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Key distribution and renewing in wireless local area networks is a crucial issue to guarantee that unauthorized users are prevented from accessing the network. In this paper, we propose a technique for allowing an automatic bootstrap and periodic renewing of the network key by exploiting physical layer security principles, that is, the inherent differences among transmission channels. The proposed technique is based on scrambling of groups of consecutive packets and does not need the use of an initial authentication nor automatic repeat request protocols. We present a modification of the scrambling circuits included in the IEEE 802.11g standard which allows for a suitable error propagation at the unauthorized receiver, thus achieving physical layer security.

The feasibility of AND, OR, and EX-OR functions based on the interaction of optical solitons is proved by use of a five-layer dielectric structure with a nonlinear core. With the exception of the OR logic gate, the design of these devices is rather flexible, offering a wide variety of choices with respect to both the geometrical parameters and the input power levels.

The authors present an analytical model for the closed form evaluation of relevant parameters characterising the process at the output of a statistical multiplexer. Compared with previous approaches, the proposed method is able to additionally describe transient conditions and, through the autocorrelation function and the mean length of adjacent packets sequences, to evaluate the extent of the correlation in the output process as a function of that in the input traffic, also taking into account the effect due to a finite buffer size. The reliability of the model is tested, under different operation conditions, by comparison with simulated results, showing everywhere an excellent agreement.

The efficiency of ECG compression is confirmed using double logarithmic quantisation of the Walsh spectrum by applying it to practical signals sourced from the MIT/BIH arrhythmia database. By classifying a compression procedure as ‘good’ when its MSE for a spectral reduction of 1:1 is smaller than 0.005, the normal/abnormal ECG mix returned an overall 87% success rate for waveforms stored with between 8 and 11 bit resolution.

A new ECG data reduction method based on a double logarithmic quantisation of the ECG Walsh spectrum is presented. The proposed solution, theoretically justified by the decay characteristics of the spectrum energy content at high spectral index, is proved to be fast and efficient.