Online algorithms for maximizing quality of link transmissions over a jammed wireless channel

We consider the problem of a transmitter transmitting to its receiver over a wireless link subject to jamming and develop two online power control algorithms for maximizing wireless link quality (transmission rate). We assume that the transmitter transmits and the jammer interferes over a period of 31 time slots. The impact of the jammer is to deteriorate the quality of the wireless channel during time slots in which it is present. We assume a powerful random jammer with the ability to arbitrarily decrease the channel quality and affect any (unknown) number of time slots. Since the presence of the jammer is arbitrary, the complete jamming pattern (channel quality) over the given time period is unknown apriori. The current channel quality is revealed to the transmitter at the start of the current time slot while future channel quality remains unknown. The transmitter must then allocate power optimally to maximize the total transmission rate over M slots given only its knowledge of the current channel quality, thus giving rise to an online power control problem. We develop two online power control algorithms for maximizing the wireless link quality (transmission rate). The first algorithm is based on constant power scaling and has O(1) competitive ratio when the average received power quality over M time slots (ĥgPT/M) is either very small or very large. However when ĥgPT= O(M), this algorithm has an upper bound on its competitive ratio of O(logM/loglogM) This upper bound is tight The setond online algorithm based on constant rate scalin has a worst case tompetitne ritio of O (1+loglogM/1+ĥgPT/M). By judiuoush choosing which algorithm to use based on the offline available parameter of average received power, we can assure an almost constant competitive ratio for maximizing link quality under all cases. © 2009 IEEE

Cluster based jamming and countermeasures for wireless sensor network MAC protocols

A wireless sensor network (WSN) is a collection of wireless nodes, usually with limited computing resources and available energy. The medium access control layer (MAC layer) directly guides the radio hardware and manages access to the radio spectrum in controlled way. A top priority for a WSN MAC protocol is to conserve energy, however tailoring the algorithm for this purpose can create or expose a number of security vulnerabilities. In particular, a regular duty cycle makes a node vulnerable to periodic jamming attacks. This vulnerability limits the use of use of a WSN in applications requiring high levels of security. We present a new WSN MAC protocol, RSMAC (Random Sleep MAC) that is designed to provide resistance to periodic jamming attacks while maintaining elements that are essential to WSN functionality. CPU, memory and especially radio usage are kept to a minimum to conserve energy while maintaining an acceptable level of network performance so that applications can be run transparently on top of the secure MAC layer. We use a coordinated yet pseudo-random duty cycle that is loosely synchronized across the entire network via a distributed algorithm. This thwarts an attacker\u27s ability to predict when nodes will be awake and likewise thwarts energy efficient intelligent jamming attacks by reducing their effectiveness and energy-efficiency to that of non-intelligent attacks. Implementing the random duty cycle requires additional energy usage, but also offers an opportunity to reduce asymmetric energy use and eliminate energy use lost to explicit neighbor discovery. We perform testing of RSMAC against non-secure protocols in a novel simulator that we designed to make prototyping new WSN algorithms efficient, informative and consistent. First we perform tests of the existing SMAC protocol to demonstrate the relevance of the novel simulation for estimating energy usage, data transmission rates, MAC timing and other relevant macro characteristics of wireless sensor networks. Second, we use the simulation to perform detailed testing of RSMAC that demonstrates its performance characteristics with different configurations and its effectiveness in confounding intelligent jammers