EP2409520A1

EP2409520A1 - Method and device for data processing in a mobile communication network

Info

Publication number: EP2409520A1
Application number: EP09779160A
Authority: EP
Inventors: Johanna Katariina Pekonen; Antti Anton Toskala
Original assignee: Nokia Siemens Networks Oy
Current assignee: Nokia Solutions and Networks Oy
Priority date: 2009-03-16
Filing date: 2009-03-16
Publication date: 2012-01-25
Also published as: WO2010105665A1

Abstract

In order to overcome this problem, a method is provided for data processing in a mobile communication network, wherein measurement information is conveyed from a first central node to a second central node, and wherein said measurement information is provided by at least one base station to the first central node and/or to the second central node. Also, a corresponding device as well as a communication system comprising such a device are suggested.

Description

Method and device for data processing in a mobile communica- tion network

The invention relates to a method and to a device for data processing in a mobile communication network.

The invention relates in particular to the field of mobility management between a macro-cell network and a home base transceiver station (BTS) and in particular to a direction of traffic from the macro cell to said home BTS.

The base transceiver station is also referred to herein as base station or NodeB. It is known to deploy home base stations or femto base stations within a macro cell, wherein said femto base station may be arranged to convey traffic between a mobile terminal and the core network via a gateway, also referred to as femto gateway or home NodeB gateway (HNB- GW) . A significant amount of femto base stations may be deployed within a macro cell and may be associated with one or more HNB-GW. The macro cell can be determined by the radio cell supplied by a BTS according to, e.g., GSM, 3G, LTE specifications. The base station of a macro cell may be con- trolled by a radio network control (RNC) of a UMTS terrestrial radio access network (UTRAN) . The RNC and the HNB-GW are connected to the core network.

The mobile terminal, which can be any cellular device, e.g., phone, is also referred to as user equipment (UE) .

In UTRAN a neighbor cell is identified by a UE measurement report with a certain primary scrambling code (PSC) value. The serving radio system has mapping information between the PSC values and the Cell IDs of the neighbor cells. However, in the femto cell scenario, it can be assumed that more than one home NodeB may be deployed using the same PSC value within the coverage area of a large macro cell. Therefore, the reported PSC value is not unique, cannot be unambiguously mapped to one Cell ID, and thus the network does not know which home NodeB (of the ones having identical PSC) was actually measured.

The problem to be solved is to overcome the disadvantages stated above and in particular to provide an efficient solution for identifying a home NodeB.

This problem is solved according to the features of the independent claims. Further embodiments result from the depending claims .

In order to overcome this problem, a method is provided for data processing in a mobile communication network

- wherein measurement information is conveyed from a first central node to a second central node,

- wherein said measurement information is provided by at least one base station to the first central node and/or to the second central node.

The network comprises in particular a radio network, e.g., a GSM, 3G, UMTS and/or LTE network.

Hence, the measurement information, e.g., a (relative and/or absolute) signal strength between a home NodeB gateway and an RNC can be used to identify a target cell (e.g., a home NodeB) in a target radio access network.

This bears the advantage that the target cell can be localized and identified with the help of measurement information provided by the home NodeBs and/or the mobile terminal.

In an embodiment, the at least one base station is a home base station.

Such home base station may also be referred to as home NodeB or a femto station (supplying a femto cell) . In another embodiment, the first central node and/or the second central node is or is associated with at least one of the following components: - a radio network controller;

- a NodeB, in particular an evolved NodeB;

- an entity managing radio resources;

- an entity for handover management;

- a gateway associated with at least one home base sta- tion.

The radio network controller (RNC) may be connected to at least one base station supplying a macro cell of the radio network and/or said gateway (HNB-GW) may be connected to at least one home base station. From a core network perspective, the RNC and the HNB-GW appear as controlling entities for supplying at least one base station each, wherein the HNB-GW may supply home base stations (home NodeBs) that are within the coverage area of the base station controlled by the RNC.

It is noted that any entity managing radio resources may be utilized. For example, in LTE, a base station itself (e.g., an eNodeB) may be responsible, e.g., for radio resource management. In particular, an entity could be utilized managing and/or handling handover or at least a portion thereof.

It is noted that more than two central nodes may be deployed and may exchange or convey said measurement information (or different measurement information) between each other.

In a further embodiment, the first central node is a radio network controller and the second central node is a gateway associated with at least one home base station, wherein measurement information provided by the at least one home base station is conveyed to the radio network controller.

Hence, the RNC may decide which home base station to select via a handover message and convey such selection information to the HNB-GW. Such handover message may comprise (additional) measurement information supplied by a mobile terminal and such additional measurement information of the mobile terminal may be utilized in order to determine which home base station to select as a destination for a handover.

