Broadcom dismisses fears of 11n traffic jams

Channel bonding grabs bandwith but there is plenty to spare, says Wif chip specialist

Broadcom demonstrated video streaming using its latest draft 11n Wifi chips in London today and said it was confident the technology will scale to mass use without jamming the airwaves in cities.

The company, which makes the Wifi chips used in many makes of wireless router, showed two HD video streams using the same single 11n channel in the 5GHz band, with a number of peripheral devices using channels in the more crowded 2.4GHz bands which are used by the 11b and 11g flavours of Wifi.

One stream was running at 10Mbits/sec and the other at around 16Mbits/sec and the system was not using controversial channel-bonding, which doubles bandwidth by the simple expedient of using two channels instead on one.

There are only three non-overlapping 20MHz channels at 2.4GHz and up to 12 at 5GHz, which is used by 11a Wifi; bonding increases the channel bandwidth to 40MHz but halves the number of non-overlapping channels.

It is common in cities for several Wifi cells to overlap, competing for airspace, and there are fears that this contention will worsen with the increased effective range and anticipated heavy-duty use of 11n.

Business development manager Clint Brown said he was sure that this would not be a problem and the video demo showed there was a lot of bandwidth to spare. He was also confident that different makes of draft 11n products, including the Intel implementation in many notebooks, would interoperate.

Channel bonding is on by default at 5GHz but at 2.4GHz can be set to revert to a single channel if there are other networks within range – which in city centres would mean virtually everywhere. But it is up to the device manufacturer whether this option is implemented.

Brown said the Broadcom silicon was compliant with the latest draft 2.0 spec of 11n and that the full version is unlikely to be finalised until autumn 2008. But the changes are likely to be in optional features and though he did not say for certain that Broadcom products could be software upgraded, they were “very programmable”.

The Broadcom demonstration was timed to coincide with the IPTV forum in London, where 11n was one of the technologies under consideration for moving content around the home.