Handover Performance Enhancement Methods Of High-speed Railway 5G Mm Wave Networks

In recent years,high-speed rail(HSR)has become an important means of transportation due to the advantages of high speed,convenient travel,and good experience.At present,the total mileage of China’s HSR has exceeded 40000 kilometers and is still under construction.In addition,the popularity of various intelligent applications has promoted HSR users’ growing demand for wireless services.To satisfy these demands,our country has greatly promoted the construction of 5G network along the railway.Millimeter wave(mm Wave),which is one of the key technologies of 5G,is expected to be applied in the future.However,many challenges in the application of the 5G mm Wave network in HSR networks are still under research.When the train passes through a mm Wave cell,it is necessary to trigger a handover event to change the base station(BS)which provides the train-ground connection,to keep the connection unblocked.Due to the small coverage area of mm Wave BS and the fast speed of a train,the time HSR takes to pass through the community is very short,which requires a fast and effective handover algorithm to help the train complete the handover in a short time.At present,the widely used A3 handover is triggered after the Reference Signal Received Power(RSRP)of the neighbor cell is higher than that of the serving cell.This will affect the transmission of handover signaling,resulting in handover failure and link outage.How to improve the performance of handover and reduce the link outage is an urgent problem to be solved.In addition,due to the large propagation loss of mm Wave,when the train passes through the cell,its transmission rate is high near the BS and low at the edge of the cell,which can not satisfy the data rate requirements of real-time users.How to make full use of the channel resources and meet the business needs of different users during the entire traveling process is also a problem to be solved.To this end,this paper has done the following two innovative works:(1)For the problem of high handover delay and link outage in the A3 handover in the HSR 5G mm Wave network,a handover-enhanced LSTM-based prediction method for5 G mm Wave handover in HSR is proposed to learn the historical change trend of RSRP,and predict the future change of RSRP based on the LSTM encoder-decoder network,to find the handover point in advance.The simulation results show that the proposed method can maintain a lower link outage probability,reduces the handover delay time by 33.9 %and the RSRP difference before and after handover by 85.14 %,and increases the average received power by 0.5dbm,effectively improving the handover performance.(2)For the problem that the transmission rate of the train is low at the edge of the mm Wave cell and can not meet the data rate requirements of real-time users,a cacheaided time-domain power allocation is proposed.When the channel quality is good,the surplus power is used to cache static resources.When the channel quality is poor,the buffered resources can be provided for non-real-time users,and the power allocation is used to satisfy the meet the data rate requirements of real-time users.Under the constraints of total available energy,maximum power,minimum data rate,and data amount demand,with the goal of maximizing Mobile Service Amount(MSA),an optimization problem is formulated to find the optimal cache time and time-domain power allocation,and a two-stage method is proposed to solve this non-convex optimization problem.The simulation results show that the proposed method can meet the business needs of different users.In addition,the increase in data rate threshold and speed leads to a decrease in MSA,while the cache usage rate has a relatively weak influence on MSA.