Filtreler
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

Performance analysis of multi chip/data rate DS-CDMA signals over multipath Rayleigh fading channels

Öztürk E.

Conference Object | 2006 | IWCMC 2006 - Proceedings of the 2006 International Wireless Communications and Mobile Computing Conference2006 , pp.15 - 20

This paper investigates the Probability error (Pe) performance of Multi-Chip/Data Rate Direct Sequence Code Divisions Multiple Access (MCDR/DS-CDMA) systems over multi-path Rayleigh fading channels. Two chip waveforms, raised cosine (RC) and an orthogonal wavelet, are compared numerically in terms of the Pe. The results represent that the wavelet based system significantly outperforms the RC based system in terms of the P e. On the other hand, the wavelets have greater bandwidths than the RC waveforms. Thus, two systems are also compared in terms of the capacity (the number of users per Hertz) for the same Pe level. The results for . . .the capacity show that the wavelet based design has 3% and 41% more capacity than the RC based system for the medium and low rate users, respectively, while the RC based system provides 7% higher capacity than the wavelet based system for high data rate users. Since the average power of wavelets is zero, they can utilize a Single Side Band (SSB) transmission. With the SSB transmission, the wavelet based system has 86%, 106% and 182% more capacity for the high, medium and low data rate users, respectively. Copyright 2006 ACM Daha fazlası Daha az

Multi-scale direct sequence ultra wide band communications

Öztürk E. | Chen H.H.

Conference Object | 2009 | Proceedings of the 2009 ACM International Wireless Communications and Mobile Computing Conference, IWCMC 2009 , pp.324 - 327

Multi-scale direct sequence ultra wide band (MS/DS-UWB) is a new multiple access technique for UWB communications. It utilizes the dyadic (i.e., with a power of two) scaled orthogonal wavelets spread by direct sequence codes creating dyadic scaled multi-band structure exposing the scalability of the spectrum. Services are assigned to different orthogonal sub-bands with respect to their data rates. Comparing to the conventional DSUWB, increased pulse durations reduce the complexity of the conventional DS-UWB system. We show that the spectral structures of MS/DS-UWB using the four scales of Daubechies-5 and Daubechies-10 wavelets fit . . .in to the FCC UWB mask. In terms of the probability of error performance over an asynchronous awgn channel, the proposed design promises better performances compared to a single band UWB design when multi-rate services are available. Copyright 2009 ACM Daha fazlası Daha az

Optimization of wavelet based OFDM for multipath powerline channel by genetic algorithm

Kumbasar V. | Kucur O. | Ergin A.A. | Öztürk E.

Article | 2009 | Wireless Communications and Mobile Computing9 ( 9 ) , pp.1243 - 1250

Using genetic algorithm (GA), optimal wavelets are obtained to reduce ISI and ICI powers of a wavelet-based orthogonal frequency division multiplexing (OFDM) system over a practical two path low-voltage powerline channel or two path fading channel by relaxing the perfect quadrate mirror filter (QMF) orthogonality. Optimum wavelet-based OFDM system experiences less interference compared to conventional and Daubechies (Db) wavelet-based OFDM systems. © 2008 John Wiley & Sons, Ltd.

Comparisons of various pulse shapes for DS-UWB signals over the UWB channel

Öztürk, Ertan | Yılmaz, Ergin

Article | 2009 | Telecommunication Systems42 ( 03.Apr ) , pp.213 - 222

In this paper, we first investigate the power spectral densities (PSD) of bipolar modulated Direct Sequence Ultra Wide Band (DS-UWB) signals using various pulse shapes under the FCC UWB emission mask. Considered pulse shapes are the first five derivatives of the Gauss pulse (p 1 , p 2 , p 3 , p 4 and p 5 ), the first four orthogonal modified Hermite waveforms, and Daubechies wavelets (db-q). It is observed in the PSD results that p 4 and p 5 Gauss pulses, the Daubechies (db-q) for q>4 comply with the FCC UWB rule by selecting proper values for the pulse duration. Then, we derive the pulse shape dependent probability of error expr . . .ession for bipolar DS-UWB signals over the standard UWB channel. The five pulse shapes (p 4 , p 5 , db-5, db-6 and db-7) complying with the FCC emission mask are numerically compared by using the derived probability of error expression over the CM1 model of the Standard UWB channel. Results reveal that the Daubechies have better performance than those of the two Gauss pulses. © 2009 Springer Science+Business Media, LLC Daha fazlası Daha az

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