WO2017091218A1

WO2017091218A1 - Event-triggered measurement reporting in 5g mmwave communication system

Info

Publication number: WO2017091218A1
Application number: PCT/US2015/062595
Authority: WO
Inventors: Mark Cudak; Ahmad AWADA; Anup Talukdar
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2015-11-25
Filing date: 2015-11-25
Publication date: 2017-06-01

Abstract

A user device's (UD) radio link with a network node is determined to satisfy an entering condition for a measurement event, where there is a specified duration such as a TTT over which the entering condition shall be satisfied. A timer associated with that determination is initiated to track the specified duration, but prior to expiry of the tracked duration the UD experiences radio link blockage with the network node. Various options are presented for what measurements can be used to satisfy the requirements of the measuring event, the end result being the UD is able to wirelessly send a measurement report about the network node that satisfies the measurement event, hi various embodiments the timer is stopped and re-started, or it is suspended and resumed, and some embodiments use estimated measurements that are extrapolated and/or interpolated from actual measurements taken before and/or after the link blockage occurs.

Description

EVENT-TRIGGERED MEASUREMENT REPORTING IN

5G MMWAVE COMMUNICATION SYSTEM

TECHNOLOGICAL FIELD:

[0001] The described invention relates to wireless communications, and more particularly to the measuring of neighbor cells and reporting such measurements in a rapidly changing radio environment such as those expected to exist in 5G/mmWave type wireless communication networks.

BACKGROUND:

[0002] The 5^th Generation (5G) wireless networks are being designed to deliver peak data rates of the order of ~10Gbps and the target latency requirements have been set to the order of -lmsec in order to serve applications with ultra-low latency perfonnance requirements. Millimeterwave (mmWave) frequency bands have been identified as a promising candidate for 5G cellular technology. Spectrum in traditional cellular bands . (below 6GHz) is finite and as cellular data traffic demand continues to grow new frequency bands must be considered. Unlike traditional cellular bands, large blocks of contiguous spectrum may be allocated at mm Wave bands allowing for bandwidths on the order of GHz or more. Moreover, the mm Wave bands allow for multi-element antenna arrays composed of very small elements, on the order of IC chip scales, providing large antenna gain and sufficient power output through over-the-air power combining. This combination of large bandwidths and novel device architectures allows mmWave cellular to provide peak rates on the order of 10 Gbps and ample capacity to meet future demands.

[0003] However the propagation characteristics in the mmWave band are more challenging than traditional cellular. Diffraction at mmWave bands is effectively non-existent and propagation of radio signals behaves similar to visible light. Transmission through most objects is diminished; foliage and other common obstacles that traditional RF signals largely pass through can produce severe shadowing of mmWave signals. On the other hand, reflective power for mmWave signals is improved which offers new opportunities for completing the wireless link, though reflected mmWave signal power may be 15dB-40dB weaker. In a typical urban deployment, mmWave access points (APs) are expected to be installed on top of street-side poles, possibly at street corners; some possible early deployment scenarios are stadiums, college campus courtyards, and tourist hotspots.

[0004] The severe shadowing loss characteristics in the mmWave band implies that the radio link between a user device (UD) and its serving AP will be disrupted if the line of sight (LOS) is blocked by obstacles. For a pedestrian walking along the sidewalk in a city block, its LOS may be blocked by fixed obstacles such as trees, or moving obstacle such as large trucks, or other pedestrians, hi a campus courtyard or a tourist hotspot LOS blocking may be caused by crowds. LOS blocking may even be caused by motions of the user him/herself such as rotating his/her hand or body. For this reason 5G is being developed with a redundancy of APs such that in the event of a LOS blocking the network connection of the UD can be rapidly rerouted via another AP.

[0005] This results in stringent requirements for dynamically knowing which other APs might be available for rerouting. In previous generation cellular networks, the UD reported neighbor cell measurements taken during specified measurement opportunities to its serving cell. But in 5G mmWave network the world of APs seen by a given UD will be changing much more rapidly. Unlike conventional cellular networks where a fading cell was generally no longer considered a viable handover candidate, in 5G mmWave the LOS blockage with a given AP can be very short-lived meaning the resulting radio link blockage with that AP might last only several seconds or less. For these and other reasons the neighbor cell measurement protocols that were developed for previous generation cellular networks are not suitable for robust mmWave mobile communications. The forthcoming teachings provide ways to provide the measurement reports suitable for sustained and robust wireless communications in a rapidly changing radio environment such as mmWave 5G-type networks.

[0006] Some background materials relevant to these teachings can be seen as follows:

• M. Cudak, A. Ghosh, T. Kovarik, R. Ratasuk, T. Thomas, F. Vook, P. Moorut, "Moving Towards mmWave-Based Beyond-4G (B-4G) Technology," in Proc. IEEE VTC-Spring 2013, June 2-5, 2013. • US Patent Application 14/413,776 entitled MILLIMETER WAVE ACCESS ARCHITECTURE WITH CLUSTER OF ACCESS POINTS (filed on Jan. 9, 2015).

• 3 GPP TS 36.331, Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol Specification (Release 12).

• 3GPP TS 25.331, Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol Specification (Release 12).

SUMMARY:

[0007] According to a first aspect of these teachings there is a method that includes determining that a radio link with a network node satisfies an entering condition for a measurement event, where there is a specified duration over which the entering condition shall be satisfied; initiating a timer in association with the determining to track the duration; experiencing radio link blockage with the network node prior to expiry of the tracked duration; and wirelessly sending a measurement report about the network node that satisfies the measurement event.

