CN113783591A - Precoding method, communication system and device for multiple multi-beam satellite communication - Google Patents
Precoding method, communication system and device for multiple multi-beam satellite communication Download PDFInfo
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Abstract
The invention provides a pre-coding method, a communication system and a device for multi-beam satellite communication, wherein the method designs two transmission modes aiming at a plurality of data streams of a single terminal, uses parallel structure optimization to decide the optimal transmission mode aiming at the plurality of data streams of each terminal and construct the optimal overall transmission mode of all terminals, and comprises the following two parts: the first part is that on the basis of referring to the overall transmission mode, the transmission mode of each terminal is respectively changed to obtain the overall transmission mode, and then the comparison performance index is calculated; the second part is a selection scheme, and the optimal transmission mode of each terminal is selected according to the comparison performance indexes and the optimal overall transmission mode is constructed. The signal to be transmitted is precoded according to the optimal channel matrix of the optimal overall transmission mode, and higher system error rate performance is obtained under the condition that the cost and the complexity of a satellite are not increased.
Description
Technical Field
The present invention relates to the field of satellite communications technologies, and in particular, to a precoding method, a communication system, and an apparatus for multiple multi-beam satellite communications.
Background
In a multi-beam satellite communication system, the multi-beam antennas are all located in the same satellite, thereby introducing severe co-channel interference between the beams of the forward link. Frequency reuse may be achieved by using multiple beams to reduce co-channel interference, but system capacity is limited by low spectral efficiency due to a high frequency reuse factor. Many studies successfully solve the problem by resource allocation, but the complexity of resource allocation is high and the realizability is low.
Unlike terrestrial systems, the gateway stations in satellite systems can concentrate the control signals of all terminals, which makes it possible to process all terminal signals at the gateway stations in a centralized manner to improve system performance. In the forward link of a satellite system, multiple-input multiple-output precoding may be used to pre-process the signal to eliminate interference. In the existing precoding technology, ZF precoding, MMSE precoding, TH precoding, and the like are mostly adopted.
The basic idea of ZF (Zero-forcing) precoding is that a transmitting end introduces artificial interference by using a precoding matrix to further cancel inter-beam interference in a multi-beam satellite channel, and the influence of noise is not considered when generating the precoding matrix.
The basic idea of MMSE (Minimum Mean Squared Error) precoding algorithm is that a transmitting end uses a precoding matrix to introduce interference between beams in an artificial interference cancellation part of a multi-beam satellite channel on the basis of considering noise influence, so that the Error between a received signal and a transmitted signal is minimized.
TH Precoding (Tomlinson-Harashima Precoding) was proposed by Tomlinson and Harashima, and was initially applied to frequency selective channels to combat inter-symbol interference, and then generalized to multiple-input multiple-output communication systems. TH precoding is precoding which can give consideration to both performance and complexity, is one-dimensional realization of dirty paper coding, and can lead a sending signal to better adapt to the time-varying characteristic of a channel and eliminate the influence caused by interference between data streams by introducing operations of modulus calculation and feedback to the cost of improving the complexity, thereby greatly improving the system performance. Similar to linear precoding, TH precoding can be designed based on ZF and MMSE criteria, but the performance of TH precoding is affected by the data stream arrangement order, and in a multi-beam satellite communication system, the performance of the conventional TH precoding technology cannot meet the system requirements.
Therefore, it is desirable to provide a precoding method for a communication system configured with a plurality of multi-beam satellites.
Disclosure of Invention
Embodiments of the present invention provide a precoding method, a communication system, and an apparatus for multiple multi-beam satellite communication, so as to eliminate or improve one or more defects in the prior art, and solve a problem of beam interference in a multiple multi-beam satellite communication process.
The technical scheme of the invention is as follows:
in one aspect, the present invention provides a precoding method for multiple multi-beam satellite communications, the method comprising:
configuring a set number of transmitting modes for each terminal respectively, and initializing;
taking the running states of all the terminals in the reference transmission mode as a reference overall transmission mode, and carrying out LQ decomposition on a channel matrix of the reference overall transmission mode to obtain a reference performance index;
under a reference overall transmission mode, sequentially replacing the transmission mode of each terminal, keeping the transmission modes of other terminals unchanged, and carrying out LQ decomposition on a channel matrix of the changed overall transmission mode to obtain a comparison performance index;
comparing the comparison performance index corresponding to each terminal with the reference performance index according to a set rule, and if the reference performance index is larger than the current comparison performance index of the terminal, marking the transmission mode after the terminal is changed as the optimal transmission mode; if the reference performance index is less than or equal to the current comparison performance index of the terminal, marking the reference emission mode of the terminal as the optimal emission mode;
and taking the running state of each terminal in the corresponding optimal transmission mode as the optimal overall transmission mode, and precoding the signals to be sent according to the optimal channel matrix of the optimal overall transmission mode.
In some embodiments, the precoding method for multiple multi-beam satellite communications comprises:
respectively setting a first transmission mode and a second transmission mode for a plurality of terminals, and initializing;
taking the running states of all the terminals in the first transmission mode as a reference overall transmission mode, and carrying out LQ decomposition on a channel matrix of the reference overall transmission mode to obtain a reference performance index;
under a reference overall transmission mode, sequentially changing the transmission mode of each terminal into the second transmission mode, keeping the transmission modes of other terminals unchanged, and carrying out LQ decomposition on a channel matrix of the changed overall transmission mode to obtain a comparison performance index;
respectively comparing the comparison performance index corresponding to each terminal with the reference performance index, and if the reference performance index is larger than the current comparison performance index of the terminal, marking the second transmission mode as the optimal transmission mode of the corresponding terminal; if the reference performance index is less than or equal to the current comparison performance index of the terminal, marking the first transmission mode as the optimal transmission mode of the corresponding terminal;
and taking the running state of each terminal in the corresponding optimal transmission mode as the optimal overall transmission mode, and precoding the signals to be sent according to the optimal channel matrix of the optimal overall transmission mode.
In some embodiments, LQ decomposition of the channel matrix of the reference overall transmission mode to obtain a reference performance indicator includes:
performing LQ decomposition on the channel matrix of the reference overall transmission mode to obtain a reference lower triangular matrix and a reference unitary matrix, and squaring and summing diagonal elements of the reference lower triangular matrix to obtain the reference performance index;
carrying out LQ decomposition on the channel matrix of the changed overall transmission mode to obtain a comparison performance index, which comprises the following steps:
and carrying out LQ decomposition on the channel matrix of the changed overall transmission mode to obtain a comparison triangular matrix and a comparison unitary matrix, and squaring and summing diagonal elements of the triangular matrix under comparison to obtain the comparison performance index.
In some embodiments, the precoding employs TH precoding.
In some embodiments, precoding a signal to be transmitted according to the optimal channel matrix of the optimal overall transmission mode includes:
performing LQ decomposition on the optimal channel matrix of the optimal overall transmission mode to obtain an optimal triangular matrix A(b)And an optimal unitary matrix B(b)；
Calculating a conjugate matrix C of the optimal unitary matrix(b)Diagonal matrix D of the optimal triangular matrix(b)And a feedback matrix E for subtracting interference(b)The calculation formula is as follows:
E(b)＝D(b)A(b)
processing the vector x of the signal to be transmitted to obtain a transmission intermediate vector v(b)The calculation formula is:
wherein,
indicating the transmission vector formed by the data streams transmitted by the terminals under different point beams at the same time and using the same frequency band, Nd＝Ns×NbRepresenting the total number of transmitted data streams, NbRepresenting the number of spot beams, N, of a multibeam satellitesRepresenting the number of multi-beam satellites; the function M represents a modulo operation, τ 2 √ 2.
In another aspect, the present invention provides a multi-beam satellite communication system comprising:
the gateway station is used for mapping the signal to be transmitted after the constellation is mapped by adopting the precoding method for the multi-beam satellite communication, and carrying out multi-carrier modulation to obtain a modulation signal;
a plurality of multi-beam satellites for transmitting the optimal transmission mode in the precoding method for multi-beam satellite communication;
and the ground terminal receives the modulation signal transmitted by the multi-beam satellite and performs multi-carrier demodulation, precoding decoding and constellation demapping.
In some embodiments, the multi-beam satellite adds white gaussian noise to the modulated signal.
In some embodiments, the precoding method for multiple multi-beam satellite communications used for mapping a constellation onto a signal to be transmitted includes:
performing LQ decomposition on the optimal channel matrix of the optimal overall transmission mode to obtain an optimal triangular matrix A(b)And an optimal unitary matrix B(b)；
Calculating a conjugate matrix C of the optimal unitary matrix(b)Diagonal matrix D of the optimal triangular matrix(b)And a feedback matrix E for subtracting interference(b)The calculation formula is as follows:
E(b)＝D(b)A(b)
processing the vector x of the signal to be transmitted to obtain a transmission intermediate vector v(b)The calculation formula is:
wherein,
indicating the transmission vector formed by the data streams transmitted by the terminals under different point beams at the same time and using the same frequency band, Nd＝Ns×NbRepresenting the total number of transmitted data streams, NbRepresenting the number of spot beams, N, of a multibeam satellitesRepresenting the number of multi-beam satellites; the function M represents a modulo operation, τ 2 √ 2.
In some embodiments, the terrestrial terminal receives vector y of the modulated signal(b)Comprises the following steps:
wherein,
the receiving vector is composed of data streams which are transmitted by terminals under different point beams and use the same frequency band at the same time;
representing a random vector of zero-mean complex Gaussian white noise superimposed on the data stream, the noise variance of each term being
Gamma is a scaling factor for controlling the transmit power; dTHP and dTHP are two TH precoding deployment modes, and the dTHP is used for converting a diagonal matrix D into a diagonal matrix D(b)Placed at the terminal, cTHP will align the diagonal matrix D(b)Placing at a gateway station;
calculating a received vector y(b)At each receiving end by
Obtaining a received intermediate vector y and a decoded vector
The calculation formula is as follows:
the received intermediate vector y is a pair of received vectors y(b)Performing line permutation to obtain a vector, decoding the vector
Is a vector obtained by performing a modulo operation on the vector y, and the function M represents the modulo operation.
In another aspect, the present invention provides an electronic device, comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the method when executing the program.
The invention has the beneficial effects that:
in the precoding method, the communication system and the device for multi-beam satellite communication, the method designs two transmission modes aiming at a plurality of data streams of a single terminal, uses parallel structure optimization to decide the optimal transmission mode aiming at the plurality of data streams of each terminal and construct the optimal overall transmission mode of all terminals, and comprises two parts: the first part is that on the basis of referring to the overall transmission mode, the transmission mode of each terminal is respectively changed to obtain the overall transmission mode, and then the comparison performance index is calculated; the second part is a selection scheme, and the optimal transmission mode of each terminal is selected according to the comparison performance indexes and the optimal overall transmission mode is constructed. The signal to be transmitted is precoded according to the optimal channel matrix of the optimal overall transmission mode, and higher system error rate performance is obtained under the condition that the cost and the complexity of a satellite are not increased.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
It will be appreciated by those skilled in the art that the objects and advantages that can be achieved with the present invention are not limited to the specific details set forth above, and that these and other objects that can be achieved with the present invention will be more clearly understood from the detailed description that follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
figure 1 is a schematic diagram of a multiple multi-beam satellite communication scenario;
FIG. 2 is a schematic diagram of multi-beam satellite inter-beam interference;
fig. 3 is a flowchart of a precoding method for multiple multi-beam satellite communications according to an embodiment of the present invention;
fig. 4 is a flow chart of a forward link system in a precoding method for multiple multi-beam satellite communications according to an embodiment of the present invention;
FIG. 5 is a block diagram of TH precoding;
FIG. 6 is a graph of dTH precoding (dTHP) bit error rate performance;
FIG. 7 is a graph of cTH precoding (cTHP) bit error rate performance;
fig. 8 is an cTH precode (cTHP) channel capacity performance graph.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following embodiments and accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present invention are shown in the drawings, and other details not so relevant to the present invention are omitted.
It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, elements, steps or components, but does not preclude the presence or addition of one or more other features, elements, steps or components.
The multi-beam satellite is a satellite which uses a plurality of antennas to respectively generate non-overlapping spot beams, the on-satellite antennas can generate a plurality of mutually adjacent beams in the coverage range of the satellite, and the multi-beam satellite has the advantages of high satellite resource utilization rate, high efficient omnidirectional radiation power, high beam coverage quality and high communication system capacity. In a multi-beam satellite communication system, the multi-beam antennas are all located in the same satellite, thereby introducing severe inter-beam interference between the beams of the forward link. The multi-satellite communication system realizes a satellite communication system of virtual MIMO (Multiple In Multiple Out Multiple output technology) communication by using a satellite diversity mode, and the system covers and simultaneously serves the same area by using a plurality of satellites, thereby effectively improving the system throughput. Based on the precoding technology, in a downlink of a multi-input multi-output communication system, a transmitting end optimizes the spatial characteristics of a transmitted signal according to known channel state information, so that the spatial distribution characteristics of the transmitted signal are matched with channel conditions, the system performance can be effectively improved, and the dependence degree of the system on a receiver algorithm is reduced.
It should be noted that, as shown in fig. 1, the present invention is applicable to a multi-multibeam satellite multi-terminal communication scenario, where terminals in different beams use the same frequency band for transmission and are affected by inter-beam interference. In a multibeam satellite communication system, each beam of the multibeam satellite generally uses a different transmitting antenna to transmit signals, and since the power pattern of the transmitting antenna of the multibeam satellite is not an ideal power pattern, the transmitting power is not completely concentrated in a target direction, but there is a power loss in different directions, which causes power aliasing among different beams of the multibeam satellite in space and further generates inter-beam interference.
As shown in fig. 2, the coverage area of a multi-beam satellite is made up of a plurality of adjacent spot beam coverage areas, each of which transmits a signal using a respective transmit antenna. Because each antenna is provided with an antenna main lobe and antenna side lobes, signals emitted by the antenna main lobe part are used for forming a spot beam coverage area of the antenna main lobe part, and the antenna side lobe part is superposed into other spot beam coverage areas. Therefore, when different spot beams adopt the same frequency band for signal transmission, the main lobes of the antennas of different spot beams are affected by the other spot beams and the antenna side lobes to generate inter-beam interference.
The inter-beam interference experienced between terminals in the same group, i.e., using the same frequency, within each spot beam can be quantized into an inter-beam interference channel matrix. The system model is as follows:
y＝Wx+z (1)
wherein,
indicating the transmission vector formed by the data streams transmitted by the terminals under different point beams at the same time and using the same frequency band, Nd＝Ns×NbRepresenting the total number of transmitted data streams, NbRepresenting the number of spot beams, N, of a multibeam satellitesRepresenting the number of multi-beam satellites;
the receiving vector is composed of data streams which are transmitted by terminals under different point beams and use the same frequency band at the same time;
representing a random vector of zero-mean complex Gaussian white noise superimposed on the data stream, the noise variance of each term being
W denotes a channel matrix composed of inter-beam interference information, whose diagonal elements denote non-interference terms and off-diagonal elements denote interference terms.
