| Narrowband Internet of Things(NB-Io T),as an important branch of the Internet of Things,can enhance coverage and reduce the complexity of user equipment(UE)implementation,while allowing operators to use only a small part of the existing spectrum for network deployment,which is very convenient.However,while bringing advantages,NB-Io T also faces challenges of low power consumption and large connections.To address these challenges,this thesis proposed to use device-to-device(D2D)communication to assist NB-Io T UE in uploading data.D2 D communication based on UE has great advantages in reduction of network energy consumption,improvement of equipment capacity and effectively utilizing spectrum resources.Therefore,a data uploading routing algorithm suitable for UE needs to be designed according to the network characteristics of NB-Io T.The main research contents of this thesis are as follows:1.This thesis proposed a reserved slots configuration optimal algorithm(RSCOA)for D2D-assisted NB-Io T system.This algorithm guarantees a certain transmission success probability by configuring an appropriate number of communication time slots for D2 D relay/receiver equipment(DRE),which is more conducive to energy saving than a multi-relay solution.And if the data transmission is completed in advance,the relay device enters the sleep state,which is conducive to further saving energy.In order to find the optimal compromise between transmission success probability and energy consumption,this thesis constructs a utility function based on weighted transmission success probability and energy consumption,and based on this utility function,constructs a DRE communication slot configuration optimization problem.The simulation results show that,compared with other algorithms such as multi-relay transmission,random relay transmission and 100% successful transmission,the reserved slots configuration optimal algorithm proposed in this thesis can obtain lower energy consumption and better transmission success probability.2.This thesis proposed a D2D-assisted transmission device number per unit energy optimization algorithm(NUEOA)for the NB-Io T system.This algorithm divides long-distance communication into two-hop short-distance D2 D communication,specifically to select the relay sequence to execute D2 D communication,and sorts the multiple relays according to the order in which they reserve time for D2 D communication.The UE first attempts to send data to the first relay in the first time slot.If the transmission is successful,the D2 D communication process is ended;If the transmission fails,it will try to send data to the corresponding relay in the next time slot until all candidate relays of the UE are tried.And an optimization algorithm based on dynamic programming is proposed to solve the transmission device number provides by unit energy(NUE),the main advantage of the algorithm is to upload data to the base station(BS)in a shorter time without waiting for the specific time slot reserved for D2 D communication,thereby optimizing the number of NB-Io T transmission device number. |
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