scispace - formally typeset
Search or ask a question

Showing papers on "Co-channel interference published in 1982"


Journal ArticleDOI
TL;DR: The results show that shadowing has a severe effect on the interference level and on the channel reuse distance ratio.
Abstract: The probability of cochannel interference is evaluated for a mobile radio system operating in Rayleigh fading and log-normal shadowing environment. All cochannel cells surrounding the base station are taken into consideration in this evaluation. The results obtained are used to calculate the reuse distance and the cluster size (number of cells in a group). The blocking probability, the number of channels in each cell, the protection ratio, and the standard deviation are taken as parameters in this evaluation. The results show that shadowing has a severe effect on the interference level and on the channel reuse distance ratio.

86 citations


Journal ArticleDOI
Yu-Shuan Yeh1, D. Reudink
TL;DR: This paper has shown that high spectrum efficiencies in mobile radio systems can be achieved with a modest number of space diversity branches and with a large number of diversity branches it is shown that frequency reuse is possible resulting in Spectrum efficiencies greater than 100 percent.
Abstract: Space diversity combining is a well-known method of smoothing amplitude fluctuations of the received signal in Rayleigh fading environments, such as mobile radio. Perhaps less well known is that space diversity combining can also be an excellent method of combating cochannel interference. In this paper, it is shown that high spectrum efficiencies in mobile radio systems can be achieved with a modest number of space diversity branches. With a large number of diversity branches it is shown that frequency reuse is possible resulting in spectrum efficiencies, as defined herein, greater than 100 percent.

46 citations


Journal ArticleDOI
TL;DR: In this article, an approximate general expression for the interference response is derived and compared with results of an experimental test, where the major uncertainty results from the variability of the gain of the antenna sidelobes in which the interferenee is received.
Abstract: Multiplying interferometers, and the more complex synthesis arrays that have been developed from them, possess the advantage of greater discrimination against interfering signals than can be obtained with single-antenna radio telescopes. The major contribution to this effect results from the relative changes of the phases of the signals received in spaced antennas, associated with the sidereal motion of a cosmic source across the sky. Signals that do not show this predictable phase behavior are substantially suppressed in the data processing. In this paper an approximate general expression for the interference response is derived and compared with results of an experimental test. The major uncertainty results from the variability of the gain of the antenna sidelobes in which the interferenee is received. Threshold levels at which interference becomes harmful are derived for the very large array (VLA) of the National Radio Astronomy Observatory. In the case of broad-band interfering signals, further rejection occurs because inequalities in the time delays of the signal paths via the individual antennas result in decorrelation. The magnitude of the decorrelation depends upon the position of the source of interference, and as an example, computations are given for broad-band signals from a satellite in geostationary orbit. General thresholds for harmful interference to radio astronomy are given in International Radio Consultive Committee (CCIR) Report 224, and the present results are not intended to supercede them. Rather, the intention is to provide data specific to synthesis arrays to allow more accurate coordination in certain frequency ranges shared with active spectrum users. A possible application to the search for extraterrestrial intelligence is mentioned.

40 citations


Proceedings ArticleDOI
01 Sep 1982
TL;DR: In this article, a qualitative analysis of the intermodulation products and a computerized method is developed to reduce and optimize the interference in a broadband frequency solid state transmitters system.
Abstract: In the state of the art of mobile radio systems in­ cluding broadband frequency solid state transmitters, the intermodulation products generated in the final power stage become influent. Their disturbing effects may become stronger than those of the intermodulation products generated inside the receiver front end, and of the other important mutual interference sources. A qualitative analysis of the intermodulation products ge­ neration in transmitters and a computerized method are developed. A realistic worse case scenario is computed. The conclusions include some methods to reduce and opti­ mize the IM interferences in the system.

12 citations


Journal ArticleDOI
TL;DR: This paper describes the design and performance of a spread-spectrum medium frequency (MF) radio network that utilizes a simulcast time slotted transmission scheme in which radios that receive a data message in one time slot repeat the message in the next slot.
Abstract: This paper describes the design and performance of a spread-spectrum medium frequency (MF) radio network. The network utilizes a simulcast time slotted transmission scheme in which radios that receive a data message in one time slot repeat the message in the next slot. Spread-spectrum radio designs that operate efficiently with simulcast under a variety of channel conditions are investigated. The performance of the radio network is characterized in terms of radio connectivity and message reaction time.

10 citations


Patent
04 Feb 1982
TL;DR: In this article, a common-frequency radio network with stationary and mobile radio stations (MS) and relay stations (R), the transmitters (Sf1) of which operate in commonfrequency mode, is considered.
Abstract: A common-frequency radio network with stationary and mobile radio stations (MS) and relay stations (R), the transmitters (Sf1) of which operate in common-frequency mode. In a region with a large area, radio traffic is to be made possible on a single common radio channel. For this purpose, the relay stations (R) of several adjacent radio networks have transmitters (Sf1) and receivers (Ef2) for a pair of frequencies (f1/f2) common to all radio networks and additionally in each case a simplex transceiver (Sf3, Ef3) suitable for common-frequency radio, via which radio signals received by means of the receiver (Ef2) are transferred to the adjacent radio networks. Delay sections (LAG) are connected into the connecting lines between the transceivers, in such a manner that the transmitters (Sf1) of all adjacent radio networks radiate synchronously.

