Routing Rules Research Articles

Optical implementation of (3, 3, 2) regular rectangular CC-Banyan optical network

CC-Banyan network plays an important role in the optical interconnection network. Based on previous reports of (2, 2, 3) the CC-Banyan network, another rectangular-Banyan network, i.e. (3, 3, 2) rectangular CC-Banyan network, has been discussed. First, according to its construction principle, the topological graph and the routing rule of (3, 3, 2) rectangular CC-Banyan network have been proposed. Then, the optically experimental setup of (3, 3, 2) rectangular CC-Banyan network has been designed and achieved. Each stage of node switch consists of phase spatial light modulator (PSLM) and polarizing beam-splitter (PBS), and fiber has been used to perform connection between adjacent stages. PBS features that s-component (perpendicular to the incident plane) of the incident light beam is reflected, and p-component (parallel to the incident plane) passes through it. According to switching logic, under the control of external electrical signals, PSLM functions to control routing paths of the signal beams, i.e. the polarization of each optical signal is rotated or not rotated 90° by a programmable PSLM. Finally, the discussion and analysis show that the experimental setup designed here can realize many functions such as optical signal switch and permutation. It has advantages of large number of input/output-ports, compact in structure, and low energy loss. Hence, the experimental setup can be used in optical communication and optical information processing.

Physical design method of MPSoC

Floorplan, clock network and power plan are crucial steps in deep sub-micron system-on-chip design. A novel diagonal floorplan is integrated to enhance the data sharing between different cores in system-on-chip. Custom clock network containing hand-adjusted buffers and variable routing rules is constructed to realize balanced synchronization. Effective power plan considering both IR drop and electromigration achieves high utilization and maintains power integrity in our MediaSoC. Using such methods, deep sub-micron design challenges are managed under a fast prototyping methodology, which greatly shortens the design cycle.

Research on network fixed point theory based on the correlation of nodes

Power laws are ubiquitous in the complex communication networks of today. Network nodes are correlated. According to the correlation, network fixed point theory is proposed and analyzed. Banach fixed point theory was used to explain the operation of networks. In this way, the validity of network fixed point theory is proved. The iterative node sequences of Markov-like chains are generated by algorithms of routing. Communication network can be considered as a space formed by the node sequences. Based on the correlation of nodes, the more nodes in the sequence, the more accurately reflected the searching object node. The property makes location finding and data mining more accurate in communication. The object node mapped from the source node by some routing rule corresponds to Banach fixed point. The fixed point in network space is the object node. The physical character of network fixed point theory will be highly evident, when the network can provide ubiquitous connection for users. The reason is that when the network scale becomes greater, the colony action of nodes is more obvious, and network fixed point theory can show its physical character better. It has great significant theoretical and practical meaning for the organic and dynamic characters and congestion analysis of complex traffic communication network.

Congestion-gradient driven transport on complex networks

We present a study of transport on complex networks with routing based on local information. Particles hop from one node of the network to another according to a set of routing rules with different degrees of congestion awareness, ranging from random diffusion to rigid congestion-gradient driven flow. Each node can be either source or destination for particles and all nodes have the same routing capacity, which are features of ad hoc wireless networks. It is shown that the transport capacity increases when a small amount of congestion awareness is present in the routing rules, and that it then decreases as the routing rules become too rigid when the flow becomes strictly congestion-gradient driven. Therefore, an optimum value of the congestion awareness exists in the routing rules. It is also shown that, in the limit of a large number of nodes, networks using routing based on local information jam at any nonzero load. Finally, we study the correlation between congestion at node level and a betweenness centrality measure.

Your network or mine? The economics of routing rules

In many markets, including payment cards and telecommunications, service providers operate networks that support customer transactions with each other. When the two sides of a transaction belong to more than one network in common, the question arises as to which network will carry the transaction. We show that the answer depends on a combination of who has the formal authority to choose and the parties' network subscription decisions. Our central finding is that granting formal authority to one side of the market can increase the extent to which transactions run over the network preferred by the other side of the market. We also characterize competing networks' equilibrium choices of routing rules and prices.

ANALYSIS AND OPTIMIZATION FOR AUTOMATED VEHICLE ROUTING ON A SINGLE LOOP(<Special Issue>Advanced Planning and Scheduling for Supply Chain Management)

This paper treats with an automated material handling system called a permutation circulation-type vehicle routing system (denoted PCVRS). In the PCVRS a fleet of vehicles unidirectionally and repeatedly circulate on a single loop to carry items to stations located along by the loop where items are served. No passing is allowed between vehicles on the loop. This may induce interferences or blocking between vehicles which may deteriorate the performance of the PCVRS. One of the most serious interferences is the one lap behind (denoted OLB) interference which occurs when the first vehicle is interfered by the last vehicle in a fleet of vehicles. Once the OLB interference occurs, the system can not reach the steady state in which no interference occur. This paper theoretically analyzes the steady state with no interference and the transient state with interferences including the OLB one. This paper considers both the infinite acceleration and deceleration and the finite ones on the vehicles, and four vehicle routing rules by which each job (and each vehicle) is allocated to a processing station for service. Two of them are existing ones and the other two are newly introduced to improve the existing ones. This paper adopts the throughput and the mean interference time for evaluating the vehicle routing rules. This paper confirms the theoretically obtained results by means of numerical simulation.

