WO2017198302A1 - Method and first wireless device for propagating a message - Google Patents

Method and first wireless device for propagating a message Download PDF

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Publication number
WO2017198302A1
WO2017198302A1 PCT/EP2016/061267 EP2016061267W WO2017198302A1 WO 2017198302 A1 WO2017198302 A1 WO 2017198302A1 EP 2016061267 W EP2016061267 W EP 2016061267W WO 2017198302 A1 WO2017198302 A1 WO 2017198302A1
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Prior art keywords
message
wireless device
group
wireless devices
required range
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PCT/EP2016/061267
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French (fr)
Inventor
Hongxin LIANG
Rafia Inam
Gábor STIKKEL
Joerg Niemoeller
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Telefonaktiebolaget Lm Ericsson (Publ)
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Priority to PCT/EP2016/061267 priority Critical patent/WO2017198302A1/en
Publication of WO2017198302A1 publication Critical patent/WO2017198302A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/80—Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/06—Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
    • H04W4/08—User group management
    • G—PHYSICS
    • G08—SIGNALLING
    • G08G—TRAFFIC CONTROL SYSTEMS
    • G08G1/00—Traffic control systems for road vehicles
    • G08G1/22—Platooning, i.e. convoy of communicating vehicles
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L67/00—Network arrangements or protocols for supporting network services or applications
    • H04L67/01—Protocols
    • H04L67/10—Protocols in which an application is distributed across nodes in the network
    • H04L67/104—Peer-to-peer [P2P] networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L67/00—Network arrangements or protocols for supporting network services or applications
    • H04L67/01—Protocols
    • H04L67/12—Protocols specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/02—Services making use of location information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/02—Services making use of location information
    • H04W4/023—Services making use of location information using mutual or relative location information between multiple location based services [LBS] targets or of distance thresholds
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/02—Services making use of location information
    • H04W4/029—Location-based management or tracking services
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/02—Power saving arrangements
    • H04W52/0209—Power saving arrangements in terminal devices
    • H04W52/0212—Power saving arrangements in terminal devices managed by the network, e.g. network or access point is master and terminal is slave
    • H04W52/0216—Power saving arrangements in terminal devices managed by the network, e.g. network or access point is master and terminal is slave using a pre-established activity schedule, e.g. traffic indication frame
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/02—Power saving arrangements
    • H04W52/0209—Power saving arrangements in terminal devices
    • H04W52/0212—Power saving arrangements in terminal devices managed by the network, e.g. network or access point is master and terminal is slave
    • H04W52/0219—Power saving arrangements in terminal devices managed by the network, e.g. network or access point is master and terminal is slave where the power saving management affects multiple terminals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/38—TPC being performed in particular situations
    • H04W52/383—TPC being performed in particular situations power control in peer-to-peer links
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices
    • H04W88/04—Terminal devices adapted for relaying to or from another terminal or user
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/04—Communication route or path selection, e.g. power-based or shortest path routing based on wireless node resources
    • H04W40/08—Communication route or path selection, e.g. power-based or shortest path routing based on wireless node resources based on transmission power
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/12—Communication route or path selection, e.g. power-based or shortest path routing based on transmission quality or channel quality
    • H04W40/16—Communication route or path selection, e.g. power-based or shortest path routing based on transmission quality or channel quality based on interference
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
    • H04W52/242—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account path loss
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
    • H04W52/243—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account interferences
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/14—Direct-mode setup
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the present disclosure relates generally to a method and a wireless device, for propagating a message to a group of wireless devices.
  • the wireless devices may operate in vehicles of a so-called vehicle platoon.
  • Platooning refers to a mode of operation of a group of automatically controlled vehicles which can travel in a line very close to each other, and they can autonomously steer, accelerate and brake in a coordinated manner.
  • Autonomous or semi-autonomous vehicles can be operated in the platooning mode if they are equipped for receiving commands and sending vehicle information related to position and movement, and also with software needed for automatic control and platooning formation.
  • a typical example of such a time-critical message that needs to be propagated to all vehicles in a vehicle platoon is a breaking or steering command where the vehicles must operate according to the message more or less immediately.
  • a message may include a set of sensors, actuators, instruments, machine parts or the like, which are installed at various locations. It may be desirable to control or support operations of the above components in some coordinated manner by means of the message. It is not unusual that certain critical or significant messages need to be propagated very fast to all wireless devices in the group, e.g. within a few milliseconds, and in that case it is not possible to convey the message across a wireless network with base stations, access points or the like which might take too much time.
  • the following description generally relates to situations where a first wireless device shall convey or propagate a message to a group of wireless devices by means of direct device-to-device communication, i.e. not using any intermediate network nodes of a wireless network.
  • a first wireless device shall convey or propagate a message to a group of wireless devices by means of direct device-to-device communication, i.e. not using any intermediate network nodes of a wireless network.
  • DSRC Dedicated Short-Range Communication
  • IEEE 802.1 1 p which is a protocol for short-range inter-vehicle communication.
  • a group of wireless devices D1 -D7 are positioned basically in a line, which could e.g. be the case of a vehicle platoon driving together on a road.
  • the message originates from a first wireless device D1 that transmits the message with relatively low power to an adjacent wireless device denoted D2 in a first communication denoted C1 .
  • wireless device D2 transmits the message to its adjacent wireless device D3 in a second communication C2, and so forth.
  • Fig. 1 B where the first wireless device D1 transmits the message with relatively high power so that it can be received properly by the outmost wireless device D7, as indicated by a communication denoted C7.
  • the dashed arrows indicate that the message can also be received properly by the other wireless devices D2-D6 as well.
  • the transmission power needed to get the message across to all devices including the outmost wireless device D7 may cause harmful interference to other wireless communications performed in the neighborhood.
  • the high transmission power required in Fig. 1 B will drain the battery in the first wireless device D1 to a greater extent than in the example of Fig 1 A. In some wireless devices such as sensors, it may be desirable to keep power consumption at a minimum so as to delay the need for battery recharge or replacement for as long as possible.
  • the above-mentioned protocol IEEE 802.1 1 p has defined a maximum range of 1000 meters. However, given that transmission is done at a frequency of ⁇ 5.9GHz, and to cover a 1000 meters range very high transmission power may be required which thus can cause too much interference to other communication, e.g.
  • a method is performed by a first wireless device for propagating a message to a group of wireless devices.
  • the first wireless device detects a latest reception time when the message must be received by all wireless devices in the group, and determines a required range for the message from the first wireless device based on the detected latest reception time, the first wireless device then transmits the message using a transmission power that corresponds to the required range so that the message is received by those wireless devices of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time.
  • a first wireless device is arranged to propagate a message to a group of wireless devices.
  • the first wireless device is configured to detect a latest reception time when the message must be received by all wireless devices in the group, and to determine a required range for the message from the first wireless device based on the detected latest reception time.
  • the first wireless device is further configured to transmit the message using a transmission power that corresponds to the required range so that the message is received by those wireless devices of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time.
  • a computer program is also provided comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method described above.
  • a carrier is also provided which contains the above computer program, wherein the carrier is one of an electronic signal, optical signal, radio signal, a computer program storage product, or a computer readable storage medium.
  • Figs 1A and 1 B are two different communication scenarios illustrating propagation of a message to multiple wireless devices, according to the prior art.
  • Fig. 2 is a communication scenario illustrating an example of how the solution may be employed, according to some possible embodiments.
  • Fig. 3 is a flow chart illustrating a procedure in a first wireless device, according to further possible embodiments.
  • Figs 4A-4E are communication scenarios illustrating examples of gradual propagation of a message to multiple wireless devices, in accordance with some possible embodiments.
  • Fig. 5 is a signaling diagram illustrating an example of a procedure when the solution is used, according to further possible embodiments.
  • Fig. 6 is a communication scenario illustrating an example where the solution is employed for a vehicle platoon, in accordance with some possible embodiments.
  • Fig. 7 is a block diagram illustrating a first wireless device in more detail, according to further possible embodiments.
  • a solution is provided to enable propagation of a message to a group of wireless devices within a given time constraint, while using a minimum of transmission power so as to reduce or even avoid any harmful interference generated by the transmission.
  • This can be achieved by means of a procedure that can be performed by a first wireless device which may be the device from which the message originates or a device that has received the message in an ongoing propagation process for further transmission.
  • a required range for the message from the first wireless device is determined based on a latest reception time of the message, i.e. the given time constraint, which may be detected based on information in the message. This information may include a timestamp indicating when the message was originated or generated, and a time constraint indicating a maximum time within which all wireless devices in the group should receive the message after it was
  • Timing information in the message may also simply indicate a point in time when the message must have been received by all devices.
  • the time left before expiry of the message's latest reception time basically dictates the maximum number of hops the message has time to take before expiry, and the required range can be determined depending on how much time is left and on the distance to the device in the group that is farthest away from the first device. If there is much time left before expiry of the message the required range can be relatively short, and vice versa. It should be noted that the number of hops used before the message has reached all devices may be chosen to be less than the available maximum number of hops.
  • the first wireless device then transmits the message using a transmission power that corresponds to the determined required range, so that the message is received by those wireless devices that are located within the required range. Having received the message, the wireless devices within the required range may in turn likewise determine a new required transmission range for the message and transmit the message using a transmission power that corresponds to the new required range. This way, the message can be propagated to all wireless devices of the group within the detected latest reception time. It should be noted that the range of the new transmission may be different than the preceding transmission range and the required range can thus be adaptive in this respect by being determined "successively" by different wireless devices. The devices may continue to forward the message until the latest reception time has expired. However, if a device receives the same message a second or third time it may refrain from transmitting it once more. In general, each device may be configured to transmit the same message no more than once.
  • FIG. 2 An example of communication when the above procedure is employed is shown in Fig. 2 again involving 7 wireless devices D1 -D7 located basically along a line, where device D1 generates a message to be propagated.
  • D1 may thus
  • device D1 may estimate that there is time for the message to take more than one hop before the time constraint, i.e. the message expires. It is thus not necessary for device D1 to transmit the message with a power so that it reaches all devices D2-
  • the first device D1 thus transmits the message using a transmission power to reach a detected required range encompassing only a subset of the devices D2- D7, as illustrated by a first communication C8.
  • the message in communication C8 reaches as far as the wireless device D4 and thereby also the more closely located wireless devices D2 and D3, as shown by dashed arrows.
  • at least the outmost wireless device D4 will act as the above-described first device and transmits the message using a transmission power to reach a new required range, as illustrated by a second communication C9 which propagates the message as far as the wireless device D7 and thereby also the closer located wireless devices D5 and D6, as shown by dashed arrows.
  • the message is thereby propagated to all wireless devices D2-D7 of the group by only two hops which in this case fulfills the latest reception time, while using a transmission power that is considerably reduced as compared to the scenario in Fig. 1 B.
  • the message is propagated in shorter time than in Fig. 1 A and with less transmission power than in Fig. 1 B.
  • the communication shown in Fig. 2 may be executed by means of a so-called "Gossip" protocol which has been designed for propagating messages to a large number of receivers, e.g. sensors of a distributed system, in an efficient manner and using less power as compared to simultaneous broadcasting to all devices.
  • Teknek-gossip is a java library that uses a gossip algorithm to discover nodes in a peer-to-peer network over User Datagram Protocol, UDP.
  • UDP User Datagram Protocol
  • each of the devices D2, D3 and D4 will thus determine a new required range and transmit the received message accordingly.
  • the devices D1 -D7 are likely to receive the same message more than once and when that happens they may be configured to transmit the message no more than once so as to limit interference and power consumption.
  • the first wireless device may be the device in which the message is originated or generated such as D1 , or it could also be a device such as D4 that has received the message from another device in the group i.e. when propagation of the message has already begun.
  • the procedure illustrated by Fig. 3 can thus be used to accomplish the functionality described above for the wireless devices D1 and D4.
  • a first action 300 illustrates that the first wireless device generates or receives the message to be propagated to a group of wireless devices, thus as described above for devices D1 and D4, respectively.
  • the group of wireless devices may operate in vehicles of a vehicle platoon.
  • wireless devices in the vehicles use wireless Device-to-Device, D2D, communication for the coordinated driving of the platoon vehicles. It can thus be assumed that all vehicles in a platoon have a wireless device or the equivalent which is configured to provide the necessary communication for platooning.
  • the wireless device may be a separate communication entity such as a mobile phone or similar which is connected to the vehicle's driving functions, or it may be integrated in the vehicle, depending on the implementation.
  • the message comprises a command to adjust any of: speed, acceleration/retardation, moving direction and position relative to at least one adjacent vehicle.
  • the message may originate from a lead vehicle of the vehicle platoon, which is a vehicle that basically acts as controller of the platoon by collecting various measurements from the vehicles and issuing driving commands to the vehicles.
  • the message may otherwise originate from another vehicle in the platoon, such a request for refueling or battery recharging in case of an electrically driven vehicle.
  • the solution is not limited to vehicle platoons and the wireless devices described herein may be used in any situation where a message needs to be propagated within a given time constraint.
  • a next action 302 illustrates that the first wireless device detects a latest reception time when the message must be received by all wireless devices in the group.
  • the latest reception time of the message may be detected based on information in the message, said information comprising a timestamp indicating when the message was originated and a time constraint indicating a maximum time within which all wireless devices in the group should receive the message.
  • the timing information in the message may just indicate a point in time when the message must have been received by all devices.
  • the first wireless device further determines a required range for the message from the first wireless device based on the detected latest reception time.
  • the required range may be determined further based on information about current position of the first wireless device in the group, total number of wireless devices in the group, and spatial extent of the group.
  • the first wireless device can estimate how far the message should reach when knowing the size of the group and how much time is left before expiry of the message.
  • the transmission range can be more or less optimized so that the transmission power used will generate as little interference as possible while making sure that the message is received by all devices before its expiry.
  • the required range may be determined further based on at least one of: a current battery level in the first wireless device and an estimated interference to other communications caused by transmitting the message. For example, if the current battery level is low it is more important to keep the transmission power low, if possible, than when it is high. Further, a fairly high transmission power can be allowed if the estimated interference is low, and vice versa.
