JP5496428B2 - Interference suppression method in mixed macro cell and femto cell networks - Google Patents

Description

  The present invention relates to the technical field of wireless communication networks, and more particularly to an interference suppression method in a mixed network of macro cells and femto cells.

  The advent of many high-data-rate wireless communication standards indicates that wireless communication has entered an era of dramatic increases in reliability and capacity. Well, I explain well that it increases by a factor of 1 every 30 months. For example, since the U.S. civilian wireless communication system was widely applied in 1957, wireless communication capacity has increased nearly 1 million times, of which 25 times has been increased by using a wider frequency band, and less time Increased by 5 times by frequency domain scheduling granularity, increased by 5 times by better modulation method, increased by 1600 times by reducing cell area and transmission distance. The enormous gain by reducing the cell area and transmission distance is actually due to improved spatial frequency spectrum utilization (ie, improved unit area throughput) and received signal strength. Thus, the emergence of cell structures that can provide low-cost, high-rate indoor coverage-Femtocell encourages widespread interest in research fields, operators and equipment manufacturers.

  A macrocell is a larger area, has a coverage radius of about 1-30, and a base station transmit antenna is typically built over a surrounding building. Usually there is no direct antenna between transmission and reception. Femtocell is a low-power, short-range wireless data access cell with a coverage range of typically 10-50 meters and feedback for broadband connections such as fiber optic or digital user line (xDSL) Used as a transmission method. The advent of Femtocell is widely emphasized, and 3GPP LTE has already incorporated it into the R8 standard and named it Home NodeB.

  As can be seen from the survey on the use of mobile communications, more than 50% voice communications and more than 70% data communications occur in the indoor environment. Voice communications can tolerate lower signal quality because the required data rate is very low, only 10 kbps or even lower. Due to the high demands on data rates for data communications, users expect to be able to provide a wired network Mbps level wireless network experience. Considering the cost, the mobile terminal is normally limited to power, and for a given transmission power, the symbol energy decreases as the transmission data rate increases. Due to the wear and tear of mobile terminal equipment of indoor users, especially equipment in the high carrier frequency band, it is difficult to achieve high signal quality and high data rate, and users are wired indoors because of dissatisfaction with the user's indoor wireless network. Continue to use schemes or other operator radio schemes.

  As the cell radius decreases, the interference signal transmission model between adjacent cells also changes, the same channel interference becomes stronger, and this problem becomes more serious when Femtocell covers densely. In addition, since the frequency band possessed by the operator is limited due to the lack of frequency spectrum resources, in the Femtocell auxiliary cellular cell, it is necessary to multiplex some or all of the frequency resources in the Femtocell and macrocell. Such a system is referred to as “whole frequency multiplexing system”. Since the difference between the transmission power of the femto base and the transmission power of the macro base station is 1 to 2 levels, the cross-layer interference between the Femtocell and the macro cell is the capacity of the Femtocell auxiliary cellular cell under such overall frequency multiplexing. It becomes one of the important factors that restrict improvement. Therefore, if there is no effective interference suppression and resource allocation algorithm, the network structure of the mixed network of Femtocell and macrocell will eventually reduce the system capacity (capacity).

  In addition, the network structure of the mixed network of Femtocell and macrocell is compared with the structure of the conventional hierarchical cell system (HCS, Hierarchical Cell System). (1) The microcell position in the conventional HCS is planned and determined in advance. However, since the femto base stations in the network structure of a mixed network of Femtocell and macrocell are arranged according to user demand, it is only required that the user satisfies the micro area coverage, so that the distribution is random And (2) the Femtocell coverage radius (10-50m) is smaller, 2 to 3 levels smaller than the normal macrocell radius (300-200m), and (3) the number of Femtocell in the macrocell As Femtocell adopts the xDSL method as a data feedback transmission method, Delay due work load is characterized in that Femtocell and macrocell will not allow coordinated directly. Therefore, the conventional interference suppression and radio resource management method in HCS is not completely applied to the network structure of a mixed network of Femtocell and macro.

  The problem to be solved by the present invention is to effectively improve the frequency spectrum utilization efficiency and system capacity of the dual network covered by overlapping the macrocell and the Femtocell, as well as the cross-layer interference between the macrocell and the Femtocell, and the same Femtocell. An object of the present invention is to provide an interference suppression method in a mixed network of macro cells and femto cells that can effectively solve the problem of layer interference.

  In order to solve the above technical problem, the present invention provides an interference suppression method in a mixed network of macro cells and femto cells. In this method, a femtocell Femtocell in a certain range is selected, and Femtocell in the range is clustered S1; for the Femtocell for which clustering is completed, the transmission power of the femto base station in the cluster is controlled in units of clusters At the same time, adjust the clustering status of Femtocell to determine Femtocell of interference sensitive area, Femtocell of non-interference sensitive area, and Femtocell of non-interference sensitive area S2; Cluster Femtocell of interference sensitive area S3; Clustering completed The Femtocell in the interference sensitive area is controlled by controlling the Femtocell transmission power in the cluster and adjusting the clustering status of the Femtocell in the interference sensitive area to determine the Femtocell in the interference sensitive area S4; Macro Non-destructing user equipment with dead zone user equipment When the intensity of interference from the Femtocell adjacent to the macro user equipment reaches a level where it cannot communicate normally with the macro base station, the macro user equipment is divided into dead zone user equipment. If the intensity of interference by adjacent Femtocell does not affect normal communication with the macro base station, the macro user equipment is divided into non-dead zone user equipment S5; and frequency spectrum resources are Dividing into three parts that do not overlap each other, the Femtocell cluster that belongs to the interference sensitive area, the dead zone user equipment, the Femtocell cluster that belongs to the non-interference sensitive area, and the non-dead zone user equipment, respectively, that do not overlap each other Partial frequency spectrum resources Including S6 assigned.

