Video Playback lagging with 1080p files over WiFi

I’m running OSMC on a Raspberry Pi 2. Files are stored in a Time Capsule, which is configured as a SMB data source over WiFi. 720 videos and music run smoothly, but 1080 files are laggy. Any suggestions? I’ve tried with basic configurations, like switching acceleration on and off, and so on.

Wifi-g ?
Wifi-n ?
Wifi-a/c ?
Try using NFS, however… 1080p movies are most likely going to buffer over wifi due to the available bandwidth available on a wifi network.

Thanks for your reply. It is WiFi N. Any possible solutions?

powerline networking.