1、 Report ITU-R M.2201(11/2010)Utilization of the 495-505 kHz band by the maritime mobile service for the digital broadcasting of safety and security related information from shore-to-shipsM SeriesMobile, radiodetermination, amateurand related satellites servicesii Rep. ITU-R M.2201 Foreword The role
2、of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopt
3、ed. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent P
4、olicy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Polic
5、y for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Reports (Also available online at http:/www.itu.int/publ/R-REP/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service
6、 (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordinatio
7、n between fixed-satellite and fixed service systems SM Spectrum management Note: This ITU-R Report was approved in English by the Study Group under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2011 ITU 2011 All rights reserved. No part of this publication may be repro
8、duced, by any means whatsoever, without written permission of ITU. Rep. ITU-R M.2201 1 REPORT ITU-R M.2201 Utilization of the 495-505 kHz band by the maritime mobile service for the digital broadcasting of safety and security related information from shore-to-ships1(2010) TABLE OF CONTENTS Page 1 Ba
9、ckground information . 2 2 Identification of the usable band 3 3 Overview of the system 3 4 Specifications for the 500 kHz coastal transmitters . 4 5 Local transmitters . 4 6 Network 4 7 Type of messages . 5 8 Type of information broadcasts 6 9 Encryption 6 10 Description of a coastal transmitting s
10、tation 6 11 Equipment for ship . 7 12 Protection for broadcasting of NAVTEX on 490 kHz and 518 kHz 8 12.1 Transmitter emissions mask . 9 13 Selection of 64-QAM modulation parameters 9 13.1 Differential coding and mapping 10 13.2 Filter roll-off factor . 11 13.3 Bit error rate versus signal-to-noise
11、ratio for 64-QAM 12 1This Report should be brought to the attention of the International Maritime Organization (IMO) (NAV Sub-Committee and COMSAR Sub-Committee (International NAVTEX Coordinating Panel), the International Electrotechnical Commission (IEC), International Association of Marine Aids to
12、 Navigation and Lighthouse Authorities (IALA), the World Meteorological Organization (WMO), the International Hydrographic Organization (IHO), and the Comit International Radio-Maritime (CIRM). 2 Rep. ITU-R M.2201 Page 14 Candidate 500 kHz digital broadcast antennas . 12 14.1 Practical vertical-towe
13、r antennas 12 14.2 Potentially available antenna assets from retiring legacy systems . 14 15 Determination of the coverage range for the broadcast data service 15 15.1 Radio-frequency propagation and noise . 15 15.2 Determination of the range achieved using NAVTEX operation . 18 15.3 Prediction of A
14、2 and NAVTEX ranges (IMO performance criteria) . 19 15.4 C/N required for NAVTEX broadcasts . 20 15.5 Prediction of 64-QAM broadcast transmission range 20 15.6 Ship receiver performance specifications . 20 16 Field tests 21 16.1 Generalities . 21 16.2 Transmitting shore station 21 16.3 Broadcast emi
15、ssions 21 16.4 Reception by the test ship station . 22 16.5 Results . 23 17 Conclusions 25 1 Background information This Report describes a technical approach allowing the reuse of the 500 kHz band for digital broadcasting of maritime safety and security related information for the benefit of ships
16、at sea. Systems based on this technical approach can coexist with the worldwide NAVTEX system that operates on 490 kHz, 518 kHz, and in some cases 424 kHz. The system will provide an improved means for an automated broadcast. It will coexist with existing services (NAVTEX, satellite, MF, HF, VHF). S
17、ince the early 1900s, the frequency 500 kHz had been the international maritime calling and distress frequency. It was used in telegraphy mode for distress and safety communications for ships at sea. This functionality has been replaced by the Global Maritime Distress and Safety System (GMDSS). The
18、International Maritime Organizations (IMO) Convention for the Safety of Life at Sea (SOLAS) required certain ships to be equipped with GMDSS equipment since 1999. Since the adoption of GMDSS, the band 495-505 kHz has no longer been globally used for maritime calling and distress and the designation
19、of this band for calling and distress was suppressed at WRC-07. In accordance with provision RR Edition of 2008 Nos. 5.79 and 5.82A, maritime mobile operations are presently limited to radiotelegraphy. Accordingly, use of the band has diminished. Rep. ITU-R M.2201 3 This frequency band 415 kHz to 52
20、6.5 kHz is ideally suited to broadcast from shore to ship. The surface wave propagation of a coast station using this band can provide a coverage area from the coast to 400 nautical miles (741 km) off shore. This is the same coverage area that the current NAVTEX system provides at 490 kHz, 518 kHz a
21、nd in some cases 424 kHz. 2 Identification of the usable band The band 415 kHz to 526.5 kHz is accessible for the maritime mobile service; however, some sharing conditions apply. The band 495 kHz to 505 kHz is an excellent candidate for introduction of new technology to the maritime mobile service.
