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Perturbation Analysis of a Variable M/M/1 Queue: A Probabilistic Approach

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HAL Id: inria-00070587

https://hal.inria.fr/inria-00070587

Submitted on 19 May 2006

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Perturbation Analysis of a Variable M/M/1 Queue: A Probabilistic Approach

Nelson Antunes, Christine Fricker, Fabrice Guillemin, Philippe Robert

To cite this version:

Nelson Antunes, Christine Fricker, Fabrice Guillemin, Philippe Robert. Perturbation Analysis of a Variable M/M/1 Queue: A Probabilistic Approach. [Research Report] RR-5419, INRIA. 2005, pp.26.

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ISRN INRIA/RR--5419--FR+ENG

a p p o r t

d e r e c h e r c h e

Thème COM

INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET EN AUTOMATIQUE

Perturbation Analysis of a Variable M / M / 1 Queue:

A Probabilistic Approach

Nelson Antunes — Christine Fricker — Fabrice Guillemin — Philippe Robert

N° 5419

Deembre 2004

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(7)

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ªjkƒY[]tu‚[‚[rµkƒr o=q€tŸnHt~€t=nr kzg¤rsikmY[]Hxm]E¢Ýouxƒ]

εp + (X(t))

tuq€‚

−εp (X(t))

rsikmY[]nHt~€t=nr kzgŸ o3izk7°

(9)

XY[]bœLtxƒrtuŽ[Ÿ]

B e ε

rsi¨kmY[]b‚jp[xvtLkƒr o=q¤o¢tŽ[p€img~]Hxmroj‚¤izkvtxmkmrq[’§&r kmYtnpizkƒou\ž]Ex7ªukƒY€tLkrsiEªh’urœu]Hq

L e ε (0) = 1

ª

B e ε = inf{s ≥ 0 : L e ε (s) = 0}.

º€oux

x ≥ 1

ªhkmY[]œLtxƒrstŽ[Ÿ]

B e x ε

‚j]Eq€okm]7i¨kmY[]#‚jp[xvtLkƒr o=qVou¢.t_Ž[p€img¤~]Hxmroj‚ilkƒtuxlkƒr q€’_§&r kmY

x

np€ilkmo=\B]Hxƒi

e B ε 1

= B e ε

¸° -ùqkmY[]#xƒ]Hilk&o¢kƒY[rsi&~€t~P]Ex7ª[§«]\žtu¥u]kmY[]kz§«oB¢ÝouŸŸ oL§&rq[’tuiƒimp[\ž~jkmrouq€iK+

kƒY[]¢Ýp[q€nkmrouq

|p(x)|

rsi&ށo=p[q€‚j]7‚Ž3gtBnEouq€ilkƒtuq3k

M > 0

H 1

¸

ε sup(|p(x)| : x ∈ S) < µ.

H 2

¸

e3kvtq€‚€txv‚¬txƒ’up[\ž]Eq3kviEª.il]H]VaM]Eghq¯tuq€‚¬X§«]E]7‚jr]L2 4Jª³imY[oL§ kmY€tk

( L e ε (t), X(t))

ri_tq¬]Hxm’=oh‚[rn aGtxƒ¥uoLœžw@xƒohnE]Hiƒi§&Y[]Eq

λ < µ

tuq€‚

ε

ri|ilpj©¤nEr ]Hq=kƒŸ gil\tŸŸ)imo_kƒY€tLk&kƒY[]#xƒ]EŸstLkmrouq

λ < µ

1 + ε Z

S

p (x) ν(dx)

rsiiƒtLkmrsil²€]H‚ï° 5}q€‚[]ExžkmY€]›nouq‚jrµkƒr o=q

ρ = λ/µ < 1

ª@kmY€rinEouq€‚jr kmrouq §&rŸ Ÿ&ŽP]›imtkmrsiz²]H‚¯~€xmoLœhrs‚j]H‚

kƒY€tLk

ε

riilpj©¤nEr ]Hq=kƒŸ gMim\tŸŸ5°bXY[]

®

p[]Hp[]§&r kmYMkƒr \ž]E¦JœLtxƒghr q€’Vil]Hxmœhrsn]xvtLkƒ]tui‚j]²q[]H‚›tuށoLœ=]§&rŸ Ÿ

ŽP]žxm]E¢Ý]Exƒxm]7‚Mkƒo›tuikmY[]~P]Exmkmp€xmŽ€tkm]7‚

®

p[]Hp[]uª‚[]Eq[oukm]H‚)ª)¢Ýoux#imY[ouxmkHªŽ3gGw³¦Ep€]Ep[]=°žXY€]žnHtuim]

ε = 0

o=Žhœ3roupilŸg¤no=xmxƒ]Him~o=q€‚[iWkmožkƒY[]e3¦FEp[]Ep[]=°

- +,+ %(5"!(,+ &%( 4,"# &2 /

XY€]WŽ€t=ilrsn³rs‚j]Ht&ou¢jkmY[]«~P]Exmkmp[xƒŽ€tLkƒr o=qtq€tuŸ gjimrinEtxƒxƒr ]7‚oupjk.r q#kƒY[rsi~€tu~]Hxrsi)kƒonEouq€ilkmxƒp€nk.t|no=p[~[Ÿr q€’

ou¢WkƒY[]Ž[p€imgG~P]Exƒr oj‚[iou¢¨kƒY[]~[xƒojn]Hiƒim]Hi

(L(t))

tuq€‚

( L e ε (t))

