Kiri

Dear Sirs, The Embassy of Poland in Tallinn kindly presents the information of Gdansk University of Technology (GUT). Researchers from the Department of Computer Communications lead by prof. Jozef Wozniak has worked out a system called "The netBaltic - a heterogeneous wireless system for maritime communication". The main aim of the netBaltic project was to develop and deploy a broadband wireless communication system providing connectivity in a heterogeneous wireless mesh network environment able to meet the requirements of e-navigation services. In particular, the lack of reliable high-throughput communications is currently the major barrier in e-navigation implementations. Existing HF and VHF technologies, although offering long link ranges, are unreliable and their bandwidth is limited, while satellite communications is often too expensive, especially for smaller vessels. Networking solutions and communication systems being developed in netBaltic aim to address data transmission needs of multiple maritime activities. The most important use of the system is directly related to maritime safety and efficiency by providing the communications platform for e-navigation services, as defined by the International Maritime Organization. The concept of e-navigation includes, for example, integration of a multitude of navigational systems and aids that currently have to be separately monitored by a bridge crew, as well as making increased use of inter-ship data exchange for purposes of safety and efficiency of maritime travel. Finally, the system aims to provide broadband Internet connectivity in locations of high concentration of participating vessels (covering a wide range of vessel types, from one-man boats to ocean tankers), to be used for access to various applications and services available in modern internetworking, starting with e- mail and web-browsing and ending with direct multimedia streaming. By solving the above issues which are common for all the Baltic states we would like, with your help and involvement, to implement it in all the countries in the area. Whether by contacting us with prospective commercial entities in Estonia or by sharing the idea among public institutions that would be interested in joining the implementation phase. The attachment: scientific paper with more technical details. Contact: Mr Robert Bajko Politechnika Gdańska Centrum Transferu Wiedzy i Technologii ul. G. Narutowicza 11/12 80-233 Gdańsk tel. 58 348 63 93 e-mail: [email protected] www.ctwt.pg.edu.pl Best regards, Marek Kolański Minister-Counsellor Economic Affairs Embassy of the Republic of Poland Suur-Karja 1/Vana Turg 2, 10140 Tallinn Tel.: +372 627 8203, fax: +372 644 5221 www.msz.gov.pl www.tallinn.msz.gov.pl This message (including attachments) is the property of the Ministry of Foreign Affairs and may contain important and/or privileged information. If you are not the intended recipient or have received this message by mistake, please notify the sender immediately and delete this message. Any unauthorized copying, disclosure or distribution of the material in this message is prohibited. A heterogenous wireless system for maritime communication - the netBaltic system architecture Krzysztof Bronk, Adam Lipka, Rafal Niski, Michal Hoeft, Krzysztof Gierlowski Krzysztof Zurek Faculty of Electronics, Telecommunications and Informatics Wireless Systems and Networks Department Gdansk University of Technology National Institute of Telecommunications Gdansk, Poland Gdansk, Poland {michal.hoeft, krzysztof.gierlowski} @pg.gda.pl {K.Bronk, A.Lipka, R.Niski, K.Zurek} @itl.waw.pl Abstract- In the article, the concept of a heterogeneous architecture are described in Section V. The paper is finished wireless maritime mesh network offering transmission for e.g., e- with summary in Section VI. navigation services is presented. The constrains of existing and competitive solutions are discussed showing the need for a new II. RELATED WORKS system. The authors present detailed information about a One of the main purposes of the heterogeneous wireless netBaltic node's architecture and networking mechanisms offering different transmission capabilities and proposed for use network that will be introduced in the following part of this on different sea areas. Moreover, the results of the performed paper is to provide access to e-navigation services and by doing measurements campaigns are presented to estimate operational so - to increase safety of maritime traffic. The e-navigation ranges of the described system and its ability to meet the itself is a relatively new concept, being developed under the requirements of e-navigation services. Practical advantages of auspices of the International Maritime Organization (IMO), but presented solutions are highlighted bringing out new possibilities its importance has grown significantly over recent years, as it in e-navigation. has been a subject of numerous activities on conceptual, standardization, scientific and implementation levels. Keywords-maritime