ETSI TR 101 613 V1.1.1 (2015-09)

Intelligent Transport Systems (ITS); Cross Layer DCC Management Entity for operation in the ITS G5A and ITS G5B medium; Validation set-up and results

DTR/ITS-0020056

General Information

• Status: Published
• Publication Date: 06-Sep-2015
• Technical Committee: ITS WG2 - Architecture and Cross Layer
• Current Stage: 12 - Completion
• Due Date: 05-Oct-2015
• Completion Date: 07-Sep-2015

Standards Content (Sample)

TECHNICAL REPORT
Intelligent Transport Systems (ITS);
Cross Layer DCC Management Entity
for operation in the ITS G5A and ITS G5B medium;
Validation set-up and results
2 ETSI TR 101 613 V1.1.1 (2015-09)

Reference
DTR/ITS-0020056
Keywords
ITS, Spectral Management
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3 ETSI TR 101 613 V1.1.1 (2015-09)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Executive summary . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 6
3 Definitions, symbols and abbreviations . 8
3.1 Definitions . 8
3.2 Symbols . 8
3.3 Abbreviations . 8
4 DCC theory . 9
5 Simulation results . 10
5.1 Characteristics of common algorithms . 10
5.1.1 Reactive table based algorithm . 10
5.1.1.1 Simulator 1: Conclusions . 10
5.1.1.2 Simulator 1: Introduction . 10
5.1.1.3 Simulator 1: Tools and setup . 11
5.1.1.4 Simulation 1.1: Study on the synchronization issue of the DCC . 14
5.1.1.5 Simulation 1.2: Study on channel load characterization . 20
5.1.1.6 Simulation 1.3: Study on non-identical sensing capabilities . 22
5.1.2 Adaptive linear control algorithms . 23
5.1.3 Comparison of different common algorithms . 23
5.1.3.1 Simulator 2: Introduction . 23
5.1.3.2 Simulator 2: Tools and Setup . 24
5.1.3.3 Simulator 2: Simulation results . 26
5.2 Mixed use of different algorithms . 28
5.2.1 Simulator 3: Conclusions . 28
5.2.2 Simulator 3: Introduction . 28
5.2.2.1 Overview . 28
5.2.2.2 DCC bac kground . 29
5.2.2.3 CAM-DCC algorithm. 29
5.2.2.4 LIMERIC algorithm . 30
5.2.3 Simulator 3: Tools and setup . 30
5.2.3.1 Simulation tools . 30
5.2.3.2 Simulator configuration . 30
5.2.3.3 CAM-DCC implementation . 31
5.2.3.4 LIMERIC implementation . 32
5.2.3.5 Simulation scenarios . 32
5.2.3.6 Alternate CAM-DCC lookup table parameters . 33
5.2.3.7 Alternate LIMERIC target CBP . 33
5.2.3.8 Simulations with the different parameter settings for the algorithms . 33
5.2.4 Simulator 3: Simulation results . 33
5.2.4.1 Introduction to the results . 33
5.2.4.2 Simulation 3.1: Default parameter setting . 34
5.2.4.3 Discussion on the performance difference of CAM-DCC and LIMERIC in the mixed network . 36
5.2.4.4 Simulation 3.2: Modified lookup table. 36
5.2.4.5 Simulation 3.3: Modified LIMERIC target value . 37
5.2.4.6 Simulation 3.4: Modified look-up table and LIMERIC target value . 39
5.3 Future aspects and algorithms . 40
5.3.1 ECPR algorithm . 40
5.3.1.1 Simulator 4: Conclusions . 40
5.3.1.2 Simulator 4: Introduction . 41
ETSI
4 ETSI TR 101 613 V1.1.1 (2015-09)
5.3.1.3 Simulator 4: Tools and setup . 41
5.3.1.4 ECPR Algorithm: Testing Different Target Rate and Awareness Distance Sets for - Urban vs.
Highway Environment . 44
5.3.1.5 Comparing ECPR, LIMERIC, Power-only, and No-DCC algorithm . 45
History . 50

ETSI
5 ETSI TR 101 613 V1.1.1 (2015-09)
Intellectual Property Rights
IPRs essential or potentially 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 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 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 ETSI Technical Committee Intelligent Transport Systems (ITS).
Modal verbs terminology
In the present document "shall", "shall not", "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 (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Executive summary
The documented simulations prove that there are functional methods to manage channel load.
Different metrics have been selected to compare the effectiveness and fairness of different methods, and also possible
coexistence of adaptive and reactive algorithms has been demonstrated in simulations.
