CN109617569B - Pseudo code design method for improving receiving performance of multipath burst signals - Google Patents

Pseudo code design method for improving receiving performance of multipath burst signals Download PDF

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CN109617569B
CN109617569B CN201811449110.0A CN201811449110A CN109617569B CN 109617569 B CN109617569 B CN 109617569B CN 201811449110 A CN201811449110 A CN 201811449110A CN 109617569 B CN109617569 B CN 109617569B
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pseudo code
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pseudo
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CN109617569A (en
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朱向鹏
张亢
王延光
刘涛
赵磊
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Xian Institute of Space Radio Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects
    • H04B1/7075—Synchronisation aspects with code phase acquisition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7097—Interference-related aspects
    • H04B1/7103—Interference-related aspects the interference being multiple access interference
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/0007—Code type
    • H04J13/0022—PN, e.g. Kronecker
    • H04J13/0029—Gold
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/10—Code generation

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Abstract

The invention discloses a pseudo code design method for improving the receiving performance of multipath burst signals, which comprises the following steps: generating a primary spreading code and storing it in RAM 1; generating a secondary spreading code and storing it in RAM 2; inserting a plurality of chip auxiliary spread spectrum code sequences into the end part of each main spread spectrum code period to obtain a variable period pseudo code; wherein, the length of the secondary spreading code inserted in the end part of each primary spreading code period satisfies the arithmetic progression with tolerance d. The invention solves the problem that the period of receiving a plurality of different users by the message communication receiver is fuzzy, greatly reduces the collision probability of 3 chips of different inbound signals of the message communication receiver, improves the success probability of the inbound signals, and greatly improves the code division multiple access inhibition capability among a plurality of users.

Description

Pseudo code design method for improving receiving performance of multipath burst signals
Technical Field
The invention belongs to the technical field of spread spectrum communication, and particularly relates to a pseudo code design method for improving the receiving performance of a multipath burst signal.
Background
The message communication receiver can simultaneously receive multiple message communication signals. The message communication receiver receives a message communication signal, and the process is called signal inbound; when a message communication signal enters, a message communication receiver firstly completes the capture of the incoming signal according to a synchronous head pseudo code, then completes the signal synchronization according to the initial position of a frame head Barker code, then performs decoding and de-framing, and extracts the content of message communication. Therefore, it is a very important link for the design of the message communication receiver to complete signal capture according to the sync header pseudo code, the performance of the sync header pseudo code directly determines the capture performance of the message communication receiver, and the selection of the pseudo code with excellent performance can improve the receiving performance of the inbound signal. In this specification, the core part is a pseudo-code design of the sync header part.
Pseudo codes in spread spectrum communication are divided according to periods, and the pseudo codes comprise periodic pseudo codes and non-periodic pseudo codes. The periodic pseudo code comprises an m sequence, a gold code and the like. The non-periodic pseudo code comprises P code adopted by GPS, and the period of the pseudo code is longer. The characteristics of the spreading code sequence directly affect the performance of the spread spectrum communication system. When designing the signal system, according to the project requirement, selecting proper pseudo code form from the aspects of safety, realizability, anti-interference capability and multiple access capability.
The period of the pseudo code directly influences the capturing time of the signal, and the longer the period of the pseudo code is, the stronger the anti-interference capability is, the higher the safety is, and the longer the capturing time is. The signal received by the message communication receiver is weaker, the length of the captured synchronous head is shorter, and the pseudo code period of the synchronous head is shortened as much as possible so as to meet the requirement of fast capturing of multiple paths of burst signals. Meanwhile, the cross correlation of the synchronous head pseudo code of the multi-channel message signals is small, and the false alarm capturing probability is reduced. The synchronous head pseudo code of the current message communication signal adopts a constant period design mode, namely, a synchronous head pseudo code sequence has periodicity, the synchronous head pseudo code only consists of a main spread spectrum code, the pseudo code sequence is an m sequence, and the period length of the pseudo code is 1023. The message communication receiver completes the acquisition of the synchronous head according to the time division principle.
