Advances in CMOS-compatible photonic elements have made it plausible to exploit nanophotonic communications to overcome the limitations of traditional NoCs. Amongst various proposed nanophotonic architectures, optical crossbars have been shown to provide high performance in terms of bandwidth and latency. In general, optical crossbars provide a vast volume of network resources that are shared among all the cores within the chip. In this paper, we present a fair and efficient admission control mechanism for shared wavelengths and buffer space in optical crossbars. We model buffer management and wavelength assignment as a utility-based convex optimization problem, whose solution determines the admission control policy. Thanks to efficient convex optimization techniques, we obtain the globally optimal solution of the admission control optimization problem by using simple and yet efficient iterative algorithms. We cast our solution procedure as an iterative algorithm to be implemented a central admission controller. Our experimental results corroborate the gain that can be obtained by using such an admission controller to manage the shared resources of the system. Furthermore, they confirm that the proposed admission control algorithm works well for various traffic patterns and parameters, and evinces a tractable scalability with increase in the number of cores of the crossbar.
is an all-optical crossbar topology, proposed by @cite_39 , which implements a crossbar consisting of Multiple Write, Single Read (MWSR) shared busses. Each bus is dedicated exclusively to one node for receiving data, whereas all nodes can write data on all busses. Corona takes advantage of an optical token-based arbitration mechanism to resolve contention among nodes for sending data on the same bus. To address the fairness issues, a fair token slot mechanism is presented in @cite_38 . @cite_8 employ MWSR token-ring busses of Corona to implement rows and columns of an optical 2D torus, and modified the token-based arbitration scheme so as to support virtual channel flow control.
@cite_38 @cite_8 @cite_39
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Future chip multi-processors (CMPs) will require high-performance yet low-energy networks-on-chip to provide scalable communication for the increasing number of cores. CMOS-compatible nanophotonic interconnects have recently emerged as a promising candidate for replacing traditional electrical network-on-chip, by providing high bandwidth chip-wide communication at low latency and power. In this paper, we utilize the emerging nanophotonic technology and propose RCBus, an optical network-on-chip topology in which multiple nanophotonic buses are uniformly distributed in each row and column of a two-dimensional torus network. Each bus employs a dense-wavelength-division-multiplexing optical waveguide to enable high-bandwidth express traversal along each dimension. We use multiple write single-read schemes and virtual channel based token protocol to implement light-speed arbitration and flow control. The optical-electrical interface is also studied in the paper. The proposed optical network-on-chip can exploit the advantages of both photonic bus and direct torus topology. Simulation results under synthetic and real-world application traffic show that RCBus is 2X better in terms of performance than the electrical mesh network-on-chip while saving nearly 30 power, and achieves on average 24 throughput improvement at much lower cost compared to the state-of-the-art optical network. DOI: http: dx.doi.org 10.5755 j01.eee.18.8.2633 This paper proposes CoNoC (Contention-free optical NoC) as a new architecture for on-chip routing of optical packets. CoNoC is built upon all-optical switches (AOSs) which passively route optical data streams based on their wavelengths. The key idea of the proposed architecture is the utilization of per-receiver wavelength in the data network to prevent optical contention at the intermediate nodes. Routing optical packets according to their wavelength eliminates the need for resource reservation at the intermediate nodes and the corresponding latency, power, and area overheads. Since passive architecture of the AOS confines the optical contention to the end-points, we propose an electrical arbitration architecture for resolving optical contention at the destination nodes. By performing a series of simulations, we study the efficiency of the proposed architecture, its power and energy consumption, and the data transmission latency. Moreover, we compare the proposed architecture with electrical NoCs and alternative ONoC architectures under various synthetic traffic patterns. Averaged across different traffic patterns, the proposed architecture reduces per-packet power consumption by 19 , 28 , 29 , and 91 and achieves per-packet energy reduction of 28 , 40 , 20 , and 99 over Columbia, Phastlane, @l-router, and electrical torus, respectively. In this paper, we investigate random walk based token circulation in dynamic environments subject to faults. We describe hypotheses on the dynamic environment that allow random walks to meet the important property that the token visits