Abstract:
Communication systems which employ multiple transmit and receive antenna-element arrays. Data streams for transmission may be interleaved among the transmit antenna elements in order to reduce decision errors. Turbo processing of equalizer output from a number of layers in a layered space-time processing architecture may be employed to reduce decision errors. Additionally, space-time equalization may be performed to maximize signal to noise ratio such as via minimum mean square error processing, rather than zero forcing, in order to achieve the Shannon limit, reduce multi-path effects and/or reduce intersymbol interference. Moreover, the receiver can select number and/or identity of receive antenna elements from among a larger group in order to optimize performance of the system.
Abstract:
A data processor develops a data signal which has a plurality of multi-level symbols. The data processor, in response to each of the symbols, determines the lowest path metric characterizing the data signal, and select one of a plurality of sets of slice values in response to the lowest path metric. A slicer (82, 82') responds to the selected set of slice values by slicing the multi-level symbols. There may be only two sets of slice values in the plurality of sets of slice values, wherein each of the only two sets has three slice levels. Alternatively, there may be only five sets of slice values in the plurality of sets of slice values, wherein each of the only five sets has five slice levels. As a still further alternative, there may be only two sets of slice values in the plurality of sets of slice values, wherein each of the only two sets has a minimum of six slice levels.
Abstract:
A receiver and method for receiving and processing a sequence of transmitted symbols in a digital communication system utilizing soft pilot symbols. A set of soft pilot symbols are transmitted with higher reliability than the remaining symbols in the sequence by modulating the soft pilot symbols with a lower order modulation such as BPSK or QPSK while modulating the remaining symbols with a higher order modulation such as 16QAM or 64QAM. The receiver knows the modulation type and location (time/frequency/code) of the soft pilot symbols, and demodulates them first. The receiver uses the demodulated soft pilot symbols as known symbols to estimate parameters of the received radio signal. Unlike traditional fixed pilots, the soft pilots still carry some data. Additionally, the soft pilots are particularly helpful in establishing the amplitude reference essential in demodulating the higher order modulation symbols.
Abstract:
A reception apparatus including: a detection unit detecting extrinsic information based on an output of a tentative symbol decision unit, an output of a channel estimation unit, and an output of a noise variance estimation unit that are obtained from a previous iteration process; a Cyclic Redundancy Check (CRC) aided channel decoding unit outputting an encoded and interleaved bit, or a posteriori information thereof based on the extrinsic information; the tentative symbol decision unit determining a tentative transmission symbol based on an output of the CRC aided channel decoding unit; the channel estimation unit estimating a channel based on an output of the tentative symbol decision unit or a pilot symbol; and the noise variance estimation unit estimating a noise variance or an initial noise variance based on the output of the tentative symbol decision unit and the output of the channel estimation unit is provided.
Abstract:
An arrangement (300) and method, for iterative channel impulse response estimation in a system such as a GSM/EDGE system employing a transmission channel, by: producing (310) from a received signal (y) a channel impulse response estimate signal (p); and producing (320) from the received signal (y) a noise estimate signal (w) which is iteratively fed back to improve the channel impulse response estimate signal (p). The noise estimate signal comprises a matrix (w) respresenting the inverse of noise covariance; the matrix may be calculated at each iteration or may be selected from predetermined values corresponding to statistics of expected noise. This provides the advantages of reduced complexity, independence of the equalization method used to produce the channel impulse response estimate signal, and consequent performance improvement.
Abstract:
The invention relates to channel estimation in a receiver (1). The channel estimation for a current data block (50) is based on a previous data block (40), where the two data blocks (40, 50) are based on common information (42, 52). Data symbol hypotheses of the previous data block (40) can be forwarded to a channel estimator (100) and used as known reference symbols when estimating the channel response for the current block (50). Alternatively, a combination of the data symbol hypotheses and preliminary data symbol estimates of the current block (50) are used as reference symbols in a refined channel estimation for the current block (50). Data bit hypotheses of the previous block (40) can also be input as a priori data in a preliminary demodulation of the current block (50). The demodulator output is used as reference data in a refined channel estimation for the current block (50). The invention is well-adapted for usage in connection with Hybrid ARQ,
Abstract:
A receiver and method for receiving and processing a sequence of transmitted symbols in a digital communication system utilizing soft pilot symbols. A set of soft pilot symbols are transmitted with higher reliability than the remaining symbols in the sequence by modulating the soft pilot symbols with a lower order modulation such as BPSK or QPSK while modulating the remaining symbols with a higher order modulation such as 16QAM or 64QAM. The receiver knows the modulation type and location (time/frequency/code) of the soft pilot symbols, and demodulates them first. The receiver uses the demodulated soft pilot symbols as known symbols to estimate parameters of the received radio signal. Unlike traditional fixed pilots, the soft pilots still carry some data. Additionally, the soft pilots are particularly helpful in establishing the amplitude reference essential in demodulating the higher order modulation symbols.