Showing papers on "Co-channel interference published in 1987"

Co-channel interference measurement method for mobile communication

Abstract: A new method of measuring co-channel interference for mobile communication systems is proposed. In this method, the carrier envelope is sampled, and signal-carrier-to-interference-carrier ratio (CIR) is calculated by signal processing. The circuits for measurement are composed of an envelope detector, an analog-to-digital converter, and a microcomputer. Theoretical and experimental evaluations of measurement errors are examined, and the method is proved to be promising. Using this method, the signal-to-interference ratio of up to 20 dB is measured, within 2 dB error for fading frequency of less than 80 Hz.

A view from Europe

Abstract: M. J. Pagones and V. K. Prabhu, “Effect of Interference from geostationary satellites on the terrestrial radio network,” Conf. Record, GLOBECOM 1985, pp. 47.7.147.7.5, Dec. 1985. I. Godier, “DRS-8 digital radio for long-haul transmission,” Conf. Record, ICC 1977, pp. 5.4.102-5.4.105. JUW 1977. R . A. Roadhouse, T. G. Fellows, and J. L. Cpencrr, “The trans-Cmada digital radio network.” Co71f. liecord. ICC 1977, pp. 5.1.91-5.1.95, June 1977. C. P. Bates, W. G. Robinson, 111. and M. A. Skinner. “DK-6-135 system design and applications,” Conf. liecord, GLOBECOM 1984, pp. 16.7.1-16.7.8, Nov. 1984. D. P. ‘raylot-and P. R. Hartmann, “Telc.cornmunic~~tiorls b y rnicl-owave digital radio,” I E E E Cornmunicatiorzs Magazine, vol. 24, no. 8, pp. 11-16, Aug. 1986. T. Noguchi. Y. Daido, and J. A. Nossek, “Modulation techrliqurs for microwave digital radio,” IEEE Communications Magazine, vol. 24, no. 10, pp. 21-30, Oct. 11186. W. D. Rummler, R. P. Coutts, and M. Linigcr, “Multipath Fading Channel Models for Microwave Digital Kadio,” lEEE Comnzunicatio?~~ Muguzine, vol. 24, no. 11, pp.

Interference nulling system for antennas

Abstract: An interference nulling system is provided which nulls out all types of interference signals received in different lobes of the receiving antenna. The data to be received is transmitted from a high quality circular polarized transmitter antenna having the same polarization as the data receiving port of the receiving antenna. The receiving antenna also has a receiving port whose circular polarization is orthogonal to the antenna port receiving the data so that this latter channel contains only interference signals. The interference signals in this latter channel are correlated with the interference components in the data channel. A control loop is employed to adaptively adjust the phase (or delay) and amplitude of the sample of the interference signal and the adaptively adjusted interference signal is subtracted from the data signal which contains some of the interference signals, thus, providing a clean data signal.

The early history of radio interference

Abstract: The need for control of interference to broadcast reception together with the realization that differing controls could constitute trade barriers led to the establishment in 1934 of the CISPR (International Special Committee on Radio Interference). Agreement on basic measuring techniques, instrumentation design and suppression methods was achieved quite rapidly. Agreement on actual limits took longer.

Mobile radio channel control system

Abstract: PURPOSE: To ensure prescribed communication quality by measuring a desired wave level and an interference wave level and switching a call of a disturbing wave to a channel having a large ratio of the desired wave level and an interference wave level if the ratio is lower than the prescribed value as the result of measurement. CONSTITUTION: A channel used by a radio zone giving interference is switched to other frequency channel if the ratio of strength of the radio wave of a measured channel during communication and the radio wave of the channel in other radio zone in the radio zone where communication is interferenced by the radio wave interference from other radio zone. In such a case, only when the channel after changeover is discriminated not to give interference to the communication of the other radio zone including the radio zone subjected to the interference of communication, the switching of the channel is executed. Thus, the quality of communication of a prescribed value or over is ensured. COPYRIGHT: (C)1988,JPO&Japio

Orthogonal Cochannel Operation for High Spectrum Efficiency Based on the Example of 16 QAM-140 Mbit/s Systems Using Rolloff 0.19

Abstract: In view of the rapidly increasing demands for transmission capacity of public networks and the limited number of radio frequencies available, the band efficiency of existing systems in general will become insufficient for future high-capacity requirements. This fact is becoming increasingly evident for 16 QAM-140 Mbit/s radio systerns at 3.9, 6.7, and 11.2 GHz which are in widespread use in todays long-haul transmission networks. Conceptual and technological measures for making cochannel operation feasible and practical are presented using the example of a system family. By these means, even the capacity of existing 16 QAM-140 Mbit/s radio routes with 40 MHz interleaved channel arrangements can be doubled with the particular advantage of reutilizing the existing antennas and radio equipment with only minor modifications. A progressive filter concept makes orthogonal cochannel transmission possible with negligible adjacent channel spectrum interference. Surface acoustic wave IF filters are used to convert existing systems from 0.5 rolloff to 0.19 rolloff. Special RF channel/antenna arrangements were developed for the transmission of all RF channels in both directions, including space diversity and using only two antennas. A field experiment verified the feasibility of the concept and indicated that a crosspolar interference canceller is generally not necessary for 16 QAM140 Mbit/s cochannel operation.

Channel hand-off strategies in cellular mobile communication systems

Abstract: This paper describes a computer simulation study of a cellular, land-mobile radio communication system with and without frequency hand-off strategies. The authors assume that cell boundary crossings for calls-in-progress exist. In the hand-off procedure, they have studied several strategies where channels are specifically reserved for hand-offs. These strategies have been evaluated in terms of the new-call rejection rate and the rate of premature terminations of calls-in-progress. In a second method the authors have found the additional base station transmitter power required to service all the calls in progress without switching them to new channels. In addition, the cochannel interference introduced by this method has been evaluated and studied as a function of the additional transmission distance, with different partitions of channels, while maintaining a blocking probability of 2% or less.

Frequency coordination of cellular systems

Abstract: The FCC has always stressed the importance of frequency coordination in all of the radio services. Good frequency coordination minimizes interference and enhances the quality of the radio system. With the advent of cellular systems, new forms of coordination are needed to predict and avoid interference both within and between systems. In several ways, cellular frequency coordination is more complex than coordination in other services. Close cooperation between carriers is required to ensure compatible frequency usage and maximum growth potential. This paper discusses the tools and techniques used in developing a frequency plan that minimizes intra- and inter-system frequency interference. Frequency reuse and close geographic proximity of cellular systems mandates careful coordination to maintain good call quality.