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Mean Field Convergence of a model of multiple TCP connections through a buffer implementing RED

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HAL Id: inria-00071733

https://hal.inria.fr/inria-00071733

Submitted on 23 May 2006

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Mean Field Convergence of a model of multiple TCP connections through a buffer implementing RED

David R. Mcdonald, Julien Reynier

To cite this version:

David R. Mcdonald, Julien Reynier. Mean Field Convergence of a model of multiple TCP connections through a buffer implementing RED. [Research Report] RR-4850, INRIA. 2003. �inria-00071733�

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a p p o r t

d e r e c h e r c h e

THÈME 1

INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET EN AUTOMATIQUE

Mean Field Convergence of a model of multiple TCP connections through a buffer implementing RED

D. R. McDonald and J. Reynier

N° 4850

June 2003

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acb]h:o,|Osƒ{…ph:„eh¯x,hg…gxoKqä¨|oo­~behg†Yx+be{hphH„vsƒ‚ƒ¤¥§¨…rqtxhwqO…,°¸†e|\­~¤¨hp„v”•hgfKhp†¸xoKqt{+{+§¥ª‹h²acbeh

o|Osƒ{…ph“x+behg†Ãox,qt{+xoq6¶¿qOo+x~{hgx+{,qt†eo+fµ§¥x."\¶ÎqOox{hp…p|\ª•hg{+yH«¸y:§¥fµfKhp„v§½qtxhg¤¥yw{hpohg†e„v§¥†ƒ”Kx+beh!¤¨|o+x

(7)

‚]qO…,°‹hgxr² ¦hqOoosƒfKh~x+beh¤¨|oohpoqt{h|O†ƒ¤¥y=”•hg†ehg{,qtxhp„:«¸y=x+behl?>ž‡Ÿ¡lqt†e„ƒ|Of £qt{+¤¥yKž!hgxhp…¯´

x+§¨|O†2©“qO…gx+§¥ª‹hµ«ƒsv±Thg{“fjqt†]qt”•hgfKhg†Rxo,…,behgfKhK|O{“«¸yx,qt§¥¤Ì´ï„v{|O‚J² Ehµ†ehg”¤¨hg…gx6x+behµ‚)|oo§¥«ƒ§¥¤¥§¥x¹y

x+b]qtx„vsƒ‚ƒ¤¥§¨…rqtxh!qO…,°¸†e|\­~¤¨hp„v”•hgfKhp†¸xocqt{,h~”•hg†ehg{,qtxhp„:«¸y=‚]qO…,°•hgxo®qt{+{+§¥ªR§¥†ƒ”|Osƒx|t¶J|O{„ƒhg{r²) ¦h

­~§¥¤¥¤qOoo+sƒfKh³x+beh“«ƒsv±Thg{be|O¤¨„ƒo

B ‚]qO…,°•hgxoqt†e„Ãx+b]qtx|O†]…gh³x+be§¥o«ƒsv±Thg{o+‚]qO…ph³§¨oh¯uRb2qtseo+xhp„

qt{+{+§¥ªR§¥†ƒ”j‚2qO…,°•hgxoqt{h„v{|O‚ƒ‚)hp„T² ¸se…,bÏx,qt§¥¤Ì´ï„v{|O‚eo…p|OfKh6§¥†qO„ƒ„v§¥x+§¨|O†x|Kx+beh6l£žÄfKhp…,b]q`´

†ƒ§¨o+fòÊhg{hc­®h~x,qt°‹h~x+beh„v{|O‚K‚ƒ{|O«]qt«ƒ§¥¤¥§¥x¹yK|t¶l?>ž Ÿ¡|t¶Jqt†K§¥†e…p|Ofµ§¥†ƒ”6‚]qO…,°‹hgx>«)h¯¶¡|O{h~«)hg§¥†ƒ”

‚ƒ{|¸…phpoo,hg„2©®x|=«)h6q¶¡sƒ†e…gx+§¨|O†É|t¶x+beh³º‹sehgseh³o+§¥¼rh“­~bƒ§¨…,bç¨o~¼rhg{|=¶Î|O{qµº‹sehgseh“¤¨hg†ƒ”x+bë)hg¤¨|\­

Qmin «ƒsƒx~{§¥o,hpo~¤¥§¥†ehrqt{+¤¥y#x|

pmax qtx Qmax qt†e„Ãhpº¸s]qt¤¨o~x|

1 qt«)|\ª•h Qmax²

ï¶qt¤¥¤

N …p|O†ƒ†ehp…gx+§¨|O†eojqt{h:§¥† …p|O†ƒ”•hpo+x+§¨|O†qrª•|O§¨„eqt†e…ph#­®hH…rqt†¬{h¯¶¡|O{+fsƒ¤½qtxh#x+bƒ§¨oµ„v{|O‚

