Mid-amble format for packets in vehicle communication networks

Abstract

In a vehicular communication network, a communication device generates a PHY preamble of a physical layer (PHY) protocol data unit (PPDU) for transmission in the vehicular communication network. The communication device generates multiple PHY data segments of the PPDU and one or more PHY midambles, each PHY midamble to be transmitted between a respective pair of adjacent PHY data segments, and each PHY midamble includes one or more training signal fields. If the PPDU is to be transmitted according to an extended range (ER) mode, generating the one or more PHY midambles includes generating each training signal field including: i) a first portion based on a Very High Throughput Long Training Field (VHT-LTF) defined by the IEEE 802.11ac standard; and ii) a second portion based on the VHT-LTF defined by the IEEE 802.11ac standard. The communication device transmits the PPDU in the vehicular communication network.

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 897,130, entitled "Next - Generation Vehicular (NGV) Midamble Format," filed on September 6, 2019, which is hereby incorporated by reference in its entirety.

[0002] The present disclosure generally relates to vehicle communication networks, and more particularly, to physical layer protocol data unit formats.

Background Art

[0003] Wireless local area networks (WLANs) have been rapidly evolving over the past decade, and the development of WLAN standards such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard family has improved single - user peak data throughput. For example, the IEEE 802.11b standard specifies a single - user peak throughput of 11 megabits per second (Mbps), the IEEE 802.11a and 802.11g standards specify a single - user peak throughput of 54 Mbps, the IEEE 802.11n standard specifies a single - user peak throughput of 600 Mbps, and the IEEE 802.11ac standard specifies a single - user peak throughput in the gigabits per second (Gbps) range. Future standards are expected to provide even higher throughputs, such as throughputs in the tens of Gbps range.

[0004] The IEEE 802.11p standard specifies a protocol for wireless access in vehicular environments (WAVE). Future WAVE standards, such as the IEEE 802.11bd standard (currently under development), aim to improve vehicle-to-vehicle or vehicle-to-infrastructure connectivity, throughput, and infotainment capabilities. Several challenges faced in vehicle communication networks are caused by the high relative speed of the transmitter and receiver. For example, when the transmitter and / or receiver are moving relative to each other at high speeds, the channel state can change significantly during packet transmission. [Overview of the project]

[0005] In one embodiment, a method for wireless communication in a vehicle communication network includes: a step of generating a PHY preamble for a Physical Layer (PHY) Protocol Data Unit (PPDU) for transmission in the vehicle communication network in a communication device according to a communication protocol for vehicle communication; a step of generating a plurality of PHY data segments of the PPDU in the communication device; and a step of generating one or more PHY midambles in the communication device, each PHY midamble to be transmitted between each pair of adjacent PHY data segments, each PHY midamble including one or more training signal fields, and the step of generating the one or more PHY midambles to be transmitted according to the Extended Range (ER) mode defined by the communication protocol, i) very high throughput long training field (VHT-LTF) as defined by the IEEE 802.11ac standard The process comprises: a step of generating one or more PHY midambles, each having a step of generating a training signal field including a first part based on the field and a second part based on the VHT-LTF as defined by the IEEE 802.11ac standard; and a step of transmitting the PPDU in the vehicle communication network by the communication device.

[0006] In another embodiment, the communication device is configured to operate in a vehicle communication network and includes a wireless network interface device. The wireless network interface device has one or more IC devices, the one or more IC devices are configured to: generate a PHY preamble for a PPDU to be transmitted in the vehicle communication network in accordance with a communication protocol for vehicle communication; generate a plurality of PHY data segments of the PPDU; generate one or more PHY midambles, each PHY midamble to be transmitted between each pair of adjacent PHY data segments, each PHY midamble comprising one or more training signal fields, and generating the one or more PHY midambles comprises generating each training signal field comprising i) a first portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, if the PPDU is to be transmitted in an extended range (ER) mode as defined by the communication protocol; and control the wireless network interface device to transmit the PPDU in the vehicle communication network.

[0007] In yet another embodiment, a method for accessing a communication channel in a vehicle communication network includes: a step of a communication device generating a PHY preamble for a PPDU for transmission in the vehicle communication network according to a communication protocol for vehicle communication; a step of the communication device generating a plurality of PHY data segments of the PPDU; and a step of the communication device selecting one or more PHY midamble formats from a set of a plurality of different PHY midamble formats based on the transmission mode of the PPDU, wherein the set of a plurality of different PHY midamble formats includes: i) a first format corresponding to an extended range transmission mode defined by the communication protocol, using an uncompressed training signal field; and ii) a format defined by the communication protocol, using a compressed training signal field. The communication device comprises: a selection step, including a second format corresponding to a defined high-throughput transmission mode; a step of generating one or more PHY midambles in the communication device according to the selected format, each PHY midamble being transmitted between each pair of adjacent PHY data segments, each PHY midamble including one or more training signal fields, the step of generating each PHY midamble comprising: i) a step of selectively including uncompressed training signal fields if the first format is selected, and ii) a step of selectively including compressed training signal fields if the second format is selected; and a step of transmitting the PPDU in the vehicle communication network by the communication device.

[0008] In another embodiment, the communication device is configured to operate in a vehicle communication network and includes a wireless network interface device. The wireless network interface device has one or more IC devices, the one or more IC devices: generating a PHY preamble for a PPDU for transmission in the vehicle communication network according to a communication protocol for vehicle communication; generating multiple PHY data segments of the PPDU; and selecting one or more PHY midamble formats from a set of multiple different PHY midamble formats based on the transmission mode of the PPDU, the set of multiple different PHY midamble formats being: i) a first format corresponding to an extended range transmission mode defined by the communication protocol, using an uncompressed training signal field; and ii) a high-throughput transmission mode defined by the communication protocol, using a compressed training signal field. The system is configured to: select a second format corresponding to a code; generate one or more PHY midambles according to the selected format, each PHY midamble being transmitted between each pair of adjacent PHY data segments, each PHY midamble including one or more training signal fields, and generating each PHY midamble having i) selectively including uncompressed training signal fields if the first format is selected, and ii) selectively including compressed training signal fields if the second format is selected; and control the wireless network interface device to transmit the PPDU in the vehicle communication network. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram of an exemplary vehicle communication network according to one embodiment.

[0010] [Figure 2A] Figure 1 shows an example of a physical layer protocol data unit (PPDU) for transmission in a vehicle communication network according to one embodiment.

[0011] [Figure 2B] In one embodiment, Figure 1 shows another exemplary PPDU for transmission in the vehicle communication network.

[0012] [Figure 3] This is a block diagram of an exemplary physical layer (PHY) midamble that may be used with the PPDU shown in Figures 2A and 2B, according to one embodiment.

[0013] [Figure 4] This is a block diagram of another exemplary PHY midamble, which may be used in conjunction with the PPDU of Figures 2A and 2B, according to another embodiment.

[0014] [Figure 5] This is a block diagram of another exemplary PHY midamble, which may be used in conjunction with the PPDU of Figures 2A and 2B, according to another embodiment.

[0015] [Figure 6] This is a flowchart illustrating an example method for transmitting a PPDU in the vehicle communication network shown in Figure 1, according to one embodiment.

[0016] [Figure 7] This is a flowchart illustrating an example method for transmitting a PPDU in the vehicle communication network shown in Figure 1, according to another embodiment.

[0017] [Figure 8] This is a flowchart illustrating yet another exemplary method for transmitting a PPDU in the vehicle communication network shown in Figure 1, according to a different embodiment.

[0018] [Figure 9] FIG. 1 is a flowchart of yet another exemplary method of transmitting a PPDU in the vehicle communication network according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] In the embodiments described below, the vehicle communication network includes communication devices such as access points and client stations that operate according to one or more protocols that define wireless access (WAVE) communication in a vehicle environment. In one embodiment, the access point is embedded in a roadside unit, and the client station is embedded in a moving vehicle that operates in the vehicle communication network. In one embodiment, a client station operating in the vehicle communication network can communicate with other client stations and / or roadside units to exchange information such as safety warnings, traffic information, etc., which can, in one embodiment, enhance the safety of the moving vehicle and improve the driving experience. To improve the performance in the vehicle communication network (e.g., to reduce the Doppler effect), packets transmitted in the vehicle communication network are generated to include a physical layer (PHY) midamble that allows the receiver to update the channel estimate value during packet reception. Various exemplary PHY midamble formats are described below.

[0020] Figure 1 is a block diagram of an exemplary vehicle communication network 110 according to one embodiment. The vehicle communication network 110 includes an access point (AP) 114. In one embodiment, the AP 114 corresponds to a roadside unit operating in the vehicle communication network. The AP 114 includes a host processor 118 coupled to a network interface device 122. In one embodiment, the network interface device 122 includes a media access control (MAC) processor 126 and a PHY processor 130. The PHY processor 130 includes a plurality of transceivers 134, the transceivers 134 being coupled to a plurality of antennas 138. Although Figure 1 shows three transceivers 134 and three antennas 138, in other embodiments, the AP 114 includes a suitable number of transceivers 134 and antennas 138 (e.g., one, two, four, five, etc.). In some embodiments, the AP 114 includes more antennas 138 than transceivers 134, and antenna switching techniques are used. In one embodiment, the MAC processor 126 and the PHY processor 130 are configured to operate according to at least a first communication protocol (e.g., the IEEE 802.11bd standard, or another suitable communication protocol designed for vehicle communications). In another embodiment, the MAC processor 126 and the PHY processor 130 are also configured to operate according to a second communication protocol different from the first communication protocol (e.g., the IEEE 802.11p standard, or another suitable communication protocol designed for vehicle communications). In some embodiments, the second communication protocol is a legacy communication protocol relative to the first communication protocol.

