KR20220129486A - Method for reducing initial time to first fix for global navigation satellite system receiver and a structure of navigation message for the same - Google Patents

Abstract

Disclosed are a method for reducing initial positioning time of a satellite navigation receiver and a navigation message structure therefor. The method for reducing initial positioning time of a satellite navigation receiver includes the steps of: preparing several words of a subframe in a single frame of a navigation message structure in a standalone operating mode; and inserting preamble and TOW LSB for A-GPS in a middle word among several words.

Description

A method for reducing the initial positioning time of a satellite navigation receiver and a navigation message structure therefor

The present invention relates to a method for reducing the initial positioning time of a satellite navigation receiver and a navigation message structure therefor.

As one of the prior art, the simplest type of navigation message structure currently used in GPS Legacy L1 C/A is shown in FIGS. 1A and 1B. In such a navigation message structure, a global navigation satellite system (GNSS) receiver has a time to first fix (TTFF) performance of 7.2 seconds to 13.2 seconds in assisted-global positioning system (A-GPS) mode, and operates alone ( In standalone) mode, it has a TTFF performance of 18 to 30 seconds, and 27.6 seconds on average.

The GNSS receiver has already improved TTFF performance by about 3 times compared to the standalone mode by using the A-GPS technology. In order to have a faster TTFF performance in the A-GPS mode, the structure of the navigation message needs to be changed.

1A shows the overall frame structure of a navigation message. One frame consists of five (#1, #2, #3, #4, #5) subframes. Each subframe consists of a telemetry word (TLM), hand over word (HOW) and data. A total of 5 subframes are repeated 25 times (25 pages), and if data is collected for 12.5 minutes, data of all 25 frames can be received.

Among the five subframes, the first, second, and third subframes are composed of ephemeris data and clock correction data, and are designed to transmit the same data in every frame. With only ephemeris data and time correction data, the position of a GNSS receiver can be calculated. When the TTFF is calculated when operating in standalone mode, the minimum time it takes to receive all subframes 1, 2, and 3 is 18 seconds, the maximum time is 30 seconds, and it takes 27.6 seconds on average.

1B shows that one subframe consists of 10 words. In one subframe, word1 (word1) and word2 (word2) are repeated every subframe by TLM and HOW, respectively. Word 1 includes 8 bits of a preamble that indicates the start point of the subframe, and word 2 includes 17 bits of TOW (time of week)-count indicating the time of the start point of the subframe. Knowing these two words enables position calculation in A-GPS mode.

Since there may be the same pattern as the preamble among data in other words, the position of the preamble can be accurately identified by confirming that the interval between at least two preambles is 6 seconds. At this time, by confirming that the TOW-count differs by 1, it is possible to know the exact position and time of the first starting point of the subframe. Therefore, when operating in A-GPS mode, the minimum TTFF takes 7.2 seconds as the sum of 6 seconds (two preamble intervals) and 1.2 seconds (TLM+HOW).

As another prior art, the navigation message structure of India's IRNSS (NaVIC), which is the latest GNSS satellite navigation system, is shown in FIG. One frame is composed of a total of 4 subframes, and FIG. 2 shows subframes 1 and 2 (#1, #2) composed of ephemeris parameters and clock parameters. The subframe transmits other data such as almanac in every frame, and GPS Legacy L1 C/A navigation except that data is 220 bits by adding 6 bits of message type and 6 bits of PRN ID in detail in the data configuration. It has the same structure as the message structure.

In addition, in the navigation message structure of FIG. 2, a 1/2 convolution error correction code and interleaving are used. It is composed of 16 bits of a sync code that plays the same role as the preamble of GPS and 584 symbols of 1/2 convolutional coded (convolutional coded). Even though one 1/2 convolution coded subframe transmits almost the same data as GPS, it takes twice as long to transmit one subframe.

And, in the receiver operating in A-GPS mode, the TTFF is at least 12 seconds and up to 24 seconds, which is because, unlike in the GPS L1 C/A structure, all subframes must be received in order to decode the TOW-count value. It takes more time. When operating in standalone mode, TTFF takes a minimum of 24 seconds, a maximum of 60 seconds, and an average of 45 seconds.

Compared with the navigation message structure of GPS Legacy L1 C/A, which is the simplest structure, one of the biggest differences in the navigation message structure of IRNSS is forward error correction (FEC) and interleaving to lower the data error rate. technology was used.

