Motivated by the need to judiciously allocate scarce sensing resources to attain the highest benefit for the applications that sensor networks serve, in this article we develop a flexible solutions methodology for maximizing the overall reward attained, subject to constraints on the resource demands under fairly general reward or demand functions. We map a broad class of related problems for data fusion in wireless sensor networks into an integer programming problem and provide an iterative Lagrangian relaxation technique to solve it. Each iteration step involves solving for a maximum-weight independent set of an appropriately constructed graph, which, in many cases, can be obtained in polynomial time. We apply our methodology to the problem of tracking targets moving over a period of time through a nonhomogeneous, energy-constrained sensor field. With rewards represented by the quality of information attained in tracking, we study its trade-offs and relationship with energy consumption and periodic measurement taking. We finally illustrate other applications of our framework in sensor networks.

In this paper, we investigate how in-network aggregation approach impacts the target tracking quality in multi-hop wireless sensor networks under network delays. Specifically, we use the mean squared error (MSE) of the target location estimate to quantify the target tracking quality, and investigate how in-network aggregation affects the MSE. To obtain insights without being obscured by onerous mathematical details, we assume a Brownian motion mobility model for the target, Gaussian measurement noise for the sensors, and independent per-hop delays. Under the above assumptions, we first propose an aggregation scheme that preserves a sufficient statistic for optimal tracking under data aggregation at the intermediate nodes and arbitrary network delays. We then analytically study the impact of aggregation in three increasingly more complicated scenarios: single task tracking with only transmission delay, single task tracking with both transmission delay and queueing delay at intermediate nodes, and multi-task tracking. Our results demonstrate that in-network aggregation improves tracking quality in all three scenarios. Furthermore, our analysis provides guidelines on how to choose aggregation parameters in practice.

The increasing use of sensor-derived information from planned, ad-hoc, and/or opportunistically deployed sensor networks provides enhanced visibility to everyday activities and processes, enabling fast-paced data-to-decision in personal, social, civilian, military, and business contexts. The value that information brings to this visibility and ensuing decisions depends on the quality characteristics of the information gathered. In this article, we highlight, refine, and extend upon our past work in the areas of quality and value of information (QoI and VoI) for sensor networks. Specifically, we present and elaborate on our two-layer QoI/VoI definition, where the former relates to context-independent aspects and the latter to context-dependent aspects of an information product. Then, we refine our taxonomy of pertinent QoI and VoI attributes anchored around a simple ontological relationship between the two. Finally, we introduce a framework for scoring and ranking information products based on their VoI attributes using the analytic hierarchy multicriteria decision process, illustrated via a simple example.

Considering physical sensors with certain sensing capabilities in an Internet-of-Things (IoT) sensory environment, in this paper, we propose an efficient energy management framework to control the duty cycles of these sensors under quality-of-information (QoI) experience in a multi-task-oriented IoT sensory environment. Contrary to past research efforts, our proposal is transparent and compatible both with the underlying low-layer protocols and diverse applications, and preserving energy-efficiency in the long run without sacrificing the QoI levels attained. Specifically, we first introduce the novel concept of QoI-aware “sensor-to-task relevancy” to explicitly consider the sensing capabilities offered by an sensor to the IoT sensory environments, and QoI requirements required by a task. Second, we propose a novel concept of the “critical covering set” of any given task in selecting the sensors to service a task over time. Third, energy management decision is made dynamically at runtime, to reach the optimum for long-term application arrivals and departures under the constraint of their service delay. Finally, an extensive case study based on utilizing the sensing sensors to perform water quality monitoring is given to demonstrate the ideas and algorithms proposed in this paper, and a complete simulation is made to support all performance analysis.

The mobile data management community is experiencing a rapid evolutionary change due to the worldwide diffusion of always-on mobile devices and to the increased popularity of location and context-aware mobile applications. Accordingly to recent studies, in two years from now one fourth of the total mobile data will come from audio and video streaming and nearly all the rest from other Internet services. A large part of the increase in mobile data will come from cloud computing applications that are massively used for storing personal data, for sharing data, as well as for utility software (such as maps) and productivity tools. Social networking will strongly influence the way mobile users choose, share and use content from mobile devices. On the other side mobile devices are changing the way social networks have been used till now introducing geo-tagging, location sharing, and many innovative location based services.

