Parallel transmission of preamble sequences with data layers for improved data detection
Methods, systems, and devices for wireless communications are described. In some systems (e.g., non-orthogonal multiple access (NOMA) systems), a base station may serve a large number of user equipments (UEs) on the uplink. To improve detectability for these uplink transmissions (e.g., if reference signals are not available for the transmissions), the UEs may implement parallel transmissions of preambles with uplink data. A UE may split the uplink data into one or more data layers, and may select one or more preamble layers to transmit superposed with the data layers. These preambles may be sequences known to both the UE and the base station to aid in detectability. The UE may assign different signature sequences to each of these layers based on cross-correlation values (e.g., assigning sequences with higher cross-correlation values to the data layers for improved detectability), and may scramble the layers into a single shared signal for transmission.
1. A method for wireless communications, comprising:
receiving, by a base station, a candidate signal from a user equipment (UE);
determining, by the base station, one or more preamble layers scrambled in the candidate signal;
determining, by the base station, a set of signature sequences for detecting one or more code layers;
descrambling, by the base station, the one or more code layers from the candidate signal based at least in part on the set of signature sequences; and
decoding, by the base station, one or more data layers scrambled in the candidate signal based at least in part on the one or more code layers
wherein:
the one or more code layers comprise the one or more data layers,
the set of signature sequences is determined for detecting the one or more data layers,
the one or more data layers are descrambled from the candidate signal based at least in part on the set of signature sequences, and
the one or more data layers scrambled in the candidate signal are decoded based at least in part on the descrambling; or
the one or more code layers comprise the one or more preamble layers,
the set of signature sequences is determined for detecting the one or more preamble layers,
the one or more preamble layers are descrambled from the candidate signal based at least in part on the set of signature sequences, and
the one or more preamble layers scrambled in the candidate signal are determined based at least in part on the descrambling.
2. The method of claim 1 , further comprising:
jointly decoding the one or more preamble layers with the one or more data layers, wherein decoding the one or more data layers comprises:
performing a message-passing procedure, wherein the one or more preamble layers are used as prior information for the message-passing procedure.
3. The method of claim 1 , further comprising:
performing channel estimation for the candidate signal based at least in part on the one or more preamble layers, wherein the one or more data layers are decoded based at least in part on the channel estimation.
4. The method of claim 3 , wherein performing the channel estimation for the candidate signal comprises:
comparing the one or more preamble layers to one or more expected preamble values.
5. The method of claim 4 , wherein a preamble value of the one or more expected preamble values comprises a default value, a pre-determined sequence, a pseudo-random sequence, or a combination thereof.
6. The method of claim 1 , further comprising:
transmitting a signature sequence allocation message to the UE, wherein the candidate signal received from the UE is based at least in part on the signature sequence allocation message.
7. A method for wireless communications, comprising:
determining a set of signature sequences;
transmitting a signature sequence allocation message to a user equipment (UE), wherein the signature sequence allocation message indicates the set of signature sequences, wherein a candidate signal received from the UE is based at least in part on the signature sequence allocation message;
receiving the candidate signal from the UE;
determining one or more preamble layers scrambled in the candidate signal, wherein determining the one or more preamble layers scrambled in the candidate signal is based at least in part on the set of signature sequences; and
decoding one or more data layers scrambled in the candidate signal based at least in part on the one or more preamble layers.
8. A method for wireless communications, comprising:
receiving a candidate signal from a user equipment (UE);
determining one or more preamble layers scrambled in the candidate signal;
decoding one or more data layers scrambled in the candidate signal based at least in part on the one or more preamble layers;
receiving one or more demodulation reference signals (DMRSs) for the candidate signal; and
performing channel estimation for the candidate signal based at least in part on the one or more DMRSs, wherein the one or more data layers are decoded based at least in part on the channel estimation.
9. The method of claim 1 , wherein the candidate signal comprises a self-decodable signal.
10. The method of claim 1 , wherein the candidate signal comprises a non-orthogonal multiple access (NOMA) signal.
11. The method of claim 1 , wherein the candidate signal comprises a shared signal.
12. An apparatus comprising a base station for wireless communications, comprising:
a processor;
memory coupled with the processor; and
instructions stored in the memory and executable by the processor to cause the apparatus to:
receive, by the base station, a candidate signal from a user equipment (UE);
determine, by the base station, one or more preamble layers scrambled in the candidate signal;
determine, by the base station, a set of signature sequences for detecting one or more code layers;
descramble, by the base station, the one or more code layers from the candidate signal based at least in part on the set of signature sequences; and
decode, by the base station, one or more data layers scrambled in the candidate signal based at least in part on the one or more code layers
wherein:
the one or more code layers comprise the one or more data layers,
the set of signature sequences is determined for detecting the one or more data layers,
the one or more data layers are descrambled from the candidate signal based at least in part on the set of signature sequences, and
the one or more data layers scrambled in the candidate signal are decoded based at least in part on the descrambling; or
the one or more code layers comprise the one or more preamble layers,
the set of signature sequences is determined for detecting the one or more preamble layers,
the one or more preamble layers are descrambled from the candidate signal based at least in part on the set of signature sequences, and
the one or more preamble layers scrambled in the candidate signal are determined based at least in part on the descrambling.
