Docstoc

International Roaming Caller ID

Document Sample
International Roaming Caller ID Powered By Docstoc
					International Roaming Caller ID


                    CDG Document 139

                           Version 1.0



                      4 December 2006



                    CDMA Development Group
                  575 Anton Boulevard, Suite 560
                   Costa Mesa, California 92626
                    PHONE +1 888 800-CDMA
                         +1 714 545-5211
                      FAX +1 714 545-4601
                        http://www.cdg.org
                           cdg@cdg.org



                                Notice
Each CDG member acknowledges that CDG does not review the
disclosures or contributions of any CDG member nor does CDG verify
the status of the ownership of any of the intellectual property rights
associated with any such disclosures or contributions. Accordingly, each
CDG member should consider all disclosures and contributions as being
made solely on an as-is basis. If any CDG member makes any use of
any disclosure or contribution, then such use is at such CDG member's
sole risk. Each CDG member agrees that CDG shall not be liable to any
person or entity (including any CDG member) arising out of any use of
any disclosure or contribution, including any liability arising out of
infringement of intellectual property rights.
International Roaming Caller ID                                     Contents




                                  <page left intentionally blank>




Ref Doc. 139, Ver. 1.0                   4 December 2006                   ii
                                                                                                                      Contents
1. Introduction ................................................................................................................................ 1
       1.1 Scope ................................................................................................................................. 1
       1.2 Definitions ........................................................................................................................... 2
       1.3 Importance ......................................................................................................................... 2
2. Roamer-Terminated Caller ID ................................................................................................... 3
       2.1 Provisioning ........................................................................................................................ 3
                  2.1.1 Subscriber Provisioning ....................................................................................... 3
                  2.1.2 Network Support .................................................................................................. 4
       2.2 Service Delivery ................................................................................................................. 4
                  2.2.1 Terminating Call Flow .......................................................................................... 4
                  2.2.2 Incoming Call to Originating MSC ....................................................................... 5
                  2.2.3 Originating MSC Interrogates HLR ...................................................................... 6
                  2.2.4 HLR Initiates RoutingRequest ............................................................................. 6
                  2.2.5 RSP Transfers RoutingRequest .......................................................................... 7
                  2.2.6 Originating MSC Sends Call Delivery Leg........................................................... 7
                  2.2.7 Serving MSC Receives Calling Party Number .................................................... 7
                  2.2.8 Serving MSC Passes Calling Party Number to Mobile ....................................... 7
                  2.2.9 Mobile Displays Received Number ..................................................................... 8
                  2.2.10 CNIR and CNIR Override .................................................................................. 8
       2.3 Discussion and Recommendations .................................................................................... 8
                  2.3.1 Delivery Mechanism ............................................................................................ 8
                  2.3.2 Two-Number Caller ID ......................................................................................... 9
                  2.3.3 Number Modification............................................................................................ 9
3. Roamer-Originated Caller ID ................................................................................................... 11
       3.1 Home Network.................................................................................................................. 11
                  3.1.1 Provisioning ....................................................................................................... 11
                  3.1.2 Transfer to Serving Network .............................................................................. 12
       3.2 Serving Network ............................................................................................................... 12
                  3.2.1 Use of Received MDN ....................................................................................... 12


Ref Doc 139 Ver. 1.0                                        4 December 2006                                                                            iii
International Roaming Caller ID                                                                                                      Contents


                  3.2.2 Use of a Dummy Calling Party Number ............................................................ 14
                  3.2.3 Support of CNIR ................................................................................................ 14
       3.3 Two-Number Caller ID Service ........................................................................................ 14
       3.4 Discussion and Recommendations .................................................................................. 15
                  3.4.1 Registration with Full International MDN ........................................................... 15
                  3.4.2 Use of Full International MDN for Roamer-Originated Calls ............................. 15
4. Glossary .................................................................................................................................... 16



                                                                Figures
   Figure 1. Roamer-Terminated Call Flow ...................................................................................... 5



                                                       Revision History

                  Date                       Version                                         Description

   16 April 2006                                 0.1          Initial release


   10 May 2006                                   0.2          Change to CDG format


   7 July 2006                                   0.3          Standards reference update to §3.1.2


   4 December 2006                               1.0          Release Version – No change from previous




Ref Doc. 139, Ver. 1.0                                     4 December 2006                                                                      iv
                                                                1. Introduction
This document describes options and recommendations for delivering the calling party’s
directory number to the called party when at least one of the parties is roaming
internationally. Of particular interest is the format of the delivered number, and its utility
in the network in which it is received.
This work item has been identified as the CDG International Roaming Team Voice and
SMS Working Group’s number one priority for 2006. In general, the service is variously
available to CDMA roamers today – subscribers of some operators, when roaming in
some destinations, will receive and provide an “accurate” calling party number. In most
cases, this number is not of the correct format to allow the called party to simply return
the call without editing the displayed digits.


