近年來奈米技術發展迅速,可被應用於生醫、軍事、工業等領域。由於單一個奈米機器的運算能力有限,要達成規模較大的任務需仰賴於多個奈米機器間的溝通。如果要採用傳統的電磁波作為通訊方式,則必須要在每一個奈米機器上裝載天線,然而考慮到奈米機器的尺寸較小,此方案的可行性較低。因此,聲波、奈米碳管和分子通訊等新的奈米通訊技術陸續被提出以解決奈米機器溝通的問題。其中,分子通訊因其生物相容性高,是近年來發展迅速、並被認為是最有可能被實現的奈米通訊技術。我們採用的擴散型分子通訊是一種利用分子在液態溶液中自由運動傳遞訊息的分子通訊方式。由於擴散型分子的自由運動性質,分子從傳送端抵達接收端的時間是隨機的,此性質會造成訊息的傳遞錯誤。因此,我們使用通道編解碼以增加擴散型分子通訊的可靠度。在傳統電磁通訊上,我們常用極大化最小的碼字(codeword) 間的漢明距離 (Hamming distance) 來設計通道編碼及解碼。但由於分子通訊的傳遞方式與傳統的電磁波通訊在本質上有很大的差異,傳統通訊上常用的距離將不再適用。因此我們建立了兩種適合擴散型分子通訊的編碼距離函式:「機率型距離函式」與「位元型距離函式」。數據顯示,以提出的這兩種編碼距離函式進行最小距離解碼,其符元錯誤率 (symbol error rate) 近乎最佳解碼方式。本論文的貢獻為在擴散型分子通訊中提出更進一步的通道編碼方式。
Molecular communication is an emerging and promising approach to communications between nanoscale devices due to its biocompatibility nature. In diffusion-based molecular communications, molecules as information carriers diffuse randomly in the fluid medium. Due to the random movements, molecules may arrive at the receiver at random times, resulting in detection errors. Applying channel coding is thus crucial for enhancing the transmission reliability. The paradigm of maximizing the minimum Hamming distance among the codewords has long been used in electromagnetic communication. However, for molecular communication environments, existing distances may be unsuitable because the nature of molecular communication differs from electromagnetic communication. We propose two categories of distance functions - the probability-based distance function and the pattern-based distance function - tailored for diffusion-based molecular communications. We apply minimum distance decoding rules with the proposed distance functions to diffusion-based molecular communication systems. The numerical results show that these decoding rules are near-optimal. The channel coding application in diffusion-based molecular communication is advanced through this thesis.