On cell parameter ID assignment in UTRA-TDD

The use of short spreading sequences in UTRA-TDD may lead to large variability in uplink performance due to the level of cross correlation between spreading codes. The effective spreading code for a particular user is derived from a cell-specific scrambling code and the channelization code allocated to that user. We show that the interference between intercell users is dependent on their cell-specific scrambling code. This leads to a proposed cell-id allocation scheme for UTRA-TDD that reduces intercell interference. We also outline how the uplink air interface for future TD-CDMA systems may be designed to reduce this effect.