在無線通訊中，多重路徑干擾對於訊號的傳收會造成很嚴重的影響。對於描述多重訊號衰弱在無線電波傳輸上所造成的效應，通道估測是一個很有效的技術。在這篇論文中，將會開發一個以軟體定義無線電為基礎的通道測量平台。對於系統開發者而言，以軟體定義無線電為基礎的實作平台提供了一個可快速架構系統和高自由度的作業環境。為了分析出通道中的多重路徑，展頻訊號因為具有高時間解析度的優點，而將被採用，特別是偽隨機雜訊序列擁有良好的相關函數特性，因而會被拿來做基頻訊號的調變。在接收端，接收訊號經過相關器後，將可以分辨出多條路徑，並且分析訊號受到多重路徑干擾而引起的失真。而為了驗證開發的系統，模擬與實際測量的結果將會被作成功率延遲分佈。此外，取得的功率延遲分佈將會用於消除多重路徑造成的干擾，其位元錯誤率的結果也會被拿來與使用最小平方等化器的結果做比較。

In wireless communications, multi-path fading significantly affects signal transceiving. Channel sounding is the de facto technique to characterize radio propagation effects due to multi-path fading. In this thesis, a channel sounding platform based on software-defined radios (SDR) is developed. SDR-based implementation allows rapid prototyping and provides great freedom to the system designer. To resolve multi-path components, the developed SDR-based channel sounding platform takes advantage of the fine temporal resolution of spread spectrum signals, where a pseudo-random noise (PN) sequence with good correlation properties is used to modulate a baseband signal. By decorrelating the received signal, the receiver is able to identify multi-path components and analyze signal distortions due to multi-path fading. In validating the developed channel sounding platform, results obtained from simulations and measurement campaigns at some selected sites are used to obtain the power delay profile (PDP). Besides, the obtained PDP is employed to mitigate multi-path fading and the resultant bit error rate (BER) performance is compared with that using the linear least square error (LLSE) equalizer.

[1] W. G. Newhall, ``Wideband propagation measurement results, simulation models, and processing techniques for a sliding correlator measurement system," Ph.D. dissertation, Virginia Polytechnic Institute and State University, 1997.
[2] E. Bejjani, J.-F. Bouquier, and B. De Cacqueray, ``Adaptive channel delays selection for wcdma mobile system," in Proc. IEEE VTC, Sep. 1999, pp. 203-207.
[3] M. Gahadza, M. Kim, and J.-I. Takada, ``Implementation of a channel sounder using gnu radio opensource sdr platform," IEICE technical report, vol. 108, no. 446, pp. 33-37, Feb. 2009. [Online]. Available: http://ci.nii.ac.jp/naid/110007325990/en/
[4] A. Le Naour, O. Goubet, C. Moy, and P. Leray, ``Spread spectrum channel sounder implementation with usrp platforms," SUPELEC/IETR, Cesson-S evign e Cedex, France, 2013.
[5] M. Islam, B.-J. Kim, P. Henry, and E. Rozner, ``A wireless channel sounding system for rapid propagation measurements," in Proc. IEEE ICC, June 2013, pp. 5720-5725.
[6] K.-C. Gan, ``Path searcher for a wcdma rake receiver," Application Note, AN2252/D, Freescale, 2005.
[7] H. Elders-Boll, ``Simplified interference-based threshold rule for delay selection in ds-cdma systems," in Proc. IEEE PIMRC, Sep. 2000, pp. 77-81.
[8] R. W. Heath Jr, ``Digital wireless communication: Physical layer exploration lab using the ni usrp," 2012.