BS-EN-60835-2-8-1996 BS-7573-2.8-1996 IEC-60835-2-8-1993.pdf

BRITISH STANDARD BS EN 60835-2-8:1996 BS 7573-2.8: 1996 IEC 835-2-8: 1993 Incorporates Amendment No. 1 to BS EN 60835-2-8: 1996 Methods of measurement for equipment used in digital microwave radio transmission systems Part 2: Measurements on terrestrial radio-relay systems Section 2.8 Adaptive equalizer The European Standard EN 60835-2-8:1993, together with its amendment A1:1996 has the status of a British Standard ICS 33.060.30 Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 11 12:26:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 60835-2-8:1996 This British Standard, having been prepared under the direction of the Electrotechnical Sector Board, was published under the authority of the Standards Board and comes into effect on 15 February 1996 © BSI 03-2000 The following BSI references relate to the work on this standard: Committee reference EPL/12 Draft for comment 91/29837 DC ISBN 0 580 25173 X Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee EPL/12, Radio communication, upon which the following bodies were represented: British Broadcasting Corporation British Radio and Electronic Equipment Manufacturers Association British Telecommunications plc ERA Technology Ltd. Institution of Electrical Engineers Radio, Electrical and Television Retailers Association Radiocommunications Agency Amendments issued since publication Amd. No.DateComments 9598September 1997 Indicated by a sideline in the margin Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 11 12:26:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 60835-2-8:1996 © BSI 03-2000i Contents Page Committees responsibleInside front cover National forewordii Foreword2 Text of EN 60835-2-85 List of referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 11 12:26:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 60835-2-8:1996 ii © BSI 03-2000 National foreword This British Standard has been prepared by Technical Committee EPL/102 (formerly EPL/12) and is the English language version of EN 60835-2-8:1993 Methods of measurement for equipment used in digital microwave radio transmission systems Part 2: Measurements on terrestrial radio-relay systems Section 8: Adaptive equalizer, including amendment A1:1996, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC 835-2-8:1993, including amendment No. 1:1996, published by the International Electrotechnical Commission (IEC) and is part of a series. BS EN 60835 is published in three Parts. The other Parts are: Part 1: Measurements common to terrestrial radio-relay systems and satellite earth stations; Part 3: Measurements on satellite earth stations. This Section of BS EN 60835-2 covers measurements pertaining to the adaptive equalizers used in digital microwave radio-relay systems. These measurements are intended to characterize the system equalizer in the presence of selective fading and may also be performed on systems without adaptive equalizers. To take account of those properties of the system which are especially influenced by the use of frequency and/or time domain equalizers, the results of measurements performed on the system are presented by so-called signatures. Additional measurements provide further means to characterize the performance of the system. It is expected that other Sections of the IEC Publication 835 will be published as identical British Standards, subject to their harmonization by CENELEC. Some Sections of this British Standard have already been published as Sections of BS 7573. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages 2 to 20, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 11 12:26:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 60835-2-8 July 1993 + A1 March 1996 UDC 621.396.7:621.317.083 Descriptors: Radiocommunications, telecommunications, communication equipment, earth stations, radio-relay systems, microwave frequencies, measurements, characteristics English version Methods of measurement for equipment used in digital microwave radio transmission systems Part 2: Measurements on terrestrial radio-relay systems Section 8: Adaptive equalizer (includes amendment A1:1996) (IEC 835-2-8:1993 + A1:1996) Méthodes de mesure applicables au matériel utilisé pour les systèmes de transmission numérique en hyperfréquence Partie 2: Mesures applicables aux faisceaux hertziens terrestres Section 8: Egaliseur auto-adaptif (inclut lamendement A1:1996) (CEI 835-2-8:1993 + A1:1996) Meßverfahren für Geräte in digitalen Mikrowellen-Funkübertragungssystemen Teil 2: Messungen an terrestrischen Richtfunksystemen Hauptabschnitt 8: Adaptive Entzerrer (enthält Änderung A1:1996) (IEC 835-2-8:1993 + A1:1996) This European Standard was approved by CENELEC on 1993-07-06. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels © 1993 Copyright reserved to CENELEC members Ref. No. EN 60835-2-8:1993 + A1:1996 E Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 11 12:26:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 60835-2-8:1993 © BSI 03-2000 2 Foreword The text of document 12E(CO)146, as prepared by subcommittee 12E, Radio relay and fixed satellite communication systems, of IEC technical committee 12, Radiocommunications, was submitted to the IEC-CENELEC parallel vote in November 1991. The reference document was approved by CENELEC as EN 60835-2-8 on 6 July 1993. The following dates were fixed: Foreword to amendment A2 The text of 12E/255/FDIS, future amendment 1 to IEC 835-2-8:1993, prepared by SC 12E, Radio-relay and fixed satellite communication systems, of IEC TC 12, Radiocommunications, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as amendment A1 to EN 60835-2-8:1993 on 1996-03-05. The following dates were fixed: Contents Page Foreword2 1Scope5 2General5 2.1Frequency domain equalizer5 2.2Time domain equalizer5 2.3Evaluation of system parameters influenced by the equalizers6 3Outage signature7 3.1Definition and general considerations7 3.2Measurement method7 3.3Presentation of results8 3.4Details to be specified8 4Return signature8 4.1Definition and general considerations8 4.2Measurement method8 4.3Presentation of results8 4.4Details to be specified8 5Measurements of dynamic fading effects9 5.1Definition and general considerations9 5.2Method of measurement9 5.3Presentation of results9 5.4Details to be specified9 6Recovery time10 6.1Definition and general considerations10 6.2Measurement method10 6.3Presentation of results10 6.4Details to be specified10 7Additional measurements11 7.1Outage signature with flat fading11 7.2Outage signature with interfering adjacent