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fed31ee936becb3fd670e1e6e2ae795e
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10.76
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8.1 Approvals within STCs
|
SMG11 Approval of Draft Stage 1 Specification at SMG11 #11 (7-11 June 1999)
SMG1 Presentation of Draft Stage 1 Specification for information, Q3 1999
Presentation of further specifications and allied information [TBD]
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10.76
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9 Specifications for Noise Suppression for the AMR Codec
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10.76
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9.1 New Specifications
|
Not Complete!
New specifications
GSM No.
02.76
Title
Noise Suppression for the AMR Codec; Service Description; Stage 1
Prime rsp STC
SMG11
2ndary rsp STC(s)
SMG1
Presented for info at SMG"
#28
Approved at SMG"
Comments
GSM No.
Title:
Prime rsp. STC:
2ndary rsp. STC(s):
presented for information at SMG#
approved at SMG#
Comments
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10.76
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9.2 Change Requests to Existing Specifications
|
[TBD]
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10.76
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10 Backwards Compatibility
|
The additions and changes caused by the work item covering Noise Suppression for the AMR Codec shall not cause backward compatibility problems with GSM phase 2 or phase 2+ equipment.
Annex 1 Project Plan (Draft)
•
•
PHASE, TASK or DEADLINE
PROVISIONAL DATE
Declaration of intention to submit a candidate
CLOSED
Agree Test Methodology or methodologies
SMG11 #9 - COMPLETED
Access to AMR C code
SMG#28 - COMPLETED
Finalise Design Constraints
Before the start of SMG11#10 - COMPLETED
Final Estimate of total cost
SMG11#11 - COMPLETED
Formal commitment to propose a candidate
During SMG11 #11 - COMPLETED
Requirements set and...
- approved by SMGll
- approved by SMG
SMG11 #11 - COMPLETED
SMG #29 - COMPLETED
Final commitment from proponents to provide funding
SMG#29 - COMPLETED
Final List of experimental conditions
Joint SQ/AMR-NS Meeting 27-29 July
Freeze Selection Rules
August 10th (with possible exception re. new proposals for using subjective SNR improvement measures - deadline August 15th)
Host, Listening, and Noise labs Identified.
Associated contracts finalised
August 20th
Host labs have access to material (speech and noise)
August 20th
Freeze Test Plan
September 3rd
Host Labs complete pre-processing of material
September 10th
ETSI receive candidates' executables
September 10th
Candidates send required cross checking data to cross-checking organisation (so that it is received no later than 3 days later)
October 1st
Candidates send processed material to host labs (so that it is received no later than 3 days later)
October 8th
Host Labs send 1st set of material to test houses (so that it is received no later than 3 days later)
October 15th
Host Labs send final set of material to test houses (so that it is received no later than 3 days later)
October 22nd
ETSI receives all remaining deliverables from candidates
November 15th
Run selection test
Results on reflector on December 3rd
Select a solution
• approved by SMG11
• approved by SMG
SMG11 (December 6-10)
SMG#31 (February 14-168)
Optimisation
Schedule and scope Tto be decided
Verification
Schedule and scope Tto be decided
Final drafting of standard and CRs
Schedule and scope Tto be decided
Approval of standards and CRs
• SMG11
• SMG
SMG11 (24-28 January)
SMG#30 (February 14-168)
Characterisation Testing
Scehdule and scope Tto be decided (and is subject to the availability of funding)
History
Document history
V0.0.1
August 1998
First Draft
V.o.o.2
January 1999
2nd Draft
V.0.0.3
January 1999
3rd Draft with updated work plan
V.0.0.4
February 1999
4th Draft with updated work plan
V.0.0.5
March 1999
5th Draft with updated work plan
V.0.0.6
April 1999
Editorial changes
V0.0.7
June 1999
Updated work plan and associated dates
V0.0.8
August 1999
Updated work plan and associated dates
Editor:
Steve Aftelak
Motorola
Tel: +44 1793 566261
Fax: +44 1793 566225
Email: [email protected]
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11.18
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1 Scope
|
The present document defines the aspects of the Subscriber Identity Module - Mobile Equipment (SIM - ME) interface which are based on 1.8V technology to be used in the Mobile Station (MS). It specifies the electrical and logical requirements necessary for the operation of the 1.8V SIM - ME interface where it differs from GSM 11.11 [1]. For all aspects of the SIM - ME interface which are not covered by the present document, GSM 11.11 [1] applies.
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11.18
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2 References
|
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or non‑specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
• A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number.
• For this Release 1998 document, references to GSM documents are for Release 1998 versions (version 7.x.y).
[1] GSM 11.11: "Digital cellular telecommunications system (Phase 2+); Specification of the Subscriber Identity Module - Mobile Equipment (SIM - ME) interface".
[2] GSM 11.12 (ETS 300 641): "Digital cellular telecommunications system (Phase 2); Specification of the 3V Subscriber Identity Module - Mobile Equipment (SIM - ME) interface".
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11.18
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3 Definitions, abbreviations and symbols
| |
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11.18
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3.1 Definitions
|
For the purposes of the present document, the following definitions apply.
1.8V technology SIM: A SIM operating at 1.8V ± 10% and 3V ± 10%.
1.8V technology ME: An ME operating the SIM - ME interface at 1.8V ± 10% according to the present document and 3V ± 10% according to GSM 11.12 [2].
1.8V only ME: An ME only operating the SIM - ME interface at 1.8V ± 10% according to the present document.
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11.18
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3.2 Abbreviations
|
For the purposes of the present document, the following abbreviations apply:
ATR Answer To Reset
CLK Clock
IC Integrated Circuit
I/O Input/Output
ME Mobile Equipment
MS Mobile Station
RST Reset
SIM Subscriber Identity Module
|
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11.18
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3.3 Symbols
|
For the purposes of the present document, the following symbols apply.
tF fall time
tR rise time
VIH Input Voltage (high)
VIL Input Voltage (low)
VOH Output Voltage (high)
VOL Output Voltage (low)
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11.18
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4 1.8V technology
| |
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11.18
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4.1 1.8V technology SIM
|
The SIM shall operate on both 3V ± 10% according to GSM 11.12 [2], and on 1.8V ± 10% according to the present document. If the ME supplies 3V to the SIM, both the ME and the SIM shall operate according to GSM 11.12 (ETS 300 641) [2]. The logical operation of the 1.8V technology SIM shall be as defined in GSM 11.11 [1]. The 1.8V technology SIM shall not give an ATR if operated at a supply voltage of 1.4V or below.
A 1.8V technology SIM may operate at 5V. If the 1.8V technology SIM operates at 5V it shall meet the electrical specifications as defined in GSM 11.11 [1].
Clock stop mode shall be supported by the SIM. The SIM shall indicate "Clock Stop Allowed" in the file characteristics of the status information as specified in GSM 11.11 [1].
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11.18
|
4.2 1.8V technology impact
|
When supplied with the supply voltage as specified in the present document the SIM shall be operated with a clock frequency of 1 to 4 MHz.
|
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11.18
|
4.3 1.8V technology SIM Identification
|
The 1.8V technology SIM shall contain an identification. The identification is coded on bits 5-7 in byte 14 of the status information as follows:
Table 0: SIM Supply Voltage Indication
SIM Supply Voltage
Bit 7
Bit 6
Bit 5
5V only SIM
0 (RFU) 1
0 (RFU) 1
0 (RFU) 1
3V Technology SIM
0 (RFU) 1
0 (RFU) 1
1
1.8V Technology SIM
0 (RFU) 1
1
1
Future Class
1
1
1
NOTE 1 The bits marked (RFU) are set to ‘0’ and reserved for future use in the SIMs. The coding schemes relies on the fact that RFU bits are set to ‘0’.
The procedure for deriving the identification bit shall be performed by the ME immediately after the Answer To Reset (ATR) and before issuing any other command. The procedure consists of the two commands "SELECT GSM" and "STATUS/GET RESPONSE"
|
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11.18
|
4.4 1.8V technology ME
|
The 1.8V technology ME shall initially activate the SIM with 1.8V according to this specification.
If the ME detects a 1.8V technology SIM, the ME may operate the SIM at 1.8V according to this specification. If the ME detects a 3V SIM, the ME shall switch to 3V operation as defined in GSM 11.12 [2] using the procedure as defined in subclause 4.7. If switching is performed, it shall take place before issuing any further commands as defined in paragraph 4.3.
If a faulty ATR is received at 1.8V, the ME shall initiate the error handling procedure described in GSM 11.11 [1] with the supply voltage remaining at 1.8V. If the error handling does not result in an errorless ATR, the ME shall activate the SIM at 3V. Activation at 3V shall be performed in accordance with GSM 11.12 [2].
If no ATR is received at 1.8V, the ME shall deactivate the SIM and activate it at 3V according to GSM 11.12 [2]. If a correct ATR is not received at 3V or the ME detects a 5V only SIM the ME shall reject the SIM without issuing any further commands.
If a 1.8V technology ME detects a SIM that indicates a future class the ME shall not activate that SIM at 3V.
|
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11.18
|
4.5 1.8V Only ME
|
The 1.8V only ME activates the SIM at 1.8V.
If the ME is able to detect a 3V technology SIM according to the procedure in subclause 4.3, or if the procedure cannot be completed, the ME shall deactivate and reject the SIM immediately (maximum of 5s) without issuing any further command.
If an ATR is corrupted or not received by the ME, error handling according to sub clause 5.10 of GSM 11.11 [1] shall apply.
|
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11.18
|
4.6 Activation and deactivation
|
The ME shall connect, activate and deactivate the SIM in accordance with the operating procedures specified in GSM 11.11 [1] taking into account the electrical characteristics specified in clause 5 of the present document. In particular, Vcc is powered when it has a value between 1,62 V and 1,98 V.