‚ƒ{|O«]qt«ƒ§¥¤¥§¥x¹y:§¥†#xhg{+fKo~|t¶

QN»Rx+beh!º‹sehgseh!o+§¥¼rh„v§¥ªR§¨„ƒhp„H«¸y

N»ƒqOo F(QN(t))»¸­~b]h¯{,h

F §¨o~q

„v§¨o+x+{+§¥«ƒsƒx+§¨|O†Ï¶Wsƒ†]…¯x§¥|O†Ï­~bƒ§¨…,bϧ¨o¼rhg{|K«)hg¤¨|\­

qmin =Qmin/N «ƒsex{+§¨ohpo¤¥§¥†ehrqt{+¤¥ywx|

pmax

qtx qmax = Qmax/N qt†e„Ã}(sƒfµ‚eox|

1 ­~behg† QN(t) qmax² +¶…p|Osƒ{ohjx+b]hjx,qt§¥¤Ì´ï„v{|O‚

o…,behgfKh®…rqt†"«)h…p|O†eo+§¨„ƒhg{hp„=qOo0x+beh¤¥§¥fµ§¥x+§¥†ƒ”!…rqOo,h£­~behg†

qmin = 0» qmax =bqt†e„ pmax= 0²

acb]hH”•|•qt¤|t¶?x+bƒ§¨o=‚]qt‚)hg{µ§¨o=x|‚ƒ{|\ª‹hHx+behw…p|O†O}(hp…gx+sƒ{hw§¥†4Á¥i¯Â~­~bƒ§¨…,b…g¤¨qt§¥fKoµx+b]qtxµx+beh

bƒ§¨o+x|O”{,qtfÈ|t¶x+beh!­~§¥†e„ƒ|\­ o§¥¼rhpoc§¥†Éqt†¸yH…g¤½qOoo

c …g|O†Rª•hg{+”•hpox|Kq"„ƒhgxhg{+fµ§¥†ƒ§¨o+x§¥…³fKhrqt†wË]hg¤¨„

¤¥§¥fµ§¥x­~§¥x+bÏfKhrqOosƒ{h

Mc(t, dw) qtx?x+§¥fKh

t qt†e„ÉfK|O{hp|\ª‹hg{x+beh6{hg¤½qtx+§¥ª‹hº¸sehgseho+§¥¼rh

QN(t)

…p|O†¸ª‹hg{+”•hpox|Kqµ„ƒhgxhg{+fµ§¥†ƒ§¨o+x+§¨…³¤¥§¥fµ§¥x

Q(t)²

Ñ¸Õ š Ñ !"#$ &%0 ('$ *) 0,+.-/

N → ∞-0"1 2

/ &"1 &3' 234. 65

7 & 1

/8 c '9% : (;

/

Mc(t, dw) 3<1 1 ("1 9% (; >=; Mc(sRc(s), dv;s, dw)-<"1

: (;

@?

A (; 9= B"1 B3' 23C D5 E "

t E " tRc(t)

F

G ={gCb1(IR+) :g(0) = 0} 3<1 Cb1(IR+) ("1 G B=2 ;

3' H"1*=2 & . "' E "'$I '; 7

gc ∈ G, c= 1, . . . d hgc, Mc(t)i − hgc, Mc(0)i

= Z t

0

h 1

Rc(s)hdgc(w)

dw , Mc(s, dw)i Ÿ(i²¥i\©

+ h(gc(w/2)g(w))v, Mc(sRc(s), dv;s, dw)i (1R˙c(s))

Rc(sRc(s))K(sRc(s))i ds.

= Z t

0

h 1

Rc(s)hdgc(w)

dw , Mc(s, dw)i

+ h(gc(w/2)g(w)), e(s, sRc(s), w)Mc(s, dw)i (1R˙c(s))

Rc(sRc(s))K(sRc(s))i ds.

(8)

= Z t

0

h 1

Rc(s)hdgc(w)

dw , Mc(s, dw)i+ 1

Rc(sRc(s))K(sRc(s))(1R˙c(s))Ÿ(i²å•©

·hgc(w), e(s, sRc(s),2w)·Mc(s,2dw)e(s, sRc(s), w)·Mc(s, dw)ii ds.

3<1

hgc, Mc(t)i=R

w=0gc(w)Mc(t, dw)- 3<1 Rc(t) =Tc+Q(tRc(t))/L

3<1

e(s, sRc(s), w) =hv,Mc(sRc(s), dv;s, dw) Mc(t, dw) i

(B"1

H 0 '

. B"1 3' 23 "1 /; %0 ('$ "1 3' 23

( 23

w

2'$"1 : ; D5

'$>% !! ; (;

" "

Q(t) . ; %

dQ(t) dt =

d

X

c=1

Z

w

wMc(t, dw)(1K(t))

Rc(t) L Ÿ(i²å‘•©

à d

X

c=1

hw, Mc(t, dw)i(1K(t)) Rc(t) L

!+

χ{Q(t) =qmax} Ÿ+i²‰¸©

à d

X

c=1

hw, Mc(t, dw)i(1K(t)) Rc(t) L

!

χ{Q(t) = 0}). Ÿ(i²åŒ•©

0< Q(t)< qmax- K(t) =F(Q(t)) 3<1 Q(t) =qmax - K(t) (( ; =;

d

X

c=1

hw, Mc(t, dw)i(1K(t)) Rc(t) =L.

oo+sefµ§Ì†e”

gc(0) = 0 qt†e„wx+b]qtx

gc(w)0 qOo w→ ∞ ­®h“…rqt†Ã{hg­~{+§¥xh:Ÿ(i²å•©~qOo

hgc, Mc(t)i − hgc, Mc(0)i

= Z t

0

h 1

Rc(s)hgc(w),Mc(s, dw)

dw i+ 1

Rc(sRc(s))K(sRc(s))(1R˙c(s))

·hgc(w), e(s, sRc(s),2w)·Mc(s,2dw)e(s, sRc(s), w)·Mc(s, dw)ii ds.

