1、STD-BSI BS EN b0835-L-Y-ENGL 1777 = Lb24bb7 b11117b7 782 m BRITISH STANDARD Methods of measurement for equipment used in digital microwave radio transmission systems Part 1. Measurements common to terrestrial radio-relay systems and satellite earth stations Section 1.4 Transmission performance BS EN
2、 BS 7573 : Section 1.4 : 1993 1992 60835-1-4 : 1997 IEC 835-1-4 : Incorpomtes Amendment No. 1 to BS 7573 : Section 1.4 : 1993 (renumbers BS as 1997) and Amendment No. 1 to BS EN 60835-1-4 : BS EN 60835-1-4 : 1997 The European Standard EN 608351-4 : 1995, together with its amendment Al : 1995, has th
3、e status of a British Standard ICs 33.060.30 BS EN 60836-1-4 : 1997 Issue 2, September 1997 Standards Board and comes into Amd. No. Date effect on Committees responsible for this British Standard lkxt affected The preparation of this British Standard was entrusted by the Electronic Equipment Standar
4、ds Policy Committee (EEL/-) to Rchnical Committee EEL/25, upon which the following bodies were represented: British Broadcasting Corporation British Radio and Electronic Equipment Manufacturers Association British Telecommunications plc Institution of Electrical Engineeis Radio, Electrical and Telev
5、ision Retailers Association Radiocommunications Agency The following body was also represented in the drafting of the standard, through subcommittees and panels: ERA Technology Ltd. 15 May 1993 0 BSI 1997 9594 I %ember I indicated by a sideline in the margin The following BSI references rD EN 608351
6、4 February 1995 NORME EUR0PEE”E EUROPAISCHE NOm + Al March 1995 ICs 33.060.30 Descriptors: Radiocommunications, telecommunications, satellite broadcasting, communication equipment, earth stations, radio-relay systems, microwave frequencies, characteristics, measurements, transmissions, quality Engli
7、sh version Methods of measurement for equipment used in digital microwave radio .transmisSion system Part 1: Measurements common to terrestrial radio-relay systems and satellite earth stations Section 4 Ilk.ansmission performance (including amendment Al : 1995) (IEC 835-1-4 : 1992 + Al : 1995) Mthod
8、es de mesure applicables au matriel utilis pour les systmes de transmission numrique en hyperfrquence Partie 1: Mesures communes aux faisceaux hertziens terrestres et aux stations terriennes de tlcommunications par satellite Section 4: Qualit de transmission (inclut lamendement Al : 1995) (CE1 8351-
9、4 : 1992 + Al : 1995) Megverfahren fr Gerte in digitalen Mikrowellen-Funkubertragungss ystemen Teil 1: Messungen an terrestrischen Richtfunksystemen und Satelliten-Erdfunkstellen Hauptabschnitt 4: CJbertragungsqualitt (enthlt nderung Al : 1995) (IEC 83514 : 1992 + Al : 1995) This European Standard w
10、as approved by CENELEC on 199403-08. CENELEC members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Upto-date lists and bibliographical references concerning such
11、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 lan
12、guage and notified to the Central Secretariat has the same status as the officiai versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Denmark, Finland, fiance, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden,
13、Switzerland and United Kingdom. CENELEC European Committee for Eectrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fur Elektrotechnische Normung Centrai Secretariat: rue de Stassart 35, B-1060 Brussels O 1995 Copyright reserved to CENELEC members Ref.
