Uplink transmissions in a wireless communications network

1. A method performed by a station for enabling an Uplink, UL, transmission to an access point in a wireless communications network, the method comprising:

determining a UL transmission rank for an UL transmission to the access point;

transmitting, to the access point, a message on a contention-based transmission resource in the wireless communications network comprising information indicating the determined UL transmission rank; and

transmitting information to the access point indicating that the station performs transmission rank adaptation for UL transmissions in the wireless communications network.

2. The method according to claim 1 , further comprising:

receiving, from the access point, a message on a contention-based transmission resource in the wireless communications network comprising information indicating a UL transmission rank to be used by the station in an UL transmission, and

transmitting, to the access point, an UL transmission on a contention-based transmission resource in the wireless communications network-using the indicated UL transmission rank received in the received message from the access point.

3. The method according to claim 1 , wherein the determined UL transmission rank is based on at least Channel State Information, CSI, estimated from reference signals received from the access point and transmission information at the station associated with the number of antennas at the station which are available for transmitting an UL transmission to the access point, wherein the message to the access point further comprises the transmission information at the station.

4. The method according to claim 3 , wherein the transmission information at the station indicates the Degrees-of-Freedom, DoF, of the number of antennas at the station which are available for transmitting an UL transmission to the access point.

5. The method according to claim 1 , further comprising determining that deferment of the transmission of the message to the access point is to be performed by the station in response to receiving other messages from the access point designated to other stations in the wireless communications network.

6. The method according to claim 1 , wherein the contention-based transmission resources in the wireless communications network over which the messages are transmitted are different than the ones over which an UL transmission from the station is transmitted to the access point, and wherein the different contention-based transmission resources may be a different frequencies, time slots, or codes.

7. The method according to claim 1 , wherein the message to the access point is an Request-to-Send, RTS, message, and the message from the access point is an Clear-to-Send, CTS, message.

8. The method according to claim 1 , further comprising:

receiving information from the access point indicating that the station is to perform transmission rank adaptation for UL transmissions in the wireless communications network.

9. A station for enabling an Uplink, UL, transmission to an access point in a wireless communications network, the station comprising radio circuitry that is configured to:

determine a UL transmission rank for an UL transmission to the access point, and transmit, to the access point, a message on a contention-based transmission resource in the wireless communications network comprising information indicating the determined UL transmission rank; and

transmit information to the access point indicating that the station performs transmission rank adaptation for UL transmissions in the wireless communications network.

10. The station according to claim 9 , wherein the radio circuitry is further configured to, from the access point, a message on a contention-based transmission resource in the wireless communications network comprising information indicating a UL transmission rank to be used by the station in an UL transmission.

11. The station according to claim 10 , wherein the radio circuitry is further configured to transmit, to the access point, an UL transmission on a contention-based transmission resource in the wireless communications network using the indicated UL transmission rank received in the received message from the access point.

12. A method performed by a station for enabling an Uplink, UL, transmission to an access point in a wireless communications network, the method comprising:

determining a UL transmission rank for an UL transmission to the access point; and

transmitting, to the access point, a message on a contention-based transmission resource in the wireless communications network comprising information indicating the determined UL transmission rank; and

receiving information from the access point indicating that the station is to perform transmission rank adaptation for UL transmissions in the wireless communications network.

13. The method according to claim 12 , further comprising:

receiving, from the access point, a message on a contention-based transmission resource in the wireless communications network comprising information indicating a UL transmission rank to be used by the station in an UL transmission, and

transmitting, to the access point, an UL transmission on a contention-based transmission resource in the wireless communications network-using the indicated UL transmission rank received in the received message from the access point.

14. The method according to claim 12 , wherein the determined UL transmission rank is based on at least Channel State Information, CSI, estimated from reference signals received from the access point and transmission information at the station associated with the number of antennas at the station which are available for transmitting an UL transmission to the access point, wherein the message to the access point further comprises the transmission information at the station.

15. The method according to claim 14 , wherein the transmission information at the station indicates the Degrees-of-Freedom, DoF, of the number of antennas at the station which are available for transmitting an UL transmission to the access point.

16. The method according to claim 12 , further comprising determining that deferment of the transmission of the message to the access point is to be performed by the station in response to receiving other messages from the access point designated to other stations in the wireless communications network.

17. The method according to claim 12 , wherein the contention-based transmission resources in the wireless communications network over which the messages are transmitted are different than the ones over which an UL transmission from the station is transmitted to the access point, and wherein the different contention-based transmission resources may be a different frequencies, time slots, or codes.

18. The method according to claim 12 , wherein the message to the access point is an Request-to-Send, RTS, message, and the message from the access point is an Clear-to-Send, CTS, message.

19. The method according to claim 12 , further comprising:

transmitting information to the access point indicating that the station performs transmission rank adaptation for UL transmissions in the wireless communications network.

20. A station for enabling an Uplink, UL, transmission to an access point in a wireless communications network, the station comprising radio circuitry that is configured to:

determine a UL transmission rank for an UL transmission to the access point, and transmit, to the access point, a message on a contention-based transmission resource in the wireless communications network comprising information indicating the determined UL transmission rank; and

receive information from the access point indicating that the station is to perform transmission rank adaptation for UL transmissions in the wireless communications network.

21. The station according to claim 20 , wherein the radio circuitry is further configured to, from the access point, a message on a contention-based transmission resource in the wireless communications network comprising information indicating a UL transmission rank to be used by the station in an UL transmission.

22. The station according to claim 21 , wherein the radio circuitry is further configured to transmit, to the access point, an UL transmission on a contention-based transmission resource in the wireless communications network using the indicated UL transmission rank received in the received message from the access point.