PERFORMANCE ANALYSIS OF 16-ary-OFFSET QAM SIGNALS THROUGH SATELLITE NONLINEAR CHANNELS

Abstract

An expression is derived for numerical computation of the symbol error probability of 16-ary offset quadrature amplitude modulation with sinusoidal shaping (16-ary offset-QAM). The channel considered here is a nonlinear satellite channel with additive Gaussian noise (AGN) in both up-link and down-link. The main source of the nonlinear distortion in two-link satellite channels is the travelling wave tube (TWT) power amplifier on-board of the satellite. The transponder nonlinearity considered in this paper is of the bandpass type (BPNL), which introduces a nonlinear input-ampliutde to outputamplitude (AM-to-AM) distortion and nonlinear input-amplitude to outputphase (AM-to-PM) distortion . Finally, a comparative study of 16-ary QAM and 16-ary offset QAM with sinusoidal shaping is performed with the BPNL operated at various levels of back-off from saturation.

Simulation Performance of CDMA/QA in Mobile Channel

“…In this model each user sends a QAM signal with inphase (I) and qudrature (Q) components spread by the respective user code sequence with high power. Analytically, The general form of an QAM signal can be defined as: [16].…”

“…Assuming that the number of chip per bit, N is large, the decision variable s p can be approximated according to the central limit theorem by a Gaussian random variable. The error probability in an AWGN channel for QAM using coherent detection can be approximated by: [16] ‫ﺍﻟﻬﻨﺩﺴﻴﺔ‬ ‫ﺍﻟﻌﻠﻭﻡ‬ ‫ﻤﺠﻠﺔ‬ -…”