[0021] Network interface device 122 is implemented using one or more integrated circuits (ICs) configured to operate as described below. For example, MAC processor 126 may be implemented, at least in part, on a first IC, and PHY processor 130 may be implemented, at least in part, on a second IC. As another example, at least a portion of MAC processor 126 and at least a portion of PHY processor 130 may be implemented on a single IC. For example, network interface device 122 may be implemented using a system-on-chip (SoC) that includes at least a portion of MAC processor 126 and at least a portion of PHY processor 130. As yet another example, the entire MAC processor 126 and the entire PHY processor 130 may be implemented on a single IC.

[0022] In one embodiment, host processor 118 includes a processor configured to execute machine-readable instructions stored in a memory device (not shown) such as random access memory (RAM), read-only memory (ROM), flash memory, etc. In one embodiment, host processor 118 may be implemented, at least in part, on a first IC, and network interface device 122 may be implemented, at least in part, on a second IC. As another example, host processor 118 and at least a portion of network interface device 122 may be implemented on a single IC.

[0023] In various embodiments, the MAC processor 126 and / or PHY processor 130 of the AP114 are configured to generate data units compliant with a first communication protocol and to process received data units. For example, the MAC processor 126 is configured to implement MAC layer functions, including MAC layer functions of the first communication protocol, and the PHY processor 130 is configured to implement PHY functions, including PHY functions of the first communication protocol. For example, the MAC processor 126 is configured to generate MAC layer data units such as MAC Service Data Units (MSDUs), MPDUs, A-MPDUs, etc., and to provide these MAC layer data units to the PHY processor 130.

[0024] The PHY processor 130 is configured to receive MAC layer data units from the MAC processor 126 and encapsulate them for transmission via the antenna 138 to generate PHY data units such as PHY protocol data units (PPDUs) and PHY protocol service data units (PSDUs). Similarly, the PHY processor 130 is configured to receive PHY data units received via the antenna 138 and extract the MAC layer data units encapsulated within those PHY data units. The PHY processor 130 may provide the extracted MAC layer data units to the MAC processor 126, which then processes the MAC layer data units.

[0025] According to one embodiment, the PHY processor 130 is configured to down-convert one or more radio frequency (RF) signals received via one or more antennas 138 into one or more baseband analog signals, and to convert the analog baseband signals into one or more digital baseband signals. The PHY processor 130 is further configured to process one or more digital baseband signals to demodulate one or more digital baseband signals and generate a PPDU. The PHY processor 130 includes one or more forward error correction (FEC) encoders (e.g., binary convolutional code (BCC) encoders, low-density parity check (LDPC) encoders, etc.), one or more FEC decoders (e.g., BCC decoders, LDPC decoders, etc.), amplifiers (e.g., low-noise amplifiers (LNAs), power amplifiers, etc.), radio frequency (RF) downconverters, RF upconverters, multiple filters, one or more analog-to-digital converters (ADCs), one or more digital-to-analog converters (DACs), one or more discrete Fourier transform (DFT) calculators (e.g., fast Fourier transform (FFT) calculators), one or more inverse discrete Fourier transform (IDFT) calculators (e.g., inverse fast Fourier transform (IFFT) calculators), one or more modulators, one or more demodulators, etc.

[0026] The PHY processor 130 is configured to generate one or more RF signals that are provided to one or more antennas 138. The PHY processor 130 is also configured to receive one or more RF signals from one or more antennas 138.

[0027] According to several embodiments, the MAC processor 126 is configured to control the PHY processor 130 to generate one or more RF signals by, for example, providing the PHY processor 130 with one or more MAC layer data units (e.g., MPDUs) and optionally providing the PHY processor 130 with one or more control signals. In one embodiment, the MAC processor 126 includes a processor configured to execute machine-readable instructions stored in a memory device (not shown), such as RAM, ROM, or flash memory. In one embodiment, the MAC processor 126 includes a hardware state machine configured to perform MAC layer functions, control the PHY processor 130, and the like.

[0028] In some embodiments, the first communication protocol defines multiple transmission modes, and the PHY processor 130 is configured to generate PPDUs having different formats and / or content for different transmission modes. As an example, the multiple transmission modes include an extended range (ER) mode and one or more non-ER modes. According to one embodiment, the ER mode is designed to increase the range over which the PPDU can be correctly decoded by the receiver. As an example, the ER mode utilizes modulation and / or coding techniques that take advantage of increased redundancy at the expense of data throughput. In another embodiment, the multiple transmission modes include, in addition to or alternatively, a high-throughput mode, which may use more complex modulation techniques that increase throughput but reduce the range over which the PPDU can be correctly decoded. In another embodiment, the multiple transmission modes include i) an ER mode as discussed above, ii) a high-throughput mode as discussed above, and iii) a default transmission mode. According to one embodiment, the default mode is designed to provide a reception range that generally tends to fall between the reception range of ER mode and the reception range of high-throughput mode, and to provide a data throughput that generally tends to fall between the data throughput of ER mode and the data throughput of high-throughput mode.

[0029] In one embodiment, the network interface device 122 (e.g., PHY processor 130) includes a PHY midamble generator 142 configured to generate PHY midambles based on an ultra-high throughput long training field (VHT-LTF) as defined by the IEEE 802.11ac standard. In some embodiments, the PHY midamble generator 142 is configured to generate one or more PHY midambles so that the PPDU has different content depending on the transmission mode of the PPDU. According to various embodiments, the PHY midamble generator 142 is configured to generate one or more PHY midambles having a format such as those described below, or having other suitable PHY midamble formats.

[0030] In one embodiment, the PHY midamble generator 142 includes hardware circuitry configured to generate a PHY midamble as described below, or other suitable PHY midambles. In one embodiment, the PHY midamble generator 142 is additionally or alternatively implemented by a processor configured to execute machine-readable instructions stored in a memory device (not shown), such as RAM, ROM, or flash memory, in various embodiments.

[0031] The vehicle communication network 110 comprises a plurality of client stations 154. Each client station 154 is included in each vehicle according to one embodiment. For example, according to an exemplary embodiment, AP 114 is located along the roadway, and the plurality of client stations 154 are located in vehicles traveling on the roadway. Although three client stations 154 are shown in Figure 1, in various embodiments the vehicle communication network 110 comprises any other suitable number of client stations 154 (e.g., one, two, four, five, six, etc.).

[0032] The client station 154-1 comprises a host processor 158 coupled to a network interface device 162. The network interface device 162 comprises a MAC processor 166 and a PHY processor 170. The PHY processor 170 comprises a plurality of transceivers 174, each transceiver 174 coupled to a plurality of antennas 178. While Figure 1 shows three transceivers 174 and three antennas 178, in other embodiments, the client station 154-1 comprises a suitable number of transceivers 174 and antennas 178 (e.g., one, two, four, five, etc.). In some embodiments, the client station 154-1 comprises more antennas 178 than transceivers 174, and antenna switching techniques are utilized. In various embodiments, the MAC processor 166 and the PHY processor 170 are configured to operate according to at least a first communication protocol (e.g., the IEEE 802.11bd standard) and / or a second communication protocol (e.g., the IEEE 802.11p standard).

[0033] The network interface device 162 is implemented using one or more ICs configured to operate as described below. For example, the MAC processor 166 may be implemented on at least a first IC, and the PHY processor 170 may be implemented on at least a second IC. As another example, at least a portion of the MAC processor 166 and at least a portion of the PHY processor 170 may be implemented on a single IC. For example, the network interface device 162 may be implemented using an SoC, the SoC including at least a portion of the MAC processor 166 and at least a portion of the PHY processor 170. As yet another example, the entire MAC processor 166 and the entire PHY processor 170 may be implemented on a single IC.

[0034] In one embodiment, the host processor 158 includes a processor configured to execute machine-readable instructions stored in a memory device (not shown) such as RAM, ROM, or flash memory. In one embodiment, the host processor 158 may be at least partially mounted on a first IC, and the network interface device 162 may be at least partially mounted on a second IC. In another example, at least a portion of the host processor 158 and the network interface device 162 may be mounted on a single IC.

[0035] In various embodiments, the MAC processor 166 and PHY processor 170 of the client station 154-1 are configured to generate data units conforming to a first communication protocol or another suitable communication protocol and to process received data units. For example, the MAC processor 166 is configured to implement MAC layer functions, including MAC layer functions of the first communication protocol, and the PHY processor 170 is configured to implement PHY functions, including PHY functions of the first communication protocol. For example, the MAC processor 166 is configured to generate MAC layer data units such as MAC Service Data Units (MSDUs), MPDUs, A-MPDUs, etc., and to provide said MAC layer data units to the PHY processor 170.

[0036] The PHY processor 170 is configured to receive MAC layer data units from the MAC processor 166 and encapsulate them for transmission via the antenna 178 to generate PHY data units such as PHY protocol data units (PPDUs) and PHY protocol service data units (PSDUs). Similarly, the PHY processor 170 is configured to receive PHY data units received via the antenna 178 and extract the MAC layer data units encapsulated within those PHY data units. The PHY processor 170 may provide the extracted MAC layer data units to the MAC processor 166, which then processes the MAC layer data units.

[0037] According to one embodiment, the PHY processor 170 is configured to down-convert one or more radio frequency (RF) signals received via one or more antennas 178 into one or more baseband analog signals, and to convert the analog baseband signals into one or more digital baseband signals. The PHY processor 170 is further configured to process one or more digital baseband signals to demodulate one or more digital baseband signals and generate a PPDU. The PHY processor 170 includes one or more forward error correction (FEC) encoders (e.g., binary convolutional code (BCC) encoders, low-density parity check (LDPC) encoders, etc.), one or more FEC decoders (e.g., BCC decoders, LDPC decoders, etc.), amplifiers (e.g., low-noise amplifiers (LNAs), power amplifiers, etc.), radio frequency (RF) downconverters, RF upconverters, multiple filters, one or more analog-to-digital converters (ADCs), one or more digital-to-analog converters (DACs), one or more discrete Fourier transform (DFT) calculators (e.g., fast Fourier transform (FFT) calculators), one or more inverse discrete Fourier transform (IDFT) calculators (e.g., inverse fast Fourier transform (IFFT) calculators), one or more modulators, one or more demodulators, etc.

