ADAPTIVE TRANSMIT POWER CONTROL FOR VEHICLE COMMUNICATIONS

Abstract

A vehicle (100), comprising: a driver assistance unit (106) for determining an expected speed of target vehicles in a vicinity of the vehicle (100); and a communication module (102) for: determining a message type of a message received from a subsystem of the vehicle (100), wherein the message type includes public safety and private service; and transmitting the message at a power level, wherein, when the message type is public safety, the power level is determined based on a range request associated with the message, and wherein the power level is increased when a difference between the expected speed of the target vehicles and an actual speed of the vehicle (100) meets a speed threshold.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to vehicle-to-everything (V2X) communications and, more particularly, to adaptive transmit power control for vehicle communications. GENERAL STATE OF THE ART

[0002] In the United States, the Dedicated Short-Range Communications (DSRC) network is a vehicle-to-everything (V2X) communication network used as part of traffic telematics. DSRC enables vehicles communicating with other vehicles to coordinate maneuvers and provide warnings about potential crash hazards. Additionally, DSRC enables communication with infrastructure-based nodes, such as toll booths and traffic lights. The use of the DSRC protocol aims to reduce fatalities, injuries, property damage, lost time in traffic, fuel consumption, and exhaust emissions, among other things.

[0003] The document US 2012 / 0 136 559 A1 describes a system and method for identifying emergency vehicles and transmitting their location. Information and data are collected and processed to identify emergency vehicles such as ambulances, fire engines, and police cars. The system includes additional devices that determine the speed and direction of travel of the vehicle and transmit the location to other drivers in the vicinity.

[0004] The document US 2014 / 0 045 556 A1 describes a control of the transmission and reception of security messages, such as so-called DSRC security messages, i.e. Dedicated Short Range Communications, by portable, wireless terminals.

[0005] Furthermore, the document US 2004 / 0 002 346 A1 shows a system and a method for determining and reporting a location of a wireless device in a wireless communication system. SUMMARY

[0006] The present invention is based on the object of creating an improved vehicle, an improved method for vehicle communication, and a corresponding computer-readable medium that avoids the disadvantages of the prior art and advantageously develops the latter. In particular, the aim is to create a vehicle communication system whose messages reliably reach a respective target vehicle without creating unnecessary potential for detrimental radio interference.

[0007] According to the invention, the stated object is achieved by a vehicle according to claim 1, a method according to claim 4, and a computer-readable medium according to claim 8. Preferred embodiments of the invention are the subject of the dependent claims.

[0008] Embodiments of adaptive transmit power control for vehicle communications are disclosed. An exemplary disclosed vehicle includes a driver assistance unit and a communications module. The driver assistance unit determines an expected speed of target vehicles in the vicinity of the vehicle. The communications module determines a message type of a message received from a subsystem of the vehicle. Furthermore, the communications module transmits the message at a power level. The power level is based on the message type and the expected speed of target vehicles.

[0009] An exemplary disclosed method includes determining an expected speed of target vehicles in the vicinity of the vehicle via a driver assistance unit. The exemplary method further includes determining a message type of a message received from a subsystem of the vehicle. Furthermore, the method includes transmitting the message at a power level with a communication module. The power level is based on the message type and the expected speed of the target vehicles.

[0010] An example tangible computer-readable medium includes instructions that, when executed, cause a vehicle to determine an expected speed of target vehicles in the vicinity of the vehicle via a driver assistance unit. The instructions further cause the vehicle to determine a type of message to be received by a subsystem of the vehicle. Furthermore, the instructions cause the vehicle to transmit the message at a power level using a communications module. The power level is based on the message type and the expected speed of the target vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a better understanding of the invention, reference is made to embodiments illustrated in the following drawings. The components in the drawings are not necessarily to scale, and related elements may be omitted, or in some cases, proportions may be exaggerated, in order to emphasize and clearly illustrate the novel features described herein. Furthermore, system components may be arranged in various ways, as is known in the art. Furthermore, in the drawings, corresponding parts are designated by like reference numerals throughout the different views. The Fig. 1A 1D illustrate vehicles with Vehicle-to-Everything (V2X) modules operated according to the teachings of this disclosure. The Fig. 2A 2C show example tables used to determine a power level for the V2X module. Fig. 3 is a block diagram of electronic components of the vehicles from the Fig. 1A 1D. Fig. Figure 4 is a flowchart of a method for determining the power level for the V2X module provided by the electronic components of Fig. 3 can be implemented. DETAILED DESCRIPTION OF EMBODIMENTS

[0012] Although the invention may be embodied in various forms, some exemplary and non-limiting embodiments are shown in the drawings and described below, it being understood that the present disclosure is to be considered as an explanation of the invention by way of example and is not intended to limit the invention to the specific embodiments illustrated.

