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Kavitha, K. V. N.
- Basis Expansion Models Analysis for MIMO/OFDM Systems
Authors
1 School of Electronics Engineering, VIT University, Vellore, Tamil Nadu, IN
2 School of Electronics Engineering, VIT University, Vellore, Tamil Nadu, IN
Source
Wireless Communication, Vol 3, No 6 (2011), Pagination: 398-402Abstract
We consider Channel estimation for multiple-input multiple-output/orthogonal frequency-division multiplexing (MIMO/ OFDM) systems in time-varying wireless channels using superimposed training (ST). By using a discrete prolate spheroidal basis expansion model (DPSS) and truncated discrete fourier bases expansion models (Fourier-BEM) for representing the time varying channel. Based on these models, a weighted average approach is adopted for estimating linear time varying (LTV) channels for OFDM symbols. The performance analysis between two BEM models based on Mean square error (MSE) is present in this paper. Simulation results show that the DPSS-BEM model outperforms the Fourier Bases expansion model.Keywords
Basis Expansion Models (BEMS), MIMO/OFDM, Slepian Sequences, Superimposed Training.
- Interference Reduction in MB-OFDM Ultra Wideband Systems using Block Turbo Code
Authors
1 VIT University, Vellore, IN
2 Communication Engineering from VIT University, IN
Source
Wireless Communication, Vol 2, No 10 (2010), Pagination: 366-371Abstract
OFDM can provide large data rates, many research centers in the world have specialized teams working in the optimization of OFDM for countless applications. Coded-OFDM is robust to radio fading channels impairments. Since the UWB spectrum has the unlicensed nature all wireless devices sharing the spectrum must coexist. According to MBOA, multiband OFDM is capable of complying with local regulations by dynamically turning off certain tones or channels in software, which speaks to their favor.To suppress the side-band interferences in Ultra wideband(UWB)caused by multiband orthogonal frequency division multiplexing (MB-OFDM), a soft-spectrum adaptation based Detect and Avoid mechanism is proposed. Detection technique is based on power spectrum density estimation and Avoidance mechanism is based on subcarrier nullifying using windowing. A type of block Turbo code modulation scheme is proposed. In the modulation scheme, the sideband interferences are attenuated quickly. Simulation result of softspectrum based detect and avoid technique is shown along with SNR performance comparison between coded and uncoded OFDM.