CN111555772B - Mixed spread spectrum communication method and device based on long and short codes - Google Patents
Mixed spread spectrum communication method and device based on long and short codes Download PDFInfo
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- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
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- H—ELECTRICITY
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- H—ELECTRICITY
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Abstract
The embodiment of the invention provides a mixed spread spectrum communication method and a device based on long and short codes, wherein the method comprises the following steps: splicing the link synchronization data and the frame synchronization data into synchronization segment data, and performing spread spectrum processing on the synchronization segment data by using a short code sequence; splicing frame header data, data domain data and frame tail data into information segment data, and performing spread spectrum processing on the information segment data by using a long code sequence; and splicing the spread synchronous segment data and the spread information segment data and then transmitting the spliced synchronous segment data and the spread information segment data. By applying the embodiment of the invention, the system user capacity is effectively improved.
Description
Technical Field
The invention relates to the technical field of satellite communication, in particular to a hybrid spread spectrum communication method based on long and short codes.
Background
In a communication system, according to the aroma formula, when the channel capacity is fixed, the channel bandwidth and the signal-to-noise ratio can be interchanged, that is, increasing the bandwidth can reduce the requirement on the signal-to-noise ratio, and the power of a useful signal can be close to or even be buried below the noise power. Based on the above principle, spread spectrum communication is exchanged for a lower signal-to-noise ratio by increasing the bandwidth. When the signal-to-noise ratio can not be improved, the bandwidth can be increased, and the purpose of improving the channel capacity is achieved. Spread spectrum is a wideband technique that appears to waste limited frequency resources since spread spectrum occupies a wider frequency band, which can be compensated for by a multi-user shared frequency band. Common spreading schemes include DS/FH (Direct Sequence Spread-Frequency Hopping Spread Spectrum), TH/DS (Time Hopping Spread Spectrum-Direct Sequence Spread Spectrum), TH/FH (Time Hopping Spread Spectrum-Frequency Hopping Spread Spectrum).
In the prior art, a DS/FH hybrid spread spectrum method is used in Master's paper published by DSFH hybrid spread spectrum measurement and control signal synchronization and anti-interference research, university of electronic technology, Chenjing, and the principle is constant rate/multiple period, and the I branch is used for transmission of telemetering and remote control data information and signal spread spectrum by short codes; the Q branch is used for ranging to not modulate signals and directly uses a long code sequence for spread spectrum. I. The two Q code rates are equal, and the requirement of high-speed data transmission can be met.
The inventor finds that the mode of short code spreading is still adopted in the prior art, but in the satellite communication field, with the explosive growth of high, medium and low orbit spacecraft and the ground important user scale, the network access of a large number of users gradually becomes the normal state of the satellite communication field in recent years. In the face of hundreds of even thousands of important spacecraft and earth surface users in the future, the number of the current spreading sequences cannot meet the system requirements. Therefore, how to increase the user capacity that can be accommodated in the system is an urgent technical problem to be solved.
Disclosure of Invention
The technical problem to be solved by the invention is how to increase the number of users that can be accommodated in the system.
The invention solves the technical problems through the following technical means:
the embodiment of the invention provides a mixed spread spectrum communication method based on long and short codes, which comprises the following steps:
splicing the link synchronization data and the frame synchronization data into synchronization segment data, and performing spread spectrum processing on the synchronization segment data by using a short code sequence;
splicing frame header data, data domain data and frame tail data into information segment data, and performing spread spectrum processing on the information segment data by using a long code sequence;
and splicing the spread synchronous segment data and the spread information segment data and then transmitting the spliced synchronous segment data and the spread information segment data.
Compared with the mode of singly adopting short codes or long code sequences to spread the whole message in the prior art, the method adopts different spreading code systems for the short message synchronous section and the short message information section, utilizes the good autocorrelation of the short codes to be beneficial to completing the capture of signals, utilizes the cross correlation among the long code sequences to avoid aggravating the multiple access interference and increase the confidentiality of information, and further can reduce and limit the conflict interval to the synchronous section data on the basis of ensuring the successful capture of the short message, reduce the conflict probability of the short message and effectively improve the user capacity of the system.
