CN108243391B - Cell search and cell access method and device in satellite communication - Google Patents

Cell search and cell access method and device in satellite communication Download PDF

Info

Publication number
CN108243391B
CN108243391B CN201611205156.9A CN201611205156A CN108243391B CN 108243391 B CN108243391 B CN 108243391B CN 201611205156 A CN201611205156 A CN 201611205156A CN 108243391 B CN108243391 B CN 108243391B
Authority
CN
China
Prior art keywords
satellite base
base stations
mobile terminal
satellite
base station
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201611205156.9A
Other languages
Chinese (zh)
Other versions
CN108243391A (en
Inventor
董宇
刘文明
汪波
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Spreadtrum Communications Shanghai Co Ltd
Original Assignee
Spreadtrum Communications Shanghai Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Spreadtrum Communications Shanghai Co Ltd filed Critical Spreadtrum Communications Shanghai Co Ltd
Priority to CN201611205156.9A priority Critical patent/CN108243391B/en
Priority to CN202010582357.0A priority patent/CN111770552B/en
Publication of CN108243391A publication Critical patent/CN108243391A/en
Application granted granted Critical
Publication of CN108243391B publication Critical patent/CN108243391B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/02—Access restriction performed under specific conditions
    • H04W48/04—Access restriction performed under specific conditions based on user or terminal location or mobility data, e.g. moving direction, speed
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/20—Selecting an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/004—Synchronisation arrangements compensating for timing error of reception due to propagation delay
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/04—Large scale networks; Deep hierarchical networks
    • H04W84/06—Airborne or Satellite Networks

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Computer Security & Cryptography (AREA)
  • Physics & Mathematics (AREA)
  • Astronomy & Astrophysics (AREA)
  • General Physics & Mathematics (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The embodiment of the invention relates to a cell searching and accessing method and device in satellite communication. The cell search method comprises the steps of calculating the distances between a plurality of satellite base stations and the mobile terminal and the Doppler frequency shift of the plurality of satellite base stations relative to the mobile terminal; selecting N satellite base stations closest to the mobile terminal from the plurality of satellite base stations; for N satellite base stations, performing frequency offset compensation by adopting Doppler frequency shift of a plurality of satellite base stations relative to the mobile terminal; and selecting a cell covered by the satellite base station with the best signal quality from the N satellite base stations for residing. Correspondingly, the cell access method comprises the steps of calculating the distance between a satellite base station accessed by a target and a mobile terminal; calculating propagation delay according to the distance between a satellite base station accessed by a target and a mobile terminal; and (4) carrying out cell access on the satellite base station accessed by the target by using the PRACH propagation delay and the frequency shift amount in advance. According to the embodiment of the invention, the application of LTE in satellite communication is realized by a method of compensation in advance.

