Allocating and receiving tones for a frame

A communication device for allocating tones is described that includes a processor and instructions in memory in electronic communication with the processor. The communication device determines whether a bandwidth for signal transmission is 20, 40, 80 or 160 megahertz (MHz). The communication device respectively allocates tones for 20, 40, 80 or 160 MHz as follows: for a very high throughput (VHT) signal A1 (VHT-SIG-A1): 52, 104, 208, 416; a VHT signal A2 (VHT-SIG-A2): 52, 104, 208, 416; a VHT short training field (VHT-STF): 12, 24, 48, 48; one or more VHT long training field(s) (VHT-LTF(s)): 56, 114, 242, 484; a VHT signal B (VHT-SIG-B): 56, 114, 242, 484; and a data field (DATA): 56, 114, 242, 484. The communication device also transmits the signal.

TECHNICAL FIELD

The present disclosure relates generally to communication systems. More specifically, the present disclosure relates to allocating and receiving tones for a frame.

BACKGROUND

Communication systems are widely deployed to provide various types of communication content such as data, voice, video and so on. These systems may be multiple-access systems capable of supporting simultaneous communication of multiple communication devices (e.g., wireless communication devices, access terminals, etc.) with one or more other communication devices (e.g., base stations, access points, etc.).

Use of communication devices has dramatically increased over the past few years. Communication devices often provide access to a network, such as a Local Area Network (LAN) or the Internet, for example. Other communication devices (e.g., access terminals, laptop computers, smart phones, media players, gaming devices, etc.) may wirelessly communicate with communication devices that provide network access. Some communication devices comply with certain industry standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 (e.g., Wireless Fidelity or “Wi-Fi”) standards. Communication device users, for example, often connect to wireless networks using such communication devices.

As the use of communication devices has increased, advancements in communication device capacity, reliability and efficiency are being sought. Systems and methods that improve communication device capacity, reliability and/or efficiency may be beneficial.

SUMMARY

A communication device for allocating orthogonal frequency division multiplexing (OFDM) tones is disclosed. The communication device includes a processor and instructions stored in memory that is in electronic communication with the processor. The communication device determines whether a bandwidth for signal transmission is 20 megahertz (MHz), 40 MHz, 80 MHz or 160 MHz. The communication device also allocates 52 tones for a very high throughput signal field A1(VHT-SIG-A1), 52 tones for a very high throughput signal field A2(VHT-SIG-A2), 12 tones for a very high throughput short training field (VHT-STF), 56 tones for one or more very high throughput long training fields (VHT-LTFs), 56 tones for a very high throughput signal field B (VHT-SIG-B) and 56 tones for a data field (DATA) if the bandwidth is 20 MHz. The communication device additionally allocates 104 tones for the VHT-SIG-A1, 104 tones for the VHT-SIG-A2, 24 tones for the VHT-STF, 114 tones for the one or more VHT-LTFs, 114 tones for the VHT-SIG-B and 114 tones for the DATA if the bandwidth is 40 MHz. The communication device further allocates 208 tones for the VHT-SIG-A1, 208 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 242 tones for the one or more VHT-LTFs, 242 tones for the VHT-SIG-B and 242 tones for the DATA if the bandwidth is 80 MHz. The communication device also allocates 416 tones for the VHT-SIG-A1, 416 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 484 tones for the one or more VHT-LTFs, 484 tones for the VHT-SIG-B and 484 tones for the DATA if the bandwidth is 160 MHz. The communication device additionally transmits the signal.

The communication device may allocate 12 tones for a non-high throughput (non-HT) short training field (L-STF), 52 tones for a non-HT long training field (L-LTF) and 52 tones for a non-HT signal field (L-SIG) if the bandwidth is 20 MHz. The communication device may also allocate 24 tones for the L-STF, 104 tones for the L-LTF and 104 tones for the L-SIG if the bandwidth is 40 MHz. The communication device may additionally allocate 48 tones for the L-STF, 208 tones for the L-LTF and 208 tones for the L-SIG if the bandwidth is 80 MHz. The communication device may further allocate 48 tones for the L-STF, 416 tones for the L-LTF and 416 tones for the L-SIG if the bandwidth is 160 MHz.

The VHT-SIG-B may carry 26 bits if the bandwidth is 20 MHz. The VHT-SIG-B may carry 27 bits per 20 MHz of bandwidth if the bandwidth is 40 MHz. The VHT-SIG-B may carry 29 bits per 20 MHz of bandwidth if the bandwidth is 80 MHz. The VHT-SIG-B may carry 29 bits per 20 MHz of bandwidth if the bandwidth is 160 MHz. The VHT-SIG-B may carry one or more pad bits if the bandwidth is 80 MHz or 160 MHz.

The communication device may generate a bandwidth message based on the bandwidth. The communication device may modulate the VHT-SIG-A2using quadrature binary phase-shift keying (QBPSK) to indicate that a frame includes a very high throughput (VHT) signal. The communication device may insert pilot tones at subcarrier indices −103, −75, −39, −11, 11, 39, 75 and 103 if the bandwidth is 80 MHz.

A communication device for receiving orthogonal frequency division multiplexing (OFDM) tones is also disclosed. The communication device includes a processor and instructions stored in memory that is in electronic communication with the processor. The communication device determines whether a bandwidth for signal reception is 20 megahertz (MHz), 40 MHz, 80 MHz or 160 MHz. The communication device also receives 52 tones for a very high throughput signal field A1(VHT-SIG-A1), 52 tones for a very high throughput signal field A2(VHT-SIG-A2), 12 tones for a very high throughput short training field (VHT-STF), 56 tones for one or more very high throughput long training fields (VHT-LTFs), 56 tones for a very high throughput signal field B (VHT-SIG-B) and 56 tones for a data field (DATA) if the bandwidth is 20 MHz. The communication device additionally receives 104 tones for the VHT-SIG-A1, 104 tones for the VHT-SIG-A2, 24 tones for the VHT-STF, 114 tones for the one or more VHT-LTFs, 114 tones for the VHT-SIG-B and 114 tones for the DATA if the bandwidth is 40 MHz. The communication device further receives 208 tones for the VHT-SIG-A1, 208 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 242 tones for the one or more VHT-LTFs, 242 tones for the VHT-SIG-B and 242 tones for the DATA if the bandwidth is 80 MHz. The communication device also receives 416 tones for the VHT-SIG-A1, 416 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 484 tones for the one or more VHT-LTFs, 484 tones for the VHT-SIG-B and 484 tones for the DATA if the bandwidth is 160 MHz. Determining whether the bandwidth for signal reception is 20 MHz, 40 MHz, 80 MHz or 160 MHz may include receiving a bandwidth indication.

The communication device may receive 12 tones for a non-high throughput (non-HT) short training field (L-STF), 52 tones for a non-HT long training field (L-LTF) and 52 tones for a non-HT signal field (L-SIG) if the bandwidth is 20 MHz. The communication device may receive 24 tones for the L-STF, 104 tones for the L-LTF and 104 tones for the L-SIG if the bandwidth is 40 MHz. The communication device may receive 48 tones for the L-STF, 208 tones for the L-LTF and 208 tones for the L-SIG if the bandwidth is 80 MHz. The communication device may receive 48 tones for the L-STF, 416 tones for the L-LTF and 416 tones for the L-SIG if the bandwidth is 160 MHz.

The VHT-SIG-B may carry 26 bits if the bandwidth is 20 MHz. The VHT-SIG-B may carry 27 bits per 20 MHz of bandwidth if the bandwidth is 40 MHz. The VHT-SIG-B may carry 29 bits per 20 MHz of bandwidth if the bandwidth is 80 MHz. The VHT-SIG-B may carry 29 bits per 20 MHz of bandwidth if the bandwidth is 160 MHz. The VHT-SIG-B may carry one or more pad bits if the bandwidth is 80 MHz or 160 MHz.

The communication device may detect a very high throughput (VHT) signal if the VHT-SIG-A2uses quadrature binary phase-shift keying (QBPSK). The communication device may receive pilot tones at subcarrier indices −103, −75, −39, −11, 11, 39, 75 and 103 if the bandwidth is 80 MHz.

A method for allocating orthogonal frequency division multiplexing (OFDM) tones on a communication device is also disclosed. The method includes determining whether a bandwidth for signal transmission is 20 megahertz (MHz), 40 MHz, 80 MHz or 160 MHz. The method also includes allocating 52 tones for a very high throughput signal field A1(VHT-SIG-A1), 52 tones for a very high throughput signal field A2(VHT-SIG-A2), 12 tones for a very high throughput short training field (VHT-STF), 56 tones for one or more very high throughput long training fields (VHT-LTFs), 56 tones for a very high throughput signal field B (VHT-SIG-B) and 56 tones for a data field (DATA) if the bandwidth is 20 MHz. The method additionally includes allocating 104 tones for the VHT-SIG-A1, 104 tones for the VHT-SIG-A2, 24 tones for the VHT-STF, 114 tones for the one or more VHT-LTFs, 114 tones for the VHT-SIG-B and 114 tones for the DATA if the bandwidth is 40 MHz. The method further includes allocating 208 tones for the VHT-SIG-A1, 208 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 242 tones for the one or more VHT-LTFs, 242 tones for the VHT-SIG-B and 242 tones for the DATA if the bandwidth is 80 MHz. The method also includes allocating 416 tones for the VHT-SIG-A1, 416 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 484 tones for the one or more VHT-LTFs, 484 tones for the VHT-SIG-B and 484 tones for the DATA if the bandwidth is 160 MHz. The method additionally includes transmitting the signal.

A method for receiving orthogonal frequency division multiplexing (OFDM) tones on a communication device is also disclosed. The method includes determining whether a bandwidth for signal reception is 20 megahertz (MHz), 40 MHz, 80 MHz or 160 MHz. The method also includes receiving 52 tones for a very high throughput signal field A1(VHT-SIG-A1), 52 tones for a very high throughput signal field A2(VHT-SIG-A2), 12 tones for a very high throughput short training field (VHT-STF), 56 tones for one or more very high throughput long training fields (VHT-LTFs), 56 tones for a very high throughput signal field B (VHT-SIG-B) and 56 tones for a data field (DATA) if the bandwidth is 20 MHz. The method additionally includes receiving 104 tones for the VHT-SIG-A1, 104 tones for the VHT-SIG-A2, 24 tones for the VHT-STF, 114 tones for the one or more VHT-LTFs, 114 tones for the VHT-SIG-B and 114 tones for the DATA if the bandwidth is 40 MHz. The method further includes receiving 208 tones for the VHT-SIG-A1, 208 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 242 tones for the one or more VHT-LTFs, 242 tones for the VHT-SIG-B and 242 tones for the DATA if the bandwidth is 80 MHz. The method also includes receiving 416 tones for the VHT-SIG-A1, 416 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 484 tones for the one or more VHT-LTFs, 484 tones for the VHT-SIG-B and 484 tones for the DATA if the bandwidth is 160 MHz.

A computer-program product for allocating orthogonal frequency division multiplexing (OFDM) tones is also disclosed. The computer-program product includes a non-transitory tangible computer-readable medium with instructions thereon. The instructions include code for causing a communication device to determine whether a bandwidth for signal transmission is 20 megahertz (MHz), 40 MHz, 80 MHz or 160 MHz. The instructions also include code for causing the communication device to allocate 52 tones for a very high throughput signal field A1(VHT-SIG-A1), 52 tones for a very high throughput signal field A2(VHT-SIG-A2), 12 tones for a very high throughput short training field (VHT-STF), 56 tones for one or more very high throughput long training fields (VHT-LTFs), 56 tones for a very high throughput signal field B (VHT-SIG-B) and 56 tones for a data field (DATA) if the bandwidth is 20 MHz. The instructions additionally include code for causing the communication device to allocate 104 tones for the VHT-SIG-A1, 104 tones for the VHT-SIG-A2, 24 tones for the VHT-STF, 114 tones for the one or more VHT-LTFs, 114 tones for the VHT-SIG-B and 114 tones for the DATA if the bandwidth is 40 MHz. The instructions further include code for causing the communication device to allocate 208 tones for the VHT-SIG-A1, 208 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 242 tones for the one or more VHT-LTFs, 242 tones for the VHT-SIG-B and 242 tones for the DATA if the bandwidth is 80 MHz. The instructions also include code for causing the communication device to allocate 416 tones for the VHT-SIG-A1, 416 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 484 tones for the one or more VHT-LTFs, 484 tones for the VHT-SIG-B and 484 tones for the DATA if the bandwidth is 160 MHz. The instructions additionally include code for causing the communication device to transmit the signal.

A computer-program product for receiving orthogonal frequency division multiplexing (OFDM) tones is also disclosed. The computer-program product includes a non-transitory tangible computer-readable medium with instructions. The instructions include code for causing a communication device to determine whether a bandwidth for signal reception is 20 megahertz (MHz), 40 MHz, 80 MHz or 160 MHz. The instructions also include code for causing the communication device to receive 52 tones for a very high throughput signal field A1(VHT-SIG-A1), 52 tones for a very high throughput signal field A2(VHT-SIG-A2), 12 tones for a very high throughput short training field (VHT-STF), 56 tones for one or more very high throughput long training fields (VHT-LTFs), 56 tones for a very high throughput signal field B (VHT-SIG-B) and 56 tones for a data field (DATA) if the bandwidth is 20 MHz. The instructions additionally include code for causing the communication device to receive 104 tones for the VHT-SIG-A1, 104 tones for the VHT-SIG-A2, 24 tones for the VHT-STF, 114 tones for the one or more VHT-LTFs, 114 tones for the VHT-SIG-B and 114 tones for the DATA if the bandwidth is 40 MHz. The instructions further include code for causing the communication device to receive 208 tones for the VHT-SIG-A1, 208 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 242 tones for the one or more VHT-LTFs, 242 tones for the VHT-SIG-B and 242 tones for the DATA if the bandwidth is 80 MHz. The instructions also include code for causing the communication device to receive 416 tones for the VHT-SIG-A1, 416 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 484 tones for the one or more VHT-LTFs, 484 tones for the VHT-SIG-B and 484 tones for the DATA if the bandwidth is 160 MHz.

An apparatus for allocating orthogonal frequency division multiplexing (OFDM) tones is also disclosed. The apparatus includes means for determining whether a bandwidth for signal transmission is 20 megahertz (MHz), 40 MHz, 80 MHz or 160 MHz. The apparatus also includes means for allocating 52 tones for a very high throughput signal field A1(VHT-SIG-A1), 52 tones for a very high throughput signal field A2(VHT-SIG-A2), 12 tones for a very high throughput short training field (VHT-STF), 56 tones for one or more very high throughput long training fields (VHT-LTFs), 56 tones for a very high throughput signal field B (VHT-SIG-B) and 56 tones for a data field (DATA) if the bandwidth is 20 MHz. The apparatus additionally includes means for allocating 104 tones for the VHT-SIG-A1, 104 tones for the VHT-SIG-A2, 24 tones for the VHT-STF, 114 tones for the one or more VHT-LTFs, 114 tones for the VHT-SIG-B and 114 tones for the DATA if the bandwidth is 40 MHz. The apparatus further includes means for allocating 208 tones for the VHT-SIG-A1, 208 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 242 tones for the one or more VHT-LTFs, 242 tones for the VHT-SIG-B and 242 tones for the DATA if the bandwidth is 80 MHz. The apparatus also includes means for allocating 416 tones for the VHT-SIG-A1, 416 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 484 tones for the one or more VHT-LTFs, 484 tones for the VHT-SIG-B and 484 tones for the DATA if the bandwidth is 160 MHz. The apparatus additionally includes means for transmitting the signal.

An apparatus for receiving orthogonal frequency division multiplexing (OFDM) tones is also disclosed. The apparatus includes means for determining whether a bandwidth for signal reception is 20 megahertz (MHz), 40 MHz, 80 MHz or 160 MHz. The apparatus also includes means for receiving 52 tones for a very high throughput signal field A1(VHT-SIG-A1), 52 tones for a very high throughput signal field A2(VHT-SIG-A2), 12 tones for a very high throughput short training field (VHT-STF), 56 tones for one or more very high throughput long training fields (VHT-LTFs), 56 tones for a very high throughput signal field B (VHT-SIG-B) and 56 tones for a data field (DATA) if the bandwidth is 20 MHz. The apparatus additionally includes means for receiving 104 tones for the VHT-SIG-A1, 104 tones for the VHT-SIG-A2, 24 tones for the VHT-STF, 114 tones for the one or more VHT-LTFs, 114 tones for the VHT-SIG-B and 114 tones for the DATA if the bandwidth is 40 MHz. The apparatus further includes means for receiving 208 tones for the VHT-SIG-A1, 208 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 242 tones for the one or more VHT-LTFs, 242 tones for the VHT-SIG-B and 242 tones for the DATA if the bandwidth is 80 MHz. The apparatus additionally includes means for receiving 416 tones for the VHT-SIG-A1, 416 tones for the VHT-SIG-A2, 48 tones for the VHT-STF, 484 tones for the one or more VHT-LTFs, 484 tones for the VHT-SIG-B and 484 tones for the DATA if the bandwidth is 160 MHz.

DETAILED DESCRIPTION

Examples of communication devices include cellular telephone base stations or nodes, access points, wireless gateways and wireless routers. A communication device may operate in accordance with certain industry standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11a, 802.11b, 802.11g, 802.11n and/or 802.11ac (e.g., Wireless Fidelity or “Wi-Fi”) standards. Other examples of standards that a communication device may comply with include IEEE 802.16 (e.g., Worldwide Interoperability for Microwave Access or “WiMAX”), Third Generation Partnership Project (3GPP), 3GPP Long Term Evolution (LTE) and others (e.g., where a communication device may be referred to as a NodeB, evolved NodeB (eNB), etc.). While some of the systems and methods disclosed herein may be described in terms of one or more standards, this should not limit the scope of the disclosure, as the systems and methods may be applicable to many systems and/or standards.

Some communication devices (e.g., access terminals, client devices, client stations, etc.) may wirelessly communicate with other communication devices. Some communication devices may be referred to as mobile devices, mobile stations, subscriber stations, user equipments (UEs), remote stations, access terminals, mobile terminals, terminals, user terminals, subscriber units, etc. Additional examples of communication devices include laptop or desktop computers, cellular phones, smart phones, wireless modems, e-readers, tablet devices, gaming systems, etc. Some of these communication devices may operate in accordance with one or more industry standards as described above. Thus, the general term “communication device” may include communication devices described with varying nomenclatures according to industry standards (e.g., access terminal, user equipment (UE), remote terminal, access point, base station, Node B, evolved Node B (eNB), etc.).

Some communication devices may be capable of providing access to a communications network. Examples of communications networks include, but are not limited to, a telephone network (e.g., a “land-line” network such as the Public-Switched Telephone Network (PSTN) or cellular phone network), the Internet, a Local Area Network (LAN), a Wide Area Network (WAN), a Metropolitan Area Network (MAN), etc.

The IEEE 802.11 group's current work involves standardizing a new and faster version of 802.11, under the name VHT (Very High Throughput). This extension may be referred to as 802.11ac. Technologies are being considered that allow for multiple transmissions to occur in parallel without causing a collision, such as Spatial Division Multiple Access (SDMA). The use of additional signal bandwidth (BW) is also being considered such as transmissions using 80 megahertz (MHz) and 160 MHz. New physical-layer (PHY) preambles may be defined according to the systems and methods herein that allow for both increased signal bandwidth and SDMA and that allow backward compatibility to 802.11n, 802.11a, and 802.11. In order for the VHT preamble to be backward compatible, it may utilize an Orthogonal Frequency Division Multiplexing (OFDM) numerology that can be demodulated by legacy devices. However, it may also use an OFDM numerology that provides for increased functionality for 802.11ac devices. This numerology may include (1) a number of data tones for each OFDM symbol in the preamble, (2) a number of data tones for an OFDM data symbol, (3) a number of pilot tones, and (4) a number of direct current (DC) zero carriers. The systems and methods disclosed herein describe an OFDM sub-carrier numerology that can be applied to such a VHT extension.

An 802.11ac frame with a preamble may be structured including several fields. In one configuration, an 802.11ac frame may include a legacy short training field or non-high throughput short training field (L-STF), a legacy long training field or non-high throughput long training field (L-LTF), a legacy signal field or non-high throughput signal field (L-SIG), a very high throughput signal field A1(VHT-SIG-A1), a very high throughput signal field A2(VHT-SIG-A2), a very high throughput short training field (VHT-STF), one or more very high throughput long training fields (VHT-LTFs), a very high throughput signal field B (VHT-SIG-B) and a data field (e.g., DATA or VHT-DATA).

The 802.11ac preamble is designed to accommodate transmit-beamforming and SDMA. The first part of the preamble may be transmitted in an omni-directional fashion (using cyclic diversity or another scheme, for example). This part of the preamble may include the L-STF, L-LTF, L-SIG, VHT-SIG-A1, and VHT-SIG-A2. It should be noted that the L-STF, L-LTF and the L-SIG may be decodable by legacy devices (e.g., devices that comply with legacy or earlier specifications). However, the VHT-SIG-A1and VHT-SIG-A2(in addition to the foregoing fields, for example) may be decodable by 802.11ac devices.

The second part of the 802.11ac preamble may be transmitted in an omni-directional fashion, may be beam-formed or may be SDMA precoded. This second part of the preamble includes the VHT-STF, one or more VHT-LTFs, and the VHT-SIG-B. The data symbols (in the data field, for example) may be transmitted with the same antenna pattern as the second part of the preamble. The data symbols and the second part of the preamble may not be decodable by legacy or even all 802.11ac devices.

The 802.11ac preamble described above has some control data that is decodable by legacy 802.11a and 802.11n receivers. This data is contained in the L-SIG. The data in L-SIG informs all receivers how long the transmission will occupy the wireless medium, so that all devices can defer their transmissions for an accurate amount of time. In addition, the 802.11ac preamble allows 802.11ac devices to distinguish the transmission as an 802.11ac transmission (and avoid determining that the transmission used an 11a or 11n format). Furthermore, the 802.11ac preamble described according to the systems and methods herein may cause legacy 11a and 11n devices to detect the transmission as an 802.11a transmission, which is a valid transmission with valid data in the L-SIG.

In accordance with the systems and methods disclosed herein, a number of data and pilot tones for an 80 MHz 802.11ac signal may be defined. This may be compared to the number of data and pilot tones for 20 MHz 802.11n and 40 MHz 802.11n signals. A 20 MHz 802.11n signal uses 56 tones (52 data, four pilots) with one direct current (DC) tone. A 40 MHz 802.11n signal uses 114 tones (108 data, six pilots) with three DC tones. The systems and methods disclosed herein describe the use of 242 tones (234 data, eight pilots) with three DC tones for an 80 MHz 802.11ac signal. Using 234 data tones in accordance with the systems and methods herein may be motivated by elegant frequency interleaver constructs, reasonable cost filtering requirements and efficiency considerations. It may also be noted that an 802.11a signal uses 52 tones (48 data tones and four pilot tones) with one DC tone.

The 802.11ac preamble described in accordance with the systems and methods herein may comprise two parts or portions. A first portion may be transmitted omnidirectionally and a second portion may be transmitted with beamforming or SDMA precoding. The first three fields of the first or omnidirectional portion may contain signals (e.g., L-STF, L-LTF, L-SIG) that are decodable by 802.11a and 802.11n receivers. Furthermore, legacy 802.11a and 802.11n devices may determine that the 802.11ac transmission is an 802.11a transmission, so that these devices decode the L-SIG as if it were an 802.11a transmission.

The systems and methods disclosed herein may provide an appropriate number of tones for each field or signal that satisfy the constraints described. This tone allocation is illustrated in Table (1). More specifically, Table (1) illustrates numbers of OFDM tones that may be utilized for an 802.11ac transmission for various signal bandwidths.

The L-STF may use 12 tones per 20 MHz signal. In this case, the time-domain signal has a repetition interval of 800 nanoseconds (ns). This repetition interval may be used for fast gain control, timing offset estimation and frequency offset estimation. The received signal strength may be quickly measured because the time-domain signal only needs to be considered for one 800 ns interval. Legacy 802.11a and 802.11n devices will expect 12 tones.

The L-LTF and L-SIG may use 52 tones for a 20 MHz signal. This may be as is expected for an 802.11a transmission by any legacy 802.11a or 802.11n device. When a 40 MHz 802.11ac signal is transmitted, the contents of these fields may be copied (and scaled by a complex number) to each 20 MHz sub-band of the 40 MHz signal. That is, L-SIG may be used in two 20 MHz sub-bands with the DC tones exactly separated by 20 MHz. Therefore, the total number of tones exactly doubles. For 80 MHz and 160 MHz, the same design may be followed, with the field scaled and copied to each of the four or eight 20 MHz sub-bands.

The L-SIG may use 48 data tones and four pilots according to 802.11a specifications. For 40 MHz, 80 MHz and 160 MHz 802.11ac transmissions, the 24 bits of data carried by the L-SIG (using binary phase-shift keying (BPSK) and 1/2 rate coding, for example) may be transmitted in each of the 20 MHz sub-bands. This allows any legacy device, which is only receiving on a single 20 MHz channel, to decode the data in the L-SIG and defer appropriately.

The VHT-SIG-A1and VHT-SIG-A2fields or symbols may use 52 tones (48 data tones and four pilot tones) in 20 MHz. The number of data tones may be the same as L-SIG, because the channel estimate (which is based on L-LTF) can only be accomplished for these data tones. For 40 MHz, 80 MHz and 160 MHz bandwidths, the number of data tones and pilot tones follow the L-LTF for the same reason.

The VHT-STF may use 12 tones per 20 MHz signal as with the L-STF. In this way, a receive gain control algorithm can quickly measure receive signal strength using only an 800 ns period. If more tones are used, the receiver may need to wait for a longer time period for accurate signal strength measurement, thereby putting constraints on the time allocated for the analog receive gains to change and settle to their new values. Gain control may be required because the received signal strength may be different for the second part of the preamble (and the DATA field) as compared to the first part of the preamble. Additionally, an update to the timing and frequency offset may be accomplished using the VHT-STF.

