Title of Invention

"SPATIAL SPREADING WITH SPACE-TIME AND SPACE-FREQUENCY TRANSMIT DIVERSITY SCHEMES FOR A WIRELESS COMMUNICATION SYSTEM"

Abstract Techniques for transmitting date using a combination of transmit diversity schemes are described. These transmit diversity schemes include spatial spreading, continuous beamforming, cyclic delay diversity, space-time transmit diversity (SITU), space-frequency transmit diversity (SFTD), and orthogonal transmit diversity (OTD). A transmitting entity processes one or more (ND) data symbol streams based on a transmit diversity scheme (e.g., STTD, SFTD, or OTD) to generate multiple (NC) coded symbol streams. Each data symbol stream may be sent as a single coded symbol stream or as multiple (e.g., two) coded symbol streams using STTD, SFTD, or OTD. The transmitting entity may perform spatial spreading on the NC coded symbol streams with different man-ices to generate multiple (NT) transmit symbol streams for transmission from NT antennas. Additionally or alternatively, the transmitting entity may perform continuous beamforming on the NT transmit symbol streams in either the time domain or the frequency domain.
Full Text SPATIAL SPREADING WITH SPACE-TIME AND
SPACE-FREQUENCY TRANSMIT DIVERSITY SCHEMES
FOR A WIRELESS COMMUNICATION SYSTEM
I. Claim of Priority under 35 U. S. C. §119
[0001] The present Application for Patent claims priority to Provisional Application
Serial No. 60/607,371, entitled "Steering Diversity with Space-Time Transmit Diversity
for a Wireless Communication System," filed September 3, 2004, and Provisional
Application Serial No. 60/608,226, entitled "Steering Diversity with Space-Time and
Space-Frequency Transmit Diversity Schemes for a Wireless Communication System,"
filed September 8, 2004, both assigned to the assignee hereof and expressly
incorporated herein by reference.
BACKGROUND
II. Field
[0002] The present disclosure relates generally to communication, and more specifically
to techniques for transmitting data in a multiple-antenna communication system.
III. Background
[0003] A multi-antenna communication system employs multiple (NT) transmit
antennas and one or more (NR) receive antennas for data transmission. The NT transmit
antennas may be used to increase system throughput by transmitting different data from
the antennas or to improve reliability by transmitting data redundantly.
[0004] In the multi-antenna communication system, a propagation path exists between
each pair of transmit and receive antennas. NT-NR different propagation paths are
formed between the NT transmit antennas and the NR receive antennas. These
propagation paths may experience different channel conditions (e.g., different fading,
multipath, and interference effects) and may achieve different signal-to-noise-andinterference
ratios (SNRs). The channel responses of the NT-NR propagation paths may
thus vary from path to path, and may further vary over time for a time-variant wireless
channel and across frequency for a dispersive wireless channel. The variant nature of
the propagation paths makes it challenging to transmit data in an efficient and reliable
manner.
[0005J Transmit diversity refers to redundant transmission of data across space,
frequency, time, or a combination of these dimensions to improve reliability for the data
transmission. One goal of transmit diversity is to maximize diversity for the data
transmission across as many dimensions as possible to achieve robust performance.
Another goal is to simplify the processing for transmit diversity at both a transmitter and
a receiver.
[0006] There is therefore a need in the art for techniques to transmit data with transmit
diversity in a multi-antenna communication system.
SUMMARY
[0007] Techniques for transmitting data using a combination of transmit diversity
schemes are described herein. These transmit diversity schemes include spatial
spreading, continuous beamforming, cyclic delay diversity, space-time transmit
diversity (STTD), space-frequency transmit diversity (SFTD), and orthogonal transmit
diversity (OTD), all of which are described below.
[0008] In an embodiment, a transmitting entity processes (e.g., encodes, interleaves, and
symbol maps) one or more (No) data streams to generate ND data symbol streams. The
transmitting entity further processes the ND data symbol streams based on a transmit
diversity scheme (e.g., STTD, SFTP, or OTD) to generate multiple (Nc) coded symbol
streams. Hach data symbol stream may be sent as a single coded symbol stream or as
multiple (e.g., two) coded symbol streams using STTD, SFTD, or OTD. The
transmitting entity may perform spatial spreading on the NC coded symbol streams with
different matrices to generate multiple (Mr) transmit symbol streams for transmission
from NT antennas. Additionally or alternatively, the transmitting entity may perform
continuous beamtbrming on the NT transmit symbol streams in either the time domain
or the frequency domain. A receiving entity performs the complementary processing to
recover the ND data streams.
[0009] Various aspects and embodiments of the invention are described in further detail
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a block diagram of a multi-antenna transmitting entity.
[0011] FIG. 2 shows a block diagram of a transmit (TX) data processor, a TX STTD
processor, and a spatial spreader at the transmitting entity.
[0012] FIG. 3 shows a block diagram of NT modulators at the transmitting entity.
[0013] FIG. 4 shows a block diagram of a single-antenna receiving entity and a multiantenna
receiving entity.
DETAILED DESCRIPTION
[0014] The word "exemplary" is used herein to mean "serving as an example, instance,
or illustration." Any embodiment described herein as "exemplary" is not necessarily to
be construed as preferred or advantageous over other embodiments.
[0015] The transmission techniques described herein may be used for multiple-input
single-output (MISO) and multiple-input multiple-output (MIMO) transmissions. A
MISO transmission utilizes multiple transmit antennas and a single receive antenna. A
MIMO transmission utilizes multiple transmit antennas and multiple receive antennas.
[0016] The transmission techniques may be used for single-carrier and multi-carrier
communication systems. A multi-carrier system may utilize orthogonal frequency
division multiplexing (OFDM), some other multi-carrier modulation scheme, or some
other construct. OFDM effectively partitions the overall system bandwidth into
multiple (Np) orthogonal frequency subbands, which are also called tones, subcarriers,
bins, frequency channels, and so on. With OFDM, each subband is associated with a
respective subcarrier that may be modulated with data. A single-carrier system may
utilize single-earner frequency division multiple access (SC-FDMA), code division
multiple access (CDMA), or some other single-carrier modulation scheme. An SCFDMA
system may utilize (1) interleaved FDMA (IFDMA) to transmit data and pilot
on subbands that are distributed across the overall system bandwidth (2) localized
FDMA (LFDMA) to transmit data and pilot on a group of adjacent subbands, or (3)
enhanced FDMA (EFDMA) to transmit data and pilot on multiple groups of adjacent
subbands. In general, modulation symbols are sent in the time domain with SC-FDMA
