CN109995496B - Pilot frequency distribution method of large-scale antenna system - Google Patents
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
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- H—ELECTRICITY
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- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
Abstract
The invention discloses a pilot frequency distribution method of a large-scale antenna system, which comprises the following steps: constructing a hypergraph; initialization: selecting two users of different cells with the largest positive weight value edge in the hypergraph, and allocating two orthogonal pilot frequencies to the two users; the users distributed with the pilot frequency form a distributed user set; allocating pilots to unallocated users, comprising: determining the highest priority unallocated user according to the hypergraph; determining an available pilot set of unallocated users having a highest priority; calculating the interference intensity sum of the pilot frequency in the available pilot frequency set when the unallocated user with the highest priority uses the pilot frequency, which is in the available pilot frequency set, to the allocated user using the same pilot frequency according to the hypergraph; allocating the pilot frequency with the minimum interference intensity sum to the unallocated user with the highest priority; updating the distributed user set; judging whether all users are allocated with pilot frequencies; if not, repeating the steps: the unallocated users are allocated with pilots. The invention improves the uplink and the speed of the system.
Description
Technical Field
The invention relates to the field of communication, in particular to a pilot frequency distribution method of a large-scale antenna system.
Background
With the development of mobile communication networks, the number of mobile users and mobile devices is rapidly increasing, and the demand for mobile data traffic is explosively increasing. The demand for mobile traffic for various new services is expected to increase by thousands of orders of magnitude over the current demand for the next decade, requiring new technologies with higher capacity than existing network deployments. However, the expected traffic growth in the future far exceeds the current mobile network bearer capability, and new communication technologies need to be introduced. Among them, a large-scale Multiple-Input Multiple-Output (MIMO) technology attracts attention. In a massive MIMO system, a Base Station (BS) having several hundred antenna arrays simultaneously serves a plurality of User terminals (UEs) in the same time-frequency resource, each UE has a single or multiple antennas, and the Base Station having multiple antennas simultaneously transmits independent data streams to the multiple terminals.
Research shows that the massive MIMO technology can greatly improve the spectrum efficiency and the energy efficiency of a system by utilizing the array gain of the massive MIMO technology to support the spatial multiplexing transmission of more users. Also, when the number of antennas at the base station end tends to infinity, the multiuser multi-cell massive MIMO system exhibits many excellent characteristics: the channel vectors among different users tend to be orthogonal, and the interference among the users in the same cell tends to be zero; the effect of uncorrelated noise in the system fades away and the small scale fading of the channel is averaged out. Although massive MIMO has many technical advantages, as the number of base station antennas increases, the performance of the system, such as user rate, is affected by the problem of pilot pollution caused by unreasonable pilot allocation.
The conventional pilot allocation scheme randomly allocates pilot sequences to each user in a cell, which brings about relatively serious pilot pollution. In the prior art, various optimization methods exist. For example, the pilot allocation scheme based on the greedy algorithm and the tabu search algorithm can sequentially obtain the local optimal solution of each pilot allocation user by continuously reducing the solution space dimension, thereby reducing the pilot allocation complexity. The learners also use artificial intelligence algorithms to solve, such as genetic algorithms, artificial fish swarm algorithms and particle swarm algorithms, and use the characteristics of the algorithms to break through the limitation of local optimal solutions and obtain pilot frequency distribution schemes similar to global optimal solutions, but the time complexity of the optimization algorithms is too high, so that the optimization algorithms are not suitable for practical scenes.
Disclosure of Invention
The invention aims to provide a pilot frequency distribution method of a large-scale antenna system, which can ensure the minimum uplink transmission rate of a user and improve the uplink and the rate of the system.
