Mitigation techniques for mobile communications over fading channels

• Main Author: Subarajan, Loganathan
• Other Authors: Li Kwok Hung
• Format: Theses and Dissertations
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/64779
• Institution: Nanyang Technological University

Wireless communications has been a major breakthrough in the communication era and has been under tremendous development over the past two decades. It has been constantly improving its quality and capacity to meet the huge growing demand and requirements of people. Hence, this has become a vital area for research and development. Mobile communications involves both wired communications as well as wireless communications. The major challenge for mobile communication lies in the latter part, wireless communications. This is due to the signal being deteriorated by attenuations due to propagation and various obstacles such as buildings, hills, lamp posts and also the relative motion between the transmitter and the mobile station. Hence, the transmitted signal undergoes various disturbances, resulting in attenuation and fading. The term fading refers to the fluctuations in amplitude and phase of the transmitted signal due to large distances and multi path environments of wireless channels. The transmitted signal can reach the receiver through various paths after getting reflected, diffracted and scattered from various obstacles. These multipath components can add up constructively or destructively, which results in fading. Apart from this, there will be external noise or thermal noise added to the signal. Hence, at the receiver, all these harmful effects need to be removed to identify and detect the original transmitted signal. Improper handling of these signals results in higher bit-error rates (BERs) and affects the quality of service (QoS). This dissertation involves the analysis of various mitigation techniques deployed to reduce the fading involved so that optimum solution can be implemented at the receiver to achieve best performance. The first step of this project work is related to the analysis of different channel models and fading environments to produce the simulation results of BER curves plotted against different signal-to-noise ratios (SNRs). These different models include single path, direct line-of-sight (LOS) path and multipath under flat-fading and frequency-selective-fading environments. The second half of the dissertation deals with equalizing the effects of channel using various equalization methods and their performance results are analyzed to reduce BERs and optimize the SNR. The results are generated and simulated in MATLAB.