CN109743149B - Interference coordination method based on carrier aggregation in heterogeneous network - Google Patents
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Abstract
The invention provides an interference coordination method based on carrier aggregation in a heterogeneous network to reduce interference aiming at a scene of the heterogeneous network and based on a carrier aggregation technology. In detail, firstly, a plurality of carrier frequency bands are aggregated; next, according to the characteristics of each carrier frequency band and the communication characteristics of each layer in the heterogeneous network, on the basis of considering frequency reuse, different frequency bands are allocated to users in a layer and the same layer with relatively serious mutual interference by methods such as clustering, simple circulation and the like, and meanwhile, the transmission power of each base station is properly adjusted. Therefore, the interference in the network is reduced, the network capacity is increased, and the throughput rate of the system is improved, belonging to the technical field of wireless communication.
Description
Technical Field
The invention belongs to the technical field of wireless communication, and particularly provides an interference coordination method based on carrier aggregation for a downlink of a three-layer heterogeneous network to reduce interference in the network. Specifically, by aggregating a plurality of carriers, according to the communication characteristics of each layer, the distribution of clusters and the characteristics of each carrier frequency band, different carriers are allocated to the layer and the user with serious interference, the transmitting power is adjusted, the interference in the network is reduced, thereby the throughput rate of the system is improved,
background
In recent years, with the rapid development of smart phones, the used mobile data traffic is increasing exponentially, and users have more and more applications to real-time services such as videos and live broadcasts. In order to ensure the user experience of the real-time service, the communication data rate must be continuously increased to ensure the seamless coverage of the user, which puts high requirements on the wireless communication system.
Relevant statistics indicate that over 80% of voice traffic and nearly 90% of real-time data traffic occur in indoor or hot spot areas. However, for indoor users, communication service quality may be affected due to wall occlusion; for a hot spot area, a large number of users are gathered in a small area, and the communication link is congested, which easily causes network access difficulty, such as a network disconnection event caused by too many people flowing in the recent Hangzhou West lake. In order to solve the above problems and improve the communication rate, a concept of a heterogeneous network is proposed, and home base stations or micro base stations are respectively deployed in indoor and hotspot areas according to requirements under the framework of a traditional network to form a three-layer heterogeneous network. The first layer is composed of a macro base station in a traditional cellular network and macro users communicating with the macro base station, and is called a macro base station layer; the second layer is composed of a micro base station of a hot spot area and a micro user communicating with the micro base station and is called a micro base station layer; the third layer is composed of indoor home base stations and home users communicating with the home base stations, and is called a home base station layer. In the heterogeneous network, the low-power base stations such as the home base station and the micro base station have lower cost and flexible arrangement, and the distance between a user and a service base station is shortened by deploying a large number of home base stations and micro base stations, so that the problems of user coverage and user capacity can be effectively solved, and the network data rate is improved.
Although heterogeneous networks can improve the capacity and coverage of the network, when three layers of networks in the heterogeneous networks share spectrum resources, relatively serious inter-layer and intra-layer interference is generated. Specifically, in the downlink, the transmission power of the macro base station in the conventional cellular network is much greater than the transmission power of the micro base station and the home base station, so that when a user connected with the low power node is closer to the macro base station, the user may experience large interlayer interference. Thus, the introduction of low power nodes further aggravates the interference in the network.
Methods for reducing heterogeneous network downlink interference include spatial interference alignment and frequency domain interference coordination methods. Spatial interference alignment compresses the interfering signals at the receiver in as small a dimension as possible, thereby leaving independent dimensions for the useful signals to be decoded correctly, but this approach is significantly compromised in the case of more interfering signals. The frequency domain interference coordination provides a channel with less interference for a user by performing interference detection on the channel, but since a heterogeneous network mechanism is complex, complex iterative operations such as lagrangian and gradient methods are often required to provide an optimal channel for the user, and the complexity is too high.
Aiming at the defects of the existing method, the invention provides an interference coordination technology based on a carrier aggregation technology, an additional high-frequency band is introduced, the interference situation of each layer is known through control centers of different layers, a part of low-power nodes and corresponding users are moved to the high-frequency band according to the network interference situation and high-frequency characteristics, the transmitting power is adjusted to reduce the interference in a heterogeneous network, and the network rate is improved.
