Doppler adaptation using pilot patterns within single user, multiple user, multiple access, and/or MIMO wireless communications
Doppler adaptation using pilot patterns within single user, multiple user, multiple access, and/or MIMO wireless communications. Within a communication system employing orthogonal frequency division multiplexing (OFDM) signaling, pilots may be adaptively and/or selectively located at different respective sub-carrier or tone locations within different respective symbols based on one or more patterns. In some implementations, decimation may also be performed such that not necessarily all respective tone or sub-carrier locations are covered within one particular group. Multiple respective groups may be employed to cover all possible tone or sub-carrier locations with at least one pilot over a particular number of symbols. In a receiver communication device operating using such decimation, interpolation over the decimated set of tones or sub-carriers may be made to effectuate channel estimate updates.
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The present U.S. Utility patent application claims priority pursuant to 35 U.S.C. §119(e) to the following U.S. Provisional Patent Applications which are hereby incorporated herein by reference in their entirety and made part of the present U.S. Utility patent application for all purposes:
1. U.S. Provisional Patent Application Ser. No. 61/478,537, entitled “Preamble for use within multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090), filed Apr. 24, 2011, pending.
2. U.S. Provisional Patent Application Ser. No. 61/493,577, entitled “Preamble for use within multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.1), filed Jun. 6, 2011, pending.
3. U.S. Provisional Patent Application Ser. No. 61/496,153, entitled “Preamble for use within multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.2), filed Jun. 13, 2011, pending.
4. U.S. Provisional Patent Application Ser. No. 61/501,239, entitled “Preamble for use within multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.3), filed Jun. 26, 2011, pending.
5. U.S. Provisional Patent Application Ser. No. 61/507,955, entitled “Preamble for use within multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.4), filed Jul. 14, 2011, pending.
6. U.S. Provisional Patent Application Ser. No. 61/512,363, entitled “Preamble for use within multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.5), filed Jul. 27, 2011, pending.
7. U.S. Provisional Patent Application Ser. No. 61/522,608, entitled “Preamble for use within multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.6), filed Aug. 11, 2011, pending.
8. U.S. Provisional Patent Application Ser. No. 61/542,602, entitled “Preamble for use within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.7), filed Oct. 3, 2011, pending.
9. U.S. Provisional Patent Application Ser. No. 61/561,722, entitled “Preamble for use within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.8), filed Nov. 18, 2011, pending.
10. U.S. Provisional Patent Application Ser. No. 61/577,597, entitled “Preamble for use within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.9), filed Dec. 19, 2011, pending.
11. U.S. Provisional Patent Application Ser. No. 61/584,142, entitled “Preamble for use within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.10), filed Jan. 6, 2012, pending.
12. U.S. Provisional Patent Application Ser. No. 61/592,514, entitled “Preamble for use within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.11), filed Jan. 30, 2012, pending.
13. U.S. Provisional Patent Application Ser. No. 61/595,616, entitled “Preamble for use within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.12), filed Feb. 6, 2012, pending.
14. U.S. Provisional Patent Application Ser. No. 61/598,293, entitled “Preamble for use within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.13), filed Feb. 13, 2012; pending.
15. U.S. Provisional Patent Application Ser. No. 61/602,504, entitled “Preamble for use within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.14), filed Feb. 23, 2012, pending.
Incorporation by ReferenceThe following U.S. Utility patent applications are hereby incorporated herein by reference in their entirety and made part of the present U.S. Utility patent application for all purposes:
1. U.S. Utility patent application Ser. No. 13/453,703, entitled “Preamble for use within multiple user, multiple access, and/or MIMO wireless communications,”, filed concurrently on Apr. 23, 2012, pending.
2. U.S. Utility patent application Ser. No. ______, entitled “Long training field (LTF) for use within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.2), filed concurrently on Apr. 23, 2012, pending.
3. U.S. Utility patent application Ser. No. ______, entitled “Short training field (STF) for use within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.3), filed concurrently on Apr. 23, 2012, pending.
4. U.S. Utility patent application Ser. No. ______, entitled “Device coexistence within single user, multiple user, multiple access, and/or MIMO wireless communications,” (Attorney Docket No. BP23090.4), filed concurrently on Apr. 23, 2012, pending.
Incorporation by ReferenceThe following IEEE standards/draft IEEE standards are hereby incorporated herein by reference in their entirety and are made part of the present U.S. Utility Patent Application for all purposes:
1. IEEE Std 802.11™—2012, “IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements; Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,” IEEE Computer Society, Sponsored by the LAN/MAN Standards Committee, IEEE Std 802.11™—2012, (Revision of IEEE Std 802.11-2007), 2793 total pages (incl. pp. i-xcvi, 1-2695).
2. IEEE Std 802.11n™—2009, “IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements; Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications; Amendment 5: Enhancements for Higher Throughput,” IEEE Computer Society, IEEE Std 802.11n™—2009, (Amendment to IEEE Std 802.11™—2007 as amended by IEEE Std 802.11k™ —2008, IEEE Std 802.11r™—2008, IEEE Std 802.11y™—2008, and IEEE Std 802.11r™—2009), 536 total pages (incl. pp. i-xxxii, 1-502).
3. IEEE Draft P802.11-REVmb™/D12, November 2011 (Revision of IEEE Std 802.11™—2007 as amended by IEEE Std 802.11k™—2008, IEEE Std 802.11r™—2008, IEEE Std 802.11y™—2008, IEEE Std 802.11w™—2009, IEEE Std 802.11n™—2009, IEEE Std 802.11p™—2010, IEEE Std 802.11z™—2010, IEEE Std 802.11v™—2011, IEEE Std 802.11u™—2011, and IEEE Std 802.11s™—2011), “IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements; Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,” Prepared by the 802.11 Working Group of the LAN/MAN Standards Committee of the IEEE Computer Society, 2910 total pages (incl. pp. i-cxxviii, 1-2782).
4. IEEE P802.11ac™/D2.1, March 2012, “Draft STANDARD for Information Technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications, Amendment 4: Enhancements for Very High Throughput for Operation in Bands below 6 GHz,” Prepared by the 802.11 Working Group of the 802 Committee, 363 total pages (incl. pp. i-xxv, 1-338).
5. IEEE P802.11ad™/D6.0, March 2012, (Draft Amendment based on IEEE P802.11REVmb D12.0), (Amendment to IEEE P802.11REVmb D12.0 as amended by IEEE 802.11ae D8.0 and IEEE 802.11 as D9.0), “IEEE P802.11ad™/D6.0 Draft Standard for Information Technology—Telecommunications and Information Exchange Between Systems—Local and Metropolitan Area Networks—Specific Requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications—Amendment 3: Enhancements for Very High Throughput in the 60 GHz Band,” Sponsor: IEEE 802.11 Committee of the IEEE Computer Society, IEEE-SA Standards Board, 664 total pages.
6. IEEE Std 802.11ae™—2012, “IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements; Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,” “Amendment 1: Prioritization of Management Frames,” IEEE Computer Society, Sponsored by the LAN/MAN Standards Committee, IEEE Std 802.11ae™—2012, (Amendment to IEEE Std 802.11™—2012), 52 total pages (incl. pp. i-xii, 1-38).
7. IEEE P802.11af™/D1.06, March 2012, (Amendment to IEEE Std 802.11REVmb™/D12.0 as amended by IEEE Std 802.11ae™/D8.0, IEEE Std 802.11aa™/D9.0, IEEE Std 802.11ad™/D5.0, and IEEE Std 802.11ac™/D2.0), “Draft Standard for Information Technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications—Amendment 5: TV White Spaces Operation,” Prepared by the 802.11 Working Group of the IEEE 802 Committee, 140 total pages (incl. pp. i-xxii, 1-118).
BACKGROUND OF THE INVENTION1. Technical Field of the Invention
The invention relates generally to communication systems; and, more particularly, it relates to effectuating long range and low rate wireless communications within such communication systems.
2. Description of Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11x, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the Internet, and/or via some other wide area network.
For each wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the receiver is coupled to the antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives inbound RF signals via the antenna and amplifies then. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signal into baseband signals or intermediate frequency (IF) signals. The filtering stage filters the baseband signals or the IF signals to attenuate unwanted out of band signals to produce filtered signals. The data recovery stage recovers raw data from the filtered signals in accordance with the particular wireless communication standard.
As is also known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts raw data into baseband signals in accordance with a particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier amplifies the RF signals prior to transmission via an antenna.
