研究の背景 無線 LAN 環境における省電力化 研究の目的 ネットワーク

• 
LAN
TCP Delayed ACK
– 
PC
PC
• 
• 
10%
[1]
50%
[1] Atheros Communications, “Power consumption and energy efficiency comparisons of
wlan products,” Atheros White Papers, May 2003.
2011/07/21
LAN
NS
TCP
?
NIC
1/10
NIC
(
)
Atheros AR5004 (2003 )
1.4 W
0.9 W
0.8 W
0.16 W
Atheros AR6002 (2007 )
0.8 W
0.5 W
0.05 W
0.002 W
[13] Wistron NeWeb Corp., “CM9: WLAN 802.11 a/b/g mini-PCI Module.” available at microcom.us/CM9.pdf.
Silex, “SX-SDCAG 802.11a/b/g SDIO card module datasheet.” available
1/2 at http://www. silexamerica.com/products/data
sheets/sx-sdcag brief.pdf.
TCP
[8]
TCP
/
2011/07/21
[8] M. Hashimoto, G. Hasegawa, and M. Murata, “Modeling and analysis of power consumption in TCP
data transmission over a wireless LAN environment,” in Proceedings of GreenComm 2011, June 2011.
NS
LAN
TCP
TCP ACK
/
802.11
WLAN
(STA)
TCP Delayed ACK
LAN
(AP)
TCP
(STA)
TCP Delayed ACK
• 
• 
•  STA
• 
• 
•  [8]
• 
RTS/CTS
TCP
AP
RTS/CTS
ACK
[8] M. Hashimoto, G. Hasegawa, and M. Murata, “Modeling and analysis of power consumption in TCP data
transmission over a wireless LAN environment,” in Proceedings of GreenComm 2011, June 2011
2011/07/21
NS
2011/07/21
NS
TCP
MAC
TCP
TCP
TCP-DATA
TCP-ACK
MAC
FS
off
DI
ck
FS
SI
Ba
RTS
ACK
FS
SI
FS
SI
CTS
t
TCP
1 RTT
1 RTT
RTT
1 RTT
W
DATA
CSMA/CA
TCP-DATA
E[α]
E[β]
TCP
CSMA/CA
1 RTT
TCP-ACK
=
E[W]
E[W]/2
/
E[X]
RTT
1 RTT
E[A]
TCP
TCP Delayed ACK
TCP
•  TCP
ACK
1
Delayed ACK
•  TCP
ACK
ACK
TCP
1 RTT
1 RTT
1 RTT
/
/
2011/07/21
NS
NS
2011/07/21
TCP delayed ACK
1 RTT
802.11
WLAN
Delayed ACK
Delayed ACK
RT T
TCP
ACK
J
TD
(m)
s
=E[Y ]J +(E[Ntd
] E[W ]/2)J r
s
s
+ P s E[Ttd
] + E[Ntd
](P as T as +
s
+ P l E[A] E[Y ]T t (E[Ntd
]
RTT
t
Delayed ACK
P sa T sa )
s
s
E[W ]/2)T r E[Ttd
] E[Ntd
](T as +T sa )
(
)
RTT
RTˆ T (m) = RT T + (m
1
2011/07/21
NS
1)
RT T
E[W ]
RT T
ACK
-
=
1 MB
m:
(m=5)
200
200
1.2
150
RTT [ms]
2ms – 200ms
1.4
1.4
1
0.8
100
0.6
0.4
50
1.2
150
RTT [ms]
802.11
WLAN
1
0.8
100
0.6
0.4
50
0.2
0.2
• 
1 MB
•  IEEE 802.11a
• 
: 54 Mbps
• 
: 1500
•  ACK
4
NIC
1.4 W
0
0.0001
[13]
0.9 W
0.8 W
0
0.0001
0
0.001
0.01
0.1
0
0.001
0.01
0.16 W
1 ms
• 
• 
RTT
[13] Wistron NeWeb Corp., “CM9: WLAN 802.11 a/b/g mini-PCI Module.” available at http://site.microcom.us/CM9.pdf.
p:
12
• 
p=0.01, RTT=100ms
p=0.01, RTT=100ms
1.5
8
TCP
1
0.5
2
4
6
p=0.005, RTT=100ms
4
p=0.005, RTT=50ms
2
8
10
12
14
16
18
20
0
• 
• 
p=0.005, RTT=100ms
6
0
LAN
10
2
[ ]
[J]
2.5
TCP delayed ACK
• 
• 
p=0.005, RTT=50ms
2
4
6
8
10
12
14
16
18
RTT
• 
1
20
m
m
5
m
m
• 
m
2011/07/21
1
5
LAN
• 
NS
TCP
TCP
p:
m:
(p=0.01, RTT=100ms)
2
m
1.5
RTT
(p=0.005, RTT=100ms)
(p=0.005, RTT=50ms)
(p=0.005, RTT=50ms)
(p=0.005, RTT=100ms)
1
m
0.5
TCP
• 
• 
• 
0
TCP
(p=0.01, RTT=100ms)
2
4
6
8
10
12
14
16
m
m
2011/07/21
NS
18
20
1
5
0.1
TCP
E[T ](m) =
[12]
RTˆ T (m)
1 p
p
+
E[W ]
2
E[W ]
2
+1 +
Q(E[W ])G(p)T0
1 p
+ Q(E[W ]) / (Sd /Sp
Sdss )
RTT
RTˆ T (m) = RT T + (m
1)
RT T
E[W ]
[12] N. Cardwell, S. Savage, and T. Anderson, “Modeling TCP latency,” in Proceedings of
INFOCOM 2000, vol. 3, pp. 1742–1751, Mar. 2000
2011/07/21
NS