The Research Of Minimum Delay Tree Constructing Algorithm And Hierarchical Recovery Strategy In Mobile ALM

At present, with the mobile communication technology rapid development and the mobile communication equipments’efficient processing power and storage capacity makes people’s demand for mobile streaming media service improve.In mobile network environment, therefore, providing efficient streaming media services to mobile users become hot spot. A large number of mobile Internet applications, such as multicast video and audio streaming media need to quickly and efficiently sends a packet from one source node to multiple destination nodes. Typically, a multicast tree is used to implement the data from the source node to destination nodes. So, constructing an efficient multicast tree is very important to implement data transmission quickly.IP multicast is earlier multicast technology implementation mechanisms, IP multicast is implementing the data replication forwarding on the router. However, although the IP multicast has high transmission rate, but it requires the underlying router must support multicast protocol; and IP multicast cannot be widely spread in the network by multicast management and safety factors. To this end, the application layer multicast (ALM) as more efficient multicast technology was put forward. ALM transfers multicast function from the router to host terminal which is responsible for the packet replication forwarding increased flexibility. But affected by its’own hardware, the host terminals’ copying forwarding packets delay is longer, resulting in a delay of multicast applications becoming a major bottleneck. At the same time, affected by the characteristic of user, the terminal left lead to the application layer multicast tree split, resulting in the downstream user cannot receive data, resulting in decreased satisfaction user experience. So how to quickly restore multicast tree become a major bottleneck of ALM.To solve above two problems and reduce latency as a target, the paper studies the application layer multicast tree multicast tree generation strategy and recovery strategy. The main innovation of this paper includes the following two aspects:First, this paper puts forward degree constraint minimum delay of multicast tree generation algorithm; analyze the shortcoming of traditional minimum delay generation algorithm; Take into account the relationship between the degree constraint and node processing time, dynamically adjust node processing time. Simulation results verify that the algorithm has a lower node join time in constructing multicast tree. Second, analyzing the mobile multicast tree split, the loss of upper-middle-class multicast tree nodes has a wide range of influence, but the loss of lower nodes, especially the leaf node has a small range of influence. According to this characteristic, Hierarchical Node Adaptive recovery algorithm (HNA) is proposed. Firstly HNA stipulates the judging method of core nodes and primary nodes, namely hierarchical method; when the node is missing, based on different nodes loss it can adopt different recovery strategy to renew the multicast tree. Also it can make the multicast tree more stable and get higher node recovery efficiency. Through the experimental comparison, it proved that HNA has lower rejoin delay.