This paper presents a simple local medium access control protocol, called , for multi-hop wireless networks with a single channel that is provably robust against adaptive adversarial jamming. The wireless network is modeled as a unit disk graph on a set of nodes distributed arbitrarily in the plane. In addition to these nodes, there are adversarial jammers that know the protocol and its entire history and that are allowed to jam the wireless channel at any node for an arbitrary @math -fraction of the time steps, where @math is an arbitrary constant. We assume that the nodes cannot distinguish between jammed transmissions and collisions of regular messages. Nevertheless, we show that achieves an asymptotically optimal throughput if there is a sufficiently dense distribution of nodes.
Our work is motivated by the work in @cite_6 and @cite_4 . In @cite_6 it is shown that an adaptive jammer can dramatically reduce the throughput of the standard MAC protocol used in IEEE 802.11 with only limited energy cost on the adversary side. @cite_4 initiated the study of throughput-competitive MAC protocols under continuously running, adaptive jammers, but they only consider single-hop wireless networks. We go one step further by considering where different nodes can have different channel states at a time, e.g., a transmission may be received only by a fraction of the nodes. It turns out that while the MAC protocol of @cite_4 can be adopted to the multi-hop setting with a small modification, the proof techniques cannot. We are not aware of any other theoretical work on MAC protocols for multi-hop networks with provable performance against adaptive jamming.
@cite_4 @cite_6
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In this paper we consider the problem of designing a medium access control (MAC) protocol for single-hop wireless networks that is provably robust against adaptive adversarial jamming. The wireless network consists of a set of honest and reliable nodes that are within the transmission range of each other. In addition to these nodes there is an adversary. The adversary may know the protocol and its entire history and use this knowledge to jam the wireless channel at will at any time. It is allowed to jam a (1-epsilon)-fraction of the time steps, for an arbitrary constant epsilon>0, but it has to make a jamming decision before it knows the actions of the nodes at the current step. The nodes cannot distinguish between the adversarial jamming or a collision of two or more messages that are sent at the same time. We demonstrate, for the first time, that there is a local-control MAC protocol requiring only very limited knowledge about the adversary and the network that achieves a constant throughput for the non-jammed time steps under any adversarial strategy above. We also show that our protocol is very energy efficient and that it can be extended to obtain a robust and efficient protocol for leader election and the fair use of the wireless channel. In this paper, we study the performance of the IEEE 802.11 MAC protocol under a range of jammers that covers both channel-oblivious and channel-aware jamming. We study two channel-oblivious jammers: a periodic jammer that jams deterministically at a specified rate, and a memoryless jammer whose signals arrive according to a Poisson process. We also develop new models for channel-aware jamming, including a reactive jammer that only jams non-colliding transmissions and an omniscient jammer that optimally adjusts its strategy according to current states of the participating nodes. Our study comprises of a theoretical analysis of the saturation throughput of 802.11 under jamming, an extensive simulation study, and a testbed to conduct real world experimentation of jamming IEEE 802.11 using GNU Radio and USRP platform. In our theoretical analysis, we use a discrete-time Markov chain analysis to derive formulae for the saturation throughput of IEEE 802.11 under memoryless, reactive and omniscient jamming. One of our key results is a characterization of optimal omniscient jamming that establishes a lower bound on the saturation throughput of 802.11 under arbitrary jammer attacks. We validate the theoretical analysis by means of Qualnet simulations. Finally, we measure the real-world performance of periodic and memoryless jammers using our GNU radio jammer prototype. We investigate the resiliency of IEEE802.11 rate adaptation algorithms (RAA) against smart jamming attacks. We consider several classes of state-of-the-art RAAs that include the SampleRate, ONOE, AMRR, and the RAA used in Atheros Microsoft Windows XP driver. We model the behavior of these algorithms, and show the existence of very efficient attacks that exploit RAA-specific vulnerabilities as well as the inherent weaknesses that exist in the design of IEEE802.11 MAC and link layer protocol: in particular the overt packet rate information being transmitted, predictable rate selection mechanism, performance anomaly caused by the equiprobability of transmissions among all nodes regardless of the data rates being employed, and the lack of interference differentiation from poor link quality by IEEE802.11 RAAs. In this work, we present algorithms that determine optimal jamming strategies against RAAs for a given jamming budget, and experimentally demonstrate the efficiency of these smart jamming attacks, which can be orders of magnitude more efficient than naive jamming. For example, in the case of SampleRate, eight reactive jamming pulses every second are sufficient to achieve the same network throughput degradation achieved by a periodic jammer with the jamming energy cost 100 times higher. Some of the RAAs react even worse to smart jamming attacks; ONOE in particular suffers from the phenomenon of congestion collapse where the nodes fail to recover from the lowest data rate even after the jammer stops jamming. At the end, we summarize fundamental reasons behind such RAA vulnerabilities and propose a preliminary set of mitigation techniques. We leave the experimental demonstration of the efficiency of the proposed mitigation mechanisms for future work. A typical wireless sensor node has little protection against radio jamming. The situation becomes worse if energy-efficient jamming can be achieved by exploiting knowledge of the data link layer. Encrypting the packets may help prevent the jammer from taking actions based on the content of the packets, but the temporal arrangement of the packets induced by the nature of the protocol might unravel patterns that the jammer can take advantage of even when the packets are encrypted. By looking at the packet interarrival times in three representative MAC protocols, S-MAC, LMAC and B-MAC, we derive several jamming attacks that allow the jammer to jam S-MAC, LMAC and B-MAC energy-efficiently. The jamming attacks are based on realistic assumptions. The algorithms are described in detail and simulated. The effectiveness and efficiency of the attacks are examined. Careful analysis of other protocols belonging to the respective categories of S-MAC, LMAC and B-MAC reveal that those protocols are, to some extent, also susceptible to our attacks. The result of this investigation provides new insights into the security considerations of MAC protocols.