  • the determined required range of the message may not extend essentially beyond the last vehicle in the vehicle platoon, that is in order to use no more power than necessary for the platoon.
  • An action 306 illustrates that the first wireless device transmits the message using a transmission power that corresponds to the required range so that the message is received by those wireless devices of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time.
  • transmitting the message may comprise any of: broadcasting, multicasting and unicasting the message. Some examples of such transmission of the message will be described later below with reference to Fig. 5.
  • beamforming may be used when transmitting the message in action 306, so as to restrict the number of wireless devices receiving the message. This can thus be used to further reduce the transmission power and to avoid that the message is received unnecessarily by devices that have already received the message in a previous transmission. Beamforming means that the transmission only covers a restricted beam which can be achieved by using a directed antenna, which is a well-known transmission technique as such.
  • a group of wireless devices includes 15 individual devices being distributed spatially in a linear or near-linear formation, and that the distance between two adjacent devices is 20 meters so the total length of the group is roughly 300 meters. It is further assumed that the preferred maximum communication range is 100 meters in order to limit the power consumption and to avoid interference as much as possible.
  • Figs 4A-4E illustrate how broadcast and gossip protocol can be used to propagate information across all devices of the group. The devices are labeled as D1 , D2, D15. In a first stage shown in Fig. 4A, D1 transmits a message with a power according to a required range.
  • the message reaches all devices located within the required range, in this case devices D2-D6.
  • the message may comprise a unique message identity (msgID), message text (msgDetail), a timestamp and a time constraint (maxtime).
  • msgID represents a unique message identifier
  • msgDetail is the actual message text together with a "message critical ity”
  • timestamp is the time when the message was originated
  • maxtime is the maximum time (e.g. in milliseconds) within which the message should or must be received by all devices of the group.
  • the message may include an absolute time when the message must have been received by all devices.
  • the message criticality basically indicates how important it is that all devices receive the message within the time constraint.
  • D2 After receiving the message from D1 , D2 saves the message and then broadcasts the same message in the same way as D1 did. In this transmission, D7 will be covered while D1 and D3-D6 will receive a duplicated message that will be discarded by the receiver. Duplication can be detected by comparing msgID and timestamp in the message with the previously received message.
  • Fig. 4C after receiving message from D1 , D3 will also save the message and start broadcasting the same message in the same way as D1 did. In this transmission, D8 will be covered while D1 , D2 and D4-D7 will receive a duplicated message, and so forth.
  • beamforming may be used by D3 in Fig. 4C, such that D2 and D1 will not receive the message since D3's antenna is directed towards D4-D8.
  • all devices will receive the message multiple times but broadcast the message only once.
  • the duplications can be either discarded directly or used for confirmation of correct reception.
  • the first broadcast of Fig. 4A covers up to D6, and the second broadcast from D6 covers up to D1 1 as illustrated by Fig. 4D.
  • the second broadcast from D1 1 covers up to D15, which completes the message propagation.
  • the maximum range is up to 300 meters, then only 2 iterations are required because each device needs to broadcast at least once for the propagation to be completed, although the broadcast from the last device is not necessary.
  • the maximum range is only up to 20 meters, the propagation will decay to point-to-point communication because each device can only convey the message to its two adjacent neighbors.
  • each device can check the timestamp and maxtime and then decide what the range of its own transmission should cover, which can be referred to as adaptive gossip protocol.
  • the first wireless device can use the following equation, as an example, to decide the required range of transmitting the message and hence the transmission power needed. More sophisticated equations may be developed according to different scenarios and objectives, but the principle remains the same. ⁇ ⁇ ⁇ ⁇ ⁇ 3 ⁇ 4
  • Range -, lower _limt ⁇ Range ⁇ upper Jimit
  • ⁇ is the coefficient computed based on charging status of current device
  • ⁇ is the estimated interference to other group of devices in the vicinity
  • n is a baseline or default range.
  • the required broadcast range e.g. determined by position, charging status of current device and estimated interference to other group of devices in the vicinity
  • the required broadcast range can be small and fewer devices will be covered in the coming iteration.
  • a can be defined as a linear function and the value decreases as reaching the end of the propagation direction.
  • ⁇ can be defined as a linear function or as a few predefined values, where the value of ⁇ decreases as the charging status declines. If some devices will never have a power shortage, such as when the device is powered by a vehicle battery or a main power supply, the value of ⁇ can be a constant that equals to 1 .
  • ⁇ can be estimated according to how many other device groups are present in the vicinity and how many of them are in the process of communicating. The value decreases as the interference increases.
  • the transmission power needed to cover that range can be calculated according to conventional procedures.
  • Fig. 4E further illustrates how the required range can be adaptive. For example, if by the above calculation, D2 decides to broadcast up to 150 meters range, the next iteration will cover up to D9 instead of D7.
  • the message may be transmitted in action 306 by broadcasting, multicasting or unicasting.
  • a first wireless device illustrates the first wireless device 500, a message origin entity 502, a number of wireless devices 504 that are within transmission range from the first device 500, and one or more adjacent wireless devices 506 which are located next to the first device 500.
  • the adjacent wireless devices 506 are thus part of the devices 504 within transmission range.
  • a first action 5:1 illustrates that the first wireless device 500 receives the message from the message origin entity 502 which may be a wireless device operating in the leader vehicle of a vehicle platoon.
  • the message may be generated within the first wireless device 500, e.g. when device 500 resides in the leader vehicle or in any vehicle of the platoon. Having received the message, the first wireless device 500 saves the message in a suitable local storage, in an action 5:2.
  • the first wireless device 500 determines the required range of transmitting the message, basically as described for action
  • the first wireless device 500 further adapts the transmission power to the determined required range, in another action 5:4.
  • the actual transmission of the message is then dependent on which transmission mode was selected in action 5:3, which is illustrated by three alternatives as follows.
  • the first wireless device 500 has determined in action 5:3 to transmit the message by broadcasting which is done in an action 5:5A.
  • the message is broadcasted once with a power that is sufficient to reach all the devices 504, 506 within the determined range.
  • the message can be received by any of the wireless devices 504, 506.
  • the first wireless device 500 has determined in action 5:3 to transmit the message by multicasting which is done in an action 5:5B.
  • Multicasting the message means that it is sent to specific addressed devices instead of to anyone within the range. In other words, the message will be received only by the wireless devices 504, 506 being addressed in the message. It is an advantage of this transmission mode that the first wireless device 500 can select which devices will receive the message.
  • the first wireless device 500 has determined in action 5:3 to transmit the message by unicasting which is done in an action 5:5C.
  • Unicasting the message means that a copy of the message is sent to each device separately, thus resulting in multiple individual transmissions. Unicasting also means that correct reception of the message is acknowledged by the devices, which thus confirms delivery of the message.
  • Fig. 6 illustrates an example of how the solution may be employed in the context of vehicle platooning. A group of vehicles are thus driving on a road in a platoon formation which is controlled by a leader vehicle 600.
