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Choose Cell Site Monitoring and Automation That's Best for Your Facilities

By Andrew Erickson

December 15, 2022


A cell site is a perfect example of facility that absolutely demands remote monitoring technology:

  • Cell sites are generally located in remote areas. Even in urban locations, no one is stationed there regularly.
  • An array of expensive telecom and power-supply gear is installed at the location.
  • A redundant backup may not exist if a site fails. 911 service or police/fire radio may go down in the vicinity.
Cell site tower monitoring diagram
In this example, tower lights are monitored using AC current transducers connected to a small RTU.

Before we get into remote monitoring, let's pause to consider what sorts of hardware you're likely to have at any cell tower site...

Common hardware you should be monitoring at cell tower sites

Because the mission at each cell site is similar, nearly every cell site has the same basic components. I joke with my clients that I've been to "the same site" all over the country. The only difference seems to be the local geography, weather patterns, and what type of critters try to cause mayhem.

If you've visited any of your company's or agency's cell sites, it's likely that you saw the following equipment types that are common at cell sites:

Diagram of TempDefender monitoring sensors
A TempDefender G2 is shown here monitoring a small hut using attached temperature, fuel, and AC current sensors.
  • The tower's aircraft obstruction lighting: This is the first thing you notice when you drive up to a cell site, and it's a helpful aid if you're trying to find the location on unfamiliar roads. The status of tower lights is critically important for aviation safety for any tower that exceeds government-determined height criteria.
  • The wireless/radio/microwave equipment: Your cell site has data it must transmit and receive. That requires functioning radios, antennas, and other sensitive equipment. A single malfunction is either a failure or a failover to a redundant system. In either case, it's something you need to know about promptly so you can respond.
  • UPS batteries: Your first line of defense against a commercial power failure is your backup battery string(s). Few UPS systems are tested often enough to assure the batteries are functioning properly.
  • Generators: The second line of defense against power outages is the generator. Diesel, natural gas, propane - you need to know if it's running and ready.
  • HVAC (air conditioners/heaters): Keeping your electronics at a stable temperature is essential for reliable performance. If your climate is extreme, or if you have a sustained power failure, the generator will be called into action.
  • Doors, gates, and fences: Most sites have a perimeter fence (to prevent unauthorized access to the tower base) and a main door to the building. These are all things you should be monitoring to detect physical intruders. This might be your only shot at detecting impending copper theft or other mischief prior to a service disruption.

This list is just the basics of what you should be monitoring and automating at any cell tower site. There may be other specific items to address based on your industry, location, or other aspects of your situation.

It's obvious that you need good monitoring to protect all of this equipment and your service reliability, but how do you go about doing that?

Collecting status data from equipment and the cell site environment

With our list of "what equipment to monitor?" out of the way, we can now drill down to which alarms and levels we want to monitor within each device/system.

The short answer here is: You need to monitor everything that could conceivably be useful in preventing a costly incident. Expense happens when something breaks, when you have to make an emergency site visit, and especially when your users or customers suffer.

Common items monitored at cell tower sites, and how to collect data from them:

  1. Tower beacon and obstruction lighting: Many tower light controller boxes have a simple contact closure output that indicates when the lights are offline. I've also worked with some clients using unusual or older tower light systems who instead place a current transducer around the power supply to the lights. If lights are off, there will be no power draw! This type of "acid test" monitoring does not depend on the system itself to report an alarm. The laws of physics don't often change!
  2. Radio/wireless equipment: Pulling SNMP data from the radio/wireless equipment is a standard way to monitor equipment health and alarms. This data can and should be integrated with your monitoring system so that you can see when an alarm has been generated, even if it didn't actually cause an interruption in service. Older systems may use discrete/digital/closure outputs instead, while newer systems may support another protocol like Modbus that you can collect with a Modbus-polling RTU.
  3. UPS batteries: Most UPS systems should have contact closure outputs that indicate whether or not the batteries are at a full charge and ready to take over power in case of an outage. You can also set thresholds for wattage draw on the UPS system, so that you know if there's something wrong with the equipment being powered by it. Again, more modern systems are evolving to offer an RS485 port with Modbus protocol supported. Check whether your batteries can be monitored using Modbus.
  4. Generators: Most generator systems should have contact closure outputs that indicate when the generator is running and ready to provide power. You can also monitor fuel levels, voltage, and other specific parameters on the generator itself. The Modbus protocol is never more common than on generators, where it's practically an industry standard. You must, of course, remember to order the appropriate communication module to make this happen. I see a lot of generator manufacturers who try to minimize the visibility of Modbus in favor of their own cloud-based monitoring that carries a monthly fee. Just be aware of all your purchase options for monitoring your generators.
  5. HVAC (air conditioners/heaters): Many HVAC systems have contact closure outputs that indicate whether or not they are running, as well as contact closures for over-temperature or low-temperature conditions. You can also set thresholds for wattage draw on the HVAC system. If you monitor both the power draw from batteries and your rectifier, you'll know when an air conditioner or heater is running off of its backup power source. Monitoring your HVAC systems properly is also great way to anticipate required maintenance like filter cleaning and replacement.
  6. Doors, gates, and fences: Monitored physical access points such as doors and gates should have contact closures installed to indicate whether or not they are open. Fences can have pretty clever new technologies like fiber optic lines that sense any physical movement (changes in the shape of the glass fiber change its noise profile, which can be detected by a simple hardware box and reported). This data can then be integrated into your monitoring system, so that you know if any unauthorized entry has occurred.