Hence, the RNC may inform the HNB-GW about the destination home base station to select. This could be done, e.g., by using an identifier of the home NodeB that may previously be conveyed to the RNC with the measurement information of the home NodeBs forwarded by the home NodeB gateway.

In a next embodiment, the first central node and the second central node are connected to a core network.

It is also an embodiment that said measurement information comprises at least one of the following:

- an absolute or a relative signal strength or quality of at least one neighboring base station, in particular based on a pilot or reference signal measurement; - a list of detected neighboring base stations;

- an absolute or a relative bit error rate of at least one neighboring base station;

- an absolute or a relative signal-to-noise ratio of at least one neighboring base station.

In particular, there may be the list of the neighboring cells only or there may be additional measurement information for each base station, which provides a further granularity if dealing with large number of base stations.

Pursuant to another embodiment, said measurement information is associated with a cell identification and/or a physical cell identity (PCI) and/or a primary scrambling code (PSC) of at least one base station.

Hence, the (home) base station may be identified by its cell ID and/or by its PSC, wherein the measurement information is provided to the first and/or second central node per such cell ID and/or PSC.

According to another embodiment, the measurement information is provided as an ordered information.

The measurement information may be provided as an ordered (or sorted) list comprising, e.g., signal strengths of neighboring cells. The measurement information can be provided by the base station, in particular by at least one home base station and/or by the mobile terminal.

In yet another embodiment, a handover of a mobile terminal is indicated by the first central node conveying a message to the second central node comprising measurement information provided by the mobile terminal, wherein said measurement information relates to at least one base station, in particular to several base stations, wherein at least one of the several base stations is a home base station.

Advantageously, the measurement information from the mobile terminal as well as from the at least one home NodeB can be utilized to determine which home NodeB to select by the HNB- GW.

The HNB-GW may maintain a "topology" regarding the measurement information supplied by its home NodeBs, e.g., based on a signal strength information, a relationship between the attached home NodeBs can be determined. When the mobile termi- nal conveys its measurement information together with, e.g., a non-unique PSC, the measurement information from the mobile terminal can be applied to said topology in order to determine the correct home NodeB the mobile terminal shall be handed over to. This topology approach applies also to the scenario with the RNC being in charge of selecting the suitable home NodeB; in such case, the RNC may maintain the topology and informs the HNB-GW about the chosen home NodeB. According to a next embodiment, the second central node determines the base station to be selected for the handover based on the measurement information provided by the mobile terminal .

For example, the handover of the mobile terminal may comprise at least a portion of the following steps:

- the mobile terminal reports a first measurement information (e.g., comprising a radio characteristic) to a first central node (e.g., a RNC), said first measurement information comprising measurement values of neighboring cells or base stations;

- each base station (HNB) comprises a receiver that obtains second measurement information from neighboring base stations;

- the base station provides said second measurement information to a second central node (HNB-GW) ;

- at least one of the first and second central node transmits first and/or second measurement information to at least one central node (e.g., to the respective other one of the first or second central node) in advance to or during a handover procedure.

These steps do not have to be executed in the order stated above. For example, the base station determining said second measurement information may do so in advance to the actual handover. Also, the second measurement information can be conveyed to the HNB-GW in advance to the actual handover. In addition, said second measurements can be determined and processed automatically on a more or less regular basis independent from any handover request. This helps to keep an updated version of said "topology" described above.

Pursuant to yet another embodiment, said measurement informa- tion is conveyed to a third central node.

Hence, at least one of the first and second central node may transmit first and/or second measurement information to a central node related to the target cell of the handover. Hence, the first measurement information from the mobile terminal as well as the second measurement information from the HNB-GW can be supplied to a third central node being differ- ent to the first and the second central nodes.

The problem stated above is also solved by a device comprising a processor unit and/or a hard-wired circuit and/or a logic device that is arranged such that the method as de- scribed herein is executable thereon.

The problem stated above is also solved by a device being associated with a processor unit and/or a hard-wired circuit and/or a logic device that is arranged such that the method as described herein is executable thereon.

According to an embodiment, the device is a communication device, in particular a or being associated with a radio network controller (RNC) .

According to an embodiment, the device is a communication device, in particular a or being associated with a home NodeB gateway (HNB-GW) .

Hence, the HNB-GW may receive (via the RNC) a handover request from the mobile terminal (UE) according to which one of the HNB-GW' s cells is identified by a PSC and several neighboring (home) NodeBs as well as their respective signal strength.

