Reconfigurable Intelligent Surface-Aided Single-Input Single-Output K-Complex Symbol Golden Codeword-Based Modulation

Narushan Pillay,Hongjun Xu

doi:10.1109/access.2021.3078884

Narushan Pillay, Hongjun Xu

Open Access

https://doi.org/10.1109/access.2021.3078884

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Journal: IEEE Access	Publication Date: Jan 1, 2021
Citations: 4	License type: CC BY 4.0

Affiliation: University of KwaZulu-Natal

Abstract

Small reconfigurable intelligent surfaces (RISs) have greater potential for flexibility and ubiquity compared to large RISs. In the literature, the theoretical average bit error probability (ABEP) of a phase-adjustable element access-point-based RIS (AP-RIS) is derived by exploiting the central-limit theorem for large surface size. Hence, the analysis does not hold for small surface sizes. In this paper, we first formulate a simple closed-form expression for the ABEP of a phase-adjustable element AP-RIS with $M$ -ary quadrature amplitude modulation ( $M$ QAM). Compared to the results available in literature, this expression is valid even for small RISs. Second, we investigate AP-RIS-aided single-input single-output $K$ -complex symbol Golden codeword-based modulation, which encodes/transmits $K~M$ QAM symbols in each of $K$ consecutive independently faded time slots. The encoding ensures that each symbol experiences $K$ different fadings, hence resulting in a $K$ -fold increase in diversity order, while the AP-RIS maximizes the received signal-to-noise ratio (SNR) in each slot and yields significant SNR gains with increasing size. An increase in $K$ yields significant SNR gains for small RISs. A theoretical bound on the ABEP is formulated and validated by simulation. Finally, a detector based on sorted symbol set sphere decoding is devised.

Highlights

R ECONFIGURABLE intelligent surfaces (RISs) [1] modify the propagation environment to enhance communication system objectives, such as reliability, capacity, security, energy and spectrum efficiency [2]
THEORETICAL average bit error probability (ABEP) FOR access-point-based RIS (AP-RIS) WITH M -ary quadrature amplitude modulation (M QAM) Assume the transmission of a symbol u, drawn from the set Ω of M QAM symbols with E{|u|2} = 1, by an N -element AP-RIS to a single receive antenna, the received signal assuming a Rayleigh frequency-flat fading channel and the presence of additive white Gaussian noise (AWGN) at the receiver, is given as: N
The proposed RIS-SISOKCSGCM showed a superior bit error rate (BER) compared to its nonRIS counterparts

Summary

INTRODUCTION

R ECONFIGURABLE intelligent surfaces (RISs) [1] modify the propagation environment to enhance communication system objectives, such as reliability, capacity, security, energy and spectrum efficiency [2]. By the application of component-interleaving between pairs of super-symbols, additional diversity gain was realized by the transmission of the interleaved super-symbols over four consecutive time slots This motivates that the key idea of the MCSGC [6] may be extended to a single transmit antenna system; based on n ≥ 1, n ∈ Z encodings, K = 2n complex input symbols may be transmitted using only a single transmit antenna in each of K consecutive time slots, which will allow significant improvement in error performance. THEORETICAL ABEP FOR AP-RISs WITH M QAM Assume the transmission of a symbol u, drawn from the set Ω of M QAM symbols with E{|u|2} = 1, by an N -element AP-RIS to a single receive antenna, the received signal assuming a Rayleigh frequency-flat fading channel and the presence of additive white Gaussian noise (AWGN) at the receiver, is given as: N y=. It is immediately evident that the diversity order achieved by the AP-RIS is N , the number of elements in the RIS

SYSTEM MODEL

THEORETICAL BOUND ON ABEP

NUMERICAL RESULTS

CONCLUSION AND FUTURE WORK