WO2015094084A1

WO2015094084A1 - Radio link failure events

Info

Publication number: WO2015094084A1
Application number: PCT/SE2014/051438
Authority: WO
Inventors: Walter Müller
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2013-12-16
Filing date: 2014-12-03
Publication date: 2015-06-25

Abstract

Methods of performing measurement reporting in a wireless device operating in a wireless communication network are disclosed. An example method comprises receiving (210) an offset parameter value, from the wireless communication network,comparing (220) one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a predetermined radio link failure threshold value for the wireless device, and detecting (230) a reporting trigger event, based on said comparing. This example method further comprises sending (240) a measurement report to the wireless communication network, in response to said detecting.

Description

RADIO LINK FAILURE EVENTS

TECHNICAL FIELD

The techniques and apparatus disclosed herein are generally related to wireless communication networks, and are more particularly related to the triggering of radio measurements and/or measurement reporting by wireless devices in such networks.

BACKGROUND

The 3 -Generation Partnership Project (3 GPP) continues to develop specifications for wireless networks known generally as the UMTS Terrestrial Radio Access Network

(UTRAN), often referred to as the Wideband Code-Division Multiple Access (WCDMA) network, and the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also commonly referred to as the LTE (Long Term Evolution) network. For both networks, the 3GPP has defined so-called "events" for triggering radio measurements and/or measurement reports by wireless devices, which are referred to as "user equipment" or "UEs" in 3 GPP terminology. In an LTE network, these events are configured by the base station, referred to as eNodeBs or eNBs in LTE documentation, while in UTRAN the events are configured by the Radio Network Controller (RNC). In both cases, the configuration of the events are made via Radio Resource Control (RRC) signaling. In LTE the RRC signaling is performed directly between the base station (eNB) and UE while in UTRAN the RRC signaling is performed between the RNC and UE via the base station, referred to as NodeB or NB in documentation for UTRAN. See, for example, the detailed requirements for performing and reporting measurements in LTE networks provided in section 5.5 of the 3 GPP document 3 GPP TS 36.331, v. 10.8.0 (December 2012), available at http://www.3gpp.org .

When a UE is connected to a wireless network, if radio link conditions between the UE and its serving cell deteriorate beyond a certain point then the UE determines that a Radio Link Failure (RLF) has occurred. RLF triggers certain actions by the UE, such as the initiation of a Radio Resource Control (RRC) re-establishment procedure. The UE is configured by the network (e.g., via RRC signaling) with one or more parameters that control the RLF triggering conditions for the UE. For LTE systems, these are described in section 5.3.11 of the same 3GPP document (3GPP TS 36.331) referenced above.

In the 3 GPP specifications, measurement value ranges and thresholds are typically defined based on minimum accuracy requirements for the values reported and the channel conditions. However, UE vendors are reluctant to permit the specification of measurements at very low signal levels, since the accuracy of radio measurements is difficult to predict and high accuracy is difficult to achieve in poor radio conditions. One consequence of this is that the channel conditions corresponding to the signal levels for which measurements and measurement accuracies are specified may be substantially different from the channel conditions under which RLF (Radio Link failure) is triggered by UE. This difference may be even larger for UEs that use more advanced receiver techniques, such as interference cancellation techniques.

Improved techniques for triggering measurement reports are needed.

SUMMARY

For optimal network performance, it is advantageous in many circumstances to allow

UEs to operate as close as possible to the level at which an RLF is triggered, while not letting conditions get worse than that level. To facilitate this, the wireless network needs to receive timely measurement reports that indicate when the link conditions for a particular UE are approaching the RLF level and/or when link conditions for the UE are improving from a level that is close to the RLF level.

However, one problem with conventional solutions for configuring events for triggering measurement reports is that the e B cannot define event thresholds at very low channel qualities, e.g., at levels very close to the level at which RLF is triggered by the UE. This problem is exacerbated by the fact that the RLF triggering point is different for different UEs, depending on the particular implementation and usage of advanced receiver techniques for each UE. Furthermore, if diversity schemes are introduced, the RLF levels for involved UEs will differ from minimum defined measurement levels. While it is possible with conventional solutions to configure Layer 3 conditions for RLF triggering, at least to some extent, the particular channel conditions at which RLF is triggered for any given UE still depend upon the receiver design and performance for that UE.

The techniques and apparatus described herein allow the system to define an event that does not use any particular measured signal quantity as the reference point for the event, but instead uses a typical level at which RLF is triggered by an individual UE for the reference point. The resulting event thus occurs at a UE-specific signal quality level that can take into account the UE's design and the use of advanced receiver techniques at the relevant time. These techniques and apparatus allow the wireless network to avoid that a given UE triggers RLF while at the same time letting the UE operate as close as possible to this level. Furthermore, these techniques allow the network (e.g., an eNB or RNC) to use the same Layer 3 parameter settings for all UEs, while allowing each individual UE to make the best use of its own implemented advantages.

Generally speaking, several of the techniques and apparatus described herein provide for the defining of a new event, according to which the UE should trigger a measurement report when it detects that a measured signal quality passes below or above a level that differs from the RLF level for the UE by an offset value, e.g., X dB, where X is an system- configured parameter (e.g., via RRC signaling) and the RLF triggering level is at least to some extent dependent on the UE's individual design and/or dependent on the usage of interference cancellation techniques and typically relates to block errors for a given signal- to-interference-plus-noise ratio (SINR) for reception of a control channel, such as for reception of the LTE Physical Downlink Control Channel (PDCCH). The new event may also apply already defined mechanisms for measurement reporting, such as the use of a Time- to-Trigger timer.

Example embodiments of the presently disclosed techniques include methods implemented in a wireless device operating in a wireless communication network, such as an LTE network (E-UTRAN) or WCDMA/HSPA network (UTRAN). One such method comprises receiving an offset parameter value, from the wireless communication network, comparing one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a predetermined radio link failure threshold value for the wireless device, and detecting a reporting trigger event, based on said comparing. This example method further comprises sending a measurement report to the wireless

communication network, in response to said detecting.

In some embodiments of this method, the predetermined radio link failure threshold value may be selected from a plurality of threshold values, based on the wireless device's usage of one of several receiver techniques or modes. Likewise, the predetermined radio link failure threshold value may be selected from a plurality of threshold values, based on whether or not a diversity mode and/or interference cancellation technique is employed.

In some embodiments of this method, the event threshold is further based on a hysteresis parameter value. In some of these embodiments, detecting the reporting trigger event comprises detecting that a measured serving cell signal quality has become higher than the predetermined radio link failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value. In other embodiments or in other instances, detecting the reporting trigger event comprises detecting that a measured serving cell signal quality has become lower than the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value. In any of these embodiments, sending the measurement report may be conditioned upon determining that the detected reporting trigger event is sustained for at least a predetermined length of time. For example, in some embodiments the triggering of the measurement report may be conditioned upon first determining that a measured serving cell signal quality has become higher than the predetermined radio link failure threshold value by an amount greater than the sum of the offset parameter and the hysteresis parameter value and subsequently determining that the measured signal quality has not fallen below a threshold level equal to the sum of the predetermined radio link failure threshold value and the offset parameter, less the hysteresis parameter value, over a predetermined time period. In other embodiments or in other instances, the triggering of the measurement report may be conditioned upon first

determining that a measured serving cell signal quality has become lower than the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value, and then subsequently determining that the measured signal quality has not risen above a threshold level equal to the sum of the predetermined radio link failure threshold, the offset parameter value, and the hysteresis parameter value, over a predetermined time period.

