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�
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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3<1
hgc, Mc(t)i=R∞
w=0gc(w)Mc(t, dw)- 3<1 Rc(t) =Tc+Q(t−Rc(t))/L
3<1
e(s, s−Rc(s), w) =hv,Mc(s−Rc(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)(1−K(t))
Rc(t) −L (i²å©
− Ã d
X
c=1
hw, Mc(t, dw)i(1−K(t)) Rc(t) −L
!+
χ{Q(t) =qmax} +i²¸©
− Ã d
X
c=1
hw, Mc(t, dw)i(1−K(t)) Rc(t) −L
!−
χ{Q(t) = 0}). (i²å©
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(1−K(t)) Rc(t) =L.
oo+sefµ§Ìe
gc(0) = 0 qtewx+b]qtx
gc(w)→0 qOo w→ ∞ ®h rqtÃ{hg~{+§¥xh:(i²å©~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(s−Rc(s))K(s−Rc(s))(1−R˙c(s))
·hgc(w), e(s, s−Rc(s),2w)·Mc(s,2dw)−e(s, s−Rc(s), w)·Mc(s, dw)ii ds.
~behg{h Mc(s,dw) dw
§¨ox+beh(e{hp ,behgx?hg{+§¥ªOqtx+§¥ªh³|t¶x+beh³fKhrqOo+s{h
Mc ~§¥x+bÃ{hpo+)hp gxx|
w²®®|Ov´
ohpº¸sehg¸x+¤¥y»
dMc(t)
dt =− 1 Rc(t)
Mc(t, dw)
dw + 1
Rc(t−Rc(t))K(t−Rc(t))(1−R˙c(s)) (i² ©
·(e(t, t−Rc(t),2w)(Mc(t, d(2w))−e(t, t−Rc(t), w)Mc(t, dw))i .
¹ Rhp gx+§¨|O:v²åv²å!§¥ÃÁ¥i¯Âe®hcfjqOhq!o+fK|¸|Ox+bjqte{|ruR§¥fjqtx+§¨|Ojx|
e(t, t−Rc(t), w) «]qOohp
|OEx+beh=¶ÎqO gxxb]qtx6|Oehµla~aħ¥$xbeh=]qOo+x³x+behµ~§¥e|\ o§¥¼rh=cqOofK|ox¤¥§¥°hg¤¥yÏx+behK gs{+{hg¸x
~§¥e|\4o§¥¼rhfµ§¥¸seo~|Oeh|O{®x¹~§¨ phx+beh gs{+{,h¯Rxc~§¥e|\4o+§¥¼rh?§Ì¶q6¤¨|oo~qOo®eh¯x,hg gxhp#§¥Hx+beh
§¥¸xhg{+§¥fò .§¥x+bÏx+b§¨o!qt{|ruv§¥fjqtx+§¨|OÅ®h6seohpY(i² ©x|:hgª|O¤¥ªh"qjv§¨o g{hgxh=qt{|ruR§¥fjqtx+§¨|O
|t¶6x+behÏfKhrqOo+s{h
Mc
¡h¯uv phgxÅÁ¥igÂ!|O¤¥y x+{hrqtxo#|Oeh g¤½qOoo¯©¯²;acbehϸsfKhg{+§¨ rqt¤!{hpo+s¤¥xowqt{h
h¯u phg¤¥¤¨hg¸x"q`¶¡xhg{6|OehK p|O{+{,hg gxo6¶¡|O{³x+behµ¶ÎqO gx6x+b]qtx"q#{|O)|O{+x+§¨|OY|t¶cx+behj p|Oehp gx+§¨|Oeo§¥Nqt
+?ehgxjo+§¥fs¤½qtx+§¨|O qt{h#§¥ x+§¥fKhp|OsxÏ¡|Os{µfK|¸hg¤?qOoo+sfKhpoK p|Oehp gx+§¨|OeoK§¥eo+x,qt¸x,qtehp|Oseo¤¥y
{hpo+sfKh³ p|Ohpox+§¨|OÏqrª|O§¨eqte ph³§¶x+behgy:¶¿qt¤¥¤T§¥¸x|µx+§¥fKhp|Osxí©¯²
a0|#§¥¤¥¤¥seo+x+{,qtxh=x+beh"fKhrqtÅË]hg¤¨¤¥§¥fµ§¥x®h")hg{(¶¡|O{fKhg¦qt +?ehgx³o+§¥fs¤½qtx+§¨|O$~§¥x+b
N = 200» N = 400 qte N = 800 o,|Os{ phpor²cqO ,bo|Os{ ph6o,hgeo]qO ,°hgxo|t¶>o+§¥¼rh
536 «¸yRxhpox|
qwa#{|Osxhg{³~§¥x+bYqHx+{,qteo+fµ§¨o,o+§¨|OE{,qtxhK|t¶ce²O Àhgqt«§¥xo³)hg{6o,hp g|O]E|O{
L = 10433
]qO ,°hgxoK)hg{:ohp p|OeT² ¦hÉqOoo+sfKhwx+behÉo|Os{ phpo:qt¤¥¤b]qrªhÉqÅx+{íqteo+fµ§¨oo+§¨|O hg¤½qry |t¶µir
fµ§¥¤¥¤¥§¨ohp p|Oeor²?acb]h6{|Osxhg{§¥fµ¤¨hgfKhg¸xo!l?> ~§¥x+b
pmax = 0.05 ¶Î|O{qt¤¥¤0x+beh"o+§¥fs¤½qtx+§¨|Oeo
«sx®h"{hpo rqt¤¨h
Qmax
x|H«)h
1000 ~§¥x+b 200 o|Os{ phpor»
2000 §Ìxb 400 o|Os{ phpo³qte
4000
~§¥x+b
800 o|Os{ phpo\² ¸§¥e ph
Qmax o rqt¤¨hpo"§Ìxb
N»x+behwqrªhg{,qth#º¸sehgsehHo+§¥¼rhH|¸hpoKqOo"®hg¤¥¤
~b§¥¤¨h!b]|O¤¥§Ìeµx+beh!¤¨|ooc{,|O«]qt«§¥¤¥§ÌxÍy:ËuhpH~b§¨ ,bç¥wx+s{+wbe|O¤¨o~x+beh³qrªhg{,qth!§Ì]|\ o+§¥¼rh
ËuhpT²?o
N §¥e g{hrqOohpo®h®o,hph£x+beh·ese gx+s]qtx+§¨|Oeo§¥"x+beh®{hg¤½qtx+§¥ªhcº¸sehgseh®o+§¥¼rh!W§¥=]qO ,°hgxo)hg{
p|Oehp gx+§¨|O2©!hp g{hrqOohpor² Eh=qt¤¨o,|Hohphx+beh"{hg¤½qtx+§¥ªh=º¸sehgseh=o+§¥¼rh"|t¶£x+beh=ÀÅqtx+¤½qt«Å¸sfKhg{+§¨ rqt¤
o+§¥fs¤½qtx+§¨|Oɧ¨oq=«§¥x~b§¥bJ²£acb§¨o~§¨o~«)hp rqtseo,h³|t¶x+§¥fKhp|OsxoqOov§¨o gseo,ohp#§¥¦Á¥i¯Âï²
hg§¥x+behg{
Mc(t, dw) |O{ Mc(s−Rc(s), dv;s, dw) §¨o³qHox,qtxh"«sxx+behKqt«)|\ªh=hpº¸s]qtx+§¨|O
|¸hpo~{|\ªR§¨hhge|Osbw§¥v¶Î|O{+fjqtx+§¨|OÃx|µhgª|O¤¥ªhx+behoyRo+xhgfò hgx
