Abstract
This work addresses the joint design of fronthaul and edge links for a cache-aided cloud radio access network (C-RAN) system with a wireless fronthaul link. Motivated by the fact that existing techniques, such as C-RAN and edge caching, come at the cost of increased energy consumption, an energy efficiency (EE) metric is defined and adopted as the performance metric for optimization. As the fronthaul links can be used to transfer quantized and precoded baseband signals or hard information of uncached files, both soft- and hard-transfer fronthauling strategies are considered. Extensive numerical results validate the impact of edge caching, as well as the advantages of the energy-efficient design over the spectrally-efficient scheme. Additionally, the two fronthauling strategies—the soft- and hard-transfer schemes—are compared in terms of EE.
Highlights
It has been envisioned that the cloud radio access network (C-RAN) architecture will be able to meet the ever-increasing traffic demands of future wireless communication systems, by migrating baseband signal processing functionalities from base stations, or remote radio heads (RRHs), to a cloud processor (CP) or baseband processing unit (BBU) [1,2].In particular, improved spectral efficiency is expected to be achieved with the C-RAN architecture, thanks to centralized baseband processing at CPs
We show that the hard-transfer fronthauling scheme outperforms the soft-transfer scheme in overall simulated set-ups, as the former is more effective in utilizing the wireless fronthaul resources for multicasting to multiple edge nodes (ENs), which may request overlapping uncached files
We validate the effectiveness of the proposed energy-efficient designs under the soft-transfer and hard-transfer fronthauling strategies proposed in Sections 3 and 4, respectively, through numerical results
Summary
It has been envisioned that the cloud radio access network (C-RAN) architecture will be able to meet the ever-increasing traffic demands of future wireless communication systems, by migrating baseband signal processing functionalities from base stations, or remote radio heads (RRHs), to a cloud processor (CP) or baseband processing unit (BBU) [1,2].In particular, improved spectral efficiency is expected to be achieved with the C-RAN architecture, thanks to centralized baseband processing at CPs. The overhead, or capacity requirements, of the fronthaul links in C-RAN systems can be alleviated by adopting narrowband IoT (NB-IoT) technology, which supports low-power and low-cost devices [20], or by adding edge caching functionalities to RRHs [21,22,23,24,25,26,27,28]. The idea of the latter is that the RRHs are equipped with local caches at which popular content frequently requested by mobile user equipment (UE) are pre-fetched, such that the amount of data delivered over the fronthaul links can be reduced at the delivery phase. In [27], an information theoretic analysis of cache-aided C-RAN systems was addressed
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