Statistical model for asynchronous interference to Mode S extended squitter

Abstract

The Mode S extended squitter is a signal to implement the random access data link in 1090 MHz channel. The International Civil Aviation Organization, ICAO, has reported on this data link as one of the candidate media for Automatic Dependent Surveillance-Broadcast, ADS-B. It is also expected that the communication with Mode S extended squitter will be applied to minimize the transponder utilization for the surveillance interrogation of Airborne Collision Avoidance System, ACAS. The estimation of communication performance of Mode S extended squitter is essential to estimate the surveillance performance for each application.

This paper describes statistical models of asynchronous interference to the Mode S extended squitter. The determination of statistical model is an essential part of the evaluation of communication performance. It is well known that the communication performance of Mode S extended squitter is degraded by the asynchronous interference with exceeding the power level that is derived from the receiving power level of Mode S extended squitter. The dominant source of asynchronous interference is the transponder replies in 1090 MHz channel.

For the model determination, the measured data on interference signal count are analyzed to compare with the Poisson distribution and the binomial distribution. They are farther compared with the Akaike Information Criterion, AIC. The Poisson distribution has been used to represent the distribution of interference signal count without verifying by measurement. The result of analysis shows that the Poisson distribution is suitable for the performance estimation model on the communication with Mode S extended squitter. Finally, an example of performance estimation is shown for the Tokyo airspace with measured interference parameters.