CN111669703A - NB-IoT terminal positioning system and method - Google Patents
NB-IoT terminal positioning system and method Download PDFInfo
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- CN111669703A CN111669703A CN202010540158.3A CN202010540158A CN111669703A CN 111669703 A CN111669703 A CN 111669703A CN 202010540158 A CN202010540158 A CN 202010540158A CN 111669703 A CN111669703 A CN 111669703A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/02—Services making use of location information
- H04W4/023—Services making use of location information using mutual or relative location information between multiple location based services [LBS] targets or of distance thresholds
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/02—Services making use of location information
- H04W4/025—Services making use of location information using location based information parameters
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- H04W56/00—Synchronisation arrangements
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- H—ELECTRICITY
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- H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
Abstract
The invention provides an NB-IoT terminal positioning system and a method, which are used for positioning an NB-IoT terminal and are characterized by comprising the following steps: at least one NB-IoT terminal comprising an application processor and a modem; the NB-IoT network comprises a plurality of NB-IoT base stations, and network signals of each NB-IoT base station cover a plurality of cells; and the cloud server is in wired connection with the NB-IoT network, and comprises a base station information storage unit, a data decompression unit, a delay estimation unit, a terminal positioning calculation unit and a positioning output unit, wherein the cloud server carries out delay estimation according to OFDM symbols acquired by the modem, and simultaneously obtains delay estimation difference RSTD between different cells and a service cell, and further calculates longitude/latitude and confidence information of a terminal position as terminal position information of the NB-IoT terminal by utilizing the delay estimation difference, the base station position information, the base station synchronization time difference and the like, and finally outputs the terminal position information.
Description
Technical Field
The invention belongs to the technical field of positioning of the Internet of things, and particularly relates to an NB-IoT terminal positioning system and method.
Background
With the development of the fifth generation mobile communication technology (5G) and the artificial intelligence technology, more and more devices need to be connected into the network. In 2020, the 5G worldwide large-scale commercial and Chinese "new infrastructure" is opened, and the Internet of Things (IoT) era of everything is coming. Currently, the internet of things has been applied to the fields of city management, traffic management, storage logistics, energy and power and the like, and widely relates to various aspects of national economy and social life. According to the global internet of things market report issued by GSMA in 2019, the market size will reach $ 1.1 trillion by 2025 when the number of global internet of things connections reaches 250 billion.
The internet of things mainly transmits data. With the continuous development of the internet of things and the diversification of application scenes, the traditional wireless communication technology of the internet of things cannot meet the development requirements of the internet of things. The wireless communication technology is driven by the application service of the internet of things to develop in two directions: firstly, the high-speed low-delay application service drives the development of a wireless communication technology to the 5G high-speed low-delay direction, such as automatic driving, telemedicine and the like; secondly, the medium-Low speed application service drives the development of the wireless communication technology to Low-Power-Wide-Area Network (LPWAN) technology, such as intelligent meter reading, intelligent street lamps and the like. Currently mainstream LPWAN technologies include non-3 GPP dominated LoRa and Sigfox, and 3GPP dominated cellular IoT, including eMTC and NB-IoT, among others. The NB-IoT technology has the advantages of low power consumption, low cost, wide coverage, large connection and the like, and the authorized frequency band is used, so that the wireless transmission quality and the data safety are guaranteed, and in addition, the technology can be directly upgraded on the existing network deployment of operators, so that the technology is supported by telecommunication operators of various countries, including China Mobile, China telecom and the like.
The narrowband internet of things NB-IoT was first present in the 3GPP Release 13 standard protocol in month 6 of 2016. If the GPS is adopted to carry out the NB-IoT terminal positioning, the NB-IoT terminal has high power consumption and short standby time, and cannot meet the standby requirement of the NB-IoT terminal, and in addition, the GPS positioning cannot work under the scenes of urban canyons, tunnels, indoor places and the like. In 2017, an NB-IoT terminal is introduced by a 3GPP Peerase 14 standard protocol to perform a positioning function by utilizing an NB-IoT network, so that the ecological development of the NB-IoT of the 3GPP narrowband IoT is accelerated. Although no positioning accuracy is set in the 3GPP standard protocol, the NB-IoT is expected to have a positioning accuracy of 50 meters in indoor and outdoor application scenarios. Compared to LTE, NB-IoT has a system bandwidth of only 180kHz, its available frequency domain resources are limited, device complexity is reduced, but challenges are posed to NB-IoT positioning because positioning accuracy is related to the spectral resolution of the system. There are only three positioning methods defined by the NB-IoT protocol of the 3GPP standard: enhanced cell identity ECID, downlink time difference of arrival OTDOA and uplink time difference of arrival UTDOA. The downlink OTDOA and the uplink UTDOA based on the time measurement item have higher positioning precision than the ECID based on the signal strength measurement item. And the uplink UTDOA has uplink interference, especially under the condition of massive access quantity, the positioning performance of the uplink UTDOA is inferior to that of the downlink OTDOA, that is, the downlink OTDOA is more suitable for the application scenario of large-scale access like NB-IoT network.
