CN111263436B - System and method for calculating distance between user terminal and base station in LTE system - Google Patents
System and method for calculating distance between user terminal and base station in LTE system Download PDFInfo
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Abstract
The embodiment of the invention provides a system and a method for calculating the distance between a user terminal and a base station in an LTE system, which comprises a radio frequency front end receiving module, a digital signal processing module, a PBCH and PCFICH decoding module, a PDCCH blind detection module, a PDSCH decoding module and a Mac layer analyzing and processing module; the radio frequency front end receiving module is used for receiving a downlink signal sent by the base station to the target user terminal and converting the downlink signal into a baseband signal from a radio frequency signal; the digital signal processing module is used for processing the downlink signal; the PBCH and PCFICH decoding module, the PDCCH blind detection module and the PDSCH decoding module are sequentially interacted so as to perform physical layer demodulation of a PDSCH on downlink signals; and the Mac layer analysis processing module is used for calculating the distance between the target user terminal and the base station according to the key information of the downlink signal without additionally increasing the transmitting power, so that the target user has zero perception and has zero interference on other users.
Description
Technical Field
The invention belongs to the technical field of mobile communication, and particularly relates to a system and a method for calculating the distance between a user terminal and a base station in an LTE (Long term evolution) system.
Background
With the rapid development of LTE (Long Term Evolution ) technology, more and more users use LTE mobile terminals. In many applications, such as search and rescue, a target user terminal needs to be located. When positioning, the distance between the target user terminal and the base station needs to be determined, and then the target user terminal is positioned according to the direction of the target user terminal and the distance from the base station.
In the prior art, a 2G interference signal or a 3G interference signal with a large power is usually sent to a target user terminal, the target user terminal is returned to a 2G network or a 3G network from an LTE network, then response information sent by the target user terminal is analyzed, and a distance between a mobile terminal and a base station is determined according to an analysis result. Therefore, the target user terminal cannot use the LTE signal, is easily perceived by the target user, and simultaneously causes interference to the peripheral LTE user terminals.
Therefore, how to locate the LTE target ue and how to avoid interference between the LTE network normally used by the target ue and other ues are an urgent problem to be solved.
Disclosure of Invention
In order to overcome the problem that the target user terminal cannot use the LTE network due to the existing user terminal positioning method, is easily perceived by the target user terminal, and simultaneously interferes with the surrounding user terminals, or at least partially solves the problem, embodiments of the present invention provide a system and a method for calculating a distance between a user terminal and a base station in an LTE system.
According to a first aspect of the embodiments of the present invention, there is provided a system for calculating a distance between a user terminal and a base station in an LTE system, including:
the system comprises a radio frequency front end receiving module, a digital signal processing module, a PBCH and PCFICH decoding module, a PDCCH blind detection module, a PDSCH decoding module and a Mac layer analysis processing module;
the radio frequency front end receiving module is used for receiving a downlink signal sent to a target user terminal by a base station in an LTE system, converting the downlink signal into a baseband signal from a radio frequency signal and sending the baseband signal to the digital signal processing module;
the digital signal processing module is used for processing the downlink signal and then sending the processed downlink signal to the PBCH and PCFICH decoding module;
the PBCH and PCFICH decoding module, the PDCCH blind detection module and the PDSCH decoding module are sequentially interacted so as to perform physical layer demodulation of a PDSCH on the downlink signal;
and the Mac layer analysis processing module is used for acquiring key information of the downlink signal according to the downlink signal demodulated by the physical layer and calculating the distance between the target user terminal and the base station according to the key information.
Specifically, the digital signal processing module is specifically configured to: and performing CP removal and FFT conversion on the downlink signal to a frequency domain, performing channel estimation, frequency offset estimation and frequency offset compensation on the downlink information of the frequency domain, and sending the processed downlink signal to the PBCH and PCFICH decoding module.
