DEVELOPMENT OF AN ENHANCED SELECTION COMBINER IN AN UNCORRELATED NAKAGAMI 0.5 FADING CHANNEL USING ADAPTIVE POWER CONTROLLED

Wireless communication has found worldwide recognition in providing acceptable signal levels due
to its 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 has a poor performance with low Spectral Efficiency (SE) and
high Bit Error Rate (BER) due to the fixed transmitting power used in the system. Hence, in this
paper, an enhanced SC that adjusts the transmitting power based on Channel State Information (CSI)
with a closed-form expression over an uncorrelated Nakagami-0.5 fading channel is proposed. The
proposed technique is developed using the conventional SC (CSC) and feedback algorithm. The
multiple copies of the transmitting signal over an uncorrelated Nakagam 0.5 fading channel are
received using multiple antennae. The resultant signals at varying paths 'L' (2, 3, 4) were scanned by
SC to choose a path with the highest Signal Noise Ratio (SNR). The output of SC which is a function
of Channel State Information (CSI) acquired was used to determine the channel gain. The
transmitting power was then adjusted based on the value of channel gain through the feedback
algorithm. A mathematical expression for BER and SE was also derived. The proposed technique
was simulated using Matrix Laboratory R2018a and evaluated using SE and BER by comparing with
each Optimal Rate Adaptation (ORA) and Channel Inversion Fixed Rate (CIFR) to determine the
performance of the system. The results obtained revealed that the proposed technique shows a
percentage reduction in BER of 33.33% and 66.67% when compared with ORA and CIFR,
respectively. The study showed that the proposed technique gave lower BER values compared to
ARA and CIFR and this is due to self-adjustment of the transmitting parameter.