Spatial spreading with space-time and space-frequency transmit diversity schemes for a wireless communication system

Description

BACKGROUND

II. Technical field

[0001] The present invention relates to communication, and more particularly to data broadcasting techniques in a multi-antenna communication system.

III. Background of the invention

[0002] A multi-antenna communication system uses a plurality of (N_T.) transmitting antennas and one or more (N_R) receiving antennas. N_T. transmit antennas can be used to increase system throughput by broadcasting different data from antennas, or improve reliability by redundant data broadcasting.

[0003] In a multi-antenna communication system, a propagation path is provided between each pair of transmit and receive antennas. N is formed_T.-N_R different propagation paths between N_T. transmitting antennas and N_R receiving antennas. Said propagation paths may experience different propagation conditions in the channels (e.g., different attenuation, multipath and interference effects) and may achieve different signal to noise and interference ratios (SNRs). N channel replies_T.-N_R The propagation paths may thus vary across paths and may further vary with time for the time-varying wireless channels and with respect to frequency for the spreading wireless channel. The variable nature of the propagation paths becomes a challenge for data transfer in an efficient and reliable manner.

[0004] Broadcast diversity refers to redundant data transmission in space, frequency, time, or a combination of these dimensions, to improve reliability.

55P35592PL00 data transmission. One of the purposes of broadcast diversity is to maximize diversity for data transmission in as many dimensions as possible in order to obtain a noise-tolerant performance. Another object is to simplify the processing for differential transmission at both transmitter and receiver.

[0005] There is therefore a need in the art for a technique for broadcasting data with differential transmission in a multi-antenna communication system.

[0006] US 2004/0136349 (A1) discloses a MIMO system that supports multiple spatial multiplexing modes for improved performance and more flexibility. Said modes may include (1) a steered single user mode in which multiple data streams on orthogonal spatial channels are sent to one receiver, (2) a non-steered single user mode in which multiple data streams from multiple antennas are transmitted to one receiver no spatial processing at the transmitter, (3) controlled multi-user mode, wherein multiple data streams are transmitted simultaneously to multiple recipients with spatial processing at the transmitter; and (4) a non-steered multi-user mode in which multiple data streams are transmitted from multiple antennas (closely spaced or non-adjacent to each other) ) without spatial processing in the transmitter (s) to receiver (s) having multiple antennas. For each set of user terminals selected for data transmission on a link to a terminal and / or on a link back to a terminal, a spatial multiplexing mode for a set of user terminals is selected from among a number of spatial multiplexing modes supported by the system.

[0007] US 2004/0146018 (A1) discloses a user terminal that supports multiple spatial multiplexing (SM) modes such as steered mode and non-steered mode. For

For data transmission, the plurality of data streams are encoded and modulated according to their selected data rates to obtain multiple data symbol streams. Said streams are then spatially processed according to the selected SM mode (e.g. using a control vector matrix for steered mode and using a unit matrix for the non-steered mode), to obtain multiple transmitted symbol streams for transmission from multiple antennas. On receiving data, the plurality of received symbol streams are spatially processed according to the selected SM mode (e.g. using an eigenvector matrix for the steered mode and using a spatial filter matrix for the uncontrolled mode) to obtain a plurality of reconstructed data symbol streams. Said streams are de-modulated and decoded according to their selected bit rates to obtain multiple decoded data streams.

SUMMARY OF THE INVENTION

[0008] Techniques for transmitting data using a combination of transmit differentiation systems will be described below. These broadcast differentiation systems include spatial spreading, continuous beamforming, cyclic delay differentiation, space-time transmission diversity (STTD: Space-Time Transmit Diversity), space-frequency transmission diversity (SFTD: Space-Frequency Transmit Diversity), and orthogonal broadcast differentiation. (OTD: Orthogonal Transmit Diversity), they will all be described below. The invention is defined in the independent claims.

In an embodiment, the transmitting unit processes (e.g., encodes, interleaves, and maps symbols) one or more (N_D) data streams in order

55P35592PL00 generating N_D data symbol streams. The transmitting unit then processes the data symbol streams based on a transmit differentiation scheme (e.g., STTD, SFTD, or OTD) to generate a plurality of (N_c) 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 for N_c streams of coded symbols using different matrices to generate multiple (N_T.) transmitted symbol streams for transmission from N_T. antennas. Additionally or alternatively, the transmitting unit may perform continuous beamforming for N_T. streams of transmitted symbols either in the time domain or in the frequency domain. The receiving entity performs complementary processing to recover the N_D data streams.

[0010] Various aspects and embodiments of the invention are described below in more detail.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]

Fig. 1 shows a block diagram of a multi-antenna transmitting unit.

Fig. 2 shows a block diagram of a transmit data (TX) processor, STTD TX processor, and spatial spreading apparatus in a transmitting entity.

Fig. 3 shows a block diagram of N_T. modulators in the transmitting unit.

Fig. 4 shows block diagrams of a single-antenna receiving unit and a multi-antenna receiving unit.

DETAILED DESCRIPTION

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[0012] The term "exemplary" is used herein as "serving as an example, instance, or illustration. Any of the embodiments described herein as "exemplary" need not be taken as being preferred or more preferred than the other embodiments.

