WO2008135933A2

WO2008135933A2 - Improved multimedia broadcast multicast service mobility and measurement capabilities

Info

Publication number: WO2008135933A2
Application number: PCT/IB2008/051713
Authority: WO
Inventors: Leping Huang; Sami Juhani Savio
Original assignee: Nokia Corporation; Nokia, Inc.
Priority date: 2007-05-02
Filing date: 2008-05-02
Publication date: 2008-11-13
Also published as: WO2008135933A3; WO2008135933A9

Abstract

An apparatus includes a controller configured with a radio frequency receiver to determine a location of a user equipment in a multicast broadcast single frequency network using at least one of a channel quality-based approach and an explicit control signal approach. The controller is further configured to initiate the making of a handover measurement in response to the user equipment being located in a border cell area of the multicast broadcast single frequency network. Also disclosed is an apparatus having a controller configured to determine a difference in the received power between cell-specific and cell-common reference symbols in a multimedia broadcast multicast service channel. The controller is further configured to use the determined difference to at least make a determination as to whether the mobile apparatus is located in a multicast broadcast single frequency network border cell or in a multicast broadcast single frequency network center cell. Corresponding methods and computer programs are also described.

Description

IMPROVED MULTIMEDIA BROADCAST MULTICAST SERVICE MOBILITY AND MEASUREMENT CAPABILITIES

TECHNICAL FIELD:

The exemplary and non-limiting embodiments of this invention relate generally to wireless communication systems, methods, devices and computer program(s) and, more specifically, relate to techniques to provide a broadcast service in a cellular-type of wireless communication system.

BACKGROUND:

Various abbreviations that appear in the specification and/or in the drawing figures are defined as follows:

3 GPP third generation partnership proj ect

UTRAN universal terrestrial radio access network

Node B base station

UE user equipment

EUTRAN evolved UTRAN eNB EUTRAN Node B (evolved Node B)

LTE long term evolution

RAN radio access network

RLC radio link control

RRC radio resource control

RRM radio resource management

CDM code division multiplexing

FDD frequency division duplex

FDMA frequency division multiple access

OFDMA orthogonal frequency division multiple access

SC-FDMA single carrier, frequency division multiple access

PDU protocol data unit UL uplink

DL downlink

HO handover

SFA single frequency network area SFN single frequency network

SINR signal to interference and noise ratio

MBSFN multicast broadcast single frequency network

MBMS multimedia broadcast multicast service

MTCH MBMS traffic channel MCCH multicast control channel

MCH MBMS channel

ISD inter-site distance

RSRP reference symbol received power

TTI transmission time interval MCE MBMS coordination entity

MCEJUP MBMS coordination entity-user plane

PtP point-to-point

PtM point-to-multipoint

BM-SC broadcast/multicast service center GW gateway

A proposed communication system known as evolved UTRAN (EUTRAN, also referred to as UTRAN-LTE or as E-UTRA) is currently under discussion within the 3GPP. The current working assumption is that the DL access technique will be OFDMA, and the UL access technique will be SC-FDMA.

The Universal Mobile Telecommunications System (UMTS) is a 3 G mobile communication system which provides a variety of multimedia services. The UMTS Terrestrial Radio Access Network (UTRAN) is a part of a UMTS network which includes one or more radio network controllers (RNCs) and one or more nodes. The EUTRAN provides new physical layer concepts and protocol architectures for UMTS. LTE MBMS will support following transmission modes: MBSFN mode, single cell PtP mode and single cell PtM. Reference can be had to section 6.19.2.2 (Synchronization Requirements for SFN) of 3GPP TR R3.018 (vθ.71), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved UTRA and UTRAN; Radio Access Architecture and Interfaces (Release 7), and to the definition of the SFN area in 6.19.2.1.1. In this latter section of 3GPP TR R3.018 (vθ.71) the following definitions are provided.

Multi-cell MBMS Synchronization Area: consists of a group of cells having the same frequency band allocated with contiguous coverage, in which ail the cells are capable to be synchronized and have the possibility to transmit MBMS data in SFN mode. Multi-cell MBMS Synchronization Areas may be configured independently from MBMS Service Area configurations. Multi-cell MBMS Synchronization Areas are capable of supporting one or more SFN Areas.

For a given geographical area and a given frequency band only one Multi-cell MBMS Synchronization Area shall be defined, i.e. multiple Multi-cell MBMS Synchronization Areas in the same geographical area have to be defined on different frequency bands.

SFN (Single Frequency Network) Area: An SFN area consists of a group of cells with contiguous coverage where all cells are using the same radio resources in the same frequency band, to synchronously transmit a single MBMS service.

