John M. Vanderau

Abstract: Minimum acceptable speech intelligibility of land mobile radios is influenced by a number of factors. These factors include the method of modulation, transmission bandwidth, channel spacing, received signal strength, and the ability of a radio receiver to capture a desired signal in the presence of interfering signals and noise. The Institute for Telecommunication Sciences has compared the speech quality performance of the new generation of Project 25 land mobile radios to analog FM systems.

Keywords: interference; bit error rate (BER); co-channel interference; land mobile radio (LMR); adjacent channel interference; delivered audio quality; Project 25 (P25); reference sensitivity level; SINAD; carrier-to-interference ratio (CIR)

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