communication; wireless heterogenous system; mesh netIVork; netIVork architecture According to the definition by IMO, e-navigation is the harmonized collection, integration, exchange, presentation and analysis of marine information on board and ashore by I. INTRODUCTION electronic means to enhance berth to berth navigation and Nowadays, amount of data generated bye-navigation related services for safety and security at sea and protection of services is increasing. As a results, the need for communication the marine environment [2]. Consequently, e-navigation should availability between vessels is more and more important with not be considered as a single service or application but rather as each year - it is evident. Thus new solutions are proposed to a concept which supports and facilitates the decision-making provide effective connectivity in maritime intelligent process through maritime information management in order to: transportation systems. One of such proposition has been worked out in the netBaltic project [1], which aims to provide a • Increase safety of navigation, communication system for economically viable, wideband • Improve protection of the maritime environment and network connectivity over sea areas, as an alternative to costly coastal areas from pollution, satellite-based solutions utilized currently. • Increase the efficiency and reduce the costs of transport Currently the lack of reliable, offering high throughput and and logistics, affordable communication is the major barrier in e-navigation implementation. Existing HFNHF technologies, although they • Support search-and rescue teams, offer long link ranges, are unreliable and their bandwidth are • Provide information that might useful for the on-board very constrained. Satellite connections, very often are too crew during the decision-making processes. expensive, especially for smaller vessels. On the other hand, cellular systems are not planned for offshore usage. Moreover, The e-navigation, besides providing new functionalities and promising VDAS system is still in the very initial phase of its services, also integrates most of the already existing systems standardization and development and tools used for the navigation support, including AIS (Automatic Identification System), ECDIS (Electronic Chart The paper is organized as follows. Related works - Section Display and Information System), LRIT (Long-Range II - describes the most important navigation services and their Identification and Tracking), GMDSS (Global Maritime requirements of as well as relevant European projects in a Distress and Safety System) and others. field of maritime communications. Section III includes foundational assumptions of the netBaltic system. Results of The most important European projects that deal with the measurement campaigns performed in the netBaltic project are topic of e-navigation in recent years are/were: EfficienSea / presented in Section IV. Details of netBaltic system' s node EfficienSea2, MonaLisa / MonaLisa2 and ACCSEAS These projects were generally dedicated to the identification of the 978-1-5090-5275-2117/$31.00 ©20 17 IEEE users' needs, establishment of technical requirements and other In Table I, a list of expected daily traffics (per vessel) for measures relevant to e-navigation and most notably to the various e-navigation categories is presented. That list might development of specific e-navigation services and applications help address one of the main issues related to e-navigation, i.e. (including their verification in real environment, using the to determine what data rates are required for a given specialized test-beds). To fully comprehend the impact and application and consequently - to select the eventual range of e-navigation, it is worthwhile to cite some of the communication link capable of supporting such application. applications and concepts that were discussed, developed, implemented and tested in some ofthese projects: The emergence of concepts such as e-navigation translates into the need for fast and reliable maritime transmission • Preparation of messages with weather forecast, weather systems. The network presented in this paper can be one of the warnings and oceanographic prognosis to be presented - examples. Another one is definitely the VDES (VHF Data and updated automatically - on the vessel's navigation Exchange System) which is currently developed by several display, standardization organization including IALA (ENAV Committee) and lTD. That system, once fully operational, will • Presentation of the Maritime Safety Information (MSI) comprise four components: terrestrial, satellite, AIS and ASM on electronic navigation maps according to the (Application Specific Messages) and will support transmission mariner's preferences, of both specific maritime data (e.g. MSI), as well as general purpose data, with the useful data rates up to 200 kb/s. The TABLE I. EXPECTED DAILTY TRAFFICS FOR DIFFERENT E-NAVIG AnON expected ranges are at least 60 NM (shore-ship) and 40 NM CATEGORIES [3] (ship-ship). The system will utilize channels from the maritime VHF range; in that respect the necessary arrangements for the Transfer Navigation terrestrial component were made during the recent World Category per day per Safety Service Radiocommunication Conference WRC-15. The first "stable" site [MB] standardization document for the VDES (ITU-R M.2092 [5]) is Meteorological 0, 125 due to be published in 2017. It should be noted that using the Environmental Ice 6,5 VDES, the 65 MB of data needed for e-navigation per day (see information Hydrological 55 Table I) could be transmitted in much less than one hour, Aids to whereas in the AIS it would take over 24 hours (provided that 0,09 navigation such transmission would even be technically possible). Charts 0,006 Because of its parameters and capabilities, the VDES might Waterways Restriction on definitely become one of the components of the wireless 0,3 network described in the following parts of this article. management navigation Vessel Traffic 0,83 III. NETBALTIC SYSTEM Services Pilotage 0,1 The real challenge, taken up in the netBaltic project is that SBAS SBAS 2,6 its research is focused on solutions located on higher layers of Search and the TCP/IP architecture. The designed mechanisms create an 0,09 Rescue architecture integrating different wireless broadband Emergency technologies. The system utilizes a concept of dynamical Environmental 0,09 dividing its operational region into three zones, presented in response Total ~65 , 6 Fig. I, where different roles of network organization and SBAS - Satellite Based AugmentatIOn System different communication mechanisms are employed. • "route exchange" services - where ships in a given area The first one (zone A), spread out along a coast, requires are able to exchange their intended routes with one mobility management mechanisms handling vessels' another and with the shore authorities, movements, to offer uninterrupted connectivity across a set of different wireless techniques. It is one-hop communication • "route suggestion" services - where shore users (e.g. using popular wireless technologies (like WiMAX, LTE, Wi- VTS centers) are able to send route suggestions directly Fi) or systems dedicated to maritime usage (e.g. RADWIN to the vessel's navigation display with an option that the Fiber-in-Motion). mariner may accept or reject that suggestion, In the range of the second area - zone B, nodes form a • Search and rescue (SAR) support - e.g. by means of heterogeneous, self-organizing mesh network, used to provide enhanced calculation of the searching patterns and their connectivity in both ship-to-ship and ship-to-shore scenarios. distribution among SAR vessels. Additional information from the AIS system will be used to provide increased efficiency and reliability of the proposed • The concept of Maritime Cloud - a communication routing mechanisms, by giving the system an ability to predict framework which enables seamless and robust exchange ongoing changes in mesh network structure [6]. of data between various maritime entities usmg available communication systems (see e.g. [3]) 2  this way are significantly shorter than those obtained using the I\ .-! . \,' \ spectrum analyzer. The observed data rates obviously AREA A depended on the network type: in case of the LTE the maximum transmission speed in the downlink was around 20 Mb/s, whereas in the uplink it didn 't exceed 10 Mb/s. For UMTS (HSP A) the rates were significantly slower: maximum /" ! 6 Mb/s in downlink and 3 Mb/s in the reverse direction. -1- Nonetheless, both the ranges and data rates can be considered ;J ~) ='~ AREA B ...-. "'" / I ~! as satisfactory in the maritime condition, therefore, cellular network is definitely the major technology to be used in the zone A of the target heterogeneous network developed in the netBaltic project. TABLE II. RANG ES OF LTE AN D UMTS SY STEMS IN MARITIME CONDITIONS Fig. I. Communication areas of the netBaltic system LTE LTE UMTS UMTS 800 1800 900 2100 The last one (zone C) is dedicated to nodes located far The range obtained away from the rest of vessels, and as a result, being able to using the spectrum 40-50 20-30 50-60 30-40 establish connections only very occasionally. The group of analyzer [km] mechanisms needed in this area utilizes a concept of a The range obtained dedicated, delay-tolerant network system [7]. using the 3G/LTE 40 40 20 25 modem [km] IV. MEASUREMENT OF WIRELESS SYSTEMS IN MARITIME CONDITIONS The measurements ofWiFi networks operating in both 2,45 One of the main tasks that determines the actual shape of GHz and 5 GHz bands took place on 22 March and 26 April the developed heterogeneous system is to establish the ranges 2016. Since WiFi is considered a main technology to be used in and data rates of the wireless technologies that will be utilized the zone B, the entire measurements were conducted in ship-to- in the proposed system. To do so, several measurement ship scenarios Consequently, in this case two vessels had to be campaigns were