CN113242065A - Sky wave large-scale MIMO uplink synchronization method using position information - Google Patents

Sky wave large-scale MIMO uplink synchronization method using position information Download PDF

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CN113242065A
CN113242065A CN202110550483.2A CN202110550483A CN113242065A CN 113242065 A CN113242065 A CN 113242065A CN 202110550483 A CN202110550483 A CN 202110550483A CN 113242065 A CN113242065 A CN 113242065A
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user side
position information
uplink synchronization
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CN113242065B (en
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高西奇
孙榛
王闻今
何思然
石丁
郑奕飞
仲文
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Southeast University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/22—Traffic simulation tools or models
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/0005—Synchronisation arrangements synchronizing of arrival of multiple uplinks

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Abstract

The invention discloses a sky wave large-scale MIMO uplink synchronization method using position information, which comprises the following steps: a base station side broadcasts and sends a downlink synchronous signal, and a user side receives the downlink synchronous signal from the base station; the user side calculates and obtains the initial position of the downlink data frame according to the downlink synchronous signal; the user side calculates and obtains the shortest propagation path distance according to the self position information and the base station position information, and obtains the minimum relative time delay of the round-trip transmission of the wireless link of the user according to the shortest propagation path distance; the user side adjusts the sending time of the uplink frame according to the initial position and the downlink relative time delay of the obtained data frame; the base station side feeds back user timing advance information to the user side according to the received uplink synchronization sequence to realize uplink synchronization; the sky wave large-scale MIMO uplink synchronization method utilizing the position information can obviously reduce the system synchronization overhead and improve the frequency spectrum efficiency of a sky wave wireless communication system.

Description

Sky wave large-scale MIMO uplink synchronization method using position information
Technical Field
The invention relates to the technical field of sky wave large-scale MIMO communication, in particular to a sky wave large-scale MIMO uplink synchronization method utilizing position information.
Background
Short-wave communication refers to wireless communication using electromagnetic waves having a frequency of 3-30MHz, i.e., short-wave communication having a wavelength of about 10-100 m. Short-wave communication is widely applied to various fields due to the characteristics of flexibility, easiness in deployment, reliability, long communication distance and the like, plays an irreplaceable role particularly in military departments, and is an important means for military strategy and tactical communication. Sky wave transmission refers to a short-wave communication transmission mode that radio waves are reflected back to a ground receiving point through an ionized layer, and single-hop (<4000km) or multi-hop short-wave communication based on ionized layer reflection can be provided. The sky wave transmission has two outstanding advantages, one is that the transmission loss is small, and long-distance communication can be carried out with smaller power; and secondly, the ionosphere as a transmission medium has strong survivability and high transmission reliability.
The large-dimensional characteristic of large-scale MIMO can bring the advantages of improving the utilization rate of frequency spectrum resources, increasing the system capacity and the like, and the OFDM orthogonal frequency division multiplexing technology distributes serial transmission data streams to a plurality of parallel orthogonal subcarriers through serial-parallel conversion, so that intersymbol interference and frequency selective fading can be effectively inhibited. In the actual sky-wave large-scale MIMO wireless communication system, especially uplink, uncorrected time offset will destroy orthogonality, generate inter-symbol interference, inter-channel interference and multi-user interference, and reduce system performance. The uplink synchronization traversal cost is increased due to the long sky wave transmission distance, so that the uplink synchronization traversal cost of the base station side can be reduced by utilizing the position information to calculate the minimum relative time delay of the round trip transmission of the wireless link of the user and complete the uplink synchronization.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a sky-wave massive MIMO uplink synchronization method using location information, in which a user side calculates a minimum relative time delay for round-trip transmission of a user radio link and completes uplink synchronization by using location information and fully considering a sky-wave transmission mode, an ionosphere height, and a curved surface distance between the user side and a base station side, so as to reduce uplink synchronization traversal cost of the base station side.
