Abstract
Wireless communication system has found worldwide acceptability in providing acceptable services due to its portability, flexibility and ease of usage. However, the system is characterized by severe multipath propagation effects that degrade its performance. Selection Combiner (SC) as one of the techniques being used to address this problem is associated with poor performance due to fixed constellation of the modulation scheme. Hence, in this paper, an Adaptive Selection Combiner (ASC) using Constellation Adaptation Algorithm (CAA) with an expression over Log-normal fading channel is proposed. ASC is developed using conventional SC (CSC) and CAA. Ten thousand randomly generated bits are modulated using each of Phase Shift Keying (PSK) and Quadrature Amplitude Modulation (QAM) schemes. The modulated signals at varying paths are scanned by CSC to choose a path with the highest Signal to Noise Ratio (SNR). The output of SC which is a function of Channel State Information (CSI) acquired is used to determine the channel gain. The constellation size is then adjusted based on the value of channel gain through CAA. The proposed adaptive technique is simulated using MATLAB software and evaluated using Bit Error Rate (BER) to determine its performance. The results obtained show that ASC gives lower BER values than CSC due to the self-adjustment of the constellation size. Therefore, the proposed ASC can be deployed to improve the performance of wireless communication systems.
Highlights
Wireless Communication (WC) which is the act of conveying information from one point to another through an unbounded environment has been receiving much attention in the field of technology due to distance limitation in a wired medium [1, 2]
This is due to the fact that, the signal strength increases as the number of path as well as Signal to Noise Ratio (SNR) increases
Closed-form expression for Probability Density Function (PDF) of the received signal is derived for the proposed adaptive technique and used to derive Bit Error Rate (BER) expression to evaluate the performance of the proposed technique
Summary
Wireless Communication (WC) which is the act of conveying information from one point to another through an unbounded environment has been receiving much attention in the field of technology due to distance limitation in a wired medium [1, 2]. Wireless systems are equipped with channel measurement to know the status of the channel at a particular time This allows the receiver to measure the fade depth of the received signal which may be controlled by adjusting the schemes constellation for suitable transmission. The Log-Normal distribution is used in modelling cellular wireless networks in which vegetation and foliage are significant factors that cause scattering and absorption of radio waves making the power of received signal varies at the receiver due to shadowing It involves fading over large distance causes random fluctuations in the mean signal power while other fading channel such as Rayleigh, Rician and Nakagami-m are fading over small distance and time [4]
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