Wireless Broadband and Other Fixed-Wireless Systems
By Peter Rysavy Our appetite for bandwidth is insatiable. And now, just as wireline modems are topping out at 56 Kbps and ISDN service is finally available in most locations, new technologies, such as DSL (Digital Subscriber Line) and cable modems that offer transmission speeds of megabits per second, are beginning field trials. Meanwhile, old standbys, such as corporate T1 connections at 1.54 Mbps, are being upgraded by many companies to T3 fiber connections. But as quickly as LECs (local exchange carriers) and competitive access providers lay new fiber, many companies are finding high-bandwidth connections difficult to obtain or prohibitively expensive. Wireless has always been an alternative for high-speed connections, but never has the range of choices been as great nor the rate of innovation as rapid. This chapter delves into the world of wireless broadband and other fixed-wireless connections that deliver data rates from T1 to 155 Mbps. These wireless connections serve the same function as a wireline-- interconnecting private networks, bypassing a local exchange carrier or connecting to the Internet.
In our first chapter on wireless networks (http://www.networkcomputing.com/netdesign/wireless1.html), we examined wide-area wireless networks, covering data over PCS (personal communications systems), packet data networks and Metricom Ricochet. In our second chapter, we surveyed wireless LANs (http://www.networkcomputing.com/netdesign/wlan1.html). Both chapters concentrated on mobile computer communications. This chapter focuses on communications that are fixed and at higher data rates. A simple form of such a system might involve a private microwave point-to-point connection; a more complex system might involve a carrier that has deployed a complete network using sophisticated point-to-multipoint hubs. A LEO (low-earth-orbiting) system of satellites would be even more complex. There are as many variations in high-speed wireless systems as there are variations in wireline systems.
Fixed-wireless systems have a long history. Point-to-point microwave connections have long been used for voice and data communications, generally in backhaul networks operated by phone companies, cable TV companies, utilities, railways, paging companies and government agencies, and will continue to be an important part of the communications infrastructure. Frequencies used range from 1 GHz to 40 GHz. But technology has continued to advance, allowing higher frequencies, and thus smaller antennas, to be used, resulting in lower costs and easier-to-deploy systems for private use and for a whole new generation of carriers that are planning to use wireless access as their last mile of communication. The terms wireless broadband and broadband wireless are not used consistently, but generally both apply to carrier-based services in which multiple data streams are multiplexed onto a single radio-carrier signal. Some vendors also use the terms to refer to privately deployed networks.
The goal of this chapter is to show how fixed-wireless systems are no longer a communications tool restricted to large or specialized organizations. They are available to almost any size company in a variety of ways for a variety of purposes. Youčll find that you have a wide range of choices, including whether to use licensed or unlicensed spectrum, whether to deploy a private network or use a carrier network, and whether to use a terrestrial network or a satellite network. In some cases, you may not even know that your service provider is using wireless technology. This chapter discusses the options available, how the various technologies work and how to go about implementing a fixed-wireless solution.
Wireline versus Wireless
Private versus Carrier
Unique Aspects of Wireless
Types of Fixed-Wireless Systems
Private Licensed Links (Microwave)
Private Unlicensed Links (Spread Spectrum)
38-GHz Carrier Service
LMDS (Local Multipoint Distribution Service)
And the Rest
Using Fixed-Wireless Systems
Choosing Between Wireless and Wireline
Understanding Geography and Climate
Choosing Between Private and Carrier
How To Deploy a Private Connection
How To Use a Wireless Broadband Carrier
When To Use Satellites
Service and Equipment Providers
Unlicensed Wireless Bridges
Wireless Broadband Carriers