[0038] The PHY processor 170 is configured to generate one or more RF signals that are supplied to one or more antennas 178. The PHY processor 170 is also configured to receive one or more RF signals from one or more antennas 178.

[0039] According to several embodiments, the MAC processor 166 is configured to control the PHY processor 170 to generate one or more RF signals by, for example, providing the PHY processor 170 with one or more MAC layer data units (e.g., MPDUs) and optionally providing the PHY processor 170 with one or more control signals. In one embodiment, the MAC processor 166 includes a processor configured to execute machine-readable instructions stored in a memory device (not shown), such as RAM, ROM, or flash memory. In one embodiment, the MAC processor 166 includes a hardware state machine configured to perform MAC layer functions, control the PHY processor 170, and the like.

[0040] In some embodiments, the PHY processor 170 is configured, similar to the PHY processor 130 described above, to generate PPDUs having different formats and / or content for different transmission modes defined by the first communication protocol.

[0041] In one embodiment, the network interface device 162 (e.g., PHY processor 170) includes a PHY midamble generator 192 configured to generate PHY midambles based on VHT-LTF as defined by the IEEE 802.11ac standard. In some embodiments, the PHY midamble generator 192 is configured to generate one or more PHY midambles so that the PPDU has different content depending on the transmission mode of the PPDU. According to various embodiments, the PHY midamble generator 192 is configured to generate one or more PHY midambles having a format such as those described below, or having other suitable PHY midamble formats.

[0042] In one embodiment, the PHY midamble generator 192 includes hardware circuitry configured to generate a PHY midamble as described below, or other suitable PHY midambles. In one embodiment, the PHY midamble generator 192 is additionally or alternatively implemented by a processor configured to execute machine-readable instructions stored in a memory device (not shown), such as RAM, ROM, or flash memory, in various embodiments.

[0043] Figure 1 shows communication between AP114 and each client station 154, but according to some embodiments, two or more client stations 154 communicate directly with each other. For example, according to some embodiments, the vehicle communication network 110 enables direct client-to-client communication that is not routed through AP114.

[0044] In one embodiment, each of client stations 154-2 and 154-3 has the same or similar structure as client station 154-1. Each of client stations 154-2 and 154-3 has the same or different number of transceivers and antennas. For example, according to one embodiment, each of client stations 154-2 and / or client station 154-3 has only two transceivers and two antennas (not shown).

[0045] Figure 2A is a diagram of an exemplary PPDU 200 for transmission in a vehicle communication network such as a vehicle communication network 110 (Figure 1) according to one embodiment. According to one embodiment, the network interface device 122 (Figure 1) is configured to generate PPDUs such as PPDU 200 and transmit them to one or more client stations 154. Similarly, according to one embodiment, the network interface device 162 (Figure 1) is configured to generate PPDUs such as PPDU 200 and transmit them to AP 114 or another client station 154. In one embodiment, the PHY processor 130 / 170 is configured to generate PPDUs such as PPDU 200. In one embodiment, the PHY processor 130 / 170 is configured to receive and process PPDUs such as PPDU 200.

[0046] According to one embodiment, the PPDU 200 conforms to a first communication protocol (e.g., the IEEE 802.11bd standard). In various embodiments, the PPDU 200 extends to suitable bandwidths such as 10 MHz, 20 MHz, etc. In other embodiments, a PPDU similar to the PPDU 200 occupies a different bandwidth such as 5 MHz, 40 MHz, or any suitable bandwidth. The PPDU is suitable for "mixed-mode" situations, i.e., when the vehicle communication network 100 has client stations (i.e., legacy client stations 154-4) that conform to a legacy communication protocol (e.g., the IEEE 802.11p standard) but not to the first communication protocol (e.g., the IEEE 802.11bd standard). The data unit 200 can be used similarly in other situations.

[0047] The PPDU 200 includes a PHY preamble 204 and a PHY data section 208. According to one embodiment, the PHY preamble 204 includes a legacy PHY preamble section 212 compliant with a second communication protocol. In one embodiment, the legacy PHY preamble section 212 includes a legacy short training field (LSTF) 216 generally used for packet detection, initial synchronization, and automatic gain control (AGC) adjustment, and a legacy long training field (LLTF) 212 generally used for channel estimation and fine synchronization. The legacy PHY preamble section 212 also includes a legacy signaling field (LSIG) 224. In one embodiment, the LSIG 224 includes signaling fields defined by the second communication protocol, including information about the PPDU 200, such as the duration of the PPDU 200. For example, in one embodiment, the LSIG 224 includes a rate subfield (not shown) and a length subfield (not shown) that together indicate the duration of the PPDU 200. In some embodiments, the duration information in LSIG224 allows client stations and / or APs (e.g., legacy communication devices) that comply with a second communication protocol but not the first to determine the duration of the PPDU200. In some embodiments, such devices will refrain from transmitting until after the PPDU200 transmission has finished, and therefore will not interfere with the PPDU200 transmission.

[0048] In some embodiments, the PHY preamble 204 includes a repeating portion of LSIG224, referred to as repeating LSIG (RL-SIG) 228. RL-SIG228 provides redundancy for LSIG224 and thus improves the decoding of LSIG224 at the receiver. In some embodiments, the first communication protocol defines multiple transmit modes, including ER modes and one or more non-ER modes (such as high-throughput modes and default modes, or one or both), and RL-SIG228 is included in PPDU200 only if PPDU200 conforms to ER modes. In other embodiments, RL-SIG228 is also included for one or more non-ER modes defined by the first communication protocol. In some embodiments, RL-SIG228 is included for all transmit modes defined by the first communication protocol.

[0049] The PHY preamble 204 also includes a signal field 232 that conforms to a first communication protocol. The signal field 232 is sometimes referred to as the Next Generation Vehicle (NGV) signal field (NGV-SIG) 232. In one embodiment, the NGV-SIG 232 conforms to the first communication protocol and is decodeable by a communication device configured to operate according to the first communication protocol. In one embodiment, the NGV-SIG 232 includes one or more subfields indicating PHY parameters corresponding to the PHY data section 208, such as an MCS subfield indicating the modulation and coding scheme (MCS) used when the data section 220 is encoded, and a DCM subfield indicating whether dual subcarrier features (e.g., dual subcarrier modulation (DCM)) are enabled with suitable parameters (e.g., carrier spacing). In some embodiments, the NGV-SIG 232 includes a subfield indicating the PHY midamble period of the PHY data section 208. In one embodiment, the PHY midamble period indicates the number of orthogonal frequency division multiplexing (OFDM) symbols between adjacent PHY midambles in the PHY data section 208.

[0050] In some embodiments, the PHY preamble 204 includes a repeating portion of the NGV-SIG 232, referred to as a repeating NGV-SIG (RNGV-SIG) 236. For example, a copy of all bits of the NGV-SIG 232 is included in the RNGV-SIG 236. The RNGV-SIG 236 provides redundancy for the NGV-SIG 232 and thus improves the decoding of the NGV-SIG 232 at the receiver. In some embodiments, the first communication protocol defines multiple transmission modes, including an ER mode and one or more non-ER modes, and the RNGV-SIG 236 is included in the PPDU 200 only if the PPDU 200 conforms to the ER mode. In other embodiments, the RNGV-SIG 236 is also included in the case of one or more non-ER modes defined by the first communication protocol. In some embodiments, the RNGV-SIG 236 is included in the case of all transmission modes defined by the first communication protocol.

[0051] The PHY preamble 204 also includes an NGV short training field (NGV-STF) 240. In some embodiments, the NGV-STF 240 is used by the receiver for synchronization and AGC adjustment. In addition, the PHY preamble 204 includes one or more NGV long training fields (NGV-LTF) 244. In some embodiments, one or more NGV-LTF 244 are used by the receiver for channel estimation. In one embodiment, the number of NGV-LTF 244 corresponds to the number of spatial streams through which the PPDU 200 is transmitted. As an illustrative example, if the PPDU 200 is transmitted through one spatial stream, only one NGV-LTF 244 is included, and if the PPDU 200 is transmitted through two spatial streams, two NGV-LTF 244 are included.

[0052] According to one embodiment, the PHY data section 208 includes a plurality of (e.g., i positive integers greater than 1) PHY data segments 252 and one or more PHY mid-ambles 256. In one embodiment, the PHY data segments 252-1 to 252-(i-1) include M OFDM symbols, where M is a suitable positive integer. In one embodiment, each PHY mid-amble includes one or more training signal fields, which are described below.

[0053] In one embodiment, the PHY preamble 204 includes a plurality of OFDM symbols, and each field of the PHY preamble 204, such as the field shown in Figure 2A, includes one or more OFDM symbols. In one embodiment, a portion of the PHY preamble 204 (e.g., legacy PHY preamble 212, RL-SIG228 (if included), NGV-SIG232, and RNGV-SIG236 (if included)) is generated for a bandwidth greater than the bandwidth of the PPDU 200, based on OFDM numerology defined by a third wireless communication standard, and using a downclock factor to generate that portion of the PHY preamble 204 that extends to the narrower bandwidth of the PPDU 200. For example, the portion of PHY preamble 204 is generated for a 20 MHz bandwidth based on OFDM numerology as defined by the IEEE 802.11a standard, and using a downclock factor of 2 (×2) to generate PHY preamble 202 extending over a 10 MHz bandwidth of PHY preamble 204. For example, the OFDM symbols of the portion of PHY preamble 204 are generated using the same FFT size and therefore the same number of OFDM tones as defined by the IEEE 802.11a standard for a 20 MHz bandwidth, but using a sampling rate that is reduced (downclocked) by half (×2) of the sampling rate specified by the IEEE 802.11a standard. Thus, in one embodiment, the OFDM tone interval within the portion of PHY preamble 204 is reduced by half (×2) of the OFDM tone interval defined by the IEEE 802.11a standard. In one embodiment, the OFDM numerology and downclock coefficients used to generate the portion of the PHY preamble 204 correspond to the OFDM numerology and downclock coefficients specified for generating the PHY preamble according to a second communication protocol (e.g., the IEEE 802.11p standard).