1.1 Scope

This document covers both delivery of the caller’s number to a subscriber who is
roaming (“roamer-terminated caller ID”), and delivery of the subscriber’s number to the
called party when they make calls while roaming (“roamer-originated caller ID”).
This document deals with international roaming only. Issues related to domestic roaming
may be similar, but are not specifically addressed in this document. In this document the
term “roaming” can generally be taken to mean international roaming.
This document considers voice calls only. Issues related to circuit-switched fax and data
calls may be similar, but are not specifically addressed in this document. SMS and
Packet Data interactions are outside the scope of this document.
This document does not address the provision of Calling Name Presentation service.
This document assumes that Plus Code Dialing is not widely available to roamers.
However, some of the relevant recommendations in IS-875 (aka N.S0027 – “Enhanced
International Dialing, Calling Number Identification & Callback, Calling Party Category
Identification”) are encouraged – see specific sections.
This document does not address Direct Routing Roamer-to-Roamer (DRRR) calls. The
call flow for this service, including Caller ID considerations, is specified in CDG
Reference Document #96.




Ref Doc 139 Ver. 1.0                  4 December 2006                                            1
International Roaming Caller ID                                                   Introduction


1.2 Definitions

The term “caller identification,” or “caller ID,” is used in this document as a general term
to refer to the display of the calling party’s directory number at the called party’s device,
without implying any particular delivery mechanism. It is also used even more generally
to refer to the transmission of the calling party’s directory number when the subscriber of
interest originates a call, regardless of whether the called party possesses the necessary
equipment or subscription information to allow actual display of the number.
The term Calling Party Number (or CgPN), when capitalized, refers specifically to the
ISUP parameter of this name. When not capitalized, it refers to the calling party’s
directory number, which can be transported through the network in various ways.
Carriers may choose to interconnect with their Roaming Partners via a Roaming Service
Provider (RSP). In this document, an RSP is assumed to be capable of examination and
modification of ANSI-41 messages as they transit its equipment.


1.3 Importance

As noted above, caller ID for roamers has received a high prioritization from IRT
operators. Caller ID is a service that is widely available to CDMA subscribers when at
home, and many operators offer the service as a free default.
Making this service available to roamers (when they receive a call) is likely to increase
customer satisfaction, as it will more closely emulate their experience while at home, as
well as allowing them to choose whether or not to answer the call. An accurate, correctly
formatted displayed number may be more likely to generate a return call by the roamer,
increasing operator revenue. Similarly, correct provision of caller ID for calls made by
roamers may increase returned, roamer-terminated calls.
It is assumed in this document that the provision of caller ID for calls to roamers is of
primary interest to CDMA operators, rather than roamer-originated calls.




Ref Doc. 139, Ver. 1.0                4 December 2006                                       2
                            2. Roamer-Terminated Caller ID
This section describes the provision of caller ID service to international roamers when
they receive a call.


2.1 Provisioning

Provisioning information ensures that a subscriber is authorized for the service, and that
the network can advertise its ability to support service delivery.

2.1.1 Subscriber Provisioning
2.1.1.1 CNIP
Subscriber provisioning for caller ID is stored in the HLR, and transferred to the serving
system in the ANSI-41 subscriber profile. In ANSI-41, the caller ID service is referred to
as Calling Number Identification Presentation (CNIP).
ANSI-41/664 defines two separate CNIP services:
   CNIP1: One number (network-provided only) Calling Number Identification
    Presentation
   CNIP2: Two number (network-provided and user-provided) Calling Number
    Identification Presentation.
Use of CNIP2 service is believed to be unusual among CDMA operators today.
Each of these services is assigned two Feature Activity bits inside the
CallingFeaturesIndicator parameter, for a value range of 0-3. The values are as follows:
   0: Not used
   1: Not Authorized
   2: Authorized but de-activated
   3: Authorized and activated
ANSI-41 states that “CNIP2 Feature Activity takes precedence over CNIP1 Feature
Activity”. In some vendors’ MSCs (which only offer a single CNIP service), this is
interpreted such that if a subscriber has CNIP2 = “Not Authorized” and CNIP1 =
“Authorized and activated”, they will not receive CNIP service. It is recommended that
operators confirm with their network vendor the exact interpretation of the provisioning
fields.


