455 results about "MIMO-OFDM" patented technology

A MIMO OFDM system includes a plurality of space-time encoders for encoding respective data blocks with independent space-time codes. The transformed data block signals are transmitted by a plurality of transmit antennas and received by a plurality of receive antennas. The received data is pre-whitened prior to maximum likelihood detection. In one embodiment, successive interference cancellation can be used to improve system performance. Channel parameter estimation can be enhanced by weighting the channel impulse response estimates based upon a deviation from average.

Disclosed is a MIMO-OFDM system, wherein the transmitter comprises a serial / parallel converter for converting continuously inputted symbols of the number of subcarriers to K parallel signals; a signal reproducer for reproducing K parallel signals by the number of transmit antennas L an eigenmode generator for generating eigenbeam of the reproduced signals outputted from the signal reproducer at each subcarrier, on the basis of Nf eigenbeam forming vectors which are fed back long-term and information of a best eigenbeam forming vector at each subcarrier which is fed back short-term, through the feedback device; and a plurality of inverse Fourier converters for receiving the signals outputted from the eigenmode generator and generating an OFDM symbol.

A method and apparatus are provided for reducing the number of pilot symbols within a MIMO-OFDM communication system, and for improving channel estimation within such a system. For each transmitting antenna in an OFDM transmitter, pilot symbols are encoded so as to be unique to the transmitting antenna. The encoded pilot symbols are then inserted into an OFDM frame to form a diamond lattice, the diamond lattices for the different transmitting antennae using the same frequencies but being offset from each other by a single symbol in the time domain. At the OFDM receiver, a channel response is estimated for a symbol central to each diamond of the diamond lattice using a two-dimensional interpolation. The estimated channel responses are smoothed in the frequency domain. The channel responses of remaining symbols are then estimated by interpolation in the frequency domain.

Methods and apparatus are provided for inserting data symbols and pilot symbols in an OFDM (orthogonal frequency division multiplexing) transmission resource utilizing frequency hopping patterns for the data symbols and / or the pilot symbols. Data symbols and pilot symbols are allocated for down link (base station to mobile station) and up link (mobile station to bases station) transmission resources in a two-dimensional time-frequency pattern. For each antenna of a MIMO-OFDM (multiple input multiple output OFDM) communication system, pilot symbols are inserted in a scattered pattern in time-frequency and data symbols are inserted in an identical frequency-hopping pattern in time-frequency as that of other antennas.

Techniques are provided for reducing feedback while maintaining performance in a MIMO-OFDM system. The disclosed techniques employ finite-rate feedback methods that uses vector quantization compression. The disclosed methods / techniques generally involve: receiving a plurality of symbols from a plurality of sub-carriers at a receiver; selecting a plurality of indices of codewords corresponding to a codebook of pre-coding weighting matrices for the sub-carriers based on vector quantization compression of the codewords; and transmitting the selected indices over a wireless channel to a transmitter. Finite state vector quantization feedback makes use of a finite state vector quantizer (FSVQ), which is a recursive vector quantizer (VQ) with a finite number of states. In finite state vector quantization feedback, optimal precoding matrices (beamforming vectors) are selected sequentially across subcarriers. In a trellis-based feedback method, the optimal precoding matrices are selected at the same time for all subcarriers by searching for the optimum choice of matrices along a trellis using the Viterbi algorithm (dynamic programming).

A MIMO-OFDM communication method for transmitting and receiving data using MIMO-OFDM communication has, on the transmitting side, a step of performing precoding processing of transmission data using a prescribed precoding method, and a step of performing OFDM modulation of the precoding-processed data and transmitting the data from a plurality of transmission antennas, and has, on the receiving side, a step of performing MIMO decoding processing of reception signals received by a plurality of reception antennas according to a ZF decoding algorithm or an MMSE decoding algorithm, and outputting the data as a transmission data stream, a step of calculating weighting coefficients according to the precoding method, and a step of performing weighted decoding processing of the transmission data obtained by the MIMO decoding processing, by multiplying path metric of the decoding processing by the weighting coefficients.

