One document matched: draft-zhou-tictoc-ran-sync-req-02.txt
Differences from draft-zhou-tictoc-ran-sync-req-01.txt
TICTOC Linlang Zhou
Internet Draft China Mobile
Intended status: Informational July 8, 2009
Expires: January 8, 2010
RAN Synchronization Requirements
draft-zhou-tictoc-ran-sync-req-02.txt
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on January 8, 2010.
Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Zhou Expires January 8, 2010 [Page 1]
Internet-Draft RAN Synchronization Requirements July 2009
Abstract
This Internet draft describes RAN synchronization requirements,
mainly about synchronization description and requirements, also
includes some applications and problem description.
Table of Contents
1. Introduction......................................... 2
2. Applications Description............................... 2
2.1. Time requirements by Service Applications............. 2
2.2. Frequency requirement by Service Applications ......... 3
3. Synchronization Description and Requirements.............. 3
3.1. Network Synchronization ........................... 4
3.1.1. Synchronization Description.................... 4
3.1.2. Minimum Requirements.......................... 4
3.2. Node Synchronization.............................. 4
3.2.1. Synchronization Description.................... 4
3.2.2. Minimum Requirements.......................... 5
4. Security Considerations................................ 5
5. IANA Considerations................................... 5
6. References.......................................... 6
6.1. Normative References.............................. 6
Author's Addresses...................................... 6
1. Introduction
RAN has its own synchronization requirements whatever its backhaul is
based on IP/MPLS packet switched networks or TDM/ATM links.
Besides radio interface synchronization for the NodeB, both Iub and
Iu have the same synchronization requirements when is based on packet
network. In this RAN synchronization requirements we give some
applications description about UTRAN synchronization. Also we list
synchronization scenarios in UTRAN and give the detail requirements.
2. Applications Description
2.1. Time requirements by Service Applications
There are many applications in telecommunications that need to know
the time with great precision. RAN system has to provide precise time
synchronization, for there would be some services which require great
precision such as position services, streaming services, etc. In TDD
mode of 2G/3G systems, in radio interface time synchronization is
also needed for smooth handover.
Zhou Expires January 8, 2010 [Page 2]
Internet-Draft RAN Synchronization Requirements July 2009
2.2. Frequency requirement by Service Applications
Cellular base stations require highly accurate frequency
synchronization as reference from which they derive transmission
frequencies and operational timing however their transport is over
E1/T1 or PSN, such as Ethernet IP and MPLS. The radio frequencies
should be accurate. To use radio spectrum efficiently transmission
frequencies which are allocated to a given base station and its
neighbors had better not interfere with each other. There is an
additional requirement derived from the need for smooth handover when
a mobile station crosses from one cell to another.
3. Synchronization Description and Requirements
As to RAN synchronization issues, we may say it include "Network
synchronization" "Node Synchronization" "Transport Channel
synchronization" "Radio Interface synchronization" "Time Alignment
Handling" "Uplink synchronization"[1]. Actually when we mention these
six "Synchronization", we mean different synchronization mechanisms
in RAN system, and not mean synchronization requirements. AS to RAN
synchronization requirements, it can be simpler. We could conclude
into only two kinds of synchronization requirements: network
synchronization and node synchronization.
|-------|
|Vocoder|
|-------| ---
| |
|TIME ALIGNMENT |
|-------| |
| | |
| RNC | |
|-------| | ---
| | NNETOWRK |
| | SYNC |
|-------| |-------| | NODE
| Node | | Node | | SYNC
| B | | B | | |
|-------| |-------| | |
| | | |
+-------+ --- ---
| |
| UE |
|-------|
Figure 1 RAN SYNC REQUIREMENTS
Zhou Expires January 8, 2010 [Page 3]
Internet-Draft RAN Synchronization Requirements July 2009
3.1. Network Synchronization
3.1.1. Synchronization Description
Network synchronization relates to the distribution of
synchronization references to the RAN Nodes and the stability of the
clocks in the RAN. This distribution of synchronization references
includes the distribution in Iu interface, Iub interface and radio
interface. To fulfill the distribution of an accurate frequency
reference to the network elements in the UTRAN, network has to
provide a synchronization reference with enough frequency accuracy.
