Showing papers in "Telecommunication Systems in 1997"
TL;DR: It is shown how several performance evaluation and optimization problems within this framework can actually be posed and solved by computing the mathematical expectation of certain functionals of point processes.
Abstract: This paper proposes a new approach for communication networks planning based on stochastic geometry. We first summarize the state of the art in this domain, together with its economic implications, before sketching the main expectations of the proposed method. The main probabilistic tools are point processes and stochastic geometry. We show how several performance evaluation and optimization problems within this framework can actually be posed and solved by computing the mathematical expectation of certain functionals of point processes. We mainly analyze models based on Poisson point processes, for which analytical formulae can often be obtained, although more complex models can also be analyzed, for instance via simulation.
367 citations
TL;DR: A theoretical framework within which call admission control schemes with multiple statistical QoS guarantees can be constructed for the Generalized Processor Sharing (GPS) scheduling discipline is provided.
Abstract: Provision of Quality?of?Service (QoS) guarantees is an important and challenging issue in the design of integrated?services packet networks. Call admission control is an integral part of the challenge and is closely related to other aspects of networks such as service models, scheduling disciplines, traffic characterization and QoS specification. In this paper we provide a theoretical framework within which call admission control schemes with multiple statistical QoS guarantees can be constructed for the Generalized Processor Sharing (GPS) scheduling discipline. Using this framework, we present several admission control schemes for both session?based and class?based service models. The theoretical framework is based on recent results in the statistical analysis of the GPS scheduling discipline and the theory of effective bandwidths. Both optimal schemes and suboptimal schemes requiring less computational effort are studied under these service models. The QoS metric considered is loss probability.
43 citations
TL;DR: The problem of gateway placement in LEO/MEO systems is introduced and a mathematical formulation of the problem is presented and the specific roles that each type will play in the global communication market are identified.
Abstract: LEO/MEO systems are moving from a dream to a reality, their global reach is becoming apparent with the launch of the first LEO satellites. The global mobility offered by these systems is expected to have a profound effect on the way that organizations and individuals operate. Billions of dollars are invested in the research and development of LEO/MEO based communication systems, and larger amounts will be needed for their ongoing operation and use. Many global satellite based systems have been announced over the last decade, Ellipsat, Globalstar, ICO, Iridium, M?Star, Odyssey, Orbcomm, and Teledesic, are just a few of the many systems in deployment or under development. Being such a risky venture, limited experience exists in developing and managing large scale civilian satellite based mobile communication systems. Many interesting and challenging research issues are faced by the designers and operators of such systems. This paper presents the different approaches to the configuration of the various LEO and MEO based communication systems. It compares their advantages and disadvantages, and analyzes their economic viability. Based on the analysis, it is possible to identify the specific roles that each type will play in the global communication market. The paper presents and discusses some of the important research areas involved in their development, configuration, maintenance, operation and management. In particular, it introduces the problem of gateway placement in LEO/MEO systems and presents a mathematical formulation of the problem.
34 citations
TL;DR: A two‐level tabu search heuristic for solving the link capacities in a dynamic routing telecommunications network that utilizes probabilistic move selection and coordinated solution recovery strategies and indicates that significant savings can be obtained over the conventional network designs.
Abstract: This paper presents a tabu search approach for optimizing the link capacities in a dynamic routing telecommunications network. The traffic between any two nodes in the network is routed over a one?link direct path or, if no direct capacity is available, over a two?link alternate path. The alternate routing paths can be changed dynamically from hour to hour as the traffic between pairs of nodes may vary with the time of day. The problem is to determine the optimal capacity level for each link in the network to minimize cost while satisfying the grade?of?service constraints. Although the problem can be formulated as a nonlinear integer programming problem, no efficient solution procedures are available. In this paper, we develop a two?level tabu search heuristic for solving the problem that utilizes probabilistic move selection and coordinated solution recovery strategies. The macro level of the algorithm iteratively determines an hour for possible improvement and then the micro level seeks to optimize the routing paths for that hour. Our computational experience with both real and simulated problems indicates that significant savings can be obtained by this approach over the conventional network designs.