(e.g., IFDMA, LFDMA, and EFDMA) and in the frequency domain with OFDM. For
clarity, much of the description below is for a system that utilizes OFDM, with all NF
subbands being available for transmission.
[0017] Transmit diversity may be achieved using various schemes including STTD,
SFTD, OTD, spatial spreading, continuous beamforming, and so on. STTD transmits a
pair of data symbols from two antennas on one subband in two symbol periods to
achieve space and time diversity. SFTD transmits a pair of data symbols from two
antennas on two subbands in one symbol period to achieve space and frequency
diversity. OTD transmits multiple (No) data symbols from NO antennas on one subband
in NO symbol periods using NO orthogonal codes to achieve space and time diversity,
where N(! > 2. As used herein, a data symbol is a modulation symbol for traffic/packet
data, a pilot symbol is a modulation symbol for pilot (which is data that is known a
priori by both the transmitting and receiving entities), a modulation symbol is a
complex value for a point in a signal constellation for a modulation scheme (e.g., MPSK
or M-QAM), a transmission symbol (e.g., an OFDM symbol) is a sequence of
time-domain samples generated by a single-carrier or multi-carrier modulation scheme
for one symbol period, and a symbol is typically a complex value.
[0018] Spatial spreading refers to the transmission of a symbol from multiple transmit
antennas simultaneously, possibly with different amplitudes and/or phases determined
by a steering vector used for that symbol. Spatial spreading may also be called steering
diversity, transmit steering, pseudo-random transmit steering, space-time scrambling,
and so on. Spatial spreading may be used in combination with STTD, SFTD, OTD,
and/or continuous beamforming to improve performance and/or to extend the normal
operation of these transmit diversity schemes. For example, STTD normally transmits
one data symbol stream from two antennas. Spatial spreading may be used with STTD
to transmit more than one data symbol stream from more than two antennas
simultaneously.
[0019] Continuous beamforming refers to the use of different beams across the NF
subbands. The beamforming is continuous in that the beams change in a gradual instead
of abrupt manner across the subbands. Continuous beamforming may be performed in
the frequency domain by multiplying the symbols for each subband with a beamforming
matrix for that subband. Continuous beamforming may also be performed in the time
domain by applying different cyclic delays for different transmit antennas. Timedomain
continuous beamforming is also called cyclic delay diversity.
[0020] Transmit diversity may be achieved using a combination of transmit diversity
schemes. For example, transmit diversity may be achieved using a combination of
STTD, SF1T3 or OTD with either spatial spreading or continuous beamforming. As
another example, transmit diversity may be achieved using a combination of STTD,
S.FTD, or OTD with both spatial spreading and cyclic delay diversity. For clarity, much
of the following description assumes the use of STTD.
[0021] FIG. 1 shows a block diagram of an embodiment of a multi-antenna transmitting
entity 110, which may be part of an access point or a user terminal. An access point
may also be called a base station, a base transceiver system, or some other terminology.
A user terminal may also be called a mobile station, a wireless device, or some other
terminology.
[0022] Pot the embodiment shown in FIG. 1, transmitting entity 110 may use a
combination of STTD, spatial spreading, and continuous beamforming for data
transmission. A TX data processor 112 receives and processes ND data streams and
provides NO data symbol streams, where ND > 1. TX data processor 112 may process
each data stream independently or may jointly process multiple data streams together.
For example, TX data processor 112 may format, scramble, encode, interleave, and
symbol map each data stream in accordance with a coding and modulation scheme
selected for that data stream. A TX STTD processor 120 receives the ND data symbol
streams, performs STTD encoding on zero, one, or multiple data symbol streams, and
provides NC coded symbol streams, where Nc > ND. In general, TX STTD processor
120 may process any number of data symbol streams with STTD, SFTD, OTD, or some
other transmit diversity scheme. Each data symbol stream may be sent as one coded
symbol stream or multiple coded symbol streams, as described below.
[0023] A spatial spreader 130 receives and multiplexes the coded symbols with pilot
symbols, performs spatial spreading by multiplying the coded symbols and pilot
symbols with different steering matrices, and provides NT transmit symbol streams for
the NT transmit antennas, where NT > Nc. Each transmit symbol is a complex value to
be sent from one transmit antenna on one subband in one symbol period. NT modulators
(MOD) 132a through 132nt receive the NT transmit symbol streams. For an OFDMbased
system, each modulator 132 performs OFDM modulation on its transmit symbol
stream and provides a stream of time-domain samples. Each modulator 132 may also
apply a different cyclic delay for its antenna, as described below. NT modulators 132a
through 132nt provide NT sample streams to NT transmitter units (TMTR) 134a through
134nt, respectively. Each transmitter unit 134 conditions (e.g., converts to analog,
amplifies, filters, and frequency upconverts) its sample stream and generates a
modulated signal. NT modulated signals from NT transmitter units 134a through 134nt
are transmitted from NT transmit antennas 136a through 136nt, respectively.
[0024] Controller 140 controls the operation at transmitting entity 110. Memory 142
stores data and/or program codes for transmitting entity 110.
[0025] Transmitting entity 110 may transmit any number of data symbol streams with
STTD and any number of data symbol streams without STTD, depending on the number
of transmit and receive antennas available for data transmission. The STTD encoding
for one data symbol stream may be performed as follows. For each pair of data symbols
i'a and 5|, to be sent in two symbol periods, TX STTD processor 120 generates two
vectors s, = [s, sb]T and s2 = [s^ - s * a ] T , where " * " denotes the complex conjugate
and " 7 " denotes the transpose. Alternatively, TX STTD processor 120 may generate
two vectors s, =[st -s^]T and s2 =[sb s*JT for the pair of data symbols ,sa and sb.
For both STTD encoding schemes, each vector s,, for t = 1, 2, includes two coded
symbols to be sent from NT transmit antennas in one symbol period, where NT > 2.
Vector BJ is sent in the first symbol period, and vector s2 is sent in the next symbol
period. Each data symbol is included in both vectors and is thus sent in two symbol
periods. The m-th coded symbol stream is formed by the m-th element of the two
vectors S; and s,. For clarity, the following description is for the STTD encoding
scheme with s, =|>a sb]r and s2 =[sb -s*]r . For this STTD encoding scheme, the
first coded symbol stream includes coded symbols sa and sb, and the second coded
symbol stream includes coded symbols s\, and - s*.
[0026] Table 1 lists four configurations that may be used for data transmission. An
NDxNc configuration denotes the transmission of ND data symbol streams as NC
