Wireless networks may learn to live together by using energy pulses

The university-developed GapSense system could help prevent interference between Wi-Fi and other networks

By , IDG News Service |  Mobile & Wireless

Wi-Fi devices can even fail to communicate among themselves on dividing up resources. Successive generations of the Wi-Fi standard have allowed for larger chunks of spectrum in order to achieve higher speeds. As a result, if an 802.11b device using just 10MHz of bandwidth tries to tell the rest of a Wi-Fi network that it has packets to send, an 802.11n device that's using 40MHz may not get that signal, Shin said. The 802.11b device then becomes a "hidden terminal," Shin said. As a result, packets from the two devices may collide.

To get all these different devices to coordinate their use of spectrum, Shin and Zhang devised a totally new communication method. GapSense uses a series of energy pulses separated by gaps. The length of the gaps between pulses can be used to distinguish different types of messages, such as instructions to back off on transmissions until the coast is clear. The signals can be sent at the start of a communication or between packets.

GapSense might noticeably improve the experience of using Wi-Fi, Bluetooth and ZigBee. Network collisions can slow down networks and even cause broken connections or dropped calls. When Shin and Zhang tested wireless networks in a simulated office environment with moderate Wi-Fi traffic, they found a 45 percent rate of collisions between ZigBee and Wi-Fi. Using GapSense slashed that collision rate to 8 percent. Their tests of the "hidden terminal" problem showed a 40 percent collision rate, and GapSense reduced that nearly to zero, according to a press release.

One other possible use of GapSense is to let Wi-Fi devices stay alert with less power drain. The way Wi-Fi works now, idle receivers typically have to listen to an access point to be prepared for incoming traffic. With GapSense, the access point can send a series of repeated pulses and gaps that a receiver can recognize while running at a very low clock rate, Shin said. Without fully emerging from idle, the receiver can determine from the repeated messages that the access point is trying to send it data. This feature could reduce energy consumption of a Wi-Fi device by 44 percent, according to Shin.

Implementing GapSense would involve updating the firmware and device drivers of both devices and Wi-Fi access points. Most manufacturers would not do this for devices already in the field, so the technology will probably have to wait for hardware products to be refreshed, according to Shin.

A patent on the technology is pending. The ideal way to proliferate the technology would be through a formal standard, but even without that, it could become widely embraced if two or more major vendors license it, Shin said.

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