E SUB-COMMITTEE ON NAVIGATION, COMMUNICATIONS AND SEARCH AND RESCUE 5th session Agenda item 12 12 December 2017 ENGLISH ONLY RESPONSE TO MATTERS RELATED TO THE RADIOCOMMUNICATION ITU R STUDY GROUP AND ITU WORLD RADIOCOMMUNICATION CONFERENCE Prediction of NAVDAT coverage and related tests Submitted by China SUMMARY Executive summary: This document provides calculation and test of field strength and external noise factor, the prediction results of NAVDAT coverage, and considerations for technology optimization Strategic direction: SD 2 High-level action: Output: 2.1 Action to be taken: Paragraph 13 Related documents: NCSR 2/INF.4 and NCSR 4/INF.11 Background 1 The 495-505 khz frequency band has been used for maritime mobile service again since the revision and adoption of the Radio regulations in the World Radiocommunication Conference 2012 (WRC-2012). In the same year, ITU-R released the Recommendation ITU R M.2010 Characteristics of a digital system, named Navigational Data (NAVDAT) for broadcasting maritime safety and security related information from shore-to-ship in the 500 khz band. 2 NAVDAT is a new shore-based digital broadcasting system based on advanced digital communication technology, for propagating maritime safety information (MSI) and other related information in the 500 khz band. It can enhance the propagation capability of maritime safety-related information.
Page 2 3 The broadcasting range is an important performance parameter of the NAVDAT system. The researches on NAVDAT ranges are mainly included in 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-ships and NCSR 4/INF.11 Evaluation of the coverage of NAVDAT submitted by Japan. Calculation and test of field strength and external noise factor 4 The year 2016 saw the starting of NAVDAT test system in China, which consists of a SIM (System of Information and Management), a shore transmitter, several ship receivers and remote monitoring receivers. The system is deployed in Shanghai, Zhoushan and on patrol vessels, as shown in annex 1. In 2016 and 2017, a large number of experiments were carried out, with statistics and analysis of received signal strength indication (RSSI), signal to noise ratio (SNR), frame error rate (FER), and calculation of field strength. Locating farthest from the coastline among all the stations and 62 nautical miles away from the shore transmitter, the Huaniao Island monitoring station is surrounded by sea and similar in environment to that of ships. Therefore, the data from it can be regarded as typical sample for analysis. 5 According to Recommendation ITU-R P.368-9, the field strength and transmission loss of Huaniao Island, calculated by ITU GRWAVE, are 67.39 db(μv/m) and 68.48 db. Detailed calculation is shown in annex 2 6 According to Recommendation ITU-R P.372-13, the external noise factor (F a) of Huaniao Island, calculated by ITU NOSEDAT, ranges from 89.6 to 107.4 db, and varies with seasons and diurnals. 7 Long term record data shows the average field strength from Huaniao Island monitoring station is 62.11 db(μv/m), which is close to the calculated value, considering the antenna efficiency and transmission loss. Figure 1 shows the average statistical data of the signal field strength and the SNR of Huaniao Island monitoring station from April to July 2017. 70.00 60.00 50.00 40.00 30.00 20.00 10.00 0.00 (db) 9 11 15 17 21 9 11 15 17 21 9 11 15 17 21 9 11 15 17 21 A P R I L M A Y J U N E J U L Y Average field strength Average SNR Figure 1: Average statistical data of the signal field strength and the SNR
Page 3 Prediction of coverage ranges 8 The broadcasting services in the MF and LF bands are mainly based on the characteristics of the ground wave propagation mode (see Recommendation ITU-R P.368-9). The limit to coverage, during daytime without interference, is determined by the intensity of radio noise and required SNR for normal operation (see Recommendation ITU R P.372-13). 9 China NAVDAT test system adopts the high-performance LDPC error correction code to reduce the SNR threshold required for signal demodulation. Based on Rayleigh fading channel, the thresholds obtained by simulation are shown in table 1. Table 1: SNR threshold required for signal demodulation (bandwidth: 10 khz) SNR (db) Modulation/code rate (BER (after error correction) = 10-5 ) 4-QAM/0.5 6.1 16-QAM/0.5 12.3 64-QAM/0.5 19.4 Note: BER means Bit Error Rate 10 According to Recommendation ITU-R P.372-13 and ITU-R P.368-9, the final results of prediction (assuming the noise characteristics of the ship environment to be -145 db) of NAVDAT coverage are shown in table 2. Area Huaniao Island, Zhoushan Copenhagen Singapore Conclusion Table 2: NAVDAT coverage (transmitting power: 1kW, bandwidth: 10 khz) Antenna Modulation F efficiency a (db) Range (NM) (code rate) 95.6 ~ 299.0 4-QAM (0.5) 25% 53.0 ~ 219.2 16-QAM (0.5) 24.7 ~ 138.0 64-QAM (0.5) 100% 25% 100% 25% 100% 89.6 ~ 107.4 87.8 ~ 99.1 91.0 ~ 113.4 154.1 ~ 380.8 4-QAM (0.5) 94.1 ~ 296.6 16-QAM (0.5) 47.4 ~ 206.0 64-QAM (0.5) 180.7 ~ 323.5 4-QAM (0.5) 115.1 ~ 242.2 16-QAM (0.5) 60.3 ~ 157.5 64-QAM (0.5) 254.6 ~ 406.3 4-QAM (0.5) 178.6~ 321.1 16-QAM (0.5) 105.2 ~ 228.6 64-QAM (0.5) 54.5 ~ 281.5 4-QAM (0.5) 28.2 ~ 203.1 16-QAM (0.5) 12.6 ~ 124.7 64-QAM (0.5) 96.4 ~ 362.5 4-QAM (0.5) 53.5 ~ 279.1 16-QAM (0.5) 25.0 ~ 190.2 64-QAM (0.5) 11 The use of LDPC code in NAVDAT system can effectively reduce the system requirements for SNR and improve the receiving performance.
Page 4 12 It is expected to optimize the NAVDAT system performance and improve transmission quality, providing the introduction of adaptive function of parameters, such as modulation and bandwidth, in the development of NAVDAT shipborne system performance standards. Action requested of the Sub-Committee 13 The Sub-Committee is invited to note the information provided. ***
Annex 1, page 1 ANNEX 1 The deployment of China NAVDAT test systems are listed and illustrated below: (a) (b) (c) SIM: Zhangjiang, Shanghai Shore transmitter: Zhoupu, Shanghai Ship receiver:.1 Patrol vessel Haixun 1668.2 Patrol vessel Haixun 167.3 Patrol vessel Haixun 1640 (d) Remote monitoring receiver:.1 Huaniao Lighthouse, Zhoushan.2 Dapeng Lighthouse, Zhoushan.3 Caohejing, Shanghai.4 Zhangjiang, Shanghai
Annex 1, page 2 Shanghai Zhangjiang, Shanghai Caohejing, Shanghai Zhoupu, Shanghai Huaniao Island Zhoushan Dapeng Island Figure 1-1: The deployment of China NAVDAT test system ***
Annex 2, page 1 ANNEX 2 Calculation of field strength and transmission loss of Huaniao Island 1 The GRWAVE is used to calculate the field strength and transmission loss. The input parameters for calculation are shown in table 2-1. σ(electrical conductivity) Table 2-1: Input parameters of GRWAVE 5 S/m ε(relative permittivity) 70 Transmitting antenna height Receiving antenna height 30 m 10 m 2 Huaniao Island monitoring station is about 62 nautical miles away from the shore transmitter in Shanghai. The calculated value of field strength and transmission loss is 67.39 db(μv/m) and 68.48 db. ***
Coverage (NM) Annex 3, page 1 ANNEX 3 Prediction of NAVDAT ranges 1 The broadcasting services in the MF and LF bands are mainly based on the characteristics of the ground wave propagation mode (see Recommendation ITU-R P.368-9). The limit to coverage, during daytime without interference, is determined by the intensity of radio noise and required SNR for normal operation (see Recommendation ITU R P.372-13). 2 According to Recommendation ITU-R P.372-13, the external noise factor (Fa) of three different latitudes (Huaniao Island, Copenhagen, Singapore) are calculated by ITU NOSEDAT. According to Recommendation ITU-R P.368-9, the values of filed strength of propagation by groundwave are calculated by ITU GRWAVE. 3 According to Recommendation ITU M.1467-1, the prediction of NAVDAT coverage range includes the following steps..1 achieving the required quality of signal;.2 determination of external noise factor Fa, for the required availability;.3 accounting for filed strength; and.4 determination of the coverage ranges. 4 Based on the above method, the relationship between coverage and Fa can be obtained, and shown in figure 3-1. By substituting the Fa into the figure, the NAVDAT ranges can therefore be predicted. 4-QAM, 0.5 16-QAM, 0.5 64-QAM, 0.5 700 600 500 400 300 200 100 0 70 80 90 100 110 120 F a (db) Figure 3-1: Range vs F a (1) Transmitting power: 1 kw, antenna efficiency: 100%, bandwidth: 10 khz
Coverage (NM) Annex 3, page 2 4-QAM, 0.5 16-QAM, 0.5 64-QAM, 0.5 600 500 400 300 200 100 0 70 80 90 100 110 120 F a (db) (2) Transmitting power: 1 kw, antenna efficiency: 25%, bandwidth: 10 khz