Protecting multicast sessions in WDM optical mesh networks

Recent advances in wavelength-division-multiplexing (WDM) technology are expected to facilitate bandwidth-intensive multicast applications. However, a single fiber (bundle) cut on such a network can disrupt the transmission of information to several destination nodes on a "light tree"-based multicast session. Thus, it is imperative to protect multicast sessions e.g., by reserving resources along backup trees. We show that, if a backup tree is directed-link-disjoint to its primary counterpart, then data loss can be prevented in the event of any single link failure. We provide mathematical formulations for efficient routing and wavelength assignment (RWA) of several multicast sessions (including their backup trees for dedicated protection) at a globally optimum cost. We present these formulations for networks equipped with two kinds of multicast-capable switch architectures: one using the opaque (O-E-O) approach and the other using transparent (all-optical) approach. We expand our formulations to accommodate sparse splitting constraints in a network, in which an optical splitter has limited splitting fanout and each node has a limited number of such splitters. We develop a profit-maximizing model that would enable a network operator to be judicious in selecting sessions and simultaneously routing the chosen ones optimally. We illustrate the solutions obtained from solving these optimization problem formulations for a representative-size network.     

PPMA, a probabilistic predictive multicast algorithm for ad hoc networks

Ad hoc networks are collections of mobile nodes communicating using wireless media without any fixed infrastructure. Existing multicast protocols fall short in a harsh ad hoc mobile environment, since node mobility causes conventional multicast trees to rapidly become outdated. The amount of bandwidth resource required for building up a multicast tree is less than that required for other delivery structures, since a tree avoids unnecessary duplication of data. However, a tree structure is more subject to disruption due to link/node failure and node mobility than more meshed structures. This paper explores these contrasting issues and proposes PPMA, a Probabilistic Predictive Multicast Algorithm for ad hoc networks, that leverages the tree delivery structure for multicasting, solving its drawbacks in terms of lack of robustness and reliability in highly mobile environments. PPMA overcomes the existing trade-off between the bandwidth efficiency to set up a multicast tree, and the tree robustness to node energy consumption and mobility, by decoupling tree efficiency from mobility robustness. By exploiting the non-deterministic nature of ad hoc networks, the proposed algorithm takes into account the estimated network state evolution in terms of node residual energy, link availability and node mobility forecast, in order to maximize the multicast tree lifetime, and consequently reduce the number of costly tree reconfigurations. The algorithm statistically tracks the relative movements among nodes to capture the dynamics in the ad hoc network. This way, PPMA estimates the node future relative positions in order to calculate a long-lasting multicast tree. To do so, it exploits the most stable links in the network, while minimizing the total network energy consumption. We propose PPMA in both its centralized and distributed version, providing performance evaluation through extensive simulation experiments.     

Reliability and cost evaluation of third-generation wireless accessnetwork topologies: a case study

The "explosive growth in bursty traffic" changes the network dynamics and requires a good evaluation of various classes of service when designing an access network. From a topological standpoint, the multiservice networks in this paper are heterogeneous systems which integrate both a core and some wireless access networks into an infrastructure similar to third-generation wireless networks. Such networks require reliable and cost-effective solutions to the problem of selecting access technologies for satisfying performance and quality of service requirements related to the services and applications envisioned. This paper analyzes the reliability aspects of some access network topologies to insure a certain level of quality of service at the lowest cost for the end users. It considers a mass market equivalent to 1.6 million subscribers, the objective being to determine the cost the users are ready to pay to benefit from services and applications provided by these multiservice networks. For these purposes, the relative behavior of 3 access-network topologies are studied: the tree with parallel backup links, the ring, and the partially meshed topologies. In ring topology, simulation results show that a great connectivity in the access network is not justified in terms of reliability requirements; the partially meshed topology, even if it has redundant links which affect its cost, outperforms the tree with parallel backup links; and the ring topology is more reliable in terms of disconnected sessions than the tree topology. By considering both reliability and cost, a tree with parallel backup links appears the best topology for the access network and its cost is acceptable for the end user. This study can be extended by: (1) establishing the cost as a function of the quality of service; (2) optimizing the partially meshed topology for more reliable networks; and (3) defining a (shaping) policy to deal with a variety of traffic schemes     

