KR20110055407A - Navigation receivers and thereof - Google Patents

Abstract

PURPOSE: A navigation receiver and method thereof are provided to determine a location based on signals received from navigation transmitters. CONSTITUTION: A receiver chain(16,18,22,24,28) down-converts signals received in a tunable receiving frequency band using a tunable local oscillator. The tunable receiving frequency band is determined by tuning. A sampler samples the down-converted signals and samples signals during first and second time slots. A processor determines the location related to a receiver based on sampled signals.

Description

Navigation receiver and its method {NAVIGATION RECEIVERS AND THEREOF}

The present invention relates to a navigation receiver, in particular a navigation receiver capable of receiving signals from one or more navigation transmitters operating in accordance with a first navigation system and one or more navigation transmitters operating in accordance with a second navigation system. To methods, apparatus and computer software associated with the software.

In one navigation system, the navigation receiver receives signals transmitted by the navigation transmitters using navigation system technology appropriate for the navigation system. The navigation receiver may be a dedicated device or equipment having functions other than navigation, such as a mobile handset of a cellular wireless system.

Global Positioning System (GPS) and Glonass or GLONASS (GLObal Navigation Satellite System) are examples of satellite navigation systems that allow users to obtain reliable and accurate position information as well as typical speed and timing information at many locations. Other satellite navigation systems are also planned, including the European Galileo system, the Indian Regional Navigation Satellite System (IRNSS) and the Compass & Beidou satellite navigation system.

Other non-satellite navigation systems are also known. Pseudolite navigation systems are ground-based alternatives to satellite navigation systems. Other terrestrial navigation systems are also known, such as Long RAnge (LORAN), a system in which a cellular wireless network access node is used as a navigation transmitter, and a system in which a Wi-Fi network access point is used as a navigation transmitter.

In order to provide reliable three-dimensional position estimation using a navigation system, the receiver must solve the equations for four unknowns: three-dimensional position coordinates and receiver clock error. Thus, the receiver ideally needs to acquire and track at least four navigation transmitter signals. In addition, since the satellite is not stationary, the satellite navigation system requires accurate information about its position and speed at the time of transmission. Such information can typically be decoded from the satellite signals themselves at a rate of 50 bits / second, but this is a waste of time and vulnerable to low signal-to-noise ratio (SNR) conditions, or in the form of auxiliary data information at the start of the navigation process. Can be obtained from a terrestrial server. The information can be transmitted to the receiver using a terrestrial wireless communication system such as a cellular wireless network. In some situations, the receiver may not be able to receive four acceptable wireless signals from satellites of one system. For example, if the user is located in a typical urban area, the line of sight may be partially blocked by surrounding buildings, blocking reception from some satellites, mainly at a low elevation angle. In this case, the accuracy of the satellite navigation system may be degraded.

The degree of usefulness based on the three navigation transmitter signals, for example, by making assumptions about the altitude of the location based on previous position estimates or on elevation estimates from sources such as other positioning or navigation systems. Two-dimensional position estimates may be achieved with accuracy.

However, if less than a predetermined number of navigation transmitters are available for reception by the receiver, the performance of position estimation may not be acceptable and position estimation using a navigation system may not be possible. In satellite navigation systems and other triangulation systems, the desired number of navigation transmitters required is typically three.

An object of the present invention is a navigation system comprising one or more navigation transmitters operating in accordance with a first navigation system and navigation receivers capable of receiving signals from one or more navigation transmitters operating in accordance with a second navigation system. To provide a reliable three-dimensional position estimation.

According to an aspect of the present invention, in a navigation receiver, the receiver down-converts signals received in a tunable reception frequency band using a tunable local oscillator, wherein the tunable reception frequency band is a tuning of the local oscillator. A receiver chain determined by; A sampler for sampling the down-converted signals and sampling a plurality of samples of the signal in first and second time slots; And a processor that determines at least one position associated with the receiver based on at least the sampled signals in first and second time slots, wherein the tunable local oscillator is tuned to a sequence of frequencies so that the tuning A possible receive frequency band corresponds to the first frequency band in first time slots and the tunable receive frequency band corresponds to at least a portion of a second frequency band in second time slots, the first and second times Slots form different elements of a time slot sequence, and the receiver operates in accordance with a first navigation system using a first frequency band and a second frequency band different from the first frequency band. One or more thereof operating in accordance with a second navigation system utilizing In determines the position based on the navigation signals received from a transmitter.

Tune the tunable local oscillator to a sequence of frequencies such that the tunable receive frequency band corresponds to a first frequency band in first time slots and the tunable receive frequency band is the second frequency band in second time slots. The advantage of allowing at least a portion of the first and second time slots to form different elements of a time slot sequence is that signals from navigation transmitters in which downconverter hardware operates in accordance with the first navigation system. Time is shared between the operation of receiving the signals and the operation of receiving signals from navigation transmitters operating in accordance with the second navigation system, thereby avoiding hardware duplication to provide an economical implementation.

Advantageously, the samplers use the same sampling clock to sample the signal in each of the first and second time slots, such that an error in the sampling clock frequency is common to both navigation systems. It has the advantage that the effect of error on the position estimate made based on measurements from both systems is substantially eliminated.

In embodiments of the present invention, the first navigation system utilizes code division multiple access, and the tunable received frequency band has a fixed bandwidth substantially the same as the signals of the first navigation system, so that the first The signal from any navigation receiver operating in accordance with the navigation system occupies a band that can be sampled and used for positioning, while the other signals that may constitute interference may not be sampled.

Advantageously, said second navigation system utilizes frequency division multiplexing, wherein the tunable received frequency band used in said second time slot has a narrower bandwidth than said second frequency band, which is said tunable receive frequency band. The same filter, which defines s, can be used for use in the first and second time slots, which has the advantage that an economical implementation is possible. In a frequency division multiplexed navigation system, a portion of the frequency band used by the navigation system includes the entire bandwidth of the signals associated with the subset of navigation transmitters operating in accordance with the navigation system, while signals from each navigation transmitter are Note that part of the frequency band used by the code division multiplexed system typically does not include the full bandwidth of the signals associated with particular navigation transmitters, since it primarily occupies the same band with each other.

