A Master Thesis Submitted To Beijing University Of Posts And Telecommunications

With the explosive development of Mobile Internet,the 5th generation of mobile communication technology(5G)is moving into our lives.Low latency communication is an important part of three use cases to future IMT.In terms of air interface of access network,shortened TTI(Transmission Time Interval)technology can effectively reduce the transmission delay.However,this transmission mode poses challenges to the traditional way of allocating radio resources,it's urgent and necessary to design the strategy of resource allocation on shortened TTI transmission mode.Based on the advantages and disadvantages of shortened TTI technology,this paper designs different time-frequency resource allocation schemes to maximize its advantages and provide guidance for the realization of fully flexible air interface allocation in the future 5G.The three strategies are designed as follows:Firstly,shortened TTI transmission mode needs to redesign the traditional LTE time-frequency frame structure.In this paper,the uplink shortened TTI physical layer time-frequency resource allocation scheme based on UE identification is designed.This scheme aims to reduce the DMRS(Demodulation Reference Signal)overhead at the cost of slightly reducing the quality of channel estimation.Through link-level simulation,it proves that the scheme can make the shortened TTI play a low latency advantage and improve resource utilization.Secondly,shortened TTI transmission mode reduces the HARQ(Hybrid Automatic Repeat reQuest)round-trip time naturally.In view of this advantage,this paper proposes a speed adaptive adjustment algorithm based on fast feedback.This algorithm can save the resources of feedback channel sufficiently.The simulation has verified the superiority of improving throughput of this scheme in time-varying channel.Thirdly,aiming at the multi-service scenario in cellular network,a scheme of resource allocation on shortened TTI transmission mode is designed.The design of this scheme is to give priority to scheduling bursty traffic so that the whole system delay is as low as possible.Through system-level simulation,the throughput and latency of single-service and multi-service are analyzed.This scheme then proposes applicable scenario of shortened TTI to provide technical support and guidance for 5G flexible time-domain allocation.