CN113194484B - Large-scale access method based on inter-satellite cooperation - Google Patents

Large-scale access method based on inter-satellite cooperation Download PDF

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CN113194484B
CN113194484B CN202110346423.9A CN202110346423A CN113194484B CN 113194484 B CN113194484 B CN 113194484B CN 202110346423 A CN202110346423 A CN 202110346423A CN 113194484 B CN113194484 B CN 113194484B
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褚建杭
陈晓明
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Zhejiang University ZJU
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    • 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
    • H04W16/18—Network planning tools
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
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    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/18521—Systems of inter linked satellites, i.e. inter satellite service
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • 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
    • H04W16/24—Cell structures
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    • H04W—WIRELESS COMMUNICATION NETWORKS
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    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
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Abstract

The invention discloses a large-scale access method based on inter-satellite cooperation. And a plurality of low-orbit satellites adopt a multi-beam technology at the same time, so that the whole system capacity is increased. Each satellite covers multiple regions, satellite users within each region share the same beam, and overlapping coverage areas may exist between adjacent satellites, thereby generating inter-satellite interference. Each satellite obtains the channel state information of each user by utilizing channel estimation, adjacent satellites share the channel state information of the users in the overlapped area through inter-satellite links, then the transmitted signal of each wave beam is subjected to superposition coding according to the channel information, and finally the signal subjected to superposition coding is transmitted out through an antenna. After receiving the signals, the users firstly decode the user signals with weak channel gain in the beam area, remove the signals of the users and finally decode the signals of the users. The invention provides an effective wireless access method for realizing space-based large-scale information network.

Description

Large-scale access method based on inter-satellite cooperation
Technical Field
The invention relates to the field of wireless communication, in particular to a large-scale access method based on inter-satellite cooperation.
Background
In recent years, fifth generation (5G) mobile communication networks are gradually popularized, 5G applications and technical innovations are continuously emerging, and the service capacity of the terrestrial communication networks reaches an unprecedented peak. However, there is a long movement away from the vision of "accessing a communication network anytime and anywhere", such as in many remote areas, such as deserts, mountains and oceans, where the communication network still does not have complete coverage, which allows many correspondents to shift their eyes from a ground-based communication network to a space-based communication network.
The service area of a terrestrial network typically does not achieve 100% coverage around the globe due to geographical location and economic cost, among other factors. In extreme areas, the difficulty and cost of deploying communication devices is enormous. Space-based communication networks based on low-orbit satellites can avoid these problems, and thus attract unprecedented attention. The low-orbit satellite has the characteristics of low cost and small time delay, and after a plurality of low-orbit satellites are jointly networked, user information in a certain area can be transmitted to any corner on the earth through an inter-satellite link, and a communication network covers the whole world and forms effective complementation with a ground network. Therefore, multi-satellite networks based on inter-satellite cooperation will be an essential part of future communication networks.
In addition, future wireless networks will need to support simultaneous access of a large number of internet of things devices. In the currently widely adopted orthogonal multiple access technology, such as Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA), one radio resource block can only be allocated to one mobile terminal, and the requirement for accessing a large amount of internet of things devices cannot be met. In this case, a non-orthogonal multiple access technology has been studied in a large amount. The non-orthogonal technology is generally divided into two categories of power domain and code domain, and the power domain non-orthogonal multiple access technology is convenient to realize, so that the power domain non-orthogonal multiple access technology is adopted in the text. The non-orthogonal multi-access technology mainly utilizes superposition coding of a transmitting end and serial interference cancellation of a receiving end to realize efficient multi-user access. Due to the limitation of serial interference performance, the bit error rate is greatly increased when the number of access users is too large. Therefore, it is necessary to divide the users into a plurality of clusters (i.e., different satellite beam coverage areas) and perform serial interference cancellation only in each cluster, thereby effectively reducing the computational complexity of the users. However, new inter-cluster interference may occur between different clusters, and inter-network interference may also occur between different satellite networks due to the same frequency band.
In order to further improve the performance of the non-orthogonal multiple access technology, various types of interference must be effectively suppressed, i.e. an effective beamforming technology needs to be adopted.
Disclosure of Invention
The invention aims to solve the problem that the coverage area of the existing ground communication network is limited, designs a multi-satellite communication network to provide an efficient access method for future wireless communication, and further provides a large-scale access method based on inter-satellite cooperation. The invention combines the non-orthogonal multiple access technology with the multi-satellite communication network to establish a large-scale space-based information network, and can effectively make up for the deficiency of the ground-based communication network, thereby further improving the capability of the current communication system and realizing the global coverage and supporting the access of mass equipment.
