Series in Broadband Communications
Techniques for Bandwidth Efficient
Fixed Wireless Access Systems.
1. edition 2002, 136 Seiten, € 64,00. ISBN 3-89649-813-4
Fixed wireless access systems can provide broadband data services to households and businesses without requiring any existing cable infrastructure. Multicarrier modulation techniques like OFDM facilitate the high-speed data transmission over time-dispersive channels. Bandwidth efficient multicarrier schemes are of particular interest, as the transmission medium needs to be shared among multiple users in fixed wireless access scenarios.
Two potential techniques for achieving higher spectral efficiencies than with a conventional OFDM modulation are proposed in this work. The first technique exploits available channel state information at the transmitter side to accomplish an adaptive modulation. An optimization of the spectral power allocation of bit-interleaved coded broadband OFDM signals transmitted over slowly time-variant channels is considered in particular. Adaptation policies are elaborated which aim to minimize the bit error rates at the decoder output of hard-decision and soft-decision based receivers, assuming either perfect or outdated channel state information.
The second part of the work focuses on alternative multicarrier transmission techniques without bandwidth wasting guard periods. Multicarrier schemes in which the elementary signal pulses relate to the elements of a Weyl-Heisenberg system are studied. Pulses with concentrated energy in both the time and frequency dimensions may be utilized to confine the overlapping of the information-bearing signal parts after dispersive channels and the resulting interference. Receiver schemes are presented which incorporate efficient filter banks and iterative detection methods, taking advantage of the confined pulse overlapping for limiting the computational effort.
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