Title :
Over-loaded DS-CDMA system waveform design using doubly orthogonal wavelet packets
Author :
Zhang, Hongbing ; Fan, H. Howard ; Lindsey, Alan
Author_Institution :
GIRD Syst. Inc., Cincinnati, OH, USA
fDate :
6/23/1905 12:00:00 AM
Abstract :
One significant difference between CDMA systems and FDMA/TDMA systems is that the number of users supported in a CDMA system is not hard-limited by the number of frequency bands or time slots. Whenever a new user is added to a CDMA system, the existing users will suffer a slightly higher interference level. The interference level highly depends on the orthogonality of user waveforms. We present an algorithm to construct a set of wavelet packet based user waveforms for CDMA systems. This algorithm provides more signature waveforms than previously proposed wavelet packet based waveform division systems. The basic waveform set is constructed utilizing double orthogonality based on wavelet packets and binary Walsh codes. This double orthogonality produces auto- and cross-correlations that are much better than the conventional wavelet packet sets and are comparable to the pseudo random binary codes. Under system overload, the waveforms introduce a tolerable interference level to the users
Keywords :
Walsh functions; binary codes; code division multiple access; packet radio networks; radiofrequency interference; random codes; spread spectrum communication; wavelet transforms; Walsh codes; autocorrelation; cross-correlation; doubly orthogonal wavelet packets; interference level; over-loaded DS-CDMA system; pseudo random binary codes; waveform design; waveform division systems; Algorithm design and analysis; Amplitude modulation; Binary codes; Contracts; Detectors; Interference; Multiaccess communication; Narrowband; Timing; Wavelet packets;
Conference_Titel :
Vehicular Technology Conference, 2001. VTC 2001 Fall. IEEE VTS 54th
Conference_Location :
Atlantic City, NJ
Print_ISBN :
0-7803-7005-8
DOI :
10.1109/VTC.2001.956929
