01-12-2012, 11:23 AM
A PAPER PRESENTATION ON AIRSHIPS AS A LOW COST ALTERNATIVE TO COMMUNICATION SATELLITES
[attachment=42021]
ABSTRACT
The demand for high-capacity wireless services is bringing increasing challenges, especially for delivery of the ‘last mile’. Terrestrially, the need for line-of-sight propagation paths represents a constraint unless very large numbers of base-station masts are deployed, while satellite systems have capacity limitations. An emerging solution is offered by high-altitude platforms (HAPs) operating in the stratosphere at altitudes of up to 22 km to provide communication facilities that can exploit the best features of both terrestrial and satellite schemes. In this paper we outline the application of airships as low cost alternative for HAPs for delivery of future broadband wireless communications.
NEED FOR HIGH ALTITUDE COMMUNICATION PLATFORM
Wireless solutions are becoming increasingly important, because wireless can offer high-bandwidth service provision without reliance on fixed infrastructure and represents a solution to the ‘last mile’ problem, i.e. delivery directly to a customer’s premises, while in many scenarios wireless may represent the only viable delivery mechanism. Wireless is also essential for mobile services, and cellular networks (e.g. 2nd generation mobile) are now operational worldwide. Fixed wireless access (FWA) schemes are also becoming established to provide telephony and data services to both business and home users. The emerging market is for broadband data provision for multimedia, which represents a convergence of high speed Internet, telephony, TV, video-on-demand and sound broadcasting.
LIMITATIONS OF SATELLITES AND TOWER NETWORKING
Based on the studies carried out on the existing methods used for communication using satellites and tower networking, it was found that these methods have several limitations. Incase of Satellites, revenue generation only begins with launch of entire constellation (for e.g. Iridium has 66 satellites). It causes high latency (signal delay) and also there is a limited signal penetration through buildings. Moreover only one company can operate on the entire system and a technology set 3-4 years prior to deployment is required. Any upgrade requires the launch of an entire new constellation. A high infrastructure cost per subscriber, more than US $ 100 million per satellite [1] is involved. Even incase of tower networks, extensive lease and transmission systems are required. There is an inconsistent penetration of buildings in the line of sight in case of tower networking. We cannot shift capacities, and also the dead zones are quite common. Upgrades require a modification at each site and coordinated cutover. Further a complex and expensive installation and network management is needed. Network building requires literally hundreds of towers. Environmental concerns also pose severed restrictions on location of the towers.
AERIAL COMMUNICATION PLATFORMS
A potential solution to the wireless delivery problem lies in aerial platforms, carrying communications relay payloads and operating in a quasi-stationary position at high altitudes. A payload can be a complete base-station, or simply a transparent transponder, akin to the majority of satellites. Line-of-sight propagation paths can be provided to most users, with a modest FSPL (free space path loss), thus enabling services that take advantage of the best features of both terrestrial and satellite communications. A single aerial platform can replace a large number of terrestrial masts, along with their associated costs, environmental impact and backhaul constraints. Site acquisition problems are also eliminated, together with installation maintenance costs, which can represent a major overhead in many regions of the world. These platforms may be manned or unmanned with autonomous operation coupled with remote control from the ground. Platforms under investigations include Airship, Airplane, unmanned aerial vehicle and tethered aerostat which reach up to 5 Km. Airships use very large semi-rigid helium-filled containers. Another form of HAP is the unmanned solar-powered plane, which needs to fly against the wind, or in a roughly circular tight path. The most highly-developed such craft are those from AeroVironment in the USA, whose planned Helios plane has a wing-span of 75m; their Pathfinder and Centurion programmes have already demonstrated flight endurance trials at up to 25km altitude 80000ft. HeliPlat is a solar-powered craft being developed under the auspices of Politecnico di Torino in Italy, as part of the HeliNet Project funded by the European Commission under a Framework V initiative.
