Spectral efficiency of equal-rate DS-CDMA systems with multiple transmit antennas

The spectral efficiency of equal-rate DS-CDMA systems with multiple transmit antennas is analyzed. Explicit expressions for the spectral efficiency are obtained in the low and high energy regions and numerical results are presented for the moderate energy region. The performance gains resulting from the use of multiple transmit antennas are discussed. An equation characterizing the diversity-multiplexing tradeoff in this situation is derived. A conclusion that adding more transmit antennas does not necessarily improve the performance with the constraint of equal rate is drawn.