The Basics of Mobile Technology
Mobile operators use radio spectrum to provide their services. Spectrum is generally considered a scarce resource, and has been allocated as such. It has traditionally been shared by a number of industries, including broadcasting, mobile communications and the military. At the World Radio Conference (WRC) in 1993, spectrum allocations for 2G mobile were agreed based on expected demand growth at the time. At WRC 2000, the resolutions of the WRC expanded significantly the spectrum capacity to be used for 3G, by allowing the use of current 2G spectrum blocks for 3G technology and allocating 3G spectrum to an upper limit of 3GHz.
Before the advent of cellular technology, capacity was enhanced through a division of frequencies, and the resulting addition of available channels. However, this reduced the total bandwidth available to each user, affecting the quality of service. Cellular technology allowed for the division of geographical areas, rather than frequencies, leading to a more efficient use of the radio spectrum. This geographical re-use of radio channels is knows as “frequency reuse”.
In a cellular network, cells are generally organized in groups of seven to form a cluster. There is a “cell site” or “ base station” at the centre of each cell, which houses the transmitter/receiver antennae and switching equipment. The size of a cell depends on the density of subscribers in an area: for instance, in a densely populated area, the capacity of the network can be improved by reducing the size of a cell or by adding more overlapping cells. This increases the number of channels available without increasing the actual number of frequencies being used. All base stations of each cell are connected to a central point, called the Mobile Switching Office (MSO), either by fixed lines or microwave. The MSO is generally connected to the PSTN (Public Switched Telephone Network):
Cellular technology allows the “ hand-off” of subscribers from one cell to another as they travel around. This is the key feature which allows the mobility of users. A computer constantly tracks mobile subscribers of units within a cell, and when a user reaches the border of a call, the computer automatically hands-off the call and the call is assigned a new channel in a different cell.
International roaming arrangements govern the subscriber’s ability to make and receive calls the home network’s coverage area
Mobile Computing Networks
Temporary or Switched Connection via Wireline WAN:-
Permanent connection between a mobile user and information source is not only expensive but is not always practical because mobile users are constantly on the move. Therefore, the most popular (though not most ubiquitous or pervasive or persistent - using the new lingo) method of providing connectivity to mobile workers continues to be one of a temporary wireline connection for a specific use and a required period of time. This can be achieved by using a dial-up connection on a traditional public telephone or cellular network. You call it switched because you switch a circuit from one user to another user for the duration of the call. You may have a switched wireline connection directly between a remote location where the user is at a given moment and the information server or indirectly through the Internet. In either case, you still need to locate a telephone jack of one kind or another. Go to PSTN, ISDN, ADSL, or VPNs (Internet based Virtual Private Networks) for further information on these temporary connections for mobile workers.
Permanent connection between a mobile user and information source is not only expensive but is not always practical because mobile users are constantly on the move. Therefore, the most popular (though not most ubiquitous or pervasive or persistent - using the new lingo) method of providing connectivity to mobile workers continues to be one of a temporary wireline connection for a specific use and a required period of time. This can be achieved by using a dial-up connection on a traditional public telephone or cellular network. You call it switched because you switch a circuit from one user to another user for the duration of the call. You may have a switched wireline connection directly between a remote location where the user is at a given moment and the information server or indirectly through the Internet. In either case, you still need to locate a telephone jack of one kind or another. Go to PSTN, ISDN, ADSL, or VPNs (Internet based Virtual Private Networks) for further information on these temporary connections for mobile workers.
Wireless PANs (Personal Area Networks):-
These are wireless networks that can be installed in a small office or home within 5-15 metre distances. Two technologies being used for this purpose are IrDA which is based on line of sight requirement within two devices, usually a few feet apart. For more details on IrDA, please go to IrDA site. The second technology is Blue Tooth. Blue tooth technology supports multipoint connection without line of sight requirement. Go to Blue Tooth topic under "Hot Topic" menu item on our site's home page.
These are wireless networks that can be installed in a small office or home within 5-15 metre distances. Two technologies being used for this purpose are IrDA which is based on line of sight requirement within two devices, usually a few feet apart. For more details on IrDA, please go to IrDA site. The second technology is Blue Tooth. Blue tooth technology supports multipoint connection without line of sight requirement. Go to Blue Tooth topic under "Hot Topic" menu item on our site's home page.