31 citations
TL;DR: It is demonstrated that the ability to maintain communication links across the seams is of relatively minor importance for user‐to‐user delay and the choice of crosslink pattern and crosslink antenna technology is shown to have no significant impact on satellite power consumption or on LEOS system capacity.
Abstract: LEOS communication systems are rapidly moving from dream to reality. When operational, the LEOS systems can offer mobile and fixed?site communications between any two points on the globe. Yet, many LEOS system design issues remain unresolved. Some of the planned systems, such as Iridium and Teledesic, rely on intersatellite communication to provide space based routing from origin to destination while others, like Globalstar, use ground based routing. This paper investigates the effect of satellite crosslink design on user?to?user delay and satellite power consumption. Delay is an important measure of quality of service and may have a significant impact on system revenues. The results indicate that the choice of crosslink architecture has a large effect on user?to?user delay. In a polar orbit LEOS system, there will be two seams from pole to pole 180° apart, where satellites in orbits on opposing sides of the seam move in opposite directions. It is demonstrated that the ability to maintain communication links across the seams is of relatively minor importance for user?to?user delay. Finally, the choice of crosslink pattern and crosslink antenna technology is shown to have no significant impact on satellite power consumption or on LEOS system capacity.
31 citations
TL;DR: In this paper, Houveia et al. formulated the clustering/layout problem as a capacitated single-commodity network flow problem with adequate capacities on the arcs.
Abstract: The design of the topology of a local access network is a complex process which builds on many different combinatorial optimization problems such as the concentrator quantity problem, the concentrator location problem, the terminal clustering problem and the terminal layout problem. Usually, these four subproblems are solved separably and sequentially and the solution of one subproblem is used as data for the next subproblem. There are two main drawbacks associated to this four?phase approach: i) without knowing the optimal solution to the global problem it is difficult to set the parameters for some of the subproblems which appear in the earlier phases and ii) in many cases, wrong decisions taken at one of the earlier phases are "passed" to the subsequent phases. Our aim in this paper is to formulate the two last subproblems, clustering and layout, as one single generalized capacitated tree problem. We formulate the clustering/layout problem as a capacitated single?commodity network flow problem with adequate capacities on the arcs. We adapt a reformulation presented in (Gouveia, 1995) of a single?commodity flow model presented in (Gavish, 1983). We present several inequalities which can be used to tighten the LP relaxation of the original formulation. We present two heuristics for obtaining feasible solutions for the clustering/layout problem. Computational results taken from tests with 50, 100 and 200 nodes indicate that in most of the cases the best heuristic produces topologies with lower cost than the ones obtained by solving separately and sequentially the two individual subproblems.
29 citations
TL;DR: An implementation of Simulated Allocation is described and its effectiveness is illustrated by means of numerical examples including multiple knapsack problem and network design, indicating that SA is capable of bypassing local minima of the problem objective function, and allows for achieving reasonable solutions in a reasonable time.
Abstract: The paper discusses a stochastic approach, called Simulated Allocation (SA), to the capacitated and uncapacitated multicommodity integral flow allocation problems. Since such problems are in general NP?complete, effective heuristic approaches are of interest, and SA is one of them. The idea of SA has its origin in discrete event simulation of alternative call routing in telecommunication networks. We describe an implementation of SA and illustrate its effectiveness by means of numerical examples including multiple knapsack problem and network design. Numerical experiments indicate that SA is capable of bypassing local minima of the problem objective function, and allows for achieving reasonable solutions in a reasonable time.
25 citations
TL;DR: The approximation of the time‐dependent blocking probability is sufficiently accurate to predict the number of lines needed to satisfy blocking probability requirements and an efficient method for simulating the two‐dimensional Markov chain is developed based on performing many replications within a single run.
Abstract: We consider a generalization of the classical Erlang loss model with both retrials of blocked calls and a time?dependent arrival rate. We make exponential?distribution assumptions so that the number of calls in progress and the number of calls in retry mode form a nonstationary, two?dimensional, continuous?time Markov chain. We then approximate the behavior of this Markov chain by two coupled nonstationary, one?dimensional Markov chains, which we solve numerically. We also develop an efficient method for simulating the two?dimensional Markov chain based on performing many replications within a single run. Finally, we evaluate the approximation by comparing it to the simulation. Numerical experience indicates that the approximation does very well in predicting the time?dependent mean number of calls in progress and the times of peak blocking. The approximation of the time?dependent blocking probability also is sufficiently accurate to predict the number of lines needed to satisfy blocking probability requirements.
