Packet Delay Distribution Research Articles

Video Broadcasting Using Queue Proportional Scheduling

Queue Proportional Scheduling (QPS) has been shown to be throughput optimal for Gaussian Broadcast Channels. This paper examines the use of QPS for Video Broadcasting. First, the behavior of QPS is examined as the scheduling frequency is reduced and a method is proposed that uses statistics on the arrival rates to improve its performance. The reduction of the scheduling frequency simplifies the scheduler and decreases the required operations. Then, the packet delay variation is modeled using a Markov Chain approach leading to a method for approximating the packet delay distribution. Based on the resulting distribution, it is discussed how the video encoding rate can be chosen in order to reduce the expected distortion of streams transmitted through Broadcast Channels.

On the performance of ad hoc wireless LANs: A practical queuing theoretic model

In this paper, two Markov chain queuing models have been developed to obtain closed-form solutions for packet delay and packet throughput distributions in a real-time wireless communication environment using IEEE 802.11 DCF. An M/G/1/K queuing model is incorporated in both models. In the first model results are based on arbitrary contention conditions, namely, collision probabilities, transmission probabilities and contention window sizes vary arbitrarily among nodes contending for channel access. In the second model, however, the contention condition is limited by the assumption that collision probabilities remain constant among contending nodes. Results are presented for the fully-connected case. Two models are compared and validated via simulation with statistical analysis. The main contributions are the analysis of DCF and the foundation for the sensitivity analysis.

Packet delay in optical circuit-switched networks

A framework is provided for evaluation of packet delay distribution in an optical circuit-switched network. The framework is based on a fluid traffic model, packet queueing at edge routers, and circuit-switched transmission between edge routers. Packets are assigned to buffers according to their destination, delay constraint, physical route and wavelength. At every decision epoch, a subset of buffers is allocated to end-to-end circuits for transmission, where circuit holding times are based on limited and exhaustive circuit allocation policies. To ensure computational tractability, the framework approximates the evolution of each buffer independently. Slack variables are introduced to decouple amongst buffers in a way that the evolution of each buffer remains consistent with all other buffers in the network. The delay distribution is derived for a single buffer and an approximation is given for a network of buffers. The approximation entails finding a fixed point for the functional relation between the slack variables and a specific circuit allocation policy. An analysis of a specific policy, in which circuits are probabilistically allocated based on buffer size, is given as an illustrative example. The framework is shown to be in good agreement with a discrete event simulation model.

Local area network analysis using end-to-end delay tomography

There has been considerable interest over the last few years in collecting and analyzing internet traffic data in order to estimate quality of service parameters such as packet loss rates and delay distributions. In this paper, we focus on fast and efficient estimation methods for network link delay distributions based on end-to-end measurements obtained by probing the underlying. We introduce a rigorous statistical framework for designing the necessary probing experiments and examine the properties of the proposed estimators. The proposed framework and the resulting methodology are validated using data collected on the University of North Carolina (UNC) local area network.

Methods for evaluation packet delay distribution of flows using Expedited Forwarding PHB

Methods for evaluation packet delay distribution of flows using Expedited Forwarding PHB

Packet Loss Probability for Bursty Wireless Real-Time Traffic Through Delay Model

In this work, two Markov chains modeling packet delay have been developed to obtain closed-form solutions for packet loss probabilities and packet delay distributions in a real-time wireless communication environment. Packets with delay constraints are queued at the source and are transmitted one by one with possible retransmissions to correct errors. The first model models packet delay and correlated packet arrivals using a one-dimensional Markov chain. Usually, at least two dimensions are needed in queuing models. The second model is a two-dimensional Markov chain modeling packet delay, correlated channel errors, and correlated arrivals. Both correlated errors and arrivals are known to have significant impact on packet loss. Possible applications of the results are also discussed.

Design and Analysis of a Channel Access Protocol for WDM-Based Single-Hop Optical Networks*

We propose a channel access protocol for single-hop wavelength division multiplexing (WDM) optical networks. Each node is equipped with a fixed-tuned transmitter, a tunable transmitter, a fixed-tuned receiver, and a tunable receiver. The proposed protocol alleviates the drawbacks of a previous protocol [1], e.g., invalid data transmissions that follows receiver collisions and possible acknowledgment packet collisions with header/data packets, while retaining many advantages. As a result, the network performance in terms of throughput and packet delay is improved. Analytical models based on the timing diagram analysis, the continuous-time Markov chain, and the randomization technique are developed to assess the proposed protocol, and are validated through event-driven simulation. The performance is evaluated in terms of channel utilization, mean packet delay, and packet delay distribution with variations in the number of nodes, the offered traffic, the size of data packets, and the network propagation delay. Through numerical results and simulation studies, we show that the proposed protocol achieves better channel utilization and incurs lower packet delays.

