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CN112449403A - Random access channel transmission method and device in low-earth-orbit satellite communication - Google Patents

Random access channel transmission method and device in low-earth-orbit satellite communication Download PDF

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Publication number
CN112449403A
CN112449403A CN201910839216.XA CN201910839216A CN112449403A CN 112449403 A CN112449403 A CN 112449403A CN 201910839216 A CN201910839216 A CN 201910839216A CN 112449403 A CN112449403 A CN 112449403A
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sequence
dft
time
frequency domain
mapping
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CN112449403B (en
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方冬梅
金星
林之楠
鲁志兵
杨芸霞
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Hytera Communications Corp Ltd
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Hytera Communications Corp Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/002—Transmission of channel access control information
    • H04W74/004—Transmission of channel access control information in the uplink, i.e. towards network
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/16—Discovering, processing access restriction or access information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/08—Non-scheduled access, e.g. ALOHA
    • H04W74/0833—Random access procedures, e.g. with 4-step access

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Computer Security & Cryptography (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The invention provides a random access channel transmission method in low earth orbit satellite communication, which comprises the following steps: selecting a PN sequence with a set sequence form from a set PN sequence set; mapping the PN sequence to a subcarrier according to a preset conversion mode; and carrying out inverse fast Fourier transform on the sub-carrier mapped with the PN sequence, transforming the sub-carrier mapped with the PN sequence to a time domain, and transmitting the sub-carrier to a base station in a preset form. The method provided by the invention adopts the PN sequence in the set sequence form to carry the signal to be transmitted, replaces the ZC sequence adopted by the existing Preamble sequence, avoids the situation of pseudo peaks in the transmission process, can more effectively identify the main peak, enables the terminal to be accessed into the base station in time and enables the base station to effectively receive the signal. In the method provided by the embodiment of the invention, the PN sequence is adopted, and the CP does not need to be transmitted when the PN sequence is transmitted to the base station, so that the time overhead is saved.

Description

Random access channel transmission method and device in low-earth-orbit satellite communication
Technical Field
The invention relates to the field of low-earth-orbit satellite communication, in particular to a random access channel transmission method and a random access channel transmission device in low-earth-orbit satellite communication.
Background
With the development of communication technology, people have higher and higher requirements on real-time information. Satellite communication has become an essential important means for global communication by virtue of its advantages of wide coverage, large communication capacity, good transmission quality, etc.
The PRACH in satellite communication is mainly used for estimating uplink transmission timing error, uplink frequency offset error and SNR when a user accesses. The channel characteristics of the satellite channel are that the coverage area of the satellite beam is very large, the area is 60km x 1000km, and the uplink timing error is very large before uplink timing is not carried out; the movement speed of satellite communication and the adopted carrier frequency cause that the uplink frequency offset error is very large, and the residual uplink frequency offset is about +/-30 kHz; and the signal-to-noise ratio of satellite communication is low, and the minimum can reach-10 dB.
The transmission power of the PRACH may be lower than that of other channels, typically by more than ten dB lower than that of the PUSCH.
Due to the problem of frequent handover in satellite communication, the PRACH may need to be transmitted frequently, so the rationality of PRACH design is very important.
The channel structure of the existing PRACH comprises three parts, namely a part 3 and three parts, namely a CP, a Preamble and a GT. The CP is used to offset interference caused by different users arriving at different times, the Preamble is a random access sequence, and the GT is used to prevent the Preamble from interfering with a signal to be transmitted subsequently. The existing Preamble sequence adopts a ZC (Zadoff-Chu) sequence to carry a signal to be transmitted. The research on the existing transmission process shows that a ZC sequence generates a pseudo peak when frequency deviation exists, and when the frequency deviation exceeds half of the interval of a subcarrier, the energy of the pseudo peak is even larger than that of a main peak, so that the main peak of a transmission signal cannot be determined, and the signal cannot be effectively received.
The frequency offset of satellite communication is as high as +/-30 kHz, and even if Preamble configuration with subcarrier spacing of 60kHz is adopted, the main peak can not be correctly judged under the frequency offset. Meanwhile, when the subcarrier spacing is large, the more frequency domain RBs are occupied, resulting in an increase in overhead for PRACH. E.g., 18 RBs occupied by 30kHz spacing of subcarriers; the subcarrier spacing of 60kHz occupies 35 RBs.
Disclosure of Invention
The invention aims to solve the technical problem of providing a random access channel transmission method in low earth orbit satellite communication, which adopts a PN sequence in a set form to carry a signal to be transmitted, avoids the condition of a pseudo peak in the transmission process, can directly determine a main peak of the transmission signal, enables a terminal to be accessed into a base station in time and further effectively receives the signal.
The invention also provides a random access channel transmission device in the low-orbit satellite communication, which is used for ensuring the realization and the application of the method in practice.
A random access channel transmission method in low earth orbit satellite communication is applied to a terminal, and the method comprises the following steps:
selecting a PN sequence with a set sequence form from a set PN sequence set;
mapping the PN sequence to a subcarrier according to a preset conversion mode;
and performing Inverse Fast Fourier Transform (IFFT) on the sub-carriers mapped with the PN sequences to transform the sub-carriers mapped with the PN sequences to a time domain and transmit the sub-carriers to a base station in a preset form.
In the above method, optionally, if the sequence form of the PN sequence is a frequency domain PN sequence;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
and directly mapping the frequency domain PN sequence to the subcarrier.
In the above method, optionally, if the sequence form of the PN sequence is a discrete fourier transform spread orthogonal frequency division multiplexing DFT-s-OFDM modulated PN sequence;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
performing fast Fourier transform on the DFT-s-OFDM modulated PN sequence to transform the DFT-s-OFDM modulated PN sequence to a frequency domain;
and mapping the DFT-s-OFDM modulated PN sequence transformed to the frequency domain to the subcarrier.
In the above method, optionally, if the sequence form of the PN sequence is a frequency domain PN sequence associated with a walsh orthogonal code;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
and directly mapping the frequency domain PN sequence associated with the walsh orthogonal code to the subcarrier.
In the above method, optionally, if the sequence form of the PN sequence is a discrete fourier transform spread orthogonal frequency division multiplexing DFT-s-OFDM modulated PN sequence associated with a walsh orthogonal code;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
performing fast Fourier transform on the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to transform the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to a frequency domain;
mapping the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code transformed to the frequency domain onto the subcarrier.
