Le RPi3 a tendance à perdre le wifi.

Il faut désactiver le power management

sudo nano /etc/network/interfaces

auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
wireless-power off
iface default inet dhcp

sudo iwconfig

wlan0 IEEE 802.11bgn ESSID:"XXXXXX"
Mode:Managed Frequency:2.447 GHz Access Point: XX:XX:XX:XX:XX:XX
Bit Rate=57.7 Mb/s Tx-Power=31 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=60/70 Signal level=-50 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:33 Invalid misc:0 Missed beacon:0