Ref Doc 139 Ver. 1.0                 4 December 2006                                         3
International Roaming Caller ID                                  Roamer-Terminated Caller ID


2.1.1.2 Other Caller ID Services
Calling Number Identification Restriction (CNIR) is a service that applies to calls
originated by the provisioned subscriber. See §3.2.3 for information relating to this
service.
CNIR Override is a service that applies to terminating calls, and allows the display of the
calling party’s number at the terminating mobile even if its presentation has been
restricted by the originator. Two bits are defined in the CallingFeaturesIndicator
parameter for CNIR Override Feature Activity, with the same values as the CNIP fields.

2.1.2 Network Support
CNIP support is not explicitly advertised by the serving MSC, however a more general
setting can affect this: the “Profile” bit of the TransactionCapability parameter indicates
whether the MSC “is capable of supporting the IS-41-C profile parameters”. If this bit is
not set to 1, some implementations may not send (or in the case of an RSP may
remove) those bytes of the CallingFeaturesIndicator parameter which include CNIP
feature activity, as they were new for IS41 Rev C.
Some vendors’ MSCs set this bit to 0 even if they are capable of supporting CNIP, to
indicate that they do not support all possible subscriber profile parameters introduced in
IS41 Rev C.
Support for CNIP1 is believed to be widespread among currently deployed MSCs.
Support for CNIP2 and CNIR-Override is less certain.


2.2 Service Delivery
This section covers the invocation of the service when a call is made to a roamer. In this
section various possibilities are discussed – specific recommendations are made in §2.3.


2.2.1 Terminating Call Flow
The call flow for a typical roamer-terminated call is shown in Figure 1 below, and
described at a high level. Subsequent sections discuss the caller ID aspects of each
step in greater detail.




Ref Doc. 139, Ver. 1.0                4 December 2006                                         4
International Roaming Caller ID                                        Roamer-Terminated Caller ID



         Orig                                 RSP                Serving
                         HLR
         MSC                                (if present)          MSC

                                                                                         a
                    LOCREQ
                                                                                         b
                                        ROUTREQ
                                                                                         c
                                                             ROUTREQ
                                                                                         d
                                                   routreq
                                                                                         e
                              routreq
                                                                                         f
           locreq
                                                                                         g
                                                                                         h
                                                                                         i


                             Figure 1. Roamer-Terminated Call Flow



    a) A call is received at a home network MSC for the roaming subscriber. The MSC
       is referred to in this document as the “originating MSC” since it will originate the
       call delivery leg. It may also be known as the home MSC, in-call MSC, or
       gateway MSC. The caller may be a mobile served by this MSC, or a party in
       another network.

    b) The originating MSC sends a LocationRequest message to the HLR to determine
       the current location of the mobile.

    c) The HLR sends a RoutingRequest to the RSP to request a Temporary Local
       Directory Number (TLDN) for the call

    d) The RSP forwards the request to the serving MSC

    e) The serving MSC returns a TLDN.

    f)    The RSP passes the TLDN to the HLR

    g) The HLR passes the TLDN to the originating MSC.

    h) The originating MSC delivers the call to the serving MSC, using the TLDN as the
       called number.

    i)    The roamer is paged, with alerting, call answer and conversation to follow.

2.2.2 Incoming Call to Originating MSC
In order for caller ID to be provided to the terminating subscriber, the calling party
number must be present when the call first enters the roamer’s home network, i.e., when
the call is received by the originating MSC.
When the calling party is a mobile in the home network, the calling party number will be
available as the MDN, stored in the VLR of the MSC serving the caller.