°VXY[rsiri‚[ouq[]tuib¢Ýo=Ÿ ŸoL§}iHª)~[xƒoLœ3rs‚j]7‚

kƒY€tLk&¢Ýo=x&ށoukmY

®

p[]Ep€]Hi«kmY€]txƒxmrœLtŸ9~[xƒohnE]Hiƒi«ri

N λ

°

“žÂ. ·–Á ˜ ³Â ½ ˜j—¹–— ½ • ´±]‚j]Hq[okƒ]|Žhg

N +

kmY[]q[ouqj¦ÕY[o=\Bo=’u]Hq[]Eo=p€i$w$oursimimouqž~[xƒojn]Hiƒi@§&Y€o=im]

rq3km]Hq€ilr kzgVrsi}’=r œ=]EqŽhg

t → εp + (X (t))

°|^¨ouq€‚jr kmrouqtŸŸ gouq

(X(t))

ª€kƒY[]qhp[\ŽP]Exo¢³~Pourq=kvi}ou¢

N +

rqkmY[]#rq3km]HxmœLtŸ

[a, b]

ª

0 ≤ a ≤ b

rsiw$oursimimouq§&r kmY~€txvt\ž]Ekm]Ex

ε Z b

a

p + (X(s)) ds.

XY€]V~Pourq=kviou¢

N +

txƒ]V‚j]Eq€okm]7‚¬Žhg

0 < t + 1 ≤ t + 2 ≤ · · · ≤ t + n · · ·

tq€‚¯tuxm]¤nHtŸŸ ]7‚¯tu‚€‚jrµkƒr o=q€tŸ

‚[]E~€tuxlkƒp[xm]7iE°>-ùq~€txmkmrsnp€ŸtuxWkƒY[]‚jrsizkƒxmrŽ[pjkƒr o=qou¢kmY€]#Ÿ ojnEtkmrouq

t + 1

ou¢kmY€]²xƒilk&~o=r q3k}o¢

N +

t¢àkm]Hx

0

rsi’urœu]HqŽhg=ªh¢Ýoux

≥ 0

ª

P(t + 1 ≥ x) = P(N + ([0, x]) = 0) = E

exp

−ε Z x

0

p + (X(s)) ds

.

¶5u¸

ej]E] xƒtuq€‚j]HŸ Ÿ2ӆ4j¢Ýoux@tuqBt=nEnEoup[q3k$ouqBq[ouqj¦ÕY[o=\Bo=’u]Hq[]Eo=p€i)w$oursiƒilo=q~[xƒojn]Hiƒim]HiHªLxm]E¢Ý]Exƒxm]7‚#kmo#t=i.‚[oup[Ž[Ÿg

ilkmojnvY€t=izkƒrnw$oursimimouq~[xƒojn]Hiƒim]HiH°

(10)

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M/M/1

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½ Á ½ ˜j—¹–— ½ • ´Š]V‚[]Eq[oukm]¤Žhg

N

kmY[]¤~Pourq3k_~[xƒojn]7imio=Žjkƒtur q[]7‚­Žhg '# ¤kmY[]

~Pourq3k«~€xmojn]7imi

N µ

¶5eh]H]b{}ouŽP]Exmk 2ˆ7 4ݸ° -Õkrsi«‚[]²€q[]7‚t=i@¢Ýo=Ÿ ŸoL§}iK+.Ã"~Pourq=k&tLk

s > 0

ou¢kmY€]w$oursiƒilo=q

~€xmojn]7imi

N µ

ri«t~Pourq3k«ou¢

N

§&r kmY~[xmo=Ž€tŽ€r Ÿrµkzg

εp (X(s))/µ

° -ùq¤kƒY[ri«§t¹guª

N

ri«t_ilkƒtkmrouq€tuxmg

~Pourq3k|~[xƒojn]Hiƒi&§&r kmY›rq3km]Hq€ilr kzg

εp (X(s))

°}Ä~o=r q3k|ou¢

N

rsi|nEtuŸ Ÿ]H‚Mt¤\žtuxm¥=]H‚‚j]H~€txmkmp[xƒ]u°&XY[]

~Pourq3kƒiou¢

N

txƒ]‚j]Eq[oukm]7‚Žhg

0 < t 1 ≤ t 2 ≤ · · · ≤ t n ≤ · · ·

°@º€oux

x > 0

ªjŽhgV‚j]E²€q[r kmrouq)ª

P(t 1 ≥ x) = E

N µ ([0,x])

Y

i=1

1 − εp (X (s i )) µ

 ,

¶(=¸

§&Y€]Exƒ]

(s i )

tuxm]kmY[]#~Pourq3kƒi&ou¢kƒY[]#~o=r q3k}~[xƒojn]7imi

N µ

°

´ár kmYkmY€]tŽPoLœu]bq[okvtLkmrouqªjrµk}rsiq[ok}‚jr ©¤np[Ÿ k&kmoimY[oL§kƒY€tLkkƒY[]a›txƒ¥uoLœž~[xƒojn]7imi

(e L ε (t))

Y€tui

kƒY[]iƒt\ž]#‚jrilkmxƒrŽ[pjkmrouqtui«kƒY[]imouŸpjkmrouqo¢.kmY[]ilkmojnvY€t=izkƒrnb‚jr=/P]Hxm]Hq3kmrstŸ)]

®

ptLkmrouq

de L ε (t) = d N λ (t) − {e L ε (t−)>0} d N µ + N + − N

(t),

¶·‡3¸

§&Y€rnvYri&kmY[]tuq€tŸou’=p[]ou¢Ä

®

p€tkmrouq¬¶zˆ7¸¨¢ÝouxkmY€]#w³¦Ep€]Ep[]=°

)f,±. «' .) #¡.