In some embodiments of the methods summarized above, the radio link

measurements comprise one or more block-error estimations, or signal-to-interference-plus- noise ratio (SINR) estimations, or one or more Reference Signal Received Power (RSRP) measurements, or one or more Reference Signal Received Quality (RSRQ) measurements, or one or more of each. In various embodiments, the measured serving cell signal quality may be based on a single radio link measurement or on a combination of one or more radio link measurements.

Other example embodiments of the presently disclosed techniques include methods for configuring and receiving measurement reports, as implemented in a base station in a wireless communication. According to one such method, the base station sends a first offset parameter to the wireless device, and subsequently receives a measurement report from the wireless device. The measurement report indicates that it was triggered based on an event threshold that is based on the offset parameter value and a predetermined radio-link-failure threshold value for the wireless device, e.g., by the inclusion of a measurement identifier that corresponds to a triggering event threshold that is based on a UE-specific threshold. In some of these embodiments, the base station also sends a hysteresis parameter to the wireless device, and the measurement report indicates that it was triggered based on a determination that a radio link measurement value has become higher than the predetermined radio-link- failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

Other embodiments, detailed below, include wireless device apparatus and base station apparatus, including radio circuitry and processing circuitry configured to control the radio circuitry and to carry out one or more of the methods summarized above, or variants thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic diagram illustrating a portion of an example Long-Term Evolution (LTE) network.

Figure 2 is a process flow diagram illustrating an example method of performing measurement reporting in a wireless device operating in a wireless communication network.

Figure 3 illustrates examples of Event CI, where a time-to-trigger condition is imposed before a measurement report is sent.

Figure 4 is a process flow diagram illustrating an example method carried out by a base station, such as an LTE eNodeB.

Figure 5 is a block diagram illustrating a node in which network-based techniques disclosed herein may be implemented.

Figure 6 is a block diagram illustrating features of an example wireless device according to some embodiments of the presently disclosed techniques and apparatus.

Figure 7 is a block diagram illustrating another representation of a wireless device configured to carry out one or more of the disclosed techniques.

DETAILED DESCRIPTION

Within the context of this disclosure, the terms "wireless terminal" or "wireless device" encompass any terminal that is able to communicate wirelessly with an access node of a wireless network by transmitting and/or receiving wireless signals. Thus, the term "wireless terminal" encompasses, but is not limited to: a user equipment (e.g., an LTE UE), a mobile terminal, a stationary or mobile wireless device for machine-to-machine

communication, an integrated or embedded wireless card, an externally plugged in wireless card, a dongle etc. Throughout this disclosure, the terms "user equipment" and "UE" are sometimes used to exemplify various embodiments. However, this should not be construed as limiting, as the concepts illustrated herein are equally applicable to other wireless terminals. Hence, whenever a "user equipment" or "UE" is referred to in this disclosure, this should be understood as encompassing any wireless terminal or wireless device as defined above.

In the discussion that follows, specific details of particular embodiments of the presently disclosed techniques and apparatus are set forth for purposes of explanation and not limitation. It will be appreciated by those skilled in the art that other embodiments may be employed apart from these specific details. Furthermore, in some instances detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted so as not to obscure the description with unnecessary detail. Those skilled in the art will appreciate that the functions described may be implemented in one or in several nodes.

Some or all of the functions described may be implemented using hardware circuitry, such as analog and/or discrete logic gates interconnected to perform a specialized function, ASICs, PLAs, etc. Likewise, some or all of the functions may be implemented using software programs and data in conjunction with one or more digital microprocessors or general purpose computers. Where nodes that communicate using the air interface are described, it will be appreciated that those nodes also have suitable radio communications circuitry. Moreover, the technology can additionally be considered to be embodied entirely within any form of computer-readable memory, including non-transitory embodiments such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.

Hardware implementations may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions.

In terms of computer implementation, a computer is generally understood to comprise one or more processors or one or more controllers, and the terms computer, processor, and controller may be employed interchangeably. When provided by a computer, processor, or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed. Moreover, the term "processor" or "controller" also refers to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.

References throughout the specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment.

Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

While the following examples are described in the context of handover in LTE systems, the principles described in the following disclosure may be equally applied to other functional contexts and other cellular networks, including, for example, cellular networks based on 3GPP standards for W-CDMA networks.

A simplified diagram of a portion of an example LTE network is shown in Figure 1.

The LTE network is also known as the Evolved UMTS Terrestrial Radio Access Network (E- UTRAN). The E-UTRAN is made up of eNBs, which are connected to each other via the X2 interface, and which are connected to at least one Mobility Management Entity (MME) and one or more Serving Gateway (S-GW) nodes by the SI interface. The MME is used for control plane signaling on the SI interface, while the S-GW is used for the SI user plane. The E-UTRAN may be supplemented by home eNBs (HeNBs) or other low-power nodes, and HeNB GW entities, which are also linked to the other nodes of the network via the SI and X2 interfaces.

In LTE networks, the radio link is monitored by the UE using Qin and Qout status, as specified by the 3GPP. Details may be found in chapter 4.2.1 of the 3GPP document 3GPP TS 36.213, v. 10.10.0 (June 2013) and chapter 7.6 of the 3 GPP document 3 GPP TS 36.133, vlO.12.0 (Sept. 2013), both of which documents are available at http://www.3gpp.org .

The UE estimates the downlink radio link quality and compares it to the thresholds Qout and Qin for the purpose of monitoring downlink radio link quality of the primary cell (PCell). The threshold Qout is defined as the level at which the downlink radio link cannot be reliably received, and corresponds to a 10% block-error rate of a hypothetical Physical Downlink Control Channel (PDCCH) transmission, taking into account errors on the Physical Control Format Indicator Channel (PCFICH). The threshold Qin is defined as the level at which the downlink radio link quality can be significantly more reliably received than at Qout, and corresponds to a 2% block-error rate of a hypothetical PDCCH transmission, taking into account PCFICH errors.

The UE is also configured, via RRC signaling, with parameters N310, N311 and T310. These parameters control UE RLF trigger conditions as detailed in chapter 5.3.11 of the 3 GPP document 3 GPP TS 36.331, v. 10.8.0 (Dec. 2012). Following is a simplified description, adapted from that document:

Detection of physical layer problems in RRC CONNECTED: The UE shall, upon receiving N310 consecutive "out-of-sync" indications for the PCell from lower layers, start timer T310. Recovery of physical layer problems: Upon receiving N311 consecutive "in- sync" indications for the PCell from lower layers while T310 is running, the UE shall stop timer T310. Detection of radio link failure: At T310 timeout the UE shall initiate the connection re-establishment procedure.

Similar parameters and procedures for monitoring radio link configurations for radio link failure are specified for UEs operating in Wideband Code-Division Multiple Access (WCDMA) networks. Details may be found, for example, in chapter 6.4.4 of the 3GPP document 3 GPP TS 25.101, 12.1.0 (Sept. 2013), available at http://www.3gpp.org .

