M. Maundrell

Trellis extracted synchronisation techniques applicable to automatic link establishment

With the ever increasing interest in automatic link establishment (ALE) and adaptive radio systems, there is much research being carried out to try and improve the performance of such systems. As well as looking at completely new systems, there is also interest in improving the performance of systems complying to the US MIL-STD 188-141A, as this is the currently established standard in this area. It has previously been shown how a new trellis structure for the (24,12) Golay code can be used to obtain the soft decision maximum likelihood of this code, which allows an improvement of a MIL-STD compliant system, without affecting its compliance. This paper addresses several techniques for making use of this trellis structure to allow maximum likelihood, or near maximum likelihood, block synchronisation within a MIL-STD compliant system.

Adaptive DSP-based MFSK modems for HF aeromobile channels

An adaptive digital-signal-processing (DSP)-based MFSK modem using the PICCOLO modulation scheme has been developed, primarily as a research platform for the investigation of adaptive HF radio modems. The authors describe several important design features of the implementation, including a novel data-derived synchronization scheme. The modem exhibits a far greater degree of responsiveness to both user requirements and channel state than previous implementations. Of particular interest are the efficient memory shadowing technique used in the tone synthesis, the ability to vary the number of samples/symbol, the frequency offset correction method, and the modulation-derived synchronization (MDS) embedded synchronization technique which eliminates the need for any specific synchronization overheads. The use of the model in a semiorthogonal MFSK mode is also discussed.<<ETX>>

MFSK and MPSK modems with intrinsic synchronization

A novel synchronization technique is described. In this method symbol timing is derived from the received data. This method of synchronization is highly suited to a communication path in which there are a number of modes of propagation, e.g. the HF channel. The operation of M-ary FSK (frequency shift keying) and PSK (phase shift keying) modems using the trellis coded modulation technique in conjunction with intrinsic synchronization is presented. HF trial test results are presented.<<ETX>>