Family ACK tree (FAT): supporting reliable multicast in mobile ad hoc networks

A new protocol, called family ACK tree (FAT), is proposed to support a reliable multicast service for mobile ad hoc networks. For each reliable multicast protocol, a recovery scheme is used to ensure end-to-end delivery of unreliable multicast packets for all group members. FAT employs a tree-based recovery mechanism that localizes ACKs and retransmissions to avoid feedback implosion. To cope with node movements, FAT constructs an ACK tree on which each node maintains reachability information to three generations of nodes on the ACK tree. When a tree is fragmented due to a departed node, the fragments are glued back to the tree using the underlying multicast routing protocol. FAT then adopts an adaptive scheme to recover missed packets that have been multicast to the group during fragmentation and are not repaired by the new reliability agent. We have conducted simulations to compare the performance of FAT with existing solutions. The results show that FAT achieves better performance for the provision of reliable service in ad hoc networks, in terms of reliability, scalability, and delivery efficiency.     

Performance of split routing algorithm for three-stage multicastnetworks

This paper studies three-stage Clos (1953) switching networks for multicast communications in terms of their blocking probabilities on a random traffic model. Even though the lack of multicast capability in input-stage switches requires a prohibitively large number of middle switches to provide compatible requests with nonblocking paths, the probabilistic model gives an observation that the blocking probability decreases drastically and then approaches zero as the number of middle switches is far less than the theoretical bound. The S-shaped curves of blocking probability versus degree of fanout indicate that high fanout requests are mostly blocked at some given reference network utilization. A split routing algorithm and its blocking probability are introduced to enhance the routability of the high fanout requests. We also corroborate the analytic model by performing network simulations based on a random request generator and a random routing strategy     

Reliability and performance evaluation of four tree multistage interconnection network

Reliability and performance of a multiprocessor system depend heavily upon the design of its interconnection network. This paper presents a comprehensive treatment to analyse a four tree network, a new class of irregular multistage interconnection networks (MIN), for reliability and performance. The results obtained are compared with the augmented shuffle exchange network (ASEN), a network with low link and switch complexity and having significantly improved reliability and performance amongst the regular type of MINs. The reliability results, both optimistic and pessimistic, are better than for the ASEN as well as for most of the other networks. The performance analysis in the circuit switched environment shows that the probability of accepting the requests is significantly improved and there is negligible degradation in performance with increasing network size.     

一种高效可靠的无人机自组网多跳TDMA协议

设计无人机自组网媒体接入控制(Medium Access Control,MAC)协议时,需要考虑其控制开销和数据传输的可靠性。鉴于此,结合现有无线自组网多跳时分多址接入(Time Division Multiple Access,TDMA)协议和无人机自组网特点,提出了一种高效可靠的无人机自组网多跳TDMA协议。首先采用高效负载均衡的时隙请求信息上传机制,选择一个负载较小的节点转发节点时隙请求信息;然后根据相互通信的父节点删除重复节点的时隙请求信息,减少相同节点的时隙请求信息转发次数;最后通过实时更新节点时隙请求信息机制,提高节点时隙请求信息传输的可靠性。仿真结果表明,该协议在数据传输成功率、平均时延、控制开销方面优于现有协议,可较好地应用在无人机自组网中。     

A Cutset Approach to Reliability Evaluation in Communication Networks

A global reliability measure called 'network reliability' (NR) is the probability that a call entering a probabilistic network at any originating node can reach every other node. This concept is quite useful in multiterminal networks such as computer networks and parallel processors, etc. A simple technique is presented for evaluating NR in symbolic form. The method is based on cutsets and is computationally advantageous with respect to the spanning tree approach. It requires fewer cutsets to be manipulated in the process of determining the NR expression. The number of cutsets is approximately half that of spanning trees even for a small sized computer communication network and there is a further improvement in the situation for larger networks.     

