WO2015113600A1

WO2015113600A1 - Mechanism for reporting radio link health status

Info

Publication number: WO2015113600A1
Application number: PCT/EP2014/051792
Authority: WO
Inventors: Mikko Saily; Tero Henttonen
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2014-01-30
Filing date: 2014-01-30
Publication date: 2015-08-06

Abstract

Various communication systems may benefit for mechanisms for reporting radio link health status. For example, such mechanisms may benefit third generation partnership project (3GPP) dual connectivity, as described in 3GPP technical report (TR) 36.842, and for example, architecture option 1A or architecture 3C. A method can include determining a link health status of a link of a secondary base station. The method can also include reporting the link health status in a report message to a primary base station associated with the secondary base station.

Description

DESCRIPTION TITLE

Mechanism for Reporting Radio Link Health Status

BACKGROUND: Field:

[0001] Various communication systems may benefit for mechanisms for reporting radio link health status. For example, such mechanisms may benefit third generation partnership project (3GPP) dual connectivity, as described in 3GPP technical report (TR) 36.842, and for example, architecture option 1 A or architecture 3C.

Description of the Related Art:

[0002] 3GPP standards may include various requirements for Primary Cell (PCell) functionality in a Secondary eNB (SeNB). For example, there may be no need to provide network access stratum (NAS) security and NAS mobility functions in the SeNB. Also, at least one cell in SeNB may have configured uplink (UL) and one of them may be configured with physical uplink control channel (PUCCH) resources.

[0003] Other requirements, or absence of requirements, may include that no radio link management (RLM) is needed on a cell not carrying PUCCH in the SeNB. Moreover, radio link failure (RLF), if supported, may occur for any Secondary Cell Group (SCG) cell but may not trigger radio resource control (RRC) connection re-establishment.

[0004] Under such requirements, the cell in the SeNB which is configured with PUCCH resources may not be permitted to be cross-carrier scheduled. Moreover, the SeNB may have one special cell containing at least PUCCH, and potentially also some other PCell functionality. This special cell can be referred to as a Primary Secondary Cell (PSCell).

However, it may not be necessary to duplicate all PCell functionality for the PSCell.

[0005] Additionally, it may be required that the channel quality information (CQI) and/or channel state information (CSI) for the master eNB (MeNB)/SeNB is sent or forwarded to the respective cell, to allow independent scheduling in each eNB. That is, the MeNB and the SeNB may each own its respective radio resources, where the channel quality indicator

(CQI) and/or channel state information (CSI) in each cell is carried by PUCCH or PUSCH of each cell for periodic and aperiodic CQI respectively.

[0006] If the connection between SeNB PSCell and UE does not have RLM, it can happen that the SeNB transmission quality for the UE drops but the SeNB may not detect the RLF occurrence and therefore has no means to control what to do for the RLF. Additionally, the MeNB might not notice this drop in transmission quality from the CQI reports, since the MeNB may not be receiving those CQI reports from the SeNB or from the UE. For example, in dual connectivity architecture 1 A, each eNB conventionally handles its own bearers and the aggregation point is only at the Serving Gateway (S-GW). Therefore an impaired link at SeNB may have high risk of failure or a relatively high error rate, which may waste radio resources due to an excessive number of retransmissions and may cause interference in uplink.

[0007] In current carrier aggregation, the SCells do not experience radio link failures and RLM for SCells has been left up to eNB implementation. For 3GPP Releasel O, either A2 measurement event or "bad" SCell CQI values (e.g. CQI=0) sent to PCell were considered to be one way for PCell to notice that the SCell is in RLF (see e.g. R2-102488, which is hereby incorporated herein by reference in its entirety), and at the time another idea was that SCell should have RLM (see e.g. R2-095482, R2-101545, and R2-102488, which are hereby incorporated herein by reference in their entirety).

[0008] Conventionally, CQI=0 is used if UE cannot receive a physical downlink shared channel (PDSCH) transport block with an error rate of less than 10% with its associated modulation and coding scheme (MCS) and transport block size corresponding to the CQI index 1 .

[0009] In certain conventional considerations of these issues, the SeNB is considered to have RLF when the network is notified about the problem. Thus, the link with the SeNB cannot be recovered before the failure.

