Communication method and communication device for orthogonal frequency division multiple access in wireless local area network

Abstract

A method for generating an orthogonal frequency division multiple access (OFDMA) data unit is described. A plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel are assigned to a plurality of devices including a first device and a second device. The plurality of different OFDM tone blocks include at least a first OFDM tone block assigned to the first device and a second OFDM tone block assigned to the second device. The first OFDM tone block and the second OFDM tone block together span a bandwidth equal to a minimum channel bandwidth of a conventional WLAN communication protocol. An OFDMA data unit for a WLAN communication channel is generated. The OFDMA unit includes a preamble portion and a data portion. The preamble portion has: i) at least a conventional portion spanning the entire WLAN communication channel, ii) a first non-conventional portion spanning the first OFDM tone block, and iii) a second non-conventional portion spanning the second OFDM tone block.

Description

[0001] This application is a divisional application of the Chinese invention patent application with the application date of November 25, 2014, application number 201480074063.X, and invention name “Communication method and communication device for orthogonal frequency division multiple access for wireless local area network”. Technical Field

[0002] The present disclosure relates generally to communication networks, and more particularly to wireless local area networks utilizing orthogonal frequency division multiple access. Background Art

[0003] When operating in infrastructure mode, a wireless local area network (WLAN) typically includes an access point (AP) and one or more client stations. WLAN has evolved rapidly over the past few decades. The development of WLAN standards (such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11n standards) 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 range of gigabits per second (Gpbs). Future standards allow for even higher throughputs, such as throughputs in the range of tens of Gpbs. Summary of the invention

[0004] In one embodiment, a method for generating an orthogonal frequency division multiple access (OFDMA) data unit includes: assigning a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device. The plurality of different OFDM tone blocks include at least a first OFDM tone block assigned to the first device and a second OFDM tone block assigned to the second device. The first OFDM tone block and the second OFDM tone block together span a bandwidth equal to a minimum channel bandwidth of a legacy WLAN communication protocol. The method also includes generating an OFDMA data unit for the WLAN communication channel. The OFDMA unit includes a preamble portion and a data portion. The preamble portion has: i) at least a legacy portion spanning the entire WLAN communication channel, ii) a first non-legacy portion spanning the first OFDM tone block, and iii) a second non-legacy portion spanning the second OFDM tone block.

[0005] In another embodiment, an apparatus includes a network interface device having one or more integrated circuits. The one or more integrated circuits are configured to assign a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device. The plurality of different OFDM tone blocks include at least a first OFDM tone block assigned to the first device and a second OFDM tone block assigned to the second device. The first OFDM tone block and the second OFDM tone block together span a bandwidth equal to a minimum channel bandwidth of a conventional WLAN communication protocol. The one or more integrated circuits are further configured to generate an OFDMA data unit for the WLAN communication channel. The OFDMA unit includes a preamble and a data portion. The preamble has: i) at least a conventional portion spanning the entire WLAN communication channel, ii) a first non-conventional portion spanning the first OFDM tone block, and iii) a second non-conventional portion spanning the second OFDM tone block.

[0006] In yet another embodiment, a method for generating a portion of an OFDM data unit includes determining an assignment of a first orthogonal frequency division multiplexing (OFDM) tone block within a wireless local area network (WLAN) communication channel. The bandwidth of the first OFDM tone block is less than a minimum bandwidth of a conventional WLAN communication protocol. The method also includes generating, at a first communication device, a first portion of an orthogonal frequency division multiple access (OFDMA) data unit for transmission over the WLAN communication channel using data tones and pilot tones within the first OFDM tone block.

[0007] In one embodiment, a first communication device includes a network interface device having one or more integrated circuits. The one or more integrated circuits are configured to determine an assignment of a first orthogonal frequency division multiplexing (OFDM) tone block within a wireless local area network (WLAN) communication channel. The bandwidth of the first OFDM tone block is less than a minimum bandwidth of a conventional WLAN communication protocol. The one or more integrated circuits are further configured to generate a first portion of an orthogonal frequency division multiple access (OFDMA) data unit at the first communication device for transmission over the WLAN communication channel using data tones and pilot tones within the first OFDM tone block.

[0008] In one embodiment, a method for generating an OFDMA data unit includes assigning a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device. The plurality of different OFDM tone blocks include at least a first OFDM tone block and a second OFDM tone block assigned to the first device and a second OFDM tone block assigned to the second device. The first OFDM tone block and the second OFDM tone block are separated in frequency by at least a third OFDM tone block. The method also includes generating an OFDMA data unit for the WLAN communication channel. The OFDMA unit includes a preamble and a data portion. The preamble has at least: i) a first conventional portion corresponding to at least the first OFDM tone block, ii) a second conventional portion corresponding to the second OFDM tone block, iii) a first non-conventional portion corresponding to the first OFDM tone block, iv) a second non-conventional portion corresponding to the second OFDM tone block, and v) a third non-conventional portion corresponding to the third OFDM tone block. The first legacy portion is modulated on at least a first OFDM tone block. The first non-legacy portion is modulated on a first OFDM tone block. The second legacy portion is modulated on at least a second OFDM tone block. The second non-legacy portion is modulated on a second OFDM tone block. The third non-legacy portion is modulated on a third OFDM tone block.

[0009] In another embodiment, an apparatus includes a network interface device having one or more integrated circuits. The one or more integrated circuits are configured to assign a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device. The plurality of different OFDM tone blocks include at least a first OFDM tone block and a second OFDM tone block assigned to the first device and a second OFDM tone block assigned to the second device. The first OFDM tone block and the second OFDM tone block are separated in frequency by at least a third OFDM tone block. The one or more integrated circuits are also configured to generate an OFDMA data unit for the WLAN communication channel. The OFDMA unit includes a preamble and a data portion. The preamble has at least: i) a first conventional portion corresponding to at least the first OFDM tone block, ii) a second conventional portion corresponding to the second OFDM tone block, iii) a first non-conventional portion corresponding to the first OFDM tone block, iv) a second non-conventional portion corresponding to the second OFDM tone block, and v) a third non-conventional portion corresponding to the third OFDM tone block. The first legacy portion is modulated on at least a first OFDM tone block. The first non-legacy portion is modulated on a first OFDM tone block. The second legacy portion is modulated on at least a second OFDM tone block. The second non-legacy portion is modulated on a second OFDM tone block. The third non-legacy portion is modulated on a third OFDM tone block.

[0010] In yet another embodiment, a method for generating a portion of an OFDMA data unit includes determining an assignment of a first orthogonal frequency division multiplexing (OFDM) tone block and a second OFDM tone block for a wireless local area network (WLAN) communication channel. The first OFDM tone block corresponds to a first fast Fourier transform (FFT) size, the first FFT size being less than the FFT size corresponding to the WLAN communication channel. The second OFDM tone block corresponds to a second FFT size, the second FFT size being less than the FFT size corresponding to the WLAN communication channel. The first OFDM tone block and the second OFDM tone block are separated in frequency by at least a third OFDM tone block. The method also includes generating a portion of an orthogonal frequency division multiple access (OFDMA) data unit at a first communication device for transmission on the WLAN communication channel using data tones and pilot tones within the first OFDM tone block and the second OFDM tone block.

[0011] In one embodiment, a method for generating an OFDMA data unit includes assigning a plurality of different orthogonal frequency division multiplexing (OFDM) frequency subbands for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device. The plurality of different OFDM frequency subbands include at least a first OFDM frequency subband assigned to the first device and a second OFDM frequency subband assigned to the second device. The method also includes generating an orthogonal frequency division multiple access (OFDMA) data unit for the WLAN communication channel. The OFDMA unit includes a preamble portion and a data portion. The preamble portion includes: a traditional portion spanning a first OFDM frequency subband and a second OFDM frequency subband using a traditional tone spacing and a traditional tone scheme, a first non-traditional portion spanning a first OFDM frequency subband and a second OFDM frequency subband using a traditional tone spacing and a traditional tone scheme, a second non-traditional portion spanning the first OFDM frequency subband using a non-traditional tone spacing and a non-traditional tone scheme, and a third non-traditional portion spanning a second OFDM frequency subband using a non-traditional tone spacing and a non-traditional tone scheme.

[0012] In another embodiment, an apparatus includes a network interface device having one or more integrated circuits. The one or more integrated circuits are configured to assign a plurality of different orthogonal frequency division multiplexing (OFDM) frequency sub-bands for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device. The plurality of different OFDM frequency sub-bands include at least a first OFDM frequency sub-band assigned to the first device and a second OFDM frequency sub-band assigned to the second device. The one or more integrated circuits are also configured to generate an orthogonal frequency division multiple access (OFDMA) data unit for the WLAN communication channel. The OFDMA unit includes a preamble portion and a data portion. The preamble portion includes: a traditional portion spanning a first OFDM frequency subband and a second OFDM frequency subband using a traditional tone spacing and a traditional tone scheme, a first non-traditional portion spanning a first OFDM frequency subband and a second OFDM frequency subband using a traditional tone spacing and a traditional tone scheme, a second non-traditional portion spanning the first OFDM frequency subband using a non-traditional tone spacing and a non-traditional tone scheme, and a third non-traditional portion spanning a second OFDM frequency subband using a non-traditional tone spacing and a non-traditional tone scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a block diagram of an example wireless local area network (WLAN) according to one embodiment.

[0014] Figure 2A and 2B is a diagram of a prior art data cell format.

[0015] Figure 3 is a diagram of another prior art data cell format.

[0016] Figure 4 is a diagram of another prior art data cell format.

[0017] Figure 5 is a diagram of another prior art data cell format.

[0018] Fig. 6A is a set of modulation patterns used to modulate symbols in a data unit of the prior art.

[0019] Figure 6B is a set of diagrams of modulation used to modulate symbols in an example data unit according to one embodiment.

[0020] Fig. 7A , 7B 7C are diagrams illustrating example orthogonal frequency division multiplexing (OFDM) sub-channel blocks of orthogonal frequency division multiple access (OFDMA) data units for an 80 MHz communication channel according to one embodiment.

[0021] Figure 8 is a diagram of an example tone scheme for a 32-FFT tone scheme, according to one embodiment.

[0022] Fig.9A is a diagram illustrating an example OFDMA data unit according to one embodiment.

[0023] Fig. 9B is a diagram illustrating an example portion of an OFDMA data unit according to another embodiment.

[0024] Fig.10 is a block diagram of an example PHY processing unit for generating an OFDMA data unit or a portion thereof according to another embodiment.

[0025] Fig.11 is a block diagram of an example PHY processing unit for generating OFDMA data units or portions thereof using channel bonding according to one embodiment.

[0026] Fig.12 is a block diagram of an example PHY processing unit for generating OFDMA data units or portions thereof using channel bonding according to another embodiment.

[0027] Fig.13 is a block diagram of an example PHY processing unit for generating OFDMA data units or portions thereof using channel bonding according to yet another embodiment.

[0028] Fig.14Ais a diagram illustrating an example OFDMA data unit for a channel bonding scenario according to one embodiment.

[0029] Fig. 14B is a diagram illustrating an example portion of an OFDMA data unit for a channel bonding scenario according to another embodiment.

[0030] Fig.15A is a block diagram of an example PHY processing unit for generating OFDMA data units or portions thereof using channel bonding according to one embodiment.

[0031] Fig. 15B is a block diagram of an example PHY processing unit for generating OFDMA data units or portions thereof using channel bonding according to another embodiment.

[0032] Fig.16 is a block diagram of an example downlink OFDMA data unit according to one embodiment.

[0033] Fig.17A is a diagram illustrating a normal mode data unit according to one embodiment.

[0034] Fig. 17B is a diagram illustrating a multi-access mode data unit according to one embodiment.

[0035] Figures 18A-18B are diagrams illustrating two possible formats of long training fields according to two example embodiments, respectively.

[0036] Fig.19A is a diagram illustrating a method according to an embodiment Fig.17A Diagram of non-legacy signal fields of a regular mode data unit.

[0037] Fig.19B is a diagram illustrating a method according to an embodiment Fig. 17B Diagram of non-legacy signal fields of a multi-access mode data unit.

[0038] Fig. 20A is a block diagram illustrating a multi-access mode data unit according to one embodiment.

[0039] Fig. 20B is a diagram illustrating a method according to an embodiment Fig. 20A Diagram of conventional signal fields for a multi-access mode data unit.

[0040] Fig. 20C is a diagram illustrating a method for performing a conventional receiving operation at a conventional receiving device according to an embodiment of the present invention. Fig. 14B Figure 2. A diagram of a Fast Fourier Transform (FFT) window of a conventional signal field.

[0041] Fig.21is a block diagram illustrating the format of a non-legacy signal field according to one embodiment.

[0042] Fig. 22 is a block diagram of an example downlink OFDMA data unit according to another embodiment.

[0043] Fig.23 is a block diagram of an example downlink OFDMA data unit using reduced tone spacing according to one embodiment.

[0044] Fig.24 is a block diagram of an example downlink OFDMA data unit according to one embodiment.

[0045] Fig.25A and 25B is a block diagram of example uplink OFDM signals from different client stations according to one embodiment.

[0046] Fig.26A is a block diagram of an example OFDMA data unit including a conventional OFDM signal according to one embodiment.

[0047] Fig.26B is a block diagram of an example OFDMA data unit including a conventional OFDM signal according to another embodiment.

[0048] Fig.27A , 27B , 27C and 27D are example diagrams of short training fields for OFDMA data units according to various embodiments.

[0049] Fig.28 is a flow chart of an example method for generating OFDMA data units according to one embodiment.

[0050] Fig.29 is a flow chart of an example method for generating OFDMA data units according to another embodiment.

[0051] Fig.30 is a flow chart of an example method for generating OFDMA data units according to one embodiment.

[0052] Fig.31 is a flow chart of an example method for generating a portion of an OFDMA data unit according to one embodiment.

[0053] Fig.32 is a flow chart of an example method for generating a portion of an OFDMA data unit according to another embodiment. DETAILED DESCRIPTION

[0054] In the embodiments described below, a wireless network device (such as an access point (AP) of a wireless local area network (WLAN)) transmits data streams to multiple client stations. The AP is configured to operate with the client stations according to at least a first communication protocol. The first communication protocol is sometimes referred to herein as "High Efficiency Wi-Fi", "HEW" communication protocol or 802.11ax communication protocol. In some embodiments described below, one or more client stations transmit corresponding data streams to the AP. In some embodiments, different client stations near the AP are configured to operate according to one or more other communication protocols that define operations in the same frequency band as the HEW communication protocol but typically have lower data throughput. Lower data throughput communication protocols (e.g., IEEE802.11a, IEEE802.11n and / or IEEE 802.11ac) are collectively referred to herein as "legacy" communication protocols. In at least some embodiments, traditional communication protocols are typically deployed in indoor communication channels, and HEW communication protocols are at least sometimes deployed for outdoor communications.

[0055] According to an embodiment, an orthogonal frequency division multiplexing (OFDM) symbol transmitted by an AP is generated according to a multi-access mode that divides a WLAN communication channel into OFDM tone blocks for simultaneous communication with multiple client stations. In some embodiments, simultaneous transmission with client stations provides a reduction in overhead due to non-user data (such as training fields and signal fields) within a data unit. In an embodiment, the HEW communication protocol defines a normal mode and a multi-access mode. In an embodiment, the normal mode is generally used for data units transmitted to a single client station, while the multi-access mode is generally used for data units transmitted to multiple client stations.

[0056] In an embodiment, a plurality of OFDM tone blocks for a WLAN communication channel are assigned to a plurality of devices. An orthogonal frequency division multiple access (OFDMA) data unit is generated for the WLAN communication channel. In some embodiments, the OFDMA unit includes a preamble portion and a data portion, the preamble portion having i) at least a conventional portion across the entire WLAN communication channel, ii) a first non-conventional portion across a first OFDM tone block, and iii) a second non-conventional portion across a second OFDM tone block. In some embodiments, the preamble is used at least in part to signal various parameters for transmission of the data portion to a receiving device. In various embodiments, the preamble of the data unit is used to signal the receiving device to be utilized in the mode of the OFDMA data unit and / or which receiving device intends to decode a specific portion of the OFDMA data unit. In some embodiments, the same preamble format is used in the conventional mode as in the multi-access mode. In one such embodiment, the preamble includes an indication set to indicate whether the conventional mode or the multi-access mode is used. In an embodiment, the receiving device determines the mode used based on the indication in the preamble of the data unit, and then decodes the indication portion of the data unit (e.g., the data portion, or a portion of the preamble and the data portion). In another embodiment, the preamble used in the multiple access mode is formatted differently from the preamble used in the normal mode. For example, the preamble used in the multiple access mode is formatted so that the receiving device can automatically (e.g., prior to decoding) detect that the data unit corresponds to the multiple access mode.

[0057] In addition, in at least some embodiments, the preamble of an OFDMA data unit in a conventional mode and / or a multi-access mode is formatted so that a client station operating according to a conventional protocol rather than an HEW communication protocol can determine certain information about the OFDMA data unit, such as the duration of the data unit, and / or whether the data unit does not conform to the conventional protocol. In addition, in an embodiment, the preamble of a data unit is formatted so that a client station operating according to the HEW protocol can determine that the data unit conforms to the HEW communication protocol and whether the data unit is formatted according to the conventional mode or the multi-access mode. Similarly, in an embodiment, a client station configured to operate according to the HEW communication protocol also transmits data units such as those described above.

[0058] In at least some embodiments, data units formatted such as described above are useful, for example, for an AP configured to operate with client stations according to multiple different communication protocols and / or with multiple client stations operating in a WLAN according to multiple different communication protocols. Continuing with the above example, a communication device configured to operate according to both a HEW communication protocol (including a conventional mode and a multi-access mode) and a traditional communication protocol is able to determine that a given data unit is formatted according to the HEW communication protocol rather than the traditional communication protocol, and is also able to determine that the data unit is formatted according to the multi-access mode rather than the conventional mode. Similarly, a communication device configured to operate according to a traditional communication protocol rather than the HEW communication protocol is able to determine that a data unit is not formatted according to the traditional communication protocol and / or determine the duration of a data unit.

