Through the VDSL2 PTM bonding function, one Ethernet packet is divided into several fragments, which will be assigned to multiple links for transmission, thus increasing the network bandwidth.
Fragmentation of an Ethernet packet and assignment of fragments are implemented by the 802.3ah protocol. In the case of bonding based on the VDSL2 access, the negotiation for the VDSL2 PTM bonding features between the CO and CPE through G.994.1 is required. Figure 4-13 shows the bonding layering of the VDSL2 PTM bonding.
Figure 4-13 VDSL2 PTM bonding layering
Service
GBS
Cross connect
TPS-TC PMS-TC PMD
BCE-1 ... BCE-32
As shown in the preceding figure, the meaning and the function of each layer is as following:
l A bonding channel entity (BCE) is a channel. The BCE here is regarded as one VDSL2 port because one port of the currently implemented VDSL2 has only one channel.
l Cross connect is optional. The Cross connect supplies the interface for the data transmission between the BCE and the GBS layer. It only aggregates the data of the BCE layer and transmits to the GBS layer.The data reorganization and splitting is realized by the GBS layer.
l The generic bonded sub-layer(GBS) reorganizes the data streams of all the bound lines and splits the downstream traffic streams.
l The upper layer of GBS is the service layer. In the case of the service layer, the GBS is equal to only an interface. The GBS regroups and transits the data to the service layer. The service layer then forwards Ethernet packets to the upper layer.
The actual implementation of the VDSL2 PTM bonding is as following:
1. Traffic streams are set up on the GBS, but are not bound to ports. The device allows service flow configuration only on the primary port in the bonding group.
2. The GBS assigns the data stream to every BCE according to certain rules and therefore each BCE carries only part of the data stream. The fragments of one packet, however, must be transmitted within one BCE.
Module
Feature Description 4 VDSL2 Access
INM
The impulse noise in the x digital subscriber line (xDSL) service severely affects line stability and quality of experience (QoE). There are multiple impulse noise sources, such as household appliance switches, devices that generate electric arcs, phones' offhook and onhook state, natural discharge, and various electromagnetic waves. A frequency spectrum covers a wide region and varies with time, increasing the system bit error rate (BER) and decreasing system stability.
The impulse noise protection (INP) technology adjusts noise parameters to improve line quality and minimize noise impact on lines. Before configuring INP, users need to monitor and collect statistics for current line noise distribution. The impulse noise monitor (INM) technology enables users to monitor and collect statistics of impulse noises.
INM can improve service QoE that is sensitive to packet loss instead of delay. Therefore, INM is significant for widely used video services. Long-period noise detection helps carriers to better learn about the live network noise environment, facilitating QoS improvement.
Figure 4-14 shows the principles for INM.
Figure 4-14 Principles for INM
Eq INP&IAT
Principles for INM are as follows:
1. An impulse noise sensor (INS) mainly detects whether discrete multi-tone (DMT) symbols are severely damaged. If yes, the INS degrades the DMT symbols. If not, the INS considers the DMT symbols normal and does not degrade them.
2. A cluster indicator uses a specific method to identify DMT symbols detected by the INS and classifies several consecutive qualified symbols into a cluster. The cluster is used for subsequent processing. Figure 4-15 shows how to identify a cluster.
Figure 4-15 Principles for INM
Cluster1 Cluster2
Gap1 Gap2 Gap3
INMCC = 2
Degraded symbol Undamaged symbol
As shown in the preceding figure, INM cluster continuation (INMCC) specifies the maximum number of consecutive undamaged DMT symbols allowed in a cluster. In the preceding figure, INMCC is 2 and Gap1 contains two DMT symbols. Therefore, the two DMT symbols belong to the same cluster, which is identified as Cluster1. Gap2 contains Module
Feature Description 4 VDSL2 Access
three DMT symbols. Therefore, Cluster1 does not contain the DMT symbols in Gap2 and the DMT symbols following Gap2. Gap2 does not belong to any cluster.
3. The Eq INP Generation module calculates equivalent INPs (INP_eq) in each cluster. The inter arrive time (IAT) Generation module calculates the IAT of an entire symbol sequence.
IAT specifies the number of symbols between the end of a cluster and the beginning of the next cluster, without Sync symbols.
4. The Eq INP&IAT Anomalies Generation module collects statistics for INP_eq and IAT.
5. The INM Counters module uses a rule to count the collected equivalent INP_eq and IAT and forms an irregular equivalent INP and IAT histogram based on the data. Users can view and use the data. In addition, users can configure INP_Min and Delay_Max based on equivalent INP and IAT.
4.10 VDSL2 Network Applications
This topic describes the network applications of the VDSL2 access feature.
