Yonghong Kuo

Energy efficient relay selection and power allocation for cooperative cognitive radio networks

Owing to environmental, financial and quality of service (QoS) considerations, energy efficient wireless communications have been paid increasing attention under the background of limited energy resource. This study considers a spectrum sharing cognitive radio network, where the primary system leases its radio spectrum to the secondary system for a fraction of time in exchange for secondary users served as relays to assist the transmission of the primary traffic. Based on the cooperative spectrum leasing protocol, the authors formulate a joint optimisation of relay selection and power allocation under QoS requirements to improve energy efficiency (EE). By employing a greedy spectrum sharing (GSS) algorithm, the optimal relay selection, power and sharing time allocation are readily obtained. Monte–Carlo simulations are performed to demonstrate that significant EE improvement is achieved by the proposed GSS algorithm, and that the network performance is enhanced.

Outage Performance of DF-Based Cooperative Multicast in Spectrum-Sharing Cognitive Relay Networks

This letter investigates the outage performance of decode-and-forward-based cooperative multicast (CM) in spectrum-sharing cognitive relay networks (CRNs). Considering a CRN coexisted with multiple primary users, a closed-form expression for the exact outage probability of CM is derived over independently and non-identically distributed Rayleigh fading channels. The asymptotic analysis is also presented to reveal that the diversity gain of CM in CRNs is determined by the number of relays, and the spectrum-sharing scenario only has impact on coding gain. Simulation results corroborate our theoretical analysis.

Improving physical-layer security in untrusted relay networks: cooperative jamming and power allocation

The inherent broadcast characteristics of wireless medium make wireless data transmission difficult to be shielded from unintended recipients. As such, secure communication over wireless channels becomes a critical issue in the design of wireless networks. In this study, the authors study cooperative jamming and power optimisation in untrusted relay networks to improve physical layer security. By exploiting the direct link, a source-based jamming (SBJ) scheme is proposed to hinder the untrusted relay from intercepting the confidential message. Considering the total power budget, a power allocation strategy is also proposed to optimally determine the power of source and untrusted relay as well as the power of information and jamming signals. Furthermore, to evaluate the secrecy performance of the proposed SBJ scheme with the power allocation strategy, tight lower bound of ergodic secrecy capacity and asymptotic secrecy outage probability are derived in closed form. Simulation verifies the advantages of the proposed SBJ scheme and the power allocation strategy.

Differential successive relaying scheme for fast and reliable data delivery in vehicular ad hoc networks

The high-speed mobility of modern transportation worsens the situation of unstable direct links and imprecise channel estimation, which poses challenges on fast and reliable data delivery in vehicular ad hoc networks (VANETs). The goal of the proposed scheme is to provide high-speed full-duplex relaying connectivity for unstable direct links, and reliable information detection without precise channel state information (CSI) in VANETs. In the proposed scheme, full-duplex relaying connectivity is provided by differential successive relays (DSRs) at roadside or inside other vehicles. To improve robustness of DSR without specific CSI, efficient blind interference cancellation is presented to mitigate inter-relay interference. Meanwhile, reliable information detection without precise CSI is enabled by superposition coding with differential modulation. Furthermore, the advantages, applications of DSR and complexities for real-world implementation are discussed, and the decision rule, bit error probability and ergodic capacity are theoretically obtained. Numerical results verify significant improvements in the performance of the proposed scheme when compared with conventional schemes with half-duplex relays and frequent channel estimation in VANETs.

Recommender system for mobile users: Enjoy internet of things socially with wireless device-to-device physical links

As predicted, trillions of devices and billions of services will be integrated into Internet of Things (IoT), where most value added applications rely on wireless physical links. In this paper, we develop a recommender system to overcome the challenges of large-scale mobile IoT. The proposed recommender system socially matches wireless devices to communicate and share their contents based on similarities, distance, velocity, wireless channel quality and remaining energy. The physical layer connections are realized by device-to-device spectrum sharing techniques, and we accordingly designed a cooperative multicast service case to make full use of the wireless broadcasting nature. A “green communication” orientated algorithm is proposed to allocate power resources, adaptively adjust data rate and recommend partners as mobile relays. Simulation results show that the proposed system can efficiently utilize the wireless resource of mobile IoT and appropriately recommend partners to assist more users into IoT services.

