Tetsuya Takine

(p,q)-Epidemic routing for sparsely populated mobile ad hoc networks

This paper considers (p, q )-Epidemic Routing, a class of store-carry-forward routing schemes, for sparsely populated mobile ad hoc networks. Our forwarding scheme includes Two-Hop Forwarding and the conventional Epidemic Routing as special cases. In such forwarding schemes, the original packet is copied many times and its packet copies spread over the network. Therefore those packet copies should be deleted after a packet reaches the destination. We analyze the performance of (p, q)-Epidemic Routing with VACCINE recovery scheme. Unlike most of the existing studies, we discuss the performance of (p, q)-Epidemic Routing in depth, taking account of the recovery process that deletes unnecessary packets from the network.

An analysis of a discrete-time queue for broadband ISDN with priorities among traffic classes

In broadband ISDN, different classes of traffic expect to receive different quality of service. One way of providing service is to implement a priority structure among traffic classes. The authors analyze a single server queue in which video and voice traffic receive priority over data traffic. Corresponding to the fixed cell size of ATM, they assume that service times are deterministic. They further assume that the high priority traffic is correlated and the arrivals are governed by a Markov chain. With these assumptions, they characterize the queue length distributions and the waiting time distributions for this problem. They show by numerical examples that the delay distribution depends highly on the correlations and that a priority service discipline is capable of providing very good service for real time traffic. >

The workload in the MAP/G/1 queue with state-dependent services: its application to a queue with preemptive resume priority

In this paper, we consider the workload process in the MAP/G/1 queue with state-dependent service time distributions. The arrival process of customers is assumed to be a MAP(Markovian arrival process), which is a class of semi-Markovian arrival processes. The amount of work brought into the system upon arrival is distributed according to a general distribution which may depend on the states of the underlying Markov chain immediately before and after arrivals. We first consider the first passage time to the idle state with an arbitrary initial condition. Based on this, we derive the time-dependent LST (Laplace-Stieltjes transform) for the amount of work in the system as well as the LST of its limiting distribution. As an application of the results, we consider a preemptive resume priority queue with independent MAP arrival streams. In the preemptive resume priority queue, the waiting time of customers in a particular priority class is considered as a first passage time (governed by higher priority customer...

A single server queue with service interruptions

In this paper we characterize the queue-length distribution as well as the waiting time distribution of a single-server queue which is subject to service interruptions. Such queues arise naturally in computer and communication problems in which customers belong to different classes and share a common server under some complicated service discipline. In such queues, the viewpoint of a given class of customers is that the server is not available for providing service some of the time, because it is busy serving customers from a different class. A natural special case of these queues is the class of preemptive priority queues. In this paper, we consider arrivals according the Markovian Arrival Process (MAP) and the server is not available for service at certain times. The service times are assumed to have a general distribution. We provide numerical examples to show that our methods are computationally feasible.

Cell loss and output process analyses of a finite-buffer discrete-time ATM queueing system with correlated arrivals

The performance of an asynchronous transfer mode (ATM) switching node is analyzed, taking cell arrival correlation into consideration. An ATM switching node is modeled as a discrete-time finite-buffer queue. Cell arrivals are assumed to follow a semi Markovian process. Various characteristics of the cell loss and the distribution function of the cell output process from an ATM switching node are analyzed. The cell loss probability, the consecutive loss probability, the distribution of loss period lengths, the joint distribution of successive cell interdeparture times, and the distributions of busy and idle periods are determined. It is shown that both the correlation and the variation of cell arrivals significantly affect the cell loss and the output process characteristics.<<ETX>>

Exact analysis of asymmetric polling systems with single buffers

A unified approach to general asymmetric polling systems with a single buffer at each station is presented. Two variations of single-buffer polling system are considered: the conventional system and the buffer-relaxation system. In the conventional system, a new massage is not allowed to queue until the previous message has been completely transmitted, while in the buffer-relaxation system, a newly arriving message can be stored in the buffer once the previous messages transmission has started. For each system, the Laplace-Stieltjies transform (LST) of the joint probability-distribution function (PDF) of station times is derived, from which the LST of the PDF of message delay is straightforwardly obtained. >

Dynamic Contention Window Control Mechanism to Achieve Fairness between Uplink and Downlink Flows in IEEE 802.11 Wireless LANs

This paper considers a fairness issue between uplink and downlink flows in IEEE 802.11 wireless LANs, where uplink flows dominate over downlink flows in terms of wireless bandwidth usage. As a solution to this unfairness, we propose modifying the IEEE 802.11 MAC protocol at access points (APs). Our scheme dynamically controls the minimum contention window size at APs and provides an ample opportunity for them to acquire the transmission right. Note that the proposed scheme does not require any modifications in the MAC protocol at wireless terminals. Furthermore, the optimal minimum contention window size is given by an explicit function of the ratio of the total packet rate of downlink flows to the packet rate of an uplink flow. Through simulation experiments with UDP and TCP flows, we show that the proposed scheme can achieve fairness between uplink and downlink flows.

A generalization of the matrix M/G/l paradigm for Markov chains with a tree structure

We generalize the theory of the M/G/1 paradigm to tree-like structures. There are two variables in the Markov chain, one of which takes values on the nodes of a d-ary tree. The other is an auxiliary variable, which takes one of m possible values. For this structure, the steady state probability depends on d matrices, G 1 ,..., G d which are solutions of a system of non-linear matrix equations. We also apply the theory to a multiple class last-come-first-served queue in which no preemption is allowed.

Queue Length Distribution in a FIFO Single-Server Queue with Multiple Arrival Streams Having Different Service Time Distributions

This paper considers the queue length distribution in a class of FIFO single-server queues with (possibly correlated) multiple arrival streams, where the service time distribution of customers may be different for different streams. It is widely recognized that the queue length distribution in a FIFO queue with multiple non-Poissonian arrival streams having different service time distributions is very hard to analyze, since we have to keep track of the complete order of customers in the queue to describe the queue length dynamics. In this paper, we provide an alternative way to solve the problem for a class of such queues, where arrival streams are governed by a finite-state Markov chain. We characterize the joint probability generating function of the stationary queue length distribution, by considering the joint distribution of the number of customers arriving from each stream during the stationary attained waiting time. Further we provide recursion formulas to compute the stationary joint queue length distribution and the stationary distribution representing from which stream each customer in the queue arrived.

On the relationship between queue lengths at a random instant and at a departure in the stationary queue with bmap arrivals

This paper considers the queue length distributions at a random point in time and at a departure in the stationary queue with a batch Markovian arrival process (BMAP). Using the rate conservation law of Miyazawa, we prove a simple relationship between the vector generating functions of the queue length distributions at a random point in time and at a departure. An interesting feature of the proof is that we do not assume any particular service mechanism. The relationship then holds for a broad class of stationary queues with BMAP arrivals.