Optionally, the frame header data includes: the concatenated user identifier and packet counter.
Optionally, the performing spread spectrum processing on the synchronization segment data by using the short code sequence includes:
and performing spread spectrum processing on the synchronous segment data by using a code breaking sequence generated by the same spread spectrum code, wherein the spread spectrum code comprises: m sequence.
Optionally, the length of the long code sequence used in the spreading process of the information segment data is n × 1023, wherein,
n is the bit number corresponding to the data field data; 1023 is the length of a short code used when spreading the sync segment data, and the long code sequence is a sequence generated by a Gold code.
Optionally, the length of the link synchronization data is 64 bits;
the length of the frame synchronization data is 14 bits;
the frame header data length is 16 bits, the user identifier length is 8 bits, and the packet counter length is 8 bits; the end of frame data length is 16 bits.
The embodiment of the invention also provides a mixed spread spectrum communication device based on the long code and the short code, and the device comprises:
the first spread spectrum module is used for splicing the link synchronization data and the frame synchronization data into synchronization segment data and performing spread spectrum processing on the synchronization segment data by using a short code sequence;
the second spread spectrum module is used for splicing the frame head data, the data domain data and the frame tail data into information segment data and performing spread spectrum processing on the information segment data by using a long code sequence;
and the sending module is used for splicing the spread synchronous segment data and the spread information segment data and then sending the spliced synchronous segment data and the spread information segment data.
Optionally, the frame header data includes: the concatenated user identifier and packet counter.
Optionally, the data field data includes: user data.
Optionally, the length of the long code sequence used in the spreading process of the information segment data is n × 1023, wherein,
n is the bit number corresponding to the data field data; 1023 is the length of a short code used when spreading the sync segment data.
Optionally, the length of the link synchronization data is 64 bits;
the length of the frame synchronization data is 14 bits;
the frame header data length is 16 bits, the user identifier length is 8 bits, and the packet counter length is 8 bits; the end of frame data length is 16 bits.
The invention has the advantages that:
compared with the mode of singly adopting short codes or long code sequences to spread the whole message in the prior art, the method adopts different spreading code systems for the short message synchronous section and the short message information section, utilizes the good autocorrelation of the short codes to be beneficial to completing the capture of signals, utilizes the cross correlation among the long code sequences to avoid aggravating the multiple access interference and increase the confidentiality of information, and further can reduce and limit the conflict interval to the synchronous section data on the basis of ensuring the successful capture of the short message, reduce the conflict probability of the short message and effectively improve the user capacity of the system.
Drawings
Fig. 1 is a schematic structural diagram of a data frame in a hybrid spread spectrum communication method based on long and short codes according to an embodiment of the present invention;
fig. 2 is a schematic diagram illustrating a spreading principle in a hybrid spreading communication method based on long and short codes according to an embodiment of the present invention;
fig. 3 is a schematic diagram illustrating data frame collision determination in a hybrid spread spectrum communication method based on long and short codes according to an embodiment of the present invention.
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 embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. 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
In recent years, in the field of satellite communication, with the explosive growth of high, medium and low orbit spacecrafts and important users on the ground, network access of a large number of relay users gradually becomes a technical problem to be solved urgently in the field of relay satellite communication.
At present, a relay satellite communication system adopts a short message working system to transmit access signaling information of users, and in the face of hundreds of thousands or even more important relay users of spacecrafts and earth surfaces in the future, the number of the current spread spectrum sequences cannot meet the system requirements, and a new spread spectrum system is urgently needed to be researched to solve the network access requirements of a large number of relay users. In addition, the low-orbit spacecraft needs full-time monitoring when in orbit operation, the low-orbit spacecraft periodically sends a state short message to the relay satellite, and the relay satellite forwards the received information to the ground station; the low-orbit spacecraft applies for service communication to the relay satellite in real time through the short message; the method comprises the following steps that (1) emergency communication is carried out on a special user on the earth surface, and a request short message is sent to a relay satellite; the global data acquisition system information needs a new system capable of accommodating more users through service types such as information returned by a relay satellite.