[0013] The broadcast techniques described herein may be used for multiple input and one output (MISO: Multiple-Input Single-Output) and multiple inputs and multiple outputs (MIMO: Multiple-Input MultipleOutput) transmission. MISO transmissions use multiple transmitting antennas and one receiving antenna. MIMO transmissions use multiple transmit antennas and multiple receive antennas.

[0014] The broadcast techniques may be used in single-carrier and multi-carrier systems. A multi-carrier system may employ orthogonal frequency division multiplexing (OFDM), some other multi-carrier modulation scheme, or some other design. OFDM effectively divides the entire system bandwidth into numerous (N_F.) orthogonal frequency subbands, which are also called tones, sub-carriers, bins, frequency channels and so on. When using OFDM, each sub-band is associated with a corresponding sub-carrier that can be modulated with data. The single carrier system may use single carrier frequency division multiple access (SC-FDMA), code division multiple access (ODMA), or some other single carrier modulation scheme. An SC-FDMA system may use (1) Interleaved FDMA (IFDMA) to transmit data and a pilot on subbands that are distributed throughout the system bandwidth, (2) a localized FDMA (LFDMA) to transmit data and a pilot in a group of adjacent sub-bands. bands, or (3) enhanced FDMA (EFDMA) transmitting data and pilot over multiple groups of adjacent subbands. Generally, modulation symbols are sent in the time domain from SC-FDMA (e.g., IFDMA, LFDMA and EFDMA) and

55P35592PL00 frequency domain with OFDM. For clarity, most of the description below applies to a system that uses OFDM, all N_F. sub-bands are available for broadcasting.

[0015] The transmit diversity may be achieved using various schemes, including STTD, SFTD, OTD, spatial spreading, continuous beamforming, etc. In STTD, a data symbol pair is transmitted from two antennas on one subband in two symbol periods to obtain spatial and temporal differentiation. In the SFTD, a pair of data symbols is transmitted from two antennas on two subbands in one symbol period to obtain spatial and frequency differentiation. Numerous (N_about) data symbols with N_about antennas in one sub-band in N_aboutsymbol periods using N_about orthogonal codes to obtain spatial and temporal differentiation, where N_about > 2. As used herein, the term data symbol refers to a modulation symbol for traffic / packet data, the pilot symbol is a modulation symbol for the pilot (which is a priori known data for both the transmitting and receiving units), the modulation symbol is a complex quantity for the point w constellation of signals for a given modulation scheme (e.g., M-PSK or M-QAM), a transmit symbol (e.g. OFDM symbol) is a sequence of time domain samples generated using a single carrier or multiple carrier modulation scheme for one symbol period, and the symbol is typically a complex quantity.

[0016] Spatial spreading refers to the transmission of symbols from a plurality of transmit antennas simultaneously, possibly with different amplitudes and / or phases, as determined by a control vector used for a given symbol. Spatial spreading may also be called control diversity, transmit control, pseudo-random transmit control, space-time scrambling, and so on. Spatial spreading can

55P35592PL00 may be used in combination with STTD, SFTD, OTD and / or continuous beamforming to improve the performance and / or extend the normal operation of said transmit differentiation schemes. For example, an STTD normally transmits one data symbol stream from two antennas. Spatial spreading can be used with an STTD to transmit more than one data symbol stream from more than two antennas simultaneously.

[0017] Continuous beamforming refers to the use of different beams for N_F. sub-bands. Beam formation is continuous in the sense that the beams change gradually among the sub-bands rather than abruptly. Continuous beamforming may be performed in the frequency domain by multiplying the symbols for each subband with the beamforming matrix for the given subband. Continuous beamforming can also be performed in the time domain by using different cyclic delays for the different transmit antennas. Continuous frequency-domain beamforming is also called cyclic delay diversity.

[0018] The transmit diversity may be achieved using a combination of the transmit diversity schemes. For example, transmit diversity may be achieved using a combination of STTD, SFTD, or OTD with either spatial spreading or continuous beamforming. As another example, transmit diversity may be achieved using a combination of an STTD, SFTD, or OTD with both spatial spread and variation in cyclic delay. For clarity, most of the description below assumes the use of STTD.

[0019] Fig. 1 shows a block diagram of an embodiment of multi-antenna transmitting unit 110, which may be part of an access point or user terminal. The access point may also be referred to as a base station, base transceiver system, or otherwise

55P35592PL00 Terminology. The user terminal may also be called a mobile station or wireless device or in some other terminology.

[0020] In the embodiment shown in Fig. 1, the transmitting unit 110 may use a combination of STTD, spatial spreading, and continuous beamforming for data transmission. TX data processor 112 receives and processes N_d data streams and provides N_D data symbol streams, with N_D > 1. TX data processor 112 may process each data stream independently, or may jointly process multiple data streams. For example, TX data processor 112 may format, scramble, encode, interleave, and map the symbols of each data stream according to the coding and modulation scheme selected for that data stream. STTD TX processor 120 receives N_Ddata symbol streams, performs STTD encoding for zero, one, or more data symbol streams, and provides N_c encoded data streams, with N_c > N_D. Generally, STTD TX processor 120 may process any number of data symbol streams according to an STTD, SFTD, OTD, or some other transmit differentiation scheme. Each data symbol stream may be sent as one coded data stream or multiple coded data streams, as described below.