Specifically, the PBCH and PCFICH decoding module is configured to decode the PBCH and PCFICH of the processed downlink signal, acquire MIB information and CFI information of the downlink signal, demodulate the downlink signal according to the MIB information and CFI information, and send the downlink signal after decoding the PCFICH to the PDCCH blind detection module.
Specifically, the PDCCH blind detection module is configured to perform blind detection on the downlink signal, and send the downlink signal to the PDSCH decoding module if the downlink signal passes through PDCCH CRC.
Specifically, the PDSCH decoding module is configured to decode the downlink signal, and send the downlink signal to the Mac layer parsing module if the downlink signal passes through PDSCH CRC.
Specifically, the PDCCH blind detection module is specifically configured to:
blind detection is carried out on the downlink signals, and RNTI of the downlink signals is calculated;
if the LTE system is a TDD system, when the RNTI is located in a first preset range, the RNTI is known to be RA-RNTI, the PDSCH of the LTE system bears RAR, otherwise, if the RNTI is not P-RNTI or is not SI-RNTI, the PDSCH bears MSG 4;
if the LTE system is in an FDD mode, when the RNTI is located in a second preset range, the RNTI is known to be RA-RNTI, the PDSCH bears RAR, otherwise, if the RNTI is not P-RNTI or is not SI-RNTI, the PDSCH bears MSG 4;
accordingly, the PDSCH decoding module is specifically configured to: and carrying out PDSCH decoding on the downlink signal by using the RNTI, and if the downlink signal passes through PDSCH CRC, sending the downlink signal to the Mac layer analysis processing module.
Specifically, the Mac layer parsing module is specifically configured to:
if the PDSCH bears RAR, decoding the MSG2 in the downlink signal to obtain TA and RNTI of the MSG 2;
if the PDSCH carries MSG4, decoding MSG4 in the downlink signal to obtain mtmsi of the MSG 4;
if the RNTI of the MSG2 is matched with the RNTI of the MSG4, the mtmsi of the MSG4 is saved in the MSG 2;
if the mtmsi of the MSG4 is matched with the target _ mtmsi of the target user terminal, and the mtmsi stored in the MSG2 is matched with the target _ mtmsi of the target user terminal, calculating the distance between the target user terminal and the base station according to the TA of the MSG 2.
Specifically, the Mac layer parsing module calculates the distance between the target ue and the base station according to TA of the MSG2 through the following formula:
S＝C*(16Ts*TA/2)；
wherein S is a distance between the target user terminal and the base station, C is a speed of electromagnetic waves, and Ts is a basic time unit.
According to a second aspect of the embodiments of the present invention, there is provided a method for calculating a distance between a user terminal and a base station in an LTE system, including:
receiving a downlink signal issued to a target user terminal by a base station in an LTE system through a radio frequency front end receiving module, converting the downlink signal into a baseband signal from a radio frequency signal, and sending the baseband signal to a digital signal processing module;
the digital signal processing module processes the downlink signal and sends the processed downlink signal to a PBCH and PCFICH module;
sequentially interacting the PBCH and PCFICH decoding module, the PDCCH blind detection module and the PDSCH decoding module to perform physical layer demodulation of the PDSCH on the downlink signal;
and acquiring key information of the downlink signal according to the downlink signal demodulated by the physical layer through a Mac layer analysis processing module, and calculating the distance between the target user terminal and the base station according to the key information.
Specifically, the step of sending the processed downlink signal to the PBCH and PCFICH decoding module by the digital signal processing module includes:
specifically, the digital signal processing module performs CP removal and FFT conversion on the downlink signal to a frequency domain, performs channel estimation, frequency offset estimation and frequency offset compensation on the downlink information of the frequency domain, and sends the processed downlink signal to the PBCH and PCFICH decoding module.
