GB2462327A

GB2462327A - Apparatus and method for a femtocell base station to identify its neighbour cells

Info

Publication number: GB2462327A
Application number: GB0814380A
Authority: GB
Inventors: Yoav Volloch; Rafy Carmon
Original assignee: Percello Ltd
Current assignee: MaxLinear Israel Ltd
Priority date: 2008-08-06
Filing date: 2008-08-06
Publication date: 2010-02-10
Anticipated expiration: 2028-08-06
Also published as: GB0814380D0; GB2462327B

Abstract

A communications apparatus(216) supporting a cell(500) comprises a processing resource arranged to solicit a response message, which may be a measurement report message, by sending a measurement request message, which may be a measurement control message, to UEs(202,514,522,530), the measurement request message identifying cells(540,510,516,526) to be measured and an associated measurement type. From the response message the processing resource determines if a cell is a neighbour cell and if so maintains the neighbour cell identity. UEs may be capable of communicating with another communications apparatus(502,508,516,524) which the communications apparatus is unable to monitor. The processing resource may generate neigbour cell identity data in response to a predetermined event such as power-up or reset. Different cells may be identified respectively in the number of measurement request messages by sequencing through a set of cell identifiers generated in accordance with a predetermined scheme.

Description

INTELLECTUAL

. .... PROPERTY OFFICE Application No. GBO8 14380.2 RTM Date:21 October 2009 The following terms are registered trademarks and should be read as such wherever they occur in this document:

GSM

UMTS 3GPP

CDMA-2000 Intellectual Property Office is an operating name of the Patent Office www.ipo.gov.uk ACCESS NETWORK, COMMUNICATIONS APPARATUS AND METHOD

THEREFOR

[0001] The present invention relates to a communications apparatus of the type that, for example, supports a cell for communicating with a user equipment unit.

The present invention also relates to an access network of the type that, for example, supports a cell for communicating with a user equipment unit. The present invention further relates to a method of maintaining neighbouring cell identity data, the method being of the type that, for example, supports a cell for communicating with a user equipment unit.

[0002] In the field of wireless communications, a large number of wireless communications systems are known employing a variety of different Radio-Frequency (RF) bands and different access schemes. In this respect, one known wireless communications system is the so-called Global System from Mobile communications (GSM) that operates in accordance with a Time Division Multiple Access (TDMA) access scheme. The GSM system is the result of standard isation activities of the European Telecommunications Standards institute (ETSI).

[0003] Since the introduction of the GSM system, and other so-called "2G" systems, consumer needs have both increased and become increasingly more sophisticated in terms of services required of a wireless communications system.

Consequently, further standardisations activities have taken place, and continue to take place, in order to develop wireless communications technology further. A so-called third generation or "3G" standard has therefore now been implemented in parts of the world, for example the Universal Mobile Telecommunication System (UMTS) in Europe and elsewhere, 3G networks implemented in accordance with this standard being designed to overlie at least in part existing 2G networks with the intention of eventually replacing the existing 2G networks. Furthermore, new technologies for so-called "fourth generation" wireless communications, or 4G, have now been standardised, for example Long Term Evolution (LTE), Ultra Mobile Broadband (UMB) and Wimax.

[0004] Like 2G networks, 3G networks provide coverage over a wide geographic area and indeed communication between different 3G networks providing different areas of coverage is possible, even between different countries. Such coverage in both generations of network is provided using a cellular pattern of smaller coverage areas, or cells, supported by individual base stations or Node Bs, the terminology varying depending upon the type of network to which the cell relates.

Typically, the cells are hexagonal in shape and are only representative of the individual coverage areas provided by each base station or Node B due to the coverage areas of base stations and Node Bs being dependent upon a number of factors, including propagation conditions and terrain in a geographic area corresponding to a given cell. In any event, antennas used by the base stations and the Node Bs generate a pattern more akin to circular or elliptical pattern rather than a hexagonal pattern. However, for convenience of planning, a notional hexagonal shape has been adopted to approximate the individual coverage areas.

[0005] In the context of a 3G network, a large number of Node Bs are strategically placed around towns and cities and along roads and motorways between towns and cities in order to provide coverage to subscribers. In such circumstances, the Node Bs support so-called macrocells and provide seamless mobility throughout the wireless network. Additionally, so-called microcells and picocells, supported by Node Bs, are also strategically placed in densely populated urban areas in order to provide additional capacity and coverage for subscribers, for example in apartments, shopping malls and airports. Such cells are coupled to Radio Network Controllers (RNC5) of the 3G network using, for example, dedicated Asynchronous Transfer Mode (ATM) links over a so-called El orTl carrier.

[0006] Third Generation wireless communications networks offer a number of benefits to subscribers that are well-known in the art and so shall not be discussed herein. However, coverage provided by cells in 3G and 4G networks is diminished somewhat in respect of indoor environments due to attenuation of RF signals transmitted by Node Bs, and even 2G base stations, by the fabric of a building, resulting in poor penetration of RF signals into and out of the building.

[0007] Consequently, so-called femtocells have been proposed for deployment in in-building environments, for example in residential buildings, such as houses. A femtocell is a small "base station" of limited coverage area, but sufficiently strong in RF output power to provide coverage within at least a substantial part of a building. The femtocell supports signalling and operates in accordance with communications protocols associated with the wireless communications network for which the femtocell is provided; the femtocell is typically provided or supported by a network operator associated with the wireless communications network for use by a subscriber in the home. In contrast with the macro-, micro-and pico-cells, the femtocell leverages existing Internet Protocol (IP) broadband communications access provided to the home in order to "backhaul" voice, video, Short Messaging Service (SMS), and data traffic from the home to a core network of the wireless communications network.

[0008] As suggested above, femtocells offer network operators increased capacity and coverage area, but also the possible opportunity to offer new services to subscribers whilst in the home. The network operator also benefits from reduced operating costs and capital expenditure. Furthermore, in contrast with cellular network deployment, femtocells are typically deployed sporadically in high volumes and without cell planning.

[0009] In order to provide the best performance, for example, a data rate, to a subscriber, a user equipment unit used by the subscriber needs to be able to connect to, or camp on, a femtocell when within a coverage area of the femtocell.

Likewise, the user equipment unit needs to be able to connect to, or camp on, another femtocell or macrocell, when performance of the user equipment unit will benefit from such a change.

[0010] Therefore, in order to support mobility procedures of the user equipment unit, for example so-called handover or handoff, or cell reselection, the femtocell needs to be "aware" of neighbouring cells so that neighbouring cell information can be broadcast on a broadcast channel of the femtocell. However, in contrast with planned macrocells, microcells and picocells, due to the sporadic and unplanned nature of deployment of, in particular, femtocell, the femtocell in not aware of all neighbouring cells. Without knowledge of the cells neighbouring the femtocell, the user equipment unit is unable to perform smooth cell reselections and handovers, resulting in dropped calls, poor service quality or periods when a service is unavailable.

[0011] In order to alleviate this problem, it is known to augment femtocells by providing dedicated elements that enable the femtocell to "map" neighbouring cells. This technique is analogous to a so-called "neighbour cell search" mechanism employed by user equipment units in order to find cells. However, situations exist where the femtocell is unable to learn of the existence of a neighbouring cell.

[0012] By way of example, where a femtocell and a neighbouring cell have overlapping coverage areas, but the coverage area of the neighbouring cell is insufficient for a communications apparatus supporting the femtocell to monitor the neighbouring cell, the above-mentioned solution is insufficient. In this respect, a user equipment unit can be located in an area of intersection between the coverage area of the femtocell and the coverage area of the neighbouring cell and so the neighbouring cell is potentially a candidate cell for use in a cell handover procedure or a cell reselection procedure. However, if the user equipment unit is camped on the femtocell and the femtocell is unable to broadcast the identity of the neighbouring cell, the user equipment unit is unable to perform smooth reselection or handover from the femtocell to the neighbouring cell, irrespective of whether the neighbouring cell is a macrocell, a microcell, a picocell or another femtocell.

[0013] Additionally, provision of the above-mentioned technique also increases the cost of production of the femtocell, because additional semiconductor die space is required as well as RF solutions to support the technique.

[0014] According to a first aspect of the present invention, there is provided a communications apparatus comprising: a processing resource capable of supporting a cell for communicating with a user equipment unit, the processing resource being arranged to solicit, when in use, a response message by sending a measurement request message for receipt by the user equipment unit, the measurement request message identifying a cell to be measured and an associated measurement type; wherein the processing resource is arranged to identify, when in use, from the response message a neighbouring cell relative to the supported cell and maintain neighbouring cell identity data using the identity of the neighbouring cell obtained.

[0015] The neighbouring cell identity data may be a list of neighbouring cells. The apparatus may support a femtocell and/or a picocell.

[0016] The processing resource may be arranged to send a number of measurement request messages comprising the measurement request message.

The sending of the number of measurement request messages may constitute scanning of a number of cell identifiers. The number of cell identifiers may be all possible cell identifiers. Each of the number of measurement request messages may comprise a first number of cell identifiers, for example a first list of cell identifiers. A subsequent number of measurement requests may be sent following the number of measurement requests; each of the subsequent number of measurement requests may comprise a second number of cell identifiers, for example a second list of cell identifiers. All possible cell identifiers may comprise the first and second number of cell identifiers.

[0017] The number of measurement request messages may comprise a first measurement request message and a second measurement request message; and the first measurement request message may identify a first cell and the second measurement request identifies a second cell, the identity of the first cell being different to the identity of the second cell.

[0018] At least some of the number of measurement request messages may respectively identify with respect to each other different cells.

[0019] The processing resource may be arranged to receive a number of response messages; the number of response messages may comprise a first response message and a second response message, the first response message being in response to the first measurement request message and the second response message being in response to the second measurement request message.

[0020] The processing resource may be arranged to receive a number of response messages from a number of user equipment units, and to map a presence of at least one neighbouring cell from the number of response messages received. Each of the number of user equipment units may be in a respective coverage area overlapped by the cell and a respective neighbouring cell.

[0021] The user equipment unit may be camped on the cell.

[0022] The user equipment unit may be capable of communicating with another communications apparatus supporting the neighbouring cell and the processing resource is unable to monitor the another communications apparatus.

[0023] The communications apparatus may be too far from the another communications apparatus to monitor the another communications apparatus.

[0024] The cell may be associated with a first access scheme and the neighbouring cell is associated with a second access scheme.

[0025] The first access scheme may be associated with a first communications standard and the second access scheme may be associated with a second communications standard. The cell may be a Universal Mobile Telecommunications System (UMTS) cell and the neighbouring cell may be a Global System for Mobile Communications (GSM) cell. The first access scheme may be a Code Division Multiple Access (CDMA) scheme, for example a Wideband-CDMA (W-CDMA) scheme, and the second access scheme may be a Time Division Multiple Access (TDMA) scheme.

[0026] The processing resource may be arranged to generate the neighbouring cell identity data in response to a predetermined event. The generation of the neighbouring cell identity data may be repeated.

[0027] The predetermined event may be a power-up event or a reset event. The predetermined event may be elapse of a predetermined or random period of time.

The predetermined event may be another user equipment unit newly camping on the cell.

[0028] The response message may indirectly identify the neighbouring cell.

[0029] The processing resource may be arranged to identify different cells respectively in the number of measurement request messages by scanning or sequencing through a set of cell identifiers generated in accordance with a predetermined scheme for allocating cell identifiers.

[0030] The measurement request message may be a Measurement Control message.

[0031] The apparatus may further comprise: a data store arranged to store, when in use, identities of a number of user equipment units camped on the cell; wherein the processing resource is arranged to send the measurement request message to each of the number of user equipment units.

[0032] A number of instances of the measurement request message may be sent; each instance of the number of instances of the measurement request message may respectively identify a different one of the number of user equipment units.

[0033] The response message may be a Measurement Report message.

[0034] The processing resource may support a third generation communications system.

[0035] According to a second aspect of the present invention, there is provided a base station comprising the communications apparatus as set forth above in relation to the first aspect of the invention.

[0036] The base station may be an access point base station.

[0037] According to a third aspect of the present invention, there is provided a femtocell apparatus comprising the communications apparatus as set forth above in relation to the first aspect of the invention.

[0038] According to a fourth aspect of the present invention, there is provided an access network comprising the base station as set forth above in relation to the first aspect of the invention and/or the femtocell apparatus as set forth above in relation to the third aspect of the invention.

[0039] According to a fifth aspect of the present invention, there is provided an integrated circuit comprising: a processing resource capable of supporting a cell, the processing resource being arranged to solicit, when in use, a response message by sending a measurement request message for receipt by a user equipment unit, the measurement request message identifying a cell to be measured and an associated measurement type; wherein the processing resource is arranged to identify, when in use, from the response message a neighbouring cell relative to the supported cell and maintain neighbouring cell identity data using the identity of the neighbouring cell obtained.

[0040] According to a sixth aspect of the present invention, there is provided a method of maintaining neighbouring cell identity data, the method comprising: supporting a cell for communicating with a user equipment unit; soliciting a response message by sending a measurement request message for receipt by the user equipment unit, the measurement request message identifying a cell to be measured and an associated measurement type; identifying from the response message a neighbouring cell relative to the supported cell; and maintaining the neighbouring cell identity data using the identity of the neighbouring cell obtained.

[0041] According to a seventh aspect of the present invention, there is provided a method of cell handover comprising the method of maintaining neighbouring cell identity data as set forth above in relation to the sixth aspect of the invention.

[0042] The cell handover may be a hard handover.

[0043] According to a eighth aspect of the present invention, there is provided a method of cell reselection comprising the method of maintaining neighbouring cell identity data as set forth above in relation to the sixth aspect of the invention.

[0044] According to a ninth aspect of the present invention, there is provided a computer program element comprising computer program code means to make a computer execute the method as set forth above in relation to the sixth aspect of the invention.

[0045] The computer program element may be embodied on a computer readable medium.

[0046] It is thus possible to provide an apparatus and method therefor that is capable of maintaining neighbouring cell identity data in respect of a neighbouring cell without the apparatus being able to monitor directly the neighbouring cell.

Also, as the apparatus identifies the neighbouring cell by making use of an existing mechanism provided in accordance with a communications standard that has to be supported by the apparatus in any event, no additional hardware provisioning is required and hence semiconductor die space is saved and cost of production is reduced. Furthermore, use of the user equipment unit to perform measurements on behalf of the apparatus enables the apparatus to have an increased monitoring range and is hence capable of obtaining information in respect of an increased geographical coverage area in which neighbouring cells can be located.

Furthermore, the apparatus and method are not limited to one particular radio access scheme and measurement in respect of cells supported by other radio access schemes supported by the user equipment unit is possible, for example Wideband-Code Division Multiple Access (W-CDMA) and Time Division Multiple Access (TDMA) access schemes.

[0047] At least one embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a part of a communications network; Figure 2 is a schematic diagram of a network architecture shown in overview in Figure 1; Figure 3 is a schematic diagram of a communications apparatus of Figure 2 constituting an embodiment of the invention; Figure 4 is a schematic diagram of a User Equipment unit of Figures 2 and 3; Figure 5 is a schematic diagram of a scenario of neighbouring cells to illustrate operation of the communications apparatus of Figure 3; Figure 6 is a flow diagram of a first part of a method constituting another embodiment of the invention; and Figure 7 is a flow diagram of a second part of the method of Figure 6.

[0048] Throughout the following description identical reference numerals will be used to identify like parts.

[0049] Referring to Figure 1, a communications network 100 comprises an Internet Protocol (IP) backbone network 102, for example an Asynchronous Transfer Mode (ATM) or an Ethernet Local Area Network (LAN). The IP backbone network 102 is coupled to a public Internet 103 and Core Network Support Services 104. The Core Network Support Services 104 comprise, for example, a LAN switch 106 coupled to a node (not shown) in the IP backbone network 102, the LAN switch 106 also being coupled to a Domain Name System (DNS) server 108. For completeness, the LAN switch 106 is also coupled to a Remote Authentication Dial-In User Service (RADIUS) server 110 and a Dynamic Host Configuration Protocol (DHCP) server 112.

[0050] The IP backbone network 102 is also coupled to a Serving GPRS (General Packet Radio Service) Support Node (SGSN) 114 by a first link 115. In this example, the SGSN 114 is coupled to a UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access Network (UTRAN) 116 by a second link 118 via a packet switched interface unit, Iu-p5. The SGSN 114 is also coupled to a GSM/EDGE Radio Access Network (GERAN) 120 by a third link 122. Additionally, the UTRAN 116 and the GERAN 120 are coupled to a Mobile Switching Centre (MSC) 124 by a fourth link 126 and a fifth link 128, respectively, the UTRAN 116 being coupled to the MSC 124 via a circuit switched interface unit, lu-cs. The MSC 124 is coupled to a Gateway MSC 130, the Gateway MSC 130 being coupled to a Public Switched Telephone Network (PSTN) 132. Network terminating equipment, for example a telephone handset 134, is also coupled to the PSTN 132.

[0051] As mentioned above, the UTRAN 116 is coupled to the IP backbone network 102 via the SGSN 114, the IP backbone network 102, the SGSN 114 and (in this example) the MSC 124 constituting a part of a core network 200 (Figure 2).

[0052] Referring to Figure 2, the core network 200 communicates with the UTRAN 116. A first User Equipment (UE) unit 202 is capable of communicating with the core network 200 via the UTRAN 116. The first UE unit 202 is capable of communicating with the UTRAN 116 via a Radio Frequency (RF) interface, Uu.

The core network 200, the UTRAN 116 and the first UE unit 202 provide an access stratum (not shown) and a non-access stratus (not shown).

[0053] The UTRAN 116 comprises a Radio Network Subsystem (RNS) or Radio Access Network (RAN) 206, the RAN 206 being capable of communicating with the core network 200. The RAN 206 is also capable of communicating with the first UE unit 202. The RAN 206 comprises a Radio Network Controller (RNC) 210 capable of communicating with the core network 200 and coupled to a Node B 212 via an lu-b interface, the Node B 212 being capable of communicating with the first UE unit 202 via the RF interface Uu.

[0054] In order to support communications in a building, for example a dwelling, such as a house, the UTRAN 116 also comprises a femtocell or Home Node B (HNB) Access Network 208, the HNB Access Network 208 also being capable of communicating with the core network 200. The HNB Access Network 208 is capable of communicating with the first UE unit 202 when in range. In accordance with the agreement of the 3rd Generation Partnership Project (3GPP) TSG RAN plenary meeting of 30 May 2008 and the minutes associated therewith, the HNB Access Network 208 comprises an HNB gateway 214 capable of communicating with the core network 200 and coupled an IP network, for example the Internet 103. A femtocell apparatus, for example an HNB 216, is coupled to the Internet 103 and hence the HNB gateway 214, via an lu-h interface. The HNB 216 is also referred to as a femtocell apparatus and is capable of communicating with the first UE unit 202 when within a first coverage area supported by the femtocell apparatus 216, the femtocell apparatus 216 supporting a first cell 218 having the first coverage area.

[0055] In the home 300 (Figure 3), the femtocell apparatus 216 comprises a pair of antennae 302 coupled to an RF Integrated Circuit (IC) 304 that is part of a chipset constituting a processing resource of the femtocell apparatus 216, the femtocell apparatus 216 constituting a communications apparatus. The RF IC 304 is coupled to a digital baseband processor 306, the digital baseband processor 306 being coupled to a digital memory, for example a flash memory 308, and a volatile memory, for example a Static Random Access Memory (SRAM) 310. The digital baseband processor 306 is also coupled to a communications interface supporting IP communications, for example an Ethernet interface 312, such as a 10/100 Mbps Ethernet interface 312. Of course, the skilled person should appreciate that other hardware implementations are possible, for example the implementation of the RF IC 304 and the pair of antennae 302 can be varied to support, for example a non-diversity implementation.

[0056] The femtocell apparatus 216 is coupled, via the Ethernet interface 312, to a home gateway 314, for example an Ethernet modem or router. The home gateway 314 is, of course, coupled to the Internet 103 via the Ia-h interface. The skilled person should, however, appreciate that other types of modem or router can be employed, for example an Asymmetric Digital Subscriber Line (ADSL) modem, Symmetric Digital Subscriber Line (SDSL) modem, router or cable modem.

[0057] Turning to Figure 4, the first UE unit 202 comprises another processing resource 400, the another processing resource 400 being, in this example, a chipset of a cellular communications terminal. The another processing resource 400 is coupled to a transmitter chain 402 and a receiver chain 404, the transmitter and receiver chains 402, 404 being coupled to a duplexing filter 406. The duplexing filter 406 is coupled to an antenna 408.

[0058] The first UE unit 202 also possesses a volatile memory, for example a RAM 410, and a non-volatile memory, for example a ROM 412, each coupled to the another processing resource 400. The another processing resource 400 is also coupled to a microphone 414, a speaker unit 416, a keypad 418 and a display 420. The skilled person should appreciate that the architecture of the first UE unit 202 described above comprises other elements, but such additional elements have not been described herein for the sake of preserving conciseness and clarity

of description.

[0059] An exaggerated scenario will now be described in order to illustrate more fully the present embodiment. However, the skilled person should appreciate that a simpler or more complex arrangement than that described herein is possible.

[0060] Referring to Figure 5, the femtocell apparatus 216 supports the first cell having the first coverage area 500. In this example, as mentioned above, the femtocell apparatus 216 is located in the house as described above. The house is, in this example, sufficiently large to require more coverage using the same technology and hence more than one femtocell in order to provide adequate coverage within the house. Consequently, a second femtocell apparatus 502 is located within the house to support a second cell (hereinafter referred to as "cell A") having a second coverage area 504. The first coverage area 500 intersects the second coverage area 504 resulting in a first area of overlapping coverage 506. In this example, the femtocell apparatus 216 is located too far from the second femtocell apparatus 502 to be able to monitor RF signals from the second femtocell apparatus 502. However, the first UE unit 202 is located in the first area of overlapping coverage 506.

[0061] A first femtocell Node B 508 is located in the vicinity of the house and supports a macrocell constituting a third cell (hereinafter referred to as "cell B") having a third coverage area 510. The third coverage area 510 also intersects the first coverage area 500 of the femtocell apparatus 216 and so a second area of overlapping coverage 512 results. In this example, the femtocell apparatus 216 is located too far from the first Node B 508 to be able to monitor RF signals from the first Node B 508. However, a second UE unit 514 is located in the second area of overlapping coverage 512.

[0062] A second Node B 516 is located in the vicinity of the house and supports another macrocell constituting a fourth cell (hereinafter referred to as "cell C") having a fourth coverage area 518. The fourth coverage area 518 also intersects the first coverage area 500 of the femtocell apparatus 216 and so a third area of overlapping coverage 520 results. In this example, the femtocell apparatus 216 is located too far from the second Node B 516 to be able to monitor RF signals from the second Node B 516. However, a third UE unit 522 is located in the third area of overlapping coverage 520.

[0063] Further, a third Node B 524 is located in the vicinity of the house and supports a further macrocell constituting a fifth cell (hereinafter referred to as "cell D") having a fifth coverage area 526. The fifth coverage area 526 also intersects the first coverage area 500 of the femtocell apparatus 216 and so a fourth area of overlapping coverage 528 results. In this example, the femtocell apparatus 216 is located too far from the third Node B 524 to be able to monitor RF signals from the third Node B 524. However, a fourth UE unit 530 is located in the fourth area of overlapping coverage 528. The first, second, third and fourth UE units 202, 514, 522, 530 are, in this example, camped on the first cell supported by femtocell apparatus 216.

[0064] In operation (Figure 6), the femtocell apparatus 216 is firstly powered-up.

Following power-up and system initialisation of the femtocell apparatus 216, the femtocell apparatus 216 commences normal operation, assuming no error states or faults. The digital baseband processor 306 therefore implements, inter alia, a process to discover neighbouring cells with respect to the first cell supported by the femtocell apparatus 216. In this respect, the processor 306 determines (Step 600) whether a predetermined event has taken place, for example power-up of the femtocell apparatus 216, elapse of a predetermined period of time, either predetermined by a fixed value or random, or detection of a UE unit newly camped on the first cell supported by the femtocell apparatus 216. In this example, immediately following power-up, unless the femtocell apparatus 216 has been reset, a sufficient number of UE units are unlikely to be present to camp on the first cell supported by the femtocell apparatus 216 immediately and so an optimum scenario for cell discovery is unlikely. Consequently, in this example and in order to better illustrate operation of the femtocell apparatus 216, the processor 306 waits the predetermined period of time, for example one hour and then proceeds to discover any neighbouring cells. Indeed, it is beneficial periodically to try to discover any neighbouring cells with respect to the femtocell apparatus 216, because the environment associated with the femtocell apparatus 216 can vary over time or one or more UE units may not yet be located in respective areas of overlapping coverage, but may subsequently move to an area of overlapping coverage. Furthermore, neighbouring cell discovery can be repeated for a sufficient period of time until a confidence has been achieved that all neighbours have been discovered. Thereafter, the neighbour discovery can be suspended for another predetermined period of time, for example a number of days, before neighbour discovery is repeated.

[0065] As the femtocell apparatus 216 needs to discover neighbouring cells, the processor 306 therefore accesses (Step 602) a stored list of UE units that are currently camped on the first cell supported by the femtocell apparatus 216. In the scenario described above, the first, second, third and fourth UE units 202, 514, 522, 530 are camped on the first cell supported by the femtocell apparatus 216 and so the identities of the first, second, third and fourth UE units 202, 514, 522, 530 are retrieved. The processor 306 then initialises (Step 604) a counter for tracking UE units that have been polled in a manner to be described hereinbelow.

Additionally, the processor 306 initialises a cell tracking variable in order to sequence through cell identities in a consistent manner of all possible neighbour cells.

[0066] The processor 306 then generates (Step 606) a measurement request message in respect of the second cell, cell A, to be sent to the first UE unit 202. In this example, the processor 306 generates an RRC MEASUREMENT CONTROL message, the RRC MEASUREMENT CONTROL message comprising an information element that identifies the second cell, for example a scrambling code, such as Pseudorandom Number or Pseudo Noise (PN) code. The RRC MEASUREMENT CONTROL message is also addressed to the first UE unit 202 and comprises another information element identifying a type of measurement to be performed, for example and Echo measurement (ratio of received energy per PN chip for a Common Pilot Channel to total transmit power) or a Received Signal Code Power (RSCP) measurement.

[0067] The processor 306 then sends (Step 608) the RRC MEASUREMENT CONTROL message. Thereafter, the processor 306 checks to determine (Step 610) whether RRC MEASUREMENT CONTROL messages have been sent for all UE units currently camped on the first cell supported by the femtocell apparatus 216. As three UE units remain to be polled in respect of the second cell, cell A, the processor 306 selects (Step 612) a next UE unit, in this example the second UE unit 514 and the above-described process (Step 606 to 612) is repeated until RRC MEASUREMENT CONTROL messages have been sent in respect of all UE units camped on the first cell supported by the femtocell apparatus 216.

[0068] Once all UE units camped on the first cell supported by the femtocell apparatus 216, in this example the first, second, third and fourth UE units 202, 514, 522, 530, have been polled in respect of the second cell, cell A, the processor 306 determines (Step 614) whether the processor 306 has sequenced through all known potential neighbour cell identifiers. In this respect, the cell identifiers can be determined in accordance with a predetermined algorithm, for example a scheme for determining the PN codes, or using a look-up table containing the PN codes for a Network Operator associated with the femtocell apparatus 216. In this respect, the potential neighbour cell identifiers can be all identifiers of cells possible according to, for example a 3GPP numbering scheme, or a predefined list existing in the flash memory 308 of the femtocell apparatus 216, the predetermined list having been pre-programmed during manufacture of the femtocell apparatus 216.

[0069] As, in this example, other cells exist, the processor 306 determines (Step 616) a next cell identified by a subsequent PN code determined using the above-mentioned look-up table, and the processor 306 also resets the counter for tracking the UE units. Thereafter, the processor 306 again generates (Step 606) another measurement request message in respect of the third cell, cell B, to be sent to the first UE unit 202. In this example, the processor 306 again generates another RRC MEASUREMENT CONTROL message, the RRC MEASUREMENT CONTROL message comprising the PN code to identify the third cell, cell B. The RRC MEASUREMENT CONTROL message is again also addressed to the first UE unit 202 and comprises another information element identifying the type of measurement to be performed.

[0070] The processor 306 then sends (Step 608) the RRC MEASUREMENT CONTROL message and then determines (Step 610) whether RRC MEASUREMENT CONTROL messages have been sent for all UE units currently camped on the first cell supported by the femtocell apparatus 216. As three UE units again remain to be polled in respect of the third cell, cell B, the processor 306 selects (Step 612) a next UE unit, in this example the second UE unit 514 and the above-described process (Step 606 to 612) is repeated until RRC MEASUREMENT CONTROL messages have been sent in respect of all UE units camped on the first cell supported by the femtocell apparatus 216.

[0071] Once all UE units camped on the first cell supported by the femtocell apparatus 216 have been polled in respect of the third cell, cell B, the processor 306 determines (Step 614) whether the processor 306 has sequenced through all known cell identifiers. As, in this example, other cells exist, the processor 306 determines (Step 616) a next cell identified by a subsequent PN code determined using the above-mentioned look-up table and the processor 306 also resets the counter for tracking the UE units.

[0072] The processor 306 then generates (Step 606) another measurement request message in respect of the fourth cell, cell C, to be sent to the first UE unit 202. In this example, the processor 306 again generates another RRC MEASUREMENT CONTROL message, the RRC MEASUREMENT CONTROL message comprising the PN code to identify the fourth cell, cell C. The RRC MEASUREMENT CONTROL message is again also addressed to the first UE unit 202 and comprises another information element identifying the type of measurement to be performed.

[0073] The processor 306 then sends (Step 608) the RRC MEASUREMENT CONTROL message and determines (Step 610) whether RRC MEASUREMENT CONTROL messages have been sent for all UE units currently camped on the first cell supported by the femtocell apparatus 216. As three UE units again remain to be polled in respect of the fourth cell, cell C, the processor 306 selects (Step 612) a next UE unit, in this example the second UE unit 514 and the above-described process (Step 606 to 612) is repeated until RRC MEASUREMENT CONTROL messages have been sent in respect of all UE units camped on the first cell supported by the femtocell apparatus 216.

[0074] Once all UE units camped on the femtocell 216 have been polled in respect of the fourth cell, cell C, the processor 306 again determines (Step 614) whether the processor 306 has sequenced through all known cell identifiers of potential neighbouring cells. As, in this example, other cells exist, the processor 306 determines (Step 616) a next cell identified by a subsequent PN code determined in using the above-mentioned look-up table and the processor 306 also resets the counter for tracking the UE units.

[0075] The processor 306 therefore generates (Step 606) another measurement request message in respect of the fifth cell, cell D, to be sent to the first UE unit 202. In this example, the processor 306 again generates another RRC MEASUREMENT CONTROL message, the RRC MEASUREMENT CONTROL message comprising the PN code to identify the fifth cell, cell D. The RRC MEASUREMENT CONTROL message is again also addressed to the first UE unit 202 and comprises another information element identifying the type of measurement to be performed.

[0076] The processor 306 then sends (Step 608) the RRC MEASUREMENT CONTROL message and then determines (Step 610) whether RRC MEASUREMENT CONTROL messages have been sent for all UE units currently camped on the first cell supported by the femtocell apparatus 216. As three UE units again remain to be polled in respect of the fifth cell, cell D, the processor 306 selects (Step 612) a next UE unit, in this example the second UE unit 514 and the above-described process (Step 606 to 612) is repeated until RRC MEASUREMENT CONTROL messages have been sent in respect of all UE units camped on the first cell supported by the femtocell apparatus 216.

[0077] Once all UE units camped on the first cell supported by the femtocell apparatus 216 have been polled in respect of the fifth cell, cell D, the processor 306 determines (Step 614) whether the processor 306 has sequenced through all known cell identifiers. As, in this example, other cells still exist in the UTRAN 116, the processor 306 determines (Step 616) a next cell identified by a subsequent PN code determined using the above-mentioned look-up table and the processor 306 also resets the counter for tracking the UE units.

[0078] In this example, the processor 306 sequences to an identifier associated with a sixth cell, cell E, that does not neighbour the femtocell apparatus 216. In any event, the processor 306 again generates (Step 606) another measurement request message in respect of the sixth cell, cell E, to be sent to the first UE unit 202. In this example, the processor 306 again generates another RRC MEASUREMENT CONTROL message, the RRC MEASUREMENT CONTROL message comprising the PN code to identify the sixth cell, cell E. The RRC MEASUREMENT CONTROL message is again also addressed to the first UE unit 202 and comprises another information element identifying the type of measurement to be performed.

[0079] The processor 306 then sends (Step 608) the RRC MEASUREMENT CONTROL message and then determines (Step 610) whether RRC MEASUREMENT CONTROL messages have been sent for all UE units currently camped on the first cell supported by the femtocell apparatus 216. As three UE units again remain to be polled in respect of the sixth cell, cell E, the processor 306 selects (Step 612) a next UE unit, in this example the second UE unit 514 and the above-described process (Step 606 to 612) is repeated until RRC MEASUREMENT CONTROL messages have been sent in respect of all UE units camped on the first cell supported by the femtocell apparatus 216.

[0080] Once all UE units camped on the first cell supported by the femtocell apparatus 216 have been polled in respect of the sixth cell, cell E, the processor 306 determines (Step 614) whether the processor 306 has sequenced through all known cell identifiers. The above process (Steps 606 to 616) is therefore continued until the processor has sequenced through all known cell identifiers.

However, for the sake of conciseness and clarity of description, the present example is only described in the context of five known cell identities.

Consequently, the processor 306 returns to awaiting (Step 600) the predetermined event before cell discovery is to be re-commence.

[0081] Following transmission, the RRC MEASUREMENT CONTROL messages are respectively received by the UE units to which each RRC MEASUREMENT CONTROL message is addressed. In this respect, the first UE unit 202 receives the RRC MEASUREMENT CONTROL message sent in respect of the second cell, cell A, and, being located in the first area of overlapping coverage 506, is able to receive RF signals from the second femtocell apparatus 502 as well as the femtocell apparatus 216. Consequently, the first UE unit 202 following performance of the measurement identified in the RRC MEASUREMENT CONTROL message for the PN code specified in the RRC MEASUREMENT CONTROL message, generates an RRC MEASUREMENT REPORT message that is sent to the femtocell apparatus 216. As the second, third and fourth UE units 514, 522, 530 are not located within the coverage area of the second cell, cell A, the second, third and fourth other UE units 514, 522, 530 are unable to receive RF signals from the second femtocell apparatus 502 and so are unable to make the measurement requested in the RRC MEASUREMENT CONTROL messages respectively addressed to each of the second, third and fourth other UE units 514, 522, 530. The second, third and fourth UE units 514, 522, 530 therefore do not send an RRC MEASURMENT REPORT message in respect of the second cell, cell A. [0082] Similarly, the second UE unit 514 receives the RRC MEASUREMENT CONTROL message sent in respect of the third cell, cell B, and, being located in the second area of overlapping coverage 512, is able to receive RF signals from the first Node B 508 as well as the femtocell apparatus 216. Consequently, the second UE unit 514, following performance of the measurement identified in the RRC MEASUREMENT CONTROL message for the PN code specified in the RRC MEASUREMENT CONTROL message, generates an RRC MEASUREMENT REPORT message that is sent to the femtocell apparatus 216. As the first, third and fourth UE units 202, 522, 530 are not located within the coverage area of the third cell, cell B, the first, third and fourth UE units 202, 522, 530 are unable to receive RF signals from the first Node B 508 and so are unable to make the measurement requested in the RRC MEASUREMENT CONTROL messages respectively addressed to each of the first, third and fourth other UE units 202, 522, 530. The first, third and fourth UE units 202, 522, 530 therefore do not send an RRC MEASURMENT REPORT message in respect of the third cell, cell B. [0083] The third UE unit 522 likewise receives the RRC MEASUREMENT CONTROL message sent in respect of the fourth cell, cell C, and, being located in the third area of overlapping coverage 520, is able to receive RF signals from the second Node B 516 as well as the femtocell apparatus 216. Consequently, the third UE unit 522, following performance of the measurement identified in the RRC MEASUREMENT CONTROL message for the PN code specified in the RRC MEASUREMENT CONTROL message, generates an RRC MEASUREMENT REPORT message that is sent to the femtocell apparatus 216. As the first, second and fourth UE units 202, 514, 530 are not located within the coverage area of the fourth cell, cell C, the first, second and fourth UE units 202, 514, 530 are unable to receive RF signals from the second Node B 516 and so are unable to make the measurement requested in the RRC MEASUREMENT CONTROL messages respectively addressed to each of the first, second and fourth other UE units 202, 514, 530. The first, second and fourth UE units 202, 514, 530 therefore do not send an RRC MEASURMENT REPORT message in respect of the fourth cell, cell C. [0084] The fourth UE unit 530 similarly receives the RRC MEASUREMENT CONTROL message sent in respect of the fifth cell, cell D, and, being located in the fourth area of overlapping coverage 528, is able to receive RF signals from the third Node B 524 as well as the femtocell apparatus 216. Consequently, the fourth UE unit 530, following performance of the measurement identified in the RRC MEASUREMENT CONTROL message for the PN code specified in the RRC MEASUREMENT CONTROL message, generates an RRC MEASUREMENT REPORT message that is sent to the femtocell apparatus 216. As the first, second and third UE units 202, 514, 522 are not located within the coverage area of the fifth cell, cell D, the first, second and third UE units 202, 514, 522 are unable to receive RF signals from the third Node B 524 and so are unable to make the measurement requested in the RRC MEASUREMENT CONTROL messages respectively addressed to each of the first, second and third other UE units 202, 514, 522. The first, second and third UE units 202, 514, 522 therefore do not send an RRC MEASURMENT REPORT message in respect of the fifth cell, cell D. [0085] The first, second, third and fourth UE units 202, 514, 522, 530 also subsequently receive respective RRC MEASUREMENT CONTROL messages sent in respect of the sixth cell, cell E. However, none of the first, second, third and fourth UE units 202, 514, 522, 530 are able to receive RF signals from a Node B that supports the sixth cell, cell E. Consequently, the first, second, third and fourth UE units 202, 514, 522, 530 are unable to make the measurement requested in the RRC MEASUREMENT CONTROL message respectively addressed to each of the first, second, third and fourth other UE units 202, 514, 522, 530. The first, second, third and fourth UE units 202, 514, 522, 530 therefore do not send an RRC MEASURMENT REPORT message in respect of the sixth cell, cell E. [0086] Referring to Figure 7, at the femtocell apparatus 216, the processor 306 awaits (Step 700) receipt of RRC MEASUREMENT REPORT messages. In this example, the femtocell apparatus 216 receives an RRC MEASUREMENT RESPONSE message from the first UE unit 202. The processor 306 therefore analyses (Step 702) the RRC MEASUREMENT RESPONSE message in order to extract the identity of the cell to which the received RRC MEASUREMENT RESPONSE message relates. In this example, the processor 306 extracts the PN code corresponding to the second cell, cell A. Consequently, receipt of the RC MEASUREMENT RESPONSE message identifying the second cell, cell A, is indicative of the fact that the first cell, cell A, is a neighbouring cell of the femtocell apparatus 216. The processor 306 maintains a list of neighbouring cells and so adds (Steps 704) the identity of the second cell, cell A, to the list of neighbouring cells.

[0087] The femtocell apparatus 216 also receives an RRC MEASUREMENT RESPONSE message from the second UE unit 202. The processor 306 therefore analyses (Step 702) the RRC MEASUREMENT RESPONSE message in order to extract the identity of the cell to which the received RRC MEASUREMENT RESPONSE message relates. In this example, the processor 306 now extracts the PN code corresponding to the third cell, cell B. Consequently, receipt of the RRC MEASUREMENT RESPONSE message identifying the third cell, cell B, is indicative of the fact that the third cell, cell B, is a neighbouring cell of the femtocell apparatus 216. The processor 306 therefore adds (Step 704) the identity of the third cell, cell B, to the list of neighbouring cells.

[0088] The femtocell apparatus 216 then receives an RRC MEASUREMENT RESPONSE message from the third UE unit 202. The processor 306 analyses (Step 702) the RRC MEASUREMENT RESPONSE message in order to extract the identity of the cell to which the received RRC MEASUREMENT RESPONSE message relates. In this example, the processor 306 now extracts the PN code corresponding to the fourth cell, cell C. Consequently, receipt of the RRC MEASUREMENT RESPONSE message identifying the fourth cell, cell C, is indicative of the fact that the fourth cell, cell C, is a neighbouring cell of the femtocell apparatus 216. The processor 306 therefore adds (Step 704) the identity of the fourth cell, cell C, to the list of neighbouring cells.

[0089] The femtocell apparatus 216 then receives an RRC MEASUREMENT REPORT message from the fourth UE unit 202. The processor 306 analyses (Step 702) the RRC MEASUREMENT REPORT message in order to extract the identity of the cell to which the received RRC MEASUREMENT REPORT message relates. In this example, the processor 306 now extracts the PN code corresponding to the fifth cell, cell D. Consequently, receipt of the RRC MEASUREMENT REPORT message identifying the fifth cell, cell D, is indicative of the fact that the fifth cell, cell D, is a neighbouring cell of the femtocell apparatus 216. The processor 306 therefore adds (Step 704) the identity of the fifth cell, cell D, to the list of neighbouring cells.

[0090] However, in respect of the RRC MEASUREMENT CONTROL message sent in respect of the sixth cell, cell E, none of the first, second, third and fourth UE units 202, 514, 522, 530 are within the coverage area provided by the Node B that supports the sixth cell, cell E, as mentioned above. Consequently, no RRC MEASUREMENT REPORT messages are received in respect of the sixth cell, cell E, and so the identifier of the sixth cell is not added to the list of neighbouring cells, because the sixth cell, cell E, does not neighbour the femtocell apparatus 216 insofar as the sixth cell can be detected by the UE units camped on the first cell supported by the femtocell apparatus 216.

[0091] In the above example, use of the RRC MEASUREMENT CONTROL message has been described in the context of individual measurement requests.

However, the skilled person should appreciate that the RRC MEASUREMENT CONTROL message is capable of identifying multiple cells, for example by PN code, in a single message and so the above example can be expedited by specifying blocks or groups of cell identifiers in each message sent to a given UE unit. This, in turn, results in the RRC MEASUREMENT REPORT messages received by the femtocell apparatus 216 containing corresponding multiple measurements.

[0092] Hence, it can be seen that the femtocell apparatus 216, using an existing mechanism provided by the UMTS standard, can discover neighbouring cells and therefore map and/or maintain a list of neighbouring cells and/or non-neighbouring cells. In the examples described herein, the neighbouring cells are discovered by soliciting one or more response messages from one or more UE units camped on the first cell supported by the femtocell apparatus 216.

[0093] The above techniques can be used to provide neighbouring cell data for network procedures, for example handover, such as hard handover. The above techniques can additionally or alternatively be used in relation to other network procedures, for example cell re-selection.

[0094] Whilst the above examples have been described in relation to direct extraction of information from the response messages in order to identify cells, the skilled person should appreciate that other information that can indirectly or infer the cell identity can be used.

[0095] The above embodiment has been described in the context of the UMTS communications standard. However, the skilled person should appreciate that the above-described apparatus and method can be applied to other radio access technologies and access points, for example including GSM, CDMA-2000, TD-SCDMA, UMB, LTE and WiMAX technologies.

[0096] It should also be appreciated that although the above examples have been described in the context of neighbouring Node Bs, the neighbour discovery apparatus and method described above can be applied to other types of "base station" for example GSM base station.

[0097] Alternative embodiments of the invention can be implemented as a computer program product for use with a computer system, the computer program product being, for example, a series of computer instructions stored on a tangible data recording medium, such as a diskette, CD-ROM, ROM, or fixed disk, or embodied in a computer data signal, the signal being transmitted over a tangible medium or a wireless medium, for example, microwave or infrared. The series of computer instructions can constitute all or part of the functionality described above, and can also be stored in any memory device, volatile or non-volatile, such as semiconductor, magnetic, optical or other memory device.

Claims

Claims: 1. A communications apparatus comprising: a processing resource capable of supporting a cell for communicating with a user equipment unit, the processing resource being arranged to solicit, when in use, a response message by sending a measurement request message for receipt by the user equipment unit, the measurement request message identifying a cell to be measured and an associated measurement type; wherein the processing resource is arranged to identify, when in use, from the response message a neighbouring cell relative to the supported cell and maintain neighbouring cell identity data using the identity of the neighbouring cell obtained.
2. An apparatus as claimed in Claim 1, wherein the processing resource is arranged to send a number of measurement request messages comprising the measurement request message.
3. An apparatus as claimed in Claim 2, wherein the number of measurement request messages comprise a first measurement request message and a second measurement request message; and the first measurement request message identifies a first cell and the second measurement request identifies a second cell, the identity of the first cell being different to the identity of the second cell.
4. An apparatus as claimed in Claim 2 or Claim 3, wherein at least some of the number of measurement request messages respectively identify with respect to each other different cells.
5. An apparatus as claimed in Claim 2, wherein the processing resource is arranged to receive a number of response messages, the number of response messages comprising a first response message and a second response message, the first response message being in response to the first measurement request message and the second response message being in response to the second measurement request message.
6. An apparatus as claimed in any one of the preceding claims, wherein the user equipment unit is camped on the cell.
7. An apparatus as claimed in any one of the preceding claims, wherein the user equipment unit is capable of communicating with another communications apparatus supporting the neighbouring cell and the processing resource is unable to monitor the another communications apparatus.
8. An apparatus as claimed in any one of the preceding claims, wherein the cell is associated with a first access scheme and the neighbouring cell is associated with a second access scheme.
9. An apparatus as claimed in any one of the preceding claims, wherein the processing resource is arranged to generate the neighbouring cell identity data in response to a predetermined event.
10. An apparatus as claimed in any one of the preceding claims, wherein the predetermined event is a power-up event or a reset event.
11. An apparatus as claimed in any one of the preceding claims, wherein the response message indirectly identifies the neighbouring cell.
12. An apparatus as claimed in any one of the preceding claims, wherein the processing resource is arranged to identify different cells respectively in the number of measurement request messages by sequencing through a set of cell identifiers generated in accordance with a predetermined scheme for allocating cell identifiers.
13. An apparatus as claimed in any one of the preceding claims, wherein the measurement request message is a Measurement Control message.
14. An apparatus as claimed in Claim 13, further comprising: a data store arranged to store, when in use, identities of a number of user equipment units camped on the cell; wherein the processing resource is arranged to send the measurement request message to each of the number of user equipment units.
15. An apparatus as claimed in any one of the preceding claims, wherein the response message is a Measurement Report message.
16. An apparatus as claimed in any one of the preceding claims, wherein the processing resource supports a third generation (3G) communications system.
17. An apparatus as claimed in Claim 2, wherein the sending of the number of measurement request messages constitutes scanning of a number of cell identifiers.
18. An apparatus as claimed in Claim 17, wherein the number of cell identifiers is all possible cell identifiers.
19. An apparatus as claimed in Claim 5, wherein the processing resource is arranged to receive a number of response messages from a number of user equipment units, and to map a presence of at least one neighbouring cell from the number of response messages received.
20. An apparatus as claimed in Claim 19, wherein each of the number of user equipment units is in a respective coverage area overlapped by the cell and a respective neighbouring cell.
21. An apparatus as claimed in Claim 9, wherein the generation of the neighbouring cell identity data is repeated.
22. A base station comprising the communications apparatus as claimed in any one of the preceding claims.
23. A femtocell apparatus comprising the communications apparatus as claimed in any one of Claims 1 to 21.
24. An access network comprising the base station as claimed in Claim 22 and/or the femtocell apparatus as claimed in Claim 23.
25. An integrated circuit comprising: a processing resource capable of supporting a cell, the processing resource being arranged to solicit, when in use, a response message by sending a measurement request message for receipt by a user equipment unit, the measurement request message identifying a cell to be measured and an associated measurement type; wherein the processing resource is arranged to identify, when in use, from the response message a neighbouring cell relative to the supported cell and maintain neighbouring cell identity data using the identity of the neighbouring cell obtained.
26. A method of maintaining neighbouring cell identity data, the method comprising: supporting a cell for communicating with a user equipment unit; soliciting a response message by sending a measurement request message for receipt by the user equipment unit, the measurement request message identifying a cell to be measured and an associated measurement type; identifying from the response message a neighbouring cell relative to the supported cell; and maintaining the neighbouring cell identity data using the identity of the neighbouring cell obtained.
27. A computer program element comprising computer program code means to make a computer execute the method as claimed in Claim 26.
28. A computer program element as claimed in Claim 27, embodied on a computer readable medium.
29. A communications apparatus substantially as hereinbefore described with reference to Figures 1, 2, 3, 4 or 5.
30. A method of generating neighbouring cell data substantially as hereinbefore described with reference to Figures 6 or 7.