Showing papers on "Spectral efficiency published in 1976"
01 May 1976
TL;DR: In this paper, the authors developed a practical modem technique providing the means to trunk a large volume of digitized vocie channels within the present FDM-FM bandwidth allocations Specifically, a bandwidth efficiency of 2 bits per hertz of RF bandwidth and a bit error of 10 to the 7th power or less at an E sub b/N sub o of 20 dB were desired.
Abstract: : The objective of this program was to develop a practical modem technique providing the means to trunk a large volume of digitized vocie channels within the present FDM-FM bandwidth allocations Specifically, a bandwidth efficiency of 2 bits per hertz of RF bandwidth and a bit error of 10 to the 7th power or less at an E sub b/N sub o of 20 dB were desired These characteristics, provided in conjunction with hard-limiting radio sets, allow efficient conversion of analog FDM-FM line-of-sight microwave systems to digital operation by replacement of the modulation elements It was determined that 4- ary FSK was the best signal design, given the performance objectives and the constant-envelope constraint A continuous-phase, coherent detection, multisymbol observation modem was constructed and successfully tested The performance objective of a 10 to the 7th power bit error rate at an E sub b/N sub o of 20dB was bettered by approximately 05 db in laboratory tests
1 citations