In view of this, the present invention provides a precoding method for multiple multi-beam satellite communications, the method comprising steps S101 to S105:
step S101: and respectively configuring a set number of transmission modes for each terminal and initializing.
Step S102: and taking the running states of all the terminals in the reference transmission mode as a reference overall transmission mode, and carrying out LQ decomposition on a channel matrix of the reference overall transmission mode to obtain a reference performance index.
Step S103: and under the reference overall transmission mode, sequentially replacing the transmission mode of each terminal, keeping the transmission modes of other terminals unchanged, and carrying out LQ decomposition on the channel matrix of the changed overall transmission mode to obtain a comparison performance index.
Step S104: comparing the comparison performance index corresponding to each terminal with the reference performance index according to a set rule, and if the reference performance index is larger than the current comparison performance index of the terminal, marking the transmission mode changed by the terminal as the optimal transmission mode; and if the reference performance index is less than or equal to the current comparison performance index of the terminal, marking the reference transmission mode of the terminal as the optimal transmission mode.
Step S105: and taking the running state of each terminal in the corresponding optimal transmission mode as the optimal overall transmission mode, and precoding the signals to be sent according to the optimal channel matrix of the optimal overall transmission mode.
In step S101, a plurality of transmission modes are designed for each terminal, where a transmission mode is a matrix with 0 or 1 element, the number of rows and columns is equal, and the number of 1 elements in each row and each column is 1. The transmitting mode is used for the gateway station to process the channel matrix (i.e. multiply with the channel matrix) before the TH precoding, and change the coding sequence of the data stream and further change the coding performance of the TH precoding.
In step S102, a reference transmission mode, which may be one of the set number of transmission modes in step S101, is set for each of all terminals. And each terminal is in a corresponding reference transmission state, and the overall transmission mode is taken as a reference overall transmission mode. And acquiring a channel matrix in a reference overall transmission mode, carrying out LQ decomposition, and calculating a corresponding reference performance index based on a reference lower triangular matrix obtained by decomposition.
Specifically, in step S102, LQ decomposition is performed on the channel matrix of the reference overall transmission mode to obtain a reference performance index, which includes: and carrying out LQ decomposition on the channel matrix of the reference overall transmission mode to obtain a reference lower triangular matrix and a reference unitary matrix, and squaring and summing diagonal elements of the reference lower triangular matrix to obtain the reference performance index.
In steps S103 and S104, the optimal transmission mode of each terminal is selected by parallel optimization. Specifically, on the basis of referring to the overall transmission mode, the transmission mode of each terminal is changed respectively, and the performance index is calculated and compared for the changed overall transmission mode and compared with the reference performance index to select the optimal transmission mode of each terminal.
Specifically, in step S103, LQ decomposition is performed on the channel matrix of the changed overall transmission mode to obtain a comparison performance index, which includes: and carrying out LQ decomposition on the channel matrix of the changed overall transmission mode to obtain a comparison triangular matrix and a comparison unitary matrix, and squaring and summing diagonal elements of the triangular matrix under comparison to obtain the comparison performance index.
In step S105, the terminal operates according to the optimal transmission mode selected by each terminal, establishes an optimal overall transmission mode among all data streams, and performs precoding based on an optimal channel matrix corresponding to the optimal overall transmission mode. Specifically, in step S105, TH precoding is used as precoding.
In some embodiments, to limit complexity, two transmission modes are set for each terminal, and as shown in fig. 3, the corresponding precoding method for multiple multi-beam satellite communications includes steps S201 to S205:
step S201: a first transmission mode and a second transmission mode are set for a plurality of terminals respectively, and initialization is performed.
Step S202: and taking the running states of all the terminals in the first transmission mode as a reference overall transmission mode, and carrying out LQ decomposition on a channel matrix of the reference overall transmission mode to obtain a reference performance index.
Step S203: and under the reference overall transmission mode, sequentially changing the transmission mode of each terminal into a second transmission mode, keeping the transmission modes of other terminals unchanged, and carrying out LQ decomposition on the channel matrix of the changed overall transmission mode to obtain a comparison performance index.
Step S204: respectively comparing the comparison performance index corresponding to each terminal with the reference performance index, and if the reference performance index is larger than the current comparison performance index of the terminal, marking the second transmission mode as the optimal transmission mode of the corresponding terminal; and if the reference performance index is less than or equal to the current comparison performance index of the terminal, marking the first transmission mode as the optimal transmission mode of the corresponding terminal.
Step S205: and taking the running state of each terminal in the corresponding optimal transmission mode as the optimal overall transmission mode, and precoding the signals to be sent according to the optimal channel matrix of the optimal overall transmission mode. In this embodiment, TH precoding may be employed.