Downlink OTDOA measures downlink narrowband positioning reference signals NPRS from multiple base stations to enable positioning of NB-IoT terminals. The general OTDOA algorithm time delay estimation adopted by the terminal mainly comprises two types, one type is that the peak-to-average ratio of related peaks is compared with a set threshold to obtain the position of a first path, and the method has the problem that a uniform or dynamic threshold cannot be set under the multipath environment and the non-line-of-sight (NLOS) scene, so that the estimation error of the first path is large; the other is to adopt a time delay interference elimination method to obtain the position of the first path. If the UE obtains a high accuracy position fix, a more complex algorithm, such as the MUSIC algorithm or the ESPIRIT algorithm, may be used for the delay estimation. An extended Kalman filtering method may be used in the positioning algorithm to further improve the positioning accuracy. However, NB-IoT terminals have greatly limited the use of these techniques due to extremely low power consumption requirements and extremely low terminal computational power.
In order to reduce the NPRS signal interference, the NPRS signal occupies one downlink subframe for transmission, that is, the NPRS signal is not transmitted in the NPDCCH, NPDSCH, NPBCH, NPSS and NSSS subframes, so that NPRS subframe scheduling should avoid simultaneous transmission with other downlink subframes. That is, the NB-IoT OTDOA positioning function is added according to 3GPP Release 14, that is, NPRS signals need to be added, and since NPRS subframe scheduling needs to occupy empty resources, scheduling of NPDSCH and NPDCCH subframes is affected at this time, and further, NB-IoT data transmission rate and the number of users that can be called at the same time are affected. The NPRS is designed to be transmitted on Mod (NprsId, 6) resource elements, but when there are more than 6 cells around the terminal, the NPRS signal transmission may be interfered by an NPRS signal of another cell, and to avoid this, the NPRS signal may be muted in a period of transmission timing to improve the OTDOA positioning accuracy, while another problem is brought about at the expense of the positioning delay.
In the 3GPP Release 14 protocol, a positioning center unit E-SMLC and LPP and LPPa protocol parts are added on the network side, and a large modification is needed to be added for supporting the positioning function, the terminal and the network side scheduling.
Currently NB-IoT networks are currently under scale, and the operator does not turn on the positioning function in NB-IoT network Release 14. Some NB-IoT end users have strong demands for positioning, especially high-precision positioning, such as logistics tracking.
Therefore, the current NB-IoT terminal is difficult to meet the positioning requirements of users, improve the positioning performance index and overcome the influence of NLOS and multipath on positioning; and the system requirements of NB-IoT terminals on low power consumption, low cost, large connection, wide coverage and the like are met, especially under the condition that an operator does not open an NB-IoT positioning function.
Disclosure of Invention
In order to solve the above problems, the present invention provides an NB-IoT terminal positioning system and method that not only can improve the positioning performance index, but also can meet the system requirements of NB-IoT terminals such as low power consumption, low cost, large connection, wide coverage, etc., and the present invention adopts the following technical solutions:
the invention provides an NB-IoT terminal positioning system, which is used for positioning an NB-IoT terminal and is characterized by comprising the following steps: at least one NB-IoT terminal comprising an application processor and a modem; the NB-IoT network comprises a plurality of NB-IoT base stations, and network signals of each NB-IoT base station cover a plurality of cells; the cloud server is in wired connection with the NB-IoT network and comprises a base station information storage unit, a data decompression unit, a time delay estimation unit, a terminal positioning calculation unit and a positioning output unit, wherein the base station information storage unit stores and stores position information of each NB-IoT base station and time synchronization information of each cell under each NB-IoT base station; the NB-IoT terminal takes a cell corresponding to a network signal as a service cell and finishes attachment when searching the network signal sent by the NB-IoT base station, once the NB-IoT terminal receives a positioning request message in an RRC _ CNNT state, the NB-IoT terminal retreats from the RRC _ CNNT state to an RRC _ IDLE state and keeps time-frequency synchronization with the NB-IoT network, a modem searches cells existing around the NB-IoT terminal according to the positioning request message by using IDLE time slots between two times of DRX to further obtain time-frequency synchronization information of each peripheral cell, receives a certain number of OFDM symbols of a base station synchronization signal NPSS/NSSS and a reference signal NRS from the NB-IoT base station according to the time-frequency synchronization information, and further sends all received OFDM symbols of the base station synchronization signal NPSS/NSSS and the reference signal NRS to an application processor, the application processor performs data compression processing on the OFDM symbols to form compressed OFDM symbols, once the NB-IoT terminal enters an RRC _ CNNT state, the modem transmits the compressed OFDM symbols to the cloud server through the wireless NB-IoT network, once the service side communication unit receives the compressed OFDM symbols, the data decompression unit performs data decompression processing on the compressed OFDM symbols to obtain decompressed OFDM symbols, the delay estimation unit performs delay estimation according to base station synchronization signals NPSS/NSSS and reference signals NRS sent by peripheral cells, and calculating the time delay estimation difference RSTD of different peripheral cells to the service cell, calculating the longitude and latitude and confidence degree information of the NB-IoT terminal as terminal positioning information by using the time delay estimation difference RSTD, the position information of the NB-IoT base station and the time synchronization information by using the terminal positioning calculation unit, and outputting the terminal positioning information by using the positioning output unit.
