Introduction

When bridging a network between two or more buildings, the choice of solution will depend on the geography of the site, the availability of sufficiently clean RF spectrum, and the current and future applications that will be run on the network.

To determine what options are available and which options are eliminated based on site geography and RF or cable path considerations, take a survey of:

• Conduit availability: is there existing conduit between the structures?
• Overhead cable path: is there an overhead cable path?
• Line of sight between antenna locations: is there a path between the structures without other structures, plants, or passing vehicles coming into the Fresnel zone? (simulate the Fresnel zone with the Ubiquiti airLink calculator)

Availability of clean spectrum will determine which wireless options will be able to provide what amounts of bandwidth. Unlicensed bands include:

Available only in North and South America, the band from 902-928 MHz is usually congested by smart meters in urban environments and wireless ISPs in rural environments. This low frequency band has a large Fresnel zone, but achieves better penetration through foliage. Product availability is limited, with only NanoStation LOCO M900 and Rocket M900 radios available from Ubiquiti. Competing options are either even slower and more outdated, or faster but very expensive.

In urban and suburban environments, the 2.4 GHz band will be almost entirely useless due to interference from multitudes of WiFi access points occupying the three (US) or four (certain other countries) non-overlapping 20 MHz channels. At short range, it can penetrate small amounts of foliage, and and for that reason may prove useful in rural environments. Numerous airMAX M-series (802.11n-based) and ac-series products, as well as the airFiber AF-2X, are available covering this band.

The 5 GHz band requires nearly perfect line of sight, but offers more spectrum than 2.4 GHz, so other than in dense urban environments, it will be more likely that a suitably clean channel can be found.