JP2001337149A - Gps receiver with adaptive cold start timeout function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a GPS receiver for recognizing the cause of incapable positioning in a power source input, and setting an optimum cold start time-out time TCS for reducing total TTFF. SOLUTION: A storage means stores whether positioning is allowed/prohibited in turning off the power source, and when the power source is turned on the next time, according to the positioning enabled/disabled conditions stored in the storage means, the cold start time-out time is set longer in the case of the positioning impossible condition, while the cold start time-out time is set shorter, in the case of the positioning possible condition. After the power source is turned on, when the positioning impossible condition is continued and the set cold start time-out time is attained, positioning operation is started in a cold start mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a GPS (Global P
The present invention relates to a GPS receiver that receives a radio wave from a satellite and performs positioning calculation.

[0002]

2. Description of the Related Art A GPS satellite transmits a carrier signal having a frequency of 1,575.42 MHz called L1 and a distance measurement signal called a C / A code. The GPS receiver receives the GPS signal, obtains satellite position information (ephemeris) and other navigation data relating to the GPS satellite, and measures the distance from the GPS satellite to the GPS receiver itself using the C / A code signal. (The distance measured in this way is called a “pseudo distance”), and a positioning calculation for calculating the position of the GPS receiver itself by a calculation based on a geometric principle based on the navigation data and the pseudo distance. I do. In this case, if four or more GPS satellites are used, a three-dimensional (latitude, longitude, altitude) positioning result can be obtained. For this reason, the GPS receiver simultaneously outputs four or more GPs.
It is configured to be able to receive the S signal.

A total of 24 GPS satellites are in six different orbits at an altitude of 2,000 km. Therefore, the GP that can be seen from the GPS receiver over time
The configuration of the S satellite changes constantly. Also, when a GPS receiver is used on a mobile object, the GPS
The arrangement of GPS satellites as seen from the receiver also changes. Therefore, it is necessary for the GPS receiver to always search for and capture a GPS satellite that can be used for positioning, and once captured, keep tracking the GPS satellite. The GPS receiver uses a carrier of a signal transmitted from a GPS satellite and C /
A GPS satellite is captured by searching for the frequency and phase of the A-code to establish synchronization with the GPS signal, and if synchronization is successfully obtained, the signal is synchronously tracked so as to follow frequency fluctuations and the like. And continue tracking the GPS satellites.

When the power is turned on, the GPS receiver sets the G
Synchronous acquisition and synchronization tracking for the PS signal are started, and when four or more satellites can be acquired, a positioning operation is performed and a positioning result is output. The time from when the power is turned on until the first positioning result is output is called TTFF (Time To First Fix). This TTFF is one of the important parameters representing the performance of the GPS receiver. Therefore, in designing a GPS receiver, shortening the TTFF is an important issue.
For example, if the general position information of a GPS satellite is known,
Since the satellites orbiting above the GPS receiver can be narrowed down based on the position of the PS receiver and the current time, it is possible to shorten the TTFF by preferentially acquiring the satellite.

[0005] The GPS receiver stores a satellite identification number of a GPS satellite that can be used for positioning during the positioning operation, the latest orbit information obtained from the GPS satellite, the position of the GPS receiver at the time of positioning, and the like as a backup memory. The TTFF is greatly reduced by determining the positioning target GPS satellite and starting the acquisition by using the information when the power is turned on next time. This operation start mode is called warm start or hot start, and the TT at this time is
FF is about several seconds to several tens of seconds. On the other hand, an operation start mode in which acquisition is attempted in the order of satellite identification numbers without using any information stored in the backup memory is called a cold start mode, and the TTFF in this case is several minutes. Because the TTFF is long in the cold start mode, the GPS receiver is set to start operating in the cold start mode only immediately after shipment from the factory or when necessary due to some trouble.

[0006] The GPS receiver usually starts operating in a warm start or hot start mode in order to shorten the TTFF. However, an error occurs in the information stored in the backup memory for some reason, and when the GPS receiver searches for a signal of a satellite different from the visible satellite, the TTFF becomes longer, and in the worst case, the positioning becomes longer. The result is that no result is obtained. In order to solve such a problem, the GPS receiver is provided with a cold start time-out time (T _CS ).
_{When CS} or more is continued, the operation is started in the cold start mode from that point.