µc(t) hge|Oxhx+beh!{|¸ phpoo
{Mc(s, dw);t−1 ≤ s ≤ t} Îqt¤¥¤la~a oqt{hK¤¨hpoo³x+b]qt
1©¯² %o+§¥N(i²¥i\©!®hK rqtNhgª|O¤¥ªh
Mc(t, dw) ¶¡{|Of t x| t+δt ~b§¥¤¨h Mc(t−s+δt, dw) §¨oH|O«x,qt§¥ehp.«¸y qEx+§¥fKhob§Ì¶Wxr²
%?v¶¡|O{+x+s2qtxhg¤Ìy
µc §¨oje|Ox:{,qO gx+§¨ rqt¤!o+x,qtx,hO² ªhg §Ì¶³®hÏv§¨o g{hgx+§¥¼rhÅqte |O¤¥y °hphg x+beh x+{,q`}+hp gx|O{+y=|t¶x+behc{|¸ phpo,o>|O:q]qt{+x+§¥x+§¨|Oj§¥ª¸§¥
{Mc(si, dw);t−1 =s0< s1. . . sn=t}
§¥xo+x+§¥¤¥¤T{hpº¸s§¥{hpox|¸|µfse ,bÉ p|Ofµsxhg{fKhgfK|O{+y#x|µo|O¤¥ªh!¸sfKhg{+§¨ rqt¤¥¤¥y²
¦h rqt qrª|O§¨.x+b§¨oH{|O«¤¨hgf «¸y h¯Ëe§¥qNo,hpºsehge phÅ|t¶x+§¥fKhpo
tck ¶Î|O{#hrqO ,b4 g¤½qOo,o o+se ,bx+b]qtx
tck+n+1−Rc(tck+n+1) = tck² ï¶>®h6§¨ ,°
n o+sj g§¨hg¸x+¤¥yɤ½qt{+hx+b§¨o§¥ªhpo!qKËeeh
]qt{+x+§¥x+§¨|OJ²>!h¯Ëeeh
Φc(t) =x+beh!Ëe{o+x°Ho+se ,bÃx+b]qtx
tck > t² ¦h~§¥¤¥¤2 p|Oeox+{+se gx®|Os{o|O¤¥sx+§¨|O
«¸y¬{hp gs{+{hge phö¡{|Ofx+§¥fKh
ti x| ti+1 «¸y h¯Ëe§¥
ti+1 = minc(tcΦc(ti)) o+x,qt{x+§¥E¶W{|Of x+§¥fKh
t0 = 0²h¯uRx"qOo,o+sfKhjx+b]qtx6¶Î|O{hrqO ,b¬ g¤½qOoo®hjb]qrªhj«)hphg qt«¤¨hjx|Ï rqt¤¨ gs¤½qtxhwqte
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
§¥s{h4iÄlhg¤½qtx+§¥ªh¬ºs]h¯s]h¬o+§¥¼rh¬~§¥x+b
o|Os{ 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§¥s{h Älhg¤½qtx+§¥ªh¬º¸sehgseh o+§¥¼rhY~§¥x+b
o|Os{ 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
§¥s{h Älhg¤½qtx+§¥ªh¬ºs]h¯s]h¬o+§¥¼rh¬~§¥x+b
o|Os{ 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§¥s{hN?sehgseh¬o+§¥¼rhN|t¶jx+behNfKhrqt;Ë]hg¤¨
¤Ì§¥fµ§¥x
o,qrªh=x+behKªhp gx|O{
VcM(t)»q#v§¨o, g{hgx+§¥¼rhpEªhg{o§¨|O¦|t¶
Mc(tck) ¶Î|O{ k = m−n, . . . m ~behg{h m= Φc(t)−1²!Wx+behpohqt{h³fjqt{+§¥]qt¤¨oe|Oxx+beh6hg¸x+§¥{h}(|O§¥¸x?v§¨o+x+{+§¥«sx+§¨|O2©¯² ¤¨o|:qOoo+sfKh
®hÉoíqrªhÃx+behêhp gx|O{:|t¶³°hg{+ehg¤¨o
VcT(t) §¥ªhg«Ry
Tc(tck) ¶¡|O{ k = m−n, . . . m ~behg{h
Mc(tck+1) =Mc(tck)◦Tc(tck+1) qte m §¨oqOoqt«)|\ªh²(§¥]qt¤¥¤¥yqOoo+sfKh"x+b]qtx!®h"o,q\ªhx+beh
°hg{+ehg¤¨o
Smc =Qm
k=m−nTc(tck)²
¦hc rqtµe|\ hgª|O¤¥ªhc|Os{>o+yvo+xhgfÄx|
ti+1²cxhrqO ,bKoxhg=®hc|O¤¥y"hgª|O¤¥ªh®x+beh~ºsehgsehqte
x+beh!|Oeh! g¤½qOo,o
d~behg{h ti+1=tdΦd(ti)
²acbeh§¥¸ªhg{o,h?°hg{+ehg¤
(Smd)−1 §¥ªhpo®x+beh! p|Oev§¥x+§¨|O]qt¤
v§¨o+x+{+§¥«sx+§¨|OÆ|t¶!x+behÉ~§¥e|\o:|t¶³ g¤½qOoo
d |OehÉla~a&«)h¯¶¡|O{hÉx+§¥fKh
ti §Ìªhgx+behÃ~§¥e|\
qtx:x+§¥fKh
ti
²;cqt¤¨ gs¤½qtxhx+behÏ p|Oev§¥x+§¨|O]qt¤h¯uv)hp gx,qtx+§¨|O
e(ti, ti −Rd(ti), w)² .§¥x+b x+b§¨o
®hÉ rqt seohN(i²å©µx|¦ rqt¤¨ gs¤½qtxh
Tm+1d ²Æ{|O Tm−nd ² ¦hÏqt¤¨o|Es)eqtxh
Sd(m+ 1) = (Tm−nd )−1Sd(m)Td(m+ 1)²'§¥]qt¤¥¤¥yH®h³ rqt¤¨ gs¤½qtxh
Q(ti+1) seo+§¥Kx+beh
Mc(Φc(ti)−1)²
¸§¥e ph6®hqt{h§¥Rxhg{hpo+xhpç¥q=fjqtx+behgfjqtx+§¨ rqO¤0{|¸|t¶£|t¶x+beh6 p|O¸ªhg{+hge ph6x|Kx+beh³fKhpqt
Ë]hg¤¨Ã®h!~§¥¤¥¤1e|Oxx+{+yHx|!}Íseox+§Ì¶Wy:x+beh¸sfKhg{+§¨ rqt¤0{|¸ phpvs{h³¤¨hrqOv§¥jx|µx+beh6qt«)|\ªh{hpo+s¤¥xor²
¦h=~§¥¤¥¤£qt¤¨o,|#§¥e|O{hµx+§¥fKhp|Osxo"qte$o¤¨|\c´ïo+x,qt{+xqOo®hg¤¥¤£qOo³o)hp g§½qt¤>hgx,qt§¥¤¨o6|t¶~ p|Ohpo+x+§¨|O
qrª|O§¨eqte phµ~b§¨ ,bE®|Os¤¨E|O¤¥yo,hg{+ªh=x|w|O«eo gs{hµx+beh=fjqt§¥E§¨hrqOor² ¦h"~§¥¤¥¤>ehgªh¯{x+behg¤¨hgo,o
o+°hgx ,bwbe|\ x+behpoh³h¯uvxhgeo+§¨|Oeo p|Os¤¨w«)hb]qtev¤¨hpT²
acb]hµo+x+{+se gx+s{hK|t¶®x+beh=]qt)hg{§¨o6qOo¶Î|O¤¥¤¨|\or² ï vhg gx+§¨|ONH®h=fK|¸hg¤>x+beh
N ]qt{+x+§¨ g¤¨h o+yvo+xhgf |t¶~§¥ee|\o p|Os¤¨hpj~§¥x+bjx+behºsehgseh?qteKx+behgK¶Î|O{+fs¤½qtxhx+b§¨o®qOoq!b§¨ox|O{,qtf |t¶