Despite currently defined methods and individual parameters, in future even more complex methods and algorithms for
managing channel load can be expected to evolve.

ETSI
6 ETSI TR 101 613 V1.1.1 (2015-09)
1 Scope
The present document covers the overall validation of the cross layer DCC functionality of the ETSI ITS architecture. It
considers the cross layer DCC specification developed in ETSI TS 103 175 [i.1] and the cross layer concept described
in ETSI TR 101 612 [i.2] and all other relevant DCC components in the communication stack.
2 References
2.1 Normative 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
reference 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 guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
Not applicable.
2.2 Informative 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
reference document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
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 TS 103 175: "Intelligent Transport Systems (ITS); Cross Layer DCC Management Entity for
operation in the ITS G5A and ITS G5B medium".
[i.2] ETSI TR 101 612: "Intelligent Transport Systems (ITS); Cross Layer DCC Management Entity for
operation in the ITS G5A and ITS G5B medium; Report on Cross layer DCC algorithms and
performance evaluation".
[i.3] IEEE 802.11-2012: "IEEE Standard for Information technology -- Telecommunications and
information exchange between systems Local and metropolitan area networks -- Specific
requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)
Specifications".
[i.4] ETSI EN 302 663: "Intelligent Transport Systems (ITS); Access layer specification for Intelligent
Transport Systems operating in the 5 GHz frequency band".
[i.5] ETSI TS 102 687 (V1.1.1): "Intelligent Transport Systems (ITS); Decentralized Congestion
Control Mechanisms for Intelligent Transport Systems operating in the 5 GHz range; Access layer
part".
[i.6] ETSI EN 302 637-2: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 2: Specification of Cooperative Awareness Basic Service".
[i.7] Oyunchimeg Shagdar: "Evaluation of Synchronous and Asynchronous Reactive Distributed
Congestion Control Algorithms for the ITS G5 Vehicular Systems", Technical Report 462, INRIA
Paris-Rocquencourt. 2015. .
ETSI
7 ETSI TR 101 613 V1.1.1 (2015-09)
[i.8] ns-2, network simulator, http://www.isi.edu/nsnam/ns/, https://en.wikipedia.org/wiki/Ns-
(simulator).
[i.9] ns-3, network simulator, http://www.nsnam.org, https://en.wikipedia.org/wiki/Ns_(simulator).
[i.10] SUMO, Simulation of Urban mobility, http://www.dlr.de/ts/en/desktopdefault.aspx/, http://sumo-
sim.org/.
[i.11] Osama Al-Gazali, Jérôme Härri: "Performance Evaluation of Reactive and Adaptive DCC
Algorithms for Safety-Related Vehicular Communications", Master Thesis, EURECOM,
January 2015.
[i.12] M. Behrisch, L. Bieker, J. Erdmann, and D. Kajzewicz: "Sumo-simulation of urban mobility-an
overview", SIMUL 2011, The Third International Conference on Advances in System Simulation.
2011.
[i.13] D. Krajzewicz: "Sumo (simulation of urban mobility)", Proc. of the 4th middle east symposium on
simulation and modelling, 2002.
[i.14] ns-3 WAVE module, http://www.nsnam.org/docs/models/html/wave.html.
[i.15] R. Jain, D. Chiu, and W. Hawe: "A Quantitative Measure Of Fairness And Discrimination For
Resource Allocation In Shared Computer Systems", DEC, Research Report TR-301,
September 1984.
[i.16] Kenney. J.B, Bansal. G, Rohrs. C.E, LIMERIC: "A linear message rate control algorithm for
vehicular DSRC systems", 8th ACM Int. Workshop on Vehicular Inter-networking VANET 11,
pp. 21-30, 2011.
[i.17] G. Bansal, J. Kenney, C. Rohrs: "LIMERIC: A Linear Adaptive Message Rate Algorithm for
DSRC Congestion Control", IEEE Transactions on Vehicular Technology, Vol. 62, No. 9,
pp. 4182-4197, Nov. 2013.
[i.18] G. Bansal, H. Lu, J. Kenney, and C. Poellabauer: "EMBARC: Error model based adaptive rate
control for vehicle-to-vehicle communications", Proc. 10th ACM Int. Workshop on Vehicular
Inter-Networking, Systems, Applications (VANET 2013), June 2013, pp. 41-50.