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11.18
|
4.7 Supply voltage switching
|
MEs supporting both 1,8V and 3V operation may switch between the two supply voltages. Switching shall always be performed by deactivating the SIM and activating it at the new supply voltage. Activation and deactivation of the SIM with 3V shall be according to GSM 11.12 [2], whereas activation and deactivation of the SIM with 1,8V shall be according to the present document.
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11.18
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4.8 Cross compatibility
|
Cross compatibility means that the ME supports 1,8V and 3V operation. This is, however, optional for the ME. In case of the 1,8V technology ME, cross compatibility is provided, whereas, a 1,8V only ME requires a 1,8V technology SIM for operation. However, the 1,8V technology SIM (see definitions and subclause 4.1) ensures cross compatibility.
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11.18
|
5 Electrical specifications of the SIM - ME interface
|
The electrical specification given in the present document covers the supply voltage range from 1,62V to 1,98V. The supply voltage range from 2,7V to 3,3V is specified in GSM 11.12 [2]. For each state (VOH, VIH, VIL and VOL) a positive current is defined as flowing out of the entity (ME or SIM) in that state. Vpp is not supported by the 1,8V technology ME or the 1,8V technology SIM.
When the SIM is in idle state the current consumption of the card shall not exceed 200 µA at 1 MHz at +25°C. When the SIM is in clock stop mode the current consumption shall not exceed 100 µA at +25 °C.
The ME shall source the maximum current as defined in table 4. It shall also be able to counteract spikes in the current consumption of the card up to a maximum charge of 12 nAs with no more than 400 ns duration and an amplitude of at most 60 mA, ensuring that the supply voltage stays in the specified range.
The clock duty cycle shall be between 40 % and 60 % of the period during stable operation. A clock cycle is defined at 50% of Vcc from rising to rising edge or falling to falling edge. When switching clock frequencies MEs shall ensure that no pulse is shorter than 100 ns which is 40 % of the shortest allowed period.
The ME need not provide contact C6 (Vpp). Contact C6 shall not be connected in the ME if provided.
Table 1: Electrical characteristics of I/O under normal operating conditions
Symbol
Conditions
Minimum
Maximum
Unit
VIH
IIHmax = ± 20 µA (Note 2)
0,7 x Vcc
Vcc+0,3
V
VIL
IILmax = + 1 mA
- 0,3
0,2 x Vcc
V
VOH (Note 1)
IOHmax = + 20 µA
0,7 x Vcc
Vcc (Note 3)
V
VOL
IOLmax = - 1mA
0 (Note 3)
0,3
V
tR tF
Cin = Cout = 30 pF
1
µs
NOTE 1: It is assumed that a pull-up resistor is used on the interface device (recommended value: 20 k ).
NOTE 2: During static conditions (idle state) only the positive value can apply. Under dynamic operating conditions (transmissions) short term voltage spikes on the I/O line may cause a current reversal.
NOTE 3: To allow for overshoot the voltage on I/O shall remain between -0,3V and Vcc+0,3V during dynamic operation.
Table 2: Electrical characteristics of Clock (CLK) under normal operating conditions
Symbol
Conditions
Minimum
Maximum
Unit
VOH
IOHmax = + 20 µA
0,7 x Vcc
Vcc (Note )
V
VOL
IOLmax = - 20 µA
0 (Note )
0,2 x Vcc
V
tR tF
Cin = Cout = 30 pF
50
ns
NOTE: To allow for overshoot the voltage on CLK should remain between -0,3V and Vcc+0,3V during dynamic operations.
Table 3: Electrical characteristics of RESET (RST) under normal operating conditions
Symbol
Conditions
Minimum
Maximum
Unit
VOH
IOHmax = + 20 µA
0,8 x Vcc
Vcc (Note)
V
VOL
IOLmax = -200 µA
0 (Note)
0,2 x Vcc
V
tR tF
Cin = Cout = 30 pF
400
µs
NOTE: To allow for overshoot the voltage on RST should remain between -0,3V and Vcc +0,3V during dynamic operations.
Table 4: Electrical characteristics of Vcc under normal operating conditions
Symbol
Minimum
Maximum
Unit
Vcc
1,62
1,98
V
Icc
4 (Note)
mA
NOTE: The supply current at 1,8V refers to a clock frequency of 4 MHz.
Annex A (informative):
Change history
This annex lists all change requests approved for this document since the the present document was approved by ETSI SMG.
SMG#
SMG
tdoc
SMG9
tdoc
VERS
CR
RV
PH
CAT
SUBJECT
Resulting
Version
s28
P-99-180
98p188
2.0.0
R98
Approval of final draft by SMG
7.0.0
History
Document history
V7.0.1
July 1999
Publication
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71e1f5e836af6acf69f6cf1aeaf24ba6
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11.10-2
|
1 Scope
|
The present document provides the Protocol Implementation Conformance Statement (PICS) proforma for Global System for Mobile Stations (MSs), operating in the 900 MHz and 1 800 MHz frequency band (GSM 900 and DCS 1 800) within the European digital cellular telecommunications system (Phase 2), in compliance with the relevant requirements, and in accordance with the relevant guidance given in ISO/IEC 9646‑7 [3] and ETS 300 406 [1].
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11.10-2
|
2 References
|
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or non‑specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
[1] ETSI ETS 300 406 (January 1995): "Methods for testing and Specification (MTS); Protocol and profile conformance testing specifications; Standardization methodology".
[2] (void)
[3] ISO/IEC 9646‑7 (1995): "Information technology - Open systems interconnection - Conformance testing methodology and framework - Part 7: Implementation Conformance Statements".
[4] to [56] (void)
[57] 3GPP TS 51.010-2 version 4 (Release 4): "Mobile Station (MS) conformance specification; Part 2: Protocol Implementation Conformance Statement (PICS) proforma specification".
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11.10-2
|
3 Definitions and abbreviations
|
(void)
|
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11.10-2
|
4 Requirements
|
The requirements of the present document are provided in 3GPP TS 51.010-2 [57].
Annex A (normative):
(void)
Annex B (informative):
Change history
ETSI Document history
December 1995
v4.14.0
Public Enquiry PE 97: 1995-12-04 to 1996-03-29
May 1996
v4.15.0
Vote V 103: 1996-05-20 to 1996-07-26
Change history
Date
TSG #
TSG Doc.
CR
Rev
Subject/Comment
Old
New
2001-08
GP-06
GP-011474
A047
Inclusion of pointer to the maintained specification.
Conversion to 3GPP TS format.
4.15.0
4.16.0
|
6e5fdf15efa25f132d2e779f583f3558
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23.920
|
1 Scope
|
The present document covers issues related to the evolution of the GSM platform towards UMTS with the overall goal of fulfilling the UMTS service requirements, the support of the UMTS role model, support of roaming and support of new functionality, signalling systems and interfaces.
|
6e5fdf15efa25f132d2e779f583f3558
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23.920
|
2 References
|
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or non‑specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
• A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number.
[1] ETSI TC-SMG UMTS TS 22-.001: "Services Principles"
[2] ETSI TC-SMG GSM TS 0323.002
[3] ETSI TC-SMG GSM TS 0323.060
[4] ETSI TC-SMG GSM 11.14
[5] ETSI TC-SMG GSM 30.01
[6] ETSI TC-SMG GSM TS 23.001.
[7] TG.3x6.
[8] UMTSYY.01, UE-UTRAN Radio Interface Protocol Architecture – Stage 2
[9] UMTSYY.03, Description of UE states and Procedures in Connected Mode
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23.920
|
3 Definitions and abbreviations
| |
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23.920
|
3.1 Definitions
|
Editors note : Reference to Definition document required.
For the purposes of the present document, the [following] terms and definitions [given in ... and the following] apply.
<defined term>: <definition>.
example: text used to clarify abstract rules by applying them literally.
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23.920
|
3.2 Abbreviations
|
For the purposes of the present document, the following abbreviations apply:
<ACRONYM> <Explanation>
|
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23.920
|
4 UMTS Concepts
|
Section 8 contains concepts that are considered as stable within SMG12 and no further input is expected but it should also be noted that consensus could not be reached on their use within UMTS.
|
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23.920
|
4.1 Reduction of UMTS signalling
| |
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|
4.1.1 GLR Concept
|
The benefits of the Gateway Location Register (GLR) are:
• reduction in signalling traffic between networks.
• potential enhancements to mobile terminated call handling
|
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23.920
|
4.1.1.1 Overview of the GLR Concept
|
The GLR is a node between the VLR and the HLR, which may be used to optimise the handling of subscriber location data across network boundaries.
In Figure 1, the GLR interacts with HLRa and VLRb for roamers on Network B. The GLR is part of the roaming subscriber's Home Environment. When a subscriber to HLRa is roaming on Network B the GLR plays the role of an HLR towards VLRb and the role of a VLR towards HLRa. The GLR handles any location change between different VLR service areas in the visited network without involving HLRa.
Figure 1: GLR Overview
The sequence of events when the subscriber roams to network B is as follows:
• VLRb sends the registration message to HLRa via the GLR, (i.e. HLRa stores the GLR's SCCP address and the GLR stores VLRb's SCCP address).
• HLRa returns the subscriber profile data
• The subscriber profile is stored in the GLR and VLRb
As the roaming subscriber moves between VLRs in network B, then the GLR is updated, but no message is sent to HLRa, therefore the number of messages between Network A and Network B is reduced. The reduction in signalling traffic is a significant benefit when the two networks are far apart, e.g. between Europe and Japan.
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23.920
|
4.1.1.2 Applications of the GLR
|
In addition to reducing the amount of mobility related signalling between networks, the GLR's function might also be extended to other aspects. These include the following:
• Enhancements for mobile terminated call handling
• Support for the Virtual Home Environment of a roaming subscriber
• Reduction of CAMEL signalling traffic between the visited and home network
• Hiding local variations in signalling between networks
• Further study is needed on these issues
|
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23.920
|
4.1.2 Super-Charger
|
The signalling load associated with subscriber roaming can be high when either the MSC/VLR areas are small or the subscriber travels significantly. The Super-Charger concept aims to optimise signalling associated with subscriber data management by retaining subscription data in previously visited VLRs, where possible.