  • a wireless device in the leader vehicle 600 sends a breaking command which must be received by all vehicles within a certain time limit so that the vehicles can execute the braking simultaneously in a coordinated manner, which is absolutely necessary in order to avoid any incident such as a collision.
  • the message is received by at least the next vehicle 602 in the platoon which has a wireless device onboard that acts as the above-described first wireless device.
  • the first wireless device in vehicle 602 performs the actions 302-306 as described above, i.e. determines a required range and transmits the message further with a transmission power that reaches the required range which extends across a succession of vehicles 604, 606 and 608.
  • at least vehicle 608 will likewise perform actions 302-306 and transmit the message onwards across the platoon, although not shown in this figure.
  • the block diagram in Fig. 7 illustrates a detailed but non-limiting example of how a first wireless device 700 may be structured to bring about the above-described solution and embodiments thereof.
  • the first wireless device 700 may be
  • the first wireless device 700 is shown to comprise a processor P and a memory M, said memory comprising instructions executable by said processor P whereby the first wireless device 700 is operative as described herein.
  • the first wireless device 700 also comprises a communication circuit C with suitable equipment for transmitting commands and receiving radio signals in the manner described herein.
  • the communication circuit C is configured for communication with other wireless devices using suitable protocols depending on the implementation. This communication may be performed in a conventional manner over a communication network employing radio links for wireless communication with the wireless devices involved, which is not necessary to describe here as such in any detail.
  • the solution and embodiments herein are thus not limited to using any specific types of technology or protocols for radio communication.
  • the wireless device 700 comprises means configured or arranged to perform at least the actions 300-306 of the flow chart in Fig. 3, and optionally also in accordance with any of the examples shown in Figs 4-6.
  • the wireless device 700 is arranged to propagate a message to a group of wireless devices.
  • the wireless device 700 may be configured to receive or otherwise obtain the message to be propagated. This receiving operation may be performed by a receiving unit 700A in the wireless device 700, e.g. in the manner described for action 300 above.
  • the wireless device 700 is further configured to detect a latest reception time when the message must be received by all wireless devices in the group. This detecting operation may be performed by a detecting unit 700B in the wireless device 700, e.g. as described for action 302 above.
  • the wireless device 700 is also configured to determine a required range for the message from the first wireless device based on the detected latest reception time. This operation may be performed by a determining unit 700C in the wireless device 700, e.g. as described for action 304 above.
  • the wireless device 700 is also configured to transmit the message using a transmission power that corresponds to the required range so that the message is received by those wireless devices of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time.
  • This transmitting operation may be performed by a transmitting unit 700D in the wireless device 700, e.g. as described for action 306 above.
  • Fig. 7 illustrates various functional units in the wireless device 700, and the skilled person is able to implement these functional units in practice using suitable software and hardware.
  • the solution is generally not limited to the shown structures of the wireless device 700, and the functional units 700A-D therein may be configured to operate according to any of the features and embodiments described in this disclosure, where appropriate.
  • the functional units 700A-D described above can be implemented in the wireless device 700 by means of suitable hardware and program modules of a computer program comprising code means which, when run by the processor P causes the wireless device 700 to perform at least some of the above-described actions and procedures.
  • the processor P may comprise a single Central Processing Unit (CPU), or could comprise two or more processing units.
  • the processor P may include a general purpose microprocessor, an instruction set processor and/or related chips sets and/or a special purpose microprocessor such as an Application Specific Integrated Circuit (ASIC).
  • the processor P may also comprise a storage for caching purposes.
  • Each computer program may be carried by a computer program product in the wireless device 700 in the form of a memory having a computer readable medium and being connected to the processor P.
  • the computer program product or memory in the wireless device 700 may thus comprise a computer readable medium on which the computer program is stored e.g. in the form of computer program modules or the like.
  • the memory may be a flash memory, a Random-Access Memory (RAM), a Read-Only Memory (ROM), an Electrically Erasable Programmable ROM (EEPROM) or hard drive storage (HDD), and the program modules could in alternative embodiments be distributed on different computer program products in the form of memories within the wireless device 700.
  • RAM Random-Access Memory
  • ROM Read-Only Memory
  • EEPROM Electrically Erasable Programmable ROM
  • HDD hard drive storage
  • the solution described herein may be implemented in the wireless device 700 by means of a computer program storage product comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the actions according to any of the above embodiments, where appropriate. While the solution has been described with reference to specific exemplifying embodiments, the description is generally only intended to illustrate the inventive concept and should not be taken as limiting the scope of the solution. For example, the terms “wireless device”, “message”, “vehicle platoon”, “timestamp” and “time constraint” have been used throughout this disclosure, although any other corresponding entities, functions, and/or parameters could also be used having the features and characteristics described here. The solution is defined by the appended claims.

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Abstract

A method and a first wireless device (500) for propagating a message to a group of wireless devices (504). When the first wireless device obtains (5:1) the message, a latest reception time when the message must be received by all wireless devices in the group is detected, e.g. based on information in the message such as a timestamp and a time constraint. Then, a required range for the message from the first wireless device is determined (5:3) based on the detected latest reception time. The first wireless device (500) finally transmits (5:5A,B,C) the message using a transmission power that corresponds to the required range, so that the message is received by those wireless devices (504, 506) of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time.

Description

METHOD AND FIRST WIRELESS DEVICE FOR PROPAGATING A MESSAGE
Technical field
The present disclosure relates generally to a method and a wireless device, for propagating a message to a group of wireless devices. Background
In the field of wireless communication, it may sometimes be required to convey a message from one wireless device to multiple other wireless devices within a certain limited time span, herein referred to as "time constraint". For example, the wireless devices may operate in vehicles of a so-called vehicle platoon. Platooning refers to a mode of operation of a group of automatically controlled vehicles which can travel in a line very close to each other, and they can autonomously steer, accelerate and brake in a coordinated manner. Autonomous or semi-autonomous vehicles can be operated in the platooning mode if they are equipped for receiving commands and sending vehicle information related to position and movement, and also with software needed for automatic control and platooning formation. A typical example of such a time-critical message that needs to be propagated to all vehicles in a vehicle platoon is a breaking or steering command where the vehicles must operate according to the message more or less immediately.
Other examples where a message needs to be conveyed to a group of wireless devices within a time constraint, may include a set of sensors, actuators, instruments, machine parts or the like, which are installed at various locations. It may be desirable to control or support operations of the above components in some coordinated manner by means of the message. It is not unusual that certain critical or significant messages need to be propagated very fast to all wireless devices in the group, e.g. within a few milliseconds, and in that case it is not possible to convey the message across a wireless network with base stations, access points or the like which might take too much time.
The following description generally relates to situations where a first wireless device shall convey or propagate a message to a group of wireless devices by means of direct device-to-device communication, i.e. not using any intermediate network nodes of a wireless network. For example, vehicles within a vehicle platoon usually communicate with each other using Dedicated Short-Range Communication, DSRC, e.g. using the protocol IEEE 802.1 1 p, which is a protocol for short-range inter-vehicle communication. However, there are some problems associated with such communication of a message from one wireless device to a group of other wireless devices, which will be briefly discussed below.
There are basically two ways of propagating a message from one wireless device to a group of other wireless devices. One way is to propagate the message in several steps, or "hops", which is illustrated in Fig. 1A where a group of wireless devices D1 -D7 are positioned basically in a line, which could e.g. be the case of a vehicle platoon driving together on a road. Here, the message originates from a first wireless device D1 that transmits the message with relatively low power to an adjacent wireless device denoted D2 in a first communication denoted C1 . Having received the message, wireless device D2 transmits the message to its adjacent wireless device D3 in a second communication C2, and so forth. In this case, six consecutive communications C1 -C6 are needed to get the message across to all wireless devices D2-D7 where each communication takes a certain time to complete. The total time this takes may exceed a given time constraint of the message and the message may thus become virtually out-of-date in some sense before reaching all devices. The above communication scheme is used in IEEE 802.1 1 p.
If the above situation is unacceptable, it will be necessary to transmit the message to all wireless devices D2-D7 simultaneously, which is illustrated in Fig. 1 B where the first wireless device D1 transmits the message with relatively high power so that it can be received properly by the outmost wireless device D7, as indicated by a communication denoted C7. The dashed arrows indicate that the message can also be received properly by the other wireless devices D2-D6 as well. However, the transmission power needed to get the message across to all devices including the outmost wireless device D7 may cause harmful interference to other wireless communications performed in the neighborhood. Further, the high transmission power required in Fig. 1 B will drain the battery in the first wireless device D1 to a greater extent than in the example of Fig 1 A. In some wireless devices such as sensors, it may be desirable to keep power consumption at a minimum so as to delay the need for battery recharge or replacement for as long as possible.
The above-mentioned protocol IEEE 802.1 1 p has defined a maximum range of 1000 meters. However, given that transmission is done at a frequency of ~5.9GHz, and to cover a 1000 meters range very high transmission power may be required which thus can cause too much interference to other communication, e.g.
performed by other road users and roadside infrastructures. The same problem may apply to the other short-range connectivity protocols as well. So in practice, it may be necessary to choose much shorter transmission range to save power and not to cause interference, which however is not possible or sensible for certain time-critical messages.
Summary
It is an object of embodiments described herein to address at least some of the problems and issues outlined above. It is possible to achieve this object and others by using a method and a first wireless device as defined in the attached independent claims.
According to one aspect, a method is performed by a first wireless device for propagating a message to a group of wireless devices. In this method, the first wireless device detects a latest reception time when the message must be received by all wireless devices in the group, and determines a required range for the message from the first wireless device based on the detected latest reception time, the first wireless device then transmits the message using a transmission power that corresponds to the required range so that the message is received by those wireless devices of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time.
According to another aspect, a first wireless device is arranged to propagate a message to a group of wireless devices. The first wireless device is configured to detect a latest reception time when the message must be received by all wireless devices in the group, and to determine a required range for the message from the first wireless device based on the detected latest reception time. The first wireless device is further configured to transmit the message using a transmission power that corresponds to the required range so that the message is received by those wireless devices of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time.
It is an advantage of this solution that the message can be propagated to all wireless devices within the given time constraint, while using no more than the transmission power needed to reach the required range so as to reduce or even avoid any harmful interference generated by the transmissions involved.
The above method and first wireless device may be configured and implemented according to different optional embodiments to accomplish further features and benefits, to be described below. A computer program is also provided comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method described above. A carrier is also provided which contains the above computer program, wherein the carrier is one of an electronic signal, optical signal, radio signal, a computer program storage product, or a computer readable storage medium.
Brief description of drawings
The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:
Figs 1A and 1 B are two different communication scenarios illustrating propagation of a message to multiple wireless devices, according to the prior art.
Fig. 2 is a communication scenario illustrating an example of how the solution may be employed, according to some possible embodiments. Fig. 3 is a flow chart illustrating a procedure in a first wireless device, according to further possible embodiments.
Figs 4A-4E are communication scenarios illustrating examples of gradual propagation of a message to multiple wireless devices, in accordance with some possible embodiments.
Fig. 5 is a signaling diagram illustrating an example of a procedure when the solution is used, according to further possible embodiments.
Fig. 6 is a communication scenario illustrating an example where the solution is employed for a vehicle platoon, in accordance with some possible embodiments. Fig. 7 is a block diagram illustrating a first wireless device in more detail, according to further possible embodiments.
Detailed description
Briefly described, a solution is provided to enable propagation of a message to a group of wireless devices within a given time constraint, while using a minimum of transmission power so as to reduce or even avoid any harmful interference generated by the transmission. This can be achieved by means of a procedure that can be performed by a first wireless device which may be the device from which the message originates or a device that has received the message in an ongoing propagation process for further transmission. First, a required range for the message from the first wireless device is determined based on a latest reception time of the message, i.e. the given time constraint, which may be detected based on information in the message. This information may include a timestamp indicating when the message was originated or generated, and a time constraint indicating a maximum time within which all wireless devices in the group should receive the message after it was
originated/generated. Timing information in the message may also simply indicate a point in time when the message must have been received by all devices. For example, the time left before expiry of the message's latest reception time basically dictates the maximum number of hops the message has time to take before expiry, and the required range can be determined depending on how much time is left and on the distance to the device in the group that is farthest away from the first device. If there is much time left before expiry of the message the required range can be relatively short, and vice versa. It should be noted that the number of hops used before the message has reached all devices may be chosen to be less than the available maximum number of hops.
The first wireless device then transmits the message using a transmission power that corresponds to the determined required range, so that the message is received by those wireless devices that are located within the required range. Having received the message, the wireless devices within the required range may in turn likewise determine a new required transmission range for the message and transmit the message using a transmission power that corresponds to the new required range. This way, the message can be propagated to all wireless devices of the group within the detected latest reception time. It should be noted that the range of the new transmission may be different than the preceding transmission range and the required range can thus be adaptive in this respect by being determined "successively" by different wireless devices. The devices may continue to forward the message until the latest reception time has expired. However, if a device receives the same message a second or third time it may refrain from transmitting it once more. In general, each device may be configured to transmit the same message no more than once.
An example of communication when the above procedure is employed is shown in Fig. 2 again involving 7 wireless devices D1 -D7 located basically along a line, where device D1 generates a message to be propagated. D1 may thus
correspond to the above-mentioned first wireless device. In this scenario, device D1 may estimate that there is time for the message to take more than one hop before the time constraint, i.e. the message expires. It is thus not necessary for device D1 to transmit the message with a power so that it reaches all devices D2-
D7. The first device D1 thus transmits the message using a transmission power to reach a detected required range encompassing only a subset of the devices D2- D7, as illustrated by a first communication C8. In this case the message in communication C8 reaches as far as the wireless device D4 and thereby also the more closely located wireless devices D2 and D3, as shown by dashed arrows. Then, at least the outmost wireless device D4 will act as the above-described first device and transmits the message using a transmission power to reach a new required range, as illustrated by a second communication C9 which propagates the message as far as the wireless device D7 and thereby also the closer located wireless devices D5 and D6, as shown by dashed arrows. The message is thereby propagated to all wireless devices D2-D7 of the group by only two hops which in this case fulfills the latest reception time, while using a transmission power that is considerably reduced as compared to the scenario in Fig. 1 B. Hence, the message is propagated in shorter time than in Fig. 1 A and with less transmission power than in Fig. 1 B. The communication shown in Fig. 2 may be executed by means of a so-called "Gossip" protocol which has been designed for propagating messages to a large number of receivers, e.g. sensors of a distributed system, in an efficient manner and using less power as compared to simultaneous broadcasting to all devices. As explained above, one wireless device starts sending a message (a gossip) to other wireless devices which will then further send out the message to their respective neighbor devices, and so forth. As an example, Teknek-gossip is a java library that uses a gossip algorithm to discover nodes in a peer-to-peer network over User Datagram Protocol, UDP. In Fig. 2, each of the devices D2, D3 and D4 will thus determine a new required range and transmit the received message accordingly. As a result, the devices D1 -D7 are likely to receive the same message more than once and when that happens they may be configured to transmit the message no more than once so as to limit interference and power consumption.