[0021] Spatial spreading system 130 receives and multiplexes coded symbols with pilot symbols, performs spatial spreading by multiplying coded symbols and pilot symbols with different control matrices, and provides N_T. transmit symbol streams for N._T.transmitting antennas, with N_T. > N_c. Each transmitted symbol is a complex value, intended to be sent from one transmit antenna on one subband in one symbol period. N_T.modulators (MOD) 132a through 132nt receive N_T. transmit symbol streams. For an OFDM based system, each modulator 132 performs OFDM modulation in its transmitted symbol stream i

The 55P35592PL00 provides a stream of time domain samples. Each modulator 132 may also apply a different cyclic delay to its antennas, as described below. N_T. of modulators 132a through 132nt are provided by N_T. sample streams to N_T. transmitting units (TMTR) 134a to 134nt, respectively. Each transmitting unit 134 conditions (e.g., analog, amplifies, filters, and transfers to higher frequencies) its sample stream and generates a modulated signal. N_T. modulated signals from N_T. transmitting units 134a through 134nt are transmitted from N_T.transmit antennas 136a through 136nt, respectively.

[0022] A controller 140 controls the operation of the transmitting unit 110. Memory 142 stores data and / or program codes for the transmitting unit 110.

[0023] The transmitting unit 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. STTD encoding for one data symbol stream may be performed as follows. For each pair of data symbols, s_and is_bto be sent in two symbol periods, STTD TX processor 120 generates two vectors Si = [s_and s_b]^T. is_b = [s_b* -s_and*]^T.where is complex conjugate and "T is transpose. Alternatively, TX STTD processor 120 may generate two vectors Si = [s_and -s_b*]^T. and sb = [sb sa *]^T. for a data symbol pair, sa is_b. For both STTD encoding schemes, each St vector, where t = 1, 2 contains two coded symbols to be sent from N_T. transmit antennas in one symbol period, where N_T. > 2. The vector Si is sent in the first symbol period and the vector £ 2 is sent in the next symbol period. Each data symbol is contained in both vectors and thus is sent in two symbol periods, the mth data coded stream is formed by the mth element of the vector bisectors sg and £ 2 For clarity, the following description is for the STTD encoding schema of Si = [s_and s_b]^T., and S2 = [s_b* -s_and*]^T.. Because

55P35592PL00 of an STTD coding scheme, the first coded symbol stream includes coded symbols s_and and Sb *, and the second coded symbol stream includes coded symbols Sb and -s_and*.

[0024] Table 1 lists four configurations that can be used for data transmission. Configuration N_D x N_c means transmission of N_D data symbol streams as N_c coded symbol streams, where N_D > 1 and N_c > N_D. The first column identifies the four configurations. For each configuration, the second column indicates the number of data symbol streams sent and the third column indicates the number of coded symbol streams. The fourth column gives N_D data symbol streams for each configuration, the fifth column lists the coded symbol streams for each data symbol stream, the sixth column lists the coded symbol to be sent in the first symbol period (t = 1) for each coded symbol stream, the seventh column lists the coded symbol to be sent in the second symbol period (t = 2) for each coded symbol stream. The number of data symbols sent at each time interval for two symbols is twice the number of data symbol streams, or 2N_D. The eighth column indicates the number of transmit antennas needed for each configuration and the ninth column indicates the number of receive antennas needed for each configuration.

Table 1

<td>Config.</td><td>Number of data symbol streams N_D</td><td>Number of coded symbol streams N_c</td><td>Stream of data symbols</td><td>Stream of coded symbols</td><td>Coded symbol (t = l) Si</td><td>Coded symbol (t = 2) p₂</td><td>Number of TX antennas needed N_T.</td><td>Number of RX antennas needed No.</td>

<td rowspan="2">1x2</td><td rowspan="2"> 1</td><td rowspan="2"> 2</td><td rowspan="2"> 1</td><td> 1</td><td>S._and</td><td>Sat</td><td rowspan="2">N_T. &gt; 2</td><td rowspan="2">No&gt; 1</td>

<td> 2</td><td>Sat</td><td>- S._and</td>

<td colspan="9"></td>

<td rowspan="3">2x3</td><td rowspan="3"> 2</td><td rowspan="3"> 3</td><td rowspan="2"> 1</td><td> 1</td><td>S._and</td><td>Sat</td><td rowspan="3">N_T. &gt; 3</td><td rowspan="3">No&gt; 2</td>

<td> 2</td><td>Sat</td><td>- S._and</td>

<td> 2</td><td> 3</td><td>Sc</td><td>Sat *</td>

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<td colspan="9"></td>

<td rowspan="4">2x4</td><td rowspan="4"> 2</td><td rowspan="4"> 4</td><td rowspan="2"> 1</td><td> 1</td><td>s_and</td><td>Sat</td><td rowspan="4">N_T. &gt; 4</td><td rowspan="4">No&gt; 2</td>

<td> 2</td><td>Sat</td><td>- s_and</td>

<td rowspan="2"> 2</td><td> 3</td><td>Sc</td><td>s_d</td>

<td> 4</td><td>Sat</td><td>-S_c</td>

<td colspan="9"></td>

<td rowspan="4">3x4</td><td rowspan="4"> 3</td><td rowspan="4"> 4</td><td rowspan="2"> 1</td><td> 1</td><td>S._and</td><td>Sat *</td><td rowspan="4">N_T. &gt; 4</td><td rowspan="4">No&gt; 2</td>

<td> 2</td><td>Sat</td><td>- s_and*</td>

<td> 2</td><td> 3</td><td>Sc</td><td>Sd</td>

<td> 3</td><td> 4</td><td>S._e</td><td>-Sf</td>

[0025] As shown in Table 1, the data symbol stream may be sent as two coded symbol streams with STTD or one coded symbol stream without STTD. In the embodiment shown in Table 1, for each data symbol stream sent without STTD, data symbols sent in the second symbol period (t = 2) are coupled to match the coupling performed on the data symbol stream sent from the STTD.

