A method and apparatus for simulating communication of an LTE base station at a custom frequency

Abstract

The application discloses a communication method and device for simulating an LTE base station at a self-defined frequency, and the method comprises the following steps: setting a preset frequency range and determining a preset center frequency of the LTE base station by using software, determining a system bandwidth range of the LTE base station according to the preset center frequency and a preset channel bandwidth of an LTE cell; the preset center frequency is a center frequency outside a frequency range specified by a 3GPP protocol; generating a synchronization signal frequency conforming to the 3GPP protocol according to the system bandwidth range and a preset rule and converting the synchronization signal frequency into a corresponding synchronization signal frequency point number; selecting a target synchronization signal frequency point number meeting a preset condition from the synchronization signal frequency point number, and realizing frequency synchronization between a terminal and the LTE base station; starting the LTE base station, and establishing an LTE cell with the preset center frequency as a center frequency and with the preset channel bandwidth as a bandwidth to send and receive radio frequency signals. The application can simulate the LTE base station at a non-3GPP protocol frequency, and has good expansibility.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication technology, in particular to a communication method and device for simulating an LTE base station at a self-defined frequency. BACKGROUND

[0002] LTE (Long Term Evolution) is a standard for 4G wireless communication technology, and has the advantages of fast communication speed, wide network spectrum, high intelligent performance, good compatibility, high frequency efficiency and high communication quality, and is therefore widely used in current public network communication and private network communication.

[0003] At present, existing commercial LTE base stations and simulated LTE base stations can only support frequency bands within the range specified by the 3GPP protocol when using frequencies, and cannot use frequencies outside the range specified by the 3GPP protocol, and cannot implement commercial mobile phone access, which is not conducive to the simulation and research and development of LTE base stations. SUMMARY

[0004] The purpose of the present application is to provide a communication method and device for simulating an LTE base station at a self-defined frequency, to solve the technical problem that existing LTE base stations cannot use frequencies outside the range specified by the 3GPP protocol.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] A communication method for simulating an LTE base station at a self-defined frequency, comprising:

[0007] Setting a preset frequency band of the LTE base station on a PC using software, determining a preset center frequency according to the preset frequency band, and determining a system bandwidth range of the LTE base station according to the preset center frequency and a preset channel bandwidth of an LTE cell; the preset center frequency is a center carrier frequency for the LTE base station to work outside the frequency range specified by the 3GPP protocol;

[0008] Generating a synchronization signal frequency that meets the requirements of the 3GPP protocol according to the system bandwidth range and a preset rule, and generating a corresponding synchronization signal frequency point number according to the synchronization signal frequency;

[0009] Selecting a target synchronization signal frequency point number that meets a preset condition from the synchronization signal frequency point number, and achieving communication synchronization between a terminal and the LTE base station according to the target synchronization signal frequency point number;

[0010] Starting the LTE base station, and establishing an LTE cell with the preset center frequency as the center frequency and the preset channel bandwidth as the bandwidth to transmit and receive radio frequency signals.

[0011] Optionally, generating the synchronization signal frequency meeting the requirement of the 3GPP protocol according to the system bandwidth range and the preset rule comprises:

[0012] According to the preset channel bandwidth, the total number of frequency resources corresponding to the preset channel bandwidth is obtained, the continuous frequency resources are intercepted from the total number of frequency resources according to the size of the synchronization signal bandwidth, and the synchronization signal frequency meeting the requirement of the 3GPP protocol is generated according to the continuous frequency resources.

[0013] Optionally, before selecting the target synchronization signal frequency point number meeting the preset condition from the synchronization signal frequency point numbers, the method further comprises:

[0014] According to the system bandwidth range, the corresponding system radio frequency point range is generated, and the system radio frequency point range comprises a minimum system radio frequency point and a maximum system radio frequency point.

[0015] Optionally, the preset condition is that:

[0016] The difference between the target synchronization signal frequency point number and the minimum system radio frequency point or the maximum system radio frequency point is greater than half of the synchronization signal bandwidth.

[0017] Optionally, the preset center frequency is 5145.0 MHZ for the downlink and 5096.0 MHZ for the uplink.

[0018] Optionally, the preset channel bandwidth of the LTE cell is 5 MHZ.

[0019] Optionally, after determining the preset center frequency according to the preset frequency band, the method further comprises:

[0020] According to the preset center frequency, the corresponding preset center frequency point number is generated.

[0021] The application further provides a communication device for simulating an LTE base station at a self-defined frequency, comprising:

[0022] A system bandwidth determination module is configured to set a preset frequency band of an LTE base station by using software on a PC, determine a preset center frequency according to the preset frequency band, and determine a system bandwidth range of the LTE base station according to the preset center frequency and a preset channel bandwidth of an LTE cell; the preset center frequency is a center carrier frequency of the LTE base station operating outside a frequency range specified by a 3GPP protocol;

[0023] A synchronization signal generation module is configured to generate a synchronization signal frequency meeting the requirement of the 3GPP protocol according to the system bandwidth range and a preset rule, and generate a synchronization signal frequency point number corresponding to the synchronization signal frequency.

