Showing papers on "Multipath routing published in 2008"

The vehicle routing problem : latest advances and new challenges

Abstract: Overviews and Surveys- Routing a Heterogeneous Fleet of Vehicles- A Decade of Capacitated Arc Routing- Inventory Routing- The Period Vehicle Routing Problem and its Extensions- The Split Delivery Vehicle Routing Problem: A Survey- Challenges and Advances in A Priori Routing- Metaheuristics for the Vehicle Routing Problem and Its Extensions: A Categorized Bibliography- Parallel Solution Methods for Vehicle Routing Problems- Recent Developments in Dynamic Vehicle Routing Systems- New Directions in Modeling and Algorithms- Online Vehicle Routing Problems: A Survey- Modeling and Solving the Capacitated Vehicle Routing Problem on Trees- Using a Genetic Algorithm to Solve the Generalized Orienteering Problem- An Integer Linear Programming Local Search for Capacitated Vehicle Routing Problems- Robust Branch-Cut-and-Price Algorithms for Vehicle Routing Problems- Recent Models and Algorithms for One-to-One Pickup and Delivery Problems- One-to-Many-to-One Single Vehicle Pickup and Delivery Problems- Challenges and Opportunities in Attended Home Delivery- Chvatal-Gomory Rank-1 Cuts Used in a Dantzig-Wolfe Decomposition of the Vehicle Routing Problem with Time Windows- Vehicle Routing Problems with Inter-Tour Resource Constraints- From Single-Objective to Multi-Objective Vehicle Routing Problems: Motivations, Case Studies, and Methods- Practical Applications- Vehicle Routing for Small Package Delivery and Pickup Services- Advances in Meter Reading: Heuristic Solution of the Close Enough Traveling Salesman Problem over a Street Network- Multiperiod Planning and Routing on a Rolling Horizon for Field Force Optimization Logistics- Health Care Logistics, Emergency Preparedness, and Disaster Relief: New Challenges for Routing Problems with a Focus on the Austrian Situation- Vehicle Routing Problems and Container Terminal Operations - An Update of Research

Regional congestion awareness for load balance in networks-on-chip

Abstract: Interconnection networks-on-chip (NOCs) are rapidly replacing other forms of interconnect in chip multiprocessors and system-on-chip designs. Existing interconnection networks use either oblivious or adaptive routing algorithms to determine the route taken by a packet to its destination. Despite somewhat higher implementation complexity, adaptive routing enjoys better fault tolerance characteristics, increases network throughput, and decreases latency compared to oblivious policies when faced with non-uniform or bursty traffic. However, adaptive routing can hurt performance by disturbing any inherent global load balance through greedy local decisions. To improve load balance in adapting routing, we propose Regional Congestion Awareness (RCA), a lightweight technique to improve global network balance. Instead of relying solely on local congestion information, RCA informs the routing policy of congestion in parts of the network beyond adjacent routers. Our experiments show that RCA matches or exceeds the performance of conventional adaptive routing across all workloads examined, with a 16% average and 71% maximum latency reduction on SPLASH-2 benchmarks running on a 49-core CMP. Compared to a baseline adaptive router, RCA incurs a negligible logic and modest wiring overhead.

An overview of routing optimization for internet traffic engineering

Abstract: Traffic engineering is an important mechanism for Internet network providers seeking to optimize network performance and traffic delivery. Routing optimization plays a key role in traffic engineering, finding efficient routes so as to achieve the desired network performance. In this survey we review Internet traffic engineering from the perspective of routing optimization. A taxonomy of routing algorithms in the literature is provided, dating from the advent of the TE concept in the late 1990s. We classify the algorithms into multiple dimensions: unicast/multicast, intra-/inter- domain, IP-/MPLS-based and offline/online TE schemes. In addition, we investigate some important traffic engineering issues, including robustness, TE interactions, and interoperability with overlay selfish routing. In addition to a review of existing solutions, we also point out some challenges in TE operation and important issues that are worthy of investigation in future research activities.

