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8d2f6f763f71e88f74e01c5dff104898 | 28.889 | 4.3.2 Potential requirements
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8d2f6f763f71e88f74e01c5dff104898 | 28.889 | 4.3.3 Potential solutions
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8d2f6f763f71e88f74e01c5dff104898 | 28.889 | 4.3.4 Evaluation of solutions
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Annex <X>:
Change history
Change history
Date
Meeting
TDoc
CR
Rev
Cat
Subject/Comment
New version
2025-08
-
n/a
-
-
-
Initial skeleton
0.0.0
2025-10
SA5#163
S5‑254702
S5‑254885
S5‑254704
pCR
-
-
pCR on Rel-20 TR 28.889 Add use case description and requirement for Network Maintenance CCL
Rel-20 pCR 28.889 CCL for LCM
Pseudo-CR on TR 28.889 Add status monitoring use case
0.1.0
3GPP TR 28.889 V0.01.0 (2025-108)
Technical Report
3rd Generation Partnership Project;
Technical Specification Group Services and System Aspects;
Management and orchestration;
Closed control loop management phase2
(Release 1920)
The present document has been developed within the 3rd Generation Partnership Project (3GPP TM) and may be further elaborated for the purposes of 3GPP.
The present document has not been subject to any approval process by the 3GPP Organizational Partners and shall not be implemented.
This Specification is provided for future development work within 3GPP only. The Organizational Partners accept no liability for any use of this Specification.
Specifications and Reports for implementation of the 3GPP TM system should be obtained via the 3GPP Organizational Partners' Publications Offices.
3GPP
Postal address
3GPP support office address
650 Route des Lucioles - Sophia Antipolis
Valbonne - FRANCE
Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16
Internet
http://www.3gpp.org
Copyright Notification
No part may be reproduced except as authorized by written permission.
The copyright and the foregoing restriction extend to reproduction in all media.
© 2025, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC).
All rights reserved.
UMTS™ is a Trade Mark of ETSI registered for the benefit of its members
3GPP™ is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners
LTE™ is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners
GSM® and the GSM logo are registered and owned by the GSM Association
Contents
Foreword 4
1 Scope 6
2 References 6
3 Definitions of terms, symbols and abbreviations 6
3.1 Terms 6
3.2 Symbols 6
3.3 Abbreviations 7
4. Use Cases 8
4.1 Use case1: Closed Control Loop for Network Maintenance 8
4.1.1 Description 8
4.1.2 Potential requirements 8
4.1.3 Potential solutions 8
4.2 CCL for network capacity optimization 8
4.2.1 Description 8
4.2.2 Potential requirements 9
4.2.3 Possible solutions 9
4.3 Use case Y: Automated status monitoring 9
4.3.1 Description 9
4.3.2 Potential requirements 9
4.3.3 Potential solutions 9
4.3.4 Evaluation of solutions 9
Annex <X>: Change history 10
Foreword 4
1 Scope 6
2 References 6
3 Definitions of terms, symbols and abbreviations 6
3.1 Terms 6
3.2 Symbols 6
3.3 Abbreviations 6
Annex <X>: Change history 7
Foreword
This Technical Report has been produced by the 3rd Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
In the present document, modal verbs have the following meanings:
shall indicates a mandatory requirement to do something
shall not indicates an interdiction (prohibition) to do something
The constructions "shall" and "shall not" are confined to the context of normative provisions, and do not appear in Technical Reports.
The constructions "must" and "must not" are not used as substitutes for "shall" and "shall not". Their use is avoided insofar as possible, and they are not used in a normative context except in a direct citation from an external, referenced, non-3GPP document, or so as to maintain continuity of style when extending or modifying the provisions of such a referenced document.
should indicates a recommendation to do something
should not indicates a recommendation not to do something
may indicates permission to do something
need not indicates permission not to do something
The construction "may not" is ambiguous and is not used in normative elements. The unambiguous constructions "might not" or "shall not" are used instead, depending upon the meaning intended.
can indicates that something is possible
cannot indicates that something is impossible
The constructions "can" and "cannot" are not substitutes for "may" and "need not".
will indicates that something is certain or expected to happen as a result of action taken by an agency the behaviour of which is outside the scope of the present document
will not indicates that something is certain or expected not to happen as a result of action taken by an agency the behaviour of which is outside the scope of the present document
might indicates a likelihood that something will happen as a result of action taken by some agency the behaviour of which is outside the scope of the present document
might not indicates a likelihood that something will not happen as a result of action taken by some agency the behaviour of which is outside the scope of the present document
In addition:
is (or any other verb in the indicative mood) indicates a statement of fact
is not (or any other negative verb in the indicative mood) indicates a statement of fact
The constructions "is" and "is not" do not indicate requirements.
|
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 1 Scope
| The present document studies on how Coverged Charging support CAPIF enhancements and new Charging scenarios brought by the CAPIF framework, as defined in 3GPP TS 23.222 [x].
The following items are studied:
• possible charging scenarios and requirements related to service API/AEF Instantiation and Multiple Provider Interoperability.
• potential charging solutions and impacts for API Invoker authorization and authentication.
