WO2014086755A1

WO2014086755A1 - Method and apparatus for detecting wireless communication terminals in the vicinity of non-serving basestations

Info

Publication number: WO2014086755A1
Application number: PCT/EP2013/075330
Authority: WO
Inventors: Nicholas Dougall Johnson
Original assignee: Ip.Access Limited
Priority date: 2012-12-04
Filing date: 2013-12-03
Publication date: 2014-06-12
Also published as: GB2508609A

Abstract

A method of detecting wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network. The method comprises, at a network element within the cellular communication network, receiving neighbour cell measurement information from at least one wireless communication terminal, deriving at least one vulnerability indication value for the at least one wireless communication terminal based at least partly on the received neighbour cell measurement information, and determining whether the at least one wireless communication terminal is in the vicinity of a basestation of a neighbour cell for which measurement information was received based at least partly on the derived at least one vulnerability indication value therefor.

Description

METHOD AND APPARATUS FOR DETECTING WIRELESS COMMUNICATION TERMINALS IN THE VICINITY OF NON-SERVING BASESTATIONS

Field of the invention

The field of the invention relates to a method and apparatus for detecting wireless communication terminals in the vicinity of non-serving basestations, and in particular to a method and apparatus for detecting wireless communication terminals in the vicinity of non- serving basestations as part of a method of performing Inter-Cell Interference Management (ICIM) within a cellular communication network.

Background of the Invention

Cellular wireless communication systems are well known. Examples of such standards and technology include GSM (Global System for Mobile communication), UMTS (Universal Mobile Telecommunications System) and LTE (Long Term Evolution). Historically, these cellular wireless communications systems have generally been developed to support macro-cell mobile phone communications. Such macro cells utilise high power basestations to communicate with wireless communication terminals within a relatively large geographical coverage area. Such networks have relied on a centrally planned configuration, with in-field adjustment based on the measurements of teams of field optimisation engineers and after- the-fact trouble tickets. Lower power basestations are currently often referred to as 'small' cells, with the terms 'cell' being used interchangeably for the transceiver equipment (properly, the basestation), and for the coverage area (properly, the cell) that the basestation serves. The term femto cell is typically reserved to refer to a residential small cell. Small cells are intended to augment the wide area macro network and support communications to UEs in a restricted, for example indoor, environment. They also offload traffic from the macro network to small cells, thereby freeing up valuable macro network resources. Since they are, by definition, small, their capacity, which is often comparable in throughput terms to a macro basestation, is shared amongst a smaller number of users than a macro cell, and so each small cell user tends to gets a better service as a result.

Other definitions used in the text below include:

RAN: Radio Access Network - provides the end user with radio access to the Cellular Network and its services. The term is used to distinguish the radio equipment that provides access to the Core Network from the Core Network itself. In third generation (3G) W-CDMA (Wideband Code Division Multiple Access) the RAN comprises the Radio Network Subsystem (RNS) and is divided into the RNC (the Radio Network Controller), and the basestation, called the node-B (NB). In GSM, the RAN is called the Basestation Subsystem (BSS) and is divided into the BSC (Base Station Controller) and the BTS (Base Transceiver System). In LTE the RAN comprises only basestations, called evolved node-Bs or eNBs. In a 3G small cell system, the RAN is re-partitioned and divided into a home-node-B (HNB), which includes most of the RNC functions of the traditional RAN and a gateway (HNB-GW) to the core which provides aggregation and tunnel security termination.

CN: Core Network - provides the voice and data switching services to the end user. lu ("eye-you") is the name of the interface between the Radio Network Controller (RNC) and the Core network in a W-CDMA (3G) network. It is the same interface as between the HNB-GW and the core network.

lu-h ("eye-you-aitch") is the name of the interface between the HNB and the HNB-GW lu-b ("eye-you-bee") is the name of the interface between the RNC and NB in a traditional macro W-CDMA network

S1 is the name of the interface between the LTE basestation (eNB) and the core network (equivalent to lu in 3G)

X2 is the name of the interface between two LTE basestations (no equivalent in 3G)

MME is the Mobility Management Entity in the LTE core network which terminates S1.

HNB: ("Home node-B") specifically a 3G small cell. Originally intended as a synonym for "femto", but now used for any 3G small cell that uses an lu-h interface

HeNB is specifically an LTE small cell.

H(e)NB is a contraction meaning "HNB or HeNB".

Typical applications for such small cells include, by way of example, residential and commercial (e.g. office) locations, communication 'hotspots', etc., whereby basestations in the form of access points can be connected to a core network via, for example, the Internet using a broadband connection or the like. In this manner, small cells can be provided in a simple, scalable deployment in specific in-building locations where, for example, UEs may come into close proximity to a femto cell HNB.

