Emergency call handling in contention-based wireless local-area networks
View Patent ↗An apparatus and methods for handling emergency message frames (e.g., “911” call frames, etc.) sent by a station in a wireless local-area network are disclosed. The illustrative embodiment increases the probability with which an emergency message frame is accorded the singularly highest quality-of-service by modifying one or more IEEE 802.11e parameters (e.g., back-off contention window length, Arbitration Inter-Frame Space [AIFS], etc.) for a station or access point that transmits an emergency message frame.
1. A method comprising:
generating a first traffic stream for transmission into a shared-communications channel, wherein said first traffic stream is the only privileged traffic stream contending for access to said shared-communications channel, and wherein said first traffic stream comprises a first traffic frame;
generating a second traffic stream for transmission into said shared-communications channel, wherein said second traffic stream is not privileged, and wherein said second traffic stream comprises a second frame;
selecting a first back-off delay for said first frame from a first back-off contention window;
selecting a second back-off delay for said second frame from a second back-off contention window;
transmitting said first frame into said shared-communications channel at said first back-off delay;
transmitting said second frame into said shared-communications channel at said second back-off delay;
detecting a collision on said shared-communications channel during the transmission of said first frame;
detecting a collision on said shared-communications channel during the transmission of said second frame;
selecting a third back-off delay for said first frame from a third back-off contention window;
selecting a fourth back-off delay for said second frame from a fourth back-off contention window;
re-transmitting said first frame into said shared-communications channel at said third back-off delay; and
re-transmitting said second frame into said shared-communications channel at said fourth back-off delay;
wherein said first back-off contention window is as long as said third back-off contention window; and
wherein said fourth back-off contention window is longer than said second back-off contention window.
2. The method of claim 1 wherein said third back-off contention window is shorter than said first back-off contention window.
3. The method of claim 1 wherein said third back-off contention window is the same as said first back-off contention window.
4. The method of claim 1 wherein said first back-off contention window is the same as said second back-off contention window.
5. The method of claim 1 wherein said first back-off contention window is shorter than said second back-off contention window.
6. An apparatus comprising:
a processor for (i) generating a first traffic stream for transmission into a shared-communications channel, wherein said first traffic stream is the only privileged traffic stream contending for access to said shared-communications channel, and wherein said first traffic stream comprises a first traffic frame, (ii) generating a second traffic stream for transmission into said shared-communications channel, wherein said second traffic stream is privileged, and wherein said second traffic stream comprises a second frame, (iii) selecting a first back-off delay for said first frame from a first back-off contention window, and (iv) selecting a second back-off delay for said second frame from a second back-off contention window, (v) selecting a third back-off delay for said first frame from a third back-off contention window, (vi) selecting a fourth back-off delay for said second frame from a fourth back-off contention window;
a transmitter for (i) transmitting said first frame into said shared-communications channel at said first back-off delay, (ii) transmitting said second frame into said shared- communications channel at said second back-off delay, (iii) re-transmitting said first frame into said shared-communications channel at said third back-off delay, and (iv) re- transmitting said second frame into said shared-communications channel at said fourth back-off delay; and
a receiver for (i) detecting a collision on said shared-communications channel during the transmission of said first frame, and (ii) detecting a collision on said shared-communications channel during the transmission of said second frame;
wherein said first back-off contention window is as long as said third back-off contention window; and
wherein said fourth back-off contention window is longer than said second back-off contention window.
7. The method of claim 6 wherein said third back-off contention window is shorter than said first back-off contention window.
8. The method of claim 6 wherein said third back-off contention window is the same as said first back-off contention window.
9. The method of claim 6 wherein said first back-off contention window is the same as said second back-off contention window.
10. The method of claim 6 wherein said first back-off contention window is shorter than said second back-off contention window.