An investigation into the use of orthogonal frequency division multiplexing in packet radio

Master Thesis


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University of Cape Town

The concept of Orthogonal Frequency Division Multiplexing has been around since the 1960s. It has resurfaced over the last decade as being the modulation scheme of choice in some newer technologies like Digital Video Broadcasting (DVB) and Asynchronous Digital Subscriber lines (ADSL). Amateur packet radio started in 1978 and has attracted thousands of enthusiasts from around the world. The interest in packet radio has waned over the years due advances in the data transmission capabilities oflandline systems and also more widespread access to the Internet. The purpose of this thesis was to develop a simple software simulation model to determine whether or not OFDM could be used to increase the data rates currently available in packet radio systems. The thesis starts out with an introduction to packet radio and OFDM in Chapter 1. A slightly more detailed discussion on OFDM is given in Chapter 2 in order to develop a basic specification for the proposed OFDM model. Chapters 2,3 and 4 discuss the development of the Transmitter model, the Receiver model and the Channel model respectively using the Simulink software package. Chapter 6 discusses the problem of Peak-to-Average Power Ratios (PAPR) in OFDM and explores the use of A-law companding to reduce this problem. In Chapter 7, the developed models are simulated and their performance compared to theoretical expectations. The full system is also simulated in this chapter in order to ascertain the possible data rate through the modelled packet radio channel. Conclusions regarding the application of OFDM to packet radio are presented in Chapter 8.

Bibliography: leaves 56-58.