3. Minimizing Message Delay of Time-Critical Traffic for Wireless Smart Grid Applications Under Jamming

In the previous chapter, we offered a comprehensive study on modeling and detecting jamming attacks against time-critical wireless networks with applications to the smart grid. However, only modeling and detection cannot provide defense against jamming attacks, and is only the first setup towards anti-jamming communication for wireless smart grid applications. Hence, spread spectrum systems, which provide jamming resilience via multiple frequency and code channels, must be adapted to the smart grid for secure wireless communications, while at the same time providing latency guarantee for control messages. An open question is how to minimize message delay for timely smart grid communication under any potential jamming attack.To address this issue, we provide a paradigm shift from the case-by-case methodology, which is widely used in existing works to investigate well-adopted attack models (also used in the previous chapter), to the worst-case methodology, which offers delay performance guarantee for smart grid applications under any attack. We first define a generic jamming process that characterizes a wide range of existing attack models. Then, we show that in all strategies under the generic process, the worst-case message delay is a U-shaped function of network traffic load. This indicates that, interestingly, increasing a fair amount of traffic can in fact improve the worst-case delay performance. As a result, we demonstrate a lightweight yet promising system, TACT (transmitting adaptive camouflage traffic), to combat jamming attacks. TACT minimizes the message delay by generating extra traffic called camouflage to balance the network load at the optimum. Experiments show that TACT can decrease the probability that a message is not delivered on time in order of magnitude for smart grid applications.