Pathloss-aided closed loop transmit power control for 3G UTRA TDD

In 3G UTRA TDD, closed loop power control is used as an inner loop power control technique for downlink DPCHs (dedicated physical channels) in the 3.84 Mcps option, and both uplink and downlink DPCHs in the 1.28 Mcps option. In the current closed loop power control, transmit power is generally updated at the frame sub-frame rate, using a semi-static step size (1,2, or 3 dB). Such a slow transmit power update by a given step size may not be enough to cope with dynamically changing environments, so that the performance of the closed loop power control is degraded. In this paper, we propose an enhanced closed loop power control technique for UTRA TDD, which adapts the step size according to relative pathloss (or power) measurements at the transmitter side. We show that the link-level performance of the proposed power control can be significantly better than the existing closed loop power control. The largest gains are obtained for slow and moderate fading channels.