[0026] For the 1x2 configuration, one data symbol stream is STTD-encoded to generate two coded symbol streams. For each time interval for 2 symbols, vectors s are generated₂ = [s_and SbJ^T., and s2 = [Sb * -sa *]^T. with data symbols sa and Sb- The vector sg is transmitted from at least two transmit antennas in the first symbol period and the vector sp is transmitted from the same antennas in the second symbol period. The receiving unit uses at least one receiving antenna to recover the data symbol stream.

[0027] 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 stream

55P35592PL00 symbols. For each time interval of 2 symbols, vectors s are generated₂ = [s_and Sat pp₀]^T., and s2 = [Sb * -sa * sd *]^T. with data symbols sa, s_b is_d, somewhere_and is_b are from the first data symbol stream, and s_c is_d are from the second data symbol stream. The Si vector is transmitted from at least three transmit antennas in the first symbol period and the sp vector is transmitted from the same antennas in the second symbol period. The receiving unit uses at least two receiving antennas to reproduce both data symbol streams.

[0028] For the 2x4 configuration, two data symbol streams are sent as four coded symbol streams. Each data symbol stream is STTD-coded to generate two coded symbol streams. For each time interval of 2 symbols, vectors s are generated₂ = [s_and s_b s_c s_d]^T. and s2 = [sb * -sa * sd * -sc *]^T. with data symbols sa, s_b, p_c is_d, somewhere_and and Sb are from the first data symbol stream, and s_c is_dare from the second data symbol stream. The Si vector is transmitted from at least four transmit antennas in the first symbol period and the sy vector is transmitted from the same antennas in the second symbol period. The receiving unit uses at least two receiving antennas to reproduce two data symbol streams.

[0029] 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 code symbol stream, and the third data symbol stream is sent without STTD as the fourth symbol code stream. For each time interval of 2 symbols, vectors s are generated₂ = [s_and s_b s_c s_e]^T. and s2 = [sb * -sa * sd * sf *]^T. with data symbols sa, Sb, s_c, p_d, p_e is₂, somewhere_and and Sb are from the first data symbol stream, s_c is_d are from the second data symbol stream, and s_e is₂ are from the third stream of symbols

55P35592PL00 data. The vector Si is transmitted from at least four transmit antennas in the first symbol period and the vector £ 2 is transmitted from the same antennas in the second symbol period. The receiving unit uses at least three receiving antennas to reproduce three streams of data symbols.

[0030] Table 1 illustrates four example configurations that may be used for data transmission, each configuration having at least one data symbol stream sent from an STTD. Other configurations can also be used for data transmission. The configuration may also use a combination of STTD, SFTD and OTD.

[0031] Generally, any number of data symbol streams may be transmitted as any number of coded symbol streams from any number of transmit antennas, where N_D &gt; 1, N._c &gt; N_D, N_T. &gt; N_c and N_r &gt; N_d. Each data symbol stream may or may not be encoded using STTD, SFTD, OTD, or some other transmit differentiation scheme. Each data symbol stream may be sent as one coded symbol stream, or multiple (e.g., two) streams of coded symbols.

[0032] The transmitting unit may process the coded symbols for spatially spreading and continuously forming the beam as follows:

x_vol(k) = B (k) V (k) G (k) s_vol(k), for t = 1, 2, Eq. (1) where sp (k) is a vector of N._cxl from N_c coded symbols, to be sent in sub-band k of symbol period t; G (k) is a diagonal matrix of N_c x N_c with N_c values ​​of the gain along the diagonal for N._c encoded symbols in .Si (k) and zeros otherwise;

V (k) is a control matrix for spatial spreading for sub-band k;

B (k) is a diagonal matrix of N_T. x N_T. for continuous beamforming for the k sub-band, and

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Xt (k) is a vector of Ν_τ χ 1 of N_T. transmitted symbols to be sent from N_T. transmitting antennas in sub-band k in symbol period t.

[0033] The vector Si comprises N_c of coded symbols to be sent in the first symbol period, and the vector s_2 includes N_c coded symbols to be sent in the second symbol period. Vectors sg and s₃ they can be molded as shown in Table 1 for the four configurations.

