CN110621030A - Opportunistic signal spatial alignment for multi-user two-way relay systems - Google Patents
Opportunistic signal spatial alignment for multi-user two-way relay systems Download PDFInfo
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- CN110621030A CN110621030A CN201910596197.2A CN201910596197A CN110621030A CN 110621030 A CN110621030 A CN 110621030A CN 201910596197 A CN201910596197 A CN 201910596197A CN 110621030 A CN110621030 A CN 110621030A
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Abstract
A base station-user networking mode in a UDN is used for the following scenes: the communication system comprises a plurality of base stations and a plurality of users, wherein the base stations are divided into different clusters, and the users in the clusters adopt a zero-forcing precoding scheme to carry out downlink transmission. The method is characterized in that: the method comprises the following two operation steps: (1) base station clustering stage: the geographical coordinate information of the base station is used as input, the base station is divided into different clusters by using a mean vector migration algorithm, and the base stations with relatively short geographical positions are ensured to be in the same cluster. (2) User network access stage: after the base station completes clustering, the base stations in the same cluster send the same reference signal, the user receives and calculates the reference signal power value, and when the condition of antenna constraint is met, the base station-user cooperation finds out the network access mode which enables the sum of the reference receiving power values of the user to be maximum through a greedy algorithm. Compared with the traditional clustering method, the clustering method of the base station has more stable and effective result and higher practicability.
Description
Technical Field
The invention relates to a base station-user networking mode, in particular to a mode that a plurality of base stations and a plurality of users are divided into a plurality of clusters, and belongs to the technical field of wireless communication.
Background
With the increasing maturity of IoT and M2M services, UDN (ultra-dense network) is gradually forming and will open up a new chapter of wireless access networks. The core idea of UDN is network densification, which is mainly characterized by the gradual reduction of the distance between the wireless access node and the user equipment (not limited to human-centric legacy devices, but also including many IoT and M2M devices). It is noted that the base station/user density in 5G networks continues to increase, and in some areas it may even exceed the user density; different kinds of base stations are deployed in the network, such as macro base stations, micro base stations, home base stations, relay base stations, distributed antennas, radio frequency remote ends, and so on. When considering that the co-frequency networking or the orthogonalizable allocation resources are limited, the UDN network will present "ubiquitous interference" in the face of the massive AP and UE connection numbers, and the occurrence of such interference will limit the performance improvement that may be brought by the network densification.
Interference management in UDN networks requires a good balance between interference management capabilities and implementation complexity. Because of the huge number of APs and UEs in the UDN network, the global centralized interference management scheme is too complex and not practical. Clustering the APs and developing user association can actually divide a target network region, and more effective local centralized interference management can be realized through AP cooperation in each cluster. In this way, the complexity of the interference management implementation and the overhead of the overall system can be effectively controlled. Aiming at a traditional two-layer heterogeneous network, a distributed AP clustering algorithm is provided, wherein the AP clustering problem is remodeled by converting into a subgraph partitioning problem in a graph theory, and then a suboptimal solution with better performance can be quickly obtained by utilizing a classical clustering algorithm and K-means clustering, but the clustering result has larger difference along with different selection of initial points. In the network access stage of the user, the currently adopted method is that the user directly selects a base station to access the network according to the reference signal power measurement value, and the problem of spatial freedom degree caused by multiple antennas is not considered.
Aiming at the problems that the existing method is unstable and the airspace degree of freedom is not completely considered, the invention provides a base station-user networking mode in a UDN network.
Disclosure of Invention
In view of this, the present invention provides a base station-user networking method for UDN network, in which a user configures a single antenna and a base station configures multiple antennas. The invention combines base station clustering and user network access, and provides a base station-user combined networking method. Under the conditions of more base stations and more complex interference, the base stations with strong interference are divided into a cluster, and the base stations in the cluster completely eliminate the interference between users in the subsequent transmission process through zero forcing precoding. Then, in the network access stage of the user, the base station of each cluster sends orthogonal reference signals to facilitate the user measurement, then the base station and the user jointly complete the network access process, and finally the sum of the reference signal power values of all users in the whole network is maximum, and since the reference signal power value and the communication rate are positively correlated, the sum of the communication rate of the whole system is indirectly also maximum.
In order to achieve the above object, the present invention provides a base station-user networking method for a UDN network, which is used in the following scenarios: the downlink communication system comprises a plurality of base stations and a plurality of users, wherein the base stations are provided with a plurality of antennas, the users are provided with a single antenna, the number of the antennas of the base stations is greater than that of the antennas of the users, at the moment, the number of the base stations is large, the generated interference is serious, and a large amount of signaling overhead is caused by the global interference elimination technology. Therefore, we propose the following method, characterized in that: the method comprises the following two operation steps:
(1) a base station networking stage: through a mean-vector migration method, base stations which are relatively close to each other are divided into clusters as much as possible, and therefore the purpose of eliminating interference in the clusters in the subsequent transmission process is achieved.