Cooperative Strategies and Achievable Rate for Tree Networks With Optimal Spatial Reuse

In this paper, a low-complexity cooperative protocol that significantly increases the average throughput of multihop upstream transmissions for wireless tree networks is developed and analyzed. A system in which transmissions are assigned to nodes in a collision free, spatial time division fashion is considered. The suggested protocol exploits the broadcast nature of wireless networks where the communication channel is shared between multiple adjacent nodes within interference range. For any upstream end-to-end flow in the tree, each intermediate node receives information from both one-hop and two-hop neighbors and transmits only sufficient information such that the next upstream one-hop neighbor will be able to decode the packet. This approach can be viewed as the generalization of the classical three node relay channel for end-to-end flows in which each intermediate node becomes successively source, relay and destination. The achievable rate for any regular tree network is derived and an optimal schedule that realizes this rate in most cases is proposed. Our protocol is shown to dramatically outperform the conventional scheme where intermediate nodes simply forward the packets hop by hop. At high signal-to-noise ratio (SNR), it yields approximately 66% throughput gain for practical scenarios.     

An application of meta-heuristic and nature-inspired algorithms for designing reliable networks based on the Internet of things: A systematic literature review

The widespread use of Internet of Things (IoT) in various wireless sensor networks applications has increased their importance in recent years. IoT is a smart technology that connects anything anywhere at any time. These smart objects, which connect the physical world with the world of computing infrastructure, are expected to permeate all aspects of our daily lives and revolutionize a number of application domains such as healthcare, energy conservation, and transportation. As wireless networking expands, the disadvantage of wireless communication is clearly obvious. People's apprehension over the IoT's dependability has therefore skyrocketed. IoT networks' key requirements are dependability, channel security, fault tolerance, and reliability. Monitoring the IoT networks depends on the availability and correct functioning of all the network nodes. Recent research has proposed promising solutions to address these challenges. This article systematically examines recent articles that use meta-heuristic and nature-inspired algorithms to establish reliable IoT networks. Eighteen articles were analyzed in four groups. Results showed that reliable enhancement mechanisms in IoT networks increase fault node detection, network efficiency, and lifetime and attain energy optimization results in the IoT concept. Additionally, it was discovered in the literature that the current studies focus on how to effectively use edge network capabilities for IoT application executions and support, along with the related needs.     

A Power-Aware Multicast Routing Protocol for Mobile Ad Hoc Networks With Mobility Prediction

A mobile ad hoc network (MANET) is a dynamically reconfigurable wireless network that does not have a fixed infrastructure. Due to the high mobility of nodes, the network topology of MANETs changes very fast, making it more difficult to find the routes that message packets use. Because mobile nodes have limited battery power, it is therefore very important to use energy in a MANET efficiently. In this paper, we propose a power-aware multicast routing protocol (PMRP) with mobility prediction for MANETs. In order to select a subset of paths that provide increased stability and reliability of routes, in routing discovery, each node receives the RREQ packet and uses the power-aware metric to get in advance the power consumption of transmitted data packets. If the node has enough remaining power to transmit data packets, it uses the global positioning system (GPS) to get the location information (i.e., position, velocity and direction) of the mobile nodes and utilizes this information to calculate the link expiration time (LET) between two connected mobile nodes. During route discovery, each destination node selects the routing path with the smallest LET and uses this smallest link expiration time as the route expiration time (RET). Each destination node collects several feasible routes and then selects the path with the longest RET value as the primary routing path. Then the source node uses these routes between the source node and each destination node to create a multicast tree. In the multicast tree, the source node will be the root node and the destination nodes will be the leaf nodes. Simulation results show that the proposed PMRP outperforms MAODV (Royer, E. M. & Perkins, C. E. (1999). In Proceedings of the ACM MOBICOM, pp. 207–218, August 1999.) and RMAODV (Baolin, S. & Layuan, L. (2005). In Proceeding of the 2005 IEEE International symposium on microwave antenna, propagation and EMC technologies for wireless communications, Vol. 2, pp. 1514–1517, August 2005.).     

Balance energy-efficient and real-time with reliable communication protocol for wireless sensor network

In many wireless sensor network applications, it should be considered that how to trade off the inherent conflict between energy efficient communication and desired quality of service such as real-time and reliability of transportation. In this paper, a novel routing protocols named balance energy-efficient and real-time with reliable communication (BERR) for wireless sensor networks (WSNs) are proposed, which considers the joint performances of real-time, energy efficiency and reliability. In BERR, a node, which is preparing to transmit data packets to sink node, estimates the energy cost, hop count value to sink node and reliability using local information gained from neighbor nodes. BERR considers not only each sender’ energy level but also that of its neighbor nodes, so that the better energy conditions a node has, the more probability it will be to be chosen as the next relay node. To enhance real-time delivery, it will choose the node with smaller hop count value to sink node as the possible relay candidate. To improve reliability, it adopts retransmission mechanism. Simulation results show that BERR has better performances in term of energy consumption, network lifetime, reliability and small transmitting delay.     

