Analysis and Optimization of Service Delay for Multi-quality Videos in Multi-tier Heterogeneous Network with Random Caching

TL;DR

This paper proposes a novel random caching scheme for multi-quality videos in heterogeneous networks, aiming to minimize service delay by optimizing transmission success probabilities across D2D, SBS, and MBS links.

Contribution

It introduces a new caching scheme supporting scalable video coding, with an analytical framework for delay minimization and an efficient algorithm for optimal cache placement.

Findings

The proposed caching scheme reduces service delay compared to benchmarks.

Analytical results match simulation outcomes, validating the model.

The scheme effectively balances cache constraints and quality support.

Abstract

Aiming to minimize service delay, we propose a new random caching scheme in device-to-device (D2D)-assisted heterogeneous network. To support diversified viewing qualities of multimedia video services, each video file is encoded into a base layer (BL) and multiple enhancement layers (ELs) by scalable video coding (SVC). A super layer, including the BL and several ELs, is transmitted to every user. We define and quantify the service delay of multi-quality videos by deriving successful transmission probabilities when a user is served by a D2D helper, a small-cell base station (SBS) and a macro-cell base station (MBS). We formulate a delay minimization problem subject to the limited cache sizes of D2D helpers and SBSs. The structure of the optimal solutions to the problem is revealed, and then an improved standard gradient projection method is designed to effectively obtain the solutions. Both theoretical analysis and Monte-Carlo simulations validate the successful transmission probabilities. Compared with three benchmark caching policies, the proposed SVC-based random caching scheme is superior in terms of reducing the service delay.