Nityananda Sarma

Routing and Spectrum Allocation in Elastic Optical Networks: A Tutorial

Flexgrid technology is now considered to be a promising solution for future high-speed network design. In this context, we need a tutorial that covers the key aspects of elastic optical networks. This tutorial paper starts with a brief introduction of the elastic optical network and its unique characteristics. The paper then moves to the architecture of the elastic optical network and its operation principle. To complete the discussion of network architecture, this paper focuses on the different node architectures, and compares their performance in terms of scalability and flexibility. Thereafter, this paper reviews and classifies routing and spectrum allocation (RSA) approaches including their pros and cons. Furthermore, various aspects, namely, fragmentation, modulation, quality-of-transmission, traffic grooming, survivability, energy saving, and networking cost related to RSA, are presented. Finally, the paper explores the experimental demonstrations that have tested the functionality of the elastic optical network, and follows that with the research challenges and open issues posed by flexible networks.

TREEPSI: tree based energy efficient protocol for sensor information

Limited battery powers of sensor nodes demand routing protocol for sensor network that consume minimum possible amount of energy and hence give longer life to the system. In a sensor network, sensor nodes are the potential source of information and they need to send their sensed/collected information to a remote base station (BS)/Sink. Generally, it needs a fixed amount of energy to receive one bit of information and an additional amount of energy to transmit the same. This additional amount depends on the transmission range. So, if all nodes transmit directly to the BS, then they will quickly deplete their energy. Therefore, a multi-hop routing protocol is needed to give longer life of the network. LEACH (aW. Heinzelman et al., 2000) (aW. Heinzelman et al., 2000) is an elegant energy efficient protocol where clusters are formed to fuse data before transmission to base station. By randomizing the cluster heads chosen to transmit to the base station, LEACH achieves a factor of 8 improvements over direct transmission, as measured in terms of nodes longevity. PEGASIS (aS. Lindsey and C. Raghavendra, 2001, 2002) is a chain based protocol that is an improvement over LEACH. In PEGASIS, each node communicates only with a close neighbor and takes turns in transmitting to the base station, thus reducing the amount of energy spent per round. It performs better than LEACH by about 100 - 300% for different network sizes and topologies. In this paper, we propose TREEPSI (tree based energy efficient protocol for sensor information) which gives up to 30% better performance (in terms of energy efficiency) than PEGASIS

Quality of Service (QoS) Provisions in Wireless Sensor Networks and Related Challenges

Wireless sensor networks (WSNs) are required to provide different levels of Quality of Services (QoS) based on the type of applications. Providing QoS support in wireless sensor networks is an emerging area of research. Due to resource constraints like processing power, memory, bandwidth and power sources in sensor networks, QoS support in WSNs is a challenging task. In this paper, we discuss the QoS requirements in WSNs and present a survey of some of the QoS aware routing techniques in WSNs. We also explore the middleware approaches for QoS support in WSNs and finally, highlight some open issues and future direction of research for providing QoS in WSNs.

Route Stability Based QoS Routing in Mobile Ad Hoc Networks

To provide high quality communications service among mobile wireless devices is basically a challenging task in wireless ad hoc networks. In this paper, we propose a Route Stability based QoS Routing (RSQR) protocol in Mobile Ad Hoc Networks (MANETs) which is an extension of QoS routing with throughput and delay constraints. Ensuring a data path to be valid for sufficiently longer period of time is a very difficult problem in MANET due to its highly dynamic nature. We propose a simple model for computing link stability and route stability based on received signal strengths. By including some extra fields in route request/reply packets, the route stability information can be utilized to select a route with higher stability among all the feasible routes between a given source destination pair. Further, inclusion of a signal strength based admission control enhances the performance of the routing. Results of our experiments show performance improvements in terms of packet delivery ratio, control overhead and average end-to-end delay in comparison with a QoS routing protocol proposed by Q. Xue and A. Ganz.

Priority based routing and wavelength assignment with traffic grooming for optical networks

One of the challenging issues in optical networks is call blocking and it increases with the number of connection requests due to the limited number of wavelength channels in each fiber link. In this paper, we propose a priority based routing and wavelength assignment scheme with incorporation of a traffic grooming mechanism (PRWATG) to reduce call blocking. In this scheme, the connection requests having the same source-destination (s-d) pair are groomed first to avoid intermediate optical-electrical-optical conversation and then these groomed connection requests are served for routing and wavelength assignment according to their priority order. The priority order of each groomed connection request is estimated based on type of path (direct link physical path or indirect link physical path) first and then the traffic volume. If the priority order of connection requests is estimated using these criteria, blocking of connection requests due to wavelength continuity constraints can be reduced to a great extent, which will in turn lead to better performance of the network in terms of lower blocking probability and congestion. The performance analysis of our proposed scheme is made in terms of blocking probability and congestion and compared with a similar non-priority based routing and wavelength assignment scheme (NPRWATG). It is seen that using the PRWATG scheme, the blocking probability and the congestion of the network are significantly reduced compared to NPRWATG. It is also seen that the performance of the proposed scheme is better compared to NPRWATG when the number of connection requests increases in the network.

