WO2014162205A2

WO2014162205A2 - Method and apparatus for power saving of idle mode user equipments

Info

Publication number: WO2014162205A2
Application number: PCT/IB2014/000797
Authority: WO
Inventors: He Wang; Hua Chao
Original assignee: Alcatel Lucent
Priority date: 2013-04-06
Filing date: 2014-04-03
Publication date: 2014-10-09
Also published as: WO2014162205A3; TW201501558A; CN104105177A; CN104105177B

Abstract

The present invention provides a method and apparatus for power saving of an idle mode user equipment. The method includes: configuring an extended DRX cycle greater than both a regular DRX cycle and an SFN cycle; and sending the extended DRX cycle to the UE for use by the UE to listen to a paging message in the idle mode.

Description

METHOD AND APPARATUS FOR POWER SAVING OF IDLE MODE

USER EQUIPMENTS

FIELD OF THE DISCLOSURE The present invention generally relates to the field of wireless communication, and in particular to a method and apparatus for power saving of an idle mode User Equipment (UE).

BACKGROUND

As we know that for the IDLE mode UE, a commonly used method is to use the Discontinuous Reception (DRX) mechanism to monitor paging message and save power. In a RRC_IDLE state, UE can use DRX to monitor the paging message only in specific subframes. In particular, according to the paging DRX cycle, Paging Frame number (PF) and Paging Occasion (PO) subframe number in this radio frame can be calculated by the UE according to the system configuration parameters and UE's IMSI (International Mobile Subscriber Identification). So in each DRX cycle, UE just needs to receive a Physical Downlink Control Channel (PDCCH) in specific paging time once, and at other times it turns to a sleeping state in order to save power.

While in the RRCJDLE state, UE is only in DRX mode. In 3 GPP TS36.304 (Reference [1]), for idle mode UE processing, there defines how to use DRX mechanism to keep the paging monitoring. In Reference [1], the Paging Frame (PF) number and Paging Occasion (PO) subframe number are defined as following:

Paging Frame number (PF) =SFN mod T =(T/N)*(UE_ID mod N) ,

Index i_s pointing to PO from subframe pattern: i_s=floor (UE_ID/N) mod

Ns. where SFN refers to a System Frame Number; T is the UE's DRX cycle. T is the smaller one of an UE specific DRX cycle value allocated by upper layers and a default paging cycle (i.e. DRX cycle) value broadcast in system information. If UE specific DRX is not allocated by upper layers, the default DRX cycle value is applied. Hereinafter, the DRX cycle is illustrated by the default DRX cycle value broadcast in the system information. Herein, floor is the rounding down operation, mod is the modular operation.

The default DRX cycle for the IDLE mode UE is equal to the default paging cycle of the cell which is broadcast within a SystemInformationBlockType2 (SIB2) message defined currently as following in RRC protocol 3GPP TS36.331 (Reference [2]):

I'CC I I ^'nn l^'ig SEQUENCE {

ilcl^'au ll l 'ag EN U M ER ATE D

ι-Γ32. ι-Γ64, ι-Π 2 1 125 !

nB ENUMERATED

fourT, twoT, one T hal lT q ai k'i oi 'l - i oncSixtccnlhT nncTli i m S 1M

nB is a value selected from a set including (4T, 2T, T, T/2, T/4, T/8, T/16, T/32);

N=min(T,nB) refers to the number of paging frames in one DRX cycle;

Ns=max(l,nB/T) refers to the number of subframes, ie. POs, in one paging frame, and it may be 1, 2 or 4; and

UE_ID=IMSI mod 1024, where IMSI refers to the International Mobile Subscriber Identification of the UE and is given as sequence of digits of type Integer (0..9).

The subframe pattern is defined by the following Table 1 :

Table 1 : subframe pattern

Currently the maximum paging cycle, i.e. regular DRX cycle, is 2.56 seconds. The SFN now is configured to a value from 0 to 1023. One SFN cycle would be 10.24 seconds. It is clearly that the DRX cycle is less than the SFN cycle, which may guarantee the calculated PF and PO are unique in one SFN cycle. Therefore there would be no confusion for UE to perform the DRX mechanism with the calculated PF and PO.

On the other hand, considering cell reselection, the idle UE should measure the Reference Signal Receiving Power (RSRP) and Reference Signal Receiving Quality (RSRQ) of its severing cell at least once every DRX cycle. And for the neighboring cell measurement including intra/inter frequency measurement or inter RAT neighboring cell measurement, the idle UE should perform the measurement once every cell reselection measurement time period (T-Reselection) as defined in 3 GPP TS 36.33 l(Reference [2]). In 3 GPP TS 36.331 (Reference [2]), the information element T-Reselection refers to the cell reselection timer Treselection_RAT for E-UTRA, UTRA, GERAN or CDMA2000, in unit of second, and is ranged within 0-7 seconds as defined in 3GPP TS 36.331.

In order to reduce the power consumption in the idle mode, it is desired that the UE wakes up not frequently to save energy. For UEs which are high delay tolerant and have infrequently transmissions, such as Machine Type Communication (MTC) devices, it's very advantageous.

Therefore, it is required to extend the DRX cycle during which the UE is waken up to monitor a paging message so as to save power consumption. According to newest Service & System Aspects (SA) discussion results, in 3GPP TR 23.887 (Reference [3])) section 7 "UE Power Consumption Optimizations (UEPCOP)", it is a major power consumption optimization solution for IDLE mode UE (such as MTC device) to use extended DRX cycle such that the UE may save battery as waking up and listening for a potential paging message. The extended DRX cycle value would be possibly larger than a SFN cycle value, for example it may be 64 times of the SNF cycle (64* 10.24s=655.36s). If current PF/PO determination scheme is used, there would be the problem that the PF and OP calculation results would be conflict and the UE may not wake up only once in each extended DRX cycle, resulting in not achieving the power saving purpose. For example, it is assumed that the default extended paging cycle T = 2048 radio frames =20.48s which is 2 times of current SNF cycle. Since nB equals to T, there will be N=T=2048, which means that, for each radio frame, there is 1 subframe with paging which would be #9 subframe. UE_ID is set to a value from 1 to 1023 since the IMSI is mod 1024. Then the PF may be calculated using SFN mod T =(T/N)*(UE_ID mod N).

It can be seen that SFN mod T is useless because SFN is in the range from 1 to 1023 which is always less than T=2048, and UE_ID mode N is also useless. That means according to the UE_ID value, in each SFN cycle, the UE would wake up once. For example, if MSI is set to 1, then UE_ID=1, and SFN mod T= (T/N)*(UE_ID mod N)=l. This means that, for each SFN cycle in the extended DRX cycle, the UE needs to wake up at each radio frame with SFN=1. Therefore, for the extended DRX cycle equaling to 2 times of SFN cycle, the UE would wake 2 times in each DRX cycle rather than one time.

It is clear that if the extend DRX cycle is greater than the SFN cycle, then the UE would wake up (DRX cycle/SFN cycle) times during each DRX cycle. It violates the power saving principle of idle mode DRX that UE wakes up only once during each DRX cycle, which is disadvantage for idle mode UE power saving. References:

[1] 3 GPP TS36.304 vl l.2.0 E-UTRA UE procedures in idle mode (Release 11), 2012-12.

[2] 3 GPP TS36.331 vl l.2.0 Radio Resource Control (RRC) Protocol specification (Release 11), 2012-12. [3] 3 GPP TR23.887 v0.8.0 Machine-Type and other Mobile Data Applications Communications Enhancements (Release 12), 2013-02.

SUMMARY

Therefore, in view of the above problems, the present invention provides solutions about how to support an extended DRX cycle greater than the length of a current SFN cycle to save the UE's power.

According to one aspect of the present invention, there is provided a method for power saving of an idle mode UE, including: configuring an extended DRX cycle greater than both a regular DRX cycle and an SFN cycle; and sending the extended DRX cycle to the UE for use by the UE to listen to a paging message in the idle mode. According to another aspect of the present invention, there is provided an apparatus for power saving of an idle mode UE, including: an extended DRX cycle configuring unit configured to configure the extended DRX cycle greater than both a regular DRX cycle and an SFN cycle; and a sending unit configured to send the extended DRX cycle to the UE for use by the UE to listen to a paging message in the idle mode. According to another aspect of the present invention, there is provided a method for power saving of an idle mode UE, including: acquiring an extended DRX cycle greater than both a regular DRX cycle and an SFN cycle; and determining a PF number and a PO subframe number used for listening to a paging message according to the extended DRX cycle.

According to another aspect of the present invention, there is provided an apparatus for power saving of an idle mode UE, including: a DRX cycle acquiring unit configured to acquire an extended DRX cycle greater than both a general DRX cycle and an SFN cycle; and a determining unit configured to determine a PF number and a PO subframe number used for listening to a paging message according to the extended DRX cycle.

With solutions of the present invention, the UE's power may be saved furthermore by supporting the extended DRX cycle.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will be understood better and other objectives, details, features and advantages of the present invention will become more evident from the description of specific embodiments of the invention given in conjunction with the following figures, wherein:

Fig. 1 illustrates a schematic drawing of a wireless communication network in the prior art;

Fig. 2 illustrates a flow chart of a method for power saving of an idle mode UE according to an embodiment of the present invention;

Fig. 3 illustrates a flow chart of a method for power saving of an idle mode UE according to an embodiment of the present invention;

Fig. 4 illustrates a block diagram of an apparatus for power saving of an idle mode UE according to an embodiment of the present invention; and

Fig. 5 illustrates a block diagram of an apparatus for power saving of an idle mode UE according to an embodiment of the present invention.

Identical or similar numbers are used to indicate identical or similar or corresponding features and function throughout the figures.

DETAILED DESCRIPTION Preferred embodiments of the present invention will now be described in more details in conjunction with accompanying figures. Although preferred embodiments of the present invention are shown in the accompanying figures, it should be understood that the present disclosure can be embodied in various ways without being limited to the embodiments depicted herein. In contrast, the embodiments are provided herein to make the disclosure more throughout and complete and convey the scope of the present disclosure to those skilled in this art.

Fig. 1 illustrates a schematic drawing of a wireless communication network 100 in prior art. As shown in Fig. 1, the network 100 includes a plurality of base stations 110 and one or more UEs 120 communicating with each base station 110. Each UE 120 communicates with its corresponding serving base station 110 through wireless links.

In the following description of this disclosure, it is described by taking as an example the current SFN cycle with cycle value of 1024 (0-1023) to cause minimal effects on the current system performance and other designed mechanisms. However, those skilled in this art is readily to understand that if the SFN cycle changes in future standards, the present invention is adaptively applied to the changed SFN cycle without any creative work.

Fig. 2 illustrates a flow chart of a method 200 for power saving of an idle mode UE according to an embodiment of the present invention. The method 200 may be performed by the base station 110 in Fig. 1, for example.

The method 200 starts at step 210, in which the base station 110 configures an extended DRX cycle greater than both a regular DRX cycle and an SFN cycle.

In one embodiment, the extended DRX cycle is configured as integral times of the SFN cycle. More preferably, the extended DRX cycle is configured as multiple powers of 2 times of the SNF cycle, such as 1, 2, 4, 8, 16, 32, 64 times of the SFN cycle.

For example, length of the extended DRX cycle may be configured as 64 times of the SFN cycle, i.e. 655.36 seconds, or about 11 minutes. However, it can be understood by those skilled in this art that the principle of the present invention may be used to any extended DRX cycle greater than the SFN cycle. Next, in step 220, the base station 110 sends the extended DRX cycle to the

UE (such as the UE 120) for use by the UE to listen to a paging message in the idle mode. In one embodiment, the extended DRX cycle is sent to the UE by adding information on the extended DRX cycle into a SystemInformationBlockType2 (SIB2) message. For example, the base station 110 may broadcast the SIB2 message containing the extended DRX cycle to a plurality of UEs 120.

