CN113938177A - LTE-based random access method for mobile communication of low-orbit satellite - Google Patents
LTE-based random access method for mobile communication of low-orbit satellite Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/08—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access]
- H04W74/0833—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using a random access procedure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1853—Satellite systems for providing telephony service to a mobile station, i.e. mobile satellite service
- H04B7/18532—Arrangements for managing transmission, i.e. for transporting data or a signalling message
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1853—Satellite systems for providing telephony service to a mobile station, i.e. mobile satellite service
- H04B7/18539—Arrangements for managing radio, resources, i.e. for establishing or releasing a connection
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04W56/00—Synchronisation arrangements
- H04W56/004—Synchronisation arrangements compensating for timing error of reception due to propagation delay
- H04W56/0045—Synchronisation arrangements compensating for timing error of reception due to propagation delay compensating for timing error by altering transmission time
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
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- H04W72/044—Wireless resource allocation based on the type of the allocated resource
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- H—ELECTRICITY
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- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
- H04W72/044—Wireless resource allocation based on the type of the allocated resource
- H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
Abstract
A low-orbit satellite mobile communication random access method based on LTE belongs to the technical field of satellite communication and comprises the following steps: the base station periodically issues a random access configuration message through a system information block SIB 2; when the terminal UE needs to initiate random access, selecting a proper RA preamble sequence according to the configuration message and sending the RA preamble sequence to the base station; the base station correspondingly executes a leader sequence detection algorithm to obtain whether a terminal UE initiates a random access request or not, obtains the propagation delay between the terminal UE and the base station, and performs Timing Advance (TA) estimation for establishing uplink synchronization of the terminal UE; aiming at each random access request, the base station feeds back a random access response RAR; after receiving the random access response RAR of the terminal, the terminal correspondingly adjusts the sending time sequence of the terminal to finish uplink synchronization.
Description
Technical Field
The invention relates to a low-orbit satellite mobile communication random access method based on LTE, belonging to the technical field of satellite communication.
Background
The Random Access (RA) technology is one of the key technologies of LTE (Long Time Evolution, Long term Evolution) uplink Access, and a terminal can establish connection with a cell and acquire uplink synchronization only through a Random Access process, and acquire its own unique user identifier in the cell. The random access has two modes of competition and non-competition access, wherein under the condition of the competition random access, a leader sequence sent by UE (user equipment) and time-frequency resources occupied by the leader sequence are randomly selected by the UE. Different UEs may initiate random access on the same time-frequency resource, causing collision, and then decide which UE wins through a contention manner. Under the condition of non-competitive random access, a leader sequence sent by the UE and time frequency resources occupied by the leader sequence are all distributed by the base station, the base station issues random access configuration information through a downlink, the UE sends leader signals on the appointed time frequency resources according to the appointed leader sequence of the base station, and the dispatching of the base station can ensure that the leader sequences or the time frequency resources of different UEs are different, so that collision can not occur.
As shown in fig. 1, an eNB (Evolved Node B) periodically issues a random access configuration message through an SIB2(System Information Block), and then the terminal selects an appropriate preamble sequence according to the configuration message to initiate random access on an appropriate time-frequency resource. After receiving the preamble sequence, the eNB detects a ta (timing advance) value corresponding to the terminal and a preamble sequence index used by the ta value, and since a plurality of terminals may initiate Random Access requests at the same time, the eNB may detect a plurality of Random Access requests, and for each Random Access request, the eNB needs to feed back a Random Access Response (RAR). After receiving the RAR of the terminal itself, the terminal needs to adjust its sending timing sequence accordingly to complete uplink synchronization. For non-contention random access, the random access process ends, but the collision may be caused by multiple terminals initiating random access simultaneously in contention random access, so that the collision needs to be resolved (i.e. the RRC message round trip in fig. 1) in the subsequent steps.
