Method and system for dynamic carrier selection

Abstract

A dynamic carrier selection method and system permit units operating on a first carrier to change to a second carrier when performance of the first carrier becomes unacceptable. Carrier quality measurements are taken in which carrier quality is a function of interference and multi-path fading and carrier-signal strength. The carriers are ranked according to measured quality in a carrier candidate list. The carrier candidate list is used to permit units to determine which carrier they should switch to when the carrier there currently operating on is determined to have unacceptable performance. Carrier measurements are retaken in response to a carrier change by unit or a predetermined time period having elapsed.

What is claimed is:  
     
         1 . A dynamic carrier-selection method comprising the steps of: 
 creating a candidate carrier list from a plurality of carriers; and    changing from a first carrier of the plurality of carriers to a second carrier of the plurality of carriers in response to a determination that the quality of the first carrier is not acceptable, the second carrier being included in the carrier list.    
     
     
         2 . The method of  claim 1  further comprising the step of: 
 measuring a quality of each of the plurality of carriers; and  
 ranking the plurality of carriers according to the measured quality, wherein the candidate carrier list is created in accordance with the ranking of the plurality of carriers.  
 
     
     
         3 . The method of  claim 2  wherein the second carrier is the carrier, other than the first carrier, having the greatest measured quality.  
     
     
         4 . The method of  claim 1  wherein the candidate carrier list is created by arbitrarily selecting at least one carrier of the plurality of carriers.  
     
     
         5 . The method of  claim 2  wherein the step of measuring occurs in a frequency-hopping mode and the candidate carrier list is used in a high-speed mode.  
     
     
         6 . The method of  claim 3  further comprising the steps of: 
 re-measuring the quality of each of the plurality of carriers;  
 re-ranking the plurality of carriers according to the re-measured quality; and  
 updating the candidate carrier list in accordance with the re-ranking of the plurality of carriers.  
 
     
     
         7 . The method of  claim 6  wherein the step of re-measuring occurs in a frequency-hopping mode and the updated candidate carrier list is used in a high-speed mode.  
     
     
         8 . The method of  claim 6  wherein the quality of the plurality of carriers is measured with reference to interference and multi-path fading.  
     
     
         9 . The method of  claim 8  wherein the quality of the plurality of carriers comprises a carrier-signal-to-interference-signal strength ratio (C/I).  
     
     
         10 . The method of  claim 9  wherein I comprises external interference and self interference.  
     
     
         11 . The method of  claim 1  further comprising the steps of: 
 communicating an identity of the second carrier; and  
 marking the second carrier as being occupied.  
 
     
     
         12 . The method of  claim 1  further comprising, following the step of changing, the step of listening by a first unit and transmitting by a second unit at a priority slot of the second carrier assigned to the second unit.  
     
     
         13 . A dynamic carrier-selection system comprising: 
 a candidate carrier list that includes a list of a plurality of carriers; and    a unit operating on a first carrier of the plurality of carriers, wherein the unit changes from the first carrier of the plurality of carriers to a second carrier of the plurality of carriers with reference to the candidate carrier list in response to a determination that the quality of the first carrier is not acceptable.    
     
     
         14 . The system of  claim 13  wherein the candidate carrier list includes a ranking according to quality of the plurality of carriers.  
     
     
         15 . The system of  claim 13  wherein the candidate carrier list includes an arbitrary selection of at least one carrier of the plurality of carriers.  
     
     
         16 . The system of  claim 14  wherein the candidate carrier list is used by the unit while the unit is operating in a high-speed mode.  
     
     
         17 . The system of  claim 13  wherein the second carrier is the carrier of the plurality of carriers other than the first carrier having the greatest quality.  
     
     
         18 . The system of  claim 13  wherein the unit is operable to measure the quality of at least one of the plurality of carriers.  
     
     
         19 . The system of  claim 18  wherein the unit is operable to measure the quality of at least one of the plurality of carriers while operating in a frequency-hopping mode.  
     
     
         20 . The system of  claim 18  wherein the quality of the plurality of carriers is measured with reference to interference and multi-path fading.  
     
     
         21 . The system of  claim 20  wherein the quality of the plurality of carriers comprises a carrier-signal-to-interference-signal strength ratio (C/I).  
     
     
         22 . The system of  claim 21  wherein I comprises external interference and self interference.  
     
     
         23 . A dynamic carrier-selection method comprising the steps of: 
 creating a candidate carrier list of a plurality of carriers;    changing by a first unit operating on a first carrier of the plurality of carriers to a second carrier of the plurality of carriers in response to a determination that the quality of the first carrier is not acceptable, the second carrier being the carrier other than the first carrier having the greatest measured quality;    measuring the quality of each of the plurality of carriers;    ranking the plurality of carriers according to the measured quality; and    updating the candidate carrier list in accordance with the re-ranking of the plurality of carriers.    
     
     
         24 . The method of  claim 23  wherein the step of measuring the quality of the plurality of carriers occurs with reference to interference and multi-path fading.  
     
     
         25 . The method of  claim 24  wherein the quality of the plurality of carriers comprises a comparison of a carrier-signal strength to an interference-signal strength.  
     
     
         26 . The method of  claim 25  wherein I comprises external interference and self interference.  
     
     
         27 . The method of  claim 23  further comprising the steps of: 
 communicating an identity of the second carrier; and  
 marking the second carrier as being occupied.  
 
     
     
         28 . The method of  claim 27  further comprising the step of communicating the updated list over a frequency-hopping (FH) carrier.  
     
     
         29 . The method of  claim 28  wherein the FH carrier operates according to an ad-hoc wireless system.  
     
     
         30 . The method of  claim 27  further comprising the step of communicating the updated list over a high-speed (HS) carrier.  
     
     
         31 . The method of  claim 23  further comprising, following the step of changing, the steps of: 
 listening by the first unit and transmitting by a second unit at a priority slot of the second carrier assigned to the second unit; and  
 transmitting by the first unit and listening by the second unit at a priority slot of the second carrier assigned to the first unit.  
 
     
     
         32 . The method of  claim 23  wherein the step of measuring occurs according to a frequency-hopping mode.  
     
     
         33 . The method of  claim 32  further comprising the step of communicating the updated list over a high-speed (HS) carrier.  
     
     
         34 . A method of updating a list of acceptable carriers comprising the steps of: 
 determining whether a predetermined time period has elapsed since a plurality of carriers was last ranked according to measured quality;    determining whether a carrier change has occurred since the plurality of carriers was ranked according to measured quality; and    in response to a determination that either the predetermined time period has elapsed or that a carrier change has occurred since the plurality of carriers was ranked according to measured quality, measuring quality of the plurality of carriers and ranking the carriers according to the most recent quality measurement.    
     
     
         35 . The method of  claim 34  wherein the quality of the plurality of carriers is measured with reference to interference and multi-path fading.  
     
     
         36 . The method of  claim 35  wherein the quality of the plurality of carriers comprises a ratio of a carrier-signal-to-interference-signal strength ratio (C/I).  
     
     
         37 . The method of  claim 36  wherein I comprises external interference and self interference.  
     
     
         38 . The method of  claim 34  wherein the step of measuring occurs in a frequency-hopping mode.  
     
     
         39 . The method of  claim 34  further comprising the step of using the ranking in a high-speed mode.