A Classification Tree Based Approach for the Development of Minimal Cut and Path Vectors of a Capacitated Network

This paper presents a holistic method that links together Monte-Carlo simulation, exact algorithms, and a data mining technique, to develop approximate bounds on the reliability of capacitated two-terminal networks. The method uses simulation to generate network configurations that are then evaluated with exact algorithms to investigate if they correspond to a network success or failure. Subsequently, the method implements commercially available software to generate a classification tree that can then be analyzed, and transformed into capacitated minimal cut or path vectors. These vectors correspond to the capacitated version of binary minimal cuts & paths of a network. This is the first time that these vectors are obtained from a decision tree, and in this respect, research efforts have been focused on two main directions: 1) deriving an efficient yet intuitive approach to simulate network configurations to obtain the most accurate information; and given that the classification tree method could for some applications provide imperfect or incomplete information without the explicit knowledge of the reliability engineer, 2) understand the relationship between the obtained vectors, and the real capacitated minimal cut & path vectors of the network, and its reliability. The proposed method has been tested on a set of case networks to assess its validity & accuracy. The results obtained show that the technique described is effective, simple, and widely applicable.     

The minimum test set problem for circuits with nonreconvergent fanout

The problem of computing the minimum size of a test set for a combinational circuit is considered. It is known that the minimum test set size of a combinational circuit can be determined in polynomial time for fanout free circuits, while even for circuits with non-reconvergent fanout, the minimum test set size problem is NP-Hard. We extend the class of circuits for which a minimum test set can be constructed in polynomial time to include a class of circuits with fanout, called restricted fanout circuits. Restricted fanout circuits are characterized using an undirected graph describing the structure of the circuit. The graph for these circuits must be free of (undirected) cycles. In addition, the paper demonstrates a novel application of dynamic programming to test generation problems.Formerly with the Electrical Eng. and Computer Science Depts. at the Technion, Haifa 32000, Israel.     

Low-latency algorithm for improving data persistence in mobile low-duty-cycle wireless sensor network

Mobile low-duty-cycle wireless sensor network (MLDC-WSN) are a kind of new ad hoc networks that are appeared in recent years.In MLDC-WSN,the nodes only have limited storage spaces.Moreover,the nodes would move or sleep from time to time.Therefore,these networks have some problems such as connectivity is hard to be maintained and data are hard to be transmitted to their destinations for storage in time.As a result,data persistence (i.e.,the probability that all data can be recovered after some nodes die in the networks) is low.A distributed algorithm named LT-MDS for improving data persistence in MLDC-WSN was proposed.The algorithm used a new infectious data dissemination method to transmit the data,which enabled the data to be received by almost all the mobile nodes in a network with low latency and improved the reliability of the network.When a node receives the data,it would use LT (Luby transform) codes to encode and save them.By this way,the nodes with limited storage spaces can save more data information.Theoretical analyses and simulations show that LT-MDS can complete the process of data dissemination and preservation with low latency,and it can achieve high data persistence.     

Reliability analysis of redundant-path interconnection networks

The reliability of some redundant-path multistage interconnection networks is characterized. The classes of networks are the generalized indra networks, merged delta networks, and augmented C-networks. The reliability measures are terminal reliability and broadcast reliability. Symbolic expressions are derived for these reliability measures in terms of component reliabilities. The results are useful in comparing network designs for a given reliability requirement     

Moralism: mobility prediction with link stability based multicast routing protocol in MANETs