In the present embodiment, two transmission modes are designed for each terminal and the transmission mode of each terminal is initialized, step S201. In step S202, the overall transmission mode of all data streams is initialized according to the transmission mode of each terminal, and the overall transmission mode is set as the reference overall transmission mode. And performing LQ decomposition on the channel matrix to obtain a performance index, and setting the performance index as a reference performance index. In step S203 and step S204, the transmission mode of each terminal is optimized using a parallel structure, the transmission mode among the multiple data streams of each terminal is respectively replaced on the basis of referring to the overall transmission mode, the transmission modes among the multiple data streams of the other terminals except the current terminal are unchanged, and the performance index is recalculated. Comparing the performance index with a reference performance index by using a selection scheme, and then selecting the best transmission mode among a plurality of data streams of the current terminal: and if the reference performance index is larger than the current performance index, the optimal transmission mode of the current terminal is the transmission mode after replacement, otherwise, the optimal transmission mode of the current terminal is the transmission mode before replacement. In step S205, after the optimal transmission mode among the multiple data streams of each terminal is selected, the optimal transmission mode among the multiple data streams of each terminal is configured as the optimal overall transmission mode among all the data streams. And obtaining the optimal channel matrix through the optimal overall transmission mode among all data streams, and then performing TH precoding.
Steps S201 to S205 are described below with reference to a specific embodiment, and a TH precoding method for a multi-beam satellite communication system is provided, as shown in fig. 3, 4 and 5, including steps 1) to 10):
1) designing a transmission mode P for a plurality of data streams of each terminal in sequenceiTo limit complexity, two transmission modes are designed for each terminal, which are expressed as the following equations 2 and 3:
wherein,
representing a matrix size of Ns×NsThe unit matrix of (a) is,
representing a matrix size of Ns×NsI represents the serial number of the terminal and satisfies that i is more than or equal to 1 and less than or equal to Nb，NbRepresenting the number of spot beams of a multi-beam satellite.
2) Transmission mode selection between multiple data streams per terminal
The overall transmission pattern P of all data streams can be obtained(0)The following formula 4:
3) by P(0)Obtaining the channel matrix W after changing the row arrangement sequence(0)And the corresponding lower triangular matrix A obtained after LQ decomposition(0)Matrix and unitary matrix B(0)Matrix, transmitting pattern P as a whole(0)Set to the reference overall transmission mode.
W(0)＝P(0)W＝A(0)B(0) (2)
Where W denotes a channel matrix composed of inter-beam interference information.
4) Will lower triangular matrix A(0)The diagonal elements of the square and sum to obtain
Wherein
Represents a lower triangular matrix A(0)The diagonal elements of the kth row and the kth column. To more intuitively represent the sum value
Order to
A transmission pattern P can be obtained(0)Corresponding delta(0)The performance index is set as a reference performance index.
5) Optimizing the transmission mode of each terminal using a parallel structure, in a reference global transmission mode P(o)Respectively changing the transmission mode among a plurality of data streams of the ith terminal into
The transmission mode among a plurality of data streams of other terminals except the ith terminal is not changed, and the transmission mode P of all the data streams can be obtained(i)Lower triangular matrix A(i)And correspondingδ(i)Wherein W is(i)＝P(i)W＝A(i)B(i)，
Obtaining delta(i)We then use an alternative scheme to compare the transmission patterns P(0)And a transmission pattern P(i)The performance of (2) is good or bad: if delta(0)≥δ(i)The best transmission mode of the ith terminal
Is composed of
Otherwise, it is
6) After the optimal transmission mode among the multiple data streams of each terminal is selected, the optimal transmission mode among the multiple data streams of each terminal is combined to obtain the optimal overall transmission mode P among all the data streams(b)。
7) By P(b)Obtaining the channel matrix W after changing the row arrangement sequence(b)。
W(b)＝P(b)W＝A(b)B(b) (3)
Where W denotes a channel matrix composed of inter-beam interference information, diagonal elements thereof denote non-interference items, and non-diagonal elements thereof denote interference items. By applying a pair of channel matrices W(b)Performing LQ decomposition to obtain matrix A(b)And B(b). Wherein A is(b)The matrix is a lower triangular matrix obtained by LQ decomposition; b is(b)The matrix is unitary matrix obtained by LQ decomposition and satisfies
I is the identity matrix.
According to A(b)And B(b)Performing TH precoding on the matrix, and calculating a conjugate matrix C of the optimal unitary matrix(b)Diagonal matrix D of the optimal triangular matrix(b)And a feedback matrix E for subtracting interference(b)The calculation formula is as follows:
E(b)＝D(b)A(b) (10)
wherein, C(b)The matrix is B(b)Conjugate transpose of matrix, B(b)Is a unitary matrix for introducing spatial correlation. D(b)The matrix is a diagonal matrix whose diagonal elements pass through A(b)The diagonal elements of the matrix are obtained. a isi，i，i＝1，2，...，NdIs A(b)The matrix has an ith row and an ith column. E(b)The matrix is a feedback matrix for subtracting interference of the previous data stream with the current data stream from the current data stream.