Dynamic Routing in Large-Scale Service Systems with Heterogeneous Servers

Motivated by modern call centers, we consider large-scale service systems with multiple server pools and a single customer class. For such systems, we propose a simple routing rule which asymptotically minimizes the steady-state queue length and virtual waiting time. The proposed routing scheme is FSF which assigns customers to the Fastest Servers First. The asymptotic regime considered is the Halfin-Whitt many-server heavy-traffic regime, which we refer to as the Quality and Efficiency Driven (QED) regime; it achieves high levels of both service quality and system efficiency by carefully balancing between the two. Additionally, expressions are provided for system limiting performance measures based on diffusion approximations. Our analysis shows that in the QED regime this heterogeneous server system outperforms its homogeneous server counterpart.

Theta Rhythms Coordinate Hippocampal–Prefrontal Interactions in a Spatial Memory Task

Decision-making requires the coordinated activity of diverse brain structures. For example, in maze-based tasks, the prefrontal cortex must integrate spatial information encoded in the hippocampus with mnemonic information concerning route and task rules in order to direct behavior appropriately. Using simultaneous tetrode recordings from CA1 of the rat hippocampus and medial prefrontal cortex, we show that correlated firing in the two structures is selectively enhanced during behavior that recruits spatial working memory, allowing the integration of hippocampal spatial information into a broader, decision-making network. The increased correlations are paralleled by enhanced coupling of the two structures in the 4- to 12-Hz theta-frequency range. Thus the coordination of theta rhythms may constitute a general mechanism through which the relative timing of disparate neural activities can be controlled, allowing specialized brain structures to both encode information independently and to interact selectively according to current behavioral demands.

OPTIMAL ROUTING IN OUTPUT-QUEUED FLEXIBLE SERVER SYSTEMS

We consider a queuing system with multitype customers and nonhomogeneous flexible servers, in the heavy traffic asymptotic regime and under a complete resource pooling (CRP) condition. For the input-queued (IQ) version of such a system (with customers being queued at the system “entrance,” one queue per each type), it was shown in the work of Mandelbaum and Stolyar that a simple parsimonious Gcμ scheduling rule is optimal in that it asymptotically minimizes the system customer workload and some strictly convex queuing costs. In this article, we consider a different—output-queued (OQ)—version of the model, where each arriving customer must be assigned to one of the servers immediately upon arrival. (This constraint can be interpreted as immediate routing of each customer to one of the “output queues,” one queue per each server.) Consequently, the space of controls allowed for an OQ system is a subset of that for the corresponding IQ system.We introduce the MinDrift routing rule for OQ systems (which is as simple and parsimonious as Gcμ) and show that this rule, in conjunction with arbitrary work-conserving disciplines at the servers, has asymptotic optimality properties analogous to those Gcμ rule has for IQ systems. A key element of the analysis is the notion of system server workload, which, in particular, majorizes customer workload. We show that (1) the MinDrift rule asymptotically minimizes server workload process among all OQ-system disciplines and (2) this minimal process matches the minimal possible customer workload process in the corresponding IQ system. As a corollary, MinDrift asymptotically minimizes customer workload among all disciplines in either the OQ or IQ system.

On the interdependence of distributed topology control and geographical routing in ad hoc and sensor networks

Since ad hoc and sensor networks can be composed of a very large number of devices, the scalability of network protocols is a major design concern. Furthermore, network protocols must be designed to prolong the battery lifetime of the devices. However, most existing routing techniques for ad hoc networks are known not to scale well. On the other hand, the so-called geographical routing algorithms are known to be scalable but their energy efficiency has never been extensively and comparatively studied. In a geographical routing algorithm, data packets are forwarded by a node to its neighbor based on their respective positions. The neighborhood of each node is constituted by the nodes that lie within a certain radio range. Thus, from the perspective of a node forwarding a packet, the next hop depends on the width of the neighborhood it perceives. The analytical framework proposed in this paper allows to analyze the relationship between the energy efficiency of the routing tasks and the extension of the range of the topology knowledge for each node. A wider topology knowledge may improve the energy efficiency of the routing tasks but increases the cost of topology information due to signaling packets needed to acquire this information. The problem of determining the optimal topology knowledge range for each node to make energy efficient geographical routing decisions is tackled by integer linear programming. It is shown that the problem is intrinsically localized, i.e., a limited topology knowledge is sufficient to make energy efficient forwarding decisions. The leading forwarding rules for geographical routing are compared in this framework, and the energy efficiency of each of them is studied. Moreover, a new forwarding scheme, partial topology knowledge forwarding (PTKF), is introduced, and shown to outperform other existing schemes in typical application scenarios. A probe-based distributed protocol for knowledge range adjustment (PRADA) is finally introduced that allows each node to efficiently select online its topology knowledge range. PRADA is shown to rapidly converge to a near-optimal solution.

