Showing papers on "Co-channel interference published in 1980"
TL;DR: A simple mathematical model is used to predict co-channel and adjacent channel interference effects in land mobile radio, valid for flat urban terrain and yields insights into the properties of differing types of modulation.
Abstract: A simple mathematical model is used to predict co-channel and adjacent channel interference effects in land mobile radio, valid for flat urban terrain. Results obtained, although oversimplified compared with real-life mobile radio systems, yield insights into the properties of differing types of modulation.
18 citations
TL;DR: The use of communications relays is examined as a means of improving the operation of line-sight-links in an interference or jamming environment and the results obtained can be used to evaluate tradeoffs among the different options for reducing vulnerability to external interference.
Abstract: The use of communications relays is examined as a means of improving the operation of line-sight-links in an interference or jamming environment. Expressions are derived that define optimum relay locations and the number of relays. These relationships are functions of the system and interference parameters, as well as of the link and interference source geometry. Bounds on flight path orbits of airborne relays are also defined. Backlink operation with and without relays is considered, and the condition for identical relay locations for both forward link and backlink data flow is derived. The results obtained can be used to evaluate tradeoffs among the different options for reducing vulnerability to external interference.
10 citations
TL;DR: In this paper, the authors examined the conditions which would allow land mobile radio systems using spread-spectrum techniques to share certain r.f. channel allocations on a mutual noninterference basis with the existing users of these channels, namely the television broadcasters.
Abstract: This paper examines the conditions which would allow land mobile radio systems using spread-spectrum techniques to share certain r.f. channel allocations on a mutual non-interference basis with the existing users of these channels, namely the television broadcasters. An experimental spread-spectrum communication system has been developed and this has been used to examine the feasibility of bandsharing from the point of view of establishing protection for the television signal from the spread-spectrum interference for imperceptible visual interference on the screen, whilst still allowing adequate reception of the spread-spectrum signal under conditions of high television interference. The results indicate that the spread-spectrum signal must be at least 42 dB below the peak television carrier level at the television carrier frequency for picture quality to be unaffected, and under these conditions an output signal with at least 25 dB signal-to-noise ratio can be obtained from the spread-spectrum receiver.
8 citations
01 Dec 1980
TL;DR: This effort was to investigate techniques to reduce the signal degradation due to co-channel and adjacent-channel voice-on-voice interference using linear prediction coefficients and an adaptive comb filter.
Abstract: : The objective of this effort was to investigate techniques to reduce the signal degradation due to co-channel and adjacent-channel voice-on-voice interference. Sorting and suppression techniques using linear prediction coefficients and an adaptive comb filter were investigated. Limited success was achieved. A procedure for estimating the frequency shift due to mistuning was developed.
6 citations
1 citations
TL;DR: The lower bound 1 on the value of A, stated in [3] occurs only when the transmitted state p has exactly one photon, and this extreme value Ad = 1 will be of little use.
Abstract: of photon antibunching; when it is maximum, A, is minimum. The lower bound 1 on the value of A, stated in [3] occurs only when the transmitted state p has exactly one photon. Although the state of the receiving mode then also has Aa = 1, the probability of detecting that one photon at a remote receiver will be very small, and this extreme value Ad = 1 will be of little use. IEEE TRANSACTIONS ON INPORMATION THEORY, VOL. IT-26, NO. 6, NOVEMBER 1980 757
01 Oct 1980
TL;DR: The magnitude and distribution of RF fields in a small power substation during an inci dent of radio transmission and exposure of commercial distribution relays to such fields are shown to produce considerable interference with normal operation.
Abstract: Because of the high level of interference signals found in electric power distribution sys tems, controls used in that environment must gen erally be designed and tested to have low suscepti bility to induced misoperation. Recently, however, increased power demands have required a new class of solid state devices which are more sensitive to RFI. In order to delineate the problem this re port examines the magnitude and distribution of RF fields in a small power substation during an inci dent of radio transmission. RF electric field strengths are of the order to 10 V/m. Exposure of commercial distribution relays to such fields are shown to produce considerable interference with normal operation. Radio frequencies from 20 to 500 MHz were employed.
15 Dec 1980
TL;DR: Cases discussed include effects of S-band uplinks on X-band downlinks and S- band downlinks, planetary radar at Goldstone, future X- band uplink, radiometer measurements, Search for Extraterrestrial Intelligence instrument, and radio astronomy projects.
Abstract: Potential radio frequency interference problems related to the colocation of antennas for the Mark 4-A Deep Space network are analyzed. Cases discussed include effects of S-band uplinks on X-band downlinks and S-band downlinks, planetary radar at Goldstone, future X-band uplink, radiometer measurements, Search for Extraterrestrial Intelligence instrument, and radio astronomy projects. Remedial actions are suggested.