Showing papers on "Co-channel interference published in 1989"
01 Jan 1989
TL;DR: Some of the theoretical concepts underlying this generalized type of filtering--called frequency-shift filtering--are developed and illushatcs them with specirrc examples, including channel interference removal and distortion removal for frequencyselective fading.
Abstract: Conventional time (and space) filtering of stationary random signals, which amounts to fonning linear combinations of time uanslates (and space uanslates), exploits the temporal (and spatial) coherence of the signals. By including frequency translates as well, the specual coherence that is characteristic of cyclostationary signals can also be exploited. This paper develops some of the theoretical concepts underlying this generalized type of filtering--called frequency-shift filteringand illushatcs them with specirrc examples, includingcochannel interference removal and distortion removal for frequencyselective fading. The suuctures and performances of optimum frequency-shift filters are presented, and adaptive adjusment of the weights in these suuctures is discussed.
55 citations
Patent•
28 Feb 1989TL;DR: In this paper, the authors proposed an interference cancellation circuit which can remove the interference signal caused by other systems and contained in received signals by combining the main signals contained in each of the received signals in a manner to offset each other to extract interference signal.
Abstract: This invention relates to an interference cancellation circuit which can remove the interference signal caused by other systems and contained in received signals. This invention circuit can cancel interference signal even if the interference signal is not directly obtained or plural interference signals exist, or the interference signal is wideband signal or raster interference simply by receiving two signals which have passed through different transmission paths, combining the main signals contained in each of the received signals in a manner to offset each other to extract interference signal, and removing interference signal component from the received signal based on the expected interference signal.
44 citations
TL;DR: It was found that the multiple-block data error check improved transmission quality in a co-channel interference environment, approaching the optimum with respect to the 99% statistical reliability criterion.
Abstract: A computer-simulation study of user access in a universal digital portable communications system is described. An access algorithm consisting of relative power channel-ranking followed by data error detection is evaluated and compared to an optimal reference in a co-channel interference environment. For typical propagation conditions and radio configurations, it was found that an access algorithm based on the ranking of system channels by relative power provides a viable means of channel selection for the portable radio. It was found that the multiple-block data error check improved transmission quality in a co-channel interference environment, approaching the optimum with respect to the 99% statistical reliability criterion. >
42 citations
11 Jun 1989
TL;DR: An adaptive method is proposed which improves these estimates and results in a better cancellation of interference, and is shown to be directly related to the cancellation quality.
Abstract: A method for co-channel interference suppression and signal separation was proposed in a previous work. It uses the amplitude variation of the composite signal to estimate the parasitic phase modulation impinged on the strong desired signal by the weak interference signal. This estimate is then used to cancel out the distortion of the composite signal, revealing the desired signal. In the cancellation process, amplitude estimates for both signals were obtained from measurements. Errors in estimating these magnitudes limit the quality of cancellation and signal separation performance. An adaptive method is proposed which improves these estimates and, hence, results in a better cancellation of interference. A criterion for performance measure was chosen to be the variance of the envelope of the weak signal estimate and is shown to be directly related to the cancellation quality. A random search algorithm was used to vary the signal magnitude estimates to achieve better estimates. Numerical simulation experiments were performed to prove the concept, including Gaussian noise. >
16 citations
15 Oct 1989
TL;DR: In this article, the authors quantify several interferers and suggest ways to improve the performance of shipboard HHF systems using self-steering, low-level filters, linearized transmitters, intermod cancellation, improved transmitter-antenna coupling, and time-disciplined data transmission.
Abstract: Cosite HF interference on shipboard is becoming more acute because of emerging requirements that call for simultaneous transmissions with antijam and frequency-hopping formats. The authors quantify several interferers and suggest ways to improve transmission. They include self-steering, low-level filters, linearized transmitters, intermod cancellation, improved transmitter-antenna coupling, time-disciplined data transmission and the exploitation of other new HF hardware developments. The poor frequency agility found in present shipboard HF systems can be improved by employing low-level, self-steering filters and the dedication of a power amplifier to each of three antennas. Reduction of radiated IM (intermodulation) can be accomplished by predistortion techniques. Shipboard IM into receivers from local transmitters can be reduced by partial cancellation. New hardware offers adaptive modems and dual diversity for improved performance. >
13 citations
11 Jun 1989
TL;DR: It is shown that using optimized block codes of insufficient length results in unstable adaptation of the transceivers and concomitant severe transmission distortion, but if the code blocks are greater than a certain critical length determined by, among other things, the number of pairs involved, near-end crosstalk can be completely eliminated.