The above method, optionally, further comprises, after transforming the DFT-s-OFDM modulated PN sequence to the frequency domain, before mapping the DFT-s-OFDM modulated PN sequence transformed to the frequency domain onto the subcarriers:
and windowing the DFT-s-OFDM modulated PN sequence transformed to the frequency domain.
The above method, optionally, after transforming the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to the frequency domain, before mapping the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code transformed to the frequency domain onto the subcarrier, further includes:
windowing the DFT-s-OFDM modulated PN sequence transformed to the frequency domain with the walsh orthogonal code associated therewith.
The method described above, optionally, the transmitting to the base station in the predetermined form, includes:
and transmitting the PN sequence transformed into the time domain to a base station in a form that a ZP is arranged in front of the PN sequence and a GT is arranged behind the PN sequence, wherein the ZP is a null field, and the length of the ZP is 1-2 times of the CP length of the OFDM symbol of the data area.
A random access channel transmission apparatus in low earth orbit satellite communication, the apparatus being applied to a terminal, the apparatus comprising:
the selection unit is used for selecting a PN sequence with a set form from the set PN sequence set;
the mapping unit is used for mapping the PN sequence to a subcarrier according to a preset conversion mode;
and the transmitting unit is used for performing Inverse Fast Fourier Transform (IFFT) on the sub-carriers mapped with the PN sequences so as to transform the sub-carriers mapped with the PN sequences to a time domain and transmitting the sub-carriers to a base station in a preset form.
A random access channel transmission method in low earth orbit satellite communication, the method being applied to a base station, the method comprising:
acquiring time-frequency resource data;
respectively correlating each PN sequence in a set sequence form in a set PN sequence set with the time frequency resource data to detect a peak value in the time frequency resource data;
and when the peak value in the time frequency resource data is detected, determining the PN sequence in the set sequence form related to the time frequency resource data as the PN sequence sent by the terminal.
Optionally, the above method, where correlating the PN sequences in the set sequence form in the set PN sequence set with the time-frequency resource data respectively, includes:
dividing each PN sequence with a set sequence form in the set PN sequence set into a plurality of PN sequence subsections;
and respectively correlating each PN sequence sub-segment of each PN sequence with a set sequence form with the time domain resource data, wherein the correlation comprises time domain sliding correlation and frequency domain correlation.
A random access channel transmission apparatus in low earth orbit satellite communication, the apparatus being applied to a base station, comprising:
the acquisition unit is used for acquiring time-frequency resource data;
a detecting unit, configured to correlate each set sequence type PN sequence in a set PN sequence set with the time-frequency resource data, so as to detect a peak value in the time-frequency resource data;
and the determining unit is used for determining the PN sequence in the set sequence form related to the time frequency resource data as the PN sequence sent by the terminal when the peak value in the time frequency resource data is detected.
Compared with the prior art, the invention has the following advantages:
the invention provides a random access channel transmission method in low earth orbit satellite communication, which comprises the following steps: selecting a PN sequence with a set sequence form from a set PN sequence set; mapping the PN sequence to a subcarrier according to a preset conversion mode; and performing Inverse Fast Fourier Transform (IFFT) on the sub-carriers mapped with the PN sequences to transform the sub-carriers mapped with the PN sequences to a time domain and transmit the sub-carriers to a base station in a preset form. The random access channel transmission method provided by the invention adopts the PN sequence in the set sequence form to carry the signal to be transmitted, replaces the ZC sequence adopted by the existing Preamble sequence, avoids the situation of a pseudo peak in the transmission process, can more effectively identify the main peak, enables the terminal to be accessed into the base station in time and enables the base station to effectively receive the signal. In the method provided by the embodiment of the invention, the PN sequence is adopted, and the CP does not need to be transmitted when the PN sequence is transmitted to the base station, so that the time overhead is saved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.
Fig. 1 is a flowchart of a method for random access channel transmission in low earth orbit satellite communication according to the present invention;
fig. 2 is a schematic structural diagram of a random access channel transmission apparatus in low earth orbit satellite communication according to the present invention;
fig. 3 is a flowchart of another method of random access channel transmission in low earth orbit satellite communication according to the present invention;
fig. 4 is another schematic structural diagram of a random access channel transmission method in low earth orbit satellite communication according to the present invention;
fig. 5 is a schematic structural diagram of a random access channel transmission system in low earth orbit satellite communication according to the present invention;
fig. 6 is a communication schematic diagram of a random access channel transmission system in low earth orbit satellite communication according to the present invention;
fig. 7 is a schematic structural diagram of an electronic device provided in the present invention.
Detailed Description
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 only a part of the embodiments of the present invention, and not all of the 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.
The invention is operational with numerous general purpose or special purpose computing device environments or configurations. For example: personal computers, server computers, hand-held or portable devices, tablet-type devices, multi-processor apparatus, distributed computing environments that include any of the above devices or equipment, and the like.
An embodiment of the present invention provides a random access channel transmission method in low earth orbit satellite communication, where an execution main body of the method may be a processor in a terminal, and a flow chart of the method of the random access channel transmission method in low earth orbit satellite communication provided in the embodiment of the present invention is shown in fig. 1, and includes:
s101: selecting a PN sequence with a set sequence form from a set PN sequence set;
the method provided by the embodiment of the invention is provided with a PN sequence set, wherein a plurality of PN sequences with set sequence forms are arranged in the PN sequence set, and the set forms of each PN sequence in the PN sequence set are the same. The PN sequences in the set of PN sequences may assume a variety of different sequence forms. In the method provided by the embodiment of the invention, the base station and each terminal can read the PN sequences in the set sequence form in the PN sequence set. When the terminal needs to perform random access channel transmission, a PN sequence with a set sequence form can be selected from the PN sequence set, and in the actual selection process, the sequence form of each PN sequence in the PN sequence set can be set according to the type of data to be transmitted, and then the PN sequence is selected randomly.