Description

Cell search and cell access method and device in satellite communication
Technical Field
The present invention relates to the field of communications, and in particular, to a cell search method and a cell access method and apparatus in satellite communications.
Background
Satellite communication is communication between two or more earth stations by using artificial earth satellites as relay stations to relay radio waves. Satellite communication is characterized by large Doppler frequency shift (70 KHz maximum) and large uplink and downlink time delay and large signal fading caused by long communication distance (more than 500 Km).
The synchronization sequence and frame structure of LTE (Long Term Evolution) limit the maximum doppler frequency shift that the current LTE protocol can work within ± 7.5KHz, and the maximum uplink and downlink delay difference is within 0.7ms (i.e. limit the maximum distance between the base station and the mobile terminal to be about 100 km). Therefore, at present, the LTE system cannot be directly used for satellite communication.
How to realize satellite communication by using an LET system becomes a technical problem to be solved urgently.
Disclosure of Invention
Therefore, the invention provides a cell search and cell access method and a device in satellite communication, which utilize the satellite orbit and the position of a mobile station to calculate the current Doppler frequency shift and uplink and downlink time delays and realize the application of LTE in the aspect of satellite communication by a method of pre-compensation.
In order to achieve the above purpose, the invention provides the following technical scheme:
according to an aspect of the embodiments of the present invention, there is provided a cell search method in satellite communication, including: calculating distances between a plurality of satellite base stations and a mobile terminal and Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal;
selecting N satellite base stations nearest to the mobile terminal from the plurality of satellite base stations, wherein N is a non-zero positive integer;
for the N satellite base stations, respectively adopting Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal to perform frequency offset compensation;
and selecting the satellite base station with the best signal quality from the N satellite base stations, and residing the cell covered by the satellite base station with the best quality.
Optionally, the calculating distances between the plurality of satellite base stations and the mobile terminal includes:
determining the current position of the mobile terminal;
and calculating the distances between the plurality of satellite base stations and the mobile terminal according to the current time, the current position of the mobile terminal and the prestored flying orbit data of the plurality of satellite base stations.
Optionally, the flight orbit data of the satellite base station comprises the flight speed and the flight trajectory of the satellite base station.
Optionally, the calculating the doppler shift of the plurality of satellite base stations relative to the mobile terminal includes:
calculating the flight angles of the plurality of satellite base stations relative to the mobile terminal;
obtaining Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal according to the flight speeds of the plurality of satellite base stations and the flight angles of the plurality of satellite base stations relative to the mobile terminal.
Optionally, the frequency offset compensation is performed by adjusting a crystal frequency of the mobile terminal or compensating the received signal by using a Cordic algorithm.
Optionally, for the N satellite base stations, performing frequency offset compensation by respectively using doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal, including:
and for each satellite base station in the N satellite base stations, accelerating frequency offset compensation by using pre-stored LTE configuration information of a satellite base station coverage cell.
According to another aspect of the embodiments of the present invention, there is provided a cell access method in satellite communication, including:
calculating the distance between a satellite base station accessed by a target and the mobile terminal;
calculating propagation delay according to the distance between the satellite base station accessed by the target and the mobile terminal;
and advancing the PRACH by taking the propagation delay and the frequency shift as time advance, and performing cell access on the satellite base station accessed by the target.
Optionally, the calculating a distance between a satellite base station accessed by a target and the mobile terminal includes:
determining the current position of the mobile terminal;
and calculating the distance between the satellite base station accessed by the target and the mobile terminal according to the current time, the current position of the mobile terminal and the prestored flight orbit data of the satellite base station accessed by the target.
Optionally, the flight orbit data of the satellite base station comprises the flight speed and the flight trajectory of the satellite base station.
According to another aspect of the embodiments of the present invention, there is provided a cell search apparatus in satellite communication, including:
the calculation module is used for calculating the distances between a plurality of satellite base stations and a mobile terminal and the Doppler frequency shift of the plurality of satellite base stations relative to the mobile terminal;
a selection module, configured to select N satellite base stations closest to the mobile terminal from the plurality of satellite base stations, where N is a non-zero positive integer;
the frequency offset compensation module is used for performing frequency offset compensation on the N satellite base stations by respectively adopting Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal;
and the resident module is used for selecting the satellite base station with the best signal quality from the N satellite base stations and residing the cell covered by the satellite base station with the best quality.
Optionally, the calculation module comprises:
a current position determining submodule for determining the current position of the mobile terminal;
and the distance calculation submodule is used for calculating the distances between the plurality of satellite base stations and the mobile terminal according to the current time, the current position of the mobile terminal and the prestored flight orbit data of the plurality of satellite base stations.
Optionally, the calculation module comprises:
the flight angle calculation submodule is used for calculating the flight angles of the plurality of satellite base stations relative to the mobile terminal;
and the Doppler frequency shift obtaining sub-module is used for obtaining the Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal according to the flight speeds of the plurality of satellite base stations and the flight angles of the plurality of satellite base stations relative to the mobile terminal.
Optionally, the frequency offset compensation module is further configured to, for each satellite base station of the N satellite base stations, accelerate frequency offset compensation by using pre-stored LTE configuration information of a coverage cell of the satellite base station.
According to another aspect of the embodiments of the present invention, there is provided a cell access apparatus in satellite communication, including:
the distance calculation module is used for calculating the distance between a satellite base station accessed by a target and the mobile terminal;
the time delay calculation module is used for calculating the propagation time delay according to the distance between the satellite base station accessed by the target and the mobile terminal;
