Evolution of TETRA through the integration with a number of communication platforms to support public protection and disaster relief (PPDR)
Hamid Jahankhani; Sufian Yousef
Abstract
PPDR organizations cannot afford the risk of having communication failures in their voice, data and video transmissions; and this can only be ensured by building robust, secure and reliable, modern PPDR mobile communications networks. Also, for these organizations to be adequately prepared to tackle any future events like those we have recently witnessed, they need to be properly equipped. There are needs for new advanced services and applications envisioned in the next generation of PPDR communication systems such as remote personnel monitoring, remote sensor networks (forest fire tracking or water/flood level monitoring), two-way real-time video, 3D positioning and GIS, mobile robots, multi-functional mobile terminals (ID verification, Transfer of images; Biometric data; Remote database access; Remotely controlled devices), etc. Also, the need for a very reliable, secure and resilient communication network for public protection that can cope with threats of terror and disaster at all levels, toward citizens all the way to its communication infrastructure, is necessary. However, this growing demand for a reliable and secure high-speed data communication means that the current capacity for PPDR communication network (i.e., TETRA) will be exceeded, requiring an upgrade or replacement at some stage in the future.
Introduction
Public Protection and Disaster Relief (PPDR) organizations such as law enforcement, ambulance services, civil emergency management/disaster recovery, fire services, coast guards services, search and rescue services, government administration, etc., are tasked with providing public safety and security service. Public safety services bring value to society by creating a stable and secure environment; and PPDR organizations address situations where human life, rescue operations and law enforcement are at stake. And due to the nature of these situations, mobile communication is a main requirement. PPDR organizations rely extensively on Professional Mobile Radio (PMR) communication systems to conduct their daily operations. Many of these communication networks are based on TETRA, TETRAPOL, GSM, Project 25 specification, etc., however, TETRA has become the widely accepted choice in Europe with TETRAPOL being used in some countries.
PPDR is a priority subject for the citizens, the National Governments and the European Union. Especially since events such as the September 11th world trade centre attacks, the Atocha (Madrid) bombings, the London underground attacks, and the recent major earthquake in Van, Turkey; security, counter-terrorism, and disaster relief have been on top of the agenda of the European decision-makers, at national as well as at EU level. Evidence from these recent disasters shows that public cellular systems are not designed to cope with major incidents and have failed at the time when good communications are needed most, hence, the importance of dedicated PPDR communication network. However, due to the nature of some of these events and the increasing globalization of terrorism (and other security and safety threats), it is very important for future PPDR organizations to work across national borders, which is a limitation of current PPDR communication networks. In Europe, especially during the early 1990s when there was a transition to a borderless society following the Schengen Agreement, the freedom to cross borders has also meant that those with criminal intent would also be able to freely cross borders. As a result it became apparent that there was a need to ensure good communications between the PPDR organizations of each of the countries and enable PPDR officers to travel across borders without losing communications. Neighboring countries’ networks must interoperate with one another for both routine day-to-day and disaster relief operations.
PPDR organizations cannot afford the risk of having communication failures in their voice, data and video transmissions; and this can only be ensured by building robust, secure and reliable, modern PPDR mobile communications networks. Also, for these organizations to be adequately prepared to tackle any future events like those we have recently witnessed, they need to be properly equipped. There are needs for new advanced services and applications envisioned in the next generation of PPDR communication systems such as remote personnel monitoring, remote sensor networks (forest fire tracking or water/flood level monitoring), two-way real-time video, 3D positioning and GIS, mobile robots, multi-functional mobile terminals (ID verification, Transfer of images; Biometric data; Remote database access; Remotely controlled devices), etc. Also, the need for a very reliable, secure and resilient communication network for public protection that can cope with threats of terror and disaster at all levels, toward citizens all the way to its communication infrastructure, is necessary. However, this growing demand for a reliable and secure high-speed data communication means that the current capacity for PPDR communication network (i.e., TETRA) will be exceeded, requiring an upgrade or replacement at some stage in the future.
