1、 Report ITU-R M.2202(11/2010)Maritime broadband wirelessmesh networksM SeriesMobile, radiodetermination, amateurand related satellites servicesii Rep. ITU-R M.2202 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequ
2、ency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocomm
3、unication 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 Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of pate
4、nt 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 Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Reports (Also a
5、vailable 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 (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satell
6、ite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management Note: This ITU-R Report was approved in Eng
7、lish 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 reproduced, by any means whatsoever, without written permission of ITU. Rep. ITU-R M.2202 1 REPORT ITU-R M.2202 Maritime br
8、oadband wireless mesh networks (2010) TABLE OF CONTENTS Page 1 Introduction 2 2 Concept of maritime mesh network and existing standards . 2 3 Feasibility of over-the-horizon wireless communication in the maritime environment 3 3.1 Propagation model 3 3.2 Reflection from nearby ships and Doppler shif
9、ts . 5 3.3 Signal variation due to boat rocking . 9 3.4 Data transmission with broadband wireless communication device 10 4 Potential frequency bands for consideration 21 5 Conclusion 21 Annex A Broadband wireless mesh networking protocols . 22 Annex B Radiocommunication range required for the formi
10、ng of a maritime mesh network . 25 Annex C Abbreviations . 29 1 Introduction Radiocommunication plays an important role in providing maritime safety and security for ships, waterways and ports. Currently, there are several maritime safety and security systems that depend heavily on radiocommunicatio
11、n. These systems include the Global Maritime Distress and Safety System (GMDSS) and automatic identification system (AIS). A common characteristic of these International Maritime Organization (IMO) mandated systems mentioned above is the low bandwidth of the wireless communication links which limit
12、information exchange rates for purposes such as the transfer of essential navigation data required to improve safety and security at sea. To improve safety at sea, IMO has proposed a concept known as e-navigation. This concept harmonizes the collection, integration, exchange, presentation and analys
13、is of maritime information onboard and ashore by electronic means to enhance berth-to-berth navigation and related services, for safety and security at sea and protection of the marine environment. A high-speed and cost- effective maritime wireless communication link is essential for the success of
14、the e-navigation concept. 2 Rep. ITU-R M.2202 In addition to the as yet undefined bandwidth requirements for e-navigation, higher demand for bandwidth is also coming from ships crews. More crew are demanding Internet access to stay connected to family and friends. Although satellite communication ca
15、n provide broadband wireless access to ships, the speed is limited and costs are quite high. This Report proposes the development of a high-speed maritime communication system using radios placed on board ships as relays to form a mesh network. The mesh network will address new bandwidth demands for
16、 ships travelling in dense traffic lanes and traffic lanes close to the shoreline. 2 Concept of maritime mesh network and existing standards Wireless technologies are widely used for terrestrial land systems providing speeds close to 1 Gbit/s in 4G cellular networks with users enabled with access in
17、 the order of tens or even several hundred Mbit/s. However, in the maritime environment, transmission speed is still in the order of several tens or several hundreds kbit/s. Due to the location of the ships at sea, using current cellular systems or wireless point-to-point systems, ships will only be
18、nefit in certain areas, such as busy ports, because base stations normally provide sufficient coverage with single hop transmission. At the present time, it is difficult to provide communication for ships beyond the cellular coverage. Mesh network technology can be used to address these nodes that a
19、re beyond the cellular coverage. Figure 1 shows the desired maritime mesh network architecture. In Fig. 1, coverage extension is achieved by forming a wireless mesh network amongst neighbouring ships, marine beacons and buoys. The mesh wireless network will be connected to the terrestrial networks v