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0

rqGkƒY[]¤e3¦FEp[]Ep[]žtq‚

w@¦Ep[]Hp[]u°1-ùqkƒY[riil]7nkƒr o=q)ª€§«]‚j]Ekm]Exƒ\žr q€]#kmY[]²€xƒilk}kƒ]Exƒ\ou¢.kƒY[]~PoL§¨]Hx|im]Exƒr ]7i&]£j~€tuq€ilrouqrq

ε

ou¢

kƒY[]]E£h~P]Hnkm]7‚œ¹tuŸ p€]#o¢

B e ε

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kƒY[]#\žouxƒ]rq3kmxƒrnHtLkƒ]im]HnEouq€‚Vkm]Hxm\o¢kmY[]#~PoL§¨]Hx}il]Hxmr]Hi«]E£h~tq€imr o=qrq

ε

°

º€ouxkmY€]²xƒilk«o=xƒ‚[]Ex«km]Hxm\ªj§«]o=q[Ÿ gVY€t¹œu]|kmono=q€ilrs‚j]Hx¨kƒY[]#nEt=il]7i¨§&Y€]EqkmY[]Hxm]rsi¨]HrµkƒY[]Ex}tžimr q€’uŸ]

t=‚[‚jr kmrouq€tuŸ@‚j]E~txmkmp[xƒ]žoux#]EŸsim]¤tMilrq[’uŸ]ž\txƒ¥u]H‚±‚j]H~€txmkmp[xƒ]u°¤XY€]~[xmo=Ž€tŽ€r Ÿrµkzg›kmY€tkށoukmY¬]Eœ=]Eq3kƒi

ojnHnp[x«r q¤kmY[]imtu\ž]|Ž[p€imgž~]Hxmroj‚¤rsi¨nEŸ ]7txƒŸ gžou¢ïkmY[]bouxv‚j]Ex¨o¢)\t’=q[r kmp€‚j]bo¢

ε 2

ilrq€nE]}kmY€]rq3km]Eqilr kmr]Hi ou¢kƒY[]tuiƒilojnErtkm]H‚Vw$oursimimouq~[xƒohnE]Hiƒil]7itxƒ]~[xƒou~PouxmkmrouqtŸPkmo

ε

°

º€oux

x ≥ 1

ª)kmY[]ilkƒtŽ€r Ÿrµkzg›t=imimp[\ž~jkƒr o=q€ib]Eq€imp[xƒ]kƒY€tLkkmY€]B]E£j~]7nkm]7‚GœLtuŸ p[]7ibo¢WkƒY[]žŽ[p€imgM~]Hxmr ¦ oj‚[i#ilkƒtuxlkƒr q€’§&r kmY

x

nEp€ilkmou\ž]HxƒiHª)q€tu\B]HŸ g

E(B x )

tuq€‚

E( B e x ε )

ª$txƒ]BށoukmY­²€q[r km]=°¤´áY[]HqŠkƒY[]ž²€xvizk t=‚[‚jr kmrouq€tuŸ)tq€‚\txƒ¥u]7‚V‚j]H~€txmkmp[xƒ]Hi&tuxm]imp€nvYkmY€tk

t + 1 > B e ε

tq€‚

t 1 > B e ε

kƒY[]Eq

B = B e ε

°

-ùqMt_²€xvizk|ilkm]H~)ªj§¨]~[xƒoLœu]kmY€]¢ÝouŸŸ oL§&rq[’Bkm]7nvY[q[rsnEtŸïŸ]E\ž\t[°

¨½ ¯˜ C '#

K

O

ε 0 > 0

N'#

ε < ε 0

n ≥ 1

sup

x∈S E

B e n ε | X (0) = x

≤ Kn.

1KF -Õ¢$ouq€]nvY€o3o3il]7i

ε 0

imoBkmY€tk

µ 0

= µ − ε 0 inf{p (x) : x ∈ S} > λ,

kƒY[]Eq›nEŸ ]7txƒŸ gVkmY[]q3p€\ŽP]Ex|ou¢@np€ilkmo=\B]Hxƒi}o¢$kmY[]w³¦Ep€]Ep[]rsi|nE]Exmkƒtur q[Ÿgim\tŸŸ ]Hx&kmYtqkmY€]qhp[\ŽP]Ex

ou¢}np€ilkmo=\B]Hxƒio¢|tq

M/M/1

® p[]Ep[]§&rµkƒY¯txƒxmrœLtŸ@xvtLkƒ]

λ

tq€‚¬im]ExƒœhrnE]xƒtkm]

µ 0

°±^¨o=q€il]