A SFN area belongs only to one Multi-cell MBMS synchronization area. SFN Area is composed only of actively transmitting cells at a certain point in time.

Maximum SFN Area: Maximum supported geographical extension of an SFN Area. It may be limited by the multi-cell MBMS synchronization area, MBMS service area and operator configuration.

SFN Guard Area: The SFN Guard Area is the group of cells where due to the resource usage in the corresponding SFN Area, the use of the same radio resources is restricted due to interference considerations.

The above referenced section 6.19.2.2 (Synchronization Requirements for SFN) of 3GPP TR R3.018 (vθ.71) states the following:

MBMS Multi-cell transmission in SFN area can use combining in the air to improve the performance on cell boundary. For this purpose some synchronization requirements are needed.

1) Physical layer frame timing synchronization where:

The physical frame timing of each eNB in SFN area should be strictly aligned at the start boundary of each frame to guarantee the physical layer framing time synchronization. The precision requirement is in microsecond level. 2) Content transmission synchronization where:

The same content of an MBMS service should be transmitted at the same time by each eNB in SFN area to guarantee that the same content can be combined in time at the UE.

3) Resource block allocation synchronization where: The physical resource block allocation pattern in each TTI should be coincident for all eNBs in SFN area to guarantee that the same resource block is used for the same MBMS service data in different eNBs.

Section 6.19 (MBMS in LTE) of 3GPP TR R3.018 (vθ.71) is incorporated herein by reference.

In Non SFN Operation, single cell PtM is defined as a transmission method in which one cell transmits the same contents to multiple UEs in the cell, and single cell PtP is defined as a transmission method in which one cell transmits the contents only to one UE in the cell. It was an open issue as to whether uplink feedback is available in single cell PtM.

Another issue is how many handover/mobility scenarios should be supported in MBMS.

At least the following mobility/handover scenarios have been discussed: (1) inter-frequency, inter-MBSFN handover; (2) intra-frequency, inter-MBSFN handover; (3) handover between MBSFN and a cell in single cell PtP; (4) handover within two cells in single cell PtP; (5) handover from MBSFN and a cell in single cell PtM; and (6) handover within two cells in single cell PtM.

In a uni-cast cellular network, such as GSM, WCDMA, LTE, and in 3GPP release 6 MBMS, the UE periodically makes HO measurements. For example, in WCDMA a typical HO measurement interval is 50ms. This is because in these systems the UE needs to make a HO between base stations. However, in MBSFN the UE does not distinguish the signal from different base stations belonging to the same MBSFN area. As a result, mobility of a UE in MBSFN mode has following features:

1) the UE makes a HO only at the border area of the MBSFN,

2) the UE does not make a HO at a center area of the MBSFN; and

3) the UE does not make a HO between base stations belonging to the same MBSFN.

In UTRA and a release 6 MBMS HO the UE makes inter-cell measurement periodically if the cell is located in the same frequency. This is done because the UE needs to handover between neighboring cells.

In LTE unicast it has been agreed in Rl -071250 (3GPP TSG-WGl Meeting #48, St. Louis, USA, Feb. 12th- 16th, 2007, "LS on LTE measurement supporting Mobility", incorporated by reference herein) that RSRP and E-UTRA carrier RSSI are good candidates for UE measurements to support mobility. One issue pertains to the proper measurement quantity to be used by the UE in MBMS to support mobility.

The reference symbol received power (RSRP) of a MBMS symbol may be classified into two parts: received power from the nearest eNB, and MBSFN combining gain (received useful power from other cells sending the same data). However, it is difficult to distinguish the MBSFN combining gain from the RSRP of an MBMS signal. The MBSFN combining gain depends on the location (MBSFN border or center cell) of a UE in a MBSFN. SUMMARY

In a first aspect thereof the exemplary embodiments of this invention provide a method that includes determining a location of a user equipment in a multicast broadcast single frequency network using at least one of a channel quality-based approach and an explicit control signal approach; and making handover measurements when it is determined that the user equipment is located in a border cell area of the multicast broadcast single frequency network.

In another aspect thereof the exemplary embodiments of this invention provide a computer-readable medium that stores program instructions, the execution of the program instructions resulting in performance of operations that comprise determining a location of a user equipment in a multicast broadcast single frequency network using at least one of a channel quality-based approach and an explicit control signal approach; and making handover measurements when it is determined that the user equipment is located in a border cell area of the multicast broadcast single frequency network.

In another aspect thereof the exemplary embodiments of this invention provide an apparatus that includes a controller configured with a radio frequency receiver to determine a location of a user equipment in a multicast broadcast single frequency network using at least one of a channel quality-based approach and an explicit control signal approach. The controller is further configured to initiate the making of a handover measurement in response to the user equipment being located in a border cell area of the multicast broadcast single frequency network.

