Abstract:
The development of direct sequence spread spectrum systems allowed various applications including design and development of wireless systems and networks. This lecture will cover research results related to the physical layer design for wireless networks applications, in particular for wireless sensor network designs. One part of the lecture will address the development and design of multi-user systems, primarily the systems based on code division multiple access systems (CDMA). It will be assumed that the presented spread spectrum systems are based on the application of non-binary orthogonal sequences to transmit the users’ information. In recent years, the non-binary sequences, primarily chaotic and random sequences, have been extensively investigated and applied in spread-spectrum systems. The chaotic sequences are generated by chaotic maps and random sequences are produced by the random number generators. In particular, the lecture will present results related to the physical layer design for wireless sensor networks, which will include theoretical modelling, simulation and practical design of the layer that is based on the application of binary and non-binary spreading sequences. Due to the semi-random or random nature of non-binary sequences, a particular problem in these systems is how to achieve sequence synchronization. For that reason, the lecture will also present the latest findings related to the mathematical modelling, simulation and design in digital technology of efficient synchronization techniques in these systems.