7 citations


Journal ArticleDOI
TL;DR: A review is given of co-channel interference in small-cell systems and of the means for its avoidance, andPropagation phenomena are described.
Abstract: A review is given of co-channel interference in small-cell systems and of the means for its avoidance. Propagation phenomena are described. A table is given for the separation of base stations having both the same channel and the same supervisory tone, for up to 16 cells per block and zero to seven tones. Curves are given versus distance for the probability of interference from one station and from one or more stations in a seven-cell arrangement. Means for avoiding such interference are reviewed.

5 citations


Journal ArticleDOI
TL;DR: In this paper, the authors derived a simple expression for the degradation in signal-to-noise ratio caused by intersymbol and adjacent channel interference in MSK systems for which the total response is nonnegative and the response is such that only two intersymbolic and one adjacent channel terms are dominant.
Abstract: In this paper, we derive a simple expression for the degradation in signal-to-noise ratio caused by intersymbol and adjacent channel interference in MSK systems for which the total response is nonnegative and the response is such that only two intersymbol and one adjacent channel terms are dominant. An MSK system with Gaussian filters in transmitter and receiver satisfy this condition. The resulting expression is simple because we simultaneously maximize the signal value from the main channel (by selecting the sampling time) and the degradation caused by the signals in the interfering channels. For such systems we derive the relation between the optimal filter bandwidth and channel frequency separation. Numerical results are presented for the case of Gaussian filters in both transmitter and receiver or receiver only and either one or two adjacent interfering channels.

4 citations


Proceedings ArticleDOI
01 Sep 1982
TL;DR: A method for minimizing the total bandwidth required to assign frequencies to all applications in a mixed service band is developed.
Abstract: A method for minimizing the total bandwidth required to assign frequencies to all applications in a mixed service band is developed. A mixed service band is allocated to at least two kinds of systems-each with its own set of frequency-distance separation rules and possibly inter-service frequency-distance separation rules. Mixing services is always at least as spectrum-efficient as segregating them and is usually more efficient.

3 citations


Journal ArticleDOI
I. Smith1
TL;DR: The interference susceptibility of various spreadspectrum radios is described, potential solutions are identified, and the tradeoff of processing gain that must be made to achieve immunity from co-site interference is determined.
Abstract: Multiple single channel spread-spectrum radio communications simultaneously transmitted and received at a small station, aircraft, or ship are subject to mutual interference. Wideband PN and/or FH radios which occupy a large fraction of the available frequency band are more difficult to protect from adjacent channel interference than conventional narrow-band radios. This paper describes the interference susceptibility of various spreadspectrum radios, identifies potential solutions, and determines the tradeoff of processing gain that must be made to achieve immunity from co-site interference.

2 citations


01 Jul 1982
TL;DR: This report describes the performance of four localizer receivers in the presence of interference from co-channel CW, PSK,PSK, FSK, and FM signals to improve navigational aid systems such as the Instrument Landing System.
Abstract: : Co-channel signals can cause harmful interference to navigational aid systems such as the Instrument Landing System. This report describes the performance of four localizer receivers in the presence of interference from co-channel CW (Continuous Wave), PSK (Phase Shift Keying), FSK (Frequency Shift Keying), and FM (Frequency Modulation) signals. The receiver parameters monitored during the measurements were course deviation voltage, warning flag voltage, AGC (Automatic Gain Control) voltage, and audio distortion. Measurement results are reported as the minimum signal-to-interference ratio required to keep each monitored parameter from exceeding specified bounds. Course deviation voltage is the most sensitive parameter to the co-channel interference.

Journal ArticleDOI
TL;DR: In this article, the statistical characteristics and error rate performance of a fading 4-phase DPSK system when multiple channel interference with an arbitrary modulation phase number is present were analyzed, and the effects of multiple co-channel interference on the error rate were studied analytically.
Abstract: In land mobile communications in a small zone, the same frequency is used repeatedly for efficient use of the frequency spectrum. Therefore, co-channel interference is easily generated. An analysis is made of the statistical characteristics and error rate performance of a fading 4-phase DPSK system when multiple channel interference with an arbitrary modulation phase number is present. It is assumed that several services in addition to voice communication will be added in the future. The probability density of two orthogonal outputs from the differential detectors is derived using the characteristic functions, and, based on this quantity, the effects of multiple co-channel interference on the error rate are studied analytically. The resulting theoretical equation contains not only the autocorrelation of the desired wave but also the correlation of each interference wave. This makes it possible to evaluate the multiple co-channel interference, the power distributions of each interference and the number of channels. It is assumed that the fading spectra of the desired and interference waves are symmetric with respect to the center frequency.