TETRA Technology
TETRA is a modern standard for digital PMR and has enjoyed wide acceptance (especially in Europe) to now be considered one of the most mature and prominent technologies for the PPDR markets. TETRA specifications are constantly being evolved by ETSI (European Telecommunications Standards Institute) and new features are being introduced to fulfill the growing and ever demanding PPDR requirements. The original TETRA standard first envisaged in ETSI was known as the TETRA Voice plus Data (V + D) standard with less emphasis on the data side with just two data services compared with the nine voice services. Because of the need to further evolve and enhance TETRA, the original V + D standard is now known as TETRA 1. Packet Data Optimized (PDO) is a completed part of the TETRA suite of standards produced for only “Data Only” wireless communications applications (i.e., pagers). However, very few manufacturers have developed PDO systems and products because: all traditional PMR users use voice communication as well as data communications; and also the obvious application area for such standard (high data size transfer) would take significant amount of time and power to operate.
Nevertheless, TETRA already provides a comprehensive portfolio of services and facilities. TETRA protocol specifies several standard interfaces to ensure an open multivendor market: (1) Air Interface (AIR IF), (2) Terminal Equipment Interface (TEI), (3) Inter-System Interface (ISI), (4) Direct Mode Operation (DMO).
However, as time progresses, there is a need to evolve and enhance all technologies to better satisfy user requirements, future proof investments and ensure longevity. Like GSM moving to GPRS, EDGE and UMTS/3G, TETRA will also evolve to satisfy increasing user demand for new services and facilities. For this reason, a TETRA 2 standard has been developed and is sufficiently complete for product development purposes. However, product availability will depend on the different manufacturers’ R&D plans, but manufacturers have not deployed product yet and take up is slow. At TETRA conferences the opinion was expressed that the earliest deployment of broadband TETRA (or equivalent) was likely to be 2020. This is because the existing network cannot be upgraded to support TETRA 2 due to spectrum availability issues; and some that could be will not because of the cost involved. Hence, there is a need for an upgraded PPDR communication system that would be highly efficient, secure, resilient and flexible with modern and sophisticated applications; and that even when the introduction of TETRA 2 and future releases (Broadband TETRA) become well established, there is a guarantee that the economic and commercial uptake of the network is justified. However, there are issues with the uptake of the network, which would have implications on future networks; and they stem from the disadvantages of the current TETRA network.
Current Trends of PPDR (i.e., TETRA) Technology
The majority of PPDR organizations in Europe currently use dedicated PMR networks, designed specifically to meet their needs, for their communications. Typically TETRA (or TETRAPOL), and operating in the 380-400 MHz spectrum band. These networks offer a range of low rate data services, but the speed and capacity available limits more widespread use of higher-speed data applications. In line with societal trends for access to information on the move, PPDR operations are becoming increasingly information driven, requiring access to a wider range of wideband and broadband applications. Given the limitations in capacity of existing dedicated networks to deliver mobile broadband services, it is considered likely that a new generation of solutions will be required across Europe in the next 5-10 years, too meet future PPDR demands. These solutions, if delivered using new dedicated mobile broadband networks that are designed to meet PPDR requirements, will still require additional spectrum to deliver the required services effectively.
The trend for current and future PPDR mobile data and multimedia applications that is being foreseen to cover a range of needs was highlighted above. Alongside these are a number of specific operational requirements that are essential for PPDR communications, in order to ensure the availability, reliability and integrity of networks, which include: High levels of network availability; High degree of network control (implementing prioritized access for specific user groups or individuals, and reserving capacity where required); Near nationwide geographic coverage (communicating in remote areas); Security; Low latency (end-to-end voice delay of no more than 200 ms); Interoperability between different PPDR authorities and across borders; Highly resilient networks (various layers of redundancy); and Ability to support mixed traffic.
Within the PPDR sector, the above demand for access to a wider range of applications and services is driven by changes in working practices, which creates requirements for access to a far wider range of data sources (textual, images, and video) that are typical in commercial mobile networks. Sharing of these data is being used in order to establish and maintain a common operational picture between PPDR agencies and between field and central command staff. This is used to improve responsiveness, aid the deployment of resources, and improve timeliness and decision making in daily PPDR operations; when responding to major planned and unplanned events.
As there is a limit to the range and volume of data and multimedia applications that existing (and possibly future) dedicated narrowband and wideband networks (and existing commercial networks) can provide, if a new-generation PPDR network is not made available, some of the envisaged applications would not be delivered. Ultimately, this will affect how already emerging changes to the ways of working within the PPDR sector might evolve, and in the longer term, constrain the further development of the sector.
