Chapter 17: Microwave− and Radio−Based Systems

Microwave and Radio Based Systems

Overview

            Many countries use the microwave and radio based systems as an emergency services, homeland security, public safety and disaster recovery organizations are heavily reliant on reliable mobile radio network coverage for mission-critical communications. Point-to-point digital microwave radio systems are deployed in these networks to inter-connect mobile radio base stations and backhaul the vital communications to the central or regional switches. The systems are typically deployed where distance, difficult terrain or harsh environments mean the speed or cost of deployment for wired, fiber and satellite communications is not viable or commercially feasible. But besides of its function there a lot of people did not know how the microwave radio systems useful. This technology has been taken for granted over the years. has been taken for granted over the years.

Possible market share for microwave products

Service	2002	2006
Point−to−point microwave radios services	$2.5 billion	$4 billion
Point−to−multipoint microwave	$700 million	$2 billion
Wireless LAN microwave products	$1.4 billion	$4 billion
Total	$4.6 billion	$10 billion

Microwave has also become a vital link in the overall backbone networks over the years. Now, it has achieved new acclaim in the wireless revolution, relaying thousands of telephone conversations from place to place, bypassing the local landlines.

Microwaves  are between 1 mm and 30 cm long, and operate in a frequency range from 300 MHz to 300 GHz. Microwaves were first used in the 1930s, when British scientists discovered the application in a new technology called radar. Microwave radio was used extensively for long−distance telephone transmission. With the need to communicate over thousands of miles, the cost of stringing wires across the country was prohibitive. However, the equipment was both heavy and expensive. the typical microwave radio used 2,100 watts to generate three groups of radio channels (each group consists of 12 channels), yielding 36−voice−grade−channel capacity. Each voice grade channel operated at the standard 4 kHz.

Throughout the world, government−owned and −controlled monopolies are being eliminated. Brazil opened its doors to international Telecom competition, allowing microwave radio systems and a mobile telephone system supplied by North American firms. In Russia, one of the leading systems manufacturers installed an integrated network along a 3,600−mile gas pipeline.

The cellular and Personal Communications Service (PCS) industries invested heavily in microwave radios to interconnect the components of their networks. Where the

interconnection is used in the cellular world.

Cellular interconnection of microwave radio:

WinStar Communications, a Competitive Local Exchange Carrier (CLEC), pioneered the use of

micro/millimeter wave radio communications in the 30+ GHz frequency range (actually 28 to 38
GHz). This allowed the CLEC to deliver broadband communications to the consumer's door without the use of telephone company wires.

Advantages of Microwave Radio:

1.    Radio systems do not require a right way acquisition between stations.

2.    Each station requires the purchase or lease of only a small area of land.

3.    Because of their high operating frequencies, microwave radio systems can carry large quantities of information.

4.    High frequencies mean short wavelengths, which require relatively small antennas.

5.    Radio signals are more easily propagated around physical obstacles such as water and high mountains.

6.    Fewer repeaters are necessary for amplification.

7.    Underground facilities are minimized.

8.    Minimum delay times are introduced. Minimal crosstalk exists between voice channels.

9.    Increased reliability and less maintenance are important factors.

Disadvantages of microwave radio:

1.    It is more difficult to analyze and design circuits at microwave frequencies.

2.    Measuring techniques are more difficult to perfect and implement at microwave frequencies.

3.    It is difficult to implement conventional circuit components at microwave frequencies like (resistors, capacitors,inductors, ….)

4.    Transient time is more critical at microwave frequencies.

5.    It is often necessary to use specialized components for microwave  frequencies.

6.    Microwave frequencies propogate in a straight line, which limits their use to line of sight applications

reference:

http://en.wikipedia.org/wiki/Microwave_transmission

Broadband Telecommunications Handbook, Second

Edition: Regis J. (Bud) Bates