An example will now be described, with reference to the flow chart in Fig. 3, of how the solution may be employed in terms of actions performed in a first wireless device, e.g. in any of the above-described devices D1 and D4, for propagating a message to a group of wireless devices. Reference will also be made, without limiting the features described, to the example shown in Fig. 2. In the procedure of Fig. 3, the first wireless device may be the device in which the message is originated or generated such as D1 , or it could also be a device such as D4 that has received the message from another device in the group i.e. when propagation of the message has already begun. The procedure illustrated by Fig. 3 can thus be used to accomplish the functionality described above for the wireless devices D1 and D4.
A first action 300 illustrates that the first wireless device generates or receives the message to be propagated to a group of wireless devices, thus as described above for devices D1 and D4, respectively. In one example embodiment, the group of wireless devices may operate in vehicles of a vehicle platoon. In platooning mode, wireless devices in the vehicles use wireless Device-to-Device, D2D, communication for the coordinated driving of the platoon vehicles. It can thus be assumed that all vehicles in a platoon have a wireless device or the equivalent which is configured to provide the necessary communication for platooning. The wireless device may be a separate communication entity such as a mobile phone or similar which is connected to the vehicle's driving functions, or it may be integrated in the vehicle, depending on the implementation.
In the case of vehicle platoon, further example embodiments may be that the message comprises a command to adjust any of: speed, acceleration/retardation, moving direction and position relative to at least one adjacent vehicle. In another example embodiment, the message may originate from a lead vehicle of the vehicle platoon, which is a vehicle that basically acts as controller of the platoon by collecting various measurements from the vehicles and issuing driving commands to the vehicles. The message may otherwise originate from another vehicle in the platoon, such a request for refueling or battery recharging in case of an electrically driven vehicle. As indicated above, the solution is not limited to vehicle platoons and the wireless devices described herein may be used in any situation where a message needs to be propagated within a given time constraint. A next action 302 illustrates that the first wireless device detects a latest reception time when the message must be received by all wireless devices in the group. In another example embodiment, the latest reception time of the message may be detected based on information in the message, said information comprising a timestamp indicating when the message was originated and a time constraint indicating a maximum time within which all wireless devices in the group should receive the message. Alternatively, the timing information in the message may just indicate a point in time when the message must have been received by all devices.
In another action 304, the first wireless device further determines a required range for the message from the first wireless device based on the detected latest reception time. In another example embodiment, the required range may be determined further based on information about current position of the first wireless device in the group, total number of wireless devices in the group, and spatial extent of the group. In essence, the first wireless device can estimate how far the message should reach when knowing the size of the group and how much time is left before expiry of the message. Thereby, the transmission range can be more or less optimized so that the transmission power used will generate as little interference as possible while making sure that the message is received by all devices before its expiry.
In further example embodiments, the required range may be determined further based on at least one of: a current battery level in the first wireless device and an estimated interference to other communications caused by transmitting the message. For example, if the current battery level is low it is more important to keep the transmission power low, if possible, than when it is high. Further, a fairly high transmission power can be allowed if the estimated interference is low, and vice versa. In another example embodiment when the wireless devices are used in a vehicle platoon, the determined required range of the message may not extend essentially beyond the last vehicle in the vehicle platoon, that is in order to use no more power than necessary for the platoon.
An action 306 illustrates that the first wireless device transmits the message using a transmission power that corresponds to the required range so that the message is received by those wireless devices of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time. In some further example embodiments, transmitting the message may comprise any of: broadcasting, multicasting and unicasting the message. Some examples of such transmission of the message will be described later below with reference to Fig. 5. beamforming may be used when transmitting the message in action 306, so as to restrict the number of wireless devices receiving the message. This can thus be used to further reduce the transmission power and to avoid that the message is received unnecessarily by devices that have already received the message in a previous transmission. Beamforming means that the transmission only covers a restricted beam which can be achieved by using a directed antenna, which is a well-known transmission technique as such.
Some examples of how the solution may be implemented in practice will now be described. It is assumed that a group of wireless devices, referred to as devices for short, includes 15 individual devices being distributed spatially in a linear or near-linear formation, and that the distance between two adjacent devices is 20 meters so the total length of the group is roughly 300 meters. It is further assumed that the preferred maximum communication range is 100 meters in order to limit the power consumption and to avoid interference as much as possible. Figs 4A-4E illustrate how broadcast and gossip protocol can be used to propagate information across all devices of the group. The devices are labeled as D1 , D2, D15. In a first stage shown in Fig. 4A, D1 transmits a message with a power according to a required range. The message reaches all devices located within the required range, in this case devices D2-D6. The message may comprise a unique message identity (msgID), message text (msgDetail), a timestamp and a time constraint (maxtime). In more detail, msgID represents a unique message identifier, msgDetail is the actual message text together with a "message critical ity", timestamp is the time when the message was originated, and maxtime is the maximum time (e.g. in milliseconds) within which the message should or must be received by all devices of the group. Instead of the maximum time, the message may include an absolute time when the message must have been received by all devices. The message criticality basically indicates how important it is that all devices receive the message within the time constraint.
As illustrated by Fig. 4B, after receiving the message from D1 , D2 saves the message and then broadcasts the same message in the same way as D1 did. In this transmission, D7 will be covered while D1 and D3-D6 will receive a duplicated message that will be discarded by the receiver. Duplication can be detected by comparing msgID and timestamp in the message with the previously received message.
As illustrated by Fig. 4C, after receiving message from D1 , D3 will also save the message and start broadcasting the same message in the same way as D1 did. In this transmission, D8 will be covered while D1 , D2 and D4-D7 will receive a duplicated message, and so forth. For example, beamforming may be used by D3 in Fig. 4C, such that D2 and D1 will not receive the message since D3's antenna is directed towards D4-D8. Essentially, all devices will receive the message multiple times but broadcast the message only once. The duplications can be either discarded directly or used for confirmation of correct reception. Hence, the first broadcast of Fig. 4A covers up to D6, and the second broadcast from D6 covers up to D1 1 as illustrated by Fig. 4D. The second broadcast from D1 1 covers up to D15, which completes the message propagation.
