Second order polynomial class of chip waveforms for band-limited DS-CDMA systems |
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| Authors: | Rongfang Song S H Leung |
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| Affiliation: | (1) College of Telecommunication and Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing, 210003, China;(2) National Mobile Communications Research Laboratory, Southeast University, Nanjing, 210096, China;(3) Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China |
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| Abstract: | 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 are worse than the Nyquist pulse for a wide range of roll-off factor,
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 continuity pulses is proposed. From this
class of pulses, we can find some members having faster decaying rate, bigger eye opening, more uniform envelope and stronger
anti-MAI capability than the Nyquist waveform. The normalized-band-width-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 continuity
pulses are addressed in the paper that provide the basic information for the selection of the chip pulse for CDMA systems. |
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| Keywords: | Chip waveform DS-CDMA Eye diagram Envelope uniformity |
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