To Ofﬂoad or Not to Ofﬂoad? The Bandwidth and Energy Costs of Mobile Cloud Computing Marco V. Barbera, Sokol Kosta, Alessandro Mei, and Julinda Stefa Department of Computer Science, Sapienza University of Rome, Italy Email: firstname.lastname@example.org
Abstract—The cloud seems to be an excellent companion of mobile systems, to alleviate battery consumption on smartphones and to backup user’s data on-the-ﬂy. Indeed, many recent works focus on frameworks that enable mobile computation ofﬂoading to software clones of smartphones on the cloud and on designing cloud-based backup systems for the data stored in our devices. Both mobile computation ofﬂoading and data backup involve communication between the real devices and the cloud. This communication does certainly not come for free. It costs in terms of bandwidth (the trafﬁc overhead to communicate with the cloud) and in terms of energy (computation and use of network interfaces on the device). In this work we study the feasibility of both mobile computation ofﬂoading and mobile software/data backups in real-life scenarios. In our study we assume an architecture where each real device is associated to a software clone on the cloud. We consider two types of clones: The off-clone, whose purpose is to support computation ofﬂoading, and the back-clone, which comes to use when a restore of user’s data and apps is needed. We give a precise evaluation of the feasibility and costs of both off-clones and back-clones in terms of bandwidth and energy consumption on the real device. We achieve this through measurements done on a real testbed of 11 Android smartphones and an equal number of software clones running on the Amazon EC2 public cloud. The smartphones have been used as the primary mobile by the participants for the whole experiment duration.
I. I NTRODUCTION The advances in technology of the last decades have undoubtedly turned yesterday’s must-have devices into today’s stock. Think of the phones with aerials of the late ’80, or the Pentium 4 PCs of a few years ago. None of them is comparable to the power of nowadays smartphones, whose recent worldwide market boost is undeniable. We use smartphones to do many of the jobs we used to do on desktops, and many new ones. We browse the Internet, send emails, organize our lives, watch videos, upload data on social networks, use online banking, ﬁnd our way by using GPS and online maps, and communicate in revolutionary ways. New apps are coming out at an incredible pace. Apple iPhone commercial’s call to action “There’s an app for everything” says a lot on this Alessandro Mei is supported by a Marie Curie Outgoing International Fellowship funded by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n. 253461. This work has been technically supported and partially funded by Telecom Italia within the Working Capital project. This work has been performed in the framework of the FP7 project TROPIC IST-318784 STP, which is funded by the European Community. The Authors would like to acknowledge the contributions of their colleagues from TROPIC Consortium (http://www.ict-tropic.eu).
matter. Nonetheless, the more eager we get when using our smartphones by installing new apps, the less happy we are with the lifetime of the battery. The problem is that we rely upon a number of crucial pieces of information that are only stored in the device (phone numbers, addresses, notes, appointments, etc.), or, in some cases, that can be got only by using the Internet on the ﬂy as many of us are used to do. It is so important to keep our smartphone operational that everyday we pay attention to our battery and try to save it by reducing the number of phone calls, or by avoiding to watch too many videos, just enough to be able to reach home and recharge it. But that means that we cannot use our device to the fullest. Many researchers believe that cloud computing is an excellent candidate to help reduce battery consumption of...
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