Paging procedures for user equipments with coverage extension
11696257 · 2023-07-04
Assignee
Inventors
Cpc classification
H04L5/006
ELECTRICITY
H04W68/02
ELECTRICITY
H04W4/70
ELECTRICITY
International classification
H04W68/02
ELECTRICITY
H04W4/70
ELECTRICITY
Abstract
The present disclosure relates to a method for paging coverage extension UEs in a cell controlled by a radio base station. At least one CE-specific paging possibility is defined for paging CE-UEs. The CE-UEs in the cell regularly monitor the at least one CE-specific paging possibility. When the radio base station determines to page all the user equipments in the cell, it pages the CE user equipments in the cell at the CE-specific paging possibility, using a coverage extension technique. The disclosure also relates to a method for paging a CE-UE, which performs radio measurements by a CE-capable user equipment to determine whether coverage extension is necessary. The radio base station is informed about whether the CE-capable user equipment needs coverage extension and then pages the CE-UEs applying or not applying a CE technique depending on whether coverage extension is necessary.
Claims
1. An integrated circuit configured to operate a radio base station, the integrated circuit comprising: receiving circuitry, which, in operation, receives information about whether a user equipment supporting coverage extension in a cell needs coverage extension based on user-equipment radio measurements; and transmitting circuitry, which is coupled to the receiving circuitry and which, in operation, pages the user equipment, the paging including selectively applying one of a plurality of coverage extension techniques based on the received information about whether the user equipment needs coverage extension.
2. The integrated circuit according to claim 1, wherein at least one regularly-occurring coverage-extension-specific paging possibility (CE-specific paging possibility) is defined for paging user equipment that requires coverage extension; wherein the radio base station comprises: processing circuitry, which, in operation, determines whether to page all user equipment in the cell; and wherein the transmitting circuitry, in operation, pages the user equipment supporting coverage extension in the cell at the CE-specific paging possibility.
3. The integrated circuit according to claim 2, wherein the CE-specific paging possibility comprises radio resources of a physical downlink control channel (PDCCH) defined by a radio frame number and a subframe number.
4. The integrated circuit according to claim 2, wherein the transmitting circuitry, in operation, broadcasts the CE-specific paging possibility.
5. The integrated circuit according to claim 2, wherein the CE-specific paging possibility refers to radio resources of a control channel defined by a radio frame number and a subframe number which are pre-configured.
6. The integrated circuit according to claim 5, wherein the transmitting circuitry, in operation, broadcasts information about the pre-configured radio frame number and the pre-configured subframe number.
7. The integrated circuit according to claim 5, wherein the pre-configured subframe number is 1, 2, 3, 6, 7 or 8.
8. The integrated circuit according to claim 2, wherein the paging includes: transmitting a first paging notification at radio resources of a control channel specified by the CE-specific paging possibility; and transmitting a second paging message at radio resources of another channel specified by the first paging notification; wherein the one of the plurality of coverage extension techniques is applied in the transmitting of the first paging notification and in the transmitting of the second paging message.
9. The integrated circuit according to claim 2, wherein, responsive to the processing circuitry determining to page all user equipment in the cell, the transmitting circuitry additionally performs paging at a plurality of UE-specific paging possibilities; wherein each of the plurality of UE-specific paging possibilities is different from the CE-specific paging possibility.
10. The integrated circuit according to claim 1, wherein the one of the plurality of coverage extension techniques includes repeatedly transmitting a paging message a defined number of times.
11. The integrated circuit according to claim 10, wherein the defined number of times is different between different coverage extension levels.
12. The integrated circuit according to claim 1, wherein the user-equipment radio measurements include measurements of a Reference Signal Received Power (RSRP), a Reference Signal Received Quality (RSRQ), a channel quality, and/or a block error rate.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DETAILED DESCRIPTION
(11) A mobile station or mobile node or user terminal or user equipment is a physical entity within a communication network. One node may have several functional entities. A functional entity refers to a software or hardware module that implements and/or offers a predetermined set of functions to other functional entities of a node or the network. Nodes may have one or more interfaces that attach the node to a communication facility or medium over which nodes can communicate. Similarly, a network entity may have a logical interface attaching the functional entity to a communication facility or medium over which it may communicate with other functional entities or correspondent nodes.
(12) The term “radio resources” as used in the set of claims and in the application is to be broadly understood as referring to physical radio resources, such as time-frequency resources.
(13) The term “paging possibility” as used in the set of claims and in the application is to be broadly understood as referring to physical radio resources (frequency-time resources) of a control channel (e.g. the PDCCH), which are defined by a radio frame number (also termed paging frame, PF) and a subframe number (also termed paging occasion, PO).
(14) The expression “coverage-extension UE” (or “CE UE”) as used in the application is to be broadly understood as referring to a UE which requires coverage extension, e.g. because it is in a bad radio condition. The expression “CE-capable UE” shall be used for a UE supporting the coverage extension techniques, irrespective of whether or not the UE indeed requires coverage extension, i.e. a UE can support coverage extension techniques but can still be understood as a “non-CE UE” in case that no coverage extension is currently necessary. From eNB-perspective, it may be unclear at any particular point in time whether a CE-capable UE indeed requires coverage extension or not. The second embodiment is directed at said drawback.
(15) Correspondingly, the expression “non-CE-UE” as used in the application is to be broadly understood as referring to a UE which either does not require coverage extension (even when actually supporting the corresponding CE techniques) or does not support coverage extension techniques.
(16) The expression “UE-specific paging possibility” as used in the set of claims and in the application is to be broadly understood as that paging possibility which is calculated based on the UE-ID (e.g. IMSI), and should be understood in the context of the CE-specific paging possibility which is specific to only coverage extension. As described in the background section, there is only a limited amount of paging possibilities available, across which the UEs are then disposed depending on their IDs. Although a particular paging possibility may be monitored by several UEs, the paging possibilities are UE-specific in the sense that the paging possibility to be monitored by a UE is determined based on the respective UE-ID.
(17) The terms “paging notification” and “paging message” are distinguished in the set of claims and in the application to respectively refer to the first PDCCH message (which is basically an indication notifying about a paging message e.g. by use of the common P-RNTI) and the subsequent PDSCH message with the actual paging information. The term “paging” does not make this distinction and shall cover both.
(18) The term “CE-page” or “CE-paging” as used in the application shall refer broadly to a paging where one out of a plurality of coverage extension techniques is used. For example, when considering the repetition technique as the CE-technique used by an eNB, the “CE-page” will involve repeating the transmission of both paging messages, i.e. the paging notification on the PDCCH and the actual paging message on the PDSCH, for a pre-configured number of times as defined for the repetition technique.
