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Will Wi-Fi run out of radio bandwidth?

Feb 02, 20043 mins
Network SecurityWi-Fi

Q: I hear that Wi-Fi may become so popular that channels may get used up at 2.4 and 5 GHz. What happens then? 60 GHz? – Bonnie, San Francisco

A: Wi-Fi usage is definitely growing considerably and will continue to grow in the future. In fact, current user demand is outpacing the deployment of networks. As deployments catch up, we will begin to have Wi-Fi access available everywhere with dense urban deployments. This will drive the creation of more enterprise and consumer applications, potentially resulting in users straining the existing 2.4 and 5 GHz bandwidth capacity.

This may be more of a concern for 802.11b/g operating at 2.4 GHz, since there are only three channels that can be used simultaneously. However, for 802.11a transmitting at 5 GHz, there are as many as 25 channels, after the recent FCC allocation of new bandwidth at 5.47 GHz. This should provide plenty of capacity, even for very dense deployments of access points in multi-tenant residential buildings.

However, making more channels available just moves the capacity problem out in time. Wireless capacity is a finite resource that requires intelligent use of channel bandwidth. There are three main means by which technology will continue to enhance the effective use of the wireless capacity currently available: radio resource algorithms, modulation techniques, and radio technology.

For example, WLAN networks incorporating existing intelligent radio resource management (RRM) and dynamic channel assignment (DCA) make the most efficient use of the limited channel resources available. This enables capacity to go farther, especially in denser WiFi environments.

Over the past couple of years, we have seen data rate standards move from 1 or 2 M bit/sec to 11 and 54M bit/sec currently. These rates will continue to grow and increase effective channel usage. Presently, the IEEE 802.11n Working Group is driving standards for rates in excess of 100M bit/sec, based on better modulation and intelligent radios.

 The high cost of intelligent radios has slowed their use in Wi-Fi products. Recent technological advances have driven the price of intelligent radios down to enable the incorporation of multiple-input multiple-output (MIMO) antennas into Wi-Fi products. The benefit of MIMO is that it establishes a virtual RF wire between the radio and the client. In a sense, MIMO changes a current access point, which acts like a wired hub, into a wired switch that can deliver the full channel bandwidth to each client device.

While it is conceivable that we may need additional radio bands in the future, that reality shouldn’t occur any time soon. There are still plenty of efficiency-promoting technologies to be implemented in the near future.