Exploitable results
Recent investigations concerning mobile communications systems include architectures based on the advanced solid state components for analogue and digital signal processing.
This project is devoted to increasing the capacity of cellular wideband communication systems with multiple access. The three principles of cellular system organization actually used are: frequency division multiple access (FDMA): time division multiple access (TDMA); code division multiple access (CDMA). Solid-state components can be used for the realization of advanced mobile communication systems with improved parameters. As far as cellular systems are concerned, we propose a new system that combines the advantages of both CDMA and TDMA. We denote this system as code time division multiple access (CTDMA). A cellular system based on the CTDMA principle implies that only one communication channel with 12.5 MHz bandwidth is used, similarly to a CDMA system division, while the signal duration correspond to that of a TDMA system. The use of a CTDMA on a solid state elementary basis allows substantial improvement of characteristics such as mass and overall dimensions, power consumption, reliability, possibility of miniaturization and processing of complex signals in analogue form without preliminary quantization.
Therefore, this project includes the design and investigation of the main capabilities of one promising radio mobile cellular communication system, mainly devoted to urban traffic control. The principal models of basic functional blocks of solid-state electronic an acousto-optical devices for the CTDMA system are being developed and the recommendations on creation of specialized functional modules will be defined.
The acoustoelectronic technology used in this project is developed in order to fabricate some fundamental components of the code time division multiple access (CTDMA) radio- interface, first of all the SAW convolver, then filters, delay lines and so on. The estimated advantages of this technology with respect to conventional electronics can be summarized as follows: easy and reproducible fabrication process, based on conventional photolithography; low cost; use of components having high performance in terms of resolution capability, size, weight, power consumption; use of materials with high acoustoelectronic properties, such as ferroelectric crystals (lithium niobate).
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