FIELD OF THE DISCLOSURE

This disclosure relates generally to wireless fidelity connectivity (Wi-Fi) and, more particularly, to methods and apparatus to facilitate a synchronous transmission opportunity in a wireless local area network.

BACKGROUND

Many locations provide Wi-Fi to connect Wi-Fi enabled devices to networks such as the Internet. Wi-Fi enabled devices include personal computers, video-game consoles, mobile phones and devices, digital cameras, tablets, smart televisions, digital audio players, etc. Wi-Fi allows the Wi-Fi enabled devices to wirelessly access the Internet via a wireless local area network (WLAN). To provide Wi-Fi connectivity to a device, a Wi-Fi access point exchanges radio frequency Wi-Fi signals with the Wi-Fi enabled device within the access point (e.g., a hotspot) signal range. Wi-Fi is implemented using a set of media access control (MAC) and physical layer (PHY) specifications (e.g., such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 protocol).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a communication system using wireless local area network Wi- Fi protocols to facilitate a synchronous transmission opportunity in a wireless local area network.

FIG. 2 is a block diagram of an example PHY level communication determiner of FIG. 1.

FIG. 3 is an example a synchronous transmission opportunity that includes frame/fields that may be generated by the example PHY level communication determiner of FIGS. 1 and/or 2.

FIGS. 4-7 are flowcharts representative of example machine readable instructions that may be executed to implement the example PHY level communication determiner of the example access point of FIG. 1.

FIGS. 8-10 are flowcharts representative of example machine readable instructions that may be executed to implement the example PHY level communication determiner of the example non-legacy station of FIG. 1. FIG. 11 is a block diagram of a radio architecture in accordance with some examples.

FIG. 12 illustrates example front-end module circuitry for use in the radio architecture of FIG. 11 in accordance with some examples.

FIG. 13 illustrates example radio IC circuitry for use in the radio architecture of FIG. 11 in accordance with some examples.

FIG. 14 illustrates example baseband processing circuitry for use in the radio architecture of FIG. 11 in accordance with some examples.

FIG. 15 is a block diagram of a processor platform structured to execute the example machine readable instructions of FIGS. 4-10 to implement the example PHY level

communication determiner.

The figures are not to scale. Wherever possible, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts.

DETAILED DESCRIPTION

Various locations (e.g., homes, offices, coffee shops, restaurants, parks, airports, etc.) may provide Wi-Fi to the Wi-Fi enabled devices (e.g., stations (STA)) to connect the Wi-Fi enabled devices to the Internet, or any other network, with minimal hassle. The locations may provide one or more Wi-Fi access points (APs) to output Wi-Fi signals to the Wi-Fi enabled devices within a range of the Wi-Fi signals (e.g., a hotspot). A Wi-Fi AP is structured to wirelessly connect a Wi-Fi enabled device to the Internet through a wireless local area network (WLAN) using Wi-Fi protocols (e.g., such as IEEE 802.11). The Wi-Fi protocol is the protocol for how the AP communicates with the devices to provide access to the Internet by transmitting uplink (UL) transmissions and receiving downlink (DL) transmissions to/from the Internet.

Autonomous systems, smart factories, professional audio/video and mobile/wireless VR are time-sensitive applications that require low and deterministic latency with high reliability. For example, professional audio/video, industrial control/automation, autonomous systems, wireless VR require ultra-low latency in the order of fraction of milliseconds to few milliseconds provided in a consistent and predictable manner.

Conventional Wi-Fi systems focus on improving throughput and efficiency. However, such conventional systems do not provide a low enough latency with high enough reliability to sufficiently operate with some time-sensitive applications. For example, in some time-sensitive applications each packet may have a target delivery deadline (latency bound) and may not be able to take advantage of aggregation techniques, conventionally used for increasing throughput efficiency.

Examples disclosed herein include an AP-initiated transmission opportunity

corresponding to a sequence of synchronous contention-free (uplink or downlink) transmissions scheduled by the AP. Examples disclosed herein include generating a synchronous transmission opportunity (S-TXOP) preamble that enables coexistence with legacy STAs (e.g., conventional non-S-TXOP capable STAs) and provides S-TXOP configuration information to non-legacy STAs (e.g., S-TXOP capable STAs). In this manner, data transmissions (e.g., ETL or DL) occur at known time boundaries and do not carry legacy synchronization (e.g., legacy short training field (L-STF) or legacy long training field (L-LTF) frames). Accordingly, non-legacy STAs use the S-TXOP preamble to synchronize to the AP and only a small synchronization field (e.g., a lite preamble) may be added to the DL/EIL physical layer convergence protocol data unit (PPDET)) to correct residual carrier frequency offsets (CFOs) and/or symbol timing offset. The S-TXOP definition enables the AP to define multiple EIL/DL interval configurations as required to meet deterministic/low latency requirements of STAs. By using the S-TXOP preamble for timing and frequency synchronization, unnecessary overhead (e.g., legacy preambles) in the scheduled DL/UL operations can be avoided thus increasing the overall system throughput/capacity while enabling low latency applications.

Examples disclosed herein provide better performance in terms of throughput efficiency, ultra-low and deterministic latency compared with conventional Wi-Fi systems. For example, using examples disclosed herein, the preamble (e.g., lite preamble) of an individual physical layer convergence protocol (PLCP) protocol data units (PPDET) is reduced by 41.6 microseconds (us) for each DL PPDU and 112 us for each UL PPDU considering Single Input Single Output (SISO) communication involving nine stations. Examples disclosed herein support a large number of STAs for given wireless resources while meeting the latency bounds for time-sensitive applications. Examples disclosed herein provide higher throughput efficiency through the reduced PHY overhead and synchronous contention-free transmissions. The S-TXOP format also enables higher reliability and facilitates

implementation of Hybrid automatic repeat request (HARQ) techniques as further described below. In some examples disclosed herein, the S-TXOP allows switching between DL and UL within a TXOP, thereby providing flexibility for the AP (scheduler) to address time- sensitive/low latency applications. However, alternating from DL/UL requires the constant switching from receiver (RX) to transmitter (TX) radio modes and vice-versa, which can result in the presence of residual carrier frequency and symbol timing offsets (e.g., after CFO correction and symbol timing estimation during S-TXOP preamble processing). Therefore, completely removing the timing/frequency synchronization from the DL/UL intervals may result in a small carrier frequency offset after every RX/TX transmission. Accordingly, examples disclosed herein include a minimal sync field in each scheduled DL/UL interval to enable small CFO correction. Because conventional L-STF or L-LTF fields are designed to correct high CFOs, examples disclosed herein may eliminate such conventional fields and replace them with a OFDM symbol sync field (instead of 2 symbols as in L-STF and L-LTF) with two symbol repetitions (3.2 us) prepended by a cyclic prefix (0.8 us). In this manner, examples disclosed herein reduce the overhead of preambles of PPDUs (e.g., for UL and/or DL transmissions) within a transmission opportunity.

Additionally, conventional Wi-Fi systems do not support HARQ mechanisms because

(A) such systems lack of support for centralized scheduling of transmissions and retransmissions,

(B) although long TXOP may be supported for some traffic classes (when TXOP limit =0), no more than one frame can be sent in such cases; therefore, there is no bound on the retransmission delay, and (C) such systems only relying on MAC layer acknowledgements (ACKs) as indication of successful transmission (e.g., as opposed to PHY later ACKs). Although MAC layer ACKs can improve reliability, they also add overhead and latency which is a problem for time-sensitive applications.

Examples disclosed herein support HARQ in legacy Wi-Fi systems within a Synchronous TXOP (S-TXOP), where access is controlled by the AP and time is divided in multiple DL/UL intervals. Examples disclosed herein support HARQ in Wi-Fi systems by decoding and detecting packet failures at the PHY layer. By adding the support for HARQ and S-TXOP operation, Wi-Fi APs and clients can benefit from improved link reliability, latency and throughput increase (e.g., especially when transmitting large data packets), thereby improving the Quality of Experience of the end users. In addition, the proposed HARQ methods for uplink communications can be easily implemented by 802.1 lax capable APs by leveraging the relatively larger compute and memory resources available compared to stations.

FIG. 1 illustrates a communication system using wireless local area network Wi-Fi protocols to facilitate a synchronous transmission opportunity. The example of FIG. 1 includes an example AP 100, example application processors l02a, l02b, example PHY level

communication determiners l04a, l04b, example radio architectures l06a, l06b, an example legacy STA 108, an example non -legacy STA 110, and an example network 112. Although the illustrated example of FIG. 1 includes two STAs 108, 110, the example AP 100 may

communicate with any number and/or type of STAs.

The example AP 100 of FIG. 1 is a device that allows the example STAs 108, 110 to wirelessly access the example network 112. The example AP 100 may be a router, a modem- router, and/or any other device that provides a wireless connection to the network 112. A router provides a wireless communication link to a STA. The router accesses the network 112 through a wire connection via a modem. A modem-router combines the functionalities of the modem and the router. In some examples, the AP 100 is a STA that is communication in the example legacy STA 108 and/or the example non-legacy STA 110. The example AP 100 includes the example PHY level communication determiner l04b to facilitate a synchronous transmission opportunity with the example non-legacy STA 110.

The example application processor l02a, l02b of FIG. 1 generates data to be transmitted to a device and/or performs operations based on data extracted from one or more data packets. For example, the application processor l02a, l02b may be a MAC controller in the MAC layer of the AP 100 and/or non-legacy STA 110. The application processor l02a, l02b instructs the example PHY level communication determiner l04a, l04b to generate data packets (e.g.,

PPDUs) based on the desired data to be transmitted. Additionally, the application processor l02a receives data that has been received from a transmitting device (e.g., the example legacy STA 108 and/or the example non-legacy STA 110). For example, the application processor l02a may receive synchronous data to synchronize itself with a connected device setting a timer at the MAC layer.

The example PHY level communication determiner l04a of the example AP 100 of FIG.