The NB-IoT terminal positioning system provided by the present invention may further have the technical features that NPSS is in subframe 5, NSSS is in subframe 9 of an even frame, and base station synchronization signals NPSS/NSSS are all 11 OFDM symbols from OFDM symbol # 3 to OFDM symbol # 13 of a subframe; the NB-IoT terminal sample rate is set to 240kHz, except that OFDM symbol # 7 contains 18 samples and the other 10 OFDM symbols contain 17 samples; the period of NPSS is 10ms, and the period of NSSS is 20 ms.
The NB-IoT terminal location system provided by the present invention may further have a technical feature that NRS is located in subframe 0, subframe 4 and subframe 9 without NSSS on the anchor carrier, and the NRS is located in OFDM symbols # 5, #6, #12 and #13 of the subframes.
The NB-IoT terminal positioning system provided by the present invention may further have the technical feature that, when the NB-IoT terminal keeps normal communication with the serving cell, the NB-IoT terminal falls back from the RRC _ CNNT state to the RRC _ IDLE state, and when the modem collects an OFDM symbol, the NB-IoT terminal positioning system has the following constraint conditions: the carrier frequency offset cannot be adjusted; the time offset cannot be adjusted; the automatic gain control AGC cannot be adjusted; sequentially collecting subsequent subframes with NPSS/NSSS/NRS from the subframe 0 of the even frame as a first collecting subframe until the number of the collected OFDM symbols meets the requirement of the set number, and then stopping the collection of the OFDM symbols; in the acquisition process, besides acquiring NPSS/NSSS/NRS OFDM symbols, the acquired cell ID, frequency point EARFCN/Band, network side information IMSI, deployment mode, AGC information, frame number, subframe number, OFDM symbol type and OFDM symbol number are recorded, and finally the cell ID, frequency point EARFCN/Band, network side information IMSI, deployment mode, AGC information, frame number, subframe number, OFDM symbol type and OFDM symbol number are transmitted to a cloud server together with the OFDM symbols; and calculating the measurement of time frequency synchronization in the acquisition process of the OFDM symbols, and adjusting the time and frequency synchronization deviation of the NB-IoT terminal after the acquisition process is finished.
The NB-IoT terminal positioning system provided in the present invention may further have the following technical features: the client is held by a client and is in communication connection with the cloud server, wherein the client is provided with a picture storage part, an input display part and a client side communication part, the picture storage part stores a positioning request picture and a positioning viewing picture, the input display part displays the positioning request picture to enable the client to select an NB-IoT terminal needing to be positioned as an NB-IoT terminal to be positioned, once the client confirms the selection, the client side communication part sends a positioning request message to the NB-IoT terminal to be positioned through the cloud server and the NB-IoT network, once the terminal positioning calculation unit calculates the terminal positioning information of the NB-IoT terminal to be positioned, the positioning output unit outputs the terminal positioning information to the client, when the client side communication part receives the terminal positioning information, the input display part displays a positioning viewing picture and displays the terminal positioning information to enable the client to view the position of the NB-IoT terminal to be positioned.
The NB-IoT terminal positioning system provided in the present invention may further have the following technical features: and the third-party positioning related application platform is in communication connection with the cloud server, and the positioning output unit outputs the terminal positioning information to the third-party positioning related application platform, so that the third-party positioning related application platform performs the functions of position display, position query and track display of the NB-IoT terminal according to the terminal positioning information.
