Internet Standards/CD2.mdf/ccitt/1992/g/g960.asc

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13.1    Recommendation G.960



DIGITAL SECTION FOR ISDN BASIC RATE ACCESS







1.    General



1.1    Scope



    This Recommendation describes the characteristics of a digital section
for the ISDN basic rate access between the user network interface
(at           T reference point, defined in Recommendation I.411 and the
local exchange (at V1reference point defined in Q.512) supporting the
recommended channel structure 2B+D and the required additional func-
tions.



    In this Recommendation and unless otherwise indicated, the term TE is
used to indicate terminating layer 1 aspects of TE1, TA and NT2 func-
tional groups.



    When the term TE indicates terminating layer 1 aspects of TE1, then
according to Figure 2/I.411, the S and T reference points coincide.



    The terminology used in this Recommendation is very specific and not
contained in the relevant terminology Recommendations. Therefore
Annex B to this Recommendation provides terms and definitions used in
this Recommendation.



1.2    Configuration



    Figure 1/G.960 shows the boundaries of the digital section in relation to
the digital system definition.



































Note - Digital transmission system refers to either a line system using
metallic pairs, optical fibres or radio systems.





Figure 1/G.960

Note - The T and V reference points are defined in Recommendations
I.411 and Q.512.



1.3    Application



    The basic access digital section may be applied as given in     Figure2/
G.960 for:



-    direct access to the local exchange (V1-reference point);



-    access via a basic access multiplex equipment (V4-interface) to the local
exchange;



-    access via a basic access concentrator (V2-interface) to the local
exchange;





2.    Modelling and relationship between the digital section and the ET



    The general model shown in Figure 3/G.960 depicts the whole ISDN cus-
tomer access layer 1 and adjacent entities and provides the basis to
describe the functions performed by the digital section and those per-
fomed by TE, ET and system management and how various functions are
grouped. In particular, according to this model the activation/deactivation
procedures and maintenance functions specified in this Recommendation
are not confined to functions perfomed by the digital section but include
functions associated with ET      layer 1.



    This model includes primitive procedures between ET layer 1,          ET
layer, 2 and system management:



i)    I.430 to I.440/I.441 interactions between ET layer 1 and        ET layer 2,
and ET layer 1 and system management based on PH and MPH
primitives, respectively, as defined in Recommendation I.430.
These interactions are for the support of functions specified in Rec-
ommendations I.440 and I.441;



ii)    interactions between ET layer 1 and system management for the sup-
port of functions associated with the digital section, based on MPH
primitives.



    The primitive procedures within TE comply with the specification
according to Recommendation I.430.



    This model does not constrain layer 1 arrangements between LT and
NT1, (it is also applicable to remote access as shown in Figure2/G.960),
or the digital transmission system technology.



3.    Functions



    Figure 4/G.960 shows the functions which have to be supported by the
basic access digital section.



































































Note 1 - These functions are conveyed by the CV1 channel across the V1
reference point.



Note 2 - This function is optional.



Note 3 - The activation and deactivation functions are concerned with the
operation of the digital section and the user-network interface. However,
for consistency with Recommendations I.430, they are described as sepa-
rate functions.



FIGURE 4/G.960



Functions of the digital section

B Channel



    This function provides, for each direction of transmission, two indepen-
dent 64 kbit/s channels for use as B Channels (as defined in Recommen-
dation I.412).



D Channel



    This function provides, for each direction of transmission, one
DChannel at a bit rate of 16 kbit/s, (as defined in Recommendation
I.412).



Bit timing



    This function provides bit (signal element) timing to enable the receiving
equipment to recover information from the aggregate bit stream.  Regard-
ing the V1 reference point, the bit timing function is used for both trans-
mit and receive data.



Octet timing



    This function provides 8 kHz octet timing for the B Channels.



Activation



Activation from ET



    This function places all the functions of the digital section into a normal
operating mode and supports the activation of the interface at the       T
reference point according to Recommendation I.430. This takes into
account:



-    power down mode;



-    initial power up;



-    a failure condition.