  Among them, the step S1 specifically acquires the position information of the Femtocell first, and based on the position information, constructs the Femtocell interference diagram and the adjacent matrix of the interference diagram, the Femtocell interference diagram and the adjacent matrix Cluster Femtocell based on it.

  Among them, the step of constructing the Femtocell interference diagram and the adjacent matrix of the interference diagram based on the position information, specifically,

Represents an Femtocell interference diagram, V represents an end point set composed of Femtocells, elements in the edge set E represent a connection relationship between Femtocells of the end points, and if there is a connection relationship between any two end points, this 2 Indicates that collision interference exists between the Femtocells corresponding to the two endpoints, and these two endpoints are not divided into the same cluster,
Suppose that there are N Femtocells and a matrix

And Ψ is an N × N matrix of all 1, I is an N × N unit matrix,

And d _ij is the distance between Femtocell i and Femtocell j, and in Q,

Indicates that there is a connection relationship between the corresponding Femtocell i and Femtocell j,

Indicates that there is no connection relationship between the corresponding Femtocell i and Femtocell j, the interference diagram G is obtained by the method described above, and the structured matrix Q indicates the relationship between the end points Femtocell in the interference diagram G. Determined, i.e., connected or disconnected, Femtocell i and Femtocell j represent i, jth Femtocell,
Here, R _th is a cluster interference distance threshold, and when the distance between any two Femtocells is smaller than a certain value, the maximum transmission power of the femto base station is the user signal-to-interference in the Femtocell. The noise ratio requirement cannot be satisfied, and the minimum value of this distance is defined as the cluster interference distance threshold,
Thereafter, the adjacent matrix A (G) of the interference diagram is acquired from the interference diagram G.

Among them, the step of clustering Femtocell based on the Femtocell interference diagram and the adjacency matrix, specifically,
1) ν _i represents an end point in the Femtocell interference diagram, d (ν _i ) represents a degree in the Femtocell interference diagram of the end point ν _i , l is a cluster number, an initial value is 1, The second Femtocell cluster (outside 1)
Represented by
2) Construct isolated point set s from 0 degree end points,
3) Construct the interference diagram and the adjacency matrix A _i (G) of the remaining endpoints with non-zero power,
4) Save the maximum frequency endpoint at A _i (G) in set B and delete the row and column corresponding to this endpoint from A _i (G) until A _i (G) is a matrix of all zeros. And the remaining endpoints in A _i (G) are clusters (outside 2)
And add 1 to the value of l,
5) Using the set B, construct a new (again) interferogram G and an adjacent matrix A _i (G) of the interferogram, and if the new A _i (G) is an all-zero matrix, the new interference Cluster from end points in Figure G (outside 3)
If N = l is the number of Femtocell clusters currently assigned in the Femtocell clustering step, then perform step 6), and the new A _i (G) is not an all-zero matrix , Repeat step 4)
6) When the Femtocell corresponding to the end point in the isolated point set s enters the Femtocell cluster obtained in the above steps and determines which Femtocell cluster the end point ν _i in the isolated point set s can be divided into,
(Outside 4)
To get the cluster number
(Outside 5)
Represents the cluster in which the maximum end point j of the distance from the isolated end point i to the minimum end point of each cluster is located.

Among them, in step S2, for Femtocell for which clustering has been completed, the operation for controlling the transmission power of the femto base station in the cluster in units of clusters is specifically,
l is the cluster number of Femtocell, its initial value is 1, and the cluster (outside 6)
The number of end points in the cluster is expressed as N _l, and the cluster (outside 7)
The transmission power of the base station of Femtocell i corresponding to the end point ν _i at is expressed as P _i, and the request for the signal-to-interference noise ratio of the reference user at Femtocell _i is expressed as γ _i ,
A reference user is defined as a user facility at the edge of the Femtocell coverage that is served by Femtocell and relatively close to the macro base station, where one Femtocell is the quality of service of that reference user If the QoS requirements can be satisfied, the QoS requirements of the user equipment at any location within the coverage range can be satisfied,
Cluster (outside 8)
Assuming that ensures the requirements of all the Femtocell reference user QoS in, a matrix of linear equations to be satisfied by P _i

Where,

N ₀ is the density of the noise power spectrum, and in the above equation,
(Outside 9)
But the macro base station and cluster (outside 10)
Is the path gain between Femtocell i and
(Outside 11)
Is a cluster (outside 12)
Is the path gain between Femtocell i and Femtocell j in
(Outside 13)
But the cluster (outside 14)
Is the path gain between the reference user in Femtocell i and the base station of Femtocell i in
(Outside 15)
Is the transmission power of the macro base station,
The solution of the above linear equation is

And the elements in p are clusters (outside 16), respectively.
If each femto base station supports the lowest transmission power on the premise of guaranteeing the QoS requirement of its reference user, the cluster (outside 17)
Femtocell i in the Femto base station transmission power is (outside 18)
To be in the range.

Among them, the clustering situation of Femtocell is adjusted in step S2, and the operation of clustering of Femtocell of interference sensitive area, Femtocell of non-interference sensitive area, and Femtocell of non-interference sensitive area is specifically,
1)

The obtained cluster (outside 19)
Is the minimum transmission power of the femto base station at
(Outside 20)
Represents the maximum transmission power of the femto base station, and all transmission powers in P are

The Femtocell corresponding to the element satisfying the above is a Femtocell belonging to the interference sensitive region, and the end point corresponding to the Femtocell of these interference sensitive regions is the cluster (outside 21).
Transferred to Femtocell set D _ISA in the interference sensitive area,
2) In power solution P,

If there are no elements, then step 3) is performed and the maximum endpoint of the sum of rows and columns in matrix H, ie (outside 22)
Number of clusters determined by (outside 23)
The corresponding end points in the cluster (outside 24)
To cluster (25 outside)
Move to a new cluster (outside 26)
And execute step S2 to create a new cluster (outside 27)
Calculate the femto base station transmit power solution P and continue with step 3) below,
3)

If it is, add 1 to l, return to step S2, and execute the calculation of the next cluster,

The operation of step S3 is completed,
The Femtocell belonging to the interference sensitive area has been determined so far, the Femtocell that does not belong to the interference sensitive area is the Femtocell of the non-interference sensitive area, and the cluster composed of the Femtocell of the non-interference sensitive area is the Femtocell of the non-interference sensitive area. Make it a cluster.

