Passive Optical Broadband Communications in Local Access Network

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					  Passive Optical Broadband
Communications in Local Access
           Network
           Kae-hsiang Kwong
            21 January 2004
       kkhsiang@eee.strath.ac.uk
     What is an Access Network?
Access Networks provide necessary interfaces
to end-users accessing telecommunication
services.
                                   Backbone
                 Access Network   Network

        Access                        Internet
                    Feeder
         unit                          PSTN
                         +
                   Distribution        CATV
  Evolution of Access Networks
Telephony         Cable TV           Internet



     Telephony                Cable TV
          +                        +
      Internet                 Internet



       Telephony + Cable TV + Internet
       Passive Optical Access Networks
  PON: network architecture constructed solely
  using passive optical devices; no signal
  regeneration in the transmission path.

                 ONU    Combiner                       Backbone
                                               OLT      network
                 ONU                                     PSTN
   users                                                 CATV
                                                        Internet
                 ONU
Copper network         Optical fibre network         Backbone network
            Medium Access Control
Interleaved Polling with Adaptive Cycle Time (IPACT)
• Provides Dynamic bandwidth allocation.
• OLT assigns each ONU for transmission based on the
information exchanged between OLT and ONUs.
• Buffer status and traffic load of ONU sent to OLT.
• OLT utilises incoming information to schedule ONU
transmissions.
• OLT issues Grants to inform individual ONUs start time and
duration of transmission.
              Medium Access Control
             ONU 1          Combiner                                   OLT
             ONU 2                   ONU 3   ONU 2       ONU 1
                                       G      G           G
 users

             ONU x

• Grant is broadcast to every ONU.

• Information is carried to OLT at the end of each ONU transmission.
                                                          IPACT Results
                    0.001

                                             16 ONUs IPACT
                                             24 ONUs IPACT
Delay (seconds)




                                             32 ONUs IPACT
                                             16 ONUs TDMA

                   0.0001




                  0.00001
                            0.1   0.15 0.2   0.25   0.3   0.35 0.4   0.45   0.5   0.55   0.6 0.65   0.7   0.75   0.8 0.85   0.9
                                                                     Traffic load
                   WDM IPACT + DiffServ
Packets
 from                     Class 1
 users                                                                           DS Network
          Classifier      Class 2        scheduler

            ONU           Class 3
                                                                    OLT
    ONU:
    • Incoming packets are classified and marked.
    • Traffic flows are grouped into traffic classes according to the similarity of QoS
    requirements.
    • Different level of reservation treatments applied to each traffic class.
    OLT:
    • Bandwidth are allocated to ONUs according to the buffer status and traffic load.
    • Associates traffic classes to bandwidth allocation schemes.
                     Conclusion
• WDM PON systems

      1. WDM-IPACT with fixed transceivers.
      2. WDM-IPACT with tuneable transmitters, fixed
      receivers.
• Highly cost efficient solution in upgrading access network.
• Single network architecture, supporting Telephony, CATV
broadcast, Internet, etc.
• DS domain extended to local access networks.
• Achieves end-to-end QoS provisioning.
• Eliminates the need for per-flow resource reservation.

				
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