Additional details may be found in 3 GPP TS 25.302, 3 GPP 25.214, and 3 GPP 25.331, each of which may also be found at http://www.3gpp.org .

In the 3 GPP specifications, measurement value ranges and thresholds are typically defined based on minimum accuracy requirements for the values reported and the channel conditions. However, UE vendors are reluctant to permit the specification of measurements at very low signal levels, since the accuracy of radio measurements is difficult to predict and high accuracy is difficult to achieve in poor radio conditions. One consequence of this is that the channel conditions corresponding to the lowest signal levels for which measurements and measurement accuracies are specified may be substantially different from the channel conditions when just before RLF (Radio Link failure) is triggered by UE. This difference may be larger for UE's that use more advanced receiver techniques, such as interference cancellation techniques.

For example, according to Release 11 of the 3 GPP specifications for LTE, the lowest value for Reference Signal Received Quality (RSRQ) threshold is -19.5 dB. However, using advanced receivers, RSRQ values down to -28 dB have been observed from UE's in connected mode. UE vendors have agreed to the establishment of -19.5 dB as lowest point for accuracy requirements. However, the RSRQ definition and the corresponding measurement requirements are the same, whether or not advanced receivers are used.

In addition, if diversity techniques are used then RLF conditions typically need to be fulfilled for all diversity branches before RLF is triggered. As a result, radio measurements performed on only a single branch do not reflect the probability for the UE to trigger RLF.

Some events are used to trigger Inter-Radio Access Technology (IRAT) handover or release with redirect, when LTE conditions are bad enough to motivate moving the UE to another LTE frequency or RAT, or to spend more resources to secure communication during these conditions. If the system were reliably informed of which UEs were close to their respective RLF levels, the system could this information to give those higher priority in scheduling, for example, or to provide more power to these UEs to avoid RLF being triggered.

As noted above, it is advantageous in many circumstances to allow UEs to operate as close as possible to the level at which an RLF is triggered, while not letting conditions get worse than that level. To facilitate this, the wireless network needs to receive timely measurement reports that indicate when the link conditions for a particular UE are approaching that level and/or when link conditions for the UE are improving from a level that is close to the RLF level.

However, one problem with conventional solutions for configuring events for triggering measurement reports is that the base station cannot define event thresholds at very low channel qualities, e.g., at levels very close to the level at which RLF is triggered by the UE. This problem is exacerbated by the fact that the RLF triggering point is different for different UEs, depending on the particular implementation and usage of advanced receiver techniques for each UE. Furthermore, if certain interference cancellation techniques and diversity schemes are introduced, the RLF levels for involved UEs may differ from minimum defined measurement levels. While it is possible with conventional solutions to configure Layer 3 (L3) conditions for RLF triggering, at least to some extent, the channel conditions at which RLF is triggered for any given UE still depend upon the receiver design and performance for that UE. As a consequence, the base station cannot use a fixed setting for "poor coverage" event thresholds, since the actual thresholds need to be different for different UEs.

The techniques and apparatus described herein allow the system to define an event that does not use any particular measured signal quantity as the reference point for the event, but instead uses a typical level at which RLF is triggered by an individual UE for the reference point. The resulting event thus occurs at a UE-specific signal level that takes into account the UE's design and the use of advanced receiver techniques at the relevant time. These techniques and apparatus allow the wireless network to avoid that a given UE triggers RLF, while at the same time letting the UE operate as close as possible to this level.

Generally speaking, several of the techniques and apparatus described herein provide for the defining of a new event, according to which the UE should trigger a measurement report when it detects that a measured signal quality passes below or above a level that differs from the RLF level for the UE by an offset value, e.g., X dB, where X is a system-configured parameter (e.g., via RRC signaling) and where the RLF triggering level is at least to some extent dependent on the UE's individual design and/or dependent on the usage of advanced receiver techniques, e.g., interference cancellation techniques, and diversity. The RLF triggering level typically relates to block-error estimates and signal-to-interference-plus-noise ratio (SINR) for reception of a control channel, such as for reception of the LTE Physical Downlink Control Channel (PDCCH).

The new event may also apply already defined mechanisms for measurement reporting, such as the use of a Time-to-Trigger timer and hysteresis. In the context of LTE and WCDMA systems, the techniques described herein can be implemented as a new event in an already existing framework for configuring and triggering measurements and

measurement reports. (See, e.g., 3GPP TS 36.331 vlO.8.0, ch. 5.5.) A UE-expected Layer 1 RLF trigger level is used as a new "quantity" in this existing framework.

Example embodiments of the presently disclosed techniques include methods implemented in a wireless device operating in a wireless communication network, such as an LTE network (E-UTRAN) or WCDMA/HSPA network (UTRAN). One such method is illustrated in Figure 2 and includes receiving an offset parameter value from the wireless communication network, e.g., from an LTE e B, as shown at block 210. As shown at block 220, the method continues with comparing one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a predetermined radio link failure threshold value for the wireless device. As shown at block 230, the method includes detecting a reporting trigger event, based on said comparing. In response to detecting the event, a measurement report is sent to the wireless communication network, as shown at block 240. In some embodiments of this method, the predetermined radio link failure threshold value may be selected from a plurality of threshold values, based on the wireless device's usage of one of several receiver techniques or modes. An example of an operating mode that may drive the selection of a particular radio link failure threshold value in some embodiments is the use of carrier aggregation or dual connectivity. The use of one or more of these operating modes may mean that one or more of the receivers in the phone are occupied, so that they cannot be used to achieve diversity gain on a connection for which the RLF threshold value applies. Likewise, the predetermined radio link failure threshold value may be selected from a plurality of threshold values, based on whether or not an interference cancellation technique is employed. Accordingly, the method illustrated in Figure 2 includes the step of selecting the RLF threshold value, as shown at block 215. However, this operation is shown with a dashed outline, indicating that this operation is optional in the sense that it need not be present in every embodiment or in every instance of the illustrated method.

It should be appreciated that while Figure 2 illustrates the detection of only a single triggering event, the specific triggering event may be any of several possible triggering events that are based on the offset parameter value and the radio link failure (RLF) threshold value for the wireless device. It should also be appreciated that a single wireless device may be configured to detect several of these triggering events. Further, it should be noted that the offset parameter value that may be set differently for different measurement

configurations/reporting configurations, in some embodiments. For instance, the system (e.g., the e B or RNC) can configure the same UE with two events that are of the same type but that use different offsets. The system can distinguish which event triggered any resulting measurement report by recognizing a measurement identifier accompanying the report, in some embodiments. In these embodiments, the measurement identifier is a unique number for that links measurement object, reporting configuration and quantity configuration together.

In some embodiments, the offset parameter value can take on either positive or negative values. For instance, the offset parameter may have a range of -15 dB to +15 dB, with 0.5 dB resolution.

Thus, for instance, in various embodiments and/or instances of the method, the triggered event corresponds to the signal quality for a serving cell becoming higher or lower than the sum of the radio link failure (RLF) threshold value for the wireless device and the offset parameter value. In other words, the triggered event indicates that the signal quality for the serving cell has become better than the RLF threshold value by an amount established by the offset, or has become worse than this level. In any of these methods, the level for triggering the event may be adjusted up (for upwards-triggered events) or down (for downwards-triggered events) by a hysteresis parameter value. The triggering may also be conditioned by a requirement that the level stay above the threshold level (for upwards- triggered events) or below the threshold level (for downwards-triggered events) for a predetermined period of time, which may be represented by a particular number of measurement instances.