®

p[]Eq3kmŸguª

(11)

kƒY[]žnouxƒxƒ]Him~o=q€‚jrq[’Ž[p€imgM~]Hxmroj‚[ibnou\ž~€tuxm]r qGkmY[]žimtu\ž]§t¹guªPY[]Eq€nE]r kbrsib]Eq[o=p[’uY›kmo¤kvt¥=]

K = 1/(µ 0 − λ)

°

rœu]HqkƒY[]tŽPoLœu]km]7nvY[q[rsnEtuŸïŸ ]H\B\t€ªj§¨]#q[oL§"no=q€ilrs‚j]Hx¨kƒY[]‚jr=/P]Hxm]Hq3k}~o3imimr Ž€r Ÿrµkƒr ]7iE°

“+• ½ ˜[ ݖ Á ˜ ¨Â ½ ˜j—¹– — ½

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(0, B e ε )

kmY€]Eq­tLk|kƒr \ž]

B e ε

ªjkmY€]#w³¦

®

p[]Hp[]#rsi]E\ž~jkzgtuq€‚

®

p€]Ep[]

L

rsi§&rµkƒYo=q[]npizkƒou\ž]Ex#¶·im]E]º.r’up[xƒ]žˆH¸°

6

- 6

e B B ε t + 1

0 1

w³¦FEp[]Ep[]

e3¦FEp[]Ep[]

º.r’up[xƒ]žˆ +³Ã(Ž[p€imgVw$]Hxmroj‚V§&r kmYMtqÃ&‚[‚jr kmrouqtŸ‹]E~€tuxlkƒp[xƒ]

´±]il~P]HnErµ²PnEtŸŸg¤~[xƒoLœu]kmY[]¢Ýo=Ÿ ŸoL§&r q€’BŸ]E\ž\t[°

¨½ ¯˜ L' < = CO

C

E

(B − B e ε ) {t +

1 <B}

= ε E ν [p(X (0)) + ]

(µ − λ) 2 + o(ε),

¶J†u¸

'

ν

3C< # 83C K O I#

(X (t))

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B e ε

rsi&ށ]Ekz§¨]H]Eq

t + 1

tq€‚

t + 2

°

´±]nEtuq§&xƒr km]

E

(B − B e ε ) {t +

1 <B}

= E

(B − B e ε ) {t +

1 < B e ε <t + 2 ,t 1 > B e ε }

+ ∆,

¶5‘=¸

§&Y€]Exƒ]kƒY[]#oO/ïim]kkm]Hxm\

nEtuqŽP]#ŽPoup[q€‚[]H‚tui«¢Ýo=Ÿ ŸoL§}i

∆ ≤ E

|B − B e ε |

{t + 2 < B e ε ,t 1 > B e ε } + {t

1 ≤ B e ε ,t + 1 ≤ B e ε }

.

¸

(12)

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M/M/1

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p€tLkƒr o=q„¶5=¸tq‚kmY[]

ŽPoup€q€‚j]H‚[q[]Hiƒio¢

p

’urœu]bkmY€tk

P(t + 1 ≤ B) = 1 − E exp −ε Z B

0

p + (X (s)) ds

!!

= εE Z B

0

p + (X (s)) ds

! + o(ε)

= εE(B) E ν

p + (X (0))

+ o(ε) = ε µ − λ E ν

p + (X (0)) + o(ε)

ŽhgBr q‚j]E~P]Eq€‚[]Eq€nE]ou¢

B

tq‚BkmY[]izkvtLkƒr o=q€txƒrµkzg_o¢

(X(t))

° G«gBkmY€]ilkmxƒouq[’aGtxƒ¥uoLœ~[xƒou~P]ExmkzgžtLkWkƒY[]

ilkmo=~[~[rq[’Bkmr\ž]

B e ε

ªnouq‚jrµkƒr o=q€tŸŸg¤ouqkmY€]]Eœ=]Eq3k

{t + 1 < B e ε < t + 2 , B e ε < t 1 }

ªjkmY[]eh¦Ep[]Hp[]ilkƒtxmkƒi tk

B e ε

tqr q‚j]E~P]Eq€‚[]Eq3k}Ž[p€imgV~P]Exƒr oj‚§&rµkƒYouq[]#npizkƒou\ž]Ex7ªhkmY[]Hxm]E¢Ýouxƒ]

E

(B − B e ε ) {t +

1 < B e ε <t + 2 ,t 1 > B e ε }

= P(t + 1 < B e ε < t + 2 , t 1 > B e ε )

× E

(B − B e ε ) | t + 1 < B e ε < t + 2 , t 1 > B e ε

= P(t + 1 < B e ε < t + 2 , t 1 > B e ε )E(B 1 ).

?|oL§#ª[ilrq€nE]

{t + 1 < B e ε } = {t + 1 < B}

o=qVkƒY[]#]Eœ=]Eq3k

{t + 1 < B e ε < t + 2 , B e ε < t 1 }

ªjkmY€]Eq

P(t + 1 < B e ε < t + 2 , t 1 > B e ε ) = P(t + 1 < B) − P(t + 1 < B e ε , t + 2 < B e ε )−

P(t + 1 < B e ε , t 1 < B e ε ) + P(t + 1 < B e ε , t + 2 < B e ε , t + 1 < B e ε )

= P(t + 1 < B) + o(ε),

imrq€n]&kz§«o#oux¨\žouxƒ]&]£hkmxvtyzp[\ž~€i¨r qžkƒY[]iƒt\ž]}Ž€p€ilgB~P]Exƒr oj‚žrsi

o(ε)

°³ejr \žrŸtuxmŸguª=Ž3gžp€imrq[’t’3trqžkmY[]

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E

|B − B e ε | {t +

2 < B e ε ,t 1 > B e ε }

≤ X

n≥2

E(B n )P(t + n ≤ B e ε ≤ t + n+1 , t 1 ≥ B e ε )

≤ 1 (µ − λ)

X

n≥2

nP(N + ([0, B]) = n).