Multiconstrained QoS multipath routing in wireless sensor networks

Abstract: Sensor nodes are densely deployed to accomplish various applications because of the inexpensive cost and small size. Depending on different applications, the traffic in the wireless sensor networks may be mixed with time-sensitive packets and reliability-demanding packets. Therefore, QoS routing is an important issue in wireless sensor networks. Our goal is to provide soft-QoS to different packets as path information is not readily available in wireless networks. In this paper, we utilize the multiple paths between the source and sink pairs for QoS provisioning. Unlike E2E QoS schemes, soft-QoS mapped into links on a path is provided based on local link state information. By the estimation and approximation of path quality, traditional NP-complete QoS problem can be transformed to a modest problem. The idea is to formulate the optimization problem as a probabilistic programming, then based on some approximation technique, we convert it into a deterministic linear programming, which is much easier and convenient to solve. More importantly, the resulting solution is also one to the original probabilistic programming. Simulation results demonstrate the effectiveness of our approach.

Implementation and Analysis of a New Selection Strategy for Adaptive Routing in Networks-on-Chip

Abstract: Efficient and deadlock-free routing is critical to the performance of networks-on-chip. The effectiveness of any adaptive routing algorithm strongly depends on the underlying selection strategy. A selection function is used to select the output channel where the packet will be forwarded on. In this paper we present a novel selection strategy that can be coupled with any adaptive routing algorithm. The proposed selection strategy is based on the concept of Neighbors-on-Path the aims of which is to exploit the situations of indecision occurring when the routing function returns several admissible output channels. The overall objective is to choose the channel that will allow the packet to be routed to its destination along a path that is as free as possible of congested nodes. Performance evaluation is carried out by using a flit-accurate simulator under traffic scenarios generated by both synthetic and real applications. Results obtained show how the proposed selection strategy applied to the Odd-Even routing algorithm yields an improvement in both average delay and saturation point up to 20% and 30% on average respectively, with a minimal overhead in terms of area occupation. In addition, a positive effect on total energy consumption is also observed under near-congestion packet injection rates.

Toward internet-wide multipath routing

Abstract: The Internet would be more efficient and robust if routers could flexibly divide traffic over multiple paths. Often, having one or two extra paths is sufficient for customizing paths for different applications, improving security, reacting to failures, and balancing load. However, support for Internet-wide multipath routing faces two significant barriers. First, multipath routing could impose significant computational and storage overhead in a network the size of the Internet. Second, the independent networks that comprise the Internet will not relinquish control over the flow of traffic without appropriate incentives. In this article, we survey flexible multipath routing techniques that are both scalable and incentive compatible. Techniques covered include: multihoming, tagging, tunneling, and extensions to existing Internet routing protocols.

Distributed energy-efficient cooperative routing in wireless networks

Abstract: Recently, the merits of cooperative communication in the physical layer have been explored. However, the impact of cooperative communication on the design of the higher layers has not been well-understood yet. Cooperative routing in wireless networks has gained much interest due to its ability to exploit the broadcast nature of the wireless medium in designing power efficient routing algorithms. Most of the existing cooperation based routing algorithms are implemented by finding a shortest path route first and then improving the route using cooperative communication. As such, these routing algorithms do not fully exploit the merits of cooperative communications, since the optimal cooperative route might not be similar to the shortest path route. In this paper, we propose a cooperation-based routing algorithm, namely, the minimum power cooperative routing (MPCR) algorithm, which makes full use of the cooperative communications while constructing the minimum-power route. The MPCR algorithm constructs the minimum-power route, which guarantees certain throughput, as a cascade of the minimum-power single-relay building blocks from the source to the destination. Thus, any distributed shortest path algorithm can be utilized to find the optimal cooperative route with polynomial complexity. Using analysis, we show that the MPCR algorithm can achieve power saving of 65.61% in regular linear networks and 29.8% in regular grid networks compared to the existing cooperation-based routing algorithms, where the cooperative routes are constructed based on the shortest-path routes. From simulation results, MPCR algorithm can have 37.64% power saving in random networks compared to those cooperation-based routing algorithms.