Fig. 1 is a schematic structural diagram of a data frame in a hybrid spread spectrum communication method based on long and short codes according to an embodiment of the present invention; fig. 2 is a schematic diagram illustrating a spreading principle in a hybrid spreading communication method based on long and short codes according to an embodiment of the present invention, as shown in fig. 1 and fig. 2,
s101: splicing the link synchronization data and the frame synchronization data into synchronization segment data, and performing spread spectrum processing on the synchronization segment data by using a short code sequence;
in the embodiment of the present invention, a complete data frame is divided into sync segment data and information segment data, and the spreading process of the sync segment data is introduced in S101, and the spreading process of the information segment data is introduced in S102.
Illustratively, the length of the link synchronization data can be designed to be 64 bits, and the link synchronization data is filled with '0' completely and is used for capturing and synchronizing the short message by the ground station; the length of the frame synchronization data is designed to be 14 bits, and the frame synchronization data is composed of 13 bits of barker codes and 1 bit of '0' added, and is used for indicating the start of the frame.
Then, as shown in fig. 2, a short code sequence with length 1023 is generated according to the m sequence, and each bit of information in the synchronization segment is spread by using the short code with length 1023, so as to obtain spread synchronization segment data.
In practical applications, the short code sequences used in each complete data frame may be the same or different.
S102: splicing frame header data, data domain data and frame tail data into information segment data, and performing spread spectrum processing on the information segment data by using a long code sequence;
the synchronization section data sequentially comprises: a user identifier, a packet counter, data field data for storing user data, and a cyclic redundancy check code. Illustratively, in the embodiment of the present invention, the length of the frame header data may be designed to be 16 bits, and the frame header data is formed by sequentially splicing an 8-bit user identifier and an 8-bit packet counter, where the user identifier is used to identify a user to which a short message corresponding to the data frame belongs; the packet counter is used for recording the packet sequence number of the high-level effective data; the length of the frame tail data is designed to be 16 bits, and the frame tail data consists of a 16-bit Cyclic Redundancy Check (CRC) code and is used for checking a frame head and a data field; the data field data is designed to carry user data from higher layers.
The field data may also be referred to as a transport frame in general.
After the information segment data for transmitting user data is prepared, a long code sequence with the length of n x 1023 is generated by using Gold codes. As shown in fig. 2, the information segment data is spread by using a long code sequence with length n × 1023, wherein,
n is data field data, namely the bit number corresponding to the user data; 1023 is the length of the short code used when spreading the sync segment data in step S101.
It should be emphasized that the processes of the spreading processing method in step S101 and the spreading processing method in step S102 are prior art, and the detailed description of the embodiments of the present invention is omitted here.
S103: and splicing the spread synchronous segment data and the spread information segment data and then transmitting the spliced synchronous segment data and the spread information segment data.
As shown in fig. 1, after the spread synchronization segment data and the spread information segment data are spliced, a spread data frame is obtained, and the data frame is modulated and transmitted.
For describing the principle of reducing the short message collision probability in the embodiment of the present invention, reference is made to fig. 3 below, where fig. 3 is a schematic diagram illustrating data frame collision determination in a hybrid spread spectrum communication method based on long and short codes according to the embodiment of the present invention, as shown in fig. 3,
the synchronous segment of the short message 1, the synchronous segment of the short message 2 and the synchronous segment of the short message 3 adopt the same short code sequence for spreading:
the synchronization segment of the short message 1 is partially overlapped with the synchronization segment of the short message 2, and because the short code sequences used by the two are both from the m sequence, the two code words are overlapped, so that a conflict exists; the information segment of short message 1 overlaps with the information segment of short message 2: because the information segments of the short message 1 and the short message 2 both adopt long code sequences from Gold codes, and because of the non-repeatability of the long code sequences from the Gold codes, the information segments of the short message 1 and the short message 2 use different long code sequences, even if the information segments of the short message 1 and the short message 2 are overlapped, collision cannot be caused; however, the synchronization segments of the short message 1 and the short message 2 use the same spreading code, and since the synchronization segments overlap, the transmission of the short message 1 and the short message 2 fails under the condition that the collision energy is strong enough.
