WO2021236304A1

WO2021236304A1 - Co-existence between multiple wireless communication technologies on the same channel using delayed transmissions

Info

Publication number: WO2021236304A1
Application number: PCT/US2021/029385
Authority: WO
Inventors: Stelios STEFANATOS; Michael Alexander RUDER; Marco Papaleo; Tien Viet NGUYEN
Original assignee: Qualcomm Incorporated
Priority date: 2020-05-19
Filing date: 2021-04-27
Publication date: 2021-11-25

Abstract

Systems, methods, and computer-readable media disclosed herein support coexistence of multiple wireless communication technologies using time division multiplexing with reduced collisions. In some implementations, a method of wireless communication includes detecting arrival of a data packet for transmission at a wireless communication device via a wireless communication channel. The method further includes, based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden via the wireless communication channel, initiating delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval. Other aspects and features are also claimed and described.

Description

CO-EXISTENCE BETWEEN MULTIPLE WIRELESS COMMUNICATION TECHNOLOGIES ON THE SAME CHANNEL USING DELAYED

TRANSMISSIONS

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Patent Application No.

63/027,249, entitled, “MODIFIED PROCEDURE FOR TIME DIVISION MULTIPLE ACCESS (TDMA)-RESTRICTED CHANNEL,” filed on May 19, 2020, and claims the benefit of and to U.S. Provisional Patent Application No. 63/030,638, entitled, “MODIFIED PROCEDURE FOR TIME DIVISION MULTIPLE ACCESS (TDM A)-RE S TRIC TED CHANNEL ACCESS,” filed on May 27, 2020, both of which are expressly incorporated by reference herein in their entirety.

TECHNICAL FIELD

[0002] Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to wireless communication systems configured to support co-existence of multiple wireless communication technologies, such as a time division multiple access (TDMA) communication scheme and a contention-based communication scheme, on the same wireless communication channel using delayed transmissions.

INTRODUCTION

[0003] A wireless local area network (WLAN) may be formed by one or more access points (APs) that provide a shared wireless communication medium for use by a number of client devices also referred to as stations (STAs). The basic building block of a WLAN conforming to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards is a Basic Service Set (BSS), which is managed by an AP. Each BSS is identified by a Basic Service Set Identifier (BSSID) that is advertised by the AP in beacon frames, which are periodically broadcasted to enable any STAs within wireless range of the AP to establish or maintain a communication link with the WLAN.

[0004] Many wireless networks use random channel access mechanisms to control access to a shared wireless medium. In these wireless networks, wireless devices (including APs and STAs) typically contend with each other using carrier sense multiple access with collision avoidance (CSMA/CA) techniques to gain access to the wireless medium. In general, the wireless device that randomly selects the lowest backoff number wins the medium access contention operation, and may be granted access to the wireless medium for a period of time commonly referred to as a transmit opportunity (TXOP). Other wireless devices are generally not permitted to transmit during the TXOP to avoid interfering with transmissions from the TXOP owner.

[0005] Another type of wireless communication used by wireless networks is time division multiple access (TDMA) communications. In TDMA communication schemes, different wireless devices may be allocated different time periods during which the wireless devices may perform communications via a wireless medium. Supporting both a TDMA communication scheme and a contention-based communication scheme in a single wireless network can lead to conflicts or inefficiencies, which may degrade performance of at least one type of wireless communication device.

SUMMARY

[0006] The following summarizes some aspects of the present disclosure to provide a basic understanding of the discussed technology. This summary is not an extensive overview of all contemplated features of the disclosure and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present some concepts of one or more aspects of the disclosure in summary form as a prelude to the more detailed description that is presented later.

[0007] In one aspect of the disclosure, a method of wireless communication includes detecting arrival of a data packet for transmission at a wireless communication device via a wireless communication channel. The method further includes, based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden via the wireless communication channel, initiating delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval.

[0008] In an additional aspect of the disclosure, an apparatus configured for wireless communication is disclosed. The apparatus includes at least one processor, and a memory coupled to the at least one processor. The at least one processor is configured to detect arrival of a data packet for transmission via a wireless communication channel. The at least one processor is further configured to initiate, based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden via the wireless communication channel, delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval.

[0009] In an additional aspect of the disclosure, an apparatus configured for wireless communication is disclosed. The apparatus includes means for detecting arrival of a data packet for transmission via a wireless communication channel. The apparatus further includes means for initiating, based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden via the wireless communication channel, delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval.

[0010] In an additional aspect of the disclosure, a non-transitory, computer-readable storage medium stores instructions that, when executed by a processor, causes the processor to perform operations. The operations include detecting arrival of a data packet for transmission from a wireless communication device via a wireless communication channel. The operations further include, based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden via the wireless communication channel, initiating delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval.

[0011] Other aspects, features, and embodiments will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary embodiments in conjunction with the accompanying figures. While features may be discussed relative to certain aspects and figures below, all embodiments can include one or more of the advantageous features discussed herein. In other words, while one or more aspects may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various aspects. In similar fashion, while exemplary aspects may be discussed below as device, system, or method aspects, the exemplary aspects can be implemented in various devices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A further understanding of the nature and advantages of the present disclosure may be realized by reference to the following drawings. In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[0013] FIG. 1 is a diagram of an example wireless communication network according to some aspects of the disclosure.

[0014] FIG. 2A illustrates an example protocol data unit (PDU) usable for communications between an access point (AP) and one or more stations (STAs) according to some aspects.

[0015] FIG. 2B illustrates an example field in the PDU of FIG. 2A.

[0016] FIG. 3A illustrates an example PDU usable for communications between an AP and one or more STAs according to some aspects.

[0017] FIG. 3B illustrates another example PDU usable for communications between an AP and one or more STAs according to some aspects.

[0018] FIG. 3C illustrates an example signal field usable in a PDU according to some aspects.

[0019] FIG. 4 illustrates an example of superframes according to some aspects.

[0020] FIG. 5 illustrates examples of performing listen-before transmit (LBT) procedures according to some aspects.

[0021] FIG. 6 illustrates examples of transmitting data packets according to some aspects.

[0022] FIG. 7 is a block diagram of an example wireless communication system configured to support a time division multiple access (TDMA) communication scheme and a contention- based communication scheme according to some aspects.

[0023] FIG. 8 illustrates examples of performing LBT procedures according to some aspects.

[0024] FIG. 9 illustrates examples of delaying transmission of data packets according to some aspects.

[0025] FIG. 10 illustrates examples of delaying transmission of data packets for slots having different durations according to some aspects.

[0026] FIG. 11 is a flow diagram illustrating an example process of wireless communication device operations for initiating delayed transmission of a data packet based on the data packet arriving during a slot during which transmission of the data packet is forbidden via a wireless communication channel according to some aspects.

[0027] FIG. 12 is a flow diagram illustrating an example process of wireless communication device operations for delaying initiation of an LBT procedure according to some aspects.

[0028] FIG. 13 is a block diagram of an example wireless communication device configured to initiate a backoff time or delayed data packet transmission after an artificial busy state associated with a wireless communication channel according to some aspects. [0029] FIG. 14 illustrates simulation results of wireless communication systems configured according to one or more aspects.

DETAILED DESCRIPTION

[0030] The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to limit the scope of the disclosure. Rather, the detailed description includes specific details for the purpose of providing a thorough understanding of the inventive subject matter. It will be apparent to those skilled in the art that these specific details are not required in every case and that, in some instances, well-known structures and components are shown in block diagram form for clarity of presentation.

[0031] The present disclosure provides systems, apparatus, methods, and computer-readable media for enabling a wireless communication system to support multiple wireless communication schemes, such as a contention-based communication scheme and a time division multiple access (TDMA) communication scheme, via the same wireless channel. To illustrate, time resources for a wireless communication channel (e.g., a wireless medium) may be partitioned in time and allocated to two different communication technologies. For example, a first set of slots (e.g., time periods) may be allocated to contention-based communications (e.g., a first communication technology), and a second set of slots may be allocated to TDMA communications (e.g., a second communication technology), such as allocating one or more slots of a superframe (e.g., a particular time period) as the first set of slots, and one or more other slots of the superframe as the second set of slots. In some implementations, the first communication technology may be a wireless local area network (WLAN) (e.g., “Wi-Fi”) protocol described by or based on one or more Institute of Electrical and Electronics Engineers (IEEE) 802.11 wireless communication standard specifications, and the second communication technology may be a communication technology described by one or more Third Generation Partnership Protocol (3 GPP) wireless communication standard specifications. To illustrate, the first wireless communication technology may include Intelligent Transport System (ITS) G5 (ITS-G5) or Dedicated Short Range Communication (DSRC), and the second wireless communication technology may include long-term evolution (LTE) vehicle-to-everything (V2X) (LTE-V2X), as non-limiting examples. The techniques described herein may enable wireless communication devices configured to communicate via the first wireless communication technology (e.g., the WLAN-based technology) to more efficiently use the slots allocated to the first wireless communication technology. Although described with reference to a TDMA-based technology and a WLAN- based technology, in other implementations, the techniques disclosed herein may enable support for two WLAN-based communication technologies allocated to different slots, or a single WLAN-based communication technology that communicates a control channel during one set of slots and a data channel during another set of slots, such as an IEEE 1609.4 communication protocol.

[0032] To illustrate, a wireless communication device (e.g., a station (STA)) configured to communicate using the first wireless communication technology may detect arrival of a data packet to be transmitted via a wireless communication channel. For example, a data packet may be added to a transmission buffer of the wireless communication device, an indication may be provided from an application executed by the wireless communication device, or the arrival may be detected in some other manner. After detecting the arrival of the data packet, the wireless communication device may sense the wireless communication channel to determine if the wireless communication channel is busy (e.g., occupied). To enable allocation of one or more slots to TDMA communications (e.g., co-existence with TDMA communications), the wireless device may be configured to sense the wireless communication channel as being in a busy state during the one or more slots allocated to the TDMA communications regardless of whether a communication is detected on the wireless channel. For example, the wireless communication device may be preconfigured with or receive an indication from an access point (AP) that indicates one or more slots allocated to the first wireless communication technology (e.g., the TDMA communications or any other wireless communications during which transmission of the data packet is forbidden), and the wireless communication device may be configured to sense the wireless communication channel as busy during the one or more slots indicated by the AP. Because this busy state is not based on detection of a communication via another wireless communication device (e.g., using a “listen-before-transmit” or “listen-before-talk” (LBT) procedure), the busy state may be referred to as an “artificial busy state.”

[0033] After sensing the busy state, the wireless communication device may determine that the busy state corresponds to an artificial busy state (e.g., based on a determination that a current slot is included in the one or more slots allocated to the second wireless communication technology). Based on the determination, the wireless communication device may initiate a backoff time based on detection of the wireless communication channel becoming idle after the artificial busy state. For example, when the wireless communication device next detects that the wireless communication channel is idle (e.g., not in the busy state), the wireless communication device initiates a backoff time. Based on the determination that the busy state corresponds to the artificial busy state, the backoff time is initiated without waiting for a duration of an arbitrary interframe symbol space (AIFS) after detection of the wireless communication channel as idle, as would otherwise occur if the busy time did not correspond to the artificial busy time. The backoff time may be a random backoff time, as in accordance with a clear channel assessment (CCA) or LBT procedure at the wireless communication device. After expiration of the backoff time, the wireless communication device transmits the data packet via the wireless communication channel if the wireless communication channel is still idle.

[0034] In some implementations, the wireless communication device may delay initiation of the backoff time, or transmission of the data packet if no backoff procedure is performed, based on a determination that the busy state corresponds to the artificial busy state. For example, the wireless communication device may assign a delay interval to initiation of a backoff time for a received data packet based on a determination that the arrival of the data packet is during the artificial busy state (e.g., is during a slot allocated for TDMA communication). In some implementations in which a slot duration of slots allocated to the first wireless communication technology is the same as a slot duration of slots allocated to the second wireless communication technology, the delay interval may be equal to the slot duration. In some other implementations in which a first slot duration of slots allocated to the first wireless communication technology is different than a second slot duration of slots allocated to the second wireless communication technology, the delay interval may be determined based on the first slot duration, the second slot duration, and the position of the arrival of the data packet within the second slot. Delaying initiation of the backoff time for data packets that arrive during the artificial busy state may more evenly spread out transmission of data packets during a slot allocated to the first wireless communication technology, which may reduce collisions between messages transmitted via the wireless communication channel and improve latency of communications by the wireless communication device.

[0035] Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. In some aspects, the present disclosure provides techniques for improving efficiency of usage of slots by wireless communication devices configured to operate according to the first wireless communication technology. To illustrate, instead of waiting a duration of an AIFS after reaching the end of a slot allocated to the second wireless communication technology (during which the wireless communication channel is sensed as being in an artificially busy state), the wireless communication device immediately initiates the backoff time. By not waiting for the AIFS before initiating the backoff time, more of a subsequent slot allocated to the first wireless communication technology may be used for communications, which improves efficiency of use of the slot, and may reduce latency and collisions associated with communications in accordance with the first wireless communication technology. Additionally or alternatively, delaying the initiation of a backoff operation, or delaying the initiation of data packet transmission without performing a backoff operation, for data packets that arrive during a slot allocated to the second wireless communication technology (e.g., a TDMA slot or any slot during which transmission of the data packet is forbidden) may further reduce collisions associated with communications performed via the wireless communication channel and in accordance with the first wireless communication technology while supporting co-existence between the first wireless communication technology and the second wireless communication technology.

