WO2017175294A1

WO2017175294A1 - Signal reception device and signal reception method

Info

Publication number: WO2017175294A1
Application number: PCT/JP2016/061083
Authority: WO
Inventors: 学高木; 元吉　克幸; 和雅鈴木
Original assignee: 三菱電機株式会社
Priority date: 2016-04-05
Filing date: 2016-04-05
Publication date: 2017-10-12
Also published as: JPWO2017175294A1

Abstract

A signal reception device according to the present invention is characterized by being provided with an antenna for receiving signals from a plurality of satellites, an extraction unit for extracting messages included in the signals received by the antenna, a parameter identification unit for reading parameters from the messages, and a combination unit for determining whether to combine the messages included in the signals from the plurality of satellites on the basis of the parameters read from the parameter identification unit and combining the messages if a determination is made to combine the messages. This configuration makes it possible to correctly receive messages included in signals broadcast from satellites such as GNSS satellites regardless of the types of the messages. In the present invention, using an appropriate combination method according to the types of messages included in signals broadcast from satellites makes it possible to correctly receive the messages within a fixed time regardless of the types of the messages.

Description

Signal receiving apparatus and signal receiving method

The present invention relates to a signal receiving apparatus and a signal receiving method for receiving a signal from a satellite.

In recent years, GPS (Global Positioning Systems) represents a global navigation satellite system (GNSS: Global Navigation Satellite Systems). Applications are drawing attention. While these devices and applications are actively used in urban mobiles, it is well known that positioning accuracy is not achieved in urban areas due to the small number of visible satellites and poor satellite placement. . In order to obtain high positioning accuracy even in such an environment, it is necessary to correctly decode information for positioning calculation called navigation message included in GNSS signals broadcast from various satellites.

Therefore, it is an important technique to accurately decode these navigation messages even in an environment where the reception level is low. As a method of obtaining a navigation message even in a situation where the reception level is low, the navigation message is divided into smaller units called words, selective reception is performed at each time, and after confirming that there are no errors in all words, the navigation message is displayed. A decoding method has been proposed. This is because the information of one's own satellite called ephemeris, which is part of the navigation message, is broadcast repeatedly for a certain period of time, so that the part of the navigation message is the same even for signals received at different times. . For example, see Patent Document 1.

Further, for example, as disclosed in Patent Document 2, a part of the content of the navigation message to be received next is predicted using the navigation message received in advance, and the predicted navigation message and the navigation message received next are received. By combining the above, a method for detecting an error in a navigation message and decoding the navigation message with high accuracy even when the reception level of the GNSS receiver is low has been proposed.

Japanese Patent No. 5480906. Japanese Patent No. 5398940.

Signals transmitted from GNSS satellites are characterized by a mixture of satellite-specific packets transmitted in a short cycle such as ephemeris and packets that can be received from multiple satellites transmitted in a long cycle called almanac. .

The methods described in Patent Literature 1 and Patent Literature 2 are methods for accurately decoding the former ephemeris, and are suitable for decoding an ephemeris that is repeatedly broadcast for a certain period at short intervals. However, when synthesizing almanac, which is a message broadcast in a longer cycle than ephemeris, with the same configuration, there is a problem that it takes a long time to improve positioning accuracy because it is broadcasted less frequently than ephemeris.

The present invention has been made to solve the above problems, and correctly receives a message contained in a signal broadcast from a satellite such as a GNSS satellite in a shorter time than the prior art regardless of the type of the message. An object of the present invention is to realize a signal receiving apparatus capable of performing the above.

A signal receiving apparatus according to the present invention includes an antenna that receives signals from a plurality of satellites, an extraction unit that extracts a message included in the signal received by the antenna, a parameter identification unit that reads a parameter from the message, Based on the parameters read by the parameter identification unit, it is determined whether or not to synthesize messages included in signals from the plurality of satellites, and when it is determined to synthesize, a synthesis unit that synthesizes the messages, It is characterized by that.

According to the signal receiving apparatus according to the present invention, a message can be correctly received within a predetermined time regardless of the type of message included in a signal broadcast from a satellite such as a GNSS satellite.

