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Showing papers on "Co-channel interference published in 1983"


Journal ArticleDOI
TL;DR: In this article, the authors proposed a linear algebraic approach to cancel the co-channel interference in asynchronous spread spectrum multiple access (SSMA) systems, where the correlations among the pseudo-noise (PN) sequences of all the active channels are known.
Abstract: A spread spectrum multiple access (SSMA) communication scheme employing asynchronous code-multiplexing technique has been used in both mobile and satellite communication systems. One shortcoming of the SSMA system is the co-channel interference due to the correlations among the pseudo noise (PN) sequences being used by multiple channels. Such co-channel interference in the reception limits the number of channels that can share one common frequency band. Furthermore, there is a distant-dependent problem of different received-powers from different transmitters. This paper describes a technique for cancelling the co-channel interference in asynchronous SSMA systems. This technique does not treat the co-channel interference as thermal noise. It considers the co-channel interference as components that can be recreated at each receiver. If the correlations among the PN sequences of all the active channels become known, the co-channel interference can be cancelled using the linear algebraic approach. As a result, a larger number of channels can share the same frequency band more efficiently. Further, if initial synchronization can be implemented then the distant-dependent problem can be alleviated.

125 citations


Journal ArticleDOI
TL;DR: In this article, the cyclostationary nature of digital signals was considered when determining crosstalk interference between such signals in multipair cable and expressions for the time-varying mean and variance of far-end and near-end crosostalk (FEXT and NEXT) were derived.
Abstract: This paper considers the cyclostationary nature of digital signals when determining crosstalk interference between such signals in multipair cable. This approach is necessary as the interference is only relevant at the decision instants in the receivers of the disturbed systems and any time variation of this interference with respect to the sampling instants changes the effect of this interference; previous studies in the area have ignored the cyclostationary nature of the digital signal. Expressions for the time-varying mean and variance of far-end and near-end crosstalk (FEXT and NEXT) have been derived. These expressions demonstrate the inherently smaller time variation of the NEXT interference when compared to the FEXT interference. An interesting result is that the calculation of the time-averaged value of the variance of FEXT and NEXT interference still requires the use of the cyclostationary properties of the digital signal. The results of this paper are extended and applied to various examples of the engineering of digital line systems in multipair cable in Part II of this paper.

51 citations


Journal ArticleDOI
TL;DR: The probability of cochannel interference, which is of importance in determining system parameters in a cellular communication scheme, is evaluated and the optimal number of radio channels to allocate to each cell is derived through the use of a simple mathematical model.
Abstract: Origination probability for cochannel interference is introduced to the study of the influence of all cochannel interferers surrounding the base station of interest. In addition, the probability of cochannel interference, which is of importance in determining system parameters in a cellular communication scheme, is evaluated for the mobile radio environment as expressed by Rayleigh fading and shadowing. As a consequence, the optimal number of radio channels to allocate to each cell is derived through the use of a simple mathematical model. The theoretical results obtained are useful not only as a step in the maturation of the cellular land mobile radio system, but also for the development of the portable radio telephone system.

46 citations


Journal ArticleDOI
TL;DR: It is expected that the IJF-OQPSK scheme will have applications in low-cost power and bandwidth efficient earth-stations and terrestrial radio systems with transmit high-power amplifiers operating in saturation.
Abstract: The error probability (P e ) performance of intersymbolinterference and jitter-free offset-QPSK (IJF-OQPSK) modems in a cochannel and adjacent-channel interference environment is evaluated using a computer simulation technique. Hardware design and experiments have been completed to verify the simulation results. The results indicate that a spectral efficiency of 1.5 bits/s/Hz can be obtained with hard-limited IJF-OQPSK channels. This is a significant improvement compared to hard-limited QPSK, OQPSK, and MSK systems. It is expected that the IJF-OQPSK scheme will have applications in low-cost power and bandwidth efficient earth-stations and terrestrial radio systems with transmit high-power amplifiers operating in saturation.

13 citations


Patent
24 Nov 1983
TL;DR: In this paper, an envelope detector is used to detect a desired signal (D) and an undesired signal (U) by envelope detection, and a level meter (26) indicates the value of the interference ratio (D/U) of the desired signal to the unwanted signal according to the ratio of the low-frequency spectrum component to the high frequency spectrum component.
Abstract: A co-channel interference measurement system for radio communications using angular modulation comprises an envelope detector (12) for detecting a desired signal (D) and an undesired signal (U) by envelope detection. A low-frequency spectrum component detector (23) detects a spectrum similar to that of a fading spectrum, the low frequency component relating to the sum of the desired signal and the undesired signal. A high-frequency spectrum component detector (27,28,29,30) detects a spectrum higher than a fading spectrum, the high frequency component relating to the product of the desired signal and the undesired signal. A divider (25) provides the ratio of the low frequency spectrum component to the high frequency spectrum component, and a level meter (26) indicates the value of the interference ratio (D/U) of the desired signal to the undesired signal according to the ratio of the low frequency spectrum component to the high frequency spectrum component.