[0036] FIG. 1 is a block diagram of an example wireless communication network 100.

According to some aspects, the wireless communication network 100 can be an example of a wireless local area network (WLAN) such as a Wi-Fi network (and will hereinafter be referred to as WLAN 100). For example, the WLAN 100 can be a network implementing at least one of the IEEE 802.11 family of wireless communication protocol standards (such as that defined by the IEEE 802.11-2016 specification or amendments thereof including, but not limited to, 802.1 lay, 802.1 lax, 802.11az, 802.11ba and 802.11be). The WLAN 100 may include numerous wireless communication devices such as an access point (AP) 102 and multiple stations (STAs) 104. While only one AP 102 is shown, the WLAN network 100 also can include multiple APs 102.

[0037] Each of the STAs 104 also may be referred to as a mobile station (MS), a mobile device, a mobile handset, a wireless handset, an access terminal (AT), a user equipment (UE), a subscriber station (SS), or a subscriber unit, among other examples. The STAs 104 may represent various devices such as mobile phones, personal digital assistant (PDAs), other handheld devices, netbooks, notebook computers, tablet computers, laptops, display devices (for example, TVs, computer monitors, navigation systems, among others), music or other audio or stereo devices, remote control devices (“remotes”), printers, kitchen or other household appliances, key fobs (for example, for passive keyless entry and start (PKES) systems), vehicles or components of vehicles, such as on-board units (OBUs), among other examples. [0038] A single AP 102 and an associated set of STAs 104 may be referred to as a basic service set (BSS), which is managed by the respective AP 102. FIG. 1 additionally shows an example coverage area 106 of the AP 102, which may represent a basic service area (BSA) of the WLAN 100. The BSS may be identified to users by a service set identifier (SSID), as well as to other devices by a basic service set identifier (BSSID), which may be a medium access control (MAC) address of the AP 102. The AP 102 periodically broadcasts beacon frames (“beacons”) including the BSSID to enable any STAs 104 within wireless range of the AP 102 to “associate” or re-associate with the AP 102 to establish a respective communication link 108 (hereinafter also referred to as a “Wi-Fi link”), or to maintain a communication link 108, with the AP 102. For example, the beacons can include an identification of a primary channel used by the respective AP 102 as well as a timing synchronization function for establishing or maintaining timing synchronization with the AP 102. The AP 102 may provide access to external networks to various STAs 104 in the WLAN via respective communication links 108.

[0039] To establish a communication link 108 with an AP 102, each of the STAs 104 is configured to perform passive or active scanning operations (“scans”) on frequency channels in one or more frequency bands (for example, the 2.4 GHz, 5 GHz, 5.9 GHz, 6 GHz or 60 GHz bands). To perform passive scanning, a STA 104 listens for beacons, which are transmitted by respective APs 102 at a periodic time interval referred to as the target beacon transmission time (TBTT) (measured in time units (TUs) where one TU may be equal to 1024 microseconds (ps)). To perform active scanning, a STA 104 generates and sequentially transmits probe requests on each channel to be scanned and listens for probe responses from APs 102. Each STA 104 may be configured to identify or select an AP 102 with which to associate based on the scanning information obtained through the passive or active scans, and to perform authentication and association operations to establish a communication link 108 with the selected AP 102. The AP 102 assigns an association identifier (AID) to the STA 104 at the culmination of the association operations, which the AP 102 uses to track the STA 104.

[0040] As a result of the increasing ubiquity of wireless networks, a STA 104 may have the opportunity to select one of many BSSs within range of the STA or to select among multiple APs 102 that together form an extended service set (ESS) including multiple connected BSSs. An extended network station associated with the WLAN 100 may be connected to a wired or wireless distribution system that may allow multiple APs 102 to be connected in such an ESS. As such, a STA 104 can be covered by more than one AP 102 and can associate with different APs 102 at different times for different transmissions. Additionally, after association with an AP 102, a STA 104 also may be configured to periodically scan its surroundings to find a more suitable AP 102 with which to associate. For example, a STA 104 that is moving relative to its associated AP 102 may perform a “roaming” scan to find another AP 102 having more desirable network characteristics such as a greater received signal strength indicator (RSSI) or a reduced traffic load.

[0041] In some cases, STAs 104 may form networks without APs 102 or other equipment other than the STAs 104 themselves. One example of such a network is an ad hoc network (or wireless ad hoc network). Ad hoc networks may alternatively be referred to as mesh networks or peer-to-peer (P2P) networks. In some cases, ad hoc networks may be implemented within a larger wireless network such as the WLAN 100. In such implementations, while the STAs 104 may be capable of communicating with each other through the AP 102 using communication links 108, STAs 104 also can communicate directly with each other via direct wireless links 110. Additionally, two STAs 104 may communicate via a direct communication link 110 regardless of whether both STAs 104 are associated with and served by the same AP 102. In such an ad hoc system, one or more of the STAs 104 may assume the role filled by the AP 102 in a BSS. Such a STA 104 may be referred to as a group owner (GO) and may coordinate transmissions within the ad hoc network. Examples of direct wireless links 110 include Wi-Fi Direct connections, connections established by using a Wi-Fi Tunneled Direct Link Setup (TDLS) link, and other P2P group connections.

[0042] The APs 102 and STAs 104 may function and communicate (via the respective communication links 108) according to the IEEE 802.11 family of wireless communication protocol standards (such as that defined by the IEEE 802.11-2016 specification or amendments thereof including, but not limited to, 802.11ay, 802.11ax, 802.11az, 802.11ba, 802.11.bd, 802.11be, and 802. lip). These standards define the WLAN radio and baseband protocols for the PHY and medium access control (MAC) layers. The APs 102 and STAs 104 transmit and receive wireless communications (hereinafter also referred to as “Wi-Fi communications”) to and from one another in the form of PHY protocol data units (PPDUs) (or physical layer convergence protocol (PLCP) PDUs). The APs 102 and STAs 104 in the WLAN 100 may transmit PPDUs over an unlicensed spectrum, which may be a portion of spectrum that includes frequency bands traditionally used by Wi-Fi technology, such as the 2.4 GHz band, the 5 GHz band, the 60 GHz band, the 3.6 GHz band, and the 900 MHz band. Some implementations of the APs 102 and STAs 104 described herein also may communicate in other frequency bands, such as the 6 GHz band, which may support both licensed and unlicensed communications. The APs 102 and STAs 104 also can be configured to communicate over other frequency bands such as shared licensed frequency bands, where multiple operators may have a license to operate in the same or overlapping frequency band or bands.

[0043] Each of the frequency bands may include multiple sub-bands or frequency channels.

For example, PPDUs conforming to the IEEE 802.11h, 802.11ac, 802.11ax and 802.11be standard amendments may be transmitted over the 2.4, 5 GHz or 6 GHz bands, each of which is divided into multiple 20 MHz channels. As such, these PPDUs are transmitted over a physical channel having a minimum bandwidth of 20 MHz, but larger channels can be formed through channel bonding. For example, PPDUs may be transmitted over physical channels having bandwidths of 40 MHz, 80 MHz, 160 MHz, or 320 MHz by bonding together multiple 20 MHz channels. As another example, physical channels may be designated as 10 MHz channels, such as by an ITS wireless communication standard specification.

[0044] Each PPDU is a composite structure that includes a PHY preamble and a payload in the form of a PHY service data unit (PSDU). The information provided in the preamble may be used by a receiving device to decode the subsequent data in the PSDU. In instances in which PPDUs are transmitted over a bonded channel, the preamble fields may be duplicated and transmitted in each of the multiple component channels. The PHY preamble may include both a legacy portion (or “legacy preamble”) and a non-legacy portion (or “non-legacy preamble”). The legacy preamble may be used for packet detection, automatic gain control and channel estimation, among other uses. The legacy preamble also may generally be used to maintain compatibility with legacy devices. The format of, coding of, and information provided in the non-legacy portion of the preamble is based on the particular IEEE 802.11 protocol to be used to transmit the payload.

[0045] FIG. 2A illustrates an example protocol data unit (PDU) 200 usable for wireless communication between an AP 102 and one or more STAs 104. For example, the PDU 200 can be configured as a PPDU. As shown, the PDU 200 includes a PHY preamble 202 and a PHY payload 204. For example, the preamble 202 may include a legacy portion that itself includes a legacy short training field (L-STF) 206, which may consist of two BPSK symbols, a legacy long training field (L-LTF) 208, which may consist of two BPSK symbols, and a legacy signal field (L-SIG) 210, which may consist of two BPSK symbols. The legacy portion of the preamble 202 may be configured according to the IEEE 802.11a wireless communication protocol standard. The preamble 202 may also include a non-legacy portion including one or more non-legacy fields 212, for example, conforming to an IEEE wireless communication protocol such as the IEEE 802.1 lac, 802.1 lax, 802.11be or later wireless communication protocol protocols.

[0046] The L-STF 206 generally enables a receiving device to perform automatic gain control (AGC) and coarse timing and frequency estimation. The L-LTF 208 generally enables a receiving device to perform fine timing and frequency estimation and also to perform an initial estimate of the wireless channel. The L-SIG 210 generally enables a receiving device to determine a duration of the PDU and to use the determined duration to avoid transmitting on top of the PDU. For example, the L-STF 206, the L-LTF 208 and the L-SIG 210 may be modulated according to a binary phase shift keying (BPSK) modulation scheme. The payload 204 may be modulated according to a BPSK modulation scheme, a quadrature BPSK (Q-BPSK) modulation scheme, a quadrature amplitude modulation (QAM) modulation scheme, or another appropriate modulation scheme. The payload 204 may include a PSDU including a data field (DATA) 214 that, in turn, may carry higher layer data, for example, in the form of medium access control (MAC) protocol data units (MPDUs) or an aggregated MPDU (A-MPDU).

[0047] FIG. 2B illustrates an example L-SIG 210 in the PDU 200 of FIG. 2A. The L-SIG

210 includes a data rate field 222, a reserved bit 224, a length field 226, a parity bit 228, and a tail field 230. The data rate field 222 indicates a data rate (note that the data rate indicated in the data rate field 212 may not be the actual data rate of the data carried in the payload 204). The length field 226 indicates a length of the packet in units of, for example, symbols or bytes. The parity bit 228 may be used to detect bit errors. The tail field 230 includes tail bits that may be used by the receiving device to terminate operation of a decoder (for example, a Viterbi decoder). The receiving device may utilize the data rate and the length indicated in the data rate field 222 and the length field 226 to determine a duration of the packet in units of, for example, microseconds (ps) or other time units.

[0048] FIG. 3A illustrates an example PPDU 300 usable for wireless communication between an AP and one or more STAs. The PPDU 300 may be used for SU, OFDMA or MU-MIMO transmissions. The PPDU 300 may be formatted as a High Efficiency (HE) WLAN PPDU in accordance with the IEEE 802.1 lax amendment to the IEEE 802.11 wireless communication protocol standard. The PPDU 300 includes a PHY preamble including a legacy portion 302 and a non-legacy portion 304. The PPDU 300 may further include a PHY payload 306 after the preamble, for example, in the form of a PSDU including a data field 324. [0049] The legacy portion 302 of the preamble includes an L-STF 308, an L-LTF 310, and an

L-SIG 312. The non-legacy portion 304 includes a repetition of L-SIG (RL-SIG) 314, a first HE signal field (HE-SIG-A) 316, an HE short training field (HE-STF) 320, and one or more HE long training fields (or symbols) (HE-LTFs) 322. For OFDMA or MU-MIMO communications, the second portion 304 further includes a second HE signal field (HE-SIG- B) 318 encoded separately from HE-SIG-A 316. Like the L-STF 308, L-LTF 310, and L-SIG 312, the information in RL-SIG 314 and HE-SIG-A 316 may be duplicated and transmitted in each of the component 20 MHz channels in instances involving the use of a bonded channel. In contrast, the content in HE-SIG-B 318 may be unique to each 20 MHz channel and target specific STAs 104.

[0050] RL-SIG 314 may indicate to HE-compatible STAs 104 that the PPDU 300 is an HE

PPDU. An AP 102 may use HE-SIG-A 316 to identify and inform multiple STAs 104 that the AP has scheduled EL or DL resources for them. For example, HE-SIG-A 316 may include a resource allocation subfield that indicates resource allocations for the identified STAs 104. HE-SIG-A 316 may be decoded by each HE-compatible STA 104 served by the AP 102. For MU transmissions, HE-SIG-A 316 further includes information usable by each identified STA 104 to decode an associated HE-SIG-B 318. For example, HE-SIG-A 316 may indicate the frame format, including locations and lengths of HE-SIG-Bs 318, available channel bandwidths and modulation and coding schemes (MCSs), among other examples. HE-SIG-A 316 also may include HE WLAN signaling information usable by STAs 104 other than the identified STAs 104.