…
|
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 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] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 23.222: "Common API Framework for 3GPP Northbound APIs".
…
[x] <doctype> <#>[ ([up to and including]{yyyy[-mm]|V<a[.b[.c]]>}[onwards])]: "<Title>".
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 3 Definitions of terms, symbols and abbreviations
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 3.1 Terms
| For the purposes of the present document, the terms given in TR 21.905 [1] and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 [1].
example: text used to clarify abstract rules by applying them literally.
|
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 3.2 Symbols
| For the purposes of the present document, the following symbols apply:
<symbol> <Explanation>
|
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 3.3 Abbreviations
| For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905 [1].
3GPP 3rd Generation Partnership Project
5GS 5g System
AEF API Exposing Function
API Application Programming Interface
CAPIF Common API Framework
<ABBREVIATION> <Expansion>
|
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 4 Concepts and background
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 4.1 General Description
|
The CAPIF core function provides the centralized CAPIF APIs that enable onboarding, discovery, security, and monitoring of exposed APIs. API invokers connect to the CAPIF core via CAPIF-1 and CAPIF-2 interfaces for onboarding and discovery of APIs, while CAPIF-1e extend these capabilities by enabling the authorization and authentication, service API discovery by an API Invoker outside the PLMN Trust domain, CAPIF-2e enable the API Invoker to communicate to the service APIS which belong to different trust domains.
The inter-operability of different CAPIF Providers is supported by the CAPIF-6e reference point, which enables integration with CCF of a trusted domain (i.e. 3rd Party, PLMN). This ensures that API invokers from one trust domain can securely discover and consume APIs exposed in another trust domain, preserving interoperability and trust management.
Figure 4.1-1: CAPIF interconnection with multiple CAPIF provider domains
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 4.2 Background
| The Common API Framework defined, in 3GPP TS 23.222 [2], provides a standardized solution for exposing and consuming network APIs in a secure and interoperable manner. CAPIF introduces common functional entities and reference points that support API invoker authentication, authorization, monitoring, and management. This framework ensures that application developers and service consumers can access APIs through consistent procedures, independent of the underlying network functions or API providers.
In the current specifications (3GPP TS 23.222 [2]), CAPIF is primarily described within a single provider’s trust domain. The framework defines reference points, as depicted in Figure [4.2-1]
Figure 4.2-1 - AEF Instantiation (Figure H-1 of 3GPP TS 23.222 [2])
Within this framework, the API Exposing Function plays a central role in exposing service APIs to the CAPIF core. Multiple AEF instances may be instantiated by an API provider, each responsible for exposing specific sets of APIs.
As the ecosystem of network-exposed APIs expands, multiple CAPIF providers are expected to coexist and interoperate. API invokers may need to consume APIs offered by providers across different administrative domains. This requires mechanisms for cross-domain trust, authentication, authorization, interconnection, and interworking between CAPIF core functions of different providers.
To support this, additional reference points such as CAPIF-2e and CAPIF-6e are introduced to enable inter-provider authentication, authorization, and interconnection between CAPIF core functions. These interfaces allow API invokers from one trust domain to securely use APIs exposed in another trust domain, regardless of which AEF instance provides the API, ensuring interoperability, scalability, and consistent trust management.
The following figure depicts a business relation between two (2) CAPIF Providers which can be interconnected
Figure 4.2-2 - CAPIF providers interconnection (Figure 4.12.1-1 of 3GPP TS 23.222 [2])
5 CAPIF Charging Scenarios and Topics
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1 Topic #1 CAPIF Converged Charging support for service API/AEF
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1.1 General description and assumptions
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1.2 Use Cases
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1.2.1 Use Case #1.1: API Invokers Service Charging
| An operator provides CAPIF Core Functions and CAPIF-1 and CAPIF-1e reference points towards API Invokers and wants to be able to charge the API Invokers for services it provides.
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1.3 Potential charging requirements
| REQ-CH_CAPIF_RP-01: Charging for services provided via the CAPIF-1 and CAPIF-1e reference points shall be supported.
|
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1.4 Key Issues
| |
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1.4.1 Key issues#1.1: Charging events and charging information required
| Identify the chargeable services and events for CAPIF-1 and CAPIF-1e.
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1.4.2 Key issues#1.2: Charging events and charging information required
| Identify the placement of the charging trigger function for CAPIF-1 and CAPIF-1e.
