WO2014111463A1 - Robust measurement report event trigger for heterogeneous networks - Google Patents

Abstract

Robust Measurement Report Event Trigger for Heterogeneous Networks Certain embodiments generally relate to wireless communication systems, such as, but not limited to, the UTRAN, LTE, E-UTRAN, and/or LTE-A. For example, heterogeneous networks, which may include any of the preceding networks, may benefit from a robust measurement report event trigger. Such a robust measurement report event trigger may be provided by methods, apparatuses, and computer program products for optimizing user equipment measurements with independent event trigger quantity parameters for event triggers with multiple thresholds. One method can include expressing a first threshold in different units/quantities from a second threshold. The method may further include using existing ASN.1 Basic Encoding Rules for CHOICE type to indicate different quantities.

Description

Description Title

Robust Measurement Report Event Trigger for Heterogeneous Networks

CROSS-REFERENCE TO RELATED APPLICATION:

[0001] The present application is related to and claims the benefit and priority of U.S. Provisional Patent Application No. 61/754,276, filed January 18, 2013, the entirety of which is hereby incorporated by reference.

BACKGROUND:

Field:

[0002] Certain embodiments generally relate to wireless communication systems, such as, but not limited to, the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN), and/or LTE-Advanced (LTE-A). For example, heterogeneous networks, which may include any of the preceding networks, may benefit from a robust measurement report event trigger.

Description of the Related Art:

[0003] Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN) refers to a communications network including base stations, or Node Bs, and for example radio network controllers (RNC). UTRAN allows for connectivity between the user equipment (UE) and the core network. The RNC provides control functionalities for one or more Node Bs. The RNC and its corresponding Node Bs are called the Radio Network Subsystem (RNS). In case of E-UTRAN (enhanced UTRAN) no RNC exists and most of the RNC functionalities are contained in the eNodeB (evolved Node B, also called E- UTRAN Node B).

[0004] Long Term Evolution (LTE) or E-UTRAN refers to improvements of the UMTS through improved efficiency and services, lower costs, and use of new spectrum opportunities. In particular, LTE is a 3rd generation partnership project (3GPP) standard that provides for uplink peak rates of at least 50 megabits per second (Mbps) and downlink peak rates of at least 100 Mbps. LTE supports scalable carrier bandwidths from 20 MHz down to 1.4 MHz and supports both Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD). Advantages of LTE are, for example, high throughput, low latency, FDD and TDD support in the same platform, an improved end-user experience, and a simple architecture resulting in low operating costs.

[0005] Further releases of 3GPP LTE (e.g., LTE Rel-1 1 , LTE-Rel-12) are targeted towards future international mobile telecommunications advanced (IMT- A) systems, referred to herein for convenience simply as LTE-Advanced (LTE-A). LTE-A is directed toward extending and optimizing the 3GPP LTE radio access technologies. A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. LTE-A will be a more optimized radio system fulfilling the international telecommunication union- radio (ITU-R) requirements for IMT-Advanced while keeping the backward compatibility.

[0006] According to 3GPP TS 36.331 , Radio Resource Control ("RRC"); Protocol specification, (Release 10), 5.5.4.6 Event A5 (PCell becomes worse than thresholdl and neighbor becomes better than threshold2), UE is required to consider the entering condition for this event to be satisfied when both condition A5-1 and condition A5-2, as specified below, are fulfilled, and to consider the leaving condition for this event to be satisfied when condition A5-3 or condition A5-4, i.e., at least one of the two, as specified below, is fulfilled. The cell(s) that triggers the event is on the frequency indicated in indicated in the associated measObject which may be different from the (primary) frequency used by the PCell.

[0007] Inequality A5-1 (Entering condition 1 ): M_P + Hy_S < Threshi

[0008] Inequality A5-2 (Entering condition 2): Mn + ofn + Ocn - H_ys > Thresh!

[0009] Inequality A5-3 (Leaving condition 1 ): M_p - H_ys > Threshi

[0010] Inequality A5-4 (Leaving condition 2): Mn + ofn + Ocn + Hys < Thresh!

