WO2014089834A1

WO2014089834A1 - Method and apparatus for managing ap clustering

Info

Publication number: WO2014089834A1
Application number: PCT/CN2012/086681
Authority: WO
Inventors: Jinhua Liu; Zhan Zhang
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2012-12-14
Filing date: 2012-12-14
Publication date: 2014-06-19
Also published as: EP2932752A4; EP2932752A1

Abstract

The embodiments disclose a method for managing AP clustering in a radio communication network. The method comprises: obtaining traffic change related information for an AP cluster, the AP cluster comprises a plurality of APs; determining to perform a cluster splitting according to the traffic change related information; and splitting the AP cluster into a plurality of child AP clusters, each child AP cluster comprises at least one of the plurality of APs originally residing in the AP cluster.

Description

METHOD AND APPARATUS FOR MANAGING AP CLUSTERING TECHNICAL FIELD

The present technology generally relates to radio communication, particularly to a method and apparatus for managing Access Point (AP) clustering in a radio communication network.

BACKGROUND

Generally, in the 3rd Generation Partnership Project (3GPP) network, the Macro-APs are responsible to ensure the coverage, while the Pico-APs are introduced to offload traffic and increase the user data rate in either coverage outage or low service quality areas, as illustrated in Fig. 1. There are multiple Pico-APs to complement the deficiency of the Signal to Interference and Noise Ratio (SINR) for User Equipments (UEs) inside the coverage of the Macro-APs. A Pico-AP usually covers a small area, which results in the frequent handover for UEs between Pico-APs or between Macro-AP and Pico-AP. Hence, the Macro-AP and Pico-APs are arranged into an AP cluster, where the individual APs share a common AP Identity (ID). The beauty of both Macro-AP and the Pico-APs being configured with the common AP ID is that the handovers, when UEs come across the border between Pico-APs or between a Pico-AP and a Macro-AP, can be transparent to UEs to save the handover signaling. In this way, the service interruption within the cluster covered area can be avoided, and the Radio Resource Control (RRC) signaling due to frequent handover can be saved.

However, with the common AP ID, numerous UEs are served by a large AP cluster employing multiple APs. These APs transmit the same control signals and share the same control and data radio resources such as the downlink (DL) Physical Hybrid-ARQ Indicator Channel (PHICH), Physical Downlink Control Channel (PDCCH)/ Physical Downlink Shared Channel (PDSCH), Physical Uplink Control Channel (PUCCH)/ Physical Uplink Shared Channel (PUSCH) and Physical Random Access Channel (PUSCH), etc. This aspect can be the bottle neck of UE access and/or system performance when there is large amount of UEs appearing in the covered area by the AP cluster. SUMMARY

Therefore, it is a strong desire to solve at least one of the above mentioned problems.

According to an aspect of the embodiments, there is provided a method for managing Access Point, AP, clustering in a radio communication network, comprising: obtaining traffic change related information for an AP cluster, the AP cluster comprises a plurality of APs; determining to perform a cluster splitting according to the traffic change related information; and splitting the AP cluster into a plurality of child AP clusters, each child AP cluster comprises at least one of the plurality of APs originally residing in the AP cluster.

According to another aspect of the embodiments, there is provided an apparatus for managing Access Point, AP, clustering in a radio communication network, the apparatus comprises an obtaining unit adapted to obtain traffic change related information for an AP cluster, the AP cluster comprises a plurality of APs, a first determining unit adapted to determine to perform a cluster splitting according to the traffic change related information and a splitting unit adapted to split the AP cluster into a plurality of child AP clusters, each child AP cluster comprises at least one of the plurality of APs.

According to further aspect of the embodiments, there is provided a computer program product, which comprises the instructions for implementing the steps of the method as described above.

According to still further aspect of the embodiments, there is provided a recording medium which stores instructions for implementing the steps of the method as described above.

