Method, apparatus, and computer program product for resolving hidden node in synchronized DCF based channel access

1. A method, comprising:

receiving by a wireless terminal device, a first message from an access point device, the first message comprising information indicating a plurality of restricted access windows, each restricted access window allocated for a different group of wireless terminal devices associated to a wireless network managed by the access point device;

receiving by the wireless terminal device, a second message from the access point device, within a restricted access window of the plurality of restricted access windows, the restricted access window allocated to a group of wireless terminal devices of which the wireless terminal device is a member, the second message comprising information indicating that a communications channel is available; and

determining by the wireless terminal device, based on the second message, that the communications channel is not occupied by hidden ones of the wireless terminal devices associated to the wireless network.

2. The method of claim 1 , wherein the restricted access window comprises multiple time slots;

receiving by the wireless terminal device, a traffic indication map in the first message, comprising an indication whether the wireless terminal device has buffered data waiting to be accessed in the access point; and

detecting by the wireless terminal device, that the second message indicates that one of the multiple time slots in the restricted access window is not occupied by hidden ones of the wireless terminal devices associated to the wireless network.

3. The method of claim 1 , further comprising:

contending by the wireless terminal device, with other wireless terminal devices that are members of the wireless terminal device's group, for access to the one of the multiple time slots, if the wireless terminal device is indicated as having buffered data waiting to be accessed and the one of the multiple time slots is indicated as not occupied by hidden ones of the wireless terminal devices; and

transmitting by the wireless terminal device, a message to the access point, in the one of the multiple time slots.

4. The method of claim 1 , wherein the second message is one of a Clear to Send frame received in a beginning portion of a time slot of a plurality of time slots within the restricted access window or an acknowledgement frame received at a time within a time slot of a plurality of time slots within the restricted access window and wherein the first message comprises information that the time slot is allocated to the wireless terminal device.

5. The method of claim 1 , wherein the first message is a beacon frame.

6. The method of claim 1 , wherein the second message is at least one of an acknowledgement frame or a Clear to Send frame that includes an offset of the one of the multiple time slots.

7. The method of claim 1 , wherein the second message is at least one of an acknowledgement frame or a Clear to Send frame that includes at least one of a number of wireless devices contending for the one of the multiple time slots or a value of the contention window for the one of the multiple time slots.

8. A method, comprising:

transmitting by a wireless access point device, a first message comprising information indicating a plurality of restricted access windows, each restricted access window allocated for a different group of wireless terminal devices associated to a wireless network managed by the access point device;

determining by the wireless access point that a communications channel is not occupied by hidden ones of the wireless terminal devices associated to the wireless network; and

transmitting by the wireless access point device, a second message within a restricted access window of the plurality of restricted access windows, the restricted access window allocated to a group of wireless terminal devices of which a wireless terminal device is a member, the second message comprising information indicating that the communications channel is available.

9. The method of claim 8 , wherein the restricted access window comprises multiple time slots;

transmitting by the wireless access point device, a traffic indication map in the first message, comprising an indication whether the wireless terminal device has buffered data waiting to be accessed in the access point; and

receiving by the wireless access point device, a message from the wireless terminal device, in the one of the multiple time slots.

10. The method of claim 8 , wherein the second message is one of a Clear to Send frame transmitted in a beginning portion of a time slot of a plurality of time slots within the restricted access window or an acknowledgement frame transmitted at a time within a time slot of a plurality of time slots within the restricted access window and wherein the first message comprises information that the time slot is allocated to the wireless terminal device.

11. The method of claim 8 , wherein the first message is a beacon frame.

12. The method of claim 8 , wherein the second message is at least one of an acknowledgement frame or a Clear to Send frame that includes an offset of the one of the multiple time slots.

13. The method of claim 8 , wherein the second message is at least one of an acknowledgement frame or a Clear to Send frame that includes at least one of a number of wireless devices contending for the one of the multiple time slots or a value of the contention window for the one of the multiple time slots.