[0024] The frequency synchronization implementation module is used for selecting a target synchronization signal frequency point number meeting a preset condition from the synchronization signal frequency point numbers, and realizing communication synchronization between the terminal and the LTE base station according to the target synchronization signal frequency point number.

[0025] The LTE cell establishment module is used for starting the LTE base station, and establishing an LTE cell with the preset center frequency as a center frequency and with the preset channel bandwidth as a bandwidth to transmit and receive radio frequency signals.

[0026] Optionally, the synchronization signal generation module generates the synchronization signal frequency meeting the requirement of the 3GPP protocol according to the system bandwidth range and a preset rule, and the method comprises the following steps.

[0027] The synchronization signal generation module acquires a total number of frequency resources corresponding to the preset channel bandwidth, intercepts continuous frequency resources on the total number of frequency resources according to the size of the synchronization signal bandwidth, and generates the synchronization signal frequency meeting the requirement of the 3GPP protocol according to the continuous frequency resources.

[0028] Optionally, the frequency synchronization implementation module further comprises the following steps before selecting the target synchronization signal frequency point number meeting the preset condition from the synchronization signal frequency point numbers.

[0029] The frequency synchronization implementation module generates a corresponding system radio frequency point range according to the system bandwidth range, and the system radio frequency point range comprises a minimum system radio frequency point and a maximum system radio frequency point.

[0030] The application provides a communication method and device for simulating an LTE base station with a self-defined frequency, and the method comprises the following steps: setting a preset frequency band of the LTE base station by using software on a PC, determining a preset center frequency according to the preset frequency band, determining a system bandwidth range of the LTE base station according to the preset center frequency and a preset channel bandwidth of an LTE cell; the preset center frequency is a center carrier frequency of the LTE base station working outside a frequency range specified by the 3GPP protocol; generating a synchronization signal frequency meeting the requirement of the 3GPP protocol according to the system bandwidth range and a preset rule, generating a corresponding synchronization signal frequency point number according to the synchronization signal frequency; selecting a target synchronization signal frequency point number meeting a preset condition from the synchronization signal frequency point numbers, and realizing communication synchronization between a terminal and the LTE base station according to the target synchronization signal frequency point number; starting the LTE base station, and establishing an LTE cell with the preset center frequency as a center frequency and with the preset channel bandwidth as a bandwidth to transmit and receive radio frequency signals.

[0031] Therefore, the application has the following beneficial effects:

[0032] The application sets the preset frequency band of the LTE base station and determines the preset center frequency by using the software on the PC, determines the system bandwidth range of the LTE base station according to the preset center frequency and the preset channel bandwidth of the LTE cell, enables the LTE system to work at the non-3GPP protocol frequency by defining the frequency of the non-3GPP protocol, and can realize the function of accessing the Internet by using the commercial mobile phone; generates all the required synchronization signal frequencies according to the system bandwidth range and the preset rule and generates the corresponding synchronization signal frequency point number, selects the target synchronization signal frequency point number meeting the preset condition from the synchronization signal frequency channel number to realize the downlink synchronization between the user terminal and the LTE base station. The simulation LTE base station can flexibly realize many functions, can be used for the LTE network system simulation, and can be used for the product development based on the system, and has good expansibility. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 a flowchart of the method of the application;

[0034] Figure 2 a schematic diagram of the architecture of the LTE base station of the application;

[0035] Figure 3 a schematic diagram of the process of the signal transmission of the LTE base station of the application;

[0036] Figure 4 a schematic diagram of the process of the signal reception of the LTE base station of the application;

[0037] Figure 5 a schematic diagram of the process of the signal transmission and reception of the LTE base station of the application;

[0038] Figure 6 a schematic diagram of the transmission and reception path of the USRP of the application;

[0039] Figure 7 a schematic diagram of the structure of the device of the application;

[0040] Figure 8 a schematic diagram of the simulation result one of the method embodiment of the application;

[0041] Figure 9 a schematic diagram of the simulation result two of the method embodiment of the application. DETAILED DESCRIPTION

[0042] Explanation of terms:

[0043] LTE (Long Term Evolution) is the standard of 4G wireless communication technology, has the advantages of fast communication speed, wide network frequency spectrum, high intelligent performance, good compatibility, high frequency efficiency and high communication quality, and is widely used in the current public network communication and private network communication.

[0044] USRP (Universal Software Radio Peripheral) is designed to make ordinary computers work like high-bandwidth software radio devices. In essence, USRP acts as a digital baseband and intermediate frequency part of a radio communication system.