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1.5 Possible Solutions
| |
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1.6 Evaluation
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.1.7 Conclusion
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.2 Topic #2 CAPIF Converged Charging of multiple API Providers
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.2.1 General description and assumptions
| |
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.2.2 Potential charging requirements
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.2.3 Key issues#1.1: Charging events and charging information required
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.2.4 Possible Solutions
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.2.5 Evaluation
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.2.6 Conclusion
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.3 Topic #3 CAPIF Converged Charging of API Invoker Authorization and Authentication Impact
| |
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.3.1 General description and assumptions
| |
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.3.2 Potential charging requirements
| |
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.3.3 Key issues#1.1: Charging events and charging information required
| |
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.3.4 Possible Solutions
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3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.3.5 Evaluation
| |
3674dad619a198e167cb9fd34338eeb9 | 28.891 | 5.3.6 Conclusion
|
6 Evaluation
7 Conclusion
Annex <A> (informative):
Change history
Change history
Date
Meeting
TDoc
CR
Rev
Cat
Subject/Comment
New version
20242025-8
SA5#162
Initial Skeleton
0.0.0
2025-10
SA5#163
S5-254806
S5-254807
S5-254808
S5-254809
S5-254810
Document Structure Update
Update of the Scope, General Description and Background
Abbreviations Update
API Invokers Service Charging Use Case
0.1.0
|
70172d647bd0430cf55959218f45740d | 25.902 | 1 Scope
| The present document is part of the Release 6 work item "FDD Enhanced Uplink".
The purpose of the present document is to help the TSG RAN WG3 group to specify the changes to existing Iub/Iur specifications, needed for the introduction of "Iub/Iur Congestion Control" measures for Release 6.
This work task belongs to the TSG RAN Building Block "FDD Enhanced Uplink: UTRAN Iub/Iur Protocol Aspects", and as such this document is expected to be completed within the Release 6 timeframe.
This document also includes 3.84 Mcps TDD Enhanced Uplink which is part of the Release 7 work item “3.84 Mcps Enhanced Uplink”.
This document also includes 7.68 Mcps TDD Enhanced Uplink which is part of the Release 7 work item “7.68 Mcps Enhanced Uplink”.
This document also includes 1.28 Mcps TDD Enhanced Uplink which is part of the Release 7 work item "1.28 Mcps Enhanced Uplink".
|
70172d647bd0430cf55959218f45740d | 25.902 | 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] void.
[2] void.
[3] void.
[4] void.
|
70172d647bd0430cf55959218f45740d | 25.902 | 3 Definitions, symbols and abbreviations
| |
70172d647bd0430cf55959218f45740d | 25.902 | 3.1 Definitions
| For the purposes of the present document, the following terms and definitions apply:
E-DCH: Enhanced DCH, a new dedicated transport channel type or enhancements to an existing dedicated transport channel type.
|
70172d647bd0430cf55959218f45740d | 25.902 | 3.2 Symbols
| For the purposes of the present document, the following symbols apply:
void
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70172d647bd0430cf55959218f45740d | 25.902 | 3.3 Abbreviations
| For the purposes of the present document, the following abbreviations apply:
CFN Connection Frame Number
DRT Delay Reference Time
FSN Frame Sequence Number
HSDPA High Speed Downlink Packet Access
RFN RNC Frame Number
RNL Radio Network Layer
SFN System Frame Number
TNL Transport Network Layer
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70172d647bd0430cf55959218f45740d | 25.902 | 4 Background and introduction
| In RAN Plenary Meeting #27, it was agreed to create a Technical Report on the subject of "Iub/Iur congestion control (Rel-6)".
The technical objective of this TR is to improve the Congestion Handling performance of the UTRAN over the Iub and the Iur interfaces.
Any solution should take into account backwards compatibility aspects.
This work item is applicable to UTRA FDD only.
In a similar manner the work items for enhanced uplink for 3.84 Mcps TDD and 7.68 Mcps TDD also lead to the need to improve the Congestion Handling over the Iub and Iur interfaces.
In a similar manner the work item for enhanced uplink for 1.28 Mcps TDD also leads to the need to improve the Congestion Handling over the Iub and Iur interfaces.
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70172d647bd0430cf55959218f45740d | 25.902 | 5 Requirements
| For Iub/Iur Congestion Controlled, the following requirements were agreed in RAN3:
• RNC shall have a means for detecting congestion.
• Receiving node shall have a means for notifying the source of congestion i.e. sending node, that congestion has occurred.
• Iub/Iur Congestion control for both HSDPA and Enhanced Uplink should – if possible – employ similar solutions.
• The development of an Iub/Iur congestion control solution should bear in mind both the existing HSDPA and soon to be completed Enhanced Uplink features.
• Any solution should take into account backwards compatibility aspects.
6 Study areas
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70172d647bd0430cf55959218f45740d | 25.902 | 6.1 Background information
| |
70172d647bd0430cf55959218f45740d | 25.902 | 6.1.1 Introduction
| There are many types of congestion control mechanisms, the main groups are window based, rate based or combination of both. The method often used for congestion detection is the method based on the loss of packets. Other methods appropriate for congestion detection are: packet delay, average queue and rate difference.
Different congestion control algorithms might be used for IP network and ATM network respectively. It is known, that in IP network as a congestion control protocol mostly TCP is used, so to ensure fairness and other quality congestion control parameters, TCP like congestion control protocol should be used. TFRC protocol (TCP-Friendly Rate-based congestion Control protocol), as one of the many examples, which intends to compete fairly for bandwidth with TCP flows, could be named.
|
70172d647bd0430cf55959218f45740d | 25.902 | 6.1.2 Example 1: TFRC
| Congestion Factor depends on the congestion control algorithm, and on the congestion detection method. By detecting the loss of packets and using some method to derive RTT, transmit rate could be prepared according to transmit rate formula X = f(s, RTT, p) where s is the packet size in bytes/second, RTT – the round trip time in seconds, p is the loss event rate (based on the packet loss derived from the congestion detection).