SUMMARY:

[0010] According to certain embodiments, a method can include determining a link health status of a link of a secondary base station. The method can also include reporting the link health status in a report message to a primary base station associated with the secondary base station.

[0011] In certain embodiments, a method can include receiving, at a primary base station, a report message indicating a link health status of a secondary base station. The method can also include processing the report message to determine the link health of the secondary base station.

[0012] An apparatus, according to certain embodiments, 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 determine a link health status of a link of a secondary base station. 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 report the link health status in a report message to a primary base station associated with the secondary base station.

[0013] An apparatus, according to certain embodiments, 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 receive, at a primary base station, a report message indicating a link health status of a secondary base station. 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 process the report message to determine the link health of the secondary base station.

[0014] According to certain embodiments, an apparatus can include means for determining a link health status of a link of a secondary base station. The apparatus can also include means for reporting the link health status in a report message to a primary base station associated with the secondary base station.

[0015] In certain embodiments, an apparatus can include means for receiving, at a primary base station, a report message indicating a link health status of a secondary base station. The apparatus can also include means for processing the report message to determine the link health of the secondary base station.

[0016] A non-transitory computer-readable medium can, according to certain embodiments, be encoded with instructions that, when executed in hardware, perform a process. The process can correspond to any of the above-described methods.

[0017] A computer program product, can in certain embodiments, encode instructions for performing a process. The process can correspond to any of the above-described methods.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0018] For proper understanding of the invention, reference should be made to the accompanying drawings, wherein:

[0019] Figure 1 illustrates a method according to certain embodiments.

[0020] Figure 2 illustrates another method according to certain embodiments.

[0021] Figure 3 illustrates a flowchart according to certain embodiments. [0022] Figure 4 illustrates a system according to certain embodiments.

DETAILED DESCRIPTION:

[0023] Certain embodiments can provide a link health status report of SeNB connection quality as a message sent to the MeNB. The report can be sent periodically, aperiodically, or in an event-triggered manner. An example of aperiodic reporting can be that the report is triggered by an eNB request. An example of an event-triggered scenario can be that an eNB can configure an event that triggers reporting the link health status report. The link health status report can also be sent together with a normal RRM measurement report.

[0024] Conventionally, there is no specific method of radio link monitoring (RLM) in SeNB. Furthermore, in a conventional approach such RLM may only be needed for cells where physical uplink control channel (PUCCH) resources are configured. Since the PCell belongs to the MeNB, it may always be under RLM, but the same would not conventionally necessarily be the same for the SeNB cell carrying PUCCH.

[0025] By contrast, in certain embodiments, a Secondary radio Link Monitoring (SLM) procedure can be defined with the purpose of triggering a link health report to provide at least an indicator of the SeNB link quality. This report can allow the MeNB to determine if actions should be taken to reconfigure the cell with PUCCH in SeNB, or inform SeNB of the potential link problem. The link health report can also consider other configured links with multiple access points.

[0026] In certain embodiments, the triggering of link health report by SLM procedure may be referred as a Secondary Link Failure (SLF).

[0027] The report can be variously triggered. For example, in certain embodiments the eNB can indicate the monitored reporting metric for triggering the link health report to be one or more of, but not limited to, the following: cell-specific reference signal (CRS) quality based on reference signal received power (RSRP), CRS quality based on reference signal received quality (RSRQ), indication based on RLM criteria (Qin/Qout result), CRS quality based on wideband CQI, CRS quality based on indicated sub-band CQI, channel state information reference signal (CSI-RS) quality, channel block error rate (BLER), and channel bit error probability (BEP).

[0028] In another embodiment, the report may be implicit, based on the SeNB configuration. For example, reporting may be always on when dual connectivity or inter- eNB carrier aggregation is configured.

[0029] In another embodiment, the link health report can be attached to an existing RRM measurement report and can be sent when the dependent event triggers. In other words, when an RRM measurement report is sent for the reasons that an RRM measurement report may need to be sent, the link health can be sent at the same time and/or in the same message.

[0030] In certain embodiments, the eNB can configure the event to which the report is tagged on. In another embodiment, the event that triggers the report is specified in a specification, such as the 3GPP specification, and consequently is fixed as far as the eNB is concerned.

