Scheduling Algorithm And Retransmission Algorithm Design For Concurrent Multipath Transfer In Heterogeneous Wireless Network

With the rapid development of a variety of wireless technologies, heterogeneous wireless network has become the development trend of future wireless networks. In heterogeneous wireless network, a variety of wireless access can coexist. Cross subnet pathfinding problems and network selection problem is a hot research topic in heterogeneous wireless network. Concurrent multipath transfer (CMT) is a kind of important network technology which can improve data throughput, bandwidth resource utilization and improve system robustness. Thus, the research of CMT has important significance in improving the existing heterogeneous wireless network transmission performance. Whereas, CMT can lead to serious reordering problem especially in heterogeneous wireless network. Reordering problem will not only cause serious cache blocking in receiving side, but also lead to unwanted packet loss and retransmission. So the research of scheduling algorithm and retransmission technology in heterogeneous wireless networks concurrent multipath transfer can improve the transmission efficiency and reduce the effects of scheduling problems. For this, this paper made the following research, the main research content and innovation are as follows,For existing packet scheduling, In order to increase the transmission efficiency, the packet will be waiting to send in the send buffer. Then the packet scheduled with the information will be transmitted into the network after a period of time, that is, out of date scheduling. Due to scheduling unit is very small, the effective Scheduling time of existing packet schedulings are short. To solve this problem, we introduce trunk as the scheduling unit instead of packet. We use trunk as the scheduling unit instead of packet. By estimating trunk’s receiving time at the receiver, the trunk scheduling scheme is decided. In order to determine the size of the data block, the concept of data transmission units is introduced in the trunk scheduling algorithm which is proposed in this paper. By determining the size and the amount of the data transmission units, the size of the trunk can be decided. In order to verify the performance of the trunk scheduling algorithm proposed in this paper, the simulation environment is built on the NS2simulation platform. Simulation results show that compared with the existing packet scheduling, when packet loss rate is more than2%, the improvement of trunk scheduling algorithm in throughput, average end-to-end delay and average reordering delay were greater than5%.Efficient retransmission algorithm can effectively alleviate the receiver buffer block, improve the transmission performance. When choosing the path of the timeout retransmission, existing retransmission algorithm is not effective to ensure that retransmission packets can arrive at the receiver as soon as possible. In order to ensure the retransmitted data of concurrent multipath transfer to arrive at the receiver as soon as possible, RTX-RMRT(Record based Minimum Retransmission Time algorithm) is proposed in this paper. Based on the minimum retransmission delay, minimum maximum path history retransmission delay and minimum retransmission timeout interval, retransmission path is selected. Minimum retransmission delay is decided with the current information of network, and can ensure packets arrive at the receiver as soon as possible. If it is unable to make decisions, the path history information will be judged in turn. If still with any results, the retransmission path will be choosed randomly. The simulation results show that, the proposed retransmission algorithm with different receiving cache limits of32KB,64KB and128KB can acquire the larger network throughput, effectively reduce the receiver buffer block, and ensure the retransmission efficiency.Finally, the paper summarizes the full text altogether, and the next research work is prospected.