Joint Selection Combining and Power Loading Transmission With Adaptive $M$-QAM in Multichannel System

In this paper, we propose an adaptive
M
-ary quadrature amplitude modulation (
M
-QAM) transmission scheme that jointly uses selection combining and power loading over multiple independent identically distributed (i.i.d.) Rayleigh-fading channels in multichannel systems. We derive exact closed-form expressions of the performance of the proposed scheme in terms of the spectral efficiency, the average bit error rate (BER), and the outage probability. Numerical results show that our proposed hybrid scheme offers higher spectral efficiency and lower outage probability than the conventional schemes presented in the literature and is more reliable in the low-signal-to-noise-ratio (SNR) region as well.