[0011] In the above formulas, Mp is the measurement result of the PCell, not taking into account any offsets. Mn is the measurement result of the neighboring cell, not taking into account any offsets. Ofn is the frequency specific offset of the frequency of the neighbor cell (i.e., offsetFreq as defined within measObjectEUTRA corresponding to the frequency of the neighbor cell). Ocn is the cell specific offset of the neighbor cell (i.e., celllndividualOffset as defined within measObjectEUTRA corresponding to the frequency of the neighbor cell), and set to zero if not configured for the neighbor cell. Hys is the hysteresis parameter for this event (i.e., hysteresis as defined within reportConfigEUTRA for this event). Threshl is the threshold parameter for this event (i.e., a5-Threshold1 as defined within reportConfigEUTRA for this event). Thresh2 is the threshold parameter for this event (i.e., A5-Threshold2 as defined within reportConfigEUTRA for this event). Mn, Mp are expressed in dBm in case of RSRP, or in dB in case of RSRQ. Ofn, Ocn, Hys are expressed in dB. Threshl is expressed in the same unit as Mp. Thresh2 is expressed in the same unit as Mn.

[0012] According to 3GPP TS 36.331 , Radio Resource Control (RRC); Protocol specification (Release 10), 5.5.5 Measurement reporting, for each included cell, the measurement report is required to include the layer 3 filtered measured results in accordance with the reportConfig for this measld, which should be ordered such that, if the measObject associated with this measld concerns E-UTRA, the measResult should be set to include the quantity/quantities indicated in the reportQuantity within the concerned reportConfig in order of decreasing triggerQuantity, i.e., the best cell is included first.

[0013] The IE ReportConfigEUTRA includes the reporting configuration of the measurements to be performed by UE. An example of ReportConfigEUTRA information element (TS 36.331 ) is shown in Figure 2. The field descriptions of ReportConfigEUTRA information element is provided in Figure 3.

[0014] The IE ReportConfigEUTRA specifies criteria for triggering an E- UTRAN measurement reporting event. According to a conventional 3GPP specification, both threshold 1 and threshold2 are assumed to be based on the same triggerQuantity, e.g., either RSRP or RSRQ. Therefore, for example, according to this conventional approach the UE is not able to trigger a measurement report when the serving cell RSRQ is worse than thresholdl and target RSRP is better than threshold2.

[0015] Nevertheless it is possible to choose the RSRP-Range as trigger quantity for thresholdl and the RSRQ-Range for threshold2 from the ASN.1 CHOICE ThresholdEUTRA. The ASN.1 BER (Basic Encoding Rules) encoding is just that of the chosen item. The decoder knows which quantity was encoded, because the tags of all alternatives in a choice are required to be distinct (ITU-T X.690 Specification of BER, Chp. 8.13). The triggerQuantity configured in reportConfigEUTRA is then only used for the ordering criteria in MeasResultEUTRA.

[0016] Such a methodology may result in early/late handovers, handovers to a wrong cell, ping-pong handovers with a short time of stay in the target cell, increased signaling load and handover failures associated with small cells and fast moving users.

SUMMARY:

[0017] According to certain embodiments, a method can include triggering a mobility event based on both a first threshold and a second threshold. The method can also include expressing the first threshold in different units, quantities, or units and quantities from the second threshold.

[0018] In certain embodiments, an apparatus can include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to trigger a mobility event based on both a first threshold and a second threshold. The at least one memory and the computer program code can also be configured to, with the at least one processor, cause the apparatus at least to express the first threshold in different units, quantities, or units and quantities from the second threshold. [0019] An apparatus, according to certain embodiments, can include means for triggering a mobility event based on both a first threshold and a second threshold. The apparatus can also include means for expressing the first threshold in different units, quantities, or units and quantities from the second threshold.

[0020] A non-transitory computer-readable medium can, in certain embodiments, be encoded with instructions that, when executed in hardware, perform a process. The process can include the above-described method.

[0021] A computer program product can, according to certain embodiments, encode instructions for performing a process. The process can include the above- described method.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0022] For proper understanding of the invention, reference should be made to the accompanying drawings, wherein:

[0023] Figure 1 illustrates RSRP and RSRQ for A5 trigger event quantity measurement.

[0024] Figure 2 illustrates an example of ReportConfigEUTRA information element of 3GPP TS 36.331.

[0025] Figure 3 illustrates field descriptions of ReportConfigEUTRA information element of 3GPP TS 36.331 .

[0026] Figure 4 illustrates a flow diagram of a method according to certain embodiments.

[0027] Figure 5a illustrates an apparatus according to an embodiment.

[0028] Figure 5b illustrates an apparatus according to another embodiment.

DETAILED DESCRIPTION:

[0029] It will be readily understood that the components of certain embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of embodiments of methods, systems, apparatuses, and computer program products for mobility robustness, as represented in the attached figures, is not intended to limit the scope of the invention, but is merely representative of selected embodiments of the invention.

