Digital communication in wireline and wireless environments

Abstract: This thesis consists of an introduction and five parts dealing with digital communication. Three parts address Discrete Multi-Tone modulation (DMT), a wireline form of Orthogonal Frequency Division Multiplexing (OFDM). One part addresses channel estimation in wireless OFDM and one addresses multiuser detection in wireless Direct Sequence-Code Division Multiple Access (DS- CDMA).The first part presents a new duplex method, called Zipper, for Very High bit rate Digital Subscriber Lines (VDSL). It is a duplex method that offer high flexibility and compatibility with existing services in the access network. The second part presents a digital Radio Frequency Interference (RFI) suppression method. It is located in the frequency domain and it can be used by any DMT-based VDSL system. The third part presents a method to run Zipper in an asynchronous mode with only a small performance loss. This can be of interest for telecom operators when constructing a VDSL system. The fourth part examines the trade-off between pilot symbol spacing and symbol error rate in a wireless OFDM system using Pilot Symbol Assisted Modulation (PSAM). The last part presents a low complexity multiuser detector for wireless DS-CDMA. It consists of a pipelined detector structure that produces Maximum Likelihood Secence Detector (MLSD) decisions on some of the received bits in the sequence. The remaining, previously undetected bits, are fed to a secondary post-processor.