Congestion Factor depends on the computed data rate X. The Credit, Interval and Repetition Period of FC Allocation message will be influenced by computed Congestion Factor in Congestion Control and the message Capacity Allocation with modified IEs will be sent to RNC.
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70172d647bd0430cf55959218f45740d | 25.902 | 6.1.3 Example 2: "ABR like" congestion control
| "ABR like" congestion control has "additive increase, exponential decrease" type of algorithms. Different formulas exist for computing ACR (Allowed Cell Rate) for increase and for decrease. ACR i.e. current transmission rate in cell/s, should be computed in octets or in number of MAC-d PDUs. Then from the computed ACR, by a given HS-DSCH Interval, HS-DSCH Credits can be derived, because ACR is equal to Credits divided by Interval. Capacity Allocation message will be sent to RNC.
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70172d647bd0430cf55959218f45740d | 25.902 | 6.2 Functional description
| |
70172d647bd0430cf55959218f45740d | 25.902 | 6.2.1 Iub/Iur congestion detection
| The Node B scheduler decides on when and with which bit rate each and every UE is allowed to transmit in the cell. Each received MAC-es PDU is placed in a frame protocol data frame and sent to the SRNC (in some cases several PDUs are bundled into the same data frame). For each data frame, the Node B attach the following information:
• A reference time, that gives an indication on when the frame was sent.
• A sequence number, that gives an indication on which frame this is in relation to other data frames.
At the reception of the data frames the SRNC can do the following:
• With the use of the reference time, the SRNC can compare the relative reception time with the relative transmission time (the reference time included in the data frame). With that information the SRNC can detect if there is a delay build-up in the transmission path. A delay build-up is an indication on that frames are being queued due to overload in the transport network.
• With the use of the sequence number, the SRNC can detect a frame loss. A frame loss is an indication that packets have been lost in the transport network due to overload reasons.
This procedure is illustrated in Figure 1.
Figure 1: Iub/Iur Congestion Detection
|
70172d647bd0430cf55959218f45740d | 25.902 | 6.2.2 Iub/Iur congestion reduction
| When the RNC has detected that there is a congestion situation in the transport network, it needs to inform the Node B that this is the case. This is done by means of a frame protocol control frame, in which the Node B is informed about the congestion situation. This control frame will be called Congestion Indication. This is illustrated in Figure 2.
Figure 2: Iub/Iur Congestion Indication
As the RNC can detect congestion in two different ways, there exist no motivation why such information should not be communicated to the Node B. For that reason the Congestion Indication Control Frame can take the following values: "Congestion – detected by frame loss", "Congestion – detected by delay build-up", and "No congestion".
At the reception of the Congestion Indication control frame, the Node B should reduce the bit rate on the Iub interface. The exact algorithm the Node B should use is outside the scope of the specifications, but the specifications should address the expected behaviour of the Node B.
Such behaviour should include:
• At the reception of a congestion indication control frame indicating "congestion" the Node B should reduce the bit rate for at least the MAC-d flow on which the congestion indication control frame was received.
• At the reception of a congestion indication control frame indicating "no congestion" the Node B can gradually go back to normal operation.
• If the Node B has not received a congestion status control frame indicating congestion for the last X seconds, the Node B can gradually go back to normal operation. The value of the parameter X is configured by higher layers.
Editor's note: Whether the third bullet above should be included in the specifications is an open issue.
This level of specification of the Node B behaviour is sufficient, for the following reasons:
|
70172d647bd0430cf55959218f45740d | 25.902 | 1 The purpose of the congestion control, is not to act as a flow control but rather as an "emergency break" in order to keep the system at a stable state.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 2 The output bit rate from the node B depends on many things, for example radio interference, distance from mobile to Node B, available hardware resources etc. The Node B scheduler will need to take all that into consideration when assigning the bit rate to each mobile.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 3 Performance wise, to specify very detailed behaviour when the control frame is received is not possible due to the reasons in bullet 2.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 6.2.3 A similar solution for HSDPA
| It has been acknowledged that similar functionality shall also be introduced for HSDPA. Further it was expressed that such a solution should be as similar as possible to any solution for Enhanced Uplink. In this clause such functionality is proposed and analysed.
From a conceptual point of view, the reuse of the concept that the detection of Iub/Iur congestion is done by measuring a delay build-up, and/or by detecting frame loss (or lost number of bytes/bits) is proposed.
For Enhanced Uplink it was required to introduce a specific congestion indication control frame for informing the Node B about the congestion. This is not required in the case of HSDPA - a working flow control mechanism already exists. In order to minimize complexity, implementation and tuning efforts, the reuse of this mechanism for the purpose of congestion control is proposed.
As a result, the only required changes in the specifications would be to add support for the Node B to detect congestion situations. From the discussion on Enhanced Uplink, it is known that this mechanism should be based on the measuring of a delay build-up or by detecting some kind of sequence loss.