However, the signal synchronization by the above method has the following problems: due to the periodicity of the synchronization header pseudo code, when the message communication signals of different users reach the message communication receiver, the synchronization header pseudo code is required to be larger than 3 chips, and then the message communication signals can be captured and received. If the inbound signals of different users collide by 3 chips, the current inbound message communication strategy is to discard the low-power users. Meanwhile, the signal power between different users needs to be less than 12dB and can be received by the message communication receiver, and if the signal power is larger than the range, the multiple access interference between different users is serious, and the receiving performance of the message communication receiver is seriously influenced.
The document of pseudo code design for improving the performance of signal acquisition proposes that the pseudo codes with different lengths are adopted by the users, and the lengths of the users meet the requirement of mutual prime. The idea of using the non-isometric pseudo code as a pseudo code design realizes the compromise design of the pseudo code length and the cross-correlation performance, thereby improving the capture sensitivity of the broken code length in a weak signal environment. In engineering application, each user independently uses a set of pseudo codes, capturing needs to be performed for each user, capturing calculation of a plurality of users cannot be completed by one-time capturing operation, more resources and longer calculation time are needed, and the method is not suitable for a multi-user burst system. The search is carried out in a patent library, and the generation of the pseudo code is mostly focused on the design of a long code, so that the design of the variable-period pseudo code related to the patent does not exist at present.
Disclosure of Invention
The technical problem of the invention is solved: the method overcomes the defects of the prior art, provides a pseudo code design method for improving the receiving performance of multi-path burst signals, solves the problem that the period of receiving a plurality of different users by a message communication receiver is fuzzy, and greatly improves the code division multiple access inhibition capability among multiple users.
In order to solve the technical problem, the invention discloses a pseudo code design method for improving the receiving performance of a multipath burst signal, which comprises the following steps:
generating a primary spreading code and storing it in RAM 1;
generating a secondary spreading code and storing it in RAM 2;
inserting a plurality of chip auxiliary spread spectrum code sequences into the end part of each main spread spectrum code period to obtain a variable period pseudo code; wherein the length of the sub-spreading code sequence inserted at the end of each main spreading code period satisfies an arithmetic progression with a tolerance of d.
In the above pseudo code design method for improving the multi-path burst signal reception performance, the generating and storing of the main spreading code in the RAM1 includes:
and generating a main spread spectrum code with a pseudo code rate of X MHz according to the pseudo code generating polynomial and the pseudo code initial phase, wherein the number of generated pseudo code chips is N1, the pseudo code chips are stored in a RAM1, and the stored addresses are 0 to N1-1.
In the above pseudo code design method for improving the reception performance of a multi-path burst signal, the generating and storing of the secondary spreading code in the RAM2 includes:
generating a secondary spread spectrum code with a pseudo code rate of X MHz according to a pseudo code generating polynomial and a pseudo code initial phase, wherein the number of generated pseudo code chips is d X (1+ N2) xN 2/2, the generated pseudo code chips are stored in a RAM2, and the stored addresses are 0 to d X (1+ N2) xN 2/2-1; where N2 represents the number of primary spreading code periods.
In the above method for designing pseudo code for improving the performance of receiving multipath burst signals, a sub-spreading code sequence of several chips is inserted at the end of each main spreading code period to obtain a variable period pseudo code, which includes:
initializing RAM1 and RAM 2;
reading the main spread spectrum code from the RAM1, wherein the reading addresses are 0 to N1-1;
reading the secondary spreading code from the RAM2 at the address: (k-1) XkXd/2 to (k +1) XdXk/2-1; wherein k represents the number of reading periods of the main spreading code;
and inserting the read secondary spreading codes into the cycle ending part of each read main spreading code to obtain the variable-cycle pseudo code.
In the pseudo code design method for improving the multi-path burst signal receiving performance, the initialization of the RAM1 and the RAM2 includes:
the RAM1 and RAM2 read addresses are initialized to 0, and the number k of main spreading code read cycles is initialized to 1.
In the above pseudo code design method for improving the reception performance of the multi-path burst signal,
reading the main spread spectrum codes stored in the RAM1 by a clock X MHz group, wherein the reading number is N1, and the reading address is 0 to N1-1;
reading the sub-spreading codes stored in the RAM2 in groups of X MHz clocks, the number of reads being k × d, the read addresses being (k-1) × k × d/2 to (k +1) × d × k/2-1;
inserting the read secondary spreading code into the tail part of the read main spreading code;
judging whether the number k of the read main spread spectrum codes is equal to N2;
if the pseudo codes are equal, obtaining a variable-period pseudo code;
if not, k +1 is executed, and then the step of reading the main spreading code from the RAM1 is skipped.