Typically, the transmitter will include one antenna for transmitting the RF signals, which are received by a single antenna, or multiple antennae (alternatively, antennas), of a receiver. When the receiver includes two or more antennae, the receiver will select one of them to receive the incoming RF signals. In this instance, the wireless communication between the transmitter and receiver is a single-output-single-input (SISO) communication, even if the receiver includes multiple antennae that are used as diversity antennae (i.e., selecting one of them to receive the incoming RF signals). For SISO wireless communications, a transceiver includes one transmitter and one receiver. Currently, most wireless local area networks (WLAN) that are IEEE 802.11, 802.11a, 802.11b, or 802.11g employ SISO wireless communications.
Other types of wireless communications include single-input-multiple-output (SIMO), multiple-input-single-output (MISO), and multiple-input-multiple-output (MIMO). In a SIMO wireless communication, a single transmitter processes data into radio frequency signals that are transmitted to a receiver. The receiver includes two or more antennae and two or more receiver paths. Each of the antennae receives the RF signals and provides them to a corresponding receiver path (e.g., LNA, down conversion module, filters, and ADCs). Each of the receiver paths processes the received RF signals to produce digital signals, which are combined and then processed to recapture the transmitted data.
For a multiple-input-single-output (MISO) wireless communication, the transmitter includes two or more transmission paths (e.g., digital to analog converter, filters, up-conversion module, and a power amplifier) that each converts a corresponding portion of baseband signals into RF signals, which are transmitted via corresponding antennae to a receiver. The receiver includes a single receiver path that receives the multiple RF signals from the transmitter. In this instance, the receiver uses beam forming to combine the multiple RF signals into one signal for processing.
For a multiple-input-multiple-output (MIMO) wireless communication, the transmitter and receiver each include multiple paths. In such a communication, the transmitter parallel processes data using a spatial and time encoding function to produce two or more streams of data. The transmitter includes multiple transmission paths to convert each stream of data into multiple RF signals. The receiver receives the multiple RF signals via multiple receiver paths that recapture the streams of data utilizing a spatial and time decoding function. The recaptured streams of data are combined and subsequently processed to recover the original data.
With the various types of wireless communications (e.g., SISO, MISO, SIMO, and MIMO), it would be desirable to use one or more types of wireless communications to enhance data throughput within a WLAN. For example, high data rates can be achieved with MIMO communications in comparison to SISO communications. However, most WLAN include legacy wireless communication devices (i.e., devices that are compliant with an older version of a wireless communication standard). As such, a transmitter capable of MIMO wireless communications should also be backward compatible with legacy devices to function in a majority of existing WLANs.
Therefore, a need exists for a WLAN device that is capable of high data throughput and is backward compatible with legacy devices.
The base stations (BSs) or access points (APs) 12-16 are operably coupled to the network hardware 34 via local area network connections 36, 38 and 40. The network hardware 34, which may be a router, switch, bridge, modem, system controller, etc., provides a wide area network connection 42 for the communication system 10. Each of the base stations or access points 12-16 has an associated antenna or antenna array to communicate with the wireless communication devices in its area. Typically, the wireless communication devices register with a particular base station or access point 12-14 to receive services from the communication system 10. For direct connections (i.e., point-to-point communications), wireless communication devices communicate directly via an allocated channel.
Typically, base stations are used for cellular telephone systems (e.g., advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), Enhanced Data rates for GSM Evolution (EDGE), General Packet Radio Service (GPRS), high-speed downlink packet access (HSDPA), high-speed uplink packet access (HSUPA and/or variations thereof) and like-type systems, while access points are used for in-home or in-building wireless networks (e.g., IEEE 802.11, Bluetooth, ZigBee, any other type of radio frequency based network protocol and/or variations thereof). Regardless of the particular type of communication system, each wireless communication device includes a built-in radio and/or is coupled to a radio. Such wireless communication devices may operate in accordance with the various aspects of the invention as presented herein to enhance performance, reduce costs, reduce size, and/or enhance broadband applications.
As illustrated, the host device 18-32 includes a processing module 50, memory 52, radio interface 54, input interface 58 and output interface 56. The processing module 50 and memory 52 execute the corresponding instructions that are typically done by the host device. For example, for a cellular telephone host device, the processing module 50 performs the corresponding communication functions in accordance with a particular cellular telephone standard.
The radio interface 54 allows data to be received from and sent to the radio 60. For data received from the radio 60 (e.g., inbound data), the radio interface 54 provides the data to the processing module 50 for further processing and/or routing to the output interface 56. The output interface 56 provides connectivity to an output display device such as a display, monitor, speakers, etc. such that the received data may be displayed. The radio interface 54 also provides data from the processing module 50 to the radio 60. The processing module 50 may receive the outbound data from an input device such as a keyboard, keypad, microphone, etc. via the input interface 58 or generate the data itself. For data received via the input interface 58, the processing module 50 may perform a corresponding host function on the data and/or route it to the radio 60 via the radio interface 54.
Radio 60 includes a host interface 62, a baseband processing module 64, memory 66, a plurality of radio frequency (RF) transmitters 68-72, a transmit/receive (T/R) module 74, a plurality of antennae 82-86, a plurality of RF receivers 76-80, and a local oscillation module 100. The baseband processing module 64, in combination with operational instructions stored in memory 66, execute digital receiver functions and digital transmitter functions, respectively. The digital receiver functions, as will be described in greater detail with reference to
In operation, the radio 60 receives outbound data 88 from the host device via the host interface 62. The baseband processing module 64 receives the outbound data 88 and, based on a mode selection signal 102, produces one or more outbound symbol streams 90. The mode selection signal 102 will indicate a particular mode as are illustrated in the mode selection tables, which appear at the end of the detailed discussion. For example, the mode selection signal 102, with reference to table 1 may indicate a frequency band of 2.4 GHz or 5 GHz, a channel bandwidth of 20 or 22 MHz (e.g., channels of 20 or 22 MHz width) and a maximum bit rate of 54 megabits-per-second. In other embodiments, the channel bandwidth may extend up to 1.28 GHz or wider with supported maximum bit rates extending to 1 gigabit-per-second or greater. In this general category, the mode selection signal will further indicate a particular rate ranging from 1 megabit-per-second to 54 megabits-per-second. In addition, the mode selection signal will indicate a particular type of modulation, which includes, but is not limited to, Barker Code Modulation, BPSK, QPSK, CCK, 16 QAM and/or 64 QAM. As is further illustrated in table 1, a code rate is supplied as well as number of coded bits per sub-carrier (NBPSC), coded bits per OFDM symbol (NCBPS), data bits per OFDM symbol (NDBPS).
The mode selection signal may also indicate a particular channelization for the corresponding mode which for the information in table 1 is illustrated in table 2. As shown, table 2 includes a channel number and corresponding center frequency. The mode select signal may further indicate a power spectral density mask value which for table 1 is illustrated in table 3. The mode select signal may alternatively indicate rates within table 4 that has a 5 GHz frequency band, 20 MHz channel bandwidth and a maximum bit rate of 54 megabits-per-second. If this is the particular mode select, the channelization is illustrated in table 5. As a further alternative, the mode select signal 102 may indicate a 2.4 GHz frequency band, 20 MHz channels and a maximum bit rate of 192 megabits-per-second as illustrated in table 6. In table 6, a number of antennae may be utilized to achieve the higher bit rates. In this instance, the mode select would further indicate the number of antennae to be utilized. Table 7 illustrates the channelization for the set-up of table 6. Table 8 illustrates yet another mode option where the frequency band is 2.4 GHz, the channel bandwidth is 20 MHz and the maximum bit rate is 192 megabits-per-second. The corresponding table 8 includes various bit rates ranging from 12 megabits-per-second to 216 megabits-per-second utilizing 2-4 antennae and a spatial time encoding rate as indicated. Table 9 illustrates the channelization for table 8. The mode select signal 102 may further indicate a particular operating mode as illustrated in table 10, which corresponds to a 5 GHz frequency band having 40 MHz frequency band having 40 MHz channels and a maximum bit rate of 486 megabits-per-second. As shown in table 10, the bit rate may range from 13.5 megabits-per-second to 486 megabits-per-second utilizing 1-4 antennae and a corresponding spatial time code rate. Table 10 further illustrates a particular modulation scheme code rate and NBPSC values. Table 11 provides the power spectral density mask for table 10 and table 12 provides the channelization for table 10.
It is of course noted that other types of channels, having different bandwidths, may be employed in other embodiments without departing from the scope and spirit of the invention. For example, various other channels such as those having 80 MHz, 120 MHz, and/or 160 MHz of bandwidth may alternatively be employed such as in accordance with IEEE Task Group ac (TGac VHTL6).
