1、 ETSI TR 136 933 V15.0.0 (2018-07) LTE; Study on Context Aware Service Delivery in RAN for LTE (3GPP TR 36.933 version 15.0.0 Release 15) TECHNICAL REPORT ETSI ETSI TR 136 933 V15.0.0 (2018-07)13GPP TR 36.933 version 15.0.0 Release 15Reference RTR/TSGR-0336933vf00 Keywords LTE ETSI 650 Route des Luc
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13、nt by ETSI of products, services or organizations associated with those trademarks. Foreword This Technical Report (TR) has been produced by ETSI 3rd Generation Partnership Project (3GPP). The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identit
14、ies or GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables. The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under http:/webapp.etsi.org/key/queryform.asp. Modal verbs terminology In the present document “should“, “should
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16、36 933 V15.0.0 (2018-07)33GPP TR 36.933 version 15.0.0 Release 15Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 4g3Introduction 4g31 Scope 5g32 References 5g33 Definitions, symbols and abbreviations . 5g33.1 Definitions 5g33.2 Abbreviations . 6g34 Defini
17、tions and problems description . 6g34.1 Issue 1: Backhaul long latency . 6g34.2 Issue 2: TCP E2E delay with throughput decreasing . 6g34.3 Issue 3: Video transmission issue cases . 6g34.4 Issue 4: UL Video transmission critical data discard . 7g35 Solutions . 7g35.1 General Principles 7g35.2 Solutio
18、ns for issue 1 . 7g35.2.1 Solution 1: UE assisted local cache solution 7g35.2.2 Conclusion for Issue 1 9g35.3 Solutions for issue 2 . 9g35.3.1 TCP Performance Enhancing Proxy (TCP PEP) 9g35.3.2 Network based Radio-Aware TCP 9g35.3.3 UE Based Radio-Aware TCP Solution . 10g35.3.4 eNB generates TCP ACK
19、 on behalf of the UE . 10g35.3.5 Conclusion for Issue 2 11g35.4 Solutions for issue 3 . 11g35.4.1 Solutions for case 1 . 11g35.4.1.1 Solution 1: UE request a higher QoS profile . 11g35.4.1.2 Solution 2: Video Context Aware Solution . 11g35.4.2 Solutions for case 2 . 12g35.4.2.1 Solution 1: PCC-based
20、 Solution 12g35.4.2.2 Solution 2: Solution of DASH optimisation 13g35.4.2.3 Solution 3: Solution of DASH optimisation via local breakout 14g35.4.3 Solutions for case 3 . 15g35.4.3.1 Solution 1 15g35.4.4 Conclusion for Issue 3 16g35.5 Solutions for issue 4 . 16g35.5.1 Solution 1: Dynamic adaptation o
21、f LTE radio resource allocation during the call . 16g35.5.2 Solution 2: Static acceptance or rejection of adaptation of LTE radio resource allocation for the call 16g3Annex A (informative): Video playout buffer aware scheduling . 17g3Annex B (informative): Change history . 18g3History 19g3ETSI ETSI
22、TR 136 933 V15.0.0 (2018-07)43GPP TR 36.933 version 15.0.0 Release 15Foreword This Technical Specification has been produced by the 3rdGeneration Partnership Project (3GPP). The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approva
23、l. 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
24、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. Introduction Voic
25、e was the major service and 3GPP defined voice specific cross-layer optimizations for 3G and 4G. Web based streaming video and Apps are expected to take majority of 4G/5G bandwidth, and are key source to further increase the ARPU for operators. MPEG and 3GPP SA4 have been considering cross-layer opt
26、imizations by RAN and App mutual aware, e.g. network assisted DASH, video-aware scheduling. It is worthwhile and right time to study whether deep cross-layer optimizations for Web based streaming video and Apps can deliver the desired benefits. It is also worthwhile to take into account the related
27、work in other SDOs/Working groups, e.g. ETSI MEC work on mobile video delivery optimization and local content caching. It is also beneficial to study and analyse the potential impact to architecture, protocol, and signalling to support RAN based local cached delivery, local breakout; and support RAN
28、 optimizations based on context awareness. ETSI ETSI TR 136 933 V15.0.0 (2018-07)53GPP TR 36.933 version 15.0.0 Release 151 Scope The present document provides descriptions and possible solutions of use cases for the Context Aware Service Delivery in RAN for LTE, and also provides analysis of these
29、solutions. Considerations with regards to requested functionality in scope of other 3GPP groups, if any, may be captured in this document as well. 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the present document. - Reference
30、s 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 d
31、ocument), 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 IETF RFC3135, Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations 3 X. Xu, Y. Ji
32、ang, T. Flach, E. Katz-Bassett, D. Choffnes, and R. Govindan, “Investigating performance enhancing proxies in cellular networks,” in AIMS: 6th Workshop on Active Internet Measurements, Mar. 2014. 4 M. Necker, M. Scharf, and A. Weber, “Performance of TCP and HTTP Proxies in UMTS Networks,” in Wireles
