Energy-Efficient Coding In Wireless Nanosensor Networks

Wireless nanoSensor Networks(WNSNs)consist of numerous nanosensors and use electromagnetic communication in terahertz(THz)band(0.1-10 THz).WNSNs have lots of promising applications,such as health monitoring systems,air monitoring systems,Internet of nano-things,as well as nuclear,biological and chemical defenses,in the biomedical,environmental,industrial,and military fields,and will improve our daily lives and influence social development.Each nanosensor in WNSNs has very limited capacities of energy storage,communication,and computation.Therefore,energy efficiency has become an important issue in WNSNs.This work investigates energy-efficient coding in WNSNs,which aims to save communication energy consumption in WNSNs by coding.This work has essential academic value to promote fundamental research for the advanced applications of WNSNs in many fields.For laying the knowledge foundation for the next research contents,we introduce the modulation schemes based on on-off keying,the THz channel model,and the low-weight coding in WNSNs.On this basis,we study different energy-saving coding schemes based on time spread on-off keying modulation under different conditions in WNSNs.The main research work and achievements are detailed as follows:First,for the scenarios that source-words occur with equal probability,we propose an Average Codeword Weight(ACW)-Minimization Coding(ACW-MC)to optimize communication energy consumption in WNSNs.The ACW-MC is a promising coding scheme for the scenarios with low bit error rate in WNSNs.Particularly,we focus on the algorithm for constructing the optimal codebook and the effect of the codeword length on the ACW.Based on energy consumption analysis,a novel energy consumption model is proposed for WNSNs by jointly accounting for the energy consumption of both a sender and a receiver.The proposed energy consumption model is different from existing works because the energy consumption of transmission and reception as well as the circuit of the sender and receiver are considered.Second,for the scenarios that source-words occur with unequal probability,we propose a Communication Energy Minimization Coding(CEMC)for non-equal-probability source-words in WNSNs.Compared with Non-Coding(NC),Pulse Position Coding(PPC),minimum energy-coding,and superior lowest-weight codes,the CEMC has better energy efficiency.By jointly taking into account the energy consumption of transmission and reception,an energy consumption model is presented.For given codeword length,the optimal codebook with the minimum ACW is constructed,and the source-words with higher probability of occurrence are mapped into codewords with lower codeword weight to minimize the weighted ACW.By considering the thresholds of codeword length and code rate,the energy consumption optimization for communication is constructed,which is solved to obtain the optimal codeword length,and the CEMC is presented for optimal codeword length.Third,by considering the scenarios of transmitting real-time source symbols in WNSNs,we propose an Energy Optimization Coding(EOC)for communication based on real-time source symbols in WNSNs.Compared with NC and nanonetwork minimum energy coding,the EOC has better energy efficiency,and it is better with smaller source-word length.As a result,it is suitable for the scenarios of transmitting the longer real-time source symbols.The EOC is based on an energy model by jointly accounting for the energy consumption of a sender and a receiver,which includes the energy consumption of transmitting the coding dictionary.Moreover,we present a coding algorithm based on an optimization problem for communication energy consumption by jointly optimizing the length of source-word and codeword.Fourth,by considering the channel capacity performance of coding in addition to the energy efficiency,we propose an Energy-Saving Coding(ESC)for joint THz channel capacity performance in WNSNs.Compared with low-weight channel coding and PPC,the ESC has the better joint performances,i.e.,the higher energy-saving rate and information rate.Based on the analysis of the coding-based channel capacity in the THz band under the single-user and multi-user scenarios in WNSNs,we present an optimization problem by jointly considering the information rate and the energy-saving rate,and then present the coding scheme based on the optimal codeword length and ACW.