coded symbol streams, where ND > 1 and Nc > ND. The first column identifies the
four configurations. For each configuration, the second column indicates the number of
data symbol streams being sent, and the third column indicates the number of coded
symbol streams. The fourth column lists the ND data symbol streams for each
configuration, the fifth column lists the coded symbol stream(s) for each data symbol
stream, the sixth column gives the coded symbol to be sent in the first symbol period
(t = 1) for each coded symbol stream, and the seventh column gives the coded symbol
to be sen! in the second symbol period (t = 2) for each coded symbol stream. The
number of data symbols sent in each 2-symbol interval is equal to twice the number of
data symbol streams, or 2No. The eighth column indicates the number of transmit
antennas required for each configuration, and the ninth column indicates the number of
receive antennas required for each configuration.
(Table Removed)
[0027] As shown in Table 1, a data symbol stream may be sent as two coded symbol
streams with STTD or one coded symbol stream without STTD. For the embodiment
shown in Table 1, for each data symbol stream sent without STTD, the data symbol sent
in the second symbol period (t = 2) is conjugated to match the conjugation performed
on the data symbol stream(s) sent with STTD.
[0028] For the 1x2 configuration, one data symbol stream is STTD encoded to
generate two coded symbol streams. For each 2-symbol interval, vectors s, = [sa sb]T
and s2 ~ [ -v* - s* |7 are generated with data symbols sa and 55. Vector S[ is transmitted
from at least two transmit antennas in the first symbol period, and vector s2 is
transmitted from the same antennas in the second symbol period. A receiving entity
uses at least one receive antenna to recover the data symbol stream.
[0029] For the 2x3 configuration, two data symbol streams are sent as three coded
•symbol streams. The first data symbol stream is STTD encoded to generate two coded
symbol streams. The second data symbol stream is sent without STTD as the third
coded symbol stream. For each 2-symbol interval, vectors Si=[ja sb sc]7 and
§2 = [Jb 'va st]T are generated with data symbols s&, s\» sc and S&, where sa and s\, are
from the first data symbol stream, and sc and Sd are from the second data symbol stream.
Vector s, is transmitted from at least three transmit antennas in the first symbol period,
and vector s? is transmitted from the same antennas in the second symbol period. A
receiving entity uses at least two receive antennas to recover the two data symbol
streams.
[0030] For the 2x4 configuration, two data symbol streams are sent as four coded
symbol streams. Each data symbol stream is STTD encoded to generate two coded
symbol streams. For each 2-symbol interval, vectors Si=[,sa sb sc sj' and
s2 = [si • ,y* s'A - 5* J T are generated with data symbols sa, s\» sc and sd, where sa and sb
are from the first data symbol stream, and sc and s^ are from the second data symbol
stream. Vector s, is transmitted from at least four transmit antennas in the first symbol
period, and vector s2 is transmitted from the same antennas in the second symbol
period. A receiving entity uses at least two receive antennas to recover the two data
symbol streams.
[0031] For the 3x4 configuration, three data symbol streams are sent as four coded
symbol streams. The first data symbol stream is STTD encoded to generate two coded
symbol streams. The second data symbol stream is sent without STTD as the third
coded symbol stream, and the third data symbol stream is sent without STTD as the
fourth coded symbol stream. For each 2-symbol interval, vectors s, =|>a sb sc st]T
and s2 - [si -s* s*d s*s]r are generated with data symbols ja. s\,, sc, Sd, se and Sf, where
sa and ,?b are from the first data symbol stream, sc and sd are from the second data
symbol stream, and se and Sf are from the third data symbol stream. Vector s, is
transmitted from at least four transmit antennas in the first symbol period, and vector s2
is transmitted from the same antennas in the second symbol period. A receiving entity
uses at least three receive antennas to recover the three data symbol streams.
[0032] Table 1 shows four exemplary configurations that may be used for data
transmission, with each configuration having at least one data symbol stream sent with
STTD. Other configurations may also be used for data transmission. A configuration
may also use a combination of STTD, SFTD, and OTD.
[0033] In general, any number of data symbol streams may be sent as any number of
coded symbol streams from any number of transmit antennas, where ND > 1, Nc > ND,
NT > N,-., and NR > ND. Each data symbol stream may or may not be encoded with
STTD, SFTD, OTD, or some other transmit diversity scheme. Each data symbol stream
may be sent as one coded symbol stream or multiple (e.g., two) coded symbol streams.
[0034] The transmitting entity may process the coded symbols for spatial spreading and
continuous beamforming, as follows:
x,(fc) = B(*)-V(fc)-G(*)-s,(*), fort = 1,2, Eq (1)
where s,(k) is an Ncxl vector with NC coded symbols to be sent on subband k in
symbol period f,
G(k) is an Nc x Nc diagonal matrix with NC gain values along the diagonal for
the Nc coded symbols in s,(k) and zeros elsewhere;
is an NT xNc steering matrix for spatial spreading for subband k;
is an NTxNT diagonal matrix for continuous beamforming for subband
k; and
x,(£) is an NTxl vector with NT transmit symbols to be sent from the NT
transmit antennas on subband k in symbol period t.
[0035] Vector s, contains NC coded symbols to be sent in the first symbol period, and
vector s2 contains NC coded symbols to be sent in the second symbol period. Vectors
s, and s2 may be formed as shown in Table 1 for the four configurations in the table.
[0036] Gain matrix G(/t) determines the amount of transmit power to use for each of
the NC coded symbol streams. The gain matrix may be a function of subband index k,
as shown in equation (1), or may be a function that is independent of index k. The total
transmit power available for transmission may be denoted as Ptotal. In an embodiment,
equal transmit power is used for the Nc coded symbol streams, and the diagonal
elements of G(£) have the same value of^/P^/N,-,. In another embodiment, equal
transmit power is used for the ND data symbol streams, and the NC gain values along the
diagonal of G(k) are defined to achieve equal transmit power for the ND data symbol
streams. The Nc gain values may or may not be equal depending on the configuration.
As an example, for the 2x3 configuration, the first data symbol stream is sent as two
coded symbol streams and the second data symbol stream is sent as one coded symbol
stream. To achieve equal transmit power for the two data symbol streams, a 3x3 gain
matrix G(fc) may include gain values of ^/Pto(al/4 , i/Ptota]/4 , and ^/P^j/2 along the
diagonal for the three coded symbol streams. Each coded symbol in the third coded
symbol stream is then scaled by yPtotal / 2 and is transmitted with twice the power as the
other two coded symbols sent in the same symbol period. For both embodiments, the
NC coded symbols for each symbol period may be scaled to utilize the maximum
transmit power available for each transmit antenna. In general, the diagonal elements of