Advantageously, said second time slots comprise a first zone in which said tunable receiving frequency band corresponds to a first portion of said second frequency band and said tunable frequency band corresponds to a second portion of said second frequency band. Including a second zone, two portions of the second frequency band have the advantage that they can be received sequentially. Thus, for example, when the second navigation system is a frequency division multiplexed system, the first subband used by the first navigation transmitter or navigation transmitters is the second used by another navigation transmitter or navigation transmitters. It can be received alternately with subbands.

In preferred embodiments, the first and / or second navigation system is a satellite navigation system. Preferably, the first navigation system may be a Global Positioning System (GPS) system, and the second navigation system may be a Global Navigation Satellite System (Glonass) system. Although the GPS and Glonass systems have different bandwidths from the frequency bands used by the GPS system and the Glonass system, the frequency division multiplexing of the Glonass system corresponds to the bandwidths of the GPS system because the frequencies used by the plurality of satellites correspond to the bandwidth of the GPS system. It is particularly beneficial when used together with a receiver having a tunable reception band with a constant bandwidth. As a result, if the bandwidth of the tunable reception band corresponds to the bandwidth used by the GPS system, signals from a plurality of satellites may be received in the second time slots.

According to a second aspect of the invention, there is provided a method of selecting a subband for reception of signals in a satellite navigation receiver, the method comprising: receiving signals from satellites operating according to a first satellite navigation system, the first satellite navigation system Based on the information received by the receiver capable of receiving signals from one or more satellites operating according to the set of satellites of the first satellite navigation system in which no allowable signals are received and in which the signals are expected to be received in a disturbing environment. Determining, based on the arrival directions associated with the set, estimating an area of arrival directions for which satellite reception is not expected, and based on the estimated area of arrival directions for which satellite reception is not expected, and a second frequency band Frequency division multiplexed second satellite navigation using The step of determining a set of one or satellite operating in accordance with the frequency division multiplexed satellite navigation system in which signals are estimated on the basis of the information received by the more capable of receiving signals from a satellite receiver operating according to the system And selecting a subband for reception of signals, which is a subband of the second frequency band for reception of signals from the determined set of satellites.

The advantage of selecting a subband for the reception of signals in the above-described manner is that the subband will correspond to the frequencies used by the satellites for which the signals are expected to be received.

Advantageously, information received by a receiver associated with said first and second satellite navigation systems is received via a connection to a terrestrial wireless network.

In particular, it is advantageous to receive information associated with the second satellite navigation system via a connection to a terrestrial wireless network rather than via a satellite operating in accordance with the second satellite navigation system, which information is received before subband selection. Because it can be.

Advantageously, the information received by the receiver associated with said first and second satellite navigation systems is almanac and / or calendar information, which enables the calculation of the position of the satellites, so that the arrival directions of the satellite reception are not accounted for. The advantage is that an appropriate zone can be determined based on which set of satellites operating in accordance with the frequency division multiplexed satellite navigation system can be determined that signals are expected.

According to a third aspect of the present invention, there is provided a signal processing method for calculating a position of a satellite navigation receiver, using a first satellite navigation system, between a first satellite operating according to the first satellite navigation system and the receiver. Determine an estimated value of a first range of the first range, wherein the first range corresponds to a first time; and a second operating according to the second satellite navigation system using the second satellite navigation system. Determine an estimate of a second range between the satellite and the receiver, wherein the second range corresponds to a second time different from the first time; and corresponding to the first time; Determining an estimate of a third range between the two satellites and the receiver based on the determined motion of the second satellite and an estimate of the second range And according to at least one of the first range, the third range, the location of the first satellite and the location of the second satellite and the one or more satellites and the second satellite navigation system operating according to the first satellite navigation system. Calculating a position of the receiver based on signals received from one or more satellites.

An advantage of the method described above is that the reception of a signal from one or more satellites operating in accordance with the first satellite navigation system is time multiplexed with a reception from one or more satellites operating in accordance with the second satellite navigation system. In other words, time sharing of parts of the wireless receiver is possible and range estimates from each system can be used together to estimate the location.

Advantageously, the determined movement of the satellite is determined based on at least one Doppler frequency calculation applied to the signal received from the second satellite so that the Doppler frequency calculation can be performed at the receiver for other purposes so that the information is nearly Can be obtained at no additional cost.

Advantageously, there is an advantage that the determined movement of the satellite is determined based at least on almanac information such that the Doppler frequency calculation can be confirmed by comparing with the almanac information and comparing whether the receiver is substantially static.

Advantageously, the method determines using said second satellite navigation system an estimate of a fourth range between a receiver and a third satellite operating in accordance with a second satellite navigation system, said fourth range being a first time and Corresponding to a third time different from the second time;

Determining an estimated value of a fifth range between the third satellite and a receiver, corresponding to the first time based on the determined movement of the second satellite and the fourth range; And

Calculating the position of the receiver based on at least the first, third and fifth ranges, wherein the calculation is performed based on signals belonging to different subbands received from the satellites and whose reception is time multiplexed. Has the advantage that can be achieved.

A method of selecting an operation mode of a navigation receiver, the method comprising: determining a number of navigation transmitters operating according to the first navigation system in which allowable signals are received, and operating the first navigation system based on the number; Or a location of a navigation receiver capable of determining a location based on signals received from one or more navigation transmitters and one or more navigation transmitters operating in accordance with the second navigation system, the one operating in accordance with the first navigation system. Or a single system mode of operation calculated based on signals received by the receiver from more navigation transmitters; And one or more navigation transmitters whose position is based on signals received by the receiver from one or more navigation transmitters operating in accordance with the first navigation system and operating in accordance with the second navigation system. And selecting from among a multi-system operating mode calculated based on the signals received from the system.