In order to achieve the purpose, the invention adopts the following technical scheme:
a sky wave massive MIMO uplink synchronization method using position information is suitable for a sky wave massive MIMO communication system, the system comprises a short wave base station and a plurality of short wave users, and the short wave base station and the short wave users realize massive MIMO communication; the method comprises the following steps:
step S1, the base station side broadcasts and sends the downlink synchronous signal, and the user side receives the downlink synchronous signal from the base station side;
step S2, the user side calculates and obtains the initial position of the downlink data frame according to the downlink synchronous signal;
step S3, the user side calculates and obtains the shortest propagation path distance according to the position information of the user side and the position information of the base station side, and obtains the minimum relative time delay of the round-trip transmission of the wireless link of the user according to the shortest propagation path distance;
step S4, the user side adjusts the sending time of the uplink frame according to the initial position of the downlink data frame calculated in step S2 and the minimum relative time delay obtained in step S3;
step S5, the base station side calculates the user timing advance information according to the received uplink synchronization sequence and feeds back the user timing advance information to the user side, and the user side adjusts the uplink frame sending time again by using the user timing advance information to realize uplink synchronization.
Furthermore, in the sky-wave large-scale MIMO communication system, a large-scale antenna array is arranged at the base station side, and a single antenna is arranged at the user side.
Further, the user side calculates and obtains the initial position of the downlink data frame by utilizing the autocorrelation, the cross correlation and the constant amplitude low peak-to-average power ratio characteristic of the downlink synchronization sequence, and completes downlink synchronization.
Further, the location information of the user side and the base station side includes longitude information and latitude information.
Further, the step S3 specifically includes: and the user side solves the approximate shortest propagation path distance or obtains the shortest propagation path distance by tracking by utilizing a ray tracing technology by considering the height of the ionization layer and the longitude and latitude information of two places according to the position information of the user side and the position information of the base station side.
Further, in step S3, when the approximate shortest propagation path distance is solved, the curved surface distance between the base station side and the user side on the earth surface is calculated first, the propagation mode is determined according to the distance, and then the minimum relative delay time of the round-trip transmission of the wireless link of the user is obtained by calculating the solution problem according to the propagation mode, the height of the ionosphere and the curved surface distance
The invention has the beneficial effects that:
1. in the traditional sky wave uplink synchronization, a base station side calculates timing advance through an uplink synchronization signal and sends the timing advance to a user side, and then the user side adjusts the uplink frame sending time to realize uplink synchronization, but the sky wave transmission distance is long, the channel time delay is large, and the cost of traversing and searching an uplink synchronization sequence by the base station is high; for the invention, the user side calculates the minimum relative time delay of the round trip transmission of the wireless link of the user and adjusts the uplink frame sending time by fully considering the sky wave transmission mode, the ionosphere height and the curved surface distance between the user side and the base station side by utilizing the position information, thereby finishing the preliminary uplink synchronization, saving the cost of traversing and searching the uplink synchronization sequence at the base station side, reducing the length of the uplink synchronization sequence and improving the transmission efficiency of the communication system.
2. The algorithm for the minimum relative time delay of the round trip transmission of the wireless link of the user has low calculation complexity and can be well applied to a large-scale MIMO system of the actual sky wave; meanwhile, the method for actually obtaining the minimum relative time delay of the round-trip transmission of the wireless link of the user is not unique, and a plurality of algorithms and ray tracing software can be used, so that the method for obtaining the minimum relative time delay by utilizing the position information has high flexibility.
Drawings
Fig. 1 is a flowchart of a sky-wave massive MIMO uplink synchronization method using location information in embodiment 1.
Fig. 2 is a comparison diagram of the steps of a general uplink synchronization method and the method provided in example 1.
Fig. 3 is a schematic diagram of the spherical distances on the user side and the base station side.
Fig. 4 is a diagram illustrating an uplink timing advance effect.
