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`US 7,570,696 B2
`(10) Patent N0.:
`(12) Un1ted States Patent
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`Maltsev et al.
`(45) Date of Patent:
`Aug. 4, 2009
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`USOO7570696B2
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`(54)
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`(75)
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`lVIUIrTIPIlE INPUT MULTIPLE OUTPUT
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`lVlULTlCARRlER CONLVIUNICATION
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`SYSTEM AND METHODS WITH QUANTIZED
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`BEAMFORMING FEEDBACK
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`Inventors: Alexander A. Maltsev, Nizhny
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`Novgorod (RU); Ali S Sadri, San Diego,
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`CA (US); Sergey A. Tiraspolsky,
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`Nizhny Novgorod (RU); Alexander
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`Flaksman, Nizhny Novgorod (RU);
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`AlexeiV Davydov, Nizhny Novgorod
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`(RII)
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`(73) Assignee:
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`( * ) Notice:
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`Intel Corporation, Santa Clara, CA
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`(US)
`
`Subject to any disclaimer, the term of this
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`patent is extended or adjusted under 35
`U.S.C. 154(b) by 1240 days.
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`(21) Appl.No.: 10/877,943
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`(22) Filed:
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`Jun. 25, 2004
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`Prior Publication Data
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`US 2005/0287978 A1
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`Int. Cl.
`H04L 27/28
`(2006.01)
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`.‘................'.......V.............................. 375/260
`(52) US. Cl.-
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`(58) held 01 Llassmcatlon Search ................. 375/260,
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`375/347, 267, 147, 150, 149; 455/403, 562.1,
`455/101, 102, 103, 69, 73; 342/372, 368,
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`342877, 383
`See application file for complete search history.
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`References Cited
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`
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`
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`
`pgS.
`
`
`
`'
`(Contlnued)
`
`
`
`Primary ExamineriKhai Tran
`
`
`
`
`
`
`(74) Al/umey, Age/12, 0,, FirmiSchwegman, Lundberg &
`
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`
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`Woessner, P.A.; Gregory J. Gorn'e
`
`
`
`(57)
`
`
`
`ABSTRACT
`
`
`
`
`
`
`
`
`
`
`A multicarrier receiver generates a quantized transmit beam-
`
`
`
`
`
`
`
`
`former matrix (V) for each subcarrier of a multicarrier com-
`munication channel for use by a multicarrier transmitting
`
`
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`
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`
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`station. The multicarrier receiver applies a corrected receiver
`beamformer matrix (UH) to received subcarriers signals gen-
`
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`
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`erated by signals received from the transmitting station.
`
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`34 Claims, 11 Drawing Sheets
`
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`rm
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`110m
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`7(1), 01(1)
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`Page 1 of 26
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`SAMSUNG EXHIBIT 1009
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`SAMSUNG EXHIBIT 1009
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`US 7,570,696 B2
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`Page 2
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`Jongren, G., et al., “Utilizing Quantized Feedback Information In
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`U.S.App1. No, 10/812,834 Response filed Oct. 9, 2007 to Non-Final
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`2008”, 9 Pgs.
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`H I”II
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`TRANSMITTING STATION PROCEDURE
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`RECEIVE QUANJIZED TRANSMIT BEAMEORMINC
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`MATRICES (V) FROM RECEIVING STATION
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`APPLY TO EACH SUBCARRIER
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`RECEIVING STATION PROCEDURE
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`US. Patent
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`Aug. 4, 2009
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`US 7,570,696 B2
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`US. Patent
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`Aug. 4, 2009
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`Sheet 11 0f 11
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`US 7,570,696 B2
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`US 7,570,696 B2
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`1
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`MULTIPLE INPUT MULTIPLE OUTPUT
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`MULTICARRIER COMMUNICATION
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`SYSTEM AND METHODS WITH QUANTIZED
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`BEAMFORMING FEEDBACK
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`TECHNICAL FIELD
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`Embodiments of the present invention pertain to wireless
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`communications, and in some embodiments, to multicarrier
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`communications.
