Personalized Federated Learning for Cellular VR: Online Learning and Dynamic Caching

TL;DR

This paper introduces a personalized federated learning-based caching strategy for wireless VR networks, improving content delivery by tailoring cache content to user preferences and channel dynamics, thereby reducing delay and increasing cache hits.

Contribution

It proposes a decentralized, personalized federated learning caching algorithm with PAC guarantees, incorporating gradient quantization and dynamic grouping for wireless VR systems.

Findings

The proposed DP-FL caching algorithm outperforms baseline methods in delay and cache hit rate.

Gradient quantization reduces communication costs without sacrificing convergence.

Dynamic grouping of VR users improves cache efficiency and content delivery.

Abstract

Delivering an immersive experience to virtual reality (VR) users through wireless connectivity offers the freedom to engage from anywhere at any time. Nevertheless, it is challenging to ensure seamless wireless connectivity that delivers real-time and high-quality videos to the VR users. This paper proposes a field of view (FoV) aware caching for mobile edge computing (MEC)-enabled wireless VR network. In particular, the FoV of each VR user is cached/prefetched at the base stations (BSs) based on the caching strategies tailored to each BS. Specifically, decentralized and personalized federated learning (DP-FL) based caching strategies with guarantees are presented. Considering VR systems composed of multiple VR devices and BSs, a DP-FL caching algorithm is implemented at each BS to personalize content delivery for VR users. The utilized DP-FL algorithm guarantees a probably approximately correct (PAC) bound on the conditional average cache hit. Further, to reduce the cost of communicating gradients, one-bit quantization of the stochastic gradient descent (OBSGD) is proposed, and a convergence guarantee of $\mathcal{O}(1/\sqrt{T})$ is obtained for the proposed algorithm, where $T$ is the number of iterations. Additionally, to better account for the wireless channel dynamics, the FoVs are grouped into multicast or unicast groups based on the number of requesting VR users. The performance of the proposed DP-FL algorithm is validated through realistic VR head-tracking dataset, and the proposed algorithm is shown to have better performance in terms of average delay and cache hit as compared to baseline algorithms.