[0031] There are various ways that link health can be indicated. For example, in certain embodiments, a report can include an indication of a choice of Qin, Qout or between Qin and Qout; or in-sync or out-of-sync.

[0032] In another embodiment, the link health report can include history information of the monitored quality metric over a period of time. This history information can be, for example, an average of the metric over time, and/or an indication of change in the metric over the time period of comparison, for example, at the start and at the end of the period, at the start and on average of the period, or at the end and on average of the period.

[0033] In certain embodiments, the period of time can be configured by the eNB. By contrast, in other embodiments, the period of time can be fixed in a specification. Similarly, in certain embodiments the comparison points can be configured by the eNB, whereas in other embodiments the comparison points can be fixed in a specification.

[0034] In another embodiment, the link health report can include an indication of change in the monitored quality over a period of time. As with the above, the period of time can be configured by the eNB or fixed by a specification.

[0035] The periodicity of the status reporting itself can be realized in a variety of ways. For example, in certain embodiments, the report can be configured to be periodical. In another embodiment, the report can be configured to be only triggered via eNB indication.

For example, the report may be subject to aperiodic reporting in which the eNB indicates when the eNB wants the report to be sent.

[0036] In certain embodiments, the eNB can indicate a period during which the eNB desires that the UE sends the report. This can be referred to as aperiodically triggered periodical reporting.

[0037] In certain embodiments, the report can be configured to be sent when a set event triggers. This can be, for example, event-triggered reporting in which the link health report is sent in addition to, instead of, or attached to a normal event-triggered measurement report.

[0038] In a dependent embodiment, such event-triggered reporting can be configured with a period during which the UE continues to periodically send the report. This can be referred to as event-triggered periodical reporting.

[0039] In certain embodiments, the Secondary radio Link Monitoring can be configured to send a report. This can be referred to as SLM triggered reporting.

[0040] Figure 1 illustrates a method according to certain embodiments. The method of Figure 1 may be performed by, for example, a user equipment. As shown in Figure 1 , a method can include, at 1 10, determining a link health status of a link of a secondary base station. The method can also include, at 120, reporting the link health status in a report message to a primary base station associated with the secondary base station.

[0041] The report message can be sent periodically. Also, or alternatively, the report message can be triggered by a request from the primary base station, at 102, or the report message can be triggered by an event occurring at 104.

[0042] A metric for the event occurring can include at least one of cell-specific reference signal (CRS) quality based on reference signal received power (RSRP), CRS quality based on reference signal received quality (RSRQ), indication based on RLM criteria (Qin/Qout result), CRS quality based on wideband channel quality indicator (CQI), CRS quality based on indicated sub-band CQI, channel state information reference signal (CSI- RS) quality, channel block error rate (BLER), or channel bit error probability (BEP). Moreover, the report message comprises information regarding a plurality of configured links with a plurality of access points.

[0043] The reporting can be based on whether secondary base station and/or the primary base station is configured for dual connectivity or inter-eNB carrier aggregation. For example, if the dual connectivity is configured, then the reporting can be set to always on.

[0044] The report message can include an indication of at least one of Qin, Qout, or between Qin and Qout. Alternatively, or in addition, the report message can include an indication of in-sync or out-of-sync.

[0045] The report message can include history information of a monitored quality metric over time. This history information can be a history of change in quality or various data points of quality associated with various times, among other options.

[0046] Figure 2 illustrates another method according to certain embodiments. The method of Figure 2 may be performed by, for example, a base station, such as an evolved

Node B (eNB). As shown in Figure 2, a method can include, at 210, receiving, at a primary base station, a report message indicating a link health status of a secondary base station. The method can also include, at 220, processing the report message to determine the link health of the secondary base station.

[0047] The method can further include, at 205, sending a request to a user equipment, wherein the request is configured to trigger sending of the report message to the primary base station.

[0048] The method can further include, at 230, configuring a periodicity of the report message. Similarly, the method can also include, at 240, configuring a monitoring period for the report message.

[0049] The processing can include determining whether an action should be taken to reconfigure a cell with physical uplink control channel in a coverage area of the secondary cell. If so, the action can be taken at 250.

[0050] As with the report message discussed in connection with Figure 1 , the report message can include an indication of at least one of Qin, Qout, or between Qin and Qout. Also or alternatively, the report message can include an indication of in-sync or out-of- sync.

[0051] In the above discussion of Figures 1 and 2, the primary base station can refer to, for example, a macro eNB providing PCell, whereas the secondary base station can refer to, for example, a secondary eNB providing SCell.

[0052] Figure 3 illustrates a signal flowchart according to certain embodiments. The signals as shown may flow among a user equipment (UE) 310, a macro evolved node B (MeNB) 320, and a secondary evolved node B (SeNB) 330. Optionally, at 340, the MeNB 320 can configure the UE 310 regarding monitoring of links with secondary cells. At 350, a link can exist between the UE 310 and the SeNB 330. The UE 310 can measure quality of this link and process it at 360.

[0053] Then, if appropriate, the UE 310 can report link health for the link to the MeNB 320. The MeNB 320 can process this report at 380 and can take action at 390, for example, by reconfiguring the SeNB 330. Alternatively, or in addition, the SeNB 330 can notice the status of UE 310's link, for example, based on UE 320 L2 HARQ feedback or the like. The SeNB 330 can process the link quality at 365 and can send a report to

MeNB 320 over, for example, an S1 /X2 interface at 375.

[0054] Figure 4 illustrates a system according to certain embodiments of the invention. In one embodiment, a system may include multiple devices, such as, for example, at least one UE 410, at least one first eNB 420 or other base station or access point, and at least one second eNB 430. In certain systems, UE 410, first eNB 420, second eNB 430, and a plurality of other user equipment may be present. Other configurations are also possible. The first eNB 420 may be, for example, an MeNB and the second eNB 430 may be, for example, an SeNB, at a particular time.

[0055] Each of these devices may include at least one processor, respectively indicated as 414, 424, and 434. At least one memory can be provided in each device, as indicated at 415, 425, and 435, respectively. The memory may include computer program instructions or computer code contained therein. The processors 414, 424, and 434 and memories 415, 425, and 435, or a subset thereof, can be configured to provide means corresponding to the various blocks of Figures 1 through 3.

[0056] As shown in Figure 4, transceivers 416, 426, and 436 can be provided, and each device may also include at least one antenna, respectively illustrated as 417, 427, and 437. The device may have many antennas, such as an array of antennas configured for multiple input multiple output (MIMO) communications, or multiple antennas for multiple radio access technologies. Other configurations of these devices, for example, may be provided. For example, first eNB 420 and second eNB 430 may additionally be configured for wired communication, and in such a case antenna 437 would also illustrate any form of communication hardware, without requiring a conventional antenna.

[0057] Transceivers 416, 426, and 436 can each, independently, be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that is configured both for transmission and reception.

[0058] Processors 414, 424, and 434 can be embodied by any computational or data processing device, such as a central processing unit (CPU), application specific integrated circuit (ASIC), or comparable device. The processors can be implemented as a single controller, or a plurality of controllers or processors.

[0059] Memories 415, 425, and 435 can independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD), random access memory (RAM), flash memory, or other suitable memory can be used. The memories can be combined on a single integrated circuit as the processor, or may be separate from the one or more processors. Furthermore, the computer program instructions stored in the memory and which may be processed by the processors can be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language.

[0060] The memory and the computer program instructions can be configured, with the processor for the particular device, to cause a hardware apparatus such as UE 410, first eNB 420, and second eNB 430, to perform any of the processes described above (see, for example, Figures 1 through 3). Therefore, in certain embodiments, a non-transitory computer-readable medium can be encoded with computer instructions that, when executed in hardware, perform a process such as one of the processes described herein. Alternatively, certain embodiments can be performed entirely in hardware.

[0061] Furthermore, although Figure 4 illustrates a system including a UE, first eNB, and second eNB, embodiments of the invention may be applicable to other configurations, and configurations involving additional elements. [0062] 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. In order to determine the metes and bounds of the invention, therefore, reference should be made to the appended claims.

[0063] Partial Glossary

[0064] AS Access Stratum

[0065] BEP Bit Error Probability

[0066] CQI Channel Quality Indication

[0067] CSI Channel State Information

[0068] LTE Long Term Evolution

[0069] MCG Master Cell Group

[0070] MeNB Master eNB

[0071] PSCell Primary Secondary Cell

[0072] RLF Radio Link Failure

[0073] RLM Radio Link Monitoring

[0074] RSRP Reference Signal Received Power

[0075] RSRQ Reference Signal Received Quality

[0076] SCG Secondary Cell Group

[0077] SeNB Secondary eNB

[0078] SLM Secondary radio Link Monitoring

[0079] SLF Secondary radio Link Failure

[0080] UE User Equipment

Claims

WE CLAIM:

1 . A method, comprising: determining a link health status of a link of a second base station; and reporting the link health status in a report message to a first base station associated with the second base station.

2. The method of claim 1 , wherein the report message is sent periodically.

3. The method of claim 1 or claim 2, wherein the report message is triggered by request from the first base station.

4. The method of claim 1 or claim 2, wherein the report message is triggered by an event occurring.

5. The method of claim 4, wherein a metric for the event occurring comprises at least one of cell-specific reference signal (CRS) quality based on reference signal received power (RSRP), CRS quality based on reference signal received quality (RSRQ), indication based on RLM criteria (Qin/Qout result), CRS quality based on wideband channel quality indicator (CQI), CRS quality based on indicated sub-band CQI, channel state information reference signal (CSI-RS) quality, channel block error rate (BLER), or channel bit error probability (BEP).

6. The method of any of claims 1 -5, wherein the report message comprises information regarding a plurality of configured links with a plurality of access points.

7. The method of any of claims 1 -6, wherein the reporting is based on whether the second base station and/or the first base station is configured for dual connectivity or inter-eNB carrier aggregation.

8. The method of any of claims 1 -7, wherein the report message comprises an indication of at least one of Qin, Qout, or between Qin and Qout.

9. The method of any of claims 1 -8, wherein the report message comprises an indication of in-sync or out-of-sync.

10. The method of any of claims 1 -9, wherein the report message comprises history information of a monitored quality metric over time.

1 1 . A method, comprising: receiving, at a first base station, a report message indicating a link health status of a second base station; and processing the report message to determine the link health of the second base station.

12. The method of claim 1 1 , further comprising: sending a request to a user equipment, wherein the request is configured to trigger sending of the report message to the first base station.

13. The method of claim 1 1 or 12, further comprising: configuring a periodicity of the report message.

14. The method of any of claims 1 1 -13, further comprising: configuring a monitoring period for the report message.

15. The method of any of claims 1 1 -14, wherein the processing comprises determining whether an action should be taken to reconfigure a cell with physical uplink control channel in a coverage area of the second cell.

16. The method of any of claims 1 1 -15, wherein the report message comprises an indication of at least one of Qin, Qout, or between Qin and Qout.

17. The method of any of claims 1 1 -16, wherein the report message comprises an indication of in-sync or out-of-sync.

18. The method of any of claims 1 1 -17, wherein the report message comprises information regarding a plurality of configured links with a plurality of access points.

19. The method of any of claims 1 1 -18, wherein the report message comprises history information of a monitored quality metric over time.

20. The method of any of claims 1 -19, wherein the first base station comprises a primary base station and the second base station comprises a secondary base station.

21 . 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 determine a link health status of a link of a second base station; and report the link health status in a report message to a first base station associated with the second base station.

22. The apparatus of claim 21 , 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 send the report message periodically.

23. The apparatus of claim 21 or claim 22, wherein the report message is triggered by a request from the first base station.

24. The apparatus of claim 21 or claim 22, wherein the report message is triggered by an event occurring.

25. The apparatus of claim 24, wherein a metric for the event occurring comprises at least one of cell-specific reference signal (CRS) quality based on reference signal received power (RSRP), CRS quality based on reference signal received quality (RSRQ), indication based on RLM criteria (Qin/Qout result), CRS quality based on wideband channel quality indicator (CQI), CRS quality based on indicated sub-band CQI, channel state information reference signal (CSI-RS) quality, channel block error rate (BLER), or channel bit error probability (BEP).

26. The apparatus of any of claims 21 -25, wherein the report message comprises information regarding a plurality of configured links with a plurality of access points.

27. The apparatus of any of claims 21 -26, 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 report based on whether the second base station and/or the first base station is configured for dual connectivity or inter-eNB carrier aggregation.

28. The apparatus of any of claims 21 -27, wherein the report message comprises an indication of at least one of Qin, Qout, or between Qin and Qout.

29. The apparatus of any of claims 21 -28, wherein the report message comprises an indication of in-sync or out-of-sync.

30. The apparatus of any of claims 21 -29, wherein the report message comprises history information of a monitored quality metric over time.

31 . 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 receive, at a first base station, a report message indicating a link health status of a second base station; and process the report message to determine the link health of the second base station.

32. The apparatus of claim 31 , 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 send a request to a user equipment, wherein the request is configured to trigger sending of the report message to the first base station.

33. The apparatus of claim 31 or 32, 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 configure a periodicity of the report message.

34. The apparatus of any of claims 31 -33, 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 configure a monitoring period for the report message.

35. The apparatus of any of claims 31 -34, 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 determine whether an action should be taken to reconfigure a cell with physical uplink control channel in a coverage area of the second cell.

36. The apparatus of any of claims 31 -35, wherein the report message comprises an indication of at least one of Qin, Qout, or between Qin and Qout.

37. The apparatus of any of claims 31 -36, wherein the report message comprises an indication of in-sync or out-of-sync.

38. The apparatus of any of claims 31 -37, wherein the report message comprises information regarding a plurality of configured links with a plurality of access points.

39. The apparatus of any of claims 31 -38, wherein the report message comprises history information of a monitored quality metric over time.

40. An apparatus, comprising: means for determining a link health status of a link of a second base station; and means for reporting the link health status in a report message to a first base station associated with the second base station.

. The apparatus of claim 40, wherein the report message is sent periodically.

42. The apparatus of claim 40 or claim 41 , wherein the report message is triggered by a request from the first base station.

43. The apparatus of claim 40 or claim 41 , wherein the report message is triggered by an event occurring.

44. The apparatus of claim 43, wherein a metric for the event occurring comprises at least one of cell-specific reference signal (CRS) quality based on reference signal received power (RSRP), CRS quality based on reference signal received quality (RSRQ), indication based on RLM criteria (Qin/Qout result), CRS quality based on wideband channel quality indicator (CQI), CRS quality based on indicated sub-band CQI, channel state information reference signal (CSI-RS) quality, channel block error rate (BLER), or channel bit error probability (BEP).

45. The apparatus of any of claims 40-44, wherein the report message comprises information regarding a plurality of configured links with a plurality of access points.

46. The apparatus of any of claims 40-45, wherein the reporting is based on whether the second base station and/or the first base station is configured for dual connectivity or inter-eNB carrier aggregation.

47. The apparatus of any of claims 40-46, wherein the report message comprises an indication of at least one of Qin, Qout, or between Qin and Qout.

48. The apparatus of any of claims 40-47, wherein the report message comprises an indication of in-sync or out-of-sync.

49. The apparatus of any of claims 40-48, wherein the report message comprises history information of a monitored quality metric over time.

50. An apparatus, comprising: means for receiving, at a first base station, a report message indicating a link health status of a second base station; and means for processing the report message to determine the link health of the second base station.

51 . The apparatus of claim 50, further comprising: means for sending a request to a user equipment, wherein the request is configured to trigger sending of the report message to the first base station.

52. The apparatus of claim 50 or 51 , further comprising: means for configuring a periodicity of the report message.

53. The apparatus of any of claims 50-52, further comprising: means for configuring a monitoring period for the report message.

54. The apparatus of any of claims 50-53, wherein the means for processing comprises means for determining whether an action should be taken to reconfigure a cell with physical uplink control channel in a coverage area of the second cell.

55. The apparatus of any of claims 50-54, wherein the report message comprises an indication of at least one of Qin, Qout, or between Qin and Qout.

56. The apparatus of any of claims 50-55, wherein the report message comprises an indication of in-sync or out-of-sync.

57. The apparatus of any of claims 50-56, wherein the report message comprises information regarding a plurality of configured links with a plurality of access points.

58. The apparatus of any of claims 50-57, wherein the report message comprises history information of a monitored quality metric over time.

59. The apparatus of any of claims 21 -58, wherein the first base station comprises a primary base station and the second base station comprises a secondary base station.

60. 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 -20.

61 . A computer program product encoding instructions for performing a process, the process comprising the method according to any of claims 1 -20.