Prerequisites & Notation

Before You Begin

This chapter provides a comprehensive performance analysis of cell-free massive MIMO, bringing together achievable rates, fairness metrics, energy efficiency, and practical deployment. We assume familiarity with the following topics from earlier chapters.

Cell-free massive MIMO concept and conjugate beamforming(Review ch11)
Self-check: Can you write the cell-free downlink signal model with $L$ distributed APs and explain the macro-diversity gain?
User-centric clustering and scalability(Review ch12)
Self-check: Can you explain why each user needs only a cluster of nearby APs and how this bounds the per-AP computational load?
Cooperation levels (Level 1-4) and distributed MMSE(Review ch13)
Self-check: Can you distinguish local MRC (Level 1) from centralized MMSE (Level 4) and describe the fronthaul cost of each?
Fronthaul quantization and compression(Review ch14)
Self-check: Can you explain how limited fronthaul capacity degrades the achievable rate and describe estimate-and-forward?
The use-and-then-forget (UatF) bound(Review ch04)
Self-check: Can you state the UatF technique: treat the estimated channel as perfect, treat the estimation error as uncorrelated noise?
Max-min fair power control(Review ch05)
Self-check: Can you formulate the max-min SINR problem as a quasi-convex optimization solved via bisection?

Notation for This Chapter

Symbols introduced or specialized in this chapter. See the NGlobal Notation Table master table for general conventions.

Symbol	Meaning	Introduced
$L$	Number of access points (APs)	s01
$K$	Number of users	s01
$N$	Number of antennas per AP	s01
$\mathbf{H}_{lk}$	Channel vector from AP $l$ to user $k$ , $\mathbf{H}_{lk} \in \mathbb{C}^N$	s01
$\beta_{lk}$	Large-scale fading coefficient between AP $l$ and user $k$	s01
$\gamma_{lk}$	Channel estimation quality: $\gamma_{lk} = \mathbb{E}[\\|\hat{\mathbf{H}}_{lk}\\|^2]/N$	s01
$\eta_{lk}$	Power control coefficient at AP $l$ for user $k$ (downlink)	s01
$\text{SE}_k$	Spectral efficiency of user $k$ (bits/s/Hz)	s01
$R_k$	Achievable rate of user $k$ (bits/s/Hz)	s01
$\tau_c$	Coherence interval length (samples)	s01
$\tau_p$	Number of pilot samples	s01
$C_{\text{fh}}$	Fronthaul capacity per AP (bits/s)	s01
$P_{\text{AP}}$	Per-AP hardware power consumption (W)	s04
$P_{\text{fh}}$	Per-AP fronthaul link power consumption (W)	s04
$\text{EE}$	Energy efficiency (bits/Joule)	s04
$\mathcal{M}_k$	Set of APs serving user $k$ (user-centric cluster)	s01

← Ch 14 Achievable Rate Expressions