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Intelligent Reflecting Surface Aided Multiple Access Over Fading Channels

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Document pages: 32 pages

Abstract: This paper considers a two-user downlink transmission in intelligentreflecting surface (IRS) aided network over fading channels. Particularly,non-orthogonal multiple access (NOMA) and two orthogonal multiple access (OMA)schemes, namely, time division multiple access (TDMA) and frequency divisionmultiple access (FDMA), are studied. The objective is to maximize the systemaverage sum rate for the delay-tolerant transmission. We propose two adjustmentschemes, namely, dynamic phase adjustment and one-time phase adjustment. Thepower budget, minimum average data rate, and discrete unit modulus reflectioncoefficient are considered as constrains. To solve the problem, two phaseshifters adjustment algorithms with low complexity are proposed to obtain nearoptimal solutions. With given phase shifters and satisfaction of time-sharingcondition, the optimal resource allocations are obtained using the Lagrangiandual decomposition. The numerical results reveal that: i) the average sum rateof proposed NOMA network aided by IRS outperforms the conventional NOMA networkover fading channels; ii) with continuous IRS adjustment in the fading block,the proposed TDMA scheme performs better than the FDMA scheme; iii) increasingthe minimum average user rate requirement has less impact on the proposedIRS-NOMA system than on the IRS-OMA system.

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