24 citations
TL;DR: Approximation methods to analyze blocking in circuit switched networks with nonstationary call arrival traffic and generalize these techniques to develop analogous formulas for a linear N‐node circuit switched network.
Abstract: In this paper, we develop approximation methods to analyze blocking in circuit switched networks with nonstationary call arrival traffic. We formulate generalizations of the pointwise stationary and modified offered load approximations used for the nonstationary Erlang loss model or M(t)/M/c/c queue. These approximations reduce the analysis of nonstationary circuit switched networks to solving a small set of simple differential equations and using the methods for computing the steady state distributions for the stationary versions of such loss networks. We also discuss how the use of time varying arrival rates literally adds a new dimension to the class of telecommunication networks we can model. For example, we can model the behavior of alternate routing due to link?failure, which is a feature that the classical stationary version of the model cannot capture. Our nonstationary model can also describe aspects of the dynamic calling traffic behavior arising in cellular mobile traffic. For the special case of a two?link, three node network, we present numerical results to compare the various approximation methods to calculations of the exact blocking probabilities. We also adapt these calculations to approximate the behavior of rerouting calling traffic due to link?failure. The results are achieved by formulating some new recursions for evaluating the steady state blocking probabilities of such networks. We also generalize these techniques to develop analogous formulas for a linear N?node circuit switched network.
18 citations
TL;DR: A simple model for packet transmission and retransmission at each node is proposed, and it is shown that saturation throughput in this model yields a sufficient condition for the stability of the packet buffers; this is interpreted as the capacity of the access method.
Abstract: We consider a system comprising a finite number of nodes, with infinite packet buffers, that use unslotted ALOHA with Code Division Multiple Access (CDMA) to share a channel for transmitting packetised data. We propose a simple model for packet transmission and retransmission at each node, and show that saturation throughput in this model yields a sufficient condition for the stability of the packet buffers; we interpret this as the capacity of the access method. We calculate and compare the capacities of CDMA?ALOHA (with and without code sharing) and TDMA?ALOHA; we also consider carrier sensing and collision detection versions of these protocols. In each case, saturation throughput can be obtained via analysis of a continuous time Markov chain. Our results show how saturation throughput degrades with code?sharing. Finally, we also present some simulation results for mean packet delay. Our work is motivated by optical CDMA in which "chips" can be optically generated, and hence the achievable chip rate can exceed the achievable TDMA bit rate which is limited by electronics. Code sharing may be useful in the optical CDMA context as it reduces the number of optical correlators at the receivers. Our throughput results help to quantify by how much the CDMA chip rate should exceed the TDMA bit rate so that CDMA?ALOHA yields better capacity than TDMA?ALOHA.
18 citations
TL;DR: The nature of the analysis and design tools needed for nomadic computing and communications, and what one might look for in the way of applying some of them are discussed.
Abstract: Nomadic computing is a phenomenon in computing and communications that is spreading rapidly. At this stage of its technology, the key problems and the basic understanding of its underlying principles are only beginning to be identified. Analysis and design tools are needed to assist in its development. In this paper, we discuss the nature of the tools and what one might look for in the way of applying some of them. We then pose some of the essential issues of nomadic computing and communications.
TL;DR: If the traffic‐flow cost function is the cable expansion cost, which occurs in the Local Access Telecommunication Network (LATN) expansion, this special ETKP can be solved by a depth‐first dynamic programming procedure in a time complexity of O(nδH), where δ is the largest existing cable capacity in LATN.