S102: mapping the PN sequence to a subcarrier according to a preset conversion mode;
in the method provided by the embodiment of the invention, aiming at the composition of CP, Preamble sequence and GT adopted by a random access channel, the original ZC sequence in the Preamble sequence is replaced by the PN sequence selected from the PN sequence set, and the selected PN sequence is mapped to a subcarrier according to a preset conversion mode in the transmission process of the random access channel.
S103: and performing Inverse Fast Fourier Transform (IFFT) on the sub-carriers mapped with the PN sequences to transform the sub-carriers mapped with the PN sequences to a time domain and transmit the sub-carriers to a base station in a preset form.
In the method provided by the embodiment of the invention, in the process of random access channel transmission, the sub-carrier mapped with the PN sequence needs to be subjected to fast Fourier inverse transformation, the sub-carrier mapped with the PN sequence is transformed to the time domain, time-frequency resource data corresponding to the sub-carrier mapped with the PN sequence in the time domain are obtained, and the time-frequency resource data are transmitted to the base station in a preset form.
The random access channel transmission method in low earth orbit satellite communication provided by the embodiment of the invention selects a PN sequence with a set sequence form as a signal bearing sequence of a Preamble sequence in a random access channel from a set PN sequence set when a terminal needs to access a base station to send a data signal to the base station, maps the selected PN sequence onto a subcarrier according to a certain transformation mode, then carries out fast inverse Fourier transform on the subcarrier mapped with the PN sequence, transforms the subcarrier to a time domain, and transmits time-frequency resource data transformed to the time domain to the base station in a preset form so as to realize the process of transmitting by using the random access channel, wherein the PN sequence with the set form is used as the bearing sequence of the signal in the process, thereby avoiding the condition of generating a pseudo peak in the access process, being capable of accurately identifying a main peak of the data and leading the terminal to be capable of accessing the base station in time, effective transmission of signals is achieved.
The method provided by the embodiment of the invention is realized on the basis of researching the existing random access channel transmission process, in the existing realization process, a ZC sequence adopted by a Preamble sequence generates a pseudo peak when frequency deviation exists, and when the frequency deviation exceeds half of the subcarrier interval, the energy of the pseudo peak is even larger than that of a main peak. Even if the frequency offset is equal to half of the subcarrier spacing, if there is timing deviation, additive white gaussian noise, phase noise, etc., the energy of the pseudo peak is lower than that of the main peak. The frequency offset of satellite communication is as high as +/-30 kHz, and even if Preamble configuration with subcarrier spacing of 60kHz is adopted, the main peak can not be correctly judged under the frequency offset. Meanwhile, when the subcarrier spacing is large, the more frequency domain RBs are occupied, resulting in an increase in overhead for PRACH. E.g., 18 RBs occupied by 30kHz spacing of subcarriers; the subcarrier spacing of 60kHz occupies 35 RBs.
On the premise of the above technical background, in the method for transmitting a random access channel in low earth orbit satellite communication according to the embodiment of the present invention, a ZC sequence in a Preamble sequence is replaced with a PN sequence. The sequence content of each PN sequence in the set of PN sequences is different. The PN sequence set provided by the embodiment of the present invention may be set in a terminal, or may be set in a base station, or may be preferably set in a local third-party system, and both the terminal and the base station may access the PN sequence set.
In the method provided in the embodiment of the present invention, multiple sequence forms may be set for each PN sequence in the PN sequence set, and preferably, in the method provided in the embodiment of the present invention, four PN sequence sets with different sequence forms are set, which may be:
the sequence form of the PN sequence is a frequency domain PN sequence;
the sequence form of the PN sequence is a PN sequence modulated by discrete Fourier transform spread orthogonal frequency division multiplexing DFT-s-OFDM;
the sequence form of the PN sequence is a frequency domain PN sequence associated with walsh orthogonal codes;
the sequence form of the PN sequence is a discrete Fourier transform spread orthogonal frequency division multiplexing DFT-s-OFDM modulated PN sequence associated with a walsh orthogonal code.
The four sequence forms of PN sequences respectively correspond to four PN sequence sets, and can be set according to the type of data signals to be transmitted in a specific random access channel transmission process.
When the random access channel transmission method provided by the embodiment of the invention adopts the frequency domain PN sequence, the PRACH has lower transmitting power, so that the time domain peak-to-average power ratio problem caused by the frequency domain PN sequence can be accepted to a certain extent. Therefore, in the actual transmission process, the PN sequence in the set form needs to be mapped onto the subcarriers in a frequency domain form in a certain manner. When the PN sequence modulated by DFT-s-OFDM or the combination of the PN sequence modulated by DFT-s-OFDM and the walsh code is adopted, the peak-to-average ratio is relatively low, and the influence on the transmission of the random access channel can be ignored in the scheme provided by the invention.
In a specific implementation process, when the sequence form of the selected PN sequence is a frequency domain PN sequence, mapping the PN sequence to a subcarrier according to a preset transformation manner includes:
and directly mapping the frequency domain PN sequence to the subcarrier.
In the method provided by the embodiment of the invention, the same PRACH time-frequency resource supports a plurality of users to carry out random access by using different PN sequences. The PN sequence can be mapped directly to its corresponding subcarrier for the frequency domain. The process is applicable to the PN sequences of four different sequence forms provided by the embodiment of the present invention, and after the PN sequences are transformed to the frequency domain, the PN sequences of a plurality of users can be allowed to perform random access.
In an actual implementation process, in the method provided in the embodiment of the present invention, when the sequence form of the PN sequence is a frequency domain PN sequence, 64 kinds of PN sequences may be set in the PN sequence set, each kind of PN sequence uses a different sequence initialization ID, and each kind of PN sequence is 512 points.
In the transmitting process, the terminal can select one PN sequence from 64 PN sequences, map the PN sequence to the corresponding subcarrier with the interval of 30kHz, occupy 12 RB positions in total, and then perform IFFT to transform to a time domain to transmit.
In the method provided by the embodiment of the present invention, before mapping the frequency domain PN sequence to the subcarrier, windowing may be performed on the frequency domain PN sequence, and the windowing may be adding a hamming window or a root raised cosine window, etc.
In the method provided by the embodiment of the present invention, the subcarrier can be understood as a subcarrier corresponding to a PN sequence selected in a transmission process.
