Low latency ACK/NACK transmission
Some embodiments of the present disclosure provide a user equipment (UE) having active device components and passive device components. Responsive to receiving downlink (DL) transmissions in time division duplexing (TDD) mode, the active device components perform DL decoding while the passive device components perform passive transmission of ACK/NACK data. Such passive transmission may involve encoding the ACK/NACK data in an altered version of received radio frequency (RF) signals and using so-called backscatter communications to reflect the received RF signals, with alteration, using the same frequency resources used to receive the DL transmissions.
1. A method for an apparatus to reduce acknowledgement (ACK) or negative acknowledgement (NACK) transmission latency, the method comprising:
receiving, by the apparatus, a first radio frequency (RF) signal comprising a first transport block;
attempting, by the apparatus, to demodulate and decode the first transport block from the first RF signal;
receiving, by the apparatus, a second RF signal after the first RF signal; and
reflecting, by the apparatus, the second RF signal while altering the second RF signal, the altered and reflected second RF signal comprising a first feedback indicative of whether the first transport block was correctly or incorrectly demodulated and decoded by the apparatus.
2. The method of claim 1 , wherein the first feedback is a first ACK/NACK codeword vector comprising a plurality of complex symbols.
3. The method of claim 2 , further comprising selecting, by the apparatus, the first ACK/NACK codeword vector from a codebook comprising a plurality of ACK/NACK codeword vectors.
4. The method of claim 3 , wherein the codebook is device-specific to the apparatus and the method further comprises:
receiving, by the apparatus, a base codebook; and
applying a function of an identifier of the apparatus to the base codebook to generate the device-specific codebook.
5. The method of claim 3 , wherein the codebook is device-specific to the apparatus and the method further comprises receiving the device-specific codebook, where the device-specific codebook forms part of a super codebook that includes a plurality of codebooks.
6. An apparatus comprising:
a memory storing computer-executable instructions;
a processor adapted, by executing the computer-executable instructions, to:
receive a first radio frequency (RF) signal including a first transport block;
attempting, by the apparatus, to demodulate and decode the first transport block from the first RF signal;
receive a second RF signal after the first RF signal; and
reflect the second RF signal while altering the second RF signal, the altered and reflected second RF signal including a first feedback indicative of whether the first transport block was correctly or incorrectly demodulated and decoded by the apparatus.
7. The apparatus of claim 6 , wherein the first feedback is a first ACK/NACK codeword vector comprising a plurality of complex symbols.
8. The apparatus of claim 7 , wherein the processor is further adapted, by executing the computer-executable instructions, to select the first ACK/NACK codeword vector from a codebook comprising a plurality of ACK/NACK codeword vectors.
9. The apparatus of claim 8 , wherein the codebook is device-specific to the apparatus and the processor is further adapted, by executing the computer-executable instructions, to:
receive a base codebook; and
apply a function of an identifier of the apparatus to the base codebook to generate the device-specific codebook.
10. The apparatus of claim 8 , wherein the codebook is device-specific to the apparatus and wherein the processor is further adapted, by executing the computer-executable instructions, to receive the device-specific codebook, where the device-specific codebook forms part of a super codebook that includes a plurality of codebooks.
11. A method, at an apparatus, of receiving acknowledgement (ACK) or negative acknowledgement (NACK) transmissions, the method comprising:
transmitting, by the apparatus, a first radio frequency (RF) signal comprising a first transport block;
transmitting, by the apparatus, a second RF signal after the first RF signal; and
receiving, by the apparatus, an altered and reflected version of the second RF signal including a first feedback indicative of whether the first transport block was correctly or incorrectly demodulated and decoded.
12. The method of claim 11 , wherein the first feedback is a first ACK/NACK codeword vector comprising a plurality of complex symbols.
13. The method of claim 12 , further comprising transmitting, by the apparatus and before the transmitting the first RF signal, a codebook including a plurality of ACK/NACK codeword vectors.
14. The method of claim 13 , wherein the plurality of ACK/NACK codeword vectors includes the first ACK/NACK codeword vector.
15. The method of claim 13 , wherein the codebook is a base codebook that may be adapted to be a device-specific codebook including the first ACK/NACK codeword vector.
16. The method of claim 11 , wherein the first feedback includes an indication that the first transport block was incorrectly demodulated and decoded, the method further comprising transmitting, by the apparatus, a third RF signal comprising the first transport block.
17. An apparatus comprising:
a memory storing computer-executable instructions;
a processor adapted, by executing the computer-executable instructions, to:
transmit a first radio frequency (RF) signal comprising a first transport block;
transmit a second RF signal after the first RF signal; and
receive an altered and reflected version of the second RF signal including a first feedback indicative of whether the first transport block was correctly or incorrectly demodulated and decoded.
18. The apparatus of claim 17 , wherein the first feedback is a first ACK/NACK codeword vector comprising a plurality of complex symbols.
19. The apparatus of claim 18 , wherein the processor is further adapted, by executing the computer-executable instructions, to transmit, before the transmitting the first RF signal, a codebook including a plurality of ACK/NACK codeword vectors.
20. The apparatus of claim 19 , wherein the plurality of ACK/NACK codeword vectors includes the first ACK/NACK codeword vector.
21. The apparatus of claim 19 , wherein the codebook is a base codebook that may be adapted to be a device-specific codebook including the first ACK/NACK codeword vector.
22. The apparatus of claim 17 , wherein the first feedback includes an indication that the first transport block was incorrectly demodulated and decoded, the processor is further adapted, by executing the computer-executable instructions, to transmit a third RF signal comprising the first transport block.