(9)

­~behg{h Mc(s,dw) dw

§¨ox+beh(e{hp…,behgx?„ƒhg{+§¥ªOqtx+§¥ª‹h³|t¶x+beh³fKhrqOo+sƒ{h

Mc ­~§¥x+bÃ{hpo+‚)hp…gxx|

w²®€®|O†v´

ohpº¸sehg†¸x+¤¥y‹»

dMc(t)

dt = 1 Rc(t)

Mc(t, dw)

dw + 1

Rc(tRc(t))K(tRc(t))(1R˙c(s)) Ÿ(i² ©

·(e(t, tRc(t),2w)(Mc(t, d(2w))e(t, tRc(t), w)Mc(t, dw))i .

¹† Rhp…gx+§¨|O†:‘v²å‘v²å!§¥†ÃÁ¥i¯Âe­®hcfjqO„ƒhq!o+fK|¸|Ox+bjqt‚e‚ƒ{|ruR§¥fjqtx+§¨|O†jx|

e(t, t−Rc(t), w) «]qOohp„

|O†Ex+beh=¶ÎqO…gx“xb]qtx6|O†ehµla~aħ¥†$xbeh=‚]qOo+x³x+behµ­~§¥†e„ƒ|\­ o§¥¼rh=­cqOo“fK|ox“¤¥§¥°‹hg¤¥yÏx+behK…gsƒ{+{hg†¸x

­~§¥†e„ƒ|\­4o§¥¼rhfµ§¥†¸seo~|O†eh|O{®x¹­~§¨…phx+beh…gsƒ{+{,h¯†Rxc­~§¥†e„ƒ|\­4o+§¥¼rh?§Ì¶q6¤¨|oo­~qOo®„eh¯x,hg…gxhp„#§¥†Hx+beh

§¥†¸xhg{+§¥fò .§¥x+bÏx+bƒ§¨o!qt‚ƒ‚ƒ{|ruv§¥fjqtx+§¨|O†Å­®h6seohp„YŸ(i² ©x|:hgª‹|O¤¥ª‹h"qj„v§¨o…g{hgxh=qt‚ƒ‚ƒ{|ruR§¥fjqtx+§¨|O†

|t¶6x+behÏfKhrqOo+sƒ{h

Mc

Ÿ¡h¯uv…phg‚ƒxÅÁ¥igÂ!|O†ƒ¤¥y x+{hrqtxo#|O†eh…g¤½qOoo¯©¯²;acbehφ¸sƒfKhg{+§¨…rqt¤!{hpo+sƒ¤¥xowqt{h

h¯uƒ…phg¤¥¤¨hg†¸x"q`¶¡xhg{6|O†ehK…p|O{+{,hg…gxo6¶¡|O{³x+behµ¶ÎqO…gx6x+b]qtx"q#‚ƒ{|O‚)|O{+x+§¨|O†Y|t¶cx+behj…p|O†ƒ†ehp…gx+§¨|O†eo§¥†Nqt†

+?‚ƒ†ehgxjo+§¥fsƒ¤½qtx+§¨|O† qt{h#§¥† x+§¥fKhp|Osƒxϟ¡|Osƒ{µfK|¸„ƒhg¤?qOoo+sƒfKhpoK…p|O†ƒ†ehp…gx+§¨|O†eoK§¥†eo+x,qt†¸x,qt†ehp|Oseo¤¥y

{hpo+sƒfKh³…p|O†ƒ”•hpox+§¨|O†Ïqrª‹|O§¨„eqt†e…ph³§¶x+behgy:¶¿qt¤¥¤T§¥†¸x|µx+§¥fKhp|Osƒxí©¯²

a0|#§¥¤¥¤¥seo+x+{,qtxh=x+beh"fKhrqt†ÅË]hg¤¨„¤¥§¥fµ§¥x“­®h"‚)hg{(¶¡|O{fKhg„¦qt† +?‚ƒ†ehgx³o+§¥fsƒ¤½qtx+§¨|O†$­~§¥x+b

N = 200» N = 400 qt†e„ N = 800 o,|Osƒ{…phpor²cqO…,bo|Osƒ{…ph6o,hg†e„ƒo‚]qO…,°•hgxo|t¶>o+§¥¼rh

536 «¸yRxhpox|

qwa‘#{|Osƒxhg{³­~§¥x+bYqHx+{,qt†eo+fµ§¨o,o+§¨|O†E{,qtxhK|t¶c‰‰e²O‘ Àhg”‹qt«ƒ§¥xo³‚)hg{6o,hp…g|O†]„E|O{

L = 10433

‚]qO…,°‹hgxoK‚)hg{:ohp…p|O†e„T² ¦hÉqOoo+sƒfKhwx+behÉo|Osƒ{…phpo:qt¤¥¤b]qrª•hÉqÅx+{íqt†eo+fµ§¨oo+§¨|O† „ƒhg¤½qry |t¶µirŽŽ

fµ§¥¤¥¤¥§¨ohp…p|O†e„ƒor²?acb]h6{|Osƒxhg{§¥fµ‚ƒ¤¨hgfKhg†¸xo!l?>ž ­~§¥x+b

pmax = 0.05 ¶Î|O{qt¤¥¤0x+beh"o+§¥fsƒ¤½qtx+§¨|O†eo

«ƒsƒx“­®h"{hpo…rqt¤¨h

Qmax

x|H«)h

1000 ­~§¥x+b 200 o|Osƒ{…phpor»