In a further aspect thereof the exemplary embodiments of this invention provide a method that includes operating a mobile apparatus to determine a difference in the received power between cell-specific and cell-common reference symbols in a multimedia broadcast multicast service channel. The method further includes using the determined difference to at least make a determination as to whether the mobile apparatus is located in a multicast broadcast single frequency network border cell or in a multicast broadcast single frequency network center cell. In a still further aspect thereof the exemplary embodiments of this invention provide an apparatus having a controller configured to determine a difference in the received power between cell-specific and cell-common reference symbols in a multimedia broadcast multicast service channel. The controller is further configured to use the determined difference to at least make a determination as to whether the mobile apparatus is located in a multicast broadcast single frequency network border cell or in a multicast broadcast single frequency network center cell.

BRIEF DESCRIPTION OF THE DRA WTNGS

In the attached Drawing Figures:

Figure 1 is an illustration of inter-SFN handover.

Figure 2 illustrates message sequence chart of an inter-SFN handover in a mixed carrier MBMS.

Figure 3 shows a message sequence chart of an inter-SFN cell reselection in a dedicated carrier MBMS.

Figure 4 shows a message sequence chart of an inter-SFN handover in mixed carrier MBMS (when single cell MCCH is used).

Figure 5 is a graph showing the results of simulations, and that shows a SINR distribution comparison at the SFN center and border (ISD 500 m and 1000 m).

Figure 6 illustrates three RSRP -based measures.

Figure 7 is an illustration of signaling to utilize a RSRP difference in a HO measurement. Figure 8 shows a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of this invention.

Figure 9 is a simplified block diagram depicting MBSFN single cell mobility.

Figure 10 graphically shows the RSRP difference as a measurement quantity in accordance with exemplary embodiments of this invention.

DETAILED DESCRIPTION

The exemplary embodiments of this invention provide techniques to ensure mobility/service continuation for MBMS services, including service continuity in a EUTRAN MBSFN.

In part, the exemplary embodiments of this invention pertain to calculating a metric related to the above-mentioned MBSFN combining gain, which may then be used as a measurement quantity to support mobility/service continuity for a UE in MBMS. The use of this metric provides a more accurate HO than using other metrics, such as the RSRP of the MBMS signal directly. Note that the MBSFN combining gain is a new feature in LTE MBMS.

Reference is made first to Figure 8 for illustrating a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of this invention. In Figure 8 a wireless network 1 is adapted for communication with a UE 10 via a Node B (base station) 12, also referred to herein without loss of generality as an eNB 12. The network 1 may include a MCE 14. The eNB 12 (one of several) and MCE 14 may be referred to as the RAN. The UE 10 includes a data processor (DP) 1 OA, a memory (MEM) 1OB that stores a program (PROG) 1OC, and a suitable radio frequency (RF) transceiver 1OD for bidirectional wireless communications with the Node B 12, which also includes a DP 12A, a MEM 12B that stores a PROG 12C, and a suitable RF transceiver 12D. The Node B 12 is coupled via a data path 13 to the MCE 14 that also includes a DP 14A and a MEM 14B storing an associated PROG 14C. At least one of the PROGs 1OC and 12C is assumed to include program instructions that, when executed by the associated DP, enable the electronic device to operate in accordance with the exemplary embodiments of this invention, as will be discussed below in greater detail.

Note that during a HO situation an eNB 12 will be considered a source eNB 12 (one that is currently serving the UE 10), and another eNB 12 will be considered a target eNB (the one to which the UE 10 will be handed over to, and that will serve the UE 10 next).

Reference in this regard may also be had to Figure 9. In general, the support of E-MBMS for the various considered modes, and for the MBSFN and single cell transmission, may be ensured with an infrastructure containing:

BM-SC; MBMS GW;

IP Multicast infrastructure; and E-MBMS enabled eNBs.

This architecture is illustrated in Figure 9, and may be viewed as representing a logical description of a "lightweight" E-MBMS deployment. One significant property of the lightweight E-MBMS deployment is that the MCE functionality is semi-statically or statically configured to the relevant nodes. The MCE functionality may be considered as encompassing the allocation of radio resources used by all eNBs 12 in the SFN area for multi-cell MBMS transmissions using SFN operation. In addition to allocating time/frequency radio resources, this may also include determining the further details of the radio configuration (e.g., the modulation and coding scheme).

Note in Figure 8 that the UE 10 is assumed to include a measurement unit 1OE associated with the receiver. The measurement unit 1OE is operated as described below in relation to Figures 2, 3, 4, 7 and 10.