The embodiment of the invention provides a system and a method for calculating the distance between a user terminal and a base station in an LTE system, wherein the system can calculate the distance between a target user terminal and the base station only by monitoring a downlink signal transmitted by the LTE base station without constructing other messages, does not need to additionally increase the transmitting power, and has the advantages of low power consumption, low cost, simple calculation and less occupied memory; the obtained distance between the target user terminal and the base station is carried out under the condition that the target user terminal is not interfered to use an LTE network, the target user has zero perception, and the distance has zero interference on other users.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a system for calculating a distance between a user terminal and a base station in an LTE system according to an embodiment of the present invention;
fig. 2 is a schematic overall flow chart of a method for calculating a distance between a user terminal and a base station in an LTE system according to an embodiment of the present invention;
00-base station; a 10-LTE signal acquisition processor; the system comprises a radio frequency front end receiving module, a digital signal processing module 12, a PBCH and PCFICH decoding module 13, a PDCCH blind detection module 14, a PDSCH decoding module 15, a Mac layer analyzing and processing module 16 and a target user terminal 20.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
In an embodiment of the present invention, a system for calculating a distance between a ue and a base station in an LTE system is provided, and fig. 1 is a schematic diagram of the system for calculating a distance between a ue and a base station in an LTE system according to an embodiment of the present invention, where the system includes a radio frequency front end receiving module 11, a digital signal processing module 12, a PBCH (Physical broadcast channel) decoding module 13, a PCFICH (Physical control format indicator channel) decoding module 13, a PDCCH (Physical downlink control channel) blind detection module 14, a PDSCH (Physical downlink shared channel) decoding module 15, and a Mac (Medium access control) layer parsing processing module 16;
in this embodiment, the radio frequency front end receiving module 11, the digital signal processing module 12, the PBCH and PCFICH decoding module 13, the PDCCH blind detection module 14, the PDSCH decoding module 15, and the Mac layer parsing processing module 16 are integrally used as the LTE signal acquisition processor 10, the LTE signal acquisition processor 10 is respectively communicated with the base station 00 and the target user terminal 20, and the connection mode is wireless connection, and data receiving and data transmitting are performed through the transceiving antenna. Base station 00 is a universal base station based on the international 3GPP standard, i.e. a public network base station laid by an operator. The target user terminal 20 is a terminal of an LTE system based on the international 3GPP standard, and is a target user terminal that needs to be positioned.
The radio frequency front end receiving module 11 is configured to receive a downlink signal sent by a base station to a target user terminal in an LTE system, convert the downlink signal from a radio frequency signal to a baseband signal, and send the baseband signal to the digital signal processing module 12; the digital signal processing module is used for processing the downlink signal and then sending the processed downlink signal to the PBCH and PCFICH decoding module;
the rf front-end receiving module 11 interacts with the digital signal processing module 12, receives the uplink signal of the target user terminal 20 and the downlink signal of the base station 00, and completes the conversion from the rf signal to the baseband signal. In addition, the radio frequency front end receiving module 11 is further configured to sweep frequency to obtain public network information where the target user terminal resides, that is, information of the base station 00, perform cell search, and perform downlink synchronization with the public network. Specifically, the information of the base station where the target user terminal resides is obtained through third-party software, the information of the target user terminal and the LTE base station where the target user terminal resides can be obtained through other software, the test interface can be set and written into the system, and a message does not need to be constructed in the system to be obtained.
The digital signal processing module 12 mainly performs CP (Cyclic Prefix) removal and FFT (Fast Fourier Transform) conversion to a frequency domain, channel estimation, frequency offset estimation, and frequency offset compensation on the downlink signal of the base station 00 received from the rf front end receiving module 11, and processes the uplink signal of the target user terminal 20 received from the rf front end receiving module 11 to obtain physical layer parameters of the target user terminal.
The PBCH and PCFICH decoding module 13, the PDCCH blind detection module 14, and the PDSCH decoding module 15 interact with each other in sequence to perform physical layer demodulation of the PDSCH on the downlink signal; the PDSCH decoding module 15 interacts with the Mac layer parsing processing module 16 to complete acquisition of the critical information TA (Timing Advance).