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 some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Referring to fig. 1 to 4, the present embodiment provides a sky-wave massive MIMO uplink synchronization method using position information, which mainly includes the following steps:
1. a base station side broadcasts and sends a downlink synchronous signal, and a user side receives the downlink synchronous signal from the base station;
2. the user side calculates and obtains the initial position of the downlink data frame according to the downlink synchronous signal;
3. the user side calculates and obtains the shortest propagation path distance according to the self position information and the base station position information, and obtains the minimum relative time delay of the round-trip transmission of the wireless link of the user according to the shortest propagation path distance;
4. the user side adjusts the sending time of the uplink frame according to the initial position and the downlink relative time delay of the obtained data frame;
5. the base station side feeds back the user timing advance information to the user side according to the received uplink synchronous sequence, and the user side adjusts the uplink frame sending time again by using the feedback information to realize uplink synchronization.
Specifically, the embodiments of the present invention are further described in detail below with reference to specific system models.
1. Sky wave large-scale MIMO system configuration and channel model using position information
In the sky wave large-scale MIMO system model, a base station side antenna array comprises more than dozens of antenna units, and each antenna adopts an omnidirectional antenna; the user side antenna is a single antenna, and each user side antenna adopts an omnidirectional antenna.
Considering a long-distance sky wave large-scale MIMO communication system, a linear uniform array with the total number of antennas being M is configured at the base station side, and U single-antenna user terminals are arranged at the user side. The ionosphere is divided into three layers D, E and F, wherein the layers E and F mainly play a role in reflecting electric waves in the transmission process to ensure long-distance transmission, and the layer D plays a role in absorbing to cause signal attenuation. Similar to a general massive MIMO transmission system, the sky wave channel also has characteristics of multipath propagation. In particular, signals typically arrive at the receiving end via multiple paths due to single or multiple reflections from the E or F layers.
Let NcIs the total number of OFDM sub-carriers, NgIs the Cyclic Prefix (CP) length, TsFor a systematic sampling interval, a single OFDM symbol duration Tc＝NcTsDuration T of CPg＝NgTc. And order
Figure BDA0003075256740000031
For the analog baseband signal transmitted by the U-th single-antenna user terminal, the received analog baseband signal at the base station side can be expressed as
Figure BDA0003075256740000041
Wherein the content of the first and second substances,
Figure BDA0003075256740000042
for time-varying uplink channel burst between Uth single-antenna user terminal and base stationVector of excitation response, zul(t) is a noise vector containing M independent complex gaussian white noises having the same power spectral density.
Similarly, order
Figure BDA0003075256740000043
For the analog baseband signal vector transmitted to the U-th single-antenna user terminal in the downlink, the analog baseband signal vector received by the U-th single-antenna user terminal may be represented as:
Figure BDA0003075256740000044
wherein, [ h ]u(t,τ)]TTime-varying downlink channel impulse response vectors for the base station and the Uth single-antenna user terminal, which are the transpose of the uplink channel impulse response vector in terms of expression,
Figure BDA0003075256740000045
is complex white gaussian noise. In practical applications, only N is generally selectedνThe subcarriers are used for data transmission and are typically chosen close to the center carrier frequency. Suppose that N isνThe sequence number set for transmitting sub-carriers is K ═ {0,1, …, Nν-1}, the remaining Nc-NνThe subcarriers serve as guard subcarriers of the system. Order to
Figure BDA0003075256740000046
For the u-th single-antenna user terminal at
Figure BDA00030752567400000417
The signal transmitted on the k sub-carrier of the symbol.
Then the u-th single-antenna user terminal is at the u-th under the condition of containing the CP
Figure BDA0003075256740000047
The analog baseband signal transmitted on one symbol can be represented as:
Figure BDA0003075256740000048
wherein, Δ f is 1/TcIndicating the subcarrier spacing. Similarly, order
Figure BDA0003075256740000049
Is arranged at the base station side
Figure BDA00030752567400000410
The signal transmitted to the u-th single-antenna user terminal on the k-th sub-carrier of each symbol. Then in the case of containing CP, in the second place
Figure BDA00030752567400000411
The analog baseband signal transmitted on one symbol to the u-th single-antenna user terminal can be represented as:
Figure BDA00030752567400000412
first of base station side
Figure BDA00030752567400000413
The demodulated signal vector for the k-th subcarrier of the symbol can be represented as:
Figure BDA00030752567400000414
wherein the content of the first and second substances,
Figure BDA00030752567400000415
indicating that the u-th single-antenna user terminal and the base station are in the second
Figure BDA00030752567400000416
The uplink channel frequency response vector on the k-th subcarrier of each symbol can be represented as:
Figure BDA0003075256740000051
wherein the content of the first and second substances,
Figure BDA0003075256740000052
to represent
Figure BDA0003075256740000053
The fourier transform of (d).