2000 ­§Ìxb 400 o|Osƒ{…phpo³qt†e„

4000

­~§¥x+b

800 o|Osƒ{…phpo\² ¸§¥†e…ph

Qmax o…rqt¤¨hpo"­§Ìxb

N»x+behwqrª•hg{,qt”•h#º¸sehgsehHo+§¥¼rhH„ƒ|¸hpoKqOo"­®hg¤¥¤

­~bƒ§¥¤¨h!b]|O¤¥„ƒ§Ì†e”µx+beh!¤¨|ooc‚ƒ{,|O«]qt«ƒ§¥¤¥§ÌxÍy:˃uƒhp„H­~bƒ§¨…,b祆wx+sƒ{+†wbe|O¤¨„ƒo~x+beh³qrª•hg{,qt”•h!­§Ì†]„ƒ|\­ o+§¥¼rh

˃uƒhp„T²?o

N §¥†e…g{hrqOohpo­®h®o,hph£x+beh·ese…gx+s]qtx+§¨|O†eo§¥†"x+beh®{hg¤½qtx+§¥ª•hcº¸sehgseh®o+§¥¼rh!ŸW§¥†=‚]qO…,°‹hgxo‚)hg{

…p|O†ƒ†ehp…gx+§¨|O†2©!„ƒhp…g{hrqOohpor² Eh=qt¤¨o,|Hohphx+beh"{hg¤½qtx+§¥ª•h=º¸sehgseh=o+§¥¼rh"|t¶£x+beh=ÀÅqtx+¤½qt«Å†¸sƒfKhg{+§¨…rqt¤

o+§¥fsƒ¤½qtx+§¨|O†É§¨oq=«ƒ§¥x~bƒ§¥”bJ²£acbƒ§¨o~§¨o~«)hp…rqtseo,h³|t¶x+§¥fKhp|OsƒxoqOo„v§¨o…gseo,ohp„#§¥†¦Á¥i¯Âï²

hg§¥x+behg{

Mc(t, dw) |O{ Mc(sRc(s), dv;s, dw) §¨o³qHox,qtxh"«ƒsƒx“x+behKqt«)|\ª‹h=hpº¸s]qtx+§¨|O†

„ƒ|¸hpo~‚ƒ{|\ªR§¨„ƒh“hg†e|Osƒ”bw§¥†v¶Î|O{+fjqtx+§¨|O†Ãx|µhgª•|O¤¥ª‹hx+beh“oyRo+xhgfò hgx

µc(t) „ƒhg†e|Oxh“x+beh!‚ƒ{|¸…phpoo

{Mc(s, dw);t1 s t} ŸÎqt¤¥¤la~a oqt{hK¤¨hpoo³x+b]qt†

1©¯² %o+§¥†ƒ”NŸ(i²¥i\©!­®hK…rqt†Nhgª‹|O¤¥ª‹h

Mc(t, dw) ¶¡{|Of t x| t+δt ­~bƒ§¥¤¨h Mc(ts+δt, dw) §¨oH|O«ƒx,qt§¥†ehp„.«¸y qEx+§¥fKhobƒ§Ì¶Wxr²

%?†v¶¡|O{+x+sƒ†2qtxhg¤Ìy

µc §¨oj†e|Ox:‚ƒ{,qO…gx+§¨…rqt¤!o+x,qtx,hO² ª•hg† §Ì¶³­®hτv§¨o…g{hgx+§¥¼rhÅqt†e„ |O†ƒ¤¥y °•hphg‚ x+beh x+{,q`}+hp…gx|O{+y=|t¶x+behc‚ƒ{|¸…phpo,o>|O†:q‚]qt{+x+§¥x+§¨|O†j”§¥ª¸§¥†ƒ”

{Mc(si, dw);t−1 =s0< s1. . . sn=t}

§¥xo+x+§¥¤¥¤T{hpº¸sƒ§¥{hpox|¸|µfse…,bɅp|Ofµ‚ƒsƒxhg{fKhgfK|O{+y#x|µo|O¤¥ª‹h!†¸sƒfKhg{+§¨…rqt¤¥¤¥y‹²

¦h…rqt† qrª‹|O§¨„.x+bƒ§¨oH‚ƒ{|O«ƒ¤¨hgf «¸y „ƒh¯Ëe†ƒ§¥†ƒ”qNo,hpº‹sehg†e…phÅ|t¶x+§¥fKhpo

tck ¶Î|O{#hrqO…,b4…g¤½qOo,o o+se…,bx+b]qtx

tck+n+1Rc(tck+n+1) = tck² ï¶>­®h6‚ƒ§¨…,°

n o+sj…g§¨hg†¸x+¤¥yɤ½qt{+”•hx+bƒ§¨o”§¥ª•hpo!qKËe†eh

‚]qt{+x+§¥x+§¨|O†J²>ž!h¯Ëe†eh

Φc(t) =x+beh!Ëe{o+x°Ho+se…,bÃx+b]qtx

tck > t² ¦h­~§¥¤¥¤2…p|O†eox+{+se…gx®|Osƒ{o|O¤¥sƒx+§¨|O†

«¸y¬{hp…gsƒ{+{hg†e…phö¡{|Ofx+§¥fKh

ti x| ti+1 «¸y „ƒh¯Ëe†ƒ§¥†ƒ”

ti+1 = minc(tcΦc(ti)) o+x,qt{x+§¥†ƒ”E¶W{|Of x+§¥fKh

t0 = 0²h¯uRx"qOo,o+sƒfKhjx+b]qtx6¶Î|O{hrqO…,b¬…g¤½qOoo­®hjb]qrª•hj«)hphg† qt«ƒ¤¨hjx|υrqt¤¨…gsƒ¤½qtxhwqt†e„

(10)

