Satellite Communications Payload and System

Chapter 13

End-to-End Communications System Model with Focus on Payload

13.1 Introduction

This chapter presents ways to model the end-to-end communications system with focus on analyzing the payload's effect on performance. System performance is assumed to be evaluated in terms of symbol error rate (SER) or bit error rate (BER) (Section 10.5.4). Modeling may be done to help develop the payload specifications, to assess the impact of a payload parameter not meeting its requirement, to figure out what could be causing an on-orbit anomaly, or to try out a system upgrade on a test bed before committing to implementing it.

There are three general ways to model: by hand mathematically or with Microsoft's Excel, by software simulation on the computer, and by hardware emulation. It is possible and even sometimes advisable to combine techniques. For example, hand calculations may show the levels of interfering signals compared to the level of the signal of interest or how interfering signals can be modeled in a simplified way; hardware can be characterized and the measurements input to a simulation; or performance of the system in the nominal operating condition may be found by emulation, and this nominal performance used to calibrate a simulation, which is then used to assess system performance sensitivity to a parameter variation.

The rest of this chapter has three sections:

• Section 13.2 Considerations common to both simulation and emulation. Mathematical techniques for model simplification ...