    The procedures and exchange of information are described in º 5 of this-
Recommendation.



    An activation should be possible to a state which allows maintenance
actions to be performed in the digital section even when there is no cus-
tomer equipment connected to the T reference point.



    In the case of a basic access digital section making use of a digital trans-
mission system for a metallic line one additional mode of operation may
be applied for activation/deactivation, which is to activate/deactivate the
digital section only. This is optional.



Request for activation from TE



    This function supports activation of the digital section and of the inter-
face at the T reference point according to Recommendation I.430.



    These functions are conveyed by the CV1 channel (see º 7).



Deactivation



    This function is specified in order to permit the interface at the     T refer-
ence point and the digital section to be placed in a low power consump-
tion mode. The procedures and exchange of informationn are described
in  º 5 of this Recommendation.



    Deactivation should be initiated only by the exchange (ET).



    This function is conveyed by the CV1 channel (see º 7).  Power feeding



    This function provides for remote power feeding of NT1 and optionally
the TE via the user network interface in accordance with Recommenda-
tion I.430, º 9.



Operation and maintenance



    This function supports required actions and information for operating and
maintaining the digital section controlled by the ET as defined in Recom-
mendation I.603.



    Four categories of functions have been identified:



-    commands regarding LT, regenerator, or NT1;



-    information from LT, regenerator, or NT1;



-    indications of fault conditions;



-    control of digital section power feeding.



    These functions are conveyed by the CV1 channel (see º 7).



4.    Network performance



4.1    Availibility



    The definition of availability is given in Annex A of Recommendation
G.821. The availability objective of the digital section should be consis-
tent with the availability requirement for the hypothetical reference digi-
tal section as given in Recommendations G.801 and I.Qnp.



4.2    Signal transfer delay



    Signal transfer delay is specified for B Channels and is defined as abso-
lute signal delay between T and V1 reference points for each direction

of transmission. The value is for further study. The relevant Recommen-
datons have to be taken into account (e.g. signal transmission delay when
the signal represents speech must be taken into account as one compo-
nent of the end-to-end delay requirement of Recommendation G.114).



4.3    Error performance



    Error performance must be consistent with the requirements given in
Recommendation G.821.



4.4    Jitter



4.4.1     Output/input jitter at T reference point



    The requirements are defined in º 8 of Recommendation I.430.



4.4.2    Jitter at V1 reference point.



    The input jitter limits are for further study.



6.    Operation and maintenance



6.1    General



    This paragraph describes the operation and maintenance functions for the
digital section of the ISDN basic rate access. For the time being only
functions for a digital transmission system for a metallic line are defined.



    Operation functions related to activation/deactivation procedure are spec-
ified in paragraph 5.



    Further assumptions regarding the system management are given in

Annex A.



    The maintenance functions recommended in I.603 provide the capability
to maintain the digital section to the level of Network Performance given
in

º 4 of this Recommendation.



    It must be possible to test and maintain the digital section in accordance
with Recommendation I.603 regardless of the customer equipment.



    The main features are:



    a)    control of maintenance and test support facilities;



    b)    monitoring of the functional elements to provide operating and

performance information and fault condition indications;



    c)    maintenance communication facility.



6.2     Control facilities



6.2.1    Loopbacks



6.2.1.1    Loopback implementation



    The location and characteristics of loopbacks are defined in Recommen-
dation I.603.



6.2.1.2    Loopback procedure



    The loopbacks are controlled by ET system management.



    A normal call activation request cannot override a request for

loopback 1, 1a or 2.



    The procedure for loopback operation always starts from the deactivated
state of the digital section.



    One possible sequence is:



    a)    ET generates an operation command for the required loopback;



    b)    ET receives MPH-AI;



    c)    ET performs the test;



    d)    ET generates a release command;



    e)    ET receives MPH-DI.