~§¥e|\4o+§¥¼rhpoc p|Os¤¨hpH~§¥x+bÃq6º¸sehgseh²'¹ Rhp gx+§¨|OÃ6®ho+sfµfjqt{+§¥¼rhx+beh?fKhrqtHË]hg¤¨:¤¥§¥fµ§¥xr²
acbeh{|¸|t¶1|t¶x+behh¯uv§¨o+xhge ph|t¶x+b§¨o£¤¥§¥fµ§¥x>¶Î|O¤¥¤¨|\o£§¥ Rhp gx+§¨|O:e²)¹ Rhp gx+§¨|OH®hhpo+x,qt«¤¥§¨o+b
x+beh³ p|O¸ªhg{+hge ph³x|Kq=s§¨ºseh¤¥§¥fµ§¥xr²0§¥]qt¤¥¤¥y#§¥ Rhp gx+§¨|O ®h³hpo+x,qt«¤¥§¨o+bÉacbehp|O{hgf i²
- 5"
N *"]'2 ,0&33'2>
", , +'
N ! "#$% !&'&
+?s{®fK|¸hg¤x,qt°hpo®§¥¸x|=qO p p|Os¸xcx+behhg¤½qryj|t¶0|Oeh?{|Ose:x+{+§¥Hx§ÌfKh«)hgx¹®hphg#x+beh?x+§¥fKh?x+beh
]qO ,°hgx§¨o°R§¥¤¥¤¨hpÏqteÃx+beh6x+§¥fKh³~behgÏx+beh³«sv±hg{?{hp ghg§¥ªhpox+beh³{,hgse phgÏ{,qtxh²# EhqOoo+sfKh
~§¥e|\ {hpvse gx+§¨|Oeoµqtx p|Oehp gx+§¨|O
n |¸ p gs{6«)hp rqtseo,hj|t¶~¤¨|o,ohpo6|OehK{|Ose¦x+{+§¥Nx+§¥fKhK§¥
x+beh"]qOo+xr²!a0|:Ëe{o+x!|O{hg{r»x+beh{|O«]qt«§¥¤¥§¥x¹y|t¶®qj~§¥ee|\Ä{hpvse gx+§¨|O$«)h¯xÍ®hphgÅx+§¥fKh
t qte
t+h §¨o
Z t+h−RNn(t+h)
t−RNn(t)
WnN(s)
RT TnN(s)F(QN(s))ds∼[1−d
dtRNn(t)]W(t−RNn(t))
RNn(t−RNn(t))F(QN(t−RNn(t)))h
o+§¥e ph=x+beh"{|O«]qt«§¥¤¥§¥x¹y$qH]qO ,°hgx§¨ov{|O)hpŧ¨o!{|O)|O{+x+§¨|O]qt¤£x|
W(t−RNn(t))/RNn(t− RNn(t))»)x+behx{,qteo+fµ§¨oo+§¨|OÅ{,qtxh=|Oehx+§¥fKh"§¥x+beh"]qOo+xr»)x+§¥fKhpo
F(QN(s))»)x+beh=v{|OÅ{,qtxh
|Oeh{|Ose:x{+§¥H§¥Hx+beh]qOo+xr²) Eh?x+behg{h¯¶¡|O{,h?fK|¸hg¤x+beh{|¸ phpooc|t¶1~§¥e|\4{hpvse gx+§¨|Oeoc«¸y
qµz|O§¨oo|OÃ{|¸ phpoo~§¥x+bÉo+x|¸ ,b]qOo+x+§¨ §¥¸xhgeo§¥x¹y
λNn(t) := [1− d
dtRNn(t)]WnN(t−RnN(t))
RNn(t−RNn(t))F(QN(t−RnN(t)))
W®hà rqt qOoosfKh
WnN(t) = wn(0) ¶Î|O{ t < 0©¯² acbehwxhg{+f
[1− dtdRNn(t)] §¥ λNn cqOo
|\ªhg{+¤¨|¸|O°hpw§¥¦Á¥i¯Âï²
hgx
