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Coexistence of D2D Communications and Cell-Free Massive MIMO Systems With Low Resolution ADC for Improved Throughput in Beyond-5G Networks

Hamed Masoumi, Mohammad Javad Emadi, Stefano Buzzi

TL;DR

In this paper, uplink transmission of a cell-free massive multiple-input multiple-output (CF-mMIMO) system coexisting with device-to-device (D2D) communication links is investigated and it is revealed that the activation of D2D links has a positive effect on the system throughput.

Abstract

In this paper, uplink transmission of a cell-free massive multiple-input multiple-output (CF-mMIMO) system coexisting with device-to-device (D2D) communication links is investigated, under the assumption that access points (APs) are equipped with low-resolution analog-to-digital converters (ADCs). Lower bounds of achievable rates for both D2D users (DUEs) and CF-mMIMO users (CFUEs) are derived in closed-form, with perfect and imperfect channel state information. Next, in order to reduce pilot contamination, greedy and graph coloring-based pilot allocation algorithms are proposed and analyzed for the considered scenario. Furthermore, to control interference and improve the performance, two power control strategies are designed and their complexity and convergence are also discussed. The first power control strategy aims at maximizing CFUEs' sum spectral efficiency (SE) subject to quality of service constraints on DUEs, while the second one maximizes the weighted product of CFUEs' and DUEs' signal-to-interference-plus-noise-ratios (SINRs). Numerical results show that the proposed pilot and power allocations bring a considerable improvement to the network SE. Also, it is revealed that the activation of D2D links has a positive effect on the system throughput, i.e. the network offloading ensured by the D2D links overcomes the increased interference brought by D2D communications.

Coexistence of D2D Communications and Cell-Free Massive MIMO Systems With Low Resolution ADC for Improved Throughput in Beyond-5G Networks

TL;DR

In this paper, uplink transmission of a cell-free massive multiple-input multiple-output (CF-mMIMO) system coexisting with device-to-device (D2D) communication links is investigated and it is revealed that the activation of D2D links has a positive effect on the system throughput.

Abstract

In this paper, uplink transmission of a cell-free massive multiple-input multiple-output (CF-mMIMO) system coexisting with device-to-device (D2D) communication links is investigated, under the assumption that access points (APs) are equipped with low-resolution analog-to-digital converters (ADCs). Lower bounds of achievable rates for both D2D users (DUEs) and CF-mMIMO users (CFUEs) are derived in closed-form, with perfect and imperfect channel state information. Next, in order to reduce pilot contamination, greedy and graph coloring-based pilot allocation algorithms are proposed and analyzed for the considered scenario. Furthermore, to control interference and improve the performance, two power control strategies are designed and their complexity and convergence are also discussed. The first power control strategy aims at maximizing CFUEs' sum spectral efficiency (SE) subject to quality of service constraints on DUEs, while the second one maximizes the weighted product of CFUEs' and DUEs' signal-to-interference-plus-noise-ratios (SINRs). Numerical results show that the proposed pilot and power allocations bring a considerable improvement to the network SE. Also, it is revealed that the activation of D2D links has a positive effect on the system throughput, i.e. the network offloading ensured by the D2D links overcomes the increased interference brought by D2D communications.

Paper Structure

This paper contains 27 sections, 7 theorems, 39 equations, 8 figures, 2 algorithms.

Table of Contents

  1. Introduction
  2. CF-mMIMO Related Works
  3. D2D Related Works
  4. Contribution
  5. System Model
  6. Channel Model
  7. Modelling Impacts of Low Resolution ADC
  8. Achievable Rate Analysis
  9. Uplink Achievable Rate with Perfect CSI
  10. Achievable rate of CFUEs
  11. Achievable rate of DUEs
  12. Uplink Achievable Rate with Imperfect CSI
  13. Channel estimation
  14. Achievable rate
  15. Pilot assignment strategies
  16. ...and 12 more sections

Key Result

Theorem 1

The closed-form achievable rate of $k$th CFUE with perfect CSI is

Figures (8)

  • Figure 1: Cell-free mMIMO with underlaid D2D communications system model.
  • Figure 2: The advantages of considering D2D users in a CF-mMIMO system.
  • Figure 3: The impact of low resolution ADCs on the performance of the system with full power allocation. (a) Per user SE of CFUEs versus $b$. (b) NMSE of estimated channel versus transmitted pilot power with orthogonal pilots of length $\tau=30$. (c) EE of CFUEs versus $b$.
  • Figure 4: Performance of CFUEs with UC CF-mMIMO system, random pilot allocation, and full power transmission. (a) CDF of per user SE for $\delta = 0.9$. (b) Percentage of the APs serving each user and corresponding SE loss for $0.8\leq \delta \leq 0.999$.
  • Figure 5: Comparison of different pilot allocation methods for CFUEs. (a) Average per user SE. (b) Average minimum SE.
  • ...and 3 more figures

Theorems & Definitions (16)

  • Theorem 1
  • proof
  • Remark 1
  • Remark 2
  • Theorem 2
  • proof
  • Remark 3
  • Theorem 3
  • proof : Sketch of Proof
  • Theorem 4
  • ...and 6 more