(19) As explained in the background section, coverage extension techniques are to be implemented for (MTC) devices, and it is unclear how the coverage extension shall be achieved for the paging procedure. However, expenditure is quite high for any of these techniques, such that they should be only used when necessary. For the paging which is initiated by the eNB, and is directed to all UEs in the cell, the currently-implemented paging is applied to all possible paging possibilities so as to reach all UEs. In order to reach also the CE-UEs, a coverage extension technique may be applied to the paging at all possible paging possibilities, which however results in a high expenditure of resources.
(20) For the paging which is initiated by the NAS, and is directed to one UE only (or a very limited number of UEs), the MME inform the eNB over the S1 interface about the capability of a RRC_Connected UE to allow coverage extension and thus to support the coverage enhancement techniques mentioned above. However, it is unclear whether the UE is actually requiring coverage extension at the time of the page, (e.g. the UE, e.g. MTC device, moved from the cellar to open terrain). Consequently, the eNB might page the UE at the UE-specific paging possibility by using one of the CE techniques, even though the UE is in a good radio condition and would not have needed a coverage extension page. Again, resources are wasted.
(21) The following exemplary embodiments are conceived by the inventors to mitigate the problems explained above.
(22) Some of these are to be implemented in the wide specification as given by the 3GPP standards and explained partly in the background section, with the particular key features as explained in the following pertaining to the various embodiments. t should be noted that the embodiments may be advantageously used for example in a mobile communication system, such as 3GPP LTE-A (Release 10/11/12/13) communication systems as described in the background section above, but the embodiments are not limited to its use in this particular exemplary communication networks.
(23) The explanations should not be understood as limiting the scope of the disclosure, but as a mere example of embodiments to better understand the present disclosure. A skilled person should be aware that the general principles of the present disclosure as laid out in the claims can be applied to different scenarios and in ways that are not explicitly described herein. Correspondingly, the following scenarios assumed for explanatory purposes of the various embodiments shall not limit the present disclosure and its embodiments as such.
(24) In the following a set of embodiments will be explained. Although in the following embodiments, the broad expressions UE, CE-UE, CE-capable UE, are used, the embodiments may be equally applied for MTC devices, i.e. a CE-MTC device or CE-capable MTC device etc.
First Embodiment
(25) According to a first exemplary embodiment, a paging procedure according to which the eNB can page all the UEs in its cell, including those UEs which require coverage extension (and of course also support coverage extension), is presented.
(26) For this first embodiment it is assumed that the paging is initiated (i.e. triggered) by the eNB itself; in contrast to paging being initiated by the Non-Access-Stratum for which the second embodiment provides an improved paging procedure. As already explained in the background section, paging may be initiated by the eNB for several reasons. For example, system information applicable to the cell may change, and the eNB wants to notify the UEs in its cell such that the UEs may acquire the updated system information immediately from the start of the next modification period. Another reason is that a warning message shall be broadcast in the cell, such as a message from the ETWS or CMAS system, or a message in relation to EAB (Enhanced Access Barring for MTC devices). More detailed information is omitted here, and reference is made to the corresponding passages in the background section which equally apply to the first embodiment.
(27) Consequently, due to nature of those reasons, the eNB wants to make sure that the paging reaches all UEs in the cell, including those UEs which need coverage extension to be successfully reached. According to the first embodiment, a paging possibility is established for specifically paging those CE-UEs, termed in the following CE-specific paging possibility. More precisely, a CE-specific paging frame and a CE-specific subframe are defined referring to radio resources of the PDCCH that can be used for the CE-paging. In a similarly manner as for the UE-specific paging possibilities defined in the current systems, the CE-specific paging possibility shall occur regularly, e.g. in a cyclic manner according to the paging cycle followed by the UE. The CE-specific paging possibility can be defined in addition to the normal UE-specific paging possibilities already established by the related art, as discussed in the background section. The CE-specific paging possibility is independent from the UE's identity and shall be the same for a plurality of CE-UEs, e.g. CE-UEs of a particular cell or all CE-UEs in general (or at least all CE-UEs of a specific CE level as will be explained later); this is different from the normal UE-specific paging possibility which—even though several UEs may monitor the same paging possibility—is specific to the UE due to being calculating based on the ID of the UE(s). This CE-specific paging possibility is known at least to the eNB and the CE-UEs; non-CE-UEs may or may not be informed about this CE-specific paging possibility; however, these non-CE-UEs shall not monitor the CE-specific paging possibility since they may be reached by “normal”, i.e. non-CE, paging.
(28) Furthermore, the paging initiated by the eNB shall reach both UEs in RRC-idle state as well as UEs in RRC-connected state. Consequently, the CE-specific paging possibility shall be monitored by UEs in RRC-idle state and UEs in RRC-connected state.
(29) The CE-UEs regularly monitor the CE-specific paging possibility to receive the CE-paging, thereby ensuring that they can be successfully paged.
(30) From the perspective of the eNB, when a page is triggered (e.g. by a system information change), in order to reach the CE-UEs, the eNB will wait for the corresponding paging opportunity given by the CE-specific paging possibility and will then perform a CE page at the CE-specific paging possibility which is monitored by all the CE-UEs in its cell. In a similar manner as for the UE-specific paging possibility, this particularly involves the transmission of the paging notification on the PDCCH at that radio frame and subframe of the CE-specific paging possibility and the corresponding transmission of the paging message on resources of the PDSCH as indicated by the paging notification on the PDCCH. This transmission of the two messages of the CE page is performed by using one appropriate technique of the plurality of CE techniques which are foreseen for achieving the coverage extension, e.g. a repetition technique or a technique where a significantly increased power is used for the transmission.
(31) The CE-UE(s) in the cell of the eNB monitor the CE-specific paging possibility and thus will receive the paging notification on the PDCCH and subsequently the paging message on the PDSCH. Furthermore, since the eNB will use a coverage extension technique for the paging, which is known to the CE-UE(s), the CE-UE(s) will correspondingly react to the CE-paging by e.g. additionally receiving the repetitions of the paging notification and paging message.
(32) The paging message will inform the CE-UE(s) about e.g. the system information change or a warning message etc. Depending on the content of the paging message on the PDSCH, the CE-UE will react accordingly, e.g. by acquiring the system information at the next modification period or by providing the warning message to the user of the CE-UE.
(33) Of course, in a preferred first embodiment the eNB will also want to page the other (non-CE) UEs and for said purpose will page them at all possible paging possibilities, as discussed in the background section, i.e. this will be done without using any CE technique. The non-CE-UEs will each monitor their UE-specific paging possibility and will thus receive one of the paging performed by the eNB.
(34) In general, the CE-specific paging possibility may be different from any of the UE-specific paging possibilities, assignable for the UEs, although this is not strictly necessary for the functioning of the first embodiment. For example, only subframes 1, 2, 3, 6, 7, and 8 might be possible for the CE-specific paging possibility, considering that the other subframes 0, 4, 5, and 9 are candidates for being selected/calculated as the UE-specific paging possibilities.