The Mac layer parsing and processing module 16 is configured to obtain key information of the downlink signal according to the downlink signal demodulated by the physical layer, and calculate a distance between the target user terminal 20 and the base station 00 according to the key information.
The system in the embodiment does not need to construct other messages, can calculate the distance between the target user terminal and the base station only by monitoring the downlink signal transmitted by the LTE base station, does not need to additionally increase the transmitting power, and has low power consumption, low cost, simple calculation and less occupied memory; the obtained distance between the target user terminal and the base station is carried out under the condition that the target user terminal is not interfered to use an LTE network, the target user has zero perception, and the distance has zero interference on other users.
On the basis of the foregoing embodiment, in this embodiment, the PBCH and PCFICH decoding module 13 is configured to decode the PBCH and PCFICH of the processed downlink signal, acquire MIB (Master Information block) Information and CFI (Control Format Indicator) Information of the downlink signal, demodulate the downlink signal according to the MIB Information and the CFI Information, and send the downlink signal after decoding the PCFICH to the PDCCH blind detection module 14.
Wherein, PBCH and PCFICH decoding comprises demapping, equalization, demodulation, descrambling and channel coding.
On the basis of the foregoing embodiment, in this embodiment, the PDCCH blind detection module 14 is configured to perform blind detection on the downlink signal, and if the downlink signal passes through a PDCCH CRC (Cyclic Redundancy Check), send the downlink signal to the PDSCH decoding module 15.
On the basis of the foregoing embodiment, in this embodiment, the PDSCH decoding module 15 is configured to decode the downlink signal, and if the downlink signal passes through PDSCH CRC, send the downlink signal to the Mac layer parsing module 16, so that the Mac layer parsing module 16 obtains a TA value according to the downlink signal and calculates a distance between the target user terminal 20 and the base station 00 according to the TA value.
On the basis of the foregoing embodiment, in this embodiment, the PDCCH blind detection module is specifically configured to: blind detection is carried out on the downlink signal, and RNTI (Radio Network temporary Identity) of the downlink signal is calculated; if the LTE system is a TDD (Time Division duplex) system, when the RNTI is located within a first preset range, it is known that the RNTI is an RA-RNTI (Random Access RNTI), a PDSCH of the LTE system bears an RAR, otherwise, if the RNTI is not a P-RNTI or is not an SI-RNTI, it is known that the PDSCH bears an MSG 4;
specifically, for the LTE with TDD, if the RNTI of the downlink signal is located in a first preset range, if 0< RNTI <61, it is known that the RNTI of the downlink signal is RA-RNTI, and the PDSCH carries RAR (Random Access Response).
If the LTE system is in an FDD (Frequency Division duplex) mode, when the RNTI is located in a second preset range, acquiring that the RNTI is RA-RNTI and the PDSCH bears RAR, otherwise, if the RNTI is not P-RNTI or is not SI-RNTI, acquiring that the PDSCH bears MSG 4;
for the LTE with FDD system, if the RNTI of the downlink signal is located in the second preset range, if 0< RNTI <11, the RNTI of the downlink signal is known as RA-RNTI, and the PDSCH carries RAR.
And if the RNTI of the downlink signal is known to be RA-RNTI, decoding the PDSCH by using the RA-RNTI, if the CRC check of the PDSCH passes, sending the downlink signal to a Mac layer analysis processing module, and otherwise, returning to continue PDCCH blind test.
If the RNTI of the downlink signal is the RNTI of the MSG4(Contention resolution message), the PDSCH is decoded using the RNTI. And if the PDSCH CRC passes the check, sending the downlink signal to a Mac layer analysis processing module, and otherwise, returning to continue the PDCCH blind test.
Accordingly, the PDSCH decoding module is specifically configured to: and carrying out PDSCH decoding on the downlink signal by using the RNTI, and if the downlink signal passes through PDSCH CRC, sending the downlink signal to the Mac layer analysis processing module.
