A Neural Network MLSE Receiver Based on Natural Gradient Descent: Application to Satellite Communications
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A Neural Network MLSE Receiver Based on Natural Gradient Descent: Application to Satellite Communications Mohamed Ibnkahla Electrical and Computer Engineering Department, Queen’s University, Kingston, Ontario, Canada K7L 3N6 Email: mohamed.ibnkahla@ece.queensu.ca
Jun Yuan Electrical and Computer Engineering Department, Queen’s University Kingston, Ontario, Canada K7L 3N6 Email: steveyuan@comm.utoronto.ca Received 30 August 2003; Revised 12 February 2004 The paper proposes a maximum likelihood sequence estimator (MLSE) receiver for satellite communications. The satellite channel model is composed of a nonlinear traveling wave tube (TWT) amplifier followed by a multipath propagation channel. The receiver is composed of a neural network channel estimator (NNCE) and a Viterbi detector. The natural gradient (NG) descent is used for training. Computer simulations show that the performance of our receiver is close to the ideal MLSE receiver in which the channel is perfectly known. Keywords and phrases: neural networks, satellite communications, high-power amplifiers.
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INTRODUCTION
The satellite communications field is getting an enormous attention in the wake of third generation (3-G) and future fourth generation (4-G) mobile communication systems challenges [1, 2]. Currently, when the telecommunications industries are planning to deploy the 3-G system worldwide and researchers are coming up with tons of new ideas for the next-generation wireless systems, a load of challenges are yet to be fulfilled. These include high data rate transmissions, multimedia communications, seamless global roaming, quality of service (QoS) management, high user capacity, integration and compatibility between 4-G components, and so forth. To meet these challenges, presently researchers are focusing their attention in the satellite domain by considering it an integrated part of the so-called information superhighway [2, 3, 4, 5]. As a result, a new generation of satellite communication systems is being developed to support multimedia and Internet-based applications. These satellite systems are developed to provide connectivity between remote terrestrial networks, direct network access, Internet services using fixed or mobile terminals, and high data rate transmissions [1, 6]. In all these research and development scenarios, non-geostationary satellite networks are considered to provide satellite-based mobile multimedia
services for their low propagation delay and low path loss [1, 2, 5, 7, 8]. Among the most important challenges of satellite mobile communications are spectral and power efficiencies. Spectral efficiency demonstrates the ability of a system (e.g., modulation scheme) to accommodate data within an allocated bandwidth. Several researchers are working to make use of spectrally efficient modulation schemes, such as M-QAM modulations, for satellite transmissions. Power efficiency represents the ability of a system to reliably transmit information at a lowest practical power level. To reach high power efficiency, satellite communication syst