organized in 2015-2016 on the Baltic Sea employed: one of them served as a source of the WiFi signal (mainly in the Bay of Gdansk). The preselected wireless data and the other acted as a receiver and carried the entire transmission systems subjected to that analysis included: measurement equipment. During the campaign, two types of 3G/4G cellular systems (UMTS and LTE) for the zone A antennas were used: an omnidirectional one and a sector one (where the ships communicate via the shore infrastructure) and (90° beamwidth in a horizontal plane and 12°/6° in a vertical WiFi/WiMAX for the zone B (where the communication is plane for 2,45 GHz and 5 GHz respectively); as it turned out, organized on a ship-to-ship basis). In this section, a short the selection of the antenna strongly influenced the summary of the measurement results will be provided. performance ofthe WiFi in maritime environment. The measurements of the cellular systems were conducted The observed ranges of WiFi are shown in Table III. in September 2015 during a lO-day campaign which covered a Clearly, even despite using a high-gain directional antennas at sea route of almost 1200 km; during the entire campaign, the transmitting and receiving sides, the range of the WiFi roughly 80000 measurement points were obtained. The systems 5GHz is substantially shorter than that of WiFi 2,45 GHz. On under analysis were: LTE in the bands 800 and 1800 MHz and the other hand, the WiFi 5 GHz had an advantage over WiFi UMTS in the bands 900 and 2100 MHz. 2,45 GHz in terms of the achievable data rates (46 Mb/s vs. 36 Generally two types of measurements sets were utilized: Mb/s). Generally, however, after considering the entire WiFi one was dedicated exclusively for the range analysis (it was campaign, the WiFi network operating in the 5 GHz band based on a spectrum analyzer), whereas the purpose of the cannot be recommended for the target heterogeneous network second one was the measurement of quality parameters of the developed in the netBaltic project. In order to achieve systems, including the achievable data rates (this set was based satisfactory rates in that network, directional, high-gain on an LTE/3G modem, so that the actual data transmission antennas need to be employed. Unfortunately, at 5 GHz such could be established and the measurements were performed in antennas will always be characterized by a very narrow compliance with [8, 9, 10]). The second measurement set could bandwidth (merely 6° in case of the campaign described here), be to estimate the ranges of the systems as well . which might prove very problematic in maritime conditions. When sea is rough, it will be very difficult for the transmitter's In Table II, the ranges of the analyzed systems have been and receiver' s beams to match and as a result, the transmission presented. As we can observe, there is a slight discrepancy will likely be interrupted. The influence of such connectivity between the results obtained using the two different gaps on transmission is discussed in the next subsection .. measurement sets, which is caused by the fact that the LTE was During the measurements it was also observed that when preferred by the automatic network selection algorithm of the directional antennas were employed at 5 GHz, the ships could 3G/LTE modem. Consequently, the UMTS ranges measured 3 only establish communication when they were a few krn apart; directional antennas (HMS2). The detailed architecture of the when ships were close to one another, the narrow beamwidth test-bed elements is presented in Fig. 2 made any kind of useful transmission impossible. The base station of the wireless system was located close to The above issue is much less of a problem for the WiFi at the Baltic Sea shore (on Sobieszewo Island) on the tower at the 2,45 GHz, where beamwidth may be significantly wider. As a height of 45m.Mobile terminals were mounted on the vessel result - and given the satisfactory ranges and data rates bow. Since small vessels are more sensitive to sea waving, a observed in such a network - the WiFi 2,45 GHz can definitely nine-meter long yacht was used in the measurement campaign. be recommended for the ship-ship communication at sea. Dedicated applications have been developed to observeand The measurements of WiMAX, i.e. another technology store values of signal parameters of wireless links (e.g. RSSI) considered to be used in zone B took place on 22, 24 June and and details of connectivity periods at the network layer 12 July 2016. The base station was located on one of the between terminals. For this purpose uplink and downlink UDP buildings in Gdynia (90 m a.s.l), whereas the measurement streams have been generated between nodes. All traffic on both equipment was installed on a rigid inflatable boat "Sonda II. terminals has been captured and stored. The datasets prepared All the measurements were carried out in a 10 MHz-channel in in this way make it possible to analyze connection gaps periods the 3,7 GHz WiMAX band. both at the wireless