Joint Optimization of Preamble Selection and Access Barring for MTC with Correlated Device Activities

TL;DR

This paper explores the joint optimization of preamble selection and access barring in machine-type communication systems with correlated device activities, proposing algorithms that significantly improve throughput by exploiting activity correlations.

Contribution

It formulates a novel nonconvex optimization problem for correlated device activities and develops two algorithms, including a low-complexity solution, to enhance throughput in MTC systems.

Findings

Proposed algorithms outperform existing schemes in throughput.

Exploiting activity correlation yields significant throughput gains.

Low-complexity solution achieves near-optimal performance.

Abstract

Most existing works on random access for machine-type communication (MTC) assume independent device activities. However, in several Internet-of-Things (IoT) applications, device activities are driven by events and hence may be correlated. This paper investigates the joint optimization of preamble selection and access barring for correlated device activities. We adopt a random access scheme with general random preamble selection parameterized by the preamble selection distributions of all devices and an access barring scheme parameterized by the access barring factor, to maximally exploit correlated device activities for improving the average throughput. First, we formulate the average throughput maximization problem with respect to the preamble selection distributions and the access barring factor. It is a challenging nonconvex problem. We characterize an optimality property of the problem. Then, we develop two iterative algorithms to obtain a stationary point and a low-complexity solution respectively by using the block coordinate descend (BCD) method. Numerical results show that the two proposed solutions achieve significant gains over existing schemes, demonstrating the significance of exploiting correlation of device activities in improving the average throughput. Numerical results also show that compared to the stationary point, the low-complexity solution achieves a similar average throughput with much lower computational complexity, demonstrating the effectiveness of the low-complexity solution.