[0054] In one embodiment, the PHY data section 208 includes a plurality of OFDM symbols, and each field of the PHY data section 208, such as the PHY data segment 252 and the PHY mid-amble 256, includes one or more OFDM symbols. Each OFDM symbol of the PHY data section 208 is generated based on OFDM numerology defined by a fourth wireless communication standard for bandwidths greater than the bandwidth of the PPDU 200, and using a downclock factor to generate the PHY data section 208 extending to a narrower bandwidth of the PPDU 200. For example, the PHY data section 208 is generated based on OFDM numerology defined by the IEEE 802.11ac standard for a 20 MHz bandwidth, and using two downclock factors (×2) to generate the PHY data section 208 extending to a 10 MHz bandwidth. Therefore, in one embodiment, for a 10 MHz wide PPDU, each OFDM symbol in the PHY data section 208 has the same format as specified for a 40 MHz bandwidth in the IEEE 802.11ac standard, except that the tone interval is reduced by half (×2). In one embodiment, an OFDM symbol generated for a 20 MHz bandwidth according to the IEEE 802.11ac standard contains 64 tones with a 156.25 kHz interval between consecutive OFDM tones, while each OFDM symbol in the PHY data section 208 contains 64 tones with a 78.125 kHz interval between consecutive OFDM tones.

[0055] In some embodiments, each of the NGV-STF240 and NGV-LTF244 includes an OFDM symbol generated based on OFDM numerology defined by a fourth wireless communication standard for bandwidths greater than the bandwidth of the PPDU200, and using a downclock factor to generate NGV-STF240 and NGV-LTF244 extending to a narrower bandwidth of the PPDU200. For example, the NGV-STF240 and NGV-LTF244 are generated based on OFDM numerology defined by the IEEE802.11ac standard for a 20MHz bandwidth, and using two downclock factors (×2) to generate NGV-STF240 and NGV-LTF244 extending to a 10MHz bandwidth. Therefore, in one embodiment, for a 10MHz wide PPDU, each OFDM symbol in NGV-STF240 and NGV-LTF244 has the same format as specified for a 40MHz bandwidth in the IEEE 802.11ac standard, except that the tone spacing is reduced by half (×2).

[0056] Figure 2B is a diagram of another exemplary PPDU 270 for transmission in a vehicle communication network such as a vehicle communication network 110 (Figure 1) according to one embodiment. According to one embodiment, the network interface device 122 (Figure 1) is configured to generate PPDUs such as PPDU 270 and transmit them to one or more client stations 154. Similarly, in one embodiment, the network interface device 162 (Figure 1) is configured to generate PPDUs such as PPDU 270 and transmit them to AP 114 or another client station 154. In one embodiment, the PHY processor 130 / 170 is configured to generate PPDUs such as PPDU 270. In one embodiment, the PHY processor 130 / 170 is configured to receive and process PPDUs such as PPDU 270.

[0057] According to one embodiment, the PPDU270 conforms to a first communication protocol (e.g., the IEEE 802.11bd standard). In one embodiment, the PPDU200 in Figure 2A has a frequency bandwidth of 10 MHz, while the PPDU270 in Figure 2B has a frequency bandwidth of 20 MHz. The PPDU270 in Figure 2B is similar to the PPDU200 in Figure 2A, and the similarly numbered elements are not described in detail for the sake of brevity.

[0058] The PPDU270 includes a PHY preamble 274 and a PHY data section 278. The PHY preamble 274 includes a legacy PHY preamble section 282. LSTF216, LLTF220, LSIG224, RL-SIG228 (if included), NGV-SIG232, and RNGV-SIG236 (if included) are replicated in each of the two 10 MHz frequency subbands. In one embodiment, the legacy PHY preamble 282 is replicated in multiple subbands and is generated based on OFDM numerology using a downclock factor specified for generating the PHY preamble according to a second communication protocol, so that a legacy or non-legacy communication device operating using a communication channel corresponding to the 10 MHz subband of the PPDU270 can detect the PPDU270 based on a portion of the legacy PHY preamble 282 in the corresponding 10 MHz subband. In one embodiment, the legacy communication device is configured to determine the duration for transmitting the PPDU270 based on internal duration information of one of the LSIG224s in the corresponding 10 MHz subband, and to wait for the determined duration before attempting to transmit into the communication medium. For example, in one embodiment, each LSIG224 has a format at least substantially as specified in the IEEE 802.11p standard and includes information that enables the legacy communication device, which is configured to operate in accordance with the IEEE 802.11p standard but not in accordance with the IEEE 802.11bd standard, to determine the duration for transmitting the PPDU270 and wait for the determined duration before attempting to transmit into the communication medium.

[0059] In one embodiment, the OFDM symbols in NGV-STF240, NGV-LTF244, and PHY data section 278 are generated to cover the entire bandwidth of PPDU 270.

[0060] Referring to Figures 2A and 2B, in one embodiment, when transmitting PPDU200 / 270 in ER mode, the LSTF216 and LLTF220 are power-boosted compared to other fields of PPDU200 / 270. As an example, when transmitting PPDU200 / 270 in ER mode, the LSTF216 and LLTF220 are power-boosted by 3 dB compared to other fields of PPDU200 / 270. In another embodiment, when transmitting PPDU200 / 270 in ER mode, the LSTF216 and LLTF220 are power-boosted by a suitable amount other than 3 dB (e.g., 2 dB, 4 dB, etc.).

[0061] Referring again to Figures 2A and 2B, the PHY mid-amble 256 includes a training signal field that allows the receiver to update or regenerate existing channel estimates while receiving PPDU 200 / 270, which is useful in vehicle communication environments where one or more communication devices are moving at relatively high speeds. As an illustrative example, according to one embodiment, the movement of the transmitter and / or receiver may cause a Doppler effect in the receiver, and the training signal field of the PHY mid-amble 256 helps the receiver update or regenerate channel estimates to mitigate the Doppler effect.

[0062] In one embodiment, each mid-amble 256 includes a number of training signal fields corresponding to the number of spatial streams through which the PPDU 200 is transmitted. As an illustrative example, each mid-amble 256 includes a single training signal field when the PPDU 200 / 270 is transmitted over a single spatial stream, and two training signal fields when the PPDU 200 / 270 is transmitted over two spatial streams.

[0063] In one embodiment, each training signal field of the mid-amble 256 is based on the VHT-LTF as defined by the IEEE 802.11ac standard. For example, according to one embodiment, for a 10MHz PPDU such as PPDU200 in Figure 2A, each training signal field of the mid-amble 256 is generated as a 2x downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 20MHz PPDU. In another example, according to one embodiment, for a 20MHz PPDU such as PPDU270 in Figure 2B, each training signal field of the mid-amble 256 is generated as a 2x downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 40MHz PPDU.

[0064] Figure 3 is a diagram of an example of a training signal field 300 included in the midamble 256 of Figures 2A and 2B according to one embodiment. The training signal field 300 includes a training signal section 304 based on the VHT-LTF as defined by the IEEE 802.11ac standard. For example, according to one embodiment, for a 10MHz PPDU such as PPDU200 in Figure 2A, the training signal section 304 is generated as a 2× downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 20MHz PPDU. In another example, according to one embodiment, for a 20MHz PPDU such as PPDU270 in Figure 2B, the training signal section 304 is generated as a 2× downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 40MHz PPDU.

[0065] According to one embodiment, the cyclic prefix 312 includes a copy of the end-time segment 316 of the second training signal unit 308. In other embodiments, the cyclic prefix 312 includes another suitable signal. In other embodiments, the cyclic prefix 312 is omitted.

[0066] Figure 4 is a diagram of another example of the training signal field 400 included within the midamble 256 of Figures 2A and 2B, according to another embodiment. The training signal field 400 includes a first training signal section 404, a second training signal section 408, and a cyclic prefix 412. Each of the first training signal section 404 and the second training signal section 408 is based on the VHT-LTF as defined by the IEEE 802.11ac standard. For example, according to one embodiment, for a 10MHz PPDU such as the PPDU200 in Figure 2A, each of the first training signal section 404 and the second training signal section 408 is generated as a 2× downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 20MHz PPDU. In another example, according to one embodiment, for a 20MHz PPDU such as the PPDU270 in Figure 2B, each of the first training signal unit 404 and the second training signal unit 408 is generated as a 2x downclocked version of the VHT-LTF as defined by the IEEE802.11ac standard for a 40MHz PPDU. In one embodiment, each of the first training signal unit 404 and the second training signal unit 408 is the same as the training signal unit 304 in Figure 3.

[0067] According to one embodiment, the cyclic prefix 412 includes a copy of the end-time segment 416 of the second training signal unit 408. In other embodiments, the cyclic prefix 412 includes another suitable signal. In other embodiments, the cyclic prefix 412 is omitted.

[0068] Due to the repetitions provided by the two training signal sections 404 and 408, the training signal field 400 provides a gain of 3 dB compared to a training signal field having only one of sections 404 and 408. This 3 dB gain provides an effect similar to the power boost applied to the LLTF220 in the ER mode discussed above.

[0069] Comparing the training signal field 400 with the training signal field 300 in Figure 3, according to one embodiment, the training signal field 400 has a longer duration than the training signal field 300. For example, according to one embodiment, the duration of the training signal field 400 is at least as long as the duration of the training signal unit 304 compared to the duration of the training signal field 300.