data-link layer and at the network layer. M a.... g.. men\ lInk. TABLE III. RANGES OF WIFI NETWORKS IN MARITIME CONDITIONS WiFi 2,45 GHz WiFi 5 GHz S-S I S-O S-S I S-O Range [km] 6 I 3,5 2,1 I 0,6 S-S: sector antennas in the transmitter and receiver S-O: sector antenna in the transmitter, omnidirectional antenna in the receiver Fig. 2. Test-bed architecture Collected data show that regardless of the antenna setting During the measurements, the signal power exceeded the used in the tests, connection interruptions at the wireless data- reference sensitivity at the distance of up to 6 krn from the base link layer follow similar distributions. As RADWIN Fiber-in- station, so that distance might be considered a theoretical range Motion uses time slots assignments for end-users of the WiMAX system. It has to be noted, though, the actual transmissions, its terminals have to be synchronized with the ranges varied depending on the boat's direction (whether it base station. This procedure in the maritime environment took approached the SB or moved away from it). The maximum about 4.5-5s, and as it can be seen in Fig. 3 (black and green data rates did not exceed 1,9 Mb/s in the uplink and 8,7 Mb/s lines), shorter connectivity gaps did not practically occur. in the downlink (similar values to those observed in UMTS but much worse than in LTE). To verify the accuracy of the probability density function estimation, in Fig. 3., there are presented empirical cumulative Generally, WIMAX in the selected configuration does not distribution functions of connectivity periods and connectivity satisfy the requirements for the heterogeneous netBaltic gaps for measured data (solid lines) and random samples network. The actual time needed to establish connection with (dashed lines) generated in accordance with estimated the BS in some case was greater than one minute and even if probability density functions using KDE method (4). the connection was established, it was rather unstable with frequent interruptions. The observed WiMAX range is rather short (shorter than e.g. in 3G networks). Given the above, the performance of this particular technology has to be rated as unsatisfactory and therefore it will not be utilized in the target network. A. Vessel motion impact on maritime connections A verification of the impact of vessels motions on performance of wireless maritime communications has been conducted in other measurements. As RADWIN Fiber-in- Motion is successfully deployed in maritime communications - measurements HMSI connenctivy systems over the world e.g. by cost-guards or search and rescue - - measurements HMS2 connenctivy measurements HMSI ga ps groups, this system (a part of Laboratory of Mobile Wireless 0 '-=L----oo--~--'= 0.0"" -~,,~m.~"~""~m.~"t:::o:'H~ M5~'~9's.P'=='J Technologies at Gdansk University of Technology [11]) has tlme( s] been chosen as a wireless technique. Fig. 3. Empirical cumulative distribution function for measurement data The experiments purpose was the evaluation of two types (solid lines) and data generated based on estimated probability density of terminals used with directional (HMSl) and omni- function (dashed lines) 4  Of the control plane mechanisms, the most universally employed one is a Link Quality Evaluation Module (LQEM). It is responsible for collecting link quality-related data from each wireless interface available to the node, and using it to calculate a metric, named Link Quality Indicator (LQI), allowing the node to estimate a data-transmission rate of a given link. As many of the necessary parameters must be obtained from a specific implementation of a given wireless transmission technology, various data gathering mechanisms (e.g. SNMP, AT commends) must be supported. Another group of data-link layer communication link's parameters (such as connectivity gaps periods) do not depend on a particular wireless technique, and can be directly measured by the netBaltic node's internal mechanisms. To provide a high level Fig. 4. Estimation of probability density function of compatibility with varied transmission technologies and transparency of their usage, the node is able to roughly estimate V. NETBALTIC NODE'S ARCHITECTURE the LQI using only internal measurement techniques, but it is vastly preferred to utilize some level of integration between To integrate the mechanisms required by the three different internal node mechanisms and the transmission technology network communication approaches utilized by the netBaltic employed in the process of link quality estimation. system: a mobility-aware point-to-multipoint access network, a self-organizing mesh network and a delay tolerant network Link Quality Indicator is also a metric used in a decision (DTN) - a node architecture presented in Fig. 5 has been making phase of the mobility management solution proposed. implemented in the netBaltic system. The wireless link providing the best connection parameters (the highest value of LQI) is chosen as based interface and used for on-going connections. In this