CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a 35 U.S.C. § 371 National Stage of International Patent Application No. PCT/SE2016/051026, filed Oct. 21, 2016, designating the United States.

TECHNICAL FIELD

The proposed technology generally relates to communication in cooperative intelligent transport systems and in particular to methods and arrangements for handling congestion.

BACKGROUND

Cooperative Intelligent Transport Systems (C-ITS) are systems that utilize Information and Communications Technology (ICT) to support improved safety and more efficient usage of the transportation infrastructure for transport of goods and humans over any transportation mean.

Intelligent Transport Systems (ITS) services, protocols and connectivity solutions are described in specifications issued by standardization bodies like IEEE, SAE, ETSI and ISO. Besides in the mentioned standards, the C-ITS system architecture is elaborated in research collaborations like COmmunication Network VEhicle Road Global Extension (CONVERGE), Nordic Way and in consortiums of automobile manufacturers, suppliers and research organizations like ERTICO and Car-2-Car Communication Consortium.

There is an ongoing discussion regarding connectivity for C-ITS. The discussion is about whether the ETSI ITS G5/IEEE WAVE DSRC solutions, cellular 3rdGeneration Partnership Project (3GPP) technologies, or a new 3GPP based Long-Term Evolution (LTE) Vehicle-to-anything (V2X) radio solutions should be used, and in what combinations (e.g. hybrid solutions).

C-ITS is based on a frequent short-range communication between different stations or units, mobile or stationary, exchanging e.g. information ranging from position, velocity, environmental conditions, traffic situation etc. When many vehicles are present in a limited area and/or when external conditions are cumbersome, the signaling load becomes large and congestion problems may arise.

One main problem with broadcast technologies and Dedicated Short-Range Communication (DSRC) or corresponding 3GPP based LTE V2X radio solutions technologies is that they rely on a distributed congestion control, i.e. each station or unit, movable or stationary, determines itself when it has to reduce its transmission rate. This means that it is up to each implementation to detect congestion and take action. Even though this is specified to a certain degree, there is a significant likelihood that implementations will differ and cause problems, e.g. cause long time to react. Congestion mitigation is therefore today considered as slightly unreliable.

Furthermore, with broadcast technologies that are using ‘listen before talk’, there is a large probability that some stations or units will only ‘listen’ in congestion situations, i.e. the medium is never free for transmission. This is also known as the hidden station problem.

SUMMARY

It is an object to provide methods and devices enabling a more reliable congestion mitigation in C-ITS.

This and other objects are met by embodiments of the proposed technology.

According to a first aspect, there is provided a method for message control in a cooperative intelligent transport system. The method comprises creating of a transmission restriction control message. The transmission restriction control message comprises restriction instructions, defining how a transmission restriction demand is to be applied by an on board unit, and validity information. The transmission restriction control message is broadcasted.

According to a second aspect, there is provided a method for message control in a cooperative intelligent transport system. The method comprises receiving, in an on board unit, a transmission restriction control message. The transmission restriction control message comprises restriction instructions, defining how a transmission restriction demand is to be applied by the on board unit, and validity information. It is determined whether or not the on board unit fulfils the validity information. If the on board unit fulfils the validity information, the transmissions of messages from the on board unit are adapted according to the restriction instructions.

According to a third aspect, there is provided a node configured for communication with on board units in a cooperative intelligent transport system. The node is configured to create a transmission restriction control message. The transmission restriction control message comprises restriction instructions, defining how a transmission restriction demand is to be applied by an on board unit, and validity information. The node is configured to broadcast the transmission restriction control message.

According to a fourth aspect, there is provided an on board unit of a cooperative intelligent transport system, wherein the on board unit is configured to receive a transmission restriction control message. The transmission restriction control message comprises restriction instructions, defining how a transmission restriction demand is to be applied by the on board unit, and validity information. The on board unit is configured to determine whether or not the on board unit fulfils the validity information: The on board unit is configured to adapt, if the on board unit fulfils the validity information, transmissions from the on board unit of messages according to the restriction instructions.

According to a fifth aspect, there is provided a computer program comprising instructions, which when executed by at least one processor, cause the at least one processor to create a transmission restriction control message. The transmission restriction control message comprises restriction instructions, defining how a transmission restriction demand is to be applied by an on board unit, and validity information. The instructions, when executed by the at least one processor, further cause the at least one processor to broadcast the transmission restriction control message.

According to a sixth aspect, there is provided a computer program comprising instructions, which when executed by at least one processor, cause the at least one processor to receive a transmission restriction control message. The transmission restriction control message comprises restriction instructions, defining how a transmission restriction demand is to be applied by the on board unit, and validity information. The instructions, when executed by the at least one processor, further cause the at least one processor to determine whether or not the on board unit fulfils the validity information. The instructions, when executed by the at least one processor, further cause the at least one processor to adapt, if the on board unit fulfils the validity information, transmissions from the on board unit of messages according to the restriction instructions.

According to a seventh aspect, there is provided a computer-program product comprising a computer-readable medium having stored there on a computer program according to the fifth or sixth aspect.

According to an eighth aspect, there is provided a carrier comprising the computer program of the fifth or sixth aspect, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

According to a ninth aspect, there is provided a node for communication with on board units in a cooperative intelligent transport system. The node comprises a message handler for creating a transmission restriction control message. The transmission restriction control message comprises restriction instructions, defining how a transmission restriction demand is to be applied by an on board unit, and validity information. The node further comprises a transmitter for broadcasting the transmission restriction control message.

According to a tenth aspect, there is provided an on board unit for communication within a cooperative intelligent transport system. The on board unit comprises a receiver for receiving a transmission restriction control message. The transmission restriction control message comprises restriction instructions, defining how a transmission restriction demand is to be applied by the on board unit, and validity information. The on board unit further comprises a validity checker for determining whether or not the on board unit fulfils the validity information. The on board unit further comprises a message handler for adapting, if the on board unit fulfils the validity information, transmissions from the on board unit of messages according to the restriction instructions.

An advantage of the proposed technology is that it makes it possible to provide a reliable, decentralized fast congestion handling for short range communication.

Other advantages will be appreciated when reading the detailed description.