1 generates S-TXOP preambles and data units when the example application processor l02a, l02b of FIG. 1 sends the PHY level communication determiner l04a instructions to transmit data units (e.g., a PPDU) or receive a data unit. As described above, legacy data packet communication includes large preambles corresponding to the initiation of data transmission and also include large preambles for each DL/UL data transmission interval, thereby causing latency issues for applications that require low latency. Accordingly, the example PHY level communication determiner l04a of the example AP 100 generates the S-TXOP preambles and lite data packet preambles with a significant PHY overhead reduction, thereby providing data transmission that correspond to better throughput efficiency, lower latency, and more

deterministic latency than legacy transmissions. The example PHY level communication determiner 140 of the example AP 100 generates the S-TXOP preamble to correspond to a synchronous contention-free transmission with low overhead. The example S-TXOP preamble includes fields corresponding to a number and duration of DL/UL intervals for DL/UL transmissions within the transmission opportunity, thereby synchronizing DL/UL transmission between devices (e.g., the example AP 100 and the example no-legacy STA 110) throughout the transmission opportunity. The example S-TXOP preamble may include a legacy portion and a non-legacy portion. In this manner, when the example legacy STA 108 receives the legacy portion of the S-TXOP preamble, the legacy STA 108 refrains from contenting in the medium, thereby providing a contention-free transmission for the transmission opportunity to the non legacy STA 110. An example of the S-TXOP preamble and lite preambles generated by the example PHY level communication determiner 140 of the example AP 100 is further described below in conjunction with FIG. 3. Once the data packet is generated, the PHY level

communication determiner l04a transmits the data packet to the example radio architecture l06a to be wirelessly transmitted. The example radio architecture l06a is further described below in conjunction with FIG. 11. Additionally, the example PHY level communication determiner l04a of the example AP 100 receives and processes lite preambles for UL data packets from the example non-legacy STA 110. As further described below, the lite preambles reduce and/or otherwise correct small CFOs (3 PPM or around 15 KHz) caused by constant switching of the RX/TX front end of radio architecture of FIG. 11. In some examples, the PHY level

communication determiner l04a of the example AP 100 performs automatic repeat request (ARQ) or HARQ to acknowledge or negative acknowledge reception of UL data packets.

The example PHY level communication determiner l04b of the example non-legacy STA 110 of FIG. 1 receives S-TXOP preambles and facilitates communication with the example AP 100 based on the received S-TXOP preambles. For example, the PHY level communication determiner l04b of the example non-legacy STA 110 receives the S-TXOP preamble at the start of a transmission opportunity and processes the S-TXOP preamble to determine the number and duration of intervals for UL/DL transmissions. Additionally, the example PHY level communication determiner l04b of the example non-legacy STA 110 generates lite preambles for UL data packets transmitted to the example AP 100. In some examples, the PHY level communication determiner l04b of the example non-legacy STA 110 performs ARQ or HARQ to acknowledge or negative acknowledge reception of DL data packets. The example PHY level communication determiner l04b of the example non-legacy STA 110 receives and/or transmits data (e.g., including S-TXOP preambles) using the example radio architecture l06b of FIG. 11. Additionally, the example PHY level communication determiner l04b of the example non legacy STA 110 communicates with the example application processor l02b (e.g., the MAC layer) to receive data (e.g., MSDUs) for converting into UL PPDUs, to forward received and ordered DL packets, and/or to send synchronization information to synchronize a timer of the example application processor l02b.

The example STAs 108, 110 of FIG. 1 is a Wi-Fi enabled computing devices. The example STAs 108, 110 may be, for example, computing devices, portable devices, mobile devices, mobile telephones, smart phones, tablets, gaming systems, digital cameras, digital video recorders, televisions, set top boxes, e-book readers, automated systems, VR-enabled devices, and/or any other Wi-Fi enabled devices. As further described below in conjunction with FIG. 3, the S-TXOP preamble includes a legacy portion that allows the example legacy STA 108 to receive S-TXOP preambles from the example AP 100 and, even though they cannot

communicate based on the S-TXOP, the example legacy STA 108 sets its network allocation vector (NAV) to avoid communication during the S-TXOP with the example non-legacy STA 110. The example non-legacy STA 110 includes the example PHY level communication determiner l04b to process S-TXOP preambles and/or generate data packets to be transmitted to the example AP 100 to process the data packets transmitted by the example AP 100.

The example network 112 of FIG. 1 is a system of interconnected systems exchanging data. The example network 112 may be implemented using any type of public or private network such as, but not limited to, the Internet, a telephone network, a local area network (LAN), a cable network, and/or a wireless network. To enable communication via the network 112, the example Wi-Fi AP 100 includes a communication interface that enables a connection to an Ethernet, a digital subscriber line (DSL), a telephone line, a coaxial cable, or any wireless connection, etc.

FIG. 2 is a block diagram of an example implementation of the PHY level

communication determiner l04a, l04b of FIG. 1, disclosed herein, to facilitate synchronous a transmission opportunity. The example PHY level communication determiner l04a, l04b includes an example component interface 200, an example S-TXOP characteristic determiner 202, an example data converter 204, an example preamble generator 206, the example communication determiner 208, and an example PHY buffer 210.

The example component interface 200 of FIG. 2 interfaces with components of the transmitting device (e.g., the example AP 100 or the example non-legacy 110 of FIG. 1) to transmit signals (e.g., data units) and/or receive signals (e.g., instructions to generate a data units) from the example application processor l02a. In some examples, when the example PHY level communication determiner l04a is implemented in the example AP 100, the component interface 200 may instruct the example radio architecture l06a of FIGS. 1 and/or 12 to transmit S-TXOP preambles, and/or transmit DL data. In such examples, the component interface 200 additionally may receive instructions from the example application processor l02a (e.g., the MAC layer) to generate the S-TXOP preamble(s) and/or DL PPDUs during the transmission opportunity. In some examples, when the example PHY level communication determiner l04b is implemented in the example non-legacy STA 110, the example component interface 200 may receive S-TXOP preambles and/or DL data from the example radio architecture l06a. In such examples, the component interface 200 may additionally transmit received DL data to the example application processor l02b, transmit synchronization information to the example application processor l02b, and/or may receive UL data from the example application processor l02b to generate UL PPDUs to be transmitted to the example radio architecture l06b.

The example S-TXOP characteristics determiner 202 of FIG. 2 determines S-TXOP characteristics for the transmission opportunity so that the example AP 100 and the example non legacy STA 110 are synchronized throughout the transmission opportunity. The S-TXOP characteristics determiner 202 determines the S-TXOP characteristics by dividing the

transmission into intervals based on the UL data and/or the DL data to be transmitted within the transmission opportunity. For example, when the PHY level communication determiner l04a, l04b reserves a transmission opportunity, the example S-TXOP characteristic determiner 202 determines a number and duration of transmission boundaries (e.g., intervals) that are dedicated for UL/DL transmission, as well as the length of the entire transmission opportunity. In this manner, the example S-TXOP characteristic determiner 202 can divide the S-TXOP into intervals corresponding to UL transmission(s) and/or DL transmission(s). In some examples, the S-TXOP characteristics determiner 202 determines the S-TXOP opportunities based on the total amount of data to be transmitted (e.g., as DL and/or UL) within the transmission duration. For example, the S-TXOP characteristics determiner 202 may select the transmission duration to be as large as possible based on channel conditions (e.g., coherence length). Additionally, the example S-TXOP characteristics determiner 202 may select a codeword (CW) (e.g., a low- density parity-check (LDPC) or a binary convolution coding (BCC) codeword) length. The example S-TXOP characteristic determiner 202 may select the codeword length based on user and/or manufacture preferences. The example S-TXOP characteristic determiner 202 selects a coded MAC protocol data unit (MPDU) size to be an integer number of the LDPC CWs. The example S-TXOP characteristic determiner 202 may select coded MPDU size based on user and/or manufacture preferences. The coded MPDU size corresponds to latency and overhead (e.g., the better latency the more overhead). In some examples, when the PHY level

communication determiner l04b is implemented in the example non-legacy STA 110, the example S-TXOP characteristics determiner 202 process a received S-TXOP preamble to determine the S-TXOP characteristics from the S-TXOP preamble.

The example data converter 204 of FIG. 2 converts UL and/or DL data packets (e.g., a MAC service data unit (MSDU) from the application processor l02a, l02b) into PPDUs for transmission within the transmission opportunity. For example, the data converter 204 may adjust the DL/UL interval size to match the selected coded MPDU size. Once the sizes are determined, the example data converter 204 fragments the MSDU into MPDUs and match the MPDU size with the unencoded MPDU size (e.g., (coded segment size)x(LDPC code rate)), scrambles the each of the MPDUs, and generates PHY service data units (PSDUs) by adding a cyclic redundancy check (CRC) to the scrambled MPDUs. Additionally, the example data converter 204 may embed the CW into the PSDUs. The example PSDU in combination with the lite preamble (e.g., generated by the example preamble generator 206) corresponds to a PPDU. As further described below, the example data converter 204 may segment, scramble and code MSDUs to enable HARQ operation.

The example preamble generator 206 of FIG. 2 generates S-TXOP preambles to initiate a transmission opportunity and/or S-TXOP lite preambles for DL/UL packets within a

transmission opportunity. The S-TXOP preamble initiates a transmission opportunity. The S- TXOP includes both a legacy portion and a non -legacy portion. The legacy portion includes fields corresponding to legacy operation. In this manner, when the example legacy STA 108 receives the S-TXOP preamble, the legacy STA 108 does not contend for the medium within the transmission opportunity, even though the example legacy STA 108 cannot process the non legacy portion of the S-TXOP preamble. In some examples, the preamble generator 206 generates the non-legacy portion of the S-TXOP preamble by modulating the constellation of the non-legacy fields (e.g., by ninety degrees) and/or otherwise format, code, and/or modulate the non-legacy fields in a manner different from legacy frames, so that the example legacy STA 108 cannot process the non-legacy frames. The example preamble generator 206 generates the S- TXOP preamble with control information fields (e.g., STXOP SIG-A1 and STXOP SIG-A2) corresponding to the S-TXOP characteristics. In this manner, the non-legacy STA 110 can remain synchronized throughout the transmission opportunity, thereby allowing for a reduced preamble for individual DL/UL transmissions (e.g., a lite preamble). In some examples, the preamble generator 206 may additionally generate an optional control field (e.g., STXOP-SIG-B) corresponding to interval specific configuration information (e.g., information specific to a particular interval of the transmission opportunity) that may be useful to the example non-legacy STA 110 prior to the corresponding interval. Such information may include scheduling, semi static scheduling, etc. Additionally, the example preamble generator 206 generates the lite preamble. As further described below in conjunction with FIG. 3, the preamble generator 206 generates the lite preamble to include a RSYNC field to correct small CFOs, thereby eliminating the need of the L-STF, L-LTF, legacy signal field (L-SIG), and repeated L-SIG (RL-SIG) fields of conventional preamble fields for DL/UL packets. In this manner, the preamble generator 206 generates a lite preamble that is much shorter than conventional preambles to decrease overhead and further decrease latency of transmission during the transmission opportunity. Additionally, the example preamble generator 206 generates a lite trigger frame for UL transmissions. As further described below, the lite trigger PPDU (e.g., lightweight trigger PPDU) may be transmitted to the example STA 108 initiate UL transmissions. As further described below in conjunction with FIG. 3, the example preamble generator 206 generates the lite trigger PPDU to be much shorter than a PPDU transporting a conventional trigger frame by not including a MAC frame in the lite trigger PPDU. Rather, the lite PPDU includes uplink resource allocation information in a field followed by a synchronization field.