  Among them, the clustering operation in step S3 is the same as the clustering operation in step S1.

Among them, for the Femtocell of the interference sensitive region that has been clustered in step S4, the operation for controlling the transmission power of the Femtocell in the cluster in units of clusters is specifically,
Assume that the Femtocell of the interference sensitive region is divided into M clusters in step S3, q is the cluster number, its initial value is 1, and the q-th cluster is represented by C _q .
The cluster C _q, the number of end points in a cluster is represented as N _q, transmission power of the base station of the Femtocell i corresponding to the end point [nu _i in cluster C _q is represented as P _i, the reference user in the Femtocell i The signal-to-interference / noise ratio requirement is expressed as γ _i ,
Assuming that ensures the requirements of the reference user SINR of all Femtocell in cluster C _q, the format of the matrix of the linear equation to be satisfied by P _i,

Where

(Outside 28)
Is the path gain between the macro base station and Femtocell i in cluster C _q ,
(Outside 29)
Is the path gain between Femtocell i and Femtocell j in cluster C _q
(Outside 30)
Is the path gain between the reference user in Femtocell i and the Femtocell i base station in cluster C _q ,
The solution of the above linear equation is

If the elements in P correspond to the lowest transmit power on the assumption that the femto base station guarantees the QoS requirement of its reference user in cluster C _q , respectively, the cluster (outside 31)
Femtocell i base station transmission power at (outside 32)
To be in the range.

Among them, the operation of adjusting the Femtocell clustering state in the interference sensitive region in step S4 and determining the Femtocell cluster in the interference sensitive region is specifically,
1)
(Outside 33)
Represents the maximum transmission power of the femto base station, and all elements in the power solution P obtained in step S4 are

If satisfied, execute step 2)

Is present, the maximum endpoint of the sum of rows and columns in matrix H of step S4, i.e.,
(Outside 34)
The corresponding end point in the cluster C _q of the number determined by is moved from the cluster C _q to the cluster C _{q + 1} to obtain a new cluster C _q , and step S4 is executed to execute the new cluster C _q Calculate the transmission power P of the femto base station in the interference sensitive area, and continue with step 2) below.
2)

Then add 1 to I and return to step S4 to perform the next cluster calculation,

, The operation to adjust the clustering status of the Femtocell in the interference sensitive region, and to determine the cluster of the Femtocell in the interference sensitive region is completed.
The Femtocell cluster in the interference sensitive area has been determined so far.

  Among them, the method of dividing the macro user equipment into the dead zone user equipment and the non-dead zone user equipment in step S5 is to divide in advance according to the position of the macro user equipment or according to the channel situation where the macro user equipment is located.

Among them, the operation of dividing the macro user equipment according to the channel situation where the macro user equipment is located in step S5 is specifically,
Macro user equipment determines whether it belongs to dead zone user equipment or non-dead zone user equipment according to the received pilot signal strength, signal-to-interference noise ratio or signal-to-noise ratio of adjacent Femtocell, or
The macro base station that provides services to the macro user equipment is configured such that the macro user equipment is a dead zone user equipment according to channel state information fed back from the macro user equipment, pilot signal strength, signal to interference noise ratio, or signal to noise ratio. Or determine whether it belongs to non-dead zone user equipment, or
The macro user equipment determines whether it belongs to the dead zone user equipment or the non-dead zone user equipment according to the received pilot signal strength, signal-to-interference noise ratio or signal-to-noise ratio of the adjacent Femtocell. Reporting to the macro base station serving the macro user equipment, the macro base station further comprising: channel state information fed back from the macro user equipment, pilot signal strength, signal to interference noise ratio or signal to noise ratio; Based on the determination result of the macro user equipment, it is determined whether the macro user equipment belongs to the dead zone user equipment or the non-dead zone user equipment.

  Among them, in step S6, the three portions that do not overlap each other are the Femtocell dedicated resource, the macro cell dedicated resource, and the shared resource of the Femtocell and the macro cell.

  Among them, in step S6, the Femtocell cluster of the interference sensitive area, the dead zone user equipment, the Femtocell cluster of the non-interference sensitive area, and the non-dead zone user equipment, respectively, the three portions of the frequency spectrum resources that do not overlap each other. The Femtocell in the Femtocell cluster in the interference sensitive area selects the Femtocell dedicated resource, the dead zone user equipment selects the macro dedicated resource, and the Femtocell and non-dead in the Femtocell cluster in the non-interference sensitive area. The zone user equipment selects a shared resource between the Femtocell and the macro cell.

  Among them, when the frequency spectrum resource is divided into three parts that do not overlap each other, the proportion of each part occupying the frequency spectrum resource is determined by the number of Femtocell clusters in the interference sensitive area and the number of dead zone user equipment.

  Among them, when allocating the three portions of frequency spectrum resources that do not overlap each other to the interference sensitive region Femtocell cluster, dead zone user equipment, non-interference sensitive region Femtocell cluster, and non-dead zone user equipment, respectively, Femtocells in the same cluster use the same resource, and the resource is a time spectrum or frequency domain frequency spectrum resource.

  The present invention effectively improves the frequency spectrum utilization efficiency and system capacity of the dual network that overlaps and covers the macro cell and the Femtocell by realizing interference suppression by resource allocation and power control. The problem of cross-layer interference and the same layer interference of Femtocell can be solved effectively.