[i.19] G. Bansal, B. Cheng, A. Rostami, K. Sjoberg, J. Kenney, and M. Gruteser: "Comparing LIMERIC
and DCC approaches for VANET channel congestion control", Wireless Vehicular
Communications (WiVeC), 2014 IEEE 6th International Symposium on, pp. 1-7, 2014.
[i.20] B. Aygun, M. Boban, A. Wyglinski: "ECPR: Environment-aware Combined Power and Rate
Distributed Congestion Control for Vehicular Communication", arXiv preprint arXiv:1502.00054:
http://arxiv-web3.library.cornell.edu/abs/1502.00054.
[i.21] M. Boban, J. Barros, and O. K. Tonguz: "Geometry-Based Vehicle-to-Vehicle Channel Modeling
for Large-Scale Simulation", IEEE Transactions on Vehicular Technology, Vol. 63, No. 9,
pp. 4146-4164, Nov. 2014.
[i.22] Open Street Map, topological data base, http://www.openstreetmap.org/.
[i.23] M. Boban and P. d'Orey: "Measurement-based evaluation of cooperative awareness for V2V and
V2I communication", IEEE Vehicular Networking Conference (VNC 2014), December 2014,
pp. 1-8.
[i.24] Claudia Campolo, Antonella Molinaro, Riccardo Scopigno: "Vehicular ad hoc Networks,
Standards, Solutions, and Research", ISBN: 978-3-319-15496-1 (Print), 978-3-319-15497-8
(Online).
[i.25] "Highway Capacity Manual", Transportation Research Board, Washington, D.C. 2010.
ISBN 978-0-309-16077-3.
ETSI
8 ETSI TR 101 613 V1.1.1 (2015-09)
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in ETSI TS 103 175 [i.1], ETSI
TR 101 612 [i.2] and the following apply:
NAV: busy flag defined in [i.3]
ns-3: discrete-event network simulator for Internet systems, targeted primarily for research and educational use.
NOTE: ns-3 is free software, licensed under the GNU GPLv2 license, and is publicly available for research,
development, and use.
3.2 Symbols
For the purposes of the present document, the following symbols apply:
α Adaption parameter that control the DCC algorithm
β Adaption parameter that control the DCC algorithm
δ Default packet length for the simulations
CBP Target channel load
Target
CBR CBR measured at the nth monitoring interval
n
CL Channel load calculated upon measurement of CBR
n n
N_GenCam Maximum number of consecutive CAM generations due to the elapsed time since the last
CAM generation
NDL_maxChannelLoad
The channel is considered to be overloaded if the CBP is larger than this value
NDL_minChannelLoad
The channel is considered to be mainly free if the CBP is smaller than this value
NDL_TimeDown controls how fast DCC reacts to channel load decrease
NDL_TimeUp controls how fast DCC reacts to channel load increase
r Message rate of ITS-S j
j
T T Total time during which the channel is indicated as busy during T
BUSY, busy mon
T_GenCam Currently valid upper limit of the CAM generation interval
T_CheckCamGen Time period for checking the generation of a new safety message
T_GenCam_Dcc Initial CAM generation time interval.
T_GenCamMin No CAM can be generated with an interval smaller than this variable
T_GenCamMax No CAM can be generated with an interval greater than this variable
T T CBR monitoring interval
monitor, mon
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
A-DCC Adaptive DCC
AIFS Arbitration Inter Frame Space
BSM Basic Safety Message
BTP Basic Transport Protocol
CAM Cooperative Awareness Message
CBP Channel Busy Percentage
CBR Channel Busy Ratio
CCA Clear Channel Assessment
CCH Control Channel
CL Channel Load
DCC Decentralized Congestion Control
DENM Decentralized Environmental Notification Message
ECPR Environment- and Context-aware Combined Power and Rate distributed congestion control
EDCA Enhanced Distributed Channel Access
FIR Finite Impulse Response
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9 ETSI TR 101 613 V1.1.1 (2015-09)
GPS Global Positioning System
iCS iTetris Control System
IP Internet Protocol
IPG Inter-Packet Gap
ITS Intelligent Transportation System
ITS-G5 Radio interface, collectively known as the 5 GHz ITS frequency band
ITS-S ITS Station
LIMERIC LInear MEssage Rate Integrated Control
LOS Line Of Sight
LOS-C stable flow Level-of-Service of traffic conditions
NOTE: As defined in [i.25].
LOS-F fully saturated (breakdown flow) Level-of-Service of traffic conditions
NOTE: As defined in [i.25].
