On the Blind Estimation of Baud-Rate Equalizer Performance
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On the Blind Estimation of Baud-Rate Equalizer Performance ˜ Joao-Batista Destro-Filho ´ FEELT-UFU, School of Electronic Engineering, Federal University of Uberlˆandia, Av Jo˜ao Naves de Avila 2121, Campus Santa Monica, 38400-902 Uberlˆandia, MG, Brazil Email: [email protected] Received 20 January 2002 and in revised form 10 August 2002 This paper proposes a new method for carrying out joint blind equalization and blind estimation of the bit error rate (BER) in the output of baud-rate FIR equalizers. A simple test for assessing decision errors in the output of the decision device is derived. A comparative study of several BER estimator methods is presented in terms of convergence rate and tracking capability of both static and dynamic channels. Simulations not only validate theoretical results but also point out the effectiveness of the new proposition in terms of low computational burden and accurate BER estimation. Finally, an application of the new proposition for the detection and correction of misconvergence due to local minima issues is also presented. Keywords and phrases: bit error rate, blind estimation, equalizer performance.
1.
INTRODUCTION
The universal mobile telecommunication system (UMTS) norm [1] is the major current trend in mobile communications. This norm aims at establishing a global mobile system, wherein any terminal may communicate with any other terminal. The terminals may be located anywhere on Earth, and the terminals may also be mobile or not. At the same time, the deployment of UMTS requires interconnection of several different local telecommunication systems in order to provide the link between the two terminals. Of course, satellite communications play an important role in UMTS since they provide cost-effective international links [2, 3]. Three major characteristics of the UMTS are discussed in the following [4]. (C1) Transmission rates currently present an increasingly growing demand [1]. (C2) The communication channel is a time-variant system of difficult characterization. In fact, temporal variations may be predicted with limited accuracy, and models are quite dependent both on the spatial or time scale [1]. In consequence, synchronization between the two communicating terminals is quite problematic due to severe fades, which requires special techniques for assuring the system performance, for example, adaptive transmission [5]. (C3) The management of a global communication system as UMTS is quite complex since it may be divided in
several local subsystems. Recent work [6] pointed out that, for assuring competitive quality, reliability, and availability, UMTS wireless fault management should employ an overlay system that continuously evaluates the signal quality at the level of local subsystems. For instance, [6] proposes a monitoring system based on the estimation of the bit error rate (BER). 2.
ADAPTIVE EQUALIZATION AND BUSSGANG ALGORITHMS
This work focuses on blind equalization [7, 8]. In this case, the equalizer update is carried out by means of an algorithm which does not require th
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