The baseband processing module 64, based on the mode selection signal 102 produces the one or more outbound symbol streams 90, as will be further described with reference to
Depending on the number of outbound streams 90 produced by the baseband module 64, a corresponding number of the RF transmitters 68-72 will be enabled to convert the outbound symbol streams 90 into outbound RF signals 92. The implementation of the RF transmitters 68-72 will be further described with reference to
When the radio 60 is in the receive mode, the transmit/receive module 74 receives one or more inbound RF signals via the antennae 82-86. The T/R module 74 provides the inbound RF signals 94 to one or more RF receivers 76-80. The RF receiver 76-80, which will be described in greater detail with reference to
In one embodiment of radio 60 it includes a transmitter and a receiver. The transmitter may include a MAC module, a PLCP module, and a PMD module. The Medium Access Control (MAC) module, which may be implemented with the processing module 64, is operably coupled to convert a MAC Service Data Unit (MSDU) into a MAC Protocol Data Unit (MPDU) in accordance with a WLAN protocol. The Physical Layer Convergence Procedure (PLCP) Module, which may be implemented in the processing module 64, is operably coupled to convert the MPDU into a PLCP Protocol Data Unit (PPDU) in accordance with the WLAN protocol. The Physical Medium Dependent (PMD) module is operably coupled to convert the PPDU into a plurality of radio frequency (RF) signals in accordance with one of a plurality of operating modes of the WLAN protocol, wherein the plurality of operating modes includes multiple input and multiple output combinations.
An embodiment of the Physical Medium Dependent (PMD) module, which will be described in greater detail with reference to
As one of average skill in the art will appreciate, the wireless communication device of
The analog filter 79 filters the analog signals 89 to produce filtered analog signals 91. The up-conversion module 81, which may include a pair of mixers and a filter, mixes the filtered analog signals 91 with a local oscillation 93, which is produced by local oscillation module 100, to produce high frequency signals 95. The frequency of the high frequency signals 95 corresponds to the frequency of the outbound RF signals 92.
The power amplifier 83 amplifies the high frequency signals 95 to produce amplified high frequency signals 97. The RF filter 85, which may be a high frequency band-pass filter, filters the amplified high frequency signals 97 to produce the desired output RF signals 92.
As one of average skill in the art will appreciate, each of the radio frequency transmitters 68-72 will include a similar architecture as illustrated in
The down-conversion module 107 includes a pair of mixers, a summation module, and a filter to mix the inbound RF signals with a local oscillation (LO) that is provided by the local oscillation module to produce analog baseband signals. The analog filter 109 filters the analog baseband signals and provides them to the analog-to-digital conversion module 111 which converts them into a digital signal. The digital filter and down-sampling module 113 filters the digital signals and then adjusts the sampling rate to produce the digital samples (corresponding to the inbound symbol streams 96).
The process then proceeds to Step 114 where the baseband processing module selects one of a plurality of encoding modes based on the mode selection signal. The process then proceeds to Step 116 where the baseband processing module encodes the scrambled data in accordance with a selected encoding mode to produce encoded data. The encoding may be done utilizing any one or more a variety of coding schemes (e.g., convolutional coding, Reed-Solomon (RS) coding, turbo coding, turbo trellis coded modulation (TTCM) coding, LDPC (Low Density Parity Check) coding, etc.).
The process then proceeds to Step 118 where the baseband processing module determines a number of transmit streams based on the mode select signal. For example, the mode select signal will select a particular mode which indicates that 1, 2, 3, 4 or more antennae may be utilized for the transmission. Accordingly, the number of transmit streams will correspond to the number of antennae indicated by the mode select signal. The process then proceeds to Step 120 where the baseband processing module converts the encoded data into streams of symbols in accordance with the number of transmit streams in the mode select signal. This step will be described in greater detail with reference to
The process then proceeds to Step 124 where the baseband processing module demultiplexes the interleaved data into a number of parallel streams of interleaved data. The number of parallel streams corresponds to the number of transmit streams, which in turn corresponds to the number of antennae indicated by the particular mode being utilized. The process then continues to Steps 126 and 128, where for each of the parallel streams of interleaved data, the baseband processing module maps the interleaved data into a quadrature amplitude modulated (QAM) symbol to produce frequency domain symbols at Step 126. At Step 128, the baseband processing module converts the frequency domain symbols into time domain symbols, which may be done utilizing an inverse fast Fourier transform. The conversion of the frequency domain symbols into the time domain symbols may further include adding a cyclic prefix to allow removal of intersymbol interference at the receiver. Note that the length of the inverse fast Fourier transform and cyclic prefix are defined in the mode tables of tables 1-12. In general, a 64-point inverse fast Fourier transform is employed for 20 MHz channels and 128-point inverse fast Fourier transform is employed for 40 MHz channels.
The process then proceeds to Step 130 where the baseband processing module space and time encodes the time domain symbols for each of the parallel streams of interleaved data to produce the streams of symbols. In one embodiment, the space and time encoding may be done by space and time encoding the time domain symbols of the parallel streams of interleaved data into a corresponding number of streams of symbols utilizing an encoding matrix. Alternatively, the space and time encoding may be done by space and time encoding the time domain symbols of M-parallel streams of interleaved data into P-streams of symbols utilizing the encoding matrix, where P=2M. In one embodiment the encoding matrix may comprise a form of:
The number of rows of the encoding matrix corresponds to M and the number of columns of the encoding matrix corresponds to P. The particular symbol values of the constants within the encoding matrix may be real or imaginary numbers.
Also, the process continues at Step 140 where the baseband processing module performs a convolutional encoding with a 64 state code and generator polynomials of G0=1338 and G1=1718 on the scrambled data (that may or may not have undergone RS encoding) to produce convolutional encoded data. The process then proceeds to Step 142 where the baseband processing module punctures the convolutional encoded data at one of a plurality of rates in accordance with the mode selection signal to produce the encoded data. Note that the puncture rates may include ½, ⅔ and/or ¾, or any rate as specified in tables 1-12. Note that, for a particular, mode, the rate may be selected for backward compatibility with IEEE 802.11(a), IEEE 802.11(g), or IEEE 802.11(n) rate requirements.
The method then continues at Step 146 where the baseband processing module encodes the scrambled data (that may or may not have undergone RS encoding) in accordance with a complimentary code keying (CCK) code to produce the encoded data. This may be done in accordance with IEEE 802.11(b) specifications, IEEE 802.11(g), and/or IEEE 802.11(n) specifications.
Then, in some embodiments, the process continues at Step 150 where the baseband processing module performs LDPC (Low Density Parity Check) coding on the scrambled data (that may or may not have undergone RS encoding) to produce LDPC coded bits. Alternatively, the Step 150 may operate by performing convolutional encoding with a 256 state code and generator polynomials of G0=5618 and G1=7538 on the scrambled data the scrambled data (that may or may not have undergone RS encoding) to produce convolutional encoded data. The process then proceeds to Step 152 where the baseband processing module punctures the convolutional encoded data at one of the plurality of rates in accordance with a mode selection signal to produce encoded data. Note that the puncture rate is indicated in the tables 1-12 for the corresponding mode.
The encoding of
In operations, the scrambler 172 adds (e.g., in a Galois Finite Field (GF2)) a pseudo random sequence to the outbound data bits 88 to make the data appear random. A pseudo random sequence may be generated from a feedback shift register with the generator polynomial of S(x)=x7+x4+1 to produce scrambled data. The channel encoder 174 receives the scrambled data and generates a new sequence of bits with redundancy. This will enable improved detection at the receiver. The channel encoder 174 may operate in one of a plurality of modes. For example, for backward compatibility with IEEE 802.11(a) and IEEE 802.11(g), the channel encoder has the form of a rate ½ convolutional encoder with 64 states and a generator polynomials of G0=1338 and G1=1718. The output of the convolutional encoder may be punctured to rates of ½, ⅔, and ¾ according to the specified rate tables (e.g., tables 1-12). For backward compatibility with IEEE 802.11(b) and the CCK modes of IEEE 802.11(g), the channel encoder has the form of a CCK code as defined in IEEE 802.11(b). For higher data rates (such as those illustrated in tables 6, 8 and 10), the channel encoder may use the same convolution encoding as described above or it may use a more powerful code, including a convolutional code with more states, any one or more of the various types of error correction codes (ECCs) mentioned above (e.g., RS, LDPC, turbo, TTCM, etc.) a parallel concatenated (turbo) code and/or a low density parity check (LDPC) block code. Further, any one of these codes may be combined with an outer Reed Solomon code. Based on a balancing of performance, backward compatibility and low latency, one or more of these codes may be optimal. Note that the concatenated turbo encoding and low density parity check will be described in greater detail with reference to subsequent Figures.