Since GPS Legacy L1 C/A uses only parity check and discards errors if there is an error in the data, the TTFF in standalone mode is much longer than 30 seconds in poor reception conditions, resulting in lower performance than IRNSS. . However, the TTFF performance of GPS Legacy L1 C/A is about 1.6 times faster than that of IRNSS under a good reception signal. That is, it is about 1.63 times faster in standalone mode and about 1.66 times faster in A-GPS mode.

That is, the first prior art described above has a TTFF performance of 7.2 seconds to 13.2 seconds in the A-PGS mode of the GNSS receiver, 18 seconds to 30 seconds in the standalone mode, and an average of 27.6 seconds, but the error rate of the message in a poor reception environment Accordingly, there is a problem in that the TTFF increases exponentially.

In addition, the second prior art described above has better TTFF performance than the first prior art because it is robust to the error rate of a message in an environment where the reception condition of the GNSS receiver is not good. It has a TTFF performance of 24 seconds, 24 seconds to 60 seconds in standalone mode, and an average of 45 seconds. As such, the second prior art has a lower TTFF performance than the first prior art.

As described above, it is necessary to design a navigation message structure having both the advantages of the GPS Legacy L1 C/A and the advantages of IRNSS.

The present invention was derived to meet the needs of the prior art, and an object of the present invention is to provide a navigation message structure having both the advantages of the GPS Legacy L1 C/A and the advantages of the IRNSS.

Another object of the present invention is to provide a method for reducing the initial positioning time of a satellite navigation receiver using the above-described navigation message structure.

In order to achieve the above object, a method for reducing the initial positioning time of a satellite navigation receiver according to an aspect of the present invention is a 10 word subframe in a single frame of a navigation message structure in a standalone operation mode. ) to prepare; and inserting a preamble for assisted-GPS (A-GPS) and a hand over word (TOW) least significant bit (LSB) into a sixth word (word6) of the ten words.

In order to achieve the above object, a method for reducing the initial positioning time of a satellite navigation receiver according to another aspect of the present invention is a 10 word subframe in a single frame of a navigation message structure in a standalone operation mode. ) to prepare; and repeatedly inserting subframes 1 to 3 of the ten words into the subframe.

According to another aspect of the present invention for achieving the above object, a method for reducing the initial positioning time of a satellite navigation receiver includes: preparing 10 words of a subframe in a single frame of a navigation message structure; and replacing subframes 1 and 2 of the 10 words with a single subframe.

According to another aspect of the present invention for achieving the above object, a method for reducing the initial positioning time of a satellite navigation receiver includes: preparing 10 words of a subframe in a single frame of a navigation message structure; and configuring 30 bits of the least significant bit (S_LSB) of the subframe using 16 bits of four sync codes and 14 bits of a TOW-count (TOWC) least significant bit (LSB).

A navigation message structure according to another aspect of the present invention for achieving the above object has a structure in which the preamble for A-GPS and the TOW LSB are inserted in the middle word (eg, word 6) of the subframe by replacing the existing preamble. .

A navigation message structure according to another aspect of the present invention for achieving the above object has a structure in which subframes 1 to 3 are repeatedly inserted when generating a subframe.

A navigation message structure according to another aspect of the present invention for achieving the above object has a structure in which subframes 1 and 2 are replaced with a single subframe.

The navigation message structure according to another aspect of the present invention for achieving the above object is the least significant bit (S_LSB) 30 bits of the existing subframe, 4 sync codes (sync code) 16 bits and TOW-count (TOWC) least significant bit (LSB) ) has a structure constructed using 14 bits.

According to the present invention, it is possible to design a structure of a satellite navigation message that minimizes Time To First Fix (TTFF) in both the case of operating in the A-GPS mode of the GNSS receiver and the case of operating in the standalone mode. This navigation message structure dramatically reduces the initial positioning time of the GNSS receiver in the satellite navigation system, enabling faster positioning than the existing navigation message, and its utility and ripple effect are expected to be very large in the military and civilian fields.

That is, according to the present invention, in the case of the navigation message in the standalone mode, the TTFF can be shortened only by changing the order of words in the navigation message transmitted from the satellite. According to this configuration, it is possible to use the GNSS receiver as it is without changing the GNSS receiver in the existing system, and the TTFF performance can be improved by 20 to 30% compared to the existing initial positioning method. By utilizing such a navigation message structure, the TTFF of the currently operating GNSS satellite navigation system can be improved.