The invention also provides an NB-IoT terminal positioning method, which is used for positioning the NB-IoT terminal and is characterized by comprising the following steps: when searching the network signal sent by the NB-IoT base station, the NB-IoT terminal takes the cell corresponding to the network signal as a service cell and completes attachment; once the NB-IoT terminal receives the location request message in the RRC _ CNNT state, the NB-IoT terminal reverts from the RRC _ CNNT state to the RRC _ IDLE state and maintains time-frequency synchronization with the NB-IoT network; the method comprises the steps that a modem of an NB-IoT terminal searches cells existing around the NB-IoT terminal according to a positioning request message by using an idle time slot between two DRX times so as to obtain time frequency synchronization information of each peripheral cell, receives a certain number of OFDM symbols of base station synchronization signals NPSS/NSSS and reference signals NRS from the NB-IoT base station according to the time frequency synchronization information, and further sends all the received OFDM symbols of the base station synchronization signals NPSS/NSSS and the reference signals NRS to an application processor of the NB-IoT terminal; the application processor performs data compression processing on the OFDM symbols to form compressed OFDM symbols; once the NB-IoT terminal enters the RRC _ CNNT state, the modem sends the compressed OFDM symbols to a cloud server through a wireless NB-IoT network, and once the cloud server receives the compressed OFDM symbols, the compressed OFDM symbols are subjected to data decompression processing to obtain decompressed OFDM symbols; the cloud server carries out time delay estimation according to base station synchronization signals NPSS/NSSS and reference signals NRS sent by peripheral cells, and calculates time delay estimation difference RSTD of different peripheral cells to a service cell; the cloud server calculates longitude and latitude and confidence information of the NB-IoT terminal as terminal positioning information by using the time delay estimation difference RSTD, the position information of the NB-IoT base station and the time synchronization information, and outputs the terminal positioning information to the NB-IoT terminal, the client or a third party positioning related application platform.
Action and Effect of the invention
According to the NB-IoT terminal positioning system and the method, when the modulator-demodulator of the NB-IoT terminal collects the base station synchronizing signal NPSS/NSSS and the reference signal NRS, different types of OFDM symbols are utilized for carrying out merging processing, and an application processor carries out data compression on the OFDM symbols, so that the performance of time delay estimation can be improved, and the problem of large time delay estimation error caused by small bandwidth of the NB-IoT system can be effectively solved. Further, the time delay estimation difference of the peripheral cells to the service cell is calculated through the cloud server, and the terminal positioning information is further calculated according to the time synchronization information of all the base stations, the position information of the base stations and the time delay estimation difference obtained through calculation, so that the estimation performance is improved on the cloud server through a complex high-precision algorithm, and a server end with high processing capacity is effectively utilized to quickly obtain a calculation result. By the NB-IoT terminal positioning system, the NB-IoT network system does not need to be modified while the NB-IoT terminal position estimation is realized, so that the NB-IoT terminal positioning method has strong universality.
Drawings
Fig. 1 is a schematic structural diagram of an NB-IoT terminal positioning system in an embodiment of the present invention;
fig. 2 is a block diagram of an NB-IoT terminal in an embodiment of the present invention;
FIG. 3 is a diagram of an NPSS/NSSS OFDM symbol in an embodiment of the present invention;
FIG. 4 is a diagram of an NRS OFDM symbol in an embodiment of the present invention;
FIG. 5 is a diagram illustrating an OFDM symbol data storage format according to an embodiment of the present invention;
fig. 6 is a block diagram of a cloud server according to an embodiment of the present invention;
FIG. 7 is a block diagram of a client in an embodiment of the invention; and
fig. 8 is a flowchart of an NB-IoT terminal positioning method in an embodiment of the present invention.
Detailed Description
In order to make the technical means, the creative features, the achievement purposes and the efficacy of the present invention easy to understand, the NB-IoT terminal positioning system and the method of the present invention are specifically described below with reference to the embodiments and the accompanying drawings.
< example >
Fig. 1 is a schematic structural diagram of an NB-IoT terminal positioning system in an embodiment of the present invention.
As shown in fig. 1, NB-IoT terminal location system 100 includes NB-IoT terminal 101, NB-IoT network 102, cloud server 103, client 104, third party location application platform 105, and communication network 106 (not shown).
The NB-IoT terminal 101 is in communication connection with the cloud server 103 through the NB-IoT network 102, and the cloud server 103 is in communication connection with the third party positioning application platform 105 and the client 104 through the communication network 106. In this embodiment, the communication network 106 is a wireless network or a wired network.
Fig. 2 is a block diagram of an NB-IoT terminal in an embodiment of the present invention.
As shown in fig. 1 and 2, the NB-IoT terminal 101 includes a Modem 11(Modem), an application processor 12(AP), a storage unit 13, and a sensing facility 14.
In this embodiment, the modem 11 completes normal access to the NB-IoT network and data transmission, and also completes cell search around the terminal, NPSS/NSSS/NRS OFDM symbol acquisition, OFDM symbol data compression, and transmission of the OFDM symbol data to the NB-IoT network through the modem 11. Specifically, the modem 11 includes a peripheral cell search unit and an OFDM symbol acquisition unit.