A data transmission method in a MIMO-OFDM communication system including at least one receiver for receiving a signal through a plurality of reception antennas and a transmitter for selecting a transmission channel using channel information being fed back from the receiver and transmitting a signal through a plurality of transmission antennas. The method includes selecting a spatial subchannel in which when bits are added by applying at least two spatial modes having different multiplexing gains for an individual subcarrier in a frequency domain, the minimum power increment is required during application of each spatial mode; allocating a spatial mode that requires the minimum total accumulated power, for each subcarrier; and selecting all subcarriers in the order of a subcarrier that requires the minimum power increment.

Techniques are described for space-time-frequency (STF) coding of multi-carrier transmissions over frequency-selective fading channels. In particular, techniques for STF coding of MIMO-OFDM systems are described that provide maximum diversity, high coding gains, and low decoding complexity are described. A set of generally correlated OFDM subcarriers are divided into groups of subcarriers creating a set of group STF (GSTF) subsystems, within which STF coding is applied to each GSTF subsystem. Subcarrier grouping preserves maximum diversity gains and simplifies both the code construction within each GSTF and decoding complexity. ST coding techniques are used in designing STF block (STFB) and STF trellis (STFT) codes which are applied within GSTF subsystems.

A method of transmitting / receiving feedback information representing channel quality in a MIMO-OFDM system, in which a receiver measures channel qualities of signals transmitted on a plurality of subbands through a plurality of transmitting antennas by a transmitter, selects a predetermined number of subbands having a highest transmission performance based on the measured channel qualities and preceding information, determines at least one subband group with a maximum rate from among the selected subbands and the preceding information associated with the at least one subband group, and transmits feedback information to the transmitter, the feedback information including channel quality information about the at least one subband group and the associated preceding information.

A method and apparatus for transmitting a preamble for frame synchronization and channel estimation in a MIMO-OFDM communication system are provided. An OFDM communication system using Q transmit antennas generates a base preamble sequence including a CP and an orthogonal sequence. If Q≦a predetermined number M, a preamble sequence for a kth antenna is S(t−(k−1)T / Q). If Q>M and k≦M, the preamble sequence transmitted for the kth antenna is S(t−(k−1)T / Q). If Q>M and k>M, the preamble sequence for the kth antenna is (−1)(ps−1)S(t−(k−1)T / Q). Here, S(t) is the orthogonal sequence, T is the period of the orthogonal sequence, and PS is an index indicating a transmission period of the preamble sequence. The preamble sequences are at least twice transmitted from the Q transmit antennas.

A method and apparatus for combining space-frequency block coding (SFBC), spatial multiplexing (SM) and beamforming in a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system. The system includes a transmitter with a plurality of transmit antennas and a receiver with a plurality of receive antennas. The transmitter generates at least one data stream and a plurality of spatial streams. The number of generated spatial streams is based on the number of the transmit antennas and the number of the receive antennas. The transmitter determines a transmission scheme in accordance with at least one of SFBC, SM and beam forming. The transmitter transmits data in the data stream to the receiver based on the selected transmission scheme.

The specification and drawings present a new method, system, apparatus and software product for resolving a feedback frame structure for implementing subspace tracking precoding for a MIMO-OFDM system, e.g., a wireless communication system. An efficient feedback frame format is generated by a receiver using a predetermined criterion and deciphered (decoded) by a transmitter when a subspace tracking preceding beamforming scheme is implemented.

A method for rate adaptation with extended MCS set for wideband eigen-beamforming transmission. A signaling method over multiple channels in a wireless telecommunication system including a transmitter and a receiver, performs the steps of obtaining an information bit stream, selecting the number of transmission streams, selecting different transmission rates for each MIMO OFDM transmission, and transmitting the information bit stream from the transmitter via said multiple channels over a plurality of transmitter antennas to the receiver according to the selected transmission rate per channel. Selecting transmission rates further includes the steps of selecting the transmission rates based on the diversity order of each stream. The method selects different transmission modes for each MIMO OFDM transmission and provides a simple, fast and efficient scheme to select the transmission rate for each eigen-mode transmission.

An optical network includes receiving inter-rack traffics from transmitter racks, converting by transmitters the inter-rack traffics to respective wavelength division multiplexing WDM optical signals, receiving and routing by a cyclic interleaver the optical signals from the transmitters to output ports in a cyclic manner, converting respective routed optical signals from the cyclic interleaver into respective electrical signals, and demodulating OFDM formats from respective converted optical signals containing signals for respective receiver racks.