In order to achieve the above object, the present invention provides a pilot allocation method for a large-scale antenna system, comprising the following steps: constructing a hypergraph: the edge in the hypergraph represents the interference strength between two users of a large-scale antenna system, and the larger the weight of the edge is, the more serious the pilot frequency pollution caused by distributing the same pilot frequency to the two users is; the super-edge in the hypergraph represents the interference strength between users of three adjacent cells in a large-scale antenna system; initialization: selecting two users of different cells with the largest positive weight value edge in the hypergraph, and allocating two orthogonal pilot frequencies to the two users; the users distributed with the pilot frequency form a distributed user set; allocating pilots to unallocated users, comprising: determining the highest priority unallocated user according to the hypergraph; determining an available pilot set of unallocated users having a highest priority; calculating the interference intensity sum of the pilot frequency in the available pilot frequency set when the unallocated user with the highest priority uses the pilot frequency, which is in the available pilot frequency set, to the allocated user using the same pilot frequency according to the hypergraph; allocating the pilot frequency with the minimum interference intensity sum to the unallocated user with the highest priority; updating the distributed user set; judging whether all users are allocated with pilot frequencies; if not, repeating the steps: the unallocated users are allocated with pilots.
Further, the user with the greatest weight of the edge between the unallocated user and the allocated user and the unallocated pilot is determined as the highest priority unallocated user.
Further, the method for determining the available pilot frequency set comprises the following steps: users in the same cell use orthogonal pilot frequency sequences, and unassigned pilot frequencies in the same cell form a first set; and the pilots used by other users in the super edge where the highest priority unallocated user is located form a second set; the pilots obtained after excluding the pilots in the second set from the first set constitute the available set of pilots.
Further, wherein if the available pilot set is an empty set, then: calculating the interference intensity sum of the unallocated users with the same pilot frequency when the unallocated user with the highest priority uses the pilot frequency in the unallocated pilot frequency set of the cell in which the unallocated user is positioned; the pilot that brings the smallest sum of interference strengths is assigned to the unassigned user with the highest priority.
Further, coloring the user according to the priority order of the user in the hypergraph.
Further, wherein the hypergraph comprises an independent interference subgraph G1＝(V,E1W (e)) setV＝{<i,k>I is more than or equal to 1 and less than or equal to L, K is more than or equal to 1 and less than or equal to K is taken as a vertex set, the vertex represents a user, and the set E1Is a set of edges formed by connecting two vertexes, each edge has a positive weight w (e) and represents the interference strength between two users.
Further, the interference strength between users is calculated by utilizing the large-scale fading factor of the base station from the users to the cell.
Further, the hypergraph also comprises an accumulated interference subgraph G2＝(V,E2) Set E of2The element in (1) is formed by connecting three vertexes, and the weight is 1 or 0.
Further, the minimum uplink reachable rate when every three users use the same pilot frequency is calculated, if the minimum uplink reachable rate is smaller than a threshold, a super edge with a weight value of 1 is established, otherwise, the weight value is 0, and the three users do not form the super edge.
Further, the minimum value of the minimum uplink achievable rates of each of the three users to the other two users is determined as the minimum uplink achievable rate when the three users use the same pilot frequency.
The invention has the following beneficial effects:
1. the invention models the two interference relationships of independent interference and accumulative interference into a common edge and a super edge in the hypergraph respectively, thereby converting the pilot frequency distribution problem into the hypergraph coloring problem.
2. The invention can ensure the minimum uplink transmission rate of the user and improve the uplink and the rate of the system at the same time.
3. The invention can realize the optimization of the system performance under the condition of less operation complexity and has better pilot frequency pollution suppression effect.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings can be obtained by those skilled in the art according to the drawings.
FIG. 1 is a schematic diagram of two types of edge users in a system provided in accordance with an embodiment of the present invention;
fig. 2 is a flowchart of a pilot allocation method for a large-scale antenna system according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A multi-cell multi-user massive MIMO system is set to have L cells, and a base station of each cell is positioned in the center of the cell and is provided with M antennas. Each cell contains K single-antenna users, which are evenly distributed throughout the cell. The system adopts a TDD mode with reciprocity between uplink and downlink. The channel gain from the kth user in the jth cell to the mth antenna in the ith cell base station is:
gimjkis a small-scale fading factor, and has an independent same distribution mean value of 0 and a covariance matrix of IMComplex gaussian random variables. Beta is aijkThe large scale fading factors mainly include shadow fading and path loss. The large-scale fading factor from the kth user in the jth cell to the ith cell base station can be obtained by the following formula
Wherein ZkRepresenting shadow fading, obeying a lognormal distribution with mean 0 and standard deviation σ, α representing the path loss coefficient in signal transmission, dijkIs the distance, R, from the kth user in the jth cell to the ith cell base stationcellIs the cell radius. From the above equation, it can be known that the large-scale fading factor is in inverse proportion to the α power of the distance from the user to the base station, and is greatly influenced by the distance from the user to the base station.
