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Node Level Vectoring (NLV)

Technical White Paper

Issue 1.0

Date 2013-11-21

HUAWEI TECHNOLOGIES CO., LTD.

Copyright © Huawei Technologies Co., Ltd. 2013. All rights reserved.

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Node Level Vectoring(NLV) Technical White Paper

Issue 1.0 (2013-11-21) Huawei Proprietary and Confidential

Copyright © Huawei Technologies Co., Ltd.

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About This Document

Change History

Date Revision Version Description Author

2013-05-30 1.0 Initial official release. You He /118811




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Contents

Change History ....................................................................................................................................3

1 Executive Summary ......................................................................................................... 6

2 Background ...................................................................................................................... 7

3 Node Level Vectoring Principle ....................................................................................... 9

3.1 Basic Principle and Node Architecture ............................................................................................9

3.2 NLV Architecture Comparison ...................................................................................................... 10

3.3 Parameter independence analysis .................................................................................................. 11

3.4 Standardization status: .................................................................................................................. 11

3.5 Fault demarcation analysis ............................................................................................................ 11

3.6 X-connection and distance ............................................................................................................ 12

4 Huawei NLV Solution ..................................................................................................... 13

5 Summary ........................................................................................................................ 14

6 Acronyms and Abbreviations ......................................................................................... 15




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1 Executive Summary

This paper will analyze technologies feasibility of cross-chassis solution, which is

used to solve crosstalk of multi-chassis.

.




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2 Background

Usually, the VDSL2 alien will badly impact the performance and stability of vectoring

line. The impact of ADSL2+ and VDSL2 alien is illustrated as in line performance, see

figure 2-1.

Figure 2-1 Vectoring performance with alien

There are some limitations in vectoring deployment, see Figure 2-2, which requires

that all VDSL2 lines in one bundle to be vector compatible or friendly. So, all

crosstalk among VDSL2 lines can be cancelled by vectoring processing (VP).




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Figure 2-2 Vectoring deployment sceneries

If parts of VDSL2 lines in one bundle belong to a different DSLAM system, it requires

a cross-chassis vectoring solution, indicated in Huawei as NLV, to cope with crosstalk

cancellation. The deployment scenario is figured as following:

Figure 2-3 Cross-Chassis Vectoring scenario




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3 Principle and Architecture

3.1 Basic Principle and Node Architecture

Figure 3-1 Cross-chassis vectoring basic principles

In each DSLAM the line boards are interconnected to the vectoring processing engine

(VP) through the backplane, approach, indicated as System Level vectoring, that

allows controlling all lines in one shelf through. To further extend the control of lines

across different shelves, as showed in Figure 3-1, two DSALM’s VP must exchange

vectoring data with each other. In Huawei , we indicate this architecture as

peer-to-peer mode as the two VPs are processing the same information at same time,

case (1) of Figure 3-2. In case of more than two DSLAMs needed to be involved a

different architecture can be selected, indicated in Figure 3-2 case (2) as centralized

mode. In this case one centralized VP on a single shelf (master shelf) processes all

lines information; not only the lines of the line boards in that shelf, but also those

coming from other shelves (slave shelves).

In general, the VP will process their victim lines with the performance impacted by the

crosstalk comes from all DSLAM lines. It requires special high-speed x-connection

cable between the VP (process board), VP and LC (line card), to exchange the

vectoring data.

DSLAM1 Bundle CPE

CrosstalkCrosstalk Canceller

DSLAM2Upstream

Downstream

CrosstalkCrosstalk Precoder

DSLAM2

DSLAM1 Bundle CPE




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Figure 3-2 Typical cross-operator architectures

3.2 NLV Architecture Comparison

The comparison of two architectures is listed as follows

.

Solution 1 – Peer to Peer mode Solution 2 – Centralized mode

VP ownership Each DSLAM owns separated VP All DSLAM share the same VP

X-connection cable

Only between VPs Each LC needs external cable to be connected to the centralized VP

X-connection

material

Copper X-connection or fiber X-connection

X-connection

length

It is limited by technique realization (such as signal delay, attenuation, etc.)

Usually, the length is:

Copper : a few meters

Fiber: a few 10-meters

Bandwidth

requirement

for X-connection

For “96L vectored DSLAM + 96L vectored DSLAM” application

Each VP requires 40Gbps interface to other VP

Each 48p Vectoring board requires 20Gbps (between LC and VP).

Totally they needs four 20Gbps

X-connections from centralized VP to

both DSLAM.

Reliability If one of VP is down, the other

DSLAM can return to SLV mode.

If centralized VP is down, all DSLAM

only work on non-vector mode.

Table 3-1Mode comparison of cross-chassis

We can conclude from the table above that the Peer to Peer mode for cross-chassis

solution has more advantages in fairness and reliability than the centralized mode. It

does not require all line to be connected to a single box and allow the vectoring can be

accessed by different DSLAM.




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3.3 Parameter independence analysis

Figure 3-3 Process of the GPON type C protection mechanism

Both DSLAMs need to exchange vectoring data of all lines in one site with each other

on cross-chassis scenarios. The cross-chassis solution requires each DSLAM to use

same configuration of frequency band plan because DSL is based on FDM (Frequency

Division Multiplexing). By all means, both DSLAMs require using the same

communication interface and same clock to guarantee the consistence on vectoring

data transmission.

The cross-chassis solution with peer to peer mode allows configuring different

parameters profile for different DSLAM, It is unnecessary to get full centralized

control of all parameters for vectoring cancellation calculation. The independent

parameters by different DSLAM include Interleave, INP, Bitrates, etc.

3.4 Standardization status:

There is not yet a standardized on vectoring interface between VP and VP, even

between VP and LC due to the data format compatibility.

Still now, there is no significant progress in cross-chassis standardization. If

cross-chassis solution is used for cross-operators scenarios, it requires all operators use

same vendor DLSAM. However, when the two different vectoring systems are not

sharing the same cable bundle, different vendor’s solution can be used.

3.5 Fault demarcation analysis

There are some challenges for fault demarcation in the cross-chassis solution. The

potential risk includes: VP failure, X-connection failure, mistake configuration of

vectoring parameter, etc.

It requires cross-chassis system to provide fault demarcation mechanism, such as:

Display the status of communication interface of X-connection




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Query essential vectoring parameter (such as band plan, fast join status, clock

status)

Query the top disturbers for a given victim line

In the case of single operators, the management system provides the necessary tools to

trouble shoot their DSLAM’s lines allowing understanding which connections are

underperforming. Moreover, due to the additional vectoring coordination, each

DSLAM will also participate to a joint crosstalk measurement and cancellation activity

and as a consequence will also have the possibility to query a jointly populated

crosstalk matrix to identify which lines of the vectoring group have the higher

coupling effects to a certain victim line.

In case of multi-operator use of cross-DSLAM vectoring, a service provider may be

allowed only to query for disturbers of its own connected lines, since this information

could be a summary aggregated on all frequencies and well abstracted by customer

data, while each service provider may not be allowed to query for any other sensible

data more related to lines connected to the other DSLAM managed by another service

provider.

As consequence, it requires operators to have cooperation friendly to achieve a more

convenient fault demarcation.

3.6 X-connection and distance

Cross-chassis vectoring solution required to add an X-connection cable between two

DSLAMs to exchange vectoring data of Cancellation & Pre-coding, vectoring

management data. Since the transmission speed is very high (up to multi 10GEs

interfaces, see Table1), X-connection requires a high requirement on quality and

reliability.

There is a limitation on X-connection distance due to the transmission delay and signal

attenuation. Fiber solution could be used to increase the X-connection distance, but the

increased costs of fiber X-connection need to be considered.




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4 Huawei NLV Solution

Huawei had released the industrial 1st NLV technical prototype in 2011, followed by

an advanced release of NLV product Demo version in 2013.

The main aspects of Huawei NLV solution in current demo version is as follows:

Based on MA5616

Two chassises

Peer to Peer VP mode

Fiber or Copper X-Connection

5 meters for copper X-connection

30 meters for fiber X-connection

SLV/NLV auto mode

Up to 96L vectoring port capacity

Figure 4-1 Huawei NLV solution




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5 Summary

The cross-chassis vectoring solution provides the possibility to resolve the coexistence of

multi-chassis crosstalk. Huawei has designed and developed the NLV solution taking into

account the requirements covered by this paper and has proved the technology available by

demo system. Beside above technologies feasibility, the management mode and business

model need to be consider as part of the overall solution. Huawei is continuously

investigating in the technologies taking into account the multi-operators and regulator’s

requirements.




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6 Acronyms and Abbreviations

Acronym/Abbreviation Full spelling

ADSL Asymmetric DSL

DSL Digital Subscriber Line

DSLAM DSL Access Multiplexer

LC Line Card

MDF Main Distribution Frame

NLV Node Level Vectoring

PSTN Public Switched Telephone Network

SLV System Level Vectoring

VDSL Very-high-speed DSL

VP Vectoring Processing Board

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