Modelling and analysis of e-mail management for improved customer relationship management

Customer contact centres represent a growing industry in which Customer Relationship Management (CRM) applications have been developed and used successfully. Customer call centres, a multi-billion dollar industry, are evolving into customer contact centres, which now include channels of communication other than the telephone. E-mail, a popular alternative to the telephone for all types of communication, is becoming a common medium for customer contact. CRM applications currently exist that allow us to implement and monitor e-mail management strategies. For example, incoming e-mail can be automatically routed to specific customer service agents according to predefined routing rules. The routing mechanisms available in the software tools are heuristic, and not based upon any scientific analysis of the performance of different routing policy alternatives. The objective of this paper is to study the impact of routing strategies and prioritisation of incoming e-mail messages on CRM objectives of an organisation. We create a model representative of and consistent with e-mail response centres in industry. The process modelled was corroborated by a domain expert. A comprehensive simulation study is conducted to analyse different routing policies and prioritisation options. The results of the simulation study indicate that specific routing strategies and the use of specific priority schemes by the e-mail agent can result in a significant improvement in the response centre's performance, as indicated by average response times and average resolution times of different categories of e-mail messages. Although call centre operations have been studied extensively, this study shows that performance of contact centres needs further investigation because of the greater flexibility that exists in the assignment and scheduling of e-mail processing tasks.

Simple water balance modelling of surface reservoir systems in a large data-scarce semiarid region / Modélisation simple du bilan hydrologique de systèmes de réservoirs de surface dans une grande région semi-aride pauvre en données

Water resources in dryland areas are often provided by numerous surface reservoirs. As a basis for securing future water supply, the dynamics of reservoir systems need to be simulated for large river basins, accounting for environmental change and an increasing water demand. For the State of Ceará in semiarid Northeast Brazil, with several thousands of reservoirs, a simple deterministic water balance model is presented. Within a cascade-type approach, the reservoirs are grouped into six classes according to storage capacity, rules for flow routing between reservoirs of different size are defined, and water withdrawal and return flow due to human water use is accounted for. While large uncertainties in model applications exist, particularly in terms of reservoir operation rules, model validation against observed reservoir storage volumes shows that the approach is a reasonable simplification to assess surface water availability in large river basins. The results demonstrate the large impact of reservoir storage on downstream flow and stress the need for a coupled simulation of runoff generation, network redistribution and water use.

Periodic routing to parallel queues and billiard sequences

In this companion paper of [10] we introduce the combinatorial notion of unbalance for a routing pattern. Using this unbalance we derive an upper bound for the total average expected waiting time of jobs which are routed to parallel queues according to a periodic routing rule. A billiard sequence is obtained with unbalance smaller than or equal to −1, where N is the number of different symbols in the sequence which corresponds to the number of parallel queues in the routing problem.

On Customer Contact Centers with a Call-Back Option: Customer Decisions, Routing Rules, and System Design

Organizations worldwide use contact centers as an important channel of communication and transaction with their customers. This paper describes a contact center with two channels, one for real-time telephone service, and another for a postponed call-back service offered with a guarantee on the maximum delay until a reply is received. Customers are sensitive to both real-time and call-back delay and their behavior is captured through a probabilistic choice model. The dynamics of the system are modeled as an M/M/N multiclass system. We rigorously justify that as the number of agents increases, the system's load approaches its maximum processing capacity. Based on this observation, we perform an asymptotic analysis in the many-server, heavy traffic regime to find an asymptotically optimal routing rule, characterize the unique equilibrium regime of the system, approximate the system performance, and finally, propose a staffing rule that picks the minimum number of agents that satisfies a set of operational constraints on the performance of the system.

