Huici Wu

Secrecy Outage Probability in Multi-RAT Heterogeneous Networks

Practical difficulty in examining all base stations (BSs) to choose the best one providing secure transmission in heterogeneous networks (HetNets), we impose a BS association constraint in this letter that the BSs providing an average received signal power at the legitimate user greater than a predetermined receiving threshold can be candidate serving BSs. With this constraint, we derive closed-form expressions for secrecy outage probability (SOP) of both homogeneous networks and K-tier HetNets based on stochastic geometry. Our analysis reveals that security performance can be improved by deploying more low-power BSs in high path-loss environments. Besides, the SOP stays unchanged when the receiving threshold is below a critical point and increases rapidly when exceeding that point. These results depict features of SOP with practical constraint, which could provide new insights into the physical layer security in HetNets.

Secure Transmission in MISOME Wiretap Channel With Multiple Assisting Jammers: Maximum Secrecy Rate and Optimal Power Allocation

This paper investigates the secrecy rate maximization problem for the multiple-input-single-output multiple-antenna-eavesdropper (MISOME) wiretap channel with multiple randomly located jammers. The multi-antenna base station (BS) transmits information signals along with artificial noise (AN) to disturb the eavesdropper. Moreover, the friendly jammers are properly selected to assist the legitimate link for better secure transmission with some payoffs. With this system model, we first formulate a Stackelberg game between the BS and the assisting jammers with full channel state information. Stackelberg equilibriums, including optimal fraction of transmit power for AN, optimal transmit power, and asking prices of assisting jammers, are first proved to exist and then analytically derived. A policy iterative algorithm is also proposed to obtain the optimal solutions. We then extend the Stackelberg game to the case of MISOME broadcast wiretap channel with channel distribution information of eavesdropper. Numerical results verify the accuracy of the derived results and the efficiency of the proposed algorithm. The results reveal that the proposed jammer-assisted secure transmission can greatly improve the secrecy performance and meanwhile save more energy for information signals, which is significant for future wireless communication.

Secrecy outage probability for the multiuser downlink with several curious users

This paper studies the physical layer security in a multi-user downlink, where a single user is selected for secret transmission during each time frame. Current works usually assume a worst case where all unselected users are curious and act as eavesdroppers, and conclude that no multiuser diversity is achievable for secrecy when the number of users is pretty large. However, the worst case may happen rarely in practice. A general scenario is that several (maybe all) of the unselected users act as eavesdroppers. In this case, selecting the user with the largest SNR (i.e., signal to noise ratio) does not necessarily achieve the maximum secrecy rate. For the general case, we derive the new closed-form expression of the secrecy outage probability, which increases with the number of curious users, and tends to converge in the high-SNR and large-user-number regime. When the number of curious users is supposed to be small, the secrecy outage probability could be any value smaller than one even in the large-user-number regime. These results provide additional insights into the system performance.

Information density–based energy-limited capacity of ad hoc networks

In this article, the inhomogeneous energy consumption is characterized by the concept of information density, which is defined as the number of bits per unit time passing through a specific region. With information density, it is possible to derive the energy consumption of each region and determine the energy configuration scheme to maximize the network lifetime. The information density of pure ad hoc network and hybrid ad hoc network is derived. It is discovered that the information density of pure ad hoc network is inhomogeneous and the information density of hybrid ad hoc network is homogeneous, except for the regions near the edge of the entire area. With information density, the energy-limited capacity of pure and hybrid ad hoc networks is derived. The information density introduced in this article provides more insights into the information transfer of ad hoc networks, which may be applied in the energy configuration of ad hoc networks.

Achievable Capacity Scaling Laws of Three-Dimensional Wireless Social Networks

With the development of aeronautical telecommunication and unmanned aerial vehicles (UAVs), wireless networks will be extended to three-dimensional (3-D) space. Besides, 3-D wireless networks have been widely deployed in battlefields, which consist of aircraft, UAVs, ground troops, and fleets. When nodes in these wireless networks form swarm and cooperate with each other, there will be social behavior among them and 3-D wireless social networks emerge. Although the study of wireless social networks has been initiated, the capacity of 3-D wireless social networks is unknown. In this paper, we derive the achievable capacity of 3-D wireless social networks. It shows that the capacity is a function of the pathloss exponent, the number of nodes, the social group concentration, the contact concentration, and the size of social group. When the social group concentration or the contact concentration exceeds a threshold, the wireless social network is scalable and the capacity of wireless social network is much larger than that of the wireless network without social behavior. Besides, we discover the existence of a singular point for social group concentration and contact concentration, where the network capacity skips to a larger value than the neighborhood. The results reveal the interplay between wireless communication and social connection in 3-D space, which brings an insight into the design of 3-D wireless networks.

Capacity- and Trust-Aware BS Cooperation in Nonuniform HetNets: Spectral Efficiency and Optimal BS Density

This paper studies base station (BS) cooperation in nonuniform heterogeneous networks. Considering the limited capacity at BS and existence of untrusted small cell BSs (SBSs) in practical scenarios, a novel capacity- and trust-aware BS cooperation strategy is proposed. The BS cooperation is performed in a user centric manner, based on the average received signal strength at users, the capacity of BSs, and the trustworthiness of SBSs. Furthermore, with the proposed BS cooperation, the statistics of aggregate information-signal strength and interference strength are theoretically analyzed, based on stochastic geometry. Then, expressions for spectral efficiency (SE) and area SE (ASE) are analytically derived. In addition, to study the impact of the SBS density on the SE and ASE, the optimal densities of normal SBSs to maximize the SE and ASE are proved to exist and obtained. Finally, simulations and numerical evaluations validate the theoretical analysis and reveal that with the awareness of BS capacity and trustworthiness, optimal cooperative thresholds achieving the maximum SE and ASE exist, which decrease with high path-loss exponent; and in high path-loss fading environment with high existence probability of untrusted SBSs, more normal SBSs are required to be deployed to achieve the maximum SE and ASE performance.