The VHT-LTF, VHT-SIG-B and DATA fields may utilize more OFDM tones than the first or omnidirectional portion of the preamble. Therefore, each of these fields may utilize the same number of tones as the DATA. For 20 MHz and 40 MHz 802.11ac transmissions, the number of tones is chosen to match the 802.11n standard. For 80 MHz and 160 MHz 802.11ac transmission, the number of tones may be chosen to be 242 and 484, respectively.

For a 20 MHz 802.11ac transmission, the VHT-SIG-B field carries 26 bits of data (52 tones, if BPSK and 1/2 rate coding is used). For a 40 MHz 802.11ac transmission, the VHT-SIG-B field may carry either 54 bits of unique data or the same 27 bits of data in each 20 MHz sub-band. An 80 MHz transmission of the VHT-SIG-B field may carry 29 bits of data in each 20 MHz sub-band or 58 bits of data in each 40 MHz sub-band or 117 bits of data. A similar selection may be made for a 160 MHz transmission. It should be noted that although BPSK and 1/2 rate coding is used as an example herein, other modulation schemes and/or coding rates may be used in a accordance with the systems and methods herein, which may allow for different numbers of bits to be included in each symbol. Table (2) illustrates one example of a number of data tones and a number of bits per signal bandwidth that may be used in accordance with the systems and methods disclosed herein.

Extra bits for wider bandwidth signals could be used to signal additional capabilities that are possible when more than 20 MHz of signal bandwidth is employed. For example, an 80 MHz signal may be composed of four independent 20 MHz signals (streams), where each 20 MHz signal could carry a different encoded stream of data. Each of these streams may have different modulation and coding (e.g., use a different modulation and coding scheme (MCS)). Each stream may additionally have a different number of bytes. Furthermore, each stream may have different amounts of packet aggregation, such as an 802.11n-type aggregated media access control (MAC) protocol data unit (A-MPDU) or aggregated physical layer convergence procedure (PLCP) protocol data unit (PPDU), where each PPDU carries its own VHT-SIG-B field, for example. All of these characteristics may be signaled and indicated by the VHT-SIG-B field bits carried in that respective 20 MHz stream.

More details regarding one configuration in which the systems and methods disclosed herein may be applied are given hereafter. In this configuration, several operational numbers are specified. It should be noted that different operational numbers may be used in different configurations. In this example, a maximum number of transmit (Tx) antennas sounded is eight. This may provide reasonable complexity, cost, and preamble length trade-off. A maximum number of spatial streams (NSS)) in a single-user (SU) case may be eight. Given that eight transmit antennas may be sounded, there is inherent support for up to eight spatial streams.

In a multi-user case, the maximum number of spatial streams (NSS)) per user (e.g., access point, client, station, wireless communication device, etc.) is four in this example. Given that multiple users may share spatial streams, it is natural to make this number smaller than eight. This also fits very high throughput signal field (VHT-SIG) size limitations and reduces the number of representation bits required. The maximum number of spatial streams (NSS)) summed over users in the multi-user case is eight in this example. Given that eight transmit antennas may be sounded, there is inherent support for up to eight spatial streams.

A maximum number of multi-user users may be four. A larger number may significantly increase media access control (MAC) and/or physical (PHY) layer complexity. This fits VHT-SIG size limitations and reduces the number of representation bits required.

Having the maximum number of transmit antennas sounded as eight meets project authorization request (PAR) requirements (e.g., IEEE standards board project authorization request (PAR) requirements). For a single user case, eight antenna with NSS=8 may allow for throughput greater than 500 megabits per second (Mbps). For a multi user case, eight-antenna sounding may allow for throughput greater than 1 gigabits per second (Gbps). Furthermore, there may be a physical limitation on access points (APs) and stations (STAs) to include more than eight antennas. Additionally, going to 16 antenna sounding increases preamble length. Furthermore, the number of bits required to indicate a number of antennas sounded also increases, even though there may be a limited number of bits available in a frame preamble.

Having the maximum number spatial streams (NSS) as eight in the single user case meets PAR requirements. For a single user case, eight spatial streams may allow for throughput greater than 500 Mbps. It should be noted that the maximum number of spatial streams (NSS) is less than or equal to the maximum number of antennas sounded.

Having the maximum number of spatial streams (NSS) per user in the multiple user case as four meets PAR requirements. For multi-user transmission, two transmissions of NSS=4 may allow throughput greater than 1 Gbps. Given that multiple users may share spatial streams, it is natural to make this number smaller than eight. This fits VHT-SIG field size limitations and reduces the number of representation bits required. For example, three bits may be required to define a number of space-time streams (NSTS) per user for multi-user transmission. For resolvable long training fields (LTFs), these bits may be included in the very high throughput signal field A (VHT-SIG-A).

Having the maximum number of spatial streams (NSS) summed over users in the multi-user case as eight meets PAR requirements. For multi-user transmission, the sum of numbers of spatial streams (NSS) equal to eight may lead to throughput greater than 1 Gbps. Given that eight transmit antennas may be sounded, there is inherent support for up to eight spatial streams.

Having the maximum number of multi-user users as four meets PAR requirements. For example, a multi-user transmission with four users and two streams per user may allow throughput greater than 1 Gbps. A larger number may significantly increase MAC and/or PHY layer complexity. For example, each user stream may need to be separately encrypted and modulated. However, having a maximum of four users in a multi-user case fits VHT-SIG size limitations and reduces the number of representation bits required. It should be noted that NSSbits may be pre-allocated for each user in the VHT-SIG-A. Even with four multi-user users, however, most of the VHT-SIG-A bits are already allocated.

One configuration of a frame preamble may include the following features. The frame preamble may provide very high throughput auto-detection using a 90-degree rotation on a second VHT-SIG field symbol (e.g., VHT-SIG-A2). This frame preamble may use modulation for the VHT-SIG field(s) that is the same as that used in 802.11a/n: binary phase-shift keying (BPSK) with 1/2 rate coding. A single frame preamble may be used, without a Greenfield format.

In this configuration, the frame preamble may include several fields: an L-STF, an L-LTF, an L-SIG field, a VHT-SIG-A field (that may include VHT-SIG-A1and VHT-SIG-A2fields or symbols, for example), a VHT-STF, one or more VHT-LTFs, a VHT-SIG-B field (which may include one symbol, for example) and a VHT-DATA field. The preamble may have a rate of 6 Mbps, with a length determined by a variable T. The second symbol in VHT-SIG-A (e.g., VHT-SIG-A2) may use a modulation or constellation mapping that is rotated by 90 degrees relative to the first symbol in VHT-SIG-A (e.g., VHT-SIG-A1). Thus, the VHT-SIG-A2may be used for VHT auto-detection.

This approach to auto-detection may provide reliable spoofing of existing 802.11n receivers (as an 802.11a packet, for example), regardless of which 802.11n auto-detect algorithm was implemented in the existing 802.11n receiver. This approach also provides reliable 802.11ac auto-detection with a largest Euclidean Distance (for BPSK versus quadrature binary phase-shift keying (QBPSK), for example). It should be noted that it may be risky to manipulate modulation of the first VHT-SIG-A symbol (e.g., VHT-SIG-A1). Given various existing implementations of 802.11n auto-detections, it may not be fair to assume any particular 802.11n auto-detect approach as in other approaches. For example, making such an assumption may make it more likely that an 802.11n device false-detects a high throughput signal field (HT-SIG) and goes into an energy detection-clear channel assessment (ED-CCA) stage.

Regarding detection timing, VHT-STF automatic gain control (AGC) may be deferred by an approximate fast Fourier transform (FFT) processing time (before VHT detection). 802.11ac devices may run a faster clock to support higher throughput. Therefore, AGC computation may be faster than high throughput (HT) devices. In one configuration, part of the guard interval (GI) for the first VHT-LTF may be used for AGC computation. Much more complex functions (e.g., downlink multiuser (DL-MU) functions, a faster decoder, etc.) than AGC computation may be required for 802.11ac. Thus, VHT AGC enhancement may be trivial. Accordingly, a reliable legacy spoofing may be more important than the extra complexity of AGC enhancement.

Concerning the modulation of the VHT-SIG fields, it may be preferable to continue using the lowest possible MCS to modulate VHT-SIG fields. For example, MCSO may be used to guarantee the longest range. This may ensure that the header is not worse than the data field.

Regarding the Greenfield (GF) format, it may be preferable not to define a second preamble format. In 802.11n, the GF format has only had limited usage so far. However, one of the arguments in favor of the GF format in 802.11n was the existence of green space in the 5 GHz range due to the limited use of 802.11a. Nevertheless, if there are no 5 GHz deployments of 802.11n, then there is no point to the 802.11ac task group (TGac). Thus, the assumption should be that there will be 5 GHz deployments of 802.11n. Similar to 802.11n, having multiple preamble types compounds the difficulty of auto-detection for a small physical layer (PHY) efficiency improvement. Thus, the PHY improvement may be offset by GF protection exchanges.

In accordance with the systems and methods disclosed herein, some preamble design goals are given hereafter. One goal is backward compatibility. For example, the preamble design may allow robust legacy 802.11a deferral and robust legacy 802.11n deferral. Another preamble design goal is reliable auto-detection among 802.11a, 802.11n (for mixed mode (MM) and GF, for example) and VHT preambles. Another goal is to have a single preamble structure in single-user (SU) and multi-user (MU) cases. Another design goal is to allow the signaling of VHT PHY information by the VHT-SIG field(s). Training for wider channels and detection and deferral in each sub-channel are further goals. Yet other preamble design goals include having a preamble with a low peak-to-average power ratio (PAPR) and minimizing or reducing overall preamble length.

In one configuration of the systems and methods disclosed herein, spoofing and auto-detection may be performed as follows. L-SIG spoofing may be used for both 802.11a and 802.11n receivers. For example, this may be done as 802.11n spoofing for 802.11a/g receivers. In one configuration, the bit rate may be 6 Mbps, where length/rate indicates duration. 90-degree rotated BPSK (QBPSK) on a VHT-SIG symbol may be used for VHT auto-detection. An 802.11n receiver will treat the packet as 802.11a packet (L-SIG spoofing).

Some additional detail on aggregation bit in VHT-SIGs for MU packets is given hereafter. There may be no need to indicate the duration of the packet in VHT-SIG again. For example, length information may be obtained from the L-SIG field. An aggregated MAC protocol data unit (A-MPDU) structure may be used to provide length information for individual MPDUs. It may be required that an A-MPDU is always used with a VHT frame. The MAC layer may provide an A-MPDU that fills the frame up to the last byte for each per-user stream, and the PHY layer provides 0-7 bits of padding. This same padding scheme may also be defined in SU packets. Thus, an “aggregation” bit may not be needed in the VHT-SIG.

In a MU case, the VHT-SIG-A field may include the “common” bits for all clients. For example, the VHT-SIG-A field may indicate the number of space-time streams (NSTS) for each user. It should be noted that prior multiuser group and user identification (ID) assignment frame exchanges may be needed before DL-MU packets are used (e.g., by sounding and/or via management frames). Thus, each user may be able to get its own NSTSinformation from the VHT-SIG-A field(s).

The VHT-SIG-B field contains user-specific information (e.g., modulation and coding rate) and may be spatially multiplexed for different clients. The VHT-SIG-B field is placed after all the VHT-LTFs to enable better receiver-side interference mitigation in DL-MU before decoding the VHT-SIG-B. This requires each client getting as many LTFs as needed to train the total number of spatial streams across all users—referred to as “resolvable VHT-LTF.” “Non-resolvable VHT-LTF” may be selected if all clients do not support receiver-side interference mitigation or if interference mitigation is not required.

Various configurations are now described with reference to the Figures, where like reference numbers may indicate functionally similar elements. The systems and methods as generally described and illustrated in the Figures herein could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of several configurations, as represented in the Figures, is not intended to limit scope, as claimed, but is merely representative of the systems and methods.

FIG. 1is a block diagram illustrating one configuration of a transmitting communication device102in which systems and methods for allocating tones for a frame may be implemented and one configuration of a receiving communication device142in which systems and methods for receiving tones for a frame may be implemented. The transmitting communication device102may include an encoder106with an input for receiving payload data104and/or preamble data116to be transmitted to one or more receiving communication devices142. The payload data104may include voice, video, audio and/or other data. The preamble data116may include control information, such as information that specifies a data rate, modulation and coding scheme (MCS), channel bandwidth, etc. The encoder106might encode data104,116for forward error correction (FEC), encryption, packeting and/or other encodings known for use with wireless transmission.

A constellation mapper110maps the data provided by the encoder106into constellations. For instance, the constellation mapper110may use modulation schemes such as binary phase-shift keying (BPSK), quadrature amplitude modulation (QAM), etc. Where quadrature-amplitude modulation (QAM) is used, for example, the constellation mapper110might provide two bits per spatial stream138, per data subcarrier140, per symbol period. Furthermore, the constellation mapper110may output a 16-QAM constellation signal for each spatial stream138for each data subcarrier140for each symbol period. Other modulations may be used, such as 64-QAM, which would result in a consumption of six bits per spatial stream138, per data subcarrier140, per symbol period. Other variations are also possible.

