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Title: Spread spectrum for a high frequency dispersed radio alarm scheme
Author: Cruickshank, David G. M.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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Alarm schemes for the elderly that are currently available are expensive. The vast majority of these schemes use a portable trigger worn by the client to transmit to a receiver unit within the client's home. This receiver unit then calls for help through the public telephone network. A large proportion of the overall cost of this type of scheme is the cost of providing each client with a receiver unit and a modem. In this thesis we look at the possibility of transmitting a high frequency alarm signal directly to a service centre from a portable transmitter worn by the client. This method should be much cheaper than a conventional telephone based system, as a receiver and modem for each client is not required. To obtain the required range, we sacrifice the speech link between the client and the service centre and use spread spectrum techniques to reduce the equivalent noise bandwidth of the system. There is a channel reserved exclusively for elderly alarm schemes, this channel in the high frequency radio band. In the high frequency radio band, the background noise is often dominated by man-made components and is therefore impulsive. The distribution of the impulsive noise in these channels is non-stationary and unknown to the system designer. An analysis of the performance of a direct sequence spread spectrum system using matched filter reception is developed. This analysis concentrates on providing a guaranteed minimum performance from a limited precision digital matched filter, regardless of the noise distribution. The performance of a non-linear clipping device preceding the matched filter is analysed and is shown to improve performance in impulsive noise. Finally, we study the design of a practical alarm scheme based on direct sequence spread spectrum.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available