Sharif Digital Repository

Nowadays, prolific usage of free air as a medium for data transmission leads interests to optimize the conditions of devices which are involved in wireless communication systems. Inter-Symbol Interference (ISI) distortion is a natural characteristic of wireless channels that occurs due to propagating electromagnetic waves in different directions. Due to different paths between a transmitter and a receiver, the received signal consists of several copies of the transmitted signal with different delays. The most common way of eliminating or mitigating the effects of ISI is channel equalization. The present work leads to implementing a supervised equalization in wireless communication. The... 

In this thesis, a simple memory limited transmitter for molecular communication is proposed, in which information is encoded in the emission rate of the molecules. Taking advantage of memory, the proposed transmitter reduces the ISI problem by properly adjusting its emission rate, which can be interpreted as water-filling on the expected interference. The error probability of the proposed scheme is derived and the result is compared with the error probability of the optimal transmitter obtained by dynamic programming methods. Further, for the special case of channel with one symbol memory, a tight lower bound on error probability is derived. Numerical results show that the performance of... 

Molecular communication is a new paradigm in communication science, which studies opportunities and challenges of information transmission in nanoscale. Unlike the classical communication, which uses electro-magnetic waves as signal carriers, in this new method of communication, tiny agents in molecular scale are the main information barriers. In this sense, studying molecular communication requires theoretical development and updating some well-known techniques of classical communications.Although there have been some successful attempts to implement communication systems based on molecular communication, the field is still in the theoretical development phase. In this thesis, we have tried... 

Recently, the nano-bio communication networks have received significant attention. Among different communication mechanisms proposed for nano communication, diffusion based molecular communication (DMC) is the most promising scheme. This thesis focuses on DMC and first proposes a theoretical model for this scheme. In the next part of the thesis, inspired by the molecule transport mechanisms in the biological cells, two biosynthetic modulator structures are proposed.In first structure, an ion channel based modulator for DMC is proposed which controls the rate of molecule release from the transmitter by modulating a gating parameter signal. The corresponding average modulated signal, i.e., the... 

The progress in the design of nano-scale machines over the past decade has motivated researchers to study the concept of nano-communications. Inspired by biological systems,diffusion-based molecular communication (MC) systems have been proposed as a potential solution for communication in nano-networks where molecules are used as information carriers.Nano-networks are envisioned to facilitate revolutionary applications in areas such as biological engineering, healthcare, and environmental monitoring. In recent years, there has been a significant amount of work on various aspects of MC systems, including transmitter and receiver design, multiple access protocols, and network layer issues.... 

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... 

Today, telecommunication links transmit information wirelessly at high rates; The transmission channel is not ideal and the transmitted signal undergoes changes in the channel and then reaches the receiver; Also, the processing blocks in the transmitter and receiver are not completely similar and ideal; These two factors make it difficult for the receiver to recover the transmitted information and actually receives a signal that bears little resemblance to the transmitted signal. The most important effect that the channel has on the transmitted signal is due to the multi-path of the channel between the transmitter and the receiver, which causes a signal to reach the receiver through the... 

The increasing tendency to offshore exploration is making the need to design efficient methods for secure underwater wireless transmission increasingly highlighted. Radio frequency used for wireless communications in open space may not be suitable for data transfer due to their extensive drop in the water. On the other hand, since sound propagates well in water, now the majority of underwater communication systems are using audio frequencies. Limited bandwidth, low emission speed, and low security are the most important disadvantages of audio systems in comparison with optical systems. Therefore, optical systems, could be appropriate alternatives for audio systems to achieve secure,...