The present application relates generally to configuration and performing of interfrequency measurements for dual connectivity.
LTE-Advanced as being developed by 3rd Generation Partnership Project (3GPP) is currently being amended to allow the use of dual connectivity. That is, a capability is being developed whereby a user equipment (UE) may consume radio resources provided by at least two different network points termed master enhanced node B (MeNB) and secondary enhanced node B (SeNB). A MeNB is characterized as a base station (eNB) that acts as mobility anchor for the UE towards a core network (CN) whereas a SeNB is characterized as an eNB which provides additional resources for the UE, but is not a MeNB.
As each of the MeNB and SeNB may employ carrier aggregation, each of the MeNB and SeNB may comprise a plurality of cells to facilitate the carrier aggregation. In general, for carrier aggregation of the MeNB, a group of serving cells is associated with the MeNB, comprising a primary cell (PCell) and one or more secondary cells (SCells). This group may be referred to as a master cell group (MCG). For carrier aggregation of the SeNB, a group of serving cells is associated with the SeNB, comprising a primary cell (PSCell) and one or more secondary cells (SCells). This group may be referred to as a secondary cell group (SCG). In the SeNB, the PSCell carries the physical uplink control channel (PUCCH) for the SCG.
As there are no limitations as to which carrier a cell is operating on, the cells in the MCG and SCG may be operating on different carriers, including carriers on different bands.
A further characterization of dual connectivity is that each of the MCG and SCG are handled by different medium access control (MAC) entities.
Various aspects of examples of the invention are set out in the claims.
According to a first aspect of the present invention, an apparatus, method or code for determining a designation of a carrier to at least one of a master cell group and a secondary cell group from at least one of at least one measurement object or at least one reporting configuration received from a network; determining measurement parameters for the carrier based on the designation from at least one of a DRX configuration and activity associated with the determined cell group; and performing measurements on the carrier corresponding to the determined measurement parameters.
According to a second aspect of the present invention, an apparatus, method or code for determining a lack of a designation of a carrier to one of at least a master cell group and a secondary cell group from at least one of at least one measurement object and at least one reporting configuration received from a network; determining measurement parameters for the carrier corresponding to a strictest parameter of at least one selected from a DRX configuration and activity associated with the master cell group and at least one selected from a DRX configuration and activity associated with the secondary cell group; and performing measurements on the carrier corresponding to the determined measurement parameters.
According to a third aspect of the present invention, an apparatus, method or code for determining a designation of a carrier to one of a master cell group and a secondary cell group from at least one of at least one measurement object and at least one reporting configuration received from a network; if the designation of the carrier is determined to be to the secondary cell group, determining measurement parameters for the carrier corresponding to at least one of a DRX configuration and activity associated with the determined secondary cell group and performing measurements on the carrier in accordance with the determined measurement parameters; and if the designation of the carrier is determined to be to the primary cell group, performing measurements on the carrier corresponding to measurement parameters associated with DRX not being configured on the primary cell group, regardless of whether DRX is configured on the primary cell group.
According to a fourth aspect of the present invention, an apparatus, method or code for determining that measurements at a user equipment on a carrier part of the user equipment's master cell group are too infrequent; in response to the determining, indicating to the user equipment a designation of the carrier as also being part of the user equipment's secondary cell group; and one of: receiving), from the user equipment, a measurement report of the carrier in accordance with measurement parameters according to the secondary cell group; receiving, from the user equipment, a measurement report of the carrier in accordance with a strictest of the measurement parameters according to the secondary cell group and the measurement parameters according to the master cell group; or receiving, from the user equipment, a measurement report of the carrier comprising an indication indicating at least whether measurement parameters used in performing measurements associated with the measurement report were associated with the user equipment's master cell group or with the user equipment's secondary cell group.
For a more complete understanding of example embodiments of the present invention, reference is now made to the following descriptions taken in connection with the accompanying drawings in which:
As MCG and SCG are handled through different MAC entities, for example example traffic characteristics and discontinuous transmission (DRX) characteristics of the MCG and SCG may substantially differ. For example, when the SCG is designated for an offloading purpose, the SCG may have low activity for the UE and have a DRX with large gaps configured. At the same time, the MCG may have high activity and have a DRX with short gaps configured, or may have no gaps configured at all. In some scenarios, the UE may not have any activity at all on either the MCG or SCG.