Technological and Economic Barriers and Issues
The capabilities of existing (and possibly future) narrowband and wideband dedicated mobile networks currently used in the PPDR sector will not be sufficient to meet the envisaged future requirements. This is inevitable, unless a steady growth approach is introduced where PPDR operation methods change gradually, voice remains the dominant method of mission critical communication, and existing data applications continue to be used alongside voice (with a gradual increase in use). However, this is not suitable in the longer term since there is already growing evidence of changes in working methods and trends within the PPDR sector that suggest that this path will not match future demands. A new generation of mobile broadband service is required to accommodate the range of future data, image and multimedia applications that PPDR users demand. The options for delivering this new generation of services are to make use of upgraded commercial networks, or to develop a new generation of dedicated mobile broadband networks for exclusive public safety use. While the new generation of data service could theoretically be delivered through upgrading and re-engineering commercial networks, there are certain barriers, which range from technical to cost and commercial considerations, that might make it difficult to achieve in practice. These include the following:
• The PPDR sector requires very extensive geographic coverage as well as in-depth coverage penetration inside buildings, irrespective of location, which does not match the typical roll-out requirements of commercial network. Commercial operators typically invest in coverage where populations exist, and capacity is designed to maximize revenue generation in those areas, with little incentive to invest in areas of low density population.
• It is likely to be very expensive to re-engineer commercial networks to achieve all the public safety sector’s operational requirements, and there are questions about whether sufficient incentives exist for commercial operators to do this. For example, typical requirements include the need for battery back-up to be available at thousands of base station sites across the network, and for networks to be designed to ensure that they are highly resilient (including overlapping coverage, standby power supplies and fall-back sites) and that no single “point of failure” exists either in access or core networks.
• There is the view that commercial networks might be more vulnerable to sabotage by criminals than dedicated networks are.
• There are questions about whether the required Grade of Service for PPDR use can be guaranteed within a network shared with commercial users, particularly in times of very high traffic loading; and whether some PPDR requirements are actually achievable in this network.
• There are conflicting views on whether signaling could be encrypted over air interface in 3G/LTE.
• Ensuring the specific requirements of carriage of “restricted” or “confidential” documents requires careful network planning and approvals, which is complex and costly to achieve.
• It is not clear that networks can be dimensioned to achieve the required immediacy and guaranteed access that PPDR requires.
• There is reluctance for public bodies to be reliant on fully commercial operators, in view of the potential lack of control upon future network investment, business plans and financing.
However, as explained before, the current (and possibly, future) dedicated PMR network (TETRA) would not be able to cope with the trend for current and future PPDR mobile high speed data and multimedia applications that is being foreseen to cover a range of needs.
Progress Beyond the State-of-the-Art
Current PPDR Communication Network Architecture Landscape
PPDR organizations currently use a range of different communications networks to meet their operational needs. In Europe, the majority of their personnel now use dedicated networks to provide narrowband mobile communications using TETRA or TETRAPOL technologies operating in the 380-400 MHz band. This spectrum allocation is based on the harmonization of spectrum for public safety that was put in place by the ECC in 1996 and provides recommendations on the harmonization of additional frequency bands for digital PPDR within the 380-470 MHz range. There are significant barriers to the implementation of this decision as the same spectrum is also identified for narrowband and wideband digital land mobile (PMR/PAMR). In nearly 20 countries, the presence of CDMA 450 networks will impact on the availability of this spectrum for PPDR organizations. Interest is also emerging in the commercial deployment of LTE technology in this band.
Recent years have seen increasingly rapid progress in the capability of technologies deployed in the commercial electronic communications sector, particularly with regard to over the air data rates and the spectrum efficiency that can be achieved. For example, when the first 3G technology standards were agreed in 1999 the maximum bit rate realizable over a 3G mobile network was 2 Mbps, though in practice most users experienced speeds in the range 64-384 kbps. By comparison the digital technology mainly deployed by the PPDR sector (TETRA) could deliver up to 28 kbps. Many of today’s 3G networks have been upgraded to the latest High Speed Packet Access (HSPA, HSPA +) technology and can theoretical peak bit rates of up to 21 Mbps (one user per cell only, best case channel, no error protection), with actual user bit rates of 1 Mbps or more in case of several users relatively commonplace in some networks in high density traffic areas, using a 5 MHz bandwidth channel. Newer systems employing such standards as the TETRA Release 2 TEDS component are capable of supporting more advanced data communications, with a theoretical maximum IP throughput of up to 500 kbps in a 150 kHz channel; however there is an increasing gulf between the capabilities of commercial networks and dedicated PPDR networks, as the increasing demands to support broadband data require more spectrally efficient technologies to be developed and implemented faster for the commercial sector.
