| The construction of smart grid is an important task of the "Thirteenth Five-Year Plan" of China’s power development.In the smart grid,the power information collection terminal is an indispensable part and is in the process of upgrading.The performance of the wireless communication module of the acquisition terminal is directly Affects the accuracy of meter reading data.In view of the shortcomings of various current meter reading methods,such as the poor real-time performance of 485 centralized meter reading,high installation and maintenance costs,and public network communication meter reading needs to pay operating costs,etc.This paper proposes a method of wireless meter reading using low-power wide area network technology(Lo Ra technology),this method can not only reduce the operating cost of wireless meter reading,but also ensure the secure transmission of information,which has practical significance for building a smart grid.According to the regulations of the Radio Commission,the wireless modules of the acquisition terminal should work in the 470-510 MHz frequency band.Therefore,there will be a large number of wireless devices accessing in this frequency band,so handling transmission power and communication conflicts of wireless devices in this frequency band is of great significance for improving the wireless network environment and improving the performance of wireless devices.This paper proposes an improved Lo Ra-based dynamic power control algorithm and a machine learning-based conflict resolution algorithm to optimize the performance of wireless devices of the acquisition terminal.At the same time,this paper designs the schematic diagram of the acquisition terminal and the PCB circuit board,and explains the software and hardware debugging of the circuit board.For the proposed improved dynamic power control algorithm,in this paper,according to Lo Ra spreading factors,receiving nodes in different distance ranges are divided into different distance range levels and node transmit power base values,and use the dynamic power fine-tuning method to further reduce the transmit power of the node under the premise of ensuring that the communication data is reachable.Through experimental simulation,it is found that the improved power control algorithm can effectively reduce the node’s transmit power.In order to verify that reducing the transmit power of the nodes has a positive effect on improving the transmission environment of the wireless network,this paper uses Chirp spread spectrum modulation(the original modulation method of Lo Ra).In MATLAB,it is simulated that the received signal error rate is affected by the interference signal strength.Through experimental simulations,it is found that reducing the node’s transmit power can indeed reduce the wireless interference of this node to other transmitting nodes.At present,the research on conflict resolution algorithms is relatively mature.In this paper,a variety of improved algorithms for conflict resolution algorithms are analyzed in detail,and based on this,an improved algorithm for conflict resolution based on machine learning is proposed.In this paper,the IEEE802.11 CSMA / CA strategy is experimentally simulated to obtain the raw data required for machine learning,including system throughput,system delay,packet retransmission rate,and backoff window increase multiples.A nonlinear regression model between the backoff window increase factor and the system performance parameters is established by using the error back-propagation algorithm.This model can effectively predict the system performance under different backoff window increase multiples.Based on the prediction results,a backoff window increase multiples that optimizes the system performance is selected and used in the CSMA / CA protocol to improve the performance of wireless communications.Through the comparison of the experimental simulation results,it is found that the improved collision resolution algorithm actually improves the system performance compared to the collision resolution algorithm in the IEEE 802.11 protocol.Finally,this paper describes each module designed in the collection terminal schematic,describes the process and idea of designing the PCB circuit board,and debugs the designed prototype. |