Disclosure of Invention
The invention aims to provide a method for reducing downlink interference in a heterogeneous network and improving data rate, which is simple in strategy, economical and practical. Firstly, introducing a plurality of discontinuous frequency bands through carrier aggregation; then, clustering is carried out on the micro base station layer according to the distance between the micro base stations, so that micro areas with serious mutual interference form clusters; and finally, according to the characteristics of different frequency bands and the transmission characteristics of different layers in the heterogeneous network, carrying out reasonable spectrum resource allocation and transmission power adjustment on different users or clusters of different layers and the same layer, thereby reducing interference and improving the data rate.
The technical scheme adopted by the invention is as follows:
an interference coordination method based on carrier aggregation in a heterogeneous network comprises the following steps:
(1) carrier aggregation: introducing discontinuous carrier frequency bands into the heterogeneous network, and performing frequency spectrum resource allocation on the heterogeneous network according to the transmission characteristics of the home base station layer, the micro base station layer and the macro base station layer and the characteristics of different carrier frequency bands;
(2) interference coordination of a home base station layer: the femtocell selects a carrier frequency band as a communication frequency band according to the transmission characteristics of the femtocell, simultaneously, each femtocell measures the signal-to-interference-and-noise ratio of the femtocell and compares the measured signal-to-interference-and-noise ratio with a set threshold, and the transmitting power of the femtocell is adjusted step by step according to the comparison result until the femtocell normally communicates in the selected carrier frequency band;
(3) interference coordination of a micro base station layer: clustering the micro base stations according to the distances among all the micro base stations, and distributing carrier frequency band resources to all the micro base stations according to clustering results; the micro base station simultaneously occupies a plurality of carrier frequency bands, sends signals at different carrier frequency bands with different transmitting powers, simultaneously measures the self received signal strength and the received signal-to-noise ratio, compares the test result with a threshold value, and adjusts the occupied carrier frequency bands according to the comparison result;
(4) and (3) interference coordination of a macro base station layer: and the macro base station transmits signals with different powers on different carrier frequency bands, and simultaneously, the macro user measures the received signal strength and the received signal to noise ratio of the macro user on different carrier frequency bands, compares the received signal strength and the received signal to noise ratio with a set threshold value, and allocates the carrier frequency bands according to the comparison result.
Wherein, the step (2) comprises the following steps:
(201) selecting a carrier frequency band;
(202) setting a signal-to-interference-and-noise ratio threshold value Ths and setting a switching control center of the home base station;
(203) each family user measures the signal-to-interference-and-noise ratio SINR and compares the SINR with a threshold value Ths, wherein the SINRijR is not less than Thsij＝1，SINRij< Ths denotes RijIf it is 0, the comparison result is returned to the switching control center of the home base station through the respective home base station; wherein the SINRijThe SINR corresponding to the downlink from the ith home base station to the jth user of the base station is shown;
(204) the exchange control center sets two arrays R and R', and stores the comparison result of the step (203) in the array R;
(205) the exchange control center checks whether the element 0 exists in the R, if not, the home base station and the home user communicate in the selected carrier frequency band; if there is a 0 element, then perform step (206);
(206) for r ij0, the switching control center finds a set S of home base stations adjacent to the target home base station ii；
(207) Incrementally increasing target home base stations iEach time the power is increased, the switching control centre informs the SiAll the femtocell updates the SINR, and each femtocell compares the new SINR with a threshold value Ths to obtain rij'the comparison result is returned to the switching control center through the respective home base station and stored in the array R';
(208) if the element in R 'is unchanged from 1 to 0 compared to the corresponding element in R, and R'ijIf yes, storing the result in the array R' into the array R, and continuing to execute the step (207); if the element in R 'is unchanged from 1 to 0 compared to the corresponding element in R, and R'ijIf the frequency band is 1, the home base station and the home user communicate in the selected carrier frequency band; if the element in R' changes from 1 to 0 compared with the corresponding element in R, the increased power of the target home base station i is withdrawn, and the operation is ended.
Wherein, the step (3) comprises the following steps: :
(301) selecting a plurality of carrier frequency bands;
(302) two thresholds are set: maximum received signal strength PrmAnd minimum received signal-to-noise ratio SNRrm；
(303) Clustering the micro base stations according to the distance between the micro base stations;
(304) according to the clustering result of the micro base stations, carrying out carrier frequency band resource allocation on the carrier frequency band exclusively occupied by the micro base station layer in the selected carrier frequency band;
(305) the micro base station sends signals with different transmitting powers in a high frequency band in the selected carrier frequency band, and all micro users measure the self received signal intensity and the received signal-to-noise ratio;
(306) if there is a micro-user whose received signal strength in the high frequency band is less than the maximum received signal strength PrmWhile the received signal-to-noise ratio is greater than the minimum received signal-to-noise ratio SNRrmIf not, all the micro users and the micro base stations are distributed in the micro base stationThe carrier frequency band is communicated.