[0013] Vehicle-to-everything (V2X) communication includes vehicle-to-vehicle (V2V) communication, vehicle-to-infrastructure (V2I) communication, and vehicle-to-pedestrian (V2P) communication. V2X communication enables interaction and coordination between vehicles (e.g., cars, trucks, motorcycles, trains, ships, etc.) and other road objects and users. One specific implementation of V2X communication is Dedicated Short Range Communication (DSRC). When there are many vehicles on the road, the radio signals transmitted by all vehicles can cause radio interference, which then impairs the signal quality to each vehicle. Even if an allocated spectrum (e.g.,As the frequency band (5.9 GHz) is divided into different channels and channel hopping techniques are employed, the potential for detrimental radio interference increases due to the increased use of V2X communication, as messages sent on the same channel reduce the signal-to-noise ratio in the surrounding area on that channel. As disclosed below, by adjusting the power used to transmit a message, it becomes possible for the intended target vehicle to receive the message while reducing the number of unintended vehicles also receiving the message on that particular channel.

[0014] Applications that communicate via V2X communication are classified as public safety and private services. Public safety applications enable vehicles to exchange operational data (e.g., speed, position, trajectory, lane, etc.) and hazard data so vehicles can coordinate their travel and avoid hazards. Public safety applications can include, for example, blind spot detection, forward collision detection, sudden deceleration detection, emergency vehicle alerts, commercial vehicle clearance, and commercial vehicle safety checks. Example public safety messages include signal phase and timing (SPaT) messages that inform vehicles of the timing of traffic lights at intersections. Private services applications enable non-safety-related communication.For example, applications for private services may include electronic parking and toll payments, social vehicle-to-vehicle (V2V) messaging systems, rental car processing, fleet management, transmissions of DAM camera video data, etc. The range of a V2X transmission is proportional to the transmit power of the V2X module. Higher transmit power increases the range of the transmitted signal.

[0015] As discussed below, the transmit power of the V2X module is determined by (a) an expected speed of the target vehicle(s), (b) a speed difference between the sending vehicle and the expected speed of the target vehicle, and / or (c) a message type. As used herein, the expected speed is a speed that the sending vehicle determines is likely in the area surrounding the sending vehicle. For example, the expected speed may be the speed limit. The sending vehicle determines the expected speed, for example, via an advanced driver assistance system (ADAS). The ADAS performs character recognition to detect the speed limit on applicable traffic signs. In some examples, the sending vehicle determines the expected speed via a navigation application running on an infotainment system.For example, the expected speed on an interstate is 70 miles per hour (mph) (113 km / h). As another example, the transmitting vehicle might make a sharp stop and decelerate quickly, while other nearby vehicles may be traveling at highway speeds. In such an example, if the transmitting vehicle's speed is 20 mph (32 km / h) and the expected traffic speed is 70 mph (113 km / h), the V2X module's transmit power can be based on the 50 mph (81 km / h) speed difference.

[0016] An application can specify a message type (e.g., public, private, short, medium, long, etc.). In some examples, the transmit power (sometimes referred to as equivalent isotropic radiated power (EIRP)) of the V2X module is determined by the message type. For example, a private short message can be sent at a first power level, and a public long message can be sent at a second power level. In some such examples, the transmit power is set based on the difference between the speed of the sending vehicle and the expected speed of the target vehicle. For example, a private medium message can be sent at a third power level instead of a second power level because the speed difference is 21 mph (34 km / h).

[0017] The Fig. 1A and 1D illustrate vehicles 100 with Vehicle-to-Everything (V2X) modules 102 operating according to the teachings of this disclosure. The vehicle 100 (e.g., a car, a truck, a motorcycle, a train, a ship, etc.) may be a standard gasoline-powered vehicle, a hybrid vehicle, an electric vehicle, a fuel cell vehicle, and / or any other type of vehicle with any other type of propulsion. The vehicle 100 includes parts related to mobility, such as a powertrain with an engine, a transmission, a suspension, a driveshaft, and / or wheels, etc. The vehicle 100 may be non-autonomous, semi-autonomous (e.g., some routine driving functions are controlled by the vehicle 100), or autonomous (e.g., driving functions are controlled by the vehicle 100 without direct driver input).In the illustrated example, the vehicle 100 includes the V2X module 102, an infotainment head unit 104, and a driver assistance system (ADAS) unit 106.

[0018] The V2X module 102 includes radio(s) and software for broadcasting messages and establishing direct connections between the vehicle 100, other vehicles, infrastructure-based modules (not shown), and mobile device-based modules (not shown). Further information about the DSRC network and how the network can communicate with vehicle hardware and software is available in the U.S. Department of Transportation's June 2011 "Core-System Requirements Specification (SyRS) Report" (available at http: / / www.its.dot.gov / meetings / pdf / CoreSystem_SE_SyRS_RevA%20(2011-06-13).pdf). V2X systems can be installed on vehicles and on roadside infrastructure. V2X systems that include infrastructure information are known as a "roadside" system.V2X can be combined with other technologies such as Global Positioning System (GPS), visible light communication (VLC), cellular communication, and short-range radar, enabling vehicles to communicate their position, speed, direction, relative position to other objects, and exchange information with other vehicles or external computer systems. V2X systems can be integrated with other systems, such as mobile phones.

[0019] Currently, the V2X network is known by the abbreviation or name DSRC. However, other names are sometimes used, usually related to a vehicle connectivity program or similar. The majority of these systems are either pure DSRC or a variation of the IEEE 802.11 radio standard. However, in addition to the pure DSRC system, dedicated wireless communication systems between vehicles and a roadside infrastructure system, combined with GPS and based on an IEEE 802.11 wireless local area network protocol (such as 802.11p, etc.), are also intended to be covered.

[0020] The V2X module 102 regulates the transmit power of signals transmitted by the antenna of the V2X module 102. In some examples, the V2X module 102 regulates the equivalent isotropic radiated power (EIRP) of the signals between 0 and 20 dBm (e.g., 1 to 100 milliwatts (mW)). For example, to ensure signals have a range of 1000 meters (3281 feet), the V2X module 102 may transmit with a signal strength of 20 dBm. As another example, to ensure a signal has a range of 300 meters (984 feet), the V2X module 102 may transmit with a signal strength of 12 dBm. The V2X module 102 defines power levels that correspond to target ranges. For example, the signal strength of 20 dBm can be defined as the fourth power level and the signal strength of 12 dBm can be defined as the third power level.

[0021] The V2X module 102 receives the expected speed for target vehicles in the area and the current speed of the vehicle 100 from the ADAS unit 106. In some examples, the V2X module 102 does not receive an actual speed (e.g., as measured by a range sensor) of any of the target vehicles from the ADAS unit 106.

[0022] Furthermore, the V2X module 102 receives a message type and / or a requested range from applications communicating via the V2X module 102. Based on the expected speed, the current speed of the vehicle 100, the message type, and / or the requested range, the V2X module 102 determines a power level at which to send the message. Fig. Figure 2A illustrates a table 200 in which the message type 202 and a requested range 204 are associated with a power level 206. For example, a private service message with a requested short range may be sent at a first power level. For example, the first power level may be 8 dBm. Fig. Figure 2B illustrates a table 208 in which the expected speed 210 of the target vehicle is associated with the power level 206. For example, if the expected speed of the target vehicle is 70 mph (113 km / h), the V2X module 102 may transmit the message at a third power level (e.g., 12 dBm). Fig. 2C is a table 212 in which the difference between the speed of the vehicle 100 and the expected speed of the target vehicle (Δ speed) is associated with a transmit power adjustment (Δ power level). For example, if an application requests a message for private medium-range services and the Δ speed is 16 mph (26 km / h), the V2X module 102 may transmit the message at the third power level instead of the second power level. In some examples, the V2X module 102 adjusts the power level based on the speed difference meeting (e.g., being less than or equal to) one or more speed thresholds.

