Communication devices and methods
The present disclosure relates to the concept of preempting PPDUs, i.e., truncating a PPDU carrying non-latency sensitive traffic to serve STAs with latency constraints. A first communication device comprises circuitry configured to receive a truncation notification during an ongoing exchange of data units with a second communication device, the truncation notification indicating that the ongoing transmission of a data unit shall be truncated and a preemptive data unit shall be received from and/or transmitted to the third communication device, terminate the ongoing transmission of the data unit before the estimated transmission time of the data unit, and receive from and/or transmit to the third communication device the preemptive data unit within the remaining duration of the truncated data unit or within the remaining duration of the transmit opportunity, established between the first and the second communication devices for the ongoing data unit exchange.
1 . A first communication device configured to communicate with a second communication device and a third communication device, the first communication device comprising circuitry configured to
receive a truncation notification during an ongoing exchange of data units with the second communication device, the truncation notification indicating that ongoing transmission of a data unit shall be truncated and a preemptive data unit shall be received from and/or transmitted to the third communication device,
terminate the ongoing transmission of the data unit before an estimated transmission time of the data unit, and
receive from and/or transmit to the third communication device the preemptive data unit within a remaining duration of the truncated data unit or within a remaining duration of the transmit opportunity, established between the first and the second communication devices for the ongoing data unit exchange,
wherein the notification is received on a different link than the one on which the ongoing data exchange between the first and second communication device is performed.
2 . The first communication device as claimed in claim 1 ,
wherein the circuitry is configured to set in the ongoing exchange of data units with the second communication device the acknowledgement policy of a data unit to no acknowledgement or acknowledgement on request.
3 . The first communication device as claimed in claim 1 ,
wherein the circuitry is configured to
transmit, as part of the ongoing exchange of data units with the second communication device, a first duration indicator indicating an intended duration of the transmit opportunity, and
transmit or receive, after the truncation of the ongoing transmission of a data unit and as part of the reception or transmission of a data unit from or to the third communication data, a second duration indicator indicating the remaining duration of the intended transmit opportunity after the transmission of the preemptive data unit is completed.
4 . The first communication device as claimed in claim 1 ,
wherein the circuitry is configured to terminate the ongoing transmission of the data unit only if a remaining duration of the intended transmission opportunity after performing the truncation of the ongoing data unit is equal to or larger than an expected duration
of the transmission or reception of the preemptive data unit and any required response to the transmitted or received preemptive data unit, or
of a frame triggering or scheduling the transmission of the preemptive data unit and any required response to the transmitted or received frame.
5 . The first communication device as claimed in claim 1 ,
wherein the circuitry is configured, if a first preemptive data unit shall be transmitted to or received from the third communication device and a second preemptive data unit shall be received from or transmitted to the third communication device and if an intended transmit opportunity of the second communication device contains a transmission time for one or more further PHY data units, to transmit the first preemptive data unit to the third communication device and to receive the second preemptive data unit from the third communication device,
wherein an amount of padding data is added to the first preemptive data unit so that the end of the first preemptive data unit corresponds to an end of an intended duration of the data unit transmitted to the second communication device, in the absence of a truncation, if the duration of the second preemptive data unit is shorter than the duration of the transmission time of the one or more further PHY data units.
6 . The first communication device as claimed in claim 1 ,
wherein the transmission of the preemptive data unit does not exceed the initially intended duration of the intended data unit or does not exceed by more than a short interframe space or a function of a short interframe space, slot time and interframe tolerance level.
7 . The first communication device as claimed in claim 1 ,
wherein the circuitry is configured to perform a truncation of the ongoing data exchange with the second device as a result of receiving a notification indicating the request to transmit or receive a low latency sensitive traffic, from the third communication device, during the transmit opportunity of the second communication device.
8 . The first communication device as claimed in claim 1 ,
wherein the circuitry is configured to transmit, as first preemptive data unit, a trigger frame requesting and/or allowing the third communication device to transmit further preemptive data units during the transmit opportunity obtained for the data exchange between the first communication device and the second communication device or a frame scheduling a preemptive data exchange with the third communication device and/or to transmit preemptive data units to the third communication device simultaneously with the transmission and/or reception of data units to the second communication device, and/or to receive preemptive data units from the third communication device simultaneously with data units from the second communication device and/or to transmit preemptive data units to the third communication device that only contain traffic corresponding to the low latency traffic stream identifier, established between the first and third communication device before the ongoing data exchange.
9 . The first communication device as claimed in claim 1 ,
wherein the circuitry is configured to transmit as part of establishing the transmit opportunity with the second communication device, within which the ongoing data exchange is performed, one or more of a control frame indicating one or more of a potential preemption, a user field indicating the third communication device as intended receiver of a preemptive data unit, and a user field indicating a set of communication devices, from which the third communication device identifies itself as intended participant in a potential preemptive data exchange, and/or to perform a truncation of the ongoing transmission of a data unit in predefined time intervals negotiated with the third communication device before the ongoing transmit opportunity.