The peripheral cell search unit is used for searching peripheral cells, and comprises the steps of carrying out time frequency synchronization by using NPSS/NSSS, acquiring cell ID and receiving MIB/SIB1 under the condition that MIB/SIB1 can be solved.
The OFDM symbol acquisition unit is used for receiving a certain number of OFDM symbols of the synchronizing signals NPSS/NSSS and the reference signals NRS from the NB-IoT base station antenna ports of the NB-IoT network according to the time frequency synchronizing information of the peripheral cells.
In this embodiment, when the NB-IoT terminal 101 receives the positioning request message in the RRC _ CNNT state, it will fall back to the RRC _ IDLE state from the RRC _ CNNT state and maintain time-frequency synchronization with the NB-IoT network 102, and at this time, the modem 11 will start to collect OFDM symbols.
In this embodiment, NB-IoT terminal 101 receives OFDM symbols with dual antennas, the sampling rate of the OFDM symbols is 240kbps, and the I/Q channels are each represented by 16 bits.
In this embodiment, the NB-IoT terminal 101 can return to the RRC _ IDLE state from the RRC _ CNNT state while maintaining normal communication with the serving cell, and perform data acquisition on the OFDM symbol. There is a constraint condition in the process of acquiring OFDM symbols, specifically:
(1) the carrier frequency offset cannot be adjusted.
(2) The time offset cannot be adjusted.
(3) The automatic gain control AGC cannot adjust.
(4) And sequentially acquiring the subframes with subsequent NPSS/NSSS/NRS from the subframe 0 of the even frame as the first acquisition subframe until the number of the acquired OFDM symbols meets the requirement of the set number, and then stopping the acquisition of the OFDM symbols.
(5) In the acquisition process, besides acquiring NPSS/NSSS/NRS OFDM symbols, the acquired cell ID, frequency point EARFCN/Band, network side information IMSI, deployment mode, AGC information, frame number, subframe number, OFDM symbol type, OFDM symbol number, and the like are also recorded at the same time, and finally, the relevant recorded information and OFDM symbols are transmitted to the cloud server 103 together.
(6) The measurement of time and frequency synchronization can be calculated in the OFDM symbol acquisition process, and after the OFDM symbol acquisition is finished this time, the time and frequency synchronization deviation of the NB-IoT terminal 101 can be adjusted if necessary.
Fig. 3 is a schematic diagram of an OFDM symbol corresponding to NPSS/NSSS in the embodiment of the present invention.
As shown in fig. 3, NPSS is in subframe 5, NSSS is in subframe 9 of the even frame, and NPSS/NSSS signals are from OFDM symbol # 3 to OFDM symbol # 13 of the subframe, for a total of 11 OFDM symbols. The NB-IoT terminal sample rate is set to 240kHz, except that OFDM symbol # 7 contains 18 samples and the other 10 OFDM symbols contain 17 samples. The period of NPSS is 10ms, and the period of NSSS is 20 ms.
Fig. 4 is a schematic diagram of an OFDM symbol corresponding to NRS in the embodiment of the present invention.
As shown in fig. 4, in a subframe 0, a subframe 4, and a subframe 9 without NSSS where NRS is on an anchor carrier, NRS signals are located at OFDM symbols # 5, #6, #12, and #13 of the subframe. Since for the Inband mode, NRS signals exist in all downlink subframes, as well as downlink subframe 0, subframe 4, and downlink subframe 9 without NSSS; for the standby/Guardband mode, NRS signals exist in all downlink subframes, and downlink subframe 0, subframe 1, subframe 3, subframe 4, and subframe 9 without NSSS, and there is a situation where the deployment mode of the network is unknown when the NRS signals are acquired. To better accommodate different NB-IoT network deployment patterns, subframe 0, subframe 4, and subframe 9 without NSSS of NRS signals on the anchor carrier are collected.
Fig. 5 is a schematic diagram of an OFDM symbol data storage format according to an embodiment of the present invention.
As shown in fig. 5, the OFDM symbol specifically includes:
(1) and acquiring OFDM symbol basic information, wherein the OFDM symbol basic information comprises acquired cell ID, frequency point EARFCN/Band, network side information IMSI, deployment mode, AGC information, frame number, subframe number, OFDM symbol type, OFDM symbol number and the like.
(2) The OFDM symbol data length refers to the total length of the OFDM symbol data, and includes CRC information.
(3) The OFDM symbol data refers to OFDM symbol data collected at 240 kHz.
(4) The CRC information is 32-bit CRC check bit information.
After the above process, the modem 11 transmits the OFDM symbol data to the application processor 12, and adds 32-bit CRC check bits when transmitting.
The application processor 12 is a processor of the NB-IoT terminal, and in this embodiment, the application processor 12 is configured to perform compression of the OFDM symbol and includes a data compression unit.
