Method for providing contention-free random access resources for NB-IOT

1. A method in a network node, the method comprising:

reserving, within a Narrowband Physical Random Access Channel (NPRACH) resource comprising a plurality of start subcarriers, a subset of the plurality of start subcarriers for performing a contention-free random access procedure; and

communicating, to one or more user equipment (UEs), information indicating which of the plurality of start subcarriers within the NPRACH resource are reserved for performing the contention-free random access procedure;

wherein the information indicating which of the plurality of start subcarriers within the NPRACH resource are reserved for performing the contention-free random access procedure comprises a number of start subcarriers within the NPRACH resource that are not reserved for performing the contention-free random access procedure.

2. The method of claim 1 , wherein the start subcarriers within the NPRACH resource that are not reserved for performing the contention-free random access procedure are available for performing a contention-based random access procedure.

3. The method of claim 1 , wherein the information is signaled as part of a radio resource control information element.

4. The method of claim 1 , wherein:

each of the plurality of start subcarriers within the NPRACH resource is a first subcarrier for a subcarrier hopping sequence.

5. The method of claim 1 , comprising:

communicating, to a first UE, an instruction to use a particular one of the reserved start subcarriers for performing the contention-free random access procedure.

6. The method of claim 1 , wherein:

the information indicating which of the plurality of start subcarriers within the NPRACH resource are reserved for performing the contention-free random access procedure comprises a number of reserved start subcarriers.

7. A method in a user equipment (UE), comprising:

receiving, from a network node, information indicating which of a plurality of start subcarriers within a Narrowband Physical Random Access Channel (NPRACH) resource are reserved for performing a contention-free random access procedure; and

performing a random access procedure based on the received information;

wherein the start subcarriers that are reserved for performing the contention-free random access procedure comprise a subset of the plurality of start subcarriers within the NPRACH resource; and

wherein one or more start subcarriers that are not in the reserved subset are available for performing a contention-based random access procedure.

8. The method of claim 7 , wherein:

the information indicating which of the plurality of start subcarriers within the NPRACH resource are reserved for performing the contention-free random access procedure comprises a number of the one or more start subcarriers that are not in the reserved subset.

9. The method of claim 8 , comprising:

determining which of the plurality of start subcarriers are reserved for performing the contention-free random access procedure based on the number of the one or more start subcarriers that are not in the reserved subset.

10. The method of claim 8 , comprising:

selecting a first start subcarrier from among the one or more start subcarriers that are not in the reserved subset; and

wherein performing the random access procedure based on the received information comprises performing a contention-based random access procedure using the selected first start subcarrier.

11. The method of claim 7 , comprising:

receiving, from the network node, an instruction to use a particular one of the reserved start subcarriers for performing a contention-free random access procedure; and

wherein performing the random access procedure based on the received information comprises performing the contention-free random access procedure using the particular one of the reserved start subcarriers.

12. The method of claim 7 , wherein:

the information indicating which of the plurality of start subcarriers within the NPRACH resource are reserved for performing the contention-free random access procedure comprises a number of reserved start subcarriers.

13. The method of claim 7 , wherein the information is received in a radio resource control information element.

14. The method of claim 7 , wherein:

each of the plurality of start subcarriers within the NPRACH resource is a first subcarrier for a subcarrier hopping sequence.

15. A network node, comprising:

processing circuitry, the processing circuitry configured to:

reserve, within a Narrowband Physical Random Access Channel (NPRACH) resource comprising a plurality of start subcarriers, a subset of the plurality of start subcarriers for performing a contention-free random access procedure; and

communicate, to one or more user equipment (UEs), information indicating which of the plurality of start subcarriers within the NPRACH resource are reserved for performing the contention-free random access procedure;

wherein the information indicating which of the plurality of start subcarriers within the NPRACH resource are reserved for performing the contention-free random access procedure comprises a number of start subcarriers within the NPRACH resource that are not reserved for performing the contention-free random access procedure.

16. The network node of claim 15 , wherein the start subcarriers within the NPRACH resource that are not reserved for performing the contention-free random access procedure are available for performing a contention-based random access procedure.

17. The network node of claim 15 , wherein the information is signaled as part of a radio resource control information element.

18. The network node of claim 15 , wherein:

each of the plurality of start subcarriers within the NPRACH resource is a first subcarrier for a subcarrier hopping sequence.

19. The network node of claim 15 , where the processing circuitry is configured to communicate, to a first UE, an instruction to use a particular one of the reserved start subcarriers for performing the contention-free random access procedure.

20. The network node of claim 15 , wherein:

the information indicating which of the plurality of start subcarriers within the NPRACH resource are reserved for performing the contention-free random access procedure comprises a number of reserved start subcarriers.

21. A user equipment (UE), comprising:

processing circuitry, the processing circuitry configured to:

receive, from a network node, information indicating which of a plurality of start subcarriers within a Narrowband Physical Random Access Channel (NPRACH) resource are reserved for performing a contention-free random access procedure; and

perform a random access procedure based on the received information;

wherein the start subcarriers that are reserved for performing the contention-free random access procedure comprise a subset of the plurality of start subcarriers within the NPRACH resource; and

wherein one or more start subcarriers that are not in the reserved subset are available for performing a contention-based random access procedure.

22. The UE of claim 21 , wherein:

the information indicating which of the plurality of start subcarriers within the NPRACH resource are reserved for performing the contention-free random access procedure comprises a number of the one or more start subcarriers that are not in the reserved subset.

23. The UE of claim 22 , wherein the processing circuitry is configured to:

determine which of the plurality of start subcarriers are reserved for performing the contention-free random access procedure based on the number of the one or more start subcarriers that are not in the reserved subset.

24. The UE of claim 22 , wherein:

the processing circuitry is configured to select a first start subcarrier from among the one or more start subcarriers that are not in the reserved subset; and

the processing circuitry configured to perform the random access procedure based on the received information comprises processing circuitry configured to perform a contention-based random access procedure using the selected first start subcarrier.

25. The UE of claim 21 , wherein:

the processing circuitry is configured to receive, from the network node, an instruction to use a particular one of the reserved start subcarriers for performing a contention-free random access procedure; and

the processing circuitry configured to perform the random access procedure based on the received information comprises processing circuitry configured to perform the contention-free random access procedure using the particular one of the reserved start subcarriers.

26. The UE of claim 21 , wherein:

the information indicating which of the plurality of start subcarriers within the NPRACH resource are reserved for performing the contention-free random access procedure comprises a number of reserved start subcarriers.

27. The UE of claim 21 , wherein the information is received in a radio resource control information element.

28. The UE of claim 21 , wherein:

each of the plurality of start subcarriers within the NPRACH resource is a first subcarrier for a subcarrier hopping sequence.