Abstract: The Extended Tree Knapsack Problem (ETKP) is a generalized version of the Tree Knapsack Problem where an arbitrary nonlinear traffic?flow cost is imposed. This problem can be solved by the straight?forward "bottom?up" approach with a time complexity of O(nH 2), where n is the number of nodes in the tree, and H is the knapsack capacity. In this paper, we show that if the traffic?flow cost function is the cable expansion cost, which occurs in the Local Access Telecommunication Network (LATN) expansion, this special ETKP can be solved by a depth?first dynamic programming procedure in a time complexity of O(n?H), where ? is the largest existing cable capacity in LATN. This result indicates that the depth?first dynamic programming algorithm can be applied for solving a general class of tree optimization problems. The computational results of our algorithm for the ETKP are also provided.
TL;DR: This paper compares two basic strategies for a network call distributor: a centralized FIFO queue and a distributed queueing strategy called Minimum‐Expected‐Delay (MED).
Abstract: New services providing automatic call distribution in the network have been one of the most hotly contested areas in the USA telecommunications arena in recent years. This has been fueled by increasing demand from large corporations for intelligent network routing that will keep their geographically distributed telemarketing/service centers operating with maximum efficiency. This paper compares two basic strategies for a network call distributor: a centralized FIFO queue and a distributed queueing strategy called Minimum?Expected?Delay (MED). According to MED, a central controller routes each arrival to the node that minimizes its expected delay (waiting time). Our main result qualifies the conventional wisdom that perceives FIFO as optimal. We show that the waiting time under FIFO is not stochastically smaller than that under MED. Furthermore, we prove that the waiting time distribution functions intersect at a single point. Numerical experiments suggest that, for certain performance criteria and over a range of parameters of interest, MED can actually outperform FIFO.
TL;DR: This paper investigates the problem of predicting loss ratios for sources described by fractional ARIMA processes, and shows that their short‐range structure can mean that a simple power‐law tail based on the Hurst parameter alone can be over‐optimistic when the buffer space allocated per source is not large.
Abstract: Consider the problem of predicting loss ratios for traffic streams sharing a buffer. Approximations based on the temporal statistical properties of single sources do not account for the economies of scale which can arise when there is statistical multiplexing gain across sources. These can occur whether the sources have long or short range dependence; in either case the economies may be positive or negative. In this paper we investigate this matter for sources described by fractional ARIMA processes, and show that their short?range structure can mean that a simple power?law tail based on the Hurst parameter alone can be over?optimistic when the buffer space allocated per source is not large.
TL;DR: Some basic results are derived for the autocorrelation function of semi?Markovian processes and for the effect of state space reduction on autOCorrelation, which show how to represent correlated traffic with given characteristic by an adequate SMP model of limited size.
Abstract: Semi?Markovian processes (SMP) serve as a versatile means to model various traffic types generated by sources or superposed from links in ATM networks. An efficient discrete time analysis method is proposed for SMP/G/1 queueing systems to evaluate ATM switches with non?renewal input. Some basic results are derived for the autocorrelation function of semi?Markovian processes and for the effect of state space reduction on autocorrelation, which show how to represent correlated traffic with given characteristic by an adequate SMP model of limited size.
TL;DR: A stochastic Petri net model assuming periodic burst arrivals for VBR and Poisson arrival processes for the Data and ABR traffic types at the burst level is developed and solved analytically (numerically) using a decomposition approach.
Abstract: The B?ISDN will carry a variety of traffic types: the Variable Bit Rate traffic (VBR), of which compressed video is an example, Continuous Bit Rate traffic (CBR), of which telemetry is an example, Data traffic, and Available Bit Rate traffic (ABR) that represents aggregate data traffic with very limited guarantees on quality. Of these, VBR and CBR have timing constraints and need synchronous bandwidth; data traffic is relatively delay insensitive. In this paper, we consider the VBR, Data and ABR traffic types and obtain the cumulative distribution function (cdf) of the queueing delay experienced by a burst of ABR traffic in the output buffer of an ATM switch. The cdf is used to trade off buffer loss probabilities against deadline violation probabilities through adjusting the buffer size and (delay) deadline values. Large buffers result in low losses but queueing delays can become excessive and cause a high level of deadline violations. Both losses and violations are detrimental and an operating point must be chosen to achieve a balance. In this paper we study the nature of the trade off. We develop a stochastic Petri net model assuming periodic burst arrivals for VBR and Poisson arrival processes for the Data and ABR traffic types at the burst level, and solve the model analytically (numerically) using a decomposition approach. This decomposition, along with the inherent decomposability of the tagged customer approach for obtaining the cdf opens up a possibility of carrying out fast computations using a parallel machine for selecting the operating point each time that a call is admitted.
