Uplink (UL) aggregation for multi-link operation (MLO)
This disclosure provides methods, devices and systems for transmitting and receiving physical protocol data units (PPDUs) over multiple links. In some aspects, a wireless communication device may determine that first random back off (RBO) for a first channel of a first link has counted down to zero. A wireless communication device may determine, when the first RBO has counted down to zero, that a second RBO for a second channel of a second link has a count down remaining. A wireless communication device may optionally transmit a medium reservation message on the first link reserving a transmission opportunity (TXOP). A wireless communication device may determine whether to wait for the second RBO before transmitting on the first link. A wireless communication device may transmit at least a first PPDU on the first link during the TXOP.
1 . A method for wireless communication by a wireless communication device, comprising:
determining that a first random back off (RBO) for a first channel of a first link has counted down to zero;
determining, when the first RBO has counted down to zero, that a second RBO for a second channel of a second link has a count down remaining;
determining to wait for the second RBO before transmitting on the first link, wherein determining to wait for the second RBO before transmitting on the first link includes:
resetting the first RBO to a new value in response to another device using the first channel; and
waiting for the first RBO and the second RBO to count down to zero after resetting the first RBO;
determining that the second RBO has counted down to zero; and
transmitting at least a first physical protocol data unit (PPDU) on the first link during a transmission opportunity (TXOP) that starts when the first RBO has counted down to zero.
2 . The method of claim 1 , further comprising:
transmitting a second PPDU on the second link, wherein a start time of the first PPDU and the second PPDU is aligned.
3 . The method of claim 1 , further comprising transmitting a medium reservation message on the first link reserving the TXOP.
4 . The method of claim 3 , wherein the medium reservation message is one of a clear to send to self (CTS2Self) message or a modified request to send (RTS) message.
5 . The method of claim 3 , wherein the medium reservation message interrupts the second RBO for the second link, further comprising resuming the second RBO after the medium reservation message.
6 . The method of claim 1 , wherein determining to wait for the second RBO before transmitting on the first link is based on a probability of accessing the second link estimated based on the second RBO.
7 . The method of claim 1 , wherein an access point (AP) refrains from transmitting a downlink PPDU on the second link during the TXOP in response to the first PPDU on the first link.
8 . The method of claim 3 , wherein an access point for the second link advertises an enhanced distributed channel access (EDCA) set including second-phase EDCA parameters, further comprising adjusting the second RBO based on the second-phase EDCA parameters in response to transmitting the medium reservation message.
9 . The method of claim 1 , wherein determining to wait for the second RBO before transmitting on the first link includes determining to wait for the second RBO before transmitting on the first link in response to determining that the second RBO is less than a threshold.
10 . The method of claim 1 , wherein determining to wait for the second RBO before transmitting on the first link includes determining to wait for the second RBO before transmitting on the first link in response to determining that the second channel is not blocked by a network allocation vector (NAV).
11 . The method of claim 1 , further comprising
determining to transmit on the first link without waiting in response to determining that the second link is blocked.
12 . The method of claim 11 , wherein determining that the second link is blocked includes determining that a waiting time has expired.
13 . The method of claim 1 , wherein the first RBO and the second RBO are initialized with a same value.
14 . The method of claim 1 , further comprising:
determining that the count down remaining of the second RBO is less than a threshold; and
setting the count down remaining of the second RBO to zero when the second channel is idle.
15 . The method of claim 14 , further comprising:
selecting a new RBO for the second channel of the second link; and
increasing the new RBO based on a residual value of the second RBO.
16 . The method of claim 15 , wherein increasing the new RBO based on the residual value of the second RBO comprises increasing the new RBO by the residual value multiplied by a configurable weighting factor.
17 . The method of claim 1 , further comprising:
adding an offset to the first RBO and to the second RBO based on a configurable weighting factor, wherein transmitting at least the first PPDU on the first link during the TXOP comprises transmitting the first PPDU on the first link and transmitting a second PPDU on the second link in response to determining that either the first RBO or the second RBO has counted down to zero, wherein a start time and an end time of the first PPDU and the second PPDU are aligned.
18 . The method of claim 1 , wherein resetting the first RBO includes setting the new value of the first RBO based on the count down remaining of the second RBO.
19 . A wireless communication device comprising:
at least one modem;
at least one processor communicatively coupled with the at least one modem; and
at least one memory communicatively coupled with the at least one processor and storing processor-readable code that, when executed by the at least one processor in conjunction with the at least one modem, is configured to:
determine that a first random back off (RBO) for a first channel of a first link has counted down to zero;
determine, when the first RBO has counted down to zero, that a second RBO for a second channel of a second link has a count down remaining;
determine to wait for the second RBO before transmitting on the first link, wherein to wait for the second RBO before transmitting on the first link, the at least one processor is configured to:
reset the first RBO to a new value in response to another device using the first channel; and
wait for the first RBO and the second RBO to count down to zero after resetting the first RBO;
determine that the second RBO has counted down to zero; and
transmit at least a first physical protocol data unit (PPDU) on the first link during a transmission opportunity (TXOP) that starts when the first RBO has counted down to zero.
20 . The wireless communication device of claim 19 , wherein the processor-readable code is configured to:
transmit a second PPDU on the second link, wherein a start time of the first PPDU and the second PPDU is aligned.
21 . The wireless communication device of claim 19 , wherein the processor-readable code is configured to transmit a medium reservation message on the first link reserving the TXOP.
22 . The wireless communication device of claim 21 , wherein the medium reservation message is one of a clear to send to self (CTS2Self) message or a modified request to send (RTS) message.
23 . The wireless communication device of claim 21 , wherein the medium reservation message interrupts the second RBO for the second link, further comprising resuming the second RBO after the medium reservation message.
24 . The method of claim 2 , wherein an end time of the first PPDU and the second PPDU is aligned.
25 . The wireless communication device of claim 20 , wherein an end time of the first PPDU and the second PPDU is aligned.