Sleep handling for user equipment

Abstract

An eNB and a method for use in a base station (eNB) for configuring a UE to be awake for a longer duration in order to detect eNB transmission after the end of initial Signalling.

Claims

1. A base station comprising a controller and an interface, wherein the controller is configured to: determine that there is a user equipment (UE) that can receive downlink subframes reliably or that is not sensitive to power consumption, or both; select that UE; and signal the selected UE with information instruction instructing the selected UE to remain awake for a certain period after the end of an interval allocated for eNB transmission of Initial Signalling (IS) in response to success of a listen-before-talk (LBT) procedure performed by the eNB.

2. The base station of claim 1, wherein the controller is further configured to determine that a eNB has succeeded with a Listen Before Talk procedure after a particular period and is therefore not able to transmit an IS.

3. The base station of claim 1, wherein the controller is further configured to configure the UE by: configuring the selected UE to be awake for a certain period after the end of a fixed IS in order to allow the UE to detect a floating IS transmission.

4. The base station of claim 1, wherein the controller is further configured to determine the length of a floating IS to be sent based on at least one of the UE's coverage or power consumption requirement.

5. The base station of claim 1, wherein the controller is further configured to reschedule Downlink data if a floating initial signalling overrides one or more scheduled Downlink transmissions.

6. The base station of claim 1, wherein the controller is further configured to schedule Downlink data to only target transmission to a selected UE.

7. The base station of claim 1, wherein the controller is further configured to base the determination on a coverage ranking of the UE.

8. The base station of claim 1, wherein the controller is further configured to base the determination on the UE's power consumption requirements.

9. The base station of claim 1, wherein the controller is further configured to base the determination on additional floating IS.

10. The base station of claim 1, wherein the controller is further configured to base the determination on eNB data transmissions containing LTE sync signals or reference signals.

11. The base station of claim 1, wherein the controller is further configured to determine a length of a floating IS based on the coverage ranking of the UE that is still awake.

12. The base station of claim 8, wherein the controller is further configured to receive the power consumption requirements from the UE.

13. A method for use in a base station, the method comprising: determining that there is a user equipment (UE) that can receive downlink subframes reliably or that is not sensitive to power consumption, or both; selecting that UE; and signaling the selected UE with information instruction instructing the selected UE to remain awake for a certain period after the end of an interval allocated for eNB transmission of Initial Signalling (IS) in response to success of a listen-before-talk (LBT) procedure performed by the eNB.

14. A User Equipment comprising: radio circuitry; and processing circuitry operatively coupled to the radio circuitry and configured to: transmit battery requirements to a base station; and receive signalling instructing the User Equipment to be awake for a certain period after the end of an interval allocated for eNB transmission of Initial Signalling (IS) in response to success of a listen-before-talk (LBT) procedure performed by the eNB, even if IS is not detected by the UE in the allocated interval.

15. The User Equipment of claim 14, wherein the processing circuitry is further configured to determine that a battery level has passed a threshold level and in response thereto transmit updated battery requirements to the base station.

16. The User Equipment of claim 14, wherein the processing circuitry is further configured to determine that a power source has been connected to the UE and in response thereto transmit updated battery requirements to the base station.

17. A method for use in a User Equipment, the method comprising: transmitting battery requirements to a base station; and receiving signalling instructing the User Equipment to be awake for a certain period after the end of an interval allocated for eNB transmission of Initial Signalling (IS) in response to success of a listen-before-talk (LBT) procedure performed by the eNB.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention will be described in detail with reference to the attached figures, of which:

(2) FIG. 1 shows a schematic view of a frame structure according to herein.

(3) FIG. 2 shows a schematic view of a User Equipment in a telecommunications system adapted according to herein.

(4) FIG. 3 shows a frame structure and how it relates to transmitting conditions according to herein.

(5) FIG. 4 shows an alternative frame structure and how it relates to transmitting conditions according to herein.

(6) FIG. 5 shows a flowchart for a method according to herein.

(7) FIG. 6 shows a flowchart for a method according to herein.