For example, in some embodiments, detecting the reporting trigger event comprises detecting that a measured serving cell signal quality has become higher than the

predetermined radio link failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value. In other embodiments or in other instances, detecting the reporting trigger event comprises detecting that a measured serving cell signal quality has become lower than the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value.

In any of these embodiments, sending the measurement report may be conditioned upon determining that the detected reporting trigger event is sustained for at least a predetermined length of time, which may have been provided to the UE by the network. For example, in some embodiments the triggering of the measurement report may be conditioned upon first determining that a measured serving cell signal quality has become higher than the predetermined radio link failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value and subsequently determining that the measured signal quality has not fallen below a threshold level equal to the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value, for a predetermined time interval beginning at the time the measured signal quality first exceeded the first threshold. These two levels may be defined as two separate events, corresponding to two different measurement identifiers, in some embodiments.

In other embodiments or in other instances, the triggering of the measurement report may be conditioned upon first determining that a measured serving cell signal quality has become lower than the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value, and then subsequently determining that the measured signal quality has not risen above a threshold level equal to the sum of the predetermined radio link failure threshold, the offset parameter value, and the hysteresis parameter value, for a predetermined time interval following the time at which it was determined that the signal quality fell below the first threshold. Once again, these two levels may be defined as two separate events, corresponding to two different measurement identifiers, in some embodiments.

In some embodiments of the methods described above, the radio link measurements comprise one or more Reference Signal Received Power (RSRP) measurements or Reference Signal Received Quality (RSRQ) measurements, or one or more of each. Other radio link measurements that might be used include estimated block-error rates and/or estimated signal- to-interference-plus-noise ratios. Bit-error rates might also be used; these can be determined from block-error rates in some embodiments. In various embodiments, the measured serving cell signal quality may be based on a single radio link measurement or on a combination of two or more radio link measurements, one or more of which may be performed on any of various control channels, such as the Physical Downlink Control Channel (PDCCH).

Example definitions of these events, as defined in the context of an LTE system, are provided below. These events are referred to here as "Event CI" and "Event C2." Of course, variations of these events (as well as of their names) are possible. Further, it will be appreciated that similar events may be defined for other wireless networks.

Event CI: Serving cell signal quality becomes better than threshold level based on absolute RLF trigger level—

The UE shall:

• consider the entering condition for this event to be satisfied when

condition Cl-1, as specified below, is fulfilled;

• consider the leaving condition for this event to be satisfied when condition Cl-2, as specified below, is fulfilled;

• for this measurement, consider the primary or secondary cell that is

configured on the frequency indicated in the associated measObjectEUTRA to be the serving cell;

Inequality Cl-1 (Entering condition) :

Ms - Hys > RLFlevel + Offset

Inequality Cl-2 (Leaving condition) :

Ms + Hys < RLFlevel + Offset The variables in the formula are defined as follows:

Ms is the measurement result of the serving cell, not taking into account any offsets.

Hys is the hysteresis parameter for this event (i.e. hysteresis as defined within reportConfigEUTRA for this event).

RLF level is the RSRP or RSRQ level when RLF will trigger for this UE. Ms is expressed in dBm in case of RSRP, or in dB in case of RSRQ.

Hys is expressed in dB.

Offset is expressed in dB.

Event C2: Serving cell signal quality becomes worse than threshold level based on absolute RLF trigger level—

The UE shall:

• consider the entering condition for this event to be satisfied when

condition C2-1, as specified below, is fulfilled;

• consider the leaving condition for this event to be satisfied when condition C2-2, as specified below, is fulfilled;

• for this measurement, consider the primary or secondary cell that is

Inequality C2-1 (Entering condition) :

Ms + Hys < RLFlevel + Offset

Inequality C2-2 (Leaving condition) :

Ms - Hys > RLFlevel + Offset

The variables in the formula are defined as follows:

RLF level is the RSRP or RSRQ level when RLF will trigger for this UE Ms is expressed in dBm in case of RSRP, or in dB in case of RSRQ.

Hys is expressed in dB.

Offset is expressed in dB. For each of the events defined above, the UE may be configured to send an event- triggered measurement report if the entering conditions have been fulfilled during a "time-to- trigger" interval, during which same interval the leaving conditions have been not been fulfilled. Figure A illustrates examples of Event CI, where a time-to-trigger condition is imposed before a measurement report is sent; it will be appreciated that there are two triggered events (of the Event CI type), each of which results in the sending of a

measurement report.

Figure 3 illustrates examples of Event CI, where a time-to-trigger condition is imposed before a measurement report is sent. As can be seen in the figure, a rising signal quality passes through a UE-specific RLF level and then through an adjusted RLF level determined by adding an offset to the UE-specific RLF level. The signal quality

subsequently exceeds the adjusted RLF level by a hysteresis quantity, at which instant a time- to-trigger (TTT) timer is triggered. Since the signal quality stays high (above the adjusted RLF level plus the hysteresis parameter) for the entire TTT interval, a measurement report is initiated, as shown in the figure. Subsequently, the signal quality level falls below the adjusted RLF level, less the hysteresis quantity, and stays below that level for the TTT interval, which means that the signal quality has "left" the event CI condition. Accordingly, when the signal quality subsequently rises again, and once more satisfies the TTT condition, a second measurement report is initiated.

It should also be appreciated that a UE may be configured for both events CI and C2; in this case, the offsets used in CI and C2 may be the same or may differ. A given UE may also be configured with more than one event of the same type (CI and/or C2), with the different events of the same type having different offset parameter values. The UE may be adapted to send a measurement identifier along with a triggered measurement report, the measurement identifier identifying the configured event that triggered the report.

It should be further understood that the events CI and C2 described above are only examples of the triggering events that may be defined using a UE-specific RLF threshold. Some events might be compound events involving multiple cells, for example. For instance, one possible event can be paraphrased as "Signal quality for a first cell (e.g., a serving cell) falls to below a level of RLF+Offset, and signal quality for a second cell (e.g., a neighbor cell) becomes better than a second threshold." Another possible event might be paraphrased as "signal quality for first cell (e.g., serving cell) falls to below a level of RLF+Offset, and signal quality for an inter-RAT cell becomes better than a second threshold." In the preceding discussion and in the detailed examples provided, it was generally assumed that the various signal quality levels, threshold values, offset parameter values, and hysteresis parameter values are specified in logarithmic form, e.g., with signal levels and corresponding thresholds being expressed in dBm and offsets and other parameters expressed in dB. Under these assumptions, the event triggering thresholds may be readily computed using simple additions and subtractions. Those familiar with radio measurements will appreciate, however, that the operations and expressions provided above may be performed using linear quantities, in which case additions and subtractions are replaced with

multiplication and division operations, respectively. It will be appreciated that these two approaches are equivalent.

