Best Practices for Mounting Outdoor APs

That AP on a Light Pole Looks Great. But What Happens When the Light Goes Out?

Key takeaways

• Outdoor Wi-Fi networks have many design challenges.
• Weather is at the top of the list. Heat, moisture (rain, fog, mist, snow, sleet, hail) and lightning cannot be controlled.
• A number of configurations exist, but all include one essential element: access points (APs).
• How and where APs are installed can affect latency and bandwidth, disconnects, and security issues.
• Best practices for mounting outdoor APs consider mitigating factors that only affect outdoor (and not indoor) installations, such as lightning.

Designing exterior wireless networks and mounting outdoor APs present unique engineering challenges ranging from security issues to increased latency and lower bandwidth. As part of our best practices webinar series, 7SIGNAL Customer Service Support Engineer Jack Clifford (CNWA, CWDP, and CWAP) recently lent his expertise to outline Best Practices for Mounting Outdoor APs.

Clifford discusses the pros and cons of point-to-point, point-to-multipoint bridging, and point-to-multi-point mesh networks, how and where to mount APs, the importance of site surveys, and power and lightning issues. His overarching advice? Keep it simple.

The unique design challenges of outdoor wireless networks

All outdoor wireless design challenges yield the same result: sub-optimal network performance. Using best practices for mounting outdoor APs can solve most issues, but perhaps the biggest obstacle to well-performing Wi-Fi is something beyond your control – the weather.

You’re trying to cover an open area where the environment can quickly change. With no walls, your coverage area might end up larger than anticipated. Some users can be too far away from an access point and from other users, creating a hidden node problem that results in excessive retries and unwanted disconnects. Other challenges include:

• A lack of attenuation sources may exist.
• Your signal propagates outside the desired coverage cell.
• Network security is a concern because
• It is difficult to limit physical access to coverage areas
• Cybercriminals don’t need to be near the actual network
• Media access control (MAC) registration on the wireless LAN controller (WLC) can easily be spoofed.
• Mesh hops can create increased latency and lower bandwidth if used.
• An exposed ethernet cable is a huge concern, as cyber thieves can simply plug in a laptop and access your entire network.
• It might be difficult to find power.

Tips to overcome design challenges

To shrink the size of your coverage area, use exterior attenuation sources to your advantage, just as you can indoors with walls and doors. In addition, assign power to APs to prevent issues where the signal propagates outside the coverage cell. Proper site surveys are essential. Simply relying on Google Earth isn’t enough because it doesn’t show electric lines, so it is critical to do an on-site survey.

Security presents another problem. It can be difficult to protect your equipment physically. Since outdoor APs must be entered into a MAC filter or a MAC registration table on the actual controller, the MAC address could easily be spoofed.

• Mount APs high enough to prevent someone from accessing, unplugging, and removing them, leaving a coverage hole.
• Use proper intrusion mechanisms on the network.
• Deploy layers of security beyond the MAC filtering table on the WLC – use certificates to verify APs and employ 801.1X EAP authentication.

Let’s look at the different types of networks available and the details of mounting outdoor APs. 

What about a mesh network?

When most people think about outdoor Wi-Fi for the enterprise, they consider mesh networks because they provide wide coverage in an outdoor environment. However, they have their own issues: with every mesh hop (link), latency is increased, and bandwidth is lowered. Every hop between routers decreases the bandwidth by 50%. Because wireless links can only perform one function at a time – transmit or receive – a long series of mesh links means a slow connection from end to end.

Point-to-point networks

Point-to-point networks work well when you want to connect two buildings together on the same network so they can share the internet link and avoid a wired infrastructure traveling between them. Security isn’t a concern because the wireless link is private, and only your data travels through, as opposed to a leased line shared with others.

The throughput rate is incredibly fast at up to 10 Gbps, with a range of over 62.14 miles (100 km).

This is a very cost-effective method versus running five miles of fiber cable, and there are fewer legal restrictions because the unlicensed spectrum is used. There is no concern about permits, easement restrictions, and so forth.

Point-to-multipoint bridging

Point-to-multipoint bridging is much like a point-to-point network, but with a central base station connecting multiple links – a spoke-type network topology, commonly used as wireless ISPs and for video surveillance.

• Line-of-sight is vital because of the multiple links, as it’s not a straight line but more of an ellipse (Fresnel zone).
• Ensure the Fresnel zone is at least 60% free of obstructions, or you’ll have signal issues. 
• You can use point-to-multipoint to expand using an additional point-to-point link, but keep in mind that with each added link, you’re adding latency and decreasing throughput.

Point-to-multipoint mesh networks

This is a common deployment for large coverage areas, usually because there are no other options, but use this method as a last resort.

In a point-to-multipoint mesh network environment, there are two types of APs – a root AP, which has a wired connection to your infrastructure, and a node AP to use the wireless link to connect to the root AP.