MAC Medium Access Control
NAR Neighborhood Awareness Ratio
PDR Packet Delivery Ratio
PER Packet Error Rate
PHY Physical Layer
PIR Packet Inter-Reception time
QPSK Quadrature Phase-Shift Keying
R-DCC Reactive DCC
RNAR Ratio of Neighbors Above Range
SINR Signal to Interference and Noise Ratio
SUMO Simulation of Urban MObility
TA Target Awareness
TC Traffic Class
TCP/IP Transmission Control Protocol/Internet Protocol
T-DCC DCC with solely CAM triggering conditions
TX Transmit
UDP User Datagram Protocol
UDP/IP User Datagram Protocol/Internet Protocol
UK United Kingdom
US United States
WAVE Wireless Access in Vehicular Environments
WLAN Wireless Local Area Network
4 DCC theory
The aim of DCC is to avoid overloading the ITS-G5 radio channel. This can be done by different means as specified in
ETSI TS 102 687 [i.5].
It has been shown recently that a pure message rate control can effectively limit the channel load [i.24], therefore most
of the simulation results presented in the present document focus on this type of DCC. Clause 5.3 gives an outlook of
how DCC can be even further improved to not only avoid channel overload, but also maximise the awareness about
other vehicles in the vicinity.
When designing a message rate DCC algorithm the following key fundamentals are important:
• Convergence to a single message rate by all network nodes
• Bounded stability in the sense that message rate changes over time should be within small bounds
Further details about convergence and stability are summarised in [i.24].
ETSI
10 ETSI TR 101 613 V1.1.1 (2015-09)
5 Simulation results
5.1 Characteristics of common algorithms
5.1.1 Reactive table based algorithm
5.1.1.1 Simulator 1: Conclusions
Using Simulator 1, the following issues targeting reactive dynamic DCC algorithm are studied.
• DCC synchronization
• Channel load characterization
• Non-identical receiver parameters
The following conclusions are drawn:
• It is very important to provide a solution to avoid the synchronization of DCC behaviour among ITS-S. If a
careful attention is given on this issue, the simple reactive DCC algorithm can perform better than having no
DCC (hereunder called DccOff). In the case of rate adaptation, introducing a random message generation rate
offset seems to be a good solution, but is not further investigated in the present document.
• If the road traffic is sparse, the reactive DCC algorithm tends to show poorer performance than DccOff.
• Resetting the message generation timer based on the actual CBR value is not advantageous.
• If the ITS-S transmits unsynchronized, the current CBR is a good indicator of the channel load. However, if
the transmissions are synchronized, it is necessary to pay attention on CBR for a longer interval.
• If the system consists of ITS-S with heterogeneous channel sensing capability, non-negligible negative impact
can be expected in terms of communications range and fairness.
• The fairness issue caused by non-identical sensing capabilities is more significant for DCC-enabled system.
5.1.1.2 Simulator 1: Introduction
The results of simulator 1 are detailed in paper [i.7], using a simulation tool combining ns-3 (network simulator) and
SUMO (Simulation of urban mobility). Simulator 1 implemented the reactive DCC algorithm, controlling the message
rate following a parameter look-up table (shown in table 2).
Following simulations are performed with simulator 1:
• Simulation 1.1: Study on the synchronization issue of the DCC.
• Simulation 1.2: Study on channel load characterization.
• Simulation 1.3: Study on non-identical sensing capabilities.
Simulation 1.1 investigates the handling of the channel busy ratio (CBR), which is the ratio of the time when the
channel is perceived as busy to the monitoring interval. It is the commonly agreed metric used to characterize channel
load. Since the wireless channel is shared by ITS-S that are in the vicinity of each other, the CBR monitored at such
ITS-S takes similar values. As a consequence, the ITS-S may take synchronized reactions to the channel load, e.g. the
ITS-S reduce/increase the transmission rate at around the same time. Simulation 1.1 studies such a synchronized DCC
behaviour observed in reactive DCC algorithm. The following different possible reactions of the CAM generator, which
is responsible for adjusting the message generation rate as a means to perform DCC, were studied:
• Timer handling: In general, a transmission of a CAM is triggered by a timer, which is set to the CAM interval.
Hence, upon being informed with a new CBR value (at an arbitrary point of time), the CAM generator may:
1) wait the expiration of the on-going timer and set the timer to the new CAM interval; or
ETSI
11 ETSI TR 101 613 V1.1.1 (2015-09)
2) cancel the on-going timer and set it to the new CAM interval. The former and latter behaviours are
respectively named Wait-and-Go and Cancel-and-Go.