In recent research, link stability is getting tremendous attention in mobile adhoc networks (MANETs), because of several impediments that occur in a reliable and robust network. Link stability metric is used to improve network performance in terms of end-to-end delay, data success delivery ratio (DSDR) and available route time (ART). Energy consumption, bandwidth and communication delay of major concern in ad hoc networks. A high mobility of MANET nodes reduces the reliability of network communication. In a dynamic networks, high mobility of the nodes makes it very difficult to predict the dynamic routing topology and hence cause route/link failures. Multicast in MANETs is an emerging trend that effectively improves the performance while lowering the energy consumption and bandwidth usage. Multicast routing protocol transmits a packet to multicast a group at a given time instant to achieve a better utilization of resources. In this paper, node mobility is considered to map better their movement in the network. So, the links with long active duration time can be identified as a stable link for route construction. Variation in signal strength is used to identify whether the direction of the node is towards or away from estimating node. We consider signal strength as QoS metric to calculate link stability for route construction. Efforts are made to identify the link with highly probable longer lifetime as the best suitable link between two consecutive nodes. We predict the movement time of nodes that define the route path to the node destination. Exata/cyber simulator is used for network simulation. The simulation results of the proposed routing protocol are compared with on-demand multicast routing protocol and E-ODMRP, which works on minimum hop count path. Analysis of our simulation results has shown improvement of various routing performance metrics such as DSDR, ART, routing overhead and packet drop ratio.     

A design technique for reliable networks under a nonuniform trafficdistribution

Many network-reliability analysis techniques define and compute a variety of reliability measures. Most techniques assume that network connectivity is the only determining factor in network reliability; and merely analyze an existing network structure but do not provide any methodology for reliable design. This paper presents a heuristic design algorithm to enhance the reliability of existing communication networks by modifying their topology. This algorithm improves the reliability of the least reliable node (reliability is the probability that messages transmitted from a given node reach their destination). To use this algorithm on large networks, a reliability analysis method is developed which determines approximate network reliability values in linear-time when an upper bound is placed upon the in-degree of all network nodes. The heuristic network design algorithm uses this approximate reliability analysis technique to place additional links. The goal of this link placement is to improve the reliability of the least-reliable node. The placement of additional links is a function of both the traffic distribution and the connectivity of the network. This process continues until either a desired level of network reliability is achieved or a maximum number of additional links has been added. A unique feature of this design strategy is that it has quadratic time-complexity when the maximum in-degree of all network nodes is limited     

Fault tolerance in the Block-Shift Network

The Block Shift Network (BSN) is a new topology for interconnection networks in multiprocessor systems. BSN is a class of networks defined by several parameters, and has a constant number of links/node for some given parameters. Many popular networks such as the hypercube, the shuffle-exchange, and the complete networks, are instances of the BSN for different parameters. Performance of BSN has been evaluated through analysis, simulation, and design of typical parallel algorithms on it. The results indicate that BSN surpasses the hypercube in several respects while retaining most of the hypercube advantages, especially when the traffic has the locality property. As the size and complexity of a system increase, however, the reliability aspects become equally important and should be included in the system-performance study. This paper discusses the reliability issue of BSN. Several reliability measures, including network connectivity, network diagnosability, and 2-terminal reliability, are obtained through analysis. This paper shows that the BSN not only surpasses the hypercube in performance as confirmed before, but also has comparable reliability to the hypercube under similar conditions. BSN is also very flexible in balancing its cost and performance. One can increase two parameters to enhance the performance and reliability of the BSN, while it is impossible to do so in the hypercube once its size is fixed. The BSN can be an effective interconnection network for future parallel computer systems     

EARQ: Energy Aware Routing for Real-Time and Reliable Communication in Wireless Industrial Sensor Networks

Wireless industrial sensor networks are wireless sensor networks which have been adapted to industrial applications. Most techniques for wireless sensor networks can be applied to wireless industrial sensor networks. However, for industrial applications of wireless industrial sensor networks, new requirements such as real-time, reliable delivery need to be considered. In this paper, we propose EARQ, which is a novel routing protocol for wireless industrial sensor networks. It provides real-time, reliable delivery of a packet, while considering energy awareness. In EARQ, a node estimates the energy cost, delay and reliability of a path to the sink node, based only on information from neighboring nodes. Then, it calculates the probability of selecting a path, using the estimates. When packet forwarding is required, it randomly selects the next node. A path with lower energy cost is likely to be selected, because the probability is inversely proportional to the energy cost to the sink node. To achieve real-time delivery, only paths that may deliver a packet in time are selected. To achieve reliability, it may send a redundant packet via an alternate path, but only if it is a source of a packet. Experimental results show that EARQ is suitable for industrial applications, due to its capability for energy efficient, real-time, reliable communications.