The output of the constellation mapper110is provided to a space-time-frequency mapper108that maps the data onto Spatial-Time-Frequency (STF) dimensions of the transmitter. The dimensions represent various constructs or resources that allow for data to be allocated. A given bit or set of bits (e.g., a grouping of bits, a set of bits that correspond to a constellation point, etc.) may be mapped to a particular place among the dimensions. In general, bits and/or signals mapped to different places among the dimensions are transmitted from the transmitting communication device102such that they are expected to be, with some probability, differentiable at one or more receiving communication devices142. In one configuration, the space-time-frequency mapper108may perform space-time block coding (STBC).

One or more spatial streams138may be transmitted from the transmitting communication device102such that the transmissions on different spatial streams138may be differentiable at a receiver (with some probability). For example, bits mapped to one spatial dimension are transmitted as one spatial stream138. That spatial stream138might be transmitted on its own antenna132spatially separate from other antennas132, its own orthogonal superposition over a plurality of spatially-separated antennas132, its own polarization, etc. Many techniques for spatial stream138separation (involving separating antennas132in space or other techniques that would allow their signals to be distinguished at a receiver, for example) are known and can be used.

In the example shown inFIG. 1, there are one or more spatial streams138that are transmitted using the same or a different number of antennas132a-n(e.g., one or more). In some instances, only one spatial stream138might be available because of inactivation of one or more other spatial streams138.

In the case that the transmitting communication device102uses a plurality of frequency subcarriers140, there are multiple values for the frequency dimension, such that the space-time-frequency mapper108might map some bits to one frequency subcarrier140and other bits to another frequency subcarrier140. Other frequency subcarriers140may be reserved as guard bands, pilot tone subcarriers, or the like that do not (or do not always) carry data104,116. For example, there may be one or more data subcarriers140and one or more pilot subcarriers140. It should be noted that, in some instances or configurations, not all subcarriers140may be excited at once. For instance, some tones may not be excited to enable filtering. In one configuration, the transmitting communication device102may utilize orthogonal frequency-division multiplexing (OFDM) for the transmission of multiple subcarriers140. For instance, the space-time-frequency mapper108may map (encoded) data104,116to space, time and/or frequency resources according to the multiplexing scheme used.

The time dimension refers to symbol periods. Different bits may be allocated to different symbol periods. Where there are multiple spatial streams138, multiple subcarriers140and multiple symbol periods, the transmission for one symbol period might be referred to as an “OFDM (orthogonal frequency-division multiplexing) MIMO (multiple-input, multiple-output) symbol.” A transmission rate for encoded data may be determined by multiplying the number of bits per simple symbol (e.g., log2of the number of constellations used) times the number of spatial streams138times the number of data subcarriers140, divided by the length of the symbol period.

Thus, the space-time-frequency mapper108may map bits (or other units of input data) to one or more spatial streams138, data subcarriers140and/or symbol periods. Separate spatial streams138may be generated and/or transmitted using separate paths. In some implementations, these paths are implemented with distinct hardware, whereas in other implementations, the path hardware is reused for more than one spatial stream138or the path logic is implemented in software that executes for one or more spatial streams138. More specifically, each of the elements illustrated in the transmitting communication device102may be implemented as a single block/module or as multiple blocks/modules. For instance, the transmitter radio frequency block(s)126element may be implemented as a single block/module or as multiple parallel blocks/modules corresponding to each antenna132a-n(e.g., each spatial stream138). As used herein, the term “block/module” and variations thereof may indicate that a particular element or component may be implemented in hardware, software or a combination of both.

The transmitting communication device102may include a pilot generator block/module130. The pilot generator block/module130may generate a pilot sequence. A pilot sequence may be a group of pilot symbols. In one configuration, for instance, the values in the pilot sequence may be represented by a signal with a particular phase, amplitude and/or frequency. For example, a “1” may denote a pilot symbol with a particular phase and/or amplitude, while a “−1” may denote a pilot symbol with a different (e.g., opposite or inverse) phase and/or amplitude.

The transmitting communication device102may include a pseudo-random noise generator128in some configurations. The pseudo-random noise generator128may generate a pseudo-random noise sequence or signal (e.g., values) used to scramble the pilot sequence. For example, the pilot sequence for successive OFDM symbols may be multiplied by successive numbers from the pseudo-random noise sequence, thereby scrambling the pilot sequence per OFDM symbol. When the pilot sequence is sent to a receiving communication device142, the received pilot sequence may be unscrambled by a pilot processor148.

The output(s) of the space-time-frequency mapper108may be spread over frequency and/or spatial dimensions. A pilot insertion block/module112inserts pilot tones into the pilot tone subcarriers140. For example, the pilot sequence may be mapped to subcarriers140at particular indices114. For instance, pilot symbols from the pilot sequence may be mapped to subcarriers140that are interspersed with data subcarriers140and/or other subcarriers140. In other words, the pilot sequence or signal may be combined with the data sequence or signal. In some configurations, one or more direct current (DC) tones may be centered at index 0.

In some configurations, the combined data and pilot signal may be provided to a rotation block/module (not illustrated inFIG. 1). The rotation block/module may use a rotation or multiplication factor to rotate pilot symbols and/or data symbols. For example, the rotation block/module may rotate a VHT-SIG-A2symbol to provide VHT auto-detection.

The transmitting communication device102may include a bandwidth determination block/module118. The bandwidth determination block/module118may determine channel bandwidth to be used for transmissions to one or more receiving communication devices142. This determination may be based on one or more factors, such as receiving communication device142compatibility, number of receiving communication devices142(to use the communication channel), channel quality (e.g., channel noise) and/or a received indicator, etc. In one configuration, the bandwidth determination block/module118may determine whether the bandwidth for signal transmission is 20 MHz, 40 MHz, 80 MHz or 160 MHz.

The bandwidth determination block/module118may provide an indication of the bandwidth determination to one or more blocks/modules. For example, this bandwidth indication may be provided to the space-time-frequency mapper108, the pilot insertion block/module112and/or the pilot generator130. Additionally or alternatively, the bandwidth indication may be provided as part of preamble data116. For instance, one or more bits in the preamble data116may be allocated to represent the bandwidth indication. Additionally or alternatively, the bandwidth indication may be implicitly indicated in the preamble data116. This bandwidth indication may thus be signaled to the one or more receiving communication devices142. This may enable the one or more receiving communication devices142to receive preamble data116using the selected channel bandwidth.

The space-time-frequency mapper108may use the bandwidth indication to map the preamble data116to a number of tones (e.g., subcarriers140). For example, the systems and methods disclosed herein may define a number of OFDM tones or subcarriers140that may be used by the transmitting communication device102for the transmission of preamble data116based on the channel bandwidth (as specified by the bandwidth indication, for example). The number of OFDM tones may also be specified according to a particular preamble field. For example, the space-time-frequency mapper108may map preamble data116to a number of OFDM tones based on the bandwidth determination and the preamble field as indicated in Table (1) above. For example, if the current field is a VHT-SIG-B and the bandwidth indication specifies a bandwidth of 80 MHz, the space-time-frequency mapper108may map preamble data116to234OFDM tones or subcarriers140, leaving eight OFDM tones for pilots and three subcarriers140as DC tones. In some configurations, the space-time-frequency mapper108may use a look-up table to determine the number of tones or subcarriers to use for a specified bandwidth.

More specifically, if the determined bandwidth is 20 MHz, the transmitting communication device102may allocate 12 OFDM tones for the L-STF, 52 for the L-LTF, 52 for the L-SIG field, 52 for the VHT-SIG-A1field or symbol, 52 for the VHT-SIG-A2field or symbol, 12 for the VHT-STF, 56 for one or more VHT-LTFs (e.g., for each of the VHT-LTFs), 56 for the VHT-SIG-B field and/or 56 for the DATA field. If the bandwidth determined is 40 MHz, the transmitting communication device102may allocate 24 OFDM tones for the L-STF, 104 for the L-LTF, 104 for the L-SIG field, 104 for the VHT-SIG-A1field or symbol, 104 for the VHT-SIG-A2field or symbol, 24 for the VHT-STF, 114 for one or more VHT-LTFs, 114 for the VHT-SIG-B field and/or 114 for the DATA field. If the bandwidth is 80 MHz, the transmitting communication device102may allocate 48 OFDM tones for the L-STF, 208 for the L-LTF, 208 for the L-SIG field, 208 for the VHT-SIG-A1field or symbol, 208 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 242 for one or more VHT-LTFs, 242 for the VHT-SIG-B field and/or 242 for the DATA field. If the bandwidth is 160 MHz, the transmitting communication device102may allocate 48 OFDM tones for the L-STF, 416 for the L-LTF, 416 for the L-SIG field, 416 for the VHT-SIG-A1field or symbol, 416 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 484 for one or more VHT-LTFs, 484 for the VHT-SIG-B field or symbol and/or 484 for the DATA field.

In some configurations, the bandwidth indication may also be provided to the pilot generator130. The pilot generator130may use the bandwidth indication to generate an appropriate number of pilot symbols. For example, the pilot generator130may generate eight pilot symbols for an 80 MHz signal (with 242 OFDM tones: 234 data tones and eight pilot tones with three DC subcarriers140).

In some configurations, the bandwidth indication may additionally be provided to the pilot insertion block/module112. The pilot insertion block/module112may use this indication to determine subcarrier indices114for pilot symbol insertion. For instance, an 80 MHz bandwidth may indicate that the pilot symbols should be inserted at indices −103, −75, −39, −11, 11, 39, 75 and 103.

The data and/or pilot signals are provided to an inverse discrete Fourier transform (IDFT) block/module120. The inverse discrete Fourier transform (IDFT) block/module120converts the frequency signals of the data104,116and inserted pilot tones into time domain signals representing the signal over the spatial streams138and/or time-domain samples for a symbol period. In one configuration, for example, the IDFT block/module120may perform a 256-point inverse fast Fourier transform (IFFT).

The time-domain signal is provided to a formatter122. The formatter (e.g., one or more formatting blocks/modules)122may take the output of the inverse discrete Fourier transform (IDFT) block/module120, convert it from parallel signals to serial (P/S), add a cyclical prefix and/or perform guard interval windowing, etc.

The formatter122output may be provided to a digital-to-analog converter (DAC)124. The digital-to-analog converter (DAC)124may convert the formatter122output from one or more digital signals to one or more analog signals. The digital-to-analog converter (DAC)124may provide the analog signal(s) to one or more transmitter radio-frequency (TX RF) blocks126.

The one or more transmitter radio frequency blocks126may be coupled to or include a power amplifier. The power amplifier may amplify the analog signal(s) for transmission. The one or more transmitter radio frequency blocks126may output radio-frequency (RF) signals to one or more antennas132a-n, thereby transmitting the data104,116that was input to the encoder106over a wireless medium suitably configured for receipt by one or more receiving communication devices142.

One or more receiving communication devices142may receive and use signals from the transmitting communication device102. For example, a receiving communication device142may use a received bandwidth indicator to receive a given number of OFDM tones or subcarriers140. Additionally or alternatively, a receiving communication device142may use a pilot sequence generated by the transmitting communication device102to characterize the channel, transmitter impairments and/or receiver impairments and use that characterization to improve receipt of data104,116encoded in the transmissions.

For example, a receiving communication device142may include one or more antennas136a-n(which may be greater than, less than or equal to the number of transmitting communication device102antennas132a-nand/or the number of spatial streams138) that feed to one or more receiver radio-frequency (RX RF) blocks158. The one or more receiver radio-frequency (RX RF) blocks158may output analog signals to one or more analog-to-digital converters (ADCs)156. For example, a receiver radio-frequency block158may receive and downconvert a signal, which may be provided to an analog-to-digital converter156. As with the transmitting communication device102, the number of spatial streams138processed may or may not be equal to the number of antennas136a-n. Furthermore, each spatial stream138need not be limited to one antenna136, as various beamsteering, orthogonalization, etc. techniques may be used to arrive at a plurality of receiver streams.

The one or more analog-to-digital converters (ADCs)156may convert the received analog signal(s) to one or more digital signal(s). These output(s) of the one or more analog-to-digital converters (ADCs)156may be provided to one or more time and/or frequency synchronization blocks/modules154. A time and/or frequency synchronization block/module154may (attempt to) synchronize or align the digital signal in time and/or frequency (to a receiving communication device142clock, for example).

The (synchronized) output of the time and/or frequency synchronization block(s)/module(s)154may be provided to one or more deformatters152. For example, a deformatter152may receive an output of the time and/or frequency synchronization block(s)/module(s)154, remove prefixes, etc. and/or parallelize the data for discrete Fourier transform (DFT) processing.

One or more deformatter152outputs may be provided to one or more discrete Fourier transform (DFT) blocks/modules150. The discrete Fourier transform (DFT) blocks/modules150may convert one or more signals from the time domain to the frequency domain. A pilot processor148may use the frequency domain signals (per spatial stream138, for example) to determine one or more pilot tones (over the spatial streams138, frequency subcarriers140and/or groups of symbol periods, for example) sent by the transmitting communication device102. The pilot processor148may additionally or alternatively de-scramble the pilot sequence. The pilot processor148may use the one or more pilot sequences described herein for phase and/or frequency and/or amplitude tracking. The pilot tone(s) may be provided to a space-time-frequency detection and/or decoding block/module146, which may detect and/or decode the data over the various dimensions. The space-time-frequency detection and/or decoding block/module146may output received data144(e.g., the receiving communication device's142estimation of the payload data104and/or preamble data116transmitted by the transmitting communication device102).