and the access module is used for advancing the PRACH by taking the propagation delay and the frequency shift as time advance and performing cell access on the satellite base station accessed by the target.
Optionally, the distance calculation module comprises:
a current position determining submodule for determining the current position of the mobile terminal;
and the calculation submodule is used for calculating the distance between the satellite base station accessed by the target and the mobile terminal according to the current time, the current position of the mobile terminal and the prestored flight orbit data of the satellite base station accessed by the target.
According to the embodiment of the invention, the mobile terminal obtains the rough Doppler frequency offset and the propagation delay between the satellite base station and the mobile terminal by calculation by utilizing the positioning information, the satellite flight orbit, the flight angle and the flight speed, performs initial frequency offset compensation on the mobile terminal by utilizing the rough Doppler frequency offset, and performs cell search on the satellite base station one by one; and the transmission time of the PRACH is advanced by utilizing the propagation delay so as to meet the PRACH delay requirement of the current LTE protocol on reaching the satellite base station.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary of the invention, and that other embodiments can be derived from the drawings provided by those skilled in the art without inventive effort.
Fig. 1 is a schematic diagram of a TD-LTE frame structure provided in an embodiment of the present invention;
fig. 2 is a schematic diagram of a physical layer random access burst signal format according to an embodiment of the present invention;
fig. 3 is a flowchart of a cell search method in satellite communication according to an embodiment of the present invention;
fig. 4 is a schematic diagram illustrating reception of PRACH format3 according to an embodiment of the present invention;
fig. 5 is a flowchart of a cell access method in satellite communication according to an embodiment of the present invention;
fig. 6 is a schematic diagram illustrating a satellite base station receiving PRACH according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a cell search apparatus in satellite communication according to an embodiment of the present invention;
FIG. 8 is a schematic structural diagram of a computing module according to an embodiment of the present invention;
FIG. 9 is a schematic structural diagram of another computing module according to an embodiment of the present invention;
fig. 10 is a schematic structural diagram of a cell access apparatus in satellite communication according to an embodiment of the present invention;
fig. 11 is a schematic hardware structure diagram of a cell access apparatus in satellite communication according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the 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.
LTE (Long Term Evolution) is a Long Term Evolution of The UMTS (Universal mobile telecommunications System) technical standard established by The 3GPP (The 3rd generation partnership Project) organization, formally established and initiated at The 3GPP multi-toronto conference in 2004 at 12 months. The LTE system introduces key technologies such as OFDM (Orthogonal frequency division Multiplexing) and MIMO (Multi-Input & Multi-Output), which significantly increases the spectrum efficiency and data transmission rate (20M bandwidth 2X2MIMO is, in 64QAM, the theoretical downlink maximum transmission rate is 201Mbps, and is approximately 150Mbps after the signaling overhead is removed, but according to the practical networking and terminal capability limitations, the downlink peak rate is generally considered to be 100Mbps, and the uplink is 50Mbps), and supports multiple bandwidth allocation: 1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz, 20MHz and the like, and supports the global mainstream 2G/3G frequency band and some newly-added frequency bands, thereby the frequency spectrum allocation is more flexible, and the system capacity and the coverage are also obviously improved.
Due to the excellent performance, the LTE technology is now well-established for terrestrial mobile terminals, and the use of the LTE technology in satellite communication has also been proposed. However, the LTE technology is used for satellite communication, and the most troublesome problems encountered are that the synchronization sequence and frame structure of LTE limit the maximum propagation delay difference (i.e. the maximum uplink and downlink delay difference) between the LTE base station and the mobile terminal, and further limit the maximum coverage distance (i.e. the maximum distance between the base station and the mobile terminal), and the maximum doppler frequency offset of LTE is also limited by the access impact of LTE. The specific analysis is as follows:
1. limitation of maximum coverage distance by GP (guard Interval) configuration
The TD-LTE frame structure (5ms switching period) is shown in fig. 1, and uses time intervals to complete duplex switching, but a certain guard interval GP needs to be reserved to avoid interference. The size of the GP is related to the maximum coverage distance, and the larger the GP is, the larger the maximum coverage distance is. The GP is mainly composed of propagation delay and device transceiving conversion delay, that is:
GP 2 × propagation delay + (TRx-Tx, Ue)
Maximum coverage distance (propagation delay × c) (GP- (TRx-Tx, Ue)) × c/2
Wherein, GP represents a guard interval, Ue represents a mobile terminal, TRx represents downlink reception, Tx represents uplink transmission, and c represents the speed of light; (TRx-Tx, Ue) is the transition time for the mobile terminal to receive the uplink transmission from the downlink, which is related to the accuracy of the output power, typically 10-40 mus, assumed to be 20 mus in this example.
DwPTS (downlink pilot time slot) is used for transmitting downlink control signaling and downlink data, and therefore, the larger GP is, the smaller DwPTS is, and the system capacity is reduced. Limited by GP, the maximum coverage distance of TD-LTE is shown in table 1 below, which is a table of correspondence between TD-LTE special subframe configurations and coverage distances.
TABLE 1
Figure BDA0001189849390000071
Figure BDA0001189849390000081
In system design, the special subframe configuration 7 (i.e. 10:2:2) of the conventional CP is a typical configuration, and the theoretical maximum coverage distance reaches 18.4km, so that sufficient coverage distance can be ensured, and the loss of downlink capacity is limited; the theoretical maximum coverage distance under the special subframe configuration 0 (namely 3:8:1) of the extended CP can reach 97km, and the method is suitable for super-long-distance coverage scenes such as sea surface, desert and the like. However, it is obvious that the requirement cannot be satisfied for satellite communication covering a distance of more than 500 km.
2. Limitation of PRACH (Physical Random Access Channel) Random Access burst Signal Format on maximum coverage distance
Five random access burst signal formats are defined in TS36.211, and a physical layer random access burst signal consists of three parts, namely a cyclic prefix CP, a Preamble sequence Preamble and a guard time GT, and the structure is shown in fig. 2. Since the access timeslot needs to overcome the propagation delay of the uplink and the interference caused by the user to the uplink, a sufficient guard time needs to be set aside in the timeslot design, and the guard time is the GT. The length of the GT determines the access radius that can be supported:
cell coverage distance GT × c/2 where c is the speed of light.
The correspondence between the format of the random access preamble signal and the coverage distance is shown in table 2 below, which is a correspondence between the format of the random access check-in signal and the coverage distance.
TABLE 2
Figure BDA0001189849390000091
Wherein:
the format of the preamble signal is 0, the maximum cell coverage distance is 14km, and the method is suitable for normally covering cells.
Preamble format 1, maximum cell coverage distance 77km, is suitable for large coverage cells.
The preamble signal format 2, the maximum cell coverage distance 29km, the preamble signal repetition 1 time, the signal reception quality is improved, and the method is suitable for large coverage cells and scenes with fast mobile terminal moving speed.
The preamble signal format3, the maximum area coverage distance is 107km, the preamble signal is repeated for 1 time, the signal receiving quality is improved, and the method is suitable for super-long distance coverage of sea surface, desert and the like.
The preamble signal format 4 is specific to the TD-LTE system, and is transmitted in the UpPTS (uplink pilot time slot) in a special time slot, and the maximum cell coverage distance is 1.4km, which is suitable for indoor and outdoor dense urban areas.
However, it is obvious that the requirement cannot be satisfied for satellite communication covering a distance of more than 500 km.
3. Effect of Doppler frequency offset on LTE Access
The flight speed of the low-orbit satellite usually reaches about 8km/s, the maximum Doppler frequency shift is 70kHz, the change rate is 3 KHz-5 KHz/s, and because the flight speed and the orbit of the satellite are relatively fixed, the Doppler frequency shift can be written as:
f _ match is F _ fix + F _ variance, the F _ fix is a fixed large frequency offset relative to the position of the mobile terminal according to the satellite moving track, the F _ variance is a small frequency offset which changes in real time, the maximum F _ fix is 70kHz, and the change rate of the F _ variance is 3 KHz-5 KHz/s. For an LTE system, in an initial network searching stage and a cell synchronization stage, the frequency offset of maximum F _ fix 70kHz needs to be synchronized, the tracking stage is entered, and the frequency offset is tracked through pilot frequency or CP, wherein the F _ variance change rate is 3 KHz-5 KHz/s.
The common LTE network searching algorithm utilizes the characteristic that the time domain correlation of the PSS sequence is insensitive to frequency offset, theoretically, network searching and cell synchronization can be realized under the frequency offset of +/-7.5 KHz, if a PSS sequence multiple correlation trying method of preset frequency offset is used, the network searching and cell synchronization can be realized under the frequency offset of +/-50 KHz, but the network searching speed is very slow. But obviously the requirement cannot be met for satellite communication with the maximum offset of 70 KHz.
In summary, the GP configuration of TD-LTE, the PRACH random access burst signal format of LTE, and the doppler frequency offset limit the application of the current LTE system in satellite communication.
In the embodiment of the invention, the mobile terminal obtains the Doppler frequency shift and the propagation delay between the satellite base station and the mobile terminal through calculation according to the positioning information (such as GPS positioning information) and the flight orbit, the flight angle and the flight speed of the satellite, and compensates the crystal oscillator and the emission time of the mobile terminal in advance, so that the Doppler frequency shift and the propagation delay meet the requirements of satellite communication, and the application of the LTE technology in the satellite communication is realized.
The invention is further illustrated by the following figures and examples:
in the embodiment of the present invention, data of all satellite base stations is stored in advance in a memory of the mobile terminal, where the data includes: flight orbit data of the satellite base station (such as the flight speed and flight trajectory of the satellite base station) and LTE configuration information of the satellite base station coverage Cell, for example, base station configuration information (for Cell search for a specific satellite base station) such as synchronization pattern, frequency point number, Cell ID, SI/P/RA/C-RNTI, antenna configuration, and CP configuration. Among them, in the synchronization scheme, TDD (time division duplex synchronization) is difficult to use compared with FDD (frequency division duplex synchronization), and it is recommended not to use TDD.
It should be noted that the mobile terminal in the embodiment of the present invention includes, but is not limited to, an electronic device with a mobile communication function, such as a mobile phone.
Please refer to fig. 3, which is a flowchart illustrating a cell search method in satellite communication according to an embodiment of the present invention, applied to a mobile terminal, the method including:
step 301, determining the current position of the mobile terminal.
For example, the mobile terminal may determine its current location according to the GPS (Global Positioning System), which includes the mobile terminal's current longitudinal and latitudinal position. Of course, the mobile terminal may also determine its current location by other positioning methods, such as the beidou positioning system.
Step 302, calculating distances between a plurality of satellite base stations and the mobile terminal according to the current position and the current time of the mobile terminal and the pre-stored flight orbit data of the plurality of satellite base stations.
It should be noted that, in the embodiment of the present invention, any method in the prior art may be adopted to calculate the distances between the plurality of satellite base stations and the mobile terminal according to the current position of the mobile terminal, the current time, and the prestored flight orbit data of the plurality of satellite base stations, and the calculation method is not limited in the embodiment of the present invention.
Step 303, selecting the N closest satellite base stations from the plurality of satellite base stations to the mobile terminal.
Where N is set according to the actual coverage of the satellite network, e.g., N-5.
Step 304, calculating the flight angles of the plurality of satellite base stations relative to the mobile terminal, and obtaining the doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal according to the flight speeds of the plurality of satellite base stations and the flight angles relative to the mobile terminal.
It should be noted that, in the embodiment of the present invention, any method in the prior art may be adopted to calculate the flight angle of each satellite base station relative to the mobile terminal, and the calculation method is not limited in the embodiment of the present invention.
Step 305, performing frequency offset compensation on the N satellite base stations by respectively using doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal.
The frequency offset compensation mode can be directly adjusting the crystal oscillator frequency, or compensating the received signal by using a Cordic algorithm, and combining the LTE configuration information of the satellite base station coverage cell pre-stored in the mobile station memory to accelerate the cell search speed.
And step 306, selecting a cell covered by the satellite base station with the best signal quality from the N satellite base stations for residing.
Meanwhile, the cells covered by adjacent satellite base stations can be tracked.
And after finishing the cell residence, continuing the cell access.
In general, in LTE, when a cell is accessed, since a mobile terminal does not know the location of a base station, a GT is reserved in a PRACH to prevent the PRACH from moving out of a base station uplink reception window.
As shown in fig. 4, the receiving schematic diagram of the PRACH format3 is that, due to the protection of the GT, it can be ensured that the CP + DATA of the uplink PRACH is within the receiving window of the PRACH as long as the propagation delay of the one-way signal is delayed by 2 times within the GT, and it is ensured that the uplink PRACH does not cause intra-cell interference.
