Sharif Digital Repository

A novel packet-based photonic label switching router for a multirate all-optical switch using generalized multiprotocol label switching is proposed. The idea is based on using optical code-division multiple access (OCDMA) as multiplexing technique and treating OCDMA codes as labels. The system can coexist with current wavelength division multiplexing systems on the same infrastructure. The concept of switch fabric is introduced. Label processing and label swapping functionalities of the switch are discussed. In-depth analyses are made for spectrally phase-encoded OCDMA (SPE-OCDMA) due to its capabilities of supporting high data rates, large code cardinality, and its secure transmission.... 

In this paper, we study two important transmission strategies in full-duplex two-way relaying in the presence of channel estimation errors. In analog network coding (ANC), the relay transmits the combined signals that were received from both sources, with the aim of achieving better spectral efficiency. However, due to imperfect channel-state information (CSI), sources cannot perfectly cancel their own data in the relayed signal. We derive an achievable information rate for ANC in imperfect-CSI conditions and show how the ANC performance can significantly be degraded as a result. Moreover, we derive cut-set bounds with channel estimation errors for traditional routing (TR), in which time... 

We study Nash equilibria in the setting of network creation games introduced recently by Fabrikant, Luthra, Maneva, Papadimitriou and Shenker. In this game we have a set of selfish node players, each creating some incident links, and the goal is to minimize times the cost of the created links plus sum of the distances to all other players. Fabrikant et al. proved an upper bound O(p ) on the price of anarchy, i.e., the relative cost of the lack of coordination. Albers, Eilts, Even-Dar, Mansour, and Roditty show that the price of anarchy is constant for = O(pn) and for ≥ 12 n [dlg] n, and that the price of anarchy is 15 1 + (min{α 2/n , n2 })1/3 for any . The latter bound shows the first... 

In this study, the performance of virtual cut-through switching in the cube-based OTIS architecture, an optoelectronic interconnection architecture for multicomputer systems, is empirically analyzed. Deadlock-free deterministic and adaptive minimal path routing algorithms for this architecture are introduced, and the effects of different network and traffic parameters on average message latency are investigated. This analysis presents a relatively more realistic view of the OTIS architecture than that presented in previous work by considering issues related to a lower level of abstraction (the routing and switching of messages). Among other results, the analysis indicates that depending on... 

Continuous down scaling of CMOS technology in recent years has resulted in exponential increase in static power consumption which acts as a power wall for further transistor integration. One promising approach to throttle the substantial static power of Field-Programmable Gate Array (FPGAs) is to power off unused routing resources such as switch boxes, known as dark silicon. In this paper, we present a Power gating Switch Box Architecture (PESA) for routing network of SRAM-based FPGAs to overcome the obstacle for further device integration. In the proposed architecture, by exploring various patterns of used multiplexers in switch boxes, we employ a configurable controller to turn off unused... 

The planar-adaptive routing algorithm is a simple method to enhance wormhole routing algorithms for fault-tolerance in meshes but it cannot handle faults on the boundaries of mesh without excessive loss of performance. In this paper, we show that this algorithm can further be improved using a flag bit introduced for guiding misrouted messages. So, the proposed algorithm can be used to route messages when fault regions touch the boundaries of the mesh. We also show that our scheme does not lead to diminish the performance of the network and only three virtual channels per physical channels are sufficient for tolerating multiple boundary faulty regions. © 2008 Springer-Verlag Berlin Heidelberg... 

All-optical multi-service path switching in optical code switched GMPLS core networks  

In this paper, we study a class of interconnection networks for multiprocessors, called the Stretched-G network, which is based on a base graph G by replacing each edge of the base network with an array of processors. Two interesting features of the proposed topology are its area-efficient VLSI layout and superior scalability over the underlying base network while preserving most of its desirable properties. We conduct a general study on the topological properties of stretched networks. We first obtain their basic topological parameters and derive some embedding results. We then present optimal routing and broadcasting algorithms for such networks. We also present a unified approach to... 

In this paper, we evaluate how traffic-load dependent vehicle routing at intersections is able to improve the connectivity status of all streets. To this end, we consider a VANET scenario, comprised of several streets and intersections. Then, we focus on two vehicle routing algorithms, one based on the distance to destination, i.e., traffic-load independent (TLI) algorithm, and another one based on both distance to destination and traffic load status of the local streets, i.e., traffic-load dependent (TLD) algorithm. By employing a simple mobility model based on an open BCMP queueing network, we derive the spatial traffic distribution at two cases. Afterwards, we propose a simple algorithm... 

In Mobile Ad hoc Networks (MANETs), nodes depend on each other for routing and forwarding their packets. However, to save power and other resources, nodes belonging to independent authorities may behave selfishly, and not cooperate in network activities. Such selfish behaviour poses a real threat to the proper functioning of MANETs. To cope with this situation, a motivation stimulation mechanism is required to provide sufficient incentives for nodes to forward other nodes' packets. One appropriate approach is to have network nodes pay in order to motivate them to cooperate with the protocol. To achieve truthfulness, the payment should be based on the cost of transmission of packets. Since... 

