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Proper AP Mounting

There are endless ways to mount APs. Some APs come with versatile mounting brackets that provide many options (see Figure 12-8a and 12-8b); others might offer only a simple keyhole mounting option (see Figure 12-8c), in which case mounting possibilities are limited unless you fabricate some type of bracket.

For antenna mounting, the style of antenna dictates the available methods. You may need to purchase different antenna mounting brackets for your particular site. Antenna mounting hardware is available from many different vendors, or even the local two-way radio shop or hardware.

The reliability of the mounting (of both the APs and the antennas) is a primary concern. The last thing that a customer wants is to have something fall from the ceiling or wall and cause injury (or cause damage to the WLAN devices) because of improper installation.

Some mounting methods are as simple as placing the AP on top of a cabinet, desktop, cubicle wall, and so on, as shown in Figure 12-9. Such simple methods are common for small sites that just require one or two APs.

Note

Make sure the antenna is not located next to the metal portion of a cabinet or desk. In Figure 12-9, the antenna sticks up vertically above any metal objects, so this is not an issue.

Other mounting options include wall mounting and ceiling mounting, as described in the next sections.

Wall Mounting

Wall mounting of APs is very simple, particularly when using the standard type of antennas. Here you can use the small keyhole-type mounts if the AP does not need to be mounted more securely. In some cases, the installer will have a standard electrical box placed in the wall, with the Ethernet cable run through the wall to the box. In such a case, a mounting bracket can be screwed to the box and the AP mounted to the bracket (and secured, if necessary). The AP covers the mounting screws and provides a bit more security.

Figure 12-10 shows two mounting examples. In both cases, the AP is mounted to a junction box in the wall, where the Ethernet cable exits and attaches to the AP without being seen.

When mounting to a wall, you generally place the AP as high as possible. However, you need to be aware of a few issues when wall mounting an AP. First, if the AP is using an omnidirectional antenna, as is the case with both APs in Figure 12-10, try to position the antennas between the wall studs so that there is limited interaction with the studs (especially if they are metal studs). Second, position the antennas vertically. If the AP is mounted like the example in Figure 12-10a, one dipole will point up and one will point down. This positioning provides omnidirectional coverage and diversity support.

Another issue to investigate is what is behind the wall. If you install an AP with omni-directional antennas on a wall that has something on the other side of it that might create multipath signals or interference, AP coverage and performance might be detrimentally effected.

Finally, when wall mounting an AP, do not place the AP so far up the wall that the antennas are close to the ceiling. In the case of drop ceilings, the metal support structure can cause the antenna performance to drop off. If the ceiling is made of drywall, there might be metal corner beads at the ceiling and wall junction. It is best to have the antennas at least a few inches below the ceiling.

Ceiling Mounting

The most common type of mounting is ceiling mounting, which provides the best overall coverage for the AP and the easiest access for running cables. If the AP has self-contained antennas (nonmovable antennas), the product might not radiate well when placed on the ceiling. The site survey engineer should address this issue by identifying the mounting orientation in the site survey report. If the AP uses a standard-type dipole, the antennas should hang straight down from the ceiling, as shown in Figure 12-11.

In many cases, the APs will be mounted above the ceiling tile and the antennas below the ceiling. When mounting in this fashion, you need to attach the AP to some structure, not just place it on top of a ceiling tile (which is actually quite common). The best method is to mount the AP to the building structure, such as to an I-beam. You can buy clamps at any electrical-supply outlet and even some home-improvement centers to securely attach WLAN products to an I-beam.