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   DataBus - Vol 40 No 3: April-May, 2000
  
Microwave Radio


Microwave radio has proven its viability, capability and benefit for voice communications since the 1950's. Data and audio/video transmissions, however, have experienced user acceptance only since the mid-1980's. This delay can be directly attributed to the radio manufacturers having focused traditionally on the common carriers, the broadcast industry and the Government. To these entities the vendors have offered customary T1, multiple T1's, T3 and OC3. These approaches have offered a means for "bypassing" the traditional leased lines but have done little to address the bandwidth necessities of the expanding metropolitan area networks ("MANs") and/or Wide Area Networks (WANs).
 
In the mid-1980's, the first modern microwave systems designed to provide full bandwidth Ethernet were introduced, delivered and implemented. Later, added capacity was needed and the Full Duplex Ethernet solutions were furnished. However, the need for greater capacity has continued to expand. Several new answers have emerged.
 
Microwave Matures
 
If capacity beyond a T1, several T1's, Ethernet or Full Duplex Ethernet were needed in a wireless environment, the next step would be to implement a T3 microwave link. This did not appear to be an expensive solution on the surface. The radios were about twice the cost of a traditional Ethernet link but provided about four times the bandwidth. The hidden expenses came from connecting the system to the network. The only accepted procedures were to utilize DS3/DSU's and to interface into a High Speed Serial Interface ("HSSI") port on the routers or to employ a direct connection to an ATM/DS3 port on the routers. These interface alternatives almost quadrupled the cost for a microwave upgrade.
 
The entrepreneurial spirit emerged with the introduction of the Fast Ethernet radios. These units, although more expensive than the DS3 radios, provided a less costly turnkey solution since there was an ability to interface the system directly into Fast Ethernet ports on either routers or a switches. Again the price/performance curve has been followed; the Fast Ethernet turnkey implementation cost about seventy-five per cent (75%) of a DS3 connection but provides over twice the bandwidth.
 
An alternative solution has now appeared in the market. This incorporates the bandwidth of the traditional DS3 radio with the interface ease of the Fast Ethernet system. Rather than the customary HSSI and DS3/DSU or ATM/DS3, this unit contains a 100baseT connection. This enhancement now brings this offering into line of the price/performance curve with the widely accepted 10/20 Mbps Ethernet and Fast Ethernet products.
 
Conclusions
 
In creating a MAN and/or WAN, a network manager has three connectivity options; these are leased lines, fiber optics cabling and microwave radios. These are the most robust and reliable alternatives/options although connections with limited distance can also be made with infrared or spread spectrum equipment. Each transmission medium has its own benefits and drawbacks in terms of price, bandwidth, availability and reliability. With constant changes with all of these approaches, a network manager must frequently evaluate these approaches and ascertain the best solution for each leg in a MAN or WAN.
Al Pfeltz is with Taylor Communications. He can be reached at (760) 749-5770, by fax at (760) 749-5790, or by e-mail at [email protected].