Provisioning 1 Gb/s Symmetrical Services with Next-Generation Passive Optical Network Technologies Speaker ： Pu-Yu Yu Advisor ： Dr. Ho-Ting Wu​ Date: 2016/3/25

OUTLINE  INTRODUCTION  Taxonomy of Fiber Access Protocols to Provide 1 Gb/s Symmetrical Services  GPON, XG-PON, and TWDM-PON with Oversubscription  Numerical Example and Analytical Results  Economic Study for an Urban Area  Summary and Discussion 1

INTRODUCTION  At present, 1 Gb/s downstream Internet access services are offered by some service providers in the United States, Europe and Asia.(12.4, 22, and 93 million fiber subscribers)  Some factors like user experience enhancement, the increasing amount of connected devices at home, are expected to boost the demand for symmetric 1Gb/s access capacity with certain quality of service (QoS) guarantees in the near future. 2

INTRODUCTION  This article aims to compare GPON, XGPON, WDM-PON, TWDM-PON approaches concerning the provisioning of 1 Gb/s symmetrical connectivity to residential customers.  Some questions are investigated throughout this article 3

INTRODUCTION  Which kind of FTTH technology is most suitable to offer 1 Gb/s symmetrical services?  Can 1 Gb/s be guaranteed 100 percent of the time?  Which parameters must be considered in the network design?  What is the cost per user associated with each technology? 4

TDM-PON  Point-to-multipoint approach  Uses a 1:N passive splitter/combiner to divide the optical signal among all users in the downstream direction and aggregate the users’ data  OLT uses DBA algorithm to arbitrate access to the shared channel in the upstream direction, avoid collisions, assign bandwidth to the users, and provide QoS for different types of flows.  Ex: G-PON XG-PON 5

WDM-PON  The power splitter/combiner is replaced by a wavelength selective filter.  Setting up a single wavelength with symmetric bandwidth between each user and the central office. (dedicated point-to-point connection)  Advantages over TDM-PON: scalable bandwidth, Long reach (given the low insertion loss of filters, optional amplification), security 6

TWDM-PON  Was selected as the primary solution for the NG-PON stage 2.  Increases the aggregate PON rate by stacking multiple XGPONs on different pairs of wavelengths. (ONU equipped colorless transmitters)  Advantages: high fan-out, compatible with older TDM-PON versions, coexistence within the same ODN. 7

Summary of features for PON technologies 8

Taxonomy of PON fiber access protocols 9

Capacity Planning  As Fig. 1. GPON, XGPON, and TWDMPONs have a first fixed splitting stage, 1:8, and a second one, 1:N, that can be configured (N = {1, 2, 4, 8}).  This section studies how many users can coexist on the same PON branch sharing its bandwidth so that they experience 1 Gb/s symmetrical service most of the time.  Analysis is performed only for the uplink direction since it is a more limiting factor than the downlink case. 10

GPON, XG-PON, and TWDM-PON with Oversubscription  Capacity planning based on oversubscription works because only a small portion of subscribers are simultaneously active at a given random instant  Ntot = total number of users.  Nact =random active users at a given random time.  Consider that every user can be active with probability q.  Nact follows a binomial distribution. 11

 B = CUL / Nact  B = bandwidth rate for per each individual user in the PON branch.  CUL = upstream capacity.(on table)  Network operators can limit the B to the bpeak when the number of active users is small and when all users are active, it can guaranteed at least a minimum rate of (CUL)/(ntot). 12

 Oversubscription ratio o = Cul / ( ntot * bpeak)  B refer to the probability that bpeak is guaranteed to the users in the oversubscription model.  And probability that no more than Nact (max) users are simultaneously active.  B can also be thought of as the percentage of time by in which bpeak is guaranteed. 13

Numerical Example and Analytical Results  Consider a GPON (CUL(GPON) = 1.25 Gb/s) with q = 0.15 (i.e., 15 percent activity per user) and ntot = 32 users.  bpeak = 1 Gb/s when Nact(max) = 1 user  The average number of active users is: E(nact) = Ntotq = 4.8 users.  The average bandwidth is E(b) = 327 Mb/s^2 14

 Following the binomial distribution, the probability of having 1 active user or less in the PON is only 3.7 percent.  Consider that the bpeak = 1 Gb/s, B = 0.2  Then the value of Ntot can be no larger than 18 total users. (second stage must be at most 1:2)  P(nact ≤ 1) = 0.22 when nact ~ B(ntot = 18) but P(nact ≤ 1) = when nact ~ B(ntot = 19).  In this case, the average bandwidth experienced by users is now E(b) = 637 Mb/s. 15

CDF of GPON and average bandwidth for different split ratios 16

Bandwidth comparison between the four NG-PON technologies 17 PS : WDM-PON got high cost

Economic Study for an Urban Area  Including both CAPEX and OPEX  The deployment of a hypothetical green field urban scenario with 5000 users  CAPEX based on commercial prices available from selected undisclosed vendors cost of equipment,not commercially available yet (TWDM-PON) is derived from market costs of components. 18

Economic Study for an Urban Area  Major equipment costs :Central Office, OLT, ONT, Passive-Street Cabinet, Feeder and Distribution Segment, In-House Segment.  Central Office : OLT shelves, one-time software licenses, uplink transceivers(dependent on split ratio)  For TWDM-PON, the cost of the WDM mux is also included here. 19

Economic Study for an Urban Area  OLT : OLT line cards are equipped with 16 ports for GPON, 4 ports for XGPON, TWDMPON, and 1 port for WDM-PON.  ONT: The lowest cost equipped at least four Gigabit Ethernet ports toward the user. In the case of a TWDM-PON ONT, the cost is derived from market costs of components of the product.  Passive-Street Cabinet: depend on spilt ratio, generally, spilt ratio up and cost up. 20

Economic Study for an Urban Area  Feeder and Distribution Segment: the length of the feeder segment in an urban area is assumed to be 850 m, whereas the length of the distribution segment is 80 m. Cost of digging and preparing the trench for an urban area has been assumed USD 120/m  In-House Segment: The cost of the optical distribution frame (ODF), patch cable, and fiber access terminal in the basement. 21

Details of TCO for FTTH options for providing 1 Gb/s symmetrical 22

Summary and Discussion  This article has compared four different flavors of fiber access protocols capable of offering 1 Gb/s symmetrical services for residential users.  The results show that GPON 1:8 and 1:16, XGPON 1:8 and 1:16, TWDM-PON, and WDMPON are good candidates to enable 1 Gb/s symmetrical services for residential users in terms of both cost and performance for next-generation optical access. 23

Summary and Discussion  However, as the user activity pattern increases, both GPON and XGPON will become insufficient. Only TWDM-PON and WDM-PON can guarantee 1 Gb/s at high levels of user activity  Other services than residential (business services and wireless backhaul), which require higher bandwidth, lower latency and physical separation of traffic (for security purposes) than residential scenarios, may require WDMPON.  In light of this, WDM-PONs with bandwidth provisioning beyond 1 Gb/s have been proposed, some supporting up to 10 Gb/s. 24

References  Author :Rafael Sanchez, Jose Alberto Hernandez, Julio Montalvo Garcia, and David Larrabeiti, IEEE Communications Magazine,P72 – P77, February