Time stamp for measuring delay build-up
For Enhanced Uplink a "time stamp" has already been agreed implicitly by the introduction of CFN and SFN for reordering purposes. The CFN and SFN fields can be used also for the purpose of detecting delay build-up and there is no need for any additional information.
For HSDPA, CFN and SFN are not used. Therefore, the introduction of a delay reference time tied to RFN is proposed. RFN is already defined and should not impose and additional complexity. The Node B can detect delay build-ups by noting the arrival time of subsequent Delay-Reference-Time (DRTs) and comparing them.
Sequence Number for detecting frame/data loss.
Furthermore, some kind of sequence number added to the data frame is required - in order to allow the receiver to detect when a frame has been lost. There are two possible options, a frame sequence number (FSN) or a quantum sequence number (QSN). The pros and cons with those has been discussed and it has been concluded that for Enhanced Uplink the usage of a 4 bit field (FSN) would be sufficient.
The HSDPA solution should be as similar as possible – if possible – to that for Enhanced Uplink. A 4 bit FSN would fit into the spare bits of today's data frame, while an introduction of a 12-16 bit (minimum) QSN would require to make use of the spare extension mechanism, adding a minimum of three octets to the data frame. Considering that data frames are not bundled for HSDPA, results in a general smaller frame, as well as a lower standard deviation of the frame size, the extra overhead with QSN is motivated.
The usage of Congestion Indication Control Frame
For Enhanced Uplink the usage of a control frame for indicating that there is a congestion situation is proposed. Such a solution would be possible to apply also for HSDPA. There is however an important difference in the functional split between HSDPA and Enhanced Uplink. HSDPA already has a flow control mechanism in order not to overflow the Node B buffers. For that reason the easiest (both specification wise and implementation wise) will be to reuse the mechanism for flow control. For that reason, only the need to specify the means for the Node B to detect a congestion situation, i.e. DRT and FSN, is required.
Conclusion
The outlined solutions for HSDPA and Enhanced Uplink are functionality wise similar, congestion detection is done by observing a time stamp and a sequence number.
Although it would be nice to have exactly the same coding of the detection and notification for both HSDPA and Enhanced Uplink, smaller differences can be accepted if that leads to more efficient coding, and implementation, saving overhead. The most obvious case is the time stamp, CFN and SFN, already exists for Enhanced Uplink, but it cannot be inserted into the HSDPA user data header. As there is no CFN and SFN defined for HSDPA, using a time stamp linked to the RFN is proposed.
There is a possibility to have the exact same coding of the sequence number: A 4 bit FSN fits into both the HSDPA and the Enhanced Uplink user data frame headers.
For the notification message a control frame for Enhanced Uplink is proposed and the reuse of the existing flow control mechanism for HSDPA.
|
70172d647bd0430cf55959218f45740d | 25.902 | 6.2.4 Handling of the Iur
| Two philosophies can be distinguished for the handling of the Iub traffic, referred to as the "Iub pipe" and the "Iub cloud".
|
70172d647bd0430cf55959218f45740d | 25.902 | 6.2.4.1 Iub pipe philosophy
|
Figure 3: "Iub pipe" philosophy
With the "Iub pipe", logic the CRNC enforces the traffic limit injected on the Iub interface in the DL, so it is able to instantaneously detect any congestion situation. The advantage of this approach is that there is no need for using any new congestion mechanisms in the Node B, because the congestion detection is instantaneous – the only place it can occur is at the "pipe" entry. The drawback of the "pipe" logic is that in some scenarios it may require complex configuration of TNL topologies in the CRNC in order to leverage statistical multiplexing.
If the "pipe" logic on the Iub is to be preserved, when the HS-DSCH connection extends across the Iur interface it is important to note that the HS-DSCH Flow Control should be terminated in the DRNC. This case is depicted in Figure 4.
Figure 4: FC termination in DRNC and "pipe" on Iub
As illustrated in Figure 4, there are two separate Flow Control loops exerted on both Iub and Iur.
|
70172d647bd0430cf55959218f45740d | 25.902 | 6.2.4.2 Iub Cloud philosophy
|
Figure 5: "Iub cloud" philosophy
With the "Iub cloud" logic, the traffic injected by the RNC is less tightly controlled i.e. the RNC is likely to inject too much traffic in the network, thus yielding a congestion situation. This approach should allow for statistical multiplexing in some scenarios without complex configuration of TNL topology in the CRNC. However, with this approach a new congestion control mechanisms become a necessity.
This "Iub cloud" logic can easily be extended to the handling of the Iur as shown in figure 6:
Figure 6: "Iub cloud" philosophy extended to the Iur
|
70172d647bd0430cf55959218f45740d | 25.902 | 6.2.4.3 Co-existence of the two philosophies
| In the situation where the HS-DSCH connection extends across the Iur interface it is important to note that – should it be employed – the HS-DSCH flow control may be terminated in the DRNC.
In this scenario, two separate flow control loops would then be employed on both Iub and Iur.