[0059] Figure 1 1 is a block diagram of an example wireless local area network (WLAN) 10 according to an embodiment. AP 14 includes a host processor 15 coupled to a network interface 16. Network interface 16 includes a medium access control (MAC) processing unit 18 and a physical layer (PHY) processing unit 20. PHY processing unit 20 includes a plurality of transceivers 21, and transceivers 21 are coupled to a plurality of antennas 24. Although Figure 1 3 transceivers 21 and 3 antennas 24 are illustrated in the figure, but the AP 14 includes other suitable numbers (e.g., 1, 2, 4, 5, etc.) of transceivers 21 and antennas 24 in other embodiments. In one embodiment, the MAC processing unit 18 and the PHY processing unit 20 are configured to operate according to a first communication protocol (e.g., a HEW communication protocol), including at least a first mode and a second mode of the first communication protocol. In some embodiments, the first mode corresponds to a multi-access mode that divides a wider communication channel into narrower sub-bands or OFDM subchannel blocks, and different data streams are transmitted to corresponding client stations in corresponding OFDM subchannel blocks. OFDM subchannel blocks are sometimes referred to as "OFDM tone blocks" (e.g., blocks of adjacent tones or subcarriers) in this document. The multi-access mode is configured to provide orthogonal frequency division multiple access (FODMA) data units including at least portions of each independent data stream to the corresponding client station. In another embodiment, the MAC processing unit 18 and the PHY processing unit 20 are further configured to operate according to a second communication protocol (e.g., the IEEE 802.11ac standard). In yet another embodiment, the MAC processing unit 18 and the PHY processing unit 20 are further configured to operate according to the second communication protocol, a third communication protocol, and / or a fourth communication protocol (e.g., the IEEE 802.11a standard and / or the IEEE 802.11n standard).

[0060] The WLAN 10 includes a plurality of client stations 25. Figure 14 client stations 25 are illustrated in the figure, but the WLAN 10 includes other suitable numbers (e.g., 1, 2, 3, 5, 6, etc.) of client stations 25 in various scenarios and embodiments. At least one of the client stations 25 (e.g., client station 25-1) is configured to operate at least according to the first communication protocol. In some embodiments, at least one of the client stations 25 is not configured to operate according to the first communication protocol, but is configured to operate according to at least one of the second communication protocol, the third communication protocol, and / or the fourth communication protocol (referred to herein as a "legacy client station").

[0061] The client station 25-1 includes a host processor 26 coupled to a network interface 27. The network interface 27 includes a MAC processing unit 28 and a PHY processing unit 29. The PHY processing unit 29 includes a plurality of transceivers 30, and the transceivers 30 are coupled to a plurality of antennas 34. Figure 1 Three transceivers 30 and three antennas 34 are shown in FIG. 2 , but the client station 25 - 1 may include other suitable numbers (eg, 1, 2, 4, 5, etc.) of transceivers 30 and antennas 34 in other embodiments.

[0062] According to an embodiment, the client station 25-4 is a legacy client station, i.e., the client station 25-4 does not support receiving and fully decoding data units transmitted by the AP 14 or another client station 25 according to the first communication protocol. Similarly, according to an embodiment, the legacy client station 25-4 does not support transmitting data units according to the first communication protocol. On the other hand, the legacy client station 25-4 supports receiving and fully decoding and transmitting data units according to the second communication protocol, the third communication protocol, and / or the fourth communication protocol.

[0063] In an embodiment, one or both of client stations 25-2 and 25-3 have the same or similar structure as client station 25-1. In an embodiment, client station 25-4 has a similar structure as client station 25-1. In these embodiments, client stations 25 that are constructed the same or similarly as client station 25-1 have the same or different numbers of transceivers and antennas. For example, according to an embodiment, client station 25-2 has only 2 transceivers and 2 antennas (not shown).

[0064] In various embodiments, the PHY processing unit 20 of the AP 14 is configured to generate data units that conform to the first communication protocol and have a format described herein. The transceiver(s) 21 are configured to transmit the generated data units via the antenna(s) 24. Similarly, the transceiver(s) 21 are configured to receive the data units via the antenna(s) 24. According to various embodiments, the PHY processing unit 20 of the AP 14 is configured to process received data units that conform to the first communication protocol and have a format described below and determine that such data units conform to the first communication protocol.

[0065] In various embodiments, the PHY processing unit 29 of the client device 25-1 is configured to generate data units that conform to the first communication protocol and have a format described herein. The transceiver(s) 30 are configured to transmit the generated data units via the antenna(s) 34. Similarly, the transceiver(s) 30 are configured to receive the data units via the antenna(s) 34. According to various embodiments, the PHY processing unit 29 of the client device 25-1 is configured to process received data units that conform to the first communication protocol and have a format described below and determine that such data units conform to the first communication protocol.

[0066] Figure 2A 1 is a diagram of a prior art OFDM data unit 200 that the AP 14 is configured to transmit to a traditional client station 25-4 via orthogonal frequency division multiplexing (OFDM) modulation according to an embodiment. In an embodiment, the traditional client station 25-4 is also configured to transmit the data unit 200 to the AP 14. The data unit 200 complies with the IEEE 802.11a standard and occupies a frequency band of 20 megahertz (MHz). The data unit 200 includes a preamble having a traditional short training field (L-STF) 202 (usually used for packet detection, initial synchronization and automatic gain control, etc.) and a traditional long training field (L-LTF) 204 (usually used for channel estimation and fine synchronization). For example, the data unit 200 also includes a traditional signal field (L-SIG) 206, which is used to carry certain physical layer (PHY) parameters using the data unit 200, such as the modulation type and coding rate used to transmit the data unit. The data unit 200 also includes a data portion 208. Figure 2B 2 is a diagram of an example data portion 208 (not low density parity check encoded), which includes a service field, a scrambled physical layer service data unit (PSDU), tail bits, and padding bits as required. The data unit 200 is designed for transmission on one spatial stream or space-time stream in a single-input single-output (SISO) channel configuration.

[0067] Figure 3is a diagram of a prior art OFDM data unit 300 that the AP 14 is configured to transmit to a legacy client station 25-4 via orthogonal frequency division multiplexing (OFDM) modulation according to an embodiment. In an embodiment, the legacy client station 25-4 is also configured to transmit the data unit 300 to the AP 14. The data unit 300 complies with the IEEE 802.11n standard, occupies a 20 MHz frequency band, and is designed for mixed mode situations, i.e., when the WLAN includes one or more client stations that comply with the IEEE 802.11a standard but not the IEEE 802.11n standard. The data unit 300 includes a preamble having an L-STF 302, an L-LTF 304, an L-SIG 306, a high throughput signal field (HT-SIG) 308, a high throughput short training field (HT-STF) 310, and M data high throughput long training fields (HT-LTFs) 312, where M is the number of spatial streams (N) typically used by transmitting the data unit 300 in a multiple-input multiple-output (MIMO) channel configuration. sts ). In particular, according to the IEEE 802.11n standard, if 2 spatial streams are used to transmit the data unit 300, the data unit 300 includes 2 HT-LTFs 312, and if 3 or 4 spatial streams are used to transmit the data unit 300, the data unit 300 includes 4 HT-LTFs 312. An indication of the specific number of spatial streams used is included in the HT-SIG field 308. The data unit 300 also includes a data portion 314.

[0068] Figure 4 is a diagram of a prior art OFDM data unit 400 that the AP 14 is configured to transmit to a legacy client station 25-4 via orthogonal frequency division multiplexing (OFDM) modulation according to an embodiment. In an embodiment, the legacy client station 25-4 is also configured to transmit the data unit 400 to the AP 14. The data unit 400 complies with the IEEE 802.11n standard, occupies a 20 MHz frequency band, and is designed for "greenfield" situations, i.e., when the WLAN does not include any client stations that comply with the IEEE 802.11a standard and only includes client stations that comply with the IEEE 802.11n standard. The data unit 400 includes a preamble having a high throughput greenfield mode short training field (HT-GF-STF) 402, a first high throughput long training field (HT-LTF1) 404, an HT-SIG 406, and M data HT-LTFs 408, where M is an integer corresponding generally to the number of spatial streams used in a multiple-input multiple-output (MIMO) channel configuration to transmit the data unit 400. The data unit 400 also includes a data portion 410.

[0069] Figure 51 is a diagram of a prior art OFDM data unit 500 that the AP 14 is configured to transmit to a legacy client station 25-4 via orthogonal frequency division multiplexing (OFDM) modulation according to an embodiment. In an embodiment, the legacy client station 25-4 is also configured to transmit the data unit 500 to the AP 14. The data unit 500 complies with the IEEE 802.11ac standard and is designed for "mixed field" situations. The data unit 500 occupies a 20 MHz bandwidth. In other embodiments or scenarios, data units similar to the data unit 500 occupy different bandwidths, such as 40 MHz, 80 MHz, or 160 MHz bandwidths. The data unit 500 includes a preamble having an L-STF 502, an L-LTF 504, an L-SIG 506, two first very high throughput signal fields (VHT-SIGA) 508 including a first very high throughput signal field (VHT-SIGA1) 508-1 and a second very high throughput signal field (VHT-SIGA2) 508-2, a very high throughput short training field (VHT-STF) 510, M very high throughput long training fields (VHT-LTF) 512 (where M is an integer), and a second very high throughput signal field (VHT-SIG-B) 514. The data unit 500 also includes a data portion 516.

[0070] Fig. 6A This is a diagram of the IEEE 802.11n standard. Figure 3 300. The L-SIG field is modulated according to binary phase shift keying (BPSK), while HT-SIG1 and HT-SIG2 are modulated according to BPSK but on a quadrature axis (Q-BPSK). In other words, the modulation of the HT-SIG1 and HT-SIG2 fields is rotated 90 degrees compared to the modulation of the L-SIG field.

[0071] Figure 6B This is a diagram defined by the IEEE 802.11ac standard. Figure 5 A set of diagrams showing modulation of the L-SIG, VHT-SIGA1, and VHT-SIGA2 fields of a data unit 500. Fig. 6A The HT-SIG1 field in the VHT-SIGA1 field is modulated according to BPSK, which is the same as the modulation of the L-SIG field. On the other hand, the VHT-SIGA2 field is rotated 90 degrees compared to the modulation of the L-SIG field.

[0072] Fig. 7A , 7B7C is a diagram illustrating an example OFDM subchannel block (or OFDM tone block) for an 80MHz communication channel according to an embodiment. In various embodiments, the communication channel is divided into a plurality of OFDM tone blocks by an AP (such as AP 14). In an embodiment, the AP assigns the plurality of OFDM tone blocks to one or more client stations (such as client stations 25-1, 25-2, 25-3, or 25-4). In an embodiment, in the downlink direction, the AP generates and transmits an OFDM data unit that spans the communication channel and includes OFDM data units for one or more client stations. In this embodiment, the OFDMA data unit includes OFDM data units for each client station that has been assigned an OFDM tone block via a corresponding tone block. In an embodiment, for example, if no data is to be transmitted to an idle client station, the OFDMA data unit omits the OFDM data unit for the client station. In this embodiment, the corresponding OFDM tone block for the idle client station is set to zero or the OFDMA data unit omits the corresponding OFDM tone block.

[0073] exist Fig. 7A In the embodiment, the communication channel 700 is divided into 4 consecutive OFDM tone blocks 701, 702, 703 and 704, each OFDM tone block having a bandwidth of 20MHz. According to various embodiments, the OFDM tone blocks 701, 702, 703 and 704 are assigned to one or more client stations. Fig. 7A In the illustrated embodiment, OFDM tone blocks 701, 702, 703, and 704 include independent data streams for four client stations STA1, STA2, STA3, and STA4, respectively. Figure 7B In the embodiment, the communication channel 710 is divided into 3 consecutive OFDM tone blocks 711, 712 and 713. 2 OFDM tone blocks 711 and 712 each have a bandwidth of 20 MHz. The remaining OFDM tone block 713 has a frequency band of 40 MHz. The OFDM tone blocks 711, 712 and 713 are assigned to 3 client stations STA1, STA2 and STA3 and include independent data streams for the 3 client stations STA1, STA2 and STA3, respectively. Figure 7CIn the embodiment, the communication channel 720 is divided into 4 consecutive OFDM tone blocks 721, 722, 723 and 724. OFDM tone blocks 721 and 722 each have a bandwidth of 10 MHz and thus span a bandwidth equal to the minimum channel bandwidth of the traditional WLAN communication protocol (i.e., 20 MHz) together. OFDM tone block 723 has a bandwidth of 20 MHz. OFDM tone block 724 has a bandwidth of 40 MHz. OFDM tone blocks 722 and 724 are assigned to 2 client stations STA2 and STA3 and include independent data streams for the 2 client stations STA2 and STA3, respectively. OFDM tone blocks 721 and 723 separated in frequency by OFDM tone block 722 are assigned to client station STA 1 and include portions of the data stream for client station STA 1 and use channel bonding techniques, as described herein.

[0074] Although in Fig. 7A , 7B In embodiments, the OFDM tone blocks are continuous across the corresponding communication channels, but in other embodiments, the OFDM tone blocks are discontinuous across the communication channels (i.e., there are one or more gaps between the OFDM tone blocks). In an embodiment, each gap is at least as wide as one of the OFDM tone blocks. In another embodiment, at least one gap is less than the bandwidth of the OFDM tone block. In another embodiment, at least one gap is at least as wide as 1 MHz. In an embodiment, different OFDM tone blocks are transmitted in different channels defined by the IEEE 802.11a and / or 802.11n standards. In one embodiment, the AP includes multiple radios and different OFDM tone blocks are transmitted using different radios.

[0075] In an embodiment, for multiple data streams transmitted by an AP in different OFDM tone blocks, different data streams are transmitted at different data rates, for example, when signal strength, SNR, interference power, etc. vary between client devices. In addition, for multiple data streams transmitted by an AP in different OFDM tone blocks, the amount of data in different data streams is typically different. Therefore, one transmitted data stream may end before another. In such a case, according to an embodiment, the data in the OFDM tone block corresponding to the ended data stream is set to zero or some other suitable predetermined value.

[0076] An OFDM signal comprising a plurality of OFDM tone blocks for transmitting independent data streams as described above is also referred to herein as an orthogonal frequency division multiple access (OFDMA) signal. According to an embodiment, the WLAN uses downlink OFDMA data units and uplink OFDMA data units. Downlink OFDMA data units are transmitted from a single AP to multiple client stations simultaneously (i.e., point-to-multipoint). Uplink OFDMA data units are jointly transmitted by multiple client stations to a single AP (i.e., multipoint-to-point). According to some embodiments, the frame format, modulation and coding scheme (MCS), number of space-time streams, tone spacing, and / or signaling scheme of the downlink OFDMA and uplink OFDMA are different. In some embodiments, the OFDM data units within the OFDMA data unit have different MCS, number of space-time streams, tone spacing, and / or signaling schemes.

[0077] about Fig.16 , 22 , 23, 24, 25A, 25B, 26A, and 26B describe various embodiments of PHY frame formats for downlink and / or uplink OFDMA data units. In the following embodiments, the OFDM tone block has a format substantially similar to the PHY format specified in the IEEE 802.11ac standard. In other embodiments, the OFDMA tone block has a format substantially similar to the PHY format specified in another communication protocol (such as the IEEE 802.a standard, the IEEE 802.11n standard, or a communication protocol that has not yet been standardized).

[0078] In an embodiment, OFDM data units for OFDM tone blocks spanning a frequency band greater than or equal to 20 MHz are generated using the same MCS and "legacy" tone scheme as defined in IEEE 802.11n and / or IEEE 802.11ac. As referred to herein, a tone scheme is a predetermined sequence of indices that indicate which OFDM tones corresponding to a Fast Fourier Transform (FFT) of an appropriate size are designated for data tones, pilot tones, and / or guard tones. For example, in an embodiment, an OFDM tone block spanning 20 MHz uses an FFT of size 64 and uses the legacy tone scheme for IEEE 802.11ac, which has 4 pilot tones (at indices -21, -7, +7, and +21), a DC tone (at index 0), guard tones (at indices -32 to -29 and 29-31), and 52 data tones (at the remaining indices). In some embodiments, OFDM tone blocks spanning 40 MHz, 80 MHz, or 160 MHz use FFT sizes of 128, 256, and 512, respectively, and use the corresponding legacy tone scheme as defined in IEEE 802.1 lac.

[0079] In some embodiments, the communication channel is divided to include OFDM tone blocks spanning a bandwidth less than 20 MHz, such as 10 Mhz, 5 MHz, or 2.5 MHz. In an embodiment, the OFDM tone blocks spanning a bandwidth less than 20 MHz use a tone scheme different from traditional tone schemes. Figure 8 is a diagram of an example tone scheme 800 for an OFDM tone block across a 10 MHz bandwidth and using an FFT of size 32, in accordance with an embodiment. The tone scheme 800 has 2 pilot tones (at indices -7 and +7), a DC tone (at index 0), guard tones 802-1 and 802-2 (at indices -16 to -14 and 14 to 15), and 24 data tones 804-1, 804-2, 804-3, and 804-4 (at the remaining indices).

[0080] Fig.9A 904-1, 904-2, and 904-3 are inserted into OFDM tone blocks that are not assigned for FFT. Fig. 9B 9 is a diagram illustrating an example portion of an OFDMA data unit for an 80 MHz communication channel according to another embodiment. In this embodiment, a client station generates and transmits an OFDMA data unit portion 910 that spans only the OFDM tone blocks assigned to the client station using the appropriate FFT size (i.e., 64 FFT size for 20 MHz, 128 FFT size for 40 MHz, etc.).

[0081] Fig.10 is a block diagram of an example PHY processing unit 1000 for generating an OFDMA data unit or an OFDMA data unit portion according to various embodiments. Figure 1 In an embodiment, the AP 14 and the client station 25-1 each include a PHY processing unit, such as the PHY processing unit 1000. In various embodiments and / or scenarios, the PHY processing unit 1000 generates an OFDM data unit, such as Fig. 7A , 7B, 7C, 9A or 9B. The PHY processing unit 1000 includes a scrambler 1002, which typically scrambles the information bit stream to be transmitted to reduce the occurrence of long sequences of 1 or 0. The FEC encoder 1004 encodes the scrambled information bits to generate encoded data bits. In one embodiment, the FEC encoder 1004 includes a binary convolutional code (BCC) encoder. In another embodiment, the FEC encoder 1004 includes a binary convolutional encoder followed by a puncturing block. In yet another embodiment, the FEC encoder 1004 includes a low density parity check (LDPC).

[0082] In an embodiment, stream parser 1006 receives the encoded data bits and parses the encoded data bits into one or more spatial streams. For each spatial stream ( Fig.10 2 spatial streams in the illustrated embodiment), the constellation mapper 1010 maps the encoded data bits to constellation points corresponding to different subcarriers of the OFDM symbol. More specifically, for each spatial stream, the constellation mapper 1010 translates each bit sequence of length log2(M) into one of the M constellation points. In some embodiments, the PHY processing unit 1000 includes multiple parallel processing paths, for example, one path for each spatial stream. In other embodiments, a single processing path is used for a spatial stream.

[0083] In an embodiment where the FEC encoder 1004 is a BCC encoder, before the constellation mapper 1010, an interleaver 1008 receives the encoded data bits and interleaves the bits (i.e., changes the order of the bits) to prevent long sequences of adjacent noise bits from entering the decoder at the receiver. In another embodiment, the interleaver 1008 is omitted. In an embodiment where the FEC encoder 1004 is an LDPC encoder, an LDPC tone mapper 1012 reorders the constellation points according to a tone remapping function. The tone remapping function is generally defined as such that continuous encoded information bits or blocks of information bits are mapped to non-continuous tones in an OFDM symbol so as to facilitate data recovery at the receiver when continuous OFDM tones are adversely affected during transmission. In some embodiments, the LDPC tone mapper 1012 is omitted.