The accelerated, on-demand deployment of sensor networks raises the challenge of selecting the providers supplying the most "relevant" sensory information to a user's needs. This paper considers the spatial relevancy of information provided that accounts for the spatial gradations in the quality of the information desired and, specifically, considers: (a) selecting the minimum number of providers that cumulatively maximizes the information relevancy; and (b) considering a cost per provider, selecting the subset of providers that cumulatively maximizes the overall information relevancy subject to a budgetary constraint. The performance and robustness of the proposed solutions are studied both analytically and by simulation for a number of provider topologies.

Participatory sensing is becoming more popular with the help of sensor-embedded smartphones to retrieve context-aware information for users. However, new challenges arise for the maintenance of the energy supply, the support of the quality-of-information (QoI) requirements, and the generation of maximum revenue for network operator, but with sparsely research exposure. This paper proposes a novel efficient network management framework to tackle the above challenges, where four key design elements are introduced. First is the QoI satisfaction index, where the QoI benefit the queries receive is quantified in relation to the level they require. Second is the credit satisfaction index, where the credits are used by the network operator to motivate the user participation, and this index is to quantify its degree of satisfaction. Third is the Gur Game-based distributed energy control, where the above two indexes are used as inputs to the mathematical framework of the Gur Game for distributed decision-making. Fourth is the dynamic pricing scheme, based on a constrained optimization problem to allocate credits to the participants while minimizing the necessary adaptation of the pricing scheme from the network operator. We finally evaluate the proposed scheme under an event occurrence detection scenario, where the proposed scheme successfully guarantees less than 7% detection outage, saves 80% of the energy reserve if compared with the lower bound solution, and achieves the suboptimum with only 4% gap if compared with optimal solution.

With the ever increasing deployment density of Wireless Local Area Networks (WLANs), more and more access points (APs) are deployed within users' vicinity. The effective management of these APs to optimize the users' throughput becomes an important challenge in high-density deployment environments. In this paper, we propose a user-centric network management framework to optimize users' throughput taking into consideration both the network conditions sensed by users and their access priorities. The proposed framework is built around an information pipeline that facilitates the sharing of the information needed for optimal management of communication resources. Theoretical analysis and extensive simulations are presented on two major management activities: AP association and channel selection, and demonstrate that the proposed user-centric network management framework significantly outperforms traditional network management framework in the high-density deployment environment.

Data loss in wireless sensing applications is inevitable and while there have been many attempts at coping with this issue, recent developments in the area of Compressive Sensing (CS) provide a new and attractive perspective. Since many physical signals of interest are known to be sparse or compressible, employing CS, not only compresses the data and reduces effective transmission rate, but also improves the robustness of the system to channel erasures. This is possible because reconstruction algorithms for compressively sampled signals are not hampered by the stochastic nature of wireless link disturbances, which has traditionally plagued attempts at proactively handling the effects of these errors. In this paper, we propose that if CS is employed for source compression, then CS can further be exploited as an application layer erasure coding strategy for recovering missing data. We show that CS erasure encoding (CSEC) with random sampling is efficient for handling missing data in erasure channels, paralleling the performance of BCH codes, with the added benefit of graceful degradation of the reconstruction error even when the amount of missing data far exceeds the designed redundancy. Further, since CSEC is equivalent to nominal oversampling in the incoherent measurement basis, it is computationally cheaper than conventional erasure coding. We support our proposal through extensive performance studies.

Assessing the quality of sensor-originated information is key for the effective and predictable operation sensor-enabled computerized applications. However, with increasing uncertainties due to alternative deployment scenarios, operational realities, and sensing resource use, it becomes very challenging in designing replicable software solutions that can be easily reused in a number of occasions with minimal customization. Leveraging semantic sensor web technologies, this paper presents an ontology-based design framework for organizing a library of quality of information (QoI) analysis algorithms specific to a data source, and interfacing to a library containing computational algorithms assessing quality of information. The ontology-based framework is broad enough to allow easy accommodation of new computational algorithms that domain experts may provide to the library as needed to reflect specific deployment, operational, sensing realities.

Extending the lifetime of wireless sensor networks requires energy-conserving operations such as duty-cycling. However, such operations may impact the effectiveness of high fidelity real-time sensing tasks, such as object tracking, which require high accuracy and short response times. In this paper, we quantify the influence of different duty-cycle schemes on the efficiency of bearings-only object tracking. Specifically, we use the Maximum Likelihood localization technique to analyze the accuracy limits of object location estimates under different response latencies considering variable network density and duty-cycle parameters. Moreover, we study the tradeoffs between accuracy and response latency under various scenarios and motion patterns of the object. We have also investigated the effects of different duty-cycled schedules on the tracking accuracy using acoustic sensor data collected at Aberdeen Proving Ground, Maryland, by the U.S. Army Research Laboratory (ARL).

This paper considers the novel area of quality-of-information (QoI)-aware network management of multitasking wireless sensor networks (WSNs). Specifically, it provides an investigation of new task admission and resource utilization mechanisms for controlling the individual QoI provided to new and existing tasks using real-time feedback-based monitoring mechanisms. The paper describes three key design elements in support of the above: (a) the QoI satisfaction index of a task, which quantifies the degree to which the required QoI is satisfied by the WSN; (b) the QoI network capacity, which expresses the ability of the WSN to host a new task with specific QoI requirements without sacrificing the attained QoI levels of other existing tasks, and (c) an adaptive, negotiation-based admission control mechanism that reconfigures and optimizes the usage of network resources in order to optimally accommodate the QoI requirements of all tasks. Finally, extensive results are presented for assessing the performance of the proposed solution for the case of an intruder detection application scenario.

Modelling based on probabilistic inference can be used to estimate the quality of information delivered by a military sensor network. Different modelling tools have complementary characteristics that can be leveraged to create an accurate model open to intuitive and efficient querying. In particular, stochastic process models can be used to abstract away from the physical reality by describing it as components that exist in discrete states with probabilistically invoked actions that change the state. The quality of information may be assessed by using the model to compute the probability that reports made by the network to its users are correct. In contrast, dynamic Bayesian network models, which have been used in a variety of military applications, are a more suitable vehicle for understanding the overall network performance and making inferences about the quality of information. Queries can be made simply by instantiating some variables and computing the probability distributions over others. We show that it is possible to combine both modelling tools by constructing a Bayesian network over the state variables of the process algebra model. The sparsity of the resulting Bayesian network allows fast propagation of probabilities, and hence interactive querying for the quality of information.

In this paper, a novel procedural framework for increasing the efficiency of the model composition process for the end-to-end transactional behavior of various classes of business-level computer applications is presented. The objectives of the framework are reducing the composition time and the level of engagement of domain experts in deploying business management solutions. Starting with application footprints (i.e., raw log data of various types) and without the need for a priori understanding of their syntax and semantics, the framework permits the analysis of the footprints based on an agnostic tokenization of log data. The framework then produces candidate states and relationships that form the basis for composing the transactional models via the framework's state and relationship manipulation utilities. The main architectural components of the framework are presented and their underlying principles discussed. A case study highlighting the use of the framework, based on an implementation of it, is given and a discussion regarding additional features of the framework and its relation to other research activities is also provided.

With the ever increasing deployment density of wireless local area networks (WLANs), more and more access points (APs) are deployed within users' vicinity. The effective management of these APs to optimize users' eventual throughput becomes an important challenge in the high-density deployment environment. In this paper, we propose a user-centric network management framework to optimize the throughput of users operating in the high-density WLANs taking into consideration the network conditions sensed by users and their access priorities. The proposed framework is built around an information pipeline that facilitates the sharing of the information needed for optimal management of communication resources. Theoretical analysis and extensive simulations are presented on two major management activities: AP association and channel selection, and demonstrate that the proposed user-centric network management framework significantly outperforms traditional network management framework in the high-density deployment environment.

