High Altitude Platforms (HAPs) have the potential to deliver broadband services cost effectively. They are essentially airships or aircraft operating in the stratosphere, and due to their altitude (17-22 km) have the potential to deliver services over a wide coverage area.

They can offer a step-change in performance and availability, and have the advantages of being able to deliver the high capacity similar to that available from terrestrial systems and wide area type coverage similar to that available from satellites.

It is not intended that HAPs will replace these existing technologies, but instead work with these in a complementary and integrated fashion to deliver "Broadband for All".

HAPs also have the potential to deliver other applications and services. They will be particularly suited to a disaster relief/emergency service application, as they can be deployed rapidly to a specific location and will have to rely on minimal ground-based infrastructure.

HAPs could also deliver 3G (UMTS) based communications directly provision has already been made for this in the 3G standards. Other non-communications based applications include remote sensing, navigation, and surveillance.

It is likely that a HAP will be multi-use with such applications and services co-located on a HAP. This potential range of applications and services presents a compelling economic case for HAP system development.

HAPs have steadily been gaining mainstream recognition since being first proposed back in 1992 , but it is only recently that substantive projects have commenced, so HAPs are at a similar stage of development as communications satellites were in the 1960s. A typical example is the recently completed project HeliNet, which was carried out within the 5th Framework Programme of the European Commission.

The HeliNet project developed a scale-sized plane HAP and three pilot applications: broadband communications, environmental monitoring, and remote sensing. The HAP craft themselves are currently some years away and to sidestep this problem a number of innovative companies are developing broadband services that will use tethered aerostat based platforms.

To further develop the state-of-the-art in broadband from aerial platforms the European Commission has recently supported a new project, CAPANINA, as part of the 6th Framework Programme funding initiative. The CAPANINA project is 3-year targeted research project that commenced on 1st November 2003.

A consortium of 13 partners is involved in the project, representing a mixture of large industry, SMEs, and academia/research organisations. All partners are European with the exception of the National Institute of Information and Communications Technology (NiCT) from Japan NiCT have a similar national project.

The CAPANINA project is focussing on development of low-cost broadband technology from HAPs aimed at providing efficient ubiquitous coverage to users who may be marginalised by geography, distance from infrastructure, or those travelling inside high-speed public transport vehicles (e.g. trains).

The aim is to exploit this future third wireless technology to deliver burst data rates to users of up to 120 Mbit/s anywhere within a 60 km coverage area. Both mm-wave band and free space optic communications technologies are taken into consideration.

Free space optic communications have the potential to deliver very high data rates in clear air conditions, and can be used for inter-platform links and to supplement mm-wave band communications for backhaul traffic. The CAPANINA scenario is illustrated below: