Category Archives: WISP Management

Aug 2014

Tower EngineerFor 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

Author: Scott Armstrong

Jun 2014

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

Power OutageProviding 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

Author: Scott Armstrong

May 2014

Providing a consistent Internet Service is a complex challenge. A strong signal and an association between the AP and the client radio is no guarantee of quality service, nor an indicator of the client’s actual online experience.

Many factors can cause either intermittent connection drops or degraded service: multi-path, network congestion, bad equipment, ice build-up, overloaded back hauls and many other unpredictable factors.

As a WISP, if you have a way of knowing the true quality of every client’s connection at all times, you can have a significant impact on your ability to provide consistent service to everyone.

For example, using Swift Fox software you can plot the quality of every client on an access point and see trends and patterns. Is weather having an impact? Is the entire sector having issues at primetime or is it just two specific clients?

Are there patterns in power failures in the service area? Is noise at play? These are all questions that can be answered quickly and easily when there is a complete view of the true status of every single connection 24/7/365.

The traditional way to manage these challenges was to monitor the backhauls and access point for association, signal level and CCQ. Unfortunately this doesn’t provide a complete picture. If the client appears in the association list on the AP, that only indicates that a packet was seen from the device recently.

CCQ is a very unreliable statistic as lightly loaded connections lack the sample size needed to give accurate calculations. Some network monitoring suites send SNMP requests or basic pings to the device every 5 or 10 minutes. This can catch major issues with a client’s connection, but int

Author: Scott Armstrong

Jan 2014

802.11 Hidden Node, how to fix it

The hidden node problem in wireless arises from a faulty way of devices talking to each other.  This causes a lot of network collisions.

Simply put, collisions are when two network devices try to talk at the same time.  This is bad, as it means that the receiving end can’t understand what just happened – and both senders have to try again.  It becomes especially troublesome at prime-time as more clients are attempting to use the network simultaneously, and collisions are often the primary cause of prime-time slowdowns.

CSMA: The default won’t work for WISPs

802.11-based equipment is great because of its low cost and wide compatibility, however the protocol was never designed with long-range WISPs in mind.  It was designed for a coffee shop or home environment.   By default, 802.11 uses a scheme called “CSMA” (Carrier Sense Multiple Access) to avoid collisions, which works as follows:


  • Client: “I don’t hear anyone so I’m going to talk now”.

This works great in coffee shops because each device can hear every other device – they’re all using small omnidirectional antennas.   With long range WISPs, all the clients have very directional antennas and because of this they can hear the access point (AP) but not each other. This means when they listen using CSMA, they hear nothing, so they can always talk.  From the AP’s point of view, everyone is talking at once, so it constantly has to say “try that again” (aka. “retransmit”).   This situation where an AP can hear a device but nobody else is able to, is called “hidden node” – because the node is hidden from other clients.

Standards-based solution: RTS/CTS


Author: Matt Beaton