Adistributed Queuing Based Multi-access Control For LoRa

In LoRa,Aloha is used to schedule the random access of stations in the shared channel.The maximum throughput can only reach 18.6%.When the load exceeds 0.5 and continues to increase,its throughput will drop sharply.The DQ protocol based on time division can not only continuously reduce the number of stations that are simultaneously accessed,thereby solving multi-stations access conllision,improving time delay and throughput performance,and has good scalability.Based on the existing research on the application of DQ protocol in LoRa,this paper first analyzes its unresolved problem about the detection of contention slot status,and improves the original queuing mechanism of the conflict resolution queue to improve system performance.Finally,a reasonable number of competing time slots is explored.To compress the length of the ARS,the Chirp modulation symbol is used to represent the access request.After receiving the feedback information,each station decides to send data immediately or wait to send data,re-compete immediately or wait to re-competition.The gateway has the ability to detect the status of each contention slot is the premise of feedback information.A multiple-access collision detection method for Chirp modulation communication is designed to detect the status of each contention slot for use of feedback information.Secondly,in case of the frames that only dealing with stations contentions in a Bcn period without transmitting station's data is too much,so combined with the depth-first algorithm to improve the way of the Conllision Resolution Queue.In the simulation of the improved scheme,the situation that the Data Transmission Queue's length in a Bcn period become to zero,in other words,the number of the frames that do not transmit station's data is greatly reduced,so the system loss can reduce,throughput will improve,the average time delay that stations successful transmit data will reduce.And the more the total number of stations,the more obvious the improvement effect.Finally,in the depth-first scheme,firstly analyze the duration of the the Conllision Resolution Queue,and the theoretical value is used to verify the correctness of the numerical simulation experiment.Then,the relationship between the number of minislots and the time delay and throughput is analyzed,to explore a reasonable number of minislots.