In order to for example balance power consumption due to measurement activity with the need for sufficiently accurate and timely measurement information to facilitate mobility, it is desirable to adapt measurement of carriers to the UEs activity and/or DRX configuration. Parameters by which measurements may be adapted are for example timing for detection of cells, identification of detected cells, measurement duration, radio link monitoring related evaluation periods, etc. These parameters may hence be adapted based on the UEs activity and/or DRX configuration.
However, for example for inter-frequency carriers, a UE may not be aware of whether cells on the carrier should be associated with the MCG or SCG as the UE may not have an existing serving cell in its configured MCG and SCG on the carrier. Hence, it may not be able to determine which DRX and/or activity should be considered for the configuration of the measurement on the inter-frequency carrier.
It may be noted that as the designation of a cell or carrier as belonging to MCG or SCG is a function of the service the cell is intended to provide to a specific UE. A cell or carrier may for example belong the MCG of one UE, but to the SCG of another. And similarly, a cell or carrier may in time transition from MCG to SCG and vice versa for a specific UE. It may hence not be determined from measurement of a broadcast characteristic of a cell whether it is intended to be comprised in the MCG or SCG of a UE.
In one embodiment of the present invention, an eNB determines for a UE a division of at least one (interfrequency) carrier into a group of carriers that belong to the MCG and a group of carriers that belong to the SCG. That is, the eNB designates the carriers as being candidates to serve as PCell or Scell in the UE's MCG or as candidates to serve as PSCell or Scell in the UE's SCG. The eNB then informs the UE of the MCG/SCG designation of at least one (interfrequency) carrier for the purpose of measurement. For example, the eNB may configure the UE with a new measurement object for the at least one (interfrequency) carrier which indicates the designation.
In one embodiment of the present invention, a UE may receive an MCG/SCG designation of at least one (interfrequency) carrier for the purpose of measurement. For example, a UE may receive a configuration for a new measurement object for the at least one (interfrequency) carrier which indicates the designation.
In some embodiments of the presention invention, a UE measures the configured measurement objects indicated to be candidates for its MCG according to the DRX and/or activity of the MCG and measures the configured measurement objects indicated to be candidates for its SCG according to the DRX and/or activity of the SCG.
The UE may, when it is actively scheduled on the MCG, for example when a DRX inactivity timer is running for the MCG, measure the configured measurement objects indicated to be MCG candidates according to non-DRX activity, for example when the UE is not configured with DRX in the MCG.
Similarly, the UE may, when it is actively scheduled on the SCG, for example when a DRX inactivity timer is running for the SCG, measure the configured measurement objects indicated to be SCG candidates according to non-DRX activity, for example when the UE is not configured with DRX in the SCG.
In an example dual connectivity network according to
In accordance with embodiments of the invention, the UE (101), would proceed with measurement of channels f1, f3, f4, f6 and f7 in accordance with the configured at least one measurement object and measure channels f1 and f3 according to the DRX and/or activity of the MCG and measure channels f4, f5 and f7 according to the DRX and/or activity of the SCG.
In an embodiment according the invention, an eNB may designate a carrier by explicitly signaling its designation, for example in a measurement object. The signaling of the cell group designation may take the form of a binary indication. In the context of LTE-A, this may for example take the following form:
In some embodiments, while in dual connectivity, the absence of the cellGroup indicator may imply that the UE should apply the strictest measurement configuration of the measurement configuration according to the MCG DRX and/or activity and the SCG DRX and/or activity. In yet an alternate embodiment, the cellGroup may allow for al least an additional value that explicitly indicates to use the strictest configuration, for example {MCG, SCG, Strictest}
In another embodiment, an eNB may designate a carrier by implicitly signaling its designation. For example, an eNB may designate a carrier to be a candidate for SCG by configuring a measurement event to relate to a PSCell quality or to relate to a carrier where a SCG serving cell is operating. This may in some embodiments be achieved by signaling a reporting configuration which cell's quality (for example reference signal received power (RSRP) or reference signal received quality (RSRQ)) is used as a reference. For example the PCell or PSCell quality could be signaled as being the reference.
In the context of LTE-A, reporting configurations (measurement events) A3 and A5 have been defined. In accordance with an embodiment of the present invention, these events may be modified to include an indication of whether the event is in reference to a PCell or PSCell. In accordance with another embodiment of the present invention, the present events A3 and A5 may be limited for events in the PCell (or MCG) and new events, for example A7 and A8, may be defined which substantially correspond to events A3 and A5, but are limited for events in the PSCell (or SCG). Naturally combinations of these two approaches may also be envisioned.
