Abstract:
Multiple-antenna systems that operate at high rates require simple yet
effective space-time transmission schemes to handle the large traffic
volume in real time. At rates of tens of bits/sec/Hz, V-BLAST, where
every antenna transmits its own independent substream of data, has
been shown to have good performance and simple encoding and decoding.
Yet V-BLAST suffers from its inability to work with fewer receive
antennas than transmit antennas---this deficiency is especially important
for modern cellular systems where a basestation typically has more antennas
than the mobile handsets. Furthermore, because V-BLAST transmits independent
data streams on its antennas there is no built-in spatial coding to guard
against deep fades from any given transmit antenna. On the other hand,
there are many previously-proposed space-time codes that have good fading
resistance and simple decoding, but these codes generally have poor
performance at high data rates or with many antennas.
We propose a high-rate coding scheme that can handle any configuration of
transmit and receive antennas and that subsumes both V-BLAST and many
proposed space-time block codes as special cases. The scheme transmits
substreams of data in linear combinations over space and time. The codes
are designed to optimize the mutual information between the transmitted and
received signals. Because of their linear structure, the codes retain the
decoding simplicity of V-BLAST, and because of their information-theoretic
optimality, they possess many coding advantages. We give examples of the
codes and show that their performance is generally superior to earlier
proposed methods over a wide range of rates and SNR's.
Status:
Submitted to IEEE Trans. Info. Theory, August 2000.
Revised April 2001.
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