Coverage Improvements for Enhanced Uplink

In UMTS Enhanced Uplink (EUL), 2 and 10 ms TTIs are supported, which substantially decreases latency and increases data rates compared to DCH. However, due to the shorter TTI compared to DCH, coverage may be an issue in situations where the use of multiple re-transmissions is not feasible. This paper evaluates four possible methods to increase the EUL coverage: Configurable minimum data power offset, Freezing the Outer Loop Power Control (Freezing OLPC), Autonomous Retransmission (AR) and Improved Layer 2 (Improved L2). The coverage gains with all these methods are considerable compared to EUL Release 6 (R6). By tuning the minimum data power offset for VoIP, it is found that a coverage gain of 4-5 dB is achievable. With Improved L2 and 120 bits as the smallest transport block size, a coverage gain of up to 7 dB is possible.