Data Rate Adaptation. Andrea Garavaglia. Marek Hajduczenia, PhD. Qualcomm Inc. ZTE Corporation.

Transcription

1 ata Rate daptation Marek Hajduczenia, Ph ZT Corporation ndrea Garavaglia Qualcomm nc.

2 Summary ata Rate daptation (R) function decouples fixed MC/XGM rate from PHY rate at PM R has nothing to do with B, bandwidth allocation in PoC / PON, etc. There are various ways to implement R in thernet; we focus on mechanism used in 10G- PON P2MP architecture This slide deck explains the need for R, its functional operation and highlights interaction between various elements in the stack This discussion in then mapped into PoC stack and individual functional layers 2

3 The Need for R (in picture) 10G Scope of ata Rate daptation (R) MC & MC Clients XGM TON FC NTRVR MC (fixed rate, e.g., 10G) XGM (fixed rate, 10G) Top of PCS (fixed rate, 10G) ata Rate daptation process Bottom of PCS (fixed rate, e.g., 3G) T PM PM (fixed rate, e.g., 3G) PM PM (fixed rate, e.g., 3G) 3G 3

4 The Need for R (in text) MC operates at a fixed data rate (e.g., 10G). XGM operates at a fixed data rate (10G) PM operates at an effective data rate lower than MC/XGM data rate (e.g., 3G) Somewhere in PCS, data rate must be adapted between fixed MC rate (10G) and effective PM data rate (3G) daptation process may rely on removal of excess characters inserted by MC between frames (see 10G-PON example) 4

5 R in 10G-PON - background t first glance, it seems much simpler to use 10G MC rate and increase PM rate to ~11.25G to transport FC parity RS(255,223) assumed However, concerns about technical feasibility of 10G optics at ~11.25G were raised in 10G-PON TF -> the group decided NOT to use super-rate PM MC rate had to remain fixed (10G) and under-rating effective data stream was the only way available to use FC and reuse existing 10G designs ata Rate daptation mechanism was developed to address XGM signaling restrictions, avoid the use of real-time signaling and provide robust mechanism to lower effective data rate observed by MC 5

6 How R works in 10G-PON? n 10G-PON, MC rate and PM rates were fixed at 10G and G, respectively (64b/66b line encoding) To accommodate FC parity in PCS, MPMC decreases the effective data rate to ~8.7G (~12.9% FC overhead) MC inserts extra characters between frames to keep data rate constant (10G) nsertion process at TX side 10G data rate is maintained across XGM and reaches top of PCS at the TX side Within PCS, eletion process removes extra characters, leaving only PGs and characters generated by MC in absence of data Resulting ~8.7G data stream is 64b/66b encoded and then fed to FC. FC parity is then inserted, bringing data rate to G which is fed into PM / PM. 6

7 R in 10G-PON (in picture) 10G MC & MC Clients XGM TON FC SCRMBR T Picture is not up-to-scale! PM PM FC + 64b/66b FC + 64b/66b ~8.7G G 7

8 Why R is needed in PoC? There are three main reasons: MC / XGM rate remains fixed at 10G (we want to support data rates up to 10G on coax) We need to accommodate FC parity interleaved in the data stream without pushing data rate above 10G like in 10G-PON today We need to accommodate a number of possible PM data rates (either fixed or dynamic) that are lower than 10G MC rate. ffectively, in PoC data rate at PM is smaller (or much smaller) than MC / XGM rate 8

9 R in PoC (in picture) - examples 10G 10G MC & MC Clients XGM TON FC NTRVR T Picture is not up-to-scale! T Picture is not up-to-scale! PM PM FC + coding + PHY overhead ~2G ~3G ~6G ~7G 9

10 R in PoC n PoC, given the range of possible (fixed / dynamic) PM rates, R needs to: 1. ccommodate insertion of FC parity (like in 10G-PON); 2. ccommodate for any PM overhead (CP, etc.) and PM de-rating (PM does not operate at full 10G due to limited availability of spectrum); 3. ccommodate T switching (note: we do not focus on T switching in these slides) The second and third bullets above are new functions for R, not seen in 10G-PON Bullet 3) would be addressed by the T sub-taskforce Next slides outline R in PoC and list challenge items ssume R eff is the effective data rate at PHY (actual data), R FC is the FC overhead due to insertion of parity R MC and R XGM are both set to 10G and referred to as R MX 10

11 ownstream in CT (TX side) nsertion eletion TX Side CT coax nsertion process Packets are properly inserted (by the Multipoint Transmission Control) and filled with s by the MC layer. MPMC keeps data rate at R eff. n this way, a fixed rate of 10G is guaranteed by MC for the XGM interface (R MX ). xtra s inserted by MC create space for FC parity bits and all PHY overhead in the data stream eletion process xtra s are then removed by the eletion process inside the PCS (upper PHY stack) to match with PM rate and include FC parity bits. t the output of eletion process, data rate is equal to R eff. 11

12 ownstream in CNU (RX side) eletion process xtra s are then removed above XGM interface and complete thernet frames are then passed to MC Clients. ata rate above MC is equal to R eff. nsertion process: FC encoded packets arrive at PCS at the PM rate and are fed into the FC decoder. fter removal of FC parity, data rate becomes R eff. Gaps between frames are filled with s to achieve data rate of R MX and match XGM data rate. CNU eletion nsertion RX Side coax 12

13 Upstream direction n the upstream direction CNU transmits and behaves like CT in downstream, adding only the burst mode transmission capabilities CT receives and behaves like CNU in downstream direction, adding only the burst mode reception capability Conclusion: the same functionalities illustrated on three previous slides is also applicable to the upstream direction. 13

14 Conclusion and Recommendation n this presentation ata Rate daptation (R) function and the need for it in PoC are illustrated R in 10G-PON is needed to account for FC parity and it is based on insertion/deletion across XGM interface PoC and 10G-PON share the FC-parity-related need for R. However, PoC will also need to use R to adapt between R MX and R eff (PM de-rating) and account for T switching (not covered in the slides) PoC R can be based on the same principles and on the same mechanisms used in 10G-PON R is applicable to both S and US directions in PoC t is therefore recommended to include R function in PoC spec, reusing mechanisms defined in 10G-PON 14