[0051] HE-SIG-B 318 may carry STA-specific scheduling information such as, for example,

STA-specific (or “user-specific”) MCS values and STA-specific RU allocation information. In the context of DL MU-OFDMA, such information enables the respective STAs 104 to identify and decode corresponding resource units (RUs) in the associated data field 324. Each HE-SIG-B 318 includes a common field and at least one STA-specific field. The common field can indicate RU allocations to multiple STAs 104 including RU assignments in the frequency domain, indicate which RUs are allocated for MU-MIMO transmissions and which RUs correspond to MU-OFDMA transmissions, and the number of users in allocations, among other examples. The common field may be encoded with common bits, CRC bits, and tail bits. The user-specific fields are assigned to particular STAs 104 and may be used to schedule specific RUs and to indicate the scheduling to other WLAN devices. Each user-specific field may include multiple user block fields. Each user block field may include two user fields that contain information for two respective STAs to decode their respective RU payloads in data field 324.

[0052] FIG. 3B illustrates another example PPDU 350 usable for wireless communication between an AP and one or more STAs. The PPDU 350 may be used for SU, OFDMA or MU-MIMO transmissions. The PPDU 350 may be formatted as an Extreme High Throughput (EHT) WLAN PPDU in accordance with the IEEE 802.1 lbe amendment to the IEEE 802.11 wireless communication protocol standard, or may be formatted as a PPDU conforming to any later (post-EHT) version of a new wireless communication protocol conforming to a future IEEE 802.11 wireless communication protocol standard or other wireless communication standard. The PPDU 350 includes a PHY preamble including a legacy portion 352 and a non-legacy portion 354. The PPDU 350 may further include a PHY payload 356 after the preamble, for example, in the form of a PSDU including a data field 374.

[0053] The legacy portion 352 of the preamble includes an L-STF 358, an L-LTF 360, and an

L-SIG 362. The non-legacy portion 354 of the preamble includes an RL-SIG 364 and multiple wireless communication protocol version-dependent signal fields after RL-SIG 364. For example, the non-legacy portion 354 may include a universal signal field 366 (referred to herein as “U-SIG 366”) and an EHT signal field 368 (referred to herein as “EHT-SIG 368”). One or both of U-SIG 366 and EHT-SIG 368 may be structured as, and carry version- dependent information for, other wireless communication protocol versions beyond EHT. The non-legacy portion 354 further includes an additional short training field 370 (referred to herein as “EHT-STF 370,” although it may be structured as, and carry version-dependent information for, other wireless communication protocol versions beyond EHT) and one or more additional long training fields 372 (referred to herein as “EHT-LTFs 372,” although they may be structured as, and carry version-dependent information for, other wireless communication protocol versions beyond EHT). Like L-STF 358, L-LTF 360, and L-SIG 362, the information in U-SIG 366 and EHT-SIG 368 may be duplicated and transmitted in each of the component 20 MHz channels in instances involving the use of a bonded channel. In some implementations, EHT-SIG 368 may additionally or alternatively carry information in one or more non-primary 20 MHz channels that is different than the information carried in the primary 20 MHz channel.

[0054] EHT-SIG 368 may include one or more jointly encoded symbols and may be encoded in a different block from the block in which U-SIG 366 is encoded. EHT-SIG 368 may be used by an AP to identify and inform multiple STAs 104 that the AP has scheduled UL or DL resources for them. EHT-SIG 368 may be decoded by each compatible STA 104 served by the AP 102. EHT-SIG 368 may generally be used by a receiving device to interpret bits in the data field 374. For example, EHT-SIG 368 may include RU allocation information, spatial stream configuration information, and per-user signaling information such as MCSs, among other examples. EHT-SIG 368 may further include a cyclic redundancy check (CRC) (for example, four bits) and a tail (for example, 6 bits) that may be used for binary convolutional code (BCC). In some implementations, EHT-SIG 368 may include one or more code blocks that each include a CRC and a tail. In some aspects, each of the code blocks may be encoded separately.

[0055] EHT-SIG 368 may carry STA-specific scheduling information such as, for example, user-specific MCS values and user-specific RU allocation information. EHT-SIG 368 may generally be used by a receiving device to interpret bits in the data field 374. In the context of DL MU-OFDMA, such information enables the respective STAs 104 to identify and decode corresponding RUs in the associated data field 374. Each EHT-SIG 368 may include a common field and at least one user-specific field. The common field can indicate RU distributions to multiple STAs 104, indicate the RU assignments in the frequency domain, indicate which RUs are allocated for MU-MIMO transmissions and which RUs correspond to MU-OFDMA transmissions, and the number of users in allocations, among other examples. The common field may be encoded with common bits, CRC bits, and tail bits. The user- specific fields are assigned to particular STAs 104 and may be used to schedule specific RUs and to indicate the scheduling to other WLAN devices. Each user-specific field may include multiple user block fields. Each user block field may include, for example, two user fields that contain information for two respective STAs to decode their respective RU payloads.

[0056] The presence of RL-SIG 364 and U-SIG 366 may indicate to EHT- or later version- compliant STAs 104 that the PPDU 350 is an EHT PPDU or a PPDU conforming to any later (post-EHT) version of a new wireless communication protocol conforming to a future IEEE 802.11 wireless communication protocol standard. For example, U-SIG 366 may be used by a receiving device to interpret bits in one or more of EHT-SIG 368 or the data field 374.

[0057] FIG. 3C illustrates an example signal field 380 that may be carried in a WLAN

PPDU. In implementations for which the signal field 380 is carried in an HE PPDU, the signal field 380 may be, or may correspond to, a HE-SIG-A field (such as the HE-SIG-A field 316 of the PPDU 300 of FIG. 3A). In implementations for which the signal field 380 is carried in an EHT PPDU, the signal field 380 may be, or may correspond to, an EHT-SIG field (such as the EHT-SIG field 368 of the PPDU 350 of FIG. 3B). The signal field 380 may include an UL/DL subfield 382 indicating whether the PPDU 300 is sent UL or DL, may include a SIGB-MCS subfield 384 indicating the MCS for the HE-SIG-B 318, and may include a SIGB DCM subfield 386 indicating whether or not the HE-SIG-B 318 is modulated with dual carrier modulation (DCM). The signal field 380 may further include a BSS color field 388 indicating a BSS color identifying the BSS. Each device in a BSS may identify itself with the same BSS color. Thus, receiving a transmission having a different BSS color indicates the transmission is from another BSS, such as an OBSS.

[0058] The signal field 380 may further include a spatial reuse subfield 390 indicating whether spatial reuse is allowed during transmission of the corresponding PPDU. The signal field 380 may further include a bandwidth subfield 392 indicating a bandwidth of the PPDU data field, such as 20 MHz, 40 MHz, 80 MHz, 160 MHz, and so on. The signal field 380 may further include a number of HE-SIG-B symbols or MU-MIMO users subfield 394 indicating either a number of OFDM symbols in the HE-SIG-B 318 or a number of MU- MIMO users. The signal field 380 may further include a SIGB compression subfield 396 indicating whether or not a common signaling field is present, may include a GI+LTF size subfield 398 indicating the guard interval (GI) duration and the size of the non-legacy LTFs. The signal field 380 may further include a doppler subfield 399 indicating whether a number of OFDM symbols in the PPDU data field is larger than a signaled midamble periodicity plus one, and the midamble is present, or that the number of OFDM symbols in the PPDU data field is less than or equal to the signaled midamble periodicity plus 1, that the midamble is not present, but that the channel is fast varying.

[0059] FIG. 4 illustrates an example of superframes 400 according to some aspects. To support wireless communications via a wireless communication channel, time may be partitioned into fixed size “superframes,” such as illustrative superframes 400. To support operation of two or more wireless communication technologies over the same band, also referred to as co-channel co-existence, superframes may be further partitioned into multiple different “technology slots” (e.g., time periods within the superframes). Devices configured to communicate according to a certain wireless communication technology can operate (e.g., perform transmissions) only with the slots allocated (e.g., dedicated) to this wireless communication technology.

[0060] In at least some implementations, time partitioning may be configured to support communications of two different wireless communication technologies using the same wireless communication channel. In such implementations, superframes may be partitioned into two different slots. For example, superframes 400 include a first superframe that includes a first slot 402 allocated to a first wireless communication technology (“Technology A”) and a second slot 404 allocated to a second wireless communication technology (“Technology B”), a second superframe that includes two different technology slots, and a third superframe that includes two different technology slots. Each superframe has a superframe duration T_Sf, each slot allocated to Technology A has a slot duration T_a, and each slot allocated to Technology B has a slot duration Tb. Each slot may be separated by a slot boundary, such as illustrative slot boundary 406 between slots of the second superframe, and each superframe may be separated by a superframe boundary, such as illustrative superframe boundary 408 between the second and third superframes. Although IEEE 802.11 configured wireless devices are not typically synchronized, in some implementations wireless devices may be synchronized to a common clock or other external reference signal, such as a global positioning system (GPS) signal or a global navigation satellite system (GNSS) signal, in order to support the time partitioning of slots and superframes, as described herein.

[0061] The superframe duration T_Sf, the slot duration T_a, and the slot duration Tb are fixed, such as by being preprogrammed or otherwise communicated to wireless communication devices, but are otherwise arbitrary. For example, the durations may be dictated by considerations such as load expected to be served by each technology. Typically, superframe duration T_Sf is selected to be smaller than a maximum packet delay budget for all supported wireless communication technologies. This allows data packets corresponding to Technology A that are not generated within a Technology A slot to be safely buffered and transmitted within one of the following Technology A slots (and similarly for Technology B data packets generated during a Technology A slot). In some implementations, Technology A slots and Technology B slots have the same size (e.g., slot duration T_a is the same as slot duration Tb). In some other implementations, Technology A slots have a different size than Technology B slots (e.g., slot duration T_a is different than slot duration Tb).

[0062] FIG. 5 illustrates examples 500 of initiating backoff times according to some aspects.

The backoff times may be initiated by a wireless communication device, such as AP 102 or STA 104 of FIG. 1. Wireless communication devices configured to communicate using a first wireless communication technology, such as a WLAN-based communication technology, may perform an LBT procedure in response to detecting that a wireless communication channel is idle (e.g., based on failing to detect a threshold energy level on the wireless communication channel) when a data packet is ready to be transmitted. By performing the LBT procedure, channel access may be fairly distributed to multiple wireless communication devices of a wireless communication network. Typically, the LBT procedure includes clear channel assessment (CCA), a random backoff, and transmission of a data packet. The CCA includes waiting for a duration of an arbitrary interframe space (AIFS) after detecting that the wireless communication channel is idle. The duration of the AIFS is typically greater than 50 microseconds (ps). For example, in at least some IEEE 802.11 wireless communication standard specifications, the AIFS may be 58, 71, 110, or 149 ps, depending on an access category (AC) (e.g., packet priority) of the data packet to be communicated. The random backoff time may be chosen by selecting a random number of backoff slots within a lower bound and an upper bound associated with the LBT procedure. Each backoff slot typically has a duration of approximately 10 ps, such as 13 ps in the IEEE 802. l ip wireless communication standard specification. Higher priority wireless communication devices may wait for a shorter duration (e.g., a duration of a shorter AIFS based on the AC/packet priority) and/or use a shorter backoff time (e.g., based on backoff slots with shorter durations, decreasing the lower bound and/or the upper bound, or a combination thereof). When the wireless communication channel is idle and the above procedure is completed without the wireless communication channel being sensed as busy (e.g., a transmission by another wireless communication device occurs) during the duration of the procedure, the wireless communication device transmits the data packet via the wireless communication channel. If, during the procedure, the wireless communication channel is sensed as busy, the procedure “freezes” (e.g., is paused) until the wireless communication channel is sensed as idle. Each time the procedure is interrupted (e.g., due to interference on the wireless communication channel), a CCA of an AIFS duration is performed after the wireless communication channel is sensed as idle before continuing the procedure (e.g., counting down the random backoff time from the time the random backoff was frozen). Although the CCA and the backoff time are individual steps of the LBT procedure, the terms LBT procedure, CCA, and backoff time may be used interchangeably herein for ease of explanation.

[0063] The examples 500 include a first example 502 of performing an LBT procedure. First example 502 corresponds to a wireless communication device completing the LBT procedure while the wireless communication channel remains idle. For example, if an arrival of a data packet for transmission is detected at reference number 504 and the wireless communication channel is idle, the wireless communication device may wait for a duration of an AIFS before initiating a random backoff time (as indicated by a four unit backoff time). Although four backoff slots are shown, in other implementations, fewer than four or more than four backoff slots may be selected according to parameters of the LBT procedure. If the wireless communication channel remains idle for the duration of the AIFS and the random backoff time, the wireless communication device transmits the data packet via the wireless communication channel at reference number 506.