6.2.2    Auxiliary equipment line switchover



    The function provides control of switchovers across the VI reference
point:



    a)    to switch the line from the LT to a line measurement device;

    b)    to switch the line from the normal LT to a standby LT;



    c)    to switch the LT to test NT1 located in the local exchange.



    This function is optional. The function definition, control options and
procedures are for further study.



6.2.3    Control of functions in the NT1



    This function allows control of specific functions within the NT1 and is
for further study.



    An example of such a function is as follows:



    -    e.g., control of switching between normal and restricted power at
the user network interface.



6.2.4    Information request



    This function allows the ET to request from the LT, regenerator and NT1
specific status reports.



6.2.5    Power switch on/off to the line



    This function allows switching of the power to the line, and may be auto-
matically applied upon reception of a power feed failure indication.



6.2.6    Continuity test



    The continuity test is described in Recommendation I.603.



    The continuity test is controlled by the ET and is initiated by MPH-AR.
System management decides when the test is passed (i.e. on reception of
MPH-DSAI or MPH-AI). When the system management receives MPH-
EI (expiry T1) the test is considered to be failed. See also Annex A to this
Recommendation.



6.3    Monitoring



6.3.1    Functions



    The following operational conditions are monitored throughout the sec-
tion:



    a)    the defect conditions;



    b)    the power feed arrangements;



    c)    transmission performance.



6.3.2    Implementation aspects



    Monitoring capabilities must be provided in the digital section (see Rec-
ommendation I.603). The handling and processing of the information is
implementation dependant. For example:



    a)    the use of registers/counters in functional groups, the use of explicit
commands and responses to establish status reports;



    b)    the transfer of information to the exchange, either when a defect
condition occurs or on a regular basis. This information is then
processed by entities outside the digital section.



6.3.3    Anomaly and defect conditions and consequent action



6.3.3.1    Defect conditions



    The following defect conditions are examples:



    i)    excessive error rate;



    ii)    loss of incoming signal;



    iii)    loss of frame alignment;



    iv)    power feed failure.



Note - One example of an anomaly is a transmission error.



6.3.3.2    Consequent actions



    Further to the detection of a defect condition appropriate actions should
be taken as specified in Table 5/G.960.



    Defect indication information (FII) is automatically transmitted from the
digital section to the ET.

TABLE 5/G.960



Defect conditions and consequent actions



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_ EQUIPMENT _       DEFECT        _          CONSEQUENT ACTIONS
_

_           _     CONDITIONS      +ûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûû
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_           _                     _ FII  _  SIGNAL AT V1  _  SIGNAL AT T   _

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_    LT     _EXCESSIVE ERROR RATE _ YES  _       FFS      _      FFS
_

_           _    LOSS OF SIGNAL   _ YES  _       FE4      _     INFO5      _

_ LINE SIDE _    LOSS OF FRAME    _ YES  _       FE4      _     INFO5
_

_           _                     _      _                _                _

_    NT     _EXCESSIVE ERROR RATE _ YES  _       FFS      _      FFS
_

_           _    LOSS OF SIGNAL   _ YES  _ NOT APPLICABLE _
INFO5      _

_ LINE SIDE _    LOSS OF FRAME    _ YES  _ NOT APPLICABLE _
INFO5      _

_           _                     _      _                _                _

_  NT AT T  _    LOSS OF SIGNAL   _ YES3 _       FE4      _ NOT
APPLICABLE _

_           _    LOSS OF FRAME    _ YES3 _       FE4      _ NOT APPLICA-
BLE _

_           _                     _      _                _                _

_    NT     _    LOSS OF POWER    _ YES2 _       FFS      _     INFO O     _

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Note 1 - If processed in the digital section.



Note 2 - Depending on power feed arrangements, optional.



Note 3 - Optional.



Note 4 - This signal is defined in paragraph 5.



Note 5 - Whether an existing INFO as defined in I.430 may be used is for
further study.



