AC_VI class frame 511 and then an RTA type frame 512, which will be mapped to an AC_VO frame. STA B 540 is also preparing data for transmission by generating an AC_BK frame 541 and an AC_BE frame 542.

[0051] STA A 510 and STA B 540 queue data for transmission and perform clear channel assessments 513 and 543 to try to detect whether a PPDU is being transmitted over the wireless medium or whether there is non-Wi-Fi energy in the frequency channel (e.g., a 2.4 GHz baby monitor signal). The STAs determine that the channel is clear, so they begin contending for the TXOP.

[0052] STA A 510 has two queues of frames waiting to be sent: AC_VO and AC_VI. Both ACs use an AIFS of 2 slots, with a standard slot length of 9 μs. Therefore, AC_VO AIFS 514 and AC_VI AIFS 515 will both take 18 μs before these queues enter their contention window timers. The AC_BK queue at STA B 540 waits for an AIFS 544 of 7 slots (63 μs), while AC_BE's AIFS 545 is 3 slots (27 μs).

[0053] The AIFS 514 and 515 at STA A 510 will complete first, and each EDCAF contending within STA A will be assigned a random contention window time selected from the range of values ​​configured for its corresponding AC. In this example, the randomly generated value for AC_VO contention window 516 is 8 μs, and the randomly generated value for AC_VI contention window 517 is 7 μs. As a result, the AC_VI EDCAF at STA A 510 will successfully contend for the medium and be granted a TXOP 572 by the AP. AC_VI is typically granted a TXOP length 519 of 4096 μs contention-free time, within which it transmits as many queued frames as are available within AC_VI.

[0054] According to existing QoS practices, RTA frame 512 must wait for the end of the AC_VI TXOP and, in addition, cannot be transmitted until the next time AC_VO at STAA wins the TXOP. However, according to one embodiment of the present invention, STA A 510 checks whether there are any RTA frames in the AC_VO queue, even though AC_VO has not won the TXOP. In this example, there is an RTA frame, so STAA begins transmitting the RTA frame 520. At the end of RTA frame transmission 520, if necessary, the AP can respond with an acknowledgment (ACK) frame 573 to notify STA A 510 of successful reception. For example, RTA frames from online games are typically characterized by short packets of status data (such as position, acceleration, sprite conflict flags, and action start commands). This way, RTA transmission 520 does not significantly delay AC_VI frame transmission 522, which begins only one SIFS (16 μs in 802.11ac) after STAA 510 receives the RTA acknowledgment frame 573. The technical advantage achieved is therefore the saving of valuable milliseconds of latency in real-time two-way communication applications, but without substantially affecting the frame rate of video transmissions, which are typically buffered for a few seconds at the beginning.

[0055] When AC_VI transmission 522 ends and AP 570 has acknowledged 574 the AC_VI frame, STA A 510 has no more frames to send. Even though TXOP limit 519 is far from over, STA A stops transmitting, allowing other STAs, including STA B 540, to sense a clear channel 548. At STA B 540, the 27μs AC_BE AIFS 545 is nearing its end, with 2μs remaining when STA A's contention window 517 ends. In this example, the AC_BE contention window 546 then begins counting down from 15μs. STA B's AC_BE will then win TXOP 549 because AC_BK did not end its AIFS before the next frame 520 appeared on the channel. AC_BK needs to restart its AIFS 544 and wait for a continuous 63μs of clear channel time before contending again.

[0056] Continuing with the flowchart, AP 570 grants AC_BE TXOP 575 to STA B 540. Consequently, STA B 540 transmits BE frame 550, and the AP responds with an ACK frame 577. It should be understood that, due to multi-core and multi-threaded architectures, processors controlling wireless electronic devices are able to perform tasks in parallel. Therefore, during the transmission of the large, multi-millisecond AC_BE frame 550, in some embodiments, STA B 540 may generate an RTA frame 551 and queue it in the AC_VO before the AC_BE frame transmission 550 is complete. According to one embodiment of the present invention, RTA frame 551 is given non-preemptive priority and is subsequently queued for transmission within TXOP 549 after the completion of frame transmission 550 and frame acknowledgment 577. While this next-in-line privilege eliminates the delay associated with re-contention for the TXOP, the RTA frame must still wait for the entire duration of the existing transmission frame. To provide further advantages in transmission timeliness, in another embodiment of the present invention, RTA frames 551 are given preemption priority, advantageously avoiding multi-millisecond delays. To implement preemption priority, STA B suspends AC_BE frame transmission 552, transmits an RTA frame 553, and receives an acknowledgment 578 for the RTA frame from AP 570. In one embodiment, STA B 540 resumes AC_BE frame transmission 554, thereby recovering the effort 550 expended in transmitting the first portion of the AC_BE frame. In another embodiment, AP 570 does not allow an extended TXOP 549 to complete AC_BE frame transmission 554, and the AC_BE must contend for the TXOP again.

[0057] The above-described embodiments of the present invention (whether employed individually or in combination) provide the technical advantage of reducing latency for real-time applications by avoiding the most common sources of transmission delay, while minimally impacting relatively delay-sensitive services such as video. The embodiments of the present invention only significantly negatively impact transmission latency for background services that are tolerant to frame retry, such as email and bulk file transfers.

[0058] Although combinations of features are shown in the illustrated embodiments, not all of these features need be combined to achieve the advantages of the various embodiments of the present invention. In other words, a system or method designed according to an embodiment of the present invention does not necessarily include all of the features shown in any of the accompanying drawings or all of the parts schematically shown in the drawings. In addition, selected features of one exemplary embodiment may be combined with selected features of other exemplary embodiments.

