1、 ETSI TS 102 687 V1.1.1 (2011-07)Technical Specification Intelligent Transport Systems (ITS);Decentralized Congestion Control Mechanisms forIntelligent Transport Systems operating in the 5 GHz range;Access layer partETSI ETSI TS 102 687 V1.1.1 (2011-07)2Reference DTS/ITS-0040014 Keywords ITS, radio,
2、 transmission ETSI 650 Route des Lucioles 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 Individual copies of the present
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6、written permission. The copyright and the foregoing restriction extend to reproduction in all media. European Telecommunications Standards Institute 2011. All rights reserved. DECTTM, PLUGTESTSTM, UMTSTMand the ETSI logo are Trade Marks of ETSI registered for the benefit of its Members. 3GPPTM and L
7、TE are Trade Marks of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. GSM and the GSM logo are Trade Marks registered and owned by the GSM Association. ETSI ETSI TS 102 687 V1.1.1 (2011-07)3Contents Intellectual Property Rights 5g3Foreword . 5g31 Scope 6g32 Re
8、ferences 6g32.1 Normative references . 6g32.2 Informative references 7g33 Definitions, symbols and abbreviations . 7g33.1 Definitions 7g33.2 Symbols 7g33.3 Abbreviations . 8g34 Decentralized congestion control overview . 8g34.1 DCC operational requirements . 8g34.2 DCC architecture 9g34.3 Network de
9、sign limits (NDL) . 9g34.4 DCC_access functional view 10g35 DCC access mechanisms 11g35.1 Transmit power control 11g35.1.1 TPC parameters 11g35.1.2 TPC Operation 12g35.2 Transmit rate control 12g35.2.1 TRC parameters 12g35.2.2 TRC Operation 13g35.3 Transmit datarate control 13g35.3.1 TDC parameters
10、13g35.3.2 TDC Operation . 14g35.4 DCC Sensitivity control . 14g35.4.1 DSC parameters 14g35.4.2 DSC operation 15g35.5 Transmit access control 15g35.5.1 TAC parameters 15g35.5.2 TAC operation 15g35.6 DCC Transmit model . 16g35.7 DCC receive model 16g35.7.1 Receive model parameters 16g35.7.2 Channel mo
11、del 17g35.7.3 Demodulation model. 17g35.7.4 Communication ranges . 18g35.7.5 Example receive model. 18g36 DCC_access components . 19g36.1 DCC transmit queueing 19g36.2 Channel probing . 19g36.3 Transmit packet statistics . 20g36.4 DCC access control loop 20g36.4.1 State machine 20g36.4.2 State trans
12、itions. 21g36.4.3 State configuration 22g36.4.4 State processing 23g37 DCC access interfaces 25g37.1 Interface 1: IN-UNITDATA service 25g37.2 Interface 2: MI-SET and MI-GET services 25g3Annex A (normative): DCC parameter 26g3ETSI ETSI TS 102 687 V1.1.1 (2011-07)4A.1 Channel load measures . 26g3A.1.1
13、 Parameters 26g3A.1.2 Channel load . 26g3A.1.3 Load arrival rate . 26g3A.1.4 Load average duration 27g3A.1.5 Receive packet arrival rate . 27g3A.1.6 Receive packet average duration 27g3A.1.7 Packet Occupancy 28g3A.1.8 Channel busy time 28g3A.2 Transmit packet statistics . 28g3A.2.1 Transmit packet r
14、ate . 28g3A.2.2 Transmit packet average duration. 29g3A.2.3 Average transmit signal power . 29g3A.2.4 Transmit channel use 29g3A.3 Communication Ranges . 30g3A.3.1 Carrier Sense Range . 30g3A.3.2 Estimated communication range 30g3A.3.3 Estimated communication range under interference 30g3A.4 Network
15、 Design Limits 31g3A.4.1 NDL types and formats 31g3A.4.2 NDL Input parameter and constants . 31g3A.4.3 NDL database . 32g3A.4.4 NDL output parameters 33g3A.4.5 Channel dependent parameter 33g3A.4.6 Priority dependent parameters 34g3A.4.7 Basic control loop NDL database . 34g3A.4.8 Enhanced DCC algor
16、ithm NDL database . 35g3Annex B (informative): Transmit power calibration 36g3B.1 Common principles of transmit power calibration . 36g3B.2 Transmit power certification process for non modular ITS stations 36g3B.2.1 Applicability and overview for non modular ITS stations . 36g3B.2.2 Determination of
17、 antenna pattern for non modular ITS stations 36g3B.2.3 Measurement of e.i.r.p. for non modular ITS stations 37g3B.3 Transmit power certification process for modular ITS stations . 37g3B.3.1 Applicability and overview for modular ITS stations 37g3B.3.2 Determination of antenna pattern for modular IT
18、S stations . 37g3B.3.3 Determination of cable loss for modular ITS stations 37g3B.3.4 Determination of output power level for modular ITS stations 37g3B.4 Specified e.i.r.p. levels and step requirements to be calibrated 38g3Annex C (informative): Example of a DCC_Net algorithm 39g3C.1 Enhanced DCC a
