1、 ETSI TR 136 933 V14.0.0 (2017-04) LTE; Study on Context Aware Service Delivery in RAN for LTE (3GPP TR 36.933 version 14.0.0 Release 14) TECHNICAL REPORT ETSI ETSI TR 136 933 V14.0.0 (2017-04)13GPP TR 36.933 version 14.0.0 Release 14Reference RTR/TSGR-0336933ve00 Keywords LTE ETSI 650 Route des Luc
2、ioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N 348 623 562 00017 - NAF 742 C Association but non lucratif enregistre la Sous-Prfecture de Grasse (06) N 7803/88 Important notice The present document can be downloaded from: http:/www.etsi.org/stand
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11、hes, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document. Foreword This Technical Report (TR) has been produced by ET
12、SI 3rd Generation Partnership Project (3GPP). The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables. The cross reference between GSM,
13、 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 not“, “may“, “need not“, “will“, “will not“, “can“ and “cannot“ are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (V
14、erbal forms for the expression of provisions). “must“ and “must not“ are NOT allowed in ETSI deliverables except when used in direct citation. ETSI ETSI TR 136 933 V14.0.0 (2017-04)33GPP TR 36.933 version 14.0.0 Release 14Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology
15、 2g3Foreword . 4g3Introduction 4g31 Scope 5g32 References 5g33 Definitions, symbols and abbreviations . 5g33.1 Definitions 5g33.2 Abbreviations . 6g34 Definitions and problems description . 6g34.1 Issue 1: Backhaul long latency . 6g34.2 Issue 2: TCP E2E delay with throughput decreasing . 6g34.3 Issu
16、e 3: Video transmission issue cases . 6g34.4 Issue 4: UL Video transmission critical data discard . 7g35 Solutions . 7g35.1 General Principles 7g35.2 Solutions 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
17、TCP Performance Enhancing Proxy (TCP PEP) 9g35.3.2 Network based Radio-Aware TCP 10g35.3.3 UE Based Radio-Aware TCP Solution . 10g35.3.4 eNB generates TCP ACK 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
18、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 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
19、.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 of LTE radio resource allocation during the call . 16g35.5.2 Solution 2: Static acceptance or rejection of adaptation of LTE radio resource all
20、ocation for the call 16g3Annex A (informative): Video playout buffer aware scheduling . 17g3Annex B (informative): Change history . 18g3History 19g3ETSI ETSI TR 136 933 V14.0.0 (2017-04)43GPP TR 36.933 version 14.0.0 Release 14Foreword This Technical Specification has been produced by the 3rdGenerat
21、ion 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 an
22、d 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 e
23、nhancements, corrections, updates, etc. z the third digit is incremented when editorial only changes have been incorporated in the document. Introduction Voice was the major service and 3GPP defined voice specific cross-layer optimizations for 3G and 4G. Web based streaming video and Apps are expect
24、ed 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 optimizations by RAN and App mutual aware, e.g. network assisted DASH, video-aware scheduling. It is worthwhile and right time to study whether d
25、eep 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 work in other SDOs/Working groups, e.g. ETSI MEC work on mobile video delivery optimization and local content caching. It is also beneficial t
26、o study and analyse the potential impact to architecture, protocol, and signalling to support RAN based local cached delivery, local breakout; and support RAN optimizations based on context awareness. ETSI ETSI TR 136 933 V14.0.0 (2017-04)53GPP TR 36.933 version 14.0.0 Release 141 Scope The present
27、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 solutions. Considerations with regards to requested functionality in scope of other 3GPP groups, if any, may be captured in this document as w
28、ell. 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, s
29、ubsequent 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 3GP
30、P TR 21.905: “Vocabulary for 3GPP Specifications“. 2 IETF RFC3135, Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations 3 X. Xu, Y. Jiang, T. Flach, E. Katz-Bassett, D. Choffnes, and R. Govindan, “Investigating performance enhancing proxies in cellular networks,” in AIMS: 6th
31、 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 Wireless Conference 2005 - Next Generation Wireless and Mobile Communications and Services (European Wireless), 11th European, April 2005, pp. 17. 5
32、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 2003. 6 F. Ren, X. Huang, F. Liu, and C. Lin, “Improving TCP Throughput over HSDPA Networks,” Wireless Communications, IEEE Transactions on, vol.
33、 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 Technologies. Springer Berlin Heidelberg, 2012, vol. 7479, pp. 263274. 8 S4-170238, Revised Work Item on “Server and Network Assisted DASH (SAND)
34、 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 services” 3 Definitions, symbols and abbreviations 3.1 Definitions For the purposes of the present document, the terms and definitions given i
35、n 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 21.905 1. ETSI ETSI TR 136 933 V14.0.0 (2017-04)63GPP TR 36.933 version 14.0.0 Release 143.2 Abbreviations For the purposes of the present docu
36、ment, the abbreviations given in 3GPP 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 3GPP TR 21.905 1. 4 Definitions and problems description 4.1 Issue 1: Backhaul long latency The issue m
37、ay 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 these cases long transportation latency may be experienced. Consequently certain kinds of service may be impacted significantly due to the long
38、 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 be affected. 4.2 Issue 2: TCP E2E delay with throughput decreasing The behavior of TCP assumes that network congestion is the primary cause fo
39、r 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 underlying radio channel conditions. Such changes can be caused by the movement of devices or interference, as well as changes in system load
40、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 delay increases, the TCP RTT increases and the TCP throughput may decrease, which may impact the user experience. 4.3 Issue 3: Video transmission
41、 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 QCI. However, there might be cases where an operator decides not to apply any dedicated QoS to a video service. These video services are name
42、d “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 internet traffic, e.g. transmitted via default bearer, which may lead to poor QoE. Nevertheless, the QoS framework allows assignment of dedicat
43、ed 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 neither use dedicated bearers nor dedicated QCI for OTT video services. Case 1: Empty buffer issue The user is watching a streaming video. When th
44、e 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 fluctuation and if the scheduling priority of the video content is not set accordingly, the video playing would probably stall depends on some conditio
45、n, 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 prediction. Throughput prediction is based on implementation specific mechanisms. The accuracy of the prediction is dependent from the specif
46、ic implementation. However, one factor that may affect the prediction is that the DASH client may base the prediction on previous downloads. The DASH client may not have an insight to whether the network conditions have changed, thus the current available throughput may be difficult to predict. Cons
47、ervative requesting low data rate video segment leads to low video quality and aggressive requesting high data rate video segment leads to more video stalling. Case 3: Long video delay issue ETSI ETSI TR 136 933 V14.0.0 (2017-04)73GPP TR 36.933 version 14.0.0 Release 14In HTTP based streaming, clien
48、t 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. 4.4 Issue 4: UL Video transmission critical
49、 data discard In conversational video (real-time streaming) the problem of PDCP discard of critical data in UL may occur. Critical data include I-frames of an H.264 video sequence and RTCP feedbacks for lost RTP packets. Both types of data are carried on the same bearer (dedicated, GBR, or non-GBR) and may be encapsulated in the same PDCP SDUs. Hence if the video bearer queue is highly loaded (e.g. in case of UL congestion), both types of data may be discarded due to expiry of the PDCP discard timer. Currently in AS, there are no means to pr