(35) In one possible embodiment, the CE-UEs may keep on regularly monitoring their UE-specific paging possibility, calculated based on their identity as explained in the background section, in addition to the CE-specific paging possibility. Alternatively, the CE-UEs may not monitor the CE-specific paging possibility and the UE-specific paging possibility at the same time, but may only monitor the CE-specific paging possibility.
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(39) The first embodiment as explained above has the advantage that the use of the coverage extension technique(s) is limited to one particular CE-specific paging possibility, instead of having to be applied to all possible UE-specific paging possibilities. By using one paging possibility, all (or at least a plurality) of CE-UEs can be paged at the same time. Corresponding downlink resources can thus be saved. Furthermore, the CE-specific paging possibility is independent from the real IMSI of any CE-UE.
(40) The CE-specific paging possibility can be defined in a number of different ways, but must always provide a CE-specific paging radio frame number and CE-specific paging subframe number, known to both the CE-UE(s) and the eNB(s).
(41) According to a first variant of the first embodiment, the CE-specific paging possibility is fixed beforehand, e.g. not calculated but directly indicated. In one example, the numbers for the CE-specific paging radio frame and subframe are directly defined e.g. in the CE-UE (e.g. in its USIM, UICC, etc.) and the eNB; in other words, the CE-UE and the eNB would have information indicating particular radio frame and subframe numbers (such as radio frame number 36 and subframe number 1, as for the example of
(42) Alternatively, instead of directly indicating the CE-specific subframe number, the parameters Ns and i_s (already known from the calculation of the UE-specific paging possibility) could be reused in said respect. In particular, the following exemplary extended table can be used, which, in comparison with the table available from TS 36.304 as explained in the background section, includes at least one additional row for e.g. Ns=5 (any other unused Ns number can be used of course) with the possible POs at subframes 1, 2, 3, and 6.
(43) TABLE-US-00003 TABLE 3 PO PO PO PO Ns when i_s = 0 when i_s = 1 when i_s = 2 when i_s = 3 1 9 N/A N/A N/A 2 4 9 N/A N/A 4 0 4 5 9 5 1 2 3 6
(44) For this alternative, Ns and i_s values would be pre-configured for the CE-specific paging possibility such that the CE-UE and eNB could determine, based on the exemplary table above, which CE-specific paging subframe to use. The CE-specific paging radio frame would in this example still be directly indicated by a corresponding radio frame number.
(45) The advantage of this first variant is that the CE-UE(s) would not need to calculate Ns and i_s, but may directly use the indicated numbers for the radio frame and subframe of the CE-specific paging possibility.
(46) According to a second variant of the first embodiment to define the CE-specific paging possibility vis-a-vis the UE-specific paging possibility, the CE-specific paging possibilities are defined by providing different parameter values to the CE-UE(s) than to the non-CE-UEs. It is assumed, that the CE-specific paging subframe is calculated following the equations and principles explained for the UE-specific paging possibility in the background section. By using different parameter values for the same UE, the calculation of the UE-specific paging subframe yields different subframe numbers than the corresponding subframe numbers of the CE-specific paging possibility. As with the first variant explained above, the radio frame number for the CE-specific paging possibility is fixed.
(47) In one example, the parameter with the different value is “nB”, i.e. indicating the number of paging subframes per paging cycle (across all UEs in the cell), where one value is defined for CE-UEs and another value is defined for non-CE-UEs. There could however be another parameter broadcasted by the network for indicating rather directly the segregation of paging subframes between CE-UEs and non-CE-UEs.
(48) According to a third variant of the first embodiment to define the CE-specific paging possibility, a CE-specific UE identity (e.g. CE-IMSI) is introduced. When considering the various CE levels a CE-UE can be configured for, a CE-level-specific UE identity can be introduced for each CE level. In any case, the CE-IMSI(s) is known to both the eNB and the CE-UE(s). The CE-specific UE identity(ies) can be provided to the CE-UEs beforehand, e.g. broadcast in the cell, or pre-stored in the SIM/USIM or UICC or even in the Mobile Device, ME. A particular CE-UE and the network will use one of these identities corresponding to the required level of coverage extension support required e.g. one CE-UE deep down in bad radio and the network will use UE-identity1; whereas the same UE when coming back in relatively better radio, but still requiring CE support, will rather use UE-identity2 which is the corresponding use UE-identity for this level of Coverage Extension required. For this to work, it is important that the UE-identity to be used and the corresponding coverage extension required is known to both the network and the CE-UE e.g. by way of specification, or broadcasting etc. and there is a hand-shake between the CE-UE and the network about what level applies to the particular CE-UE at any given point in time. The hand-shake includes the measurement configuration and reporting as described previously.
(49) It is assumed that basically the same calculation and principles are applied when calculating the CE-specific paging possibility as explained for the UE-specific paging possibility in the background section. Both the eNB and the CE-UE(s) can calculate the same CE-(level)-specific paging possibility by the CE-(level)-specific IMSI instead of using the CE-UE's real IMSI.
(50) As already mentioned in the background section, different coverage extension levels can be defined (e.g. 15 dB, 13 dB etc.), where the respective coverage extension technique can be adapted appropriately to ensure achieving the corresponding coverage extension level. When e.g. considering the repetition CE technique, a coverage extension level to ensure 15 dB might require 100 repetitions, whereas less or more repetitions may be necessary to ensure a different CE level. Similarly considerations apply to the other CE-techniques.
(51) A particular CE-UE is configured for one of those coverage extension levels. Correspondingly, according to further examples of the first embodiment, one CE-specific paging possibility is defined per CE level, i.e. a CE-level-specific paging possibility, such that a CE-UE will only monitor the CE-level-specific paging possibility of the CE-level for which it is configured but not other CE-level-specific paging possibilities that are defined for other CE-levels.
(52) A further improvement to the first embodiment is that CE-UEs which are in RRC-connected mode may try to read and receive paging at the UE-specific paging possibilities of other UEs. The UE_ID, which is IMSI mod 1024, can only take up to 1024 different values, and the radio frame is calculated based on “UE_ID mod N” such that only N different radio frames are used in each paging cycle. Consequently, a CE-UE could be configured to monitor some or all of the possible radio frames and subframes available for other UEs. This allows the network to not make as many repetitions as would otherwise be required if the UE was not receiving paging other than the UE-specific paging possibilities.
