Using 802.11 in an FTTP Application
FTTP Application
Video Network
PSTN
Internet
Optical Line Terminal(OLT)
Telephone
Computer
Optical Network Terminal(ONT)
Television
Set Top Box
Residential Gateway
Twisted Pair
Cat5 Wiring
Coax
Feeder Fiber
Optical Splitter
ResidenceCentral Office Outside Plant
FTTP with 802.11
Video Network
PSTN
Internet
Optical Line Terminal(OLT)
Telephone
Computer
Optical Network Terminal(ONT)
Television
Set Top Box
Feeder Fiber
Optical Splitter
ResidenceCentral Office Outside Plant
802.11Network
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 RatesData 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 FunctionPIFS
Listen before talk
BeaconSIFS
Data+CF+poll
SIFS
Data+ CF+ ACK
SIFS
CF+poll
SIFS
CF +ACK
CF-END
• 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
Distributed Coordinaton Function (DCF)
PointCoordination
Function(PCF)
HCFContention
Access(EDCA)
HCFControlled
Access(HCCA)
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