In addition, in the case of A-GPS mode, since the algorithm change in the GNSS receiver must be performed along with the structure change in the satellite navigation system to be used, the message structure of the satellite navigation system to be used in the future rather than the currently serviced satellite navigation system It can be effectively used to shorten the TTFF by reflecting in

As described above, according to the present invention, in the case of upgrading the current GNSS system or the Korean Positioning System (KPS) for constructing a new GNSS system, the initial positioning time (TTFF) is minimized in the message structure of the future GNSS satellite navigation system. can make a significant contribution to

1A and 1B are diagrams illustrating a conventional GPS legacy L1 C/A message structure.
2 is a diagram illustrating a conventional IRNSS (NaVIC) message structure.
3 is a diagram illustrating a structure of a navigation message that can be employed in a method for shortening a time to first fix (TTFF) of a satellite navigation receiver according to an embodiment of the present invention.
4 is a diagram illustrating a navigation message structure of a comparative example.
5 to 7 are diagrams for explaining a structure of a navigation message that can be employed in a TTFF shortening method of a satellite navigation receiver according to another embodiment of the present invention.
8 is a diagram illustrating a structure of a navigation message that can be employed in a TTFF shortening method of a satellite navigation receiver according to another embodiment of the present invention.
FIG. 9 is a diagram for explaining the structure of a specific subframe of the navigation message structure of FIG. 8 .
10 is a block diagram showing the main configuration of a satellite navigation receiver capable of adopting the TTFF shortening method of the present embodiment.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but it is understood that other components may exist in between. it should be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that the other element does not exist in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that this does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

A communication system or a memory system to which embodiments according to the present invention are applied will be described. A communication system or memory system to which embodiments according to the present invention are applied is not limited to the contents described below, and embodiments according to the present invention may be applied to various communication systems. Here, a communication system may be used in the same meaning as a communication network (network).

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

The present invention described below is conceived to improve performance of time to first fix (TTFF) by considering A-GPS (assisted-GPS) mode when designing a navigation message structure. That is, the GNSS (global navigation satellite system) receiver achieves about three times the TTFF performance improvement in the A-GPS mode than in the standalone mode, but it is intended to improve the TTFF performance by improving the limit accordingly. That is, even in the case of the standalone mode, when designing the structure of the navigation message currently used, the TTFF performance can be further improved by considering the A-GPS mode.

The present invention provides a navigation message structure that enables a GNSS receiver to quickly determine an initial position in standalone mode and A-GPS mode, and provides a method for reducing the initial positioning time of a satellite navigation receiver by using the navigation message structure can do. That is, if the satellite navigation message structure currently used is broadly classified, the simplest structure that determines whether there is an error in the data only by parity check and does not use it if there is an error in the data, for example, GPS L1 C/A and an error correction code are used. Thus, it can be divided into the latest navigation message structure, such as IRNSS, which determines whether there is an error in data and corrects it and uses it. The present invention provides a navigation message structure that can improve TTFF performance in both of these navigation message structures.

3 is a diagram illustrating a navigation message structure that can be employed in a method for shortening a time to first fix (TTFF) of a satellite navigation receiver according to an embodiment of the present invention.

Referring to FIG. 3, first, when the satellite navigation receiver operates in A-GPS (Assisted-GPS) mode based on GPS L1 C/A, the navigation message structure that minimizes TTFF can know the starting point of the subframe. The message structure is changed in a form in which the preamble and the time of week (TOW)-count, which can know the time of the starting point, are repeatedly arranged in a subframe in a shorter time than before. The preamble corresponds to the sync code of the navigation message structure of the IRNSS.

The subframe structure of the existing navigation message consists of 8 bits of preamble in word1 and 17 bits of TOW-count in word2. In this embodiment, the existing preamble is placed in word6, which is the middle of the subframe. Instead, 8 bits of the preamble for A-GPS mode are added, and 4 bits of the TOW least significant bit (LSB) that can represent the decimal 1 digit of the TOW-count are added.

That is, in the present embodiment, the entire encoded content enters one subframe without distinction in word units in the encoding structure such as IRNSS, and at this time, it may be configured to be inserted in the middle of the encoded subframe.

According to this configuration, it is possible to double the TTFF performance compared to the basic. To this end, information on word 6 may be stored as predetermined bits, for example, 12 bits in a teletry word (TLM) of word 1 of the subframe.