(53) A further improvement to the first embodiment focuses on when to actually perform a CE page. Until now it has been (silently) assumed that there would be always a CE-UE in a cell, such that any eNB, at any time when paging is triggered, would perform the CE-paging at the CE-specific paging possibility(ies). The eNB is aware of all (CE-)UEs that are in RRC-Connected mode, since these have an active connection with the eNB, and thus the eNB determines whether a CE-UE that require coverage extension is in its cell or not. However, the eNB is not aware of which CE-UEs in RRC-Idle mode are currently in its cell. Consequently, assuming that no CE-UEs in RRC-Connected mode are in the cell of the eNB, the eNB is unaware of whether there is at least one CE-UE in RRC-Idle mode in its cell. To make sure that any possible CE-UEs in Idle mode are reached too, in these cases, the eNB will always have to perform the CE paging. This however may result in a waste of resources for the case where no CE-UE(s) in RRC-Idle mode were in its cell either.
(54) According to this improvement, this waste of resources shall be avoided by providing a procedure that allows the eNB to determine whether any CE-UEs are in its cell, be it in RRC-Idle or RRC-Connected state. To said end, the eNB might first determine whether there are any CE-UEs in RRC-Connected mode, which could be done e.g. by maintaining a table with UE-capability information received from the MME or UE. Subsequently, in case the eNB determines that there are no CE-UEs in RRC-Connected mode, a counting procedure is initiated which allows the eNB to determine/estimate the number of CE-UEs in RRC-idle state in its cell. In one example of a counting procedure the UEs in RRC-Idle on a more or less round robin fashion go to RRC-Connected state and inform the network about the presence of the CE UE in RRC-Idle mode (i.e. about itself). The round robin method can e.g. be implemented using a persistence check method wherein the Idle UEs compare a randomly drawn number against a number broadcasted by the network. Only the one(s) drawing a smaller value will transit to RRC Connected to inform the network. The network can keep the broadcasted value to be small enough so that only a very small percentage of UEs should really pass this test at a given time. This is similar to what is done in MBMS Counting procedure as depicted in RRC specification 3GPP TS 36.331, current version 12.4.1 incorporated herein by reference.
(55) In consequence, the eNB will only perform the CE page when it has determined that there is at least one CE-UE in its cell, be it in RRC-Idle or RRC-Connected state. As a result, the additional resources for a CE-page are not used in vain.
Second Embodiment
(56) As explained above, the first embodiment relates to an improvement for a paging procedure initiated by the eNB, which then shall page all UEs in its cell. The second embodiment to be presented relates to an improvement for a paging procedure that is initiated by the NAS (Non-Access-Stratum), e.g. the MME, and which is dedicated to just a single UE, or a rather limited number of UEs.
(57) In particular, for this second embodiment it is assumed that the paging is initiated by the NAS, for instance in order to establish a call with a particular CE-UE; details in said respect have already been provided in the background section (see also
(58) In the above-described scenario, the MME informs the eNBs (over the S1 interface) about the capability(ies) of a (CE-)UE, e.g. whether the UE is capable of supporting coverage extension (and optionally which level of coverage extension). As explained before, this general capability information however gives no information on whether a particular CE-capable UE indeed requires coverage extension at the moment or not; e.g. while a CE-capable UE might have been in a basement for a long time, i.e. thus requiring coverage extension for compensating the bad radio conditions, this very same CE-capable UE might in mean time have emerged from the basement and thus might no longer require coverage extension or still require coverage extension but corresponding to a less demanding coverage extension level.
(59) Consequently, according to the second embodiment, a procedure is implemented according to which the eNB can learn whether a CE-capable UE is indeed requiring coverage extension or not at the time of paging. To said end, a new measurement and reporting procedure is implemented between the UE and the eNB as will be explained in detail below.
(60) The CE-capable UE is configured to perform radio measurements that allow determining whether the CE-capable UE is currently indeed requiring coverage extension or not. The radio measurements could refer for example to one or more of the following: Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), channel quality etc. e.g. as defined in Chapter 5 of 3GPP TS 36.214, “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer; Measurements”, version 10.1.0, or even current Block Error Rate (BLER) estimates or HARQ operating point and any other suitable measurement target. In any case, a skilled person is well aware of how to determine the current radio conditions of a CE-capable UE that allow, in a subsequent step, to determine whether coverage extension is indeed necessary or not.
(61) After performing the appropriate radio measurements, the CE-capable UE shall then determine whether coverage extension is necessary based on the results of the measurements. In one example, two appropriate thresholds can be defined, to which the measurements results are compared by the CE-capable UE so as to determine the current CE status of the CE-capable UE. For example, an upper threshold can be defined, where if the measurements results (e.g. RSRP or RSRQ) exceed the upper threshold, the CE-capable UE would determine that it does not require coverage extension, i.e. that it currently is a non-CE-UE. Conversely, a different lower threshold can be defined, where if the measurement results (e.g. again RSRP or RSRQ) fall below the lower threshold, the CE-capable would conclude that it does require coverage extension, i.e. that is currently is a CE-UE. Instead of using two thresholds, the determination of whether CE is required or not, could of course also be determined by simply using one threshold, where measurements results exceeding the threshold would mean that coverage extension is not necessary, and measurements results falling below the threshold would mean that coverage extension is necessary. The same technique can also be used for other measurement possibility like for HARQ operating point i.e. where HARQ operating point exceeding the corresponding HARQ operating point-threshold would mean that coverage extension is not necessary, and HARQ operating point falling below the HARQ operating point-threshold would mean that coverage extension is necessary.
(62) The radio measurements and CE status determination can be performed regularly by the CE-capable UE, i.e. at specific, pre-configured, intervals, and/or event triggered (one even for exceeding the threshold in either direction as described above), e.g., and/or triggered by the eNB. In addition to the absolute threshold for the corresponding measurement, the network might also provide the corresponding Hysteresis and Time to Trigger values as described in 3GPP TS 36.331, current version 12.4.1. Hysteresis basically gives a margin or allowance in breaching the threshold in either direction, and the Time to Trigger (TTT) indicates at least how long the said threshold should remain breached/exceeded for the UE to trigger the corresponding event.
(63) Which radio measurements shall be performed, at which intervals, against which threshold(s) the measurement results should be compared, and any other necessary information can be pre-configured in the CE-capable UE or provided to the CE-capable UEs from the eNB, e.g. within a corresponding control message which could be signaled by RRC or Layer2 (MAC) or Layer1 (Physical layer signal) and may contain additional parameters including Hysteresis, TTT and the target object like current/serving and neighbor cell list.
(64) The CE-capable UE has to make sure that the eNB is kept updated on the current CE status, i.e. on whether the CE-capable UE needs coverage extension or not. This may be done e.g. by reporting every change of CE status to the eNB, such that the eNB knows at the time of paging whether a coverage extension technique shall be applied to the paging or not. Of course the same information can be used for DL messages other than paging and also to UL messages including paging response and other non-paging related messages. Depending on whether the CE-capable UE is in idle mode or connected mode, the reporting of the CE status to the eNB may be different. If the CE-capable UE is in RRC connected state and thus has an active connection with the eNB, the CE-capable UE can directly transmit a CE-status report, e.g. RRC Measurement Report, to the eNB.
