Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0868—Hybrid systems, i.e. switching and combining
  • H04B7/0871—Hybrid systems, i.e. switching and combining using different reception schemes, at least one of them being a diversity reception scheme
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0868—Hybrid systems, i.e. switching and combining
  • H04B7/0874—Hybrid systems, i.e. switching and combining using subgroups of receive antennas
  • H04B7/0877—Hybrid systems, i.e. switching and combining using subgroups of receive antennas switching off a diversity branch, e.g. to save power

Definitions

• the invention relates to a method for operating a communication system, preferably a motor vehicle in the wireless vehicle-to-environment communication
• C2X communication which can take place as vehicle-to-infrastructure communication (C2I) or vehicle-to-vehicle communication (C2C).
• C2I vehicle-to-infrastructure communication
• C2C vehicle-to-vehicle communication
• different information is transmitted according to their content as signals on different radio channels.
• wireless communication in the specification IEEE 802.11p according to a standard for the communication of intelligent transport systems (ITS) is used in Europe and the USA.
• the communication takes place in Europe in a frequency range of 5,850 to 5,925 GHz, in which a control channel (Control Channel CCH) and at least two service channels (Service Channel SCH) are realized.
• the control channel is used for broadcast communication, in which information is to be transmitted to several or all subscribers in the communication network. This channel is reserved for short, low-latency, safety-critical information and communication management.
• the service channels are used to transmit additional, non-safety-critical data, for example for application-specific information, road geometry, etc.
• the communication system used according to the invention for this communication has a plurality of, at least two, reception paths each having at least one independent antenna and an associated independent receiver for receiving the transmitted signals.
• a receive path is usually reserved for the control channel.
• Other receive paths are used to receive (and send) on one or possibly also several service channels.
• a reception path may preferably transmit or receive at exactly a certain time on a radio channel. The fixed allocation of a receiving channel to the control channel ensures that the important control channel is always ready to communicate.
• the invention relates to a correspondingly established communication system.
• data is exchanged between the vehicle and objects in its environment.
• the objects in the vicinity of the vehicle may be other on-vehicle units (OBUs), fixed roadside units (RSUs) or pedestrians equipped with appropriate transmitters and / or receivers act.
• the exchanged data fulfill various functions, for example a protection, warning and / or information function, and can accordingly also be used by the driver assistance system.
• the data is exchanged depending on their function on different radio channels.
• the explicit nature and nature of the information as well as the requirements of sender and receiver are defined by an industry standard and are not the subject of this invention.
• a common problem in mobile communication is caused by the constant change in position of at least a majority of the communication partners. This problem is especially pronounced in mobile devices that move at a fast speed (relative to each other), such as the OBUs mounted in motor vehicles.
• the movement constantly changes the environment of the mobile device.
• the propagation paths of the transmitted information are subject to constant change. Due to the nature of the environment, reflections can lead to multipath propagation of the transmitted information.
• This is pronounced, for example, in urban traffic, where the electromagnetic radio waves are reflected on house fronts. In certain spatial constellations, interference can occur. In this case, the electromagnetic wave with the information impressed on it is partially or completely extinguished by destructive interference.
• US 2010/0173600 A1 discloses a receiver with diversity and a method for switching the receiver. Each receive path has a stand-alone antenna and a separate receive decoder, wherein it can be selected between different receive modes: In a single-channel reception, a specific channel is fixedly selected by a controller. In the diversity reception mode, the signals of both reception paths are combined.
• the device decides between the two first-mentioned receive modes based on selected receive characteristics. This allows the user to decide for themselves whether and when they want as reliable a quality of reception as possible. By temporarily deactivating one of the two reception paths, the energy consumption can be reduced.
• US 2009/0097599 A1 introduces a method for operating a Digital Video Broadcasting Handheld (DVB-H) receiver, which manages with a low power consumption.
• the receiver independently decides when a diversity reception is advantageous or necessary, depending on predetermined performance criteria.
• the performance criteria are measures that reflect the transmission quality of the information, such as the signal-to-noise ratio, the bit error rate or the packet error rate.
• US 6,678,508 Bl describes a mobile communication device having two separate receivers. Receives the communication device via a receiver with sufficient quality, the other receiver is placed in a sleep mode. If the reception quality of the first receiver is no longer sufficient, the signal is received via the second receiver. If the reception quality of the signals is not sufficient for any of the receivers, the signals received simultaneously by the two receivers are used to construct a single one.
• the object of the present invention is to achieve a better reception at least for one radio channel in a communication system in the C2X communication with low additional costs and low additional energy consumption.