By collecting this data on a regular basis, you can be alerted to potential issues before they become costly problems. Automating the monitoring of cell tower sites is essential for ensuring service reliability and protecting.

Choosing an RTU to be your remote cell site monitoring device

OK, so now we've covered both the equipment we have at our cell tower site and the main items that we want to monitor for each. Next, we need to talk about how you'll choose the right RTU (Remote Telemetry Unit or Remote Terminal Unit) for your site.

An RTU is a computerized device that collects data from remote sensors and sends it back to the main monitoring system. It's essentially a "gateway" for all of your cell tower site data, allowing you to monitor everything from one place and make sure all systems are running smoothly.

When selecting an RTU, you must make sure it meets the following criteria:

  • Compatibility: Make sure your RTU is compatible with all of the equipment at your cell tower site. If you're using a Modbus system, for example, make sure your RTU supports it. At least some reasonable quantity (16 or more) of discrete inputs ("contact closure inputs") is recommended. Relay closures like these are still an industry standard. Relays are also useful on an RTU to control equipment. Modbus also supports control commands issued by the RTU to newer "smart" devices.
  • Durability: Your RTU needs to be able to handle extreme weather conditions, vibrations from generators, and other conditions found at cell tower sites. Durability comes in both physical and temperature variations. Look for devices with little to no moving parts and for an industrial temperature rating.
  • Security: Your RTU needs to be secure enough that you can trust it with sensitive data. Look for robust security measures such as encryption and authentication protocols. These change regularly, so keep up with standards dictated by your IT department or general best practices. For example, TLS 1.2 superseded earlier versions and the prior "SSL" method of encryption.
  • Reliability: Choose an RTU that is reliable and resilient so it won't fail when you need it most. There are aspects of durability here as described above, but reliability is a fair bit softer. What you're really looking for is a proven design from a manufacturer with a lot of industry experience.
  • Fit: Does the RTU fit in the physical space that you have available? Does it mount in a standard equipment rack, on a DIN rail, or on the wall? Choose something that can actually be installed where you need it.
  • Cost: Ultimately, you need to consider your budget when selecting an RTU. Fortunately, there are many cost-effective solutions out there that offer great performance. Don't forget, also, that there is a cost associated with choosing a poor-quality RTU. An RTU isn't a tremendous expense, even if you buy an "expensive" one. The cost of an undetected cell site emergency, however, can be massive. Don't skimp.
Small cabinet with NetGuardian RTU
If you have a cabinet holding cell-site infrastructure, look for a DIN-mount RTU

By taking the time to research and choose an appropriate RTU for your cell tower site monitoring needs, you'll be able to ensure reliable service and protect your investment in equipment and personnel.

Example RTU Choice: NetGuardian

As with almost anything, it can be useful to step through the above buying criteria with an example product. This will help you as you start your own product research.

Let's use the NetGuardian RTU line as one example. We won't look at a specific model, but rather the various different models that are available under that brand name. Because we're dealing with a hypothetical cell site, we might need different capacities depending on the specific site that requires monitoring.

First up on our shopping list is "compatibility". Let's say that we've counted 13 different contact closures to monitor among our various site gear. We might choose a NetGuardian M16, which (as the name implies) has 16 discrete inputs to capture those contacts. We'll have 3 to spare for future site growth.