Wherein, the step (303) specifically comprises the following steps:
(3031) presetting a distance threshold value d1If the distance between two adjacent micro base stations is less than d1Then the two base stations interfere with each other seriously;
(3032) all micro base stations are combined into a set PB;
(3033) starting from the first micro base station in the set PB, sequentially detecting the distance from the rest micro base stations in the set PB to the first micro base station, and detecting that the distance from the first micro base station to the first micro base station is less than d1After the micro base station, the micro base station and the first micro base station form a micro base station cluster;
(3034) continuing the detection, if detecting that the distance from one micro base station to the first micro base station is less than d1Detecting the distance between the micro base station and all micro base stations in the formed micro base station cluster, if the distance is less than d1If not, the distance between the micro base station and the formed micro base station cluster is less than d1The micro base station forms a new micro base station cluster, the new micro base station cluster is a related cluster of the formed micro base station clusters, and the clusters form a generalized cluster;
(3035) after traversing all the rest micro base stations in the set PB, deleting the micro base stations which form the common cluster or the related cluster from the set PB, and updating the set PB;
(3036) steps (3033) to (3035) continue until the set PB is empty.
Wherein, the step (304) specifically comprises the following steps:
(3041) counting the number of micro base stations in each micro base station cluster, selecting the maximum Num of the number of the micro base stations, and equally dividing the carrier frequency band exclusively occupied by the micro base station layer into Num sub-frequency bands to form a sub-frequency band set;
(3042) for a generalized cluster, selecting the micro base station with the most occurrence times in the related cluster, randomly allocating a sub-frequency band to the micro base station, selecting the micro base station with the second most occurrence times in the related cluster, randomly selecting one from the rest sub-frequency bands to allocate to the micro base station, and sequentially performing the steps until the micro base stations which repeatedly appear in the related clusters are all allocated to the sub-frequency bands;
(3043) for each related cluster in the generalized cluster, determining whether a micro base station which is already allocated to a sub-frequency band exists in the related cluster, if so, deleting the allocated sub-frequency band from a sub-frequency band set, counting the number f of the micro base stations to be allocated and the number n of the remaining sub-frequency bands in the related cluster, if n can be divided by f, randomly allocating n/f continuous sub-frequency bands for each micro base station to be allocated, if not, calculating the remainder re of dividing n by f, randomly selecting one micro base station, allocating (n-re)/f + re continuous sub-frequency bands, and then randomly allocating (n-re)/f continuous sub-frequency bands for each remaining micro base station;
(3044) for a common cluster, counting the number f of micro base stations in the cluster, randomly allocating Num/f continuous sub-bands for each micro base station to be allocated if Num can be divided by f, calculating the remainder rem of division of Num and f if Num cannot be divided by f, randomly selecting one micro base station, allocating (Num-rem)/f + rem continuous sub-bands, and randomly allocating (Num-re)/f continuous sub-bands for each remaining micro base station.
Wherein, the step (4) comprises the following steps:
(401) selecting a plurality of carrier frequency bands;
(402) setting M pairs of maximum received signal strength threshold values and minimum received signal-to-noise ratio threshold values which are respectively matched with the M multiplex carrier frequency bands according to the number M of the multiplex carrier frequency bands of the macro base station layer, the micro base station layer and the home base station layer;
(403) the macro base station transmits signals with different powers on different carrier frequency bands, and the macro user measures the received signal strength and the received signal-to-noise ratio of the macro user on different carrier frequency bands;
(404) if a macro user exists, the received signal intensity on a certain multiplexing carrier frequency band is smaller than the maximum received signal intensity corresponding to the multiplexing frequency band, and meanwhile, the received signal-to-noise ratio on the multiplexing carrier frequency band is larger than the minimum received signal-to-noise ratio threshold corresponding to the multiplexing frequency band, the macro user works in the multiplexing carrier frequency band;
(405) and the rest macro users communicate in a low frequency band in the selected carrier frequency band.