In a specific implementation process, when the sequence form of the PN sequence is a discrete Fourier transform spread orthogonal frequency division multiplexing DFT-s-OFDM modulated PN sequence;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
performing fast Fourier transform on the DFT-s-OFDM modulated PN sequence to transform the DFT-s-OFDM modulated PN sequence to a frequency domain;
and mapping the DFT-s-OFDM modulated PN sequence transformed to the frequency domain to the subcarrier.
In the method provided by the embodiment of the invention, when the sequence form of each PN sequence in the PN sequences is a PN sequence modulated by DFT-s-OFDM, 64 PN sequences can be set in the PN sequence set, the sequence form of each PN sequence is a PN sequence modulated by DFT-s-OFDM, each PN sequence uses different sequence initialization IDs, and each PN sequence is 512 points.
During the transmission process of the terminal, one PN sequence can be selected from 64 PN sequences, then a fast Fourier transform FFT (fast Fourier transform) with 512 points is carried out, so as to transform the PN sequence modulated by DFT-s-OFDM into a frequency domain, and then the PN sequence is mapped to a corresponding subcarrier with the interval of 30kHz, and the total 12 RB positions are occupied. In the method provided by the embodiment of the present invention, in order to reduce the interference to the PUSCH of other subcarriers, the window processing may be performed on the DFT-s-OFDM modulated PN sequence transformed to the frequency domain after the DFT-s-OFDM modulated PN sequence is transformed to the frequency domain and before the DFT-s-OFDM modulated PN sequence transformed to the frequency domain is mapped to the subcarrier.
The windowing process can be adding a Hamming window or a root raised cosine window and the like, and then performing IFFT to transform the window into a time domain to be transmitted.
In the method provided by the embodiment of the invention, if the sequence form of the PN sequence is a frequency domain PN sequence associated with a walsh orthogonal code;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
and directly mapping the frequency domain PN sequence associated with the walsh orthogonal code to the subcarrier.
In the method provided by the embodiment of the present invention, the correlation mode between the frequency domain PN sequence and the walsh orthogonal code may be a frequency domain PN sequence + walsh orthogonal code.
Under the form of frequency domain PN sequence + walsh orthogonal code, 4 frequency domain PN sequences can be set, each frequency domain PN sequence uses different sequence initialization IDs, and each PN sequence is 512 points. And 16 walsh codes with length of 16 are set, and the combination of the frequency domain PN sequence and the walsh code has 64 kinds in total, and 64 kinds of frequency domain PN sequences associated with walsh orthogonal codes are in the PN sequence set.
In the transmitting process, the terminal can select one of the 64 combinations of frequency domain PN sequence and walsh code, map the selected combination to the corresponding subcarrier with the interval of 30kHz, occupy 12 RB positions in total, and then perform IFFT to transform to the time domain to transmit. The sequence form of the frequency domain PN sequence + walsh code can be directly mapped to the subcarrier corresponding to the PN sequence.
In the method provided in the embodiment of the present invention, before mapping the combination of the frequency domain PN sequence and the walsh code onto the subcarrier, a windowing process may be performed on the combination of the frequency domain PN sequence and the walsh code, where the windowing process may be a hamming window addition or a root-raised cosine window addition.
In the method provided by the embodiment of the invention, when the sequence form of the PN sequence is the PN sequence modulated by the discrete Fourier transform spread orthogonal frequency division multiplexing DFT-s-OFDM associated with the walsh orthogonal code;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
performing fast Fourier transform on the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to transform the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to a frequency domain;
mapping the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code transformed to the frequency domain onto the subcarrier.
In the method provided by the embodiment of the invention, the association mode of the DFT-s-OFDM modulated PN sequence and the walsh orthogonal code can be in the form of the DFT-s-OFDM modulated PN sequence + walsh code.
Under the form of DFT-s-OFDM modulated PN sequence + walsh code, 4 DFT-s-OFDM modulated PN sequences can be set, each using a different sequence initialization ID. Each DFT-s-OFDM modulated PN sequence is 512 points and 16 walsh codes of length 16 are set. There are 64 combinations of DFT-s-OFDM modulated PN sequence and walsh code. The PN sequence set comprises 64 DFT-s-OFDM modulated PN sequences which are associated with walsh codes.
In the transmitting process, a terminal can select one of 64 combinations of DFT-s-OFDM modulated PN sequences and walsh codes, then performs 512-point FFT, converts the DFT-s-OFDM modulated PN sequence associated with walsh orthogonal codes to the frequency domain, and maps the frequency domain to subcarriers corresponding to 30kHz intervals, so that 12 RB positions are occupied in total.
In the method provided by the embodiment of the present invention, in the form of a DFT-s-OFDM modulated PN sequence + walsh code, in order to reduce interference to the PUSCH of another subcarrier, after the DFT-s-OFDM modulated PN sequence associated with walsh orthogonal code is transformed into a frequency domain, the DFT-s-OFDM modulated PN sequence associated with walsh orthogonal code transformed into the frequency domain may be windowed before being mapped onto the subcarrier.
The windowing process can be hamming window adding or root raised cosine window adding.
After windowing, IFFT is carried out and the time domain is transformed to be transmitted.
Under the background that the existing Preamble sequence adopts a ZC sequence based on OFDM, the ZC sequence needs a CP length, wherein the CP length is longer, the CP under 30kHz is repeated 3 times by a Preamble symbol, and the CP under 60kHz is repeated 12 times by the Preamble symbol. And every time a Preamble symbol appears, a main peak and a pseudo peak appear, and the final result is that many peak values appear, so that the difficulty of judging the first peak and the difficulty of distinguishing the multi-user peak are increased. Therefore, in the random access channel transmission method provided in the embodiment of the present invention, no matter which sequence form of the PN sequence is used for transmission, in the process of mapping the PN sequence to the subcarrier and transmitting the PN sequence, a CP may not be needed, but ZP (Zero-Padding) is added before the Preamble symbol, and the length of ZP is not sent, and may be 1 to 2 times the length of CP of the OFDM symbol in the data area, for example, the CP of the OFDM symbol in the data area in the satellite communication protocol is 0.59us, the CP of the OFDM symbol in the Preamble is 200us, and the length of ZP is 0.59us to 1.18 us. The function of the ZP is to avoid the interference of the delay of the uplink symbol of other users to the Preamble symbol of the user. Because other users have already carried on the uplink synchronization while transmitting the uplink symbol, so delay generally does not exceed CP length of the ordinary OFDM symbol, so ZP length is set as 1-2 times of CP length of OFDM symbol of the data area.