When assuming the group is comprised of 15 devices, it takes ceiling (15/ 5 ) = 3 iterations, i.e. hops, to propagate the message to all devices; while using a linear propagation as shown in Fig. 1 A, it will take is - 1 = 14 iterations to complete the propagation.
Energy-wise, broadcasting consumes more energy compared with lower energy point-to-point communication, but this is a normal tradeoff, because an increase in the maximum range (from 100 m) will result in fewer iterations but higher energy consumption. However, a decrease in the maximum range will save energy but will require increased number of iterations.
In yet another example, if the maximum range is up to 300 meters, then only 2 iterations are required because each device needs to broadcast at least once for the propagation to be completed, although the broadcast from the last device is not necessary. On the other hand if the maximum range is only up to 20 meters, the propagation will decay to point-to-point communication because each device can only convey the message to its two adjacent neighbors.
To meet the time constraint, each device can check the timestamp and maxtime and then decide what the range of its own transmission should cover, which can be referred to as adaptive gossip protocol. By knowing its own position in the group and the current time, the first wireless device can use the following equation, as an example, to decide the required range of transmitting the message and hence the transmission power needed. More sophisticated equations may be developed according to different scenarios and objectives, but the principle remains the same. ■ β · γ■ ¾
Range = -, lower _limt < Range < upper Jimit
■maxtime — {cvrrent time— timestamp)
Where a is the coefficient computed based on location of current device within the group, β is the coefficient computed based on charging status of current device, γ is the estimated interference to other group of devices in the vicinity, and n is a baseline or default range. The above equation can be interpreted as follows:
A) If there is much time left, the required broadcast range (e.g. determined by position, charging status of current device and estimated interference to other group of devices in the vicinity) can be small and fewer devices will be covered in the coming iteration.
B) If there is only a short time left, the required broadcast range needs to be larger and hence more devices will be covered in the coming iteration. a can be defined as a linear function and the value decreases as reaching the end of the propagation direction. β can be defined as a linear function or as a few predefined values, where the value of β decreases as the charging status declines. If some devices will never have a power shortage, such as when the device is powered by a vehicle battery or a main power supply, the value of β can be a constant that equals to 1 . γ can be estimated according to how many other device groups are present in the vicinity and how many of them are in the process of communicating. The value decreases as the interference increases.
Based on the required range determined as described above, the transmission power needed to cover that range can be calculated according to conventional procedures.
Fig. 4E further illustrates how the required range can be adaptive. For example, if by the above calculation, D2 decides to broadcast up to 150 meters range, the next iteration will cover up to D9 instead of D7.
It was mentioned above that the message may be transmitted in action 306 by broadcasting, multicasting or unicasting. Some examples of how the message could be transmitted by a first wireless device are illustrated in the signaling diagram of Fig. 5. This figure illustrates the first wireless device 500, a message origin entity 502, a number of wireless devices 504 that are within transmission range from the first device 500, and one or more adjacent wireless devices 506 which are located next to the first device 500. The adjacent wireless devices 506 are thus part of the devices 504 within transmission range. A first action 5:1 illustrates that the first wireless device 500 receives the message from the message origin entity 502 which may be a wireless device operating in the leader vehicle of a vehicle platoon. Alternatively, the message may be generated within the first wireless device 500, e.g. when device 500 resides in the leader vehicle or in any vehicle of the platoon. Having received the message, the first wireless device 500 saves the message in a suitable local storage, in an action 5:2.
As illustrated by another action 5:3, the first wireless device 500 then determines the required range of transmitting the message, basically as described for action
304, and also determines which transmission (Tx) mode to use, i.e. either of the above-mentioned modes of broadcasting, multicasting and unicasting. The first wireless device 500 further adapts the transmission power to the determined required range, in another action 5:4. The actual transmission of the message is then dependent on which transmission mode was selected in action 5:3, which is illustrated by three alternatives as follows.
In a first alternative, the first wireless device 500 has determined in action 5:3 to transmit the message by broadcasting which is done in an action 5:5A. In this case the message is broadcasted once with a power that is sufficient to reach all the devices 504, 506 within the determined range. In other words, the message can be received by any of the wireless devices 504, 506.
In a second alternative, the first wireless device 500 has determined in action 5:3 to transmit the message by multicasting which is done in an action 5:5B.
Multicasting the message means that it is sent to specific addressed devices instead of to anyone within the range. In other words, the message will be received only by the wireless devices 504, 506 being addressed in the message. It is an advantage of this transmission mode that the first wireless device 500 can select which devices will receive the message.
In a third alternative, the first wireless device 500 has determined in action 5:3 to transmit the message by unicasting which is done in an action 5:5C. Unicasting the message means that a copy of the message is sent to each device separately, thus resulting in multiple individual transmissions. Unicasting also means that correct reception of the message is acknowledged by the devices, which thus confirms delivery of the message. Fig. 6 illustrates an example of how the solution may be employed in the context of vehicle platooning. A group of vehicles are thus driving on a road in a platoon formation which is controlled by a leader vehicle 600. A wireless device in the leader vehicle 600 sends a breaking command which must be received by all vehicles within a certain time limit so that the vehicles can execute the braking simultaneously in a coordinated manner, which is absolutely necessary in order to avoid any incident such as a collision. The message is received by at least the next vehicle 602 in the platoon which has a wireless device onboard that acts as the above-described first wireless device. Thus, the first wireless device in vehicle 602 performs the actions 302-306 as described above, i.e. determines a required range and transmits the message further with a transmission power that reaches the required range which extends across a succession of vehicles 604, 606 and 608. Then, at least vehicle 608 will likewise perform actions 302-306 and transmit the message onwards across the platoon, although not shown in this figure.
The block diagram in Fig. 7 illustrates a detailed but non-limiting example of how a first wireless device 700 may be structured to bring about the above-described solution and embodiments thereof. The first wireless device 700 may be
configured to operate according to any of the examples and embodiments of employing the solution as described above, where appropriate, and as follows. The first wireless device 700 is shown to comprise a processor P and a memory M, said memory comprising instructions executable by said processor P whereby the first wireless device 700 is operative as described herein. The first wireless device 700 also comprises a communication circuit C with suitable equipment for transmitting commands and receiving radio signals in the manner described herein. The communication circuit C is configured for communication with other wireless devices using suitable protocols depending on the implementation. This communication may be performed in a conventional manner over a communication network employing radio links for wireless communication with the wireless devices involved, which is not necessary to describe here as such in any detail. The solution and embodiments herein are thus not limited to using any specific types of technology or protocols for radio communication.
The wireless device 700 comprises means configured or arranged to perform at least the actions 300-306 of the flow chart in Fig. 3, and optionally also in accordance with any of the examples shown in Figs 4-6. The wireless device 700 is arranged to propagate a message to a group of wireless devices. The wireless device 700 may be configured to receive or otherwise obtain the message to be propagated. This receiving operation may be performed by a receiving unit 700A in the wireless device 700, e.g. in the manner described for action 300 above. The wireless device 700 is further configured to detect a latest reception time when the message must be received by all wireless devices in the group. This detecting operation may be performed by a detecting unit 700B in the wireless device 700, e.g. as described for action 302 above.