[0008] According to a second aspect of these teachings there is a computer readable memory storing computer program instructions that, when executed by one or more processors, cause a host radio device to determine that a radio link with a network node satisfies an entering condition for a measurement event, where there is a specified duration over which the entering condition shall be satisfied; initiate a timer in association with the determining to track the duration; experience radio link blockage with the network node prior to expiry of the tracked duration; and wirelessly send a measurement report about the network node that satisfies the measurement event.

[0009] According to a third aspect of these teachings there is an apparatus such as a radio device. The apparatus comprises at least one computer readable memory storing computer program instructions and at least one processor. The computer readable memory with the computer program instructions is configured, with the at least one processor, to cause the apparatus to at least: determine that a radio link with a network node satisfies an entering condition for a measurement event, where there is a specified duration over which the entering condition shall be satisfied; initiate a timer in association with the determining to track the duration; experience radio link blockage with the network node prior to expiry of the tracked duration; and wirelessly send a measurement report about the network node that satisfies the measurement event.

[0010] According to a fourth aspect of these teachings there is an apparatus that comprises radio communication means, control means and timing means. The radio communication means is for determining that a radio link with a network node satisfies an entering condition for a measurement event, where there is a specified duration over which the entering condition shall be satisfied. The control means is for initiating the timing means to track the duration in association with the determining. The apparatus experiences radio link blockage with the network node prior to expiry of the tracked duration (the radio communication means can recognize when the radio link blockage first occurs as well as when the radio link blockage expires). The radio communication means wirelessly sends a measurement report about the network node that satisfies the measurement event. In one non-limiting example the radio communication means includes a wireless transmitter and a wireless receiver, the control means includes one or more processors running executable code stored tangibly on a computer readable memory, and the timing means may be implemented as a clock or as tangibly stored software implementing a clock using timing or clock signals from the one or more processors.

BRIEF DESCRIPTION OF THE DRAWINGS:

[001 1] FIG. 1 is a schematic diagram illustrating an example radio environment of a user device and its cluster set of access points in which embodiments of these teachings may be practiced. [0012] FIG. 2 is a plot showing filtered measurement results at various time instances in the presence of a temporary radio link blockage, where for this filtering technique there are no filtered measurements provided when the radio link is blocked.

[0013] FIG. 3 is similar to FIG. 2 except that for this filtering technique interpolated or extrapolated filtered measurements are provided when the radio link is blocked.

[0014] FIG. 4 is a plot showing filtered measurement results at various time instances in the presence of a temporary radio link blockage with timer and sample instants according to a first embodiment, where no filtered measurements are available to the user device when the radio link is blocked.

[0015] FIG. 5 is similar to FIG. 4 but showing timer and sample instants according to a second embodiment, where still there are no filtered measurements available to the user device when the radio link is blocked.

[0016] FIG. 6 is similar to FIG. 4 but showing timer and sample instants according to a third embodiment,' but where filtered measurements are available to the user device when the radio link is blocked.

[0017] FIG. 7 is similar to FIG. 4 but showing timer and sample instants according to a fourth embodiment, but where filtered measurements are available to the user device when the radio link is blocked.

[0018] FIG. 8 is a process flow diagram summarizing certain of the above teachings from the perspective of the user device.

[0019] FIG. 9 is a high level schematic block diagram illustrating certain apparatus/devices that are suitable for practicing various aspects of these teachings. DETAILED DESCRIPTION:

[0020] To better appreciate the advantages of these teachings first the radio environment for a mmWave communication system as envisioned for 5G cellular is explained with respect to FIG. 1, without loss of generality of these teachings for other types of networks that are not 5G and which may use other than mmWave bands for communicating. Bidirectional communication links are represented as dual-tipped arrows and logical interfaces are denoted X5 in FIG. 1.

[0021] The UD 10 in a mmWave network is served by a cluster of APs, commonly known as the UD's cluster set. The UD 10 maintains a wireless radio link 16 A, 16B, 16C with each respective AP of its cluster set. Members of the cluster set of a UD 10 are selected based on the accessibility of the APs from the UD 10. In a given cluster set there is one particular AP selected as the serving- AP 12A (APo in FIG. 1) for the UD 10, through which the network communicates with the UD 10, while the other APs are designated as standby-APs 12B, 12C (APi and AP₂ in FIG. 1) which may be used to reroute the UD's network connection when its radio link 16A to the serving- AP 12A is blocked. The UD 10 maintains continuous connectivity with each member of its cluster set by maintaining synchronization with the symbol and frame structure, downlink and uplink control channels, and also maintain beam synchronization by selecting the best beams for downlink (DL) and uplink (UL) communication.

[0022] Although the standby-APs 12B, 12C are primarily intended to be used to provide robust connectivity to the network in the event of radio link blockages, it is also possible to utilize them to improve the network performance. For example, during uplink access procedure where the UD 10 requests an allocation of uplink radio resources, a UD 10 may send uplink resource requests over the uplink access opportunities (such uplink random access channel or uplink polling channel) of the stand-by APs 12B, 12C. This technique reduces the uplink access latency and also improves robustness of uplink access in presence of frequent radio link blockages.

[0023] The cluster set of a UD 10 is configured and managed by a Cluster Set Manager (CSM). There is a logical instance of the CSM 14 located in the network for each UD 10. The location of the CSM 14 should be close to the APs in the cluster set to enable low-latency communication with those APs and the UD 10. In FIG. 1 the cluster set containing three APs 12A, 12B, 12C and the cluster set manager (CSM) 14 are shown for a UD 10. The APs may be referred more generically as network nodes.

