AU2008230159B2 - Method and system for radio communication with vehicles - Google Patents

Description

WO 2008/118075 PCT/SE2008/050307 METHOD AND SYSTEM FOR RADIO COMMUNICATION WITH VEHICLES Technical Field The present invention relates to a method for radio communication with different kinds of vehicles, in particular vehicles of a public transport system. The invention also concerns a system for implementation of the method. 5 Background of the Invention In communication systems comprising a plurality of vehicles there is often a need for intercommunication between a central system and the vehicles of the system. One example is a public transport traffic routing and 10 information system, according to which buses deliver brief reports each time they leave a stop, for example. Another example is systems for managing commercial traffic, according to which lorries and taxis, for instance, deliver brief reports on their positions and/or reports on accomplished commissions. A typical feature of systems of this kind is that more data is transmitted from 15 the vehicles to the central system than the other way around. One reason for this is that it is complicated to send all these types of reports to all the vehicles concerned in order to obtain the desired functionality in the vehicles concerned. The messages from the vehicles can be comparatively brief. As system of this kind is disclosed in WO0176105, which is 20 incorporated herein by reference. In some situations it is important to be able to provide information about other vehicles of the system locally, for instance in an individual vehicle or at an individual stop. A few examples: - By synchronising connections, it is ensured that passengers of a 25 vehicle are given adequate time to transfer to another vehicle at a stop. If a vehicle is late, a consequence may be that another departing vehicle will also be delayed, since the departing vehicle must wait for the late vehicle to arrive. In this case, and in the case where a vehicle is early, there may be a frustrating wait for the 30 passengers of the waiting vehicle. If the driver of the vehicle that is expected to arrive first to the transfer stop is aware of the other 2 vehicle's adherence to its schedule, he can adapt his driving by driving more slowly to allow both buses to arrive at the transfer stop at about the same time. Traffic lights along the route may also be controlled to give or not give priority to the vehicles involved with a view to giving higher priority to one vehicle than 5 to the other to allow both vehicles to arrive at the transfer stop at the same time. - When the frequency of services is high, it is convenient for the vehicles to arrive at relatively regular intervals. If the driver of a vehicle knows how far ahead the vehicle in front is and how far behind the vehicle behind is he can adapt his driving to help even out the gap between him and the vehicle in front to and the gap between him and the vehicle behind, respectively. Vehicles that are too close to the vehicle in front can always slow down, thereby evening out the time gaps between the vehicles. - In a vehicle, it is desirable to provide passengers with information on the departures from (n) upcoming stops and information on how these departures is relate to the vehicle in which a certain passenger is travelling, to allow that passenger to choose the most appropriate transfer stop. This type of information can be provided if the vehicle has access to information about other vehicles. With a system according to WO0176105 the above situations can be managed 20 from the central. Special-purpose messages with high information content can be transmitted from the central system to vehicles, stops, traffic lights, etc. to enable improved dissemination of information. However, these special-purpose messages are likely to have high information content, thus requiring a very large bandwidth and complex system solutions. This reduces reliability, which may have a detrimental effect 25 on the credibility of the system. Summary According to an aspect of the present disclosure, there is provided a system for communication of information from a plurality of vehicles, comprising a vehicle unit, 30 which is mounted in each vehicle and arranged to communicate WO 2008/118075 PCT/SE2008/050307 3 with an information system provided in the vehicle and to transmit reports comprising information related to the current journey of the vehicle, one or more receiver nodes, which are arranged to receive reports transmitted from said vehicle unit on one or more public receiving frequencies, and a data 5 communication network, which connects together said receiver nodes to allow an information exchange between them. The system further comprises at least one transmitter node, which is in contact with said receiver nodes through the data communication network and is arranged to receive reports from the vehicle units through the receiver nodes and to transmit, from each 10 receiver unit, the most recently received reports on a transmitting frequency that is unique to the service area of the transmitting node, and a plurality of local receiver units, which are arranged to receive reports from said transmitter node(s), and a processing unit, which is connected to each receiver unit and arranged to process received reports with a view to 15 generating processed traffic information. This system enables a local stationary and/or mobile processing unit to gain access to unprocessed report data from a whole fleet of vehicles. In this way, the processing units themselves can generate processed traffic information without the need for a complex system structure for 20 communicating special-purpose messages with high information content. Reports are transmitted from the vehicles on one or more public frequencies. Thus, reports from different vehicles may collide with one another during transmission, but this is managed by using redundancy, so that a receiver node may perceive the report from one vehicle and another 25 receiver node may perceive the report from the other vehicle despite the fact that the two vehicles transmitted their reports simultaneously. Moreover, important reports can be transmitted several times, and superfluous identical copies can be eliminated in the receiver nodes. If necessary, multiple frequencies can be used for transmissions from the vehicles. In this case, 30 some vehicles will transmit on one frequency while other vehicles will transmit on a different frequency. Altogether, the vehicles may transmit, for example, on five different frequencies and the receiver nodes listen on all the transmission frequencies used by the vehicles.