[0007]

[Problems that the Invention is to Solve In a conventional GPS receiver, T _CS is not set to only one value, if the duration of the non-positioning state after power has reached the value of the T _CS is The operation always started again in the cold start mode. By the way, in a situation where a positioning result cannot be obtained even after a predetermined time has elapsed after the power is turned on, as described above, other than when there is an error in the information stored in the backup memory,
When the GPS receiver is applied to a car navigation system, the engine may be started in an environment where the GPS receiver cannot receive radio waves, such as an underground parking lot. Here, when _TCS is used as one value, the following problem occurs.

[0008] The graph of FIG. 3 schematically shows the overall TTFF until the GPS receiver obtains the positioning result for each situation. In FIG. 3, TTFF representing the cold start mode is described as TTFF _c, and TTFF representing the warm start or the hot start is represented as TTFF _h.
It is described. Case A in FIG. 3 is a case where information stored in the backup memory has an error, and T _CS
Since the start of operation in the course after a cold start mode of the time, the overall TTFF of this case, the _TTFF = T CS + TTFFc. As is apparent from the above equation, in case A, T
_The shorter the value of _CS is set, the more comprehensive TT
FF is reduced.

In cases B and C, when the power is turned on,
This is a case where a vehicle equipped with a transceiver is in an underground parking lot. This
Where T_D1And T_D2Can be positioned from underground parking lot
It represents the time it takes to move to a functional position. Case
B, ie, T when the vehicle is set to a GPS receiver_CS
If you can move to a position where positioning can be
TTFF is: TTFF = T_D1+ TTFF_h  This case is not a particular problem. Meanwhile, the case
C, ie, T when the vehicle is set to a GPS receiver_CS
If you move to a position that can
TTFF is: TTFF = T_D2+ TTFF_c  It is. In this case, as shown in case D, time T_D2
Start operation in hot start mode after elapse
TTFF = TTFF = T_D2+ TTFF_h  And shorten the overall TTFF compared to Case C.
And it is possible. As is clear from the above, case B,
Car equipped with GPS receiver when power is turned on, like C
For cases where both cars are in underground parking, T_CSThe long
The more time you set, the shorter the overall TTFF
Will increase the likelihood.

However, in the conventional GPS receiver,
T used as a cold start timeout time
The value of _CS is the only one, if you set the value of T _CS in a short time, the overall TTFF but is shortened, vehicle underground car park of the case there is an error in the information that is stored in the backup memory In the case of departure from, the possibility that the overall TTFF becomes longer increases. On the other hand, setting the value of T _CS long time, the vehicle is increased overall possibility TTFF is shortened in case of departure from the underground parking, but there is an error in the information stored in the backup memory case The overall TTFF for increases.

The present invention has been made in view of the above circumstances. That is, the present invention aims to provide a GPS receiver that can recognize the cause of the positioning disabled state to set the optimum cold start timeout T _CS at power up, to shorten the overall TTFF And

[0012]

SUMMARY OF THE INVENTION Therefore, a GPS receiver according to claim 1 of the present invention has a GPS receiver which has been acquired during operation.
A GPS receiver that stores information about PS satellites and can use the stored information at the next power-on to capture the GPS satellites and perform positioning, and the positioning result is not calculated after power-on. If the continuation is performed, the cold start mode (all GPS without using the information stored about the GPS captured during the previous operation before the power is turned on) is used.
The cold start timeout time T _CS until restarts the positioning operation in the sequential operation start mode attempt acquisition) to the satellite, and sets depending on the condition of reception of the GPS signals at the previous power-off. Longer can be set to T _CS depending on the condition of reception of the GPS signal at the time of power-off, when power is shut down, the T _CS if a vehicle equipped with a GPS receiver is in a situation which can not receive the GPS signal, such as underground parking Is set to, and when the power is turned off, the vehicle
If that matches the conditions capable of receiving S signals can be shorter setting the T _CS.