It is advantageous to perform the cluster splitting according to the traffic change in the AP cluster to split the AP cluster into multiple child AP clusters, when, for example, the AP cluster is overloaded such that the network resource becomes a bottleneck, thereby degrading the quality of service provided to the UEs. Since different child AP clusters make use of different AP IDs, i.e. using different control resource, the large amount of UEs can be served with different control resources, therefore network resource supply is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

The technology will now be described, by way of example, based on embodiments with reference to the accompanying drawings, wherein:

Fig. 1 illustrates a schematic view of AP cluster in the radio communication network suitable for implementing an embodiment;

Fig.2 illustrates a flowchart of managing AP clustering in the radio communication network in accordance with an embodiment;

Fig.3 illustrates a flowchart of managing AP clustering in the radio communication network in accordance with another embodiment;

Fig.4 is the block diagram of the apparatus used to managing AP clustering in accordance with an embodiment; and

Fig.5 is the block diagram of the apparatus used to managing AP clustering in accordance with another embodiment.

DETAILED DESCRIPTION

Embodiments herein will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments are shown. This embodiments herein may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The elements of the drawings are not necessarily to scale relative to each other. Like numbers refer to like elements throughout.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" "comprising," "includes" and/or "including" when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Also, use of ordinal terms such as "first," "second," "third," etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The present technology is described below with reference to block diagrams and/or flowchart illustrations of methods, apparatus (systems) and/or computer program products according to the present embodiments. It is understood that blocks of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, may be implemented by computer program instructions. These computer program instructions may be provided to a processor, controller or controlling unit of a general purpose computer, special purpose computer, and/or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer and/or other programmable data processing apparatus, create means for implementing the functions/acts specified in the block diagrams and/or flowchart block or blocks.

Accordingly, the present technology may be embodied in hardware and/or in software (including firmware, resident software, micro-code, etc.). Furthermore, the present technology may take the form of a computer program product on a computer-usable or computer-readable storage medium having computer-usable or computer-readable program code embodied in the medium for use by or in connection with an instruction execution system. In the context of this document, a computer-usable or computer-readable medium may be any medium that may contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.

Although specific terms in some specifications are used here, such as AP, it should be understand that the embodiments are not limited to those specific terms but may be applied to all similar entities, such as cell, sector, base station, femto base station, Core Network (CN), NodeB, eNodeB, etc. The embodiments herein are described in the context of the Long Term Evolution (LTE) system, however, it should be understood that the embodiments may also be adapted to other existing communication protocols/standards, such as Global System for Mobile Communication (GSM), General Packet Radio Service (GPRS), Time Division Synchronous Code Division Multiple Access (TD-SCDMA), Wireless Fidelity (WiFi), Bluetooth, Universal Mobile Telecommunications System (UMTS), Worldwide Interoperability for Microwave Access (WiMAX), Code Division Multiple Access (CDMA) , Wideband Code Division Multiple Access High Speed Packet Access (WCDMA-HSPA) etc, and communication protocols/standards developed in the future.

Embodiments herein will be described below with reference to the drawings.

Fig. 1 illustrates a schematic view of AP cluster in the radio communication network suitable for implementing an embodiment.

As shown in Fig. l, the AP cluster 100 comprises the Macro-AP 1 10, Pico-AP 120, Pico-AP 130 and Pico-AP 140, hereinafter also referred to as AP 1 10, AP 120, AP 130 and AP 140. The AP 1 10 is serving the UE 150 and UE 160, the AP 120 is serving UE 170, the AP 130 is serving the UE 180, and the AP 140 is serving the UE 190. Although the AP cluster 100 herein consists of multiple APs, the AP cluster also can be constructed by one or more sectors belonging to different sites, or in other suitable ways. The APs in the AP cluster may share the same AP ID, but it is noted that the clustered APs are not necessarily configured with the same AP ID, for example, in the Coordinated Multipoint Transmission/Reception (CoMP) scenario. The term "UE" used herein may indicate all forms of devices enabling the user to communicate via a radio communication network, such as smart phones, cellular phone, Personal Digital Assistant (PDA), and the like.

For simplicity and clarity, only four APs are shown in the AP cluster, it will be appreciated that one or more APs may exist in AP cluster to participate in the implementation of the method described herein.

Fig.2 illustrates a flowchart of managing AP clustering in the radio communication network in accordance with an embodiment.

The method for managing AP clustering can be implemented in, but not limited to, the one of the APs in the AP cluster or another external AP communicating with the AP cluster via wired/wireless connection. For purpose of illustration, the method is implemented by an external AP (hereinafter also referred to as managing AP) communicating with the AP cluster.