[0030] If desired, the different functions discussed below may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the described functions may be optional or may be combined. As such, the following description should be considered as merely illustrative of the principles, teachings and embodiments, and not in limitation thereof.

[0031] Certain embodiments more particularly relate to enhancements of measurement reporting event triggers and handovers in a multi-layer cellular network, where users are moving at different velocities. Multi-layer networks can also be referred to as heterogeneous networks ("HetNet"). In this context, multilayer refers to cases with a mixture of macro base stations and small power base stations (e.g., pico and micro). A multi-layer LTE network is used as an example for describing certain embodiments, although other embodiments could be applied to other cellular standards as well. A macro-layer and a pico/micro layer may be implemented in a different radio access technology (RAT), for example, high speed packet access (HSPA) macro layer and LTE micro layer.

[0032] Measurement reporting configuration can define how user equipment ("UE") will report the radio environment to a network. A measurement report can act as an input to network mobility management in a connected mode. The measurement report event triggers are specified in 3GPP technical specification (TS) 36.331 , section 5.5.4, "Measurement report triggering," in which triggers are labeled as Am (m = 1...6 for intra-RAT), and Bn (n=1...2 for inter-RAT mobility). 3GPP TS 36.331 is hereby incorporated herein by reference.

[0033] Mobility performance in the "RRC_Connected" state can be based on the UE measurements configured by the network. The UE can perform the configured measurements. When the measurement report event trigger conditions are fulfilled, the UE can prepare a measurement report. One example measurement report event trigger in HetNet is A5, which can trigger a measurement report when the serving cell is worse than thresholdl and the target is better than threshold2. These thresholds together can be compared to either Reference Signal Received Power ("RSRP") or Reference Signal Received Quality ("RSRQ") when conditioning the event trigger entry or leaving condition. RSRP and RSRQ are defined in 3GPP TS 36.214, which is hereby incorporated herein by reference.

[0034] Figure 1 illustrates RSRP and RSRQ for A5 trigger event quantity measurement. In an example conventional co-channel scenario, UE can be located in proximity of small cells, and can experience radio conditions where the current macro cell connection is limited by RSRQ due to the interference coming from the small cell, and hence a mobility event may be needed. In order to trigger a measurement report based on the A5 entry condition, the target cell also needs to be measured using the same RSRQ quantity, which needs to be better than threshold2.

[0035] This poses potential mobility robustness challenges because the macro cell is not able to maintain connection and the target cell RSRQ is not better than threshold2. In practice, this means that when the serving cell is running outside of the target quality (RSRQ) and the target cell quality is not stable enough to meet the RSRQ threshold2 within TimeToTrigger, UE is not able to trigger a measurement report even if it would be located within the coverage (RSRP) of the target cell. Similarly, a conventional example in HetNet, a fast moving UE located in a co-channel small cell may need to perform a quick outbound handover to a macro cell due to degradation of the serving RSRQ cell quality. The event trigger can be more robust toward the macro footprint if the trigger quantity could be selected by a configuration process to be either RSRP or RSRQ, independent of the serving cell threshold quantity.

[0036] The RSRQ measurement can be useful when detecting a poor radio condition, which is likely to cause a radio link failure. A low value of RSRQ also implies that there is a high likelihood of a low value of signal to interference and noise ratio (SINR). Therefore, with low value of RSRQ there is a high probability that radio link failure detection has started (e.g. by T310 timer as specified by 3GPP TS 36.331 ). In such a case it is advantageous to try to connect to another cell. The main cause of decrease in RSRQ and SINR is the co-channel interfering signal received from the cell being approached. The level of interfering signal depends on the load in the target cell, which means that the RSRQ is a load- dependent measure. Similarly, signal from the current serving cell acts as interference load towards the cell being approached. In both cases the interfering signals and load from other neighboring cells have an influence on the RSRQ measure. The RSRQ is a good indicator of poor radio conditions in the serving cell, but it is not a good measure for target cell coverage. On the contrary, the RSRP measurement of the target cell signal exceeding the given threshold is better indicator of having entered the coverage area of this cell. As an example, the A5 measurement event can be used to detect when the radio conditions are poor in the serving cell, while UE is in the coverage area of another cell. This would imply triggering based on RSRQ for serving cell being lower than given threshold, thresholds while RSRP for the other cell being above given threshold, threshold2, which demands for specifying the two threshold with different quantities (RSRQ and RSRP), and a trigger implementation that compares these thresholds to the measurement of corresponding quantity.