In some configurations, the receiving communication device142knows the transmit sequences sent as part of a total information sequence. The receiving communication device142may perform channel estimation with the aid of these known transmit sequences. To assist with pilot tone tracking, processing and/or data detection and decoding, a channel estimation block/module160may provide estimation signals to the pilot processor148and/or the space-time-frequency detection and/or decoding block/module146based on the output from the time and/or frequency synchronization block/module154. Alternatively, if the de-formatting and discrete Fourier transform is the same for the known transmit sequences as for the payload data portion of the total information sequence, the estimation signals may be provided to the pilot processor148and/or the space-time-frequency detection and/or decoding block/module146based on the output from the discrete Fourier transform (DFT) blocks/modules150.

The bandwidth determination block/module134may use the time/frequency synchronization block/module154output to determine a channel bandwidth (for received communications). For example, the bandwidth determination block/module134may receive a bandwidth indication from the transmitting communication device102that indicates a channel bandwidth. For instance, the bandwidth determination block/module134may obtain an explicit or implicit bandwidth indication. In one configuration, the bandwidth indication may indicate a channel bandwidth of 20 MHz, 40 MHz, 80 MHz or 160 MHz. The bandwidth determination block/module134may determine the bandwidth for received communications based on this indication and provide an indication of the determined bandwidth to the pilot processor148and/or to the space-time-frequency detection/decoding block/module146.

More specifically, if the determined bandwidth is 20 MHz, the receiving communication device142may receive 12 OFDM tones for the L-STF, 52 for the L-LTF, 52 for the L-SIG field, 52 for the VHT-SIG-A1field or symbol, 52 for the VHT-SIG-A2field or symbol, 12 for the VHT-STF, 56 for one or more VHT-LTFs, 56 for the VHT-SIG-B field and/or 56 for the DATA field. If the bandwidth determined is 40 MHz, the receiving communication device142may receive 24 OFDM tones for the L-STF, 104 for the L-LTF, 104 for the L-SIG field, 104 for the VHT-SIG-A1field or symbol, 104 for the VHT-SIG-A2field or symbol, 24 for the VHT-STF, 114 for one or more VHT-LTFs, 114 for the VHT-SIG-B field and/or 114 for the DATA field. If the bandwidth is 80 MHz, the receiving communication device142may receive 48 OFDM tones for the L-STF, 208 for the L-LTF, 208 for the L-SIG field, 208 for the VHT-SIG-A1field or symbol, 208 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 242 for one or more VHT-LTFs, 242 for the VHT-SIG-B field and/or 242 for the DATA field. If the bandwidth is 160 MHz, the receiving communication device142may receive 48 OFDM tones for the L-STF, 416 for the L-LTF, 416 for the L-SIG field, 416 for the VHT-SIG-A1field or symbol, 416 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 484 for one or more VHT-LTFs, 484 for the VHT-SIG-B field or symbol and/or 484 for the DATA field.

The pilot processor148may use the determined bandwidth indication to extract pilot symbols from the discrete Fourier transform block/module150output. For example, if the determined bandwidth indication specifies that the bandwidth is 80 MHz, the pilot processor148may extract pilot symbols from the indices −103, −75, −39, −11, 11, 39, 75 and 103.

The space-time frequency detection/decoding block/module146may use the determined bandwidth indication to detect and/or decode preamble data and/or payload data from the received signal. For example, if the current field is a VHT-SIG-B field and the determined bandwidth indication specifies that the bandwidth is 80 MHz, then the space-time frequency detection/decoding block/module146may detect and/or decode preamble data from 234 OFDM tones or subcarriers140(while eight OFDM tones are pilot tones and three subcarriers140are used for DC tones, for instance). In some configurations, the space-time-frequency detection/decoding block/module146may use a look-up table to determine the number of tones or subcarriers to receive for a specified bandwidth.

FIG. 2is a diagram illustrating one example of a communication frame200that may be used in accordance with the systems and methods disclosed herein. The frame200may include one or more sections or fields for preamble symbols, pilot symbols and/or data symbols. For example, the frame200may comprise an 802.11ac preamble260and a data field282(e.g., DATA or VHT-DATA field). In one configuration, the 802.11ac preamble260may have a duration of 40 to 68 μs. The preamble260and/or pilot symbols may be used (by a receiving communication device142, for example) to synchronize, detect, demodulate and/or decode preamble116and/or payload data104included in the frame200.

The frame200with an 802.11ac preamble260may be structured including several fields. In one configuration, an 802.11ac frame200may include a legacy short training field or non-high throughput short training field (L-STF)266, a legacy long training field or non-high throughput long training field (L-LTF)268, a legacy signal field or non-high throughput signal field (L-SIG)270, a very high throughput signal symbol or field A1(VHT-SIG-A1)272, a very high throughput signal symbol or field A2(VHT-SIG-A2)274, a very high throughput short training field (VHT-STF)276, one or more very high throughput long training fields (VHT-LTFs)278, a very high throughput signal field B (VHT-SIG-B)280and a data field (DATA)282.

The 802.11ac preamble260may accommodate transmit beamforming and SDMA. The first part or portion262of the preamble260may be transmitted in an omni-directional fashion (using cyclic diversity or another scheme, for example). This first part262of the preamble260may include the L-STF266, L-LTF268, L-SIG270, VHT-SIG-A1272, and VHT-SIG-A2274. This first part262of the preamble260may be decodable by legacy devices (e.g., devices that comply with legacy or earlier specifications).

A second part or portion264of the 802.11ac preamble260may be transmitted in an omni-directional fashion, may be beam-formed or may be SDMA precoded. This second part264of the preamble260includes the VHT-STF276, one or more VHT-LTFs278, and the VHT-SIG-B280. The data symbols (in the data field282, for example) may be transmitted with the same antenna pattern as the second part264of the preamble260. The data field282may also be transmitted omnidirectionally, may be beam-formed or may be SDMA precoded. The data symbols and the second part264of the preamble260may not be decodable by legacy devices (or even by all 802.11ac devices).

The 802.11ac preamble260may include some control data that is decodable by legacy 802.11a and 802.11n receivers. This control data is contained in the L-SIG270. The data in the L-SIG270informs all receivers how long the transmission will occupy the wireless medium, so that all devices may defer their transmissions for an accurate amount of time. Additionally, the 802.11ac preamble260allows 802.11ac devices to distinguish the transmission as an 802.11ac transmission (and avoid determining that the transmission is in an 802.11a or 802.11n format). Furthermore, the 802.11ac preamble260described according to the systems and methods herein may cause legacy 802.11a and 802.11n devices to detect the transmission as an 802.11a transmission, which is a valid transmission with valid data in the L-SIG270.

In accordance with the systems and methods disclosed herein, a number of data and pilot tones for an 80 MHz 802.11ac signal may be defined. This may be compared to the number of data and pilot tones for 20 MHz 802.11n and 40 MHz 802.11n signals. A 20 MHz 802.11n signal uses 56 tones (52 data, four pilots) with one direct current (DC) tone. A 40 MHz 802.11n signal uses 114 tones (108 data, six pilots) with three DC tones. The systems and methods disclosed herein describe the use of 242 tones (e.g., 234 data tones and eight pilot tones) with three DC tones for an 80 MHz 802.11ac signal. Using 234 data tones in accordance with the systems and methods herein may be motivated by elegant frequency interleaver constructs and reasonable cost filtering requirements. It may also be noted that an 802.11a signal uses 52 tones (48 data tones and four pilot tones) with one DC tone.

The 802.11ac preamble260described in accordance with the systems and methods herein may comprise two parts or portions. A first portion262may be transmitted omnidirectionally (with cyclic delay diversity, for example) and a second portion264may be transmitted omnidirectionally, with beamforming or with SDMA precoding. The first three fields (e.g., L-STF266, L-LTF268, L-SIG270) of the first or omnidirectional portion262may contain signals that are decodable by 802.11a and 802.11n receivers. Furthermore, legacy 802.11a and 802.11n devices may determine that the 802.11ac transmission is an 802.11a transmission, such that these legacy devices decode the L-SIG270as if it were an 802.11a transmission.

The systems and methods disclosed herein may provide an appropriate number of tones for each preamble260field and/or the data field282that satisfy the constraints described. This tone allocation is illustrated in Table (3). More specifically, Table (3) illustrates numbers of OFDM tones that may be utilized for an 802.11ac transmission for various signal bandwidths.

The L-STF266may use 12 tones per 20 MHz signal. In this case, the time-domain signal may have a repetition interval of 800 nanoseconds (ns). This repetition interval may be used for fast gain control, timing offset estimation and frequency offset estimation. The received signal strength may be quickly measured because the time-domain signal only needs to be considered for one 800 ns interval. Legacy 802.11a and 802.11n devices will expect 12 tones.

The L-LTF268and L-SIG270may use 52 tones for a 20 MHz signal. This may be as is expected for an 802.11a transmission by any legacy 802.11a or 802.11n device. When a 40 MHz 802.11ac signal is transmitted, the contents of these fields268,270may be copied (and scaled by a complex number) to each 20 MHz sub-band of the 40 MHz signal. That is, the L-SIG field270may be used in two 20 MHz sub-bands with the DC tones exactly separated by 20 MHz. Therefore, the total number of tones exactly doubles. For 80 MHz and 160 MHz, the same design may be followed, with the field scaled and copied to each of the four or eight 20 MHz sub-bands.

The L-SIG270may use 48 data tones and four pilots according to 802.11a specifications. For 40 MHz, 80 MHz and 160 MHz 802.11ac transmissions, the 24 bits of data carried by the L-SIG (using binary phase-shift keying (BPSK) and 1/2 rate coding, for example) may be transmitted in each of the 20 MHz sub-bands. This allows any legacy device, which is only receiving on a single 20 MHz channel, to decode the data in the L-SIG270and defer appropriately.

The VHT-SIG-A1symbol or field272and VHT-SIG-A2symbol or field274may use 52 tones (48 data tones and four pilot tones) in 20 MHz. The number of data tones may be the same as L-SIG270, because the channel estimate (which is based on the L-LTF268) may be accomplished for these data tones. For 40 MHz, 80 MHz and 160 MHz bandwidths, the number of data tones and pilot tones may follow the L-LTF268for the same reason.

The VHT-STF276may use 12 tones per 20 MHz signal as with the L-STF266. In this way, a receive gain control algorithm can quickly measure receive signal strength using only an 800 ns period. If more tones are used, the receiver may need to wait for a longer time period for accurate signal strength measurement, thereby putting constraints on the time allocated for the analog receive gains to change and settle to their new values. Gain control may be required because the received signal strength may be different for the second part264of the preamble260(and the DATA field282) as compared to the first part262of the preamble260. Additionally, an update to the timing and frequency offset may be accomplished using the VHT-STF276.

The one or more VHT-LTFs278, the VHT-SIG-B field280and the DATA field282may utilize more OFDM tones than the first or omnidirectional portion262of the preamble260. Therefore, each of these fields278,280may utilize the same number of tones as the DATA field282. For 20 MHz and 40 MHz 802.11ac transmissions, the number of tones may be chosen to match the 802.11n standard. For 80 MHz and 160 MHz 802.11ac transmissions, the number of tones may be chosen to be 242 and 484, respectively.

For a 20 MHz 802.11ac transmission, the VHT-SIG-B field280carries 26 bits of data if BPSK and 1/2 rate coding is used, for example. For a 40 MHz 802.11ac transmission, the VHT-SIG-B field280may carry either 54 bits of unique data or the same 27 bits of data in each 20 MHz sub-band. An 80 MHz transmission of the VHT-SIG-B field280may carry 29 bits of data in each 20 MHz sub-band or 58 bits of data in each 40 MHz sub-band or 117 bits of data. A similar selection may be made for a 160 MHz transmission. Thus, the VHT-SIG-B280may carry more information bits as the bandwidth increases from 20 MHz to 40 MHz to 80 MHz.

Extra bits for wider bandwidth signals may be used to signal additional capabilities that are possible when more than 20 MHz of signal bandwidth is employed. For example, an 80 MHz signal may be composed of four independent 20 MHz signals (streams), where each 20 MHz signal could carry a different encoded stream of data. Each of these streams may have different modulation and coding (e.g., use a different modulation and coding scheme (MCS)). Each stream may additionally have a different number of bytes. Furthermore, each stream may have different amounts of packet aggregation, such as an 802.11n-type aggregated media access control (MAC) protocol data unit (A-MPDU) or aggregated physical layer convergence procedure (PLCP) protocol data unit (PPDU), where each PPDU carries its own VHT-SIG-B field280, for example. All of these characteristics may be signaled and indicated by the VHT-SIG-B field280bits carried in that respective 20 MHz stream.

FIG. 3is a diagram illustrating examples of several frames300. In particular,FIG. 3illustrates an 802.11a preamble384, an 802.11n Greenfield (GF) preamble394, an 802.11n mixed-mode (MM) preamble325and an 802.11ac preamble360in accordance with the systems and methods disclosed herein. More specifically, a legacy 802.11a preamble384, a legacy 802.11n Greenfield preamble394and a legacy 802.11n mixed mode preamble325are illustrated. The 802.11a preamble384illustrated may have a duration of 20 μs. The 802.11n Greenfield preamble394illustrated may have a duration of 28 to 36 μs. The 802.11n mixed mode (MM) preamble325illustrated may have a duration of 36 to 48 μs. According to the systems and methods disclosed herein, the 802.11ac preamble360illustrated may have a duration of 40 to 68 μs.

