An Efficient Square-root Algorithm for BLAST
Babak Hassibi
Abstract:
Bell Labs Layered Space-Time (BLAST) is a scheme for transmitting
information over a rich-scattering wireless environment using
multiple receive and transmit antennas. The main computational
bottleneck in the BLAST algorithm is a ``nulling and cancelation''
step, where the optimal ordering for the sequential estimation and
detection of the received signals is determined. To reduce the
computational cost of BLAST, in this paper we develop an efficient
square-root algorithm for the nulling and cancellation step. The main
features of the algorithm include efficiency: the
computational cost is reduced by 0.7M, where M is the number of
transmit antennas, and numerical stability: the algorithm is
division-free and uses only orthogonal transformations. In a 14
antenna system designed for transmission of 1 Mbit/sec over a 30 kHz
channel, the nulling and cancellation computation is reduced from 190
MFlops/sec to 19 MFlops/sec, with the overall computations being
reduced from 220 MFlops/sec to 49 MFlops/sec. The numerical stability
of the algorithm also make it attractive for implementation in
fixed-point, rather than floating-point, architectures.
Status:
Bell Labs Technical Memorandum, 1999. Submitted to
IEEE Transactions on Signal Processing.
Files:
Compressed PostScript (.ps.gz) (111K),
PostScript (.ps) (535K),
PDF v3.0 (.pdf) (256K).
Babak Hassibi<hassibi@bell-labs.com>