Channel access procedures for directional systems in unlicensed bands
A method to reserve a directional channel, such as in an unlicensed spectrum for instance, is disclosed. In an example embodiment, the method may be performed by a receiving node, such as a user equipment (UE) for instance. In such method, the receiving node may receive an enhanced directional transmit request message from a transmitting node and transmit an enhanced directional transmit confirmation message using one or more first beams, with at least one first beam being directed in a first direction towards the transmitting node. Further, the receiving node may transmit at least one additional enhanced directional transmit confirmation message using one or more second beams, with at least one second beam being directed in a second direction towards a potentially interfering node. In the method, the second direction is a different direction than the first direction.
1. A method performed by a receiving node, the method comprising:
receiving a Request-to-Send (RTS) message from a transmitting node;
transmitting a Clear-to-Send (CTS) message using one or more first beams, with at least one first beam being directed in a first direction towards the transmitting node;
determining a second direction, the second direction being a different direction than the first direction;
transmitting at least one additional CTS message using one or more second beams, with at least one second beam being directed in the second direction;
receiving data from the transmitting node; and
in between receiving the data from the transmitting node, periodically transmitting subsequent one or more additional CTS messages in at least the second direction within a maximum channel occupancy time (MCOT).
2. The method of claim 1 , wherein:
the receiving node is a wireless transmit/receive unit, and
the transmitting node is a base station.
3. The method of claim 1 , wherein determining the second direction comprises:
determining the second direction based on information from a listen-before-talk (LBT) assessment.
4. The method of claim 1 , wherein the RTS message contains an indication of the second direction, and wherein determining the second direction comprises:
determining the second direction based on the indication in the RTS message.
5. The method of claim 1 , wherein determining the second direction comprises:
determining the second direction based on directional channel measurements.
6. The method of claim 1 , wherein:
the RTS message is an enhanced RTS (eRTS) message, and
the CTS message is an enhanced CTS (eCTS) message.
7. The method of claim 1 , wherein the at least one additional CTS message is an enhanced CTS-to-Self (eCTS-to-Self) message.
8. The method of claim 1 , wherein the CTS message transmitted towards the transmitting node indicates a count of eCTS-to-Self message transmissions to be performed by the receiving node.
9. The method of claim 1 , wherein the at least one additional CTS message includes a defer duration field that specifies an amount of time for which a transmission is to be deferred.
10. The method of claim 1 , wherein the at least one additional CTS message indicates a remaining time for which the directional channel is reserved.
11. The method of claim 1 , wherein transmitting the at least one additional CTS message comprises:
transmitting the at least one additional CTS message multiple times within the maximum channel occupancy time (MCOT).
12. The method of claim 1 , wherein transmitting the at least one additional CTS message using the one or more second beams comprises:
transmitting the at least one additional CTS message on different beams.
13. The method of claim 1 , further comprising:
receiving a second RTS message from the transmitting node; and
on condition that the receiving node detects interferences in a direction of one of the receiving node or transmitting node, transmitting a Deny-to-Send (DTS) message to the transmitting node in response to the second RTS message when the receiving node detects potential directional interference.
14. The method of any of claim 13 , wherein:
the DTS message is an enhanced DTS (eDTS) message, and
the eDTS message identifies a node transmitting an interfering signal.
15. The method of claim 1 , wherein a number of the at least one additional CTS message to be transmitted is based on at least one of (i) a number of potentially interfering nodes, (ii) a power of the one or more second beams, and (iii) a width of the one or more second beams.
16. The method of claim 1 , wherein contents of each of the RTS, CTS, and the at least one additional CTS message is scrambled using a sequence that is common to a group of cells.
17. The method of claim 1 , further comprising:
performing a first directional listen-before-talk (LBT) assessment in a direction towards another node to which the receiving node intends to transmit, wherein the another node is different from the transmitting node;
determining if a channel between the receiving node and the another node is busy based on the performed first directional LBT assessment;
performing a second directional LBT assessment in a reverse direction; and
determining if an interfering signal is detected from the reverse direction so as to either proceed with a transmission to the another node or defer the transmission if the interfering signal is detected.
