On the Benefits of Bandwidth Limiting in Decentralized Vector Multiple Access Channels

TL;DR

This paper investigates how limiting the number of frequency bands accessible to transmitters in decentralized vector MACs affects spectral efficiency, revealing an optimal bandwidth limit and comparing resource partitioning versus sharing strategies.

Contribution

It introduces the concept of bandwidth limiting in decentralized vector MACs, derives a closed-form optimal bandwidth for resource partitioning, and compares its effectiveness with resource sharing strategies.

Findings

Optimal number of bands depends on number of transmitters and SNR

Bandwidth limiting improves spectral efficiency in resource partitioning

Limited benefit of bandwidth limiting in resource sharing scenarios

Abstract

We study the network spectral efficiency of decentralized vector multiple access channels (MACs) when the number of accessible dimensions per transmitter is strategically limited. Considering each dimension as a frequency band, we call this limiting process bandwidth limiting (BL). Assuming that each transmitter maximizes its own data rate by water-filling over the available frequency bands, we consider two scenarios. In the first scenario, transmitters use non-intersecting sets of bands (spectral resource partition), and in the second one, they freely exploit all the available frequency bands (spectral resource sharing). In the latter case, successive interference cancelation (SIC) is used. We show the existence of an optimal number of dimensions that a transmitter must use in order to maximize the network performance measured in terms of spectral efficiency. We provide a closed form expression for the optimal number of accessible bands in the first scenario. Such an optimum point, depends on the number of active transmitters, the number of available frequency bands and the different signal-to-noise ratios. In the second scenario, we show that BL does not bring a significant improvement on the network spectral efficiency, when all transmitters use the same BL policy. For both scenarios, we provide simulation results to validate our conclusions.