Dispelling Spread-Spectrum Myths

April 7, 2010

About the author: Dan Steele is business development executive for FreeWave Technologies. Steele can be reached by e-mail at [email protected]. Bill King is owner of E & M Services. King can be reached at [email protected].


Many municipal water systems have had to broaden the area from which they gather, use and reclaim water. Most growing areas have had to face the dilemma of higher service demands while trying to stay within shrinking budgets and manpower cutbacks. While many have seen the need for electronic data gathering, it has been something of a want instead of a need until now.

Several years ago, choices were few to address the needs of data gathering and recording. Water utilities had to be able to use a ‘fits-all’ unit with set parameters and make their systems adaptable to the technology of the day. Now a wide variety of equipment is available to render solutions of varying levels, which requires an attempt to integrate older systems with newer technology where possible.

As the installed base of spread-spectrum devices has increased, a number of myths, misconceptions or urban legends have begun to circulate. You may have heard of some of these myths:

  • Security. Spread spectrum is not secure; your data can be stolen or tampered.
  • Saturation. Spread-spectrum radios will shut down when there are too many radios on the same frequency or in the same area.
  • Range. Spread-spectrum devices output only 1W, so they cannot perform as well as licensed radios that have 2W or 5W of power.
  • Compatibility. If you are using licensed radios, you can use only licensed radios and/or repeaters to expand your network.
  • Interference. If you mix licensed radios with spread-spectrum units or different brands of spread-spectrum radios in the same system, interference and lost data will result.
  • Obstruction. You must have a clear line of sight, or spread spectrum will not communicate.

But none of these statements are accurate. Misconceptions always will accompany the advancement of a new technology. Spread spectrum is an extremely valuable tool when used in the correct environment. Exploring each of these myths will provide a better understanding of how to apply the technology and where you can expect to succeed with spread-spectrum communication solutions.

Wireless data radios are very secure and have several parameters that protect the system from security attacks and allow several thousand radios to be collocated in the same area. Today, you can have a mix of Ethernet, serial, IO and cathodic protection radios all on the same network that are able to receive data in several ways and protocols. The most common use of a protocol will be explained below, but the ability to send water tank levels, pressure readings, water flow measurement, security alarms and even video images back to the water utility operators’ office is not just convenient—it is critical. With Ethernet radios, you have the ability to look at the SCADA system anywhere in the world with an IP connection. This is incredibly valuable to water system operators, water districts and utilities.

The first issue to resolve when transmitting data from one point to another is protocol. In the context of data communication, a network protocol is a formal set of rules, conventions and data structure that governs how computers and other network devices exchange information over a network. In other words, protocol is a standard procedure and format that two data communication devices must understand, accept and use to be able to talk to each other.

Odd as it may seem, there are many choices to pick from in this area, whether you are transmitting via hardwire, telephone line, cellular, satellite, microwave, fiber-optic or ISM band wireless radios. Many of these options are carryovers from a time when data transmission was first attempted and there were as many types of protocols as there were personalities trying to solve this issue. Each thought theirs was the best method and each different protocol addressed a pet issue with the developer—but not all issues facing the end-user.

One protocol that has, for the most part, become a standard for a majority of devices is ModBus. Today, it is the single most supported protocol among automation devices. Most devices, being able to communicate serial, talk ModBus or can be configured to do so.

One ray of hope when integrating older technology with new technology is being able to pass data using the ModBus protocol. Integration of data systems often will utilize this protocol for many areas where small pockets of data are to be gathered and transferred to the system “backbone,” where the data is sent to the main control and gathering area. This is where the term “SCADA” was implemented.

Using these methods of coverage, the network has a backbone system that is more than 100 ln miles in length and branches out, covering many more miles. The IO count is in the thousands, with more than 200 data sites. The sites are a mix of utility-powered and solar-powered devices, with the solar sites designed to perform for several cloudy days without interruption of service. The combination of hardware with the ModBus protocol also has minimized the need to replace or upgrade field hardware.

More often than not, there is more than one water district in areas of coverage in the larger metropolitan areas. This may be county and city entities or several cities in close proximity. To further minimize costs, memorandums of understanding (MOUs) allow them to utilize the same backbone and/or data points, reducing duplication of effort.

This has worked well with the ability to secure separate systems, passing only data contained in their MOUs from one to another. Most large districts have their own IT departments, and once they are assured everything in their world is secure, they are very helpful in setting up security and routing data to the correct system points.

Secure, Versatile & Helpful
900-MHz spread-spectrum radios are secure, robust and have several different communication interfaces for serial, Ethernet and IO. The radios transmit data quickly, are easy to deploy and can expand the network easily as the system grows. They can be used for several different applications at the same time on the same network. The user can use the radios with other types of communication equipment to utilize the infrastructure that may be in place.

Each radio can be a repeater if necessary for greater coverage. The new IO radios offer very high IO counts and, with Modbus, the capability to have more than 65,500 devices on the same network. Ethernet radios have faster speeds, reduce the polling time and can connect any type of IP device to the network, and security cameras can be deployed to monitor the network.

Water utilities have more time to maintain the water system and be able to do preventative work on pipelines, valve installations and meter connections. Municipalities or water utilities in the same area may be able to combine or share some of the infrastructure costs and engineering.

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