Performance Analysis of Several Functional Splits in C-RAN

Abstract

International audienceCentralized/Cloud Radio Access Network (C-RAN) is a promising future mobile network architecture, which can potentially increase the capacity of mobile network meanwhile reducing operators' cost. In standard C-RAN, frequency shifting is made in Remote Radio Heads (RRHs), which are close to the antennas. Signal processing and upper layers are made in Baseband Unit (BBU) pool for multiple base stations. However, this results in high burden on the optical transport network between RRHs and BBU pool. This paper investigates new functional split architectures between RRH and BBU, to reduce the transmission throughput between RRHs and BBUs. Two new architectures are proposed and modeled for the uplink. We propose to move part of physical layer functions of the BBU to the RRH. For the proposed architectures, the transmission rate between RRHs and BBUs depends on the mobile network load, while that of current architecture is constant. Simulation results illustrate that 30 to 40 percent bandwidth can be saved when all the radio channel capacity is used, and up to 70 percent bandwidth when half of the radio channel capacity is used

A Survey of the Functional Splits Proposed for 5G Mobile Crosshaul Networks

“…[62] investigates the fronthaul behavior using a game based model and shows how this leads to higher efficiency in different deployment scenarios. Simulations in [55], [73] confirms how large amount of bandwidth can be saved when moving to other functional splits than option 8. Simulations in [63] uses a fronthaul frame aggregation strategy to improve the packet transmission efficiency, while keeping the average fronthaul queueing delay and jitter constant, when multiplexing fronthaul and backhaul traffic.…”

“…This split has been known for several years and the literature in this area is very comprehensive. Therefore, several directions within using this split is investigated focusing on the CPRI transport interface: both the traditional CPRI transport, the option of transporting CPRI over the Ethernet network and the option of compressing [4], [5], [12], [19], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46], [47], [48], [49], [50], [51], [52] Simulations: [53], [54], [55], [56], [57], [58], [59], [60], [61], [62], [63], [64] Practical experiments: [65], [66],…”

Towards the deployment of a fully centralized Cloud-RAN architecture

“…The transmission rate is constant since CPRI is a serial Constant Bit Rate (CBR) interface. It is then independent of the mobile network load [7]. The data throughput depends on the cell configuration and can be obtained as…”

“…Research studies are focusing on bandwidth compression techniques and packetisation of CPRI data via Ethernet [10]. Others solutions propose different functional split architectures in order to reduce the required bandwidth [11], [7]. For example, when including the demapping process in the RRH, it is possible to adapt the bandwidth as a function of the traffic load in the cell, then the required front-haul capacity is directly given by the fraction of utilized radio resources [11].…”

Tradeoff Caching Strategy of the Outage Probability and Fronthaul Usage in a Cloud-RAN

“…If the files requested by mobile users are cached in the access points of the RAN, the files will be transmitted directly from the RAN's cache without being fetched from the core network, which can significantly reduce the fronthaul/backhaul traffic and meanwhile shorten the access latency of the files, thus improve users' quality of experience (QoE). In Cloud-RAN, thanks to the ongoing evolution of fronthaul technology and function splitting between the BBU and RRHs [16], [21], there comes possibility to realize content caching in RRHs, which allows users fetching required content files directly from RRHs and thus can further reduce fronthaul traffic.…”