The specific steps of the clustering method are as follows: and taking the geographic position information coordinates of all the base stations as data points, randomly selecting one data point as a drift center, calculating all the base stations within the drift radius, recalculating the drift center according to the coordinates of the base stations, and adding 1 to the access times of the cluster to the base stations. And repeating the process until the module value of the two drifting centers is smaller than the preset threshold value. The initial drift center is reselected until all base stations are visited at least once.
(2) User network access stage: after finishing the networking of the base stations, the base stations of the same cluster transmit the same reference signals, the base stations of different clusters transmit orthogonal reference signals, a user measures the power value of the reference signals, then the user transmits a network access application to the cluster with the maximum power value of the reference signals, the base station judges the relationship between the number of users applying at the moment and the number of antennas of all the base stations, if the number of users applying is larger than the number of antennas of the base station, the network access request of part of users with lower power values of the reference signals is refused, and then the refused users transmit the network access request to the cluster with the second maximum power value of the reference signals again until all the users finish the network access.
(3) After finishing base station-user networking, the user sends an uplink reference signal, the base station in the cluster finishes channel estimation in the cluster through the signal, and the base station can calculate the downlink channel parameters on the assumption that the uplink/downlink channel has reciprocity. And the base stations in the same cluster adopt zero-forcing precoding to eliminate the interference among users. Therefore, strong interference is limited in the cluster through clustering, interference elimination is carried out through zero forcing, and interference borne by a user is reduced. Moreover, no coordination is performed between clusters, so that the signaling overhead is less.
The invention relates to a base station-user networking mode suitable for a UDN network, which is used for carrying out base station clustering and user network access through joint design. The advantages are that: under the condition that the number of base stations and users is large, strong interference is limited in a cluster through base station clustering, the users predict the transmission performance after network access through downlink reference signals, and then the cluster with better communication performance is selected for network access. The key points of the innovation of the method are as follows: in the UDN network, a traditional clustering method is adopted for clustering, the final clustering result is influenced by the selection of an initial point, and the clustering is carried out by a mean-vector drift method, so that the clustering result is stable, and the final communication performance is good; in the user network access stage, a distributed method is used for finding the optimal solution close to the global situation, a whole network center is not required to make a global decision, and the base station in each cluster makes a decision, so that the signaling interaction overhead is reduced.
Drawings
Fig. 1 is an application scenario of the present invention: a UDN network;
fig. 2 is a flow chart of base station-subscriber networking of the present invention.
Fig. 3 is a simulation diagram of communication rate varying with transmission power according to different networking modes in the embodiment of the present invention.
Fig. 4 is a simulation diagram of communication rate with the number of base stations according to different networking modes in the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the accompanying drawings. ' Qiyi
Referring to fig. 1, an application scenario of the method of the present invention is described first: the system comprises a communication system consisting of a plurality of base stations and a plurality of users, wherein the base stations are provided with J antennas, and the users are provided with a single antenna. Here, a situation that the intra-cluster base station can acquire perfect channel state information so as to perform cooperative transmission and the inter-cluster base station does not exchange information is mainly considered. By HiAnd (3) representing a channel matrix from the ith user to the relay, wherein i is more than or equal to 1 and less than or equal to K. v. ofiRepresenting the beamforming vector for the ith user. The communication is completed in two stages, the first stage being a base station networking stage, in which the base stations are divided into different clusters. The second phase is the user's network entry phase, during which the user testsMeasuring the reference signal, and then the base station and the user cooperate together to complete the connection of the cluster and the user. After network access is finished, a user sends an uplink reference signal, a base station in a cluster can acquire channel state information of the user in the cluster, and then the base station eliminates intra-cluster interference through zero-forcing precoding to perform downlink transmission.
With reference to fig. 2, the following two operating steps of the method of the invention are described:
(1) a base station networking stage: and taking the geographic coordinates of the base stations as input data, and dividing the base stations into different sets by a mean-vector migration method. The specific implementation flow is as follows:
(3) in the user network access stage, the base stations in the same cluster transmit the same reference signal, and the base stations in different clusters transmit orthogonal reference signals. The reference signal power value of each cluster measured by the user k is sequentiallyAnd the user k selects the cluster with the maximum power value to send a network access request, and the rest users execute the operation in sequence.
a. First, a drift radius and a convergence threshold are set
b. Randomly selecting a point as an initial drifting center
c. Selecting points with a distance from the drifting center smaller than the drifting radius, and calculating a new point by the following formula
And (4) a drifting center.
