In on-board processing satellite systems in which FDMA/SCPC access schemes are employed. transmultiplexers are required for the frequency demultiplexing of the SCPC signals. Digital techniques for the implementation of the transmultiplexer for such application were examined in this project. The signal processing in the transmultiplexer operations involved many parameters which could be optimized in order to reduce the hardware complexity whilst satisfying the level of performance required of the system. An approach for the assessment of the relationship between the various parameters and the system performance was devised. which allowed hardware requirement of practical system specifications to be estimated. For systems involving signals of different bandwidths a more flexible implementation of the trans multiplexer is required and two computationally efficient methods. the DFT convolution and analysis/synthesis filter bank. were investigated. These methods gave greater flexibility to the input frequency plan of the transmultiplexer. at the expense of increased computational requirements. Filters were then designed to exploit specific properties of the flexible transmultiplexer methods. resulting in considerable improvement in their efficiencies. Hardware implementation of the flexible transmultiplexer was considered and an efficient multi-processor architecture in combination with parallel processing software algorithms for the signal processing operations were designed. Finally. an experimental model of the payload for a land-mobile satellite system proposal. T -SAT. was constructed using general-purpose digital signal processors and the merits of the on-board processing architecture was demonstrated.

No description available.

No description available.

No description available.

No description available.

No description available.

This thesis examines a new market for satellite communication serving small fixed-station business systems. This market requires transmission between a large number of smaller and cheaper earth terminals. The traffic requirements for satellite business services in Europe by the year 2000 have been reviewed. An advanced regenerative on-board processing business satellite with 13 spot-beams for the European coverage was then proposed to meet the expected traffic growth. This satellite system is designed to meet the needs of the user rather than, as traditionally, the user fitting in with the satellite. SCPC/FDMA and R-TDMA (reservation-TDMA) multiple access schemes were found to be most suitable for the proposed system serving many small users whose traffic was mixed voice, data and video. The architecture of the satellite payload has been studied and two main functional blocks, transmultiplexer and baseband switch were identified. The use of the transmultiplexer is to transform the EDM channels into TDM and the baseband switch is to provide full connectivity between all the stations so that the revolutionary idea of having a "switchboard in the sky" can be realised. The development work for the baseband switch is reported in detail in this thesis together with a comparison of different architectures for the baseband switch. A proof-of-concept model for the baseband switch was designed, built and tested. From the test results, the feasibility of implementing the baseband switch using the chosen architecture was proved. Another main area studied in this thesis was device technology. The present and future capability of bipolar, CMOS and GaAs technology has been investigated concentrating mainly on digital devices and semi-custom technology. Since the satellite is operating in an hostile environment, it has been necessary to study the effects of radiation on semiconductor devices. The outcome of these studies indicate that it is very promising to launch such advanced satellite payloads in the late 1990's.

Not available / text

The purpose of this study was to investigate the extent to which PECS would generalise from the training setting to other familiar settings as a function of properties of the settings. It was predicted that PECS would generalise better to the setting where PECS use facilitated was by having the same communicative partners and items available. Three preschool children all with a diagnosis of Autism Spectrum Disorder (ASD) were trained to use the Picture Exchange Communication System (PECS) to a minimum proficiency level of Phase 3. The experiment employed an ABA single case design with multiple target measures, replicated across participants, acknowledging that observations in the first baseline would be zero. Transfer of PECS across settings varied for each participant. One participant generalised PECS to the facilitated environment more than the non-facilitated environment as predicted. Another participant transferred PECS better to the non-facilitated environment compared to the facilitated environment contrary to the research prediction. The final participant did not generalise PECS to either environment, switching to functional verbal communication instead.

The picture exchange communication system (PECS) is a functional communication system frequently used with individuals diagnosed with autism (Frost & Bondy, 2002). Few empirical investigations have evaluated staff training procedures to train staff how to teach consumers to use PECS, and none have been published to date on training staff to promote the use of PECS outside of the training environment. Using a multiple probe design the current investigation evaluated staff training procedures for teaching Phases 1-3 of PECS to adults with autism spectrum disorders, with direct care staff. Typical staff training procedures resulted in little improvement from baseline performances for each participant. Performance following behavioral skills training improved significantly, approaching mastery criterion levels.