A new multiple-access telecommunication system

This thesis records the research and development work carried out on a new telecommunications multiple-access system called the 'Complex Valued Collaborative Coding Multiple-Access' (CV-CCMA) system. The CV-CCMA system enables more than one transmission to use a communication channel without significant bandwidth expansion. The work has been completed between 1995 and 2000 whilst researching for a (part-time) Doctor of Philosophy degree at the University of Warwick. The new multiple-access system follows the general trend in communication systems that has been taking place over recent years. The reduction in the cost of processing power (million floating-point operation devices are now only a few pounds), has meant that the complex processing components of communication systems have moved from the analogue to the digital domain. Systems once regarded as too expensive to implement (except by the military) are now commonplace. The main digital processing element used for development of the system is a standard floating-point digital signal processor (DSP). A summary of the algorithm developed and software produced is included in this thesis. New techniques were developed to solve the multi-access resolution problems using the DSP and these are presented. The fundamental theory underlying the CV-CCMA system is described in detail with simplified examples showing the processes involved. A practical two-transmitter, one-receiver implementation was designed and constructed in order to prove the viability of the system, and details of this work are included in the thesis. Computer programs were written to solve the various linear algebraic equations relating to the operation of the decoding algorithm. Simulation programs enabling parameter variation without circuit construction are also recorded in the thesis. Problems encountered with the new circuitry are discussed and the solutions detailed. This includes a new high-stability oscillator that was designed, built, and tested and which was required in order for the system to function properly. Also described is the high-speed conversion circuitry. A new sequence of codewords has been developed, helping to reduce the stringent requirement on timing and synchronisation, and results are presented. New methods of synchronisation are discussed together with future development of the system. Projections as to possible uses of the system are also presented. Finally, there is a short comparative discussion of the CV-CCMA system and the broadband code division multiple-access system, recently on trial in the United Kingdom. This is of specific interest to Cable and Wireless PLC, the main sponsor of the research