We present a novel optical code division multiple access (OCDMA) scheme based on spatial optical heterodyning for free-space optical communication systems. In this technique, in particular, the decoding process is established by means of a spatial optical heterodyne receiver. The spatial heterodyning OCDMA introduced can be considered to be in the class of spread-space techniques, which implies that there is no structural limitation on the shape of time domain signals, e.g., digital or analog modulation. For the sake of simplicity and practicality we considered onoff keying modulation. However, there is no limitation on using more advanced modulation schemes such as pulse position... 

Analytical modelling is indeed the most cost-effective method to evaluate the performance of a system. Several analytical models have been proposed in the literature for different interconnection network systems. This paper proposes an accurate analytical model to predict message latency in wormhole-switched star graphs with fully adaptive routing. Although the focus of this research is on the star graph but the approach used for modelling can be, however, used for modelling some other regular and irregular interconnection networks. The results obtained from simulation experiments confirm that the proposed model exhibits a good accuracy for various network sizes and under different operating... 

Numerous analytical performance models have been proposed for deterministic wormhole-routed mesh networks while only a single model, to our best knowledge, has been suggested for fully adaptive wormhole routing in mesh interconnection networks. This paper proposes a new and accurate analytical performance model for fully adaptive wormhole-routed mesh networks. Simulation results show that unlike the previously proposed model which is only accurate in light traffic loads, this model can be used for the performance analysis of almost all traffic loads. © 2007 Elsevier B.V. All rights reserved  

Rumor routing is a classic routing algorithm based on the random walk of agents. In this paper, a method to improve the performance of this routing algorithm is proposed. Here, we try to improve the latency and energy consumption of the traditional algorithm using propagation of query and event agents in straight lines, instead of using purely random walk paths. As our results confirm, this method improves the delivery ratio of the queries which is a drawback of traditional rumor routing. To compare the performance measures with traditional algorithm, a simulation framework is developed and extensive simulations are performed. ©2007 IEEE  

Peer-to-peer overlay networks provide a useful infrastructure for building distributed applications. These networks provide efficient and fault-tolerant routing and object locating within a self-organizing overlay network. This paper presents a multi-dimensional overlay network called RAQNet which is based on RAQ1. RAQ supports exact match queries and range queries over multi-dimensional data efficiently. Moreover, its routing cost does not depend on the dimension of the search space. In RAQNet, we have improved its original routing algorithms and extended it to have topology awareness property. In RAQNet, nodes are connected to each other if their labels are "close" to each other with... 

Most of the energy efficient routing algorithms proposed for sensor networks are reactive routing algorithms. By definition, reactive algorithms are those in which routes are constructed whenever there is data transmission. In such algorithms, to transmit data packets from a certain transmitter to the corresponding receiver, efficient route will be constructed using RREQ delivery. This delivery is performed via flooding and modified flooding algorithms. One of the most important criteria of such flooding algorithm is not to miss the best final route during RREQ delivery. Most of major algorithms ignored this fact and instead tried to minimize energy consumption during flooding algorithm. But... 

Cooperation of nodes for routing and packet forwarding is inevitable in a mobile ad hoc network. Selfishness in such networks is a significant challenge and can cause network performance to noticeably degrade. In this paper, we propose some new selfishness models elicited from psychological behavior of human beings. We also evaluate performance of MANET in the presence of different percentages of selfish nodes that act based on our selfishness models. Results show that energy-based selfishness is a serious problem that could affect performance depends on mobility of nodes, density of network, and time of simulation. This kind of selfishness needs a comprehensive mechanism to cope with and we... 

In this paper, we introduce an efficient route discovery mechanism to enhance the performance and multicast efficiency of On-Demand Multicast Routing Protocol (ODMRP). Our framework, called limited flooding ODMRP, improves multicasting mechanism by efficiently managing flooding mechanism based on delay characteristics of the contributing nodes. In our model, only the nodes that satisfy the delay requirements can flood the Join-Query messages. We model the contributing nodes as M/M/1 queuing systems. Our framework considers the significant parameters in delay analysis, including random packet arrival, service process, and random channel access in the relying nodes, and exhibits its best... 

Information-centric network (ICN) has become a basic research topic with regard to the future architecture of the Internet. Storage and routing data is an important feature of ICN, as it improves network performance and content distribution. One of the challenges in this type of network is the routing problem. The objective of this paper is to propose a routing algorithm in the named data network. Owing to the impressive results presented by the enhanced heuristic methods, tabu search has been selected to develop the proposed algorithm. This work has been carried out in five major steps, Creating the initial solution, The mechanisms of generating a neighborhood, Evaluating the neighbor... 

Probabilistic key pre-distribution schemes have recently emerged as major tools of addressing secure routing challenge in wireless networks. In our previous work, we propose an algorithm capable of finding optimal secure paths in overlay wireless networks. An important concern related to that algorithm is the scalability of the solution for large scale networks containing thousands of nodes. In this paper, we propose two alternative solutions for the previously formulated problem of secure overlay routing that can effectively scale to thousands of nodes. The first one is a deterministic Dijkstra-based algorithm analytically proven to find the optimal path with a time complexity much lower...