NR paging supports LTE networks like TDM, but whether it supports paging of FDM needs further discussion. In multi-beam deployment, broadcast signals including paging require scanning of multi-beams, especially high-frequency. NR supports wide carriers, and the broadband can be configured as multiple BWPs. If only TDM paging is supported in NR, the paging overhead will be concentrated on a specific paging bandwidth, which may belong to a BWP. This BWP will suffer from high loads of the broadcast signal, while unicast traffic will be concentrated in this BWP. The FDM in a paging occasion can allocate the paging load to multiple paging bandwidths. A BWP congestion can be avoided. The bandwidth of the PO of the FDM should be limited to the minimum bandwidth of the UE. The configuration of FDM PO can be issued in RMSI or OSI.
In NR, multiple FDMed SSBs may exist in one broadband carrier. The UE may assume QCL between SSB, paging DCI, and paging messages. If FDM is supported for paging occasions, the QCL association between the SSB of FDM and the paging of FDM should be configured. For example, the UE will assume the QCL between the SSB and the paging DCI/message, which belong to the same BWP.
Moreover, NR supports slot and Non-slot-based PDSCH paging transmission. In order to achieve beam scanning for paging, FDMed can be performed by paging and SSB in paging occasions. However, the transmission of the SSB is limited to a 5 ms time window. In time slots that do not contain SSBs, it is not clear how to define paging occasions, including the time/frequency resources of the PO. The resources of the PO can be predefined or configured in the system information. The latter approach requires more signal overhead. And flexible paging resource allocation seems unnecessary. For predefined paging resources, the nominal resources of the SSB can be used for paging resources. The nominal SSB resource includes candidate resource locations in the time slot defined for SSB transmission. The following figure illustrates the mapping of nominal SSB resources in a time slot in a 15 kHz SCS case.
UE represents the periodicity of the actual transmitted SSB and SS burst set, and determines the candidate paging resource in the following cases:
In the nominal SSB resource that actually sends the SSB, the predefined resource FDM with the nominal SSB resource is determined as the candidate paging resource
In the nominal SSB resource that does not actually send the SSB, it is at least the nominal SSB resource that is determined as the candidate paging resource. The predefined resource FDM with nominal SSB resources can be further used as a candidate paging resource
For non-slot-based PDSCH transmission for paging transmission, the following PO definition can be considered to effectively scan beam :
- 4 OFDM symbol duration, PO can define
- 2 or 4 The OFDM symbol continues, and the PO can use paging resources including nominal SSB resources to define
Nominal SSB resources design has taken into account several aspects, such as the location of other channels/signals, upstream and downlink transmission, URLLC, etc. Paging delivery using nominal SSB resources has minimal impact on other channels/signal transmissions. The signaling of the paging resource can be reduced, because the nominal SSB resource is predefined in a time slot. Therefore, it is proposed that nominal SSB resources can be defined as paging delivery resources.
In LTE, the UE in RRC_IDLE mode is regularly awakened and listened for paging during paging cycle (PO: Paging Occasion). At other times, the UE may go to bed to save power. PF is
SFN mod T= (T div N)*(UE_ID mod N)
where N=min(T, nB) represents the number of PFs in the DRX cycle. T is defined as DRX cycle, UE_ID=IMSI mod 1024. The DRX parameter ‘nB’ is a determinant of paging capacity in a cell, which represents the number of pages in the DRX cycle.
PO is a subframe that carries the paging messages in PDCCH addressed by PF, given by the following table.
Ns is defined as the number of pages in PF. The value of i_s is determined by a formula.
i_s = floor(UE_ID/N) mod Ns
According to the predefined table above, subframes 0, 1, 5, and 6 can be observed for paging in PF of TDD. They are either downlink subframes or special subframes under all TDD DL/UL configurations. Therefore, one of the most direct ways to design a PO in NR is to associate it with the NR semi-static DL/UL allocation.
In NR, for semi-static DL/UL allocation, the DL/UL transmission direction is assigned by a high-level signal through a cell-specific signal (SIB) and a UE-specific signal. For cell-specific high-level signaling, transmission indicates a mode in DL-unknown-UL, where DL and UL are configured as resources related to basic information (eg, synchronization signals, broadcast system information, and PRACH), which is a common DL and UL resource set for all UEs in the cell. It is recommended to design PO in resources configured as "DL" in cell-specific high-level signaling.
In addition, the period values of the semi-static allocation of DL/UL transmission include 0.5 ms, 1 ms, 2 ms, 5 ms, 10 ms. For values below 6 GHz, 15 kHz, 30 kHz and 60 kHz are included, respectively. Therefore, the time slot of a semi-static frame should change with the change of nuclearology.