20、ia land stations, which are placed at regular intervals along the shoreline. Each ship will carry a mesh radio that has the capability of frequency agility where frequencies can be switched to suit country-specific frequency regulations or sea conditions. FIGURE 1 Maritime mesh network Frequencies o
21、f interest for traffic lanes closer to shore could be in the GHz range whereas locations far away from land could be based on UHF or VHF bands. Multi-hop wireless network technologies have been a field of research for several decades and have been deployed for some practical applications. Currently
22、in IEEE, there are several standards that address mesh networking technology. However, application of these standards for direct use in maritime environments is not straightforward. Rep. ITU-R M.2202 3 One such mesh standard, IEEE 802.11s 1, which is a mesh network amendment to the IEEE 802.11 stand
23、ard, uses the basic carrier sense multiple access with collision avoidance (CSMA/CA) technology for channel access. It is suitable for networks with short communication ranges of up to several hundred metres, but it is not suitable for maritime mesh communication networks, which require distances of
24、 several tens of kilometres. According to analysis based on real ship traffic movement data obtained from the Maritime Port Authority of Singapore (MPA), in order to form a well-connected mesh network in a maritime environment as shown in Fig. 1, the transmission range among ships should be at least
25、 18 km. Annex B shows the details of the analysis. Therefore, the mesh networking technologies based on 802.11s are not suitable for the maritime communication environment unless some amendments are made. Another standard, IEEE 802.16, defines a mesh network standard for a wireless metropolitan acce
26、ss network (MAN). Typical communication ranges of wireless MAN may vary from a few kilometres to about 50 km. From a range standpoint, the IEEE 802.16 standard is suitable for maritime mesh networks. Existing results have shown that broadband transmission in a maritime ship-to-ship environment using
27、 IEEE 802.16e can reach 44 km with an antenna height of 16 m 2. Unlike IEEE 802.11s, the mesh technology proposed in the IEEE 802.16-2004 Standard 3 uses time-division multiple access (TDMA) as a basic channel access method at the media access control (MAC) layer. Channel time used for data transmis
28、sion is reserved before use. Both the IEEE 802.11s and 802.16 standards employ orthogonal frequency division multiple access (OFDMA) technology in the physical layer. Based on field tests and simulation studies, IEEE 802.16 was found to be a suitable technology for maritime broadband communication.
29、In Annex A, a brief introduction to the 802.16-2004 mesh technology is provided. Evaluation of mesh network technology proposed in the IEEE 802.16-2004 standards indicate that some amendments to the standard are necessary before it can be put into practical use in a maritime environment. 3 Feasibili
30、ty of over-the-horizon wireless communication in the maritime environment Deploying wireless communication systems in the maritime environment has its own challenges see 4, 5, 6. The wireless channel responses are different from that over land because of ships movements, ships properties, reflective
31、 properties of the sea surface, and the way ships are situated in a maritime environment. In the following section, some basic characteristics of broadband wireless communication systems in a maritime environment are discussed. Performance results were collected using RF test equipment as well as pr
32、ototype broadband mesh wireless devices designed to handle the observed impairments. Presented first are propagation loss measurements in the maritime environment, and illustration of the Doppler Shift caused by movement of the ship and reflections from metal bodies. Next, signal variations due to s
33、hip rocking are discussed. In these sub-sections, recommendations for improving the reception of signal are provided. Finally, some performance results on data transmission using prototype mesh broadband wireless devices are discussed and are used to validate the findings. 3.1 Propagation model In 2
34、006 and 2007, several propagation measurements in the Singapore Straits were carried out. In the set-up, a 10 dBm continuous wave (CW) signal was transmitted at 2.43 GHz using a signal generator. The output signal from the signal generator was increased to 27 dBm using an amplifier. 4 Rep. ITU-R M.2