[0023] Additionally, in some examples, the V2X module 102 distinguishes between public safety and private service messages. In such examples, the V2X module 102 (a) limits ranges requested for private service messages and (b) does not adjust the power level for private service messages. For example, the V2X module 102 may limit private service messages to a short range (e.g., 0 to 15 meters) and a medium range (e.g., 0 to 90 meters). For example, if a medium-range private service message is requested and the speed difference between the speed of the vehicle 100 and the expected speed of the target is 16 mph (26 km / h), the V2X module 102 transmits the message at the second power level, which corresponds to the medium range. The infotainment head unit 104 provides an interface between the vehicle 100 and a user.The infotainment head unit 104 includes digital and / or analog interfaces (e.g., input devices and output devices) to receive input from the user(s) and display information. The input devices may include, for example, a control knob, an instrument panel, a digital camera for image capture and / or visual command recognition, a touch screen, an audio input device (e.g., a cabin microphone), buttons, or a touch pad. The output devices may include instrument cluster outputs (e.g., dials, illumination devices), actuators, a heads-up display, a center console display (e.g., a liquid crystal display ("LCD"), an organic light-emitting diode ("OLED") display, a flat panel display, a solid-state display, etc.), and / or speakers. In the illustrated example, the infotainment head unit 104 includes hardware (e.g.,a processor or controller, memory, storage, etc.) and software (e.g., an operating system, etc.) for an infotainment system 108 (such as SYNC® and MyFord Touch® from Ford®, Entune® from Toyota®, IntelliLink® from GMC®, etc.).

[0024] Additionally, the infotainment main unit 104 displays the infotainment system 108, for example, on the center console display. The infotainment system 108 runs applications, such as navigation applications, communication applications, entertainment applications, etc., that may use the V2X module 102 to communicate. Such applications request the V2X module 102 to broadcast messages. In some examples, the requests from the applications include a type (e.g., public safety or private service) and / or a range. For example, a payment application may request that the V2X module 102 broadcast a short-range message.

[0025] The FAS unit 106 facilitates situational awareness around the vehicle 100. The FAS unit 106 may include or be integrated with vehicle systems that provide guidance and assistance to drivers, such as blind spot detection and rear collision warning, etc. The FAS unit 106 uses sensors (e.g., the below-mentioned sensors 304 from Fig. 3) to detect and identify objects (e.g., vehicles, pedestrians, traffic signs, etc.) around the vehicle 100. In the illustrated examples, the ADAS unit 106 detects speed limit signs. Furthermore, the ADAS unit 106 performs optical character recognition to detect the speed limit on the corresponding signs. In some examples, the ADAS unit 106 requests that a message be broadcast via the V2X module 102. For example, if the ADAS unit 106 includes rear impact detection, the ADAS unit 106 may request that a medium-range private message be broadcast.

[0026] The Fig. 1A and Fig. 1B illustrate examples where the vehicle sends 100 messages for private services. In the Fig. 1A, the vehicle 100 is parked near a parking meter 110. The parking meter 110 includes an infrastructure-based V2X node 112. The infrastructure-based V2X node 112 sends and receives messages from the V2X modules 102 of the vehicles 100. For example, a payment application executed by the infotainment system 108 may instruct the V2X module 102 of the vehicle 100 to send a private short-range message to initiate a payment at the parking meter 110. In the Fig. In the example illustrated in Figure 1B, vehicle 100 sends a message to a target vehicle 114. Vehicle 100 instructs V2X module 102 to send a private, medium-range message. Because the message is for a private service, V2X module 102 does not consider the speed of vehicle 100 or the expected speed of target vehicle 114.

[0027] The Fig. 1C and Fig. 1D illustrate examples where the vehicle sends 100 public safety messages. In the Fig. 1C, vehicle 100 is parked on the side of the road. Vehicle 100 instructs its V2X module 102 to transmit a public safety message to inform others (e.g., vehicles 118 and 120) that it has experienced an emergency. V2X module 102 determines the expected speed of vehicles 118 and 120 via ADAS unit 106. ADAS unit 106 determines the expected speed by performing optical character recognition on speed limit sign 122. Since the expected traffic speed is 55 mph (89 km / h), V2X module 102 may transmit the message using a third power level (e.g., an extended range). In the example illustrated in Fig. In the example illustrated in Figure 1D, vehicle 100 is an emergency vehicle. Vehicle 100 instructs V2X module 102 to transmit a long-range public safety message.

[0028] Fig. 3 is a block diagram of electronic components 300 of the vehicles 100 of the Fig. 1A 1D. In the illustrated example, the electronic components include the V2X module 102, the infotainment head unit 104, the ADAS unit 106, electronic control units (ECUs) 302, sensors 304, and a vehicle data bus 306.

[0029] In the illustrated example, the V2X module 102 includes a processor or controller 308 and a memory 310. The processor or controller 308 may be any suitable processing device or set of processing devices, such as, but not limited to: a microprocessor, a microcontroller-based platform, a suitable integrated circuit, one or more field-programmable

[0030] Field-Processed Gate Arrays (FPGAs) and / or one or more Application-Specific Integrated Circuits (ASICs). Memory 310 may be volatile memory (e.g., RAM, which may include non-volatile RAM, magnetic RAM, ferroelectric RAM, and any other suitable forms); non-volatile memory (e.g., disk storage, FLASH memory, EPROMs, EEPROMs, memristor-based non-volatile semiconductor memory, etc.); immutable memory (e.g., EPROMs), read-only memory, and / or high-capacity storage devices (e.g., hard disks, solid-state drives, etc.). In some examples, memory 310 includes multiple memory types, specifically volatile memory and non-volatile memory.

[0031] Memory 310 is computer-readable media on which one or more sets of instructions, such as software for carrying out the methods of the present disclosure, may be embedded. The instructions may implement one or more of the methods or logic described herein. In a particular embodiment, the instructions may reside entirely or at least partially within any one or more of memory 310, the computer-readable medium, and / or within processor 308 during execution of the instructions.

[0032] The terms "non-transitory computer-readable medium" and "computer-readable medium" are intended to include a single medium or multiple media, such as a centralized or distributed database and / or associated caches and servers, on which one or more sets of instructions are stored. The terms "non-transitory computer-readable medium" and "computer-readable medium" further include any tangible medium capable of storing, encoding, or carrying a set of instructions for execution by a processor or for causing a system to perform any one or more of the methods or acts disclosed herein. As used herein, the term "computer-readable medium" is expressly defined to include any type of computer-readable storage device and / or storage disk and excludes the propagation of signals.

[0033] The ECUs 302 monitor and control the subsystems of the vehicle 100. The ECUs 302 communicate and exchange information over a vehicle data bus (e.g., vehicle data bus 306). Furthermore, the ECUs 302 may communicate properties (such as the status of the ECU 302, sensor readings, control status, error and diagnostic codes, etc.) to and / or receive requests from other ECUs 302. Some vehicles 100 may have seventy or more ECUs 302 located at various locations around the vehicle 100 and communicatively coupled to the vehicle data bus 306. The ECUs 302 are discrete sets of electronic components that include their own circuitry(s) (such as integrated circuits, microprocessors, memory, data storage, etc.) and firmware, sensors, actuators, and / or mounting elements. In the illustrated example, the ECUs 302 include a brake control unit, an engine control unit, and a throttle control unit.For example, the ADAS unit 106 may receive a message from the brake control unit indicating a sudden application of the brakes of the vehicle 100. In such an example, the ADAS unit 106 may instruct the V2X module 102 to transmit a public safety message informing other vehicles of the sudden deceleration.

[0034] Sensors 304 may be arranged in and around vehicle 100 in any suitable manner. Sensors 304 may measure characteristics around the exterior of vehicle 100. Additionally, some sensors 304 may be mounted within the cabin of vehicle 100 or in the body of vehicle 100 (such as the engine compartment, wheel wells, etc.) to measure characteristics inside vehicle 100. For example, such sensors 304 may include accelerometers, odometers, speedometers, pitch and yaw sensors, wheel speed sensors, microphones, tire pressure sensors, and biometric sensors, among others. In the illustrated example, sensors 304 include range detection sensors 312 (e.g., ultrasonic sensors, RADAR, LIDAR, infrared sensors, etc.), camera(s) 314, and a speed sensor 316.The example sensors 304 are communicatively coupled to the ADAS unit 106 to enable the ADAS unit 106 to detect and sense objects around the vehicle 100.

[0035] The vehicle data bus 306 communicatively couples the V2X module 102, the infotainment head unit 104, the ADAS unit 106, and the ECUs 302. In some examples, the vehicle data bus 306 includes one or more data buses. The vehicle data bus 306 may be implemented in accordance with a Controller Area Network (CAN) bus protocol as defined by International Standards Organization (ISO) 11898-1, a Media-Oriented Systems Transport (MOST) bus protocol, a CAN Flexible Data (CAN-FD) bus protocol (ISO 11898-7), a K-line bus protocol (ISO 9141 and ISO 14230-1), and / or an IEEE 802.3 Ethernet™ bus protocol (2002 and later), etc.