The invention adopts the following specific technical scheme:
a large-scale access method based on inter-satellite cooperation comprises the following steps:
1) a first satellite and a second satellite collaboratively serve a plurality of users, the satellite users belong to different satellite beam coverage areas according to the areas in which the satellite users are located, the first satellite has M satellite beams, and the second satellite has L satellite beams; the first satellite and the second satellite have A wave beams covering an overlapping area, wherein B users in the overlapping area belong to the first satellite, the second satellite generates interference to signals of the B users in the overlapping area, and (A-B) users in the overlapping area belong to the second satellite, and the first satellite generates interference to signals of the (A-B) users in the overlapping area;
2) the ground gateway station sends the user channel state information to the first satellite or the second satellite through a feedback link, and the first satellite obtains the nth satellite user UE in the mth satellite area1，m，nChannel state information h of1，m，nThe second satellite obtains the s satellite user UE in the l satellite area2，l，sChannel state information h of2，l，sAnd the user channel state information of the overlapping area is transmitted to the adjacent satellite through the inter-satellite link; m is an element of [0, M ]]，l∈[0，L]；
3) The first satellite is a satellite user UE1，m，nSignal x of1，m，nPower allocation factor alpha in allocation region1，m，nAnd a transmission beam w is designed for the mth satellite region1，mThe second satellite is a satellite user UE2，l，sSignal x of2，l，sPower allocation factor alpha in allocation region2，l，sAnd a transmission beam w is designed for the ith satellite region2，l；
4) According to the power division factor alpha1，m，，nThe first satellite performs superposition coding on the signals of all satellite users in the satellite area and then transmits a beam w1，mBeamforming generation of superposition coded signalsBroadcast signal x1(ii) a The second satellite carries out superposition coding on the signals of all satellite users in the satellite area and then transmits a wave beam w2，lBeamforming the superposition coded signal to generate a broadcast signal x2(ii) a Then each satellite broadcasts respective broadcast signals to respective users through a downlink channel;
5) after receiving the signals transmitted by the satellite, each satellite user performs serial interference cancellation on the user signals in the same area, and then decodes the signals of the user.
Preferably, the beam design method in step 3) is:
a) initializing a transmit beam
Figure BDA0003000868610000031
Figure BDA0003000868610000032
Wherein
Figure BDA0003000868610000033
And
Figure BDA0003000868610000034
are all feasible points in the previous iteration, P1，maxIs the maximum transmission power, P, of the first satellite2，maxIs the maximum transmit power of the second satellite; power allocation factor in first satellite region
Figure BDA0003000868610000035
NmRepresenting a total number of users in the mth satellite region, i representing an ith user in the mth beam of the first satellite; power allocation factor in the second satellite region
Figure BDA0003000868610000036
SlRepresenting the total number of users in the ith satellite area, wherein i represents the ith user of the ith beam of the second satellite;
b) due to the rapid change of the satellite channel, the channel state information acquired by each satellite is stored with the actual channelIn phase deviation; the actual user channel state information of the first satellite is
Figure BDA0003000868610000037
The second satellite actual user channel state information is
Figure BDA0003000868610000038
Interference channel of first satellite to second satellite user in overlapping area
Figure BDA0003000868610000039
Figure BDA00030008686100000310
The interference channel of the second satellite to the first satellite user in the overlapping region is
Figure BDA00030008686100000311
All superscripts j in the formula represent imaginary numbers;
for the user of the first satellite:
Figure BDA00030008686100000312
A1，m，n＝real(Z1，m，n)，B1，m，n＝imag(Z1，m，n)，E1，m，n＝f1(A1，m，n)，e1，m，n＝f2(B1，m，n)，
Figure BDA00030008686100000313
A2，m，n＝real(Z2，m，n)，B2，m，n＝imag(Z2，m，n)，E2，m，n＝f1(A2，m，n)，e2，m，n＝f2(B2，m，n)，
Figure BDA0003000868610000041
Figure BDA0003000868610000042
Figure BDA0003000868610000043
for the users of the second satellite:
Figure BDA0003000868610000044
A2，l，s＝real(Z2，l，s)，B2，l，s＝imag(Z2，l，s)，E2，l，s＝f1(A2，l，s)，e2，l，s＝f2(B2，l，s)，
Figure BDA0003000868610000045
A1，l，s＝real(Z1，l，s)，B1，l，s＝imag(Z1，l，s)，E1，l，s＝f1(A1，l，s)，e1，l，s＝f2(B1，l，s)，
Figure BDA0003000868610000046
Figure BDA0003000868610000047
Figure BDA0003000868610000048
Figure BDA0003000868610000049
Figure BDA00030008686100000410
