In order to increase the capacity of next generation mobile networks, network densification is a key aspect to provide better coverage and increased data rates to end users. Network operators are thinking to deploy wireless backhaul solutions to cut down cabling costs for connecting the small cell nodes. Consequently, the next generation mobile network architecture may contain a massive amount of small cells that are connected through wireless backhaul links, forming mesh or tree structures towards the core network, under the umbrella coverage of eNodeB type macro cells. In this paper, we use a Software-Defined Networking (SDN) based architecture for the operation and management of such small cell backhaul networks. By extending OpenFlow, the SDN controller is able to reconfigure not only the routing, but also the wireless backhaul configuration, such as channel assignment to backhaul links. We demonstrate the effectiveness of our approach by using testbed measurements and show that, when using our SDN-based reconfiguration, the network downtime for existing traffic due to channel re-assignment is significantly reduced, when comparing to a distributed routing based approach. Moreover, by using SDN based fast-failover techniques, we can instantaneously redirect traffic to other neighbors when links fail or neighbors are powered down, without the need for controller interaction.

As a solution to cope with the increase of wireless network traffic for future 5G networks, the IEEE 802.11ad standard enables multi-gigabit connectivity within the 60 GHz spectrum. Since these networks typically have low range, a vast number of small cells is required to form a wireless backhaul that can be easily affected by temporary failures due to blockage/interference. Software-defined Networking (SDN) is a paradigm that allows the centralization of the control plane management, which can be applied to mmWave wireless backhaul networks. Using SDN enables the possibility of having resilience mechanisms in the network, such as Fast-Failover (FF) group tables in the OpenFlow (OF) protocol. In this paper, we analyse resilient forwarding configurations upon temporary link failures. We perform our evaluation on a 4 small cell testbed with multiple IEEE 802.11ad interfaces, showing how OF-based resiliency can be applied, through FF and the Bidirectional-Forwarding Detection (BFD) protocol. Our results show how BFD can be tuned to improve the link state monitoring, and how a local reactive failover mechanism can benefit ongoing traffic in small cell meshed backhaul networks.

Future 5G mobile networks will require increased backhaul (BH) capacity to connect a massive amount of high capacity small cells (SCs) to the network. Because having an optical connection to each SC might be infeasible, mmWave-based (e.g. 60 GHz) BH links are an interesting alternative due to their large available bandwidth. To cope with the increased path loss, mmWave links require directional antennas that should be able to direct their beams to different neighbors, to dynamically change the BH topology, in case new nodes are powered on/off or the traffic demand has changed. Such BH adaptation needs to be orchestrated to minimize the impact on existing traffic.This paper develops a Software-defined networking-based framework that guides the optimal reconfiguration of mesh BH networks composed by mmWave links, where antennas need to be mechanically aligned.By modelling the problem as a Mixed Integer Linear Program (MILP), its solution returns the optimal ordering of events necessary to transition between two BH network configurations. The model creates backup paths whenever it is possible, while minimizing the packet loss of ongoing flows. A numerical evaluation with different topologies and traffic demands shows that increasing the number of BH interfaces per SC from 2 to 4 can decrease the total loss by more than 50%. Moreover, when increasing the total reconfiguration time, additional backup paths can be created, consequently reducing the reconfiguration impact on existing traffic.