Joanna Tomasik

Ad hoc network in a disaster area: A composite mobility model and its evaluation

Ad hoc network is an essential means of communication in disaster scenes. Validation of new communication protocols for these networks requires exhaustive simulation runs because real life experiences can be performed exclusively during expensive civil protection exercises. The necessity of these simulations calls for realistic and reliable mobility models which take into account numerous aspects of rescue worker interventions. We propose a composite model of mobility for disaster scenarii which includes a realistic model of human displacement, team mobility, and obstacle avoidance. The comparison of its performance with those of other available models is encouraging. We believe that it can improve the veracity of rescue operation simulations.

Resource Allocation in Ad Hoc Networks with Two-Hop Interference Resolution

The multi-user medium access mechanism OFDMA has to provide each node with a given amount of radio resources. In this paper we present a new distributed algorithm for the allocation of resource blocks in an OFDMA ad hoc network. We are principally interested in allocating resources fairly because the ad hoc networks which we work on are dedicated to be deployed in the areas of natural or man-made disasters and where the guarantee of connectivity is an important issue. Contrary to the commonly applied approach, we consider a resource allocation on the links under a two hop interference distance. The proposed allocation procedure is coupled with our other algorithm which detects and corrects two hop interferences and which has been revised and improved. The performance of our algorithm is evaluated by simulation for different topologies. We observed that simultaneous allocations in large networks allow a constant convergence time to be kept despite the networks size.

Bandwidth Optimization for Multicast Transmissions in Virtual Circuit Networks

The CARRIOCAS project aims to guarantee QoS connectivity services to distributed applications in a Telecom carrier network. A large number of these applications (for example video applications) use a multicast service packet delivery. Multicast which minimizes the total used bandwidth in the MPLS network has become an important subject. We study multicast routing in the network where only some routers can duplicate packets. We prove that the construction of a multicast tree minimizing the bandwidth used in such a network is a NP -complete problem and we propose an heuristic algorithm to solve it. We evaluate the performance of the heuristic in terms of total bandwidth used by the multicast for different network sizes.

A centralised control mechanism for network resource allocation in grid applications

In a high-speed network, application-network interactions are considerations of paramount importance for service responsiveness. The CARRIOCAS project aims to study the high-speed networking features that are needed to support distributed applications in an operator network. These features will be implemented later. The proposed architectural solutions will be validated in a pilot network used as a grid infrastructure for distributed applications. This network will be a part of the CARRIOCAS project outcome. We propose a mechanism for the introduction of application data in the network with respect to CARRIOCAS architecture. Using simulations, we study the system performance for applications that demand the quality of service in terms of latency and data loss. Our results show that a centralised control of application-network applications is efficient for small and fast networks.

The inter-domain hierarchy in measured and randomly generated AS-level topologies

Independent operator networks are called either Autonomous Systems (AS) or domains. Numerous studies based on complex measurement platforms have been carried out for over ten years now in order to discover the Internet topology on domain level. The routing realized by Border Gateway Protocol (BGP) is strongly influenced by commercial relationships which exist between domains, because domain operators do not want to make public the routes they know, as announcing certain routes would deprive them of a possible financial benefit. Consequently, routes available in BGP tables are valley-free and they are “spanned” on the inter-domain hierarchy. This property of BGP routes has an impact on the performance of protocols which are proposed to assure the QoS. We examined the existing Internet topologies gathered on the domain level over the six year period in the context of their hierarchy. We used aSHIIP, our random hierarchical topology generator, to induct the hierarchy into the collected topologies. We proposed new methods for detecting the core of a network. Thanks to this analysis we have been able to put forward solid inter-domain hierarchy induction methods which are implemented in our publicly available tool.

Self-stabilizing algorithm of two-hop conflict resolution

Ad hoc networks are increasingly used by the civil protection forces to coordinate their actions in emergency situations. To enable them to work properly, the satisfaction of the demanded quality of service (QoS) is crucial. One of the most effective methods of assuring the QoS is to use multiplexing modes based on a resource reservation like TDMA or FDMA. The principal demands in terms of QoS concern a guarantee of connectivity and resource availability. Our idea consists in the separation of the interference detection mechanism in order to make it independent of the pure resource allocation algorithm. We present an algorithm which detects and corrects conflicts of assignment. Our algorithm is proved to be self-stabilizing and reaches a stable state in up to five rounds.

Automatic Network Services Aligned with Grid Application Requirements in CARRIOCAS Project

Automatic Service framework named Scheduling, Reconfiguration and Virtualization (SRV) is developed in CARRIOCAS project to enhance existing Telecom network infrastructures for supporting grid applications sharing IT resources interconnected with ultra-high performance optical networks. From the requirements of Grid applications a classification is pro po sed to specify the network services and their attributes. In large-scale collaborative environments, SRV solution is described to enable automatic network service operations according to high-performance computing service access. The resources hosted at datacenters are virtualized to be attached to transport network infrastructure offering uniform interfaces towards external cus tomers. New level of service bindings is defined with network services du ring executions of Grid applications’ workflows. On-demand intensive com puting and visualization services scenario is described in Telecom environment.

Markovian performance analysis of a synchronous optical packet switch

Switch architectures applicable to fixed-length optical packet networks is studied and we compare their performance in terms of packet loss ratio. We propose analytical models of these switches (as discrete time Markov chains) and we compare their performance with those obtained by simulation, varying statistical properties of incoming traffic. We show that Markovian models of future optical architectures can be applied as a tool to studies of network design.

Minimization of the Receiver Cost in an All-Optical Ring with a Limited Number of Wavelengths

A new all-optical node architecture, known as POADM, may lead to a considerable cost reduction for the infrastructure of the rings ensuring at the same time their excellent performance. We present a dimensioning problem which consists of minimizing the total number of receivers in nodes for a ring with a fixed number of wavelengths and a given traffic matrix. We prove the problem NP-completeness and provide a heuristic whose principle is to match and to group transmissions instead of considering them independently. We justify the group matching approach by confronting the results of our algorithm with its version without matching. The results obtained allow us to recommend the heuristic in the planning of POADM rings.

Validation of spectrum management schemes for PMR networks based on LTE with interference detection

Private Mobile Radio (PMR) networks are cellular infrastructures dedicated to be used by professionals. We have been working on allocation algorithms in LTE based PMR networks equipped with an innovative sensing mechanism which estimates interference probability between UEs (User Entities). We proposed spectrum management schemes which take advantage of sensed data to operate parsimoniously. As the underlying problems are NP-hard, the performance evaluation of the proposed solutions has to be made. At the stage of algorithm design we are obliged to generate representative series of interference graphs. We describe the methodology of random interference graph generation. We take into consideration numerous aspects of PMR networks, notably the QoS requirements. We offer a procedure which allows anybody intending to develop algorithms for this new PMR technology to have a complete modeling support.