[0034] The gain matrix G (k) determines the amount of transmit power that must be used for each of N_c encoded symbol streams. The gain matrix may be a function of the index k of the sub-band as shown in equation (1), or it may be a function that is independent of the index k. The total transmit power available for transmit may be expressed as P_thistai · In an embodiment, equal transmit power is used for N_c the coded symbol streams and the diagonal elements of G (k) have the same y / Ptotai / Nc value. In another embodiment, the same transmit power is used to transmit N_Ddata symbol streams and N_c the gain values ​​along the diagonal G (k) are determined to obtain equal transmit power for N._D data symbol streams. N_c the gain values ​​may or may not be equal depending on the configuration. For example, for a 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. In order to obtain the same transmit power for two data symbol streams, the gain matrix G (k) 3x3 may include gain values ​​equal to ^ Ptotai / 4, ^ / Ptotai / 4 and y / P_total/ 2 along the diagonal for the third symbol coded streams. Each coded symbol in the third coded symbol stream is then scaled by y / Ptotai / 2 and is transmitted at twice the power of the other two coded symbols sent in the same symbol period. For both embodiments, you can

55P35592PL00 select N_c coded symbols for each symbol period to use the maximum transmit power available for each transmit antenna. Generally, the diagonal elements G (k) may be selected to use any amount of transmit power for N_c coded symbol streams i to obtain any desired SNR for N_D data symbol streams. Power scaling for N_c coded symbol streams can also be obtained by scaling the columns of the control matrix V (k) with the appropriate gains.

[0035] A given data symbol stream (which is denoted by {s}) may be sent as one symbol coding stream (which is denoted by {s}) in various manners. In one embodiment, the gain matrix G (k) includes ones along the diagonal and the coded symbol stream {s} is transmitted at the same power level as the other coded symbol streams. In this embodiment, the data symbol stream {s} is transmitted at a lower transmit power than the STTD-encoded data symbol stream, and thus achieves a lower received SNR value at the receiving entity. The encoding and modulation of the data symbol stream {s} may be selected to achieve the desired performance, e.g., a desired packet error rate. In another embodiment, each data symbol in the data symbol stream {s} is repeated and transmitted over two symbol periods. For example, for the 2x3 configuration, the data symbol s_cmay be sent in two symbol periods, then data symbol Sd may be sent in two symbol periods, and so on. This embodiment can obtain a similar received SNR for N_Ddata symbol streams, which may simplify the encoding and modulation at the transmitting unit and the demodulation and decoding at the receiving entity.

[0036] The control matrix V (k) spatially spreads N_c symbols are coded in each symbol period such that each

55P35592PL00 the coded symbol is transmitted from all N_T. transmitting antennas and achieves spatial differentiation. Spatial spreading may be implemented using various types of control matrices such as Walsh matrices, Fourier matrices, pseudo-random matrices etc., which can be generated as described below. The same control matrix V (k) is used for the two vectors sp (k) and ^₂(k) for each sub-band k. Different control matrices may be used for different sub-bands and / or different time intervals, with each time interval being an integer multiple of two symbol periods for the STTD.

[0037] The matrix B (k) performs continuous beamforming in the frequency domain. For an OFDM based system, different beamforming matrices may be used for each subband. The beam forming matrix for each k subband may be a diagonal matrix having the following form:

b₂(k) 0 ... 0 b₂(k) ... 0

B (k) = ... ... ... ... Eq. (2)

0 ... Ónt (k) for k = 1, ..., N_F. where b₂(k) is the weight for sub-band k of transmitting antenna i. The weight bi (k) can be defined as follows:

bi (k) = exp (- j 2π ΔΤί 1 (k) Δί Eq. (3) for i = 1, ..., N_T. ik = l, ..., N_F. where Δτ₂ is the time delay in the transmitting antenna and;

Δί is the frequency difference between adjacent subbands and l (k) Af is the current frequency, corresponding to the index k of the sub-band.

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For example, if N_F. = 64, then the sub-band index k can be 1 to 64 and l (k) can be k-33 and can range from -32 to +31. If the total system bandwidth is equal to 20 MHz and N_F. = 64, then Δί = 20 MHz / 64 = 3.125 kHz. l (k) -Af specifies the current frequency (in hertz) for each value of k. Balance b_F.(k), shown in equation (3) correspond to the progressive phase shift among total N_F.subbands for each transmit antenna, the phase shift changing at different rates in N_T. transmitting antennas. These weights effectively form a different bundle for each sub-band.

[0038] Continuous beamforming may also be performed in the time domain as follows. For each symbol period, N._F. - Point Inverse Discrete Fourier Transform (IDFT) or Inverse Fast Fourier Transform (IFFT) can be performed on N_F. transmit symbols, sent in N_F. the subbands of each transmit antenna i, to generate N_F. time domain samples for a given transmitting antenna. N_F. time domain samples for each transmitting antenna and may be circularly or circularly delayed by Ti. For example, T._F. can be determined as follows: T._F. = (ί-Ι) -ΔΤ for i = 1, ..., N_T., where ΔΤ can be equal to one sample period, a fraction of the sample period, or more than one sample period. The time domain samples for each antenna are then cyclically delayed by different amounts.

In equation (1), the scaling by the gain matrix G (k) may be omitted by specifying G (k) = spatial spreading may be omitted by specifying V (k) = and continuous beamforming may be omitted by specifying B ( k) = where _! is an identity matrix containing 1s along the diagonal and zeros otherwise. The transmitting unit can thus selectively perform scaling, spatial spreading, and continuous

Beam forming using appropriate matrices. Spatial spreading and continuous beamforming matrices can also be combined like V_B(k) = B (k) -V (k).