14、No. EN 6083514 : 1995 + Al : 1995 E - STD-BSI BS EN b0835-L-q-ENGL 1797 Lb24bb7 Ob44773 1b EN 60835-1-4 : 1995 bue 1, September 1997 Foreword The text of the International Standard IEC 83514 : 1992, prepared by SC 12E, Radio-relay and ked SatelJite communications systems, of IEC TC 12, Radiocommunic
15、ations, was submitted to the formal vote and was approved by CENELEC as EN 60835-14 on 199403-08 without any modification. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical nationai standard or by endorsement (dop) 1995
16、12-15 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 199512-15 Foreword to amendment Al The text of document 12E(C0)165, future amendment 1 to IEC 83514 : 1992, prepared by SC 12E, Radbrelay and SatelJite comunications systems, of IEC TC 12, Radiocommu
17、nications, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as amendment Al to EN 60083514 : 1995 on 19950306. The foiiowing dates were fured - latest date by which the amendment has to be implemented at national level by publication of an identical nationai standard or by
18、endorsement (dop) 19964301 latest date by which the nationai standards coricting with the amendment have to be withdrawn (dow) 1996-0301 - iib O BSI 1997 STD-BSI BS EN b0835-L-q-ENGL 1777 = Lb2LibbS bLiLi774 012 = BS 7573 : Section 1.4 : 1993 INTRODUCTION The transmission performance of a digital tr
19、ansmission system is expressed by several parameters, such as bit-error ratio (BER), jitter and acceptable input interruption. The BER is the most important parameter related to system transmission pedormance. Parameters other than the BER, for example, error-free seconds, are applicable to trans- m
20、ission rates up to 64 kbis. Their application to higher bit rates is under consideration (see 121). References in brackets are given in annex A: Bibliography. STD*BSI BS EN bU835-L-g-ENGL 1997 1b24bb7 Ob44775 T57 BS 7573 : Section 1.4 : 1993 METHODS OF MEASUREMENT FOR EQUIPMENT USED IN DIGITAL MICRO
21、WAVE RADIO TRANSMISSION SYSTEMS Part 1 : Measurements common to terrestrial radio-relay systems and satellite earth stations Sec ti on 4 : Transmission perf orma nce 1 Scope This section of IEC 835-1 deals with the measurement of transmission performance and is applicable to simulated digital microw
22、ave transmission systems or sub-systems. The transmission parameters should normally be measured at interface points recom- mended by the CCITT (see l). In special cases when equipment specifications require measurements at other ports (e.9. between modulator input and demodulator output termi- nals
23、), interface circuits between the measuring equipment and the equipment under test may be necessary. 2 Bit error ratio 2.1 Definition and general considerations The bit-error-ratio, BER, is defined as follows (see 3) where: N, is the number of bit errors in a time interval 1, N, is the total number
24、of transmitted bits in a time interval 1, 8 is the bit-rate of the signal at the point where the measurement is made 1, is the measurement time interval in seconds (error-counting time) The BER is measured by comparing, bit by bit, the coincidence, or non-coincidence, of the transmitted and received
25、 bit streams. The arrangement for BER measurement is shown in figure 1. The comparison of the transmitted and received bit streams is made and the number of errored bits is counted. The preferred test signal to be applied to the equi ment under test is one having a pseudo- random pattern with a patt
26、ern length of either 2“-1 or 223-l. depending on the nominal bit-rate of the transmission system (see 4), but a selectable or programmable word pattern is sometimes used for testing the effect of specific patterns on the BER charac- te ris t i cs. 2 STD-BSI BS EN b0835-L-Li-ENGL 1997 I Lb2Libb9 ObLi
27、Li77b 795 = BS 7573 : Section 1.4 : 1993 Equation (3-1) can give an estimate of the error probability. The accuracy of this estimate increases as Ne increases, but the practical limitations of the measurement time interval usually set a limit to the value of Ne. Assuming a random distribution of err
28、ors independent of each other and with a constant probability, .e. according to Poissons law, the minimum acceptable value of Ne is approxi- mately 10. In this case, the true error probability is contained in a range equal to I50 % around Ne/N, with a confidence coefficient of 90 % (see 3). Dependin
29、g on the circuit configuration, for example high spectral efficiency systems, the distribution of errors may be structured. In such cases the minimum acceptable value of Ne should be correspondingly increased. The measurement time interval of the BER needs to be long enough to obtain the required ac
30、curacy. If a BER of n x lo- is to be measured on a bit-stream having a bit rate 8, the required measuring time to is given by: Ne x 10 nB to z (3-2) For example, assuming Ne = 10 and a BER of lo- is to be measured at 6,3 Mbitls, to shall be longer than 16 s. 2.2 Method of measurement The arrangement
31、 for the measurement of BER is shown in figure 1. The measuring instru- ment has a transmit portion comprising a pseudo-random test-pattern generator, a receive portion comprising an identical local reference-pattern generator and a comparator for comparing the received and locally generated referen
32、ce patterns. An error counter counts the errors whenever the received and locally generated bits are not identical, and the ratio of the errored bits to the total number of bits, .e. the BER, is displayed by the error counter. The bit rate of the test pattern is usually selectable to permit the gene