When UE needs to initiate random access, an RA preamble sequence must be sent first, eNB correspondingly executes a preamble sequence detection algorithm, through the algorithm, eNB can know whether UE initiates a random access request, and can also obtain propagation delay between UE and eNB, namely timing advance TA estimation is carried out, and the purpose of TA estimation is to help UE establish uplink synchronization.
The random access leader sequence under the LTE system comprises a cyclic prefix CP, a sequence SEQ and a guard interval GT, and the duration time of the cyclic prefix CP, the sequence SEQ and the guard interval GT is respectively marked as TCP、TSEQAnd TGTThe time domain form is shown in fig. 2.
In LTE, the duration of CP and GT is typically the maximum round-trip delay difference in a cell, the duration of the sequence TSEQShould be as long as possible and larger than the maximum round trip delay difference in the cell. For FDD (frequency Division duplex) mode, LTE defines four different random sequence formats according to different application scenarios of terrestrial mobile communication, as shown in fig. 3.
Typically, the larger the cell coverage, the longer the sequence duration, and the longer CP and GT are needed to compensate for the longer round trip delay caused by the large cell radius.
Because the LEO-LTE system has larger satellite-to-ground link time delay and wider beam coverage range, the coverage radius and the maximum round-trip time delay difference of a cell are both larger than those of the cell in the terrestrial LTE system, and the random access in the terrestrial LTE system is not suitable for the LEO-LTE system any more.
[ patent No.: 201210019547.7, method and device for realizing initial synchronization in satellite communication system, aiming at larger satellite-to-ground link time delay in satellite mobile communication system, the method that terminal determines time delay difference of the terminal according to system longitude and latitude related configuration information carried by network side broadcast message is provided. However, this method requires the position information of the terminal to be acquired through the GPS, and is not suitable for the satellite mobile communication system when the position information of the terminal cannot be acquired.
[ patent No.: 201310271772.4, compatible with LTE mode satellite communication initial random access two-step time delay measurement method, aiming at the time delay of a larger satellite-ground link in a satellite mobile communication system, the two-step time delay measurement method is adopted to solve the problem of large time delay. Firstly, dividing a cell in a satellite communication system into a plurality of subareas according to a time delay value, and when the random access is performed in the first step, sending an uplink random access signal by a user terminal to reach a satellite side receiving end through transmission time delay; when the random access is carried out in the second step, the user sends a preamble in advance, and the amount of time in advance is the first round-trip delay difference of the first step; obtaining a third round-trip delay difference between the terminal and the cell center of the satellite communication system according to the first round-trip delay difference and the second round-trip delay difference; and according to the third round-trip delay difference, measuring the transmission delay difference of the current user relative to the user closest to the satellite. However, this method increases the number of times of system random access, which increases the system overhead.
Therefore, in order to solve the problems of large satellite-to-ground link delay and wide beam coverage in the LEO-LTE system, a random access method suitable for being applied to the LEO-LTE system needs to be designed.
The main disadvantages of the prior art are: because a large satellite-to-ground link delay and a wide beam coverage range exist in the LEO-LTE system, the coverage radius and the maximum round-trip delay difference of a cell are both larger than those of the cell in the terrestrial LTE system, and the random access scheme of the terrestrial LTE system is not suitable for the LEO-LTE system. The first method needs to acquire the terminal location information through the GPS, but cannot calculate the delay inequality when the GPS cannot be used or the terminal location information is unknown due to other problems. The second method increases the number of times of system random access, which increases the system overhead.
Disclosure of Invention
The technical problem solved by the invention is as follows: the method is suitable for designing a random access scheme applied to an LEO-LTE system, and particularly relates to an RA configuration method and a frame structure.
The technical solution of the invention is as follows: the LTE-based random access method for the mobile communication of the low-earth orbit satellite comprises the following steps:
the base station periodically issues a random access configuration message through a system information block SIB 2;
when the terminal UE needs to initiate random access, selecting a proper RA preamble sequence according to the configuration message and sending the RA preamble sequence to the base station;
the base station correspondingly executes a leader sequence detection algorithm to obtain whether a terminal UE initiates a random access request or not, obtains the propagation delay between the terminal UE and the base station, and performs Timing Advance (TA) estimation for establishing uplink synchronization of the terminal UE; aiming at each random access request, the base station feeds back a random access response RAR;
after receiving the random access response RAR of the terminal, the terminal correspondingly adjusts the sending time sequence of the terminal to finish uplink synchronization.
Further, in the RA leader sequence, T is satisfiedCP＝TGT＝ΔTRTD(ii) a Wherein, TCPIs a cyclic prefix time, TGTFor guard interval time, Δ TRTDIs the difference value between the maximum round-trip delay and the minimum round-trip delay of the cell in the LEO-LTE system.
Further, the system information block SIB2 includes a leoFlag value for identifying a LEO-LTE cell, a number for identifying a satellite to which the current beam belongs in the entire low-orbit constellation, a number for indicating a position of the current beam on the LEO satellite, and a longitude and latitude for indicating a position of a satellite below the current satellite.
Further, when the terminal UE detects that leoFlag in the system information block SIB2 is TRUE, the procedure and parameters for generating and transmitting the RA preamble sequence are operated and set in the LEO-LTE manner.
Further, in the LEO-LTE scheme, the RA preamble sequence further includes a long preamble sequence; the RA configuration information includes a frequency domain start position and time-frequency resource configuration of the long preamble sequence.
Further, in the RA configuration information, two fields of PRACH configuration SIB and PRACH configuration include a long preamble sequence PRACH configuration field for indicating a time-frequency resource configuration index and a frequency domain offset value of the long preamble sequence; the prach-ConfigInfo field is used to indicate a time domain resource configuration index and a frequency domain offset value of the short preamble sequence.
Further, the terminal UE uses the long preamble sequence or the short preamble sequence, respectively, according to whether the location information is known.
Further, the long preamble sequence or the short preamble sequence occupies the same frequency domain resource, there is no overlap in time domain, and the long preamble sequence or the short preamble sequence appears in a staggered manner.
Further, the long preamble sequence or the short preamble sequence occupies different frequency domain resources, overlap is allowed in the time domain, and the start time of the long preamble sequence or the short preamble sequence is different.
Further, in the random access response RAR, the time unit of the TA Command is increased to 128TsCorresponding TA time range is [0,5.34ms ]]。
Compared with the prior art, the invention has the advantages that:
1) the terminal may send a long preamble sequence or a short preamble sequence by itself, depending on whether the terminal location is known.
2) For the improvement of SIB2 random access configuration information, a LEO-LTE cell identification field (leoFlag) and a long preamble PRACH configuration information field (PRACH-ConfigInfo _ long) are added.
3) Configuration scheme, interleaving scheme and overlapping scheme of preamble sequence time frequency resources. The method has the beneficial effects that the base station can simultaneously receive two leader sequences, so that the number of users supported by the system is increased.
4) In the time domain resource allocation scheme, the long and short preamble sequences cannot start at the same time. The beneficial effect brought by the method is that RA-RNTIs obtained by calculating the long and short leader sequences are different, so that RARs responded by the eNB cannot appear in the same subframe aiming at the long and short leader sequences, and the eNB does not need to indicate that the long leader sequence or the short leader sequence is detected in the RAR.
5) The time unit value of the TA Command in the RAR field increases. The method has the beneficial effect that the 11-bit TA Command in the terrestrial LTE is continuously used, so that the compatibility with the terrestrial LTE is ensured.
Drawings
Fig. 1 is a schematic diagram of a random access procedure;
FIG. 2 is a time domain representation of a random access preamble sequence;
fig. 3 is a LTE FDD random access preamble sequence format;
FIG. 4 is a time domain resource allocation diagram (allocation indexes 0 and 1) of the interleaving scheme of the present invention;
FIG. 5 is a time domain resource allocation diagram (allocation index 0) of the overlapping scheme of the present invention;
fig. 6 is a schematic diagram of a MAC RAR of the present invention;
fig. 7 shows a random access procedure of the LEO-LTE system according to the present invention.