The example communication determiner 208 of FIG. 2 facilitates communication with a connected device including facilitating ARQ and/or HARQ operation to acknowledge reception of data packets. In some examples, if HARQ is not enabled and data reception has ended (e.g., reception of DL packets at the example non-legacy STA 110 or reception of UL packets at the example AP 100), the example communication determiner 208 transmits an ACK if all the packets have been received and transmits a negative ACK (NACK) or does not transmit anything if all the data packets have not been received. Additionally, the example communication determiner 208 discards the received data and wait for a retransmission of the data packet. In other examples, if HARQ is enabled and data reception has ended, the example communication determiner 208 transmits an ACK if the packet has been received and transmits a NACK if all the data packets have not been received. Additionally, the example communication determiner 208 stores the received data in the example PHY buffer 210. In this manner, if a retransmission includes the missing data of a preceding transmission, the example communication determiner 208 determines that all the data of the transmission has been received in at least one of the transmissions and the example communication determiner 208 transmits an ACK, regardless if the recent transmission is complete or not.

The example PHY buffer 210 of FIG. 2 stores received data packets when HARQ is enabled. In this manner, the example communication determiner 208 can determine that all the DL packets have been received with the DL packets are stored in the example PHY buffer 210, as opposed to if the current DL/UL transmission includes all the DL/UL data packets. When the example PHY buffer 210 includes all the data packets for a DL/UL transmission, the PHY buffer 210 transmits the data packets to the example application processor (e.g., the MAC layer) for further processing.

FIG. 3 is an example S-TXOP 300 for UL/DL transmission between the example AP 100 and the example non-legacy STA 110. The example S-TXOP 300 includes an example S-TXOP preamble 302 an example DL interval 304a, an example UL interval 304b, and an example UL/DL interface 304n. The example S-TXOP preamble 302 includes an example legacy portion 306 and an example non-legacy portion 307. The example non-legacy portion 307 includes an example STXOP-SIG-A1 control field 308a, an example STXOP-SIG-A2 control field 308b, and an optional example STXOP-SIG-B control field 310. The example UL/DL interval 304n may correspond to the example DL interval 304a or the example UL interval 304b. The example DL interval 304a includes an example DL PPDU 312 and an example ACK/ARQ/HARQ frame 314 and the example UL interval 304b includes the example ACK/ARQ/HARQ frame 314, an example lightweight (LW) trigger frame 316, an example UL lite preamble (LP) 317, and an example UL PPDU 318. The example DL PPDU 312 and/or the example UL PPDU 318 includes an example RSYNC field 320, an example STXOP-SIG-D field 322, an example HE- LTF frame(s) 324, and example data 326. The example ACK/HARQ frame may include an example RSYNC field 320 and an example STXOP-SIG-D field 322. The example LW trigger PPDU 316 includes the example RSYNC field 320 and the example STXOP-SIG-D field 322. Although, the example S-TXOP 300 may include three intervals for UL/DL transmission, the S- TXOP 300 may include any number of intervals corresponding to any duration of time.

Additionally, some field/frames may be rearranged, excluded, or added in the example of FIG. 4.

The example legacy portion 306 of the example S-TXOP preamble 302 of FIG. 3 includes legacy fields (e.g., L-STF, L-LTF, L-SIG, RL-SIG) that may be processed by the example legacy STA 108. In this manner, when the example legacy STA 108 receives the legacy portion 306 of the example S-TXOP preamble 302, the example legacy STA 108 refrains from communicating during the transmission opportunity. The example non-legacy portion 307 may be coded and/or modulated so that the example non-legacy STA 110 can process the information stored in the non-legacy portion 307 but the example legacy STA 108 cannot. In this manner, the S-TXOP 300 can be executed in an environment with both STAs 108, 110 (e.g., co-exist). The example PHY level communication determiner l04a of the example AP 100 may modulate and/or code the non-legacy portion 307 with a 90 degree phase shift, for example.

The example STXOP-SIG-A1 field 308a and the STXOP-SIG-A2 field 308b of the example S-TXOP preamble 302 of FIG. 3 are control information fields including data corresponding to the timing of the DL/UL transmission within the transmission opportunity. The STXOP-SIG-A1 field 308a and/or the STXOP-SIG-A2 field 308b include a number and duration of intervals inside the transmission opportunity after the S-TXOP preamble. For example, because the example S-TXOP 300 includes three UL/DL intervals, the example STXOP-SIG-A1 field 308a and/or the STXOP-SIG-A2 field 308b include data identifying the three intervals and the duration of each interval. Additionally, the example STXOP-SIG-A1 field 308a and the STXOP-SIG-A2 field 308b may include data related to the type of ACK signaling to use for each interval (e.g., no ACK, ARQ, or HARQ). If all of the control information data can be embedded into one of the example STXOP-SIG-A1 field 308a, the STXOP-SIG-A2 field 308b may repeat the data to increase the robustness of the data. Alternatively, if all of the control information data can be embedded into one of the example STXOP-SIG-A1 field 308a, the STXOP-SIG-A2 field 308b may be eliminated, thereby decreasing overhead.

The example STXOP-SIG-B field 310 of FIG. 3 is an optional control information field including data corresponding to interval specific configuration information. For example, if there is information that the example AP 100 would like to provide to the example non-legacy STA 110 corresponding to interval 3 prior to interval 3 occurring, the example AP 100 encodes such interval specific configuration information into the example STXOP-SIG-B field 310. Such information, for example, may include resource allocation and acknowledgement type applicable for the interval.

The example DL interval 304a of FIG. 3 is reserved for DL transmission (e.g., from the AP 100 to the non-legacy STA 110). The example DL interval 304a includes the example DL PPDU 312. The example DL PPDU is a portion of a MSDU that has been scrambled and encoded with a CRC by the example AP 100. The example AP 100 transmits the DL PPDU 312 during the DL interval 304a. Once the DL PPDU 312 has been transmitted, the example non legacy STA 110 responses with the example ACK/ARQ/HARQ frame 314 corresponding to whether or not the DL PPDU 312 has been received based on the ACK signaling used for each interval. For example, if the ACK signaling corresponds to a ACK/no ACK protocol, the non legacy STA 110 transmits an ACK to the AP 100 when the entire DL PPDU 312 was received and does not transmit an ACK to the AP 100 when some or all of the DL PPDU 312 was not received. If the ACK signaling corresponds to ARQ or HARQ, the non-legacy STA 110 transmits an ACK to the AP 100 when the entire DL PPDU 312 was received and transmits a NACK to the AP 100 when some or all of the DL PPDU 312 was not received and/or when the example PHY buffer 210 does not include all data corresponding to the interval. An example of the example ACK/ARQ/HARQ frame 314 being a HARQ signal, as further described below. The example UL interval 304b of FIG. 3 is reserved for UL transmission (e.g., from the non-legacy STA 110 to the AP 100). The example UL interval 304b includes the LW trigger PPDU 316 to initiate the UL transmission. The example LW trigger PPDU 316 is a control signal sent from the AP 100 to the non-legacy STA 110 to initiate UL transmission. The LW trigger PPDU 316 may correspond to spatial streams and/or orthogonal frequency division multiplexing (OFDMA) allocations for each connected STA and corresponds to the exact moment when the example non-legacy STA 110 should initiate UL transmission. The LW trigger PPDU 316 includes the example RSYNC field 320 and the example STXOP-SIG-D field 322, as further described below. The example LW trigger PPDU 316 is much shorter than a PPDU transporting a conventional trigger frame (e.g., a trigger frame including a full MAC layer frame), because the LW trigger PPDU 316 does not include a MAC frame. Rather, the LW trigger PPDU 316 includes uplink resource allocation information in the example STXOP-SIG-D field 322 following the RYNC field 320. The example UL interface 304b includes the example UL LP 319, as further described below. Additionally, the example UL interval 304b includes the example UL PPDU 318. The example UL PPDU 318 is a portion of a MSDU that has been scrambled and encoded with a CRC by the example non-legacy STA 110. The example non legacy STA 110 transmits the UL PPDU 318 during the DL interval 304a. Once the UL PPDU 318 has been transmitted, the example AP 100 responds with the example ACK/ARQ/HARQ frame 314 corresponding to whether or not the UL PPDU 318 has been received based on the ACK signaling used for each interval.

The example DL PPDU 312 and the example UL PPDU 318 include the example lite preamble 319. As described above, because the example S-TXOP preamble 302 synchronizes the non-legacy STA 110 and the AP 100 for the duration of the example S-TXOP 300, the preamble of individual intervals can be sized down to remove legacy fields (e.g., the L-STF, L- LTF, L-SIG, and RL-SIG frames). However, alternating between UL and DL requires switching of RX and TX front ends of the example radio architecture l06a, l06b of FIG. 11. Such switching may cause small CFO every UL/DL transmission. Accordingly, the example lite preamble 319 includes the example RSYNC field 320 to correct such small CFOS. The example RSYNC field 320 is a OFDM symbol sync field that includes two symbol repetitions (e.g., for 3.2 microseconds (us)) prepended by a cyclic prefix (0.8 us). The OFDM symbol may be generated by a 64 point inverse fast Fourier transform (IFFT) with 52-point frequency coefficients (e.g., subcarriers). For example, the RSYNC field 320 may include 52 subcarriers (e.g., 20 Megahertz) where the first 26 are repeated. In this manner, the receiving device can determine and correct the small CFO based on the repeated pattern. Alternatively, the RSYNC field 320 may include a sequence based on Zadoff-Chu or m-sequences.

