What is CCK (complementary code keying)?

Complementary code keying (CCK) is utilized with wireless networks (WLANs) that utilize the IEEE 802.11b specification. CCK was accepted to improve the Barker code in wireless digital networks to achieve a data rate higher than 2 Mbit/s at the expense of shorter distance, in 1999.
This is because of the limited chipping arrangement in CCK that implies less spreading to obtain a higher data rate but more susceptibility to narrowband interference resulting in limited radio transmission range. CCK also has more chipping sequences to encode more bits, expanding the data rate even further. The Barker code, however, only has a single chipping sequence.