Transmission scheduling in optical CDMA networks using hybridized overlap and threshold (HOT) scheduling algorithm

Abstract

The bane of optical network is multiuser interference as a result of codewords overlap from different nodes simultaneously transmitting. Transmission scheduling is a good interference avoidance scheme which helps prevent throughput degradation at high offered load in an optical code division multiple access local area network. Interference avoidance consists of state estimation and transmission scheduling. This work examines different scheduling algorithms and parameter variations. This work investigated the performance of three scheduling algorithms (Pure Selfish Scheduling, Threshold Scheduling and Overlap Section Scheduling) against the ALOHA CDMA and our novel Hybrid--Hybridized Overlap and Threshold Scheduling--HOT algorithms using the modified padded prime codeset. The performance of the scheduling algorithms are measured in terms of its normalized network throughput, packet error rate and the average number of codewords allow into the line against the normalized offered load. The analysis shows that under this condition, the Hybridized Overlap--Threshold scheduling perform best and has throughputs as high as the 52 % with nearly zero packet error rate while the non-scheduled algorithm produce a throughput as low as 10 % and very high error rate at maximum offered load. Overall, the Threshold Scheduling and HOT algorithm are head to head and performed best in terms of normalized network throughput, however the HOT scheduling is best in terms of the packet error rate. Analysis also shows that the throughput is not affected by changes in codeset length and the mean packet size but it is affected by changes in the codeset weight. The study also analyzes the performance of the network under a bimodal packet distribution and with the Prime code codeset family. Optical Orthogonal Codeset and the Prime codeset family are used in the study under the assumption of perfect state estimation; that all nodes have the same view of the network and the transmission lines and the distance between the nodes and the central star coupler is assumed to be zero. A novel hybrid Scheduling Algorithm, the HOT Scheduling which proved better than traditional Scheduling Algorithms is peddled here.