[0036] Fig. 4 is a flowchart of a method for determining the power level for the V2X module 106 provided by the electronic components 300 of Fig. 3 can be implemented. First, at block 402, the V2X module 106 receives a message to be broadcast. The message to be broadcast may, for example, originate from an application executing on the infotainment system 108, one of the ECUs 302, or the ADAS unit 106. At block 404, the V2X module 106 determines the type (e.g., public safety or private service) of the message received at block 402. At block 406, the V2X module 106 determines whether the message type is public safety. If the message type is public safety, the method continues to block 408. If the method is a private service, the method continues to block 412.

[0037] At block 408, the V2X module 106 determines the expected speed of the target vehicle(s). In some examples, the V2X module 106 receives the expected speed from the ADAS unit 106. Alternatively or additionally, in some examples, the V2X module 106 receives the expected speed from a navigation program executing in the infotainment system 108. At block 410, the V2X module 106 transmits the message received at block 402 at a power level based on the expected speed of the target vehicle(s). At block 412, the V2X module 106 transmits the message received at block 402 at a power level based on the requested range.

[0038] The flow chart from Fig. 4 is representative of machine-readable instructions comprising one or more programs that, when executed by a processor (such as processor 308 of Fig. 3) cause the vehicle 100 to select the exemplary V2X module 102 from the Fig. 1A, Fig. 1B, Fig. 1C, Fig. 1D and Fig. 3. Although the exemplary program(s) are in relation to the Fig. 4, many other methods may alternatively be used to implement the example V2X module 102. For example, the order of execution of the blocks may be changed and / or some of the described blocks may be altered, omitted, or combined.

[0039] In this application, the use of disjunction is intended to include conjunction. The use of definite or indefinite articles is not intended to indicate cardinality. In particular, a reference to "the" object or "an" object is also intended to refer to one of a possible plurality of such objects. Furthermore, the conjunction "or" can be used to indicate features that are present simultaneously, rather than mutually exclusive alternatives. In other words, the conjunction "or" should be understood to include "and / or." The terms "includes," "including," and "comprise" are inclusive and have the same scope as "comprises," "comprising," and "include," respectively.

[0040] The embodiments described above, and in particular any "preferred" embodiments, are possible examples of implementations and are presented merely for a clear understanding of the principles of the invention. Many variations and modifications may be made to the embodiment(s) described above without materially departing from the spirit and principles of the techniques described herein. All modifications are intended to be included within the scope of this disclosure and protected by the following claims.

Claims

[1] Vehicle (100), comprising: a driver assistance unit (106) for determining an expected speed of target vehicles in a vicinity of the vehicle (100); and a communication module (102) for: Determining a message type of a message received from a subsystem of the vehicle (100), the message type including public safety and private service; and Sending the message at a power level, wherein, when the message type is public safety, the power level is determined based on a range requirement associated with the message, and wherein the power level is increased when a difference between the expected speed of the target vehicles and an actual speed of the vehicle (100) meets a speed threshold. [2] The vehicle (100) of claim 1, wherein, when the message type is private service, the communication module (102) is to transmit the message at the power level determined based on a range request associated with the message. [3] Vehicle (100) according to claim 1, wherein the driver assistance unit (106) is to determine the expected speed without measuring the actual speed of the target vehicles. [4] Method comprising: Determining an expected speed of target vehicles of a vehicle (100) via a driver assistance unit (106); Determining a message type of a message received from a subsystem of the vehicle (100) with a processor, the message type including public safety and private service; and Sending the message at a power level with a communication module (102), wherein, when the message type is public safety, the power level is determined based on a range requirement associated with the message, and wherein the power level is increased when a difference between the expected speed of the target vehicles and an actual speed of the vehicle (100) meets a speed threshold. [5] The method of claim 4, wherein when the message type is private service, the message is transmitted at the power level determined based on a range requirement associated with the message. [6] A method according to claim 4, including determining the expected speed without measuring the actual speed of the target vehicles. [7] A tangible computer-readable medium comprising instructions that, when executed, cause a vehicle (100) to: Determining an expected speed of target vehicles in a vicinity of the vehicle (100) via a driver assistance unit (106); and Determining a type of message received from a subsystem of the vehicle (100), the type including public safety and private service, and Transmitting the message at a power level with a communication module (102), wherein the power level is based on the message type and the expected speed of the target vehicles, wherein when the message type is public safety, the power level is determined based on a range requirement associated with the message, and wherein the power level is increased when a difference between the expected speed of the target vehicle and an actual speed of the vehicle (100) meets a speed threshold. [8] The computer-readable medium of claim 7, wherein, when the message type is private service, the instructions cause the vehicle (100) to: Transmit the message at the power level determined based on a range requirement associated with the message.

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