In one embodiment, information on the extended DRX cycle is added into the PCCH-Config IE of the SIB2. The PCCH-Config IE of SIB2 modified in this way is for example defined as below:

where in the description of the field RadioResourceConfigCommon, the parameter defaultExtendLongPagingCycle is described to have a value of sfnCyclel corresponding to 1024 radio frames, a value of sfnCycle2 corresponding to 2048 radio frames, and so on.

Fig. 3 illustrates a flow chart of a method 300 for power saving of an idle mode UE according to an embodiment of the present invention. The method 300 may be performed by the UE 120 in Fig. 1, for example.

The method 300 starts at step 310, in which the UE 120 acquires an extended DRX cycle greater than both a regular DRX cycle and an SFN cycle.

In one embodiment, the extended DRX cycle is configured as integral times of the SFN cycle. More preferably, the extended DRX cycle is configured as multiple powers of 2 times of the SNF cycle, such as 1, 2, 4, 8, 16, 32, 64 times of the SFN cycle. However, it can be understood by those skilled in this art that the principle of the present invention may be used to any extended DRX cycle greater than the SFN cycle.

In one embodiment, the UE 120 acquires the extended DRX cycle by receiving the SIB2 message from the base station 110 and extracting information on the extended DRX cycle.

In one embodiment, after receiving the SIB2 message broadcast by the base station 110, the UE such as an MTC device with power saving requirement can acquire this extended DRX cycle (defaultExtendLongPagingCycle) from the SIB2 message for use in its following idle mode DRX mechanism, and ignore a default paging cycle (defaultPagingCycle, i.e. the regular DRX cycle). On the other hand, normal UEs or other types of MTC devices may extract the default paging cycle (defaultPagingCycle) from the SIB2 message for use in its following idle mode DRX mechanism, and ignore the extended DRX cycle (defaultExtendLongPagingCycle). In this way, the method for supporting the extended DRX cycle of the present invention has little impact on normal UEs' cycle mechanism.

Next, in step 320, the UE 120 determines a Paging Frame (PF) number and a Paging Occasion (PO) subframe number used for listening to a paging message according to the extended DRX cycle.

The calculation method of the PF and the PO for the extended DRX cycle is based on that for normal UEs but with some modifications. For example, the same parameters are used as that for normal UEs but with some modifications. In one embodiment, similar to normal UEs, index i_s pointing to PO is calculated according to the formula i_s=floor (UE_ID/N) mod Ns and the PO subframe number is determined according to the subframe pattern in the above Table 1.

The calculation method of the PF would have some modifications to adapt to the extended DRX cycle greater than the SFN cycle. There are 3 substeps to calculate the PF number.

Substep 1 : calculating the paging frame index i_PF in one extended DRX cycle, wherein i_PF =(T/N)*(UE_ID mod N).

Here, the value range of i_PF is {0...T-1 } . And i_PF would be possibly greater than the maximum SFN which is 1023, because the extended DRX cycle T is greater than the SFN cycle (1024).

Substep 2: calculating the index of SFN cycle i_SFN in one extended DRX cycle according to the calculated paging frame index, wherein i_SFN=floor(i_PF/1024)+l .

Here, the value range of i_SFN is { 1... T/1024} . And there are T/1024 SFN cycles in one extended DRX cycle. Substep 3: calculating the paging frame radio frame number PF_SFN in the SFN cycle according to the calculated paging frame index, wherein PF_SFN=i_PF mod 1024.

Then the UE can determine a PF number comprised of the i_SFN and PF_SFN, which determines in which SFN cycle and in which radio frame the paging frame is in the DRX cycle.

In the PO/PF calculation as above, T is the extended DRX cycle, which is the smaller one of an UE specific DRX cycle value allocated by upper layers and a default extended paging cycle (i.e. extended DRX cycle) broadcast in SIB2. If there is no UE specific DRX cycle allocated by upper layers, the default extended DRX cycle is applied.

Here, nB is a value selected from a set (4T, 2T, T, T/2, T/4, T/8, T/16, T/32),

N=min(T, nB) refers to the number of paging frames having POs, Ns=max(l, nB/T) refers to the number of subframes for paging in one paging frame, ilMSI mod 1024 , where T < SFN cycle

UE ID= with SFN cycle of 1024, which

IMSI mod T , whereT > SFN cycle

is different from original UE_ID (IMS I mod 1024). It can be seen that, the calculation of UE_ID is varied as the extended DRX cycle varies. Using this modification, it's guaranteed that the UE can be well-distributed to the whole extended DRX cycle.

Hereinafter, we give an example to illustrate the PF calculation method. The parameters may be set as following:

- T = sfnCycle2 = 2048 radio frames = 20.48 seconds;

- nB = T/32 = 64 radio frames; - N = min(T, nB) = min (2048, 64) = 64;

- Ns = max(l, nB/T) = max(l, 1/32) = 1;

- Assuming the UE having IMS 1=2040, its UE_ID = IMS I mod T = 2040 mod 2048 = 2040 Then according to the above substep 1, i_PF =(T/N)*(UE_ID mod N) = (2048/64) *(2000 mod 64) = 32*56=1792.

According to the above substep 2, i_SFN=floor(i_PF/1024)+l= floor(1792/1024) +1= 2. According to the above substep 3, PF_SFN=i_PF mod 1024= 1792 mod

1024 =768.

In this example, there are 2 SFN cycles in the extended DRX cycle, therefore for this UE, its paging radio frame is located in the second SFN cycle and its radio frame number is 768. i_s =floor (UE_ID/N) mod Ns = floor (2040/64) mod 1 = 31 mod 1 = 0.

Then the subframe number of PO is 9 according to the subframe pattern of Table 1.

Finally, it can be concluded that for such extended DRX cycle and parameters set as above, the UE will listen to the paging message in subframe #9 of radio frame #768 of the second SFN cycle in one extended DRX cycle. As can be seen, in the PO and PF calculation for the extended DRX cycle, the SFN cycle index is crucial information for the base station and the UE to determine the exact position of the paging radio frame. Therefore, in the mechanism using the extended DRX cycle, it's necessary to keep the SFN cycle synchronization between the base station and the UE. To this end, at the base station side, the method 200 further includes step

230 in which the base station (such as the base station 110) counts SFN cycle index and sends the counted SFN cycle index to the UE (such as the UE 120) for the SFN cycle synchronization between the base station and the UE.

For example, for the first SFN, the base station determines its index as 1, then continues to count the SFN cycle index. The maximum value of the SFN cycle index is determined by the extended DRX cycle of this cell, therefore, the SFN cycle index is valued in the range of l ... ^{extended DRX c}y^cle _{The SFN le index is}

{ SFN cycle J

. ,. „ , „ extended DRX cycle „ „

periodically counted from one to . For different cell, since the

SFN cycle configured extended DRX cycle may be different, the maximum value of SFN cycle index will also be different.

In one embodiment, the base station sends the SFN cycle index to the UE through a Master InformaitonB lock (MIB) message.

Currently, the SFN is transmitted in MIB message. Therefore, the base station may indicate a SFN cycle index in the MIB message broadcast from the base station to the UE. Then when the UE receive the SFN in the MIB message, it also can get the exact SFN cycle index in the extended DRX cycle corresponding to that SFN. After that, the UE can synchronize the SNF cycle count with the base station.

In one embodiment, the base station can add SFN Cycle Index information into the MIB message. For example, if it is assumed that the extended DRX cycle equals to 64 times of the SFN cycle, the MIB message with an IE SFN Cycle Index {sfnCyclelndex) added is defined as following:

MasterlnformationBlock

In the description of the MasterlnformationBlock field, sfnCyclelndex is defined as 6 bits SFN cycle index which is in the range from 1 to 64 and is corresponding to the maximum extended DRX cycle sfnCycle64. The value of 000000 indicates an abnormal case that means no extended DRX cycle is supported in this cell. Normal UEs without extra power saving requirement could ignore this value. In another embodiment, the base station sends the SFN cycle index to the

UE through a SystemlnformationBlockTypel (SIB 1) message.

As mentioned above, although currently, the SFN is transmitted in MIB message, the periodical transmissions of SIB 1 message and MIB message have some specific correspondence that a radio frame having a SIB 1 message must also have an MIB message. The UE needs to acquire the SIB 1 message to camp on the cell. If the SFN cycle index is sent through the SIB 1 message, the UE may easily obtain the relationship between the SFN in the MIB message and the SFN cycle index in the SIB 1 message when it receives the MIB message and the SIB1 message. Therefore, it is an advantageous manner to transmit the SFN cycle index through the SIB 1 message.

For example, the base station may add the SFN cycle index corresponding to that radio frame into the SIB 1 message.

Considering the flexibility of the SFN Cycle Index, a constant maxSfnCyclelndex may be defined to indicate the maximum SFN cycle index, which can be adjusted as needed. It is clear that the SIB 1 method may support more SFN cycle indexes than the MIB method because of the less critical requirement for size of SIB 1 message.

For example, the following IE can be added in the SystemlnformationBlockTypel message: sfnCycIelndcx INTEGER (0.. maxSfnCyclelndex) OPTIONAL.

If it does not need to support the extended DRX cycle, the UE may ignore this IE since it is an optional IE rather than mandatory.

Similarly, to keep the SFN cycle synchronization between the base station and the UE, at the base station side, the method 300 further includes step 330 in which the UE (such as the UE 120) receives from the base station (such as the base station 110) the counted SFN cycle index for the SFN cycle synchronization between the base station and the UE. The SFN cycle synchronization performed by the base station and the UE is as described above in conjunction with step 230.

Fig. 4 illustrates a block diagram of an apparatus 400 for power saving of an idle mode UE according to an embodiment of the present invention. The apparatus 400 may be implemented within or by the base station.

As shown in Fig. 4, the apparatus 400 includes an extended DRX cycle configuring unit 410 configured to configure the extended DRX cycle greater than both a regular DRX cycle and an SFN cycle. The apparatus 400 further includes a sending unit 420 configured to send the extended DRX cycle to the UE for use by the UE to listen to a paging message in the idle mode.

In one embodiment, the apparatus 400 further includes a counting unit 430 configured to count the SFN cycle index, and the sending unit 420 is further configured to send the counted SFN cycle index to the UE for the SFN cycle synchronization between the base station and the UE.

In one embodiment, the sending unit 420 sends the SFN cycle index to the UE through a SystemlnformationBlockTypel (SIB 1) message. In one embodiment, the sending unit 420 sends the SFN cycle index to the

UE through a MasterlnformaitonBlock (MIB) message.

In one embodiment, the extended DRX cycle configuring unit 410 configures the extended DRX cycle as integral times of the SFN cycle.

In one embodiment, the extended DRX cycle configuring unit 410 configures the extended DRX cycle as multiple powers of 2 times of the SNF cycle.

In one embodiment, the sending unit 420 sends the extended DRX cycle to the UE through adding information on the extended DRX cycle into a SystemInformationBlockType2 (SIB2) message.

Fig. 5 illustrates a block diagram of an apparatus 500 for power saving of an idle mode UE according to an embodiment of the present invention. The apparatus 500 may be implemented within or by the UE.

As shown in Fig. 5, the apparatus 500 includes a DRX cycle acquiring unit 510 configured to acquire an extended DRX cycle greater than both a regular DRX cycle and an SFN cycle. The apparatus 500 further includes a determining unit 520 configured to determine a PF number and a PO subframe number used for listening to a paging message according to the extended DRX cycle.

In one embodiment, the apparatus 500 further includes a receiving unit 530 configured to receive the SFN cycle index counted by the base station for the SFN cycle synchronization between the base station and the UE. In one embodiment, the extended DRX cycle is integral times of the SFN cycle.

In one embodiment, the extended DRX cycle is multiple powers of 2 times of the SNF cycle.