A wireless receiving apparatus includes antennas, a receiving unit configured to receive multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) signals via the antennas, an estimation unit configured to estimate channel response values of subcarriers included in the MIMO-OFDM signals, a first computation unit configured to compute an estimated channel-response error common to the subcarriers based on the estimated channel response values, a response correction unit configured to correct the estimated channel response values using the estimated channel-response error, and a second computation unit configured to perform preprocessing for demodulating the MIMO-OFDM signals, using the corrected channel response values.

Disclosed is an apparatus having a detector for an iterative LDPC-coded MIMO-OFDM system, where the detector is configured to use a structured irregular LDPC code in conjunction with a belief propagation algorithm. Also disclosed is an apparatus having a detector for a structured irregular LDPC-coded MIMO-OFDM system, where the detector is configured to use an iterative Recursive Least Squares-based data detection and channel estimation technique. Corresponding methods and computer program products are also disclosed.

A method and apparatus are provided for performing acquisition, synchronization and cell selection within an MIMO-OFDM communication system. A coarse synchronization is performed to determine a searching window. A fine synchronization is then performed by measuring correlations between subsets of signal samples, whose first signal sample lies within the searching window, and known values. The correlations are performed in the frequency domain of the received signal. In a multiple-output OFDM system, each antenna of the OFDM transmitter has a unique known value. The known value is transmitted as pairs of consecutive pilot symbols, each pair of pilot symbols being transmitted at the same subset of sub-carrier frequencies within the OFDM frame.

The invention provides an indoor range finding and positioning method based on MIMO-OFDM channel state information. A present commercial WiFi network card based on OFDM is fully utilized, channel state information CSI is obtained by a client at a position to be measured, an MIMO system whose receiving / transmitting end includes multiple antennas is combined, a free-space path loss model based on MIMO-OFDM is provided, the line of sight LOS distance between a WiFi access point AP of an indoor anchor point and a user at the position to be measured is calculated, and finally the position of the user is obtained by a classic three-side positioning method. The method is based on the multi-antenna WiFi AP which is used most widely at present and a mainstream wireless network card based on OFDM, and can realize rapid, simple and efficient indoor range finding and positioning.

A low overhead long preamble and the corresponding channel estimator for MIMO-OFDM systems that are backward compatible with current 802.11a systems. The preamble has a first training sequence and a second training sequence, wherein the second training sequence is a phase rotation of the first training sequence. The first training sequence comprises a 802.11a training sequence. The preamble can further include multiple training sequences, wherein each training sequence is a different phase rotation of the first training sequence.

A method for sparse channel estimation in MIMO OFDM systems with a plurality of subchannels having the same sparsity structure is presented. The inventive method comprises initializing a plurality of residual vectors and observation generating matrices modeling the channel, sending a pilot signal for each subcarrier, converting the pilot signals to tap positions, detecting an optimal tap position, updating the residual vectors by removing the one residual vector having the optimal tap position, updating the generating matrices in accordance with the optimal residual vector, calculating weighted residuals based on the updated residual vectors, and repeating the steps, except initializing, until a stopping condition is met, wherein the updated observation matrices estimate the sparse channel. In one embodiment, the observation generating matrices are omitted. In one embodiment, multiple vectors are removed during one iteration. Pilot placement and pilot allocation techniques are presented to optimize the method.

A method of receiving Multiple Input Multiple Output—Orthogonal Frequency Division Multiple Accessing (MIMO-OFDMA) signals using a single receiver rather than multiple receivers and performing measurements specific to various parts of MIMO-OFDMA systems using all measurable parameters of MIMO-OFDMA systems is disclosed. In addition, a method of receiving and completing impairment estimation of WiMAX MIMO signals using a single receiver according to the IEEE 802.16 standards is provided.

A multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) transceiving system is provided, in which an MIMO-OFDM receiver feeds back ordering information, such as the order of power intensities of reception signals of a plurality of reception antennas, to an MIMO-OFDM transmitter. The MIMO-OFDM transmitter arranges subcarriers, to which data symbols have been allocated, so that the subcarriers respectively correspond to a plurality of transmission antennas, according to the fed-back information. Thus, a specific substream can be transmitted via a transmission antenna having the greatest channel gain. Consequently, the probability of properly recovering the specific substream is greatly increased.