An advantage of the method described above is that if there are enough navigation transmitters operating in accordance with the first navigation system where the permit signals are received, the determination of location can take place using the first navigation system without time sharing with other systems, thereby providing a location. Determination can be made quickly, and power can be saved by a receiver whose power is intermittent.

Advantageously, the selection of the multiple system mode is made based on the case where the number is less than three and greater than zero. Selecting a multi-operation mode when the number is less than 3 means that reliable positioning will not be achieved even in two dimensions when a signal is received from three or less navigation transmitters, so multi-mode operation is three or more. It would be desirable to increase the probability of receiving a signal from further navigation transmitters.

Preferably, when the first navigation system is a satellite navigation system, when the number is zero, a terrestrial operating mode is selected in which the position of the receiver is calculated based on the terrestrial navigation system. When no signal is received with acceptable quality from satellites operating in accordance with the first navigation system, the signal is very disturbed and has a signal with acceptable quality from three or less satellites operating in accordance with the second satellite navigation system. Will be received. In this case, it would be more reliable to calculate the position of the receiver based on the terrestrial navigation system.

Further aspects of the invention have been described in the appended claims, and further features and advantages will be apparent from the following description of the preferred embodiments of the invention, which are provided by way of example only.

1 is a schematic diagram showing a frequency band used by a GPS and a Glonass satellite navigation system.
2 is a schematic diagram illustrating a receiver in a location where signals from low altitude satellites are blocked.
3 is a schematic diagram showing the distribution of satellites in the hemisphere where signals from some satellites are blocked.
4 is a schematic diagram illustrating a receiver according to an embodiment of the present invention.
5 is a schematic diagram illustrating a time slot sequence according to an embodiment of the present invention.
6 is a flowchart illustrating a method of selecting a subband for receiving a signal according to an embodiment of the present invention.
7 is a schematic diagram illustrating estimation regions in an arrival direction in which satellite reception is not expected according to an embodiment of the present invention.
8 is a schematic diagram illustrating a time reference for range calculation using a GPS and a Glonass satellite navigation system according to an embodiment of the present invention.
9 is a flowchart illustrating a method of selecting an operation mode of a satellite navigation receiver according to an embodiment of the present invention.

By way of example, one embodiment of the invention is based on a signal received from one or more satellites operating in accordance with a GPS satellite navigation system and a signal received from one or more satellites operating in accordance with a Glonass navigation system. This is described in the context of a satellite navigation receiver that can be determined. However, it will be appreciated that this is only an example and that other embodiments may be associated with the use of navigation transmitters operating in accordance with other navigation systems.

1 shows frequency bands used by GPS and Glonass satellite navigation systems, and it can be seen that the frequency band used by GPS 1 is different from the frequency band used by Glonass 3. FIG.

GPS satellite navigation systems use code division multiple access (CDMA) for multiplexed signals transmitted from different satellites, while Glonass uses frequency division multiple access (FDMA) for multiplexed signals transmitted from different satellites. I use it. Thus, in the Glonass system, it is possible to use a subband of the frequency band 3 used by the system to receive a signal from a subset of satellites. In Fig. 1, five subbands, designated A 5a, B 5b, C 5c, D 5d, and E 5e, respectively, are shown, where each subband includes frequencies used by three respective satellites.

Alternatively, a system may be advantageously employed in which each subband contains frequencies used by four satellites. Portions of these subbands may overlap each other. For example, four subbands are used, each centered at 1598.90625 MHz (including Glonass frequencies specified as -7, -6, -5, and -4) 1601.15625 MHz (Glonass frequency designated as 1, 2, 3, and 4) And 1604.53125 MHz (including Glonass frequencies designated 3, 4, 5 and 6). The last two bands listed above may overlap one another, which may be advantageous to adjust the downconversion frequency plan to avoid problems with image frequencies, especially when a direct conversion scheme is used, as shown in FIG. In this arrangement, the second local oscillator 26 and the mixer 24 are omitted.

1, it can be seen that the Glonass system uses a wider frequency band 3 than the frequency band 1 used by the GPS system. Typically, the GPS system uses a bandwidth of about 2 to 2.5 MHz, while the Glonass system uses a bandwidth of about 12 MHz. Note that the GPS system transmits signals in bands other than those shown in FIG. 1, for example for use by high precision military receivers. However, usually a receiver for a general user device is designed to receive the frequency band 1 shown in FIG.

2 illustrates a scenario in which signals from one or more satellites may be blocked. The receiver 4 is shown at a typical urban street canyon, ie at a distance with buildings 2a, 2b which may obstruct the satellite on one side. In the case of Fig. 1, the building height is shown to be about 15m, and since the line of sight is typically required for good signal reception at frequencies within the 1-2 GHz range used by the satellite navigation system, satellites of low elevation angles are blocked. Able to know. It should be noted that satellite systems are arranged to operate near the noise floor in order to limit the transmit power at the satellite, so that a small amount of attenuation may render the signal from the satellite unacceptable. Of course, the height of the building may be much higher than 15 m so that this obstruction may affect signals received from satellites with elevation angles much larger than the elevation angle shown in the example of FIG.

3 is a hemispherical view showing an example of the position of a satellite using GPS and a Glonass satellite navigation system. The position near the circumference of the circles in FIG. 3 represents an azimuth, the position along the radius represents altitude, and the center represents a point directly overhead. This type of drawing may be referred to as the top of a head view. The placement of satellites is sometimes called constellation.

FIG. 3 shows, by way of example, in a scenario similar to the scenario shown in FIG. 2, whether using GPS or Glonass, the position of the satellite 6a, where no acceptable signals are received due to blocking. 6h) is shown as a square. The positions (8a, 8b, 8c, 8d) of the satellites receiving the allowed signals using GPS are indicated by circles, and the positions (10a, 10b, 10c, 10d) of the satellites receiving the allowed signals using the Glonass are triangles. Marked as. As indicated by the area within the dotted line 12, it can be seen that there is a zone in the direction of arrival where satellite reception is expected. Outside this area, it is not expected as satellite reception may be blocked.