At step 210, the managing AP may obtain the traffic change related information for the AP cluster, e.g. AP cluster 100. The traffic change related information comprises the information on the utilization of the radio resources in the AP cluster, the resource demanded by UEs served by the AP cluster relative to the available network resource, such as control resource in the AP cluster, and the traffic change cycle, for example, the predefined high traffic hours and low traffic hours. The utilization of the radio resources in the AP cluster may refer to one or any combination of the utilizations of the radio resource at the control/data channels, such as PDCCH/PDSCH, PHICH, PUCCH/PUSCH, PRACH preamble. The managing AP may monitor the traffic change, for example, the increase with respect to the utilization of the radio resource and/or the radio resource demanding from the UEs in real time or periodically. Alternatively, the managing AP may obtain the traffic change related information by querying the database for the predetermined traffic change cycle in the AP cluster.

It should be appreciated that the above ways to obtain the traffic change related information are described by way of example, and any other suitable ways can be used in the embodiment.

At step 220, the managing AP may determine whether to perform a cluster splitting according to the traffic change related information obtained at step 210. Specifically, for example, when the traffic change related information indicates that the utilization of the radio resource, such as PDCCH/PDSCH exceeds a threshold, it is determined to perform the cluster splitting. Alternatively, if the increasing rate for the resource demanded by UEs relative to the available network resource is higher than a threshold, then the managing AP will determine to perform the cluster splitting. Alternatively, the cluster splitting can be performed when it is in the predefined busy hour for the AP cluster. It should be understood that the above traffic change related information can be separately or jointly used to determine whether the cluster splitting should be performed.

At step 230, the managing AP may split the AP cluster into a plurality of child AP clusters; each child AP cluster comprises at least one of the plurality of APs. The AP cluster can be split simply by the predefined criteria, for example, splitting the AP cluster into two child AP clusters arbitrarily. Theoretically, the two child AP clusters can be further split until each resulting child AP cluster only has one AP.

Preferably, the cluster splitting can be implemented based on the inter-AP interference among the APs in the AP cluster. Generally speaking, when the inter-AP interference level among the APs in an AP cluster is larger than a threshold, the AP cluster will not be split further. In other words, whenever the interference between APs becomes a major limiting factor to the system throughput, a further cluster splitting is prevented. In this way, after cluster splitting, the inter-cluster interference among the child AP clusters can be kept relatively in an acceptable level.

The inter-AP interference level can be determined by, but not limited to, at least one of the physical position of the APs, path loss among APs, and UE traffic distribution.

Specifically, the inter-AP interference among neighboring APs is higher than that among distant APs. Hence, APs in neighborhood, for example within the designated distance, are preferably assigned to the same child AP cluster. For example, as illustrated in Fig. l, according to the physical location of the APs, AP 1 10 and AP 140 are assigned to one child AP cluster A, and AP 120 and AP 130 are assigned to the other child AP cluster B, where the child AP cluster A and B are configured with different AP ID.

As known in the art, path loss is the reduction in power density (attenuation) of an electromagnetic wave as it propagates through space. The larger path loss among the APs represents the lower inter-AP interference. Therefore, when the path loss between two APs is more than a threshold, the two APs are recommended to be split into different child AP clusters. In such situation, the inter-cluster interference due to the inter-AP interference between the two APs is regarded as endurable.

The inter-AP interference level also can be ascertained by the UE traffic distribution. For example, the AP 120 results in the higher downlink (DL) interference for the downlink data receiving of UE 180 served by the AP 130, because the UE 180 is at the edge of the area covered by the AP 130, approaching the AP 120. In this case, the inter-AP interference level between the AP 120 and AP 130 is considered to be high, such that the two APs should be assigned into one child AP cluster. Here, the DL interference can be estimated through such as uplink measurements, UE position information, sector specific Channel State Indication Reference Signal (CSI-RS) reporting, Channel Quality Indicator (CQI) reports, Hybrid Automatic Repeat Request (HARQ) reports, and the like. The DL inference estimation technique is well known in the art, which will not be described in more detail here.

Through splitting the AP cluster into a number of child AP clusters with each using respectively different control/data resource at the time the control/data resource in the AP cluster is becoming a bottleneck, for example, as a result of a large amount of UEs emerging in the covered area by the AP cluster in a short time period, the adequate network resource is ensured to serve the ever increasing UEs.