[0037] Another issue is related to fast moving users and mobility state estimation (MSE), where a fluctuating source and/or target cell quality (e.g. due to instantaneous load variation of bursty traffic) and scaled down TimeToTrigger by MSE, (3GPP TS 36.331 , which is hereby incorporated by reference) may trigger unnecessary measurement reports and short time of stay in target cells after the handover when the measurement quantities cannot be independently configured.

[0038] Other cases are also possible where independent trigger quantities would be useful.

[0039] Accordingly, certain embodiments provide a method and a device to, for example, optimize the UE measurements with independent event trigger quantity parameters for event triggers with multiple thresholds. Event trigger A5 is used as an example, but also other measurements instances with multiple event trigger thresholds are possible.

[0040] Figure 4 illustrates a flow diagram of a method, according to certain embodiments. The method can be used to optimize UE measurements with independent event trigger quantity parameters for event triggers with multiple thresholds. As mentioned above, event trigger A5 is simply one illustrative example.

[0041] The method can include an enhanced measurement configuration and reporting configuration, allowing definition of event trigger quantities for event trigger entry and leaving condition thresholds, where the event trigger quantities can represent measured signal power and/or quality. Thus, for example, at 410, the method can include expressing a first threshold using different units or quantities than a second threshold. The method can also include, at 420, using existing ASN.1 Basic Encoding Rules for CHOICE type to indicate different quantities.

[0042] In the RRC idle state, the event trigger specific parameters can be signaled to UE using the broadcasted System Information Blocks ("SIB"). Moreover, implementations can use existing ASN.1 types and encoding to indicate different quantities.

[0043] According to certain embodiments, it can be specified in a standard like 3GPP TS 36.331 , that a first threshold, such as Thresh 1 , can be expressed in different unit/quantity than a second threshold, such as Thresh2. Moreover, ReportConfigEUTRA field descriptions can be modified, such that the description for triggerQuantity indicates that in case an event has more than one threshold criteria (e.g. A5) the triggerQuantity is only used for the ordering in measResultEUTRA and the quantities used for evaluation of the triggering conditions are taken from choice ThresholdEUTRA for each threshold.

[0044] Hence, certain embodiments can improve the robustness of measurement reporting and provide more options for measurement configuration, especially in HetNet with co-channel intra-frequency deployments.

[0045] Certain embodiments can also improve the UE reporting accuracy and/or relevance of reporting, and can reduce the instances of early/late handovers, ping-pong handovers and handovers to a wrong cell. For fast moving users, certain embodiments can reduce the number of handovers with short time of stay in target cell and reduce handover failures associated with small cells. All these benefits can also contribute to reducing the signaling load as more robust measurement reporting in RRC connected state can be achieved.

[0046] Certain embodiments can be used to complement a "Gray-listing" approach for mobility performance optimization. For more information about Gray- listing, 3GPP RAN2 contribution "R2-124027, "Mobility State Estimation and HetNet" can be referenced, which is hereby incorporated by reference.

[0047] Certain embodiments can be used to complement the "HetNet mobility enhancements for LTE" Working Item Description "RP-122007" in 3GPP standardization body, where one of the objective is to standardize improvements to overall HO performance with regard to HO failure rate and ping-pong in HetNet environments, which is hereby incorporated by reference.

[0048] Enhanced measurement event triggers can be used to support mobility event optimization using both mobility state estimation and different source/target cell type characteristics.

[0049] For non-stationary and irregularly moving users, the enhanced measurements can solve the problem related to diverse user mobility profiles, and parameters do not need to be a compromise between slowly moving and fast moving user profiles.

[0050] Self-Organizing networks ("SON") and customer experience management ("CEM") can also use the mobility information and differentiate the user performance by defining UE specific parameters per measurement report event trigger. SON methods may thus avoid the generic pedestrian parameters that are not optimum for stationary user and are also not optimum for fast moving users.

[0051] Figure 5a illustrates an example of an apparatus 10 according to an embodiment. In one embodiment, apparatus 10 may be a base station (BS), such as an eNB, or access point (AP). It should be noted that one of ordinary skill in the art would understand that apparatus 10 may include components or features not shown in Figure 5a. Only those components or features selected for illustration of certain embodiments are depicted in Figure 5a.

[0052] As illustrated in Figure 5a, apparatus 10 includes a processor 22 for processing information and executing instructions or operations. Processor 22 may be any type of general or specific purpose processor. While a single processor 22 is shown in Figure 5a, multiple processors may be utilized according to other embodiments. In fact, processor 22 may include one or more of general- purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples.