Since the distance of satellite communication is very far, the propagation delay is ten times or even tens of times of that of ordinary land mobile communication, and thus, the PRACH is necessarily windowed according to the normal LTE processing manner.
Please refer to fig. 5, which is a flowchart illustrating a cell access method in satellite communication according to an embodiment of the present invention, applied to a mobile terminal for accessing a PRACH satellite to an LTE cell, the method includes:
step 501, determining the current position of the mobile terminal.
Step 502, calculating the distance between the mobile terminal and the satellite base station accessed by the target according to the current position and the current time of the mobile terminal and the flight orbit data of the satellite base station accessed by the target.
Step 503, calculating propagation delay according to the distance between the mobile terminal and the target accessed satellite base station.
The propagation delay between the mobile terminal and the target access satellite base station can be calculated according to the following formula:
and d/c, the Delay is propagation Delay, d is the distance between the mobile terminal and the target access satellite base station, and c is the speed of light.
Step 504, the PRACH is advanced by the propagation delay and the frequency shift amount thereof to perform an access attempt.
Wherein, can be + -512 × TS、±1024×TSOr 2048 × TS as an offset of the propagation delay at the access attempt.
Fig. 6 is a schematic diagram illustrating a satellite base station receiving PRACH according to an embodiment of the present invention.
According to the embodiment, the mobile terminal obtains the rough Doppler frequency offset and the propagation delay between the satellite base station and the mobile terminal through calculation by utilizing the positioning information, the satellite flight orbit, the flight angle and the flight speed, performs initial frequency offset compensation on the mobile terminal by utilizing the rough Doppler frequency offset, and performs cell search on the satellite base station one by one;
and the transmission time of the PRACH is advanced by utilizing the propagation delay so as to meet the PRACH delay requirement of the current LTE protocol on reaching the satellite base station.
In addition to the above method, an embodiment of the present invention further provides a cell search apparatus in satellite communication, as shown in fig. 7, the apparatus includes:
a calculating module 701, configured to calculate distances between a plurality of satellite base stations and a mobile terminal and doppler shifts of the plurality of satellite base stations relative to the mobile terminal;
a selecting module 702, configured to select, from the plurality of satellite base stations, N satellite base stations closest to the mobile terminal, where N is a non-zero positive integer;
a frequency offset compensation module 703, configured to perform frequency offset compensation on the N satellite base stations by using doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal, respectively;
and the frequency offset compensation mode is to adjust the crystal oscillator frequency of the mobile terminal or compensate the received signal by utilizing a Cordic algorithm.
A residing module 704, configured to select a satellite base station with the best signal quality from the N satellite base stations, and reside in a cell covered by the satellite base station with the best signal quality.
In an alternative embodiment of the present invention, as shown in fig. 8, the calculation module 701 includes:
a current position determining submodule 7011, configured to determine a current position of the mobile terminal;
and the distance calculating submodule 7013 is configured to calculate distances between the plurality of satellite base stations and the mobile terminal according to the current time, the current position of the mobile terminal, and the prestored flight orbit data of the plurality of satellite base stations.
The flight orbit data of the satellite base station comprises the flight speed and the flight orbit of the satellite base station.
In addition to the structure shown in fig. 8, in another alternative embodiment of the present invention, as shown in fig. 9, the calculation module 701 includes:
an angle-of-flight calculation submodule 7012 configured to calculate angles of flight of the plurality of satellite base stations with respect to the mobile terminal;
a doppler shift obtaining sub-module 7014, configured to obtain doppler shifts of the plurality of satellite base stations relative to the mobile terminal according to the flight speeds of the plurality of satellite base stations and the flight angles of the plurality of satellite base stations relative to the mobile terminal.
Of course, it should be noted that, in practical applications, the calculation module 701 may include all the sub-modules shown in fig. 8 and 9.
In another optional embodiment of the present invention, the frequency offset compensation module 703 is further configured to, for each satellite base station of the N satellite base stations, accelerate frequency offset compensation by using pre-stored LTE configuration information of a coverage cell of the satellite base station.
Correspondingly, an embodiment of the present invention further provides a cell access apparatus in satellite communication, as shown in fig. 10, the apparatus includes:
a distance calculation module 1001, configured to calculate a distance between a satellite base station to which a target is accessed and the mobile terminal;
a delay calculating module 1002, configured to calculate a propagation delay according to a distance between the target-accessed satellite base station and the mobile terminal;
an access module 1003, configured to advance a physical random access channel PRACH by using the propagation delay and the frequency shift amount as a time advance, and perform cell access on the target-accessed satellite base station.
In an alternative embodiment, the distance calculating module 1001 includes:
a current position determining submodule for determining the current position of the mobile terminal;
and the calculation submodule is used for calculating the distance between the satellite base station accessed by the target and the mobile terminal according to the current time, the current position of the mobile terminal and the prestored flight orbit data of the satellite base station accessed by the target.
The division of the modules in the above embodiments of the present invention is schematic, and only one logical function division is provided, and there may be another division manner in actual implementation, and in addition, each functional module in each embodiment of the present application may be integrated in one processor, may also exist alone physically, or may also be integrated in one module by two or more modules. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode.
When the integrated module may be implemented in the form of hardware, the physical hardware corresponding to the calculating module 701, the selecting module 702, the frequency offset compensating module 703 and the residing module 704 may be the processor 1101, or the physical hardware corresponding to the distance calculating module 1001, the delay calculating module 1002 and the access module 1003 may be the processor 1101, as shown in fig. 11. The mobile terminal may also include a memory 1102 for storing program code that is executed by the processor 1101.
The memory 1102 may be a volatile memory (RAM), such as a random-access memory (RAM); the memory 1102 may also be a non-volatile memory (non-volatile memory), such as a read-only memory (ROM), a flash memory (flash memory), a Hard Disk Drive (HDD) or a solid-state drive (SSD), or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, but is not limited thereto. Memory 1102 may be a combination of the memories described above.