The information segment data of the short message 3 is overlapped with the synchronization segment and the information segment of the short message 2: however, the synchronization segment data of the short message 2 uses a short code sequence, which is different from the long code spreading sequence used by the information segment data of the short message 3, so that the synchronization segment data of the short message 2 does not conflict with the information segment data of the short message 3; similarly, although the information segment of the short message 2 and the information segment of the short message 3 both use the long code sequence generated by the Gold code, the long code sequence of the Gold code is non-repetitive, so that the information segment of the short message 2 and the information segment of the short message 3 do not collide with each other, and the short message 3 is successfully transmitted. Similarly, in the absence of short message 2, both short message 2 and short message 3 may be successfully transmitted.
Each digital sequence uses the same 1023 m sequence to perform spread spectrum, the short message information time difference of each user generally exceeds 2chip time, and the receiver can distinguish the information of different users, namely the collision interval is 2chip, wherein the chip is the time length of the chip.
The synchronization segment contains m bits, the information segment contains n digital sequences of bits, and the total contains m + n digital sequences, so that the total collision window is m + n. With the increase of bits of the information segment, the number of collision windows is more and more, and when the number reaches a certain degree, the user capacity of the short message is affected.
In the embodiment of the invention, the same 1023-length m sequence is adopted for the m bit digital sequences of the synchronization segment for frequency spreading, different 1023-length gold sequences are adopted for the n bit digital sequences for frequency spreading, and when the conflict intervals of the information segment and the synchronization segment are overlapped, the received information conflict can not be caused, so that the conflict window of the scheme is m, the increase of the conflict window can not be caused along with the increase of the bits of the information segment, and the capacity of a short message user can not be influenced. With the increasing of the number of users, the collision interval can be reduced and limited to synchronous segment data on the basis of ensuring the successful capture of the short message, the short message collision probability is reduced, and the system user capacity is effectively improved.
Compared with the mode of singly adopting short codes or long code sequences to spread the whole message in the prior art, the method adopts different spreading code systems for the short message synchronous section and the short message information section, utilizes the good autocorrelation of the short codes to be beneficial to completing the capture of signals, utilizes the cross correlation among the long code sequences to avoid aggravating the multiple access interference and increase the confidentiality of information, and further can reduce and limit the conflict interval to the synchronous section data on the basis of ensuring the successful capture of the short message, reduce the conflict probability of the short message and effectively improve the user capacity of the system.
In addition, compared with the method using long code sequence spread spectrum, the method shortens the length of the data frame on the premise of ensuring the confidentiality and anti-interference of information, and the short message format design is simpler;
finally, the invention divides the short message format design into two parts of a synchronization segment and an information segment. The synchronization section consists of link synchronization and frame synchronization, short codes are used for spread spectrum, and the signal acquisition is completed by utilizing the good autocorrelation of the short codes; the information section is composed of a frame head, a data domain and a frame tail, each bit of data of the information section is subjected to spread spectrum by adopting different long code sequences, and the cross correlation among the long code sequences is utilized to avoid aggravating the multiple access interference and increase the confidentiality of the information.
Moreover, with the progress of society, more spacecraft and surface users upload their own state information at the same time, and send burst information at any time and any place, and the requirement of supporting the user to conceal communication also needs to be met. The invention solves the problem that a large number of users access the satellite communication system, and simultaneously is easy to realize the capture of signals, thereby meeting the sudden demand of short messages.
Example 2
Corresponding to embodiment 1 of the present invention, embodiment 2 of the present invention further provides a hybrid spread spectrum communication apparatus based on long and short codes, where the apparatus includes:
the first spread spectrum module is used for splicing the link synchronization data and the frame synchronization data into synchronization segment data and performing spread spectrum processing on the synchronization segment data by using a short code sequence;
the second spread spectrum module is used for splicing the frame head data, the data domain data and the frame tail data into information segment data and performing spread spectrum processing on the information segment data by using a long code sequence;
and the sending module is used for splicing the spread synchronous segment data and the spread information segment data and then sending the spliced synchronous segment data and the spread information segment data.