In the particular arrangement shown in FIG. 3, it can be seen that there are four GPS satellites and four Glonass satellites from which a permit signal can be received. As already explained, it should be possible to determine the location with good accuracy using either satellite navigation system.

However, since the satellite is not in stationary orbit, its position may change over time so that a case where only a few allowable signals can be received can occur. In addition, in street canyons with buildings higher than the buildings shown in FIG. 2, an allowable signal can be received from fewer satellites, that is, fewer satellites are "visible". As described above, if less than three satellites are available for reception by the receiver, using one satellite navigation system, the performance of location estimation may not be acceptable or location estimation may not be possible. .

Signals received from one or more satellites operating in accordance with a GPS satellite navigation system and one or more satellites operating in accordance with the Glonass navigation system, in particular for use in a location where insufficient satellites from a single system are visible. A receiver according to an embodiment of the present invention is provided that can determine a location based on a signal received from the device. Such a receiver is illustrated in FIG. 4.

The signal is received from the satellite at the antenna 14 and then transmitted to the receive chains 16, 18, 22, 24, 28. The constant receive chain is arranged to down-convert the received signal in the tunable receive frequency band using the tunable local oscillator 20, the tunable receive frequency band determined by the tuning of the local oscillator 20. The receive chain typically receives a front end filter, which is primarily a surface acoustic wave (SAW) filter, a low noise amplifier (LNA) 16, and a received, filtered, and amplified signal followed by a local oscillator ( A tunable receive band, including a mixer 18 that mixes with the signal from 20, is defined by an intermediate frequency (IF) band pass filter 22. The second local oscillator signal is provided to the second mixer 24 by the frequency divider 26. The signal from the IF band pass filter 22 is mixed by the second mixer 24 to the second IF, which is sampled by a sampler, i.e. an analog-to-digital converter (ADC) 28. The local oscillator 20 and the divider 26 can obtain their frequency reference from the common frequency source 30.

The tunable local oscillator is tuned to a series of frequencies such that the tunable receive frequency band corresponds to the GPS frequency band 1 in the first time slot, and the tunable receive frequency band is the Glonass frequency band 3 in the second time slot. Corresponding to at least a portion 5a, 5b, 5c, 5d, 5e, wherein the first and second time slots form different elements of the time slot sequence. The terms "first" and "second" are arbitrary and do not imply that the time slot for receiving the GPS signal precedes the time slot for receiving the Glonass signal at the start.

The sampler samples a plurality of samples of the signal in each of the first and second time slots, and the processor is configured to determine at least one location associated with the receiver based at least on the sampled signal in the first and second time slots. do. Thus, the processor receives signals from satellites operating according to GPS and satellites operating according to Glonass in a time sharing manner.

The digitized signals from the ADC are passed to a processor, which typically measures the measurement engine 36, positioning engine 38, controller 34, which is time-shared between the operations on signals from each satellite. ), An extended assisted GPS (AGPS) aiding function block 32.

The measurement engine 36 performs frequency shift measurements on signals from each received satellite operating in accordance with an applicable GPS or Glonass system. The frequency shift measurement is a calculation of the so-called pseudo Doppler shift, and the arrival time is also calculated from which a range estimate between the satellite and the receiver, known as pseudo range, is calculated. The calculated amount is also known as the "pseudo" range and Doppler because it is obtained using a clock that may have inaccuracies. The effect of the inaccuracy may be eliminated by subsequent calculations.

Pseudo ranges and pseudo Doppler measurements for each of the satellites operating in accordance with each of the GPS and Glonass systems are passed to a positioning engine 38 to determine the location, ie the location of the receiver and thus the user location.

Pre-checking and calculation 40 is performed after the calculation of position and typically the calculation of speed and time (PVT calculation) 42. The calculated position, velocity and time values are passed to a Kalman filter, which determines an estimate of position, velocity and time based on the history of the estimated data. The determined position is later output from the positioning engine 38.

The location associated with the receiver is therefore determined based on at least sampled signals in the first and second time slots. That is, the determination of location is determined based at least on signals received from a satellite operating in accordance with both GPS and Glonass satellite navigation systems.

In this embodiment, the sampler uses the same sampling clock to sample the signal in each of the first and second time slots used to sample signals from satellites operating in accordance with GPS and Glonass satellite systems. All sampling clock errors are preferably the same for both systems so that position calculations based on signals from satellites operating in accordance with both systems are accurate.

5 shows a typical time slot sequence according to an embodiment of the invention, in particular the first time slots 15, 21a, 21b and Glonass system used for the reception of signals from satellites operating according to the GPS system. The sequence of second time slots 17, 19, 23a, 23b for the reception of signals from operating satellites is shown.

Initially, when a position needs to be determined, the acquisition process is performed during time slots 15 and 17, which may be longer than the time slots used for subsequent tracking once the signals are acquired. Since the acquisition process is a well known process in satellite navigation systems where range estimation is performed, satellites from which allowable signals can be received must be identified, primarily cellular using terrestrial communication systems such as almanac and calendar information. The location of the satellites needs to be set (using information that can be received over a wireless link, such as a wireless network connection), and the timing parameters also need to be set.

5 shows that a shorter interval is allocated for Glonass acquisition 15 than for Glonass acquisition 17. This may be the case when fewer Glonass satellites need to be acquired than GPS satellites.