[0045] The core idea of SDR (Software Define Radio) is to build an open, standardized, modular general-purpose hardware platform, and to realize various communication modules based on the general-purpose hardware platform by using software. The base station signal processing function can be realized by software as much as possible, and the general-purpose hardware platform can quickly realize signal modulation and demodulation, coding operation, and SDR provides a new way of thinking for existing communication system construction. Software can speed up the development speed of communication module, reduce development cost, and facilitate debugging and maintenance.

[0046] The embodiment of the present application provides a communication method and device for simulating an LTE base station at a self-defined frequency, so as to solve the technical problem that the existing LTE base station cannot use the frequency outside the range specified by the non-3GPP protocol.

[0047] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the related drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0049] Generally, according to the hardware platform of SDR, the SDR system is divided into three categories: FPGA-based SDR system, DSP-based SDR system and GPP-based SDR system, wherein the GPP-based SDR system (GPP-Based SDR system) is the most common form of SDR system implementation at present.

[0050] The GPP-based SDR system usually comprises two parts, one part is a GPP, and the other part is a peripheral. The GPP is a general purpose processor, which can be simply understood as a desktop computer, a notebook computer, etc. The GPP can be used to efficiently develop various communication modules and communication systems based on various high-level programming languages and various link libraries to realize various communication functions such as coding and modulation. Moreover, the development of the GPP-based SDR system has a lower development threshold, a lower development cost, a shorter development cycle, and is convenient for debugging, compared with other two kinds of SDR systems.

[0051] The application utilizes a self-defined frequency band, so that the analog base station can not only meet the functions of an ordinary base station, but also can transmit a frequency out of the range specified in the 3GPP protocol.

[0052] Please refer to Figure 1 The application provides an embodiment of a communication method of an analog LTE base station with a self-defined frequency, which comprises the following steps.

[0053] S100: a preset frequency band of the LTE base station is set on a PC by using software, a preset center frequency is determined according to the preset frequency band, and a system bandwidth range of the LTE base station is determined according to the preset center frequency and a preset channel bandwidth of an LTE cell; the preset center frequency is a center carrier frequency of the LTE base station operating out of the frequency range specified in the 3GPP protocol;

[0054] S200: a synchronization signal frequency meeting the requirements of the 3GPP protocol is generated according to the system bandwidth range and a preset rule, and a corresponding synchronization signal frequency point number is generated according to the synchronization signal frequency;

[0055] S300: a target synchronization signal frequency point number meeting a preset condition is selected from the synchronization signal frequency point number, and communication synchronization between a terminal and the LTE base station is realized according to the target synchronization signal frequency point number;

[0056] S400: the LTE base station is started, and an LTE cell with the preset center frequency as a center frequency and with the preset channel bandwidth as a bandwidth is established to transmit and receive radio frequency signals.

[0057] The application realizes the self-defined frequency analog LTE base station based on a general purpose computer (GPP) and a universal software radio peripheral (USRP), the general purpose computer is used to complete the processing function of a baseband signal, and the USRP is used to complete the radio frequency transmission and reception of the baseband signal, so that the function of the complete LTE base station hardware is realized, and the LTE system can work at a non-3GPP protocol frequency.

[0058] The application is based on Linux standard operating system, uses C++ language to realize communication function of LTE system, uses USRP hardware to transmit and receive radio signal in the air, and realizes 4G LTE base station hardware system function completely in software. Commercial mobile phone access can be realized, and the system can be used with third party core network solution. Based on general server and software radio front end, communication function is realized through transceiver connection, and access of common computer terminal and commercial terminal is supported.

[0059] Please refer to Figure 2 , and the specific software implementation is as follows:

[0060] The software mainly includes OpenAir1, OpenAir2 and OpenAir3 three layers, OpenAir1 mainly realizes physical layer module function in the LTE base station, OpenAir2 mainly realizes PDCP, RLC and MAC module function in the LTE base station, and OpenAir3 mainly realizes RRC module function in the LTE base station. IP data packet from the core network is processed through multiple protocol layers on the software side, and then the signal is transmitted through the radio frequency front end.

[0061] Physical layer: located at the bottom layer, responsible for encoding and decoding, modulation, demodulation and multi-antenna mapping. The main functions of the PHY layer: provide time and frequency resources for data and signaling transmission, channel coding for data transmission, physical channel modulation and demodulation, provide MIMO, transmit diversity and beamforming and other multi-antenna technologies. The uplink adopts SC-TDMA technology, and the downlink adopts OFDMA technology.

[0062] PDCP layer: located between RRC layer and RLC layer, responsible for compressing IP data packet to reduce the number of bits transmitted on the wireless link as much as possible, and the header compression mechanism is based on robust header compression (ROHC) algorithm, a standard header compression algorithm, also used in other mobile communication systems. PDCP is also responsible for data encryption and data consistency protection, and adds PDCP header carrying mobile terminal decryption information.