The above navigation message structure is an example, and the preamble and TOW for the A-GPS mode may be more frequently arranged in the subframe. In this case, the TTFF in the GNSS receiver operating in the A-GPS mode can be further improved. The conventional TTFF performance took 7.2 seconds to 13.2 seconds, but using the navigation message structure of the present embodiment, it takes 3.6 seconds to 7.2 seconds, so it can be seen that the TTFF performance is improved more than twice.

And, in order to minimize TTFF when operating in a standalone mode, the transmission order of subframes is set differently so that ephemeris data and clock correction data can be quickly collected.

4 is a diagram illustrating a navigation message structure of a comparative example. 5 to 7 are diagrams for explaining a structure of a navigation message that can be employed in a TTFF shortening method of a satellite navigation receiver according to another embodiment of the present invention.

The most basic structure of an existing navigation message used by a GNSS receiver operating in a standalone mode based on GPS L1 C/A is shown in FIG. 4 . The basic navigation message structure of FIG. 4 is a structure in which five subframes (subframes 1 to 5) are sequentially transmitted in one frame. TTFF performance takes a minimum of 18 seconds, a maximum of 30 seconds, and an average of 27.6 seconds. That is, it takes 12.5 minutes to receive all 25 frames.

Meanwhile, referring to FIG. 5, in the navigation message structure of the first embodiment, subframes 1 to 3 (subframes 1,2,3) affecting TTFF performance are sent twice in one frame, and times 4 and 5 By sending subframes (subframes 4 and 5) only once, one frame is configured to have 8 subframes. In this case, TTFF performance takes a minimum of 18 seconds, a maximum of 24 seconds, and an average of 23.3 seconds. The time it takes to receive all 25 frames, that is, the time it takes to collect almanac data, is 20 minutes (6 seconds × 8 subframes × 25 pages).

6, the navigation message structure of the second embodiment sends subframes 1 to 3 (subframes 1,2,3) 4 times in one frame and subframes 4 and 5 (subframe 4, By sending 5) only once, one frame is configured to have 14 subframes. TTFF performance is 18 seconds minimum, 24 seconds maximum, and 21 seconds average. The time it takes to receive a total of 25 frames, i.e., the time it takes to collect almanac data, is 35 minutes.

Because it is more important for the GPS satellite navigation system to accurately and faster to calculate the position of the satellite, even if it takes more time to collect all the almanac data, a structure that reduces the time to collect ephemeris data is It is better from the point of view Compared with the existing structure, the TTFF performance of the first embodiment was reduced by 20% on average, and the second embodiment was reduced by 30%.

If the number of repetitions of subframes 1 to 3 (subframes 1,2,3) in one frame is increased in this way, as shown in FIG. 7 , subframes 1 to 3 (subframes 1,2,3) are increased. ,3) can lead to convergence. At this time, the 4th and 5th subframes (subframes 4 and 5) are almost in a state that cannot be received. The TTFF performance at this time takes 18 seconds.

8 is a diagram illustrating a structure of a navigation message applicable to a TTFF shortening method of a satellite navigation receiver according to another embodiment of the present invention. FIG. 9 is a diagram for explaining the structure of a specific subframe of the navigation message structure of FIG. 8 .

Referring to FIG. 8 , when the error correction code is used and the standalone mode is operated, the navigation message structure as described above with reference to FIG. 5 may be designed in order to minimize the TTFF performance.

In addition, in the case of using the error correction code and operating in the A-GPS mode, in order to minimize the TTFF performance, similar to the modification of the navigation message structure described above with reference to FIG. 3 , a sync code is used in the middle of the subframe. and TOW-count can be configured to deploy more frequently. The sync code corresponds to the preamble in the case of GPS L1 C/A.

In this case, when the error correction code is used, the subframe is not divided into small word sizes as in GPS L1 C/A, and thus the design should not be performed in the same way. Therefore, the structure shown in FIG. 8 is designed.

Referring to FIG. 8 , the TTFF performance of the GNSS receiver operating in the A-GPS mode can be maximized based on IRNSS, which is the latest navigation message structure using an error correction code. That is, in the existing IRNSS navigation message structure, there are 4 subframes, and subframes 1 and 2 (subframes 1 and 2) each have a length of 600 symbols and are composed of ephemeris and time correction parameters, but the navigation message of this embodiment In the structure, one subframe consists of ephemeris parameters and clock correction parameters. The navigation message structure of this embodiment is configured to arrange four sync codes and TOW-count in one subframe differently from IRNSS, and one subframe has a length of 1200 symbols. That is, in this embodiment, two subframes of the existing IRNSS navigation message are configured as one subframe.