• Interval setting: As mentioned above, the CBR measured for the shared channel may lead to the situation
where the nearby ITS-S increase/decrease the CAM interval at around the same time. This is especially true
for the reactive DCC algorithm, which controls the rate following a parameter look-up table. Therefore, one
can think of avoiding such a synchronized behaviour by applying random intervals. Hence, two possible
behaviours can be envisioned: upon determination of a new CBR value, in the simulation the CAM generator
sets the message generation interval to:
1) the value (say new_CAM_interval) provided by the table; or
2) a random value (e.g. taken from the range [0, new_CAM_interval]) for the first packet and then follows
the table.
The former and latter behaviours are respectively named Synchronized and Unsynchronized. In practice,
synchronization could happen when the CAM transmissions are triggered based on the common GPS clock.
Considering the above-mentioned behaviours of the CAM generator, the following four different versions of Reactive
DCC are simulated:
• DccReactive-1: Wait-and-Go & Synchronized
• DccReactive-2: Cancel-and-Go & Synchronized
• DccReactive-3: Wait-and-Go & Unsynchronized
• DccReactive-4: Cancel-and-Go & Unsynchronized
Simulation 1.1 studies and compares the performances of these different versions of reactive DCC to understand the
synchronization issue and their underlying reasons.
Simulation 1.2 investigates the optimum time interval for the channel load characterization. While it is commonly agreed
that CBR should be monitored over a certain interval (e.g. 100 ms), it is not clear whether the channel load should be
characterized only by the current value of CBR or whether it should also consider the past CBR values. To evaluate this
aspect, channel load (CL) is defined as follows.
CL = (1 - α) × CL + α × CBR (1)
n n-1 n
th
In equation 1, CBR is the CBR measured at the n monitoring interval and CL is the channel load calculated upon
n n
measurement of CBR . The weight factor α defines whether the channel load considers only the last CBR or also takes its
n
history into account by applying a discrete time first order low pass filtering to the CBR. Obviously, by choosing α = 1,
the channel load is characterized by the "current" channel condition only. In simulation 1.2 the performances of a reactive
DCC algorithm for different values of α is evaluated.
Simulation 1.3 studies the DCC performance in heterogeneous road systems, made of ITS-S with different levels of
sensing capability. Specifically, it is considered that different ITS-S sense the wireless channel at different threshold
levels; as a consequence CL is measured differently, what leads to different reactions of each ITS-S. To perform this
study, the ITS-S in the simulations are provided with random sensitivity offset values in the range of [-6, +6] dBm.
5.1.1.3 Simulator 1: Tools and setup
Simulator 1 uses the open discrete event simulation environment ns-3 (version 3.21) [i.9], combined with the traffic
simulator SUMO (version 0.22) [i.10]. The key simulation modules, which are relevant to simulator 1, are illustrated in
figure 1, where the modules highlighted in red are newly developed extensions to ns-3.
ETSI
12 ETSI TR 101 613 V1.1.1 (2015-09)
SUMO NS3
CAM generator
Demand
DCC rate adaptation
generation
IEEE 802.11p module
Mobility
SUMO
Module
Channel load
measurement
Road network
generation
Radio Propagation
module
Figure 1: Simulators and the key modules relevant to the work
The latest stable version of ns-3, ns-3.21, is used as basis for simulator 1. Among a number of new functionalities, it
includes the WAVE system [i.14], which supports the vehicular functionalities of IEEE 802.11 [i.3] similar to
ITS-G5 [i.4]. The system follows the TCP/IP communication architecture. The key software components used in
simulator 1 are a CAM generator, UDP/IP, the vehicular functionalities of IEEE 802.11 MAC, radio propagation, and
mobility modules.
The CAM generator is a newly developed module, which receives position and mobility information from the mobility
module and periodically generates CAMs. The module is implemented with DCC rate adaptation algorithms.
Simulator 1 focuses on the reactive DCC algorithm as described in ETSI TS 102 687 [i.5]. When the reactive DCC
module is provided with a CL value (see equation 1), it adjusts the CAM generation interval following the parameter
lookup table shown in table 2.
The messages generated by the CAM generator are processed by the UDP and IP modules, and received at the MAC.
Even though the protocols standardized in ETSI are BTP/GeoNetworking, utilizing UDP/IP is equivalent regarding the
objective of studying channel congestion caused by 1-hop broadcast messages (CAM). It should be noted that since the
header lengths of UDP/IP and BTP/GeoNetworking are different, the necessary message length adjustment is made at
the CAM generator such that the length of the frames transmitted on the wireless channel have the same length as when
using BTP/GeoNetworking.