{Nn(t);n = 1, . . .} «)h:§¥ehg)hgehg¸xjz|O§¨oo|O¬{|¸ phpoo,hpo"~§¥x+b¬§¥¸xhgeo+§¥x¹y
1 qte
¤¨hgx
ΛNn(t) =Rt
0λNn(s)ds «)h"x+beh=o+x|¸ ,b]qOox+§¨ "§¥¸xhgeo+§¥x¹yɶÎ|O{x+beh=z|O§¨o,o|OÅ)|O§¥¸x{|¸ phpoo|t¶
¤¨|oo,hgo~|t¶0 p|Oehp gx+§¨|O
n²Êhge phx+beh¤¨|oohpoc|t¶ p|Oehp gx+§¨|O
n|¸ p gs{qO p p|O{v§¥Kx|xbehx+§¥fKh ,b]qthpÉz|O§¨oo|OÃ{|¸ phpo,o
Nn(ΛNn(t))²
¾chg¤¨|\.®h?~§¥¤¥¤)fjqt°hq·ese§¥wqt{|ruR§¥fjqtx+§¨|OÃ|t¶Jx+beh?x+behºsehgseh!qte:x+beh?~§¥e|\Æo§¥¼rhpo
x+b¸seo§¥e|O{+§¥·ese gx+s]qtx+§¨|Oeo®qtxx+behc]qO ,°hgx>¤¨hgªhg¤¿²acb§¨o£qt¤¥¤¨|\oseox,|!hpo, g{+§¥«)hcx+behc~§¥e|\o
qOo~§¥ehg)hgehg¸xv§Ì±Thg{hg¸x+§½qt«¤¨h6vyR]qtfµ§¨ rqt¤1o+yvo+xhgfKo p|Os¤¨hpÃ~§¥x+bÏq·es§¨w«sv±Thg{r²
£Ñ Ñ Ñ 1v WÕ¹Õ Ô Ö ÕRÔ acbehg{hcqt{hx+b{hph®ohg]qt{,qtxheb]qOohpo 1 p|Ohpo+x+§¨|O
qrª|O§¨eqte ph»x+§¥fKhp|Osx£qte=o+¤¨|\ o+x,qt{+xr²?s{+§¥³ p|Ohpo+x+§¨|Ojqrª|O§¨eqte ph»~behgµe|?¤¨|o,o|¸ p gs{o
x+beh³~§¥e|\;o+§¥¼rh§¥e g{hrqOohpo¤¥§¥ehrqt{+¤¥yÃqtx{,qtxh
1/RNn(t) «sx§Ì¶x+beh6o|Os{ ph³hgxhp gxox+beh³¤¨|oo
|t¶q"]qO ,°hgx?qtx~x+§¥fKh
t−RNn(t) «)hp rqtseo,hx+b{hph³vs¤¥§¨ rqtxh6qO ,°Re|\~¤¨hpvhgfKhg¸x,o?qt{+{§Ìªh»x+beh o|Os{ ph~ gsxox+behc gs{+{hg¸x
WnN(t−)o+§¥¼rh®«¸y6b]qt¤Ì¶2x|
WnN(t−)/2²acbehco+¤¨|\ ox,qt{+xx+b{hpo+bbe|O¤¨
¡oox+b{hpo+b2©§¨oohgxx|
HnN(t) =WnN(t−)/2²
acb]hÏo|Os{ phÉx+behg «)hg§¥eo:¶ÎqOoxj{hgx+{,qteo+fµ§¥xwqte ¶¿qOo+xj{hp p|\ªhg{+y² acbehɤ¨|o+x:]qO ,°hgx:§¨o
{hgx+{,qteo+fµ§¥x+xhp qte¬x+b{|Osb §Ì]|\&§¥v·2qtx+§¨|O ]qO ,°h¯x,oµ p|ORx+§¥¸sehwx|Å«)hwohg¸xjqOo=§Ì¶x+beh
~§¥e|\ o+§¥¼rh~§¨o> p|Oeo+x,qt¸x¡|O{qtx¤¨hrqOoxx+behqrªhg{,qth~x+{,qteofµ§¨oo+§¨|OK{,qtxh~§¨o> p|Oeo§¨o+xhg¸x>~§¥x+b:q
p|Oeo+x,qt¸x~§¥e|\Äo+§¥¼rh