[0063] RLC layer: located between PDCP layer and MAC layer, responsible for splitting and concatenating upper layer PDCP data packet, retransmission control and in-sequence transmission. It communicates with the PDCP layer through SAP (Service Access Point) and communicates with the MAC layer through logical channel. Each UE has an RLC entity for each logical channel. The data received by the RLC entity from the PDCP layer, or the data sent to the PDCP layer is called RLC SDU (or PDCP PDU). The data received by the RLC entity from the MAC layer, or the data sent to the MAC layer is called RLC PDU (or MAC SDU.

[0064] MAC layer: between RLC and PHY, which realizes the processing of logical channel to physical channel, including channel conversion, priority processing and scheduling management, responsible for controlling HARQ retransmission and scheduling of uplink and downlink.

[0065] RRC is responsible for air interface connection, management and control of wireless resources, provides wireless resource parameters for upper layer and controls main parameters and behaviors of lower layer. Through certain strategies and means, wireless resource management, control and scheduling are carried out, limited wireless network resources are used as much as possible under the requirement of service quality, the planned coverage area is ensured, and the business capacity and resource utilization rate are improved as much as possible.

[0066] From the software implementation of the overall architecture of LTE, the functions of each layer of physical layer (Physical Layer, PHY), medium access control (Media Access Control, MAC), radio link control protocol (Radio Link Control, RLC), packet data convergence protocol (Packet Data Convergence Protocol, PDCP), radio resource control (Radio Resource Control, RRC) are realized. Finally, the baseband signal is transmitted to the USRP through the USB interface, and the USRP performs sampling and up-conversion and down-conversion to convert the digital signal into electromagnetic wave and emit it.

[0067] In an embodiment of the present application, please refer to Figure 3 and Figure 5 The specific process of simulating the LTE base station signal is as follows:

[0068] The communication module is realized by using the analog base station software on the PC, for example, the communication module is written by using C++ programming language on the PC, and the communication module mainly includes Turbo coding module and OFDM coding module. The complete protocol stack (PHY, MAC, RLC, PDCP, RRC) of the communication system is realized in the software program, and the main function is to process the baseband data of the system.

[0069] Firstly, the upper layer of the LTE system has data to be sent by the physical layer, and the upper layer encodes the data into a Bit stream and gives it to the physical layer, that is, the physical layer receives a series of 100110. After the Bit stream is transmitted to the physical layer, it starts to be encoded, and the software adopts 1 / 3 code rate Turbo encoding and then is scrambled. It should be noted that scrambling can be understood as randomizing the Bit stream to avoid a large number of continuous 0 or 1.

[0070] In addition, the cell-specific scrambling sequence is used for scrambling at the sending end, and the receiving end is scrambled again. Only the UE (user terminal) in the cell can form the cell-specific scrambling sequence according to the ID of the cell to scramble the information received in the cell, so that the interference of the adjacent cell can be reduced to a certain extent.

[0071] Then the Bit stream is modulated into complex numbers after the modulation module. The analog base station software uses QPSK, 16QAM and 64QAM modulation modes, and the modulated data form is 0.707+0.707j. Then the complex sequence is mapped to the time-frequency resource of LTE, and finally the OFDM signal conversion is performed on the signals to convert them to time domain signals (time domain data is generally 10ms or other fixed time length baseband data). At this time, the computer analog base station program generates the baseband data of the LTE system, and then transmits the baseband data to the USRP through the USB interface. In a preferred embodiment, the interface between GPP and USRP is USB3.0, and the interface speed of USB3.0 can reach 500MBps, which can basically meet the needs of most communication systems.

[0072] The two modules at the bottom of the USRP are the sending control module and the digital up-conversion module (DUC), which are implemented by FPGA, which has the advantage of fast processing speed. The sending control module can be used to control the sending behavior of the entire USRP, such as when to send, etc. The digital up-conversion module can be used to up-convert the baseband data generated by the computer to an intermediate frequency, and then the digital signal is converted to an analog domain data through the digital analog converter (DAC) of the USRP. After digital-to-analog conversion, a low-pass filter is needed to make the signal smoother. Finally, the intermediate frequency analog domain data is multiplied by the signal generated by the crystal oscillator to modulate the intermediate frequency signal to the specified radio frequency point, and the radio frequency signal is transmitted through the power amplifier.

[0073] In an embodiment of the present application, please refer to Figure 4 and Figure 5 The specific process of receiving signals by the analog LTE base station is as follows:

[0074] The radio frequency signal is multiplied with the signal generated by the USRP crystal oscillator after low noise amplification to down-convert the signal to an intermediate frequency. Similarly, the signal is smoothed by a low pass filter. Then, the intermediate frequency signal is converted from an analog domain signal to a data domain signal by an analog-to-digital converter (ADC). The ADC is an important component in the USRP, and the ADC mainly includes two parameters, sampling accuracy and sampling rate. The sampling accuracy indicates how many bits are used to represent the sampled signal. Similarly, after the signal passes through the ADC, the digital signal is sent to the FPGA module for processing. The FPGA includes two modules, a digital down-conversion module and a reception control module. The reception control module is used to control the reception process of the entire USRP system, such as when to start receiving. The digital down-conversion module (DDC) down-converts the signal from the intermediate frequency to the baseband. The USRP transmits the baseband data to the analog base station program on the computer through a USB or network interface.

[0075] The analog base station program first demodulates the received series of complex numbers by OFDM, and then performs channel estimation / equalization. At this time, the data is still in the form of complex numbers. After soft demodulation, the complex data is converted into a bit stream. Finally, the data is recovered into ASCII code by descrambling and decoding. Finally, the data is handed over to the upper layer.

[0076] Please refer to Figure 6 The general-purpose processor (GPP) of the application uses SDR (software radio) to complete all signal-related processing, such as modulation and demodulation; all high-speed general-purpose operations are performed on the FPGA of the USRP, such as digital up-conversion and down-conversion, sampling, and interpolation. The main design concept of the USRP is to complete waveform processing, such as modulation and demodulation, by the CPU, and to complete high-speed processing processes, such as digital up-conversion and down-conversion, sampling, and interpolation, by the field programmable gate array (FPGA). The hardware device of the USRP includes two parts: an FPGA motherboard with high-speed signal processing and one or more replaceable daughter boards covering different frequency ranges. Each motherboard has 2 or 4 daughter board interfaces, i.e., each USRP motherboard can support at most 2 or 4 daughter boards; if there are 2 paths, parallel transmission or reception can be supported. The daughter board serves as an RF front end to complete the conversion between radio frequency signals and signals of different frequency bands.

[0077] In this embodiment, in step S100, the simulation base station program defines and sets the preset center frequency of the LTE base station using a structure in C++, which is a user-defined non-3GPP protocol frequency, i.e., the preset center frequency is the center carrier frequency of the LTE base station transmitting signal outside the frequency range specified by the 3GPP protocol. For example, assume that the preset frequency band defined by the LTE base station to be simulated is: the frequency band number is 108, the uplink minimum frequency is 5091 MHz, the uplink maximum frequency is 5101 MHz, the downlink minimum frequency is 5140 MHz, the downlink maximum frequency is 5150 MHz, and the working mode is FDD (frequency division duplex), i.e., the frequency range of the preset frequency band is 5091 MHZ-5150 MHz, wherein the downlink is 5140 MHz-5150 MHz, and the uplink is 5091 MHz-5101 MHz.

[0078] According to the mapping relationship between the frequency and the frequency point, the minimum frequency point number corresponding to the above frequency range is 3450, and the maximum frequency point number is 21450, so the frequency point number range corresponding to the preset frequency band is (3450, 21450). According to the uplink and downlink frequency range, it can be known that the frequency interval is 49 MHZ (5150 MHZ-5101 MHZ=5140 MHZ-5091 MHZ), and the format of the user-defined frequency band can be set as: (frequency band number, downlink minimum frequency, minimum frequency point number, maximum frequency point number, frequency interval, area constraint), so the corresponding user-defined frequency band can be expressed as: (108, 5140, 3450, 21450, 49, BAND_GEO_AREA_ALL).

[0079] In step S100, the preset frequency band of the LTE base station is set on the PC using software, and the preset center frequency is determined according to the preset frequency band, which is the center carrier frequency of the LTE base station working outside the frequency range specified by the 3GPP protocol, and the center carrier frequency includes the uplink center carrier frequency and the downlink center carrier frequency. In a preferred embodiment, the user-defined preset center frequency can be set as 5145.0 MHZ downlink and 5096.0 MHZ uplink. After the preset center frequency is determined, an LTE base station system bandwidth range can be generated in combination with the channel bandwidth requirement of the LTE cell. For example, if the preset center frequency is 5145.0 MHZ and the channel bandwidth requirement of the LTE cell is 5 MHZ, then it can be known that the corresponding system bandwidth range is: downlink 5142.5 MHZ-5147.5 MHZ, and uplink 5093.5 MHZ-5098.5 MHZ. Then, the uplink and downlink corresponding system radio frequency point ranges are generated according to the obtained system bandwidth range, which include the minimum system radio frequency point and the maximum system radio frequency point.

[0080] It should be noted that according to the relevant provisions of the 3GPP protocol, when the channel bandwidth is 5MHz, the total number of RB resources is 25. The RB is a resource unit for service channel resource allocation. Since the working mode of the LTE system is set as FDD in the foregoing, the RB resource herein mainly refers to a frequency resource.

[0081] In step S200, a synchronization signal frequency conforming to the requirements of the 3GPP protocol is generated according to the obtained system bandwidth range and preset rules, and a corresponding synchronization signal frequency point number is generated according to the obtained synchronization signal frequency.

