隨著全球行動上網的需求以及網路流量不斷地上升，以及電信、電視、廣播、衛星、5G等應用，造成頻譜的需求擴大，而TV White Space(TVWS)共享技術便是將頻譜使用做最佳化運用的一個方法，TVWS是在電視廣播服務數位化後，由原先類比訊號所空出的頻段。在不影響原有無線數位電視訊號的前提下，這些未使用的頻段可以提供類似Wi-Fi、藍芽等無線網路裝置使用，且不需要執照，而這些裝置必須遵守相關的無線網路協定，包括IEEE 802.11af以及IEEE 802.22等。本研究透過軟體定義無線電(Software Defined Radio；SDR)實作一個測試干擾的實驗平台，使用RF設備USRP B200 mini來發射及接收訊號。本實驗以DVB-T (Digital Video Broadcasting-Terrestrial)作為實驗的受害者，在軟體內利用加法器來同時接收干擾源及解調預錄檔，並發射一個符合IEEE 802.11af標準的干擾源。在同頻干擾方面，固定干擾源的中心頻率並調整其增益值(gain)，測試不同干擾訊號強度對DVB-T的影響；在鄰頻干擾方面，固定干擾源的增益值並調整其中心頻率，測試在DVB-T及干擾訊號間不同頻譜位移(frequency offset)需要預留的保護頻寬(guard band)。實驗結果以64QAM星座圖以及FFT頻譜圖觀察受害者被干擾的程度，並以VLC媒體撥放器觀看DVB-T解調變後的節目影片，最後以節目影片的音訊遺失數、視訊遺失數及輸入丟棄數來判斷節目影片受干擾的程度，由實驗結果可以發現，干擾源之訊號強度越強則影響節目影片之品質越大，而頻譜位移小於3MHz時會開始影響節目影片之品質。本研究透過設計GNURadio上的模組實現一個可測試干擾的實驗平台，不僅節省許多成本，也體現了SDR其運用的靈活度。

With the increasing demand of global mobile Internet and wireless communications, TV white space (TVWS) sharing technology is a way to optimize the use of spectrum. TVWS is the frequency band vacated by the original analog signal after the digitalization of TV broadcasting services. Without affecting the original wireless digital TV signal, these unused frequency bands can be used by wireless network devices such as Wi-Fi, Bluetooth, etc. This kind of spectrum usage does not require a license. However, these radio devices must comply with the relevant wireless network protocols, including IEEE 802.11af and IEEE 802.22. In this study, software-defined radio technology is used to implement an experimental platform for testing interference, and the RF equipment USRP B200 mini is used to transmit and receive signals. This experiment takes DVB-T as the victim of radio communication. On the other hand, we have an interference source that complies with the IEEE 802.11af standard. For co-channel interference, we fix the center frequency of the interference source and adjust its gain to test the effect of different interference signal strengths on DVB-T. For adjacent-channel interference, we fix the gain of the interference source and adjust its center frequency for the purpose of finding the guard band that need to be reserved for different frequency offsets between DVB-T and interference signals. The experimental results use 64QAM constellation diagram and FFT spectrum diagram to observe the degree of victim's interference, and use VLC media player to observe the DVB-T demodulated program video. Finally, the number of audio loss, video loss, and the number of discards to determine the degree of interference of the program video. From the experimental results, it can be found that the stronger the signal strength of the interference source, the greater impacts on the quality of the program video. The frequency offset of less than 3MHz will begin to affect the quality of the program video. This study realized an experimental platform that can test interference by designing modules on GNURadio, which not only saves a lot of costs, but also reflects the flexibility of SDR in its application.

[1] 國家通訊傳播委員會, “電視白頻段(TVWS)之應用與發展,” NCC NEWS, vol. 9, no. 6, pp. 16-21, Oct 2015.
[2] ETSI, “Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for digital terrestrial television,” ETSI Std. EN 300 744 V1.6.2, Oct. 2015.
