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Since its advent, the wavelet filtering technique provides time-diversity gains to M-ary digital communications systems, while it keeps their spectral efficiency unaffected. However, the receiver design is more critical under this novel time-diversity transmission system. To tackle this problem, we propose a MMSE-based receiver. This paper presents the performance evaluation of a novel wavelet-filtered...
This paper proposes a novel OFDM demodulation scheme, which achieves superior performance even in fast time-varying multipath fading channels where the conventional OFDM demodulator degrades seriously because of time selectivity in the channel. The proposed scheme consists of several equalizers which equalize received signals with channel impulse responses at different time instants in parallel. A...
Within the context of high-data rate transmissions over time varying multipath fading channels, this article presents a new receiver design for orthogonal frequency division multiplexing (OFDM) systems. The received signal is processed jointly in time and frequency domains. A Discrete Wavelet Transform is applied to the received signal before equalization which is based on the minimum mean square...
Traditionally, the performance of blind SIMO channel estimates has been characterized in a deterministic fashion, by identifying those channel realizations that are not blindly identifiable. In this paper, we focus instead on the performance of Linear Equalizers for fading channels when they are based on blind channel estimates. Our analysis shows that with Zero Forcing Linear Equalizer (ZF-LE) at...
This paper proposes a scheme of continuous phase modulation (CPM) receivers using frequency domain equalization and conventional parallel and serial CPM receiver structures. Frequency domain equalizers for CPM block transmissions provide spectral and power efficient wireless communications with less complexity than conventional time-domain processing receivers over frequency selective fading channels...
Multicarrier-based waveforms offer significant advantages for opportunistic cognitive radio systems through the ability to shape the spectrum of transmitted signal by deactiving subcarriers. In MC-CDMA based cognitive radio, deactiving some subcarriers to avoid interference with primary users, causes the loss of orthogonality among the spreading codes and therefore the performance of the system reduces...
A factor in designing the future personal mobile radio systems is undoubtedly a comprehensive knowledge about propagation characteristics over different types of environments. Propagation studies are therefore essential as these studies will lead to channel models and statistical parameters which could be used to design intelligent systems. The transmitted signal most often reaches the receiver through...
In this paper, we consider joint iterative equalization and channel estimation for TDMA systems over a frequency selective, quasi-static fading channel. We assume a slowly varying channel impulse response from one burst to the following one. We modify the maximum a posteriori (MAP) criterion by taking into account an a priori channel estimate obtained from the burst preceding the one processed. Assuming...
A linear chip-level equalizer based on the subband adaptive decomposition is investigated for downlink direct-sequence (DS) ultrawideband (UWB) systems to cope with both the inter-symbol interference (ISI) and the multiple-access interference (MAI) in multipath fading channels. The sub-band decomposition technique is employed to improve substantially the downlink DS-UWB reception of mobileterminal...
This paper proposes a new orthogonal frequency-division multiplexing (OFDM) structure to smooth the frequency notches of a wireless fading channel. The proposed system is based on a property that the KN-point inverse fast Fourier transform (IFFT) transmitter of an OFDM system can be realized by utilizing an N-point IFFT transmitter. The proposed OFDM system will generate a filter to smooth the frequency...
We present an adaptive soft-input soft-output (SISO) turbo equalization receiver for doubly-selective multiple-input-multiple-output (MIMO) channels. The proposed receiver exploits the complex exponential basis expansion model (CE-BEM) for the overall channel variations, and an autoregressive (AR) model for the BEM coefficients. We extend an existing single-user turbo equalization approach based on...
In this paper, we investigate the use of cyclic frequency diversity (CFD) scheme for single-carrier packet retransmission over frequency-selective channels in the context hybrid automatic repeat request protocols (HARQ). For each retransmission of the same packet, the transmitted signal is cyclically shifted in the frequency-domain in order to compensate for channel fading over a part of the channel...
In this paper, a novel demodulation structure in high-frequency (HF) channel is introduced and studied. Frequency-offset estimation, fractionally spaced adaptive equalization and carrier recovery techniques are involved. Frequency-offset correction is carried out based on channel impulse response estimation. Fractionally spaced adaptive equalization and carrier recovery are combined with non-linear...
A joint estimation and compensation algorithm of the carrier frequency offset (CFO) and sampling clock offset (SCO) is proposed for orthogonal frequency division multiplexing (OFDM) systems under multipath fading channels. First, we propose the joint weighted least-squares (JWLS) algorithm with intercarrier interference (ICI) cancellation to enhance the accuracy of the CFO and SCO estimation. Next,...
In this work we analyse the performance of a joint coding-precoding scheme for OFDM systems over fading channels. The design of the precoder is based on the information redistribution of the input modulated symbols amongst all the output precoded symbols. The proposed precoder decreases the variance of the instantaneous noise power at the receiver produced by the channel variability. In this sense,...
In this paper, we propose a novel receiver consists of the Inter Symbol Interference (ISI) canceller and the turbo equalizer for orthogonal frequency division multiplexing (OFDM) systems over frequency selective fading channels where the multipath delay exceeds the guard interval duration. The proposed turbo equalization algorithm performs soft Inter Carrier Interference (ICI) cancellation and frequency...
We address the issue of low complexity linear equalization for cyclic-prefix (CP) and zero-padded (ZP) block transmissions (OFDM). While cyclic-prefix (CP) OFDM does not exploit frequency diversity offered by multipath fading, use of appropriate redundant linear preceding permits a linear equalizer (LE) to benefit from full diversity in the frequency selective channel. We exploit excess time of block...
In this paper, we analysis the receiver of orthogonal frequency division multiplexing (OFDM) systems over frequency selective fading channels where the multipath delay exceeds the guard interval duration and propose a novel receiver scheme. The proposed receiver consists of the Inter Symbol Interference (ISI) canceller and the turbo equalizer. At each iteration, the proposed turbo equalization algorithm...
To cope with the deleterious channel fading effects on the system performance, diversity-enriched transmitters and receivers have well-appreciated merits. When the channel state information is available at the transmitter, precoders are designed to suppress the channel effect and enable the diversity and low-complexity receiver designs. In addition, the peak-to-average power ratio (PAR) issue has...
We address diversity order of linear equalization for block transmission in fading channels. It is known that zero-padded (ZP) block transmission allows LE to achieve full multipath diversity present in frequency selective channels. We show here that, in a dual fashion, LE can achieve full Doppler-diversity in time-selective channels when guard bands are inserted in the transmit signal. For these...
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