And, in this embodiment, as shown in FIG. 9, the least significant bit (S_LSB) of 30 bits of the subframe of the existing navigation message structure is set to 4 sync codes 16 bits and TOW- to improve TTFF performance in the A-GPS mode. It can be configured using count(TOWC) least significant bit (LSB) 14bits. TOWC LSB 14 bits may be composed of sub count 2 bits, TOWC LSB 4 bits, parity check 6 bits, and L6/S flag 2 bits.

In the navigation message structure of this embodiment, when the GNSS receiver operates in the A-GPS mode, the TTFF performance takes a minimum of 3.3 seconds and a maximum of 6.3 seconds. Simply, if subframe 1 is transmitted twice in one frame and subframe 2 is transmitted once, TTFF performance when the GNSS receiver operates in standalone mode may take a minimum of 12 seconds, a maximum of 36 seconds, and an average of 22 seconds.

In the above navigation message structure, the length of the error correction code of one subframe is approximately twice that of the existing IRNSS, that is, the length of the existing 584 symbols increases to 1080 symbols in the fixed format. This can make it more robust to errors, thereby enabling faster data transmission. As such, according to the present embodiment, it is possible to provide a navigation message structure having a transmission speed of 50sps to 100sps that is twice as fast as that of an IRNSS and having almost the same error rate.

10 is a block diagram showing the main configuration of a satellite navigation receiver capable of adopting the TTFF shortening method of the present embodiment.

Referring to FIG. 10, the satellite navigation receiver may be configured to use the satellite navigation message structure of at least one of the above-described embodiments. The satellite navigation receiver 100 may include at least one processor 110 , a memory 120 , and a transceiver 130 connected to a network including a satellite to perform communication. In addition, the satellite navigation receiver 100 may further include an input interface device 140 , an output interface device 150 , a storage device 160 , and the like. Each of the components included in the satellite navigation receiver 100 may be connected by a bus 170 to communicate with each other.

The processor 110 may execute a program command stored in at least one of the memory 120 and the storage device 160 . The processor 110 may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed.

Each of the memory 120 and the storage device 160 may be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 120 may be configured as at least one of a read only memory (ROM) and a random access memory (RAM).

The transceiver 130 is a sub-communication system supporting a communication connection with a satellite, a sub-communication system supporting wired or wireless communication with a general-purpose base station, or an ideal backhaul link with a mobile edge core network or a core network. (ideal backhaul link) or non- (non) may include a sub-communication system for the connection of the ideal backhaul link. Here, the processor 110 may generate or process the navigation message exchanged with the satellite through the transceiver 130 in the structure according to at least one of the above-described embodiments.

The input interface device 140 includes at least one selected from input means such as a keyboard, a microphone, a touch pad, and a touch screen and an input signal processing unit for mapping or processing a signal input through at least one input means with a pre-stored command. may include

The output interface device 150 includes an output signal processing unit that maps or processes a signal generated or output according to the control of the processor 110 to a pre-stored signal type or level, and a form of vibration, light, etc. according to the signal of the output signal processing unit It may include at least one output means for outputting the raw signal or information. The at least one output means may include at least one selected from output means such as a speaker, a display device, a printer, an optical output device, and a vibration output device.

In addition, the program command executed by the processor 110 is a command for inserting the preamble for A-GPS and the TOW LSB into the middle word (eg, word 6) of the subframe of the navigation message structure by replacing the existing preamble, generation of the subframe A command to repeatedly insert subframes 1 to 3, a command to replace subframes 1 and 2 with a single subframe, 30 bits of the least significant bit (S_LSB) of the existing subframe to 4 sync codes 16 bits and TOW-count(TOWC) Least Significant Bit(LSB) 14bits.

The methods according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the computer readable medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the art of computer software.

Examples of computer-readable media include hardware devices specially configured to store and carry out program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as at least one software module to perform the operations of the present invention, and vice versa.

Although it has been described with reference to the above embodiments, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. will be able

Claims (1)

preparing several words of a subframe within a single frame of a navigation message structure in a mode of operating in standalone; and
inserting a preamble for assisted-GPS (A-GPS) and a hand over word (TOW) least significant bit (LSB) into an intermediate word among the plurality of words;
A method for reducing the initial positioning time of a satellite navigation receiver comprising a.

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