Network Optimisation.



Location, distance and obstructions are all factors that will affect your wi-fi performance.

Try to avoid locating your router, access point or device close to other electrical items, try also to locate devices as near as practical to the router or access point as performance will be affected by range. Obstacles such as walls and floors are often unavoidable, but you should try to get an understanding of how obstacles might affect your wi-fi network, so that you can optimise its performance.

Generally speaking dense materials such as concrete walls and floors will reduce the range of your network more than light materials such as wood and plasterboard, although you should also make allowances for their thicknesses as well as their density, since a thick wall made of lightweight thermal block is likely to be more of a problem than glass which although quite dense usually has a thickness of around 1/4”.

Be aware that higher frequencies are more easily blocked than lower frequencies. There are many scenarios where a 5 GHz network will be desirable, but those where obstacles represent a problem are unlikely to work as well over one running at 2.4 GHz.

Theoretically, a router, access point or device transmits in all directions equally, but this may not always be the case. If your router or access point has external antenna(s) refer to the manual that came with it to determine the best position for them, if it has internal antennas try moving it round or switching from a horizontal installation to a vertical one. If you are using an Apple TV you might also try different positions.

General Interference

There are potentially a number of sources of interference for a wi-fi network, unfortunately some of these can be difficult to detect without specialist equipment, these include regular electrical household items. There are some specific items which tend to cause more problems than others such as microwave ovens, baby monitors, cordless phones and other wi-fi networks, but other items should be considered too.

There are two areas of interference you should be aware of when considering the effects of other electrical items on your wi-fi network, magnetism and phasing.


Your wi-fi network uses radio waves to transmit information, radio waves create a weak but nonetheless noteworthy magnetic field, interfering or distorting this magnetic field with another magnetic field can interfere with the radio waves themselves. All electrical items create magnetic fields when they are in use, the size of these magnetic fields is proportional to the current drawn by the appliance, so you should be aiming to keep your router, access point or device away from high power appliances such as microwave ovens, electric cookers, air conditioning units etc.

Whilst these items create magnetic fields whilst in use, other household items can create magnetic fields whether they are in use or not because they contain permanent magnets, typical household items that contain permanent magnets are TV’s, audio equipment and hard drives. You should avoid placing your router, access point or device near such items unless you know they are magnetically shielded, as are some TV’s and speakers. Modern TV’s no longer have large magnets, but generally speaking you should be keeping your equipment a sufficient distance from a TV for other reasons.

As radio waves create magnetic fields, one source of interference for the radio waves from your network is from other radio waves. In addition to TV’s and Radios which might be obvious sources of such interference, you should also think about cordless phones, microwave ovens, emergency service scanners, walkie talkies, citizen band radios and of course other devices that use wi-fi.


Phasing is where two or more similar sources of waves can cancel each other out when they collide, many may be familiar with such effects when it comes to waves in water or audio waves, but the same is true for radio waves. The important factor here is the frequency of the radio waves, which need to be the same or similar for phasing to occur.

Additionally, if your device is receiving radio waves from two different sources operating at the same frequency, it’s rather difficult for your device to tell them apart.

Problems caused by similar frequencies are different to problems from magnetism since the devices don’t really need to be all that near to each other to be affected. When considering household items that might interfere with your router, access point or device, you should look at microwave ovens, cordless phones, baby monitors, bluetooth enabled devices and of course other networks.

Most cordless phones, baby monitors and bluetooth devices operate around the 2.4 GHz frequency, so switching to 5 GHz may be a solution if your equipment supports it, but it has to be remembered that radio waves at 5 GHz don’t travel as far and are more easily blocked by walls and other obstacles.

Other Networks

Problems associated with other networks such as those belonging to your neighbours, can often be addressed by changing the frequency your own network works over. A simple example of this is by switching between the 2.4 GHz frequency and 5 GHz frequency which is supported by many (but not all) devices. Whilst simple it may not necessarily be possible, all devices need to support the same frequency and if you are operating over long distance or have too many obstacles the 5 GHz frequency may simply not work.

Fortunately there are sub frequencies within the 2.4 GHz and 5 GHz ranges which are referred to as wi-fi channels. The channels available in the 5GHz range vary substantially throughout the world but those within the 2.4 GHz range are much more standardised and are therefore a better example when considering changing the channel your equipment works over.

2.4 GHz

There are generally speaking 13 channels available in this range. (There are 14 in Japan and many manufacturers don’t include channels 12 and 13 in North America), these are numbered 1 through 13. Each channel covers a 22 MHz bandwidth and each channel is 5 MHz apart. Channel 1 for example operates between 2401 MHz and 2423 MHz and channel 2 between 2406 MHz and 2428 MHz.

As you can see this causes overlapping of channels, so if your neighbour was using channel 1, you wouldn’t want to be using channel 2. It’s not necessary to know the frequencies of all the channels involved or completely understand the technical stuff in the paragraph above, you just need to keep at least 4 unused channels between the one you use and the channels any other networks in the vicinity use.