Optionally, before splitting the AP cluster, the managing AP may select a new serving AP cluster for the individual UEs being served by the AP cluster, and send a handover command to the UEs to handover to the respective new serving AP clusters. The managing AP may select one of the resulting child AP clusters as the new serving AP cluster for specific UE. Alternatively, the new serving AP cluster may also be selected from the APs other than those served by the AP cluster in the radio communication network.

The selection of the new serving AP cluster for specific UE can be based on either the position relationship between the UE and the APs belonging to an AP cluster, or the UL measurement on signals from the UE to the individual APs belonging to an AP cluster. As an example, the AP cluster which owns the closest AP to the UE can be selected as the new serving AP cluster. In addition, the AP cluster including the AP with the optimal UL measurement result should be selected as the new serving AP cluster. As for such handover procedure, there is usually no A3 measurement report from the handing-over UEs. For example, before actually splitting the AP cluster, the managing AP firstly selects which UEs are to be served by the respective child AP clusters, and then sends handover commands to the selected UEs to handover to the corresponding child AP clusters without dependence on the A3 measurement report from the selected UEs. After the child AP clusters are created, handover commands are sent out by the managing AP. Afterwards, the UEs prepare the random access to the new serving child AP cluster and the newly-generated child AP cluster starts to handle the random access of the corresponding UEs.

Fig.3 illustrates a flowchart of managing AP clustering in the radio communication network in accordance with another embodiment.

In the embodiment, the steps 310, 320 and 330 in Fig.3 work in the similar way to the steps 210, 220 and 230 in Fig.2 as described above, which will not be repeated for purpose of conciseness.

After cluster splitting, more frequent UE handover between the APs in the different child AP clusters will occur. Hence, it is desirable to merge the child AP cluster into a large size AP cluster, when the traffic load in the individual child AP clusters is lower than a threshold. In this case, the radio resource bottleneck will not present in the merged large size AP cluster, meanwhile the UE handover frequency will be reduced due to the large size AP cluster.

Specifically, the managing AP may determine to perform a cluster merging according to the traffic change related information at step 340. For example, when the traffic change related information indicates that the total utilization of the radio resource, such as PDCCH/PDSCH, PHICH, PUCCH/PUSCH, PRACH preamble in the individual child AP clusters is under a threshold, it is determined to perform a cluster merging. Alternatively, if the decreasing rate for the resource demanded by UEs relative to the available network resource in the individual child AP clusters is higher than a threshold, then the managing AP will determine to perform the cluster merging. Alternatively, the cluster merging can be performed when it is in the predefined idle hours for the individual child AP clusters. It should be understood that the above traffic change related information can be separately or jointly used to determine whether the cluster merging should be performed.

After determining to perform a cluster merging among at least part of the plurality child

AP clusters, the managing AP may merge part or all of the plurality of child AP clusters into one or more parent AP clusters. For example, there are three child AP clusters CA, CB and CC, the cluster CA includes AP 120 and 130, the cluster CB includes AP 1 10, and the cluster CC includes AP 140. After cluster merging, the three clusters can be merged into one parent AP cluster. Alternatively, only cluster CA and CB are merged into one new parent AP cluster including the APs 1 10-130.

Preferably, the cluster merging may take the inter-AP interference among the APs in the plurality of child AP clusters into account. Generally speaking, when the inter-AP interference level among the APs in two child AP clusters is larger than a threshold, the two child AP clusters are preferred to be merged together with a high priority. In this way, after cluster merging, the inter-cluster interference among the AP clusters can be reduced.

Specifically, the inter-AP interference among neighboring APs is higher than that among distant APs. Hence, the neighboring child AP clusters within a designated distance are preferably merged together. Moreover, less path loss among APs represents higher inter-AP interference as described above. Therefore, when the path loss among the APs in two child AP clusters is smaller than a threshold, the child AP clusters can be merged together.

It should be understood that the child AP cluster may merge with other existing APs and/or

AP clusters in the radio communication network, instead of those in the plurality of child AP clusters. Furthermore, the cluster merging has no dependency on the cluster splitting. They are can be performed independently with respect to different AP clusters.

In the embodiment, an optimized trade-off between the network resource (control/data channels) availability by cluster splitting and the UE handover decrease by cluster merging can be achieved. This is implemented by dynamically adjusting AP cluster size, i.e. the number of APs in the AP cluster, according to the UE activity and/or AP cluster traffic load situation. This is especially important when there is a wide coverage area by a single AP cluster.

