ITU-R S 614-4-2005 Allowable Error Performance for a Hypothetical Reference Digital Path in the Fixed-Satellite Service Operating Below 15 GHz When Forming Part of an International Net.pdf
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1、 Rec. ITU-R S.614-4 1 RECOMMENDATION ITU-R S.614-4 Allowable error performance for a satellite hypothetical reference digital path in the fixed-satellite service operating below 15 GHz when forming part of an international connection in an integrated services digital network*(1986-1990-1992-1994-200
2、5) The ITU Radiocommunication Assembly, considering a) that the concept of an integrated services digital network (ISDN) has been defined by the ITU-T; b) that satellites operating in the fixed-satellite service (FSS) will have an important role to play in extending the concept of the ISDN to intern
3、ational connections; c) that satisfactory error performance is an essential feature of any digital transmission system; d) that the error performance of an international digital connection forming part of an ISDN has been specified by the ITU-T in ITU-T Recommendation G.821 at 64 kbit/s; e) that the
4、 costs of establishing and maintaining digital communication satellite systems are critically dependent on overall error performance; f) that in defining error performance criteria, it is necessary to take account of all foreseeable error-inducing mechanisms, especially time-varying propagation cond
5、itions and interference, noting 1 that there are satellite hypothetical reference digital paths (HRDP) still in operation that have been designed taking into account the objectives of ITU-T Recommendation G.821, including degrading minutes parameter that was subsequently deleted in the 1996 version
6、of ITU-T Recommendation G.821, recommends 1 that the bit error ratio (BER) (see Note 2) at the output (i.e. at either end of a two-way connection) of a satellite HRDP (as defined in Recommendation ITU-R S.521) operating below 15 GHz and forming part of a 64 kbit/s ISDN connection should not exceed d
7、uring the available time the values given below: 1.1 1 107for more than 10% of any month, 1.2 1 106for more than 2% of any month, 1.3 1 103for more than 0.03% of any month (see Note 5); *This version of the Recommendation refers to ITU-T Recommendation G.821 as drafted before 1996 when the degraded
8、minute parameter was removed. All future satellite system designs should be based upon the latest version of Recommendation ITU-R S.1062. 2 Rec. ITU-R S.614-4 2 that the following Notes should be regarded as part of the Recommendation: NOTE 1 Section 1 was established utilizing the method outlined i
9、n Annex 1. It is based on, and sufficient to meet, the required fixed-satellite HRDP error performance objectives given in ITU-T Recommendation G.821 under all envisaged operating conditions. The ITU-T allocations for an FSS HRDP, which are considered to apply to the available time over a period of
10、the order of any one month, can be stated as: fewer than 2% of the 1 min intervals to have a bit error ratio worse than 1 106 ; fewer than 0.03% of 1 s intervals to have a bit error ratio worse than 1 103 ; fewer than 1.6% of 1 s intervals to have errors. NOTE 2 The BERs in 1 should be measured over
11、 a sufficiently long period of time in order to ensure that they provide a good estimate of the bit error probability (see Annex 1). NOTE 3 The BERs given in this Recommendation have been based on the assumption that contributions to severely errored seconds can be produced by two different error me
12、chanisms: those occurring randomly and those occurring in bursts. For the major portion of the time, the errors are random and are constrained by 1.1 and 1.2. Severely errored seconds are excluded from the random error measurements made to verify 1.1 and 1.2, but are included in 1.3 (see Annex 1). N
13、OTE 4 The BERs in 1 provide a margin for some burst errors that could arise from sources identified in Annex 1. NOTE 5 The value 0.03% of any month relates to the measured BER during the available time. This objective could be met, for example, by designing the satellite system to an unavailability
14、objective of 0.2% of the worst month (total time). By using a 10% availability factor (ratio of available to total time while the BER is worse than 103), this would correspond to 0.02% of the available time of any month. Further, it is necessary to include an allowance to accommodate contributions t
15、o those severely errored seconds which occur when the BER is better than 103. Taking as an example 0.01% of the worst month for this allowance, the total performance objective would be 0.03% of the available time of the worst month (see Annex 1). NOTE 6 The HRDP referred to in this Recommendation is
16、 specified in Recommendation ITU-R S.521. NOTE 7 It may be necessary to make special provision regarding the performance of satellite-to-satellite links. The extent of this provision is a matter requiring further study. NOTE 8 The Recommendation applies only when the system is considered available i
17、n accordance with Recommendation ITU-R S.579 and includes periods of high bit error ratio exceeding 103which persist for periods of less than 10 consecutive seconds. Short interruptions (less than 10 s) shall be treated as equivalent to the case in which the BER exceeds 103. NOTE 9 The error perform
18、ance objectives given in this Recommendation are designed to meet the specified end-to-end performance of a 64 kbit/s circuit switched, ISDN connection consistent with ITU-T Recommendation G.821. Performance objectives for satellite systems carrying PCM encoded telephony in a non-ISDN connection are
19、 given in Recommendation ITU-R S.522. Recommendation ITU-R S.614 may be used in the design of satellite systems carrying other forms of digital information, such as voice band data (e.g. facsimile) or low rate encoded (LRE) speech (under 64 kbit/s), until more specific studies are completed which ma
20、y lead to improved performance objectives. Rec. ITU-R S.614-4 3 NOTE 10 The objectives for BERs indicated in 1 are not unique in meeting the required performance objectives given in ITU-T Recommendation G.821. Other masks for the BERs may be used by the designer where appropriate as long as these ma
21、sks satisfy ITU-T Recommendation G.821. Examples of alternative masks are shown in Annex 1. NOTE 11 It is desirable that systems be planned on the basis of propagation data covering a period of at least four years. The performance recommended to be met for “any month” should be based on the propagat
22、ion data corresponding to the median “worst month of the year” taken from the monthly statistics of all the years for which reliable data are available. NOTE 12 The error performance described in 1 was developed based on the use of the HRDP in the “high grade” section of the hypothetical reference c
23、onnection (HRX) (see ITU-T Recommendation G.821). Other applications of the HRDP in the HRX are possible and the error performance objectives can be adjusted accordingly. NOTE 13 In order to comply with the values given in 1, for systems operating above 10 GHz, it may be advantageous to make use of
24、fade countermeasures strategies and techniques for which basic guidance is provided in Recommendation ITU-R S.1061. NOTE 14 A method of measuring BERs against percentage of time is given in Annex 1. Annex 1 Characteristics of a fixed-satellite service hypothetical reference digital path forming part
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