GB2507821A

GB2507821A - Generating measurement reports in a wireless communications network employing coordinated multi-point transmissions

Info

Publication number: GB2507821A
Application number: GB1220427.7A
Authority: GB
Inventors: Himke Van Der Velde; Gert-Jan Van Lieshout
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2012-11-13
Filing date: 2012-11-13
Publication date: 2014-05-14
Also published as: GB201220427D0; GB2507829A; GB201302687D0; GB2507829B; WO2014077547A1

Abstract

A method of operating a mobile terminal and a base station in a wireless communications network employing coordinated multi-point (CoMP), in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals (Channel State Information, CSI), the method comprising: in response to a report trigger, the mobile terminal generating a measurement report (that can be used during a handover procedure) including a first set of measurement data, the first set of measurement data including either cell-specific reference signal measurement data or non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signal measurement data. Also disclosed is a method in a base station of transmitting configuration data about q set of channel state indicator reference signal resources to a neighbouring base station, for the purpose of indicating what measurement data the base station would like to receive, during handover preparation, for the channel state indicator reference signal resources.

Description

Mobile Terminal Measurements Fi&d of the Invention The present invention relates generally to wireless communication networks, and more specifically to making and reporting measurements in the network.

Background of the Invention

Wirclcss mobile nctworks, in which a uscr equipment (BE) such as a mobile handset communicates via a radio link to a network of base stations or other wireless access points connected to a telecommunications network, have undergone rapid development through a number of generations. The initial deploymcnt of systcms using analogue signalling has becn supcrsedcd by sccond generation (20) digita' systcms such as OSM (Glob& System for Mobflc communications), which typically use a radio access technology known as GERA (GSM Enhanced Data rates for OSM Evolution Radio Access), combined with an improved core network.

The second generation systems have themselves been replaced by or augmented by third generation (3G) digital systems such as UMTS (Universal Mobile Telecommunications System), using the UTRA (Iiniyersal Terrestrial Radio Access) radio acccss technology and a similar corc network to OSM.

Third generation staildards providc for a greater throughput of data than is provided by second generation systems, and this trend is continued with the proposals by the Third Generation Partnership Project (3GPP) of a new 4G systcm known as thc cvolved packet systcm (EPS) but morc commonly rcferrcd to as the Long Term Evolution (LTE) system. LTE systems use an improved radio access technology known as E-LJTRA (Evolved VTRA), which offers potentially greater capacity and additional features compared with the previous standards, combined with an improved core network technology refened to as the evolved packet core (EPC).

As in earlier wireless mobile standards, LTE is designed as a cellular system in which base stations, known as eNBs, provide coverage over one or more cells. In general, a mobile terminal in LTE, known as the user equipment (UE), typically communicates with one base station and one cell at a time. From LTE REL-10 onwards, an eNB may configure the UE with multiple serving cells, one on each serving frequency, a feature known as Carrier Aggregation.

The base station itself typically includes a tower with one or more antennas for transmitting and receiving wireless signals to and from a mobile terminal.

The mobile terminal can exist in one of two communication states in LTE: an IDLE state in which the mobile terminal is basically on standby, and a CONNECTED statc in which thc mobilc tcrminal has an activc radio link to thc base station.

In the IDLE state in LTE, the mobile terminal is tracked by the network to a specific tracking area, which may cover several base stations. The mobile terminal is not assigned to any particular base station but may itself choose which base station or base stations it listens to. The main aim in this state is to minimise signalling and resources, and thereby maximise standby time for terminals with limited battery power.

In contrast, in the CONNECTED state in LTE, the mobile terminal has a serving base station allocated to it, has its location tracked to the serving base station, and has active bearers which allow the terminal to transmit and receive at relatively high data rates.

In a rcccnt dcvclopmcnt of LTE known as coordinatcd multi-point transmission (C0MP), the base station is able to configure multiple transmission points per serving frequency which are geographically remote from each other.

Each transmission point may consist of a set of geographically co-located transmit antennas. For downlink in CoMP, the E-UTRAN coordinates the signals transmitted from the different TPs to increase signal strength or to reduce co-channel interference as perceived by the mobile terminal.

Physical signals are used in LTE in both the uplink and downlink in order to support physical layer operations such as channel estimation, scheduling, and synchronisation. A subset of the physical signals are reference signals, which are used, among other things, to enable feedback from the UE on various channels used by the E-UTRAIN. For example, cell-specific reference signals (CR5) can be used by a UE to provide estimates of phase and amplitude of transmissions from different antennas of a base station. These estimates are fed back to the base station in real-time for optimisation of transmissions. CRSs arc also measured by the UE in order to establish power and quality indicators for the channel. These indicators can be reported back in a measurement report to the network for mobility management and network optimisation.

In CoMP, the transmission points (TP5) can be monitored and measured using a diffcrcnt set of reference signals known as channel state indicator rcfcrcncc signals. Each configuration of a channcl statc indicator rcfcrcncc signal (CSI-RS) is known as a CSI-RS resource configuration. Although it is possible to configure a CSI-RS resource configuration per transmission point (TP), the LTE standards allows other usage e.g. the cNB may configure a single CSI-RS resource configuration for multiple transmission points.

Summary of the Invention

In accordance with a first aspect of the present invention, there is provided a method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a sct of non-ccll-spccific rcfcrcncc signals, thc mcthod comprising: in response to a report trigger, the mobile terminal generating a measurement report including a first set of measurement data, the first set of measurement data including either cell-specific reference signal measurement data or non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signal measurement data.

This has an advantage that the mobile terminal is able to provide a measurement report which includes data that can be used by the network during, for example, a handover or other mobility process. This in turn allows the network to prepare a base station, or eNB, better for the arrival of the mobile terminal after handover.

In an embodiment of the invention, the report trigger relates to an event comprising detection of a condition in the cell specific reference signals, This has an advantage that the second set of measurement data is included in the measurement report even though the report trigger and the first set of measurement data relate to either cell specific reference signals in one case or non-cell specific reference signals in another case.

In an embodiment of the invention, the report trigger relates to an event comprising detcction of a condition in the non-cell-specific reference signals.

This has an advantagc that thc first sct of measurement data is included in the measurement report even though the report trigger and the second set of measurement data relate to non-cell-specific reference signals.

In an embodiment of the invention, the report trigger is expiry of a timer.

Suitably, the report is triggered periodicafly such that there is a predetermined time interval in-between successive reports.

In an embodiment of the invention, the method comprises receiving configuration signalling from the network to configure the report trigger.

Accordingly, the report trigger can be configured to relate to a suitable handover condition in the network.

In an embodiment of the invention, the report trigger determines the measurement data included in the first measurement data.

In an embodiment of thc invention, in case thc first set of measurement data includes cell-specific reference signal measurement data, the second set of measurement data includes non-cell-specific reference signal measurement data for any frequency for which the mobile terminal has non-cell-specific reference signal measurement data available based on measurements the mobile terminal has previously been configured to perform.

In an embodiment of the invention, in case the first set of measurement data includes non-cell-specific reference signal measurement data, the second set of measurement data includes non-cell-specific reference signal measurement data for frequencies other than the frequency for which the report is triggered, and for which the mobile terminal has non-cell-specific reference signal measurement data available based on measurements the mobile terminal has previously been configured to perform.

In an embodiment of the invention, the set of frequencies for which the mobile terminal includes measurement data is limited to a subset of the frequencies for which the mobile terminal has measurement data available.

In an embodiment of the invention, the subset of frequencies for which the mobile terminal includes measurement data is determined by a configuration parameter provided by the network.

In an embodiment of the invention, the second sct of measuremcnt data comprises measurement data only on a limited number of best non-cell-specific reference signal resources.

In an embodiment of the invention, the number of best non-cell-specific reference signal resources for which the mobile terminal includes measurement data is fixed.

In an embodiment of the invention, the number of best non-cell-specific reference signal resources for which the mobile includes measurement data is determined by a configuration parameter provided by the network.