RNC should be able to pick-up synchronization information from Iu
interface. Synchronization of Iub interface is provided from RNC. The
clock to be implemented in UTRAN Nodes shall be chosen with
characteristics that depend on the adopted L1 or L2 medium. For
example in order to support STM-N interfaces at the RNC, the ITU-T
Recommendation G.813 (see reference) may be sufficient. But we still
have some common requirement for RNC.
3.1.2. Minimum Requirements
The reference frequency accuracy of RNC shall be better than or equal
to 4.6ppm.When outside reference clock is invalid, system clock of
RNC should be able to change into Holdover mode. Output of system
clock should be able to hold original phase and accuracy of 4.6ppm.
As to Iub and Iu interfaces, different kinds of links and interfaces
have different synchronization requirement. For E1 interfaces
frequency accuracy should be better than or equal to 50ppm(see
reference to ITU-T G.703). For STM-N interfaces frequency accuracy
should be better than or equal to 4.6ppm see (reference to ITU-T
G.813). For packet switched network frequency accuracy requirement
level is not so strict.
The frequency accuracy of base stations shall be better than or equal
to 0.05ppm on the radio interface whatever based TDD mode or FDD mode.
3.2. Node Synchronization
3.2.1. Synchronization Description
Node Synchronization relates to the estimation and compensation of
timing difference among RAN nodes. Node synchronization includes two
types: "RNC-NodeB" and "Inter NodeB" Node Synchronization.
Zhou Expires January 8, 2010 [Page 4]
Internet-Draft RAN Synchronization Requirements July 2009
"RNC-NodeB" Node Synchronization allows getting knowledge of the
timing differences between RNC and its NodeBs. When there is some
position service, "RNC-NodeB" Node Synchronization would be important.
"Inter NodeB" Node Synchronization aims to achieve a common timing
reference among NodeB's. The achievement of a common timing reference
among NodeB's may be used in TDD to support Cell synchronization in
order to minimize cross-interference.
3.2.2. Minimum Requirements
As to "RNC-NodeB" Node Synchronization, timing accuracy requirement
level in packet switched network is not so strict. For example, as to
Ethernet, accuracy better than 1ms may be sufficient. If position
service is provided, the requirements of "RNC-NodeB" synchronization
are to be discussed.
"Inter NodeB" Node Synchronization in TDD should be better than or
equal to 3us(3GPP TS 25.123). Base station synchronization accuracy
is defined as the maximum deviation in frame start times between any
pair of base stations on the same frequency that have overlapping
coverage areas.
If "Inter NodeB" Node Synchronization pick-up radio timing reference
from external clock reference, such as GPS, then the timing accuracy
requirement between NodeB and reference clock should be better than
or equal to 1.5us.
If "Inter NodeB" Node Synchronization pick-up radio timing reference
from Iu interface, then the timing accuracy requirement between NodeB
and reference RNC should be better than or equal to 1.5us.
4. Security Considerations
Time and frequency services are critical in RAN. Hence time and
frequency transfer services MUST be protected from being compromised.
The most significant threat is a false time or frequency server being
accepted instead of a true one, thus enabling a hacker to bring down
critical services. Protection mechanisms must be deployed and these
mechanisms should not degrade the quality of synchronization.
5. IANA Considerations
No IANA actions are required as a result of the publication of this
document.
Zhou Expires January 8, 2010 [Page 5]
Internet-Draft RAN Synchronization Requirements July 2009
6. References
6.1. Normative References
[1] "Synchronization in UTRAN Stage 2(Release7)", 3GPP TR 25.402
V7.3.0, June 2007.
[2] S.Bryant, Y(J).Stein, "TICTOC Problem Statement", January 19,
2007, <draft-bryant-tictoc-probstat-00>
Author's Addresses
LinLang Zhou
China Mobile
53A, Xibianmennei Ave.
Xuanwu District
Beijing China
Email: zhoulinlang@chinamobile.com
Zhou Expires January 8, 2010 [Page 6]
| PAFTECH AB 2003-2026 | 2026-04-24 02:47:28 |