The example lite preamble 319 of FIG. 3 further includes the example STXOP-SIG-D field 322. The example STXOP-SIG-D field 322 is a control information field (e.g.,

corresponding to UL transmission or DL transmission, depending on the data transmission type) including data related to resource allocation information for the example STA 110. Additionally, the example lite preamble 319 includes the example HE-LTF fields 324. The HE-LTF fields 324 are control information fields correspond to the multiple parameters for interpolation/smoothing during UL/DL transmission. Once the example lite preamble 319 is transmitted, the example data 326 is transmitted.

In some examples, the example ACK/ARQ/HARQ frame 314 corresponds to HARQ signaling. In such examples, the example HARQ frame 314 includes the example RSYNC field 320. As described above the RSYNC field 320 corrects small CFOs. Additionally, the example HARQ frame 314 includes the example STXOP-SIG-D field 322. The example STXOP-SIG-D field 322 includes a bitmap that corresponds to the received data packets that are stored in the example PHY buffer 210 of FIG. 2. In this manner, when the responding device transmits a NACK using the example HARQ frame 314, the bitmap identifies which parts of the example data 326 has been received and/or which parts of the example data 326 are missing (e.g., to initiate a retransmission). In some examples, the bitmap may correspond to 9 bits to denote ACK/NACK of nine 2 MHZ users operating in a 20 MHz operational band. Using the example ACK/ARQ/HARQ frame 314, a conventional preamble is not needed (e.g., because of the relevant information has already been provided in the example S-TXOP preamble 302) in , thereby reducing the amount of data need to transmit an acknowledgement.

While an example manner of implementing the example PHY level communication determiner l04a, l04b of FIG. 1 is illustrated in FIG. 2, one or more of the elements, processes and/or devices illustrated in FIG. 2 may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example component interface 200, the example S-TXOP characteristic determiner 202, the example data converter 204, the example preamble generator 206, the example communication determiner 208, the example PHY buffer 210 and/or, more generally, the example PHY level communication determiner l04a, l04b of FIG. 2 may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example component interface 200, the example S-TXOP characteristic determiner 202, the example data converter 204, the example preamble generator 206, the example communication determiner 208, the example PHY buffer 210 and/or, more generally, the example PHY level communication determiner l04a, l04b of FIG. 2 could be implemented by one or more analog or digital circuit(s), logic circuits, programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)). When reading any of the apparatus or system claims of this patent to cover a purely software and/or firmware implementation, at least one of the example, the example component interface 200, the example S-TXOP characteristic determiner 202, the example data converter 204, the example preamble generator 206, the example communication determiner 208, the example PHY buffer 210 and/or, more generally, the example PHY level communication determiner l04a, l04b of FIG. 2 is/are hereby expressly defined to include a non-transitory computer readable storage device or storage disk such as a memory, a digital versatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc., including the software and/or

firmware. Further still, the example PHY level communication determiner l04a, l04b of FIG. 2 may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated in FIG. 2, and/or may include more than one of any or all of the illustrated elements, processes and devices.

Flowcharts representative of example machine readable instructions for implementing the example PHY level communication determiner l04a, l04b of FIG. 2 is shown in FIGS. 4-10. In this example, the machine readable instructions comprise a program for execution by a processor such as the processor 1512 shown in the example processor platform 1500 discussed below in connection with FIG. 15. The program may be embodied in software stored on a non-transitory computer readable storage medium such as a CD-ROM, a floppy disk, a hard drive, a digital versatile disk (DVD), a Blu-ray disk, or a memory associated with the processor 1512, but the entire program and/or parts thereof could alternatively be executed by a device other than the processor 1512 and/or embodied in firmware or dedicated hardware. Further, although the example program is described with reference to the flowchart illustrated in FIGS. 4-10, many other methods of implementing the example PHY level communication determiner l04a, l04b may alternatively be used. For example, the order of execution of the blocks may be changed, and/or some of the blocks described may be changed, eliminated, or combined. Additionally or alternatively, any or all of the blocks may be implemented by one or more hardware circuits (e.g., discrete and/or integrated analog and/or digital circuitry, a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), a comparator, an operational- amplifier (op-amp), a logic circuit, etc.) structured to perform the corresponding operation without executing software or firmware.

As mentioned above, the example processes of FIGS. 4-10 may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a non- transitory computer and/or machine readable medium such as a hard disk drive, a flash memory, a read-only memory, a compact disk, a digital versatile disk, a cache, a random-access memory and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term non-transitory computer readable medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media.

“Including” and“comprising” (and all forms and tenses thereof) are used herein to be open ended terms. Thus, whenever a claim lists anything following any form of“include” or “comprise” (e.g., comprises, includes, comprising, including, etc.), it is to be understood that additional elements, terms, etc., may be present without falling outside the scope of the corresponding claim. As used herein, when the phrase "at least" is used as the transition term in a preamble of a claim, it is open-ended in the same manner as the term "comprising" and “including” are open ended.

FIG. 4 is an example flowchart 400 representative of example machine readable instructions that may be executed by the example PHY level communication determiner l04a of FIGS. 1 and/or 2 within the example AP 100 of FIG. 1 to facilitate a synchronous transmission opportunity in a wireless local area network (e.g., Wi-Fi network). Although the example of FIG. 4 is described in conjunction with the example AP 100 in the network of FIG. 1, the instructions may be executed by any type of AP in any network. At block 402, the example PHY level communication determiner l04a determines the S- TXOP characteristics (e.g., a number and duration of intervals for the S-TXOP). The example PHY level communication determiner l04a may determine the S-TXOP characteristics based on the data that needs to be communicated and/or channel conditions, as further described below in conjunction with FIG. 5. At block 404, the example preamble generator 206 determines if the transmission opportunity includes interval specific configuration information. The example application processor l02a may determine that the transmission opportunity includes interval specific configuration information that needs to be included in the S-TXOP preamble. If the example preamble generator 206 determines that the S-TXOP includes interval specific configuration information (block 404: YES), the example preamble generator 206 generates the S-TXOP preamble 302 based on the S-TXOP characteristics with the interval specific configuration information in the example STXOP-SIG-B field 310 of FIG. 3 (block 406). If the example preamble generator 206 determines that the S-TXOP does not include interval specific configuration information (block 404: NO), the example preamble generator 206 generates the S- TXOP preamble 302 based on the S-TXOP characteristics without the interval specific configuration information in the example STXOP-SIG-B field 310 of FIG. 3 (block 408).

At block 410, the example component interface 200 transmits the S-TXOP preamble 302 to the example radio architecture l06a to be wireless transmitted to the example STAs 108, 110. The example S-TXOP preamble 302 is further described above in conjunction with FIG. 3. At block 412, the example communication determiner 208 determines if the current interval of the transmission opportunity corresponds to UL transmission or DL transmission. The example communication determiner 208 determines whether the current interval corresponds to UL transmission or DL transmission based on the S-TXOP characteristics determined by the example PHY level communication determiner l04a and a timer of the example application processor l02a (e.g., the timer keeps track of time and the S-TXOP characteristics identify the number and duration of intervals of the S-TXOP).

If the example communication determiner 208 determines that the current interval of the S-TXOP corresponds to DL transmission (block 412: DL), the example PHY level

communication determiner l04a facilitates DL transmission with the example non -legacy STA 110 (block 414), as further described below in conjunction FIG. 6. If the example

communication determiner 208 determines that the current interval of the S-TXOP corresponds to UL transmission (block 412: UL), the example PHY level communication determiner l04a facilitates UL transmission with the example non-legacy STA 110 (block 416), as further described below in conjunction FIG. 7. At block 418, the example communication determiner 208 determines if the transmission opportunity has ended. The example communication determiner 208 determines that the transmission opportunity has ended based on a duration corresponding to the S-TXOP characteristics. If the example communication determiner 208 determines that the transmission opportunity has not ended (block 418: NO), the process returns to block 412. If the example communication determiner 208 determines that the transmission opportunity has ended (block 418: YES), the process ends.

FIG. 5 is an example flowchart 402 representative of example machine readable instructions that may be executed by the example PHY level communication determiner l04a of FIGS. 1 and/or 2 within the example AP 100 of FIG. 1 to determine S-TXOP characteristics, as described above in conjunction with block 402 of FIG. 4. Although the example of FIG. 5 is described in conjunction with the example AP 100 in the network of FIG. 1, the instructions may be executed by any type of AP in any network.

At block 502, the example S-TXOP characteristics determiner 202 determines the S- TXOP length (e.g., duration). The example S-TXOP characteristics determiner 202 may select the S-TXOP length to be as large as possible depending on the channel conditions (e.g., coherence length). At block 504, the example S-TXOP characteristic determiner 202 selects a codeword size. The code word is a LDPC and/or BCC code used for high-performance error correcting. In some examples, the CW size does not change during the S-TXOP operation. The example S-TXOP characteristics determiner 202 selects the CW size based on user and/or manufacture preferences. At block 506, the example S-TXOP characteristics determiner 202 selects a coded MPDU size to be an integer number of code words. The example S-TXOP characteristics determiner 202 selects the integer number based on user and/or manufacture preferences (e.g., the size of the number balancing latency vs. overhead).

