RE: HIGH ALTITUDE AERONAUTICAL PLATFORMS (HAAPS) (Download Full Report And Abstract)
||HIGH ALTITUDE AERONAUTICAL PLATFORMS (HAAPS)
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High Altitude Aeronautical Platform Stations (HAAPS) is the name of a technology for providing wireless narrowband and broadband telecommunication services as well as broadcasting services with either airships or aircrafts. The HAAPS are operating at altitudes between 3 to 22 km. A HAAPS shall be able to cover a service area of up to 1'000 km diameter, depending on the minimum elevation angle accepted from the user's location. The platforms may be airplanes or airships (essentially balloons) and may be manned or un-manned with autonomous operation coupled with remote control from the ground. HAAPS mean a solar-powered and unmanned airplane or airship, capable of long endurance on-station –possibly several years.
A high altitude telecommunication system comprises an airborne platform – typically at high atmospheric or stratospheric altitudes – with a telecommunications payload, and associated ground station telecommunications equipment. The combination of altitude, payload capability, and power supply capability makes it ideal to serve new and metropolitan areas with advanced telecommunications services such as broadband access and regional broadcasting. The opportunities for applications are virtually unlimited. The possibilities range from narrowband services such as paging and mobile voice to interactive broadband services such as multimedia and video conferencing. For future telecommunications operators such a platform could provide blanket coverage from day one with the added advantage of not being limited to a single service. Where little or unreliable infrastructure exists, traffic could be switched through air via the HAAPS platform. Technically, the concept offers a solution to the propagation and rollout problems of terrestrial infrastructure and capacity and cost problems of satellite networks. Recent developments in digital array antenna technology make it possible to construct 100+ cells from one platform. Linking and switching of traffic between multiple high altitude platforms, satellite networks and terrestrial gateways are also possible. Economically it provides the opportunity for developing countries to have satellite-like infrastructure without the funds flowing out of the country due to gateways and control stations located outside of these countries.
Various classes of service can be provided to subscribers sharing the bandwidth of a given beam, for example, 1 to 10 Mbps peak data rates to small businesses, and 10 to 25 Mbps peak data rates to business users with larger bandwidth appetites. Because each link can be serviced according to "bandwidth on demand," the bandwidth available in a beam can be shared between sessions concurrently active within that beam. While the average data rate may be low for a given user, the instantaneous rate can be grown to a specified upper bound according to demand. A dedicated beam service can also be provided to those subscribers requiring 25-155 Mbps.
The HALO aircraft is being flight-tested in Mojave, California. The first flight was accomplished there in July 1998 and the flight envelope is being steadily expanded. The aircraft has been specially designed for the HALO Network and it can carry a large pod suspended from the underbelly of its fuselage. If encountering a persistent wind at altitude, the aircraft will vary its roll angle as it attempts to maintain its station. Various antenna concepts allow the signal footprint to be maintained on the ground as the airplane rolls.
The HALO Network will use an array of narrow beam antennas on the HALO aircraft to form multiple cells on the ground. Each cell covers a small area, e.g., several to several tens of square miles. The wide bandwidths and narrow beam widths of each beam or cell are achieved by using MMW carrier frequencies. Small aperture antennas with high gains can be used at opposite ends of the subscriber link, corresponding to the user terminal and the airborne antenna.
Subscriber units (user terminals)
The user terminal entails three major sub-groups of hardware: the radio frequency unit (RU), which contains the MMW Antenna and MMW Transceiver, the Network Interface Unit (NIU), and the application terminals such as PCs, telephones, video servers, video terminals, etc. The RU consists of a small dual-feed antenna and MMW transmitter and receiver mounted to the antenna. An antenna tracking unit uses a pilot tone transmitted from the HALO aircraft to point its antenna at the airplane.
The MMW transmitter accepts an L-band intermediate frequency (IF) input signal from the network interface unit (NIU), translates it to MMW frequencies, amplifies the signal using a power amplifier to a transmit-power level of 100 - 500 mW, and feeds the antenna. The MMW receiver couples the received signal from the antenna to a Low Noise Amplifier (LNA), down converts the signal to an L-band IF, and provides subsequent amplification and processing before outputting the signal to the NIU. The MMW transceiver will process a single channel at any one time, perhaps as narrow as 40 MHz. The particular channel and frequency are determined by the NIU.