A Class of Band-limited Chip Waveforms for DS-CDMA Systems

The conventional frequency domain square-root raised cosine （Nyquist） chip waveform has much poorer anti-multiple-access-interference （anti-MAI） capability than the optimal band-limited waveform in direct sequence code division multiple access （DS-CDMA） systems. However, the digital implementation of the optimal chip pulse is very costly due to the slow decaying rate of the time waveform. In addition, its eye diagram and envelope uniformity arc worse than those of the Nyquist pulse for a wide range of roll-off factors, which will incur performance degradation due to timing jitters and post non-linear processing. In this paper, based on an elementary density function of a second order polynomial, a class of second order continuous pulses is proposed. From this class of pulses, we ban find some members have faster decaying rate, bigger eye opening, more uniform envdope and stronger anti-MAI capability than the Nyquist waveform. The normalized-bandwidth-pulse-shape-factor product, the decaying rate of the tail of the time waveform, the opening of the eye diagram and the envelope uniformity of the second order continuous pulses are addressed in this paper which provides the basic information for the selection of the chip pulse for CDMA systems.

A Class of Band-limited Chip Waveforms for DS-CDMA Systems