About 802.15
802.15 are popularly known as WPAN (Wireless Personal Area Network). 802.15 entirely deal with short distance wireless networks and addresses wireless networking of portable and mobile computing devices. WPAN has laid down the standards for communication, interoperability of such devices.

Salient Features of 802.15
Short Range
Low Power
Low Cost
Handle small Networks
Communication with in a proximity

802.15 Working Groups
IEEE 802.15 working group addresses the standards for WPANs. It has been split into four groups.
802.15.1: This task group is responsible for developing the standards for low-power, low-cost, flexible WPANs and is fully based on Bluetooth Specification and is fully compatible with Bluetooth 1.1.
802.15.2: This task group is responsible for developing recommended practices on how 802.11 WLAN and 801.15 WPAN can co-exist in the 2.4 GHz band.
802.15.3 (High Speed): This task group is responsible for developing and delivering the  higher  speed WPANs from  10 Mbps to 55 Mbps at a distance less than 10 meters.
802.15.4 (Low Speed): This task group is responsible for creating standard for simple, low-cost, low speed WPANs. Data transmission ranges from 2 Kbps to 200 Kbps and uses DSSS modulation in the 2.4 GHz and 915 MHz ranges. It uses 16 channels in the 2.4 GHz band, 10 channels in the 915 MHz band, and one channel in 868 MHz band.