It should also be appreciated that operations complementary to those illustrated in Figure 2 are carried out by a base station, such as an LTE eNB. Accordingly, Figure 4 illustrates a method, implemented in a base station, for configuring and receiving

measurement reports. As shown at block 410, the illustrated method begins with the sending of an offset parameter value to the wireless device. In some embodiments, the base station may also send a hysteresis parameter. As shown at block 420, the base station subsequently receives a measurement report from the wireless device, where the measurement report is triggered based on an event trigger threshold that is based on the offset parameter value and an RLF threshold value for the wireless device (and, if applicable, the hysteresis parameter). The specific triggering event, and thus the fact that the event trigger threshold that triggered the report was based on the offset parameter value and a UE-specific RLF threshold value may be indicated by the inclusion of a particular measurement identifier in the report, for example, where the measurement identifier corresponds to a triggering event threshold that is based on a UE-specific threshold. The base station may take further actions, such as triggering a handover, based on the received measurement report.

Advantages realizable with the new triggering events described above, which are based on the use of UE-specific RLF levels as reference levels, include that the base station (e.g., an LTE eNB) can let each UE fully exploit its available receiver performance (e.g., using advanced receivers) in bad radio conditions, e.g., to stay on LTE as long as possible. The new events allow the base station to control the margin for avoid RLF, without obtaining UE-specific RLF performance information for the UE, thus allowing time to trigger inter- frequency or inter-radio access technology (IRAT) handover or Release with Redirect. New UE implementations with either better or worse RLF performance can easily be used while still using the same eNB solution. Also, if new schemes like interference cancellation and or diversity are introduced then the events can still be used by eNB without the need for eNB changes.

Several of the techniques and processes described above can be implemented in a network node, such as an eNodeB (eNB) or HeNB. Figure 5 is a schematic illustration of a node 1 in which a method embodying any of the presently described network-based techniques can be implemented.

A computer program for controlling the node 1 to carry out a method embodying any of the presently disclosed techniques is stored in a program storage 30, which comprises one or several memory devices. Data used during the performance of a method embodying the present invention is stored in a data storage 20, which also comprises one or more memory devices, one or more of which may be the same as those used for program storage 30, in some embodiments. During performance of a method embodying the present invention, program steps are fetched from the program storage 30 and executed by a Central Processing Unit (CPU) 10, retrieving data as required from the data storage 20. Output information resulting from performance of a method embodying the present invention can be stored back in the data storage 20, or sent to an Input/Output (I/O) interface 40, which includes a network interface for sending and receiving data to and from other network nodes, e.g., via an X2 and/or SI interface, and which may also include a radio transceiver for communicating with one or more terminals. The CPU 10 and its associated data storage 20 and program storage 30 may collectively be referred to as a "processing circuit." It will be appreciated that variations of this processing circuit are possible, including circuits include one or more of various types of programmable circuit elements, e.g., microprocessors, microcontrollers, digital signal processors, field-programmable application-specific integrated circuits, and the like, as well as processing circuits where all or part of the processing functionality described herein is performed using dedicated digital logic.

Accordingly, in various embodiments of the invention, processing circuits, such as the CPU 10, data storage 20, and program storage 30 in Figure 5, are configured to carry out one or more of the techniques described in detail above. More particularly, for example, the illustrated node 1 may represent means for sending a first offset parameter value to a first wireless device and subsequently receiving a measurement report from the first wireless device, where the measurement report indicates that it was triggered based on an event threshold calculated from the first offset parameter value and a predetermined radio-link- failure threshold value for the first wireless device. Likewise, it should be appreciated that the processing circuit, when configured with appropriate program code, may be understood to comprise several functional "modules," where each module comprises program code for carrying out the corresponding function, when executed by an appropriate processor. Thus, node 1 may be understood to comprise a "sending module" for sending a first offset parameter to a first wireless device and a "receiving module" for subsequently receiving a measurement report from the first wireless device, where the measurement report indicates that it was triggered based on an event threshold calculated from the first offset parameter value and a predetermined radio-link-failure threshold value for the first wireless device. While some embodiments may comprise an e B or He B in an LTE network, for example, other embodiments may include base station nodes and/or radio network controllers designed for operation in other types of networks and including one or more such processing circuits. In some cases, these processing circuits are configured with appropriate program code, stored in one or more suitable memory devices, to implement one or more of the techniques described herein. Of course, it will be appreciated that not all of the steps of these techniques are necessarily performed in a single microprocessor or even in a single module.

Figure 6 illustrates features of an example wireless device 600 that can be used in one or more of the non-limiting example embodiments described herein. UE 600 comprises a transceiver circuit 620 configured to communicate with one or more base stations as well as a processing circuit 610 for processing the signals transmitted and received by the transceiver unit 620. Transceiver circuit 620 includes a transmitter 625 coupled to one or more transmit antennas 628 and receiver 630 coupled to one or more receiver antennas 633. The same antenna(s) 628 and 633 may be used for both transmission and reception.

Receiver 630 and transmitter 625 use known radio processing and signal processing components and techniques, typically according to a particular telecommunications standard such as the 3GPP standards for LTE. Note also that transceiver circuit 620 may comprise separate radio and/or baseband circuitry for each of two or more different types of radio communication, such as radio/baseband circuitry adapted for E-UTRAN access and separate radio/baseband circuitry adapted for D2D communication; thus, transceiver circuit 620 may also be configured to carry out D2D communications with one or more other UEs, likewise using standardized protocols. The same applies to the antennas - while in some cases one or more antennas may be used for accessing multiple types of networks or for multiple modes of communication, in other cases one or more antennas may be specifically adapted to a particular radio access network or communication mode. Because the various details and engineering tradeoffs associated with the design and implementation of such circuitry are well known and are unnecessary to a full understanding of the invention, additional details are not shown here.

Processing circuit 610 comprises one or more processors 640 coupled to one or more memory devices 650 that make up a data storage memory 655 and a program storage memory 660. Processor 640, identified as CPU 640 in Figure 6, may be a microprocessor, microcontroller, or digital signal processor, in some embodiments. More generally, processing circuit 610 may comprise a processor/firmware combination, or specialized digital hardware, or a combination thereof. Memory 650 may comprise one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc. Because terminal 600 supports a cellular radio access network in addition to D2D communications, processing circuit 610 may include separate processing resources dedicated to one or several radio access technologies or radio communications modes, in some embodiments. Again, because the various details and engineering tradeoffs associated with the design of baseband processing circuitry for mobile devices are well known and are unnecessary to a full understanding of the invention, additional details are not shown here.

Typical functions of the processing circuit 610 include modulation and coding of transmitted signals and the demodulation and decoding of received signals. In several embodiments of the present invention, processing circuit 610 is adapted, using suitable program code stored in program storage memory 660, for example, to carry out one of the techniques described above for performing event-triggered measurement reporting.

Figure 7 is another representation of a wireless device that is configured to carry out one or more of the techniques described herein. In this case, a wireless device 700 is represented as comprising several functional circuits, each of which may comprise one or more processing circuits and/or analog circuits. It will be appreciated that two or more of the functional circuits shown in Figure 7 may be implemented using a single processing circuit. It will be further be appreciates that each of one or more of these functional circuits may be understood to correspond to a functional "module," which may in turn correspond to program code that carries out the corresponding function when executed by a suitable processor.

Wireless device 700 includes a receiving circuit 710 for receiving an offset parameter value from the wireless communication network, e.g., from an LTE e B. Receiving circuit comprises a measurement circuit 715, for performing radio measurements. Wireless device 700 further includes a comparing circuit 730 for comparing one or more radio link measurements to a threshold that is based on an application of the offset parameter value to a predetermined radio link failure threshold value for the wireless device, as well as an event detecting circuit for detecting a reporting trigger event, based on the results of the comparing by comparing circuit 730. In response to detecting the event, a measurement report is sent to the wireless communication network, using measurement reporting circuit 750.