Typically 3 networks using channels 3, 8 and 13 can co-exist without interference, although you are more likely to see 1, 6 and 11 because many manufacturers choose one of these 3 channels as default on their equipment.

If the opportunity to keep at least 4 unused channels between you and the other networks, you will need to choose a channel based on the best mix of unused channels between you and the signal strength of the other networks, which may take some experimenting. For example, you may find things work better if there are 2 unused channels and the other network has a signal strength of 10% rather than 3 unused channels where the other network has a signal strength of 80%.

5 GHz

Without going into specific details for the 5GHz range the same rule of thumb applies and 4 unused channels should be maintained between your network and the others in the vicinity. 5 GHz also offers dual band selection, in which case you should keep 9 unused channels between your network and other networks in the vicinity. This is likely easier to do than on the 2.4 GHz range since sequential channels are not available. (For example channel numbers offered are ....52, 56, 60, 64 etc)

More About 2.4 GHz Vs 5 GHz

I mentioned earlier that the 5 GHz frequencies do not have the range that the 2.4 GHz range does, but this isn’t the only factor to consider, there are other differences that you might want to think about.

5 GHz can carry more data in certain conditions, but some 2.4 GHz equipment may include dual radios, You can suffer interference in both ranges but generally speaking less other equipment uses 5 GHz, so it’s somewhat less prone to interference than 2.4 GHz.

Determining Which Channel To Use

There are several tools you can use to determine what channels are being used by other networks in the vicinity of yours, they will also tell you the signal strength associated with each so that you can plan your optimised channel set up.

  1. BulletIf you are working from a Mac, you might try installing iStumbler.

  2. BulletIf you are working from a PC, you might try installing NetStumbler.

The following screenshot is taken using iStumbler:

  1. BulletThe first area to look at is which channels are being used, or more correctly not being used. If you are able to assign your network to an unused channel with 4 other unused channels between your own and any other, you can make your decision on the channel information alone.

  2. BulletIf you need to compromise on channel selection, use the signal strength information (which is represented here both numerically and graphically) to make an informed decision, you may want to try several options.

  3. BulletSignal Noise only really becomes relevant when examining your own network. Noise at its basic level represents a disturbance to the waveform that bears no relationship to the fundamental frequency and which therefore can interfere with the waveform's signal-carrying capabilities.

Signal strength may vary over a period of time, this could even result in some networks being undetected that may at other times cause a problem, so check the results over an appropriate period of time, you can also use the graphical representation in the top left corner to examine the consistency of a signal over a period of time.

Consider Connected Devices.

Generally speaking the decision to choose a channel for your network should be largely based around any interference your router or access point might suffer from other networks, however the position of connected devices can also become important particularly if they aren’t close to the router or access point. If you used a laptop to run your network tests you should be able to move it around and get an overall picture of interference around your home. Unfortunately, I’m not aware of any mobile apps for mobile devices that can run the same checks.

If you use mobile devices, it may be impossible to foresee all the areas in your home that you might want to use them, you can probably suffice examining the areas where you are most likely to use your mobile. However you should examine areas where non-mobile, non-computer installations such as Apple TV’s or wi-fi printers are located.

The Apple TV has a simple way of gauging signal strength with a simple 5 bar graphical representation which can be viewed at Settings General > About > Signal Strength. It should be noted however that a strong signal is not necessarily a good one.

You can likely use your router or access point to provide information which can be of help in examining the performance of these devices on your network. Unfortunately equipment from different manufacturers can vary significantly in layout and nomenclature, so it’s not possible to provide guidance in all cases.

The following screenshot is taken using the Apple AirPort Extreme Base Station:

The areas of interest in this particular case are Quality, Data Rate and Signal Strength.

Quality reflects the amount of signal within the channel formed between the router or access point and your device, the ‘Quality’ of the signal will indicate the ability of the device to achieve the stated data rate.

The Data Rate may not always be what you expect, but generally speaking should be well in excess of the calculated constant data rate required by the device. Low data rates can result in slow downloads or transfers, which may or may not be a nuisance to you. However when streaming media a minimum data rate must be maintained or the media will stutter during playback. For guidance 10 Mbps usually covers all types of iTunes Store content, but if you create home video you may find it uses higher data rates.

Signal strength may be represented graphically or numerically, Apple use RSSI (Received Signal Strength Indicator) which is measured in dBm (other manufacturers may use dBmW), it isn’t important to understand the specifics of these measurements, but you should know the range the RSSI is measured over. Apple use the range 0 dBm to -100 dBm, with 0 dBm being perfect (and from a practical standpoint unachievable). -40 dBm to -50 dBm is good, -60 dBm is quite acceptable. Other manufacturers may use RCPI (Received Channel Power Indicator) which is considered more accurate than RSSI.

It should be remembered that quality and signal strength measurements are not consistent between manufacturers and therefore shouldn’t be used for comparative purposes between different devices, nor should they be used as an absolute measurement but rather as a guide to obtaining the best conditions.