The matrices for scaling, spatial spreading, and continuous beamforming can also be combined like V_BG(k) = B (k) V (k) -G (k). The transmitting unit may therefore perform spatial processing on the data vector St (k) using V_B (k) or V_BG (k).

[0040] The transmitting unit may also use combinations of SFTD, spatial spreading, and optionally continuous beamforming. For SFTD, the transmitting unit can generate two vectors sp and sp as described above for STTD, and can send these vectors in two subbands in one symbol period. For a 1x2 configuration, two Si = [s] vectors can be generated_and SbJ^T. i Si = [Sb * -sa *]^T. for each data symbol pair, to be sent in two subbands in one symbol period for one data symbol stream. For a 2x3 configuration, two data symbol vectors sg = [sa Sb s_c]^T.can be generated for two data symbol pairs to be sent on two subbands in one symbol period for two data symbol streams. For a 2x4 configuration, two vectors sg = [sa Sb sc SdJ can be generated^T. and Si = [Sb * —sa * Sd * -s_c*]^T. for two data symbol pairs, to be sent on two subbands in one symbol period for two data symbol streams. For a 3x4 configuration, two vectors sg = [sa Sb sc se] can be generated^T. i S2 = [Sb * —sa * Sd * Sf *]^T. for three data symbol pairs, to be sent on two subbands in one symbol period for three data symbol streams. For all configurations, the transmitting unit may spatially spread and transmit sp vector in one subband in one symbol period, and may spatially spread and transmit £ 2 vector in another subband in the same symbol period. Both sub-bands are usually adjacent to each other.

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[0041] The transmitting unit may also use a combination of OTD, spatial spreading and optionally continuous beamforming. For OTD, the transmitting unit may generate multiple (N_about) vectors sp and £_N0 and can send these vectors on one subband in N_about symbol periods. For N_about = 2, the transmitting unit can generate two vectors sp and sp for two data symbols s_and and Sb by (1) multiplying the data symbol s_and through the first orthogonal code {+1 +1}, to generate the two coded symbols s_and is_and for one transmit antenna, (2) multiplying the data symbol Sb by the second orthogonal code {+ 1-1} to generate two coded symbols Sb and -Sb for the other transmit antenna, and (3) forming sp = [s_and s_b]^T. and s2 = [sa -sb]^T.. Generally, No data symbols can be multiplied by N_about various orthogonal codes to generate N._about sequence of coded symbols for N_about transmitting antennas. Each sequence of coded symbols includes N_about coded symbols and is generated by multiplying one data symbol by a specific orthogonal code of length N_about. Orthogonal codes can be Welsh codes, OVSF codes, etc.

[0042] Generally, transmit diversity can be achieved in various manners and in time, frequency and / or space domains. In one embodiment, transmit diversity is obtained by multiplying vector s__vol(k) through the control matrix V (k) to generate a transmit vector Xt (k) as shown in equation (1). In another embodiment, transmit diversity is achieved by periodically delaying the time domain samples for each transmit antenna. In yet another embodiment, transmit diversity is obtained using a combination of spatial processing with V (k) and cyclic time domain sample delay. For all embodiments, the vector s_vol(k) Can be molded using STTD,

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SFTD, OTD, or some other transmit differentiation scheme.

[0043] Fig. 2 shows a block diagram of an embodiment of a TX data processor 112, a TX STTD processor 120, and a spatial spreader 130 in a transmitting unit 110. For the embodiment shown in Fig. 2, TX data processor 112 includes N_D processors 210a through 210nd of data streams that independently process N_D data streams. Within each data stream processor 210, an encoder 212 encodes the traffic data according to the encoding scheme and generates encoding bits. The coding scheme may include a convolution code, a Turbo code, a low density parity check (LDPC) code, a cyclic redundancy check (CRC) code, a block code, etc., or a combination thereof. The interleaver 214 interleaves (or reorders) the code bits based on the interleaving scheme. The symbol mapping system 216 maps the interleaved bits according to the modulation scheme and provides data symbols. The coding and modulation for each data stream may be determined by the bit rate selected for the given data stream. Processors 210a through 210nd of data streams provide N_Ddata symbol streams.

[0044] In another embodiment, not shown in Fig. 2, TX data processor 112 jointly processes the data symbol stream (s) to be sent from the STTD and the data symbol stream (s) to be sent without STTD. For example, TX data processor 112 may receive one data stream, code the data stream based on the coding scheme, de-multiplex the code bits onto N_d encoded bit streams and interleave and map symbols separately for N_D encoded bit streams to generate N_D data symbol streams. In yet another embodiment, also not shown in Fig. 2, TX data processor 112 processes the stream independently

Data symbol stream (s) to be sent from the STTD and data symbol stream (s) to be sent without the STTD. For example, data processor 112 TC may receive a first data stream to be sent from STTD and a second data stream to be sent without STTD. TX data processor 112 may code, interleave, symbol map and de-multiplex the first data stream to generate (N_C.-N_D data symbol streams to be sent from the STTD. TX data processor 112 may also code, interleave, symbol map, and demultiplex the second data stream to generate (2N_d-N_c) data symbol streams to be sent without an STTD. TX data processor 112 may also process the data streams in other ways, and this is within the scope of the invention.