G(&) may be selected to utilize any amounts of transmit power for the Nc coded
symbol streams and to achieve any desired SNRs for the ND data symbol streams. The
power scaling for the NC coded symbol streams may also be achieved by scaling the
columns of the steering matrix V(£) with appropriate gains.
[0037] A given data symbol stream (which is denoted as {s}) may be sent as one coded
symbol stream (which is denoted as {?}) in various manners. In one embodiment, the
gain matrix G(k) contains ones along the diagonal, and coded symbol stream {?} is
transmitted at the same power level as other coded symbol streams. For this
embodiment, data symbol stream {s} is transmitted at lower transmit power than an
STTD encoded data symbol stream and hence achieves a lower received SNR at the
receiving entity. The coding and modulation for data symbol stream {s} may be
selected to achieve the desired performance, e.g., the desired packet error rate. In
another embodiment, each data symbol in data symbol stream {s} is repeated and
transmitted in two symbol periods. As an example, for the 2x3 configuration, data
symbol sc may be sent in two symbol periods, then data symbol sa may be sent in two
symbol periods, and so on. This embodiment may achieve similar received SNRs for
the ND data symbol streams, which may simplify the coding and modulation at the
transmitting entity and the demodulation and decoding at the receiving entity.
[0038] Steering matrix V(&) spatially spreads the Nc coded symbols for each symbol
period such that each coded symbol is transmitted from all NT transmit antennas and
achieves spatial diversity. Spatial spreading may be performed with various types of
steering matrices, such as Walsh matrices, Fourier matrices, pseudo-random matrices,
and so on, which may be generated as described below. The same steering matrix V(fe)
is used for the two vectors Sj(fc) and s2(Jt) for each subband k. Different steering
matrices may be used for different subbands and/or different time intervals, where each
time interval may span an integer multiple of two symbol periods for STTD.
[0039] Matrix B(fc) performs continuous beamforming in the frequency domain. For
an OFDM-based system, a different beamforming matrix may be used for each subband.
The beamforming matrix for each subband k may be a diagonal matrix having the
following form:
where £.(&) is a weight for subband k of transmit antenna i. The weight bt(k) may be
defined as:
j (k) = e-J**WM-*f i for i = 1,.... NT and fc = 1,.... NF , Eq (3)
where AT, is the time delay on transmit antenna i;
A/ is the frequency spacing between adjacent subbands; and
l(k) • A/ is the actually frequency corresponding to subband index k.
For example, if NF =:64, then subband index k may go from 1 to 64, and l(k) may be
equal to k - 33 and may range from -32 to +31. If the overall system bandwidth is 20
MHz and NF = 64, then A/ = 20 MHz / 64 = 3.125 kHz. l(k) • A/ provides the actual
frequency (in Hertz) for each value of k. The weights b,(k) shown in equation (3)
correspond to a progressive phase shift across the NF total subbands for each transmit
antenna, with the phase shift changing at different rates for the NT transmit antennas.
These weights effectively form a different beam for each subband.
[0040] Continuous beamforming may also be performed in the time domain as follows.
For each symbol period, an Np-point inverse discrete Fourier transform (IDFT) or
inverse fast Fourier transform (IFFT) may be performed on NF transmit symbols to be
sent on Np subbands of each transmit antenna i to generate NF time-domain samples for
that transmit antenna. The NF time-domain samples for each transmit antenna z may be
cyclically or circularly delayed by T,. For example, Tf may be defined as:
T; =(i-'!)• AT, for z = l,...,NT, where AT may be equal to one sample period, a
fraction of a sample period, or more than one sample period. The time-domain samples
for each antenna are then cyclically delayed by a different amount.
[0041] In equation (1), the scaling by the gain matrix G(fe) may be omitted by setting
jG(fe) = 1, the spatial spreading may be omitted by setting V(fc) = I, and the continuous
beamforming may be omitted by setting B(ife) = I, where I is the identity matrix
containing ones along the diagonal and zeros elsewhere. The transmitting entity may
thus selectively perform scaling, spatial spreading, and continuous beamforming by
using appropriate matrices. The matrices for spatial spreading and continuous
beamforming may also be combined as VB(fc) = B(&) • V(&). The matrices for scaling,
spatial spreading, and continuous beamforming may also be combined as
YBG(/c) = §(&)• V(/c)-G(fc). The transmitting entity may then perform spatial
processing on data vector s,(fc) with VB(ifc) or YBO(fc).
[0042] The transmitting entity may also use a combination of SFTD, spatial spreading,
and possibly continuous beamforming. For SFTD, the transmitting entity may generate
two vectors s4 and s2 as described above for STTD and may send these vectors on two
subbands in one symbol period. For the 1x2 configuration, two vectors s, = [sa sb]T
and s2 -• [si - s*a]' may be generated for each pair of data symbols to be sent on two
subbands in one symbol period for one data symbol stream. For the 2x3 configuration,
two data symbol vectors §j = [sa sb sc]T and s2 = [s^ -s* s"A]T may be generated for
two pair of data symbols to be sent on two subbands in one symbol period for two data
symbol streams. For the 2x4 configuration, two vectors s, =[5a sb sf SA]T and
§2 = iX - sl sd - s*]r may be generated for two pairs of data symbols to be sent on
two subhands in one symbol period for two data symbol streams. For the 3x4
configuration, two vectors s,-^:, sb sc se ] T and s2=[X -s* s'A s"f]T may be
generated for three pair of data symbols to be sent on two subbands in one symbol
period for three data symbol streams. For all configurations, the transmitting entity may
spatially spread and transmit vector s, on one subband in one symbol period and may
spatially spread and transmit vector s2 on another subband in the same symbol period.
The two subbands are typically adjacent to one another.
[0043] The transmitting entity may also use a combination of OTD, spatial spreading,
and possibly continuous beamforming. For OTD, the transmitting entity may generate
multiple (N0) vectors Sj and sNo and may send these vectors on one subband in N0
symbol periods. For N0 = 2, the transmitting entity may generate two vectors Sj and
s2 for two data symbols ja and s\, by (1) multiplying data symbol sa with a first
orthogonal code of {+1 +1} to generate two coded symbols sa and sa for one transmit
antenna, (2) multiplying data symbol Sb with a second orthogonal code of (+1 -1} to
generate two coded symbols s\, and -m, for another transmit antenna, and (3) forming
s, = Oa i'b]7 and s2 = [sa - s J T. In general, NO data symbols may be multiplied with
NO different orthogonal codes to generate NO coded symbol sequences for NO transmit
antennas. Each coded symbol sequence contains NO coded symbols and is generated by
multiplying one data symbol with a specific orthogonal code of length N0. The
orthogonal codes may be Walsh codes, OVSF codes, and so on,
[0044] In general, transmit diversity may be achieved in various manners and in the
time, frequency and/or spatial domains. In one embodiment, transmit diversity is
