802.11p models in NS3 simulation environment and we realized in general both WAVE and plain 802.11p models models work well. Our current results described in the presentation Update from 22 Mar 2017: slide #10 added to describe problem we discovered in fixed in WAVE protocol model.

1. Evaluation of WAVE and
802.11p Models in
Network Simulator ns3
Pavel Vasilyev, Senior Software Engineer, Sreda Software Solutions
Vasilii Aleksandrov, Senior Software Engineer, Sreda Software Solutions

2. 2
This presentation shows the results of WAVE and 802.11p models evaluation in Network Simulator (ns3). The goal of the
evaluation is to understand how both models work in ns3 in purpose of using it for simulating V2X scenarios.
The evaluation consist of two types of scenarios: static and dynamic using variable data rates, distances and speeds. The
purpose of researching both models is to compare results in order to understand which differences WAVE model introduces to
plain 802.11p since IEEE 802.11p standard is used as a physical layer for WAVE protocol stack.
WAVE model in ns3 simulator has only IEEE 1609.4 (multi-channel operation) standard implementation. On top of this
implementation can be used WSMP protocol with both control and service channels access and IPv4/IPv6 applications with
service channel access.
WAVE model in ns3 has configuration that allows to provide continuous (full time) access for service channel in wireless
medium. It means that both channels’ intervals: SCH interval and CCH interval will be accessible for service channel. In order to
compare both models in similar way it has been decided to use this configuration.
Introduction

3. 3
Common parameters
In simulation scenarios we use two cars equipped with WAVE and 802.11p devices. All scenarios simulated for all supported
data rates (3, 4.5, 6, 9, 12, 18, 24 and 27 Mbit/s) defined in 802.11p standard with 10 MHz bandwidth. For traffic generation we
use UDP application which generates data-flow with throughput higher than selected data rate in order to fill up channel
bandwidth. Results were measured on a receiving side.
Static scenarios
In static scenarios cars don’t move. We change distance from 200 to 1000 meters with 200 meters step. As the result, we
executed 40 tests for the static scenarios.
Dynamic scenarios
In dynamic scenarios cars are starting at distance 1000 meters between each other and are moving towards each other, so they
meet at 500 meters after the start. We change car speeds from 20 to 180 km/h with 20 km/h step. As the result, we executed 72
tests for the dynamic scenarios.
Scenarios
1000m
20 km/h ... 180 km/h
20 km/h ... 180 km/h
200m … 1000m
0 km/h 0 km/h

4. 4
NS3 Setup for WAVE and 802.11p
Devices configuration
● We use Yans model (YansWavePhyHelper for WAVE, YansWifiPhyHelper for 802.11p) to set up channel and phy layer.
● We set Tx Power Level according to US regulatory domain to - 44.8 dBm.
● We use mobility models with constant distance for static scenarios and with constant speed for dynamic scenarios.
● We set WAVE specific configuration as:
○ SCH3 (channel number 176) with continuous access used for applications.
Applications configuration
● UDP over IPv4 is used for throughput measurements.
● Modified BulkSendApplication is used on transmitting side
○ UDP support has been added
● PacketSink application is used on receiving side.
● FlowMonitor is used for throughput logging.

5. 5
Static Scenarios Results for WAVE and 802.11p
The following graphics show measured throughput of static scenarios for each
data rate at different distances for WAVE and 802.11p simulation.
The figures show a couple of differences in comparison between WAVE and
802.11p simulation results:
1. The first four data rates: 3, 4.5, 6 and 9 Mbit/s show absolutely the same
result for WAVE model. Moreover, data rate 9 Mbit/s works in WAVE
model at distance 1000 meters, but doesn’t work in 802.11p model.
2. Throughput in 802.11p a bit higher than in WAVE (As continuous access
was used to simulate WAVE the results are perfectly matches theory).
There are also some similarities for both models:
1. As expected that the highest data rates stop working at higher distances.
2. The lowest data rates show results more close to theoretical values than
the highest data rates.

6. 6
The figures show throughput results of different speed for
the same data rate. First three data rates are omitted,
because as was observed in the static tests, they show the
same throughput results for WAVE.
Data rate 24 Mbit/s shows results close to 27 Mbit/s.
Dynamic scenarios showed that WAVE model in ns3
mostly has no dependency on speed factor. All tests with
different speeds for the same data rate have close
average throughput.
For the 802.11p these figures show that there are more
bandwidth available for data when using 802.11p
comparing to WAVE. But at low data rates (9 Mbit/s) the
distance is less than while using WAVE for data transfer.
Also the distance between connection established and
maximum throughput achieved is higher for 802.11p.
Dynamic Scenarios Results for WAVE and 802.11p
WAVE
802.11p

7. 7
These figures also indicate at what exact distance
particular data rate starts working.
A spread in first results in the figures is linked with ARP
Request delay since both nodes don’t know about each
other.
Data rates 12 Mbit/s, 18 Mbit/s and 27 Mbit/s have
comparable throughput results while low data rate 9 Mbit/s
shows that 802.11p could provide more throughput versus
WAVE.
Dynamic Scenarios Results for WAVE and 802.11p (Cont)
WAVE
802.11p

8. 8
Dynamic Scenarios Results for WAVE and 802.11p
Separated figures have been created to understand how close the results of different speed factor are lying.
These figures show throughput measurements of data rate at 27 Mbit/s with 3 different speed factors: 20 km/h, 80 km/h and 180
km/h for WAVE and 802.11p models
It could be observed that higher speed the nodes have, higher spread of throughput results will be. The lowest speed shows
results close to average throughput, but the highest speed periodically shows throughput results much higher than average
throughput.
Results for WAVE and 802.11p are look very similar
WAVE 802.11p

9. 9
Taking into account that WAVE model is build on top of 802.11p model in ns3, there are couple of major and minor issues
that WAVE model has introduced:
● Data rates 3, 4.5, 6 and 9 Mbit/s have an issue since they all show the same result and 9 Mbit/s data rate in WAVE
model works at the highest distance. The other data rates (12, 18, 24 and 27 Mbit/s) have no such issue.
● Throughput in WAVE a bit lower than in 802.11p that is probably related to a guard interval time between channel
access that is introduced in standard IEEE 1609.4.
● Data rates 12, 18, 24 and 27 Mbit/s could be used to simulate V2X environment with continuous access to the
service channel. In order to enable all possible modes of operations ns3 should be adjusted.
Summary

10. 10
The issue with the first four data rates (3, 4.5, 6, 9Mbps) described in the previous slide is in TxProfile class implementation
of ns3 WAVE module. According to IEEE 1609.4 section 7.3.4.2 MLMEX-REGISTERTXPROFILE.request tx profile
registration primitive shall provide a data rate parameter. In ns3 version 3.26 the TxProfile class implementation doesn’t
provide data rate as a parameter so it doesn't allow user to specify transmission data rate according to IEEE 1609.4
standard.
Additionally it forces to use 6Mbps data rate for lowest data rate. That is why throughput results were the same and 9Mbps
data rate worked at distance 1000 meters, but it shouldn’t since in 802.11p model it doesn’t work so.
The following graphics show measurements of WAVE model with modified TxProfile class in comparison with 802.11p
model:
WAVE data rate issue investigation