Mohammad Masud Hasan

Traffic Grooming in Green Optical Networks

Compared to energy-awareness research in wireless and copper networks, less attention has been given to energy awareness in optical counterparts. In this paper, we introduce energy-aware traffic grooming problems for optical networks. We show that by looking further into the modular physical architecture of a node during request allocations, we can significantly reduce the number of active components and, hence, total energy consumption in the network, especially when traffic load is low. Since energy usage is an important element of operational expenditure (OPEX), this approach provides the financial motivation for service providers along with the desired environmental motivation. We present auxiliary graph based heuristics and justify our cases compared to traditional approaches with simulation results.

Energy-awareness in dynamic traffic grooming

We introduce an energy-efficient traffic grooming scheme for promoting greener optical networks. The scheme considers a modular node architecture, reuses already active components during request allocations, and conserves total energy consumption in the network.

A Study of Energy-Aware Traffic Grooming in Optical Networks: Static and Dynamic Cases

Less attention has been given to energy aware optical counterparts, compared to the research in energy-aware wireless and ethernet networks. In this paper, we consider energy-aware traffic grooming problems in optical networks for both static and dynamic cases. Rather than simply considering a logical architecture of an optical node, we specifically look further into the modular physical architecture. We show that by reusing already active physical components during request allocations, we can significantly reduce the total number of active components and, hence, total energy consumption in the network, especially when traffic load is low. Since energy usage is an important element of operational expenditure, this approach provides the financial motivation for service providers along with the desired environmental motivation. We present a mathematical formulation of the problems, propose auxiliary graph based heuristics, and justify our cases compared to traditional approaches, based on simulation results.

WLC35-3: Survivable Wireless Access Network Design with Dual-homing Capabilities

With the growth of mobile users and the increasing deployment of wireless access network infrastructures, the issue of quality of service is becoming an important component of efficient wireless access network design. In this paper, we study the survivability problem for users that are connected to the core network by fully or partially dual homed paths, or by a single path. Given a hierarchical wireless access network with the available capacity and reliability at each level, the problem is to minimize overall connection cost for multiple requests such that the capacity and minimum survivability requirements are not violated. We formulate the problem using mixed integer linear programming and propose a genetic-algorithm-based heuristic.

Online Clustering for Hierarchical WDM Networks

This paper presents an easy-to-implement, distributed, and scalable clustering technique that determines clusters adaptively in response to the current conditions (i.e., bandwidth availability) in large WDM optical networks. Simulation results verify the feasibility of the approach.

Survivable path computation in PCE-based multi-domain networks

We propose an optimal scheme for finding end-to-end shortest disjoint paths with a given sequence of domains in path computation element-based multi-domain networks. We compute the shortest path over multiple domains in the forward direction and compute the disjoint path in the backward direction. The scheme has lower time and message complexity compared to contemporary schemes for finding optimal survivable paths across domains. We prove the optimality of the proposed scheme. To further simplify the implementations in practical scenarios, we also provide heuristic algorithms. Simulation results exhibit superior performance of the proposed optimal and heuristic algorithms compared to existing approaches.

Survivable Self-Organization for Prolonged Lifetime in Wireless Sensor Networks:

More often than not, wireless sensor networks (WSNs) are deployed in adverse environments, where failures of sensor nodes and disruption of connectivity are regular phenomena. Therefore, the organization or clustering of WSNs needs to be survivable to the changing situations. On the other hand, energy efficiency in WSNs remains the main concern to achieve a longer network lifetime. In this work, we associate survivability and energy efficiency with the clustering of WSNs and show that such a proactive scheme can actually increase the lifetime. We present an easy-to-implement method named DED (distributed, energy-efficient, and dual-homed clustering) which provides robustness for WSNs without relying on the redundancy of dedicated sensors, that is, without depending on node density. DED uses the information already gathered during the clustering process to determine backup routes from sources to observers, thus incurring low message overhead. It does not make any assumptions about network dimension, node capacity, or location awareness and terminates in a constant number of iterations. The correctness of the algorithm is proved analytically. Simulation results comparing with contemporary approaches demonstrate that our approach is effective both in providing survivability and in prolonging the network lifetime.

Differentiated Energy Savings in Optical Networks with Grooming Capabilities

This paper investigates the benefits of enabling services with differentiated energy-saving (DiffEnS) in WDM optical networks with traffic grooming capabilities. DiffEnS can reduce the operating cost (OPEX) as more customers gradually join green programs and subscribe to the energy efficient traffic services referred to as the Green. Based on a modular node design with grooming capabilities, two heuristic algorithms are introduced for minimizing energy consumption during provisioning of energy-aware services. Using our previously developed auxiliary graph, we report on performance of these heuristic algorithms. Our results indicate that, thanks to DiffEnS moderate energy saving can be achieved, even when a small percentage of customers switch to Green services. A major trade-off is the possibility of an increased average endto- end delay experienced by Green services.

Online Partitioning for Scalable and Survivable Optical Networks

Given the trend of rapid growth, the manageability and survivability of future optical networks, even for a single administrative domain, are imminent challenges. For a large-scale mesh network with dynamic traffic, maintaining the global state information in a centralized fashion is impractical. Hence, distributed schemes are needed to organize nodes and to manage state information in a more localized manner. One such scheme for organizing nodes is to logically partition or cluster the nodes into a hierarchical structure. However, in optical networks, physically disjoint routes are sought for failure-protection purposes, where the working path and the backup path of a request traverse diverse shared risk link groups (SRLGs). Hence, the clustering of nodes should also be effective in yielding SRLG diversity. In this paper, we address the problem of determining the appropriate clustering of nodes for a large wavelength division multiplexed (WDM) network. We suggest an easy-to-implement, dynamic, and distributed technique that forms clusters adaptively in response to the current network conditions, e.g., node connectivity, bandwidth availability (or traffic load), and SRLGs. We find that considering risk group sharing in network partitioning best handles both scalability and survivability. Simulation results verify the viability of the proposed approach.

Domain-Disjoint Routing Based on Topology Aggregation for Survivable Multi-Domain Optical Networks

In a multi-domain network, domains may be defined based on geography or administrative boundaries. For domains that are constructed based on geographic locations, multiple links within the same domain may fail simultaneously due to geographically localized failure events. For domains that are defined administratively, a domain administrator may not be able to provide link-disjointness for two paths traversing the domain. Thus, in some cases, it may be necessary to find two domain-disjoint paths to improve survivability. In this paper, we propose an algorithm to find domain-disjoint working and backup paths for multi-domain routing requests. We prove that our approach is optimal in finding domain disjoint paths with minimum total cost.