動態式OFDM調變與60-GHz光載微波無線訊號系統

Abstract

對於使用需求大量增長的giga-bit無線通信，在60GHz的7GHz的免授權頻段裡吸引了很多的興趣及研究。由於在60GHz這個頻段上，對於空氣傳輸有著非常大的衰減，於是透過Radio-over-Fiber system這樣的一個傳輸技術能夠有效的解決這樣的問題，然而，60GHz無線網路仍然存在著許多技術上的挑戰，由於高載波頻率以及寬頻訊號的使用，會受到不平坦的通道響應所影響，而有著高達10dB多的偏差範圍，一個如此大的偏差值會導致OFDM訊號的每個副載波有著不同的雜訊比，如此一來每個副載波會有不同的傳輸效率。 在本篇論文裡，我們使用Bit-loading演算法去調校每個副載波已達到最佳的傳輸效率並且提升訊號的傳輸量。實驗結果成功的顯示出在60GHz的免授權7GHz頻段下，產生高達32Gbps OFDM訊號，在沒有任何色散補償的狀況下，經過25公里的單模光纖傳輸，此訊號幾乎沒有任何的損耗。

Rapidly increasing demand for multi-Gbps wireless communication has attacted a lot of interest in the 7-GHz license-free spectrum at 60 GHz. Due to higher air-link loss at 60 GHz, the radio-over-fiber (RoF) system is a promising solution for extending the coverage of 60GHz wireless signals. However, 60 GHz wireless networking presents many technical challenges owing to the high carrier frequency and the wide channel bandwidth used. One of challenges is the non-flat channel response with up to 10 dB deviation within the 7 GHz spectrum. In this thesis, bit-loading algorithm significantly improves performance and data throughput of ultra-wideband mm-wave RoF systems employing all-optical I/Q up-conversion architectures. By using bit-loading algorithm, we demonstrate bit-loading OFDM signal generation and transmission with a record of 32.65 Gb/s within 7-GHz license-free spectrum at 60 GHz band. Transmission over 25-km SMF transmission with negligible penalty is achieved without any dispersion compensation.