The DIR series of routers don't usually support Repeater mode. Some DIR series model routers support client wireless bridge mode. Looking at the user manual on this model router, I don't see any repeater or bridge mode features.
D-Link reserves that feature for DAP model products so they probably will not be adding this feature to this model router since the model router has been discontinued here in the NA rgion:
"This product has been discontinued.
Free support for this product has ended on 03/01/2016"
http://support.dlink.com/ProductInfo.aspx?m=DIR-816LYou might check out DD-WRT or OpenWRT to see if any of those 3rd party FW sites support this model router.