channels11 Annex A (informative) Bibliography20 Figure 1 Linear distortion and crosstalk in a QAM system caused by multipage fading11 Figure 2 Block diagram of a linear baseband equalizer11 Figure 3 Basic arrangement for the measurement of signatures12 Figure 4 Example of an outage signature12 Figure 5 Example of an outage signature with possible unusual signature values13 Figure 6 Presentation of the signature, minimum phase and non-minimum phase, on the same ordinate scale13 Figure 7 Example of the return signature14 latest date of publication of an identical national standard(dop) 1994-07-01 latest date of withdrawal of conflicting national standards(dow) 1994-07-01 latest date by which the amendment has to be implemented at national level by publication of an identical national standard or by endorsement(dop) 1996-12-01 latest date by which the national standards conflicting with the amendment have to be withdrawn(dow) 1996-12-01 Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 11 12:26:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 60835-2-8:1993 © BSI 03-20003 Page Figure 8 Arrangement for the measurement of recovery time14 Figure 915 Figure 10 Schematic for the measurement of dynamic fading effects16 Figure 11a Illustration of sweep waveform for the measurement of the system sensitivity to dynamic fading: sweep of the notch effect frequency17 Figure 11b Graphical representation of the relative system sensitivity to dynamic fading: sweep of the notch offset frequency18 Figure 12a Illustration of sweep waveform for the measurement of the system sensitivity to dynamic fading: sweep of the relative echo amplitude18 Figure 12b Graphical representation of the relative system sensitivity to dynamic fading: sweep of the relative echo amplitude19 Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 11 12:26:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 4 blank Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 11 12:26:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 60835-2-8:1993 © BSI 03-20005 1 Scope This section of IEC 835-2 deals with measurements pertaining to the adaptive equalizers used in digital microwave radio-relay systems. These measurements are intended to characterize the system equalizer in the presence of selective fading and may also be performed on systems without adaptive equalizers. To take account of those properties of the system which are especially influenced by the use of frequency and/or time domain equalizers, the results of measurements performed on the system are presented by so-called signatures. Additional measurements provide further means to characterize the performance of the system. 2 General The performance of a digital radio-relay link may be influenced by multipath propagation 11). This is especially true in the case of high capacity multi-state QAM systems. In addition to reducing the received signal level, i.e. “flat fading”, multipath propagation results in linear distortion, i.e. “dispersive fading”, producing amplitude and phase distortion. Multistate modulation systems are especially vulnerable to this form of fading see 835-2-4: Part 2: Measurements on terrestrial radio-relay systems Section 4: Transmitter/receiver (in preparation). For a system operating under multipath propagation conditions the vulnerability of the time-variant channel to linear distortion is of utmost importance. In the majority of high-capacity line-of-sight digital radio-relay systems, adaptive equalizers are used to counteract “dispersive fading” in order to decrease outages. The following types of equalizers are generally in use: frequency-domain equalizers, which are mainly, but not necessarily, implemented at i.f, and time-domain equalizers, which are mainly, but not necessarily, implemented at baseband. 2.1 Frequency domain equalizer It is the purpose of a frequency domain equalizer to correct the power density spectrum of the received signal, which, for example, can be analyzed with the aid of a bank of band-pass filters. Since there is usually no major redundant information in the transmitted signal, it is not possible to gain any information about the phase or group delay distortion of the channel; only the attenuation distortion can be recognized properly. In some cases, the equalization network is of the minimum-phase type where the phase and magnitude responses are linked to each other via the Hilbert transform. If the channel distortion is also of the minimum-phase type, then by equalizing the magnitude response the phase response is equalized as well. If the channel distortion is of the non-minimum phase type, for example in the case of two-path propagation where the weaker signal arrives before the stronger signal at the receiver site, the phase distortion may be increased and in some cases even doubled when the attenuation is equalized. This is the basic shortcoming of such a frequency domain equalizer. Its main advantage, however, is that it will operate correctly, with certain limitations, without any need for a recovered carrier signal (for synchronous demodulation), or for a recovered timing signal (for making correct timing decisions). Therefore, in contrast to time domain equalization systems, lock-in/lock-out properties need not be investigated. 2.2 Time domain equalizer It is the purpose of a time domain equalizer to achieve an intersymbol-interference-free (ISI-free) pulse shape at the input of the decision circuitry, although the channel itself may cause a considerable amount of ISI due to multipath propagation. Basically, time domain equalizers optimize the eye-opening either in the worst-case sense, i.e. by using the zero-forcing algorithm, or in the minimum-mean-square-error (MMSE) sense, i.e. using the MMSE algorithm 2. For proper operation, they require at least a correctly recovered timing signal. On the other hand, it is possible for the carrier- and timing-recovery circuits to take advantage of the operation of the equalizer by using the already equalized signal for the control of these loops. 1) The figures in square brackets refer to Annex A. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 11 12:26:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 60835-2-8:1993 6 © BSI 03-2000 By looking at the pulse response of the channel, time domain equalizers are usually capable of counteracting both minimum and non-minimum phase channel distortion. In general, multipath propagation causes not only distortion in the I-I path and in the Q-Q path but also cross-talk contamination between the quadrature signals in a QAM syste