In such a Heterogeneous Network (HetNet) environment with randomly distributed

UEs, the presence of small cells within the coverage area of larger macro cells can lead to the problem of UEs connected to the macro cell suffering from interference from small cells in their vicinity, and of the access points of such small cells suffering from interference from those UEs in their vicinity. One known example technique for mitigating such interference is the specific technique of Inter-Cell Interference Coordination (ICIC) implemented in LTE. Within the LTE RAN such ICIC related messaging is provided over the X2 interface, as defined in 3GPP TS 36.420.

The X2 interface provides for uplink interference load management and downlink interference avoidance. Uplink interference load management allows uplink interference overload and resource blocks to be indicated to neighbouring basestations, such that the neighbouring basestations can coordinate with each other such that the mutual interference caused by their uplink radio resource allocations is mitigated. Conversely, downlink interference avoidance allows a basestation to inform its neighbours about downlink power restrictions in its own cells, per resource block or per subframe, for interference aware scheduling by its neighbouring basestations. However, a problem with all such existing interference management techniques is that the information shared between basestations and/or access points does not enable the recipient to determine whether UEs vulnerable to interference are within their close vicinity. Accordingly, a recipient basestation/access point may invoke interference mitigation techniques (most likely reducing the cell's performance) needlessly when no vulnerable UEs are within its vicinity. Conversely, the recipient basestation/access point may sustain high performance to a served UE, and generate interference on a nearby non-served UE, reducing the network performance with respect to that user. In either scenario, the total network performance suffers.

Thus, there is a need for an improved method and apparatus for detecting vulnerable

UEs within the vicinity of non-serving basestations, and a method and apparatus for performing Inter-Cell Interference Management based thereon whereby at least some of the above mentioned problems with known techniques are substantially alleviated. Summary of the Invention

Accordingly, the invention seeks to mitigate, alleviate or eliminate one or more of the abovementioned disadvantages singly or in any combination.

According to a first aspect of the invention, there is provided a method of detecting wireless communication terminals in the vicinity of non-serving (neighbour) basestations within a cellular communication network. The method comprises, at a network element within the cellular communication network, receiving neighbour cell measurement information from at least one wireless communication terminal, deriving at least one vulnerability indication value for the at least one wireless communication terminal based at least partly on the received neighbour cell measurement information, and determining whether the at least one wireless communication terminal is in the vicinity of a basestation of a neighbour cell for which measurement information was received based at least partly on the derived at least one vulnerability indication value therefor.

In this manner, measurement information received from a wireless communication terminal corresponding to a neighbour cell may be used to derive a vulnerability indication value for the UE with respect to a basestation of that neighbour cell. For example, a received power measurement taken by the wireless communication terminal for that neighbour cell may be used to derive an indication of how close to the basestation of that neighbour cell the wireless communication terminal is. Accordingly, such a derived vulnerability indication value may be used to determine whether the wireless communication terminal is in the vicinity of the neighbour cell basestation, and thus vulnerable to downlink interference from the neighbour cell basestation as well as a potential source of significant uplink interference to the neighbour cell basestation.

In one optional embodiment of the invention, the neighbour cell measurement information may comprise at least one received power measurement indication for at least one neighbour cell. In one optional embodiment of the invention, deriving a vulnerability indication value for a wireless communication terminal may comprise subtracting a received power measurement indication for a neighbour cell from a known transmit power value for that neighbour cell.

In one optional embodiment of the invention, the method may comprise determining that the at least one wireless communication terminal is in the vicinity of a basestation of a neighbour cell if a vulnerability indication value for that neighbour cell is less than a threshold value.

In one optional embodiment of the invention, the method may comprise instructing the at least one wireless communication terminal to obtain pathloss measurement information for all neighbour cells, and deriving vulnerability indication values for the at least one wireless communication terminal in relation to each neighbour cell for which pathloss measurement information is received from the at least one wireless communication terminal.

According to a second aspect of the invention, there is provided a method of performing Inter-cell Interference Management (ICIM) within a cellular communication network. The method comprises, at a network element within the cellular communication network, detecting wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network in accordance with the first aspect of the invention.

In this manner, improved ICIM may be implemented based on whether wireless communication terminals have actually been detected within the vicinity of non-serving basestations, thereby reducing the likelihood of a recipient basestation invoking interference mitigation techniques needlessly when no vulnerable wireless communication terminals are within its vicinity, and/or the likelihood of the recipient basestation sustaining high performance to a served wireless communication terminal when a vulnerable non-served wireless communication terminal is within its vicinity, and thus generating interference on the nearby non-served wireless communication terminal.