Despite improvements in spectral efficiency through the deployment of new technologies which will yield some relief to the spectrum shortage, demand growth for frequencies is likely to outstrip growth of supply into the foreseeable future. The spectrum available to existing PPDR operations will not satisfy future needs for these essential services. One example of this is the current situation with TETRA TEDS in that not all EU Members States are able to identify radio channels. Therefore, communications policy must evolve to empower new systems by reallocating spectrum from the Digital Dividend to PPDR mission critical communications. This decision is not to be taken lightly since it sits on the critical path for numerous other decisions necessary before deploying next-generation PPDR networks. Historically, it has been the usual practice to identify suitable spectrum well in advance because of the timescales for releasing the spectrum, development of standards and equipment. It may require as long as 10 years to plan and deploy such networks. Adding to the urgency of the matter is the growing need for new services to emerge due to the increase in terrorist threats, frequency of natural environmental disasters, and normal population growth. The 450-470 MHz band is also widely used in Europe by analog private mobile radio services which in some cases (notably UK and Ireland) are not aligned with relevant CEPT recommendations and it seems unlikely that sufficient harmonized spectrum to support broadband mobile operation could be made available in a reasonable time frame.
In practice, many PPDR users already make use of commercial 3G networks alongside their own dedicated networks; however, the coverage of the commercial networks is inferior, mainly because of commercial considerations in part because of the higher frequencies deployed and the corresponding smaller cell sizes. Moreover, networks are likely to suffer capacity constraints at times of high demand, which would tend to be the case in the aftermath of major public safety incidents. There could be significant benefit in extending the capabilities provided by commercial mobile broadband technologies such as HSPA, LTE, CDMA 2000 EV-DO, and WiMAX to the PPDR sector. Adopting such standards within dedicated PPDR spectrum would overcome the capacity limitations of commercial networks and also provide scope for interoperability with public networks which could facilitate inter-agency communication. Such an approach could also provide economies of scale with only the RF modules differing from standard commercial networks. Such technologies would be well suited to future application trends discussed earlier.
State-of-the-Art on Mobile Communication Standard
General PMR standards
Professional Mobile Radio (also known as Private Mobile Radio [PMR] in the UK and Land Mobile Radio [LMR] in North America) are field radio communications systems which use portable, mobile, base station, and dispatch console radios and are based on standards such as MPT-1327, TETRA, TETRAPOL and APCO 25 which are designed for dedicated use organizations. Typical examples are the radio systems used by police forces and fire brigades. Key features of professional mobile radio systems can include: Point to multi-point communications (as opposed to cell phones which are point to point communications); Push-to-talk, release to listen (a single button press opens communication on a radio frequency channel); fast call set up; large coverage areas; closed user groups; Use of VHF or UHF frequency bands. The most important factor for the effective and successful deployment of PPDR operatives is secure and reliable communication. In an emergency, the reliability of the communication system can make the difference between human life and death. However, the usefulness of professional mobile radio networks should not be limited to voice communication, but to be able to send sensitive data and information securely and timely. Being able to integrate more sensors (to enable access to more high speed critical data) into the PMR terminals would be very beneficial to emergency response and preventive responses.
TETRAPOL
TETRAPOL is a digital Professional Mobile Radio standard, as defined by the Tetrapol Publicly Available Specification (PAS), in use by professional user groups, such as public safety, military, industry and transportation organizations throughout the world. TETRAPOL is a fully digital, FDMA, Professional Mobile Radio system for closed user groups, standardizing the whole radio network from data and voice terminal via base stations to switching equipment, including interfaces to the Public switched telephone network and data networks. End-to-end encryption is an integral part of the standard just as in TETRA. Matra/EADS developed TETRAPOL and delivered an operational digital trunked radio system at an early date. Among the first users was the French Gendarmerie Nationale in 1988 for its RUBIS system. EADS (Connexity) and Siemens (S-PRO) are among the major manufacturers of professional radio systems based on the TETRAPOL specification. TETRA, however, is a more recent standard than TETRAPOL and trend in Europe is seeing a very significant move to the TETRA standards due to the longevity and evolutionary capability of the TETRA standard as it has moved from TETRA 1 to TETRA 2 and has the potential to evolve to more enhanced functionality and features (similar to the route taken by GSM).
