Bandwidth Efficient Multi-carrier System for Wireless Channels

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The research work proposed here investigates the means to develop a bandwidth efficient communication method, for future wireless systems, based on multicarrier techniques. In the last decade wireless communications have experienced an explosive growth with the demand for higher data rates to accommodate new services. This led to a plethora of standards being adopted and commercialised. In the communications and wireless research communities, substantial effort has been dedicated to develop bandwidth efficient signalling schemes to convey such high data rates in the adverse wireless environment, where transmission performance is severely compromised by frequency selective fading, interference and noise. Wideband code division multiple access (WCDMA) techniques have been adopted for third generation wireless mobile systems in order to accommodate data rates of the order of few Mbits/s and orthogonal frequency division multiplexing (OFDM) techniques have become serious contenders studied for future generation wireless systems. The OFDM schemes are based on the concept of dividing the data into several streams and then sending the streams on separate carriers, where the adjacent carriers have a frequency separation equal to the rate of each of the data streams. At UCL we developed a scheme where such frequency separation can be halved and therefore the bandwidth can be doubled. Such scheme has its limitation in terms of the nature of the data to be transmitted and is very susseptible to channel imperfections. Following that we carried out initial studies on a more efficient scheme of modulation and demodulation where the carrier separation can be further reduced, thereby providing even higher bandwidth efficiency advantages. The feasibility of this proposed scheme has been proven through basic analytical work and detailed modelling/simulation. In this proposal we aim to carry out further studies of our proposed scheme and assess its advantages, disadvantages and its limitations. This work will be carried out through detailed analytical studies and mathematical modelling, as well as, basic implementation using Digital Signal Processing (DSP) techniques.