Showing papers by "Timothy A. Thomas published in 2001"

Method and device for multiple input/multiple output transmit and receive weights for equal-rate data streams

Abstract: The invention provides a method of operating a communication system. A channel matrix of a gain and phase between each transmit antenna and each receive antenna of the communication system is provided. At least one receive weight vector is computed as a function of the channel matrix and at least one of transmit weight vectors. An updated transmit weight vector is computed as a function of the transmit weight vector, the receive weight vector, the channel matrix.

Data transmission and reception method and apparatus

Abstract: A datastream of bits (which may itself be comprised of a plurality of datastreams as derived from a plurality of sources) are coded (21) and then interleaved (12) across a plurality of transmitters (25 and 26) and a plurality of subcarriers (27) as supported and shared by the transmitters. If desired, the bits can be mapped to corresponding symbols prior to transmission. The resultant information is transmitted simultaneously by the transmitters using the shared channel of subcarriers. Upon reception, the received signals are de-interleaved and decoded to recover the original datastream for each sources.

Frequency-domain MIMO processing method and system

Abstract: A communication system based upon frequency-domain MIMO processing is disclosed. A transmitting device of the communication system transforms time-domain signals into frequency-domain signals, and weights each frequency-domain signal to form weighted frequency-domain signals with each weighted frequency-domain signal being a function of each frequency-domain signal. The transmitting device transmits weighted time-domain waveforms as a function of the weighted frequency-domain signals. In response thereto, a receiving device of the communication system provides frequency-domain samples that are a function of the one or more weighted time-domain waveforms and weights each frequency-domain sample to form one or more weighted frequency-domain samples with each weighted frequency-domain sample being a function of each frequency-domain sample. The receiving device decodes the weighted frequency-domain sample to obtain the information represented by the time-domain signals.

MIMO strategies for equal-rate data streams

Abstract: This paper explores strategies for multiple-input/multiple-output (MIMO) communications where the number of data streams is fixed and each stream has the same modulation type. For the fixed data stream case, transmit and receive weights based on the singular value decomposition (SVD) approach may not give the best BER performance. This paper explores two alternate strategies to the SVD approach for jointly calculating the transmit and receive weights based on minimizing the mean-squared error summed over all data streams. The first strategy finds linear transmit and receive weights, and the second strategy finds linear transmit weights and successive cancellation receive weights.

Method and system for adaptive channel estimation techniques

Abstract: The invention provides a method of determining an adaptive channel estimation by providing a channel estimate, determining at least one channel condition, and determining an adapted channel estimate as a function of the channel estimate and the channel condition.

Stream transmission method and device

Abstract: A transmitter for implementing a stream transmission method is disclosed. Optionally, the transmitter first determines an equal weighting of a plurality of stream weights and transmits a plurality of transmission signals as a function of a plurality of data streams and the equal weighting of the plurality of stream weights. Thereafter, the transmitter reiterates as needed a determination of an unequal weighting of the plurality of stream weights and a transmission of the plurality of transmission signals as a function of the plurality of data streams and the unequal weighting of the plurality of stream weights.

Quasi-static antenna array processing for rapidly time-varying channels

Abstract: This paper explores the use of quasi-static frequency-domain antenna combining weights for multi-user (e.g., SDMA) or multi-stream (e.g., MIMO) communication systems operating in rapidly time-varying frequency-selective channels. By implementing combining weights that are constant across a time slot but are updated from slot-to-slot (i.e., "quasi-static"), great computational complexity savings can be realized compared to calculating new weights at each data block within a time slot. The quasi-static weights are computed by first modeling, the time-varying channel for each user as the superposition of multiple time-invariant channels, called Doppler channels. The weights are then calculated based on all users' Doppler channels. These new weights work by using some of the degrees of freedom of the antenna array to suppress time variations as well as multiple access interference. Despite being fixed across a time slot, these weights can equalize and suppress SDMA interference even when the channel varies significantly over the slot. Simulation results show the effectiveness of these weights for equalization and interference suppression.