1、 - ITU-R RECMN+PI. 842-1 94 Y855232 O523974 039 Rec. IT-R PI.842-1 207 RECOMMENDATION ITU-R PI.842-1 COMPUTATION OF RELIABILITY AND COMPATIBILITY OF HF RADIO SYSTEMS (Question ITU-R 217/3) (1992-1994) The ITU Radiocommunication Assembly, considering 4 b) that the reliability of a radio system is def
2、ined as the probability that a required performance is achieved; that reliability is a figure of merit of performance; c) that compatibility is a measure of the degradation caused by interference to the performance of a radio system; d) that predicted reliabilities and compatibilities are valuable i
3、n the selection of preferred combinations of antennas (including, where necessary, their design optimization), frequencies and necessary transmitter power to achieve a desired performance, recommends that the following methods for calculating the various types of reliability and compatibility should
4、 be used in the planning and design of radio systems. 1. Introduction The reliabilities discussed in this Recommendation form a hierarchy as illustrated in Fig. 1. Basic reliabilities are discussed in $ 2 to 5, overall reliability in 0 6, reliability in HF networks in $ 7 and compatibility in $ 8. S
5、pecific definitions of different types of reliability are given in Appendix 1. 2. Inputs to the basic reliability computation For the computation of basic circuit reliability the method involves the following parameters: monthly median available receiver signal power (Recommendation ITU-R PI.533); m
6、onthly median atmospheric, man-made and galactic noise powers (Recommendation IW-R PI.372); upper and lower decile deviations from the monthly median signal and noise powers - long term (day-to-day) and short term (within-the-hour); required signal-to-noise. ratio (Recommen- dation IT-R F.339). 3. C
7、omputation of basic circuit reliability (BCR) Basic circuit reliability may be estimated according to the procedure outlined in Table 1 using the information in Table 2. This procedure involves the intermediate calculation of the composite median available receiver power of the wanted signal (Step 1
8、), the median signal-to-noise ratio (Steps 2-3), the resultant upper decile of the signal-to-noise ratio (Steps 4-6), and the resultant lower decile of the signal-to-noise ratio (Steps 7-9). The required signal-to-noise ratio (Step 10) is user defined (Recommendation ITU-R FW.339 tabulates signal- t
9、o-noise ratios required to provide specific performances). The basic circuit reliability is then estimated using the statistical distribution given in Step 11. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services208 reliability -Single mod
10、e-, Single frequency- ITU-R RECMNrPI. 842-1 94 = 4855232 0523775 T75 m + Single circuit 8 - Single path 8 4 Single reception location 8 0 reliability Ail modes Rec. ITU-R PI.842-1 FIGURE 1 Chart of reliabilities Reception (i reliability All frequencies 0 reliability Circuits in series Communi- catio
11、ns reliability Paths in parallel Service ci reli ability Many locations 4. Basic reception reliability (BRR) Fornfrequencies BRR = 100 % where BCRCfi) is the percentage basic circuit reliability for frequencyf;:. For a single operational frequency, BRR is equal to BCR. 5. Basic service reliability (
12、BSR) The determination of basic service reliability involves the use of test points within.the required service area. Basic service reliability is the value of ERR exceeded by a required percentage of the test points. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed b
13、y Information Handling Services _ ITU-R RECMN*PI. 842-3 74 4855232 0523976 703 Rec. ITU-R PI.842-1 209 N, b CI a k 2 2 u n N 4 v s 0 3 m v Y Q .- M o L 8 h O .- Y t! 3 .- O 3 m v) Y C m Y d 2 E c m 3 E io I I x 1 3 + 0 + h 3 Y 8 O .- Y t! 3 .- O - m C M v) .- Y m 8 E Y - cci O C O d 8 o .I Y .e 4 -0
14、 8 - .e a 3. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services210 Y 5 e 0 a W i U % voo .e In 2 M e .- In a N W r- rio 22 o U - .- -0 3 i W a oo Rec. ITU-R PI.842-1 COPYRIGHT International Telecommunications Union/ITU Radiocommunication
15、sLicensed by Information Handling Services ITU-R RECMN*PI- 842-3 94 4855232 0523978 784 Geomagnetic latitude (1 c60“ Rec. ITU-R PI.842-1 260“ TABLE 2 LD 11 16 17 13 11 11 11 9 8 7 Lower decile (LD) and upper decile (UD) deviations from the predicted monthly median value of available receiver power o
16、f the wanted signai and interfering signals, arising from day-to-day variability UD 9 11 12 13 12 9 9 8 7 I Transmitting frequency/predicted basicMUF , - m C Q 3 E h 3 O 1- Y E 2 a2 U C 3 8 Fi 4-2 .- Y e m .- 8 ,JI Y C m 3 . Communications reliability Probability for a pair of terminals that a speci
17、fied performance is achieved by taking into account all the paths between them and all3requencies associated with the desired signals. Service reliability Probability for a service area that a specified performance is achieved by taking into account all transmitted frequencies. Area reliability The
18、percentage of test points in a service area for which the basic reception reliability is greater than a specified required value. Note I - In the above terms circuit means a transmission link from one transmitter to one receiving location with or without diversity. Note 2 - The above terms are prece
19、ded by the word “basic” when the background is noise alone and by “overall” when the background is noise and interference. Note 3 - When the background is noise and interference, the above terms may relate either to the effects of a single interferer or to multiple interference from Co-channel and a
20、djacent-channel transmissions. Note 4 - For many applications it is convenient to adopt a given value of signal-to-background ratio as the specified performance. Note 5 - The above terms (i.e. reliabilities) relate to one or more periods of time which should be stated. Note 6 - For broadcasting appl
21、ications, the term service reliability is replaced by the term broadcast reliability, and is calculated for a specified number of test points within the service area. 2. Terms relevant to prediction techniques Mode reliability Probability for a circuit that a specified performance is achieved by a s
22、ingle mode at a single frequency. Mode availabilio Probability for a single circuit that a single mode at a single frequency can propagate by ionospheric refraction alone. Mode performance achievement Probability for a single circuit that a specified performance is achieved by a single mode at a single frequency given that the mode can propagate by ionospheric refraction alone. Note i - Notes 4 and 5 of Q 1 apply. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services
