Cooperation-based Wireless Wiretap Channel Secure Communication And Power Allocation

Due to the broadcast nature of wireless media, all nodes in the coverage of transmitter can capture its signals, thus wireless transmission is sensitive to wiretap. In wire network, effective strategies to defend eavesdropping rely on different protocols and schemes above the physical layer, such as the encryption schemes and key agreements in the application layer. The precondition of applying these schemes is that the transmission in physical layer is free error. The critical that the encryption scheme can promise information transmission security is that, without sharing the knowledge of encryption/decryption keys, decryption by eavesdropper is computationally infeasible. With the progress of process ability of CPU, and the presence of quantum computer and encryption deciphering algorithms, using encryption scheme or key agreement to protect transmission security is no longer valid. Also, applying the key-based security scheme in wireless network faces the challenges of key-distribution and management. The increasing of wireless communication demands, and the growing wireless applications and people take more attentions on communication security and privacy make the wireless network transmission security is more important than ever before.Recently, information-theoretic security or physical layer security which as a new wireless network communication security idea has been proposed and widely studied. Contrast to cryptography-based encryption scheme, the basic idea of the information theoretic security is to use the inherent randomness of the wireless channel to obtain unconditional security. In other words, the information theoretic security has no additional assumptions on the computation ability of the eavesdropper and also no need share encryption keys between the legal transceiver.Although the broadcasting nature of wireless media makes it is sensitive to eavesdropping, it also provides us the opportunity of enhancing the communication security by using cooperation. The concept of cooperation comes from cooperative communication, in which some additional nodes are introduced in the network. Based on the adopted protocols, cooperation can provide additional diversity branch from source node to destination, and which then can improve the utilization of spectrum, extend network coverage, and reduce node power consumption and enhance communication reliability. In the presence of eavesdropper, node cooperation in secure communication network has wider significance and more flexible cooperative strategies, such as cooperation jamming and noise forwarding in which invalid information is transmitted by the cooperator, or source node signal forwarding as relay. On the other hand, the cooperator can also assist the eavesdropper, or itself plays the role of eavesdropper. In the latter case, the cooperator wiretaps the source-destination secure communication when forwards the information. Currently, lots of research have been done for the information-theoretic security and cooperative wireless wiretap channel secure communication, such as the secrecy capacity for point to point wiretap channel, the secrecy capacity region for multiple users? scenario and also communication signal processing, transmission protocol and resource allocation for cooperative wireless wiretap channels. This paper studies cooperative wireless wiretap channel secure communication and corresponding power allocation problem. We focus on three new scenarios and discuss the cooperative transmission protocol and power allocation. In particular, the studies highlights include: cooperative jamming-based parallel cognitive wiretap channel secure communication and power allocation, orthogonal and non-orthogonal transmission protocol-based untrusted relay cooperation secure communication and power allocation, and untrusted relay cooperation-based multiple users? secure communication and power allocation.â‘  For parallel cognitive wiretap channel-based secure communication, the power allocation problem to maximize system secrecy rate is discussed under both the scenario with and without cooperative jammer(CJ). Firstly, we consider cognitive transmitter power allocation without the cooperation of CJ. The optimal power allocation strategy is derived and we propose a cognitive transmitter power discretization-based suboptimal algorithm, in which the core idea is to solve the problem by using greedy-like idea for 0-1 multi-dimensional knapsack problem(MDKP). Contrast to optimal power allocation, the complexity of this suboptimal algorithm is insensitive to the varying of primary network interference constraint. Since the optimal power allocation for the scenario of no CJ cooperation leads to spectrum resource waste. We further discuss the joint cognitive transmitter and CJ power allocation under the scenario of CJ cooperation for parallel cognitive wiretap channel. Due to the fact that the simultaneous transmissions by cognitive transmitter and CJ cause coupled interference at primary receiver. Thus we can not obtain closed solution of the optimal joint power allocation. Therefore, we first analyze the channel conditions under which we can obtain secrecy rate gain by using CJ. Then, under the fixed transmission power at cognitive transmitter, we discuss the optimal jamming power allocation. At last, the suboptimal power allocation scheme used in scenario without CJ cooperation is extended to the scenario of CJ cooperation and we propose a cognitive transmitter power discretization-based joint power allocation algorithm, i.e., JTJP-GLA. Simulation results indicate that, under most scenarios, introducing CJ and using the proposed algorithm JTJP-GLA can increase the system sum secrecy rate and also improve the resource utilization. In the worst case, though we may not get improvement in system secrecy rate performance by the cooperation of CJ, the performance by applying JTJP-GLA is approximately converged to the optimal power allocation for the scenario without CJ cooperation.â‘¡ For untrusted relay cooperation wiretap channel secure communication, we study the wiretap channel security enhancement transmission protocol and the secrecy rate maximization-based joint source-relay/joint source-relay-destination power allocation. Firstly, based on the relay channel non-orthogonal transmission protocol, two non-orthogonal transmission protocols for the untrusted relay cooperation wiretap channel are proposed, i.e., NAF-I protocol and NAF-II protocol. With the half-duplex constraints at the untrusted relay and also the multiple access schemes, source node and untrusted relay simultaneously transmit confidential messages to destination in the second slot. This protocol provides a non-wiretap signal branch for destination and then enhances communication security. Then, with the assumption that destination has no transmission ability, we discuss the joint source-relay power allocation to maximize the system secrecy rate for untrusted relay cooperation wiretap channel, for both orthogonal and non-orthogonal transmission protocols. The optimal power allocation and alternative source and relay optimization-based suboptimal power allocation algorithms are presented. At last, with the assumption that destination has transmission ability, we discuss joint source-relay-destination power allocation to maximize system secrecy rate for untrusted relay wiretap channel, for both orthogonal and non-orthogonal transmission protocols. The nest alternative optimization-based power allocation algorithm is provided. Simulation results show that, non-orthogonal transmission protocol can significantly improve system secrecy rate performance and in the worst case, its performance converges to orthogonal transmission protocol. Also, contrast to the scenario that destination has no transmission ability, the scenario that destination has transmission ability can obtain secrecy rate gain in some relay node location area.â‘¢ For the scenario of multiple cell-edge mobile stations(MS) all without direct links to the base station(BS) but have confidential messages in the uplink to the BS with the cooperation of untrusted relay(UR). Destination-based jamming(DBJ) scheme is introduced to implement secure communication between BS and MS. With the assumption that all MS are with fixed transmission power, we study the joint BS and UR power allocation to maximize the system secrecy rate. Two different scenarios are considered: 1)BS and UR have separate power constraint; 2)BS and UR have joint power constraint. Problem analysis indicates that the joint power allocation problems for both scenarios are equivalent to joint MS access control and power allocation which shows combinatorial property; even with given accessed MS set, the joint power allocation is non-convex and thus difficult to solve. Therefore, two minimum secrecy rate MS removing-based access control and alternative power optimization-based power allocation suboptimal algorithms are proposed. We also prove the convergence of these algorithms. The algorithm complexity analysis shows that, joint power constraint-based algorithm has lower complexity but the considered scenario is impractical. Thus, we explore the approach how to extend the algorithm for joint power constraint scenario to the scenario with separate power constraint. Simulation results indicate that, joint power constraint-based algorithm(Jo Power Opt) has the best system sum secrecy rate performance, while the separate power-based alternative relay and jamming power optimization algorithm takes the second place. The performance of joint power constraint extension-based separate power constraint algorithm(Ex Jo Power Opt) is scenario depended.