Introduction<br />The markets of broadband, wireless, and multimedia network services are growing rapidly. Those markets are demanding infrastructure that can be deployed quickly and economically. Services must be delivered to businesses and consumers, the end users of the network, at affordable prices. Quality of service (QoS) must be guaranteed. Also, the information bandwidth must respond dynamically to the needs of the end user with an imperceptible latency following a request for more bandwidth. Innovative communications networks are being pioneered to meet rapidly evolving demands. Such a network is the High Altitude Long Operation (HALO) Network.<br />The HALO Network<br />The HALO Network is a broadband wireless metropolitan area network with a star topology.The solitary hub is located in a HALO aircraft also known as the High Altitude Aeronautical Platform Station(HAAPS) operating at an altitude higher than commercial airline traffic and adverse weather. The HALO Network combines the advantages of two well-established wireless communication services: satellite networks and terrestrial wireless. The HALO network will be located in the atmosphere, at an altitude miles above terrestrial wireless, but hundreds to thousands of miles below satellite networks. It will provide broadband services to businesses and small offices/home offices in an area containing a typical large city and its neighbouring towns.<br />HALO Architecture <br />The three main components of the HALO network are<br />HALO Aircraft<br />It is a long-winged light aircraft powered by two turbo-fan engines capable of extended high-altitude flights. It houses the one-ton airborne-network hub, which consists of an antenna array and electronics for wireless communication. It flies at a height of 16 KMS to provide broadband communications services over a footprint 60 miles (96km) in diameter. The HALO aircraft will be operated in shifts from regional airports. A fleet of three aircraft will be cycled in shifts to achieve continuous service. Each shift on station will have an average duration of approximately eight hours. Each plane will accommodate two pilots, who will split flying duties during their eight-hour flight.<br />Onboard Network Hub<br />It is carried in a large pod suspended from the underbelly of the HALO aircraft’s fuselage. In the stratosphere, it can weigh approximately one ton. The payload houses an array of narrow beam antennas and wireless communication equipments which creates hundreds of contiguous virtual cells on the ground to serve thousands of users.<br />Subscriber Terminals<br />Broadband facilities are provided through <br />1. Customer Premise Equipment (CPE) to home and small offices.<br />2. Business Premise Equipment (BPE) for business purposes such as for companies, universities, factories, etc.<br />It can also be connected with non-HALO networks like Asynchronous transfer mode (ATM) networks, ISPs and frame relay through HALO Gateway (HG)interworking unit (IWU). <br />Advantages<br />The following are the advantages<br />Rapid Build out<br />A HALO Network can be put into operation within weeks. Upon network activation, it provides service to the full super metropolitan area and its surrounding communities.<br /> High Signal Quality and Availability<br />At frequencies above 20 GHz, where wireless broadband services are being licensed, high losses of signals are caused by ground terrain, foliage and rain. The high viewing angles to HALO aircraft (20 degrees or greater) assure signal paths free of absorbing objects. The combination of a large aperture and high signal power utilized by the HALO Network allows service availability in regions with high rainfall rates.<br />High Bandwidth<br />The initial capacity of the network will be on the scale of 10 Gb/s, with growth beyond 100 Gb/s. This enables services including but not limited to T1 access, ISDN access, Web browsing, high-resolution videoconferencing, large file transfers, offsite training and Ethernet LAN bridging. <br />Low Cost<br />Negligible ground infrastructure, coupled with a large footprint and multi-megabit-per-second data rates make it extremely competitive on a $/bit/square mile basis.<br />Advantages Over Terrestrial Networks<br /><ul><li>Unlike terrestrial networks, the HALO network does not require complex geometries involving many base stations interlinked by cabling or microwaves.
Increasing the system capacity is much more easier in the case of HALO network than the terrestrial networks which require significant reengineering using cell-splitting techniques.
In terrestrial networks, the communication paths have low look angles with multipath Rayleigh fading. The HALO networks have a high look angle preventing signal fading.
Satellite networks require more expensive terminals with high power to achieve the same data rates possible through the HALO Network operating at much lower costs.
The capacity of a satellite network can be increased only by adding more satellites, which is very expensive.
Unlike satellite systems, which are multi-billion dollar investments, the HALO Network can be financed one market at a time, which makes it more suitable for developing countries like India.
The HALO aircraft is 10 to 1,000 times closer to the user than a satellite, with 10 times the available electrical power. Consequently, the HALO Network can allocate significant capacity directly to densely populated regions.
The satellite networks have longer propagation delays which demand more complex algorithms to achieve interactivity.
The central node i.e. the HALO aircraft, can be routinely serviced for optimal performance, and be steadily enhanced with emerging technologies.
The HALO network will provide wireless broadband communication services at a much affordable rate. The feasibility of this network depends on the advancement of technologies like GaAs(Gallium arsenide) RF modules operating at MMW frequencies, ATM/SONET technology, digital signal processing of wideband signals, video compression, ultra-dense memory modules, lightweight aircraft technology including composite airframes, and small fanjets. The HALO network has already been deployed in certain parts of USA by Angel Technologies Inc. and its strategic partners since 2003.