Ad-Hoc Communication System for Intelligent Transportation with Simultaneous Transmission and Sensing

Background

• The performance of an intelligent transportation system depends on many factors, but most significantly the supporting V2X communication technologies.
• 3GPP standardised C-V2X technology is shown only being able to support basic applications, and advanced applications require a better communication system.
• An ad-hoc V2X scenario is regarded as the baseline mode since safety also has to be guaranteed when vehicles are outside the coverage of base stations, or when the connection to a base station is not stable.

Challenges

• A conventional acknowledgement mechanism cannot be deployed in VANETs, vehicles do not know whether a packet is transmitted successfully or lost.
• Dynamic transmission (i.e., aperiodic transmission and dynamic time-frequency resource occupancy) is not supported.
• There are only priorities between different V2X applications within one single vehicle. But future intelligent vehicles will have different autonomous levels and in turn different QoS requirements. Communication priority between different vehicles should be enabled.
• Continuous signal collision problem: when multiple vehicles have selected the same resource, multiple packets will be lost and cannot be recovered.
• Blind re-transmission problem: To improve reliability, each packet is transmitted twice, which sacrifices spectrum efficiency and latency.

Solution

• The full-duplex simultaneous transmission and sensing feature can support vehicles to sense the channel status proactively whilst transmitting data, so that signal collisions can be detected and avoided.
• Full-duplex weighted sensing method gives each sensed signal sample a different weight, so that the sensing accuracy of aperiodic transmission and dynamic resource occupancy can be kept at a high level.
• According to the SAE defined autonomous levels of vehicles, a novel communication prioritisation scheme is proposed, so that not only different V2X applications, but also different vehicles can enjoy QoS-oriented prioritised service.
• A novel collided RBs exclusion feature enables vehicles to exclude collided RBs from candidate RBs list based on the PHY layer sensing probabilities. Meanwhile, it is real-time updated, so that collision probability is reduced.
• A novel transmission abortion feature allows vehicles to stop the ongoing transmission as soon as a collision is detected, and activate the next mechanism immediately, so that the continuous signal collision problem is conquered, and collision duration and latency are both reduced.
• A novel prioritised contention resolution mechanism is introduced to conquer the blind re-transmission challenge, so that the reliability is improved without sacrificing spectrum efficiency and latency.

Figure 1: Average system performance in terms of a) left: packet delivery ratio (i.e., reliability) and b) right: latency in different network density scenarios. Note that SB-SPS is the 3GPP standardised technology, and FDPS is the proposed technology. FDPS outperforms SB-SPS in terms of both reliability and latency.

Opportunity

• King’s are currently seeking commercial partners to help us develop this communication system and bring the system to market. A prospective development partner could take an option to a licence over the patent and associated know-how.

IP Status

UK patent application has been filed.