(65) Since such a direct report is not possible for CE-capable UEs in RRC-IDLE (since no active connection with the eNB is available), the CE-capable UE in idle will report the CE status to the MME, which thus knows whether coverage extension is indeed required or not (independent from the CE-capability of a UE). The MME may either keep the eNB(s) regularly up to date in said respect, or might only provide the corresponding information to the eNB(s) when also triggering the eNB for paging. Of course, also CE-capable UEs in RRC connected could inform the MME, instead of or in addition to the eNB.
(66) In another alternative, the CE-capable UE in idle will report the CE status and UE NAS identity directly to the serving eNB where the UE is camped in currently e.g. upon cell Selection and Reselection(s), which thus knows whether coverage extension is indeed required or not by maintaining a new Table including the UE NAS identity and CE-requirement.
(67) Alternatively, another improvement provides that the CE-capable UEs do not change into RRC-idle state and thus remain all the time in RRC-connected state, such that the CE-capable UE can always transmit the measurement report directly to the eNB. The eNB can ensure that the UE remains in connected state by never sending the RRC Connection Release message to the UE i.e. basically ignoring any inactivity timer in the eNB for this UE.
(68) In any case, the eNB, when being triggered to page a particular CE-capable UE, will be informed about and will consider whether said CE-capable UE indeed requires coverage extension or not. Based on the thus known current CE status of the UE, the eNB will or will not apply an appropriate CE technique to the paging of the CE-capable UE. As explained in detail for the first embodiment already, applying the CE technique to paging involves applying the CE technique to both the paging notification transmitted on the PDCCH and the actual paging message transmitted on the PDSCH as addressed by the PDCCH.
(69) In other words, two measurement events are defined, one referring to the case where the radio measurements indicate that coverage extension is required, and the other referring to the case where the radio measurements indicate that coverage extension is not required. When any of the two events occur, this is reported to the eNB (either directly or via the core network entity, e.g. MME).
(70)
(71)
(72)
(73)
(74) Another improvement of the second embodiment, which is also illustrated in
(75) Still a further improvement of the second embodiment is also illustrated in
Third Embodiment
(76) According to a third embodiment, the first embodiment and the second embodiment are combined such that CE devices can be paged both at the NAS level and the AS level (i.e. initiated by NAS and initiated by eNB). Thus, the separation of NAS and AS is maintained as in legacy systems. Furthermore, the first and second embodiments are simple to implement and have no impact on legacy procedures.
(77) One non-limiting and exemplary embodiment provides an improved method for paging all user equipments in a cell, particularly involving user equipments which need coverage extension. Another non-limiting and exemplary embodiment provides an improved method for paging one user equipment in a cell, particularly a user equipment which needs coverage extension.
(78) The independent claims provide non-limiting and exemplary embodiments. Advantageous embodiments are subject to the dependent claims.
(79) According to a first aspect, the present disclosure improves the paging procedure by which a radio base station can page the user equipments in its cell, particularly for the case where the paging shall also reach user equipments which require coverage extension, i.e. user equipments that are in poor radio conditions but support coverage extension techniques as explained in the background section. The first aspect refers to the case were paging is initiated by the radio base station and shall reach all user equipments in the cell of the radio base station; in other words, the paging is not UE specific but cell specific, and can be for example used so as to broadcast a warning message or to inform UEs about an imminent system information change.
(80) Consequently, the paging must reach user equipments that require coverage extension as well as “normal” user equipments which do not require coverage extension. One main idea of the first aspect is the definition of a coverage-extension-specific paging possibility, which is specifically defined for those user equipments that support coverage extension techniques, and more precisely which need coverage extension to be reliably reached. Correspondingly, the CE-UEs not only monitor the UE-specific paging possibility, calculated based on their identities, but additionally monitor a (at least one) different paging possibility dedicated to achieve coverage extension paging. Both CE-user equipments in idle and connected state can be configured to monitor this CE-specific paging possibility. Consequently, in order to reach those CE-UEs, the radio base station pages the CE-UEs at said CE-specific paging possibility, and uses one of the plurality of available techniques (e.g. repetition or increased transmission power) for extending the coverage of the paging and thus to reliably reach the CE-UE.
(81) Like a usual UE-specific paging possibility, this CE-specific paging possibility is defined by a particular radio frame number and subframe number, and occurs regularly e.g. at every paging cycle.
(82) Since the CE-specific paging possibility shall preferably only be monitored by CE-UEs, the radio base station still needs to reach the other non-CE-UEs and can thus, as described in the background section, perform the paging at all possible paging possibilities of a paging cycle, so as to reach all UEs in the cell. In this case the radio base station would not use a coverage extension technique, since the radio base station can be sure that the CE-UEs will be reached by the paging at the CE-specific paging possibility and not for all possible.
(83) One advantage of the above-described first aspect is that, by providing one dedicated paging possibility for CE-UEs, downlink resources can be saved. The coverage extension techniques, which can be a heavy burden to the radio base station(s) are applied in a very limited manner, namely for just one paging possibility.
(84) One set of variants of the first aspect differs as to how this CE-specific paging possibility is defined. In general, it can be said that the CE-specific paging possibility must be known to both the CE-UE(s) and the radio base station(s), so as to ensure that the paging can be successful. However, how exactly the CE-specific paging possibility is defined can vary. One solution is that the radio frame number and the subframe number of the CE-specific paging possibility is fixed beforehand such that corresponding information can be e.g. pre-stored at the radio base station and the CE-UE (e.g. in the USIM), or the radio base station can broadcast same in its cell. Another possible solution is that a plurality of possible paging subframes, generally configured for the system by the radio base station, is divided to be used either as a UE-specific paging subframe or as a CE-specific paging subframe. By correspondingly configuring the paging parameter(s) (e.g. nB) of normal UEs and CE-UEs it is possible that CE-UEs are assigned e.g. one normal UE-specific paging subframe and one CE-specific paging subframe. Still another solution is based on an additional CE-specific UE identity that is assigned exclusively to CE-UEs and which can be used for calculating the CE-specific paging possibility; in addition, as in the prior art, the UE-specific paging possibility is calculated based on the usual identity of the CE-UE (e.g. IMSI).
(85) According to a second aspect, the paging procedure by which a radio base station pages a user equipment which requires coverage extension in its cell is improved. This second aspect refers to the case where the paging is initiated in the core network (NAS) and is destined to a single UE (or a very limited number of UEs), in contrast to the first aspect dealing with cell-wide paging initiated by the eNB. The paging which is directed at a particular CE-UE shall reliably reach the CE-UE, and thus the radio base station shall use one appropriate coverage extension technique for the CE paging. In order to avoid unnecessary CE paging from the radio base station, the CE-capable UEs will implement a measurement and reporting procedure according to which the radio base station is informed as to the current CE status of the UE. The radio base station will thus only perform a CE paging for a CE-capable UE that is indeed currently in the CE status, i.e. currently requiring coverage extension. CE-UEs, although CE capable, will not be paged with a coverage extension technique, if the status of the CE-capable UE, informed to the radio base station, indicates that no coverage extension is actually required by this CE-capable UE at the moment.
