Modified Walsh‐Hadamard sequences for DS CDMA wireless systems

We propose a simple but efficient method for modifying Walsh–Hadamard sequences to achieve correlation properties suited for asynchronous DS CDMA applications. The proposed method can be used to minimize the mean square value of aperiodic cross‐correlation or the mean square value of aperiodic autocorrelation, the maximum value of aperiodic cross‐correlation functions, merit factor or other properties of the sequence set. The important feature of the method is that it modifies correlation properties of the sequence set, while preserving their orthogonality for the perfect synchronization. The proposed method can be applied to obtain bipolar, quadri‐phase, or general polyphase sequences.