for a certain satellite user, the subscript j represents the jth beam coverage area of the satellite, and i represents the ith user in a certain beam coverage area of the satellite;
wherein the subscript [1, m, n ]]Representing a user parameter of the first satellite, i.e. within the mth satellite beam area of the first satelliteThe nth user; subscript [2, l, s ]]Representing a second satellite user parameter, i.e., representing an s-th satellite user within an l-th satellite beam area of the second satellite; subscript [2, m, n ]]Representing a parameter acquired by a first satellite user in an overlapping area by a second satellite; subscript [1, l, s ]]Representing a parameter acquired by a first satellite to a second satellite user in an overlapping area; f. of1，m，n，f2，m，n，f1，l，sAnd f2，l，sAre all intermediate parameters;
Figure BDA00030008686100000411
and
Figure BDA00030008686100000412
representing the noise variance of the first satellite user and the second satellite user respectively;
Figure BDA00030008686100000413
and
Figure BDA00030008686100000414
respectively obtaining imperfect channel state information of a satellite channel of a first satellite user and imperfect channel state information of an interference channel of the first satellite to a second satellite user in an overlapping area;
Figure BDA0003000868610000051
and
Figure BDA0003000868610000052
respectively obtaining imperfect channel state information of a satellite channel of a second satellite user and imperfect channel state information of an interference channel of the second satellite to a first satellite user in an overlapping area; theta1，m，nAnd theta1，l，sThe phase errors of a first satellite user satellite channel and a first satellite to a second satellite user interference channel in an overlapping area are respectively; theta2，l，sAnd theta2，m，nThe phase errors of a second satellite user satellite channel and a second satellite to a first satellite user interference channel in an overlapping area are respectively;
Figure BDA0003000868610000053
and
Figure BDA0003000868610000054
the covariance matrix of the phase errors of the satellite channel of the first satellite user and the interference channel of the second satellite user in the overlapping area of the first satellite are respectively;
Figure BDA0003000868610000055
and
Figure BDA0003000868610000056
the covariance matrix of the phase errors of the satellite channel of the first satellite user and the interference channel of the second satellite user in the overlapping area of the first satellite are respectively; w1，m＝w1，mw1，m HIs a first satellite beam matrix, W2，l＝w2，lw2，l HIs a second satellite beam matrix, P1，kAnd P2，kAntenna power limits for a first satellite having K1 antennas and a second satellite having K2 antennas, Z[i，j]Represents the ith row and jth column element of matrix Z,
Figure BDA0003000868610000057
the representative matrix T is a semi-positive definite matrix; eta1，m，nAnd η2，l，sThe residual interference coefficient, gamma, generated by imperfect decoding caused by successive interference cancellation technique when the first satellite user and the second satellite user decode respectively1，m，nAnd gamma2，l，sMinimum signal to interference and noise ratio requirements, p, for the first satellite user and the second satellite user, respectively1，m，nAnd p2，l，sThe interruption probability that the first satellite user and the second satellite user can not meet the communication signal-to-interference-and-noise ratio requirement is respectively, a1，m，n，b1，m，nAnd a2，l，s，b2，l，sIs an auxiliary parameter, E1，m，n、Z1，m，n、T1，m，n、A1，m，n、B1，m，n、
Figure BDA0003000868610000058
e1，m，n、e1，l，sAnd E2，m，n、Z2，l，s、T2，l，s、A2，l，s、B2，l，s、
Figure BDA0003000868610000059
e2，m，n、e2，l，sAre all intermediate variables; tr (Z) is a trace of the matrix Z, H in the upper right corner of the variable represents a Hermite transpose, and 2 in the upper right corner of the variable represents a square; f. of1(A) And f2(B) Is two linear transformations, of which
Figure BDA00030008686100000510
K represents the number of columns of the matrix; δ (m, n) and δ (l, s) take values of 0 or 1, wherein 1 represents that the nth user in the mth beam of the first satellite is interfered by the second satellite or the mth user in the mth beam of the second satellite is interfered by the first satellite, and 0 represents that the user is not interfered; i isK1And IK2Is an identity matrix, with subscript K denoting the dimension;
solving the minimum value of each transmitting power by using an iterative method, wherein the minimum value is
Figure BDA0003000868610000061
Figure BDA0003000868610000062
Each iteration obtains corresponding W1，mAnd W2，lUp to W1，mAnd W2，lWhen the rank approaches 1, a singular value decomposition method is utilized to obtain a final wave beam w1，mAnd w2，lAnd in each iteration process, an interior point method is adopted or a CVX tool package is directly called to solve.
