A Study of Cycle Compression Problem on CRMA High Speed Networks

• Main Authors: Chang, Chiu Sen, 張秋森
• Other Authors: Huang, Nen Fu
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/61808610946468451498

碩士 === 國立清華大學 === 資訊科學學系 === 82 === Cyclic-Reservation Multiple-Access (CRMA) is an access scheme for high-speed local and metropolitan area networks based on a dual-bus configuration. CRMA provides high throughput efficiency and fairness independent of the network speed or distance. In CRMA, the headend generates the reserve commands periodically. Each station reserves a number of slots in each reserve command if necessary. The headend will generate a sequence of cycles each of which is used to service the reservations on the corresponding reserve command. The length of each cycle is equal to the total number of slots reserved by the stations in the corresponding reserve command. Generally, a longer cycle length will conduct a longer access delay and a lower slots utilization. It is desirable to have a scheme to make the cycle length as short as possible. In this dissertation, we prove that the problem of finding a shortest cycle for a CRMA reservation (called as cycle compression problem) is NP-complete by showing that it is equivalent to the interval coloring problem. We also propose an O(n^2) approximation algorithm to solve this problem; where n is the number of stations in the network. The effectiveness of the algorithm is evaluated via simulation. Simulations results show that compared to the traditional CRMA reservation scheme, the new scheme makes a much shorter cycle length and hence the obtained throughput is much better than the traditional scheme.