Microwave and Radio Based Systems, a simple discussion

Microwave system is always a Line-of-Sight system which is based on the visibility between the Transmit End & Receive End.

•It is mandatory to avoid any physical obstruction in the line of sight design.

•The obstructions would include High rise buildings, Hillocks & Vegetations like tall trees.

•To overcome these obstructions we may have to increase the number of towers or increase

the height of the towers.

•The microwave systems can operate in LOS mode for around a few hundred meters to over 60 Km.

•So it is imperative to determine the LOS over the complete hop length between

 he Transmit end & Receive end

When a microwave signal is sent it travels from the transmit end to the receive end the signals take the form of an ellipsoid. The size of ellipsoid depends on the frequency of operation. The higher the operating frequency the smaller is the size of the ellipsoid. The size of the ellipsoid is biggest at the center of the LOS. If any obstruction is allowed into the fresnel zone, the obstruction will reflect the signal. This reflected signal will cancel out and distort the main signal thus reducing the strength of the main signal.

The height of the LOS should be high enough to not permit any obstructions to enter the fresnel zone.

The microwave signals do not travel in a straight line but tend to travel in a curved path following the curvature of the earth. The reason for the effect is the refractive index of the atmosphere reduces with the increase in altitude. This is known as the earth bulge factor ( k).

The antenna is a device that converts the electrical signals into the electromagnetic waves that propagate through free space.

 In Microwave systems the Standard Antenna used are Parabolic Antennas.

Antenna gain is a measure of the antenna’s ability to transmit the waves in a specific direction instead of in all direction.

Whats with Microwave Radio Based System?

Series 875 LAN+T1 Microwave Radio System is a low cost, high bandwidth, radio system capable of transporting full bandwidth LAN traffic and T1 telephony up to 3 miles. The radio system offers the following features:

The Ethernet interface of the radio system supports all 802.3 protocols and includes an AUI connection to network devices and BNC connections to the microwave unit. The T1 data interface of the radio system supports Bell Standard 100 ohm, two-wire twisted pair designed to connect to telephony and multimedia interfaces. No on-site programming is required and no additional test equipment is needed.

The Series 875 LAN+T1 system provides point-to-point connections for hubs, bridges, routers and repeaters allowing full 10 Mbps Ethernet connectivity. The 875 LAN+T1 interface has been designed to connect directly to standard T1 PBX's, Channel Banks or Telecom Multiplexers without the need for additional equipment. 

The Series 875 LAN+T1 is designed for rapid installation and alignment without special tools or test equipment. Rugged, modular radio design for ease of service and field support for years of trouble free operation in harsh weather conditions.

Why Microwave Radio Based Sytem?

Microwave Radio System offers the following features Standard IEEE 802.3 LAN Interface Standard Bell T1 1.544 Mbps Interface Standard 10 Mbps or Full Duplex Ethernet Lightweight package 7 Ibs (3.2kg) Interference free operation -30C to +55C temperature range EMI/RFI protection Compact Size 9" antenna Easy to Install Easy to Maintain

Sources:

http://www.arcelect.com/Wireless_875_LAN+T1_23GHz.htm

http://www.ehow.com/list_6137210_microwave-radio-communications-advantages-disadvantages.html

nystec.com/files/Microwave.pdf

http://www.dpstele.com/dpsnews/techinfo/microwave_knowledge_base/microwave_system.php

Broadband Telecommunications Handbook