Compared with the prior art, the invention has the advantages that:
the invention designs an interference coordination method aiming at a three-layer heterogeneous network downlink. By carrier aggregation, spectrum resource allocation and transmission power optimization, the interference between layers is reduced, the spectrum utilization rate is improved, and the user capacity of the network is expanded. Meanwhile, aiming at the intra-layer interference of a micro cell layer, a micro base station clustering method is designed, and the intra-layer interference is reduced by eliminating the main interference. The algorithm of the method is low in complexity and simple to operate, and the method is very suitable for being applied to an actual heterogeneous network.
Drawings
FIG. 1 is a flow chart of the process of the present invention.
Fig. 2 is a system diagram of a three-tier heterogeneous network of the present invention.
Fig. 3 is a schematic diagram of the aggregated carrier components of the present invention.
Fig. 4 is a schematic diagram of micro base station clustering in accordance with the present invention.
Detailed Description
The following detailed description of specific embodiments of the present invention is made with reference to the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Fig. 1 is a flowchart of a downlink interference coordination method for a three-layer heterogeneous network proposed by the present invention; FIG. 2 illustrates a system diagram of a three-tier heterogeneous network scenario to which the method of the present invention is directed; fig. 3 shows 4 carrier components aggregated by the carrier aggregation technique, i.e., four frequency bands of 450 to 470MHz, 698 to 862MHz, 2.3G to 4.2GHz, and 4.4G to 4.99 GHz. Fig. 4 shows a schematic diagram of clustering and frequency allocation according to mutual positions between micro base stations.
The invention relates to an interference coordination method based on carrier aggregation in a heterogeneous network, which comprises the following steps with reference to fig. 1:
(1) carrier aggregation: introducing discontinuous carrier frequency bands into the heterogeneous network, and performing frequency spectrum resource allocation on the heterogeneous network according to the transmission characteristics of the home base station layer, the micro base station layer and the macro base station layer and the characteristics of different carrier frequency bands;
(2) interference coordination of a home base station layer: the femtocell selects a carrier frequency band as a communication frequency band according to the transmission characteristics of the femtocell, simultaneously, each femtocell measures the signal-to-interference-and-noise ratio of the femtocell and compares the measured signal-to-interference-and-noise ratio with a set threshold, and the transmitting power of the femtocell is adjusted step by step according to the comparison result until the femtocell normally communicates in the selected carrier frequency band;
(3) interference coordination of a micro base station layer: clustering the micro base stations according to the distances among all the micro base stations, and distributing carrier frequency band resources to all the micro base stations according to clustering results; the micro base station simultaneously occupies a plurality of carrier frequency bands, sends signals at different carrier frequency bands with different transmitting powers, simultaneously measures the self received signal strength and the received signal-to-noise ratio, compares the test result with a threshold value, and adjusts the occupied carrier frequency bands according to the comparison result;
(4) and (3) interference coordination of a macro base station layer: and the macro base station transmits signals with different powers on different carrier frequency bands, and simultaneously, the macro user measures the received signal strength and the received signal to noise ratio of the macro user on different carrier frequency bands, compares the received signal strength and the received signal to noise ratio with a set threshold value, and allocates the carrier frequency bands according to the comparison result.
At the home base station layer, the distance between home base stations is small, mutual interference is easy to occur at a low frequency band, meanwhile, the sending power of the home base station is small, and the home base station layer is easy to be interfered with a common low frequency band of other layers, so that the home base station layer only occupies the high frequency band. The interference coordination method for the femtocell layer comprises the following steps:
(201) the femtocell layer selects the 4.4G-4.99 GHz frequency band with the highest frequency in the carrier components as the communication frequency band of the layer.
(202) In order to guarantee the communication quality of each home subscriber, a signal-to-noise-and-interference ratio (SINR) threshold value Ths is preset, the downlink SINR of the subscriber is higher than the Ths, the higher communication quality can be guaranteed, and a switching control center of the home base station is arranged;
(203) each family user measures his own interferenceThe noise ratio SINR is compared with a threshold value ThsijR is not less than Thsij＝1，SINRij< Ths denotes RijIf it is 0, the comparison result is returned to the switching control center of the home base station through the respective home base station; wherein the SINRijThe SINR corresponding to the downlink from the ith home base station to the jth user of the base station is shown;
(204) the exchange control center sets two arrays R and R', and stores the comparison result of the step (203) in the array R;
(205) the exchange control center checks whether the element 0 exists in the R, if not, the home base station and the home user communicate in the selected carrier frequency band; if there is a 0 element, then perform step (206);
(206) for r ij0, the switching control center finds a set S of home base stations adjacent to the target home base station ii；
(207) The transmitting power of the target home base station i is increased step by step, and the switching control center informs S every time the power is increasediAll the home base stations in the system update the SINR, and each home user compares the new SINR with a threshold value Ths again to obtain r'ijThe comparison result is returned to the switching control center through the respective home base station and stored in the array R';
(208) if the element in R 'is unchanged from 1 to 0 compared to the corresponding element in R, and R'ijIf yes, storing the result in the array R' into the array R, and continuing to execute the step (207); if the element in R 'is unchanged from 1 to 0 compared to the corresponding element in R, and R'ijIf the frequency band is 1, the home base station and the home user communicate in the selected carrier frequency band; if the element in R' changes from 1 to 0 compared with the corresponding element in R, the increased power of the target home base station i is withdrawn, and the operation is ended.
And on the micro base station layer, the user and the home base station layer in the area close to the micro base station multiplex a high frequency band, and the power is reduced for transmission in the high frequency band. And the users in the rest area occupy the higher frequency band, and normally transmit power in the higher frequency band. Therefore, interference between the micro base station layer and the home base station layer is avoided, interference between users of each micro base station can be reduced, the frequency spectrum utilization rate is improved, and the capacity of the micro base station layer is expanded. It should be noted that, in the micro base station layer, it often happens that several micro base stations are deployed in a hot spot area, in this case, the sharing of a higher frequency band by several closely-spaced micro base stations may cause serious interference. In order to reduce the interference in the layer, the invention designs a micro base station clustering method, and certain frequency spectrum allocation is carried out according to the clustering result. The interference coordination method of the micro base station layer comprises the following steps:
(301) the micro base station layer selects two frequency bands with the highest frequency of 2.3G-4.2 GHz and 4.4G-4.99 GHz from the carrier components as the communication frequency band of the layer.
(302) Two thresholds are set: maximum received signal strength PrmAnd minimum received signal-to-noise ratio SNRrm；
(303) In the micro base station switching control center, all micro base stations form a set PB. The micro base station exchange control center stores the distances between all the micro base stations. Clustering the micro base stations according to the distance of the micro base stations, and the specific steps of clustering are described as follows in conjunction with fig. 3.
a. A distance threshold value d is preset by the micro base station switching control center1If the distance between two adjacent micro base stations is less than d1Then the two base stations are considered to interfere with each other more seriously. All micro base stations constitute a set PB.
b. From micro base station 1 (PBS)1) Initially, PBS was detected in sequence in PB1Is less than or equal to d1The PBS (1). As shown in FIG. 3, the PBS2To the PBS1Is less than d1Forming a cluster { PBS1，PBS2Detection continues, PBS3To the PBS1Is also less than d1At this time, the PBS1Has been mixed with PBS2Clustering followed by detection of PBS3And PBS2A distance between them, the distance being greater than d1Therefore, PBS3Cannot be incorporated into { PBS1，PBS2Rather, a cluster is formed that correlates with the first cluster, denoted as a generalized cluster { { PBS1，PBS2}；{PBS1，PBS3}}. Continue detection, other PBS to PBS1Are all greater than d1Removal of PBS from PB1、PBS2And PBS3。
c. PBS from the first element in PB4Initially, the PBS was examined5Forming a cluster { PBS4，PBS5}; detection of PBS6Formation of related clusters { { PBS4，PBS5}；{PBS4，PBS6}; detection of PBS7Distance greater than d1Skipping; detection of PBS8，PBS8To the PBS4And PBS6Are all less than d1Adding the cluster { PBS4，PBS6Get { { PBS4，PBS5}；{PBS4，PBS6，PBS8}; detection of PBS9Distance greater than d1Skip. Removal of PBS from PB4、PBS5、PBS6And PBS8。
d. PBS from the first element in PB7Initially, the other PBSs in the PB are brought to the PBS7Are all greater than d1Therefore, PBS7Forming ordinary clusters { PBS alone7}. Removal of PBS from PB7。
e. PBS from the first element in PB9Initially, at this point, the PB is left with PBS only9So as to form a cluster { PBS alone9}. Removal of PBS from PB9。
f. And detecting that the PB is empty, and finishing clustering.