We consider the problem of online monitoring of transaction instances in enterprise environments, based on footprints left by the instances in system logs and using a state-based reference model of the transaction. Unlike existing approaches, we do not rely on any platform-specific knowledge, neither do we assume footprints to carry correlating identifiers, as injected through instrumentation. We outline a solution for tracking transaction instances at individual and aggregate levels, present preliminary results on theoretical analysis of monitoring precision and conclude with directions of ongoing and future research.

The problem of tracking end-to-end service-level transactions in the absence of instrumentation support is considered. The transaction instances progress through a state-transition model and generate time-stamped footprints on entering each state in the model. The goal is to track individual transactions using these footprints even when the footprints may not contain any tokens uniquely identifying the transaction instances that generated them. Assuming a semi-Markov process model for state transitions, the transaction instances are tracked probabilistically by matching them to the available footprints according to the maximum likelihood (ML) criterion. Under the ML-rule, for a two-state system, it is shown that the probability that all the instances are matched correctly is minimized when the transition times are i.i.d. exponentially distributed. When the transition times are i.i.d. distributed, the ML-rule reduces to a minimum weight bipartite matching and reduces further to a first-in first-out match for a special class of distributions. For a multi-state model with an acyclic state transition digraph, a constructive proof shows that the ML-rule reduces to splicing the results of independent matching of many bipartite systems.

Transmit-power estimation is an important part in power-aware designs of mobile ad-hoc networks (MANETs). In this paper, we consider the cooperation among multiple monitor-nodes to estimate the transmit power of other nodes. Utilizing a geometric approach, we characterize the theoretical performance of such cooperative monitoring schemes and propose transmit-power estimation techniques with different number of cooperating nodes. We introduce the novel concept of confidence region that provides a fundamental confidence level for the accuracy of the power estimation and enables the development of techniques for allocating network monitors. Finally, we present a simple, distributed cooperative estimation scheme for a large-scale wireless network and give illustrative simulation results to quantify its performance.

The deployment of converged services of TV, telephony, and Internet access over IP entails a significant initial investment for service providers. This investment is not only for the underlying network infrastructure but also for provisioning and managing vast data centers needed to provide sophisticated IP-based TV (IPTV) experience, including multiple camera views, live (broadcast) and on demand programming, etc., to a large number of viewers. Thus the service providers need to carefully plan and manage the IPTV service deployment to maximize the return-on-investment while providing a good quality of experience to the subscribers. In this paper, we develop a methodology to aid service providers to effectively plan for the staggered deployment of IPTV services in this fledgling market. We present the utility of this framework by demonstrating a planning tool developed from this framework.

The paper introduces a methodology for the analysis of energy consumption that can be attributed to scheduling procedures for medium accessing. In particular, it showcases the methodology for a family of tree-search contention resolution algorithms and demonstrates how traditional performance analysis tools for throughput analysis can be augmented to study energy consumption. The paper introduces the concept of energy efficiency as a first class performance metric and evaluates this metric for the selected family of contention resolution algorithms.

Access to data services via wireless LANs at private (e.g., corporations or home) and public "hot-spot" (e.g., hotels and airports) setting is becoming a common place daily. Data access via (for profit) public wireless LAN (PWLAN) installations is typically based on user subscription and preconfigured services profiles pertaining primarily access to the global Internet. The goal of the ts-PWLAN project is to define an architecture and a prototype implementation that enables the provision of premium and non-premium tiers of services to transient and non-transient users. ts-PWLAN provides for dynamic renegotiations of tier of services and enables various billing modes, e.g., based on connectivity time and usage, thus enabling service providers to increase their revenue opportunities via multiple service offerings.