Figure 4-16 VDSL2 network applications
PC
PC
ADSL/ADSL2+ CPE
VDSL2 CPE
PON
IPTV Server
PC
PC
ADSL/ADSL2+ CPE
VDSL2 CPE Copper Access
FTTx+xDSL Access
ONU splitter
splitter
MA5600T/MA5603T
PSTN Voice Stream
As shown in Figure 4-16, VDSL2 in actual application applies to two typical scenarios.
1. The MA5600T/MA5603T directly provides the VDSL2 access.
On the user side, ADSL/ADSL2+ CPEs (working in the ATM mode) or VDSL2 CPEs (working in the PTM mode) can be connected to the MA5600T/MA5603T to provide high-speed Internet access service and video service for subscribers.
Module
Feature Description 4 VDSL2 Access
2. The MA5600T/MA5603T provides PON optical ports for connecting to ONUs and the ONUs provide the VDSL2 access.
The ONUs are placed on street side or in corridors. In the downstream direction, the ONUs provide the VDSL2 access for subscribers; in the upstream direction, the ONUs are connected to the MA5600T/MA5603T by PON. The FTTx+VDSL2 network topology addresses the distance restriction on the VDSL2 access.
Module
Feature Description 4 VDSL2 Access
5 SHDSL Access
About This Chapter
SHDSL is an xDSL access technology, just like ADSL and VDSL. SHDSL provides the symmetric upstream and downstream rates.
5.1 ATM SHDSL Access
This topic describes the definition, purpose, specifications, and limitations of ATM SHDSL access feature. It also provides the glossary and the acronyms and abbreviations related to the ATM SHDSL access feature.
5.2 EFM SHDSL Access
This topic describes the definition, purpose, specifications, and limitations of EFM SHDSL access feature. It also provides the glossary and the acronyms and abbreviations related to the EFM SHDSL access feature.
5.3 TDM SHDSL Feature Module
Feature Description 5 SHDSL Access
5.1 ATM SHDSL Access
This topic describes the definition, purpose, specifications, and limitations of ATM SHDSL access feature. It also provides the glossary and the acronyms and abbreviations related to the ATM SHDSL access feature.
5.1.1 Introduction
Definition
SHDSL is an xDSL access technology, just like ADSL and VDSL. SHDSL provides the symmetric upstream and downstream rates.
The symmetric upstream and downstream rates of ATM SHDSL determine that bi-directional rates of the supported service must be basically the same. In addition, ATM SHDSL features a longer transmission distance. Hence, ATM SHDSL can be widely used.
Purpose
ATM SHDSL provides symmetric broadband access services for subscribers to meet the requirement for high downstream rate from SOHO subscribers. ATM SHDSL applications are similar to ADSL applications and the ATM SHDSL and ADSL applications are mutually complementary.
5.1.2 Specifications
The specifications of SHLB and SHLM are as follows:
l These boards support the single-pair and two-pair modes.
l Network timing reference (NTR) clock.
l Automatic rate adjustment according to the line conditions during initialization.
NOTE
For the two, three, or four bound ATM ports, the system does not support automatic rate adjustment.
l Reporting of the alarms and maintenance information of lines.
l PPPoE+ sub option.
l Dynamic adjustment of the specifications of the SHDSL line profile and alarm profile.
l Power-saving of the xDSL line.
l Supports wetting current.
l A maximum transmission distance of 6 km.
l Supports the configuration, modification, and query of the SHDSL line profile.
l Four modes of binding EFM or ATM ports: single-pair (two-wire), two-pair (four-wire), three-pair (six-wire), and four-pair (eight-wire).
l Line rate ranging from 192 kbit/s to 5696 kbit/s in the single-pair mode.
l Supports crosstalk cancellation.
l The line rate of the bound two, three, or four ATM/EFM ports is double, triple, or quadruple the line rate of a single port.
Module
Feature Description 5 SHDSL Access
NOTE
l Each port in an EFM bonding group can be activated or deactivated independently. Hence, in a specific application, the line rate of the bonding group varies according to the number of the activated ports in the group.
l As defined in IEEE 802.3ah, the ratio of the maximum rate to the minimum rate in an EFM bonding group cannot exceed 4. For example, if the minimum rate is 192 kbps, the maximum rate cannot exceed 768 kbps.
l Supports F5 OAM loopback.
l Supports the configuration of ATM/EFM mode based on port.
The specifications that are supported only by the SHLM are as follows:
l Supports IMA bonding of G.SHDSL.
l Supports MELT function.
5.1.3 Availability
Hardware Support
The SHLB board supports 16 channels of ATM and PTM SHDSL service.
The SHLM board with MELT function supports 16 channels of G.SHDSL.BIS service.
License Support
The port rate measurement function and cross talk cancellation supported by the MA5600T/
MA5603T is under license. Therefore, the corresponding service is also under license.
5.1.4 Reference
The following lists the reference documents of this feature:
l ITU-T Recommendation G.991.2 Annex A and Annex F.
l ITU-T Recommendation G.991.2 Annex B and Annex G.