D′center＝Dcenter+S
Wherein D iscenterIs the original drift center coordinate, S is the drift vector, B is the base station coordinate in the drift radius,
m is the number of base stations within the drift radius.
d. The cluster at this time is denoted as cluster 1, and the number of accesses to the base station within the drift radius of cluster 1 is increased by 1.
e. And repeating the drifting process until the modulus value of the drifting vector S is smaller than the convergence threshold value.
f. And repeating b-e until all base stations are accessed by at least one cluster.
g. And adding the base station into the cluster with the maximum access times to complete the clustering process.
(4) And after the cluster receives the network access request of the user, detecting the number of the users applying for network access and the total number of the antennas of the base station in the cluster. And if the number of the antennas in the cluster is larger than the number of the users requesting to access the network, allowing the application for accessing the request of the cluster user. Otherwise, calculating the difference X between the number of the application users and the number of the antennas, sequencing the reference signal power values of the application access users, and rejecting the network access application of the X users with the minimum reference signal power values.
In order to show the practical performance of the method, the applicant carries out a plurality of simulation implementation tests. The network configuration model in the experimental system is an application scenario shown in fig. 1. The results of the simulation experiments are shown in fig. 3 and 4, and the simulation was performed under different transmission powers and different numbers of antennas.
As can be seen from fig. 3, the communication rate obtained by the method of the present invention increases with the increase of the transmission power, and the main points of interest are: the mean-vector drift scheme has a superior communication rate performance compared to the conventional K-means scheme. Fig. 4 shows that, in the network access stage of the user, the distributed scheme proposed by the present invention has performance close to that of the centralized scheme, but the signaling overhead of the distributed scheme is much smaller than that of the centralized scheme, so the performance is better.
The above description is only exemplary of the present invention and should not be taken as limiting the invention, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. Under the ultra-dense network, the method is used for the following scenes: the downlink communication system comprises a plurality of base stations and a plurality of users, wherein the base stations are provided with a plurality of antennas, the users are provided with a single antenna, and the number of transmitting antennas is larger than that of receiving antennas. The method is characterized in that: the method comprises the following two operation steps:
(1) a base station networking stage: taking the geographic coordinates of the base station as the characteristics of the base station, taking the base station as a point, and dividing the base station into different clusters (2) through a mean vector migration algorithm, wherein the user access stages comprise: on the basis of finishing clustering, the base stations in the same cluster send the same reference signals, the base stations in different clusters send orthogonal reference signals, and a user selects a cluster to access the network according to the power value of the reference signals measured by the user. And after the network access is finished, eliminating the intra-cluster interference in the same cluster through zero-forcing precoding.
2. The method of claim 1, wherein:
the specific steps of the proposed base station networking are as follows:
(1) first, a drift radius and a convergence threshold are set
(2) Randomly selecting a point as an initial drifting center
(3) And selecting points with the distance from the drifting center smaller than the drifting radius, and calculating a new drifting center through the following formula.
D’center＝Dcenter+S
Wherein D iscenterIs the original drift center coordinate, S is the drift vector, B is the base station coordinate in the drift radius, and M is the number of base stations in the drift radius.
(4) The cluster at this time is denoted as cluster 1, and the number of accesses to the base station within the drift radius of cluster 1 is increased by 1.
(5) And repeating the drifting process until the modulus value of the drifting vector S is smaller than the convergence threshold value.
(6) And repeating (2) - (5) until all the base stations are accessed by at least one cluster.
(7) And adding the base station into the cluster with the maximum access times to complete the clustering process.
3. The method of claim, wherein:
the proposed user network-accessing stage comprises the following steps
(1) The base stations in the same cluster transmit the same reference signal, and the base stations in different clusters transmit orthogonal reference signals. The user measures the reference signal power value.
(2) And the user selects the cluster with the maximum reference signal power according to the measurement result and sends a network access request.
(3) After the initial network access is finished, the base station detects the relationship of the number of the base station-user antennas requesting network access at the moment. And if the number of the base station antennas in the same cluster is greater than that of the user antennas, receiving network access requests of all users. Otherwise, rejecting the network access request of X users with the minimum reference signal power value. Wherein X is the integrated difference between the number of the network access application users and the number of the base station antennas in each cluster.
(4) And repeating the process until all the users complete the network access process.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102545989A (en) * | 2010-12-17 | 2012-07-04 | 华为技术有限公司 | Communication method, device and system used for distributed antenna system |
| CN109495945A (en) * | 2018-12-18 | 2019-03-19 | 河海大学常州校区 | A kind of collaboration charging method based on cluster sub-clustering in WSNs |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102545989A (en) * | 2010-12-17 | 2012-07-04 | 华为技术有限公司 | Communication method, device and system used for distributed antenna system |
| CN109495945A (en) * | 2018-12-18 | 2019-03-19 | 河海大学常州校区 | A kind of collaboration charging method based on cluster sub-clustering in WSNs |
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