(86) Appropriate radio measurements are regularly performed by the CE-capable UE(s) to determine whether coverage extension is necessary or not at the moment. The measurements could also be triggered by the radio base station or a core network entity when being interested in the current CE status. These measurements could include e.g. at least one of RSRQ, RSRP, channel quality, block error rate, or any other suitable measurement parameter. Appropriate threshold(s) can be defined to which the CE-capable UE(s) compare(s) the measurement results to determine whether it requires or not coverage extension.
(87) Consequently, a particular CE-capable UE can change it CE-status, i.e. toggle between being a CE-UE (i.e. indeed requiring coverage extension) and a non-CE-UE (i.e. supporting CE but not requiring CE at the moment).
(88) The radio base station is kept updated on the current CE status of the CE-capable UE and thus (should) knows at the time of paging whether coverage extension is indeed necessary or not for the paging. In order to limit uplink traffic, the informing of the radio base station could be limited to the cases where the CE status of the CE-capable UE is changed, i.e. from non-CE-UE to CE-UE and vice versa. Of course it should also be possible for the CE-capable UE to measure and report such information/measurements periodically even in the absence of said toggling. In this case, the eNB could, based on its implementation, perform some averaging of the received information including measurement reports and determine that a toggling of CE state is indeed helpful. The step of informing may be done, e.g. directly between the CE-capable UE and the radio base station, e.g. for CE-capable UEs that are in connected state and thus may provide the corresponding CE status to the radio base station. Alternatively, the CE-capable UE may report to a core network entity, which in turn may inform the radio base station, at the latest when triggering for paging; this may be done e.g. for those cases where the CE-capable UE is in idle state and thus has no active connection with the radio base station.
(89) Correspondingly, the paging for CE-UE is performed by the radio base station by using a CE technique, whereas paging for a non-CE-UE is performed without using a CE technique. The CE-capable UE appropriately receives the CE paging or normal paging.
(90) Correspondingly, in one general first aspect, the techniques disclosed here feature a method for paging all user equipments in a cell controlled by a radio base station in a mobile communication system. At least one regularly-occurring coverage-extension-specific paging possibility, in short CE-specific paging possibility, is defined for paging user equipments that require coverage extension, in short CE user equipments. The radio base station is capable to use one of a plurality of techniques for achieving a coverage extension for a CE user equipment. The CE user equipments in the cell regularly monitor the at least one CE-specific paging possibility. When the radio base station determines to page all the user equipments in the cell, the radio base station pages the CE user equipments in the cell at the CE-specific paging possibility, using one of the plurality of techniques for achieving the coverage extension.
(91) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, a plurality of UE-specific paging possibilities is defined for paging a specific user equipment in the cell of the radio base station. The CE user equipments and non-CE user equipments each monitor a respective UE-specific paging possibility out of the plurality of UE-specific paging possibilities. The radio base station—upon determining to page all the user equipments in the cell—additionally performs paging at all of the plurality of UE-specific paging possibilities without using one of the plurality of techniques for achieving coverage extension. According to a further example, each of the plurality of UE-specific paging possibilities is different from the at least one CE-specific paging possibility.
(92) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, each of the at least one CE-specific paging possibility refers to radio resources of a control channel defined by a radio frame number and subframe number and is repeated every paging cycle. The at least one CE-specific paging possibility is only monitored by CE user equipments. For example, the at least one CE-specific paging possibility is monitored by CE user equipments in idle state and CE user equipments in connected state.
(93) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, the step of paging includes transmitting by the radio base station a first paging notification at radio resources of a control channel specified by the at least one CE-specific paging possibility, and includes transmitting by the radio base station a second paging message at radio resources of another channel specified by the first paging notification. For example, the technique for achieving the coverage extension is applied to both steps of transmitting the first paging notification and of transmitting the second paging message.
(94) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, the plurality of techniques for achieving the coverage extension comprise at least one of a repetition technique where a message is repeated by the radio base station for a pre-configured number of times, an increase in transmission power, where a message is transmitted by the radio base station with an increased transmission power, a bundling technique where a .same message is transmitted in a plurality of consecutive subframes, and a spreading technique where a message is transmitted by a larger resource, e.g. via a larger frequency-time resource or channelization code.
(95) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, the step of determining by the radio base station to page all user equipments in the cell is triggered by a change of system information applicable to the cell controlled by the radio base station or by the presence of a message, e.g. a warning message, to be broadcast in the cell controlled by the radio base station.
(96) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, each of the at least one CE-specific paging possibility refers to radio resources of a control channel defined by a radio frame number and a subframe number which are pre-configured such that the radio frame number and the subframe number are fixed for the CE-specific paging possibility. For example, information to determine the pre-configured radio frame number and the pre-configured subframe number is stored in a Universal Subscriber Identity Module, USIM, of the CE user equipment, or broadcast by the radio base station in the cell. Further exemplary, the pre-configured subframe number is 1, 2, 3, 6, 7, or 8.
(97) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, a plurality of paging possibilities are defined for paging in the cell of the radio base station, wherein a first value of at least one parameter for calculating the UE-specific paging possibility is different from a second value of the at least one parameter for calculating a CE-specific paging possibility such that the plurality of paging possibilities are divided to be used either as the CE-specific paging possibility or the UE-specific paging possibility. CE user equipments are configured to use the first value of the at least one parameter for calculating the UE-specific paging possibility and to use the second value of the at least one parameter for calculating the CE-specific paging possibility. Non-CE user equipments are configured to use the first value of the at least one parameter for calculating the UE-specific paging possibility and to not calculate the CE-specific paging possibility.
(98) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, 6, wherein CE user equipments are assigned a CE-specific user equipment identity based on which the CE-specific paging possibility is calculated by the radio base station and the CE user equipments. For example, the CE-specific user equipment identity is the same for all CE-configured user equipments, and the CE-specific user equipment identity is stored in a Universal Subscriber Identity Module, USIM, of the CE user equipment or broadcast by the radio base station in the cell. Further for example, a plurality of different levels of coverage extension is defined, and wherein for each level of coverage extension a different CE-specific user equipment identity is defined.
(99) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, wherein a plurality of different levels of coverage extension is defined, and wherein for each level of coverage extension a different CE-specific paging possibility is defined for paging the CE user equipments configured for that level of coverage extension.
(100) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, the radio base station determines whether there are CE user equipments in idle state in its cell by performing a counting procedure where the CE user equipments in idle state inform the radio base station about their presence in the cell controlled by the radio base station. For example, the determination is only performed in case there are no CE user equipments in connected state in the cell.
