Extended discontinuous reception signaling for connected mode user equipments

A user equipment uses extended discontinuous reception (DRX) when the user equipment is in connected mode with a communication network. The extended DRX comprises extended DRX cycles and offsets, which are based on a value of a specific DRX cycle. The user equipment receives (S31) signaling from the communication network, the signaling comprising an extended DRX cycle indication and offset value, calculates (S32) an extended DRX cycle from the extended DRX cycle indication and an offset from the offset value, using the value of the specific DRX cycle, and executes (S33) the DRX when the user equipment is in the connected mode with the extended DRX cycle calculated and the offset calculated.

RELATED APPLICATION

This application was originally filed as PCT Application No. PCT/CN2015/073979 filed Mar. 11, 2015.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to extended discontinuous reception (DRX) signaling for connected mode user equipments (UEs).

Related Background Art

The following meanings for the abbreviations used in this specification apply:

C-RNTI Cell Radio Network Temporary Identifier

DRX Discontinuous Reception

LTE Long Term Evolution

PDCCH Physical Downlink Control Channel

RAN Radio Access Network

RRC Radio Resource Control

SIB System Information Block

UE User Equipment

For UE energy saving purpose, DRX has been defined in LTE. If an UE is configured with DRX by higher layer, the UE is not required to monitor PDCCH when it is not in active time as show inFIG. 1.FIG. 1illustrates a DRX cycle in which the UE monitors PDCCH during “On Duration” (active time), and does not monitor PDCCH during “Opportunity for DRX”.

DRX is configured by RRC with the following parameters:

The above parameter “longDRX-CycleStartOffset” comprises longDRX-Cycle and drxStartOffset. The value of longDRX-Cycle is in number of sub-frames. Value sf10 corresponds to 10 sub-frames, sf20 corresponds to 20 sub-frames and so on. If shortDRX-Cycle is configured, the value of longDRX-Cycle should be a multiple of the shortDRX-Cycle value. The value of drxStartOffset value is in number of sub-frames.

The above parameter “onDurationTimer” is a timer for DRX. Its value is in number of PDCCH sub-frames. Value psf1 corresponds to 1 PDCCH sub-frame, psf2 corresponds to 2 PDCCH sub-frames and so on.

The above parameter “drx-InactivityTimer” is a timer for DRX. Its value is in number of PDCCH sub-frames. Value psf1 corresponds to 1 PDCCH sub-frame, psf2 corresponds to 2 PDCCH sub-frames and so on.

The above parameter “drx-RetransmissionTimer” is a timer for DRX. Its value is in number of PDCCH sub-frames. Value psf1 corresponds to 1 PDCCH sub-frame, psf2 corresponds to 2 PDCCH sub-frames and so on.

The value of the above parameter “shortDRX-Cycle” is in number of sub-frames. Value sf2 corresponds to 2 sub-frames, sf5 corresponds to 5 subframes and so on.

The above parameter “drxShortCycleTimer” is a timer for DRX. Its value is in multiples of shortDRX-Cycle. A value of 1 corresponds to shortDRX-Cycle, a value of 2 corresponds to 2*shortDRX-Cycle and so on.

For power saving purposes, RAN is considering extending connected mode DRX way beyond the current maximum of 2560 ms, e.g. to one hour.

For example, in order to support a DRX cycle of one hour (3600 s or 3,600,000 ms), a straightforward extension of the current signaling would be to introduce as long DRX-CycleStartOffset parameter the following:

Clearly, when introducing very large DRX cycles (or extended DRX), a 1 ms granularity is not needed to spread the UEs: the number of ms within a cycle is largely superior to the number of UEs that can be supported. For instance, only 65,536 C-RNTI can be allocated (16 bits long), which is to be compared to the 3,600,000 possible offsets in the example of the 1 hour DRX cycle above: ˜100 times more offsets than required.

SUMMARY OF THE INVENTION

According to at least one embodiment of the invention, extended DRX is introduced with minimized signaling overhead and without compromising flexibility.

According to the present invention, methods, a user equipment, a network apparatus and a computer program product are provided as set out in the appended claims.

In the following the invention will be described by way of embodiments thereof with reference to the accompanying drawings.

DESCRIPTION OF THE EMBODIMENTS

As a preliminary matter before exploring details of various implementations, reference is made toFIG. 2for illustrating a simplified block diagram of a control unit10and a control unit20suitable for use in practicing the exemplary embodiments of this invention.