The 802.11ac preamble360may accommodate transmit beamforming and SDMA. The first part or portion362of the preamble360may be transmitted in an omni-directional fashion (using cyclic diversity or another scheme, for example). This first part362of the preamble360may include the L-STF366, L-LTF368, L-SIG370, VHT-SIG-A1372, and VHT-SIG-A2374. This first part362of the preamble360may be decodable by legacy devices (e.g., devices that comply with legacy or earlier specifications).

A second part or portion364of the 802.11ac preamble360may be transmitted in an omni-directional fashion, may be beam-formed or may be SDMA precoded. This second part364of the preamble360includes the VHT-STF376, one or more VHT-LTFs378, and the VHT-SIG-B380. The data symbols (in the data field382, for example) may be transmitted with the same antenna pattern as the second part364of the preamble360. The data field382may also be transmitted omnidirectionally, may be beam-formed or may be SDMA precoded. The data symbols and the second part364of the preamble360may not be decodable by legacy devices (or even all 802.11ac devices).

The 802.11ac preamble360may include some control data that is decodable by legacy 802.11a and 802.11n receivers. This control data is contained in the L-SIG370. The data in the L-SIG370informs all receivers how long the transmission will occupy the wireless medium, so that all devices may defer their transmissions for an accurate amount of time. Additionally, the 802.11ac preamble360allows 802.11ac devices to distinguish the transmission as an 802.11ac transmission (and avoid determining that the transmission is in an 802.11a or 802.11n format). Furthermore, the 802.11ac preamble360described according to the systems and methods herein may cause legacy 802.11a and 802.11n devices to believe the transmission is an 802.11a transmission, which is a valid transmission with valid data in the L-SIG370.

The legacy 802.11a preamble384includes an L-STF386, an L-LTF388and an L-SIG390, which may be transmitted along with a data field392. The 802.11n Greenfield (GF) preamble394includes a high throughput short training field (HT-STF)396, a high throughput long training field1(HT-LTF1)398, a high throughput signal1(HT-SIG-1)301, a high throughput signal2(HT-SIG-2)303and one or more high throughput long training fields (HT-LTF(s))305, which may be transmitted with a data field307. The 802.11n mixed mode (MM) preamble325includes an L-STF309, an L-LTF311an L-SIG313, an HT-SIG-1315, an HT-SIG-2317, a high throughput short training field (HT-STF)319and one or more HT-LTFs321, which may be transmitted along with a data field323. As can be observed fromFIG. 3, some of the fields included in the 802.11ac preamble360correspond to similar fields in legacy preambles384,325. This may allow backwards compatibility with legacy devices when the 802.11ac preamble360is used.

FIG. 4is a diagram illustrating constellations for a legacy signal field (L-SIG)470, a very high throughput signal A1(VHT-SIG-A1)472(e.g., first symbol) and a very high throughput signal A2(VHT-SIG-A2)474(e.g., second symbol). Each constellation is illustrated on an in-phase (I) axis and a quadrature (Q) axis. More specifically,FIG. 4illustrates examples of modulation schemes that may be used for the first and second symbols in the VHT-SIG-A field and for the L-SIG field in accordance with the systems and methods disclosed herein.

A transmitting communication device102may use BPSK modulation with 1/2 rate coding for the L-SIG field470in an 802.11ac frame200. In this scheme, a bit with a “1” value may be represented with a modulation symbol at +1 on the in-phase axis. Additionally, a bit with a “0” value may be represented with a modulation symbol at −1 on the in-phase axis.

In accordance with the systems and methods disclosed herein, a transmitting communication device102may use BPSK modulation with 1/2 rate coding for the VHT-SIG-A1472in an 802.11ac frame200. In this scheme, a bit with a “1” value may be represented with a modulation symbol at +1 on the in-phase axis. Additionally, a bit with a “0” value may be represented with a modulation symbol at −1 on the in-phase axis.

In accordance with the systems and methods disclosed herein, a transmitting communication device102may use QBPSK modulation (e.g., BPSK modulation with a 90-degree rotation) with 1/2 rate coding for the VHT-SIG-A2474in an 802.11ac frame200. In this scheme, a bit with a “1” value may be represented with a modulation symbol at +1 on the quadrature axis. Additionally, a bit with a “0” value may be represented with a modulation symbol at −1 on the quadrature axis.

FIG. 5is a diagram illustrating one example of data and pilot tones for an 80 MHz signal543in accordance with the systems and methods disclosed herein. Data and pilot tones for a 20 MHz 802.11n signal527and data and pilot tones for a 40 MHz 802.11n signal535are also illustrated. In accordance with the systems and methods disclosed herein, a number of data tones and pilot tones545a-hfor an 80 MHz 802.11ac signal543may be defined. This may be compared to the number of data tones and pilot tones529a-dfor a 20 MHz 802.11n signal527and the number of data tones and pilot tones537a-ffor a 40 MHz 802.11n signal535.

A 20 MHz 802.11n signal527uses 56 tones, including 52 data tones and four pilot tones529a-dwith one direct current (DC) tone531. The data tones and pilot tones529a-dmay be located according to a subcarrier number or index533. For example, pilot A529ais located at −21, pilot B529bis located at −7, pilot C529cis located at 7 and pilot D529dis located at 21. In this case, the single DC tone531is located at 0.

A 40 MHz 802.11n signal535uses 114 tones, including 108 data tones and six pilot tones537a-fwith three DC tones539. The data tones and pilot tones537a-fmay be located according to a subcarrier number or index541. For example, pilot A537ais located at −53, pilot B537bis located at −25, pilot C537cis located at −11, pilot D537dis located at 11, pilot E537eis located at 25 and pilot F537fis located at 53. In this case, three DC tones539are located at −1, 0 and 1.

The systems and methods disclosed herein describe the use of 242 tones, including 234 data tones and eight pilot tones545a-hwith three DC tones547for an 80 MHz 802.11ac signal543. The data tones and pilot tones545a-hmay be located according to a subcarrier number or index549. For example, pilot A545ais located at −103, pilot B545bis located at −75, pilot C545cis located at −39, pilot D545dis located at −11, pilot E545eis located at 11, pilot F545fis located at 39, pilot G545gis located at 75 and pilot H545his located at 103. In this case, three DC tones547are located at −1, 0 and 1. Using 234 data tones in accordance with the systems and methods herein may be motivated by elegant frequency interleaver constructs and reasonable cost filtering requirements. When a transmitting communication device102determines a channel bandwidth of 80 MHz, for example, it102may allocate subcarriers140for data tones and pilot tones545a-haccording to the 802.11ac signal543illustrated inFIG. 5. Additionally, when a receiving communication device142determines a channel bandwidth of 80 MHz, for instance, it142may receive subcarriers140for data and pilot tones545a-haccording to the 802.11ac signal543illustrated inFIG. 5. It may be noted that an 802.11a signal (not shown inFIG. 5) uses 52 tones (e.g., 48 data tones and four pilot tones) with one DC tone.

FIG. 6is a flow diagram illustrating one configuration of a method600for allocating tones for a frame. A transmitting communication device102may determine602whether a bandwidth for signal transmission is 20 MHz, 40 MHz, 80 MHz or 160 MHz. This determination602may be based on one or more factors, such as receiving communication device142compatibility, number of receiving communication devices142(to use the communication channel), channel quality (e.g., channel noise) and/or a received indicator, etc.

If the bandwidth determined602is 20 MHz, the transmitting communication device102may allocate60412 OFDM tones for the L-STF, 52 for the L-LTF, 52 for the L-SIG field, 52 for the VHT-SIG-A1field or symbol, 52 for the VHT-SIG-A2field or symbol, 12 for the VHT-STF, 56 for one or more VHT-LTFs, 56 for the VHT-SIG-B field and/or 56 for the DATA field. If the bandwidth determined602is 40 MHz, the transmitting communication device102may allocate60624 OFDM tones for the L-STF, 104 for the L-LTF, 104 for the L-SIG field, 104 for the VHT-SIG-A1field or symbol, 104 for the VHT-SIG-A2field or symbol, 24 for the VHT-STF, 114 for one or more VHT-LTFs, 114 for the VHT-SIG-B field and/or 114 for the DATA field.

If the bandwidth determined602is 80 MHz, the transmitting communication device102may allocate60848 OFDM tones for the L-STF, 208 for the L-LTF, 208 for the L-SIG field, 208 for the VHT-SIG-A1field or symbol, 208 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 242 for one or more VHT-LTFs, 242 for the VHT-SIG-B field and/or 242 for the DATA field. If the bandwidth determined602is 160 MHz, the transmitting communication device102may allocate61048 OFDM tones for the L-STF, 416 for the L-LTF, 416 for the L-SIG field, 416 for the VHT-SIG-A1field or symbol, 416 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 484 for one or more VHT-LTFs, 484 for the VHT-SIG-B field or symbol and/or 484 for the DATA field.

The transmitting communication device102may transmit612the signal. For example, the transmitting communication device102may perform an IDFT on the signal, format the signal, convert the signal to an analog signal and radiate the signal using one or more antennas132a-n.

FIG. 7is a flow diagram illustrating one configuration of a method700for receiving tones for a frame. A receiving communication device142may determine702whether a bandwidth for signal reception is 20 MHz, 40 MHz, 80 MHz or 160 MHz. For example, the receiving communication device142may receive an indicator or message that specifies a bandwidth for signal reception. It should be noted that the indicator or message may be explicit or implicit. For instance, the indicator or message may explicitly include bits that specify a bandwidth. In another configuration, the indicator or message may be embedded with another type of data or a characteristic of the transmission, such as a choice of modulation type, information ordering, etc.

If the bandwidth determined702is 20 MHz, the receiving communication device142may receive70412 OFDM tones for the L-STF, 52 for the L-LTF, 52 for the L-SIG field, 52 for the VHT-SIG-A1field or symbol, 52 for the VHT-SIG-A2field or symbol, 12 for the VHT-STF, 56 for one or more VHT-LTFs, 56 for the VHT-SIG-B field and/or 56 for the DATA field. If the bandwidth determined702is 40 MHz, the receiving communication device142may receive70624 OFDM tones for the L-STF, 104 for the L-LTF, 104 for the L-SIG field, 104 for the VHT-SIG-A1field or symbol, 104 for the VHT-SIG-A2field or symbol, 24 for the VHT-STF, 114 for one or more VHT-LTFs, 114 for the VHT-SIG-B field and/or 114 for the DATA field.

If the bandwidth determined702is 80 MHz, the receiving communication device142may receive70848 OFDM tones for the L-STF, 208 for the L-LTF, 208 for the L-SIG field, 208 for the VHT-SIG-A1field or symbol, 208 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 242 for one or more VHT-LTFs, 242 for the VHT-SIG-B field and/or 242 for the DATA field. If the bandwidth determined702is 160 MHz, the receiving communication device142may receive71048 OFDM tones for the L-STF, 416 for the L-LTF, 416 for the L-SIG field, 416 for the VHT-SIG-A1field or symbol, 416 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 484 for one or more VHT-LTFs, 484 for the VHT-SIG-B field or symbol and/or 484 for the DATA field.

FIG. 8is a block diagram illustrating one configuration of an access point802in which systems and methods for allocating tones for a frame may be implemented. The access point802may include an encoder806with an input for receiving payload data804and/or preamble data816to be transmitted to one or more access terminals842. The payload data804may include voice, video, audio and/or other data. The preamble data816may include control information, such as information that specifies a data rate, modulation and coding scheme (MCS), channel bandwidth, etc. The encoder806might encode data804,816for forward error correction (FEC), encryption, packeting and/or other encodings known for use with wireless transmission. For example, the encoder806may encode the data804,816using convolutional or low-density parity check (LDPC) coding.

A constellation mapper810maps the data provided by the encoder806into constellations. For instance, the constellation mapper810may use modulation schemes such as binary phase-shift keying (BPSK), quadrature amplitude modulation (QAM), etc. Where quadrature-amplitude modulation (QAM) is used, for example, the constellation mapper810might provide two bits per spatial stream838, per data subcarrier840, per symbol period. Furthermore, the constellation mapper810may output a 16-QAM constellation signal for each spatial stream838for each data subcarrier840for each symbol period. Other modulations may be used, such as 64-QAM, which would result in a consumption of six bits per spatial stream838, per data subcarrier840, per symbol period. Other variations are also possible.

The output of the constellation mapper810is provided to a space-time-frequency mapper808that maps the data onto Spatial-Time-Frequency (STF) dimensions of the transmitter. The dimensions represent various constructs or resources that allow for data to be allocated. A given bit or set of bits (e.g., a grouping of bits, a set of bits that correspond to a constellation point, etc.) may be mapped to a particular place among the dimensions. In general, bits and/or signals mapped to different places among the dimensions are transmitted from the access point802such that they are expected to be, with some probability, differentiable at one or more access terminals842. In one configuration, the space-time-frequency mapper808may perform space-time block coding (STBC).