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`BACKGROUND
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`Wireless communication systems conventionally use feed-
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`back to allow a transmitting station to adapt it’ s transmissions
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`to changing channel conditions. One problem with multicar-
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`rier communication systems that use many subcarriers, such
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`as systems employing orthogonal frequency division multi-
`plexed (OFDM) signals, is that the channel conditions may be
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`different for each ofthe subcarriers. The amount of feedback
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`to adapt to changing channel conditions may be significant
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`and consumes bandwidth as well as uses additional energy.
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`This is especially a concern when multiple antennas are used
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`to communication additional data streams over the same sub-
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`carriers; as in the case of multiple input multiple output
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`(MIMO) systems. Thus, there are general needs for systems
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`and methods that may adapt to changing channel conditions
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`with less feedback.
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`BRIEF DESCRIPTION OF TIIE DRAWINGS
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`2
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`quency division multiplexed (OFDM) receiver in accordance
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`with some embodiments of the present invention.
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`DETAILED DESCRIPTION
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`The following description and the drawings illustrate spe-
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`cific embodiments of the invention sufficiently to enable
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`those skilled in the art to practice them. Other embodiments
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`may incorporate structural; logical; electrical; process; and
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`other changes. Examples merely typify possible variations.
`Individual components and functions are optional unless
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`explicitly required, and the sequence of operations may vary.
`Portions and features of some embodiments may be included
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`in or substituted for those of others. Embodiments of the
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`invention may be referred to; individually or collectively;
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`herein by the term “invention” merely for convenience and
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`without intending to voluntarily limit the scope of this appli-
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`cation to any single invention or inventive concept if more
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`than one is in fact disclosed.
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`FIG. 1 is a block diagram of a multicarrier transmitter in
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`accordance with some embodiments of the present invention.
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`Multicarrier transmitter 100 may be part of a wireless com—
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`munication device and may transmit multicarrier communi-
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`cation signals comprising a plurality of subcarriers; such as
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`orthogonal frequency division multiplexed (OFDM) commu-
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`nication signals; although the scopc of thc invention is not
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`limited in this respect.
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`In accordance with some embodiments; multicarrier trans-
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`mitter 100 may apply quantized transmit beamforming coef—
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`ficients to symbol-modulated subcarriers of a multicarrier
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`communication signal in a signal path before an inverse Fou-
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`rier transform (IFFT) is performed on the subcarriers. The
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`quantized transmit beamforming coefficients may comprise
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`predetermined numbers of bits for each subcarrier indicating
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`amounts to weight an amplitude and shift a phase of an
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`associated symbol-modulated subcarrier. In some embodi-
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`ments; multicarrier transmitter 100 may comprise a plurality
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`of transmit subcarrier bearnformers 108 to apply the quan-
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`ti zed transmit beamforming coefficients to symbol-modu-
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`lated subcarriers 107.
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`In some embodiments, the transmit subcarrier beamform-
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`ers 108 may apply the quantized transmit beamforming coef-
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`ficients in the frequency domain to frequency-domain sym-
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`bol-modulated subcarriers 107 before an IFFT is performed
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`on the symbol-modulated subcarriers. In some embodiments;
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`a quantized transmit beamformer matrix (C) generated by a
`receiving station includes the transmit beamforming coeffi—
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`cients. In some embodiments; the transmit beamforming
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`coefficients may be complex values.
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`The use of quantized transmit beamforming coefficients
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`may significantly reduce the amount of feedback provided by
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`a receiving station. In some embodiments; closed loop adap-
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`tive beamforming may performed by transmitter 100. The
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`adaptive beamforming may generate signals for different spa-
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`tial channels by taking into account multipath differences in
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`the communication channel. Another purpose of the adaptive
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`beamforming is to take into account the channel conditions
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`(i.e., adapt to changing channel conditions of a fading chan-
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`nel) as wcll as takc into account channcl conditions between
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`the transmitting and receiving stations.