Further, the step 4) specifically comprises: the total signal transmitted by the first satellite for all users is
Figure BDA0003000868610000063
Wherein is alpha1，m，nAllocating a factor, w, to the power in the beam region1，mIs the m < th > oneTransmission beam of the region, x1，m，nIs the signal of the nth user in the mth satellite beam area; the total signal transmitted by the second satellite for all users is
Figure BDA0003000868610000064
Wherein alpha is2，l，sIs the power allocation factor, w, within the beam region2，lIs a transmission beam in the l region, x2，l，sIs the signal of the s-th user in the area of the l-th satellite beam.
Further, the method for canceling the serial interference in step 5) includes: any satellite user firstly decodes the signals of users with weaker channel gain than the satellite user in the same area, subtracts the signals from the received signals, and finally decodes the satellite user's signal.
Compared with the prior art, the invention has the following beneficial effects:
the large-scale access method based on inter-satellite cooperation provided by the invention overcomes the defect that global coverage cannot be realized by a land Internet of things, makes global communication seamless connection possible, and has the advantages of high spectrum efficiency, capability of effectively inhibiting interference, actual and reliable scene and the like.
Drawings
FIG. 1 is a block diagram of the method of the present invention;
FIG. 2 is a graphical comparison of the minimum power required for the method of the present invention at different phase error magnitudes;
fig. 3 is a diagram showing a comparison of the minimum power required in the method of the present invention and the orthogonal access method (time division multiplexing).
Detailed Description
The invention will be further elucidated and described with reference to the drawings and the detailed description. The technical features of the embodiments of the present invention can be combined correspondingly without mutual conflict.
The system block diagram of the large-scale access method based on inter-satellite cooperation is shown in fig. 1, and a plurality of low-orbit satellites simultaneously adopt the multi-beam technology to increase the whole system capacity. Each satellite covers multiple regions, satellite users within each region share the same beam, and overlapping coverage areas may exist between adjacent satellites, thereby generating inter-satellite interference. Each satellite obtains the channel state information of each user by utilizing channel estimation, adjacent satellites share the channel state information of users in an overlapped area through inter-satellite links, then superposition coding is carried out on the transmitting signal of each wave beam according to the channel information, and finally the signal after superposition coding is transmitted out through a wave beam forming network. After receiving the signals, the users firstly decode the user signals with weak channel gain in the beam area, remove the signals of the users and finally decode the signals of the users.
Wherein, the satellite 1 has K1Root antenna, satellite 2 having K2And 1 antenna is configured for each satellite user. Users in different beam areas share one beam, so that successive interference cancellation is performed in respective areas, thereby reducing the complexity of successive interference cancellation. The satellite earth station receives training sequences from users to estimate partial channel state information. Based on the obtained partial channel state information, each satellite designs a robust transmission beam for each user signal in each region. After receiving the signal, the user performs serial interference cancellation on the signal in the area to further reduce interference and improve the performance of the system.
The specific technical scheme adopted by the invention comprises the following steps:
1) a first satellite and a second satellite collaboratively serve a plurality of users, the satellite users belong to different satellite beam coverage areas according to the areas where the satellite users are located, the first satellite has M satellite beams, and the second satellite has L satellite beams; the first satellite and the second satellite have a beams covering an overlap region, wherein users in the B overlap regions belong to the first satellite, and the second satellite interferes with signals of the B overlap region users, and (a-B) users in the overlap region belong to the second satellite, and the first satellite interferes with signals of the (a-B) overlap region users;
2) the ground gateway station sends the user channel state information to the first satellite or the second satellite through a feedback link, and the first satellite obtains the mth satelliteNth satellite user UE in area1，m，nChannel state information h of1，m，nThe second satellite obtains the s satellite user UE in the l satellite area2，l，sChannel state information h of2，l，sAnd the user channel state information of the overlapping area is transmitted to the adjacent satellite through the inter-satellite link; wherein M is [0, M ]]，l∈[0，L]；
