CN112135354A - T-3G signal discovery method based on signaling guidance - Google Patents
T-3G signal discovery method based on signaling guidance Download PDFInfo
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Abstract
The invention discloses a T-3G signal discovery method based on signaling guidance, which adopts satellite signal interception equipment to detect and discover a T-3G signal, wherein the satellite signal interception equipment comprises a hardware module and a software module, the hardware module acquires a downlink signal from a T satellite mobile communication system, converts the downlink signal into a baseband signal through down-conversion, and performs DDC processing on the baseband signal; the software module demodulates and decodes the baseband signal processed by the DDC to obtain the frequency and bandwidth of the T-3G service indicated by the downlink signaling; the hardware module selects and configures corresponding uplink DDC channels and downlink DDC channels according to the obtained frequency and bandwidth, receives uplink DDC data through the uplink DDC channels, and receives downlink DDC data through the downlink DDC channels; the software module carries out T-3G burst detection and demodulation processing on the received DDC data, and restores information in the DDC data. The method can effectively acquire the available information in the T-3G signal, and reduces the design and development difficulty of the hardware module.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a T-3G signal discovery method based on signaling guidance.
Background
The T-3G signal has various bandwidth configurations, the existing traditional processing method for receiving the T-3G signal by a third party generally performs broadband burst detection through hardware, and when the broadband burst detection is performed through the hardware, if a burst signal is found, channelizing processing is performed according to the bandwidth of the burst signal, and then processed data and information are transmitted out. The detection is carried out by adopting the method, the current sudden blind detection of the whole bandwidth is carried out, the data processing and the channelization are all required to be completed in a hardware part, the requirement on the processing capacity of the hardware is extremely high, and the algorithm is very complex.
Disclosure of Invention
The present invention aims to provide a signalling-guided T-3G signal discovery method which alleviates the above problems.
In order to alleviate the above problems, the technical scheme adopted by the invention is as follows:
the invention provides a T-3G signal discovery method based on signaling guidance, which adopts satellite signal detection and reception equipment to detect and discover a T-3G signal, wherein the satellite signal detection and reception equipment comprises a hardware module and a software module, and the specific steps are as follows:
s1, the hardware module receives downlink signals from the T satellite mobile communication system;
s2, the hardware module converts the downlink signal into a baseband signal through down-conversion;
s3, the hardware module carries out DDC processing on the baseband signal;
s4, the software module demodulates, decodes and analyzes the base band signal processed by DDC, to obtain the T-3G service frequency and bandwidth indicated by the signaling in the downlink signal;
s5, selecting and configuring corresponding uplink DDC channel and downlink DDC channel by the hardware module according to the obtained 3G service frequency and bandwidth;
s6, the hardware module receives the up DDC data through the up DDC channel, receives the down DDC data through the down DDC channel, the software module carries out burst detection and demodulation processing to the received DDC data, restores the information in the DDC data, and completes the discovery of the T-3G signal.
The technical effect of the technical scheme is as follows: the method can effectively acquire the available information in the T-3G signal, and does not need a hardware module to perform sudden blind detection and dynamically configure a channel, thereby reducing the design and development difficulty of the hardware module and shortening the development period of a system.
Optionally, in step S1, the method for acquiring the downlink signal includes: the hardware module is accessed to the THURAYA satellite mobile communication system in a broadcasting mode, and then passively receives downlink signals sent by the T satellite mobile communication system.
Optionally, the hardware module is provided with multiple sets of DDC channels with different bandwidths, and the method for selectively configuring the DDC channels includes the following steps:
a1, the software module sends the T-3G service frequency and bandwidth in the downlink signaling to the hardware module through the appointed protocol;
a2, selecting a matched DDC channel by the hardware module according to the bandwidth in the downlink signaling;
a3, configuring T-3G service frequency for the selected DDC channel by the hardware module, and receiving signal data of corresponding bandwidth by the DDC channel with the frequency value as a center frequency.
The technical effect of the technical scheme is as follows: the method can avoid the situation that hardware needs to occupy a large amount of hardware resources and performance to perform complex detection and operation to match the bandwidth of the T-3G signal when the hardware runs in real time, and can match a proper DDC channel to perform DDC processing on the T-3G signal only by using two simple logic judgments.
According to
Optionally, the specified protocol is a custom interface protocol between a software module and a hardware module.
Optionally, in step S6, the software module performs burst detection on DDC data by using a sliding window method.
The technical effect of the technical scheme is as follows: when the burst signal enters, the burst signal can be detected quickly and accurately.
