如何使用openwrt路由系统剔除弱信号设备？

#!/bin/bash
while true;
do
    maclist=(`iw dev wlan0 station dump | grep "Station" | cut -f 2 -s -d " "`)
    rxlist=(`iw dev wlan0 station dump | grep "signal:" | cut -f 3 -s -d " "`)
    #maclist=(`iwinfo wlan0 assoclist | grep "dBm" | cut -f 1 -s -d " "`)
    #rxlist=(`iwinfo wlan0 assoclist | grep "dBm" | cut -f 3 -s -d " "`)
    rxref="-80"  #threshold
    len=${#maclist[@]}
    for((i=0;i<$len;i++))
    do
        mac=${maclist[$i]}
        rx=${rxlist[$i]}
        # here, use string comparation, simple but error prone
        if [[ "$rx" > "$rxref" ]]; then
            #echo $mac $rx
            ubus call hostapd.wlan0 del_client ‘{"addr":"‘"$mac"‘", "reason": 5, "deauth": True, "ban_time": 3000}‘
            #ubus call hostapd.wlan0 list_bans
        fi
    done
    sleep 1
done