The benefits of the Super-Charger concept are:
• Reduction of signalling traffic for subscribers located in the home PLMN,
• Reduction of signalling traffic between the visited PLMN and the home PLMN,
• No new network nodes are required,
• Applicable to a wide range of protocol used for the transfer of data.
|
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23.920
|
4.1.2.1 Overview of the Super-Charger Concept
|
The concept of the Super-Charged network is described with examples from GSM mobility management. However, Super-Charger can be applied to other scenarios and protocols. This is a further study.
Super-Charger retains subscriber data stored in VLRs after the subscriber has moved to a location area served by a different VLR. The HLR performs the insertion of subscriber data to the VLR serving the location area to which the subscriber has roamed. The subscriber data stored at previously visited VLRs shall not be maintained while the subscriber is located in a location area serviced by a different VLR.
When the subscriber moves to a location area served by a VLR that has retained the subscriber’s subscription data, the VLR shall indicate to the HLR whether subscriber data is required. If the VLR indicates that subscription data is not required but the user’s subscription data has changed the HLR shall send the new subscription data to the VLR. Figure x 2 shows an example message flow in a Super-Charged network.
To ensure data consistency for super-charged VLRs a sequence numbering method can be used. A sequence number is added to the subscriber data record. This sequence number is incremented whenever the subscriber data record is changed for any reason. The sequence number is sent to the VLR in ISD. For non-super-charged VLRs this can be ignored. For super-charged VLRs it is stored and returned to the HLR in subsequent UpdateLocation messages. The HLR can then compare this sequence number with the value currently stored in the HLR to determine if the cached data is still valid.
With the Super-Charger activated subscriber information is no longer deleted from the VLR database when a mobile station moves from the location area served by the VLR. This results in the continuous growth of the VLR database size. Consequently, a new VLR data management system is required so that the VLR can handle newly arrived mobile stations. Two options for subscriber data management systems are:
• subscriber data for subscribers that are not currently served by the VLR shall be deleted periodically using a VLR audit system and/or,
• subscriber data for subscribers that are not currently served by the VLR shall be deleted dynamically to make room for the newly arrived subscribers.
Figure 2: Example message flow in a Super-Charged network.
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23.920
|
4.1.3 Turbo Charger
|
The signalling load associated with subscriber roaming can be high when either the location areas are small or the subscriber travels significantly. The Turbo-Charger concept aims to optimise signalling associated with subscriber data management by assigning one MSC/VLR to perform the Call Control and Mobility Management functions while the subscriber remain attached or until signalling routes require further optimisation.
The benefits of the Turbo-Charger concept are:
• the substantial reduction in signalling traffic for subscribers located in the home PLMN,
• the substantial reduction in signalling traffic between the visited PLMN and the home PLMN,
• no new network nodes are required,
• applicable to a wide range of protocol used for the transfer of data.
The disadvantages of the turbo-charger concept are:
• Connections are required from the access network to be fully meshed to all MSCs in the turbo-charger area.
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4.1.3.1 Overview of the Turbo-Charger Concept
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A Turbo-Charged network constitutes a network architecture designed to reduce mobility management costs and provide automatic load-sharing between MSC/VLRs.
The architectural philosophy is to equally divide the subscribers between the available MSC/VLRs, irrespective of their location. In the context of GSM, this could be achieved by placing a routing function (e.g. evolved STP) between the BSC and the pool of MSC/VLRs. The purpose of the routing function is to route A-interface messages to the MSC/VLR that is serving the mobile station. The solution requires the MS to store a discriminate that can be used to identify the serving MSC/VLR and for routing to be applied on this discriminate on the connection between the MSC/VLR and access network. A TMSI partitioning scheme could be utilised. This scheme allocates a sub-set of the TMSI range to each MSC/VLR, Figure 3. The A-interface messages are then routed to the right MSC based on the TMSI. This could be done by a routing function external to the access network implying no access network modification (see figure 3). If a TMSI partitioning scheme is used then new SIM cards are not required.
The temporary identity used for paging (TMSI) must be unique within all the MSCs in the turbocharger area. This implies that there must be a mechanism to ensure that this requirement is met for turbocharged MSCs (e.g. TMSI partitioning).
Two mechanism to provide load-sharing are envisaged, random load-sharing and dynamic load-sharing.
Random load-sharing requires the routing function to randomly assign a MSC/VLR to serve a particular mobile station when it first comes in to the network. Regardless of where the mobile is the same MSC/VLR will always serve it provided the mobile remains in the area served by all the turbocharged MSC/VLRs linked by the routing function.
In large metropolitan areas where subscribers are served by multiple MSC/VLRs, some MSC/VLRs may be very busy while others are not fully utilised. Dynamic load-sharing requires the implementation of an intelligent router. Since the routing function routes all A-interface traffic, it can participate in load-sharing and balancing based on the current loading of each MSC however linkage between MSC load and the routing algorithm would be required.
In the case of a Turbo-Charged network where the network is sub-divided into large regions, further optimisation can be achieved by adding the Super-Charger functionality.
Figure 3: Example of GSM Turbo-Charger Network Architecture
In the context of UMTS, the routing function becomes a feature of the RNC.
Figure 4: Example of UMTS Turbo-Charger Network Architecture
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4.1.4 Relationship between GLR and TurboCharger
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The GLR and TurboCharger are two independent schemes for reducing the amount of MAP traffic generated in UMTS networks.
• The GLR works by reducing traffic between PLMNs associated with Location Updates. This is achieved by "caching" the roaming subscriber's data in the visited network
• The TurboCharger works by eliminating the need to perform location updates. The same VLR can hold a subscriber's data for the duration of his attachment to the network.
A TurboCharged network requires that each MSC/VLR can physically connect to all RNCs. Therefore TurboCharging may be best suited to areas of the network characterised by dense geographic coverage. On the other hand, the GLR function is independent of the network density.
The network structure shows that the GLR and a TurboCharged area within the same PLMN are independent. In fact, it shows benefits from using the two techniques in the same network. The Turbo-Charger reduces the location registration signals between the MSC/VLR and GLR:
• There is no new update location signal between MSC/VLR and GLR if roamer moves inside of the Region A.
• There is no new update location signal between GLR and HLR if roamer moves between regions.
Figure 4bis. [editor's note: to be deleted]
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5 Key issues
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{Editors note: These key issues have arisen from the scenario work, it is agreed within SA 2 that the focus should be on solving these key issues, Once these issues have become relatively stable, they are moved to 23.121 or removed from this document}. Study of these items is ongoing.
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5.1 Core network transport
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• L1 and L2 technologies
• Signalling protocols
• How to use ATM?
• Nx64k transport
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5.2 Core network layer 3
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5.2.1 Common Communication Channel
A common communication channel (name to be defined) provides nodes of the Core Network the ability to reach every RNC of the UTRAN. This communication channel can be used for application like SMS cell broadcast or location services (LCS).
This communication mechanism would use e.g. an IP routing functionality of the 3G-SGSN. The according protocol stack is outlined in figure 5.
Figure 5: Protocol Stack of the Common Communication Channel
The placeholder Xx should be replaced by the according reference points of the applications e.g. Bc for cell broadcast.
The following issues until now are identified and have to be solved:
1. IP Routing functionality in the 3G-SGSN,
2. An appropriated layer 3 protocol has to be chosen (TCP or UDP) per application,
3. Addressing of the Application and Application node by the RNC(s),
4. Addressing (dynamic or static) of the application (e.g. CBC) on the RNC(s).
• L3 technologies
• GTP vs. IP-in-IP tunneling
In UMTS/GPRS, it should be possible for operators to use different packet switching protocol (e.g. ATM-SVC) under single GTP standard.
Between GSNs GTP uses UDP/IP (or TCP/IP) for addressing regardless whether IP routing or ATM-SVC switching is used. The use of ATM-SVC will not impact on GTP standardisation
User IP
GTP
UDP / TCP
IP Addressing of SGSN/GGSN
Operator’s selection ATM-SVC Routing capability
Figure 6
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5.3 Benefits of the Gs interface applied to UMTS
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The Gs interface defined within GSM/GPRS provides a number of benefits to a GSM/GPRS operator [03.60]. These include: combined attach/detach procedures, combined location/routing area updates, paging of CS connection via the SGSN, identification procedures, MM information procedures. The main aims of these include saving of GSM/GPRS radio resources, harmonised security procedures and reduction of MS battery consumption.
As GSM operators roll out GPRS and as the numbers of mobiles increase the benefits of the Gs interface to the network operator will increase as the percentage of GPRS enabled mobiles grows. GSM/GPRS operators with mature networks will also be looking to roll out UMTS using evolved CN infrastructure, they will also be looking to apply the benefits of the Gs interface reaped for GSM to UMTS. Many of the capabilities of the Gs interface will be applicable to UMTS (such as combined updates, combined attach and MS/Ue information procedures), this will save on radio resource usage. The presence of the MSC-GSN interface will also offer the opportunity for developments to ease seamless service support between CS and PS platforms (such as SoLSA and Camel).
In the future, network operators who have incorporated Gs functionality into their networks will be looking to connect UTRAN to their GSM/GPRS Core Networks with minimal changes (excepting those for service development, network and radio optimisation, network evolution and flexibility), thus the Gs interface should be maintained and enhanced for UMTS.
The Gs interface also offers opportunities for suppliers and operators regarding integrated MSC/GSN products (which may support internal proprietary Gs functionality as well as standardised MSC-GSN functionality). Operator’s networks which have separated MSC/GSN nodes will be able to add integrated nodes into their GSM/GPRS/UMTS networks (and vice versa), depending upon the MM solutions developed for UMTS this could enable combined updates to be performed between (Gs supporting) integrated and separated nodes. If the Gs interface is not present operators will not be able to optimise resource between (integrated or separated) nodes.
