Space-time processing techniques with application to broadband wireless systems

by Roy, Sébastien

This thesis consists of a study of spacetime receivers used at base stations to a. mitigate mchannel interfwence and b. provide robustness against fading. Many rdts herein are of a fuadamental nature and muid apply generally to any dular narrowband or broadbsnd wireiess system including mobile systems. However, their application to a spdc real-world system -the Local Multipoïnt Communication Syetem or LMCS which is charricterized by fixed suùscribers, broadbsnd operation and millimeter wadengths -is also considered. The contributionscan be classifiecl into three broad themes: 1. The efkt ofchannel envelope correlationbetween the array elements of a space time receiver has been carefully aPsessed through the useof two mdyticait thre dimensional propagation modeis applicable to both narrowband and wîdeband contexts. Fixrthermore, a mmprehensive field meastuement experiment has been camed out to heip validate and refine th- modeis. 2. As an upper bound on optimal array performance, a nowl analysis of the matchdfilter bound is presented which includes the effect of correlation. It is known that the performance of the best possible divefsjty receiver, the array mwimum-likelihood receiver, is bounded by the MFB. Specincally, the main two novd aspects of our analysb are - the inclusion of spatial correletion through ou. proposed mnmtenated anuy-equivdent channel; - a treatment of the Rician fading case based on the Nakagarni distribution (and the fact that it can cidy apprcximate the Rice distribution). A novel S-T proceskg architecturehas beenstudied which isdesigned toexploit the multi-user information avaüable at the base station (i.e. joint detection). Mdti-werdecision-feedht spuce-lime processing is a system whereby decisions from other usem are coupled through adaptive feedback flters into the desireci user's receiver in order to remove not ody the post-clusor ISI but also the post-cursor CC1 hm in-ceIl interferers. This architecture therefore exploits the mdtiuser information to obtain more effective interference nulling at the cost of i n d cornplexity. Numerical rdts are provided comparing this architecturewith various ünear and non-linet~ll array structuresin both a genenc singiecell scenario and broadband wireiess multi-cell contexts.