[0084] In an embodiment, the output of the constellation mapper 1010 (or LDPC tone mapper 1012, if included) for each stream is operated by a space-time block encoder (STBC) 1014. In an embodiment, the space-time block encoder 1014 obtains a single constellation symbol output and maps it to multiple transmission chains for transmission by separate radio transmitters, thereby transforming the spatial stream into a space-time stream. In an embodiment or scenario in which the PHY processing unit 1000 operates to generate data units for transmission via multiple spatial streams, one or more cyclic shift diversity (CSD) units 1016 insert cyclic shifts into all but one spatial stream to prevent unintentional beamforming. In an embodiment, a spatial mapper 1018 maps the space-time streams to the transmission chains. In an embodiment, the PHY processing unit 1000 includes an inverse discrete Fourier transform (IDFT) processor 1020 for each transmission chain. In an embodiment, FEC encoder 1004, stream parser 1006, interleaver 1008, constellation mapper 1010, LDPC tone mapper 1012, STBC 1014, CSD unit 1016, and spatial mapper 1018 operate according to the IEEE 802.11ac protocol.

[0085] In an embodiment, the IDFT processor 1020 receives pilot tones from the pilot generator 1022 and receives spatially mapped constellation points from the spatial mapper 1018. In an embodiment, the IDFT processor 1020 converts a block of spatially mapped constellation points corresponding to data tones within the OFDM tone block and pilot tones into a time domain signal. In some embodiments, the IDFT processor 1020 processes one or more tones from the tone input 1024 to be included in the time domain signal. For example, in an embodiment, the PHY processing unit 1000 generates an OFDMA data unit (i.e., a downstream OFDMA data unit) with OFDM data units for multiple users to be transmitted from the AP. In this embodiment, the tone input 1024 provides a separately generated data tone and / or pilot tone corresponding to another user. The IDFT processor 1020 thus performs IDFT jointly for all tones of all users at the same time.

[0086] In another embodiment, the PHY processing unit 1000 generates a portion of an OFDMA data unit to be transmitted from a client station to an AP (i.e., a portion of an uplink OFDMA data unit). In an embodiment, the tone input 1024 provides a null tone to an unassigned OFDM tone block for generating an OFDMA data unit using a full-size FFT, as described above with respect to Fig.9A In another embodiment, a client station generates and transmits a portion of an OFDMA data unit that spans only the OFDM tone blocks assigned to the client station using an appropriate FFT size, as described above with respect to Fig. 9B Described.

[0087] Fig.11 1 is a block diagram of an example PHY processing unit 1100 for generating OFDMA data units or OFDMA data unit portions using channel bonding according to an embodiment. The PHY processing unit 1100 is configured to provide OFDMA data units or portions thereof where a client station has been assigned two or more non-contiguous OFDM tone blocks ("bonded channels"). Fig. 7A , 7B As described in , 7C, the communication channel is divided into a plurality of OFDM tone blocks. Figure 7C As shown, OFDM tone blocks 721 and 723 separated in frequency by OFDM tone block 722 are assigned to client station STA 1 and include portions of a data stream for client station STA 1 and use channel bonding techniques. In some embodiments, the PHY processing unit 1100 provides separate encoders and modulators to allow different MCS values ​​for different OFDM tone blocks. In an embodiment, the PHY processing unit 1100 includes a scrambler 1002, a pilot generator 1022, a tone input 1024, and an IDFT processor 1020, as described above with respect to Fig.10 In an embodiment, the PHY processing unit 1100 further includes a plurality of processing paths 1150 that operate substantially in parallel and correspond to the assigned OFDM tone blocks. In another embodiment, the processing paths 1150 are a single processing path. The processing paths 1150 each include an FEC encoder 1004, a stream parser 1006, an interleaver 1008, a constellation mapper 1010, an LDPC tone mapper 1012, an STBC 1014, a CSD unit 1016, and a spatial mapper 1018, as described above with respect to Fig.10 Described.

[0088] In an embodiment, the scrambler 1002 provides the scrambled information bits to the segment parser 1140. In an embodiment, the segment parser 1140 divides the scrambled information bits into multiple segments and passes each segment to the assigned OFDM tone block. In an embodiment, the AP assigns OFDM tone blocks of the same size to the client station, such as 10MHz+10MHz, 20MHz+20MHz, or other suitable combinations. In another embodiment, the AP assigns OFDM tone blocks of different sizes to the client station, such as 10MHz+20MHz+20MHz, 10MHz+40MHz, or other suitable combinations. In other embodiments, additional OFDM tone blocks are bundled together, for example, 3 or 4 OFDM tone blocks are bundled together.

[0089] In an embodiment, each OFDM tone block as a bonded channel uses the same tone scheme as in a non-bonded channel scenario. For example, in an embodiment, a 10 MHz OFDM tone block corresponds to 0 when bonded with a 20 MHz OFDM tone block using an FFT size of 64 and using the legacy tone scheme of IEEE 802.11ac. Figure 8 In some embodiments, each OFDM tone block assigned to the same client station uses the same MCS value. In some embodiments, each OFDM tone block assigned to the same client station has a different MCS value. In some embodiments, each OFDM tone block assigned to the client station has the same number of space-time streams.

[0090] Fig.12 1 is a block diagram of an example PHY processing unit 1200 for generating an OFDMA data unit or a portion of an OFDMA data unit using channel bonding according to another embodiment. The PHY processing unit 1200 is configured to provide an OFDMA data unit or a portion thereof in which a client station has been assigned two or more non-contiguous OFDM tone blocks. In an embodiment, the PHY processing unit 1200 includes a scrambler 1002, an FEC encoder 1004, a stream parser 1006, a pilot generator 1022, a tone input 1024, and an IDFT processor 1020, as described above with respect to Fig.10 Described. Fig.12 In the illustrated embodiment, the PHY processing unit 1200 provides a joint encoder to each user, for example, the FEC encoder 1004 performs joint encoding on the OFDM tone blocks assigned to a single user. The segment parser 1240 divides the spatial stream from the stream parser 1006 into a plurality of stream segments. In an embodiment, the PHY processing unit 1200 includes a plurality of processing paths 1250 that operate substantially in parallel and correspond to the assigned OFDM tone blocks. In another embodiment, the processing paths 1250 are a single processing path. The processing paths 1250 each include an interleaver 1008, a constellation mapper 1010, an LDPC tone mapper 1012, an STBC 1014, a CSD unit 1016, and a spatial mapper 1018, as described above with respect to Fig.10 In an embodiment, segment parser 1240 passes the spatial streams of OFDM tone blocks from stream parser 1006 to corresponding processing path 1250 .

[0091] Fig.131 is a block diagram of an example PHY processing unit 1300 for generating an OFDMA data unit or a portion of an OFDMA data unit using channel bonding according to yet another embodiment. The PHY processing unit 1300 is configured to provide an OFDMA data unit or a portion thereof, wherein a client station has been assigned two or more non-contiguous OFDM tone blocks, wherein each OFDM tone block uses the same MCS value. In an embodiment, the PHY processing unit 1300 includes a scrambler 1002, an FEC encoder 1004, a stream parser 1006, an interleaver 1008, a constellation mapper 1010, an LDPC tone mapper 1012, an STBC 1014, a CSD unit 1016, a spatial mapper 1018, a pilot generator 1022, a tone input 1024, and an IDFT processor 1020 (as described above with respect to Fig.10 ) and a tone distributor 1340 configured to divide the spatial stream from the spatial mapper 1018 into the assigned OFDM tone blocks and provide the divided spatial stream to the IDFT processor 1020.

[0092] Fig.14A 1 is a diagram illustrating an example OFDMA data unit for a channel bonding scenario for an 80 MHz communication channel in accordance with an embodiment. In an embodiment, in the uplink direction, a PHY processing unit (such as PHY processing unit 1100, 1200, or 1300) generates and transmits a portion of an OFDMA data unit 1400 that spans a communication channel using an FFT of size 256 (e.g., a "full size" FFT). In this embodiment, the OFDMA data unit 1400 includes a first OFDMA data unit portion 1402 spanning a first assigned OFDM tone block, a second OFDMA data unit portion 1404 spanning a second assigned OFDM tone block, and zero tones 1406-1 and 1406-2 inserted into OFDM tone blocks not assigned for FFT.

[0093] Fig. 14B 1450 is a diagram illustrating an example portion of an OFDMA data unit for a channel bonding scenario according to another embodiment. In this embodiment, in the uplink direction, the PHY processing unit generates and transmits an OFDMA data unit portion 1450 that spans only the assigned OFDM tone blocks 1452 and 1454. In an embodiment, the PHY processing unit generates and transmits data on OFDM tone blocks 1452 and 1454 using separate transmit chains and using the appropriate FFT size (i.e., 64 FFT size for 20 MHz, 128 FFT size for 40 MHz, etc.).

[0094] Fig.15Ais a block diagram of an example PHY processing unit 1500 for generating OFDMA data units or OFDMA data unit portions using channel bonding according to an embodiment. In an embodiment, the PHY processing unit 1500 is configured to generate and transmit OFDMA data unit portions (such as OFDMA data unit portion 1450) that span only the OFDM tone blocks assigned to the client station for uplink transmission. In some embodiments, the PHY processing unit 1500 includes a separate transmission chain 1502 for filtering and transmitting portions of the OFDMA data unit portion via each assigned OFDM tone block of the client station. In an embodiment, transmission chain 1502-1 corresponds to OFDM data unit 1452 and transmission chain 1502-2 corresponds to OFDMA data unit 1454. In various embodiments, each transmission chain 1502 includes an IDFT processor 1520, such as Fig.10 , 11 , 12 or 13. In an embodiment, the IDFT processor 1520 performs IDFT using only those tones within the corresponding assigned OFDM tone blocks. A guard interval (GI) insertion and windowing unit 1542 appends a loopback extension of the OFDM symbol before the OFDM symbol received from the IDFT processor 1520 and smoothes the edge of each symbol to increase spectral attenuation. The output of the GI insertion and windowing unit 1542 is provided to an analog and radio frequency (RF) unit 1544, which converts the signal into an analog signal and up-converts the signal to an RF frequency for transmission.

[0095] Fig. 15B is a block diagram of an example PHY processing unit 1550 for generating OFDMA data units or OFDMA data unit portions using channel bonding according to another embodiment. In an embodiment, the PHY processing unit 1550 is configured to generate and transmit OFDMA data unit portions (such as OFDMA data unit portions 1450) that span only OFDM tone blocks assigned to a client station for uplink transmission. In some embodiments, the PHY processing unit 1550 includes a separate transmission chain 1552 corresponding to each assigned OFDM tone block of the client station. In an embodiment, transmission chain 1552-1 corresponds to OFDM data unit 1452, and transmission chain 1552-2 corresponds to OFDM data unit 1454. In various embodiments, each transmission chain 1552 includes an IDFT processor 1520 and a GI insertion and windowing unit 1542, as described above with respect to FIG. Fig.15A Described.

[0096] In an embodiment, the PHY processing unit 1550 is configured to filter and combine the output from each GI insertion and windowing unit 1542 for transmission by a single radio transmitter (i.e., a broadband radio transmitter). For example, in an embodiment, each transmission chain 1552 includes a low-pass filter 1556 (such as a digital filter) that filters the output from each GI insertion and windowing unit 1542. In an embodiment, a signal multiplier 1558 combines phasors 1560 to provide frequency shifts in all except one of the outputs after the filter. In an embodiment, phasors 1560 are configured to provide a phase shift corresponding to the frequency interval between the assigned OFDM tone blocks. Each filtered and shifted output is combined by a signal combiner 1562 and provided to an analog and RF unit 1554 as a single time domain signal, and the analog and RF unit 1554 transforms the signal into an analog signal and up-converts the analog signal to an RF frequency for transmission.

[0097] Fig.16 1 is a block diagram of an example OFDMA data unit 1600 according to an embodiment, wherein the AP 14 is configured to transmit to a plurality of client stations over a communication channel via OFDM modulation. In an embodiment, the AP 14 divides the communication channel into a plurality of OFDM tone blocks and assigns the OFDM tone blocks to the plurality of client stations, as described above with respect to Fig. 7A , 7B and 7C. OFDMA data unit 1600 complies with the first communication protocol. In other embodiments, OFDMA data units conforming to the first communication protocol similar to OFDMA data unit 1600 may occupy a bandwidth such as, for example, 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz, 640 MHz, or other suitable bandwidths. Fig.16 In the embodiment of the present invention, the communication channel spans an 80 MHz bandwidth and is divided into four equal width 20 MHz OFDM tone blocks, which are distributed by AP 14 to four client stations (e.g., STA 1, STA 2, STA 3, and STA 4). In other embodiments, two or more OFDM tone blocks are assigned to the same client device using channel bonding techniques, such as with respect to Fig.11 , 12 , 13, 14A, 14B, 15A and 15B. In some embodiments, the OFDM tone blocks span different subbands within the communication channel, such as 2.5 MHz, 5 MHz, 10 MHz, 20 MHz, 40 MHz, 80 MHz, 160 MHz subbands or other suitable subbands.

[0098] In an embodiment, the OFDMA data unit 1600 includes an OFDM data unit 1640 corresponding to each assigned OFDM tone block. The OFDMA data unit 1600 is suitable for use in a "mixed mode" scenario, i.e., the WLAN 10 includes client stations (e.g., the legacy client station 25-4) that conform to a legacy communication protocol rather than the first communication protocol. In some embodiments, the OFDMA data unit 1600 is also used in other scenarios. In some embodiments, the OFDM data unit 1640 has a PHY format substantially similar to the IEEE 802.11 standard (such as IEEE 802.11a, IEEE 802.11g, and / or IEEE 802.11n). In an embodiment, each OFDM data unit 1640 has the same PHY format. In another embodiment, the OFDMA data unit 1600 includes OFDM data units having different PHY formats.

[0099] In an embodiment, the OFDM data unit 1600, and thus each OFDM data unit 1640, includes a preamble portion 1601 and a data portion 1616 (e.g., a data field for a corresponding client station). In other embodiments, the OFDM data unit 1640 omits the data portion 1616. In an embodiment, the preamble portion 1601 of each OFDM data unit 1640 includes at least a legacy portion 1602 and a non-legacy portion 1603. In an embodiment, the legacy portion 1602 includes a legacy short training field (L-STF) 1604, a legacy long training field (L-LTF) 1605, and a legacy signal (L-SIG) field 1606. Therefore, in an embodiment, each of the L-STF 1604, the L-LTF 1605, and the L-SIG 1606 is repeated over a corresponding number of 20 MHz subbands of the entire bandwidth of the OFDMA data unit 1600. In one embodiment, Fig.16 Each OFDM tone block 1640 in is 20 MHz wide. In another embodiment, Fig.16 The width of each OFDM tone block 1640 in is 40 MHz. According to an embodiment, if the width of the OFDM tone block is 40 MHz, the legacy portion 1602 (i.e., L-STF, L-LTF, and L-SIG) is replicated in the upper half 20 MHz and the lower half 20 MHz, where the subchannels in the upper 20 MHz are phase shifted 90 degrees with respect to the subchannels in the lower 20 MHz.

[0100] The non-legacy portion 1603 includes a HEW signal (HEW-SIGA) field 1608, a HEW short training field (HEW-STF) 1610, M HEW long training fields (HEW-LTF) 1612 (where M is an integer), and a third HEW signal field (HEW-SIGB) 1614. Each of the L-STF 1604, L-LTF 1605, L-SIG 1606, HEW-SIGA 1608, HEW-STF 1610, M HEW-LTFs 1612, and HEW-SIGB 1614 includes an integer number of one or more OFDM symbols. For example, in an embodiment, HEW-SIGA 1608 includes 2 OFDM symbols. In another embodiment, for example, the non-legacy portion 1603 of the preamble portion 1601 includes an additional OFDM symbol for the HEW signal field 1608. In some embodiments, the HEW-SIGB field 1614 is omitted.

[0101] According to an embodiment, the legacy portion 1602 (i.e., L-STF, L-LTF, and L-SIG) of the preamble portion 1601 is the same in all OFDM data units 1640. In another embodiment, at least the L-SIG field is different in at least some of the OFDM data units 1640, for example, where at least some of the OFDM data units 1640 have different durations. For the non-legacy portion 1603 (i.e., starting with the HEW-SIGA) of the preamble portion 1601, the content of the OFDM data unit 1640 may vary for different client stations depending on factors such as the data rate, data amount, configuration (e.g., number of antennas, number of supported multiple-input multiple-output (MIMO) data streams, etc.) of different client stations. In some embodiments and / or scenarios, the non-legacy portion 1603 and / or the data portion 1616 are generated to include at least one padding OFDM symbol.

[0102] In an embodiment, the AP uses zero padding within the data portion 1616 to ensure that each OFDM data unit 1640 has the same duration and / or the same number of OFDM symbols (i.e., the duration of the longest OFDM data unit). In an embodiment, the MAC unit of the AP performs zero padding on one or more MAC service data units (MSDUs) included in a MAC protocol data unit (MPDU), which in turn is included in a PHY protocol data unit (PPDU). By zero padding the MSDU, for example, the length of the MPDU and PPDU is increased.

[0103] In some embodiments, the AP inserts additional HEW long training fields into the non-legacy portion 1603. In an embodiment, the AP generates OFDMA data units such that each OFDM tone block has the same number of HEW-LTF fields. For example, in an embodiment, the AP generates OFDMA data units such that each OFDM data unit uses the same number of spatial streams. In another embodiment, the number of spatial streams is different for at least some OFDM tone blocks, and the AP generates OFDMA data units with additional HEW-LTF fields such that each OFDM data unit has the same number (i.e., the maximum number) of HEW-LTF fields.

[0104] In an embodiment, the AP determines the number of padding OFDM symbols to be included in OFDM data unit 1640-2 as the difference between the total number of OFDM symbols of OFDM data unit 1640-3 and the total number of OFDM symbols of OFDM data unit 1640-2. For example, in an embodiment, at least one of OFDM data units 1640 (i.e., data units 1640-1, 1640-2, and 1640-4) includes padding such that the total length of non-legacy portion 1603 and OFDM data unit 1616 is equal to the total length of non-legacy portion 1603 and data portion 1616 of OFDM data unit 1640-3.

[0105] In another embodiment, the AP generates OFDM data unit 1640-2 to include at least one padded OFDM symbol so that the sum of the number of OFDM symbols in the non-legacy portion 1603 of OFDM data unit 1640-2 and the number of OFDM symbols of OFDM data unit 1616 is equal to the sum of the number of OFDM symbols in the non-legacy portion 1603 of OFDM data unit 1640-3 and the number of OFDM symbols of OFDM data unit 1616.

