Presented By:
MADHUSUDHAN.G
SIVA KUMAR REDDY.D

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ABSTRACT
Wireless communication is simply data communication without the use of landlines. This may involve cellular telephone, two-way radio, fixed wireless (broadband wireless), laser (freespace optics) or satellite communications. Mobile wireless technologies are going to act as glue towards bringing together the wired and wireless to share and distribute information seamlessly across each other’s areas of reference.
The paper firstly introduces the wireless communications and then switches to fourth generation in wireless communications.
The paper then discusses about High Altitude Airships, the “STRATELLITES” which are actually unmanned Kelvar balloons filled with helium which are used instead of towers for wireless communication, each of which replace hundreds of towers and reduce the cost of wireless communications. They also overcome the disadvantage of simple towers which could not provide proper coverage in the hilly areas.
INTRODUCTION
Wireless communication is simply data communication without the use of landlines. This may involve cellular telephone, two-way radio, fixed wireless (broadband wireless), laser (freespace optics) or satellite communication systems. Mobile wireless technologies are going to act as glue towards bringing together the wired and wireless to share and distribute information seamlessly across each other’s areas of reference.
Since from the beginning of wireless communications, there have been a number of developments in each generation. Considering the future generation of wireless communication i.e; 4G.
4GENERATION
To achieve the goals of true broadband cellular service, the systems have to make the leap to a fourth-generation (4G) network. 4G is intended to provide high speed, high capacity, low cost per bit, IP based services. The goal is to have data rates up to 20 Mbps. Most probable the 4G network would be a network which is a combination of different technologies (current cellular networks, 3G cellular network, wireless LAN, etc.)
4G-cellular systems should not only be high-speed but also high-capacity, with low bit cost, high capacity with reasonable frequency bandwidth, the cell radius of 4G-cellular systems shall be decreased from that of present cellular systems.
4G Mobile Communication
Systems
Some of the systems for future mobile communications are:
1. Broad-Band Wireless Systems
2. Intelligent Transport Systems
3. High Altitude Stratospheric Platform Station Systems.
High Altitude Stratospheric Platform Station Systems (HAPS)
HAPS has the potential to become the third communications infrastructure after terrestrial and satellite communications. The platforms keep their positions at about 20 km high in the stratosphere. By optical intercommunication links, they make a mesh-like network in the sky. A broadband access page link is the page link between the platform station and the user station. The typical bit rate of the access page link is 25 Mb/s for most fixed and portable terminals, while a several hundred megabits per second page link is available for limited fixed terminals with antennas larger than the typical ones. Because of using millimeter-wave bands, a small antenna with high gain is feasible. For example, a bit rate of 144 kb/s can be provided for vehicles by only a 5 cm dish antenna with 20 dB gain.
STRATELLITE
A “stratellite” is a high-altitude airship (HAA) “25 times larger than the Goodyear blimp” employed much like a satellite for remote sensing, navigation, and communications. Instead of being stationed on orbit, stratellites are positioned in the stratosphere approximately 13 miles above the Earth.
This altitude places the airships above both commercial air traffic and weather effects but significantly lower than standard low earth orbits. From this height stratellites can service a 300,000-square-mile-area. The North American Aerospace Defense Command (NORAD) projects that eleven such airships could provide radar coverage of the entire maritime and southern borders of the United States.
Construction Of Stratellite
The initial Stratellite was 188 feet long, 60 feet wide and 42 feet high. It is provided with a new steering method which uses a hybrid electric system that drives large, slow-turning propellers. This gives the airship helicopter-like agility by being able to move both up and down, and side to side. The outside layer, or "envelope," is made out of a high-tech material called Spectra - a fabric used in bullet-proof vests and parts of space shuttles. Spectra contains fibre 10 times as strong as steel of the same weight and has the unique feature of being easy to cut but virtually impossible to tear.
The inside layer, made from a thin but strong polyester film called Mylar, is fitted inside the envelope and filled with a mixture of helium and air as helium is an inert gas and is therefore not flammable. With this design, the helium expands as the airship rises, forcing air out and lifting the airship. The cycle continues, allowing the airship to gain more and more altitude until the helium has expanded to fill the envelope completely. Because the pressure is so low inside the envelope, a puncture would only result in a very slow leak, taking a long time to totally deflate.
Stratellite Technology and Advantages
Stratellites are actually unmanned Kevlar balloons filled with helium. They use thin-film photovoltaic cells sprayed on their surfaces to generate electricity, which drives propellers that work with GPS technology to keep the stratellite positioned over one spot on the Earth’s surface. Prototype airships are projected to carry payloads as large as 4,000 pounds, and later models are expected to carry over 20,000 pounds of radars and other remote imaging equipment, navigational aids, and telecommunications relays. Stratellites are planned to remain on station for a year at a time and will cost a fifth as much as a comparable satellite
Drawbacks Of Satellites
These firms are becoming involved with stratellites because they avoid the two main drawbacks of satellites. The first is signal latency, which can cause problems in establishing broadband links.Most telecommunications satellites are in geostationary orbit to remain above a certain point on the Earth’s surface. That orbit, however, is 22,240 miles above the Earth, (i.e; in the area called CLARKE’S BELT), which means that a signal going up to the satellite(uplink) and back to the Earth(downlink) travels nearly 45,000 miles, which equates to about a quarter of a second delay. Even users of satellite voice links notice the delay.
The second drawback is that satellites are in space, requiring expensive space launches, an additional level of regulation by national space authorities, and an orbital allotment by the International Telecommunications Union (ITU). Stratellites remain in national airspace and are
Stratellites remain in national airspace and are therefore not subject to these licensing and technology requirements. However, they do make use of space technology and, as stated above, are in development by at least one space industry firm.