Congestion control for NR V2X
In one aspect, a method includes determining, by a user equipment (UE), a channel busy ratio (CBR) window for a CBR measurement for one or more resources; determining, by the UE, a CBR measurement value for the CBR window and for the one or more resources; determining, by the UE, a channel occupancy ratio (CR) window based on a first number of subframes used for a history of past transmissions and based on a second number of subframes used for future planned transmissions and corresponding retransmissions; and determining, by the UE, a CR value for the CR window based on subchannels used for the one or more resources for the first number of subframes and based on subchannels estimated for the one or more resources for the second number of subframes. In another aspect, a method includes determining a CR window based on a CBR measurement value.
1 . A method of wireless communication comprising:
obtaining, by a user equipment (UE), sidelink channel congestion control information;
determining, by the UE, a channel occupancy ratio (CR) value for a CR window based on subchannels used for one or more sidelink resources for a first number of subframes used for a history of past transmissions and based on subchannels estimated for the one or more sidelink resources for a second number of subframes used for future planned transmissions and corresponding retransmissions, wherein a duration of the CR window includes the first number of subframes for the history of the past transmissions and includes the second number of subframes for the future planned transmissions and the corresponding retransmissions, wherein the duration of the CR window does not exceed a time resource of a last planned transmission or retransmission of the future planned transmissions and the corresponding retransmissions, and wherein the first number of subframes for the history of the past transmissions is greater than half of the duration of the CR window; and
performing, by the UE, a congestion control operation based on the CR value and the sidelink channel congestion control information.
2 . The method of claim 1 , wherein obtaining the sidelink channel congestion control information includes:
receiving, by the UE, a radio resource control (RRC) transmission including the sidelink channel congestion control information.
3 . The method of claim 1 , wherein the sidelink channel congestion control information includes or corresponds to CR limit information.
4 . The method of claim 3 , wherein the CR limit information includes one or more CR thresholds for sidelink channel operations.
5 . The method of claim 1 , wherein performing the congestion control operation based on the CR value and the sidelink channel congestion control information includes:
determining, based on channel busy ratio (CBR) information, a particular CR limit from the sidelink channel congestion control information; and
comparing the CR value to the particular CR limit.
6 . The method of claim 1 , wherein the last planned transmission or retransmission of the future planned transmissions and the corresponding retransmissions is a last retransmission of a currently scheduled transmission.
7 . The method of claim 1 , wherein determining the CR window includes refraining from including future periodic transmissions scheduled by a previously received periodic grant in the second number of subframes.
8 . The method of claim 1 , wherein the CR value corresponds to a particular subframe of the CR window, and wherein determining the CR value includes:
evaluating the particular subframe of the CR window based on a first number of subchannels used for the first number of subframes used for the history of the past transmissions of the CR window, based on a second number of subchannels used for the second number of subframes used for the future planned transmissions and the corresponding retransmissions of the CR window to determine the CR value, and based on a total number of configured subchannels available for the one or more sidelink resources in the CR window.
9 . The method of claim 1 , wherein the future planned transmissions and the corresponding retransmissions include retransmissions of a currently scheduled transmission, wherein the retransmissions occur within a packet delay budget for each packet from generation of the currently scheduled transmission.
10 . The method of claim 1 , wherein a maximum number of the corresponding retransmissions is based on Hybrid Automatic Repeat Request (HARQ) feedback parameters.
11 . The method of claim 1 , further comprising:
determining, by the UE, a channel busy ratio (CBR) window for a CBR measurement for the one or more sidelink resources;
determining, by the UE, a CBR measurement value for the CBR window and for the one or more sidelink resources; and
determining, by the UE, the CR window based on the first number of subframes used for the history of past transmissions and based on the second number of subframes used for the future planned transmissions and the corresponding retransmissions.
12 . The method of claim 11 , wherein the CR window is determined based further on a duration of the CBR window.
13 . The method of claim 1 , wherein performing the congestion control operation based on the CR value includes performing one or more operations including adjusting an amount of subchannels to use for the one or more sidelink resources, adjusting an amount of retransmissions, adjusting a modulation coding scheme (MCS), adjusting a communication channel frequency, refraining from transmitting a communication during a channel busy ratio (CBR) window associated with the CR window, or a combination thereof.
14 . The method of claim 1 , wherein the future planned transmissions and the corresponding retransmissions comprise a currently planned transmission and corresponding retransmissions of the currently planned transmission, and further comprising:
receiving a scheduling message for the future planned transmissions and the corresponding retransmissions prior to determining the CR window and the CR value; and
determining the future planned transmissions and the corresponding retransmissions based on the scheduling message prior to determining the CR window and the CR value.
15 . The method of claim 1 , wherein a sum of a subframe number for a current subframe and the second number of subframes is less than or equal to a subframe number corresponding to the last planned transmission or retransmission.