FIG. 3 is a diagram illustrating signal reception in the signal reception device 100 according to the first embodiment. The figure which shows the structure of the L1C / A signal transmitted from the GNSS satellite which concerns on Embodiment 1. FIG. FIG. 3 shows a configuration of an L2C signal transmitted from a GNSS satellite according to the first embodiment. The figure which shows the page part of the navigation message of I / NAV which concerns on Embodiment 1. FIG. The figure which shows the data format which the two GNSS satellites which concern on Embodiment 1 transmit. FIG. 3 shows a configuration example of a signal receiving apparatus 100 according to the first embodiment. 5 is a flowchart in the parameter identification unit 105 according to the first embodiment. 5 is a flowchart in the synthesis processing unit 106 according to the first embodiment. The figure which shows the environment where the GNSS signal receiver 101 which concerns on Embodiment 1 receives a navigation message. FIG. 4 is a diagram showing composition of navigation messages in the first embodiment. The figure which implement | achieves each function of the signal receiver 100 which concerns on Embodiment 1 with hardware. FIG. 6 is a diagram illustrating a configuration example of a signal reception device 200 according to Embodiment 2. The figure which shows the bit information in the navigation message which concerns on Embodiment 2. FIG. Health confirmation processing according to the second embodiment. 10 is a flowchart in the synthesis processing unit 111 according to the second embodiment.

Embodiment 1 FIG.
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments to which the present invention is applied will be described in detail based on the drawings. In this embodiment, a navigation message, which is a message broadcast from a plurality of GNSS satellites 1 as shown in FIG. 1, is received by a GNSS signal receiving apparatus 100, and a positioning calculation is performed using the GNSS signal. It is applied to the satellite positioning system to obtain the result. The present invention is not limited to the embodiments. In each figure, the same code | symbol shows the same or an equivalent part.

The GNSS positioning signal is modulated by a BPSK (Binary Phase Shift Keying) modulation method according to the bit value of the navigation message. A GNSS receiver receives a GNSS positioning signal, demodulates it, acquires navigation messages, and uses them for positioning calculations.

The L1C / A signal, which is one of the GPS signals, includes a navigation message called LNAV (Lateral Navigation). The navigation message is binary and consists of an ephemeris and an almanac. The navigation message is transmitted at 50 bps, and one bit is 20 ms. The navigation message is composed of units called frames, and one frame is composed of five sets of subframes. Each subframe has a size of 300 bits. As shown in FIG. 2, subframes 1 to 3 include ephemeris, which is information unique to each satellite, and the same information is repeatedly transmitted for a certain period. On the other hand, the subframes 4 and 5 include information common to all satellites called almanac. Since almanac has a huge amount of data, it is contained in pages 1 to 25 of subframes 4 and 5 separately.

Subframes are transmitted in order from 1, and when transmission of subframe 5 is completed, transmission of subframe 1 starts again. That is, the same information appears once every 30 seconds for ephemeris and once every 12 minutes and 30 seconds for almanac.

Similarly, the GPS signal L2C signal includes a navigation message called CNAV (Civil Navigation). Like LNAV, the navigation message is composed of binary ephemeris and almanac. CNAV, which is a navigation message for the L2C signal, is 25 bps data, but is transmitted after convolutional coding at a coding rate of 1/2, so the symbol rate is 50 sps, and one symbol is 20 ms. The CNAV navigation message is composed of units called messages, and has the structure shown in FIG. The message has a total size of 300 bits including 276 data bits and 24 check bits. This navigation message is transmitted in 6 seconds by L2C signal. The transmission pattern differs for each satellite and signal. The message is classified by 6 bits added to the PRN (Pseudo Random Noise) number (satellite number) of each frame called message type ID (Identification).

The E1 signal of the Galileo signal, which is a kind of GNSS satellite, includes a navigation message called I / NAV. Like LNAV and CNAV, the navigation message is binary and consists of ephemeris and almanac. As in CNAV, since transmission is performed after convolutional coding at a coding rate of 1/2, the symbol rate is 50 sps (symbol per second), and one symbol is 20 ms. The I / NAV navigation message is composed of units called pages, and one page is further divided into two page parts. Each page part has a configuration shown in FIG. The page part has a size of 120 bits in total including data bits and 24 check bits. The feature is that the data bits straddle page part 1 and page part 2.

As described above, although the structure (data format) of the navigation message varies depending on the type of satellite and the type of signal, the information included is ephemeris and almanac. The signal formats and numerical values shown in FIGS. 2 to 4 are examples of the signal format to which the present invention is applied. The present invention is not limited to this signal format, and is applied to various signal formats. Can do.