3) The first satellite is a satellite user UE1，m，nSignal x of1，m，nPower allocation factor alpha in allocation region1，m，nAnd a transmission beam w is designed for the mth satellite region1，mThe second satellite is a satellite user UE2，l，sSignal x of2，l，sPower allocation factor alpha in allocation region2，l，sAnd a transmission beam w is designed for the ith satellite region2，l。
In practical application, the beam design method in step 3) may adopt the following method:
a) initializing a transmit beam
Figure BDA0003000868610000081
Figure BDA0003000868610000082
Wherein
Figure BDA0003000868610000083
And
Figure BDA0003000868610000084
are all feasible points in the previous iteration, P1，maxIs the maximum transmission power, P, of the first satellite2，maxIs the maximum transmit power of the second satellite; power allocation factor in first satellite region
Figure BDA0003000868610000085
NmRepresenting the total number of users in the mth satellite area, i representing the ith user in the mth wave beam of the first satellite; power allocation factor in the second satellite region
Figure BDA0003000868610000086
SlRepresenting the total number of users in the ith satellite area, wherein i represents the ith user of the ith beam of the second satellite;
b) due to the rapid change of satellite channels, the channel state information acquired by each satellite has phase deviation with an actual channel; the actual user channel state information of the first satellite is
Figure BDA0003000868610000087
The second satellite actual user channel state information is
Figure BDA0003000868610000088
Interference channel of a first satellite to a second satellite user in an overlapping region
Figure BDA0003000868610000089
Figure BDA00030008686100000810
The interference channel of the second satellite to the first satellite user in the overlapping region is
Figure BDA00030008686100000811
Wherein all superscripts j represent imaginary numbers;
for the user of the first satellite, the following is specified:
Figure BDA00030008686100000812
A1，m，n＝real(Z1，m，n)，B1，m，n＝imag(Z1，m，n)，E1，m，n＝f1(A1，m，n)，e1，m，n＝f2(B1，m，n)，
Figure BDA00030008686100000813
A2，m，n＝real(Z2，m，n)，B2，m，n＝imag(Z2，m，n)，E2，m，n＝f1(A2，m，n)，e2，m，n＝f2(B2，m，n)，
Figure BDA00030008686100000814
Figure BDA00030008686100000815
Figure BDA0003000868610000091
for the user of the second satellite, the following is specific:
Figure BDA0003000868610000092
A2，l，s＝real(Z2，l，s)，B2，l，s＝imag(Z2，l，s)，E2，l，s＝f1(A2，l，s)，e2，l，s＝f2(B2，l，s)，
Figure BDA0003000868610000093
A1，l，s＝real(Z1，l，s)，B1，l，s＝imag(Z1，l，s)，E1，l，s＝f1(A1，l，s)，e1，l，s＝f2(B1，l，s)，
Figure BDA0003000868610000094
Figure BDA0003000868610000095
Figure BDA0003000868610000096
Figure BDA0003000868610000097
Figure BDA0003000868610000098
for a certain satellite user, the subscript j represents the jth beam coverage area of the satellite, and i represents the ith user in a certain beam coverage area of the satellite;
wherein the subscript [1, m, n ]]Representing a first satellite user parameter, i.e., representing an nth user within an mth satellite beam region of the first satellite; subscript [2, l, s ]]Representing a second satellite user parameter, i.e., representing an s-th satellite user within an l-th satellite beam area of the second satellite; subscript [2, m, n ]]Representing a parameter acquired by a first satellite user in an overlapping area by a second satellite; subscript [1, l, s ]]Representing a parameter acquired by a first satellite to a second satellite user in an overlapping area; f. of1，m，n，f2，m，n，f1，l，sAnd f2，l，sAre all intermediate parameters;
Figure BDA0003000868610000099
and
Figure BDA00030008686100000910
representing the noise variance of the first satellite user and the second satellite user respectively;
Figure BDA00030008686100000911
and
Figure BDA00030008686100000912
respectively obtaining imperfect channel state information of a satellite channel of a first satellite user and imperfect channel state information of an interference channel of the first satellite to a second satellite user in an overlapping area;
Figure BDA00030008686100000913
and
Figure BDA00030008686100000914
respectively, imperfect channel state information of a satellite channel of a second satellite user and imperfect channel state information of an interference channel of the second satellite to a first satellite user in an overlapping area; theta1，m，nAnd theta1，l，sThe phase errors of a first satellite user satellite channel and a first satellite to a second satellite user interference channel in an overlapping area are respectively; theta2，l，sAnd theta2，m，nThe phase errors of a second satellite user satellite channel and a second satellite to a first satellite user interference channel in an overlapping area are respectively;
Figure BDA0003000868610000101
and
Figure BDA0003000868610000102
the covariance matrix of the phase errors of the satellite channel of the first satellite user and the interference channel of the second satellite user in the overlapping area of the first satellite are respectively;
Figure BDA0003000868610000103
and
Figure BDA0003000868610000104