As an example, the path loss coefficient α takes a constant of 3.
In a cellular network, the radio transmission may be divided into a number of data frames occupying T seconds, which causes the channel between each user and the base station to have a constant channel response within a frame, but to be different from frame to frame. Assuming that τ symbols in T are allocated for pilot signaling, the remaining T- τ symbols are used for data transmission. Whereas the tau symbols allow only tau orthogonal pilot sequences. More specifically, only τ users in the whole system can send pilot frequency without interfering other users, and accurate channel state information is obtained. Therefore, in a massive MIMO system where the number of expected users is large and due to resource scarcity, only the same cell users are guaranteed to have orthogonal sequences
(wherein,
representing the complex field) the users of other cells reuse the same set of pilots. The pilot pollution problem limits the uplink and downlink performance of massive MIMO systems and cannot be eliminated by increasing the number of base station antennas.
When the number of antennas tends to infinity, if each user uses the same uplink transmit power, the uplink signal-to-interference-and-noise ratio of the user can be simplified and is only related to the large-scale fading factor, and assuming that the kth user in each cell uses the same orthogonal pilot sequence, the uplink reachable rate of the whole system can be represented as follows:
wherein, betaiikA large-scale fading factor from the kth user of the ith cell to the base station of the ith cell; beta is aijkA large-scale fading factor from the kth user of the jth cell to the base station of the ith cell; l is the number of cells in the system, K is the number of users in the cell, and M is the number of antennas of the base station.
The invention provides a pilot frequency allocation scheme for maximizing uplink and rate on the premise of ensuring the communication quality of all users in a system. That is, pilot allocation is required to achieve the following goals:
in the formula betaijkThe large-scale fading factor from the kth user in the jth cell to the ith cell base station consists of shadow fading and path loss.
Represents all (K!)LPilot allocation scheme, sikIndicating the pilot sequence used by the kth user in the ith cell. Gamma raythIndicating a threshold limiting the minimum uplink transmission rate for each user.
Constructing hypergraphs based on interference relationships
As can be seen from equation (3), the signal-to-interference-and-noise ratio of a user is closely related to the large-scale fading factor, and therefore, the interference relationship between the user and the user can be expressed by the large-scale fading. And calculating the interference degree between every two users or every few users, wherein the large interference degree indicates that the users can bring more serious pilot pollution when distributing the same pilot, and orthogonal pilot should be distributed to strong-interference users as much as possible when distributing the pilot. Since the large-scale fading factor is greatly affected by the path loss, and the path loss is mainly determined by the distance from the user to the target base station, it is considered that the user located at the cell boundary is more easily interfered by other users, and the communication quality is greatly reduced. As shown in fig. 1, for a system composed of hexagonal cells, the users at the cell edge are mainly divided into two types, one is the intersection of two cellsEdge users at the border (please see region P)1、P3、P4Triangular users in (c), and the other is edge users at the boundary of three cells (see region P)2Triangle users in (1).
First consider the independent interference between two users. Assuming that there are only two adjacent cells in a massive MIMO system, each cell has a user, and both cells use the same pilot sequence, the uplink achievable rate expression of the system is as follows according to equation (3):
in the formula betaijRepresenting the large-scale fading factor from the user in the jth cell to the ith cell base station. From the formula (5), R can be seensumThe larger the interference that two users will cause to each other using the same pilot sequence.
Therefore, the interference strength η between the kth user in the ith cell and the kth' user in the jth cellikjk′Expressed as follows:
ηikjk′the larger the interference between users k and k 'is, the more strong the interference between users k and k' is, the pilot sequences orthogonal to each other need to be allocated to both users to avoid pilot pollution.
