室內LED光源應用正交分頻多工技術之高速可見光通訊

Abstract

由於行動數據資料使用量快速的增長，使得目前使用的射頻頻譜資源正在大量的減少，可預測不久的將來將會面臨資源匱乏的窘境。因此無線網路服務提供商正在尋找可替代補充的技術。而可見光通訊技術綜合使用現成的商用發光二極體(LED)以及可見光頻段頻譜不需使用執照費用等優點，被視為無線區域網路的潛力發展技術。然而商用的白色磷光LED有較窄的調變頻寬難以支持>Gbps的系統傳輸速度。 在本篇論文中，使用前向等化電路應用有較高頻譜使用效率的正交分頻多工調變技術以及自適應位元負載演算法，在22多重輸入輸出成像系統中，達到>Gbps傳輸速度。接著在第二部分，使用紅，綠，藍發光二極體(RGB LEDs)在22多重輸入輸出成像系統架構下，使用正交分頻多工調變技術以及自適應位元負載演算法並以偏振片技術做訊號解調，系統達到單一波長2.12 Gbit/s傳輸速度。在第三部份中，建構了可見光通訊模擬環境，在44多重輸入輸出非成像系統架構下，以zero-forcing演算法以及 singular value decomposition演算法做訊號解調，分別達到429.6 Mbit/s以及 439.3 Mbit/s的系統傳輸速度。

Driven by the enormous growth of mobile data, as expected, the depleting radio frequency (RF) bandwidth has intensified the competetion among wireless service providers and eventaully turned into a hot potato. Using the off-the-shelf phosphor light-emitting diodes (LEDs) and license-free band, visible light communication (VLC) has been emerging as an complementary technology for wireless access network. Typically, however, phosphor LEDs exhibit narrow modulation bandwidth (few to ten MHz) and therby are difficult to support >Gbps traffic rate. Extending modulation bandwidth by using pre-equalizer and applying spectral-efficient modulation scheme might be the key to high-speed VLC, First, by the use of the pre-equalizer and orthogonal frequency division multiplexing (OFDM) modulation with bit-loading algorithm, we demonstrated >Gbps data throughput under a under 2×2 imaging multiple input and multiple output (MIMO) configuration. Second, using commercial red-green-blue (RGB) LEDs, optical polarizers, and OFDM modulation with bit-loading algorithm, we successfully achieved a high data rate per wavelength of 2.12 Gbit/s under a 2×2 imaging MIMO wavelength division multiplexing (WDM) configuration. In the third part, using OFDM modulation and bit-loading algorithm, we compared zero-forcing (ZF) and singular value decomposition (SVD) as MIMO demultiplexing algorithms under a non-imaging 4×4 MIMO configuration by building a VLC simulation environment. Simulation results show total data rates of 429.6 Mbit/s and 439.3 Mbit/s by the use of ZF algorithm and SVD algorithm, respectively.