Dealing with lost acknowledgements when power-saving

A method comprising:

• (a) transmitting to a station a frame f in a sequence of one or more frames;
• (b) receiving from said station a first acknowledgement that acknowledges said frame f;
• (c) transmitting to said station, after (b), a second acknowledgement that acknowledges said first acknowledgement when (i) said frame f is the final frame of said sequence, and (ii) said station is the last polled station during a contention-free period;
• and
• (d) transmitting to said station, after (b), the frame following said frame f in said sequence when said frame f precedes the final frame of said sequence.

A method comprising:

• (a) receiving a final frame of a sequence of one or more frames via a shared-communications channel;
• (b) transmitting via said shared-communications channel a first acknowledgement to the sender of said final frame, wherein said first acknowledgement acknowledges said final frame;
• (c) listening, after (b), to said shared-communications channel for a second acknowledgement;
• and
• (d) entering a reduced-power state when said second acknowledgement acknowledges said first acknowledgement.

An apparatus comprising:

• a transceiver for:
• receiving a final frame of a sequence of one or more frames,
• transmitting to the sender of said final frame a first acknowledgement that acknowledges receipt of said final frame, and
• receiving, from the sender of said final frame, a second acknowledgement that acknowledges receipt of said first acknowledgement by the sender;
• and
• a logic circuit for outputting, after said transceiver receives said second acknowledgement, a signal that causes said transceiver to enter a reduced-power state.

An apparatus comprising:

• a transmitter for transmitting to a station a frame f of a sequence of one or more frames;
• a receiver for receiving from said station a first acknowledgement that acknowledges said frame f;
• and
• a logic circuit for:
• outputting, when said frame f is the final frame of said sequence and said station is the last polled station during a contention-free period, a signal that causes said transmitter to transmit a second acknowledgement that acknowledges said first acknowledgement, and
• outputting, when said frame f precedes the final frame of said sequence, a signal that causes said transmitter to transmit the second acknowledgement following said frame f in said sequence.

An apparatus comprising:

• a transceiver for:
• receiving a final frame of a sequence of one or more frames via a shared-communications channel,
• transmitting to the sender of said final frame, via said shared-communications channel, a first acknowledgement that acknowledges said final frame, and
• listening, after transmitting said first acknowledgement, to said shared-communications channel for a second acknowledgement;
• and
• a logic circuit for outputting, when said second acknowledgement acknowledges said first acknowledgement, a signal that causes said transceiver to enter a reduced-power state.