120810621 microwave clock transmission solutions

HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

Huawei Confidential

Security Level:

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2013/1/17

Transmission Network Marketing Support

Department

Microwave Clock

Transmission

Solutions

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

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Document Description

Document

Name Microwave Clock Transmission Solutions

Objective Intended for the field product managers to learn and make clock transmission solutions,

and to communicate with customers.

Intended

Audience Sales personnel and marketing personnel

Content This document describes the meaning and principle of microwave clock synchronization,

clock transmission capability, and common clock synchronization solutions.

Usage Guide

Version Information

Version Date Prepared by Approved by Issued by

V1.00 June 2010 Huang Zengsong, Zong

Yong Wang Xiaozhong

Transmission

Network Marketing

Support Department

V1.10 Nov 2010 Huang Zengsong Wang Xiaozhong

Transmission

Network Marketing

Support Department


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Version Date Modification Prepared by Approved by Issued by

V1.2 Jun 2011 Modify the roadmap

of 1588V2 Huabinshan Zhou xiao

Transmission

Network

Marketing

Support

Department


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Contents

3 Microwave Clock Transmission Solutions

1 Why Is the Clock Synchronization Necessary

2 Microwave Clock Transmission Modes

4 FAQ


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Concepts of Clock Synchronization

What is a clock?

A clock is a device that generates time signals.

Clock signals involve the reference

specifications such as frequency, period, jitter,

and wander.

What is synchronization?

Synchronization refers to that two signals

appear or disappear in the same state at the

same moment.

Clock synchronization refers to that all the

devices on the network operate at the same rate.


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Modes of Clock Synchronization

Frequency synchronization

The signals remain a relative relationship in

frequency and phase.

The corresponding valid instances appear at the

same average rate.

As shown in Figure 1, clock B is six hours later than

clock A.

Clock synchronization generally refers to frequency

synchronization.

Time synchronization

The signals remain a consistent relationship in

frequency and phase.

The phase of a clock is expressed in value, that is,

moment.

As shown in Figure 2, clock B and clock A remain

the same in time at any moment.

Frequency synchronization

Clock A

Clock B

Clock A

Clock B

Figure 1

Figure 2

Time synchronization


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What Are the Impacts When the Clocks Are

not Synchronized?

Data:

Characters in fax application are missed.

The Internet is offline frequently.

Mosaic images occur in the video services

Voice application:

Calling fails

conversation is not consecutive, and even crosstalk occurs. In the case of cross-boundary handover or dual-band handover, handoff occurs or the communication is unilateralism available.

Frequency

Deviation Slips/per day

10E -11 0.007

10E -9 0.69

10E -7 69.1

10E -6 691.2

Clocks not

synchronized

Impact of slip

accumulation

Slip

Communication

quality is degraded


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Requirements of Mobile Communication for

Clock Synchronization

Mobile Communication

Technology

Requirement for Frequency

Synchronization

Requirement for Time

Synchronization

GSM 0.05 ppm NA

WCDMA 0.05 ppm NA

TD-SCDMA 0.05 ppm 3 us

CDMA2000 0.05 ppm 3 us

WiMax FDD 0.05 ppm NA

WiMax TDD 0.05 ppm To be determined

LTE 0.05 ppm 1.66 us (temporarily)

The requirements for clock synchronization are higher and higher!


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Contents

3 Microwave Clock Transmission Solution


2 Microwave Clock Transmission Mode

4 FAQ

Comparison of Application Scenarios

Overview of Common Clock Transmission Modes

Introduction to Microwave Clocks


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Overview of Common Clock Transmission Modes

Physical synchronization: a clock synchronization mode in which clock information is saved in a service stream.

Packet synchronization: a clock synchronization mode in which clock information is saved in a service packet.

Packet synchronization and time synchronization future-proof the clock synchronization technology.

Frequency synchronization Time synchronization

Not supported by RTN equipment

Packet

synchronization 1588v2

Physical

synchronization SyncEth GPS

1588 ACR

CES

NTP

PDH/SDH

Supported by RTN equipment

Supported by wireless equipment

Microwave clock Overview Application scenario


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PDH Clock Synchronization

Transmit end: E1 signals are loaded into container C through bit adjustment, multiplexed into high-speed signals, and

sent out at the system clock frequency f at the transmit end. (On the OptiX RTN equipment , the E1 retiming function

needs to be enabled on the part as shown in the figure.)

Receive end: E1 signals are demultiplexed from container C by eliminating bit adjustment. The features of E1 signals

remain the same. The OptiX RTN equipment extracts and traces E1 clocks to achieve clock synchronization , as shown

on the dotted-line part.

Advantages: The principles and technologies are simple, facilitating the transparent transmission of clocks.

Disadvantages: Multiplexing and demultiplexing cause signal deterioration, which affects the transmission of high traffic.

Note: The traditional PDH network is a pseudo synchronous network. It does not need to extract clocks or support the

E1 retiming function.

High-speed

signal

NE A NE B

f System

clock unit

Service

stream

bearer clock

E1 Container C E1 Container C

f System

clock unit


High-speed

signal


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SDH Clock Synchronization

Container Vc Container Vc

NE A NE B

f System

clock unit

Service

stream

bearer clock

Service Service

System

clock unit f

Transmit end: Signals are loaded into container Vc, and sent out at the system clock frequency f at the transmit end.

The STM-N bears the clock signal f.

Receive end: The clock signal f is recovered from the STM-N services, and sent to the system clock unit. The signals

are considered as the system clock of the local NE and send out (as shown on NE A) to achieve the frequency

synchronization between NE A and NE B.

Advantages: This technology is widely used and can meet the synchronization requirements of the SDH transmission

network.

Disadvantages: The precision of the SDH clock synchronization only reach the millisecond level.



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Synchronous Ethernet

Transmit end: The Ethernet interface sends out Ethernet services at the system clock frequency f through the PHY chip.

The service stream bearers the clock signal f.

Receive end: The clock signal f is recovered from the STM-N services, and sent to the system clock unit. The signals

are considered as the system clock of the local NE and send out (as shown on NE A) to achieve the frequency

synchronization between NE A and NE B.

Advantages: This technology is widely used and can meet the synchronization requirements of the Ethernet

transmission network.

Disadvantages: The precision of the SDH clock synchronization technology is not high, and can only reach the

millisecond level.

Note: The processing of synchronous Ethernet is similar to the processing of the SDH synchronization. The difference is

that the service stream is the Ethernet service stream but not the STM-N service stream.

Ethernet

interface

NE A NE B

f

System

clock unit

Service

stream

bearer clock

Data

service

Data

service

System

clock unit f


Ethernet

interface


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IEEE 1588 V2 (Clock Architecture)

TC Primary time

input

BC-1 1 2 3

S M M

OC-1

M

BC-2 1 2 3

S M M

S

TC TC

TC

BC: boundary clock

OC: ordinary clock

TC: transparently

transmitted clock

S OC-2

OC-4

M : master clock

S: slave clock

OC model: only one port supports the transmission and extraction of IEEE 1588 V2 packets, and can either be the

source or sink of the packets.

BC model: multiple ports support the IEEE 1588 V2 packets. To be specific, one port extracts and terminates the IEEE

1588 V2 packets, and the other ports generate and send out the new IEEE 1588 V2 packets. The BC contains the

source and sink of the IEEE 1588 V2 packets.

TC model: processes the delay and transparently transmits clocks. The model does not extract and recover clocks.

Two NEs perform the relevant calculation based on the time stamps in the packets to achieve time synchronization.

S OC-3



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IEEE 1588 V2 (Master and Slave Clock

Synchronization)

Delay request

packet

Synchronization

packet

Delay response

packet

t1 t2

t1 t2 t3

t1 t2 t3 t4

t1

t4

t2

t3

Transmit end Receive end

t1

t2

The master clock transmits the synchronization packet at the moment t1, and the slave clock receives the packet at

the moment t2 and obtains the time t1.

The slave clock transmits the delay request packet at the moment t3, and the master clock receives the packet 2 at

the moment t4 and obtains the time t2.

Compute the trail delay and offset, and correct the time of the slave clock.

Delay = ( t1 + t2)/2

Offset = ( t1 - t2)/2

Advantage: supports time synchronization, and is slightly associated with the PSN. The packets are transmitted

independently, which is irrelevant to service transmission.

Disadvantage: All the equipment on the link needs to support the IEEE 1588 V2 protocol.



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1588 ACR

Transmit end: transmits the synchronization packets 1, 2, and 3 at the frequency f with time stamps t1, t1', and

t1'' respectively.

Receive end: receives the synchronization packets 1, 2, and 3, and records the arrival times t2, t2', and t2''. Due

to the impact of different delays, t1, t2, and t3 may be different. However, the received end adds different

weights for the time stamps to achieve frequency synchronization.

Advantage: The clock synchronization is of good quality, and the protocol is standardized to support the

interconnection of equipment from different vendors.

Disadvantage: only supports frequency synchronization but not time synchronization, and is easily affected by

the PDV.

synchronization

packet 1

t1 t2

t1

t2

Transmit end Receive end

t1

t2

synchronization

packet 2

synchronization

packet 3

t3

f f

synchronization

packet N



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GPS

The global positioning system (GPS) is operated by the astronomical observatory of the U.S navy. As a

precise satellite-based global navigation and location system, the GPS is composed of 24

communications satellites, three of which work as standby ones. The GPS can provide high precision

clocks to the BTS, NodeB, or BITS.

Advantage: the clock synchronization is of good quality, and time synchronization is supported.

Disadvantage: is costly and cannot be widely deployed.

GPS satellite

BITS

11

11

1 Costly deployment

NodeB/BTS



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Comparison Between Synchronization

Technologies

Synchronization

Technology

Frequency

Synchronization

Time

Synchronization

Application Scenario

PDH X

1. The PDH network needs to be synchronized.

2. The network provides PDH service interfaces only.

3. The service needs to traverse the third-party PDH and SDH

lines.

SDH X 1. The SDH network needs to be synchronized.

2. The network provides SDH service interfaces only.

Synchronous

Ethernet X

1. PSN

2. The network provides Ethernet service interfaces only.

IEEE 1588 ACR X

1. PSN

2. The services need to transparently traverse the third-party

PSN.

IEEE 1588 V2 The network requires time synchronization.

GPS BITS and base stations that require high precision clocks from

the GPS.



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NodeB/BTS E1/FE/GE/external

clock interface

The OptiX RTN equipment supports the transmission and reception of clocks at

the slave clock interface, service interface, and air interface.

In actual networking, multiple clock bearer modes can be configured at the

same time.

Air interface

External clock

interface

Stm-1/E1/GE /FE

service interface

Clock Bearer Mode

With 3-Party Design principle Typical scenario RTN network

3

2

1 BITS

RTN RTN


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Contents

3 Microwave Clock Transmission Solutions


2 Microwave Clock Transmission Modes

4 FAQ

Network Consisting of the OptiX RTN and Third-party Equipment

Design Principles

Typical Scenarios

Network Consisting of the OptiX RTN Equipment only


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Clock Bearer Technology(Except 900R3)

Type/Version 620R1/R2 620R3/R5 605R1 605R3/R5 900R1 900R2

Service

interface

SDH

E1

Transparent

transmission

Retiming

ETH

Synchronous

Ethernet

1588V2

1588ACR

Air interface

External clock

Two clock transmission modes are available for E1 services:

1. Clock transparent transmission: Transmitted E1 clocks are irrelevant to the

equipment.

2. Retiming: Transmitted E1 clocks are equipment clocks.



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Clock Bearer Technology (RTN900R3)

Type/Version

900R3C00(2011Q1) 900R3C02(2011Q2)

910 950/980 910 950/980

Service

interfac

e

SDH

E1

Transparent

transmissio

n

Retiming

CES ACR

ET

H

Synchronou

s Ethernet

1588V2 Hardware ready 1588ACR

Air interface

External clock

With 3rd-Party Design principle Typical scenario RTN network


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Note: m1 and m2 are the hop counts of the link IF boards, and k1 and k2 are the transmission

capability coefficients of the IF board in the corresponding modes.

Equipment

Series IF Board Clock Type

Transport

Capability

Coefficient k

Hop Count

Supported Remarks

RTN 620

IF0 E1 0.1 10

IF1 E1/STM-1 0.1 10

IFX E1 0.1 10

IFH2

Transparently transmitted E1 0.1 10

System clock/Synchronous Ethernet/Retiming E1 0.05 20

RTN 605

1A/1B/2B Transparently transmitted E1 0.1 10

1F/2F Transparently transmitted E1 0.1 10

1D/2D/1E/2E Transparently transmitted E1/Synchronous

Ethernet 0.0625 16

RTN 950/910

IFE2 Transparently transmitted E1 0.1 10

IF1 System clock/Synchronous Ethernet/Retiming E1 0.05 20

IFU2 Transparently transmitted E1 0.1 10

Supported by only the OptiX

RTN 900 V100R002


IFX2 Transparently transmitted E1 0.1 10

Supported by only the OptiX

RTN 900 V100R002


Clock Transmission Capability



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Clock Injection

Clock input point

Clock signal trail

Chain network: The length of the radio link whose clock transmission capability is

insufficient is L, and the clock transmission capability is N.

1. 0 < L < N. The clock is injected at an upstream node.

2. N =< L < 2N. The clock is injected at an intermediate node.

Star network: The clock is injected at a hub node.


Clock input Clock input Clock input

Clock injection at

an upstream node

Clock injection at an

intermediate node

Clock injection

at a hub node


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Injecting the Clock from the BITS to the OptiX

RTN Equipment

A

BSC/RNC

E1

B

NodeB/BTS

E1/FE

Injecting the clock

from the BITS

The clock is transmitted through the external clock interface/E1, Ethernet, or SDH service

interface and the air interface.

Note: When the clock transmission capability of the OptiX RTN equipment is insufficient,

the clock needs to be injected from the BITS for clock compensation.

BITS

The clock is transmitted through

the OptiX RTN equipment

Injecting the clock into

the base station



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Injecting the Clock from the Transmission

Equipment to the OptiX RTN Equipment

A

BSC/RNC

E1

B

NodeB/BTS

E1/FE

Injecting the clock from the

transmission equipment

The clock is transmitted through the external clock interface/E1, Ethernet, or SDH service

interface and the air interface.

Note: When the clock transmission capability of the OptiX RTN equipment is insufficient,

the clock needs to be injected from the BITS equipment for clock compensation.

BITS

The clock is transmitted through

the OptiX RTN equipment

Injecting the clock

into the base station


120810621 microwave clock transmission solutions

Documents

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