NATURE: March 2010

Mar 19, 2010

A Faster Wireless Web

Transfers of large amounts of data across the Internet to wireless devices suffer from a key problem: The Transmission Control Protocol (TCP) used to send and receive that data can be unnecessarily slow.

Mobile speed: Fasp-AIR will make its first appearance in the wild as an iPhone application designed to speed media uploads over wireless networks.
Credit: Aspera

A company called Aspera has now announced an alternative protocol designed to accelerate wireless transfer speeds. Called fasp-AIR, it includes new proprietary approaches to addressing problems of data transfer that are unique to wireless communications. The original fasp protocol is already used to boost regular Internet transfers. It was used, for instance, to speed up the transfer of files from New Zealand to the U.S. during production of the movie Avatar.
The main problem with the TCP protocol, which was designed before wireless connections to the Internet were commonplace, is that it doesn't know the difference between packets of data that are lost because of network congestion and those that are lost because of a weak wireless signal. TCP automatically throttles the speed of data transfer when it sees dropped packets, so that congestion doesn't overwhelm the network. That's fine when packets are lost because of congestion, but when the problem is a weak signal, it causes an unnecessary drop in transfer speeds that can bring downloads and uploads to a crawl.
For some applications, like streaming video and Internet telephony, it's possible to use an alternative like the User Datagram Protocol (UDP), which doesn't bother to confirm that all data has arrived intact. The price of UDP's speed is dropped packets of data--a result familiar to anyone who has endured the degraded quality of a video stream or telephone conversation when at the limits of a wireless network's range.
Fasp-AIR achieves faster speeds than TCP but doesn't result in any dropped packets, making it suitable for transferring data that must arrive complete and intact. "The drop-off in performance we see with fasp-AIR is almost linear," says Aspera CEO Michelle Munson. "So a 10 percent loss in the available bandwidth means we're still getting transfer rates that are 90 percent of what's specified."

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At first, fasp-AIR will be available as an iPhone app that can be used to access enabled servers. Fasp-AIR requires that both the client and the server are running software developed by Aspera. In the future, Aspera hopes that developers will incorporate fasp-AIR into their applications directly. Aspera licensees currently include Amazon and several other large Internet companies.
Fasp-AIR certainly isn't the only novel approach being used to speed up transfers of wireless data. Jon Crowcroft, Marconi Professor of Communications Systems at the University of Cambridge, says that some wireless carriers use a proxy server between the wireless and the wired networks to intelligently adapt to changing network conditions. This gets around the problem of whether or not a TCP alternative like FaspAIR is hogging bandwidth on a congested network.

Wireless Controlled from the Cloud

Rolling out next-generation wireless networks can be painstakingly slow and patchy at the best of times, as the U.S. deployment of 3G has shown. But IBM researchers in China reckon that shifting the signal-processing requirements from base stations into the cloud will make it cheaper and easier to upgrade networks. Ultimately, the approach could lead to wireless networks that can provide better coverage by rapidly adapting to user demand.

Credit: Technology Review

A new architecture called the Wireless Network Cloud (WNC) marks a step away from using dedicated hardware in the radio base stations that serve wireless networks like GSM and 3G cell phone networks, says Ling Shao, senior manager of System Software and Appliances at IBM's China Research Lab, in Beijing. With WNC, the radio antennas are physically decoupled from the base stations, with the latter existing virtually, within general-purpose data centers at distant locations.
All of the signal processing--the modulation and encoding of the signals to and from the physical antennas--is carried out using software radio technology, adds Yonghua Lin, manager of IBM's Next Generation Network Appliance. With multicore and multithreading techniques, it is possible to use general-purpose data centers to carry out the signal processing entirely in software, she says.
This allows the network to be managed in a more centralized way, with the raw signals being relayed to and from multiple antennas, which IBM calls "remote radio heads," via optical fibers from as far away as 40 kilometers.
The main attraction to network operators is cost, says Lin. Traditional base stations currently account for about 40 percent of a network's total cost, she says. And yet because of the proprietary design of the hardware used, whenever a network is upgraded, almost all of this equipment has to be replaced. WNC upgrades can be implemented relatively cheaply by installing new software.

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The centralized nature of this approach also means operators can manage their networks more efficiently. In areas where cell traffic may vary dramatically depending upon the time of day--business districts where daytime traffic is heavy but evening traffic is light, or residential areas where the opposite is true--WNC should allow the network operator to allocate resources when they're needed, says Lin.
Existing base stations tend to be linked directly to the network gateway, but not to other base stations. Pooling the software radio resources within a data center makes the network much more adaptive to user demand, says Lin. "We can dynamically reallocate resources across different base station cells," she says.