Device and method for position information

The present invention relates to a device for position information, comprising a satellite-based position measuring device with an energy-consuming measuring mode in which it measures the current position of the device and makes it available at an output, and an energy-saving sleep mode in which no position measurement takes place, one connected to said output cellular network-supported communication device for sending the position via a cellular cellular network, wherein the communication device provides the local received field strength and the local cell identifier of the cellular network at an interface

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

Combined satellite navigation and mobile radio devices are used, for example, to track freight or in fleet management. A major problem is the high power consumption of the known devices because, especially in the case of mobile freight such as containers, refrigerated goods, etc., an on-board power supply is not always available.

Alternative supplies via solar cells and accumulators have therefore already been proposed. In the logistics industry in particular, however, there are often long downtimes in the dark, for example in a warehouse, on an unlit siding, etc., which would require extremely large batteries.

From EP 1 132 713 a position information device of the type mentioned in the introduction is known, in which the satellite-supported position measuring device is a GPS receiver that can be put into an energy-saving sleep mode (“standby”). EP 1 132 713 proposes that the GPS receiver only be put into measuring mode when, for example a button on the communication device (a mobile phone) is pressed, a certain number is dialed, a call is received in the mobile phone, the mobile phone is outside of its reception range or a timer expires. The first variants require active action on the part of the user to initiate the position determination, while the variant with the timer results in periodic power consumption of the GPS receiver.

From US 2004/0209625 A1 a further device of the type mentioned is known in which the GPS receiver is switched on periodically for a short time and then reverts to a power-saving idle mode in which no position measurement takes place. The time of the next "waking up" of the GPS receiver is set by the GPS receiver itself, ie the position measurement of the GPS receiver controls the power-saving mode of the GPS receiver. This has the disadvantage that changes in position cannot be recognized during the sleep phase of the GPS receiver, which greatly impairs the reliability of the device.

The aim 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 conditions of use without impairing the reliability of the position information. This goal is achieved in a first aspect of the invention with a device of the type mentioned, which is characterized by a control device connected to the output of the position measuring device and the interface of the communication device, which, when the received field strength changes or when there is a change in the received field strength, which exceeds a threshold value Cell identifier switches the position measuring device to measuring mode and, if the position remains the same for a predetermined period of time, the position measuring device

AT 502 811 B1 switches to idle mode

The invention is based on the knowledge that the “rough” position information, which can be obtained from a change in the reception field strength or the cell identifier of the cellular mobile network, can be used to switch on the satellite-based position measuring device for the “fine” position determination. If the determined position does not change for a while, the position measuring device is set back into the power-saving sleep mode. As a result, a decisive reduction in electricity consumption or energy requirement can be achieved on average over time.

A 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, which means that commercially available components can be used and wide applicability is ensured.

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

Power consumption.

It is particularly favorable if the threshold value mentioned is in turn a function of the local received field strength, as a result of which largely the same position measurement accuracy can be achieved in the entire mobile radio network.

In a second aspect, the invention provides a method for position information by means of a satellite-based position measuring device with an energy-consuming measuring mode for measuring the position and an energy-saving idle mode without position measurement, as well as a cellular network-based communication device for sending the position via a cellular cellular network, which is characterized according to the invention by the following steps in any order:

Determination of the local reception field strength or the local cell identifier of the mobile radio network with the aid of the communication device and, if the reception field strength changes at least by a predetermined threshold value or the cell identifier changes, switching the position measuring device to the measuring mode;

Determining the current position of the device with the aid of the position measuring device and, if the position remains the same over a predetermined period of time, switching the position measuring device to the idle mode.

Further features and advantages of the invention emerge from the following invention of a preferred embodiment in conjunction with the accompanying drawing, FIG. 1 of which shows the device of the invention in a schematic block diagram.

1 shows a device 1 with a GPS receiver 2, which receives navigation signals 3 from one or more satellites 4, determines its position pos therefrom and provides them at an output 5. A GSM mobile radio module 6 is connected to the output 5 and sends the determined position pos via a cellular mobile radio network 7 to a control center 8 for further evaluation, for example the control center of a fleet management or freight tracking system.

Instead 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 receiver, etc. In the same way, instead of a

GSM cellular module also any other cellular network-supported known in the art

AT 502 811 B1

Communication device are used, for example a mobile phone or modern according to the TDM, GPRS, UMTS standard, etc.

The 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 makes it available at output 5, and an energy-saving idle mode ("standby"), in which it e.g. saves the determined position or is simply switched off completely. The GPS receiver 2 can be switched between its measuring mode and its idle mode via a control input 9, shown schematically.

Commercially available GSM receivers 2 have, for example, a current consumption of approx. 200 mA in the measuring mode (operating mode), and a current consumption of approx. 20 mA in the idle mode or standby.

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

In the case of a GSM network, the local received field strength E is defined, for example, as the power level in the ETSI specification GSM 05.05, and the cell identifier cell (“cell ID”) in the ETSI specification GSM 03.03.

The device 1 further comprises one connected to the output 5 of the GPS receiver 2 and the

Interface 10 of the GSM mobile radio module 6 connected control device 11, which from the position pos, the received field strength E and the cell identifier cell generates a control signal pwr for the control input 9 of the GPS receiver 2, in the following way:

1. GPS receiver is in sleep mode:

If the received field strength E changes by at least a predetermined threshold value S, ie | ΔΕ | > S, then the control device 11 switches the GPS receiver 2 to the measuring mode.

2. GPS receiver is in measuring mode:

If the position pos determined by the GPS receiver 2 remains the same over a predetermined period of time T (or the same position is determined several times in succession when the position pos is determined periodically), the control device 11 switches the GPS receiver 2 back to idle mode .

The threshold value S is determined with a view to minimizing the average energy requirement of the entire device 1 in the selected application environment; is preferably the

Threshold value S 2 to 10 dBm, particularly preferably 3 to 5 dBm.

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

The local received field strength E depends on the distance between the device 1 and the nearest base station of the mobile radio network 7. For example, at a distance of 250 m, the received field strength E is -20 dBm, and a change ΔΕ of +/- 5 dBm corresponds to a change in distance of approx. 150 m. At a greater distance from the nearest base station, the same change in distance corresponds to a smaller change ΔΕ by, for example, +/- 3 dBm, so that the threshold value S must be reduced accordingly if the position changes5

AT 502 811 B1 tion should be determined with the same accuracy.

It 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).

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

The invention is not restricted to the illustrated embodiments, but rather encompasses all variants and modifications that fall within the scope of the attached claims.