Evaluation of cellular mobile telephone data receivers

Abstract

This paper describes some measurement techniques and results employed to evaluate AMPS mobile telephone data receivers being driven by a Rayleigh fading channel. These performance measurements were used as a mechanism for comparing the design effectiveness of various bit clock recovery systems. Of five data receiver types evaluated, two models employed a full wave rectifier in the bit clock recovery system. In this system nominal diode unbalance may cause the derived bit clock to lock 180 degrees from the phase required to properly decode the incoming bit stream. This condition may even occur at high carrier to noise ratios when message structures containing long strings of ones or zeroes are received. The other three data receiver types employed digital signal processing for clock recovery to circumvent this phase ambiguity problem. Performance data of the five data receivers are compared to non-coherent FSK as a model. In most cases test results are in good agreement with this model. Performance measurements presented include derived clock jitter, single and average bit error rates as a function of average carrier to noise ratios. Implementation of test instrumentation and interpretation of test results are discussed. The objective of this paper is to stress the capability of simulation measurements to evaluate mobile receiver designs in a laboratory environment.