One or more spatial streams838may be transmitted from the access point802such that the transmissions on different spatial streams838may be differentiable at a receiver (with some probability). For example, bits mapped to one spatial dimension are transmitted as one spatial stream838. That spatial stream838might be transmitted on its own antenna832spatially separate from other antennas832, its own orthogonal superposition over a plurality of spatially-separated antennas832, its own polarization, etc. Many techniques for spatial stream838separation (involving separating antennas832in space or other techniques that would allow their signals to be distinguished at a receiver, for example) are known and can be used.

In the example shown inFIG. 8, there are one or more spatial streams838that are transmitted using the same or a different number of antennas832a-n(e.g., one or more). In some instances, only one spatial stream838might be available because of inactivation of one or more other spatial streams838.

In the case that the access point802uses a plurality of frequency subcarriers840, there are multiple values for the frequency dimension, such that the space-time-frequency mapper808might map some bits to one frequency subcarrier840and other bits to another frequency subcarrier840. Other frequency subcarriers840may be reserved as guard bands, pilot tone subcarriers, or the like that do not (or do not always) carry data804,816. For example, there may be one or more data subcarriers840and one or more pilot subcarriers840. It should be noted that, in some instances or configurations, not all subcarriers840may be excited at once. For instance, some tones may not be excited (e.g., DC tones) to enable filtering. In one configuration, the access point802may utilize orthogonal frequency-division multiplexing (OFDM) for the transmission of multiple subcarriers840. For instance, the space-time-frequency mapper808may map (encoded) data804,816to space, time and/or frequency resources according to the multiplexing scheme used.

The time dimension refers to symbol periods. Different bits may be allocated to different symbol periods. Where there are multiple spatial streams838, multiple subcarriers840and multiple symbol periods, the transmission for one symbol period might be referred to as an “OFDM (orthogonal frequency-division multiplexing) MIMO (multiple-input, multiple-output) symbol.” A transmission rate for encoded data may be determined by multiplying the number of bits per simple symbol (e.g., log2of the number of constellations used) times the number of spatial streams838times the number of data subcarriers840, divided by the length of the symbol period.

Thus, the space-time-frequency mapper808may map bits (or other units of input data) to one or more spatial streams838, data subcarriers840and/or symbol periods. Separate spatial streams838may be generated and/or transmitted using separate paths. In some implementations, these paths are implemented with distinct hardware, whereas in other implementations, the path hardware is reused for more than one spatial stream838or the path logic is implemented in software that executes for one or more spatial streams838. More specifically, each of the elements illustrated in the access point802may be implemented as a single block/module or as multiple blocks/modules. For instance, the transmitter radio frequency block(s)826element may be implemented as a single block/module or as multiple parallel blocks/modules corresponding to each antenna832a-n(e.g., each spatial stream838). As used herein, the term “block/module” and variations thereof may indicate that a particular element or component may be implemented in hardware, software or a combination of both.

The access point802may include a pilot generator block/module830. The pilot generator block/module830may generate a pilot sequence. A pilot sequence may be a group of pilot symbols. In one configuration, for instance, the values in the pilot sequence may be represented by a signal with a particular phase, amplitude and/or frequency. For example, a “1” may denote a pilot symbol with a particular phase and/or amplitude, while a “−1” may denote a pilot symbol with a different (e.g., opposite or inverse) phase and/or amplitude.

The access point802may include a pseudo-random noise generator828in some configurations. The pseudo-random noise generator828may generate a pseudo-random noise sequence or signal (e.g., values) used to scramble the pilot sequence. For example, the pilot sequence for successive OFDM symbols may be multiplied by successive numbers from the pseudo-random noise sequence, thereby scrambling the pilot sequence per OFDM symbol. When the pilot sequence is sent to an access terminal842, the received pilot sequence may be unscrambled by a pilot processor848.

The output(s) of the space-time-frequency mapper808may be spread over frequency and/or spatial dimensions. A pilot insertion block/module812inserts pilot tones into the pilot tone subcarriers840. For example, the pilot sequence may be mapped to subcarriers840at particular indices. For instance, pilot symbols from the pilot sequence may be mapped to subcarriers840that are interspersed with data subcarriers840and/or other subcarriers840. In other words, the pilot sequence or signal may be combined with the data sequence or signal. In one example, if an 80 MHz band863is used for transmission, the pilot tones or subcarriers840may be located at indices k={−103, −75, −39, −11, 11, 39, 75, 103}. In some configurations, one or more direct current (DC) tones may be centered at index 0.

In some configurations, the combined data and pilot signal may be provided to a rotation block/module (not illustrated inFIG. 8). The rotation block/module may use a rotation or multiplication factor to rotate pilot symbols and/or data symbols. For example, the rotation block/module may rotate a VHT-SIG-A2symbol by 90 degrees related to a VHT-SIG-A1to provide VHT auto-detection.

The access point802may include a bandwidth determination block/module818. The bandwidth determination block/module818may determine channel bandwidth to be used for transmissions to one or more access terminals842. This determination may be based on one or more factors, such as access terminal842compatibility, number of access terminals842(to use the communication channel), channel quality (e.g., channel noise) and/or a received indicator, etc. In one configuration, the bandwidth determination block/module818may determine whether the bandwidth for signal transmission is 20 MHz, 40 MHz, 80 MHz or 160 MHz. In one example, the bandwidth determination block/module818may determine that an 80 MHz band863will be used for transmissions.

The bandwidth determination block/module818may provide an indication of the bandwidth determination to one or more blocks/modules. For example, this bandwidth indication may be provided to the space-time-frequency mapper808, the pilot insertion block/module812and/or the pilot generator830. Additionally or alternatively, the bandwidth indication may be provided as part of preamble data816. For instance, one or more bits in the preamble data816may be allocated to represent the bandwidth indication. Additionally or alternatively, the bandwidth indication may be implicitly indicated in the preamble data816. This bandwidth indication may thus be signaled to the one or more access terminals842. This may enable the one or more access terminals842to receive preamble data816using the selected channel bandwidth.

The space-time-frequency mapper808may use the bandwidth indication to map the preamble data816to a number of tones (e.g., subcarriers840). For example, the systems and methods disclosed herein may define a number of OFDM tones or subcarriers840that may be used by the access point802for the transmission of preamble data816based on the channel bandwidth (as specified by the bandwidth indication, for example). The number of OFDM tones may also be specified according to a particular preamble field. For example, the space-time-frequency mapper808may map preamble data816to a number of OFDM tones based on the bandwidth determination and the preamble field as indicated in Table (1) above. For example, if the current field is a VHT-SIG-B and the bandwidth indication specifies an 80 MHz bandwidth863, the space-time-frequency mapper808may map preamble data816to 234 OFDM tones or subcarriers840, leaving eight OFDM tones for pilots and three subcarriers840as DC tones. In some configurations, the space-time-frequency mapper808may use a look-up table to determine the number of tones or subcarriers to use for a specified bandwidth.

More specifically, if the determined bandwidth is 20 MHz, the access point802may allocate 12 OFDM tones for the L-STF, 52 for the L-LTF, 52 for the L-SIG field, 52 for the VHT-SIG-A1field or symbol, 52 for the VHT-SIG-A2field or symbol, 12 for the VHT-STF, 56 for one or more VHT-LTFs, 56 for the VHT-SIG-B field and/or 56 for the DATA field. If the bandwidth determined is 40 MHz, the access point802may allocate 24 OFDM tones for the L-STF, 104 for the L-LTF, 104 for the L-SIG field, 104 for the VHT-SIG-A1field or symbol, 104 for the VHT-SIG-A2field or symbol, 24 for the VHT-STF, 114 for one or more VHT-LTFs, 114 for the VHT-SIG-B field and/or 114 for the DATA field. If the bandwidth is 80 MHz, the access point802may allocate 48 OFDM tones for the L-STF, 208 for the L-LTF, 208 for the L-SIG field, 208 for the VHT-SIG-A1field or symbol, 208 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 242 for one or more VHT-LTFs, 242 for the VHT-SIG-B field and/or 242 for the DATA field. If the bandwidth is 160 MHz, the access point802may allocate 48 OFDM tones for the L-STF, 416 for the L-LTF, 416 for the L-SIG field, 416 for the VHT-SIG-A1field or symbol, 416 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 484 for one or more VHT-LTFs, 484 for the VHT-SIG-B field or symbol and/or 484 for the DATA field.

In some configurations, the bandwidth indication may also be provided to the pilot generator830. The pilot generator830may use the bandwidth indication to generate an appropriate number of pilot symbols. For example, the pilot generator830may generate eight pilot symbols for an 80 MHz signal (with 242 OFDM tones: 234 data tones and eight pilot tones with three DC subcarriers840).

In some configurations, the bandwidth indication may additionally be provided to the pilot insertion block/module812. The pilot insertion block/module812may use this indication to determine subcarrier indices for pilot symbol insertion. For instance, an 80 MHz bandwidth may indicate that the pilot symbols should be inserted at indices −103, −75, −39, −11, 11, 39, 75 and 103.

The data and/or pilot signals are provided to an inverse fast Fourier transform (IFFT) block/module820. The inverse fast Fourier transform (IFFT) block/module820converts the frequency signals of the data804,816and inserted pilot tones into time domain signals representing the signal over the spatial streams838and/or time-domain samples for a symbol period. In one configuration, for example, the IFFT block/module820may perform a 256-point inverse fast Fourier transform (IFFT).

The time-domain signal is provided to a formatter822. The formatter (e.g., one or more formatting blocks/modules)822may take the output of the inverse fast Fourier transform (IFFT) block/module820, convert it from parallel signals to serial (P/S), add a cyclical prefix and/or perform guard interval windowing, etc.

The formatter822output may be provided to a digital-to-analog converter (DAC)824. The digital-to-analog converter (DAC)824may convert the formatter822output from one or more digital signals to one or more analog signals. The digital-to-analog converter (DAC)824may provide the analog signal(s) to one or more transmitter radio-frequency (TX RF) blocks826.

The one or more transmitter radio frequency blocks826may be coupled to or include a power amplifier. The power amplifier may amplify the analog signal(s) for transmission. The one or more transmitter radio frequency blocks826may output radio-frequency (RF) signals to one or more antennas832a-n, thereby transmitting the data804,816that was input to the encoder806over a wireless medium suitably configured for receipt by one or more access terminals842.

One or more access terminals842may receive and use signals from the access point802. For example, an access terminal842may use a received bandwidth indicator to receive a given number of OFDM tones or subcarriers840. Additionally or alternatively, an access terminal842may use a pilot sequence generated by the access point802to characterize the channel, transmitter impairments and/or receiver impairments and use that characterization to improve receipt of data804,816encoded in the transmissions.

For example, an access terminal842may include one or more antennas836a-n(which may be greater than, less than or equal to the number of access point802antennas832a-nand/or the number of spatial streams838) that feed to one or more receiver radio-frequency (RX RF) blocks858. The one or more receiver radio-frequency (RX RF) blocks858may output analog signals to one or more analog-to-digital converters (ADCs)856. For example, a receiver radio-frequency block858may receive and downconvert a signal, which may be provided to an analog-to-digital converter856. As with the access point802, the number of spatial streams838processed may or may not be equal to the number of antennas836a-n. Furthermore, each spatial stream838need not be limited to one antenna836, as various beamsteering, orthogonalization, etc. techniques may be used to arrive at a plurality of receiver streams.

The one or more analog-to-digital converters (ADCs)856may convert the received analog signal(s) to one or more digital signal(s). These output(s) of the one or more analog-to-digital converters (ADCs)856may be provided to one or more time and/or frequency synchronization blocks/modules854. A time and/or frequency synchronization block/module854may (attempt to) synchronize or align the digital signal in time and/or frequency (to an access terminal842clock, for example).

The (synchronized) output of the time and/or frequency synchronization block(s)/module(s)854may be provided to one or more deformatters852. For example, a deformatter852may receive an output of the time and/or frequency synchronization block(s)/module(s)854, remove prefixes, etc. and/or parallelize the data for fast Fourier transform (FFT) processing.

One or more deformatter852outputs may be provided to one or more fast Fourier transform (FFT) blocks/modules850. The fast Fourier transform (FFT) blocks/modules850may convert one or more signals from the time domain to the frequency domain. A pilot processor848may use the frequency domain signals (per spatial stream838, for example) to determine one or more pilot tones (over the spatial streams838, frequency subcarriers840and/or groups of symbol periods, for example) sent by the access point802. The pilot processor848may additionally or alternatively de-scramble the pilot sequence. The pilot processor848may use the one or more pilot sequences described herein for phase and/or frequency and/or amplitude tracking. The pilot tone(s) may be provided to a space-time-frequency detection and/or decoding block/module846, which may detect and/or decode the data over the various dimensions. The space-time-frequency detection and/or decoding block/module846may output received data844(e.g., the access terminal's842estimation of the payload data804and/or preamble data816transmitted by the access point802).

In some configurations, the access terminal842knows the transmit sequences sent as part of a total information sequence. The access terminal842may perform channel estimation with the aid of these known transmit sequences. To assist with pilot tone tracking, processing and/or data detection and decoding, a channel estimation block/module860may provide estimation signals to the pilot processor848and/or the space-time-frequency detection and/or decoding block/module846based on the output from the time and/or frequency synchronization block/module854. Alternatively, if the de-formatting and fast Fourier transform is the same for the known transmit sequences as for the payload data portion of the total information sequence, the estimation signals may be provided to the pilot processor848and/or the space-time-frequency detection and/or decoding block/module846based on the output from the fast Fourier transform (FFT) blocks/modules850.