In an embodiment of the invention, the method comprises receiving configuration signalling from the network comprising an indicator, and when the indicator is active, responding to the report trigger to generate the measurement report including the first and second set of measurement data, and when the indicator is inactive, responding to the report trigger to generate a measurement report not including the second set of measurement data.

This has an advantage that the generation of a measurement report containing both the first and second measurement data can be configured with an indicator. For mobile terminals that are not capable of generating such a measurement report, the indicator can be ignored. Also, in situations where the measurement report does not need to contain both the first and second measurement data, the indicator can be made inactive. The indicator may be activated by means of a flag, with a lack of flag rendering the indicator inactive.

In an embodiment of the invention, the mobile terminal includes parameters for determining the second set of measurement data to include in the measurement report.

In an embodiment of the invention, the parameters comprise an indication to include, in the second set of measurement data, non-cell-specific reference signal measurement data derived from reference signals on a carrier frequency associated with the report trigger.

In an embodiment of the invention, the parameters comprise one or more carrier frequencies, and the second set of measurement data includes non-cell-specific rcfcrcncc signal measurement data dcrivcd from rcfcrcncc signals on thc onc or morc carricr frcqucncics.

This has an advantage that in case the network provides the parameters, it is able to specify which frequencies it is interested in receiving non-cell-specific information for.

In an embodiment of the invention, the said one or more carrier frequencies are a subset of the frequencies used for the first set of measurement data.

In an embodiment of the invention, the parameters comprise an indication to include, in the second set of measurement data, non-cell-specific reference signal measurement data derived from reference signals on any carrier frequency.

In an cmbodimcnt of the invention, the paramctcrs comprise a threshold valuc, and thc sccond sct of mcasurcmcnt data contains mcasurcmcnts of non-cell-specific reference signals that exceed the threshold value.

This has an advantage that the second set of measurement data may only contain measurements that are suitable for a particular purpose, such as handover to a new cell.

in an embodiment of the invention, the parameters comprise a threshold value, and the second set of measurement data contains measurements of non-cell-specific reference signals that differ from or fall within known measurement data by the threshold value.

In an embodiment of the invention, the parameters comprise an indication of the maximum number non-cell-specific reference signals resources for which measurements of non-ceH-specifie reference signals may be included in the second set of measurement data.

In an embodiment of the invention, the non-cell-specific reference signal resources for which measurements are included are the resources up to the maximum number which provide the best measurements.

This has an advantage that the measurement data in the second set can be limited to a manageable size. The second set of measurement data may, for example, include the three non-cell-specific measurements with the strongest signals or highcst quality.

In an embodiment of the invention, the method comprises receiving configuration signalling from the network to configure the parameters.

This has an advantage that the set of measurement data to be included in the measurement report can be adapted according to the requirements of the network. For example, the set of measurement data can be adapted according to the configuration of base stations in the network, or to a particular handovcr setup in the network.

In an embodiment of the invention, the configuration parameters apply to a plurality of report triggers such that a plurality of report triggers are configured upon receiving configuration signalling from the network.

This has an advantagc that thc same configuration paramctcrs can apply to multiple rcport triggers. This in turn can simpliI' thc configuration of thc second set of measurement data for a variety of measurement report generation.

In an embodiment of the invention, the second set of measurement data includes non-cell-specific reference signals measurement data derived from reference signals received on all frequencies for which the mobile terminal has earlier provided non-cell-specific reference signals measurement data.

In an embodiment of the invention, the non-cell-specific reference signals are channel state information reference signals.

In accordance with a second aspect of the present invention, there is provided a method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in response to a report trigger, the mobile terminal generating a measurement report including measurement data, including a first set of measurement data, the first set of measurement data including non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including cell-specific reference signal measurement data.

In an cmbodimcnt of the invention, the rcport triggcr relates to an event comprising detection of a condition in the non-cell-specific reference signals.

In an embodiment of the invention, the report trigger is expiry of a timer.

In an embodiment of the invention, the report is triggered periodically such that there is a predetermined time interval in-between successive reports.

In an embodiment of the invention, the the second set of measurement data includes cell-specific reference signal measurement data for any frequency for which the mobile terminal has the cell-specific reference signal measurement data available based on measurements the mobile terminal has previously been configured to perform.

In an embodiment of the invention, the second set of measurement data includes cell-specific reference signal measurement data for frequencies other than the frequencies for which the mobile terminal has previously included cell-specific reference signal measurement data.

In an embodiment of the invention, the further subset of frequencies for which thc mobile terminal includes measurement data is determined by a configuration parameter provided by the network.

In an embodiment of the invention, the second set of measurement data only comprises measurement data on a limited number of best cells.

in an embodiment of the invention, the number of best cells for which the mobile terminal includes measurement data is fixed.

In an embodiment of the invention, the number of best cells for which the mobile includes measurement data is determined by a configuration parameter provided by the network.

In an embodiment of the invention, the method comprising receiving configuration signalling from the network comprising an indicator, and when the indicator is active, responding to the report trigger to generate the measurement report including the first and second set of measurement data, and when the indicator is inactive, responding to the report trigger to generate a measurement report not including the second set of measurement data.

In an embodiment of the invention, the parameters comprise an indication to include, in the second set of measurement data, cell-specific reference signal measurement data derived from reference signals on a carrier frequency associated with the report trigger.

In an embodiment of the invention, the parameters comprise one or more carrier frequencies, and the second set of measurement data includes cell-specific reference signal measurement data derived from reference signals on the one or more carrier frequencies.

in an embodiment of the invention, the parameters comprise an indication to include, in the second set of measurement data, cell-specific reference signal measurement data derived from reference signals on any carrier frequency.

In an embodiment of the invention, the parameters comprise a threshold value, and the second set of measurement data contains measurements of cell-specific reference signals that exceed the threshold value.

In an embodiment of the invention, the parameters comprise a threshold value, and the second set of measurement data contains measurements of cell-specific reference signals that differ from or fall within known measurement data by the threshold value.

In an embodiment of the invention, the parameters comprise an indication of the maximum number of cell-specific reference signals resources for which measurements of cell-specific reference signals may be included in the second set of measurement data.

In an embodiment of the invention, the cell-specific reference signal resources up to the maximum number are chosen to provide the best measurements.

In an embodiment of the invention, the configuration parameters apply to a plurality of report triggers such that more than one report trigger is configured upon receiving configuration signalling from the network.

In an embodiment of the invention, the second set of measurement data includes cell-specific reference signal measurement data derived from reference signals received on a single carrier frequency for which the report is initiated.

In an embodiment of the invention, the second set of measurement data includes cell-specific reference signals measurement data derived from reference signals received on all frequencies for which the mobile terminal has earlier provided cell-specific reference signals measurement data.

In an embodiment of the invention, the method comprises sending the measurement report to a base station of the network for the purpose of initiating a handover.

In accordance with a third aspect of the present invention, there is provided a method of operating a base station in a wireless communications network, in which the base station employs coordinated transmissions from multiple points towards a mobile terminal, the method comprising: connecting with a mobile terminal, broadcasting reference signals for measurement by the mobile terminal, receiving from the mobile terminal a first set of measurement data including cell-specific reference signal measurement data, and a second set of measurement data including non-cell-specific reference signal measurement data, determining that the mobile terminal should handover to a target base station, and sending a handovcr rcqucst to a target base station, the handovcr rcqucst including the second set of mcasurcmcnt data, for the purposc of enabling the target base station to configure the set of non-cell-specific resource signals for the mobile terminal.

This has an advantage that the target base station can be provided with information that enables it to configure transmission points of a CoMP configuration in anticipation of the mobile terminal handing over to the target base station. Since CoMP can improve thc quality ofa connection with a mobile terminal at cell-edge, this embodiment can in turn improve the chances of the mobile terminal successifilly handing over to the target base station.

In accordance with a fourth aspect of the present invention, there is provided a method of operating a base station in a wireless communications network, in which thc basc station employs coordinated transmissions from multiplc points towards a mobile tcrminal, the mcthod comprising: connccting with a mobile terminal, broadcasting reference signals for measurement by the mobile terminal, and receiving from the mobile terminal physical layer feedback on a set of non-cell-specific reference signal resources, receiving from the mobile terminal a first set of measurement data including non-cell-specific reference signal measurement data, and a second set of measurement data including further non-cell-specific reference signal measurement data, determining that the mobile terminal should handover to a target base station, and sending a handover request to a target base station, the handover request including the second set of measurement data, for the purpose of enabling the target base station to configure the set of non-cell-specific resource signals for the mobile terminal.

In accordance with a fifth aspect of the present invention, there is provided a method of operating a base station in a wireless communications network, in which the base station employs coordinated transmissions from multiple points towards a mobile terminal, the method comprising: connecting with a mobile terminal, broadcasting reference signals for measurement by the mobile terminal, and receiving from the mobile terminal physical layer feedback on a set of non-cell-specific reference signal resources, receiving from the mobile terminal a first set of mcasurcmcnt data including non-cell-specific rcfcrcncc signal mcasurcmcnt data, and a sccond set of mcasurcmcnt data including cell-specific reference signal measurement data, determining that the mobile terminal should handover to a target base station, and sending a handovcr request to a target base station, the handovcr request including the second set of measurement data, for the purpose of enabling the target base station to configure the set of cell-specific resource signals for the mobile terminal.

In an embodiment of the invention, the first set of measurement data is received in a first measurement report, and the second set of measurement data is received in a second measurement report, the first measurement report arriving later than the second measurement report.

This has an advantage that earlier received channel state information can still be included in the handover request.

In an embodiment of the invention, the method comprises providing an indication in the handover request that the second measurement data was received from the mobile terminal earlier than the first measurement data.

This has an advantage that the target base station can be informed about how up to date the second measurement data is using the indication.

In an embodiment of the invention, the first and second sets of measurement data are received from the mobile terminal in a single measurement report.

This has an advantage that the most up to date information on the second set of measurement data can be included in the single measurement report.

In an embodiment of the invention, the method comprises providing an indication in the handover request that the first and second sets of measurement data were received from the mobile terminal in a single measurement report.

This has an advantage that the target base station can be informed that the information in the first and second sets of measurement data are relatively up to date.

In an embodiment of the invention, the method comprises determining that the mobile tcrminal should handover on the basis of the first set of measurement data.

This has an advantage that handover decision can be made in a relatively straightforward way without needing to take account of the second set of measurement data.

In an embodiment of the invention, the method comprises determining that the mobile terminal should handover on the basis of a capacity determination at the base station.

This has an advantage that the base station is able to decide on the handover of the mobile station independently of the first and second measurement data.

In an embodiment of the invention, the handover request includes the measurement data in mobile terminal context data, or radio resource management configuration data.

In accordance with a sixth aspect of the present invention, there is provided a method of operating a base station in a wireless communications network, in which the base station employs coordinated transmissions from multiple points towards a mobile terminal, the method comprising: determining a set of channel state indicator reference signal resources associated with the transmissions from multiple points, and transmitting configuration data about the set of channel state indicator reference signal resources to a neighbouring base station, for the purpose of indicating to the neighbouring base station what measurement data thc base station would like to receive, during handover preparation, for the channel statc indicator reference signal resources.

This has an advantage that a target base station can inform a source base station what measurements should be made on channel state information reference signal resources in advance of any handover situation.

In an embodiment of the invention, the configuration data includes parameters for the channel state indicator reference signal resources.

This has an advantage that the target base station can share information to enable listening and measuring on the specified CSI-RS resources. The parameters may include scrambling identity information for one or more of the channel state information reference signal resources, and/or resource configuration information for one or more of the channel state information reference signal resources.

In an embodiment of the invention, the parameters include scrambling identity information for one or more of the channel state indicator reference sign& resources.

In an embodiment of the invention, the parameters include resource configuration information for one or more of the channel state indicator reference signal resources.

In an embodiment of the invention, the configuration data includes an identification of an area for which the channel state indicator reference signal resources are relevant.

In accordance with a seventh aspect of the present invention, there is provided a method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in response to a handover failure report request from the network, the mobile terminal generating a report including measurement data; including a first set of measurement data, the first set of measurement data including either cell-specific reference signal measurement data or non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signal measurement data.

In accordance with a eighth aspect of the present invention, there is provided a method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in response to a connection establishment failure report request from the network, thc mobilc tcrminal gcncrating a report including mcasurcmcnt data; including a first sct of mcasurcmcnt data, thc first sct of mcasurcmcnt data including cithcr cell-specific reference signal measurement data or non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signal measurement data.

In accordance with a ninth aspect of the present invention, there is provided a method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in response to a handover failure report request from the network, the mobile tcrminal generating a report including measurement data; including a first sct of mcasurcmcnt data, the first sct of mcasurcmcnt data including cithcr cdl-specific reference signal measurement data or non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signal measurement data.

in accordance with a tenth aspect of the present invention, there is provided a method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in an idle mode, periodically logging measurement data on cell-specific reference signals and non-cell-specific reference signals; and in response to a request from the network, a periodic logging trigger in an idle mode, the mobile terminal generating a report including a first set of measurement data, the first set of measurement data including either cell-specific reference signal measurement data or non-cell-specific reference signal measurement data; and a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signal measurement data.

The above aspects of the invention may be implemented in a computer program comprising instructions such that whcn thc computcr program is executed on a computing dcvicc, thc computing device is arrangcd to carry out a described methods.

Brief Description of the Drawings

Figure 1 is a schematic diagram illustrating a typical LTE system using multiple transmission points (TP5); Figure 2 is a schematic diagram illustrating the layers of communication protocols between various network elements; Figure 3 is a signalling diagram illustrating signals flowing between a IJE, a source eNB, and a target eNB during a handover procedure; Figure 4 is another signalling diagram illustrating signals during a handovcr procedure; Figure 5 is a flow diagram illustrating steps in generating a measurement report; Figure 6 is a flow diagram illustrating steps in generating a handover request; Figure 7 is a flow diagram illustrating steps in preparing a configuration message prior to handovcr; and Figure 8 is another flow diagram illustrating steps in preparing a configuration message during handover.

Detailed Description of the Invention

By way of examp'e, embodiments of the invention will now be described in the context of an LTE (Long Term Evolution) cellular wireless communications system operating in accordance with Release-li and beyond of the LTE system standards. However, it will be understood that this is by way of example only and that other embodiments may involve other wireless systems, operating to other releases and other standards.

A typical LTE cellular wireless communications system is illustrated schematically in Figure 1. The LTE system comprises a core nctwork, a radio access network, one or more mobile terminals, and ideally an interface to external networks such as the internet or private corporate networks. The radio access network is known as the evolved UIvITS terrestrial radio access network (E-TJTRAN) in LTE, and handles communications between mobile terminals, known as user equipment (DEs) in LTE, and the core network, known as the evolved packet core (EPC) in LTE.

The E-UTRAN consists of a network of base stations known as evolved Node Bs (eNBs), labelled eNBI and eNB2 in Figure 1. Each eNB is a base station that serves and controls DEs in one or more cells. In Figure 1, eNBI is the serving eNB for the cell 25 and the UE 10, while eNB2 is the serving eNB for the cell 35. Thc eNBs can communicate with each other over an optional X2 interface, to the evolved packet core (EPC) via the Si interface, and to the UEs over the radio interface. The evolved packet core (EPC) includes a mobility management entity (MME) 40, as well as a serving gateway (S-OW) 50 and packet data network gateway (P-GW) 60. The MME 40 handles high-level issues such as security, while the S-GW 50 and P-GW 60 are generally responsible for data traffic, including data to or from external networks.

OSI Model Referring to Figure 2, there is shown a diagram illustrating the communication protocol layers for the E-UTRAN between the eNB, the UE, and the MME in the control plane.

The Non-Access Stratum (NAS) layer 250 is known as the NAS control protocol (terminated in MME on the network side) and performs among other things: -EPS bearer management; -Authentication; -ECM-IDLE mobility handling; -Paging origination in ECM-IDLE; -Sccurity control.

The Radio Resource Control (RRC) layer 255 (terminated in eNB on the network side) is part of Layer 3 in the OSI model, and performs the following functions: -Broadcast; -Paging; -RRC connection management; -Radio Bearer (RB) control; -Mobility functions; -UE measurement reporting and control.

Thc Packet Data Convcrgcncc Protocol (PDCP) layer 260 (terminated in cNB on the network side) is part of Layer 2 in the OSI model, and performs functions for the control plane such as ciphering and integrity protection.

The Radio Link Control (RLC) and Medium Access Control (MAC) layers 265, 270 (terminated in eNB on the network side) are also part of Layer 2 in the OSI model, and perform the functions for the control plan such as scheduling information reporting, priority handling between TiEs by means of dynamic scheduling, padding, paging, and duplicate detection.

The lowest protocol layer is the Physical Layer (PHY) 275 which provides Layer 1 of the 051 modeL The physical layer contains the digital and analogue signal processing Ilinctions to that the UE and eNB use to send and receive information.

Handover In LTE, the network conirols the mobility of a UE that is in connected mode (or, to be precise in RRC_CONNECTED state). In other words, the network decides withwhichcdllthcuEmaintainsthcradioconnccflon(aLsorcfcrredtoasthc sewing ccli). The network applies thc handovcr procedurc to movc the LiE from one cell, the serving cell, to another cell, the target cell.

The network decides the cell the TIE should connect to typically based on radio quality, but it may also take into account other factors such as cell load, UE capabilities, the type of bearers that are being established. To assist the handover decision process, the network normally configures the LiE to perform cell specific reference signal measurements on the serving frequency, on other E-TJTRA frequencies (referred to as inter-frequency measurements) and! or on frequencies used by other Radio Access Technologies (referred to as inter-RAT measurements).

Handovcr in LTE may use the X2 interface or the Si interfitce shown in Figure 1. Referring to Figure 3, there is shown, by way of example, the X2 interfitce handover procedure. The main steps of the handover procedure are as follows: Step 1: The LiE is configured to report back on cell specific reference signal (CR8) measurements when a handover Irigger condition is met (such as a neighbouring cell CR5 signal strength exceed the sercing cell CR5 signal strength).

Step 2 (optional): The liE sends a measurement report to the source eNB that it has detected a neighbouring cell that meets the measurement report triggering criteria.

Based on the provided measurement information and! or other knowledge present in the source eNB, the source eNB can now decide whether to start a handover preparation or not.

Step 4: If the source eNB starts handover preparation, it will send a HANDOVER REQUEST message to the target eNB. This message carries the handover preparation information which includes: the UE radio access capabilities, the current radio access (i.e. access stratum, AS) configuration, the RRM configuration, i.e. information kept only by the eNB that is used primarily for Radio Resource Management. Usage of the information is up to eNB implementation the radio access (AS) context i.e. information kept only by the eNB (i.e. not exchanged across the radio interface) e.g. information needed to perform RRC connection re-establishment the target cell identification Step 5: The target eNB decides based on admission control criteria whether it wishes to accept the handover request.

Step 6: If the target eNB accepts the handover, it reserves the radio resources and decides the details of the radio access configuration to be used by the UE in the target cell. This configuration is returned to the source eNB within the HANDOVER REQUEST ACK message. This message carries the radio access configuration within the HandoverCommand message in which is embedded an RRCConnectionReconfiguration message. When used to perform a handover within E-UTRA, this message includes the radio access configuration to be used in the target ccli, including: thc measurement configuration, expressed by the delta compared to the configuraton used in the source cell (i.e. the target eNB indicating changes in the measurement configuration); the mobility control information, which specifies the target cell identity (by means of an cell identity) and characteristics (a frequency, a bandwidth and additional spectrum emission information, all only if different from what is used in the source cell i.e. delta), the new radio access identity to be used in the target cell, the cell specific radio resource configuration (common for all liEs), dedicated resources used for initial access in the target cell and a timer to limit the duration the liE tries connecting to the target cell; the liE-specific radio resource configuration (i.e. the dedicated radio configuration), also expressed as a delta compared to the configuration used in the source cell; and the security configuration i.e. the algorithms, if different from the ones used in the source cell (delta), as well as parameters affecting the derivation of radio access security keys (i.e. an indication whether a new base key is to be used and a counter that is incremented upon every handover).

Step 7: When the source eNB proceeds with the handoyer, it starts the execution phase, which includes: The source eNB transparently forwards RRCConnectionReconfiguration message to the liE i.e. it does not change the message contents. The source does however perform the integrity protection and ciphering of the message; The liE detaches from the source eNB and attempts to connect to the new target eNB.

Transmission Points Referring back to Figure 1, the base stations eNB 1 and eNB2 have been configured with transmission points TPI to TP6. In this illustration, the transmission points are implemented as remote radio heads (RRHs). However, the transmission points may be implemented in other ways such as via pico cells. eNBI includes transmission points TP4, TP5, and TP6, while eNB2 includes transmission points TP1, TP2, and TP3. The transmission points are coupled to their respective base stations via suitable high capacity and low latency data connections such as fiber optic links. The connections are made at a distance so that the transmission points can be located remotely from the geographic location of the base station itself The transmission points are also geographically remote from each other, which in practice means they may be at Icast a few metcrs apart.

The transmission points provide support for coordinated multi-point transmissions (C0MP). CoMP is a relatively recent development in LTE which may be deployed in the uplink (IlL) and downlink (DL) directions. When transmitting data to the UE, the network may emp'oy multiple transmission points (TP), a TP being a set of geographical co-located transmit antennas.

When using CoMP in DL, the E-UTRAN coordinates the signals transmitted from the different TPs to increase signal strength or to reduce co-channel interference as perceived by the UE. The UE may be unaware of which transmission points are actually involved in a transmission (contributing or blanking).

In order to assist thc E-UTRAN with dcciding which TPs to usc whcn scheduling a particular data transmissions, the UE may be configured to provide information in the form of feedback to the E-IJTRAN.

This feedback is based on measurements of reference signals transmitted from the transmission points using physical layer (PHY) procedures (i.e. Layer 1).

The reference signals used for this purpose are channel state information reference signals (CSI-RS). The CSI-reference signals can be configured in a number of ways which are identifiable and readable provided a mobile terminal is aware of the configuration. Each configuration of a CSI-RS is known as a CSI-RS resource. The Layer I feedback is based on these CSI RS resources.

Typically, cach transmission point (TP) is assigned with a CSI-RS resource.

The CSI RS resources for which the UE is configured to provide feedback using physical layer procedures may be referred to as a Layer 1 (LI) feedback set. The tiE may be required to support an Li feedback set including up to 3 CSI RS resources. In other words, 3 transmission points (TP5) are typically used with CSI-RS feedback provided for each TP.

In Figure 1, thc UE 10 receives transmissions from thc basc station using CoMP via thc transmission points TP4, TP5, and TP6, and has bccn configured to provide feedback using physical layer procedures on 3 CSI-RS resources, one for each TP.

Due to the mobility of the UE, the most optimal set of CSI RS resources to be configured as the Li feedback set may change. Thus, the E-UTRAN may continuously decide which CSI RS resources should be configured for the tiE from a number of potential CSI RS resource candidates. In order to make these decisions, the UE may be configured to provide information in the form of a measurement report on the potential CSI RS resource candidates to the E-UTRAN. Since the E-UTRAN is aware of the mapping of the CSI RS resources to the Transmission Points, this process allows the E-UTRAN to pick the most appropriate TPs for coordinated multipoint transmissions (CoMP).

This measurement report may use the RRC procedures (i.e. procedures at Layer 3), to provide information on potential TPs, by referring to their associated CSI-RS resources. The CSI RS resources for which the tiE is configured to provide feedback using RRC procedures may be referred to here as the L3 reporting set.

E-UTRAN may use the L3 reporting set to manage the Li feedback set. For example, with reference to Figure 1, the eNBi may send an RRC connection reconfiguration request (on Layer 3) to the UE 10 asking the UE to report back on potential CSI-RS resources which the eNBI knows are assigned to certain TPs. For example, eNB1 may request the UE to report back on CSI-RS resources I to 6 associated with TPs I to 6. At the same time, the UE may already be configured to provide feedback on Layer 1 for transmission points TP4, TPS, and TP6.

If, for example, one of the CSI-RS resources becomes better than a threshold value (say, the CSI-RS resource associated with TP2) then the information on that CSI-RS resource may be reported back to eNBI using a Layer 3 measurement report for thc purpose of deciding if the LI feedback set should be modified.

The eNBI may then decide to modify the LI CSI RS resource set. To do this, the eNBl may use an RRC connection reconfiguration request on Layer 3 to specif,r which 3 CSI-RS resources should be used to provide feedback on Layer 1.

Measurement Reports for Handover As discussed in relation to handover, in connected mode the E-U'TRAN is in control of UE mobility. It may configure the VEto provide measurement reports to assist the network with this task. The measurements defined for the purpose of assisting UE mobility arc based on cell specific reference symbols (CRS).

A single CRS measurement always concerns a single frequency. The VE may however be configured to perform multiple measurements at the same time. For each CRS measurement, the E-UTRAN configures when the UE should send a Measurement Report message, including the related CRS measurement information. This is done by specifying so-called triggering conditions, of which there are 2 basic types namely periodic and event triggered. In case of periodic triggering, the TJE provides a report at regular intervals, possibly up to a configurable number of reports.

Both periodic and event triggered reports can be used for handover (HO) but event triggered is more commonly used in order to limit the reporting signalling overhead. In case the UE is configured for event triggered reporting, it provides a report when certain (entering or leaving) conditions are met for one or more applicable cells. The CRS measurement report used to include measurement results of the serving cell as well as of cells those cells, on the frequency for which the measurement was configured, that triggered the entering condition but not the leaving condition (referred to as the cellsTriggered).

When the TIE is configured with Carrier Aggregation (CA), it is connected to more than one cell -one on each frequency. There is one primary cell, re&ned to as the PCeII, which is used for a number of essential functions. The other cells, referred to a secondary cells or SCclls, are merely used to enhance the data transfer rate. UE mobility may result in either change of PCeII as well as in the addition! removal of S Cells. When the UE is configured with a single serving cell (i.e. UE is not configured with CA), the concerned cell is (still) referred to as PCell.

With the iniroduction of CA, the measurement reporting procedures are extended somewhat. The UE now always includes the measurement results of all serving cells in a CR5 measurement report message. Moreover, ibr each individual measurement E-UTRAN can indicate if the UE shall aLso include the best non-serving cell on each frequency the UE is configured to measure/ for which the UE has measurements available. This reporting of cells on other frequencies than the frequency of the associate measurement is also referred to as additional measurement reporting. The mechanism was introduced to fhdiitate the immediate configuration of SCells upon handover.

CoMP in Handover Coordinated multi-point (C0MP) transmission is a mechanism that is particularly relevant at ccli edge. At ccli edge CoMP provides most performance gains. Hence it is desirable to activate CoMP when performing a handovcr, meaning that the target eNB shouid preferabiy be provided with up to date measurement information so it can configure an optimal Li feedback set in the handovcr message (RRCConncctionRcconfiguration message including field mobilityControllnfo).

To achieve this, the following functionality can be provided: Functionality A. Providing the targct cNB with up to date CSI RS measurement information. One general approach would be that the UE provides available CSI RS measurement results to the source NB when handover is imminent, which the source subsequently transfers to the target cNB when initiating handovcr preparation Functionality B: Providing the source cNB with knowledge of the CSI RS resources that are likely to be relevant only after handover. Preferably, the source eNB should know this, so it can make sure that the UE has CSI RS measurements available for these resources when handover is imminent.

Functionality C: Configuring the UE with suitable CSI-RS resources at the point of being commanded to handover.

Regarding functionality A, Figure 5 illustrates the procedure for providing up to date CSI-RS measurements in a handovcr scenario. In step 510, the UE measures a CRS value and determines that a handover condition based on CRS criteria has been satisfied. This event triggers the liE to prepare in step 520 a measurement report containing the relevant CRS measurement data related to the event, such as the CRS measurements associated with a possible target base station. In step 530, the UE determines if additional reporting has been configured for this particular measurement. If no additional reporting has been configured in the liE then the liE reports the measurement report to the base station in step 550. The base station can then use the CRS measurement report to determine if the handover shou'd occur. If the UE is configured with additiona' reporting then the procedure follows step 540 after step 530. In step 540, the UE includes available CSI-RS measurement data in the previously generated measurement report containing CRS measurement data.

In step 550, the UE sends the measurement report containing both CRS and CSI-RS measurement data to the base station.

As an alternative to the above procedure, it is possible that the handover trigger event could be based on CSI-RS measurements. Here, in step 510, the UE would measure a CSI-RS value and determine that a handover condition based on CSI-RS criteria has been satisfied. The handover condition could, for example, be based on an abs&ute or relative threshold value being exceeded by the CSI-RS measurement value. The CSI-RS resources for which the measurements are made could relate to transmission points on a non-serving frequency which could then make handover desirable.

In the case that handover is triggered by CSI-RS measured values, it is possible to then include the specific CSI-RS measurements in the measurement report triggered. In addition, CRS based measurements can be included in the measurement report triggered by the CSI-RS event. In this case, the CSI RS measurements might give some indication about a data rate that can be achieved when employing CoMP, while the CRS based measurements may provide some general indication of the strength or quality when configuring a cell on the concerned frequency.

In a further alternative, the CSI-RS measurements may trigger a measurement report for the purposes of handover, and the measurement report may then include additional CSI-RS measurement data unrelated to the trigger. For example, the additional CSI-RS measurement data may include CSI-RS measurements on a non-serving frequency. In this case, the CRS based measurement data in the measurement report may be optional. In other words, the CRS based measurement data may not be included in the measurement report.

Prior to step 510 in Figure 5, the base station configures the tiE with the relevant handover configuration reporting triggers as discussed in relation to Figure 3. Furthermore, in supporting Functionality A, the base station may further configure the additional reporting referred to in step 530 in Figure 5. The additional reporting configuration signalling may include one or more of the following: a) an on! off indicator to switch on or off the additional reporting configuration in the UE. The indicator can be in the form of a 1-bit indication in the message from the base station to the UE. Other types of flag may also be suitable. If the additional reporting configuration in the UE has been switched off by the on! off indicator, then the answer to step 530 in Figure 5 will be no (N). If the additional reporting configuration in the UE has been switched on by the on! off indicator, then the answer to step 530 in Figure 5 will be yes (Y). The current status of the on! off configuration can be stored in a register in the UE so that in step 530 the register is checked to see what would be the correct outcome of the decision step 530.

b) an indication that the UE should report in step 540 on any CSI-RS measurements available in the tiE irrespective of the frequency the measurement has been made on.

c) an indication that the tiE should report in step 540 on the CSI-RS measurements available in the tiE that arc on the same frequency as the frequency of the signal triggering the measurement report in step 510.

d) a list of specific frequencies, whereby the tiE should report in step 540 on the CSI-RS measurements available in the lIE that are on one of the listed frequencies.

e) a maximum number N of CSI RS resources that may be included in the report, whereby the tiE may select the CSI-RS measurements to report up to the maximum N by, for example, grading the CSI-RS measurements and only reporting the N best results. In the event that CoMP has been configured on multiple frequencies, then the value N may speci' the maximum number of best CSI RS resources on a frequency.

a threshold value X, whereby the UE only includes CSI RS measurements which exceed the threshold value X. Also there could be a relative threshold Y such that the UE can include CS! RS measurements that fall within an offset Y from an earlier configured CSI RS resource e.g. the best CS! RS resource has to exceed X while additional CSI RS resources must fall within Y compared to the best CSI RS resource.

The UE may be configured separately to make measurements on CSI-RS resources for other purposes such as determining the LI reporting set for the CSI-RS resources. These measurements made for other purposes can be included in the additional reporting of step 540 in accordance with the above additional reporting configurations. Alternatively or additionally, the liE can make measurements of CSI-RS resources specifically in accordance with the above additional reporting configurations.

The above additional reporting configurations may either apply to all measurements configured, or more likely be provided per measurement. In the first case, the parameters may be provided in a measurement configuration message from the base station so that they are understood to apply to all measurement reports. In the second case, the parameters are provided in the configuration of each measurement separately. In the second case, a flag may be provided in the part of the configuration that specifies the type of trigger and the information to report, often called the reportConfig. In this case, the measurement may be identified by a measurement identification (measid), which specifies an associated measurement object measObject), which may be a serving or a non-serving frequency, and the reportConfig. Together, the reportConfig, measid, and measObjeet form the configuration of a measurement.

The tilE may trigger numerous measurement reports for one such measurement.

For example, whenever a new cell meets the entry criteria and/ or whenever a cell that previously triggered the entry condition now triggers the leave condition.

If configured to do so by the base station, the UE may additionally report the CSI-RS resources for all available frequencies. The reporting for serving frequencies may be separate from the reporting for non-serving frequencies.

Furthermore, if CoMP is configured over multiple frequencies, the reporting for frequencies for which CoMP is configured may be separate from frequencies for which CoMP is not configured. In this case, the reporting for frequencies for which CoMP is not configured can be split frirther into reporting for serving and non-serving frequencies.

Measurements can be made for CSI RS resources only on sewing frequencies used by the source cNB. Measurements can also be made for CSI-RS resources for non-serving frequencies, or for frequencies that are not used by the source eNB.

Referring now to Figure 6, there is shown a second stage of the functionality A, in which available CSI RS measurements additionally reported by the tiE to the source eNB are transferred from the source eNB to the target eNB during handover preparation. In step 610, the UE triggers a measurement report with additional CSI-RS measurement data, for example, as set out in steps 510 to 550 in Figure 5. In step 620, the source eNB decides that a handover should take place, and initiates the handover preparation by sending a HO request to the neighbouring target eNB including the additional CSI-RS measurements received from the UE. in step 630, the handover procedure continues, for example, following the general procedure outlined in Figure 3.

In step 620, the source eNB may either forward L3 CSI RS measurement information it stored when previously receiving a measurement report (for example. a measurement report specifically for the purpose Li CSI RS management), or it may forward CSI RS measurement information additionally includcd by the UE in the measurcmcnt report that triggercd the handovcr. The source cNB may indicate to the target eNB whether the forwarded information was freshly received from the UE i.e. just before it initiated handover.

The decision to handover in step 620 may be due to information received in a measurement report received by the source eNB. Alternatively, the source eNB may decide to initiate a handover of the UE for other reasons such as congestion on the source eNB. In this alternative handover, the source eNB may forward CSI-RS measurement data received from earlier measurement reports.

The source eNB can forward the L3 CSI RS measurement information either by including it in the liE context or by including it in the RRM configuration.

Referring now to functionality B which addresses the issue of providing the source eNB knowledge of the CSI RS resources that are relevant after handover.

Preferably, the source eNB should to know this, so it can make sure that the tiE has CSI RS measurements available for these resources when handover is imminent.

Referring to Figure 7, there is illustrated a general procedure for addressing the configuration of a liE for CSI-RS measurement reporting. In step 710, the UE is connected with a source eNB, and approaches a cell served by a potential target eNB (here a neighbour eNB). In step 720, the source eNB determines if CoMP is employed for the cell controlled by a neighbour eNB (based on configuration information previously received from the neighbour eNB). If CoMP is not employed then the procedure continues to step 740 where normal TJE mobility control continues. If CoMP is employed by the neighbour eNB then the procedure moves to step 730 in which the source eNB configures the UE to perform the CSI RS measurements relevant for the neighbour cell and to include such results in a measurement the tilE may trigger for handover purposes. The message indicates to the source eNB that it should make use of the procedures in Figures 5 and 6 during the handover process. The message can include a list of L3 CSI RS resources for which the neighbour eNB would like to receive measurement data during the handover preparation.

The target eNB can provide, for one or more carrier frequencies, all parameters required by the neighbouring source eNB to configure L3 measurements for the concerned CSI-RS resources. The parameters can be, for example, the.

scrambling identity, or the CSI RS resource configuration.

The target eNB can also indicate in which area each of the indicated L3 CSI RS resources is relevant. This may be done by indicating for which target cell or source cell or combination of source and target cell specific CSI RS resources are relevant.

Reference is now made to frmnctionality C which relates to the final stages of the handover process in which the target eNB sends a handover command to the source eNB in the form of a handover request acknowledgement, and the source eNB forwards the handover command to the tiE.

Referring to Figure 8, there is illustrated a general procedure for configuring a IJE for CSI-RS measurement reporting during handover. In step 810, the handover has been initiated by the source eNB, and the target eNB receives the handover request from the source eNB. This handover preparation message includes all the handover information referred to in the above description of step 4 of Figure 3. However, the message also includes additional CSI-RS measurement data which helps the target cNB decide whether to employ CoMP with the FE. Tn step 820, the target eNB decides whether or not to emp'oy CoMP and thus whether the FE should be configured with CoMP. If CoMP is not employed then the liE is not configured with CoMP, and the handover command is initiated from the target eNB to the source eNB in the normal way in step 840. If the UE is to be configured with CoMP, then the procedure moves to step 830, in which the target eNB specifies which Li CSI-RS resources are included in the configuration message of the handover command. Regardless whcthcr or not the target cNB configures Li CSI RS resources, thc targct may configurc L3 CSI RS rcsourccs.

Once the relevant CSI-RS resources have been configured, the procedure moves to step 840 where the handover command (with the configuration information including LI and/or L3 CSI RS resource configurations) is sent to the source eNB which forwards it on to the UE.

The additional reporting, decision making and configurations associated with the CSI-RS resources in CoMP are illustrated frirther in Figure 4 which shows the basic message sequence for the case of a handover of a liE from a source to a target eNB.

In step 1, thc target cNB indicates for which CSI RS resources it would like to receive measurement information during handover preparation to its neighbouring eNB over the X2 interface. For each frequency (if multiple frequencies are involved), the target eNB provides all configuration information the neighbour requires to be able to configure L3 CSI RS measurements for these resources. Compared to the procedure of Figure 3, this additional messaging can bc achieved by extensions to the X2 setup and/ or the X2 configuration update messages and procedures.

In step 3, the source eNB configures the liE to perform measurement reporting, including: Regular measurement reporting for the purpose of liE mobility; L3 CSI RS measurement reporting, to make sure the UE has the requested CSI RS measurements availaNe when initiating measurement reporting aimed to trigger handover; and The source eNB configures the TJE to include available CSI RS measurement when initiating a measurement report for the purpose of handover.

In step 4, the UE might initiate a measurement report to report good CSI RS resources. This makes it possible for the source to include CSI RS information even in case of a blind handover i.e. whcn handover is not triggered by a measurement report (but for other reasons such as congestion).

In step 5, the liE initiates a measurement report for the purpose of handover.

The tilE includes the additional CSI RS measurements in the report.

In step 6, the source eNB initiates handover preparation. The source eNB includes additional measurement information i.e. either information collected before handover, or information included in the measurement report that triggered the handover complete.

In step 7, the target eNB generates the RRC connection reconfiguration message. The target eNB configures Li CSI RS reporting based on the information received in the handover preparation information.

Other usage of L3 CSI RS measurement information Apart from the RRM measurements defined in connected mode, the E-UTRA specifications include mechanisms by which the liE stores measurement information either upon specific events (radio link failure, handover failure, connection establishment failure) or periodically (i.e. measurement logging in idle mode). Moreover, the RRIVI measurement procedures by which the UE can be requested to report the strongest cells it detects on a frequency as well as to report specific information about a detected cell. The specific information may be information broadcast by thc ccli such as ccli identity, tracking area, PLMIN identities, or CSG information. These proccdurcs havc bccn introduced to facilitate the initial configuration of the network (ANR), as well as for the further optimisation and monitoring of the network without the need to do manual tcst drives (SON, MDT). Note: MDT is about getting covcrage maps, finding coverage holes, finding problematic hot-spots.

The above would benefit from additional reporting of L3 CSI RS measurement information by thc liE. Accordingly, the flowchart of Figurc 5 can altcmativcly providc additional information in other reports including thc radio link failurc-, handover failure-and connection establishment failure reports. Furthermore, the procedure of Figure 5 can be used to include L3 CSI RS measurement information in the logged measurements collected during idle mode.

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not describcd abovc may also bc employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

Claims 1. A method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in response to a report trigger, the mobile terminal generating a measurement report including a first set of measurement data, the first set of measurement data including either cell-specific reference signal measurement data or non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signa' measurement data.
2. A method according to claim 1, wherein the report trigger relates to an event comprising detection of a condition in the cell specific reference signals.
3. A method according to claim 1, wherein the report trigger relates to an event comprising detection of a condition in the non-cell-specific reference signals.
4. A method according to claim 1, wherein the report trigger is expiry of a timer.
5. A method according to claim 1, wherein the report is triggered periodically such that there is a predetermined time interval in-between successive reports.
6. A method according to any preceding claim, comprising receiving configuration signalling from the network to configure the report trigger.
7. A method according to any preceding claim, wherein the report trigger determines the measurement data included in the first measurement data.
8. A method according to any preceding claim, wherein, in case the first set of measurement data includes cell-specific reference signal measurement data, the second set of measurement data including non-cell-specific reference signal measurement data for any frequency for which thc mobile terminal has non-cell-specific reference signal measurement data available based on measurements the mobile terminal has previously been configured to perform.
9. A method according to any of claims 1 to 7, wherein, in ease the first set of measurement data includes non-cell-specific reference signal measurement data, the second set of measurement data including non-cell-specific reference signal measurement data for frequencies other than the frequency for which the report is triggered, and for which the mobile terminal has non-cell-specific reference signal measurement data available based on measurements the mobile terminal has previously been configured to perform.
10. A method as claimed in any preceding claim, wherein the set of frequencies for which the mobile terminal includes measurement data is limited to a subset of the frequencies for which the mobile terminal has measurement data available.
11. A method as claimed in claim 10, wherein the subset of frequencies for which the mobile terminal includes measurement data is determined by a configuration parameter provided by the network.
12. A method as claimed in any preceding claim, wherein the second set of measurement data comprises measurement data only on a limited number of best non-cell-specific refcrence signal resources.
13. A method as claimed in claim 12, wherein the number of best non-cell-specific reference signal resources for which the mobile terminal includes measurement data is fixed.
14. A method as claimed in claim 12, wherein the number of best non-cell-specific reference signal resources for which the mobile includes measurement data is determined by a configuration parameter provided by thc network.
15. A method according to any preceding claim, comprising receiving configuration signalling from the network comprising an indicator, and when the indicator is active, responding to the report trigger to generate the measurement report including the first and second set of measurement data, and when the indicator is inactive, responding to the report trigger to generate a measurement report not including the second set of measurement data.
16. A method according to any preceding claim, wherein the mobile terminal includes parameters for determining the second set of measurement data to include in the measurement report.
17. A method according to claim 16, wherein the parameters comprise an indication to include, in the second set of measurement data, non-cell-specific reference signal measurement data derived from reference signals on a carrier frequency associated with the report trigger.
18. A method according to claim 16, wherein the parameters comprise one or more canier frequencies, and the second set of measurement data includes non-cell-specific reference signal measurement data derived from reference signals on the one or more carrier frequencies.
19. A mcthod according to claim 18, wherein said one or more carricr frequencies arc a subset of thc frequencies uscd for thc first sct of measurement data.
20. A method according to claim 16, whcrcin thc parameters comprise an indication to include, in the second set of measurement data, non-cell-specific reference signal measurement data derived from reference signals on any carrier frequency.
21. A mcthod according to claim 16, whcrcin thc paramctcrs comprise a threshold value, and the second set of measurement data contains measurements of non-cell-specific reference signals that exceed the threshold value.
22. A mcthod according to claim 16, whcrcin the parameters comprisc a threshold value, and the second set of measurement data contains measurements of non-cell-specific rcfcrcncc signals that diffcr from or fall within known measurement data by the threshold value.
23. A method according to any of claims 16 to 22, wherein the parameters comprise an indication of the maximum number non-cell-specific reference signals resourccs for which mcasurcmcnts of non-cell-spccific rcfcrcncc signals may bc includcd in thc sccond sct of mcasurcmcnt data.
24. A method as claimed in claim 23, wherein the non-cell-specific reference signal resourccs for which mcasurcmcnts arc includcd arc thc rcsourccs up to thc maximum number which provide the best measurements.
25. A method according to any of claims 16 to 23, comprising receiving configuration signalling from the network to configure the parameters.
26. A method according to any of claims 16 to 23, wherein the configuration parameters apply to a plurality of rcport triggers such that a plurality of report triggers are configured upon receiving configuration signalling from the network.
27. A method according to any preceding claim, wherein the second set of measurement data includes non-cell-specific reference signals measurement data derived from reference signals received on all frequencies for which the mobile terminal has earlier provided non-cell-specific reference signals measurement data.
28. A method according to any preceding claim, wherein the non-cell-specific reference signals are channel state information reference signals.
29. A method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in response to a report trigger, the mobile terminal generating a measurement report including a first set of measurement data, the first set of measurement data including non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including cell-specific reference signal measurement data.
30. A method according to claim 29, wherein the report trigger relates to an event comprising detection of a condition in the non-cell-specific reference signals.
31. A method according to claim 29, wherein the report trigger is expiry of a timcr.
32. A method according to claim 29, wherein the report is triggered periodically such that there is a predetermined time interval in-between succcssivc reports.
33. A method according to any of claims 29 to 32, comprising receiving configuration signalling from the network to configure the report trigger.
34. A mcthod according to any of claims 29 to 33, whcrcin thc rcport trigger determines the measurement data included in the first measurement data.
35. A method according to any of claims 29 to 34, wherein the second set of measurement data inc'udes cell-specific reference signal measurement data for any frequency for which the mobile terminal has the cell-specific reference signal mcasurement data available bascd on measurements the mobile terminal has previously been configured to perform.
36. A method according to any of claims 29 to 34, wherein the second set of measurement data includes cell-specific reference signal measurement data for frequencies other than the frequencies for which the mobile terminal has previously included cell-specific reference signal measurement data.
37. A method as claimed in any of claims 29 to 36, wherein the set of frequencies for which the mobile terminal includes measurement data is limited to a subset of the frequencies for which the mobile terminal has measurement data available.
38. A method as claimed in any of claims 29 to 37, wherein the further subset of frequencies for which the mobile terminal includes measurement data is determined by a configuration parameter provided by the network.
39. A method as claimed in any of claims 29 to 38, wherein the second set of measurement data only comprises measurement data on a limited number of best cells.
40. A method as claimed in claim 39, wherein the number of best cells for which the mobile terminal includes measurement data is fixed.
41. A method as claimed in claim 39,herein the number of best cells for which the mobile includes measurement data is determined by a configuration parameter provided by the network.
42. A method according to any of claims 29 to 41, comprising receiving configuration signalling from the network comprising an indicator, and when the indicator is active, responding to the report trigger to generate the measurement report including the first and second set of measurement data, and when the indicator is inactive, responding to the report trigger to generate a measurement report not including the second set of measurement data.
43. A method according to any of claims 29 to 42, wherein the mobile terminal includes parameters for determining the second set of measurement data to include in the measurement report.
44. A method according to claim 43, wherein the parameters comprise an indication to include, in the second set of measurement data, cell-specific reference signal measurement data derived from reference signals on a carrier frequency associated with the report trigger.
45. A method according to claim 43, wherein the parameters comprise one or more canier frequencies, and the second set of measurement data includes cell-specific reference signal measurement data derived from reference signals on the one or more canier frequencies.
46. A mcthod according to claim 43, whcrcin the parameters comprise an indication to include, in thc sccond sct of mcasurcmcnt data, ccll-spccific reference signal measurement data derived from reference signals on any carrier frequency.
47. A method according to claim 43, wherein the parameters comprise a threshold value, and the second set of measurement data contains measurements of cell-specific reference signals that exceed the threshold value.
48. A mcthod according to claim 43, whcrcin thc parameters comprisc a threshold value, and the second set of measurement data contains measurements of cell-specific reference signals that differ from or fall within known mcasurcmcnt data by the thrcshold valuc.
49. A method according to any of claims 43 to 48, wherein the parameters comprisc an indication of thc maximum numbcr of ccll-spccific rcfcrcncc signals resources for which measurements of cell-specific reference signals may be included in the second set of measurement data.
50. A method as claimed in claim 49, wherein the cell-specific reference signal rcsourccs up to thc maximum numbcr arc choscn to provide thc bcst measurcmcnts.
51. A method according to any of claims 43 to 50, comprising receiving configuration signalling from the network to configure thc paramctcrs.
52. A method according to any of claims 43 to 51, wherein the configuration parameters apply to a plurality of rcport triggers such that morc than onc rcport trigger is configured upon receiving configuration signalling from the network.
53. A method according to any of claims 43 to 52, wherein the second set of measurement data includes cell-specific reference signal measurement data derived from reference signa's received on a single carrier frequency for which the report is initiated.
54. A method according to any of claims 29 to 53, wherein the second set of measurement data includes cell-specific reference signals measurement data derived from reference signals received on all frequencies for which the mobile terminal has earlier provided cell-spccific refcrence signals measurement data.
55. A method according to any preceding claim, comprising sending the measurement report to a base station of the network for the purpose of initiating a handover.
56. A method according to any preceding claim, wherein the non-cell-specific reference signals are channel state information reference signals.
57. A method of operating a base station in a wireless communications network, in which the base station employs coordinated transmissions from multiple points towards a mobile terminal, the method comprising: connecting with a mobile terminal, broadcasting reference signals for measurement by the mobile terminal, receiving from the mobile terminal a first set of measurement data including cell-specific reference signal measurement data, and a second set of measurement data including non-cell-specific reference signal measurement data, determining that the mobile terminal should handover to a target base station, and sending a handover request to a target base station, the handover request including the second set of measurement data, for the purpose of enabling the target base station to configure the set of non-cell-specific resource signals for the mobile terminal.
58. A method of operating a base station in a wireless communications network, in which the base station employs coordinated transmissions from multiple points towards a mobile terminal, the method comprising: connecting with a mobile terminal, broadcasting reference signals for measurement by the mobile terminal, and receiving from the mobile terminal physical layer feedback on a set of non-cell-specific reference signal resources, receiving from the mobile terminal a first set of measurement data including non-cell-specific reference signal measurement data, and a second set of measurement data including further non-cell-specific reference signal measurement data, determining that the mobile terminal should handover to a target base station, and sending a handover request to a target base station, the handover request including the second set of measurement data, for the purpose of enabling the target base station to configure the set of non-cell-specific resource signals for the mobile terminal.
59. A method of operating a base station in a wireless communications network, in which the base station employs coordinated transmissions from multiple points towards a mobile terminal, the method comprising: connecting with a mobile terminal, broadcasting reference signals for measurement by thc mobilc tcrminal, and receiving from thc mobilc tcrminal physical layer feedback on a set of non-cefl-specific reference signal resources, receiving from the mobile terminal a first set of measurement data including non-cell-specific reference signal measurement data, and a second set of measurement data including cell-specific reference signal measurement data, determining that the mobile terminal should handover to a target base station, and sending a handover request to a target base station, the handover request including the second set of measurement data, for the purpose of enabling the target base station to configure the set of cell-specific resource signals for the mobile terminal.
60. A method as claimed in any of claims 57 to 59, wherein the first set of measurement data is received in a first measurement report, and the second set of measurement data is received in a second measurement report, the first measurement report arriving later than the second measurement report.
61. A method as claimcd in claim 60, comprising providing an indication in the handover request that the second measuremcnt data was received from the mobile terminal earlier than the first measurement data.
62. A method as claimed in any of claims 57 to 59, wherein the first and second sets of measurement data are received from the mobile terminal in a single measurement report.
63. A method as claimed in claim 62, comprising providing an indication in the handover request that the first and second sets of measurement data were received from the mobile terminal in a single measurement report.
64. A method as claimed in any of claims 57 to 63, comprising determining that the mobile terminal should handover on the basis of the first set of measurement data.
65. A method as claimed in any of claims 57 to 64, comprising determining that the mobile terminal should handover on the basis of a capacity determination at the base station.
66. A method as claimed in any of claims 57 to 65, whcrein the handover request includes thc measurement data in mobile terminal context data, or radio resource management configuration data.
67. A method according to any of claims 57 to 66, wherein the non-cell-specific reference signals are channel state information reference signals.
68. A method of operating a base station in a wireless communications network, in which the base station employs coordinated transmissions from multiple points towards a mobile terminal, the method comprising: determining a set of channel state indicator reference signal resources associated with the transmissions from multiple points, and transmitting configuration data about the set of channel state indicator reference signal resources to a neighbouring base station, for the purpose of indicating to the neighbouring base station what measurement data the base station would like to receive, during handover preparation, fbr the channel state indicator reference signal resources.
69. A method as claimed in claim 68, wherein the configuration data includes parameters for the channel state indicator reference signal resources.
70. A method as claimed in claim 69, wherein the parameters include scrambling identity information for one or more of the channel state indicator reference signal resources.
71. A method as claimed in any of claims 68 to 70, wherein the parameters include resource configuration information for one or more of the channel state indicator reference signal resources.
72. A method as claimed in any of claims 68 to 71, wherein the configuration data includcs an identification of an area for which the channel state indicator reference signal resources arc relevant.
73. A method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in response to a handover failure report request from the network, the mobile terminal generating a report including a first set of measurement data, the first set of measurement data including either cell-specific reference signal measurement data or non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signal measurement data.
74. A method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in response to a connection establishment failure report request from the network, the mobile terminal generating a report including a first set of measurement data, the first set of measurement data including either cefl-specific reference signal measurement data or non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signal measurement data.
75. A mcthod of opcrating a mobile tcrminal in a wirclcss communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in response to a handover failure report request from the network, the mobile terminal generating a report including a first set of measurement data, the first set of measurement data including either cell-specific reference signal measurement data or non-cell-specific reference signal measurement data; and including a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signal measurement data.
76. A method of operating a mobile terminal in a wireless communications network employing coordinated transmissions from multiple points towards the mobile terminal, in which the mobile terminal supports physical layer feedback on a set of non-cell-specific reference signals, the method comprising: in an idle mode, periodically logging measurement data on cell-specific reference signals and non-cell-specific reference signals; and in response to a request from the network, a periodic logging trigger in an idle mode, the mobile terminal generating a report including a first set of measurement data, the first set of measurement data induding either cell-specific reference signal measurement data or non-cell-specific reference signal measurement data; and a second set of measurement data in said measurement report, said second set of measurement data including non-cell-specific reference signal measurement data.
77. A computer program comprising instructions such that when the computer program is executed on a computing device, the computing device is arranged to carry out a method according to any one of claims I to 76.
78. A mobile station configured to carty out the method according to any of claims ito 56, and 73 to 76.
79. A base station configured to carry out the method according to any of claims 57 to 72.