[0106] In an embodiment, the AP determines the number of OFDM symbols (N) for each user based on the number of data bytes for each user and the MCS value. sym,u ) and insert padding OFDM symbols so that each OFDM data unit 1640 has a number equal to N sym =max(N sym,u ) symbols. In some embodiments, the AP determines the number of OFDM symbols based on the non-legacy portion 1603 of the preamble portion 1601, e.g., where the number of HEW-LTFs in the OFDM tone block is different for at least some of the OFDM tone blocks (e.g., due to different numbers of spatial streams of OFDMA data units for different users). In one such embodiment, the AP determines the number of OFDM symbols for each user to be N sym,u =N sym,u (Data)+Nsym,u In another embodiment, the AP determines the number of OFDM symbols for each user to be N. sym,u =N sym,u (data) + Delta_HEWLTF, where Delta_HEWLTF is the number of HEW-LTFs for the current user minus the minimum number of HEW-LTFs among all users in the OFDMA data unit 1600. In yet another embodiment, the AP determines the number of OFDM symbols per user to be N sym (leading + data) = max(N sym,u (Data)+N HEWLTF,u In some embodiments, the AP determines the number of data field symbols used to set the L-LENGTH field in L-SIG 1606 to be N. sym The value of (data) is reduced by the number of HEWLTF symbols added or by the delta value. In an embodiment, the AP determines the number of padding OFDM symbols for each client station in the uplink OFDMA data unit and sends a synchronization frame with the determined number of padding OFDM symbols or another suitable indicator to inform each client station of the PHY parameter (e.g., N sym ). Each client station then jointly transmits a portion of the uplink OFDMA data unit according to the PHY parameters included in the synchronization frame.

[0107] In some embodiments, the AP sets an OFDMA indicator (OI) 1650 in the OFDMA data unit 1600 to signal to the receiver that the current data unit is a downlink OFDMA data unit. According to an embodiment, the OFDMA indicator 1650 is set to indicate one of the following: i) multiple access mode or ii) regular mode. In an embodiment, the OFDMA indicator 1650 includes 1 bit, wherein the first value of the bit indicates the regular mode and the second value of the bit indicates the multiple access mode. In some embodiments, the OFDMA indicator 1650 is combined with a modulation and coding scheme (MCS) indicator or other suitable subfield. In an embodiment, for example, the regular mode corresponds to an MCS value determined to be valid by a traditional receiver device (e.g., compatible with the IEEE 802.11ac protocol), and the multiple access mode corresponds to an MCS value determined to be invalid (or not supported) by the traditional receiver device (e.g., incompatible with the IEEE 802.11ac protocol). In other embodiments, the OFDMA indicator 1650 has multiple bits indicating multiple regular mode MCS values ​​and multiple range extension mode MCS values.

[0108] In an embodiment, the OFDMA indicator 1650 is a "reserved bit" in each L-SIG field, which is set to "1" by the AP (IEEE 802.11ac and IEEE 802.11n standards specify that the "reserved bit" in the L-SIG is set to 0) to signal to the receiver that the current data unit is a downlink OFDMA data unit. In addition, the AP sets the length and rate subfields in each L-SIG field to correspond to T - the duration of the longest OFDM data unit 1640 and the non-legacy portion 1603 (i.e., OFDM data unit 1640-3). According to another embodiment, the OFDMA indicator 1650 is a "reserved bit" in each HEW-SIGA field, which is set to "0" by the AP to signal to the receiver that the current data unit is a downlink OFDMA data unit.

[0109] In some embodiments, the OFDMA indicator 1650 includes a group ID subfield within the HEW-SIGA 1608. In an embodiment, the group ID subfield identifies an OFDMA group (i.e., a plurality of client stations intended to decode the OFDMA data unit 1600). In one such embodiment, the group ID subfield includes a group ID value indicating any of a multi-user (MU) MIMO data unit, an OFDMA data unit, or a single-user data unit. In this embodiment, a separate indication field is not required to distinguish between OFDMA data units and non-OFDMA data units, so that the receiver can determine what type of data unit is by parsing the group ID field. In one embodiment, the group ID subfield indicates that OFDMA and MU-MIMO are used together in the same data unit.

[0110] In another embodiment, the OFDMA indicator 1650 includes an OFDMA indication subfield (i.e., to indicate that the data unit is an OFDMA data unit) and a group ID subfield (i.e., to indicate which group of client stations intend to decode the data unit). In some embodiments, the OFDMA indicator 1650 also includes a user ID subfield, which indicates which client station within the OFDMA group intends to decode the corresponding OFDM tone block. In an embodiment, the OFDMA indicator 1650 is configured to signal the MCS, number of spatial streams, coding scheme, space-time block coding, or other PHY parameters for decoding each corresponding OFDM tone block. In some embodiments, the number of HEW-LTFs for all users in different OFDM tone blocks is the same (i.e., to fill or correspond to the maximum N between client stations). sts The OFDMA indicator 1650 signals the number of HEW-LTFs inserted into the current client station. sts The maximum number N between all client stations sts both.

[0111] In some embodiments, the OFDMA indicator 1650 includes a tone block assignment indication that indicates which OFDM tone blocks have been assigned to the client station. In an embodiment, the tone block assignment indication is a mapping table that maps user IDs to OFDM tone block IDs. In some embodiments, the OFDMA indicator 1650 is different for subsequent OFDMA data units, which enables the AP to dynamically divide and / or assign OFDM tone blocks to client stations on a per data unit basis. In other embodiments, the tone block assignment indication is omitted, such as in the case where the OFDM tone block assignments are fixed for a longer duration (e.g., fixed when an OFDMA group is formed or changed after a predetermined data unit is sent).

[0112] In other embodiments, the AP uses other techniques in addition to the techniques described above to signal that the data unit is a downlink OFDMA data unit. For example, according to one embodiment, the AP reserves a time period for transmitting the downlink OFDMA data unit using MAC layer signaling. In this embodiment, MAC layer signaling is used to specify the duration T of the downlink OFDMA data unit 1600. In another embodiment, the MAC layer signaling does not specify the duration T of the downlink OFDMA data unit 1600, but specifies different corresponding times at which the corresponding client stations should send corresponding acknowledgments of the downlink OFDMA data unit 1600. In another embodiment, the AP or the client station uses MAC layer signaling to specify a single time at which all client stations corresponding to the downlink OFDMA data unit 1600 should simultaneously transmit corresponding acknowledgments at this moment.

[0113] In some embodiments, L-SIG 1606 and HEW-SIGA 1608 have the same modulation as the modulation of the corresponding fields defined in the IEEE 802.11ac standard. Thus, the first subfield of HEW-SIGA 1608 is modulated identically to the L-SIG field. On the other hand, the second subfield of HEW-SIGA 1608 is rotated 90 degrees compared to the modulation of the L-SIG field. In some embodiments having a third subfield of HEW-SIGA 1608, the second subfield is modulated identically to the L-SIG field and the first subfield, while the third subfield is rotated 90 degrees compared to the modulation of the L-SIG field, the first subfield, and the second subfield.

[0114] In an embodiment, since the subfields of the HEW-SIGA 1608 and the modulation of the L-SIG 1606 of the OFDM data unit 1640 correspond to corresponding fields in a data unit conforming to the IEEE 802.11ac standard (eg, Figure 511ac standard and will process the OFDM data unit 1640 accordingly. For example, a client station compliant with the IEEE 802.11a standard will recognize the legacy IEEE 802.11a standard portion of the leading portion of the data unit 1640 and will set the duration of the data unit (or data unit duration) according to the duration indicated in the L-SIG 1606. For example, according to an embodiment, the legacy client station 25-4 will calculate the duration of the data unit based on the rate and length (e.g., number of bytes) indicated in the L-SIG field 1606. In an embodiment, the rate and length in the L-SIG field 1606 are set so that a client station configured to operate according to a legacy communication protocol will calculate a packet duration (T) that corresponds to or is at least close to the actual duration of the data unit 1640 based on the rate and length. For example, in one embodiment, the rate is set to indicate the minimum rate defined by the IEEE 802.11a standard (i.e., 6 Mbps), and the length is set to a value calculated so that the packet duration calculated using the minimum rate is at least close to the actual duration of data unit 1640.

[0115] In an embodiment, a legacy client station compliant with the IEEE 802.11a standard, upon receiving data unit 1640, will calculate the packet duration of data unit 1640 using, for example, the rate field and the length field of the L-SIG field 1606, and will wait until the end of the calculated packet duration and then perform a clear channel assessment (CCA). Thus, in this embodiment, the communication medium is protected from access by legacy client stations at least during the duration of data unit 1640. In an embodiment, the legacy client station will continue to decode data unit 1640, but will fail error checking (e.g., using a frame check sequence (FCS)) at the end of data unit 1640.

[0116] Similarly, in an embodiment, a legacy client station configured to operate according to the IEEE 802.11n standard, upon receiving data unit 1640, will calculate the packet duration (T) of data unit 1640 based on the rate and length indicated in L-SIG1606 of data unit 1640. The legacy client station will detect that the modulation of the first subfield of the HEW signal field (HEW-SIGA) is BPSK and assume that data unit 1640 is a legacy data unit compliant with the IEEE 802.11a standard. In an embodiment, the legacy client station continues to decode data unit 1640, but fails error checking (e.g., using a frame check sequence (FCS)) at the end of the data unit. In any case, according to the IEEE 802.11n standard, in an embodiment, the legacy client station will wait until the end of the calculated packet duration (T) and then perform a clear channel assessment (CCA). Therefore, in an embodiment, the communication medium is protected from access by the legacy client station at least during the duration of data unit 1640.

[0117] In an embodiment, a legacy client station configured to operate according to the IEEE 802.11ac standard rather than the first communication protocol, when receiving the data unit 1640, will calculate the packet duration (T) of the data unit 1640 based on the rate and length indicated in the L-SIG 1606 of the data unit 1640. However, in an embodiment, the legacy client station is unable to detect that the data unit 1640 does not conform to the IEEE 802.11ac standard based on the modulation of the data unit 1640. In some embodiments, one or more subfields of the HEW signal field 1608 of the data unit 1640 are formatted to intentionally cause the legacy client station to detect an error when decoding the data unit 1640 and thus stop decoding (or "discard") the data unit 1640. For example, in an embodiment, the HEW-SIGA 1608 of the data unit 1640 is formatted to intentionally cause an error when the SIGA field is decoded by a legacy device according to the IEEE 802.11 standard. Additionally, in an embodiment, in accordance with the IEEE 802.11ac standard, when an error is detected when decoding the VHT-SIGA field, the client station discards the data unit 1640 and waits until the end of a duration (T) calculated, for example, based on the rate and length indicated in the L-SIG of the data unit 1640, and then performs a clear channel assessment (CCA). Thus, in an embodiment, the communication medium is protected from access by legacy client stations during the duration of the OFDM data unit 1640.

[0118] In some embodiments, a different preamble format is used for multi-access mode data units than for preambles for normal mode data units. In such embodiments, a device receiving a data unit can automatically detect whether the data unit is a normal mode data unit or a multi-access mode data unit based on the format of the preamble of the data unit. Fig.17A 1 is a diagram illustrating a normal mode data unit 1700 according to an embodiment. The normal mode tree unit 1700 includes a normal mode preamble 1701. The normal mode preamble 1701 is generally Fig.16 The preamble 1701 of the OFDM data unit 1640 is the same as the preamble 1601 of the OFDM data unit 1640. In an embodiment, the preamble 1701 includes a HEW-SIGA field 1708, which includes a first HEW-SIGA1 field 1708-1 and a second first HEW-SIGA2 field 1708-1. In an embodiment, the HEW-SIGA field 1708 (e.g., HEW-SIGA1 1708-1 or HEW-SIGA2 1708-2) of the preamble 1701 includes an OFDMA indication 1702. In an embodiment, the OFDMA indication 1702 is set to indicate whether a multi-access mode or a normal mode is used for the data unit 1700. In an embodiment, the OFDMA indication 1702 includes 1 bit, wherein a first value of the bit indicates a normal mode, and a second value of the bit indicates a multi-access mode. As explained in more detail below, in an embodiment, a device receiving the data unit 1700 is able to detect that the preamble 1701 is a normal mode preamble rather than a multi-access mode preamble based on the format of the preamble 1701. In an embodiment, upon detecting that preamble 1701 is a normal mode preamble, the receiving device determines whether multiple access mode or normal mode is used for OFDM symbols of data portion 1616 based on OFDMA indication 1702, and accordingly decodes data portion 1616. In some embodiments, when OFDMA indication 1702 indicates that multiple access mode is used, OFDM symbols of portions of preamble 1701 (e.g., HEW-LTF and HEW-SIGB) and OFDM symbols of data portion 1616 are generated using OFDM modulation having a smaller tone spacing than the tone spacing used for normal mode OFDM symbols.

[0119] Fig. 17B 1 is a diagram illustrating a multi-access mode data unit 1750 according to an embodiment. The multi-access mode data unit 1750 includes a multi-access mode preamble 1751. The data unit 1750 is generally similar to Fig.17AThe data unit 1700 of FIG. 1750 is a data unit 1700, except that the preamble 1751 of the data unit 1750 is formatted differently from the preamble 1701 of the data unit 1700. In an embodiment, the preamble 1751 is formatted so that a receiving device operating according to the HEW communication protocol can determine that the preamble 1751 is a multi-access mode preamble rather than a normal mode preamble. In an embodiment, the multi-access mode preamble 1751 includes L-STF 1604, L-LTF 1605 and L-SIG 1606, and one or more first HEW signal fields (HEW-SIGA) 1752. In an embodiment, the preamble 1750 also includes one or more secondary L-SIG 1754 after the L-SIG field 1606. In some embodiments, the secondary L-SIG 1754 is followed by a second L-LTF field (L-LTF2) 1756. In other embodiments, the preamble 1751 omits the L-SIG 1754 and / or the L-LTF2 1756. In some embodiments, the preamble 1751 also includes a HEW-STF 1758, one or more HEW-LTF fields 1760, and a second HEW signal field (HEW-SIGB) 1762. In other embodiments, the preamble 1751 omits the HEW-STF 1758, (one or more) HEW-LTF 1760, and / or the HEW-SIGB 1762. In an embodiment, the data unit 1750 also includes a data portion 1616 ( Fig. 17B In some embodiments, the HEW signal field (HEW-SIGA) 1752 is modulated using the same multi-access mode as the data field 1616.

[0120] In an embodiment, one or more symbols of the HEW-SIGA 1752 are modulated using, for example, QBPSK instead of BPSK to enable automatic detection between normal mode and multi-access mode by a receiving device operating according to the HEW communication protocol. In embodiments, for example, where the normal mode preamble includes 2 BPSK symbols and 1 Q-BPSK symbol after the L-SIG 1606 field, the multi-access mode preamble includes 3 BPSK symbols and 1 Q-BPSK symbol after the L-SIG 1606 field. In some embodiments, for example, where automatic detection distinguishes between normal mode and multi-access mode, some bits are omitted from the HEW-SIGA 1752, such as bits for indicating signal bandwidth, MCS value, or other suitable bits.

[0121] In one embodiment where the preamble 1751 includes one or more secondary L-SIGs 1754, the content of each L-SIG 1754 is the same as the content of the L-SIG 1606 of the data unit 1750. In an embodiment, a receiving device receiving the data unit 1750 determines that the preamble 1751 corresponds to a multi-access mode preamble by detecting repetitions of the L-SIG fields 1606, 1754. In addition, in an embodiment, the rate subfield and the length subfield of the L-SIG 1606 and, therefore, the rate subfield and the length subfield of the secondary L-SIG 1754 are set to fixed (e.g., predetermined) values. In this case, in an embodiment, upon detecting repetitions of the L-SIG fields 1606, 1754, the receiving device uses the fixed value in the repeated L-SIG field as additional training information to improve channel estimation. However, in some embodiments, at least the length subfield of the L-SIG 1606 and, accordingly, at least the length field of the secondary L-SIG 1754 are not set to fixed values. For example, in an embodiment, the length field is instead set to a value determined based on the actual length of the data unit 1750. In one such embodiment, the receiving device first decodes the L-SIG 1606, and then uses the value of the length subfield in the L-SIG 1606 to detect repetitions of the L-SIG field 1606, 1754. In another embodiment, the receiving device first detects repetitions of the L-SIG field 1606, 1754, and then combines the detected multiple L-SIG fields 1606, 1754 to improve decoding reliability of the L-SIG field 1606, 1754 and / or improve channel estimation using redundant information in the multiple L-SIG fields 1606, 1754.

[0122] In an embodiment in which the preamble 1751 includes L-LTF2 1756, the OFDM symbols of L-LTF2 1756 are generated using a multi-access mode. In another embodiment in which the preamble 1751 includes L-LTF2 1756, the OFDM symbols of L-LTF2 1756 are generated using a regular mode. For example, in an embodiment, if the double guard interval (DGI) used in the L-LTF 1605 is long enough for the communication channel in which the data unit 1750 travels from the transmitting device to the receiving device, the OFDM symbols of L-LTF2 1756 are generated using a regular mode, or alternatively, the preamble 1751 omits L-LTF2 1756.

[0123] In another embodiment, preamble 1751 omits secondary L-SIG 1754 but includes L-LTF2 1756. In this embodiment, the receiving device detects that preamble 1751 is a multi-access mode preamble by detecting the presence of L-LTF2 1756. Figures 18A-18Bis a diagram illustrating two possible formats of LTF suitable for use as L-LTF2 1756 according to two example embodiments. Turning first to Fig.18A In a first example embodiment, L-LTF2 1800 is formatted in the same manner as L-LTF 1605, i.e., as defined in conventional communication protocols (e.g., IEEE 802.11a / n / ac standards). In particular, in the illustrated embodiment, L-LTF2 1800 includes a double guard interval (DGI) 1802 followed by 2 repetitions 1804, 1806 of a long training sequence. Turning now to Fig.18B In another example embodiment, L-LTF2 1808 is formatted differently than L-LTF 1605. In particular, in the illustrated embodiment, L-LTF2 1808 includes a first normal guard interval 1810, a first repetition 1812 of a long training sequence, a second normal guard interval 1814, and a second repetition 1816 of a long training sequence.

[0124] Reference again Fig. 17B In an embodiment, HEW-SIGA 1752 is generated using a multi-access mode. In an embodiment, the number of HEW-SIGAs 1752 is the same as the number of HEW-SIGAs 1708 of a normal mode preamble 1701. Similarly, in an embodiment, the content of the HEW-SIGA 1752 is the same as the content of the HEW-SIGA 1708 of the normal mode preamble 1701. In other embodiments, the number and / or content of the HEW-SIGAs 1752 are different from the number and / or content of the HEW-SIGAs 1708 of the normal mode preamble 1701. In an embodiment, the device receiving the data unit 1750 decodes the HEW-SIGA 1752 using the multi-access mode based on detecting that the preamble 1751 corresponds to a multi-access mode preamble and appropriately interprets the HEW-SIGA 1752 as defined for the multi-access mode.