Three‐path successive relaying protocol with blind inter‐relay interference cancellation and cooperative non‐coherent detection

Successive relaying has recently emerged as a spectral-efficient technique for cooperative wireless communications. However, in scenarios with uncertain accuracy of instantaneous channel state information (CSI), the scope of conventional two-path successive relaying protocol shrinks. This is due to the challenges of cancelling inter-relay interference (IRI) and detecting signals efficiently without specific CSI. The two challenges motivate us to propose a novel double listening 3-path successive relaying (DL3PSR) protocol to mitigate the successive relayings dependence on accurate instantaneous CSI. We overcome the first challenge by proposing a blind IRI cancellation technique, and its effectiveness is proven. After blind IRI cancellation, the challenge of efficient signal detection is overcome by robust cooperative non-coherent detection, which consists of exclusive OR (XOR) demodulation and joint decoding. Based on constellation mapping, XOR demodulation is designed to demodulate M-ary phase-shift keying symbols without instantaneous CSI. Moreover, joint forward and backward decoding strategy is proposed to improve the robustness of data detection by retrieving two independent versions of the original data. Furthermore, the detection threshold, bit error probability, and achievable rate of DL3PSR are theoretically obtained. Simulations verify that in scenarios without full knowledge of CSI, DL3PSR protocol outperforms conventional two-path successive relaying in bit error performance and that the rate of DL3PSR is close to that of the full-duplex relaying. Copyright

Energy-efficiency resource allocation for cognitive heterogeneous networks with imperfect channel state information

In this study, the authors focus on the downlink resource allocation to optimise energy-efficiency (EE) of orthogonal frequency division multiplexing-based cognitive heterogeneous network (HetNet), where network service providers operate multi-radio access technologies. A more practical case is considered, in which imperfect channel state information (CSI) is available for wireless channels between secondary base stations and secondary users (SUs), primary users (PUs). Since imperfect CSI may result in outage in secondary networks and make collision occur in primary networks, a joint subcarrier and power allocation scheme for the cognitive HetNet is proposed to guarantee quality of service requirements for both SUs and PUs in probabilistic manners. Then the probabilistic EE optimisation scheme is approximated into a deterministic convex form, and the optimal solutions for the scheme are derived by double-loop iteration method. Afterwards, the authors develop a low-complexity algorithm in the presence of imperfect CSI with a small reduction of system performance. Simulation results are provided to show the impact of channel estimation error on the EE optimisation problem and to highlight the performance improvement from considering channel estimation error in the joint subcarrier and power allocation scheme for the cognitive HetNet system.

An improved distributed compressed video sensing scheme in reconstruction algorithm

Under the new video application scene of resource-constrained coding side such as wireless sensor networks, compressed sensing technique provides the possibility to solve the high-complexity problem of encoder because of its highly efficient compression encoding performance. Distributed compressed video sensing system provides a solution to satisfy the requirements of low encoder complexity and high coding efficiency in the new scene. This paper proposes a new distributed compressed video sensing scheme, which effectively improves the reconstruction quality of non-key frames. An auxiliary iterative termination decision algorithm is proposed to improve the performance of key frames initial reconstruction. An adaptive weights prediction algorithm is put forward to reduce the overall complexity. Besides, this paper proposes a position-based cross reconstruction algorithm to improve the decoded quality of the middle non-key frames in the group of pictures. The simulation results show that the proposed scheme effectively improves the overall performance of the distributed compressed video sensing system especially for high motion sequences.

Resource Allocation for Information-Centric Virtualized Heterogeneous Networks With In-Network Caching and Mobile Edge Computing

In order to better accommodate the dramatically increasing demand for data caching and computing services, storage and computation capabilities should be endowed to some of the intermediate nodes within the network, therefore increasing the data throughput and reducing the network operation cost. In this paper, we design a novel information-centric heterogeneous networks framework aiming at enabling content caching and computing. Furthermore, due to the virtualization of the whole system, communication, computing, and caching resources can be shared among all users associated with different virtual service providers. We formulate the virtual resource allocation strategy as a joint optimization problem, where the gains of not only virtualization but also caching and computing are taken into consideration in the proposed information-centric heterogeneous networks virtualization architecture. In addition, a distributed algorithm based on alternating direction method of multipliers is adopted in order to solve the formulated problem. Since each base station only needs to solve its own problem without exchange of channel state information by using the distributed algorithm, the computational complexity and signaling overhead can be greatly reduced. Finally, extensive simulations are presented to show the effectiveness of the proposed scheme under different system parameters.

Cooperative Cross-Layer Resource Allocation for Self-Healing in Interworking of WLAN and Femtocell Systems

We investigate resource allocation for self-healing in wireless local area network (WLAN) and femtocell interworking system to compensate abrupt network failure. To enable self-healing for the interworking system, we propose a cooperative cross-layer resource allocation scheme based on multiple medium access control layer and physical layer techniques of the two networks. The simulation results demonstrate that the proposed scheme can ensure the fairness between the utilizations of the downlink and the uplink in the WLANs, and improves the system utility while compensating the network failure.