Source: http://patents.com/us-9544095.html
Timestamp: 2017-09-20 05:45:32
Document Index: 220418075

Matched Legal Cases: ['art 11', 'art 11', 'art 11', 'art 11', 'art 11', 'art 11']

US Patent # 9,544,095. Channel estimation for phase-only feedback and methods for use therewith - Patents.com
United States Patent 9,544,095
Kim , et al. January 10, 2017
Kim; Joonsuk (Saratoga, CA), Fischer; Matthew James (Mountain View, CA)
Family ID: 1000002339380
13/875,835
US 20140126398 A1 May 8, 2014
61722279 Nov 5, 2012
61805855 Mar 27, 2013
Current CPC Class: H04L 1/0681 (20130101); H04L 1/00 (20130101); H04L 1/0643 (20130101); H04L 5/0057 (20130101); H04L 25/022 (20130101); H04L 25/0202 (20130101); H04L 27/2613 (20130101); H04L 2001/0092 (20130101)
Current International Class: H04L 25/02 (20060101); H04L 25/00 (20060101); H04L 1/00 (20060101); H04L 1/06 (20060101); H04L 5/00 (20060101); H04L 27/26 (20060101)
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The present U.S. Utility Patent Application claims priority pursuant to 35 U.S.C. .sctn.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 Application Ser. No. 61/722,279 , entitled "CHANNEL ESTIMATION FOR PHASE-ONLY FEEDBACK AND CORRESPONDING PIGGYBACK FEEDBACK FORMAT WITHIN SINGLE USER, MULTIPLE USER, MULTIPLE ACCESS, AND/OR MIMO WIRELESS COMMUNICATIONS," filed Nov. 5, 2012 ; and 2. U.S. Provisional Application Ser. No. 61/805,855 , entitled CHANNEL ESTIMATION FOR PHASE-ONLY FEEDBACK AND METHODS FOR USE THEREWITH, filed Mar. 27, 2013.
1. IEEE Std 802.11 .TM.-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 .TM.-2012 , (Revision of IEEE Std 802.11 -2007 ), 2793 total pages (incl. pp. i-xcvi, 1-2695 ).
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6. IEEE P802.11af.TM./D1.06, March 2012, (Amendment to IEEE Std 802.11REVmb.TM./D12.0 as amended by IEEE Std 802.11ae.TM./D8.0, IEEE Std 802.11aa.TM./D9.0, IEEE Std 802.11ad.TM./D5.0, and IEEE Std 802.11ac.TM./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).
FIG. 3 is a diagram illustrating an embodiment of an access point (AP) and multiple wireless local area network (WLAN) devices operating according to one or more various aspects and/or embodiments of the invention. The AP point 300 may compatible with any number of communication protocols and/or standards, e.g., IEEE 802.11(a), IEEE 802.11(b), IEEE 802.11(g), IEEE 802.11(n), as well as in accordance with various aspects of invention. According to certain aspects of the present invention, the AP supports backwards compatibility with prior versions of the IEEE 802.11x standards as well. According to other aspects of the present invention, the AP 300 supports communications with the WLAN devices 302, 304, and 306 with channel bandwidths, MIMO dimensions, and at data throughput rates unsupported by the prior IEEE 802.11x operating standards. For example, the access point 300 and WLAN devices 302, 304, and 306 may support channel bandwidths from those of prior version devices and from 40 MHz to 1.28 GHz and above. The access point 300 and WLAN devices 302, 304, and 306 support MIMO dimensions to 4.times.4 and greater. With these characteristics, the access point 300 and WLAN devices 302, 304, and 306 may support data throughput rates to 1 GHz and above.
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.
The use of phase-only information in accordance with feedback with only a few bits per tone feedback may provide adequately accurate channel estimation in some instances. For example, if desired, a quick-estimation-and-go approach may be sufficient. Using such an approach would obviate any need to estimate the channel with the quality of -30-ish dB of MSE (mean squared error). With only a few bits quantization for one or two parameters, such operation may have a relatively or quite bad quantization error already. However, in some applications, a -5 to -10 dB of MSE quality may be adequate, acceptable, or good enough for that purpose.
A description of such an abbreviated channel estimation is provided below. For an Nt.times.1 configuration, a transmitter may send a single stream packet with one long training field (LTF). Estimation of Nt.times.1 channels may be made from one LTF, without initiating NDP sounding frames. Such feedback information (e.g., a few bytes) can be delivered back to the transmitter wireless communication device (e.g., access point (AP), wireless station (STA) operating as an AP, etc.) via piggyback (e.g., such as within FIG. 15). Such a receiver wireless communication device (e.g., STA, etc.) may also group Ng tones for channel estimation process.
Q is a unitary matrix, D is a diagonal cyclic shift delay (CSD) matrix and T is a tall training vector (N is AWGN). Q, D and T can be different per tone k, i.e., Q is a Ng.times.(Nt Ng) matrix, D is a (Nt Ng).times.(Nt Ng) block diagonal matrix and T is a (Nt Ng).times.1 column vector. Assuming h.sub.ikj=h.sub.ikm, where 1<=j,m <=Ng and i=1, . . . , Nt, the estimate h of the channel can be made from the received signal, y, as long as Ng>=Nt. The feedback information is grouped per Ng tones anyway.
