Design of Balanced QPSK Space-Time Trellis Codes for Several Transmit Antennas

A new class of QPSK space time trellis codes (STTC) for several transmit antennas is proposed in this paper. We call these codes balanced STTC because they use the points of the constellation with the same probability. Comparing to known codes, these codes offer the best performance. Therefore, the systematic search for good codes can be reduced to this class. It is shown that all the best published codes are balanced. The paper presents the design of these balanced STTC and gives a complete list of the best 4-state codes for 2 transmit antennas. Several 16-state balanced codes for 2 and 3 transmit antennas are also given.