Device and method for position information

p0001The present invention relates to a position information apparatus comprising A satellite-based position measuring device with an energy-consuming measuring mode in which it provides the current position of the device at an output and an energy-saving rest mode, A mobile radio-controlled communication device connected to said output for transmitting the position via a cellular mobile radio network, Wherein the communication device provides at an interface the local reception field strength and the local cell identification of the mobile radio network.

p0002The invention also relates to a method for positional information with the aid of such position measuring and communication devices.

p0003Combined satellite navigation and mobile radio devices are used, for example, for tracking (tracking) freight goods or fleet management. A great problem is the high current consumption of the known devices, because an electrical system is not always available, especially for mobile freight goods such as containers, refrigerated goods containers, etc.

p0004Alternative supplies have already been proposed for solar cells and accumulators. In the logistics sector, however, long standing times often arise in the dark, for example in a warehouse, on an unlit storage shed, etc., which would require extremely large accumulators.

p0005From the <patcit id="pcit0001" dnum="EP1132713A"><text>EP 1 132 713</text></patcit> There is known a position information device of the type mentioned in the opening paragraph, in which the satellite-based position measuring device is a GPS receiver which can be placed in an energy-saving "standby" mode. The<patcit id="pcit0002" dnum="EP1132713A"><text>EP 1 132 713</text></patcit> Proposes that the GPS receiver be placed in the measuring mode only when, for example, a key is pressed on the communication device (a mobile telephone), a specific number is dialed, a call is received in the mobile telephone, the mobile telephone is outside its reception area Or a timer is running. The first variants require an active intervention by the user to initiate the position determination, whereas the variant with the timer results in a periodic current consumption of the GPS receiver.

p0006From the <patcit id="pcit0003" dnum="US20020102990A1"><text>US 2002/0102990 A1</text></patcit> There is known an apparatus and a method in which the determining determination rate of the GPS receiver is determined by the speed of the communication means. This requires a speed determination in the mobile radio network, for example by means of the double-effect analysis of base station frequencies of the mobile radio network.

p0007From the <patcit id="pcit0004" dnum="WO0013034A1"><text>WO 00/13034 A1</text></patcit> It is known to omit the GPS position determination of a satellite telephone when the reception field strength for communication satellite falls below a predetermined threshold value.

p0008The object of the invention is to further develop a device and a method for position information in such a way that they have a particularly low average energy requirement under practical operating conditions. This object is achieved in a first aspect of the invention by a device of the type mentioned which is characterized by a control device which is connected to the output of the position measuring device and the interface of the communication device, Which switches the position measuring device into the measuring mode in the case of a reception field strength change, the magnitude of which exceeds a threshold value, or changes the cell detection, and, if the position remains constant for a predetermined period of time, switches the position measuring device into the idle mode.

p0009The invention is based on the discovery that the "coarse" position information resulting from a change in the reception of the invention is based on the recognition that the "coarse" position information which can be obtained from a change in the reception field strength or the cell recognition of the cellular mobile radio network , Can be used to turn on the satellite-based position measuring device for the "fine" position determination. If the determined position does not change for a period of time, the position measuring device is returned to the energy-saving rest mode. As a result, a decisive reduction in electricity consumption or energy consumption can be achieved over time.

p0010A preferred embodiment of the invention is characterized in that the position measuring device is a GPS receiver and the communication device is a GSM mobile radio module, whereby commercially available components can be used and wide applicability is ensured.

p0011According to a further preferred embodiment of the invention, said threshold value is 2 to 10 dBm, particularly preferably 3 to 5 dBm. Furthermore, the period of time mentioned is preferably 3 to 15 minutes, more preferably about 10 minutes. These values ​​represent a practical compromise between sufficient accuracy and minimum average power consumption.

p0012It is particularly favorable if the said threshold value is, for its part, a function of the local reception field strength, as a result of which a substantially equal positional measuring accuracy can be achieved in the entire mobile radio network.

p0013In a second aspect, the invention provides a method for positional information by means of a satellite-based position measuring device with an energy-absorbing measuring mode and its energy-saving rest mode as well as a mobile radio-networked communication device for transmitting the position via a cellular mobile radio network which is distinguished according to the invention by the following steps in any sequence: <ul><li>Determining the local reception field strength or the local cell identification of the mobile radio network with the aid of the communication device and, if the magnitude of the reception field strength change exceeds a predetermined threshold value or the cell identifier changes, switching the position measuring device into the measuring mode;</li><li>Determining the current position of the device with the aid of the position measuring device and, if the position remains constant for a predetermined period of time, switching the position measuring device into the idle mode.</li></ul>

p0014Further features and advantages of the invention result from the following invention of a preferred embodiment in conjunction with the enclosed drawing, <figref idrefs="f0001">FIG</figref> The apparatus of the invention is shown in a schematic block diagram.

p0015In <figref idrefs="f0001">FIG</figref> A device 1 with a GPS receiver 2 is shown which receives navigation signals 3 from one or more satellites 4, determines its position p 2 from this and provides it at an output 5. Connected to the output 5 is a GSM mobile radio module 6, which detects the determined position<i>pos</i> Via a cellular mobile radio network 7 to a central station 8 for further evaluation, for example, the center of a fleet management or freight tracking system.

p0016Instead of the GPS receiver 2, any other satellite-based position measuring device known in the art can also be used, for example an A-GPS, D-GPS, GLONASS, GALILEO, EGNOS, WAAS receivers, etc. In the same way, GSM mobile radio module, any other mobile radio-communication device known in the art may also be used, for example a mobile telephone or modem according to the TDM, GPRS, UMTS standard, etc.

p0017The GPS receiver 2 has two different operating modes, namely an energy consuming measuring mode (operating mode), in which it determines the current position pos and provides it at the output 5, and an energy-saving standby mode in which it has, for example, the most recently determined Position or simply is completely switched off. Via a schematically illustrated control input 9, the GPS receiver 2 can be switched between its measuring and its idle mode.

p0018For example, commercially available GPS receivers 2 have a current consumption of approx. 200 mA in the measuring mode (operating mode), and a current consumption of approx. 20 mA in the quiescent mode or standby mode.

p0019The GSM mobile radio module 6 also has various operating modes, including an energy-consuming transmitting mode, in which it transmits the ascertained position pos to the control center 8, and an energy-saving standby or reception mode. The GSM mobile radio module 6 has an interface 10 at which it provides in at least the local reception field strength E and the cell identifier cell of the cellular mobile radio network 7 in each mode of operation.

p0020In the case of a GMS network, the local reception field strength E is defined, for example, as a power level in the ETSI specification GSM 05.05, and the cell identifier cell ( "cell ID") in the ETSI specification GSM 03.03.

p0021The device 1 further comprises a control device 11, which is connected to the output 5 of the GPS receiver 2 and the interface 10 of the GSM mobile radio module 6 and which generates a control signal pwr for the control input 9 of the GPS from the position pos, the reception field strength E and the cell identification cell Receiver 2, in the following manner:<ol><li>1. GPS receiver is in idle mode:<ul><li>If the reception field strength E changes at least by a predetermined threshold value S, ie | ΔE | > S, then the control device 11 switches the GPS receiver 2 into the measuring mode.</li></ul></li><li>2. GPS receiver is in measurement mode:<ul><li>If the position determined by the GPS receiver 2 remains the same for a predetermined period of time T (or the same position is determined successively in the case of a periodic determination of the position p 2), then the control device 11 switches the GPS receiver 2 back into the idle mode .</li></ul></li></ol>

p0022The threshold value S is determined with a view to minimizing the average energy requirement of the entire device 1 in the selected application environment; The threshold value S is preferably 2 to 10 dBm, more preferably 3 to 5 dBm.

p0023The measure for the reception field strength E used here is the power level (received power level) according to the ETSI specification GSM 05.05 in dBm.

p0024The local reception field strength E depends on the distance of the device 1 from the nearest base station of the mobile radio network 7. For example, at a distance of 250 m, the reception field strength is E -20 dBm, and a change ΔE of +/- 5 dBm corresponds to a distance change of approximately 150 m. At a greater distance from the nearest base station, the same change in distance corresponds to a smaller change ΔE by, for example, +/- 3 dBm, so that the threshold value S is to be correspondingly reduced if the positional change is to be determined with the same accuracy.

p0025It is therefore also possible to set the threshold value S as a function of the local reception field strength E in order to always achieve the same positioning accuracy, ie S = f (E).

p0026The period T is also determined with a view to minimizing the average energy requirement; The period of time T is preferably 3 to 15 minutes, more preferably about 10 minutes.

p0027The invention is not limited to the illustrated embodiments but includes all variants and modifications which fall within the scope of the appended claims.