(304) Because the micro base stations in the cluster interfere with each other seriously, different frequency bands need to be allocated to the micro base stations. The specific steps are as follows:
a. firstly, counting the number of micro base stations in each micro base station cluster, selecting a maximum Num, and dividing the frequency band exclusively occupied by the micro base station layer into Num sub-bands to form a sub-band set, wherein the step (303) shows that at most 3 micro base stations are included in one cluster, so that the frequency band 2.3G-4.2 GHz is divided into 3 sub-bands, as shown in FIG. 3;
b. then, sub-bands are allocated to the generalized clusters, and the sub-bands in the related clusters are selectedThe micro base station with the most times randomly allocates a sub-frequency band for the micro base station, and for the cluster { { PBS1，PBS2}；{PBS1，PBS3}, PBS first1Allocating subband 1;
c. for each related cluster in the generalized cluster, determining whether a micro base station allocated to a sub-band exists in the related cluster, if so, deleting the allocated sub-band from a sub-band set, counting the number f of micro base stations to be allocated and the number n of remaining sub-bands in the related cluster, if n can be evenly divided by f, randomly allocating n/f continuous sub-bands for each micro base station to be allocated, if not, calculating the remainder re of n divided by f, randomly selecting one micro base station, allocating (n-re)/f + re continuous sub-bands, then randomly allocating (n-re)/f continuous sub-bands for each remaining micro base station, and according to the rule, the related cluster { PBS (PBS) randomly allocates (n-re)/f continuous sub-bands1，PBS2Is PBS2Allocate remaining subbands 2 and 3, correlated cluster PBS1，PBS3Is PBS3Allocating remaining subbands 2 and 3 as shown in fig. 2 and 3;
d. for a common cluster, counting the number f of micro base stations in the cluster, randomly allocating Num/f continuous sub-bands for each micro base station to be allocated if Num can be evenly divided by f, calculating the remainder rem of division of Num and f if Num cannot be evenly divided, randomly selecting one micro base station, allocating (Num-rem)/f + rem continuous sub-bands, and randomly allocating (Num-re)/f continuous sub-bands for each remaining micro base station, wherein the common cluster { PBS (PBS) is7Is PBS7Sub-bands 1, 2 and 3 are allocated as shown in fig. 2 and 3;
(305) p of micro base station in high frequency band 4.4G-4.99 GHz far lower than normal transmitting power levelLAnd transmitting a signal, and measuring the self received signal strength and the received signal-to-noise ratio at high frequency by the micro user. If the received signal strength of the micro-user in the high frequency band is less than PrmWhile the received signal-to-noise ratio is greater than the SNRrmThen these micro-users and home user layers share the high frequency band. The effect can be approximately expressed as that the micro users within the solid line circle near the micro base station communicate on the frequency band of 4.4G to 4.99GHz, as shown in fig. 2;
(306) and the rest micro users communicate in the lower frequency band allocated by the corresponding micro base station.
In a macro base station layer, a user in a region close to the macro base station and other two layers share a high frequency band and transmit power at high frequency; multiplexing a higher frequency band at a user and a micro base station layer in an area closer to the macro base station, and transmitting power reduction at the macro base station in the higher frequency band; and the users in the residual area occupy the low frequency band. Therefore, the interference between layers can be avoided, the interference between users in the macro cell can be reduced, the frequency spectrum utilization rate can be improved, and the user capacity of the macro cell can be increased. The interference coordination method of the macro base station layer comprises the following steps:
(401) the macro user sets four thresholds: maximum received signal strength PthAnd PtmAnd minimum received signal-to-noise ratio SNRthAnd SNRtm；
(402) P of macro base station far lower than normal transmitting power level in high frequency range of 4.4G-4.99 GHzM1And transmitting signals, and measuring the self received signal strength and the received signal-to-noise ratio by the macro user in the frequency band. If the received signal strength of the macro user in the high frequency band is less than PthWhile the received signal-to-noise ratio is greater than the SNRthThen these macro users share the high band. In effect, the macro user communicating in the 4.4G to 4.99GHz band can be approximately represented as a macro user within a solid circle near the macro base station, as shown in fig. 2.
(403) P of macro base station far lower than normal transmitting power level in higher frequency band 2.3G-4.2 GHzM2(PM2Is significantly greater than PM1) And transmitting signals, and measuring the self received signal strength and the received signal-to-noise ratio by the macro user in the frequency band. If the received signal strength of the macro user in the higher frequency band is less than PtmWhile the received signal-to-noise ratio is greater than the SNRtmThen these macro users share the higher frequency band. In effect, a macro user communicating in the 2.3G-4.2 GHz band can be approximately represented as a macro user within a dotted circle near the macro base station, as shown in fig. 2;
(404) and the rest macro users are far away from the macro base station, and communication is carried out on low-frequency bands of 450-470 MHz and 698-862 MHz.
