物聯網(Internet of Things)中一項重要的基本能力是物件追蹤，
意即可以提供某特定物件在任意時間點的位置，
而此定位追蹤能力更是情景感知技術的關鍵基礎。
目前雖然已有許多基於影像處理或無線訊號處理的定位演算法被提出了，
但前提是這些演算法都必須先建置基礎設施。
此外，其定位能力也僅限於這些基礎設施的感測範圍內。
然而，此假設並不符合實際的運用，
這些需要被追蹤的物件的活動範圍(如穿戴式裝置等)
在使用上不一定會被侷限于在一個固定區域內。
為了克服這項缺點，
我們提出了以相遇資訊經由粒子過濾進行的合作式追蹤演算法。
藉由電子地圖，在不仰賴基礎設施的情況下，
具備無線通訊能力與慣性感測器的電子裝置(如手機等)
即可以依此演算法協同地互相追蹤，
並運算出各個裝置的路徑軌跡。
此合作式追蹤演算法以粒子過濾追蹤法為基礎，
並將多個粒子的相遇資訊納入考量對其改進。
本篇論文的主要貢獻是我們成功地利用時空的交集資訊
，快速地將可能錯誤的粒子消除。
與原本的粒子過濾追蹤法相比，在相同的輸入資料下，
實驗結果顯示我們的演算法有顯著的進步。

One of the fundamental features of the Internet of Things (IoT) is the ability to track its users location over time as a way to provide service in the right context. While many localization and tracking techniques have been proposed using cameras and RF-based techniques,they are ultimately limited by the ability to deploy tracking infrastructure and cannot operate when outside coverage area.
To overcome this limitation, we propose encounter-based cooperative tracking for proximity-enabled wireless nodes. These nodes, carried by the subjects being tracked, roam inside a mapped area and can sense their trajectories (e.g., by inertial sensing) and each other's proximity but without access to localizing infrastructure such as beacons.
We model their locations over time on the map as particles
and apply particle filtering as the basis for tracking. Our
contribution is to augment the base technique with encounter
information to dramatically reduce the number of possible particles in the model by spatial-temporal intersection. Experimental results show our techniques to be effective even in maps that contain layouts that have many possible matches for given trajectories.

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