# Efficient Scheduling for the Massive Random Access Gaussian Channel

## TL;DR

This paper proposes a novel grant-based scheme for massive random access Gaussian channels with small payloads, demonstrating competitive performance to grantless schemes and highlighting the potential of grant-based methods with small feedback.

## Contribution

It introduces a new grant-based scheme utilizing small feedback and improvements to existing methods, challenging the notion that grantless schemes are always superior.

## Key findings

- Proposed scheme performs close to state-of-the-art with small feedback.
- Improvements enable handling of message collisions and efficient transmission.
- Grant-based schemes can be competitive for small payloads in massive access scenarios.

## Abstract

This paper investigates the massive random access Gaussian channel with a focus on small payloads. For this problem, grant-based schemes have been regarded as inefficient due to the necessity of large feedbacks and the use of inefficient scheduling request methods. This papers attempts to answer whether grant-based schemes can be competitive against state-ot-art grantless schemes and worthy of further investigation. In order to compare these schemes fairly, a novel model is proposed, and, under this model, a novel grant-based scheme is proposed. The scheme uses Ordentlich and Polyanskiy's grantless method to transmit small coordination indices in order to perform the scheduling request, which allows both the request from the users to be efficient and the feedback to be small. We also present improvements to the Ordentlich and Polyanskiy's scheme, allowing it to transmit information through the choice of sub-block, as well as to handle collisions of the same message, significantly improving the method for very small messages. Simulation results show that, if a small feedback is allowed, the proposed scheme performs closely to the state-of-art while using simpler coding schemes, suggesting that novel grant-based schemes should not be dismissed as a potential solution to the massive random access problem.