(101) Correspondingly, in one general first aspect, the techniques disclosed here feature a user equipment located in a cell controlled by a radio base station in a mobile communication system. The user equipment, in short CE user equipment, requires coverage extension, wherein at least one regularly-occurring coverage-extension-specific paging possibility, in short CE-specific paging possibility, is defined for the CE user equipment. The radio base station is capable to use one of a plurality of techniques for achieving a coverage extension for the CE user equipment. A processor of the CE user equipment regularly monitors the at least one CE-specific paging possibility. A receiver of the CE user equipment receives a paging from the radio base station at the CE-specific paging possibility, using one of the plurality of techniques for achieving the coverage extension.
(102) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, a plurality of UE-specific paging possibilities is defined for paging a specific user equipment in the cell of the radio base station. The processor of the CE user equipment monitors a respective UE-specific paging possibility out of the plurality of UE-specific paging possibilities. In a further example, each of the plurality of UE-specific paging possibilities is different from the at least one CE-specific paging possibility.
(103) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, wherein each of the at least one CE-specific paging possibility refers to radio resources of a control channel defined by a radio frame number and subframe number and is repeated every paging cycle. In a further example, the at least one CE-specific paging possibility is monitored by the CE user equipment when in idle state and when in connected state.
(104) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, the receiver receiving the paging includes: receiving a first paging notification at radio resources of a control channel specific by the at least one CE-specific paging possibility, and includes receiving a second paging message at radio resources of another channel specific by the first paging notification. In a further example, the technique for achieving the coverage extension is used by the CE user equipment to both receive the first paging notification and receive the second paging message.
(105) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, each of the at least one CE-specific paging possibility refers to radio resources of a control channel defined by a radio frame number and a subframe number which are pre-configured such that the radio frame number and the subframe number are fixed for the CE-specific paging possibility. In a further example, a memory of the CE user equipment is adapted to store information to determine the pre-configured radio frame number and the pre-configured subframe number. Exemplarily, the memory is a Universal Subscriber Identity Module, USIM, of the CE user equipment. Or, the receiver of the CE user equipment receives information to determine the pre-configured radio frame number and the pre-configured subframe number, broadcast by the radio base station in the cell.
(106) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, the CE user equipment is assigned a CE-specific user equipment identity, wherein the processor of the CE user equipment is adapted to calculate the CE-specific paging possibility based on the CE-specific user equipment identity. Exemplarily, the CE-specific user equipment identity is the same for all CE-configured user equipments. In a further example, a plurality of different levels of coverage extension is defined. For each level of coverage extension a different CE-specific user equipment identity is defined.
(107) Correspondingly, in one general first aspect, the techniques disclosed here feature a radio base station for paging all user equipments in a cell controlled by the radio base station in a mobile communication system. At least one regularly-occurring coverage-extension-specific paging possibility, in short CE-specific paging possibility, is defined for paging user equipments that require coverage extension, in short CE user equipments. The radio base station is capable to use one of a plurality of techniques for achieving a coverage extension for a CE user equipment. A processor of the radio base station determines whether to page all the user equipments in the cell. A transmitter of the radio base station pages the CE user equipments in the cell at the CE-specific paging possibility, using one of the plurality of techniques for achieving the coverage extension.
(108) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, a plurality of UE-specific paging possibilities are defined for paging a specific user equipment in the cell of the radio base station, wherein transmitter of the radio base station—upon the processor determining to page all the user equipments in the cell—additionally pages at all of the plurality of UE-specific paging possibilities without using one of the plurality of techniques for achieving coverage extension. For example, each of the plurality of UE-specific paging possibilities is different from the at least one CE-specific paging possibility.
(109) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, the transmitter of the radio base station is adapted to transmit a first paging notification at radio resources of a control channel specified by the at least one CE-specific paging possibility, and to transmit a second paging message at radio resources of another channel specified by the first paging notification. Exemplarily, the technique for achieving the coverage extension is applied to both the transmitting of the first paging notification and the transmitting of the second paging message.
(110) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, the processor determines to page all the user equipments in the cell when being triggered by a change of system information applicable to the cell controlled by the radio base station or by the presence of a message, e.g. a warning message, to be broadcast in the cell controlled by the radio base station.
(111) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, each of the at least one CE-specific paging possibility refers to radio resources of a control channel defined by a radio frame number and a subframe number which are pre-configured such that the radio frame number and the subframe number are fixed for the CE-specific paging possibility. Exemplarily, information to determine the pre-configured radio frame number and the pre-configured subframe number is stored in the radio base station, wherein the transmitter of the radio base station broadcasts the information to determine the pre-configured radio frame number and subframe number.
(112) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, a CE-specific user equipment identity is assigned to the CE user equipments, wherein the processor of the radio base station is adapted to calculate the CE-specific paging possibility based on the CE-specific user equipment identity. Exemplarily, the transmitter of the radio base station is adapted to broadcast the CE-specific user equipment identity in the cell.
(113) According to an advantageous variant of the first aspect which can be used in addition or alternatively to the above, the processor of the radio base station determines whether there are CE user equipments in idle state in its cell by performing a counting procedure. Exemplarily, the determination is only performed in case there are no CE user equipments in connected state in the cell.
(114) Correspondingly, in one general second aspect, the techniques disclosed here feature a method for paging a user equipment in a cell controlled by a radio base station in a mobile communication system. The user equipment supports coverage extension techniques, wherein the radio base station is capable to use one of a plurality of techniques for achieving a coverage extension for the CE-capable user equipment. Radio measurements are performed by the CE-capable user equipment, which determines whether coverage extension is necessary or not, based on the results of the radio measurements. The radio base station is informed about whether the CE-capable user equipment needs coverage extension or not, based on the determination result. When paging the CE-capable user equipment, the radio base station applies or not applies one of the plurality of techniques for achieving coverage extension depending on whether coverage extension is necessary or not for the CE-capable user equipment.
(115) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the radio measurements performed by the CE-capable user equipment include measurements of a Reference Signal Received Power, RSRP, and/or Reference Signal Received Quality, RSRQ, and/or a channel quality, and/or a block error rate and/or HARQ operating point.
(116) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the step of determining whether coverage extension is necessary comprises the step of comparing by the CE-capable user equipment the result of the radio measurements with a first threshold to determine whether coverage extension is necessary. For example, the comparison determines that coverage extension is necessary when the result of the radio measurements falls below the first threshold. The step further comprises comparing by the CE-capable user equipment the result of the radio measurements with a second threshold to determine whether coverage extension is not necessary. For example, the comparison determines that coverage extension is not necessary when the result of the radio measurement exceeds the second threshold.