33、s Conference 2005 - Next Generation Wireless and Mobile Communications and Services (European Wireless), 11th European, April 2005, pp. 17. 5 M. Meyer, J. Sachs, and M. Holzke, “Performance evaluation of a TCP proxy in WCDMA networks,” Wireless Communications, IEEE, vol. 10, no. 5, pp. 7079, Oct 200
34、3. 6 F. Ren, X. Huang, F. Liu, and C. Lin, “Improving TCP Throughput over HSDPA Networks,” Wireless Communications, IEEE Transactions on, vol. 7, no. 6, pp. 19931998, June 2008. 7 V. Farkas, B. Hder, and S. Novczki, “A Split Connection TCP Proxy in LTE Networks,” in Information and Communication Tec
35、hnologies. Springer Berlin Heidelberg, 2012, vol. 7479, pp. 263274. 8 S4-170238, Revised Work Item on “Server and Network Assisted DASH (SAND) for 3GPP Multimedia Services” 9 3GPP TR 26.957: “Study on Server And Network-assisted Dynamic Adaptive Streaming over HTTP (DASH) (SAND) for 3GPP multimedia
36、services” 3 Definitions, symbols and abbreviations 3.1 Definitions For the purposes of the present document, the terms and definitions given in 3GPP 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 3GPP TR 2
37、1.905 1. ETSI ETSI TR 136 933 V15.0.0 (2018-07)63GPP TR 36.933 version 15.0.0 Release 153.2 Abbreviations For the purposes of the present document, the abbreviations given in 3GPP TR 21.905 1 and the following apply. An abbreviation defined in the present document takes precedence over the definitio
38、n of the same abbreviation, if any, in 3GPP TR 21.905 1. 4 Definitions and problems description 4.1 Issue 1: Backhaul long latency The issue may arise in cases where the distance between the RAN and the node hosting the application content is long or the number of routers on this route is high. In t
39、hese cases long transportation latency may be experienced. Consequently certain kinds of service may be impacted significantly due to the long latency. For example, backhaul delay increases the TCP RTT, therefore if TCP is configured in a way that it cannot cope with such delays, TCP throughput can
40、be affected. 4.2 Issue 2: TCP E2E delay with throughput decreasing The behavior of TCP assumes that network congestion is the primary cause for packet loss and high delay. In cellular networks the bandwidth available for each UE can vary by an order of magnitude on a TTI basis due to changes in the
41、underlying radio channel conditions. Such changes can be caused by the movement of devices or interference, as well as changes in system load due to bursty traffic sources or when other UEs enter and leave the network. TCP has difficulties adapting to these rapidly varying conditions. If the E2E del
42、ay increases, the TCP RTT increases and the TCP throughput may decrease, which may impact the user experience. 4.3 Issue 3: Video transmission issue cases The Operator video is a video service under the LTE operators control. It is usually transmitted over a dedicated EPS bearer or using a dedicated
43、 QCI. However, there might be cases where an operator decides not to apply any dedicated QoS to a video service. These video services are named “Over-The-Top” (OTT) video and are video services that LTE operators have no control on. Such service traffic is usually treated in the same way as normal i
44、nternet traffic, e.g. transmitted via default bearer, which may lead to poor QoE. Nevertheless, the QoS framework allows assignment of dedicated QCI for video. Dedicated bearer and QCI is helpful in lessening the video issues. Below are some of the issues that may occur when operators decide to neit
45、her use dedicated bearers nor dedicated QCI for OTT video services. Case 1: Empty buffer issue The user is watching a streaming video. When the UE requests for some not yet buffered video segments e.g. by dragging a play scroll bar or when playout buffer is exhausted due to link throughput fluctuati
46、on and if the scheduling priority of the video content is not set accordingly, the video playing would probably stall depends on some condition, e.g. eNBs load and UEs QoS profile. Case 2: Inaccurate throughput prediction for DASH issue DASH client requests video quality based on downlink throughput
47、 prediction. Throughput prediction is based on implementation specific mechanisms. The accuracy of the prediction is dependent from the specific implementation. However, one factor that may affect the prediction is that the DASH client may base the prediction on previous downloads. The DASH client m
48、ay not have an insight to whether the network conditions have changed, thus the current available throughput may be difficult to predict. Conservative requesting low data rate video segment leads to low video quality and aggressive requesting high data rate video segment leads to more video stalling
49、. Case 3: Long video delay issue In HTTP based streaming, client first buffers some content, i.e. initial buffering, before playout in order to absorb the throughput and delay fluctuation. Assuming that scheduling priority is not appropriately set, a large buffer may cause long delay, thus lead to bad user experience. ETSI ETSI TR 136 933 V15.0.0 (2018-07)73GPP TR 36.933 version 15.0.0 Release 154.4 Issue 4: UL Video transmission critical data discard In conversational video (real-time streaming) the problem of PDCP discard of critical data i