The wireless device 700 is also configured to determine a required range for the message from the first wireless device based on the detected latest reception time. This operation may be performed by a determining unit 700C in the wireless device 700, e.g. as described for action 304 above.
The wireless device 700 is also configured to transmit the message using a transmission power that corresponds to the required range so that the message is received by those wireless devices of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time. This transmitting operation may be performed by a transmitting unit 700D in the wireless device 700, e.g. as described for action 306 above.
It should be noted that Fig. 7 illustrates various functional units in the wireless device 700, and the skilled person is able to implement these functional units in practice using suitable software and hardware. Thus, the solution is generally not limited to the shown structures of the wireless device 700, and the functional units 700A-D therein may be configured to operate according to any of the features and embodiments described in this disclosure, where appropriate. The functional units 700A-D described above can be implemented in the wireless device 700 by means of suitable hardware and program modules of a computer program comprising code means which, when run by the processor P causes the wireless device 700 to perform at least some of the above-described actions and procedures. The processor P may comprise a single Central Processing Unit (CPU), or could comprise two or more processing units. For example, the processor P may include a general purpose microprocessor, an instruction set processor and/or related chips sets and/or a special purpose microprocessor such as an Application Specific Integrated Circuit (ASIC). The processor P may also comprise a storage for caching purposes. Each computer program may be carried by a computer program product in the wireless device 700 in the form of a memory having a computer readable medium and being connected to the processor P. The computer program product or memory in the wireless device 700 may thus comprise a computer readable medium on which the computer program is stored e.g. in the form of computer program modules or the like. For example, the memory may be a flash memory, a Random-Access Memory (RAM), a Read-Only Memory (ROM), an Electrically Erasable Programmable ROM (EEPROM) or hard drive storage (HDD), and the program modules could in alternative embodiments be distributed on different computer program products in the form of memories within the wireless device 700.
The solution described herein may be implemented in the wireless device 700 by means of a computer program storage product comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the actions according to any of the above embodiments, where appropriate. While the solution has been described with reference to specific exemplifying embodiments, the description is generally only intended to illustrate the inventive concept and should not be taken as limiting the scope of the solution. For example, the terms "wireless device", "message", "vehicle platoon", "timestamp" and "time constraint" have been used throughout this disclosure, although any other corresponding entities, functions, and/or parameters could also be used having the features and characteristics described here. The solution is defined by the appended claims.

Claims

1 . A method performed by a first wireless device (500, 700) for propagating a message to a group of wireless devices, the method comprising:
- detecting (302) a latest reception time when the message must be received by all wireless devices in the group,
- determining (304) a required range for the message from the first wireless device based on the detected latest reception time, and
- transmitting (306) the message using a transmission power that corresponds to the required range so that the message is received by those wireless devices (504, 506) of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time.
2. A method according to claim 1 , wherein the latest reception time of the message is detected based on information in the message, said information comprising a timestamp indicating when the message was originated and a time constraint indicating a maximum time within which all wireless devices in the group should receive the message.
3. A method according to claim 1 or 2, wherein the required range is determined further based on information about current position of the first wireless device in the group, total number of wireless devices in the group, and spatial extent of the group.
4. A method according to any of claims 1 -3, wherein the required range is determined further based on at least one of: a current battery level in the first wireless device (500, 700) and an estimated interference to other communications caused by transmitting the message.
5. A method according to any of claims 1 -4, wherein the group of wireless devices operate in vehicles of a vehicle platoon.
6. A method according to claim 5, wherein the message comprises a command to adjust any of: speed, acceleration/retardation, moving direction and position relative to at least one adjacent vehicle.
7. A method according to claim 5 or 6, wherein the message originates from a lead vehicle (600) of the vehicle platoon.
8. A method according to any of claims 5-7, wherein the determined required range of the message does not extend essentially beyond the last vehicle in the vehicle platoon.
9. A method according to any of claims 1 -8, wherein transmitting (306) the message comprises any of: broadcasting, multicasting and unicasting the message.
10. A method according to any of claims 1 -9, wherein beamforming is used when transmitting (306) the message to restrict the number of wireless devices (504, 506) receiving the message.
1 1 . A first wireless device (700), arranged to propagate a message to a group of wireless devices, wherein the first wireless device (700) is configured to:
- detect (700B) a latest reception time when the message must be received by all wireless devices in the group,
- determine (700C) a required range for the message from the first wireless device based on the detected latest reception time, and
- transmit (700D) the message using a transmission power that corresponds to the required range so that the message is received by those wireless devices (504, 506) of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time.
12. A first wireless device (700) according to claim 1 1 , wherein the first wireless device (700) is configured to detect the latest reception time of the message based on information in the message, said information comprising a timestamp indicating when the message was originated and a time constraint indicating a maximum time within which all wireless devices in the group should receive the message.
5 13. A first wireless device (700) according to claim 1 1 or 12, wherein the first wireless device (700) is configured to determine the required range further based on information about current position of the first wireless device in the group, total number of wireless devices in the group, and spatial extent of the group.
14. A first wireless device (700) according to any of claims 1 1 -13, wherein 0 the first wireless device (700) is configured to determine the required range further based on at least one of: a current battery level in the first wireless device (500, 700) and an estimated interference to other communications caused by
transmitting the message.
15. A first wireless device (700) according to any of claims 1 1 -14, wherein5 the group of wireless devices operate in vehicles of a vehicle platoon.
16. A first wireless device (700) according to claim 15, wherein the message comprises a command to adjust any of: speed, acceleration/retardation, moving direction and position relative to at least one adjacent vehicle.
17. A first wireless device (700) according to claim 15 or 16, wherein the o message originates from a lead vehicle (600) of the vehicle platoon.
18. A first wireless device (700) according to any of claims 15-17, wherein the determined required range of the message does not extend essentially beyond the last vehicle in the vehicle platoon.
19. A first wireless device (700) according to any of claims 1 1 -18, wherein 5 the first wireless device (700) is configured to transmit the message by any of: broadcasting, multicasting and unicasting the message.
20. A first wireless device (700) according to any of claims 1 1 -19, wherein the first wireless device (700) is configured to use beamforming when transmitting the message to restrict the number of wireless devices receiving the message.
21 . A computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any one of claims 1 -10.
22. A carrier containing the computer program of claim 21 , wherein the carrier is one of an electronic signal, optical signal, radio signal, a computer program storage product or a computer readable storage medium.
23. A first wireless device (700), arranged to propagate a message to a group of wireless devices, wherein the first wireless device (700) comprises:
- a detecting unit (700B) configured to detect a latest reception time when the message must be received by all wireless devices in the group,
- a determining unit (700C) configured to determine a required range for the message from the first wireless device based on the detected latest reception time, and
- a transmitting unit (700D) configured to transmit the message using a
transmission power that corresponds to the required range so that the message is received by those wireless devices (504, 506) of the group that are located within the required range, and so that the message can be propagated to all wireless devices of the group within the detected latest reception time.
PCT/EP2016/061267 2016-05-19 2016-05-19 Method and first wireless device for propagating a message WO2017198302A1 (en)

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