The above description is only an example of the present invention and should not be taken as limiting the invention, and any modifications, equivalents, improvements and the like which are within the principle of the present invention should be included in the scope of the present invention.
Claims (4)
1. An interference coordination method based on carrier aggregation in a heterogeneous network is characterized by comprising the following steps:
(1) carrier aggregation: introducing discontinuous carrier frequency bands into the heterogeneous network, and performing frequency spectrum resource allocation on the heterogeneous network according to the transmission characteristics of the home base station layer, the micro base station layer and the macro base station layer and the characteristics of different carrier frequency bands;
(2) interference coordination of a home base station layer: the femtocell selects a frequency band with the highest frequency in the carrier components as a communication frequency band according to the transmission characteristics of the femtocell, simultaneously, each femtocell measures the signal-to-interference-and-noise ratio of the femtocell and compares the measured signal-to-interference-and-noise ratio with a set threshold, and the transmitting power of the femtocell is adjusted step by step according to the comparison result until the femtocell normally communicates in the selected carrier frequency band;
(3) interference coordination of a micro base station layer: clustering the micro base stations according to the distances among all the micro base stations, and distributing carrier frequency band resources to all the micro base stations according to clustering results; the micro base station selects two frequency bands with the highest frequency in the carrier components as communication frequency bands, sends signals at different carrier frequency bands with different transmitting powers, simultaneously measures the self received signal strength and the received signal-to-noise ratio, compares the test result with a threshold value, and adjusts the occupied carrier frequency band according to the comparison result;
(4) and (3) interference coordination of a macro base station layer: the macro base station transmits signals with different powers on different carrier frequency bands, meanwhile, the macro user measures the received signal strength and the received signal to noise ratio of the macro user on different carrier frequency bands, compares the received signal strength and the received signal to noise ratio with a set threshold value, and allocates the carrier frequency bands according to the comparison result;
wherein, the step (3) specifically comprises the following steps:
(301) the micro base station layer selects two frequency bands with the highest frequency in the carrier components as communication frequency bands of the layer;
(302) two thresholds are set: maximum received signal strength PrmAnd minimum received signal-to-noise ratio SNRrm；
(303) Clustering the micro base stations according to the distance between the micro base stations;
(304) according to the clustering result of the micro base stations, carrying out carrier frequency band resource allocation on the carrier frequency band exclusively occupied by the micro base station layer in the selected carrier frequency band;
(305) the micro base station sends signals with different transmitting powers in a high frequency band in the selected carrier frequency band, and all micro users measure the self received signal intensity and the received signal-to-noise ratio;
(306) if there is a micro-user whose received signal strength in the high frequency band is less than the maximum received signal strength PrmWhile the received signal-to-noise ratio is greater than the minimum received signal-to-noise ratio SNRrmIf not, all the micro users and the micro base stations communicate in the carrier frequency band distributed by the micro base station;
wherein the step (4) specifically comprises the following steps:
(401) a macro base station layer selects a plurality of carrier frequency bands as communication frequency bands of the macro base station layer;
(402) setting M pairs of maximum received signal strength threshold values and minimum received signal-to-noise ratio threshold values which are respectively matched with the M multiplex carrier frequency bands according to the number M of the multiplex carrier frequency bands of the macro base station layer, the micro base station layer and the home base station layer;
(403) the macro base station transmits signals with different powers on different carrier frequency bands, and the macro user measures the received signal strength and the received signal-to-noise ratio of the macro user on different carrier frequency bands;
(404) if a macro user exists, the received signal intensity on a certain multiplexing carrier frequency band is smaller than the maximum received signal intensity corresponding to the multiplexing frequency band, and meanwhile, the received signal-to-noise ratio on the multiplexing carrier frequency band is larger than the minimum received signal-to-noise ratio threshold corresponding to the multiplexing frequency band, the macro user works in the multiplexing carrier frequency band;
(405) and the rest macro users communicate in a low frequency band in the selected carrier frequency band.