[0070] Figure 5 is a diagram of another exemplary training signal field 500 included in the midamble 256 of Figures 2A and 2B, according to yet another embodiment. The training signal field 500 includes a compressed VHT-LTF 504 and a cyclic prefix 508. According to one embodiment, the cyclic prefix 508 includes a copy of the end-point segment of the compressed VHT-LTF 504. In other embodiments, the cyclic prefix 508 includes another suitable signal. In yet another embodiment, the cyclic prefix 508 is omitted.

[0071] The compressed VHT-LTF504 has a shorter (or compressed) duration compared to the VHT-LTF used in the mid-amble described above. In one embodiment, the compressed VHT-LTF504 is generated by setting every other OFDM tone in the VHT-LTF tone sequence defined by the IEEE 802.11ac standard to zero before performing the IFFT, and by truncating half of the resulting time-domain sequence after performing the IFFT. In one embodiment, the IFFT is a 64-tone IFFT for a 10 MHz wide PPDU and a 128-tone IFFT for a 20 MHz wide PPDU.

[0072] In another embodiment, the compressed VHT-LTF504 is generated by applying a smaller-sized IFFT to a sequence containing every other tone value within the VHT-LTF tone sequence as defined by the IEEE 802.11ac standard. For example, in one embodiment, a 32-tone IFFT is used for a 10 MHz wide PPDU, and a 128-tone IFFT is used for a 20 MHz wide PPDU.

[0073] Since the compressed VHT-LTF504 has a shorter (or compressed) duration compared to other VHT-LTFs used in the midamble described above, the communication medium time consumed in overhead is reduced (compared to other VHT-LTFs used in the midamble described above), allowing for a longer communication medium time for transmitting user data.

[0074] Comparing the training signal field 500 with the training signal field 300 in Figure 3, according to one embodiment, the training signal field 500 has a shorter duration than the training signal field 300. For example, according to one embodiment, the duration of the training signal field 500 is at least half the duration of the training signal unit 304 than the duration of the training signal field 300.

[0075] Referring here to Figures 3 to 5, in exemplary embodiments, the training signal field 300 excluding the cyclic prefix 312 has a duration of X, where X is a suitable duration; the training signal field 400 excluding the cyclic prefix 412 has a duration of 2X; and the training signal field 500 excluding the cyclic prefix 508 has a duration of X / 2. The training signal field 500 may be referred to as the compressed training signal field, while the training signal fields 300 and 400 may be referred to as the uncompressed training signal fields. In one embodiment, X is equal to the duration of the VHT-LTF as defined by the IEEE 802.11ac standard multiplied by 2. In another embodiment, X is equal to the duration of the VHT-LTF without cyclic prefixes as defined by the IEEE 802.11ac standard multiplied by 2. In one embodiment, X is 8 microseconds. In other embodiments, X has a different suitable duration.

[0076] In some embodiments, two or more of the training signal field 300, training signal 400, and training signal 500 are used in a single communication protocol for vehicle communication. For example, in some embodiments, two or more of the training signal field 300, training signal 400, and training signal 500 are used in each transmission mode defined by the communication protocol for vehicle communication. In an exemplary embodiment, training signal 400 is used in ER transmission mode, training signal 500 is used in high-throughput mode, and training signal 400 is used in another transmission mode different from ER transmission mode and high-throughput mode (e.g., normal mode, default mode, etc.).

[0077] Figure 6 is a flowchart of an exemplary method 600 for wireless communication in a vehicle communication network according to one embodiment. Referring to Figure 1, in various embodiments, method 600 is implemented by a network interface device such as network interface device 122 or network interface device 162. For example, in one such embodiment, a PHY processor such as PHY processor 130 or PHY processor 170 is configured to implement method 600. In other embodiments, method 600 is implemented by another suitable communication device.

[0078] In block 604, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates a PHY preamble for PPDU transmission in the vehicle communication network according to a communication protocol for vehicle communication. For example, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates a PHY preamble such as PHY preamble 204 described with reference to Figure 2A, PHY preamble 274 described with reference to Figure 2B, or another suitable PHY preamble, according to various embodiments.

[0079] In block 608, the communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates multiple PHY data segments of the PPDU. For example, the communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates PHY data segments such as PHY data segment 252 described with reference to Figures 2A and 2B, or another suitable PHY data segment, according to various embodiments.

[0080] In block 612, a communication device (e.g., network interface device 122, PHY processor 130, PHY midamble generator 142, network interface device 162, PHY processor 170, PHY midamble generator 192, etc.) generates one or more PHY midambles of the PPDU, each PHY midamble being transmitted between each pair of adjacent PHY data segments generated in block 608. Each PHY midamble includes one or more training signal fields, and generating one or more PHY midambles in block 612 includes generating each training signal field including a portion based on the VHT-LTF as defined by the IEEE 802.11ac standard.

[0081] In one embodiment, for a 10MHz PPDU such as PPDU200 in Figure 2A, generating one or more PHY mid-ambles in block 612 includes generating each training signal field including a 2x downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 20MHz PPDU. In another embodiment, for a 20MHz PPDU such as PPDU270 in Figure 2B, generating one or more PHY mid-ambles in block 612 includes generating each training signal field including a 2x downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 40MHz PPDU.

[0082] In one embodiment, generating one or more PHY mid-ambles in block 612 includes generating each mid-amble containing the training signal field 300 as described with reference to Figure 3.

[0083] In one embodiment, generating one or more PHY midambles in block 612 includes generating each training signal field including a portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, when the PPDU is to be transmitted according to a non-ER mode as defined by the communication protocol. In another embodiment, generating one or more PHY midambles in block 612 includes generating each training signal field including a portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, in response to the communication device determining that the PPDU is to be transmitted according to a non-ER mode as defined by the communication protocol. In yet another embodiment, when the PPDU is to be transmitted according to any one of several modes (including ER mode) as defined by the communication protocol, in block 612, each training signal field is generated to include a portion based on the VHT-LTF as defined by the IEEE 802.11ac standard.

[0084] In block 616, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) transmits a PPDU in the vehicle communication network. In one embodiment, transmitting a PPDU in block 616 includes transmitting a PHY preamble generated in block 604, transmitting a PHY data segment generated in block 608, and transmitting one or more PHY midambles generated in block 612 between each pair of adjacent PHY data segments generated in block 608.

[0085] Figure 7 is a flowchart of another exemplary method 700 for wireless communication in a vehicle communication network according to another embodiment. Referring to Figure 1, in various embodiments, method 700 is implemented by a network interface device such as network interface device 122 or network interface device 162. For example, in one such embodiment, a PHY processor such as PHY processor 130 or PHY processor 170 is configured to implement method 700. In other embodiments, method 700 is implemented by another suitable communication device.

[0086] In block 704, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates a PHY preamble for PPDU transmission in the vehicle communication network according to a communication protocol for vehicle communication. For example, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates a PHY preamble such as PHY preamble 204 described with reference to Figure 2A, PHY preamble 274 described with reference to Figure 2B, or another suitable PHY preamble, according to various embodiments.

[0087] In block 708, the communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates multiple PHY data segments of the PPDU. For example, the communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates PHY data segments such as PHY data segment 252 described with reference to Figures 2A and 2B, or another suitable PHY data segment, according to various embodiments.

[0088] In block 712, a communication device (e.g., network interface device 122, PHY processor 130, PHY midamble generator 142, network interface device 162, PHY processor 170, PHY midamble generator 192, etc.) generates one or more PHY midambles of the PPDU, each PHY midamble being transmitted between each pair of adjacent PHY data segments generated in block 708. Each PHY midamble includes one or more training signal fields, and generating one or more PHY midambles in block 712 includes generating each training signal field including i) a first part based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second part based on the VHT-LTF as defined by the IEEE 802.11ac standard.

[0089] In one embodiment, for a 10MHz PPDU such as PPDU200 in Figure 2A, generating one or more PHY midambles in block 712 includes generating each of the first and second parts of each training signal field, each including a 2x downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 20MHz PPDU. In one embodiment, for a 20MHz PPDU such as PPDU270 in Figure 2B, generating one or more PHY midambles in block 712 includes generating each of the first and second parts of each training signal field, each including a 2x downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 40MHz PPDU.

[0090] In one embodiment, generating one or more PHY mid-ambles in block 712 includes generating each mid-amble containing the training signal field 400 as described with reference to Figure 4.

[0091] In one embodiment, generating one or more PHY midambles in block 712 includes generating each training signal field including i) a first portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, when the PPDU is to be transmitted according to the ER mode defined by the communication protocol. In another embodiment, generating one or more PHY midambles in block 712 includes generating each training signal field including i) a first portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, in response to the communication device determining that the PPDU is to be transmitted according to the ER mode defined by the communication protocol. In other embodiments, if the PPDU is to be transmitted according to one of several modes (including non-ER modes) defined by the communication protocol, then in block 712, each training signal field is generated to include i) a first part based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second part based on the VHT-LTF as defined by the IEEE 802.11ac standard.

[0092] In block 716, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) transmits a PPDU in the vehicle communication network. In one embodiment, transmitting a PPDU in block 716 includes transmitting a PHY preamble generated in block 704, transmitting a PHY data segment generated in block 708, and transmitting one or more PHY midambles generated in block 712 between each pair of adjacent PHY data segments generated in block 708.

[0093] Figure 8 is a flowchart of yet another exemplary method 800 for wireless communication in a vehicle communication network according to another embodiment. Referring to Figure 1, in various embodiments, method 800 is implemented by a network interface device such as network interface device 122 or network interface device 162. For example, in one such embodiment, a PHY processor such as PHY processor 130 or PHY processor 170 is configured to implement method 800. In other embodiments, method 800 is implemented by another suitable communication device.

[0094] In block 804, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates a PHY preamble for PPDU transmission in the vehicle communication network according to a communication protocol for vehicle communication. For example, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates a PHY preamble such as PHY preamble 204 described with reference to Figure 2A, PHY preamble 274 described with reference to Figure 2B, or another suitable PHY preamble, according to various embodiments.