[0064] The examples 500 also include a second example 510 of performing an LBT procedure. Second example 510 corresponds to the wireless communication channel entering a busy state and interrupting the LBT procedure by the wireless communication device. For example, if an arrival of a data packet for transmission is detected at reference number 512 and the wireless communication channel is idle, the wireless communication device may begin the LBT procedure by waiting for a duration of an AIFS and a random backoff time. Because a first backoff slot (designated “3”) of the backoff time in second example 510 does not expire before interference is detected on the wireless communication channel (e.g., the wireless communication channel is in a busy state), the wireless communication device freezes the backoff time during the busy state. After the wireless communication channel becomes idle (e.g., no other wireless communication device is transmitting via the wireless communication channel), the wireless communication device may wait for a duration of an AIFS before resuming the backoff countdown at the next backoff slot (e.g., for the remaining three backoff slots). If the wireless communication channel remains idle during the remainder of the random backoff time, the wireless communication device may transmit the data packet via the wireless communication channel, at reference number 514.

[0065] The examples 500 also include a third example 520 of performing an LBT procedure.

Third example 520 corresponds to detecting arrival of a data packet for transmission at the wireless communication device while the wireless communication channel is in a busy state. For example, if an arrival of a data packet for transmission is detected at reference number 522 and the wireless communication channel is in a busy state (e.g., interference satisfying a threshold is detected on the wireless communication channel), the wireless communication device may freeze the LBT procedure until the wireless communication channel becomes idle. After the wireless communication channel is detected to be idle, the wireless communication device may wait for a duration of an AIFS before initiating a random backoff time that includes four backoff slots, similar to the examples 502 and 510. If the wireless communication channel remains idle for the duration of the AIFS and the random backoff time, the wireless communication device may transmit the data packet via the wireless communication channel, at reference number 524.

[0066] Aspects of the present disclosure support co-channel existence between multiple wireless communication technologies, including at least a first wireless communication technology and a second wireless communication technology. The first wireless communication technology may be WLAN-based (e.g., contention-based), and the second wireless communication technology may be TDMA-based. To support the co-channel existence, superframes may be partitioned into slots allocated to the first wireless communication technology and slots allocated to the second wireless communication technology. Wireless communication devices configured to communicate according to the second wireless communication technology may support such division of superframes into allocated slots due to the use of TDMA underlying the second wireless communication technology. To support the division of superframes into multiple slots, wireless communication devices configured to communicate according to the first wireless communication technology may be configured to “assume” (e.g., sense) an artificial busy state of a wireless communication channel during slots allocated to the second wireless communication technology. In this manner, wireless communication devices configured to communicate according to the first wireless communication technology will not contend for access to the wireless communication channel during slots allocated to the second wireless communication technology while still contending for access during slots allocated to the first wireless communication technology.

[0067] FIG. 6 illustrates examples of transmitting data packets according to some aspects.

The data packets may be transmitted by one or more wireless communication devices, such as AP 102 or STA 104 of FIG. 1, that are configured to communicate according to a first wireless communication technology (e.g., a WLAN-based communication technology) over a wireless communication channel that supports co-channel existence between the first wireless communication technology and a second wireless communication technology (e.g., a TDMA- based communication technology).

[0068] FIG. 6 illustrates packet arrival times 600, LBT initiation times 610, and packet transmission times 620 during multiple slots allocated to different wireless communication technologies. To illustrate the packet arrival times 600, the one or more wireless communication devices may detect arrival of data packets for transmission via the first wireless communication technology at various times (as represented by the hatched arrows in FIG. 6) during a slot allocated to the second wireless communication technology (e.g., the “second technology slot”) and at various times (as represented by the empty arrows in FIG. 6) during a slot allocated to the first wireless communication technology (e.g., the “first technology slot”). [0069] After receipt of a respective data packet at the one or more wireless communication devices, an LBT procedure corresponding to each received data packet may be initiated by the one or more wireless communication devices during the first technology slot. The LBT procedures for the data packets arriving during the first technology slot may be initiated as the data packets arrive (e.g., upon detection by at least some of the one or more wireless communication devices). However, wireless communication devices that detect arrival of data packets during the second technology slot may wait to initiate the LBT procedures for these data packets until the beginning of the first technology slot, as indicated by the alignment of the hatched arrows at the beginning of the first technology slot in the LBT initiation times 610.

[0070] The packet transmission times 620 represent transmission of the data packets at the expiration of the respective LBT procedures initiated by the one or more wireless communication devices. Packet transmission times 620 are shifted to the right and spread out as compared to LBT initiation times 610 due to the one or more wireless communication devices waiting for the duration of an AIFS and a random backoff time to expire between initiation of the LBT procedures and transmission of the data packets. However, because the LBT procedures for the data packets received during the second technology slot are all initiated at the beginning of the first technology slot, data transmissions may occur in bursts (e.g., multiple transmissions at the same or similar times) early on in the first technology slot due to congestion on the wireless channel, with transmissions becoming more spread out toward the end of the first technology slot as the congestion decreases. Such early transmission bursts may cause collisions between data packets and result in packet loss at receiving devices, which decreases a packet reception rate at the receiving devices configured to communicate according to the first wireless communication technology. The decreased packet reception rates may result in degraded performance and/or increased latency associated with the first wireless communication technology.

[0071] The present disclosure provides systems, apparatus, methods, and computer-readable media for enabling a wireless communication system to support a contention-based communication scheme and a TDMA communication scheme via the same wireless channel. To illustrate, time resources for a wireless communication channel (e.g., a wireless medium) may be partitioned in time and allocated to two different communication technologies. For example, a first set of slots (e.g., time periods) may be allocated to contention-based communications (e.g., a first communication technology), and a second set of slots may be allocated to TDMA communications (e.g., a second communication technology), such as allocating one or more slots of a superframe (e g., a particular time period) as the first set of slots, and one or more other slots of the superframe as the second set of slots. In some implementations, the first communication technology may be a WLAN (e.g., “Wi-Fi”) protocol described by or based on one or more IEEE 802.11 wireless communication standard specifications, and the second communication technology may be a communication technology described by one or more 3GPP wireless communication standard specifications. To illustrate, the first wireless communication technology may include ITS-G5 or DSRC, and the second wireless communication technology may include LTE-V2X, as non-limiting examples. The techniques described herein may enable wireless communication devices configured to communicate via the first wireless communication technology (e.g., the WLAN-based technology) to more efficiently use the slots allocated to the first wireless communication technology.

[0072] To illustrate, a wireless communication device (e.g., a STA) configured to communicate using the first wireless communication technology may detect arrival of a data packet to be transmitted via a wireless communication channel. For example, a data packet may be added to a transmission buffer of the wireless communication device, an indication may be provided from an application executed by the wireless communication device, or the arrival may be detected in some other manner. After detecting the arrival of the data packet, the wireless communication device may sense the wireless communication channel to determine if the wireless communication channel is busy (e.g., occupied). To enable allocation of one or more slots to TDMA communications (e.g., co-existence with TDMA communications), the wireless device may be configured to sense the wireless communication channel as being in a busy state during the one or more slots allocated to the TDMA communications regardless of whether a communication is detected on the wireless channel. For example, the wireless communication device may be preconfigured with or receive an indication from an AP that indicates one or more slots allocated to the first wireless communication technology (e.g., the TDMA communications or any other wireless communications during which transmission of the data packet is forbidden), and the wireless communication device may be configured to sense the wireless communication channel as busy during the one or more slots indicated by the AP. Because this busy state is not based on detection of a communication via another wireless communication device (e.g., based on an LBT procedure), the busy state may be referred to as an “artificial busy state.”

[0073] After sensing the busy state, the wireless communication device may determine that the busy state corresponds to an artificial busy state (e.g., based on a determination that a current slot is included in the one or more slots allocated to the second wireless communication technology). Based on the determination, the wireless communication device may initiate a backoff time based on detection of the wireless communication channel becoming idle after the artificial busy state. For example, when the wireless communication device next detects that the wireless communication channel is idle (e.g., not in the busy state), the wireless communication device initiates a backoff time. Based on the determination that the busy state corresponds to the artificial busy state, the backoff time is initiated without waiting for a duration of an AIFS after detection of the wireless communication channel as idle, as would otherwise occur if the busy time did not correspond to the artificial busy time. The backoff time may be a random backoff time, as in accordance with a CCA or LBT procedure at the wireless communication device. After expiration of the backoff time, the wireless communication device transmits the data packet via the wireless communication channel if the wireless communication channel is still idle.

[0074] In some implementations, the wireless communication device may delay initiation of the backoff time, or transmission of the data packet if no backoff procedure is performed, based on a determination that the busy state corresponds to the artificial busy state. For example, the wireless communication device may assign a delay interval to initiation of a backoff time for a received data packet based on a determination that the arrival of the data packet is during the artificial busy state (e.g., during a slot allocated to TDMA communications via the wireless communication channel). In some implementations in which a slot duration of slots allocated to the first wireless communication technology is the same as a slot duration of slots allocated to the second wireless communication technology, the delay interval may be equal to the slot duration. In some other implementations in which a first slot duration of slots allocated to the first wireless communication technology is different than a second slot duration of slots allocated to the second wireless communication technology, the delay interval may be determined based on the first slot duration, the second slot duration, and a position of the arrival of the data packet during the second slot. Delaying initiation of the backoff time for data packets that arrive during the artificial busy state may more evenly spread out transmission of data packets during a slot allocated to the first wireless communication technology, which may reduce collisions between messages transmitted via the wireless communication channel and improve latency of communications by the wireless communication device.

[0075] Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. In some aspects, the present disclosure provides techniques for improving efficiency of usage of slots by wireless communication devices configured to operate according to the first wireless communication technology. To illustrate, instead of waiting a duration of an AIFS after reaching the end of a slot allocated to the second wireless communication technology (during which the wireless communication channel is sensed as being in an artificially busy state), the wireless communication device immediately initiates the backoff time. By not waiting for the AIFS before initiating the backoff time, more of a subsequent slot allocated to the first wireless communication technology may be used for communications, which improves efficiency of use of the slot, and may reduce latency and collisions associated with communications in accordance with the first wireless communication technology. Additionally or alternatively, delaying the initiation of a backoff operation, or delaying the initiation of data packet transmission without performing a backoff operation, for data packets that arrive during a slot allocated to the second wireless communication technology (e.g., a TDMA slot or any slot during which transmission of the data packet is forbidden) may further reduce collisions associated with communications performed via the wireless communication channel and in accordance with the first wireless communication technology while supporting co-existence between the first wireless communication technology and the second wireless communication technology.

[0076] FIG. 7 is a block diagram of an example wireless communications system 700 for supporting a contention-based communication scheme (e.g., a first wireless communication technology) and a TDMA communication scheme (e.g., a second wireless communication technology) according to some aspects of the present disclosure. Wireless communications system 700 includes a wireless communication device 702 (also referred to as a STA) and an AP 750. In some implementations, wireless communication device 702 may include or correspond to STA 104 of FIG. 1 and AP 750 may include or correspond to AP 102 of FIG. 1. In some implementations, AP 750 may include or correspond to a network entity, such as a base station, a network, a network core, or another network device, as illustrative, non limiting examples. Although one wireless communication device 702 and one AP 750 are illustrated, in some other implementations, wireless communications system 700 may generally include multiple wireless communication devices 702, and may include more than one AP 750.

[0077] Wireless communication device 702 can include a variety of components (such as structural, hardware components) used for carrying out one or more functions described herein. For example, these components can include a processor 704, a memory 706, a backoff timer 714, a transmitter 716, and a receiver 718. Processor 704 may be configured to execute instructions stored at memory 706 to perform the operations described herein.

[0078] In some implementations, memory 706 may be configured to store slot duration 708, delay interval 710, superframe parameters 712, or a combination thereof. Slot duration 708 may include a duration of a slot allocated to the second wireless communication technology (e.g., TDMA communications). Delay interval 710 may include a delay interval for delaying initiation of a backoff time, as further described herein. Superframe parameters 712 may include parameters, such as a starting time and a duration, of a superframe that includes a first slot allocated to the first wireless communication technology and a second slot allocated to the second wireless communication technology.

[0079] Backoff timer 714 may include a timer configured to track a backoff time, such as a time prior to transmission of a data packet by wireless communication device 702. Backoff timer 714 may be initiated after detecting the data packet and if a wireless communication channel is idle, as part of performance of an LBT procedure.

[0080] Transmitter 716 is configured to transmit reference signals, control information, and data to one or more other devices, and receiver 718 is configured to receive reference signals, synchronization signals, control information, and data from one or more other devices. For example, transmitter 716 may transmit signaling, control information, and data, and receiver 718 may receive signaling, control information, and data, via a network, such as a wired network, a wireless network, or a combination thereof. For example, wireless communication device 702 may be configured to transmit or receive signaling, control information, and data via a direct device-to-device connection, a local area network (LAN), a wide area network (WAN), a modem-to-modem connection, the Internet, intranet, extranet, cable transmission system, cellular communication network, any combination of the above, or any other communications network now known or later developed within which permits two or more electronic devices to communicate. In some implementations, transmitter 716 and receiver 718 may be integrated in a transceiver.

