Direct-sequence spread spectrum overlay in the microwave landing system band

We examine the performance of a direct-sequence spread spectrum (DS-SS) code-division multiple-access (CDMA) system used in a spectral overlay mode in the microwave landing system (MLS) band, from 5091-5150 MHz. The purpose of the overlay system is to enable increased spectral efficiency (higher data throughput), for future potential aeronautical datalink communications. We estimate the performance degradation incurred by both systems for a range of transmit powers, DS-SS bandwidths and data rates, and example MLS and DS-SS system parameters. We also explore the use of multicarrier (MC) DS-SS signaling techniques. Our study uses both analysis and computer simulations. We provide examples that explore both MLS and DS-SS system parameter values appropriate for the successful application of overlay.