GSM
Global system for mobile communication (GSM) is a globally accepted standard for digital cellular communication. GSM is the name of a standardization group established in 1982 to create a common European mobile telephone standard that would formulate specifications for a pan-European mobile cellular radio system operating at 900 MHz. GSM is a cellular network, which means that mobile phones connect to it by searching for cells in the immediate vicinity. However, GSM was designed with a moderate level of security. Communications between the subscriber and the base station can be encrypted. GSM uses several cryptographic algorithms for security. The A5/1 and A5/2 stream ciphers are used for ensuring over-the-air voice privacy. A5/1 was developed first and is a stronger algorithm used within Europe and the United States; A5/2 is weaker and used in other countries. Serious weaknesses have been found in both algorithms: it is possible to break A5/2 in real-time with a cipher text-only attack, and in February 2008, Pico Computing, Inc. revealed its ability and plans to commercialize FPGAs that allow A5/1 to be broken with a rainbow table attack. The system supports multiple algorithms so operators may replace that cipher with a stronger one.
TETRA
The TETRA standard (originally aimed to the European market) has now become a global standard with a potential worldwide market. TETRA is often used next to established frequency bands with different standards. Usually TETRA’s frequency bands are adjacent to important communication bands so they must not interfere in any way with the established adjacent channels. Thus, transmission of TETRA signals must have very low out-of-band signals and spurious frequency output power. Reception of TETRA signals can be virtually in any spectral environment and so TETRA radio receivers require high blocking and linearity specifications. TETRA uses a non-constant envelope modulation which requires a highly linear transmitter to prevent high levels of adjacent channel interference (ACI) due to spectral re-growth. Linear power amplifiers (PA) typically have low efficiency which is undesirable in mobile communications as the efficiency of the PA is one of the most important parameters in a system determining talk time, battery size, etc. The conventional approach for achieving low distortion is to use power amplifiers operating at an output level far below their real capabilities (back-off approach). However, such an approach drastically reduces the power efficiency, increasing the power consumption of the system to unacceptable levels. This has hindered the growth on the user uptake. An important advantage, however, of the TETRA standard is that it has a number of open interface specifications that can be used by application developers to further enhance the capabilities of TETRA. Although TETRA uses many of the principles of GSM, TETRA has been specifically designed to enable communication by the emergency services (Police, Fire, Ambulance, etc.) as it has distinct features from and over GSM including:
• Group communication—the ability of one individual to talk to a large number of other operatives in a walkie-talkie type mode of operation.
• Very quick call setup times to ensure critical communication can occur rapidly.
• Priority/Congestion management techniques to ensure that during overload periods important (potentially life threatening) communication can occur.
• Security of communication. A number of techniques are included in the standard and restrictions are placed on the way the products are designed to ensure that communication cannot be “eaves dropped” and the units tampered with.
• Dependability—through the different levels of grade of services and the way the infrastructure is installed TETRA networks are more resilient during times of emergencies than commercial communication bearers.
TETRA is a clear winner in the commercial battle for a communications technology within the PPDR sector. However, in order for TETRA to deliver its potential and for the advanced services envisioned in the next generation of PPDR communication network to be achieved, significant development is required.
Despite the advantages of TETRA there are a number of issues which prevent TETRA’s more widespread adoption. These include: Product Cost; Product Size; Data capability of the products. These are driven by the demanding protocol, performance, and security requirements that differ from a commercial mobile network. These aspects in turn prevent both the full integration of the emergency staff using a secure communication system and critical/useful data not being transferred over secure and guaranteed communication bearers. By improving the technology used by the emergency services within European and specifically TETRA the quality and value for money of the services will be improved.
