基於擴散分子通訊之多輸入多輸出技術研究

Abstract

分子通訊(Molecular communication)是一種奈米裝置(Nanomechines)中新興的通訊方式，奈米裝置之間利用分子(Molecules)作為訊息的載波進行通訊。有別於一般傳統通訊，分子通訊主要探討的情況在於生物體內，裝置之間的距離約為非常短，分子傳送過程會以布朗尼運動(Brownian motion)飄移(Diffusion-based)的方式到達接收端，接收端點依單位符號區間內所到達的分子數量來決策所傳送的訊息。 在基於擴散過程的分子通訊，前一個訊息所遺留下來的分子數量會干擾到目前所要傳送的訊息分子數，稱之為分子通訊裡的符號間干擾(Intersymbol interference, ISI)，本篇論文對此提出了多傳送端點與多接收端點(Multi-input Multi-output, MIMO)所使用的調變方法，降低符號間干擾的影響，利用不同的分子種類與分子濃度進行調變。分別討論多個傳送端對一個接收端的方法，使用時間與空間調變(Space-Time modulation)、設計多個接收端的接收權重配置以提升訊號與干擾比(Signal to Interference ratio, SIR)，以求出更好的錯誤率表現，並且探討分子通訊與傳統通訊上的差異。

In molecular communications nanomachines are the transceivers and molecules are message carrier for communication between nanomachines. Different from conventional communications, the scenario of molecular communication is mostly discussed and applied in human body with short communication range over which molecules drift. The channel is generally modeled as a diffusion one based on Brownian motion. The receiver detects molecules within a symbol duration for determining carried messages. In diffusion-based molecular communications, intersymbol interference arises from the fact that molecules emitted in the previous symbol duration may arrive at the receiver in current symbol time, causing interference to current symbol detection. To cope with the issue and improve system performance, we propose space-time modulation techniques and a weighted combining approach for MIMO transmissions and reception, respectively. We further discuss the impact of transmission range, symbol duration, and diffusion coefficient on system performance. Finally we address difference between molecular communication and conventional communication.