If, in the "Iub pipe" logic, a DRNC detects congestion, it will either buffer or discard the excess data. In either case, a CC-enabled NodeB (i.e. a Node B with the "Iub cloud" logic) would detect the congestion situation as well.
In order to avoid race conditions between the two competing mechanisms (Congestion Control in the Node B and Congestion Control in the CRNC), it is thus proposed to introduce the possibility to turn off Congestion Control in the Node B via Control Plane mechanisms. By doing so, congestion will be detected and handled in only one place in the network.
There are two possible solutions to achieve that result:
|
70172d647bd0430cf55959218f45740d | 25.902 | 1 The DRNC makes the decision to use Congestion Control and indicates to the Node B – via Control Plane - not to perform Congestion Control (e.g. using the Physical Shared Channel Reconfiguration procedure).
| |
70172d647bd0430cf55959218f45740d | 25.902 | 2 The DRNC makes the decision and indicates to the SRNC that it shall include the user plane protocol extensions that are used by the Node B to detect congestion (namely the timestamp and the Frame Sequence Number) by introducing a new User Plane Congestion Field Inclusion IE in the HS-DSCH FDD/TDD Information Response IEs.
| This would allow the DRNC to indicate to the SRNC if User Plane fields destined to be used for Congestion detection by the Node B are to be included or not in the HS-DSCH Data Frames. If not included, Congestion detection and Congestion Control will not be employed by the Node B.
This second approach is preferred as it allows to save bandwidth on the UTRAN interfaces and it really allows not to perform any Congestion Control in the Node B as no information is available.
|
70172d647bd0430cf55959218f45740d | 25.902 | 6.3 Impacts on Iub/Iur control plane protocols
| TS 25.423
• a new User Plane Congestion Field Inclusion IE in the HS-DSCH FDD/TDD Information Response IEs.
|
70172d647bd0430cf55959218f45740d | 25.902 | 6.4 Impacts on Iub/Iur user plane protocols
| TS 25.427
• EDCH data frame: Introduction of a 4 bit Frame Sequence Number (FSN) field.
• EDCH data frame: Clarification that CFN and SFN can be used for dynamic delay measurements.
• Introduction of a Congestion Status control frame.
• Specification of desired behaviour when Node B receives the Congestion Status control frame.
TS 25.425 and TS 25.435
• HS-DSCH data frame: Introduction of a 4 bit Frame Sequence Number (FSN) field.
• HS-DSCH data frame: Introduction of a 16 bit Delay Reference Time (DRT) field.
TS 25.435
• Usage of 2 of 4 previously spare bits within Capacity Allocation Procedure payload for indication of congestion in TNL. Used for Congestion Indication for HSDPA only.
|
70172d647bd0430cf55959218f45740d | 25.902 | 6.5 Open issues
| • Thus far Iub/Iur Congestion Control has been considered for HSDPA and Enhanced Uplink only. Could any final solution be applicable for UL and DL DCH?
|
70172d647bd0430cf55959218f45740d | 25.902 | 6.6 Backwards compatibility
| void
|
70172d647bd0430cf55959218f45740d | 25.902 | 7 Agreements and associated contributions
| |
70172d647bd0430cf55959218f45740d | 25.902 | 1 The development of an Iub/Iur Congestion control solution should bear in mind both the E-DCH and HSDPA features.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 2 Iub/Iur Congestion control for both HSDPA and Enhanced Uplink should – if possible – employ similar solutions.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 3 The RNC remains the entity in charge of the Congestion Control function.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 4 NodeB behaviour when receiving the congestion indication shall be specified.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 5 The detection algorithm will not be specified in the TR. (However example algorithms may be given in an annex.)
| |
70172d647bd0430cf55959218f45740d | 25.902 | 6 Congestion indication should be signalled via the user plane.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 7 Signalling of Congestion via the user plane will also include varying levels of congestion severity.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 8 Congestion Detection will be performed on a per flow basis.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 9 Within the E-DCH data frame (user plane), congestion detection will be based upon a time reference or a sequence number.
| 10 For the handling of Iub/Iur Congestion due to HSDPA, the CRNC decides whether all or none of the HS-DSCH MAC-d Flows of a context are subject to Congestion Control.
|
70172d647bd0430cf55959218f45740d | 25.902 | 11 A "counter" field be attached to EVERY E-DCH data frame.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 12 The "counter" field within the E-DCH frame will take the form of a "frame sequence number" (FSN).
| |
70172d647bd0430cf55959218f45740d | 25.902 | 13 Different levels of congestion shall be indicated by "No congestion", "TNL Congestion – detected by delay build-up", "TNL Congestion – detected by frame loss".
| |
70172d647bd0430cf55959218f45740d | 25.902 | 14 The resulting behaviour following the signalling of Congestion Indication will not be defined – this is an implementation matter.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 15 For impacts upon RNL xxxAP Signalling protocols, please refer to CR 1080 against TS 25.423. This CR allows a CRNC to decide whether a particular E-DCH flow is subject to congestion control at flow setup.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 16 Regarding the possibility of an Iub/Iur Congestion Control solution incorporating Rate Adaptation, this functionality was discussed, but a solution was not found, nor foreseen as possible at this time.
| |
70172d647bd0430cf55959218f45740d | 25.902 | 17 With respect to Softhandover, no issues have been found concerning the relationship/interaction with E-DCH Congestion Control.
| 8 Specification impact and associated Change Requests
This clause is intended to list the affected specifications and the related agreed Change Requests. It also lists the possible new specifications that may be needed for the completion of the Work Task.
