Research On Resource Allocation Optimization And Target Signal Enhancement In Molecular Communication Systems

As the 5G standard gradually solidifies,researchers have begun to explore the dominant direction for the next generation of mobile communication systems.Inspired by “Internet of Everything”,the 6G or beyond 6G era should be of “intelligent connectivity”,“deep connectivity”,“holographic connectivity”,and “ubiquitous connectivity”,whose core is supposed to be human-centered.However,the “Internet of Everything” in the 5G era has not yet been fully realized.This arises from the fact below: first,there exist some extreme and complex environments where electromagnetic communication is hard to reach;second,the access of nanoscale devices further poses a great challenge to the accessibility of electromagnetic communication in micro-environments.In this context,how to achieve effective access in the aforementioned scenarios is greatly important for future wireless communication.Molecular communication employs the property of molecules to convey information,which is suitable for scenarios where the use of conventional information carriers(e.g.,electromagnetic waves)is restricted.Based on the unique convey mechanism of molecular communication,it can be extensively studied as a complement to the existing communication mode.Besides,molecular communication is considered one of the most promising communication modes due to its great bio-compatibility and low energy consumption.Owing to the limited storage and computational capacity of transceivers and the severe inter-symbol interference(ISI),the feasibility of molecular communication in practice is still an open issue,especially for the micro scene.To overcome the above challenges,the main work of this thesis is summarized as follows.1)We explore the resource allocation strategy for the point-to-point molecular communication system.Specifically,a generalized molecular shift keying algorithm is designed to achieve dynamic scheduling of information molecule types so as to realize a performance tradeoff between the ISI resistance and data rate.Besides,an idealized detector is proposed to tap the performance potential of the proposed scheme.Meanwhile,two low-complexity detectors are also designed to enhance the engineering practicality of the proposed algorithm.2)We investigate the resource allocation strategy for point-to-multipoint molecular communication systems.Specifically,the assignment strategy under three different performance criteria,namely the bit error rate(BER)fairness,achievable rate fairness,and weighted sum rate maximization,are explored.Unlike the existing research,information molecules with different diffusion coefficients are employed to serve different users so as to extend available molecule types in the multi-node communication scene.The best-to-best(BTB)and best-to-worst(BTW)criterion associated with the optimal allocation for the number of molecules can provide lower and upper bounds for the system performance,when different criteria are considered.3)We investigate the target signal enhancement algorithm for severe ISI scenarios.Specifically,an optimal detection time window is proposed to circumvent the negative effects of the severe ISI region to enhance the target signal.Constrained by the high complexity of the optimization process,an enhanced performance metric is designed to quantify the performance of the system with variable detection durations.Based on this metric,the optimal detection time window is derived in closed-form when different interferences or powers are considered.4)We explore the feasibility of the discarded duration being reusable,when the optimal detection time window is used.By further decomposing the signal composition in the discarded duration,the interval in which ISI signals are absolutely dominant can be obtained,i.e.,the reusable duration.Based on the property that ISI symbols remain unchanged during a single transmission,the received signal of the reusable duration can be subtracted from the target received signal so as to weaken the interference.Moreover,the optimal reusable duration is derived in closed-form for absorbing and passive receivers.