[0095] In block 808, the communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates multiple PHY data segments of the PPDU. For example, the communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates PHY data segments such as PHY data segment 252 described with reference to Figures 2A and 2B, or another suitable PHY data segment, according to various embodiments.

[0096] In block 812, a communication device (e.g., network interface device 122, PHY processor 130, PHY midamble generator 142, network interface device 162, PHY processor 170, PHY midamble generator 192, etc.) generates one or more PHY midambles of the PPDU, each PHY midamble being transmitted between each pair of adjacent PHY data segments generated in block 808. Each PHY midamble includes one or more training signal fields, and generating one or more PHY midambles in block 812 includes generating each training signal field including a compressed training signal field based on VHT-LTF as defined by the IEEE 802.11ac standard.

[0097] In one embodiment, the compressed training signal field generated in block 812 is generated by setting every other OFDM tone in the VHT-LTF tone sequence defined by the IEEE 802.11ac standard to zero before performing the IFFT, and by truncating half of the resulting time-domain sequence after performing the IFFT. In one embodiment, the IFFT is a 64-tone IFFT for a 10 MHz wide PPDU and a 128-tone IFFT for a 20 MHz wide PPDU.

[0098] In another embodiment, the compressed training signal field generated in block 812 is generated by applying a smaller-sized IFFT to a sequence containing every other tone value in the VHT-LTF tone sequence defined by the IEEE 802.11ac standard. For example, in one embodiment, a 32-tone IFFT is used for a 10 MHz wide PPDU, and a 128-tone IFFT is used for a 20 MHz wide PPDU.

[0099] In one embodiment, generating one or more PHY mid-ambles in block 812 includes generating each mid-amble containing the training signal field 500 as described with reference to Figure 5.

[0100] In one embodiment, generating one or more PHY midambles in block 812 includes generating each training signal field, which includes a compressed training signal field, when the PPDU is to be transmitted according to a high-throughput mode defined by the communication protocol. In another embodiment, generating one or more PHY midambles in block 812 includes generating each training signal field, which includes a compressed training signal field, in response to the communication device determining that the PPDU is to be transmitted according to a high-throughput mode defined by the communication protocol. In yet another embodiment, when the PPDU is to be transmitted according to any one of several modes (including non-high-throughput modes) defined by the communication protocol, each training signal field in block 812 is generated to include a compressed training signal field.

[0101] In block 816, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) transmits a PPDU in the vehicle communication network. In one embodiment, transmitting a PPDU in block 816 includes transmitting a PHY preamble generated in block 804, transmitting a PHY data segment generated in block 808, and transmitting one or more PHY midambles generated in block 812 between each pair of adjacent PHY data segments generated in block 808.

[0102] In some embodiments, two or more of methods 600, 700, and 800 are implemented by a communication device operating according to a single communication protocol for vehicle communication. For example, in some embodiments, two or more of methods 600, 700, and 800 are performed in connection with the transmission of different packets according to their respective transmission modes defined by the communication protocol for vehicle communication. In exemplary embodiments, method 700 is performed when transmitting packets according to the ER transmission mode, method 800 is performed when transmitting packets according to the high-throughput mode, and method 600 is performed when transmitting packets according to a different transmission mode (e.g., normal mode, default mode, etc.) other than the ER transmission mode and the high-throughput mode.

[0103] Figure 9 is a flowchart of yet another exemplary method 900 for wireless communication in a vehicle communication network according to another embodiment. Referring to Figure 1, in various embodiments, method 900 is implemented by a network interface device such as network interface device 122 or network interface device 162. For example, in one such embodiment, a PHY processor such as PHY processor 130 or PHY processor 170 is configured to implement method 900. In other embodiments, method 900 is implemented by another suitable communication device.

[0104] In block 904, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates a PHY preamble for PPDU transmission in the vehicle communication network according to a communication protocol for vehicle communication. For example, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates a PHY preamble such as PHY preamble 204 described with reference to Figure 2A, PHY preamble 274 described with reference to Figure 2B, or another suitable PHY preamble, according to various embodiments.

[0105] In block 908, the communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates multiple PHY data segments of the PPDU. For example, the communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) generates PHY data segments such as PHY data segment 252 described with reference to Figures 2A and 2B, or another suitable PHY data segment, according to various embodiments.

[0106] In block 912, the communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) determines whether the PPDU will be transmitted according to ER mode. In response to the communication device determining that the PPDU will be transmitted according to ER mode, the flow proceeds to block 916.

[0107] In block 916, a communication device (e.g., network interface device 122, PHY processor 130, PHY midamble generator 142, network interface device 162, PHY processor 170, PHY midamble generator 192, etc.) generates one or more PHY midambles of the PPDU, each PHY midamble being transmitted between each pair of adjacent PHY data segments generated in block 908. Each PHY midamble includes one or more training signal fields, and generating one or more PHY midambles in block 916 includes generating each training signal field including i) a first part based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second part based on the VHT-LTF as defined by the IEEE 802.11ac standard.

[0108] In one embodiment, for a 10MHz PPDU such as PPDU200 in Figure 2A, generating one or more PHY midambles in block 916 includes generating each of the first and second parts of each training signal field, each including a 2x downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 20MHz PPDU. In one embodiment, for a 20MHz PPDU such as PPDU270 in Figure 2B, generating one or more PHY midambles in block 916 includes generating each of the first and second parts of each training signal field, each including a 2x downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 40MHz PPDU.

[0109] In one embodiment, generating one or more PHY mid-ambles in block 916 includes generating each mid-amble containing the training signal field 400 as described with reference to Figure 4.

[0110] In one embodiment, generating one or more PHY midambles in block 916 includes generating each training signal field including i) a first portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, when the PPDU is to be transmitted according to the ER mode defined by the communication protocol. In another embodiment, generating one or more PHY midambles in block 916 includes generating each training signal field including i) a first portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, in response to the communication device determining that the PPDU is to be transmitted according to the ER mode defined by the communication protocol. In other embodiments, if the PPDU is to be transmitted according to one of several modes (including non-ER mode) defined by the communication protocol, then in block 916, each training signal field is generated to include i) a first part based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second part based on the VHT-LTF as defined by the IEEE 802.11ac standard.

[0111] On the other hand, in response to the communication device determining in block 912 that the PPDU will not be transmitted according to ER mode, the flow proceeds to block 920. In block 920, the communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) determines whether or not the PPDU will be transmitted according to high-throughput mode. In response to the communication device determining that the PPDU will be transmitted according to high-throughput mode, the flow proceeds to block 924.

[0112] In block 924, a communication device (e.g., network interface device 122, PHY processor 130, PHY midamble generator 142, network interface device 162, PHY processor 170, PHY midamble generator 192, etc.) generates one or more PHY midambles of the PPDU, each PHY midamble being transmitted between each pair of adjacent PHY data segments generated in block 908. Each PHY midamble includes one or more training signal fields, and generating one or more PHY midambles in block 924 includes generating each training signal field including a compressed training signal field based on VHT-LTF as defined by the IEEE 802.11ac standard.

[0113] In one embodiment, the compressed training signal field generated in block 924 is generated by setting every other OFDM tone in the VHT-LTF tone sequence defined by the IEEE 802.11ac standard to zero before performing the IFFT, and by truncating half of the resulting time-domain sequence after performing the IFFT. In one embodiment, the IFFT is a 64-tone IFFT for a 10 MHz wide PPDU and a 128-tone IFFT for a 20 MHz wide PPDU.

[0114] In another embodiment, the compressed training signal field generated in block 924 is generated by applying a smaller-sized IFFT to a sequence containing every other tone value in the VHT-LTF tone sequence defined by the IEEE 802.11ac standard. For example, in one embodiment, a 32-tone IFFT is used for a 10 MHz wide PPDU, and a 128-tone IFFT is used for a 20 MHz wide PPDU.

[0115] In one embodiment, generating one or more PHY midambles in block 924 includes generating each midamble containing the training signal field 500 as described with reference to Figure 5.

[0116] On the other hand, in response to the communication device determining in block 920 that the PPDU will not be transmitted according to the high-throughput mode, the flow proceeds to block 928. In block 928, the communication device (e.g., network interface device 122, PHY processor 130, PHY midamble generator 142, network interface device 162, PHY processor 170, PHY midamble generator 192, etc.) generates one or more PHY midambles of the PPDU, each PHY midamble being transmitted between each pair of adjacent PHY data segments generated in block 908. Each PHY midamble includes one or more training signal fields, and generating one or more PHY midambles in block 928 includes generating each training signal field including a portion based on the VHT-LTF as defined by the IEEE 802.11ac standard.

[0117] In one embodiment, for a 10MHz PPDU such as PPDU200 in Figure 2A, generating one or more PHY mid-ambles in block 928 includes generating each training signal field including a 2x downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 20MHz PPDU. In one embodiment, for a 20MHz PPDU such as PPDU270 in Figure 2B, generating one or more PHY mid-ambles in block 928 includes generating each training signal field including a 2x downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard for a 40MHz PPDU.

[0118] In one embodiment, generating one or more PHY mid-ambles in block 928 includes generating each mid-amble containing the training signal field 300 as described with reference to Figure 3.

[0119] In block 932, a communication device (e.g., network interface device 122, PHY processor 130, network interface device 162, PHY processor 170, etc.) transmits a PPDU in the vehicle communication network. In one embodiment, transmitting a PPDU in block 932 includes transmitting a PHY preamble generated in block 904, transmitting a PHY data segment generated in block 908, and transmitting one or more PHY midambles generated in blocks 916, 924, or 928 between each pair of adjacent PHY data segments generated in block 908.