It is a figure which shows the flow in the Example of the method concerning this invention. 4 is a flowchart of interference adjacency diagram structure (generation) and interference adjacency matrix acquisition in an embodiment of the method according to the present invention. 4 is a flowchart of a clustering algorithm in an embodiment of the method according to the present invention. It is an illustration figure of the interference distance threshold value used for the Example of the method based on this invention. 5 is a flowchart of power control and clustering adjustment of a non-interference sensitive region in an embodiment of the method according to the present invention. 6 is a flowchart of interference sensitive region power control and clustering adjustment in an embodiment of the method according to the present invention. It is a division example figure of the frequency resource of the frequency spectrum in the Example of the method concerning this invention. It is a figure which shows the resource allocation of the interference sensitive area | region and non-sensitive area | region and the downlink dead zone of a macro user, and a non-dead zone in the Example of the method based on this invention. FIG. 4 is a diagram illustrating an example of a self-adaptive heuristic clustering algorithm used in an embodiment of the method according to the present invention. It is a figure which shows the example of the result after clustering by the sequential transfer algorithm in the Example of the method which concerns on this invention.

  In order to clarify the objects, contents, and advantages of the present invention, embodiments of the present invention will be described below in more detail with reference to the drawings.

  The basic idea of the present invention is to cluster Femtocell within a certain range, control the transmission power of femto base stations in the cluster and adjust the clustering status of Femtocell in units of clusters, and be sensitive to interference. Determine the cluster of the Femtocell of the region, the Femtocell of the non-interference sensitive region, and the Femtocell of the non-interference sensitive region, cluster the Femtocell of the interference sensitive region, and then cluster the cluster for the interference sensitive region Femtocell for which clustering has been completed Control femto base station transmission power in the cluster, adjust the Femtocell clustering situation in the interference sensitive area, determine the Femtocell cluster in the interference sensitive area, and simultaneously make the macro user equipment dead zone user equipment and non-dead zone Divide into user equipment and frequency spectrum resources overlap each other It is divided into three parts that are not overlapped, and frequency spectrum resources of three parts that do not overlap each other are allocated to the Femtocell of the interference sensitive area, the dead zone user equipment, the Femtocell of the non-interference sensitive area, and the non-dead zone user equipment, respectively. .

  FIG. 1 is a flowchart of an embodiment of a method for performing joint resource allocation and power control for Femtocell based on Femtocell clustering in a communication system according to the present invention. This embodiment includes the following steps.

  Step 101: Structure (generate) an interference diagram to obtain an interference diagram adjacency matrix, and based on the interference diagram adjacency matrix, adopt a clustering algorithm to cluster all Femtocells in a certain range.

  Step 102: Control the transmission power of the femto base station in the cluster in units of clusters, adjust the Femtocell clustering situation using a sequential transfer algorithm, and finally, the Femtocell in the interference sensitive area and the Femtocell in the non-interference sensitive area And the Femocell cluster in the non-interference sensitive area are determined, and the clustering and power allocation operation of the femtocell in the non-interference sensitive area is completed.

  Step 103: For the Femtocell in the interference sensitive area, construct an interference adjacent map, obtain an interference adjacent map matrix, and perform clustering using the above clustering algorithm.

  Step 104: Control the transmission power of the femto base station in the cluster for each Femtocell in the interference sensitive area for which clustering has been completed (by constructing a power control simultaneous equation), and at the same time perform interference using the sequential transfer algorithm. Adjust the clustering status of the Femtocell in the sensitive area to determine the Femtocell cluster in the interference sensitive area.

  Step 105: Divide macro user equipment (also referred to as macro user, ie, a mobile terminal that is served by a macro base station) into dead zone user equipment and non-dead zone user equipment, among which adjacent Femtocell of macro user equipment When the interference intensity due to the signal reaches a level at which communication with the macro base station cannot be normally performed (that is, the communication quality requested by the user, for example, the bit error rate and the communication rate cannot be reached), If the macro user equipment is divided into dead zone user equipment and the macro user equipment does not receive interference from the Femtocell, or if the strength of interference from the adjacent Femtocell does not affect normal communication with the macro base station, the macro Divide user equipment into non-dead zone user equipment.

  Step 106: Divide the frequency spectrum resources into three parts that do not overlap each other and overlap each other in the Femtocell cluster and dead zone user equipment belonging to the interference sensitive area, and in the Femtocell cluster and non dead zone user equipment belonging to the non-interference sensitive area, respectively. Not allocate frequency spectrum resources for three parts.

  Hereinafter, specific steps for clustering Femtocell in the coverage range of one macro cell in Step 101 will be shown.

Step 201 (as shown in FIG. 2): constructing the interference diagram G = (V, E), the elements in the endpoint set V represent Femtocell, the elements in the edge set E represent the interference collision relationship between Femtocell, 2 An edge between two endpoints indicates an interference collision relationship between the two endpoints. The cluster interference distance threshold is represented by R _th , and as shown in FIG. 4, any two Femtocells whose distances are smaller than R _th may interfere with each other, and therefore cannot belong to the same cluster. two mutual distance R _th larger than Femtocell of, since it can be solved by power control in effective power range between interference can be divided into the same cluster.

  Suppose there are a total of N femtocells, and the matrix

Where Ψ is an N × N matrix of all 1, I is an N × N unit matrix,

And d _ij is the distance between Femtocell i and Femtocell j, and in Q, d _ij -R _th <0 indicates that Femtocell i and Femtocell j are connected, and d _ij -R _th When ≧ 0, Femtocell i and Femtocell j are not connected. If a term in the matrix Q is less than 0, the term is set to 1. Otherwise, the term is set to 0. The interference diagram G is obtained by the above method, and 0 or 1 in the structured matrix Q determines the relationship between the Femtocells of the endpoints in the interference diagram G, that is, in the relationship of connected (0) or disconnected (1) Yes, Femtocell i and Femtocell j represent i and jth Femtocell, respectively.