TL;DR: This paper presents a data compaction/randomization based approach as a mode of block encryption for ATM (Asynchronous Transfer Mode) cells that converts a plaintext into pseudo‐random plaintext before ciphering to conceal patterns in the plaintext.
Abstract: This paper presents a data compaction/randomization based approach as a mode of block encryption for ATM (Asynchronous Transfer Mode) cells. The presented approach converts a plaintext into pseudo?random plaintext before ciphering to conceal patterns in the plaintext. The underlying idea behind this scheme is the Shannon's principles of "confusion" and "diffusion" which involve breaking dependencies and introducing as much randomness as possible into the ciphertext. In this scheme, confusion and diffusion are introduced into the system by first compressing the ATM cell payload and then spreading a continuously changing random data over the entire content of the cell. As a mode of operation for block ciphering, this scheme offers the following attractive features:(i) plaintext patterns are pseudo?randomized and chained with ciphertext (thereby, preventing against "dictionary", "known plaintext", and "statistical analysis" attacks), (ii) it is self?synchronizing, (iii) cell loss has no additional negative effect, (iv) no IV (Initialization Vector) storage is required, (v) it is encryption?algorithm independent, (vi) there is no cell?to?cell dependency (no feedback from previous cells), and (vii) it is highly scalable (i.e., cells from the same stream can be ciphered and deciphered in parallel). This paper also presents a secure mechanism for in?band synchronization of encryption/decryption key updates using a "marker?cell" that is carried within the data channel. An important aspect of both the above mechanisms is that they do not require any changes to the ATM cell header or ATM infrastructure.
TL;DR: This work considers a network expansion problem for fiber optic networks, shows that NEP is strongly NP‐complete for general graphs, and presents three heuristic algorithms and their performance analyses.
Abstract: We consider a network expansion problem for fiber optic networks. Given the network topology, edge costs, and node profit per period, the network is built over T periods due to limited budget available per period. The problem is to find edges to be added at each period so that their edge cost does not exceed the budget limit and the resulting network is connected, with the objective of maximizing profit over T periods. We first consider some special graphs: lines, cycles, and trees. Then we show that NEP is strongly NP?complete for general graphs, and present three heuristic algorithms and their performance analyses. Computational results show evidence that the simple greedy algorithm performs very effectively for finding a near optimal solution.
TL;DR: This work studies the problem of using dynamic routing to VP‐based ATM networks by transforming it into an equivalent multi‐rate circuit‐switched network problem and proposes a dynamic routing algorithm based on the Least Loaded Routing (LLR) with packing.
Abstract: We consider a Virtual Path (VP) based ATM network supporting multiple traffic classes with heterogeneous traffic characteristics Using simple FIFO scheduling policy at the ATM multiplexer, we assume that all traffic require identical end?to?end quality of service (QoS) requirement The concept of effective bandwidth is used to determine the required bandwidth to guarantee the specified QoS requirement We study the problem of using dynamic routing to VP?based ATM networks by transforming it into an equivalent multi?rate circuit?switched network problem To further simplify the analysis, we restrict the choice of path to single?link and two?link routes We propose a dynamic routing algorithm based on the Least Loaded Routing (LLR) with packing Simulation results are used to compare the performance of this algorithm with other dynamic routing schemes
TL;DR: Extensive simulations show that the prior provision of trunk pipes and a suitable choice of the route selecting rule for new customers are effective in constructing a highly reliable network with low cost.
Abstract: This paper discusses reliability problems for local public communication networks such as cable television networks and the subscriber?loops of telecommunication networks They have tree?shapes and expand continuously as new customers join By introducing a simple model, it is shown that most principal reliability measures and cost measures for such networks can be described through the networks' graphical characteristic quantities Extensive simulations show that the prior provision of trunk pipes and a suitable choice of the route selecting rule for new customers are effective in constructing a highly reliable network with low cost
TL;DR: It is shown that a direct approach, where the quantity measured is the QoS of interest, combined with an extrapolation technique to speed up the estimation process, offers a promising solution to the problem of accepting calls with incomplete traffic statistics.