-ùq‚j]E]7‚ïªH’=r œ=]EqbkmY€]We3¦Ep€]Ep[]=ª

N + ([0, B])

Y€t=i)tw$oursimimouq‚jrsizkƒxmrŽ[pjkƒr o=q#§&rµkƒY#~€txvt\ž]kƒ]Ex

R B

0 εp + (X (s)) ds

ª

§&Y€rnvYr \ž~[Ÿr]HikƒY€tLk

X

n≥2

nP(N + ([0, B]) = n) =

E Z B

0

εp + (X (s)) ds

!

− E Z B

0

εp + (X(u)) du e −ε R 0 B p + (X(s)) ds

!

= o(ε)

(13)

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®

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p + 1

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Žhg ]E\ž\tˆu°¨`qkmY[]#oukmY[]Hx&Y€tq€‚)ª

E e B ε − B { B e ε <B,t 1 ≤B,t + 1 ≤B}

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1 ≤B,t + 1 ≤B}

= o(ε).

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E e B ε − B

{t 1 B e ε ,t + 1 ≤ B e ε }

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+ E

B {t

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o(ε)

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o(ε)

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0

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(B, B e ε )

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B 1

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(14)

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0 1

w³¦FEp[]Ep[]

t 1 B

e3¦FEp[]Ep[]

B e ε

º.r’up[xƒ] +@à G«p€imgVw$]Exƒr oj‚§&rµkƒYMtB‹]EŸ]kƒ]H‚‹]E~€tuxlkƒp[xm]

¨½ ¯˜ L' < = O CO C

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( B e ε − B) {t

1 ≤B}

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M=¸

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E

( B e ε − B) {t

1 ≤B}

= E

B 1 {t 1 ≤B, B+B 1 <min(t + 1 ,t 2 )}

+ o(ε)

= E(B 1 )P(t 1 ≤ B) + o(ε).

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P(t 1 ≤ B)

ª€xƒ]HnEtuŸ Ÿ)kmY€tk

(D i )

‚j]Eq€okm]kƒY[]im]

®

p[]Hq€n]#ou¢$‚j]H~€txmkmp€xm]7i«kmr\B]7i}rqkmY[]

S

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N

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B

ª€kƒY[]Eq

Ä ®

ptLkmrouq­¶(3¸«’urœu]7iWkƒY[]#rs‚j]Eq3kmr kzg

P(t 1 ≤ B) = E

 X N i=1

εp (X (D i )) µ

i−1 Y

j=1

1 − εp (X (D j )) µ

= ε µ E

X N i=1

p (X (D i ))

! + o(ε)

= ε

µ E(N)E p (X (D 1 )) + o(ε)

Žhg­izkvtLkƒr o=q€txƒrµkzgŠo¢

(X(t))

tq€‚­´­tŸs‚iº[o=xm\_p[Ÿst[°›ehrq€n]

E(N ) = µ/(µ − λ)

¶·im]E]VÃ|~[~P]Eq€‚jr £€¸ª Ä ®

ptLkmrouq­¶M3¸¨¢ÝouŸŸ oL§}iH°

-ùqŠkmY[]B]£j~€tuq€imr o=q›o¢@kƒY[]BŽ[p€imgM~]Hxmroj‚›o¢WkmY[]Bw³¦FEp[]Ep[]=ª9kmY[]_km]Hxm\»rq

ε

ri’urœu]HqGŽhgkmY[]Bkz§«o ]Hœu]Hq=kvinEouq€imrsizkƒr q[’r q_ouq[Ÿgouq[]«\txƒ¥u]7‚oux.ouq[Ÿgouq[]tu‚[‚[rµkƒr o=q€tŸh‚j]E~txmkmp[xƒ]¨‚jp€xmrq[’}kƒY[]«Ž[p€img#~]Hxmroj‚

ou¢

L

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®

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(15)

— Á WÁ •·– Á ݗL•H–—L ½ — ˜ • Á

E( B e ε ) = 1

µ − λ − ε E ν [p(X(0))]

(µ − λ) 2 + o(ε).