After acquisition, the processor performs a tracking process wherein the position estimates are updated using signals received from the acquired satellites. The time slots 19, 21a, 23a, 21b, 23b for tracking are mainly shorter than the time slots for acquisition 15, 17. In the example illustrated in FIG. 5, GPS acquisition is allocated 30 seconds, Glonass acquisition is allocated 10 seconds, and each tracking interval is set to 200 ms. The time allotted to the acquisition phase may vary depending on the time needed for the acquisition process, which will depend on factors including how recently the positioning has been performed, so called position fix, and these factors It will also affect the relevance of the stored system parameters. In general, when using assistance with information received using a terrestrial communication system, the acquisition time is in the range of 5 to 60 seconds, and the tracking time in the range of 0.1 to 0.5 seconds has been found to provide good performance. In particular, the first and second time slot intervals of 0.2 seconds have been found to provide good performance when the processor is in the tracking phase, resulting in fast reacquisition at the beginning of the time slot and the clock frequency between one time slot and the next time slot. Normal drift in sampling is acceptable.

Since it is necessary to leave time for the stabilization of the local oscillator frequency after tuning, there may be a period at the start of the time slot when the samples of the received signals are discarded.

It may be advantageous to disable processing for portions of time slots to reduce power consumption.

The time slots in which signals are received from the Glonass system are characterized in that the tunable receiving frequency band corresponds to the first portion 5a of the Glonass frequency band 3, called the subband, and the tuning A possible reception frequency band may comprise a second zone corresponding to the second part or subband 5b of the Glonass frequency band 3. In this way, the reception of signals in one subband can be time multiplexed with the signals in the other subband, whereby the signals can be processed to be received from Glonass satellites included in different subbands.

In the present embodiment, since the Glonass frequency band 3 is divided into subbands in which not all need to be received, a method for selecting a subband for reception of signals is provided.

Signals are received according to satellites operating in accordance with the GPS satellite navigation system (GPS satellites) and based on information received by a receiver associated with the GPS navigation system, no allowable signals are received but in an unobstructed environment. The set of GPS satellites from which signals are expected to be received is determined. In other words, they are "invisible" satellites.

Based on the arrival direction associated with the invisible satellite set, an area of arrival directions for which satellite reception is not expected is estimated, and may be referred to as a blind area. This may include angles within a particular angular range of arrival directions of invisible satellites. Glonass satellites with arrival directions within the blind area are also assumed to be invisible. Compared with the information associated with the blind area, a Glonass satellite set for which signals are expected is determined based on information received by a receiver associated with the Glonass satellite navigation system, in particular almanac and calendar information, the information being terrestrial radio It may be received by the receiver via a connection to the network.

In the determined Glonass satellite set where signals are expected, a subband is determined for the reception of signals from the satellite.

Signals from some Glonass satellites may be included in the same subband selected above. It may be the case that one or more subbands are selected to receive the desired number of Glonass satellites. Each subband is received in a time sharing manner as already mentioned.

6 is a flowchart illustrating a method of selecting a subband for reception of signals.

In steps 52 and 54, based on the information associated with the GPS system received by the receiver from the AGPS server, a satellite set of GPS systems for which signals are not expected but for which signals are expected to be received is determined. The information typically includes almanac information. Acceptability of satellite signals may be determined, for example, according to capture quality, ie the degree of success of the acquisition process.

In steps 56 and 58, an area of arrival directions in which satellite reception is not expected is estimated based on arrival directions in the altitude and orientation associated with the set determined in steps 52 and 54.

In steps 60 and 62, also known as a space vehicle (SV) where signals are expected, based on the estimated area of arrival directions for which satellite reception is not expected and the information received by the receiver from the AGPS server associated with Glonass. Glonass satellite set is determined.

In steps 64, 66 and 68, a subband for receiving signals is selected, the selected subband being a subband of a frequency band used by Glonass, and the receiver is configured according to the selected subband. The subband may be selected based on, for example, a priority list of candidate Glonass satellites. The priority in the priority list can be determined by many factors, such as the elevation of the satellite.

7 shows an example of estimation zones (blind zones) of arrival directions for which satellite reception is not expected. It was determined that no allow signals could be received from GPS satellites at locations 6a, 6b, 6c (the locations shown in FIG. 7 are not assumed to correspond to the locations in FIG. 3). Blind zone 74a is estimated for arrival angles near 6a, likewise blind area 74b is estimated for arrival angles near 6b, and blind zone 74c is estimated for arrival angles near 6c. do.

The position, velocity and time calculations 42 performed by the positioning engine 38 are based on pseudo range information corresponding to different times, thus operating in accordance with a first satellite navigation system (e.g. GPS). Computing the position of the satellite navigation receiver based on signals received from one or more satellites and signals received from one or more satellites operating according to a second satellite navigation system (eg Glonass). A signal processing method is provided. The two systems may be transposed in the description, but it does not matter which one is the first or second system.

An estimated value for a first range between a first satellite and a receiver operating in accordance with the first satellite navigation system is determined using a first satellite navigation system, the first range corresponding to a first time.

An estimate of a second range between a second satellite operating in accordance with the second satellite navigation system and a receiver is determined using a second satellite navigation system, the second range being at a second time different from the first time. Corresponds. Since the GPS and Glonass systems are time multiplexed and operate at different times, the second time is different from the first time.

Based on the determined motion of the second satellite and the predicted value of the second range, an estimate of the third range between the second satellite and the receiver is determined, the third range corresponding to the first time. In other words, the range estimate corresponding to the second time slot is adjusted for the satellite's movement between the first time and the second time to provide a third range.

The position of the receiver can be calculated based on at least the first and third ranges. In other words, the pseudo range information determined by the measurement engine 36 from the signal received from the GPS satellites is determined by the measurement engine 36 from the signals received from the Glonass satellites in the positioning engine 38 for positioning. It may be used with the determined pseudo range information.

The location and movement estimates of the second satellite derived from the Glonass system are mapped to a GPS time reference and a GPS location reference. The mapping between the Glonass position criterion and the GPS position criterion is preset. The mapping between the Glonass time reference and the GPS time reference is preset and takes into account the time difference between the GPS and Glonass time reference systems and the receiver between the time corresponding to the start of the GPS subframe and the time corresponding to the start of the Glonass string. This is achieved by considering a precision correction based on the time difference measured at.