8) Processing the vector x of the signal to be transmitted to obtain a transmission intermediate vector v(b)The calculation formula is:
wherein,
indicating at different spot beamsThe terminal uses the transmission vector, N, formed by the data streams transmitted in the same frequency band at the same timed＝Ns×NbRepresenting the total number of transmitted data streams, NbRepresenting the number of spot beams, N, of a multibeam satellitesRepresenting the number of multi-beam satellites; transmitting intermediate vector v(b)Is a vector obtained after processing the emission vector x; the function M represents a modulo operation that is,
9) corresponding received vector y(b)Comprises the following steps:
wherein,
the receiving vector is composed of data streams which are transmitted by terminals under different point beams and use the same frequency band at the same time;
representing a random vector of zero-mean complex Gaussian white noise superimposed on the data stream, the noise variance of each term being
Gamma is a scaling factor used to control the transmit power. dTHP and dTHP are two TH precoding deployment modes, and the dTHP is used for converting a diagonal matrix D into a diagonal matrix D(b)Placed at the terminal, cTHP will align the diagonal matrix D(b)Placed at the gateway station as shown in the TH precoding block diagram.
10) Receiving vector y(b)At each receiving end by
Obtaining a received intermediate vector y and a decoded vector
The following formula:
wherein the receiving intermediate vector y is a pair of receiving vectors y(b)Performing line permutation to obtain a vector, decoding the vector
Is a vector obtained by performing a modulo operation on the vector y, and the function M represents the modulo operation.
The performance simulation of the TH precoding method for a multi-beam satellite communication system according to this embodiment is performed, where specific simulation parameters are as follows:
TABLE 1 simulation parameters Table
| Name of simulation parameter | Parameter value |
| Multi-beam satellite orbital altitude | 1175km |
| Multibeam satellite spot beam type | Conical type |
| Multi-beam satellite spot beam covering mode | 4 x 4 matrix overlay |
| Multi-beam satellite spot beam coverage radius | 102.8km |
| Number of spot beams of multi-beam satellite | Nb＝16 |
| Number of antennas provided for each terminal | Ns＝2 |
| Distance between multibeam satellites | 436.14km |
| Modulation system | QPSK |
| Multi-carrier modulation system | Single carrier frequency division multiple access |
| Number of occupied sub-carriers | 3168 |
| Total number of subcarriers | 4096 |
| Cyclic prefix length | 256 |
| Number of simulation symbols | 9504000 |
As shown in FIG. 6, the bit error rate is 10-4When the modulation mode is QPSK (quadrature phase shift keying), the parallel ordering MMSE-dTHP (distributed TH precoding based on the minimum mean square error criterion combined with the parallel ordering technique) based on the present invention has a gain of about 5dB compared to the multi-branch MMSE-dTHP (distributed TH precoding based on the minimum mean square error criterion combined with the distributed technique) and MMSE-dTHP (distributed TH precoding based on the minimum mean square error criterion), and has a gain of about 9dB compared to both ZF precoding and MMSE precoding algorithms. The reason for this is that the parallel ordering MMSE-dTHP uses a parallel structure to obtain the best transmission pattern among all data streams.
As shown in FIG. 7, the bit error rate is 10-4When the modulation scheme is QPSK, the parallel-ordered MMSE-cTHP (localized TH precoding based on the minimum mean square error criterion combined with the parallel ordering technique) based on the present invention has a gain of about 1.2dB compared to the multi-branch MMSE-cTHP (localized TH precoding based on the minimum mean square error criterion combined with the distributed technique) and MMSE-cTHP (localized TH precoding based on the minimum mean square error criterion).
As shown in fig. 8, the parallel ordering cTHP (localized TH precoding in combination with parallel ordering technique) based on the present invention has higher channel capacity performance than the multi-branch cTHP (localized TH precoding in combination with distributed technique) and the cTHP (localized TH precoding).
In another aspect, the present invention provides a multi-beam satellite communication system comprising:
and the gateway station is configured to perform multi-carrier modulation on the signal to be transmitted after constellation mapping by using the precoding method for multiple multi-beam satellite communication described in steps S101 to S105 or steps S201 to S205 to obtain a modulated signal.
A plurality of multi-beam satellites for transmitting the optimal transmission mode in the precoding method for multi-beam satellite communication of steps S101 to S105 or steps S201 to S205;
and the ground terminal receives the modulation signal transmitted by the multi-beam satellite and performs multi-carrier demodulation, precoding decoding and constellation demapping.
In some embodiments, the multi-beam satellite adds white gaussian noise to the modulated signal.
In some embodiments, the precoding method for multiple multi-beam satellite communications used for mapping a constellation onto a signal to be transmitted includes:
performing LQ decomposition on the optimal channel matrix of the optimal overall transmission mode to obtain an optimal triangular matrix A(b)And an optimal unitary matrix B(b)；
Calculating a conjugate matrix C of the optimal unitary matrix(b)Diagonal matrix D of the optimal triangular matrix(b)And a feedback matrix E for subtracting interference(b)The calculation formula is as follows:
E(b)＝D(b)A(b) (10)
wherein, C(b)The matrix is B(b)Conjugate transpose of matrix, B(b)Is a unitary matrix for introducing spatial correlation. D(b)The matrix is a diagonal matrix whose diagonal elements pass through A(b)The diagonal elements of the matrix are obtained. a isi，i，i＝1，2，...，NdIs A(b)The matrix has an ith row and an ith column. E(b)The matrix is a feedback matrix for subtracting interference of the previous data stream with the current data stream from the current data stream.