In the above method for designing pseudo code to improve the performance of receiving multiple burst signals, the method further includes:
generating a secondary spread spectrum code by using a GOLD sequence, and performing autocorrelation calculation of a main spread spectrum code and cross-correlation calculation of the main spread spectrum code and the secondary spread spectrum by using a matlab tool; and according to the correlation calculation result, subtracting the maximum value of the cross-correlation calculation from the peak value of the main lobe of the main spread spectrum code autocorrelation calculation to obtain a calculation result, if the calculation result is more than 15dB, the selection of the code pattern of the auxiliary spread spectrum code can be met, and otherwise, the code pattern of the auxiliary spread spectrum code and the initial phase need to be reselected.
In the above method for designing pseudo code to improve the performance of receiving multiple burst signals, the method further includes:
and determining the value of X according to the design parameters of the actual communication system.
In the above pseudo code design method for improving the reception performance of the multi-path burst signal,
the value of N1 is positive integer, when the main spreading sequence is m sequence and GOLD sequence, the value of N1 is 2n-1; wherein n is a positive integer and represents the length of the register for generating the pseudo code.
The invention has the following advantages:
(1) the variable-period pseudo code inserts a plurality of chip auxiliary spread spectrum code sequences at the end part of each main spread spectrum code period, and the period of the constant-period pseudo code is changed, so that the problem that a message communication receiver receives a plurality of different user periods in a fuzzy manner is solved, the collision probability of the message communication receiver receiving different user signals and generating 3 chips is greatly reduced, and the user experience is greatly improved;
(2) compared with the constant period pseudo code, when the arrival time of the multi-user message communication inbound signals respectively differs by more than N1 chips, the code division multiple access inhibition capability among multiple users is greatly improved; the capacity of the message communication receiver for receiving the user is obviously increased, and the capacity of the message communication receiver for receiving multi-channel message signals is improved;
(3) compared with a capturing method of a constant period pseudo code, the variable period pseudo code inserts a secondary spread spectrum code with a tolerance d after each main spread spectrum period, and the setting of the tolerance d causes that when the sliding correlation is carried out between the local pseudo code and a received signal, the backward sliding with the tolerance d also occurs to the correlation value of the same pseudo code phase; compared with the method for capturing the constant-period pseudo code, when the FFT calculation is carried out on the correlation value of the same pseudo code phase, the correlation value needs to be correctly read according to the setting of the tolerance d. Compared with the traditional method for capturing all pseudo codes in a sliding correlation mode, the design of the variable-period pseudo codes can optimize the capture design and reduce the capture time.
Drawings
FIG. 1 is a flowchart illustrating the steps of a pseudo code design method for improving the performance of receiving multiple bursts according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a variable-period pseudo code insertion structure according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a variable-period pseudo code design structure according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1 and fig. 2, in this embodiment, the method for designing a pseudo code to improve the performance of receiving multiple paths of burst signals includes:
in step 101, a primary spreading code is generated and stored in RAM 1.
In this embodiment, a main spreading code with a pseudo code rate of XMHz may be generated based on a pseudo code generating polynomial and a pseudo code initial phase, the number of pseudo code generating chips being N1, stored in RAM1, and stored at addresses 0 to N1-1.
At step 102, a secondary spreading code is generated and stored in RAM 2.
In this embodiment, a sub-spreading code with a pseudo code rate of XMHz may be generated based on a pseudo code generating polynomial and a pseudo code initial phase, the number of pseudo code chips generated being d × (1+ N2) × N2/2, stored in the RAM2, and stored at addresses of 0 to d × (1+ N2) × N2/2-1; where N2 represents the number of primary spreading code periods.
And 103, inserting a plurality of chips of auxiliary spread spectrum code sequences at the end part of each main spread spectrum code period to obtain a variable-period pseudo code.
As shown in fig. 3, in the present embodiment, the length of the secondary spreading code inserted at the end portion of each primary spreading code period satisfies the arithmetic progression with the tolerance d. The generation flow of the insertion may be as follows: initializing RAM1 and RAM 2; reading the main spreading code from the RAM1 at the address: 0 to N1-1; reading the secondary spreading code from the RAM2 at the address: (k-1) XkXd/2 to (k +1) XdXk/2-1; and inserting the read auxiliary spread spectrum code into the cycle ending part of the read main spread spectrum code to obtain the variable cycle pseudo code. Where k represents the number of primary spreading code reads.
