1、 ITU-R RECMN*SA. 1021 94 m 4855212 0523383 b79 m Rec. ITU-R SA.1021 97 RECOMMENDATION ITU-R SA. 1 O2 1 METHODOLOGY FOR DETERMINING PERFORMANCE OBJECTIVES FOR SYSTEMS IN THE EARTH EXPLORATION-SATELLITE AND METEOROLOGICAL-SATELLITE SERVICES (Question ITU-R 138/7) (1994) The ITU Radiocommunication Asse
2、mbly, considering a) that permissible levels of interference for systems operating in the Earth exploration-satellite and meteorological-satellite services should be based on performance objectives for those services; b) that the hypothetical reference system (Recommendation ITU-R SA. 1020) defines
3、several radiocommunication functions of the Earth exploration-satellite and meteorological-satellite services, each of which may have particular performance objectives; c) that, although specific systems may have performance objectives that differ from those recommended for the service, all systems
4、operating in the Earth exploration-satellite and meteorological-satellite services should accommodate interference at levels greater than or equal to the permissible levels of interference that are recommended for the service; d) meteorological-satellite services may be applied to specific systems;
5、that the methodology used to develop performance objectives for the Earth exploration-satellite and e) interference, that for remote sensors, systematic degradation of data from the same locations is a particularly severe type of recommends 1. exploration-satellite and meteorological-satellite servi
6、ces; that the methodology of Annex 1 be used for the development of performance objectives for the Earth 2. that the methodology of Annex 1 be used for the development of performance objectives for specific systems. ANNEX 1 Methodology for determining performance objectives 1. Form of performance ob
7、jectives Performance objectives should be specified for a particular function, even though the data associated with the function may be multiplexed with other data that are associated with other functions and performance objectives. In order to provide a basis for performance analyses and for deriva
8、tion of permissible levels of interference, the performance objectives should denote the threshold(s) of required signal quality (e.g. bit error ratio (BER) or signal-to-noise ratio (SIN) and associated percentage) of time or locations for which the threshold(s) should be met. Table 1 lists the form
9、 in which performance objectives typically are specified. In addition, special operating conditions associated with the performance threshold should be specified, such as minimum elevation angles, antenna standards, or the nature of the media being remotely observed (by active or passive sensors). C
10、OPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesITU-R RECMNxSA. 1021 74 4855212 0523184 505 Service function 98 Form of probability specification Type of performance threshold Percentage of time Percentage of locations Rec. ITU-R SA.102
11、1 TABLE 1 Form of performance objectives Data collection Data dissemination BER or SIN of baseband signal Y es Y es BER or SIN of baseband signai Y es no Data collection platform Passive sensing interrogation Data block error rate or SIN of baseband signal Y es Y es Percentage loss of sensitivity()
12、Yes Yes Active sensing Percentage loss of data() Yes Y es Direct data readout BER or SIN of baseband signal Y es no Recorded data acquisition BER or SIN of baseband signal Y es no (I) Performance objectives are different in the case of loss which occurs randomly and in the case of loss which is syst
13、ematic (see 0 e). 2. Steps for determining performance objectives Step I Determine the performance objectives of the ultimate users of the data. It will be necessary to consider the objectives for the accuracy, availability, resolution and reliability. For passive sensors that use the radio spectrum
14、 it is also necessary to determine the dynamic range and precision of the physical measurement which will be derived from the sensor data. This information must be transformed into the equivalent range and sensitivity of microwave temperature measurements made by the sensor. Similar objectives can
15、be formulated for other operational functions. Step 2 Define one or more representative systems which include the satellite, earth station, and as appropriate, sensors, and systems for data collection, data relay and data dissemination. The relevant transmission and operating characteristics must be
16、 considered. Step 3 Evaluate the degradation in performance of the representative system caused by intra-system factors (e.g. fading of the desired signal). Step 4 Taking intra-system degradation into account, assess the performance achievable with the representative system. Step 5 If necessary, rep
17、eat steps 2, 3 and 4 until either the performance objectives determined in step 1 are satisfied or the performance objectives are modified to be harmonized with achievable performance when intra-system degradation is taken into account. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services