In one embodiment, the determining unit 520 determines the PF number and the PO subframe number in the way described in conjunction with the method 300. In one embodiment, the receiving unit 530 is further configured to receive a SIB 2 message from the base station, and the DRX cycle acquiring unit 510 is further configured to extract information on the extended DRX cycle from the SIB2 message.

Moreover, for cell reselection of the idle UE, the serving cell measurement is performed once every DRX cycle. For the extended DRX cycle, it will not cause any problem, but for the neighboring cell measurement, it is controlled by the time interval T-Reselection for cell reselection measurement on neighboring cells. In this regard, the time interval T-Reselection for the idle mode UE to perform periodic cell reselection measurement on neighboring cells should be better greater than the extended DRX cycle. So the value range definition of T-Reselection in TS36.331 needs to be expanded to guarantee the maximum value being greater than the extended DRX cycle.

The present disclosure proposes solutions to support extended DRX cycle in Radio Access Network (RAN) for the power saving of UEs (such as MTC devices), which considers the backward compatibility and would not impact on the existing normal UEs. Furthermore, it is very flexible with the adjustable parameter settings and current signaling procedures may be reused with limited addition to exchange necessary information. The proposed method would not only cause less impact on the existing protocol standard and system, but also can achieve the purpose of UE power saving with the extended DRX cycle. It would impact on the current 3GPP standardization of the RRC protocol 3 GPP TS 36.331 and idle mode UE operation definition in 3 GPP TS 36.304.

In this description, the term "base station" may refer to the coverage area of a base station and/or a base station or a base station system serving the coverage area, dependent on the context the term is used. In the disclosure, the term "base station" is exchangeable with "cell", "Node B" and "eNodeB" and as on.

Here, the method as disclosed has been described with reference to the accompanying drawings. However, it should be appreciated that the sequence of the steps as illustrated in the figures and described in the description are only illustrative, and without departing from the scope of the claims, these method steps and/or actions may be executed in a different sequence, without being limited to the specific sequence as shown in the drawings and described in the description. In one or more exemplary designs, the functions of the present application may be implemented using hardware, software, firmware, or any combinations thereof. In the case of implementation with software, the functions may be stored on a computer readable medium as one or more instructions or codes, or transmitted as one or more instructions or codes on the computer readable medium. The computer readable medium comprises a computer storage medium and a communication medium. The communication medium includes any medium that facilitates transmission of the computer program from one place to another. The storage medium may be any available medium accessible to a general or specific computer. The computer-readable medium may include, for example, but not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disc storage devices, magnetic disk storage devices, or other magnetic storage devices, or any other medium that carries or stores desired program code means in a manner of instructions or data structures accessible by a general or specific computer or a general or specific processor. Furthermore, any connection may also be considered as a computer-readable medium. For example, if software is transmitted from a website, server or other remote source using a co-axial cable, an optical cable, a twisted pair wire, a digital subscriber line (DSL), or radio technologies such as infrared, radio or microwave, then the co-axial cable, optical cable, twisted pair wire, digital subscriber line (DSL), or radio technologies such as infrared, radio or microwave are also covered by the definition of medium.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any normal processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

The above depiction of the present disclosure is to enable any of those skilled in the art to implement or use the present invention. For those skilled in the art, various modifications of the present disclosure are obvious, and the general principle defined herein may also be applied to other transformations without departing from the spirit and protection scope of the present invention. Thus, the present invention is not limited to the examples and designs as described herein, but should be consistent with the broadest scope of the principle and novel characteristics of the present disclosure.

Claims

What is Claimed:

1. A method for power saving of an idle mode User Equipment (UE), comprising: configuring an extended Discontinuous Reception (DRX) cycle greater than both a regular DRX cycle and a System Frame Number (SFN) cycle; and sending the extended DRX cycle to the UE for use by the UE to listen to a paging message in the idle mode.

2. The method of claim 1, further comprising: counting SFN cycle index and sending the counted SFN cycle index to the UE for SFN cycle synchronization between an base station and the UE.