  Step 202: Obtain the adjacency matrix A (G) from the interference diagram G. In the acquisition method, each end point in the interference diagram G is a row and a column of the adjacent matrix, the arrangement order of the corresponding end points in the row and the column of the adjacent matrix is the same, and when two end points are connected, it corresponds to the row and the column. The value is 1, otherwise the corresponding value is 0.

Step 203: A clustering algorithm is executed. ν _i represents an end point in the interference diagram, and d (ν _i ) represents a degree in the interference diagram of the end point ν _i . l is the number of the cluster, the initial value is 1, and “remove” (remove) or “export” of an endpoint is to remove the row and column corresponding to the endpoint from the interferogram adjacency matrix A (G) As shown in Fig. 3, step 203 includes the following steps.

Step 3-1: Set S represents an isolated point from an end point of 0 degrees, and Set B represents a temporary set. Remove the 0 degree endpoint row and column in the interferogram adjacency matrix A (G) to obtain the remaining endpoint adjacency matrix and name it A _i (G).

Step 3-2: Move out the maximum frequency endpoint from A _i (G) until A _i (G) is an all-zero matrix, and the remaining endpoints in A _i (G) are clusters (outside 35).
And the transferred endpoints are stored in set B. Add 1 to the l value, ie
(Outside 36)
It is. Here, it should be explained that 0 or 1 in the matrix A _i (G) represents the non-connection or connection relationship between the end points, and the dimensionality of the matrix represents the number of end points.

Step 3-3: When the interference diagram G and the interference diagram adjacency matrix A _i (G) are newly constructed using the set B and the new A _i (G) is all zero, the new interference diagram G The end point at is a cluster (outside 37)
N = l is the number of Femtocell clusters finally divided, and then perform step 3-4, and if the new A _i (G) is not an all-zero matrix, set B And repeat step 3-2.

Step 3-4: Femtocell corresponding to the end point in isolated point set s is put into the Femtocell cluster obtained by the above steps, and rule (outside 38)
The cluster number of the end point ν _i in the isolated point set s is determined by

  In the following, the transmission power of femto base stations in the cluster is controlled in units of clusters, and the Femtocell clustering status is adjusted, and finally the Femtocell in the interference sensitive area, the Femtocell in the non-interference sensitive area, and the Femtocell in the non-interference sensitive area The specific implementation steps of step 102 for determining the clusters are shown in FIG.

Step 501: First, some code definitions are provided. l is the cluster number, and the initial value is 1. Cluster (outside 39)
, The number of end points in the cluster is expressed as N _l, and the cluster (outside 40)
The transmission power of the base station of Femtocell i corresponding to the end point ν _i in p is expressed as p _i, and the maximum transmission power of the femto base station is (outside 41)
And the reference user's SINR (signal-to-interference and noise ratio) needs in Femtocell i are represented as r _i . A reference user is defined as a user facility on one side that is served by Femtocell, at the edge of Femtocell and relatively close to the macro base station. If one Femtocell can satisfy the service quality needs of its standard users, it can satisfy the service quality needs of the user equipment at any location in that range.

Step 502: Cluster (Outside 42)
For linear equations

Find the power value

And each element in p is a cluster (outside 43)
Corresponds to the minimum transmission power of the femto base station. Linear equation

Then

It is.

(Outside 44)
Is a macro base station and cluster (Outside 45)
Is the path gain between Femtocell i and
(Outside 46)
Is a cluster (outside 47)
Is the path gain between Femtocell i and Femtocell j in
(Outside 48)
Is a cluster (outside 49)
Is the path gain between the reference user in Femtocell i and the base station of Femtocell i in
(Outside 50)
Is the transmission power of the macro base station.

Step 503: The absolute value of the power solution (value) of the femtocell user in any cluster | P _k | is the maximum power of the femto base station (outside 51)
Determine if greater than. That is, in the power solution (vector) p, all (outside 52)
When the Femtocell corresponding to the element of the interference is divided into the Femtocell of the interference sensitive area, the end point corresponding to the Femtocell of these interference sensitive areas is the cluster (outside 53).
Femtocell set (outside 54)
The subscript ISA indicates an interference sensitive area (Interference Sensitive Area). Otherwise, the following steps are executed.

Step 504: Furthermore, the user's power solution in any cluster is set (outside 55)
To determine whether
(Outside 56)
If there is no element, step 505 is executed next.

(Outside 57)
In the matrix H in step 502,
(Outside 58)
The symbol determined by is a cluster (outside 59)
If the corresponding end point (ie, Femtocell) is 1 = N, the Femtocell set (outer 60) in the interference sensitive region
If not, cluster (outside 61)
From (outside 62)
And go back to step 502 to get a new cluster (outside 63)
The minimum transmission power of the femto base station is calculated, and the operation after step 502 is continued.

  Step 505:

If so, go back to step 501 to perform calculations related to the next cluster,

If it is, the process ends.

  The Femtocell of the interference sensitive region has been determined so far, and the Femtocell that does not belong to the interference sensitive region is a Femtocell that belongs to the non-interference sensitive region.

  The Femtocell clustering method of the interference sensitive area in step 103 is the same as the clustering method in step 101.

  In the following, for Femtocell in the interference sensitive area where clustering has been completed, the transmission power of the Femtocell base station in the cluster is controlled in units of clusters, and the clustering status of the Femtocell in the interference sensitive area is adjusted, and the Femtocell in the interference sensitive area is adjusted. The specific steps of step 104 for determining the cluster are shown as shown in FIG.

Step 601: q is the number of the cluster, the initial value is 1, the cluster C _q, the number of end points in the cluster represents an N _q, the transmission of the Femtocell i base station corresponding to the end point νi in cluster C _q The power is expressed as p _i, and the maximum transmission power of the Femtocell base station is (External 64)
And the SINR needs of the reference user in Femtocell i are represented as γ _i .