Review and Performance Analysis on Routing and Wavelength Assignment Approaches for Optical Networks

Abstract For the past several years, traffic especially, Internet traffic has been increased tremendously and this growth demands for a high-speed communication network such as optical network. Routing and Wavelength Assignment (RWA) is one of the key tasks for the optical network, due to its information transparency and wavelength reuse characteristics. In this paper, we discuss different conventional RWA approaches in the wavelength-routed optical networks and compare them with our proposed Priority-based RWA (PRWA) scheme under wavelength continuity constraint. The performance analysis of different conventional RWA approaches including our PRWA scheme is conducted in terms of blocking probability. Finally, we address a number of research issues that appear to us to be both important and challenging.

A Multipath QoS Routing with Route Stability for Mobile Ad Hoc Networks

Abstract Multihop wireless networks have emerged recently as an evolution of wireless network technology and are likely to be the integral part of future communication environment. In this context, support for quality of service (QoS) is becoming an inherent necessity rather than an additional feature of the network. This paper presents a route stability-based multipath QoS routing protocol for mobile ad hoc networks to support throughput and delay sensitive real-time applications in these networks. We incorporate a hop-by-hop admission control and a soft resource reservation scheme in a route discovery process to ensure QoS assurance to real-time applications. Further, a simple route stability model is utilized during both route discovery and maintenance phases for selecting QoS routes with higher stability. The reliability of the multiple QoS routes is improved through node disjointness and stability properties of the discovered routes. Following an effective QoS violation detection and route maintenance mechanism, the protocol reduces the frequency of route recovery leading to a significant reduction in QoS disruption. Extensive simulation studies show that the proposed routing protocol can support higher level of QoS in terms of packet delivery ratio, average end-to-end delay, maximum jitter, and overall network throughput.

Priority Based Fairness Provisioning QoS-Aware MAC Protocol

This paper studies the issues of channel allocation subject to QoS constraint(s) and fairness issues in mobile ad hoc networks (MANETs). While a solution to the hidden-terminal problem is paramount, a QoS- aware Medium Access Control (MAC) protocol must also provide a channel access mechanism that considers the QoS constraints of real-time flows. We propose a new MAC protocol called PFQAMP (Priority based Fairness provisioning QoS-Aware MAC Protocol) which supports QoS for real-time applications and provides fairness in accessing the channel. Nodes are assigned priorities dynamically based on i) their roles as sender, receiver or forwarding node and ii) type of the traffic they have to forward or send. Our approach ensures both QoS (through differentiating traffic types) and fairness (among the traffic in the same class). This leads to better network throughput, lower delay and avoidance of starvations for same priority traffic flow. Through simulation we show that our proposal outperforms IEEE 802.11 in terms of average throughput, delay and fairness.

Priority Based Dispersion-Reduced Wavelength Assignment for Optical Networks

Dispersion in optical fiber degrades the quality of signal in optical networks. Although the use of dispersion compensating fiber (DCF) reduces the effects of dispersion, it is expensive and has more propagation loss compared to step-index fiber (SIF). In this paper, we propose a priority based dispersion-reduced wavelength assignment (PDRWA) scheme to reduce overall dispersion in optical network. In this scheme, the connection requests having a same source-destination (s-d) pair are groomed first to avoid intermediate optical-electrical-optical (O/E/O) conversation and then these groomed connection requests with longer lightpath are assigned the wavelengths having lesser dispersion and the wavelengths having a higher dispersion are assigned to the lightpaths with shorter distance. If the connection requests are assigned to the wavelengths using such constraint on dispersion, the overall dispersion in the network can be reduced to a great extent, which will in turn lead to better performance of the network in terms of overall signal quality (Q-factor) without increasing network setup cost. The performance analysis of the proposed scheme using SIF is conducted with different channel speeds (10, 40 and 100 Gbps) in terms of total dispersion and compared the same with the use of DCF. Furthermore, we have studied the overall Q-factor in the network with different channel speeds and considering polarization mode dispersion (PMD) effect using SIF and DCF.

A Route Stability Based Multipath QoS Routing (SMQR) in MANETs

Providing high quality communications service among mobile wireless devices is basically a challenging task in wireless ad hoc networks. In this paper, we propose a route stability based multipath quality of service (QoS) routing (SMQR) protocol for mobile ad hoc networks (MANETs) to support throughput and delay sensitive real-time applications in MANETs. Reliability of QoS-aware path is improved through the selection of a maximum of three node-disjoint routes with higher stability. With an effective QoS violations detection and route maintenance mechanism followed, the frequency of route recovery and hence QoS disruption is reduced significantly in moderate to highly mobile scenarios. Extensive simulation studies show that SMQR can support higher level of QoS in terms of packet delivery ratio, average end-to-end delay, maximum jitter, and overall network throughput.