[0024] To assist the CSM 14 with the decision to add/remove/replace an AP from the cluster set, the UD 10 reports to CSM 14 the measurements of already existing APs in the cluster set or newly discovered APs. These measurements can be made either periodically or as triggered by some event. In the latter case, the measurement report is sent when a certain condition, known as the entering condition of the measurement event, is fulfilled for a certain time duration or interval known in the wireless arts as Time-to-Trigger (TTT). Measurement events are specified in published wireless protocols so that both network and UDs have a common understanding of exactly what the measurement indication reported by the UD to the network represents, and each measurement event is associated with a specific TTT. There are many known measurement events used in the LTE and even 3G systems that may be appropriate for use in 5G mmWave systems, or new ones may be defined.

[0025] The UD 10 applies layer 3 (L3) filtering for physical layer measurements before evaluating the reporting criteria of a measurement event. This also applies for periodic measurements. Measurement filtering is needed to remove the impact of fast fading and noise and to obtain stable estimates for the signal so that the reported measurements results in reliable decisions at the network. Even though filtering reduces the impact of fast fading and noise, measuring the network node for the TTT duration is still required to deal with any residual measurement errors and fluctuations, and to guarantee that the entering condition of the measurement event is not caused by measurement outliers.

[0026] As one example, in very simplified form the entering condition for the LTE measurement event A4 expires when:

F_n + Ocn + Hyst > Thresh

where: F_n is the filtered measurement of a neighboring cell served by an AP computed at time step n, Ocn is a cell-specific offset of the neighbor cell, Hyst is the hysteresis parameter for this measurement event and Thresh is the threshold which for the A4 measurement event is configured by the network.

[0027] Once the aforementioned condition is fulfilled for a TTT, the UD 10 sends a measurement report to the network. For 5G it is anticipated that different measurement events will be used for adding, removing and replacing an AP from the cluster set. Regardless, for event- triggered reporting there will always be a certain condition which has to be fulfilled for a certain TTT in order for the measurement event to be satisfied.

[0028] Due to the difference in mm Wave over traditional cellular bands, for 5G there are expected to be new methods for filtering the physical layer measurements so as to allow the UD 10 to derive from physical layer measurements new filtered measurements that are not biased by the measurement samples when the link is blocked. These filtered and unbiased measurements can help the CSM 14 to make proper decisions as to adding / removing an AP to or from the cluster set that has a strong / weak link even if that link is blocked for some short time.

[0029] While not yet decided for 5G, these new filtering methods can be broken into two main groups. The first group represented by FIG. 2 provides filtered measurements only in time instants when the link of the AP is not blocked. At FIG. 2 the filtered measurement strength or quality is along the vertical axis and time is along the horizontal axis. The UD's actual measurements are plotted as discrete instances, separated by the measurement sampling interval. The measurement taken at time n has a measurement value F_n and the measurement at time (n-r) has a measurement value F_n-_r? and between these two times there is a radio link blockage. Since this filtering approach does not provide filtered measurements in time instants when the link is blocked, so there are none between times (n-r) and n.

[0030] The second group represented by FIG. 3 in which filtered measurements are provided in all time instants, and the filtered measurements of time instants when the link is blocked are acquired by the UD 10 via interpolation extrapolation using the actual measurement samples that the UD 10 takes when the link is not blocked. [0013] FIG. 3 shows the specific interpolated or extrapolated filtered measurements during the link blockage between sampling times (n-r) and n.

[0031] For slow moving UDs, the typical blockage duration is in the range of several hundreds of ms (for example, if the LOS is blocked by a passing track) to several seconds (for example, if the LOS is blocked by a tree). For a fast moving UD such as one in a fast moving car the blockage duration can be much shorter. The UD can detect a radio link blockage if its physical layer measurement of the link fell below a certain threshold.

[0032] Now consider the effect of temporary link blockage when reporting measurements of an AP according to a measurement event with a specified TTT. If the measurements are filtered as in FIG. 2 so that there are no measurements while the link is blocked, the UD cannot check if the entering condition of the measurement event is fulfilled or not during the link blockage. Handling this issue cannot be left for different implementation by different UD manufacturers since it will have an impact on cluster set management (adding/removing/replacing an AP in the cluster set) and in turn on the operation of 5GmmWave systems. Whatever the solution it needs to be standardized across all of 5G, and that means being specified in a published wireless standard or protocol.

[0033] Now consider if the measurements are filtered as in FIG. 3 so that filtered measurements (including interpolated or extrapolated measurements) will be provided at all time instants including those when the link is blocked. In this case the UD 10 might have to wait until the link is detectable again if the filtered or physical layer measurements of time instants occurring after the link blockage are to be used in this interpolation/e trapolation filtering technique. For example, it could happen that the entering condition of the measurement event is fulfilled during the link blockage but the UD is aware of this only after the link is detected again at time n. In this case there might be a gap between the time instant when the entering condition of the measurement event is fulfilled and the time instant when the measurement report is sent. This issue is not addressed in 3G/LTE systems where the UD sends the measurement report once the entering condition of the measurement event is fulfilled for the specified TTT period. [0034] In another example, if the extrapolation filtering technique is using only the filtered or physical layer measurements of time instants occurring before the link blockage (time n-r and earlier), the measurement event may become fulfilled for the TTT during the link blockage but this blockage itself may make it inconvenient for the UD to send a report for adding (or replacing) an AP that is currently blocked to the cluster set, since the AP is anyway blocked and cannot be used by the CSM 14 for fast-rerouting. Again the solution for the issues arising with the inteipolation/extrapolation filtering technique are suitable for being standardized across all of 5G.

[0035] In 3G/LTE systems, the filtered measurements are provided at each time instant as long as the UD did not leave the coverage of the AP. As such, the UD in 3G/LTE networks is able to check at each time instant if the entering condition of the measurement event is fulfilled or not. If the entering condition of the measurement event is fulfilled at a certain time instant, the timer of TTT is started. If the condition is constantly fulfilled for each measurement over the length/duration of the TTT, the timer expires, the measurement event is fulfilled and the UD serids a measurement report; otherwise the TTT timer is stopped.

[0036] In 5G mm Wave for the FIG. 2 filtering technique, filtered measurements might not be provided during link blockage even if the UD still resides in the "coverage area" of the AP. For the FIG. 3 filtering technique there might be a gap between the time instant when the entering condition of a measurement event is fulfilled for the TTT and the time when the measurement report is sent. These problems are new and have not been treated so far by 3G or LTE standards. Below are several techniques to address these problems.

[0037] The examples herein assume the measurement event is for adding an AP to the UD's cluster set (for example, where this AP is newly discovered by the UD), but are illustrative for any event- triggered measurement event. FIGs. 4-5 present two different solutions for the case in which the UD's measurements of the AP are filtered in accordance with FIG. 2, with no filtered measurements while the blockage is ongoing. FIGs. 6-7 present two further solutions for the case in which the UD's measurements of the AP are filtered in accordance with FIG. 3, there are filtered measurements for the period while the blockage is ongoing which the UD might for example obtain by interpolating and/or extrapolating from its actual measurements of the AP prior to and/or following the radio link blockage.

[0038] For each of FIGs. 4-7, the UD determines that a radio link with a network node/AP satisfies an entering condition for a measurement event, where there is a specified duration/TTT over which the entering condition of the measurement event shall be satisfied to send a measurement report. The UD initiates a timer in association with that determination to track the duration, but experiences radio link blockage with the network node/AP after initiating the timer. After the radio link blockage expires, the UD wirelessly sends to its CSM a measurement report about the network node that satisfies the measurement event. FIGs. 4-7 present four different techniques for how the UD can take measurements of that node/AP and track the duration TTT so as to satisfy that measurement event, and any of these can be adopted into a published wireless standard/protocol so that all APs, CSMs and UDs operating according to that wireless standard/protocol will have a common understanding of exactly what underlies such reports and indications. For all of these FIG. 4-7 examples assume for ease of explanation that the TTT duration spans four measurement time instances.

[0039] FIG. 4 is a data plot illustrating a first embodiment of these teachings and shows filtered measurement results at various time instances in the presence of a temporary radio link blockage 10.1, where for this filtering technique there are no filtered measurements provided when the radio link is blocked and so the only measurement samples for this AP available to the UD are the filtered actual measurements 130. The entering condition 102 for the add-AP measurement event is an add-threshold shown by the dotted horizontal line. The UD takes measurements at each measurement instant and once the filtered measurement meets or exceeds the add-threshold the entering condition of the measurement event is fulfilled for the first time and the UD initiates 110 its timer associated with this event to track the TTT. At time instant n- r-1 of FIG. 4 the UD's filtered measurement of the AP is above the Add_thr 102 for the first time. The entering condition of the measurement event is satisfied only if the filtered measurements across the duration of the TTT specified for this measurement event meet or exceed the add-threshold. [0040] After initiating 110 the timer to track the duration/TTT the UD 10 experiences a radio link blockage 101 with the new network node/AP it is measuring. There are no measurements available to the UD while the radio link blockage 101 is ongoing and so when the UD determines there is radio link blockage (this occurs after time instant n-r of FIG. 4, specifically at time instant n-r+1) it stops the timer (resets it to zero) and re-starts 112 it after the radio link blockage expires (the UD first sees the radio link blockage expiring at time instant n of FIG. 4).

[0041] The entering condition of the measurement event is satisfied if the UD's filtered measurement of this newly discovered AP is above the predefined threshold Add_thr 102 for a certain TTT 120 which in this example is four measurement instances. The entering condition of the measurement event is satisfied at the timer end 114 at time instant n+3, and so the UD then wirelessly reports an indication of a measurement of the network node/AP that satisfies the measurement event. The UD sends this report uplink to the CSM in the network, preferably over the wireless link 16A to its serving AP 12A but in some cases it may be sent over links 16B, 16C to another AP 12B, 12C already in its cluster set.

[0042] FIG. 5 is a data plot illustrating a second embodiment of these teachings similar to FIG. 4, but for this second embodiment the UD suspends the timer of TTT each time the link is blocked and resumes the TTT timer when the link is not blocked again. Like the first embodiment at FIG. 4, for FIG. 5 there are no filtered measurements provided when the radio link is blocked. The entering condition 102 for the add-AP measurement event is an add- threshold shown by the dotted horizontal line. The UD takes measurements at each measurement instant and once the filtered measurement meets or exceeds the add-threshold the entering condition of the measurement event is fulfilled for the first time and the UD initiates 110 its timer associated with this event to track the TTT. At time instant n-r-1 of FIG. 5 the UD's filtered measurement of the AP is above the Add_thr 102 for the first time, fulfilling the entering condition for this measurement event. The entering condition of the measurement event is satisfied only if the filtered measurements across the duration of the TTT specified for this measurement event meet or exceed the add-threshold. [0043] After initiating 110 the timer to track the duration/TTT the UD 10 experiences radio link blockage 101 with the new network node/AP it is measuring; this radio link blockage 101 begins at time instant (n-r+1) and ends at time instant (n-1). The timer runs from (n-r-1) until it is suspended 11 1A at the time instant (n-r+1) when the radio link blockage 101 begins, and the timer resumes 11 IB once the radio link blockage 101 expires at time instant (n-1). In these examples we assume the TTT spans four samples, and FIG. 5 shows that while the timer is running the UD collects measurement samples from this AP at time instants (n-r-1), (n-r), (n) and (n+1) which is when the TTT timer ends 114.

