Precoding of correlated symbols for STBC systems design

Abstract

A problem with transmitting correlated symbols over multiple transmit channel paths is that there is no diversity gain achieved at the receiver. Precoding technique provides a smart approach to achieving diversity gains at the receiver even when correlated symbols are transmitted; by phase variation, amplitude variation or both provided by the precoder. The space-time block code (STBC) technique, for example, is well-known when transmitting the same symbols by making them appear as different symbols using conjugation. We observe that correlated symbols can be transmitted over multiple transmit channel paths over STBC scheme while still achieving diversity. The correlated symbols can be made to appear as different symbols by using precoders; this enables diversity and improves data rate. Combining the proposed with the equivalent channel matrix (EVCM) permits the proposed design to outperform the conventional precoding of uncorrelated symbols technique by 2 dB at all bit error ratio (BER) for 2 × 1 and 2 × 2 antenna configurations. This is useful in increasing data rates with better BER performance.