Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Cost-Effectiveness Analysis and Design of Cost-Efficient Cell-Free Massive MIMO Systems

Wei Jiang, Hans D. Schotten

TL;DR

This work analyzes the cost-effectiveness of cell-free massive MIMO by introducing a unified model that allows different numbers of antennas per access point (AP). It derives uplink spectral efficiency under maximum-ratio combining and examines downlink performance for conjugate beamforming and zero-forcing precoding, while integrating a comprehensive cost model that separates fixed and per-antenna costs. Key contributions include closed-form uplink SINR expressions, downlink SINR expressions for both CB and ZFP, and a cost-efficiency metric that balances sum spectral efficiency against total deployment cost. The results show that multi-antenna APs can substantially improve cost-effectiveness by reducing the required AP density, though there are trade-offs in per-user throughput and fronthaul overhead depending on the precoding and antenna configuration.

Abstract

Cell-free massive multi-input multi-output (MIMO) has recently attracted much attention, attributed to its potential to deliver uniform service quality. However, the adoption of a cell-free architecture raises concerns about the high implementation costs associated with deploying numerous distributed access points (APs) and the need for fronthaul network installation. To ensure the sustainability of next-generation wireless networks, it is crucial to improve cost-effectiveness, alongside achieving high performance. To address this, we conduct a cost analysis of cell-free massive MIMO and build a unified model with varying numbers of antennas per AP. Our objective is to explore whether employing multi-antenna APs could reduce system costs while maintaining performance. The analysis and evaluation result in the identification of a cost-effective design for cell-free massive MIMO, providing valuable insights for practical implementation.

Cost-Effectiveness Analysis and Design of Cost-Efficient Cell-Free Massive MIMO Systems

TL;DR

This work analyzes the cost-effectiveness of cell-free massive MIMO by introducing a unified model that allows different numbers of antennas per access point (AP). It derives uplink spectral efficiency under maximum-ratio combining and examines downlink performance for conjugate beamforming and zero-forcing precoding, while integrating a comprehensive cost model that separates fixed and per-antenna costs. Key contributions include closed-form uplink SINR expressions, downlink SINR expressions for both CB and ZFP, and a cost-efficiency metric that balances sum spectral efficiency against total deployment cost. The results show that multi-antenna APs can substantially improve cost-effectiveness by reducing the required AP density, though there are trade-offs in per-user throughput and fronthaul overhead depending on the precoding and antenna configuration.

Abstract

Cell-free massive multi-input multi-output (MIMO) has recently attracted much attention, attributed to its potential to deliver uniform service quality. However, the adoption of a cell-free architecture raises concerns about the high implementation costs associated with deploying numerous distributed access points (APs) and the need for fronthaul network installation. To ensure the sustainability of next-generation wireless networks, it is crucial to improve cost-effectiveness, alongside achieving high performance. To address this, we conduct a cost analysis of cell-free massive MIMO and build a unified model with varying numbers of antennas per AP. Our objective is to explore whether employing multi-antenna APs could reduce system costs while maintaining performance. The analysis and evaluation result in the identification of a cost-effective design for cell-free massive MIMO, providing valuable insights for practical implementation.
Paper Structure (12 sections, 22 equations, 3 figures)

This paper contains 12 sections, 22 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Cell-Free Massive MIMO System
  3. System Model
  4. Channel Model
  5. Spectral-Efficiency and Cost-Effectiveness Analysis in Uplink Transmission
  6. Spectral-Efficiency Analysis
  7. Cost Analysis
  8. Spectral-Efficiency and Cost-Effectiveness Analysis in Downlink Transmission
  9. Conjugate Beamforming
  10. Zero-Forcing Precoding
  11. Numerical Results
  12. Conclusions

Figures (3)

  • Figure 1: A unified model for cell-free massive MIMO with a varying number of antennas per AP, where a total of $M$ antennas are distributed over $N_{AP}$ sites. If $N_{AP}=M$, it stands for typical cell-free massive MIMO with single-antenna APs, whereas we are interested in applying multi-antenna APs to improve cost-effectiveness by reducing the number of AP sites.
  • Figure 2: Performance of cell-free massive MIMO systems in terms of the number of antennas at each AP (i.e., $N_t$), where a total of $M=300$ antennas serve $K=16$ (default) or $K=32$ users (marked by -32 in the legend), including (a) the sum capacity; (b) the 5-percentile spectral efficiency; and (c) the 50-percentile spectral efficiency.
  • Figure 3: Cost-effectiveness results of cell-free massive MIMO systems in terms of the number of antennas at each AP (i.e., $N_t$), where a total of $M=300$ antennas serve $K=16$. The ratio between the $N_t$-dependent and $N_t$-independent costs takes four values, i.e., $C_v/C_f=0.05,0.1,0.25$ and $0.5$.