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Abstract
Recent advances in multimedia mobile communications and wireless services have motivated researchers to investigate techniques that ensure the reliable transmission of very high data rates signals in multi-path fading channels. The thesis aims to propose and evaluate some new trends in multiple-access techniques for multimedia mobile communication channels with high and variable data rates.
Traditional single carrier modulation techniques can achieve only limited data rates due to the restrictions imposed by the multi-path fading nature of the channel and the receiver complexity. Wireless channels are also characterized by multiple access interference. Moreover, future wireless systems like 4th generation (4G) cellular systems will have to handle a variety of bit rates to allow for multi-rate transmission for multimedia applications.To combat the problems of multi-path fading and channel frequency selectivity for single-carrier transmission techniques, a multi-carrier (MC) transmission technique which is also known as Orthogonal Frequency Division Multiple-Access (OFDM) is considered. To better utilize the spectrum and radio resources for multimedia services, the combination of both the MC and the spread spectrum CDMA techniques is studied. New MC techniques based on this combination are proposed such as Multi-carrier Code Division Multiple-Access (MC-CDMA) and Multi-Carrier Direct- Sequence Code-Division-Muhiple-Access (MC-DS-CDMA). In this thesis, these techniques are investigated in detail through computer simulation that prevail the advantages of each technique as compared to classical multiple-access techniques.