achieved by multiplying vector s,(k) with steering matrix V(fc) to generate transmit
vector x, ( k ) , as shown in equation (1). In another embodiment, transmit diversity is
achieved by cyclically delaying the time-domain samples for each transmit antenna. In
yet another embodiment, transmit diversity is achieved with a combination of spatial
processing with V(fc) and cyclic delay of the time-domain samples. For all of the
embodiments, vector s,(k) may be formed with STTD, SFTD, OTD, or some other
transmit diversity scheme.
[0045] FIG. 2 shows a block diagram of an embodiment of TX data processor 112, TX
STTD processor 120, and spatial spreader 130 at transmitting entity 110. For the
embodiment shown in FIG. 2, TX data processor 112 includes ND data stream
2lOa through 2lOnd that independently process the ND data streams. Within
each data stream processor 210, an encoder 212 encodes traffic data in accordance with
a coding scheme and generates code bits. The encoding scheme may include a
convolutional code, a Turbo code, a low density parity check (LDPC) code, a cyclic
redundancy check (CRC) code, a block code, and so on, or a combination thereof. An
interleave!' 214 interleaves (or reorders) the code bits based on an interleaving scheme.
A symbol mapper 216 maps the interleaved bits in accordance with a modulation
scheme and provides data symbols. The coding and modulation for each data stream
may be determined by a rate selected for that data stream. Data stream processors 210a
through 2lOnd provide N0 data symbol streams.
[0046] In another embodiment, which is not shown in FIG. 2, TX data processor 112
jointly processes the data symbol stream(s) to be sent with STTD and the data symbol
stream(s) to be sent without STTD. For example, TX data processor 112 may receive a
single data stream, encode the data stream based on a coding scheme, demultiplex the
code bits into ND coded bit streams, and perform interleaving and symbol mapping
separately for the NO coded bit streams to generate ND data symbol streams. In yet
another embodiment, which is also not shown in FIG. 2, TX data processor 112
independently processes the data symbol stream(s) to be sent with STTD and the data
symbol slream(s) to be sent without STTD. For example, TX data processor 112 may
receive a first data stream to be sent with STTD and a second data stream to be sent
without STTD. TX data processor 112 may encode, interleave, symbol map, and
demultiplex the first data stream to generate (Nc - ND) data symbol streams to be sent
with STTD. TX data processor 112 may also encode, interleave, symbol map, and
demultiplex the second data stream to generate (2ND — Nc) data symbol streams to be
sent without STTD. TX data processor 112 may also process the data stream(s) in other
manners, and this is within the scope of the invention.
[0047] For the embodiment shown in FIG. 2, TX STTD processor 120 includes ND
STTD encoders 220a through 220nd for the ND data symbol streams. Each STTD
encoder 220 performs STTD encoding on its data symbol stream and provides two
coded symbol streams to a multiplexer (Mux) 222. Multiplexer 222 receives the ND
data symbol streams from TX data processor 112 and the ND pairs of coded symbol
streams from STTD encoders 220a through 220nd. For each data symbol stream,
multiplexer 222 provides either that data symbol stream or the associated pair of coded
symbol streams. Multipliers 224a through 224nc receive and scale the Nc symbol
streams from multiplexer 222 with gains g\ through #NC , respectively, and provides Nc
coded symbol streams. The scaling may also be performed at other locations within the
transmit path.
[0048] For the embodiment shown in FIG. 2, spatial spreader 130 includes NF spatial
processors 230a through 230nf for the. NF subbands. A demultiplexer (Demux) 228
receives the NC coded symbol streams and pilot symbols, provides the coded symbols
on subbands and symbol periods used for data transmission, and provides pilot symbols
on subbands and symbol periods used for pilot transmission. Each spatial processor 230
receives NC coded symbols and/or pilot symbols to be sent on the associated subband k
in one symbol period, multiplies the coded symbol and/or pilot symbols with a steering
matrix Y(k), and provides NT transmit symbols to be sent from the NT transmit antenna
on subband k. A multiplexer 232 receives the transmit symbols from all NF spatial
processors 230a through 230nf and maps the NT transmit symbols from each spatial
processor 230 to the NT transmit symbol streams. Each transmit symbol stream includes
NF transmit symbols from the NF spatial processors 230a through 230nf for one transmit
antenna.
[0049] FIG. 3 shows a block diagram of an embodiment of modulators 132a through
132nt at transmitting entity 110. Within each modulator 132, an IDFT unit 312
performs an Np-point IDFT or IFFT on NF transmit symbols to be sent on the NF
subbands in one symbol period and provides NF time-domain samples. A parallel-toserial
converter (P/S Conv) 314 serializes the NF time-domain samples. A circular shift
unit 316 performs a cyclic or circular shift of the NF time-domain samples by
T, =(i-l)-AT, where AT is a fixed period (e.g., one sample period) and T, is the
amount of cyclic shift for transmit antenna i. A cyclic prefix generator 318 receives the
NF circularly shifted samples from unit 316, appends a cyclic prefix of Ncp samples, and
provides an OFDM symbol (or transmission symbol) containing NF + Ncp samples.
The time-domain continuous beamforming may be disabled by having cyclic shift units
316a through 3l6nt simply pass the time-domain samples from P/S converters 314a
through 3L64nt to cyclic prefix generators 318a through 3168nt, respectively. Circular
shift units 316a through 316nt may also just delay (instead of circularly delay) the timedomain
samples from P/S converters 314a through 3164nt by different amounts, so that
the transmissions from antennas 136a through 136nt are delayed by different amounts.
16
[0050] FIG. 4 shows a block diagram of an embodiment of a single-antenna receiving
entity 15f)x and a multi-antenna receiving entity 150y. Each receiving entity may be
part of a base station or a user terminal.
[0051] At single-antenna receiving entity 150x, an antenna 152x receives the NT
modulated signals transmitted by transmitting entity 110 and provides a received signal
to a receiver unit (RCVR) 154x. Receiver unit 154x conditions (e.g., amplifies, filters,
frequency downconverts, and digitizes) the received signal and provides a stream of
received samples to a demodulator (Demod) 156x. For an OFDM-based system,
demodulator 156x performs OFDM demodulation on the received samples to obtain
received symbols, provides received data symbols to a detector 158, and provides
received pilot symbols to a channel estimator 162. Channel estimator 162 derives an
effective channel response estimate for a single-input single-output (SISO) channel
between transmitting entity 110 and receiving entity 150x for each subband used for
data transmission. Detector 158 performs data detection (e.g., equalization) on the
received data symbols for each subband based on the effective SISO channel response
estimate for that subband and provides recovered data symbols for the subband. An RX