Wireless LAN:-
Where the movement is within a contained geographical area, you can provide mobility by implementing a wireless LAN and equipping your mobile device with a corresponding wireless adapter - a PC card variety that goes into a notebook, hand-held PDA, a Windows CE-compatible device or Palm Pilot organizer. Go to Wireless LANs page for more info.
Where the movement is within a contained geographical area, you can provide mobility by implementing a wireless LAN and equipping your mobile device with a corresponding wireless adapter - a PC card variety that goes into a notebook, hand-held PDA, a Windows CE-compatible device or Palm Pilot organizer. Go to Wireless LANs page for more info.
Wireless MAN (Metropolitan Area Network):-
Metricom's Ricochet, a specialized wireless network is available at 128 kbps, 24 hours 7 days always on, in the following major metropolitan areas: Atlanta, Baltimore, Dallas, Denver, Detroit, Houston, Los Angeles, Minneapolis St. Paul, New York City, Philadelphia, Phoenix, San Francisco Bay Area and San Diego and 15 airports nationwide. These areas join the Washington DC and Seattle 28.8 kbps service areas. The service is offered through WWC, Worldcom, Earthlink, GoAmerica and Juno for $79.95/month and under. " (circa Spring 2001). Go to Metricom network description on this site for more.
Metricom's Ricochet, a specialized wireless network is available at 128 kbps, 24 hours 7 days always on, in the following major metropolitan areas: Atlanta, Baltimore, Dallas, Denver, Detroit, Houston, Los Angeles, Minneapolis St. Paul, New York City, Philadelphia, Phoenix, San Francisco Bay Area and San Diego and 15 airports nationwide. These areas join the Washington DC and Seattle 28.8 kbps service areas. The service is offered through WWC, Worldcom, Earthlink, GoAmerica and Juno for $79.95/month and under. " (circa Spring 2001). Go to Metricom network description on this site for more.
Wireless WAN - Private or Public:-
Once we move out of the limited geography of a wireless LAN in a campus or factory setting, we have to utilize wide area wireless network. These networks may be private or public. Large organizations, such as Fedex or public safety agencies, have implemented private CDPD or SMR networks to give wireless connectivity to courier drivers and police officers. However, the current trend is to move towards shared public networks, such as Motient or BellSouth (ex RAM Mobile Data - called Mobitex in Europe and Canada). Go to wireless WANs for more info.
Once we move out of the limited geography of a wireless LAN in a campus or factory setting, we have to utilize wide area wireless network. These networks may be private or public. Large organizations, such as Fedex or public safety agencies, have implemented private CDPD or SMR networks to give wireless connectivity to courier drivers and police officers. However, the current trend is to move towards shared public networks, such as Motient or BellSouth (ex RAM Mobile Data - called Mobitex in Europe and Canada). Go to wireless WANs for more info.
Satellite Networks :-
Even wireless wide area networks may not provide coverage in extremely remote areas, because networks can not justify the economics of installing a base station everywhere. True universal coverage for these types of mobile users is possible only through wireless networks based on satellites. There are several GEOS, LEOS, and MEOS satellite-based networks that transmit from different heights from the surface of the earth. Refer to these terms in the glossary.
Even wireless wide area networks may not provide coverage in extremely remote areas, because networks can not justify the economics of installing a base station everywhere. True universal coverage for these types of mobile users is possible only through wireless networks based on satellites. There are several GEOS, LEOS, and MEOS satellite-based networks that transmit from different heights from the surface of the earth. Refer to these terms in the glossary.
The Last Mile Problem for Wireless Networks :-
One thing worth noting is that it is only the last mile (or so!) where we need wireless or radio-frequency-based connection. Once we reach a terrestrial network, we can utilize the bandwidth of traditional wireline permanent connections. By the same token, once we reach the Internet Service Provider through a wireless hub or concentrator, we can be home free for riding high-speed connection to the universal information highway.
One thing worth noting is that it is only the last mile (or so!) where we need wireless or radio-frequency-based connection. Once we reach a terrestrial network, we can utilize the bandwidth of traditional wireline permanent connections. By the same token, once we reach the Internet Service Provider through a wireless hub or concentrator, we can be home free for riding high-speed connection to the universal information highway.
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