1、STD-ITU-R RECMN M-LZIO-ENGL 1777 m 4855212 05274b5 84T Rec. ITU-R M.1230 43 1 RECOMMENDATION ITU-R M. 1230 PERFORMANCE OBJECTIVES FOR SPACE-TO-EARTH LINKS OPERATING IN THE MOBILE-SATELLITE SERVICE WITH NON-GEOSTATIONARY SATELLITES IN THE 137-138 MJh BAND (Question ITU-R 83/8) (1997) Summary The perf
2、ormance objectives for downlinks of FDMA non-geostationary-satellite orbit (GSO) mobile-satellite service (MSS) networks and spread spectrum multiple access (SSMA) non-GSO MSS networks are stipulated in this Recommendation. The Radiocommunication Assembly, considering a) methodology similar to that
3、described in Recommendation -R SA.1021; that performance objectives for mobile-satellite service (MSS) networks may be determined using a b) of actual systems that must operate in a frequency sharing environment; c) that performance objectives for these transmissions must be consistent with the asso
4、ciated functional requirements and with the performance limitations associated with the systems and frequency bands in which the requirements will be fulfilled; d) that performance objectives are a prerequisite for the determination of interference criteria; e) that two general types of modulations
5、are to be considered for non-geostationary (non-GSO) MSS operating in the 137-138 MHz band, which are: narrow-band modulation with frequency division multiple access (FDMA), and wideband modulation with direct sequence spread spectrum multiple access S-SSMA), that performance objectives for represen
6、tative systems are intended to provide guidelines for the development recommends 1 Table 1; that MSS (space-to-Earth) systems using non-GSO satellites have the performance objectives specified in 2 are the minimum levels of interference to be accepted by specific systems. that the objectives defined
7、 in Table 1 are used as a basis for deriving the permissible levels of interference that COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Servicesi Function, and earth station platform and antenna STDoITU-R RECMN M*1230-ENGL 1997 Li855212 0529L
8、ibb 78b = 432 Rec. ITU-R M.1230 Applicable elevation Minimum angles (degrees) Modulation and bandwidth TABLE 1 Data downlink to gateway (15 dBi horn antenna) Performance objectives for space-to-Earth links in the MSS in the 137-138 MHz band OQPSK 5.0 and 20 10.6 44 kHz narrow-band modulation with FD
9、MA Data downlink to subscriber terminal (O dI3i monopole antenna with a cos2 pattern) Data downlink to gateway (16 dBi antenna) BPSK 19.2 kHz narrow-band modulation with FDMA MSWDS-SSMA 885 kHz wideband modulation with DS-SSMA 5.0 and 20 5.0 and 20 10.3 3.7 Percentage of time 99 99 99 NOTE 1 - Perfo
10、rmance objectives for specific systems may differ from the objectives presented in this Recommendation. NOTE 2 - It is assumed that an availability of 99% is appropriate (short-term interference criteria is not exceeded for more than 1% of the message time). This value was deemed appropriate given t
11、he error protocol being used in proposed satellite systems, namely the use of cyclic redundancy check (CRC) codes for error detection and retransmission of erroneous data. NOTE 3 - For wideband transmissions, reception by mobile terminals is not contemplated at the moment. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services