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5.3.1 Periodic updates
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5.3.1.1 Why do we have Periodic updates
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Periodic updates are within the network to increase the efficiency of the CN while also increasing the quality of service perceived by calling parties to mobiles. The periodic timer is set within the CN node to a figure which enables absent mobiles to have their (VLR based) information removed after the timer expires. People calling mobiles which are registered as ‘detached’ (either implicitly or via periodic expiry) will receive faster treatment of the call in the CFNRc case or ‘Not been possible to connect your call’ RANN case as the mobile is not paged by the network.
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5.3.1.2 Support of periodic updates in UMTS
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One of the current proposals for SRNS relocation [1, incl.: section 9.3.4, 2] propose that when in CMM connected mode (PMM idle) or PMM connected (CMM idle) the relevant location/routing updates to the (idle) CN are performed while in RRC connected mode.
For periodic updates the UE may be RRC connected (know to the UTRAN as ‘active’) when the (UE based) periodic timer is due to expire, the (idle) CN node will also have a timer about to expire and be ready to detach the UE.
If the methodology of [1, Section 9.3.4] is followed a location update will be performed within the same RRC connection to the (MM idle state) CN node to re-set the periodic timer.
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5.3.1.3 Impact upon UMTS
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The impact upon UMTS of this is that the UTRAN, UE and one CN node have an active session (‘xMM connected) in place with accurate knowledge of the (periodic) attached/detached status of the UE. It is a waste of (valuable) radio resource for the UE to perform a LA/RA update purely to reset the periodic timer in the (idle) CN node: this also contradicts working assumption [1, section 11].
As UMTS is envisaged as a mass market system supporting very large numbers of mobiles within the network, many of these could potentially have very long (i.e. all day) duration (but low packet volume) Packet sessions (as per GPRS). It is folly to consider additionally loading the radio resource to update the (periodic) detach status of the mobile on the CN side of the radio interface when elements on the CN side of the radio interface already know the status of the mobile.
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5.4 Authentication
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5.5 Management of ciphering keys
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5.5.1 Cipher Mode Control – 2MM concept
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The assumptions in this section is based upon the assumption that ciphering in performed between UE and RNC.
It is assumed that in UMTS the ciphering key and the allowed ciphering algorithms are supplied by CN domains to the UTRAN usually in the beginning of the connection. Receipt of the ciphering command message at the UTRAN will cause the generation of a radio interface ciphering command message and, if applicable, invoke the encryption device and start data stream ciphering. The CN domain is noted if the ciphering is executed successfully in the radio interface and the selected ciphering algorithm.
When new connection is established from other CN domain, which is not having any connection to the UE, the new CN domain also supplies the ciphering key and the ciphering algorithms allowed to use to UTRAN in the beginning of the connection. This is due to the fact CN domains are independent from each other.
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5.5.1.1 One ciphering key used in UTRAN
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If it is assumed that only one ciphering key and one ciphering algorithm are used for all connections, this leads to a situation, in which there are two ciphering keys supplied from CN domains and only one of them is used.
To handle this situation, UTRAN must select either one of the ciphering keys. If there are no differences between the ciphering requirements1 requested by two CN domains then, e.g., the first ciphering key and the algorithm is maintained (see Figure 3 7).
Figure 3Figure 7. One ciphering key use in the UTRAN
As a result of the selection of the ciphering key between two different CN domains (if both CN domains have active connection(s) to the UE) either one or both of the CN domains do not know the present ciphering key used for the connection(s). Only UTRAN and UE know the present ciphering key used.
Further, if the case described in figure 1 is still considered and if after the MSC connection is released, but before SGSN connection is released, a new connection from MSC is established, the MSC may initiate a new authentication resulting in a new MSC ciphering key supplied to UTRAN. In this case, the UTRAN may follow the same key selection approach as it used previously, i.e., the first ciphering key is maintained2.
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5.5.1.2 Multiple ciphering keys used in UTRAN
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It may be required to use more than one ciphering key for different radio access bearer, e.g., user plane bearers associated to one CN domain are ciphered by the ciphering key supplied by the associated CN domain. However, in the control plane only one ciphering key is used and therefore in the control plane there must be co-ordination between ciphering keys supplied by CN domains.
The co-ordination in the control plane is similar to what is presented for one ciphering key used in UTRAN option (ch. 2.1). In the control plane, UTRAN must select either one of the ciphering keys supplied from CN domains if both CN domains are active. The change of the used ciphering key in the control plane during active RRC connection is for further study.
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5.5.1.3 Serving RNC relocation and ciphering
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In GSM, when inter-BSC handover is performed, MSC sends the ciphering key and allowed algorithms to the target BSC in the BSSMAP HANDOVER REQUEST message. In GPRS, because the SGSN performs the ciphering, the inter-BSC handover does not cause any need for the ciphering key management.
For UMTS, the GSM approach is not applicable on the serving RNC (SRNC) relocation, because CN domains do not necessary know the present ciphering key(s) used as it is described in the chapter 2.
It is recommended that the ciphering key(s) or a relevant information indicating used ciphering key(s) is transferred in the transparent UTRAN information field from the source RNC to the target RNC in the RANAP SRNC RELOCATION REQUIRED and RANAP SRNC RELOCATION REQUEST messages (see Figure 48.). In this way the present ciphering key(s) is transferred to the target RNC.
Figure 4Figure 8. The ciphering key transfer in SRNC relocation procedure (one ciphering key)
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5.5.2 UMTS-GSM handover
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In the handover from UMTS to GSM, the ciphering key cannot be transferred transparently like it is proposed for UMTS. The CN has to build the BSSMAP HO REQUEST message, having the ciphering key from the MSC. 2G-SGSN receives its ciphering key from the old 3G-SGSN via Gn-interface as it is done in GPRS.
If the ciphering keys used in UMTS are different compared to GSM, e.g., the ciphering key length is different, both MSC and SGSN ciphering keys must be changed in UMTS-GSM handover. This type of interoperation is left for further study in this paper.
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5.5.3 Interworking with 2g-MSC
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In GSM, the A-interface BSSMAP [2] supports a transparent field in the BSSMAP HO REQUIRED and HO REQUEST messages, which allows to utilise the proposed solution also for GSM CN connected to the UTRAN.
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5.6 Mobile IP in UMTS
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5.6.1 Mobile IP
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A single generic mobility handling mechanism that allows roaming between all types of access networks would allow the user to conveniently move between fixed and mobile networks, between public and private as well as between PLMN’s with different access technologies. The ongoing work in IETF Mobile IP working group [MIP WG] is targeted towards such a mechanism3. Thus it is important to offer Mobile IP also to UMTS users and UMTS must be developed to support Mobile IP. Mobility within the UMTS CN could also be handled by Mobile IP. This would allow transparency to networks external to the UMTS PLMN. Potentially, this would allow cost savings for operators and a broadening of the market for manufacturers.
It is important to understand the different driving forces:
• Mobile IP as an overlay to the UMTS-GPRS would make it possible to offer easy roaming between different types of networks
• An integration of Mobile IP within the UMTS CN would additionally allow the operators to use standard IP technology to a larger extent and thus lower the cost for deployment and maintenance of networks.
Operators shall have the possibility to offer Mobile IP to end customers for R99. A flexible approach should be taken in order to extend the use of Mobile IP to handle mobility within the UMTS CN. UMTS standards should be aligned to when new Mobile IP functionality, that is needed for the different steps, will come out on the market. As not all operators will introduce Mobile IP at the same time, compatibility with GPRS based PLMN’s is needed. Such a flexible, yet backward compatible, approach is outlined below.
The concept of surrogate registration [TEP] allows MS’s without Mobile IP to benefit from Mobile IP infrastructure by letting the network perform the registration with the HA on behalf of the MS. However, this issue needs further investigation.
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5.6.2 A staged introduction of Mobile IP in the UMTS CN
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Three steps, which are discussed more in detail further down, have been identified. Briefly, these are:
1. 1. Step 1 represents a minimum configuration for an operator, who wishes to offer the mobile IP service. The current GPRS structure is kept and handles the mobility within the PLMN, while MIP allows user to roam between other systems, such as LAN’s, and UMTS without loosing an ongoing session, e.g. TCP.
2. 2.The SGSN and GGSN can be co-located without any alterations of the interfaces. However, to obtain more efficient routing, the MS could change GGSN/FA, i.e. PDP context and care-of address after an inter SGSN handover if it is not transferring data. MS’s which are transferring data during the inter SGSN handover could perform the streamlining after the data transfer is completed, using the old GGSN as anchor during the completion of the data transfer.
3. 3. The third step is to let MIP handle also handover during ongoing data transfer. The Gn interface is here only needed for handling roaming customers without support for MIP.
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5.6.2.1 Step 1 – Offering Mobile IP service
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Mobile IP has the benefit of being access system independent, which allows users to roam from one environment to another, between fixed and mobile, between public and private as well as between different public systems. Assuming a minimal impact on the GPRS standard and on networks whose operators do not wish to support MIP, leads to the following requirements:
Figure 5Figure 9. Core network architecture with GPRS MM in and between GPRS PLMN’s and Mobile IP MM between different types of systems and optionally between GPRS PLMN’s.
• The MS must be able to find a FA, preferably the nearest one. The underlying assumption is that FA’s are located at GGSN’s and that not all GGSN’s may have FA’s. One FA in a PLMN is sufficient for offering MIP service, however for capacity and efficiency reasons, more than one may be desired. This means that the MS must request a PDP context to be set up with a GGSN that offers FA functionality.
• While setting up the PDP context, the MS must be informed about network parameters of the FA, e.g. care-of address.