Optionally, before merging the child AP clusters, the managing AP may send a handover command to the individual UEs being served by the child AP clusters to handover to the respective parent AP clusters corresponding to the serving child AP clusters.

As for such handover procedure, there is usually no A3 measurement report from the handing-over UEs. That is, even without receiving the A3 measurement reports from the served UEs, the child AP cluster sends a handover command to the UEs first to start a handover procedure to the target parent AP cluster. Then the child AP cluster is merged into the target parent AP cluster and the APs in the target parent AP cluster starts to monitor the random access process of the UEs originally served by the child AP cluster. Fig.4 is the block diagram of the apparatus used to managing AP clustering in accordance with an embodiment.

As illustrated in Fig.4, the apparatus 400 comprises an obtaining unit 410, a first determining unit 420 and a splitting unit 430. The apparatus 400 can be implemented as part of one AP (e.g. AP 1 10) of the AP cluster to be managed or an external AP communicating with the AP cluster via wired/wireless connection. It may also be implemented separately. The functions of the elements in the apparatus 400 will be described with reference the Fig.3 and Fig. l now.

Firstly, the obtaining unit 410 may obtain the traffic change related information for the AP cluster, e.g. AP cluster 100. The traffic change related information comprises the information on the utilization of the radio resources in the AP cluster, the resource demanded by UEs served by the AP cluster relative to the available network resource, such as control resource in the AP cluster, and the traffic change cycle, for example, the predefined high traffic hours and low traffic hours. The utilization of the radio resources in the AP cluster may refer to one or any combination of the utilizations of the radio resource at the control/data channels, such as PDCCH/PDSCH, PHICH, PUCCH/PUSCH, PRACH preamble, the obtaining unit 410 may monitor the traffic change, for example the increase with respect to the utilization of the radio resource and/or the radio resource demanding from the UEs in real time or periodically. Alternatively, the obtaining unit 410 may obtain the traffic change related information by querying the database for the predetermined traffic change cycle in the AP cluster.

Then, the first determining unit 420 may determine whether to perform a cluster splitting according to the traffic change related information obtained by the obtaining unit 410. Specifically, for example, when the traffic change related information indicates that the utilization of the radio resource, such as PDCCH/PDSCH, PHICH, PUCCH/PUSCH, PRACH preamble exceeds a threshold, it is determined to perform the cluster splitting. Alternatively, if the increasing rate for the resource demanded by UEs relative to the available network resource is higher than a threshold, then the first determining unit 420 will determine to perform the cluster splitting. Alternatively, the cluster splitting can be performed when it is in the predefined busy hour for the AP cluster. It should be understood that the above traffic change related information can be separately or jointly used to determine whether the cluster splitting should be performed.

Subsequently, the splitting unit 430 may split the AP cluster into a plurality of child AP clusters; each child AP cluster comprises at least one of the plurality of APs. The AP cluster can be split simply by the predefined criteria, for example, splitting the AP cluster into two child AP clusters arbitrarily. Theoretically, the two child AP clusters can be further split until each resulting child AP cluster only has one AP.

Preferably, the cluster splitting can be implemented based on the inter-AP interference among the APs in the AP cluster. Generally speaking, when the inter-AP interference level among the APs in a AP cluster is larger than a threshold, the AP cluster will not be split further. In other words, whenever the interference between APs becomes a major limiting factor to the system throughput, a further cluster splitting is prevented. In this way, after cluster splitting, the inter-cluster interference among the child AP clusters can be kept relatively low.

The third determining unit (not shown) may determine the inter-AP interference level by, but not limited to, at least one of the physical position of the APs, path loss among APs, and UE traffic distribution.

The third determining unit may also ascertain the inter-AP interference level by the UE traffic distribution. For example, the AP 120 results in the higher downlink (DL) interference for the downlink data receiving of UE 180 served by the AP 130, because the UE 180 is at the edge of the area covered by the AP 130, approaching the AP 120. In this case, the inter-AP interference level between the AP 120 and AP 130 is considered to be high, such that the two APs should be assigned into one child AP cluster. Here, the DL interference can be estimated through such as uplink measurements, UE position information, sector specific Channel State Indication Reference Signal (CSI-RS) reporting, Channel Quality Indicator (CQI) reports, Hybrid Automatic Repeat Request (HARQ) reports, and the like. The DL inference estimation technique is well known in the art, which will not be described in more detail here.

