This letter considers a fluid antenna system (FAS)-aided secure and covert communication system, where the transmitter adjusts multiple fluid antennas’ positions to achieve secure and covert transmission under the threat of an eavesdropper and the detection of a warden. This letter aims to maximize the secrecy rate while satisfying the covertness constraint. Unfortunately, the optimization problem is nonconvex due to the coupled variables. To tackle this, we propose an alternating optimization (AO) algorithm to alternatively optimize the optimization variables in an iterative manner. In particular, we use a penalty-based method and the majorization-minimization (MM) algorithm to optimize the transmit beamforming and fluid antennas’ positions, respectively. Simulation results show that FAS can significantly improve the performance of secrecy and covertness compared to the fixed-position antenna (FPA)-based schemes.

Recent work demonstrates that IEEE 802.11 networks are vulnerable to cascading DoS attacks, wherein a single node can remotely and suddenly congest an entire network. In this paper, we propose, analyze, simulate, and experimentally verify a counter-measure against such attacks. Our main idea is to optimize the duration of packet transmissions in order to weaken coupling effects between neighboring pairs of nodes. Toward that end, we propose a new theoretical model that relates the utilization of neighboring pairs of nodes using a sequence of iterative equations. The model captures important specifications of the IEEE 802.11 MAC layer. Through a fixed point analysis of the sequence, we show how to optimally set the packet duration so that, on one hand, cascading DoS attacks are avoided and, on the other hand, throughput is maximized. We validate the analysis through extensive ns-3 simulations and demonstrate the effectiveness of the mitigation through experiments with real Wi-Fi cards. A key insight is that IEEE 802.11 networks with relatively large MAC overhead are less susceptible to cascading DoS attacks than networks with smaller MAC overhead.

Millimeter wave wireless systems rely heavily on directional communication in narrow steerable beams. Tools to measure the spatial and temporal nature of the channel are necessary to evaluate beamforming and related algorithms. This paper presents a novel 60 GHz phased-array based directional channel sounder and data analysis procedure that can accurately extract paths and their transmit and receive directions. The gains along each path can also be measured for analyzing blocking scenarios. The sounder is validated in an indoor office environment.

Channel measurements at millimeter wave (mmWave) frequencies are typically carried out using directional antennas to overcome high path loss at mmWave frequencies. Unlike traditional directional channel measurements using narrow beam horn antennas where ray paths can be uniquely mapped to a direction with sufficient high accuracy, phased arrays with irregular beam pattern offers additional complexity in determining the arrival statistics of ray paths. In this work, we propose a systematic method to infer the ray path characteristics with the knowledge of beam patterns used by the phased array. We leverage on the channel measurement data obtained from extensive 60 GHz measurement campaign performed for indoor living room scenario and extract the ray path information from the measured data with high reliability. We also verify our findings through ray tracing simulation.

Many performance characteristics of wireless devices are fundamentally influenced by their vendor-specific physical layer implementation. Yet, characterizing the physical layer behavior of wireless devices usually requires complex testbeds with expensive equipment, making such behavior inaccessible and opaque to the end user. In this work, we propose and implement a new testbed architecture for software-defined radio-based wireless device performance benchmarking. The testbed is capable of accessing and measuring physical layer protocol features of real wireless devices. The testbed further allows tight control of timing events, at a microsecond time granularity. Using the testbed, we measure the receiver sensitivity and signal capture behavior of Wi-Fi devices from different vendors. We identify marked differences in their performance, including a variation of as much as 20 dB in their receiver sensitivity. We further assess the response of the devices to truncated packets and show that this procedure can be employed to fingerprint the devices.

Recent work shows that an adversary can exploit a coupling effect induced by hidden nodes to launch a cascading attack causing global congestion in a Wi-Fi network. The underlying assumption is that the power of interference caused by a hidden node is an order of magnitude stronger than the signal sent to the receiver. In this paper, we investigate the feasibility of cascading attacks with weakly interfering hidden nodes, that is when the signal-to-interference ratio is high. Through extensive ns-3 simulations, including for an indoor building model, we show that cascading attacks are still feasible. The attacks leverage two PHY-layer phenomena: receiver capture and bit rate adaptation. We show that the attack relies on a coupling effect, whereby the average bit rate of a transmission pair drops sharply as the channel utilization of a neighboring pair gets higher. This coupling effect facilitates the propagation of the attack throughout the network.

We present TeaCP, a prototype toolkit for the evaluation and analysis of collection protocols in both simulation and experimental environments running on TinyOS. Our toolkit consists of a testing system, which runs a collection protocol of choice, and an optional SD card-based logging system, which stores the logs generated by the testing system. The SD card datalogger allows a wireless sensor network (WSN) to be deployed flexibly in various environments, especially where wired transfer of data is difficult. Using the saved logs, TeaCP evaluates a wide range of performance metrics, such as reliability, throughput, and delay. TeaCP further allows visualization of packet routes and the topology evolution of the network, under both static and dynamic conditions, even in the face of transient disconnections. Through simulation of an intra-car WSN and real lab experiments, we demonstrate the functionality of TeaCP for comparing the performance of two prominent collection protocols, the Collection Tree Protocol (CTP) and the Backpressure Collection Protocol (BCP). We also present the usage of TeaCP as a high level diagnosis tool, through which an inconsistency of the BCP implementation for the CC2420 radio chips is identified and resolved.