At block 508, the example S-TXOP characteristics determiner 202 adjusts the individual DL/UL interval sizes to match the coded MPDU size. At block 510, the example S-TXOP characteristic determiner 202 determines the order/timing of the UL/DL packet transmissions in the transmission opportunity to divide the S-TXOP into intervals. At block 512, the example data converter 204 fragments the MSDU into MPDUs to match the MPDU size with the uncoded MPDU size of the DL packet. At block 514, the example data converter 204 scrambles the MPDUs of the DL packets. At block 516, the example data converter generates the PSDUs by adding the CRC to the scrambled MPDUs of the DL packet. In this manner, the AP 100 enables PHY level ACK/NACK capabilities corresponding to HARQ. At block 518, the example data converter 204 embeds code words into the PSDUs of the DL packets and the process returns to block 404 of FIG. 4.

FIG. 6 is an example flowchart 414 representative of example machine readable instructions that may be executed by the example PHY level communication determiner l04a of FIGS. 1 and/or 2 within the example AP 100 of FIG. 1 to facilitate DL transmission during the current interval, as described above in conjunction with block 414 of FIG. 4. Although the example of FIG. 6 is described in conjunction with the example AP 100 in the network of FIG. 1, the instructions may be executed by any type of AP in any network.

At block 602, the example preamble generator 206 generates the lite preamble 319 for the DL packet. As described above in conjunction with FIG. 3, the example lite preamble 319 includes the RSYNC field 320, as opposed to the legacy preamble fields, to correct small CFOs. At block 604, the example component interface 200 transmits the DL data packet 326 with the lite preamble 319 to the example non-legacy STA 110 via the example radio architecture l06a.

At block 606, the example communication determiner 208 determines if an ACK has been received. As described above, the ACK signaling may correspond to ACK/no ACK or

ACK/NACK signaling. Accordingly, the example communication determiner 208 determines if an ACK has been received if the ACK is received by the example component interface 200 via the radio architecture l06a and determines if the ACK is not received when (A) no ACK is received or (B) a NACK is received at the component interface 200 via the radio architecture l06a.

If the example communication determiner 208 determines that the ACK has been received (block 606: YES), the process returns to block 418 of FIG. 4. If the example communication determiner 208 determines that the ACK has not been received (block 606: NO), the example communication determiner 208 determines if a threshold number of attempts has been exceeded (e.g., based on user and/or manufacture preferences) (block 608). If the example communication determiner 208 determines that the threshold number of attempts has not been exceeded (block 608: NO), the process returns to block 604 to perform a retransmission. If the example communication determiner 208 determines that the threshold number of attempts has been exceeded (block 608: YES), the example communication determiner 208 discards DL data packet (block 610), and the process returns to block 418 of FIG. 4.

FIG. 7 is an example flowchart 416 representative of example machine readable instructions that may be executed by the example PHY level communication determiner l04a of FIGS. 1 and/or 2 within the example AP 100 of FIG. 1 to facilitate UL transmission during the current interval, as described above in conjunction with block 416 of FIG. 4. Although the example of FIG. 7 is described in conjunction with the example AP 100 in the network of FIG. 1, the instructions may be executed by any type of AP in any network.

At block 702, the example component interface 200 transmits the lite trigger PPDU to the non-legacy STA 110 corresponding to the UL data transmission. The example preamble generator 202 generates the lite trigger PPDU. As described above, the trigger PPDU initiates the UL transmission. At block 704, the example component interface 200 receives the UL data via the example radio architecture l06a from the non-legacy STA 110. In some examples, the communication determiner 208 may utilize the RSYNC field 320 to correct CFOs within the reception of the UL packet. For example, the communication determiner 208 may utilize CFO estimation techniques on the RSYNC field 320 to find the residual CFO. In this manner, the communication determiner 208 may apply compensation for the estimated CFO to the received data. At block 706, the example communication determiner 208 determines if HARQ is enabled. HARQ may be enabled based on initial communications with the example non-legacy STA 110.

If the example communication determiner 208 determines that HARQ is enabled (block 706: YES), the example communication determiner 208 stores the received UL data into the example PHY buffer 210 (block 708). If only part of the UL data is received, the example communication determiner 208 stores the partial data in the example PHY buffer 210. At block 710, the example communication determiner 208 determines that the example PHY buffer 210 includes all the data 326 of the example UL PPDU 318. For example, if the UL transmission is faulty or otherwise corrupt, the example PHY buffer 210 stores the portion of the data 326 that is not corrupt. If a retransmission includes the missing data, the example PHY buffer 210 can include all of the data 326. In this manner, the retransmission may only correspond to the missing data and/or the example PHY buffer 210 may determine that all of the data has been received even when a subsequent retransmission is faulty, so long as the subsequent retransmission includes the missing data.

If the example communication determiner 208 determines that the example PHY buffer 210 does not include all the data 326 of the example UL PPDU 312 (block 712: NO), the example component interface 200 transmits a NACK (block 712) via the example radio architecture l06a and the process returns to block 704 to process a retransmission or a subsequent transmission. For example, the component interface 200 may transmit the example HARQ field 3 l2a of FIG. 3 including a bitmap of the received and stored data in the PHY buffer 210. The example preamble generator 206 may generate the NACK frame. If the example communication determiner 208 determines that the example PHY buffer 210 includes all the data 326 of the example UL PPDU 318 (block 710: YES), the example component interface 200 transmits an HARQ field 3 l2a (block 714) via the example radio architecture l06a and the process returns to block 418 of FIG. 4. For example, the component interface 200 may transmit the example HARQ field 3 l2a of FIG. 3 including a complete bitmap (e.g., corresponding to an ACK) of the received and stored data in the PHY buffer 210. The example preamble generator 206 may generate the HARQ/ ACK frame.

Returning to block 706, if the example communication determiner 208 determines that HARQ is not enabled (block 706: NO), the example communication determiner 208 determines that the data 326 of the example UL PPDU 318 is complete (block 716). If the example communication determiner 208 determines that the data 326 of the example UL PPDU 318 is complete (block 716: YES), the example component interface 200 transmits the

ACK/ARQ/HARQ field 312 (block 714) corresponding to an ACK via the example radio architecture l06a and the process returns to block 418 of FIG. 4. If the example communication determiner 208 determines that the data 326 of the example UL PPDU 318 is not complete (block 716: NO), the example component interface 200 transmits the ACK/ARQ/HARQ field 312 (block 718) corresponding to an NACK via the example radio architecture l06a or the example component interface 200 refrains from transmitting an ACK and the process returns to block 704 to process a retransmission or subsequent transmission.

FIG. 8 is an example flowchart 800 representative of example machine readable instructions that may be executed by the example PHY level communication determiner l04b of FIGS. 1 and/or 2 within the example non-legacy STA 110 of FIG. 1 to facilitate a synchronous transmission opportunity in a wireless local area network (e.g., Wi-Fi network). Although the example of FIG. 8 is described in conjunction with the example non-legacy STA 110 in the network of FIG. 1, the instructions may be executed by any type of STA in any network.

At block 802, the example component interface 200 receives the example S-TXOP preamble 302 via the example radio architecture l06b. At block 804, the example S-TXOP characteristic determiner 202 processes the received S-TXOP preamble 302 to determine the S- TXOP configuration/synchronization information. For example, the S-TXOP characteristics determiner 202 determines the number of intervals, the length of each interval, the interval characteristics (e.g., which intervals are reserved for UL transmissions and which intervals are reserved for DL transmissions), the ACK/ARQ/HARG signaling protocol, and/or any interval specific information from the example S-TXOP preamble 302. At block 806, the example component interface 200 transmits the configuration/synchronization information to the MAC layer at the example application processor l02b. In this manner, the example MAC layer can synchronize a timer of the application processor l02b with the S-TXOP.

At block 808, the example communication determiner 208 determines if the transmission opportunity includes intervals corresponding to a UL transmission (e.g., based on the S-TXOP configurations and/or instructions from the example application processor l02b). If the example communication determiner 208 determines that the transmission opportunity does not include a UL transmission (block 808: NO), the process continues to block 812. If the example communication determiner 208 determines that the transmission opportunity includes a UL transmission (block 808: YES), the example data converter 204 converts the UL data (e.g., a MSDU) into UL data packets (e.g., PPDUs). For example, the data converter 204 may convert the UL data from the example application processor l02b to UL data packets to be transmitted to the example AP 100 in a similar manner to blocks 512-518 of FIG. 5.

At block 812, the example communication determiner 208 determines if the current interval of the transmission opportunity corresponds to UL transmission or DL transmission.

The example communication determiner 208 determines whether the current interval corresponds to UL transmission or DL transmission based on the S-TXOP characteristics determined by the example PHY level communication determiner l04b and a timer of the example application processor l02b (e.g., the timer keeps track of time and the S-TXOP characteristics identify the number and duration of intervals of the S-TXOP). If the example communication determiner 208 determines that the current interval of the S-TXOP corresponds to DL transmission (block 812: DL), the example PHY level

communication determiner l04b facilitates DL transmission with the example non-legacy STA 110 (block 814), as further described below in conjunction FIG. 7. If the example

communication determiner 208 determines that the current interval of the S-TXOP corresponds to UL transmission (block 812: UL), the example PHY level communication determiner l04b facilitates UL transmission with the example non-legacy STA 110 (block 816), as further described below in conjunction FIG. 10. At block 818, the example communication determiner 208 determines if the transmission opportunity has ended. The example communication determiner 208 determines that the transmission opportunity has ended based on a duration corresponding to the S-TXOP characteristics. If the example communication determiner 208 determines that the transmission opportunity has not ended (block 818: NO), the process returns to block 812. If the example communication determiner 208 determines that the transmission opportunity has ended (block 818: YES), the process ends.

FIG. 9 is an example flowchart 814 representative of example machine readable instructions that may be executed by the example PHY level communication determiner l04b of FIGS. 1 and/or 2 within the example non-legacy STA 110 of FIG. 1 to facilitate DL transmission during the current interval, as described above in conjunction with block 814 of FIG. 8.

Although the example of FIG. 9 is described in conjunction with the example non-legacy STA 110 in the network of FIG. 1, the instructions may be executed by any type of STA in any network.

At block 902, the example component interface 200 receives the DL data via the example radio architecture l06b from the non-legacy STA 110. In some examples, the communication determiner 208 may utilize the RSYNC field 320 to correct CFOs within the reception of the DL packet. At block 904, the example communication determiner 208 determines if HARQ is enabled. HARQ may be enabled based on initial communications with the example non-legacy STA 110.

