Research On Wireless IoT Cooperative Transmission Mechanism With Relay Enhancement

With the rapid development of 5G communication,as an important part of 5G communication,the Internet of Things(IoT)has penetrated into all aspects of daily life.Due to the large number of sensor nodes in the IoT and low energy storage,it is not suitable for long-distance transmission,and it is impossible to construct a comprehensive coverage IoT communication system.This paper proposes the application of relay cooperative technology to the IoT communication system,combined with ambient backscatter to improve the stability and reliability of the system.Based on the system performance,this paper studies the relay enhanced wireless IoT cooperative transmission mechanism.The main work and innovations of the thesis are as follows:1.Aiming at the scenario of multi-hop cooperative transmission in IoT system,in order to meet the requirements of system transmission such as low power consumption and high reliability,a transmission scheme is proposed in which both the direct link and the multi-hop relaying caching wireless transmission from the source node to the destination node.Maximum ratio combining technique is adopted in destination node.The key feature is the Nakagami-m channels of the wireless channel from the source node to the destination node,which results in the difficulty of the theoretical analysis over the system performance.To tackle this difficulty,the probability distribution function(PDF)of the received signal to noise ratio(SNR)at the destination node is derived by exploiting the function and integral properties.Then,the outage probability and bit error rate(BER)of the whole wireless IoT system are derived in the analytical expression without any approximation.Numerical simulations demonstrate the accuracy of the derived theoretical analysis for this system.Based on this,the effect of multi-hop path and number of relays on the error rate and outage probability of IoT system is simulated and compared.2.In view of the low energy efficiency of wireless IoT multi-hop communication system,the energy collection and information transmission algorithms of the relay nodes using the collected energy by power shunting method are designed.The algorithms is formulated to maximize the energy efficiency defined as the ratio of the wireless information throughput of the first destination node over the power consumed by the whole IoT systems,which is subject to the required minimum energy harvested at the second destination node of the energy transfer.The relay node uses the signal sent by the source node for energy harvesting.Considering the actual power conversion efficiency and hardware circuit loss power factor in the EARTH plan,the analytical solution of the optimal power allocation scheme for the energy-collecting and information transmission of the Multi-user wireless coordinated IoT system is derived.To tackle the non-convex problem,the exact expression of the wireless information throughput is approximated by the high SNR approximation method.Hence,the asymptotically optimal solution is derived in analytical expression by employing the Lagrangian method and Lambert W function.The optimization problem is verified by numerical simulation.3.According to the limited communication distance and the low transmission efficiency for massive electronic tags/sensors of traditional or bistatic backscatter technology,the information transmission design based on energy harvesting of massive multi-hop electronic tags/sensors were investigated in amibient backscatter communication systems.Since the energy of ambient backscatter communication systems originates from the environment,its communication mode is different from that of existing wireless communication systems.The paper proposed the large scale tags/sensors multi-hop communication protocols based on energy harvesting under WiFi architecture.A multi-user relay cooperative network with stable and energy-efficient is constructed and an optimization scheme according to energy efficiency performance is proposed and performance analysis is carried out.Numerical simulations verify the effectiveness of the proposed scheme.