The PHY layer of ns-3 is extended with a CBR monitoring functionality, which monitors the channel activities and
calculates the CL. Since ns-3 is an event-based simulator, the CBR monitoring module exploits the event notifications
installed in ns-3. In addition, the module holds a timer and calculates the CBR value at every T interval following
monitor
equation 2. It should be mentioned that the timer setting is made independently at each ITS-S, and hence the CL
notifications to the CAM generator are not synchronized among the individual ITS-S.
∑
���= (2)
The ns-3 mobility module is responsible for handling the mobility of ITS-S and is the interface of ns-3 with the SUMO
traffic simulator. The SUMO traffic simulator is used to generate road network and traffic following user-specified
scenarios. The outputs of the traffic simulator are converted in a file format readable by the mobility module of the ns-3
simulator.
Unless otherwise noted, the communication and road parameters used by simulator 1 are listed in table 1.
ETSI
13 ETSI TR 101 613 V1.1.1 (2015-09)
Table 1: Default simulation parameters of simulator 1
Parameters Value
Communication
CAM default TX rate 10 Hz
CAM message size 400 Bytes
TX Power 23 dBm
threshold
-95 dBm
ED
EDCA Queue/TC 1 DENM/3 CAM
Modulation scheme QPSK ½ 6 Mbits/s
Antenna pattern Omnidirectional, gain = 1 dBi
Access technology ITS G5A
ITS G5 Channel CCA
Fading model LogDistance, exponent 2
Road network
Lane width 3 m
Lanes in-flow 3
Lanes contra-flow 3
DCC parameters
CBR monitor interval (T ) 100 ms
monitor
α (see (1)) 1
The parameter table of the reactive DCC algorithm is shown in table 2.
Table 2: Reactive DCC parameter lookup table used in simulator 1
States CL (%) T
off
Relaxed 0 % ≤ CL < 19 % 60
Active_1 19 % ≤ CL < 27 % 100
Active_2 27 % ≤ CL < 35 % 180
Active_3 35 % ≤ CL < 43 % 260
Active_4 43 % ≤ CL < 51 % 340
Active_5 51 % ≤ CL < 59 % 420
Restricted CL ≥ 59 % 460
The simulations are carried out for homogenous highway scenarios. Table 3 provides the road configuration. As shown
in table 3 and illustrated in figure 2, the roadside ITS-S are installed every 100 m in the road centre (i.e. the separation
between the two centre lanes).
The scenario consists of sparse, medium, dense, and extreme dense traffic. The density parameters are listed in table 4.
Table 3: Simulator 1 road configuration
Class Inter-vehicle distance
Highway length 1 000 m
Lanes/Directions 3 lanes/2 directions
Roadside ITS-S inter-location 100 m
Vehicle size 2 m x 5 m
Figure 2: Illustration of a homogenous highway scenario used by simulator 1
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14 ETSI TR 101 613 V1.1.1 (2015-09)
Table 4: Simulator 1 traffic density parameters for homogenous highway scenarios
Class Inter-Vehicle distance Mobility
Sparse 100 m inter-distance (3 lanes/2 directions) Static/Mobile
Medium 45 m inter-distance (3 lanes/2directions) Static/Mobile
Dense 20 m inter-distance (3 lanes/2directions) Static/Mobile
Extreme 100 m inter-distance (3 lanes/2directions) Static

The following metrics are used for performance investigations of simulator 1.
• Packet delivery ratio (PDR): the ratio of the number of received packets to the number of transmitted
(generated) packets. PDR is measured at individual ITS-S (vehicles and roadside) targeting CAMs transmitted
by each mobile ITS-S (i.e. vehicles).
• Packet Inter-Reception time (PIR): time gap between consecutive CAM messages. PIR is measured at
individual ITS-S for received CAMs from each mobile ITS-S.
• Number of transmissions: the total number of CAM transmissions is counted for 20 milliseconds of time bins.
• CBR: the average CBR is calculated for 20 milliseconds of time bins.
• Jain's fairness index [i.15] is calculated for the total number of transmissions from individual mobile ITS-Ss.
5.1.1.4 Simulation 1.1: Study on the synchronization issue of the DCC
In the present clause the results of the four different versions of Reactive DCC are shown for a homogeneous static
highway scenario: DccReactive-1, DccReactive-2, DccReactive-3, and DccReactive-4. The performances of these
mechanisms are compared with DccOff, which is the ITS-G5 MAC without distributed congestion control.