The exemplary embodiments of this invention may be implemented at least in part by computer software executable by the DP 1 OA of the UE 10 and/or by the DP 12A of the Node B 12, or by hardware, or by a combination of software and hardware (and firmware).

In general, the various embodiments of the UE 10 can include, but are not limited to, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.

The MEMs 1OB, 12B and 14B may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

The DPs 1OA, 12A and 14A may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architecture, as non-limiting examples.

In accordance with exemplary embodiments of this invention, in LTE MBMS the UE 10 measures a neighboring SFN or neighboring non-SFN cell only at border areas of the MBSFN. Furthermore, in LTE MBMS, the UE 10 does not measure neighboring SFN or neighboring non-SFN cell at center areas of the MBSFN. In addition, in LTE MBMS, the UE 10 begins a mobility procedure at border cells of the MBSFN, and before moving out of the MBSFN. In addition in LTE MBMS, the UE 10 begins a mobility procedure just after moving out of the MBSFN.

In accordance with exemplary embodiments of this invention, and in addition, at least two procedures to detect the location of the UE 10 in a MBSFN are provided: (1) a channel quality-based approach; and (2) an explicit control signal approach. In the channel quality-based approach, the UE 10 periodically measures some radio link metric(s), such as the SNIR of the MCCH/MCH, the reference symbol signal power (RSRP), or the RSRP Difference (power difference between cell common and cell specific reference symbol, as described in further detail below). A threshold value applied to the signal strength metric may be used to determine the location of the UE 10 in the MBSFN, and to trigger a mobility related measurement. In the explicit control signal approach, all border cells notify the UE 10 of its location via control channels, such as via the single cell MCCH.

Figure 1 shows the inter-SFN handover. In this non-limiting example three SFNs (SFN_1, SFN__2, SFN_3) are deployed either in the same or different frequency and transmit exactly the same data content to the UE 10. Assuming the UE 10 is first located in SFN_1, the UE 10 either measures the channel quality of the MBSFN periodically, or decodes the contents in a single cell MCCH periodically to detect its location in the MBSFN. When it detects that it is in a border cell, the UE 10 executes HO signaling to move to the neighboring SFN.

Figures 2, 3 and 4 are message sequence charts related to handover procedures in mixed carrier and dedicated carrier, separately, in accordance with exemplary embodiments of this invention.

More specifically, Figure 2 illustrates an inter-SFN handover procedure in a mixed carrier MBMS. In the following discussion the numbers (e.g., 1., 2., etc.) correspond to the like-numbered message flows in Figure 2.

1. The UE 10 receives two measurement events from a session start message. A RSRP Difference event is used to distinguish between a border area or a center area of the MBSFN, while a RSRP event is used to compare the serving SFN and the neighboring SFN.

2. MBMS data is sent from the source MCEJJP 14 to the UE 10 via eNBs 12.

3. Based on the received measurement event, the UE 10, utilizing the measurement unit 1OE, measures the RSRP difference (RSRPDiff) of a MCH periodically. 4. When the RSRP difference is less than some certain threshold, the UE 10 detects that it is already located in border cells of a MBSFN. As a result, the UE 10 is triggered to read neighbor SFN information. 5. Border eNBs 12 transmit neighboring SFN information periodically in single cell mode.

6. Based on the received neighbor SFN information, the UE 10 measures and compares the RSRP of those SFNs.

7. The UE 10 sends a measurement report to the eNB 12 of the source SFN if a measurement event is triggered. It can be noted that a measurement event similar to one used for uni-cast mobility may be employed. For example, the presence of a 3dB margin between the target eNB and the source eNB may be employed.

8. Based on the received measurement, the source eNB 12 makes a HO decision. Note that since the same contents are broadcast by the target eNB, it is not necessary to forward DL PDUs to target eNB .

9. If the UE 10 is using a subscription-based service, there will likely be some context stored in the source eNB 12. In such a case the source eNB forwards the UE 10 context to the target eNB.

10. The source eNB 12 sends a HO command to UE 10, including additional information about target SFN/eNB.

11. Based on the received HO command, the UE 10 detaches from the source (old) eNB and synchronizes to the target eNB/SFN. Subsequently, the UE 10 starts to receive the MBMS service from the target eNB.

Figure 3 illustrates an inter-SFN handover procedure in a dedicated carrier MBMS.

1. The UE 10 receives two measurement events from a session start message. The RSRP measurement event 1 is used to distinguish between the border area or the center area of the MBSFN, and the RSRP measurement event 2 is used to compare the serving SFN and the neighboring SFN.

