Q: Will interference limit the value of wireless LANs in the future? What happens when every company, resident and such has a wireless LAN?
The Wizards gaze into their crystal ball and respond:
Greg Murphy, Airwave
Increasing usage will not limit the value of WLANs in the future, but it will mean that organisations will need to grow more sophisticated in managing the RF environment. For the first time, IT organisations (and even home network users) will have to pay a great deal of attention to what is happening outside their four walls.
When I first installed a wireless network in my home, I didn’t give a moment’s thought to the RF channel setting. It never occurred to me to think about it until my previously blazing fast Wi-Fi connection unexpectedly slowed to a crawl one day. What happened? My neighbour had installed an access point on exactly the same channel and our networks were interfering with each other. I couldn’t get a strong signal, so my throughout dropped precipitously.
Did that limit the value of my WLAN? No. It just meant that I had to become a slightly more sophisticated user. By changing to a non-overlapping channel and fine-tuning the RF transmission power of my access point, I got my blazing speed back.
This same scenario is going to play out over and over again in businesses and homes in the next few years. The answer is not to abandon WLANs but to learn and manage the airspace to achieve optimal performance.
Alan Cohen, Airespace
With wireless, interference is a way of life. There are several forms of interference a WLAN system must account for, including non-802.11 radiation (eg microwave oven), 2.4 GHz cordless telephony, and even Bluetooth. There are also several forms of 802.11 interference (including co-channel interference), in which adjacent access points interfere with access points on the same channel. But interference should not inhibit the global rollout of WLANs. The cellular network operates successfully with more than 1 billion users by applying several of the approaches noted below.
To offset the potential challenges of interference, next-generation wireless systems must achieve several key capabilities. The most important is dynamic RF management. An active wireless system must maximise its spectral capacity by adjusting channel assignment, transmit power and load balancing among clients on a WLAN. For example, if your neighbour’s access point is on channel 1, you want your WLAN to move to channel 6 or 11. With the introduction of new “Uniband” frequencies, 802.11a provides a substantially larger amount of spectrum for wireless transmissions (more than 20 vs. the three bands of 802.11 b/g).
Access points must constantly scan all channels, and if a major source of interference is detected, pinpoint where the amount of traffic crosses the predefined threshold. If your WLAN system can increase system performance in the presence of the interference, the system will rearrange the channel assignment. This rearrangement might end up with adjacent access points on the same channel, but logically that would be a better choice (due to utilisation) than sitting on a channel that is totally unusable due to an interfering access point.
New antenna technologies, including beam switching and MIMO, focus transmit energy around the client rather than radiating in an omni-directional pattern around an access point. These new smart antenna technologies can also reduce the impact of interference for your WLAN.
Marcel Wiget, Chantry Networks
There is indeed a concern on interferences in locations where multiple interest groups want to deploy WLANs. The best known examples are probably airports. News articles like “Airports in Boston, Denver and L.A. are ground zero in the airwaves battle” are a good example. However, there are far more places where WLAN deployments can be controlled to minimise interference. The FCC limits the power output for WLANs (including any possible antenna gains) to very low values, far lower than any cell phones. As a result, the coverage area is limited and can be managed by intelligent WLANs that support dynamic channel and power level adjustments.