[0081] AP 750 can include a variety of components (such as structural, hardware components) used for carrying out one or more functions described herein. For example, these components can include a processor 752, a memory 754, a transmitter 756, and a receiver 758. Processor 752 may be configured to execute instructions stored at memory 754 to perform the operations described herein.

[0082] Transmitter 756 is configured to transmit reference signals, synchronization signals, control information, and data to one or more other devices, and receiver 758 is configured to receive reference signals, control information, and data from one or more other devices. For example, transmitter 756 may transmit signaling, control information, and data, and receiver 758 may receive signaling, control information, and data, via a network, such as a wired network, a wireless network, or a combination thereof. For example, AP 750 may be configured to transmit or receive data via a direct device-to-device connection, a LAN, a WAN, a modem-to-modem connection, the Internet, intranet, extranet, cable transmission system, cellular communication network, any combination of the above, or any other communications network now known or later developed within which permits two or more electronic devices to communicate. In some implementations, transmitter 756 and receiver 758 may be integrated in a transceiver.

[0083] In some implementations, the first wireless communication technology may be defined by a WLAN (e.g., “Wi-Fi”) protocol described by one or more IEEE 802.11 wireless communication standard specifications, and the second wireless communication technology may be defined by one or more 3 GPP wireless communication standard specifications, such as a fourth generation (4G) standard specification or a fifth generation (5G) new radio (NR) standard specification, as non-limiting examples. In some implementations, the second wireless communication technology may include long-term evolution (LTE) vehicle-to- everything (V2X) (LTE-V2X), and the first wireless communication technology may include Intelligent Transport System (ITS) G5 (ITS-G5) or Dedicated Short Range Communication (DSRC), as non-limiting examples. Although described with reference to a TDMA-based technology and a WLAN-based technology, in other implementations, different slots may be allocated to two WLAN-based communication technologies, or to a single WLAN-based communication technology that communicates a control channel (e.g., a first message type) during one set of slots and a data channel (e.g., a second message type) during another set of slots, such as an IEEE 1609.4 communication protocol, as a non-limiting example.

[0084] During operation of the wireless communications system 700, different slots may be allocated to the first wireless communication technology and to the second wireless communication technology. For example, a superframe may include a first slot allocated to the first wireless communication technology for use at a wireless communication channel and a second slot allocated to the second wireless communication technology for use at the wireless communication channel. Other superframes may be similarly partitioned. During slots allocated to the first wireless communication technology, transmissions according to the second wireless communication technology may be forbidden, and during slots allocated to the second wireless communication technology, transmissions according to the first wireless communication technology may be forbidden. To enable partitioning of time slots between multiple wireless communication devices, wireless communication device 702, AP 750, and other devices may be synchronized to a common clock or other external signal, such as a GPS or GNSS signal, as non-limiting examples.

[0085] To indicate the allocation to wireless communication device 702, AP 750 may transmit an indication 770 to wireless communication device 702. Indication 770 may indicate a first set of slots 772 allocated to non-TDMA communications (e.g., the first wireless communication technology) and a second set of slots 774 allocated to TDMA communications (e.g., the second wireless communication technology). Wireless communication device 702 may use the information indicated by indication 770 in determining when to initiate backoff timer 714. Although indication of the allocation of slots to the first wireless communication technology and the second wireless communication technology is described as being transmitted by AP 750, in some other implementations, wireless communication device 702 determines the allocation of first set of slots 772 and second set of slots 774 on its own. For example, wireless communication device 702 may determine timing and duration of first set of slots 772 and second set of slots 774 based on measurements of a wireless communication channel (e.g., a wireless medium) used to communicate with AP 750. The measurements may indicate communications by other wireless devices in accordance with the first wireless communication technology and communications by other wireless devices in accordance with the second wireless communication technology, such that in some implementations, the allocation of slots is based on a proportion of communications performed during a particular time period and in accordance with each wireless communication technology to a total number of communications performed via the wireless communication channel.

[0086] After receiving indication 770 (or determining the allocation of the slots), wireless communication device 702 may detect arrival of data packet 776 for transmission to AP 750. For example, data packet 776 may be added to a transmission buffer of wireless communication device 702, an indication may be provided from an application executed by wireless communication device 702, or the arrival may be detected in some other manner. After detecting the arrival of data packet 776, wireless communication device 702 may sense a wireless communication channel (e.g., a wireless medium) to determine if the wireless communication channel is associated with a busy state (e.g., is occupied). For example, wireless communication device 702 may perform a CCA based on the wireless communication channel. The wireless communication channel may be busy if another wireless communication device is communicating with AP 750 via the first wireless communication technology. Additionally, to support co-existence of the second wireless communication technology (e.g., the TDMA communications) with the first wireless communication technology, wireless communication device 702 may be configured to sense that the wireless communication channel is busy during slots allocated to the second wireless communication technology (e g., second set of slots 774). This may be referred to as an “artificial busy state,” because the busy state is not detected based on energy sensed on the wireless communication channel (e g., the artificial busy state is detected for an entirety of a second technology slot regardless of whether any transmissions are being performed via the wireless communication channel at a time of measuring).

[0087] After sensing the busy state, wireless communication device 702 may determine whether the busy state corresponds to the artificial busy state. For example, wireless communication device 702 may determine whether a current slot (e.g., a slot during which the arrival of data packet 776 is detected) is included in second set of slots 774. If the busy state corresponds to the artificial busy state (e.g., if the arrival of the data packet 776 is detected during a TDMA slot or any slot during which transmission of data packet 776 is forbidden), wireless communication device 702 may perform an LBT procedure and initiate a backoff time based on detection of the wireless communication channel being idle. For example, upon detection of the wireless communication channel becoming idle, wireless communication device 702 may initiate backoff timer 714.

[0088] Unlike the LBT procedures described with reference to FIG. 5, in initiating backoff timer 714, wireless communication device 702 does not wait for a duration of an arbitrary interframe space (AIFS) before initiating backoff timer 714. For example, the LBT procedure performed by wireless communication device 702 may omit or eliminate the AIFS. Because the busy state corresponds to the artificial busy state, there is no concern that another communication was being performed in accordance with the first wireless communication technology. Accordingly, waiting for the duration of the AIFS in this situation leads to inefficient use of the slot allocated to the first wireless communication technology. For at least this reason, wireless communication device 702 may omit or eliminate the AIFS that would otherwise be included between the time that the wireless communication channel becomes idle (e.g., the beginning of one of the first set of slots 772) and the time of initiation of the backoff time (e.g., initiation of backoff timer 714).

[0089] In some implementations, the backoff time is a random backoff time. For example, a duration of backoff timer 714 may be set to a randomly generated value between a lower bound and an upper bound associated with a the LBT procedure performed by wireless communication device 702. In this manner, different wireless communication devices communicating in accordance with the first wireless communication technology may be able to access the wireless communication channel based on different random value selections.

[0090] Alternatively, wireless communication device 702 may determine that the busy state does not correspond to the artificial busy state. For example, wireless communication device 702 may sense, during one of first set of slots 772, a level of energy on the wireless communication channel that indicates communication by another wireless communication device. Based on a determination that the busy state does not correspond to the artificial busy state (e.g., that the data packet 776 is received during one of first set of slots 772), wireless communication device 702 may perform an LBT procedure that includes waiting for the duration of an AIFS after sensing the wireless communication channel becoming idle before initiating backoff timer 714.

[0091] After expiration of the backoff time (e.g., expiration of backoff timer 714), wireless communication device 702 may access the wireless communication channel to transmit data packet 776 to AP 750. Additional data packets may be transmitted to AP 750 in a similar manner (e.g., by waiting an additional backoff time, and possibly a duration of an AIFS, after detecting arrival of the additional data packets).

[0092] In some implementations, wireless communication device 702 may delay the initiation of backoff timer 714 or, if backoff timer 714 is not used, delay transmission of data packet 776 to AP 750. The delayed transmission may be performed by delaying the initiation of transmission of data packet 776 by a delay interval, and this delay may be performed with respect to “higher” layers of the open system interconnections (OSI) reference model for data transmission (e.g., layers above the medium access control (MAC) layer or physical (PHY) layer). As a non-limiting example, if the arrival of data packet 776 is detected during the artificial busy state (e.g., during one of second set of slots 774), wireless communication device 702 may delay initiation of backoff timer 714 by slot duration 708 (e.g., a duration of one of second set of slots 774) from a time when the arrival of data packet 776 is detected. Such delaying is further described with reference to FIG. 9.

[0093] As another example, if slots allocated to the first wireless communication technology have different slot durations than slots allocated to the second wireless communication technology, wireless communication device 702 may delay the initiation of backoff timer 714 by a delay interval 710 from a time when the arrival of data packet 776 is detected. Delay interval 710 may be based on a duration of a TDMA slot (e.g., a duration of one of second set of slots 774 during which transmission of data packet 776 is forbidden) and a duration of a non-TDMA slot (e.g., a duration of one of first set of slots 772 allocated to transmission of data packet 776). In some implementations, wireless communication device 702 determines delay interval 710 (At) based on Equation 1 below:

Equation 1 where T_a is the duration of the TDMA slot, t_a is the start time of the TDMA slot, Tb is the duration of the non-TDMA slot, tb is the start time of the non-TDMA slot, and t is the time when the arrival of data packet 776 is detected. Such delaying is further described with reference to FIG. 10. Additionally or alternatively, delay interval 710 may be further based on a superframe duration of a current superframe that includes the TDMA slot and the non- TDMA slot. For example, wireless communication device 702 may determine delay interval

710 according to ⁿ is a positive integer value, and T_Sf is the

superframe duration. In some such implementations, an upper bound of delay interval 710 is equal to the superframe duration. The duration and start time of the superframe may be given by superframe parameters 712. Delays determined in this manner may map transmission of one or more data packets into a later superframe (e.g., a later first technology slot). Additionally or alternatively, wireless communication device 702 may be configured to determine one or more packets that arrive within a threshold time of a slot boundary of a current first technology slot, and wireless communication device 702 may delay initiation of the LBT procedures for the one or more packets until a next first technology slot (e.g., delay by at least a sum of the threshold time and a duration of the second technology slot) because the LBT procedures would overlap with an intervening second technology slot. Additionally or alternatively, wireless communication device 702 may delay initiation of the LBT procedures for one or more packets that arrive during a first technology slot to reduce bursty transmissions during a beginning portion of the first technology slot.

[0094] Although delaying the initiation of the LBT procedures is described as being in addition to skipping the AIFS, the present disclosure is not so limited. In some implementations, wireless communication device 702 may skip the AIFS when initiating the LBT procedure without delaying initiation of the backup time. In some other implementations, wireless communication device 702 may delay initiation of the LBT procedure without skipping the AIFS. In some other implementations, wireless communication device 702 may delay the initiation of the LBT procedure and may skip the AIFS. Alternatively, wireless communication device 702 may delay the transmission of data packet 776 without using the LBT procedure, with or without skipping the AIFS, such that transmission of data packet 776 is initiated in response to expiration of the delay interval.

[0095] As described with reference to FIG. 7, the present disclosure provides techniques for enabling wireless communication device 702 to reduce a wait time of an LBT procedure (e.g., by not waiting for/omitting/eliminating a duration of an AIFS) when initiating backoff timer 714 after an artificial busy state of the wireless communication channel. Reducing the wait time enables more efficient use of slots allocated to the first wireless communication technology (e.g., the contention-based communications), which may reduce latency or reduce collisions associated with communications performed in accordance with the first wireless communication technology. Additionally or alternatively, delaying the initiation of backoff timer 714, such as based on delay interval 710 as described above, or delaying the initiation of data packet transmission without performing a backoff operation for data packets that arrive during a slot allocated to the second wireless communication technology (e.g., a TDMA slot) may further reduce collisions associated with communications performed via the wireless communication channel and in accordance with the first wireless communication technology while supporting co-existence between the first wireless communication technology and the second wireless communication technology.

[0096] FIG. 8 illustrates examples 800 of performing LBT procedures according to some aspects. The LBT procedures may be performed by a wireless communication device, such as wireless communication device 702 of FIG. 7. The LBT procedures may be performed by wireless communication device 702 in response to determining that a wireless communication channel has become idle after an artificial busy state (e.g., after a slot allocated to the second wireless communication technology), as described above.

[0097] FIG. 8 illustrates a first example 802 of performing an LBT procedure. For example, if an arrival of a data packet for transmission is detected at reference number 804 (e.g., during a slot allocated to the first wireless communication technology - a WLAN-based technology/contention-based technology), wireless communication device 702 may perform an LBT procedure that includes waiting for a duration of an AIFS before initiating a random backoff time (as indicated by a four unit backoff time). Because the backoff time does not expire before (e.g., overlaps with) a slot allocated to the second wireless communication technology (e.g., a TDMA technology), wireless communication device 702 “freezes” the backoff time during the slot due to detection of an artificial busy state of the wireless communication channel. After the wireless communication channel becomes idle (e.g., at the beginning of the next slot allocated to the first wireless communication technology), wireless communication device 702 may resume the backoff countdown (e.g., for the remaining three units) without waiting for a duration of an AIFS. If the wireless communication channel remains idle for the remainder of the backoff time, wireless communication device 702 may transmit the data packet via the wireless communication channel, at reference number 806. Although the backoff time is shown as including four units (e.g., backoff slots), in other implementations, fewer than four or more than four backoff slots may be selected for the backoff time (e.g., between an upper bound and a lower bound associated with the LBT procedure).

[0098] FIG. 8 also illustrates a second example 810 of performing an LBT procedure. For example, if an arrival of a data packet for transmission is detected at reference number 812 (e.g., during a slot allocated to the second wireless communication technology), wireless communication device 702 may perform an LBT procedure that omits an AIFS interval and includes initiating a backoff time immediately after detecting that the wireless communication channel has become idle (e.g., at the beginning of a next slot allocated to the first wireless communication technology). In second example 810, wireless communication device 702 does not wait for a duration of an AIFS before initiating the backoff time. If the wireless communication channel remains idle for the duration of the backoff time, wireless communication device 702 may transmit the data packet via the wireless communication channel, at reference number 814.

[0099] As described with reference to FIG. 8, two examples of LBT procedures have shorter durations than corresponding LBT procedures described with reference to FIG. 5. For example, in first example 802 and second example 810, the LBT procedure does not include waiting for a duration of an AIFS after detecting that the wireless communication channel has become idle after an artificial busy state. The reduced-duration LBT procedures may enable more efficient use of the slots allocated to the first wireless communication technology.

[00100] FIG. 9 illustrates examples of delaying transmission of data packets according to some aspects. Delaying the transmission of packets may be performed by one or more wireless communication devices, such as wireless communication device 702 of FIG. 7. The delaying techniques described with reference to FIG. 9 may be performed when slots allocated to the first wireless communication technology have the same slot duration as slots allocated to the second wireless communication technology. [00101] FIG. 9 illustrates packet arrival times 900 during multiple slots allocated to different wireless communication technologies. For example, the one or more wireless communication devices may detect arrival of data packets for transmission at various times (as represented by the hatched arrows in FIG. 9) during a slot allocated to the second wireless communication technology (e.g., the “second technology slot” allocated to TDMA-based technology) and at various times (as represented by the empty arrows in FIG. 9) during a slot allocated to the first wireless communication technology (e.g., the “first technology slot” allocated to WLAN-based or other contention-based technology).

[00102] FIG. 9 also illustrates LBT initiation times 910. For example, an LBT procedure corresponding to each received data packet may be initiated by the one or more wireless communication devices during the first technology slot. The LBT procedures for the data packets arriving during the first technology slot may be initiated as the data packets arrive (e.g., are detected by at least some of the one or more wireless communication devices). Others of the one or more wireless communication devices may delay initiation of the LBT procedures for the data packets arriving during the second technology slot by a delay interval such that the LBT procedures are initiated during the first technology slot. In some implementations, the delay interval is equal to a slot duration of the second technology slot. If arrival of data packets for transmission are at least somewhat uniformly distributed during each slot (e.g., due to data packets being generated by higher layers that are agnostic to the partition of time into different slots), delaying the initiation of the LBT procedures by the delay interval may result in the LBT procedures being at least somewhat uniformly distributed during an entirety of the first technology slot.

[00103] FIG. 9 also illustrates packet transmission times 920. For example, packet transmission times 920 may correspond to expiration of the LBT procedures initiated by the one or more wireless communication devices. Packet transmission times 920 are shifted to the right and spread out as compared to LBT initiation times 910 due to waiting for expiration of a random backoff time (and potentially a duration of an AIFS). Because the LBT procedures for packets that arrive during the second technology slot are delayed by the delay interval, the transmissions are more uniformly distributed during an entirety of the first technology slot and bursts are reduced (or eliminated) as compared to the transmissions described with reference to FIG. 6. Reducing the number of transmission bursts may decrease collisions between data packets and result in decreased packet loss, which increases a packet reception rate at wireless communication devices configured to communicate according to the first wireless communication technology. These increased packet reception rates may result in improved performance and/or decreased latency associated with the first wireless communication technology. In some other implementations, instead of waiting for an LBT time, contention for the wireless channel to transmit the arrived data packets may be initiated upon arrival during the first technology slot or after the delay if arrival occurs during the second technology slot, corresponding to LBT initiation times 910. In some such implementations, wireless communication devices may delay packets that arrive during the first technology slot by a smaller delay (e.g., less than a duration of the first technology slot) to more uniformly distribute transmission of data packets during the first technology slot.

[00104] FIG. 10 illustrates examples of delaying transmission of data packets for slots having different durations according to some aspects. Delaying the transmission of packets may be performed by one or more wireless communication devices, such as wireless communication device 702 of FIG. 7. The delaying techniques described with reference to FIG. 10 may be performed when slots allocated to the first wireless communication technology have different slot durations than slots allocated to the second wireless communication technology. To prevent the delay applied to a packet that arrives for transmission during a second communication slot from causing the LBT procedure to be initiated in a subsequent second technology slot, each packet that arrives for transmission during the second technology slot may have its LBT procedure delayed by an individually determined delay interval that is based on the position of the arrival time within the second technology slot and both slot durations. In some implementations, the delay interval may be determined based on Equation 1 above. Delaying the initiation of the LBT procedure in this manner may scale the delay based on differences between the different slot durations.

[00105] FIG. 10 illustrates a first example 1000 corresponding to slots allocated to the second wireless communication technology having longer slot durations than slots allocated to the first wireless communication technology. As illustrated in FIG. 10, data packets have packet arrival times during multiple slots allocated to different wireless communication technologies. For example, the one or more wireless communication devices may detect arrival of data packets for transmission at various times (as represented by the hatched arrows in FIG. 10) during a slot allocated to the second wireless communication technology (e.g., the “second technology slot” allocated to TDMA-based technology) and at various times (as represented by the empty arrows in FIG. 10) during a slot allocated to the first wireless communication technology (e.g., the “first technology slot” allocated to WLAN-based or other contention-based technology). [00106] FIG. 10 also illustrates LBT initiation times for first example 1000. For example, an LBT procedure corresponding to each received data packet may be initiated by the one or more wireless communication devices during the first technology slot. The LBT procedures for the data packets arriving during the first technology slot may be initiated as the data packets arrive (e g., are detected by at least some of the one or more wireless communication devices). Others of the one or more wireless communication devices may delay initiation of the LBT procedures for the data packets arriving during the second technology slot by a delay interval such that the LBT procedures are initiated during the first technology slot. Each delay interval may be determined individually for each data packet that arrives during the second technology slot, such as based on Equation 1. Because the slot duration of the second technology slot is longer than the slot duration of the first technology slot in first example 1000, the delay intervals are less than the slot duration of the second technology slot, and initiation of the LBT procedures for these data packets are closer together in time during the first technology slot than the arrivals of these data packets are during the second technology slot, while maintaining an at least somewhat uniform distribution during the first technology slot (if the data packets arrived with an at least somewhat uniform distribution during the second technology slot).

[00107] FIG. 10 also illustrates a second example 1010 corresponding to slots allocated to the second wireless communication technology having smaller slot durations than slots allocated to the first wireless communication technology. As illustrated in FIG. 10, data packets have various packet arrival times during the second technology slot and the first technology slot. FIG. 10 also illustrates LBT initiation times for second example 1010. For example, an LBT procedure corresponding to each received data packet may be initiated by the one or more wireless communication devices during the first technology slot. The LBT procedures for the data packets arriving during the first technology slot may be initiated as the data packets arrive (e.g., are detected by at least some of the one or more wireless communication devices). Others of the one or more wireless communication devices may delay initiation of the LBT procedures for the data packets arriving during the second technology slot by a delay interval such that the LBT procedures are initiated during the first technology slot. Each delay interval may be determined individually for each data packet that arrives during the second technology slot, such as based on Equation 1. Because the slot duration of the second technology slot is less than the slot duration of the first technology slot in second example 1010, the delay intervals may be greater than the slot duration of the second technology slot, and initiation of the LBT procedures for these data packets are more separated in time during the first technology slot than the arrivals of these data packets are during the second technology slot, while maintaining an at least somewhat uniform distribution during the first technology slot (if the data packets arrived with an at least somewhat uniform distribution during the second technology slot).

[00108] In some other implementations, instead of waiting for an LBT time in either the first example 1000 or the second example 1010, contention for the wireless channel to transmit the arrived data packet may be initiated upon arrival during the first technology slot or after the delay if arrival occurs during the second technology slot. In some such implementations, wireless communication devices may delay packets that arrive during the first technology slot by a smaller delay (e g., less than a duration of the first technology slot) to more uniformly distribute transmission of data packets during the first technology slot.

[00109] Referring to FIGS. 11-12, flow diagrams illustrating example processes of wireless communication device operations according to some aspects are shown. FIG. 11 includes a flow diagram for an example process 1100 of wireless communication device operations for initiating delayed transmission of a data packet based on the data packet arriving during a slot during which transmission of the data packet is forbidden via a wireless communication channel according to some aspects. FIG. 12 includes a flow diagram for an example process 1200 of wireless communication device operations for delaying initiation of an LBT procedure according to some aspects. In some implementations, processes 1100 and 1200 may be performed by STA 104 of FIG. 1, wireless communication device 702 of FIG. 7, or a wireless communication device as described with reference to FIG. 13. In some other implementations, processes 1100 and 1200 may be performed by an apparatus configured for wireless communication. For example, the apparatus may include at least one processor, and a memory coupled to the processor. The processor may be configured to perform operations of processes 1100 or 1200. In some other implementations, processes 1100 and 1200 may be performed or executed using a non-transitory computer-readable medium having program code recorded thereon. The program code may be program code executable by a computer for causing the computer to perform operations of processes 1100 or 1200.

[00110] Example operations (also referred to as “blocks”) of processes 1100 and 1200 will also be described with respect to wireless communication device 1300 as illustrated in FIG. 13. FIG. 13 is a block diagram illustrating an example wireless communication device 1300 configured to initiate a backoff time or delayed data packet transmission after an artificial busy state associated with a wireless communication channel according to some aspects. Wireless communication device 1300 may include STA 104 of FIG. 1 or wireless communication device 702 of FIG. 7, as illustrative, non-limiting examples. Wireless communication device 1300 includes the structure, hardware, and components to perform the operations described with reference to FIGS. 11-12. For example, wireless communication device 1300 may include controller/processor 1301, which operates to execute logic or computer instructions stored in memory 1302, as well as controlling the components of wireless communication device 1300 that provide the features and functionality of wireless communication device 1300. Wireless communication device 1300, under control of controller/processor 1301, transmits and receives signals via wireless radios 1310a-r and antennas 1312a-r. Wireless radios 1310a-r may include various components and hardware, such as modulator/demodulators, a transmit processor, and a receive processor, as non limiting examples.

[00111] As shown, memory 1302 may include data packet arrival detection logic 1303, sensing logic 1304, busy state determination logic 1305, LBT initiation logic 1306, backoff timer 1307, and delay interval determination logic 1308. Data packet arrival detection logic 1303 may be configured to detect arrival of a data packet for transmission by wireless communication device 1300. Sensing logic 1304 may be configured to sense a state (e.g., busy or idle) of a wireless communication channel. Busy state determination logic 1305 may be configured to determine whether a busy state associated with the wireless communication channel is an artificial busy state. LBT initiation logic 1306 may be configured to initiate an LBT procedure. Backoff timer 1307 may be configured to count down a backoff time, such as a random backoff time, of the LBT procedure. Delay interval determination logic 1308 may be configured to determine a delay interval for delaying initiation of the LBT procedure. Wireless communication device 1300 may receive signals from or transmit signals to one or more STAs or APs, such as STA 104 or AP 102 of FIG. 1 or wireless communication device 702 or AP 750 of FIG. 7.

[00112] Returning to process 1100 described with reference to FIG. 11, as illustrated at block 1102, wireless communication device 1300 detects arrival of a data packet for transmission at wireless communication device 1300 via a wireless communication channel. As an example of block 1102, wireless communication device 1300 may execute, under control of controller/processor 1301, data packet arrival detection logic 1303 stored in memory 1302. The execution environment of data packet arrival detection logic 1303 provides the functionality to detect arrival of a data packet for transmission at wireless communication device 1300 via a wireless communication channel, such as presence of the data packet in a transmission buffer or receipt of an indicator from an application executed by wireless communication device 1300, as non-limiting examples. Wireless communication device 1300 may be configured to transmit such data packets via a wireless communication channel.