2 4 6 8 10 12 14 0

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Time

Queue size / N

OPNET N=200

§¥”sƒ{h4iÄlhg¤½qtx+§¥ª‹h¬º‹s]h¯s]h¬o+§¥¼rh¬­~§¥x+b ŽŽ

o|Osƒ{…phpo

0 2 4 6 8 10 12 14

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Time

Queue size / N

OPNET N=400

0§¥”sƒ{h Älhg¤½qtx+§¥ª‹h¬º¸sehgseh o+§¥¼rhY­~§¥x+b ‰‹ŽŽ

o|Osƒ{…phpo

0 2 4 6 8 10 12 14

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Time

Queue size / N

OPNET N=800

§¥”sƒ{h ‘Älhg¤½qtx+§¥ª‹h¬º‹s]h¯s]h¬o+§¥¼rh¬­~§¥x+b ŠŽŽ

o|Osƒ{…phpo

0 2 4 6 8 10 12 14

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Time

Q limit

"N=infinity" Matlab

0§¥”sƒ{hN‰?sehgseh¬o+§¥¼rhN|t¶jx+behNfKhrqt†;Ë]hg¤¨„

¤Ì§¥fµ§¥x

o,qrª‹h=x+behKª•hp…gx|O{

VcM(t)»q#„v§¨o,…g{hgx+§¥¼rhp„Eª•hg{o§¨|O†¦|t¶

Mc(tck) ¶Î|O{ k = mn, . . . m ­~behg{h m= Φc(t)1²!ŸWx+behpohqt{h³fjqt{+”§¥†]qt¤¨o†e|Oxx+beh6hg†¸x+§¥{h}(|O§¥†¸x?„v§¨o+x+{+§¥«ƒsƒx+§¨|O†2©¯² ¤¨o|:qOoo+sƒfKh

­®hÉoíqrª•hÃx+behê‹hp…gx|O{:|t¶³°•hg{+†ehg¤¨o

VcT(t) ”§¥ª•hg†«Ry

Tc(tck) ¶¡|O{ k = mn, . . . m ­~behg{h

(11)

Mc(tck+1) =Mc(tck)Tc(tck+1) qt†e„ m §¨o“qOo“qt«)|\ª•h²(§¥†]qt¤¥¤¥yqOoo+sƒfKh"x+b]qtx!­®h"o,q\ª•hx+beh

°‹hg{+†ehg¤¨o

Smc =Qm

k=m−nTc(tck)²

¦hc…rqt†µ†e|\­ hgª•|O¤¥ª‹hc|Osƒ{>o+yvo+xhgfÄx|

ti+1²cxhrqO…,bKoxhg‚=­®hc|O†ƒ¤¥y"hgª‹|O¤¥ª‹h®x+beh~º‹sehgsehqt†e„

x+beh!|O†eh!…g¤½qOo,o

d­~behg{h ti+1=tdΦd(ti)

²acbeh§¥†¸ª•hg{o,h?°‹hg{+†ehg¤

(Smd)−1 ”§¥ª‹hpo®x+beh!…p|O†e„v§¥x+§¨|O†]qt¤

„v§¨o+x+{+§¥«ƒsƒx+§¨|O†Æ|t¶!x+behÉ­~§¥†e„ƒ|\­o:|t¶³…g¤½qOoo

d |O†ehÉla~a&«)h¯¶¡|O{hÉx+§¥fKh

ti ”§Ìª‹hg†x+behí~§¥†e„ƒ|\­

qtx:x+§¥fKh

ti

²;€cqt¤¨…gsƒ¤½qtxhx+behυp|O†e„v§¥x+§¨|O†]qt¤“h¯uv‚)hp…gx,qtx+§¨|O†

e(ti, ti Rd(ti), w)² .§¥x+b x+bƒ§¨o

­®hɅrqt† seohNŸ(i²å•©µx|¦…rqt¤¨…gsƒ¤½qtxh

Tm+1d ²Æž{|O‚ Tm−nd ² ¦hÏqt¤¨o|Esƒ‚)„eqtxh

Sd(m+ 1) = (Tm−nd )−1Sd(m)Td(m+ 1)²'§¥†]qt¤¥¤¥yH­®h³…rqt¤¨…gsƒ¤½qtxh

Q(ti+1) seo+§¥†ƒ”Kx+beh

Mcc(ti)1)²

¸§¥†e…ph6­®hqt{h“§¥†Rxhg{hpo+xhp„祆q=fjqtx+behgfjqtx+§¨…rqO¤0‚ƒ{|¸|t¶£|t¶x+beh6…p|O†¸ª‹hg{+”•hg†e…ph6x|Kx+beh³fKhpqt†

Ë]hg¤¨„í®h!­~§¥¤¥¤1†e|Oxx+{+yHx|!}Íseox+§Ì¶Wy:x+beh“†¸sƒfKhg{+§¨…rqt¤0‚ƒ{|¸…php„vsƒ{h³¤¨hrqO„v§¥†ƒ”jx|µx+beh6qt«)|\ª‹h“{hpo+sƒ¤¥xor²