In one optional embodiment of the invention, the method may comprise, if at least one wireless communication terminal is detected in the vicinity of a basestation of a neighbour cell, sending ICIM information to the neighbour cell comprising an indication of the presence of the at least one wireless communication terminal in the vicinity of the basestation thereof.

In one optional embodiment of the invention, the method may comprise, if no neighbour cell measurement information is received from any wireless communication terminal relating to a neighbour cell, sending no ICIM information to the neighbour cell for which no neighbour cell measurement information is received.

In one optional embodiment of the invention, the network element at which the method is implemented may comprise a serving network element for the at least one wireless communication terminal. For example, the network element may comprise a radio network controller of a serving cell of the at least one wireless communication terminal. According to a third aspect of the invention, there is provided a network element arranged to detect wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network element. The network element comprises at least one signal processing module arranged to receive neighbour cell measurement information from at least one wireless communication terminal, derive at least one vulnerability indication value for the at least one wireless communication terminal based at least partly on the received neighbour cell measurement information, and determine whether the at least one wireless communication terminal is in the vicinity of a basestation of a neighbour cell for which measurement information was received based at least partly on the derived at least one vulnerability indication value therefor.

In one optional embodiment of the invention, the at least one signal processing module of the network element may be arranged to perform Inter-cell Interference Management (ICIM) within the cellular communication network comprising detecting wireless communication terminals in the vicinity of non-serving basestations.

According to a fourth aspect of the invention, there is provided a cellular communication network incorporating at least one network element in accordance with the third aspect of the invention.

According to a fifth aspect of the invention, there is provided a non-transitory computer program product having computer-readable code stored thereon for programming a signal processing module to perform a method of detecting wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network. The code is operable for, within at least one network element of the cellular communication network, receiving neighbour cell measurement information from at least one wireless communication terminal, deriving at least one vulnerability indication value for the at least one wireless communication terminal based at least partly on the received neighbour cell measurement information, and determining whether the at least one wireless communication terminal is in the vicinity of a basestation of a neighbour cell for which measurement information was received based at least partly on the derived at least one vulnerability indication value therefor.

These and other aspects, features and advantages of the invention will be apparent from, and elucidated with reference to, the embodiments described hereinafter.

Brief Description of the Drawings

Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 illustrates a simplified example of part of a cellular communication system. FIG. 2 illustrates a simplified example of a wireless communication terminal located within the vicinity of a non-serving basestation. FIG. 3 illustrates a simplified flowchart of an example of a method of performing Inter- Cell Interference Management (ICIM) comprising detecting wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network.

FIG. 4 illustrates a simplified example of a message flow within the cellular communication network for the method of FIG. 3.

FIG. 5 illustrates a simplified block diagram of an example of a typical computing system.

Detailed Description

Examples of the invention will be described in terms of a method and apparatus for detecting wireless communication terminals in the vicinity of non-serving basestations within a Universal Mobile Telecommunications System (UMTS™) cellular communication network, and a method and apparatus for performing Inter-Cell Interference Management within a UMTS network. However, it will be appreciated by a skilled artisan that the inventive concept herein described may equally be implemented within cellular communication networks adapted in accordance with alternative wireless communication technologies and standards, for example such as cellular communication networks adapted in accordance with the fourth generation (LTE - Long Term Evolution) of cellular communication networks.

Furthermore, because the illustrated embodiments of the present invention may for the most part, be implemented using electronic components and circuits known to those skilled in the art, details will not be explained in any greater extent than that considered necessary as illustrated below, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention.

In a number of applications, a network element adapted in accordance with examples of the invention effectively performs a method of detecting wireless communication terminals in the vicinity of non-serving basestations (e.g. a neighbour cell basestation) within a cellular communication network. The method comprises receiving neighbour cell measurement information from at least one wireless communication terminal, deriving at least one vulnerability indication value for the at least one wireless communication terminal based at least partly on the received neighbour cell measurement information, and determining whether the at least one wireless communication terminal is in the vicinity of a neighbour cell basestation for which measurement information was received based at least partly on the derived at least one vulnerability indication value therefor.

In this manner, measurement information received from a wireless communication terminal corresponding to a neighbour cell may be used to derive a vulnerability indication value for the UE with respect to a basestation of that neighbour cell. For example, and as described below, a received power measurement taken by the wireless communication terminal for that neighbour cell may be used to derive an indication of how close to the basestation of that neighbour cell the wireless communication terminal is. Accordingly, such a derived vulnerability indication value may be used to determine whether the wireless communication terminal is in the vicinity of the neighbour cell basestation, and thus vulnerable to downlink interference from the neighbour cell basestation as well as a potential source of significant uplink interference to the neighbour cell basestation.