Detailed Description
In order to better understand the technical solutions, the technical solutions of the present application are described in detail below with reference to the drawings and specific embodiments, and it should be understood that the specific features in the embodiments and examples of the present application are detailed descriptions of the technical solutions of the present application, and are not limitations of the technical solutions of the present application, and the technical features in the embodiments and examples of the present application may be combined with each other without conflict.
The random access scheme of the LTE-based low-orbit mobile satellite communication is to correspondingly improve the random access process of the terrestrial LTE, and mainly improves the first three steps of a random access process, namely RA configuration information, a leader sequence and a random access response, so that the random access scheme is suitable for an LEO-LTE system.
The LTE-based random access method for low earth orbit satellite mobile communication provided in the embodiments of the present application is further described in detail below with reference to the drawings of the specification, and specific implementation manners may include (as shown in fig. 1 to 7):
design of new leader sequence, long leader sequence
Aiming at larger satellite-to-ground link delay and wider beam coverage in an LEO-LTE system, a new leader sequence needs to be designed, so that the T of the new leader sequenceCP、TSEQAnd TGTCan satisfy TCP＝TGT＝ΔTRTDWherein Δ TRTDIs the difference value between the maximum round-trip delay and the minimum round-trip delay of a cell in an LEO-LTE system, namely delta TRTD＝RTDmax-RTDminDuration of the sequence TSEQShould be as long as possible and larger than the maximum round trip delay difference in the cell. Taking an iridium satellite system as an example, the track height is 780km, the minimum communication elevation angle is 8.2 degrees, each satellite can provide 48 spot beams, 48 cells are formed on the earth, the radius of each cell is about 333.5km, the maximum round-trip delay difference of the outermost cell is about 4.48ms, the maximum cell radius which can be supported in a terrestrial LTE system is 100km, the maximum round-trip delay difference is 0.68ms, and all the cells are all the sameIs smaller than the cell radius and the maximum round-trip delay difference in the iridium satellite system. Therefore, a new leader sequence needs to be designed, and the specific design and detection method of the new leader sequence is out of the scope of the patent and only needs the T of the new leader sequenceCPAnd TGTDuration 4.8ms, TSEQThe duration is 6.4ms, and the total duration is 16 ms. The new preamble sequence is defined in this patent to be called long preamble sequence, and the original preamble sequence in LTE system is called short preamble sequence.
RA configuration information improvements
Under an LEO-LTE system, UE needs to acquire relevant information about satellites and beams, and SIB2 is used for transferring cell access restriction information and common channel parameter information, so that SIB2 of terrestrial LTE is improved, specifically, a 1-bit Boolean type leoFlag is added in an SIB2 system message block to identify an LEO-LTE cell, if the UE detects that the bit is TRUE, the UE is considered to reside in the LEO-LTE cell, all subsequent working parameters and processes are set according to the LEO-LTE system, and if not, the UE is set according to the terrestrial LTE system; adding a 1-byte numerical value for identifying the number of the satellite to which the current beam belongs in the whole low-orbit constellation; adding 1 byte for indicating the position number of the current beam on the LEO satellite; two Double type values are added to represent the latitude and longitude of the current satellite sub-satellite position. The detailed SIB2 information element is shown in figure 4, with the bold portion being the newly added satellite broadcast information.
And when the UE detects that the leoFlag in the SIB2 is TRUE, the RA flow and the parameters are operated and set according to the LEO-LTE mode. In the LEO-LTE system, a long preamble sequence is added, so that the RA configuration information must have a frequency domain starting position and a time-frequency resource configuration of the long preamble sequence, two fields of a PRACH configuration SIB (PRACH-ConfigSIB) and a PRACH configuration (PRACH-Config) are improved, a long preamble sequence PRACH configuration (PRACH-ConfigInfo _ long) field is added to indicate a time-frequency resource configuration index and a frequency domain offset value of the long preamble sequence, and the original PRACH-ConfigInfo field is used to indicate a time-frequency resource configuration index and a frequency domain offset value of the short preamble sequence. The specific modification is shown in the bold part of fig. 5.
And the terminal respectively uses different leader sequences, long leader sequences or short leader sequences according to whether the position information is known or not.
When the terminal position information is known, a short preamble sequence or a long preamble sequence may be used; when the terminal location information is unknown, only a long preamble sequence can be used. The PRACH (Physical Random Access Channel) corresponding to each of the long and short preamble sequences is denoted as PRACH _ L and PRACH _ S, respectively. In LEO-LTE, in order to support the above two types of terminals at the same time, time-frequency resources must be arranged for PRACH _ L and PRACH _ S correspondingly.
This patent proposes two time domain resource allocation schemes, called interleaving scheme and overlapping scheme respectively
The interleaving scheme means that PRACH _ L and PRACH _ S occupy the same frequency domain resource, but are not allowed to overlap in the time domain, and the PRACH _ L and PRACH _ S are interleaved. Since the overlap is allowed in the frequency domain, the interleaving scheme can be applied at any system bandwidth. As shown in table 1, some possible time domain resource configuration schemes for the interleaving scheme are shown, wherein the time domain configuration effects corresponding to configuration schemes No. 0 and No. 1 are shown in fig. 6.
Table 1 interleaving scheme time domain resource configuration example
The overlapping scheme means that PRACH _ L and PRACH _ S occupy different frequency domain resources, and overlap is allowed in the time domain, but PRACH _ L and PRACH _ S cannot start simultaneously, that is, when PRACH _ S occurs, PRACH _ L must not occur simultaneously, but PRACH _ L may occur on a subsequent subframe. Since the PRACH _ L and the PRACH _ S occupy different frequency domain resources, the overlapping scheme is suitable for a larger system bandwidth. As shown in table 2, are some possible time domain resource configuration schemes for the overlapping scheme. The time domain configuration effect corresponding to the configuration scheme No. 0 is shown in fig. 7.
Table 2 overlapping scheme time domain resource configuration example
Since the PRACH _ L and the PRACH _ S do not start at the same time, so that RA-RNTIs (Random Access RNTIs, Random Access radio network identifiers) calculated by the long and short preamble sequences are different, RAR responded by the eNB does not occur in the same subframe for the long and short preamble sequences, and since the base station can receive two preamble sequences at the same time, the number of supported users can be increased by 1 time compared with the terrestrial LTE system.
The RAR was improved accordingly.
In the terrestrial LTE protocol, the RAR field is shown in fig. 6, where the TA Command takes 11 bits and has a value range of [0,1282 ]]In the unit of 16Ts(minimum sampling interval at 1.4M bandwidth), the corresponding TA time range is [0,667.66 μ s []However, the time delay in the LEO-LTE system is large, taking an iridium satellite system as an example, the maximum round-trip delay difference of the outermost cell is 4.48ms, and the original 11-bit TA Command in the RAR is not enough to represent the large time delay.
To ensure compatibility with terrestrial LTE, this patent continues to use an 11-bit TA Command, but with the time unit increased to 128Ts(this value corresponds to a time length of 8 samples when the bandwidth is 1.4 MHz), and the corresponding TA time range is [0,5.34ms ]]Therefore, the time delay under the iridium satellite system can be represented by a TA Command of 11 bits.
The terminal needs to start a receiving window to receive a Random Access Response (RAR) after sending an RA preamble sequence, in a terrestrial LTE protocol, the receiving window starts from a 3 rd subframe after a subframe (if the preamble sequence spans a plurality of subframes in a time domain, the last subframe is calculated) where the preamble sequence is sent, and the scheme specifies that compared with the terrestrial LTE, the satellite-to-ground minimum round trip delay is RTDminRounded down to [ RTDmin]([]Indicating rounding down) of the subframe, the RAR receive window start time is advanced by RTDmin]One sub-frame with maximum round trip delay difference of deltaTRTDRounded down to [ Delta T ]RTD]The size of the receiving window is increased on the basis of the terrestrial LTE [ Delta T ]RTD]And a sub-frame.
The following further describes the present patent with reference to specific embodiments.
Taking an iridium orbit parameter as an example, the orbit height is 780km, the minimum communication elevation angle is 8.2 degrees, the communication frequency band uses an L frequency band, the uplink and downlink frequencies are 1610 to 1626.5MHz, each satellite can provide 48 spot beams to form 48 cells on the earth, the radius of each cell is about 333.5km, and the maximum round-trip delay difference in the outermost cell is delta TRTD4.48ms, the duration of CP and GT of the random access preamble should be 2 times the propagation delay difference, T, according to the previous analysisCP＝TGT＝ΔTRTDDuration of the sequence TSEQShould be as long as possible and larger than the maximum round trip delay difference in the cell. Therefore, the design parameter for long preamble duration should be TCP＝TGT＝4.8ms，TSEQTotal duration is 16ms, 6.4 ms.
The main content of the patent includes the first three steps of the random access procedure, namely RA configuration information, a preamble sequence and a random access response. The random access procedure is shown in fig. 7.
As shown in fig. 7, step 1 is that the eNB sends random access configuration information, where a number field (leoSN) of a satellite to which a beam belongs in the SIB2 in the entire low-earth-orbit constellation, a location number field (cellLocSN) of the beam on the LEO satellite, and a longitude and latitude field (leoLoc) of a satellite lower-satellite location are set according to satellite-related information, which is not described herein again. Setting a LEO-LTE cell representation flag in the SIB2 as TRUE for indicating that the subsequent working parameters and procedures are set according to the LEO-LTE system. Both interleaving scheme and overlapping scheme can be used, and the PRACH-ConfigInfo _ long field of the two fields of PRACH-ConfigSIB and PRACH-Config can be set according to table 1 or table 2.
In step 2, the terminal selects a long preamble sequence or a short preamble sequence according to whether the position information is known. If the terminal location information is known, a short preamble sequence or a long preamble sequence is selected, if the terminal location information is unknown, a long preamble sequence is selected, and time domain resource configuration is performed according to the random access configuration information in step 1, for example, the random access configuration information selects a time domain resource configuration scheme with an index of 0 in table 2, that is, an overlap scheme is adopted, the long preamble sequence is transmitted in a subframe No. 4 of any system frame, the short preamble sequence is transmitted in any subframe except the subframe No. 4 of any system frame, and the configuration scheme is shown in fig. 7.
In the terrestrial LTE protocol, the receiving window starts at the 3 rd subframe after the subframe (if the preamble sequence spans multiple subframes in the time domain, the last subframe is calculated), where the preamble sequence is located, in which the receiving window starts, in a terrestrial LTE protocol, the minimum transmission delay of a satellite-to-ground link in an iridium system is 2.6ms, the minimum round-trip delay is 5.2ms, and the whole is taken down to about 5 subframes, then the RAR receiving window start time is advanced by 5 subframes, that is, the RAR receiving window starts at the 8 th subframe after the subframe, where the preamble sequence is located. The maximum transmission time delay of the satellite-ground link is 8.24ms, the maximum round-trip time delay is about 16ms, the difference between the maximum round-trip time delay and the minimum round-trip time delay is about 11ms, and the size of a receiving window is increased by 11 subframes on the basis of the terrestrial LTE.
And 3, detecting the leader sequence sent by the terminal by the eNB, calculating to obtain RA-RNTI, Preamble ID and TA value, and encapsulating to obtain RAR and sending the RAR to the terminal. Under the iridium system, the maximum round-trip delay difference of the outermost cell is 4.48ms, the patent continues to use the TACOMandd with 11 bits in the RAR field, and the time unit is 16TSIncrease to 128TSCorresponding TA time range is [0,5.34ms ]]The time delay under the iridium satellite system can be represented by a TACommand with 11 bits.
So far, the first three steps of the random access procedure specified in this patent, that is, the random access configuration information, the terminal sending preamble sequence, and the random access response are all completed, and the subsequent random access procedure is still performed along with the random access procedure of the terrestrial LTE system, and are not described here again.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.
Claims (10)
1. The LTE-based random access method for the mobile communication of the low-earth orbit satellite is characterized by comprising the following steps of:
the base station periodically issues a random access configuration message through a system information block SIB 2;
when the terminal UE needs to initiate random access, selecting a proper RA preamble sequence according to the configuration message and sending the RA preamble sequence to the base station;
the base station correspondingly executes a leader sequence detection algorithm to obtain whether a terminal UE initiates a random access request or not, obtains the propagation delay between the terminal UE and the base station, and performs Timing Advance (TA) estimation for establishing uplink synchronization of the terminal UE; aiming at each random access request, the base station feeds back a random access response RAR;
after receiving the random access response RAR of the terminal, the terminal correspondingly adjusts the sending time sequence of the terminal to finish uplink synchronization.
2. The LTE-based low-earth-orbit satellite mobile communication random access method according to claim 1, characterized in that: in the RA leader sequence, T is satisfiedCP＝TGT＝ΔTRTD(ii) a Wherein, TCPIs a cyclic prefix time, TGTFor guard interval time, Δ TRTDIs the difference value between the maximum round-trip delay and the minimum round-trip delay of the cell in the LEO-LTE system.
3. The LTE-based low-earth-orbit satellite mobile communication random access method according to claim 1, characterized in that: the system information block SIB2 includes a leoFlag value for identifying a LEO-LTE cell, a number for identifying a satellite to which a current beam belongs in a whole low-orbit constellation, a number for indicating a position of the current beam on the LEO satellite, and a longitude and latitude for indicating a position of a satellite lower than the current satellite.
4. The LTE-based random access method for low-earth-orbit satellite mobile communication of claim 3, wherein when the terminal UE detects that the leoFlag in the system information block SIB2 is TRUE, the process and parameters for generating and transmitting the RA preamble sequence are operated and set according to LEO-LTE mode.
5. The LTE-based random access method for low-earth-orbit satellite mobile communication according to claim 4, wherein in the LEO-LTE scheme, the RA preamble sequence further comprises a long preamble sequence; the RA configuration information includes a frequency domain start position and time-frequency resource configuration of the long preamble sequence.
6. The LTE-based random access method for low-earth orbit satellite mobile communication of claim 5, wherein in the RA configuration information, two fields of the SIB and the PRACH configuration comprise a PRACH configuration field with a long preamble sequence, which is used for indicating a time-frequency resource configuration index and a frequency domain offset value of the long preamble sequence; the prach-ConfigInfo field is used to indicate a time domain resource configuration index and a frequency domain offset value of the short preamble sequence.
7. The LTE-based low-earth-orbit satellite mobile communication random access method of claim 4, wherein the terminal UE uses a long preamble sequence or a short preamble sequence according to whether the position information is known or not.
8. The LTE-based random access method for low-earth-orbit satellite mobile communication of claim 7, wherein the long preamble sequence or the short preamble sequence occupies the same frequency domain resource, has no overlap in time domain, and appears in a staggered manner.
9. The LTE-based random access method for low-earth-orbit satellite mobile communication of claim 7, wherein the long preamble sequence or the short preamble sequence occupies different frequency domain resources, the time domain allows overlapping, and the starting time of the long preamble sequence or the short preamble sequence is different.
10. The LTE-based low-earth-orbit satellite mobile communication random access method according to claim 1, characterized in that: in the random access response RAR, the time unit of the TA Command is increased to 128TsCorresponding TA time range is [0,5.34ms ]]。
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