Optionally, the specific process of burst detection includes:
the software module identifies a model of DDC data received by the hardware module as DDC data in a wireless channel with white Gaussian noise
x(n)＝i*s(n)+w(n)
Where w (n) represents input noise, i has a value of 1 or 0, and when i is 0, x (n) is w (n), and only noise is present in the signal, and when i is 1, it indicates that a digital signal is present in DDC data;
assuming a sliding window length L, the energy E (n) sliding into the window is as follows:
a threshold value Th is set, if E (n) > Th, then it is considered that there is a burst signal entering at this time.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a schematic diagram of a satellite signal detection device receiving T-3G uplink signals and downlink signals in an embodiment;
FIG. 2 is a flow chart of a signaling-based T-3G signal discovery method according to an embodiment;
fig. 3 is a guiding schematic diagram of downlink signaling in an embodiment;
fig. 4 is a schematic diagram of a demodulation process in the embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Fig. 1 is a physical schematic diagram of a satellite signal detection device receiving T-3G uplink signals and downlink signals, wherein upper and lower arrows represent uplink and downlink communication links established between a mobile communication satellite (SBSS) and a T-satellite mobile terminal (MES), respectively; an uplink, a physical channel for a signal from the terminal to the satellite, for transmitting an uplink signal; a downlink, a physical channel for a signal from a satellite to a terminal, for transmitting a downlink signal; the oblique arrows represent the process of the passive listening device obtaining the uplink signal and the downlink signal from the uplink and the downlink in the satellite mobile communication system through the antenna.
Referring to fig. 1 and fig. 2, the present embodiment provides a method for discovering a T-3G signal based on signaling, the method detects and discovers the T-3G signal by using a satellite signal detecting and receiving device, the satellite signal detecting and receiving device includes a hardware module and a software module, and the method includes the following specific steps:
s1, the hardware module receives downlink signals from the T satellite mobile communication system;
s2, the hardware module converts the downlink signal into a baseband signal through down-conversion;
s3, the hardware module carries out DDC processing on the baseband signal;
s4, the software module demodulates, decodes and analyzes the base band signal processed by DDC, to obtain the T-3G service frequency and bandwidth indicated by the signaling in the downlink signal;
s5, selecting and configuring corresponding uplink DDC channel and downlink DDC channel by the hardware module according to the obtained T-3G service frequency and bandwidth;
s6, the hardware module receives the up DDC data through the up DDC channel, receives the down DDC data through the down DDC channel, the software module carries out burst detection and demodulation processing to the received DDC data, restores the information in the DDC data, and completes the discovery of the T-3G signal.
In step S1 of this embodiment, the method for acquiring the downlink signal is: the hardware module is accessed to the T satellite mobile communication system in a broadcasting mode, and then passively receives downlink signals sent by the T satellite mobile communication system.
In this embodiment, referring to fig. 3, the guiding of the downlink signaling includes two cases, in which both the satellite signal detecting and receiving device can acquire the downlink signaling in a broadcast manner.
In the first case: the MES is asynchronous with the network, when entering the coverage of the satellite network, the MES sends an RACH random access request, and the mobile communication satellite sends an AGCH channel assignment command to the terminal through a downlink signal after receiving the RACH random access request, wherein the AGCH command comprises uplink and downlink bandwidth and frequency;
in the second case: the MES is synchronous with the network, after the random access is finished, the satellite distributes an uplink (PAGCH) and a downlink (PACCH) to the terminal through a downlink signal, and after the distribution is finished, the T satellite terminal and the satellite network carry out packet data transmission through the link.
In this embodiment, the frequency converter used for the down-conversion is CMC-L-IF01, and the down-signaling is converted into a baseband signal by the frequency converter.
The DDC processing procedure specifically includes: converting the baseband broadband analog signal generated in the step S2 into a digital signal through ADC sampling; converting the baseband broadband digital signal into narrow-band DDC data through an extraction filter according to the frequency point and the bandwidth set by people; narrow-band DDC data is output.
In step S4 of this embodiment, after receiving the narrow-band DDC data S (t), the baseband data obtained after down-conversion is IQ data after quadrature modulation;
assuming that the data we need to transmit is a and b, after quadrature modulation we identify the signal as s (t) ═ acos ω0t-bsinω0t；
After receiving a signal, in order to obtain data a and b which need to be transmitted, a received signal is divided into two paths, and one path is multiplied by cos omega0t in one cycle
Integrating to obtain a, one path is multiplied by-sin omega0t in one cycle
Integrating; b, T is
Integer multiples of (a) and the demodulation process is shown in fig. 4.
In this embodiment, the software module adopts C + +, where C + + is mainly the implementation of the bottom layer logic, and its implemented functional parts include:
1. demodulating and decoding the downlink baseband signal to obtain baseband signal data;
2. analyzing the baseband signal data according to a protocol to obtain the frequency and bandwidth of the corresponding T-3G service;
3. and constructing a TCP connection with hardware equipment, assembling the frequency value and the bandwidth value into a structural body which is configured to receive a DDC channel of the T-3G signal according to a protocol defined between the TCP connection and the hardware, serializing the structural body, and transmitting the structural body to the hardware.
In this embodiment, the hardware module is provided with multiple sets of DDC channels with different bandwidths, and the method for selectively configuring the DDC channels includes the following steps:
a1, the software module sends the T-3G service frequency and bandwidth in the downlink signaling to the hardware module through the appointed protocol;
a2, selecting a matched DDC channel by the hardware module according to the bandwidth in the downlink signaling;
a3, configuring T-3G service frequency for the selected DDC channel by the hardware module, and receiving signal data of corresponding bandwidth by the DDC channel with the frequency value as a center frequency.
The designated protocol is a custom interface protocol between the software module and the hardware module, and the structure of the designated protocol is different according to the structure of the software module and the hardware module, so that the designated protocol is not particularly limited.
In this embodiment, 24 channel bandwidths are set in advance in a hardware module, and according to long-term test and practical work experience, we can determine that the bandwidth of a T-3G signal can basically determine that 4 groups of bandwidths exist, the 24 channels are divided into 4 groups of channels and 6 channels, each group of channels respectively has four bandwidth values of A, B, C, D, when bandwidth values are configured to hardware by software, the hardware matches a group of channels through the four bandwidth values, and an idle channel is screened from the group of channels.
In step S6 of this embodiment, the software module performs burst detection on DDC data by using a sliding window method, which includes the following specific steps:
the software module identifies a model of DDC data received by the hardware module as DDC data in a wireless channel with white Gaussian noise
x(n)＝i*s(n)+w(n)
Wherein w (n) represents noise that is received when the signal is transmitted over the channel; the value of i is 1 or 0, when i is 0, x (n) is w (n), only noise exists in the signal, and when i is 1, the DDC data has a digital signal; s (n) represents the digital intermediate frequency signal at the corresponding carrier frequency; n represents a sampling time point, which can be understood as a coordinate value on the horizontal axis.
Assuming a sliding window length L, the energy E (n) sliding into the window is as follows:
a threshold value Th is set, if E (n) > Th, then it is considered that there is a burst signal entering at this time.
In step S6 of the present embodiment, the specific procedure of the demodulation process includes:
a1, moving the frequency spectrum which is near the carrier and carries useful information to the baseband;
a2, filtering out the baseband signal using a corresponding filter.
Table 1 shows data blocks indicating frequency and bandwidth information in a channel assignment protocol, which are obtained by receiving DDC data and restoring the DDC data by the method.
TABLE 1
The baseband signal is demodulated and decoded to obtain a series of binary data streams, table 1 is a protocol stack of the T satellite signal, each 8 bits is one byte, and four bytes in table 1 contain all parameters required by the DDC channel configuration.
Matching in binary data stream by using the protocol stack so as to obtain the required frequency point and bandwidth information;
the frequency point can be analyzed from the 8bit data occupied by the ARFCN, and the corresponding uplink and downlink frequencies can be obtained through a formula; (FreqUp: upstream frequency; FreqDn: downstream frequency; ARFCN: frequency points)
FreqUp＝(152500000+aRFCN*3125)*10；
FreqDn＝(162650000+ARFCN*3125)*10；
3bit data occupied by downlink bandwidth is downlink bandwidth;
the 3bit data occupied by the uplink bandwidth is the uplink bandwidth.
In the method for discovering the T-3G signal based on signaling guidance in this embodiment, a communication frequency point and a bandwidth of a T-3G service are obtained through analysis, a DDC channel frequency of a corresponding bandwidth is configured in real time, a T-3G burst signal in narrowband DDC data is simply searched and demodulated, and information is restored. Because hardware is not needed to carry out sudden blind detection and dynamically configure a channel, the design and development difficulty of the hardware is reduced, the development period of a system is shortened, and the available information in the T-3G signal can be effectively acquired.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A T-3G signal discovery method based on signaling guidance adopts satellite signal detection and reception equipment to detect and discover T-3G signals, the satellite signal detection and reception equipment comprises a hardware module and a software module, and the method is characterized by further comprising the following steps:
s1, the hardware module receives downlink signals from the T satellite mobile communication system;
s2, the hardware module converts the downlink signal into a baseband signal through down-conversion;
s3, the hardware module carries out DDC processing on the baseband signal;
s4, the software module demodulates, decodes and analyzes the base band signal processed by DDC, to obtain the T-3G service frequency and bandwidth indicated by the signaling in the downlink signal;
s5, selecting and configuring corresponding uplink DDC channel and downlink DDC channel by the hardware module according to the obtained T-3G service frequency and bandwidth;
s6, the hardware module receives the up DDC data through the up DDC channel, receives the down DDC data through the down DDC channel, the software module carries out burst detection and demodulation processing to the received DDC data, restores the information in the DDC data, and completes the discovery of the T-3G signal.
2. The method for discovering T-3G signals based on signaling steering according to claim 1, wherein in step S1, the method for acquiring downlink signals is: the hardware module is accessed to the T satellite mobile communication system in a broadcasting mode, and then passively receives downlink signals sent by the T satellite mobile communication system.
3. The signaling-based T-3G signal discovery method according to claim 1, wherein said hardware module is provided with multiple sets of DDC channels with different bandwidths, and the DDC channel configuration selection method comprises the following steps:
a1, the software module sends the T-3G service frequency and bandwidth in the downlink signaling to the hardware module through the appointed protocol;
a2, selecting a matched DDC channel by the hardware module according to the bandwidth in the downlink signaling;
a3, configuring T-3G service frequency for the selected DDC channel by the hardware module, and receiving signal data of corresponding bandwidth by the DDC channel with the frequency value as a center frequency.
4. The method of claim 3, wherein the specified protocol is a custom interface protocol between a software module and a hardware module.
5. The method for discovering T-3G signal based on signaling guidance according to claim 1, wherein in step S6, the software module performs burst detection on DDC data by sliding window method.
6. The method of claim 5, wherein the specific procedure of the burst detection comprises:
the software module identifies a model of DDC data received by the hardware module as DDC data in a wireless channel with white Gaussian noise
x(n)＝i*s(n)+w(n)
Where w (n) represents input noise, i has a value of 1 or 0, and when i is 0, x (n) is w (n), and only noise is present in the signal, and when i is 1, it indicates that a digital signal is present in DDC data;
assuming a sliding window length L, the energy E (n) sliding into the window is as follows:
a threshold value Th is set, if E (n) > Th, then it is considered that there is a burst signal entering at this time.
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| CN201911321724.5A CN110958703A (en) | 2019-12-20 | 2019-12-20 | Signaling guide-based THURAYA3G signal discovery method |
| CN2019113217245 | 2019-12-20 |
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| CN202011078324.9A Active CN112135354B (en) | 2019-12-20 | 2020-10-10 | T-3G signal discovery method based on signaling guidance |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102307135A (en) * | 2011-05-24 | 2012-01-04 | 中国电子科技集团公司第十研究所 | Method for processing baseband data transmission data in real time by utilizing VxWorks platform |
| US20130016798A1 (en) * | 2007-04-30 | 2013-01-17 | V Corp Technologies, Inc. | Adaptive digital receiver |
| CN103188010A (en) * | 2011-12-29 | 2013-07-03 | 北京信威通信技术股份有限公司 | Satellite mobile communication method and satellite mobile communication device based on satellite switch |
| CN108289091A (en) * | 2017-12-25 | 2018-07-17 | 西安空间无线电技术研究所 | Remote sensing satellite ground base band data processing system based on rack-mount server |
| CN108833037A (en) * | 2018-05-18 | 2018-11-16 | 上海欧科微航天科技有限公司 | A kind of the ground detection method and device of satellite |
| CN109831821A (en) * | 2019-03-18 | 2019-05-31 | 中国电子科技集团公司第五十四研究所 | A kind of satellite mobile communication terminal and its timing and frequency-tracking compensation method |
-
2019
- 2019-12-20 CN CN201911321724.5A patent/CN110958703A/en not_active Withdrawn
-
2020
- 2020-10-10 CN CN202011078324.9A patent/CN112135354B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20130016798A1 (en) * | 2007-04-30 | 2013-01-17 | V Corp Technologies, Inc. | Adaptive digital receiver |
| CN102307135A (en) * | 2011-05-24 | 2012-01-04 | 中国电子科技集团公司第十研究所 | Method for processing baseband data transmission data in real time by utilizing VxWorks platform |
| CN103188010A (en) * | 2011-12-29 | 2013-07-03 | 北京信威通信技术股份有限公司 | Satellite mobile communication method and satellite mobile communication device based on satellite switch |
| CN108289091A (en) * | 2017-12-25 | 2018-07-17 | 西安空间无线电技术研究所 | Remote sensing satellite ground base band data processing system based on rack-mount server |
| CN108833037A (en) * | 2018-05-18 | 2018-11-16 | 上海欧科微航天科技有限公司 | A kind of the ground detection method and device of satellite |
| CN109831821A (en) * | 2019-03-18 | 2019-05-31 | 中国电子科技集团公司第五十四研究所 | A kind of satellite mobile communication terminal and its timing and frequency-tracking compensation method |
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| CN112135354B (en) | 2021-04-20 |
| CN110958703A (en) | 2020-04-03 |
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Denomination of invention: A signaling guided t-3g signal discovery method Effective date of registration: 20210616 Granted publication date: 20210420 Pledgee: Wenjiang Branch of Bank of China Ltd. Pledgor: CHENGDU CHUANMEI NEW TECHNOLOGY Co.,Ltd. Registration number: Y2021510000120 |