Definition - What does Complementary Code Keying (CCK) mean?
Complementary code keying (CCK) is a modulation method used in wireless local area networks (WLANs). CCK replaced the Barker Code in wireless digital networks in 1999 to achieve data rates higher than 2 Mbps, although this was at the expense of shorter range distances. The higher data rates are the result of a shorter chipping sequence in CCK, which is eight bits versus the 11 bits in Barker Code. This means that there is less spreading to obtain higher data rates, but the signal becomes more susceptible to narrowband interference, resulting in a shorter radio transmission range.
Complementary code keying is an improvement and variation of Mary Orthogonal Keying (MOK). Both use polyphase complementary codes. CCK is the modulation form used in the 802.11b standard when operating in 5.5 Mbps or 11 Mbps. CCK was chosen because it uses the same approximate bandwidth as MOK and can use the same header and preamble of pre-existing 1 and 2 Mbps wireless networks, thus facilitating interoperability.
WLANs with the 802.11b standard specification use CCK to operate at either 5.5 Mbps or 11 Mbps in the radio frequency band at 2.4 GHz to 2.4835 GHz. WLANs following the 802.11g standard use CCK when running at 802.11b speeds and at 54 Mbps. These WLANs use a more sophisticated modulation scheme called orthogonal frequency division multiplexing.
Complementary codes were first introduced by Marcel Golay in 1961. These codes are sets of finite sequences of equal length, or pairs of complementary binary codes.