Final Report Summary - SMART-FIWI-HETNETS (Advanced Coordination Paradigms for FiWi Enhanced HetNets and Smart Grid Applications) Converged fiber-wireless (FiWi) access networks, also referred to as hybrid optical-wireless access networks (HOWANs) and wireless-optical broadband access networks (WOBANs), aim at combining the reliability, robustness, and high capacity of optical fiber networks with the flexibility, ubiquity, and cost savings of wireless networks.In “Smart-FiWi-HetNets”, new possibilities and novel ways of unifying low-cost Ethernet based capacity-centric FiWi access networks and coverage-centric HetNets by capitalizing on high-capacity low-latency fiber backhaul infrastructures and WiFi offloading of mobile data traffic have been explored and investigated. We have also examined the benefits of enhancing the resultant FiWi-HetNets with both fiber optic and wireless sensors to enable M2M communications, paying particular attention to their interdisciplinary deployment in the area of emerging smart grid applications. The proposed research activities have targeted the aforementioned trends and tackle the identified open layer-2 and layer-3 research challenges, as described in technically greater detail in the following two sections.The main objectives of the projects were:(i) the design of high-capacity low-latency NG-PON based mobile backhaul infrastructures with inter-ONU communications and multi-failure recovery capabilities.(ii) the investigation of advanced traffic steering and real-time self-healing techniques for FiWi enhanced HetNets with WiFi offloading capability.(iii) the development of energy- and traffic-aware contention resolution and coordination techniques for event-driven M2M communications in FiWi-HetNet based smart grid communications infrastructures. The following results wereachieved:1. A backhaul-aware user association algorithm for FiWi-LTE HetNets and investigated its performance. The performance limiting factors of current state-of-the-art fiber backhaul infrastructures without any inter-ONU communications capabilities were highlighted and a variety of countermeasures were described. In order to mitigate the vulnerability of NG-PON based backhaul infrastructures against fiber cuts, we proposed to utilize fiber interconnection links and fiber protection rings for closely located ONUs as well as single- and multi-hop wireless protection links between neighbouring ONUs. Taking the condition of the backhaul in terms of delay and reliability into account, we presented our distributed BA-LB algorithm for user association in FiWi-LTE HetNets. The proposed algorithm was analyzed and evaluated numerically by comparing its performance with BU-BL, BU-MS, and BA-MS alternative user association schemes in terms average delay, blocking probability, average achievable throughput, and service interruption percentage. The obtained results show that our proposed algorithm outperforms BU-LB and BU-MS in terms of delay and service interruption percentage, while its average achievable throughput performance is comparable to that of BU-LB. Furthermore, our findings show that the blocking probability of BA-LB is higher than that of BU-LB and BU-MS and lower than that of BA-MS.2. We evaluated the FiWi connectivity, delay, maximum aggregate throughput, and offloading efficiency performance of FiWi enhanced LTE-A HetNets, including the beneficial impact of various localized fiber-lean backhaul redundancy and wireless protection techniques, by means of probabilistic analysis and verifying simulations. In our performance evaluation, we paid close attention to fiber backhaul reliability issues and WiFi offloading limitations due to WiFi mesh node failures as well as temporal and spatial WiFi coverage constraints. The obtained results show that the presented interconnection fiber, protection ring, and wireless protection techniques are instrumental in providing fixed wired and mobile users with highly fault-tolerant FiWi connectivity. Our results also provide insights into finding the optimal WiFi offloading ratio for different WiFi availability scenarios and traffic patterns. The localized fiber-lean backhaul redundancy and wireless protection schemes help increase the temporal FiWi connectivity probability of mobile users and thereby improve the offloading efficiency for both delayed and on-the-spot offloading significantly.3. We proposed a novel game theory based power control algorithm in order to reduce the effect of interference in D2D multicast, taking multiple WiFi Direct groups and network assistance into account. We investigated a regret matching algorithm with perfect information and a modified regret matching algorithm, which does not consider other D2D transmitters’ information. Both algorithms are able to let D2D multicast converge towards the set of correlated equilibrium. The correlated equilibrium implies that each D2D transmitter optimally responds to the multicast environment and to the actions of other D2D transmitters. Our obtained results show that the proposed algorithms help GOs improve their data rate as well as significantly reduce their multicast delay compared to the benchmark approach with fixed power. We noticed that the modified regret based algorithm achieves almost the same performance as the perfect regret matching approach with much less overhead.
