METHOD FOR OPERATING A COMMUNICATION SYSTEM AND OBJECTS FOR SUCH A SYSTEM

Abstract: It is disclosed a method for operating a communication system for communication between a central station (10) and one or a plurality or remote objects (20 to 25), as well as such an object, wherein at least one object is operated in a battery saving mode in which it is switched alternatively between a wake period for conducting communication between the object and the central station and a sleep period in which communication is inactive, and that each object is designated a predetermined first time (t0) and a time interval (Dt), wherein each object initiates the wake periods at times t0+n (Dt) with n=0, 1, 2, ... and wherein the time interval is longer than the wake period.

Description: Method for operating a communication system and objects for such a system The invention relates to a method for operating a communication system for communication between a central station like a service center and one or a plurality of remote objects like vehicles, trucks, airplanes, plants, houses or other such facilities which comprise a battery-based electric power supply. The invention further relates to a computer program for conducting this method, as well as to said objects for application with said method. Remote objects are usually equipped with an independent power supply which comprises a battery and an electric generator for supplying on board electric and electronic devices and other electrical equipment with electric energy. The generator is driven by a motor when the object is operated. However, in periods when the object is out of operation, many devices nevertheless have to be active or at least in a sleep mode. For such periods, the battery is provided for supplying these devices with the necessary electric energy. From time to time the battery has to be recharged by means of the electric generator according to the amount of energy consumption. A common problem with such a battery power supply resides in the risk that a discharge of the battery may impair the operation, readiness and / or safety of the object, if the object as well as the electric generator are not operated for a longer time. For avoiding this risk, it is known to monitor the battery output-power and to give an alarm if the battery is going to be discharged so that appropriate actions for re-charging the battery (e.g. starting the motor so that the electric generator can re-charge the battery) can be taken. However, in case of remote objects with no personnel or staff or in case of a vehicle which is parked in a remote area for a longer time, it is often difficult or expensive to handle such a situation. This problem is especially serious if a communication system on board of the object is concerned which is used e.g. for monitoring, controlling or locking / unlocking the object and its functions via a central station and which has to be in an active mode permanently for communicating with the central station. US-PS 5,251,325 and US-PS 5,392,457 disclose a battery saving method and apparatus for selectively supplying power to each receiver function of a battery powered communication receiver at predetermined time intervalls for enabling the reception of coded message signals with each receiver function being powered only as long as is required for each receiver function to stabilize prior to the reception of said coded message signals. EP 0 319 219 discloses a paging apparatus with a battery saving function wherein a power supply control means is provided for periodically switching on a receiving means for a predetermined period in response to the detecting of synchronization signals and in the absence of a predetermined signal sequence, and for switching off the same when the predetermined signal sequence is detected and immediately after reception of a paging signal for the apparatus . However, in case of a communication system comprising a central station like a ser ice center and a plurality of remote objects, a random switching of such objects between on- and off -status or between a wake and a sleep mode or period can cause problems with respect to availability of the objects as well as with respect to the network load, if at one time too many objects are in a sleep period or in a wake period simultaneously. It is a primary object of the invention to provide a method for operating a communication system for communication between a central station like a service center and a plurality of remote objects in a battery saving mode in such a way that availability of the objects is improved and the load of the communication network is decreased. Further, it is an object of the invention to solve the above problem of limited operability of electric and electronic devices at remote objects which are equipped with a battery-based power supply and which are not operated for a longer time. Further, it is an object of the invention to provide a method for operating a communication system which allows an extension of time duration which is available for communication between a central station like a service center and one or a plurality of said objects, before a related battery supplying the object has to be re-charged. Further, it is an object of the invention to provide an object (apparatus, means) for application with the above method. These and other objects are solved by a method according to claim 1 as well as by an object (apparatus, means) according to claim 7. By designating each object a predetermined first time to and a predetermined time interval Dt, for initiating the wake periods at times t 0 + n (Dt) , the wake periods can equally be distributed among the objects so that there is no overload of the communication network. Further, such designated first time to and time interval Dt can be stored for each object at the central station, so that it is known at the central station, when an object is active for conducting communication. The subclaims are directed to advantageous embodiments of the solutions according to claims 1 and 7 , respectively. Further details, features and advantages become apparent from the following description of preferred embodiments of the invention with reference to the drawings, in which shows: Fig. 1 a schematic diagram of the environment in which an inventive method is conducted and of the related objects; Fig. 2 a schematic block diagram of the major electronic components of an object including a circuit for implementing the method. A communication system and its environment for application of an inventive method for operating the same is shown in Figure 1. It comprises a central station (customer service center) 10 with an operator 11. At least one vehicle 20, at least one boat or ship 24, as well as one or more stationary equipments 25 like a remote facility, plant or other objects communicate with the service center 10 via a cellular communication network 30 like GSM (European standard) or AMPS (US standard) and / or a satellite communication network 31, both for exchanging of information, data and voice communication, each in both directions. Even software programs can be transmitted if necessary. Emergency assistance vehicles 22 and a roadside assistance vehicle 23 communicate with the service center 10 in a similar manner or in any other way and are activated by the service center in case of need by one of the remote objects 20, 24, 25. A position of each object can be detected by means of a global positioning system (GPS) 40. Figure 2 shows a schematic block diagram of the major electric and electronic components and devices inside an object which components are a part of the communication system. An on-board network 1 is provided for controlling, monitoring and connecting a plurality of sensors 2, actuators 3, locking / unlocking means 4 and other devices 5 in a known manner. This network 1 has an interface to a transmitter / receiver means 6, which is preferably a mobile communication unit (GSM or AMPS) or a satellite communication unit, so that various operating conditions and functions of the object like motor and oil temperature, can be transmitted to the service center for evaluation and check. Further, e.g. software programs for operating the object by means of the actuators can be transmitted from the service center to the object and loaded. A reliable communication between the service center and the objects is demanded. According to the prior art, the transmitter / receiver means 6 as well as the onboard network 1 have to be permanently active even in periods in which the object is not operated, because in a sleep mode, the service center would not be able to communicate with the object. The required power is supplied by a battery 8 which is charged by a motor- driven generator 9 when the object is operated. However, if the object is not operated, the battery is steadily discharged and after a time of between one week and one month, depending on the age and capacity of the battery, the temperature and other conditions, the battery is even emptied. Consequently, the reliability of the communication system cannot be ensured. According to the invention, a control unit 7 with a memory 71, a timing circuit 72 and a programmable microprocessor means 73 is provided at each object for operating such a communication system and the related objects in a battery saving mode for saving battery power. The basic idea resides in that each object is switched alternately between a wake period for conducting communication between the object and the central station and a sleep period in which communication is inactive. During the wake periods the above mentioned communication is conducted and the transmitter / receiver means 6, the on-board network 1 and the onboard electronic components 2 to 6 are active as required or requested by the service center. During the sleep periods the transmitter / receiver means 6, the on-board network 1 and the on-board electronic components 2 to 6 are in a sleep status and only the control unit 7 is active, so that as much battery power is saved as possible. However, if an operator returns to the object like a driver returns to his car and gets in, the battery saving mode is terminated anyway and the operation is started as usual. Preferably, each object is designated a predetermined (and different) first time t 0 and a time interval Dt, and each object initiates the wake periods at times t 0 + n (Dt) with n = 0, 1, 2,... The time interval Dt is longer than the estimated longest duration of a wake period. The duration of the time interval Dt is e.g. constantly 15 minutes for all objects, or, alternatively, the time interval Dt is set to a different duration for each object. The first time t 0 and the time interval Dt are preferably stored in the memory 71 and are read out by the microprocessor 73 for enabling the wake periods. The duration of the wake periods depends on how much actions and communications have to be conducted and transmitted. The control unit 7 is provided for terminating the wake periods and initiating the sleep periods after conduction of such communication requested by the central station as well as any other actions . The only component which needs to be active permanently is the control unit 7 for monitoring time by means of the timing circuit 72 and for initiating the wake periods and building up communication with the service center. This is preferably controlled by the microprocessor means 73. By such a timely limited wake period, not only battery power at each object, but also network load is saved. For a further improvement in this regard, and to avoid . an overload of the service center, the wake periods are ■ distributed among the objects as regular as possible by choosing the first time t 0 for each object, so that at one time there are not too many objects active simultaneously. This is achieved for example by associating the beginning (time to) of the wake period, relative to a full hour, to an unique identification of the object. This identification can be a motor number or a vehicle number or any other individually designated and unique number, from which the beginning (time t 0 ) in terms of minutes or seconds after a full hour is derived and stored in the memory 71. So every object starts with its wake periods at a different time. Alternatively, the memory 71 is provided for storing the unique identification number of the object, for deriving the first time to therefrom by means of the control unit 7. Preferably, the association between each object and the said beginning of its wake period is stored in a memory at the service station as well, so that it is known at the service station, when an object is active for conducting communication. If for example the designated and predetermined first time to for an object is 3min (and the time interval Dt is 15 minutes for all objects as mentioned above) , so this object starts its wake periods at each full hour plus 3min, and again each 15, 30 and 45 minutes after that time, i.e. at Oh 3min, Oh 18min, Oh 33 min, Oh 48 min, and so on, beginning with the full hour in which the battery saving mode has been selected. In case of very many objects, the first time to can be extended to seconds (e.g. 4 min 28 sec) . The inventive method is preferably programmed as a computer program and implemented in the microprocessor means 73 for switching alternately between the wake periods and the sleep periods.

Claims: Claims 1. Method for operating a communication system for communication between a central station and a plurality of remote objects, characterized in that for operating said objects in a battery saving mode in which an object is switched alternately between a wake period for conducting communication between the object and the central station and a sleep period in which communication is inactive, each said object is designated a predetermined first time (to) and a predetermined time interval (Dt) , for initiating the wake periods at times to + n (Dt) with n = 0, 1, 2,... 2. Method according to claim 1, characterized in that each object is designated a different first time (t 0 ) and / or a different time interval (Dt) . 3. Method according to claim 1 or 2 , characterized in that the predetermined first time (t 0 ) is a number of minutes and / or seconds which are counted from the beginning of a full hour. 4. Method according to one of claims 1 to 3 , characterized in that the first time (t 0 ) is derived from a unique identification number of the object which is stored at the related object and at the central station in a memory. 5. Method according to one of claims 1 to 4, characterized in that during the sleep period all electric and / or electronic devices (1 to 6) are set inactive and that these devices are activated during the wake period. 6. Method according to one of claims 1 to 5, characterized in that a wake period is terminated and a sleep period is initiated by an object after conduction of a communication. 7. Object for application in a method according to one of claims 1 to 6, characterized in that a control unit (7) is provided for operating power consuming electric and / or electronic devices in a battery saving mode, in which said devices are alternately switched between a wake period for conducting communication between the object and the central station and a sleep period in which communication is inactive and for initiating the wake periods at times t 0 + n (Dt) with n = 0, 1, 2,.. wherein to is a designated and predetermined first time and Dt is a predetermined time interval. 8. Object according to claim 7, characterized in that the control unit (7) is provided for terminating the wake periods and initiating the sleep periods after conduction of any communication requested by a central station. 9. Object according to one of claims 7 or 8, characterized in that the control unit (7) comprises a memory (71) for storing the predetermined first time (to) and the time interval (Dt) , and that a timing circuit (72) is provided for monitoring time and causing the control unit (7) to initiate the wake periods . 10. Object according to claim 9, characterized in that the memory (71) is alternatively provided for storing a unique identification number of the object for deriving the first time (t 0 ) therefrom by means of the control unit (7) . 11. Object according to one of claims 7 to 9, characterized in that the control unit (7) comprises a programmable microprocessor means (73) for conducting the method according to one of claims 1 to 6. 12. Computer program comprising computer program code means adapted to perform a method according to one of claims 1 to 6 when said program is run on the programmable microprocessor means (73) . 13. Computer program product stored on a computer usable medium, comprising computer program code means to perform a method according to one of claims 1 to 6 when loaded into the internal memory of the programmable microprocessor means (73) .

Inventors: GUDMUNDSSON STEFAN, GUDMUNDSSON, STEFAN
Applicants: GUDMUNDSSON STEFAN, VOLVO TEKNISK UTVECKLING AB, GUDMUNDSSON, STEFAN
Application year: 2001
Main classification: H04Q7
IPC codes: H04Q9, H04W52