Interference in In-vehicle Networks

Wireless in-vehicle networks are considered as a flexible and cost-efficient solution for the new generation of cars. One of the candidate wireless technologies for these wireless sensor networks is the IEEE 802.15.4 standard which operates in the 2.4 GHz ISM band. This is while the number of wireless devices that operate in this band is ever increasing. This broad usage of the same RF band may cause considerable performance degradation of wireless networks due to interference.

Experimental setup

In this work, we investigated the interference behavior in in-vehicle environments using real-world experiments. We categorized the interference sources for wireless IVNs into in-car and out-of-car sources. For each category we considerd different scenarios and measured the interference on all the 16 channels of IEEE 802.15.4 in the 2.4 GHz band. For in-car interference sources, each scenario was designed to investigate the effect of one type of interference sources and/or applications. In this case, we picked up three measurement scenarios to study the behavior of Wi-Fi and Bluetooth transmissions. The three scenarios are:

  • Bluetooth connection of a mobile phone and a music player device with an audio streaming application.
  • Bluetooth connection between two smart phones with a file transfer application which requires more bandwidth and handshaking than that of scenario 1.
  • Wi-Fi connection between two smart phones with a file transfer application.
The out-of-car interference is caused by the devices that are operating out of the car along the roads or in other cars. We defined four scenarios in this case:
  • Driving along a route near some apartments.
  • Driving along an office area in downtown.
  • Driving in a suburb area.
  • Driving along a highway with no buildings around.
Since there can be a scenario with lots of interferers that block communications on all the channels, discussing about the possible worst case interference scenario is pointless. Thus, we considered an example real-world scenario with multiple sources of interference for an in-vehicle WSN. The measurement resluts gathered toether as a data set tha can be used for realistic and accurate in-vehicle network simulations.

Data logs

We developed a TSCH simulator on top of Matlab to evaluate the performance of an IEEE 802.15.4e TSCH link, using the IVN interference data logs. The simulation results show that the packet error rate for some interference scenarios is considerably high and dynamic over time. The following Figure shows the captured interference of this scenario together with the simulation results of average PRP of TSCH communications. The simulations was done for different transmission powers (Ptx) and path-loss exponents (alpha). As it can be seen, in such a scenario, the PRP of the TSCH protocol may be reduced more than 50% in some points.

Effect of the mixed interference scenario on the IEEE 802.15.4 channels.

The project data-set and matlab scripts are available here:
Interference Behavior in IVN
The available README file provides a guide to use this data-set.

In the case of any question about the IVN interference data logs, please contact Rasool Tavakoli or Majid Nabi.