Measuring signal strength of a home wi-fi network
Wikipedia's article on wi-fi

Metageek's home page for inSSIDer

inSSIDer User Guide

How to change the channel of your wireless network

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Wi-Fi = wireless, access point = router
With the decline of Windows XP and especially of XP desktop computers, folks are trading up to Windows 7 and Windows 8 laptops and the mobility they provide. Laptops are mobile because they typically include wi-fi adapters that are based on the IEEE 802.11 technology, which allows two-way radio communication with internet transmitters, called “routers” or “access points.” This communication is usually on the first 11 channels in the 2.4 Gigahertz band. Wireless routers can connect a group of wireless devices including other computers and wireless printers. Desktop computers may have inexpensive wireless adapters added to them.

Wi-fi routers, are relatively cheap and easy to set up and use with cable and DSL modems, and so are found in many homes these days. Verizon often supplies their DSL modems with wi-fi capability; if yours has a little antenna, that's the type you got. Within a cozy indoor setting, and within a range of 65 feet or more, a wi-fi laptop can be taught to connect to that router every time it is started. In fact it can remember all the routers used with it, and will connect conveniently and automatically when started in range of any of them.

Wi-Fi problems
In any home network setting, the router should be centrally located because signal strength weakens logarithmically with distance. Computers equipped with wi-fi adapters come with wi-fi manager software that shows a set of bars that illustrate the “Can you hear me now?” signal strength of any potential access point, just like a cell phone. When ranging too far, the bars get too few, and connecting and staying connected becomes a problem.

Slow or intermittent connectivity in an area can be caused by competing networks on the same or overlapping channels. This is because a wi-fi signal occupies and overlaps five channels. If a router is set to channel 6, for example, it occupies channels 4, 5, 6, 7 AND 8. Because of this, instead of 11 channels to use, there are really only three good choices: 1, 6 and 11, and folks who choose the in-between channels aren’t doing anyone any good. Networks in large apartment complexes and office buildings with many routers are forced to share channels. Every router with activity on a shared channel cooperates with neighboring routers on the same channel and negotiates with them for opportunities to transmit. This sharing, which slows performance for every connected computer, is part of the technology. Overlapping channels are not shared this way, but cause an even worse problem as they interfere with one another and further slow performance.

Home networks are not alone in the 2.4 GHz band. Other devices in the mix include microwave ovens, security cameras, cordless phones and baby monitors. These use the same channels and they don't share at all, they just interfere! A home network may also find itself in competition with large-area access point coverage from municipalities, universities and internet hotspot providers like Optimum.

In open air, radio wave signal strength is subject only to distance. However, the different materials used in home building and the objects we place in our homes all affect wi-fi use there. The more dense the wall or object, the more signal strength drops. For this reason, it's a good idea to place your router up, say on a high shelf or mounted on a wall.

The signal strength meter: inSSIDer
Diagnosing wi-fi problems can be difficult using only the wi-fi manager and the bars it shows. A better tool is “inSSIDer for Home,” published by Metageek. The older Windows version of this free program works well with XP, but the newer one, version 3, requires Vista and later editions of Windows. The Macintosh version of inSSIDer costs $4.99 and only works with OS X 10.7 and later. This tool makes it very easy to measure wi-fi signal strength in decibels, the higher resolution units that technicians use, and to compare your signal's channel and strength against those of your neighbors. It's easy to determine the effect of your neighbors' networks as well as your own walls, stairways, doors and other objects on the range and performance of your network.

The inSSIDer display is neatly divided into sections. The upper left shows the Networks Table, a list of all the networks that your adapter can sense (but none of the kinds of devices like baby monitors, which the computer's adapter cannot sense.) For each network detected it shows data in columns: the SSID or name given to the network, the RSSI or signal strength in decibels, the Channel, the Vendor of the router, and the type of Security in use. There are more columns, but their explanation is beyond the scope of this article. All the data may be sorted by any category by clicking its column header, though RSSI and Channel are the most useful for diagnosing connection problems. Further, the data may be filtered to show only relevant channels or vendors, for example.

The upper right section of the display has the Network Details Panel. This area shows extra information about the network to which you're connected and any network you select in the Networks Table. The upper right corner of this panel shows the Link Score, a number calculated from the signal strength and the amount of interference and cooperation from neighboring networks. You'll also find the number of co-channel and of overlapping neighboring networks. There's also a button to 'star' a network for special treatment in the Channels Graph.

The bottom half of the display has the Channels Graph. This is a signal strength line graph wherein the (up-down) Y-axis represents signal strength and the (right-left) X-axis represents channels. Networks are labeled by name and drawn showing their real-time appearance in the wi-fi spectrum. Once a network has been starred in the Network Details Panel, the color of each network shown in the graph changes to highlight your network, those networks on the same channel as your network and those that overlap your network.

Use inSSIDer to optimize your network's signal
Download and install inSSIDer. Launch it. When the program opens, it's set to the Learn tab and you're presented with a little guide to using inSSIDer. Click the Networks tab to get down to business. Next, click your network in the Networks Table, and then click the star next to your network's name in the Network Details Panel. If you haven't changed your router's channel, it's probably set to channel 6, the customary default for new routers. For this reason alone, channel 6 is likely to be overcrowded in any given area.

Take your laptop for a walk around your place, stopping at every possible location where someone might want to use wi-fi. Make a note of the decibels and link score at every stop. A decibel reading below -73 could be a problem. Now change the channel on your access point (see link below) to another “good” channel and repeat the walk around. Finally, change the channel to the third good channel and repeat the walk around a third time. Choose for your network the channel that produced the highest Link Scores. If you must share a channel, choose a channel with at least 20 decibels separation between your network's RSSI and that of your neighbor's for best performance.

In the next article in this series, expect a detailed account of the process of changing your router's channel.
August 8, 2013

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