[0082] In an embodiment of the present application, a synchronization signal frequency conforming to the requirements of the 3GPP protocol is generated according to the obtained system bandwidth range and preset rules. Specifically, a total number of frequency resources corresponding to a preset channel bandwidth is obtained, continuous frequency resources are intercepted on the total number of frequency resources according to the size of the synchronization signal bandwidth, and a synchronization signal frequency conforming to the requirements of the 3GPP protocol is generated according to the continuous frequency resources.

[0083] In the LTE system, the synchronization signal is usually located at the center of the carrier bandwidth. According to the provisions of the 3GPP protocol, the synchronization signal occupies 6 continuous RB resources, that is, the length of the synchronization signal bandwidth is fixed as 6. Since the synchronization signal is determined by its starting position and bandwidth, the corresponding synchronization signal can be determined according to the starting position of the synchronization signal and the size of the synchronization signal bandwidth. In the embodiment, a self-defined algorithm such as a random algorithm can be used to dynamically select the starting position of the synchronization signal. In theory, any one of the 25 RB resources can be selected as the starting position of the synchronization signal, but it is necessary to ensure that there are 6 continuous RBs.

[0084] After obtaining the synchronization signal frequency in the embodiment, a corresponding synchronization signal frequency point number is generated according to the obtained synchronization signal frequency. For example, all the synchronization signal frequency point numbers obtained are: 3551, 3552, …, 3559.

[0085] In step S300, a target synchronization signal frequency point number satisfying a preset condition is selected from the synchronization signal frequency point numbers, and communication synchronization between a terminal and an LTE base station is realized according to the target synchronization signal frequency point number.

[0086] Specifically, the preset condition is that a difference between the target synchronization signal frequency point number and the minimum system radio frequency point or the maximum system radio frequency point is greater than half of the synchronization signal bandwidth, wherein the synchronization signal bandwidth is fixed as 6, and half of the synchronization signal bandwidth is 3, that is, the following two conditions are simultaneously satisfied: (1) target synchronization signal frequency point number - minimum system radio frequency point > 3; (2) maximum system radio frequency point - target synchronization signal frequency point number > 3; a minimum value that simultaneously satisfies conditions (1) and (2) is taken as the target synchronization signal frequency point number. Specifically, a minimum value min can be found from the synchronization signal radio frequency points that satisfy condition (1), a maximum value max can be found from the synchronization signal radio frequency points that satisfy condition (2), and a smaller value of min and max is selected as the target synchronization signal frequency point number. Alternatively, the synchronization signal radio frequency points that satisfy condition (1) and the synchronization signal radio frequency points that satisfy condition (2) can be intersected, and a minimum value in the intersection is taken as the target synchronization signal frequency point number.

[0087] For example, assuming that the system radio frequency point range corresponding to the downlink system bandwidth range is (3552, 3562), all the synchronization signal frequency point numbers are {3551, 3552, …, 3559}, among all the synchronization signal frequency point numbers, the synchronization signal frequency point numbers greater than 3 from the minimum system radio frequency point are 3556 to 3559, wherein the minimum synchronization signal frequency point number is 3556; the synchronization signal frequency point numbers greater than 3 from the maximum system radio frequency point are 3551 to 3558, wherein the maximum synchronization signal frequency point number is 3558; in combination with the two comparison results, the minimum synchronization signal frequency point number greater than 3 from the minimum system radio frequency point is 3556 (min), and the maximum synchronization signal frequency point number greater than 3 from the maximum system radio frequency point is 3558 (max), and a smaller value of min and max is selected as the target synchronization signal frequency point number, that is, 3556 is taken as the final target synchronization signal frequency point number, and communication synchronization between the terminal and the LTE base station is realized according to the target synchronization signal frequency point number. Alternatively, {3556 to 3559} and {3551 to 3558} can be intersected to obtain {3556, 3557, 3558}, and the minimum value 3556 in the intersection is taken as the final target synchronization signal frequency point number.

[0088] It should be noted that, for initial access, due to invalid or outdated system information or out-of-sync, the UE must be periodically provided with a synchronization signal in the downlink to obtain downlink synchronization in the frequency domain and the time domain, and therefore the synchronization signal is important for the LTE system.

[0089] It should be noted that the three values of frequency band, channel bandwidth and center frequency can uniquely determine the specific frequency range of the LTE system.

[0090] In step S400, the LTE base station is started, and an LTE cell with a preset center frequency as a center frequency and a preset channel bandwidth as a bandwidth is established to transmit and receive radio frequency signals. After the software completes the above steps, the LTE base station is started, and an LTE cell with the preset center frequency as a center frequency is established to transmit and receive radio frequency signals, and the LTE cell transmits and receives radio frequency signals with the preset channel bandwidth as a bandwidth. For example, an LTE cell with a downlink center frequency of 5145.0 MHz, an uplink center frequency of 5096.0 MHz, and a bandwidth of 5 MHz is established to transmit a downlink broadcast signal and receive an uplink signal.