The control unit10may be part of and/or used by a user equipment. The control unit10comprises processing resources (e.g. processing circuitry)11, memory resources (e.g. memory circuitry)12which may store a program, and interfaces (e.g. interface circuitry)13, which are connected via a link14. The interfaces13may comprise a suitable radio frequency (RF) transceiver (not shown) coupled to one or more antennas (not shown) for bidirectional wireless communications over one or more wireless links including a signaling link15with the control unit20.

The control unit20may be part of and/or used by an apparatus of the communication network, e.g. an eNB. The control unit20comprises processing resources (e.g. processing circuitry)21, memory resources (e.g. memory circuitry)22which may store a program, and interfaces (e.g. interface circuitry)23, which are connected via a link24. The interfaces23may comprise a suitable radio frequency (RF) transceiver (not shown) coupled to one or more antennas (not shown) for bidirectional wireless communications over one or more wireless links including the signaling link15with the control unit10.

At least one of the programs stored in the memory resources11is assumed to include program instructions that, when executed by the associated processing resources11, enable the electronic device to operate in accordance with the exemplary embodiments of this invention. Inherent in the processing resources11is a clock to enable synchronism among the various apparatus for transmissions and receptions within the appropriate time intervals and slots required, as the scheduling grants and the granted resources/subframes are time dependent. The transceivers include both transmitter and receiver, and inherent in each is a modulator/demodulator commonly known as a modem.

In general, the exemplary embodiments of this invention may be implemented by computer software stored in the memory resources12and executable by the processing resources11of the control unit10, or by hardware, or by a combination of software and/or firmware and hardware in any or all of the devices shown.

The memory resources12,22may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The processing resources11,21may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi core processor architecture, as non-limiting examples.

Now reference is made toFIG. 3illustrating a process30according to at least one embodiment of the invention.

The process30is for use in a UE accessing a communication network. The UE is configured to use DRX when it is in connected mode with the communication network. The extended DRX comprises extended DRX cycles and offsets, which are based on a value of a specific DRX cycle (e.g. 2560 ms).

In step S31, signaling from the communication network is received. The signaling comprises an extended DRX cycle indication and an offset value.

In step S32, an extended DRX cycle is calculated from the extended DRX cycle indication and an offset is calculated from the offset value, using the value of the specific DRX cycle.

In step S33, DRX is executed when the UE is in the connected mode, with the extended DRX cycle calculated and the offset calculated.

The value of the specific DRX cycle may be received from the communication network, or may be fixed e.g. to the maximum length of long DRX cycle (e.g. 2560 ms).

According to first and second embodiments of the invention, the extended DRX cycle indication received in step S31indicates an extended DRX cycle (“longDRX-Cycle”, “eDRX-CycleLength”, as will be explained later on in more detail) and is a first multiplication value of the value of the specific DRX cycle. As an example, the DRX cycle corresponds to long DRX cycle (e.g. 2560 ms).

According to the first embodiment, the offset value received in step S31indicates a DRX start offset (“drxStartOffset”, as will be explained later on in more detail) and is a second multiplication value of the value of the specific DRX cycle, e.g. long DRX cycle.

According to the second embodiment of the invention, the offset value received in step S31indicates an extended DRX cycle start offset (“eDRX-CycleStartOffset”, as will be explained in more detail later on) and is a second multiplication value of the extended DRX cycle divided by the value of the specific DRX cycle, e.g. long DRX cycle.

In order to configure DRX cycles longer than the current maximum, i.e. extended DRX, according to an implementation example of the first embodiment of the invention, new values are introduced as multiple of the current maximum longDRX-Cycle, i.e. 2560 ms. Further, an offset granularity is defined as 2560 ms.

For instance, in order to introduce an extended DRX cycle of ˜90 s:the DRX cycle (extended DRX cycle indication) is signaled as 35 (35×2560 ms=89600 ms), andthe offset value is signaled as 0 . . . 34, where a value of 0 means no offset, 1 means an offset of 2560 ms, 2 means an offset of 5120 ms, and so on.

Alternatively, the basis (i.e. value of the specific DRX cycle) for DRX and offset calculation can be signaled instead of being fixed to the 2560 ms, as suggested above.

According to an implementation example of the second embodiment, new values are introduced for extended DRX length as multiple of the current maximum, i.e. 2560 ms. Further, an offset granularity is defined as the cycle length/2560 ms, and offset is defined as number of cycle length/2560 ms.