Abstract: The feasibility of using adaptive transmitter-receiver combinations on several pairs in the same cable to suppress mutual crosstalk is investigated. It is shown that using optimized block codes of insufficient length results in unstable adaptation of the transceivers and concomitant severe transmission distortion. However, if the code blocks are greater than a certain critical length determined by, among other things, the number of pairs involved, near-end crosstalk can be completely eliminated. >
12 citations
01 May 1989
TL;DR: The overall outage probability is assessed for some coverages of practical interest for a pan-European cellular TDMA digital land mobile radio system currently under study and frequency plans avoiding strong adjacent channel interferences are presented.
Abstract: A novel method for the evaluation of the overall outage probability in cellular mobile radio is proposed. This method involves both links, i.e., M to B (mobile-to-base) and B to M (base-to-mobile), taking into account the joint effects of co-channel and adjacent channel interferences, the net filter discrimination, the radiation patterns of the base station antennas, the power control characteristic, the traffic distribution, and some typical propagation phenomena of the mobile radio environment, such as shadowing effects. The overall outage probability is assessed for some coverages of practical interest for a pan-European cellular TDMA (time division multiple access) digital land mobile radio system currently under study. Cellular coverages with centrally located omnidirectional antennas and with sectoral antennas are considered. For each coverage, frequency plans avoiding strong adjacent channel interferences are presented. The results are given in terms of cumulative distributions of the overall outage probability. >
10 citations
01 Dec 1989
TL;DR: In the paper, a receiver architecture is presented which is optimally suited for spectral analysis and makes heavy use of signal processing techniques.
Abstract: With the expansion of the Loran-C radionavigation system in Europe, serious research into interference rejection techniques for Loran-C receivers is necessary. This is because the LF-spectrum is heavily used in Europe, and many signals in this frequency band can adversely affect Loran-C receiver performance. Previous analysis of interference signals has shown that the most important parameter determining the influence of an interference signal on receiver performance is its frequency. Conventional Loran-C receivers employ hardware filters to get rid of interference signals; a method for obtaining an optimum filter configuration in a specific area is described in the paper. New receiver designs can incorporate software rejection techniques and some kind of spectrum analysis to determine the frequencies of interference signals and therefore their influence on receiver performance. Such receivers can adapt themselves to changes in the interference spectrum. In the paper, a receiver architecture is presented which is optimally suited for spectral analysis. It makes heavy use of signal processing techniques.
8 citations
TL;DR: The effect of cochannel interference on a fast handover algorithm for microcellular mobile radio systems is described and it is shown that increasing the mobile speed increased the effective cell length.
Abstract: The effect of cochannel interference on a fast handover algorithm for microcellular mobile radio systems is described. The presence of cochannel interference had only a marginal effect on the handover point when the microcell base stations were spaced by 300m. Increasing the mobile speed increased the effective cell length.
8 citations
TL;DR: A simple multipath delay spread estimation method by crosschannel-interference (CCI) measurement in a mobile radio channel is presented and shown that CCI is a good measure of multipathdelay spread.
Abstract: A simple multipath delay spread estimation method by crosschannel-interference (CCI) measurement in a mobile radio channel is presented. The theoretical analyses and field test results shown that CCI is a good measure of multipath delay spread.
7 citations
TL;DR: In this paper, the authors examined the interference requirements of ATV systems and considered approaches that might lead to effective interference reduction and/or elimination or reduction of the taboos, and showed that the reduction of interference by means of transmission system design and modern signal processing techniques in the spectrum compatible HDTV system is shown as an example.
Abstract: The author discusses some of the spectrum and interference issues that arise in connection with HDTV (high-definition television). It is noted that if a large percentage of the present VHF and UHF broadcasters are to be accommodated with extra spectrum for ATV (advanced TV) service, two things are obvious from the preliminary results of a study by the Spectrum Scenarios Specialist Group: ATV systems will have to operate at significantly reduced cochannel spacings, and taboo spectrum will have to be used. In this context the author examines the interference requirements of ATV systems and considers approaches that might lead to effective interference reduction and/or elimination or reduction of the taboos. The reduction of interference by means of transmission system design and modern signal processing techniques in the spectrum-compatible HDTV system is shown as an example. >
TL;DR: A method to cancel interference waves by extracting them from TV signals through quadrature synchronous detection and then transforming the signals with a Hilbert transform method is introduced, which will greatly contribute to eliminating abnormal interference waves caused by the sporadic-E layer as well as other undesired interference with TV signals.
Abstract: A method to cancel interference waves by extracting them from TV signals through quadrature synchronous detection and then transforming the signals with a Hilbert transform method is introduced. The system eliminates interference waves at any frequency within the TV signal band. It is easily applied to rebroadcast stations, since it is possible to cancel interference waves at the intermediate-frequency stage. The system automatically eliminates a maximum of five interference waves. It suppresses interference waves by more than 40 dB at a desired-to-undesired signal ratio of 10 dB. The system will greatly contribute to eliminating abnormal interference waves caused by the sporadic-E layer as well as other undesired interference with TV signals. >
TL;DR: The lattice planning method offers the possibility of arranging the transmitters according to a mathematical law, such that all the distances between adjacent transmitters are equal and all the channel distances are equal, resulting in equal interference.
Abstract: The most frequently utilized methods of radio frequency planning are briefly reviewed, and the lattice method (also known as the linear rhombic network method) is examined in detail. Unlike other methods, the lattice planning method offers the possibility of arranging the transmitters according to a mathematical law. The arrangement is such that all the distances between adjacent transmitters are equal and all the channel distances are equal, resulting in equal interference, both in type and level, at each transmitter location. This makes it possible to minimize the interference level during planning. >
TL;DR: In this article, a method for evaluating power transmission line interference with microwave radio communication circuits due to microwave scattering is presented and used to predict digital radio transmission performance degradation, since power lines cause quadrature distortion and intersymbol interference as well as average level reduction.
Abstract: A method for evaluating power transmission line interference with microwave radio communication circuits due to microwave scattering is presented and used to predict digital radio transmission performance degradation. Numerical results show that the effects of power line screening on highly efficient digital radio systems are more serious than on analog (FM) radio systems since power lines cause quadrature distortion and intersymbol interference as well as average level reduction. An experimental result using a communication satellite beacon shows that conductors within the first Fresnel zone cause the interference. >
27 Nov 1989
TL;DR: Simulation shows that the STS protocol performs better than the BTMA (busy tone multiple access) protocol, especially when the traffic is heavy, however the variable power tone sense protocol gives still better throughput performance.
Abstract: The simple tone sense (STS) protocol is designed for multihops PRNs (packet radio networks) with multiple directional antenna stations. The protocol can minimize transmission interference by using a group of tones to identify the active neighbors. A variation of the STS protocol, the variable power tone sense (VPTS) protocol, is also designed to further reduce interference. Algorithms for assigning tones and for determining the orientation and broadcasting angles of the directional antennas are designed. Design examples are given. Simulation shows that the STS protocol performs better than the BTMA (busy tone multiple access) protocol, especially when the traffic is heavy. VPTS, however gives still better throughput performance. >
23 May 1989
TL;DR: In this article, a qualitative analysis of mutual interference arising when two perfectly shielded transceivers, sited at the same location, are operating simultaneously is presented, and the restrictions imposed on the antennas for achieving reliable operation of a third remote system victim receiver are also considered.
Abstract: A qualitative analysis is presented of mutual interference arising when two perfectly shielded transceivers, sited at the same location, are operating simultaneously. The restrictions imposed on the antennas for achieving reliable operation of a third remote system victim receiver are also considered. In addition, some recently developed semiempirical, computer methods are discussed that allow the mutual interference factors affecting several worst-case scenarios to be computed. These computed results are then used to check design modifications and to improve system operational performance, including frequency management. >
11 Jun 1989
TL;DR: The author examines the multiple-access capability of frequency-hopped, receiver-oriented, spread-spectrum packet radio networks and results indicate that the byte errors exhibit a Markovian structure.
Abstract: The author examines the multiple-access capability of frequency-hopped, receiver-oriented, spread-spectrum packet radio networks. The most important indicator of the multiple-access capability of a spread-spectrum packet radio network is the induced packet error probability. The interdependence of byte errors of the desired transmission (i.e. packet) due to the multiple access interference caused by other packets is determined. An exact method and two approximation methods for the computation of the packet error probability are proposed. The results indicate that the byte errors exhibit a Markovian structure. >
22 Nov 1989
TL;DR: No significant improvements of the BER-performance seem to be obtained by increasing the number of states in the Ungerboeck codes, while remarkable coding gains can be attained for carrier to interference average power ratios greater than 20 dB.