any node infinitely often. The randomness of this scheme allows it to work on any topology, and requires no adaptation after a topological change, which is a desirable property for applications to dynamic systems. For random walks to be a traversal scheme and to solve the concurrency problem, one needs to guarantee that exactly one token circulates in the system. In the presence of transient faults, configurations with multiple tokens or with no token can occur. The meeting property of random walks solves the cases with multiple tokens. The reloading wave mechanism we propose, together with timeouts, allows us to detect and solve cases with no token. This traversal scheme is self-stabilizing, and universal, meaning that it needs no assumption on the system topology. We describe conditions on the dynamicity (with a local detection criterion) under which the algorithm is tolerant to dynamic reconfigurations. We conclude with a study on the time between two visits of the token to a node, which we use to tune the parameters of the reloading wave mechanism according to some system characteristics. This paper presents an analysis of the following load balancing algorithm. At each step, each node in a network examines the number of tokens at each of its neighbors and sends a token to each neighbor with at least 2d+1 fewer tokens, where d is the maximum degree of any node in the network. We show that within @math steps, the algorithm reduces the maximum difference in tokens between any two nodes to at most @math , where @math is the global imbalance in tokens (i.e., the maximum difference between the number of tokens at any node initially and the average number of tokens), n is the number of nodes in the network, and @math is the edge expansion of the network. The time bound is tight in the sense that for any graph with edge expansion @math , and for any value @math , there exists an initial distribution of tokens with imbalance @math for which the time to reduce the imbalance to even @math is at least @math . The bound on the final imbalance is tight in the sense that there exists a class of networks that can be locally balanced everywhere (i.e., the maximum difference in tokens between any two neighbors is at most 2d), while the global imbalance remains @math . Furthermore, we show that upon reaching a state with a global imbalance of @math , the time for this algorithm to locally balance the network can be as large as @math . We extend our analysis to a variant of this algorithm for dynamic and asynchronous networks. We also present tight bounds for a randomized algorithm in which each node sends at most one token in each step. The many cores design research community have shown high interest in optical crossbars on chip for more than a decade. Key properties of optical crossbars, namely a) contention free data routing b) low latency communication and c) potential for high bandwidth through the use of WDM, motivate several implementations of this type of interconnect. These implementations demonstrate very different scalability and power efficiency ability depending on three key design factors: a) the network topology, b) the considered layout and the c) the injection losses induced by the fabrication process. In this paper, the worst-case optical losses of crossbar implementations are compared according to the factors mentioned above. The comparison results has the potential to help many cores system designer to select the most appropriate crossbar implementation according, for instance, to the number of IP cores and the chip die size. We identify and present a major interaction approach for tangible user interfaces based upon systems of tokens and constraints. In these interfaces, tokens are discrete physical objects which represent digital information. Constraints are confining regions that are mapped to digital operations. These are frequently embodied as structures that mechanically channel how tokens can be manipulated, often limiting their movement to a single degree of freedom. Placing and manipulating tokens within systems of constraints can be used to invoke and control a variety of computational interpretations.We discuss the properties of the token+constraint approach; consider strengths that distinguish them from other interface approaches; and illustrate the concept with eleven past and recent supporting systems. We present some of the conceptual background supporting these interfaces, and consider them in terms of 's [2002] five questions for sensing-based interaction. We believe this discussion supports token+constraint systems as a powerful and promising approach for sensing-based interaction. In this paper, we present a reservation-based medium access control (MAC) protocol with multicast support for wavelength-division multiplexing networks. Our system is based on the single-hop, passive optical star architecture. Of the available wavelengths (channels), one channel is designated as a control channel, and the remaining channels are used for data transmission. Each node is equipped with a pair of fixed transceiver to access the control channel, and a fixed transmitter and a tunable receiver to