In this paper, we propose a securely precoded OFDM (SP-OFDM) system for efficient and reliable transmission under disguised jamming, where the jammer intentionally misleads the receiver by mimicking the characteristics of the authorized signal and causes complete communication failure. More specifically, we bring off a dynamic constellation by introducing secure randomness shared between the legitimate transmitter and receiver, and hence, break the symmetricity between the authorized signal and the disguised jamming. We analyze the channel capacities of both the traditional OFDM and SP-OFDM under hostile jamming using the arbitrarily varying channel (AVC) model. It is shown that the deterministic coding capacity of the traditional OFDM is zero under the worst disguised jamming. On the other hand, due to the secure randomness shared between the authorized transmitter and receiver, SP-OFDM can achieve a positive capacity under disguised jamming since the AVC channel corresponding to SP-OFDM is not symmetrizable. A remarkable feature of the proposed SP-OFDM scheme is that while achieving strong jamming resistance, it has roughly the same high spectral efficiency as the traditional OFDM system. The robustness of the proposed SP-OFDM scheme under disguised jamming is demonstrated through both theoretic and numerical analyses.

Securely precoded OFDM (SP-OFDM) is a newly proposed secure and efficient anti-jamming scheme designed to enhance the physical layer security of OFDM based 4G and 5G systems under hostile environments. In this paper, by exploiting tools in constrained functional optimization, we explore the worst jamming distribution that minimizes the channel capacity of SP-OFDM under practical assumptions, where the transmitted symbols are uniformly distributed over a finite alphabet, and the jamming interference is subject to an average power constraint, but may or may not have a peak power constraint. First, we prove the existence and uniqueness of the worst jamming distribution. Second, by analyzing the Kuhn-Tucker conditions for the worst jamming, we prove that the worst jamming distribution is discrete in amplitude with a finite number of mass points, either with or without peak power constraints. Numerical results are provided on the worst jamming distribution and the minimum channel capacity under disguised jamming. It is shown that the minimum channel capacity of SP-OFDM is guaranteed to be positive under the worst disguised jamming, while the minimum capacity of the traditional OFDM under disguised jamming is zero. Both our theoretical and numerical results demonstrate the robustness of SP-OFDM and also reveal its performance lower bound under disguised jamming.

This paper considers malicious link detection in multi-hop wireless sensor networks (WSNs). Existing work on malicious link detection generally requires that the detection process being performed at the intermediate nodes, leading to considerable overhead in system design, as well as unstable detection accuracy due to limited resources and the uncertainty in the loyalty of the intermediate nodes themselves. In this paper, we propose an efficient and robust malicious link detection scheme by exploiting the statistics of packet delivery rates only at the base station. More specifically, first, we present a secure packet transmission protocol to ensure that except the base station, any intermediate nodes on the route cannot access the contents and routing paths of the packets. Second, we design a malicious link detection algorithm that can effectively detect the irregular dropout at every hop (or link) along the routing path. We prove that the proposed algorithm has guaranteed false alarm rate and low miss detection rate. Simulation results are provided to validate the proposed approaches.

In this paper, we address the problem of finding the worst jamming distribution in terms of channel capacity for the securely precoded OFDM (SP-OFDM) system, so as to evaluate the performance of SP-OFDM under destructive hostile jamming. We consider a practical communication scenario, where the transmitting symbols are uniformly distributed over a discrete and finite alphabet, and the jamming interference is subject to both average and peak power constraints. Using tools in functional analysis and complex analysis, first, we show the existence and uniqueness of the worst jamming distribution; then we further prove that the worst jamming distribution is discrete in amplitude with a finite number of mass points. Numerical examples are provided under different scenarios to demonstrate our theoretical results.

This paper introduces the mobile access coordinated wireless sensor network (MC-WSN)-a novel energy efficient scheme for time-sensitive applications. In conventional sensor networks with mobile access points (SENMA), the mobile access points (MAs) traverse the network to collect information directly from individual sensors. While simplifying the routing process, a major limitation with SENMA is that data transmission is limited by the physical speed of the MAs and their trajectory length, resulting in low throughput and large delay. In an effort to resolve this problem, we introduce the MC-WSN architecture, for which a major feature is that: through active network deployment and topology design, the number of hops from any sensor to the MA can be limited to a pre-specified number. In this paper, we investigate the optimal topology design that minimizes the average number of hops from sensor to MA, and provide the throughput analysis under both single-path and multipath routing cases. Moreover, putting MC-WSN in the bigger picture of network design and development, we provide a unified framework for wireless network modeling and characterization. Under this general framework, it can be seen that MC-WSN reflects the integration of structure-ensured reliability/efficiency and ad-hoc enabled flexibility.