Of course, the mobile terminal may further include a display 1103 and an input/output interface 1104, the display 1103 may include a touch screen for detecting an input of the user, and the display 1103 may not include the touch screen. A user may input signals to the processor 1101 through the input/output interface 1104. The processor 1101, the memory 1102, the display 1103, the input/output interface 1104, and the color camera 1105 may be connected via a bus 1106. The connection between other components is merely illustrative and not intended to be limiting. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 11, but this is not intended to represent only one bus or type of bus.
A processor 1101 configured to execute the program code stored in the memory 1102, and specifically configured to perform the following operations:
calculating distances between a plurality of satellite base stations and a mobile terminal and Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal;
selecting N satellite base stations nearest to the mobile terminal from the plurality of satellite base stations, wherein N is a non-zero positive integer;
for the N satellite base stations, respectively adopting Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal to perform frequency offset compensation;
and selecting the satellite base station with the best signal quality from the N satellite base stations, and residing the cell covered by the satellite base station with the best quality.
Alternatively, the processor 1101 is specifically configured to perform the following operations:
calculating the distance between a satellite base station accessed by a target and the mobile terminal;
calculating propagation delay according to the distance between the satellite base station accessed by the target and the mobile terminal;
and advancing the PRACH by taking the propagation delay and the frequency shift as time advance, and performing cell access on the satellite base station accessed by the target.
According to the embodiment, the mobile terminal obtains the rough Doppler frequency offset and the propagation delay between the satellite base station and the mobile terminal through calculation by utilizing the positioning information, the satellite flight orbit, the flight angle and the flight speed, performs initial frequency offset compensation on the mobile terminal by utilizing the rough Doppler frequency offset, and performs cell search on the satellite base station one by one;
and the transmission time of the PRACH is advanced by utilizing the propagation delay so as to meet the PRACH delay requirement of the current LTE protocol on reaching the satellite base station.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable 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 methods described in the embodiments or some parts of the embodiments.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A method for cell search in satellite communications, comprising:
calculating distances between a plurality of satellite base stations and a mobile terminal and Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal;
selecting N satellite base stations nearest to the mobile terminal from the plurality of satellite base stations, wherein N is a non-zero positive integer;
for the N satellite base stations, respectively adopting Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal to perform frequency offset compensation;
and selecting the satellite base station with the best signal quality from the N satellite base stations, and residing the cell covered by the satellite base station with the best signal quality.
2. The method of claim 1, wherein calculating distances between the plurality of satellite base stations and the mobile terminal comprises:
determining the current position of the mobile terminal;
and calculating the distances between the plurality of satellite base stations and the mobile terminal according to the current time, the current position of the mobile terminal and the prestored flying orbit data of the plurality of satellite base stations.
3. The method of claim 2, wherein the satellite base station flight trajectory data comprises a satellite base station flight speed and a satellite base station flight trajectory.
4. The method of claim 1, wherein the calculating the doppler shifts of the plurality of satellite base stations relative to the mobile terminal comprises:
calculating the flight angles of the plurality of satellite base stations relative to the mobile terminal;
obtaining Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal according to the flight speeds of the plurality of satellite base stations and the flight angles of the plurality of satellite base stations relative to the mobile terminal.
5. The method according to any of claims 1-4, wherein the frequency offset is compensated by adjusting the crystal frequency of the mobile terminal or compensating the received signal by using Cordic or other algorithm.
6. The method according to any of claims 1-4, wherein performing frequency offset compensation for the N satellite base stations by using Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal respectively comprises:
and for each satellite base station in the N satellite base stations, accelerating frequency offset compensation by using pre-stored LTE configuration information of a satellite base station coverage cell.
7. An apparatus for cell search in satellite communication, comprising:
the calculation module is used for calculating the distances between a plurality of satellite base stations and a mobile terminal and the Doppler frequency shift of the plurality of satellite base stations relative to the mobile terminal;
a selection module, configured to select N satellite base stations closest to the mobile terminal from the plurality of satellite base stations, where N is a non-zero positive integer;
the frequency offset compensation module is used for performing frequency offset compensation on the N satellite base stations by respectively adopting Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal;
and the resident module is used for selecting the satellite base station with the best signal quality from the N satellite base stations and residing the cell covered by the satellite base station with the best quality.
8. The apparatus of claim 7, wherein the computing module comprises:
a current position determining submodule for determining the current position of the mobile terminal;
and the distance calculation submodule is used for calculating the distances between the plurality of satellite base stations and the mobile terminal according to the current time, the current position of the mobile terminal and the prestored flight orbit data of the plurality of satellite base stations.
9. The apparatus of claim 7, wherein the computing module comprises:
the flight angle calculation submodule is used for calculating the flight angles of the plurality of satellite base stations relative to the mobile terminal;
and the Doppler frequency shift obtaining sub-module is used for obtaining the Doppler frequency shifts of the plurality of satellite base stations relative to the mobile terminal according to the flight speeds of the plurality of satellite base stations and the flight angles of the plurality of satellite base stations relative to the mobile terminal.
10. The apparatus of any of claims 7-9, wherein the frequency offset compensation module is further configured to, for each of the N satellite base stations, expedite frequency offset compensation using pre-stored LTE configuration information for the satellite base station coverage cell.
CN201611205156.9A 2016-12-23 2016-12-23 Cell search and cell access method and device in satellite communication Active CN108243391B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CN201611205156.9A CN108243391B (en) 2016-12-23 2016-12-23 Cell search and cell access method and device in satellite communication
CN202010582357.0A CN111770552B (en) 2016-12-23 2016-12-23 Cell access method and device in satellite communication

