 key technology and system evolutions will be introduced. 2.4.1 Key Technology Evolution Map TD-SCDMA is based on CDMA, utilizes a single antenna on the user equip- ment (UE) side, adopts low chip rate transmission, and employs joint detection to bring performance improvement. In comparison, the MIMO-OFDM technique is adopted in FuTURE, the sampling rate is relatively much higher, and FuTURE adopts advanced detection techniques to benefit the system. Hence, the evolved systems should be gradually equipped with some techniques. 2.4.1.1 Generalized Distributed Antenna Arrays Combined with Dynamical Channel Allocation The capacity of TD-SCDMA is mainly limited by intercell interference, rather than by the intracell interference for the smart antenna with joint detection © 2009 by Taylor & Francis Group, LLC Evolution from TD-SCDMA to FuTURE adopted; thus, the effect of cell breadth is not serious. If the intercell interference can be decreased, then the system capacity will be further improved. A distributed antenna can be used to improve the coverage in indoor scenarios and mitigate fast fading. For the generalized distributed antenna arrays (GDAAs), the whole cell is divided into several subcells and every subcell is centrally covered by an indepen- dent antenna array. The radio resource of one cell is shared by three of its subcells. Then the transmit power of every subcell is reduced for a small coverage radius and the intercell interference is reduced as well; thus, the capacity can be improved. Furthermore, DCA can be combined with a smart antenna and GDAA SO as to improve the system performance using SDMA. 2.4.1.2 Improved Joint Detection Joint detection is one of the key techniques of TD-SCDMA; it can eliminate MAI and ISI. The enhancement and improvement of joint detection can provide the potential for further performance improvement. When SDMA is implemented with a smart antenna, the same codes can be reused in the same cell, and interfer- ence may exist between different users who use the same codes becau