¶5‰=¸

Ä ®

p€tkmrouq±¶·‰=¸Wrsi«nEouq€imrsizkƒ]Eq3k¨§&r kmYkmY[]imo¦ùnEtŸŸ]H‚{&]7‚jp€n]7‚eh]Hxmœhrsn]b{}tLkƒ]btu~[~[xƒo¹£hr\tLkƒr o=q)°Ãi«t

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M/M/1

® p[]Ep[]§&rµkƒYim]ExƒœhrnE]#xƒtkm]

µ + εE ν [p(X (0))]

tq€‚GtxƒxmrœLtŸ)xvtLkƒ]

λ

°-ùqMkƒY€tLk

®

p[]Ep[]=ªPkmY[]B\ž]HtqMŸ]Eq€’kmYŠo¢³kƒY[]Ž[pilg~P]Exƒr oj‚Mrsi

’=r œ=]EqŽ3g

1

µ + εE ν [p(X (0))] − λ = 1

µ − λ − ε E ν [p(X (0))]

(µ − λ) 2 + o(ε),

§&Y€rnvYVnEourq€nrs‚j]7iW§&r kmY¤Ä

®

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kƒ]Exƒ\ tq‚imY[oL§ákƒY€tLk&kƒY[]{|ej{(tu~[~[xƒo¹£hr\tLkƒr o=qVrsiq[ož\Bo=xm]œLtŸrs‚ï°

) $ ­'ž&*« # ¡

-ùq_kmY€ri@im]Hnkmrouq)ªkmY[]&noh]E©nEr ]Hq3k$ou¢

ε 2

o¢kmY[]&\ž]7tqBŽ[p€img~]Hxmroj‚

E( B e ε )

rsi³nEtuŸnEp[ŸstLkm]7‚ï°;-ùqBkƒY[]}imtu\ž]

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‚[p[xmrq[’MtŽ[p€img›~P]Exƒr oj‚±o¢«kmY€]~]Hxlkƒp[xmށtLkm]7‚

M/M/1

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ε 2

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t + 1

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t + 2

tuq€‚

t 1

ª

t 2

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t + 3

o=x

t 3

ghr]EŸs‚[i&t_km]Hxm\¡ou¢

kƒY[]#ouxv‚j]Hx

ε 3

rqVkƒY[]#]£j~€tuq€imr o=qou¢

E( B e ε − B)

°

‹]²€q€]

A + = {t + 1 ≤ B, t 1 ≥ t + 1 + B L(t +

1 )−1 }.

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B L(t +

1 )−1

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ilkƒtuxlkƒr q€’Btk&kmr\B]

t 1

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L(t + 1 ) − 1

nEp€ilkmou\ž]Hxƒiv¸°W`qkmY[]#]Hœu]Eq3k

A ± = {t 1 ≤ B, B ≤ t + 1 ≤ B + B 1 },

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Ž€p€ilgG~]Hxmroj‚Gou¢WkmY€]w³¦

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p[]Hp[]uª§&Y[]Exƒ]

B 1

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A − = {t 1 ≤ B, B + B 1 ≤ t + 1 },

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kƒY[]#Ž[p€img¤~P]Exƒr oj‚

B

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(16)

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A = A + ∪ A ± ∪ A

ª=kmY[]

]E£j~[xm]7imimrouq

E(( B e ε − B) A c )

ri

o(ε 2 )

¶5tq€‚G]Eœu]Hq›]

®

p€tuŸkƒoVr q±ilo=\B]BnEt=il]7iEª¢Ýouxbr qizkvtq€nE]§&Y[]Hq

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B e ε = B

¸°³XY[]

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E(( B e ε − B) A )

¢Ýo=x

A ∈ {A + , A ± , A }

ª

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B

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E(( B e ε − B) A + )

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[0, B]

ªïohnHnp[xƒxƒr q[’tLkbkmr\ž]

t + 1

tq€‚

t + 2

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ε 2

o¢

E(B − B e ε )

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kƒY[rsibnHtuim]uªPkmY€]ž‚[r0/9]Exƒ]Eq€nE]_ŽP]kz§«]E]Hq

B − B e ε

rib] ® p€tuŸ.kmokmY[]BŽ[p€imgM~]Hxmroj‚Gou¢¨tq±e3¦Ep€]Ep[]B§&Y[rsnvY ilkƒtuxlkvi@§&r kmY¤]HrµkƒY[]Ex¨ouq[]ouxWkz§¨onEp€ilkmou\ž]HxƒiHª=‚j]H~]Hq€‚jrq[’o=qžkmY[]¢·tunk@kmYtLkHªho=qkmY[]]Eœ=]Eq3k

{t + 1 ≤ B}

ª

kƒY[]#Ž[p€img¤~P]Exƒr oj‚o¢kmY[]#w@¦Ep[]Hp[]ri|tŸxm]7tu‚jg¤nEou\ž~[Ÿ]km]7‚tLkkmr\ž]

t + 2

o=x«q€okH°Wej]E]º.r ’=p[xƒ] ([°

Íi|ŽP]¢Ýo=xm]=ª

B 2

‚[]Eq[oukm]Hibtxvtq€‚[ou\-œ¹tuxmrstŽ€Ÿ ]§&r kmYGkmY[]Bimtu\ž]_‚jrsizkƒxmrŽ[pjkƒr o=qGtui}kmY[]žimp[\o¢³kz§«o

rq€‚j]H~]Hq€‚j]Hq=k}œLtuxmrstŽ[Ÿ]Hi‚jrsilkmxƒr Ž[p[km]H‚t=i

B 1

tuq€‚Vrq€‚j]H~]Hq€‚j]Hq=ko¢

B

ª

t + 1

tq€‚

t + 2

°¨`q[]#’u]Ekƒi

E

(B − B e ε ) A +

= E

(B − B e ε ) {t +

1 ≤B,t 1 ≥t + 1 +B L(t + 1 )−1 }

= E (B 2 ) P

t + 1 < B, t + 2 < t + 1 + B L(t +

1 )−1 , t 1 ≥ t + 1 + B L(t +

1 )−1

+ E (B 1 ) P

t + 1 < B, t + 2 ≥ t + 1 + B L(t +

1 )−1 , t 1 ≥ t + 1 + B L(t +

1 )−1

+ o(ε 2 ).

XY€ri&‚j]7no=\B~Po=imr kmrouq]Eq3kƒtur Ÿsi«kmY€tk

E

(B − B e ε ) A +

= (E (B 2 ) − E (B 1 )) P

t + 1 < B, t + 2 < t + 1 + B L(t +

1 )−1

+ E (B 1 )

P t + 1 < B

− P

t + 1 < B, t 1 ≤ t + 1 + B L(t +

1 )−1

+ o(ε 2 ).

¶lˆH=¸

6

- 6



ˆ

t + 1 B

e3¦FEp[]Ep[]

t + 2 B e ε

w³¦FEp[]Ep[]

ºr’up€xm]3(C+³X§¨oÃ&‚[‚[rµkƒr o=q€tŸ‹]E~txmkmp[xƒ]Hi

º€xmo=\ Ä ®

p€tkmrouqG¶lˆHu¸ª=o=q[]}Y€t=i³kƒo]£j~€tuq€‚BkmY€xm]H]}]£j~[xƒ]Hiƒilrouqi³§&rµkƒYxm]7il~P]HnkWkƒo

ε

°$XY€riWri¨‚jouq[]

Žhg¤~€xmoLœhrq[’kƒY[]kmY€xm]H]¢Ýo=Ÿ ŸoL§&rq[’žŸ ]H\B\t=iE°

(17)

¨½ ¯˜ C '#

P

t + 1 < B, t + 2 < t + 1 + B L(t +

1 )−1

8 < '

P

t + 1 < B, t + 2 < t + 1 + B L(t +

1 )−1

= ρε 2 E Z B

0

(B − v)E ν p + (X (0))p + (X(v)) !

dv + o(ε 2 ),

¶lˆuˆ7¸

1KF ]k@p€i@xm]7nEtŸŸjkƒY[]&xm]H’u]Hq[]ExvtLkƒr œ=]«‚j]7imnExmr~jkƒr o=qBou¢9tŽ€p€ilg_~]Hxmroj‚žizkvtxmkmrq[’#tLk³kmr\ž]

0

§&r kmYžouq[]

nEp€ilkmou\ž]HxK+ëk#kmr\ž]

E 1

¶Ý]E£h~Pouq€]Eq3kmrstŸŸ gŠ‚jrilkmxƒrŽ[pjkm]7‚G§&r kmY­~€tuxƒtu\ž]km]Hx

λ + µ

¸ª§&r kmY­~[xƒouށtŽ[rŸ r kzg

µ/(λ+µ)

kmY[]&Ž[pilg~P]Exƒroh‚_rsi$²€q[rsilY€]H‚ï°@`|kmY[]Hxm§&rsim]uª§&r kmYB~[xƒouŽ€tuŽ[r Ÿr kzg

λ/(λ+µ)

ª3tq€]E§np€ilkmo=\B]Hx tuxmxƒrœu]Hi.tq‚Btimp[Žj¦ÕŽ[p€img~P]Exƒr oj‚_o¢ï‚jp[xvtLkmrouq

B 1 1

¶·§&rµkƒYBkmY[]}iƒt\ž]&‚jrsizkƒxmrŽ[pjkƒr o=qžt=i

B 1

¸.ށ]H’urq€i³p[q3kƒr Ÿ

kƒY[]qhp[\ŽP]Exo¢$np€ilkmo=\ž]Exvi¨xƒ]Ht=nvY[]Hi

1

t’=tur q° -ùqkmY[rsi§t¹guª3kmY[]œLtxƒrstŽ[Ÿ]

B

nEtuqVŽP]xm]H~[xm]7il]Hq3km]H‚tui

¢Ýo=Ÿ ŸoL§}i

B = E 0 + X H i=1

E i + B i 1

,

¶lˆ7u¸

§&Y€]Exƒ]

H

ri’=]Eo=\B]EkmxƒrnHtŸŸ g ‚jrilkmxƒrŽ[pjkm]7‚§&rµkƒY~€tuxƒtu\B]Ekm]Hx

λ/(λ + µ)

ª

(E i )

txƒ]Mr5°rJ°‚]E£h~Pouq€]Eqj¦

kƒrtuŸ Ÿg›‚jrsizkƒxmrŽ[pjkƒ]H‚G§&rµkƒYG~€tuxƒtu\B]Ekm]Hx

λ + µ

tq‚

(B 1 i )

tuxm]_r5°rJ°‚ï°Ã|Ÿ Ÿ.kƒY[]Him]_xvtq‚jou\œLtxƒrtuŽ[Ÿ]Hibtxƒ]

rq€‚j]H~]Hq€‚j]Hq=k7°@º[o=x

0 ≤ i ≤ H

ª

c

s i

‚j]Eq€okm]7i.kmY[]&]Hq€‚Bo¢PkmY[]

