There are two ways to think of outdoor perimeter coverage of buildings; On top of roof down and side of building out.
1) Mount antennas and radios on top of building with either sectors or down-tilt omnis connected to the fascia of the building. This is used more where buildings are 50ft to 150ft tall. This enables the down-tilt omni to cover a larger radius and the sector/panel antennas to cover a more focused area. Buildings over 150ft tall should not use this method because of the distance between the client and AP. Normal outdoor coverage for laptop clients should be kept to a maximum of 300ft from the client to the antenna. If you are using VoIP or VoWiFi clients, you will need to have a overall signal strength of -70dB or better which would entail the distance between client and antenna to be less than 150ft on average. This mounting topology is most useful for covering open parking lots, small warehouse yards, and courtyards. The normal use of clients in this topology is nomadic, not mobile.
2) Mount antennas and radios at eight to fifteen feet off of ground using panel or sector antennas. This is used where you are trying to cover areas in between buildings where obstacles, such as trees, can hinder your coverage. You would normally try to cover a common area, between buildings, with a 25% overlap between AP coverage. The overall distance between the two buildings should be under 500ft. Normally, the radio can be installed in the interior of the building with a small penetration for antenna cable. This can also allow you to use indoor radios without weatherproof enclosures. All client distances and signal levels apply in this scenario. The panel/sector antennas allow you to have a more focused area with a wide horizontal coverage, but minimal vertical coverage. You should always allow for the occurrence of large vehicles or stationary objects in the antenna’s path. This scenario works better for the mobile client. It can also serve the nomadic client very well.
Whenever mounting any antenna or radio in the outdoors, please follow all local building codes. A lightning must be used whether a radio is mounted inside or outside of the building. Proper grounding is always essential, especially when mounting equipment on the top of structures. Areas of the country that experience moderate to high amounts of lightning should consider the side-mount option as their primary choice.
Aruba recommends that all installations of outdoor equipment be done by a licensed electrician or professional installation company. Lightning arrestors are very inexpensive devices considering the investment in equipment. Please consult an Aruba approved partner when considering outdoor installations to make sure your goals are achieved with your installation.