Avoiding 2.4GHz Frequency Conflicts

Resolve a potential conflict between an 802.11b network and 2.4GHz phones.

Sean Daily

March 24, 2003

2 Min Read
ITPro Today logo

I run an 802.11b network, and I'm having some problems that are significantly reducing its usefulness. When the network is very active (e.g., pulling down large files over the DSL connection) my Siemens 2.4GHz phones cut in and out in quick sound waves. I also experience other strange phenomena, such as the phones suddenly resetting for no apparent reason. I've heard that these problems might be occurring because I'm running too many devices in the same 2.4GHz range. Is this explanation accurate and if so, what can I do to get my network running smoothly again?

Despite the potential problems caused by contention in the unlicensed 2.4GHz frequency range, 2.4GHz devices work together fairly well most of the time. Frequency contention might be the culprit in your scenario but isn't the only possible cause.

First, unplug all your 802.11b network devices and determine whether the problem with your phones goes away. If so, you might have a conflict between the phones, which use the Frequency Hopping Spread Spectrum (FHSS), and the network, which uses the Direct Sequence Spread Spectrum (DSSS). In that case, try physically separating your phones from your network Access Points (APs) as much as possible and, if your devices support doing so, change the channels that the devices use.

If these actions don't help, you might want to consider a different brand of phone that uses a different frequency range (e.g., 900MHz, 5GHz) or another technology that's more compatible with 802.11b networks. Or you might consider replacing your 802.11b network with an 802.11a network that operates in the 5GHz spectrum and provides the additional benefit of faster operation. (Note that although 802.11g networks also provide faster throughput than 802.11b networks, 802.11g operates in the same 2.4GHz frequency range as 802.11b and thus won't help in this situation.)

However, be aware that because they use shorter wavelengths, 802.11a networks have much worse in-building penetration than 802.11b networks do, particularly in areas with many partitions, rooms, or intervening objects. Therefore, your signal strength to various areas might decrease significantly in an 802.11a scenario.

I wouldn't be surprised, however, if your problems don't go away even after you unplug the network. I've seen plenty of older Siemens phones exhibit the effect you describe. If this is the case, simply replacing the handsets (or getting a newer or different system) might alleviate the problem.

Sign up for the ITPro Today newsletter
Stay on top of the IT universe with commentary, news analysis, how-to's, and tips delivered to your inbox daily.

You May Also Like