i

kƒYžimp[Žj¦ÕŽ[p€imgnEghnEŸ ]$+

s 0 = 0

tuq€‚ïªL¢Ýo=x

i ≥ 1

ª

s i = s i−1 +E i +B 1 i

ª

B = s H + E 0

c

N i

‚j]Hq[okƒ]HikƒY[]qhp[\ŽP]Ex}ou¢.tuxmxƒr œLtuŸi‚jp[xƒrq[’BkmY[]

i

kmYMimp[Žj¦ÕŽ[p€imgVngjnEŸ ]

c

s i−1 + D i 1

ª)°E°H°Eª

s i−1 + D i N i

txƒ]kƒY[]#rq€izkvtq3kƒiou¢.‚j]H~€txmkmp€xm]7io¢.nEp€ilkmou\ž]Hxƒi&‚jp€xmrq[’BkmY[]

i

kƒY

ilp€Žj¦JŽ€p€ilgngjnŸ]u°

º€oux«kmY€]yzourq=k|‚[rilkmxƒr Ž€pjkmrouqo¢kmY[]#œ=]Hnkƒoux

(N i , D i 1 , . . . , D N i i )

ª[il]H]kƒY[]Ã}~€~]Hq€‚jr £9°¨ºr’up€xm]b‡ž’urœu]Hi tuqrŸŸ p€ilkmxvtLkƒr o=qou¢kƒY[]#tŽPoLœu]#‚j]E²€q[r kmrouq€iH°

-Õk#rsi]7tuimgkmoil]H]kƒY€tLk¢Ýo=xkƒY[]ž]Eœ=]Eq3k

{t + 1 ≤ B , t + 2 < t + 1 + B L(t +

1 )−1 }

kmoojnEnEp[xHª

t + 1

tq€‚

t + 2

Yt¹œu]}kƒo_ŽP]r qkmY€]biƒt\ž]ilp[Ž[¦JŽ[pilg~P]Exƒr oj‚ïª

[s i−1 + E i , s i ]

ªh¢Ýoux&ilo=\ž]

i ∈ {1, . . . , H }

°³º[oux&t²[£j]H‚

i

ªhkƒY[]#~[xƒouŽ€tuŽ[r Ÿr kzgkmY€tkkmY[]²€xvilk&kz§¨ožtu‚[‚[rµkƒr o=q€tŸhyzp[\ž~€i|txƒ]brqkmY[]

i

¦JkmYilp€Žj¦JŽ€p€ilgV~]Hxmroj‚ïª[rsi

E Z s i

s i −1 +E i

εp + (X (u))e −ε R 0 u p + (X(s)) ds

1 − e −ε R u si p + (X(s)) ds du

!

= ε 2 E Z s i

s i−1 +E i

p + (X(u)) Z s i

u

p + (X(s)) ds du

!

+ o(ε 2 ).

(18)

"!#$%

M/M/1

& '' ˆ7†

-

6

- - 1

B 1 1

s 0 =0 E 1 s H −1 s H B

E 0

s 1

º.r’up[xƒ]‡'+³‹]Hno=\ž~o3ilr kmrouqo¢³t G¨pilg¤w$]Hxmroj‚

ehrq€nE]uª

B 1 i = s i − s i−1 − E i−1

YtuikƒY[]iƒt\ž]‚jrsizkƒxmrŽ[pjkƒr o=q›tui

B

tq€‚ŽhgkmY[]BizkvtLkmrouqtxƒrµkzg¤ou¢

((X (t))

ª[kmY[]nEo3]E©¤nr]Eq3k&o¢

ε 2

nEtqŽP]#]£j~[xƒ]Hiƒil]7‚Vtui«¢Ýo=Ÿ ŸoL§}iHª

E Z

0≤u≤v≤B

p + (X(u))p + (X(v)) du dv

= E Z

0≤u≤v≤B

E ν p + (X (0))p + (X(v − u) ) du dv

.

º.rq€tŸŸ g=ªimr qn]

H

ri’=]Eo=\B]EkmxƒrnHtŸŸ g›‚[rilkmxƒr Ž€pjkm]7‚Ч&r kmY¬~txvt\ž]kƒ]Ex

λ/(λ + µ)

ªÄ ® p€tkmrouq¶lˆuˆ7¸

¢Ýo=Ÿ ŸoL§}iH°

´±]&kmp€xmqžq[oL§ kmokmY€]}]£j~€tuq€ilrouqBo¢PkmY€]

®

p€tq3kmr kzg

P(t + 1 ≤ B)

ª=§&Y[rsnvYžri@o¢ïnoup€xƒim]«txƒ]²q[]E\ž]Eq3k ou¢§&Y€tk}Y€tuiŽP]E]HqM‚jouq[]rq›eh]Hnkmrouq([°

¨½ ¯˜ C '#

P(t + 1 ≤ B)

8 < '

P(t + 1 ≤ B) = ε E ν (p + (X (0)))

µ − λ

− ε 2 E Z B

0

(B − v) E ν p + (X (0))p + (X(v)) dv

!

+ o(ε 2 ).

¶lˆK(=¸

1KF }´±]nŸ]HtuxmŸgY€t¹œ=]

P(t + 1 ≤ B) = E

1 − e −ε R 0 B p + (X(s)) ds

= ε E ν [p + (X (0))]

µ − λ − ε 2 2 E

 Z B 0

p + (X(s)) ds

! 2 

 + o(ε 2 ).

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