A GPS receiver according to a second aspect of the present invention stores information on a GPS satellite captured during operation, and uses the stored information at the next power-on to capture a GPS satellite and perform positioning. A GPS receiver capable of performing the positioning, when the power is turned off, a positioning state in which a positioning result is obtained or a non-positioning state in which a positioning result is not obtained; a time-out time setting means for setting a different timeout period T _CS according to different positioning / non positioning obtained from the positioning state storage means, after the power is turned on, it operates in cold start mode if the non positioning state continues more than T _CS And a cold start time-out execution means for starting the operation. When the vehicle equipped with the GPS receiver stops the engine in an underground parking lot or the like, the non-positioning state is stored by the positioning state storage means. when turned on, time-out time setting unit that the vehicle is to set the optimum value as T _CS accordingly recognizes that the power is turned on by the positioning impossible place because it has been parked in an underground parking lot or the like It is possible. On the other hand, when the vehicle equipped with the GPS receiver stops the engine in a situation where positioning is possible, the positioning state storage means stores that the vehicle is in the positioning state.
When the power of the S receiver is turned on, time-out time setting unit is capable of recognizing that the power is turned on by positioning a location to set the optimum value as T _CS accordingly.

[0014] In this case, as in the case of engine start in the underground parking, a T _CS of state stored in the positioning state storage means is set when a non-positioning state, the stored state is the positioning state By setting the value larger than the _TCS set in the case, the case A in FIG.
The overall TTFF can be shortened for the case where the information stored regarding the GPS satellites captured during the operation has an error, and the GPS reception can be performed at the time of power-on, such as the cases B and C in FIG. It is possible to shorten the overall TTFF even in the case where the vehicle equipped with the machine is in an underground parking lot.

Further, the GPS receiver according to claim 4 is
Stores information about GPS satellites captured during operation and uses the stored information at the next power-on to GP
A GPS receiver capable of capturing an S satellite and performing positioning, a counting means for counting the elapsed time when a non-positioning state is established during operation, and a counting means for counting the count value when the power is turned off. and count storing means for storing a value, at power up, the time-out time setting means for setting a time-out time T _CS based on the count value obtained from the regimen numeric storage unit, after the power is turned on, the non-positioning state T _CS A cold start time-out execution means for starting the operation in the cold start mode when the operation is continued as described above is provided. When the vehicle equipped with the GPS receiver stops the engine in an underground parking lot or the like, the elapsed time in the non-positioning state is stored by the count value storage means. Is turned on, the timeout time setting means recognizes, based on the elapsed time, that the vehicle has been parked in an underground parking lot or the like and has been turned on in a location where positioning is impossible and T
It is possible to set an optimal value as _CS . On the other hand, when the vehicle equipped with the GPS receiver stops the engine in a situation where positioning is possible, the count value stored by the count value storage means becomes 0 or a value close to 0,
When more power GPS receiver is turned on at the next engine start-up, time-out time setting unit, based on the elapsed time, recognizes that the power is turned on by positioning a location, best as T _CS It is possible to set a value.

That is, the timeout time setting means includes:
By comparing the count value obtained from the count value storage means with a predetermined threshold value K, it is recognized whether the vehicle is in a place where positioning is possible or in a place where positioning is impossible when the GPS receiver is turned on. it can. Moreover, the time-out time setting unit, the time-out time T _CS of counts acquired from the count value storage means is set if it is more than the threshold value K, the timeout period is set when the count value is less than the threshold value K T _By setting it to a value greater than _CS, it is possible to reduce the overall TTFF for case A of FIG. 3, i.e., where there is an error in the information stored about the GPS satellites acquired during operation. In addition, it is possible to shorten the overall TTFF even in a case where a vehicle equipped with a GPS receiver is in an underground parking lot when the power is turned on, such as cases B and C in FIG. 5).

Further, the count value storage means remembers the elapsed time that was in the non-positioning state by the time of power down, the waiting time T _CS to set the time-out time setting unit,
It is possible to set a value proportional to the elapsed time. Elapsed time non positioning state until it at engine stop of the vehicle, given the example of the case C of FIG. 3, the time T _D2 to be moved from the position where the vehicle was parked to the location that enables positioning Therefore, by setting T _CS to a value proportional to the length of the elapsed time, for example, T _D2 + α, the total TTFF is always set to (T _D2 + TTFF _h ) (claim 6).

[0018]

FIG. 1 is a block diagram showing functions of a GPS receiver according to the present invention. Hereinafter, the details of the GPS receiver 10 according to the present invention will be described with reference to FIG.
The GPS signal having a carrier frequency of 1,575.42 MHz input from the GPS antenna 8 to the GPS receiver 10 is down-converted into an intermediate frequency signal by being multiplied by the local oscillation frequency signal in the frequency converter 2. The signal of the intermediate frequency is converted into a digital signal by the A / D converter 3 and input to the signal demodulator 4.

