Research On Short-packet Communications On MIMO-NOMA Systems

In order to meet the requirement of ultra-reliable and low-latency communications in Internet of Things of 5G,short-packet which has finite block-length was put forward,and also the higher demands of this system are imposed.Non-orthogonal multiple access technology can greatly improve spectrum efficiency and increase the number of device connections by serving multiple users at the same time-frequency resource block.Multiple-Input and Multiple-Output technology can effectively use space resources,improve the transmission rate,and reduce the symbol error rate.Therefore,the application of NOMA and MIMO technologies to short packet communication can greatly improve the performance gains.Considering that in a real communication scenario,the far users have lower performance when multiple clusters of MIMONOMA system communicate through short packets.This paper proposes a method of power allocation to improve the throughput of far users while meeting the delay constraints.In addition,massive MIMO can effectively improve system communication capacity and reliability without increasing base station density and bandwidth compared with traditional MIMO.At the same time,the number of antennas will affect the transmission delay in URLLC,and so delay performance of massive MIMO-NOMA system transmitted by short packet was studied in this paper.First of all,the problem of throughput of short packet transmission in MIMONOMA system is studied.Based on multi-user ultra-reliable and low-latency applications in the downlink,this paper analyzes the throughput of user pairs of a cluster in the multi-user cluster MIMO-NOMA system by short packet transmission.This paper eliminates inter-cluster interference through singular value decomposition and maximum ratio combining.Considering that decoding error probability is lower than a given threshold,power allocation and maximal achievable rate are jointly designed to maximize the throughput by the alternate iterative algorithm.The numerical results show that the MIMO-NOMA system based on short packet transmission has better performance advantages,and it could effectively improve the throughput of far users under the condition of ensuring the block error probability.Secondly,this paper studies the delay of short packet transmission in the system of massive MIMO-NOMA.Constructing a massive MIMO-NOMA short-packet communication system model,and obtaining the channel estimation matrix of imperfect channel estimation by channel reciprocity under imperfect channel state information.At the same time,the precoding was utilized by zero-forcing beamforming(ZFBF)to obtain the signal on receiver,and determine the effective signal-to-interference-plus-noise(SINR)and effective transmission rate of users in short packet transmission.Finally the closed-form expression of upper bound for queuing delay can be derived by stochastic network calculus(SNC)and Mellin transform.The numerical results show that the proposed scheme of massive antennas has better performance about achievable downlink sum rates and delay violation probability,and it is verified that MIMO and NOMA technologies play an important role in URLLC.