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Medium-Based Communication and Modulation in Molecular Communication Networks

Farahnak Ghazani, Maryam | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54543 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Nasiri Kenari, Masoumeh; Aminzadeh Gohari, Amin
  7. Abstract:
  8. Molecular communication (MC), which utilizes molecules as its carriers of information, is one of the oldest mechanisms among micro-organisms on earth. In recent years, using MC for communication among nanomachines has attracted enormous interest because of its simplicity and bio-compatibility. Diffusion-based MC mechanism is one of the most important communication mechanisms, which has wide applications because of no needs for energy and prior infrastructure. The important challenges in MC systems include node complexity, inter-symbol interference (ISI), and co-channel interference (CCI). Due to the small sizes of the nodes in MC, complexity is a serious issue. Because nanomachines are simple devices with limited resources. In this thesis, we are looking for appropriate methods of modulation and signal transmission which are simple and efficient at the same time. To this end, we use the characteristics of MC systems such as chemical reaction and medium flow velocity to perform calculations in the medium and implement medium-based communication to reduce the complexity of the nodes. In addition, we use medium-based communication to propose new ISI and CCI mitigation techniques.In the first part, we propose the use of chemical reactions to reduce signal-dependent observation noise of receivers (by reducing the signal density), to realize molecular physical-layer network coding (molecular PNC) (by performing the natural XOR operation inside the medium), and to reduce the inter-symbol interference (ISI) of other transmitters (by canceling out the remaining molecules from previous transmissions). To make these ideas more clear, we present these ideas in the form of an example of a two-way molecular relay network and use these ideas to define a new modulation scheme called physical-layer network coding (PNC). We compare the proposed scheme with a previously proposed scheme called straightforward network coding (SNC) and show that the proposed scheme addition to its simplicity, outperforms the SNC scheme, especially in the presence of ISI. In the second part, we propose a molecular flow velocity meter using a MC structure including a molecule releasing node and a molecular receiver. We design this flow velocity meter for detection and estimation of the flow velocity and obtain the error performance and the optimum and sub-optimum sampling times. This flow velocity meter can be used to design a new modulation scheme in MC, i.e., instead of changing the properties of the released signal, we can change the properties of the medium specifically the medium flow velocity for communication according to the message. This reduces the complexity of the transmitter, which is one of the challenges in MC systems, since changing the flow velocity is much easier in molecular channels.In the third part, we propose an interference alignment (IA) technique in molecular interference channels to mitigate the CCI. IA is a promising method to mitigate CCI in classic communication systems. However, due to the signal noise in MC systems, the existing IA methods in classic communication systems are not very useful in MC systems. In this thesis, we propose an IA scheme in molecular interference channels by the choice of the releasing times at the transmitters and the sampling times at the receivers. We use the chemical reaction to cancel the aligned interference in the proposed scheme and reduce the signal dependent noise. In addition, by performing the computations in the medium using reaction, the complexity of the receiver is also reduced
  9. Keywords:
  10. Molecular Communication ; Diffusion-based Molecular Communication (DMC) ; Medium-Based Molecular Communication ; Inter-Symbol Interference (ISI)

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