[0120] In various embodiments, method 900 can be modified by changing the order of blocks, omitting blocks, adding additional blocks, etc. As an illustrative example, in another embodiment, the order of blocks 912 and 920 is swapped. As another illustrative example, in another embodiment, block 912 may be replaced with a similar block that checks whether the PPDU will be transmitted according to a mode other than ER mode and high throughput mode (e.g., a third transmission mode), and the positions of blocks 916 and 928 may be swapped. Similarly, as another illustrative example, in another embodiment, block 920 may be replaced with a similar block that checks whether the PPDU will be transmitted according to a mode other than ER mode and high throughput mode (e.g., a third transmission mode), and the positions of blocks 920 and 928 may be swapped.

[0121] Embodiment 1: A method for wireless communication in a vehicle communication network, comprising: a step of generating a PHY preamble for a PPDU to be transmitted in the vehicle communication network in accordance with a communication protocol for vehicle communication in a communication device; a step of generating a plurality of PHY data segments of the PPDU in the communication device; a step of generating one or more PHY midambles in the communication device, each PHY midamble to be transmitted between each pair of adjacent PHY data segments, each PHY midamble comprising one or more training signal fields, the step of generating the one or more PHY midambles comprising, if the PPDU is to be transmitted in accordance with the ER mode defined by the communication protocol, a step of generating one or more PHY midambles comprising a step of generating each training signal field comprising i) a first portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second portion based on the VHT-LTF as defined by the IEEE 802.11ac standard; and a step of transmitting the PPDU in the vehicle communication network by the communication device.

[0122] Embodiment 2: The method according to Embodiment 1, wherein the step of generating the one or more PHY midambles further comprises the step of generating each training signal field further including a cyclic prefix, if the PPDU is to be transmitted according to the ER mode defined by the communication protocol.

[0123] Embodiment 3: The method according to Embodiment 2, wherein the step of generating each training signal field including the cyclic prefix includes the step of generating each training signal field including the end-time segment of the second portion of the training signal field.

[0124] Embodiment 4: The method of any one of Embodiments 1 to 3, wherein the step of generating the one or more PHY midambles further comprises, if the PPDU is to be transmitted in accordance with the ER mode defined by the communication protocol, the first part of which includes a downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard, and the second part of which includes each training signal field including the downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard.

[0125] Embodiment 5: The method according to any one of Embodiments 1 to 4, wherein the step of generating the one or more PHY midambles comprises generating each training signal field including the first portion and omitting the second portion, if the PPDU is defined by the communication protocol and will be transmitted according to a mode other than the ER mode.

[0126] Embodiment 6: The method of any one of Embodiments 1 to 4, wherein the step of generating the one or more PHY midambles includes, if the PPDU is defined by the communication protocol and is to be transmitted according to a mode other than the ER mode, the step of generating each training signal field including a time-compressed training signal based on the VHT-LTF as defined by the IEEE 802.11ac standard, the time-compressed training signal having a duration shorter than the duration of the first portion that would be included if the PPDU were to be transmitted according to the ER mode.

[0127] Embodiment 7: A communication device configured to operate in a vehicle communication network, comprising a wireless network interface device. The wireless network interface device has one or more IC devices, the one or more IC devices are configured to: generate a PHY preamble for a PPDU to be transmitted in the vehicle communication network in accordance with a communication protocol for vehicle communication; generate a plurality of PHY data segments of the PPDU; generate one or more PHY midambles, each PHY midamble to be transmitted between each pair of adjacent PHY data segments, each PHY midamble comprising one or more training signal fields, and generating the one or more PHY midambles comprises generating each training signal field comprising i) a first portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, if the PPDU is to be transmitted in an extended range (ER) mode as defined by the communication protocol; and control the wireless network interface device to transmit the PPDU in the vehicle communication network.

[0128] Embodiment 8: The communication device according to Embodiment 7, wherein the one or more IC devices are further configured to generate each training signal field, which further includes a cyclic prefix, when the PPDU is to be transmitted according to the ER mode defined by the communication protocol.

[0129] Embodiment 9: The communication device according to Embodiment 8, wherein the one or more IC devices are further configured to generate each training signal field including the end-time segment of the second portion of the training signal field.

[0130] Embodiment 10: A communication device according to any one of Embodiments 7 to 9, wherein the one or more IC devices are further configured to generate each training signal field, which includes, as a first part, a downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard, and as a second part, the downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard, when the PPDU is to be transmitted in accordance with the ER mode defined by the communication protocol.

[0131] Embodiment 11: A communication device according to any one of Embodiments 7 to 10, wherein the one or more IC devices are further configured to generate each training signal field including the first portion and omitting the second portion when the PPDU is defined by the communication protocol and will be transmitted according to a mode other than the ER mode.

[0132] Embodiment 12: The communication device according to any one of Embodiments 7 to 10, wherein the one or more IC devices are further configured to generate each training signal field including a time-compressed training signal based on the VHT-LTF as defined by the IEEE 802.11ac standard, when the PPDU is defined by the communication protocol and is to be transmitted according to a mode other than the ER mode, the time-compressed training signal has a duration shorter than the duration of the first portion that would be included if the PPDU were to be transmitted according to the ER mode.

[0133] Embodiment 13: A method for accessing a communication channel in a vehicle communication network, comprising: a step of a communication device generating a PHY preamble for a PPDU for transmission in the vehicle communication network according to a communication protocol for vehicle communication; a step of the communication device generating a plurality of PHY data segments of the PPDU; and a step of the communication device selecting one or more PHY midamble formats from a set of plurality of different PHY midamble formats based on the transmission mode of the PPDU, wherein the set of plurality of different PHY midamble formats is: i) a first format corresponding to an extended range transmission mode defined by the communication protocol, using an uncompressed training signal field; and ii) a format defined by the communication protocol, using a compressed training signal field. A method comprising: a step of selecting a second format corresponding to a high-throughput transmission mode; a step of generating one or more PHY midambles in the communication device according to the selected format, each PHY midamble to be transmitted between each pair of adjacent PHY data segments, each PHY midamble including one or more training signal fields, the step of generating each PHY midamble having i) a step of selectively including uncompressed training signal fields if the first format is selected, and ii) a step of selectively including compressed training signal fields if the second format is selected; and a step of transmitting the PPDU in the vehicle communication network by the communication device.

[0134] Embodiment 14: The method according to Embodiment 13, wherein the step of generating the one or more PHY midambles according to the selected format comprises generating each training signal field including i) a first portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, when the PPDU is to be transmitted according to the ER mode defined by the communication protocol.

[0135] Embodiment 15: The method according to Embodiment 14, wherein the step of generating the one or more PHY midambles further comprises, if the PPDU is to be transmitted in accordance with the ER mode defined by the communication protocol, the first part of which includes a downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard, and the second part of which includes each training signal field including the downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard.

[0136] Embodiment 16: The method according to any one of Embodiments 13 to 15, wherein the step of generating the one or more PHY midambles according to the selected format includes, when the PPDU is to be transmitted according to the high-throughput mode defined by the communication protocol, the step of generating each training signal field including a time-compressed training signal based on the VHT-LTF as defined by the IEEE 802.11ac standard, and each training signal field has a shorter duration than the duration of each training signal field generated when the PPDU is to be transmitted according to another mode that is different from the ER mode and different from the high-throughput mode.

[0137] Embodiment 17: The method according to any one of Embodiments 13 to 16, wherein the step of generating the one or more PHY midambles according to the selected format includes a step of generating each training signal field including a downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard, if the PPDU is to be transmitted according to a different mode that is different from the ER mode and different from the high throughput mode, and each training signal field has a shorter duration than the duration of each training signal field that would be generated if the PPDU were to be transmitted according to the ER mode.

[0138] Embodiment 18: A communication device configured to operate in a vehicle communication network, comprising a wireless network interface device. The wireless network interface device comprises one or more IC devices, the one or more IC devices: generating a PHY preamble for a PPDU for transmission in the vehicle communication network according to a communication protocol for vehicle communication; generating multiple PHY data segments of the PPDU; and selecting one or more PHY midamble formats from a set of multiple different PHY midamble formats based on the transmission mode of the PPDU, wherein the set of multiple different PHY midamble formats includes: i) a first format corresponding to an extended range transmission mode defined by the communication protocol, using an uncompressed training signal field; and ii) a high-throughput transmission mode defined by the communication protocol, using a compressed training signal field. The system is configured to: select a second format corresponding to a code; generate one or more PHY midambles according to the selected format, each PHY midamble being transmitted between each pair of adjacent PHY data segments, each PHY midamble including one or more training signal fields, and generating each PHY midamble having i) selectively including uncompressed training signal fields if the first format is selected, and ii) selectively including compressed training signal fields if the second format is selected; and control the wireless network interface device to transmit the PPDU in the vehicle communication network.

[0139] Embodiment 19: The communication device according to Embodiment 18, wherein the one or more IC devices are configured to generate each training signal field including i) a first portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, and ii) a second portion based on the VHT-LTF as defined by the IEEE 802.11ac standard, when the PPDU is to be transmitted in accordance with the ER mode defined by the communication protocol.

[0140] Embodiment 20: The communication device according to Embodiment 19, wherein the one or more IC devices are configured to generate each training signal field, which, when the PPDU is to be transmitted in accordance with the ER mode defined by the communication protocol, includes, as a first part, a downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard, and as a second part, the downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard.

[0141] Embodiment 21: The communication device according to any one of Embodiments 18 to 20, wherein the one or more IC devices are configured to generate each training signal field including a time-compressed training signal based on the VHT-LTF as defined by the IEEE 802.11ac standard when the PPDU is to be transmitted according to the high-throughput mode defined by the communication protocol, and each training signal field has a shorter duration than the duration of each training signal field generated when the PPDU is to be transmitted according to another mode that is different from the ER mode and different from the high-throughput mode.

[0142] Embodiment 22: The communication device according to any one of Embodiments 18 to 21, wherein the one or more IC devices are configured to generate each training signal field including a downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard when the PPDU is to be transmitted according to a mode different from the ER mode and different from the high throughput mode, and each training signal field has a shorter duration than the duration of each training signal field generated when the PPDU is to be transmitted according to the ER mode.

