Two-stage scrambling for polar coded PDCCH transmission

1. A wireless transmit/receive unit (WTRU) comprising:

a memory; and

a processor configured to at least:

receive a physical downlink control channel (PDCCH) transmission;

descramble the PDCCH transmission using a first scrambling sequence to generate polar encoded bits;

decode the polar encoded bits to generate polar decoded bits, wherein being configured to decode the polar encoded bits comprises being configured to determine a position of at least one assistance bit within the polar decoded bits;

descramble a portion of the polar decoded bits using a second scrambling sequence, wherein the portion of the polar decoded bits is a last sixteen (16) bits of a twenty four (24) bit cyclic redundancy check (CRC); and

on a condition that the descrambling of the portion of the polar decoded bits is successful, obtain downlink control information (DCI) bits from the polar decoded bits.

2. The WTRU of claim 1 , wherein the first scrambling sequence is generated using a Gold sequence that is initialized using an identifier associated with the WTRU.

3. The WTRU of claim 2 , wherein the identifier associated with the WTRU is a cell radio network temporary identifier (C-RNTI).

4. The WTRU of claim 1 , wherein the (24) CRC bits comprise the at least one assistance bit and are interleaved with the DCI bits.

5. The WTRU of claim 1 , wherein the second scrambling sequence is based on an identifier associated with the WTRU.

6. A base station comprising:

a memory; and

a processor, configured to:

attach twenty four (24) cyclic redundancy check (CRC) bits to downlink control information (DCI) bits, wherein a last sixteen (16) bits of the (24) CRC bits are scrambled using a second scrambling sequence;

interleave the (24) CRC bits and the DCI bits to generate interleaved CRC and DCI bits, wherein being configured to interleave the (24) CRC bits comprises being configured to distribute a portion of the (24) CRC bits, wherein the portion of the (24) CRC bits are assistance bits associated with the DCI;

perform polar coding of the interleaved (24) CRC bits and the DCI bits to generate polar coded bits;

scramble the polar coded bits with a first scrambling sequence; and

send a physical control channel (PDCCH) transmission comprising the scrambled polar coded bits.

7. The base station of claim 6 , wherein the processor is configured to generate the first scrambling sequence using a Gold sequence that is initialized using an identifier associated with a wireless transmit/receive unit (WTRU), wherein the identifier associated with the WTRU is a cell radio network temporary identifier (C-RNTI).

8. The base station of claim 6 , wherein the base station is a gNB.

9. The base station of claim 6 , wherein the second scrambling sequence is based on an identifier associated with a wireless transmit receive unit WTRU.

10. A method implemented by a wireless transmit/receive unit (WTRU), the method comprising:

receiving a physical downlink control channel (PDCCH) transmission;

descrambling the PDCCH transmission using a first scrambling sequence to generate polar encoded bits;

decoding the polar encoded bits to generate polar decoded bits, wherein decoding the polar encoded bits comprises determining a position of at least one assistance bit within the polar decoded bits;

descrambling a portion of the polar decoded bits using a second scrambling sequence, wherein the portion of the polar decoded bits is a last sixteen (16) bits of a twenty four (24) bit cyclic redundancy check (CRC); and

on a condition that the descrambling of the portion of the polar decoded bits is successful, obtaining downlink control information (DCI) bits from the polar decoded bits.

11. The method of claim 10 , wherein the first scrambling sequence is generated using a Gold sequence that is initialized using a cell radio network temporary identifier (C-RNTI).

12. The method of claim 10 , and the second scrambling sequence is based on an identifier associated with the WTRU.

13. The method of claim 10 , wherein the (24) CRC bits comprise the at least one assistance bit and are interleaved with the DCI bits.

14. A method comprising:

attaching twenty four (24) cyclic redundancy check (CRC) bits to downlink control information (DCI) bits, wherein a last sixteen (16) bits of the (24) CRC bits are scrambled using a second scrambling sequence;

interleaving the (24) CRC bits and the DCI bits to generate interleaved CRC and DCI bits, wherein interleaving the (24) CRC bits comprises distributing a portion of the (24) CRC bits, wherein the portion of the (24) CRC bits are assistance bits associated with the DCI;

performing polar coding of the interleaved (24) CRC bits and the DCI bits to generate polar coded bits;

scrambling the polar coded bits with a first scrambling sequence; and

transmitting the scrambled polar coded bits via a physical control channel (PDCCH).

15. The method of claim 14 , wherein the first scrambling sequence is generated using a Gold sequence that is initialized using an identifier associated with a wireless transmit/receive unit (WTRU), and the identifier associated with the WTRU is a cell radio network temporary identifier (C-RNTI).

16. The method of claim 14 , wherein the second scrambling sequence is based on an identifier associated with a wireless transmit receive unit WTRU.