Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/02—Power saving arrangements
  • H04W52/0209—Power saving arrangements in terminal devices
  • H04W52/0212—Power saving arrangements in terminal devices managed by the network, e.g. network or access point is master and terminal is slave
  • H04W52/0216—Power saving arrangements in terminal devices managed by the network, e.g. network or access point is master and terminal is slave using a pre-established activity schedule, e.g. traffic indication frame
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
  • Y02D30/00—Reducing energy consumption in communication networks
  • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

• 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).
• UE User Equipment
• DRX Discontinuous Reception
• UE can use DRX to monitor the paging message only in specific subframes.
• 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.
• PDCCH Physical Downlink Control Channel
• PF Paging Frame
• PO Paging Occasion
• 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.
• the DRX cycle is illustrated by the default DRX cycle value broadcast in the system information.
• 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]):
• SIB2 SystemInformationBlockType2
• 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;
• 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 :
• the maximum paging cycle i.e. regular DRX cycle
• 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.
• 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]).
• RSRP Reference Signal Receiving Power
• RSRQ Reference Signal Receiving Quality
• the information element T-Reselection refers to the cell reselection timer Treselection R AT 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.
• MTC Machine Type Communication
• UE Power Consumption Optimizations 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 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.
• 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.
• 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.
• 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.
• 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.
• the UE's power may be saved furthermore by supporting the extended DRX cycle.
• 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.
• 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.
• Fig. 1 illustrates a schematic drawing of a wireless communication network 100 in prior art.
• 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.
• 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.
• 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.
• 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.
• the principle of the present invention may be used to any extended DRX cycle greater than the SFN cycle.
• the extended DRX cycle is sent to the UE by adding information on the extended DRX cycle into a SystemInformationBlockType2 (SIB2) message.
• SIB2 SystemInformationBlockType2
• the base station 110 may broadcast the SIB2 message containing the extended DRX cycle to a plurality of UEs 120.
• 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:
• RadioResourceConfigCommon 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.
• 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.
• 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.
• the UE 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).
• defaultPagingCycle i.e. the regular DRX cycle
• 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.
• 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.
• PF Paging Frame
• PO Paging Occasion
• 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.
• i_PF the value range of i_PF is ⁇ 0...T-1 ⁇ .
• 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).
• the value range of i_SFN is ⁇ 1... T/1024 ⁇ . And there are T/1024 SFN cycles in one extended DRX cycle.
• 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.
• 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.
• 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 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.
• the parameters may be set as following:
• the subframe number of PO is 9 according to the subframe pattern of Table 1.
• 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.
• 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.
• the method 200 further includes step
• 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.
• 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 configured extended DRX cycle may be different, the maximum value of SFN cycle index will also be different.
• the base station sends the SFN cycle index to the UE through a Master InformaitonB lock (MIB) message.
• MIB Master InformaitonB lock
• 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.
• 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:
• 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.
• the base station sends the SFN cycle index to the
• SIB 1 SystemlnformationBlockTypel
• 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.
• the base station may add the SFN cycle index corresponding to that radio frame into the SIB 1 message.
• 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.
• IE can be added in the SystemlnformationBlockTypel message: sfnCycIelndcx INTEGER (0.. maxSfnCyclelndex) OPTIONAL.
• the UE may ignore this IE since it is an optional IE rather than mandatory.
• 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.
• 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.
• 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.
• 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 SIB 1
• MIB MasterlnformaitonBlock
• the extended DRX cycle configuring unit 410 configures the extended DRX cycle as integral times of the SFN cycle.
• the extended DRX cycle configuring unit 410 configures the extended DRX cycle as multiple powers of 2 times of the SNF cycle.
• 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.
• SIB2 SystemInformationBlockType2
• 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.
• 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.
• 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.
• the extended DRX cycle is integral times of the SFN cycle.
• the extended DRX cycle is multiple powers of 2 times of the SNF cycle.
• the determining unit 520 determines the PF number and the PO subframe number in the way described in conjunction with the method 300.
• 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.
• the serving cell measurement is performed once every DRX cycle.
• the time interval T-Reselection for 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.
• 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.
• base station is exchangeable with “cell”, “Node B” and “eNodeB” and as on.
• 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.
• the functions of the present application may be implemented using hardware, software, firmware, or any combinations thereof.
• 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.
• any connection may also be considered as a computer-readable medium.
• co-axial cable an optical cable, a twisted pair wire, a digital subscriber line (DSL), or radio technologies such as infrared, radio or microwave
• 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.
• DSP digital signal processor
• ASIC application specific integrated circuit
• FPGA field programmable gate array
• 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.

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• 2013
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