Showing papers on "Co-channel interference published in 1988"

User access in portable radio systems in a co-channel interference environment

Abstract: A computer simulation study of user access in a universal digital portable communications system is described. The performance of a portable radio access algorithm is evaluated in a cochannel interference environment. For typical propagation conditions, the ranking of channels by relative power provides a viable means of channel selection with respect to optimal performance. >

A wideband HF interference and noise model based on measured data

Abstract: Describes the first results of a high-resolution, wide-bandwidth North American HF band interference measurements program in terms of the correspondence of these results with a model for the interference derived from earlier European measurements. The preliminary conclusion is that the model is valid. The interference-dominated portion of the frequency distribution is approximately linear on a log-log plot which relates the fraction of the resolution cells occupied with interference at a power level to that power level. >

Co-channel interference suppression and signal separation method

Abstract: A method for interference suppression and signal separation of angle modulated signals is presented. The method is particularly useful for cochannel interference suppression. The main idea is to use the amplitude variation of the composite signal (the strong plus weak signals) to estimate the parasitic phase distortion incurred by the interferer. The authors utilize this estimate to cancel out the distortion at the composite signal and obtain (strong) signal's angle information. The weak signal is then obtained by suitable subtraction from the composite signal after limiting. >

Computation of single-tone spurious effects in radio communication systems

Abstract: A semiempirical computational method for obtaining a list of forbidden, potentially disturbing, single-tone spurious frequencies for each receiver system operating channel is described. A UHF/FM radio communication system, including two frequency converter stages, is used to demonstrate the method's ability to improve system performance. The forbidden list is shown to be a very useful tool for improving system frequency interference immunity during the initial stages of system design and for improving frequency allocation. This method can be applied to systems operating in various frequency ranges and using different modulation methods. >

Joint intersymbol interference and cross-pol interference cancellation for dually-polarized radio systems

Abstract: The issues of joint intersymbol interference and cross-polarized channel-interference-cancellation for dually-polarized digital microwave radio systems are addressed. Several two-stage cancelers and one three-stage canceler are presented, and compared to more conventional receivers based on a generalization of adaptive equalization to dually-polarized radio systems. The results show that although the ideal canceler considerably outperforms the ideal decision-feedback receiver, practical cancelers lose most of this advantage. >

Interference canceller and method of interference cancelling

Abstract: In a digital radio transmission system for transmitting independent dual data by using cross polarization, an interference canceller detects cross polarization interference either directly or indirectly. An interference compensating signal is generated and applied to the main signal to cancel the interference element. In a case where no interference element is present, deterioration of cross polarization discrimination from an interference cancelling circuit is prevented by first determining whether an interference element actually exists and applying the interference compensating signal only when it does exist. The interference compensating signal can be attenuated based on the value of interference element so as to prevent undo deterioration of the cross polarization discrimination when the interference element is minimal.

On the joint statistics of amplitude and phase of a signal with co-channel interference

Abstract: The joint probability density function (pdf) of the resultant amplitude and phase of a signal in presence of cochannel interference is given. The marginal pdf of the amplitude variable is evaluated. This joint pdf can be used to evaluate the receiver performance in presence of interfering signals. >

Error rate considerations for 256-QAM systems in presence of adjacent channel interference

Abstract: Performance degradation of 256-QAM systems in the presence of adjacent channel interference and thermal noise is studied. The authors consider two adjacent interferers of the same modulation format as the useful signal, placed symmetrically around it. The results are presented as equivalent carrier-to-noise (C/N) degradation for different channel spacings and carrier-to-interference (C/I) ratios. To allow easy comparison with 64-QAM systems, the authors present the degradation of these systems for the same values as those of the 256-QAM schemes. It is found that for C/I=0 dB and for a 256-QAM system using raised-cosine filters with alpha =0.5

An extension of Rice's click model for frequency hopping interference

Abstract: The output signal-to-noise and interference ratios are obtained for the case of frequency-hopping interference in spread-spectrum systems. Performance curves are obtained for different numbers of users and band-sharing ratios. The results show a severe loss in output signal-to-noise ratio for low-input signal-to-noise ratio and a large number of users. >

VHF radio transmission installation using at least two transmitters with a different frequency

Abstract: In order to prevent the generation of interfering signals, e.g. in adjacent frequency ranges, in a VHF radio transmission installation with at least two transmitters connected via a transmitter filter to a common antenna, the input of the power amplifier of one transmitter is supplied with part of the output power of the control amplifier of at least one of the other transmitters in such a way as to compensate for the interference power of the other transmitter.