node level vectoring(nlv) technical white paper
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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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Huawei Technologies Co., Ltd.
Address: Huawei Industrial Base
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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
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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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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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
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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1 Executive Summary
This paper will analyze technologies feasibility of cross-chassis solution, which is
used to solve crosstalk of multi-chassis.
.
Node Level Vectoring(NLV) Technical White Paper
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Copyright © Huawei Technologies Co., Ltd.
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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).
Node Level Vectoring(NLV) Technical White Paper
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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
Node Level Vectoring(NLV) Technical White Paper
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Copyright © Huawei Technologies Co., Ltd.
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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
Node Level Vectoring(NLV) Technical White Paper
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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.
Node Level Vectoring(NLV) Technical White Paper
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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
Node Level Vectoring(NLV) Technical White Paper
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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.
Node Level Vectoring(NLV) Technical White Paper
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Copyright © Huawei Technologies Co., Ltd.
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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
Node Level Vectoring(NLV) Technical White Paper
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Copyright © Huawei Technologies Co., Ltd.
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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.
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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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