[0045] In the embodiment shown in Fig. 2, STTD TX processor 120 includes N_D STTD encoders 220a to 220nd for N_Ddata symbol streams. Each STTD encoder 220 performs STTD encoding in its data symbol stream and provides two coded symbol streams to a mux 222. A mux 222 receives N_D data symbol streams from TX and N data processor 112_D pairs of coded symbol streams from STTD encoders 220a through 220nd. For each data symbol stream, mux 222 provides either a given data symbol stream or an associated pair of coded symbol streams. The multipliers 224a through 224nc receive and scale N_c symbol streams from mux 222 using the gains_F. to g_Nc, respectively, and provide N_c symbol codecs. Scaling may also be performed elsewhere within the transmission path.

[0046] In the embodiment shown in Fig. 2, the spatial spread pattern 130 comprises N_F. spatial processors 230a through 230nf for N._F. sub-bands. A demultiplexer (Demux) 228 receives N_c streams of coded symbols and symbols

Pilot symbols are provided in the sub-bands and symbol periods used for transmitting data, and it provides pilot symbols in the sub-bands and symbol periods used for transmitting the pilot. Each spatial processor 230 receives N_cthe coded symbols and / or pilot symbols, to be sent in the associated sub-band k in one symbol period, multiplies the coded symbol and / or pilot symbols by the control matrix V (k) and provides N_T. transmit symbols to be sent from N_T. transmit antennas in subband k. A multiplier 232 receives transmit symbols from all spatial processors 230a to 230nf and maps N_T. transmit symbols from each spatial processor 230 on N_T. transmit symbol streams. Each transmit symbol stream includes N_F. transmit symbols with N_F. spatial processors 230a through 230nf for one transmit antenna.

[0047] Fig. 3 shows a block diagram of an embodiment of modulators 132a through 132nt in transmitting unit 110. Within each modulator 132, the IDFT unit 312 performs N_F.- scoring IDFT or IFFT on N_F. transmit symbols to be sent in N_F. sub-bands in one symbol period and provides N_F. time domain samples. Parallel to serial (P / S Conv) converter 314 serializes N_F.time domain samples. Circular shift unit 316 performs a circular or circular shift N_F. time domain samples on T._F. = (ί-Ι) -ΔΤ, where ΔΤ is a constant period (e.g. one sample period) and T_F. is the cyclic shift amount for transmit antenna i. Cyclic prefix generator 318 receives N_F. circularly shifted samples from unit 316, appends the cyclic prefix with N_F. samples and provides an OFDM symbol (or transmit symbol) including N_f+ N_cf samples. Continuous time-domain beamforming can be blocked by simply passing through units 316a to 316nt to cyclically shift the time-domain samples from P / S converters 314a to 314nt to

55P35592PL00 of generators 318a to 318nt of cyclic prefixes, respectively. The circular shift units 316a through 136nt may also simply delay (rather than circularly) the time domain samples from the converters P / S 314a through 314nt by different amounts such that transmissions from antennas 136a through 136nt are delayed by different amounts.

[0048] Fig. 4 shows a block diagram of an embodiment of a single-antenna receiving unit 150x and a multi-antenna receiving unit 150y. Each receiving unit may be part of a base station or user terminal.

[0049] At the single-antenna receiving unit 150x, the antenna 152x receives N_T. modulated signals, transmitted by the transmitting unit 110, and provides the received signals to the receiving unit (RCVR) 154x. Receiving unit 154x conditions (e.g., amplifies, filters, downcovers, and digitizes) the received signal and provides the received sample stream to a demodulator (Demod) 156x. For an OFDM based system, a demodulator 156x performs OFDM demodulation on the received samples to obtain the received symbols, provides the received data symbols to a detector 158, and provides the received pilot symbols to a channel estimator 162. The channel estimator 162 provides an estimate of the effective channel response for a channel with one input and one output (SISO: Single-Input Single-Output) between transmitting unit 110 and receiving unit 150x for each subband used for data transmission. Detector 158 performs data detection (e.g. equalization) in the received data symbols for each sub-band, based on an estimate of the effective SISO channel response for a given sub-band, and provides the reconstructed data symbols for the sub-band. RX data processor 160 processes (e.g., de-maps the symbols, deinterleaves, and decodes) the received data symbols and provides decoded data.

55P35592PL00

[0050] At the multi-antenna receiving unit 150y, N_R antennas 152a through 152nr receive N_T. each of the modulated signals and each antenna 152 provides the received signal to a respective receiver unit 154. Each receiver unit 154 conditions its received signal and provides a stream of received samples to the associated demodulator (Demod) 156. Each demodulator 156 performs OFDM demodulation (if necessary) in its received stream. samples, provides the received data symbols to RX spatial processor 170, and provides the received pilot symbols to the channel estimator 166.

[0051] The channel estimator 166 obtains received pilot symbols for all N_R receive antennas and determine a channel response estimate for an actual or effective MIMO channel between the transmitting unit 110 and the receiving unit 150y for each subband used for data transmission. If the transmitting unit 110 performs spatial processing of pilot symbols in the same manner as data symbols as shown in Fig. 1, then control matrices may be considered as portions of wireless channels. In this case, the receiving unit 150y may determine an effective MIMO channel estimate that includes the actual MIMO channel response as well as the control matrix effects. If the transmitting unit 110 does not perform spatial pilot symbol processing, then the receiving unit 150y may determine the actual MIMO channel estimation and, then, may estimate the actual MIMO channel based on the response estimation of the actual MIMO channel and the control matrix.

[0052] A matched filter generator 168 determines a spatial filter matrix M (k) for each subband used for transmission based on the estimation of the channel response for that subband. A RX spatial processor 170 obtains the received data symbols for all N_R receiving antennas and performs preprocessing of the received data symbols

55P35592PL00 according to the STTD scheme used by the transmitting unit 110. The RX spatial processor 170 further performs receiver spatial processing (or spatial matched filtering) of the preprocessed data symbols for each subband using the spatial filter matrix for the given subband and provides the detected symbols. for sub-band. STTD RX processor 172 performs post-processing of the symbol detections based on the STTD scheme used by the transmitting unit 110 and provides the reconstructed data symbols. RX data processor 174 processes (e.g., de-maps the symbols, deinterleaves, and decodes) the reconstructed data symbols and provides decoded data.

[0053] Controllers 180x and 180y control the operation of receiver units 150x and 150y, respectively. Memories 182x and 182y store data and / or program codes for receiver units 150x, 150y, respectively.

[0054] Various types of control matrices may be used for spatial spreading. For example, the control matrix V (k) may be a Walsh matrix, a Fourier matrix, or some other matrix. Walsh matrix 2x2 W._2x2 can be expressed as follows: 1 1

IN_2x2 = 1 -1

Walsh matrix of larger sizes W_2Nx2N can be created from a smaller W matrix_NxN in the following way:

Wnxn W_RxN

IN₂nx2n = W_NxN _IN_NxN Eq. (4)

Fourier matrix NxN D_NxN has a d element_n,_m in the nth row of the mth column, which can be expressed as follows:

d_n,_m = exp (-j 2π (n-1) (ml) / N),

Eq. (5) for n = l, ..., N and m = l, ..., N

55P35592PL00

You can create Fourier matrices of any square dimension (e.g. 2, 3, 4, 5, etc.).

[0055] Walsh matrix W_NxN, Fourier matrix D_NxN, or some other matrix, may be used as the underlying matrix B_NxN to create other control matrices. For an underlying N × N matrix, each row 2 through N of the underlying matrix may be independently multiplied by one of the M different possible scalars. M.^N-1different control matrices can be obtained from M.^N-1 different permutations of M scalars for Nl orders. For example, each row 2 through N can be independently multiplied by a scalar +1, -1, + j, or -j, where j = ^ / - 3. For N = 4, 64 different control matrices can be generated from the underlying matrix B_4x4 using four different scalars. Additional control matrices can be generated using other scalars, e.g. exp (± j3% / 4), exp (± j% / 4), exp (± j% / 8) etc. In general, each row of the underlying matrix can be multiplied by any scalar, having the form exp (j0), where Θ can be any phase value. A control matrix set NxN can be generated from a base NxN matrix as V (i) = gN-Ę »¹, where gN = l / ą / ϊϊ, and Βνχν¹is the ith control matrix generated from the base BNxN matrix. Scaling with g_N = 1 / ą / N ensures that each column V (i) has a unit power. The control matrices in the kit may be applied to different sub-bands and / or time intervals.

[0056] The control matrices may also be pseudo-randomly generated. Control matrices are typically unitary matrices, having columns that are orthogonal to each other. The control matrices can also be orthonormal matrices, having orthogonal columns and a unit power for each column such that V^H.V = £. A control matrix with dimensions that are not square may be obtained by removing one or more columns from the square control matrix.

55P35592PL00

[0057] Different control matrices may be used for different time intervals. For example, different control matrices may be used for different symbol periods for the SFTD and for different symbol time intervals for the STTD and OTD. For an OFDM based system, different control matrices may be used for different subbands for STTD and OTD and for different pairs of subbands for the SFTD. Different control matrices may also be used for different sub-bands and different symbol periods. The randomization (as a function of time and / or frequency) provided by differentiated controls using different control matrices can mitigate the deleterious effects of the wireless channel.

[0058] The broadcasting techniques described herein may be implemented in various manners. For example, the techniques mentioned may be implemented in hardware, in an embedded program, an application program, or a combination thereof. In a hardware implementation, the processing units in the transmitting unit may be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), logic boards programmed with an electromagnetic field (FPGA), processors, controllers, microcontrollers, microprocessors, other electronic units, adapted to perform the functions described herein, or combinations thereof.

[0059] In a software implementation, the techniques may be implemented with modules (e.g., procedures, functions, etc.) that perform the functions described herein. Program codes can be stored in memory and executed by the processor. The memory may be implemented within the processor or external to the processor and in this case may be communicatively coupled to the processor by various means, as is known in the art.

55P35592PL00

[0060] The previous description of the disclosed embodiments is provided to enable one skilled in the art to use the present invention. Various modifications to said embodiments may be readily apparent to one skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the invention. Thus, the present invention is not limited to the embodiments shown herein, but is as broadly as possible in accordance with the claims.

Qualcomm Incorporated

Proxy:

55P35592PL00