The interleaver 176 receives the encoded data and spreads it over multiple symbols and transmit streams. This allows improved detection and error correction capabilities at the receiver. In one embodiment, the interleaver 176 will follow the IEEE 802.11(a) or (g) standard in the backward compatible modes. For higher performance modes (e.g., such as those illustrated in tables 6, 8 and 10), the interleaver will interleave data over multiple transmit streams. The demultiplexer 170 converts the serial interleave stream from interleaver 176 into M-parallel streams for transmission.
Each symbol mapper 180-184 receives a corresponding one of the M-parallel paths of data from the demultiplexer. Each symbol mapper 180-182 lock maps bit streams to quadrature amplitude modulated QAM symbols (e.g., BPSK, QPSK, 16 QAM, 64 QAM, 256 QAM, etc.) according to the rate tables (e.g., tables 1-12). For IEEE 802.11(a) backward compatibility, double Gray coding may be used.
The map symbols produced by each of the symbol mappers 180-184 are provided to the IFFT/cyclic prefix addition modules 186-190, which performs frequency domain to time domain conversions and adds a prefix, which allows removal of inter-symbol interference at the receiver. Note that the length of the IFFT and cyclic prefix are defined in the mode tables of tables 1-12. In general, a 64-point IFFT will be used for 20 MHz channels and 128-point IFFT will be used for 40 MHz channels.
The space/time encoder 192 receives the M-parallel paths of time domain symbols and converts them into P-output symbols. In one embodiment, the number of M-input paths will equal the number of P-output paths. In another embodiment, the number of output paths P will equal 2M paths. For each of the paths, the space/time encoder multiples the input symbols with an encoding matrix that has the form of
The rows of the encoding matrix correspond to the number of input paths and the columns correspond to the number of output paths.
In operation, the number of radio paths that are active correspond to the number of P-outputs. For example, if only one P-output path is generated, only one of the radio transmitter paths will be active. As one of average skill in the art will appreciate, the number of output paths may range from one to any desired number.
The digital filtering/up-sampling modules 194-198 filter the corresponding symbols and adjust the sampling rates to correspond with the desired sampling rates of the digital-to-analog conversion modules 200-204. The digital-to-analog conversion modules 200-204 convert the digital filtered and up-sampled signals into corresponding in-phase and quadrature analog signals. The analog filters 206-214 filter the corresponding in-phase and/or quadrature components of the analog signals, and provide the filtered signals to the corresponding I/Q modulators 218-222. The I/Q modulators 218-222 based on a local oscillation, which is produced by a local oscillator 100, up-converts the I/Q signals into radio frequency signals.
The RF amplifiers 224-228 amplify the RF signals which are then subsequently filtered via RF filters 230-234 before being transmitted via antennae 236-240.
In operation, the antennae receive inbound RF signals, which are band-pass filtered via the RF filters 252-256. The corresponding low noise amplifiers 258-262 amplify the filtered signals and provide them to the corresponding I/Q demodulators 264-268. The I/Q demodulators 264-268, based on a local oscillation, which is produced by local oscillator 100, down-converts the RF signals into baseband in-phase and quadrature analog signals.
The corresponding analog filters 270-280 filter the in-phase and quadrature analog components, respectively. The analog-to-digital converters 282-286 convert the in-phase and quadrature analog signals into a digital signal. The digital filtering and down-sampling modules 288-290 filter the digital signals and adjust the sampling rate to correspond to the rate of the baseband processing, which will be described in
The symbol demapping modules 302-306 convert the frequency domain symbols into data utilizing an inverse process of the symbol mappers 180-184. The multiplexer 308 combines the demapped symbol streams into a single path.
The deinterleaver 310 deinterleaves the single path utilizing an inverse function of the function performed by interleaver 176. The deinterleaved data is then provided to the channel decoder 312 which performs the inverse function of channel encoder 174. The descrambler 314 receives the decoded data and performs the inverse function of scrambler 172 to produce the inbound data 98.
The AP 1200 supports simultaneous communications with more than one of the WLAN devices 1202, 1204, and 1206. Simultaneous communications may be serviced via OFDM tone allocations (e.g., certain number of OFDM tones in a given cluster), MIMO dimension multiplexing, or via other techniques. With some simultaneous communications, the AP 1200 may allocate one or more of the multiple antennae thereof respectively to support communication with each WLAN device 1202, 1204, and 1206, for example.
Further, the AP 1200 and WLAN devices 1202, 1204, and 1206 are backwards compatible with the IEEE 802.11(a), (b), (g), and (n) operating standards. In supporting such backwards compatibility, these devices support signal formats and structures that are consistent with these prior operating standards.
Generally, communications as described herein may be targeted for reception by a single receiver or for multiple individual receivers (e.g. via multi-user multiple input multiple output (MU-MIMO), and/or OFDMA transmissions, which are different than single transmissions with a multi-receiver address). For example, a single OFDMA transmission uses different tones or sets of tones (e.g., clusters or channels) to send distinct sets of information, each set of set of information transmitted to one or more receivers simultaneously in the time domain. Again, an OFDMA transmission sent to one user is equivalent to an OFDM transmission (e.g., OFDM may be viewed as being a subset of OFDMA). A single MU-MIMO transmission may include spatially-diverse signals over a common set of tones, each containing distinct information and each transmitted to one or more distinct receivers. Some single transmissions may be a combination of OFDMA and MU-MIMO. Multi-user (MU), as described herein, may be viewed as being multiple users sharing at least one cluster (e.g., at least one channel within at least one band) at a same time.
MIMO transceivers illustrated may include SISO, SIMO, and MISO transceivers. The clusters employed for such communications (e.g., OFDMA communications) may be continuous (e.g., adjacent to one another) or discontinuous (e.g., separated by a guard interval of band gap). Transmissions on different OFDMA clusters may be simultaneous or non-simultaneous. Such wireless communication devices as described herein may be capable of supporting communications via a single cluster or any combination thereof. Legacy users and new version users (e.g., TGac MU-MIMO, OFDMA, MU-MIMO/OFDMA, etc.) may share bandwidth at a given time or they can be scheduled at different times for certain embodiments. Such a MU-MIMO/OFDMA transmitter (e.g., an AP or a STA) may transmit packets to more than one receiving wireless communication device (e.g., STA) on the same cluster (e.g., at least one channel within at least one band) in a single aggregated packet (such as being time multiplexed). In such an instance, channel training may be required for all communication links to the respective receiving wireless communication devices (e.g., STAs).
The wireless communication device of this diagram may be of any of the various types and/or equivalents described herein (e.g., AP, WLAN device; or other wireless communication device including, though not limited to, any of those depicted in
Such clusters may be used for transmissions of signals via various one or more selected antennae. For example, different clusters are shown as being used to transmit signals respectively using different one or more antennae.
Also, it is noted that, with respect to certain embodiments, general nomenclature may be employed wherein a transmitting wireless communication device (e.g., such as being an Access point (AP), or a wireless station (STA) operating as an ‘AP’ with respect to other STAs) initiates communications, and/or operates as a network controller type of wireless communication device, with respect to a number of other, receiving wireless communication devices (e.g., such as being STAs), and the receiving wireless communication devices (e.g., such as being STAs) responding to and cooperating with the transmitting wireless communication device in supporting such communications. Of course, while this general nomenclature of transmitting wireless communication device(s) and receiving wireless communication device(s) may be employed to differentiate the operations as performed by such different wireless communication devices within a communication system, all such wireless communication devices within such a communication system may of course support bi-directional communications to and from other wireless communication devices within the communication system. In other words, the various types of transmitting wireless communication device(s) and receiving wireless communication device(s) may all support bi-directional communications to and from other wireless communication devices within the communication system. Generally speaking, such capability, functionality, operations, etc. as described herein may be applied to any wireless communication device.
Various aspects and principles, and their equivalents, of the invention as presented herein may be adapted for use in various standards, protocols, and/or recommended practices (including those currently under development) such as those in accordance with IEEE 802.11x (e.g., where x is a, b, g, n, ac, ad, ae, af, ah, etc.).
For example, the IEEE 802.11ah is a new protocol/standard currently under development and is intended for long range and low rate applications operating in worldwide spectrum below 1 GHz. The available spectrum in each country differs and requires flexible design to accommodate different options. As such, modifications to the IEEE 802.11 standards, protocols, and/or recommended practices may be made to effectuate longer delay spread and lower data rate applications such as may be employed in accordance with the IEEE 802.11 ah developing standard.