2. The MBMS data is sent from the source MCEJJP to the UE 10 via source eNBs 12.

3. Based on the received measurement event, the UE 10 measures the RSRP of the MCH periodically.

4. When the RSRP is below some certain threshold, the UE 10 is triggered to read the neighbor SFN information.

5. The eNBs 12 transmit neighboring SFN information periodically in single cell mode. 6. Based on the received neighbor SFN information, the UE 10 measures and compares the RSRP of those SFNs.

7. The UE 10 detaches from the source (old) eNB 12, and synchronizes to the target eNB/SFN, and subsequently starts to receive MBMS service from the target eNB 12.

Figure 4 illustrates the signal flow of an inter-SFN handover in a mixed carrier MBMS (when the explicit control signal approach is used). The differences as compared with Figure 2 are explained as follows:

3. The UE 10 reads the single cell MCCH periodically to detect its cell location in the MBSFN.

4. A border cell broadcasts its location (BORDER_CELL) in the single cell MCCH.

5. When the BORDER CELL information is identified from the single cell MCCH, the UE 10 is triggered to read the neighbor SFN information.

In accordance with exemplary embodiments of this invention, and providing still further examples of the utility of the exemplary embodiments of this invention, in LTE MBMS the UE 10 measures a neighboring cell in the single cell PtP/PtM mode. The UE 10 may move to this neighboring cell in a single cell PtP or PtM mode after it identifies that the neighboring cell is better than the current MBSFN. The handover procedure may begin before the UE 10 enters the neighboring cell. This means that the UE 10 exchanges HO-related signaling, such as a measurement report and/or HO command, when it is still located in a border cell region of the MBSFN. The handover procedure may also begin after the UE 10 enters the neighboring cell. This means that the UE 10 exchanges HO-related signaling, such as a measurement report and/or HO command, after it moves out of the MBSFN. Furthermore, instead of mobility from one cell in MBSFN mode to a different cell in single cell mode, it is also possible for the UE 10 to first switch to single cell PtP mode in the border cell of the MBSFN, and then make a HO between a single cell PtP link.

Figure 5 shows that the SINR of worst-case users in the middle of a SFN, as compared to worst-case users at the border, can be 10-20 dB (or greater). This shows that it is possible to configure a reliable threshold to trigger HO measurement. As a non-limiting example, one may assign a SNIR of IOdb as the threshold if Async = 0ms.

It can be noted that if the UE 10 is receiving data from the MCH it can use the received quality of the data as input to the HO measurement trigger. A typical mobile TV program can provide a reliable channel indicator. However, if the UE 10 is not receiving any data, it still needs to monitor the MCCH. The interval of the primary MCCH may be expected to range (possibly) from about 10ms to about 100ms. As such, the received signal quality of the MCCH is sufficiently reliable to be used as an input to the HO measurement event. Note that a time domain filter method may be used in processing measurement result, if desired.

The use of the exemplary embodiments of this invention described above can clearly be seen to avoid redundant mobility measurements and, as a result, to improve the power efficiency of the UE 10.

The use of the exemplary embodiments of this invention described above can clearly be seen as a valuable procedure to avoid interruption time during handover between neighboring MBSFNs/cells. As a result, the quality perceived by the user is improved at the UE 10.

Further now in accordance with exemplary embodiments of this invention, and referring to Figure 10, there is described a new measurement metric to support mobility, i.e., the difference of the received power between cell-specific and cell-common reference symbols in the same MBMS sub-frame that was briefly mentioned above. This measurement metric may be referred to for convenience as RSRPDiff. The value of this measurement metric depends on the MBSFN combining gain of the UE 10 in the MBSFN, and it indicates the SFN combining gain directly. Consequently, it can be used to determine the location of the UE 10 in an MBSFN (e.g., is the UE 10 located in a MBSFN border cell or in a MBSFN center cell?). This measurement metric can also be used in the HO procedure, and to aid the MBSFN to switch between point-to-point and point-to-multipoint services.

The relevant signaling to implement the RSRPDiff measurement is discussed below, and includes the measurement event from the eNB 12 to the UE 10, and the measurement report from UE 10 to the eNB 12.

Figure 6 compares three measurement quantities: (Figure 6(a) the RSRP of MBMS symbols, Figure 6(b) the RSRP of uni-cast symbols, and Figure 6(c) the RSRP difference between uni-cast and MBMS symbols. More specifically, Figure 6(a) indicates the dependence of the MBMS RSRP on the distance from the MBSFN center, and Figure 6(b) indicates the dependence of the uni-cast (cell-specific) RSRP on the distance from the nearest unicast cell. Note that the UE 10 receives a higher RSRP from the uni-cast channel when it is in a cell center and a lower RSRP when it is located at a cell edge. Figure 6(c) indicates the dependence of the RSRPDiff on the distance of the MBSFN center. When the UE 10 in located in a MBSFN center cell, it obtains a larger RSRP difference measure than when in a MBSFN border cell. This directly indicates the location of the UE 10 within the MBSFN. The RSRP difference should always be greater than zero. If the RSRP difference approaches zero it indicates that the UE 10 is near to the MBSFN border, where the SFN gain is minimal.

