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Título: Interference characterization and suppression for integrated wireless DS-CDMA networks
Autores: Das, Kaushik.
Fecha: 1998
Publicador: McGill University - MCGILL
Fuente:
Tipo: Electronic Thesis or Dissertation
Tema: Engineering, Electronics and Electrical.
Descripción: This dissertation addresses the impact of integrated services on future third generation wireless DS-CDMA networks. The first part of the research characterizes the multiple-access interference (MAI) in an integrated DS-CDMA system. The system model is designed to accommodate bursty packed-based data services (e.g., packet or multimedia data) in addition to stream-based services (e.g., voice or facsimile) on a shared spectrum basis. Consequently, this study incorporates features associated with both packet- and stream-based services in order to provide a complete interference characterization. The results of a detailed and precise simulation study are presented in which the influence of traffic burstiness, voice activity, spatial distribution of mobiles, and transmitter powers on the fluctuation of the interference and signal-to-interference ratio (SIR) is assessed. The interference and SIR statistics are also evaluated in terms of the cumulative distribution function. Since a DS-CDMA network is interference limited, studies of this type are essential for system design, capacity evaluation, and bandwidth management.
The second part of the research explores adaptive interference suppression techniques. The motivation of this segment of the work comes from our observation in the first part of the research that MAI may be modeled as a wideband, time-varying stochastic process. The challenge is twofold: (i) interference suppression techniques should consider demodulation in a dynamic environment (e.g., entry/exit of users), rather than a static situation and (ii) interference suppression techniques must also address the worst case scenario where the sources and sinks of stream-based services must be able to handle data in bursts on a realtime basis and without the knowledge of different parameters and signature sequences of the interferers. A neural network based decision feedback scheme for interference suppression in the CDMA context is proposed and investigated. It is demonstrated that a decision feedback functional link equalizer (DFFLE) network in combination with an eigenvector network can closely approximate a Bayesian receiver with significant advantages, such as improved BER performance and adaptive operation. The convergence performance and error propagation of the DFFLE receiver are also considered and show reasonable promise for third generation wireless DS-CDMA networks.
Idioma: en