Also, the HNB-GW may receive measurement information from neighboring or adjacent NodeBs (home NodeBs assigned to the HNB-GW, other home NodeBs or from the NodeB of (at least one) macro cell) . Such information can be used to define and main- tain said topology described above.

The problem stated supra is further solved by a communication system comprising the device as described herein. Embodiments of the invention are shown and illustrated in the following figures:

Fig.l shows a block diagram of a network scenario comprising a macro cell that is connected to a RNC and another macro cell that is connected to another RNC as well as a HNB-GW that is connected to several home NodeBs;

Fig.2 shows a central node, in particular a HNB-GW;

Fig.3 shows steps to be conducted at a central node, in particular a HNB-GW, preferably prior to a handover request received at such central node;

Fig.4 shows steps to be conducted at a central node, in particular a HNB-GW, when a handover request is received.

The mobile terminal may determine and/or report cell measurements regarding an actual target cell as well as at least one neighbor cell. Based on such neighbor cell measurement results it is possible to determine a home NodeB location within a macro cell's coverage area.

The target cell may be identified via a transparent container comprising a PSC and a list of further adjacent or neighboring cells based on the mobile terminal's measurement report. Such list of neighboring cells may comprise identifiers for neighboring cells (e.g., a Cell ID and/or a PSC), e.g., in a particular order (e.g., based on a signal strength determined) or for each cell a cell identifier and the signal strength may be reported by the mobile terminal to the source system.

The home NodeB may comprise a receiver to monitor an adjacent cell environment. Based on this monitoring the home NodeB is able to identify its neighboring cells and it may provide information regarding the neighboring cells, e.g., the detected cells in a macro layer and/or their signal strengths, to the network. For example, such information may be conveyed to a femto gateway and/or to an RNC of the macro cell network.

When the handover request is received in the target system, the target cell can be identified by comparing the PSC value of the handover request message with the PSC values used in the home NodeB cells and/or by comparing the reported neighboring cells with the neighbor cell information of the home NodeB cells.

This approach bears in particular the advantage that it is interoperable with legacy mobile terminals (e.g., UEs that do not provide a neighbor frequency BCH decoding capability) . Furthermore, the approach provides a high reliability for large macro-cells with a huge number of home NodeBs in their coverage area to determine the correct home NodeB even if the same PSC is used by several home NodeBs.

The approach suggested is applicable in a LTE scenario as well, where instead of primary scrambling codes the primary synchronization signals (PSS) and secondary synchronization signals (SSS) are used to separate cells (before BCH decoding) . The respective reported measurements are instead of the measurements based on the relative or absolute strength of a common pilot channel (CPICH) in UTRAN, the Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ) thus reporting the absolute strength or quality of the reception of the cell specific reference signals.

The RSRP can be determined for a cell considered as a linear average of the power contributions (in [W] ) of the resource elements that carry cell-specific reference signals within the considered frequency bandwidth. If a receiver diversity is used by the mobile terminal, the reported value can be substantially equivalent to the linear average of the power values of the diversity branches.

The RSRQ can be determined as a ratio

NxRSRP / (E-UTRA carrier RSSI),

wherein N is a number of resource blocks (RBs) of the E-UTRA carrier RSSI measurement bandwidth. The measurements in the numerator and denominator can be made over the same set of resource blocks.

Fig.l shows a block diagram of a network scenario comprising a macro cell 101 that is connected to a RNC 103 and a macro cell 102 that is connected to a RNC 104. Each macro cell 101, 102 is supplied by a base station or a NodeB. According to the example of Fig.l, the macro cell 101 has a PSC of "3".

In the coverage area of said macro cell 101 a first group of femto cells or home NodeBs (HNB) 105, 106 and 107 are deployed. The HNBs 105 and 107 each have a PSC of "1" and the HNB 106 has a PSC of "2". The first group of HNBs 105 to 107 is connected to a HNB gateway (HNB-GW) 108. The coverage area of the macro cell 101 also contains a further HNB 109 that is connected to a further HNB-GW (not shown) .

The RNCs 103, 104 and the HNB-GW 108 are connected to a core network 110.

Furthermore, in the coverage area of the macro cell 101 a UE 111 is connected to the NodeB of the macro cell 101.

In an exemplary scenario, the UE 111 connected to said macro cell 101 may enter the coverage area of the HNB 105 and a handover from the macro cell 101 to the HNB 105 shall be conducted. As shown in Fig.l, from the network side, there exist two HNBs with the same PSC of "1", i.e. HNB 105 and 107. Nev- ertheless, the handover needs to be directed to the HNB 105 and not to the HNB 107. Hereinafter, it will be explained in detail how the handover decision is made to determine the correct HNB for the UE 111.

