Channel Condition Prediction Employing Transmit Queuing Model

Abstract

Channel condition prediction employing a transmit queuing model. An average transmission queue delay monitor generates an indication of average transmit queue latency during the transmission of a video stream to a remote wireless device. The average transmit queue latency is compared to a predetermined threshold for purposes of adjusting encoding bit rate (or other encoding parameter) of the video stream. In one mode, the predetermined threshold reflects a maximum tolerable average queue depth beyond which video data is likely to be lost or unacceptably delayed under certain channel conditions. If the average transmit queue latency exceeds the predetermined threshold, the encoding bit rate (or related encoding parameter) is lowered or raised as necessary to decrease or increase the transmit queue depth to a desired level. In another mode, the transmit queuing model is used in conjunction with channel throughput estimation information to adaptively adjust one or more encoding parameters.

1 . A method for adaptively encoding a video stream for transmission to a remote wireless device, comprising:
 monitoring the MAC transmit queue of a transmitting device to generate an indication of average transmit queue latency for a portion of the video stream;   comparing the indication of average transmit queue latency to a predetermined threshold; and   adjusting the encoding bit rate for the video stream if the indication of average transmit queue latency exceeds the predetermined threshold.   
     
     
         2 . The method of  claim 1 , wherein the predetermined threshold is a maximum tolerated delay threshold, and the step of adjusting the encoding bit rate comprises reducing the encoding bit rate. 
     
     
         3 . The method of  claim 1 , wherein the predetermined threshold is a minimum tolerated delay threshold, and the step of adjusting the encoding bit rate comprises increasing the encoding bit rate. 
     
     
         4 . The method of  claim 1 , further comprising monitoring the MAC transmit queue to generate a new indication of average transmit queue latency for transmissions associated with an adjusted encoding bit rate. 
     
     
         5 . The method of  claim 1 , wherein the step of monitoring the MAC transmit queue comprises:
 marking video packets of the video stream with an indication of the time the respective video packet is submitted for transmission by the transmitting device;   receiving associated transmission acknowledgment information for the video packets;   calculating transmission delays for the video packets by comparing the indication of the time a video packet is submitted for transmission with the associated transmission acknowledgment information; and   generating average transmit queue latency information based on the calculated transmission delays.   
     
     
         6 . The method of  claim 1 , wherein the predetermined threshold is based at least in part on prior measurement(s) of transmit queue latency. 
     
     
         7 . The method of  claim 5 , wherein the average transmit queue latency information is maintained for video packets based on at least one of access category or traffic ID information associated with the video packets. 
     
     
         8 . A method for adaptively encoding a video stream for transmission to a remote wireless device over a wireless channel, comprising:
 receiving at least one transmitter side indication of the available throughput of the wireless channel at a first PHY data rate;   utilizing the received indication to generate an estimate of the throughput of the wireless channel at a second PHY data rate;   identifying a transition or pending transition to wireless channel operation at the second PHY data rate;   altering the encoding bit rate of the video stream based on the estimate;   monitoring a MAC transmit queue of the transmitting device to generate an indication of average transmit queue latency for a portion of the video stream;   comparing the indication of average transmit queue latency to a predetermined threshold; and   further adjusting the encoding bit rate for the video stream if the indication of average transmit queue latency exceeds the predetermined threshold.   
     
     
         9 . The method of  claim 8 , wherein the indicia of the available throughput of the wireless channel comprises at least one of channel bandwidth information, acknowledgement policy parameters, packetizer parameters, channel load information and a channel gain estimate. 
     
     
         10 . The method of  claim 8 , wherein the predetermined threshold is a maximum tolerated delay threshold, and the step of further adjusting the encoding bit rate comprises reducing the encoding bit rate. 
     
     
         11 . The method of  claim 8 , wherein the predetermined threshold is a minimum tolerated delay threshold, and the step of further adjusting the encoding bit rate comprises increasing the encoding bit rate. 
     
     
         12 . The method of  claim 8 , wherein the step of monitoring a MAC transmit queue comprises:
 marking video packets of the video stream with an indication of the time the respective video packet is submitted for transmission by the transmitting device;   receiving associated transmission acknowledgment information for the video packets;   calculating transmission delays for the video packets by comparing the indication of the time a video packet is submitted for transmission with the associated transmission acknowledgment information; and   generating an indication of average transmit queue latency based on the calculated transmission delays.   
     
     
         13 . The method of  claim 12 , wherein the indication of average transmit queue latency information is maintained for video packets based on at least one of access category or traffic ID information associated with the video packets. 
     
     
         14 . An apparatus, comprising:
 a network interface for supporting video stream transmission over a wireless channel;   an encoder for encoding the video stream for provision to the network interface; and   encoder bit rate adaptation circuitry operable to adaptively adjust an encoding bit rate of the encoder by:   monitoring the MAC transmit queue of a transmitting device to generate an indication of average transmit queue latency for a portion of the video stream;   comparing the indication of average transmit queue latency to a predetermined threshold; and   adjusting the encoding bit rate for the video stream if the indication of average transmit queue latency exceeds the predetermined threshold.   
     
     
         15 . The apparatus of  claim 14 , wherein the predetermined threshold is a maximum tolerated delay threshold, and adjusting the encoding bit rate comprises reducing the encoding bit rate. 
     
     
         16 . The apparatus of  claim 14 , wherein the predetermined threshold is a minimum tolerated delay threshold, and adjusting the encoding bit rate comprises increasing the encoding bit rate. 
     
     
         17 . The apparatus of  claim 14 , wherein monitoring the MAC transmit queue comprises:
 marking video packets of the video stream with an indication of the time the respective video packet is submitted for transmission by the transmitting device;   receiving associated transmission acknowledgment information for the video packets;   calculating transmission delays for the video packets by comparing the indication of the time a video packet is submitted for transmission with the associated transmission acknowledgment information; and   generating an indication of average transmit queue latency based on the calculated transmission delays.   
     
     
         18 . The method of  claim 17 , wherein the indication of average transmit queue latency is maintained for video packets based on at least one of access category or traffic ID information associated with the video packets. 
     
     
         19 . The apparatus of  claim 14 , wherein the apparatus comprises a wireless dongle, the apparatus further comprising a standardized audio/video interface for providing video stream data to the encoder for encoding. 
     
     
         20 . The apparatus of  claim 19 , wherein the standardized audio/video interface is compliant with an HDMI standard.