Interference management for Small Cell (SC) networks has drawn great attention from both academia and industry due to its importance in Long-Term Evolution (LTE) and emerging 5G networks. Although various approaches have been proposed in the literature, many of them face practical limitations such as showing gains only in specific scenarios, relying on ideal fronthaul, or becoming computationally intractable as the network size increases. In this paper, a novel framework is proposed for interference management in centralized SC networks by jointly utilizing graph theory and optimization theory. It extends the classic center-edge frequency reuse schemes into a more fine-grained scale, thus capturing the complex interference relationships in SC networks. The cell-level resource partition can be semi-statically updated according to the traffic dynamics while existing Medium Access Control (MAC) schedulers can be used for subframe-level resource allocation, not requiring fiber fronthaul. LTE system-level simulation results show that the proposed scheme can significantly improve both cell edge and mean user throughput with practical complexity.

In this paper we present an analytical framework that aims to improve the energy efficiency of traffic offloading via Wireless Local Area Networks, taking into account the energy consumption for both data transmission and network discovery operations. More specifically, the network scanning period is optimized in order to minimize the energy consumption in a vehicular scenario where a user moves along a road covered by a long range cellular network and a number of randomly deployed Wireless Local Area Networks. The performance of the system that performs periodic network scanning with the optimal period is compared against a sub-optimal system that does not take into consideration the user and network context information when determining the network scanning period. According to performance evaluation results, the use of the optimal network scanning period achieves significant improvement in terms of energy consumption and network detection delay.

In cognitive radio networks, the arrival of Primary Users (PUs) may force Secondary Users (SUs) to terminate their ongoing sessions or degrade their Quality of Service (QoS) level. Given the time-varying spectrum availability, an immediate challenge arising is to support the QoS of SUs under spectrum mobility. In this paper, we propose an optimal decision-making framework for joint admission control, eviction control and bandwidth adaptation in cognitive radio networks. The problem is formulated as a Semi-Markov Decision Process (SMDP) and the optimal decision for each system state is derived to maximize the long-term network revenue as a function of the spectrum utilization, the SU blocking probability and the bandwidth adaptation cost under the SU dropping probability constraint. It is shown that the derived optimal strategy outperforms the threshold-based channel reservation schemes with/without bandwidth adaptation. And among the schemes with bandwidth adaptation, more performance improvement can be achieved by the proposed one when the bandwidth adaptation cost is taken into account.

Cognitive Radio (CR) has been recognized as a promising solution to solve the current spectrum inefficiency problem. We consider a CR Base Station (CR-BS) has multiple spectrum bands over a wide frequency range and uses channel-dependent data rates to communicate with the Secondary Users (SUs). To maximize the spectrum utilization while supporting the Quality of Service (QoS) of the SUs, various decisions needs to be made during the operational period of the CR system taking into account not only the behavior of Primary Users (PUs) and SUs but also the current utilization of each spectrum band. In this paper, we propose an optimal policy for joint spectrum resource management in multi-band CR networks, which consists of admission control, spectrum band selection, spectrum handover and eviction control. The problem is formulated as a Semi-Markov Decision Process (SMDP) and the optimal decision for each system state is derived to reduce the SU blocking probability while keeping the SU dropping probability upper-bounded. Performance evaluation shows that the proposed policy outperforms other three policies in terms of both the SU blocking probability and the SU dropping probability.

Network virtualization has been recognized as a promising solution to enable the rapid deployment of customized services by building multiple Virtual Networks (VNs) on a shared substrate network. Whereas various VN embedding schemes have been proposed to allocate the substrate resources to each VN requests, little work has been done to provide backup mechanisms in case of substrate network failures. In a virtualized infrastructure, a single substrate failure will affect all the VNs sharing that resource. Provisioning a dedicated backup network for each VN is not efficient in terms of substrate resource utilization. In this paper, we investigate the problem of shared backup network provision for VN embedding and propose two schemes: shared on-demand and shared pre-allocation backup schemes. Simulation experiments show that both proposed schemes make better utilization of substrate resources than the dedicated backup scheme without sharing, while each of them has its own advantages.

Exploiting path diversity to enhance communication reliability is a key desired property in Internet. While the existing routing architecture is reluctant to adopt changes, overlay routing has been proposed to circumvent the constraints of native routing by employing intermediary relays. However, the selfish inter-domain relay placement may violate local routing policies at intermediary relays and thus affect their economic costs and performances. With the recent advance of the concept of network virtualization, it is envisioned that virtual networks should be provisioned in cooperation with infrastructure providers in a holistic view without compromising their profits. In this paper, the problem of policy-aware virtual relay placement is first studied to investigate the feasibility of provisioning policy-compliant multipath routing via virtual relays for inter-domain communication reliability. By evaluation on a real domain-level Internet topology, it is demonstrated that policy-compliant virtual relaying can achieve a similar protection gain against single link failures compared to its selfish counterpart. It is also shown that the presented heuristic placement strategies perform well to approach the optimal solution.