Herein, from certain perspectives, certain adaptation and/or modification may be made with respect to IEEE 802.11ac standards, protocols, and/or recommended practices to provide efficient support for longer delay spread and lower data rate applications.
OFDM modulation operates by performing simultaneous transmission of a larger number of (narrowband) tones or sub-carriers (or multi-tones). Oftentimes a guard interval (GI) or guard space is also employed between the various OFDM symbols to try to minimize the effects of ISI (Inter-Symbol Interference) that may be caused by the effects of multi-path within the communication system (which can be particularly of concern in wireless communication systems). In addition, a CP (Cyclic Prefix) may also be employed within the guard interval to allow switching time (when jumping to a new band) and to help maintain orthogonality of the OFDM symbols. Generally speaking, OFDM system design is based on the expected delay spread within the communication system (e.g., the expected delay spread of the communication channel).
Herein, a novel preamble structure is presented that is suitable for a variety of operational modes including those applicable for single-user (SU) case, multi-user (MU) case, and a low Doppler/high Doppler case. For example, with respect to the low Doppler/high Doppler case, additional long training fields (LTFs) may be needed to assist in channel estimation, channel training, etc. If desired, a single bit may be included to indicate the high Doppler case. Such Doppler effects may be realized in situations in which a wireless communication device has a relatively high mobility (e.g., a wireless communication device being operated within a fast moving vehicle, on a train, etc.). In such a situation, multi-path effects and/or various reflections may deleteriously affect performance.
With respect to IEEE 802.11ac, it is noted that only a single preamble is included with respect to the SU case (e.g., the second signal field (SIG-B) is disregarded for the SU case. With respect to the lower frequency, narrowband channel, and longer range applications associated with the currently developing IEEE 802.11ah standard (e.g., in accordance with the Task Group TGah), a proposal for two different types of preambles is presented herein (e.g., with respect to embodiments for a short preamble structure and a long preamble structure).
The following signaling may be included in the preamble employed for wireless communication.
An indication of the preamble having a format corresponding to either single-user (SU) or multi-user (MU) applications may be provided in the SIG-A field. For example, 1 or 2 bits (or a series or group of bits) may be implemented to provide indication for different preamble types and/or types of transmissions (e.g., MU, SU Open Loop, SU Beamforming).
An indication of the preamble having a format corresponding to a high Doppler suitable packet may be provided by a bit (e.g., one bit) in the SIG-A or SIG-B field. For example, long training fields (LTFs) (and/or possibly short training fields (STFs)) may periodically be repeated after some number of orthogonal frequency division multiplexing (OFDM) DATA symbols in order to track the high Doppler channel. If desired, the LTFs may be repeated only for the SU case. For the MU case, repeated symbols may result in a significantly longer packet. In addition, MU transmissions may be vulnerable to high Doppler (e.g., increased inter-user interference). Rotation of the pilot symbols may be made over different positions within a packet or a communication. A high Doppler bit may not necessarily be included in which case there are two possibilities: (1) high Doppler suitable packet as default, and (2) no high Doppler provision in the packet as default.
In addition, there may be some indication before the Signal field (SIG-A) that would indicate one of the two (or more) modulation coding set (MCS) possibilities of SIG-A and/or a second Signal field (SIG-B). This indication may be in the short training field (STF) and/or within the long training field (LTF). The indication may be related to field content, inverted polarity, and/or phase shifts.
With respect to the lower frequency, narrowband channel, and longer range applications associated with the currently developing IEEE 802.11 ah standard (e.g., in accordance with the Task Group TGah), it may be desirable to construct relatively shorter preambles (as opposed relatively long fields being employed within the preambles thereof). As such, novel approaches are presented herein by which the preamble may be shortened such as in accordance with the construction of the STF and/or LTF fields therein.
For example, bits start to appear in a packet within the signal field (SIG-A) to indicate information related to the packet. However, herein, additional information may be provided even before those bits related to the signal field (SIG-A) begin to appear (e.g., such as in accordance with what may be viewed as being an encrypted pre-SIG-A field). That is to say, even if the MCS of SIG-A is specified (e.g., usually as being a relatively lowest order so that all wireless communication devices can properly receive, demodulate, decode, etc. at least the SIG-A of the packet), but some means of communicating such information can be provided changing some indication that the signal field (SIG-A) is not of that default MCS (e.g., by effectuating at least one phase shift, and/or at least one polarity shift, etc.) because up to and before the SIG-A field, there are no bits there to indicate such. A change may be effectuated for certain properties of the signal corresponding to these proportions of the signal to indicate what is happening later in the field (e.g., such as in accordance with an encrypted pre-SIG-A field as may be effectuated by these at least one phase shift, and/or at least one polarity shift, etc.).
As may be seen, beamforming (precoding) may be applied after the signal field (SIG-A). The preamble structure may be used for both the MU Beamforming and SU Beamforming cases. The indicia of N1, N2 (and/or N3, N4) indicate that symbols may be repeated by a different number of repetitions (e.g., any integer between 1-4 in one embodiment).
A preamble structure such as may be suitable for the currently developing IEEE 802.11ah standard may have some attributes that are analogous to that which is compliant with IEEE 802.11ac. For example, the signal field (SIG-A) may be implemented to include bits that must be seen by all users and uses the lowest MCS in the system (e.g., lower order modulation, lower code rate, etc.) so that all wireless communication devices can receive, demodulate, decode, etc. at least that portion of the packet. Also, the second signal field (SIG-B) may be implemented to include bits that are user specific.
However, a preamble structure such as may be suitable for the currently developing IEEE 802.11ah standard may have other attributes that are different and particularly suited for such lower frequency, narrowband channel, and longer range applications. For example, the signal field (SIG-A) may be implemented to include bits that may signal the MCS used for Data and the MCS used for the second signal field (SIG-B). In an embodiment in which the Data MCS and SIG-B MCSs are different, a delta (difference, such as A) between the two MCSs may be signaled in the signal field (SIG-A). For example, the signal field (SIG-A) may signal the MCS used for the second signal field (SIG-B) and the second signal field (SIG-B) then signals the MCS used for DATA. That is to say, the signal field (SIG-A) may indicate within the MCS for each of the separate and respective different, following fields.
Alternatively, the signal field (SIG-A) may indicate a ΔMCS (e.g., a difference based on at least one additional MCS) such that the ΔMCS is with respect to the MCS of the second signal field (SIG-B) so that the MCS of the second signal field (SIG-B) and the ΔMCS may be used for properly processing the DATA.
A variety of preamble combinations (e.g., from among 5 rep combinations) may be chosen. For example, the signal field (SIG-A) may contain 1 or 2 bits (or a series or group of bits) may be implemented to provide indication for different preamble types and/or types of transmissions (e.g., MU, SU Open Loop, SU Beamforming).
With respect to these various combinations, it is submitted that at least one column (such as with respect to
Combination #1:
-
- SU Option 1 may be used for both SU Beamforming and SU Open loop
- MU preamble may be used for MU transmissions
- Two preamble types
Combination #2:
-
- SU Option 2 may be used for both SU Beamforming and SU Open loop
- MU preamble may be used for MU transmissions
- Two preamble types
Combination #3:
-
- SU Option 1 may be used for Open Loop SU transmissions only
- SU Option 2 in that case may be used for SU Beamforming (Closed Loop) transmissions
- MU preamble may be used for MU transmissions
- Three preamble types
Combination #4:
-
- SU Option 1 may be used for Open Loop SU transmissions only
- MU preamble may be used for both SU Beamforming and MU case
- In the SU Beamforming case SIG-B may not be relevant, it may be ignored
- Two preamble types
Combination #5:
-
- To reduce the implementation complexity, only MU preamble may be selected for SU (Open Loop and Beamforming) and MU transmissions
- Single preamble type
- SIG-A indicates SU or MU transmission case
With respect to the STF1 field indicated in the beginning of the packet, the STF1 field may be implemented in accordance with power boosting when compared to the other fields of the packet. The increased power may provide for better packet detection, timing and synchronization.
In some embodiments, the STF2 field may be considerably shorter than the STF1 field since it is used for automatic gain control (AGC) and/or AGC estimation, which can be coarse. For example, in accordance with IEEE 802.11a/n/ac, there are 10 short repetitions of 0.8 μs in the STF. In accordance with one embodiment that may be employed within the currently developing IEEE 802.11ah standard, one or two short repetitions may be used only. However, in accordance with the currently developing IEEE 802.11ah standard, each repetition may be longer because of the bandwidth scaling (down-clocking).
