FAST ADAPTIVE EQUALIZERS FOR NARROW-BAND TDMA MOBILE RADIO

The future European cellular digital mobile radio system in the 900-MHz band adopts a narrow-band time division multiple access (TDMA) with GMSK modulation and a burst-type transmission based on a basic time slot consisting of a very short preamble (26-bit long) for synchronization and equalizer training purposes and of an information data section of 116 bits. Consequently, very fast adaptation methods are necessary to cope with the time- and frequency-selective distortions produced by Rayleigh and multipath fadings. This paper introduces a few theoretical aspects for the application of recursive least squares (RLS) adaptation algorithms to the narrowband TDMA mobile radio system and gives the relevant performance results for the fast Kalman algorithm, which turns out to be suitable for the considered application. In particular, signature curves, bit error rate, speed of convergence, steady-state behavior, numerical stability, required accuracy, and hardware complexity are discussed. Both linear transversal and nonlinear decision-feedback equalizers are considered.