RECOMMENDATION ITU-R M.2092-0, Technical characteristics for a VHF data exchange system in the VHF maritime mobile band (2015) Scope This Recommendation provides the technical characteristics of a VHF data exchange system (VDES) which integrates the functions of VHF data exchange (VDE), application specific messages (ASM) and the automatic identification system (AIS) in the VHF maritime mobile band (156.025-162.025 MHz). Keywords Maritime, VHF, VDES, ASM, data, exchange Glossary 3GPP generation partnership project ACK Acknowledgement ADDC Assigned data transfer ACPR Adjacent channel power ratio AIS Automatic identification system AOS Acquisition-of-signal APSK Amplitude phase shift keying ARQ Automatic repeat request ARSC Announcement response channel ASC Announcement signalling channel ASM Application-specific messages AWGN Additive white Gaussian noise BBSC Bulletin signalling channel BCH Bose Chaudhuri Hocquenghem, an error-correcting-code BER Bit error rate BPSK Binary phase shift keying BT Bandwidth-time CEPT European conference of postal and telecommunications administrations CDMA Code division multiple access CG Coding gain CIR Carrier to interference ratio C/M Carrier to multipath CNR Carrier to noise ratio COMSTATE Communication state CPM Continuous modulation CQI Channel quality indicator CR Code rate
TABLE A4-15 (end) Name Description Total size (bytes) Repeat interval (frames) Comment Validity of this version Lifetime of this version in number of 1 minute frames. 16 bits used. 4 1 Future satellite status change Packet providing information about planned future status change. From Julian day of year start, frame no, today and frame, new status. 13 1 Back-up bulletin board frequency Channel number above 156 MHz, 25 kHz resolution 3 1 Satellite protocol capability Index showing which protocols are supported by this satellite 3 1 Downlink channel configuration Packet providing centre frequency, slot, format no, logical channel number 6 1 8 bits are used for slots corresponding to actual slot number/10. A frame may contain multiple announcement channels to reduce protocol latency Downlink data channel configuration Packet providing centre frequency, start slot , format no, logical channel number 6 1 A frame may contain multiple data channels Uplink random access/signalling channel configuration Packet providing centre frequency, slot , format no, logical channel number 6 1 A may contain multiple uplink signalling channels to reduce protocol latency Uplink demand assign channel configuration Packet providing centre frequency, start slot , format no, logical channel number 6 1 A frame may contain multiple data channels This satellite ephemeris Packet containing the ephemeris, validity 25 Flexible GPS almanac format may be used. satellite ephemeris Packet containing network ID, satellite ID, status , ephemeris, validity 46 Flexible GPS almanac format may be used.
8.2.4 Realistic receiving antenna Four different antennas are considered: − The 0 dBd point in the Recommendation ITU-R F.1336 antenna pattern and vertical polarization (antenna 1) − A 1.25 λ vertical antenna (commercially available antenna, computed pattern when mounted on the top of the bridge a 200 m long tanker), vertical polarization (antenna 2) − A satellite dedicated Turnstile antenna, with right hand circular polarization (RHCP) (antenna 3) − A hemispherical 0 dBi gain antenna, vertical polarization (antenna 4). Using professional software tools for satellite communications, simulations have been carried out to determine the carrier power level at the receiver input and to determine the Eb/N0 in the following cases: − Overhead pass − Side pass − Very low pass. Results corresponding to each scenario are reported in the following sections. 8.2.4.1 Overhead satellite pass A7-22 Overhead satellite pass, carrier at receiver input A7-23 Overhead satellite pass, Eb/N0 at demodulator input 8.2.4.2 Side satellite pass Consider a 16° elevation pass, the signal power and corresponding signal quality measured in Eb/N0 are presented in the following figures. Due to the variation of the signal strength at the receiver over time (due to the change of elevation and distance), the signal may fall below the detection threshold. The use of highly robust waveform (as a combination of modulation, coding and structure) can potentially improve the performance at the expense of reduced throughput. A7-24 Carrier level at receiver input, side satellite pass