(117) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the step of informing the radio base station about the CE-capable user equipment needing coverage extension or not, includes the steps of either transmitting by the CE-capable user equipment information about whether the CE-capable user equipment needs coverage extension or not to the radio base station. In this case, for example the CE-capable user equipment is in a connected state. In a further example, it is avoided that the CE-capable user equipment is changing into the idle state by keeping it in the connected state. Alternatively, the step of informing includes the steps of transmitting by the CE-capable user equipment information about whether the CE-capable user equipment needs coverage extension or not to a core network entity. In this case, the core network entity provides the received information to the radio base station. For example, the CE-capable user equipment is in a connected state or in an idle state. In a further example, the core network entity is a mobility management entity.
(118) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the radio base station is triggered to page the CE-capable user equipment by a core network entity that initiates and controls the paging, preferably wherein the core network entity initiating the paging is a mobility management entity.
(119) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the steps of performing the radio measurements and of determining whether coverage extension is necessary or not is performed regularly at a pre-configured time interval and/or triggered by the radio base station.
(120) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the step of informing the radio base station is only performed when the result of the determination is different from the result of the determination previously informed to the radio base station.
(121) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the radio base station determines whether the CE-capable user equipment needs coverage extension or not based on the radio resources selected by the CE-capable user equipment for initially attaching to the radio base station; for example, based on the selected preamble or access slot used for a random access procedure performed by the CE-capable user equipment when initially attaching to the radio base station.
(122) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the step of paging the CE-capable user equipment comprises the steps of transmitting by the radio base station a first paging notification at radio resources of a control channel specified by a paging possibility specific to the CE-capable user equipment, and transmitting by the radio base station a second paging message at radio resources of another channel specified by the first paging notification. In a further example, the technique for achieving the coverage extension is applied to both steps of transmitting the first paging notification and of transmitting the second paging message.
(123) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, upon successfully being paged by the radio base station, the CE-capable user equipment informs the radio base station about the successful paging, and the radio base station can inform a core network entity responsible for initiating the paging about the successful paging.
(124) Correspondingly, in one general second aspect, the techniques disclosed here feature a user equipment located in a cell controlled by a radio base station in a mobile communication system. The user equipment, in short CE user equipment, supports coverage extension techniques. The radio base station is capable to use one of a plurality of techniques for achieving a coverage extension for the CE-capable user equipment. A processor of the CE user equipment performs radio measurements, and determines whether coverage extension is necessary or not, based on the results of the radio measurements. A transmitter of the CE user equipment informs the radio base station about whether the CE-capable user equipment needs coverage extension or not, based on the determination result. A receiver of the CE user equipment receives paging from the radio base station, applying or not applying one of the plurality of techniques for achieving coverage extension depending on whether coverage extension is necessary or not.
(125) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the radio measurements performed by the CE-capable user equipment include measurements of a Reference Signal Received Power, RSRP, and/or Reference Signal Received Quality, RSRQ, and/or a channel quality, and/or a block error rate and/or HARQ operating point.
(126) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the processor determines whether coverage extension is necessary or not by comparing the result of the radio measurements with a first threshold to determine whether coverage extension is necessary. For example, the comparison determines that coverage extension is necessary when the result of the radio measurements falls below the first threshold. Furthermore, the result of the radio measurements is compared with a second threshold to determine whether coverage extension is not necessary. For example, the comparison determines that coverage extension is not necessary when the result of the radio measurement exceeds the second threshold.
(127) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the transmitter informs the radio base station by transmitting information about whether the CE-capable user equipment needs coverage extension or not to the radio base station. For example, the CE-capable user equipment is in a connected state, and furthermore it is avoided that the CE-capable user equipment is changing into the idle state by keeping it in the connected state. Alternatively, information about whether the CE-capable user equipment needs coverage extension or not is transmitted to a core network entity. The core network entity provides the received information to the radio base station, preferably wherein the CE-capable user equipment is in a connected state or in an idle state.
(128) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the processor performing the radio measurements and determining whether coverage extension is necessary or not is performed regularly at a pre-configured time interval and/or triggered by the radio base station.
(129) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the transmitter informs the radio base station only when the result of the determination is different from the result of the determination previously informed to the radio base station.
(130) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the receiver receiving the paging includes receiving a first paging notification at radio resources of a control channel specific by a paging possibility specific to the CE-capable user equipment, and receiving a second paging message at radio resources of another channel specific by the first paging notification. For example, the technique for achieving the coverage extension is used by the CE user equipment to both receive the first paging notification and receive the second paging message.
(131) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the transmitter is further adapted to inform the radio base station about the successful paging.
(132) Correspondingly, in one general second aspect, the techniques disclosed here feature a radio base station for paging a user equipment in a cell controlled by the radio base station in a mobile communication system. The user equipment supports coverage extension techniques. The radio base station is capable to use one of a plurality of techniques for achieving a coverage extension for the CE-capable user equipment. A receiver of the radio base station receives information about whether the CE-capable user equipment needs coverage extension or not. A transmitter of the radio base station, when paging the CE-capable user equipment, applies or not applies one of the plurality of techniques for achieving coverage extension depending on whether coverage extension is necessary or not for the CE-capable user equipment.
(133) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the receiver receiving the information includes receiving from the CE-capable user equipment or from a core network entity the information about whether the CE-capable user equipment needs coverage extension or not.
(134) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, the transmitter of the radio base station transmit a first paging notification at radio resources of a control channel specified by a paging possibility specific to the CE user equipment, and transmit a second paging message at radio resources of another channel specified by the first paging notification. For example, the technique for achieving the coverage extension is applied to both the transmitting of the first paging notification and the transmitting of the second paging message.
(135) According to an advantageous variant of the second aspect which can be used in addition or alternatively to the above, a receiver of the radio base station receives information about the successful paging of the CE user equipment, and the transmitter of the radio base station informs a core network entity responsible for initiating the paging about the successful paging.
(136) Hardware and Software Implementation of the Present Disclosure
(137) Other exemplary embodiments relate to the implementation of the above described various embodiments using hardware and software. In this connection a user terminal (mobile terminal) and an eNodeB (base station) are provided. The user terminal and base station is adapted to perform the methods described herein, including corresponding entities to participate appropriately in the methods, such as receiver, transmitter, processors.
(138) It is further recognized that the various embodiments may be implemented or performed using computing devices (processors). A computing device or processor may for example be general purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, etc. The various embodiments may also be performed or embodied by a combination of these devices.
(139) Further, the various embodiments may also be implemented by means of software modules, which are executed by a processor or directly in hardware. Also a combination of software modules and a hardware implementation may be possible. The software modules may be stored on any kind of computer readable storage media, for example, RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc.
(140) It should be further noted that the individual features of the different embodiments may individually or in arbitrary combination be subject matter to another embodiment.
(141) It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present disclosure as shown in the specific embodiments. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.