Research On The Energy-efficient NOMA Short Packet Transmission Technology Of The Internet Of Things

With the rapid development of mobile Internet,both mobile data and the requirements of networks have grown sharply.Meanwhile,the coming of the Internet of things also increases the demands of wireless networks for large numbers of devices,which brings about challenges to wireless communication technologies.The main issue of the fifth generation of mobile communications is how to design the wireless networks with high transmission rate,low latency,high reliability and energy efficiency.Thus,this paper mainly focuses on short-packet transmission with non-orthogonal multiple access(NOMA)network,and energy efficient downlink transmission design,user pairing strategy and buffer aided adaptive transmission design.Firstly,a two-user NOMA based downlink short-packet transmission system is investigated.Given the desired target effective transmission throughput requirements by two NOMA users,this paper formulates the energy consumption minimization problem to derive the least required energy consumption for the requested effective transmission throughput performance.And the analysis reveals some insights: when the sum of the requested effective throughput by two users in the NOMA based downlink short packet transmission system is fixed,the least required transmit power is fixed as well.Furthermore,the analysis discloses that,there exists such a region,in which the least required power allocated to the user closer to the AP will be primarily dependent on its requested effective throughput and its channel conditions.Moreover,it is unveiled that,selecting the user that is closer to the AP with larger effective transmission throughput requirement is more recommended to realize energy efficient NOMA based short-packet downlink transmission system.Secondly,a 2K-user NOMA based downlink short-packet transmission network is considered.Given the limited power,this thesis studied the efficient user pairing scheme for maximizing the sum effective throughput.And the analysis unveils that,simulated annealing algorithm utilized to find the user pairing results is found to be very close to the optimal exhaustive searching results.Furthermore,it is shown that,by dividing all users into two groups with relatively good channel conditions and relatively poor channel conditions provides us a useful basis to further simplify the user pairing design complexity.In addition,the analysis also discloses that,when least transmission rate requirements are taken into consideration,sorting all users according their channel conditions and selecting two users with a fixed ordering spacing will be the best user pairing policy for the downlink short-packet NOMA system.Besides,there exists such a situation,in which the users have less distinct channel conditions but require for some certain different effective throughput requirements,the best user paring strategy in the NOMA based short-packet system is different from that in the conventional NOMA system.Moreover,when the Max-min scheme is considered,it is shown that,the best user pairing strategy for max maximizing the sum effective throughput is different from that for the Max-min scheme.The analysis also unveils that,in addition to the user pairing design,the power allocation between two users with distinct channel conditions in every user cluster can be employed to further improve the achieved sum effective throughput performance.Finally,adaptive transmission design for buffer aided downlink short-packet network with NOMA system is investigated.The Lyapunov method is utilized to maximize the sum arrival rates by transforming the long-time arrival rates optimization into online adaptive transmission design on the basis of efficient user paring strategies,peak power constraint and average power constraint.The analysis indicates that,by deploying buffer at the AP,the achieved system sum rate can be improved and the average power can be saved.There also exists a tradeoff among the sum rate,the delay and the power consumption in the buffer aid downlink short-packet transmission with NOMA system.