William Shelton et al.

Abstract: This report examines the use of Amplitude Compandored Single Sideband (ACSB) and/or 12.5 kHz FM (NBFM) as possible solutions to the spectrum congestion in the Government Land Mobile Service in the VHF bands. These narrowband modulation techniques are investigated by looking into three different aspects of the problem. These are: operation and use, spectrum efficiency and implementation. In the operation and use area, the different capabilities and deficiencies of the NBFM and ACSB are identified and compared with the conventional 25 kHz FM presently used in the VHF band. Also, a review is made of both U.S. and foreign operational experience in these narrowband techniques. In the spectrum efficiency area, a definition is given for technical spectrum efficiency factor (spectrum resource used by reference system relative to spectrum resource used by evaluated system). Using this definition, the technical spectrum efficiency factor of both NBFM and ACSB relative to a reference 25 kHz FM is calculated for several different operational scenarios. Also, a discussion is made of the laboratory and field measurements on the ACSB and NBFM radios. These measurements were made by the Department of Defense Electromagnetic Compatibility Analysis Center, the Department of Agriculture, the FCC, and the Department of Commerce NTIA. In the implementation area, a rather comprehensive list of factors comparing the NBFM and ACSB to the 25 kHz FM is given. Also, a discussion is made of several implementation schemes and spectrum management strategies that the Government agencies might adopt in order to implement these narrowband modulation techniques. The conclusions from this study along with a number of definite recommendations for Government action are also included.

Keywords: Amplitude Compandored Single Sideband (ACSB); 12.5 kHz FM (NBFM); 25 kHz FM; land mobile radio (LMR)

Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

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