Abstract Wireless research activities span a wide range of disciplines: communications engineering, software engineering and computer sciences covering all aspects of communication and services including client platforms and server deployment, network protocols and infrastructure, service development and deployment and so on. Our research group at the IBM T. J. Watson Research Center has initiated a number of research activities covering several aspects of the wireless research. In this paper, we highlight our work on the Bluetooth™ wireless technology and the BlueDrekar™ software stack, the WebSplitter middleware for content distribution, and we will share our vision for interconnecting trillion devices. Copyright © 2002 John Wiley & Sons, Ltd.

This paper introduces PARO, a power-aware routing optimization that helps to minimize the transmission power needed to forward packets between wireless devices in ad hoc networks. Using PARO, one or more intermediate nodes called "redirectors" elects to forward packets on behalf of source-destination pairs thus reducing the aggregate transmission power consumed by wireless devices. PARO is applicable to a number of networking environments including sensor networks, home networks and mobile ad hoc networks. In this paper, we present the detailed design of PARO and evaluate the protocol using simulation and experimentation. We show through simulation that PARO is capable of outperforming traditional broadcast-based routing protocols (e.g., MANET routing protocols) due to its power conserving point-to-point on-demand design. We discuss some initial experiences from an early implementation of the protocol in an experimental wireless testbed using off-the-shelf radio technology.

The bulk of proposed pervasive computing devices such as PDAs and cellular telephones operate as thin clients within a larger infrastructure. To access services within their local environment, these devices participate in a service discovery protocol which involves a master directory that registers all services available in the local environment. These directories typically are isolated from each other. Devices that move across service discovery domains have no access to information outside their current local domain. In this paper we propose an application-level protocol called VIA that enables data sharing among discovery domains. Each directory maintains a table of active links to other directories that share related information. A set of linked directories forms a data cluster that can be queried by devices for information. The data cluster is distributed, self-organizing, responsive to data mobility, and robust to failures. Using application-defined data schemas, clusters organize themselves into a hierarchy for efficient querying and network resource usage. Through analysis and simulation we describe the behavior of VIA under different workloads and show that the protocol overhead for both maintaining a cluster and handling failures grows slowly with the number of gateways.

In order to support quality-of-service (QoS) for real-time data communications such as voice, video and interactive services, multiaccess networks must provide an effective priority mechanism. The context of this work is the IEEE 802.14 standard for hybrid fiber coaxial (HFC) networks which has a shared upstream channel for transmissions from stations to the headend. This work presents a multilevel priority collision resolution scheme, which separates and resolves collisions between stations in a priority order, thereby, achieving the capability for preemptive priorities. We present a set of simulation scenarios which show the robustness and efficiency of the scheme, such as its ability to isolate higher priority traffic from lower priorities and to provide quick access to high-priority requests. In March 1998, a framework for handling priorities in the collision resolution process, which adopts a semantics similar to the semantics of our scheme, was included in the 802.14 standard.

Palmtop computers are rapidly becoming the popular platform of choice for running personal productivity applications, but their networking capabilities are still lagging behind user expectations.Due to memory size, cost, and power considerations most palmtop computers support only limited form of point-to-point communication, namely, connection via a PSTN modem or a serial RS-232 cable.Due to wired point-to-point nature of these interfaces, satisfactory solutions for multi-point communication and direct LAN connection do not yet exist..The BlueSky project aims at providing a low-cost, lowpower, indoor RF wireless networking solution for handheld devices.Our solution consists of two components; a BlueSky wireless attachment that plugs into the standard serial port of any palmtop device, and a LAN access point that acts as a layer 213 bridge between the wireless and the wired part of the network.Palmtop devices use dialup networking software and PPP to connect via BlueSky to the network.BlueSky enables MobileIP style seamless roaming between access points without requiring any changes to the communication stack of plamtop devices.Our roaming enhancements to PPP are implemented in the PPP server, the access point, and the BlueSky attachment, all of which are completely transparent to the palmtop device.In this paper, we present our design rationale and implementation experience of building the BlueSky system.We show in what ways low cost, low power, and form factor constraints affect the choice of protocols and function placement in wireless networking systems.We use PPP based mobility solution as an example to illustrate what design adjustments and compromises one has to make to build a working solution.Based on our experience, we recommend making a slight modification to the dialup networking stack of palmtop computers.Our proposed modification offers an efficient, lower cost, and lighter-weight wireless networking solution which is particularly attractive for enabling mobility over emerging short range, low power wireless technologies, such as IrDA, HomeRF and Bluetooth.Permission Lo make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the tirst page.To copy otherWe, to republish, to post on servers or to redistribute to lists.rcquircs prior specific permission and/or a fee.