BENEFITS OF HAPS OVER OTHER SYSTEMS
HAPs are highly suitable for broadband wireless communications. They appear at a high elevation angle compared to terrestrial base stations, thereby mitigating the terrestrial propagation effects. With a visibility of around 200 Km at 5 Deg elevations, they can replace a large number of terrestrial base stations; and being considerably closer to the ground than satellites offer much lower path loss than satellites - better by ~ 34 dB for LEO satellites and ~ 66 dB for GEO satellites. HAPs have been assigned frequency bands in 47/48 GHz and 28 GHz bands where at present spare spectrum is in plenty. HAP telecommunication systems can be designed to respond dynamically to traffic demands; they are relatively low cost compared to satellites; they can be deployed incrementally and rapidly when necessary; the platforms and payload are upgradeable; and they are environmentally friendly using solar power, without need of launchers and eliminate the need of terrestrial masts. Typical cell size of HAPs range between 1-10 Km and the communication throughout can range between 25-155 Mb/s. The coverage is regional, though it is possible to inter-link HAPs creating a national grid, or alternatively they can be connected to distant gateways via satellites. They have been proposed for broadband fixed wireless access (B-FWA), mobile communications as base stations, rural telephony, broadcasting, emergency or disaster applications, military communications, etc.
CURRENT DEVELOPMENTS WORLDWIDE
The airship has a semi-rigid hull of ellipsoidal shape with an overall length of nearly 200 m. It is composed of an air-pressurized hull for maintaining a fixed contour, and internal bags filled with the buoyant helium gas. Two air ballonets are installed inside the hull to keep the airship at a required attitude. For a load balance to the lifting force, catenary curtains are connected to a lower rigid keel, directly attached to the envelope. Propulsive propellers are mounted on both the stem and stern of the airship, and tail wings are installed on the rear end of the hull. A solar photovoltaic power subsystem of solar cells and regenerative fuel cells is provided to supply a day/night cycle of electricity for airship propulsion.
CONCLUSION
Terrestrially, the need for line-of-sight propagation paths represents a constraint unless very large numbers of base-station masts are deployed, while satellite systems have capacity limitations. Hence, airships may acts as a low cost alternative for communication satellites for delivery of future broadband wireless communications.
[attachment=42021]
ABSTRACT
The demand for high-capacity wireless services is bringing increasing challenges, especially for delivery of the ‘last mile’. Terrestrially, the need for line-of-sight propagation paths represents a constraint unless very large numbers of base-station masts are deployed, while satellite systems have capacity limitations. An emerging solution is offered by high-altitude platforms (HAPs) operating in the stratosphere at altitudes of up to 22 km to provide communication facilities that can exploit the best features of both terrestrial and satellite schemes. In this paper we outline the application of airships as low cost alternative for HAPs for delivery of future broadband wireless communications.
NEED FOR HIGH ALTITUDE COMMUNICATION PLATFORM
Wireless solutions are becoming increasingly important, because wireless can offer high-bandwidth service provision without reliance on fixed infrastructure and represents a solution to the ‘last mile’ problem, i.e. delivery directly to a customer’s premises, while in many scenarios wireless may represent the only viable delivery mechanism. Wireless is also essential for mobile services, and cellular networks (e.g. 2nd generation mobile) are now operational worldwide. Fixed wireless access (FWA) schemes are also becoming established to provide telephony and data services to both business and home users. The emerging market is for broadband data provision for multimedia, which represents a convergence of high speed Internet, telephony, TV, video-on-demand and sound broadcasting.
LIMITATIONS OF SATELLITES AND TOWER NETWORKING
Based on the studies carried out on the existing methods used for communication using satellites and tower networking, it was found that these methods have several limitations. Incase of Satellites, revenue generation only begins with launch of entire constellation (for e.g. Iridium has 66 satellites). It causes high latency (signal delay) and also there is a limited signal penetration through buildings. Moreover only one company can operate on the entire system and a technology set 3-4 years prior to deployment is required. Any upgrade requires the launch of an entire new constellation. A high infrastructure cost per subscriber, more than US $ 100 million per satellite [1] is involved. Even incase of tower networks, extensive lease and transmission systems are required. There is an inconsistent penetration of buildings in the line of sight in case of tower networking. We cannot shift capacities, and also the dead zones are quite common. Upgrades require a modification at each site and coordinated cutover. Further a complex and expensive installation and network management is needed. Network building requires literally hundreds of towers. Environmental concerns also pose severed restrictions on location of the towers.
