1、 ETSI TR 102 861 V1.1.1 (2012-01) Intelligent Transport Systems (ITS); STDMA recommended parameters and settings for cooperative ITS; Access Layer Part Technical Report ETSI ETSI TR 102 861 V1.1.1 (2012-01) 2Reference DTR/ITS-0040020 Keywords CSMA, ITS, MAC, MS-Aloha, STDMA ETSI 650 Route des Luciol
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6、he foregoing restriction extend to reproduction in all media. European Telecommunications Standards Institute 2012. All rights reserved. DECTTM, PLUGTESTSTM, UMTSTMand the ETSI logo are Trade Marks of ETSI registered for the benefit of its Members. 3GPPTM and LTETMare Trade Marks of ETSI registered
7、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 TR 102 861 V1.1.1 (2012-01) 3Contents Intellectual Property Rights 5g3Foreword . 5g3Introduction 5g31 Scope 6g32 References 6g32.1 Norma
8、tive references . 6g32.2 Informative references 6g33 Definitions, symbols and abbreviations . 8g33.1 Definitions 8g33.2 Symbols 8g33.3 Abbreviations . 9g34 Introduction 10g35 Simulation settings . 11g35.1 Introduction 11g35.2 Data traffic model . 11g35.2.1 Packet structure. 12g35.2.2 Slot length, gu
9、ard time and clock hold-on 12g35.2.3 Frame length . 13g35.2.3.1 STDMA . 13g35.2.3.2 MS-Aloha 13g35.3 Vehicle traffic model 14g35.3.1 Highway scenario (STDMA) 14g35.3.2 Urban scenario (MS-Aloha) 15g35.4 Channel model 16g35.4.1 Highway scenario . 16g35.4.2 Urban obstructed and non-obstructed scenarios
10、 . 19g35.4.2.1 Receiver model used for the urban scenarios 21g35.5 CSMA specific parameters . 22g35.6 Performance metrics . 23g35.6.1 Introduction. 23g35.6.2 Channel access delay 23g35.6.3 Packet reception probability . 24g36 Simulation results of STDMA 25g36.1 Introduction 25g36.2 Parameter setting
11、s. 25g36.3 Simulation results: highway scenario . 25g36.3.1 Packet reception probability . 25g36.3.1.1 Normal vehicle density . 25g36.3.1.2 High vehicle density 26g36.3.2 Simultaneous transmissions 27g36.3.3 Channel access delay 31g36.4 Conclusions 32g37 Simulation results of MS-Aloha . 33g37.1 Guid
12、e to the Interpretation of Results from Simulations 33g37.1.1 Rational and Effects of Spatial Multiplexing 33g37.1.2 Configuration Rules 34g37.1.2.1 Framing rules 35g37.1.2.2 Re-Use and Threshold Algorithm . 36g37.1.2.3 Pre-emption . 36g37.1.3 Hidden terminals in an urban environment . 36g37.2 Simul
13、ation Results: Urban Scenario . 38g3ETSI ETSI TR 102 861 V1.1.1 (2012-01) 47.2.1 Analysis of Results: Urban Obstructed . 38g37.2.2 Analysis of Results: Urban Non-Obstructed . 41g37.2.2.1 Motivation of the Analysis in Non-Obstructed Scenarios . 41g37.2.2.2 Analysis of Results 42g37.3 Conclusions: Rec
14、ommended Parameter Settings . 44g38 Executive summary 45g3Annex A: Bibliography 47g3History 48g3ETSI ETSI TR 102 861 V1.1.1 (2012-01) 5Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these esse
15、ntial 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 notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest update
16、s 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 as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server)
17、which are, or may be, or may become, essential to the present document. Foreword This Technical Report (TR) has been produced by ETSI Technical Committee Intelligent Transport System (ITS). Introduction It is essential to decrease the number of fatalities on our roads, not only because it causes muc
18、h grief for individuals each year, but also because it costs enormous amounts of money for society. There are different ways of increasing the road traffic safety, which all contribute to a better and more efficient road traffic environment. One way is to build new highways with separated lanes as t
19、hese are less prone to traffic accidents. However, this is only possible to some extent due to space limitations. Another way is to introduce wireless communications between vehicles which enable new applications for increasing road traffic safety such as wrong way warning, red light violation, inte
20、rsection collision warning and emergency brake warnings. This is termed cooperative intelligent transport systems (ITS). The impact of road traffic safety applications as well as road traffic efficiency applications is likely dependent of a considerably amount of vehicles being equipped with communi
21、cation devices. The exact penetration of course depends on the application in question, but generally the more vehicles that are equipped the better. However, it is also at this stage the current technology chosen for cooperative ITS may encounter problems. When the number of ITS equipped vehicles i
22、ncreases, the standardized technology based on CSMA will face problems with scalability. The scalability of CSMA directly influences the reliability of the transmission, the channel access delay and thereby the fairness. When the number of nodes increases, the number of simultaneous transmissions wi
23、ll increase, resulting in lower reliability and decoding problems due to interference. One way to counteract the scalability issue of CSMA is to introduce decentralised congestion control methods (DCC) such that the amount of data traffic transmitted is restricted and transmit power levels adjusted.