Abstract: The BER (bit error rate) performance of uncoded 4-DPSK (differential phase shift keying) and coded 8-DPSK (with 8 and 16 state codes) modulation schemes have been studied. A Rayleigh mobile channel and the presence of co-channel interferers have been assumed. BER calculations have been performed by means of computer simulation. In this simulation a Nyquist signaling and an ideal block interleaving process are assumed. Decoding of trellis codes with 8 and 16 states is performed by a soft Viterbi decoder. Results obtained for the uncoded 4-DPSK modulation scheme are considered as reference to determine the improvements introduced by the coding process. Remarkable coding gains can be attained for carrier to interference average power ratios greater than 20 dB. No significant improvements of the BER-performance seem to be obtained by increasing the number of states in the Ungerboeck codes. >
02 Apr 1989
TL;DR: In this paper, the authors examined the features and potential problems associated with the use of 256QAM systems in an existing radio network to meet current transmission performance standards, including multipath propagation effects, intersystem interference and thermal noise as well as degradations imposed by practical manufacturing constraints.
Abstract: Radio-relay systems currently provide a significant fraction of the total long-haul capacity in the UK telecommunication network. The need to reduce transmission costs and to use the spectrum more efficiently has led to the adoption of higher level modulation techniques such as 16QAM, 64QAM, 256QAM etc. The systems which employ these higher level modulation techniques are potentially more sensitive to multipath propagation effects, intersystem interference and thermal noise as well as the degradations imposed by practical manufacturing constraints. The paper examines the features and potential problems associated with the use of 256QAM systems in an existing radio network to meet current transmission performance standards. >
01 May 1989
TL;DR: The dispersed-carrier-wave format is proposed for the execution of simultaneous multistation transmission for mobile communications and the diversity effects of this format were calculated, and the results were confirmed for the case of simultaneous two-station transmission.
Abstract: The dispersed-carrier-wave format is proposed for the execution of simultaneous multistation transmission for mobile communications. Signals are transmitted by modulating the carrier wave, which is frequency-modulated by sinusoidal waves. The diversity effects of this format were calculated, and the results were confirmed for the case of simultaneous two-station transmission. In cellular zone systems, in the case when the transmission distance of the radio waves is sufficiently large compared with the radius of the zone, there would be areas where several radio zones overlap. Therefore, for the theoretical calculations, the maximum number of simultaneous transmission bases was considered to be up to six stations. Also, numerical calculations of the transmission diversity effects have been made in the case of simultaneous multiple-station transmissions for a base station network with configurations of regular hexagonal meshes. >
15 Oct 1989
TL;DR: The author considers the cosite modeling and its application to the analysis of improvements in cosite performance achieved by the PROFFAR cosite filter and modeling of important receiver and transmitter properties to allow analysis of densely colocated radios is included.
Abstract: A computerized method (called SIGFRID) to simulate the amount of frequency-hopping interference in a receiver subjected to a number of interfering transmitters in a cosite situation was developed a few years ago. The method handles full scenarios, including friendly and hostile distant transmitters, jammers, ambient noise, and propagation characteristics. Modeling of important receiver and transmitter properties to allow analysis of densely colocated radios, as encountered in army vehicles and command posts, is included. In the present work the author considers the cosite modeling and its application to the analysis of improvements in cosite performance achieved by the PROFFAR cosite filter. It was shown that, using the facilities of SIGFRID, the improvement achieved by using PROFFAR can be readily demonstrated by subjecting a laboratory radio link to the simulated interference. >
27 Nov 1989
TL;DR: It is shown how current coordination and design procedures must be revised if one wants to optimize the use of SS technology without harmful interference to victim terrestrial receivers.
Abstract: With the advent of micro earth stations using spread-spectrum (SS) technology, a victim terrestrial radio receiver is likely to be subjected to uplink interference from many earth stations, especially near metropolitan areas. Statistical methodology is used to characterize the intermittent use of SS transmitters, making it possible develop a model for the interference generated from such a cluster of transmitters. It is shown how current coordination and design procedures must be revised if one wants to optimize the use of SS technology without harmful interference to victim terrestrial receivers. For example, for a cluster size of 50 and activity factor of 10%, it is shown that the effective number of exposures can be taken to be 15. This numer is not exceeded 99.99% of the time when one or more transmitters are active and transmitting. >