Wireless-loss Aware Cross-layer Congestion Control Algorithm In LTE Networks

The number of Internet users and applications are showing explosive growth with the rapid development and deployment of the 4G / LTE(4 Generation / Long Term Evolution) network making congestion has become one of the most important factors influencing data transmission performance, it will seriously affect the quality of communication if not timely and effective control in the event of congestion.The characteristics of high error rate, large delay, bandwidth asymmetry and more short-term flows in wireless network which different from wired network making bit error may be the main reason for the packet loss,therefore the traditional TCP is greatly restricted in wireless network. TCP Westwood(TCPW) is specially designed for wireless characteristics but it can not distinguish packet loss types, the algorithm will take the same window decreases strategy when packet loss occurs and still use blind incremental mechanism like Reno’s in the congestion avoidance phase often can not relieved network congestion, otherwise, the algorithm overestimate the available bandwidth due to the impact of packet burst, ACK compression and other factors.The paper reviews the 4G / LTE features and systematically expounded the various congestion control protocols used in wireless network environments, the main work is as follows:In view of the traditional TCPW algorithm can not distinguish the type of packet loss, a cross layer solution which uses ACK/NACK information to estimate the quality of the wireless link with the help of RLC layer is proposed for distinguishing packet loss. The simulation results show that the scheme can distinguish the packet loss type effectively and improve the throughput of system.Aiming at the problem of blindness and unity characters of TCPW, the improved algorithm adjust windows according to the tendency of delay which is feedbacked in RLC layer to eliminate the impact of retransmission mechanism. The experimental results show that the algorithm can effectively increases resource utilization and reduces the packet loss rate.Otherwise, to avoid high bandwidth estimation reduce the performance of TCP protocol the thesis improves the method of calculating bandwidth sampling value and introduces the degree of congestion in estimation prcocess,The experimental results show that the improved algorithm can significantly improve the performance of network transmission and improve its fairness.