ePMP 3000 down link percentage 0

My ePMP 3000 module's downlink percentage in MIB is always 0. 

1.3.6.1.4.1.17713.21.2.1.113.0

dlWLanTotalAvailableFrameTimePercentage OBJECT-TYPE
        SYNTAX     Integer32
        MAX-ACCESS read-only
        STATUS     current
        DESCRIPTION
                "Aggregated downlink frame 10X percentage time
                Range = [1..1000] 0.1% = 1; 100% = 1000
                Device Allocation: AP"
        ::= { cambiumPerformanceMonitoring 113 }