For instance, in order to introduce an extended DRX cycle of ˜80 s:the DRX cycle (extended DRX cycle indication) is signaled as 32 (32×2560 ms=81920 ms) or 81920 sub-frames, andthe offset value is signaled as 0 . . . 2559, with a granularity of 81920/2560=32 ms, where a value of 0 means no offset, 1 means an offset of 32 ms, 2 means an offset of 2×32 ms, and so on.

As described above for the first and second embodiments, the basis (i.e. value of specific DRX cycle) for DRX and offset calculation can be signaled instead of being fixed to the 2560 ms.

With the proposed introduction of extended DRX according to the first and second embodiments, signaling overhead can be minimized without compromising flexibility: enough offset is provided to spread UEs that support extended DRX while legacy UEs can still benefit from 1 ms granularity. Further, overlap between legacy UEs and UEs supporting extended DRX can be minimized.

Taking as an example an extended DRX cycle length up to 60 min defined as follows:

For the first embodiment, the signaling is:

The above parameter “extendedDRX-CycleStartOffset” for extended DRX according to the first embodiment comprises longDRX-Cycle and drxStartOffset. The value of longDRX-Cycle is in number of sub-frames. Value sf5120 corresponds to 5120 sub-frames, sf10240 corresponds to 10240 sub-frames and so on. If shortDRX-Cycle is configured, the value of longDRX-Cycle should be a multiple of the shortDRX-Cycle value. The value of drxStartOffset value is in number of 2560 sub-frames.

For the second embodiment, the signaling is:

The above parameter “eDRX-CycleLength” for extended DRX according to the second embodiment is an extended DRX cycle. Its value is in number of sub-frames. Value sf5120 corresponds to 5120 sub-frames, sf10240 corresponds to 10240 subframes and so on.

The value of the above parameter “eDRX-CycleStartOffset” for extended DRX according to the second embodiment is number of eDRX-CycleLength/2560 subframes. Value 0 corresponds to 0 sub-frames, 1 corresponds to 1*eDRX-CycleLength/2560 sub-frames, 2 corresponds to 2*eDRX-CycleLength/2560 subframes and so on.

When calculating which subframe to wake up, the timing maintained in the UE based on SIB16 can be used with the formulation below:
if the Extended DRX Cycle is used and Timing modulo(eDRX-CycleLength)=eDRX-CycleStartOffset*eDRX-CycleLength/2560:
start onDurationTimer.

According to an aspect of the present invention, a user equipment is provided which may include and/or use the control unit10shown inFIG. 2. The user equipment accesses a communication network, using extended discontinuous reception (DRX) when the user equipment is in connected mode with the communication network. The extended DRX comprises extended DRX cycles and offsets, which are based on a value of a specific DRX cycle. The user equipment comprises means for receiving signaling from the communication network, the signaling comprising an extended DRX cycle indication and offset value, means for calculating an extended DRX cycle from the extended DRX cycle indication and an offset from the offset value, using the value of the specific DRX cycle, and means for executing the DRX when the user equipment is in the connected mode with the extended DRX cycle calculated and the offset calculated.

According to an embodiment of the invention, the means for receiving receive signaling from the communication network, the signaling comprising the value of the specific DRX cycle.

According to another embodiment of the invention, the value of the specific DRX cycle is the maximum length of long DRX cycle.

According to an implementation example of the invention, the means for receiving, calculating and executing are implemented by the processing resources11, memory resources12and interfaces13of the control unit10.

According to another aspect of the invention, an apparatus of a communication network, which may include and/or use the control unit20shown inFIG. 2is provided. The apparatus comprises means for signaling an extended DRX cycle indication and offset value to a user equipment accessing the communication network, the user equipment using extended discontinuous reception (DRX) when the user equipment is in connected mode with the communication network, wherein the extended DRX comprises extended DRX cycles and offsets, which are based on a value of a specific DRX cycle.

According to an embodiment of the invention, the means for signaling signal the value of the specific DRX cycle to the user equipment.

According to an implementation example of the invention, the means for signaling are implemented by the processing resources21, memory resources22and interfaces23of the control unit20.

In the above aspects, according to an embodiment of the invention, the extended DRX cycle indication indicates an extended DRX cycle and is a first multiplication value of the value of the specific DRX cycle.

In the above aspects, according to an embodiment of the invention, the offset value indicates a DRX start offset and is a second multiplication value of the value of the specific DRX cycle.

In the above aspects, according to another embodiment of the invention, the offset value indicates an extended DRX cycle start offset and is a second multiplication value of the extended DRX cycle length divided by the value of the specific DRX cycle.

It is to be understood that the above description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.