• Furthermore, the interaction between the GGSN and the FA needs to be studied more in detail. With the assumption that FA care-of addresses are used, the FA needs to detunnel incoming packets and, together with the GGSN, map the home address of the MS to a PDP context.
Roaming can be handled either via the Gp interface or via Mobile IP. This is described in the section on roaming further down. It is assumed that the MS keeps the same care-of address as long as the PDP context is activated.
A typical network is shown in Figure 59. The detailed solutions of this step are to be worked out in the Mobile IP technical report.
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5.6.2.2 Step 2 – Intermediate GPRS-Mobile IP system
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One way to implement a GPRS backbone is to co-locate the SGSN and GGSN, as depicted in Figure 6 10 . This might be favourable for operators with a strong interest in utilising standard IP (IETF) networks as far as possible and does not require any changes in the current GPRS protocol architecture.
In step 1, the assumption was that the MS stays with the same care-of address, during a session, i.e. as long as a PDP context is activated. A very mobile MS, might perform several inter SGSN HO’s during a long session which may cause inefficient routing. As an initial improvement, a streamlining procedure, with a temporary anchoring point in the GGSN, could be introduced:
If the MS is not transferring data while moving from one SGSN to another, a new PDP context could be setup between the new SGSN and its associated GGSN at the handover. The MS will get a new care-of address. The procedure for informing the MS that it has arrived to a new network has to be defined.
If the MS is transferring data, e.g. being involved in a TCP session, the MS would move from the old SGSN to the new one while keeping the PDP Context in the old (anchor) GGSN for the duration of the data transfer. Once the data transfer is terminated, the PDP Context can be moved to the GGSN associated with the new SGSN and a new care-of address can be obtained.
The buffer and forward mechanism, which already exists between the SGSN’s for preventing data loss at inter SGSN HO’s, will, with this procedure, be reused as it is. This procedure also has some advantage regarding the handling of firewalls, which are assumed to be attached to the GGSN’s. Today, there is no standard for changing firewall during e.g. a TCP session.
As in the previous step, the GPRS interfaces (Gn and Gp) need to be deployed for roaming customers, since there might be networks which not yet supports Mobile IP. Roaming between PLMN’s can be handled either with Mobile IP or with GPRS.
Figure 6Figure 10. Core network architecture where GPRS MM handles active mobiles and Mobile IP streamlining at inter SGSN handover. The SGSN and GGSN are here co-located.
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5.6.2.3 Step 3 – Using Mobile IP for Intra System Mobility
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The third and last step is to let Mobile IP handle all intra system mobility, including all handovers between GGSN’s or IGSN’s. This is depicted in Figure 711, where the IGSN represents an integrated SGSN/GGSN. The Gn and Gp interfaces may optionally be kept to handle roaming customers, whose terminals do not support MIP and the operator’s own customers roaming to networks without MIP functionality. The main difference compared to the previous step is that lossless handovers between IGSN’s must be handled. This architecture is investigated by the Mobile IP ad hoc group in a feasibility study.
Figure 7Figure 11. Core network architecture with Mobile IP MM within the CN and between different types of systems and between GPRS PLMN’s.
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5.6.3 Roaming
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Depending on the capabilities of a visited network, two roaming schemes can be identified; GPRS roaming and MIP roaming. With GPRS roaming, we mean roaming via the Gp interface and the use of a GGSN in the home network, which is necessary when the visited network does not offer any FA’s. In those cases where the visited network offers a FA, either a GGSN/FA in the visited or in the home network can be utilised. Networks, which use Mobile IP for all its own customers can provide GPRS roaming to visiting users by deploying the Gn and Gp interfaces.
5.6.4 Mobile IP and UMTS terminals
The mobile equipment needs to be enhanced with MIP software. For compatibility with other systems, it is of great importance that standard IETF Mobile IP and not a special UMTS version is used. Although it should be kept to a minimum, any interaction between the IP layer and the “UMTS layer” needs to be identified and defined. To avoid future updates of the mobile equipment, which is supposed to support Mo bile IP, it should be considered to include the UMTS specific functionality, needed to support Mobile IP in all three steps in the MS at once.
Surrogate Registrations
The concept of surrogate registration has a potential use in supporting non Mobile IP aware terminals using a Mobile IP based infrastructure. Instead of the MS performing registration with the Home Agent according to [RFC 2002], the FA could surrogate the mobile node in performing Mobile IP registrations with the Home Agent. One solution is proposed in [TEP] (Tunnel Establishment Protocol). However, surrogate registration may cause IP level authentication to be dependent on UMTS authentication and hence increase the dependence of Mobile IP on the access technology. Further study is required on this topic.
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5.7 Iu reference point
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5.7.1 General
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As a first step, UMTS will be based on the GSM/GPRS network, i.e. one circuit switched and one packet oriented domain. Due to the differences of the domains, the Iu reference point will be realised by two Iu instances, one for each domain. This enables each domain to develop according to their specific characteristics. At the same time, an aligned view of the Iu reference point should be achieved where this is deemed suitable
5.7.2 Control structure for the Iu reference point.
• A multi-vendor interface shall be defined at the Iu reference point (Iu interface). The interface embodies a protocol suite allowing different protocol stacks towards the PSTN/ISDN domain and the IP domain.
• Over the Iu interface, user information to one UE is carried in one or several logical user flows, controlled by a signalling protocol (RANAP). Additionally some control elements (potentially relevant for only one domain) may be carried inband in the user flows.
• A common syntax for RANAP messages for both the IP and the PSTN/ISDN domain is the target as long as the functionality of either domain is not compromised.
• A guideline for defining the control procedures over the Iu reference point is to reuse, to the extent possible, control procedures defined in BSSMAP and BSSGP/GTP. The use of BSSMAP and BSSGP/GTP as the base when defining the control procedures over Iu does not preclude new control procedures to be introduced over Iu reference point.
• For each domain the protocol stack used by RANAP may be based on one of SS7, TCP/IP or a combination (e.g. SCCP on TCP/IP or UDP/IP). The protocol stack used by RANAP may be different for the PSTN/ISDN domain and the IP domain.
• The protocol stack used by the user data transport over Iu may be different from the protocol stack used by RANAP. Furthermore the user plane protocol stack may be different for the two domains.
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5.7.3 Iu reference point – User plane towards IP domain
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• Any problems within the UTRAN which cause loss of data addressed to a UE shall be indicated to the 3G-SGSN to maintain the conformance of the data volume counted by the 3G-SGSN with the successfully transferred data volume. It is FFS whether this mechanism provides a degree of conformance required for volume dependent charging.
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5.8 Dualmode operation (GSM/UMTS)
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5.8.1 Will dualmode terminals also support GPRS?
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5.8.1.1 Handovers between GSM/GPRS class A and UMTS terminals
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In the following some problems and suggestions to solve the problems are made concerning the case where UMTS must support handovers from GSM to UMTS and/or UMTS to GSM for mobile stations with CS and PS service capability (GPRS class A).
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5.8.1.2 Handover from GSM to UMTS
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This type of handover could be needed, e.g., due to traffic reasons in a congested GSM network. In GSM the control for CS connection remains in the MSC from which the call was originated. This is called anchoring. Figure 8 12 illustrates the situation before the HO into UMTS (i.e., to UMTS UTRAN).
Figure 8Figure 12. Before HO to UMTS from GSM. The PS services are provided from SGSN in GSM.
In order to have access to PS services after the HO, the MS has to perform the necessary update, obviously. The reason for this is that there are no means to change SGSN in GSM without doing so. However, as there is an active connection from GSM MSC, no updating can be done for CS services (i.e., to MSC connected to UMTS UTRAN) until the call has ended, i.e., the control and MM for CS remains in GSM. As a result, only the PS MM can be activated in UMTS and thus the MM is split into two due to the HO.
Figure 9 13 After HO to UMTS from GSM.
The PS services can only be accessed from UMTS CN. To avoid severe limitation on accessing the PS service during the length of the CS connection, "MM for PS" must be setup into UMTS CN. To support that, the MM in UMTS CN has to be able to be split into two like MM in GSM. Moreover, to support PS access the UTRAN needs to perform co-ordination similar to the one required for the core network architecture with two edge nodes (e.g. scenario 2).
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5.8.1.3 Handover from UMTS to GSM
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Figure 10 14 illustrates the situation before the HO; anchoring is assumed in UMTS CN. This type of handover could be needed, e.g., due to limited coverage of UMTS.
Figure 10 Figure 14 Before HO from UMTS to GSM.
This type of handovers are seen as important especially in the first stages of UMTS due to limited coverage. Without these, the end user perception may be seriously affected.
Again, to have access to the PS services after the HO, an appropriate update is needed and also no updating can be done for CS. As a result, MM instance only for PS can now be activated in GSM as long as the call lasts and as a result, the MM in UMTS is split into two due to the HO..
Figure 11 15 After HO from UMTS to GSM.
To have access for PS service in GSM, the "PS part of MM in UMTS" has to be transferred to GSM.
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5.8.1.4 Suggestions
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From the discussion above one can suggest that to support handovers between UMTS and GSM for class A type of mobiles:
4. UMTS MM must support some distinction between CS and PS services in the registration related procedures. An example is a dedicated update/cancel only to PS services in UMTS. This is likely to affect to the states of UMTS MM sublayer in MS and CN (independent of the selected MM solution)
5. The MS has to be capable of handling the GSM – UMTS dualism
6. The UTRAN has to support the operation. Required functions bear resemblance to the architecture where the core network has two edge nodes (MSC, SGSN).
Some of these problems may be alleviated if the UMTS core network node provides also GSM functionality (A and Gb) and there is no need to change the UMTS core network node during the handover. This is for further study.
Requirements due to handover for dualmode "UMTS class A" – GPRS class B terminal are ffs.