Figure 3 plots the average PDR of the reactive DCC mechanisms in contrast to that of DccOff. The horizontal axis is
the distance between the receivers and the transmitters. DccOff shows an optimum PDR performance in the sparse
scenario (defined in table 4), where the channel is not congested. The channel congestion becomes an issue for medium,
dense and extreme density classes, where PDR degrades down to 10 % in DccOff. DccReactive mechanisms show
better PDR than DccOff. The PDR improvement is much more significant for unsynchronized DCC schemes
(DccReactive-3 and DccReactive-4) than for synchronized scheme (DccReactive-1 and DccReactive-2). For timer
handling, Cancel-and-Go schemes show poorer performances (DccReactive-2 in comparison to DccReactive-1 and
DccReactive-4 in comparison to DccReactive-3).
ETSI
15 ETSI TR 101 613 V1.1.1 (2015-09)
DccOff-Sparse DccOff-Dense DccOff-Sparse DccOff-Dense
DccReactive_1-Sparse DccReactive_1-Dense DccReactive_2-Sparse DccReactive_2-Dense
DccOff-Medium DccOff-Extreme DccOff-Medium DccOff-Extreme
DccReactive_1-Medium DccReactive_1-Extreme DccReactive_2-Medium DccReactive_2-Extreme
1 1 1 1
0.9 0.9 0.9 0.9
0.8 0.8 0.8 0.8
0.7 0.7 0.7 0.7
0.6 0.6 0.6 0.6
0.5 0.5 0.5 0.5
0.4 0.4 0.4 0.4
0.3 0.3 0.3 0.3
0.2 0.2 0.2 0.2
0.1 0.1 0.1 0.1
0 0 0 0
0 100 200 300 400 500 0 100 200 300 400 500
Distance (m) Distance (m)
DccOff-Sparse DccOff-Dense DccOff-Sparse DccOff-Dense
DccReactive_3-Sparse DccReactive_3-Dense DccReactive_4-Sparse DccReactive_4-Dense
DccOff-Medium DccOff-Extreme DccOff-Medium DccOff-Extreme
DccReactive_3-Medium DccReactive_3-Extreme DccReactive_4-Medium DccReactive_4-Extreme
1 1 1 1
0.9 0.9
0.9 0.9
0.8 0.8
0.8 0.8
0.7 0.7
0.7 0.7
0.6 0.6
0.6 0.6
0.5 0.5
0.5 0.5
0.4 0.4
0.4 0.4
0.3 0.3 0.3 0.3
0.2 0.2
0.2 0.2
0.1 0.1
0.1 0.1
0 0
0 0
0 100 200 300 400 500
0 100 200 300 400 500
Distance (m)
Distance (m)
Figure 3: Comparison of Packet Delivery Ratio for different density classes
Figure 4 plots the average PIR of the reactive DCC mechanisms in contrast to that of DccOff. Similar to the PDR case,
DccOff shows an excellent PIR performance in the sparse scenario, but the performance largely degrades for higher
density classes and it can exceed one second in the extreme density class. The reactive DCC mechanisms show better or
worse PIR performances, depending on the synchronized or unsynchronized behaviour. Both synchronized schemes,
DccReactive-1 and DccReactive-2, show poorer performance w.r.t . DccOff, except for the case of DccReactive-1
(Wait-and-Go) in the extreme density class. On the other hand, the unsynchronized schemes, DccReactive-3 and
DccReactive-4, provide improved performances for dense and extreme classes. The performance improvement is
significant for the DccReactive-3 (Wait-and-go & Unsynchronized) and the performance degradation is significant for
DccReactive-2 (Cancel-and-Go & Synchronized).