[0091] In the embodiment, the configuration of the LTE cell is generated according to the configuration information of the synchronization signal, an LTE cell transmitting signals with a preset downlink center frequency and receiving signals with a preset uplink center frequency is established to transmit and receive signals, and the software can read and identify the preset frequency range in the running, so that the LTE system works at a non-3GPP protocol frequency. The configuration information of the synchronization signal includes a preset center frequency point number (corresponding to the preset center frequency) related to the frequency, a synchronization signal frequency point number, and other cell information, and the other cell information is weakly related to the frequency, which is not listed in detail here.

[0092] It should be noted that for the frequencies within the range specified by the 3GPP protocol, the 3GPP protocol is executed, the frequency point number is automatically configured, the configuration of the LTE cell is automatically generated, and the LTE cell is established to transmit and receive signals.

[0093] The application realizes the function of the custom frequency analog LTE base station by using the general-purpose processor GPP and the USRP, can customize the non-3GPP protocol specified frequency, can realize the access of commercial mobile phones to the Internet, and can be used as an LTE network system simulation, for students and researchers to test or learn, or based on the system to develop products.

[0094] The communication method for simulating the LTE base station at the custom frequency provided in the embodiment can completely realize the function of the LTE base station hardware system, for example, the frequency in the range of 70 MHz-6 GHz can be customized. Commercial mobile phones can be accessed, and the system can be used with third-party core network solutions to build a complete end-to-end mobile wireless network. The LTE base station simulated in the embodiment can flexibly realize many functions and has good scalability, can quickly realize signal modulation and demodulation, coding operation, and can be used as an experimental platform to perform prototype verification, reduces the cost of technical research and development, and provides a faster implementation method, and is used for verifying various communication algorithms.

[0095] The embodiment provided in the application simulates the LTE base station at the self-defined frequency, sets the preset frequency band of the LTE base station by using the software on the PC, determines the preset center frequency, determines the system bandwidth range of the LTE base station according to the preset center frequency and the preset channel bandwidth of the LTE cell, and enables the LTE system to work at the non-3GPP protocol frequency by defining the non-3GPP protocol frequency, so that the commercial mobile phone can access the Internet function; the all required synchronization signal frequencies are generated according to the system bandwidth range and the preset rule, and the corresponding synchronization signal frequency point numbers are generated, the minimum synchronization signal frequency point number meeting the preset condition is selected from the synchronization signal frequency channel numbers, so that the downlink synchronization of the user terminal and the LTE base station is realized. The LTE base station can flexibly realize many functions, can be used for LTE network system simulation, students and researchers can test or learn, or products can be developed based on the system, and the LTE base station has good expansibility.

[0096] Please refer to Figure 7 The application further provides an embodiment of a communication device for simulating an LTE base station at a self-defined frequency, comprising:

[0097] The system bandwidth determination module 11 is used for setting the preset frequency band of the LTE base station by using the software on the PC, determining the preset center frequency according to the preset frequency band, and determining the system bandwidth range of the LTE base station according to the preset center frequency and the preset channel bandwidth of the LTE cell; the preset center frequency is the center carrier frequency of the LTE base station working outside the frequency range specified by the 3GPP protocol;

[0098] The synchronization signal generation module 22 is used for generating the synchronization signal frequencies meeting the requirements of the 3GPP protocol according to the system bandwidth range and the preset rule, and generating the corresponding synchronization signal frequency point numbers according to the synchronization signal frequencies;

[0099] The frequency synchronization implementation module 33 is used for selecting the target synchronization signal frequency point number meeting the preset condition from the synchronization signal frequency point numbers, and realizing the communication synchronization of the terminal and the LTE base station according to the target synchronization signal frequency point number;

[0100] The LTE cell establishment module 44 is used for starting the LTE base station, and establishing the LTE cell with the preset center frequency as the center frequency and the preset channel bandwidth as the bandwidth to transmit and receive the radio frequency signals.

[0101] Please refer to Figure 8 and Figure 9 The system and simulation data are as follows:

[0102] For example, when the preset center frequency is 5145.0MHZ, the LTE base station is simulated by using the self-defined center frequency, and the civil aviation airport scene communication frequency signal transmission can be realized.

[0103] Taking the process of transmitting a signal of an LTE base station as an example, when the program starts running, a preset center carrier frequency 5145.0 MHz is first called, the corresponding frequency point number is generated according to the preset center frequency, the synchronization signal frequency and the corresponding synchronization signal frequency point number are generated according to the algorithm related to the physical layer, the configuration of the cell is automatically generated according to the configuration of the synchronization signal, and then the LTE cell with the downlink center frequency of 5145.0 MHz, the uplink center frequency of 5096.0 MHz and the channel bandwidth of 5 MHz is established to transmit the downlink broadcast signal. The LTE downlink signal with the bandwidth of 5 MHz is transmitted on this frequency.

