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This paper focuses on the spectrum sensing mechanisms, which could improve network throughput through the sensing strategy optimization and cooperative spectrum sensing methods. In order to guarantee an integrated and effective research, we take the whole channel scenarios into consideration, i.e., Single Secondary user with Single and Multiple Channels (SSSC and SSMC), Multiple Secondary users with Single and Multiple Channels (MSSC and MSMC). Moreover, according to the specific feature of each scenario, different sensing methods are adopted, i.e., optimal sensing period to maximize network throughput for SSSC, a novel sensing method to minimize searching time for SSMC, partial cooperative spectrum sensing mechanism for MSMC, and setting a spectrum pool in the fusion center to record the channel states for MSMC. Simulation results demonstrate that our methods can improve spectrum efficiency, network throughput and channel utilization, especially when the spectrum is utilized inadequately. [ABSTRACT FROM AUTHOR]

Highlights: [•] Our work has considered the QoS factors and constructed a reward function to model the QoS properties. [•] Our work has considered MT’s velocity, network access cost and switching cost for vertical handoff decision. [•] We have applied G1 and entropy methods to calculate the weight of each QoS factor in the reward function. [•] By taking the MT’s velocity into consideration, our work can avoid unnecessary handoffs. [ABSTRACT FROM AUTHOR]

Abstract: Physical-layer network coding (PNC) is a promising approach for wireless networks: it allows nodes to transmit simultaneously and encode packets by superposing signals at the physical layer, which can improve throughput. Because of the difficulty in scheduling simultaneous transmissions, we propose an opportunistic scheduling algorithm in the media access control (MAC) layer and analyze the achievable throughput of the Denoise-and-Forward (DF) PNC scheme for both symmetric and asymmetric channel statuses, where random errors may occur for both BPSK and QPSK modulation techniques. Simulation results show that our algorithm cannot only improve throughput but can also adapt to varying channel conditions. It is further revealed that for the same throughput, our algorithm is more power-efficient with an asymmetric channel status than with a symmetric channel status. [Copyright &y& Elsevier]

Abstract: Wireless mesh network (WMN) is a promising solution for last mile broadband internet access. Mesh nodes or mesh routers are connected via wireless links to form a multi-hop backbone infrastructure and improving throughput is the primary goal. While previous works mainly focused on either link level protocol design or complex mathematical model, in this paper, we investigate the performance gains from jointly optimizing scheduling and routing in a multi-radio, multi-channel and multi-hop wireless mesh network. Then, two optimization objectives are addressed by considering wireless media contention and spatial multiplexing. The first objective is to maximize throughput by exploiting spatial reuse while the second one is to ensure fairness among different links. We design a cross-layer algorithm by considering both MAC layer and network layer. Simulation results show that our joint optimization algorithm can significantly increase throughput as well as fairness. [Copyright &y& Elsevier]

Highlights: [•] We consider a multi-hop network situation instead of traditional two-hop topologies in OFDMA network. [•] We adopt Tabu searching algorithm to reduce the possibility of choosing low-quality subcarriers. [•] Our methods can combine the link groups with subcarrier groups in a global optimization method. [•] Our proposed algorithms can not only increase resource utilization but also realize dynamic selection of each link. [ABSTRACT FROM AUTHOR]

Abstract With the increasing conflict between population growth and limited environmental resources, building intelligent and efficient data transmission networks is crucial to cleaner production in smart and sustainable cities. More and more people are eager to exchange all kinds of information in urban life through an efficient network. Therefore, designing a smart data distribution and transmission mechanism can not only improve people's quality of life but also pave the way for reducing environmental pollution. Optical networks have been widely used in the core network due to high-capacity characteristics. However, in inter-data-center (Inter-DC) optical networks, the coexisted heterogeneous optical devices and multi-granularity network resources bring new challenges to network management and traffic scheduling. Recently, software-defined network (SDN) and network function virtualization (NFV) have been introduced to enable the unified control for improving network agility and automation. Thus for software-defined multi-granularity Inter-DC optical networks, we propose a list of online service provisioning strategies. Moreover, in terms of the network controller, the novel routing applications are also developed by extended OpenFlow protocol. Finally, we experimentally demonstrate the overall feasibility of proposed solutions in a semi-practical platform. Numerical simulations conducted to quantitatively evaluate the algorithm efficiency also verify the superiorities of improving spectrum efficiency and reducing service blocking probability. [ABSTRACT FROM AUTHOR]

In Intensity-Modulation Direct-Detection (IM/DD) Orthogonal Frequency Division Multiplexing Passive Optical Networks (OFDM-PONs), aside from Subcarrier-to-Subcarrier Intermixing Interferences (SSII) induced by square-law detection, the same laser frequency for data sending from Optical Network Units (ONUs) results in ONU-to-ONU Beating Interferences (OOBI) at the receiver. To mitigate those interferences, we design a Low-Density Parity Check (LDPC)-coded and spectrum-efficient upstream transmission system. A theoretical channel model is also derived, in order to analyze the detrimental factors influencing system performances. Simulation results demonstrate that the receiver sensitivity is improved 3.4 dB and 2.5 dB under QPSK and 8QAM, respectively, after 100 km Standard Single-Mode Fiber (SSMF) transmission. Furthermore, the spectrum efficiency can be improved by about 50%. [ABSTRACT FROM AUTHOR]