In a number of further applications, a network element adapted in accordance with examples of the invention effectively performs a method of performing Inter-cell Interference Management, (ICIM), within a cellular communication network, the method comprising detecting wireless communication terminals in the vicinity of non-serving basestations as described above. In this manner, improved ICIM may be implemented based on whether wireless communication terminals have actually been detected within the vicinity of non- serving basestations, thereby reducing the likelihood of a recipient basestation invoking interference mitigation techniques needlessly when no vulnerable wireless communication terminals are within its vicinity, and/or the likelihood of the recipient basestation sustaining high performance to a served wireless communication terminal when a vulnerable non-served wireless communication terminal is within its vicinity, and thus generating interference on the nearby non-served wireless communication terminal.

For clarity, the term basestation used herein is intended to cover all types of basestations, including for example high power basestations (NodeBs in 3GPP parlance) of macro cells as well as low power basestations of small cells (otherwise referred to as Access Points (APs) with the term Home NodeBs (HNBs) identifying femto cell access points).

Referring now to the drawings, and in particular FIG. 1 , a simplified example of part of a cellular communication system is illustrated and indicated generally at 100. In FIG. 1 , there is illustrated an example of a communication system in a form of a third generation partnership project (3GPP™) Universal Mobile Telecommunication System (UMTS™) network 100 that comprises a combination of a macro cell 185 and a plurality of small cells 150, 152. For the example embodiment illustrated in FIG. 1 , sub-systems within the UMTS network 100 comprise two distinct architectures to handle the respective macro cell and small cell communications.

In the macro cell scenario, the macro radio access network (RAN) sub-system 1 10 comprises a controller in a form of a Radio Network Controller (RNC) 136 having, inter alia, one or more signal processing module(s) 138. The RNC 136 is operably coupled to at least one NodeB 124, via an lub interface 125, for supporting communications within the macro cell 185. The NodeB 124 comprises signal processing module 126 and transceiver circuitry 128 arranged to enable communication with one or more wireless communication terminals located within the coverage area of the macro communication cell 185, such as User Equipment (UE) 1 14. The RNC 136 is further operably coupled to a core network element 142, such as a serving general packet radio system (GPRS) support node (SGSN) and/or a mobile switching centre (MSC), via an lu interface, such as the packet switched lu interface, lu-PS, as shown.

In a small cell scenario, a radio access network (RAN) sub-system 1 12 comprises an access point, 130, which in the context of a residential femto cell is referred to as a Home NodeB (HNB), that is arranged to perform a number of functions generally associated with a cellular communication basestation, and a controller in a form of an Access Point Gateway (GW) 140. As will be appreciated by a skilled artisan, an access point (AP) is a communication element that supports communications within a communication cell, such as a small cell 150, and as such may provide access to a cellular communication network via the small cell 150. The AP 130 may then be connected to an AP GW 140 via an luh interface 135, for example implemented over, say, the owner's broadband internet connection (not shown).

Thus, an AP 130 may be considered as encompassing a scalable, multi-channel, two- way communication device that may be provided within, say, residential and commercial (e.g. office) locations, communication 'hotspots' etc., to extend or improve upon network coverage within those locations. An example of a typical third generation (3G) AP for use within a 3GPP™ system by definition comprises some NodeB functionality and some aspects of radio network controller (RNC) 136 functionality. For the illustrated example embodiment, the AP 130 comprises signal processing module 165 and transceiver circuitry 155 arranged to enable communication with one or more wireless communication terminals located within the coverage area of the small cell 150, such as User Equipment (UE) 1 14, via a wireless interface (Uu) 132.

The GW 140 may be coupled to the core network (CN) 142 via an lu interface, such as the packet switched lu interface, lu-PS, as shown. In this manner, the AP 130 is able to provide voice and data services to a cellular handset, such as UE 1 14, in a small cell, in the same way as a conventional NodeB would in a macro cell, but with the deployment simplicity of, for example, a Wireless Local Area Network (WLAN) access point.