The calculation of the position of the receiver is based on at least the first and third ranges and the positions of the first and second satellites (and preferably in addition other ranges and satellite positions) known as the GPS time and frequency reference system. Is determined.

In order to adjust for the movement of the second satellite between the first time and the second time, the position and motion estimates of the second satellite derived from the Glonass system are mapped to the GPS time reference and the GPS location reference.

The motion of the satellite may be determined based on Doppler frequency calculations applied to the signal received from the second satellite, ie pseudo Doppler measurements and / or calendar information associated with the Glonass satellite.

The method can be extended to be applicable to cases where the time slots allocated for reception of the Glonass system are subdivided into parts for receiving frequency subbands by correcting the pseudo ranges as above separately for the frequency subbands. have.

FIG. 8 shows time references for range calculation correspondence using GPS and Glonass satellite navigation systems, when the time slots allocated for reception of the Glonass system are subdivided into parts for receiving frequency subbands. Range calculation using GPS satellites corresponds to time 57a, and range calculation using Glonass satellites corresponds to time 53a for the first frequency subband and time 55a for the second frequency subband. Range calculations corresponding to the times 53a and 55a are mapped appropriately to time 57a before being used to calculate the location. Similarly, in the following time slots, the range calculation corresponding to times 53b and 55b is mapped to be appropriate for time 57b.

In the embodiments described so far, it is assumed that the receiver operates in a multiplexing mode of operation, more specifically in dual mode (GPS / Glonass). However, if sufficient satellites are visible and operate in a single mode, there is no need to operate in multiple mode, and it may be advantageous to operate in single mode in terms of reducing power consumption or allocating more processor resources to single mode operation. have. Thus, a method of selecting an operating mode of a receiver is provided. The technique is described in terms of single mode operation for using a GPS system, and it should be understood that single mode operation may use the Glonass system as the two systems may be interchanged.

First, the number of satellites operating in accordance with a first satellite navigation system (e.g., GPS) from which allow signals are received is determined.

Depending on the number, there is a single system mode of operation in which the position of the receiver is calculated based on signals received by the receiver from one or more satellites operating according to the first satellite navigation system (e.g., GPS). Signals received by the receiver from one or more satellites, wherein the receiver is selected or whose position is operated according to the first satellite navigation system (e.g., GPS), and the second satellite navigation system (e.g., A multi-system operating mode may be selected that is calculated based on signals received from one or more satellites operating in accordance with Glonass.

Typically, the multi-system mode is selected when the number is less than 3 and greater than zero. In other words, if only two-dimensional position estimation or fix is required, for example, it may be allowed to operate in a single mode (eg, GPS mode) when only three satellites provide the allowable signals.

Alternatively, when the number is 4 or less, the multi system mode may be selected. In other words, it may be allowed to operate in a single mode (eg, GPS mode) if at least four satellites provide tolerant signals, for example when a three-dimensional position fix is required.

When the number is zero, the ground operating mode can be selected, where the position of the receiver is calculated based on the ground navigation system. A suitable terrestrial navigation system may use, for example, a cell ID based on the positioning of the cellular radio system. In the absence of a suitable visible satellite operating in accordance with one satellite system, reception may be very disturbed such that a satellite operating in accordance with another satellite system is invisible or only a few satellites are visible.

9 is a flowchart illustrating a method of selecting an operation mode of a satellite navigation receiver. In steps 80, 82 and 84, GPS signals are typically obtained using AGPS.

In step 86, the number of GPS satellites from which allow signals are received is determined.

If the determined number is zero, in step 88, the cell ID from the cellular wireless system is used to determine a location, ie, create a fix.

If the determined number is 3, a two-dimensional fix is made in step 90 and a three-dimensional fix is attempted.

If the determined number is greater than three, three-dimensional GPS tracking is enabled in step 92.

If the determined number is greater than zero but less than three, in step 94 it is determined to obtain Glonass (GLS) bands and satellites (spatial media, SV).

In step 96, the determined Glonass satellites are obtained.

In step 98, a location is determined.

The operation of the controller 34, the measurement engine 36 and the positioning engine 38 as shown in FIG. 4 will be described in more detail. Typically, the controller 34, the measurement engine 36 and the positioning engine 38 are implemented in software.

The controller 38 controls the GPS signal processing channels, selects satellites to be searched, calculates frequency and code step search windows and determines the appropriate start mode (AGPS, cold, warm or hot start). If the last fix is old enough, then the AGPS mode is used since acquisition of information about the locations of the satellites is required. Cold, warm and hot start refer to the reacquisition modes to be selected according to the time elapsed since the last update of the tracking parameters. The satellite is selected based on prior search results and priority calculations made according to prior data amounts such as almanac, calendar and previous location and fix time. If the latter is not available, the control software may be associated with predicting almanac data. It also controls the communication between the measurement engine and location engine process sequences, the two engines and the external location manager.

The measurement engine 36 reads the digitized RF samples from the ADC 28, obtains visible satellites, and starts simultaneous tracking of active channels. This unit performs digital processing of the GPS signals and estimates the navigation parameters required for the navigation task. The main procedures of this unit are as follows.

Acquisition & Reacquisition: Search for signals at both frequency and C / A code levels, identify the presence of signals, and confirm detection.

Signal tracking: After successful acquisition of the GPS satellite signals, an approximate estimate of both code alignment and Doppler shift is obtained. To achieve accurate measurements and to ensure continuous adjustment of these two entities, the Doppler frequency is tracked using a combination of both code steps and a frequency locked loop (FLL) using a first order delay locked loop (DLL). Should be performed immediately after detection.

Bit synchronization: using 20 coherent correlators with 20 ms accumulation time. Deferent time positions of the bit boundary are used in the CA code generation process. The estimation of the bit boundary corresponds to the correlator with the maximum output value.