It is noted that the STF2 field may not be present in all embodiments. For example, a cyclic prefix of the next orthogonal frequency division multiplexing (OFDM) symbol may be used for automatic gain control (AGC) and/or AGC estimation. In some situations, the cyclic prefix can be longer than in other embodiments.
If desired, rotating pilots may be utilized. For example, a subset of pilots assumes different positions over consecutive OFDM symbols. The pilots over time span the frequency band of interest (e.g., the signal bandwidth). Puncturing of the data sub-carriers can be used to augment data pilots.
Additional preamble structure considerations may be made. For example, if one or more of the fields in the preamble has more than one symbol, then information about different frame formats may be conveyed on the consecutive symbols such as in accordance with an encrypted pre-SIG-A field before the bits of the SIG-A field begin to arrive using:
-
- Different symbol content (e.g., using different periodicities for certain fields within a preamble, such as with respect to the STF, and/or portions thereof)
- Inverted polarity
- Phase shifts
The number of symbols of each field may vary (e.g., N1, N2, SIG-A, SIG-B, etc.). As such, the size of the packet may be modified/varied indirectly in accordance with a modification/variation of the preamble size. The variability of such differing numbers of symbols in each field may be made:
-
- On the pre-configured basis
- On the semi-static basis
- Dynamically, per packet basis
The number of symbols of each field may vary (for example N1, N2, SIG-A, SIG-B) depending on any number of factors, including:
-
- Application (usage scenario)
- MCS of the data
- SNR requirement
- Desired Range
- Desired power consumption
With respect to various High Doppler Frame Format Options (e.g., such as continued from
Option 1
The Doppler frame format support is optional and part of the capabilities exchange. The transmitter communication device decides whether or not to use this operational mode. One value for N is specified in the specification and could be somewhere between 30 to 80 symbols (or generally between two numbers X1 and X2) with an overhead between approximately 10% to 4% (or generally between two percentages Y1% and Y2%).
Option 1 a
Same as Option 1 described above with up to 4 values for N specified in the specification for different respective modulations (e.g., 2/4/16/64QAM). In such an embodiment, the receiver communication device combines the MCS information with the Doppler bit to know the mid-amble periodicity.
Option 1b
In this embodiment, instead of signaling one value of N as in Option 1 above, the SIG field uses 2 bits to signal up to 3 values of N allowing the transmitter communication device better to match the channel Doppler for the appropriate option of no Doppler, low Doppler, medium Doppler and high Doppler.
Option 2
Doppler frame format support is mandatory at the transmitter. All transmissions use a mid-amble every 80-100 symbols (or generally between two numbers Z1 and Z2) with overhead less than some desired percentage (e.g., <4%). This option simplifies an outdoor access point (AP) operation as it guarantees robust operation of beacons and low MCS under high Doppler without the need for feedback from specific users. The receiver communication device doesn't have to update the channel estimation, and the receiver communication device can simply skip those 3 symbols. Receiver communication devices only need to understand where a mid-amble is place in the frame. If the SIG field bit is set to a value of one (1), the transmitter communication device may be implemented to place a mid-amble every certain number of symbols (e.g., every 30 or so symbols) with overhead increase to some desired percentage (e.g., 10%). It is noted that this can be done only with receiver communication devices that declare ‘receive Doppler format capability’.
In order to enable the receiver communication device to request high Doppler frame format, it is also proposed herein to add a capability to the VHT control field to be used with unsolicited feedback to enable the receiver to request high Doppler frame format.
It is also proposed that if the unsolicited MFB bit is set to 1 and the FB is generated from an SU PPDU, then signaling all zeros (value 0) in the GID-L and GID-H fields may be implemented to indicate a request for a high Doppler frame format (e.g., otherwise, use the all ones (i.e., 11 . . . 111 for depicting a value of 63) as in IEEE 802.11ac).
With respect to determining when to use High Doppler Frame Format, a receiver communication device may be implemented to measure communication channel variation across the packet to decide if the communication channel is rapidly changing (e.g., typically mobility of a communication device may be viewed as lasting for several seconds and doesn't change fast that a decision may be viewed as being good or acceptable at least for a relatively short period of time). Also, the measurement of communication channel variation may be difficult in packets that do not have a mid-amble. Also, an improved approach may be effectuated by the receiver communication device requesting a high Doppler frame format in order to aid it in measuring communication channel variation (e.g., from preamble to mid-amble) by comparing the LTF symbols during the preamble and mid-amble.
In accordance with IEEE 802.11 ac, as well as all respective prior versions of IEEE 802.11x (where x refers to the particular version, many of which are described in referenced above), the pilot location is fixed throughout a packet such that the pilots occur only in known, specified locations. That is to say, within a given packet having at least one field therein that includes pilots, the locations of those respective pilots are known, predetermined, fixed, etc.
Herein, pilot placement may be adaptively or selectively made among respective tones or sub-carriers within different respective symbols, such that the respective pilot locations within different respective symbols may be different. In some instances, such pilot placement within respective tones or sub-carriers is based upon at least one pattern which may have a periodicity covering a number of respective symbols (e.g., such that the pattern itself may be repeated after a particular number of symbols have been processed). In an alternative possible embodiment, the respective locations of tones or sub-carriers within different respective symbols may be adaptively or selectively determine in real time, based upon any of a number of desired considerations (e.g., such as local and/or remote operating conditions or characteristics, mobility of a given communication device, and/or any other desired one or more considerations).
Generally speaking, the locations of pilots are rotated from tone to tone (e.g., or sub-carrier to sub-carrier) among different respective symbols. In certain embodiments, all respective tones or sub-carriers are covered by at least one pilot after at least a certain number of symbols have passed. In a preferred embodiment, covering of all respective data tones are sub-carriers within a signal may be performed in accordance with such rotating pilots.
As may be seen with respect to the table of this diagram, a number of pilots, occupied tones, and the required rotation periodicity (e.g., the number of symbols required to cover all respective tones are sub-carriers with pilots) is shown for different respective fast Fourier transform (FFT) sizes. The number of occupied tones corresponds to those which may be employed for channel estimation, channel characterization, etc. For consideration of one example as depicted within the diagram, rotating of 2 pilots over 32 FFT over 13 symbols will cover all of the possible 26 tones or sub-carrier positions for data tones. Generally speaking, different respective symbols have different respective tone or sub-carrier locations used as pilots such that the locations of the pilots in different respective symbols are with respect to different tone or sub-carrier locations.
Generally speaking, in certain preferred embodiments, a pilot rotation pattern should maintain a relatively large gap between pilot locations in each respective symbol to allow frequency offset tracking on a per symbol basis. For example, having a relatively large gap (e.g., as large as may be possible within a particular embodiment) says will allow for appropriate frequency offset tracking in an easier manner. However, it is noted generally that any such desired pilot rotation pattern may be employed, including those that do not necessarily have a relatively largest gap possible between pilots in respective symbols (e.g., even though such pilot rotation patterns not having a largest gap possible may be less than optimal in accordance with performing frequency offset tracking).
Again, it is noted here with respect to this exemplary embodiment employing particular numbers (e.g., tone or sub-carrier spacing of 14, 14 symbol periodicity, employing 4 respective pilots, etc.), The particular values employed may be different with respect to other desired embodiments, such that any desired sets of numbers may be employed for such operational parameters in accordance with effectuating rotating pilots among different respective sub-carrier or tone locations within different respective symbols. That is to say, similar designs for other FFT sizes are of course possible where the tones are sub-carriers to be covered by the rotating pilots may be divided into a particular number of groups (e.g., N groups, where N is the number of pilots and each pilot steps over the tones or sub-carriers in its respective group from symbol to symbol). For example, considering the case of 256 FFT (and 512 FFT), the number of occupied tones or sub-carriers is not divisible by the number of tones (e.g., 242/8=30.25), and the periodicity may then be rounded up to the next integer (e.g., rounded up to 31 in this particular case). Again, a designer is provided a great deal of latitude inflexibility in selecting any desired operational parameters in accordance with effectuating rotating pilots among different respective sub-carrier told locations within different respective symbols.
