Overcoming Wi-Fi Interference in Your SMB

Paul Mah
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I chanced upon a comprehensive list of myths about Wi-Fi interference published by Cisco. You can check out the list here, which talked about how interference can impact wireless performance and cause instability in a wireless network.


While the list was really as marketing material to highlight the capabilities of Cisco Spectrum Expert, the write-up did get me thinking about how SMBs may overcome potential interference at their premises. I've selected a short list of the most common myths about wireless interference that SMBs rolling out Wi-Fi may want to bear in mind.


Interference comes only from other Wi-Fi networks


Interference originating from non-Wi-Fi wireless sources is perhaps the most overlooked factor when it comes to rolling out a wireless network. This is especially true in the overcrowded 2.4GHz band, with devices such as microwave ovens, cordless phones, fluorescent lights and even Bluetooth devices as sources of potential interference. Worsening the situation would be how some of this interference results in subpar performance or disconnections only intermittently, with the fault pinned to a poor wireless infrastructure instead of the actual cause.


Everything seems to be working, so there is no interference


The design of the 802.11 protocol means that wireless devices will perform an automatic "back-off" in the face of interference, which may eventually result in network speeds being dynamically lowered to cope with frequent retransmissions. The amount of self-healing means that a simple "ping" test or loading of Web pages is insufficient to detect the presence of serious wireless interference. However, the issue may well rear its head under heavy loading, and could render latency-sensitive applications unusable.


Using a higher density of access points to increase performance


I admit to once harboring the mistaken notion that interference issues can be overcome by simply packing in more (and more powerful) Wi-Fi access points (AP). I was quickly debunked of this myth in my conversations with various Wi-Fi makers, however, who told me that having more improperly configured APs could actually worsen the problem. Cisco agrees here, observing that it's actually necessary to reduce individual transmit power when deploying a dense network of APs. In a nutshell, properly configured APs can be used to support a higher density of Wi-Fi devices - just don't expect to solve interference problems in this manner.


There is no interference at 5GHz


It is "generally true" that fewer devices currently operate at 5GHz compared to 2.4GHz devices, says Cisco, though the company cautioned that some devices already exist in the 5GHz band. Among others, this ranges from cordless phones, digital satellite and perimeter sensors. While I do not doubt the veracity of Cisco's assertion here, I think it also serves as an endorsement to make more active use of the 5GHz band when deploying Wi-Fi in your business.


Indeed, when I spoke to CEO Dirk Gates of Xirrus earlier this year, he specifically mentioned the 5GHz band as a criterion for Wi-Fi being able to replace traditional wired networks.


Have you deployed Wi-Fi in your small and mid-sized business yet? Feel free to share your experiences in the comments section below.

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