Processing the vector x of the signal to be transmitted to obtain a transmission intermediate vector v(b)The calculation formula is:
wherein,
indicating the transmission vector formed by the data streams transmitted by the terminals under different point beams at the same time and using the same frequency band, Nd＝Ns×NbRepresenting the total number of transmitted data streams, NbRepresenting the number of spot beams, N, of a multibeam satellitesRepresenting the number of multi-beam satellites; m (-) represents a modulo operation,
in some embodiments, the terrestrial terminal receives vector y of the modulated signal(b)Comprises the following steps:
wherein,
the receiving vector is composed of data streams which are transmitted by terminals under different point beams and use the same frequency band at the same time;
representing dataA zero-mean complex Gaussian white noise random vector superposed on the flow, wherein the noise variance of each term is
Gamma is a scaling factor for controlling the transmit power; dTHP and dTHP are two TH precoding deployment modes, and the dTHP is used for converting a diagonal matrix D into a diagonal matrix D(b)Placed at the terminal, cTHP will align the diagonal matrix D(b)Placing at a gateway station;
calculating a received vector y(b)At each receiving end by
Obtaining a received intermediate vector y and a decoded vector
The calculation formula is as follows:
the received intermediate vector y is a pair of received vectors y(b)Performing line permutation to obtain a vector, decoding the vector
Is a vector obtained by performing a modulo operation on the vector y, and M (·) represents a modulo operation.
In another aspect, the present invention provides an electronic device, comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the method when executing the program.
In summary, in the precoding method, the communication system and the apparatus for multiple multi-beam satellite communications according to the present invention, the method designs two transmission modes for multiple data streams of a single terminal, and uses parallel structure optimization to decide an optimal transmission mode for the multiple data streams of each terminal and construct an optimal overall transmission mode for all terminals, which includes two parts: the first part is that on the basis of referring to the overall transmission mode, the transmission mode of each terminal is respectively changed to obtain the overall transmission mode, and then the comparison performance index is calculated; the second part is a selection scheme, and the optimal transmission mode of each terminal is selected according to the comparison performance indexes and the optimal overall transmission mode is constructed. The signal to be transmitted is precoded according to the optimal channel matrix of the optimal overall transmission mode, and higher system error rate performance is obtained under the condition that the cost and the complexity of a satellite are not increased.
Those of ordinary skill in the art will appreciate that the various illustrative components, systems, and methods described in connection with the embodiments disclosed herein may be implemented as hardware, software, or combinations of both. Whether this is done in hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. When implemented in hardware, it may be, for example, an electronic circuit, an Application Specific Integrated Circuit (ASIC), suitable firmware, plug-in, function card, or the like. When implemented in software, the elements of the invention are the programs or code segments used to perform the required tasks. The program or code segments may be stored in a machine-readable medium or transmitted by a data signal carried in a carrier wave over a transmission medium or a communication link. A "machine-readable medium" may include any medium that can store or transfer information. Examples of a machine-readable medium include electronic circuits, semiconductor memory devices, ROM, flash memory, Erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, Radio Frequency (RF) links, and so forth. The code segments may be downloaded via computer networks such as the internet, intranet, etc.
It should also be noted that the exemplary embodiments mentioned in this patent describe some methods or systems based on a series of steps or devices. However, the present invention is not limited to the order of the above-described steps, that is, the steps may be performed in the order mentioned in the embodiments, may be performed in an order different from the order in the embodiments, or may be performed simultaneously.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments in the present invention.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes may be made to the embodiment of the present invention by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A precoding method for multiple multi-beam satellite communications, the method comprising:
configuring a set number of transmitting modes for each terminal respectively, and initializing;
taking the running states of all the terminals in the reference transmission mode as a reference overall transmission mode, and carrying out LQ decomposition on a channel matrix of the reference overall transmission mode to obtain a reference performance index;
under a reference overall transmission mode, sequentially replacing the transmission mode of each terminal, keeping the transmission modes of other terminals unchanged, and carrying out LQ decomposition on a channel matrix of the changed overall transmission mode to obtain a comparison performance index;
comparing the comparison performance index corresponding to each terminal with the reference performance index according to a set rule, and if the reference performance index is larger than the current comparison performance index of the terminal, marking the transmission mode after the terminal is changed as the optimal transmission mode; if the reference performance index is less than or equal to the current comparison performance index of the terminal, marking the reference emission mode of the terminal as the optimal emission mode;
and taking the running state of each terminal in the corresponding optimal transmission mode as the optimal overall transmission mode, and precoding the signals to be sent according to the optimal channel matrix of the optimal overall transmission mode.
2. The precoding method for multiple multi-beam satellite communications according to claim 1, comprising:
respectively setting a first transmission mode and a second transmission mode for a plurality of terminals, and initializing;
taking the running states of all the terminals in the first transmission mode as a reference overall transmission mode, and carrying out LQ decomposition on a channel matrix of the reference overall transmission mode to obtain a reference performance index;
under a reference overall transmission mode, sequentially changing the transmission mode of each terminal into the second transmission mode, keeping the transmission modes of other terminals unchanged, and carrying out LQ decomposition on a channel matrix of the changed overall transmission mode to obtain a comparison performance index;
respectively comparing the comparison performance index corresponding to each terminal with the reference performance index, and if the reference performance index is larger than the current comparison performance index of the terminal, marking the second transmission mode as the optimal transmission mode of the corresponding terminal; if the reference performance index is less than or equal to the current comparison performance index of the terminal, marking the first transmission mode as the optimal transmission mode of the corresponding terminal;
and taking the running state of each terminal in the corresponding optimal transmission mode as the optimal overall transmission mode, and precoding the signals to be sent according to the optimal channel matrix of the optimal overall transmission mode.