Abstract: We propose a resource allocation scheme that takes into account both the QoS requirements and the characteristics of traffic streams. In our scheme, the decision to allocate buffer and bandwidth resources to a QoS class depends on whether buffering will be effective in reducing loss probability for this class. We present analytical techniques based on the theory of large deviations for estimating the small loss probability. Furthermore, we address the problem of accepting calls with incomplete traffic statistics. Existing proposals of traffic descriptors call for specification of only the first?order statistics such as the peak rate and the sustainable cell rate. To guarantee QoS, the admission policy must be conservative by assuming the worst?case distribution compliant to the traffic descriptor. We demonstrate that on---off sources exhibit such worst?case behavior. However, a static conservative policy results in under?utilization of network resources. We devise and analyze dynamic algorithms that improve the estimates of the actual bandwidth requirements for existing sources by collecting information on?line. We show that a direct approach, where the quantity measured is the QoS of interest, combined with an extrapolation technique to speed up the estimation process, offers a promising solution.
TL;DR: In this paper, the authors present an algorithm that ensures that multimedia data with real-time deadlines are delivered to the application layer in causal order, by focusing on a form of causal ordering violations caused by "the triangle inequality".
Abstract: Messages that are sent to and received by multiple sites need to have a consistent order imposed by all sites. Causal ordering allows the cause and effect relations of messages to be maintained. This paper presents an algorithm that ensures that multimedia data with real?time deadlines are delivered to the application layer in causal order. The algorithm is designed to ensure that any message that arrives at a destination site before its deadline will be delivered to the application before the message expires. In addition, by focusing on a form of causal ordering violations caused by "the triangle inequality", this algorithm has a low overhead with respect to the amount of information that must be appended to each message.
TL;DR: It is shown how data‐structures and models arise naturally within the application areas of environmental epidemiology and software reliability, and lead to statistical analyses using novel forms of Poisson regression models with random effects.
Abstract: A broad array of data series have embedded discrete event?occurrences, cumulative counts of which can be viewed as superpositions $$N(t) = \sum {_{i = 1}^n } N_i (t)$$ of independent identically distributed (iid) counting processes with intensities of the form $$\lambda _i (t) = h(Z_i ,V(t),\vartheta )$$ , where ? is unknown, n may be unknown, Z i are unobservable iid vectors, and V(t) is an observable "environmental" vector process, but the function h is known or hypothesized. It is shown how such data?structures and models arise naturally within the application areas of environmental epidemiology and software reliability, and lead to statistical analyses using novel forms of Poisson regression models with random effects. Such models are potentially very useful in analysis and characterization of teletraffic patterns.
TL;DR: A comprehensive overview of the discrete time batch Markovian arrival process and related results are presented, and graphically the simulation of the original processes and shaped process with different parameters are shown.
Abstract: In this paper, we study a traffic shaping scheme, frames with peak rate emission (FPRE), for ATM network. The arrival process is modeled by a discrete Markovian arrival process with single arrivals. A comprehensive overview of the discrete time batch Markovian arrival process and related results are presented. Some performance measurements of the scheme FPRE, the loss probability, the delay and the interarrival time distributions are derived. Examples are shown, applying both the analytical results and simulation, to demonstrate the effectiveness of the traffic shaping schemes. We also show graphically the simulation of the original processes and shaped process with different parameters.
TL;DR: The paper analyzes the switching performance and shows that this switch has lower cell loss probability vs. buffer size than other two known solutions given in (Tobagi et al., 1991; Urushidani, 1991; Hino et al, 1995).
Abstract: In this paper a new N×N space division ATM switch architecture based on banyan network is presented. This architecture is a multistage interconnection network with more than n (n=log2 N) switching stages. The interconnection algorithm offers many access outputs and resolves output contention by laying buffers. The paper analyzes the switching performance and shows that this switch has lower cell loss probability vs. buffer size than other two known solutions given in (Tobagi et al., 1991; Urushidani, 1991; Hino et al., 1995).