[0125] In an embodiment in which the preamble 1751 omits L-SIG 1754 and / or L-LTF2 1756, the receiving device determines whether the preamble corresponds to the multi-access mode preamble 1751 or the normal mode preamble 1701 by detecting whether the HEW-SIGA field in the preamble uses the multi-access mode or the normal mode based on autocorrelation detection of the HEW-SIGA field using the multi-access mode and the normal mode. Figures 19A-19B1 and 17. Figures 1708 of a normal mode preamble 1701 and a HEW-SIGA 1752 of a multi-access mode preamble 1751 according to an embodiment, respectively. In the illustrated embodiment, the HEW-SIGA 1708 of the normal mode preamble 1701 includes a first NGI 1902, a first HEW-SIGA field 1904, a second NGI 1906, and a second HEW-SIGA field 1908. On the other hand, the HEW-SIGA 1752 of the multi-access mode preamble 1751 includes a first LGI 1910, a first HEW-SIGA field 1912, a second LGI 1914, and a second HEW-SIGA field 1916. In an embodiment, the receiving device uses a normal guard interval structure (such as Fig.19A The first autocorrelation of the HEW-SIGA field is performed using a long guard interval structure (such as Fig.19B 1701. In an embodiment, if the autocorrelation of the HEW-SIGA field using the long guard interval produces a larger result than the autocorrelation structure of the HEW-SIGA field using the normal guard interval structure, the receiving device determines that the preamble corresponds to the multi-access mode preamble 1751. On the other hand, in an embodiment, if the autocorrelation of the HEW-SIGA field using the normal guard interval produces a larger result than the autocorrelation result of the HEW-SIGA field using the long guard interval, the receiving device determines that the preamble corresponds to the normal mode preamble 1701.

[0126] Reference again Fig. 17B In an embodiment, the preamble 1751 is formatted so that a legacy client station can determine the duration of the data unit 1750 and / or that the data unit does not conform to a legacy communication protocol. In addition, in an embodiment, the preamble 1751 is formatted so that a client station operating according to the HEW protocol can determine that the data unit conforms to the HEW communication protocol. For example, at least two OFDM symbols (such as L-SIG 1754 and / or L-LTF2 1756 and / or HEW-SIGA 1752) of the L-SIG 1606 following the preamble 1751 are modulated using BPSK modulation. In this case, in an embodiment, the legacy client station treats the data unit 1750 as a legacy data unit, determines the duration of the data unit based on the L-SIG 1606, and avoids accessing the medium during the determined duration. Additionally, in an embodiment, one or more other OFDM symbols of preamble 1751, such as one or more of HEW-SIG 1752, are modulated using Q-BPSK modulation to enable client stations operating according to the HEW communication protocol to detect that data unit 1750 conforms to the HEW communication protocol.

[0127] In some embodiments, the HEW communication protocol allows beamforming and / or multi-user MIMO (MU-MIMO) transmission. Fig. 17B , in an embodiment where the preamble 1751 includes the HEW-STF 1758 and the HEW-LTF 1760, the AP 14 applies beamforming and / or multi-user transmission starting from the HEW-STF 1758. In other words, in an embodiment, the fields of the preamble 1751 before the HEW-STF 1758 are omnidirectional and are intended to be received by all intended recipients of the data unit 1750 in the multi-user mode, while the HEW-STF field 1758 and the preamble fields after the HEW-STF field 1758 and the data portion after the preamble 1751 are beamformed and / or include different portions intended to be received by different intended recipients of the data unit 1750. In an embodiment, the HEW-SIGB field 1762 includes user-specific information for the intended recipients of the data unit 1750 for the MU-MIMO mode. Depending on the embodiment, the HEW-SIGB field 1762 is generated using the normal mode or the multi-access mode. Similarly, depending on the embodiment, the HEW-STF 1758 is generated using a normal mode or a multi-access mode. In an embodiment, the training sequence used on the HEW-STF 1758 is a sequence defined in a conventional communication protocol, such as the IEEE 802.11ac protocol.

[0128] In some embodiments, the receiver device uses the HEW-STF field 1758 to restart the automatic gain control (AGC) process for receiving the data portion 716. In an embodiment, the HEW-STF has the same duration as the VHT-STF (i.e., 4 microseconds). In other embodiments, the duration of the HEW-STF is longer than the VHT-STF. In an embodiment, the time domain period of the HEW-STF is the same as the VHT-STF, so that there is 1 non-zero tone for every 4 tones in the frequency domain and the same tone spacing as IEEE 802.11ac is used. In other embodiments with 1 / N tone spacing, the HEW-STF has 1 non-zero tone for every 4*N tones. In embodiments where the overall bandwidth of the data unit is greater than 20 MHz (e.g., 40 MHz, 80 MHz, etc.), the HEW-STF uses the same wider bandwidth VHT-STF as in IEEE 802.11ac (i.e., repetition of the 20 MHz VHT-STF for the overall bandwidth of 40 MHz, 80 MHz, 160 Mhz, etc.).

[0129] Fig. 20A 2 is a block diagram illustrating a multi-access mode data unit 2000 according to an embodiment. The data unit 2000 includes a multi-access mode preamble 2001. The multi-access mode preamble 2001 is generally similar to Fig. 17BThe multi-access mode preamble 1751 , except that the L-SIG 1606 and the secondary L-SIG 1754 of the preamble 1751 are combined into a single L-SIG field 2006 in the preamble 2001 . Fig. 20B 2006 is a diagram illustrating an L-SIG field 2006 according to one embodiment. Fig. 20B In the embodiment of the present invention, the L-SIG field 2006 includes a double guard interval 2010, a first L-SIG field 2012 and a second L-SIG field 2014, the first L-SIG field 2012 includes the content of the L-SIG field 1606 of the preamble 1751, and the second L-SIG field 2014 includes the content of the secondary L-SIG2 field 1754 of the preamble 1751. In various embodiments, the L-SIG field 2006 includes a length subfield that is set to a fixed value or set to a variable value, as described above with respect to Fig. 17B In various embodiments, the redundant (repeated) bits in the L-SIG field 2006 are used to improve channel estimation, as discussed with respect to Fig. 17B The L-SIG fields 1606 and 1754 are discussed.

[0130] In an embodiment, a legacy client station receiving data unit 2000 assumes that L-SIG field 2006 includes a normal guard interval. Fig. 20C As illustrated in FIG. 2 , in the present embodiment, the FFT window of the L-SIG information bits assumed at the legacy client station is shifted compared to the actual L-SIG field 2012. In an embodiment, to ensure that the constellation points within the FFT window correspond to BPSK modulation, as expected by the legacy client station, and thus enable the legacy client station to correctly decode the L-SIG field 2012, the modulation of the L-SIG field 2012 is phase shifted relative to the regular BPSK modulation. For example, in a 20 MHz OFDM symbol, if the normal guard interval is 0.8 μs and the double guard interval is 1.6 μs, then the modulation of the OFDM tone k of the L-SIG field 2012 is shifted with respect to the corresponding OFDM tone k of the original L-SIG, as can be seen from the following equation:

[0131]

[0132] Thus, in an embodiment, the L-SIG field 2012 is modulated using inverse Q-BPSK rather than conventional BPSK. Thus, for example, in an embodiment, bits with a value of 1 are modulated onto -j and bits with a value of 0 are modulated onto j, resulting in {j,-j} modulation rather than conventional {1,-1} BPSK modulation. In an embodiment, due to the inverse Q-BPSK modulation of the L-SIG field 2012, a legacy client station is able to correctly decode the L-SIG field 2012 and determine the duration of the data unit 2000 based on the L-SIG 2012 field. On the other hand, in an embodiment, a client station operating according to the HEW protocol is able to automatically detect that the preamble 2001 is a multi-access mode preamble by detecting a repetition of the L-SIG field 2012 or by detecting the inverse Q-BPSK modulation of the L-SIG field within the FFT window of the legacy client station. Alternatively, in other embodiments, a client station operating according to the HEW protocol detects that the preamble 2001 is a multi-access mode preamble using other detection methods discussed above, such as based on the modulation or format of the HEW-SIGA field 1752 .

[0133] refer to Figures 17A-17B 20A, in some embodiments, a long guard interval is used for the initial OFDM symbol of both the normal mode preamble (e.g., preamble 1701) and the multi-access mode preamble (e.g., preamble 1751 or preamble 2001). Figures 17A-17B In an embodiment, the L-STF field 1604, the L-LTF field 1605, the L-SIG field 1606, 1754, and the HEW-SIGA field 1752 are each generated using a long guard interval. Fig. 20A In an embodiment, the L-STF field 1604, the L-LTF field 1605, the L-SIG field 2006, and the HEW-SIGA 1752 are each generated using a long guard interval. In various embodiments, the receiving device may determine whether the preamble corresponds to a normal mode preamble or a multi-access mode preamble based on the modulation (e.g., Q-BPSK) of the HEW-SIGA field 1752 or based on an indication included in the HEW-SIGA field 1752. In addition, similar to Fig. 17B The leading 1751, Fig. 20A The preamble 2001 includes or omits the second L-LTF2 field 1756 depending on the embodiment and / or scenario.

[0134] Fig.211 is a block diagram illustrating the format of the HEW-SIGA field 2100 according to an embodiment. In some embodiments, the HEW-SIGA field 1752 of the data unit 1750 or the data unit 2000 is formatted as the HEW-SIGA field 2100. In some embodiments, the HEW-SIGA field 1708 is formatted as the HEW-SIGA field 2100. The HEW-SIGA field 2100 includes a double guard interval 2102, a first repetition 2104 of the HEW-SIGA field, and a second repetition 2106 of the HEW-SIGA field. In an example embodiment, the DGI is 1.8 μs and each repetition of the HEW-SIGA is 3.2 μs. In an embodiment, the repetition bits in the HEW-SIGA field 2100 are used to increase the reliability of the decoding of the HEW-SIGA field 2100. In an embodiment, the format of the HEW-SIGA field 2100 is used to automatically detect a multi-access mode preamble based on a comparison between an autocorrelation of an HEW-SIGA field of a preamble using the format of the HEW-SIGA field 2100 and an autocorrelation of an HEW-SIGA field of a preamble using a conventional HEW-SIGA field format used in a conventional mode.

[0135] Fig. 22 is a block diagram of an example downlink OFDMA data unit 2200 according to another embodiment. Fig. 22 In the embodiment, the 80MHz communication channel is divided into 4 consecutive OFDM tone blocks 2241, 2242, 2243 and 2244. OFDM tone block 2241 and OFDM tone block 2242 are adjacent and each has a bandwidth of 10MHz, so that OFDM tone block 2241 and OFDM tone block 2242 together span a bandwidth equal to the minimum channel bandwidth of the traditional WLAN communication protocol (i.e., the traditional tone block of 20MHz). The bandwidth of OFDM tone block 2243 is 20Mhz. OFDM tone block 2244 spans a bandwidth of 40MHz. OFDM tone blocks 2242 and 2244 are assigned to two client stations STA 2 and STA 3 and include independent data streams for the two client stations STA 2 and STA 3, respectively. OFDM tone blocks 2241 and 2243, separated in frequency by OFDM tone block 2242, are assigned to client station STA 1 and contain portions of the data stream for client station STA 1 and use channel bonding techniques as described herein.

[0136] In an embodiment, OFDM data unit 2200, and thus each OFDM data unit 2241, 2242, 2243, and 2244, includes a preamble portion 2201 and a data portion 1616 (e.g., a data field for a corresponding client station). In other embodiments, at least some of the OFDM data units omit the data portion 1616. In an embodiment, the preamble portion 2201 of each OFDM data unit includes at least a legacy portion 2202 and a non-legacy portion 2203. The legacy portion 2202 and the non-legacy portion 2203 are generally respectively Fig.16 The legacy portion 1602 and the non-legacy portion 1603 of the OFDM data unit 1640 are the same.

[0137] In an embodiment, each 20 MHz sub-band (i.e., legacy tone block) of the communication channel includes a legacy portion 1202 having an L-STF 1604, an L-LTF 1605, and an L-SIG 1606 so that a legacy client station can correctly decode the L-SIG field 1606 of the 20 MHz sub-band. Fig. 22 In an embodiment, first legacy tone block 2261 spans OFDM tone blocks 2241 and 2242, second legacy tone block 2262 spans OFDM tone block 2243, third legacy tone block 2263 spans portion 2244-1 of OFDM tone block 2244, and fourth legacy tone block 2264 spans portion 2244-2 of OFDM tone block 2244. In an embodiment, legacy portion 2202 of OFDM data units 2241 and 2242 spans the same 20 MHz subband (i.e., legacy tone block 2261) and therefore overlaps in frequency. In this embodiment, OFDM data units 2241 and 2242 use the same legacy portion 2202.

[0138] In an embodiment, the L-SIG field 1606 corresponding to each legacy tone block 2261, 2262, 2263, and 2264 indicates the duration of the OFDM data unit within the corresponding legacy tone block. In some embodiments, the L-SIG field 1606 corresponding to each legacy tone block of OFDM data unit 2200 has the same value, for example where the corresponding OFDM data units have the same duration (e.g., due to OFDM symbol padding). In other embodiments, the L-SIG field 1606 of the legacy tone blocks has at least some different values. In embodiments where channel bonding is used and a client station is assigned multiple OFDM tone blocks, the L-SIG fields corresponding to different 20 MHz subbands comprising OFDM tone blocks assigned to the same client station have the same L-LENGTH value such that each L-LENGTH value decoded by the client station indicates the same packet duration. For example, in Fig. 22In the embodiment of the present invention, the L-LENGTH value of the L-SIG field 1606 of the OFDM data units 2241 and 2243 indicates the same value.

[0139] In some embodiments, at least the legacy portion 2202 of the legacy tone blocks 2261, 2262, 2263, and 2264 is modulated using a legacy tone scheme. In an embodiment, the non-legacy portion 2203 and the data portion 1616 of at least one OFDM tone block of the OFDMA data unit 2200 are modulated using a non-legacy tone scheme (i.e., a tone scheme that is different from the legacy tone scheme). For example, in an embodiment, the non-legacy portion 2203 and the data portion 1616 corresponding to an OFDM tone block spanning a bandwidth of less than 20 MHz are modulated using a non-legacy tone scheme. Fig. 22 In the embodiment of the present invention, OFDM tone block 2241 and OFDM tone block 2242 each span a bandwidth of 10 MHz and thus the corresponding non-legacy portion 2203 and data portion 1616 use a non-legacy tone scheme (such as with respect to Figure 8 In other embodiments, the legacy portion 2202 and the non-legacy portion 2203 are modulated using the legacy tone scheme, while the data portion 1616 is modulated using the non-legacy tone scheme. In an embodiment, at least some OFDM symbols of the HEW-SIGA field 1608 of the non-legacy portion 2203 are modulated using the legacy tone scheme, and thus the HEW-SIGA field 1608 is shared by the OFDM data units corresponding to the OFDM tone blocks 2241 and 2242.

[0140] Fig.23 2 is a block diagram of an example downlink OFDMA data unit 2300 using reduced tone spacing according to an embodiment. The tone spacing is the spacing between subcarrier frequencies of an OFDM tone block. In an embodiment, OFDMA data unit 2300 is substantially the same as OFDMA data unit 2200, however, at least some of the OFDM tone blocks use reduced tone spacing for at least a portion of the corresponding OFDM data unit. Fig.23 In an embodiment, first OFDM tone block 2341 and second OFDM tone block 2342 (instead of OFDM tone block 2241 and OFDM tone block 2242) use reduced tone spacing. In other embodiments, OFDMA data unit 2300 uses reduced tone spacing for each OFDM tone block, for at least a portion of OFDMA data unit 2300.

[0141] exist Fig.23In an embodiment, the first legacy tone block 2361 spans across OFDM tone block 2341 and OFDM tone block 2342. In some embodiments, for example, at least the legacy portion 2202 of the legacy tone blocks 2361, 2362, 2263, and 2264 is modulated using a legacy tone spacing (i.e., a spacing of 312.5 kHz between tones) according to IEEE 802.11ac. In an embodiment, the non-legacy portion 2203 and the data portion 1616 of at least one OFDM tone block of the OFDMA data unit 2200 are modulated using a reduced tone spacing compared to the legacy tone spacing. In an embodiment, at least some OFDM symbols of the non-legacy portion 2203 (such as the HEW-SIGA field 1608 and / or the HEW-STF 1610) are modulated using a legacy tone spacing and thus the HEW-SIGA field 1608 is shared by the OFDM data units corresponding to the OFDM tone block 2341 and the OFDM tone block 2242. In some embodiments, the OFDM data units corresponding to OFDM tone blocks 2341 and 2342 use a non-legacy tone scheme, as described above with respect to Fig. 22 Described in conjunction with non-traditional pitch intervals.

[0142] In some embodiments, for example, while the conventional mode (i.e., 20 MHz) of the legacy tone block uses a 64-point discrete Fourier transform (DFT), resulting in 64 OFDM tones (e.g., tone indices -32 to +31), at least some of the OFDM tone blocks in the OFDMA data unit 2300 use a 128-point DFT for at least some of the OFDM symbols in the legacy tone block, resulting in 128 OFDM tones within the same bandwidth (e.g., indices -64 to +63). In this case, the tone spacing is reduced by a factor of 2 (1 / 2) compared to the conventional mode OFDM symbols while using the same tone scheme. As another example, while the conventional mode of the legacy tone block uses a 64-point discrete Fourier transform (DFT), resulting in 64 OFDM tones, the OFDMA data unit 2300 uses a 256-point DFT for at least some of the OFDM symbols in the legacy tone block, resulting in 256 OFDM tones within the same bandwidth. In this case, the tone spacing is reduced by a factor of 4 (1 / 4) compared to the normal mode OFDM symbol. In such an embodiment, a long guard interval duration of, for example, 1.6 μs is used. However, in an embodiment, the duration of the information portion of the multi-access mode OFDM symbol is increased (e.g., from 3.2 μs to 6.4 μs), and the percentage of the guard interval portion duration to the total OFDM symbol duration remains unchanged. Therefore, in this case, in at least some embodiments, the efficiency loss due to longer guard interval symbols is avoided. In various embodiments, the term "long guard interval" as used herein includes the increased guard interval duration and the reduced OFDM tone spacing that effectively increases the duration of the guard interval. In other embodiments, other multiples, such as 4x, 8x, or other suitable values, are used for the reduced tone spacing.

[0143] In some embodiments, the OFDMA data unit 2300 uses a reduced tone spacing in conjunction with a range extension mode. In an embodiment, the range extension mode is used in a communication channel characterized by a relatively longer channel delay extension (e.g., an outdoor communication channel) or a generally lower SNR value. In an embodiment, the range extension mode corresponds to a range extension coding scheme (e.g., block coding, bit-by-bit replication, or symbol replication), a signal modulation scheme (e.g., phase shift keying or quadrature amplitude modulation), or both a range extension coding scheme and a signal modulation scheme. The range extension mode is configured to increase the range of successful decoding of a PHY data unit in which the range extension mode is performed compared to a second mode (e.g., a conventional mode using a conventional coding scheme) and / or reduce the signal-to-noise (SNR) ratio. In various embodiments, the range extension mode reduces the data transmission rate compared to the conventional mode to achieve successful decoding while increasing the range and / or reducing the SNR ratio.