When the UE 10 is located in the center of a MBSFN center cell, its RSRP difference (or MBSFN combining gain) is typically about 12dBm to about 2OdBm, depending on the ISD. When it is located at the cell edge of the MBSFN center cell, the RSRP difference is even larger.

However, when the UE 10 is located in a MBSFN border cell the RSRP difference (or MBSFN combining gain) is typically less than about 3dB to about 5 dB, depending on the ISD. When the RSRPDiff is below some threshold it can be used as a trigger to begin a mobility measurement on neighboring MBSFNs/cells. Note that in this case it is also possible to use the SNIR or the RSRP of the MBMS symbol as a trigger, but since the SNIR and RSRP of the MBMS symbol includes both the effect of transmission power from the serving eNB 12 and the SFN combining gain, it may not as accurately reflect the location of a UE 10.

Figure 7 illustrates signaling to utilize the RSRP difference in the HO measurement. The serving eNB 12 configures the measurement event to the UE 10 via RRC signaling. Following reception of the measurement event the UE 10 periodically measures the RSRP difference and may calculate the average of RSRP difference measurement results. When the UE 10 detects that the RSRP difference is below the certain threshold it makes a measurement report to the current serving eNB 12 which in turn may trigger the intεr-MBSFN handover measurement and/or execution procedure.

Note that the RSRPDiff (SFN gain) measurement may have further utility. For example, if the RSRPDiff (SFN gain) is very low for all UEs 10 in a MBSFN border cell, it may be useful to transmit by uni-cast (e.g., controlled by a link adaptation function in the eNB 12) in that cell, instead of by the use of the MBSFN operation. As a result, the RSRPDiff (SFN gain) measurement may be used as a trigger to switch a cell's transmission mode between single cell PtP and single cell PtM.

These further exemplary embodiments of this invention clearly provide additional advantages. As non-limiting examples, the RSRPDiff measurement value aids the UE 10 in determining its location in the MBSFN, which in turn can be used to facilitate the HO procedure in MBSFN. In addition, the RSRPDiff measurement value may be used to trigger a switch between PtP and PtM type of communications.

Based on the foregoing it should be apparent that the exemplary embodiments of this invention provide a method, apparatus and computer program(s) product to provide a UE procedure to make handover measurements at border cell areas of a MBSFN, where the location of the UE in the MBSFN is determined based on a channel quality-based approach and/or on an explicit control signal approach, such as via single cell MCCH. In accordance with the method, apparatus and computer program(s) of the preceding paragraph, for the channel quality-based approach the UE periodically measures at least one radio link metric including at least one of a SNIR of the MCCH/MCH, a reference symbol signal power (RSRP), or a RSRP Difference (RSRPDiff), which is the power difference between a cell common reference symbol and a cell-specific reference symbol.

In accordance with the method, apparatus and computer program(s) of the preceding paragraph, a threshold value is applied to the measured radio link metric to determine the location of the UE in the MBSFN, and to trigger at least one further measurement to support mobility, and/or to trigger mobility procedures.

In accordance with the method, apparatus and computer program(s) of the preceding paragraphs, in the explicit control signal approach all SFN border cells in a SFA notify the UE of its location via single cell MCCH.

In accordance with the method, apparatus and computer program(s) of the preceding paragraphs, further including detecting when a value of the RSRPDiff is below a threshold value, and in response triggering at an eNB a UE mobility procedure between different MMBS cells in the same or different MBMS transmission modes, such as a MBSFN mode, a single cell PtP mode, and a single cell PtM mode.

In accordance with the method, apparatus and computer program(s) of the preceding paragraphs, further including using the value of RSRPDiff to trigger between point-to-point communication operation and point-to-multipoint communication operation.

Based on the foregoing it should be apparent that the exemplary embodiments of this invention provide a device that comprises means for measuring radio signals at border cell areas of a MBSFN, and means for determining the location of the device in the MBSFN based on at least one of a channel quality-based approach and an explicit control signal approach, such as via single cell MCCH. The device of the preceding paragraph, where for the channel quality-based approach the device is configured to periodically measure at least one radio link metric including at least one of a SNIR of the MCCH/MCH, a reference symbol signal power (RSRP), or a RSRP Difference (RSRPDiff), which is the power difference between a cell common reference symbol and a cell-specific reference symbol, and further comprising means for reporting a measurement result.