If the example communication determiner 208 determines that HARQ is enabled (block 904: YES), the example communication determiner 208 stores the received DL data into the example PHY buffer 210 (block 906). If only part of the DL data is received, the example communication determiner 208 stores the partial data in the example PHY buffer 210. At block 908, the example communication determiner 208 determines if the example PHY buffer 210 includes all the data 326 of the example DL PPDU 312. For example, if the DL transmission is faulty or otherwise corrupt, the example PHY buffer 210 stores the portion of the data 326 that is not corrupt. If a retransmission includes the missing data, the example PHY buffer 210 can include all of the data 326. In this manner, the retransmission may only correspond to the missing data and/or the example PHY buffer 210 may determine that all of the data has been received even when a subsequent retransmission is faulty, so long as the subsequent

retransmission includes the missing data.

If the example communication determiner 208 determines that the example PHY buffer 210 does not include all the data 326 of the example DL PPDU 312 (block 910: NO), the example component interface 200 transmits a NACK (block 910) via the example radio architecture l06b and the process returns to block 902 to process a retransmission or a subsequent transmission. For example, the component interface 200 may transmit the example HARQ field 3 l2a of FIG. 3 including a bitmap of the received and stored data in the PHY buffer 210. The example preamble generator 206 may generate the NACK frame. If the example communication determiner 208 determines that the example PHY buffer 210 includes all the data 326 of the example DL PPDU 312 (block 908: YES), the example component interface 200 transmits an HARQ field 3 l2a (block 912) via the example radio architecture l06b and the process returns to block 818 of FIG. 8. For example, the component interface 200 may transmit the example HARQ field 3 l2a of FIG. 3 including a complete bitmap (e.g., corresponding to an ACK) of the received and stored data in the PHY buffer 210. The example preamble generator 206 may generate the HARQ/ ACK frame.

Returning to block 904, if the example communication determiner 208 determines that HARQ is not enabled (block 904: NO), the example communication determiner 208 determines if the data 326 of the example DL PPDU 312 is complete (block 914). If the example communication determiner 208 determines that the data 326 of the example DL PPDU 312 is complete (block 914: YES), the example component interface 200 transmits the

ACK/ARQ/HARQ field 312 (block 912) corresponding to an ACK via the example radio architecture l06b and the process returns to block 818 of FIG. 8. If the example communication determiner 208 determines that the data 326 of the example DL PPDU 312 is not complete (block 914: NO), the example component interface 200 transmits the ACK/ARQ/HARQ field 312 (block 916) corresponding to an NACK via the example radio architecture l06b or the example component interface 200 refrains from transmitting an ACK and the process returns to block 902 to process a retransmission or subsequent transmission.

FIG. 10 is an example flowchart 816 representative of example machine readable instructions that may be executed by the example PHY level communication determiner l04b of FIGS. 1 and/or 2 within the example non-legacy STA 110 of FIG. 1 to facilitate UL transmission during the current interval, as described above in conjunction with block 816 of FIG. 8.

Although the example of FIG. 10 is described in conjunction with the example non-legacy STA 110 in the network of FIG. 1, the instructions may be executed by any type of STA in any network.

At block 1002, the example component interface receives the example lite trigger PPDU 316. As described above in conjunction with FIG. 3, the LW example trigger PPDU 316 initiates the UL transmission. At block 1004, the example preamble generator 206 generates the lite preamble 319 for the UL packet. As described above in conjunction with FIG. 3, the example lite preamble 319 includes the RSYNC field 320, as opposed to the legacy preamble fields, to correct small CFOs. At block 1006, the example component interface 200 transmits the UL data packet 326 with the lite preamble 319 to the example non-legacy STA 110 via the example radio architecture l06b corresponding to the trigger PPDU (e.g., based on the timing of the reception of the trigger PPDU). At block 1008, the example communication determiner 208 determines if an ACK has been received. As described above, the ACK signaling may correspond to ACK/no ACK or ACK/NACK signaling. Accordingly, the example

communication determiner 208 determines if an ACK has been received if the ACK is received by the example component interface 200 via the radio architecture l06b and determines if the ACK is not received when no ACK is received or a NACK is received at the component interface 200 via the radio architecture l06b.

If the example communication determiner 208 determines that the ACK has been received (block 1008: YES), the process returns to block 418 of FIG. 4. If the example communication determiner 208 determines that the ACK has not been received (block 1008:

NO), the example communication determiner 208 determines if a threshold number of attempts has been exceeded (e.g., based on user and/or manufacture preferences) (block 1010). If the example communication determiner 208 determines that the threshold number of attempts has not been exceeded (block 1010: NO), the process returns to block 1006 to perform a retransmission. If the example communication determiner 208 determines that the threshold number of attempts has been exceeded (block 1010: YES), the example communication determiner 208 discards UL data packet (block 1012), and the process returns to block 418 of FIG. 4.

FIG. 11 is a block diagram of a radio architecture l06a, l06b in accordance with some embodiments that may be implemented in the example AP 100 and/or the example non -legacy STA 110 of FIG. 1. Radio architecture l06a, l06b may include radio front-end module (FEM) circuitry 1 l04a-b, radio IC circuitry 1 l06a-b and baseband processing circuitry 1 l08a-b. Radio architecture l06a, l06b as shown includes both Wireless Local Area Network (WLAN) functionality and Bluetooth (BT) functionality although embodiments are not so limited. In this disclosure,“WLAN” and“Wi-Fi” are used interchangeably.

FEM circuitry 1 l04a-b may include a WLAN or Wi-Fi FEM circuitry 1 l04a and a Bluetooth (BT) FEM circuitry 1 l04b. The WLAN FEM circuitry 1 l04a may include a receive signal path comprising circuitry configured to operate on WLAN RF signals received from one or more antennas 1101, to amplify the received signals and to provide the amplified versions of the received signals to the WLAN radio IC circuitry 1 l06a for further processing. The BT FEM circuitry 1 l04b may include a receive signal path which may include circuitry configured to operate on BT RF signals received from one or more antennas 1101, to amplify the received signals and to provide the amplified versions of the received signals to the BT radio IC circuitry 1 l06b for further processing. FEM circuitry 1 l04a may also include a transmit signal path which may include circuitry configured to amplify WLAN signals provided by the radio IC circuitry 1 l06a for wireless transmission by one or more of the antennas 1101. In addition, FEM circuitry 1 l04b may also include a transmit signal path which may include circuitry configured to amplify BT signals provided by the radio IC circuitry 1 l06b for wireless transmission by the one or more antennas. In the embodiment of FIG. 11, although FEM 1 l04a and FEM 1 l04b are shown as being distinct from one another, embodiments are not so limited, and include within their scope the use of an FEM (not shown) that includes a transmit path and/or a receive path for both WLAN and BT signals, or the use of one or more FEM circuitries where at least some of the FEM circuitries share transmit and/or receive signal paths for both WLAN and BT signals. Radio IC circuitry 1 l06a-b as shown may include WLAN radio IC circuitry 1 l06a and BT radio IC circuitry 1 l06b. The WLAN radio IC circuitry 1 l06a may include a receive signal path which may include circuitry to down-convert WLAN RF signals received from the FEM circuitry 1 l04a and provide baseband signals to WLAN baseband processing circuitry 1 l08a.

BT radio IC circuitry 1 l06b may in turn include a receive signal path which may include circuitry to down-convert BT RF signals received from the FEM circuitry 1 l04b and provide baseband signals to BT baseband processing circuitry 1 l08b. WLAN radio IC circuitry 1 l06a may also include a transmit signal path which may include circuitry to up-convert WLAN baseband signals provided by the WLAN baseband processing circuitry 1 l08a and provide WLAN RF output signals to the FEM circuitry 1 l04a for subsequent wireless transmission by the one or more antennas 1101. BT radio IC circuitry 1 l06b may also include a transmit signal path which may include circuitry to up-convert BT baseband signals provided by the BT baseband processing circuitry 1 l08b and provide BT RF output signals to the FEM circuitry 1 l04b for subsequent wireless transmission by the one or more antennas 1101. In the embodiment of FIG. 11, although radio IC circuitries 1 l06a and 1 l06b are shown as being distinct from one another, embodiments are not so limited, and include within their scope the use of a radio IC circuitry (not shown) that includes a transmit signal path and/or a receive signal path for both WLAN and BT signals, or the use of one or more radio IC circuitries where at least some of the radio IC circuitries share transmit and/or receive signal paths for both WLAN and BT signals.

Baseband processing circuity 1 l08a-b may include a WLAN baseband processing circuitry 1 l08a and a BT baseband processing circuitry 1 l08b. The WLAN baseband processing circuitry 1 l08a may include a memory, such as, for example, a set of RAM arrays in a Fast Fourier Transform or Inverse Fast Fourier Transform block (not shown) of the WLAN baseband processing circuitry 1 l08a. Each of the WLAN baseband circuitry 1 l08a and the BT baseband circuitry 1 l08b may further include one or more processors and control logic to process the signals received from the corresponding WLAN or BT receive signal path of the radio IC circuitry 1 l06a-b, and to also generate corresponding WLAN or BT baseband signals for the transmit signal path of the radio IC circuitry 1 l06a-b. Each of the baseband processing circuitries 1 l08a and 1 l08b may further include physical layer (PITY) and medium access control layer (MAC) circuitry, and may further interface with the example PITY level communication determiner l04a, l04b for generation and processing of the baseband signals and for controlling operations of the radio IC circuitry 1 l06a-b.

Referring still to FIG. 11, according to the shown embodiment, WLAN-BT coexistence circuitry 1113 may include logic providing an interface between the WLAN baseband circuitry 1 l08a and the BT baseband circuitry 1 l08b to enable use cases requiring WLAN and BT coexistence. In addition, a switch 1103 may be provided between the WLAN FEM circuitry 1 l04a and the BT FEM circuitry 1 l04b to allow switching between the WLAN and BT radios according to application needs. In addition, although the antennas 1101 are depicted as being respectively connected to the WLAN FEM circuitry 1 l04a and the BT FEM circuitry 1 l04b, embodiments include within their scope the sharing of one or more antennas as between the WLAN and BT FEMs, or the provision of more than one antenna connected to each of FEM 1104a or H04b.