access data channels. For easy implementation of the protocol in hardware and for precisely computing the protocol's processing overhead, we give a register-transfer model of the protocol. We simulate the protocol to study its throughput behavior, and present its analytic model. For a node to be able to send data packets in successive data slots with no time gap between them, in spite of the situation that the protocol's execution time may be longer than data transmission time, we propose the idea of multiple MAC units at each node. Unicast throughput of our protocol reaches the theoretically possible maximum throughput for MAC protocols with distributed control, and the multicast throughput is at least as good as, and even better than, those delivered by existing MAC protocols with distributed control. RFID-based tokens are increasingly used in electronic payment and ticketing systems for mutual authentication of tickets and terminals. These systems typically use cost-effective tokens without expensive hardware protection mechanisms and are exposed to hardware attacks that copy and maliciously modify tokens. Physically Unclonable Functions (PUFs) are a promising technology to protect against such attacks by binding security critical data to the physical characteristics of the underlying hardware. However, existing PUF-based authentication schemes for RFID do not support mutual authentication, are often vulnerable to emulation and denial-of service attacks, and allow only for a limited number of authentications. Abstract A transportation graph is a directed graph with a designated input node and a designated output node. Initially, the input node contains an ordered set of tokens 1,2,3, … The tokens are removed from the input node in this order and transferred through the graph to the output node in a series of moves; each move transfers a token from a node to an adjacent node. Two or more tokens cannot reside on an internal node simultaneously. When the tokens arrive at the output node they will appear in a permutation of their original order. The main result is a description of the possible arrival permutations in terms of regular sets. This description allows the number of arrival permutations of each length to be computed. The theory is then applied to packet-switching networks and has implications for the resequencing problem. It is also applied to some complex data structures and extends previously known results to the case that the data structures are of bounded capacity. A by-product of this investigation is a new proof that permutations which avoid the pattern 321 are in one to one correspondence with those that avoid 312. We use network coding to improve the speed of distributed computation in the dynamic network model of Kuhn, Lynch and Oshman [STOC '10]. In this model an adversary adaptively chooses a new network topology in every round, making even basic distributed computations challenging. show that n nodes, each starting with a d-bit token, can broadcast them to all nodes in time O(n2) using b-bit messages, where b > d + log n. Their algorithms take the natural approach of token forwarding: in every round each node broadcasts some particular token it knows. They prove matching Ω(n2) lower bounds for a natural class of token forwarding algorithms and an Ω(n log n) lower bound that applies to all token-forwarding algorithms. We use network coding, transmitting random linear combinations of tokens, to break both lower bounds. Our algorithm's performance is quadratic in the message size b, broadcasting the n tokens in roughly d b2 * n2 rounds. For b = d = Θ(log n) our algorithms use O(n2 log n) rounds, breaking the first lower bound, while for larger message sizes we obtain linear-time algorithms. We also consider networks that change only every T rounds, and achieve an additional factor T2 speedup. This contrasts with related lower and upper bounds of implying that for natural token-forwarding algorithms a speedup of T, but not more, can be obtained. Lastly, we give a general way to derandomize random linear network coding, that also leads to new deterministic information dissemination algorithms. We expect that many-core microprocessors will push performance per chip from the 10 gigaflop to the 10 teraflop range in the coming decade. To support this increased performance, memory and inter-core bandwidths will also have to scale by orders of magnitude. Pin limitations, the energy cost of electrical signaling, and the non-scalability of chip-length global wires are significant bandwidth impediments. Recent developments in silicon nanophotonic technology have the potential to meet these off- and on-stack bandwidth requirements at acceptable power levels. Corona is a 3D many-core architecture that uses nanophotonic communication for both inter-core communication and off-stack communication to memory or I O devices. Its peak floating-point performance is 10 teraflops. Dense wavelength division multiplexed optically connected memory modules provide 10 terabyte per second memory bandwidth. A photonic crossbar fully interconnects its 256 low-power multithreaded cores at 20 terabyte per second bandwidth. We