Step 602: For the cluster C _q , the matrix form for finding the linear equation is

And power solution

And the element in p is the minimum transmission power of the corresponding Femtocell base station in cluster C _q . Linear equation

Then

It is.

(Outside 65)
Is the path gain between the macro base station and Femtocell i in cluster C _q
(Outside 66)
Is the path gain between Femtocell i and Femtocell j in cluster C _q
(Outside 67)
Is the path gain between the reference user in Femtocell i and the base station of Femtocell i in cluster C _q .

  Step 603: In power solution p, all elements are

If satisfied, execute step 604,

In the matrix H,
(Outside 68)
The corresponding endpoint in the cluster C _q of the symbol determined by is moved from the cluster C _q to C _{q + 1} , returning to step 602 to calculate the femto base station transmit power value p of the new cluster C _q , Continue the operation of 602.

  Step 604:

If so, the process returns to step 601 to perform the related calculation of the next cluster, and if q = M, the process ends.

  So far, Femtocell clusters in the interference sensitive area have been established.

  Hereinafter, step 106 will be described with reference to FIGS. The frequency spectrum resource is divided into three parts that do not overlap each other, and each is a dedicated Femtocell resource, a dedicated macrocell resource, and a shared resource between the Femtocell and the macrocell. FIG. 7 shows the division in the frequency domain, and FIG. 8 shows an example of the allocation of the Femtocell resource in the interference sensitive area and the non-interference sensitive area, and the allocation resource in the downlink dead zone of the macro user.

  Hereinafter, an example will be described. It is assumed that there are six femtocells, and the distribution is as shown in FIG. 9 (a). In the figure, each femtocell is called one end point, and the positional distance relationship between them is

And the distance between the other end points is larger than Rth. The Femtocell interference diagram as shown in FIG. 9 is constructed according to the positional distance relationship, and the adjacent matrix corresponding to the Femtocell interference diagram is
(Outside 69)
It is.

  The frequency of the terminal 6 is 0, and as shown in FIG. 9 (b), the end point 6 is first exported and stored in the set s. Thereafter, as shown in FIG. 9 (c), the endpoints 1, 2 and 4 having the largest frequencies in the figure are sequentially transferred and stored in the set B, whereby the degrees of the endpoints 3 and 5 become 0, and 1 The second cluster, ie

It is. After that, as shown in FIG. 9 (d), using the end points recorded in the set B, a new Femtocell interference diagram and an adjacent matrix are constructed, the set B is set to zero, and the end point 1 having the maximum frequency is set. Export and form a second cluster, ie

It is. As shown in Fig. 9 (e), there is only one end point in set B, so it is the third cluster.

And the relational expression for the end point 6 in the isolated point set s.

The third cluster

It is composed. FIG. 9 (f) shows the result of clustering.

  As shown in FIG. 10, the relationship between the Femtocell distributed as shown in FIG. 9 and the macro base station is as shown in FIG. 10. If the first-stage clustering of the femtocell in FIG. Construct a simultaneous equation of power control for the cluster,

Among them,

It is.

  Find a solution of a quadratic system of equations

And the solution is (outside 70)
And then establish a power control simultaneous equation for the second cluster and the solution vector

And the solution is (outside 71)
And establish a power control simultaneous equation for the third cluster and its solution is

, End point 1 is the third cluster (outside 72)
To the interference sensitive area set D _ISA ,
(Outside 73)
The power for the remaining endpoint 6 at is newly calculated.

Construct an interference diagram for endpoint 1 in D _ISA to get its adjacency matrix, and since there is only one endpoint, that is, its frequency is 0, endpoint 1 constitutes the only cluster in the interference sensitive region . The power control simultaneous equations are established and obtained to obtain the power P ₁ .

  Therefore, in the final clustering result, the femtocell belonging to the non-interference sensitive area (NISA) is femtocell 2 to 6, and the cluster is

The femtocell belonging to the interference sensitive area (Interference Sensitive Area, ISA) is femtocell 1, and the cluster is

It is divided into.

  The above embodiments are merely used to explain the present invention, but are not intended to limit the present invention, and various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention. All the same technical schemes belong to the scope of the present invention since modifications can be made, and the patent protection scope of the present invention should be limited by the claims.

Claims (15)

