also complementary pairs. There is a simple constructive method to create arbitrarily long complementary sequences. For the case of cyclic autocorrelation, other sequences have the same property of having perfect (and uniform) sidelobes, such as prime-length Legendre sequences, Zadoff–Chu sequences (used in 3rd and 4th generation cellular radio) and maximum length sequences (MLS). Arbitrarily long cyclic sequences can be constructed. Barker modulation In wireless communications, sequences are usually chosen for their spectral properties and for low cross correlation with other sequences likely to interfere. In the 802.11 standard, an 11-chip Barker sequence is used for the 1 and 2 Mbit/sec rates. The value of the autocorrelation function for the Barker sequence is 0 or −1 at all offsets except zero, where it is +11. This makes for a more uniform spectrum, and better performance in the receivers. References Wireless networking Line codes Binary sequences Coding theory Digital signal processing