Measurement information is conveyed to the HNB-GW 108 from all its associated HNBs 105 to 107 or at least from a selection thereof. Such measurement information can be obtained by the HNB on a regular basis or it may be event-triggered. The measurement information may comprise signal strength information, bit error information or signal-to-noise ratio information. The measurement information may be obtained by a HNB from at least one of its neighboring HNBs.

In the example of Fig.l, the HNB 105 conveys measurement information 112 to the HNB-GW 108, said measurement information comprising signal strength information from neighboring HNBs 106 and 107 evaluated by a receiver of the HNB 105. The neighboring HNBs 106 and 107 may be identified by it PSC. Hence, the measurement information 112 may comprise:

PSC2: -8 PSC3: +4

This indicates that the HNB 105 determines a signal strength of a base station (here the HNB 106) with a PSC of "2" to amount to "-8" and a signal strength of a base station (here the base station of the macro cell 101) with a PSC of "3" to amount to "+4".

Accordingly, the HNB 107 may provide measurement information 113 to the HNB-GW 108 as follows:

PSC2: -9 PSC3: +3

indicating that the HNB 107 determines a signal strength of the HNB 106 with the PSC of "2" to amount to "-9" and a sig- nal strength of the macro cell 101 with the PSC of "3" to amount to "+3".

The UE 111 determines a measurement information as follows

PSCl: -5

PSC2: -7

PSC3: +5.

It is noted that the HNBs may utilize only a limited set of

PSCs, i.e. the macro cells may be uniquely identified via its PSC, which is not the case for the PSCs used for HNBs within such a macro cell.

The handover request may be initiated by the RNC 103 sending a corresponding message 114 to the HNB-GW 108. Such message advantageously comprises measurement information as provided by the UE 111. Hence, the handover request may comprise a target ID of the HNB-GW 108, in particular a number to (uni- quely) identify the HNB-GW 108. The handover request may comprise within its transport container a target cell information, i.e. a PSC (in this example of Fig.l, the PSC amounts to "1" as the UE 111 intends to handover to HNB 105), as well as measurement information regarding neighboring cells of the HNB 105, e.g., PSC2 : -6, PSC3 : +4.

The HNB-GW 108 is then enabled to determine the target cell, i.e. the destination of the handover, to be HNB 105 based on the message 114 received from the RNC 103 as well as the mea- surement information 112, 113 received from the HNBs 105, 107. Thus, based on the information provided by the UE 111 itself (conveyed through the RNC) and the HNBs (showing a signal status between the HNBs) , it is with high likelihood possible to determine whether the UElIl wants to connect to HNB 105 or to HNB 107 both being controlled by the HNB-GW 108 and both having assigned the PSC of "1". For example, if the topology of Fig.l is assumed, the UE 111 reaching the coverage area of HNB 105 may result in measurement information regarding the HNB 106 and the macro cell 101, wherein (assumed that the macro cell 101 has a strong signal around the center of the cell) a signal strength of the macro cell 101 is higher than a signal strength of the HNB 106. The HNB-GW 108 may now determine the HNB 105 to be the correct destination to be assigned to the UE 111, because the HNB 107 would show less signal strength in relation to the macro cell 101 than does the HNB 105.

However, different measurement mapping schemes may apply accordingly. Also, not only signal strength may be used as measurement information, but also, e.g., bit error rate, signal- to-noise ratio or the like. Also, relative or absolute values of at least one of these may be utilized.

It is in particular noted that the decision about which HNB to become the destination of the handover may be made at the RNC. In such case, the measurement information provided by the HNBs to the HNB-GW may be forwarded to the RNC. Hence, the RNC has an overview of the measurement information of the HNBs and is provided by the measurement information from the UE. It may thus decide which HNB to choose and communicate the result to the HNB-GW for processing the handover. However, a unique identifier for each HNB may advantageously be used for communicating the destination of the handover to the HNB-GW. As unique identifier, a combination of the PSC and a HNB ID may be used, or a unique ID of the HNB may be used. Such unique identifier may at least partially be conveyed - e.g., together with the measurement information - from the HNB-GW to the RNC.

It is noted that the RNC may be aware of the mapping rela- tionship between HNBs with a PSC and the corresponding HNB-

GW. The RNC will be associated with one HNB-GW if all HNBs of a macro cell coverage area are associated with one HNB-GW. Alternatively, the RNC may be aware of PSC values used for HNBs associated with different HNB-GWs.

