Optimal Routing and Link Configuration for Covert Heterogeneous Wireless Networks

TL;DR

The paper studies covert routing in heterogeneous wireless networks where nodes hold multiple modalities, and adversaries seek to detect communications. It develops Het-Opt, a polynomial-time algorithm that jointly selects routes and multimode link configurations to maximize end-to-end capacity under an end-to-end covertness constraint, and extends the model to multiple observers and imperfect CSI. A key result is a closed-form characterization of per-link capacity and a route-optimization approach that reduces to a shortest-path problem with weights derived from link metrics, enabling scalable network planning. Numerical results show substantial gains of Het-Opt over single-mode and fixed-per-link schemes, and demonstrate its effectiveness under diverse adversary configurations and CSI uncertainties, highlighting practical benefits for covert HetNets.

Abstract

Nodes in contemporary radio networks often have multiple interfaces available for communication: WiFi, cellular, LoRa, Zigbee, etc. This motivates understanding both link and network configuration when multiple communication modalities with vastly different capabilities are available to each node. In conjunction, covertness or the hiding of radio communications is often a significant concern in both commercial and military wireless networks. We consider the optimal routing problem in wireless networks when nodes have multiple interfaces available and intend to hide the presence of the transmission from attentive and capable adversaries. We first consider the maximization of the route capacity given an end-to-end covertness constraint against a single adversary and we find a polynomial-time algorithm for optimal route selection and link configuration. We further provide optimal polynomial-time algorithms for two important extensions: (i) statistical uncertainty during optimization about the channel state information for channels from system nodes to the adversary; and, (ii) maintaining covertness against multiple adversaries. Numerical results are included to demonstrate the gains of employing heterogeneous radio resources and to compare the performance of the proposed approach versus alternatives.

Figures (6)

• Figure 1: Sample optimal path using Algorithm 1 (Het-Opt); a given link employs the optimal combination of Mode 1 (AWGN channel, marked with blue), and Mode 2 (fading channel, marked with green). The thickness of an edge corresponds to the power allocated to that mode for a given link.
• Figure 2: Single-link capacity of the proposed optimal combination of modes (Het-Opt) and the capacity when employing either of the modes in isolation. Note that the gains of Het-Opt are significant here, but will be even further enhanced with the additional freedom (routing) of the multi-hop scenario.
• Figure 3: Capacity for the proposed scheme (Het-Opt), Mode 1 (AWGN channel) only, Mode 2 (fading channel) only, and Per-link-DEP with the maximum number of hops set to 10.
• Figure 4: Capacity versus distance between source and adversary for the proposed scheme (Het-Opt), Mode 1 (AWGN channel) only, and Mode 2 (fading channel) only.
• Figure 5: Comparison of the capacity of Het-Opt for different values of the path loss exponent $\alpha$.