UMTSguy
join:2007-01-27
Tuckahoe, NY
| reply to alchav
Re: useless...
ODNs are shared -- a BPON distribution hub (in the metal box at the end of your street) splits 622/155 Mbps among 32 users. In other words, if all 32 Fios users on a hub took 20/20 service and maxed out the upstream they would only be able to get 4.84 Mbps each. |
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Heyya
@verizon.net | Thats incorrect. Fios uses two data lightwaves upstream and downstream and both are up to 622mbps on BPON. Plus its using TDM so its not actually shared like cable. |
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espaeth
Digital Plumber
Premium,MVM
join:2001-04-21
Minneapolis, MN
 ·voip.ms
·Vitelity VOIP
·Callcentric
·VoiceStick
·ViaTalk
 ·Comcast
 ·Embarq
| said by Heyya :
Thats incorrect. Fios uses two data lightwaves upstream and downstream and both are up to 622mbps on BPON. Plus its using TDM so its not actually shared like cable. FiOS uses TDMA on the upstream as well to solve the "multiple speaker" problem in the same way as cable. Based on my understanding of FiOS, each neighborhood distribution would share 1 port on the head-end. The downstream light path is split to 32 homes with the head-end being the only speaker so there's no chance of transmit collision. Each of the 32 homes off the distribution node sees the same downstream data feed just like cable. On the upstream each home is fed into an optical combiner to go back to a common upstream node port. The reason you are limited to 155mbps upstream is because of the TDMA timing overhead to ensure that upstream data transmissions are handled in a controlled fashion and 2 ONTs don't transmit at the same time.
The biggest difference is network scaling; Verizon needs one head-end port per 32 homes, whereas Comcast can go as wide as 1 head-end port per 1000 homes in some cases. |
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BosstonesOwn
join:2002-12-15
Everett, MA
clubs:
·Comcast
| said by espaeth  :said by Heyya :
Thats incorrect. Fios uses two data lightwaves upstream and downstream and both are up to 622mbps on BPON. Plus its using TDM so its not actually shared like cable. FiOS uses TDMA on the upstream as well to solve the "multiple speaker" problem in the same way as cable. Based on my understanding of FiOS, each neighborhood distribution would share 1 port on the head-end. The downstream light path is split to 32 homes with the head-end being the only speaker so there's no chance of transmit collision. Each of the 32 homes off the distribution node sees the same downstream data feed just like cable. On the upstream each home is fed into an optical combiner to go back to a common upstream node port. The reason you are limited to 155mbps upstream is because of the TDMA timing overhead to ensure that upstream data transmissions are handled in a controlled fashion and 2 ONTs don't transmit at the same time. The biggest difference is network scaling; Verizon needs one head-end port per 32 homes, whereas Comcast can go as wide as 1 head-end port per 1000 homes in some cases. But did you know that Verizon can also add amplitude modulation on top of the time division ?just by updating the "headend" what it does is functionally make up to 4 muxes able to send on the same light wave at different timing intervals after a handshake , pretty neat stuff I say.
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"It's always funny until someone gets hurt......and then it's absolutely friggin' hysterical!" |
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