Fig.2 shows a central node, in particular a HNB-GW, e.g., the HNB-GW 108 of Fig.l, comprising a processing unit 201, which may comprise a processor unit and/or a hard-wired circuit and/or a logic unit, at least one interface 202, a memory 203 and a measurement database 204.

The at least one interface 202 is connected to the processing unit 201, the memory 203 is associated with said processing unit 201 and the measurement database 204 is controlled by the processing unit 201.

The measurement database 204 can be used for storing measurement information that can be retrieved and utilized, e.g., for handover purposes, in particular for identification purposes to decide which home NodeB to be used as target cell.

Fig.3 shows steps to be conducted at a central node, in particular a HNB-GW, preferably prior to a handover request received at such central node.

In a step 301, measurement information is received from at least one base station, in particular from at least one home base station, which measurement information is stored in a step 302 in said measurement database.

Hence, the HNB-GW obtains measurement information from its associated home base stations. As each home base station may provide measurement information regarding at least one other base station, the HNB-GW is able to determine a "topology" or distribution of the home base stations within its reach.

Fig.4 shows steps to be conducted at a central node, in particular a HNB-GW, when a handover request is received. In a step 401, a handover request is received from a central node. Said handover is one example of an action to be conducted (at least partially) at the central node. In a step 402, measurement information and cell information are re- trieved from the handover request. Hence, the handover request contains such information, which may initially be determined by the mobile terminal that is subject to the actual handover. In a step 403, the measurement information retrieved is compared with measurements information stored in the measurement database. In a next step 404, the cell is determined that matches the stored measurement information best and the handover is further processed in a step 405.

List of Abbreviations

3GPP 3rd Generation Partnership Project

BCH Broadcast Channel BTS Base Transceiver Station

CPICH Common Pilot Channel eNodeB evolved NodeB

GSM Global System for Mobile Communications

GW Gateway HNB Home NodeB

ID Identification or Identifier

LTE Long Term Evolution

PSC Primary Scrambling Code

PCI Physical Cell Identity PSS Primary Synchronization Signal

RB Resource Block

RNC Radio Network Controlled

RSRP Reference Signal Received Power

RSRQ Reference Signal Received Quality RSSI Received Signal Strength Indicator

SSS Secondary Synchronization Signal

UE User Equipment

UMTS Universal Mobile Telecommunications System

UTRAN UMTS Terrestrial Radio Access Network WCDMA Wideband Code Division Multiple Access

Claims

Claims :

1. Method for data processing in a mobile communication network,

2. The method according to claim 1, wherein the at least one base station is a home base station.

3. The method according to any of the preceding claims, wherein the first central node and/or the second central node is or is associated with at least one of the following components: - a radio network controller;

- a NodeB, in particular an evolved NodeB;

- an entity managing radio resources;

- an entity for handover management;

- a gateway associated with at least one home base sta- tion.

4. The method according to any of claims 1 and 2, wherein the first central node is a radio network controller and the second central node is a gateway associated with at least one home base station, wherein measurement infor- mation provided by the at least one home base station is conveyed to the radio network controller.

5. The method according to any of the preceding claims, wherein the first central node and the second central node are connected to a core network.

6. The method according to any of the preceding claims, wherein said measurement information comprises at least one of the following: - an absolute or a relative signal strength or quality of at least one neighboring base station, in particular based on a pilot or reference signal measurement;

- a list of detected neighboring base stations; - an absolute or a relative bit error rate of at least one neighboring base station;

7. The method according to any of the preceding claims, wherein said measurement information is associated with a cell identification and/or a physical cell identity and/or a primary scrambling code of at least one base station .

8. The method according to any of the preceding claims, wherein the measurement information is provided as an ordered information.

9. The method according to any of the preceding claims, wherein a handover of a mobile terminal is indicated by the first central node conveying a message to the second central node comprising measurement information provided by the mobile terminal, wherein said measurement information relates to at least one base station, in particular to several base stations, wherein at least one of the several base stations is a home base station.

10. The method according to claim 9, wherein the second central node determines the base station to be selected for the handover based on the measurement information provided by the mobile terminal.

11. The method according to any of the preceding claims, wherein said measurement information is conveyed to a third central node.

12. A device comprising a processor unit and/or a hardwired circuit and/or a logic device that is arranged such that the method according to any of the preceding claims is executable thereon.

13. The device according to claim 12, wherein said device is a communication device, in particular a or being associ- ated with a radio network controller.

14. The device according to claim 12, wherein said device is a communication device, in particular a or being associated with a home NodeB gateway.

15. Communication system comprising the device according to any of claims 12 to 14.