have simulated a 1024 thread Corona system running synthetic benchmarks and scaled versions of the SPLASH-2 benchmark suite. We believe that in comparison with an electrically-connected many-core alternative that uses the same on-stack interconnect power, Corona can provide 2 to 6 times more performance on many memory intensive workloads, while simultaneously reducing power. This paper reports our implementation of the Virtual Corpus approach to deriving ngram statistics for ngrams of any length from large-scale corpora based on the suffix array data structure. In order to enable the VC to accommodate corpora with a vocabulary of different size, we first convert corpus tokens into integer codes. To accelerate the processing, we employ a bucket-radixsort for sorting the VC indices (or pointers, each of which represents a sequence of corpus tokens from its position to the end of the corpus). The time complexity of the sorting algorithm is of O(N log n N) in token code comparisons. Chip multiprocessor (CMP) is becoming an attractive platform for applications seeking both high performance and high energy efficiency. In large-scale CMPs, the communication efficiency among cores is crucial for the overall system performance and energy consumption. In this article, we propose a ring-based optical network-on-chip, called SUOR, to fulfill the communication requirement of CMPs. SUOR effectively explores the distinctive properties of optical signals and photonic devices, and dynamically partitions each data channel into multiple sections. Each section can be utilized independently to boost performance as well as reduce energy consumption. We develop a set of distributed control protocols and algorithms for SUOR, but physically allocate the corresponding cluster agents close to each other to benefit from the strengths of optical interconnects at long distances as well as electrical interconnects at short distances. Simulation results show that SUOR outperforms the alternative optical networks under a wide range of traffic patterns. For example, compared with MWSR design, SUOR achieves 2.58× throughput as well as saves 64p energy consumption on average in a 256-core CMP. Compared with MWMR design, SUOR achieves 1.52× throughput and reduces 73p energy consumption on average. We present the design, implementation, and evaluation of an API for applications to control a software-defined network (SDN). Our API is implemented by an OpenFlow controller that delegates read and write authority from the network's administrators to end users, or applications and devices acting on their behalf. Users can then work with the network, rather than around it, to achieve better performance, security, or predictable behavior. Our API serves well as the next layer atop current SDN stacks. Our design addresses the two key challenges: how to safely decompose control and visibility of the network, and how to resolve conflicts between untrusted users and across requests, while maintaining baseline levels of fairness and security. Using a real OpenFlow testbed, we demonstrate our API's feasibility through microbenchmarks, and its usefulness by experiments with four real applications modified to take advantage of it. Point-to-multipoint broadband wireless access (BWA) is an attractive solution to provide advanced data services to users who do not have easy access to wireline data services. However, BWA will need to support delay sensitive services as users and applications are becoming increasingly sophisticated. Wireless packet scheduling is an important part of quality-of-service (QoS) provisioning in BWA. The biggest difficulty in wireless packet scheduling is the location-dependent channel errors. Channel condition independent fair scheme (CIF) (T.S. Eugene, et al, March 1998) uses explicit leading lagging approach to compensate for the erroneous channel state, but is not able to satisfy both rapid convergent guaranteed throughput and fairness. In this paper, we propose to use the token bank fair queuing (TBFQ) scheduling algorithm as a QoS provisioning mechanism for an asymmetric broadband point-to-multipoint wireless LAN. We consider the throughput and fairness performance of TBFQ under location-dependent channel error condition with variable packet length. This work is an extension of our previous work in applying TBFQ in next generation cellular networks. In NMT, how far can we get without attention and without separate encoding and decoding? To answer that question, we introduce a recurrent neural translation model that does not use attention and does not have a separate encoder and decoder. Our eager translation model is low-latency, writing target tokens as soon as it reads the first source token, and uses constant memory during decoding. It performs on par with the standard attention-based model of (2014), and better on long sentences. Link-layer fairness models that have been proposed for wireline and packet cellular networks cannot be generalized for shared channel wireless networks because of the unique characteristics of the wireless channel, such as location-dependent contention, inherent conflict between optimizing channel