Vehicular Opportunistic Communication Under the Microscope

5th International Conference on Mobile Systems, Applications, and Services

David Hadaller†, Srinivasan Keshav†, Tim Brecht†, Shubham Agarwal‡

PID  :  81325

来源: CEUR

【 摘 要 】

We consider the problem of providing vehicular Internet ac cess using roadside 802.11 access points. We build on pre vious work in this area [18, 8, 5, 11] with an extensive ex perimental analysis of protocol operation at a level of detail not previously explored. We report on data gathered with four capture devices from nearly 50 experimental runs con ducted with vehicles on a rural highway. Our three primary contributions are: (1) We experimentally demonstrate that, on average, current protocols only achieve 50% of the overall throughput possible in this scenario. In particular, even with a streamlined connection setup procedure that does not use DHCP, high packet losses early in a vehicular connection are responsible for the loss of nearly 25% of overall throughput, 15% of the time. (2) We quantify the eects of ten problems caused by the mechanics of existing protocols that are re sponsible for this throughput loss; and (3) We recommend best practices for using vehicular opportunistic connections. Moreover, we show that overall throughput could be sig nicantly improved if environmental information was made available to the 802.11 MAC and to TCP. The central mes sage in this paper is that wireless conditions in the vicinity of a roadside access point are predictable, and by exploit ing this information, vehicular opportunistic access can be greatly improved. Categories and Subject Descriptors: C.2.2 [Computer Communications Networks]: Network Protocols General Terms: Experimentation, Performance, Measure ment