• Radio channel if required, ie if pre-selected switching criteria are met, be equipped with diversity. This is preferably done when the reception of this one radio channel is particularly important. The increased number of receiving paths for this important radio channel is charged to another radio channel, whose reception is subordinate to this time, however. Conversely, if there is no such need, the receiving device can receive different information by parallel use of the two receive paths on two different radio channels.
• This solution also meets requirements imposed on a communication system under the ITS standard and allows signals to be received with diversity without substantially increasing the cost and power consumption of an ITS-standard communication system, as antenna diversity in the field of communication Demand is achieved in that an otherwise otherwise used reception path for increasing the reception probability is used temporarily for a radio channel. Existing resources that exist in an ITS communication system are thus used effectively.
• control channel is equipped with antenna diversity as needed in accordance with the invention.
• the resulting temporary suspension of reception on the / a service channel brings no significant disadvantages, since no security-relevant information is transmitted on the service channel and they can also be received delayed in time.
• the invention is not limited to the case that exactly two receive paths are provided in the communication system and are provided secondarily for one radio channel and secondly for two different radio channels, i. H. for antenna diversity. It can also be provided according to the invention more than two receiving channels, all or part of which is used for the inventive antenna diversity / is.
• the proposed method can be used in so-called software defined radios (SDR) as a reception path or reception paths.
• SDR software defined radios
• Such a receive path in the sense of a receiving device ideally consists only of an antenna, an analog-digital converter and a computing unit, for example a programmable integrated chip.
• a reception path has a very high flexibility, since functional adjustments can be achieved by new software or the specification of parameters without having to make any adjustments to the hardware.
• the hardware of the receiving channel is individually suitable for all eligible radio channels, each with a Software Defined Radio (SDR) is used for a receive path, with multiple Software Defined Radios (SDR) in a hardware or a chip rockas can be stably and in be summarized a computing unit.
• SDR Software Defined Radio
• the switching between the operating modes takes place on the basis of one (or more) predetermined switching criterion, which may itself be a parameter-dependent variable or a variable determined by a functional dependence on a variable.
• a comparison variable for the switching criterion is formed and / or derived from the received signals.
• the switching of the operating mode can currently be adapted to the transmission quality and / or the content of the transmission, without the need for an additional controller (requiring extensive and resource-consuming and energy-consuming control).
• the system can independently improve the quality or reliability of the received information, in particular on the security-related control channel.
• the control channel is not equipped with diversity and therefore the communication system can be operated efficiently because a parallel communication (sending or receiving) on different channels is possible, for example, to serve less security-related applications quickly .
• provision can be made for determining the comparison variable for the switching criterion on the basis of the received quality of the received signals. For this purpose, for example, a signal analysis can be carried out and in particular the reception field strength of the signals can be measured or determined on a radio channel. This comparison variable can then be compared with a threshold value forming the switching criterion. As a measure of the received field strength, the Received Signal Strength Indication (RSSI) can be determined, which is an indicator of the
• Receive field strength which is specified in the IEEE 802.11 standards and specified as a byte value. If, for example, this value undershoots or exceeds a predetermined threshold value over a period of several milliseconds, then the operating modes are changed, with poor reception quality activating the antenna diversity on the radio channel of interest and a threshold value of a reliable reception signal exceeding the antenna diversity is switched back in a radio channel to a parallel communication in different radio channels. This applies according to the invention according to all switching criteria.
• Signals are determined.
• the switching of the operating mode then takes place on the basis of a comparison between the number (quantity) of the received signals and the number (quantity) of the expected signals.
• the number of received messages is determined over a definable period of time and compared with the expected number.
• a communication system operated according to the method according to the invention can also respond to periodically occurring interference of the messages.
• the invention can take advantage of the fact that in the context of C2X communication according to the ITS standard so-called announcement messages are sent out to the environment by those involved in the C2X communication. These announcement messages are thus sent out like a beacon and can be constantly received by the other participants, for example, in networks with constantly changing participants in the C2X communication to get an overview of the communication partners and their ground state.
• This communication can take place, for example, via the control channel, in which case additional information can be exchanged via a service channel.
• these announcement messages are also referred to as CAM (Cooperative Awareness Message) for short.
• CAM messages are sent out at regular intervals of 100 to 500 ms (2-10 Hz) according to the intended standard and include, among other things, the type of vehicle, the position, the speed and the direction of the vehicle participating in the C2X communication. In principle, however, it can be all information that has a benefit for the environment and thus are security-relevant. The invention is therefore not necessarily limited to the reception of CAM messages.
• Disturbed reception of CAM messages can thus be detected quickly according to the invention by monitoring the quantity of the messages, in particular with respect to a period of time.
• CAM messages transmitted at regular time intervals of 100 to 500 ms (2 to 10 Hz)
• the CAM messages and enables the setting of a corresponding transmission rate (quantity per period of time) as a comparison variable in order to quickly detect a reception failure.
• it may additionally or alternatively be provided to analyze the content of signals received in particular on a radio channel and to determine the comparison variable for the switching criterion based thereon.
• the transmitted information is analyzed per se.
• the system can by default receive the antenna diversity control channel and switch to parallel two-channel reception as soon as a message or service message to be received on the service channel is announced.
• the system can receive by default on two or more radio channels, each with an associated receive path and change the operating mode due to the transmitted information, for example, to receive the control channel via both receive paths.
• a further possibility for bringing about the switching according to the invention between the two operating modes “antenna diversity” and “parallel reception spans in different radio channels” lies in the comparison variable for the switching criterion as a function of the recognition of a situation in which the vehicle is located, or to determine a condition of the vehicle. For this it is possible to determine environmental information and thereby discover a difficult reception situation or a dangerous situation.
• vehicle conditions such as a strong deceleration, the intervention of driver assistance systems, a high speed or the like can be detected.
• such information already exists as messages or vehicle parameters in the communication network between different vehicle applications anyway, so that access to this information is particularly easy according to the invention. In situations or vehicle states in which anyway only one receiving channel is needed, this is equipped with diversity. This is conceivable if the car has been parked and is still to be paid, or a garage service is to be carried out via this channel.
• the environment information can, if they are not already present, for example, via environmental sensors (camera, radar, lidar, GPS) of the vehicle and / or map information of a positioning system can be determined.
• a difficult reception situation can exist, inter alia, because of the topology, ie in winding country roads, urban canyons or in mountainous regions, which can be removed both maps and / or derivable by analysis of camera images.
• a diversity reception in dangerous situations is advantageous, which are often recognizable by the road and / or traffic conditions and increasingly at traffic-technically excellent points, such as intersections, traffic lights, exits or traffic jams occur.
• the weather conditions can be used to detect a dangerous situation or difficult reception situation.
• either directly sensors of the vehicle such as temperature or rain sensor can be used.
• it is also possible to make use of external weather forecasts which can be called up, for example, via the service channel.
• the vehicle status for example as a function of functions activated in the vehicle, which relate in particular to vehicle safety and are therefore safety-relevant and / or for which a continuous reception of specific information is required.
• the recognition of certain activated vehicle functions is used as a comparison variable for the switching criterion.
• a list of corresponding functions can be kept in the vehicle.
• a function that is safety-relevant for example, by whose SI levels are identified, which is specified in ISO 26262 and recorded as a benchmark.
• the present invention is not limited to the respective sole application of the above-described switching criteria.
• decision criteria as many decision criteria as possible are combined with each other in order to have the best possible basis for decision-making.
• a selected radio channel is assigned to the receive path with the best reception quality.
• the control channel is always the receiving path with the best
• reception quality This thus ensures that, for example, the CAM messages which are received via the control channel are received with the best possible quality, while the service channel remains ready to receive in parallel.
• This sub-form of diversity reception thus ensures that the control channel has the best possible reception quality, while at the same time signals can be received in parallel on two radio channels.
• This can be technically achieved, for example, by changing the assignment of the antennas to the receiving paths, for example by means of a software command. This is easily possible, especially with multipath software defined radios.
• At least two antennas are used in transmitting signals. It is advantageous if the signals are transmitted offset in time to each other, since it prevents the signals from influencing each other. In this situation, it must be ensured that the addressee can receive the signals over a plurality of propagation paths and subsequently reconstruct a single signal from them.
• Em communication system on which the above-described method can be performed is also the subject of the invention.
• the communication system formed by a suitable unit for example a vehicle unit, has at least two reception paths each having at least one independent antenna and a separate receiver for receiving signals in a radio channel, and further comprises a computing unit arranged to perform the above-described Process or parts thereof.
• the antennas have a different reception characteristic in the at least two different reception paths. This further improves the reception quality compared to the normal diversity.
• This embodiment is particularly advantageous for topological regions in which different antennas have a qualitatively better reception.
• one of the antennas may be particularly sensitive in the inner-city area, while the other antenna is particularly sensitive to open areas, in mountainous or forested regions.
• Fig. La, b schematically traffic situations in which the inventive method for operating a communication system can be used
• 2 is a schematic flowchart for the method according to the invention for operating a communication system.
• Fig. La) and lb) two different traffic situations are shown, in each of which two with a not shown, according to the invention communication system for participation in the C2X communication equipped vehicles 1, 2 meet on different roads 3, 4, on a Intersection 5 meet each other.