In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the exemplary embodiments of this invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

As such, it should be appreciated that at least some aspects of the exemplary embodiments of the inventions may be practiced in various components such as integrated circuit chips and modules. It should thus be appreciated that the exemplary embodiments of this invention may be realized in an apparatus that is embodied as an integrated circuit, where the integrated circuit may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor, a digital signal processor, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention.

Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this invention.

For example, while the exemplary embodiments have been described above in the context of the 3GPP LTE MBMS system, it should be appreciated that the exemplary embodiments of this invention are not limited for use with only this one particular type of wireless communication system, and that they may be used to advantage in other wireless communication systems. As non-limiting examples, at least some aspects of the exemplary embodiments may be used with the Integrated Services Digital Broadcasting (ISDB), DVB-H (Digital Video Broadcasting-Handheld), and MediaFLO technologies.

It should be noted that the terms "connected," "coupled," or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are "connected" or "coupled" together. The coupling or connection between the elements can be physical, logical, or a combination thereof. As employed herein two elements may be considered to be "connected" or "coupled" together by the use of one or more wires, cables and/or printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as several non-limiting and non-exhaustive examples.

Furthermore, some of the features of the various non-limiting and exemplary embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.

Claims

CLAIMSWhat is claimed is:

1. A method, comprising:

determining a location of a user equipment in a multicast broadcast single frequency network using at least one of a channel quality-based approach and an explicit control signal approach; and

making handover measurements when it is determined that the user equipment is located in a border cell area of the multicast broadcast single frequency network.

2. The method of claim 1, where for the channel quality-based approach the method comprises periodically determining at least one radio link metric including a signal to noise plus interference ratio of a multicast control channel / multicast broadcast single frequency network channel.

3. The method of claim 1, where for the channel quality-based approach the method comprises periodically determining at least one radio link metric including a reference symbol signal power RSRP.

4. The method of claim 1, where for the channel quality-based approach the method comprises periodically determining at least one radio link metric including a reference symbol signal power RSRP Difference RSRPDiff, which is a power difference between a cell common reference symbol and a cell-specific reference symbol.

5. The method as in any of claims 2, 3 or 4, further comprising applying a threshold value to the radio link metric to at least one of determine the location of the user equipment in the multicast broadcast single frequency network, trigger at least one further measurement to support mobility, and trigger mobility procedures.

6. The method of claim 4, further comprising detecting when a value of the RSRPDiff is below a threshold value, and in response triggering a mobility procedure between different cells in same or different multimedia broadcast multicast service transmission modes.

7. The method of claim 6, where the multimedia broadcast multicast service transmission modes comprise at least one of a multicast broadcast single frequency network mode, a single cell point-to-point mode, and a single cell point-to-multipoint mode.

8. The method of claim 4, further comprising using the value of RSRPDiff to trigger moving between point-to-point communication operation and point-to-multipoint communication operation.

9. The method of claim 1, where the explicit control signal approach uses a single cell multicast control channel.

10. The method of claim 1, where in the explicit control signal approach single frequency network border cells in a single frequency area notify the user equipment of its location via a single cell multicast control channel.

11. A computer-readable medium that stores program instructions, the execution of the program instructions resulting in performance of operations that comprise:

12. The computer-readable medium of claim 11, where for the channel quality-based approach the method comprises periodically determining at least one radio link metric including a signal to noise plus interference ratio of a multicast control channel / multicast broadcast single frequency network channel.

13. The computer-readable medium of claim 11, where for the channel quality-based approach the method comprises periodically determining at least one radio link metric including a reference symbol signal power RSRP.

14. The computer-readable medium of claim 11, where for the channel quality-based approach the method comprises periodically determining at least one radio link metric including a reference symbol signal power RSRP Difference RSRPDiff, which is a power difference between a cell common reference symbol and a cell-specific reference symbol.

15. The computer-readable medium as in any of claims 12, 13 or 14, further comprising applying a threshold value to the radio link metric to at least one of determine the location of the user equipment in the multicast broadcast single frequency network, trigger at least one further measurement to support mobility, and trigger mobility procedures.

16. The computer-readable medium of claim 14, further comprising detecting when a value of the RSRPDiff is below a threshold value, and in response triggering a mobility procedure between different cells in same or different multimedia broadcast multicast service transmission modes.

17. The computer-readable medium of claim 16, where the multimedia broadcast multicast service transmission modes comprise at least one of a multicast broadcast single frequency network mode, a single cell point-to-point mode, and a single cell point-to-multipoint mode.

