Optical Switching Network Multicast Scheduling Algorithms And Performance

With the rapid development of the communication technology, network applications, especially the application of multimedia video conference and distance learning, network audio/video frequency, need more bandwidth than the network at present can provide. This problem can be solved by the optical network because of the wide bandwidth of optical fiber, and the DWDM has become the bone network in the communication field. Multicast can send data to multiple receivers from one source or more in an efficient and extendable way, and that it can save bandwidth and reduce the possibility of congestion. The optical switching network introducing multicast can improve the performance of the optical network and the bandwidth usage efficiency. The core node of optical switching network with multicast function is the key technology of the multicast applications. Multicast scheduling algorithm and the performance parameters based on the optical switching network are analyzed in this paper.First, we introduce three typical structures of optical packet switch, and compare their performance. The multicast scheduling algorithm based on the structure of the optical packet switch with shared limited range wavelength converters is studied in this paper. In DWDM switching networks, contention occurs when one output fiber is the destinations of more than M inputs, where M is the number of wavelengths on each fiber. The multicast scheduling algorithm selects a group of multicast connection requests that are contention-free, and it is a key technology in the DWDM switching network. It is proved that scheduling the maximum number of such connection requests through the network simultaneously is a NP-hard problem, so we have to develop approximation scheduling algorithms that can provide sub-optimal solutions. In this paper, we present a new approximation scheduling algorithm based on the algorithm has been presented before, and compare their performance. We can confirm that the new algorithm can improve the network throughput through simulations. For example, the network throughput of the new algorithm is improved by 14% when the number of fibers and wavelength channels is 8, the load is 1.0. Next, the multicast scheduling algorithm is analyzed when the traffic at the inputs is divided into different priorities according to their significance. For simple, we only have two classes in the paper: class 1 and class 2. According to this problem, the multicast scheduling algorithm with priorities is proposed. Our results demonstrate that: the throughput of the class 1 is higher than the class 2, and the performance of the higher class can be guaranteed. For example, the throughput of the higher class is 0.75 while the throughput of the lower class is decreased to zero.Finally, the parameters about multicast performance in the DWDM switching network are presented: throughput, blocking probability, transimitting rounds. The throughput is the number of connect requests which are realized to the total number. The rate of the number of connect requests which are lost to the total number of connect requests is called blocking probability. The transmitting rounds is defined as the times taken to transmit all the connection requests, and we have to select a group of multicast connection requests that are contention-free every time.