Select Femtocell in a certain range, and S1 clustering Femtocell in the range,
For Femtocell that has completed clustering, the transmission power of femto base stations in the cluster is controlled in units of clusters, and the clustering status of Femtocell is adjusted, so that Femtocell in interference sensitive area, Femtocell in non-interference sensitive area, and non-interference S2 to determine the cluster of sensitive Femtocell,
S3 clustering Femtocell in interference sensitive area,
For the Femtocell in the interference sensitive area for which clustering has been completed, the Femtocell transmission power in the cluster is controlled in units of clusters, and the clustering status of the Femtocell in the interference sensitive area is adjusted to determine the Femtocell cluster in the interference sensitive area. S4,
Macro user equipment is divided into dead zone user equipment and non-dead zone user equipment, and when the strength of interference by Femtocell adjacent to macro user equipment reaches a level where it cannot communicate normally with the macro base station, the macro user equipment is designated as dead zone user equipment. If the macro user equipment is not subject to interference from the Femtocell, or if the strength of interference by the adjacent Femtocell does not affect normal communication with the macro base station, the macro user equipment is classified as a non-dead zone user equipment. S5 divided into
The frequency spectrum resource is divided into three parts that do not overlap each other, and the Femtocell cluster belonging to the interference sensitive area, the dead zone user equipment, the Femtocell cluster belonging to the non-interference sensitive area, and the non-dead zone user equipment respectively overlap each other. S6 that allocates no frequency spectrum resources of the three parts,
An interference suppression method in a mixed network of macro cells and femto cells,   Specifically, step S1 first acquires Femtocell position information, and constructs an Femtocell interference diagram and an adjacent matrix of the interference map based on the position information, and Femtocell based on the Femtocell interference map and the adjacent matrix. The method according to claim 1, characterized in that clustering is performed. The step of constructing the Femtocell interference diagram and the adjacent matrix of the interference diagram based on the position information specifically includes:
Represents an Femtocell interference diagram, V represents an end point set composed of Femtocells, elements in the edge set E represent a connection relationship between Femtocells of the end points, and if there is a connection relationship between any two end points, this 2 Indicates that collision interference exists between the Femtocells corresponding to the two endpoints, and these two endpoints are not divided into the same cluster,
Suppose that there are N Femtocells and a matrix
And Ψ is an N × N matrix of all 1, I is an N × N unit matrix,
And d _ij is the distance between Femtocell i and Fetocell j, and in Q,
Indicates that there is a connection relationship between the corresponding Femtocell i and Femtocell j,
Indicates that there is no connection relationship between the corresponding Femtocell i and Femtocell j, the interference diagram G is obtained by the method described above, and the structured matrix Q indicates the relationship between the end points Femtocell in the interference diagram G. Determined, i.e., connected or disconnected, Femtocell i and Femtocell j represent i, jth Femtocell,
Here, R _th is a cluster interference distance threshold, and when the distance between any two Femtocells is smaller than a certain value, the maximum transmission power of the femto base station is the user signal-to-interference in the Femtocell. The noise ratio requirement cannot be satisfied, and the minimum value of this distance is defined as the cluster interference distance threshold,
3. The method according to claim 2, further comprising: obtaining an adjacent matrix A (G) of the interference diagram by the interference diagram G. Specifically, the step of clustering Femtocell based on the Femtocell interference diagram and the adjacency matrix includes:
1) ν _i represents the end point in the Femtocell interference diagram, d (ν _i ) represents the degree in the Femtocell interference diagram of the end point ν _i , l is the cluster number, the initial value is 1, and the l th Femtocell Cluster of (outside 74)
Represented by
2) Construct isolated point set s from 0 degree end points,
3) Construct the interferogram G and the adjacency matrix A _i (G) of the endpoints where the remaining frequencies are not 0,
4) Save the maximum frequency endpoint at A _i (G) in set B and delete the row and column corresponding to this endpoint from A _i (G) until A _i (G) is a matrix of all zeros. And the remaining endpoints in A _i (G) are clusters (outside 75)
And add 1 to the value of l,
5) Using the set B, construct a new interference diagram G and an adjacent matrix A _i (G) of the interference diagram, and if the new A _i (G) is an all-zero matrix, Cluster from end point (outside 76)
If N = l is the number of Femtocell clusters currently assigned in the Femtocell clustering step, then perform step 6), and the new A _i (G) is not an all-zero matrix , Repeat step 4)
6) When the Femtocell corresponding to the end point in the isolated point set s enters the Femtocell cluster obtained in the above steps and determines which Femtocell cluster the end point ν _i in the isolated point set s is divided into,
(Outside 77)
To get the cluster number
(Outside 78)
3. The method according to claim 2, wherein the method represents the cluster where the maximum endpoint j of the distance from the isolated endpoint i to the minimum endpoint of each cluster is located. For Femtocell for which clustering has been completed in step S2, the operation for controlling the transmission power of the femto base station in the cluster in units of clusters is specifically,
l is the cluster number of Femtocell, its initial value is 1, and the cluster (outside 79)
, The number of end points in the cluster is expressed as N _l ,
The transmission power of the base station of Femtocell i corresponding to the end point ν _i at is expressed as P _i, and the request for the signal-to-interference noise ratio of the reference user at Femtocell _i is expressed as γ _i ,
A reference user is defined as a user facility at the edge of the Femtocell coverage area that is served by the Femtocell and relatively close to the macro base station, and one Femtocell is defined as the reference user's quality of service QoS. If the requirements can be satisfied, the QoS requirements of the user equipment at any location within the coverage range can be satisfied,
Cluster (outside 81)
Assuming that ensures the requirements of all the Femtocell reference user QoS in, a matrix of linear equations to be satisfied by P _i
Where,
N ₀ is the density of the noise power spectrum, and in the above equation,
(Outside 82)
Is a macro base station and cluster (outside 83)
Is the path gain between Femtocell i and
(Outside 84)
Is a cluster (outside 85)
Is the path gain between Femtocell i and Femtocell j in
(Outside 86)
Is cluster (outside 87)
Is the path gain between the reference user in Femtocell i and the base station of Femtocell i in
(Outside 88)
Is the transmission power of the macro base station,
The solution of the above linear equation is
And each element in p is a cluster (outside 89)
, Each femto base station corresponds to the lowest transmit power on the premise that it guarantees the QoS requirement of its reference user, and the cluster (outside 90)
The femto base station's transmission power at Femtocell i is (outside 91)
The method according to claim 1, wherein the method falls within the range of: In step S2, the clustering situation of the Femtocell is adjusted, and the operation of clustering the Femtocell of the interference sensitive region, the Femtocell of the non-interference sensitive region, and the Femtocell of the non-interference sensitive region is specifically,