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`In some embodiments; multicarrier transmitter 1 00 may be
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`part ofa closed loop multiple—input multiple—output (MIMO)
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`system that performs adaptive beamforming based on singu-
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`lar value decomposition (SVD). In these embodiments; the
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`MIMO system may be viewed as a plurality of decoupled
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`(independent or orthogonal)
`single—input
`single—output
`(SISO) systems referred to as orthogonal spatial channels.
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`The appended claims are directed to some of the various
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`embodiments of the present invention. However, the detailed
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`description presents a more complete understanding of
`embodiments of the present invention when considered in
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`connection with the figures, wherein like reference numbers
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`refer to similar items throughout the figures and:
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`F G. 1 is a block diagram of a multicarrier transmitter in
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`accordance with some embodiments ofthe present invention;
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`F G. 2 is a block diagram of a multicarrier receiver in
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`accordance with some embodiments ofthe present invention;
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`F GS. 3A and 3B illustrate quantization schemes in accor-
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`dance with some embodiments of the present invention;
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`F GS. 4A and 4B illustrate amplitude and phase subfields
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`of quantized beamforming coefficients in accordance with
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`some embodiments of the present invention;
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`F G. 5 illustrates channel measurements for use in gener-
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`ating quantized beamformer coefficients for groups of sub—
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`carriers in accordance with some embodiments ofthe present
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`invention;
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`F GS. 6A and 6B illustrate quantized transmit beamform-
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`ing coefficients in accordance with some embodiments of the
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`present invention;
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`F G. 7 is a flow chart of a multicarrier signal transmission
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`procedure in accordance with some embodiments of the
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`present invention;
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`F G. 8 is a flow chart of a multicarrier signal reception
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`procedure in accordance with some embodiments of the
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`present invention;
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`F G. 9 is a functional diagram illustrating the operation of
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`a 4x2 multiple-input multiple-output (MIMO) orthogonal
`frequency division multiplexed (OFDM) transmitter in accor-
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`dance with some embodiments of the present invention; and
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`F G. 10 is a functional diagram illustrating the operation of
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`a multiple-input multiple-output (MIMO) orthogonal fre-
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`Page 14 of 26
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`3
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`The number of orthogonal spatial channels is generally not
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`greater than a minimum number of transmit and minimum
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`number of receive antennas.
`In accordance with some
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`embodiments of this invention, the spatial channels may be
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`substantially orthogonal. The substantial orthogonality is
`achieved by applying appropriate transmit and receive beam—
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`forming coefficients.
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`In some embodiments, encoded bit stream 103 may be
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`separated by bit demultiplexer of circuitry 104 into several
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`flows (data streams) in accordance with the number of spatial
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`channels. These flows may be referred to as spatial bit streams
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`and may comprise the same number of bits when identical
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`modulation and/or coding schemes are used for each of the
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`spatial channels. The spatial bit streams may contain different
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`numbers of bits when different modulation and/or coding
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`schemes are used for each of the spatial channels, although
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`the scope of the invention is not limited in this respect.
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`In some embodiments, each spatial channel may be used
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`communicate separate and/or independent data streams on
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`the same subcarriers as the other spatial channels allowing the
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`transmission of additional data without an increase in fre—
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`quency bandwidth. The use of spatial channels takes advan-
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`tage of the multipath characteristics of the channel.
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`In accordance with closed loop MIMO embodiments ofthe
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`present invention, when spatial channels are substantially
`orthogonal, each spatial channel may be associated with a
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`beamforming pattern, rather than an antenna. Signals in each
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`spatial channel may be transmitted from the available anten-
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`nas simultaneously. In other words, each antenna may trans-
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`mit signals with different weights which are specific to the
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`individual antenna. Examples of these embodiments are
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`described in more detail below.
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`In some embodiments, multicarrier transmitter 100 may
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`comprise encoder 102, which may be a forward error correct-
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`ing (FEC) encoder, 0 apply error-correcting codes to bit
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`stream 101 and generate encoded bit stream 103. In some
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`embodiments, multicarrier transmitter 100 may also com-
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`prise bit demultiplexer and interleaver circuitry 104 to per-
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`mute bits of encoded bit stream 103 and demultiplex the bits
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`into a plurality of spatial/frequency channels.