Recently there is a growing interest in adaptive multimedia networking where the bandwidth of an ongoing multimedia call is variable. In this paper, we propose a measurement-based call admission control (CAC) which guarantees the upper bound of the call degradation probability defined herein. Our CAC measures the state of the cellular system in a distributed manner and reflects the observed history of the system on making call admission decisions. Also, a bandwidth adaptation algorithm to minimize the call degradation probability is presented. Simulations reveal that our CAC algorithm outperforms the upper limit CAC algorithm while maintaining quality of service.

We provide simple techniques for estimating the end-to-end jitter incurred by a periodic traffic in an asynchronous transfer mode (ATM) network. Our analysis is based on the careful examination of light and heavy traffic behavior of jitter incurred to a tagged renewal stream in a single node. Our results indicate that, in the heavy traffic as the number of nodes increases, the jitter distribution approaches to a limiting distribution which only depends on the behavior of the background traffic. We provide the functional equation satisfying this limit which bounds the moments of the jitter for arbitrary level of traffic. A simple approximation method based on the heavy and light traffic analysis of the jitter process is also provided and the results is supported by extensive simulation.

We present the multimedia gateway solution which represents an evolutionary approach for providing a natural migration to digital switched video services. We also present some initial analysis reflecting performance issues for a multimedia gateway.

Shaping of traffic at its source is a prominent congestion control solution in ATM networks. The "leaky bucket" with a "cell spacer" is a very popular traffic shaping approach. By sizing the leaky bucket and spacer parameters, an end-station shapes its traffic to conform to a "good behavior" contract with the network. The leaky bucket delays the transmission of selected number of cells, while the spacer forces a minimum time-distance between transmitted cells. When a contracted transmission rate is close to the traffic generation rate by the end-station, this traffic stream will utilize most of the bandwidth available on its virtual connection. The high utilization of such a connection leads to large queues of frames and cells at the end-station, With high adverse consequences to the end-to-end delay and jitter. In this paper, based on the negotiated traffic parameters and source traffic characteristics, we study, through simulations, the contribution of the leaky bucket plus cell spacer subsystem to the delay and jitter in an end-station. We also study the distribution of the size of the burst of cells leaving the end-station and entering the network. Finally, we derive the theoretical upper bound for the size of bursts of cells.

The emergence of wireless and personal communication networks has brought random access protocols for packet radio networks back to the research forefronts. Most such protocols are based on the ever popular ALOHA protocol. Unfortunately, this protocol is inherently unstable and requires sophisticated schemes to stabilize it. Another class of random access schemes, called limited sensing or stack algorithms, has been proposed that is stable and allows for the dynamic incorporation of new stations into the network. In this paper, we will review the simple to implement n-ary Stack Algorithm, and we will demonstrate its performance in the presence of capture under various system parameters. As a by-product of this work, we will show that random access schemes have throughput conditions that are sensitive to the traffic generation process.