Frame Synchronization: Search the preamble to determine the start of each subframe. To avoid false preambles, it is necessary to check the parity bits of the navigation words. Frame synchronization is achieved when the best hypothesis with the maximum number of successful parity checks is found to be successful at least 10 times.

The outputs of the ME are channel data such as raw data of the frames, pseudo range and pseudo Doppler measurements and SNR for each active channel.

Positioning engine (PE) 38 uses pseudo range and pseudo Doppler measurements as well as satellite calendars to calculate receiver position, velocity and time (PVT). The PE also determines satellite positions (azimuth and elevation) and the Dilution of Precision (DOP) for the receiver. The latter provides an estimate of positional accuracy based on the angular separation between satellites used to calculate the position of the receiver.

The positioning engine has the following functions.

NAV message decoder: decodes the data from a 50 bps L1 NAV message. The message consists of a 1500 bit long frame consisting of five subframes, each 300 bits long. The decoder includes parity based error checking to ensure that only valid data is returned to the positioning engine. This is based on the description provided in document [1].

Satellite position & velocity calculation: from each satellite position and pseudo range measurements in ECEF (x, y, z) coordinates based on calendar and clock correction parameters provided in subframes (1, 2, 3) Calculate the time of signal transmission as determined.

Corrected pseudo range calculation: Clock correction parameters are broadcast in subframe (1). In order to reduce the positioning errors, the measured pseudo ranges should be corrected to account for the small time differences and relative effects between the clocks of each satellite.

Receiver Position 3D Computation: The receiver knows the exact satellite ECEF positions at a given transmission time. It knows the difference in pseudo range or reception time for each satellite. To calculate the receiver ECEF position, it is necessary to calculate the exact range or transmission delay between each satellite and the receiver. Since there are four unknowns, at least four satellites are required for this calculation. If there are more than four satellites, they can be generalized to overdetermined linear algebra, which does not have the correct solution. The least squares solution is iteratively calculated using a pseudo inverse.

Receiver position 2D calculation: In order to calculate the 2D position, a good previous 3D position fix is required. Assuming that the altitude is fixed at the last known value, we can calculate the 2D position using only three satellites.

DOP calculation: DOP is used to describe the influence of geometric strength of satellite constellations on the accuracy of position calculations. Good (low) DOP occurs when there is wide angle separation between the satellites used in the location solution. The DOP is derived from the diagonal elements of the covariance matrix of the least squares solution. Horizontal dilution of precision (HDOP) is part of the NMEA GPGSA sentiment.

Kalman Filter: Adjusts the final PVT output between prediction and measurement. Decisions on this are based on both the dynamic model employed and the calculated standard deviation of the measurements.

It will be understood that the above embodiments are only examples of the present invention.

Although the specific embodiments have been described in connection with satellite navigation systems, other non-satellite navigation systems, such as pseudo-satellite navigation systems, LORAN navigation systems, cellular wireless network navigation systems and Wi-Fi network navigation systems It should be noted that it may be included as one or more of the systems used by the multi-system navigation receiver in accordance with FIG.

It should also be noted that the combined GPS / Galileo system may constitute a first or second navigation system or a satellite navigation system. In addition, third or other navigation systems or satellite navigation systems may be employed in a manner similar to the second and satellite navigation systems. For example, when a GPS or combined GPS / Galileo system can receive up to three or four satellites (or other transmitters) at an acceptable quality, the system may select another satellite navigation to determine the position of the receiver. You may wish to obtain Glonass or Compass satellites or transmitters from the system or navigation system.

Any feature described in connection with one embodiment may be used alone or in combination with other features described above, and may be used with one or more features of other embodiments or a combination of other embodiments. Can be. Also, equivalents and modifications not described above may be employed without departing from the scope of the invention as defined in the claims.

16.LNA Filter 34.Controller
36. Measuring engine 38. Positioning engine

Claims (23)