The signal demodulation unit 4 multiplies the signal input from the A / D conversion unit 3 by a signal whose frequency and phase are made equal to the carrier frequency under the control of the reception control unit 5 to obtain an A / D signal. The carrier component is removed from the signal input from the / D conversion unit 3. Further, the signal demodulation unit 4 multiplies the signal from which the carrier component has been removed by a C / A code signal unique to the GPS satellite generated under the control of the reception control unit 5, and The output signal is a baseband signal. The calculation unit 6 acquires navigation data including satellite orbit information (ephemeris) and the like from the baseband signal. The arithmetic unit 6 measures the arrival time of the C / A code signal from the satellite from the navigation data and the current time obtained from the clock provided in the arithmetic unit 6 to calculate the pseudo distance. Further, the calculation unit 6 performs a GPS calculation by a geometric calculation based on the pseudo distance and the navigation data.
A positioning calculation for calculating the position of the receiver is executed. Although only one signal demodulation unit 4 is shown in FIG. 1, by providing a plurality of signal demodulation units 4 in parallel, signals from a plurality of GPS satellites can be received at the same time. In addition, the latest identification number, satellite orbit information (ephemeris, almanac), and positioning result of the GPS satellite used for positioning while the power is turned on are always written in the nonvolatile memory 7.

The arithmetic unit 6 reads out these information from the nonvolatile memory 7 when the power is turned on, sets the GPS satellites that were in the positionable state at the time of the previous operation before the power was turned on as positioning targets, and the signal processing unit 4 and the receiving unit. In the signal processing by the control unit 5, control is performed so that signals from these positioning target satellites are received, and positioning calculation is performed. The operation start mode in which the GPS satellite is captured using the information backed up in the nonvolatile memory 7 is the hot start mode. On the other hand, the information backed up in the nonvolatile memory 7 is not used at all, and for example, the GP
The operation start mode for trying to capture the S satellite is the cold start mode.

The counter 11 counts based on a clock signal of a predetermined frequency when the GPS signal is not received and the positioning result obtained by the arithmetic unit 6 cannot be obtained. When the positioning result is obtained, the counter 11 counts the count value. clear. That is, the count value of the counter 11 always indicates the continuation time in the non-positioning state. When the power of the GPS receiver 10 is turned off, the count value R / W unit 12 writes the count value of the counter 11 into the nonvolatile memory 7.

When the power is turned on, the count value R / W unit 12
Reads the count value backed up in the nonvolatile memory 7. _{Further, T CS} setting unit 13, when power is turned on to set the cold start time-out time _{T CS} according to the count value read out from the count value R / W section 12. The comparator 14 counts up the count value of the counter 11 when the non-measurement state continues with the power-on and the _TCS set by the _TCS setting unit 13.
Compare the value of _CS . Count value of the counter 11 becomes the above value of T _CS, i.e., after the power is turned on when the non-positioning state continues more than T _{C S,} the comparator 14
The operation unit 6 starts operation in the cold start mode in accordance with the instruction from.

Further, referring to the flowchart of FIG.
The cold start timeout _TCS setting performed when the power is turned on in the GPS receiver 10 will be described.
While the GPS receiver 10 is operating, the duration of the non-positioning state is counted up by the counter 11 (S10).
1). When the power is turned off, the count value R / W unit 12 writes the count value in the nonvolatile memory 7 (S1).
02). Next, when the power is turned on, the _TCS setting unit 13
Compares the count value read out via the count value R / W section 12, and a predetermined threshold value K, when the count value is the threshold value K is smaller than (S104: _YES), the value of _{T CS} short Set to the value T _SHORT . When the cold start timeout time is set to T _SHORT , if the positioning result cannot be obtained even after the elapse of the T _{S HORT} time after the power is turned on, the GPS receiver 10 starts the positioning operation in the cold start mode (S107). ). On the other hand, when the count value is equal to or larger than the threshold value K (S104: NO),
The value of T _CS is set to the longer value T _{LONG G} (S10
6). Cold start timeout time T _LONG
When the positioning result is not obtained even after the lapse of T _LONG time after the power is turned on, the GPS receiver 10 starts the positioning operation in the cold start mode (S10).
8).

