TD-LTE Trunking System Handover Algorithms

With the rapid development of communication technology in recent years,the advantage of trunking system in command and dispatch has been more and more important,especially in police,fire control and so on.In order to better meet the demand of communication,a lot of trunking communication system have been established on public network.And the LTE trunking communication system is the most common system.LTE system in TDD mode called simply TD-LTE system,TD-LTE system is the extend technology of TD-SCDMA system which is developed by our country independently.TD-LTE system is also one of the important broadband mobile communication standards.So it is meaningful to research on TD-LTE trunking communication system.Handover is one of the most crucial technology in mobile communication system.Moreover,handover plays an important role in communication mobility management and radio resource management.Under the requirement of high speed and low delay,the improvement of the process of handover is more and more important for TD-LTE trunking communication system because its performance can influence directly conversation among users.Based on the domestic and foreign literature,this paper analyzes and summarizes TD-LTE trunking communication system framework,the process of handover and the present advantage and disadvantage of algorithm by combining the characteristics of trunking communication.In the beginning,this paper researches LTE system and the handover of traditional trunking system.Moreover,this paper categorizes and summarizes the present LTE handover algorithm and trunking handover algorithm.And this paper also analyzes the characteristics of LTE handover and traditional trunking handover through measurement report,handover preparation and handover judgement.Then this paper analyzes the difference of LTE system and LTE trunking system,which lays the groundwork for the latter algorithm research.Considering the difference of the handover situation,LTE can be divided into handover in eNB,handover between eNBs and handover between wireless access technology.The handover between eNBs is the most common,so this paper research mainly on the handover between eNB.The characteristic of a hundred responses to single call in LTE trunking communication system results in the fact that traditional LTE handover algorithm can not meet users' need of LTE trunking handover situation.This paper makes some improvement in the process of handover based on the process of LTE trunking communication handover.As for measurement report,this paper proposes themeasurement report based on bridge users and users' movement state to improve the search time when users handover and avoid the message collision because of more handover requests.As for handover judgement process,this paper proposes an algorithm based on ANP handover judgement by analyzing many elements of users and eNBs.Finally this paper finds the most suitable goal eNB to improve the accuracy of handover.The measurement report based on users movement state is to solve the problem of traditional LTE system handover algorithm search time TTT using empirical value.Users' search time are different with the different movement state.This paper classify the users by the intersection angle between users' speed and movement direction.Then this paper adjusts TTT automatically by using users grades and tests its effectiveness through simulation.The measurement report based on bridge users is to solve the problem of the message collision when many users send measurement report at the same time.This method can avoid message collision by the reduction of communication between users and eNBs.At last,to improve the accuracy of handover and reduce the call drop rate during the usage,this paper designs a handover judgement algorithm based on ANP after the research on the characteristics of LTE trunking system.This algorithm considers goal eNB's signal strength and load,users type(word power user and not word power user)and movement state,and at last finds the optimal eNB using ANP algorithm.