TL;DR: It is shown that correlation in branch noise can be used to improve the combiner performance by dynamically adjusting the weightings so as to partially cancel the noise.
Abstract: In this paper the performance of predetection maximal ratio and equal gain combiners are investigated under conditions of correlated branch noise. A statistical model is devised to determine the spatial noise correlation coefficients at metropolitan?area base stations, and the cases where significant correlation is likely are clarified. Optimal weighting coefficients for a maximal ratio combiner with two?branch space diversity are derived under correlated noise. Based on this result it is shown that correlation in branch noise can be used to improve the combiner performance by dynamically adjusting the weightings so as to partially cancel the noise. Performance of equal gain combiners is also shortly discussed.
TL;DR: A burst assignment problem for satellite‐switched time‐division multiple access networks is generalized to distinguish traffic requirements of earth stations in a network, leading to shorter transmission time in general.
Abstract: A burst assignment problem for satellite?switched time?division multiple access networks is generalized to distinguish traffic requirements of earth stations in a network. This distinction leads to shorter transmission time in general. The satellite provides coverage for u uplink spotbeams and v downlink spotbeams with prescribed limits on the maximum number of available carriers in each spotbeam, subject to a total of K carriers in use at any one time. Earth stations are equipped for simultaneous transmission on and reception of multiple carriers. If U+V is O(K), the number of switching modes required is O(K 2) and a transmission?time optimal schedule can be found in O(K 4) time. Technology considerations are discussed.
TL;DR: The focus of this report is the effect of traffic loading on data delivery, which shows steady‐state latencies in the range of tenths of milli‐seconds under a mild loading condition.
Abstract: This is a follow?up report on the end?to?end data link performance of the NASA deep space network. The focus of this report is the effect of traffic loading on data delivery. Architecture of the existing network is modeled via COMNET. The contribution of the data latency to the overall acquisition time is simulated as a function of network traffic conditions. The results show steady?state latencies in the range of tenths of milli?seconds under a mild loading condition. During heavy traffic, a delay rate of over a hundred seconds of increased delay per hour of network operation time is observed. This is primarily due to the queueing delays associated with large volume of data stored in the buffers throughout the link.
TL;DR: The traffic estimation and dynamic bandwidth adaptation function of the NBBS architecture is described and the dynamic Connection Admission Control (CAC) procedures described enable more efficient bandwidth management in high‐speed networks.
Abstract: Networking BroadBand Services (NBBS) is IBM's control point architecture for next generation high?speed packet? or cell?switched networks and is implemented in a family of network switching nodes. In this paper, we describe the traffic estimation and dynamic bandwidth adaptation function of the NBBS architecture. The dynamic Connection Admission Control (CAC) procedures we describe in this paper enable more efficient bandwidth management in high?speed networks. The dynamic CAC procedures we propose rely on traffic identification at the access points to the network and adjustments in bandwidth allocated through the network. This framework allows the NBBS network to provide enhanced variable?bit?rate services for non?stationary traffic sources in addition to providing standards compliant variable?bit?rate services based on deterministic rule?based traffic descriptors. The traffic estimation methodology discussed here can also be used to devise easy?to?implement statistical conformance tests for Usage Parameter Control (UPC) mechanisms.
TL;DR: It is shown in this paper how the proposed schemes offer an improved performance over other access control mechanisms such as moving boundaries and other static priority strategies.
Abstract: In this paper, an intelligent scheme for controlling the QoS in multimedia, multi?rate networks is presented. The scheme implements a dynamic control mechanism, based on buffers with vaguely defined thresholds represented with fuzzy sets. This approach guarantees the QoS of real?time traffic and delivers non?realtime traffic at acceptable performance levels. The fuzzy mechanism, based on the principles of fuzzy control, dynamically responds to the alternating traffic patterns at the access node using a set of fuzzy control rules. The fuzzy control rules are carefully formulated to reduce the starvation of non?realtime traffic which is usually assigned a low priority. We also show in this paper how the proposed schemes offer an improved performance over other access control mechanisms such as moving boundaries and other static priority strategies.