As previously mentioned, in some example embodiments a network element of the UMTS network 100 adapted in accordance with examples of the invention effectively performs a method of detecting wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network. For example, FIG. 2 illustrates a simplified example of a UE 1 14 located within the vicinity of an AP 130 of a small cell, such as a femto cell HNB. The UE 1 14 has as a serving cell a macro cell supported by NodeB 124, and as such the UE 1 14 is connected to the cellular network 100 (FIG. 1 ) via a Uu interface 132 established between the UE 1 14 and the NodeB 124. As is known in the art, any UE active within a cellular communications network has a serving cell (to which it is synchronised and with which it transacts certain relatively frequent active mode procedures). Thus, in this scenario the AP 130 comprises a non-serving basestation from the point of view of the UE 1 14. R_VU| 200 illustrated in FIG. 2 represents a radius about the AP 130 within which non- served UEs, such as UE 1 14, may be vulnerable to downlink interference therefrom, and which may also be potential sources of significant uplink interference to the AP 130. In the illustrated example, UE 1 14 is located within R_vu! 200 and thus is vulnerable to downlink interference from the AP 130, and also may be a source of significant uplink interference to the AP 130. In conventional macro-cell architectures, such close proximity of the UE 1 14 to a basestation would typically result in the UE 1 14 handing over to the cell of the basestation within the vicinity of which the UE 1 14 is located. However, it is often the case that a small cell such as a femto cell is configured to operate in a closed mode, whereby only certain users that are part of a "closed subscriber group" (CSG) are allowed to connect thereto. As such, if UEs are in the coverage area of such a femto cell but not part of a CSG for that femto cell, those UEs will remain connected to an overlying macro cell. Accordingly, in the illustrated example, although the UE 1 14 is in such close proximity to the AP 130, the macro cell supported by the NodeB 124 may remain the serving cell for the UE 1 14.

As previously mentioned, in order to mitigate interference resulting from such situations, it is known for inter-cell interference management (ICIM to be implemented. However, a problem with existing ICIM techniques is that the information shared between basestations and/or access points does not enable the recipient to determine whether UEs vulnerable to interference are within their close vicinity.

Referring now to FIG. 3, there is illustrated a simplified flowchart 300 of an example of a method of performing Inter-cell Interference Management (ICIM) comprising detecting wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network. In some examples, the method of FIG. 3 may be implemented within a network element of a radio access network (RAN) subsystem of the cellular communication network, for example within a radio network controller of the cellular communication network such as the RNC 136 illustrated in FIG. 1. In particular, it is contemplated that the method may be implemented by way of one or more signal processing modules of such a network element, such as the signal processing module(s) 138 of the RNC 136 illustrated in FIG. 1 , executing computer program code for programming the signal processing module(s) to perform the method. It will be appreciated that the present invention is not limited to being implemented within an RNC of a cellular communication network, and may equally be implemented within alternative types of network element. For example, the present invention may additionally/alternatively be implemented within, say, one or more basestations (e.g. NodeBs, HNBs, etc.) of the cellular communication network and/or one or more access point gateways, such as the AP GW 140 illustrated in FIG. 1 , and/or within a part of the core network 142.

The method starts at step 305, and moves on to step 310 where, in the illustrated example, a wireless communication terminal (UE) is instructed to obtain pathloss measurement information for neighbour cells by performing power level measurements therefor (neighbour cells typically being defined within a neighbour cell list broadcast by the serving cell). For example, as illustrated in FIG. 4, the RAN 1 10 of the serving macro cell for the UE 1 14 may send an instruction 410 to the UE 1 14, via the NodeB 124 of the serving cell, instructing the UE 1 14 to perform pathloss measurement for neighbour cells such as the small cell supported by the AP 130 and AP GW 140. In some examples, the UE 1 14 may be instructed to obtain pathloss measurement information for all neighbour cells within the neighbour cell list broadcast by the UE's serving cell. Referring back to FIG. 3, at step 315, one or more measurement reports are received from the UE comprising the pathloss measurement information for the neighbour cells. Thus, for the example in FIG. 4, the UE 1 14 may perform power level measurements for neighbour cells including for the small cell supported by the AP 130, as illustrated generally at 420, and transmit them to the RAN 1 10 via the NodeB 124 within one or more measurement reports, as illustrated at 430.

Referring back to FIG. 3, having received the neighbour cell measurement information from the UE(s), the method moves on to steps 320 to 355, which in the illustrated example may be performed for each neighbour cell. At step 320, it is determined whether measurement information is available for the current neighbour cell from at least one UE. If no measurement information is available for the current neighbour cell, it may be assumed that no UE is within range of the current neighbour cell, and thus that there is no likelihood of inter-cell interference. Accordingly, the method ends at 360. In some examples, only measurement information received within a certain time period may be taken into consideration in step 325. In this manner, the use of obsolete measurement information may be avoided.

