https://www.dtc.umn.edu/s/resources/gg-se.pdf

A bibliography on nonlinear system identification

The principles and applications of a new baseband linearizer are described. It is demonstrated that, with the use of our linearizer, significant improvements in the effective radiated power of the earth station high-power amplifier can be attained. In a particular example, the characteristics of the recommended INTELSAT V satellite simulator model are used. For the 120 Mbit/s QPSK transmission system operating in a complex interference environment, we show that with the new iinearizer the earth station high-power amplifier may be operated almost in full saturation while meeting the current INTELSAT requirements. This is a significant improvement in power utilization efficiency. Similar improvements could be obtained for small digital singlechannel-per-carrier earth stations.

A New Baseband Linearizer for More Efficient Utilization of Earth Station Amplifiers Used for QPSK Transmission

The design of symbol sequences to be used in quasi-analytical simulation to estimate performance parameters of digital transmission systems is considered. An efficient method is presented for including the effects of external interfering signals in the evaluation of error probabilities. It consists of using simulated signals to obtain the moments of interference samples and applying the Gauss quadrature rule to calculate error probabilities. Several results are presented that confirm both the accuracy and efficiency of this procedure in the simulation of some interference environments. >

On the efficient use of computer simulated digital signals to evaluate performance parameters

The performance of continuous-phase FSK (frequency-shift keying) systems with rectangular modulation pulse shaping and limiter-discriminator detection is analytically evaluated in the presence of transmission nonlinearities as well as adjacent channel and cochannel interference. Consideration of modulation pulses with length tau , shorter than symbol time, T, is investigated. The algorithm developed to evaluate bit-error probability shows that the choice tau /T=1, and even more so in the presence of adjacent channel interference. Moreover, for tau /T=0.5, numerical results are reported that describe system performance under different working conditions and can be used to develop design criteria. >

Adjacent channel and cochannel interferences in CPFSK systems with nonlinear transmitters and limiter-discriminator detection

The effect of a bandpass limiter in code division multiple access quadriphase shift keying (QPSK) satellite spread spectrum communication systems is investigated. The case of a cochannel interferer on the uplink is analyzed in detail. The nonlinear characteristics of the bandpass limiter result in the generation of intermodulation products which become narrowband signals after the despreading process in the spread spectrum receiver. These intermodulation products and the cochannel interference affect system performance. The assumptions made in deriving the theoretical performance of the system were checked by simulating the entire system using the Block Oriented Systems Simulator (BOSS) software package. The results of the simulation show good agreement with the theoretical calculations, within 1 to 2 dB in signal-to-noise ratio. In addition, by means of simulation, it was possible to explore some features of the system that could not be addressed analytically, such as the effect of processing gain and unbalanced codes on system performance. >

Cochannel uplink interference in PN spread QPSK satellite systems

Increased frequency reuse in satellite systems will result in increased levels of cochannel interference. Such interference can in fact become the limiting factor affecting system performance. In this paper, the effects of cochannel interference on the bit error rate (BER) of a QPSK satellite system are analyzed. A nonlinear satellite transponder having a specified AM-AM and AM-PM transfer characteristic is assumed. An arbitrary number of up- and downlink interferers is considered. The theoretical results are compared with results obtained from time-domain computer simulations. Two facets of the cochannel interference problem which are of particular interest are investigated: the non-Gaussian nature of the interference and the small-signal suppression which may occur for uplink interferers.

O. Shimbo

Papers

Cochannel Interference in Nonlinear QPSK Satellite Systems