The future mobile networks have to be flexible and dynamic to address the exponentially increasing demand with the scarce available radio resources. Hence, 5G systems are going to be virtualised and implemented over cloud data-centres. While elastic computation resource management is a well-studied concept in IT domain, it is a relatively new topic in Telco-cloud environment. Studying the computational complexity of mobile networks is the first step toward enabling elastic and efficient computational resource management in telco environment. This paper presents a brief overview of the latency requirements of Radio Access Networks (RANs) and virtualisation techniques in addition to experimental results for a full virtual physical layer in a container-based virtual environment. The novelty of this paper is presenting a complexity study of virtual RAN through experimental results, in addition to presenting a model for estimating the processing time of each functional block. The measured processing times show that the computational complexity of PHY layer increases as the Modulation and Coding Scheme (MCS) index increases. The processes in uplink such as decoding take almost twice the time comparing to the related functions in the downlink. The proposed model for computational complexity is the missing link for joint radio resource and computational resource management. Using the presented complexity model, one can estimate the computational requirement for provisioning a virtual RAN as well as designing the elastic computational resource management.

Vertical markets and industries are addressing a large diversity of heterogeneous services, use cases, and applications in 5G. It is currently common understanding that for networks to be able able to satisfy those needs, a flexible, adaptable, and programmable architecture based on network slicing is required. Moreover, a softwarization and cloudification of the communications networks is already happening, where network functions (NFs) are transformed from monolithic pieces of equipment to programs running over a shared pool of computational and communication resources. However, this novel architecture paradigm requires new solutions to exploit its inherent flexibility. In this paper, we introduce the concept of resource elasticity as a key means to make an efficient use of the computational resources in 5G systems. Besides establishing a definition as well as a set of requirements and key performance indicators (KPIs), we propose mechanisms for the exploitation of elasticity in three different dimensions, namely computational elasticity in the design and scaling of NFs, orchestration-driven elasticity by flexible placement of NFs, and slice-aware elasticity via cross-slice resource provisioning mechanisms. Finally, we provide a succinct analysis of the architectural components that need to be enhanced to incorporate elasticity principles.