The bandwidth determination block/module834may use the time/frequency synchronization block/module output to determine a channel bandwidth (for received communications). For example, the bandwidth determination block/module834may receive a bandwidth indication from the access point802that indicates a channel bandwidth. For instance, the bandwidth determination block/module834may obtain an explicit or implicit bandwidth indication. In one configuration, the bandwidth indication may indicate a channel bandwidth of 20 MHz, 40 MHz, 80 MHz or 160 MHz. The bandwidth determination block/module834may determine the bandwidth for received communications based on this indication and provide an indication of the determined bandwidth to the pilot processor848and/or to the space-time-frequency detection/decoding block/module846.

More specifically, if the determined bandwidth is 20 MHz, the access terminal842may receive 12 OFDM tones for the L-STF, 52 for the L-LTF, 52 for the L-SIG field, 52 for the VHT-SIG-A1field or symbol, 52 for the VHT-SIG-A2field or symbol, 12 for the VHT-STF, 56 for one or more VHT-LTFs, 56 for the VHT-SIG-B field and/or 56 for the DATA field. If the bandwidth determined is 40 MHz, the access terminal842may receive 24 OFDM tones for the L-STF, 104 for the L-LTF, 104 for the L-SIG field, 104 for the VHT-SIG-A1field or symbol, 104 for the VHT-SIG-A2field or symbol, 24 for the VHT-STF, 114 for one or more VHT-LTFs, 114 for the VHT-SIG-B field and/or 114 for the DATA field. If the bandwidth is 80 MHz, the access terminal842may receive 48 OFDM tones for the L-STF, 208 for the L-LTF, 208 for the L-SIG field, 208 for the VHT-SIG-A1field or symbol, 208 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 242 for one or more VHT-LTFs, 242 for the VHT-SIG-B field and/or 242 for the DATA field. If the bandwidth is 160 MHz, the access terminal842may receive 48 OFDM tones for the L-STF, 416 for the L-LTF, 416 for the L-SIG field, 416 for the VHT-SIG-A1field or symbol, 416 for the VHT-SIG-A2field or symbol, 48 for the VHT-STF, 484 for one or more VHT-LTFs, 484 for the VHT-SIG-B field or symbol and/or 484 for the DATA field.

The pilot processor848may use the determined bandwidth indication to extract pilot symbols from the fast Fourier transform block/module850output. For example, if the determined bandwidth indication specifies an 80 MHz bandwidth863, the pilot processor848may extract pilot symbols from the indices −103, −75, −39, −11, 11, 39, 75 and 103.

The space-time frequency detection/decoding block/module846may use the determined bandwidth indication to detect and/or decode preamble data from the received signal. For example, if the current field is a VHT-SIG-B field and the determined bandwidth indication specifies that the bandwidth is 80 MHz, then the space-time frequency detection/decoding block/module846may detect and/or decode preamble data from 234 OFDM tones or subcarriers840(while eight OFDM tones are pilot tones and three subcarriers840are used for DC tones, for instance). In some configurations, the space-time-frequency detection/decoding block/module846may use a look-up table to determine the number of tones or subcarriers to receive for a specified bandwidth.

In one configuration, an access terminal842may also transmit data857(e.g., preamble data and/or payload data) to the access point802. For example, an access terminal842may include a transmitter859. The transmitter859may include a transmission bandwidth determination block/module861(illustrated as “Transmission Bandwidth” inFIG. 8for convenience). The transmission bandwidth determination block/module861may determine a communication bandwidth for a transmission to the access point802. For instance, the transmitter859may perform the same or similar operations for allocating tones for a frame as performed by the access point802. Thus, for example, the transmitter859may obtain data857, determine a bandwidth, allocate tones for a frame based on the bandwidth (and a frame field or signal), map data and pilots to the tones and/or transmit the resulting signal similar to the access point802.

In some configurations, the access point802may include a receiver853for receiving data and/or pilot symbols. For example, the access point802may receive a bandwidth indication, data and/or a pilot symbols from the access terminal842. The receiver853may include a reception bandwidth determination block/module855(illustrated as “Reception Bandwidth” inFIG. 8for convenience). The reception bandwidth determination block/module855may determine a reception bandwidth in a similar manner as the bandwidth determination block/module834included in the access terminal842. For instance, the access point802may receive a bandwidth indication or message from the access terminal842, which it802may use to determine a reception bandwidth. The access point802may use this reception bandwidth determination to detect, decode, demodulate, etc. one or more signals received from the access terminal842. For instance, the receiver853may similarly perform one or more operations performed by the access terminal842. In other words, the receiver853may similarly perform one or more operations to receive tones for a frame (e.g., received data851) that are performed by the access terminal842to obtain its received data844.

FIG. 9is a block diagram of a communication device965that may be used in a multiple-input and multiple-output (MIMO) system. Examples of the communication device965may include transmitting communication devices102, receiving communication devices142, access points802, access terminals842, base stations, user equipment (UEs), etc. In the communication device965, traffic data for a number of data streams is provided from one or more data sources967and/or an application processor969to a baseband processor973. In particular, traffic data may be provided to a transmit processing block/module977included in the baseband processor973. Each data stream may then be transmitted over a respective transmit antenna995a-n. The transmit processing block/module977may format, code and interleave the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

The transmit processing block/module977may perform the method600illustrated inFIG. 6. For example, the transmit processing block/module977may include a tone allocation block/module979. The tone allocation block/module979may execute instructions in order to allocate tones for a frame.

The coded data for each data stream may be multiplexed with pilot data from a pilot generator975using orthogonal frequency-division multiplexing (OFDM) techniques. The pilot data may be a known data pattern that is processed in a known manner and used at a receiver to estimate the channel response. The multiplexed pilot and coded data for each stream is then modulated (i.e., symbol mapped) based on a particular modulation scheme (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), multiple phase shift keying (M-PSK), quadrature amplitude modulation (QAM) or multi-level quadrature amplitude modulation (M-QAM)) selected for that data stream to provide modulation symbols. The data rate, coding and modulation for each data stream may be determined by instructions performed by a processor.

The modulation symbols for all data streams may be provided to a transmit (TX) multiple-input multiple-output (MIMO) processing block/module989, which may further process the modulation symbols (e.g., for OFDM). The transmit (TX) multiple-input multiple-output (MIMO) processing block/module989then provides a number of modulation symbol streams to the transmitters993a-n. The TX transmit (TX) multiple-input multiple-output (MIMO) processing block/module989may apply beamforming weights to the symbols of the data streams and to the antenna995from which the symbol is being transmitted.

Each transmitter993may receive and process a respective symbol stream to provide one or more analog signals, and further condition (e.g., amplify, filter, and upconvert) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. Modulated signals from the transmitters993a-nare then respectively transmitted from the antennas995a-n. For example, the modulated signal may be transmitted to another communication device (not illustrated inFIG. 9).

The communication device965may receive modulated signals (from another communication device). These modulated signals are received by antennas995and conditioned by receivers993(e.g., filtered, amplified, downconverted, digitized). In other words, each receiver993may condition (e.g., filter, amplify, and downconvert) a respective received signal, digitize the conditioned signal to provide samples, and further process the samples to provide a corresponding “received” symbol stream.

A receive processing block/module983included in the baseband processor973then receives and processes the received symbol streams from the receivers993based on a particular receiver processing technique to provide a number of “detected” streams. The receive processing block/module983demodulates, deinterleaves and decodes each stream to recover the traffic data for the data stream.

The receive processing block/module983may perform the method700illustrated inFIG. 7. For example, the receive processing block/module983may include a tone reception block/module985. The tone reception block/module985may execute instructions to receive tones for a frame.

A precoding processing block/module981included in the baseband processor973may receive channel state information (CSI) from the receive processing block/module983. The precoding processing block/module981then determines which pre-coding matrix to use for determining the beamforming weights and then processes the extracted message. It should be noted that the baseband processor973may store information on and retrieve information from baseband memory987.

The traffic data recovered by the baseband processor973may be provided to the application processor969. The application processor969may store information in and retrieve information from the application memory971.

FIG. 10illustrates certain components that may be included within a communication device, base station and/or access point1097. The transmitting communication device102, receiving communication device142, access point802and/or communication device965described above may be configured similarly to the communication device/base station/access point1097that is shown inFIG. 10.

The communication device/base station/access point1097includes a processor1015. The processor1015may be a general purpose single- or multi-chip microprocessor (e.g., an ARM), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor1015may be referred to as a central processing unit (CPU). Although just a single processor1015is shown in the communication device/base station/access point1097ofFIG. 10, in an alternative configuration, a combination of processors (e.g., an ARM and DSP) could be used.

The communication device/base station/access point1097also includes memory1099in electronic communication with the processor1015(i.e., the processor1015can read information from and/or write information to the memory1099). The memory1099may be any electronic component capable of storing electronic information. The memory1099may be random access memory (RAM), read-only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable PROM (EEPROM), registers, and so forth, including combinations thereof.

Data1001and instructions1003may be stored in the memory1099. The instructions1003may include one or more programs, routines, sub-routines, functions, procedures, code, etc. The instructions1003may include a single computer-readable statement or many computer-readable statements. The instructions1003may be executable by the processor1015to implement the methods600,700described above. Executing the instructions1003may involve the use of the data1001that is stored in the memory1099.FIG. 10shows some instructions1003aand data1001abeing loaded into the processor1015.

The communication device/base station/access point1097may also include a transmitter1011and a receiver1013to allow transmission and reception of signals between the communication device/base station/access point1097and a remote location (e.g., another communication device, access terminal, access point, etc.). The transmitter1011and receiver1013may be collectively referred to as a transceiver1009. An antenna1007may be electrically coupled to the transceiver1009. The communication device/base station/access point1097may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers and/or multiple antenna.

The various components of the communication device/base station/access point1097may be coupled together by one or more buses, which may include a power bus, a control signal bus, a status signal bus, a data bus, etc. For simplicity, the various buses are illustrated inFIG. 10as a bus system1005.

FIG. 11illustrates certain components that may be included within a wireless communication device and/or access terminal1117. One or more of the transmitting communication device102, receiving communication device142, access terminal842and communication device965described above may be configured similarly to the wireless communication device/access terminal1117that is shown inFIG. 11.

The wireless communication device/access terminal1117includes a processor1137. The processor1137may be a general purpose single- or multi-chip microprocessor (e.g., an ARM), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor1137may be referred to as a central processing unit (CPU). Although just a single processor1137is shown in the wireless communication device/access terminal1117ofFIG. 11, in an alternative configuration, a combination of processors1137(e.g., an ARM and DSP) could be used.

The wireless communication device/access terminal1117also includes memory1119in electronic communication with the processor1137(i.e., the processor1137can read information from and/or write information to the memory1119). The memory1119may be any electronic component capable of storing electronic information. The memory1119may be random access memory (RAM), read-only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor1137, programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable PROM (EEPROM), registers, and so forth, including combinations thereof.

Data1121aand instructions1123amay be stored in the memory1119. The instructions1123amay include one or more programs, routines, sub-routines, functions, procedures, code, etc. The instructions1123amay include a single computer-readable statement or many computer-readable statements. The instructions1123amay be executable by the processor1137to implement one or more of the methods600,700described above. Executing the instructions1123amay involve the use of the data1121athat is stored in the memory1119.FIG. 11shows some instructions1123band data1121bbeing loaded into the processor1137(which may come from instructions1123aand data1121ain memory1119).

The wireless communication device/access terminal1117may also include a transmitter1133and a receiver1135to allow transmission and reception of signals between the wireless communication device/access terminal1117and a remote location (e.g., another electronic device, wireless communication device, etc.). The transmitter1133and receiver1135may be collectively referred to as a transceiver1131. An antenna1129may be electrically coupled to the transceiver1131. The wireless communication device/access terminal1117may also include (not shown) multiple transmitters1133, multiple receivers1135, multiple transceivers1131and/or multiple antenna1129.

In some configurations, the wireless communication device/access terminal1117may include one or more microphones1125for capturing acoustic signals. In one configuration, a microphone1125may be a transducer that converts acoustic signals (e.g., voice, speech) into electrical or electronic signals. Additionally or alternatively, the wireless communication device/access terminal1117may include one or more speakers1127. In one configuration, a speaker1127may be a transducer that converts electrical or electronic signals into acoustic signals.

The various components of the wireless communication device/access terminal1117may be coupled together by one or more buses, which may include a power bus, a control signal bus, a status signal bus, a data bus, etc. For simplicity, the various buses are illustrated inFIG. 11as a bus system1139.

The functions described herein may be stored as one or more instructions on a processor-readable or computer-readable medium. The term “computer-readable medium” refers to any available medium that can be accessed by a computer or processor. By way of example, and not limitation, such a medium may comprise RAM, ROM, EEPROM, flash memory, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer or processor. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. It should be noted that a computer-readable medium may be tangible and non-transitory. The term “computer-program product” refers to a computing device or processor in combination with code or instructions (e.g., a “program”) that may be executed, processed or computed by the computing device or processor. As used herein, the term “code” may refer to software, instructions, code or data that is/are executable by a computing device or processor.