Phone’s running out of juice? That?s easily among the list of daily crises that people face, and more likely so when the device is constantly called upon to transmit data or stream video. A group of researchers at Microsoft Research India (MSRI), probably, has an answer to that problem: make the smartphone?s radio communication smarter. Put simply, their solution is to reduce the constant to-and-fro transmission to short ?bursts? and to schedule tasks for when the signal reception is good, using a cloud-based proxy.
The combination of ?bursts? of communication and scheduling downloads helped achieve up to 50% energy savings for web browsing and up to 25% energy savings for a media streaming application.
?Stratus?, the project by researchers Venkat Padmanabhan, Ram Ramjee and Vishnu Navda of MSRI?s Mobility, Networks and System group in Bangalore, is based on the understanding that cellular radio communication can, at times, add at least five times the energy cost of the base device. Stratus involves a proxy sitting on a cloud, which optimises incoming and outgoing traffic to match the energy characteristics of the radio interface.
?The energy savings depends on what workload you are using,? says Vishnu Navda, adding that, for a typical browsing session, the radio is kept on for long periods of time because of the number of `round trips’ involved. If a website has 150 objects, the browser sends requests to the server for each of them. In an aggregation scheme, it simply sends the main domain request and the server fetches all the content and pushes it to the client helping it to cut down on the round trips.
?Since the data is coming in bursts, the radio just has to turn on, take this bulk content and turn off. So, the radio remains in an active state for a shorter duration of time,? says Navda, adding that the data sent from the cloud is compressed into fewer bytes, thereby, reducing radio time even further.
Besides the first set of optimisation using aggregation and compression, the researchers demonstrated that tasks could be scheduled according to the signal quality the user experiences, for example, on his daily commute between work and home.
?The idea is that most users have very predictable mobility profile. So, you can know what type of signal coverage they go through during their daily commute,? he says. Once the signal quality during the person’s commute is mapped, Stratus, which acts like a background service on the phone, carries out the requests for downloads when the signal quality is good and remains quiet when the connectivity is poor.
“That will be useful while downloading large webpages or streaming while one is moving,” said Ashok Jhunjhunwala, professor, Department of Electrical Engineering at the Indian Institute of Technology, Chennai. There are currently some attempts in 3G technology to include similar concepts, he added.
The extra work a phone has to do when a signal is poor is also why it tends to heat up. Still, mobile phones are far more energy efficient than computers and laptops partly because of their smaller screen size, says Jhunjhunwala.
In a subsequent paper in 2010, the MSR team also demonstrated that it was possible to predict when the signal would be weak and strong based not just on location but also by using traces from actual drives. The energy aware scheduling algorithm, which they named Bartendr, showed energy savings of upto 60% during experiments on four cellular networks in two metropolitan areas in India and the US, the researchers reported.
MSRI says its research was not undertaken with any specific plan to commercialise the technology, because the lab typically does not follow a product-based approach. Navda, however, reckons that the energy and bandwidth savings from Stratus would make it appealing to users.
?A single proxy can easily support few thousands of clients as the memory and computation required to support each client is not very significant,? he says, adding that the cloud can be leveraged to scale up or distribute the service to different parts of the world. In India, value added services, such as web browsing and video streaming, are currently a minuscule part of the revenues of telecom companies, as low as 10-11% of which SMS accounts for nearly half.
In contrast, data services contribute to about 65% of telecom revenue in some European countries and 40% in countries like Japan and Korea, says Romal Shetty, National Head for Telecom at KPMG.
He attributes the low usage in India partly to the quality of content available currently, but adds that efforts are on by companies to at least double the revenue from value added services in the next three to four years.