The count value stored in S102 of FIG. 2 indicates the duration of the non-positioning state when the GPS receiver 10 is in the non-positioning state when the power is turned off. In other words, this duration is GP in the case of FIG.
This indicates a value close to the time _TD2 until the vehicle equipped with the S receiver moves to a position where positioning can be performed after the engine is started. In S106 of FIG. 2, when the duration of the non-measurement state is read at power-on is long, since it is set to a cold-start time-out time _{T CS} also longer value _{T LONG, T CS} time elapses within _{T D2} And the overall TTFF is reduced to T
It is possible to shorten to T _D2 + TTFF _h instead of _D2 + TTFF _c .

[0025] In the example of FIG. 2, has been set to T _{C S} into two values by comparing the duration of the non-positioning state to a threshold, the T _CS to a value proportional to the duration of the non-positioning state It is also possible to set. Again, considering the example of FIG. _3, it means that the value of _{T CS} is increased in proportion to _{T D2,} overall TTFF is _T D2 + TTFF _h.

[0026]

As described above, the GPS of the present invention
According to the receiver, if the non-measurement state continues after the power of the GPS receiver is turned on due to an error in information stored for the hot start mode, the engine of the vehicle equipped with the GPS receiver is used. starting place is to recognize whether it is a case of either of the case due to the location where the GPS signal of the underground parking lot or the like is not received, set the optimum cold start time-out time T _{C S,} the overall TTFF
Can be shortened.

[Brief description of the drawings]

FIG. 1 is a block diagram of a GPS receiver according to the present invention.

FIG. 2 is a flowchart illustrating a method of setting a cold start time-out period (T _CS ) performed at power-on in the GPS receiver of the present invention.

FIG. 3 is a diagram illustrating a time TTFF from when the power is turned on to when a first positioning result is obtained, for each situation when the engine is started in a vehicle equipped with a GPS receiver.

[Explanation of symbols]

2 frequency conversion unit 3 A / D conversion unit 4 signal demodulation unit 5 reception control unit 6 calculation unit 7 nonvolatile memory 8 GPS antenna 10 GPS receiver 11 counter 12 count value R / W unit 13 _TCS setting unit 14 comparator

Claims (6)

[Claims] 1. A GPS receiver capable of storing information about GPS satellites captured during operation, and capturing and positioning GPS satellites by using the stored information at the next power-on. Then, when the state where the positioning result is not calculated after the power is turned on continues, the positioning operation is started again in the cold start mode (the operation starting mode in which successive acquisition is attempted for all the GPS satellites without using the stored information). A cold start time-out period T _{CS up} to the previous time according to the GPS signal reception status at the time of the previous power-off. 2. A GPS receiver capable of storing information on GPS satellites captured during operation and using the stored information at the next power-on to capture GPS satellites and perform positioning. A positioning state storage means for storing whether a positioning result is obtained when a power is turned off, or a non-positioning state where a positioning result is not obtained; and a positioning / positioning information obtained from the positioning state storage means when the power is turned on. a time-out time setting means for setting a different timeout period T _CS in accordance with another non-positioning, after power-on, when the non-positioning state continues more than T _CS is all GPS satellites without using the stored information A cold start time-out executing means for starting an operation in a cold start mode for successively attempting to acquire the GPS receiver. 3. The timeout time setting means sets a timeout time T set when a power-off state obtained from the positioning state storage means is a non-positioning state.
_CS and GPS receiver according to claim 2, the state at the time of power-off, characterized in, that the value greater than the timeout period T _CS to be set if a positioning state. 4. A GPS receiver capable of storing information about GPS satellites captured during operation, and capturing and positioning GPS satellites using the stored information at the next power-on. Counting means for counting the elapsed time when the positioning is not performed during operation; counting value storing means for storing a value of the counting value when the power is turned off; a time-out time setting means for setting a time-out time T _CS based on the count value obtained from the numerical storage means, after the power is turned on when the non-positioning state continues more than T _CS does not use the stored information A cold start time-out execution means for starting operation in a cold start mode for sequentially trying to acquire all GPS satellites. Wherein said time-out time setting means compares the count value with a threshold value K obtained from the counted value storage means, the time-out time T _CS to be set if the regimen value is equal to or larger than the threshold value K, the GPS receiver according to claim 4 in which the count value to be set to a value larger than the time-out time T _CS to be set if it is less than the threshold value K, and wherein. Wherein said time-out time setting unit, GPS receiver according to claim 4, wherein, to increase the value of the timeout time T _CS in proportion to the count value read from the counted value storage unit Machine.