Ultra-low latency end-to-end communication with high reliability is one of the most important requirements in 5G networks to support latency-critical applications. A recent approach towards this target is to deploy edge computing nodes with networking capabilities, known as Multi-access edge computing (MEC), which can greatly reduce the service end-to-end latency. However, the use of MEC nodes poses radical changes to the access network architecture. This requires to move from the classical point-tomultipoint (or point-to-point) structure, used to deliver residential broadband and Cloud-RAN services, to a mesh architecture that can fully embed the MEC nodes with all other end points (i.e., mobile cells, fixed residential and businesses, etc.).
In this paper, we propose a novel PON based Mobile Fronthaul (MFH) transport architecture based on PON virtualisation, that allows EAST-WEST communication along with traditional NORTH-SOUTH communication.The architecture enables the endpoints of a PON tree, where usually ONUs are located, to also host MEC nodes by deploying an edge OLT capable of communicating directly with adjacent ONUs, by reflecting wavelength signals from the splitter nodes. We experimentally show that signal backscattering due to the reflection at the splitter does not affect the system performance. In addition, using protocol level simulations, we show how this architecture can maintain low-latency (≈ 100µs) in varying mobile traffic conditions by offloading ONUs (i.e., where remote units of Cloud-RAN cells are located) to other edge OLTs through dynamic formation of virtual PON (vPON) slices. Furthermore, our results show how an efficient migration strategy for ONUs can be chosen depending on the traffic load, different functional split configurations, and the PON capacity.
Cloud Radio Access Networks (C-RANs) are considered one of the most promising candidates for implementing 5G mobile communication systems. C-RAN enables centralisation of baseband processing, enabling advanced coordination between base stations, such as coordinated multi-point and inter-cell interference cancellation. In addition, it allows pooling of resources across several cells, providing statistical multiplexing gains of computing resources. However, the link between the remote radio unit and the baseband unit requires high transmission capacity, making the fronthaul link a potential bottleneck for future dense cell deployments. One of the current solutions to this issue is to compress the fronthaul transmission rate. A second under standardisation is to adopt a different functional split that can reduce the transmission capacity requirement. While this solution decreases the capacity requirements on the transport link, it decentralises some of the computational resources, requiring a more complex remote radio unit (e.g., compared with a CPRI type of solution), whose resources cannot be utilised by other cells when not in use. It is thus expected that in the future, multiple solutions (different functional splits and CPRI) will coexist.In this paper, we introduce the concept of Variable Rate Fronthaul (VRF) for C-RAN. This scheme operates on a CPRI type of interface (e.g., one that transmits I/Q data samples) with the novelty of dynamically changing the cell bandwidth, and consequently the fronthaul data rates, depending on the cell load, with the support of a Software Defined Network (SDN) controller. This allows for a more efficient transport of C-RAN cells' data over a shared backhaul. We first propose a mathematical analysis of the VRF performance using a queuing theory approach based on the Markov model. We then provide the results of our simulation framework both for validation and in support of the mathematical analysis. Our results show that the proposed VRF scheme provides significantly lower blocking probability over a shared backhaul than standard CPRI.
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