Multicast-based inference of network-internal delay distributions

Packet delay greatly influences the overall performance of network applications. It is therefore important to identify causes and locations of delay performance degradation within a network. Existing techniques, largely based on end-to-end delay measurements of unicast traffic, are well suited to monitor and characterize the behavior of particular end-to-end paths. Within these approaches, however, it is not clear how to apportion the variable component of end-to-end delay as queueing delay at each link along a path. Moreover, there are issues of scalability for large networks. In this paper, we show how end-to-end measurements of multicast traffic can be used to infer the packet delay distribution and utilization on each link of a logical multicast tree. The idea, recently introduced in Caceres et al. (1999), is to exploit the inherent correlation between multicast observations to infer performance of paths between branch points in a tree spanning a multicast source and its receivers. The method does not depend on cooperation from intervening network elements; because of the bandwidth efficiency of multicast traffic, it is suitable for large-scale measurements of both end-to-end and internal network dynamics. We establish desirable statistical properties of the estimator, namely consistency and asymptotic normality. We evaluate the estimator through simulation and observe that it is robust with respect to moderate violations of the underlying model.

Performance analysis of CFDAMA-PB protocol for packet satellite communications

Combined free/demand-assignment multiple-access (CFDAMA) schemes are suitable for broad-band packet satellite communications systems serving a finite number of bursty data sources. The performance analysis of the CFDAMA using piggy-backed (PB) reservation is presented. The probability generating function (PGF) of the packet delay is developed. The performance is evaluated in terms of three performance measures: average packet delay, variance of packet delay, and cumulative probability distribution of packet delay. Performance comparison with other pertinent schemes shows CFDAMA-PB to be superior for a wide range of user population sizes.

Performance Of An Input/output Buffered-type Atm Lan Switch With Back-pressure Function

An ATM switch with both input and output buffers provided with a back-pressure function has been proposed as a cost-effective switch architecture. The back-pressure function prohibits cell transmission from the input buffer to the corresponding output buffer to avoid cell loss at the output buffer due to a temporary congestion. Especially when this switch is applied to ATM LANs for data transfer services, its performance should be evaluated by taking into account bursty traffic. In this paper, we show the maximum throughput, the packet delay distribution, and the approximate packet loss probability of such an ATM switch for bursty traffic through an analytic method. In addition to a balanced traffic condition, an unbalanced traffic and a mixture of bursty and stream traffic are also analyzed. Through several numerical examples, we quantitatively show the effects of the average packet length and the output buffer size on its performance.

Nonuniform traffic in the Manhattan street network

The Manhattan Street Network is a toroidal network proposed for application as a Metropolitan Area Network. The network uses deflection routing, an adaptive routing scheme where nodes attempt to send packets along shortest paths to their destinations. Contention for communication link access is resolved by forcing packets to travel longer paths. We consider a network operating with deflection routing and nonuniform traffic. In addition, each communication link may be characterized by an arbitrary but known propagation delay. We study a contention resolution rule giving priority to packets in the network longest. Independence approximations are used to describe the distribution of packet arrivals at each node, and we derive approximate steady-state packet delay distributions. Examples are presented and compared to simulation results, and the independence assumption is discussed.

Analysis of an M/G/1/N queue with vacations and its iterative application to FDDI timed-token rings

We present the analysis of an M/G/1/N queueing system with vacations under a dynamic time-limited service policy. This method is used to develop a procedure for performance analysis of a fiber distributed data interface (FDDI) network serving buffer-limited stations under asynchronous service. An efficient iteration procedure is employed to evaluate the limiting state distribution of the embedded Markov chain representing the system state process. Using supplementary variables and sample biasing techniques, we derive the queue size distribution at an arbitrary instant of time as well as the packet blocking probability and the mean packet delay. By exploiting the subtle structure of conditional supplementary variables and the recursive property of the conditional residual delay, the Laplace-Stieltjes transform of the packet delay distribution and a time-domain approximation of the packet delay distribution are obtained. For the analysis of a heterogeneous multi-station FDDI network, an iterative procedure which uses repeatedly the M/G/1/N vacation model described above is presented. This procedure provides for a numerically efficient analysis method by employing constructions of the approximate vacation time distributions. We illustrate the application of our analytical techniques to both symmetric and nonsymmetric FDDI network systems.

Packet delay and queue length for statistical multiplexers with low-speed access lines

A slotted statistical multiplexer is considered to which variable-length messages arrive via low-speed access lines. More specifically, messages are assumed to consist of multiple packets and to enter the multiplexer buffer at a rate of one packet per slot, which results in a correlated packet arrival stream into the multiplexer. Assuming a geometric distribution for the message lengths, the system is analyzed by using a two-dimensional state description, and a functional equation characterizing the queue-length behavior of the multiplexer buffer is found. An (implicit) expression for the probability generating function of the packet delay is also obtained. A technique is then developed to derive from these results closed-form expressions for the moments of the queue-length and the packet-delay distributions. Explicit formulas are given for the mean and the variance of both distributions. The results are illustrated by means of a practical example and the influence of the correlation in the packet arrival stream is investigated.