the covariance matrix of the phase errors of the satellite channel of the first satellite user and the interference channel of the second satellite user in the overlapping area of the first satellite respectively; w1，m＝w1，mw1，m HIs a first satellite beam matrix, W2，l＝w2，lw2，l HIs a second satellite beam matrix, P1，kAnd P2，kAntenna power limits for a first satellite having K1 antennas and a second satellite having K2 antennas, Z[i，j]Represents the ith row and jth column element of matrix Z,
Figure BDA0003000868610000105
the representative matrix T is a semi-positive definite matrix; eta1，m，nAnd η2，l，sThe residual interference coefficient, gamma, generated by imperfect decoding caused by successive interference cancellation technique when the first satellite user and the second satellite user decode respectively1，m，nAnd gamma2，l，sMinimum signal to interference plus noise ratio requirements, p, for the first satellite user and the second satellite user, respectively1，m，nAnd p2，l，sAre respectively the firstThe probability of interruption that a satellite user and a second satellite user cannot meet the SINR requirement of communication, a1，m，n，b1，m，nAnd a2，l，s，b2，l，sIs an auxiliary parameter, E1，m，n、Z1，m，n、T1，m，n、A1，m，n、B1，m，n、
Figure BDA0003000868610000106
e1，m，n、e1，l，sAnd E2，m，n、Z2，l，s、T2，l，s、A2，l，s、B2，l，s、
Figure BDA0003000868610000107
e2，m，n、e2，l，sAre all intermediate variables; tr (Z) refers to the trace of the matrix Z, H in the upper right corner of the variable represents Hermite transpose, and 2 in the upper right corner of the variable represents the square; f. of1(A) And f2(B) Is two linear transformations, of which
Figure BDA0003000868610000108
K represents the number of columns of the matrix; δ (m, n) and δ (l, s) take values of 0 or 1, wherein 1 represents that the nth user in the mth beam of the first satellite is interfered by the second satellite or the mth user in the mth beam of the second satellite is interfered by the first satellite, and 0 represents that the user is not interfered; i isK1And IK2Is an identity matrix, with subscript K denoting the dimension;
solving the minimum value of each transmitting power by using an iterative method, wherein the minimum value is
Figure BDA0003000868610000109
Figure BDA00030008686100001010
Each iteration obtains corresponding W1，mAnd W2，lUp to W1，mAnd W2，lWhen the rank approaches 1, a singular value decomposition method is utilized to obtain a final wave beam w1，mAnd w2，lUsing interior points in each iterationAnd (4) solving by a method or directly calling a CVX tool package.
4) According to the power division factor alpha1，m，nThe first satellite performs superposition coding on the signals of all satellite users in the satellite area and then transmits a beam w1，mBeamforming the superposition coded signal to generate a broadcast signal x1(ii) a The second satellite performs superposition coding on the signals of all satellite users in the satellite area and then transmits a beam w2，lBeamforming the superposition coded signal to generate a broadcast signal x2(ii) a Each satellite then broadcasts a respective broadcast signal to a respective user via a downlink channel.
In practical application, the following method can be adopted in the step 4): the total signal transmitted by the first satellite for all users is
Figure BDA0003000868610000111
Wherein is alpha1，m，nAllocating a factor, w, to the power in the beam region1，mIs the transmission beam of the m-th region, x1，m，nIs the signal of the nth user in the mth satellite beam area; the total signal transmitted by the second satellite for all users is
Figure BDA0003000868610000112
Wherein alpha is2，l，sIs the power allocation factor, w, within the beam region2，lFor the transmission beam in the l region, x2，l，sIs the signal of the s-th user in the area of the l-th satellite beam.
5) After receiving the signals transmitted by the satellite, each satellite user performs serial interference cancellation on the user signals in the same area, and then decodes the signals of the user.
In practical application, the method for canceling the serial interference in step 5) may specifically adopt the following steps: any satellite user firstly decodes the signals of users with weaker channel gain than the user in the same area, subtracts the signals from the received signals, and finally decodes the signal of the user.
Computer simulation shows that, as shown in fig. 2, the large-scale access method based on inter-satellite cooperation provided by the invention can effectively resist the interference caused by imperfect serial interference cancellation. In addition, fig. 3 shows that the method of the present invention is sensitive to the outage probability, and when the power required for the outage probability is much larger than the outage probability, a nonlinear relationship exists between the terminal probability and the power consumption. Therefore, the large-scale access method based on inter-satellite cooperation provided by the invention provides a feasible and effective large-scale user access method for a high-efficiency information network covering the whole world.