In some embodiments, the front-end module circuitry 1 l04a-b, the radio IC circuitry 1 l06a-b, and baseband processing circuitry 1 l08a-b may be provided on a single radio card, such as wireless radio card 1102. In some other embodiments, the one or more antennas 1101, the FEM circuitry 1 l04a-b and the radio IC circuitry 1 l06a-b may be provided on a single radio card. In some other embodiments, the radio IC circuitry 1 l06a-b and the baseband processing circuitry 1 l08a-b may be provided on a single chip or integrated circuit (IC), such as IC 1112.

In some embodiments, the wireless radio card 1102 may include a WLAN radio card and may be configured for Wi-Fi communications, although the scope of the embodiments is not limited in this respect. In some of these embodiments, the radio architecture l06a, l06b may be configured to receive and transmit orthogonal frequency division multiplexed (OFDM) or orthogonal frequency division multiple access (OFDMA) communication signals over a multicarrier communication channel. The OFDM or OFDMA signals may comprise a plurality of orthogonal subcarriers.

In some of these multicarrier embodiments, radio architecture l06a, l06b may be part of a Wi-Fi communication station (STA) such as a wireless access point (AP), a base station or a mobile device including a Wi-Fi device. In some of these embodiments, radio architecture l06a, l06b may be configured to transmit and receive signals in accordance with specific

communication standards and/or protocols, such as any of the Institute of Electrical and

Electronics Engineers (IEEE) standards including, 802. l ln-2009, IEEE 802.11-2012, IEEE 802.11-2016, 802.11h-2009, 802.1 lac, 802. l lah, 802.1 lad, 802.1 lay and/or 802.1 lax standards and/or proposed specifications for WLANs, although the scope of embodiments is not limited in this respect. Radio architecture l06a, l06b may also be suitable to transmit and/or receive communications in accordance with other techniques and standards.

In some embodiments, the radio architecture l06a, l06b may be configured for high- efficiency Wi-Fi (HEW) communications in accordance with the IEEE 802.1 lax standard. In these embodiments, the radio architecture l06a, l06b may be configured to communicate in accordance with an OFDMA technique, although the scope of the embodiments is not limited in this respect.

In some other embodiments, the radio architecture l06a, l06b may be configured to transmit and receive signals transmitted using one or more other modulation techniques such as spread spectrum modulation (e.g., direct sequence code division multiple access (DS-CDMA) and/or frequency hopping code division multiple access (FH-CDMA)), time-division

multiplexing (TDM) modulation, and/or frequency-division multiplexing (FDM) modulation, although the scope of the embodiments is not limited in this respect.

In some embodiments, as further shown in FIG. 11, the BT baseband circuitry 1 l08b may be compliant with a Bluetooth (BT) connectivity standard such as Bluetooth, Bluetooth 12.0 or Bluetooth 10.0, or any other iteration of the Bluetooth Standard. In embodiments that include BT functionality as shown for example in FIG. 11, the radio architecture l06a, l06b may be configured to establish a BT synchronous connection oriented (SCO) link and or a BT low energy (BT LE) link. In some of the embodiments that include functionality, the radio architecture l06a, l06b may be configured to establish an extended SCO (eSCO) link for BT communications, although the scope of the embodiments is not limited in this respect. In some of these embodiments that include a BT functionality, the radio architecture may be configured to engage in a BT Asynchronous Connection-Less (ACL) communications, although the scope of the embodiments is not limited in this respect. In some embodiments, as shown in FIG. 11, the functions of a BT radio card and WLAN radio card may be combined on a single wireless radio card, such as single wireless radio card 1102, although embodiments are not so limited, and include within their scope discrete WLAN and BT radio cards In some embodiments, the radio-architecture l06a, l06b may include other radio cards, such as a cellular radio card configured for cellular (e.g., 5GPP such as LTE, LTE-Advanced or 7G communications).

In some IEEE 802.11 embodiments, the radio architecture l06a, l06b may be configured for communication over various channel bandwidths including bandwidths having center frequencies of about 900 MHz, 2.4 GHz, 5 GHz, and bandwidths of about 2 MHz, 4 MHz, 5 MHz, 5.5 MHz, 6 MHz, 8 MHz, 10 MHz, 20 MHz, 40 MHz, 80 MHz (with contiguous bandwidths) or 80+80 MHz (IόOMHz) (with non-conti guous bandwidths). In some

embodiments, a 920 MHz channel bandwidth may be used. The scope of the embodiments is not limited with respect to the above center frequencies however.

FIG. 12 illustrates WLAN FEM circuitry 1 l04a in accordance with some embodiments. Although the example of FIG. 12 is described in conjunction with the WLAN FEM circuitry 1 l04a, the example of FIG. 12 may be described in conjunction with the example BT FEM circuitry 1 l04b (FIG. 11), although other circuitry configurations may also be suitable.

In some embodiments, the FEM circuitry 1 l04a may include a TX/RX switch 1202 to switch between transmit mode and receive mode operation. The FEM circuitry 1 l04a may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry 1 l04a may include a low-noise amplifier (LNA) 1206 to amplify received RF signals 1203 and provide the amplified received RF signals 1207 as an output (e.g., to the radio IC circuitry 1 l06a-b (FIG. 11)). The transmit signal path of the circuitry 1 l04a may include a power amplifier (PA) to amplify input RF signals 1209 (e.g., provided by the radio IC circuitry 1 l06a- b), and one or more filters 1212, such as band-pass filters (BPFs), low-pass filters (LPFs) or other types of filters, to generate RF signals 1215 for subsequent transmission (e.g., by one or more of the antennas 1101 (FIG. 11)) via an example duplexer 1214.

In some dual-mode embodiments for Wi-Fi communication, the FEM circuitry 1 l04a may be configured to operate in either the 2.4 GHz frequency spectrum or the 12 GHz frequency spectrum. In these embodiments, the receive signal path of the FEM circuitry 1 l04a may include a receive signal path duplexer 1204 to separate the signals from each spectrum as well as provide a separate LNA 1206 for each spectrum as shown. In these embodiments, the transmit signal path of the FEM circuitry 1 l04a may also include a power amplifier 1210 and a filter 1212, such as a BPF, a LPF or another type of filter for each frequency spectrum and a transmit signal path duplexer 1204 to provide the signals of one of the different spectrums onto a single transmit path for subsequent transmission by the one or more of the antennas 1101 (FIG. 11). In some embodiments, BT communications may utilize the 2.4 GHz signal paths and may utilize the same FEM circuitry 1 l04a as the one used for WLAN communications.

FIG. 13 illustrates radio IC circuitry 1 l06a in accordance with some embodiments. The radio IC circuitry 1 l06a is one example of circuitry that may be suitable for use as the WLAN or BT radio IC circuitry 1 l06a/l006b (FIG. 11), although other circuitry configurations may also be suitable. Alternatively, the example of FIG. 13 may be described in conjunction with the example BT radio IC circuitry 1 l06b.

In some embodiments, the radio IC circuitry 1 l06a may include a receive signal path and a transmit signal path. The receive signal path of the radio IC circuitry 1 l06a may include at least mixer circuitry 1302, such as, for example, down-conversion mixer circuitry, amplifier circuitry 1306 and filter circuitry 1308. The transmit signal path of the radio IC circuitry 1 l06a may include at least filter circuitry 1312 and mixer circuitry 1314, such as, for example, up- conversion mixer circuitry. Radio IC circuitry 1 l06a may also include synthesizer circuitry 1304 for synthesizing a frequency 1305 for use by the mixer circuitry 1302 and the mixer circuitry 1314. The mixer circuitry 1302 and/or 1314 may each, according to some embodiments, be configured to provide direct conversion functionality. The latter type of circuitry presents a much simpler architecture as compared with standard super-heterodyne mixer circuitries, and any flicker noise brought about by the same may be alleviated for example through the use of OFDM modulation. FIG. 13 illustrates only a simplified version of a radio IC circuitry, and may include, although not shown, embodiments where each of the depicted circuitries may include more than one component. For instance, mixer circuitry 1314 may each include one or more mixers, and filter circuitries 1308 and/or 1312 may each include one or more filters, such as one or more BPFs and/or LPFs according to application needs. For example, when mixer circuitries are of the direct-conversion type, they may each include two or more mixers.

In some embodiments, mixer circuitry 1302 may be configured to down-convert RF signals 1207 received from the FEM circuitry 1 l04a-b (FIG. 11) based on the synthesized frequency 1305 provided by synthesizer circuitry 1304. The amplifier circuitry 1306 may be configured to amplify the down-converted signals and the filter circuitry 1308 may include a LPF configured to remove unwanted signals from the down-converted signals to generate output baseband signals 1307. Output baseband signals 1307 may be provided to the baseband processing circuitry 1 l08a-b (FIG. 11) for further processing. In some embodiments, the output baseband signals 1307 may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry 1302 may comprise passive mixers, although the scope of the embodiments is not limited in this respect.

In some embodiments, the mixer circuitry 1314 may be configured to up-convert input baseband signals 1311 based on the synthesized frequency 1305 provided by the synthesizer circuitry 1304 to generate RF output signals 1209 for the FEM circuitry 1 l04a-b. The baseband signals 1311 may be provided by the baseband processing circuitry 1 l08a-b and may be filtered by filter circuitry 1312. The filter circuitry 1312 may include a LPF or a BPF, although the scope of the embodiments is not limited in this respect.

In some embodiments, the mixer circuitry 1302 and the mixer circuitry 1314 may each include two or more mixers and may be arranged for quadrature down-conversion and/or up- conversion respectively with the help of synthesizer 1304. In some embodiments, the mixer circuitry 1302 and the mixer circuitry 1314 may each include two or more mixers each configured for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuitry 1302 and the mixer circuitry 1314 may be arranged for direct down-conversion and/or direct up-conversion, respectively. In some embodiments, the mixer circuitry 1302 and the mixer circuitry 1314 may be configured for super-heterodyne operation, although this is not a requirement.