Secondly, further considering the accumulated interference of users using the same pilot frequency in other cells to a certain user, considering the distribution specific to the hexagonal cell and the time complexity of the algorithm, etc., the interference strength between every three users in different cells is considered here. In order to ensure the communication quality of all users in the system and improve the minimum uplink reachable rate of the users in the system, the invention adopts eta' to approximately represent the minimum uplink reachable rate when three users (one user in each cell) in three adjacent cells use the same pilot frequency sequence:
the smaller η' indicates that if the three users are allocated the same pilot sequence, there will be strong interference between users, resulting in a user having a smaller uplink transmission rate. In order to increase the minimum uplink achievable rate, the invention introduces a threshold value gammathTo decide whether three users in different cells can use the same pilot. If η' < γthThen it means that these three users cannot be allocated exactly the same pilot sequence. Threshold value gammathIs determined in advance according to the minimum rate requirements of users in the system. When the set threshold is smaller, the system reachable rate is higher, but the reachable rate of the edge user is lower; when the set threshold is larger, the system reachable rate is lower, but the reachable rate of the edge user is higher.
According to the analysis, the interference relationship and the restriction relationship between the users can be obtained. Therefore, a undirected weighted hypergraph G ═ (V, E, w (E)) can be constructed. Set V { < i, k>I is more than or equal to 1 and less than or equal to L, K is more than or equal to 1 and less than or equal to K, the vertex represents the user, and the element of the set V represents all the users in the cell. Set E is a set of edges formed by the connection of vertices, representing the interference relationships between vertices, where element E is composed of a subset of multiple V. The hypergraph G ═ (V, E, w (E)) can be divided into independent interference subgraphs G according to the independent interference and the accumulated interference1＝(V,E1W (e)) and cumulative interference subgraph G2＝(V,E2)。
Independent interference subgraph G1Edge set E in1Is a collection of edges formed by connecting two vertices. Every two vertexes have an edge connected, and each edge has a positive weight w (e) and represents the interference strength between two users. And (4) calculating the interference strength between every two users in the system according to the formula (6) as a positive weight w (e) of the edge between the two vertexes. The larger the weight between two users represents the more serious the pilot pollution caused by allocating the same pilot to the two users.
Cumulative interference subgraph G2Edge set E in2The element in (A) is composed of three vertex phasesThe formed overedge (as shown in the region P of FIG. 1)2The edge formed by the middle three vertices) with a weight of 1 or 0, the set representing the limit for low rate users. And (3) calculating the minimum uplink reachable rate eta 'value among every three users according to the formula (7), comparing the minimum uplink reachable rate eta' value with a threshold, if the minimum uplink reachable rate eta 'value is smaller than the threshold, establishing a super edge with the weight of 1, and if the minimum uplink reachable rate eta' value is larger than the threshold, establishing a super edge with the weight of 0, wherein the three users do not form the super edge. If three vertexes are connected by a super edge, namely the weight is 1, the three vertexes avoid using the same pilot frequency as much as possible; otherwise, the pilots of the three vertices are not so limited.
Independent interference subgraph G1And cumulative interference subgraph G2For determining the correlation matrix of the hypergraph. The rows of the hypergraph correlation matrix are associated with each vertex and the columns are associated with each edge. If the vertex v isiAnd edge ejIf the two are related, the v th in the hypergraph correlation matrix isiLine ejThe value of the column is edge ejOtherwise, it is 0. Containing the vertex viThe edge set composed of the edges of (a) is E (v)i) And (4) showing. Vertex viCan be defined as E (v)i) Radix of | E (v)i) And | represents.
Coloring of hypergraph
And coloring the established hypergraph by selecting a proper graph coloring algorithm to finish the process of pilot frequency allocation. The invention determines which users are more easily interfered by other users through the sum of the weight values of the edges, and colors the users firstly, namely colors the users according to the priority order of the users. Unlike graph coloring for other problems, in the pilot allocation problem, the orthogonal pilots in each cell are determined, i.e., the color set in each cell is fixed, so after determining the user, further pilot selection is needed. Finally, the selected pilot frequency is allocated to the user, and the allocation process is limited by the excess edge.
