Queuing Theory.

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Presentation transcript:

Queuing Theory

M/M/1 Queue Rate Transitions 1 2 3 n-1 n E t times process enters state n L leaves ( ) # = - £ 1

M/M/1 Queue Rate Transitions 1 2 3 n-1 n lim ( ) t n E L ® ¥ - £ = 1 lim ( ) t n E L ® ¥ = rate in = rate out

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m In steady state, rate at which process enters a state = rate at which a process leaves a state state 0 l m p 1 =

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m State Balance Eq. l m p 1 =

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m State Balance Eq. 1 l m p 1 = l m p 2 1 + =

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m State Balance Eq. 1 n l m p 1 = l m p 2 1 + = l m p n 1 + = -

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m Balance Eq. p 1 = l m l m p 1 = 2 + n -

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m Balance Eq. p 1 = l m l m p 1 = 2 + n - l m p 2 + = ( )

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m l m p 2 + = - ( ) p 1 = l m

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m l m p 2 + = - ( ) / m p 1 = l m

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m l m p 2 + = - ( ) / m p 1 = l m l m p 2 = ( )

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m p n = ( ) l m In general,

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m p n = ( ) l m In general, We also know that in steady state, we must be somewhere. That is,

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m p n = ( ) l m In general, We also know that in steady state, we must be somewhere. That is, p n = ¥ å 1

M/M/1 Queue Rate Transitions l l l l l l l 1 2 3 n-1 n m m m m m m m ¥ p n = å 1 p n = ¥ å 1 ( ) l m p = - 1 ( ) l m

M/M/1 Queue p = - 1 ( ) l m p 1 = - ( ) l m 1 p n 1 = - ( )n ( ) l m

Performance Criteria m L average in system np n = - ¥ å # ( ) 1 l

Performance Criteria å å m L average in system np n = - # ( ) 1 l Re , ¥ å # ( ) 1 l Re , ( ) call nx x n = ¥ å - 2 1

Performance Criteria å L = - ( ) 1 l m Re , ( ) call nx x - 1 2 ¥ n 2 2 1

Performance Criteria l W average wait in system L = - m 1

Performance Criteria W avg wait time in system service E S = - [ ] ( ) q = - [ ] ( ) 1 m l

Performance Criteria L avg in queue w q = - # ( ) l m 2

Performance Criteria L W q = - l m 1 2 ( )