Robust Low-Cost Multiple Antenna Processing for V2V Communication
Doctoral thesis, 2022

Cooperative V2V communication with frequent, periodic broadcast of messages between vehicles is a key enabler of applications that increase traffic safety and traffic efficiency on roads. Such broadcast V2V communication requires an antenna system with omnidirectional coverage, which is difficult to achieve using a single antenna element. For a mounted, omnidirectional antenna on a vehicle is distorted by the vehicle body, and exhibits a nonuniform directional pattern with low gain in certain directions. The thesis addresses this problem by developing schemes that employ multiple antennas (MAs) to achieve an effective radiation pattern with omnidirectional characteristics at both the transmit- and the receive-side. To ensure robust communication, the MA schemes are designed to minimize the burst error probability of several consecutive status messages in a scarce multipath environment with a dominant path between vehicles.

First, at the receive-side, we develop a hybrid analog-digital antenna combiner. The analog part of the combiner is composed of low-cost analog combining networks (ACNs) of phase shifters that do not depend on channel stateinformation (CSI), while the digital part uses maximal ratio combining. We show that the optimal phase slopes of the analog part of the combiner (i.e., the phase slopes that minimize the burst error probability) are the same found under the optimization of a single ACN, which was done in earlier work. We then show how directional antennas can be employed in this context to achieve an effective omnidirectional radiation pattern of the antenna system that is robust in all directions of arrival of received signals.


Secondly, at the transmit-side, we develop two low-cost analog MA schemes, an analog beamforming network (ABN) of phase shifters, and an antenna switching network (ASN), for the case when receivers employ the ACN or the hybrid combiner. Both schemes are shown to achieve an effective radiation pattern with improved omnidirectional characteristics at the transmit-side without relying on CSI.

Thirdly, the schemes above were developed assuming that all vehicles broadcast their messages with the same fixed period. Therefore, we tackle the practical scenario when different vehicles use different and potentially varying broadcast periods. We show that the phase slopes of the MA schemes at the receiver and/or transmitter can be designed to support multiple broadcast periods.
 
Lastly, the optimal phase slopes of the MA schemes were analytically derived under a worst-case propagation corresponding to a dominant path with an angle of departure, and an angle of arrival that are approximately non-varying over the time it takes to transmit and receive several packets. We relax this assumption and study the system performance under a time-varying dominant component instead. We derive a design rule that yields robust phase slopes that effectively mitigate the losses due to the time-variation of the dominant path.

Directional antennas

Beamforming

Multiple antennas

Periodic communication

Broadcast V2V communication

Hybrid combining

Room ED, floor 5, Hörsalsvägen 11
Opponent: Principal Scientist Thomas Zemen, AIT Austrian Institute of Technology, Vienna, Austria

Author

Chouaib Bencheikh Lehocine

Chalmers, Electrical Engineering, Communication, Antennas and Optical Networks

In a world where 1.3 million human beings lose their lives due to traffic accidents, one may wonder, is there a way to make
our roads safer? The answer is, luckily, yes.
 
One promising way towards increased safety on our roads, is the use of vehicle-to-vehicle (V2V) communication, where vehicles, such as cars, busses, trucks, etc., broadcast their position, speed, and direction to all vehicles in their vicinity. Information is updated periodically, 1 to 10 times per second. This allows vehicles to be aware of their neighboring vehicles, and enables them to cooperate and coordinate their maneuvers and decisions. Thereby, the risk of accidents is reduced
while the traffic flow and efficiency are increased.
 
To enable vehicle-to-vehicle (V2V) communication, antennas need to have 360° coverage. Antennas in today’s cars are mounted in a shark-fin case on top of the vehicle. Unfortunately, due to the physical properties of the materials used in the construction of a vehicle (e.g., metallic roof, sunglass roof) the antennas are distorted and do not exhibit a 360° coverage. This means that under unfortunate events, packets from other vehicles can be lost if they arrive at angles where the antenna system has bad coverage. Therefore, signal processing techniques that use several antennas are proposed in this thesis to enable good coverage in all directions. The techniques ensure robust V2V communication that functions properly even under unfortunate circumstances.
 
This work, is one among many other research works that pave the way towards a future where cars (human-driven or autonomous) talk, hear, and collaborate with each other to ensure safer, more efficient, and more comfortable mobility on our roads.

Subject Categories

Telecommunications

Communication Systems

Signal Processing

ISBN

978-91-7905-717-6

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5183

Publisher

Chalmers

Room ED, floor 5, Hörsalsvägen 11

Online

Opponent: Principal Scientist Thomas Zemen, AIT Austrian Institute of Technology, Vienna, Austria

More information

Latest update

10/27/2023