¦h=­~§¥¤¥¤£qt¤¨o,|#§¥”†e|O{hµx+§¥fKhp|Osƒxo"qt†e„$o¤¨|\­c´ïo+x,qt{+xqOo“­®hg¤¥¤£qOo³o‚)hp…g§½qt¤>„ƒhgx,qt§¥¤¨o6|t¶~…p|O†ƒ”•hpo+x+§¨|O†

qrª‹|O§¨„eqt†e…phµ­~bƒ§¨…,bE­®|Osƒ¤¨„E|O†ƒ¤¥yo,hg{+ª•h=x|w|O«eo…gsƒ{hµx+beh=fjqt§¥†E§¨„ƒhrqOor² ¦h"­~§¥¤¥¤>†ehgª‹h¯{x+behg¤¨hgo,o

o+°‹hgx…,bwbe|\­ x+behpoh³h¯uvxhg†eo+§¨|O†eo…p|Osƒ¤¨„w«)h“b]qt†e„v¤¨hp„T²

acb]hµo+x+{+se…gx+sƒ{hK|t¶®x+beh=‚]qt‚)hg{“§¨o6qOo¶Î|O¤¥¤¨|\­or² ï† vhg…gx+§¨|O†NH­®h=fK|¸„ƒhg¤>x+beh

N ‚]qt{+x+§¨…g¤¨h o+yvo+xhgf |t¶­~§¥†e„e|\­o…p|Osƒ‚ƒ¤¨hp„j­~§¥x+bjx+behº‹sehgseh?qt†e„Kx+behg†K¶Î|O{+fsƒ¤½qtxhx+bƒ§¨o®qOoq!bƒ§¨ox|O”{,qtf |t¶

­~§¥†e„ƒ|\­4o+§¥¼rhpoc…p|Osƒ‚ƒ¤¨hp„H­~§¥x+bÃq6º¸sehgseh²'¹† Rhp…gx+§¨|O†Ã‘6­®ho+sƒfµfjqt{+§¥¼rhx+beh?fKhrqt†HË]hg¤¨„:¤¥§¥fµ§¥xr²

acbeh‚ƒ{|¸|t¶1|t¶x+behh¯uv§¨o+xhg†e…ph|t¶x+bƒ§¨o£¤¥§¥fµ§¥x>¶Î|O¤¥¤¨|\­o£§¥† Rhp…gx+§¨|O†:‰e²)¹† Rhp…gx+§¨|O†HŒ“­®hhpo+x,qt«ƒ¤¥§¨o+b

x+beh³…p|O†¸ª‹hg{+”•hg†e…ph³x|Kq=sƒ†ƒ§¨º‹seh“¤¥§¥fµ§¥xr²0§¥†]qt¤¥¤¥y#§¥† Rhp…gx+§¨|O† ­®h³hpo+x,qt«ƒ¤¥§¨o+bÉacbehp|O{hgf i²

- 5"

N *"]'2 ,0&3“3ƒ'2>

", , +'

N ! "#$% !&'&

+?sƒ{®fK|¸„ƒhg¤x,qt°•hpo®§¥†¸x|=qO…p…p|Osƒ†¸xcx+beh„ƒhg¤½qryj|t¶0|O†eh?{|Osƒ†e„:x+{+§¥‚Hx§ÌfKh«)hgx¹­®hphg†#x+beh?x+§¥fKh?x+beh

‚]qO…,°‹hgx§¨o°R§¥¤¥¤¨hp„Ïqt†e„Ãx+beh6x+§¥fKh³­~behg†Ïx+beh³«ƒsv±hg{?{hp…ghg§¥ª‹hpox+beh³{,hg„ƒse…phg„Ï{,qtxh²# EhqOoo+sƒfKh

­~§¥†e„ƒ|\­ {hp„vse…gx+§¨|O†eoµqtx…p|O†ƒ†ehp…gx+§¨|O†

n |¸…p…gsƒ{6«)hp…rqtseo,hj|t¶~¤¨|o,ohpo6|O†ehK{|Osƒ†e„¦x+{+§¥‚Nx+§¥fKhK§¥†

x+beh"‚]qOo+xr²!a0|:Ëe{o+x!|O{„ƒhg{r»x+beh‚ƒ{|O«]qt«ƒ§¥¤¥§¥x¹y|t¶®qj­~§¥†e„e|\­Ä{hp„vse…gx+§¨|O†$«)h¯xÍ­®hphg†Åx+§¥fKh

t qt†e„

t+h §¨o

Z t+h−RNn(t+h)

t−RNn(t)

WnN(s)

RT TnN(s)F(QN(s))ds[1−d

dtRNn(t)]W(tRNn(t))

RNn(tRNn(t))F(QN(t−RNn(t)))h

o+§¥†e…ph=x+beh"‚ƒ{|O«]qt«ƒ§¥¤¥§¥x¹y$qH‚]qO…,°•hgx“§¨o“„v{|O‚ƒ‚)hp„ŧ¨o!‚ƒ{|O‚)|O{+x+§¨|O†]qt¤£x|

W(tRNn(t))/RNn(t RNn(t))»)x+behx{,qt†eo+fµ§¨oo+§¨|O†Å{,qtxh=|O†ehx+§¥fKh"§¥†x+beh"‚]qOo+xr»)x+§¥fKhpo

F(QN(s))»)x+beh=„v{|O‚Å{,qtxh

|O†eh{|Osƒ†e„:x{+§¥‚H§¥†Hx+beh‚]qOo+xr²) Eh?x+behg{h¯¶¡|O{,h?fK|¸„ƒhg¤x+beh‚ƒ{|¸…phpooc|t¶1­~§¥†e„ƒ|\­4{hp„vse…gx+§¨|O†eoc«¸y

qµz|O§¨oo|O†Ã‚ƒ{|¸…phpoo­~§¥x+bÉo+x|¸…,b]qOo+x+§¨…“§¥†¸xhg†eo§¥x¹y

λNn(t) := [1 d

dtRNn(t)]WnN(tRnN(t))

RNn(tRNn(t))F(QN(tRnN(t)))

(12)