Ref Doc. 139, Ver. 1.0                    4 December 2006                                       5
International Roaming Caller ID                                Roamer-Terminated Caller ID


When the call arrives from outside the mobile network, the calling party number must be
received in the signaling for the incoming call (e.g., ISUP Calling Party Number
parameter in Initial Address Message). It is assumed that numbers will typically be
received in National Significant Number format, e.g., national area code, no country
code, no international or national dialing prefix.
Calls that were initiated from outside the home country may not provide a correct calling
party number when received by the originating MSC. For those that do, it is assumed
that the number will usually be in E.164 format, i.e., Country Code + National Significant
Number, and contain an International indicator (e.g., ISUP Nature of Address indicator
set to “international number”).
For the two-number CNIP service, the second number could be received in the ISUP
Generic Number or Generic Address parameter. For a call originating from a CDMA
mobile, the user-provided number could be sent in the Calling Party Number information
record of an IS-2000 Origination Continuation Message.

2.2.3 Originating MSC Interrogates HLR
Note: ANSI-41 describes two mechanisms for transferal of the calling party number from
the Originating MSC to the Serving MSC: Via ANSI-41; and via ISUP. This section
applies to the ANSI-41 method only. See §2.2.6 and §2.2.7 for more description of the
ISUP method.
The Originating MSC is responsible for transferring the calling party number(s) from the
incoming interface (e.g., ISUP, MFCR2, VLR for IS-2000) to the outgoing ANSI-41
interface in the LocationRequest message.
IS-807 (“TIA/EIA-41-D Internationalization“) notes that when a mobile in its home country
makes a mobile-to-mobile call, the MDN sent in the LocationRequest should be in
National format (implying that an inbound international roamer will use a fully
international MDN – see §3.4.1).
Two calling party number parameters are available in the LocationRequest:
CallingPartyNumberDigits1 (CPND1) and CallingPartyNumberDigits2 (CPND2). CPND1
is used if only one number is available, and (if two numbers are available) to carry the
network-provided number.
The MSC should ensure that the Nature of Number (NoN) octet in these parameters is
set correctly according to the received Nature of Address field (or equivalent) from the
incoming call.

2.2.4 HLR Initiates RoutingRequest
(This section applies only to the ANSI-41 method of calling party number delivery.)
The HLR can include the calling party number(s) received in the LocationRequest in the
CallingPartyNumberString1 (CPNS1) and CallingPartyNumberString2 (CPNS2)
parameters in the RoutingRequest.




Ref Doc. 139, Ver. 1.0               4 December 2006                                       6
International Roaming Caller ID                                 Roamer-Terminated Caller ID


The HLR (knowing the location of the called mobile) has the opportunity to modify the
received CPND1/2 parameters to ensure that they are in a suitable format for receipt in
the serving network. IS-875 specifies procedures for “internationalizing” the calling party
number(s): If the received CNPD parameters have a national NoN, and the mobile is
known to be roaming outside its home country, then the HLR should prefix the home
country code, and set the NoN to international.
A further step could be for the HLR to prefix not only the country code, but also the
International Access Code (IAC) for the serving country. If the home and serving
networks are connected via a RSP that hides the true serving network identity, this may
not be possible for the HLR.


2.2.5 RSP Transfers RoutingRequest
(This section applies only to the ANSI-41 method of calling party number delivery.)
The RSP (if present) is also in a position to modify the calling party number(s) to a
format more appropriate for the serving network. The RSP could perform the IS-875
internationalization, or (perhaps based on previous knowledge of the serving system’s
capabilities) add the International Access Code.

2.2.6 Originating MSC Sends Call Delivery Leg
(This section applies only to the ISUP method of calling party number delivery.)
ANSI-41 notes that the calling party number can be transferred to the serving system in
the ISUP call delivery leg. The originating MSC can transfer the received Calling Party
Number (and Generic Address/Number if present) from the incoming call to the ongoing
call delivery leg.
In today’s networks, the Calling Party Number is often removed or changed as the call
transits the international network to the serving MSC.

2.2.7 Serving MSC Receives Calling Party Number
The serving MSC may receive the calling party number(s) either from the CPNS1/2
parameters in the RoutingRequest Invoke message, or from the incoming ISUP call
delivery leg, or both. ANSI-41 makes no comment as to which method should take
precedence if both are received, and the “MSC CNIP Terminating Call Invocation“
procedure makes no mention of the ISUP parameters.