Claims (4)

1. A large-scale access method based on inter-satellite cooperation is characterized by comprising the following steps:
1) a first satellite and a second satellite collaboratively serve a plurality of users, the satellite users belong to different satellite beam coverage areas according to the areas where the satellite users are located, the first satellite has M satellite beams, and the second satellite has L satellite beams; the first satellite and the second satellite have A wave beams covering an overlapping area, wherein B users in the overlapping area belong to the first satellite, the second satellite generates interference to signals of the B users in the overlapping area, and (A-B) users in the overlapping area belong to the second satellite, and the first satellite generates interference to signals of the (A-B) users in the overlapping area;
2) the ground gateway station sends the user channel state information to the first satellite or the second satellite through a feedback link, and the first satellite obtains the nth satellite user UE in the mth satellite area1，m，nChannel state information h of1，m，nThe second satellite obtains the s satellite user UE in the l satellite area2，l，sChannel state information h of2，l，sAnd the user channel state information of the overlapping area is transmitted to the adjacent satellite through the inter-satellite link; m is an element of [0, M ]]，l∈[0，L]；
3) The first satellite is a satellite user UE1，m，nSignal x of1，m，nPower allocation factor alpha in allocation region1，m，nAnd a transmission beam w is designed for the mth satellite region1，mThe second satellite is a satellite user UE2，l，sSignal x of2，l，sWithin the distribution areaPower division factor alpha2，l，sAnd a transmission beam w is designed for the ith satellite region2，l；
4) According to the power division factor alpha1，m，nThe first satellite performs superposition coding on the signals of all satellite users in the satellite area and then transmits a beam w1，mBeamforming the superposition coded signal to generate a broadcast signal x1(ii) a The second satellite performs superposition coding on the signals of all satellite users in the satellite area and then transmits a beam w2，lBeamforming the superposition coded signal to generate a broadcast signal x2(ii) a Then each satellite broadcasts the respective broadcast signal to the respective user through a downlink channel;
5) after receiving the signals transmitted by the satellite, each satellite user performs serial interference cancellation on the user signals in the same area, and then decodes the signals of the user.
2. The massive access method based on inter-satellite cooperation according to claim 1, wherein the beam design method in step 3) is:
a) initializing a transmit beam
Figure FDA0003560231090000021
Figure FDA0003560231090000022
Wherein
Figure FDA0003560231090000023
And
Figure FDA0003560231090000024
are all feasible points in the previous iteration, P1，maxIs the maximum transmission power, P, of the first satellite2，maxIs the maximum transmit power of the second satellite; power allocation factor in first satellite region
Figure FDA0003560231090000025
NmRepresenting the total number of users in the mth satellite area, i representing the ith user in the mth wave beam of the first satellite; power allocation factor in the second satellite region
Figure FDA0003560231090000026
SlRepresenting the total number of users in the ith satellite area, wherein i represents the ith user of the ith beam of the second satellite;
b) due to the rapid change of satellite channels, the channel state information acquired by each satellite has phase deviation with an actual channel; the actual user channel state information of the first satellite is
Figure FDA0003560231090000027
The second satellite actual user channel state information is
Figure FDA0003560231090000028
Interference channel of first satellite to second satellite user in overlapping area
Figure FDA0003560231090000029
Figure FDA00035602310900000210
The interference channel of the second satellite to the first satellite user in the overlap region is
Figure FDA00035602310900000211
All superscripts j in the formula represent imaginary numbers;
for the users of the first satellite:
Figure FDA00035602310900000212
A1，m，n＝real(Z1，m，n)，B1，m，n＝imag(Z1，m，n)，E1，m，n＝f1(A1，m，n)，e1，m，n＝f2(B1，m，n)，
Figure FDA00035602310900000213
A2，m，n＝real(Z2，m，n)，B2，m，n＝imag(Z2，m，n)，E2，m，n＝f1(A2，m，n)，e2，m，n＝f2(B2，m，n)，
Figure FDA00035602310900000214
Figure FDA00035602310900000215
Figure FDA00035602310900000216
Figure FDA0003560231090000031
Figure FDA0003560231090000032
for the user of the second satellite:
Figure FDA0003560231090000033
A2，l，s＝real(Z2，l，s)，B2，l，s＝imag(Z2，l，s)，E2，l，s＝f1(A2，l，s)，e2，l，s＝f2(B2，l，s)，
Figure FDA0003560231090000034
A1，l，s＝real(Z1，l，s)，B1，l，s＝imag(Z1，l，s)，E1，l，s＝f1(A1，l，s)，e1，l，s＝f2(B1，l，s)，
Figure FDA0003560231090000035
Figure FDA0003560231090000036
Figure FDA0003560231090000037
Figure FDA0003560231090000038
Figure FDA0003560231090000039
for a certain satellite user, the subscript j represents the jth beam coverage area of the satellite, and i represents the ith user in a certain beam coverage area of the satellite;
wherein the subscript [1, m, n ]]A parameter representing a first satellite user, i.e., representing an nth user within an mth satellite beam region of the first satellite; subscript [2, l, s ]]Representing a second satellite user parameter, i.e., representing an s-th satellite user within an l-th satellite beam area of the second satellite; subscript [2, m, n ]]Representing a parameter acquired by a first satellite user in an overlapping area by a second satellite; subscript [1, l, s ]]Representing a parameter acquired by a first satellite to a second satellite user in an overlapping area; f. of1，m，n，f2，m，n，f1，l，sAnd f2，l，sAre all intermediate parameters;