Mixer circuitry 1302 may comprise, according to one embodiment: quadrature passive mixers (e.g., for the in-phase (I) and quadrature phase (Q) paths). In such an embodiment, RF input signal 1207 from FIG. 13 may be down-converted to provide I and Q baseband output signals to be sent to the baseband processor

Quadrature passive mixers may be driven by zero and ninety-degree time-varying LO switching signals provided by a quadrature circuitry which may be configured to receive a LO frequency (fLO) from a local oscillator or a synthesizer, such as LO frequency 1305 of synthesizer 1304 (FIG. 13). In some embodiments, the LO frequency may be the carrier frequency, while in other embodiments, the LO frequency may be a fraction of the carrier frequency (e.g., one-half the carrier frequency, one-third the carrier frequency). In some embodiments, the zero and ninety-degree time-varying switching signals may be generated by the synthesizer, although the scope of the embodiments is not limited in this respect.

In some embodiments, the LO signals may differ in duty cycle (the percentage of one period in which the LO signal is high) and/or offset (the difference between start points of the period). In some embodiments, the LO signals may have an 85% duty cycle and an 80% offset.

In some embodiments, each branch of the mixer circuitry (e.g., the in-phase (I) and quadrature phase (Q) path) may operate at an 80% duty cycle, which may result in a significant reduction is power consumption.

The RF input signal 1207 (FIG. 12) may comprise a balanced signal, although the scope of the embodiments is not limited in this respect. The I and Q baseband output signals may be provided to low-noise amplifier, such as amplifier circuitry 1306 (FIG. 13) or to filter circuitry 1308 (FIG. 13).

In some embodiments, the output baseband signals 1307 and the input baseband signals 1311 may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals 1307 and the input baseband signals 1311 may be digital baseband signals. In these alternate embodiments, the radio IC circuitry may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry.

In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, or for other spectrums not mentioned here, although the scope of the embodiments is not limited in this respect.

In some embodiments, the synthesizer circuitry 1304 may be a fractional -N synthesizer or a fractional N/N+l synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry 1304 may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider. According to some embodiments, the synthesizer circuitry 1304 may include digital synthesizer circuitry. An advantage of using a digital synthesizer circuitry is that, although it may still include some analog components, its footprint may be scaled down much more than the footprint of an analog synthesizer circuitry.

In some embodiments, frequency input into synthesizer circuity 1304 may be provided by a voltage controlled oscillator (VCO), although that is not a requirement. A divider control input may further be provided by either the baseband processing circuitry 1 l08a-b (FIG. 11) or a link aggregator depending on the desired output frequency 1305. In some embodiments, a divider control input (e.g., N) may be determined from a look-up table (e.g., within a Wi-Fi card) based on a channel number and a channel center frequency as determined or indicated by the link aggregator. The application processor l02a, l02b may include, or otherwise be connected to, the example PHY communication determiner l04a, l04b of FIG. 1. The application processor l02a, l02b includes an example timer 1110. The example application processor l02a, l02b may synchronize its timer 1110 based on information from the example PHY communication determiner l04a, l04b.

In some embodiments, synthesizer circuitry 1304 may be configured to generate a carrier frequency as the output frequency 1305, while in other embodiments, the output frequency 1305 may be a fraction of the carrier frequency (e.g., one-half the carrier frequency, one-third the carrier frequency). In some embodiments, the output frequency 1305 may be a LO frequency (fLO).

FIG. 14 illustrates a functional block diagram of baseband processing circuitry 1 l08a in accordance with some embodiments. The baseband processing circuitry 1 l08a is one example of circuitry that may be suitable for use as the baseband processing circuitry 1 l08a (FIG. 11), although other circuitry configurations may also be suitable. Alternatively, the example of FIG. 133 may be used to implement the example BT baseband processing circuitry 1 l08b of FIG. 11.

The baseband processing circuitry 1 l08a may include a receive baseband processor (RX BBP) 1402 for processing receive baseband signals 1309 provided by the radio IC circuitry 1 l06a-b (FIG. 11) and a transmit baseband processor (TX BBP) 1404 for generating transmit baseband signals 1311 for the radio IC circuitry 1 l06a-b. The baseband processing circuitry 1 l08a may also include control logic 1406 for coordinating the operations of the baseband processing circuitry 1108a.

In some embodiments (e.g., when analog baseband signals are exchanged between the baseband processing circuitry 1 l08a-b and the radio IC circuitry 1 l06a-b), the baseband processing circuitry 1 l08a may include ADC 1410 to convert analog baseband signals 1409 received from the radio IC circuitry 1 l06a-b to digital baseband signals for processing by the RX BBP 1402. In these embodiments, the baseband processing circuitry 1 l08a may also include DAC 1412 to convert digital baseband signals from the TX BBP 1404 to analog baseband signals 1411.

In some embodiments that communicate OFDM signals or OFDMA signals, such as through baseband processor 1 l08a, the transmit baseband processor 1404 may be configured to generate OFDM or OFDMA signals as appropriate for transmission by performing an inverse fast Fourier transform (IFFT). The receive baseband processor 1402 may be configured to process received OFDM signals or OFDMA signals by performing an FFT. In some

embodiments, the receive baseband processor 1402 may be configured to detect the presence of an OFDM signal or OFDMA signal by performing an autocorrelation, to detect a preamble, such as a short preamble, and by performing a cross-correlation, to detect a long preamble. The preambles may be part of a predetermined frame structure for Wi-Fi communication.

Referring back to FIG. 11, in some embodiments, the antennas 1101 (FIG. 11) may each comprise one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas or other types of antennas suitable for transmission of RF signals. In some multiple-input multiple-output (MIMO) embodiments, the antennas may be effectively separated to take advantage of spatial diversity and the different channel characteristics that may result. Antennas 1101 may each include a set of phased-array antennas, although embodiments are not so limited.

Although the radio-architecture l06a, l06b is illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including digital signal processors (DSPs), and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), radio-frequency integrated circuits (RFICs) and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, the functional elements may refer to one or more processes operating on one or more processing elements.

FIG. 15 is a block diagram of an example processor platform 1500 capable of executing the instructions of FIGS. 4-10 to implement the example PHY level communication determiner l04a, l04b of FIGS. 1 and 2. The processor platform 1500 can be, for example, a server, a personal computer, a mobile device (e.g., a cell phone, a smart phone, a tablet such as an iPad™), a personal digital assistant (PDA), an Internet appliance, or any other type of computing device.

The processor platform 1500 of the illustrated example includes a processor 1512. The processor 1512 of the illustrated example is hardware. For example, the processor 1512 can be implemented by integrated circuits, logic circuits, microprocessors or controllers from any desired family or manufacturer.

The processor 1512 of the illustrated example includes a local memory 1513 (e.g., a cache). The example processor 1512 of FIG. 15 executes the instructions of FIGS. 4-10 to implement the example component interface 200, the example S-TXOP characteristic determiner 202, the example data converter 204, the example preamble generator 206, the example communication determiner 208, and/or the example PHY buffer 210 of FIG. 2, and/or the example application processor l02a, l02b of FIGS. 1 and/or 11. The processor 1512 of the illustrated example is in communication with a main memory including a volatile memory 1514 and a non-volatile memory 1516 via a bus 1518. The volatile memory 1514 may be

implemented by Synchronous Dynamic Random Access Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM) and/or any other type of random access memory device. The non-volatile memory 1516 may be

implemented by flash memory and/or any other desired type of memory device. Access to the main memory 1514, 1516 is controlled by a clock controller.

The processor platform 1500 of the illustrated example also includes an interface circuit 1520. The interface circuit 1520 may be implemented by any type of interface standard, such as an Ethernet interface, a universal serial bus (USB), and/or a PCI express interface.

In the illustrated example, one or more input devices 1522 are connected to the interface circuit 1520. The input device(s) 1522 permit(s) a user to enter data and commands into the processor 1512. The input device(s) can be implemented by, for example, a sensor, a microphone, a camera (still or video), a keyboard, a button, a mouse, a touchscreen, a track-pad, a trackball, isopoint and/or a voice recognition system.

One or more output devices 1524 are also connected to the interface circuit 1520 of the illustrated example. The output devices 1524 can be implemented, for example, by display devices (e.g., a light emitting diode (LED), an organic light emitting diode (OLED), a liquid crystal display, a cathode ray tube display (CRT), a touchscreen, a tactile output device, and/or speakers). The interface circuit 1520 of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip or a graphics driver processor.

The interface circuit 1520 of the illustrated example also includes a communication device such as a transmitter, a receiver, a transceiver, a modem and/or network interface card to facilitate exchange of data with external machines (e.g., computing devices of any kind) via a network 1526 (e.g., an Ethernet connection, a digital subscriber line (DSL), a telephone line, coaxial cable, a cellular telephone system, etc.).

The processor platform 1500 of the illustrated example also includes one or more mass storage devices 1528 for storing software and/or data. Examples of such mass storage devices 1528 include floppy disk drives, hard drive disks, compact disk drives, Blu-ray disk drives,

RAID systems, and digital versatile disk (DVD) drives.

The coded instructions 1532 of FIGS. 4-10 may be stored in the mass storage device 1528, in the volatile memory 1514, in the non-volatile memory 1516, and/or on a removable tangible computer readable storage medium such as a CD or DVD.

From the foregoing, it would be appreciated that the above disclosed method, apparatus, and articles of manufacture facilitate a synchronous transmission opportunity in a wireless local area network. Examples disclosed herein provide a synchronous contention-free transmission with low overhead and low latency within a transmission opportunity using a S-TXOP preamble for the S-TXOP and a lite preamble for UL/DL PPDUs within the transmission opportunity. Using examples disclosed herein, the PPDU preamble (e.g., the lite preamble compared to a regular preamble) is reduced by 41.6 us for each DL PPDU and 112 us for each UL PPDU considering Single Input Single Output (SISO) communication involving nine stations. Further, the lite preamble provides a peak to average power reduction (P PR) of 1.83 decibel (dB), with 15 dB separation between a correlation peak and a side lobe peak, allowing a maximum CFO correction of 312.5 KHz (± l/l.6us/2). Accordingly, examples disclosed herein provide a synchronous transmission opportunity with significantly lower overhead and latency than conventional Wi-Fi techniques.

Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the claims of this patent.