Uplink Spectral Efficiency Analysis of Decoupled Access in Multiuser MIMO Communications

TL;DR

This paper analyzes uplink spectral efficiency in multiuser MIMO systems with decoupled access, showing it improves spectral efficiency by allowing independent uplink and downlink associations based on BS densities.

Contribution

It derives association probabilities and spectral efficiency bounds for decoupled access, highlighting its independence from BS transmit powers and its advantages over coupled access.

Findings

Decoupled access association probabilities depend only on BS densities.

Uplink spectral efficiency under decoupled access is independent of BS transmit powers.

Decoupled access improves spectral efficiency compared to coupled access.

Abstract

In a heterogeneous network consisting of macro base stations (MBSs) and small base stations (SBSs), the traditional cell association policy, i.e., coupled access (CA), is far from optimal, due to the significant difference between the coverage and transmit powers of MBSs and SBSs. Hence, users may choose to associate with different types of BSs in downlink (DL) and uplink (UL), i.e., decoupled access (DA), to enhance spectral efficiency. In this paper, DA in multiuser MIMO communications is investigated in terms of UL spectral efficiency. Firstly, we obtain the UL association probabilities. In contrast to the CA scenario, association probabilities for DA scenario only depend on the densities of BSs. Hence, DA allows UL and DL to be totally independent. Secondly, we derive lower bounds on the spectral efficiency. The lower bounds show that, different from CA, the UL spectral efficiency for DA scenario is irrelative with the transmit powers of BSs, which implies DA allows users to associate with any BSs that can achieve the highest UL spectral efficiency. Finally, the spectral efficiencies for DA and CA scenarios are compared via simulation results, where it can be concluded that the spectral efficiency in multiuser MIMO systems is improved by DA.