Time Sync Lee 01 0509
Time Sync Lee 01 0509
Time Sync Lee 01 0509
IEEE 802.3 TS Interim, May. 2009 J. Kevin Rhee1, Kyusang Lee2, and Seung-Hwan Kim3
Acknowledgment
ChanKyun Lee, KAIST SeongJin Lim, KAIST
AAA Authentication, Authorization and Accounting ACR Access Control Router AR Access Router BR Broader Router GSN GPRS Support Node HA Home Agent IMS IP Multimedia Sub-system PSDN Packet Data Serving Node RAS Radio Access Station AAA
PSN
BR
Internet
Home NodeB Gateway
GSN/PSDN
Femtocell
CN
Femto ACR ACR
3G RAN NodeB/BTS RNC/BSC
RAS
RAS
3G MS
Femtocell WiMAX
CDMA EV-DO
Wireless backhaul
Wireless backhaul network connects wireless base stations to the corresponding BSC It delivers the expected bandwidth requirements of new technologies such as WiMAX, 3G, and 4G. PSN and TDM can be used for wireless backhaul network
Cell Site
TDM TDM ATM Ethernet FR/HDLC CSAG Ethernet Ethernet/DSL/PON Multiservice Edge Router
Backhaul Medium
TDM/SONET/SDH
BS
Radio Interface Bearer Technology Backhaul Medium
SGSN
Wireless Backhaul Network BSC: Base Station Controller PSN: Packet Switched Network
Ethernet should support the aforementioned functions and meet time/sync requirements!!
Synchronization in Backhaul
Why Synchronization?
BTS/NodeB are synchronized to BSC, RNC, MSC, and MGW for end-to-end sync For Radio Framing Accuracy and Hand-over, 0.05ppm sync at BTS/NodeB is needed Significant to interference control on cell boundaries
Radio Framing Accuracy
POP HUB
BSC
SDH
HLR
MSC
2G BTS
TDM
Hand-over BSC
TDM
SGSN
2G BTS
Cellular Network
MS
BTS
Circuit Emulation E1 E1
(Packet Switched Network)
BSC
Ref. Clock
GE IP BSC
2G/GSM Networks
GE PSN RNC
3G/TD-CDMA Networks
Synchronization of Femtocell
Related handover and interference. Time sync accuracy (Timing difference bet. Macro BS and the Femto BS) 0.2 us (The distance bet. Femto BSs = 30m)
WiMAX
Freq. and phase accuracy by WiMAX Forum: 2ppm, 1us (for TDD) IEEE 1588 over IP/Ethernet backhaul Low-cost-standalone solution Provides sub microsecond accuracy IEEE 1588 to WiMAX/Femtocell is under study at IEEE 802.16m.
Source: WiMAX Forum Tech. WG,WiMAX Forum Mobile System Profile Specification: Release 1.5 Common Part, rev. 0.2.1, Feb 2009. Source: Guang Han, et al., Time synchronization for Femtocells, IEEE 802.16m, Oct2008
0.05 ppm
Source: Patrick Diamond, Packet Synchronization in Cellular Backhaul Networks, Semtech White Paper Oct. 2008) Source: S.-P. Yeh, et al, WiMAX Femtocells: A Perspective on Network Architecture, Capacity, and Coverage, IEEE Comm. Mag., Vol. 46, Issue 10, Oct. 2008 Source: V. Chandrasekhar, et al., Femtocell Networks: A Survey, IEEE Comm. Mag., Vol. 46, Issue 9, SEP. 2008
Options
Use of very accurate clock Timestamp in physical Layer
Conclusions
Time synchronization in fast growing mobile backhaul market
Time sync application in the backhaul market is anticipated to be even larger than AV applications in the near future.
Current timestamp at MAC or client layer may not be qualified for ppb level synchronization accuracy requirements. IEEE 802.3 needs to provide more accurate timestamp information.
IEEE 802.3 may require a timestamp function in the PCS, PMA, or PMD sublayer.