With the assumption h.sub.ikj=h.sub.ikm, the received signal can be expressed as follows:
{tilde over (y)}.sub.k=y.sub.ikis coming from h.sub.ikj=h.sub.ikm assumption
P.sub.k=Q.sub.ik.times.D.sub.ik.times.T.sub.ik where Q.sub.k is a unitary matrix (Nt.times.Nt), P.sub.ik is a diagonal matrix with CSD (Nt.times.Nt), T.sub.ik is a training sequence (Nt.times.1) and AWGN N (1.times.Ng).
.function..times..times..times. ##EQU00003## and N.sub.0 is AWGN noise power.
As such, there will be Nt variables to estimate by using inverse matrix of PP.sup.H. So, the condition number of P matrix may give an impact on the inversion operation. A better design may be provided such that each column of P matrix to be orthogonal each other. In other words, in some embodiments, it may be better to randomize P.sub.k tone by tone. In either example, the P.sub.k design needs to be known at the receiver wireless communication device (e.g., STA). A larger CSD value in Dk may be employed, which varies more tone by tone. Also, CSD values are fixed in the IEEE 802.11 specification, but additional CSD values may be added in the diagonal Q matrix. In such a design, Qk can be generated via fast Fourier transform (FFT) matrix or Hadamard matrix, and the cyclic-shift may be implemented on a tone by tone basis. Iterative design may be applied, and the value of y.sub.k may be reconstructed from the estimated channel and then used to re-estimate h.sub.k.
FIG. 10 illustrates an embodiment 1000 of a performance diagram with spatial channel model (SCM) at 900 MHz (31.25 kHz)). In particular, an example is shown for a 4.times.1 channel configuration for three different CSD values with grouping 8 tones. FIG. 11 illustrates an embodiment 1100 of another performance diagram for a 3.times.1 channel configuration for using an FFT Q matrix with groupings of either 4 or 8 tones. FIG. 12 illustrates an embodiment 1200 of another performance diagram for a 4.times.1 channel configuration for a grouping 8 tones and either an FFT Q matrix or a Hadamard Q matrix. As shown in these examples, this abbreviated form of channel estimation achieves better than -5 dB of MSE channel estimation error. In some embodiments, smaller groupings may help the assumption (h.sub.ikj=h.sub.ikm) to be more realistic, but the P matrix may have a greater condition number as well. This technique may perform better that a CSD D.sub.k matrix, in some circumstances.
FIG. 13 illustrates an embodiment 1300 of a performance diagram showing the impact of CSD channel estimation on phase-aligned space time block coding (STBC). While not expressly shown, similar impacts are achieved in output signal to noise ratio (SNR) with a SCM channel. As may be understood, performing channel estimation in such a manner obviates any need to send an NDP frame only for the channel estimation. A regular data packet (with a single stream) may be employed to estimate the Nt.times.1 channel accurately enough to obtain the phase information for Phase-Aligned STBC. A significant amount of feedback overhead savings may be achieved by piggybacking phase-only feedback information in an Nt.times.1 system, within an ACK frame. This phase-only feedback can be as little as 2-bits/tone for an 8-tone grouping, without a significant impact on the channel quality estimation. The information bits required to transmit such phase-only feedback for the 2 MHz band are only 13 information bits. The impact of additional 13 bits (2 bytes) on the throughput is negligible.
In an embodiment, the data frame 1402 is a single data frame with a single long training field and a non-null data payload. The baseband processor of the receiving device generates the channel estimation from an analysis of this single data frame--and not based on a null data packet (NDP). As previously discussed, the baseband processor can generate the channel estimation based on a diagonal cyclic shift delay matrix or other CSD data.
As may be seen in with respect to diagram, a combined ACK with phase feedback information (a "FACK" frame) can be transmitted. This may allow for a relatively simple frame format with the addition of only a few bytes in the acknowledgement frame, such as three of fewer bytes of phase feedback information (MgmtActionFB). While the phase feedback is described above as being incorporated in an acknowledgement frame, such as via a modified acknowledgement frame format, other alternatives can be employed to transfer the requested phase feedback information back to the requesting communication device. Other alternatives may allow for formatting the phase feedback information in either a special purpose frame format apart from an acknowledgement frame or in an aggregated frame format that includes the acknowledgement frame. For example, the receiving device can transmit the ACK and MgmtActionFB as separate respective frames. With respect to the SIFS+PHY Header, a MAC Header should be additionally employed. There may be some considerations regarding TXOP control (e.g., the TXOP owner expect a transmitter to include a SIFS after ACK. Other alternatives may allow for using ACK+MgmtActionFB aggregated MAC (media access control) data protocol unit (A-MPDU). Some considerations include the overhead of AMPDU density and many bytes in management Frame (e.g. MAC header bytes).
With 8 OFDM symbols of PHY preamble, the airtime for legacy ACK=52 .mu.sec in 802.11n/ac, and the airtime approximately for FACK will be approximately 52 .mu.sec (if BW=20 MHz) to 68 .mu.sec (if BW=160 MHz) in 802.11n/ac. The first three fields still conform to IEEE 802.11 ProtocolVersion=00b.
Herein, a novel frame is proposed (e.g., a new FACK frame), which includes feedback information (phase-only) whose length is only a few bytes (e.g., 2 to 14 bytes, depending on bandwidth). Such phase-only information of Nt.times.1 channel can be obtained by Ng tone grouping, assuming the channel is quite flat, from a single stream packet transmission (with one LTF). The channel estimation quality of the proposed scheme has only marginal performance degradation (0 to 1 dB) on the phase-aligned STBC scheme. As may be understood, this does not require any additional sounding frame exchange (e.g., NDP), and only a few extra bytes of information, so the impact on overhead is negligible.
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 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.
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