• Handovers between GSM and UMTS for N-ISDN and packet oriented services (e.g. IP)
• Idle mode operation of dual mode terminals (e.g. cells in same or different location areas)
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5.9 Anchor concept
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UMTS Mobility Management (UMM) for release 99 shall use packet anchoring at the GGSN, providing this meets the QoS requirements, including those for real time services.
Disassociation of SRNS relocation and PS session transfer should be evaluated for release 99
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5.9.1 Introduction to the concept of anchoring communications in GPRS
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GPRS is being developed to include Quality of Service, this includes real time aspects. At present within GSM/GPRS the Core Network part of inter SGSN RA update procedure- is used to maintain communications within the network for a change of SGSN. GPRS will need development to support real time QoS requirements, the current mechanisms for changing the current SGSN (inter SGSN RA update) may also need developments to maintain the QoS requirements.
For UMTS the notion of Serving and Drift RNC provides a no loss of data at Hand-over inside a UTRAN as long as SRNS relocation (or a UMTS<=>GSM handover) is not performed (use of RLC between SRNC and UE in case of non-real time packet data, and use of soft handover in case of real time). The SRNC could be considered as an “anchor” point for the UTRAN. Therefore only the case of SGSN change induced by SRNS relocation has to be considered.
Within the UMTS CN two proposals have been made to satisfy the QoS requirements, the anchor SGSN concept and the non-anchor SGSN concept, both are illustrated in Figure 12 16 and are discussed in the following sections.
Figure 12Figure 16: The "anchor SGSN" and the "non-anchor" SGSN architectures
5.9.2 The Anchor SGSN concept
This section proposes that the current technique for anchoring communications within the MSC is considered for application to the QoS based GPRS communications (i.e. between SGSNs). This technique is termed ‘the Anchor SGSN concept’ and is used to maintain the communications between the GGSN and the UE , with the SGSN(old) making a bearer link to the SGSN(new).
It should be noted that this concept may be applicable for UMTS as well as GPRS.
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5.9.2.1 Requirements for the anchor SGSN
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The requirements for the support of the SGSN anchor concept are discussed below
GPRS: With added QoS
To date GPRS has used a number of different QoS Criteria, however the GPRS (and UMTS) community have been looking at enhancing this to enable better support for real-time type features. The current Core Network GPRS inter SGSN RA update (SGSN change) relies upon the Old SGSN to suspend and buffer packet transmission, the new SGSN to interact with the GGSN/HLR to maintain the active session. The new SGSN then re-commences transmission and buffered packets (from the old SGSN) are passed to the mobile. The impact of this is potential breaks in transmission which would not satisfy Real-time/QoS requirements.
The Core Network part of GPRS Cell re-selection: convergence with (inter MSC) handover?
As GPRS adopts real time QoS, developments will be needed within the routing elements (GSN) to cater for the real-time nature of the packet communications. One upshot of this is within the QoS based environment the resource reservation paradigm moves towards a ‘circuit switched’ one (with resources ‘reserved’ for the QoS stream). With this in mind the support of the CN part of inter SGSN RA update in a QoS environment could become closer to a ‘circuit switched’ handover where the old and new paths are ‘connected/bridged’ during the actual handover. For UMTS the SRNS relocation within a QoS based GPRS network may require developments between SGSN to enable the paths to be connected at an inter SGSN level, rather than the current method of using the GGSN. Effectively the current GPRS inter SGSN RA update mechanism uses the GGSN as the anchor point.
To maintain the QoS requirements during a change of SGSN an SGSN based anchor point (similar to the current VMSC based anchor in GSM CS) could be applied. Following the successful SGSN change it may be possible to optimise the packet routing between the GGSN and new SGSN, this requires further study.
SGSN based Anchor
The adoption of an SGSN based anchor could ease some of the problems highlighted within UMM } where the MM becomes split between GSM/GPRS and UMTS when a handover between the two radio mechanisms occurs. At present the (GPRS) MM location follows the Packet Switched serving node (SGSN) as it moves within and between the networks, whereas the Circuit switched (CS) MM remains within the anchor MSC. Further study should be made to see if the concept of anchoring of all services within the ‘initial’ network (network where communications were initiated) will ease the ‘split MM’ problem.
MM enhancements
Within the Circuit switched world the MM information is retained at the old MSC following an inter MSC handover and no location update is performed until the CS session (call) has been terminated. The adoption of a similar mechanism for Packet switched Services could ease the GSM-UMTS MM problem. If a CS session is in place the location update/routing area update would be constrained until the CS session is terminated (from the UTRAN perspective any PS packets would be routed over the common RRC session with no need for paging (in the now ‘new’ UTRAN RA/LA)).
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5.9.2.2 Developments of GSM/GPRS for the SGSN based anchor
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To enable the SGSN anchor concept to be supported the following developments will be needed to the contemporary GSM/GPRS network: these should be linked in to the overall UMTS developments:
a) Support for GPRS/UMTS QoS during SGSN change (inter SGSN RA update). Modification of the contemporary inter SGSN RA update mechanisms to become similar (if not converged with) GSM inter MSC handover type mechanisms.
b) Modification of the inter SGSN signalling mechanisms to support the transfer of related information directly between SGSNs (e.g. SRNC relocation parameters, cipher/security information).
c) Development of mechanisms to support single MM (the relation of updates between the MSC/SGSN and HLR is for further study). The Gs interface may be enhanced to support this capability.
Developments in contemporary GSM/GPRS network are also required to enable the UMTS <=>GSM/GPRS interworking since the anchor point is currently the GGSN.
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5.9.3 The non-Anchor SGSN concept
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The non-anchor SGSN concept may be viewed as the method currently used within GPRS (R97) for a change of SGSN.
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5.9.3.1 Current GPRS operation
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Current GPRS does not use an anchor SGSN (the SGSN used at PDP context activation may not be used by the MS during the lifetime of this PDP context).
The main reason is that, while in Circuit Switched GSM the call duration is very short, the PDP context duration may be very long (and the user be very far away from the SGSN where it activated the PDP context).
Furthermore, current inter-2G-SGSN mechanisms do not support a ‘drift’ SGSN since, at the reception of a downstream PDU, it is not possible to page a MS in standby state through another SGSN (there is no support of this requirement for a (R97) SGSN).
Note: When in (UMTS) RRC Connected mode, the UTRAN caters for paging of the mobile when in PS CONNECTED.
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5.9.3.2 Developments of GSM/GPRS for the non-SGSN based anchor
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To satisfy the identified requirements for GSM/GPRS/UMTS R99, the following developments will be needed to the contemporary GSM/GPRS network:
a) Support for GPRS/UMTS QoS mechanisms during inter SGSN RA update, this will involve continued linkage of the GGSN with the inter SGSN RA Update.
The current mechanisms for inter (2G)SGSN RA update are different to the mechanisms for inter MSC handover .
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5.9.4 Analysis and comparison of the “anchor SGSN” and “non-anchor SGSN” concepts
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The following aspects need to be considered when considering inter SGSN RA update concepts for GPRS/UMTS:
• Support of QoS requirements (e.g. transfer delay (for real time traffic), reliability (ability to handle correctly traffic requiring a high reliability), service interruption (for real time traffic)
• Relationship to mobility management
• Support of Class A/Simultaneous mode operation
• Resource usage within the network
• Developments needed within the standards
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5.9.5 Support of QoS requirements
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Transfer delay
Both the network and radio paths create delay within GPRS/UMTS communications. The non-anchor mechanism always crosses three GPRS nodes during communications (RNC, current SGSN, GGSN). The “anchor SGSN” architecture uses the same 3 nodes until an SGSN RA update occurs, then a new node (the drift SGSN) is added, with the communications ‘anchored’ at the initial SGSN. After an inter SGSN RA update in the SGSN anchor mechanism 4 nodes are used (RNC, drift SGSN, anchor SGSN, GGSN), the anchor SGSN relays user packets to the drift SGSN. The “non-anchor” architecture provides a lower network transfer delay and a lower jitter on this delay (less nodes implies less queuing). This is likely to be an issue for real time traffic such as VoIP. The impact of this needs to be assessed in relation to the delay over the radio path.
Reliability
Within the UTRAN the (acknowledged) RLC layer between UE and SRNC provides the reliability required by some (non real time – high reliability) traffic within the UTRAN. When there is a change of SRNC:
• - either the RNCs (if there is no LLC in the protocol definition of Iu) using packet transfer between old and new RNC
• - or the CN (if there is an acknowledged LLC in the protocol definition of Iu) using packet transfer between old and new SGSN
can repeat the non acknowledged packets ensuring the reliability requested by the user.
The same reliability can be provided in both “anchor SGSN” / “non-anchor” SGSN architecture.
It should be noted that ARQ mechanisms (using acknowledged mode with repeats) do not guarantee to avoid break in transmission for real time applications (such as speech/VoIP).
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5.9.5.1 Service interruption at SRNS relocation
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With the anchor SGSN architecture service interruption may exist during the change over of path from old RNC to new RNC, mechanisms such as parallel paths could be used to prevent or minimise this. The anchor SGSN would acts as the anchor for multiple PDP contexts (potentially to different GGSN which could be located within different networks).
With the non-anchor mechanism service interruption may exist during the change over of path within the GGSN between the old SGSN and the new SGSN. The impacts (upon timing of inter SGSN RA update) of multiple PDP contexts (potentially to different GGSN which could be located within different networks) needs to be studied.
The impact on nodal buffering and path change requirements for both concepts
(e.g. between GGSN and old/new SGSN in non Anchor concept, and between anchor SGSN and drift SGSN in anchor concept), combined with the support of real time and non real time traffic needs to be assessed further.
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5.9.5.2 Network resources used
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As shown in Figure 1216, the non-anchor SGSN architecture requires less nodes and transmission resources than the anchor SGSN architecture. However, the impacts upon the network resources in terms of signalling, buffering and processing load requirements need to be addressed.