As shown in fig. 2, coloring the hypergraph includes the steps of:
step 210: various system variables are input, including the number of cells L in the system, the number of users K in the cells, and the number of antennas M of the base station.
Step 220: initialization: selecting two users, e.g. users, of different cells with the most positive weight edges from the hypergraph<i1,k1>And the user<i2,k2>，<i1,k1>Indicates cell i1User k in1，<i2,k2>Indicates cell i2User k in2. And randomly assigning two orthogonal pilots to the two users, e.g. pilot number 1 to user<i1,k1>Allocating pilot frequency No. 2 to user<i2,k2>. Meanwhile, a set Θ is defined as a set of allocated users, and the two users that have been allocated pilots are added to the set.
Step 230: by a priority variable deltaikTo represent the user<i，k>The sum of the weights of the edges connected to the assigned users in the set Θ. DeltaikThe larger the representative user<i，k>The larger the interference caused to the whole allocated users, the higher the priority, the more the pilot needs to be allocated to the allocated users first. This step is used to determine the user that is not in the set Θ and has the highest priority unassigned pilot, e.g., user<i0,k0>。
Step 240: determining available pilots for unallocated users: to avoid intra-cell interference, orthogonal pilot sequences are all used in the same cell. First, define S1Is the ith0A set of users of unassigned pilots in a cell. Second, due to the exposure to set E2And in the limit of the middle super edge, three users in the super edge are not allocated with the same pilot frequency sequence as much as possible. Thus, all unallocated users containing the selected entries are traversed<i0,k0>The excess edge of (2). If the users in the super edge are allocated the same pilot frequency sequence, the pilot frequency is added to the set S2The pilots in the set represent users due to over-edge limitation<i0,k0>Unusable pilot sequences. Finally, define S3For the available pilot set, S3Of (2) belong to the set S1But not belonging to the set S2。
Step 250: in order to mitigate the pilot pollution,it is desirable to avoid as much as possible the interference between different cells using the same pilot users, so it is desirable to select the pilot from the available pilot sequences to allocate to the users that causes the least pilot pollution<i0,k0>. Suppose a user<i0,k0>Using the same pilot as each user in the set Θ, define λsAs a user<i0,k0>When pilot s is used, the sum of the interference strength to the users to which pilot s is allocated in the system.
Wherein if set S3If the set is not an empty set, then the user is calculated<i0,k0>Using set S3When pilot in (c), the interference strength and λ caused by the pilot in (e) set to the users using the same pilotsWill be the minimum lambdasCorresponding S3Pilot allocation in (1) to users<i0,k0>。
Considering a special case, if the set S is limited by the over-edge3For the empty set, then calculate the user<i0,k0>Using set S1When pilot in (c), the interference strength and λ caused by the pilot in (e) set to the users using the same pilotsSelecting the smallest lambdasCorresponding S1Pilot allocation in (1) to users<i0,k0>。
Step 270: the set Θ is updated. After each user is assigned a pilot, the user needs to be assigned<i0,k0>Added to the set of users Θ to which pilots have been allocated.
Step 280: it is determined whether all users have been assigned pilots.
If yes, go to step 290: and outputting one-to-one correspondence between the pilot frequency and the user. Otherwise, returning to step 230, and looping back to step 230 and step 270 until all users are allocated pilots.
As an embodiment, the pseudo code corresponding to the pilot allocation method provided by the present invention is as follows:
the invention has the following beneficial effects:
1. the invention models the two interference relationships of independent interference and accumulative interference into a common edge and a super edge in the hypergraph respectively, thereby converting the pilot frequency distribution problem into the hypergraph coloring problem.
2. The invention can ensure the minimum uplink transmission rate of the user and improve the uplink and the rate of the system at the same time.
3. The invention can realize the optimization of the system performance under the condition of less operation complexity and has better pilot frequency pollution suppression effect.