On the basis of the foregoing embodiment, the Mac layer parsing processing module is specifically configured to: if the PDSCH carries RAR, decoding MSG2(Random access response message) in the downlink signal to obtain TA and RNTI of the MSG 2;
if the PDSCH carries the MSG4, decoding the MSG4 in the downlink signal to obtain an mtmsi (MME-temporary mobile subscriber identity) of the MSG 4;
if the RNTI of the MSG2 is matched with the RNTI of the MSG4, the mtmsi of the MSG4 is saved in the MSG 2;
if the mtmsi of the MSG4 is matched with the target _ mtmsi (temporary identifier of the target user) of the target user terminal, and the mtmsi stored in the MSG2 is matched with the target _ mtmsi of the target user terminal, calculating the distance between the target user terminal and the base station according to the TA of the MSG 2.
On the basis of the foregoing embodiment, in this embodiment, the Mac layer parsing module specifically calculates the distance between the target ue and the base station according to the TA of the MSG2 through the following formula:
S＝C*(16Ts*TA/2)；
wherein S is a distance between the target ue and the base station, C is a velocity of the electromagnetic wave, which is approximately equal to 300000000m/S, Ts (Time units) is a basic Time unit, and 1Ts is 1/(2048 × 15000) S.
In another embodiment of the present invention, a method for calculating a distance between a user terminal and a base station in an LTE system is provided, and the method is implemented based on the systems in the foregoing embodiments. Therefore, the description and definition in the embodiments of the system for calculating the distance between the ue and the base station in the LTE system can be used for understanding the steps performed in the embodiments of the present invention. Fig. 2 is a schematic flow chart of a method for calculating a distance between a user terminal and a base station in an LTE system according to an embodiment of the present invention, where the method includes: s201, receiving a downlink signal issued to a target user terminal by a base station in an LTE system through a radio frequency front end receiving module, converting the downlink signal into a baseband signal from a radio frequency signal, and sending the baseband signal to a digital signal processing module;
receiving a downlink signal issued to a target user terminal by a base station in an LTE system through a radio frequency front end receiving module, converting the downlink signal into a baseband signal from a radio frequency signal, and sending the baseband signal to a digital signal processing module; the digital signal processing module is used for processing the downlink signal and then sending the processed downlink signal to the PBCH and PCFICH decoding module;
the radio frequency front end receiving module interacts with the digital signal processing module, receives an uplink signal of a target user terminal and a downlink signal of a base station, and simultaneously completes conversion from the radio frequency signal to a baseband signal. In addition, the frequency sweeping of the radio frequency front end receiving module is used for acquiring the public network information where the target user terminal resides, namely the information of the base station, and carrying out cell search and downlink synchronization with the public network. Specifically, the information of the base station where the target user terminal resides is obtained through third-party software, the information of the target user terminal and the LTE base station where the target user terminal resides can be obtained through other software, the test interface can be set and written into the system, and a message does not need to be constructed in the system to be obtained.
S202, the downlink signal is processed by the digital signal processing module and then sent to a PBCH and PCFICH module;
the digital signal processing module is mainly used for removing CP and FFT from the downlink signal of the base station received from the radio frequency front end receiving module, converting the downlink signal into a frequency domain, carrying out channel estimation, frequency offset estimation and frequency offset compensation, and processing the uplink signal of the target user terminal received from the radio frequency front end receiving module so as to obtain the physical layer parameters of the target user terminal.
S203, sequentially interacting through a PBCH and PCFICH decoding module, a PDCCH blind detection module and a PDSCH decoding module to perform physical layer demodulation of a PDSCH on the downlink signal; and the PDSCH resolving module interacts with the Mac layer analysis processing module to complete the acquisition of the key information TA.
And S204, acquiring key information of the downlink signal according to the downlink signal demodulated by the physical layer through a Mac layer analysis processing module, and calculating the distance between the target user terminal and the base station according to the key information.
In the embodiment, other messages are not required to be constructed, and the distance between the target user terminal and the base station can be calculated only by monitoring the downlink signal transmitted by the LTE base station, so that the transmission power does not need to be additionally increased, the power consumption is low, the cost is low, the calculation is simple, and the occupied memory is less; the obtained distance between the target user terminal and the base station is carried out under the condition that the target user terminal is not interfered to use an LTE network, the target user has zero perception, and the distance has zero interference on other users.
On the basis of the foregoing embodiment, in this embodiment, the step of processing the downlink signal by the digital signal processing module and then sending the processed downlink signal to the PBCH and PCFICH demodulating module includes: specifically, the digital signal processing module performs CP removal and FFT conversion on the downlink signal to a frequency domain, performs channel estimation, frequency offset estimation and frequency offset compensation on the downlink information of the frequency domain, and sends the processed downlink signal to the PBCH and PCFICH decoding module.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (9)
1. A system for calculating the distance between a user terminal and a base station in an LTE system is characterized by comprising a radio frequency front end receiving module, a digital signal processing module, a physical broadcast channel PBCH and physical control format indication channel PCFICH decoding module, a physical downlink control channel PDCCH blind detection module, a physical downlink shared channel PDSCH decoding module and a media access control Mac layer analysis processing module;
the radio frequency front end receiving module is used for receiving a downlink signal sent to a target user terminal by a base station in an LTE system, converting the downlink signal into a baseband signal from a radio frequency signal and sending the baseband signal to the digital signal processing module;
the digital signal processing module is used for processing the downlink signal and then sending the processed downlink signal to the PBCH and PCFICH decoding module;
the PBCH and PCFICH decoding module, the PDCCH blind detection module and the PDSCH decoding module are sequentially interacted so as to perform physical layer demodulation of a PDSCH on the downlink signal;
the Mac layer analysis processing module is used for acquiring a Time Advance (TA) of the downlink signal according to the downlink signal demodulated by the physical layer and calculating the distance between the target user terminal and the base station according to the TA;
the Mac layer parsing module is specifically configured to:
if the PDSCH bears a Random Access Response (RAR), decoding a random access response message (MSG 2) in the downlink signal to acquire a TA (timing advance) of the MSG2 and a Radio Network Temporary Identifier (RNTI);
if the PDSCH carries a contention resolution message MSG4, decoding the MSG4 in the downlink signal to obtain a temporary mobile subscriber identity (mtmsi) of the MSG 4;
if the RNTI of the MSG2 is matched with the RNTI of the MSG4, the mtmsi of the MSG4 is saved in the MSG 2;
if the mtmsi of the MSG4 is matched with the target user temporary identifier target _ mtmsi of the target user terminal, and the mtmsi stored in the MSG2 is matched with the target _ mtmsi of the target user terminal, calculating the distance between the target user terminal and the base station according to the TA of the MSG 2;
the PDCCH blind detection module is specifically configured to: and performing blind detection on the downlink signal, and calculating the RNTI of the downlink signal.
2. The system of claim 1, wherein the digital signal processing module is specifically configured to: and performing cyclic prefix CP removal and Fast Fourier Transform (FFT) conversion on the downlink signal to a frequency domain, performing channel estimation, frequency offset estimation and frequency offset compensation on the downlink information of the frequency domain, and sending the processed downlink signal to the PBCH and PCFICH decoding module.
3. The system of claim 1, wherein the PBCH and PCFICH decoding module is configured to decode PBCH and PCFICH from the processed downlink signal, acquire master information block, MIB, information and control format indicator, CFI, information of the downlink signal, demodulate the downlink signal according to the MIB and CFI information, and send the downlink signal after decoding PCFICH to the PDCCH blind detection module.
4. The system according to claim 1, wherein the PDCCH blind detection module is configured to perform blind detection on the downlink signal, and send the downlink signal to the PDSCH decoding module if the downlink signal passes PDCCH cyclic redundancy check CRC.
5. The system of claim 1, wherein the PDSCH decoding module is configured to decode the downlink signal, and send the downlink signal to the Mac layer parsing module if the downlink signal passes PDSCH CRC.
6. The system of claim 4, wherein the PDCCH blind detection module is specifically configured to:
if the LTE system is a time division duplex TDD system, when the RNTI is located in a first preset range, acquiring that the RNTI is a random access radio network temporary identifier RA-RNTI, and the PDSCH of the LTE system bears RAR, otherwise, acquiring that the PDSCH bears MSG4 if the RNTI is not P-RNTI or is not SI-RNTI;
if the LTE system is in an FDD mode, when the RNTI is located in a second preset range, the RNTI is known to be RA-RNTI, the PDSCH bears RAR, otherwise, if the RNTI is not P-RNTI or is not SI-RNTI, the PDSCH bears MSG 4;
accordingly, the PDSCH decoding module is specifically configured to: and carrying out PDSCH decoding on the downlink signal by using the RNTI, and if the downlink signal passes through PDSCH CRC, sending the downlink signal to the Mac layer analysis processing module.
7. The system of claim 1, wherein the Mac layer parsing processing module calculates the distance between the target ue and the base station according to TA of the MSG2 by using the following formula:
S=C*（16Ts*TA/2）；
wherein S is a distance between the target user terminal and the base station, C is a speed of electromagnetic waves, and Ts is a basic time unit.
8. A method for calculating a distance between a user terminal and a base station in an LTE system, comprising:
receiving a downlink signal issued to a target user terminal by a base station in an LTE system through a radio frequency front end receiving module, converting the downlink signal into a baseband signal from a radio frequency signal, and sending the baseband signal to a digital signal processing module;
the digital signal processing module processes the downlink signal and sends the processed downlink signal to a physical broadcast channel PBCH and physical control format indicator channel PCFICH module;
sequentially interacting a PBCH and PCFICH decoding module, a PDCCH blind detection module and a PDSCH decoding module to perform physical layer demodulation of a PDSCH on the downlink signal;
acquiring a Time Advance (TA) of the downlink signal according to the downlink signal demodulated by a physical layer through a media access control (Mac) layer analysis processing module, and calculating the distance between the target user terminal and the base station according to the TA;
blind detection is carried out on the downlink signal through a PDCCH blind detection module, and RNTI of the downlink signal is calculated;
the calculating, by the Mac layer, the distance between the target user equipment and the base station according to the TA includes:
if the PDSCH bears a Random Access Response (RAR), decoding a random access response message (MSG 2) in the downlink signal to acquire a TA (timing advance) of the MSG2 and a Radio Network Temporary Identifier (RNTI);
if the PDSCH carries a contention resolution message MSG4, decoding the MSG4 in the downlink signal to obtain a temporary mobile subscriber identity (mtmsi) of the MSG 4;
if the RNTI of the MSG2 is matched with the RNTI of the MSG4, the mtmsi of the MSG4 is saved in the MSG 2;
if the mtmsi of the MSG4 is matched with the target user temporary identifier target _ mtmsi of the target user terminal, and the mtmsi stored in the MSG2 is matched with the target _ mtmsi of the target user terminal, calculating the distance between the target user terminal and the base station according to the TA of the MSG 2.
9. The method of claim 8, wherein the step of processing the downlink signal by the digital signal processing module and then sending the processed downlink signal to the PBCH and PCFICH decoding module comprises:
specifically, the digital signal processing module performs CP removal and FFT conversion on the downlink signal to a frequency domain, performs channel estimation, frequency offset estimation and frequency offset compensation on the downlink information of the frequency domain, and sends the processed downlink signal to the PBCH and PCFICH decoding module.
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| CN202010054383.6A CN111263436B (en) | 2020-01-17 | 2020-01-17 | System and method for calculating distance between user terminal and base station in LTE system |
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| CN202010054383.6A CN111263436B (en) | 2020-01-17 | 2020-01-17 | System and method for calculating distance between user terminal and base station in LTE system |
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