35、202 This signal was transmitted using a vertically linearly polarized antenna, which has an omnidirectional radiation pattern. The gain of the antenna is approximately 2 dBi. The same antenna was used at the receiver. The receiver was placed on a divers boat and was mounted 7.2 m above the sea surfa
36、ce. The antenna was connected to a low noise amplifier (LNA) with 20 dB gain, and then to a spectrum analyzer. A laptop computer was connected to the spectrum analyzer to acquire peak power readings from the spectrum analyzer every second. The collected peak power data was time-stamped. A Global Pos
37、itioning System (GPS) receiver placed on the boat provided the distance from the transmitter. Distance and received signal strength were recorded and a path loss analysis was carried out by using linear regression. In one of the set-ups, the transmitter was placed on top of Bedok Light House (BLH),
38、which is 76 m tall. The light house is about a half kilometre away from the shore. The received power as a function of Tx-Rx separation distance d is written as follow: PR(d) = PR(d0) 10n log(d/d0) X(1) where: PR(d0): the average path loss at reference distance d0; n: the path loss exponent X: a zer
39、o mean log-normally distributed random variable with standard deviation . The parameters n and can be determined using linear regression of the path loss values against the log of normalized distance (d/d0) in a minimum mean square error (MMSE) manner. In the measurements, d0is 10 m and the PR(d0) i
40、s 10.5 dBm. In this measurement involving BLH, the LoS condition was dominant. In Fig. 2, the dots represent measured mean received power while the boat was making way. The normalized distance log (d/d0) includes the light house height. The curve that has peaks and nulls is the calculated received p
41、ower using two-ray model at a normalized distance of the collected data. The first ray/path is line-of-sight (LoS) signal from the transmitter to the receiver. The second ray/path is a reflected signal from the sea surface received at the receiver on the boat. FIGURE 2 Received power vs. log of norm
42、alized distance y = -20.963x - 10.5-120-110-100-90-80-70-60-50-4022.533.5log(d/d0)ReceivedPower(dBm)Rep. ITU-R M.2202 5 The sea surface at 2.43 GHz still satisfies a good conductor condition. Good conductor condition is satisfied when f 1), is conductivity, 0 and Rare permittivity and relative permi
43、ttivity, respectively. For sea water, = 5 S/m, R= 81. As long as the frequency of the signal is dA= 20hThR/. The corresponding normalized distance is 3.94 and this is beyond the distance coverage during this measurement. Single linear regression is sufficient to curve fit the data to find the expone
44、nt path loss n and the standard deviation. The exponent path loss is found to be 2.09 and the standard deviation is 6.43. From Fig. 2, it is clear that the reflected wave causes destructive interference at a certain distance causing up to 20 dB drop in signal. An ideal over-the-horizon mesh radio sh
45、ould include methods to overcome the destructive interference at the receiver. 3.2 Reflection from nearby ships and Doppler shifts FIGURE 3 Measurement location in Singapore Port To observe Doppler Shift spectrum, a transmitter was placed at “A” (land) and a spectrum analyzer was placed on the boat
46、at “B” as in Fig. 3. Point “S” in Fig. 3 is a ship in the vicinity of the test. The transmitter consists of a signal generator generating a CW signal frequency of 5.8 GHz and power level of 0 dBm. It was connected to a power amplifier with 30 dB gain. The output of the amplifier was connected to a s
47、ector antenna pointing towards the boat. Spectrum analyzer on the boat was connected to a receive antenna (both omnidirectional and sectorized were used) to observe the received spectrum. The CW spectrum received was saved in the spectrum analyzer. When the sector antenna was used, the antenna was a
48、lways pointed toward the transmitter at A. Figure 4 shows a snapshot of the received spectrum when the boat is moving away from A toward S. The omnidirectional antenna was used. The boat was moving at the speed of 5 m/s. There are two dominant peak signals received with amplitudes close to each othe
49、r. The lower frequency was the received Doppler-shifted signal from A due to the boats motion away from transmitter at A. The higher frequency was the received Doppler-shifted signal from S. S can be seen as a virtual transmitter to the boat because it reflected the signal from transmitter A. Since the boat is moving toward S, the received signal is Doppler shifted to a frequency higher than that of the transmitter. 6 Rep. ITU-R M.2202 According to the Doppler shift calculation, the difference in these two frequencies is: (2vfc)/c (2) wher