Although the present application has been described with reference to examples, which are intended to be illustrative only and not to be limiting of the invention, changes, additions and/or deletions may be made to the embodiments without departing from the scope of the invention.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (8)
1. A pilot frequency distribution method of a large-scale antenna system is characterized by comprising the following steps:
constructing a hypergraph: the edge in the hypergraph represents the interference strength between two users of a large-scale antenna system, and the larger the weight of the edge is, the more serious the pilot frequency pollution caused by distributing the same pilot frequency to the two users is; the super-edge in the hypergraph represents the interference strength between users of three adjacent cells in a large-scale antenna system;
initialization: selecting two users of different cells with the largest positive weight value edges in the hypergraph, and allocating two orthogonal pilot frequencies to the two users; the users distributed with the pilot frequency form a distributed user set;
allocating pilots to unallocated users, comprising:
determining the highest priority unallocated user according to the hypergraph;
determining an available pilot set of the unallocated user with the highest priority;
calculating the interference intensity sum of the unallocated users with the highest priority to the allocated users using the same pilot frequency when the unallocated users use the pilot frequency in the available pilot frequency set according to the hypergraph;
allocating the pilot frequency with the minimum interference intensity sum to the unallocated user with the highest priority;
updating the distributed user set;
judging whether all users are allocated with pilot frequencies;
if not, repeating the steps: allocating pilot frequency to the unallocated user;
determining the weight of the edge between the unallocated user and the allocated user and the user with the largest unallocated pilot frequency as the unallocated user with the highest priority;
the method for determining the available pilot frequency set comprises the following steps:
users in the same cell use orthogonal pilot frequency sequences, and unassigned pilot frequencies in the same cell form a first set; and is
Forming a second set by the pilots used by other users in the super edge where the highest priority unallocated user is located;
the pilots obtained after excluding the pilots in the second set from the first set constitute the available set of pilots.
2. The method of claim 1, wherein if the available pilot set is an empty set, then:
calculating the interference intensity sum of the unallocated users with the same pilot frequency when the unallocated users with the highest priority use the pilot frequency in the unallocated pilot frequency set of the cell in which the unallocated users are positioned;
and allocating the pilot frequency with the minimum interference intensity sum to the unallocated user with the highest priority.
3. The method of claim 1, further comprising coloring users in the hypergraph according to their priority order.
4. The method of claim 1, wherein the hypergraph comprises an independent interference subgraph G1＝(V,E1W (e)), set V ═ tone<i,k>I is more than or equal to 1 and less than or equal to L, K is more than or equal to 1 and less than or equal to K is taken as a vertex set, the vertex represents a user, and the set E1Is a set of edges formed by connecting two vertexes, each edge has a positive weight w (e) and represents the interference strength between two users.
5. The method of claim 4, wherein the interference strength between users is calculated using large scale fading factors from the users to the base station of the cell.
6. The method of claim 4 or 5, wherein the hypergraph further comprises a cumulative interference subgraph G2＝(V,E2) Set E of2The element in (1) is formed by connecting three vertexes, and the weight is 1 or 0.
7. The method of claim 6 wherein the minimum uplink reachable rate when every three users use the same pilot is calculated, and if the minimum uplink reachable rate is less than a threshold, a super-edge with a weight of 1 is established, otherwise, the weight is 0, and the three users do not form the super-edge.
8. The method of claim 7 wherein the minimum of the uplink achievable rates of each of the three users to the other two users is determined as the minimum uplink achievable rate for the three users using the same pilot.
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| CN106452714A (en) * | 2016-11-09 | 2017-02-22 | 重庆大学 | Pilot frequency distribution method for multi-cell multi-user large-scale MIMO system |
| CN107872255A (en) * | 2017-11-10 | 2018-04-03 | 江苏省邮电规划设计院有限责任公司 | Suitable for the pilot tone dispatching method of extensive MIMO cellular mobile communication networks |
| CN108923903A (en) * | 2018-06-26 | 2018-11-30 | 北京邮电大学 | Pilot distribution method, system and the electronic equipment of multiaerial system |
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