[0059] Although the present invention has been described with reference to illustrative embodiments, this description is not intended to limit the invention. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will become apparent to those skilled in the art upon reference to this description. Therefore, the appended claims are intended to cover any such modifications or embodiments.

Claims

1. A method for communicating via a wireless LAN, characterized in that: The method comprises: The wireless electronic device obtains a transmission opportunity for the first access category through enhanced distributed channel access; and The wireless electronic device transmits a first service frame including a frame header, wherein the frame header includes a frame type subfield and a frame subtype subfield, and values ​​of the frame type subfield and the frame subtype subfield identify the first service frame as a real-time application frame. The first service frame is mapped to a second access category different from the first access category, and the first service frame is the first frame transmitted in the transmission opportunity; before transmitting any traffic frames belonging to the first access category, transmitting a plurality of traffic frames within the transmission opportunity, each of the plurality of traffic frames including a frame type subfield and a frame subtype subfield identifying the plurality of traffic frames as real-time application frames; and After any service frame belonging to the first access category is transmitted, service frames including a frame type subfield and a frame subtype subfield identifying the service frame as a real-time application frame are not transmitted within the transmission opportunity.

2. The method according to claim 1, characterized in that The second access category is AC_VO.

3. The method according to claim 1 or 2, characterized in that The value of the frame type subfield is equal to the 2-bit value "11".

4. A method for communicating via a wireless LAN, characterized in that The method comprises: The wireless electronic device obtains a transmission opportunity for a first access category through enhanced distributed channel access; The wireless electronic device transmits a portion of a first service frame; pausing transmission of the first service frame; and The wireless electronic device transmits a second service frame including a frame header, wherein the frame header includes a frame type subfield and a frame subtype subfield, and values ​​of the frame type subfield and the frame subtype subfield identify the second service frame as a real-time application frame. The second service frame is mapped to a second access category different from the first access category; before transmitting any traffic frames belonging to the first access category, transmitting a plurality of traffic frames within the transmission opportunity, each of the plurality of traffic frames including a frame type subfield and a frame subtype subfield identifying the plurality of traffic frames as real-time application frames; and After any service frame belonging to the first access category is transmitted, service frames including a frame type subfield and a frame subtype subfield identifying the service frame as a real-time application frame are not transmitted within the transmission opportunity.

5. The method according to claim 4, characterized in that The wireless electronic device resumes transmitting the first service frame after the second service frame is completely transmitted.

6. The method according to claim 4 or 5, characterized in that The second access category is AC_VO.

7. The method according to claim 4 or 5, characterized in that The value of the frame type subfield is equal to the 2-bit value "11".

8. A wireless electronic device for communicating via a wireless LAN, characterized in that The wireless electronic device comprises: One or more processors coupled to a network interface and to a computer-readable storage medium, wherein the storage medium stores instructions executable by the processors to: acquiring a transmission opportunity for the first access category through enhanced distributed channel access; and transmitting a first service frame including a frame header, wherein the frame header includes a frame type subfield and a frame subtype subfield, and values ​​of the frame type subfield and the frame subtype subfield identify the first service frame as a real-time application frame, The first service frame is mapped to a second access category different from the first access category, and the first service frame is the first frame transmitted in the transmission opportunity; before transmitting any traffic frames belonging to the first access category, transmitting a plurality of traffic frames within the transmission opportunity, each of the plurality of traffic frames including a frame type subfield and a frame subtype subfield identifying the plurality of traffic frames as real-time application frames; and After any service frame belonging to the first access category is transmitted, service frames including a frame type subfield and a frame subtype subfield identifying the service frame as a real-time application frame are not transmitted within the transmission opportunity.

9. The wireless electronic device according to claim 8, wherein: The second access category is AC_VO.

10. The wireless electronic device according to claim 8 or 9, characterized in that: The value of the frame type subfield is equal to the 2-bit value "11".

11. A wireless electronic device for communicating via a wireless LAN, characterized in that The wireless electronic device comprises: One or more processors coupled to a network interface and to a computer-readable storage medium, wherein the storage medium stores instructions executable by the processors to: acquiring a transmission opportunity for a first access category through enhanced distributed channel access; transmitting a portion of a first service frame; pausing transmission of the first service frame; and transmitting a second service frame including a frame header, wherein the frame header includes a frame type subfield and a frame subtype subfield, and values ​​of the frame type subfield and the frame subtype subfield identify the second service frame as a real-time application frame, The second service frame is mapped to a second access category different from the first access category; before transmitting any traffic frames belonging to the first access category, transmitting a plurality of traffic frames within the transmission opportunity, each of the plurality of traffic frames including a frame type subfield and a frame subtype subfield identifying the plurality of traffic frames as real-time application frames; and After any service frame belonging to the first access category is transmitted, service frames including a frame type subfield and a frame subtype subfield identifying the service frame as a real-time application frame are not transmitted within the transmission opportunity.

12. The wireless electronic device according to claim 11, wherein: The transmission of the first service frame is resumed after the second service frame is completely transmitted.

13. The wireless electronic device according to claim 11 or 12, characterized in that: The second access category is AC_VO.

14. The wireless electronic device according to claim 11 or 12, characterized in that: The value of the frame type subfield is equal to the 2-bit value "11".

Images