End-to-end Performance in Vehicular Networks with an Emphasis on Safety and Security Applications.

摘要

In wireless networks, the presence of interference among wireless links introduces dependencies among wireless links introduces dependencies among flows that do not share a single link or node. As a result, when designing a resource allocation scheme, be it a medium access scheduler or a ow rate controller, one needs to consider the interdependence among nodes within interference range of each other. Specically, control plane information needs to reach nearby nodes which often lie outside the communication range, but within the interference range of a node of interest. But how can one communicate control plane information well beyond the existing communication range. To address this fundamental need we introduce tag spotting. Tag spotting refers to a communication system which allows reliable control data transmission at SNR values as low as 0 dB. It does this by employing a number of signal encoding techniques including adding redundancy to multitone modulation, shaping the spectrum to reduce inter-carrier interference, and the use of algebraic coding. Making use of a detection theory-based model betweenze the performance achievable by our modulation as the rate of the information transmitted and the likelihood of error. Using real-world experiments on an OFDM system built with software radios, we show that we can transmit data at the target SNR value of 0 dB with a 6% overhead; that is, 6% of our packet is used for our low-SNR decodable tags (which carry up to a couple of bytes of data in our testbed), while the remaining 94% is used for traditional header and payload data. We also demonstrate via simulations how tag spotting can be used in implementing fair and ecient rate control and scheduling schemes in the context of wireless multi-hop networks, while pointing out that the idea of tag spotting is useful in the context of any wireless network in which control-plane information must travel beyond the communication range of a node.