In the method provided by the embodiment of the invention, the GT is reserved to avoid the interference to the subsequent signal symbols.
In summary, the method provided in the embodiment of the present invention, where the transmitting to the base station in the predetermined form includes:
and transmitting the PN sequence transformed into the time domain to a base station in a form that a ZP is arranged in front of the PN sequence and a GT is arranged behind the PN sequence, wherein the ZP is a null field, and the length of the ZP is 1-2 times of the CP length of the OFDM symbol of the data area.
In the method provided by the embodiment of the invention, after the selected PN sequence is converted to the time domain, the time-frequency resource data after the selected PN sequence is converted to the time domain is obtained, ZP is set in front of the time-frequency resource data, GT is set behind the time-frequency resource data, and the data is sent to the base station.
In the method provided by the embodiment of the invention, after the PN sequence is adopted, a Preamble CP with larger time overhead is not needed, only a ZP with smaller time is needed, and the time overhead is saved.
Corresponding to the method described in fig. 1, an embodiment of the present invention further provides a random access channel transmission apparatus in a low earth orbit communication satellite, which is used to implement the method in fig. 1 specifically, the random access channel transmission apparatus provided in the embodiment of the present invention may be applied to a computer terminal or various mobile devices, and a schematic structural diagram of the random access channel transmission apparatus is shown in fig. 2, where the apparatus includes:
a selecting unit 201, configured to select a PN sequence in a set form from a set of PN sequences;
a mapping unit 202, configured to map the PN sequence to a subcarrier according to a preset transformation manner;
a transmitting unit 203, configured to perform inverse fast fourier transform IFFT on the subcarrier mapped with the PN sequence, so as to transform the subcarrier mapped with the PN sequence to a time domain, and transmit the time domain to a base station in a predetermined form.
The random access channel transmission device in low earth orbit satellite communication provided by the embodiment of the invention selects a PN sequence with a set sequence form as a signal bearing sequence of a Preamble sequence in a random access channel in a set PN sequence set when a terminal needs to send a data signal to a base station, maps the selected PN sequence onto a subcarrier according to a certain transformation mode, then carries out fast inverse Fourier transform on the subcarrier mapped with the PN sequence, transforms the subcarrier to a time domain, and transmits time-frequency resource data transformed to the time domain to the base station in a preset form so as to realize the process of transmitting by using the random access channel, wherein the PN sequence with the set form is used as the bearing sequence of the signal in the process, thereby avoiding the situation of generating a pseudo peak in the transmission process, being capable of accurately identifying a main peak of the data and leading the terminal to be capable of accessing the base station in time, the base station can effectively receive the signals, and the effective transmission of the signals is realized.
Referring to fig. 3, an embodiment of the present invention further provides a process implemented on a base station side of a random access channel transmission method in low earth orbit satellite communication, where an execution subject of the random access channel transmission method implemented on the base station side may be a processor at the base station, and the processor may read each PN sequence in a set of PN sequences, where the method includes:
s301: acquiring time-frequency resource data;
in the method provided by the embodiment of the invention, when the terminal sends the time domain signal to the base station, the base station side acquires the time frequency resource data sent by the terminal, the time frequency resource data is the time frequency resource data corresponding to the PN sequence selected by the terminal side after being mapped to the time domain, and a GT is arranged behind the time frequency resource data.
S302: respectively correlating each PN sequence in a set sequence form in a set PN sequence set with the time frequency resource data to detect a peak value in the time frequency resource data;
in the method provided by the embodiment of the present invention, a processor on the base station side reads PN sequences in the set PN sequence set in each set sequence form one by one, and correlates each read PN sequence in the set sequence form with the time-frequency resource data, so as to detect a peak value in the time-frequency resource data. It should be noted that the PN sequence set read by the base station side and the PN sequence set read by the terminal side are the same PN sequence set.
S303: and when the peak value in the time frequency resource data is detected, determining the PN sequence in the set sequence form related to the time frequency resource data as the PN sequence sent by the terminal.
In the method provided by the embodiment of the invention, when the peak value in the time frequency resource data is detected, the PN sequence in the set sequence form related to the time frequency resource data can be determined as the PN sequence adopted by the terminal, and the terminal can be allowed to access the base station.
In the random access channel transmission method in low earth orbit satellite communication provided by the embodiment of the present invention, after acquiring time-frequency resource data sent by a terminal side, a base station side detects a peak value in the time-frequency resource data by acquiring PN sequences in set forms in a set of PN sequences and correlating the acquired PN sequences, and further determines a PN sequence used by the terminal side to allow the terminal to access the base station through the PN sequence, thereby implementing effective reception of signals by the base station.
In the method provided in the embodiment of the present invention, the correlating the PN sequences in the set sequence form in the set PN sequence set with the time-frequency resource data respectively includes:
dividing each PN sequence with a set sequence form in the set PN sequence set into a plurality of PN sequence subsections;
and respectively correlating each PN sequence sub-segment of each PN sequence with a set sequence form with the time domain resource data, wherein the correlation comprises time domain sliding correlation and frequency domain correlation.
To describe the above peak detection process in more detail, the following example is provided in the embodiment of the present invention, and the related process is described in detail:
first example
When the set format of the PN sequence selected by the terminal in the PN sequence set is a frequency domain PN sequence, the base station performs the following operations:
the receiving end of the base station intercepts Preamble symbols plus GT length (ZP partial data is not intercepted), obtains data of corresponding time frequency resources, traverses local 64 PN sequences, and makes segment correlation with the received PRACH data, if the number of segments is 4, the data of 512 points divided into 4 segments of 128 points is correlated with the transmitted data respectively. Wherein the correlation can be both time domain sliding correlation and frequency domain correlation. When the peak value is searched, the PN sequence sent by the terminal and the corresponding TO position of the timing deviation can be obtained. The frequency deviation FO can be calculated from the phase difference of the 4-segment correlation values corresponding to the peak.
The specific implementation process is as follows:
suppose that the PRACH time domain signal received by the base station is y (N), and the length is NPSS(including Preamble symbol + GT length), the time domain sequence corresponding to a local PN frequency domain sequence is s (n), n is 0.