Preferably, initializing the RAM1 and the RAM2 may specifically include: the RAM1 and RAM2 read addresses are initialized to 0, and the number k of main spreading code reads is initialized to 1.
Preferably, the main spreading codes stored in the RAM1 can be read in groups of X MHz in clock, where the number of reads is k, and the read addresses are 0 to N1-1; reading the sub-spreading codes stored in the RAM2 in groups of X MHz clocks, the number of reads being k × d, the read addresses being (k-1) × k × d/2 to (k +1) × d × k/2-1; judging whether the number k of the read main spread spectrum codes is equal to N2; if the two codes are equal, inserting the read auxiliary spread spectrum codes into the cycle ending part of each read main spread spectrum code to obtain variable-cycle pseudo codes; if not, k +1 is executed, and then the step of reading the main spreading code from the RAM1 is skipped.
Preferably, in this embodiment, the secondary spreading code is generated by using GOLD sequence (or other form of pseudo-random sequence), and the self-correlation calculation of the primary spreading code and the cross-correlation calculation of the primary spreading code and the secondary spreading are performed by using matlab tool; and according to the correlation calculation result, subtracting the peak value of the main lobe of the autocorrelation calculation of the main spreading code from the maximum value of the cross-correlation calculation to obtain a calculation result, if the calculation result is less than 15dB, the selection of the code pattern of the auxiliary spreading code can be met, and if not, the code pattern of the auxiliary spreading code and the initial phase need to be reselected.
It should be noted that the values of X, N1, N2, and d may be set according to actual situations. X is the pseudo code rate of spread spectrum communication, the pseudo code rate of a frequency point of a GPS navigation system L1 is 1.023M Hz, the pseudo code rate of a frequency point of a Beidou navigation system B2B is 10.23MHz, the value range of X has no special requirement, and the pseudo code rate is consistent with that of a spread spectrum ranging communication system, and the pseudo code rate needs to be determined according to the design of an actual communication system. N1 represents the pseudo code length of one period of the main spread spectrum code, the value of N1 is a positive integer, when the main spread spectrum sequence is an m sequence and a GOLD sequenceWhen listed, the value of N1 is 2nAnd 1, n is a positive integer and represents the length of a pseudo code register, and when the main spreading sequence is other forms of spreading sequences, the length of the pseudo code sequence is not required and needs to be determined according to the design of an actual communication system. The value of d is an integer, and the value of d is suggested to be as small as possible in consideration of the complexity of the design of capturing the pseudo code by the receiving part and needs to be determined according to the design of an actual communication system. N2 represents the number of primary spreading code periods, that is, the number of secondary spreading code sequence positions where a plurality of chips are inserted into the end portion of each primary spreading code period, and the value of N2 is a positive integer, and has no specific range requirement, and needs to be determined according to the design of an actual communication system. GOLD sequence, m sequence are 'communication principle' proper nouns, matlab tool is computer software name, GPS navigation system is proper noun, RAM1 and RAM2 are names of data storage, and other codes can be named as well.
