Wireless as in WISP, WiMAX, or Mobile (HSPA, LTE, CDMA, etc)?
There's no "standard" speed, because what constitutes wireless Internet varies greatly. Things like weather interfere with it (cloudy, humidity, rain/snow, dust, wind, etc), building materials, distance from nearest tower, what the nearest tower's theoretical maximum output is, MIMO support, number of clients connected to that tower, load-balancing, and, as noted above, the technology being used to provide the wireless Internet.