If we have a lot of analog levels to monitor, like site battery voltages or fuel readings, we might instead choose a larger model like the NetGuardian 832A. It has 8 analog inputs and 32 discrete inputs (discrete inputs are a huge driver of hardware cost, so it's better to have too many than too few).

Most NetGuardians have at least a small handful of relay outputs, and you should match these to the number of devices at your cell tower site that support this control method. It's common to use RTU control relays to control generators or perhaps even unlock electrically actuated doors.

Second on our list is "durability". The NetGuardian line prides itself on its industrial-grade components and "industrial temperature rated" (optional) builds, built-in surge suppression (opto-isolated inputs) and optional accessories for lightning-prone areas (SPDs), and ability to operate in temperatures ranging from -40°F to 158°F. You can trust these devices to survive the rigors of the cell tower environment.

Third is "security". NetGuardian features a variety of secure protocols, such as TLS 1.2 on the latest "G6" models, to protect both your monitoring data and configuration settings. You'll also be able to choose from a variety of authentication methods, such as local access control lists or RADIUS authentication, to ensure that your monitoring data is kept safe.

RTU with beacon light
Monitoring tower lights is serious business for aviation safety.

Fourth is "reliability". NetGuardian has been around for decades, and it's a name that engineers have come to trust over the years. It's amazing how often I run into people considering a purchase who say, "I know I've seen those at a bunch of sites at my last job."

It's designed for reliability and comes with a variety of backup strategies in case of network failure. Historically, this included "dial out on alarm", but now can include wireless-modem options.

More than anything, NetGuardians utilize a variety of design and manufacturing techniques to minimize the chance of any failure. This includes brutal in-house diagnostic testing of each new device and EMI-aware design that places grounding precisely where it's needed on the in-house PCB designs.

"Fit" is a choice you get to make with NetGuardian RTUs. For most cell sites, you'll have the required 1 RU (rack unit) of rack space available on a 19" rack (or 23" rack with the included longer rack ears). If you have a cabinet and need a DIN rail mounting style, there's the NetGuardian DIN. Small RTUs like the NetGuardian LT can mount either in a rack or on the wall.

With engineering and manufacturing both housed in California, USA, NetGuardians are not the absolutely cheapest devices available. You can find prices below $1000 and upwards of $5000, depending on the model and options you select.

That said, we're hardly talking about numbers that break the bank. A quality RTU can literally save hundreds of thousands of dollars during a prevented incident. It's amazing how many times my clients refer to RTUs as "rounding error" in a multi-million-dollar infrastructure project.

Shopping for an RTU is a long-term decision and can be quite challenging

An RTU is a durable good. You shouldn't need to buy a new one for at least another decade.

Sadly, I do have people contacting me often to replace RTUs that just aren't doing the job. They didn't do enough homework during the initial purchase, and now they're hoping a NetGuardian will do a better job. I'm hoping they have enough budget left after making a costly buying mistake.

Don't let this happen to you. Relative to the massive headache of buying and installing the wrong gear, only to find out that you didn't do enough pre-purchase research.

Best next step: Talk to an expert in cell site monitoring

Monitoring cell tower sites is essential for ensuring service reliability and protecting your investment in equipment and personnel. By carefully selecting an RTU that meets your criteria for compatibility, durability, security, reliability and cost-effectiveness, you can be sure you are making the best decision for your business.

The best way to accomplish that is to speak with an expert as soon as possible. After you conversation, all of the web-based research that you do will make more sense in less time. Get answers to your questions, get a clearer picture of the different solutions available, and make a decision that you be 100% confident about.

The better informed you are before beginning a cell site monitoring project, the more likely it is that you will end up with an RTU (NetGuardian or otherwise) that meets all of your needs. Don't take chances with your cell site monitoring - take the time to speak with an expert. You'll be glad you did.

Call DPS at any time at 1-800-693-0351 or send a quick email to sales@dpstele.com to speak with an engineer.

Andrew Erickson

Andrew Erickson

Andrew Erickson is an Application Engineer at DPS Telecom, a manufacturer of semi-custom remote alarm monitoring systems based in Fresno, California. Andrew brings more than 17 years of experience building site monitoring solutions, developing intuitive user interfaces and documentation, and opt...