As may be understood as respect to certain of the previous embodiments (e.g., such as the high Doppler related situation corresponding
With respect to the implementation described just above, this design allows for updating of a channel estimates every 14 symbols (e.g., for the 64 FFT implementation described). However, there may be situations or implementations in which a given receiver communication device doesn't necessarily need all of the respective tone or sub-carrier locations to be covered by at least one pilot in order to estimate the communication channel. That is to say, there may be some instances in which a subset (e.g., such as a decimated subset of all of the respective tone or sub-carrier locations) may be sufficient for performing channel estimation. Generally speaking, the amount of decimation may correspond to the maximum delay spread of the communication channel and based on the CP (Cyclic Prefix) length within a current design or implementation that supports a delay spread up to a particular number. That is to say, if the CP length of a given design or implementation supports a delay spread up to a quarter of the symbol length, then decimation by a factor of 4 may be performed. Of course, depending upon the particular delay spread which may be supported, different respective decimation factors may be alternatively employed.
It is noted that interpolation performed by a receiver communication device may be more optimally performed when there is equal spacing between the pilots. As such, in a preferred embodiment, each respective group of symbols will cover at least a uniformly decimated group of tones are sub-carriers. For example, in one possible embodiment, each group of 4 symbols will cover at least uniformly a decimated group of tones. For example, considering such an embodiment, a first group may be as shown below for respective pilot spacing except where the DC tone is replaced by two adjacent tones.
As may be understood, this corresponds to 16 respective tone or sub-carrier locations split among 4 pilots over 4 symbols. That is to say, within a first symbol, a first pilot is located at −28, a second file is located of −12, a third pilot is located at 1, and a fourth pilot is located at 16. Within a second symbol, the first pilot is located at −24, the second pilot is located at −8, the third pilot is located at 4, and the fourth pilot is located at 20; and so on.
Such a set of tone or sub-carrier locations may be used for beamforming feedback (e.g., such as in accordance with Ng=4 in IEEE 802.11ac) using uniformly spaced tones are sub-carriers.
Referring to
As may be understood, this corresponds to 14 respective tone or sub-carrier locations split among 4 pilots over 4 symbols. As may be seen, two pilots are repeated two times at the same location within successive symbols, namely the tone or sub-carrier location 14 and 26 within the third and fourth symbols respectively. It is noted that any desired tone or sub-carrier location may be selected for repetition of a pilot.
Referring to
With respect to the embodiment encompassed by
With respect to the embodiment encompassed by
With respect to the embodiment encompassed by
Generally, it is noted that any desired FFT sizes may similarly be employed following the design principles described herein. For example, if a particular factor of 4 is employed, then the respective tones are sub-carriers may be split into 4 groups that uniformly decimate the available tones are sub-carriers modulo 4, such that each respective group is covered by the available pilots.
For example, a first group can use the tones or sub-carriers used for beamforming feedback with Ng=4. For example, for 128 FFT [−58:4:58], 30 respective tones or sub-carriers are covered using the 6 pilots over 5 symbols (e.g., the first 5 numbers are used by pilot 1, the second 5 numbers are used by pilot 2, and so on). Analogously, for 256 FFT [-122:4:122], 62 respective tones or sub-carriers are covered using the 8 pilots over 8 symbols (e.g., the first 8 numbers are used by pilot 1, the second 8 numbers are used by pilot 2, and so on). In such an embodiment, the last pilot may be designed to occupy tone or sub-carrier 122 two more times (e.g., considering 64 available pilot locations but only 62 different locations).
A second group may be designed to use the tones or sub-carriers used for beamforming feedback with Ng=2 (which were not covered by the first group). For example, for 128 FFT [−56:4:56], excluding tone 0 (DC) but with added tones −2 and +2, 30 respective tones or sub-carriers are covered using the 6 pilots over 5 symbols (e.g., the first 5 numbers are used by pilot 1, the second 5 numbers are used by pilot 2, and so on). Analogously, for 256 FFT [−120:4:120], excluding tone 0 (DC), 60 respective tones or sub-carriers are covered using the 8 pilots over 8 symbols (e.g., the first 8 numbers are used by pilot 1, the second 8 numbers are used by pilot 2, and so on).
The third and fourth groups cover the last two offsets modulo 4 [−57:4:55] and [−55:4:57] four 128 FFT to be covered by 6 pilots over 5 symbols bringing the total number of symbols to 30 and [−121:4:119] and [−119:4:121] for 256 FFT to be covered by 8 pilots over 8 symbols bringing the total number of symbols to 32.
A 512 FFT design may be implemented as being an exact duplicate of the 256 FFT design. A 32 FFT design may be made using a similar approach. It is, however, noted that IEEE 802.11ac does not specifically defined beamforming feedback for 32 FFT in accordance with the new operational mode described with reference to IEEE 802.11ah.
With respect to 32 FFT groups, [−13:4:11], [−12:4:12], excluding tone 0 (DC), with added ±1 instead, [−11:4:13], [−10:4:10] may be employed were each respective group is spanned by 2 pilots covering it over 4 symbols.
With respect to certain embodiments herein relating to pilots, pilot patterns, etc., certain such embodiments have been described with reference to one spatial stream (e.g., whether the singular spatial stream correspond to one physical antenna or multiple antennae using beamforming, cyclic delay diversity and/or any other technique operative to combine the antenna at the transmitter communication device (TX) to look like one antenna to a receiver communication device (RX)).
However, it is also noted that an advanced pilot structure can be used to estimate the channel for 2 or higher number of spatial streams (or space time block coding STBC) by splitting the groups between the respective spatial streams (e.g., 2 or more spatial streams). For example, considering one possible embodiment including 2 spatial streams, the respective the pilots belonging to the two first groups (belonging to tones that are part of beamforming report with Ng=2) shall be used for spatial stream #1, and the rest of the pilots in the two other groups shall belong to spatial stream #2. Generally speaking, this is applicable to any FFT size. The same approach can be applied to four (or even more) spatial streams whereby each group is used to estimate the channel for each stream.
In some instance, some embodiments operating with respect to more than one spatial stream will not particularly cover all tones. In such embodiments, a receiver can perform interpolation in accordance with certain of the various aspects, embodiments, and/or their equivalents described above with respect to embodiments in which not all of the tones are covered.
Also, it is noted that in this case, it may be advantageous to not use the matrix P (e.g., to reduce processing delay, unlike LTF, pilots are spread across many symbols and the receiver communication device complexity may in fact increase by storing all those pilots) that is currently used to mix all the spatial streams together when one or more LTFs are used to estimate the channel per spatial stream. The formula used to modulate the pilots corresponding to each spatial stream may then be the same as the formula in IEEE 11ac (shown below) used for LTF for multiple streams, but without using matrix P.
LTF pilot sign in tone k, being either +1 or −1.
It is also noted that the various operations and functions as described with respect to various methods herein may be performed within a wireless communication device, such as using a baseband processing module and/or a processing module implemented therein, (e.g., such as in accordance with the baseband processing module 64 and/or the processing module 50 as described with reference to
In some embodiments, such a baseband processing module and/or a processing module (which may be implemented in the same device or separate devices) can perform such processing to generate signals for transmission using at least one of any number of radios and at least one of any number of antennae to another wireless communication device (e.g., which also may include at least one of any number of radios and at least one of any number of antennae) in accordance with various aspects of the invention, and/or any other operations and functions as described herein, etc. or their respective equivalents. In some embodiments, such processing is performed cooperatively by a processing module in a first device, and a baseband processing module within a second device. In other embodiments, such processing is performed wholly by a baseband processing module or a processing module.
As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “operably coupled to”, “coupled to”, and/or “coupling” includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “operable to” or “operably coupled to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform, when activated, one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item. As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater magnitude than signal 2, a favorable comparison may be achieved when the magnitude of signal 1 is greater than that of signal 2 or when the magnitude of signal 2 is less than that of signal 1.
As may also be used herein, the terms “processing module”, “module”, “processing circuit”, and/or “processing unit” (e.g., including various modules and/or circuitries such as may be operative, implemented, and/or for encoding, for decoding, for baseband processing, etc.) may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module, module, processing circuit, and/or processing unit may have an associated memory and/or an integrated memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of the processing module, module, processing circuit, and/or processing unit. Such a memory device may be a read-only memory (ROM), random access memory (RAM), volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing module, module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that if the processing module, module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element may store, and the processing module, module, processing circuit, and/or processing unit executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the Figures. Such a memory device or memory element can be included in an article of manufacture.
The present invention has been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claimed invention. Further, the boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality. To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claimed invention. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof.
The present invention may have also been described, at least in part, in terms of one or more embodiments. An embodiment of the present invention is used herein to illustrate the present invention, an aspect thereof, a feature thereof, a concept thereof, and/or an example thereof. A physical embodiment of an apparatus, an article of manufacture, a machine, and/or of a process that embodies the present invention may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more of the embodiments discussed herein. Further, from figure to figure, the embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers and, as such, the functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different ones.