[0143] At least some of the various blocks, operations, and techniques described above can be implemented using hardware, a processor that executes firmware instructions, a processor that executes software instructions, or any combination thereof. When implemented using a processor that executes software or firmware instructions, the software or firmware instructions can be stored in any computer-readable memory, such as RAM, ROM, flash memory, or the processor's integrated memory. When executed by the processor, the software or firmware instructions may include machine-readable instructions that cause the processor to perform various actions.

[0144] When implemented in hardware, the hardware may include one or more discrete components, one or more ICs, application-specific integrated circuits (ASICs), programmable logic devices (PLDs), etc.

[0145] Although the present invention has been described with reference to specific examples, these examples are for illustrative purposes only and are not intended to limit the invention, and modifications, additions, and / or deletions may be made to the disclosed embodiments without departing from the scope of the invention.

Claims

1. A method for wireless communication in a vehicle communication network, A communication device comprising the steps of generating a PHY preamble for a physical layer (PHY) protocol data unit (PPDU) for transmission in the vehicle communication network in accordance with a communication protocol for vehicle communication, The communication device includes the steps of generating multiple PHY data segments of the PPDU, The communication device comprises the step of generating one or more PHY midambles, each PHY midamble being transmitted between each pair of adjacent PHY data segments, each PHY midamble including one or more training signal fields, the number of training signal fields in the one or more training signal fields corresponding to the number of spatial streams through which the PPDU is transmitted, The communication device transmits the PPDU in the vehicle communication network. Equipped with, A method comprising the step of generating one or more PHY midambles, wherein, if the PPDU is to be transmitted in an extended range (ER) mode as defined by the communication protocol, each training signal field includes: i) a cyclic prefix; ii) a first portion having a downclocked version of an ultra-high throughput long training field (VHT-LTF) as defined by the IEEE 802.11ac standard; and iii) a second portion having the downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard.

2. The method according to claim 1, wherein the step of generating each training signal field including the cyclic prefix includes the step of generating each training signal field including the end-time segment of the second portion of the training signal field.

3. The method according to claim 1 or 2, wherein the step of generating the one or more PHY midambles includes the step of generating each training signal field which includes the first portion and omits the second portion, if the PPDU is defined by the communication protocol and is to be transmitted according to a mode other than the ER mode.

4. The method according to any one of claims 1 to 3, wherein the step of generating the one or more PHY midambles includes, if the PPDU is defined by the communication protocol and is to be transmitted according to a mode other than the ER mode, the step of generating each training signal field including a time-compressed training signal based on the VHT-LTF as defined by the IEEE 802.11ac standard, the time-compressed training signal having a duration shorter than the duration of the first portion included if the PPDU is to be transmitted according to the ER mode.

5. The method according to any one of claims 1 to 4, wherein the second part is an iteration of the first part.

6. A communication device configured to operate in a vehicle communication network, A wireless network interface device having one or more integrated circuit (IC) devices, wherein the one or more IC devices are To generate a PHY preamble for a Physical Layer (PHY) protocol data unit (PPDU) for transmission in the vehicle communication network in accordance with a communication protocol for vehicle communication, To generate multiple PHY data segments of the aforementioned PPDU, The method involves generating one or more PHY midambles, each PHY midamble being transmitted between each pair of adjacent PHY data segments, each PHY midamble comprising one or more training signal fields, the number of training signal fields in the one or more training signal fields corresponding to the number of spatial streams through which the PPDU is transmitted. In the aforementioned vehicle communication network, the wireless network interface device is controlled to transmit the PPDU. A wireless network interface device configured to perform the following actions. Equipped with, The one or more IC devices are further configured to generate each training signal field including, when the PPDU is to be transmitted in accordance with the Extended Range (ER) mode defined by the communication protocol, i) a cyclic prefix, ii) a first portion having a downclocked version of an ultra-high throughput long training field (VHT-LTF) as defined by the IEEE 802.11ac standard, and iii) a second portion having the downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard.

7. The communication device according to claim 6, wherein the one or more IC devices are further configured to generate each training signal field including the end-time segment of the second portion of the training signal field.

8. The communication device according to claim 6 or 7, wherein the one or more IC devices are further configured to generate each training signal field including the first portion and omitting the second portion when the PPDU is defined by the communication protocol and is to be transmitted according to a mode other than the ER mode.

9. The communication device according to any one of claims 6 to 8, wherein the one or more IC devices are further configured to generate each training signal field including a time-compressed training signal based on the VHT-LTF as defined by the IEEE 802.11ac standard, where the PPDU is to be transmitted according to the communication protocol and in a mode other than the ER mode, and the time-compressed training signal has a duration shorter than the duration of the first portion included when the PPDU is to be transmitted according to the ER mode.

10. The communication device according to any one of claims 6 to 9, wherein the second part is an iteration of the first part.

11. A method for accessing a communication channel in a vehicle communication network, A communication device comprising the steps of generating a PHY preamble for a physical layer (PHY) protocol data unit (PPDU) for transmission in the vehicle communication network in accordance with a communication protocol for vehicle communication, The communication device includes the steps of generating multiple PHY data segments of the PPDU, The communication device comprises a step of selecting one or more PHY midamble formats from a set of multiple different PHY midamble formats based on the transmission mode of the PPDU, wherein the set of multiple different PHY midamble formats includes: i) a first format corresponding to an extended range (ER) transmission mode defined by the communication protocol, which uses an uncompressed training signal field; and ii) a second format corresponding to a high-throughput transmission mode defined by the communication protocol, which uses a compressed training signal field. The communication device comprises the step of generating one or more PHY midambles according to the selected format, each PHY midamble being transmitted between each pair of adjacent PHY data segments, each PHY midamble including one or more training signal fields, and the step of generating each PHY midamble comprising i) a step of selectively including uncompressed training signal fields if the first format is selected, and ii) a step of selectively including compressed training signal fields if the second format is selected, The communication device transmits the PPDU in the vehicle communication network. Equipped with, A method comprising the step of generating one or more PHY midambles, wherein the PPDU is to be transmitted in accordance with the ER transmission mode defined by the communication protocol, each training signal field includes: i) a cyclic prefix; ii) a first portion having a downclocked version of an ultra-high throughput long training field (VHT-LTF) as defined by the IEEE 802.11ac standard; and iii) a second portion having the downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard.

12. The step of generating the one or more PHY midambles according to the selected format is performed when the PPDU will be transmitted according to the high-throughput transmission mode defined by the communication protocol. The method according to claim 11, comprising the step of generating each training signal field including a time-compressed training signal based on the VHT-LTF as defined by the IEEE 802.11ac standard, wherein each training signal field has a duration shorter than the duration of each training signal field generated when the PPDU is to be transmitted according to another mode different from the ER transmission mode and different from the high-throughput transmission mode.

13. The step of generating the one or more PHY midambles according to the selected format is performed if the PPDU is to be transmitted according to a mode different from the ER transmission mode and different from the high-throughput transmission mode, The method according to claim 12, comprising the step of generating each training signal field including a downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard, wherein each training signal field has a duration shorter than the duration of each training signal field generated when the PPDU is to be transmitted according to the ER transmission mode.

14. The method according to any one of claims 11 to 13, wherein the second part is an iteration of the first part.

15. A communication device configured to operate in a vehicle communication network, A wireless network interface device having one or more integrated circuit (IC) devices, wherein the one or more IC devices are To generate a PHY preamble for a Physical Layer (PHY) protocol data unit (PPDU) for transmission in the vehicle communication network in accordance with a communication protocol for vehicle communication, To generate multiple PHY data segments of the aforementioned PPDU, Based on the transmission mode of the PPDU, the selection involves selecting one or more PHY midamble formats from a set of multiple different PHY midamble formats, wherein the set of multiple different PHY midamble formats includes: i) a first format corresponding to an extended range (ER) transmission mode defined by the communication protocol, using an uncompressed training signal field; and ii) a second format corresponding to a high-throughput transmission mode defined by the communication protocol, using a compressed training signal field. Generating one or more PHY midambles according to the selected format, each PHY midamble being transmitted between each pair of adjacent PHY data segments, each PHY midamble containing one or more training signal fields, and each PHY midamble being generated having i) selectively including uncompressed training signal fields when the first format is selected, and ii) selectively including compressed training signal fields when the second format is selected, In the aforementioned vehicle communication network, the wireless network interface device is controlled to transmit the PPDU. A wireless network interface device configured to perform the following actions. Equipped with, The one or more IC devices are configured to generate each training signal field, which, when the PPDU is to be transmitted in accordance with the ER transmission mode defined by the communication protocol, includes: i) a cyclic prefix; ii) a first portion having a downclocked version of an ultra-high throughput long training field (VHT-LTF) as defined by the IEEE 802.11ac standard; and iii) a second portion having the downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard.

16. The one or more IC devices mentioned above, when the PPDU is to be transmitted in accordance with the high-throughput transmission mode defined by the communication protocol, The communication device according to claim 15, configured to generate each training signal field including a time-compressed training signal based on the VHT-LTF as defined by the IEEE 802.11ac standard, wherein each training signal field has a duration shorter than the duration of each training signal field generated when the PPDU is transmitted according to a different mode that is different from the ER transmission mode and different from the high-throughput transmission mode.

17. If the PPDU is transmitted according to a mode different from the ER transmission mode and different from the high-throughput transmission mode, the one or more IC devices described above will be used. The communication device according to claim 16, configured to generate each training signal field including a downclocked version of the VHT-LTF as defined by the IEEE 802.11ac standard, wherein each training signal field has a duration shorter than the duration of each training signal field generated when the PPDU is transmitted according to the ER transmission mode.

18. The communication device according to any one of claims 15 to 17, wherein the second part is an iteration of the first part.

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