[0144] In some embodiments, the OFDMA data unit 2300 supports any of the normal mode, the multiple access mode, and the range extension mode. In an embodiment, the OFDMA data unit 2300 supports any of the normal mode, the multiple access mode, the range extension mode, and the range extension mode combined with the multiple access mode. In an embodiment, at least some of the modes supported by the OFDMA data unit 2300 are indicated by a mode indicator (such as the one described above with respect to Fig.16 In another embodiment, at least some modes are indicated to the receiving device via a preamble 2201 of a different format, as described above with respect to Fig.17A , 17B , 18A, 18B, 19A, 19B, 20A, 20B, 20C or 21 described.

[0145] Fig.24 2400, but in an embodiment, a first portion 2451 of the OFDMA data unit 2400 is generated and transmitted by a first client station and a second portion 2452 of the OFDMA data unit 2400 is generated and transmitted by a second client station for reception by an access point. In some embodiments, the OFDMA indicator 1650 and / or other subfields within the HEW-SIGA field 1608 are omitted, for example, where the AP has already determined the corresponding PHY parameters.

[0146] exist Fig.24 In the illustrated embodiment, the communication channel spans a conventional tone block 2461 (i.e., 20 MHz) and is divided into two consecutive OFDM tone blocks 2441 and 2442, each of which spans a 10 MHz sub-band. In an embodiment, OFDM tone block 2241 is assigned (i.e., by AP 14) to client station STA 1 (e.g., client 25-1) and includes a portion of a data stream from client station STA 1, and OFDM tone block 2242 is assigned to client station STA 2 (e.g., client 25-2) and includes a portion of a data stream from client station STA 2. For example, in an embodiment, client 25-1 and client 25-2 are members of an OFDMA group, as described above with respect to Fig.16 In other embodiments, the communication channel has a bandwidth of 40 MHz, 80 MHz, 160 MHz, or other suitable bandwidth, and is divided for a suitable number of client stations, as described above with respect to Fig. 7A , 7B , 7C, 9A, 9B, 14A or 14B.

[0147] In an embodiment, each client station of the OFDMA group determines a corresponding assigned OFDM tone block. In some embodiments, the client station determines the corresponding assigned OFDM tone block based on a sync frame received from the AP 14 containing PHY parameters, such as an indication of which OFDM tone blocks are assigned to a particular client station. In an embodiment, each client station of the OFDMA group transmits a corresponding portion of the OFDMA data unit 2400 after a short interframe space (SIFS) following receipt of the sync frame.

[0148] Fig.25A 24 is a block diagram of an example uplink OFDM data unit portion, such as the first portion 2451 of the OFDM data unit 2400. In some embodiments, the client station 25-1 includes a PHY processing unit, such as described above with respect to Fig.10 , 11 , 12, 13, 14A, 14B, 15A and 15B describe the PHY processing units 1000, 1100, 1200, 1300, 1500 and / or 1550 for generating and transmitting the first part 2451 of the OFDMA data unit 2400. Fig.25B is a block diagram of another example uplink OFDM data unit portion, such as the second portion 1452 of the OFDM data unit 2400, according to an embodiment. In some embodiments, the client station 25-2 includes a PHY processing unit, such as described above with respect to Fig.10 , 11 , 12, 13, 14A, 14B, 15A and 15B describe the PHY processing units 1000, 1100, 1200, 1300, 1500 and / or 1550 for generating and transmitting the first part 2452 of the OFDMA data unit 2400.

[0149] In some embodiments, client station 25-1 generates first portion 2451 for transmission on a communication channel using data tones and pilot tones within first OFDM tone block 2441, and client station 25-2 generates first portion 2452 for transmission on a communication channel using data tones and pilot tones within second OFDM tone block 2442. In an embodiment, client station 25-1 generates and transmits first portion 2451 using data tones and pilot tones within first OFDM tone block 2441 and second OFDM tone block 2442. For example, in an embodiment, client station 25-1 generates and transmits legacy portion 2402 using first OFDM tone block 2441 and second OFDM tone block 2442, and generates and transmits non-legacy portion 2403 and data portion 1616 using only first OFDM tone block 2441. In an embodiment, the client station 25 - 2 generates and transmits the legacy portion 2402 using the first OFDM tone block 2441 and the second OFDM tone block 2442 , and generates and transmits the non-legacy portion 2403 and the data portion 1616 using only the second OFDM tone block 2442 .

[0150] In an embodiment, each of the first portion 2451 and the second portion 2452 includes a legacy portion 2402 and thus overlaps in frequency, the legacy portion 2402 spanning both the first OFDM tone block 2441 and the second OFDM tone block 2442. In an embodiment, the legacy portions 2402 of the first portion 2451 and the second portion 2452 are identical such that the AP 14 receives substantially the same signal when the client station 25-1 and the client station 25-2 transmit the respective legacy portions 2402. In an embodiment, the non-legacy preamble 2403 and the data portion 1616 of the first portion 1451 span only the first OFDM tone block 2441, and the non-legacy preamble 2403 and the data portion 1616 of the second portion 1452 span only the second OFDM tone block 2442, and thus the first portion and the second portion do not overlap in frequency.

[0151] In an embodiment, the client station 25-1 is configured to transmit the legacy portion 2402, the non-legacy portion 2403, and the data portion 1616 using the same per-tone transmission power. In one such embodiment, the total power of the legacy portion 2402 is approximately twice the total power of the non-legacy portion 2403 and the data portion 1616. In some embodiments, the client device 25-1 is configured to transmit the legacy portion 2402, the non-legacy portion 2403, and the data portion 1616 using the same total power. In one such embodiment, the per-tone power of the non-legacy portion 2403 and the data portion 1616 is approximately twice the per-tone power of the legacy portion 2402 (i.e., due to the use of half a tone). In this embodiment, the AP 14 (or other suitable receiving device) compensates for the difference in per-tone power prior to demodulation of the OFDMA data unit 2400, for example, where an amplitude modulated signal (i.e., a greenfield mode transmission with the HEW-LTF field omitted) is demodulated using an L-LTF-based channel estimate.

[0152] Fig.26A 1 is a block diagram of an example OFDMA data unit 2600 including a legacy data unit 2643 according to an embodiment. OFDMA data unit 2600 is substantially the same as OFDMA data unit 2200, however, in an embodiment, OFDM tone block 2262 corresponds to legacy OFDM data unit 2643 rather than OFDM data unit 2243. For clarity, non-legacy portion 2203 is shown as a single preamble portion. In an embodiment, legacy OFDM data unit 2643 generally conforms to a legacy communication protocol, such as IEEE 802.11ac. In some embodiments, data portion 1616 includes padding OFDM symbols such that legacy OFDM data unit 2643 has the same number of OFDM symbols as OFDM data units 2241, 2242, and 2244.

[0153] Fig.26B 1 is a block diagram of an example OFDMA data unit 2650 including a legacy data unit 2663 according to an embodiment. OFDMA data unit 2650 is substantially the same as OFDMA data unit 2200, however, in an embodiment, OFDM tone block 2262 corresponds to legacy OFDM data unit 2663 rather than OFDM data unit 2243. For clarity, non-legacy portion 2203 is shown as a single preamble portion. In an embodiment, legacy OFDM data unit 2663 generally conforms to a legacy communication protocol, such as IEEE 802.11a or IEEE 802.11n. In some embodiments, data portion 1616 does not include padding OFDM symbols because legacy communication protocols do not support symbol padding.

[0154] Fig.27A , 27B, 27C and 27D are example diagrams of short training sequences for OFDMA data units according to various embodiments. In an embodiment, short training sequence 2701 is a training sequence for a HEW-STF 1610 spanning a 20 MHz sub-band (such as the HEW-STF 1610 of OFDM data unit 2243). In an embodiment, a HEW-STF 1610 spanning a sub-band less than 20 MHz (such as the HEW-STF 1610 corresponding to OFDM data unit 2243) is a training sequence for a HEW-STF 1610 spanning a sub-band less than 20 MHz (such as the HEW-STF 1610 corresponding to OFDM data unit 2243). Fig.25A In an embodiment, the HEW-STF 1610 of the OFDM tone blocks 2441 and 2442 uses only the corresponding tone of the short training sequence 2701 (i.e., the "upper" tone for the OFDM tone block 2441 and the "lower" tone block for the OFDM tone block 2442). In an embodiment, the short training sequence 2702 is a training sequence for the HEW-STF 1610 (such as the HEW-STF 1610 of the OFDM data unit 2244) across the 40MHz sub-band. In an embodiment, the short training sequence 2703 is a training sequence for the HEW-STF 1610 across the 80MHz sub-band. In an embodiment, the short training sequence 2704 is a training sequence for the HEW-STF 1610 across the 160MHz sub-band.

[0155] Fig.28 is a flow chart of an example method 2800 for generating an OFDMA data unit according to an embodiment. Figure 1 In an embodiment, the method 2800 is implemented by the network interface 16. For example, in one such embodiment, the PHY processing unit 20 is configured to implement the method 2800. According to another embodiment, the MAC processing 28 is also configured to implement at least part of the method 2800. Figure 1 In yet another example, the method 2800 is implemented by the network interface 27 (eg, the PHY processing unit 29 and / or the MAC processing unit 28). In other embodiments, the method 2800 is implemented by other suitable network interfaces.

[0156] At box 2802, a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel are assigned to a plurality of devices including a first device and a second device. In an embodiment, the plurality of different OFDM tone blocks include at least a first OFDM tone block assigned to the first device and a second OFDM tone block assigned to the second device. In an embodiment, the second OFDM tone block is adjacent to the first OFDM tone block. In an embodiment, the first OFDM tone block and the second OFDM tone block together span a bandwidth equal to the minimum channel bandwidth of a conventional WLAN communication protocol. As an illustrative example only, in an embodiment, the first OFDM tone block and the second OFDM tone block together span 20 MHz. In some embodiments, the WLAN communication channel corresponds to the above description of Fig. 7A , 7B , the communication channel described in 7C or other suitable communication channels.

[0157] At block 2804, an orthogonal frequency division multiple access (OFDMA) data unit is generated for a WLAN communication channel. The OFDMA unit includes a preamble portion and a data portion, and in an embodiment, the preamble portion has: i) at least a legacy portion spanning the entire WLAN communication channel, ii) a first non-legacy portion spanning a first OFDM tone block, and iii) a second non-legacy portion spanning a second OFDM tone block. In some embodiments, the OFDMA data unit corresponds to the above-described Fig.16 , 17A , 17B, 20A, 22, 23, 24, 26A, 26B described OFDMA data units or other suitable OFDMA data units.

[0158] In an embodiment, generating an OFDMA data unit includes: i) generating a first OFDM data unit of a data portion using first data received for a first device, and ii) generating a second OFDM data unit of a data portion using second data received for a second device. In this embodiment, generating an OFDMA data unit also includes: i) modulating the first OFDM data unit on tones in a first OFDM tone block, and ii) modulating the second OFDM data unit on tones in a second OFDM tone block. In an embodiment, the first data is independent of the second data.

[0159] In an embodiment, modulating the first OFDM data unit and the second OFDM data unit comprises: i) modulating the first OFDM data unit on tones in a first OFDM tone block using a first tone scheme, and ii) modulating the second OFDM data unit on tones in a second OFDM tone block using a second tone scheme. In some embodiments, the legacy portion uses a legacy tone scheme (e.g., Figure 8In an embodiment, one or more of the first non-legacy tone scheme or the second non-legacy tone scheme corresponds to a Fast Fourier Transform (FFT) width that is less than a Fast Fourier Transform (FFT) width of a WLAN communication channel. In some embodiments, generating an OFDMA data unit for the WLAN communication channel includes modulating the OFDMA data unit to span an entire bandwidth of the WLAN communication channel. In another embodiment, modulating the first OFDM data unit and the second OFDM data unit includes i) modulating the first OFDM data unit using the same bandwidth as the first OFDM tone block with an integer number of tones and a corresponding reduced tone spacing, and ii) modulating the second OFDM data unit using the same bandwidth as the second OFDM tone block with an integer number of tones and a corresponding reduced tone spacing.

[0160] In another embodiment, generating a first OFDM data unit and a second OFDM data unit includes: generating a first data tone using the first data and a first pilot tone for a first OFDM tone block; separately generating a second data tone using the second data and a second pilot tone for a second OFDM tone block; and jointly performing an inverse fast Fourier transform (IFFT) on the first data tone, the first pilot tone, the second data tone, and the second pilot tone.

[0161] In yet another embodiment, generating the first OFDM data unit and the second OFDM data unit includes: generating the second OFDM data unit to include at least one padding OFDM symbol so that the first OFDM data unit and the second OFDM data unit have the same number of OFDM symbols. In an embodiment, the number of padding OFDM symbols to be included in the second OFDM data unit is determined as the difference between the total number of OFDM symbols of the first OFDM data unit and the total number of OFDM symbols of the second OFDM data unit.

[0162] In an embodiment, generating a first OFDM data unit and a second OFDM data unit includes: generating the second OFDM data unit to include at least one padding OFDM symbol so that the sum of the number of OFDM symbols in the first non-traditional part and the number of OFDM symbols of the first OFDM data unit is equal to the sum of the number of OFDM symbols in the second non-traditional part and the number of OFDM symbols of the second OFDM data unit.

[0163] In an embodiment, the first non-legacy portion and the second non-legacy portion include a non-legacy signal field having a corresponding group identifier (ID) subfield, the group ID subfield indicating whether the corresponding OFDM data unit is any of the following: i) a single-user data unit, ii) a multi-user multiple-input multiple-output data unit to be decoded by an indicated device among the multiple devices, or iii) a portion of the OFDM data unit to be decoded by an indicated device among the multiple devices.

[0164] In another embodiment, the first non-legacy portion and the second non-legacy portion include non-legacy signal fields having respective tone block assignment identifiers indicating an assignment of the first OFDM tone block to the first device and an assignment of the second OFDM tone block to the second device.

[0165] Fig.29 is a flow chart of an example method 2900 for generating an OFDMA data unit according to another embodiment. Figure 1 In an embodiment, the method 2900 is implemented by the network interface 16. For example, in one such embodiment, the PHY processing unit 20 is configured to implement the method 2900. According to another embodiment, the MAC processing 18 is also configured to implement at least part of the method 2900. Figure 1 In yet another example, the method 2900 is implemented by the network interface 27 (eg, the PHY processing unit 29 and / or the MAC processing unit 28). In other embodiments, the method 2900 is implemented by other suitable network interfaces.

[0166] At block 2902, in an embodiment, a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel are assigned to a plurality of devices including a first device and a second device. In an embodiment, the plurality of different OFDM tone blocks include at least a first OFDM tone block and a second OFDM tone block assigned to the first device and a third OFDM tone block assigned to the second device. The first OFDM tone block and the second OFDM tone block are separated in frequency by at least the third OFDM tone block. In some embodiments, the WLAN communication channel corresponds to the above description of Fig. 7A , 7B , the communication channel described in 7C or other suitable communication channels.

[0167] At box 2904, an orthogonal frequency division multiple access (OFDMA) data unit is generated for a WLAN communication channel. The OFDMA unit includes a preamble portion and a data portion. In an embodiment, the preamble portion includes at least: i) a first legacy portion corresponding to at least a first OFDM tone block, ii) a second legacy portion corresponding to a second OFDM tone block, iii) a first non-legacy portion corresponding to the first OFDM tone block, iv) a second non-legacy portion corresponding to the second OFDM tone block, and v) a third non-legacy portion corresponding to a third OFDM tone block. In this embodiment, the first legacy portion is modulated on at least the first OFDM tone block, the first non-legacy portion is modulated on the first OFDM tone block, the second legacy portion is modulated on at least the second OFDM tone block, the second non-legacy portion is modulated on the second OFDM tone block, and the third non-legacy portion is modulated on the third OFDM tone block. In some embodiments, the OFDMA data unit corresponds to the above description of Fig.16 , 17A , OFDMA data units described in 17B, 20A, 22, 23, 24, 26A, 26B or other suitable OFDMA data units.

[0168] In an embodiment, the first OFDM tone block and the third OFDM tone block together span a bandwidth equal to the minimum channel bandwidth of a conventional WLAN communication protocol. In another embodiment, the first conventional portion is modulated on a conventional tone block corresponding to the minimum channel bandwidth of a conventional WLAN communication protocol. In this example, the conventional tone block i) overlaps the first OFDM tone block in frequency and ii) has a bandwidth greater than the bandwidth of the first OFDM tone block. In a further embodiment, the conventional tone block includes a first OFDM tone block assigned to a first device and a third OFDM tone block assigned to a second device. In this example, the first conventional portion is modulated on at least the first OFDM tone block and the third OFDM tone block. In a further embodiment, the data portion includes a first OFDM data unit for the first device modulated on the first OFDM tone block and a second OFDM data unit for the second device modulated on the third OFDM tone block. In this embodiment, at least one of the first OFDM data unit and the second OFDM data unit includes padding such that a total length of the first non-legacy portion and the first OFDM data unit is equal to a total length of the third non-legacy portion and the second OFDM data unit.

[0169] In another embodiment, the data portion includes a first OFDM data unit for the first device modulated on a first OFDM tone block and a second OFDM data unit for the first device modulated on a second OFDM tone block. In this embodiment, the first legacy portion and the second legacy portion include a legacy signal field that indicates a same total duration for: i) the first non-legacy portion and the first OFDM data unit and ii) the second non-legacy portion and the second OFDM data unit.

[0170] In yet another embodiment, the first OFDM tone block and the second OFDM tone block use the same modulation and coding scheme. In an embodiment, the first OFDM tone block uses a different modulation and coding scheme (MCS) than the second OFDM tone block. In a further embodiment, the first OFDM tone block and the second OFDM tone block use the same number of space-time streams. In another embodiment, the first OFDM tone block and the second OFDM tone block use different numbers of space-time streams.

[0171] In an embodiment, generating an OFDMA data unit for a WLAN communication channel includes encoding first data for a first block of OFDM tones separately from second data for a second block of OFDM tones. In another embodiment, generating an OFDMA data unit for a WLAN communication protocol includes encoding and interleaving first data for a first block of OFDM tones together with second data for a second block of OFDM tones.

[0172] Fig.30 is a flow chart of an example method 3000 for generating an OFDMA data unit according to an embodiment. Figure 1 In an embodiment, the method 3000 is implemented by the network interface 16. For example, in one such embodiment, the PHY processing unit 20 is configured to implement the method 3000. According to another embodiment, the MAC processing 18 is also configured to implement at least part of the method 3000. Figure 1 In yet another example, the method 3000 is implemented by the network interface 27 (eg, the PHY processing unit 29 and / or the MAC processing unit 28). In other embodiments, the method 3000 is implemented by other suitable network interfaces.