Unless specifically stated to the contra, signals to, from, and/or between elements in a figure of any of the figures presented herein may be analog or digital, continuous time or discrete time, and single-ended or differential. For instance, if a signal path is shown as a single-ended path, it also represents a differential signal path. Similarly, if a signal path is shown as a differential path, it also represents a single-ended signal path. While one or more particular architectures are described herein, other architectures can likewise be implemented that use one or more data buses not expressly shown, direct connectivity between elements, and/or indirect coupling between other elements as recognized by one of average skill in the art.
The term “module” is used in the description of the various embodiments of the present invention. A module includes a functional block that is implemented via hardware to perform one or module functions such as the processing of one or more input signals to produce one or more output signals. The hardware that implements the module may itself operate in conjunction software, and/or firmware. As used herein, a module may contain one or more sub-modules that themselves are modules.
While particular combinations of various functions and features of the present invention have been expressly described herein, other combinations of these features and functions are likewise possible. The present invention is not limited by the particular examples disclosed herein and expressly incorporates these other combinations.
Mode Selection Tables:
Claims
1. An apparatus, comprising:
- a baseband processing module selectively to generate at least one packet having a plurality of symbols, wherein at least a subset of the plurality of symbols, corresponding to at least one long training field (LTF) preceded by a short training field (STF) among a plurality of data fields within the at least one packet, having a plurality of pilots at different respective subcarrier or tone locations therein based on at least one pattern; and
- at least one antenna to transmit a signal corresponding to the at least one packet to at least one additional apparatus; and wherein:
- a first symbol of the at least a subset of the plurality of symbols including a first pilot at a first subcarrier or tone location therein and a second pilot at a second subcarrier or tone location therein; and
- a second symbol of the at least a subset of the plurality of symbols including the first pilot at a third subcarrier or tone location therein and the second pilot at a fourth subcarrier or tone location therein; and
- the apparatus to employ the STF for at least one of automatic gain control (AGC) and AGC estimation.
2. The apparatus of claim 1, wherein:
- the second plurality of subcarrier or tone locations each respectively being offset from the first plurality of subcarrier or tone locations.
3. The apparatus of claim 1, wherein:
- at least one of the first plurality of subcarrier or tone locations and the second plurality of subcarrier or tone locations being uniformly distributed among an available plurality of subcarrier or tone locations within at least one orthogonal frequency division multiplexing (OFDM) symbol of the signal.
4. The apparatus of claim 1, wherein:
- the at least one additional apparatus to receive the signal including the plurality of symbols from the apparatus;
- based on a first at least one symbol of the at least a subset of the plurality of symbols within the signal, the at least one additional apparatus to make a first channel estimate of a communication channel between the apparatus and the at least one additional apparatus; and
- based on a second at least one symbol of the at least a subset of the plurality of symbols within the signal, the at least one additional apparatus to make a second channel estimate of the communication channel between the apparatus and the at least one additional apparatus.
5. The apparatus of claim 1, wherein:
- the apparatus is an access point (AP); and
- the at least one additional apparatus is a wireless station (STA).
6. An apparatus, comprising:
- a baseband processing module selectively to generate at least one packet having a plurality of symbols, wherein at least a subset of the plurality of symbols having a plurality of pilots at different respective subcarrier or tone locations therein based on at least one pattern; and
- at least one antenna to transmit a signal corresponding to the at least one packet to at least one additional apparatus.
7. The apparatus of claim 6, wherein:
- the at least a subset of the plurality of symbols corresponding to at least one long training field (LTF) preceded by a short training field (STF) among a plurality of data fields within the at least one packet; and
- the apparatus to employ the STF for at least one of automatic gain control (AGC) and AGC estimation.
8. The apparatus of claim 6, wherein, based on the at least one pattern:
- a first symbol of the at least a subset of the plurality of symbols including a first plurality of pilots at a first plurality of subcarrier or tone locations therein; and
- a second symbol of the at least a subset of the plurality of symbols including a second plurality of pilots at a second plurality of subcarrier or tone locations therein each respectively being offset from the first plurality of subcarrier or tone locations.
9. The apparatus of claim 6, wherein, based on the at least one pattern:
- at least one symbol of the at least a subset of the plurality of symbols including a plurality of pilots at a plurality of subcarrier or tone locations therein; and
- the plurality of subcarrier or tone locations being uniformly distributed among an available plurality of subcarrier or tone locations within at least one orthogonal frequency division multiplexing (OFDM) symbol of the signal.
10. The apparatus of claim 6, wherein, based on the at least one pattern:
- a first symbol of the at least a subset of the plurality of symbols including a first pilot at a first subcarrier or tone location therein and a second pilot at a second subcarrier or tone location therein; and
- a second symbol of the at least a subset of the plurality of symbols including the first pilot at a third subcarrier or tone location therein and the second pilot at a fourth subcarrier or tone location therein.
11. The apparatus of claim 6, wherein, based on the at least one pattern:
- a first symbol of the at least a subset of the plurality of symbols including a first pilot at a first subcarrier or tone location therein and a second pilot at a second subcarrier or tone location therein; and
- a second symbol of the at least a subset of the plurality of symbols including the first pilot at the first subcarrier or tone location therein and the second pilot at a third subcarrier or tone location therein.
12. The apparatus of claim 6, wherein:
- the at least one additional apparatus to receive the signal including the plurality of symbols from the apparatus;
- based on a first at least one symbol of the at least a subset of the plurality of symbols within the signal, the at least one additional apparatus to make a first channel estimate of a communication channel between the apparatus and the at least one additional apparatus; and
- based on a second at least one symbol of the at least a subset of the plurality of symbols within the signal, the at least one additional apparatus to make a second channel estimate of the communication channel between the apparatus and the at least one additional apparatus.
13. The apparatus of claim 6, wherein:
- the apparatus is an access point (AP); and
- the at least one additional apparatus is a wireless station (STA).
14. A method for operating a communication device, the method comprising:
- selectively generating at least one packet having a plurality of symbols, wherein at least a subset of the plurality of symbols having a plurality of pilots at different respective subcarrier or tone locations therein based on at least one pattern; and
- via at least one antenna of the communication device, transmitting a signal corresponding to the at least one packet to at least one additional communication device.
15. The method of claim 14, wherein:
- the at least a subset of the plurality of symbols corresponding to at least one long training field (LTF) preceded by a short training field (STF) among a plurality of data fields within the at least one packet; and further comprising:
- employing the STF for at least one of automatic gain control (AGC) and AGC estimation.
16. The method of claim 14, wherein:
- a first symbol of the at least a subset of the plurality of symbols including a first plurality of pilots at a first plurality of subcarrier or tone locations therein; and
- a second symbol of the at least a subset of the plurality of symbols including a second plurality of pilots at a second plurality of subcarrier or tone locations therein each respectively being offset from the first plurality of subcarrier or tone locations.
17. The method of claim 14, wherein:
- at least one symbol of the at least a subset of the plurality of symbols including a plurality of pilots at a plurality of subcarrier or tone locations therein; and
- the plurality of subcarrier or tone locations being uniformly distributed among an available plurality of subcarrier or tone locations within at least one orthogonal frequency division multiplexing (OFDM) symbol of the signal.
18. The method of claim 14, wherein:
- a first symbol of the at least a subset of the plurality of symbols including a first pilot at a first subcarrier or tone location therein and a second pilot at a second subcarrier or tone location therein; and
- a second symbol of the at least a subset of the plurality of symbols including the first pilot at a third subcarrier or tone location therein and the second pilot at a fourth subcarrier or tone location therein.
19. The method of claim 14, wherein:
- the at least one additional communication device receiving the signal including the plurality of symbols from the communication device;
- based on a first at least one symbol of the at least a subset of the plurality of symbols within the signal, the at least one additional communication device making a first channel estimate of a communication channel between the communication device and the at least one additional communication device; and
- based on a second at least one symbol of the at least a subset of the plurality of symbols within the signal, the at least one additional communication device making a second channel estimate of the communication channel between the communication device and the at least one additional communication device.
20. The method of claim 14, wherein:
- the communication device is an access point (AP); and
- the at least one additional communication device is a wireless station (STA).
Type: Application
Filed: Apr 23, 2012
Publication Date: Oct 25, 2012
Applicant: BROADCOM CORPORATION (IRVINE, CA)
Inventors: Ron Porat (San Diego, CA), Vinko Erceg (Cardiff by the Sea, CA)
Application Number: 13/453,998
International Classification: H04W 72/04 (20090101); H03G 3/20 (20060101);