Figure BDA0003075256740000054
Is subject to
Figure BDA0003075256740000055
A distributed complex gaussian noise vector.
Analogous u th single-antenna user terminal
Figure BDA0003075256740000056
The demodulated signal of the k-th subcarrier of the symbol can be expressed as
Figure BDA0003075256740000057
Wherein the content of the first and second substances,
Figure BDA0003075256740000058
indicating that the base station and the u-th single-antenna user terminal are in the second place
Figure BDA0003075256740000059
The downlink channel frequency response vector of the k-th subcarrier of the symbol,
Figure BDA00030752567400000510
is subject to
Figure BDA00030752567400000511
Distributed complex gaussian noise.
The uplink synchronization process generally refers to a process between a user sending an uplink synchronization signal and a basic connection established between the user and a base station. Implementing user side and baseThe significance of uplink synchronization at the station side is that because the uplink data transmission in the sky wave massive MIMO-OFDM system is based on OFDM modulation, the OFDM modulation requires that the time for the signals of different users to reach the base station is basically the same, otherwise, the inter-subcarrier interference can be generated. The user side can only realize the synchronization of the user side through the downlink synchronization process, if the user side sends uplink signals according to the downlink synchronization timing, the time difference of the signals of different users reaching the base station can reach 2R due to different distances between different user sides and the base stationcC, wherein RcAnd c is the propagation speed of the electromagnetic wave. By the uplink synchronization method, the time difference of the user signal reaching the base station can be calculated, so that the uplink sending time of the user is adjusted, and preliminary uplink synchronization is realized. Fig. 2 is a comparison between a general uplink synchronization method and a sky-wave massive MIMO uplink synchronization method using position information, where a user side uses the position information to estimate and calculate a timing advance to adjust an uplink frame transmission time, so as to save the cost of traversing and searching an uplink synchronization sequence at a base station side, reduce the length of the uplink synchronization sequence, and improve the transmission efficiency of the system.
2. Calculating and obtaining shortest propagation path distance by using position information
The user side knows its own location information and base station location information, and the location information includes, but is not limited to, longitude and latitude information. And the user side approximates the shortest propagation path distance by considering the height of an ionization layer and latitude and longitude of two places or obtains the shortest propagation path distance by tracing by utilizing a ray tracing technology according to the known self position information and the base station position information.
User side known user position P1And base station position P2In which position Pi(i-1, 2) determining the position, i.e. the user position P, from the latitude and longitude information of the position1Has a longitude and latitude of (alpha)1,β1) Base station position P2Has a longitude and latitude of (alpha)2,β2) In which α isi(i-1, 2) is position PiLongitude, beta ofi(i-1, 2) is position PiThe latitude of (c). For the sake of calculation, the earth is assumed to be a perfect sphere,the radius of the earth is 6378.137km, which is the average radius R of the earth. According to the definition of longitude and latitude, the north and the south are respectively divided into 90 degrees from the equator, which are called north latitude and south latitude, and the north latitude takes a positive value and the south latitude takes a negative value. According to the reference of 0 degree of longitude, the east longitude takes positive value, the west longitude takes negative value, namely alphai∈(-180,180],βi∈[-90,90]. Fig. 3 is a schematic diagram of the spherical distances of the user side and the base station side, and the spherical distance S between the user side and the base station side can be expressed by solving the geodetic problem as follows:
Figure BDA0003075256740000061
because possible propagation modes of sky-wave communication are different according to different propagation distances, the shortest propagation path distance is considered, the propagation distance is considered to be within the range of 0-2000km, and the sky-wave transmission is carried out in a propagation mode of once passing through E-layer ionosphere reflection; within the range of 2000-4000km of propagation distance, the sky wave transmission is carried out in a propagation mode of once passing through the F-layer ionosphere reflection; the propagation distance is 4000-. Let E layer ionosphere reflection height hE100km, ionospheric reflection height h of F layerF300km, the shortest propagation path distance S between the user side and the base station sideSWCan be expressed as:
Figure BDA0003075256740000062
3. uplink timing advance
According to the shortest path propagation distance S obtained by calculationSWThe user can obtain the shortest time difference theta of the user signal to the base station as SSWC, adjusting the uplink sending time of the user to be 2 theta earlier than the original uplink sending time, thereby realizing that the time of the signals of a plurality of users reaching the base station is basically the same, saving the cost of traversing and searching the uplink synchronous sequence at the base station side, calculating the timing advance of the user and feeding the timing advance back to the user at the base station side according to the uplink synchronous sequence, and feeding the user back to the user according to the received user settingAnd updating the uplink frame sending time by the time advance to realize uplink synchronization. Fig. 4 is a schematic diagram of an uplink timing advance effect, and a plurality of users make the time for receiving signals of the plurality of users by the base station side substantially the same through the uplink timing advance, so that the cost for traversing and searching the uplink synchronization sequence by the base station side is saved, uplink synchronization is realized, and interference between subcarriers is avoided.
The invention is not described in detail, but is well known to those skilled in the art. The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims (6)

1. An sky-wave massive MIMO uplink synchronization method using position information is characterized in that the method is suitable for an sky-wave massive MIMO communication system, the system comprises a short wave base station and a plurality of short wave users, and the short wave base station and the short wave users realize massive MIMO communication;
the method comprises the following steps:
step S1, the base station side broadcasts and sends the downlink synchronous signal, and the user side receives the downlink synchronous signal from the base station side;
step S2, the user side calculates and obtains the initial position of the downlink data frame according to the downlink synchronous signal;
step S3, the user side calculates and obtains the shortest propagation path distance according to the position information of the user side and the position information of the base station side, and obtains the minimum relative time delay of the round-trip transmission of the wireless link of the user according to the shortest propagation path distance;
step S4, the user side adjusts the sending time of the uplink frame according to the initial position of the downlink data frame calculated in step S2 and the minimum relative time delay obtained in step S3;
step S5, the base station side calculates the user timing advance information according to the received uplink synchronization sequence and feeds back the user timing advance information to the user side, and the user side adjusts the uplink frame sending time again by using the user timing advance information to realize uplink synchronization.
2. The sky-wave massive MIMO uplink synchronization method using position information as claimed in claim 1, wherein in the sky-wave massive MIMO communication system, the large-scale antenna array is at the base station side, and the single antenna is at the user side.
3. The sky-wave massive MIMO uplink synchronization method using position information as claimed in claim 2, wherein the user side calculates to obtain the start position of the downlink data frame by using autocorrelation, cross correlation and constant amplitude low peak-to-average ratio characteristics of the downlink synchronization sequence to complete downlink synchronization.
4. The sky-wave massive MIMO uplink synchronization method using location information as claimed in claim 3, wherein the location information of the user side and the base station side comprises longitude information and latitude information.
5. The skywave massive MIMO uplink synchronization method according to claim 4, wherein the step S3 specifically includes: and the user side solves the approximate shortest propagation path distance or obtains the shortest propagation path distance by tracking by utilizing a ray tracing technology by considering the height of the ionization layer and the longitude and latitude information of two places according to the position information of the user side and the position information of the base station side.
6. The sky-wave massive MIMO uplink synchronization method using position information as claimed in claim 5, wherein in the step S3, when the approximate shortest propagation path distance is solved, the curved surface distance between the earth surface and the base station side and the user side is calculated first, and the propagation mode is determined according to the distance, and then the minimum relative time delay of the round trip transmission of the user wireless link is obtained by calculating the ground problem according to the propagation mode, the height of the ionosphere and the curved surface distance.
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