High altitude platforms for broadband - pie in the sky?

High altitude platforms (HAPs) are planned to operate in the stratosphere in quasi-stationary positions at altitudes around 20 km. They offer considerable potential for effective delivery of wireless services. In particular, they are attractive for broadband communications, allowing effective and flexible resource allocation, high capacity, and high spectral efficiency. To this must be added benefits of rapid deployability and potential to supplant extensive ground infrastructure. There are a number of programmes worldwide working on this technology. The main downside is that suitable long-endurance platforms have yet to be demonstrated, and a number of technical challenges remain on the platform side, not least of which is energy storage. There are also issues of spectral allocation and operational regulatory constraints for this emerging technology. This talk review the state-of-the-art and current activities, including work on the 6th Framework CAPANINA project, and gives some pointers towards the future, especially for broadband service delivery.