(8) FIG. 7 shows eNB scheduling of good coverage UEs in the latency period according to herein.

DETAILED DESCRIPTION

(9) The invention will now be disclosed in detail through example embodiments.

(10) FIG. 2 shows a schematic view of a telecommunications system according to the teachings herein where a User Equipment (UE) comprises a controller (CPU) for controlling the overall operation of the UE. The controller may comprise of one or more processors each assigned a task or arranged to cooperate to perform a task. For the purpose of this text, the controller will be treated as one entity, but many variants exist as would be understood to a skilled person.

(11) The UE further comprises an interface, especially a radio frequency interface (RF) for establishing communication with other UEs or a base station (eNB) such as an evolved NodeB. The base station or eNB comprises a controller (CPU) for controlling the overall operation of the eNB and an interface RF for communicating with other entities such as a telecommunications server (not shown) and the UE.

(12) Returning to the invention, the purpose of the initial signal is to be robust for all UE in the cell to detect and establish timing to the cell and receive the DL scheduled data and transmit UL data. The robustness is primarily embodied in the fact that it is tolerant to frequency error so that the UE can perform AGC, AFC and set the fine timing prior to the DL data burst. It is assumed that the UE has coarse timing, enough to detect the IS signal and establish fine tune with the cell.

(13) But not all UEs need the IS signal to perform AGC, AFC and set the fine timing prior to receiving the DL data subframes. eMTC is targeting low mobility scenarios where the cell timing does not drift too much so it is possible if the signal is of good quality to set the gain, frequency and timing with the actual DL data subframes. Naturally the DL data subframes also contains reference signal on which to tune. Data subframes also contain very short signal which have similar composition to the IS signal. In LTE synchronization signals, such as the Primary and Secondary Synchronization Signals (PSS/SSS) are such signals that the UE can use to tune to the cell.

(14) So, one point is that some UEs in the cell have the potential to receive DL data subframes without the aid of the IS. The second point is that these first few subframes have already been processed and are ready for transmission on a radio head which in some configurations are remote from the baseband unit.

(15) The invention lies in signalling certain UEs to remain awake even if the IS signal is not detected. Signalling can be done via RRC messages. If the UE moves out of the good coverage area, it can be signalled to immediately go to sleep when the IS is not detected.

(16) In some embodiments, if the eNB clears LBT after the end of the fixed IS occasion, the eNB may still send another floating IS between LBT success and the next scheduled DL transmission which is typically at subframe boundary. If the eNB determines this time is not sufficient for UEs to detect its transmission, it may send a longer floating IS that overrides part of the scheduled DL transmissions which leads to rescheduling of the overridden DL data at a later time.

(17) Upon detecting the floating IS the UE can continue with processing subsequent data transmissions in the same way as detecting the fixed IS. See FIG. 3 showing a frame structure and how it relates to transmitting conditions. As can be seen, during the initial signalling, there might be a period where UEs sensitive to power consumption have entered a sleep mode or where there is bad coverage and a period where UEs that are tolerant to power consumption are still awake (i.e. not in a sleep mode) or there is good coverage. And where the UE keeps awake after the fixed IS session or period and detects eNB transmission based on floating IS.

(18) Since UEs could go to sleep mode when not detecting the fixed IS at the end of the fixed IS occasion, the eNB may configure UEs to keep awake for a certain period even after the end of the fixed IS. This is however not good for UE's power consumption thus causing shorter battery life which is essential for some IoT UEs. The eNB may configure good coverage UEs for being awake for a short while since these UEs has higher chance to detect short floating IS and thus have less impact on power consumption.

(19) There may be UEs that are not sensitive to power consumption, e.g. connected to power supply, and thus do not need long sleeping cycles or short wakeup time. Such UE may inform the eNB its power consumption requirement so that the eNB can configure longer wakeup time, or even without sleep configuration.

(20) The eNB may dynamically configure the length of the floating IS in order to allow UEs above the corresponding coverage ranking to be able to detect the eNB transmission. If eNB determines that no UE is awake after the end of the fixed IS, it can skip sending the floating IS and data, until re-attempting channel access at the next fixed IS occasion.