18. The computer-readable medium of claim 14, further comprising using the value of RSRPDiff to trigger moving between point-to-point communication operation and point-to-multipoint communication operation.

19. The computer-readable medium of claim 11, where the explicit control signal approach uses a single cell multicast control channel.

20. The computer-readable medium of claim 11, where in the explicit control signal approach single frequency network border cells in a single frequency area notify the user equipment of its location via a single cell multicast control channel.

21. An apparatus, comprising:

a controller configured with a radio frequency receiver to determine a location of a user equipment in a multicast broadcast single frequency network using at least one of a channel quality-based approach and an explicit control signal approach, said controller further configured to initiate the making of a handover measurement in response to the user equipment being located in a border cell area of the multicast broadcast single frequency network.

22. The apparatus of claim 21, where for the channel quality-based approach said controller is further configured to periodically determine at least one radio link metric including a signal to noise plus interference ratio of a multicast control channel / multicast broadcast single frequency network channel.

23. The apparatus of claim 21, where for the channel quality-based approach said controller is further configured to periodically determine at least one radio link metric including a reference symbol signal power RSRP.

24. The apparatus of claim 21, where for the channel quality-based approach said controller is further configured to periodically determine at least one radio link metric including a reference symbol signal power RSRP Difference RSRPDiff, which is a power difference between a cell common reference symbol and a cell-specific reference symbol.

25. The apparatus as in any of claims 22, 23 or 24, where said controller is further configured to apply a threshold value to the radio link metric to at least one of determine the location of the user equipment in the multicast broadcast single frequency network, trigger at least one further measurement to support mobility, and trigger mobility procedures.

26. The apparatus of claim 24, where said controller is further configured to detect when a value of the RSRPDiff is below a threshold value, and in response to trigger a mobility procedure between different cells in same or different multimedia broadcast multicast service transmission modes.

27. The apparatus of claim 26, where the multimedia broadcast multicast service transmission modes comprise at least one of a multicast broadcast single frequency network mode, a single cell point-to-point mode, and a single cell point-to-multipoint mode.

28. The apparatus of claim 24, where said controller is further configured to use the value of RSRPDiff to trigger moving between point-to-point communication operation and point-to-multipoint communication operation.

29. The apparatus of claim 21, where the explicit control signal approach uses a single cell multicast control channel.

30. The apparatus of claim 21, where said controller is further configured, when operating with the explicit control signal approach, to receive location information from single frequency network border cells in a single frequency area using a single cell multicast control channel.

31. A method, comprising:

operating a mobile apparatus to determine a difference in the received power between cell-specific and cell-common reference symbols in a multimedia broadcast multicast service channel; and

using the determined difference to at least make a determination as to whether the mobile apparatus is located in a multicast broadcast single frequency network border cell or in a multicast broadcast single frequency network center cell.

32. The method of claim 31, further using the determined difference to make a switch between a point-to-point service and a point-to-multipoint service.

33. The method of claim 31, further using the determined difference when making a handover decision.

34. The method of claim 31 where, in response to determining that the mobile apparatus is not located in a multicast broadcast single frequency network center cell, initiating a measurement procedure.

35. The method of claim 31, where the mobile apparatus initiates determining the difference in response to receiving a measurement event from a network access node.

36. The method of claim 35, further comprising reporting the determined difference to the network access node.

37. The method as in either claim 35 or claim 36, where the network access node is associated with a first single frequency network, and further comprising handing over to another network access node associated with a second single frequency network.

38. The method of claim 31, performed as a result of execution of program instructions stored in a memory medium of the mobile apparatus.

39. An apparatus, comprising: a controller configured to determine a difference in the received power between cell-specific and cell-common reference symbols in a multimedia broadcast multicast service channel and to use the determined difference to at least make a determination as to whether the mobile apparatus is located in a multicast broadcast single frequency network border cell or in a multicast broadcast single frequency network center cell.

40. The apparatus of claim 39, said controller further configured to use the determined difference to make a switch between a point-to-point service and a point-to-multipoint service.

41. The apparatus of claim 39, said controller further configured to report the determined difference for use in making a handover decision.

42. The apparatus of claim 39, said controller further configured, in response to determining that the mobile apparatus is not located in a multicast broadcast single frequency network center cell, to initiate a measurement procedure.

43. The apparatus of claim 39, said controller further configured to initiate determining the difference in response to receiving a measurement event from a network access node.

44. The apparatus of claim 43, said controller further configured to report the determined difference to the network access node.

44. The apparatus as in either claim 43 or claim 44, where the network access node is associated with a first single frequency network, and said controller is further configured to hand over to another network access node associated with a second single frequency network.