Think of all the competing signals flying overhead at this very moment with your wireless device in the unlicensed spectrum or ‘white space’ as it is commonly known – Bluetooth headsets, Wi-Fi enabled laptops, walkie talkies, automatic syncing, even baby monitors.
“The unlicensed spectrum is overcrowded with a large number of wireless devices,” said Ranveer Chandra of Microsoft Research Redmond in the US.
This crowding can lead to under-performance on your wireless network and slow down data transfer but were these networks to become smart or ‘spectrum aware’, specifically by adjusting the spectrum width over which they send signals, they can achieve greater speed or range depending on the width.
“To achieve the best performance of wireless networks in this setting, it is necessary to make the wireless networks ‘spectrum aware’. They should operate in the cleanest frequency spectrum,” said Chandra.
While it might seem as though operating on as wide a spectrum as possible would make for a more robust wireless network, Chandra and his colleagues Ratul Mahajan, Thomas Moscibroda and Paramvir Bahl, report that narrower channels have lower throughput but a longer range and consume less power.
They are also better able to withstand multipath delay spread, which happens when a wireless networks not only sends line-of-sight signals but also reflected waves which can be delayed.
“Furthermore, the network should operate on as much of the spectrum that is available. Hence, they should not only adapt the channel number (centre frequency), but also the channel width,” explained Chandra.
The Microsoft researchers will be presenting this information in their paper A Case for Adapting Channel Width in Wireless Networks at the Sigcomm 2008 conference, an annual gathering for the Special Interest Group on Data Communications.
“In this work, we have shown the feasibility of adapting the channel width – a fundamental, yet unexplored parameter – from software on off-the-shelf Wi-Fi cards,” added Chandra.
By Marie Boran
