在都市環境中，尋找停車位一直是個令駕駛人相當困擾的問題。在車用無線網路出現後，這個問題的解決方法便多了一個思考的方向。利用裝設在停車收費器(parking meter)和車輛上的網路裝置形成的車用無線網路，可以將空停車位的資訊散播出去。在這篇論文中，我們提出了一個以廣播為基礎的通訊協定，能夠以較少的封包傳輸量，達成讓駕駛人得到可接受的資訊量和精確度。在我們的方法中使用了許多技巧，例如輪流廣播機制、離散餘弦轉換(DCT)、判斷封包的品質好壞並減少較差的封包和依空停車位的數量動態調整廣播週期和TTL等，都有助於減少通信開銷(communication overhead)並維持資訊可得性和正確率。在模擬的結果中顯示，我們所提出的方法比過去的方法有更高的適應性和資訊散播的效率。

Looking for parking spaces is usually a serious problem in urban cities. In order to reduce the time for seeking parking spaces and save the fuel, the parking spaces finding schemes become an important research issue in vehicular ad hoc networks (VANETs). Using the embedded wireless devices on parking meters and vehicles, the parking spaces information can be spread in the VANETs. With the help of this information, drivers will not have to waste a lot of time for finding parking spaces. In this article, we propose a distributed scheme to discover the parking spaces efficiently. Our scheme is based on a hierarchical structure to transmit parking spaces information to other parking meters in the VANETs. According to the characteristic that drivers are interested in detail parking spaces information nearby the destination but just have to know rough information about parking spaces in a distant place. We use discrete cosine transform to convert parking spaces information to a rough spatial distribution and have less data size to be able to transfer in VANETs and cost less overhead. The simulation results show that the availability and accuracy of parking spaces information is high in nearby region and slightly lower in distant place. The communication overhead of our scheme is lower than previous work.

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