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201611205156.9A CN108243391B (en) 2016-12-23 2016-12-23 Cell search and cell access method and device in satellite communication

Related Child Applications (1)

Application Number Title Priority Date Filing Date
CN202010582357.0A Division CN111770552B (en) 2016-12-23 2016-12-23 Cell access method and device in satellite communication

Publications (2)

Publication Number Publication Date
CN108243391A CN108243391A (en) 2018-07-03
CN108243391B true CN108243391B (en) 2020-06-12

Family

ID=62704143

Family Applications (2)

Application Number Title Priority Date Filing Date
CN201611205156.9A Active CN108243391B (en) 2016-12-23 2016-12-23 Cell search and cell access method and device in satellite communication
CN202010582357.0A Active CN111770552B (en) 2016-12-23 2016-12-23 Cell access method and device in satellite communication

Family Applications After (1)

Application Number Title Priority Date Filing Date
CN202010582357.0A Active CN111770552B (en) 2016-12-23 2016-12-23 Cell access method and device in satellite communication

Country Status (1)

Country Link
CN (2) CN108243391B (en)

Families Citing this family (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110830101B (en) * 2018-08-10 2021-07-27 展讯半导体(南京)有限公司 Cell ID determining and acquiring method, network equipment, terminal and readable medium
CN110972217B (en) * 2018-09-30 2021-12-03 大唐移动通信设备有限公司 Satellite base station access control method, device and readable storage medium
US12028908B2 (en) 2018-10-15 2024-07-02 Ipcom Gmbh & Co. Kg Random access in a satellite communication system
CN111163416B (en) * 2018-10-22 2021-05-11 中国移动通信有限公司研究院 Information acquisition method, information transmission method, terminal and first network equipment
CN111294733B (en) * 2018-12-17 2021-07-06 展讯通信（上海）有限公司 Mobility management method, device and storage medium in satellite communication
CN111356185A (en) * 2018-12-21 2020-06-30 电信科学技术研究院有限公司 Switching control method and equipment
CN111586802A (en) 2019-02-15 2020-08-25 索尼公司 User equipment, central unit device, wireless communication method, and storage medium
CN109788548B (en) * 2019-02-19 2020-06-12 上海交通大学 Satellite mobile communication random access method, system and medium with time advance compensation
GB2582284B (en) 2019-03-11 2023-04-05 Airspan Ip Holdco Llc Frequency adjustment within a wireless communication system for a moving vehicle
GB2582188B (en) 2019-03-11 2022-07-06 Airspan Ip Holdco Llc Handover analysis for a moving vehicle
GB2582136B (en) 2019-03-11 2022-08-03 Airspan Ip Holdco Llc Timing adjustment within a wireless communication system for a moving vehicle
CN111800851B (en) * 2019-04-08 2022-12-09 大唐移动通信设备有限公司 Time delay compensation method and device
CN111800830B (en) * 2019-04-08 2021-07-09 华为技术有限公司 Communication method and device
CN114364009A (en) * 2019-04-29 2022-04-15 华为技术有限公司 TA (timing advance) determination method and device of terminal equipment
WO2021026838A1 (en) * 2019-08-14 2021-02-18 Nokia Shanghai Bell Co., Ltd. Accessing approach in integrated network
WO2021028850A1 (en) * 2019-08-15 2021-02-18 Telefonaktiebolaget Lm Ericsson (Publ) RANDOM ACCESS IN NETWORK SUPPORTING UEs WITH DIFFERENT PRE-COMPENSATION AND/OR GNSS CAPABILITIES
CN112929899A (en) * 2019-12-06 2021-06-08 华为技术有限公司 Method and apparatus for access
EP4090121A4 (en) * 2020-01-20 2023-01-11 Guangdong Oppo Mobile Telecommunications Corp., Ltd. Random access method and apparatus
CN115004722A (en) * 2020-02-14 2022-09-02 Oppo广东移动通信有限公司 Cell selection method, device, equipment and storage medium
WO2021163877A1 (en) * 2020-02-18 2021-08-26 Mediatek Singapore Pte. Ltd. Methods and system of frequency synchronization mechanisms for integration terrestrial network and non terrestrial network
US20230224974A1 (en) * 2020-06-15 2023-07-13 Beijing Xiaomi Mobile Software Co., Ltd. Random access method, random access apparatus, and storage medium
CN111970746B (en) * 2020-08-31 2023-07-04 西安蜂语信息科技有限公司 Star searching and network access method and device
CN114520713B (en) * 2020-11-20 2024-03-01 上海华为技术有限公司 Channel detection period configuration method, base station, equipment and medium
CN116261909A (en) * 2020-12-11 2023-06-13 Oppo广东移动通信有限公司 Pre-compensation method for timing advance in NTN (network time network), terminal equipment and network equipment
CN113115429B (en) * 2021-03-05 2022-05-06 北京邮电大学 Crystal oscillator frequency offset determination method, device and communication system
CN113271558A (en) * 2021-05-08 2021-08-17 东方红卫星移动通信有限公司 Internet of things information transmission method, terminal and system in low-orbit satellite Internet of things
CN115968563A (en) * 2021-08-10 2023-04-14 北京小米移动软件有限公司 Method and device for selecting service cell
CN117279072B (en) * 2023-11-20 2024-02-23 上海卫星互联网研究院有限公司 Terminal access method and device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN202918292U (en) * 2012-10-09 2013-05-01 大连大学 Satellite access selecting device for LEO (Low Earth Orbit) satellite communication network
CN103580732A (en) * 2012-08-08 2014-02-12 华为技术有限公司 Method, device and system for frequency offset compensation
CN103795455A (en) * 2014-01-14 2014-05-14 北京邮电大学 User comprehensive weighted access method suitable for satellite data collection system
CN105682035A (en) * 2016-02-03 2016-06-15 努比亚技术有限公司 Terminal and method for implementing beam communication
WO2016205765A1 (en) * 2015-06-17 2016-12-22 Hughes Network Systems, Llc Approaches for high speed global packet data services leo/meo satellite systems

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102104978B (en) * 2011-02-23 2013-09-04 电信科学技术研究院 Random access method for terminal with positioning function under large time delay, terminal and base station
CN103379435B (en) * 2012-04-28 2017-02-08 电信科学技术研究院 Broadcast message transmission method and device based on satellite mobile communication system
CN103428782B (en) * 2012-05-18 2016-08-24 电信科学技术研究院 Changing method in a kind of satellite communication system and device
CN103346829B (en) * 2013-07-01 2016-04-20 北京大学 Measurement method for satellite communication compatible with LTE mode initial random access two step time-delay measuring method
CN104297765B (en) * 2014-09-25 2017-04-26 上海欧科微航天科技有限公司 Ground terminal simulator used for low-orbit satellite synchronous communication system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103580732A (en) * 2012-08-08 2014-02-12 华为技术有限公司 Method, device and system for frequency offset compensation
CN202918292U (en) * 2012-10-09 2013-05-01 大连大学 Satellite access selecting device for LEO (Low Earth Orbit) satellite communication network
CN103795455A (en) * 2014-01-14 2014-05-14 北京邮电大学 User comprehensive weighted access method suitable for satellite data collection system
WO2016205765A1 (en) * 2015-06-17 2016-12-22 Hughes Network Systems, Llc Approaches for high speed global packet data services leo/meo satellite systems
CN105682035A (en) * 2016-02-03 2016-06-15 努比亚技术有限公司 Terminal and method for implementing beam communication

Also Published As

Publication number Publication date
CN111770552B (en) 2022-10-28
CN111770552A (en) 2020-10-13
CN108243391A (en) 2018-07-03

Similar Documents

Publication Publication Date Title
CN108243391B (en) Cell search and cell access method and device in satellite communication
KR20210005004A (en) Timing advance for non-terrestrial network communication
EP4027727A1 (en) Data processing method and apparatus, and storage medium
EP3457768B1 (en) Pilot frequency transmission method for uplink shared channel, and related device
US9107160B2 (en) Uplink synchronization method and apparatus
CN111615215B (en) Communication method, terminal device and network device
CN112583752B (en) Signal transmission method and device based on satellite communication
US20210392703A1 (en) Random Access Method and Apparatus
US9918338B2 (en) Method and apparatus for detecting uplink synchronization signal of each level in wireless access system supporting high-frequency band
CN114830792A (en) Random access preamble transmission and reception in non-terrestrial network communications
US12015473B2 (en) Method and apparatus for sequence determination in wireless transmission
CN113661751A (en) Data transmission method and related equipment
CN114666885A (en) Synchronization method, apparatus, device and computer readable storage medium
WO2021056385A1 (en) Wireless communication method, terminal device and network device
KR20230044489A (en) RACH Procedures for Non-Terrestrial Networks to Base Stations
US20240031067A1 (en) Method, device and computer storage medium for communication
WO2022027230A1 (en) Method and apparatus for timing advance compensation
WO2022036686A1 (en) Method and apparatus for delay indication
WO2021042394A1 (en) Sequence repetition for unsynchronized uplink transmission
CN116319189B (en) Method and apparatus for wireless communication
WO2021243579A1 (en) Method and apparatus for slot format indication in ntn system
WO2023102768A1 (en) Enhancements on uplink transmission
CN104170503A (en) Cell switching instruction sending method and device
WO2023206355A1 (en) Uplink transmission method and apparatus, and terminal device and network device
RU2772977C1 (en) Method for signal transmission, terminal apparatus and network apparatus

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant