摘要:
Techniques for performing phase correction for wireless communication are described. Received pilot symbols and received data symbols may be obtained from an orthogonal frequency division multiplexing (OFDM) and/or multiple-input multiple-output (MIMO) transmission. First phase information is obtained based upon the received pilot symbols. Second phase information is obtained based upon the received data symbols. The phase of the received data symbols is corrected based upon the first and second phase information (directly and/or indirectly). For example, the phase of the received data symbols may be corrected based upon the first phase information, detection may be performed on the phase corrected data symbols to obtain estimated data symbols, the second phase information may be obtained based upon the estimated data symbols, and the phase of the estimated data symbols may be corrected based upon the second phase information. The phase correction may also be performed in other manners.
摘要:
Techniques to schedule terminals for data transmission on the downlink and/or uplink in a MIMO-OFDM system based on the spatial and/or frequency “signatures” of the terminals. A scheduler forms one or more sets of terminals for possible (downlink or uplink) data transmission for each of a number of frequency bands. One or more sub-hypotheses may further be formed for each hypothesis, with each sub-hypothesis corresponding to (1) specific assignments of transmit antennas to the terminal(s) in the hypothesis (for the downlink) or (2) a specific order for processing the uplink data transmissions from the terminal(s) (for the uplink). The performance of each sub-hypothesis is then evaluated (e.g., based on one or more performance metrics). One sub-hypothesis is then selected for each frequency band based on the evaluated performance, and the one or more terminals in each selected sub-hypothesis are then scheduled for data transmission on the corresponding frequency band.
摘要:
Techniques to transmit data on a number of transmission channels in a multi-channel communication system using multiple transmission schemes requiring less channel-state information (CSI). These schemes may include a partial-CSI transmission scheme that transmits a single data stream on each transmit antenna selected for use and a “beam-forming” transmission scheme that allocates all transmit power to a single transmission channel having the best performance. Each transmission scheme may provide good or near-optimum performance for a specific range of operating conditions (or operating SNRs). These multiple transmission schemes may then be combined in a piece-wise fashion to form a “multi-mode” transmission scheme that covers the full range of operating conditions supported by the MIMO system. The specific transmission scheme to be used for data transmission at any given moment would then be dependent on the specific operating condition experienced by the system at that moment.
摘要:
A receiving entity obtains received symbols for a data transmission having at least one data symbol stream sent with space-time transmit diversity (STTD). The receiving entity derives an overall channel response matrix in accordance with the STTD encoding scheme used for the data transmission, derives a spatial filter matrix based on the overall channel response matrix, and performs spatial matched filtering on a vector of received symbols for each 2-symbol interval to obtain a vector of detected symbols for the 2-symbol interval. The receiving entity may perform post-processing (e.g., conjugation) on the detected symbols if needed. Alternatively, the receiving entity derives a spatial filter matrix based on an effective channel response matrix, performs spatial matched filtering on the received symbols for each symbol period to obtain detected symbols for that symbol period, and combines multiple estimates obtained for each data symbol sent with STTD.
摘要:
Techniques for performing detection and decoding at a receiver are described. In one scheme, the receiver obtains R received symbol streams for M data streams transmitted by a transmitter, performs receiver spatial processing on the received symbols to obtain detected symbols, performs log-likelihood ratio (LLR) computation independently for each of D best data streams, and performs LLR computation jointly for the M−D remaining data streams, where M>D≧1 and M>1. The D best data streams may be selected based on SNR and/or other criteria. In another scheme, the receiver performs LLR computation independently for each of the D best data streams, performs LLR computation jointly for the M−D remaining data streams, and reduces the number of hypotheses to consider for the joint LLR computation by performing a search for candidate hypotheses using list sphere detection, Markov chain Monte Carlo, or some other search technique.
摘要:
Techniques to schedule downlink data transmission to a number of terminals in a wireless communication system. In one method, one or more sets of terminals are formed for possible data transmission, with each set including a unique combination of one or more terminals and corresponding to a hypothesis to be evaluated. One or more sub-hypotheses may further be formed for each hypothesis, with each sub-hypothesis corresponding to specific assignments of a number of transmit antennas to the one or more terminals in the hypothesis. The performance of each sub-hypothesis is then evaluated, and one of the evaluated sub-hypotheses is selected based on their performance. The terminal(s) in the selected sub-hypothesis are then scheduled for data transmission, and data is thereafter coded, modulated, and transmitted to each scheduled terminal from one or more transmit antennas assigned to the terminal.
摘要:
Techniques for performing sphere detection to recover data symbols sent in a MIMO transmission are described. In an aspect, sphere detection is performed for data symbols generated with at least two modulation schemes. In another aspect, sphere detection is performed for the data symbols in an order determined based on at least one attribute of the data symbols, which may be error probabilities, modulation schemes, and/or link margins for the data symbols. In yet another aspect, rates for multiple data streams detected with sphere detection are selected based on channel state information. Signal qualities of the data streams may be estimated based on the channel state information, e.g., (1) an upper triangular matrix used for sphere detection and/or (2) an assumption that interference from data streams already detected is canceled. The rates for the data streams may be selected based on the estimated signal qualities.
摘要:
For eigenvalue decomposition, a first set of at least one variable is derived based on a first matrix being decomposed and using Coordinate Rotational Digital Computer (CORDIC) computation. A second set of at least one variable is derived based on the first matrix and using a look-up table. A second matrix of eigenvectors of the first matrix is then derived based on the first and second variable sets. To derive the first variable set, CORDIC computation is performed on an element of the first matrix to determine the magnitude and phase of this element, and CORDIC computation is performed on the phase to determine the sine and cosine of this element. To derive the second variable set, intermediate quantities are derived based on the first matrix and used to access the look-up table.
摘要:
Techniques for transmitting data from a transmitter unit to a receiver unit in a multiple-input multiple-output (MIMO) communication system. In one method, at the receiver unit, a number of signals are received via a number of receive antennas, with the received signal from each receive antenna comprising a combination of one or more signals transmitted from the transmitter unit. The received signals are processed to derive channel state information (CSI) indicative of characteristics of a number of transmission channels used for data transmission. The CSI is transmitted back to the transmitter unit. At the transmitter unit, the CSI from the receiver unit is received and data for transmission to the receiver unit is processed based on the received CSI.
摘要:
Techniques for processing a data transmission at the transmitter and receiver. In an aspect, a time-domain implementation is provided which uses frequency-domain singular value decomposition and “water-pouring” results to derive time-domain pulse-shaping and beam-steering solutions at the transmitter and receiver. The singular value decomposition is performed at the transmitter to determine eigen-modes (i.e., spatial subchannels) of the MIMO channel and to derive a first set of steering vectors used to “precondition” modulation symbols. The singular value decomposition is also performed at the receiver to derive a second set of steering vectors used to precondition the received signals such that orthogonal symbol streams are recovered at the receiver, which can simplify the receiver processing. Water-pouring analysis is used to more optimally allocate the total available transmit power to the eigen-modes, which then determines the data rate and the coding and modulation scheme to be used for each eigen-mode.