In this case basically If other Wi-Fi sources such as neighboring wireless access points are using the same wireless channel, this may cause intermittent connectivity issues, even if the competing signal is relatively weak. Changing the wireless channel within the  gateway can improve connectivity. so please follow the steps mentioned on the below article. After changing WIFI channel as recommended on the link restart the modem then i would request you to monitor the connection for next 24hrs. If still issue persist we need to check the cable signal level on your modem to work on this case further.

http://arris.force.com/consumers/articles/General_FAQs/SBG6950AC2-Changing-the-Wi-Fi-Channel

http://arris.force.com/consumers/articles/General_FAQs/SBG6950AC2-Cable-Signal-Levels