case, the advanced mobility management CONTROL PLANE DATA PLANE mechanisms are used to provide uninterrupted communication at the network layer with IPv6 protocol ([12]). c=::J Legacy functionalities Remaining control plane modules are employed mainly by c=::J netBaltic functionalities self-organizing mesh mechanisms, however, DTN mechanisms also utilize some of the information provided by them. DTN Applications Classical Applications A Neighbor Discovery Module (NDM) provides the node Classical Transport Protocols with an ability to detect other neighboring nodes of the system DTN Transport Layer (TCP/UDP/SCTP) and advertise its presence to them in tum, allowing creation of Path Discovery Module single-hop direct communication links. Such links are created IPv6 forwarding in the network layer, using IPv6 protocol, allowing them to Q) utilize any IPv6-compatible communication system. To other _ :; 0 Secure Communication Module mechanisms of the node, they are presented as virtual network >"0 2 ~~ Cl Z Transmission Efficiency Module interfaces. o:J 0+=i0C Local Connectivity Module ~ c ro Over a structure of such links, a Path Discovery Module ::;~ ro Data-Link Layer (PDM) performs multihop mesh path discovery procedures, ~ Physical Interfaces utilizing a hybrid solution, which combines a proactive and reactive path discovery. For communication with external networks (for example the Internet) a proactive approach is Fig. 5. Networking stack of netBaltic node used, constantly providing each of network nodes with a proactively maintained set of possible network gateways to be While designing the abovementioned architecture, a special used for that purpose. In case of communication between nodes care has been taken to utilize already present, well-tested and within the mesh, a reactive procedure is used to obtain a stable network mechanisms, such as IPv6 forwarding and allow current transmission path only when it is required, preventing a transparent use of different data-link layer solutions, without an excessive management traffic from being generated. In both a need to modify the node's mechanisms in any significant cases, the already mentioned LQI link metric is used to select way. the path providing the most efficient transmission capabilities. The architecture depicted in 5 presents both control plane The described PDM procedures result in creation of (composed exclusively of netBaltic-specific functional appropriate entries in a standard IPv6 forwarding table and thus modules) and data plane, which includes a number of a classic IPv6 packet forwarding mechanisms can be employed standardized solutions integrated with and supplemented by to forward IPv6 data packets between virtual interfaces original mechanisms developed to allow the node to operate representing communication links between different system efficiently in its intended, multi-zone, maritime environment. nodes. 5  Apart from the above control plane mechanisms, a number utilizes the DA address, while the second requires the use of of data plane solutions is required for the netBaltic node to MDA. efficiently operate in its intended deployment environment - The most straightforward solutions satisfying the above they are indicated in Fig. 5 using blue color. addressing requirements would be to use a triple IPv6-IPv6 One of the most important of such mechanisms involves tunneling by employing 3 complete IPv6 packet headers at an addressing information required for an IPv6 packet to be inter-node link level. As such a packet would be received by a forwarded through the mesh network to its destination. As destination node, the outer (TAIRA) header would be used by a indicated before, the netBaltic node utilizes a standard IPv6 node to verify if it is a destination of the packet and should forwarding mechanisms, which, in turn expect a standard IPv6 process it further. If so, the outer header would be stripped and header (containing a pair ofIPv6 addresses) to be present at a the packet would be delivered to IPv6 forwarding mechanisms beginning of a network packet. However, if we analyze our in with IPv6 header containing MSAlMDA addresses as its addressing requirements, it quickly becomes clear that a single outer of its 2 remaining IPv6 headers. This would allow the pair of addresses is not enough to allow a data packet to be packet to be forwarded correctly within the netBaltic mesh forwarded through netBaltic system and to a destination in an structure by standard IPv6 forwarding mechanisms external network. appropriately configured by netBaltic-specific control plane mechanisms (PDM). When the forwarding decision would be Due to the fact that inter-node links are implemented in the made in the node, the packet would be sent using one of the network layer and that we can expect to use multiple-access available virtual interfaces, causing a new TAIRA header transmission technologies, each packet leaving a physical (appropriate to the inter-node link being used) to be added to interface must contain an