In summary, the structural design of the variable period pseudo code of the present invention is implemented based on two spreading codes with shorter periods, which are respectively called a primary spreading code and a secondary spreading code. The main spread spectrum code constructs a longer synchronous head by periodically repeating the spread spectrum code, and the auxiliary spread spectrum code forms a variable period pseudo code by inserting pseudo codes with unequal lengths into each main spread spectrum code period. The pseudo code sequence of the constant period pseudo code has periodicity and only consists of the main spread spectrum code. Different from the constant period pseudo code, the variable period pseudo code inserts a plurality of chip secondary spreading code sequences after each main spreading code period, and the periodicity of the synchronization head can be effectively destroyed by reasonably designing the number of the spreading code chips in each period, so that the probability that the message communication receiver simultaneously receives the collision of different users at the synchronization head part is avoided, and the specific insertion mode is shown in fig. 2. The pseudo code rate is X MHz, the pseudo code length of one period of the main spread spectrum code of the synchronization head is N1, and the period number of the main spread spectrum code of the synchronization head is N2. The schematic diagram of inserting the secondary spreading codes among the primary spreading codes is shown in fig. 3, in which the secondary spreading codes are inserted at the tail of each period ending of the primary spreading codes, the number of the pseudo codes of the inserted secondary spreading codes meets the arithmetic progression, the tolerance d of the arithmetic progression needs to be configured according to the project requirements. The number of chips of the inserted secondary spreading code is d × (1+ N2) × N2/2, and the number of pseudo codes generated by the secondary spreading code should be equal to the calculated value.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with actual simulation data. The number of users of the message communication signal is 16, the message communication signal is in a random or uniform inbound mode, the Doppler of the 16 users is randomly changed within the range of +/-4 KHz, and the synchronous head sequences of the 16 users are simulated by adopting constant-period pseudo codes and variable-period pseudo codes respectively. The constant period code adopts GOLD sequence with length of 1023, and the variable period pseudo code inserts a secondary spread spectrum code with tolerance d equal to 1 on the basis of the constant period pseudo code. The code sequence of the secondary spreading code still adopts a GOLD sequence, and is constructed by adopting tap coefficients different from a generator polynomial of the main spreading code, and the initial phase of the main spreading code to the secondary spreading code is all 1. And (3) finishing the autocorrelation calculation of the main spreading codes with the same length and the cross-correlation calculation of the main spreading codes and the auxiliary spreading codes by using a matlab tool. According to the correlation calculation result, the maximum value of subtracting the cross-correlation calculation from the peak value of the main lobe of the autocorrelation calculation of the main spreading code is 18dB, and the requirement of selecting the auxiliary spreading code can be met.
In the message communication project, the performance simulation verification is carried out on the synchronous head pseudo code design, and the test conditions are as follows:
signal center frequency point: 85.9MHz
Primary spreading code pseudo code period number N2: 50 are provided with
Number of one-period chips of primary spreading code N1: 1023
Pseudo code rate: 1.023MHz
Length of variable period secondary spreading code: 1275 are provided with
Length tolerance d of inserted secondary spreading code: 1
Generating a pseudo code rate X MHz: 1.023MHz
Pseudo code period: 1ms
Frequency of signal inbound: 1 s/time
The message communication users are in random inbound mode, the time of arriving at the message communication receiver meets Poisson random distribution, and the entrance carrier-to-noise ratio CN0 of the message communication receiver is 33 dBHz. The synchronous head pseudo code adopts a constant period pseudo code and a variable period pseudo code respectively to carry out simulation verification on 10 ten thousand incoming signals. Under the condition of constant-period pseudo code design, 120 users collide with 3 chips, the user collision rate is about zero per thousand, and the colliding users cannot complete signal entering. Under the condition of variable-period pseudo code design, the test condition is the same as that under the random test mode, 1 ten thousand inbound signals are subjected to simulation verification, 2 users collide with 3 chips, the user collision rate is about zero two of ten-thousandth, and the user collision rate is obviously reduced.
The message communication users have uniform inbound, the time intervals of all the users reaching the message communication receiver are different by 3 chips, the lowest carrier-to-noise ratio CN0 at the entrance of the message communication receiver is 33dBHz, the inbound signals of all the users have different powers, and when the power difference of the users is 12dB, 10 ten thousand inbound signals are subjected to simulation verification. Under the condition of the constant-period pseudo code design, 99950 successful inbound messages are sent by the user, and the inbound success rate is 99.95%. When the power difference of the signals with the larger and the smaller users continues to increase, the mutual influence of multiple access interference among the users becomes more and more serious, when the power difference of the signals with the larger and the smaller users is 14dB, simulation verification is carried out on 1 ten thousand of inbound signals, 94580 users successfully inbound, and the message communication receiving success rate is 94.58%. Under the condition of variable-period pseudo code design, the test condition is that the inbound time of each user differs by more than 1ms, 10 ten thousand inbound signals are subjected to simulation verification, when the power difference of the user is 17dB, the 10 ten thousand inbound signals are subjected to simulation verification, 99920 users are successfully accessed, and the receiving success rate is 99.92%.