Dissimilarity Maximization Method for Real-time Routing of Parts in Random Flexible Manufacturing Systems

This paper presents a dissimilarity maximization method (DMM) for real-time routing selection and compares it via simulation with typical priority rules commonly used in scheduling and control of flexible manufacturing systems (FMSs). DMM aims to reduce the congestion in the system by selecting a routing for each part among its alternative routings such that the overall dissimilarity among the selected routings is maximized. In order to evaluate the performance of DMM, a random FMS, where the product mix is not known prior to production and off-line scheduling is not possible, is selected for the simulation study. A software environment that consists of a computer simulation model, which mimics a physical system, a C++ module, and a linear program solver is used to implement the DMM concept. In addition to DMM, the simulation study uses two priority rules for routing (i.e., machine) selection and seven priority rules for selecting parts awaiting service at machine buffers. The results show (1) DMM outperforms the other two routing selection rules on production rate regardless of the part selection rule used, and (2) its performance is highly dependent on the part selection rules it is combined with.

Dialogue device for call screening and classification

The call screener employs a telephone system interface connected between a telephone network and a telephone device of a user. The interface selectively routes calls (and refrain from routing calls) based on the results from the dialogue system. The dialogue system elicits speech from an incoming caller and causes the telephone system interface to route calls from the incoming caller based on a comparison of the elicited speech with a set of stored speaker models. The stored speaker models may be maintained automatically by the system, using either a passive mode, in which calls exceeding a predetermined duration are assumed to be “acceptable” callers; and a proactive mode in which the system prompts the user at the end of the call to elect whether to save the speech models developed during that call in the acceptable user database. If desired, the user can attach other attributes or special tags to the stored models, indicating special handling or call routing rules to be applied when that caller calls again.

Performance evaluation of a flexible machining/assembly system and routing comparisons

This paper discusses the performance evaluation of the flexible machining/assembly systems (FMS/FAS) of a central server type, and gives a comparative consideration of a fixed, dynamic versus an ordered-entry routing rule. First, the steady-state equations are given, and the system throughput is obtained. Next, the system configurations of FMS/FAS are numerically discussed on the basis of system throughput. Finally, the superiority of an ordered-entry routing rule is numerically discussed for development of routing theory.

Study and status consistency duplicate-read protection in a distributed architecture

This presentation will discuss the benefits and pitfalls of implementing a study status and duplicate-read protection mechanism within a distributed picture archiving and communication system (PACS) architecture. There are many advantages to a distributed PACS network in which image studies are proactively pushed to reading stations before they are required by a radiologist. The absence of a central server, which serves on demand, makes managing study status and protecting against duplicate reads challenging. The system to manage study status and read access must be efficient, robust, and easy to administer. A system is presented that accomplishes these goals while maintaining the advantages of a distributed architecture. The basic workflow of the system is that image studies acquired at a modality device are automatically sent to an archive server. Using a set of advanced routing rules, the archive automatically routes studies to diagnostic workstations where studies are candidates for diagnostic read. The workstations display a list of all local studies available for reading. A monitor application running on the workstations coordinates access to studies for diagnostic read. Once the status of a study has been changed, the workstations on the networks and the archive are notified, which causes the study to be automatically removed from any list on a workstation where it might be a read candidate. Implementation of this system provides a balanced workflow throughout the system while minimizing the need for costly high-speed network hardware. Additionally studies are read as soon as they are available by the next available radiologist. This workflow is enabled without the need for specific interaction by any of the radiologists on the network. By having the images available at the workstation in an organized worklist, this methodology increases the efficiency of the radiologist. The implementation of this system enables a radiology department, or even a specialty group within a department, to gain the benefit of a distributed system as well as the benefits provided by a central-server architecture. This can be done very cost effectively with minimal configuration overhead and hardware requirements.

COMPUTATION OF STEADY-STATE PROBABILITIES FOR RESOURCE-SHARING CALL-CENTER QUEUEING SYSTEMS

Two routing rules for a queueing system of two stations are considered as alternative models for modeling a call-center network. These routing rules allow customers to switch queues under certain server and other resource availability conditions, either external to the system upon arrival to the network, or internal to the system after arrival to a primary call center. Under the assumption of Poisson arrivals and exponentially distributed service times, these systems are analyzed using matrix-geometric techniques, yielding a non-trivial set of ergodicity conditions and the steady-state joint probability distribution for the number of customers at each station. An extensive numerical analysis is conducted, yielding some physical insight into these systems and related generalizations.

Dynamic Scheduling for a Flexible Processing Network

We study flexible processing systems where there are multiple paths for a certain type of customer to follow through the system. This paper analyzes an open processing network model with discretionary routing. The underlying methodology is the heavy traffic approximation, which has been well publicized by many researchers. Allowing priority sequencing in addition to dynamic routing as our control policy, we show that the balanced workload routing rule does not necessarily give us an optimal solution. In general unbalanced workload routing with priority sequencing is shown to give us better performance than a balanced one. Through some simulation results we compare our recommendation with other scheduling policies for a flexible processing network.