The data compression unit is configured to compress the OFDM symbol data acquired by the modem 11, so as to occupy less air interface resources of the NB-IoT network 102 and facilitate data transmission. When the data compression unit performs data compression processing, 32 bits of CRC check bits are added.
Once NB-IoT terminal 101 enters RRC _ CNNT state, modem 11 sends the compressed OFDM symbols to cloud server 103 through wireless NB-IoT network 102.
In this embodiment, the positioning request message received by NB-IoT terminal 101 is sent to NB-IoT terminal 101 by cloud server 103 through NB-IoT network 102. In addition, in this embodiment, the application processor 12 further includes some applications that need to use positioning, and when the applications trigger the positioning requirement, the NB-IoT terminal also receives the positioning request message triggered by the application processor 12 and falls back to the RRC _ IDLE state from the RRC _ CNNT state.
The NB-IoT network 102 is configured by an NB-IoT base station 21(eNodeB), a core network 22(EPC), and the like, and is configured to complete wireless connection and data transmission with the NB-IoT terminal 101, and perform data transmission with the cloud server 103 through a wired network. The NB-IoT network 102 has functions of terminal access, attachment, and data transmission, and supports NB-IoT FDD duplexing and all frequency bands of NB-IoT FDD.
The cloud server 103 is configured to complete positioning related functions such as OFDM symbol data decompression, delay estimation, and position location estimation, and output terminal positioning information obtained finally.
Fig. 6 is a block diagram of a cloud server according to an embodiment of the present invention.
In order to complete the NB-IoT terminal positioning function, the cloud server 103 includes a base station information storage unit 31, a data decompression unit 32, a time delay estimation unit 33, a terminal positioning calculation unit 34, a positioning output unit 35, a server communication unit 36, and a server control unit 37 for controlling the above units.
The base station information storage unit 31 stores location information of each NB-IoT base station and time synchronization information of each cell under each NB-IoT base station.
The data decompression unit 32 is configured to perform decompression processing on the compressed OFDM symbol data received by the server communication unit 36 from the NB-IoT terminal 101.
The delay estimation unit 33 is configured to perform delay estimation according to NPSS/NSSS/NRS signals collected from all neighboring cells around the base station of the serving cell, and calculate a delay estimation difference RSTD between different neighboring cells and the serving cell.
The terminal location calculating unit 34 is configured to calculate longitude/latitude and confidence information of the position of the NB-IoT terminal 101 as terminal location information by using the delay estimation difference RSTD and the position information of the NB-IoT base station and the base station synchronization time difference information stored in the base station information storage unit 31.
The positioning output unit 35 is configured to send the terminal positioning information to the NB-IoT terminal 101, the client 104, or the third party positioning related application platform 105 through a wireless network or a wired network (i.e., the communication network 106).
The client 104 is a user terminal held by a client, such as a mobile phone, a tablet, a computer, and the like.
Fig. 7 is a block diagram of the client in the embodiment of the present invention.
In the present embodiment, the client 104 includes a screen storage unit 41, an input display unit 42, a client communication unit 43, and a client control unit 44 that controls the above units.
The screen storage unit 41 stores a positioning request screen and a positioning check screen.
The positioning request screen is used for enabling the client to select one NB-IoT terminal needing to confirm the position as the NB-IoT terminal to be positioned.
In this embodiment, once the client confirms to select, the client side communication unit 43 sends a positioning request message to the NB-IoT terminal to be positioned through the communication network 106, the cloud server 104, and the NB-IoT network 102, so that the NB-IoT terminal starts to acquire and position the OFDM symbol. Once the cloud server 103 calculates the terminal positioning information of the NB-IoT terminal to be positioned, the positioning output unit 35 outputs the terminal positioning information to the client.
The positioning viewing screen is used for displaying when the client side communication unit 43 receives the terminal positioning information, and displaying the terminal positioning information of the NB-IoT terminal to be positioned in the screen for the client to view, thereby implementing the presentation of the positioning information.
The input display unit 42 is used for displaying the above-mentioned screens, so that the customer can complete the corresponding human-computer interaction through the screens.
The third party positioning application platform 105 is a positioning application platform used by a third party, and is configured to complete functions of position display, query, trajectory display, and the like of the NB-IoT terminal 101 according to the terminal positioning information output by the cloud server.
Fig. 8 is a flowchart of an NB-IoT terminal positioning method in an embodiment of the present invention.
