Zebing Feng

A survey of security issues in Cognitive Radio Networks

In the last decade, cognitive radio (CR) has emerged as a major next generation wireless networking technology, which is the most promising candidate solution to solve the spectrum scarcity and improve the spectrum utilization. However, there exist enormous challenges for the open and random access environment of CRNs, where the unlicensed secondary users (SUs) can use the channels that are not currently used by the licensed primary users (PUs) via spectrum-sensing technology. Because of this access method, some malicious users may access the cognitive network arbitrarily and launch some special attacks, such as primary user emulation attack, falsifying data or denial of service attack, which will cause serious damage to the cognitive radio network. In addition to the specific security threats of cognitive network, CRNs also face up to the conventional security threats, such as eavesdropping, tampering, imitation, forgery, and noncooperation etc‥ Hence, Cognitive radio networks have much more risks than traditional wireless networks with its special network model. In this paper, we considered the security threats from passive and active attacks. Firstly, the PHY layer security is presented in the view of passive attacks, and it is a compelling idea of using the physical properties of the radio channel to help provide secure wireless communications. Moreover, malicious user detection is introduced in the view of active attacks by means of the signal detection techniques to decrease the interference and the probabilities of false alarm and missed detection. Finally, we discuss the general countermeasures of security threats in three phases. In particular, we discuss the far reaching effect of defensive strategy against attacks in CRNs.

An effective approach to 5G: Wireless network virtualization

Nowadays, the explosively growing demands for mobile service bring both challenges and opportunities to wireless networks, giving birth to fifth generation (5G) mobile networks. The features and requirements of different services are diverse in 5G. The management and coordination among heterogeneous networks, applications, and user demands need the 5G network to be open and flexible to ensure that network resources are allocated with high efficiency. To fulfill these requirements, wireless network virtualization is used to integrate heterogeneous wireless networks and coordinate network resources. In this article we propose a model of wireless network virtualization consisting of three planes: the data plane, the cognitive plane, and the control plane. A novel control signaling scheme has also been designed to support the proposed model. From the implementation perspective of network virtualization, a hierarchical control scheme based on cell-clustering has been used with dynamically optimized efficiency of resource utilization. Two use cases have been analyzed to demonstrate how the schemes work under the proposed model to improve resource efficiency and the user experience.

Spectrum sensing in cognitive radios based on enhanced energy detector

Spectrum sensing is regarded as a key technology in cognitive radio (CR). Energy detector has been performed as an alternative spectrum sensing method because of its low computational complexity and not requiring a priori information of the primary signal. This study proposes an enhanced energy detector by making an arbitrary positive power operation of the received signal amplitude instead of the squaring operation in the traditional energy detector (TED). The detection probability of the proposed detector is theoretically derived under a constant false alarm probability in additive white Gaussian noise (AWGN) channels. Performance analysis and simulation results indicate that the enhanced energy detector with the optimum power operation outperforms the traditional energy detector, especially in low signal-to-noise ratio (SNR) regime.

Security management based on trust determination in cognitive radio networks

Security has played a major role in cognitive radio networks. Numerous researches have mainly focused on attacking detection based on source localization and detection probability. However, few of them took the penalty of attackers into consideration and neglected how to implement effective punitive measures against attackers. To address this issue, this article proposes a novel penalty mechanism based on cognitive trust value. The main feature of this mechanism has been realized by six functions: authentication, interactive, configuration, trust value collection, storage and update, and punishment. Data fusion center (FC) and cluster heads (CHs) have been put forward as a hierarchical architecture to manage trust value of cognitive users. Misbehaving users would be punished by FC by declining their trust value; thus, guaranteeing network security via distinguishing attack users is of great necessity. Simulation results verify the rationality and effectiveness of our proposed mechanism.

Downlink and uplink splitting user association in two-tier heterogeneous cellular networks

Traditional cellular network standards require users downlink(DL) and uplink(UL) associated to the same BS. However, due to the power gap between BSs and users and different transmission environment(e.g. the path gain) of DL and UL, a serving BS with the strongest downlink would yield to a non-serving BS in the uplink. In this paper we propose the DL/UL splitting user association framework under a two-tier heterogeneous network, in which femtocell base stations are randomly located over a macro base station in a specific area. Downlink and Uplink network ergodic throughput are analysed according to our DL/UL splitting association model. Simulation results show a great throughput promotion compared with the traditional DL/UL coupled association manner. We believe downlink and uplink splitting as a flexible connection mode between users and base stations would be an essential approach to realize the high capacity requirements, which is a evolution of the network connection art.

Effective Small Social Community Aware D2D Resource Allocation Underlaying Cellular Networks

Social-aware device-to-device (D2D) resource allocation utilizes social ties in human-formed social networks to allocate spectrum resources between D2D users and cellular users. In this letter, we consider the small size social communities formed by people with similar interests and exploit them to optimize the resource allocation of the communities. This results in an optimal graph matching problem among communities to solve the D2D resource allocation problem. Solutions are derived via bipartite graph matching and an effective small social community resource allocation algorithm corresponding to the cases of small and high D2D user loads.

An Optimal Service Strategy for Grouped Machine-Type Communications in Cellular Networks

Machine-type communication devices (MTCDs) served as groups are an efficient way to solve device management and resource allocation problems in cellular networks. We propose an MTCD group model based on the traffic of devices in the network. A group state transition matrix and revenue and constraint vectors are introduced and the optimal service solution is derived that the best service strategy is to serve devices in only two groups. Results can be used as a guide for cellular base stations to efficiently manage resources for MTCD applications.

Joint user association and resource partition for downlink-uplink decoupling inmulti-tierHetNets

Traditional cellular networks require the downlink (DL) and uplink (UL) of mobile users (MUs) to be associated with a single base station (BS). However, the power gap between BSs and MUs in different transmission environments results in the BS with the strongest downlink differing from the BS with the strongest uplink. In addition, the significant increase in the number of wireless machine type communication (MTC) devices accessing cellular networks has created a DL/UL traffic imbalance with higher traffic volume on the uplink. In this paper, a joint user association and resource partition framework for downlink-uplink decoupling (DUDe) is developed for a tiered heterogeneous cellular network (HCN). Different from the traditional association rules such as maximal received power and range extension, a coalition game based scheme is proposed for the optimal user association with DUDe. The stability and convergence of this scheme are proven and shown to converge to a Nash equilibrium at a geometric rate. Moreover, the DL and UL optimal bandwidth partition for BSs is derived based on user association considering fairness. Extensive simulation results demonstrate the effectiveness of the proposed scheme, which enhances the sum rate compared with other user association strategies.

Discrete location-aware power control for D2D underlaid cellular networks

Device-to-device (D2D) communication is a promising method to reduce power consumption and improve the throughput of cellular networks. However, densely deployed D2D pairs could result in severe interference to cellular users without proper power control. Therefore, the discrete location-aware power control (DLPC) scheme is proposed in uplink D2D underlaid cellular networks. The entire cell area is divided into several regions, and a total power budget for each region is conducted with weighted allocation, to meet the constraint on the outage probability of cellular user. Then DLPC scheme requires only the locations of active D2D pairs rather than channel information or massive calculations, which is of low complexity in implementation. Simulation indicates that DLPC can improve the outage probability of D2D pairs and the network throughput compared with the traditional greedy power control scheme.

Discrete location-aware resource allocation for underlay device-to-device communications in cellular networks

Device-to-device (D2D) communications underlaying a cellular network is an efficient way to enhance spectral efficiency via resource sharing between D2D and cellular users (CUs). In this study, a discrete location-aware (DLA) interference model for D2D users is presented to allocate cellular resources. The vicinity of a CU is discretised into multiple regions, and the number of active D2D users in each region is constrained to satisfy the CU QoS requirements. Considering the locations of D2D users affecting the interference to CUs and thus the achievable rate, the formulated non-linear 0–1 knapsack resource allocation (RA) problem is divided into two subproblems: (i) the optimal amount of shared resources between the two types of users; (ii) the optimum subset of D2D users which transmit. The conditions of D2D users spatial deployment and resources reuse portion to achieve the solutions of the two subproblems are theoretically derived and proven. Then a DLA-RA algorithm is proposed to solve the corresponding subproblems in both single CU and multiple CUs cases. Extensive simulations results are presented which verify the effectiveness of the proposed DLA interference model and the RA scheme.