`In some
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`embodiments, permuted bits may be separated by bit demul-
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`tiplexer of circuitry 104 into one or more spatial streams
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`associated with each spatial channel. Each of the spatial
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`streams may be permuted by an interleaver of circuitry 1 04 in
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`accordance with an interleaving pattern. Then, bit demulti-
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`plexer of circuitry 104 may separate each of the permuted
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`spatial streams into groups for modulation on the data sub—
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`carriers of the multicarrier communication channel. The
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`grouping of bits may depend on the modulation levels for the
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`subcarrier and may be provided by processing circuitry 116,
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`although the scope of the invention is not limited in this
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`respect.
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`In some embodiments, multicarrier transmitter 100 may
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`also comprise symbol mapping circuitry 106 for each spatial
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`stream and/or spatial channel to generate symbol-modulated
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`subcarriers 107 from spatial chaimel multiplexed bit streams
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`105. Transmit subcarrier beamformers 108 may be associated
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`nel and may apply quantized transmit beamforming coeffi-
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`cients 118 to each subcarrier signal to generate frequency-
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`domain symbol-modulated subcarriers 109 for each transmit
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`antenna 114.
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`In some embodiments, multicarrier transmitter 100 may
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`also comprise inverse fast Fourier transform circuitry (IFFT)
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`circuitry 110 for each transmit antenna 114 to perform an
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`IFFT on symbol—modulated subcarriers 109 after application
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`of quantized transmit beamfonning coeflicients 118 by trans-
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`US 7,570,696 B2
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`mit subcarrier beamformers 108 to generate time-domain
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`samples 111 for each transmit antenna 114. In some embodi-
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`ments, a cyclic extension may be added to time-domain
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`samples 111 to help reduce the effects of intersymbol inter-
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`ference, although the scope of the invention is not limited in
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`this respect.
`In some embodiments, multicarrier transmitter 100 may
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`also comprise digital to analog conversion (DAC) circuitry
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`and radio-frequency (RF) circuitry 112 which may be asso-
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`ciated with one of transmit antennas 114. Circuitry 112 may
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`generate RF signals for transmission from time-domain
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`samples 111 generated by the IFFT circuitry 10.
`In some embodiments, multicarrier transmitter 100 may
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`also comprise processing circuitry 116 to provide transmit
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`parameters to various elements of transmitter 100. For
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`example, processing circuitry 116 may provide interleaving
`parameters 120 for the interleaver ofcircuitry 104, subcarrier
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`modulation levels 122 to each of symbol mapping circuitry
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`106, IFFT size information 124 to IFFT circuitry 110, and
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`code type and/or coding rate information 126 to encoder 102,
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`although the scope of the invention is not limited in this
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`respect. In some embodiments, circuitry 116 may assign the
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`transmit parameters based on channel feedback information
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`115 received from another communication station for fast
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`link adaptation.
`In some embodiments, transmit antennas 114 may be used
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`for transmitting a plurality of spatial streams on a plurality of
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`spatial channels over the multicarrier communication chan-
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`nel. In these embodiments, the number of the spatial streams
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`and/or spatial channels may be less than or equal to the
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`number of the transmit antennas. In some embodiments, four
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`antennas 114 may be used to transmit up to four spatial
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`streams over corresponding spatial channels, although the
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`scope of the present invention is not limited in this respect.
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`In some embodiments, the quantized transmit beamform-
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`ing coefficients for each subcarrier may represent a quantized
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`transmit beamforming matrix (V) for each subcarrier. In some
`embodiments, each quantized transmit beamforming matrix (
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`\7) may be a unitary matrix having a number of rows equaling
`the number of the transmit antennas. and a number of col-
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`umns equaling the number of the spatial streams (or spatial
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`channels). As used herein, the use of the terms “rows” and
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`“columns” is interchangeable.
