Transcript Graham Higgins

Using 802.11 in an FTTP
Application
FTTP Application
Central Office
Residence
Outside Plant
Feeder Fiber
Internet
Twisted Pair
Telephone
Cat5 Wiring
PSTN
Optical Network Terminal
(ONT)
Optical Line Terminal
(OLT)
Optical Splitter
Residential Gateway
Computer
Video Network
Coax
Set Top Box
Television
FTTP with 802.11
Central Office
Residence
Outside Plant
Feeder Fiber
Internet
Telephone
PSTN
Optical Line Terminal
(OLT)
Optical Network Terminal
(ONT)
802.11
Network
Optical Splitter
Computer
Video Network
Set Top Box
Television
Issues to Consider
•
•
•
•
•
Equipment Availability
Security
Bandwidth
Propagation distances
Quality of Service
Service Offerings
• Data Services
– 5Mbps downstream / 2Mbps upstream
– 15Mbps downstream / 2 Mbps upstream
– 30 Mbps downstream / 5 Mbps upstream
• Video Services
– Today optical wavelength overlay
– Future – IP TV
• 3-4 Mbps per channel
• 19 Mbps per channel (high definition)
• Telephony Service
– 4 voice channels (analog today)
– VOIP – 100Kbps per voice channel
802.11 Data Rates
Data Rate (Mbps)
802.11b
802.11a
802.11g
1
90+
-
90+
2
75
-
75
5.5(b)/6(a/g)
60
60+
65
9
-
50
55
11(b)/12(a/g)
50
45
50
18
-
40
50
24
-
30
45
36
-
25
35
48
-
15
25
54
-
10
20
Quality Of Service
• Voice and video data have QOS
requirements
• Data services can be supported using
DCF
• Consider using PCF
• Enhanced QOS mechanisms are specified
in 802.11e
Point Coordination Function
P
I
F
S
Beacon
S
I
F
S
Data+CF+
poll
S
I
F
S
CF+
poll
Listen before talk
Data+ CF
+ ACK
•
•
•
•
•
•
S
I
F
S
S
I
F
S
CFEND
CF +
ACK
ONT could be used as Point Coordinator
ONT polls phones for voice traffic
ONT can “pace” the downstream video traffic
No control over upstream data packet size
If VOIP packet size could be set, then PCF may achieve QOS
Better alternatives available from 802.11e
802.11e QOS Methods
Point
Coordination
Function
(PCF)
HCF
Contention
Access
(EDCA)
HCF
Controlled
Access
(HCCA)
Distributed Coordinaton Function (DCF)
802.11e Traffic Priorities
•
8 traffic priorities are used from 802.1d
–
–
–
–
–
–
–
–
•
Background (1)
Background (2)
Best Effort (0)
Best Effort (3)
Video (4)
Video (5)
Voice (6)
Voice (7)
These are mapped to 4 Access Categories
–
–
–
–
Voice
Video
Best Effort
Background
Arbitration Inter Frame Space
HCCA
• QOS equivalent to PCF
• Allows for contention period and
contention free period
• Polling in contention free period include
QOS details
• Allows HC to fairly allocate medium
considering QOS
• Contention period uses EDCA
Results from Simulation DCF vs
EDCA
Conclusions
• 802.11 could be used to deliver current FTTP
services
• 802.11e can provide QOS
• No growth path for HD TV
• Not useful for MDU application
• IP phones currently too expensive
• Security can be managed with pre-shared keys
• Unlikely to become a common ONT interface