Spectral Overlay of Direct-Sequence Spread Spectrum in the Instrument Landing System Glideslope Band
David W. Matolak, Joshua T. Neville · Journal of Aerospace Computing Information and Communication · 2004
In this paper, we examine the effects of intentional spectral overlay between a directsequence spread spectrum (DS-SS) code-division multiple-access (CDMA) system and the glide slope signal of the Instrument Landing System (ILS) currently employed by the Federal Aviation Administration (FAA). The purpose of the overlay system is to enable increased spectral efficiency (higher data throughput), for future potential aeronautical datalink communications, e.g., an “airborne internet.” That is, this overlay would enable simultaneous use of the ILS glideslope band by the current glide slope systems and a new DS-SS CDMA digital communication system. We estimate the performance degradation incurred by both systems for several values of transmit powers, DS-SS bandwidths and data rates, and typical ILS glideslope and CDMA system parameters. Our study uses both analysis and computer simulations. We provide examples that explore both ILS glideslope and CDMA system parameter values appropriate for the successful application of the overlay technique.