Optionally, before cluster splitting, the first handover unit (not shown) may select a new serving AP cluster for the individual UEs being served by the AP cluster, and send a handover command to the UEs to handover to the respective new serving AP clusters. The first handover unit may select one of the resulting child AP clusters as the new serving AP cluster for specific UE. Alternatively, the new serving AP cluster may also be selected from the APs other than those served by the AP cluster in the radio communication network.

The selection of the new serving AP cluster for specific UE can be based on either the position relationship between the UE and the APs belonging to an AP cluster, or the UL measurement on signals from the UE to the individual APs belonging to an AP cluster. As an example, the AP cluster which owns the closest AP to the UE will be selected as the new serving AP cluster. In addition, the AP cluster including the AP with the optimal UL measurement result should be selected as the new serving AP cluster.

As for such handover procedure, there is usually no A3 measurement report from the handing-over UEs. For example, before actual cluster splitting, the first handover unit firstly selects which UEs are to be served by the respective child AP clusters, and then send handover commands to the selected UEs to handover to the corresponding child AP clusters without dependence on the A3 measurement report from the selected UEs. After the child AP clusters are created, handover commands are sent out by the first handover unit. Afterwards, the UEs prepare the random access to the new serving child AP cluster and the newly-generated child AP cluster starts to handle the random access of the corresponding UEs.

Fig.5 is the block diagram of the apparatus used to managing AP clustering in accordance with another embodiment. In the embodiment, the obtaining unit 5 10, the first determining unit 520 and the splitting unit 530 in the apparatus 500 function in the similar way to the obtaining unit 410, the first determining unit 420 and the splitting unit 430 in the apparatus 400 as described above, which will not be repeated for purpose of conciseness.

After cluster splitting, more frequent UE handover between the APs in the different child

AP clusters will occur. Hence, it is desirable to merge the child AP cluster into a large size AP cluster, when the traffic load in the individual child AP clusters is lower than a threshold. In this case, the radio resource bottleneck will not present in the merged large size AP cluster, meanwhile the UE handover frequency will be reduced due to the larger size AP cluster.

Specifically, the second determining unit 540 in the apparatus 500 may determine to perform a cluster merging among at least part of the plurality child AP clusters according to the traffic change related information. For example, when the traffic change related information indicates that the total utilization of the radio resource, such as PDCCH/PDSCH, PHICH, PUCCH/PUSCH, PRACH preamble in the individual child AP clusters is under a threshold, it is determined to perform a cluster merging. Alternatively, if the decreasing rate for the resource demanded by UEs relative to the available network resource in the individual child AP clusters is higher than a threshold, then the second determining unit 540 will determine to perform the cluster merging. Alternatively, the cluster merging can be performed when it is in the predefined idle hours for the individual child AP clusters. It should be understood that the above traffic change related information can be separately or jointly used to determine whether the cluster merging should be performed.

After the second determining unit 540 determines to perform a cluster merging among at least part of the plurality child AP clusters, the merging unit 5550 may merge part or all of the plurality of child AP clusters into one or more parent AP clusters. For example, there are three child AP clusters CA, CB and CC, the cluster CA includes AP 120 and 130, the cluster CB includes AP 1 10, and the cluster CC includes AP 140. After cluster merging, the three clusters can be merged into one parent AP cluster. Alternatively, only cluster CA and CB are merged into one new parent AP cluster including the APs 1 10-130.

Preferably, the cluster merging may take the inter-AP interference among the APs in the plurality of child AP clusters into account. Generally speaking, when the inter-AP interference level among the APs in two child AP clusters is larger than a threshold, the two child AP clusters are preferred to be merged together. In this way, after cluster merging, the inter-cluster interference among the AP clusters can be reduced.

It should be understood that the child AP cluster may merge with other existing APs and/or AP clusters in the radio communication network, instead of those in the plurality of child AP clusters. Furthermore, the cluster merging has no dependency on the cluster splitting. They are can be performed independently with respect to different AP clusters.

Optionally, before merging the child AP clusters, the second handover unit (not shown) may send a handover command to the individual UEs being served by the child AP clusters to handover to the respective parent AP clusters corresponding to the serving child AP clusters.