Figure FDA00035602310900000310
and
Figure FDA00035602310900000311
representing the noise variance of the first satellite user and the second satellite user respectively;
Figure FDA00035602310900000312
and
Figure FDA00035602310900000313
respectively obtaining imperfect channel state information of a satellite channel of a first satellite user and imperfect channel state information of an interference channel of the first satellite to a second satellite user in an overlapping area;
Figure FDA00035602310900000314
and
Figure FDA00035602310900000315
respectively obtaining imperfect channel state information of a satellite channel of a second satellite user and imperfect channel state information of an interference channel of the second satellite to a first satellite user in an overlapping area; theta1，m，nAnd theta1，l，sThe phase errors of a first satellite user satellite channel and a first satellite to a second satellite user interference channel in an overlapping area are respectively; theta2，l，sAnd theta2，m，nThe phase errors of a second satellite user satellite channel and a second satellite to a first satellite user interference channel in an overlapping area are respectively;
Figure FDA0003560231090000041
and
Figure FDA0003560231090000042
the covariance matrix of the phase errors of the satellite channel of the first satellite user and the interference channel of the second satellite user in the overlapping area of the first satellite are respectively;
Figure FDA0003560231090000043
and
Figure FDA0003560231090000044
the covariance matrix of the phase errors of the satellite channel of the first satellite user and the interference channel of the second satellite user in the overlapping area of the first satellite are respectively; w1，m＝w1，mw1，m HIs the first satelliteSatellite beam matrix, W2，l＝w2，lw2，l HIs a second satellite beam matrix, P1，kAnd P2，kAntenna power limits for a first satellite having K1 antennas and a second satellite having K2 antennas, Z[i，j]Represents the ith row and the jth column element of the matrix Z, and T is more than or equal to 0, and represents that the matrix T is a semi-positive definite matrix; eta1，m，nAnd η2，l，sThe residual interference coefficient, gamma, generated by imperfect decoding caused by successive interference cancellation technique when the first satellite user and the second satellite user decode respectively1，m，nAnd gamma2，l，sMinimum signal to interference and noise ratio requirements, P, for the first satellite user and the second satellite user, respectively1，m，nAnd p2，l，sThe interruption probability that the first satellite user and the second satellite user can not meet the communication signal-to-interference-and-noise ratio requirement is respectively, a1，m，n，b1，m，nAnd a2，l，s，b2，l，sIs an auxiliary parameter, E1，m，n、Z1，m，n、T1，m，n、A1，m，n、B1，m，n、
Figure FDA0003560231090000049
e1，m，n、e1，l，sAnd E2，m，n、Z2，l，s、T2，l，s、A2，l，s、B2，l，s、
Figure FDA0003560231090000045
e2，m，n、e2，l，sAre all intermediate variables; tr (Z) is a trace of the matrix Z, H in the upper right corner of the variable represents a Hermite transpose, and 2 in the upper right corner of the variable represents a square; f. of1(A) And f2(B) Is two linear transformations, of which
Figure FDA0003560231090000046
K represents the number of columns of the matrix; delta (m, n) and delta (l, s) are 0 or 1, wherein 1 represents that the nth user in the mth wave beam of the first satellite is interfered by the second satellite or the nth userThe s-th user in the l-th wave beam of the two satellites is interfered by the first satellite, and 0 represents no; i isK1And IK2Is an identity matrix, with subscript K denoting the dimension;
solving the minimum value of each transmitting power by using an iterative method, wherein the minimum value is
Figure FDA0003560231090000047
Figure FDA0003560231090000048
Each iteration obtains corresponding W1，mAnd W2，lUp to W1，mAnd W2，lWhen the rank approaches 1, a singular value decomposition method is utilized to obtain a final wave beam w1，mAnd w2，lAnd in each iteration process, an interior point method is adopted or a CVX tool package is directly called to solve.
3. The massive access method based on inter-satellite cooperation according to claim 2, wherein the step 4) is specifically: the total signal transmitted by the first satellite for all users is
Figure FDA0003560231090000051
Wherein alpha is1，m，nAllocating a factor, w, to the power in the beam region1，mIs the transmission beam of the m-th region, x1，m，nIs the signal of the nth user in the mth satellite beam area; the total signal transmitted by the second satellite for all users is
Figure FDA0003560231090000052
Wherein alpha is2，l，sIs the power allocation factor, w, within the beam region2，lIs a transmission beam in the l region, x2，l，sIs the signal of the s-th user in the area of the l-th satellite beam.
4. The massive access method based on inter-satellite cooperation according to claim 3, wherein the method for serial interference cancellation in step 5) is: any satellite user firstly decodes the signals of users with weaker channel gain than the satellite user in the same area, subtracts the signals from the received signals, and finally decodes the satellite user's signal.
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