14. An apparatus, comprising:

at least one processor;

at least one memory including computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

receive a first message from an access point device, the first message comprising information indicating a plurality of restricted access windows, each restricted access window allocated for a different group of wireless terminal devices associated to a wireless network managed by the access point device;

receive a second message from the access point device, within a restricted access window of the plurality of restricted access windows, the restricted access window allocated to a group of wireless terminal devices of which the apparatus is a member, the second message comprising information indicating that a communications channel is available; and

determine based on the second message, that the communications channel is not occupied by hidden ones of the wireless terminal devices associated to the wireless network.

15. The apparatus of claim 14 , wherein the restricted access window comprises multiple time slots;

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

receive a traffic indication map in the first message, comprising an indication whether the apparatus has buffered data waiting to be accessed in the access point; and

detect that the second message indicates that one of the multiple time slots in the restricted access window is not occupied by hidden ones of the wireless terminal devices associated to the wireless network.

16. The apparatus of claim 14 , further comprising:

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

contend with other wireless terminal devices that are members of the apparatus' group, for access to the one of the multiple time slots, if the apparatus is indicated as having buffered data waiting to be accessed and the one of the multiple time slots is indicated as not occupied by hidden ones of the wireless terminal devices; and

transmit a message to the access point, in the one of the multiple time slots.

17. The apparatus of claim 14 , wherein the second message is one of a Clear to Send frame received in a beginning portion of a time slot of a plurality of time slots within the restricted access window or an acknowledgement frame received at a time within a time slot of a plurality of time slots within the restricted access window and wherein the first message comprises information that the time slot is allocated to the wireless terminal device.

18. The apparatus of claim 14 , wherein the first message is a beacon frame.

19. The apparatus of claim 14 , wherein the second message is at least one of an acknowledgement frame or a Clear to Send frame that includes an offset of the one of the multiple time slots.

20. The apparatus of claim 14 , wherein the second message is at least one of an acknowledgement frame or a Clear to Send frame that includes at least one of a number of wireless devices contending for the one of the multiple time slots or a value of the contention window for the one of the multiple time slots.

21. An apparatus, comprising:

at least one processor;

at least one memory including computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

transmit a first message comprising information indicating a plurality of restricted access windows, each restricted access window allocated for a different group of wireless terminal devices associated to a wireless network managed by the apparatus;

determine that a communications channel is not occupied by hidden ones of the wireless terminal devices associated to the wireless network; and

transmit a second message within a restricted access window of the plurality of restricted access windows, the restricted access window allocated to a group of wireless terminal devices of which a wireless terminal device is a member, the second message comprising information indicating that the communications channel is available.

22. The apparatus of claim 21 , wherein the restricted access window comprises multiple time slots;

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

transmit a traffic indication map in the first message, comprising an indication whether the wireless terminal device has buffered data waiting to be accessed in the access point; and

receive a response message from the wireless terminal device, in the one of the multiple time slots.

23. The apparatus of claim 21 , wherein the second message is one of a Clear to Send frame transmitted in a beginning portion of a time slot of a plurality of time slots within the restricted access window or an acknowledgement frame transmitted at a time within a time slot of a plurality of time slots within the restricted access window and wherein the first message comprises information that the time slot is allocated to the wireless terminal device.

24. The apparatus of claim 21 , wherein the first message is a beacon frame.

25. The apparatus of claim 21 , wherein the second message is at least one of an acknowledgement frame or a Clear to Send frame that includes an offset of the one of the multiple time slots.

26. The apparatus of claim 21 , wherein the second message is at least one of an acknowledgement frame or a Clear to Send frame that includes at least one of a number of wireless devices contending for the one of the multiple time slots or a value of the contention window for the one of the multiple time slots.

27. A computer program product comprising computer executable program code recorded on a computer readable, non-transitory storage medium, the computer executable program code comprising:

code for receiving by a wireless terminal device, a first message from an access point device, the first message comprising information indicating a plurality of restricted access windows, each restricted access window allocated for a different group of wireless terminal devices associated to a wireless network managed by the access point device;

code for receiving by the wireless terminal device, a second message from the access point device, within a restricted access window of the plurality of restricted access windows, the restricted access window allocated to a group of wireless terminal devices of which the wireless terminal device is a member, the second message comprising information indicating that a communications channel is available; and

code for determining by the wireless terminal device, based on the second message, that the communications channel is not occupied by hidden ones of the wireless terminal devices associated to the wireless network.