WnN(t−)/2©¯² behgÏx+beh6{,h¯x{,qteo+fµ§¥x+xhpÏ]qO ,°hgx?§¨o!qO ,°¸e|\~¤¨hpvhp
p|Ohpo+x+§¨|O#qrª|O§¨eqte ph{hpo+sfKhpor²Êhge ph~x+behhgª|O¤¥sx+§¨|O:|t¶Tx+beh~~§¥e|\.o+§¥¼rh~§¥Kx+beh p|Ohpo(´
x+§¨|OÏqrª|O§¨eqte phb]qOo,h!§¨ohpo, g{+§¥«)hpw«¸yHx+beh!¶¡|O¤¥¤¨|\~§¥:o+x|¸ ,b]qOo+x+§¨ ³v§Ì±Thg{hg¸x+§½qt¤0hpºs]qtx+§¨|O
dWnN(t) = 1
RnN(t)(1−SnN(t))dt−WnN(t−)
2 dNn(ΛNn(t)),
~§¥x+b
WnN(0) = wn(0)» n = 1, . . . , N o)hp ¯§ÌË]hpT²³Êhg{h
SnN(t) = 1 §Ì¶£x+b§¨o! p|Oehp gx+§¨|O$§¨o o+x+§¥¤¥¤J§¥#¶¿qOo+x~{hp p|\ªhg{+yÃqtx~x+§¥fKh
t qtew§¨o~¼rhg{|K|Ox+behg{+~§¨oh²
ï¶ WnN(t−)<4 x+behgÏxbeho|Os{ ph" rqt x{hp phg§¥ªh6x+b{hph"vs¤¥§¨ rqtxh ?oo|j§¥x?~§¥¤¥¤|
§¥¸x|?x+beh£x+§¥fKhp|Osxb]qOoh£¶¡|O{qt{|ruv§¥fjqtxhg¤¥y|Oeho,hp p|OeT²'+?x+behg{hgªhg¸x,o0¤¥§¥°h£x+beh¤¨|oo|t¶ex+beh
{hgx+{,qteo+fµ§¥x+xhp:]qO ,°hgx£~§¥¤¥¤)qt¤¨o|{|\ª|O°hq!x+§¥fKhp|Osxr²¿¶®h~§¨o+behpKx|fK|¸hg¤2x+§¥fKhp|Osxo£®h
p|Os¤¨:h¯Ëeehq¶Wse gx+§¨|O
U(WnN(t−))hpº¸s]qt¤2x|6|Oeh§Ì¶Tx+beh? p|Oehp gx+§¨|Oeo¶Îqt¤¥¤¨o£§¥¸x|6x+§¥fKhp|Osx
vs{+§¥K¶ÎqOox~{hp p|\ªhg{+yÃqtew¼rhg{|µ§Ì¶e|Oxr²£Ê?hge phx+beh³)|O§¥¸x{|¸ phpoo|t¶¶¿qt¤¥¤¥§¥K§¥¸x|µx+§¥fKhp|Osx
§¨o6§¥ªhg¦«¸y
U(WnN(t−))dNn(ΛNn(t))²#?s{+§¥Ïx+behKx+§¥fKhp|Osx"b]qOohKx+behK~§¥e|\ o§¥¼rhµ§¨o
¼rhg{|²>acbeh³ p|Oehp gx+§¨|Oϧ¨ohpo g{+§¥«)hpë¸yHoox+b{hpo+bÉqtewx+beh{hgfjqt§¥§¥jx+§¥fKh§¥Ãx+§¥fKhp|Osxr²
¶¡xhg{x+beh?x+§¥fKhp|Osxcb]qOohhg¤½qteohpo®x+beho|Ose{ phhg¸xhg{oco+¤¨|\c´ïo+x,qt{+x~qt]H|Os«¤¨hpo®§¥xo®~§¥v´
|\ o+§¥¼rhÏox,qt{+x+§¥N¶W{|Of |OehÏhgªhg{+y la~aÈs¸x+§¥¤x+behÏ~§¥e|\ o+§¥¼rhÏ{hrqO ,behpo#oo+x+b{hpo+bÆqtx
~b§¨ ,b#x+§¥fKh p|Ohpo+x+§¨|OÃqrª|O§¨eqte ph{hpo+x,qt{+xor²'ï¶0qte|Ox+behg{c¤¨|oo§¨ochgxhp gxhpH«)h¯¶Î|O{h?{hrqO ,b§¥