A vacation queueing system, where the server idles until a random number N of customers accumulates in a queue is investigated. Following the arrival of the N-th customer, the server serves exhaustively the queue and then a new idling period commences. The vacation queuing system is a generalization of the conventional N-policy queue with N a constant number. The steady state distribution of the queue size and the waiting time of a customer are derived in transform forms for both the FIFO and LIFO service disciplines.>

The authors formulate and analyse the jitter process in an ATM environment. The jitter analysis is presented for a tagged renewal stream. The queueing model consists of the superposition of the tagged renewal stream and background traffic. In the case of periodic tagged stream, the correlated background traffic is also considered. A solution methodology is developed which can be utilized in solving a large class of problems. They investigate the impact of various traffic parameters (e.g. the background traffic load and burstiness, the interarrival time of the renewal stream, etc.) on the jitter of the tagged stream. Numerical examples provide insight into the behavior of the system. They observe that the variance of the jitter behaves (almost) linearly with the variance of the background traffic. Some interesting heavy traffic results are also provided when the background traffic consists of number of identical two state ON-OFF sources.>

The authors provide sample techniques for estimating the end-to-end jitter incurred to a periodic traffic in an ATM network. The analysis is based on carefully examining the light and heavy traffic behavior of jitter incurred to a general tagged renewal stream in a single node. The results indicate that for any number of nodes, the jitter variance is almost proportional to the variance of the background traffic competing for resources with the tagged stream. They also find that in general, as the number of nodes increases, the jitter distribution approaches a limit. In the heavy traffic, they provide the functional equation satisfying this limit which readily gives all the moments of the jitter in closed form for large number of nodes in the network.>

Presents a new scheme that enables destination nodes in a slotted shared medium network to release some received slots, hence making them available for reuse by other downstream nodes in the network. This scheme ensures a significant increase in the effective capacity of the network without any noticeable degradation in node processing delays, or increase of node complexity.>

Traffic shaping at a (traffic) source station as a prominent congestion control solution in ATM networks. The "leaky bucket" scheme in conjunction with a cell spacer is an extensively studied and used mechanism for such a traffic shaping. By dimensioning the leaky bucket and spacer parameters, a source station attempts to regulate the behavior of its own traffic in order to conform to a "good behavior" contract with the network. In this paper, we study the effect of the a single source's traffic characteristics and its leaky bucket parameters on the maximum burst size and the burst size distribution as seen by the network. The theoretical upper bound for the burst size is derived and simulation is used to study the effect of leaky bucket parameters on probability distribution of burst sizes. It is shown that while traffic shaping is done to abide to negotiated traffic characteristics, traffic shaping can lead to large queues of cells and result in large cell delay and delay jitter in the source station.>

The authors propose a mechanism for implementing priorities in an IEEE 802.6 (DQDB) subnetwork of a metropolitan area network. The mechanism allows the priorities to be preemptively multiplexed among each other, thus, always guaranteeing maximum bandwidth to the highest priority traffic whenever it is requested. The proposed mechanism responds fast in the presence of high priority traffic and it takes full effect within at most one round trip propagation delay.>

The suitability of IEEE 802.5 token ring LANs for the transport of multimedia traffic is examined. The token ring priority mechanisms and end-station queuing policies are studied in order to understand their effect on the delay characteristics of multimedia traffic. The multimedia traffic is modeled as isochronous data streams. Simulation results are presented to illustrate the access and queuing delays under various load conditions and traffic mixes.

The performance of a control (CNTR) and information (INF) frame multiplexer which intermixes control and information traffic by accommodating the relatively short CNTR frames between two consecutive INF frames is investigated. It is shown that the delay performance of one class can be improved at the price of degrading the performance of the other. The delay performance of a transaction between two nodes of the communication subsystem can be improved by selecting the parameters of this multiplexer appropriately. The relative importance of CNTR and INF frame delays for a transaction is determined. The results of a simulation study give insight into the behavior of this multiplexer. Based on these results, it is concluded that if the control traffic intensity is high, or the relative importance of control delay is high, then larger values of gap length improve the performance.

