A Stochastic Geometry Approach To Wireless Networks Security

With the fast development of mobile network and wireless communications technologies, security is always a critical concern in the process of network evolution due to the broadcast nature of wireless networks. The physical layer security, based on the Shannon information theory, is regarded to provide "absolute security" without relying on decoding complexity. Thus, it will be an effective method to ensure information security in the future wireless networks. The physical security has become an important research hotspot in the field of wireless communications. One of challenges is the secrecy performance analysis for the random network, where the location and channel information of nodes are hard to be obtained exactly Based on the stochastic geometry, we model the secrecy performance for the typical scenario of random networks, and propose the methods to improve the secrecy performance. In the process of in-depth analysis and research, the main contributions for the dissertation are summarized as follows:(1) The dissertation studies the secure connectivity in single-cell and single-antenna random wireless network, where the BS, legitimate users and eavesdroppers are equipped with one antenna. The legitimate nodes and eavesdroppers are modeled as independent Poisson processes. A method is proposed to obtain the closed-form expressions for secrecy outage probability at the l closest legitimate user for non-colluding eavesdropper in Rayleigh fading channel. For colluding eavesdropper’s scenario, the closed-form expressions for secrecy outage probability at the ith closest legitimate user in Nakagami-m fading channel are derived. In addition, cooperation between legitimate users is proposed to be robust to eavesdropping. Compared with non-cooperation, the secrecy outage probability can de reduced 33%.(2) The dissertation considers the problem of secure connectivity in MIMO random wireless network, where the BS, legitimate users and eavesdroppers are equipped with multiple antennas. The enhancement for secrecy performance by exploiting the transmit-receiver diversity (TRD) technology is investigated. The closed-form expressions for the upper bound of secrecy connection probability are derived for the non-colluding and colluding eavesdropper’s scenarios. Compared with MISO system, less legitimate nodes are needed for reaching the same secrecy outage probability.(3) The dissertation investigates the problem of secure connectivity in random relay wireless networks. The decode-and-forward (DF) and randomize-and-forward (RF) two relay protocols are considered. A new metric is defined to obtain the exact closed-form expressions for the secrecy outage probability for the best relay selection and random relay selection. Simulation results show that the secrecy outage probability can be reduced quickly with the increase of relay node density for the best relay selection, while for random relay selection the secrecy outage probability tends to a constant.(4) For the secrecy performance analysis in the multi-cell wireless networks, based on random martrix theory and RCI precoding, the screcy sum-fate is obtained by exploiting interference coordination technology. The simulation results show that the bigger positive secrecy rate can be achieved with BSs interference coordination. For multi-cell wireless networks, the paper proposes a new interference model from the user-dominant perspective. In contract with the exiting interference model, it is assumed that desired BSs and interferers belong to the same PPP, and eavesdroppers are distributed according to another independent PPP. Based on the model, the average secrecy transmission capacity is derived in simply analytical forms with interference coordination. Compared to non-cooperation case, the average secrecy transmission capacity can be improved by 20% by exploiting inter-cell interference cancelling (ICIC) technology.In summation, the dissertation introduces the physical layer security into different typical wireless networks (single cell, single antenna network, MIMO network, relay wireless network, and multi-cell network). Based on secrecy rate and secrecy outage probability, the paper analyzes the secrecy performance improvement by exploiting TRD, relay selection diversity, interference coordination technologies. The above results can provide theoretical guidance for supporting the effective integrating between physical physical layer security and the future wireless network.