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5.9.5.3 Quality of service requirements
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The optimum mechanism to satisfy the service requirements need to be considered, for example for a non real time, long duration packet session the anchor SGSN may not be optimum. Alternatively, for a real-time short duration packet session the non-anchor concept may not satisfy the QoS requirements at SRNS relocation. However, if SRNS relocation is not performed for real-time short duration packet session, there is no break in transmission at all (It is acceptable since the duration is short).
A mix of solutions may need to be considered in relation to the Quality of Service requirements of the packet session.
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5.9.5.4 Support for Class A (GSM/GPRS) and UMTS Simultaneous Mode operation
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Within GSM/GPRS the mechanisms used within the MS and the network to support Class B/C operation are different to those required for Class A. Simultaneous mode is required within UMTS (R99) which will place requirements to the GSM/.GPRS/UMTS R99 standards. The impacts on the network and MS usage and control of radio resource need to be addressed.
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5.9.5.5 Mobility Management
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For MM point of view, interworking with 2G-SGSN has to be considered. A non-anchor SGSN architecture makes it easy since the GGSN is the anchor point in both 2G-GPRS and UMTS networks. The concepts chosen for UMTS and GSM/GPRS for R99 need to be compatible.
In the case SGSN anchor concept is introduced in R99 GPRS, several issues have to be considered:
• A new relaying protocol has to be introduced since BSSGP does not fulfil this requirement,
• The MS behaviour has to be modified: in standby state, it has to initiate a cell update instead of a RA update,
• The drift SGSN has to route the cell update to the anchor SGSN it does not already knows,
• When receiving a downstream PDU, the anchor SGSN has to page the MS under another SGSN. The use of P-TMSI may lead to conflicts since the same P-TMSI value may be already used for another MS.
• Interception and charging aspects, since the GGSN and the MS could be in different regions.
The current mechanism with UMM uses different mechanisms for PS and CS MM. The impacts of both mechanisms on GPRS MM/UMM and security/ciphering need to be addressed.
Within the anchor concept there are no RA updates as long as the MS has an active PDP context via anchor SGSN.
The non-anchor concept leads to RA updates with every change of SGSN; however, there is no RA update as long as the SRNS is not changed since the SRNS acts as an anchor point in the UTRAN.
The impacts of inter SGSN RA update for both anchor and non anchor solution in conjunction with location based services (such as SoLSA) needs to be addressed.
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5.9.5.6 Comparison of developments needed within the standards for GSM/GPRS/UMTS R99
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• R99 will include the support of QoS within GSM/GPRS and UMTS.
• Class A operation and UMTS simultaneous mode will be required for R99.
• The anchor SGSN concept would include the specification of drift SGSN and packet forwarding mechanisms.
• The non-anchor concept may need enhancement to satisfy the QoS concepts and will need development to ensure the interruption for inter SGSN RA update can be achieved within the QoS requirements.
• The changes and developments needed to GPRS R97 to satisfy these requirements as well as inter-working to pre R99 networks needs to be addressed.
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5.10 Quality of service
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• Application/End to end QoS
• QoS Segments (e.g. Radio, UTRAN, CN, Internet)
• QoS Mapping (between different segments/layers)
• Radio Access Bearers
• Resource management
• Interfaces/APIs between Application, TE, MT
• Charging of QoS aware applications
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5.11 Others
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5.11.1 GPRS/IP support for Multi-media service
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The following developments are needed within IP/GPRS to support the expected multi-media requirements of UMTS (note this list is not exhaustive):
QoS for GPRS: To enable real-time ‘streaming’ developments.
Adoption of IP Telephony, H.323 and equivalent PSTN/Internet technologies: To support the control and interworking of multi-media and telephony applications with non-UMTS networks.
Interrogation of the HLR with the Gateway functionality: To enable terminated communications to be delivered to the mobile terminal. This can include the PIG and H323 functionality.
Figure Z 17 illustrates a potential architecture which could be used to deliver telephony and multi-media features.
Figure 173: Evolved GPRS/IP support for Multi-media services
Telephony and multi-media requirements for UMTS may be supported via the evolved IP/GPRS network of Figure Z17. This architecture does not need a separate non-IP based circuit switched (MSC) platform.
• Multimedia service control
• Phasing. What is for release -99, -00, etc. ?
• Network migration
• Handling and type of coded speech over Iu
• Location of ciphering functionality
• Link access control for user data (LAC-U)
• Data compression
• Allocation of resources of Iu
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5.11.2 Separation of switching and control
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Proposed Architecture
In this section the concept of a logically Separated Call Control (SCC) server is introduced. Currently CC is integrated with each of the MSCs in a network. Here it is suggested (and shown in figure 18) that a single CC function is implemented which is logically separated from the switch. The physical location of the SCC server is an implementation issue. Examples of implementation include:
• SCC integrated with IWU.
• SCC integrated with one or more switches. In this case a IWU may not be required between the SCC and the switch(s) with which it is implemented. IWUs would be used to connect to other switches.
• Standalone SCC.
Data required by the SCC could be held locally so as to reduce signalling load. This is likely to include data currently held in the HLR and VLR and a network resource database which allows the SCC to determine what network resources are available and record the state of resources e.g. used, reserved or free. Figures 2 19 and 3 20 show the signalling flows in the network for mobile originated and mobile terminated calls respectively.
In figure 1 MM is shown as being integrated with the SCC. It could equally well be separated from the SCC.
Figure 184 Network Architecture
Notes:
1. DBs represents all databases necessary for SCC operation, e.g. HLR, VLR, Network Resource database.
2. MAP (with some new operations) could be used here which would probably represent minimum change. Alternatively a more general protocol such as MGCP could be used which would represent more change but have the advantage that the switch would be made more generic.
3. ISUP (with some modified messages) could be used to communicate between the SCC and the transit switch of a neighbouring network.
4. This signalling is shown to pass through the transit switch as this is a likely (but not mandatory) route for it to take. The logical connection is between the SCC and the neighbour network.
5. MAP (with some new operations) could be used here which would probably represent minimum change. Alternatively a more general protocol could be used which would represent more change but have the advantage that the databases would become more generic. If an IN implementation is adopted the SSF could form part of the SCC which could communicate with an SCF via MAP or INAP which in turn could communicate with the DB via DAP.
6. This interface could be the same vendor specific propriety interface that is implemented today internally to the MSC.
Mobile Originated Call
Figure 1519. Signalling Flow for MO call.
Notes:
1. A modified SRI operation could be used by the SCC to request routing information from the databases. The response contains all the information required to route the call from the serving switch to the point of interconnect.
2. A modified IAM and ACM could be used to communicate between the SCC and the transit switch. Because the SCC serves multiple switches a switch ID (in addition to a route ID and circuit ID) is required.
3. EST (establish) and EST ACK could be a new MAP) or could be provided by a new protocol such as MGCP. Here EST is used to instruct the switch to establish the backward connection. EST ACK confirms that the required connection has been established. Note that the SCC executes the EST operation to all involved switches simultaneously. In the event of a handover the SCC would execute EST operations only to those switches involved in the handover. In the event that the neighbour network is not controlled by an SCC the transit switch is unlikely to be involved.
4. Here EST is used to instruct the switch to establish the forward connection.
Mobile Terminated Call
Figure 1620. Signalling Flow for MT Call.
Notes:
1. A modified IAM and ACM could be used to communicate between the SCC and the transit switch. Because the SCC serves multiple switches a switch ID (in addition to a route ID and circuit ID) is required.
2. A modified SRI operation is used by the SCC to request routing information from the databases. The response contains all the information required to route the call from the serving switch to the point of interconnect.
3. For clarity MM is considered as part of SCC here.
4. EST (establish) and EST ACK could be a new MAP) or could be provided by a new protocol such as MGCP. Here EST is used to instruct the switch to establish the backward connection. EST ACK confirms that the required connection has been established.
5. Here EST is used to instruct the switch to establish the forward connection.
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5.11.2.1 Benefits
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The separation of switching and control functions offers the following benefits:
Architectural Flexibility: The separation of bearer from the control allows flexibility in locating the desired functions.(functions could either be centralised or distributed). For instance, the switching and call control functions performed by a circuit or packet switch can now be separated and located in physically distinct locations. The control functions (all or a part thereof) could be located in a “call control server”, which can provide the information necessary to appropriately route the bearer. Further, this allows the use of platforms designed specifically for the task being performed to be used. Dedicated platforms will allow easier and faster software development and less work will be involved in rolling out new software versions.
Efficient Utilisation of Network Resources Given that most of the traffic associated with a call is bearer traffic, optimal routing of bearers (facilitated by separating control from the bearer) allows efficient utilisation of network resources. For instance, call control may be routed to a “ Call Control server” for purposes of address resolution, billing, enabling of services, and others, but the bearer does not have to traverse through the call control server. Further, optimal routing can be maintained during mobility (the concept of an anchor MSC can be removed)since the bearers can be re-routed after a change in location. Optimising the routing in this way will have greater significance for UMTS calls which are likely to be high bandwidth and may also consist of multiple streams.
• Further optimal routing can be achieved in the case of call divert.
Bearer Flexibility and Robustness: The separation of bearer and control allows the communicating parties to negotiate the resources required (even possibly re-route the bearers) even after call setup has been completed. Bearers could be re-routed during a call due to a change in the performance required or to work around failure of network elements.
Future-Proof: The separation of bearers from control makes the protocols used more modular (than before). For instance, the same control protocols can be used over multiple transport technologies. Further, the same control protocol can be used for establishing multiple bearer types. This facilitates improvements in technologies being used with minimal impact.
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5.11.2.2 Drawbacks
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Separation of switching and control means defining the interfaces between the various control functions (such as cal control, mobility management, session control, etc.) and the switching functions (i.e., switching matrix). For example in the case of a GSM MSC, this would mean defining an open interface between the MSC service switching functionality and the TDM switching matrix.
