Method and apparatus for optimized short PRACH preamble detection
A method performed in at least one processor of a network node includes receiving, from at least one user equipment (UE) over a wireless communication network, a plurality of physical random access channel (PRACH) preamble sequences in the frequency domain. The method further includes determining, in the frequency domain, an average of the received plurality of preamble sequences. The method further includes performing a correlation function between the average of the received plurality of preamble sequences and a base sequence. The method further includes converting an output of the correlation function to the time domain to generate time domain samples in a sampling window. The method further includes determining power samples from the time domain samples. The method further includes performing a search of the power samples in the sampling window for a peak corresponding to the plurality of PRACH preamble sequences.
1. A method performed in at least one processor of a network node, comprising:
receiving, from at least one user equipment (UE) over a wireless communication network, a plurality of physical random access channel (PRACH) preamble sequences in the frequency domain;
determining, in the frequency domain, an average of the received plurality of preamble sequences;
performing, in the frequency domain, a correlation function between the average of the received plurality of preamble sequences and a base sequence;
converting an output of the correlation function to the time domain to generate time domain samples in a sampling window;
determining power samples from the time domain samples; and
performing a search of the power samples in the sampling window for a peak corresponding to the plurality of PRACH preamble sequences.
2. The method according to claim 1 , further comprising:
determining a noise threshold based on the power samples; and
performing, using the noise threshold, the search of the power samples in the sampling window for the peak.
3. The method according to claim 2 , wherein the performing the search for the peak from the power samples in the sampling window includes identifying a power sample from the power samples having a power level above the noise threshold.
4. The method according to claim 1 , wherein the plurality of preamble sequences includes at least twelve repetitions of the same preamble sequence.
5. The method according to claim 4 , wherein each repetition of the preamble sequence is a short preamble sequence including 139 samples or less.
6. The method according to claim 2 , wherein the determining the noise threshold includes determining a peak to peak average ratio of the power samples.
7. The method of claim 1 , further comprising determining a preamble identifier ID associated with the UE based on the peak.
8. The method of claim 1 , wherein the network node includes a plurality of antennas, and the steps of (i) determining the average of the received plurality of preamble sequences, (ii) performing the correlation function between the average of the received plurality of preamble sequences and the base sequence, and (iii) converting the output of the correlation function to the time domain to generate the time domain samples is performed for each antenna.
9. The method according to claim 1 , wherein the performing the search of the power samples in the sampling window for the peak corresponding to the plurality of PRACH preamble sequences comprises using a search window to traverse the sampling window to identify the peak corresponding to the plurality of PRACH preamble sequences, and wherein the search window has a sampling size less than a sampling size of the sampling window.
10. A network node comprising:
at least one memory configured to store computer program code; and
at least one processor configured to access said at least one memory and operate as instructed by said computer program code, said computer program code including:
receiving code configured to cause at least one of said at least one processor to receive, from at least one user equipment (UE) over a wireless communication network, a plurality of physical random access channel (PRACH) preamble sequences in the frequency domain,
averaging code configured to cause at least one of said at least one processor to determine, in the frequency domain, an average of the received plurality of preamble sequences,
correlation code configured to cause at least one of said at least one processor to perform, in the frequency domain, a correlation function between the average of the received plurality of preamble sequences and a base sequence,
converting code configured to cause at least one of said at least one processor to convert an output of the correlation function to the time domain to generate time domain samples in a sampling window,
first determining code configured to cause at least one of said at least one processor to determine power samples from the time domain samples; and
searching code configured to cause at least one of said at least one processor to perform a search of the power samples in the sampling window for a peak corresponding to the plurality of PRACH preamble sequences.
11. The network node according to claim 10 ,
wherein said computer program code further includes second determining code configured to cause at least one of said at least one processor to determine a noise threshold based on the power samples, and
wherein the searching code is further configured to cause at least one of said at least one processor to perform, using the noise threshold, the search of the power samples in the sampling window for the peak.
12. The network node according to claim 11 , wherein the searching code is further configured to cause at least one of said at least one processor to identify a power sample from the power samples having a power level above the noise threshold.
13. The network node according to claim 10 , wherein the plurality of preamble sequences includes at least twelve repetitions of the same preamble sequence.
14. The network node according to claim 13 , wherein each repetition of the preamble sequence is a short preamble sequence including 139 samples or less.
15. The network node according to claim 10 , wherein the first determining code is further configured to cause at least one of said at least one processor to determine a peak to peak average ratio of the power samples.
16. The network node of claim 9 , wherein said computer program code further includes third determining code configured to cause at least one of said at least one processor to determine a preamble identifier ID associated with the UE based on the peak.
17. The network node of claim 10 , wherein the network node includes a plurality of antennas, and the steps of (i) determining the average of the received plurality of preamble sequences, (ii) performing the correlation function between the average of the received plurality of preamble sequences and the base sequence, and (iii) converting the output of the correlation function to the time domain to generate the time domain samples is performed for each antenna.
18. A non-transitory computer readable medium having instructions stored therein, which when executed by at least one processor in a network node cause the at least one processor to execute a method comprising:
receiving, from at least one user equipment (UE) over a wireless communication network, a plurality of physical random access channel (PRACH) preamble sequences in the frequency domain;
determining, in the frequency domain, an average of the received plurality of preamble sequences;
performing, in the frequency domain, a correlation function between the average of the received plurality of preamble sequences and a base sequence;
converting an output of the correlation function to the time domain to generate time domain samples in a sampling window;
determining power samples from the time domain samples; and
performing a search of the power samples in the sampling window for a peak corresponding to the plurality of PRACH preamble sequences.
19. The non-transitory computer readable medium according to claim 18 , wherein the method further comprises:
determining a noise threshold based on the power samples; and
performing, using the noise threshold, the search of the power samples in the sampling window for the peak.
20. The non-transitory computer readable medium according to claim 19 , wherein the performing the search for the peak from the power samples in the sampling window includes identifying a power sample from the power samples having a power level above the noise threshold.
21. The non-transitory computer readable medium according to claim 18 , wherein the plurality of preamble sequences includes at least twelve repetitions of the same preamble sequence.