Configuration of measurement subframes for a user equipment (UE)

1. An apparatus of an eNodeB operable to configure measurement subframes for a user equipment (UE), the apparatus comprising one or more processors and memory configured to:

identify, at the eNodeB, a first set of orthogonal frequency division multiplexing (OFDM) symbols of a measurement subframe to transmit a plurality of primary synchronization signals (PSS) to the UE in the measurement subframe, wherein the first set of OFDM symbols used to transmit the PSS is configured based on a number of cell-specific reference signal (CRS) antenna ports (APs), wherein the measurement subframe includes CRS OFDM symbols and non-CRS OFDM symbols, wherein the CRS OFDM symbols include CRS resource elements (REs) and non-CRS REs;

identify, at the eNodeB, a second set of OFDM symbols of the measurement subframe to transmit a plurality of secondary synchronization signals (SSS) to the UE in the measurement subframe, wherein the second set of OFDM symbols used to transmit the SSS is configured based on the number of CRS APs;

encode, at the eNodeB, the plurality of primary synchronization signals (PSS) for transmission to the UE using the first set of OFDM symbols of the measurement subframe; and

encode, at the eNodeB, the plurality of secondary synchronization signals (SSS) for transmission to the UE using the second set of OFDM symbols of the measurement subframe;

transmit the plurality of primary synchronization signals (PSS) to the UE using the first set of OFDM symbols of the measurement subframe, wherein the plurality of PSS are transmitted from the eNodeB to the UE using non-cell specific reference signal (non-CRS) OFDM symbols of a single measurement subframe; and

transmit the plurality of secondary synchronization signals (SSS) to the UE using the second set of OFDM symbols of the measurement subframe, wherein the plurality of SSS are transmitted from the eNodeB to the UE using non-cell specific reference signal (non-CRS) OFDM symbols of the single measurement subframe.

2. The apparatus of claim 1 , wherein the non-CRS REs in the CRS OFDM symbols are configured as blank.

3. The apparatus of claim 1 , wherein the one or more processors and memory are further configured to: process CRS on CRS REs in the CRS OFDM symbols for transmission to the UE.

4. The apparatus of claim 1 , wherein: a first portion of the REs in the CRS OFDM symbols are configured as blank to reduce inter-cell interference and a second portion of the REs in the CRS OFDM symbols are used to transmit CRS to increase a reference symbol density.

5. The apparatus of claim 1 , wherein:

the PSS is repetitively transmitted in the first set of OFDM symbols in the measurement subframe, and the first set of OFDM symbols includes symbols 1 , 2 and 5 ; and

the SSS is repetitively transmitted in the second set of OFDM symbols in the measurement subframe, and the second set of OFDM symbols includes symbols 3 and 6 ,

wherein the measurement subframe includes a non-extended cyclic prefix (CP) for a first slot and a second slot included in the measurement subframe, and a number of cell-specific reference signal (CRS) antenna ports (APs) is two.

6. The apparatus of claim 1 , wherein:

the PSS is repetitively transmitted in the first set of OFDM symbols in the measurement subframe, and the first set of OFDM symbols includes symbols 2 and 5 ; and

the SSS is repetitively transmitted in the second set of OFDM symbols in the measurement subframe, and the second set of OFDM symbols includes symbols 3 and 6 ,

wherein: the measurement subframe includes a non-extended cyclic prefix (CP) for a first slot and a second slot included in the measurement subframe, a number of cell-specific reference signal (CRS) antenna ports (APs) is two, and symbol I is blank.

7. The apparatus of claim 1 , wherein:

the PSS is repetitively transmitted in the first set of OFDM symbols in the measurement subframe, and the first set of OFDM symbols includes symbols 2 and 5 ; and

the SSS is repetitively transmitted in the second set of OFDM symbols in the measurement subframe, and the second set of OFDM symbols includes symbols 3 and 6 ,

wherein the measurement subframe includes a non-extended cyclic prefix (CP) for a first slot and a second slot included in the measurement subframe, and a number of cell-specific reference signal (CRS) antenna ports (APs) is four.

8. The apparatus of claim 1 , wherein:

the PSS is repetitively transmitted in the first set of OFDM symbols in the measurement subframe, and the first set of OFDM symbols includes symbols I and 4 ; and

the SSS is repetitively transmitted in the second set of OFDM symbols in the measurement subframe, and the second set of OFDM symbols includes symbols 2 and 5 ,

wherein the measurement subframe includes an extended cyclic prefix (CP) for both slots and a number of CRS APs is two.

9. The apparatus of claim 1 , wherein the measurement subframe occurs on at least one of subframe 0 and subframe 5 in a given frame.

10. The apparatus of claim 1 , wherein a periodicity of the measurement subframe is configured based on a velocity of the UE and a delay sensitivity of the UE, wherein the periodicity of the measurement subframe is configured as 40 milliseconds (ms), 80 ms or 160 ms.

11. An apparatus of a user equipment (UE) operable to process synchronization signals received from an eNodeB, the apparatus comprising one or more processors and memory configured to:

process, at the UE, a plurality of primary synchronization signals (PSS) received from the eNodeB in a measurement subframe, wherein the plurality of PSS are transmitted to the UE using a first set of orthogonal frequency division multiplexing (OFDM) symbols of the measurement subframe, wherein the first set of OFDM symbols used to transmit the PSS is configured based on number of cell-specific reference signal (CRS) antenna ports (APs); and

process, at the UE, a plurality of secondary synchronization signals (SSS) received from the eNodeB in the measurement subframe, wherein the plurality of SSS are transmitted to the UE using a second set of orthogonal frequency division multiplexing (OFDM) symbols of the measurement subframe, wherein the second set of OFDM symbols used to transmit the SS is configured based on the number of CRS APs.

12. The apparatus of claim 11 , wherein the plurality of PSS and the plurality of SSS are received from the eNodeB using non-cell specific reference signal (non-CRS) OFDM symbols of a single measurement subframe.

13. The apparatus of claim 11 , wherein the UE is configured for narrowband cellular Internet of Things (CIOT) or machine type communication (MTC).

14. At least one non-transitory machine readable storage medium having instructions embodied thereon for configuring measurement subframes for a user equipment (UE), the instructions when executed perform the following:

identifying, using one or more processors at an eNodeB, a first set of orthogonal frequency division multiplexing (OFDM) symbols of a measurement subframe to transmit a plurality of primary synchronization signals (PSS) to the UE, wherein the first set of OFDM symbols used to transmit the PSS is configured based on a number of cell-specific reference signal (CRS) antenna ports (APs);

identifying, using the one or more processors at the eNodeB, a second set of OFDM symbols of the measurement subframe to transmit a plurality of secondary synchronization signals (SSS) to the UE, wherein the second set of OFDM symbols used to transmit the SSS is configured based on the number of CRS APs;

processing, using the one or more processors at the eNodeB, the plurality of primary synchronization signals (PSS) for transmission to the UE using the first set of OFDM symbols of the measurement subframe; and

processing, using the one or more processors at the eNodeB, the plurality of secondary synchronization signals (SSS) for transmission to the UE using the second set of OFDM symbols of the measurement subframe.

15. The at least one non-transitory machine readable storage medium of claim 14 , wherein:

the measurement subframe includes cell-specific reference signal (CRS) OFDM symbols and non-CRS OFDM symbols, wherein the CRS OFDM symbols include CRS resource elements (REs) and non-CRS REs; and

a first portion of the REs in the CRS OFDM symbols are configured as blank to reduce inter-cell interference and a second portion of the REs in the CRS OFDM symbols are used to transmit CRS to increase a reference symbol density.

16. The at least one non-transitory machine readable storage medium of claim 14 , wherein:

the measurement subframe includes a non-extended cyclic prefix (CP) for both slots or the measurement subframe includes an extended CP for both slots; and

a number of CRS-APs is two or four.

17. The at least one non-transitory machine readable storage medium of claim 14 , wherein the plurality of PSS and plurality of SSS are transmitted from the eNodeB to the UE using non-cell specific reference signal (non-CRS) OFDM symbols of a single measurement subframe.

18. The at least one non-transitory machine readable storage medium of claim 14 , wherein:

the measurement subframe occurs on at least one of subframe 0 and subframe 5 in a given frame; or

a measurement subframe is configured based on a velocity of the UE and a delay sensitivity of the UE.