To
introduce determinism in the frame delivery, different noncontention schemes based
on request/grant mechanisms have been proposed [10-13].
Figure 7.5 Upstream channel transmission in an EPON (M2P operation)??”standard TDM-based channel
sharing with ONU3 transmitting out of assigned timeslot
PSC
Random patterns (cross-talk)
Timeslot
1 1
3
2
1 1
Residential
subscriber
MDU
subscribers
LAN/PAN
2
3
1 1 2
3
OLT
ONU1
ONU2
ONU3
Collision pattern
Out of band transmission
Figure 7.4 Upstream channel transmission in an EPON (MP2P operation)??”standard TDM-based
channel sharing
PSC
Header
Ethernet 802.3 frame Guard-band
Timeslot
Payload FCS
1 1
3
2
1 1
Residential
subscriber
MDU
subscribers
LAN/PAN
2
3
1 1 2 3
OLT
ONU1
ONU2
ONU3
Passive Optical Networks (PONs) 181
Ongoing Developments
EPONs constitute a giant leap forward, when compared with DSL and cable modem
technologies. With an effective data rate of 1 Gbps (1.25 Gbps line rate due to 8B10B
encoding performed at the PHY layer) and 16+ subscribers typically served per single
EPON system, each ONU is capable of receiving between 15 and 60 Mbps of usable
bandwidth in a fully equipped EPON with all ONUs active.
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