ŸW­®hÅrqt† qOoosƒfKh

WnN(t) = wn(0) ¶Î|O{ t < 0©¯² acbehwxhg{+f

[1 dtdRNn(t)] §¥† λNn ­cqOo

|\ª‹hg{+¤¨|¸|O°•hp„w§¥†¦Á¥i¯Âï²

hgx

{Nn(t);n = 1, . . .} «)h:§¥†e„ƒhg‚)hg†e„ƒhg†¸xjz|O§¨oo|O†¬‚ƒ{|¸…phpoo,hpo"­~§¥x+b¬§¥†¸xhg†eo+§¥x¹y

1 qt†e„

¤¨hgx

ΛNn(t) =Rt

0λNn(s)ds «)h"x+beh=o+x|¸…,b]qOox+§¨…"§¥†¸xhg†eo+§¥x¹yɶÎ|O{x+beh=z|O§¨o,o|O†Å‚)|O§¥†¸x“‚ƒ{|¸…phpoo“|t¶

¤¨|oo,hgo~|t¶0…p|O†ƒ†ehp…gx+§¨|O†

n²Êhg†e…phx+beh¤¨|oohpoc|t¶…p|O†ƒ†ehp…gx+§¨|O†

n|¸…p…gsƒ{qO…p…p|O{„v§¥†ƒ”Kx|xbehx+§¥fKh …,b]qt†ƒ”•hp„Éz|O§¨oo|O†Ã‚ƒ{|¸…phpo,o

NnNn(t))²

¾chg¤¨|\­.­®h?­~§¥¤¥¤)fjqt°‹hq“·ese§¥„wqt‚ƒ‚ƒ{|ruR§¥fjqtx+§¨|O†Ã|t¶Jx+beh?x+behº‹sehgseh!qt†e„:x+beh?­~§¥†e„ƒ|\­Æo§¥¼rhpo

x+b¸seo§¥”†e|O{+§¥†ƒ”“·ese…gx+s]qtx+§¨|O†eo®qtxx+behc‚]qO…,°•hgx>¤¨hgª•hg¤¿²acbƒ§¨o£qt¤¥¤¨|\­oseox,|!„ƒhpo,…g{+§¥«)hcx+behc­~§¥†e„ƒ|\­o

qOo~§¥†e„ƒhg‚)hg†e„ƒhg†¸x„v§Ì±Thg{hg†¸x+§½qt«ƒ¤¨h6„vyR†]qtfµ§¨…rqt¤1o+yvo+xhgfKo…p|Osƒ‚ƒ¤¨hp„í~§¥x+bÏq·esƒ§¨„w«ƒsv±Thg{r²

£Ñ š Ñ ™ › Ñ 1›v™ WÕ¹Õ š Ô Ö ÕRÔ ˜ acbehg{hcqt{hx+bƒ{hph®ohg‚]qt{,qtxh‚eb]qOohpo 1…p|O†ƒ”•hpo+x+§¨|O†

qrª‹|O§¨„eqt†e…ph»x+§¥fKhp|Osƒx£qt†e„=o+¤¨|\­ o+x,qt{+xr²ž?sƒ{+§¥†ƒ”³…p|O†ƒ”•hpo+x+§¨|O†jqrª‹|O§¨„eqt†e…ph»­~behg†µ†e|?¤¨|o,o|¸…p…gsƒ{o

x+beh³­~§¥†e„ƒ|\­;o+§¥¼rh“§¥†e…g{hrqOohpo¤¥§¥†ehrqt{+¤¥yÃqtx{,qtxh

1/RNn(t) «ƒsƒx§Ì¶x+beh6o|Osƒ{…ph³„ƒhgxhp…gxox+beh³¤¨|oo

|t¶q"‚]qO…,°‹hgx?qtx~x+§¥fKh

tRNn(t) «)hp…rqtseo,h“x+bƒ{hph³„vsƒ‚ƒ¤¥§¨…rqtxh6qO…,°R†e|\­~¤¨hp„v”•hgfKhg†¸x,o?qt{+{§Ìª‹h»ƒx+beh o|Osƒ{…ph~…gsƒxox+behc…gsƒ{+{hg†¸x

WnN(t)o+§¥¼rh®«¸y6b]qt¤Ì¶2x|

WnN(t)/2²acbehco+¤¨|\­ ox,qt{+xx+bƒ{hpo+bƒbe|O¤¨„

Ÿ¡oox+bƒ{hpo+b2©§¨oohgxx|

HnN(t) =WnN(t)/2²

acb]hÏo|Osƒ{…phÉx+behg† «)hg”§¥†eo:¶ÎqOoxj{hgx+{,qt†eo+fµ§¥xwqt†e„ ¶¿qOo+xj{hp…p|\ª‹hg{+y•² acbehɤ¨|o+x:‚]qO…,°‹hgx:§¨o

{hgx+{,qt†eo+fµ§¥x+xhp„ qt†e„¬x+bƒ{|Osƒ”b ­§Ì†]„ƒ|\­&§¥†v·2qtx+§¨|O† ‚]qO…,°‹h¯x,oµ…p|O†Rx+§¥†¸sehwx|Å«)hwohg†¸xjqOo=§Ì¶x+beh

­~§¥†e„ƒ|\­ o+§¥¼rh~§¨o>…p|O†eo+x,qt†¸xŸ¡|O{qtx¤¨hrqOoxx+behqrª‹hg{,qt”•h~x+{,qt†eofµ§¨oo+§¨|O†K{,qtxh~§¨o>…p|O†eo§¨o+xhg†¸x>­~§¥x+b:q