Proposed PPDR Communication Network Architectural Solutions
TETRA over Mobile IP Network
Multi-technology communication mobile IP gateway (MIPGATE)
There has been strong research effort in the last decade on the development and integration of new wireless access technologies for mobile Internet access. Among the main research concepts for taking advantage of the availability of various heterogeneous networking technologies in place, Always Best Connected (ABC), Quality of Experience (QoE), Bandwidth Aggregation concepts have been at the centre of attention. Always Best Connected implies that end-users expect to be able to connect anytime, anywhere—also when on the move—by their terminal of choice. End-users also expect to be able to specify in each situation whether “best” is defined by price or capability. However, the current state-of-the-art solutions, such as IETF Mobile IPv6 (MIP) or the emerging Host Identity Protocol (HIP), mainly focus on mobility management, instead of considering additional user-related issues, such as user preferences, associated cost, access-network operator reputation, and trust and mainly application-related issues like (Quality of Service) QoS and failure recovery in conjunction with mobility. Quality of Experience (QoE) reflects the collective effect of service performances that determines the degree of satisfaction of the end-user, e.g., what user really perceives in terms of usability, accessibility, retain-ability and integrity of the service. Seamless communications is mostly based on technical Network QoS parameters so far, but a true end-user view of QoS is needed to link between QoS and QoE. While existing 3GPP or IETF specifications describe procedures for QoS negotiation, signaling and resource reservation for multimedia applications (such as audio/video communication and multimedia messaging, support for more advanced services, involving interactive applications with diverse and interdependent media components) is not specifically addressed. Additionally, although the QoS parameters required by multimedia applications are well known, there is no standard QoS specification enabling to deploy the underlying mechanisms in accordance with the application QoS needs.
One of the early attempts to provide all-IP architecture and integrate different access technologies for public safety communications was by the project MESA (Mobility for Emergency and Safety Applications), an international partnership project by ETSI and TIA dating back to 2000 (Project MESA, 2001). Salkintzis (2002) proposed a solution for integrating WLAN and TETRA networks that fits to the all-IP architecture of MESA and allows TETRA terminals to interface the TETRA infrastructure over a broadband WLAN radio access network instead of the conventional narrowband TETRA radio network, while remaining fully interoperable with conventional TETRA terminals and services. Chiti et al. (2008) propose a wireless network that aims to interconnect several heterogeneous systems and provide multimedia access to groups of people for disaster management. The authors address the issues of heterogeneous network interconnection, full and fault tolerant coverage of the disaster area, localization to enable an efficient coordination of the rescue operations, and security. The focus of this work is on the use of WiMAX-based wireless network as a backbone to provide reliable and secure multimedia communications to operators during the disaster management. Durantini et al. (2008) present a solution for interoperability and integration among Professional Mobile Radio systems (TETRA and Simulcast), public systems (GSM/GPRS/UMTS), and broadband wireless technologies, such as WiMAX, with the aim of enabling distributed service provisioning while guaranteeing always best connection to bandwidth demanding applications provided by an IP-based core network. Furthermore, the authors address the issue of optimizing the quality of service management in a multi-network environment, and propose a QoS mapping between WiMAX QoS classes and TETRA service typologies. There is a multitude of other similar work focusing on the integration of various network technologies in and out of the scope of public safety communications. However, solutions available to date are fragmented and each considers only a subset of the ideal QoE-aware and autonomous connectivity solution that can also simultaneously exploit all available network interfaces. During large scale emergencies and disasters, it is crucial to aggregate the scarce communication resources of multiple technologies and be able to use simultaneously, since the left-over capacity of a single technology may suffer due to infrastructural damages.
Multipath TCP
The transmission control protocol (TCP), which serves as the data transport basis of many telecommunication services of today, was designed to work on single links and does not cope well with the simultaneous use of multiple links at the same time. A survey of TCP performance in heterogeneous networks (Barakat, 2000) shows the existing solutions to date and their problems. Magalhaes et al. (2001) present a solution for channel aggregation at the transport layer, called R-MTP (Reliable Multiplexing Transport Protocol), which multiplexes data from a single application data stream across multiple network interfaces (Magalhaes, 2001). The recently finished EU-funded Trilogy project introduced the MultiPath TCP (MPTCP) solution, toward enabling the simultaneous use of several paths by a modification of TCP that presents a normal TCP interface to applications, while in fact spreading data across several subflows (Barré, 2011). An IETF working group has been formed to develop the MPTCP protocol, which is an ongoing effort. However, through extensive evaluation studies over MPTCP, some authors (Nguyen, 2011) report that heterogeneous network environment (Ethernet, Wifi, and 3G) has a great impact on MPTCP throughput and reveals the need of an intelligent algorithm for interface selection in MPTCP.