Referring back to step 320, if (valid) measurement information is available for the current neighbour cell, the method moves on to step 325 where a vulnerability indication value may then be derived for the or each UE from which measurement information was received. For example, the measurement information for a neighbour cell may comprise a received power measurement indication (in dB) for that neighbour cell. A vulnerability indication value may be derived by subtracting the received power measurement indication for the neighbour cell from a known transmit power value for that neighbour cell. For example, the RAN 1 10 performing the method of FIG. 3 may have access to, or otherwise be able to obtain, transmit power values for the neighbouring cells from, say, the core network 142 and/or more directly from the RNCs/GWs and/or basestations of those neighbouring cells. In this manner, a difference (in dB) between the known transmit power for a neighbour cell and the received transmit power as measured by the UE 1 14, which may be obtained by subtracting the received power measurement indication for the neighbour cell from a known transmit power value, provides an indication of the propagation distance of the transmitted signal, and thus an indication of the distance between the basestation of the neighbour cell and the UE 1 14.

The method then moves on to step 330, where it is determined whether the vulnerability indication value for that UE exceeds a threshold value. For example, where a larger vulnerability indication value is representative of the UE being a larger distance from the basestation of the current neighbour cell, then the vulnerability indication value may be deemed to exceed the threshold value if it comprises a larger value than the threshold value. Conversely, if a smaller vulnerability indication value is representative of the UE being a larger distance from the basestation of the current neighbour cell, then the vulnerability indication value may be deemed to exceed the threshold value if it comprises a smaller value than the threshold value. In the illustrated example, if the vulnerability indication value exceeds the threshold value, the UE is considered not to be in close proximity to the basestation of the current neighbour cell, for example outside of the radius R_vu! 200 illustrated in FIG. 2. Accordingly, it may be determined that the UE is not vulnerable to downlink interference from the basestation of the current neighbour cell, nor a potential source of significant uplink interference to the basestation of the current neighbour cell. As such, in the illustrated example the method ends at 345.

Conversely, if the vulnerability indication value does not exceed the threshold value, the UE may be considered to be in the vicinity of the basestation of the current neighbour cell, for example within the radius R_vu! 200 illustrated in FIG. 2. Accordingly, it may be determined that the UE is vulnerable to downlink interference from the basestation of the current neighbour cell, and a potential source of significant uplink interference to the basestation of the current neighbour cell. As such, in the illustrated example the method moves on to 335 where an ICIM message is generated comprising an indication that a vulnerable UE is in the vicinity of the target cell basestation. In the illustrated example, the ICIM message generated at step 335 further comprises ICIM information such as, for example, transmit power that the serving cell intends to use until further notice, etc. In this manner, the radio network subsystem (RNS) of the target neighbour cell is made aware of the fact that a UE is vulnerable to downlink interference from the neighbour cell and that the target neighbour cell basestation may be vulnerable to uplink interference from that UE. The ICIM message is then sent to the current neighbour cell at step 340, and the method ends, at 345.

Referring back to FIG. 4, the sending of the ICIM message to the neighbour cell is illustrated generally at 440, and may be performed as for conventional ICIM messages. In this manner, the ICIM message may be routed by the core network 142 to the RAN 1 12 of the neighbour cell. The RAN 1 12 of the recipient neighbour cell may then implement appropriate ICIM measures in accordance with the received ICIM message, and in particular in accordance with the indication that a vulnerable UE 1 14 is in the vicinity of the basestation of the cell to which the ICIM message corresponds. For example, in FIG. 4 the AP GW 140 may simply forward the ICIM message, or some or all of the information contained therein, to the basestation 130, whereby the basestation 130 may implement appropriate ICIM measures in accordance with the received ICIM message. Additionally/alternatively, the AP GW 140 may provide ICIM configuration setting commands to the basestation 130, for example to configure ICIM power levels within the supported cell to reduce the downlink interference caused to the vulnerable UE 1 14.

Referring back to FIG. 3, it is contemplated that steps 320 to 340 of the method need not be performed substantially immediately upon receipt of measurement information for the respective neighbour cell, and may be performed substantially independently of the receipt of neighbour cell measurement information. Furthermore, it is contemplated that the generation and transmission of ICIM messages in steps 335, and 340 need not be performed substantially immediately upon derivation of vulnerability indication values for the respective neighbour cells. For example, the derivation of vulnerability indication values and/or the generation and transmission of ICIM messages may be event driven and/or periodic, independently or in combination. Events used to trigger the messaging may include anything that would lead to a significant change in the radio conditions in the cell. For example, any radio bearer establishment success case, or bearer release, where there is a significant change (either positive or negative) in the interference power generated by a cell on its neighbours may be included as such an event. Once a bearer is established, then a periodic refresh of the interference information may be appropriate, so that as a UE moves in or out of coverage of a neighbour cell, then the vulnerability of the UE to the neighbour transmissions (and vice versa) may be regularly re-assessed and used in the ICIM messaging.

