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Use microwave, fiber to build new network.


Ron Taylor has some encouragement for anyone thinking about building his own network.

"Don't be afraid. It can be done," says the senior engineer for the Salt River Project (SRP) in Arizona, one of the nation's biggest utilities.

"Our policy here is to be as effective as possible," he explains in discussing SRP's microwave and fiber-optic network. "If it makes sense to turnkey a project, we do; if it doesn't, we don't.

"We like to do our own engineering, installation, and maintenance to take full advantage of our in-house expertise. We spliced the fiber various ways and found the proper and improper ways of doing it.

"Nobody's afraid of it. If it goes down, we can fix it."

SRP is converting its extensive network to digital.

There are 50 sites on the network: Phoenix offices, hydroelectric dams, the huge Palo Verde nuclear power plant switchyard, numerous substations, and two major coal-fired generating plants.

There is heavy data usage, but most system traffic is still voice. There are 2500 terminals and workstations associated with the corporate business computer network.

Most company data is sent via SRP's communications systems. The network is used for other data like SCADA (Supervisory Control And Data Acquisition).

Power Flows And Canals

"We are a power and a water company, so on the power side we are controlling power flows and switching breakers. On the water side, we're actually controlling the canal system, with radio gate controls of water levels and flow rates," says Taylor.

"SCADA is our biggest data user. We have power production at dams, and we can remotely control that and monitor what's going on."

But corporate data use is accelerating.

"With the higher speeds, there are things they're wanting to do that they couldn't until now," he says.

The analog system served SRP well but had limitations.

"Our major problem was we couldn't transport highspeed data. Our upper limit was 19.2 kb/s, over a voice channel. We didn't really have the baseband capacity to add a T1 mux," Taylor explains.

Prompting the move to digital was SRP's decision to regionalize maintenance to better serve 518,000 electric and 33,000 water customers.

"We ended up with three regional service centers for customer service calls. We chose then instead of just extending analog to go with the digital network," he says.

SRP has a private network.

"Our only connection for our voice switch system to the public network is the DID and outgoing lines. Within the company, it is all our own. We have saved a lot of money."

The network is mainly microwave, migrating to fiber.

"Based on circuit miles, at most 5-10% is fiber now. Based on capacity, 99% of it is fiber. As far as point-to-point circuitry, it is still mostly microwave. But we're just getting started," Taylor says.

"Soon we'll be looking at fiber as a backbone, with the remaining microwave being our backup," he says.

Many Right-Of-Ways

"Because we are a utility, we have a lot of right of way, a lot of ways of getting there. Microwave is limited by today's technology anyway to DS3, with the 10 MHz bandwidth the FCC allows us.

"If we want to go faster than DS3 we have to put fiber in, that's all there is to it."

One tradeoff SRP had to make was in high-speed digital microwave radios. It is going with shorter hops for the sake of speed.

"The DS3 digital radios don't meet the system-gain specs of the old analog radios," Taylor explains.

"They are nice replacements and a lot more versatile, but their range is shorter. We haven't put anything in DS3 longer than 17 miles. In our analog network we have some long paths, such as a 92-mile path at 2 GHz.

"There are lower-speed digital radios that run the distance, so if you don't want intermediate repeaters you have to go at a lower speed."

As far as redundancy, the SRP network features full hot standby on the microwave and the fiber. Two transmitters and two receivers are at each end. Either one can switch in or out.

"The same is true with the fiber-optic equipment: two receivers and two transmitters--actually four fibers connecting each path together," he says.

SRP uses Licom's SynTran standard equipment, the IMX-30 Integrated Multiplexer, which is versatile.

"It's hard to describe the simplicity. I can sit at the head end at a computer terminal and start at one location, putting that DSI slot number in the DS0 slot number, connect it into an unrelated slot number, and it will find its way through. We can fully utilize the bandwidth."
COPYRIGHT 1990 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1990 Gale, Cengage Learning. All rights reserved.

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Title Annotation:includes a related article on synchronization in building a network; Salt River Project
Author:Tanzillo, Kevin
Publication:Communications News
Date:Jul 1, 1990
Previous Article:ISDN saves over T1 on college campus.
Next Article:AEP customers set consumption rates.

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