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M/D/1 queue: Difference between revisions

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Define ''ρ''&nbsp;=&nbsp;''λ''/''μ'' as the utilization; then the mean delay in an M/D/1 queue is<ref>{{cite book|title=Wide Area Network Design:Concepts and Tools for Optimization|page=319|first=Robert S.|last=Cahn|year=1998|publisher=Morgan Kaufmann|isbn=1558604588}}</ref>
Define ''ρ''&nbsp;=&nbsp;''λ''/''μ'' as the utilization; then the mean delay in an M/D/1 queue is<ref>{{cite book|title=Wide Area Network Design:Concepts and Tools for Optimization|page=319|first=Robert S.|last=Cahn|year=1998|publisher=Morgan Kaufmann|isbn=1558604588}}</ref>
::<math>\frac{1}{\mu}\cdot\frac{2-\rho}{2-2\rho}.</math>
::<math>\frac{1}{\mu}\cdot\frac{2-\rho}{2-2\rho}.</math>

==Multiple servers==

Write ''c'' for the number of servers.

===Waiting time distribution===

Erlang showed that when ''ρ''&nbsp;=&nbsp;''λ''&nbsp;''D''/''c''&nbsp;<&nbsp;1, the waiting time distribution has distribution F(''y'') given by<ref name="franx">{{cite doi|10.1016/S0167-6377(01)00108-0}}</ref>

::<math>F(y) = \int_0^\infty F(x+y-D)\frac{\lambda^c x^{c-1}}{(c-1)!} e^{-\lambda x} \text{d} x, \quad y \geq 0 \quad c \in \mathbb N.</math>

Crommelin showed that, writing ''P''<sub>''n''</sub> for the stationary probability of a system with ''n'' or fewer customers,
<ref>{{cite journal | first = C.D. | last = Crommelin | title = Delay probability formulas when the holding times are constant | journal = P.O. Electr. Engr. J.| volume = 25| year=1932| pages= 41–50}}</ref>

::<math>\mathbb P(W \leq x) = \sum_{n=0}^{c-1} P_n \sum_{k=1}^m \frac{(-\lambda(x-kD))^{(k+1)c-1-n}}{((K+1)c-1-n)!}e^{\lambda(x-kD)}, \quad mD \leq x <(m+1)D.</math>


==Finite capacity==
==Finite capacity==

Revision as of 10:52, 14 June 2013

In queueing theory, a discipline within the mathematical theory of probability, an M/D/1 queue represents the queue length in a system having a single server, where arrivals are determined by a Poisson process and job service times are fixed (deterministic). The model name is written in Kendall's notation.[1] Agner Krarup Erlang first published on this model in 1909, starting the subject of queueing theory.[2][3]

Model definition

An M/D/1 queue is a stochastic process whose state space is the set {0,1,2,3,...} where the value corresponds to the number of customers in the system, including any currently in service.

  • Arrivals occur at rate λ according to a Poisson process and move the process from state i to i + 1.
  • Service times are deterministic time D (serving at rate μ = 1/D).
  • A single server serves customers one at a time from the front of the queue, according to a first-come, first-served discipline. When the service is complete the customer leaves the queue and the number of customers in the system reduces by one.
  • The buffer is of infinite size, so there is no limit on the number of customers it can contain.

Delay

Define ρ = λ/μ as the utilization; then the mean delay in an M/D/1 queue is[4]

Finite capacity

Transient solution

The transient solution of an M/D/1 queue of finite capacity N, often written M/D/1/N, was published by Garcia et al in 2002.[5]

References

  1. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1214/aoms/1177728975, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1214/aoms/1177728975 instead.
  2. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1007/s11134-009-9147-4, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1007/s11134-009-9147-4 instead.
  3. ^ "The theory of probabilities and telephone conversations" (PDF). Nyt Tidsskrift for Matematik B. 20: 33–39. 1909.
  4. ^ Cahn, Robert S. (1998). Wide Area Network Design:Concepts and Tools for Optimization. Morgan Kaufmann. p. 319. ISBN 1558604588.
  5. ^ Attention: This template ({{cite jstor}}) is deprecated. To cite the publication identified by jstor:3216008, please use {{cite journal}} with |jstor=3216008 instead.