Interference-Minimized Multipath Routing with Congestion Control in Wireless Sensor Network for High-Rate Streaming

Abstract: High-rate streaming in WSN is required for future applications to provide high-quality information of battlefield hot spots. Although recent advances have enabled large-scale WSN to be deployed supported by high-bandwidth backbone network for high-rate streaming, the WSN remains the bottleneck due to the low-rate radios used and the effects of wireless interferences. First, we propose a technique to evaluate the quality of a pathset for multipath load balancing, taking into consideration the effects of wireless interferences and that nodes may interfere beyond communication ranges. Second, we propose an interference- minimized multipath routing (I2MR) protocol that increases throughput by discovering zone-disjoint paths for load balancing, requiring minimal localization support. Third, we propose a congestion control scheme that further increases throughput by loading the paths for load balancing at the highest possible rate supportable. Finally, we validate thepath-set evaluation technique and also evaluate the I2MR protocol and congestion control scheme by comparing with AODV protocol and node-disjoint multipath routing (NDMR) protocol. Simulation results show that I2MR with congestion control achieves on average 230% and 150% gains in throughput over AODV and NDMR respectively, and consumes comparable or at most 24% more energy than AODV but up to 60% less energy than NDMR.

Optimal routing and data aggregation for maximizing lifetime of wireless sensor networks

Abstract: An optimal routing and data aggregation scheme for wireless sensor networks is proposed in this paper. The objective is to maximize the network lifetime by jointly optimizing data aggregation and routing. We adopt a model to integrate data aggregation with the underlying routing scheme and present a smoothing approximation function for the optimization problem. The necessary and sufficient conditions for achieving the optimality are derived and a distributed gradient algorithm is designed accordingly. We show that the proposed scheme can significantly reduce the data traffic and improve the network lifetime. The distributed algorithm can converge to the optimal value efficiently under all network configurations.

Ad hoc networks beyond unit disk graphs

Abstract: In this paper, we study an algorithmic model for wireless ad hoc and sensor networks that aims to be sufficiently close to reality as to represent practical real-world networks while at the same time being concise enough to promote strong theoretical results The quasi unit disk graph model contains all edges shorter than a parameter d between 0 and 1 and no edges longer than 1 We show that--in comparison to the cost known for unit disk graphs--the complexity results of geographic routing in this model contain the additional factor 1/d2 We prove that in quasi unit disk graphs flooding is an asymptotically message-optimal routing technique, we provide a geographic routing algorithm being most efficient in dense networks, and we show that classic geographic routing is possible with the same asymptotic performance guarantees as for unit disk graphs if d ≥ 1/√2

The impact of spatial correlation on routing with compression in wireless sensor networks

Abstract: The efficacy of data aggregation in sensor networks is a function of the degree of spatial correlation in the sensed phenomenon. The recent literature has examined a variety of schemes that achieve greater data aggregation by routing data with regard to the underlying spatial correlation. A well known conclusion from these papers is that the nature of optimal routing with compression depends on the correlation level. In this article we show the existence of a simple, practical, and static correlation-unaware clustering scheme that satisfies a min-max near-optimality condition. The implication for system design is that a static correlation-unaware scheme can perform as well as sophisticated adaptive schemes for joint routing and compression.

Design Guidelines for Routing Metrics in Multihop Wireless Networks

Abstract: The design of a routing protocol must be based on the characteristics of its target networks. The diversity of wireless networks motivates the design of different routing metrics, capturing different aspects of wireless communications. The design of routing metrics, however, is not arbitrary since it has a great impact on the proper operation of routing protocols. Combining a wrong type of routing metrics with a routing protocol may result in routing loops and suboptimal paths. In this paper, we thoroughly study the relationship between routing metrics and routing protocols. Our work provides important guidelines for designing routing metrics and identifies the specific properties that a routing metric must have in order to be combined with certain type of routing protocols.