2.2.8 Serving MSC Passes Calling Party Number to Mobile
Before sending the calling party number to the called mobile, the MSC may make some
modification to the digit string. In a domestic scenario, this could for example involve the
prefixing of a national access code.
For international roaming, the MSC may be able to perform number modifications
instead of or as well as the HLR and RSP to ensure that the presented number is
formatted correctly for the serving network (e.g., addition of country code and IAC). A


Ref Doc. 139, Ver. 1.0               4 December 2006                                       7
International Roaming Caller ID                                 Roamer-Terminated Caller ID


key input to the number modification logic would be the received Nature of Number (or
Nature of Address for ISUP).
The Calling Party Number information record in the IS-2000 Alert With Information
message is used to provide CNIP1 service to the mobile. Provision for carriage of a
second number is assumed to be via the inclusion of a second Calling Party Number
information record, with the screening indicator field set to one of the “user provided”
values.

2.2.9 Mobile Displays Received Number
Most, if not all, CDMA user devices available today support the display of a calling party
number (provided they have a suitable screen).
In the air interface, the Calling Party Number information record contains a
NUMBER_TYPE field which can be set to mean “International number”. Support for this
value will typically require support for Plus Code Dialing in the mobile, something not
widely available today.
Most mobiles will display a name from an addressbook entry if a match is found between
the stored digits and those received over the air. Some mobiles will display a match if a
certain number of least significant digits match (potentially allowing a number formatted
with the IAC and country code to match an addressbook entry even if the number were
stored in home country domestic format).

2.2.10 CNIR and CNIR Override
To preserve the calling party’s privacy, preservation of the caller’s CNIR status is
required as the calling party number is delivered to the serving MSC. The ANSI-41
CPND/CPNS parameters, the ISUP Calling Party Number and Generic Address/Number
parameters and the IS-2000 Calling Party Number information record all include a field
which indicates whether presentation of the number is allowed. Since the subscriber’s
CNIR-Override status is not stored at the mobile, the serving MSC should check this
information in the VLR before sending the Alert With Information Message.
A typical implementation involves transmission of the Calling Party Number information
record, with the Presentation Indicator set to “restricted”, but the actual digits not
present. Other approaches may also be possible.


2.3 Discussion and Recommendations

2.3.1 Delivery Mechanism
As described above, ASNI-41 allows for the transfer of the calling party number(s) to the
serving MSC both via ANSI-41 (LOCREQ and ROUTREQ messages) and via ISUP
(Initial Address Message). Perhaps unsurprisingly, the ANSI-41 method is fully
described in ANSI-41, with only a passing mention to the ISUP approach.
In the ISUP method, the Calling Party Number may not be reliably preserved through the
international network. In addition, some implementations use the roamer’s MDN as the

Ref Doc. 139, Ver. 1.0               4 December 2006                                         8
International Roaming Caller ID                                  Roamer-Terminated Caller ID


Calling Party Number for this leg. Care is required if changing settings for this call leg not
to inadvertently charge the calling party for the international call delivery leg (e.g., based
on international gateway exchange CDRs).
The originating MSC may be less equipped to perform the kind of internationalization on
the CgPN than the HLR is on the CPNS as specified in IS-875.

Recommendation
   Use of the ANSI-41 method is recommended for international roaming. Where the
    serving MSC receives calling party information via both methods, the information
    received via ANSI-41 should take precedence for presentation to the mobile.

2.3.2 Two-Number Caller ID
Although specified in ANSI-41, use of two-number caller ID (aka CNIP2) is believed to
be rare, and the level of support for the mechanism for delivering both numbers over-
the-air is unclear.

Recommendation
   CNIP2 should not be offered for international roaming. Provisioning of CNIP2 in the
    subscriber profile (or RSP manipulation of this field) may still be desired in some
    cases depending on serving MSC parsing of this field (see §2.1.1.1 ).

2.3.3 Number Modification
IS-875 states that “the call back number shall not require editing before use while the
subscriber is located within the country in which the call was received.” In the absence of
Plus Code Dialing, the recommended (by this document) format for presentation to the
mobile is IAC + CC + NSN. For the case where the calling party is from the serving
country (and their calling party number is successfully preserved over the international
leg to the home system), IS-875 notes that the serving system should accept a call to a
number in the serving country prefixed with IAC and country code. This approach seems
easier than requiring the “de-internationalization” of the presentation digits.
In some cases the resulting digit string may exceed the 15-digit limit assumed in ANSI-
664. An example would be a call from a mobile subscriber in China (13-digit E.164 MDN)
to a roamer in Australia (4-digit IAC). Actual limits for mobiles and MSCs are unknown.
Section 2.2 lists several places where the calling party number can be modified. IS-875
states that the HLR should internationalize the number, but no mention is made of
adding the IAC (since the standard assumes Plus Code Dialing capabilities in the
mobile). The recommendations below provide a suggested “division of labor” among the
various network elements. As per §2.3.1, use of the ANSI-41 delivery method is
assumed.
In the absence of any number modification, some serving operators have chosen to
disallow CNIP to inbound roamers, for fear that the display of a number formatted for
dialing in the home network may confuse the roamer, as well as potentially result in call-
back attempts that mistakenly terminate to numbers in the serving country (see §3.2.1.3


