On Effects Of DRSS Channel Nonlinearity On 16-order Modulation Signals And Research & Implementation Of Channel Equalization

Data Relay Satellite System (DRSS) is one of the focuses for study in wireless signal communication field, and is also an important part in Chinese space information network. Future DRSS requires higher transmission rates, and based on the present satellite platform, modulation modes of higher order must be adopted. A key point in the adoption in DRSS is that effects of channel nonlinearity on modulation signals of high order shouldn't be neglected, thus technologies that compensate for nonlinearity effects of DRSS channel must be researched in deep. In light of the nonlinearity of DRSS channel, the study conducted a detailed analysis of the performance of 16-order modulation signals under DRSS nonlinear channel, which includes five main aspects: (1) Modeling of DRSS nonlinear channel; (2) Performance analysis of 16-order modulation signals in DRSS; (3) A study of linear equalization technology; (4) Equalizationof DRSS Nonlinear channel based on sparse Volterra filter; (5) Design and implementation of linear equalizer of DRSS channel fit for 4 +12- APSK modulation signal.The first section of the paper studied models of DRSS channel, ranging from the general DRSS model to the ideal model of DRSS URE link step by step. And the modeling of DRSS channel was conducted by making use of an extended Volterra-Wiener model.The second section of the paper studied the performance of 16-order modulation signals in DRSS, analyzed minimum Euclidean distance and maximum tolerable phase error, the two key factors that determine the performance of signal transmission in channel, and concluded that 4 +12- APSK modulation signal is the 16-order modulation mode that most fits DRSS transmission. This conclusion was demonstrated by simulation.The third section of the paper studied linear equalizationtechnology. The theory of linear equalizationwas introduced,convergence characteristics and complexity of adaptive algorithm were analyzed, performance of linear equalization in DRSS channel was simulated and it was finally concluded that linear equalization can not equalize nonlinear ISI of DRSS channel.The fourth section of the paper studied adaptive equalization of DRSS nonlinear channel based on sparse Volterra filter. Characteristics of sparse Volterra filter were firstly analyzed, then, improved QR-RLS algorithm fit for the application of sparse Volterra filter was focused on to study, and what's more, convergence characteristics of improved QR-RLS algorithm and its effectiveness of nonlinear equalization based on sparse Volterra filter were simulated and analyzed.The fifth section of the paper designed and implemented the linear equalizer of DRSS channel fit for 4 +12- APSK modulation signal.