[0044] For FIG. 5 the entering condition of the measurement event is satisfied at time instant (n+1) and so the UD then wirelessly reports uplink to its network an indication of a measurement of the network node/AP that satisfies the measurement event. Due to the resumption feature of the TTT timer after the link blockage 101, the UD 10 is able to send the measurement report earlier with the second embodiment of FIG. 5 than with the first embodiment of FIG. 4.

[0045] In describing FIGs. 4-5 it was assumed four measurement samples span the TTT duration. In- another implementation of this second embodiment the network, whether the CSM, its serving AP, or some other network entity, can configure the UD 10 with the number N of consecutive times the entering condition of the measurement event shall be fulfilled for sending the measurement report. This would be in place of the TTT duration. The configuration of N could be sent using either a system information block or dedicated radio resource control (RRC) signaling. With this implementation the UD would not have any need to suspend and resume the timer of TTT when the link is respectively blocked and non-blocked; the UD would simply track the number of times the entering condition of the measurement event is fulfilled consecutively and the UD would send the measurement report once the number reaches the network-decided value for N. The end result is very much the same as if the UD were running a timer as in FIG. 5.

[0046] But if the network configured its UDs with a value for N the different UDs might be using different measurement sampling times (durations) or different intervals between samples. In order to normalize this from the network's perspective the network can configure the UD with the TTT and the individual UDs would then compute the value of N from the network-controlled TTT, so for example N = TTT/measurement sampling time of the given UD. If N is not an integer, the UD can apply a rounding operator such as a ceiling operator. Once N is acquired by the UD, the UD would send the measurement report if the entering condition of the measurement event is fulfilled for N consecutive times, regardless of whether the filtered measurements are separated by more than one measurement sampling time due to a link blockage 101.

[0047] Depending on the duration of the link blockage the network could configure the UD as well to apply either the first or the second embodiment. For this, the network can configure the UD with a threshold Tbiock and with the decision whether to employ the first or the second embodiment to apply for the timer of TTT depending on the duration of the link blockage. For example, the network can specify a TTT, and also specify that if the link blockage lasts for a duration longer than Tbiock then use the first embodiment else use the second embodiment. The configuration could be sent using either a system information block or dedicated RRC signaling.

[0048] As a summary for the first and second embodiments, if the measurement filtering in use by the UD does not provide filtered measurements in time instants when the link is blocked: in the first embodiment the UD stops the timer of TTT when the link is blocked and restarts the timer when the link is non-blocked again; while in the second embodiment the UD suspends the timer of TTT each time the link is blocked and resumes the timer of TTT when the link is not blocked again. One implementation for either of these is that the network could configure the UD with a threshold Tbiock and with instructions to apply the first or the second embodiments for the timer of TTT depending on the duration of the link blockage relative to Tbiock-

[0049] In a specific implementation for the second embodiment the network (CSM or any other network entity) can configure the UD with the number N of times the entering condition of the measurement event shall be fulfilled consecutively for sending the measurement report instead of TTT. One variation of this is that the network configures the UD with TTT and the UD computes N from TTT, for example, N = TTT/measurement sampling time of the UD. In any case, once the UD acquires the value for N the UD would send the measurement report if the entering condition of the measurement event is fulfilled for N consecutive times, irrespective whether the filtered measurements are separated by more than the measurement sampling time due to a link blockage.

[0050] As detailed above with respect to FIG. 3, it may be that the controlling radio protocols allow the UD to use interpolated and/or extrapolated sample results when compiling a measurement report, where the interpolated/extrapolated measurement samples represent time instants during which the link is blocked (radio link blockage 101). FIGs. 6-7 are examples of the third and fourth embodiments for checking the entering condition of the measurement event and reporting the measurement results when such interpolated/extrapolated measurement samples are available for use.

[0051] In the third embodiment at FIG. 6 the UD checks if the entering condition 102 (Add threshold) of the measurement event is fulfilled for TTT at any time instant during link blockage 101. There are two main possibilities, of which the first is shown at FIG. 6 and the second is explained afterwards. In the first case at FIG. 6 the UD, determines that its radio link with the newly discovered AP satisfies the entering condition 102 for the Add-AP measurement event, and there is a specified duration/TTT over which the measurement event is considered to be satisfied. At FIG. 6 the entering condition 102 is first satisfied at time instant (n-r-1), prior to the link blockage 101, and so the UD initiates 110 its TTT timer to track the duration/TTT.

[0052] During the radio link blockage 101 there are estimated measurement samples 130A available from the UD's interpolation and/or extrapolation from the actual samples 130. In this example the TTT timer expires 114 while the radio link blockage 101 is ongoing and the estimated samples also satisfy the Add-AP measuring event threshold 102 so the conditions of the measuring event are satisfied when the timer expires 114. The UD uses the actual measurements 130 and the estimated measurements 130A for those time instants while the TTT timer was running and compiles a measurement report from them. But in this case the UD only sends that measurement report at its earliest opportunity after the radio link blockage 101 also expires. In the FIG. 6 example the UD used one or more actual measurements 130 that occurred after the link blockage 101 expired to interpolate or extrapolate one or more of the estimated measurements 130A used to compile its measurement report. So in the FIG. 6 example if the UD used the sample taken at time instant (n) for this interpolation or extrapolation, its first opportunity to transmit that measurement report would be at time instant (n+1).

[0053] It may be that the entering condition of the measurement event is fulfilled for the first time while the radio link is blocked, which the UD recognizes from an estimated measurement. In this case the timer initiation 110 itself occurs during the link blockage, but in any case the link blockage occurs prior to expiiy of the TTT duration that is tracked by that initiated timer. So for the third embodiment of FIG. 6, if the physical layer or filtered measurements occurring before and/or after the link blockage 101 are used in the interpolation/extrapolation 130A, and if the entering condition 102 of the measurement event is fulfilled for the duration/TTT at any time instant during the link blockage 101, then the UD sends the measurement report at the earliest time instant possible when the link is detected again after the link blockage 101.

[0054] The other main possibility for this third embodiment is if the UD gets the estimated samples 130A it needs from extrapolating from the actual samples 130 taken prior to the blockage 101. Unlike the first main possibility above, in this extrapolation-only case the UD does not need an actual sample at time (n) in order to get the estimated examples it needs to fulfill the TTT and compile the measurement report. In this case the UD can send the measurement report at the first transmission opportunity after expiry of the radio link blockage 101, which in FIG. 6 would be at time instant (n). This is suitable if the measurement event is for adding or replacing an AP in the cluster set, which avoids the CSM adding or replacing to a cluster set an AP that is still blocked and which cannot be used for fast re-routing of the UD user and control plane in case the link of the serving AP becomes blocked. But if the measurement event is for removing an AP from the cluster set the network can choose whether the UD is to send its corresponding measurement report directly after the UD's timer of TTT has expired (which per FIG. 6 may occur while the radio link blockage 101 is ongoing) or at the first time instant when the UD detects the link again (time instant (n) in FIG. 6), and the network can configure the UD with that choice via broadcast or dedicated signaling for example. [0055] FIG. 7 illustrates an example of the fourth embodiment, in which the UD checks if the entering condition of the measurement event is fulfilled or not starting from a predefined time instant during link blockage 101. As with other examples, the UD first meets the measurement event entering condition 102 prior to the blockage 101, namely at time instant (n-r- 1) of FIG. 7. The UD experiences link blockage at time instant (n-r+1) which is prior to expiry of the TTT timer, and so the UD stops that timer when it determines there is link blockage 101 which is at time instant (n-r+1) in FIG. 7.

[0056] While the link failure 101 is ongoing in this fourth embodiment the UD is able to extrapolate estimated measurement samples 130A, or it may interpolate or extrapolate if it waits to make those estimates until after the blockage 101 ends. The network configures the UD with a measurement sampling time (n-x) which is spaced a fixed distance in time from (n-r), and this configuring can be via system information or dedicated RRC signaling. If the network- configured value for x is not an integer the UD can apply a rounding operator such as a ceiling operator on it. The UD can use the interpolated or extrapolated samples 13 OA to check whether or not the entering condition 102 of the measurement event is fulfilled starting from that network-configured time instant (n-x), and if yes the UD will re-start 1 12 its timer of TTT. As with other diagrams, in FIG. 7 the time instant (n) is the first instance where the link to this newly discovered AP is no longer blocked. Assuming as FIG. 7 shows that the link remains above the threshold 102 for the duration of the timer of TTT, then the measuring event conditions for sending the measurement report are met once the timer ends 114 and the UD compiles the measurement report using both estimated 130 A and actual 130 measurements, and sends it to the network as soon as the UD is able to send it. hi this fourth embodiment, the filtered measurements of time instants occurring after the link blockage, which in FIG. 7 are those time instants > n , would have impact on whether or not the measurement report is triggered. For example, if the sample at time (n+1) were below the threshold 102 in Fig. 7 then the UD would not send the measurement report corresponding to the Add-AP measurement event.

[0057] In summary, the third and fourth embodiments assume that the measurement filtering method in use by the UD provides filtered measurements in all time instants including those when the link is blocked. In the third embodiment the UD checks if the entering condition of the measurement event is fulfilled for TTT at any time instant during link blockage. If the UD's interpolation/extrapolation method is using the physical layer or filtered measurements occurring after the link blockage and if the entering condition of the measurement event is fulfilled for TTT at any time instant during the link blockage, the UD sends the measurement report at the earliest time instant possible when the link is detected again after the link blockage. If instead the UD's extrapolation method is using the physical layer or filtered measurements occurring before the link blockage, then if the entering condition of the measurement event for adding/replacing an AP from the cluster set is fulfilled for TTT at any time instant during the link blockage the UD would send the measurement report at the first time instant when the link is detected again after the link blockage; else if the entering condition of the measurement event for removing an AP from the cluster set is fulfilled for TTT at any time instant during the link blockage the UD can send the measurement report either 1) directly after the timer of TTT has expired or 2) at. the first time instant when the link is detected again after the link blockage, as configured by the network.

[0058] In the fourth embodiment the UD checks if the entering condition of the measurement event is fulfilled or not starting from a predefined time instant during link blockage. The UD resets the timer of TTT when the link is blocked and checks if the entering condition of the measurement event is fulfilled or not starting from time instant n-x where x =1, (TTT/measurement sampling time of the UD) is configured by the network and n is the first time instant when the link is non-blocked again. The value of x that the network configures for the UD in this fourth embodiment can more generally be considered as an offset from the time the UD first sees the link is blocked.

[0059] FIG. 8 is a process flow diagram that summarizes some of the above aspects from the perspective of the user device, and details a method for sending a measurement report corresponding to a measurement event. At block 802 the UD determines that a radio link with a network node (for example, a newly discovered AP not yet in the UD's cluster set) satisfies an entering condition for a measurement event, where there is a specified duration over which the entering condition shall be satisfied. The measurement event itself is satisfied when the entering condition is satisfied over the specified duration. Then at block 804 the UD initiates a timer in association with the determining to track the duration and at block 806 it experiences radio link blockage with the network node prior to expiry of the tracked duration. The UD compiles the measurement report at block 808 according to any of the first through fourth embodiments detailed above which describe the specific measurement samples to use and how to run the timer of TTT at block 804. Then finally at block 810 the UD wirelessly sends that measurement report about the network node that satisfies the measurement event.

[0060] For completeness, Fig. 9 is a schematic diagram illustrating some components of a network node/network access point 20 such as the UD's serving AP 12A and the UD 10 shown at FIG. 1. In the wireless system a wireless network is adapted for communication over a wireless link 16A with an apparatus such as a mobile communication device which may be referred to as a user device UD 10, via a radio network access node 20 such as an eNB. The network may include functionality for managing a cluster set for the UD 10, shown as the CSM 14. The network may also have (not shown) mobility management entity/serving gateway (MME/S-GW) functionality, and which provides connectivity with a further network such as a telephone network and/or a data communications network (e.g., the internet).

[0061] The UD 10 includes a controller, such as a computer or a data processor (DP) 10D, a computer-readable memory medium embodied as a memory (MEM) 10B that stores a program of computer instructions (PROG) IOC, and a suitable wireless interface, such as radio frequency (RF) transmitter/receiver combination 10D for bidirectional wireless communications with the network node/AP 20 via one or more antennas. There is also a timer of TTT 10E in the UD, which may be implemented as tangibly stored software tracking clock signals output by the DP 10A.^*

[0062] The wireless link 16A between the UD 10 and the network node/AP 20 can be measured for signal strength or signal quality, which may then be compared against a measurement event entering condition as detailed above. [0063] The network node/AP 20 also includes a controller, such as a computer or a data processor (DP) 20A, a computer-readable memory medium embodied as a memory (MEM) 20B that stores a program of computer instructions (PROG) 20C, and a suitable wireless interface, such as RF transmitter/receiver combination 20D for communication with the UD 10 (as well as other UDs) via one or more antennas. The network node/AP 20 may also have the UD's CSM function 14 for tracking and maintaining the UD's cluster set, though this functionality can be in other APs apart from the UD's serving AP. The network node/AP 20 may be coupled via a data/control path (not shown) to a higher network control element (such as the above MME/S- GW) and this path may be implemented as an interface. The network node/AP 20 may also be coupled to another node/AP via another data/control path, which may be implemented as a different interface (see FIG. 1).

[0064] At least one of the PROGs 10C/20C is assumed to include program instructions that, when executed by the associated DP 10A/20A, enable the device to operate in accordance with exemplary embodiments of this invention as detailed above. That is, various exemplary embodiments of this invention may be implemented at least in part by computer software executable by the DP 10A of the UD 10; by the DP 20A of the network node/AP 20, or by hardware or by a combination of software and hardware (and firmware).

[0065] In various exemplary embodiments the UD 10 and/or the network node/AP 20 may also include dedicated processors, for example a RRC module, a radiofrequency (RF) front end, and the like. There may also be one or more modules that is/are constructed so as to operate in accordance with various exemplary embodiments of these teachings.

[0066] The computer readable MEMs 10B/20B may be of any type suitable to the local technical environment and may be implemented using any one or more suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, electromagnetic, infrared, or semiconductor systems. Following is a non-exhaustive list of more specific examples of the computer readable storage medium/memory: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD- ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0067] The DPs 1 OA/20 A may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multicore processor architecture, as non-limiting examples. The wireless interfaces (e.g., the radios 10D/20D) may be of any type suitable to the local technical environment and may be implemented using any suitable communication technology such as individual transmitters, receivers, transceivers or a combination of such components.

[0068] In general, the various embodiments of the UD 10 can include, but are not limited to, smart phones, machine-to-machine (M2M) communication devices, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital ' cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions. Any of these may be embodied as a hand-portable device, a wearable device, a device that is implanted in whole or in part, a vehicle- mounted communication device, and the like.

[0069] It should be understood that the foregoing description is only illustrative. Various alternatives and modifications can be devised by those skilled in the art. For example, features recited in the various dependent claims could be combined with each other in any suitable combination(s). In addition, features from different embodiments described above could be selectively combined into an embodiment that is not specifically detailed herein as separate from the others: Accordingly, the description is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.

Claims

CLAIMS: What is claimed is:

1. A method comprising:

determining that a radio link with a network node satisfies an entering condition for a measurement event, where there is a specified duration over which the entering condition shall be satisfied;

initiating a timer in association with the deteraiining to track the duration;

experiencing radio link blockage with the network node prior to expiry of the tracked duration; and

wirelessly sending a measurement report about the network node that satisfies the measurement event.

2. The method according to claim 1 , the method further comprising, after experiencing the radio link blockage and before wirelessly reporting the indication:

stopping the timer in response to experiencing the radio link blockage;

re-starting the timer in response to the radio link blockage expiring and measuring the network node at consecutive measurement instances that span the specified duration; and

compiling the measurement report from the measuring;

wherein the measurement report is wirelessly sent after the radio link blockage expires.

3. The method according to claim 1, the method further comprising:

measuring the network node at measurement instances prior to and subsequent to the radio link blockage; and

compiling the measurement report from the measuring done prior to and subsequent to the radio link blockage;

4. The method according to claim 3, the method further comprising after experiencing the radio link blockage and before wirelessly reporting the indication:

suspending the timer in response to experiencing the radio link blockage; and resuming the timer in response to the radio link blockage expiring.

5. The method according to claim 3, wherein:

the duration is specified via wireless downlink signaling and the method further comprises determining a number N of consecutive measurement instances to satisfy the duration; some but not all of the N measurement instances are prior to the radio link blockage; and all remaining ones of the N measurement instances are subsequent to the radio link blockage.

6. The method according to claim 1, the method further comprising:

receiving in downlink signaling a value for a parameter Tbiock;

determining an elapsed time for the radio link blockage; and

if the elapsed time is greater than the value, compile the measurement report using measurements of the network node taken after the radio link blockage expires;

else if the elapsed time is less than the value, compile the measurement report using some measurements of the network node taken prior to experiencing the radio link blockage and further measurements of network node taken after the radio link blockage expires.

7. The method according to claim ί , wherein:

the measurement event is for adding and/or replacing a network node;

the measurement report is wirelessly sent at a first transmission opportunity after the radio link blockage expires, and

the method further comprises compiling the measurement report using at least estimated measurements of the network node derived from one or more actual measurements of the network node taken before and/or after the radio link blockage.

8. The method according to claim 7, wherein for a case in which the measurement event is for removing the network node, the measurement report is wirelessly sent at a first transmission opportunity regardless of the radio link blockage.

9. The method according to claim 1, the method further comprising, after experiencing the radio link blockage subsequent to initiating the timer and before wirelessly reporting the indication:

stopping the timer in response to experiencing the radio link blockage;

re-starting the timer at a time offset from when the radio link blockage was first experienced, said offset configured by downlink signaling;

between the time offset and when the radio link blockage expires, estimating measurements of the network node;

between when the radio link blockage expires and an end of the specified duration as tracked by the re-started timer, taking actual measurements of the link; and

using the estimated measurements and the actual measurements of the network node to compile the measurement report.

10. A computer readable memory storing computer program instructions that, when executed by one or more processors, cause a host radio device to:

determine that a radio link with a network node satisfies an entering condition for a measurement event, where there is a specified duration over which the entering condition shall be satisfied;

initiate a timer in association with the determining to track the duration; experience radio link blockage with the network node prior to expiry of the tracked duration; and

wirelessly send a measurement report about the network node that satisfies the measurement event.

11. An apparatus comprising:

at least one computer readable memory storing computer program instructions; and at least one processor;

wherein the computer readable memory with the computer program instructions is configured, with the at least one processor, to cause the apparatus to at least:

determine that a radio link with a network node satisfies an entering condition for a measurement event, where there is a specified duration over which the entering condition shall be satisfied; initiate a timer in association with the determining to track the duration;

experience radio link blockage with the network node prior to expiry of the tracked duration; and

12. The apparatus according to claim 1 1, wherein the computer readable memory with the computer program instructions and the at least one processor are configured to cause the apparatus further to at least, after experiencing the radio link blockage and before wirelessly reporting the indication:

stop the timer in response to experiencing the radio link blockage;

re-start the timer in response to the radio link blockage expiring and measuring the network node at consecutive measurement instances that span the specified duration; and

compile the measurement report from the measuring;

13. The apparatus according to claim 11, wherein the computer readable memory with the computer program instructions and the at least one processor are configured to cause the apparatus further to at least:

measure the network node at measurement instances prior to and subsequent to the radio link blockage; and

compile the measurement report from the measuring done prior to and subsequent to the radio link blockage;

14. The apparatus according to claim 13, wherein the computer readable memory with the computer program instructions and the at least one processor are configured to cause the apparatus further to at least, after experiencing the radio link blockage and before wirelessly reporting the indication:

suspend the timer in response to experiencing the radio link blockage; and

resume the timer in response to the radio link blockage expiring.

15. The apparatus according to claim 13, wherein:

the duration is specified via wireless downlink signaling and the method further comprises deteraiining a number N of consecutive measurement instances to satisfy the duration; some but not all of the N measurement instances are prior to the radio link blockage; and all remaining ones of the N measurement instances are subsequent to the radio link blockage.

16. The apparatus according to claim 11, wherein the computer readable memory with the computer program instaictions and the at least one processor are configured to cause the apparatus further to at least:

receive in downlink signaling a value for a parameter biock;

determine an elapsed time for the radio link blockage; and

17. The apparatus according to claim 11 , wherein:

the measurement event is for adding and/or replacing a network node;

18. The apparatus according to claim 17, wherein for a case in which the measurement event is for removing the network node, the measurement report is wirelessly sent at a first transmission opportunity regardless of the radio link blockage.

19. The apparatus according to claim 11, wherein the computer readable memory with the computer program instructions and the at least one processor are configured to cause the apparatus further to at least, after experiencing the radio link blockage subsequent to initiating the timer and before wirelessly reporting the indication:

stop the timer in response to experiencing the radio link blockage;

between the time offset and when the radio link blockage expires, estimate measurements of the network node;

between when the radio link blockage expires and an end of the specified duration as tracked by the re-started timer, take actual measurements of the link; and

use the estimated measurements and the actual measurements of the network node to compile the measurement report.

20. An apparatus comprising: radio communication means; control means; and timing means; the radio communication means for determining that a radio link with a network node satisfies an entering condition for a measurement event, where there is a specified duration over which the entering condition shall be satisfied;

the control means for initiating the timing means to track the duration in association with the determining;

the control means further for recognizing radio link blockage with the network node prior to expiry of the tracked duration, and the radio communication means further for wirelessly sending a measurement report about the network node that satisfies the measurement event.

21. The apparatus according to claim 20, wherein:

the radio communication means comprises a wireless transmitter and a wireless receiver; the control means comprises one or more processors running executable code stored tangibly on a computer readable memory of the apparatus; and

the timing means comprises at least one of a clock and tangibly stored software implementing a clock using timing or clock signals from the one or more processors.