A method and apparatus for synchronizing in the receiver of an orthogonal frequency division multiplexing (OFDM) wireless communication system, and in particular a multiple input multiple output (MIMO) OFDM system. The OFDM transmitter inserts training symbols into the transmission signals, and when the transmission is received a frequency synchronization module develops from them a weighted representation of the received signal from which frequency offset estimates for use in frequency offset compensation may be made.

Maximum diversity in multiple antenna distributed frequency broadband systems such as MIMO-OFDM is achievable through space-frequency (SF) and space-time-frequency (STF) coding. Full-rate full-diversity coding is achieved through a combination of maximal minimum product distance symbol set design and formation of codeword blocks. Full-diversity codes are also achieved which have reduced symbol transmission rates, such as through mapping of space-time (ST) codes to SF codes. The reduction in symbol rate may be offset by the fact that any ST code may be mapped to a full-diversity SF code.

Disclosed is an apparatus having a detector for an iterative LDPC-coded MIMO-OFDM system, where the detector is configured to use a structured irregular LDPC code in conjunction with a belief propagation algorithm. Also disclosed is an apparatus having a detector for a structured irregular LDPC-coded MIMO-OFDM system, where the detector is configured to use an iterative Recursive Least Squares-based data detection and channel estimation technique. Corresponding methods and computer program products are also disclosed.

The present invention provides an antenna-array-based multiple-input multiple-output orthogonal-frequency-division-multiplexing (MIMO-OFDM) system and a pre-coding and feedback method used in the same. The present invention uses QR decompositions of the MIMO channel matrixes to parameterize the channel state information (CSI) of every OFDM frequency band. In addition, the present invention feeds back the information related to θ and φ in the Givens rotation matrixes of the partial frequency bands and then uses an interpolation method to generate θ and φ in the Givens rotation matrixes of all the frequency bands, which further is able to represent the CSI of all the frequency bands. In this way, the present invention has advantages of low complexity and low feedback rate requirement.

An antenna selection technique (transmitter / receiver antenna selection) that reduces the cost of the MIMO system while maintaining high performance. A combined selection algorithm for MIMO-OFDM is provided which offers the best tradeoff between spatial correlation and instantaneous SNR. In one case, antenna selection is based on instant channel information. In another case antenna is based on statistical channel state information. In another case, antenna selection is based on a hybrid of instant channel state information and statistical channel state information.

A method and apparatus are provided for performing acquisition, synchronization and cell selection within an MIMO-OFDM communication system. A coarse synchronization is performed to determine a searching window. A fine synchronization is then performed by measuring correlations between subsets of signal samples, whose first signal sample lies within the searching window, and known values. The correlations are performed in the frequency domain of the received signal. In a multiple-output OFDM system, each antenna of the OFDM transmitter has a unique known value. The known value is transmitted as pairs of consecutive pilot symbols, each pair of pilot symbols being transmitted at the same subset of sub-carrier frequencies within the OFDM frame.

A method and apparatus are provided for reducing the number of pilot symbols within a MIMO-OFDM communication system, and for improving channel estimation within such a system. For each transmitting antenna in an OFDM transmitter, pilot symbols are encoded so as to be unique to the transmitting antenna. The encoded pilot symbols are then inserted into an OFDM frame to form a diamond lattice, the diamond lattices for the different transmitting antennae using the same frequencies but being offset from each other by a single symbol in the time domain. At the OFDM receiver, a channel response is estimated for a symbol central to each diamond of the diamond lattice using a two-dimensional interpolation. The estimated channel responses are smoothed in the frequency domain. The channel responses of remaining symbols are then estimated by interpolation in the frequency domain.

Provided is a transmitting device which improves a data rate while maintaining channel estimation accuracy, or improves channel estimation accuracy while maintaining a data rate, in a MIMO-OFDM system. In the transmitting device, a transmitting antenna information adding section (104) adds transmitting antenna information to a pilot signal by performing different phase rotation to the separate pilot signal by transmitting antenna by having a common pilot signal as a reference phase. A pilot arranging section (107) is previously provided with, as a conversion table, a corresponding relationship between combination information of the transmitting antenna and a subcarrier to be used for transmission of the pilot signal and control information. The pilot arranging section (107) allocates the pilot signal outputted from the transmitting antenna information adding section (104) to the subcarrier to have the combination information in accordance with the control information.