Bit Error Rate Estimation in UMTS in the Absence of an Amplitude Reference

Abstract:
The estimation of uncoded bit error rates (BERs) for received symbols in wireless communication systems is relatively straightforward when a reliable amplitude reference is available. However, estimation of uncoded BERs is also useful in the absence of any amplitude reference or error detection / correction information. In this paper we propose a family of techniques for performing such estimations, based on derived moments of the amplitudes of the received symbols. We show how simple ratios of moments can be used, enabling straightforward implementation in a mobile terminal. The described techniques find particular application in the UMTS 3rd Generation mobile communications system, where they may be employed by mobile terminals to estimate the error rate of received power-control commands. Knowledge of the reliability of these power-control commands is important for the efficient operation of the UMTS uplink (from mobile to base station). The described techniques are especially useful in the implementation of the feature known as "Fractional Dedicated Physical Channel", which has recently been included in the "Release 6" evolution of the UMTS specifications to make more efficient use of the available spreading codes for communications from base station to mobile.