Security
Terrestrial Trunked Radio (TETRA) supports two types of security: air-interface security and end-to-end security. Air-interface security (TETRA, 2010) protects user’s identity, signaling, voice and data between mobile station (MS) and base station (BS). It specifies air-interface encryption, (mutual) authentication, key management (OTAR: over-the-air-rekeying) and enable/disable functionality. End-to-end security (TETRA, 2010) encrypts the voice from MS to MS. Current candidates as encryption algorithms are IDEA (owned by MediaCrypt AG) and AES as the encryption schemes. One of the main challenge for multi-technology communication is the compatibility problem between the security mechanisms (encryption, authentication, integrity, and key management) supported by these technologies. Wireless LAN supports various security mechanisms, uses of which are mostly optional. MAC address filtering and hidden service set identifier (SSID) are the simplest techniques. Today very few access points use Wired Equivalent Privacy (WEP) because many cracking tools are publicly available on Internet. Wi-Fi Protected Access (WPA and WPA2 based on 802.11i) are introduced to overcome this problem but weak passwords are still problem. 802.1x defines the encapsulation of the Extensible Authentication Protocol (EAP), and enables authentication through third-party authentication servers such as Radius and Diameter. End-to-end security can be provided by use of Internet Protocol Security (IPSEC), Transport Layer Security (TLS), Secure Sockets Layer (SSL), Secure Shell (SSH), pretty Good Privacy (PGP), etc. Security of GSM and 3G suffers from similar compatibility problems with TETRA. GSM security defines Subscriber Identity Module (SIM), the MS, and the GSM network. SIM hosts subscribe authentication key (K), Personal Identification Number (PIN), key generation algorithm (A8), and authentication algorithm (A3). MS contains the encryption algorithm (A5) for air interface. Encryption is only provided for the air interface. 3G security builds upon the security of GSM. It addresses the weaknesses in 2G systems with integrity and enhanced authentication as well as with enhanced encryption using longer keys and stronger algorithms. Seamless communication for crisis management (SECRICOM—FP7) project partially addresses this challenge for secure push to talk systems over existing infrastructures (GSM, UMTS networks).
Another challenge in multi-technology communication is that the most of the security mechanisms are optional, and they are maintained based on the policies of different administrative domains. An end-to-end connection between two MS may go through an unsecure public network which may permit in variety of attacks including denial-of-service and man-in-the-middle. Cost of mitigating these attacks on MS side may be higher than the benefit of the connection in terms of Quality of Service (QoS) and Quality of Experience (QoE) metrics. Therefore, QoS and QoE mechanisms must involve related metrics to provide predictable security service levels to the end users (Spyropoulou, 2002).
TETRA over Mobile Ad-Hoc Network
Mobile Ad-Hoc Networks are multi hop networks where nodes can be stationary or mobile; and they are formed on a dynamic basis. They allow people to perform tasks efficiently by offering unprecedented levels of access to information. In mobile ad-hoc networks, topology is highly dynamic and random; and in addition, the distribution of nodes and their capability of self-organizing play an important role. Their main characteristics can be summarized as follows: The topology is highly dynamic and frequent changes in the topology may be hard to predict; Mobile ad-hoc networks are based on wireless links, which will continue to have a significantly lower capacity than their wired counterparts; Physical security is limited due to the wireless transmission; Mobile ad-hoc networks are affected by higher loss rates, and can present higher delays and jitter than fixed networks due to the wireless transmission; and Mobile ad-hoc network nodes rely on batteries or other exhaustible means for their energy. As a result, energy savings are an important system design criterion. Furthermore, nodes have to be power-aware: the set of functions offered by a node depends on its available power (CPU, memory, etc.).
A well-designed architecture for mobile ad-hoc networks involves all networking layers, ranging from the physical to the application layer. Power management is of paramount importance; and general strategies for saving power need to be addressed, as well as adaptation to the specifics of nodes of general channel and source coding methods, of radio resource management and multiple accesses. In mobile ad-hoc networks, with the unique characteristic of being totally independent from any authority and infrastructure, there is a great potential for the users. In fact, roughly speaking, two or more users can become a mobile ad-hoc network simply by being close enough to meet the radio constraints, without any external intervention.
Routing problems have been addressed through research; where routing protocols between any pair of nodes within an ad-hoc network can be difficult because the nodes can move randomly and can also join or leave the network. This means that an optimal route at a certain time may not work seconds later.