In some embodiments of this method, the predetermined radio link failure threshold value may be selected from a plurality of threshold values, based on the wireless device's usage of one of several receiver techniques or modes. Likewise, the predetermined radio link failure threshold value may be selected from a plurality of threshold values, based on whether or not an interference cancellation technique is employed. Accordingly, the wireless device 700 includes a RLF threshold value selecting circuit 720 for selecting the predetermined radio link failure threshold value from the plurality of possible values. However, this circuit is shown with a dashed outline, indicating that this circuit is optional in the sense that it need not be present in every embodiment of the illustrated device.

In view of the detailed examples described above, it will be appreciated that embodiments of the presently disclosed technology include, but are not limited to, the example embodiments listed below.

1. A method of performing measurement reporting in a wireless device operating in a wireless communication network, the method comprising: receiving an offset parameter value from the wireless communication network; comparing one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a predetermined radio-link-failure threshold value for the wireless device; detecting a reporting trigger event, based on said comparing; and sending a measurement report to the wireless communication network, in response to said detecting.

2. The method of example embodiment 1, wherein the method further comprises, prior to said comparing, selecting the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, based on the wireless device's usage of one of a plurality of receiver techniques or modes.

3. The method of example embodiment 1, wherein the method further comprises, prior to said comparing, selecting the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, based on whether an interference cancellation technique is employed by the wireless device.

4. The method of example embodiment 1, wherein the method further comprises, prior to said comparing, selecting the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, based on whether a diversity mode is employed by the wireless device.

5. The method of any of example embodiments 1-4, wherein the event threshold is calculated by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link-failure threshold value for the wireless device, such that detecting the reporting trigger event comprises detecting that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

6. The method of any of example embodiments 1-4, wherein the event threshold is calculated by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link-failure threshold value for the wireless device, such that detecting the reporting trigger event comprises detecting that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio-link-failure threshold value and the offset parameter value, less the hysteresis parameter value.

7. The method of any of example embodiments 1-6, wherein sending the

measurement report to the wireless network is conditioned on determining that the detected reporting trigger event is sustained for at least a predetermined length of time.

8. The method of example embodiment 7, wherein sending the measurement report to the wireless network is conditioned on determining that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter and the hysteresis parameter value and subsequently determining that the measured signal quality has not fallen below a threshold level equal to the sum of the predetermined radio link failure threshold value and the offset parameter, less the hysteresis parameter value, over a predetermined time period.

9. The method of example embodiment 7, wherein sending the measurement report to the wireless network is conditioned on determining that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value, and subsequently determining that the measured signal quality for a serving cell has not risen above a threshold level equal to the sum of the predetermined radio-link-failure threshold, the offset parameter value, and the hysteresis parameter value, over a predetermined time period.

10. The method of any of example embodiments 1-9, wherein the radio link measurements comprise one or more of any of the following: block-error estimations; signal- to-interference-plus-noise ratio, SINR, estimations; Reference Signal Received Power, RSRP, measurements; and Reference Signal Received Quality, RSRQ, measurements.

11. A method, in a base station in a wireless communication system, for configuring and receiving measurement reports from a wireless device, the method comprising: sending a first offset parameter value to the wireless device; and subsequently receiving a measurement report from the wireless device, wherein the measurement report indicates that it was triggered based on an event threshold that is based on the offset parameter value and a predetermined radio-link-failure threshold value for the wireless device.

12. The method of example embodiment 11, further comprising sending a hysteresis parameter to the wireless device, wherein the measurement report indicates that it was triggered based on a determination that a radio link measurement value has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

13. A wireless device for operating in a wireless communication network, the wireless device comprising a transceiver circuit configured to communicate with one or more base stations and a processing circuit operatively coupled to the transceiver circuit and configured to: receive an offset parameter value from the wireless communication network, using the transceiver circuit; compare one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a predetermined radio-link-failure threshold value for the wireless device; detect a reporting trigger event, based on said comparing; and send a measurement report to the wireless communication network, using the transceiver circuit, in response to said detecting.

14. The wireless device of example embodiment 13, wherein the processing circuit is further configured to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, based on the wireless device's usage of one of a plurality of receiver techniques or modes.

15. The wireless device of example embodiment 13, wherein the processing circuit is further configured to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, based on whether an interference cancellation technique is employed by the wireless device.

16. The wireless device of example embodiment 13, wherein the processing circuit is further configured to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, based on whether a diversity mode is employed by the wireless device.

17. The wireless device of any of example embodiments 13-16, wherein the processing circuit is configured to calculate the event threshold by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link-failure threshold value for the wireless device, such that the processing circuit is configured to detect the reporting trigger event by detecting that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

18. The wireless device of any of example embodiments 13-16, wherein the processing circuit is configured to calculate the event threshold by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link-failure threshold value for the wireless device, such that the processing circuit is configured to detect the reporting trigger event by detecting that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio-link-failure threshold value and the offset parameter value, less the hysteresis parameter value.

19. The wireless device of any of example embodiments 13-18, wherein the processing circuit is configured to condition the sending of the measurement report to the wireless network on a determination that the detected reporting trigger event is sustained for at least a predetermined length of time.

20. The wireless device of example embodiment 19, wherein the processing circuit is configured to condition the sending of the measurement report to the wireless network on (i) a determination that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter and the hysteresis parameter value and (ii) a subsequent determination that the measured signal quality has not fallen below a threshold level equal to the sum of the predetermined radio link failure threshold value and the offset parameter, less the hysteresis parameter value, over a predetermined time period. 21. The wireless device of example embodiment 19, wherein the processing circuit is configured to condition the sending of the measurement report to the wireless network on (i) a determination that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value, and (ii) a subsequent determination that the measured signal quality has not risen above a threshold level equal to the sum of the predetermined radio-link-failure threshold, the offset parameter value, and the hysteresis parameter value, over a predetermined time period.

22. The wireless device of any of example embodiments 13-21, wherein the processing circuit is configured to use the radio transceiver circuit to perform radio link measurements comprising one or more of any of the following: block-error estimations; signal-to-interference-plus-noise ratio (SINR) estimations; Reference Signal Received Power (RSRP) measurements; and Reference Signal Received Quality (RSRQ) measurements.

23. A wireless device for operating in a wireless communication network, the wireless device adapted to: receive an offset parameter value from the wireless communication network; compare one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a predetermined radio-link-failure threshold value for the wireless device; detect a reporting trigger event, based on said comparing; and send a measurement report to the wireless communication network, in response to said detecting.

24. The wireless device of example embodiment 23, wherein the wireless device is further adapted to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, prior to said comparing, based on the wireless device's usage of one of a plurality of receiver techniques or modes.

25. The wireless device of example embodiment 23, wherein the wireless device is further adapted to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, prior to said comparing, based on whether an interference cancellation technique is employed by the wireless device.

