WISP Archives - Swift Fox Systems

Aug 2014

Building Robust Connections Between Tower Sites

For any WISP, having a robust, fast and high capacity distribution infrastructure between sites is one of the key factors in getting clients the full speeds they expect with predictable latency and reliability.

Many WISPs start by building a multi-point access point on their first tower, and then install a number of clients on that access point. This is a typical and ideal configuration.

Often at some point later, there is a need to install another AP at one of those client’s locations to act as a repeater to additional clients. Using clients as repeaters can be a good, low cost way to expand coverage and reach additional clients. There are legal and business considerations with this, but for this article I will focus on the technical considerations.

Many WISPs will simply connect another access point at the client location, using the existing connection as the feed for that AP. In some cases, simply enabling AP-Repeater mode can also look like a quick and inexpensive way to get service to more subscribers. These two techniques have some significant challenges and are not suited to professional grade services that will then be resold. These features were included by manufacturers for hobbyists to use as experimental or home-use features only.

What’s wrong with AP-Repeater mode?

Every time an AP-Repeater is used, speed and capacity for all the customers on those access points are cut in half. Some might say “No big deal, I only have a few users out there, I can afford to reduce speeds”, but the issue is much larger than that. Here’s how AP-Repeater mode works:

AP#1 is where the Internet feed is supplied, it has 20 subscribers on it, one of them is a

Jun 2014

WISP Backup Power Solution

Provide reliable monitored multi-day backup power at a tower site for under $500

Providing multi-day backup power at all transmitters reduces service calls and improves network reliability significantly. On many WISP networks, power disruption is the leading cause of client outages.

Most off-the-shelf retail UPS units (eg. APC1100) have very limited run time for their size. They are designed to provide computers with high wattage, short term power while they are shut down during a power outage. What a wireless site needs is low wattage, but exceptionally long run times. In order to obtain monitored long-runtime UPS from vendors like APC, one would have to invest in enterprise UPS products which are typically thousands of dollars and take up significant amounts of space, and will intentionally shut down when operated below freezing. They are also designed for high wattage applications which raises the cost and space requirements significantly. Typical tower sites have exceptionally low power draw, but require long run times. Computer UPS units are simply not designed for this application.

If there is a power failure at a remote location on a Friday night at 10PM it is of great business utility and savings to fix the issue on the following Monday, during business hours. Often by then, the cause of the outage has been resolved by the power utility or landlord and no site visit with a generator is required. Also, if there are widespread power outages due to acts of nature, it is not uncommon to have several sites lose power and road access closed by emergency services or impassable roads. If six sites all lost power, most WISPs do not have enough generator

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