12 citations


ReportDOI
01 Sep 1983
TL;DR: In this article, the authors present a review of the literature on processing techniques that improve the intelligibility of the desired speech signal in the presence of voice interference, including subjective test procedures for evaluating enhancement algorithms for the voice interference problem.
Abstract: : Enhancing speech that has been corrupted during transmission or recording is a widely researched problem. A special case is when the interference is a second talker's voice. This report summarizes research on processing techniques that improve the intelligibility of the desired speech signal in the presence of such voice interference. Formal subjective intelligibility test procedures for evaluating enhancement algorithms for the voice interference problem are first developed. Computational objective measures based on spectral criteria are also developed to provide testing during intermediate stages of algorithm development.

6 citations


Proceedings ArticleDOI
01 Aug 1983
TL;DR: The additional bandwidth required when adjacent channel separation distances are imposed, is computed as a function of the distance separation for first and second-adjacent channel distance separations.
Abstract: If co-channel stations in a service must be separated by a given distance to prevent interference, a computable amount of total bandwidth is required to assign all transmitters in an area. If adjacent channel distance separations are now im­ posed, more total bandwidth may be re­ quired to assign the transmitters. In this paper, the additional bandwidth required when adjacent channel separation distances are imposed, is computed as a function of the distance separation for firstand second-adjacent channel distance separations.

3 citations


01 Dec 1983
TL;DR: In this paper, the relative spectrum efficiency of wideband and narrowband land mobile radio systems is analyzed and empirical results concerning the relative spectral efficiency of two different types of radio systems are presented.
Abstract: Analytical and empirical results concerning the relative spectrum efficiency of twogenerjc (wideband and narrowband) land mobile radio systems are presented. Graph theoretic frequency assignment techniques are used to relate spectrum usage to transmitter bandwidth, interference rejection characteristics, t ransmi tter 1ocati ons, frequency assignment techniques, and other system and deployment characteristics. A curve–fit equation is presented for estimating the amount of spectrum needed to assign frequencies to transmitters of both types when they are randomly located in a square geographical area. Spectrum usage when transmitters are located at preferred sites or clustered near city centers is also discussed. In most cases considered the narrowband systems use less spectrum than the wideband systems even though the narrowband systems requi re greater protection from cochannel interference.

2 citations


Proceedings ArticleDOI
01 Aug 1983
TL;DR: The paper analyzes the mutual interference of asynchronous frequency hopping communication networks and shows that the total average bit error of the desired link is almost independent of the particular distribution (Bell shaped, Rayleigh or Uniform).
Abstract: The paper analyzes the mutual interference of asynchronous frequency hopping (F.H.) communication networks. The transmitter-receiver pair is located in the same area where N interfering users are dis­ tributed according to a specified probability density function. The modulation is CBPSK and all users employ the same F.H. parameters. Linear interference (co-channel and adjacent channel) is assumed and the analysis is performed for various distributions of the interferers. It is shown that the total average bit error probabi­ lity of the desired link is almost independent of the particular distribution (Bell shaped, Rayleigh or Uniform).

1 citations


Patent
28 Jul 1983
TL;DR: In this article, a radio system for transmission of short data telegrams, in particular for radio remote control, in which a plurality of radio transmitters are connected to a multiplicity of radio receivers, and all radios transmit simultaneously on a common RF channel is presented.
Abstract: Radio system for transmission of short data telegrams, in particular for radio remote control, in which a plurality of radio transmitters are connected to a plurality of radio receivers and all radio transmitters transmit simultaneously on a common RF channel. The RF channel is divided into n RF control channels (K1 to Kn), each having a width of approximately 100 to 400 Hz. An RF control channel of this type is allocated to each of the radio transmitters and their associated radio receivers. The RF carrier (fo) common to all radio transmitters has high stability. The radio transmitters carry out single-sideband amplitude modulation with a reduced carrier and, within their AF channel (K1 to Kn), soft keying in time with the data telegrams.

1 citations


Book ChapterDOI
01 Jan 1983
TL;DR: In this paper, the choice of particular frequencies within those bands is guided mostly by the need to avoid interference between deep-space missions, but interference may also result from terrestrial sources making transmissions not related to space research.
Abstract: Successful radio communication between spacecraft and earth stations depends upon the use of appropriate radio frequencies and upon having sufficient freedom from interference. Radio frequencies for deep-space research may be chosen from bands that are allocated for that purpose. The choice of particular frequencies within those bands is guided mostly by the need to avoid interference between deep-space missions. Interference may also result from terrestrial sources making transmissions not related to space research.