IPv6 address of this interface as a the packet for the duration of its transmission over a next hop source address and an IPv6 address assigned to a physical on the mesh data path. interface of a destination node as its destination address. For this purpose, we are going to employ automatically assigned When the packet would reach the intended gateway node, IPv6 link-local addresses and name them Transmitter Address as specified by its originator in the MDA address, the standard (T A) and Receiver Address (RA), respectively. IPv6 forwarding mechanisms would analyze the MSAlMDA header and decide that the packet reached its final destination The TAIRA address pair is used only to identify a particular and should be handled to upper layers for further processing. In inter-node link and it is going to be removed before a virtual that case the upper layer mechanism would be a netBaltic interface representing such a link delivers the received packet interworking mechanisms which would strip the MDAlMSA to main IPv6 forwarding mechanisms of a netBaltic system IPv6 header, exposing the last one, containing DAIS A IPv6 node. To allow these mechanisms to operate and forward IPv6 address pair. The resulting packet would be fed to IPv6 packets between destinations within the netBaltic system, forwarding mechanisms again (this time with DAIS A header another pair of IPv6 addresses is required. These addresses, being the outer one), which will either forward the packet out a called Mesh Source Address (MSA) and Mesh Destination network interface to which a local network is connected or to Address (MDA) are used to uniquely identify endpoints of a some next-hop node in the external network (see Fig. 7). mesh data transmission path, as shown in 6. netBaltlc Inter-node link Traffic Source Mesh Originator (SA) Node (MSA) .... ·Inter-node link (TA-RA, .... 1-: netBaltlC Virtual Interface LAN or External network Interface IPv6 forwardmg IPv6 forwardmg Mesh Node net Baltic IntelWorkmg Destination Mesh Transmitter Receive r Traffic Destination (DA) Node (MDA) (TA) (RA) Fig. 7. IPv6 headers processing in a netBaltic node. Fig. 6. The addressing in netBaltic communication. The presented method is a simple and effective one, but in case of a maritime environment, where we can expect the use As the netBaltic system is intended to provide IPv6 of relatively long-range and low-bandwidth transmission connectivity with external networks using a number of technologies, the need to use three full IPv6 headers, each of gateways from which a sending node selects a specific one to them requiring at least 40 bytes, is a costly solution. use for communication, a third pair of addresses, indicating Fortunately, as the adding and stripping of such headers is global endpoints of the communication must be used - a source performed by custom netBaltic mechanisms, a compression (SA) and destination (DA) addresses. It should be noted, that methods can easily be employed. The first such modification MSAlMDA cannot be used for this purpose, because in multi- consists of representing only the outer IPv6 header in its full gateway environment it is necessary to both clearly indicate a structure, while other two are reduced to a form of two address final destination node of the packet and a mesh gateway to be fields each. When the outer header is to be stripped, it is in fact used for inter-network traffic exchange. The first of these tasks left in place, but with address fields being rewritten. 6  Moreover, taking into account that each node of the minimize consumption of network bandwidth and node storage netBaltic system is assigned a 64-bit IPv6 prefix to allow them space, a number of optimizations have been proposed to the to act as a router for a locally connected LAN network and the well-known Epidemic DTN routing [13] based on additional fact that the netBaltic system as a whole is expected to be information obtained from popular Automatic Identification assigned a single, 48-bit IPv6 prefix, we can divide the node's System (AIS) [14]. IPv6 address as shown in Fig. 8. VI. SUMMARY ,..---------,---..., ........................................................................................ netBa ltic In the paper the netBaltic system is presented as a solution 1M Prefix of nel88l1ic Syslem (48bils) NodelD nelBallic Node's Local Pv6 Network (64 bits) providing maritime communication by means of heterogeneous (16 bits) ' - -_ _ _ _ _ _ _ _-'---_ _...J •••.••.••. _._._ .••.••.•••••••••••••.••.••. _. _ ._._ .••.••.•••••••••••••.••. _._ .