Filtreler
Performance of optimum wavelet waveform for DS-CDMA chip waveform over QS-AWGN channel

Öztürk E. | Kucur O. | Atkin G.E.

Article | 2006 | International Journal of Communication Systems19 ( 1 ) , pp.1 - 16

In this paper, we search for a better chip waveform based on orthogonal wavelets for direct sequence-code division multiple access (DS-CDMA) signals to improve the probability of error (Pe) performance with minimal signal bandwidth variations. First, we derive the Pe expression over a quasi-synchronous additive white Gaussian noise channel for DS-CDMA signals, which use various pulse shaping waveforms including orthogonal wavelets as chip waveforms. It is observed that this expression depends on the chip waveform. Then, we design an optimum wavelet by using the relationship between wavelets and filter coefficients to reduce the prob . . .ability of error. The DS-CDMA system using the optimum wavelet waveform results in a lower probability of error than those using the conventional chip waveforms such as raised cosine, half-sine and rectangular waveforms. Especially, the Pe of the optimum wavelet-based scheme becomes significantly better than those of the conventional chip waveforms-based schemes under the heavy loading that is the case for commercial wireless systems. When the systems work with full load (i.e. the number of users equals the processing gain), the optimum wavelet-based system results in 0.5, 2.1 and 4 dB better SNR values than those of the raised cosine, half-sine and rectangular-based systems, respectively, for a Pe value of 10-3. Copyright © 2005 John Wiley & Sons, Ltd Daha fazlası Daha az

Performance of optimum wavelet for DS-CDMA chip waveform over multi-path Rayleigh fading channels

Öztürk E. | Şahin B.

Article | 2007 | International Journal of Communication Systems20 ( 9 ) , pp.1081 - 1095

In this paper, the probability of error (Pe) expression of asynchronous direct sequence-code division multiple access (DS-CDMA) signals using band-limited chip waveforms is derived over multi-path Rayleigh fading channels. In receiver, a matched filter-based rake receiver in conjunction with maximum ratio combiner (MRC) is considered. Numerical values for the P e are calculated for various chip waveforms including an optimum wavelet waveform. Analytical results are verified by conducting simulations. Results show that the optimum wavelet-based scheme outperforms time-limited raised cosine, half sine, rectangular and band-limited squ . . .are-root raised cosine chip waveform-based schemes in terms of the Pe and the capacity defined as the number of users per Hertz for a same Pe level. Copyright © 2006 John Wiley & Sons, Ltd Daha fazlası Daha az

Bit error rate performance of Haar wavelet based scale-code division multiple access (HW/S-CDMA) over the asynchronous AWGN channel

Kucur O. | Öztürk E. | Atkin G.E.

Article | 2007 | International Journal of Communication Systems20 ( 4 ) , pp.507 - 514

In this paper, we study a recently proposed multirate system, called wavelet based scale-code division multiple access (W/S-CDMA). W/S-CDMA depends on the code, time and scale orthogonality introduced by pseudo-noise (PN) sequences, and wavelets. In this system, the channel is partitioned into different scales, and each scale into time slots. In addition, the PN sequences are used in each scale to identify multiple users. In W/S-CDMA, each user is assigned a specific scale and PN sequence, and transmits its successive information symbols with its PN sequence and the wavelets in that scale. More symbols are transmitted in finer scale . . .s. We analyse the bit error rate performance of Haar wavelet based S-CDMA (HW/S-CDMA) over an asynchronous additive white Gaussian noise (AWGN) channel by using a conventional detector for deterministic PN sequences. The performance of the system is compared to that of an equivalent multirate CDMA (MR-CDMA) system for Gold and Kasami PN sequences. Results show that HW/S-CDMA outperforms MR-CDMA. In addition, because of its suitable format HW/S-CDMA is also capable of employing the optimal PN sequence families with limited number of sequences such as Kasami, Bent, etc. repeatedly in different scales. Copyright © 2006 John Wiley & Sons, Ltd Daha fazlası Daha az

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