Enabling the Multi-User Generalized Degrees of Freedom in the Gaussian Cellular Channel

TL;DR

This paper demonstrates that multi-user operation in Gaussian cellular channels provides additional generalized degrees of freedom, enabling higher sum-rates through signal scale alignment, and closes the gap between deterministic and Gaussian models.

Contribution

It proves the existence of multi-user GDoFs in Gaussian cellular channels and provides an achievable sum-rate within a constant gap of the LDM capacity.

Findings

Multi-user GDoFs exist in Gaussian cellular channels.

Signal scale alignment enables near-optimal sum-rate.

Multi-user gain reduces interference by half in 2-user per cell scenario.

Abstract

There has been major progress over the last decade in understanding the classical interference channel (IC). Recent key results show that constant bit gap capacity results can be obtained from linear deterministic models (LDMs). However, it is widely unrecognized that the time-invariant, frequency-flat cellular channel, which contains the IC as a special case, possesses some additional generalized degrees of freedom (GDoF) due to multi-user operation. This was proved for the LDM cellular channel very recently but is an open question for the corresponding Gaussian counterpart. In this paper, we close this gap and provide an achievable sum-rate for the Gaussian cellular channel which is within a constant bit gap of the LDM sum capacity. We show that the additional GDoFs from the LDM cellular channel carry over. This is enabled by signal scale alignment. In particular, the multi-user gain reduces the interference by half in the 2-user per cell case compared to the IC.