[0173] At block 3002, a plurality of different orthogonal frequency division multiplexing (OFDM) frequency subbands for a wireless local area network (WLAN) communication channel are assigned to a plurality of devices including a first device and a second device. In an embodiment, the plurality of different OFDM tone blocks include at least a first OFDM frequency subband assigned to the first device and a second OFDM frequency subband assigned to the second device. In some embodiments, the WLAN communication channel corresponds to the above description of Fig. 7A ,7B , the communication channel described in 7C or other suitable communication channels.

[0174] At block 3004, an orthogonal frequency division multiple access (OFDMA) data unit is generated for a WLAN communication channel. The OFDMA unit includes a preamble portion and a data portion, the preamble portion including: a legacy portion spanning a first OFDM frequency subband and a second OFDM frequency subband using a legacy tone spacing and a legacy tone scheme, a first non-legacy portion spanning the first OFDM frequency subband and the second OFDMA frequency subband using a legacy tone spacing and a legacy tone scheme, a second non-legacy portion spanning the first OFDM frequency subband using a non-legacy tone spacing and a non-legacy tone scheme, and a third non-legacy portion spanning the second OFDMA frequency subband using a non-legacy tone spacing and a non-legacy tone scheme. In some embodiments, the OFDMA data unit corresponds to the above description of the OFDMA data unit. Fig.16 , 17A , 17B, 20A, 22, 23, 24, 26A, 26B or other suitable OFDMA data units. In some embodiments, the conventional tone spacing is an integer multiple of the non-conventional tone spacing.

[0175] In an embodiment, generating an OFDMA data unit for a WLAN communication channel includes: i) generating a first OFDM data unit of a data portion using first data received for a first device, and ii) generating a second OFDM data unit of a data portion using second data received for a second device, wherein the first data is independent of the second data. In this embodiment, generating an OFDMA data unit for a WLAN communication channel also includes: i) modulating the first OFDM data unit using a non-legacy tone scheme for a first OFDM frequency sub-band, and ii) modulating the second OFDM data unit using a non-legacy tone scheme for a second OFDM frequency sub-band.

[0176] Fig.31 is a flow chart of an example method 3100 for generating a portion of an OFDMA data unit according to an embodiment. Figure 1 In an embodiment, the method 3100 is implemented by the network interface 16. For example, in one such embodiment, the PHY processing unit 20 is configured to implement the method 3100. According to another embodiment, the MAC processing 18 is also configured to implement at least part of the method 3100. Figure 1 In yet another example, the method 3100 is implemented by the network interface 27 (eg, the PHY processing unit 29 and / or the MAC processing unit 28). In other embodiments, the method 3100 is implemented by other suitable network interfaces.

[0177] At block 3102, an assignment of a first orthogonal frequency division multiplexing (OFDM) tone block within a wireless local area network (WLAN) communication channel is determined. In an embodiment, a bandwidth of the first OFDM tone block is less than a minimum bandwidth of a conventional WLAN communication protocol. In some embodiments, the WLAN communication channel corresponds to the above description of Fig.9A , 9B The communication channels described herein or other suitable communication channels.

[0178] At block 3104, at the first communications device, a first portion of an orthogonal frequency division multiple access (OFDMA) data unit is generated for transmission over a WLAN communications channel using data tones and pilot tones within a first OFDM tone block. In some embodiments, the portion of the OFDMA data unit corresponds to the above with respect to Fig.24 , 25A , part of the OFDMA data unit described in 25B or other suitable OFDMA data units.

[0179] In an embodiment, generating the first portion of the OFDMA data unit includes performing an Inverse Fast Fourier Transform (IFFT) on the first portion of the OFDMA data unit with an FFT size equal to the first OFDM tone block.

[0180] In another embodiment, generating the first portion of the OFDMA data unit includes performing an IFFT on the first portion of the OFDMA data unit with an FFT size equal to the WLAN communication channel and using zero values ​​for data tones and pilot tones not within the first OFDM tone block.

[0181] In an embodiment, a first communication device transmits a first portion of an OFDMA data unit on a WLAN communication channel while a second communication device transmits a second portion of an OFDMA data unit on a WLAN communication channel. In this embodiment, the second portion of the OFDMA data unit spans a second OFDM tone block within the WLAN communication channel. In another example, a first communication device transmits a conventional portion of a preamble portion using the first OFDM tone block and the second OFDM tone block while a conventional portion of a preamble of an OFDMA data unit is transmitted by the second communication device using the first OFDM tone block and the second OFDM tone block.

[0182] In an embodiment, transmitting the first portion of the OFDMA data unit includes: transmitting the first OFDM data unit using only the first OFDM tone block while the second communication device transmits the second OFDM data unit using only the second OFDM tone block. In some embodiments, the legacy portion and the first OFDM data unit are transmitted by the first communication device at the same total power. In other embodiments, the legacy portion and the first OFDM data unit are transmitted by the first communication device at the same per-tone power.

[0183] Fig.32 is a flow chart of an example method 3200 for generating a portion of an OFDMA data unit according to another embodiment. Figure 1 In an embodiment, the method 3200 is implemented by the network interface 16. For example, in one such embodiment, the PHY processing unit 20 is configured to implement the method 3200. According to another embodiment, the MAC processing 18 is also configured to implement at least part of the method 3200. Figure 1 In yet another example, the method 3200 is implemented by the network interface 27 (eg, the PHY processing unit 29 and / or the MAC processing unit 28). In other embodiments, the method 3200 is implemented by other suitable network interfaces.

[0184] At block 3202, an assignment of a first orthogonal frequency division multiplexing (OFDM) tone block within a wireless local area network (WLAN) communication channel is determined. In an embodiment, the first OFDM tone block corresponds to a first fast Fourier transform (FFT) size, the first FFT size is less than an FFT size corresponding to the WLAN communication channel, the second OFDM tone block corresponds to a second FFT size, the second FFT size is less than an FFT size corresponding to the WLAN communication channel, and the first OFDM tone block and the second OFDM tone block are separated in frequency by at least a third OFDM tone block. In some embodiments, the WLAN communication channel corresponds to the above-described Fig.14A , 14B The communication channels described herein or other suitable communication channels.

[0185] At block 3204, the first communications device generates a first portion of an orthogonal frequency division multiple access (OFDMA) data unit for transmission over a WLAN communications channel using data tones and pilot tones within a first OFDM tone block. In some embodiments, the portion of the OFDMA data unit corresponds to the portion of the OFDM data unit described above with respect to Fig.24 , 25A , part of the OFDMA data unit described in 25B or other suitable OFDMA data unit.

[0186] In an embodiment, generating the first portion of the OFDMA data unit includes: i) performing an inverse fast Fourier transform (IFFT) on a first OFDM data unit of the OFDMA data unit with the first FFT size, and ii) performing an IFFT on a second OFDM data unit of the OFDMA data unit with a second FFT size. In this embodiment, generating the first portion of the OFDMA data unit also includes filtering and transmitting the first OFDM data unit and the second OFDM data unit from a separate radio transmitter of the first communication device.

[0187] In another embodiment, the portion of generating an OFDMA data unit includes: i) performing an inverse fast Fourier transform (IFFT) on a first OFDM data unit of the OFDMA data unit with an FFT size corresponding to a first FFT size, and ii) performing an IFFT on a second OFDM data unit of the OFDMA data unit with an FFT size corresponding to a second FFT size; filtering and shifting the first OFDM data unit and the second OFDM data unit; and combining and transmitting the first OFDM data unit and the second OFDM data unit.

[0188] In an embodiment, generating the portion of the OFDMA data unit comprises performing an IFFT on the portion of the OFDMA data unit with an FFT size corresponding to the WLAN communication channel and using zero values ​​for data tones and pilot tones not within the first OFDM tone block or the second OFDM tone block.

[0189] In some embodiments, the first communications device transmits a portion of the OFDMA data unit on the WLAN communications channel while the second communications device transmits another portion of the OFDMA data unit on the WLAN communications channel. In one such embodiment, the another portion of the OFDMA data unit spans a third OFDM tone block of the WLAN communications channel.

[0190] Further aspects of the invention relate to one or more of the following clauses.

[0191] In an embodiment, a method includes: assigning a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device, wherein the plurality of different OFDM tone blocks include at least a first OFDM tone block assigned to the first device and a second OFDM tone block assigned to the second device, and the first OFDM tone block and the second OFDM tone block together span a bandwidth equal to a minimum channel bandwidth of a legacy WLAN communication protocol. The method also includes: generating an orthogonal frequency division multiple access (OFDMA) data unit for the WLAN communication channel, the OFDMA unit including a preamble portion and a data portion, the preamble portion having i) at least a legacy portion spanning the entire WLAN communication channel, ii) a first non-legacy portion spanning the first OFDM tone block, and iii) a second non-legacy portion spanning the second OFDM tone block.

[0192] In other embodiments, the method includes any suitable combination of one or more of the following features.

[0193] Generating the OFDMA data unit for the WLAN communication channel comprises: i) generating a first OFDM data unit for the data portion using first data received for the first device, and ii) generating a second OFDM data unit for the data portion using second data received for the second device, wherein the first data is independent of the second data; and i) modulating the first OFDM data unit on tones in the first OFDM tone block, and ii) modulating the second OFDM data unit on tones in the second OFDM tone block.

[0194] Generating the OFDMA data unit for the WLAN communication channel includes modulating the OFDMA data unit to span an entire bandwidth of the WLAN communication channel.

[0195] Modulating the first OFDM data unit and the second OFDM data unit comprises: i) modulating the first OFDM data unit on tones in the first OFDM tone block using a first tone scheme, and ii) modulating the second OFDM data unit on tones in the second OFDM tone block using a second tone scheme, wherein the legacy portion is modulated using a legacy tone scheme different from at least the first tone scheme.

[0196] In some embodiments, one or more of the first non-legacy tone scheme or the second non-legacy tone scheme corresponds to a Fast Fourier Transform (FFT) width that is less than a FFT width of the WLAN communication channel.

[0197] Generating the first OFDM data unit and the second OFDM data unit includes: generating a first data tone using the first data and a first pilot tone for the first OFDM tone block; separately generating a second data tone using the second data and a second pilot tone for the second OFDM tone block; and jointly performing an inverse fast Fourier transform (IFFT) on the first data tone, the first pilot tone, the second data tone, and the second pilot tone.

[0198] Generating the first OFDM data unit and the second OFDM data unit includes generating the second OFDM data unit to include at least one padding OFDM symbol so that the first OFDM data unit and the second OFDM data unit have the same number of OFDM symbols.

[0199] The method further comprises determining a number of padding OFDM symbols to be included in the second OFDM data unit as a difference between a total number of OFDM symbols of the first OFDM data unit and a total number of OFDM symbols of the second OFDM data unit.

[0200] Generating the first OFDM data unit and the second OFDM data unit includes: generating the second OFDM data unit to include at least one padding OFDM symbol, so that the sum of the number of OFDM symbols in the first non-traditional part and the number of OFDM symbols of the first OFDM data unit is equal to the sum of the number of OFDM symbols in the second non-traditional part and the number of OFDM symbols of the second OFDM data unit.

[0201] In some embodiments, the first non-legacy portion and the second non-legacy portion include a non-legacy signal field having a corresponding group identifier (ID) subfield, wherein the group ID subfield indicates whether the corresponding OFDM data unit is any of the following: i) a single-user data unit, ii) a multi-user multiple-input multiple-output data unit to be decoded by the indicated device among the multiple devices, or iii) a portion of the OFDMA data unit to be decoded by the indicated device among the multiple devices.

[0202] In some embodiments, the first non-legacy portion and the second non-legacy portion include non-legacy signal fields having corresponding tone block assignment identifiers indicating an assignment of the first OFDM tone block to the first device and an assignment of the second OFDM tone block to the second device.

[0203] Modulating the first OFDM data unit and the second OFDM data unit includes i) modulating the first OFDM data unit using the same bandwidth as the first OFDM tone block having an integer number of tones and a corresponding reduced tone spacing, and ii) modulating the second OFDM data unit using the same bandwidth as the second OFDM tone block having the integer number of tones and a corresponding reduced tone spacing.

[0204] In another embodiment, an apparatus includes: a network interface device having one or more integrated circuits, the one or more integrated circuits configured to: assign a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device, wherein the plurality of different OFDM tone blocks include at least a first OFDM tone block assigned to the first device and a second OFDM tone block assigned to the second device, and the first OFDM tone block and the second OFDM tone block together span a bandwidth equal to a minimum channel bandwidth of a legacy WLAN communication protocol; and wherein the one or more integrated circuits are further configured to generate an orthogonal frequency division multiple access (OFDMA) data unit for the WLAN communication channel, the OFDMA unit including a preamble portion and a data portion, the preamble portion having i) at least a legacy portion spanning the entire WLAN communication channel, ii) a first non-legacy portion spanning the first OFDM tone block, and iii) a second non-legacy portion spanning the second OFDM tone block.

[0205] In other embodiments, the apparatus includes any suitable combination of one or more of the following features.

[0206] One or more integrated circuits are configured to: i) generate a first OFDM data unit of the data portion using first data received for the first device, and ii) generate a second OFDM data unit of the data portion using second data received for the second device, wherein the first data is independent of the second data; and i) modulate the first OFDM data unit on tones in the first OFDM tone block, and ii) modulate the second OFDM data unit on tones in the second OFDM tone block.

[0207] An OFDMA data unit spans the entire bandwidth of the WLAN communication channel.

[0208] One or more integrated circuits are configured to: i) modulate the first OFDM data unit on tones in the first OFDM tone block using a first tone scheme, and ii) modulate the second OFDM data unit on tones in the second OFDM tone block using a second tone scheme, wherein the legacy portion is modulated using a legacy tone scheme different from at least the first tone scheme.

[0209] One or more of the first non-legacy tone scheme or the second non-legacy tone scheme corresponds to a Fast Fourier Transform (FFT) width that is less than a FFT width of the WLAN communication channel.

[0210] One or more integrated circuits are configured to: generate a first data tone using the first data and a first pilot tone for the first block of OFDM tones; separately generate a second data tone using the second data and a second pilot tone for the second block of OFDM tones; and jointly perform an inverse fast Fourier transform (IFFT) on the first data tone, the first pilot tone, the second data tone, and the second pilot tone.

[0211] The one or more integrated circuits are configured to generate the second OFDM data unit to include at least one padding OFDM symbol such that the first OFDM data unit and the second OFDM data unit have the same number of OFDM symbols.

[0212] The first non-legacy portion and the second non-legacy portion include a non-legacy signal field having a corresponding group identifier (ID) subfield, wherein the group ID subfield indicates whether the corresponding OFDM data unit is any of the following: i) a single-user data unit, ii) a multi-user multiple-input multiple-output data unit to be decoded by the indicated device of the multiple devices, or iii) a portion of the OFDM data unit to be decoded by the indicated device of the multiple devices.

[0213] In an embodiment, a method includes determining an assignment of a first orthogonal frequency division multiplexing (OFDM) tone block within a wireless local area network (WLAN) communication channel, wherein the bandwidth of the first OFDM tone block is less than a minimum bandwidth of a conventional WLAN communication protocol; and generating, at a first communication device, a first portion of an orthogonal frequency division multiple access (OFDMA) data unit for transmission over the WLAN communication channel using data tones and pilot tones within the first OFDM tone block.

[0214] In other embodiments, the method includes any suitable combination of one or more of the following features.

[0215] Generating the first portion of the OFDMA data unit includes performing an inverse fast Fourier transform (IFFT) on the first portion of the OFDMA data unit with an FFT size equal to the first OFDM tone block.

[0216] Generating the first portion of the OFDMA data unit includes performing an IFFT on the first portion of the OFDMA data unit with an FFT size equal to the WLAN communication channel and using zero values ​​for data tones and pilot tones not within the first OFDM tone block.

[0217] The method also includes transmitting, by the first communications device, the first portion of the OFDMA data unit on the WLAN communications channel concurrently with transmitting, by a second communications device, a second portion of the OFDMA data unit on the WLAN communications channel, wherein the second portion of the OFDMA data unit spans a second OFDM tone block within the WLAN communications channel.

[0218] The method also includes transmitting, by the first communications device, the legacy portion of the preamble portion using the first OFDM tone block and the second OFDM tone block concurrently with transmitting, by the second communications device using the first OFDM tone block and the second OFDM tone block, the legacy portion of the preamble portion of the OFDMA data unit.

[0219] Transmitting the first portion of the OFDMA data unit includes transmitting, by the first communications device, a first OFDM data unit using only the first OFDM tone block while transmitting, by the second communications device, a second OFDM data unit using only the second OFDM tone block.

[0220] The legacy portion and the first OFDM data unit are transmitted by the first communication device with the same total power.

[0221] The legacy portion and the first OFDM data unit are transmitted by the first communication device with the same power per tone.

[0222] In yet another embodiment, a first communication device includes: a network interface device having one or more integrated circuits, wherein the one or more integrated circuits are configured to: determine an assignment of a first orthogonal frequency division multiplexing (OFDM) tone block within a wireless local area network (WLAN) communication channel, wherein a bandwidth of the first OFDM tone block is less than a minimum bandwidth of a conventional WLAN communication protocol; wherein the one or more integrated circuits are further configured to generate, at the first communication device, a first portion of an orthogonal frequency division multiple access (OFDMA) data unit for transmission on the WLAN communication channel using data tones and pilot tones within the first OFDM tone block.

[0223] In other embodiments, the device includes any suitable combination of one or more of the following features.

[0224] One or more integrated circuits are configured to perform an inverse fast Fourier transform (IFFT) on the first portion of the OFDM data unit with an FFT size equal to the first OFDM tone block.

[0225] One or more integrated circuits are configured to perform an IFFT on the first portion of the OFDMA data unit with an FFT size equal to the WLAN communication channel and using zero values ​​for data tones and pilot tones not within the first OFDM tone block.

[0226] The one or more integrated circuits are configured to transmit, by the first communications device, the first portion of the OFDMA data unit over the WLAN communications channel concurrently with transmitting, by a second communications device, a second portion of the OFDMA data unit over the WLAN communications channel, wherein the second portion of the OFDMA data unit spans a second OFDM tone block within the WLAN communications channel.

[0227] One or more integrated circuits are configured to transmit the legacy portion of the preamble portion using the first OFDM tone block and the second OFDM tone block concurrently with transmission of the legacy portion of the preamble of the OFDMA data unit by the second communications device using the first OFDM tone block and the second OFDM tone block.

