10.2.6A Narrowband positioning reference signal (NPRS)
36.2113GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Physical channels and modulationRelease 17TS
Narrowband positioning reference signals (NPRSs) shall only be transmitted in resource blocks in NB-IoT carriers configured for NPRS transmission. In a subframe configured for NPRS transmission, the starting positions of the OFDM symbols configured for NPRS transmission shall be identical to those in a subframe in which all OFDM symbols have the same cyclic prefix length as the OFDM symbols configured for NPRS transmission. NPRS are defined for 
and normal CP only.
NPRSs are transmitted on antenna port 2006.
10.2.6A.1 Sequence generation
The NPRS sequence 
is defined by
where 
is the slot number within a radio frame, 
is the OFDM symbol number within the slot. The pseudo-random sequence 
is defined in clause 7.2. The pseudo-random sequence generator shall be initialised with
at the start of each OFDM symbol where 
equals 
unless configured by higher layers and where 
10.2.6A.2 Mapping to resource elements
For an NB-IoT carrier which is configured for NPRS transmission, the reference signal sequence 
shall be mapped to complex-valued modulation symbols 
used as reference signal for antenna port 
in slot 
according to, for Type 1 NPRS:
or for Type 2 NPRS:
according to higher layer configuration, where
– when the higher layer parameter operationModeInfoNPRS for the configured NB-IoT carrier is set to in-band
where 
is signalled by higher layers nprs-SequenceInfo, and 
if the higher layer parameter nprs-SequenceInfo indicates 
is odd, and 
if the higher layer parameter nprs-SequenceInfo indicates 
is even.
– when the higher layer parameter operationModeInfoNPRS for the configured NB-IoT carrier is set to standalone or guard-band
and where 
. If 
is not configured by higher layers, 
. The number of PBCH antenna ports is signalled by higher layers.
If higher layer parameter nprsBitmap is not configured, resource elements in OFDM symbols 5 and 6 in each slot shall not be used for transmission of NPRS. If the configured periodicity of Type 1 NPRS is equal to that of Type 2 NPRS, the UE is not expected to be configured with overlapped resource elements between Type 1 NPRS and Type 2 NPRS. Otherwise, a resource element configured for Type 1 NPRS shall not be used for Type 2 NPRS.
Figure 10.2.6A.2-1: Mapping of NPRS (operationModeInfoNPRS is set to in-band, nprsBitmap configured)
Figure 10.2.6A.2-2: Mapping of NPRS (operationModeInfoNPRS is set to standalone or guard-band, nprsBitmap configured)
10.2.6A.3 NPRS subframe configuration
On a NB-IoT DL carrier configured for NPRS transmission, an NB-IoT UE can assume NPRSs are transmitted in DL subframes configured by all higher layer parameters nprsBitmap, the NB-IoT carrier-specific subframe configuration period 
the NB-IoT-carrier-specific starting subframe offset 
and the number of consecutive downlink subframes 
where NPRS shall be transmitted. If frame structure type 2 is used, the UE shall not assume NPRSs are transmitted in special subframes.
– If 
, 
and 
are not configured for an NB-IoT downlink carrier configured for NPRS transmission, an NB-IoT UE shall assume NPRSs are transmitted in downlink subframes configured by higher layer parameter nprsBitmap.
– If nprsBitmap is not configured for an NB-IoT downlink carrier configured for NPRS transmission, an NB-IoT UE shall assume NPRSs are transmitted in downlink subframes configured by the higher layer parameters 
, 
and 
.
– If the higher layer parameter operationModeInfoNPRS for the configured NB-IoT carrier is set to in-band, the higher layer parameters nprsBitmap shall be configured.
– If 
, 
and 
are configured, the NPRS instances in the first subframe of the 
downlink subframes, shall satisfy 
.
The NPRSs shall not be mapped to resource elements 
allocated to resource blocks of NPBCH, NPSS, NSSS, or SystemInformationBlock-Type1-NB regardless of their antenna port 
.