Low rate coding considerations for space-time coded DS/CDMA

In this paper the construction and performance evaluation of a space-time coded processing system employing a combined low-rate layered coded and antenna transmission diversity scheme for DS/CDMA communication systems are addressed. In this combined coding/signalling scenario the turbo coder structure is exploited for a space-time processing approach which results in an improved quality of communication. The space-time system, employing either a convolutional or turbo coding scheme, combines coding (temporal diversity), with RAKE (multipath diversity) and MRC (spatial diversity) to realize high-capacity DS/CDMA mobile communication systems. The transceiver considered employs n_T antennas at the transmitter and a single antenna at the receiver. In addition a L_R-branch space-path RAKE receiver, followed by a soft-input (soft-output) channel decoder are employed. We analyze the BER performance and capacity tradeoff between various system parameters under a fixed total bandwidth expansion and error correction code complexity constraint requirements. It is shown that when turbo codes are considered, the potential for large coding gains and increased system capacity is substantial