Thus, a method and apparatus have been described that enable a cell receiving ICIM messaging to reliably tell if there are vulnerable UEs in the vicinity thereof or not, enabling ICIM measures to be more accurately invoked and thereby improving network performance. In addition, the method and apparatus herein described further enable a network element sending ICIM information to reliably tell if a target neighbour cell has vulnerable UEs in the vicinity thereof or not, enabling the network element to decide whether to send the ICIM message to that target neighbour cell or not, and thus enabling the saving of messaging processing cycles when no vulnerable UEs are present without compromising network performance.

Referring now to FIG. 5, there is illustrated a typical computing system 500 that may be employed to implement signal processing functionality in embodiments of the invention. For example, a computing system of this type may be used within the GW 140 and/or RNC 136 of FIG. 1. Those skilled in the relevant art will also recognize how to implement the invention using other computer systems or architectures. Computing system 500 may represent, for example, a desktop, laptop or notebook computer, hand-held computing device (PDA, cell phone, palmtop, etc.), mainframe, server, client, or any other type of special or general purpose computing device as may be desirable or appropriate for a given application or environment. Computing system 500 can include one or more processors, such as a processor 504. Processor 504 can be implemented using a general or special-purpose processing engine such as, for example, a microprocessor, microcontroller or other control module. In this example, processor 504 is connected to a bus 502 or other communications medium.

Computing system 500 can also include a main memory 508, such as random access memory (RAM) or other dynamic memory, for storing information and instructions to be executed by processor 504. Main memory 508 also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 504. Computing system 500 may likewise include a read only memory (ROM) or other static storage device coupled to bus 502 for storing static information and instructions for processor 504.

The computing system 500 may also include information storage system 510, which may include, for example, a media drive 512 and a removable storage interface 520. The media drive 512 may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a compact disc (CD) or digital video drive (DVD) read or write drive (R or RW), or other removable or fixed media drive. Storage media 518 may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by media drive 512. As these examples illustrate, the storage media 518 may include a computer-readable storage medium having particular computer software or data stored therein.

In alternative embodiments, information storage system 510 may include other similar components for allowing computer programs or other instructions or data to be loaded into computing system 500. Such components may include, for example, a removable storage unit 522 and an interface 520, such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units 522 and interfaces 520 that allow software and data to be transferred from the removable storage unit 518 to computing system 500.

Computing system 500 can also include a communications interface 524.

Communications interface 524 can be used to allow software and data to be transferred between computing system 500 and external devices. Examples of communications interface 524 can include a modem, a network interface (such as an Ethernet or other NIC card), a communications port (such as for example, a universal serial bus (USB) port), a PCMCIA slot and card, etc. Software and data transferred via communications interface 524 are in the form of signals which can be electronic, electromagnetic, and optical or other signals capable of being received by communications interface 524. These signals are provided to communications interface 524 via a channel 528. This channel 528 may carry signals and may be implemented using a wireless medium, wire or cable, fibre optics, or other communications medium. Some examples of a channel include a phone line, a cellular phone link, an RF link, a network interface, a local or wide area network, and other communications channels.

In this document, the terms 'computer program product', 'computer-readable medium' and the like may be used generally to refer to media such as, for example, memory 508, storage device 518, or storage unit 522. These and other forms of computer-readable media may store one or more instructions for use by processor 504, to cause the processor to perform specified operations. Such instructions, generally referred to as 'computer program code' (which may be grouped in the form of computer programs or other groupings), when executed, enable the computing system 500 to perform functions of embodiments of the present invention. Note that the code may directly cause the processor to perform specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g. libraries for performing standard functions) to do so.

As used herein, the expression non-transitory will be understood to refer to the non- ephemeral nature of the storage medium itself rather than to a notion of how long the stored information itself may persist in a stored state. Accordingly, memories that might otherwise be viewed, for example, as being volatile (such as many electronically-erasable programmable read-only memories (EPROMs) or random-access memories (RAMs)) are nevertheless to be viewed here as being "non-transitory" whereas a signal carrier in transit is to be considered "transitory" notwithstanding that the signal may remain in transit for a lengthy period of time. Specifically, a non-transitory computer program product may comprise one or more of a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, ROM, a Programmable Read Only Memory, PROM, an Erasable Programmable Read Only Memory EPROM, EPROM, an Electrically Erasable Programmable Read Only Memory, EEPROM, and a Flash memory.

In an embodiment where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into computing system 500 using, for example, removable storage drive 522, drive 512 or communications interface 524. The control module (in this example, software instructions or computer program code), when executed by the processor 504, causes the processor 504 to perform the functions of the invention as described herein.