A tabu search algorithm for the periodic vehicle routing problem with multiple vehicle trips and accessibility restrictions

Abstract: In this paper, we consider a periodic vehicle routing problem that includes, in addition to the classical constraints, the possibility of a vehicle doing more than one route per day, as long as the maximum daily operation time for the vehicle is not exceeded. In addition, some constraints relating to accessibility of the vehicles to the customers, in the sense that not every vehicle can visit every customer, must be observed. We refer to the problem we consider here as the site-dependent multi-trip periodic vehicle routing problem. An algorithm based on tabu search is presented for the problem and computational results presented on randomly generated test problems that are made publicly available. Our algorithm is also tested on a number of routing problems from the literature that constitute particular cases of the proposed problem. Specifically we consider the periodic vehicle routing problem; the site-dependent vehicle routing problem; the multi-trip vehicle routing problem; and the classical vehicle routing problem. Computational results for our tabu search algorithm on test problems taken from the literature for all of these problems are presented.

Randomized 3D Geographic Routing

Abstract: We reconsider the problem of geographic routing in wireless ad hoc networks. We are interested in local, memoryless routing algorithms, i.e. each network node bases its routing decision solely on its local view of the network, nodes do not store any message state, and the message itself can only carry information about O(1) nodes. In geographic routing schemes, each network node is assumed to know the coordinates of itself and all adjacent nodes, and each message carries the coordinates of its target. Whereas many of the aspects of geographic routing have already been solved for 2D networks, little is known about higher-dimensional networks. It has been shown only recently that there is in fact no local memoryless routing algorithm for 3D networks that delivers messages deterministically. In this paper, we show that a cubic routing stretch constitutes a lower bound for any local memoryless routing algorithm, and propose and analyze several randomized geographic routing algorithms which work well for 3D network topologies. For unit ball graphs, we present a technique to locally capture the surface of holes in the network, which leads to 3D routing algorithms similar to the greedy-face-greedy approach for 2D networks.

Routing in a cyclic mobispace

Abstract: A key challenge of routing in delay tolerant networks (DTNs) is finding routes that have high delivery rates and low end-to-end delays. When oracles are not available for future connectivity, opportunistic routing is preferred in DTNs, in which messages are forwarded to nodes with higher delivery probabilities. We observe that real objects have repetitive motions, but no prior research work has investigated the cyclic delivery probability of messages between nodes. In this paper, we propose to use the expected minimum delay (EMD) as a new delivery probability metric in DTNs with repetitive but non-deterministic mobility. Specifically, we model the network as a probabilistic time-space graph with historical contact information or prior knowledge about the network. We then translate it into a probabilistic state-space graph in which the time dimension is removed. Finally, we apply the Markov decision process to derive the EMDs of the messages at particular times. Our proposed EMD-based routing protocol, called routing in cyclic MobiSpace (RCM), outperforms several existing opportunistic routing protocols when simulated using both real and synthetic traces.

An algorithmic approach to geographic routing in ad hoc and sensor networks

Abstract: The one type of routing in ad hoc and sensor networks that currently appears to be most amenable to algorithmic analysis is geographic routing. This paper contains an introduction to the problem field of geographic routing, presents a specific routing algorithm based on a synthesis of the greedy forwarding and face routing approaches, and provides an algorithmic analysis of the presented algorithm from both a worst-case and an average-case perspective.

Survey on routing protocols for wireless sensor networks

Abstract: This paper presented the problems and challenges of routing protocols by the analysis and comparison of typical flat and hierarchical routing protocols.Finally,summaried the important features that ideal routing protocols possess as well as its future research strategies and trends.

Synopsis diffusion for robust aggregation in sensor networks

Abstract: Previous approaches for computing duplicate-sensitive aggregates in wireless sensor networks have used a tree topology, in order to conserve energy and to avoid double-counting sensor readings. However, a tree topology is not robust against node and communication failures, which are common in sensor networks. In this article, we present synopsis diffusion, a general framework for achieving significantly more accurate and reliable answers by combining energy-efficient multipath routing schemes with techniques that avoid double-counting. Synopsis diffusion avoids double-counting through the use of order- and duplicate-insensitive (ODI) synopses that compactly summarize intermediate results during in-network aggregation. We provide a surprisingly simple test that makes it easy to check the correctness of an ODI synopsis. We show that the properties of ODI synopses and synopsis diffusion create implicit acknowledgments of packet delivery. Such acknowledgments enable energy-efficient adaptation of message routes to dynamic message loss conditions, even in the presence of asymmetric links. Finally, we illustrate using extensive simulations the significant robustness, accuracy, and energy-efficiency improvements of synopsis diffusion over previous approaches.

MaizeRouter : Engineering an Effective Global Router

Abstract: In this paper, we present the complete design and architectural details of MaizeRouter. MaizeRouter reflects a significant leap in progress over existing publicly available routing tools yet relies upon relatively simple operations, including extreme edge shifting, a technique aimed primarily at the efficient reduction of routing congestion, and edge retraction, a counterpart to extreme edge shifting that serves to reduce unnecessary wirelength. We present enhanced variations of these operations to enable the rapid exploration of candidate paths, along with a form of dynamic cost deflation that provides our various path computation procedures with progressively more accurate (and less optimistic) cost information as search continues. These algorithmic contributions are built upon a framework of interdependent net decomposition, a representation that improves upon traditional two-pin net decomposition by preventing duplication of routing resources while enabling cheap and incremental topological reconstruction. Collectively, these operations permit a broad search space that previous algorithms have been unable to achieve, resulting in solutions of considerably higher quality than those of well-established routers.

BioRoute: A Network-Flow-Based Routing Algorithm for the Synthesis of Digital Microfluidic Biochips

Abstract: Due to recent advances in microfluidics, digital microfluidic biochips are expected to revolutionize laboratory procedures. One critical problem for biochip synthesis is the droplet routing problem. Unlike traditional very large scale integration routing problems, in addition to routing path selection, the biochip routing problem needs to address the issue of scheduling droplets under practical constraints imposed by the fluidic property and timing restriction of synthesis results. In this paper, we present the first network-flow-based routing algorithm that can concurrently route a set of noninterfering nets for the droplet routing problem on biochips. We adopt a two-stage technique of global routing followed by detailed routing. In global routing, we first identify a set of noninterfering nets and then adopt the network-flow approach to generate optimal global-routing paths for nets. In detailed routing, we present the first polynomial-time algorithm for simultaneous routing and scheduling using the global-routing paths with a negotiation-based routing scheme. Our algorithm targets at both the minimization of cells used for routing for better fault tolerance and minimization of droplet transportation time for better reliability and faster bioassay execution. Experimental results show the robustness and efficiency of our algorithm.

Efficient unicast and multicast support for CMPs

Abstract: Beyond a certain number of cores, multi-core processing chips will require a network-on-chip (NoC) to interconnect the cores and overcome the limitations of a bus. NoCs must be carefully designed to meet constraints like power consumption, area, and ultra low latencies. Although 2D meshes with DOR (dimension-order-routing) meet these constraints, the need for partitioning (e.g. virtual machines, coherency domains) and traffic isolation may prevent the use of DOR routing. Also, core heterogeneity and manufacturing and run-time faults may lead to partially irregular topologies. Routing in these topologies is complex, and previously proposed solutions required routing tables, which drastically increase power consumption, area, and latency. The exception is LBDR (logic-based distributed routing), a flexible routing method for irregular topologies that removes the need for using routing tables (both at end-nodes and switches), thus achieving large savings in chip area and power consumption. But LBDR lacks support for multicast and broadcast, which are required to efficiently support cache coherence protocols both for single and multiple coherence domains. In this paper we propose bLBDR, an efficient multicast and broadcast mechanism built on top of LBDR. bLBDR performs multicast operations using a logic-based broadcast within a domain (a region with bounds). This allows us to isolate the traffic into different domains, thus enabling the concept of visualization at the NoC level. Also, bLBDR extends the concept of routing regions in LBDR by providing a mechanism that allows the flexible definition of multiple domains, sets of network resources. bLBDR fulfills all the practical requirements, including not only low latency and power and area efficiency, but also support for visualization, partitionability, fault-tolerance, traffic isolation and broadcast across the entire network as well as constrained to coherency domains or regions. All this is achieved by a small and power efficient routing logic (7times area savings and 17times power reduction when compared to a routing table in an 8 times 8 mesh network).

Energy Constrained Multipath Routing in Wireless Sensor Networks

Abstract: This paper addresses the issue of Quality of Service (QoS) Routing to improve energy consumption in wireless sensor networks (WSNs). Building upon a previously proposed QoS provisioning benchmark model, we formulate the problem of routing sensed information in a WSN network as a path-based energy minimization problem subject to QoS routing constraints expressed in terms of reliability, delay and geo-spatial energy consumption. Using probabilistic approximations, we transform the path-based model into a link-based model and apply methods borrowed from the zero-one optimization framework to solve this problem. By comparing the performance achieved by its solution to the benchmark model, simulation results reveal that our model outperforms the benchmark model in terms of energy consumption and quality of paths used to route the sensed information.

Optimized Multipath Network Coding in Lossy Wireless Networks

Abstract: Network coding has been a prominent approach to a series of problems that used to be considered intractable with traditional transmission paradigms. Recent work on network coding includes a substantial number of optimization based protocols, but mostly for wireline multicast networks. In this paper, we consider maximizing the benefits of network coding for unicast sessions in lossy wireless environments. We propose Optimized Multipath Network Coding (OMNC), a rate control and routing protocol that dramatically improves the throughput of lossy wireless networks. OMNC employs multiple paths to push coded packets to the destination, and uses the broadcast MAC to deliver packets between neighboring nodes. The coding and broadcast rate is allocated to transmitters by a distributed optimization algorithm that maximizes the advantage of path diversity while avoiding congestion. With extensive experiments on an emulation testbed, we find that OMNC achieves significant throughput improvement over traditional best path routing protocols, and existing multipath routing protocols with network coding.

Robust cooperative routing protocol in mobile wireless sensor networks

Abstract: In wireless sensor networks, path breakage occurs frequently due to node mobility, node failure, and channel impairments It is challenging to combat path breakage with minimal control overhead, while adapting to rapid topological changes Due to the Wireless Broadcast Advantage (WBA), all nodes inside the transmission range of a single transmitting node may receive the packet, hence naturally they can serve as cooperative caching and backup nodes if the intended receiver fails to receive the packet In this paper, we present a distributed robust routing protocol in which nodes work cooperatively to enhance the robustness of routing against path breakage We compare the energy efficiency of cooperative routing with noncooperative routing and show that our robust routing protocol can significantly improve robustness while achieving considerable energy efficiency

Maximally radio-disjoint multipath routing for wireless multimedia sensor networks

Abstract: In wireless sensor networks, bandwidth is one of precious resources to multimedia applications. To get more bandwidth, multipath routing is one appropriate solution provided that inter-path interferences are minimized. In this paper, we address the problem of interfering paths in the context of wireless multimedia sensor networks and consider both intra-session as well as inter-session interferences. Our main objective is to provide necessary bandwidth to multimedia applications through non-interfering paths while increasing the network lifetime. To do so, we adopt an incremental approach where for a given session, only one path is built at once. Additional paths are built when requi red, typically in case of congestion or bandwidth shortage. Interference awareness and energy saving are achieved by switching a subset of sensor nodes in a passive state in which they do not take part in the routing process. Despite the routing overhead introduced by the incremental approach we adopt, our simulations show that this can be compensated by the overall achieved throughput and the amount of consumed energy per correctly received packet especially for relatively long sessions such as multimedia ones. This is mainly due to the fact that a small number of non-interfering paths allows for better performances than a large number of interfering ones.

Dice: a game theoretic framework for wireless multipath network coding

Abstract: Network coding has emerged as a promising approach that enables reliable and efficient end-to-end transmissions in lossy wireless mesh networks. Existing protocols have demonstrated its resilience to packet losses, as well as the ability to integrate naturally with multipath opportunistic routing. However, these heuristics do not take into account the inherent resource competition in wireless networks, thereby compromising the coding advantages. In this paper, we take a game-theoretic perspective towards optimized resource allocation for network coding based unicast protocols. We design decentralized mechanisms that achieve better efficiency-fairness tradeoff, for both cooperative and selfish users. Our framework features a modularized optimization of two subproblems: the multipath routing of coded information flows for each player, and the broadcast and coding rate allocation among competing players. We have implemented the framework on a wireless emulation testbed and demonstrated its high performance in terms of throughput and fairness.

A fault-aware dynamic routing algorithm for on-chip networks

Abstract: Given the spatial and temporal randomness of soft and permanent errors in the state-of-the-art system-on-chips (SoCs), dynamic routing algorithms that can adapt themselves accordingly are highly required for network-on-chip (NoC) applications. In this paper, we present a new dynamic routing algorithm for NoC applications that has the ability to locate and deal with both static and dynamic permanent failures and distinguish them from soft errors. In addition, our presented algorithm has the advantage of distributing the load over the whole network by considering the stress factors. Simulation results demonstrate the advantage of our routing algorithm in terms of functionality, latency, and energy consumption compared to directed flooding based fault tolerant routing algorithms in the presence of both soft errors and permanent faults. Our algorithm can achieves 1.95 times less latency and consumes 3.15 times less energy consumption on average.

Logic-Based Distributed Routing for NoCs

Abstract: The design of scalable and reliable interconnection networks for multicore chips (NoCs) introduces new design constraints like power consumption, area, and ultra low latencies. Although 2D meshes are usually proposed for NoCs, heterogeneous cores, manufacturing defects, hard failures, and chip virtualization may lead to irregular topologies. In this context, efficient routing becomes a challenge. Although switches can be easily configured to support most routing algorithms and topologies by using routing tables, this solution does not scale in terms of latency and area. We propose a new circuit that removes the need for using routing tables. The new mechanism, referred to as logic-based distributed routing (LBDR), enables the implementation in NoCs of many routing algorithms for most of the practical topologies we might find in the near future in a multicore chip. From an initial topology and routing algorithm, a set of three bits per switch output port is computed. By using a small logic block, LHDR mimics (demonstrated by evaluation) the behavior of routing algorithms implemented with routing tables. This result is achieved both in regular and irregular topologies. Therefore, LBDR removes the need for using routing tables for distributed routing, thus enabling flexible, fast and power-efficient routing in NoCs.

Cooperative Routing in Multi-Source Multi-Destination Multi-Hop Wireless Networks

Abstract: In a network supporting cooperative communication, the sender of a transmission is no longer a single node, which causes the concept of a traditional link to be reinvestigated. Thus, the routing scheme basing on the link concept should also be reconsidered to ";truly"; exploit the potential performance gain introduced by cooperative communication. In this paper, we investigate the joint problem of routing selection in network layer and contention avoidance among multiple links in MAC layer for multi-hop wireless networks in a cooperative communication aware network. To the best of our knowledge, it is the first work to investigate the problem of cooperative communication aware routing in multi-source multi-destination multi-hop wireless networks. Several important concepts, including virtual node, virtual link and virtual link based contention graph are introduced. Basing on those concepts, an optimal cooperative routing is achieved and a distributed routing scheme is proposed after some practical approximations. The simulation results show that our scheme reduces the total transmission power comparing with non-cooperative routing and greatly increases the network throughput comparing with single flow cooperative routings.