In a navigation receiver,
A receiver chain down converting signals received in a tunable reception frequency band using a tunable local oscillator, wherein the tunable reception frequency band is determined by tuning of the local oscillator;
A sampler for sampling the down-converted signals and sampling a plurality of samples of the signal in first and second time slots; And
A processor that determines at least one location associated with the receiver based on at least the sampled signals in first and second time slots,
The tunable local oscillator is tuned in a sequence of frequencies such that the tunable receive frequency band corresponds to the first frequency band in first time slots and the tunable receive frequency band is a second frequency in second time slots. Corresponding to at least a portion of a band, wherein the first and second time slots form different elements of a time slot sequence,
The receiver is one or more navigation transmitters operating in accordance with a first navigation system utilizing a first frequency band and one or more navigation transmitters operating in accordance with a second navigation system using a second frequency band different from the first frequency band. And determine a location based on signals received from the above navigation transmitters. The navigation receiver of claim 1, wherein the sampler uses a sampling clock for sampling the signal in each of the first and second time slots. 2. The navigation receiver of claim 1, wherein the first navigation system utilizes code division multiple access, and wherein the tunable receive frequency band has the same fixed bandwidth as the signals of the first satellite navigation system. 2. The navigation receiver of claim 1, wherein the second navigation system utilizes frequency division multiplexing, and wherein the tunable receive frequency band used in the second time slot is narrower in bandwidth than the second frequency band. The second zone of claim 1, wherein the second time slots comprise a first zone in which the tunable received frequency band corresponds to a first portion of the second frequency band and a second portion of the second frequency band in the tunable frequency band. And a second zone corresponding to the navigation receiver. The navigation receiver of claim 1, wherein the first navigation system is a Global Positioning System (GPS) system, and the second navigation system is a Global Navigation Satellite System (GLONASS) system. A method of selecting a subband for reception of signals at a satellite navigation receiver, the method comprising:
Acceptance signals are received based on information received by a receiver capable of receiving signals from satellites operating in accordance with the first satellite navigation system and receiving signals from one or more satellites operating in accordance with the first satellite navigation system. Determining a satellite set of the first satellite navigation system that is not received and is expected to receive signals in an unobstructed environment;
Estimating an area of arrival directions for which satellite reception is not expected based on the arrival directions associated with the set;
Received by a receiver capable of receiving signals from one or more satellites operating according to a frequency division multiplexed second satellite navigation system based on the estimated region of the arrival directions for which satellite reception is not expected and utilizing a second frequency band. Determining a satellite set operating according to the frequency division multiplexed satellite navigation system for which signals are expected based on the information; and
Selecting a subband for reception of signals, which is a subband of the second frequency band for reception of signals from the determined set of satellites; Band Selection Method. 8. The subband for reception of signals at a satellite navigation receiver according to claim 7, wherein the information received by the receiver associated with the first and second satellite navigation systems is received via a connection to a terrestrial wireless network. How to choose. 10. The sub receiver of claim 7 or 8, wherein the information received by the receiver associated with the first and second satellite navigation systems is almanac and / or calendar information. Band Selection Method. In the signal processing method for calculating the position of the satellite navigation receiver,
Determine an estimated value of a first range between a receiver and a first satellite operating in accordance with the first satellite navigation system, the first range corresponding to a first time Process of doing;
Using the second satellite navigation system, determine an estimate of a second range between the receiver and a second satellite operating in accordance with the second satellite navigation system, the second range being different from the first time. A process characterized in that corresponding to two hours;
Determining an estimated value of a third range between the second satellite and a receiver, corresponding to the first time, based on the determined motion of the second satellite and an estimated value of the second range; And
At least one of the first range, the third range, the location of the first satellite and the location of the second satellite, and one or more satellites operating in accordance with the first satellite navigation system and one operating in accordance with the second satellite navigation system. Or calculating the position of the receiver based on signals received from more satellites. 11. The method of claim 10, wherein the determined movement of the second satellite is determined based at least on a Doppler frequency calculation applied to the signal received from the second satellite. . 11. The method of claim 10, wherein the determined movement of the second satellite is determined based at least on calendar information. 11. The method of claim 10, wherein the position of the second satellite and / or the determined movement of the second satellite is determined based on a mapping between a GPS time reference and a Glonass time reference. Signal processing method. The method of claim 13, wherein the mapping between the Glonass location criterion and the GPS location criterion is:
Correcting a preset estimate of the time difference between the GPS time reference and the Glonass time reference based on the time difference measured at the receiver between the time corresponding to the start of the GPS subframe and the time corresponding to the start of the Glonass string. And a signal processing method for calculating the position of a satellite navigation receiver. The method according to any one of claims 10 to 13,
Determine an estimate of a fourth range between a third satellite operating in accordance with the second satellite navigation system and the receiver, wherein the fourth range corresponds to a third time different from the first time and the second time; Process,
Determining an estimated value of a fifth range between the third satellite and a receiver, corresponding to the first time, based on the determined movement of the second satellite and the fourth range; and
Calculating the position of the receiver based on at least the first, third and fifth ranges. In the method for selecting the operation mode of the navigation receiver,
Determining a number of navigation transmitters operating according to the first navigation system for which allow signals are received;
Based on the number,
The location of the navigation receiver capable of determining a location based on signals received from one or more navigation transmitters operating in accordance with the first navigation system and one or more navigation transmitters operating in accordance with the second navigation system is A single system mode of operation calculated based on signals received by the receiver from one or more navigation transmitters operating in accordance with a first navigation system; And
From one or more navigation transmitters whose position is based on signals received by the receiver from one or more navigation transmitters operating in accordance with the first navigation system and operating in accordance with the second navigation system. And selecting among multiple system operating modes calculated based on the received signals. 17. The method of claim 16, wherein the selection of the multi-system mode is based on a number less than three and greater than zero. 17. The method of claim 16, wherein the first navigation system is a navigation system, and the method further comprises selecting a ground operating mode in which the position of the receiver is calculated based on a terrestrial navigation system when the number is zero. A method for selecting an operation mode for calculating the position of a navigation receiver, characterized in that. In a satellite navigation receiver,
Receive signals from one or more satellites operating in accordance with a first navigation system utilizing a first frequency band and from one or more satellites operating in accordance with a frequency division multiplexed satellite navigation system using a second frequency band. Arranged to select a subband for reception of signals,
Receive signals from satellites operating in accordance with the first satellite navigation system, and no allowable signals are received based on the information received by the receiver associated with the first satellite navigation system and that signals will be received in an unobstructed environment. Determine a set of satellites of the expected first satellite navigation system,
Estimate an area of arrival directions for which satellite reception is not expected based on the arrival directions associated with the set,
Operating in accordance with the frequency division multiplexed satellite navigation system in which signals are expected based on the estimated area of arrival directions for which satellite reception is not expected and based on information received by the receiver associated with the frequency division multiplexed satellite navigation system. Determine three satellites,
Selecting a subband for reception of signals, the subband of the second frequency band for reception of signals from the determined set of satellites. 20. A computer readable medium encoded with computer executable instructions for executing the operation of the satellite navigation receiver of claim 19. A computer readable medium encoded with computer executable instructions for executing a signal processing method for calculating the position of the satellite navigation receiver of claim 10. In a navigation receiver,
The navigation receiver,
Determine the number of navigation transmitters operating in accordance with the first navigation system for which allow signals are received;
Based on the number,
The location of the navigation receiver capable of determining a location based on signals received from one or more navigation transmitters operating in accordance with the first navigation system and one or more navigation transmitters operating in accordance with the second navigation system is A single system mode of operation calculated based on signals received by the receiver from one or more navigation transmitters operating in accordance with a first navigation system; And
From one or more navigation transmitters whose position is based on signals received by the receiver from one or more navigation transmitters operating in accordance with the first navigation system and operating in accordance with the second navigation system. And select from among a multi-system operating mode calculated based on the received signals. A computer readable medium encoded with computer executable instructions for executing a method of selecting an operating mode of a navigation receiver of claim 16.

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