…p|O†eo+x,qt†¸x­~§¥†e„ƒ|\­Äo+§¥¼rh

WnN(t)/2©¯² behg†Ïx+beh6{,h¯x{,qt†eo+fµ§¥x+xhp„Ï‚]qO…,°‹hgx?§¨o!qO…,°¸†e|\­~¤¨hp„v”•hp„

…p|O†ƒ”•hpo+x+§¨|O†#qrª•|O§¨„eqt†e…ph{hpo+sƒfKhpor²Êhg†e…ph~x+behhgª•|O¤¥sƒx+§¨|O†:|t¶Tx+beh~­~§¥†e„ƒ|\­.o+§¥¼rh~§¥†Kx+beh…p|O†ƒ”•hpo(´

x+§¨|O†Ïqrª‹|O§¨„eqt†e…ph“‚ƒb]qOo,h!§¨o„ƒhpo,…g{+§¥«)hp„w«¸yHx+beh!¶¡|O¤¥¤¨|\­~§¥†ƒ”:o+x|¸…,b]qOo+x+§¨…³„v§Ì±Thg{hg†¸x+§½qt¤0hpº‹s]qtx+§¨|O†

dWnN(t) = 1

RnN(t)(1SnN(t))dtWnN(t)

2 dNnNn(t)),

­~§¥x+b

WnN(0) = wn(0)» n = 1, . . . , N o‚)hp…¯§ÌË]hp„T²³Êhg{h

SnN(t) = 1 §Ì¶£x+bƒ§¨o!…p|O†ƒ†ehp…gx+§¨|O†$§¨o o+x+§¥¤¥¤J§¥†#¶¿qOo+x~{hp…p|\ª•hg{+yÃqtx~x+§¥fKh

t qt†e„w§¨o~¼rhg{|K|Ox+behg{+­~§¨oh²

ï¶ WnN(t)<4 x+behg†Ïxbeho|Osƒ{…ph"…rqt† x{hp…phg§¥ª‹h6x+bƒ{hph"„vsƒ‚ƒ¤¥§¨…rqtxh ?€“oo|j§¥x?­~§¥¤¥¤”•|

§¥†¸x|?x+beh£x+§¥fKhp|Osƒx‚ƒb]qOoh£¶¡|O{qt‚ƒ‚ƒ{|ruv§¥fjqtxhg¤¥y|O†eho,hp…p|O†e„T²'+?x+behg{hgª•hg†¸x,o0¤¥§¥°•h£x+beh¤¨|oo|t¶ex+beh

{hgx+{,qt†eo+fµ§¥x+xhp„:‚]qO…,°•hgx£­~§¥¤¥¤)qt¤¨o|“‚ƒ{|\ª‹|O°‹hq!x+§¥fKhp|Osƒxr²¿¶­®h­~§¨o+behp„Kx|“fK|¸„ƒhg¤2x+§¥fKhp|Osƒxo£­®h

…p|Osƒ¤¨„:„ƒh¯Ëe†ehq“¶Wsƒ†e…gx+§¨|O†

U(WnN(t))hpº¸s]qt¤2x|6|O†eh§Ì¶Tx+beh?…p|O†ƒ†ehp…gx+§¨|O†eo¶Îqt¤¥¤¨o£§¥†¸x|6x+§¥fKhp|Osƒx

„vsƒ{+§¥†ƒ”K¶ÎqOox~{hp…p|\ª•hg{+yÃqt†e„w¼rhg{|µ§Ì¶†e|Oxr²£Ê?hg†e…ph“x+beh³‚)|O§¥†¸x‚ƒ{|¸…phpoo|t¶¶¿qt¤¥¤¥§¥†ƒ”K§¥†¸x|µx+§¥fKhp|Osƒx

§¨o6”§¥ª•hg†¦«¸y

U(WnN(t))dNnNn(t))²#ž?sƒ{+§¥†ƒ”Ïx+behKx+§¥fKhp|Osƒx"‚ƒb]qOohKx+behK­~§¥†e„ƒ|\­ o§¥¼rhµ§¨o

¼rhg{|ƒ²>acbeh³…p|O†ƒ†ehp…gx+§¨|O†Ï§¨o„ƒhpo…g{+§¥«)hp„ë¸yHoox+bƒ{hpo+bÉqt†e„wx+beh“{hgfjqt§¥†ƒ§¥†ƒ”jx+§¥fKh“§¥†Ãx+§¥fKhp|Osƒxr²

¶¡xhg{x+beh?x+§¥fKhp|Osƒxc‚ƒb]qOohhg¤½qt‚eohpo®x+beho|Ose{…phhg†¸xhg{oco+¤¨|\­c´ïo+x,qt{+x~qt†]„H„ƒ|Osƒ«ƒ¤¨hpo®§¥xo®­~§¥†v´

„ƒ|\­ o+§¥¼rhÏox,qt{+x+§¥†ƒ”N¶W{|Of |O†ehÏhgª‹hg{+y la~aÈsƒ†¸x+§¥¤x+behÏ­~§¥†e„ƒ|\­ o+§¥¼rhÏ{hrqO…,behpo#oo+x+bƒ{hpo+bÆqtx

­~bƒ§¨…,b#x+§¥fKh…p|O†ƒ”•hpo+x+§¨|O†Ãqrª‹|O§¨„eqt†e…ph{hpo+x,qt{+xor²'ï¶0qt†e|Ox+behg{c¤¨|oo§¨oc„ƒhgxhp…gxhp„H«)h¯¶Î|O{h?{hrqO…,bƒ§¥†ƒ”

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