Furthermore, the inventive concept can be applied to any signal processing circuit. It is further envisaged that, for example, a semiconductor manufacturer may employ the inventive concept in a design of a stand-alone device, such as a microcontroller, digital signal processor, or application-specific integrated circuit (ASIC) and/or any other sub-system element.

It will be appreciated that, for clarity purposes, the above description has described embodiments of the invention with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units or processors may be used without detracting from the invention. For example, functionality illustrated to be performed by the same processor or controller may be performed by separate processors or controllers. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.

Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented, at least partly, as computer software running on one or more data processors and/or digital signal processors or configurable module components such as FPGA devices. Thus, the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term 'comprising' does not exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by, for example, a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Thus, references to 'a', 'an', 'first', 'second', etc. do not preclude a plurality.

Thus, an improved method and apparatus for detecting wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network have been described, wherein the aforementioned disadvantages with prior art arrangements for performing Inter-Cell Interference Management have been substantially alleviated.

Claims

1. A method of detecting wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network; the method comprising, at a network element within the cellular communication network:

receiving neighbour cell measurement information from at least one wireless communication terminal;

deriving at least one vulnerability indication value for the at least one wireless communication terminal based at least partly on the received neighbour cell measurement information; and

determining whether the at least one wireless communication terminal is in the vicinity of a basestation of a neighbour cell for which measurement information was received based at least partly on the derived at least one vulnerability indication value therefor.

2. The method of Claim 1 , wherein the neighbour cell measurement information comprises at least one received power measurement indication for at least one neighbour cell.

3. The method of Claim 2, wherein deriving a vulnerability indication value for a wireless communication terminal comprises subtracting a received power measurement indication for a neighbour cell from a known transmit power value for that neighbour cell.

4. The method of any preceding Claim, wherein the method comprises determining that the at least one wireless communication terminal is in the vicinity of a basestation of a neighbour cell if a vulnerability indication value for that neighbour cell is less than a threshold value.

5. The method of any preceding Claim, wherein the method comprises instructing the at least one wireless communication terminal to obtain pathloss measurement information for all neighbour cells, and deriving vulnerability indication values for the at least one wireless communication terminal in relation to each neighbour cell for which pathloss measurement information is received from the at least one wireless communication terminal.

6. A method of performing Inter-Cell Interference Management, ICIM, within a cellular communication network, the method comprising, at a network element within the cellular communication network, detecting wireless communication terminals in the vicinity of non- serving basestations within a cellular communication network in accordance with any one of the preceding Claims.

7. The method of Claim 6, wherein the method comprises, if at least one wireless communication terminal is detected in the vicinity of a basestation of a neighbour cell, sending ICIM information to the neighbour cell comprising an indication of the presence of the at least one wireless communication terminal in the vicinity of the basestation thereof.

8. The method of Claim 6 or Claim 7, wherein the method comprises, if no neighbour cell measurement information is received from any wireless communication terminal relating to a neighbour cell, sending no ICIM information to the neighbour cell for which no neighbour cell measurement information is received.

9. The method of any one of the preceding Claims, wherein the network element at which the method is implemented comprises a serving network element for the at least one wireless communication terminal.

10. The method of Claim 1 1 , wherein the network element comprises a radio network controller of a serving cell of the at least one wireless communication terminal.

1 1. A network element arranged to detect wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network element; the network element comprising at least one signal processing module arranged to:

receive neighbour cell measurement information from at least one wireless communication terminal;

derive at least one vulnerability indication value for the at least one wireless communication terminal based at least partly on the received neighbour cell measurement information; and

determine whether the at least one wireless communication terminal is in the vicinity of a basestation of a neighbour cell for which measurement information was received based at least partly on the derived at least one vulnerability indication value therefor.

12. The network element of Claim 1 1 , wherein the at least one signal processing module of the network element is arranged to perform Inter-Cell Interference Management, ICIM, within the cellular communication network comprising detecting wireless communication terminals in the vicinity of non-serving basestations.

13. A cellular communication network incorporating at least one network element in accordance with Claim 1 1 or Claim 12.

14. A non-transitory computer program product having computer-readable code stored thereon for programming a signal processing module to perform a method of detecting wireless communication terminals in the vicinity of non-serving basestations within a cellular communication network, the code operable for, within at least one network element of the cellular communication network: receiving neighbour cell measurement information from at least one wireless communication terminal;

15. The non-transitory computer program product of Claim 14, wherein the non-transitory computer program product comprises at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, an Electrically Erasable Programmable Read Only Memory, and a Flash memory.