The conservation law formula for work-conserving queues with batch arrivals is derived for when the arrival instants of customers are assumed to constitute an arrivals see time averages (ASTA) process. The derivation is based on the analysis of the corresponding first-in first-out (FIFO) multiclass queue and its steady state. Hence, the mean work load in the queue at an arbitrary time instant can be equated with the mean time that an arbitrary customer has to wait in the FIFO queue.>

An exact queuing model for a station that operates within the IEEE 802.6 subnetwork of a metropolitan area network (MAN) is developed. The model reflects the station's perception of the subnetwork and it has been developed by mapping the media access control (MAC) protocol to a queuing service discipline. The model is a discrete-time single-server queue with two classes of customers served according to a quasi-gated discipline. The one class of customers represents the data packets generated by the station, while the other class represents the requests registered by the station. The model gives useful insight into the operation of the station and it can be used as a cornerstone module for analytical and/or simulation models of the whole IEEE 802.6 subnetwork.>

A token-ring local area network (LAN) with an infinite number of nodes uniformly distributed around the ring is considered. A token that circulates around the ring at a constant speed stops to serve fixed length packets that are generated by the nodes. It is assumed that the cumulative arrival process of packets constitutes a two-dimensional Poisson process. Given a fixed point on the ring, called the origin, the first-order statistics of the interarrival times of packets at the origin are obtained in the form of their Laplace-Stieltjes transform.>

The interconnection of two single-hop random-access networks is considered. In each network a station, called the bridge node, receives internetwork packets from the local users and forwards them to the bridge node of the other network via a point-to-point link, for subsequent broadcasting to the users of that network. In each network, the bridge node shares the available broadcast channel with the local users either via contention or via frequency division. Under the infinite population Poisson user model, conditions for the stability of the interconnected system are derived.>

The statistics of the request and countdown counters of a user in a network that operates with the DQDB (distributed queue dual bus) media access protocol are investigated. Assuming that a user can have at most one packet waiting for transmission, an expression is obtained for the steady-state generating function of the number of requests queued ahead of an arriving packet. Given this number, the waiting time of the packet can be easily obtained. The results provide an insight on how traffic, generated from the left and the right of a user in the network, affects the waiting time characteristics of packets generated by the user.>

The statistics of the request and countdown counters of a user in a network that operates with the DQDB (distributed queue dual bus) media access protocol are investigated. Assuming that a user can have at most one packet waiting for transmission, an expression is obtained for the steady-state generating function of the number of requests queued ahead of an arriving packet. Given this number, the waiting time of the packet can be easily obtained. The results provide an insight on how traffic, generated from the left and the right of a user in the network, affects the waiting time characteristics of packets generated by the user.>

The interconnection of token-ring local area networks (LANs) via store-and-forward bridges is considered. The mean-packet-delay performance of a system of token rings connected in series is analyzed by approximating the interarrival times at the bridges by renewal processes. The approximation gives simple formulas for the mean waiting times and agrees reasonably well with simulation results in most of the cases considered. Also, the conditions under which the performance of a single token-ring LAN can be improved by partitioning it into bridged subrings are investigated. It is found that splitting can improve performance as long as the fraction of the internetwork traffic is below a threshold which depends on the total input traffic.>

An analysis is presented of the delay performance of the n-ary stack algorithm, an easy-to-implement random-access algorithm that uses collision-no-collision binary feedback and requires only limited feedback sensing by the users. Utilizing the regenerative character of the stochastic processes that are associated with the random-access system, tight upper and lower bounds on the mean packet delay and on the packet delay variance are derived. It is shown that the algorithm with n=3 has the best delay characteristics. Simulation results for the percentiles of the packet delay distribution are given.>

This paper considers the interconnection of two local area networks, each of which connects a large population of users via a carrier-sense multiple-access (CSMA) channel. In each network a bridge node receives internetwork packets from the local users and forwards them to the bridge node of the other network via a point-to-point link; the bridge node of the destination network queues these internetwork packets for subsequent broadcasting to the local users. The available broadcast channel in each of the two networks is frequency divided into a bridge node subchannel, used for bridge node transmissions, and a CSMA user subchannel, used for user transmissions. For the interconnected system, stability conditions, optimal bandwidth allocations, and throughput delay characteristics are found. Also it is shown that the performance of a single CSMA network can be substantially improved by partitioning it into smaller interconnected networks.