In the aforementioned embodiments, there is no need for explicit indication of a MCG/SCG designation in a measurement object, as a UE may infer the designation from at least one reporting configuration linked to a measurement object. Such a UE may hence proceed with measurement of an (interfrequency) carrier in accordance with the DRX and/or activity as inferred from the at least one reporting configurations linked to a measurement object.
It is envisioned that reporting configurations for a measurement object may conflict. For example, both PCell and PSCell reporting configurations may be linked to a measurement object for a carrier. For such cases, a UE measure a carrier according to the strictest of the measurement requirements corresponding to the MCG and SCG DRX and/or activity. Strict in this context may be interpreted as requiring the most frequent measurement. For example, if DRX is configured for the MCG and no DRX is configured for SCG, the UE measures the carrier according to the stricter SCG configuration. In another embodiment where such conflict occurs, the UE may be configured to always measure according to the MCG DRX and/or activity.
In yet another embodiment, where a UE receives a designation of a carrier as being for MCG, the UE may always apply measurements as if the MCG does not have DRX configured, regardless of whether it is enabled at the time of measurement.
In yet another embodiment, a UE receives no designation whether an interfrequency carrier measurement is for MCG or SCG, the UE may always apply measurements as if the carrier would not have DRX configured.
Because carriers f2 and f5 are configured as intrafrequency carriers and belong to the UE's MCG and SCG respectively, explicit indication through measurement objects or implicitly through linked reporting is not necessary. Should the indications be present and conflict with the actual allocation of these carriers to MCG and SCG respectively, then the UE may choose or be configured to follow the indications or ignore them.
A UE may for example choose or be configured to selectively follow conflicting indications. For example in a scenario where the MCG is not scheduled and the SCG is scheduled, measurement according to MCG DRX and/or activity parameters may result in infrequent measurement, which increases the chance of losing the connection. In a single connection scenario this is generally acceptable as the lack of scheduled traffic doesn't make reconnection delay problematic. However, in dual connectivity, the loss of MCG connection results in loss of the SCG connection as the SCG connection is tied to the MCG connection. Therefore, loss of the MCG connection would disrupt activity on the SCG. In accordance with an embodiment of the present invention, an eNB may hence explicitly or implicitly designate a carrier currently part of the UE's MCG as SCG, for example to reduce the probability of connection loss. A UE may hence follow such a conflicting designation in performing the corresponding measurements.
Similarly, scenarios may be envisioned where the network wishes to transfer a carrier currently being part of a UE's MCG to the UE's SCG (or vice versa currently being part of a UE's SCG to the UE's MCG) and provides a designation conflicting with the current MCG or SCG to initiate measurements to support the transfer. A UE may hence follow such a conflicting designation in performing the corresponding measurements.
In at least some embodiments according to the invention, a UE providing a measurement report may indicate whether the measurement has been performed according to measurement parameters consistent with the MCG or SCG DRX and/or activity. In the absence of such an explicit indication, an eNB may assume the measurements have been performed consistent with at least one of explicit indications in measurement objects provided by the network to the UE or implicit indications in reporting configurations provided by the network to the UE, for example also including any mutually understood conflict resolution handling as generally disclosed herein.
Embodiments of the present invention may be implemented in software, hardware or a combination thereof. The software and/or hardware may reside on chips comprising for example dedicated circuits or DSPs. In an example embodiment, the software or an instruction set is maintained on any one of various conventional computer-readable media. In the present disclosure, a “computer-readable medium” may be any non-transitory media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. A computer-readable medium may comprise a computer-readable storage medium that may be any non-transitory media or means that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.
It is also noted herein that while the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims While embodiments of the invention are described with examples relating to LTE-A, the invention may be applied to other communication systems applying scheduling requests or messages similar to scheduling requests without departing from the scope of the present invention.
Although various aspects of the invention are set out in combination, other aspects of the invention comprise other combinations of features from the described embodiments. The invention is hence not limited solely to combinations explicitly set out.
While embodiments of the invention are described with examples relating to LTE-A, the invention may be applied to other communication systems.
3GPP TS36.133 v 12.4.0, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); Requirements for support of radio resource management” is hereby incorporated in its entirety.
3GPP TS36.331 v 12.3.0, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification” is hereby incorporated in its entirety.
This application claims priority from U.S. Provisional Patent Application No. 62/056,472 filed Sep. 9, 2014, which is hereby incorporated in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/IB2015/057315 | 9/22/2015 | WO | 00 |
Number | Date | Country | |
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62056472 | Sep 2014 | US |