Sidelink communications and automatic gain control in cellular communication networks

1 . An apparatus comprising:

at least one processor; and

at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

determine a common automatic gain control symbol to be transmitted during a first symbol of a slot, wherein the first symbol of the slot is for a transmission of a first automatic gain control symbol by a transmitting sidelink user equipment and for a transmission of a second automatic gain control symbol by a receiving sidelink user equipment and the apparatus is the transmitting sidelink user equipment, wherein the common automatic gain control symbol comprises the first automatic gain control symbol and the second automatic gain control symbol; and

transmit the first automatic gain control symbol during the first symbol of the slot, wherein:

the first symbol is symbol 0 of a fourteen-symbol New Radio sidelink slot in Frequency Range 1 having a 30 kHz subcarrier spacing;

determining the common automatic gain control symbol comprises determining that the symbol 0 of the slot temporally overlaps, on a same 5.9 GHz carrier frequency, a first symbol of a Long Term Evolution vehicle-to-everything sidelink subframe that is an automatic gain control symbol of a Long Term Evolution sidelink receiving user equipment; and

transmitting the first automatic gain control symbol during the symbol 0 comprises transmitting the first automatic gain control symbol with a highest transmit power that the transmitting sidelink user equipment uses for physical sidelink shared channel and physical sidelink control channel transmissions in symbols between symbol 2 through symbol 9 of the slot;

refrain from transmitting during symbol 1 of the slot, the symbol 1 being a guard symbol enabling a New Radio sidelink receiving user equipment to transition from transmitting to receiving;

transmit an additional first automatic gain control symbol during the symbol 2 of the slot, the additional first automatic gain control symbol being a replica of the first automatic gain control symbol enabling the receiving sidelink user equipment to set an automatic gain control gain for reception of the physical sidelink shared channel and the physical sidelink control channel transmitted in the symbols between the symbol 2 through the symbol 9 of the slot;

switch, during symbol 10 of the slot, from transmitting to receiving;

receive, during symbol 11 of the slot, an additional second automatic gain control symbol transmitted by the receiving sidelink user equipment for automatic gain control setting for reception of a physical sidelink feedback channel; and

receive, during symbol 12 of the slot, hybrid automatic repeat request feedback transmitted on the physical sidelink feedback channel from the receiving sidelink user equipment.

2 . The apparatus according to claim 1 , wherein the transmission of the first automatic gain control symbol is frequency multiplexed with the transmission of the second automatic gain control symbol.

3 . A method performed by an apparatus, the method comprising:

determining a common automatic gain control symbol to be transmitted during a first symbol of a slot, wherein the first symbol of the slot is for a transmission of a first automatic gain control symbol by a transmitting sidelink user equipment and for a transmission of a second automatic gain control symbol by a receiving sidelink user equipment and the apparatus is the transmitting sidelink user equipment, wherein the common automatic gain control symbol comprises the first automatic gain control symbol and the second automatic gain control symbol;

transmitting the first automatic gain control symbol during the first symbol of the slot, wherein:

the first symbol is symbol 0 of a fourteen-symbol New Radio sidelink slot in Frequency Range 1 having a 30 kHz subcarrier spacing;

determining the common automatic gain control symbol comprises determining that the symbol 0 of the slot temporally overlaps, on a same 5.9 GHz carrier frequency, a first symbol of a Long Term Evolution vehicle-to-everything sidelink subframe that is an automatic gain control symbol of a Long Term Evolution sidelink receiving user equipment; and

transmitting the first automatic gain control symbol during the symbol 0 comprises transmitting the first automatic gain control symbol with a highest transmit power that the transmitting sidelink user equipment uses for physical sidelink shared channel and physical sidelink control channel transmissions in symbols between symbol 2 through symbol 9 of the slot;

refraining from transmitting during symbol 1 of the slot, the symbol 1 being a guard symbol enabling a New Radio sidelink receiving user equipment to transition from transmitting to receiving;

transmitting an additional first automatic gain control symbol during the symbol 2 of the slot, the additional first automatic gain control symbol being a replica of the first automatic gain control symbol enabling the receiving sidelink user equipment to set an automatic gain control gain for reception of the physical sidelink shared channel and the physical sidelink control channel transmitted in the symbols between the symbol 2 through the symbol 9 of the slot;

switching, during symbol 10 of the slot, from transmitting to receiving;

receiving, during symbol 11 of the slot, an additional second automatic gain control symbol transmitted by the receiving sidelink user equipment for automatic gain control setting for reception of a physical sidelink feedback channel; and

receiving, during symbol 12 of the slot, hybrid automatic repeat request feedback transmitted on the physical sidelink feedback channel from the receiving sidelink user equipment.

4 . The method according to claim 3 , wherein transmitting the first automatic gain control symbol during the symbol 0 comprises transmitting the first automatic gain control symbol across all physical resource blocks allocated for the physical sidelink shared channel and the physical sidelink control channel in the slot.

5 . The method according to claim 4 , wherein the additional first automatic gain control symbol transmitted during the symbol 2 is identical in sequence and transmit power to the first automatic gain control symbol transmitted during the symbol 0.

6 . The method according to claim 5 , wherein the symbols between the symbol 2 through the 9 of the slot comprise transmission of the physical sidelink shared channel and associated demodulation reference signals and the physical sidelink control channel using the same transmit power as used for the first automatic gain control symbol transmitted during the symbol 0.

7 . The method according to claim 6 , wherein the symbol 11 comprises the additional second automatic gain control symbol transmitted by the receiving sidelink user equipment with a highest transmit power that the receiving sidelink user equipment uses for transmission of the physical sidelink feedback channel in the symbol 12.

8 . The method according to claim 7 , wherein the first automatic gain control symbol transmitted during the symbol 0 and the second automatic gain control symbol transmitted by the receiving sidelink user equipment during the symbol 0 are frequency multiplexed within the slot using disjoint sets of physical resource blocks.

9 . The method according to claim 8 , wherein physical resource blocks used for the first automatic gain control symbol are contiguous and adjacent in frequency to physical resource blocks used for the second automatic gain control symbol within the symbol 0.

10 . The method according to claim 9 , wherein the first automatic gain control symbol comprises a reference sequence selected from a Zadoff-Chu sequence or a Gold sequence, the reference sequence being determined based on a radio network temporary identifier of the transmitting sidelink user equipment.

11 . The method according to claim 10 , wherein the slot is used for transmission of the physical sidelink feedback channel only in every fourth slot, such that symbols between the symbol 10 through the symbol 12 are present only in slots configured for physical sidelink feedback channel transmission.

12 . The method according to claim 11 , wherein the fourteen-symbol slot is aggregated with N−1 additional fourteen-symbol slots, and the switching from transmitting to receiving occurs at a symbol corresponding to (N×14−4) and reception of an additional second automatic gain control symbol occurs at a symbol corresponding to (N×14−3).