Two-level Transmission Scheme for Cache-enabled Fog Radio Access Networks

TL;DR

This paper proposes a two-level transmission scheme for cache-enabled fog radio access networks to optimize delivery rate and reduce latency by effectively utilizing local caches and signal processing at remote radio heads.

Contribution

It introduces a novel two-level transmission scheme with centralized and decentralized algorithms for cache and network-level transmissions in fog RANs.

Findings

The proposed scheme improves delivery rate and reduces latency.

Algorithms converge to optimal KKT solutions.

Numerical results validate the effectiveness of the scheme.

Abstract

In this paper, we investigate the downlink transmission for cache-enabled fog radio access networks aiming at maximizing the delivery rate under the constraints of fronthaul capacity, maximum transmit power, and size of files. To reduce the delivery latency and the burden on fronthaul links and make full use of the local cache and baseband signal processing capabilities of enhanced remote radio heads (eRRHs), a two-level transmission scheme including cache-level and network-level transmission is proposed. In cache-level transmission, only requested files cached at the local cache are transmitted to the corresponding users. The duration of cache-level transmission is the delay caused by the transfer between the baseband unit (BBU) and eRRHs as well as the signal processing at the BBU. The remaining requested files are jointly transmitted to the corresponding users at network-level transmission. For cache-level transmission, a centralized optimization algorithm is firstly presented and then a decentralized optimization algorithm is provided to avoid the exchange of signaling among eRRHs. Meanwhile, another centralized optimization algorithm is presented to tackle the optimization problem for network-level transmission. All presented algorithms are proved to converge to the Karush-Kuhn-Tucker (KKT) solutions of the problems. Numerical results are provided to validate the effectiveness of the proposed transmission scheme as well as evaluating the system performance.