18. A wireless transmit/receive unit (WTRU) comprising:
a processor; and
a memory storing a plurality of instructions that, when executed by the processor, cause the processor to:
receive a Request-to-Send (RTS) message from a transmitting node;
transmit a Clear-to-Send (CTS) message using one or more first beams, with at least one first beam being directed in a first direction towards the transmitting node;
determine a second direction, the second direction being a different direction than the first direction;
transmit at least one additional CTS message using one or more second beams, with at least one second beam being directed in the second direction;
receive data from the transmitting node; and
in between receiving the data from the transmitting node, periodically transmit subsequent one or more additional CTS messages in at least the second direction within a maximum channel occupancy time (MCOT).
19. A method performed by a receiving node, the method comprising:
receiving an enhanced Request-to-Send (eRTS) message from a transmitting node;
transmitting an enhanced Clear-to-Send (eCTS) message using one or more first beams, with at least one first beam being directed in a first direction towards the transmitting node;
determining a second direction, the second direction being a different direction than the first direction; and wherein the eRTS message contains an indication of the second direction, and wherein determining the second direction comprises determining the second direction based on the indication in the eRTS message; and
transmitting at least one additional CTS message using one or more second beams, with at least one second beam being directed in the second direction; wherein the at least one additional CTS message is an enhanced CTS-to-Self (eCTS-to-Self) message.
20. A receiving node comprising:
a processor; and
a memory storing a plurality of instructions that, when executed by the processor, cause the processor to:
receive an enhanced Request-to-Send (eRTS) message from a transmitting node;
transmit an enhanced Clear-to-Send (eCTS) message using one or more first beams, with at least one first beam being directed in a first direction towards the transmitting node;
determine a second direction, the second direction being a different direction than the first direction; and wherein the eRTS message contains an indication of the second direction, and wherein determining the second direction comprises determining the second direction based on the indication in the DRTS message; and
transmit at least one additional CTS message using one or more second beams, with at least one second beam being directed in the second direction; wherein the at least one additional CTS message is anenhanced DCTS-to-Self (eCTS-to-Self) message.
21. The method of claim 1 , wherein the second direction is a direction toward a potentially interfering node.
22. The method of claim 18 , wherein the second direction is a direction toward a potentially interfering node.
23. The method of claim 19 , wherein the second direction is a direction toward a potentially interfering node.
24. The method of claim 20 , wherein the second direction is a direction toward a potentially interfering node.
25. The WTRU of claim 18 further configured to:
determine the second direction based on information from a listen-before-talk (LBT) assessment.
26. The WTRU of claim 18 , wherein the RTS message contains an indication of the second direction, and wherein determining the second direction comprises:
determining the second direction based on the indication in the RTS message.
27. The WTRU of claim 18 , wherein determining the second direction comprises:
determining the second direction based on directional channel measurements.
28. The WTRU of claim 18 , wherein the at least one additional CTS message includes a defer duration field that specifies an amount of time for which a transmission is to be deferred.
29. The WTRU of claim 18 , wherein the at least one additional CTS message indicates a remaining time for which the directional channel is reserved.
30. The WTRU of claim 18 , wherein transmitting the at least one additional CTS message comprises:
transmitting the at least one additional CTS message multiple times within the maximum channel occupancy time (MCOT).
31. The WTRU of claim 18 , wherein transmitting the at least one additional CTS message using the one or more second beams comprises:
transmitting the at least one additional CTS message on different beams.
32. The WTRU of claim 18 , wherein a number of the at least one additional CTS message to be transmitted is based on at least one of (i) a number of potentially interfering nodes, (ii) a power of the one or more second beams, and (iii) a width of the one or more second beams.