Outdoor measurements with a TD (time division)-CDMA hardware demonstrator for UMTS

In the UMTS air interface standardisation within ETSI, TD (time division)-CDMA has been chosen for the unpaired band operation. TD-CDMA makes use of all three basic multiple access schemes FDMA, TDMA and CDMA. It combines the advantages of these three schemes and seamlessly fits into the world of GSM. In contrast to DS (direct sequence)-CDMA without joint detection (JD), intracell interference is eliminated in the reception by using the a priori knowledge of the CDMA codes of the users of one and the same cell. This elimination is performed by a process termed joint detection and increases spectrum efficiency and capacity. In order to practically verify and to demonstrate the advantages of TD-CDMA, a TD-CDMA hardware demonstrator was implemented, which is suited for a real mobile radio environment. In the paper, first the basic features of the hardware demonstrator are described. Then, measurement results obtained with the hardware demonstrator are presented. Particular emphasis is spent on the critical issues of power control and timing advance control