1)
The obtained cluster (outside 92)
Is the minimum transmission power of the femto base station at
(Outside 93)
Represents the maximum transmission power of the femto base station, and all transmission powers in P are
The Femtocell corresponding to the element satisfying the above is a Femtocell belonging to the interference sensitive region, and the end point corresponding to the Femtocell of these interference sensitive regions is the cluster (outside 94).
Transferred to Femtocell set D _ISA in the interference sensitive area,
2) In power solution P,
If there is no element, then perform step 3), and the maximum endpoint of the sum of rows and columns in matrix H, ie (outside 95)
Number of clusters determined by (outside 96)
Cluster corresponding end points in (outside 97)
Cluster from (outside 98)
Move to a new cluster (outside 99)
And execute step S2 to create a new cluster (outside 100)
Calculate the femto base station transmit power solution P and continue with step 3) below,
3)
If it is, add 1 to l, return to step S2, and execute the calculation of the next cluster,
The operation of step S3 is completed,
The Femtocell belonging to the interference sensitive area has been determined so far, the Femtocell that does not belong to the interference sensitive area is the Femtocell of the non-interference sensitive area, and the cluster composed of the Femtocell of the non-interference sensitive area is the Femtocell of the non-interference sensitive area. 6. The method of claim 5, wherein the method is a cluster.   The method according to claim 1, wherein the clustering operation of step S3 is the same as the clustering operation of step S1. For the Femtocell in the interference sensitive region that has been clustered in step S4, the operation for controlling the Femtocell transmission power in the cluster in units of clusters is specifically:
Assume that the Femtocell of the interference sensitive region is divided into M clusters in step S3, q is a cluster number, an initial value is 1, and a q-th cluster is represented by C _q .
The cluster C _q, the number of end points in a cluster is represented as N _q, transmission power of the base station of the Femtocell i corresponding to the end point [nu _i in cluster C _q is represented as P _i, the reference user in the Femtocell i The signal-to-interference / noise ratio requirement is expressed as γ _i ,
Assuming that ensures the requirements of the reference user SINR of all Femtocell in cluster C _q, the format of the matrix of the linear equation to be satisfied by P _i,
Where
(Outside 101)
Is the path gain between the macro base station and Femtocell i in cluster C _q ,
(Outside 102)
Is the path gain between Femtocell i and Femtocell j in cluster C _q
(Outside 103)
Is the path gain between the reference user in Femtocell i and the Femtocell i base station in cluster C _q ,
The solution of the above linear equation is
And the elements in P correspond to the lowest transmit power on the premise that the femto base station guarantees the QoS requirement of its reference user in cluster C _q , respectively.
The transmission power of the Femtocell i base station at (outside 105)
2. The method according to claim 1, wherein the method falls within the following range. In step S4, the operation of adjusting the clustering status of the Femtocell in the interference sensitive region and determining the Femtocell cluster in the interference sensitive region is specifically,
1)
(Outside 106)
Represents the maximum transmission power of the femto base station, and all elements in the power solution P obtained in step S4 are
If satisfied, execute step 2)
Is present, the maximum endpoint of the sum of rows and columns in matrix H of step S4, i.e.,
(Outside 107)
The corresponding end point in the cluster C _q of the number determined by is moved from the cluster C _q to the cluster C _{q + 1} to obtain a new cluster C _q , and step S4 is performed to interfere with the new cluster C _q Calculate the transmission power P of the femto base station in the sensitive area and continue with step 2) below.
2)
Then add 1 to I and return to step S4 to perform the next cluster calculation,
, The operation to adjust the clustering status of the Femtocell in the interference sensitive region, and to determine the cluster of the Femtocell in the interference sensitive region is completed.
9. The method according to claim 8, wherein a cluster of Femtocells in the interference sensitive area has been determined so far.   The method of dividing the macro user equipment into the dead zone user equipment and the non-dead zone user equipment in step S5 is characterized in that it is divided in advance according to the position of the macro user equipment or according to the channel situation where the macro user equipment is located. The method of claim 1. Specifically, the operation of dividing the macro user equipment according to the channel situation where the macro user equipment is located in step S5 is as follows.
Macro user equipment determines whether it belongs to dead zone user equipment or non-dead zone user equipment according to the received pilot signal strength, signal-to-interference noise ratio or signal-to-noise ratio of adjacent Femtocell, or
The macro base station that provides the service to the macro user equipment is configured such that the macro user equipment is a dead zone user equipment or a channel state information fed back from the macro user equipment, a pilot signal strength, a signal to interference noise ratio, or a signal to noise ratio. Determine whether it belongs to non-dead zone user equipment, or
The macro user equipment determines whether it belongs to the dead zone user equipment or the non-dead zone user equipment according to the received pilot signal strength, signal to interference noise ratio or signal to noise ratio of the adjacent Femtocell, Reporting to the macro base station serving the macro user equipment, the macro base station further comprising: channel state information fed back from the macro user equipment, pilot signal strength, signal to interference noise ratio or signal to noise ratio; The method according to claim 10, further comprising determining whether the macro user equipment belongs to a dead zone user equipment or a non-dead zone user equipment based on a determination result of the macro user equipment. .   2. The method according to claim 1, wherein, in step S <b> 6, the three portions that do not overlap each other are a Femtocell dedicated resource, a macrocell dedicated resource, and a shared resource between the Femtocell and the macrocell.   In step S6, when the frequency spectrum resources of the three parts that do not overlap each other are allocated to the Femtocell cluster of the interference sensitive area, the dead zone user equipment, the Femtocell cluster of the non-interference sensitive area, and the non-dead zone user equipment, respectively. The Femtocell in the Femtocell cluster in the interference sensitive area selects the Femtocell dedicated resource, the dead zone user equipment selects the macro dedicated resource, and the Femtocell and non-dead zone user equipment in the Femtocell cluster in the non-interference sensitive area The method according to claim 12, further comprising: selecting a shared resource between the Femtocell and the macrocell.   When dividing frequency spectrum resources into three parts that do not overlap each other, the proportion of each part occupying the frequency spectrum resources is determined by the number of Femtocell clusters in the interference sensitive area and the number of dead zone user equipment. The method of claim 12.   Femtocell in the same cluster when allocating the three non-overlapping frequency spectrum resources to the interference sensitive area Femtocell cluster, dead zone user equipment, non-interference sensitive area Femtocell cluster and non-dead zone user equipment respectively. 14. The method of claim 13, wherein the same resource is used and the resource is a time spectrum or frequency domain frequency spectrum resource.