utilization and achieving fairness, and the absence of any centralized control. In this paper, we propose a general analytical framework that captures the unique characteristics of shared wireless channels and allows the modeling of a large class of system-wide fairness models via the specification of per-flow utility functions. We show that system-wide fairness can be achieved without explicit global coordination so long as each node executes a contention resolution algorithm that is designed to optimize its local utility function. We present a general mechanism for translating a given fairness model in our framework into a corresponding contention resolution algorithm . Using this translation, we derive the backoff algorithm for achieving proportional fairness in wireless shared channels, and compare the fairness properties of this algorithm with both the ideal proportional fairness objective, and state-of-the-art backoff-based contention resolution algorithms. We believe that the two aspects of the proposed framework, i.e. the ability to specify arbitrary fairness models via local utility functions, and the ability to automatically generate local contention resolution mechanisms in response to a given utility function, together provide the path for achieving flexible service differentiation in future shared channel wireless networks. We measure media bias by estimating ideological scores for several major media outlets. To compute this, we count the times that a particular media outlet cites various think tanks and policy groups, and then compare this with the times that members of Congress cite the same groups. Our results show a strong liberal bias: all of the news outlets we examine, except Fox News' Special Report and the Washington Times, received scores to the left of the average member of Congress. Consistent with claims made by conservative critics, CBS Evening News and the New York Times received scores far to the left of center. The most centrist media outlets were PBS NewsHour, CNN's Newsnight, and ABC's Good Morning America; among print outlets, USA Today was closest to the center. All of our findings refer strictly to news content; that is, we exclude editorials, letters, and the like. "The editors in Los Angeles killed the story. They told Witcover that it didn't ‘come off’ and that it was an ‘opinion’ story.… The solution was simple, they told him. All he had to do was get other people to make the same points and draw the same conclusions and then write the article in their words" (emphasis in original). Timothy Crouse, Boys on the Bus [1973, p. 116]. The task of balancing dynamically generated work load occurs in a wide range of parallel and distributed applications. Diffusion based schemes, which belong to the class of nearest neighbor load balancing algorithms, are a popular way to address this problem. Originally created to equalize the amount of arbitrarily divisible load among the nodes of a static and homogeneous network, they have been generalized to heterogeneous topologies. Additionally, some simple diffusion algorithms have been adapted to work in dynamic networks as well. However, if the load is not divisible arbitrarily but consists of indivisible unit size tokens, diffusion schemes are not able to balance the load properly. In this paper we consider the problem of balancing indivisible unit size tokens on heterogeneous systems. By modifying a randomized strategy invented for homogeneous systems, we can achieve an asymptotically minimal expected overload in l1, l2 and l1 norm while only slightly increasing the run-time by a logarithmic factor. Our experiments show that this additional factor is usually not required in applications. Unbalanced energy consumption is an inherent problem in wireless sensor networks characterized by multihop routing and many-to-one traffic pattern, and this uneven energy dissipation can significantly reduce network lifetime. In this paper, we study the problem of maximizing network lifetime through balancing energy consumption for uniformly deployed data-gathering sensor networks. We formulate the energy consumption balancing problem as an optimal transmitting data distribution problem by combining the ideas of corona-based network division and mixed-routing strategy together with data aggregation. We first propose a localized zone-based routing scheme that guarantees balanced energy consumption among nodes within each corona. We then design an offline centralized algorithm with time complexity O(n) (n is the number of coronas) to solve the transmitting data distribution problem aimed at balancing energy consumption among nodes in different coronas. The approach for computing the optimal number of coronas in terms of maximizing network lifetime is also presented. Based on the mathematical model, an energy-balanced data gathering (EBDG) protocol is designed and the solution for extending EBDG to large-scale data-gathering sensor networks is also presented. Simulation results demonstrate that EBDG significantly outperforms conventional multihop transmission schemes, direct transmission schemes, and cluster-head rotation schemes in terms of network lifetime.