As shown in fig. 8, the NB-IoT terminal positioning method implemented by the NB-IoT terminal positioning system 100 when positioning the NB-IoT terminal 101 specifically includes the following steps:
step 201, on the basis that NB-IoT terminal 101 searches for a network cell signal and successfully attaches, NB-IoT network 102 triggers or NB-IoT terminal 101 itself triggers a positioning request, and issues the positioning request message to modem 11 through AT command message, NB-IoT terminal 101 receives the positioning request message in RRC _ CNNT state, and then retreats from RRC _ CNNT state to RRC _ IDLE state, and then enters step 202;
in step 210, the cloud server 103 sends the terminal location information to the client 104 or the third party positioning related application platform 105 through the communication network 106, and then enters an end state.
Examples effects and effects
According to the NB-IoT terminal positioning system and the method provided by the embodiment, when the modem of the NB-IoT terminal collects the base station synchronization signal NPSS/NSSS and the reference signal NRS, different types of OFDM symbols are utilized for carrying out combination processing, and an application processor is utilized for carrying out data compression on the OFDM symbols, so that the performance of delay estimation can be improved, and the problem of large delay estimation error caused by small bandwidth of the NB-IoT system can be effectively resisted. Further, the time delay estimation difference of the peripheral cells to the service cell is calculated through the cloud server, and the terminal positioning information is further calculated according to the time synchronization information of all the base stations, the position information of the base stations and the time delay estimation difference obtained through calculation, so that the estimation performance is improved on the cloud server through a complex high-precision algorithm, and a server end with high processing capacity is effectively utilized to quickly obtain a calculation result. By the NB-IoT terminal positioning system, the NB-IoT network system does not need to be modified while the NB-IoT terminal position estimation is realized, so that the NB-IoT terminal positioning method has strong universality.
In the embodiment, the time delay estimation performance and the terminal position estimation performance are positively correlated with the number of OFDM symbols collected by the terminal.
The above-described embodiments are merely illustrative of specific embodiments of the present invention, and the present invention is not limited to the description of the above-described embodiments.
Claims (7)
1. An NB-IoT terminal positioning system for positioning an NB-IoT terminal, comprising:
at least one of the NB-IoT terminals comprising an application processor and a modem;
an NB-IoT network comprising a plurality of NB-IoT base stations, network signals of each of the NB-IoT base stations covering a plurality of cells; and
a cloud server in wired connection with the NB-IoT network,
wherein, the cloud server comprises a base station information storage unit, a data decompression unit, a time delay estimation unit, a terminal positioning calculation unit and a positioning output unit,
the base station information storage unit is used for storing the position information of each NB-IoT base station and the time synchronization information of each cell under each NB-IoT base station;
the NB-IoT terminal takes the cell corresponding to the network signal as a service cell and completes attachment when searching the network signal sent by the NB-IoT base station,
upon receipt of the location request message by the NB-IoT terminal in the RRC _ CNNT state, the NB-IoT terminal reverts from the RRC _ CNNT state to an RRC _ IDLE state and maintains time-frequency synchronization with the NB-IoT network,
the modem searches the cells existing around the NB-IoT terminal according to the positioning request message by using the idle time slot between two DRX times so as to obtain the time frequency synchronization information of each surrounding cell, receives a certain number of OFDM symbols of the base station synchronization signal NPSS/NSSS and the reference signal NRS from the NB-IoT base station according to the time frequency synchronization information, and further sends all the received OFDM symbols of the base station synchronization signal NPSS/NSSS and the reference signal NRS to the application processor,
the application processor performs data compression processing on the OFDM symbols to form compressed OFDM symbols,
upon the NB-IoT terminal entering the RRC _ CNNT state, the modem sends the compressed OFDM symbols to the cloud server over the wireless NB-IoT network,
once the service-side communication unit receives the compressed OFDM symbols, the data decompression unit performs data decompression processing on the compressed OFDM symbols to obtain decompressed OFDM symbols,
the time delay estimation unit carries out time delay estimation according to a base station synchronization signal NPSS/NSSS and a reference signal NRS sent by the peripheral cells and calculates the time delay estimation difference RSTD of different peripheral cells to the service cell,
the terminal positioning calculation unit calculates longitude and latitude and confidence information of the NB-IoT terminal as terminal positioning information by using the time delay estimation difference RSTD, the position information of the NB-IoT base station and the time synchronization information,
and the positioning output unit outputs the terminal positioning information.
2. The NB-IoT terminal location system in accordance with claim 1, wherein:
where NPSS is in subframe 5, NSSS is in subframe 9 of the even frame,
the base station synchronization signals NPSS/NSSS are all from OFDM symbol #3 to OFDM symbol #13 of the subframe, and 11 OFDM symbols are all adopted;
the sample rate of the NB-IoT terminal is set to 240kHz, with the exception that OFDM symbol #7 contains 18 samples and the other 10 OFDM symbols contain 17 samples;
the period of NPSS is 10ms, and the period of NSSS is 20 ms.
3. The NB-IoT terminal location system in accordance with claim 1, wherein:
where NRS is in sub-frame 0 on the anchor carrier, sub-frame 4 and sub-frame 9 without NSSS,
NRS is located at OFDM symbols #5, #6, #12, and #13 of the subframe.
4. The NB-IoT terminal location system in accordance with claim 1, wherein:
wherein the NB-IoT terminal falls back from the RRC _ CNNT state to the RRC _ IDLE state while maintaining normal communication with the serving cell,
when the modem collects the OFDM symbols, the following constraint limiting conditions are provided:
the carrier frequency offset cannot be adjusted;
the time offset cannot be adjusted;
the automatic gain control AGC cannot be adjusted;
sequentially collecting subsequent subframes with NPSS/NSSS/NRS from a subframe 0 of an even frame as a first collecting subframe until the number of the collected OFDM symbols meets the requirement of a set number, and then stopping the collection of the OFDM symbols;
in the acquisition process, besides acquiring NPSS/NSSS/NRS OFDM symbols, the acquired cell ID, frequency point EARFCN/Band, network side information IMSI, deployment mode, AGC information, frame number, subframe number, OFDM symbol type and OFDM symbol number are recorded, and finally the cell ID, the frequency point EARFCN/Band, the network side information IMSI, the deployment mode, AGC information, the frame number, the subframe number, the OFDM symbol type and the OFDM symbol number are transmitted to the cloud server together with the OFDM symbols;
and calculating the measurement of time frequency synchronization in the acquisition process of the OFDM symbols, and adjusting the time and frequency synchronization deviation of the NB-IoT terminal after the acquisition process is finished.
5. The NB-IoT terminal location system in accordance with claim 1, further comprising:
a client held by a client in communication connection with the cloud server,
wherein the client has a screen storage section, an input display section, and a client-side communication section,
the picture storage part stores a positioning request picture and a positioning check picture,
the input display part displays the positioning request picture to enable the client to select an NB-IoT terminal needing to confirm the position as an NB-IoT terminal to be positioned,
upon the client confirmation selection, the client side communication part sends a positioning request message to the NB-IoT terminal to be positioned through the cloud server and the NB-IoT network,
once the terminal location calculating unit calculates the terminal location information of the NB-IoT terminal to be located, the location output unit outputs the terminal location information to the client,
when the client side communication part receives the terminal positioning information, the input display part displays the positioning viewing picture and displays the terminal positioning information to enable the client to view the position of the NB-IoT terminal to be positioned.
6. The NB-IoT terminal location system in accordance with claim 1, further comprising:
a third party location related application platform in communication connection with the cloud server,
the positioning output unit outputs the terminal positioning information to the third-party positioning related application platform, so that the third-party positioning related application platform performs the functions of position display, position query and track display of the NB-IoT terminal according to the terminal positioning information.
7. An NB-IoT terminal positioning method is used for positioning NB-IoT terminals and is characterized by comprising the following steps:
when the NB-IoT terminal searches the network signal sent by the NB-IoT base station, the cell corresponding to the network signal is used as a service cell and attachment is completed;
once the NB-IoT terminal receives the positioning request message in the RRC _ CNNT state, the NB-IoT terminal retreats from the RRC _ CNNT state to the RRC _ IDLE state and maintains time-frequency synchronization with the NB-IoT network;
the modem of the NB-IoT terminal searches the cells existing around the NB-IoT terminal according to the positioning request message by using the idle time slot between two DRX times so as to obtain the time frequency synchronization information of each surrounding cell, receives a certain number of OFDM symbols of the base station synchronization signal NPSS/NSSS and the reference signal NRS from the NB-IoT base station according to the time frequency synchronization information, and further sends all the received OFDM symbols of the base station synchronization signal NPSS/NSSS and the reference signal NRS to the application processor of the NB-IoT terminal;
the application processor performs data compression processing on the OFDM symbols to form compressed OFDM symbols;
upon the NB-IoT terminal entering the RRC _ CNNT state, the modem sends the compressed OFDM symbols to a cloud server over the wireless NB-IoT network,
once the cloud server receives the compressed OFDM symbols, performing data decompression processing on the compressed OFDM symbols to obtain decompressed OFDM symbols;
the cloud server performs time delay estimation according to a base station synchronization signal NPSS/NSSS and a reference signal NRS sent by the peripheral cell, and calculates time delay estimation difference RSTD of different peripheral cells to the service cell;
the cloud server calculates longitude and latitude and confidence degree information of the NB-IoT terminal as terminal positioning information by using the time delay estimation difference RSTD, the position information of the NB-IoT base station and the time synchronization information,
and the cloud server outputs the terminal positioning information to an NB-IoT terminal, a client or a third party positioning related application platform.
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