13. The apparatus of claim 12 , wherein the instructions are further executable by the processor to cause the apparatus to:
jointly decode the one or more preamble layers with the one or more data layers, wherein the instructions to decode the one or more data layers are executable by the processor to cause the apparatus to:
perform a message-passing procedure, wherein the one or more preamble layers are used as prior information for the message-passing procedure.
14. The apparatus of claim 12 , wherein the instructions are further executable by the processor to cause the apparatus to:
perform channel estimation for the candidate signal based at least in part on the one or more preamble layers, wherein the one or more data layers are decoded based at least in part on the channel estimation.
15. The apparatus of claim 14 , wherein the instructions to perform the channel estimation for the candidate signal are executable by the processor to cause the apparatus to:
compare the one or more preamble layers to one or more expected preamble values.
16. The apparatus of claim 15 , wherein a preamble value of the one or more expected preamble values comprises a default value, a pre-determined sequence, a pseudo-random sequence, or a combination thereof.
17. The apparatus of claim 12 , wherein the instructions are further executable by the processor to cause the apparatus to:
transmit a signature sequence allocation message to the UE, wherein the candidate signal received from the UE is based at least in part on the signature sequence allocation message.
18. A apparatus for wireless communications comprising:
one or more processors;
one or more memories coupled with the one or more processors; and
instructions stored in the one or more memories and executable by the one or more processors to cause the apparatus to:
determine a set of signature sequences;
transmit a signature sequence allocation message to a user equipment (UE), wherein the signature sequence allocation message indicates the set of signature sequences wherein a candidate signal received from the UE is based at least in part on the signature sequence allocation message;
receive the candidate signal from the UE;
determine one or more preamble layers scrambled in the candidate signal, wherein determining the one or more preamble layers scrambled in the candidate signal is based at least in part on the set of signature sequences; and
decode one or more data layers scrambled in the candidate signal based at least in part on the one or more preamble layers.
19. An apparatus for wireless communications, comprising:
one or more processors;
one or more memories coupled with the processor; and
instructions stored in the memory and executable by the processor to cause the apparatus to:
receive a candidate signal from a user equipment (UE);
determine one or more preamble layers scrambled in the candidate signal;
decode one or more data layers scrambled in the candidate signal based at least in part on the one or more preamble layers;
receive one or more demodulation reference signals (DMRSs) for the candidate signal; and
perform channel estimation for the candidate signal based at least in part on the one or more DMRSs, wherein the one or more data layers are decoded based at least in part on the channel estimation.
20. The apparatus of claim 12 , wherein the candidate signal comprises a self-decodable signal.
21. The apparatus of claim 12 , wherein the candidate signal comprises a non-orthogonal multiple access (NOMA) signal.
22. The apparatus of claim 12 , wherein the candidate signal comprises a shared signal.
23. An apparatus for wireless communications, comprising:
means for receiving, by a base station, a candidate signal from a user equipment (UE);
means for determining, by the base station, one or more preamble layers scrambled in the candidate signal;
means for determining, by the base station, a set of signature sequences for detecting one or more code layers;
means for descrambling, by the base station, the one or more code layers from the candidate signal based at least in part on the set of signature sequences; and
means for decoding, by the base station, one or more data layers scrambled in the candidate signal based at least in part on the one or more code layers
wherein:
the one or more code layers comprise the one or more data layers,
the set of signature sequences is determined for detecting the one or more data layers,
the one or more data layers are descrambled from the candidate signal based at least in part on the set of signature sequences, and
the one or more data layers scrambled in the candidate signal are decoded based at least in part on the descrambling; or
the one or more code layers comprise the one or more preamble layers,
the set of signature sequences is determined for detecting the one or more preamble layers,
the one or more preamble layers are descrambled from the candidate signal based at least in part on the set of signature sequences, and
the one or more preamble layers scrambled in the candidate signal are determined based at least in part on the descrambling.
24. The apparatus of claim 23 , further comprising:
means for jointly decoding, by the base station, the one or more preamble layers with the one or more data layers, wherein the means for decoding the one or more data layers comprises:
means for performing, by the base station, a message-passing procedure, wherein the one or more preamble layers are used as prior information for the message-passing procedure.
25. A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to:
receive, by a base station, a candidate signal from a user equipment (UE);
determine, by the base station, one or more preamble layers scrambled in the candidate signal;
determine, by the base station, a set of signature sequences for detecting one or more code layers;
descramble, by the base station, the one or more code layers from the candidate signal based at least in part on the set of signature sequences; and
decode, by the base station, one or more data layers scrambled in the candidate signal based at least in part on the one or more code layers
wherein:
the one or more code layers comprise the one or more data layers,
the set of signature sequences is determined for detecting the one or more data layers,
the one or more data layers are descrambled from the candidate signal based at least in part on the set of signature sequences, and
the one or more data layers scrambled in the candidate signal are decoded based at least in part on the descrambling; or
the one or more code layers comprise the one or more preamble layers,
the set of signature sequences is determined for detecting the one or more preamble layers,
the one or more preamble layers are descrambled from the candidate signal based at least in part on the set of signature sequences, and
the one or more preamble layers scrambled in the candidate signal are determined based at least in part on the descrambling.
26. The non-transitory computer-readable medium of claim 25 , wherein the instructions are further executable by the processor to:
jointly decode the one or more preamble layers with the one or more data layers, wherein the instructions to decode the one or more data layers are executable by the processor to: perform a message-passing procedure, wherein the one or more preamble layers are used as prior information for the message-passing procedure.