A Code-reuse Scheme in the Downlink of TD-SCDMA System

The TD-SCDMA system is code-limited. A code-reuse scheme is proposed to make the limited spreading codes support more subscribers. The smart antenna technique is used to realize the scheme. It takes advantaged of the big differences of space characteristic among subscribes to meet the demand of reuse of same spreading codes for several high data rate of users. This can improve utilization of code resources. In comparisons of system performances using several beam-forming algorithms, the results show that performance of the system using the code-reuse scheme is almost the same as that of traditional system; Moreover, an improved algorithm based on tradition null-steering method is proposed, which can improve system performance, especially for the high data rate downlink with a few subscribers.