As for such handover procedure, there is usually no A3 measurement report from the handing-over UEs. That is, even without receiving the A3 measurement reports from the served UEs, the child AP cluster sends a handover command to the UEs first to start a handover procedure to the target parent AP cluster. Then the child AP cluster is merged into the target parent AP cluster and the APs in the target parent AP cluster starts to monitor the random access process of the UEs originally served by the child AP cluster.

While the embodiments have been illustrated and described herein, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the present technology. In addition, many modifications may be made to adapt to a particular situation and the teaching herein without departing from its central scope. Therefore it is intended that the present embodiments not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the present technology, but that the present embodiments include all embodiments falling within the scope of the appended claims.

Claims

1. A method for managing Access Point, AP, clustering in a radio communication network, comprising:

- Obtaining (210) traffic change related information for an AP cluster, the AP cluster comprises a plurality of APs;

- Determining (220) to perform a cluster splitting according to the traffic change related information; and

- Splitting (230) the AP cluster into a plurality of child AP clusters, each child cell cluster comprises at least one of the plurality of APs.

2. The method according to claim 1, the method further comprising:

- Determining (340) to perform a cluster merging according to the traffic change related information;

- Merging (350) two or more of the plurality of child AP clusters into one or more parent AP clusters.

3. The method according to claim 1 or 2, wherein the traffic change related information comprises at least one of an utilization of the network resource, the resource demanding of UEs relative to available network resource, and a traffic change cycle.

4. The method according to claim 1 or 2, wherein splitting (230) the AP cluster and merging (350) the plurality of child AP clusters are based on an inter- AP interference among the plurality of APs.

5. The method according to claim 4, the method further comprising:

- Determining the inter-AP interference by at least one of an AP position, path loss among APs, and User Equipment, UE, traffic distribution.

6. The method according to claim 2, the method further comprising:

- Before splitting the AP cluster, selecting a new serving AP cluster for the individual UEs being served by the AP cluster, and sending a handover command to the UEs to handover to the respective new serving AP clusters; and

- Before merging the plurality of child AP clusters, sending a handover command to the individual UEs being served by the child AP clusters to handover to the respective parent AP clusters corresponding to the serving child AP clusters.

7. An apparatus for managing Access Point, AP, clustering in a radio communication network, the apparatus comprises:

An obtaining unit (410) adapted to obtain traffic change related information for an AP cluster, the AP cluster comprises a plurality of APs;

A first determining unit (420) adapted to determine to perform a cluster splitting according to the traffic change related information; and

A splitting unit (430) adapted to split the AP cluster into a plurality of child AP clusters, each child cell cluster comprises at least one of the plurality of APs.

8. The apparatus according to claim 7, the apparatus further comprising:

A second determining unit (540) adapted to determine to perform a cluster merging according to the traffic change related information;

A merging unit (550) adapted to merge two or more of the plurality of child AP clusters into one or more parent AP clusters.

9. The apparatus according to claim 7 or 8, wherein the traffic change related information comprises at least one of an utilization of the network resource, the resource demanding of UEs relative to available network resource, and a traffic change cycle.

10. The apparatus according to claim 7 or 8, wherein the splitting unit (430) is adapted to split the AP cluster bases on an inter-AP interference among the plurality of APs, and the merging unit (550) is adapted to merge the plurality of child AP clusters based on the inter-AP interference among the plurality of APs.

1 1. The apparatus according to claim 10, the apparatus further comprising:

A third determining unit adapted to determine the inter-AP interference by at least one of an AP position, path loss among APs, and User Equipment, UE, traffic distribution.

12. The apparatus according to claim 8, the apparatus further comprises:

A first handover unit adapted to, before splitting the AP cluster, select a new serving AP cluster for the individual UEs being served by the AP cluster, and send a handover command to the UEs to handover to the respective new serving AP clusters; and

A second handover unit adapted to, before merging the plurality of child AP clusters, send a handover command to the individual UEs being served by the child AP clusters to handover to the respective parent AP clusters corresponding to the serving child AP clusters.

13. A computer program product, comprising instructions for implementing the steps of the method according to any one of the claims 1-6.

14. A recording medium which stores instructions for implementing the steps of the method according to any one of the claims 1 -6