IEEE 802.11 PHY supports multiple transmission rates according to multiple different modulations and coding schemes. Each WiFi station selects its own transmission rate according to its ownalgorithm; in particular, the IEEE 802.11 standards do not specify the bit-rate selection method.Although many adaptive bit-rate selection algorithms have been proposed, there is limited researchand evaluation on the performance of such algorithms for roadside networks, especially in cases with multi-vehicle roadside multi-vehicular WiFi networks.In this thesis we propose an opportunistic highest bit-rate algorithm, Opportunistic Highest Bit-Rate Multi-Vehicular WiFi Networks (OHBR-MVN), specifically for roadside multi-vehicular WiFi networks. Our proposal is based on three key characteristics of such networks: (1) vehicles will drive closer to, and eventually pass, the roadside WiFi station, experiencing a progressively bettertransmission environment; (2) the vast majority of data transmitted in single-vehicle drive-by downloading scenarios occurs at the maximum transmission rate; (3) vehicles that transmit at less than the maximum rate do so at the expense of those that could send more data at a highertransmission rate. We therefore believe that transmitting only at the highest possible bit-rate is the preferred algorithm for such networks. Further, this approach keeps the bit-rate selection extremely simple, avoiding the complexity and resulting problems of adaptive approaches.Through a series of experiments that compare the throughput of both fixed and adaptive bit-rateselection algorithms we show that our approach yields both higher throughput and better fairness characteristics, while being significantly simple, and thus more robust.
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Experimental Performance Evaluation of Bit-Rate Selection Algorithms in Multi-Vehicular Networks
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