INTRODUCTION TO WIRELESS SYSTEMS

The ability to communicate with people on the move has evolved remarkably since Guglielmo-Marconi first demonstrated radio's ability to provide continuous contact with ships sailing the English channel that was in 1897, and since then new wireless communications methods and services have been enthusiastically adopted by people throughout the world. Particularly during the past ten years, the mobile radio communications industry was grown by orders of magnitude, fueled by digital and RF circuit fabrication improvements, new -large scale circuit integration, and other miniaturization technologies which make portable radio equipment smaller, cheaper and more reliable .Digital switching techniques have facilitated the large-scale development of affordable ,easy to use radio communication networks. These trends will continue at an even greater pace during the next decade.

EVOLUTION OF MOBILE RADIO COMMUNICATION:

Brief history of evolution of mobile communication throughout the world is useful in order to appreciate the enormous impact that cellular radios and personal communication service will have on all of us over the next several decades .It is also useful for a newcomer to the cellular radio field to understand the tremendous impact that government regularity agencies and service competitors yield in the evaluation of new wireless system services and technologies.

Wireless Technology

Wireless means transmitting signals over invisible radio waves instead of wires. Garage door openers and television remote controls were the first wireless devices to become a part of everyday life. Now the cordless keyboard and mouse, PDAs, and digital and cellular phones are commonplace.

Wireless technologies are used for things as simple as making a phone call or as complex as letting the sales force get information from a SAP application. For businesses, wireless technology means new ways to stay in touch with customers, suppliers and employees. The future of wireless lies in faster, more reliable methods of transferring data and, to a lesser extent, increased use of voice commands and audio improvements.

What's the difference between wireless and mobile?
Mobile just means portable. A laptop is a mobile-device, as is a PDA. A desktop would be a mobile-device if you had the inclination to carry it around with you. A wireless device has some sort of network connectivity. A cell phone is wireless, and a laptop or PDA would be wireless if they had a wireless modem. Similarly, applications are wireless when they connect and exchange data with a network.

wireless networks
Wireless data is predominately transferred over two kinds of networks: wide area networks (WANs) and local area networks (LANs). These networks are similar to their wired counterparts-they just use radio waves instead of copper or fiber. WANs can cover areas as large as several countries AT&T Wireless, Cingular Wireless, Sprint PCS and Verizon and are among the carriers that use wireless WANs. Wireless LANs, already popular in airports and hotels, are often used to replace or enhance wired LANs. LANs can cover 1.25 miles indoors and up to 4.35 miles outdoors in extreme cases, but work best in the 500-foot range. They may service a smaller area than their WAN cousins, but LANs can transfer data much faster, with speeds of 54Mbps now possible. Several companies are now beginning to use Wireless LANs for voice over IP.

More on LANs

Wireless LANs all use some standard in the 802.11 family to communicate. There's an 802.11 standard for just about every letter in the alphabet. You don't really need to worry about most of them - they are security and clarity standards that mean only that wireless LANs are getting even safer and easier to use. There are only three standards you really need to worry about:

802.11b -

This protocol, which uses the 2.4GHz spectrum, dominated the market first, earning it the nickname Wi-Fi. It's a busy spectrum, full of baby monitors, cordless phones and microwave ovens, and the more traffic builds the greater the chance for interference and drops in speed. Today, service is good and speeds remain fast. An 802.11b user can get connection rates of up to 11Mbps from up to three different information sources at a time - for maximum throughput availability of 33Mbps - before interference becomes a problem.

802.11a -

A competing wireless LAN standard that operates in the 5GHz spectrum allows for speeds of up to 54Mbps from up to eight different access points at a time, giving it a greater range and max speeds up to 13 times faster. However, in order to use 802.11a you need all of those access points. The primary reason to choose one is a need for lots of bandwidth, for example, for transmitting voice or video over your network. Since b is ubiquitous - and a and b aren't compatible - 802.11a equipment isn't good for portability.

802.11g -

This is the next generation of 802.11b, promising the price and range of b (it operates on the same 2.4GHz spectrum) with the speed of a. It is compatible with existing b infrastructure and is generally believed to be the heir to most LAN connections.

More on WANs

The first generation wireless WAN was analog voice (the earliest cell phones). The second generation was digital - more efficient cell phones that could move data at rates of 9.6Kbps to 14.4Kbps. Most U.S.carriers are now at 2.5 generation, or 2.5G transmission rates, which will carry data up to 114Kbps, but will most likely perform similar to a dial-up modem. During the next few years, carriers
will roll out 3G, which will include theoretical transmission rates of up to 2Mbps to 5Mbps, advanced
roaming capabilities, as well as the sought after (by some) "always-on" potential.

Like LANs, WANs have many acronyms, mainly because carriers use different standards. Each works, but they don't always work with each other.

wireless adoption
Real wireless projects depend on three elements: the device, the network (i.e. the WAN) and the application. If one of those elements isn't up to par,then the project won't work. No one uses cumbersome devices; people give up if they can't connect to the network, and there's no point in doing a project if you can't deliver the data. Until recently, most devices had small screens that made it hard to view data, they ran out of batteries quickly-sometimes wiping out all the information in the process-and they were expensive. Networks, meanwhile, were proprietary and expensive.

Those that succeeded fell into predictable categories.
They were the companies that had large mobile workforces, depended on data from those workforces and, most importantly, could afford to invest in custom devices, proprietary coverage plans and homegrown applications. Common examples were trucking companies that tracked their drivers with GPS devices,shipping companies offering delivery confirmation, and utility companies whose repair crews collected large amounts of data about problems and fixes in the field.


limitations of wireless

When it comes to WANs, bandwidth is still limited. When transmitting data, users must sometimes send smaller bits of data so the information moves more quickly. The size of the device that's accessing the information is also still an issue. Even the most recent phones and PDAs have small screens-often only a couple of inches in diameter-and it is hard to read large documents on them.

Many applications need to be reconfigured if they are going to be used through wireless connections. Most client/server applications rely on a persistent connection, which is not the case with wireless. Transactional systems require safeguards for dropped wireless connections. Remedies for all of these
shortcomings cost money.

Need for wireless

Just because your company can go wireless doesn't mean it should-not every company needs wireless.Critical, time-sensitive applications are the best candidates for WAN projects. If getting information in real-time makes or breaks a sale, give your salespeople access to that data. But remember that WANs are best suited for accessing small pieces of information because of bandwidth constraints.

Wireless LANs are often installed for convenience, such as when an enterprise doesn't want to wire the building, or when an IT staff is dispersed throughout the building. They are often used in hospitals, where doctors and clinicians can check in while on rounds or on the floor. Wireless LANs are faster and more reliable than WANs.