Two of the best multicast protocols to be adopted are MAODV (Multicast Ad-hoc on-demand Distance Vector Routing Protocol) and ODMRP (On Demand Multicast Routing Protocol). The performance measures that were evaluated are the PDR (Packet Delivery Ratio) and the Latency. Previous studies have evaluated these algorithms with respect to the network traffic, the node speed, the area and the antenna range for different simulation scenarios. In general, MAODV performs better for high traffic. ODMRP performs better for large areas and high node speeds but poorer for small antenna ranges. Therefore, MAODV and its derivative AODV ALMA will be adopted in this project. A number of technical challenges are faced today due to the heterogeneous, dynamic nature of this hybrid MANET. The hybrid routing scheme AODV ALMA can act simultaneously combining mobile agents to find path to the gateway and on-demand distance vector approach to find path in local MANET is one of the unique solution. An adaptive gateway discovery mechanism based on mobile agents making use of pheromone value, pheromone decay time and balance index is used to estimate the path and next hop to the gateway. The mobile nodes automatically configure the address using mobile agents first selecting the gateway and then using the gateway prefix address. The mobile agents are also used to track changes in topology enabling high network connectivity with reduced delay in packet transmission to Internet.
Clustering is an effective technique for node management in a MANET. Cluster formation involves election of a mobile node as Cluster head to control the other nodes in the newly formed cluster. The connections between nodes and the cluster head changes rapidly in a mobile ad-hoc network. Thus cluster maintenance is also essential. Prediction of mobility-based cluster maintenance involves the process of finding out the next position that a mobile node might take based on the previous locations it visited. The overhead can be reduced in communication by predicting mobility of node using linear autoregression and cluster formation.
TETRA over DVB-T/DTTV Network
Digital Video Broadcasting—Terrestrial (DVB-T) is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and the first DVB-T broadcast was in the UK in 1998. The DVB-T system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing (COFDM or OFDM) modulation (ETSI, 2004-2006). Recently, there are many efforts toward the use of the DVB-T infrastructure for emergency warning and alert of the public in the view of disastrous events, as part of integrated Emergency Warning Broadcast Systems (EWBS) (Azmi, 2011). EWBS usually use TV and radio broadcasting networks to alert people about impending disasters and enable them to prepare for emergencies. The EWBS uses special warning or alert signals embedded in TV and radio broadcasting signals to automatically switch on the receiver equipment (if so equipped) in the home, and issue an emergency bulletin, alerting people to an impending disaster such as a tsunami or an earthquake. Besides, at least one special disaster emergency warning system standard for DVB-T which involves a specific message flow architecture and transmitter and receiver standard have been proposed (Shogen, 2009).
However, there are no available implementations of DVB-T-based systems that are especially suited for Public Protection and Disaster Relief (PPDR) environments, essentially being part of an integrated Emergency Response Broadcast System (ERBS). Since TV broadcasting systems, including Digital TV (DTV) systems, are widely available across rural and urban areas, and their operation and RF coverage are not affected by the land type, the terrain morphology or the weather conditions, the use of DVB-T based systems in terms of emerging ERBS systems would be highly beneficial, especially considering: The higher video and audio transmission rate of the DVB-T-based systems compared to their analog counterparts or previous digital TV implementations; The higher spectral efficiency compared to their analogue counterparts; The advanced Forward Error Detection (FEC) capabilities, which also provide a major capacity enhancement; and The improved signal robustness against external influences such as the impact(s) caused by geography, weather conditions and buildings/technical obstacles.
Conclusion
In general, it is important to provide a framework which will exploit additional networks (Mobile IP, Ad-Hoc Mobile Networks, and DVB-T) to support emergency relief communications (which at this point and the foreseeable future is going to be TETRA) and resource management during disasters in two aspects:
(i) guaranteed communication capabilities and services among the response teams and units regardless of the location and level of crisis,
(ii) communication opportunities between responders and general public, affected people and their families
Involvement of families, citizens and social groups in rescue operations (millions of eyes/agents over the Internet providing unstructured time critical information such as possible locations of trapped people) has already illustrated its benefits during the rescue operations after the recent major earthquake in Van, Turkey.
In the context, we consider three regions in a disaster area in terms of communication locality: emergency site, first response site, and a local site for additional resources. Each of these regions may have different requirements. For example, local site for additional resource may already have an infrastructure to support the operations. First response site may be better organized compared to emergency site which may be the most challenging environment for providing resilient, secure and high quality communication service. The objective is to create a framework that can adapt itself based on the requirements and available resources in the environment it is operating.