tailieunhanh - SenseLess: A Database-Driven White Spaces Network

We then use this formula to derive the average disk access latency for each application, when given a cer- tain quota of the disk bandwidth. We assume that think time per thread is negligible compared to request pro- cessing time, ., we assume that I/O requests are ar- riving relatively frequently, and disk access time is sig- nificant. If this is not the case, the I/O component of a workload is likely not going to impact overall application performance. However, if necessary, more precision can be easily afforded ., by a context tracking approach, which allows the storage server to distinguish requests from different application threads [25], hence infer the average think. | SenseLess A Database-Driven White Spaces Network Rohan Murty Harvard University rohan@ Ranveer Chandra Microsoft Research ranveer@ Thomas Moscibroda Microsoft Research moscitho@ Paramvir Bahl Microsoft Research bahl@ Abstract The most recent FCC ruling proposes relying on a database of incumbents as the primary means of determining white space availability at any white spaces device WSD . While the ruling provides broad guidelines for the database the specifics of its design features implementation and use are yet to be determined. Furthermore architecting a network where all WSDs rely on the database raises several systems and networking challenges that have remained unexplored. Also the ruling treats the database only as a storehouse for incumbents. We believe that the mandated use of the database has an additional opportunity a means to dynamically manage the RF spectrum. Motivated by this opportunity in this paper we present SenseLess a database driven white spaces network. As suggested by its very name in SenseLess WSDs obviate the need to sense the spectrum by relying entirely on a database service to determine white spaces availability. The service using a combination of an up-to-date database of incumbents sophisticated signal propagation modeling and an efficient content dissemination mechanism ensures efficient scalable and safe white space network operation. We build deploy and evaluate SenseLess and compare our results to ground truth spectrum measurements. We present the unique system design considerations that arise due to operating over the white spaces. We also evaluate its efficiency and scalability. To the best of our knowledge this is the first paper that identifies and examines the systems and networking challenges that arise from operating a white space network which is solely dependent on a channel occupancy database. I. INTRODUCTION The recent FCC ruling 3 has obviated mandatory spectrum

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