Design of despreading sequences with low cross-correlation properties

In this paper, we propose and investigate despreading sequences in co-channel interference environment. Spread spectrum (SS) techniques usually spread the information signal by a sequence and despread the spreading signal using the transmitted sequence. This method (using matched filter MF) is optimum in the AWGN channel without co-channel interference. However, MF isn´t necessarily optimum with co-channel interference. Because there are cross-correlation values between the interference signal and the despreading sequence. We propose the despreading sequences which can cancel the interference sequence. In other words, the despreading sequences are orthogonal with the interference sequence. The despreading sequences are generated toward two goals. One is to be orthogonal with the interference sequence. The other is to obtain the largest correlation value between the desired sequence and the despreading sequence under an orthogonal condition. We evaluated correlation and bit error performance by computer simulation. Comparisons show that the method suppress co-channel interference and improves BER performance.