CR Title
Impacted Specification
CR implemented against version:
CR Number
Transport Network Congestion Detection and Control
TS 25.427
V6.2.0
109
Transport Network Congestion Detection and Control
TS 25.425
V6.1.0
99
Transport Network Congestion Detection and Control
TS 25.435
V6.1.0
142
Congestion Indication for HSDPA
TS 25.435
V6.3.0
143
Congestion control for HSDPA
TS 25.423
V6.5.0
1080
For 3.84 Mcps TDD the concepts added for FDD in the above CRs are also added in the general CR for TDD that add the feature to the specifications. For 7.68 Mcps TDD the concepts added for FDD in the above CRs are also added in the general CR for TDD that add the feature to the specifications. For 1.28 Mcps TDD the concepts added for FDD in the above CRs are also added in the general CR for TDD that add the feature to the specifications.
Annex A:
Change history
Change history
Date
TSG #
TSG Doc.
CR
Rev
Subject/Comment
Old
New
06/2005
TSG-RAN#28
RP-050231
Presentation of TR for information
-
1.0.0
09/2005
TSG-RAN#29
RP-050436
Presentation of TR for approval
1.0.0
2.0.0
09/2005
TSG-RAN#29
RP-050436
TR approved at TSG-RAN#29 and placed under change control
2.0.0
6.0.0
09/2006
TSG-RAN#33
RP-060507
3
1
Removal of erroneous References from TR 25.902 Iub/Iur Congestion Control
6.0.0
6.1.0
09/2006
TSG-RAN#33
RP-060511
2
Introduction of 3.84 Mcps and 7.68Mcps TDD Enhanced Uplink
6.1.0
7.0.0
03/2007
TSG-RAN#35
RP-070062
4
Introduction of 1.28 Mcps TDD Enhanced Uplink
7.0.0
7.1.0
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 1 Scope
| This present document is for the 3GPP Release 6 Work Item "Network Assisted Cell Change – Network Side Aspects.".
The purpose of the present document is to aid TSG RAN WG3 to standardise the signalling of relevant GERAN information during cell re-selection across the relevant UTRAN interfaces.
This document is intended to gather all information in order to compare the solutions and to draw a conclusion on the way forward.
This document is a 'living' document, i.e. it is permanently updated and presented to TSG-RAN meetings.
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 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] 3GPP TS 44.060: "3rd Generation Partnership Project; Technical Specification Group GSM/EDGE Radio Access Network; General Packet Radio Service (GPRS); Mobile Station (MS) - Base Station System (BSS) interface; Radio Link Control/Medium Access Control (RLC/MAC) protocol".
[2] 3GPP TS 44.901: "3rd Generation Partnership Project:; Technical Specification Group GSM/EDGE Radio Access Network; External Network Assisted Cell Change".
[3] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 3 Definitions, symbols and abbreviations
| |
873bb0765fb9905ca579985e57bc695e | 25.901 | 3.1 Definitions
| For the purposes of the present document, the following terms and definitions apply.
Local RNC: the local RNC(s) to a given cell or BSS is/are the RNC(s) with cells which are neighbouring to the GERAN cell or BSC.
Remote RNC: an RNC is remote to a given GERAN cell or BSS if none of its cells are neighbours of the GERAN cell or BSS.
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 3.2 Symbols
| For the purposes of the present document, the following symbols apply:
Gb Interface between the BSS and the 2G SGSN
Gn Interface between two GSNs in the same PLMN
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 3.3 Abbreviations
| Applicable abbreviations can be found in [3]. For the purposes of the present document, the following abbreviations apply:
BSSGP Base Station Subsystem GPRS Protocol
DRNC Drift RNC
GERAN Gsm/Edge Radio Access Network
NACC Network Assisted Cell Change
PSI Packet System Information
RAN Radio Access Network
RIM Ran Information Management
RNC Radio Network Controller
SI System Information
SRNC Serving RNC
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 4 Introduction
| At the 3GPP TSG RAN #19 meeting, the Work Item Description on "Network Assisted Cell Change from UTRAN to GERAN – Network Aspects" was approved.
In today's GPRS networks (without NACC), cell re-selection can causes a service interruption in the region of 4 – 8 seconds, which obviously has an impact on the user experience. Similar interruption times can be expected in mixed UMTS and GPRS networks, during UE cell re-selection from UTRAN to GERAN.
Consequences of this: e.g. TCP applications may time-out at cell change and suffer from the slow-start mechanism, streaming applications may stop at cell change due to client buffer depletion. All such problems will lead to an unacceptable user experience.
This "Network Assisted Cell Change" feature has already been introduced in the GERAN specifications and the appropriate changes have been to the RLC/MAC protocol [1] within Release 4. Additional enhancements were approved in Release 5 in order to exchange (Packet) System Information between BSSs, so that NACC can work across BSS boundaries.