24、 However, by decreasing the amount of data traffic transmitted the road traffic safety applications may suffer with performance degradation as a result. Another way to counteract the scalability issue is to investigate the performance of other medium access control (MAC) protocols in terms of scalab
25、ility, reliability, delay and fairness. Self-organizing time division multiple access (STDMA) and mobile slotted Aloha (MS-Aloha) are two time slotted MAC approaches designed for ad hoc networking (they are self-organizing and decentralized) and both can cope with a high and varying number of nodes
26、without collapsing. When the number of nodes increases within radio range and all free resources are exhausted, both algorithms still admit transmissions through careful scheduling to maintain a high reliability for the nodes closest to the transmitter. This implies that the channel access delay has
27、 a maximum upper limit and the resulting network is fair and predictable. In the present document, the performance of CSMA, STDMA and MS-Aloha are investigated through simulations with a varying number of vehicles, all equipped with cooperative ITS units. In particular, the performance measures chan
28、nel access delay and packet reception probability are evaluated as these measures captures the reliability, the delay and the fairness of resulting system as well as how these depend on scalability. ETSI ETSI TR 102 861 V1.1.1 (2012-01) 61 Scope The present document summarises the result from perfor
29、mance evaluations of CSMA and two time slotted MAC approaches through simulations. Two different time slotted MAC approaches, self-organizing time division multiple access (STDMA) and mobile slotted Aloha (MS-Aloha), have been considered in two different scenarios; highway and urban. CSMA, the MAC a
30、lgorithm proposed for the current generation of vehicular ad hoc networks (VANETs) has been used as a benchmark. Packet reception probability at different distances from the transmitter together with the channel access delay has been used as performance measures. The purpose is first and foremost to
31、 evaluate the scalability of the resulting system, as initial results have shown that CSMA may degrade in performance when the number of vehicles equipped with cooperative ITS units increase. NOTE 1: Hkan Lans holds a patent on STDMA i.25, which expires in July 2012. The patent has been re-examined
32、in the US cancelling all claims on March 30, 2011. NOTE 2: A European patent procedure has been started by ISMB on MS-Aloha techniques (European patent request filed with number 10163964.9, May 26, 2010). They have received in September 2011 Communication Under Rule 71(3) EPC of the intention to gra
33、nt a patent. 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 referenced document (including any ame
34、ndments) 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 guarantee their long term validity. 2.1
35、 Normative references Not applicable. 2.2 Informative references The following referenced documents are not necessary for the application of the present document but they assist the user with regard to a particular subject area. i.1 ETSI TR 102 862: “Intelligent Transport Systems (ITS); Performance
36、Evaluation of Self-Organizing TDMA as Medium Access Control Method Applied to ITS; Access Layer Part“. i.2 IEEE 802.11p: 2010: “IEEE Standard of Information Technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Specific requirements; Part 1
37、1: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications; Amendment 6: Wireless Access in Vehicular Environments“. i.3 M. Nakagami: “The m-distribution, a general formula of intensity distribution of the rapid fading“, Oxford, England, Pergamon, 1960. i.4 V. Taliwal, D. Ji
