Narrow band physical random access channel frequency hopping patterns and detection schemes
Methods, systems, and devices are described for wireless communication. Dedicated frequency resources of a physical random access channel (PRACH) may be designated for large and small frequency hops to facilitate the determination of timing offsets for PRACH transmissions. For instance, a frequency hopping pattern within the PRACH channel having a plurality of single tone transmission may include a first number of hops associated with a first frequency hopping distance (e.g., large frequency hops), and a second number of hops associated with a second frequency hopping distance (e.g., small frequency hops).
1. A method for wireless communication, comprising:
identifying a physical random access channel (PRACH) for communication between a base station and a user equipment (UE), the PRACH comprising a plurality of subcarriers; and
determining a frequency hopping pattern within the PRACH for a single random access preamble of a single random access attempt for establishing a connection with the base station, the single random access preamble comprising a plurality of single subcarrier transmissions, the frequency hopping pattern comprising a plurality of frequency hops across the plurality of subcarriers, at least one frequency hop of the plurality of frequency hops being associated with a pseudo-random frequency hop distance and at least one frequency hop of the plurality of frequency hops being associated with a fixed frequency hop distance.
2. The method of claim 1 , wherein the pseudo-random frequency hop distance is determined based on at least one of a pseudo-random linear hash function or a pseudo-random linear cyclic shift.
3. The method of claim 1 , wherein the pseudo-random frequency hop distance is based on a number of subcarriers of the PRACH.
4. The method of claim 1 , further comprising:
detecting, by the base station, the single random access preamble based at least in part on the determined frequency hopping pattern.
5. The method of claim 4 , further comprising:
determining a timing offset for uplink transmissions from the UE based at least in part on phase information in a plurality of tones of the detected single random access preamble.
6. The method of claim 5 , wherein detecting the single random access preamble comprises:
mapping the phase information for the plurality of tones to a sequence based at least in part on respective preamble tone intervals and respective subcarriers of the plurality of single subcarrier transmissions; and
performing a frequency transform on the mapped sequence.
7. The method of claim 6 , wherein obtaining the timing offset comprises:
identifying a location of a maximum value of an output of the frequency transform of the mapped sequence.
8. The method of claim 7 , wherein detecting the single random access preamble comprises:
comparing the maximum value with a threshold.
9. The method of claim 5 , wherein detecting the single random access preamble comprises:
mapping differential phase information between two or more tones of the plurality of tones to a sequence based at least in part on the respective preamble tone intervals and respective subcarriers of the plurality of single subcarrier transmissions; and
performing a frequency transform on the mapped sequence.
10. The method of claim 1 , further comprising:
transmitting, by the UE, the single random access preamble according to the determined frequency hopping pattern.
11. An apparatus for wireless communication, comprising:
means for identifying a physical random access channel (PRACH) for communication between a base station and a user equipment (UE), the PRACH comprising a plurality of subcarriers; and
means for determining a frequency hopping pattern within the PRACH for a single random access preamble of a single random access attempt for establishing a connection with the base station, the single random access preamble comprising a plurality of single subcarrier transmissions, the frequency hopping pattern comprising a plurality of frequency hops across the plurality of subcarriers, at least one frequency hop of the plurality of frequency hops being associated with a pseudo-random frequency hop distance and at least one frequency hop of the plurality of frequency hops being associated with a fixed frequency hop distance.
12. The apparatus of claim 11 , wherein the pseudo-random frequency hop distance is determined based on at least one of a pseudo-random linear hash function or a pseudo-random linear cyclic shift.
13. The apparatus of claim 11 , wherein the pseudo-random frequency hop distance is based on a number of subcarriers of the PRACH.
14. The apparatus of claim 11 , further comprising:
means for detecting, by the base station, the single random access preamble based at least in part on the determined frequency hopping pattern.
15. The apparatus of claim 14 , further comprising:
means for determining a timing offset for uplink transmissions from the UE based at least in part on phase information in a plurality of tones of the detected single random access preamble.
16. The apparatus of claim 15 , wherein the means for detecting the single random access preamble comprises:
means for mapping the phase information for the plurality of tones to a sequence based at least in part on respective preamble tone intervals and respective subcarriers of the plurality of single subcarrier transmissions; and
means for performing a frequency transform on the mapped sequence.
17. The apparatus of claim 16 , wherein the means for obtaining the timing offset comprises:
means for identifying a location of a maximum value of an output of the frequency transform of the mapped sequence.
18. The apparatus of claim 17 , wherein the means for detecting the single random access preamble comprises:
means for comparing the maximum value with a threshold.
19. The apparatus of claim 15 , wherein the means for detecting the single random access preamble comprises:
means for mapping differential phase information between two or more tones of the plurality of tones to a sequence based at least in part on the respective preamble tone intervals and respective subcarriers of the plurality of single subcarrier transmissions; and
means for performing a frequency transform on the mapped sequence.
20. The apparatus of claim 11 , further comprising:
means for transmitting, by the UE, the single random access preamble according to the determined frequency hopping pattern.
21. An apparatus for wireless communication, in a system comprising:
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory and operable, when executed by the processor, to cause the apparatus to:
identify a physical random access channel (PRACH) for communication between a base station and a user equipment (UE), the PRACH comprising a plurality of subcarriers; and
determine a frequency hopping pattern within the PRACH for a single random access preamble of a single random access attempt for establishing a connection with the base station, the single random access preamble comprising a plurality of single subcarrier transmissions, the frequency hopping pattern comprising a plurality of frequency hops across the plurality of subcarriers, at least one frequency hop of the plurality of frequency hops being associated with a pseudo-random frequency hop distance and at least one frequency hop of the plurality of frequency hops being associated with a fixed frequency hop distance.
22. The apparatus of claim 21 , wherein the pseudo-random frequency hop distance is determined based on at least one of a pseudo-random linear hash function or a pseudo-random linear cyclic shift.
23. The apparatus of claim 21 , wherein the pseudo-random frequency hop distance is based on a number of subcarriers of the PRACH.
24. The apparatus of claim 21 , wherein the instructions are further executable by the processor to:
detect, by the base station, the single random access preamble based at least in part on the determined frequency hopping pattern.
25. The apparatus of claim 24 , wherein the instructions are further executable by the processor to:
determine a timing offset for uplink transmissions from the UE based at least in part on phase information in a plurality of tones of the detected single random access preamble.
26. The apparatus of claim 25 , wherein the instructions are further executable by the processor to:
map the phase information for the plurality of tones to a sequence based at least in part on respective preamble tone intervals and respective subcarriers of the plurality of single subcarrier transmissions; and
perform a frequency transform on the mapped sequence.
27. The apparatus of claim 26 , wherein the instructions are further executable by the processor to:
identify a location of a maximum value of an output of the frequency transform of the mapped sequence.
28. The apparatus of claim 27 , wherein the instructions are further executable by the processor to:
compare the maximum value with a threshold.
29. The apparatus of claim 25 , wherein the instructions are further executable by the processor to:
map differential phase information between two or more tones of the plurality of tones to a sequence based at least in part on respective preamble tone intervals and respective subcarriers of the plurality of single subcarrier transmissions; and
perform a frequency transform on the mapped sequence.
30. The apparatus of claim 21 , wherein the instructions are further executable by the processor to:
transmit, by the UE, the single random access preamble according to the determined frequency hopping pattern.
31. A non-transitory computer readable medium storing code for wireless communication, the code comprising instructions executable by a processor to:
identify a physical random access channel (PRACH) for communication between a base station and a user equipment (UE), the PRACH comprising a plurality of subcarriers; and
determine a frequency hopping pattern within the PRACH for a single random access preamble of a single random access attempt for establishing a connection with the base station, the single random access preamble comprising a plurality of single subcarrier transmissions, the frequency hopping pattern comprising a plurality of frequency hops across the plurality of subcarriers, at least one frequency hop of the plurality of frequency hops being associated with a pseudo-random frequency hop distance and at least one frequency hop of the plurality of frequency hops being associated with a fixed frequency hop distance.