Showing papers on "Co-channel interference published in 1981"
TL;DR: A new achievable rate region for the general interference channel which extends previous results is presented and evaluated and the capacity of a class of Gaussian interference channels is established.
Abstract: A new achievable rate region for the general interference channel which extends previous results is presented and evaluated. The technique used is a generalization of superposition coding to the multivariable case. A detailed computation for the Gaussian channel case clarifies to what extent the new region improves previous ones. The capacity of a class of Gaussian interference channels is also established.
1,872 citations
TL;DR: The capacity region of a Gaussian interference channel with two separate messages is obtained for the case of moderately strong interference and it is shown that the region coincides with the one where both messages are required in both receiving terminals.
Abstract: The capacity region of a Gaussian interference channel with two separate messages is obtained for the case of moderately strong interference. It is shown that the region coincides with the one where both messages are required in both receiving terminals.
769 citations
01 Aug 1981
TL;DR: This paper addresses the problem of devising reasonably accurate and widely applicable frequency allocation and assignment algorithms by automated via a FORTRAN program which incorporates the general frequencydistance assignment model.
Abstract: This paper addresses the problem of devising reasonably accurate and widely applicable frequency allocation and assignment algorithms. The theoretical approach is summarized and the algorithms are described. The algorithms are automated via a FORTRAN program which incorporates the general frequencydistance assignment model. The program is structured to minimize the difficulty of replacing this model with models of other assignment problems. Applications to several important spectrum management problems are discussed.
35 citations
Patent•
09 Jun 1981
TL;DR: In this paper, a simulated interference system is provided where an interference signal of an interference source is simulated by a narrow band coded control signal that is transmitted from a control transmitter (3) to a target receiver (2) that is engaged in normal communications.
Abstract: A simulated interference system is provided wherein an interference signal of an interference source is simulated by a narrow band coded control signal (C) that is transmitted from a control transmitter (3) to a target receiver (2) that is engaged in normal communications. The control signal (C) is received by the target receiver (2) and is applied to an interference injector (5) that is coupled to the antenna (4) of the receiver. The interference injector (5) decodes the control signal (C) and couples a corresponding interference signal to the antenna of the receiver. The interference signal of the interference injector (5) operates to disrupt the normal communications signals (S) that are received by the target receiver (2). The system has the advantage that it affects only the equipment under test and does not substantially interfere with communication between nontest transmitters and receivers.
27 citations
TL;DR: In this paper, the probability that one signal exceeds another one at least p (protection ratio) times is determined for the case when both signals are Rayleigh distributed and correlated, and its applications in radiocommunication are discussed.
Abstract: Radio signals from various sources may be correlated due to propagation irregularities Here, the probability that one signal exceeds another one at least p (protection-ratio) times is determined for the case when both signals are Rayleigh distributed and correlated The closed-form result is exact and simple Its applications in radiocommunication are discussed
2 citations
TL;DR: In this paper, the magnitude and distribution of RF electric fields in a small power substation during an incident of radio transmission were examined and exposure of cormercial distribution relays to such fields are shown to produce considerable interference with normal operation.
Abstract: Controls used in electric power distribution systems are generally tolerant of the high level of interference signals found in that environment. Recently, however, increased power demnds have required a new class of solid state controls which are more sensitive to RFI. In order to delineate the problem this report examines the magnitude and distribution of RF fields in a small power substation during an incident of radio transmission. RF electric field strengths were of the order of 10 V/m. Exposure of cormercial distribution relays to such fields are shown to produce considerable interference with normal operation. Radio frequencies from 20 to 500 MHz were employed
2 citations
TL;DR: In this article, a technique for the improvement of signal/crosstalk-noise ratio in local digital transmission is proposed, for subscribers' circuits shorter than some maximum permissible length the transmit levels at both ends of the circuits are reduced.
Abstract: A technique for the improvement of signal/crosstalk-noise ratio in local digital transmission is proposed. For subscribers' circuits shorter than some maximum permissible length the transmit levels at both ends of the circuits are reduced. The effect of these changes on intersystem compatibility is also shown to be beneficial.
1 citations
TL;DR: The results show that above suppression ratio above 40 dB over a band-with of 50 MHz can be achieved regardless of whether the signal is CW, FM or PSK or the undesired and desired signals are co-channel signals.
Abstract: This paper presents an interference cancellation circuit based on a side-lobe canceller. A new interference canceller is investigated in which the receiving interference signal of the auxilary antenna is modulated by a low-frequency signal. When this signal is combined with the main antenna receiving signal, envelope detection is used and the error voltage of the interference canceller will be obtained from the detection of the low-frequency signal and the phase. The interference cancellation effect is measured. The results show that above suppression ratio above 40 dB over a band-with of 50 MHz can be achieved regardless of whether the signal is CW, FM or PSK or the undesired and desired signals are co-channel signals. For a PSK signal even with D/U = −10 dB prior to cancellation, the bit error rate after cancellation can still be maintained equal to that without interference at all. Also a good suppression ratio can even be achieved in outdoor situations and the circuit presented here has obvious practical value.
1 citations
Patent•
30 Jul 1981
TL;DR: In this article, the authors proposed to implement the radio coverage of large radio areas which are directly adjacent to small radio areas not by means of centrally located radio concentrators with omnidirectional antennas, but to have these areas jointly supplied with the aid of sector antennas which are allocated to the small adjacent areas.
Abstract: In mobile radio systems with cellular radio area division, direct adjacency of radio areas of extremely differing sizes may occur, typically in peripheral zones of built-up areas. If the known seven-frequency distribution plan (honeycomb structure) is taken as a basis, this frequency distribution can no longer be sustained in peripheral zones since the smaller radio areas are so physically close to substantially more powerful transmitters of the large radio areas that co-channel interference in the smaller radio areas assumes unacceptable proportions. It is proposed to implement the radio coverage of large radio areas which are directly adjacent to small radio areas not by means of centrally located radio concentrators with omnidirectional antennas, but to have these areas jointly supplied with the aid of sector antennas which are allocated to the radio concentrators of the small adjacent areas.
01 Feb 1981
TL;DR: In this article, the authors present a brief analysis of a second-order, type-one, phase-locked loop and associate AGC circuit and conclude that spectral purity of local oscillators and VCO's will be a major factor in determining the amount of signal cancellation possible with such a scheme.
Abstract: Interference to radio receivers, such as those used in radio astronomy, can present problems. Adding conventional filters to a radio astronomy receiver's input generally results in an appreciable increase in noise temperature if the filters have any significant losses or if they are not cryogenically cooled. This report takes a cursory look at the possibility of using signal cancellation techniques as an alternate method for eliminating interference in these cases. The technique is particularly suited to interference from the proposed solar-power satellite which would transmit a coherent, cw, microwave, power signal from a geosynchronous satellite. The analysis concludes that a phase-locked loop and associate AGC circuit could be used to generate a replica of the interfering signal which would then be subtracted from the composite signal. The report also concludes that signal suppression of the order of -30 dB should be possible with current technology.
The report presents a brief analysis of a second-order, type-one, phase-locked loop. Computer simulation of the loop is shown and tracking errors are assessed for various hypothetical SPS phase perturbations. The report concludes that spectral purity of local oscillators and VCO's will be a major factor in determining the amount of signal cancellation possible with such a scheme.