38、ang, H. Mangold, C. Chen and R. Sengupta: “Empirical determination of channel characteristics for DSRC vehicle-to-vehicle communication,“ in Proc. ACM Workshop on Vehicular Ad Hoc Networks (VANET), Philadelphia, PA, USA, October 2004, pp. 88-88. i.5 L. Cheng, B. E. Henty, D. D. Stancil, F. Bai and P
39、. Mudalige: “Mobile vehicle-to-vehicle narrow-band channel measurement and characterization of the 5.9 GHz dedicated short range communication (DSRC) frequency band,“ IEEE Journal on Selected Areas in Communications, vol. 25, no. 8, pp. 1501-1516, October 2007. ETSI ETSI TR 102 861 V1.1.1 (2012-01)
40、7i.6 R. Scopigno and H.A. Cozzetti: “Evaluation of time-space efficiency in CSMA/CA and slotted Vanets,“ in Proc of the IEEE 71st Vehicular Technology Conference (VTC Fall 2010), Ottawa, Canada, Sept. 2010. i.7 H.A. Cozzetti and R. Scopigno: “Scalability and QoS in slotted VANETs: forced slot re-use
41、 vs pre-emption,“ in Proc of the 14th Int. IEEE Conf. on Intelligent Transportation Systems (ITSC 2011), Washington, DC, USA, October 2011. i.8 ETSI ES 202 663: “Intelligent Transport Systems (ITS); European profile standard for the physical and medium access control layer of Intelligent Transport S
42、ystems operating in the 5 GHz frequency band“. i.9 R. Scopigno, and H.A. Cozzetti: “Signal shadowing in simulation of urban vehicular communications“, Proc. of the 6th Int. Wireless Communications and Mobile Computing Conference (IWCMC), Valencia, Spain, September 2010. i.10 L. Pilosu, F. Fileppo an
43、d R. Scopigno: “RADII: a computationally affordable method to summarize urban ray-tracing data for VANETs“ in Proc. of the 7th Int. Conf. on Wireless Communications, Networking and Mobile Computing (IEEE WiCOM 2011), Wuhan, China, September 2011. i.11 T. Jiang, H. H. Chen, H. C. Wu and Y. Yi: “Chann
44、el modeling and inter-carrier interference analysis for V2V communication systems in frequency-dispersive channels,“ in The Journal Mobile Networks and Applications, vol. 15, no. 1, pp. 4-12, 2010. i.12 The European Road Safety Observatory. NOTE: http:/erso.swov.nl/. i.13 “SUMO - Simulation of Urban
45、 MObility“, developed by employees at the Institute of Transportation Systems at the German Aerospace Center June 2010. NOTE: http:/. i.14 C. Campolo, A. Molinaro, H.A. Cozzetti and R. Scopigno: “Roadside and moving WAVE providers: effectiveness and potential of hybrid solutions in urban scenarios“,
46、 in Proc. of the 11th IEEE Int. Conf. on ITS Telecommunications (ITST), St. Petersburg, Russia, August 2011. i.15 E.G. Strm: “On medium access and physical layer standards for cooperative intelligent transport systems in Europe“, in Proceedings of the IEEE, vol. 99, no. 7, pp. 1183-1188, July 2011.
47、i.16 E. Giordano, R. Frank, G. Pau and M. Gerla: “CORNER: A radio propagation model for VANETs in urban Scenarios“, in Proceedings of the IEEE, vol. 99, no. 7, pp. 1280-1294, July 2011. i.17 D. Jiang, Q. Shen and L. Delgrossi: “Optimal data rate selection for vehicle safety communications,“ in Proc.
48、 of the 5th Int. Workshop on Vehicular Inter-Networking (VANET), San Francisco, CA, US, September 2008. i.18 K. Sjberg, E. Uhlemann and E. G. Strm: “How severe is the hidden terminal problem in VANETs when using CSMA and STDMA?“, in Proc. of the 4th IEEE Symposium on Wireless Vehicular Communication
49、s (WiVEC), San Francisco, CA, US, September 2011. i.19 Q. Chen, F. Schmidt-Eisenlohr, D. Jiang, M. Torrent-Moreno, L. Delgrossi and H. Hartenstein: “Overhaul of IEEE 802.11 modeling and simulation in NS-2,“ in Proc. of the 10th ACM International Symposium on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM 2007), Chania, Crete island, Greece, October 2007, pp. 159-168. i.20 R. Meireles, M. Boban, P. Steenkiste, O. Tonguz and J. Barros: “Experimental study on the impact of vehicular obstr
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