2. The method for interference coordination based on carrier aggregation in a heterogeneous network according to claim 1, wherein the step (2) specifically includes the following steps:
(201) the femtocell layer selects a carrier frequency band as a communication frequency band of the home layer;
(202) setting a signal-to-interference-and-noise ratio threshold value Ths and setting a switching control center of the home base station;
(203) each family user measures the signal-to-interference-and-noise ratio SINR and compares the SINR with a threshold value Ths, wherein the SINRijR is not less than Thsij＝1，SINRij< Ths denotes RijIf it is 0, the comparison result is returned to the switching control center of the home base station through the respective home base station; wherein the SINRijThe SINR corresponding to the downlink from the ith home base station to the jth user of the base station is shown;
(204) the exchange control center sets two arrays R and R', and stores the comparison result of the step (203) in the array R;
(205) the exchange control center checks whether the element 0 exists in the R, if not, the home base station and the home user communicate in the selected carrier frequency band; if there is a 0 element, then perform step (206);
(206) for Rij0, the switching control center finds a set S of home base stations adjacent to the target home base station ii；
(207) The transmitting power of the target home base station i is increased step by step, and the switching control center informs S every time the power is increasediAll the home base stations in the system update the SINR, and each home user compares the new SINR with a threshold value Ths again to obtain r'ijThe comparison result is returned to the switching control center through the respective home base station and stored in the array R';
(208) if the element in R' does not change from 1 to 0 compared to the corresponding element in R, andr′ijif yes, storing the result in the array R' into the array R, and continuing to execute the step (207); if the element in R 'is unchanged from 1 to 0 compared to the corresponding element in R, and R'ijIf the frequency band is 1, the home base station and the home user communicate in the selected carrier frequency band; if the element in R' changes from 1 to 0 compared with the corresponding element in R, the increased power of the target home base station i is withdrawn, and the operation is ended.
3. The method for interference coordination based on carrier aggregation in a heterogeneous network according to claim 1, wherein the step (303) specifically comprises the following steps:
(3031) presetting a distance threshold value d1If the distance between two adjacent micro base stations is less than d1Then the two base stations interfere with each other seriously;
(3032) all micro base stations are combined into a set PB;
(3033) starting from the first micro base station in the set PB, sequentially detecting the distance from the rest micro base stations in the set PB to the first micro base station, and detecting that the distance from the first micro base station to the first micro base station is less than d1After the micro base station, the micro base station and the first micro base station form a micro base station cluster;
(3034) continuing the detection, if detecting that the distance from one micro base station to the first micro base station is less than d1Detecting the distance between the micro base station and all micro base stations in the formed micro base station cluster, if the distance is less than d1If not, the distance between the micro base station and the formed micro base station cluster is less than d1The micro base station forms a new micro base station cluster, the new micro base station cluster is a related cluster of the formed micro base station clusters, and the clusters form a generalized cluster;
(3035) after traversing all the rest micro base stations in the set PB, deleting the micro base stations which form the common cluster or the related cluster from the set PB, and updating the set PB;
(3036) steps (3033) to (3035) continue until the set PB is empty.
4. The method for interference coordination based on carrier aggregation in heterogeneous network according to claim 3, wherein the step (304) specifically comprises the following steps:
(3041) counting the number of micro base stations in each micro base station cluster, selecting the maximum Num of the number of the micro base stations, and equally dividing the carrier frequency band exclusively occupied by the micro base station layer into Num sub-frequency bands to form a sub-frequency band set;
(3042) for a generalized cluster, selecting the micro base station with the most occurrence times in the related cluster, randomly allocating a sub-frequency band to the micro base station, selecting the micro base station with the second most occurrence times in the related cluster, randomly selecting one from the rest sub-frequency bands to allocate to the micro base station, and sequentially performing the steps until the micro base stations which repeatedly appear in the related clusters are all allocated to the sub-frequency bands;
(3043) for each related cluster in the generalized cluster, determining whether a micro base station allocated to a sub-band exists in the related cluster, if so, deleting the allocated sub-band from the sub-band set, and counting the number f of micro base stations to be allocated in the related cluster1And the number n of remaining sub-bands, if n can be f1Dividing, then randomly allocating n/f to each micro base station to be allocated1If the continuous sub-frequency band can not be divided completely, n divided by f is calculated1Randomly selecting a micro base station, and allocating (n-re)/f1+ re consecutive sub-bands, and then randomly allocating (n-re)/f to each of the remaining micro base stations1A number of consecutive sub-bands;
(3044) for the common cluster, counting the number f of micro base stations in the cluster2If Num can be f2Dividing, then randomly distributing Num/f for each micro base station to be distributed2If the continuous sub-frequency bands can not be divided completely, calculating Num and f2Dividing remainder rem, randomly selecting a micro base station, and distributing (Num-rem)/f2+ rem consecutive sub-bands, and then randomly allocating (Num-rem)/f for each remaining micro base station2A number of contiguous sub-bands.
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