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無線通訊系統訊號涵蓋率的設計與應用

The Design and Application of Coverage in the Wi-Fi System

摘要


訊號涵蓋分為下行(Down-Link)涵蓋和上行(Up-Link)涵蓋兩種。有效涵蓋的涵蓋率,應被定義為《兩種涵蓋面積的交集》範圍。下行涵蓋率的計算,由於基地台的位置是無法移動的,工程師可以選用適當的訊號計算模組(Propagation Model),來計算訊號涵蓋的面積範圍。上行涵蓋率的計算,由於行動裝置是移動的,首先假設在系統要求的涵蓋範圍(Service Area)裡,只有一個行動裝置存在,行動裝置在此範圍中的任何位置上,至少有一個以上基地台的接收功率(RSSI)大於通訊標準的要求(章其源、張育成,2010),這個位置就被視為上行涵蓋。涵蓋率可以用「土地面積」、「人口密度」、「通話量」做為不同的涵蓋率計算基礎(Lu, 2000)。通話量是這三種方法中計算涵蓋率,最符合實際且最有效的方法。目前的Wi-Fi 系統所使用的IEEE802.11n 及802.11ac 協議中,使用了2.4GHz 和5GHz 兩種頻段,由於兩種頻率的不同,訊號涵蓋的結果呈現差異。這個問題也列入本文探討的範圍。

並列摘要


The signal coverage is divided into Down-Link coverage and Up-Link coverage. The effective coverage rate should be defined as the "intersection of two covered areas". For the calculation of the downlink coverage rate, since the location of the base station cannot be moved, the engineer can select an appropriate Propagation Model to calculate the area covered by the signal. Because the mobile device is moving, the calculation of uplink coverage must have only one mobile device in the service area. Inside of the service area, any location can be received (RSSI) by more than one base stations (-85dBm), and this location is considered to be covered on the uplink. The coverage rate can be calculated based on "land area", "population density", and "traffic quantity" as the basis for calculation of different coverage rates. Traffic quantity is the most practical and effective method for calculating coverage among these three methods. The two protocols of IEEE 802.11n and 802.11ac are being adopted in the Wi-Fi system, the two frequency bands of 2.4 GHz and 5 GHz are currently used. Owing to the two different frequency bands, the results of the signal coverage vary. This issue is also included in the scope of this article.

參考文獻


章其源 、 張育成 ( 2010 ) : WIMAX 實驗場域建置及維運計畫期末報告 , 99 年度經濟部科技專案建立通訊系統整合能量研究計畫 。
Bilbro, G. L., and Snyder, W. E. (1991). Optimization of Functions with Many Minima. IEEE Trans, on Systems, Man, and Cybernetics. 21(4), 840-849.
Chang, C. M. (2005). WiFi RF System Design. Retrieved July 2, 2005, from Ling Tung University, Web site: http://www.ltu.edu.tw/~cmc/data/5.pdf
Ho, K. Y. (2008). RF System Design with Real World Examples. Wanqiao-Chung-Hua Journal of General Education. 8,91-127.
Lu, Z. M. (2000). RF System Design of Coverage Optimization. Unpublished Master dissertation, Tung Hai University, Taichung.

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