(21) In other embodiments, the UE may detect eNB transmission based on non-IS transmissions e.g. LTE PSS/SSS, reference signals, or PDCCH/PDSCH, if the eNB clears LBT after the end of the IS.

(22) One embodiment is to signal the number of subframes after the IS expected position to remain awake, or via DRX configurations where the UE's sleeping cycle starts in a period after the end of IS. One embodiment is for the eNB to signal via PDCCH in the first one or more subframes how long for UEs to remain awake and receive DL data transmission.

(23) One embodiment is to set the number of subframes to remain awake to match the eNB processing delays between LBT and baseband signal processing.

(24) One embodiment is to understand the battery life requirements of UE in the good coverage area and adjust the number of subframes they should be awake. The requirements may contain recommended sleep cycle, wake-up ratio or an indicator of the power save level (e.g. no power save if connected to power supply, or strict power save in case a IoT device that needs to operate many years with constrained battery). The UEs with strict (long life) battery consumption requirements, are scheduled first while other UEs with shorter battery life requirements are scheduled in later subframes. Given the short time frame we are addressing in the order of milliseconds it probably is not so efficient for these UE to perform a short sleep and wake up before receiving the scheduled subframe for that UE. See FIG. 4 showing a frame structure as in FIG. 3, but where the UE keeps awake after fixed IS occasion and detects eNB transmission based on sync signals or reference signals within DL data transmissions

(25) FIG. 5 illustrates how the eNB could utilize UE's power consumption requirement report after having received it through a flowchart for a method according to herein in an example system as in FIG. 7 showing eNB scheduling of good coverage UEs in the latency period. FIG. 6 also shows a flowchart for a method according to herein in an example system as in FIG. 7 showing eNB scheduling of good coverage UEs in the latency period. In the system of FIG. 6, three UEs are shown, UEH, UEL and UEM along with frame structures showing the transmissions. As can be seen the eNB baseband has already been processed, scheduled and sent to radio head subframes at point A. At this point the UEs that can receive without the aid of IS signals are receiving.

(26) Returning to the flowchart, as it has been determined that a eNB has not been able to transmit any IS, the eNB determines to configure the UE to be awake for a longer duration in order to detect eNB transmission after the end of IS by performing the following steps. The eNB receives UE power consumption requirement(s) in a first step 501 and thereafter determines whether there is a UE with good coverage or not sensitive to power consumption. If there is such a UE, the eNB selects that UE in step 502 and configures the selected UE to be awake for a certain period after the end of the fixed IS in order to allow UE detecting any floating IS transmission(s) in step 503.

(27) The eNB may then determine the length of the floating IS to be sent based on the UE's coverage and/or power consumption requirement and reschedules DL data if the floating IS overrides some of the scheduled DL transmissions.

(28) FIG. 6 shows a flowchart for handling floating IS an eNB schedules DL transmission to UEs and perform LBT for channel access and then determines if fixed IS is transmitted.

(29) If fixed IS is transmitted, the eNB determines the length of the IS, reschedules UEs if the length of the fixed IS is under a threshold value (i.e., being too short) and transmits DL data to the re-scheduled UEs.

(30) If fixed IS is not transmitted, the eNB determines if there is a UE with good coverage or not sensitive to power consumption, and if there is the eNB determines the length of the floating IS to be sent based on the UE's coverage and/or power consumption requirement, reschedules the DL transmission based on the selected UEs and the length of the floating IS and transmits the floating IS and the DL data to the re-scheduled UEs.

(31) The UE is thus configured to receive configurations and to adapt accordingly. The UE receives these configurations after having transmitted its battery requirements to the eNB. The UE may be configured to determine that the battery requirements have changed and in response thereto transmit updated battery requirements to the eNB. The eNB may then in turn determine a new configuration that is transmitted back to the UE.

(32) The UE may determine that the battery requirements have changed based on that the battery level has become too low or passed under a threshold value (such as 5%, 10%, 15% of the total battery power) or that a power source has been connected to the UE.