22、It is ideally suited for this purpose due to: its ground-wave propagation characteristics; the current frequency bands of NAVTEX transmissions; the under-utilization of 495-505 kHz due to the cessation of the 500 kHz distress frequency requirement with the adoption of GMDSS. 3 Overview of the system
23、 This system may operate in one of two modes, a mode similar to the current NAVTEX system, which is a “sequential mode” based on timing, or possibly a “permanent mode” on another basis. The coast stations will be spaced along the coast approximately 500 nautical miles (926 km) apart. In the “sequent
24、ial mode”, all the transmitters on a coast will share the 10 kHz channel by transmitting in a specific time slot. Some time slots will remain free for unforeseen broadcasts. Table 1 is an example of time slot allocations for a network of 500 kHz broadcast transmitters for the Atlantic coast of Europ
25、e. It is based on 3-minute slots of a 60-minute cycle. The current NAVTEX system has a data rate of 100 bit/s with a 300 Hz channel. This system would have a data rate of up to 47 400 bit/s with a 10 kHz channel. TABLE 1 Example of allocations of 500 kHz broadcast transmitters for the West Atlantic
26、(Base: 60 min) Stations T0 T1 +3 T2 +6 T3 +9 T4 +12 T5 +15 T6+18T7+21T8+24T9+27T10+30T11+33T12+36T13+39T14 +42 T15 +45 T16 +48 T17+51T18+54T19+57Niton (UK) X X Corsen (France) X X Monsanto (Lisbon, Portugal) X X W X X X X X Y X X Z X X 4 Rep. ITU-R M.2201 4 Specifications for the 500 kHz coastal tra
27、nsmitters The radiated power from the regional coast station transmitter should be what is sufficient to cover the intended service area of that coast station. The power would be decreased at night during periods of better RF propagation. A conservative estimate of the coverage area from shore is ap
28、proximately 320 nautical miles (593 km) with a radiated power of 1 kW and 400 nautical miles (741 km) with a radiated power of 5 kW. The modulation is OFDM with N-QAM. Section 13 illustrates an example of 64-QAM 47.4 kbit/s that is capable of reaching 400 nautical miles (741 km) with an appropriate
29、antenna effecctive height and a sufficient transmitter power. Where antenna effective height and/or transmitter power are limited, 16-QAM is preferrable. This type of modulation, OFDM with N-QAM, works very well in DRM system (sound broadcasting). The modulation scheme is similar to that described i
30、n Recommendation ITU-R M.1798-1, Annex 4, which uses both 16-QAM and 64-QAM. 16-QAM has the advantage of 6 dB more energy per bit, and therefore it is more robust and more commonly used in radio systems with power and antenna effective height limitations, but it has only half the data-rate of 64-QAM
31、. 5 Local transmitters Local transmitters can be used to fill in coverage gaps if needed, especially in significant harbour areas. Local transmitters would have simplified antenna systems and less radiated power then the regional coast stations. An example implementation of this was used for field t
32、ests described in 15. 6 Network The static allocation of the broadcasting slots allows the installation of a simplified broadcasting network (refer to Fig. 1). Each national authority would have a certain number of coastal stations connected to a standard Ethernet virtual private network (VPN) contr
33、olled by the national authority. It is not essential to establish a national server because each station will collect on the VPN network the messages meant for them and will broadcast them within the timing of the allocated slot. The exchange of files among various countries for broadcasting by tran
34、smitters outside their national boundary is feasible. It would be managed by an identified national coordination centre, as used currently for some automatic identification system (AIS) and GMDSS networks. Rep. ITU-R M.2201 5 FIGURE 1 National digital 500 kHz network 7 Type of messages It is appropr
35、iate that any emission of messages is controlled perfectly and from a secure originating source. Several possible origins: safety of navigation messages; meteorological messages; safety and security messages; search and rescue information and pirate attack warnings; pilotage service messages; harbou
36、r messages; file transfer, e.g.: harbour VTS display; cartographic update. 6 Rep. ITU-R M.2201 8 Type of information broadcasts Three types of broadcast messages are included: General broadcast These messages are broadcast for the attention of all ships. Selective broadcast These messages are broadc
37、ast for the attention of the ships located in a given area. Dedicated messages These messages are addressed to one or more specific ships. 9 Encryption It is completely possible to envisage the encryption of certain files transmitted in agreement with the administration concerned and with evolutiona
38、ry keys. 10 Description of a coastal transmitting station A coastal transmitting station would consist of (refer to Fig. 2): 1 local server connected to a protected VPN network; 1 modulator coder charged to transpose the files in modulation OFDM/N-QAM on frequency 500 kHz; 1 RF power amplifier with
39、its power supply and filtering; 1 antenna matching unit; 1 transmitting antenna with ground radials; 1 GPS antenna with clock output for the synchronization of slots and frequencies; 1 monitoring receiver in order to check that the frequency is free. Rep. ITU-R M.2201 7 FIGURE 2 Coastal transmitting
40、 station 11 Equipment for ship This equipment would be like a “black box” which can be connected on the existing on-board equipment or a dedicated display (computer) as shown in Fig. 3. The 500 kHz receiver would be connected to a 500 kHz magnetic receiving antenna of very small dimension and to an
41、existing GPS receiver for the selection of messages according to the position of the ship. Its consumption in energy would be about 10 W. 8 Rep. ITU-R M.2201 FIGURE 3 Synoptic 500 kHz reception ship station 12 Protection for broadcasting of NAVTEX on 490 kHz and 518 kHz NAVTEX transmitter emissions
42、are narrow-band at 490 kHz and 518 kHz using a modulating centre frequency of 1 700 Hz and a deviation of 85 Hz. The bandwidth of the receivers is about 300 Hz. The 500 kHz transmitter notional emission mask must be fitted to protect the NAVTEX transmissions as shown in Fig. 4. FIGURE 4 Notional emi
43、ssion mask Rep. ITU-R M.2201 9 12.1 Transmitter emissions mask For transmitters designed to operate on this 10 kHz channel, any emission must be attenuated below the peak envelope power (P) of the transmitter as follows (refer to Fig. 5): 1. On any frequency from the centre of the authorized bandwid
44、th f0 to 4.5 kHz removed from f0 : 0 dB. 2. On any frequency removed from the centre of the authorized bandwidth by a displacement frequency (fd in kHz) of more than 4.5 kHz but no more than 10 kHz: at least 5.82(fd 2.30 kHz) dB. 3. On any frequency removed from the centre of the authorized bandwidt
45、h by a displacement frequency (fd in kHz) of more than 10 kHz: at least 50 + 10 log (P) dB or 70 dB, whichever is the lesser attenuation. FIGURE 5 10 kHz channel emissions mask (N-QAM modulation) 13 Selection of 64-QAM modulation parameters For the prospective 495 kHz to 505 kHz digital broadcast ch
46、annel, a 64-QAM modulation at 47.4 kbit/s would meet these requirements and would fit the transmitter emissions mask in 12.1. 64-QAM modulation is customarily used in high-performance digital RF systems to provide a maximum data transmission rate in a limited channel bandwidth. The characteristics i
47、n Table 2 are taken from the high data-rate ISDB (Integrated Services Digital Broadcasting) standard for 64-QAM modulation. These characteristics were scaled in Table 3 to fit the 10 kHz channel mask. 10 Rep. ITU-R M.2201 TABLE 2 High data-rate ISDB (Integrated Services Digital Broadcasting) standar
48、d for 64-QAM transmission Specification of 64-QAM transmission system Input signal MPEG2-TS packets Frame synchronization Sync byte inversion for every 8 packets Randomization PRBS (polynomial 1 + X14 + X15) FEC Reed-Solomon (204,188)Interleave Byte unit convolutional (depth: 12) Modulation 64-QAM M
49、apping Given in Fig. 6 Roll-off 13% as shown in Fig. 7 Bandwidth 6 MHz Symbol rate 5.274 M baud Transmission rate 31.644 Mbit/s Information rate 29.162 Mbit/s TABLE 3 ISDB standard scaled for 64-QAM transmission in a 10 kHz channel Specification of 64-QAM transmission system Input signal MPEG2-TS packets Frame synchronization Sync byte inversion for every 8 packets Randomization PRBS (polynomial 1 + X14 + X15) FEC Reed-Solomon (204,188)Interleave Byte unit