WO 2008/118075 PCT/SE2008/050307 4 However, each transmitter node transmits on a frequency that is unique within the service range of the transmitter node. This means that transmissions from the transmitter node will not collide with other transmissions, and can be safely received in the receiver units. 5 A node may be a combined transmitter and receiver node, in which case reports received by the node are immediately made accessible for transmission. Alternatively, the transmitter nodes may obtain received reports through the data communication network from the other receiver nodes, either directly or through the data communication network. This enables a 10 transmitter node to repeat the majority of all reports transmitted from the vehicles. According to a preferred embodiment, the processing unit is located in a vehicle, and uses the vehicle unit to receive the reports. The processed information can then be used to provide the functions mentioned above. 15 The reports that are transmitted from the transmitter nodes may also be used in other ways. For instance, traffic signal systems may be provided with corresponding processing units and may listen to all the reports that are repeated by a radio node. The processed information may, thus, utilize the information to give priority to vehicles. This may, advantageously, be 20 combined with the invention defined in the simultaneously filed application entitled "Method for controlling traffic signals to give signal priority to a vehicle". The system may also be used to provide information units that are arranged, for example, at stops or waiting rooms with unprocessed traffic 25 information in the form of high-content reports from the vehicles. Processing units may process the information and provide waiting passengers with a number of services. Another example of system use is to allow personal mobile units, typically handheld computers, to listen to the appropriate transmitter node and 30 have them process the unprocessed information to generate information that the person can actually use, for instance if the person is on their way to the stop or is riding a public transport vehicle and is wondering about the chances of efficiently transferring to another vehicle some stops ahead.

WO 2008/118075 PCT/SE2008/050307 5 A further example of system use is to let, for example, an information unit at a stop, which has information on all vehicles, either repeat all the reports or the ones relating to the immediate surroundings or, alternatively, transmit processed information regarding estimated departures from the stop 5 concerned. The communication from the information unit at the stop concerned may, for example, be effected via Bluetooth to road users' mobile phones, which have been set to listen to the information unit of the stop concerned. 10 Brief Description of the Drawings The present invention will be described in more detail below with reference to the accompanying drawings, which for exemplifying purposes show a preferred embodiment of the invention. Fig. 1 is a general view of a system in accordance with one 15 embodiment of the invention. Fig. 2 is a schematic drawing of a device with which is fitted the vehicle of Fig. 1. Fig. 3 is a timing chart for the functioning of a vehicle unit according to Fig. 2. 20 Fig. 4 is a schematic block diagram of a transmitting and receiving node. Description of a Preferred Embodiment The invention will be described below with reference to a public 25 transport system. This is but one of several possible applications and should not be regarded as a limitation of the scope of the invention as defined in the appended claims. The system shown in Fig 1 comprises a central unit 1, which communicates with one or more nodes 2. The nodes 2 may be transmitters 30 2a or receivers 2b or both 40 (see Fig. 4). The nodes are suitably provided with interfaces 3, 4 to allow communication over a data communication network, for example TCP/IP interfaces which allow communication over the Internet 5. The nodes may further be connected, via the data communication WO 2008/118075 PCT/SE2008/050307 6 network 5, to a central unit 1. This is not essential to the invention, but may be advantageous for other reasons. The transmitting nodes 2a are suitably located in radio masts 7 or the like, and are arranged to transmit, at high power and on a common frequency 5 (or several alternating frequencies in different time slots), radio messages 4 over an area such as the area surrounding a radio mast, a town or a region (so called broadcasting). The transmission power is adapted to ensure that an emitted radio message can be received by vehicles 6 present within a predetermined area. 10 The receiving nodes 2b comprise, in addition to the interface 4, a radio aerial 12 designed to perceive messages that are transmitted from a vehicle, and a radio receiver 15. Each vehicle 6 is further provided with a device 16 for transmitting short radio reports 25 on a public frequency, without particularly taking into 15 consideration where they are located or whether there are other vehicles close by. The system may use one or more such public frequencies, depending on the number of vehicles covered by the system. The reports that are transmitted from each vehicle are intended to be received by a suitable number of receiver nodes 2b. The report may, for 20 example, concern the absolute position of the vehicle, the line and route that it is serving, its adherence to the timetable and any relevant information on internal conditions of the vehicle. The report may be triggered by an event, and transmitted when a door is being opened, the vehicle stops or starts, etc. It may also be triggered by time, such that a report is transmitted within a 25 certain period of time if no event occurs. The device 16 shown schematically in Fig. 2 comprises a first data communication unit (I/O gate) 17, which communicates with the internal information system 18 of the vehicle, for example a KomFram system and/or an ELSY system delivered by AB Thoreb. This unit 17 is connected to a radio 30 transceiver 19, which via an aerial 20 is capable of transmitting reports on a specific carrier frequency or, alternatively, of receiving messages on another frequency or, in smaller systems, of listening on the same frequency as that employed for transmissions from the vehicle. The unit 16 may, of course, WO 2008/118075 PCT/SE2008/050307 7 have a transmitter and a receiver instead of a transceiver. The radio transmitter could for example correspond to a radio modem of the Satel brand. In addition, a control unit 21 is connected to the radio transceiver 19 and to the 1/O unit 17 for the purpose of operating the transceiver 19 5 according to a predetermined schedule. A vehicle computer 22 is connected to the information system 17, and can be programmed with the aid of any suitable software. Each vehicle unit 16 may be adapted to alternatingly transmit and listen, for example as illustrated in Fig. 3. As soon as the vehicle 6 has transmitted its standard 10 report 31, it proceeds to listening on a specific frequency or, in smaller systems, on the same frequency as that employed for transmissions from the vehicle. During this listening period A, the vehicle of the example receives two reports 32 from two other vehicles. When it is time again to transmit a standard report (event- or time-controlled), the listening is interrupted. 15 Obviously, the vehicle will miss some reports as the radio set transmits its report, but with two radio sets in each vehicle one can transmit status messages while the other only listens to the status messages being repeated by the radio node concerned. To obtain information about adjacent vehicles, a vehicle may, during 20 the listening phase, listen on its own transmitting frequency, which is shared by other vehicles of the system. This allows the vehicle to perceive the standard reports as they are being transmitted from other vehicles. Reports from the vehicles (public transport vehicles, emergency vehicles, etc.) can be received by receiving radio nodes on a number of 25 frequencies. For instance, each node can listen on a plurality of different frequencies, for example five frequencies, or different nodes can listen on different frequencies. Moreover, each radio node can by way of the Internet obtain copies of all reports perceived by the other radio nodes. A radio node 2a, which conveniently is centrally located, or several 30 transmitting radio nodes 2a, transmits a copy of each report that in general is perceived by all radio nodes. The transmitting radio transmits at higher power on this particular frequency - the frequency on which all vehicles listen, as described above - and has an aerial that is mounted in an elevated position.

WO 2008/118075 PCT/SE2008/050307 8 It should be noted that there is a risk of reports from different vehicles "colliding", since more than one vehicle transmit on the same frequency. Since a system preferably comprises several receiver nodes, two reports that "collide" may become "unintelligible" in one of the receiver nodes, while 5 another receiver node perceives the report from one vehicle and another receiver node perceives the report from the other vehicle. Furthermore, vehicles may send important reports, for example reports indicating that a vehicle has left a stop, more than once. Other reports of great importance on a certain section may be sent more often, but always with updated 10 information. For this reason, each node may be arranged to eliminate identical reports. Alternatively, this selection may occur centrally, in the central unit 1. However, transmissions from the transmitter nodes 2a occur on a frequency (SA) that is unique to the service range of each node, and can 15 therefore be reliably received. Nodes whose coverage areas do not overlap may, of course, be allowed to use the same frequency. Since, in this case, there is no risk of collision, it is not necessary to repeat copies of messages; instead it is enough to transmit each report only once. If multiple transmitter nodes have overlapping coverage areas, they will 20 have different frequencies or, alternatively, they may share a frequency, in which case, for example, one transmitter node is allowed to transmit during the first third of each second, the second transmitter node during the second third of each second, and the third transmitter node during the last third of each second. By giving the transmitter nodes access to the very precise 25 "seconds pulse" emitted by GPS receivers, all the transmitter nodes are provided with a highly accurate time indication and are thus able to split the transmission time in this way for every second. Mobile receivers (for example the units 16 of the vehicles 6) should be arranged to select their listening frequency depending on the location of the vehicle. This can be easily 30 achieved by using a GPS navigation system that has been divided into a plurality of listening zones. In a city with up to 700 or so public transport vehicles, it may be enough for one of the radio nodes 2 to repeat all (status) reports. The number WO 2008/118075 PCT/SE2008/050307 9 of vehicles can be increased to 1,500 public transport vehicles if the radio node does not repeat all the status reports but only the more significant ones. Reports relating to vehicles located close to a traffic light should always be given the highest priority. If the radio node has to prioritise, one way would be 5 to not repeat every other report from vehicles serving remote residential areas. The numbers stated are based on the assumption that the vehicles on average transmit a standard message every fifth second. This is an average reporting frequency that cannot be obtained by conventional methods. If the system comprises a lot of vehicles, several different frequencies 10 may be used for transmissions from the vehicles, and a common frequency may be used for receptions in the vehicles. An example of a node that is capable of both receiving and transmitting messages is shown in Fig. 4. The node 40 has a plurality of radio receivers 15, which listen on the frequencies Li,..., LN. Moreover, the radio node receives, via the interface 4, 15 radio reports that the other radio nodes 2 of the system perceive from other vehicles, outside the service range of the node 40. In addition, the node 40 has a transmitter 41, which is intended to transmit on the frequency SA. Radio reports received in the radio node directly through the radio receivers 15 or indirectly through the data communication network 5 are retransmitted 20 in the form of a copy through the radio transmitter 41 of the radio node. To include emergency vehicles in the same radio system, an additional radio receiver 22 is added, for example, to all the radio nodes that listen on the frequency LE. Also the radio reports that the radio node perceives directly by listening on LE or indirectly from other radio nodes are transmitted through 25 the radio transmitter on the frequency SA. According to this embodiment of the invention, each vehicle receives the latest report from all vehicles and can use this information in any convenient manner. The vehicle computer 22 may, for instance, be programmed to collect all the reports from the vehicles serving the same 30 route as the vehicle itself. This allows the vehicle computer to indicate to the driver the position of the vehicle relative to all the other vehicles serving the route.

WO 2008/118075 PCT/SE2008/050307 10 The vehicle's own vehicle computer has data relating to all routes. If the route concerned has a connection that is synchronised with another route, this is included in the route data. For this reason, the vehicle computer also collects all the reports relating to the connection with which the vehicle is 5 synchronised, thereby allowing the desired information, as described above, to be shown to the driver, but realised in a much simpler manner. Since the vehicle computer 22 knows where all the other vehicles are located, the vehicle computer or a parallel computer can make forecasts for all the relevant transfer stops. The forecasts may then be displayed, for 10 example, on one or more screens 23. It is also conceivable to have a special inquiry terminal onboard the vehicles, through which passengers may obtain information on how to get to a certain street. Since the vehicle computer has the latest report from all the vehicles, these reports can be continuously transferred to the inquiry 15 computer, which is thus capable of providing all the necessary information to passengers, including departure forecasts for the relevant vehicles at each transfer stop along the route. It is a premise of a system according to the invention that the reports being transmitted are short, i.e. that the information is compressed. A suitable 20 way of transmitting large quantities of information using little data is to split the report into groups of status bits, each group having a certain meaning. The example below illustrates how much information can be transferred using only 13 bytes, i.e. 104 data bits, each data bit representing either "0" or "1". (3 characters). 25 Variable Bits Limit value 1 Vehicle no. 14 16384 2 Sequence no. of report 3 8 3 Type of route 2 4 4 Route no. 15 32768 5 Route variant 7 128 Starting time for route 6 variant 11 2 048 7 Current stop 18 262 144 8 Journey traffic status 4 16 9 Driving distance to 16 65 536 WO 2008/118075 PCT/SE2008/050307 11 current stop 10 Speed 7 128 11 Punctuality 11 2048 12 ALARM FIRE 1 2 13 ALARM driver 1 2 14 Stops at the next stop 1 2 15 New guiding route 1 2 It should be noted that 2 data bits (four values) are often enough for many variables. For instance, the four values may be "OK", "almost yellow warning light", "yellow warning light", "red warning light". The variable for the 5 temperature inside the bus may have the values "too low", "acceptably low", "acceptably high" and "too high". Other variables can be coded in the same way, which results in very short reports. According to one embodiment, the reports may be extended with one byte (8 data bits). This allows, for example, three data bits to be used for the 10 vehicle occupancy rate (eight occupancy levels). One data bit could be used to indicate that although a vehicle is late, it does not request priority treatment, since the vehicle operating the connection with which the route is synchronised is even more late (0= requests priority treatment and 1= requests no priority treatment). Thus, traffic lights that under 15 normal circumstances would give priority to this vehicle may instead give priority to other vehicles. Before arriving at the transfer stop with synchronised connections the passengers on a late bus have the possibility of communicating (for example by means the "stop button") that someone intends to transfer to the waiting 20 bus. One bit can then be used to indicate whether the vehicle has passengers who wish to transfer to a waiting bus. If this bit is set to 0, the bus waiting at the transfer stop will know that there are no transferring passengers and, thus, is free to depart according to schedule, instead of waiting for the late bus. 25 In the above example, the extra byte in the (status) report is used as follows: Bit 1 Bit 1-3 indicate occupancy rate Bit 2 and 010 thus means that the bus WO 2008/118075 PCT/SE2008/050307 12 Bit 3 has an occupancy rate of 3/8. Bit 4 The value 1 means that traffic lights do not give priority treatment even if the bus is late Bit 5 The value 0 means that there will be no transfer 5 Bit 6 Extra, used for additional functionality Bit 7 Extra, used for additional functionality Bit 8 Extra, used for additional functionality By extending the report in this way, information about conditions can 10 be disseminated, thereby allowing the three examples mentioned by way of introduction to be solved in a very elegant manner. Three extra bits remain, which can be used to inform all units, i.e. vehicles, traffic lights and stops about any other conditions which may contribute to increasing functionality even more without adding to the complexity of the system solution. 15 In addition to status reports, the vehicles may transmit so-called ELSY reports. Obviously, these reports are not repeated, since they are only used for traffic routing and in the maintenance application. It is also conceivable to increase the number of reporting vehicles without reducing the reporting frequency by letting several radio nodes repeat 20 status reports on different frequencies. The vehicles can choose on which frequency (to which radio node) to listen based on the current position of the vehicle. In this connection, each transmitting node may be arranged to repeat all the reports originating from vehicles within a certain distance from the node, whereas, for example, only every second or every third report 25 originating from vehicles further away is repeated. When a node decides which status reports are to be repeated it may give priority to status reports triggered by a bus leaving a stop. Of course, it is possible to re-use the frequencies used to repeat status messages according to common methods. 30 Advantageously, also signboards at stops may be equipped with receivers to receive reports from the transmitting nodes. By providing them with computers that are powerful enough to make forecasts, the signboards would be able to make their own departure forecasts based on the status reports repeated by the radio node.

WO 2008/118075 PCT/SE2008/050307 13 When a road-user uses the signboard to determine how to travel from the current stop to any optional stop (possibly located by means of the street name), the signboard computer can display a travel plan including departure times according to the timetable, but also departure time forecasts should 5 departure times deviate from the timetable. The results of the above search could be transferred via Bluetooth to the road-user's mobile phone or handheld computer. Route number, destination and all the stops prior to the passenger leaving the vehicle or changing to another vehicle. This would allow the passenger to monitor the 10 information displayed on the onboard signboard without having to worry about possibly going the wrong way. Using Bluetooth, the departure forecasts for the stop could also be broadcast, thereby allowing road-users to receive the data in their mobile phone during their walk to the stop. 15 The details of the design of the radio and data communication systems is best left to the expert, who should have no problems in designing a system operating in accordance with the description above. The system preferably is realised as a combination of hardware and software, the expert being the best judge of which solutions are the most adequate. This is true also as regards 20 the choice of frequencies, time intervals, information contents, and so on.

Claims (15)

1. A system for communication of information from a plurality of vehicles, comprising: 5 a vehicle unit, which is mounted in each vehicle and arranged to communicate with an information system provided in the vehicle and to transmit reports comprising information related to the current journey of the vehicle; one or more receiver nodes, which are arranged to receive reports transmitted from said vehicle unit on one or more public receiving frequencies; 10 a data communication network, which connects said receiver nodes with each other to allow an information exchange between them; at least one transmitter node, which is in contact with said receiver nodes through said data communication network and is arranged to receive reports from said vehicle units and to transmit the most recently received report on a transmitting frequency is that is unique to the service area of the transmitting node; a plurality of local receiver units, which are arranged to receive reports from said transmitter nodes; and a processing unit, which is connected to each receiver unit and arranged to process received reports with a view to generating processed traffic information. 20

2. A system according to claim 1, wherein at least one of said receiver units is mobile.

3. A system according to claim 2, wherein said mobile receiver unit is 25 incorporated in said vehicle unit, and its processing unit is arranged in the vehicle.

4. A system according to claim 2, wherein a mobile unit for personal use, such as a mobile phone or handheld computer, receives reports directly from a transmitter node. 30

5. A system according to claim 1, wherein at least one of said receiver units is stationary.

6. A system according to claim 5, wherein said stationary receiver unit and the associated processing unit are incorporated in an information unit at a stop or other public 35 meeting point. 15

7. A system according to claim 6, wherein said information unit is further arranged to retransmit received reports via short-range radio to a mobile receiver for personal use. 5

8. A system according to claim 7, wherein the short-range radio is Bluetooth.

9. A system according to claim 7, wherein the mobile receiver for personal use is either a mobile phone or a handheld computer.

10 10. A system according to claim 5, wherein said stationary receiver unit and the associated processing unit are incorporated in a signal priority unit to facilitate priority treatment of vehicles used in public transport.

11. A system according to claim 1, further comprising: is at least one node, which is both a transmitter node and a receiver node, comprising a radio transmitter which communicates with one or more radio receivers.

12. A system according to any one of the preceding claims, wherein variables included in said reports are expressed in terms of one or more binary digits. 20

13. A system according to claim 3, wherein the report contains information indicating whether the vehicle has passengers who wish to transfer to a waiting bus.

14. A system according to any one of the preceding claims, wherein said receiver 25 nodes are arranged to remove, where necessary, any identical copies of received reports from the vehicle units.

15. A system for communication of information from a plurality of vehicles, said system being substantially as herein disclosed with reference to any one or more of Figs. 30 1-4 of the accompanying drawings. DATED this Nineteenth Day of January, 2011 AB Tryggit Patent Attorneys for the Applicant 35 SPRUSON & FERGUSON