ETSI
Packet delivery ratio Packet delivery ratio
Packet delivery ratio Packet delivery ratio

16 ETSI TR 101 613 V1.1.1 (2015-09)
DccOff-Sparse DccOff-Dense DccOff-Sparse DccOff-Dense
DccReactive_1-Sparse DccReactive_1-Dense DccReactive_2-Sparse DccReactive_2-Dense
DccOff-Medium DccOff-Extreme DccOff-Medium DccOff-Extreme
DccReactive_1-Medium DccReactive_1-Extreme DccReactive_2-Medium DccReactive_2-Extreme
1.1 1.1 2.2 2.2
2 2
1 1
1.8 1.8
0.9 0.9
1.6 1.6
0.8 0.8
1.4 1.4
0.7 0.7
1.2 1.2
0.6 0.6
1 1
0.5 0.5
0.8 0.8
0.4 0.4
0.6 0.6
0.3 0.3
0.4 0.4
0.2 0.2 0.2 0.2
0 0
0.1 0.1
0 50 100 150 200 250 300 350 400
0 50 100 150 200 250 300 350 400
Distance (m) Distance (m)
DccOff-Sparse DccOff-Dense DccOff-Sparse DccOff-Dense
DccReactive_3-Sparse DccReactive_3-Dense DccReactive_4-Sparse DccReactive_4-Dense
DccOff-Medium DccOff-Extreme DccOff-Medium DccOff-Extreme
DccReactive_3-Medium DccReactive_3-Extreme DccReactive_4-Medium DccReactive_4-Extreme
1.1 1.1 1.1 1.1
1 1 1 1
0.9 0.9 0.9 0.9
0.8 0.8 0.8 0.8
0.7 0.7
0.7 0.7
0.6 0.6
0.6 0.6
0.5 0.5 0.5 0.5
0.4 0.4 0.4 0.4
0.3 0.3 0.3 0.3
0.2 0.2 0.2 0.2
0.1 0.1 0.1 0.1
0 50 100 150 200 250 300 350 400 0 50 100 150 200 250 300 350 400
Distance (m) Distance (m)
Figure 4: Comparison of PIR performances
Figure 5 and figure 6 plot the total number of transmissions and the channel load measured during a 5 seconds time
interval for the dense scenario. For DccOff the number of transmissions during 20 milliseconds of time bins takes
values in the range of [27, 35]. In contrast, this value oscillates in the range of [5, 30], [0, 35], [10, 20], and [7, 12] for
DccReactive-1, DccReactive-2, DccReactive-3, and DccReactive-4, mechanisms respectively. Similar behaviours can
be observed for the measured CBR (figure 6). In the dense scenario, the CBR of DccOff is stable at 0,84 %. In contrast,
the CBR value oscillates in the range of [0,2, 0,8], [0,1, 0,7], [0,55, 0,8], and [0,4, 0,6] for DccReactive-1, DccReactive-
2, DccReactive-3, and DccReactive-4, respectively.
ETSI
Packet inter-reception time (s) Packet inter-reception time (s)
Packet inter-reception time (s) Packet inter-reception time (s)

17 ETSI TR 101 613 V1.1.1 (2015-09)
DccOff-Dense DccReactive_1-Dense DccOff-Dense DccReactive_2-Dense
60 60 60 60
50 50 50 50
40 40 40 40
30 30 30 30
20 20 20 20
10 10 10 10
0 0 0 0
3 4 5 6 7 8 3 4 5 6 7 8
Time (s) Time (s)
DccOff-Dense DccReactive_3-Dense DccOff-Dense DccReactive_4-Dense
60 60 60 60
50 50
50 50
40 40 40 40
30 30
30 30
20 20
20 20
10 10
10 10
0 0
0 0
3 4 5 6 7 8
3 4 5 6 7 8
Time (s)
Time (s)
Figure 5: Distribution of the number of transmissions during a 5 seconds interval for dense traffic
ETSI
Number of transmissions Number of transmissions
Number of transmissions
Number of transmissions
18 ETSI TR 101 613 V1.1.1 (2015-09)

DccOff-Dense DccReactive_1-Dense DccOff-Dense DccReactive_2-Dense
1 1 1 1
0.8 0.8 0.8 0.8
0.6 0.6 0.6 0.6
0.4 0.4
0.4 0.4
0.2 0.2
0.2 0.2
0 0 0 0
3 4 5 6 7 8 3 4 5 6 7 8
Time (s) Time (s)
DccOff-Dense DccReactive_3-Dense DccOff-Dense DccReactive_4-Dense
1 1 1 1
0.8 0.8 0.8 0.8
0.6 0.6 0.6 0.6
0.4 0.4 0.4 0.4
0.2 0.2 0.2 0.2
0 0 0 0
3 4 5 6 7 8 3 4 5 6 7 8
Time (s) Time (s)
Figure 6: Average CBR during a time interval of 5 seconds
Figure 7 plots the setting and actual values of the CAM generation intervals as well as the measured CBR at a randomly
selected ITS-S in the dense scenario (for clarity, the parameters are plotted only when their values change). Similar to
what is seen in figure 6, the CBR fluctuation is higher for the synchronized mechanisms and lower for the
unsynchronized mechanisms. The setting value of the CAM interval tends to jump between the highest (460 ms) and
lowest (60 ms) values of the DCC parameter lookup table (table 2), for the synchronized mechanisms (DccReactive-1
and DccReactive-2
...