[0228] In an embodiment, a method includes: assigning a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device, wherein the plurality of different OFDM tone blocks include at least a first OFDM tone block assigned to the first device, a second OFDM tone block assigned to the first device, and a third OFDM tone block assigned to the second device, wherein the first OFDM tone block and the second OFDM tone block are separated in frequency by at least the third OFDM tone block; and generating an orthogonal frequency division multiple access (OFDMA) data unit for the WLAN communication channel, the OFDMA unit including a preamble portion and a data portion, the preamble portion having at least: i) corresponding to a first OFDM tone block; a first legacy portion of at least the first OFDM tone block, ii) a second legacy portion corresponding to the second OFDM tone block, iii) a first non-legacy portion corresponding to the first OFDM tone block, iv) a second non-legacy portion corresponding to the second OFDM tone block, and v) a third non-legacy portion corresponding to the third OFDM tone block, wherein the first legacy portion is modulated on at least the first OFDM tone block, the first non-legacy portion is modulated on the first OFDM tone block, the second legacy portion is modulated on at least the second OFDM tone block, the second non-legacy portion is modulated on the second OFDM tone block, and the third non-legacy portion is modulated on the third OFDM tone block.

[0229] In other embodiments, the method includes any suitable combination of one or more of the following features.

[0230] The first block of OFDM tones and the third block of OFDM tones together span a bandwidth equal to a minimum channel bandwidth of a conventional WLAN communication protocol.

[0231] The first legacy portion is modulated on a legacy tone block corresponding to a minimum channel bandwidth of a legacy WLAN communication protocol, wherein the legacy tone block i) overlaps in frequency with the first OFDM tone block and ii) has a bandwidth greater than a bandwidth of the first OFDM tone block.

[0232] The legacy tone block includes the first OFDM tone block assigned to the first device and the third OFDM tone block assigned to the second device, wherein the first legacy portion is modulated on at least the first OFDM tone block and the third OFDM tone block.

[0233] The data portion includes a first OFDM data unit for the first device modulated on the first OFDM tone block and a second OFDM data unit for the second device modulated on the third OFDM tone block; wherein at least one of the first OFDM data unit and the second OFDM data unit contains padding so that the total length of the first non-traditional portion and the first OFDM data unit is equal to the total length of the third non-traditional portion and the second OFDM data unit.

[0234] The data portion includes a first OFDM data unit for the first device modulated on the first OFDM tone block and a second OFDM data unit for the first device modulated on the second OFDM tone block; wherein the first traditional portion and the second traditional portion include a traditional signal field, the traditional signal field indicating the same total duration for the following items: i) the first non-traditional portion and the first OFDM data unit and ii) the second non-traditional portion and the second OFDM data unit.

[0235] The first block of OFDM tones and the second block of OFDM tones use the same modulation and coding scheme.

[0236] The first block of OFDM tones uses a different modulation and coding scheme (MCS) than the second block of OFDM tones.

[0237] The first block of OFDM tones and the second block of OFDM tones use the same number of space-time streams.

[0238] The first block of OFDM tones and the second block of OFDM tones use different numbers of space-time streams.

[0239] Generating the OFDMA data unit for the WLAN communication channel includes encoding first data for the first OFDM tone block separately from second data for the second OFDM tone block.

[0240] Generating the OFDMA data unit for the WLAN communication protocol includes encoding and interleaving first data for the first OFDM tone block with second data for the second OFDM tone block.

[0241] In another embodiment, an apparatus includes: a network interface device having one or more integrated circuits, the one or more integrated circuits configured to: assign a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device, wherein the plurality of different OFDM tone blocks include at least a first OFDM tone block and a second OFDM tone block assigned to the first device and a third OFDM tone block assigned to the second device, wherein the first OFDM tone block and the second OFDM tone block are separated in frequency by at least the third OFDM tone block; and generate an orthogonal frequency division multiple access (OFDMA) data unit for the WLAN communication channel, the OFDMA unit including a preamble portion and a data portion , the preamble portion has at least: i) a first legacy portion corresponding to at least the first OFDM tone block, ii) a second legacy portion corresponding to the second OFDM tone block, iii) a first non-legacy portion corresponding to the first OFDM tone block, iv) a second non-legacy portion corresponding to the second OFDM tone block, and v) a third non-legacy portion corresponding to the third OFDM tone block, wherein the first legacy portion is modulated on at least the first OFDM tone block, the first non-legacy portion is modulated on the first OFDM tone block, the second legacy portion is modulated on at least the second OFDM tone block, the second non-legacy portion is modulated on the second OFDM tone block, and the third non-legacy portion is modulated on the third OFDM tone block.

[0242] In other embodiments, the device includes any suitable combination of one or more of the following features.

[0243] The first block of OFDM tones and the third block of OFDM tones together span a bandwidth equal to a minimum channel bandwidth of a conventional WLAN communication protocol.

[0244] The first legacy portion is modulated on a legacy tone block corresponding to a minimum channel bandwidth of a legacy WLAN communication protocol, wherein the legacy tone block i) overlaps in frequency with the first OFDM tone block and ii) has a bandwidth greater than a bandwidth of the first OFDM tone block.

[0245] The legacy tone block includes the first OFDM tone block assigned to the first device and the third OFDM tone block assigned to the second device, wherein the first legacy portion is modulated on at least the first OFDM tone block and the third OFDM tone block.

[0246] The data portion includes a first OFDM data unit for the first device modulated on the first OFDM tone block and a second OFDM data unit for the second device modulated on the third OFDM tone block; and at least one of the first OFDM data unit and the second OFDM data unit includes padding so that the total length of the first non-traditional portion and the first OFDM data unit is equal to the total length of the third non-traditional portion and the second OFDM data unit.

[0247] One or more integrated circuits are configured to encode first data for the first block of OFDM tones separately from second data for the second block of OFDM tones.

[0248] In an embodiment, a method includes determining an assignment of a first orthogonal frequency division multiplexing (OFDM) tone block and a second OFDM tone block for a wireless local area network (WLAN) communication channel, wherein the first OFDM tone block corresponds to a first fast Fourier transform (FFT) size, the first FFT size is smaller than an FFT size corresponding to the WLAN communication channel, the second OFDM tone block corresponds to a second FFT size, the second FFT size is smaller than an FFT size corresponding to the WLAN communication channel, and the first OFDM tone block and the second OFDM tone block are separated in frequency by at least a third OFDM tone block; and generating, at a first communication device, a portion of an orthogonal frequency division multiple access (OFDMA) data unit for transmission on the WLAN communication channel using data tones and pilot tones within the first OFDM tone block and the second OFDM tone block.

[0249] In other embodiments, the method includes any suitable combination of one or more of the following features.

[0250] Generating the portion of the OFDMA data unit includes: i) performing an inverse fast Fourier transform (IFFT) on a first OFDM data unit of the OFDMA data unit with the first FFT size, and ii) performing an IFFT on a second OFDM data unit of the OFDMA data unit with the second FFT size; and filtering and transmitting the first OFDM data unit and the second OFDM data unit from separate radio transmitters of the first communication device.

[0251] Generating the portion of the OFDMA data unit includes: i) performing an inverse fast Fourier transform (IFFT) on a first OFDM data unit of the OFDMA data unit with an FFT size corresponding to the first FFT size, and ii) performing an IFFT on a second OFDM data unit of the OFDMA data unit with an FFT size corresponding to the second FFT size; filtering and shifting the first OFDM data unit and the second OFDM data unit; and combining and transmitting the first OFDM data unit and the second OFDM data unit.

[0252] Generating the portion of the OFDMA data unit includes performing an IFFT on the portion of the OFDMA data unit with an FFT size corresponding to the WLAN communication channel and using zero values ​​for data tones and pilot tones not within the first OFDM tone block or the second OFDM tone block.

[0253] The method further includes transmitting, by the first communications device, the portion of the OFDMA data unit on the WLAN communications channel concurrently with transmitting, by a second communications device, another portion of the OFDMA data unit on the WLAN communications channel, wherein the another portion of the OFDMA data unit spans the third OFDM tone block of the WLAN communications channel.

[0254] In an embodiment, a method includes: assigning a plurality of different orthogonal frequency division multiplexing (OFDM) frequency subbands for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device, wherein the plurality of different OFDM frequency subbands include at least a first OFDM frequency subband assigned to the first device and a second OFDM frequency subband assigned to the second device; and generating an orthogonal frequency division multiple access (OFDMA) data unit for the WLAN communication channel, the OFDMA unit including a preamble portion and a data portion, the preamble portion The method comprises: a conventional portion spanning the first OFDM frequency subband and the second OFDM frequency subband using a conventional tone spacing and a conventional tone scheme, a first non-traditional portion spanning the first OFDM frequency subband and the second OFDM frequency subband using the conventional tone spacing and the conventional tone scheme, a second non-traditional portion spanning the first OFDM frequency subband using a non-traditional tone spacing and a non-traditional tone scheme, and a third non-traditional portion spanning the second OFDM frequency subband using the non-traditional tone spacing and the non-traditional tone scheme.

[0255] In other embodiments, the method includes any suitable combination of one or more of the following features.

[0256] Generating the OFDMA data unit for the WLAN communication channel includes: i) generating a first OFDM data unit for the data portion using first data received for the first device, and ii) generating a second OFDM data unit for the data portion using second data received for the second device, wherein the first data is independent of the second data; i) modulating the first OFDM data unit using the non-traditional tone scheme for the first OFDM frequency subband, and ii) modulating the second OFDM data unit using the non-traditional tone scheme for the second OFDM frequency subband.

[0257] The conventional tone spacing is an integer multiple of the non-conventional tone spacing.

[0258] In another embodiment, an apparatus includes: a network interface device having one or more integrated circuits, the one or more integrated circuits being configured to: assign a plurality of different orthogonal frequency division multiplexing (OFDM) frequency sub-bands for a wireless local area network (WLAN) communication channel to a plurality of devices including a first device and a second device, wherein the plurality of different OFDM frequency sub-bands include at least a first OFDM frequency sub-band assigned to the first device and a second OFDM frequency sub-band assigned to the second device; and generate an orthogonal frequency division multiple access (OFDMA) data unit for the WLAN communication channel, the OFDMA unit The element includes a preamble portion and a data portion, wherein the preamble portion includes: a traditional portion spanning the first OFDM frequency subband and the second OFDM frequency subband using a traditional tone spacing and a traditional tone scheme, a first non-traditional portion spanning the first OFDM frequency subband and the second OFDM frequency subband using the traditional tone spacing and the traditional tone scheme, a second non-traditional portion spanning the first OFDM frequency subband using a non-traditional tone spacing and a non-traditional tone scheme, and a third non-traditional portion spanning the second OFDMA frequency subband using the non-traditional tone spacing and the non-traditional tone scheme.

[0259] In other embodiments, the device includes any suitable combination of one or more of the following features.

[0260] One or more integrated circuits are configured to: i) generate a first OFDM data unit of the data portion using first data received for the first device, and ii) generate a second OFDM data unit of the data portion using second data received for the second device, wherein the first data is independent of the second data; and i) modulate the first OFDM data unit using the non-traditional tone scheme for the first OFDM frequency subband, and ii) modulate the second OFDM data unit using the non-traditional tone scheme for the second OFDM frequency subband.

[0261] The conventional tone spacing is an integer multiple of the non-conventional tone spacing.

[0262] 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 a disk, optical disk, or other storage medium), in RAM or ROM or flash memory, a processor, a hard disk drive, an optical disk drive, a tape drive, etc. Similarly, the software or firmware instructions can be delivered to a user or system via any known or desired delivery method (including, for example, on a computer-readable disk or other portable computer storage mechanism or via a communication medium). Communication media typically implement computer-readable instructions, data structures, program modules, or other data in a modulated data signal (such as a carrier wave or other transmission mechanism). The term "modulated data signal" means a signal that has one or more of its characteristics set or changed in a manner that can encode information in the signal. As an example and not limitation, communication media include wired media (such as a wired network or a direct wired connection) and wireless media (such as auditory, radio frequency, infrared, or other wireless media). Thus, software or firmware instructions may be delivered to a user or system via a communication channel (such as a telephone line, DSL line, cable television line, fiber optic line, wireless communication channel, the Internet, etc.) (which is considered the same as or interchangeable with providing such software via a portable storage medium). Software or firmware instructions may include machine-readable instructions that, when executed by a processor, cause the processor to perform various actions.

[0263] When implemented in hardware, the hardware may include one or more of discrete components, integrated circuits, application specific integrated circuits (ASICs), and the like.

[0264] Although the present invention has been described with reference to specific examples which are intended to be illustrative only and not limiting, variations, additions and / or deletions may be made to the disclosed embodiments without departing from the scope of the present invention.

Claims

1. A communication method in a wireless network, the method comprising: At a first communication device, assigning a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel to a plurality of other communication devices includes: i) assigning a first OFDM tone block and a second OFDM tone block to a second communication device, and ii) assigning a third OFDM tone block to a third communication device, wherein: The first OFDM tone block spans a first frequency bandwidth less than 20 MHz, the third OFDM tone block spans a second frequency bandwidth less than 20 MHz, The first block of OFDM tones and the third block of OFDM tones are within a first subchannel, the first subchannel spanning a frequency bandwidth of 20 MHz, The second OFDM tone block overlaps with a second subchannel, the second subchannel spanning a frequency bandwidth of 20 MHz, and The third OFDM tone block has a frequency between the first OFDM tone block and the second OFDM tone block; and At the first communication device, generating an Orthogonal Frequency Division Multiple Access (OFDMA) physical layer (PHY) data unit for transmission in the WLAN communication channel includes: generating a PHY preamble for the OFDMA PHY data unit spanning at least the first subchannel and the second subchannel, and A PHY data portion of the OFDMA PHY data unit is generated, the PHY data portion including respective independent data of the plurality of other communication devices modulated to respective OFDM tone blocks, including: i) first data of the second communication device modulated to a) the first OFDM tone block in the first subchannel and to b) the second OFDM tone block overlapping the second subchannel, and ii) second data of the third communication device modulated to the third OFDM tone block in the first subchannel.

2. The method of claim 1, wherein the first OFDM tone block and the third OFDM tone block together span the first subchannel.

3. The method of claim 1 , wherein the PHY preamble is generated to include: a first legacy portion spanning across the first subchannel; and A second legacy portion spans across the second subchannel.

4. The method of claim 3, wherein the first legacy portion and the second legacy portion include a legacy signal field indicating a duration of the OFDMA PHY data unit.

5. The method of claim 4, wherein the legacy signal field is generated to indicate that the OFDMA PHY data unit includes a plurality of data streams for respective ones of the plurality of other communication devices.

6. The method of claim 1, wherein the first block of OFDM tones and the second block of OFDM tones use a same modulation coding scheme in the PHY data portion.

7. The method according to claim 1, wherein: The first block of OFDM tones uses a first modulation and coding scheme (MCS) in the PHY data portion and the second block of OFDM tones uses a second MCS in the PHY data portion; and The first MCS is different from the second MCS.

8. The method of claim 1, wherein the first block of OFDM tones and the second block of OFDM tones use the same number of spatial streams in the PHY data portion.

9. The method according to claim 1, wherein: The first block of OFDM tones uses a first number of spatial streams in the PHY data portion and the second block of OFDM tones uses a second number of spatial streams in the PHY data portion; and The first number of spatial streams is different from the second number of spatial streams.

10. The method of claim 1, wherein generating the OFDMA data unit comprises: First data for the first block of OFDM tones is encoded separately from first data for the second block of OFDM tones.

11. The method of claim 1 , wherein generating the OFDMA data unit comprises: The first data for the first block of OFDM tones is encoded and interleaved with the first data for the second block of OFDM tones.

12. A first communication device, comprising: A network interface device having one or more integrated circuit (IC) devices configured to: Assigning a plurality of different orthogonal frequency division multiplexing (OFDM) tone blocks for a wireless local area network (WLAN) communication channel to a plurality of other communication devices, comprising: i) assigning a first OFDM tone block and a second OFDM tone block to a second communication device, and ii) assigning a third OFDM tone block to a third communication device, wherein: The first OFDM tone block spans a first frequency bandwidth less than 20 MHz, the third OFDM tone block spans a second frequency bandwidth less than 20 MHz, The first block of OFDM tones and the third block of OFDM tones are within a first subchannel, the first subchannel spanning a frequency bandwidth of 20 MHz, The second OFDM tone block overlaps with a second subchannel, the second subchannel spanning a frequency bandwidth of 20 MHz, and The third OFDM tone block has a frequency between the first OFDM tone block and the second OFDM tone block; and wherein the one or more IC devices are further configured to generate an Orthogonal Frequency Division Multiple Access (OFDMA) physical layer (PHY) data unit for transmission in the WLAN communication channel, including: generating a PHY preamble for the OFDMA PHY data unit spanning at least the first subchannel and the second subchannel, and A PHY data portion of the OFDMA PHY data unit is generated, the PHY data portion including respective independent data of the plurality of other communication devices modulated to respective OFDM tone blocks, including: i) first data of the second communication device modulated to a) the first OFDM tone block in the first subchannel and to b) the second OFDM tone block overlapping the second subchannel, and ii) second data of the third communication device modulated to the third OFDM tone block in the first subchannel.

13. The first communications device of claim 12, wherein the first block of OFDM tones and the third block of OFDM tones together span the first subchannel.

14. The first communication device of claim 12, wherein the one or more IC devices are further configured to generate the PHY preamble to include: a first legacy portion spanning across the first subchannel; and A second legacy portion spans across the second subchannel.

15. The first communications device of claim 14, wherein the first legacy portion and the second legacy portion include a legacy signal field indicating a duration of the OFDMA PHY data unit.

16. The first communications device of claim 15, wherein the one or more IC devices are further configured to generate the legacy signal field to indicate that the OFDMA PHY data unit includes a plurality of data streams for respective ones of the plurality of other communications devices.

17. The first communications device of claim 12, wherein the one or more IC devices are further configured to use a same modulation coding scheme in the PHY data portion for the first block of OFDM tones and the second block of OFDM tones.

18. The first communication device according to claim 12, wherein: The one or more IC devices are further configured to: i) use a first modulation and coding scheme (MCS) for the first block of OFDM tones, and ii) use a second MCS in the PHY data portion for the second block of OFDM tones; and The first MCS is different from the second MCS.

19. The first communications device of claim 12, wherein the one or more IC devices are further configured to use a same number of spatial streams in the PHY data portion for the first block of OFDM tones and the second block of OFDM tones.

20. The first communication device according to claim 12, wherein: The one or more IC devices are further configured to: i) use a first number of spatial streams in the PHY data portion for the first block of OFDM tones, and ii) use a second number of spatial streams in the PHY data portion for the second block of OFDM tones; and The first number of spatial streams is different from the second number of spatial streams.

21. The first communication device of claim 12, wherein the one or more IC devices are further configured to: First data for the first block of OFDM tones is encoded separately from first data for the second block of OFDM tones.

22. The first communication device of claim 12, wherein the one or more IC devices are further configured to: The first data for the first block of OFDM tones is encoded and interleaved with the first data for the second block of OFDM tones.

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