Moreover, as a feature of the navigation message, the same information is included for a certain period of time if the data format is the same. The GNSS satellite has a fixed data format order.

As shown in FIG. 5, even if the order of the data formats transmitted by the two GNSS satellites is different, the same information is included if the data formats are the same. However, when the navigation message is updated, that is, when information called a data set is changed, the content of the information included in the same data format may change. GNSS satellites are equipped with atomic clocks, and the timing of data set changes does not shift between satellites.

The present invention is based on the feature that the ephemeris and almanac, which are information of the navigation message, are based on the feature that the own satellite repeatedly broadcasts for a certain period of time, and a plurality of satellites broadcast the same information. It can be applied when demodulating navigation messages of GNSS signals broadcast from GNSS satellites such as GPS, QZSS (Quasi Zenith Satellite System), GLONASS (GLObal NAvigation Satellite System) and Galileo. Show.

FIG. 6 is a diagram illustrating a configuration example of the GNSS signal receiving apparatus 100 according to the first embodiment of the present invention. As shown in FIG. 6, the signal receiving apparatus 100 according to the present embodiment includes an antenna 101 that receives GNSS signals from the GNSS satellite 1 and the GNSS satellite 2, and a navigation message that is a message included in the signal received by the antenna 101. Based on the parameters read by the parameter identification unit 105, the parameter identification unit 105 that reads parameters such as identification numbers representing the characteristics of the navigation message from the navigation message extracted by the extraction unit 120, It is determined whether or not to synthesize a message included in a signal from the satellite of the satellite, and when it is determined to synthesize, a synthesizer 121 that synthesizes the message, and a positioning calculator 108 that performs a positioning calculation using the synthesized navigation message And an output unit 109 for outputting a positioning calculation result.

Here, the extraction unit 120 adjusts the gain for each received signal of each satellite, converts it into a baseband signal and performs AD (Analog-to-Digital) conversion, and each satellite. Acquisition and tracking unit 103 for capturing and tracking the carrier and code phase of the GNSS signal, and demodulation for decoding the navigation messages of

GNSS satellites

1 and 2 by performing frame synchronization and error correction based on the signal acquisition and tracking results The unit 104 is provided. The synthesizing unit 121 includes a synthesis processing unit 106 that synthesizes navigation messages that can be synthesized based on the identification number of the navigation message, and a storage unit 107 that stores the navigation message synthesized by the synthesis processing unit.

In this example, an example of a configuration for receiving GNSS signals of two GNSS satellites has been shown, but a configuration in which the number of received satellites and the types of signals are further increased may be used.

Next, the operation will be described. The GNSS signal received by the antenna 101 is output to the RF processing unit 102, and the reception signal converted into the baseband by the RF processing unit 102 is output to the signal acquisition / tracking unit 103 after receiving filter processing. The signal acquisition / tracking unit 103 performs correlation processing on the received signal and the reference signal to acquire and track the carrier phase and the code phase, and obtains the tracking result (correlation processing result) from the demodulation unit 104 and the positioning calculation unit 108. Output to. The demodulator 104 performs error correction on the tracking result using a Viterbi decoder, an LDPC (low-density parity-check code) decoder, etc., then searches for a preamble and performs subframe and page synchronization processing. The received signal after synchronization is subjected to parity and CRC (Cyclic Redundancy Code) error detection, processed as a navigation message in accordance with a predetermined data format, and output to the parameter identifying unit 105. As shown in FIG. 7, the parameter identification unit 105 reads bits in the navigation message from the navigation message and determines an identification number that is a parameter for determining the data format (S71). Here, the identification number includes an index that can identify whether the data format is ephemeris or almanac. Similarly, the data set bit in the navigation message is read as a parameter (S72), and the data set is updated, that is, whether the navigation message has been updated since the last reception (S73). The set flag is set to 0 (S74), and if there is an update, the data set flag is set to 1 (S75) and output to the synthesis processing unit 106.