•• wireless networks. Potential ranges of the popular wireless techniques e.g. LTE, WIMAX, WiFi, being potentially a part Fig. 8. AnetBaltic IPv6 address structure. of the netBaltic system, are estimated based on real-world measurements. Moreover, the analysis of on-going It can be observed, that the first 48 bits are the same for all standardization is presented with summary showing the e- NetBaltic nodes. Additionally, last 64 bits are insignificant as navigation services requirements. As the requirements can be far as node identification is concerned. In this situation, the potentially met in the netBaltic system, it is a promising unique identification of the node in the netBaltic system solution enhancing capabilities of existing wireless techniques requires only the remaining 16 bits of its IPv6 address. Taking and bringing closer the usage of e-navigation services. advantage of this address structure, we can substitute these 16 bit values for MDAlMSA addresses when they are currently ACKNOWLEDGMENT not in the outer IPv6 header. As a result, the final header This work has been partially supported by the Applied structure required to accommodate the addressing necessary in Research Program under the Grant: ID PBS3/A3/20/2015, netBaltic system is reduced to the one presented in Fig. 9. founded by the National Center for Research and Header 3 Development. The infrastructure was supported by "PL- FiJlDAlSAaddresses (2xI 6B) Dalafield (varied size) LAB2020" project, contract POIG.02.03 .0 1-00-1 04/13-00 and "Future Internet Engineering" project, contract POIG.O 1.01.02- Fig. 9. Header compression in the netBaltic system. 00-045/09-00. REFERENCES Apart from the above addressing procedures, another very [1] Hoeft, M., Gierlowski, K., Nowicki, K., et al.: netBaltic: Enabling Non- important group of data plane mechanisms consists of a Link- Satellite Wireless Communications over the Baltic Sea. IEEE Comm. Local Connectivity Module (LCM) and Transmission Magazine (2016) Efficiency Module (TEM) Together, they performs a complete [2] International Maritiem Organization (IMO) website: set of functions necessary to perform an efficient transmission http://www.imo.org/en/OurWork/safety/navigationipages/enavigation.as px of IPv6 packets which have been forwarded to specific virtual [3] Input document for the 15 th Session of the ENAV Committee (IALA). interfaces representing inter-node links. The LCM's functions include adding/removing of appropriate local-link header, [4] K.Bronk, A. Lipka, R.Niski, B.Wereszko, K.Wereszko, "Hybrid communication network for the purpose of maritime applications", performing header and data compression and ensuring a International Joumal of Maritime Engineering, in press. reliable packet transfer through the link. This last functionality [5] ITU-T M.2092-0 (10/2015) Technical characteristics for a VHF data has proven to be crucial for efficient operation of multihop exchange system in the VHF maritime mobile band network in maritime deployment and currently several [6] Gierlowski , K.: Characteristics of self-organizing, multihop wireless solutions are under evaluation, including ARQ mechanisms, netwrok for netBaltic systems's zone B. Telecom. Rewiew + Telecom. network coding and tunneling over streaming protocol (such as News 12. pp. 1316-1321 (2016) TCP orURP). [7] Guminski, W.: The concept of providing access to services in network of discontinues and sporadic communication. Telecom. Rewiew + To provide security in our heterogeneous mesh system Telecom. News 12. pp.1339-1342 (2016) mechanisms of authentication, confidentiality and integrity are [8] ETSI EG 202 057-4 v 1.1.1 (2005-10), Speech Processing, Transmission employed at IPv6 level by a Secure Communication Module and Quality Aspects (STQ); User related QoS parameter definitions and (SCM). They take advantages of mature IPsec standard, measurements; Part 4 Internet Access supplemented with dedicated management procedures [9] ITU-T Y.1540 (03/2011), Intemet protocol data communication service - IP packet transfer and availabili ty performance parameters providing reliable identity management (including X.509 certificates enrollment, distribution and revocation) in all three [10] ITU-T Y.1541 (12/2011), Network perfonnance objectives for IP-based services of netBaltic networking environments, by employing DTN [11] K. Gierlowski , M. Hoeft, T. Gierszewski , W. Guminski , K. Nowicki , J. techniques. WoZniak, "Laboratory of Mobile Wireless Technologies", Telecom. The DTN procedures of netBaltic zone C operate using an Rewiew + Telecom. News 12. pp. 1422-1431 (2015) overlay model, over the IPv6 network provided by described [12] Hoeft, Michal; Kaminski , Pawel; Wozniak, Jozef, "Logicallnterface for Soft Handover - An Effective Scheme of Handovers in Proxy Mobile mobility or mesh networks. Their operation allows for data IPv6," in IFIP Wireless and Mobile Networking Conference (WMNC), packages of significant sizes to be securely delivered within the 2015 8th, vol. , no., pp.72-79, 5-7 Oct. 2015 netBaltic system by being exchanged between neighboring [13] A. Vahdat, D. Becker, Epidemic routing for partially-connected ad hoc system nodes and then stored within them for extended periods networks, Technical Report, Duke Uni versity ,2000 of time, until the node movement makes it possible to pass [14] IMO Resolution A.917(22) Guidelines for the onboard operational use them to some other newly detected neighboring node. To of shipborne automatic identification systems (AIS) 7