data processor 160 processes (e.g., symbol demaps, deinterleaves, and decodes) the
recovered data symbols and provides decoded data.
[0052] At multi-antenna receiving entity 150y, NR antennas 152a through 152nr receive
the NT modulated signals, and each antenna 152 provides a received signal to a
respective receiver unit 154. Each receiver unit 154 conditions its received signal and
provides a received sample stream to an associated demodulator (Demod) 156. Each
demodulator 156 performs OFDM demodulation (if applicable) on its received sample
stream, provides received data symbols to an RX spatial processor 170, and provides
received pilot symbols to a channel estimator 166.
[0053] Channel estimator 166 obtains received pilot symbols for all NR receive
antennas and derives a channel response estimate for the actual or effective MIMO
channel between transmitting entity 110 and receiving entity 150y for each subband
used for data transmission. If transmitting entity 110 performs spatial processing on the
pilot symbols in the same manner as the data symbols, as shown in FIG. 1, then the
steering matrices may be viewed as being part of the wireless channel. In this case,
receiving entity 150y may derive an estimate of the effective MIMO channel, which
includes the actual MIMO channel response as well as the effects of the steering
matrices. If transmitting entity 110 does not perform spatial processing on the pilot
symbols, then receiving entity I50y may derive an estimate of the actual MIMO channel
and may then derive an estimate of the effective MIMO channel based on the actual
MIMO channel response estimate and the steering matrices.
[0054] A matched filter generator 168 derives a spatial filter matrix M(fc) for each
subband used for transmission based on the channel response estimate for that subband.
RX spatial processor 170 obtains received data symbols for all NR receive antennas and
performs pre-processing on the received data symbols to account for the STTD scheme
used by transmitting entity 110. RX spatial processor 170 further performs receiver
spatial processing (or spatial matched filtering) on the pre-processed data symbols for
each subband with the spatial filter matrix for that subband and provides detected
symbols for the subband. An RX STTD processor 172 performs post-processing on the
detected symbols based on the STTD scheme used by transmitting entity 110 and
provides recovered data symbols. An RX data processor 174 processes (e.g., symbol
dernaps, deinterleaves, and decodes) the recovered data symbols and provides decoded
data.
[0055] Controllers 180x and 180y control the operation at receiving entities 150x and
150y, respectively. Memories 182x and 182y store data and/or program codes for
receiving entities 150x and 150y, respectively.
[0056] Various types of steering matrices may be used for spatial spreading. For
example, steering matrix V(&) may be a Walsh matrix, a Fourier matrix, or some other
"1 1"
matrix. A 2x2 Walsh matrix W^ be expressed as W2x2 = . A larger size
Walsh matrix W2NX2N may be formed from a smaller size Walsh matrix WNxN, as
follows:
An Nx N Fourier matrix DNxN has element dnm in the n-th row of the m-th column,
which may be expressed as:
d =e N , for n = l,...,N and m = l,...,N. Eq (5) ' n ,m
Fourier matrices of any square dimension (e.g., 2, 3, 4, 5, and so on) may be formed.
[0057] A Walsh matrix WNxN, a Fourier matrix DNxN , or some other matrix may be
used as a base matrix BNxN to form other steering matrices. For an N xN base matrix,
each of rows 2 through N of the base matrix may be independently multiplied with one
of M different possible scalars. MN~' different steering matrices may be obtained from
MN~' different permutations of the M scalars'for the N-l rows. For example, each of
rows 2 through N may be independently multiplied with a scalar of +1, -1, +j, or -y,
where j - v-1 - For N = 4, 64 different steering matrices may be generated from a
base matrix B4x4 with the four different scalars. Additional steering matrices may be
generated with other scalars, e.g., e±J^"'4, e±]"14, e±J"'a, and so on. In general, each
row of the. base matrix may be multiplied with any scalar having the form e j d , where 0
may be any phase value. A set of NxN steering matrices may be generated from the
NxN base matrix as V(z') = gN • B^, where gN =1/VN and B'NXN is the j-th
steering matrix generated with the base matrix BNxN. The scaling by gN =1/VN
ensures that e.ach column of V(i') has unit power. The steering matrices in the set may
be used for different subbands and/or time intervals.
[0058] The steering matrices may also be generated in a pseudo-random manner. The
steering matrices are typically unitary matrices having columns that are orthogonal to
one another. The steering matrices may also be orthonormal matrices having
orthogonal columns and unit power for each column, so that Vw -V-I. A steering
matrix of dimension that is not square may be obtained by deleting one or more
columns of a square steering matrix.
[0059] Different steering matrices may be used for different time intervals. For
example, different steering matrices may be used for different symbol periods for SFTD
and for different 2-symbol intervals for STTD and OTD. For an OFDM-based system,
different steering matrices may be used for different subbands for STTD and OTD and
for different pairs of subbands for SFTD. Different steering matrices may also be used
for different subbands and different symbol periods. The randomization provided by
steering diversity (across time and/or frequency) with the use of different steering
matrices can mitigate deleterious effects of a wireless channel.
[0060] The transmission techniques described herein may be implemented by various
means. For example, these techniques may be implemented in hardware, firmware,
software, or a combination thereof. For a hardware implementation, the processing
units at the transmitting entity may be implemented within one or more application
specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal
processing devices (DSPDs), programmable logic devices (PLDs), field programmable
gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other
electronic units designed to perform the functions described herein, or a combination
thereof.
[0061] For a software implementation, the techniques may be implemented with
modules (e.g., procedures, functions, and so on) that perform the functions described
herein. The software codes may be stored in a memory and executed by a processor.
The memory may be implemented within the processor or external to the processor, in
which case it can be communicatively coupled to the processor via various means as is
known in the ait.
[0062] The previous description of the disclosed embodiments is provided to enable any
person skilled in the art to make or use the present invention. Various modifications to
these embodiments will be readily apparent to those skilled in the art, and the generic
principles defined herein may be applied to other embodiments without departing from
the spirit or scope of the invention. Thus, the present invention is not intended to be
limited to the embodiments shown herein but is to be accorded the widest scope
consistent with the principles and novel features disclosed herein.
[0063] WHAT IS CLAIMED IS:




We Claim:
1. An apparatus comprising:
at least one processor configured to process data symbols based on a transmit diversity scheme to generate coded symbols, and to perform spatial processing on the coded symbols to generate transmit symbols for transmission via a plurality of antennas; and a memory coupled to the at least one processor.
2. The apparatus as claimed in claim 1, wherein the at least one processor is configured to perform spatial spreading with a plurality of matrices and to use different matrices for different frequency subbands, different time intervals, or both.
3. The apparatus as claimed in claim 1, wherein the at least one processor is configured to perform beamforming with a plurality of matrices and to use different matrices for different frequency subbands.
4. The apparatus as claimed in claim 1, wherein the at least one processor is configured to process the data symbols based on a space-time transmit diversity (STTD) scheme to generate the coded symbols.
5. The apparatus as claimed in claim 1, wherein the at least one processor is configured to process the data symbols based on a space-frequency transmit diversity (SFTD) scheme to generate the coded symbols.
6. The apparatus as claimed in claim 1, wherein the at least one processor is configured to process the data symbols based on an orthogonal transmit diversity (OTD) scheme to generate the coded symbols.
7. The apparatus as claimed in claim 1, wherein the at least one processor is configured to obtain at least two data symbols to be sent on a frequency subband in two symbol periods, to process the at least two data symbols based on the transmit diversity scheme to generate two sets of coded symbols, and to provide the two sets of coded symbols for transmission on the frequency subband in two symbol periods.
8. The apparatus as claimed in claim 1, wherein the at least one processor is configured to obtain at least two data symbols to be sent on two frequency subbands in a symbol period, to process the at least two data symbols based on the transmit diversity scheme to generate two sets of coded symbols, and to provide the two sets of coded symbols for transmission on the two frequency subbands in the symbol period.
9. The apparatus as claimed in claim 1, wherein the at least one processor is configured to perform orthogonal frequency division multiplexing (OFDM) modulation on the transmit symbols for each antenna to generate transmission symbols for the antenna.
10. The apparatus as claimed in claim 1, wherein the at least one processor is configured to perform single-carrier frequency division multiple access (SC-FDMA) modulation on the transmit symbols for each antenna to generate transmission symbols for the antenna.
11. The apparatus as claimed in claim 1, wherein the at least one processor is configured to apply different cyclic delays for the plurality of antennas.
12. The apparatus as claimed in claim 1, wherein the at least one processor is configured to generate transmission symbols for the plurality of antennas based on the transmit symbols, and to cyclically delay the transmission symbols for the plurality of antennas by different non-negative integer numbers of samples.
13. A method comprising:
processing data symbols based on a transmit diversity scheme to generate coded symbols; and performing spatial processing on the coded symbols to generate transmit symbols for transmission via a plurality of antennas.
14. The method as claimed in claim 13, wherein the processing the data symbols based on the transmit diversity scheme comprises processing the data symbols based on a space-time transmit diversity (STTD) scheme, a space-frequency transmit diversity (SFTD) scheme, or an orthogonal transmit diversity (OTD) scheme to generate the coded symbols.
15. The method as claimed in claim 13, wherein the performing spatial processing on the coded symbols comprises performing spatial spreading with a plurality of matrices, and using different matrices for different frequency subbands, different time intervals, or both.
16. The method as claimed in claim 13, comprising: applying different cyclic delays for the plurality of antennas.

