Outer-loop power control based on hybrid ARQ protocol for WCDMA enhanced uplink

Abstract

In this article, a node B-located outer-loop power control (OLPC) algorithm for WCDMA enhanced uplink (E-UL) based on the number of hybrid automatic repeat request (HARQ) transmission attempts is introduced. The proposed OLPC algorithm can take full advantage of the HARQ protocol since its operation is not affected by the signaling delay between node B and radio network controller (RNC). However, when the Node B-located OLPC is considered in a soft handover (SHO) situation, the Carrier-to-interference Ratio (CIR)-drift problem that emerges compromises the OLPC performance, and some mechanism to compensate for the CIR-drift problem is required. Both an aggressively tuned anti-windup function and an retransmission sequence number (RSN)-based functionality handle this problem. The proposed Node B-located OLPC is evaluated for 2 ms and 10 ms transmission time intervals (TTIs). It is observed that the Node B-located OLPC provides gains in terms of lower CIR and is more beneficial for 2 ms TTI, since the RNC signaling delay has rather severe impact in a shorter round trip time (RTT).