• the vehicle 2 additionally has a radar sensor as environmental sensor.
• the vehicle 2 receives information from its surroundings both by the radar sensor and by the CAM messages emitted by the vehicle 1 during the C2X communication.
• the CAM messages of the vehicle 1 include the position, speed and direction of the vehicle 1 and are indicated in the coordinates of a defined coordinate system of a global positioning system that both vehicles 1, 2 share.
• the vehicle 2 can integrate this information into its assistance system and determine that the areas 6 and 7 classified as safety-relevant of the two vehicles 1, 2 overlap.
• the classification of a detected traffic situation as a potential dangerous situation, which requires a reliable reception of further CAM messages therefore forms a comparison variable according to the invention, which is compared with the switching criterion and in this case also the switching criterion Fulfills.
• the vehicle 2 switches over to a reception with antenna diversity for the control channel on which the CAM messages are transmitted and received.
• the control channel is received via two reception paths independent in their function and the probability for the secure reception of the CAM messages or other important information on the control channel is significantly increased.
• the service channel otherwise received via the receive path now connected to the control channel can not be received during the antenna diversity-at least via this receive path.
• the assistance system of the vehicle which is formed in particular by an arithmetic unit from the environment sensor of its radar sensor and the CAM messages of the vehicle 1, detects that the cruising vehicle 1 is not in the areas 6 classified as safety-relevant , 7 is located. Therefore, the switching criterion is not met and the reception with antenna diversity (diversity reception) is not activated.
• the receive paths each receive information about different radio channels.
• a stationary transmitter 8 a so-called road-side unit (RSU)
• RSU road-side unit
• This stationary transmitter also broadcasts CAM messages and, in addition, so-called MAP messages (messages describing topology in the environment) and informs the incoming vehicles 1, 2 to move to an intersection 5, which is considered to be particularly critical and / or in their vicinity, for example by a structural shield, the reception of signals from other vehicles 1, 2 in the
• FIG. 2 schematically shows a method sequence for operating a communication system 9 according to the invention.
• the receiver can, for example, also carry out an analog-to-digital conversion of the signals and forward them as digital data via an interface 10 to a computing unit 11 of the communication system 9.
• the arithmetic unit 11 is set up to derive one or more comparison variables Vi, V2 from the received signals and / or other information from the recognition of a situation in which the vehicle is located or a state of the vehicle.
• Vi stands for one or more
• comparison variables Vi, V2 are subsequently compared in the calculation unit to a comparison U (V1, V2) with switching criteria Ul and U2, which can each be adapted to the comparison quantity Vi, V2 which has just been formed. It is optional It is also possible to subject only a part of the comparison quantities Vi or V2, for example the comparison variables formed from signals of a specific reception path PI or P2, to the comparison U (V1, V2).
• the arithmetic unit decides which receive path PI, P2 is assigned to which of the possible radio channels (CCH, SCH), where CCH corresponds to the control channel of the C2X communication and SCH to the service channel of the C2X communication.
• the arithmetic unit 11 In the case of a reception with antenna diversity for the control channel CCH, the arithmetic unit 11 thus assigns both the reception path PI and the reception path P2 to the control channel CCH. Otherwise, it assigns a reception path PI, P2 to one radio channel CCH, SCH and the other reception path P2, PI to the other radio channel SCH, CCH, so that each reception path PI, P2 can communicate simultaneously on another radio channel CCH, SCH. Also in the operation of the two reception paths PI, P2 on different radio channels CCH, SCH, d. H. an operation without antenna diversity, it may be provided that the arithmetic unit to the safety-relevant control channel CCH the receiving path PI, P2 are assigned with the best Empfangsgu Rund Q.
• the reception quality Q1 and Q2 of the two reception paths PI and P2 are formed as comparison variables Vi and V2.
• the maximum of the reception qualities Q1 and Q2 is then formed.
• the reception path PI or P2 with the maximum reception quality Q1 or Q2 is then assigned the control channel CCH.
• the other reception path P2 or PI is then assigned the service channel SCH. In this way, the reception quality on the control channel CCH is also optimized independently of antenna diversity.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)
• Radio Transmission System (AREA)

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• 2011
  • 2011-10-25 DE DE102011085185A patent/DE102011085185B3/de active Active
• 2012
  • 2012-10-22 WO PCT/EP2012/070851 patent/WO2013060639A1/de active Application Filing
  • 2012-10-22 CN CN201280052374.7A patent/CN103891169B/zh active Active
  • 2012-10-22 US US14/353,997 patent/US9264112B2/en active Active
  • 2012-10-22 EP EP12778709.1A patent/EP2771982A1/de not_active Withdrawn

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