[0053] Apparatus 10 further includes a memory 14, which may be coupled to processor 22, for storing information and instructions that may be executed by processor 22. Memory 14 may be one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory 5 device and system, fixed memory, and removable memory. For example, memory 14 can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, or any other type of non-transitory machine or computer readable media. The instructions stored in memory 14 may include program instructions or computer i o program code that, when executed by processor 22, enable the apparatus 10 to perform tasks as described herein.

[0054] Apparatus 10 may also include one or more antennas 25 for transmitting and receiving signals and/or data to and from apparatus 10. Apparatus 10 may further include a transceiver 28 configured to transmit and

15 receive information. For instance, transceiver 28 may be configured to modulate information on to a carrier waveform for transmission by the antenna(s) 25 and demodulates information received via the antenna(s) 25 for further processing by other elements of apparatus 10. In other embodiments, transceiver 28 may be capable of transmitting and receiving signals or data directly.

20 [0055] Processor 22 may perform functions associated with the operation of apparatus 10 including, without limitation, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus 10, including processes related to management of communication resources.

25 [0056] In an embodiment, memory 14 stores software modules that provide functionality when executed by processor 22. The modules may include, for example, an operating system that provides operating system functionality for apparatus 10. The memory may also store one or more functional modules, such as an application or program, to provide additional functionality for apparatus 10.

30 The components of apparatus 10 may be implemented in hardware, or as any suitable combination of hardware and software.

[0057] As mentioned above, according to one embodiment, apparatus 10 may be a BS or AP. In an embodiment, apparatus 10 may be controlled, by memory 14 and processor 22, to perform or cooperate with the method illustrated in Figure 35 4 or any of the methods described herein.

[0058] Figure 5b illustrates an example of an apparatus 20 according to another embodiment. In an embodiment, apparatus 20 may be network element. It should be noted that one of ordinary skill in the art would understand that apparatus 20 may include components or features not shown in Figure 5b. Only those components or features selected for illustration of certain embodiments are depicted in Figure 5b.

[0059] As illustrated in Figure 5b, apparatus 20 includes a processor 32 for processing information and executing instructions or operations. Processor 32 may be any type of general or specific purpose processor. While a single processor 32 is shown in Figure 5b, multiple processors may be utilized according to other embodiments. In fact, processor 32 may include one or more of general- purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples.

[0060] Apparatus 20 further includes a memory 34, which may be coupled to processor 32, for storing information and instructions that may be executed by processor 32. Memory 34 may be one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and removable memory. For example, memory 34 can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, or any other type of non-transitory machine or computer readable media. The instructions stored in memory 34 may include program instructions or computer program code that, when executed by processor 32, enable the apparatus 20 to perform tasks as described herein.

[0061] Apparatus 20 may also include one or more antennas 35 for transmitting and receiving signals and/or data to and from apparatus 20. Apparatus 20 may further include a transceiver 38 configured to transmit and receive information. For instance, transceiver 38 may be configured to modulate information on to a carrier waveform for transmission by the antenna(s) 35 and demodulates information received via the antenna(s) 35 for further processing by other elements of apparatus 20. In other embodiments, transceiver 38 may be 5 capable of transmitting and receiving signals or data directly.

[0062] Processor 32 may perform functions associated with the operation of apparatus 20 including, without limitation, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus 20, i o including processes related to management of communication resources.

[0063] In an embodiment, memory 34 stores software modules that provide functionality when executed by processor 32. The modules may include, for example, an operating system that provides operating system functionality for apparatus 20. The memory may also store one or more functional modules, such

15 as an application or program, to provide additional functionality for apparatus 20.

The components of apparatus 20 may be implemented in hardware, or as any suitable combination of hardware and software.

[0064] As mentioned above, according to one embodiment, apparatus 20 may be a network element. In this embodiment, apparatus 20 may be controlled by 20 memory 34 and processor 32 to carry out or cooperate in the method described in Figure 4.

[0065] According to certain embodiments, a method can include triggering a mobility event based on both a first threshold and a second threshold. The method can also include expressing the first threshold in different units, quantities, or units 25 and quantities from the second threshold. The method may further include using existing ASN.1 Basic Encoding Rules for CHOICE type to indicate different quantities.