Currently, there are procedures defined on the Gb and Gn interfaces to enable signalling of GERAN SI/PSI between BSSs. This RAN Information Management (RIM) mechanism was defined initially for the use of NACC, although in a manner that could be extended for applications other than NACC. It consists of the following messages:
- RAN INFORMATION REQUEST - from Source BSS to Target BSS – requests GERAN SI/PSI.
- RAN INFORMATION – from target BSS to source BSS – analogous to the Information Exchange over Iur and includes GERAN SI/PSI for one or more GERAN cells.
- RAN INFORMATION ACKNOWLEDGE – from Source BSS to Target BSS.
- RAN INFORMATION ERROR - to inform about e.g. message syntax errors.
In Release 5, TSG RAN approved the provision of the GERAN (P)SI messages in the CELL CHANGE ORDER FROM UTRAN message. In order for this feature to work successfully, a standardised method is required to signal relevant GERAN information across the relevant UTRAN interfaces.
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 5 Requirements
| The standardisation of NACC from UTRAN to GERAN shall meet the following requirements:
1) The impact to the Gb and Gn interfaces shall be minimised.
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 6 Study Areas
| |
873bb0765fb9905ca579985e57bc695e | 25.901 | 6.1 UTRAN NACC signalling architecture
| |
873bb0765fb9905ca579985e57bc695e | 25.901 | 6.1.1 General
| Three possible mechanisms have been identified to gain access to the GERAN SI/PSI at the SRNC, whilst minimising the impacts on the existing Gb/Gn procedures:
1) The (P)SI is stored by the SRNC.
2) The (P)SI is stored by the local RNC
3) O&M-based distribution of (P)SI.
These solutions are explained in the following sub-clauses.
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 6.1.2 Solution 1: (P)SI stored by the SRNC
| |
873bb0765fb9905ca579985e57bc695e | 25.901 | 6.1.2.1 General description
| This solution is based on the serving RNC directly requesting and receiving the SI/PSI from the target BSS and it is depicted in figure 1.
1) The SRNC receives a measurement report from the UE and decides to move the UE to GERAN.
NOTE: The SRNC could request the info earlier on receiving GERAN n_cell info from DRNC.
2) The SRNC triggers a REQUEST to the SGSN.
3) The SGSN then uses existing RIM procedure to forward the request to the BSS.
4) The BSS uses existing RIM procedure towards SGSN to pass the GERAN SI/PSI back to the SRNC via SGSN either "on-demand" (i.e. single report) or on an "on-modification" basis (i.e. multiple reports).
5) The SGSN then relays this information to the SRNC via the Iu interface.
6) If multiple reports are used, the SRNC could terminate the reporting using a procedure TERMINATION/END message.
NOTE: The measurement report from the UE is a connection oriented procedure, whereas the RAN Information Request procedure is connectionless. It was noted for further study that currently the RNC does not have the functionality to deal with this situation.
Figure 1: Signalling diagram for Solution 1 of GERAN SI/PSI Retrieval
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 6.1.2.2 Analysis of the solution
| Pros:
1) No additional Iur load generated.
2) No additional Iur implementation required.
3) Synchronised update of SI/PSI is possible using "on-modification" measurement reporting.
Cons:
1) Generally more SI/PSI stored in each RNC than in other solutions.
2) Additional load on the SGSN due to signalling path of RIM procedures.
3) Additional load on the BSS due to a potentially high number of measurement contexts being required (for each different SRNC).
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 6.1.3 Solution 2: (P)SI stored by the local RNC
| |
873bb0765fb9905ca579985e57bc695e | 25.901 | 6.1.3.1 General description
| This solution is based on the local RNC requesting SI/PSI from the BSS, and receiving it on an "on-modification" basis. This procedure is depicted in figure 2.
1) After installation and configuration of the GERAN neighbouring cell lists in the local RNC, a REQUEST message is sent to the SGSN requesting GERAN SI/PSI for the GERAN cells that are configured in the local RNC neighbouring cell list.
2) The SGSN then uses existing RIM procedure to forward the request to the BSS.
3) BSS uses existing RIM procedure towards SGSN to pass the GERAN SI/PSI back to the (D)RNC via SGSN "on-modification".
4) The SGSN would then relay this information to DRNC via the Iu interface.
5) The GERAN SI/PSI is transferred using existing RNSAP procedures over the Iur interface towards the SRNC when it requires it.
Figure 2: Signalling diagram for Solution 2 of GERAN SI/PSI Retrieval
|
873bb0765fb9905ca579985e57bc695e | 25.901 | 6.1.3.2 Analysis of the solution
| Pros:
1) Generally less SI/PSI stored in each RNC than in other solutions.
2) Synchronised update of SI/PSI is possible using "on-modification" measurement reporting.
3) Impact on SGSN load is minimised.
Cons:
1) More Iur signalling than SRNC terminated solution.
2) Additional load on the DRNC due to potentially high number of measurement contexts being created (for each different SRNC).
|
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