Wake up signal for machine type communication and narrowband-internet-of-things devices
Systems and methods of reducing power consumption associated with paging or cDRX mode are described. A wake-up receiver (WUR) wakes up from an idle mode or cDRX state. Whether a wake-up signal (WUS) has been received by the WUR is determined. The WUS is a low-complexity signal that is less complicated than a PDCCH or PDSCH and is repeated multiple times at resource elements as indicated in a configuration from an eNB. If received, a baseband transceiver wakes up for reception of a PDCCH for the UE in a PO when the UE is in the idle mode or a PDSCH for the UE when the UE is in the cDRX state.
1. An apparatus, comprising:
a memory; and
processing circuitry in communication with the memory and arranged to:
determine whether a wake-up signal (WUS) has been received in idle mode from a base station;
in response to a determination that the WUS has been received, monitor one or more of a Machine Type Communication (MTC) Physical Downlink Control Channel (MPDCCH) or a Narrowband Physical Downlink Control Channel (NPDCCH) in a paging occasion (PO), wherein reception of the WUS is based on a timing offset between the WUS and the PO; and
in response to a determination that the WUS has not been received, not monitor the PO in idle mode.
2. The apparatus of claim 1
wherein the processing circuitry is further configured to determine whether the WUS has been received by decoding a preamble sequence of the WUS, the preamble sequence comprising, at least one of:
a Zadoff-Chu (ZC) sequence that comprises at least one of a different root index or different length than a legacy primary synchronization signal, legacy secondary synchronization signal and demodulation reference signal, or
a pseudo-random sequence that is dependent on one of a subframe or slot index, and the WUS is based on a default value for the one of the subframe or slot index, or
a pseudo-random sequence that is different from a Cell Specific Reference Signal (CRS) and Narrowband Reference Signal (NRS), and the pseudo-random sequence is one of:
common to all cells and the pseudo-random sequence is generated using a default cell identification (ID),
cell-specific and the pseudo-random sequence is defined as a function of a cell, ID of the base station,
UE-group specific and the pseudo-random sequence is defined by a mapping indicated by mod (UE-group ID, N), where N is a number of available pseudo-random sequences to be used, or
UE-specific and the pseudo-random sequence is defined by a mapping indicated by mod (UE ID, N), where N is the number of available pseudo-random sequences to be used.
3. The apparatus of claim 1 ,
wherein at least one of:
resource elements (REs) containing reference signals that overlap the WUS are punctured to carry the WUS, or
the WUS is mapped around the REs and the WUS is rate matched around the REs.
4. The apparatus of claim 1 ,
wherein the processing circuitry is further configured to decode a configuration from the base station that indicates that the WUS is supported by the base station, and
wherein the configuration is cell-specific and indicates a maximum number of repetitions of the WUS.
5. The apparatus of claim 4 ,
wherein the maximum number of repetitions of the WUS is dependent on a coverage level of the apparatus.
6. The apparatus of claim 1 ,
wherein the WUS spans a plurality of successive physical resource blocks (PRBs) in a same frequency band.
7. The apparatus of claim 1 ,
wherein the PO is a PO immediately after a search space defined for the WUS.
8. The apparatus of claim 1 :
wherein the processing circuitry comprises:
a first baseband processor configured to decode the WUS, and
a second baseband processor configured to decode the MPDCCH or NPDCCH,
and
wherein the first baseband processor is deactivated during reception of the MPDCCH or NPDCCH and the second baseband processor is deactivated during reception of the WUS.
9. The apparatus of claim 8 ,
wherein the first and second baseband processors are disposed in different receiver chains, each receiver chain having active analog and digital radio frequency (RF) components, the receiver chain associated with the first baseband filter configured to tap a signal from passive filters of the receiver chain associated with the second baseband filter.
10. The apparatus of claim 9 ,
wherein the processing circuitry is further arranged to:
decode the WUS over a duration dependent on a modulation scheme of the WUS.
11. The apparatus of claim 1 ,
wherein a WUS frequency resource allocation includes configuration of a subset of Physical Resource Blocks (PRBs) from paging resources.
12. The apparatus of claim 11 ,
wherein the subset of PRBs includes a first PRB from the paging resources.
13. The apparatus of claim 1 ,
wherein the determination whether the wake-up signal (WUS) has been received is performed based on a Radio Resource Control (RRC) configuration provided by System Information Broadcast (SIB) signaling that indicates that WUS is supported in a cell.
14. A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors of a user equipment (UE), the instructions executable by the one or more processors to configure the UE to:
receive a wake-up signal (WUS) configuration from a base station that indicates that a WUS is supported by the base station, the WUS being included in a physical downlink control channel (PDCCH);
enter a connected mode Discontinuous Reception (cDRX) state; and
wake up from the cDRX state at a resource indicated by the WUS configuration and determine whether the WUS has been received, wherein reception of the WUS is based on a timing offset between the WUS and a start of cDRX active time;
in response to a determination that the WUS has been received, wake up for monitoring a PDCCH; and
in response to a determination that the WUS has not been received, do not wake up for monitoring a PDCCH.
15. The non-transitory computer-readable storage medium of claim 14 ,
wherein one of:
the instructions, when executed, further configure the UE to monitor for the WUS in response to a determination that the UE is in an area in which the WUS is supported and otherwise monitor for legacy paging;
the WUS configuration is cell-specific and indicates a maximum number of repetitions of the WUS; or
the WUS is received at a predetermined time offset from a start of a paging occasion when the UE is in idle mode.
16. An apparatus, comprising:
a memory; and
processing circuitry in communication with the memory and arranged to:
transmit, to a user equipment (UE) in an idle mode, a wake-up signal (WUS); and
encode, for transmission to the UE after transmission of the WUS and during a paging occasion (PO), paging information on one or more of a Machine Type Communication (MTC) Physical Downlink Control Channel (MPDCCH) or Narrowband Physical Downlink Control Channel (NPDCCH), wherein transmission of the WUS is based on a timing offset between the WUS and the PO.
17. The apparatus of claim 16 ,
wherein a WUS frequency resource allocation includes configuration of a subset of Physical Resource Blocks (PRBs) from paging resources.
18. The apparatus of claim 17 ,
wherein the subset of PRBs includes a first PRB from the paging resources.
19. The apparatus of claim 16 ,
wherein a Radio Resource Control (RRC) configuration provided by System Information Broadcast (SIB) signaling that indicates that WUS is supported in a cell.
20. The apparatus of claim 16 ,
wherein the WUS comprises a preamble sequence comprising at least one of:
a Zadoff-Chu (ZC) sequence that comprises at least one of a different root index or different length than a legacy primary synchronization signal, legacy secondary synchronization signal and demodulation reference signal, or
a pseudo-random sequence that is dependent on one of a subframe or slot index, and the WUS is based on a default value for the one of the subframe or slot index, or
a pseudo-random sequence that is different from a Cell Specific Reference Signal (CRS) and Narrowband Reference Signal (NRS), and the pseudo-random sequence is one of:
common to all cells and the pseudo-random sequence is generated using a default cell identification (ID),
cell-specific and the pseudo-random sequence is defined as a function of a cell, ID of the base station,
UE-group specific and the pseudo-random sequence is defined by a mapping indicated by mod (UE-group ID, N), where N is a number of available pseudo-random sequences to be used, or
UE-specific and the pseudo-random sequence is defined by a mapping indicated by mod (UE ID, N), where N is the number of available pseudo-random sequences to be used.