Rician Factor-Based Joint User Selection and Feedback Bit Allocation in Cell-Free MIMO Systems 


Vol. 47,  No. 10, pp. 1447-1456, Oct.  2022
10.7840/kics.2022.47.10.1447


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  Abstract

In 5G/6G communication systems, cell-free multiple-input multiple-output (MIMO) systems have attracted much attention, where the multiple distributed access points (APs) serve each user from a user perspective so that cell boundary no longer exists at each user. In addition, line-of-sight (LoS) communications are widely considered in cell-free networks, high-frequency bands, and non-terrestrial networks, which are typically modeled by Rician fading channels. In this paper, we consider the downlink of a frequency-division duplex (FDD) cell-free MIMO system, where channel state information at each user is quantized and conveyed to APs via limited feedback links, and propose a joint user selection and feedback bit allocation scheme. In our proposed scheme, APs perform distributed zero-forcing (DZF) beamforming without sharing any channel information and jointly optimize user selection and feedback bit allocation by considering the Rician factors. Using aband-structured non-homogeneous (BS-NH) codebook tailored for Rician fading channels, we first analyze the effect of feedback bit allocation on the average achievable sum rate. Then, we find the optimal user selection and feedback bit allocation. In the simulation part, we evaluate our proposed scheme and show that our proposed scheme significantly increases the average achievable sum rate compared with conventional schemes.

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[IEEE Style]

K. Lee and W. Choi, "Rician Factor-Based Joint User Selection and Feedback Bit Allocation in Cell-Free MIMO Systems," The Journal of Korean Institute of Communications and Information Sciences, vol. 47, no. 10, pp. 1447-1456, 2022. DOI: 10.7840/kics.2022.47.10.1447.

[ACM Style]

Kwangjae Lee and Wan Choi. 2022. Rician Factor-Based Joint User Selection and Feedback Bit Allocation in Cell-Free MIMO Systems. The Journal of Korean Institute of Communications and Information Sciences, 47, 10, (2022), 1447-1456. DOI: 10.7840/kics.2022.47.10.1447.

[KICS Style]

Kwangjae Lee and Wan Choi, "Rician Factor-Based Joint User Selection and Feedback Bit Allocation in Cell-Free MIMO Systems," The Journal of Korean Institute of Communications and Information Sciences, vol. 47, no. 10, pp. 1447-1456, 10. 2022. (https://doi.org/10.7840/kics.2022.47.10.1447)