16 . An apparatus configured for wireless communication at a user equipment (UE), the apparatus comprising:
one or more processors; and
a memory coupled to the one or more processors, with instructions stored in the memory and executable by the one or more processors to cause the apparatus to:
obtain sidelink channel congestion control information;
determine a channel occupancy ratio (CR) value for a CR window based on subchannels used for one or more sidelink resources for a first number of subframes used for a history of past transmissions and based on subchannels estimated for the one or more sidelink resources for a second number of subframes used for future planned transmissions and corresponding retransmissions, wherein a duration of the CR window includes the first number of subframes for the history of the past transmissions and includes the second number of subframes for the future planned transmissions and the corresponding retransmissions, wherein the duration of the CR window does not exceed a time resource of a last planned transmission or retransmission of the future planned transmissions and the corresponding retransmissions, and wherein the first number of subframes for the history of the past transmissions is greater than half of the duration of the CR window; and
perform a congestion control operation based on the CR value and the sidelink channel congestion control information.
17 . The apparatus of claim 16 , wherein the instructions are further executable by the one or more processors to cause the apparatus to:
receive a radio resource control (RRC) transmission including the sidelink channel congestion control information.
18 . The apparatus of claim 16 , wherein the sidelink channel congestion control information includes or corresponds to CR limit information.
19 . The apparatus of claim 18 , wherein the CR limit information includes one or more CR thresholds for sidelink channel operations.
20 . The apparatus of claim 16 , wherein the instructions to perform the congestion control operation further include instructions executable by the one or more processors to cause the apparatus to:
determine, based on channel busy ratio (CBR) information, a particular CR limit from the sidelink channel congestion control information; and
compare the CR value to the particular CR limit.
21 . The apparatus of claim 16 , wherein the duration of the CR window is 1000 milliseconds, and wherein the future planned transmissions and the corresponding retransmissions comprise aperiodic transmissions, periodic transmissions, or both.
22 . The apparatus of claim 16 , wherein the instructions are further executable by the one or more processors to cause the apparatus to:
set a duration of a channel busy ratio (CBR) window, the duration of the CR window, or both, based on the sidelink channel congestion control information.
23 . The apparatus of claim 16 , wherein the future planned transmissions and the corresponding retransmissions represent actually scheduled transmissions or retransmission which take place after determining the CR window and the CR value.
24 . The apparatus of claim 16 , wherein the instructions are further executable by the one or more processors to cause the apparatus to determine the CR window based on the following formula: a sum of a total number of used subchannels for subframes [n−a, n−1] and a total number of granted subchannels for subframes [n, n+b] is divided by total number of configured subchannels for subframes [n−a, n+b], where a+b+1=C, wherein ‘a’ corresponds to the first number of subframes for the history of past transmissions to consider for the CR window, wherein ‘b’ corresponds to the second number of subframes for the future planned transmissions and the corresponding retransmissions to consider for the CR window, and wherein ‘C’ is the duration of the CR window.
25 . The apparatus of claim 24 , wherein the first number of subframes for the history of past transmissions to consider for the CR window is greater than or equal to half of the duration of the CR window, and wherein a sum of a current frame and the second number of subframes is less than or equal to a subframe number corresponding to a last retransmission of a current transmission.
26 . The apparatus of claim 16 , wherein the instructions to perform the congestion control operation based on the CR value further include instructions executable by the one or more processors to cause the apparatus to perform one or more operations including adjusting an amount of subchannels to use for the one or more sidelink resources, adjusting an amount of retransmissions, adjusting a modulation coding scheme (MCS), adjusting a communication channel frequency, refraining from transmitting a communication during a channel busy ratio (CBR) window, or a combination thereof.
27 . An apparatus configured for wireless communication at a user equipment (UE), the apparatus comprising:
one or more processors; and
a memory coupled to the one or more processors, with instructions stored in the memory and executable by the one or more processors to cause the apparatus to:
obtain sidelink channel congestion control information;
determine a channel occupancy ratio (CR) value for a CR window based on subchannels used for one or more sidelink resources for a first number of subframes used for a history of past transmissions and based on subchannels estimated for the one or more sidelink resources for a second number of subframes used for future planned transmissions and corresponding retransmissions, wherein a duration of the CR window includes the first number of subframes for the history of the past transmissions and includes the second number of subframes for the future planned transmissions and the corresponding retransmissions, wherein the duration of the CR window does not exceed a time resource of a last planned transmission or retransmission of the future planned transmissions and the corresponding retransmissions, and wherein the first number of subframes for the history of the past transmissions is greater than half of the duration of the CR window; and
refrain, based on the CR value and the sidelink channel congestion control information, from transmitting a communication during a channel busy ratio (CBR) window associated with the CR window.
28 . The apparatus of claim 16 , wherein a subcarrier spacing (SCS) associated with the CR value is 15 kHz, 30 kHz, 60 kHz, or 120 kHz.
29 . The apparatus of claim 16 , wherein the instructions are further executable by the one or more processors to cause the apparatus to determine the CR window based on the following formula: a sum of a total number of used subchannels for slots [n−a, n−1] and a total number of granted subchannels for slots [n, n+b] is divided by total number of configured subchannels for slots [n−a, n+b], where a+b+1=C, wherein ‘a’ corresponds to the first number of slots for the history of past transmissions to consider for the CR window, wherein ‘b’ corresponds to the second number of slots for the future planned transmissions and the corresponding retransmissions to consider for the CR window, and wherein ‘C’ is the duration of the CR window.
30 . The apparatus of claim 16 , wherein the last planned transmission or retransmission of the future planned transmissions and the corresponding retransmissions corresponds to a last time resource of a sidelink grant for a current transmission.