System and method for information verification based on channel awareness

Abstract

This disclosure describes techniques for operating a client device to communicate with a wireless access point to validate data within a frame by comparing channel quality metrics and duration metrics to thresholds. Information received within a validity window may be treated as correctly received even if the frame fails a subsequent verification process or if reception of the frame is terminated prior to the end of the frame.

What is claimed is: 
     
         1 . A client device for communicating with a wireless access point, wherein the client device comprises a data processing module configured to receive at least a portion of a frame transmitted by the access point to an intermediate location within the frame and a channel assessment module configured to determine a validity window with respect to the intermediate location when at least one channel quality metric is greater than or equal to a given threshold, wherein data processing module is configured to validate information received within the validity window. 
     
     
         2 . The client device of  claim 1 , wherein the channel assessment module is configured to determine the validity window by setting a range of symbols upstream and downstream of a period of time when the channel quality metric is determined. 
     
     
         3 . The client device of  claim 2 , wherein the channel quality metric comprises confidence metrics from the output of a Viterbi decoder. 
     
     
         4 . The client device of  claim 1 , wherein the channel assessment module is configured to determine the validity window based upon a coherence time for a channel used to transmit the frame. 
     
     
         5 . The client device of  claim 1 , wherein the channel quality metric comprises a receiver error vector magnitude. 
     
     
         6 . The client device of  claim 1 , wherein the channel quality metric is based upon signal strength of the frame. 
     
     
         7 . The client device of  claim 1 , wherein the given threshold is based upon a modulation coding set used for the transmitted frame. 
     
     
         8 . The client device of  claim 1 , wherein the client device is configured to update system parameters based upon the information received within the validity window. 
     
     
         9 . The client device of  claim 1 , wherein the client device is configured to terminate reception of the frame when the channel quality metric does not exceed the given threshold. 
     
     
         10 . The client device of  claim 1 , wherein the channel assessment module is further configured to determine a plurality of validity windows, such that each validity window is determined in reference to a channel quality metric determined at a different time during the frame. 
     
     
         11 . The client device of  claim 1 , wherein the frame is received though a verification field and the channel assessment module is further configured to diagnose a failure of the verification field on the basis of a duration metric and a difference between a first channel quality metric measured during a preamble of the frame and a second channel quality metric measured during a time corresponding to the intermediate location, wherein the information within the validity window is validated when the failure diagnosis is attributable to deteriorating channel conditions. 
     
     
         12 . The client device of  claim 1 , wherein the information received within the validity window comprises a DTIM information element and wherein the client device if configured to terminate reception of the frame and enter a low power mode if the DTIM information element indicates there is no pending data at the access point for the client device. 
     
     
         13 . The client device of  claim 1 , wherein the channel assessment module is further configured to assign a confidence level to the validity window based upon the channel quality metric and the given threshold. 
     
     
         14 . The client device of  claim 1 , wherein the channel assessment module is further configured to determine the validity window by comparing a first duration metric corresponding to a time period between a preamble of the frame and the intermediate location to a coherence time and determining whether a first channel quality metric determined from the preamble exceeds a given threshold. 
     
     
         15 . The client device of  claim 14 , wherein the channel assessment module is further configured to determine the validity window by comparing a second duration metric corresponding to a time period between the intermediate location and a verification field to a coherence time and comparing the difference between the first channel quality metric and a second channel quality metric to a channel quality difference threshold. 
     
     
         16 . A method for wireless communication with an access point, comprising:
 a) receiving at least a portion of a frame transmitted by the access point to an intermediate location within the frame with a client device;   b) determining a channel quality metric;   c) establishing a validity window when the channel quality metric is greater than or equal to a given threshold; and   d) validating information from the frame received within the validity window.   
     
     
         17 . The method of  claim 16 , wherein establishing the validity window comprises setting a range of symbols upstream and downstream of a period of time when the channel quality metric is determined. 
     
     
         18 . The method of  claim 17 , wherein determining the channel quality metric comprises obtaining confidence metrics from the output of a Viterbi decoder. 
     
     
         19 . The method of  claim 16 , wherein establishing the validity window comprises using a range based upon a coherence time for a channel used to transmit the frame. 
     
     
         20 . The method of  claim 16 , wherein determining the channel quality metric comprises measuring a receiver error vector magnitude. 
     
     
         21 . The method of  claim 16 , wherein determining the channel quality metric comprises measuring a signal strength of the frame. 
     
     
         22 . The method of  claim 16 , wherein the given threshold is based upon a modulation coding set used for the transmitted frame. 
     
     
         23 . The method of  claim 16 , further comprising updating system parameters of the client device based upon the information received within the validity window. 
     
     
         24 . The method of  claim 16 , further comprising terminating reception of the frame when the channel quality metric does not exceed the given threshold. 
     
     
         25 . The method of  claim 16 , further comprising determining a plurality of channel quality metrics at different times during the frame and establishing a plurality of validity windows, each validity window corresponding to the plurality of channel quality metrics. 
     
     
         26 . The method of  claim 16 , wherein the frame is received though a verification field, further comprising diagnosing a failure of the verification field on the basis of a duration metric and a difference between a first channel quality metric measured during a preamble of the frame and a second channel quality metric measured during a time corresponding to the intermediate location, wherein the information within the validity window is validated when the failure diagnosis is attributable to deteriorating channel conditions. 
     
     
         27 . The method of  claim 16 , wherein the validated information includes a DTIM information element, further comprising terminating reception of the frame and placing the client device in a low power mode if the DTIM information element indicates there is no pending data at the access point for the client device. 
     
     
         28 . The method of  claim 16 , further comprising assigning a confidence level to the validity window based upon the channel quality metric and the given threshold. 
     
     
         29 . The method of  claim 16 , wherein establishing the validity window comprises comparing a first duration metric corresponding to a time period between a preamble of the frame and the intermediate location to a coherence time and determining whether a channel quality metric determined from the preamble exceeds a given threshold. 
     
     
         30 . The method of  claim 29 , wherein establishing the validity window further comprises comparing a second duration metric corresponding to a time period between the intermediate location and a verification field to a coherence time and comparing the difference between the first channel quality metric and a second channel quality metric to a channel quality difference threshold.