As shown in FIG. 8, the composition processing unit 106 confirms that the data set is the same and the navigation message is not updated (S81), and is stored in the storage unit 107 having the same identification number as the input navigation message. It is confirmed whether there is a navigation message (S82). Thereafter, in the case of a navigation message related to time information (S83), the time information of the stored navigation message is incremented (S84), and time adjustment is performed with the received navigation message. Thereafter, the received navigation message is synthesized with a navigation message of the same data format. Here, the synthesis method is switched depending on whether the data to be synthesized is ephemeris or almanac (S85). If the data to be synthesized is almanac, data of the same data format is synthesized regardless of the transmitted satellite (S86), and if it is ephemeris, the ephemeris transmitted from the same satellite is synthesized (S87). Thereafter, the data is output to the storage unit 107 and the positioning calculation unit 108. If the navigation message is updated, the corresponding navigation message is deleted from the storage unit 107 (S88), data collection is started again, and the navigation message is saved (S89). The storage unit 107 stores an almanac for each signal and transmitted satellite, and the ephemeris stores each signal. The positioning calculation unit 108 calculates a pseudo distance and the like based on the correlation processing result of the signal acquisition / tracking unit 103 and the navigation message from the synthesis processing unit 106, and performs positioning calculation. Finally, the positioning unit outputs the positioning calculation result to the outside.

According to the above-described operation, since almanac is a packet that can be received from a plurality of satellites, instead of synthesizing the information of one satellite as in Patent Document 1 and Patent Document 2, it receives signals from a plurality of satellites, and The performance can be improved in a short time. In the prior art described in Patent Document 1, a subframe is output only when all of the errors-free words are gathered. However, in an environment with many errors, a correct word cannot be received and a subframe cannot be output in one direction. There is a problem in that the initial fixing time (TTFF: Time To First Fix) is increased. On the other hand, in the invention shown in this embodiment, the reception quality can be improved by combining signals from a plurality of satellites, and the initial fixed time (TTFF: Time To First Fix) can be increased. Can be suppressed.

Next, as an example, the operations of the parameter identification unit 105, the synthesis processing unit 106, and the storage unit 107 will be specifically described using an L1C / A signal that is one of GPS signals. Assume that the GNSS signal receiver 101 receives navigation messages # 1 and # 2 from two GNSS satellites 1 as shown in FIG. Navigation message # 1 is received in order from subframe 3, and navigation message # 2 is received in order from subframe 1. It is assumed that the data set is updated in the second subframe 3 of the navigation message # 1. The storage unit 107 of the signal receiving apparatus 100 stores the ephemeris of navigation message # 2 and the almanac from pages 1 to 25, but the ephemeris of navigation message # 1 is not stored. It is assumed that the navigation message # 1 and the navigation message stored in the storage unit 107 have low received power, and an error bit exists in page 2 of subframe 4 of the navigation message.

First, the parameter identification unit 105 sequentially reads the satellite number and the subframe ID as parameters in units of subframes from the received navigation message # 1 and navigation message # 2. By reading the subframe ID, it can be determined which of the subframes 1-5 is applicable. Further, since the L1C / A signal restarts from subframe 1 at the beginning / end of the week, the subframe ID can be similarly determined using the Z count. In this example, satellite number 1 and subframe ID 3, satellite number 2 and subframe ID 1 are read. Next, the update of the data set is confirmed. Since IODE (Issue of Data, Ephemeris) contained in subframe 1 is the same value as LSB (Least Significant Bit) 8 bits of 10-bit IODC (Issue of Data, Clock) in the same data set, IODE and IODC are confirmed. By doing so, the identity of the data set can be determined. In this example, since the data set is not updated, the data set flag is set to “0”.

The synthesis processing unit 106 processes the navigation message received from each satellite. First, since both the navigation messages # 1 and # 2 have the data set flag “0”, it is confirmed whether the navigation message of the same data format is stored in the storage unit 107. The storage unit 107 has the subframe ID 3 of the satellite 1 in it. Since it is not saved, the received navigation message # 1 is newly saved. Since the subframe ID1 of the navigation message # 2 is already stored in the storage unit 107, the synthesis process is started. In the navigation message of the L1C / A signal, since subframes 1 to 3 are information unique to the satellite, subframes 1 to 3 having the same satellite number are combined. In subframes 4 and 5, all the satellites broadcast the same information, so the navigation messages received from a plurality of satellites are combined. This is done each time a navigation message is received. Further, since the data set is updated from page 3 of subframe 4 of navigation message # 1 and subframe 2 of navigation message # 2, the data set flag becomes “1”, and the storage unit is cleared.