For packet data nodes, the separation might be more realistic as a client-server type of architecture is more natural in that domain. However, this is a deviation from the current GPRS and therefore may require additional standardisation effort.
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5.12 New Handover functionalities
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The radio access network has to be capable of connecting to a variety of existing core networks. This leads to a requirement that the UTRAN will be allowed to connect with evolved forms of existing CNs. There will be the need to support new Handover functionalities between UMTS and 2G systems.
The support of multimedia services and the separation of Call Control and Connection Control (many connections: telephony, video, data could be associated with one single call and handed over separately), together with a micro or pico-cellular environment will cause increased complexity of Handovers compared with GSM.
Developments will be needed of the contemporary GSM/GPRS platforms to enable handover/cell reselection of communications between GSM/GPRS and UMTS. To enable this specific developments are needed for:
• Handover/cell reselection of communications which have inherent delay and error requirements (e.g. speech as for contemporary GSM circuit switched and speech/ video).
(This may be viewed as an equivalent of GSM circuit switched handover).
• Handover/cell reselection of communications which may not have inherent delay requirements but do have error requirements (e.g. packet data communications such as IP/GPRS, file transfer, SMS).
(This may be viewed as an equivalent of GPRS cell-reselection).
This also requires the ability to potentially ‘negotiate’ and modify communications parameters when handing over between GSM/GPRS and UMTS.
• It would be useful to provide new procedures in UMTS in order to make handover a totally Radio Resource Management procedure fulfilled as far as possible by the BSS without the intervention of the NSS part. The proposed interconnection of BSSs to allow for handover streamlining could be a step in this direction. (This may be difficult when performing hand-over between different environments, and a traditional GSM-like handover procedure is likely to be used in this case).
• It is likely that the network performance during handovers will be increased by restricting handover to the access network, leaving the core Network to deal with the Streamlining procedure without any real-time constraints. (In the case of a successful GSM inter-BSC handover, eight messages are exchanged real time on the A interface between the MSC and the two BSC; if Streamlining is used, this could be potentially reduced to two messages (Streamlining Request - Streamlining Acknowledge) with a significant saving in the signalling overhead.
As part of the overall QOS negotiation between user and network, mechanisms will be needed to enable parameters such as handover delay, jitter, packet/information loss/acceptable error etc. to be applied as part of the communications path requirements utilised during the communications ’session’.
A number of options are available to support handover within the UMTS Core Network; real time support within the core network, real time handover within the UTRAN with subsequent ‘streamlining’. Irrespective of the final mechanism developed within the UMTS Core Network for UMTS handover, functional developments are needed within the Core Networks (both GSM/GPRS and UMTS) to support handover between UMTS Core Networks and evolved GSM/GPRS core networks.
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5.13 Reduction of UMTS signalling
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5.13.1 Turbo Charger
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The signalling load associated with subscriber roaming can be high when either the location areas are small or the subscriber travels significantly. The Turbo-Charger concept aims to optimise signalling associated with subscriber data management by assigning one MSC/VLR to perform the Call Control and Mobility Management functions while the subscriber remain attached or until signalling routes require further optimisation.
The benefits of the Turbo-Charger concept are:
• the substantial reduction in signalling traffic for subscribers located in the home PLMN,
• the substantial reduction in signalling traffic between the visited PLMN and the home PLMN,
• no new network nodes are required,
• applicable to a wide range of protocol used for the transfer of data.
The disadvantages of the turbo-charger concept are:
• Connections are required from the access network to be fully meshed to all MSCs in the turbo-charger area.
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5.13.1.1 Overview of the Turbo-Charger Concept
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A Turbo-Charged network constitutes a network architecture designed to reduce mobility management costs and provide automatic load-sharing between MSC/VLRs.
The architectural philosophy is to equally divide the subscribers between the available MSC/VLRs, irrespective of their location. In the context of GSM, this could be achieved by placing a routing function (e.g. evolved STP) between the BSC and the pool of MSC/VLRs. The purpose of the routing function is to route A-interface messages to the MSC/VLR that is serving the mobile station. The solution requires the MS to store a discriminate that can be used to identify the serving MSC/VLR and for routing to be applied on this discriminate on the connection between the MSC/VLR and access network. A TMSI partitioning scheme could be utilised. This scheme allocates a sub-set of the TMSI range to each MSC/VLR, Figure X. The A-interface messages are then routed to the right MSC based on the TMSI. This could be done by a routing function external to the access network implying no access network modification (see figure x). If a TMSI partitioning scheme is used then new SIM cards are not required.
The temporary identity used for paging (TMSI) must be unique within all the MSCs in the turbocharger area. This implies that there must be a mechanism to ensure that this requirement is met for turbocharged MSCs (e.g. TMSI partitioning).
Two mechanism to provide load-sharing are envisaged, random load-sharing and dynamic load-sharing.
Random load-sharing requires the routing function to randomly assign a MSC/VLR to serve a particular mobile station when it first comes in to the network. Regardless of where the mobile is the same MSC/VLR will always serve it provided the mobile remains in the area served by all the turbocharged MSC/VLRs linked by the routing function.
In large metropolitan areas where subscribers are served by multiple MSC/VLRs, some MSC/VLRs may be very busy while others are not fully utilised. Dynamic load-sharing requires the implementation of an intelligent router. Since the routing function routes all A-interface traffic, it can participate in load-sharing and balancing based on the current loading of each MSC however linkage between MSC load and the routing algorithm would be required.
In the case of a Turbo-Charged network where the network is sub-divided into large regions, further optimisation can be achieved by adding the Super-Charger functionality.
Figure 17: Example of GSM Turbo-Charger Network Architecture
In the context of UMTS, the routing function becomes a feature of the RNC, see Error! Reference source not found..
Figure 18: Example of UMTS Turbo-Charger Network Architecture
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5.13.2 Relationship between GLR and TurboCharger
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The GLR and TurboCharger are two independent schemes for reducing the amount of MAP traffic generated in UMTS networks.
The GLR works by reducing traffic between PLMNs associated with Location Updates. This is achieved by "caching" the roaming subscriber's data in the visited network
The TurboCharger works by eliminating the need to perform location updates. The same VLR can hold a subscriber's data for the duration of his attachment to the network.
A TurboCharged network requires that each MSC/VLR can physically connect to all RNCs. Therefore TurboCharging may be best suited to areas of the network characterised by dense geographic coverage. On the other hand, the GLR function is independent of the network density.
The network structure illustrated in Error! Reference source not found. shows that the GLR and a TurboCharged area within the same PLMN are independent. In fact, it shows benefits from using the two techniques in the same network. The Turbo-Charger reduces the location registration signals between the MSC/VLR and GLR:
There is no new update location signal between MSC/VLR and GLR if roamer moves inside of the Region A.
There is no new update location signal between GLR and HLR if roamer moves between regions.
Figure 19.
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5.14 Transcoder Control
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In order to improve voice quality for mobile-to-mobile calls (MS-MS calls) in GSM Phase 2+ networks, Tandem Free Operation (TFO) using in-band signalling has been specified. The equivalent function in Japan's PDC (Personal Digital Cellular) network is known as Transcoder Bypass, which has been specified to make use of out-of-band signalling control (i.e. by the PDC-MAP protocol).
It is likely that UMTS terminals will support a wider range of codecs than is currently the case for GSM terminals. In the case of calls between UMTS terminals, codec negotiation will be needed to:
• match terminal capabilities during call establishment
• support supplementary services interactions such as with conference/Multi-party calling, ECT, CFNRy
• support changes in radio interface conditions.
This requires control of the transcoder unit in the UMTS Core Network during (and after) call establishment and handover. However, the inband signalling technique currently specified for GSM-TFO has limitations in this area. For example:
• UMTS call setup; the GSM-TFO mechanism is designed to support a limited set of codecs. Each time a new codec is introduced into UMTS the transcoder would need to be upgraded.
• UMTS call in progress; codec negotiation using the GSM-TFO mechanism would need complex in band signalling.
The different solutions to support the required functionality for transcoder control in UMTS need to be studied in detail. Signalling for codec negotiation and control may be achieved by:
• New control mechanisms between the mobile terminal and the network based transcoder (out of band and in-band solutions need to be studied).
• Revisions to ISUP signalling.
• Revisions to MAP signalling.
• Inband signalling mechanism developed for AMR
It is for further study what impact transcoder control has upon networks external to the PLMN.
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5.15 Support of multimedia services
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One of the most important requirements for UMTS is the capability of supporting multimedia services.
The following principles should guide and apply to the support of multimedia services in UMTS:
• Multimedia services in relation to UMTS should be standardised and handled according to emerging multimedia standards. SMG should not standardise multimedia services solely for UMTS networks. SMG should take advantage of existing and emerging main stream standards for multimedia, in reality defined outside of the UMTS.
• Multimedia applications according to such main stream standards should be supported (transported and handled) efficiently in the UMTS.
• Multimedia requirements on the UMTS should, as far as possible, explicitly be related to such multimedia application standards to be supported – rather than to generic statements or assumptions related to the architecture.
• The multimedia bearer capability requirements, incl. QoS, are expected to effect the core as well as the radio network.
Among others, two requirements for an efficient support for multimedia applications, which currently can not be achieved by GSM, are sufficient bandwidth allocation and flexibility of bearers.
• The bandwidth requirement relates to the transport technology used on (both the radio and network sides). In particular switching and transport capabilities within the network must be able to support, in an efficient and flexible way, air interface rates of at least up to 2 Mbit/s. It is unlikely that a 64 kbit/s based switching system will be able to do this in the most efficient manner.
• Separation of call control from connection and bearer control. This is an important requirement to satisfy the concept of Quality of Service for media components: a call/session may use various connections at any one particular instant (making use of one or several bearers). It should then be possible to add or remove bearers during such a call in order to cope with user needs or problems on the radio path. (Ref. ETS 22.01 Service Principles)
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