AERIAL COMMUNICATION PLATFORMS
A potential solution to the wireless delivery problem lies in aerial platforms, carrying communications relay payloads and operating in a quasi-stationary position at high altitudes. A payload can be a complete base-station, or simply a transparent transponder, akin to the majority of satellites. Line-of-sight propagation paths can be provided to most users, with a modest FSPL (free space path loss), thus enabling services that take advantage of the best features of both terrestrial and satellite communications. A single aerial platform can replace a large number of terrestrial masts, along with their associated costs, environmental impact and backhaul constraints. Site acquisition problems are also eliminated, together with installation maintenance costs, which can represent a major overhead in many regions of the world. These platforms may be manned or unmanned with autonomous operation coupled with remote control from the ground. Platforms under investigations include Airship, Airplane, unmanned aerial vehicle and tethered aerostat which reach up to 5 Km. Airships use very large semi-rigid helium-filled containers. Another form of HAP is the unmanned solar-powered plane, which needs to fly against the wind, or in a roughly circular tight path. The most highly-developed such craft are those from AeroVironment in the USA, whose planned Helios plane has a wing-span of 75m; their Pathfinder and Centurion programmes have already demonstrated flight endurance trials at up to 25km altitude 80000ft. HeliPlat is a solar-powered craft being developed under the auspices of Politecnico di Torino in Italy, as part of the HeliNet Project funded by the European Commission under a Framework V initiative.
BENEFITS OF HAPS OVER OTHER SYSTEMS
HAPs are highly suitable for broadband wireless communications. They appear at a high elevation angle compared to terrestrial base stations, thereby mitigating the terrestrial propagation effects. With a visibility of around 200 Km at 5 Deg elevations, they can replace a large number of terrestrial base stations; and being considerably closer to the ground than satellites offer much lower path loss than satellites - better by ~ 34 dB for LEO satellites and ~ 66 dB for GEO satellites. HAPs have been assigned frequency bands in 47/48 GHz and 28 GHz bands where at present spare spectrum is in plenty. HAP telecommunication systems can be designed to respond dynamically to traffic demands; they are relatively low cost compared to satellites; they can be deployed incrementally and rapidly when necessary; the platforms and payload are upgradeable; and they are environmentally friendly using solar power, without need of launchers and eliminate the need of terrestrial masts. Typical cell size of HAPs range between 1-10 Km and the communication throughout can range between 25-155 Mb/s. The coverage is regional, though it is possible to inter-link HAPs creating a national grid, or alternatively they can be connected to distant gateways via satellites. They have been proposed for broadband fixed wireless access (B-FWA), mobile communications as base stations, rural telephony, broadcasting, emergency or disaster applications, military communications, etc.
CURRENT DEVELOPMENTS WORLDWIDE
The airship has a semi-rigid hull of ellipsoidal shape with an overall length of nearly 200 m. It is composed of an air-pressurized hull for maintaining a fixed contour, and internal bags filled with the buoyant helium gas. Two air ballonets are installed inside the hull to keep the airship at a required attitude. For a load balance to the lifting force, catenary curtains are connected to a lower rigid keel, directly attached to the envelope. Propulsive propellers are mounted on both the stem and stern of the airship, and tail wings are installed on the rear end of the hull. A solar photovoltaic power subsystem of solar cells and regenerative fuel cells is provided to supply a day/night cycle of electricity for airship propulsion.
CONCLUSION
Terrestrially, the need for line-of-sight propagation paths represents a constraint unless very large numbers of base-station masts are deployed, while satellite systems have capacity limitations. Hence, airships may acts as a low cost alternative for communication satellites for delivery of future broadband wireless communications.