The time domain segment correlation method when the set form of the PN sequence is the frequency domain PN sequence is as follows:
computing
Figure BDA0002193148600000151
Finding the effective peak in R (n), if the effective peak appears, it represents that a user has transmitted PRACH by using said PN sequence, and setting the n value of R (n) corresponding to the peak position as npeak，npeakI.e. the corresponding timing deviation TO position. Computing
Figure BDA0002193148600000152
Frequency deviation FO of
Figure BDA0002193148600000153
The corresponding frequency domain piecewise correlation method is as follows:
setting a vector
Figure BDA0002193148600000154
This is transformed into the frequency domain, resulting in a vector fs (l) of 1 × 256, l 0. Setting a vector
Figure BDA0002193148600000155
Transforming it into the frequency domain to obtain a vector fy (i) of 1 x 256,
Figure BDA0002193148600000156
then calculating fsy (i, l) ═ f<fy(i)，conj(fs(l))>Where conj (-) denotes the conjugation of each element of the vector,<·，·>representing a dot product of two vectors. Fsy (i, l) is then transformed into the time domain to obtain a 1 × 256 vector tsy (i, l), the first 128 elements of the vector are taken to obtain a 1 × 128 vector r (i, l), and each element in r (i, l) is given as r (i, l, m), m is 0. Computing
Figure BDA0002193148600000161
Finding the effective peak in R (n), if the effective peak appears, it represents that a user has transmitted PRACH by using said PN sequence, and setting the n value of R (n) corresponding to the peak position as npeak，npeakI.e. the corresponding timing deviation TO position. Computing
Figure BDA0002193148600000162
Frequency deviation FO of
Figure BDA0002193148600000163
Second example
When the set format of the PN sequence selected by the terminal in the PN sequence set is the PN sequence modulated by DFT-s-OFDM, the base station side executes the following operations:
the receiving end of the base station intercepts Preamble symbols plus GT length (ZP partial data is not intercepted), obtains data of corresponding time frequency resources, traverses local 64 PN sequences, and makes segment correlation with the received PRACH data, if the number of segments is 4, the data of 512 points divided into 4 segments of 128 points is correlated with the transmitted data respectively. Wherein the correlation can be both time domain sliding correlation and frequency domain correlation. When the peak value is searched, the PN sequence sent by the terminal and the corresponding TO position of the timing deviation can be obtained. The frequency deviation FO can be calculated from the phase difference of the 4-segment correlation values corresponding to the peak. The time domain sliding correlation and the frequency domain correlation method are similar to those of the first example, and are not described herein again, and those skilled in the art can understand the actual process of the second example on the basis of the first example, where the difference is that the time domain sequence s (n), where n is 0.
Third example
When the set format of the PN sequence selected by the terminal in the PN sequence set is frequency domain PN sequence + walsh code, the base station performs the following operations:
the receiving end of the base station intercepts Preamble symbols and GT length (ZP partial data is not intercepted), obtains data of corresponding time-frequency resources, traverses the local combination of 64 PN sequences and Walsh codes, and makes segment correlation on each combination of the PN sequences and the Walsh codes and the received PRACH data, if the number of the segments is 4, the data of 512 points divided into 4 segments of 128 points is correlated with the transmitted data respectively. Wherein the correlation can be both time domain sliding correlation and frequency domain correlation. When the peak value is searched, the PN sequence sent by the terminal and the corresponding TO position of the timing deviation can be obtained. The frequency deviation FO can be calculated from the phase difference of the 4-segment correlation values corresponding to the peak. The time domain sliding correlation and the frequency domain correlation method are similar to those of the first example, and are not described herein again, and those skilled in the art can understand the actual process of the second example on the basis of the first example, and different from the first example, the third example is different from the first example in terms of the code word.
Fourth example
When the preset format of the PN sequence selected by the terminal in the PN sequence set is the PN sequence + walsh code modulated by DFT-s-OFDM, the base station side executes the following operations:
the receiving end of the base station intercepts Preamble symbols and GT length (ZP partial data is not intercepted), obtains data of corresponding time-frequency resources, traverses the local combination of 64 PN sequences and Walsh codes, and makes segment correlation on each combination of the PN sequences and the Walsh codes and the received PRACH data, if the number of the segments is 4, the data of 512 points divided into 4 segments of 128 points is correlated with the transmitted data respectively. Wherein the correlation can be both time domain sliding correlation and frequency domain correlation. When the peak value is searched, the PN sequence sent by the terminal and the corresponding TO position of the timing deviation can be obtained. The frequency deviation FO can be calculated from the phase difference of the 4-segment correlation values corresponding to the peak. The time domain sliding correlation and frequency domain correlation methods are similar to the second example, except that the code words are different.
In the method provided by the embodiment of the invention, the PN sequence or the PN sequence plus the Walsh orthogonal code is used as the random access code word in the low-orbit satellite communication. The same PRACH time frequency resource supports a plurality of users to carry out random access by using different PN sequences and Walsh orthogonal codes. The PRACH does not require a CP ahead, only a relatively short ZP.
In the method provided by the embodiment of the invention, the sequence for generating the uplink PRACH in the satellite communication protocol is changed into the PN sequence from the ZC sequence, or the PN sequence and the Walsh sequence, so that the multi-peak problem of the ZC sequence under high frequency deviation is avoided, the detection success probability, the TA estimation precision and the frequency deviation estimation precision are greatly improved under multiple users, and the time length occupied by the PRACH channel can be reduced.
In the method provided by the embodiment of the present invention, a simulation experiment is performed on the basis of the second example, the frequency offset is set to be 30kHz, the SNR is-10 dB, only one peak appears in the test process, and the estimated frequency offset is 31.67 kHz.
The peak is clearer when setting the frequency offset to 30kHz and SNR to 8dB, and the estimated frequency offset is 30.05 kHz.
Therefore, the timing and the frequency offset can be effectively and accurately estimated by using the new sequence, and only one peak value is needed, so that the retrieval is convenient. And the CP is saved in the time domain, the RB number of the frequency domain can also be reduced, and the PRACH expense is effectively saved under the conditions of large time delay and large frequency offset.