19、lgorithm 39g3C.2 Remote information 40g3Annex D (informative): Validation . 42g3D.1 Validation scenarios . 42g3D.2 Validation performance criteria 43g3Annex E (informative): Bibliography . 44g3History 45g3ETSI ETSI TS 102 687 V1.1.1 (2011-07)5Intellectual Property Rights IPRs essential or potentiall
20、y essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in ETSI SR 000 314: “Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs
21、 notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (http:/ipr.etsi.org). Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given
22、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 Specification (TS) has been produced by ETSI Technical Committee Intelligent Transport System (I
23、TS). ETSI ETSI TS 102 687 V1.1.1 (2011-07)61 Scope ITS road safety and traffic efficiency systems include both vehicle to vehicle communications and related vehicle to roadside communication in highly dynamic vehicular ad hoc networks. These systems (ITS stations) are based on a set of protocols and
24、 parameters called ITS-G5 as specified in the European profile standard on the physical and medium access layer of 5 GHz ITS 2. Many applications and services in ITS rely on the cooperative behavior of the vehicles and roadsides units which form a vehicular ad hoc network (VANET). The VANET enable t
25、he time critical road safety applications where fast information exchange is necessary to timely warn and support the driver. Special care should be taken to ensure proper functioning of the VANET and this includes decentralized congestion control (DCC) for the channels of ITS-G5. DCC is a cross lay
26、er function, i.e. it has functions located on several layers of the ITS station reference architecture. Therefore the present document defines which DCC components are located on which layer of the ITS station communication architecture 5. Furthermore the present document specifies the DCC mechanism
27、s on the access layer (DCC_access) including transmit power control (TPC) per packet, transmit rate control (TRC) and transmit datarate control (TDC). The latter two control functions modify the average transmit power by modifying the duty cycle of the ITS station, i.e. the fraction of time that the
28、 ITS station is in “transmit“ state. Additionally, DCC sensitivity control (DSC) adapts the clear channel assessment to resolve local channel congestion. Packets with higher priority are handled less restrictive introducing a transmit queueing concept and transmit access control (TAC). The DCC mecha
29、nisms rely on knowledge about the channel. The channel state information is gained using channel probing. Channel probing measures are defined that enable the DCC methods TPC, TRC and TDC. The measures are on receive signal level thresholds or preamble information of detected packets. The present do
30、cument does not define the mechanisms at other layers than the access layer nor defines management aspects. These other mechanisms and the management aspects are necessary in order to make DCC work properly. The present document is primarily intended for trial use and may need to be updated after va
31、lidation in field trials and/or other projects. 2 References References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the ref
32、erence document (including any amendments) applies. Referenced documents which are not found to be publicly available in the expected location might be found at http:/docbox.etsi.org/Reference. NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guara
33、ntee their long term validity. 2.1 Normative references The following referenced documents are necessary for the application of the present document. 1 IEEE 802.11-2007: “IEEE Standard for Information technology - Telecommunications and information exchange between systems - Local and metropolitan a
34、rea networks - Specific requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications“. 2 ETSI ES 202 663: “Intelligent Transport Systems (ITS); European profile standard for the physical and medium access control layer of Intelligent Transport Systems oper
35、ating in the 5 GHz frequency band“. 3 ETSI EN 302 571: “Intelligent Transport Systems (ITS); Radiocommunications equipment operating in the 5 855 MHz to 5 925 MHz frequency band; Harmonized EN covering the essential requirements of article 3.2 of the R Testing; Conformance test specification for Co-
