USTS (Uplink Synchronous Transmission Scheme)

To maximize the usage of 3G uplink capacity the 3GPP (Third Generation Partnership Project) is exploring techniques in which channel redundancy can be exploited. One approach is to implement USTS in which signals from mobiles within the cell are orthogonalized. That is, a number of mobiles are allocated the same scrambling code, but different channelization codes. This paper explores aspects of USTS including OVSF (Orthogonal Variable Spreading Factor) code allocation and timing both for initial synchronization and closed loop timing in order to maintain the channel timing reference within tolerable limits.