[00113] At block 1104, wireless communication device 1300 initiates, based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden via the wireless communication channel, delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval. As an example of block 1104, wireless communication device 1300 may execute, under control of controller/processor 1301, sensing logic 1304, busy state determination logic 1305, and LBT initiation logic 1306 stored in memory 1302. The execution environment of sensing logic 1304 and busy state determination logic 1305 provides the functionality to determine that the arrival of the data packet is detected during a slot allocated to a second wireless communication technology (e g., a TDMA-based technology) or otherwise during which transmission of the data packet is forbidden. In some implementations, the determination may be referred to as detecting an artificial busy state, as described with reference to FIG. 7. The execution environment of LBT initiation logic 1306 provides the functionality to initiate, based on the determination, delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval, such as by contending for access to the wireless communication channel after expiration of the delay interval. In some implementations, the transmission may be initiated in response to expiration of the delay interval (e g., immediately or nearly-immediately after expiration of the delay interval). In some other implementations, the initiation may occur after expiration of a delayed backoff time that is initiated in response to expiration of the delay interval. The delayed backoff time may be initiated by initiating backoff timer 1307 after expiration of the delay interval. Transmission of the data packet may be initiated after expiration of the delayed backoff time (e.g., expiration of backoff timer 1307), such as if the wireless communication device 1300 successfully contends for access to the wireless communication channel after expiration of the backoff timer 1307.

[00114] In some implementations, the delay interval does not include (e.g., omits or eliminates) a duration of an arbitrary interframe space (AIFS). Additionally or alternatively, the delay interval includes a random backoff time corresponding to a listen-before-transmit (LBT) procedure at wireless communication device 1300.

[00115] In some implementations, process 1100 further includes receiving an indication from an access point (AP) that one or more slots are allocated for time division multiple access (TDMA) communication by other wireless communication devices via the wireless communication channel. In some such implementations, the determination that the arrival of the data packed is detected during the slot allocated for TDMA communications may be based on a determination that the slot (e.g., a current slot during which the arrival is detected) is included in the one or more slots allocated for TDMA communication. Additionally or alternatively, process 1100 may also include sensing an artificial busy state associated with the wireless communication channel during slots included in the one or more slots.

[00116] In some implementations, process 1100 further includes determining one or more slots allocated for TDMA communications based on measurements of the wireless communication channel. The determination that the arrival of the data packet is detected during the slot allocated for TDMA communications is based on a determination that the slot is included in the one or more slots allocated for TDMA communications determined based on the measurements, as described with reference to FIG. 7.

[00117] In some implementations, process 1100 further includes sensing a busy state (e.g., a non-artificial busy state) associated with the wireless communication channel based on sensing that the wireless communication channel is occupied. In some such implementations, sensing that the wireless communication channel is occupied may include sensing a level of energy on the wireless communication channel that indicates a communication by another wireless communication device.

[00118] In some implementations, process 1100 further includes detecting arrival of a second data packet for transmission at the wireless communication device via the wireless communication channel, sensing a busy state associated with the wireless communication channel and associated with the arrival of the second data packet, determining that the busy state does not correspond to an artificial busy state, and, based on a determination that the arrival of the second data packet is not during a slot allocated for TDMA communication via the wireless communication channel, initiating transmission of the second data packet after sensing that the wireless communication channel is idle for a duration of an arbitrary interframe space (AIFS). The busy state may be sensed in response to expiration of a duration of an AIFS started upon detection of the arrival of the second data packet.

[00119] In some implementations, process 1100 further includes detecting arrival of a second data packet for transmission via the wireless communication channel and according to the non-TDMA communication scheme, and initiating, based on a determination that the arrival of the second data packet is detected during a slot allocated for non-TDMA communication via the wireless communication channel and within a threshold time of a slot boundary of the slot, delayed transmission of the second data packet via the wireless communication channel after expiration of a second delay interval. For example, a second data packet that is detected within a threshold time of an ending slot boundary of the first technology slot depicted in FIG. 9 may have transmission (or initiation of an LBT procedure) delayed by a second delay interval based on detection occurring within the threshold time. The second delay interval is equal to or exceeds a sum of the threshold time and a duration of a TDMA slot such that the initiation of transmission is delayed to a next non-TDMA slot, as further described with reference to FIG. 7.

[00120] In some implementations, process 1100 further includes receiving an indication from an access point (AP), or determining at the wireless communication device based on one or more predetermined settings, that one or more slots are allocated for time division multiple access (TDMA) communication by other wireless communication devices via the wireless communication channel. In some such implementations, the delay interval may include a duration of one of the one or more slots from a time when the arrival of the data packet is detected.

[00121] In some implementations, process 1100 further includes receiving an indication from an access point (AP), or determining at the wireless communication device based on one or more preconfigured settings, that a first set of slots are allocated for time division multiple access (TDMA) communication via the wireless communication channel by other wireless communication devices and that a second set of slots are allocated for non-TDMA communications via the wireless communication channel. The determination that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden is based on a determination that the slot is included in the first set of slots. In some such implementations, the delay interval begins at a time when the arrival of the data packet is detected, and the delay interval is based on a duration of the slot during which transmission of the data packet is forbidden (e g., a TDMA slot), a duration of a next slot allocated for transmission of the data packet (e.g., a non-TDMA slot), and a location of the arrival of the data packet within the slot during which transmission of the data packet is forbidden. In some such implementations, the delay interval is determined based on the following:

where At is the delay interval, T_a is the duration of the slot during which transmission of the data packet is forbidden, ta is the start time of the slot during which transmission of the data packet is forbidden, Tt, is the duration of the next slot allocated for transmission of the data packet, tb is the start time of a next slot allocated for transmission of the data packet, and t is the time when the arrival of the data packet is detected. Additionally or alternatively, the delay interval may be further based on a start time of a current superframe that includes at least one of the slot during which transmission of the data packet is forbidden and the next slot allocated for transmission of the data packet. In some such implementations, an upper bound of the delay interval may be equal to a duration of the current superframe. Alternatively, the delay interval may exceed a superframe duration based on a distance in time between arrival of the data packet and a next slot boundary satisfying a threshold.

[00122] FIG. 12 shows process 1200 of wireless communication device operations for delaying initiation of an LBT procedure according to some aspects. At block 1202, wireless communication device 1300 detects arrival of a data packet for transmission from wireless communication device 1300. As an example of block 1202, wireless communication device 1300 may execute, under control of controller/processor 1301, data packet arrival detection logic 1303 stored in memory 1302. The execution environment of data packet arrival detection logic 1303 provides the functionality to detect arrival of a data packet for transmission from wireless communication device 1300, such as presence of the data packet in a transmission buffer or receipt of an indicator from an application executed by wireless communication device 1300, as non-limiting examples.

[00123] At block 1204, wireless communication device 1300 senses a busy state associated with the wireless communication channel. As an example of block 1204, wireless communication device 1300 may execute, under control of controller/processor 1301, sensing logic 1304 stored in memory 1302. The execution environment of sensing logic 1304 provides the functionality to sense a busy state associated with the wireless communication channel.

[00124] At block 1206, wireless communication device 1300 determines that the busy state corresponds to an artificial busy state. As an example of block 1206, wireless communication device 1300 may execute, under control of controller/processor 1301, busy state determination logic 1305 stored in memory 1302. The execution environment of busy state determination logic 1305 provides the functionality to determine that the busy state corresponds to an artificial busy state, such as based on a current slot being allocated to a second wireless communication technology (e.g., a TDMA-based technology).

[00125] At block 1208, wireless communication device 1300 delays, based on the determination, initiation of an LBT procedure associated with transmission of the data packet by a delay interval. As an example of block 1208, wireless communication device 1300 may execute, under control of controller/processor 1301, delay interval determination logic 1308 stored in memory 1302. The execution environment of delay interval determination logic 1308 provides the functionality to determine a delay interval and to delay, based on the determination, initiation of an LBT procedure associated with transmission of the data packet by the delay interval.

[00126] In some implementations in which a slot duration of a slot allocated to a first wireless communication technology (e.g., a contention-based/WLAN-based technology) is the same as a slot duration of a slot allocated to a second wireless communication technology (e.g., a TDMA-based technology), the delay interval is equal to the slot duration of the slot allocated to the second wireless communication technology. Alternatively, in some implementations in which the slot duration of the slot allocated to the first wireless communication technology is different than the slot duration of the slot allocated to the second wireless communication technology, the delay interval may be determined based on the slot duration of the slot allocated to the first wireless communication technology, the slot duration of the slot allocated to the second wireless communication technology, starting times of each slot, and a location within the slot allocated to the second wireless communication technology of the arrival of the data packet. For example, the delay interval may be determined using Equation 1 above. Alternatively, the delay interval may be determined to be longer than a duration of a superframe, such as if the location of the arrival of the data packet within the slot allocated to the second wireless communication technology is within a threshold of a slot boundary of the slot allocated to the second wireless communication technology.

[00127] It is noted that one or more blocks (or operations) described with reference to FIGS. 11-12 may be combined with one or more blocks (or operations) of another figure. For example, one or more blocks (or operations) of FIG. 11 may be combined with one or more blocks (or operations) of FIG. 12. As another example, one or more blocks of FIG. 11 may be combined with one or more blocks (or operations) of another of FIGS. 1 or 7. Additionally, or alternatively, one or more operations described above with reference to FIGS. 1-12 may be combined with one or more operations described with reference to FIG. 13.

[00128] FIG. 14 illustrates simulation results 1400 of wireless communication systems configured according to one or more aspects. As shown in FIG. 14, the simulation results include first simulation results 1402 associated with a wireless communication system that only supports ITS-G5 communications (e.g., a contention-based communication scheme), second simulation results 1404 associated with a wireless communication system that supports co-existence of ITS-G5 communications and LTE-Y2X communications (e g., a TDMA-based communication scheme) and that uses the packet delay scheme (e.g., initiating delayed transmission of contention-based data packets that arrive during TDMA slots) described with reference to FIGS. 7, 9, and 10, third simulation results 1406 associated with a wireless communication system that supports co-existence and that uses an increased duration contention window (e.g., 80 ms as compared to 16 ms), fourth simulation results 1408 associated with a wireless communication system that supports co-existence and that does not use the packet delay scheme (or increase the contention window duration), and fifth simulation results 1410 associated with a wireless communication system that supports both ITS-G5 communications and LTE-V2X communications with no co-existence (e.g., no technology specific slots). The simulation results 1400 are generated for an example scenario of 123 vehicles traveling at approximately 140 kilometers/hour (km/h) along a 2000 km freeway. In the example shown in FIG. 14, a threshold distance to support a 90% packet reception rate (PRR) for the first simulation results 1402 is approximately 190 m, the threshold distance to support 90% PRR for the second simulation results 1404 is approximately 180 m, the threshold distance to support 90% PRR for the third simulation results 1406 is approximately 160 m, the threshold distance to support 90% PRR for the fourth simulation results 1408 is approximately 140 m, and the threshold distance to support 90% PRR for the fifth simulation results 1410 is approximately 70 m.

[00129] As shown in FIG. 14, using the packet delay scheme increases the threshold distance between vehicles for 90% PRR by approximately 40 meters as compared to using co existence without the packet delay scheme (e.g., as shown by a comparison of the second simulation results 1404 and the fourth simulation results 1408 at 90% PRR), which is a larger increase than results from increasing a duration of a contention window (e.g., as shown by a comparison of the third simulation results 1406 and the fourth simulation results 1408 at 90% PRR). Additionally, as shown in FIG. 14, a wireless communication system that supports both ITS-G5 communications and LTE-V2X communications using the packet delay scheme experiences negligible performance degradation compared to a wireless communication system that only supports ITS-G5 communications (e.g., the distance at 90% PRR for the second simulation results 1404 is approximately 180 m and the distance at 90% PRR for the first simulation results 1402 is approximately 190 m, a difference of only 10 m). Hence, co existence between two communication schemes using the packet delay scheme described herein improves packet reception as compared to conventional, co-existence free schemes. The magnitude of the benefits provided by the packet delay scheme may increase for implementations having longer superframe durations or unequal technology slot lengths.

[00130] In some aspects, techniques for enabling sharing of a wireless communication channel between a contention-based wireless communication technology and a TDMA-based wireless communication technology may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes or devices described elsewhere herein. In some aspects, enabling sharing of a wireless communication channel between a contention-based wireless communication technology (e.g., a WLAN-based technology) and a TDMA-based wireless communication technology may include an apparatus detecting arrival of a data packet for transmission via a wireless communication channel. The apparatus may further initiate, based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden via the wireless communication channel, delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval. In some implementations, the apparatus includes a wireless communication device, such as a STA. In some implementations, the apparatus may include at least one processor, and a memory coupled to the processor. The processor may be configured to perform operations described herein with respect to the wireless device. In some other implementations, the apparatus may include a non-transitory computer-readable medium having program code recorded thereon and the program code may be executable by a computer for causing the computer to perform operations described herein with reference to the wireless device. In some implementations, the apparatus may include one or more means configured to perform operations described herein.

[00131] In a first aspect, the delay interval does not include a duration of an AIFS.

[00132] In a second aspect, alone or in combination with the first aspect, the apparatus initiates transmission of the data packet after expiration of a random backoff time corresponding to an LBT procedure after expiration of the delay interval.

[00133] In a third aspect, alone or in combination with one or more of the first through second aspects, the apparatus receives an indication from an network device that one or more slots are designated as forbidden for communication via the wireless communication channel according to a particular wireless communication scheme associated with the data packet.