Compared with the mode of singly adopting short codes or long code sequences to spread the whole message in the prior art, the method adopts different spreading code systems for the short message synchronous section and the short message information section, utilizes the good autocorrelation of the short codes to be beneficial to completing the capture of signals, utilizes the cross correlation among the long code sequences to avoid aggravating the multiple access interference and increase the confidentiality of information, and further can reduce and limit the conflict interval to the synchronous section data on the basis of ensuring the successful capture of the short message, reduce the conflict probability of the short message and effectively improve the user capacity of the system.
In a specific implementation manner of the embodiment of the present invention, the frame header data includes: the concatenated user identifier and packet counter.
In a specific implementation manner of the embodiment of the present invention, the first spreading module is configured to perform spreading processing on synchronization segment data by using a code-breaking sequence generated by the same spreading code, where the spreading code includes: m sequence.
In a specific implementation manner of the embodiment of the present invention, the length of the long code sequence used when the information segment data is spread is n × 1023, wherein,
n is the bit number corresponding to the data field data; 1023 is the length of a short code used when spreading the sync segment data, and the long code sequence is a sequence generated by a Gold code.
In a specific implementation manner of the embodiment of the present invention, the length of the link synchronization data is 64 bits;
the length of the frame synchronization data is 14 bits;
the frame header data length is 16 bits, the user identifier length is 8 bits, and the packet counter length is 8 bits; the end of frame data length is 16 bits.
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 (2)
1. A method for hybrid spread spectrum communication based on long and short codes, the method comprising:
splicing the link synchronization data and the frame synchronization data into synchronization segment data, and performing spread spectrum processing on the synchronization segment data by using a short code sequence;
splicing frame header data, data domain data and frame tail data into information segment data, and performing spread spectrum processing on the information segment data by using a long code sequence;
splicing the spread synchronous segment data with the spread information segment data and then transmitting the spliced synchronous segment data and the spread information segment data;
the frame header data includes: the spliced user identifier and the grouping counter;
the spreading process of the synchronization segment data by using the short code sequence includes:
and performing spread spectrum processing on the synchronous segment data by using a short code sequence generated by the same spread spectrum code, wherein the spread spectrum code comprises: m sequence;
the length of the long code sequence used when the information segment data is spread is n x 1023, wherein,
n is the bit number corresponding to the data field data; 1023 is the length of short code used when spreading synchronous segment data, the long code sequence is generated by Gold code;
the length of the link synchronization data is 64 bits;
the length of the frame synchronization data is 14 bits;
the frame header data length is 16 bits, the user identifier length is 8 bits, and the packet counter length is 8 bits; the end of frame data length is 16 bits.
2. A hybrid spread spectrum communication apparatus based on long and short codes, the apparatus comprising:
the first spread spectrum module is used for splicing the link synchronization data and the frame synchronization data into synchronization segment data and performing spread spectrum processing on the synchronization segment data by using a short code sequence;
the spreading process of the synchronization segment data by using the short code sequence includes:
and performing spread spectrum processing on the synchronous segment data by using a short code sequence generated by the same spread spectrum code, wherein the spread spectrum code comprises: m sequence;
the second spread spectrum module is used for splicing the frame head data, the data domain data and the frame tail data into information segment data and performing spread spectrum processing on the information segment data by using a long code sequence;
the transmitting module is used for splicing the spread synchronous segment data and the spread information segment data and then transmitting the spliced synchronous segment data and the spread information segment data;
the frame header data includes: the spliced user identifier and the grouping counter;
the data field data comprising: user data;
the length of a long code sequence used when the information segment data is spread is n x 1023, the long code sequence is a sequence generated by Gold code, wherein,
n is the bit number corresponding to the data field data; 1023 is the length of the short code used when the spread spectrum processing is carried out on the synchronous segment data;
the length of the link synchronization data is 64 bits;
the length of the frame synchronization data is 14 bits;
the frame header data length is 16 bits, the user identifier length is 8 bits, and the packet counter length is 8 bits; the end of frame data length is 16 bits.
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