Q&A: Interference could hamper Wi-Fi mobile broadband

 

Gallery

By Stewart Mitchell

Posted on 1 Jul 2010 at 11:50

Wi-Fi is increasingly being used to relieve the strain from mobile phone networks, but one access point manufacturer believes networks will have to be upgraded to avoid problems with interference and capacity.

Ruckus Wireless's John McGann explains that new technology can improve signal clarity in busy network areas and why some public venues suffer from capacity problems.

Q. Why is service often so poor in public spaces like football grounds and rarely used venues?

A. Firstly, the economics of a service provider installing large bandwidth pipes to a stadium simply don’t add up. Typically, there is very little data traffic in between events, and then suddenly the networks have to cope with a huge three hour peak. This means that 99% of the time, there’s no traffic – just cost.

Another factor that contributes to poor service is that stadiums typically suffer from a barrage of interference caused by a wide range of devices and constantly changing obstructions. This situation is made worse by the huge volume of mobile devices hitting the network, at the same time.

Q. Surely airports and other business centres should have enough access points to cover the amount of traffic?

A. At the moment, networks in most major airports seem to provide a reasonable level of wireless coverage – although many of us are likely to have experienced black spots at some point. The question is whether the deployments they have in place today will be able to cope with the increase in data traffic they are bound to witness as the popularity of mobile devices grows.

Q. What problems will we see as Wi-Fi is increasingly used as an alternative to 3G networks for web access?

A. Many mobile operators are still concerned about problems with radio interference that have plagued Wi-Fi in the past. While Wi-Fi was conceived as a technology of convenience, it has historically been subject to unreliability and interference, especially in crowded spaces.

However, recent technical breakthroughs in a service we call ‘Smart Wi-Fi’, transmit signals directly to each client only when they are needed, using the highest performing signal path, which reduces interference without network administrators having to position APs or antennas.

Q. Can't they just put in more access points?

A. I believe a two fold strategy is needed – increasing the number of access points (APs) can help to provide better coverage and cope with the increased subscriber usage, but it’s also important to consider migrating to the latest 802.11n technology to take advantage of the additional bandwidth it provides.

Q. You mentioned interference - what problems do more APs pose to interference?

A. You can reach a saturation point with APs – installing more and more off-the-shelf units can actually do more harm than good. Most Wi-Fi APs on the market today blast signals everywhere, transmitting and receiving in all directions like a radio speaker. If interference crops up, these systems have no recourse but to listen to it, becoming unable to do much else.

By directing Wi-Fi signals only where they are needed, users experience much more stable connections that reach two to four times further than traditional systems.

Q. What throughput rates might people expect to see with this technology?

A. In low noise/low density environments, there's little difference in performance between different vendors’ APs. Speed and performance is driven by the physics on the spectrum available. In tests, we see 7-10Mbits/sec to an iPhone 3G client from most vendors. However, in high noise/high density environments "Smart Wi-Fi" maintains 5-6Mbits/sec, while most vendors struggle to get 3Mbits/sec.