[0066] In certain embodiments, an apparatus may include at least one processor and at least one memory including computer program code. The at least one

30 memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to trigger a mobility event based on both a first threshold and a second threshold. The at least one memory and the computer program code can also be configured to, with the at least one processor, cause the apparatus at least to express the first threshold in different units, quantities, or

35 units and quantities from the second threshold. The at least one memory and the computer program code can further be configured to, with the at least one processor, cause the apparatus at least to use existing ASN.1 Basic Encoding Rules for CHOICE type to indicate different quantities.

[0067] According to certain embodiments, an apparatus can include means for triggering a mobility event based on both a first threshold and a second threshold. The apparatus can also include means for expressing the first threshold in different units, quantities, or units and quantities from the second threshold. The apparatus may further include means for using existing ASN.1 Basic Encoding Rules for CHOICE type to indicate different quantities.

[0068] A non-transitory computer-readable medium is, in certain embodiments, encoded with instructions that, when executed in hardware, perform a process. The process can include triggering a mobility event based on both a first threshold and a second threshold. The process can also include expressing the first threshold in different units, quantities, or units and quantities from the second threshold. The process may further include using existing ASN.1 Basic Encoding Rules for CHOICE type to indicate different quantities.

[0069] One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention.

[0070] Glossary

[0071] 3GPP 3rd Generation Partnership Project

[0072] BER Basic Encoding Rules

[0073] CEM Customer Experience Management

[0074] E-UTRAN Evolved-Universal Terrestrial Radio Access Network

[0075] LTE Long Term Evolution

[0076] LTE-Advanced Long Term Evolution-Advanced

[0077] MSE Mobility State Estimation

[0078] PCell Primary Cell

[0079] RAT Radio Access Technology

[0080] SIB System Information Block [0081] Self-Organizing Network

[0082] Radio Resource Control

[0083] Time To Trigger

[0084] User Equipment (for example, terminal)

Claims

1. A method, comprising:

triggering a mobility event based on both a first threshold and a second threshold; and

expressing the first threshold in different units, quantities, or units and quantities from the second threshold.

2. The method of claim 1 , further comprising:

using existing ASN.1 Basic Encoding Rules for CHOICE type to indicate different quantities.

3. The method of claim 1 or claim 2, wherein the first threshold corresponds to a serving cell and the second threshold corresponds to a cell other than the serving cell.

4. The method of any of claims 1 -3, wherein the first threshold comprises a value of reference signal received quality.

5. The method of any of claims 1-4, wherein the second threshold comprises a value of reference signal received power.

6. The method of any of claims 1-5, wherein the first threshold is met when a value is lower than the threshold.

7. The method of any of claims 1 -6, wherein the second threshold is met when a value is greater than the threshold.

8. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to

trigger a mobility event based on both a first threshold and a second threshold; and

express the first threshold in different units, quantities, or units and quantities from the second threshold.

9. The apparatus of claim 8, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to use existing ASN.1 Basic Encoding Rules for CHOICE type to indicate different quantities.

10. The apparatus of claim 8 or claim 9, wherein the first threshold corresponds to a serving cell and the second threshold corresponds to a cell other than the serving cell.

1 1. The apparatus of any of claims 8-10, wherein the first threshold comprises a value of reference signal received quality.

12. The apparatus of any of claims 8-1 1 , wherein the second threshold comprises a value of reference signal received power.

13. The apparatus of any of claims 8-12, wherein the first threshold is met when a value is lower than the threshold.

14. The apparatus of any of claims 8-13, wherein the second threshold is met when a value is greater than the threshold.

15. An apparatus, comprising:

means for triggering a mobility event based on both a first threshold and a second threshold; and

means for expressing the first threshold in different units, quantities, or units and quantities from the second threshold.

16. The apparatus of claim 15, further comprising:

means for using existing ASN.1 Basic Encoding Rules for CHOICE type to indicate different quantities.

17. The apparatus of claim 15 or claim 16, wherein the first threshold corresponds to a serving cell and the second threshold corresponds to a cell other than the serving cell.

18. The apparatus of any of claims 15-17, wherein the first threshold comprises a value of reference signal received quality.

19. The apparatus of any of claims 15-18, wherein the second threshold comprises a value of reference signal received power.

20. The apparatus of any of claims 15-19, wherein the first threshold is met when a value is lower than the threshold.

21. The apparatus of any of claims 15-20, wherein the second threshold is met when a value is greater than the threshold.

22. A non-transitory computer-readable medium encoded with instructions that, when executed in hardware, perform a process, the process comprising the method according to any of claims 1-7.

23. A computer program product encoding instructions for performing a process, the process comprising the method according to any of claims 1-7.