In TD-SCDMA (UMTS TDD 1.28 Mcps mode) advanced techniques such as closed loop transmit diversity (CLTD) are foreseen. Deployment of CLTD influences the choice of receiver architecture and depends on propagation conditions, mobile speed, feedback delay, antenna weight computation and quantization. The impact of these factors is quantified and analyzed. In addition, due to recent interest in increasing the number of diversity antennas, results are presented using four antennas for CLTD. All simulations were performed using a setup very similar to TD-SCDMA conformance tests. The results obtained advise the use of a MMSE joint detection receiver architecture. For two transmit antennas, large gains up to 10 dB are achieved for low diversity propagation conditions, however the gains are smaller (/spl sim/2 dB) otherwise. The use of four antennas approximately doubles the gain achieved by two antennas. Also, it was found that higher mobile speeds do not decrease the gain of using CLTD, whereas larger feedback delays negatively impact performance.
[1]
Hsiao-Hwa Chen,et al.
China's perspectives on 3G mobile commuunications and beyond: TD-SCDMA technology
,
2002,
IEEE Wireless Communications.
[2]
S. Parkvall,et al.
Transmit diversity in WCDMA: link and system level results
,
2000,
VTC2000-Spring. 2000 IEEE 51st Vehicular Technology Conference Proceedings (Cat. No.00CH37026).
[3]
P. W. Baier,et al.
Zero forcing and minimum mean-square-error equalization for multiuser detection in code-division multiple-access channels
,
1996
.
[4]
Paul Walter Baier,et al.
Low Cost Channel Estimation in the Uplink Receiver of CDMA Mobile Radio Systems
,
1993
.