10 . The first communication device as claimed in claim 1 ,
wherein the circuitry is configured to end or to share a current transmit opportunity with the third communication device in case an access category of the traffic to be exchanged with the third communication device indicates a low latency sensitive access category and/or in case a low latency sensitive session had been established between the first and the third communication device before the ongoing data exchange.
11 . A first communication device configured to communicate with a second communication device and a third communication device, the first communication device comprising circuitry configured to
receive a truncation notification during an ongoing exchange of data units with the second communication device, the truncation notification indicating that the ongoing transmission of a data unit shall be truncated and a preemptive data unit shall be received from and/or transmitted to the third communication device,
transmit an end notification indicating an end of a current transmit opportunity before the end of the current transmit opportunity, and
establish a new transmit opportunity with the third communication device, wherein a duration of said new transmit opportunity covers at least the transmission of the preemptive data to and/or the reception of the preemptive data from the third communication device,
wherein the notification is received on a different link than the one on which the ongoing data exchange between the first and second communication device is performed.
12 . The first communication device as claimed in claim 11 ,
wherein, if the duration of the preemptive data unit is longer than the current transmit opportunity duration if it had not been truncated minus the duration of the end indication and minus the duration of the establishment of the transmit opportunity with the third communication device, said difference representing a remaining net duration, transmit a first part of the preemptive data unit before said remaining net duration and a second part of the preemptive data unit after said remaining net duration.
13 . The first communication device as claimed in claim 12 ,
wherein the circuitry is configured to transmit the first part of the preemptive data unit aligned with the end of current transmit opportunity if it had not been truncated, and/or to transmit the first part and/or a second part of the preemptive data unit in a multi user PPDU comprising data units for the second communication device and data units for the third communication device.
14 . A third communication device configured to communicate with a first communication device, the third communication device comprising circuitry configured to
receive a data unit addressed to a second communication device,
determine a duration indication indicating an expected duration of an ongoing transmission of a data unit and/or of an ongoing transmit opportunity,
determine if transmission of a data unit has been terminated before an estimated transmission time of the data unit,
reset a network allocation vector (NAV) upon determining that the transmission of the data unit has been terminated before the estimated transmission time of the data unit, and
receive from and/or transmit to the first communication device a preemptive data unit within a remaining duration of the truncated data unit and/or within the remaining duration of the transmit opportunity.
15 . The third communication device as claimed in claim 14 ,
wherein the circuitry is configured
to subtract the estimated reception duration of the truncated data unit, the reception duration of the preemptive data unit and an interframe space from the sum of the intended duration of the truncated data unit and a data unit indicator, the data unit indicator being an integer larger than zero and indicating that the truncated data unit has not been the last data unit to be transmitted within the current transmit opportunity and indicating the expected duration of the ongoing transmission duration, and
to transmit a preemptive data unit with a duration indication, equal to said subtraction.
16 . The third communication device as claimed in claim 14 ,
wherein the NAV, is reset before the end of the ongoing transmit opportunity and/or before the end of the expected duration of the data unit from the first to the second communication device upon determination of one or more of:
an intentional early termination of the ongoing data exchange,
reception of a trigger frame requesting a preemptive data unit transmission from the third communication device,
reception of a preemptive data unit with a request for response and
a time interval defined with potential truncation indication.
17 . A first communication method for communicating with a second communication device and a third communication device, the first communication method comprising:
receiving a truncation notification during an ongoing exchange of data units with the second communication device, the truncation notification indicating that ongoing transmission of a data unit shall be truncated and a preemptive data unit shall be received from and/or transmitted to the third communication device,
terminating the ongoing transmission of the data unit before an estimated transmission time of the data unit, and
receiving from and/or transmitting to the third communication device the preemptive data unit within a remaining duration of the truncated data unit or within a remaining duration of the transmit opportunity, established between the first and the second communication devices for the ongoing data unit exchange,
wherein the notification is received on a different link than the one on which the ongoing data exchange between the first and second communication device is performed.
18 . The first communication method for communicating with a second communication device and a third communication device, the first communication method comprising:
receiving a truncation notification during an ongoing exchange of data units with the second communication device, the truncation notification indicating that ongoing transmission of a data unit shall be truncated and a preemptive data unit shall be received from and/or transmitted to the third communication device,
transmitting an end notification indicating an end of a current transmit opportunity before the end of the current transmit opportunity, and
establishing a new transmit opportunity with the third communication device, wherein a duration of said new transmit opportunity covers at least the transmission of the preemptive data to and/or the reception of the preemptive data from the third communication device,
wherein the notification is received on a different link than the one on which the ongoing data exchange between the first and second communication device is performed.
19 . A third communication method for communicating with a first communication device, the third communication device comprising:
receiving a data unit addressed to a second communication device,
determining a duration indication indicating an expected duration of an ongoing transmission of a data unit and/or of an ongoing transmit opportunity,
determining if transmission of a data unit has been terminated before an estimated transmission time of the data unit,
resetting a network allocation vector (NAV) upon determining that the transmission of the data unit has been terminated before the estimated transmission time of the data unit, and
receiving from and/or transmitting to the first communication device a preemptive data unit within a remaining duration of the truncated data unit and/or within a remaining duration of the transmit opportunity.