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.
Highlights
T O COPE with the continuously increasing number of wireless devices, to satisfy the demand of high data rates, and to meet the stringent quality-of-service (QoS) requirement of the emerging wireless services, various advanced communication technologies have been proposed in recent years [1]
In order to release the coupling among enhanced remote radio heads (eRRHs) and to achieve autonomous optimization of the beamformers, we introduce a new concept that is defined as the signal-to-interference-leakage-plus-noise ratio (SILNR), i.e., (17), at the top of this page
Different from the signal processing at each eRRHs, due to the fact that the baseband signal processing unit (BBU) has the whole channel state information (CSI) and data files of all users, the BBU can centrally design the precoders for all users and jointly transmit data files to each user
Summary
T O COPE with the continuously increasing number of wireless devices, to satisfy the demand of high data rates, and to meet the stringent quality-of-service (QoS) requirement of the emerging wireless services, various advanced communication technologies have been proposed in recent years [1]. Cooperative communication [2], massive multiple-input multiple-output (MIMO) [3], and network densification [4] are key technologies to achieve high capacity, high data rate, and guarantee network coverage in the fifth generation (5G) mobile cellular systems. In C-RAN, the remote radio heads (RRHs) are connected to a central processor, i.e., baseband signal processing unit (BBU), through fronthaul links [9]–[11]. Performing completely joint processing requires signaling overhead and payload data sharing among all coordinated RRHs, resulting in tremendous burden on fronthaul links [12]–[16]. In [15], the data-sharing strategy and compression strategy were studied regarding the energy efficiency of the C-RANs. In [16], joint design of fronthaul and radio access links for C-RANs was investigated. Note that a common assumption in aforementioned literature is that the coordinated RRHs do not have the ability to cache data files
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