3. The method of claim 2, wherein the SFN cycle index is sent to the UE through a SystemlnformationBlockTypel (SIB 1) message.

4. The method of claim 2, wherein the SFN cycle index is sent to the UE through a MasterlnformaitonBlock (MIB) message.

5. The method of claim 1, wherein the extended DRX cycle is configured as integral times of the SFN cycle.

6. The method of claim 1, wherein the extended DRX cycle is configured as multiple powers of 2 times of the SNF cycle.

7. The method of claim 1, wherein the extended DRX cycle is sent to the UE through adding information on the extended DRX cycle into a SystemInformationBlockType2 (SIB2) message.

8. The method of claim 1, further comprising: setting a time interval for performing cell reselection measurement on neighboring cells to be greater than the extended DRX cycle.

9. An apparatus for power saving of an idle mode User Equipment (UE), comprising: an extended DRX cycle configuring unit configured to configure the extended DRX cycle greater than both a regular DRX cycle and an SFN cycle; and a sending unit configured to send the extended DRX cycle to the UE for use by the UE to listen to a paging message in the idle mode.

10. A method for power saving of an idle mode User Equipment (UE), comprising: acquiring an extended DRX cycle greater than both a regular DRX cycle and an SFN cycle; and determining a Paging Frame (PF) number and a Paging Occasion (PO) subframe number used for listening to a paging message according to the extended DRX cycle.

11. The method of claim 10, wherein the extended DRX cycle is configured as integral times of the SFN cycle.

12. The method of claim 10, wherein the extended DRX cycle is set as multiple powers of 2 times of the SNF cycle.

13. The method of claim 10, wherein in case that value of the SFN cycle is 1024, index i_s pointing to PO is calculated according to the following formula and the PO subframe number is determined according to a predetermined subframe pattern: i_s=floor (UE_ID/N) mod Ns, where T is the extended DRX cycle, nB is a value selected from a set (4T, 2T, T, T/2, T/4, T/8, T/16, T/32),

N=min(T, nB) refers to number of paging frames having POs,

Ns=max(l, nB/T) refers to number of subframes for paging in one paging frame, ilMSI mod 1024 , where T < SFN cycle

UE ID= < where IMSI refers to International

IMSI mod T , whereT > SFN cycle

Mobile Subscriber Identification of the UE and is given as sequence of digits of type Integer, floor is a rounding down operation, and mod is a modular operation.

14. The method of claim 10, wherein in case that value of the SFN cycle is 1024, determining the PF number comprise: calculating a paging frame index number i_PF in one extended DRX cycle, wherein i_PF=(T/N)*(UE_ID mod N), calculating index of SFN cycle i_SFN in one extended DRX cycle according to the calculated paging frame index number, wherein i_SFN=floor(i_PF/1024)+l, calculating a paging frame radio frame number PF_SFN in the SFN cycle according to the calculated paging frame index number, wherein PF_SFN=i_PF mod 1024, and the PF number being indicated by both the calculated SFN cycle index i_SFN and the paging frame radio frame number PF_SFN, where T is the extended DRX cycle, nB is a value selected from a set (4T, 2T, T, T/2, T/4, T/8, T/16, T/32), N=min(T, nB) refers to number of paging frames having POs,

UE ID= < where IMSI refers to International

IMSI mod T , whereT > SFN cycle

15. The method of claim 10, further comprising: receiving the SFN cycle index counted by an base station for SFN cycle synchronization between the base station and the UE.

16. The method of claim 10, wherein the extended DRX cycle is acquired through receiving a SystemInformationBlockType2 (SIB2) message from a base station and extracting information on the extended DRX cycle.

17. An apparatus for power saving of an idle mode User Equipment (UE), comprising: an discontinuous reception (DRX) cycle acquiring unit configured to acquire an extended DRX cycle greater than both a regular DRX cycle and an SFN cycle; and a determining unit configured to determine a Paging Frame (PF) number and a Paging Occasion (PO) subframe number used for listening to a paging message according to the extended DRX cycle.