33、ration of the hierarchical bit rates given in l. However an external clock input is also usually available for generating non-hierarchical bit rates. The receive pattern generator is normally synchronized by the clock signal extracted from the incoming bit stream. A BER measure- ment range of at lea
34、st or lo- should be covered. The choice of the extreme values depends on the hardware configuration and on the digital rate. or to In making the test, the demodulator input should be connected and disconnected several times and the highest measured BER should be recorded. When there are two or more
35、baseband channels in the equipment under test, sufficiently uncorrelated pulse streams need to be applied to the channels and the measurements made one channel at a time. The BER is measured as a function of the specified receiver input conditions as described in the appropriate sections of parts 2
36、and 3 of IEC 835. 3 STDSBSI BS EN b0835-1-4-ENGL 1997 H LbZqbbS b1111777 821 D EN 60836-1-4 : 1995 issue 2, September 1997 2.3 Presentation of results The BER is expressed as a function of some appropriate parameter of the equipment being measured, such as receiver input level. 2.4 Details to be spe
37、cified The following items should be included, as required, in the detailed equipment speci- f cat ion: a) ports between which the measurement is to be made; b) main interface conditions. e.g. bit rate, level, impedance and coding of the signal; c) specified receiver input levels, as appropriate; d)
38、 type and length of the test pattern: e) limiting bit error ratio characteristic; f) measurement time interval or number of errors by measurement. 3 Additional parameters This clause describes residual bit-error ratio. Other additional parameters remain under consideration by other international org
39、anizations. 3.1 Residual bit-error ratio 3.1 .1 Definition and general considerations Residual bit-error ratio (RBER) for digital microwave radio transmission systems is an indispensable factor to guarantee the system performance. NOTE - The RBER is the error ratio in the absence of fading and inclu
40、des allowance for system-inherent errors, environmental and ageing effects and long-term intederence. The RBER should be measured with the equipment under test operating under normal conditions. An integration time should be chosen using a value given by equation (3-2) in 3.2. The BER measurements a
41、re carried out repeatedly with the fixed integration time and the RBER may be defined as the highest BER not exceeded in a specified percentage of integration intervals. The BER measurement period of one day may be appropriate. 3.1 -2 Method of measurement The RBER is obtained by taking BER measurem
42、ents (see clause 2) over a long period, e.g. 24 h. using a long integration time, e.g. 15 min. These examples are related for systems with a capacity of about 100 Mbit/s and an RBER of 1 x lo”*. In case of terrestrial radio-relay systems, the measurements should be carried out with long-term interfe
43、rence. if required, in the absence of fading (see IEC 835-2-10). In the case of satellite communication systems, a high carrier-to-noise ratio condition should be applied (see IEC 835-3-12). The measuring of the BER shall be recorded in order to obtain the highest BER not exceeded in a specified per
44、centage of integration intervals. It is advisable to record the power supply voltage and room temperature. etc at the same time as the BER, in order to identify any causes of error and to discard incorrect measurements produced by environmental effects which would not happen in a real link. 4 O BSI
45、1997 , STD-BSI BS EN b0835-1-4-ENGL 1997 Lb2LIbb-bY4778 7b8 issue 1, September 1997 EN 60836-1-4 : 1996 3.1.3 Presentation of results The residual bit-error ratio shall be expressed as the highest BER not exceeded in a specified percentage of integration intervals. 3.1.4 Details to be specified The
46、following items should be included, as required, in the detailed equipment specif cat ion : a) ports between which the measurements are to be made; b) main interface conditions such as bit-rate, level, impedance and code format; c) receiver input level; d) type and length of the test pattern; e) int
47、egration time (e.g. 15 min), percentage of integration time intervals in order to discard periods with incorrect measurements during factory tests or fading periods during field tests; f) permitted residual bit-error ratio for the specified percentage of integration time intervals ; I g) total measu
48、rement time (e.g. 24 h). 4 Timing jitter 4.1 Definition and general considerations liming jitter is defined as the short-term deviation of the significant instants of a digital signal from their ideal positions in time. The jitter as a function of time can be charac- terized in terms of frequency an
49、d amplitude, as shown in the example of figure 2. Two types of jitter may be distinguished according to the jitter generating process: Justification jitter - which is caused by the insertion and extraction of justification bits in time-division multiplexing and de-multiplexing processes, and Timing jiffer - which is due to the imperfection of the timing recovery circuits in the regeneration process. Only timing jitter measurements are of importance for determining the performance of digital microwave radio transmission systems. Thr
