# C-RAN Traffic Aggregation on Latency-Controlled Ethernet Links
## 2 Related Works  
Any transport network has among its main targets to serve different kinds of applications while being able to handle Quality of Service (QoS) requirements. These aspects are widely investigated  
Figure 1: Converged fronthaul/backhaul scenario. in literature to design networks with enhanced flexibility and scalability, which have turned out recently to be the key enablers for cost-efficient 5G deployments [8; 9]. The C-RAN concept jointly takes advantage of NFV/SDN [10] and different splitting options for 5G network design optimization [11]. As a consequence, the traffic on transport network links can have different QoS requirements, it being related to different sections of splitting [12]. Ethernet based networks play an important role in a wide variety of fields. For example, industrial communications are one of the technologies which benefit a lot from the Ethernet concept. As explained in detail in [13], the core of such systems is essential, being reliable for the exchange of information. The latest trend in technologies which influences industrial technologies is IoT (Internet of Things), which from the communication point of view relies largely on Internet-based communications. Since the real-time capabilities are one of the major characteristics of such systems, the IEEE TSN (Time Sensitive Networking) working group currently aims at improving the real-time capabilities of the standard of Ethernet. They are mainly targeting issues like reducing latency, independence from physical transmission rates, fault tolerance without additional hardware and support for higher security and safety. From another point of view [14], IoT can transform Electric Power and Energy Systems (EPESs) by providing a solution in order to meet the growing demands of access to affordable, clean and sustainable energy. The adaptation of IoT in EPES is also favored by the significant reduction of costs associated with sensors, bandwidth processing, and memory storage. Realizing the full potential of IoT is critical to enhancing the flexibility, asset management, operations and reliability of intelligent electric power networks. To ensure continued growth of IoT for EPESs, it is essential to develop viable solutions to handle its growing complexity. The work referenced in [15] is focused on the evaluation of the best configuration for C-RAN in terms of cost of network resources such as wavelength. The authors present an implementable solution that can be useful in 5G studies. They specifically introduce an analytical model which proves that using multiple rings can eventually be more cost-effective in comparison with a single ring in terms of wavelengths. This is due to the fact that, although a single ring can provide the lowest cost solution because of high statistical multiplexing, it also needs a switching apparatus with a high number of ports. They proposed a transport solution for the fronthaul segment based on optical technology that allows for dynamic bandwidth allocation needed to carry Ethernet and CPRI flows with the consequent saving of bandwidth. They successfully show the 90% savings on wavelengths. Ethernet interfaces are of increasing interest to implement packet-based multiplexing of FH and BH traffic for the wide adoption of this standard in transport networks [16]. Ethernet as a packet based technology suffers from statistical multiplexing delay, which is typically not bounded and variable. This is a key issue to be solved to design integrated interfaces for different levels of service [17]. The packet-based integrated hybrid optical network with ultra-low Packet Delay Variation (PDV) services and statistically multiplexed traffic was firstly proposed in [7]. A hybrid packet/circuit node was defined in order to add the ability to the network to manage priority and non-priority traffic. As introduced in the paper, the traffic in the network can be divided into two categories. The traffic with fixed delay and zero packet loss will be routed through the optical network.