Corresponding to the method described in fig. 3, an embodiment of the present invention further provides a random access channel transmission apparatus in low earth orbit satellite communication, which is used to implement the method in fig. 3 specifically, and the random access channel transmission apparatus in low earth orbit satellite communication provided in the embodiment of the present invention may be applied to a base station, and a schematic structural diagram of the random access channel transmission apparatus is shown in fig. 4, where the apparatus includes:
an obtaining unit 401, configured to obtain time-frequency resource data;
a detecting unit 402, configured to correlate each set sequence type PN sequence in a set PN sequence set with the time-frequency resource data, so as to detect a peak value in the time-frequency resource data;
a determining unit 403, configured to determine, when a peak in the video resource data is detected, a PN sequence in the set sequence form currently related to the time-frequency resource data as a PN sequence sent by a terminal.
In the random access channel transmission apparatus provided in the embodiment of the present invention, after acquiring time-frequency resource data sent by a terminal side, a base station side detects a peak value in the time-frequency resource data by acquiring PN sequences in set forms in a set of PN sequences and correlating the acquired PN sequences, so as to determine a PN sequence used by the terminal side, so as to allow the terminal to access the base station through the PN sequence, and thus, the base station can effectively receive a signal.
In the method provided by the embodiment of the present invention, referring to fig. 5, there is further provided a random access channel transmission system in low earth orbit satellite communication, where the transmission system includes a terminal side and a base station side,
the terminal side includes:
the selection unit is used for selecting a PN sequence with a set form from the set PN sequence set;
the mapping unit is used for mapping the PN sequence to a subcarrier according to a preset conversion mode;
and the transmitting unit is used for performing Inverse Fast Fourier Transform (IFFT) on the sub-carriers mapped with the PN sequences so as to transform the sub-carriers mapped with the PN sequences to a time domain and transmitting the sub-carriers to a base station in a preset form.
The base station side includes:
the acquisition unit is used for acquiring time-frequency resource data;
a detecting unit, configured to correlate each set sequence type PN sequence in a set PN sequence set with the time-frequency resource data, so as to detect a peak value in the time-frequency resource data;
and the determining unit is used for determining the PN sequence in the set sequence form related to the time frequency resource data as the PN sequence sent by the terminal when the peak value in the time frequency resource data is detected.
According to the random access channel transmission system in the low-orbit satellite communication, the ZC sequence in the existing Preamble sequence is replaced by the PN sequence, so that the problem that a main peak cannot be accurately determined due to the fact that a pseudo peak occurs in the transmission process is effectively solved. The terminal can be accessed to the base station in time, and effective transmission of signals is realized. The principle process of terminal-to-satellite communication in the random access channel transmission system in the low earth orbit satellite communication provided by the embodiment of the present invention can refer to fig. 6 provided by the embodiment of the present invention, wherein a very small aperture satellite communication terminal 501 communicates with a satellite-borne platform 502 through a service link, and the satellite-borne platform 502 is connected with a gateway through a feeder link.
An embodiment of the present invention further provides a storage medium, where the storage medium includes a stored program, where when the program runs, a device where the storage medium is located is controlled to execute a random access channel transmission method in the low earth orbit satellite communication, and when the method is applied to a terminal, the method may specifically include:
the method comprises the following steps:
selecting a PN sequence with a set sequence form from a set PN sequence set;
mapping the PN sequence to a subcarrier according to a preset conversion mode;
and performing Inverse Fast Fourier Transform (IFFT) on the sub-carriers mapped with the PN sequences to transform the sub-carriers mapped with the PN sequences to a time domain and transmit the sub-carriers to a base station in a preset form.
In the above method, optionally, if the sequence form of the PN sequence is a frequency domain PN sequence;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
and directly mapping the frequency domain PN sequence to the subcarrier.
In the above method, optionally, if the sequence form of the PN sequence is a discrete fourier transform spread orthogonal frequency division multiplexing DFT-s-OFDM modulated PN sequence;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
performing fast Fourier transform on the DFT-s-OFDM modulated PN sequence to transform the DFT-s-OFDM modulated PN sequence to a frequency domain;
and mapping the DFT-s-OFDM modulated PN sequence transformed to the frequency domain to the subcarrier.
In the above method, optionally, if the sequence form of the PN sequence is a frequency domain PN sequence associated with a walsh orthogonal code;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
and directly mapping the frequency domain PN sequence associated with the walsh orthogonal code to the subcarrier.
In the above method, optionally, if the sequence form of the PN sequence is a discrete fourier transform spread orthogonal frequency division multiplexing DFT-s-OFDM modulated PN sequence associated with a walsh orthogonal code;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
performing fast Fourier transform on the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to transform the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to a frequency domain;
mapping the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code transformed to the frequency domain onto the subcarrier.
The above method, optionally, further comprises, after transforming the DFT-s-OFDM modulated PN sequence to the frequency domain, before mapping the DFT-s-OFDM modulated PN sequence transformed to the frequency domain onto the subcarriers:
and windowing the DFT-s-OFDM modulated PN sequence transformed to the frequency domain.
The above method, optionally, after transforming the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to the frequency domain, before mapping the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code transformed to the frequency domain onto the subcarrier, further includes:
windowing the DFT-s-OFDM modulated PN sequence transformed to the frequency domain with the walsh orthogonal code associated therewith.
The method described above, optionally, the transmitting to the base station in the predetermined form, includes:
and transmitting the PN sequence transformed into the time domain to a base station in a form that a ZP is arranged in front of the PN sequence and a GT is arranged behind the PN sequence, wherein the ZP is a null field, and the length of the ZP is 1-2 times of the CP length of the OFDM symbol of the data area.
The method, when applied to a base station, may include:
acquiring time-frequency resource data;
respectively correlating each PN sequence in a set sequence form in a set PN sequence set with the time frequency resource data to detect a peak value in the time frequency resource data;
and when the peak value in the time frequency resource data is detected, determining the PN sequence in the set sequence form related to the time frequency resource data as the PN sequence sent by the terminal.
Optionally, the above method, where correlating the PN sequences in the set sequence form in the set PN sequence set with the time-frequency resource data respectively, includes:
dividing each PN sequence with a set sequence form in the set PN sequence set into a plurality of PN sequence subsections;
and respectively correlating each PN sequence sub-segment of each PN sequence with a set sequence form with the time domain resource data, wherein the correlation comprises time domain sliding correlation and frequency domain correlation.
An electronic device is provided in an embodiment of the present invention, and its schematic structural diagram is shown in fig. 7, specifically including a memory 601, and one or more programs 602, where the one or more programs 602 are stored in the memory 601, and configured to be executed by one or more processors 603, and the one or more programs 602 include instructions for:
selecting a PN sequence with a set sequence form from a set PN sequence set;
mapping the PN sequence to a subcarrier according to a preset conversion mode;
and performing Inverse Fast Fourier Transform (IFFT) on the sub-carriers mapped with the PN sequences to transform the sub-carriers mapped with the PN sequences to a time domain and transmit the sub-carriers to a base station in a preset form.
It should be noted that, in the present specification, the embodiments are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. For the device-like embodiment, since it is basically similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The term "comprising", without further limitation, means that the element so defined is not excluded from the group consisting of additional identical elements in the process, method, article, or apparatus that comprises the element.
For convenience of description, the above devices are described as being divided into various units by function, and are described separately. Of course, the functions of the units may be implemented in the same software and/or hardware or in a plurality of software and/or hardware when implementing the invention.
From the above description of the embodiments, it is clear to those skilled in the art that the present invention can be implemented by software plus necessary general hardware platform. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which may be stored in a storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the method according to the embodiments or some parts of the embodiments.
The method and the device for transmitting the random access channel in the low earth orbit satellite communication provided by the invention are described in detail, a specific example is applied in the text to explain the principle and the implementation mode of the invention, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims (12)

1. A random access channel transmission method in low earth orbit satellite communication is characterized in that the method is applied to a terminal, and the method comprises the following steps:
selecting a PN sequence with a set sequence form from a set PN sequence set;
mapping the PN sequence to a subcarrier according to a preset conversion mode;
and performing Inverse Fast Fourier Transform (IFFT) on the sub-carriers mapped with the PN sequences to transform the sub-carriers mapped with the PN sequences to a time domain and transmit the sub-carriers to a base station in a preset form.
2. The method of claim 1, wherein if the sequence of the PN sequence is in the form of a frequency domain PN sequence;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
and directly mapping the frequency domain PN sequence to the subcarrier.
3. The method of claim 1, wherein if the sequence of the PN sequence is in the form of a discrete fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM, modulated PN sequence;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
performing fast Fourier transform on the DFT-s-OFDM modulated PN sequence to transform the DFT-s-OFDM modulated PN sequence to a frequency domain;
and mapping the DFT-s-OFDM modulated PN sequence transformed to the frequency domain to the subcarrier.
4. The method of claim 1, wherein if the sequence of the PN sequence is in the form of a frequency domain PN sequence associated with a walsh orthogonal code;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
and directly mapping the frequency domain PN sequence associated with the walsh orthogonal code to the subcarrier.
5. The method of claim 1, wherein if the sequence of the PN sequence is in the form of a discrete fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM, modulated PN sequence associated with a walsh orthogonal code;
the mapping the PN sequence to the subcarrier according to a preset conversion mode comprises the following steps:
performing fast Fourier transform on the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to transform the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to a frequency domain;
mapping the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code transformed to the frequency domain onto the subcarrier.
6. The method of claim 3, wherein after transforming the DFT-s-OFDM modulated PN sequence to the frequency domain, before mapping the DFT-s-OFDM modulated PN sequence transformed to the frequency domain onto the subcarriers, further comprising:
and windowing the DFT-s-OFDM modulated PN sequence transformed to the frequency domain.
7. The method of claim 5, wherein after transforming the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code to a frequency domain, before mapping the DFT-s-OFDM modulated PN sequence associated with the walsh orthogonal code transformed to the frequency domain onto the subcarrier, further comprising:
windowing the DFT-s-OFDM modulated PN sequence transformed to the frequency domain with the walsh orthogonal code associated therewith.
8. The method of claim 1, wherein the transmitting to the base station in the predetermined form comprises:
and transmitting the PN sequence transformed into the time domain to a base station in a form that a ZP is arranged in front of the PN sequence and a GT is arranged behind the PN sequence, wherein the ZP is a null field, and the length of the ZP is 1-2 times of the CP length of the OFDM symbol of the data area.
9. An apparatus for random access channel transmission in low earth orbit satellite communication, the apparatus being applied to a terminal, the apparatus comprising:
the selection unit is used for selecting a PN sequence with a set form from the set PN sequence set;
the mapping unit is used for mapping the PN sequence to a subcarrier according to a preset conversion mode;
and the transmitting unit is used for performing Inverse Fast Fourier Transform (IFFT) on the sub-carriers mapped with the PN sequences so as to transform the sub-carriers mapped with the PN sequences to a time domain and transmitting the sub-carriers to a base station in a preset form.
10. A random access channel transmission method in low earth orbit satellite communication, wherein the method is applied to a base station, and the method comprises:
acquiring time-frequency resource data;
respectively correlating each PN sequence in a set sequence form in a set PN sequence set with the time frequency resource data to detect a peak value in the time frequency resource data;
and when the peak value in the time frequency resource data is detected, determining the PN sequence in the set sequence form related to the time frequency resource data as the PN sequence sent by the terminal.
11. The method according to claim 10, wherein the correlating the PN sequences in the form of respective set sequences in the set of set PN sequences with the time-frequency resource data comprises:
dividing each PN sequence with a set sequence form in the set PN sequence set into a plurality of PN sequence subsections;
and respectively correlating each PN sequence sub-segment of each PN sequence with a set sequence form with the time domain resource data, wherein the correlation comprises time domain sliding correlation and frequency domain correlation.
12. An apparatus for random access channel transmission in low earth orbit satellite communication, wherein the apparatus is applied to a base station, and comprises:
the acquisition unit is used for acquiring time-frequency resource data;
a detecting unit, configured to correlate each set sequence type PN sequence in a set PN sequence set with the time-frequency resource data, so as to detect a peak value in the time-frequency resource data;
and the determining unit is used for determining the PN sequence in the set sequence form related to the time frequency resource data as the PN sequence sent by the terminal when the peak value in the time frequency resource data is detected.
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