Year

2013

Degree Name

Master of Engineering - Research

Department

School of Electrical, Computer and Telecommunications Engineering

Abstract

Multiband orthogonal frequency division multiplexing ultra-wideband (MB-OFDM UWB) is an emerging technology proposed for wireless personal area network (WPAN) communication. It provides high data rate transmission with low power consumption. However, it has a disadvantage that the MB-OFDM UWB channels are much more dispersive than the channel in a conventional wireless system. Therefore, the communication range of MB-OFDM UWB systems is relatively short, which is typically up to ten meters.

This thesis targets at finding efficient techniques to increase further the data rate and communication range of MB-OFDM UWB systems without increasing the power consumption. One of the possible solutions is to adapt the concepts of the emerging techniques, namely cooperative communication, multiple-input multiple-output (MIMO) and space-time-frequency codes (STFCs), in order to tailor for their implementations in MB-OFDM UWB systems.

This research area has been almost unexplored with the cooperative communication scheme namely 2-OCCS for a two-source node MB-OFDM UWB system being proposed [4]. This thesis thus extends that idea to propose several cooperative communication schemes for four-source node MB-OFDM UWB systems, namely the 4- OCCS and 4-QOCCS schemes. These proposed schemes have been proved to improve significantly the system error performance in numerous cases, compared to a noncooperative MB-OFDM UWB system, without any increase of transmission power.

Although cooperative communication with space-time codes (STCs) is beneficial in ix various cases, it is unfortunately not always better than non-cooperative communication due to the erroneous decoding at the source nodes. One important question from the source nodes’ perspective is when they need to cooperate with one another. This research thus continues by analysing the bit error performance of cooperative communication systems in comparison with that of a non-cooperative communication one to find out the threshold conditions where cooperative communication starts to be useful.

In summary, the proposed cooperative communication schemes facilitate a flexible network design of up to four cooperative source nodes in MB-OFDM UWB systems. This thesis also derives for the first time an in-depth mathematical analysis of the usefulness of cooperative communication in both non-OFDM and OFDM-based systems. This analysis allows source nodes to know whether they should be in cooperation. It is believed that the contributions of this research are important pavements to a future, intelligent cooperative communication in wireless personal area networks WPANs, wireless body area networks (WBANs), and wireless sensor networks (WSNs).

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