Performance analysis of a stack random access algorithm for CSMA and CSMA/CD channels

A stack random access algorithm for CSMA (carrier sense multiple access) and CSMA/CO (CSMA with collision detection) channels is presented. The algorithm adapts its operation to the characteristics of the channel at hand by means of two parameters. Utilizing the regenerative character of the induced packet delay process, a lower bound on the algorithm's maximum stable throughput and very tight upper and lower bounds on the mean packet delay are derived. The packet delay distribution is estimated using the regenerative simulation method. The proposed algorithm is inherently stable, easy to implement, and combines high performance with modest channel monitoring requirements. >

A selective-repeat-ARQ protocol for parallel channels and its resequencing analysis

A communications system in which multiple parallel channels are available to carry traffic from a transmitter to a receiver is considered, and an extension of the selective-repeat automatic repeat request (SR-ARQ) protocol that dynamically assigns packets to channels for each (re)transmission is presented. Because of selective retransmission, packets arrive at the receiver out of order and must be stored in a resequencing buffer. A queuing model for the resequencing buffer is constructed. The generating function of the buffer occupancy and the packet-delay distribution are derived, and procedures for simplifying the computation are presented. The dynamic assignment scheme is compared with, and shown to have performance superior to, a static assignment scheme. >

Performance Analysis Of An Integrated Services Switch

AbstractThe queueing perfonnance of a single server packet-switched system serving two priority classes is analyzed. High priority (HP) packets are assumed to be correlated while low priority (LP) inputs are assumed to obey a Poisson distribution. The system is modeled as a discrete-time single server system and the analysis of the priority service discipline is formulated using an alternating work/vacation model. The transition probabilities of the work/vacation model are manifestations of the correlations within the HP sources. Generating functions (GF) for the queue length, busy period, and packet delay distribution are obtained. It is shown that the correlation present in the HP traffic exerts a significant effect on the queueing performance ofthe LP traffic.

Delay analysis of the n-ary stack random-access algorithm

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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance Analysis of Finite Nonhomogeneous Population Tree Conflict Resolution Algorithms Using Constant Size Window Access

Multiple-access protocols control access to a broadcast communication channel. Tree conflict resolution algorithms are the heart of some distributed multiple-access protocols with nice properties like stability, high capacity, and low delay under light load. We consider a random access protocol based on a tree conflict resolution algorithm similar to one first proposed by Capetanakis, but in which constant size windows on the arrival time axis are used to admit packets into the algorithm instead of the more common "free" or "blocked" access methods. We obtain exact recursive relationships for the (steady-state) distribution of packet delay, and thus, the exact throughput-delay curve for any finite (in general, nonhomogeneous) configuration under a Bernoulli-per-window arrival model. Then, we consider the address assignment problem. We show that by choosing an appropriate addressing scheme, we can improve the performance of the algorithm with respect to both mean delay and maximum throughput.

A Markov Modulated Characterization of Packetized Voice and Data Traffic and Related Statistical Multiplexer Performance

We study the performance of a statistical multiplexer whose inputs consist of a superposition of packetized voice sources and data. The performance analysis predicts voice packet delay distributions, which usually have a stringent requirement, as well as data packet delay distributions. The superposition is approximated by a correlated Markov modulated Poisson process (MMPP), which is chosen such that several of its statistical characteristics identically match those of the superposition. Matrix analytic methods are then used to evaluate system performance measures. In particular, we obtain moments of voice and data delay distributions and queue length distributions. We also obtain Laplace-Stieitjes transforms of the voice and data packet delay distributions, which are numerically inverted to evaluate tails of delay distributions. It is shown how the matrix analytic methodology can incorporate practical system considerations such as finite buffers and a class of overload control mechanisms discussed in the literature. Comparisons with simulation show the methods to be accurate. The numerical results for the tails of the voice packet delay distribution show the dramatic effect of traffic variability and correlations on performance.

Queueing analysis of buffered slotted multiple access protocols

Much of the literature on the performance evaluation of multiple access protocols has assumed a buffer capacity of one unit. This assumption is not realistic. In practice the buffer capacities used are larger than one unit in order to reduce the probability of packet rejection. This is more crucial for multiple access protocols, which allow moderate to high values of the expected throughput (URN, Random TDMA etc.). In this paper, a model appropriate for the analysis of buffered slotted multiple access schemes is proposed. The method can be applied to several multiple access protocols such as the URN protocol, the ALOHA protocol, Random TDMA etc. The cases of infinite and finite buffer capacity are examined separately but under the same basic assumptions. The analysis is based on the assumption that each user process can be modelled as an M/G/1 queueing system. The proposed method requires a small amount of computation and is characterized by a high speed, a fact that simplifies the buffer's design as well. The solution obtained is extremely accurate and exhibits excellent agreement with simulation results, which corroborate the accuracy of the model. The special case when the buffer capacity is equal to 1 is examined. In that case, the present approach also allows for computation of the packet delay distribution.