The feasibility of using spread-spectrum communication systems for the land mobile service on a non-interference basis with other users

This paper examines the conditions which would allow land mobile radio systems using spread-spectrum techniques to share certain r.f. channel allocations on a mutual non-interference basis with the existing users of these channels, namely the television broadcasters. An experimental spread-spectrum communication system has been developed and this has been used to examine the feasibility of bandsharing from the point of view of establishing protection for the television signal from the spread-spectrum interference for imperceptible visual interference on the screen, whilst still allowing adequate reception of the spread-spectrum signal under conditions of high television interference. The results indicate that the spread-spectrum signal must be at least 42 dB below the peak television carrier level at the television carrier frequency for picture quality to be unaffected, and under these conditions an output signal with at least 25 dB signal-to-noise ratio can be obtained from the spread-spectrum receiver.