Directional antenna physical layer steering for WLAN

Abstract

A technique for steering a directional antenna such as may be used in a Wireless Local Area Network (WLAN) device. The technique detects signal parameters during reception of short sync pulses in the very beginning portion of a Packet Protocol Data Unit (PPDU) frame. As a result, the antenna can be steered to an optimum direction for reception prior to receiving other portions of a preamble that may be needed to acquire carrier signal phase and frequency.

1 . A method for controlling a directional angle of a steerable antenna array, the method comprising the steps of: 
 (a) configuring the array in an omnidirectional mode;    (b) determining a metric from a synchronization pulse contained in a radio signal received by the array;    (c) steering the array to a candidate angle based on the determined metric;    (d) repeating steps (b) and (c) for at least one additional candidate angle; and    (e) selecting a candidate angle based on the determined metrics.    
     
     
         2 . A method as defined in  claim 1  wherein the radio signal comprises short synchronization pulses and long synchronization pulses and the synchronization pulse from which the metric is determined is a short synchronization pulse.  
     
     
         3 . A method as defined in  claim 1  further comprising: 
 correlating a portion of the synchronization pulse against an expected version of that portion to provide a measure of how well the pulse has been received.    
     
     
         4 . A method as defined in  claim 3  wherein the portion of the synchronization pulse is a first half of the pulse.  
     
     
         5 . A method as defined in  claim 1  further comprising: 
 swapping real and imaginary samples of a portion of the synchronization pulse to provide a response of the antenna array to the radio signal.    
     
     
         6 . A method as defined in  claim 5  wherein the metric is determined from the provided response.  
     
     
         7 . A method as defined in  claim 5  wherein the portion of the synchronization pulse is a second half of the pulse.  
     
     
         8 . A method as defined in  claim 1  wherein the metric is determined from a portion of the synchronization pulse.  
     
     
         9 . A method as defined in  claim 1  wherein steps (b) and (c) are performed over a first portion of the synchronization pulse and step (d) is performed over a second portion of the synchronization pulse.  
     
     
         10 . A method as defined in  claim 9  wherein the first portion is a first half of the synchronization pulse and the second portion is a second half of the synchronization pulse.  
     
     
         11 . An apparatus comprising: 
 a steerable antenna array configured to receive a radio signal; and    a processor configured to: 
 (a) configure the array in an omnidirectional mode,  
 (b) determine a metric from a synchronization pulse contained in a radio signal received by the array,  
 (c) steer the array to a candidate angle based on the determined metric,  
 (d) repeat (b) and (c) for at least one additional candidate angle, and  
 (e) select a candidate angle based on the determined metrics.  
   
     
     
         12 . An apparatus as defined in  claim 11  wherein the radio signal comprises short synchronization pulses and long synchronization pulses and the synchronization pulse from which the metric is determined is a short synchronization pulse.  
     
     
         13 . An apparatus as defined in  claim 11  wherein the processor is further configured to: 
 correlate a portion of the synchronization pulse against an expected version of that portion to provide a measure of how well the pulse has been received.    
     
     
         14 . An apparatus as defined in  claim 11  wherein the processor is further configured to: 
 swap real and imaginary samples of a portion of the synchronization pulse to provide a response of the antenna array to the radio signal.    
     
     
         15 . An apparatus as defined in  claim 14  wherein the metric is determined from the provided response.  
     
     
         16 . An apparatus as defined in  claim 11  wherein (b) and (c) are performed over a first portion of the synchronization pulse and (d) is performed over a second portion of the synchronization pulse.  
     
     
         17 . An apparatus as defined in  claim 16  wherein the first portion is a first half of the synchronization pulse and the second portion is a second half of the synchronization pulse.  
     
     
         18 . An apparatus comprising: 
 (a) means for configuring the array in an omnidirectional mode;    (b) means for determining a metric from a synchronization pulse contained in a radio signal received by the array;    (c) means for steering the array to a candidate angle based on the determined metric;    (d) means for repeating steps determining a metric and steering the array for at least one additional candidate angle; and    (e) means for selecting a candidate angle based on the determined metrics.    
     
     
         19 . An apparatus as defined in  claim 18  wherein the radio signal comprises short synchronization pulses and long synchronization pulses and the synchronization pulse from which the metric is determined is a short synchronization pulse.  
     
     
         20 . An apparatus as defined in  claim 18  further comprising: 
 means for correlating a portion of the synchronization pulse against an expected version of that portion to provide a measure of how well the pulse has been received.    
     
     
         21 . An apparatus as defined in  claim 18  further comprising: 
 means for swapping real and imaginary samples of a portion of the synchronization pulse to provide a response of the antenna array to the radio signal.    
     
     
         22 . An apparatus as defined in  claim 21  wherein the metric is determined from the provided response.