# Summary of 3GPP TR 26.501 Change Request ## Document Information - **CR Number**: 0016 rev 3 - **Specification**: 26.942 v19.0.0 - **Work Item**: FS_Energy_Ph2_MED - **Category**: B (addition of feature) - **Release**: Rel-20 ## Change Request Overview This CR proposes a solution for Key Issue #6 addressing client-driven management of media delivery service energy optimization, specifically focusing on switching between multipath and single-path media delivery based on energy information from the network. ## Main Technical Contributions ### 1. Solution Scope and Mapping The candidate solution addresses **Key Issue #6** on client-driven switching between multipath and single-path transport sessions based on network energy consumption information. The solution is mapped in Table 7.1-1 showing the relationship between solutions and key issues. ### 2. Functional Description #### 2.1 Multipath Transport Context - Leverages existing multi-access media delivery features from TR 26.804 clause 5.18 - Utilizes multipath transport protocols (MPTCP/MPQUIC) for transparent use of multiple access networks - References Configuration and Settings API from TS 26.512 clause 13.2.4 for multipath operation configuration - Multipath sessions can span multiple access networks to improve resilience and throughput #### 2.2 Core Mechanism The solution introduces switching between: - **Multipath transport session**: potentially over multiple access networks - **Single-path session**: based on energy consumption information from network to UE Two operational modes are supported: - Transparent to application layer (hidden behind virtual tunnel interface per TS 23.501 clause 5.32.2) - Explicitly indicated to Media Access Function by Media Session Handler or Media-Aware Application (per TS 23.512 clause 13.2.4) ### 3. Reference Architecture #### 3.1 Architecture Components Figure 7.X.2.13-1 depicts the reference architecture based on the generalized Media Delivery architecture (TS 26.501 clause 4.1.2): **Network Side:** - **Energy Information Function (EIF)**: Collects energy consumption information per TS 23.501 clause 5.51.2.2 - **Energy Information AF**: Instantiated in Media AF, receives information from EIF **UE Side:** - **Energy Information Collector**: Instantiated in Media Session Handler of Media Client - **Media-Aware Application**: Makes switching decisions - **Media Access Function**: Implements transport session changes **Key Reference Points:** - **E5**: Energy information delivery from Energy Information AF to Energy Information Collector - **M4**: Media flow exchange and switching decision interface No new reference points are defined; existing architecture is reused. ### 4. Energy-Related Information #### 4.1 Access Network Energy Cost Information Table 7.X.25.21-1 defines the baseline information structure: - **Access network energy cost information**: Array of descriptors providing network energy cost for delivering application flows over specific access networks for the current Media Delivery session This enables UE to determine relative cost of establishing transport connections over different available access networks. ### 5. Procedures Figure 7.X.36-1 details the complete procedure with the following key steps: #### 5.1 Session Establishment and Subscription (Steps 1-4) 1. Media delivery session established, energy information subscription performed, EIF sends energy information to UE via EIAF (references baseline procedure clause 7.6.6 steps 1-14) - **NOTE 1**: AS configuration and AS Energy Information reports are not mandatory for this solution - **NOTE 2**: Network Energy Information includes access network energy cost information per clause 7.X.5.1 2. Media delivery session established between UE and network entities, potentially using multipath transport (TR 26.804 clause 5.18.4) 3. Media Session Handler configures Energy Information Collector to subscribe to energy events via internal client API 4. Energy Information Collector subscribes to receive energy events from Energy Information AF over E5 #### 5.2 Media Delivery and Energy Monitoring (Steps 5-8) 5. M4 media flows exchanged between Media Access Function and Media AS 6. EIF provides NF energy information to Energy Information AF per TS 23.501 clause 5.51.2.2 - Includes per-UE granularity - For Multi-Access PDU Sessions: includes UE-specific energy consumption estimates per access network - May be relayed via NEF if Media AF is untrusted 7. Energy Information AF forwards energy consumption information to Energy Information Collector over E5 8. Energy Information Collector forwards energy information to Media Session Handler via internal client API #### 5.3 Decision and Switching (Steps 9-12) 9. Media Session Handler and Media-Aware Application decide on switching between multipath and single-path based on: - Access network energy cost information from network - UE internal energy consumption to support multipath over multiple access networks 10. Media Session Handler updates transport session parameters per TS 26.512 clause 13.2.4 (if needed) 11. Media Access Function applies updated configuration to media delivery transport session 12. Media Access Function and Media AS switch to new transport session for M4 application flows ### 6. Gap Analysis The solution identifies gaps beyond the baseline procedure (clause 7.6.4): **Additional Gaps for This Solution:** - Energy Information AF must acquire per-access network energy cost information (clause 7.X.5.1) - Energy Information AF must include per-access network energy cost in Network Energy Information report to UE - Media Aware Application and Media Session Handler must implement decision logic for switching between single-path and multi-path based on received Network Energy Information ### 7. Proposed Normative Work Beyond baseline normative changes in clause 7.6.5, the following additional normative work is proposed: #### 7.1 New Stage 2 Specification - Define generic architecture and procedures for Energy Information AF and Energy Information Collector - Include parameters for exposure of network energy cost information per access via E5 #### 7.2 TS 26.501 [23] Updates - Design principles and procedures for exposure of network energy information per access to Energy Information Collector - Procedures for Media Aware Application to switch between single-path and multi-path based on clause 7.X.6 #### 7.3 TS 26.506 [59] Updates (RTC System) - Design principles and procedures for exposure of network energy information per access - Procedures for RTC Application to switch between single-path and multi-path #### 7.4 TS 26.512 [26512] Updates (5GMS System) - Extensions to procedures and service-based interfaces at E5 for additional per-access energy-related information for media streaming sessions - Extensions to client API at M6, M7, and M11 reference points #### 7.5 TS 26.113 [26113] Updates (RTC System) - Extensions to procedures and service-based interfaces at E5 for additional per-access energy-related information for RTC sessions - Extensions to client API at RTC-6, RTC-7, and RTC-11 reference points ## Revision History - **S4-251924**: Initial contribution - **S4-252096**: Updated with SA4#134 comments - **S4aI260021**: Updated with SA4#134 comments and aligned with baseline procedure S4aI260016 - **S4-260243**: Resubmission (noted without presentation due to time) with alignment to baseline procedure on energy consumption and exposure