6.3.4    Error performance monitoring



6.3.4.1    General



    Provision has to be made in order to monitor the error performance of the
digital section and to report on such performance.



6.3.4.2    Error performance parameters



    The digital section must deliver to the ET the necessary information to
allow it to evaluate the error performance parameters defined in

Recommendation G.821.



6.3.5    Status report functions



    Status report functions cover information which relate to the overall
operation and performance of the digital section. The information may be
transmitted either automatically or under request of ET.





    Listed below are descriptions of the status report functions:



    i)    Transmission errors



        This information, derived in the digital section, allows the ET to

evaluate the transmission error performance;



    ii)    Loopback 1 status



This information, sent from the LT, gives the status of

loopback 1;



iii)    Loopback 1A status



This information, sent from the regenerator, gives the status of
loopback 1A;



    iv)    Loopback 2 status



        This information, sent from the NT1, gives the status of

loopback 2;



    v)    User network interface power feed status



This information indicates the status of the user network inter-
face at T reference point power feed, e.g., normal or restricted
power feed mode;



    vi)    User network interface power feed fault



This information indicates a failure of the normal or restricted
power source.



This function may be split into two reports.



This information is reported on request of the ET;



    vii)    User network interface power feed overload



        This information indicates that the power drawn from any source
within the NT1 exceeds the maximum power that is available.



        This information is reported on request of the ET;



    viii)    Defect indication information



This information is transmitted automatically under conditions
specified in 6.3.3.1.

TABLE 6/G.960



Status report functions



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_        FUNCTION          _ LOCATION _ MANDATORY/OPTIONAL _

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_ Transmission errors      _   LT     _         M          _

_                          _  REG.    _         O          _

_                          _   NT     _         O          _

_                          _          _                    _

_ Loopback 1 status (Note) _   LT     _         M          _

_                          _          _                    _

_ Loopback 1A status (Note)_  REG.    _         M          _

_                          _          _                    _

_ Loopback 2 status (Note) _   NT1    _         M          _

_                          _          _                    _

_ T reference point power  _   NT1    _         O          _

_      feed status         _          _                    _

_                          _          _                    _

_ T reference point power  _   NT1    _         0          _

_      feed fault          _          _                    _

_                          _          _                    _

_ T reference point power  _   NT1    _         O          _

_    feed overload         _          _                    _

_                          _          _                    _

_         FII              _   LT     _         M          _

_                          _  REG.    _         M          _

_                          _   NT     _         M          _

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Note - The information may be implicit (e.g., activation indication).





6.3.6    System dependent status report functions



    These status reports will be dependent upon the type of digital transmis-
sion system used and require further study.



    Some examples of a particular system are given in Table 7/G.960.





































TABLE 7/G.960



System dependent status report functions



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_            FUNCTION            _ LOCATION _

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_ Line test relay state          _    LT    _

_ LT test relay state            _    LT    _

_ Remote power switch state      _    LT    _

_ Remote power feed              _    LT    _

_ Induced overvoltage on line    _    LT    _

_ Abnormal current condition     _    LT    _

_ Receive eye opening            _    LT    _

_                                _   REG.   _

_                                _   NT1    _

_ Echo cancellation coefficients _    LT    _

_                                _   REG.   _

_                                _   NT1    _

_ Battery test                   _    NT    _

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7.    Control channel CV1



    This control channel provides, for each direction of transmission, the
capability to transfer the commands, status report information and FII.



    Although described as a single channel, the control channel may be real-
ized by a number of sub-channels which may use different transport
mechanisms (as appropriate to the functions). Even though some of the
functions mentioned in º 6 have optional status, the CV1 channel shall
have the capability to convey all the control information to allow their
implementation.



















































ANNEX B



(to Recommendation G.960)



Vocabulary of terms used in connection with

Recommendations I.430, I.431, G.960 and G.961





(Will reproduce the text of Annex E to Recommendation I.430,

see COM XVIII-R 61/AP IX-146.)