26. The wireless device of example embodiment 23, wherein the wireless device is further adapted to select the predetermined radio-link- failure threshold value from a plurality of predetermined threshold values, prior to said comparing, based on whether a diversity mode is employed by the wireless device. 27. The wireless device of any of example embodiments 23-26, wherein the wireless device is further adapted to calculate the event threshold by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link-failure threshold value for the wireless device, such that the wireless device detects the reporting trigger event by detecting that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

28. The wireless device of any of example embodiments 23-26, wherein the wireless device is further adapted to calculate the event threshold by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link-failure threshold value for the wireless device, such that the wireless device detects the reporting trigger event by detecting that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio-link-failure threshold value and the offset parameter value, less the hysteresis parameter value.

29. The wireless device of any of example embodiments 23-28, wherein the wireless device is further adapted to send the measurement report to the wireless network conditioned on a determination that the detected reporting trigger event is sustained for at least a predetermined length of time.

30. The wireless device of example embodiment 29, wherein the wireless device is further adapted to send the measurement report to the wireless network conditioned on a determination that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter and the hysteresis parameter value and a subsequent determination that the measured signal quality has not fallen below a threshold level equal to the sum of the predetermined radio link failure threshold value and the offset parameter, less the hysteresis parameter value, over a predetermined time period.

31. The wireless device of example embodiment 29, wherein the wireless device is further adapted to send the measurement report to the wireless network conditioned on a determination that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value, and a subsequent determination that the measured signal quality for a serving cell has not risen above a threshold level equal to the sum of the predetermined radio-link-failure threshold, the offset parameter value, and the hysteresis parameter value, over a predetermined time period.

32. The wireless device of any of example embodiments 23-31, wherein the radio link measurements comprise one or more of any of the following: block-error estimations; signal- to-interference-plus-noise ratio, SINR, estimations; Reference Signal Received Power, RSRP, measurements; and Reference Signal Received Quality, RSRQ, measurements.

33. A wireless device for operating in a wireless communication network, the wireless device comprising a receiving module for receiving an offset parameter value from the wireless communication network; a comparing module for comparing one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a predetermined radio-link-failure threshold value for the wireless device; a detection module for detecting a reporting trigger event, based on said comparing; and a sending module for sending a measurement report to the wireless communication network, in response to said detecting.

34. A base station for use in a wireless communication network, the base station comprising a processing circuit configured to: send a first offset parameter value to a first wireless device; and subsequently receive a measurement report from the first wireless device, wherein the measurement report indicates that it was triggered based on an event threshold calculated from the first offset parameter value and a predetermined radio-link- failure threshold value for the first wireless device.

35. The base station of example embodiment 34, wherein the processing circuit is further configured to send a hysteresis parameter to the first wireless device, wherein the measurement report indicates that it was triggered based on a determination that a radio link measurement value has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

36. A base station for use in a wireless communication network, the base station adapted to: send a first offset parameter value to a first wireless device; and to subsequently receive a measurement report from the first wireless device; wherein the measurement report indicates that it was triggered based on an event threshold calculated from the first offset parameter value and a predetermined radio-link-failure threshold value for the first wireless device. 37. The base station of example embodiment 36, wherein the base station is further adapted to send a hysteresis parameter to the wireless device, wherein the measurement report indicates that it was triggered based on a determination that a radio link measurement value has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

38. A base station for use in a wireless communication network, the base station comprising: a sending module for sending a first offset parameter value to a first wireless device; and a receiving module for subsequently receiving a measurement report from the first wireless device, wherein the measurement report indicates that it was triggered based on an event threshold calculated from the first offset parameter value and a predetermined radio- link-failure threshold value for the first wireless device.

Examples of several embodiments of the present techniques have been described in detail above, with reference to the attached illustrations of specific embodiments. Because it is not possible, of course, to describe every conceivable combination of components or techniques, those skilled in the art will appreciate that the inventive techniques and apparatus disclosed herein can be implemented in other ways than those specifically set forth herein, without departing from essential characteristics of those techniques and apparatus. The present embodiments are thus to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS What is claimed is:

1. A method of performing measurement reporting in a wireless device operating in a wireless communication network, the method comprising:

receiving (210) an offset parameter value from the wireless communication network; comparing (220) one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a predetermined radio- link-failure threshold value for the wireless device;

detecting (230) a reporting trigger event, based on said comparing; and

sending (240) a measurement report to the wireless communication network, in

response to said detecting.

2. The method of claim 1, wherein the method further comprises, prior to said comparing, selecting (215) the predetermined radio-link- failure threshold value from a plurality of predetermined threshold values, based on the wireless device's usage of one of a plurality of receiver techniques or modes.

3. The method of claim 1, wherein the method further comprises, prior to said comparing, selecting (215) the predetermined radio-link- failure threshold value from a plurality of predetermined threshold values, based on whether an interference cancellation technique is employed by the wireless device.

4. The method of claim 1, wherein the method further comprises, prior to said comparing, selecting (215) the predetermined radio-link- failure threshold value from a plurality of predetermined threshold values, based on whether a diversity mode is employed by the wireless device.

5. The method of any of claims 1-4, wherein the event threshold is calculated by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link- failure threshold value for the wireless device, such that detecting (230) the reporting trigger event comprises detecting that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

6. The method of any of claims 1-4, wherein the event threshold is calculated by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link- failure threshold value for the wireless device, such that detecting (230) the reporting trigger event comprises detecting that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio-link-failure threshold value and the offset parameter value, less the hysteresis parameter value.

7. The method of any of claims 1-6, wherein sending (240) the measurement report to the wireless network is conditioned on determining that the detected reporting trigger event is sustained for at least a predetermined length of time.

8. The method of claim 7, wherein sending (240) the measurement report to the wireless network is conditioned on determining that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter and the hysteresis parameter value and subsequently determining that the measured signal quality has not fallen below a threshold level equal to the sum of the predetermined radio link failure threshold value and the offset parameter, less the hysteresis parameter value, over a predetermined time period.

9. The method of claim 7, wherein sending (240) the measurement report to the wireless network is conditioned on determining that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value, and subsequently determining that the measured signal quality for a serving cell has not risen above a threshold level equal to the sum of the predetermined radio-link-failure threshold, the offset parameter value, and the hysteresis parameter value, over a predetermined time period.

10. The method of any of claims 1-9, wherein the radio link measurements comprise one or more of any of the following:

block-error estimations;

signal-to-interference-plus-noise ratio, SINR, estimations;

Reference Signal Received Power, RSRP, measurements; and Reference Signal Received Quality, RSRQ, measurements.

11. A method, in a base station in a wireless communication system, for configuring and receiving measurement reports from a wireless device, the method comprising:

sending (410) a first offset parameter value to the wireless device; and

subsequently receiving (420) a measurement report from the wireless device, wherein the measurement report indicates that it was triggered based on an event threshold that is based on the offset parameter value and a predetermined radio-link-failure threshold value for the wireless device.

12. The method of claim 11, further comprising sending a hysteresis parameter to the wireless device, wherein the measurement report indicates that it was triggered based on a determination that a radio link measurement value has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

13. A wireless device (600) for operating in a wireless communication network, the wireless device comprising

a transceiver circuit (620) configured to communicate with one or more base stations and

a processing circuit (610) operatively coupled to the transceiver circuit (620) and configured to:

receive an offset parameter value from the wireless communication network, using the transceiver circuit (620);

compare one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a

predetermined radio-link-failure threshold value for the wireless device

(600);

detect a reporting trigger event, based on said comparing; and send a measurement report to the wireless communication network, using the transceiver circuit (620), in response to said detecting.