It can be known from the above simulation experiment that when the variable-period pseudo code is applied to the design of the message communication receiver, for the condition of multi-user inbound, the collision probability of the message communication receiver for generating 3 chips of different inbound signals is greatly reduced, and the code division multiple access suppression capability among multiple users is greatly improved.
The embodiments in the present description are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The above description is only for the best mode of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.

Claims (9)

1. A pseudo code design method for improving the receiving performance of a multipath burst signal is characterized by comprising the following steps:
generating a primary spreading code and storing it in RAM 1;
generating a secondary spreading code and storing it in RAM 2;
the number of the periods of the main spread spectrum codes is N2, and an auxiliary spread spectrum code sequence with a plurality of chips is inserted into the ending part of each period of the main spread spectrum codes to obtain a variable period pseudo code; the relationship between the lengths of N2 inserted sub-spreading code sequences is an arithmetic progression satisfying a tolerance d.
2. The method of claim 1, wherein generating the main spreading code and storing the main spreading code in the RAM1 comprises:
and generating a main spread spectrum code with a pseudo code rate of X MHz according to the pseudo code generating polynomial and the pseudo code initial phase, wherein the number of generated pseudo code chips is N1, the pseudo code chips are stored in a RAM1, and the stored addresses are 0 to N1-1.
3. The method of claim 1, wherein the generating and storing the secondary spreading codes in the RAM2 comprises:
generating a secondary spread spectrum code with a pseudo code rate of X MHz according to a pseudo code generating polynomial and a pseudo code initial phase, wherein the number of generated pseudo code chips is d X (1+ N2) xN 2/2, the generated pseudo code chips are stored in a RAM2, and the stored addresses are 0 to d X (1+ N2) xN 2/2-1; where N2 represents the number of primary spreading code periods.
4. The method as claimed in claim 1, wherein the step of inserting a secondary spreading code sequence having several chips into the end portion of each primary spreading code period to obtain a variable period pseudo code comprises:
initializing RAM1 and RAM 2;
reading the main spread spectrum code from the RAM1, wherein the reading addresses are 0 to N1-1;
reading the secondary spreading code from the RAM2 at the address: (k-1) XkXd/2 to (k +1) XdXk/2-1; wherein k represents the number of reading periods of the main spreading code;
and inserting the read secondary spreading codes into the cycle ending part of each read main spreading code to obtain the variable-cycle pseudo code.
5. The method as claimed in claim 4, wherein initializing the RAM1 and the RAM2 comprises:
the RAM1 and RAM2 read addresses are initialized to 0, and the number k of main spreading code read cycles is initialized to 1.
6. The method of claim 4, wherein the pseudo code is designed to improve the performance of receiving the multi-path burst signal,
reading the main spread spectrum codes stored in the RAM1 by a clock X MHz, wherein the reading number is N1, and the reading addresses are 0 to N1-1;
reading the sub-spreading codes stored in the RAM2 at a clock X MHz, the number of reads being k × d, the read addresses being (k-1) × k × d/2 to (k +1) × d × k/2-1;
inserting the read secondary spreading code into the tail part of the read main spreading code;
judging whether the number k of the read main spread spectrum codes is equal to N2;
if the pseudo codes are equal, obtaining a variable-period pseudo code;
if not, k +1 is executed, and then the step of reading the main spreading code from the RAM1 is skipped.
7. The method of claim 1, further comprising:
generating a secondary spread spectrum code by using a GOLD sequence, and performing autocorrelation calculation of a main spread spectrum code and cross-correlation calculation of the main spread spectrum code and the secondary spread spectrum by using a matlab tool; and according to the correlation calculation result, subtracting the maximum value of the cross-correlation calculation from the peak value of the main lobe of the main spread spectrum code autocorrelation calculation to obtain a calculation result, if the calculation result is more than 15dB, the selection of the code pattern of the auxiliary spread spectrum code can be met, and otherwise, the code pattern of the auxiliary spread spectrum code and the initial phase need to be reselected.
8. The method as claimed in claim 2 or 3, further comprising:
and determining the value of X according to the design parameters of the actual communication system.
9. The method of claim 2, wherein the pseudo code is designed to improve the performance of receiving the multi-path burst signal,
the value of N1 is positive integer, when the main spreading sequence is m sequence and GOLD sequence, the value of N1 is 2n-1; wherein n is a positive integer and represents the length of the register for generating the pseudo code.
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