By performing such processing, as shown in FIG. 10, even if there is an error bit in the navigation message of the storage unit 107 and the navigation message # 1, the result of the navigation message received by the navigation message # 2 is obtained. By adding, the likelihood of the navigation message increases, and it is possible to correct bit errors.

As shown in FIG. 11, in order to implement each function of the signal receiving apparatus 100 of the present invention with hardware, a circuit, a programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or A combination of these applies. The various functions may be realized separately by different processing circuits, or may be realized together. When each function of the signal receiving device 100 is realized by software, it is described as a program and stored in a memory.

A part of each function of the signal receiving apparatus 100 may be realized by hardware and a part may be realized by software. For example, RF processing and signal acquisition / tracking may be implemented by a processing circuit, and demodulation and positioning calculation may be described as a program, stored in a memory, and operated by a CPU (Central Processing Unit).

As described above, the signal receiving apparatus 100 according to the present invention receives GNSS signals broadcast from a plurality of satellites, determines whether the received signal belongs to an ephemeris or an almanac, and switches the synthesis method. Thus, it is possible to obtain both the diversity effect depending on the time and the number of satellites. Obtaining a diversity effect leads to obtaining a navigation message with few errors, and indicates that positioning using the result can be performed stably, and thus has an effect of improving positioning accuracy.

As described above, the signal receiving apparatus 100 according to the first embodiment includes the antenna 101 that receives signals from the plurality of satellites 1, the extraction unit 120 that extracts messages included in the signals received by the antenna 101, When determining whether to combine messages included in signals from a plurality of satellites 1 based on the parameters read by the parameter identification unit 105 that reads parameters from the message and the parameter identification unit 105 And a combining unit 121 that combines the messages. With this configuration, an appropriate combining method can be used according to the type of message, and a diversity effect based on time and the number of satellites can be obtained. As a result, a message contained in a signal broadcast from a satellite such as a GNSS satellite can be correctly received within a predetermined time regardless of the type of message.

Thus, in the signal receiving apparatus 100 according to the first embodiment, the signals from the plurality of satellites 1 are signals broadcast from the global navigation satellite system (GNSS), the message is a navigation message, and the combining unit A positioning calculation unit 108 that performs a positioning calculation using the message synthesized in 121 is provided. With this configuration, it is possible to correctly receive a message included in a signal broadcast from GNSS and perform highly accurate positioning. *

Further, in the signal receiving apparatus 100 according to the first embodiment, the parameter read by the parameter identifying unit 105 includes an index indicating whether the navigation message is an ephemeris or an almanac. With this configuration, the signal receiving apparatus 100 can recognize whether the received message is an ephemeris or an almanac, and can correctly receive the message by using an appropriate synthesis method according to the type of the message. it can.

In the signal receiving apparatus 100 according to the first embodiment, the extraction unit 120 includes a tracking unit such as a signal capturing / tracking unit 103 that tracks signals from the plurality of satellites 1, and the positioning calculation unit 108 includes the tracking unit. The positioning calculation is performed using the tracking result obtained in the above. With this configuration, it is possible to perform more accurate positioning calculation using the tracking result.

Further, in the signal receiving apparatus 100 according to the first embodiment, the parameter is an identification number representing a data format of the message. With this configuration,
The combining method in the combining unit 121 can be changed according to the data format of the message, and an appropriate diversity effect can be obtained according to the message.

In the signal receiving apparatus 100 according to the first embodiment, the parameter identifying unit 105 determines whether there is an update of the data set of the message, and the synthesizing unit 121 performs the updating at the parameter identifying unit 105. When it is determined, the storage unit 107 is provided for clearing a stored message used for synthesis. With this configuration, when there is an update of a data set, the message is not combined, and data mixing caused by combining between different data sets can be avoided.

Embodiment 2. FIG.
In the present embodiment, a health check unit that determines the health status of the satellite is added to the configuration of the first embodiment, so that the synthesis method is switched based on the health status of the satellite. Describes how to prevent.

FIG. 12 is a diagram showing the configuration of the signal receiving apparatus 200 in this embodiment. The difference from the signal receiving apparatus 100 in FIG. 6 is that there is a health confirmation unit 110 that determines the health state of the satellite. Other components are the same as those in FIG.

