Enhanced random access channel procedure
Systems, methods, apparatuses, and computer program products for an enhanced random access channel (RACH) procedure are provided. One method may include receiving an access request comprising a signature from at least one user equipment. The method may then include providing, to the at least one user equipment, multiple at least partially overlapping resource opportunities for a first scheduled transmission, and performing blind decoding of the first scheduled transmission for the multiple at least partially overlapping resource opportunities.
1. An apparatus, comprising:
at least one processor; and
at least one memory including computer program code,
the at least one memory and computer program code configured, with the at least one processor, to cause the apparatus at least to:
receive an access request comprising a signature from at least one user equipment;
provide, to the at least one user equipment, multiple at least partially overlapping resource opportunities for a first scheduled transmission; and
perform blind decoding of the first scheduled transmission for the multiple at least partially overlapping resource opportunities.
2. The apparatus according to claim 1 , wherein the multiple at least partially overlapping resource opportunities occupy a same resource space defined in frequency and time.
3. The apparatus according to claim 1 , wherein the at least one memory and computer program code are further configured, with the at least one processor, to cause the apparatus at least to provide the multiple at least partially overlapping resource opportunities in a random access response.
4. The apparatus according to claim 1 , wherein the multiple at least partially overlapping resource opportunities comprise different demodulation reference signal sequences (DMRS) for the first scheduled transmission.
5. The apparatus according to claim 4 , wherein the at least one memory and computer program code are further configured, with the at least one processor, to cause the apparatus at least to calculate channel estimate for each of the at least one demodulation reference signal sequences (DMRS) and employ interference rejection combining (IRC) between antennas.
6. The apparatus according to claim 1 , wherein the at least one memory and computer program code are further configured, with the at least one processor, to cause the apparatus at least to reserve at least one partially overlapped time or frequency domain resources for the first scheduled transmission.
7. A method, comprising:
transmitting, by a user equipment, an access request comprising a signature;
receiving a response;
receiving, by the user equipment, at least partial configuration of multiple at least partially overlapping resource opportunities for the first scheduled transmission from an evolved node B (eNodeB); and
selecting, by the user equipment, one of the multiple at least partially overlapping resource opportunities to transmit a first scheduled transmission.
8. The method according to claim 7 , wherein the receiving comprises receiving at least partial configuration for the multiple at least partially overlapping resource opportunities in a random access response.
9. The method according to claim 7 , wherein the selecting comprises selecting one of the multiple at least partially overlapping resource opportunities in random or pseudo-random manner.
10. The method according to claim 7 , wherein at least partially overlapping resources comprise different demodulation reference signal sequences (DMRS) for the first scheduled transmission.
11. The method according to claim 7 , wherein the receiving comprises receiving estimated time offset from an eNodeB, and wherein the selecting comprises selecting a time offset for the first scheduled transmission based on the estimated time offset received from the eNodeB.
12. An apparatus, comprising:
at least one processor; and
at least one memory including computer program code,
the at least one memory and computer program code configured, with the at least one processor, to cause the apparatus at least to:
transmit an access request comprising a signature;
receive a response;
receive multiple at least partially overlapping resource opportunities for a first scheduled transmission; and
select one of the multiple at least partially overlapping resource opportunities to transmit a first scheduled transmission.
13. The apparatus according to claim 12 , wherein the at least one memory and computer program code are further configured, with the at least one processor, to cause the apparatus at least to receive the multiple at least partially overlapping resource opportunities in a random access response.
14. The apparatus according to claim 12 , wherein at least one demodulation reference signal sequences (DMRS) are reserved for the first scheduled transmission.
15. The apparatus according to claim 14 , wherein the at least one memory and computer program code are further configured, with the at least one processor, to cause the apparatus at least to select one out of the at least one demodulation reference signal sequences (DMRS) for the first scheduled transmission.
16. The apparatus according to claim 14 , wherein the at least one demodulation reference signal sequences (DMRS) comprises at least one cyclic shift of a same base sequence.
17. The apparatus according to claim 12 , wherein the at least one memory and computer program code are further configured, with the at least one processor, to cause the apparatus at least to receive estimated time offset from an eNodeB, and to select a time offset for the first scheduled transmission based on the estimated time offset received from the eNodeB.
18. The apparatus according to claim 17 , wherein the time offset is made cyclically in symbol level inside single carrier frequency division multiple access (SC-FDMA) symbol or is set on sample level prior discrete Fourier transform (DFT).