有效擴展「無線感測網路做為室內自我調整誤差定位法」定位區域之研究

Study on An Effective Expanded Coverage Scheme for Self-Adjustment Error Indoor Positioning Method Using ZigBee Networks

林佳瑩(Chai-Ying Lin)

指導教授 ： 黃國鼎

國立虎尾科技大學/電機資訊學院/電機工程研究所/碩士(2015年)

摘要

使用ZigBee無線感測網路做室內定位研究，具有「低成本、低功率消耗、支援大量節點」的特點，主要是利用待測點接收訊號強度指標(Received Signal Strength Indicator, RSSI)判斷與參考點間距離的特性。因為不需要額外的硬體設備，所以進行距離估算是較容易實現的。而本文所使用之無線感測網路做為室內自我調整誤差定位法在3公尺×3公尺、3公尺×5公尺的單位定位區域做定位時，其定位誤差已可大幅縮小至85公分以內，定位精準度高。然而一般的室內空間環境必定大於3公尺×3公尺或3公尺×5公尺範圍，已經超出單位定位區域的大小，無法在單位定位區域外進行定位，所以在定位範圍上受到限制。因此在本研究中，將以不破壞原有方法有效的單位定位區域的解析度，提出了一個新的擴展定位區域的方法，有效涵蓋需定位之完整室內空間。我們的方法是以類似細胞式行動電話系統架構的做法提出一個棋盤式概念的拓樸策略，在定位範圍內，以一個單位定位區域定義為一細胞，像一個棋盤方格，利用複製細胞來擴展方格圍成一個矩形棋盤。因此在使用室內自我調整誤差定位法的定位對待測節點進行定位前，先判斷待測節點位於矩形棋盤的哪個細胞底下。在判斷待測節點位於哪個細胞底下時，我們以待測節點最接近的四個相鄰細胞做為判斷範圍。在這四個相鄰的細胞上共會佈置有13個參考節點，因此我們將利用待測節點收集到的所有參考節點的RSSI值中，取最強的13個參考節點判斷為其所在相鄰的四個細胞後，再來判斷待測節點位於哪個細胞底下。我們提出的判定正確定位細胞法採分階段的條件式，將其分為兩個階段判別式，進而達到判斷待測節點定位細胞之目的。當細胞面積為3m×3m時，定位細胞的正確率達100%。然而將單位細胞面積加大為4m×4m或4.5m×4.5m時，定位細胞的正確率下降至82%跟76%。因此本文針對單位細胞面積加大進一步提出非對稱參考節點擺放策略。實驗結果顯示，定位細胞的正確率提升至90%左右。本研究提出的有效擴展可定位區域方法，確實可繼續使用室內自我調整誤差定位法於任意範圍之室內環境進行有效定位。

關鍵字

ZigBee ； 訊號強度指標 ； 室內定位

並列摘要

This thesis adopts the ZigBee wireless sensor networks for indoor positioning, which uses the received signal strength indicator (RSSI) of the target node to estimate its distance with the reference nodes. With the merits of low cost and low power consumption, it also supports large quantity of nodes. In addition, distance estimation can also be easier to be implemented since there is no extra hardware being needed with this method. Moreover, this thesis also adopts the self-adjustment error indoor positioning method which is experimented with position areas of 3×3 m2 and 3×5 m2, respectively, showing that the positioning error distance can be reduced to less than 85 cm, with high precision. However, in practical situations, the indoor space is normally greater than 3×5 m2 which is out of the position area range. In order to solve this problem, this thesis has proposed an expanded coverage without decreasing the original resolution, which is a chessboard pattern topology bases on the mobile phone system. Furthermore, in order to implement the ZigBee wireless sensor network for the self-adjustment error indoor positioning method, the first step is to find out the cell location of the target node. This can be done by regarding 13 reference nodes as a four-adjacent cell and then underestimate them with a two-phase formula. When the cell area is 3×3 m2, the accuracy of the positioning cells can reach up to 100%. If we increase the area to 4×4 m2 or even to 4.5×4.5 m2, however, the accuracy will be decreased to 82% and 76%, respectively. Therefore, this thesis has proposed a strategy of asymmetric reference nodes locating for the enlarged single cell area. The experimental results show that the precision rate is raised up to 90%, convincing that the proposed expanded coverage can effectively solve the short distance positioning problem of ZigBee.

並列關鍵字

ZigBee ； RSSI ； Indoor position

參考文獻

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