[3] NCTU, “OFDM,” [Online]. Available: https://ir.nctu.edu.tw/bitstream/11536/45879/7/350507.pdf.
[4] D. Valerio, “Open source software-defined radio: A survey on GNU Radio and its application,” Forschungszentrum Telekommunikation Wien, Vienna, Austria, FTW Tech. Rep., Aug. 2008.
[5] Flores, A. B., Guerra, R. E., Knightly, E. W., Ecclesine, P., & Pandey, S. (2013). IEEE 802.11 af: A standard for TV white space spectrum sharing. IEEE Communications Magazine, 51(10), 92-100.
[6] Stevenson, C. R., Chouinard, G., Lei, Z., Hu, W., Shellhammer, S. J., & Caldwell, W. (2009). IEEE 802.22: The first cognitive radio wireless regional area network standard. IEEE communications magazine, 47(1), 130-138.
[7] Setiawan, D., Gunawan, D., & Sirat, D. (2009, November). Interference analysis of guard band and geographical separation between DVB-T and E-UTRA in digital dividend UHF band. In International Conference on Instrumentation, Communication, Information Technology, and Biomedical Engineering 2009 (pp. 1-6). IEEE.
[8] Guidotti, A., Guiducci, D., Barbiroli, M., Carciofi, C., Grazioso, P., & Riva, G. (2011, May). Coexistence and mutual interference between mobile and broadcasting systems. In 2011 IEEE 73rd Vehicular Technology Conference (VTC Spring) (pp. 1-5). IEEE.
[9] Popescu, V., Fadda, M., Murroni, M., Morgade, J., & Angueira, P. (2014). Co-channel and adjacent channel interference and protection issues for DVB-T2 and IEEE 802.22 WRAN operation. IEEE Transactions on Broadcasting, 60(4), 693-700.
[10] Celidonio, M., Masullo, P. G., Pulcini, L., Die, M. V., Fusco, G., & Ferrante, M. (2015, October). LTE services over the 800 MHz band: Interference effects on DVB-T channels caused by the uplink signal. In 2015 AEIT International Annual Conference (AEIT) (pp. 1-6). IEEE.
[11] Ribadeneira-Ramírez, J., Martínez, G., Gomez-Barquero, D., & Cardona, N. (2015). Interference analysis between digital terrestrial television (DTT) and 4G LTE mobile networks in the digital dividend bands. IEEE Transactions on Broadcasting, 62(1), 24-34.
[12] GNURadio, “GNURadio,” [Online]. Available: http://gnuradio.org/redmine/projects/show/gnuradio.
[13] 羅乾汶，“以軟體定義無線電技術測量Wi-Fi頻道間干擾對通訊品質的影響，” 碩士論文，電信管理研究所，國立成功大學，2016.
[14] Ettus Research, “USRP B200mini,” [Online]. Available: https://www.ettus.com/product/details/USRP-B200mini.
[15] SDRPlay, “RSP2,” [Online]. Available: http://www.sdrplay.com/rsp2/.
[16] 陳靖姿，“以軟體定義無線電實作廣播電視監測系統之數位訊號分析、即時影像解碼與效能分析，” 碩士論文，電信管理研究所，國立成功大學，2018.
[17] BogdanDIA, “gr-dvbt,” [Online]. Available: https://github.com/BogdanDIA/gr-dvbt.
[18] BogdanDIA, “DVB-T implementation in GNUradio,” [Online]. Available: https://yo3iiu.ro/blog/?p=1220.
[19] Ishizu, K., Hasegawa, K., Mizutani, K., Sawada, H., Yanagisawa, K., Keat-Beng, T., ... & Harada, H. (2014, September). Field experiment of long-distance broadband communications in TV white space using IEEE 802.22 and IEEE 802.11 af. In 2014 International Symposium on Wireless Personal Multimedia Communications (WPMC) (pp. 468-473). IEEE.