擴散式分子通訊之同步與通道估計

Synchronization And Channel Estimation For Diffusion-based Molecular Communications

許博凱(Bo-Kai Hsu)

指導教授 ： 葉丙成

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01721

摘要

奈米科技發展於實現在生醫、產業、環境及軍事上的應用，最近越來越多的研究人員關注奈米尺度的裝置間合作的模式以建構更複雜的系統，在奈米尺度下的通訊中最被看好的一種就是分子通訊，奈米機器人藉由在流體中釋放與接收分子來交換訊息，這種通訊跟傳統電磁波通訊有很大的不同，分子通訊不受到天線尺寸的限制，也與生物系統有較佳的相容性，而且以分子擴散的形式傳遞訊息是一種相當節省能量的機制，然而，分子擴散的隨機性會在通道中產生雜訊，很多研究員紛紛提出通訊系統的設計以對抗通道中的雜訊及干擾來增進分子通訊的品質，大多數在文獻中提出的設計都需要傳送端與接收端的同步，在這篇論文中我們主要探討擴散式分子通訊下的同步問題，我們考慮兩種非同步效應包括時鐘偏移與時鐘偏斜，在訓練式同步下，我們提出的疊代線性估計式比起其他方法只需要相當低的計算量，在盲同步下，我們應用費雪計分演算法來對抗符元間干擾並且有效的更新時鐘偏移估計，這兩種方法的估計效率都蠻接近最低均方誤差的比特曼估計，此外，即使在沒有通道資訊的情況下，我們也可以藉由疊代估計通道與時鐘偏移量來達到同步，這種方法的均方誤差也相當接近在沒有通道資訊的克拉馬羅下限。

關鍵字

分子通訊 ； 奈米機器 ； 擴散 ； 符元同步 ； 時間偏移估計 ； 可加性逆高斯雜訊通道

並列摘要

Nanotechnology has been developing to fulfill applications in biomedicine, industry, environment, and military. Recently, more and more researchers have discussed on the cooperation between nano-scale devices to form a more complicated system. One of most promising solutions to construct nano-scale communications is molecular communications. In a fluid medium, nano-scale devices exchange messages by releasing and capturing molecules. This type of communications is quite different from the conventional microwave communications. Unrestricted by the antenna size, molecular communications has a good compatibility with biological systems at the nanoscale. Moreover, molecular diffusion is really a good power saving mechanism to propagate information. However, the randomness in the diffusion process arises noises in molecular communication channel. Many researchers have designed communication systems against noises and interferences to improve communication quality. Among most systems proposed in literature, synchronization between transmitter and receiver nanomachines is inevitable. In this thesis, we deal with synchronization problem in diffusion-based molecular communications. Non-synchronous effects including clock offset and clock skew have been considered. In training-based synchronization, we proposed the Iterative Linear Estimator (ILE) with much lower complexity than other methods. In blind synchronization, we applied Fisher's Score Algorithm (FSA) to efficiently update clock offset estimation against the Inter Symbol Interference (ISI) effect. The efficiencies of ILE and FSA are close to lower bound of Mean Square Error (MSE) by the Pitman estimator. Even without channel information, we proposed a method to iteratively update channel estimation and clock offset estimation. Its MSE is close to Cramer Rao Lower Bound (CRLB) without channel information.

並列關鍵字

Molecular communications ； nanomachine ； diffusion ； symbol synchronization ； timing offset estimation ； Additive Inverse Gaussian Noise Channel

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