We describe block oriented multidimensional pulse position modulation and its resilience against ... more We describe block oriented multidimensional pulse position modulation and its resilience against impulsive noise. The modulation implements the encoder and part of the decoder of the BBC algorithm. We tested the modulation on circuits that send and detect a pulse based signal in the presence of impulsive noise. We measured the packet error rate vs. signal to noise ratio and we compared it with published error rates for OFDM. We found an error rate of 2 10 −5 at a signal to noise ratio of 16 dB without forward error correction and a data rate of 64 kbit/sec.
We consider the problem of establishing jam-resistant, wireless, omnidirectional communication ch... more We consider the problem of establishing jam-resistant, wireless, omnidirectional communication channels when there is no initial shared secret. No existing system achieves this. We propose a general algorithm for this problem, the BBC algorithm, and give several instantiations of it. We develop and analyze this algorithm within the framework of a new type of code, concurrent codes, which are those superimposed codes that allow efficient decoding. Finally, we propose the Universal Concurrent Code algorithm, and prove that it covers all possible concurrent codes, and give connections between its theory and that of monotone Boolean functions.
The advent of concurrent coding theory means that omnidirectional communication systems can posse... more The advent of concurrent coding theory means that omnidirectional communication systems can possess a level of keyless jam-resistance comparable to that of traditional spread spectrum systems, all of which rely on shared secret keys. To achieve this, concurrent codecs possess the ability to efficiently separate multiple legitimate codewords that have been superimposed. This is achieved by leveraging a highly asymmetric sensitivity to bit errors and, consequently, a reliance on communication channels having correspondingly high degrees of asymmetry in their bit error probabilities. While suitable physical channels must possess inherently high degrees of asymmetry, this asymmetry can be artificially enhanced using post processing techniques with the effect that system designers can trade small amounts of jam-resistance for increases in noise immunity. Furthermore, to rob potential adversaries of the option of attacking the receiver's ability to synchronize with the transmitted signal, concurrent codecs do not perform real-time adaptive synchronization and instead use asynchronous protocols. To avoid bit misalignments over the length of the packet, such protocols normally require that transmitters and receivers have oscillators with frequency tolerances on the order of one part in ten times the packet length. However, a concurrent codec can use simple post-processing techniques to exploit the asymmetry in bit error sensitivity to give receivers high degrees of immunity to timing jitter as well as high tolerances to oscillator mismatch. This has implications not only for processing gain, but also for implementation cost since transceivers can utilize oscillators having greatly relaxed specifications compared to that required by traditional systems. This paper presents these techniques and analyzes their impact on jam-resistance and oscillator performance requirements.
2007 IEEE SMC Information Assurance and Security Workshop, 2007
Traditionally, omnidirectional, radio frequency (RF) communication has been made resistant to jam... more Traditionally, omnidirectional, radio frequency (RF) communication has been made resistant to jamming by the use of a secret key that is shared by the sender and receiver. There are no known methods for achieving jam resistance without that shared key. Unfortunately, wireless communication is now reaching a scale and a level of importance where such secret-key systems are becoming impractical. For example, the civilian side of the Global Positioning System (GPS) cannot use a shared secret, since that secret would have to be given to all 6.5 billion potential users, and so would no longer be secret. So civilian GPS cannot currently be protected from jamming. But the FAA has stated that the civilian airline industry will transition to using GPS for all navigational aids, even during landings. A terrorist with a simple jamming system could wreak havoc at a major airport. No existing system can solve this problem, and the problem itself has not even been widely discussed. The problem of keyless jam resistance is important. There is a great need for a system that can broadcast messages without any prior secret shared between the sender and receiver. We propose the first system for keyless jam resistance: the BBC algorithm. We describe the encoding, decoding, and broadcast algorithms. We then analyze it for expected resistance to jamming and error rates. We show that BBC can achieve the same level of jam resistance as traditional spread spectrum systems, at just under half the bit rate, and with no shared secret. Furthermore, a hybrid system can achieve the same average bit rate as traditional systems.
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Papers by Mike Collins