14. The wireless device (600) of claim 13, wherein the processing circuit (610) is further configured to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, based on the wireless device's usage of one of a plurality of receiver techniques or modes.

15. The wireless device (600) of claim 13, wherein the processing circuit (610) is further configured to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, based on whether an interference cancellation technique is employed by the wireless device.

16. The wireless device (600) of claim 13, wherein the processing circuit (610) is further configured to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, based on whether a diversity mode is employed by the wireless device.

17. The wireless device (600) of any of claims 13-16, wherein the processing circuit (610) is configured to calculate the event threshold by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link-failure threshold value for the wireless device, such that the processing circuit (610) is configured to detect the reporting trigger event by detecting that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

18. The wireless device (600) of any of claims 13-16, wherein the processing circuit (610) is configured to calculate the event threshold by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link-failure threshold value for the wireless device, such that the processing circuit (610) is configured to detect the reporting trigger event by detecting that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio-link-failure threshold value and the offset parameter value, less the hysteresis parameter value.

19. The wireless device (600) of any of claims 13-18, wherein the processing circuit (610) is configured to condition the sending of the measurement report to the wireless network on a determination that the detected reporting trigger event is sustained for at least a predetermined length of time.

20. The wireless device (600) of claim 19, wherein the processing circuit (610) is configured to condition the sending of the measurement report to the wireless network on (i) a determination that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter and the hysteresis parameter value and (ii) a subsequent determination that the measured signal quality has not fallen below a threshold level equal to the sum of the predetermined radio link failure threshold value and the offset parameter, less the hysteresis parameter value, over a predetermined time period.

21. The wireless device (600) of claim 19, wherein the processing circuit (610) is configured to condition the sending of the measurement report to the wireless network on (i) a determination that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value, and (ii) a subsequent determination that the measured signal quality has not risen above a threshold level equal to the sum of the predetermined radio-link- failure threshold, the offset parameter value, and the hysteresis parameter value, over a predetermined time period.

22. The wireless device (600) of any of claims 13-21, wherein the processing circuit (610) is configured to use the radio transceiver circuit (620) to perform radio link measurements comprising one or more of any of the following:

block-error estimations;

signal-to-interference-plus-noise ratio (SINR) estimations;

Reference Signal Received Power (RSRP) measurements; and

Reference Signal Received Quality (RSRQ) measurements.

23. A wireless device (600) for operating in a wireless communication network, the wireless device (600) adapted to:

receive an offset parameter value from the wireless communication network; compare one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a predetermined radio-link- failure threshold value for the wireless device (600);

detect a reporting trigger event, based on said comparing; and

send a measurement report to the wireless communication network, in response to said detecting.

24. The wireless device (600) of claim 23, wherein the wireless device (600) is further adapted to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, prior to said comparing, based on the wireless device's usage of one of a plurality of receiver techniques or modes.

25. The wireless device (600) of claim 23, wherein the wireless device (600) is further adapted to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, prior to said comparing, based on whether an interference cancellation technique is employed by the wireless device.

26. The wireless device (600) of claim 23, wherein the wireless device (600) is further adapted to select the predetermined radio-link-failure threshold value from a plurality of predetermined threshold values, prior to said comparing, based on whether a diversity mode is employed by the wireless device.

27. The wireless device (600) of any of claims 23-26, wherein the wireless device (600) is further adapted to calculate the event threshold by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link-failure threshold value for the wireless device (600), such that the wireless device (600) detects the reporting trigger event by detecting that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

28. The wireless device (600) of any of claims 23-26, wherein the wireless device (600) is further adapted to calculate the event threshold by applying a hysteresis parameter value and the offset parameter value to the predetermined radio-link-failure threshold value for the wireless device (600), such that the wireless device (600) detects the reporting trigger event by detecting that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio-link-failure threshold value and the offset parameter value, less the hysteresis parameter value.

29. The wireless device (600) of any of claims 23-28, wherein the wireless device (600) is further adapted to send the measurement report to the wireless network conditioned on a determination that the detected reporting trigger event is sustained for at least a

predetermined length of time.

30. The wireless device (600) of claim 29, wherein the wireless device (600) is further adapted to send the measurement report to the wireless network conditioned on a

determination that a measured signal quality for a serving cell has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter and the hysteresis parameter value and a subsequent determination that the measured signal quality has not fallen below a threshold level equal to the sum of the predetermined radio link failure threshold value and the offset parameter, less the hysteresis parameter value, over a predetermined time period.

31. The wireless device (600) of claim 29, wherein the wireless device (600) is further adapted to send the measurement report to the wireless network conditioned on a

determination that a measured signal quality for a serving cell has become lower than the sum of the predetermined radio link failure threshold value and the offset parameter value, less the hysteresis parameter value, and a subsequent determination that the measured signal quality for a serving cell has not risen above a threshold level equal to the sum of the predetermined radio-link-failure threshold, the offset parameter value, and the hysteresis parameter value, over a predetermined time period.

32. The wireless device (600) of any of claims 23-31, wherein the radio link measurements comprise one or more of any of the following:

block-error estimations;

signal-to-interference-plus-noise ratio, SINR, estimations;

33. A wireless device (700) for operating in a wireless communication network, the wireless device (700) comprising

a receiving module (710) for receiving an offset parameter value from the wireless communication network;

a comparing module (730) for comparing one or more radio link measurements to an event threshold that is based on an application of the offset parameter value to a predetermined radio-link-failure threshold value for the wireless device; a detection module (740) for detecting a reporting trigger event, based on said

comparing; and

a sending module (750) for sending a measurement report to the wireless

communication network, in response to said detecting.

34. A base station (1) for use in a wireless communication network, the base station (1) comprising a processing circuit (10, 20, 30) configured to:

send a first offset parameter value to a first wireless device; and

subsequently receive a measurement report from the first wireless device, wherein the measurement report indicates that it was triggered based on an event threshold calculated from the first offset parameter value and a predetermined radio- link-failure threshold value for the first wireless device.

35. The base station (1) of claim 34, wherein the processing circuit (10, 20, 30) is further configured to send a hysteresis parameter to the first wireless device, wherein the

measurement report indicates that it was triggered based on a determination that a radio link measurement value has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

36. A base station (1) for use in a wireless communication network, the base station (1) adapted to:

send a first offset parameter value to a first wireless device; and to subsequently receive a measurement report from the first wireless device, wherein the measurement report indicates that it was triggered based on an event threshold calculated from the first offset parameter value and a predetermined radio-link-failure threshold value for the first wireless device.

37. The base station (1) of claim 36, wherein the base station (1) is further adapted to send a hysteresis parameter to the wireless device, wherein the measurement report indicates that it was triggered based on a determination that a radio link measurement value has become higher than the predetermined radio-link-failure threshold value by an amount greater than the sum of the offset parameter value and the hysteresis parameter value.

38. A base station (1) for use in a wireless communication network, the base station comprising:

a sending module for sending a first offset parameter value to a first wireless device; and

a receiving module for subsequently receiving a measurement report from the first wireless device, wherein the measurement report indicates that it was triggered based on an event threshold calculated from the first offset parameter value and a predetermined radio-link-failure threshold value for the first wireless device.