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`In some embodiments, elements of each quantized trans-
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`mit beamforming matrix W) may comprise an amplitude
`subfield and a phase subfield with each field having predeter-
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`mined numbers of bits. In some embodiments, the amplitude
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`subfield represents the square of the amount to weight the
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`amplitude of an associated symbol—modulated subcarrier.
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`This is discussed more detail below with reference to FIGS.
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`4A and 4B. Some embodiments may use uniform quantiza-
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`tion of the square amplitudes of the transmit beamforming
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`coefficients. This uniform quantization may be near to opti-
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`mal for a typical random Rayleigh indoor channel because the
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`square amplitudes of the transmit beamforming coefficients
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`have a distribution that is close to uniform.
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`In some embodiments, multicarrier transmitter 100 may be
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`part of a transmitting station and may receive channel feed-
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`back information 115 comprising a quantized transmit beam—
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`forming matrix (V) for each subcarrier from a receiving sta-
`tion. In these embodiments, processing circuitry 116 may
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`provide quantized transmit beamforming coefficients 118
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`from the quantized transmit beamforming matrix (V) to a
`corresponding one of transmit subcarrier beamformers 108.
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`In these embodiments, the receiving station may measure
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`signals received from transmitter 100 to estimate a channel
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`Page 15 of 26
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`5
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`transfer matrix (H) for each subcarrier of the multicarrier
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`communication channel, and may generate the quantized
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`beamforming matrix ((7) for each subcarrier from the channel
`transfer matrix (H). In these embodiments, the receiving sta-
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`tion may transmit the quantized beamforming matrix (\7) for
`each subcarrier to the transmitting station in a response
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`packet, although the scope of the invention is not limited in
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`this respect. In some of these embodiments, the receiving
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`station may measure a preamble of a packet received from the
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`transmitting station to estimate the channel transfer matrix
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`(H) for each subcarrier of the multicarrier communication
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`channel. In some embodiments, the receiving station may
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`measure a physical
`layer convergence protocol
`(PLCP)
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`header of a packet received from the transmitting station to
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`estimate the channel transfer matrix (H) for each subcarrier,
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`although the scope of the invention is not limited in this
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`respect. In some of these embodiments, the receiving station
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`may perform a singular value decomposition (SVD) on the
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`channel transfer matrix (H) to generate the quantized beam-
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`forming matrix (Q) for each subcarrier. These embodiments
`are discussed in more detail below.
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`In some embodiments, the predetermined numbers of bits
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`comprising the quantized beamforming matrix (V) may be
`lower during initial portions of a packet exchange between a
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`transmitting station and a receiving station (i.e., during a
`coarse quantization mode) and may be greater during subse-
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`quent portions of the packet exchange (i.e., during a fine
`quantization mode). In this way, a transmitting station may
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`quickly adjust to the channel conditions and may subse-
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`quently fine tune its transmissions as time goes on allowing
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`for faster link adaptation.
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`In some embodiments, elements of the quantized beam-
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`forming matrix (\~/) may represent differences from previ-
`ously received beamforming coefficients. In some embodi-
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`ments, the quantized beamformer coefficients may be applied
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`to groups of subcarriers. These embodiments are described in
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`more detail below.
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`In some embodiments, multicarrier transmitter 100 (FIG.
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`1) and/or multicarrier receiver 200 (FIG. 2) may communi-
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`cate over a wideband multicarrier communication channel.
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`The wideband channel may comprise one or more multicar—
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`rier subchannels. The subchannels may be frequency-divi-
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`sion multiplexed (i.e., separated in frequency from other sub-
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`channels) and may be within a predetermined frequency
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`spectrum. The subchannels may comprise a plurality of
`orthogonal subcarriers. In some embodiments, the orthogo-
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`nal subcarriers of a subchannel may be closely spaced OFDM
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`subcarriers. To achieve orthogonality between closely spaced
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`subcarriers, in some embodiments, the subcarriers of a par-
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`ticular subchannel may have a null at substantially a center
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`frequency of the other subcarriers of that subchannel.
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`In some embodiments, multicarrier transmitter 100 (FIG.
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`1) and/or multicarrier receiver 200 (FIG. 2) may communi-