In this type of network, you want to minimize your hop count because as with any mesh network, each hop will increase latency and decrease throughput. The ideal result is to maximize the signal between those hops to the -40 to -50 range, but that is difficult to achieve. Use -65 or better between nodes to optimize performance.

Boost the network by clustering your node APs around the root AP so there is only one hop, keeping latency and throughput issues to a minimum. This action also protects against possible failures of node APs – clustered together, a nearby node AP will only encounter a few additional hops to reach the root AP, forming a type of self-healing network.

Run ethernet and fiber to each root AP or use a point-to-point link as a virtual wireless cable, but again, you’re dealing with latency and throughput issues. A mesh network will never reach the performance level of a traditional Wi-Fi network with nodes.

Mounting outdoor APs

Poorly installed APs, whether inside or outside, can create RF and disconnection issues and reduced network speed due to the number of client retries. Metal objects nearby deflect the wireless signal, which is one of the reasons you don’t use a metal enclosure for APs – all your signals end up inside the enclosure. Correct outdoor installation is even more important than proper interior installation because of exposure to the elements.

Here are the installation requirements of outdoor APs.

• If your AP is not IP rated for outdoor use, encase it in a National Electrical Manufacturers Association (NEMA) enclosure.
• To prevent interior electrical buildup in the enclosure, use ethernet surge protectors.
• Ensure there is line-of-sight to the APs, which means installing them at most 30 feet. Start at a height of 15 feet and adjust from there.
• A wireless bridge backhaul for a mesh root AP can be installed at up to 40 feet.

2. To help with troubleshooting, it’s essential to orient APs so the operating LEDs are visible from the ground (skip the ladder). You also can run a cable connected to the console port of the AP.

Mounting options

Physical security is always a concern. The choice must meet your needs and offer physical protection from theft, tampering, and weather. No matter what type of enclosure is chosen, you want to ensure it offers physical protection and that it maintains the right ambient operating temperature. A black enclosure in the sun is a poor choice because it will attract and trap heat, while a white enclosure will reflect it. Some NEMA enclosures are vented, and others have cooling fans to mitigate heat issues.

Today’s outdoor AP enclosures can be attached to a wall or a pole, and a bollard can be installed in the ground to deter thieves. These bollards blend into the environment, and as a bonus, they bring the signal to the client at its level.

Selecting the proper antenna

The suitable antenna and its placement are important for every wireless installation, but it’s even more crucial for an exterior installation. Avoid common mistakes. Consider the antenna’s radiation pattern, and make sure to avoid obstructions such as trees. Close proximity to metal objects can change the antenna’s properties.

Power supplies for mounting outdoor APs

Supplying outdoor power to your AP can be difficult, so before purchasing APs, verify power requirements with the manufacturer. Some require AC power, some DC power, and others PoE

• Indoor-rated injectors need to be installed in NEMA enclosures.
• Verify the injector meets the environmental conditions of your deployment.
• If mounted on a light pole, use a light pole tap.
  • However, if the pole uses a solar eye to control the light, it is possible the AP will shut down when the light is scheduled to turn off.
  • Battery banks can be used to power the AP during the day.

Consider lightning

It’s easy to forget about lightning and the damage it can cause. This makes grounding your equipment crucial. Excess energy in the area can transfer to the equipment installed outside as well as to the inside switches to which you’re connected.

Some manufacturers include internal circuitry that protects against lightning. Keep in mind that cables can attract lightning, so be sure to ground them with a lightning arrester.

Grounding

Grounding your equipment prevents many problems. Doing it improperly can cause device failures, poor performance, or a static buildup that can result in hard-to-find issues. If you’ve mounted your AP on a light pole, check if it has an installed ground wire. If not, run a new one directly into the earth from the pole.

Grounding will include multiple metals, some of which can corrode. Use anti-corrosion compounds.

Non-IP rated equipment must be enclosed. Metal caps should be used for exposed parts to prevent moisture damage.

Use the rubber gaskets provided, especially for ethernet connections. Always use shielded cables. Buried cables have different requirements. Coax seal can help with exposed connections.

Proper installation and mounting of outdoor APs takes planning

There’s a lot to consider when installing and mounting outdoor APs. A proper site survey can help avoid problems up front. The most important thing to remember is simple networks usually run better and yield optimal outcomes.

Proper installations are more costly but are worth their weight in gold over time.

Let 7SIGNAL help

Have outdoor APs? Keep things running the way they should with 7SIGNAL. As a leader in Wi-Fi performance management, 7SIGNAL’s monitoring tools can find problems quickly, to solve them before anyone notices an issue.

Founded by wireless networking pioneers, 7SIGNAL delivers applications that continuously monitor the stability of our clients' Wi-Fi networks to mitigate risk.

The 7SIGNAL platform is designed for the world's most innovative organizations, educational institutions, hospitals, and government agencies, and is currently deployed at IBM, Kaiser Permanente, Nike, and other Fortune 500 companies. 7SIGNAL continuously monitors the connectivity of an estimated 20 million global devices. Learn more at www.7signal.com.