Greener computers talk in their sleep

Currently large numbers of people leave their computers running so they stay connected to a network or the Internet – be it to ensure remote access, availability for virus scans and backup, maintaining presence on instant messaging (IM) or voice-over-IP (VoIP) networks, or for file sharing and downloading. Although such tasks mean the PCs are relatively idle, they remain in awake mode and draw more power than they really need. To address this waste of electricity computer scientists at UC San Diego and Microsoft Research have created a plug-and-play hardware prototype for personal computers that induces a new energy saving state known as "sleep talking", which provides much of the energy savings of sleep mode and some of the network-and-Internet-connected convenience of awake mode.

To achieve "sleep talking", the team built a small USB-connected hardware and software plug-in system that supports IM applications, VoIP, large background web downloads, peer-to-peer file sharing networks such as BitTorrent, and remote access. The system could also be extended to support other applications.

Dubbed Somniloquy, which means "the act or habit of talking in one's sleep", the system allows a PC to appear to "say" to other hosts on the network, "I'm awake and I can perform non-power-intensive tasks"—even though it's in sleep mode. If more computational muscle is required, Somniloquy wakes it up.

The team gave Somniloquy its own low-power processor, some memory, a lightweight operating system, and a small amount of flash memory to store data. Somniloquy's low-power processor functions at the PC's network interface and runs an embedded operating system allowing it to impersonate the sleeping PC to other hosts on the network.

Somniloquy can also wake up the PC over the USB bus if necessary. For example, during a movie download, when the flash memory fills up, Somniloquy will wake up the PC and transfer the data. When the transfer is complete, it will go back to sleep mode and Somniloquy will again impersonate the computer on the network.

The current prototypes of the system work on both desktops and laptops, over wired and wireless networks. It also doesn’t require any changes to the operating system on the PC, to routers or other network infrastructure, or to remote application servers.

The researchers say they evaluated Somniloquy in various settings and that it consumes 11 to 24 times less power than a PC in idle state, which could translate to energy savings of 60 to 80 percent depending on their use model. In the future, Somniloquy could be incorporated into the network interface card of new PCs, which would eliminate the need for the prototype's external USB plug-in hardware.

Given the huge number of people and businesses who leave their PCs running after business hours just to facilitate basic networking tasks, the potential energy savings for the widespread adoption of the team’s technology would be equally huge. Obviously this is not only good for the bottom line, but also good news for the environment.

The paper detailing the project, "Somniloquy: Augmenting Network Interfaces to Reduce PC Energy Usage", was presented on April 23, 2009 at USENIX Symposium on Networked Systems Design and Implementation by UC San Diego computer science Ph.D. student Yuvraj Agarwal.

Darren Quick