Documents:

2145-delnp-2007-abstract.pdf

2145-DELNP-2007-Claims-(08-11-2011).pdf

2145-delnp-2007-claims.pdf

2145-delnp-2007-Correspondence Others-(05-06-2012).pdf

2145-DELNP-2007-Correspondence Others-(08-11-2011).pdf

2145-DELNP-2007-Correspondence Others-(21-09-2011).pdf

2145-delnp-2007-correspondence-others 1.pdf

2145-delnp-2007-corresponence-others.pdf

2145-delnp-2007-description (complete).pdf

2145-delnp-2007-Drawings-(05-06-2012).pdf

2145-delnp-2007-drawings.pdf

2145-delnp-2007-form-1.pdf

2145-delnp-2007-form-18.pdf

2145-delnp-2007-form-2.pdf

2145-DELNP-2007-Form-3-(08-11-2011).pdf

2145-DELNP-2007-Form-3-(21-09-2011).pdf

2145-delnp-2007-form-3.pdf

2145-delnp-2007-form-5.pdf

2145-DELNP-2007-GPA-(08-11-2011).pdf

2145-delnp-2007-gpa.pdf

2145-delnp-2007-pct-210.pdf

2145-delnp-2007-pct-237.pdf

2145-delnp-2007-pct-304.pdf

2145-DELNP-2007-Petition-137-(08-11-2011).pdf

abstract.jpg


Patent Number 252871
Indian Patent Application Number 2145/DELNP/2007
PG Journal Number 23/2012
Publication Date 08-Jun-2012
Grant Date 06-Jun-2012
Date of Filing 20-Mar-2007
Name of Patentee QUALCOMM INCORPORATED
Applicant Address 5775 MOREHOUSE DRIVE, SAN DIEGO, CALIFORNIA 92121-1714, USA
Inventors:
# Inventor's Name Inventor's Address
1 JAY RODNEY WALTON 85 HIGHWOODS LANE, CARLISLE, MA 01741, USA
2 JOHN W. KETCHUM 37 CANDLEBERRY LANE, HARVARD, MA 01451, USA
3 MARK S.WALLACE 4 MADEL LANE, BEDFORD, MA 01730 USA
4 STEVEN J.HOWARD 75 HERITAGE AVENUE, ASHLAND, MA 01721, USA
PCT International Classification Number H04B 7/06
PCT International Application Number PCT/US2005/031467
PCT International Filing date 2005-09-02
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/607,371 2004-09-03 U.S.A.
2 60/608,226 2004-09-08 U.S.A.