Amit Kumar Garg

Integration of Optical and Wireless Technology as High-Capacity Communication System: Issues and Challenges

Radio over Fiber (also referred as Radio on the Fiber, Hybrid Fiber Radio and Fiber Radio Access) is a desegregated technology that merges wireless system with optical fiber for the imminent distribution of broadband services. RoF significant feature is to transmit radio frequency signals (20 Hz–300 GHz) over optical fiber to fulfill the demand of large data traffic by using the merits of optical fiber which gives large bandwidth (50 THz), less attenuation (0.2 dB/km), and low electromagnetic interference. In the present work, various issues and challenges related to RoF system architecture concerned with the efficient utilization of centralized control capability have been compared along with the current state of art of RoF system.

Impact of Mathematical Optimization on OSPF Routing in WDM Optical Networks

High-speed communication systems require robust routing protocol. The selection and optimization of the routing protocol in Wavelength Division Multiplexed (WDM) optical networks decide utilization of bandwidth capacity offered by these networks. When Open Shortest Path First (OSPF) protocol is used for routing, link weight selection is one of the main concerns in order to optimize the routing. In this paper, OSPF link weight selection is performed through Ant Colony Optimization (ACO) and Evolutionary Algorithm (EA). The novelty of the work lies in the implementation of optimization techniques in offline network mode on networks of variable densities with an objective is to reduce utilization of bottleneck link, i.e., to reduce congestion. As a result, knowledge of optimization specific to type of network can be retained in online networking mode. ACO and EA are implemented on random network which is composed of 4 nodes and 5 links (4n5e), standard National Science Foundation NETwork (NSFNET), and standard COST 239 networks in order to test the optimization on networks of different densities. Maximum End-to-End (E2E) latency and bottleneck Link Utilization (LU) obtained after application of optimization techniques is compared for networks considered. It is observed that EA optimization has a better optimized denser network (COST 239) and ACO has optimized NSF and 4n5e networks better than EA optimization.

Investigations of Optimized Optical Network Performance Under Different Traffic Models

Network planning for existing as well as future high-speed networks is important for extracting best performance of networks. Network planning requires reliable traffic model which can serve constant as well as variable ingress traffic. In this paper, network performance is investigated with uniform and population-distance traffic models. Open Shortest Path First (OSPF) protocol is used for routing and link weight determination is a crucial task for this routing. Link weights in networks of different densities are optimized with an objective of minimizing network congestion. Ant Colony Optimization (ACO), Genetic Algorithm (GA) and Simulated Annealing (SAN) optimization techniques are applied to examine link weights of National Science Foundation NETwork (NSFNET) and standard COST 239 networks. The novelty of the work lies in investigations of network performance with different optimization techniques, traffic models and density. The outcome of this work can assist in optimizing overall network planning. Maximum latency and congestion of both networks are compared for each optimization and traffic model. It is observed that population-distance traffic modeling has reduced network congestion for both the networks but this traffic model has increased maximum latency of NSFNET. Performance of COST 239 network which is denser than NSFNET, has improved with population-distance traffic model w.r.t. congestion and latency.

Analysis of Packet Size Variation Supporting QoS for Survivable Optical High-Speed Networks

OPS (optical packet switching) is a promising technology for high-speed networks. In this paper, impact of ingress packet size on QoS (quality of service) of survivable networks is investigated. DV (distance vector) and LS (link state) dynamic routing techniques are applied to ensure survivability. Analysis is performed on 10-, 50-, and 100-node mesh networks for ingress packet size of 500, 1000, 1500, and 2000 bytes. Using the results obtained, it is observed that maximum percentage deviation of 2.45% in average E2E (end-to-end) delay and 14.71% in average jitter is obtained with respect to packet size variation in the network with 10 nodes and DV routing. As network size increases, average E2E delay and jitter variation with packet size are reduced. Throughput is almost constant with packet size variation under DV routing. This framework provides deep understanding about impact of network and packet size on QoS of high-speed networks.

Performance Analysis of OSPF Routing Protocol Under Single and Multiple Link Failure

This study aims at highlighting OSPF (Open Shortest Path First) routing technique and its performance under different network failures. A single failure in high-speed networks even for fraction of second can disrupt millions of users. Therefore it is imperative to analyze performance of routing protocol under network failure. In this paper, OSPF routing technique is examined under single and multiple link failures. Investigations are performed on basis of average E2E (end to end) delay, throughput and jitter. In this investigation, convergence time for link failures is calculated. It is observed that network has least average E2E delay when working path does not experience any failure. Under single link failure, average E2E delay is least when failed link is nearest to the source node. Under double link failure, average E2E delay is maximum when failed links are farthest apart. Convergence time for multiple link failure is more than single link failure. It is observed that convergence is least for failed link immediately connected to the source node. As observed from plots, network achieves high throughput when working path does not experience any failure and throughput reduces for multiple link failures. Average jitter is maximum for the network without failure and its value reduces for multiple link failures. The investigations in this paper provide insight into the performance of OSPF routing technique. Analysis performed and values of performance metrics obtained for various link failures provide knowledge of critical links and backup routes with respect to application specific QoS (Quality of Service) requirements.

Impact of location of bottleneck link on TCP-Tahoe performance

TCP (Transmission Control Protocol) is reliable and one of the main protocols of transmission layer in a communication system. Congestion control mechanisms in TCP allow a reliable flow of bursty traffic. This paper investigates the response of TCP-Tahoe connection to the location of bottleneck link on working path. Further analysis is performed for different size of current TCP window in the network. The network under consideration is NSFNET (National Science Foundation Network). Impact of the location of bottleneck link is analyzed for all the links on working path. Using the results obtained, it is observed that for current window size of 50 and 100 packets, network throughput is maximum when the position of bottleneck link is nearest to the destination node of working path. As window size is increased to 150, 200, 250, 300, 400 packets, maximum throughput is obtained when bottleneck link is located nearest to the source node. The present analysis provides an understanding of current window size selection and routing path to be adopted if bottleneck link in the network is pre-estimated.