36、operative Awareness Messages (CAM); Part 1: Test requirements and Protocol Implementation Conformance Statement (PICS) proforma“. 5 ETSI EN 302 665: “Intelligent Transport Systems (ITS); Communications Architecture“. 6 IEEE 802.2-1998: “Standard for Information technology - Telecommunications and in
37、formation exchange between systems - Local and metropolitan area networks - Specific requirements - Part 2: Logical Link Control“, (ISO/IEC 8802-2:1998). 2.2 Informative references The following referenced documents are not necessary for the application of the present document but they assist the us
38、er with regard to a particular subject area. i.1 ETSI TS 102 724: “Intelligent Transport Systems (ITS); Harmonized Channel Specifications for Intelligent Transport Systems operating in the 5 GHz frequency band“. i.2 ETSI TS 102 723-3: “Intelligent Transport Systems; OSI cross-layer topics; Part 3: I
39、nterface between management entity and access layer“. i.3 ETSI TS 102 723-10: “Intelligent Transport Systems; OSI cross-layer topics; Part 10: Interface between access layer and network and transport layers“. i.4 ETSI TS 102 723-1: “Intelligent Transport Systems; OSI cross-layer topics; Part 1: Arch
40、itecture and addressing schemes“. 3 Definitions, symbols and abbreviations 3.1 Definitions For the purposes of the present document, the terms and definitions given in 1, 2, 3, 5 and the following apply: DCC component: part of the DCC, located in one layer, e.g. DCC_access DCC_access mechanism: func
41、tionality of DCC_access usually using several DCC_access components NDL database: database that contains DCC_access configuration parameters, input parameters and output parameters reference parameter: parameter controlled by a control loop 3.2 Symbols For the purposes of the present document, the s
42、ymbols given in 1, 2, 3, 5 and the following apply: acPrio access priority NOTE: Provided by network layer or derived as specified in 1. dB(x) decibel function: 10log10(x) cl variable for channel load cs variable for carrier sense threshold ds variable for DCC sensitivity MIN(x1; ;xN) minimum functi
43、on, returns its lowest argument minCL(t) minimum channel load for time time period t MAX(x1; ;xN) maximum function, returns its largest argument maxCL(t) maximum channel load for time time period t Mpkt measured number of packets Np number of probes ETSI ETSI TS 102 687 V1.1.1 (2011-07)8NPR number o
44、f OFDM symbols in the preamble NDPMS data bits per OFDMsymbol pow(p, x) exponentiation: xp S signal power level Sth signal level threshold TAIR packet air time TCAaverage time for channel access Tmmeasuring interval Tp probing interval txQ number of DCC_access transmit queues 3.3 Abbreviations For t
45、he purposes of the present document, the abbreviations given in 1, 2, 3, 5 and the following apply: DCC Decentralized Congestion Control DCC_access DCC component of the access layer DCC_app DCC component of the facility layer DCC_mgmt DCC component of the management layer DCC_net DCC component of th
46、e network layer D-CCA CCA sensitivity for DCC DPSK Digital Phase Shift Keying DSC DCC sensitivity controlNDL Network Design Limits SM State Machine SNR Signal to Noise Ratio TAC Transmit Access Control TDC Transmit Datarate Control TPC Transmit Power Control TRC Transmit Rate Control VANET Vehicular
47、 Ad-hoc NETwork 4 Decentralized congestion control overview 4.1 DCC operational requirements “Decentralized congestion control“ (DCC) is a mandatory component of ITS-G5 stations operating in ITS-G5A and ITS-G5B frequency bands to maintain network stability, throughput efficiency and fair resource al
48、location to ITS-G5 stations. DCC requires components on several layers of the protocol stack and these components jointly work together to fulfil the following operational requirements: Provide fair allocation of resources and fair channel access among all ITS stations in the same communication zone
49、. Keep channel load caused by periodic messages below pre-defined thresholds. Reserve communication resources for the dissemination of event driven high priority messages. Provide fast adoption to a changing environment (busy / free radio channel). Keep oscillations in the control loops within well-defined limits. Comply to specific system requirements, e.g. reliability. ETSI ETSI TS 102 687 V1.1.1 (2011-07)94.2 DCC architecture The DCC architecture is displayed in Figure 1. It consists of the DCC componen