Next, the operation will be described. The process up to the point where the parameter identification unit 105 determines the data format of the navigation message and the identity of the data set is the same as in the first embodiment. As shown in FIG. 13, when each GNSS satellite broadcasts a signal whose output level has decreased due to phase noise, the attitude of the satellite, etc., the status is notified by an item called SV (Space Vehicle) Health in the navigation message. ing. Therefore, as shown in FIG. 14, the health confirmation unit 110 reads bits in the navigation message to grasp the health state of each GNSS signal (S140).

The synthesis processing unit 111 performs the same processing until a data format that can be synthesized is called from the storage unit 107 as shown in FIG. 15, but the health state is based on the health information confirmed by the health confirmation unit 110 at the time of synthesis. It is determined whether or not it is good (S151, S154). If the health condition is good, the bits are synthesized as in the first embodiment (S152, S155), and the signal with poor health condition is weighted. Are switched to prevent the erroneous bit from being added to the synthesized navigation message (S153, S156). In this example, weighted synthesis is performed, but it may be possible to select a process in which navigation messages with poor health are not synthesized. Subsequent operations are the same as those in the first embodiment.

As described above, according to the signal receiving device 200 of the present invention, the combined navigation by reading the SV Health included in the navigation message and switching the synthesis method such as weighted synthesis or not synthesis of the navigation message with poor health. Since it is configured to prevent erroneous bits from being added to the message, it is possible to realize the signal receiving device 200 that is resistant to transmission path fluctuations between the satellite and the receiver.

As described above, the signal receiving apparatus 200 according to the second embodiment includes the health confirmation unit 110 that determines the health states of the plurality of satellites 1, and the combining unit 122 confirms the health states of the satellites confirmed by the health confirmation unit 110. Based on the above, a method for combining messages included in signals from a plurality of satellites 1 is determined. With this configuration, it is possible to avoid the addition of erroneous bits to the synthesized navigation message, and it is possible to realize the signal receiving apparatus 200 that is resistant to transmission path fluctuations between the satellite and the receiver.

In the first and second embodiments, the present invention has been described by taking the case of the GNSS satellite as an example. However, the present invention is not limited to the GNSS satellite and can be generally applied to signals from the satellite. Further, although an example of identifying ephemeris and almanac data has been described, the present invention is not limited to this example, and can be applied to different types of messages.

1: GNSS satellite, 100, 200: signal receiving device, 101: antenna, 102: RF processing unit, 103: signal acquisition / tracking unit, 104: demodulation unit, 105: parameter identification unit, 106: synthesis processing unit, 107: Storage unit, 108: positioning calculation unit, 109: output unit, 110: health confirmation unit, 111: synthesis processing unit, 120: extraction unit, 121, 122: synthesis unit

Claims

An antenna for receiving signals from multiple satellites;
An extraction unit for extracting a message included in the signal received by the antenna;
A parameter identification unit for reading parameters from the message;
Based on the parameters read by the parameter identification unit, it is determined whether or not to synthesize messages included in signals from the plurality of satellites.
A signal receiving apparatus comprising:
The signal receiving apparatus according to claim 1, wherein the parameter is an identification number representing a data format of the message.
The signal is a signal broadcast from the Earth Navigation Satellite System,
The message is a navigation message;
The signal receiving apparatus according to claim 1, further comprising a positioning calculation unit that performs a positioning calculation using the message combined by the combining unit.
The signal reception apparatus according to claim 3, wherein the parameter includes an index indicating whether the navigation message is an ephemeris or an almanac.
The extraction unit includes a tracking unit that tracks signals from the plurality of satellites,
The signal receiving apparatus according to claim 3 or 4, wherein the positioning calculation unit performs a positioning calculation using a tracking result obtained by the tracking unit.
The parameter identification unit determines whether there is an update of the data set of the message,
The said synthetic | combination part is provided with the memory | storage part which clears the preservation | save message used for a synthesis | combination, when it determines with the said parameter identification part having the update of the said data set. The signal receiving device described.
A health check unit for determining the health status of the plurality of satellites;
The said synthesis | combination part determines the method to synthesize | combine the message contained in the signal from these satellites based on the health state confirmed by the said health confirmation part. A signal receiving apparatus according to claim 1.
Receiving signals from a plurality of satellites;
An extraction step of extracting a message included in the signal received by the antenna;
A reading step of reading parameters from the message extracted in the extraction step;
Based on the parameters read in the reading step, it is determined whether to synthesize messages included in signals from the plurality of satellites.
A signal receiving method comprising: