METHOD AND APPARATUS FOR ESTIMATING CARRIER PHASE OFFSET IN SATELLITE NAVIGATION SYSTEM

A method of a terminal may comprise: receiving satellite navigation augmentation information including phase offset correction information for a pair of two carriers among satellite navigation signals transmitted by each of satellites of a global navigation satellite system through multiple carriers; receiving satellite navigation signals from each of the satellites through the multiple carriers; calculating parameters for estimating a location of the terminal using the received satellite navigation signals; correcting the parameters based on the phase offset correction information for the pair of two carriers; and estimating the location of the terminal using the corrected parameters.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean Patent Application No. 10-2023-0047008, filed on Apr. 10, 2023, with the Korean Intellectual Property Office (KIPO), the entire contents of which are hereby incorporated by reference.

BACKGROUND

1. Technical Field

Exemplary embodiments of the present disclosure relate to a technique for carrier offset estimation in a wireless communication system, and more specifically, to a technique for estimating a phase offset of a carrier in a satellite navigation system.

2. Related Art

In a satellite navigation system (e.g., Global Navigation Satellite System, GNSS), a receiver estimates its location by receiving satellite navigation signals transmitted from a plurality of satellites. Various accuracy augmentation methods for the GNSS receiver, such as Differential GNSS (DGNSS) and Precise Point Positioning (PPP), have been proposed and utilized to achieve positioning accuracy at the level of several centimeters to several tens of centimeters. Within the context of augmenting positioning accuracy, key factors include the utilization of augmentation information and the estimation of carrier phase offsets of the navigation signals. Here, the augmentation information may refer to satellite navigation augmentation information.

SUMMARY

Exemplary embodiments of the present disclosure are directed to providing a method and an apparatus for augmenting accuracy of carrier phase offsets in a satellite navigation system.

According to a first exemplary embodiment of the present disclosure, a method of a terminal may comprise: receiving satellite navigation augmentation information including phase offset correction information for a pair of two carriers among satellite navigation signals transmitted by each of satellites of a global navigation satellite system (GNSS) through multiple carriers; receiving satellite navigation signals from each of the satellites through the multiple carriers; calculating parameters for estimating a location of the terminal using the received satellite navigation signals; correcting the parameters based on the phase offset correction information for the pair of two carriers; and estimating the location of the terminal using the corrected parameters.

The satellite navigation augmentation information may be information transmitted by a station generating the satellite navigation augmentation information through at least one of the satellites, information transmitted by the station through the Internet, a mobile communication network, or a separate network, or information directly transmitted by the station.

The phase offset correction information for the pair of two carriers may be information on a phase difference between the two carriers constituting the pair.

The parameters may be corrected using weights between the multiple carriers when correcting the parameters.

The weights between the multiple carriers may be received as being included in the satellite navigation augmentation information.

The weights between the multiple carriers may be determined based on information of received signal strengths of the respective multiple carriers.

The method may further comprise updating previously stored satellite navigation augmentation information when the satellite navigation augmentation information is received.

According to a second exemplary embodiment of the present disclosure, a terminal may comprise a processor, and the processor may cause the terminal to perform: receiving satellite navigation augmentation information including phase offset correction information for a pair of two carriers among satellite navigation signals transmitted by each of satellites of a global navigation satellite system (GNSS) through multiple carriers; receiving satellite navigation signals from each of the satellites through the multiple carriers; calculating parameters for estimating a location of the terminal using the received satellite navigation signals; correcting the parameters based on the phase offset correction information for the pair of two carriers; and estimating the location of the terminal using the corrected parameters.

The satellite navigation augmentation information may be information transmitted by a station generating the satellite navigation augmentation information through at least one of the satellites, information transmitted by the station through the Internet, a mobile communication network, or a separate network, or information directly transmitted by the station.

The phase offset correction information for the pair of two carriers may be information on a phase difference between the two carriers constituting the pair.

The processor may further cause the terminal to correct the parameters using weights between the multiple carriers when correcting the parameters.

The weights between the multiple carriers may be received as being included in the satellite navigation augmentation information.

The weights between the multiple carriers may be determined based on information of received signal strengths of the respective multiple carriers.

The processor may further cause the terminal to update previously stored satellite navigation augmentation information when the satellite navigation augmentation information is received.

According to a third exemplary embodiment of the present disclosure, a method of a station in a global navigation satellite system (GNSS) may comprise: receiving satellite navigation signals through multiple carriers from each of satellites of the GNSS; calculating phase offset correction information for a pair of two carriers among the satellite navigation signals received through the multiple carriers; generating satellite navigation augmentation information including the calculated phase offset correction information; and broadcasting the satellite navigation augmentation information based on a transmission period of the satellite navigation augmentation information.

The satellite navigation augmentation information may be broadcasted through at least one of the satellites, broadcasted through the Internet, a mobile communication network, or a separate network, or broadcasted directly by the station.

The phase offset correction information for the pair of two carriers may be information on a phase difference between the two carriers constituting the pair.

According to exemplary embodiments of the present disclosure, a station (e.g., augmentation station) of a satellite navigation system may generate and broadcast satellite navigation augmentation information, which includes phase differences among satellite navigation signals transmitted through multiple carriers. As a result, a terminal can receive the satellite navigation augmentation information from the station or a satellite, including the phase differences, and utilize it to correct the satellite navigation signals, allowing for a more accurate estimation of the terminal's location.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments of the present disclosure are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing exemplary embodiments of the present disclosure. Thus, exemplary embodiments of the present disclosure may be embodied in many alternate forms and should not be construed as limited to exemplary embodiments of the present disclosure set forth herein.

A communication system to which exemplary embodiments according to the present disclosure are applied will be described. The communication system to which the exemplary embodiments according to the present disclosure are applied is not limited to the contents described below, and the exemplary embodiments according to the present disclosure may be applied to various communication systems. Here, the communication system may have the same meaning as a communication network.

Throughout the present disclosure, a terminal may refer to a mobile station, mobile terminal, subscriber station, portable subscriber station, user equipment, access terminal, or the like, and may include all or a part of functions of the terminal, mobile station, mobile terminal, subscriber station, mobile subscriber station, user equipment, access terminal, or the like.

Here, a desktop computer, laptop computer, tablet PC, wireless phone, mobile phone, smart phone, smart watch, smart glass, e-book reader, portable multimedia player (PMP), portable game console, navigation device, digital camera, digital multimedia broadcasting (DMB) player, digital audio recorder, digital audio player, digital picture recorder, digital picture player, digital video recorder, digital video player, or the like having communication capability may be used as the terminal.

Hereinafter, preferred exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. In describing the present disclosure, in order to facilitate an overall understanding, the same reference numerals are used for the same elements in the drawings, and duplicate descriptions for the same elements are omitted.

FIG.1is a conceptual diagram illustrating an exemplary embodiment of a satellite navigation system according to the present disclosure.

Referring toFIG.1, a satellite navigation system (e.g., GNSS) may include a satellite110and an augmentation service station120and a terminal130located on the ground. InFIG.1, only one satellite110is illustrated for convenience of description, but the satellite navigation system may include a plurality of satellites. Accordingly, it should be noted thatFIG.1is an example for describing a case in which one satellite transmits one or more carriers. In addition, the augmentation service station120may be a configuration for broadcasting augmentation information according to the present disclosure, and may be referred to as an ‘augmentation station’. In the following description, it will be described as a ‘station’ or ‘augmentation station’ for convenience of description.

The satellite110may transmit satellite navigation signals101and102using multiple carriers. InFIG.1, the satellite navigation signals101and102may be transmitted through different carriers. For example, the first satellite navigation signal101may be a satellite navigation signal transmitted (or broadcasted) to a configured area through a first carrier having a first frequency f1, and the second satellite navigation signal102may be a satellite navigation signal transmitted (or broadcasted) to the same terrestrial area as the area for the first satellite navigation signal or an area at least partially overlapping the area for the first satellite navigation signal through a second carrier having a second frequency f2.

In the example ofFIG.1, only two carriers are illustrated as f1and f2due to drawing limitations, but the satellite110may transmit satellite navigation signals through three or more carriers. In addition, each of the satellite navigation signals101and102may be transmitted after being spread by a spreading code for identifying the satellite. Accordingly, satellite navigation signals transmitted by each of a plurality of satellites may be identified by different spreading codes.

The augmentation station120may be installed at a specific location on the ground. As another example, when the augmentation station120is installed in a moving object, for example, a vehicle, it may stay in one location for a long time. The augmentation station120may generate satellite navigation augmentation information according to the present disclosure. In the following description, for convenience of description, it is assumed that the augmentation station120is a terrestrial station installed in a specific location on the ground.

The augmentation station120may receive the satellite navigation signals101and102from the satellite110through multiple carriers. The augmentation station120may generate satellite navigation augmentation information according to the present disclosure by using the satellite navigation signals101and102received at a predetermined time period. It is assumed that the augmentation station120knows its exact location. In addition, since the augmentation station120is located in a specific fixed location or is located in a specific location for a long time, it can receive signals more reliably than the moving terminal130. Accordingly, when compared with the terminal130, the augmentation station120may generate more accurate augmentation information. For example, when the terminal130moves at a high speed or at a low speed, a Doppler effect may be generated based on the movement speed of the terminal130. In addition, when vibration occurs due to movement of the terminal130, phase noises due to a shock may occur in an oscillator inside the terminal130. On the other hand, since the augmentation station120is located in a specific location, it may be free from such the phenomenon. Accordingly, satellite navigation augmentation information generated by the augmentation station120may be generally more accurate than information obtained by the terminal130for position estimation (i.e., positioning).

The augmentation station120may transmit (or broadcast) the generated satellite navigation augmentation information to the terminal130at a predetermined time period. For example, the augmentation station120may transmit (or broadcast) the generated satellite navigation augmentation information to the terminal130through a predetermined network140and/or the satellite110. For example, the satellite navigation augmentation information generated by the augmentation station120may be provided to the terminal130through the network140as shown by reference numerals151and152. As another example, the satellite navigation augmentation information generated by the augmentation station120may be provided to the terminal130through the satellite110as shown by reference numerals153and154. As yet another example, the satellite navigation augmentation information generated by the augmentation station120may be directly transmitted from the augmentation station120to the terminal130as shown by reference numeral155.

The network140illustrated inFIG.1may be a network of various types. For example, the network140may be a wireless Internet such as wireless fidelity (WiFi), portable Internet such as wireless broadband internet (WiBro) or world interoperability for microwave access (WiMax), 2G mobile network such as global system for mobile communication (GSM) or code division multiple access (CDMA), 3G mobile network such as wideband code division multiple access (WCDMA) or CDMA2000, 3.5G mobile network such as high speed downlink packet access (HSDPA) or high speed uplink packet access (HSUPA), 4G mobile communication network such as a long term evolution (LTE) network or an LTE-Advanced network, and 5G mobile communication network. As another example, the network140may be at least one of various networks such as a wired IP network using the Internet protocol and/or terrestrial Internet.

The terminal130may be any type of terminal capable of determining the location of the terminal130by receiving the satellite navigation signals101and102and satellite navigation augmentation information according to the present disclosure. The terminal130according to the present disclosure may receive the satellite navigation augmentation information directly from the augmentation station120, through the network140, or through the satellite110. In the present disclosure, the method for the augmentation station120to transmit such satellite navigation augmentation information is not particularly limited.

FIG.2is a block diagram of an augmentation station according to an exemplary embodiment of the present disclosure in a satellite navigation system.

Referring toFIG.2, the augmentation station may include a processor210, memory220, input/output interface230, satellite signal transceiver240, network transceiver250, and wireless communication device260. In addition, the respective components210,220,230,240,250, and260of the augmentation station may perform communications as being connected by a bus270. However, the components210to270of the augmentation station illustrated inFIG.2are shown merely as an exemplary embodiment. In other words, the augmentation station may further include additional components in addition to the components illustrated inFIG.2. For example, the augmentation station may further include various devices such as a separate storage device, sensor(s), and separate output device.

The processor210may have one or more cores. As another example, the processor210may be implemented as a complex processor including two or more processors. Specifically, the processor may be configured to include at least one of an application processor (AP) operating as a central processing unit (CPU), communication processor (CP) performing transmission/reception of satellite signals, or graphics processing unit (GPU) for providing an operating state of the augmentation station to a user or operator.

The processor210may execute program commands stored in the memory220. For example, the processor210may execute program commands stored in the memory220to control operations of the augmentation station, output of the operating state of the augmentation station to a user or operator, and generation and transmission of satellite navigation augmentation information according to the present disclosure. In other words, the processor210may perform control of generation of satellite navigation augmentation information and transmission of the generated satellite navigation augmentation information according to the present disclosure, as well as various controls to be performed by the augmentation station120.

The memory220may include at least one of volatile storage media and non-volatile storage media. The memory220may include at least one of read only memory (ROM), random access memory (RAM), or hard disk. The memory220may store the program commands to be executed by the processor210and may temporarily store data generated when the program commands are executed by the processor210. Also, the memory220may have a region for storing satellite navigation augmentation information according to the present disclosure.

The input/output interface230may include an input interface and an output interface. The input interface may be connected to various types of input devices, and may receive various commands or information input by a user or operator of the augmentation station and provide the received information to the processor210. In addition, the output interface may be connected to various types of output devices, and may provide a user or operator of the augmentation station120with state information of the augmentation station, visual and/or audio information for input, and the like.

The satellite signal transceiver240may include antenna(s) capable of receiving satellite navigation signals transmitted by a plurality of satellites through multiple carriers. In addition, the satellite signal transceiver240may have a configuration for converting multiple carriers of a radio frequency (RF) band, which are received through the antenna(s), into a digital intermediate frequency (IF) band or converting signals in the digital IF band into baseband signals. The satellite signal transceiver240may include a configuration for generating satellite navigation augmentation information according to the present disclosure using the baseband signals or provide the baseband signals to the processor210through the bus270. The satellite signal transceiver240may include a configuration for converting baseband signals to be transmitted to a satellite into digital IF band signals and RF band signals.

In addition, since the augmentation station120stays at a specific location for a long time when it is fixedly installed at a specific place on the ground or located on a moving object, the satellite signal transceiver240can reliably receive satellite navigation signals from a plurality of satellites through multiple carriers.

The network transceiver250may include a configuration for transmitting data to the network140described inFIG.1. For example, when the network140is a mobile communication network, the network transceiver250may provide an interface for communication with the mobile communication network in a wired or wireless communication scheme. When the network140is an IP-based Internet network, the network transceiver250may provide an interface for Internet communication.

[Generation and Broadcasting of Satellite Navigation Augmentation Information]

Hereinafter, methods of generating satellite navigation augmentation information and methods of broadcasting the generated satellite navigation augmentation information according to the present disclosure will be described with reference toFIGS.1and2.

Since the following description is based on the configuration of the satellite navigation system ofFIG.1, a case in which multiple carriers broadcasted by one satellite are received will be described. However, even when each of a plurality of satellites transmits multiple carriers, the augmentation station120may generate satellite navigation augmentation information according to the present disclosure in the same manner as the method of receiving multiple carriers broadcasted by one satellite.

Referring toFIG.1, the satellite110may generate the satellite navigation signals101and102. Then, the satellite110may spread the satellite navigation signals101and102using a specific spreading code assigned to the satellite, and then broadcast them through multiple carriers. Each of the augmentation station120and the terminal130located on the ground may receive the satellite navigation signals101and102broadcasted by the satellite110.

The satellite signal transceiver240of the augmentation station120may receive the satellite navigation signals101and102through antenna(s), and convert the received RF band signals into IF band signals of the IF band. In addition, the satellite signal transceiver240may convert the IF band signals into digital IF band signals or baseband signals. Since the satellite signal transceiver240receives multiple carriers, it is possible to obtain digital IF band or baseband signals for each carrier. The satellite signal transceiver240may provide the obtained digital IF band or baseband signals to the processor210. Each of the satellite navigation signals converted into digital signals may be expressed as in Equation 1 below.

In Equation 1, A denotes the size of the received satellite navigation signal, d (t) denotes a modulated signal of satellite navigation data, c (t) denotes a spreading code signal for satellite identification, and n (t) denotes a noise signal. In addition, t′ denotes a reception time offset, f′ denotes a frequency offset, and @ denotes a phase offset. In order to estimate the location of the receiver, that is, the augmentation station120, the three offsets (i.e., reception time offset, frequency offset, and phase offset) need to be accurately estimated.

In the present disclosure, a method for accurately estimating the phase offset among the three offsets will be described. Therefore, the satellite navigation augmentation information according to the present disclosure described hereinafter may include at least information on the phase offset.

Since only the phase offset is considered in the present disclosure, a signal transmitted through a carrier i excluding the modulated signal, spreading code, time offset, and frequency offset in Equation 1 may be briefly expressed as in Equation 2 below.

As described above, the satellite110may broadcast the satellite navigation signals using multiple carriers. Accordingly, the processor210of the augmentation station120may measure (or estimate) and obtain phase offsets of a plurality of carrier signals, that is, the multiple carriers. In addition, when a plurality of satellites broadcast satellite navigation signals using multiple carriers, the processor210of the augmentation station120may measure (or estimate) a phase offset of each of a plurality of carriers received from each of the plurality of satellites.

As described above with reference toFIGS.1and2, the augmentation station120may generally know its location. In detail, information on the location may be stored in the memory220of the augmentation station120. Therefore, the processor210of the augmentation station120may measure and obtain the phase offsets of the multiple carriers based on the location of the augmentation station120, which is read from the memory220, and/or other various information. In this case, as described above, since the augmentation station120can perform reliable estimation for a long time in a stationary state, it can generally obtain the phase offsets of the multiple carriers more accurately than the terminal130.

The processor210of the augmentation station120may calculate a difference between the phase offsets of several carriers (e.g., carrier i and carrier j) as shown in Equation 3 below.

The phase offsets in Equation 3 may be generated by combinations of pairs of two carriers based on the number of the multiple carriers. For example, when there are three carriers, the number of cases in which two carriers are selected from the three carriers may be three. As another example, when satellite navigation signals are transmitted through five carriers, the number of cases in which two carrier are selected from the five carriers may be ten.

Accordingly, the processor210may generate as many phase offsets as the number of cases in which carrier pairs each composed of two carriers can be selected based on the number of multiple carriers. The generated phase offsets may be included in the satellite navigation augmentation information as the phase offset correction information. In this case, the phase offset correction information may further include information on the pairs of the carriers. For example, assuming three carriers, a first carrier f1, a second carrier f2, and a third carrier3, the phase offset correction information may include information on three phase offsets and information on three pairs.(1) Information on the first carrier, the second carrier, and Δϕf1,f2(tn)(2) Information on the second carrier, the third carrier, and Δϕf2,f3(tn)(3) Information on the third carrier, the first carrier, and Δϕf3,f1(tn)

The processor210of the augmentation station120may generate satellite navigation augmentation information including at least information on the phase offsets, and broadcast it at predetermined time intervals. The broadcasting of the satellite navigation augmentation information may be performed through the network140or the satellite110, or the satellite navigation augmentation information may be directly broadcasted by the augmentation station120. In addition, the broadcasting of the satellite navigation augmentation information may be performed using all of the above-described methods or a combination of two or more among the above-described methods.

In this case, when the satellite navigation augmentation information is broadcasted through the satellite110, the processor210may control the satellite signal transceiver240to transmit, to the satellite110, the navigation satellite augmentation information and satellite broadcast control information for configuring the satellite110to transmit the satellite navigation augmentation information through all carriers for transmission of the satellite navigation signals. Here, the satellite broadcast configuration information may be information indicating the satellite110to broadcast specific information (e.g., satellite navigation augmentation information). When receiving the satellite broadcast configuration information configured such that satellite navigation augmentation information is transmitted through all satellite navigation signals, the satellite110may transmit the satellite navigation augmentation information through all carriers for transmission of the satellite navigation signals.

As another example, the processor210may configure the satellite broadcast configuration information such that the satellite navigation augmentation information is to be transmitted only through a specific representative carrier. In addition, the processor210may transmit, to the satellite110, the satellite broadcast configuration information and the satellite navigation augmentation information. The satellite110receiving the satellite broadcast configuration information and the satellite navigation augmentation information may transmit the satellite navigation augmentation information only through the representative carrier configured by the augmentation station120.

FIG.3is a flowchart of a method for an augmentation station to broadcast satellite navigation augmentation information according to an exemplary embodiment of the present disclosure.

FIG.3illustrates operations of the augmentation station120according to the present disclosure, and the operations of the augmentation station120will be described with reference to the components ofFIG.2.

In a step S300, the processor210of the augmentation station120may control the satellite signal transceiver240to receive the satellite navigation signals101and102from satellites through multiple carriers. In addition, the processor210may control the satellite signal transceiver240to convert the received signals into digital signals. In other words, the processor210may control the satellite signal transceiver240to convert received RF band signals into digital IF band signals or digital baseband signals.

In a step S302, the processor210of the augmentation station120may calculate phase offsets between the satellite navigation signals. The calculation may be performed as shown in Equation 3 described above. When there are three or more satellite navigation signals, three or more phase offsets may be calculated. As described above, the processor210may generate as many phase offsets as the number of cases in which carrier pairs each composed of two carriers can be selected based on the number of multiple carriers.

Since the augmentation station120is located in a specific location for a long time in a stationary state, the exact location of the augmentation station120may be known. In addition, since the augmentation station120stays in one location for a long time in a stationary state, the augmentation station120can receive multiple carriers more reliably. As such, the augmentation station120may reliably receive the multiple carriers and more accurately estimate the phase offsets thereof.

In a step S304, the processor210of the augmentation station120may generate phase offset correction information based on the calculated phase offsets. In this case, the generated phase offset correction information may include only the phase offsets or may further include information on carriers corresponding to the phase offsets. In addition, the processor210may store the generated phase offset correction information in the memory220.

In a step S306, the processor210of the augmentation station120may generate satellite navigation augmentation information including the phase offset correction information. The processor210may store the satellite navigation augmentation information generated in the above-described manner in the memory220.

In a step S308, the processor210of the augmentation station120may identify whether a transmission timing of the satellite navigation augmentation information arrives. The satellite navigation augmentation information may be broadcasted at preset time intervals, that is, at a predetermined time period. For example, a transmission period of the satellite navigation augmentation information may be assumed to be set in units of preset periods such as 10 seconds, 1 minute, or 5 minutes. In this case, the processor210may drive a timer corresponding to the predetermined period at a previous transmission timing to identify whether a transmission timing of the satellite navigation augmentation information arrives.

The processor210may proceed to a step S310when the transmission timing of satellite navigation augmentation information arrives, and may stand by when the transmission timing of satellite navigation augmentation information does not arrive.

In the step S310, the processor210of the augmentation station120may broadcast the satellite navigation augmentation information generated in the step S306and stored in the memory220. For example, the processor210may control the satellite signal transceiver240to transmit the satellite navigation augmentation information through satellites. As another example, the processor210may control the network transceiver250to transmit the satellite navigation augmentation information through the network140. As yet another example, the processor210may control the wireless communication device260to directly transmit the satellite navigation augmentation information to terminals. As yet another example, the processor210may control at least two or more of the satellite navigation augmentation information transmission methods described above to be performed together.

A time required for the terminal130to initially estimate a more accurate location may be determined based on the transmission timing, that is, the transmission periodicity, of the satellite navigation augmentation information described above. Accordingly, the transmission period of the satellite navigation augmentation information may be determined based on loads of the satellite110and/or the network140and an allowable time for initial accurate position estimation of the terminal130.

In the method described above, the case in which satellite navigation augmentation information is transmitted at a specific period has been described. However, when the satellite110is used to transmit the satellite navigation augmentation information, the augmentation station120may control the satellite110to transmit the satellite navigation augmentation information together with the satellite navigation signals. In this case, information on a timing at which the satellite navigation augmentation information is updated may be transmitted. Through this, the satellite navigation augmentation information may be transmitted based on information on a timing at which the satellite navigation augmentation information is provided to the satellite110or the timing at which the satellite navigation augmentation information is updated.

[Phase Offset Correction Using Satellite Navigation Augmentation Information]

FIG.4is a block diagram of a terminal according to the present disclosure.

The terminal illustrated inFIG.4may be one of various types of devices for performing navigation by receiving the satellite navigation signals. For example, the terminal may be in various forms, such as a receiving terminal exclusively for navigation, a notebook computer, a vehicle terminal, a smart phone, smart glasses, a smart watch, a ship or an aircraft, or an unmanned aerial vehicle (UAV). Therefore, it should be noted that components of the terminal disclosed inFIG.4exemplify only components required to describe the features of the present disclosure. In other words, additional components may be further included in addition to the components illustrated inFIG.4.

The terminal may include a processor410, a memory420, an input/output interface430, a satellite signal transceiver440, and a network transceiver450. In addition, the respective components410,420,430,440, and450of the terminal may perform communications with each other as being connected by a bus470.

The processor410may have one or more cores. As another example, the processor410may be implemented as a complex processor including two or more processors. Specifically, the processor may be configured to include at least one of an AP operating as a CPU, communication processor (CP) performing transmission/reception of satellite signals, or GPU for providing an operating state of the terminal to a user or operator.

The processor410may execute program commands stored in the memory420. For example, the processor410may execute program commands stored in the memory420to control operations of the terminal. For example, the processor410may control reception of satellite navigation signals, and measure (or estimate) a time offset, a frequency offset, and a phase offset from the received satellite navigation signal. In addition, the processor410may receive the satellite navigation augmentation information to obtain the phase offset correction information according to the present disclosure. The processor410may correct the phase offset of the satellite navigation signal based on the obtained phase offset correction information. In addition, the processor410may determine the location of the terminal through phase offset correction. In addition, the processor410may perform overall control for navigation of the terminal.

The memory420may include at least one of volatile storage media and non-volatile storage media. The memory420may include at least one of ROM, RAM, or hard disk. The memory420may store the program commands to be executed by the processor410and may temporarily store data generated when the program commands are executed by the processor410. Also, the memory220may have a region for storing satellite navigation augmentation information according to the present disclosure.

The input/output interface430may include an input interface and an output interface. The input interface may be connected to various types of input devices, and may receive various commands or information input by a user or operator of the augmentation station and provide the received information to the processor410. In addition, the output interface may be connected to various types of output devices, and may provide a user or operator of the terminal with state information of the terminal, visual and/or audio information for input, and the like.

The satellite signal receiver440may have a configuration of converting RF band signals of antenna(s) for receiving the satellite navigation signals through multiple carriers, which are transmitted by a plurality of satellites, into digital IF band signals of the IF band, or converting them into digital baseband signals. In addition, the satellite signal receiver440may provide the satellite navigation signal converted into the digital IF band signals or digital baseband signals of the IF band to the processor410. When the satellite transmits the satellite navigation augmentation information, the satellite signal receiver440may convert the satellite navigation augmentation information into a digital IF band signal or a digital baseband signal of the IF band and further provide the converted signal to the processor410.

When necessary, the satellite signal receiver440may further include a transmitter for transmitting signals to the satellite. In the present disclosure, since an operation of transmitting signals to the satellite by the terminal is not required, a configuration for transmitting signals to the satellite will not be further described.

The network transceiver450may include a configuration for communicating with the network140described inFIG.1. For example, when the network140is a mobile communication network, the network transceiver450may transmit and receive signals based on a mobile communication scheme corresponding to the mobile communication network. When the network140is an IP-based Internet network, the network transceiver450may provide an interface for Internet communication. The network transceiver450may be a component required when the augmentation station120according to the present disclosure transmits satellite navigation augmentation information through the network140. Accordingly, it should be noted that the network transceiver450is indicated by a dotted line inFIG.4.

The wireless communication device460may be configured to receive the satellite navigation augmentation information when the augmentation station120directly transmits the satellite navigation augmentation information based on a predetermined wireless communication scheme. The wireless communication device460may be a configuration required only when only the augmentation station120transmits the satellite navigation augmentation information. If, for example, the augmentation station120directly transmits the satellite navigation augmentation information and simultaneously transmits it through the satellite and/or network, the wireless communication device460may become an unnecessary configuration.

Hereinafter, a procedure for the terminal to obtain satellite navigation information based on satellite navigation augmentation information will be described with reference toFIGS.1and4.

The satellite signal receiver440of the terminal130may receive the satellite navigation signals101and102through antenna(s), and convert the received RF band signals into digital IF band signals of the digital IF band or digital baseband signals. The satellite navigation signals converted into the digital IF band signals or digital baseband signals may be expressed as in Equation 1 described above. The satellite signal receiver440may provide the received satellite navigation signals to the processor410.

In addition, the satellite signal receiver440or the network transceiver450of the terminal may receive the satellite navigation augmentation information transmitted from the augmentation station120according to the present disclosure. The satellite navigation augmentation information may include phase offset correction information as described above. The satellite signal receiver440or the network transceiver450may provide the obtained phase offset correction information or satellite navigation augmentation information including the phase offset correction information to the processor410.

The processor410may use the satellite navigation augmentation information transmitted by the augmentation station120in estimating the satellite navigation signals. In particular, the processor410according to the present disclosure may use the phase offset correction information included in the satellite navigation augmentation information in estimating phase offsets of multiple carrier signals received from satellites.

The processor410may estimate the phase offsets of the respective carrier signals, and calculate the location of the terminal using the estimated phase offsets. A detailed method of calculating the location of the terminal by the processor410is beyond the scope of the present disclosure, and thus will not be described in detail herein.

Then, the correction of the phase offset will be described.

The processor410may estimate a phase offset ϕi′(tn+τ) of a carrier i through which the satellite navigation signal is transmitted. The phase offset may be obtained by measuring a correlation between the carrier signal received at the terminal130from the satellite110and a carrier signal known to the terminal in advance. More specifically, the terminal may generate in advance the carrier i for transmitting the satellite navigation signal. Then, the terminal may measure a phase difference between the carrier i received from the satellite and the carrier i generated by itself. The processor410may obtain the measured phase difference, that is, the phase offset ϕi′(tn+τ).

The processor410may calculate a corrected phase offset as shown in Equation 4 below using the difference between the phase offset obtained through measurement and the offset of the carrier frequency obtained through the satellite navigation augmentation information.

In Equation 4, ϕ′i(tn+τ) denotes the phase offset estimated by the terminal for the satellite navigation signal i, Δϕ′j,i(tn) denotes the phase offset difference most recently broadcast by the augmentation station120, and ωj,idenotes a weight for the carrier j through which the satellite navigation signal is transmitted relative to the carrier I through which the satellite navigation signal to be estimated. When the weight ωj,iof the carrier j through which the satellite navigation signal is transmitted relative to the carrier i through which the satellite navigation signal to be estimated is transmitted is 1, the same weight may be applied to all signals.

Information on weights for the respective carriers through the satellite navigation signals are transmitted may be determined by the terminal itself, or may be transmitted as being included in augmentation information broadcasted by the satellite110or the augmentation station120. When the terminal determines the weights by itself, the determination may be made based on a received signal strength of the satellite navigation signal i and a received signal strength of the satellite navigation signal j.

As described above, the processor410of the terminal130may additionally correct the phase offset obtained from the signal received from the satellite by using the phase offset correction information in the satellite navigation augmentation information broadcasted by the augmentation station120, so that a more accurate correction on the phase offset can be performed. In other words, the satellite110may transmit the satellite navigation signals through multiple carriers, and the augmentation station120receiving the satellite navigation signals may broadcast the phase offset difference between each pair of the carriers to terminals by including it in the satellite navigation augmentation information. Then, the processor410of the terminal130receiving the satellite navigation signals and the satellite navigation augmentation information may more accurately estimate the location of the terminal130by additionally correcting the estimated satellite offset using the phase offset difference for each frequency. In other words, the processor410may more accurately calculate the location of the terminal by correcting the phase offset of the received satellite navigation signal.

A method of estimating the location of the receiver using phase offsets of a plurality of navigation signals received from a plurality of satellites may be performed in several known schemes, and a detailed description thereof will be omitted since it is out of the scope of the present disclosure.

FIG.5is a flowchart for a method of determining a location of a terminal according to an exemplary embodiment of the present disclosure.

FIG.5illustrates operations of the terminal130according to the present disclosure, and the operations of the terminal130will be described with reference to the components ofFIG.4.

In a step S500, the processor410of the terminal130may receive satellite navigation augmentation information and store it in the memory420. As described above, the satellite navigation augmentation information may be broadcast by the augmentation station120at a preconfigured periodicity. The satellite navigation augmentation information may be broadcasted through the satellite110or the network140or directly by the augmentation station120, or two or more among the satellite, network, or augmentation station may broadcast the satellite navigation augmentation information together. Accordingly, the processor410may control one of the satellite receiver440, the network transceiver450, or the wireless communication device460to receive the satellite navigation augmentation information based on the scheme in which the satellite navigation augmentation information is transmitted. When the satellite navigation augmentation information is transmitted from all of the satellite110, the network140, and the augmentation station120, the processor410may receive the satellite navigation augmentation information using only the satellite receiver440. This is because it is a method of saving power of the terminal130, and also because there is no need to receive the same information through multiple devices.

In addition, the processor410may be in a state in which the satellite navigation augmentation information is not received. The case when the satellite navigation augmentation information is not received may be a case when the power of the terminal130is immediately turned on from a power off state, or a case when the user requests to perform a navigation (or determination of the location of the terminal130) in a state in which execution of a navigation (or location determination) is not requested.

When the power of the terminal130is turned on from the power off state, the terminal130may not have performed the step S500because the terminal130has not received the satellite navigation augmentation information periodically broadcasted by the augmentation station120. In addition, if the user does not request navigation (or location determination) from the terminal130, the processor410may not receive satellite navigation augmentation information because it does not need to receive the satellite navigation information. Therefore, in this case, the step S500may not be performed. As another example, when the satellite navigation augmentation information is transmitted using the network400and the terminal130cannot communicate with the corresponding network400, the step S500may not be performed. InFIG.5, the step S500is indicated by a dotted line to confirm that it may or may not be performed in advance.

When receiving the satellite navigation augmentation information, the processor410may update satellite navigation augmentation information previously stored in the memory420with the newly received satellite navigation information. As another example, the processor410may accumulate and store the satellite navigation augmentation information by a predetermined number. Also, the processor410may determine that the satellite navigation augmentation information is not valid in certain cases. For example, if a timing at which the satellite navigation augmentation information is received is older than a preconfigured time from the current time, the processor410may determine that it is unreliable. The processor410may delete the satellite navigation augmentation information when it is determined that it is unreliable. The step S500may be preceded by at least one of the operations described above.

A step S510may be performed when the user instructs the terminal130to perform a navigation (location determination). Also, the step S510may be continuously performed when the navigation is running. Accordingly, in the step S510, the processor410may control the satellite signal receiver440to receive satellite navigation signals transmitted from the satellite110through multiple carriers. In this case, when the satellite110transmits the satellite navigation augmentation information together, in the step S510, the satellite signal receiver440may convert the satellite navigation signals and the satellite navigation augmentation information together into digital IF band signals or digital baseband signals of the IF band, and provide them to the processor410. That is, the processor410may receive baseband satellite navigation signals from the satellite signal receiver440. In addition, when the satellite110broadcasts the satellite navigation signals and the satellite navigation augmentation information together, the processor410may also receive the satellite navigation augmentation information.

In a step S512, the processor410may calculate first parameters using the digital IF band signals or the digital baseband signals of the IF band received from the satellite signal receiver440. The first parameters described in the present disclosure may be parameters for estimating the location of the terminal, and may include a time offset, frequency offset, and phase offset of each of multiple carriers. In other words, the first parameters may be parameters for accurate estimation of multiple carriers through which the satellite navigation signals are transmitted. Since the present disclosure proposes a method for correcting the phase offset, the time offset and frequency offset will not be further described. Among the first parameters, the phase offset may be calculated as described inFIG.4.

When the satellite signal receiver440receives both the satellite navigation augmentation information and the satellite navigation signals according to the present disclosure, in the step S512, the processor410may extract the satellite navigation augmentation information from the digital baseband signals and may store in the memory420in the step S512.

In a step S514, the processor410may identify whether satellite navigation augmentation information pre-stored in the memory420exists or whether satellite navigation augmentation information has been received from the satellite signal receiver440. As a result of the identification in the step S514, if satellite navigation augmentation information is previously stored in the memory420or if satellite navigation augmentation information is received together with the satellite navigation signals, the processor410may proceed to a step S516. On the other hand, as a result of the identification in the step S514, if satellite navigation augmentation information is not previously stored in the memory420and satellite navigation augmentation information is not received along with the satellite navigation signals, the processor410may proceed to s step S518.

The step S518may correspond to a case where there is no satellite navigation augmentation information. Accordingly, in the step S518, the processor410may determine the first parameters calculated in the step S512as location estimation parameters. The step S518may correspond to a general positioning operation to which satellite navigation augmentation information according to the present disclosure is not applied. Therefore, it may correspond to a case of using the first parameters as the location determination parameters as they are in order to estimate (or determine) the location of the terminal. After determining the location estimation parameters as described above, the processor410may proceed to a step S522.

The step S518may be an initial procedure in which power is initially turned on for the terminal130or navigation is requested by the user. Thereafter, when the satellite navigation augmentation information transmitted by the augmentation station120is received, the step S518may not be performed. Accordingly, how long the step S518is performed may be determined based on a scheme and period in which the augmentation station120transmits the satellite navigation augmentation information.

For example, when the augmentation station120is configured to broadcast the satellite navigation augmentation information together with the satellite navigation signals through the satellite110, the step S518may be performed once or may be performed without the step S518.

As another example, when the augmentation station120is configured to broadcast the satellite navigation augmentation information together with satellite navigation signals through the specific network140without using the satellite110, based on a broadcasting period of the network140, the number of performing the step S518may be determined.

As yet another example, when the augmentation station120directly broadcasts the satellite navigation augmentation information at a specific periodicity, the number of performing the step S518may be determined based on the transmission period of the satellite navigation augmentation information by the augmentation station120.

The step S516may a case where the satellite navigation augmentation information transmitted by the augmentation station120is received. Accordingly, the processor410may generate correction parameters using the satellite navigation augmentation information. The satellite navigation augmentation information according to the present disclosure may include phase offset correction information. Based thereon, the processor410may correct the phase offset among the first parameters. The correction of the phase offset may be performed as in Equation 4 described above. In more detail, the correction of the phase offset according to the present disclosure may be performed using weights. Since these weights have already been described above, the redundant description will be omitted.

In the step S520, the processor410may determine the correction parameters generated in the step S518as location estimation parameters. In the step S522, the processor410may estimate (or determine) the location of the terminal using the location estimation parameters. The step S522may use the location estimation parameters determined in the step S518or step S520. Therefore, the step S522may be applied both when the phase offset is corrected based on the satellite navigation augmentation information according to the present disclosure or when the satellite navigation augmentation information is not received.

FIG.6is a conceptual timing diagram illustrating broadcasting of phase differences of different carriers by the augmentation station according to the present disclosure.

The satellites of the GNSS may transmit satellite navigation signals using multiple carriers of different frequencies.FIG.6illustrates a case in which a GNSS satellite transmits a first carrier610of a first frequency and a second carrier620of a second frequency. A phase offset at a timing tnof the first carrier610of the first frequency may be expressed as Δϕ1(tn). In addition, a phase offset at the timing tnof the second carrier620of the second frequency may be expressed as Δϕ1(tn).

The augmentation station120may calculate a difference value Δϕ21(tn) between the phase offset Δϕ1(tn) for the first carrier610and the phase offset Δϕ2(tn) for the second carrier620before the broadcast timing tn, and broadcast the difference value of the phase offset at the timing tn.

As described above, such broadcasting may be performed based on a preset period, for example, a broadcasting period630of the augmentation station. Accordingly, the augmentation station120may calculate the phase difference value of the next timing before a next broadcasting period arrives. For example, a difference Δϕ21(tn+1) between a phase offset Δϕ1(tn+1) at a timing tn+1for the first carrier610of the first frequency and a phase offset Δϕ2(tn+1) at the timing tn+1for the second carrier620of the second frequency may be calculated. It may be preferable to perform the calculation immediately prior to the broadcast timing based on computational capability of the augmentation station120.