3. The precoding method for multiple multi-beam satellite communications of claim 1, wherein LQ decomposition of the channel matrix for the reference overall transmission pattern yields a reference performance indicator comprising:
performing LQ decomposition on the channel matrix of the reference overall transmission mode to obtain a reference lower triangular matrix and a reference unitary matrix, and squaring and summing diagonal elements of the reference lower triangular matrix to obtain the reference performance index;
carrying out LQ decomposition on the channel matrix of the changed overall transmission mode to obtain a comparison performance index, which comprises the following steps:
and carrying out LQ decomposition on the channel matrix of the changed overall transmission mode to obtain a comparison triangular matrix and a comparison unitary matrix, and squaring and summing diagonal elements of the triangular matrix under comparison to obtain the comparison performance index.
4. The precoding method for multiple multi-beam satellite communications according to claim 1, wherein the precoding employs TH precoding.
5. The precoding method for multiple multi-beam satellite communications according to claim 1, wherein precoding the signal to be transmitted according to the optimal channel matrix for the optimal overall transmission pattern comprises:
performing LQ decomposition on the optimal channel matrix of the optimal overall transmission mode to obtain an optimal triangular matrix A(b)And an optimal unitary matrix B(b)；
Calculating a conjugate matrix C of the optimal unitary matrix(b)Diagonal matrix D of the optimal triangular matrix(b)And a feedback matrix E for subtracting interference(b)The calculation formula is as follows:
E(b)＝D(b)A(b)
processing the vector x of the signal to be transmitted to obtain a transmission intermediate vector v(b)The calculation formula is:
wherein,
indicating the transmission vector formed by the data streams transmitted by the terminals under different point beams at the same time and using the same frequency band, Nd＝Ns×NbRepresenting the total number of transmitted data streams, NbRepresenting the number of spot beams, N, of a multibeam satellitesRepresenting the number of multi-beam satellites; m (-) represents a modulo operation,
6. a multi-beam satellite communication system, comprising:
a gateway station, configured to perform multi-carrier modulation on a signal to be transmitted after constellation mapping by using the precoding method for multiple multi-beam satellite communication according to any one of claims 1 to 5 to obtain a modulated signal;
a plurality of multi-beam satellites for transmitting the modulated signal according to the optimal transmission mode in the precoding method for multi-beam satellite communication according to any one of claims 1 to 5;
and the ground terminal receives the modulation signal transmitted by the multi-beam satellite and performs multi-carrier demodulation, precoding decoding and constellation demapping.
7. The multi-beam satellite communication system of claim 6, wherein the multi-beam satellite adds white gaussian noise to the modulated signal.
8. The multi-beam satellite communication system according to claim 7, wherein the constellation-mapped signal to be transmitted using the precoding method for multiple multi-beam satellite communication according to any one of claims 1 to 5, comprises:
performing LQ decomposition on the optimal channel matrix of the optimal overall transmission mode to obtain an optimal triangular matrix A(b)And an optimal unitary matrix B(b)；
Calculating a conjugate matrix C of the optimal unitary matrix(b)Diagonal matrix D of the optimal triangular matrix(b)And a feedback matrix E for subtracting interference(b)The calculation formula is as follows:
E(b)＝D(b)A(b)
processing the vector x of the signal to be transmitted to obtain a transmission intermediate vector v(b)The calculation formula is:
wherein,
indicating the transmission vector formed by the data streams transmitted by the terminals under different point beams at the same time and using the same frequency band, Nd＝Ns×NbRepresenting the total number of transmitted data streams, NbRepresenting the number of spot beams, N, of a multibeam satellitesRepresenting the number of multi-beam satellites; the function M represents a modulo operation that is,
9. the multi-beam satellite communication system according to claim 8, characterized in that said ground terminal receives vector y of said modulated signal(b)Comprises the following steps:
wherein,
the receiving vector is composed of data streams which are transmitted by terminals under different point beams and use the same frequency band at the same time;
representing a random vector of zero-mean complex Gaussian white noise superimposed on the data stream, the noise variance of each term being
Gamma is a scaling factor for controlling the transmit power; dTHP and dTHP are two TH precoding deployment modes, and the dTHP is used for converting a diagonal matrix D into a diagonal matrix D(b)Placed at a terminal, cTHP diagonal matrix D(b)Placing at a gateway station;
calculating a received vector y(b)At each receiving end by
Obtaining a received intermediate vector y and a decoded vector
The calculation formula is as follows:
the received intermediate vector y is a pair of received vectors y(b)Performing line permutation to obtain a vector, decoding the vector
Is a vector obtained by performing a modulo operation on the vector y, and the function M represents the modulo operation.
10. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the steps of the method according to any of claims 1 to 9 are implemented when the processor executes the program.
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