[0104] It should be noted that 5091 MHz-5150 MHz is a special frequency band allocated by the International Telecommunication Organization to the airport surface communication of civil aviation.

[0105] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system, device and unit described above can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0106] In the embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0107] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, that is, they can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0108] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0109] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application or the entire or part of the technical solutions that essentially contribute to the prior art can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0110] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A communication method for simulating an LTE base station using a custom frequency, characterized in that, include: On a PC, software is used to set the preset frequency band of the LTE base station, and the preset center frequency is determined based on the preset frequency band. The system bandwidth range of the LTE base station is determined based on the preset center frequency and the preset channel bandwidth of the LTE cell. The preset center frequency is the center carrier frequency of the LTE base station that operates outside the frequency range specified by the 3GPP protocol. A synchronization signal frequency conforming to the 3GPP protocol is generated based on the system bandwidth range and preset rules, and a corresponding synchronization signal frequency point number is generated based on the synchronization signal frequency. Select a target synchronization signal frequency point that meets the preset conditions from the synchronization signal frequency point numbers, and realize the communication synchronization between the terminal and the LTE base station according to the target synchronization signal frequency point number; Start the LTE base station and establish an LTE cell with the preset center frequency as the center frequency and the preset channel bandwidth as the bandwidth for transmitting and receiving radio frequency signals; Before selecting a target synchronization signal frequency point that meets the preset conditions from the synchronization signal frequency point numbers, the following steps are also included: A corresponding system radio frequency point range is generated based on the system bandwidth range, and the system radio frequency point range includes a minimum system radio frequency point and a maximum system radio frequency point. The preset conditions are: The difference between the target synchronization signal frequency point and the minimum or maximum system radio frequency point is greater than half of the synchronization signal bandwidth.

2. The communication method for simulating an LTE base station using a custom frequency according to claim 1, characterized in that, Generating synchronization signal frequencies that comply with 3GPP protocol requirements based on the system bandwidth range and preset rules includes: The total number of frequency resources is obtained according to the preset channel bandwidth. Continuous frequency resources are extracted from the total number of frequency resources according to the size of the synchronization signal bandwidth. Synchronization signal frequencies that meet the requirements of the 3GPP protocol are generated based on the continuous frequency resources.

3. The communication method for simulating an LTE base station using a custom frequency according to claim 1, characterized in that, The preset center frequency is 5145.0MHz for downlink and 5096.0MHz for uplink.

4. The communication method for simulating an LTE base station using a custom frequency according to claim 1, characterized in that, The preset channel bandwidth of the LTE cell is 5MHz.

5. The communication method for simulating an LTE base station using a custom frequency according to claim 1, characterized in that, After determining the preset center frequency based on the preset frequency band, the following steps are also included: A corresponding preset center frequency number is generated based on the preset center frequency.

6. A communication device for simulating an LTE base station at a custom frequency, characterized in that, include: The system bandwidth determination module is used to set the preset frequency band of the LTE base station on a PC using software, determine the preset center frequency based on the preset frequency band, and determine the system bandwidth range of the LTE base station based on the preset center frequency and the preset channel bandwidth of the LTE cell; the preset center frequency is the center carrier frequency of the LTE base station that operates outside the frequency range specified by the 3GPP protocol. The synchronization signal generation module is used to generate a synchronization signal frequency that conforms to the 3GPP protocol requirements according to the system bandwidth range and preset rules, and to generate a corresponding synchronization signal frequency point number according to the synchronization signal frequency. The frequency synchronization implementation module is used to select a target synchronization signal frequency point number that meets preset conditions from the synchronization signal frequency point numbers, and realize communication synchronization between the terminal and the LTE base station according to the target synchronization signal frequency point number; The LTE cell establishment module is used to start the LTE base station and establish an LTE cell with the preset center frequency as the center frequency and the preset channel bandwidth as the bandwidth for transmitting and receiving radio frequency signals. Before the frequency synchronization implementation module selects a target synchronization signal frequency point that meets preset conditions from the synchronization signal frequency point numbers, it also includes: The frequency synchronization module generates a corresponding system radio frequency point range based on the system bandwidth range, and the system radio frequency point range includes a minimum system radio frequency point and a maximum system radio frequency point. The preset conditions are: The difference between the target synchronization signal frequency point and the minimum or maximum system radio frequency point is greater than half of the synchronization signal bandwidth.

7. The communication device for simulating an LTE base station at a custom frequency according to claim 6, characterized in that, The synchronization signal generation module generates synchronization signal frequencies that conform to 3GPP protocol requirements based on the system bandwidth range and preset rules, including: The synchronization signal generation module obtains the total number of frequency resources corresponding to the preset channel bandwidth, extracts continuous frequency resources from the total number of frequency resources according to the size of the synchronization signal bandwidth, and generates a synchronization signal frequency that conforms to the requirements of the 3GPP protocol based on the continuous frequency resources.

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