Ref Doc. 139, Ver. 1.0                4 December 2006                                       9
International Roaming Caller ID                                  Roamer-Terminated Caller ID


for a similar impact in the opposite direction). There is no billing implication of the
number formatting (other than the roamer being charged for a misdirected call-back call)
– the CPNS parameters from the RoutingRequest are not used to indicate a chargeable
party in any scenario. The assertion is made in this document that the availability of
CNIP in a familiar although non-dialable format is preferable to roamers than no CNIP at
all, and that the adverse impact to both roamers and serving country subscribers would
be negligible.
In some cases the “incorrect” number may be more problematic – for example the New
Zealand “dummy” international Caller ID of 0000 may not be suitable for display in
Australia, where the emergency services number is 000.

Recommendations
   Calls should always be presented to roamers in IAC+CC+NSN format.
   The HLR should modify the CPNS parameters to be in international format, as per IS-
    875.
   The serving MSC should use the received Nature of Number as a key to prefix the
    applicable IAC to the digit string before presentation to the mobile.
   Both the HLR and serving MSC can delegate their number modification
    responsibilities to the RSP, if present.
   In the absence of any number modification capability, CNIP service should still be
    offered to roamers.




Ref Doc. 139, Ver. 1.0                4 December 2006                                     10
                               3. Roamer-Originated Caller ID
This section describes the calling party number(s) that accompany a call made by an
international roamer. The ability for a specific called party to display this number is out-
of-scope for this document, although the format of the number and its general suitability
for display are considered.
The calling party number presented (or offered for presentation) by a roamer depends
on a combination of information provided by the home network, and choices/capabilities
in the serving network. These aspects are discussed in the following subsections.
Provision of a single (network) number only is considered – the issues relating to a
second, user-provided number are addressed in their own subsection.


3.1 Home Network

3.1.1 Provisioning
The key part of the subscriber profile for roamer-originated Caller ID is the Mobile
Directory Number (MDN). This is assigned in the HLR and is transferred to the serving
system at registration time. The format of the MDN is an important factor in determining
whether a meaningful calling party number can be provided for a roamer-originated call.
Possible formats include:
   National: a National Significant Number (NSN), e.g., in the US a 10-digit number.
   National with prefix: in some networks the NSN is prefixed with a national dialing
    code in the MDN.
   Country Code: MDN includes Country Code (CC) and NSN.
   International: as above but with the Nature of Number field set to International. Also
    referred to as “full E.164 format”. This method is recommended in IS-807.
   Absent: Some networks may not send a MDN parameter at all. The MIN is used in
    its place.
Also relevant is the subscriber’s CNIR status. This is carried in two bits in the
CallingFeaturesIndicator parameter. The meaning of the various values is the same as
given in §2.1.1.1 .




Ref Doc 139 Ver. 1.0                  4 December 2006                                          11
International Roaming Caller ID                                   Roamer-Originated Caller ID



3.1.2 Transfer to Serving Network
When a subscriber registers from a location known to be outside his/her home country,
the HLR could in theory modify the returned MDN to ensure it is in International format.
This behavior is roughly analogous to the calling party number modification described in
IS-875. Care would be required in any cases where the MDN was required by another
system, e.g., the MC for mobile-originated SMS, or the billing system for CIBER 22
records.
A similar modification could also be performed by the RSP (if present), which could have
the advantage that all elements in the home network need not be aware of the change.
IS-807 notes that “MobileDirectoryNumber … should be encoded as International when
… it is known that the Serving MSC can accept … this format“. The presence of the
MSCIdentificationNumber parameter is taken as an indication that the MSC can accept
an internationally formatted MDN. This approach does not distinguish between national
and international roaming.


3.2 Serving Network

On receipt of the roamer’s MDN in the subscriber profile, the serving network has
various handling options:
   Use the received MDN: While this allows for true Caller ID for roamer-originated
    calls, it opens up the possibility of some negative side effects.
  Use a dummy calling party number: All roamers use the same number. This is a
   simple option for the serving network, but does not allow for true Caller ID.
These options are described in detail in the following subsections.

3.2.1 Use of Received MDN
In a basic sense, this approach typically requires no special handling in the MSC – use
of the subscriber’s MDN as the calling party number for originated calls should be the
default behavior for the MSC. Additional modifications may be possible at the MSC, e.g.,
the prefixing of the roamer’s Country Code (providing the MSC knows this – may not be
possible if all roamers appear to come from the RSP as home system).
Uses of and potential issues with the MDN are discussed below.

3.2.1.1 Presentation of Number and Call-Back
Presentation of the MDN regardless of its format would often allow the called party to
recognize the caller, especially if there were repeated calls. However it would be more
convenient for the called party if the number were to be presented in a format which
enabled return of the call (“call-back”) with a minimum of modification to the presented
digit string.
For a call-back from a number anywhere other than in the roamer’s home country, an
international call is required. This is greatly facilitated by the presence of the Country
Code in the calling party number.

Ref Doc. 139, Ver. 1.0                4 December 2006                                        12
International Roaming Caller ID                                   Roamer-Originated Caller ID


The serving network may choose (assuming it has the capability) to prefix the local IAC
to the calling party number, so that call-back requires no modification at all from
numbers in the serving country. Assuming that the Calling Party Number was
successfully passed for international calls, call-back may not be so simple from other
countries if they use a different IAC. If the number is not passed, nothing is lost by
formatting the number exclusively for the serving country.
Alternatively, the serving network may choose to send the calling party number in full
E.164 format (e.g., an international Nature of Address in the ISUP Calling Party
Number), and let the receiving network apply modifications as it deemed necessary.
Legislation in particular countries may require that calls to emergency services present a
true calling party number that allows for the call to be returned (e.g., if the connection is
lost mid-call). Special handling may be needed for compliance if calls from inbound
international roamers are not exempt.

3.2.1.2 MDN Clash
If the MDN is received from the home network (or RSP) in anything other than full
international format, the possibility exists that the MDN may be the same as that of
another subscriber in the same MSC (either a local subscriber or an inbound roamer
from another country).
The impacts of such a clash are unknown. MSID is typically the primary key for a VLR
entry, however some vendor documentation states that their MSC is unable to serve two
subscribers with the same MDN. Confusing Caller ID from the roamers’ originating calls
may be the least of the serving operator’s concerns.
If an RSP is used an MDN clash between two roamers regardless of location may still
have an impact (depending on the RSP internal architecture).
Use of full E.164 format MDNs should remove this risk. Even the use of the “Country
Code” format described in §3.1.1 is susceptible to clashes, e.g., “972…” could refer to a
number in Israel or Texas.

3.2.1.3 MDN Conflict
“MDN Conflict” is used to refer to the case where the received roamer’s MDN is the
same as (or similar to) another number in the serving country. The issues are distinct
from the specific MSC processing problems that may occur in the “MDN Clash” scenario
described above.
A roamer that originates a call using the calling party number of another (e.g., PSTN)
subscriber may potentially cause billing problems – for example, if international calls are
billed from CDRs produced at the international gateway exchange, the PSTN subscriber
may be charged for calls originated by the roamer. The likelihood of such impacts is very
dependent on the billing mechanisms used in each individual serving country.
Call-back may also be affected, with the wrong subscriber receiving returned calls. If the
roamers’ number length is longer than that used for domestic subscribers, return call




Ref Doc. 139, Ver. 1.0                4 December 2006                                      13
International Roaming Caller ID                                  Roamer-Originated Caller ID


attempts for a range of roamers could potentially all be sent to a single subscriber. Again
the exact risk will depend on individual network configurations.
The risk of such impacts is likely to be mitigated by the use of the full E.164 format MDN.
Even in this case the result is dependent on the capability of the receiving network to
react to the international indicator (e.g., Nature of Address) to allow roamer calls to be
distinguished from the domestic dialplan.

3.2.1.4 Unrecognized MDN
This scenario refers to the possibility that calls may be refused because an exchange
does not believe it will be able to bill the necessary party. A typical example could be the
international gateway exchange in the serving network – it may refuse to allow calls from
international numbers to enter from the domestic side of the exchange, fearing fraud.
A similar situation could arise in the home network for a roamer-originated call home.
The gateway exchange may not allow calls with a home country calling party number to
enter from the international side of the exchange, fearing circular routing and/or fraud.

3.2.2 Use of a Dummy Calling Party Number
Some operators choose not to use the received MDN as the calling party number for
roamer-originated calls. Instead, a per-network or per-MSC number is applied to all
roamer originations. Use of this dummy number removes any chance of conflict with the
serving country numbering plan (although an MDN clash in the serving MSC may still
have an impact). No meaningful Caller ID can be provided for roamer-originated calls
with such an approach. Rather than reveal the (non-individual, and useless for call-back)
dummy number, CNIR may be globally applied to use of this calling party number.
Regardless of the use of a dummy number, the true MDN must be maintained in the
VLR and used for other purposes as appropriate (e.g., MO-SMS addressing, CIBER 22
population).

3.2.3 Support of CNIR
The serving MSC should honor the subscriber’s received Calling Number Identification
Restriction status, and map this into the appropriate parameters in the call signaling
(e.g., ISUP “Address presentation restricted indicator”).


3.3 Two-Number Caller ID Service

If present, a second calling party number is designated as “user-provided”. As such, it is
stored in the mobile, and is independent of any home network provisioning information. It
may be transmitted when a call is made via the Calling Party Number information record
of the Origination Continuation Message. The user could theoretically modify this
number themselves prior to making the call to add any desired formatting.
The extent of support for transmission of a user-provided calling party number among
mobiles and MSCs is unknown, although its use is believed to be rare.


Ref Doc. 139, Ver. 1.0               4 December 2006                                     14
International Roaming Caller ID                                    Roamer-Originated Caller ID


3.4 Discussion and Recommendations

3.4.1 Registration with Full International MDN
A full international MDN (including international Nature of Number indicator) is the best
format for allowing meaningful Caller ID for roamer-originated calls, and for preventing
clashes with other mobile and fixed subscribers. It is the recommended approach in IS-
807.
The level of support among currently deployed serving MSCs for receiving an
international MDN (and correctly storing the international indicator) is unknown

Recommendations
       The HLR should transmit the MDN in full E.164 international format to an
        international destination. (Use of an international MDN for domestic roaming is
        out of scope).
       Alternatively, the HLR can designate the internationalization of the MDN to the
        RSP (if present)

3.4.2 Use of Full International MDN for Roamer-Originated Calls
Use of a dummy calling party number does not allow for correct Caller ID on a roamer-
originated call. Assuming the received (internationally formatted) MDN is used instead,
the MSC may choose to add the IAC for the serving country. This function seems more
appropriate to the receiving network – delivery of the calling party in full E.164 format will
allow the receiving network to determine the best way to present this number to its
subscribers (which may or may not be capable of Plus Code Dialing, for example).
Where the serving network is also the receiving network (i.e., a call from an inbound
roamer to a domestic mobile subscriber on the same network) the IAC may be added as
a terminating function (similar to §2.2.8).
The transport of a full international calling party number may have impacts on networks
outside the serving network. Coordination with the appropriate national authority may be
required before implementing changes.

Recommendations
   A dummy number should not be used for roamer originations.
   The transmitted calling party number should be the full E.164 MDN, including
    international indicator. IAC should not be prefixed by the MSC as part of its handling
    of the origination.




Ref Doc. 139, Ver. 1.0                 4 December 2006                                       15
                                                                       4. Glossary

Acronym                Meaning

CC                     Country Code

CgPN                   Calling Party Number

CLIP                   Calling Line Identification Presentation. See CNIP.

CLIR                   Calling Line Identification Restriction. See CNIR

CNIP                   Calling Number Identification Presentation

CNIR                   Calling Number Identification Restriction

CPND                   Calling Party Number Digits

CPNS                   Calling Party Number String

HLR                    Home Location Register

IAC                    International Access Code

ISUP                   Integrated Services Digital Network User Part

MDN                    Mobile Directory Number

MSC                    Mobile Switching Center

NoN                    Nature of Number

NSN                    National Significant Number

PSTN                   Public Switched Telephone Network

RSP                    Roaming Service Provider

VLR                    Visitor Location Register




Ref Doc 139 Ver. 1.0           4 December 2006                                  16

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:16
posted:6/10/2011
language:English
pages:20