[00134] In a fourth aspect, in combination with the third aspect, the determination that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden is based on a determination that the slot is included in the one or more slots.

[00135] In a fifth aspect, alone or in combination with one or more of the first through second aspects, the apparatus determines one or more slots allocated for TDMA communications via the wireless communication channel based on measurements of the wireless communication channel. The determination that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden is based on a determination that the slot is included in the one or more slots allocated for TDMA communications.

[00136] In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the apparatus detects arrival of a second data packet for transmission via the wireless communication channel. The apparatus also initiates, based on a determination that the arrival of the second data packet is detected during a slot allocated for transmission of the second data packet via the wireless communication channel and within a threshold time of a slot bounder of the slot, delayed transmission of the second data packet via the wireless communication channel after expiration of a second delay interval.

[00137] In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, the apparatus senses whether the wireless communication channel is occupied based on sensing whether a level of energy on the wireless communication channel indicates a communication by another wireless communication device, and the apparatus senses a non artificial busy state associated with the wireless communication channel based on a determination that the wireless communication channel is occupied..

[00138] In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, the apparatus detects arrival of a second data packet for transmission via the wireless communication channel, senses a busy state associated with the wireless communication channel and associated with the arrival of the data packet, and, based on a determination that the arrival of the second data packet is not detected during any slot during which transmission of the second data packet is forbidden via the wireless communication channel, initiates transmission of the second data packet after sensing that the wireless communication channel is idle for a duration of an AIFS.

[00139] In a ninth aspect, in combination with the eighth aspect, the apparatus senses the busy state in response to expiration of a duration of an AIFS started upon detection of the arrival of the second data packet.

[00140] In tenth aspect, alone or in combination with one or more of the first through ninth aspects, the apparatus receives an indication from a network device that a first set of slots are allocated for TDMA communication via the wireless communication channel by other wireless communication devices and that a second set of slots are allocated for non-TDMA communications via the wireless communication channel. The determination that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden is based on a determination that the slot is included in the first set of slots.

[00141] In an eleventh aspect, alone or in combination with one or more of the first through ninth aspects, the apparatus determines, based on one or more preconfigured settings at the apparatus, that a first set of slots are allocated for TDMA communication via the wireless communication channel by other wireless communication devices and that a second set of slots are allocated for non-TDMA communications via the wireless communication channel. The determination that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden is based on a determination that the slot is included in the first set of slots

[00142] In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, the delay interval begins at a time when the arrival of the data packet is detected. The delay interval is based on a duration of the slot during which transmission of the data packet is forbidden, a duration of a next slot allocated for transmission of the data packet via the wireless communication channel, and a location of the arrival of the data packet within the slot during which transmission of the data packet is forbidden.

[00143] In a thirteenth aspect, in combination with the twelfth aspect, the delay interval is determined based on the following:

where At is the delay interval, T_a is the duration of the slot during which transmission of the data packet is forbidden, t_a is the start time of the slot during which transmission of the data packet is forbidden, Tb is the duration of the next slot allocated for transmission of the data packet, tb is the start time of the next slot allocated for transmission of the data packet, and t is the time when the arrival of the data packet is detected.

[00144] In a fourteenth aspect, alone or in combination with one or more of the twelfth through thirteenth aspects, the delay interval is further based on a start time of a current superframe that includes at least one of the slot during which transmission of the data packet is forbidden and the next slot allocated for transmission of the data packet. [00145] In a fifteenth aspect, in combination with the fourteenth aspect, an upper bound of the delay interval is equal to a duration of the current superframe.

[00146] In a sixteenth aspect, alone or in combination with one or more of the first through eleventh aspects, the delay interval exceeds a superframe duration based on a distance in time between arrival of the data packet and a slot boundary satisfying a threshold.

[00147] In a seventeenth aspect, alone or in combination with one or more of the first through eleventh aspects, the delay interval includes a duration of the slot during which transmission of the data packet is forbidden.

[00148] In an eighteenth aspect, alone or in combination with one or more of the first through seventeenth aspects, the apparatus determines that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden based on the slot being included in a first set of slots allocated for communication of a first message type via the wireless communication channel. A second set of slots are allocated for communication of a second message type via the wireless communication channel. The data packet is associated with the second message type.

[00149] Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[00150] Components, the functional blocks and modules described herein with respect to FIGS. 7 and 13 may comprise processors, electronics devices, hardware devices, electronics components, logical circuits, memories, software codes, firmware codes, etc., or any combination thereof. In addition, features discussed herein relating to FIGS. 1-14 may be implemented via specialized processor circuitry, via executable instructions, and/or combinations thereof.

[00151] Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps (e.g., the logical blocks in FIGS. 11-12) described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. Skilled artisans will also readily recognize that the order or combination of components, methods, or interactions that are described herein are merely examples and that the components, methods, or interactions of the various aspects of the present disclosure may be combined or performed in ways other than those illustrated and described herein.

[00152] The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[00153] The steps of a method or algorithm described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

[00154] In one or more exemplary designs, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. Computer-readable storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general- purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, a connection may be properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, or digital subscriber line (DSL), then the coaxial cable, fiber optic cable, twisted pair, or DSL, are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), hard disk, solid state disk, and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[00155] As used herein, including in the claims, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination. Also, as used herein, including in the claims, “or” as used in a list of items prefaced by “at least one of’ indicates a disjunctive list such that, for example, a list of “at least one of A, B, or C” means A or B or C or AB or AC or BC or ABC (i .e., A and B and C) or any of these in any combination thereof.

[00156] The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. A method of wireless communication, the method comprising: detecting arrival of a data packet for transmission at a wireless communication device via a wireless communication channel; and based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden via the wireless communication channel, initiating delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval.

2. The method of claim 1, further comprising receiving, from a network device, an indication that a first set of slots are allocated for time division multiple access (TDMA) communication via the wireless communication channel by other wireless communication devices and that a second set of slots are allocated for non- TDMA communications via the wireless communication channel, wherein the determination that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden is based on a determination that the slot is included in the first set of slots allocated.

3. The method of claim 1, further comprising determining, based on one or more preconfigured settings at the wireless communication device, that a first set of slots are allocated for time division multiple access (TDMA) communication via the wireless communication channel by other wireless communication devices and that a second set of slots are allocated for non-TDMA communications via the wireless communication channel, wherein the determination that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden is based on a determination that the slot is included in the first set of slots.

4. The method of claim 1, wherein the delay interval begins at a time when the arrival of the data packet is detected, and wherein the delay interval is based on a duration of the slot during which transmission of the data packet is forbidden, a duration of a next slot allocated for transmission of the data packet via the wireless communication channel, and a location of the arrival of the data packet within the slot during which transmission of the data packet is forbidden.

5. The method of claim 4, wherein the delay interval is determined based on the following:

where At is the delay interval, T_a is the duration of the slot during which transmission of the data packet is forbidden, ta is the start time of the slot during which transmission of the data packet is forbidden, Tb is the duration of the next slot allocated for transmission of the data packet, tb is the start time of the next slot allocated for transmission of the data packet, and t is the time when the arrival of the data packet is detected.

6. The method of claim 4, wherein the delay interval is further based on a start time of a superframe that includes at least one of the slot during which transmission of the data packet is forbidden and the next slot allocated for transmission of the data packet.

7. The method of claim 6 wherein an upper bound of the delay interval is equal to a duration of the superframe.

8. The method of claim 1, wherein the delay interval exceeds a superframe duration based on a distance in time between the arrival of the data packet and a next slot boundary satisfying a threshold.

9. The method of claim 1, wherein the delay interval comprises a duration of the slot during which transmission of the data packet is forbidden.

10. An apparatus configured for wireless communication, the apparatus comprising: at least one processor; and a memory coupled to the at least one processor, wherein the at least one processor is configured to: detect arrival of a data packet for transmission via a wireless communication channel; and initiate, based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden via the wireless communication channel, delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval.

11. The apparatus of claim 10, wherein the delay interval does not include a duration of an arbitrary interframe space (AIFS).

12. The apparatus of claim 10, wherein the at least one processor is configured to initiate transmission of the data packet after expiration of a random backoff time corresponding to a listen-before-transmit (LBT) procedure after expiration of the delay interval.

13. The apparatus of claim 10, wherein the at least one processor is further configured to receive an indication from a network device that one or more slots are designated as forbidden for communication via the wireless communication channel according to a particular wireless communication scheme associated with the data packet.

14. The apparatus of claim 13, wherein the determination that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden is based on a determination that the slot is included in the one or more slots.

15. The apparatus of claim 10, wherein the at least one processor is further configured to determine one or more slots allocated for time division multiple access (TDMA) communication via the wireless communication channel based on measurements of the wireless communication channel, and wherein the determination that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden is based on a determination that the slot is included in the one or more slots allocated for TDMA communication.

16. The apparatus of claim 10, wherein the at least one processor is further configured to: detect arrival of a second data packet for transmission via the wireless communication channel; and initiate, based on a determination that the arrival of the second data packet is detected during a slot allocated for transmission of the second data packet via the wireless communication channel and within a threshold time of a slot boundary of the slot, delayed transmission of the second data packet via the wireless communication channel after expiration of a second delay interval.

17. The apparatus of claim 10, wherein the at least one processor is further configured to: sense whether the wireless communication channel is occupied based on sensing whether a level of energy on the wireless communication channel indicates a communication by another wireless communication device; and sense a non-artificial busy state associated with the wireless communication channel based on a determination that the wireless communication channel is occupied.

18. The apparatus of claim 10, wherein the at least one processor is further configured to: detect arrival of a second data packet for transmission via the wireless communication channel; sense a busy state associated with the wireless communication channel and associated with the arrival of the second data packet; and based on a determination that the arrival of the second data packet is not detected during any slot during which transmission of the second data packet is forbidden via the wireless communication channel, initiate transmission of the second data packet after sensing that the wireless communication channel is idle for a duration of an arbitrary interframe space (AIFS).

19. The apparatus of claim 18, wherein the at least one processor is configured to sense the busy state in response to expiration of a duration of an arbitration interframe space (AIFS) started upon detection of the arrival of the second data packet.

20. An apparatus configured for wireless communication, the apparatus comprising: means for detecting an arrival of a data packet for transmission via a wireless communication channel; and means for initiating, based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden via the wireless communication channel, delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval.

21. The apparatus of claim 20, further comprising means for receiving, from another communication device, an indication that a first set of slots are designated as forbidden for communication via the wireless communication channel according to a particular communication scheme associated with the data packet and that a second set of slots are allocated for communications via the wireless communication channel according to the particular communication scheme, wherein the determination that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden is based on a determination that the slot is included in the first set of slots.

22. The apparatus of claim 20, wherein the delay interval begins at a time when the arrival of the data packet is detected, and wherein the delay interval is based on a duration of the slot during which transmission of the data packet is forbidden, a duration of a next slot allocated for transmission of the data packet via the wireless communication channel, and a location of the arrival of the data packet within the slot during which transmission of the data packet is forbidden.

23. The apparatus of claim 22, wherein the delay interval is based on the following:

24. The apparatus of claim 22, wherein the delay interval is further based on a start time of a current superframe that includes at least one of the slot during which transmission of the data packet is forbidden and the next slot allocated for transmission of the data packet.

25. The apparatus of claim 24, wherein an upper bound of the delay interval is equal to a duration of the current superframe.

26. The apparatus of claim 20, wherein the delay interval exceeds a superframe duration based on a distance in time between the arrival of the data packet and a next slot boundary satisfying a threshold.

27. A non-transitory, computer-readable storage medium storing instructions that, when executed by a processor, cause the processor to perform operations comprising: detecting arrival of a data packet for transmission at a wireless communication device via a wireless communication channel; and based on a determination that the arrival of the data packet is detected during a slot during which transmission of the data packet is forbidden, initiating delayed transmission of the data packet via the wireless communication channel after expiration of a delay interval.

28. The non-transitory, computer-readable storage medium of claim 27, wherein the operations further comprise determining that the arrival of the data packet is detected during the slot during which transmission of the data packet is forbidden based on the slot being included in a first set of slots allocated for communication of a first message type via the wireless communication channel, and wherein a second set of slots are allocated for communications of a second message type via the wireless communication channel, the data packet associated with the second message type.

29. The non-transitory, computer-readable storage medium of claim 27, wherein the delay interval starts at a time when the arrival of the data packet is detected, wherein the slot during which transmission of the data packet is forbidden is a time division multiple access (TDMA) slot, and wherein the delay interval is based on a duration of the TDMA slot, a duration of a non-TDMA slot, and a location of the arrival of the data packet within the TDMA slot.

30. The non-transitory, computer-readable storage medium of claim 29, wherein the delay interval is determined based on the following:

where At is the delay interval, T_a is the duration of the TDMA slot, t_a is the start time of the TDMA slot, Tb is the duration of the non- TDMA slot, tb is the start time of the non-TDMA slot, and t is the time when the arrival of the data packet is detected.