Wireless communication scenarios are characterised by the coexistence of a variety of radio communication systems. Wireless networks differ from each other in the specific air interface technology, supported services, bit rate capabilities, coverage, mobility support, etc. Whilst different applications and needs have led to the deployment of such heterogeneous networks (e.g. commercial cellular systems, public-safety, etc.), all of them respond to society’s fundamental demand for communications. Wireless communications technologies play an irreplaceable role in emergency and disaster relief situations. Appropriate communications between first responders, authorities and citizens is crucial. It is generally acknowledged that existing wireless communication networks frequently fall short of meeting users’ needs and consequently cannot properly support the management of these critical situations. Even though the public safety community's technological needs have been understood for a long time, the capabilities of current public safety communications systems (e.g. Private Mobile Radio, PMR) are still lagging far behind some of the capabilities available in commercial mobile networks. Some of the major limitations of public safety systems in emergency and disaster relief scenarios are:

• Lack of network capacity in emergency scenarios. Whilst the PMR network operators have optimised the use of their communication systems in their day-to-day service, the situation changes dramatically when an emergency causes additional stress for the system (and the operators). Emergency scenarios usually lead to exceptionally high traffic loads, that a single (e.g. PMR) wireless communication system may not be able to support. This situation can be worsened in scenarios with limited radio coverage (e.g., a traffic crash in a tunnel) or when parts of the communications infrastructure are damaged in the incident area.
• Lack of interoperability. The diversity of technologies used by public safety organisations often inhibits the cooperation between different agencies. Moreover, even when using the same technology, the networks can’t interoperate and the constraints on the security level constitute an additional barrier. As a result, first responders are frequently required to manage several separate (often incompatible) radio-communication systems. Furthermore, the political evolution of Europe has called for an increased collaboration among public safety organisations from different European countries. This has increased the need for harmonised procedures and interoperable technologies.
• Lack of support for broadband data rates. The evolution of public safety operations has created the need for applications where large amounts of data are exchanged between first responders or between the tactical front line responders and multi levels of a hierarchical command structure. Data-intensive multimedia applications have a great potential to improve the efficiency of disaster recovery operations (e.g. real-time access to critical data such as high resolution maps or floor plans, on-field live video transmission from cameras on helmets to a central unit, telemedicine, etc.).

Furthermore, emergency and disaster relief situations exhibit additional inherent challenges that often impose severe difficulties on public safety communications. Examples of these are: The locations where emergency and disaster relief operations occur are unpredictable and the availability of communications facilities is not guaranteed in the incident area. Even if wireless communications infrastructure exists in the incident area, the first responders may not have the appropriate terminals. Public safety responders need wide area coverage, e.g., in the event of natural disasters like earthquakes or flooding, where a large area may be affected. Public safety organisations must operate in uncertain conditions and difficult environments both from a physical as well as from a radio propagation point of view, due to the presence of interferences or obstacles. Public safety responders have special requirements regarding reliability, responsiveness and security of their communication systems. Based on these observations, it is evident that more efficient and effective advanced wireless communication solutions than today’s PMR systems are needed. In this context, Project HELP will establish a comprehensive solution framework aspiring to significantly enhance the secured communications resilience and responsiveness in emergency situations. Only a solution that takes into account multiple wireless communications technologies and strategies can address the complex requirements of modern emergency and disaster relief communications. Therefore, the proposed solution framework is built on the two following pillars:

• The capacity and efficiency of public safety communications networks can be increased by implementing “network sharing” concepts between different PMR networks (e.g., a PMR network belonging to a given public safety organisation is made available to other first responder agencies that participate in the crisis management) as well as between PMR and commercial cellular networks. In addition to cellular networks, other communications infrastructures (e.g., broadcast networks) can also be considered for integration with public safety communication systems. Hence, existing communication resources in the incident area will be potentially exploited for use by public safety organisations as well as for direct communication with the population. “Network sharing” refers to the capability of sharing network resources like traffic capacity, communication services and broadband connectivity between networks, which may have been designed for different tasks. This approach is particularly beneficial since it is very unlikely that a new private globally harmonised public safety multimedia communication solution will be introduced in the foreseeable future. On top of political and competitive obstacles, the comparatively small volume of the PMR market in comparison with commercial cellular networks would make it difficult to realise the immense investments required for such a task.
• Network capacity and efficiency can be increased by implementing “spectrum sharing” techniques between public safety and commercial networks in case of emergencies or natural or man-made disasters. “Spectrum sharing” refers to the possibility of managing spectrum in a flexible way, such as: both public safety and commercial communication services can be provisioned over the same frequency bands (e.g., allocate a public safety licensed band with mechanisms for interruptible spectrum leasing to commercial devices), sharing spectrum between different public safety license holders (e.g., spectrum pooling concept), exploiting spectrum opportunities over other licensed bands (e.g. TV bands) without causing harmful interference, dynamic frequency planning over the pool of licensed frequencies in order to meet the requirements arisen in an emergency situation, etc. As a whole, the ultimate target of “spectrum sharing” mechanisms is to provision further spectrum availability in the incident area together with suitable management functionalities.