Resource Allocation in TDM-WDM PON under Multicast Video Delivery

1. Resource Allocation in TDM-WDM PONunder Multicast Video Delivery Jorge M. Finochietto, Fabio Neri Politecnico di Torino, Italy VDA Meeting - February 26th 2007, Barcelona

2. VDA Activities at PoliTo • Tutorial about PON • Resource Allocation in TDM-WDM PON • Unicast Traffic (Data) • Multicast Traffic (Video) VDA Meeting - February 26th, 2007, Barcelona

3. Tutorial about PON • Contents • Physical layer • Power budget issues • Downstream/Upstream scheduling • Current standards for PONs (TDM) • APON/BPON, EPON & GPON • Proposals for WDM PONs • Set of 150 powerpoint slides VDA Meeting - February 26th, 2007, Barcelona

4. Resource Allocation in TDM-WDM PON • Long-term goal • TDM-WDM PON architectures vs. Resource utilization • Short-term goal • Assess benefits of introducing (slow) tunability at ONUs • Keep PON’s complexity/cost low • ONU’s  one TX and one RX • OLT + wavelengths + splitters  shared by all ONU’s • Provide algorithms to (dynamically) assign ONU’s transceivers (resources) to efficiently match traffic conditions VDA Meeting - February 26th, 2007, Barcelona

5. TDM-WDM PON Architecture ONUs RX OLT TXs RX RX ONUs TX OLT RXs TX TX • Given • N nodes (ONUs) • W wavelengths • Assume that • N > W • OLT capacity = W • ONU capacity = 1 • Tunability at ONUs Downstream Architecture Upstream Architecture VDA Meeting - February 26th, 2007, Barcelona

6. Problem Formulation GIVEN THAT: • ONUs have ingress/egress bandwidth demands • Typically, lower than wavelength bandwidth • Dedicated bandwidth, bidirectional (unicast traffic)  data traffic • Shared bandwidth, unidirectional (multicast traffic)  video traffic • Nodes can transmit/receive to/from only one wavelength. THEN: • How many ONUs (N) can share W wavelengths... • IF tunability is available at ONUs? • IF NOT? • How ONU’s transceivers must be tuned to wavelengths? VDA Meeting - February 26th, 2007, Barcelona

7. Overlay vs. Integrated Models • Overlay Model • Unicast and multicast traffic use separated wavelengths •  Requires separate transceivers for unicast and multicast traffic •  The problem can be divided in two independent sub-problems • Resource allocation under unicast traffic • Resource allocation under multicast traffic • Integrated Model • Unicast and multicast traffic share all available wavelengths •  Requires shared transceivers for unicast and multicast traffic •  The problem must be solved considering all constraints VDA Meeting - February 26th, 2007, Barcelona

8. N nodes  i M groups  j W wavelengths  k ui : unicast traffic mj : multicast traffic Lmax : maximum allocated bandwidth on a wavelength xik : 1, iff node I assigned to wavelength k 0, otherwise yjk : 1, iff at least one member of group j is assigned to wavelength k 0, otherwise Problem Formalization: ILP Model VDA Meeting - February 26th, 2007, Barcelona

9. Overlay Model: Unicast Traffic • Since traffic is bidirectional, resource allocation considers: • Upstream unicast traffic  assigns ONU’s TX to wavelengths • Downstream unicast traffic  assigns ONU’s RX to wavelengths • Resource allocation can be constrained by ONU’s node architecture • 1) TX and RX wavelengths can be different • Independent transceivers at ONUs • Implies solving 2 independent (and analogue) problems • 2) TX and RX wavelengths must be the same • “Colourless ONUs” • More difficult problem (not considered) VDA Meeting - February 26th, 2007, Barcelona

10. Example: Receiver Allocation k k j j m m l l i i • Independent transceivers • Given ONU’s ingress bandwidth requirements • ONU’s RX must be tuned to only one wavelength • Allocation must balance traffic among wavelengths • Well-known problem, scheduling of parallel machines • Simple and fast heuristic exists (Longest Processing Time, LPT) Node receivers load wavelengths VDA Meeting - February 26th, 2007, Barcelona

11. Overlay Model: Multicast Traffic ONU RX • Multicast Traffic model • Assumes TV channels (multicast groups) distribution • Users select a TV channel with a given probability • Many users (U1) may be connected to a single ONU • Thus, an ONU may belong to more than one multicast group VDA Meeting - February 26th, 2007, Barcelona

12. User Preference Model • User probability of belonging to a multicast group • Zipf’s Discrete Distribution (E parameter) • Uniform • Power Law VDA Meeting - February 26th, 2007, Barcelona

13. Efficient Allocation Under Multicast • The solution of the ILP model gives us the optimal resource allocation • NP-hard problem, difficult and time consuming • Proposal of efficient allocation algorithm • Distribute groups uniformly among wavelengths • Assign each ONU to the wavelength where more subscriptions are present VDA Meeting - February 26th, 2007, Barcelona

14. Scenario N=128 U=2 M=50 E=0 Some Results No RX tunability available RX Tunability available VDA Meeting - February 26th, 2007, Barcelona

15. Future Work • Improve current algorithm performance • Add some complexity, use clustering techniques • Propose algorithms for the unicast traffic problem (overlay model) with “colourless” ONUs • Propose algorithms for the integrated model VDA Meeting - February 26th, 2007, Barcelona