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In this paper, we propose an iteration scheme for the virtual layered space frequency communication architecture. The architecture enables the decoding of the transmitted orthogonal frequency division multiplexing (OFDM)-QPSK signals even if the number of spatial multiplexed layers is twice that of receiving antennas over multipath fading channels. In the proposed iteration scheme, the MAP decoder...
In time domain synchronous (TDS)-OFDM, the channel estimation is conventionally carried out based on the pseudo noise (PN) sequence. The PN sequence based channel estimation however suffers interference from adjacent OFDM data symbols. This paper proposes a new low-complexity data-aided channel estimation method with two-dimensional (2-D) estimate refinement and interpolation. Data-aided channel estimation...
The performance reduction caused by inter-carrier interference (ICI) on orthogonal frequency division multiplexing (OFDM) systems over time-varying channels is relevant especially when large OFDM symbols are employed in order to achieve an higher throughput. In this paper we propose a design method of an equalization scheme using several full-length FFTs operating on non-overlapping windows of the...
In this paper, we employ to provide a method which combines Turbo codes and Low-Density Parity-Check (LDPC) codes based on Orthogonal Frequency Division Multiplexing (OFDM) system by adaptive encoding. The technique of channel estimation is used. The code rate and encoding scheme are all adaptive selection in the light of different channel conditions, so that we can make good use of these two types...
This paper deals with the Matlab implementation of the DVB-H (Digital Video Broadcasting to Handhelds) channel coding in AWGN (Additive White Gaussian Noise) transmission channel. Developed application structure and its functions are described. Channel encoder and decoder were implemented in Matlab as it is specified in the DVB-H standard. Created application can evaluate and shows two types of BER...
Phase noise is a topic of theoretical and practical interest in electronic circuits. Although progress has been made in the characterization of its description, there are still considerable gaps in its effects especially on multi-carrier spreading systems. In this paper, we investigate the impact of a local oscillator phase noise on the multi-carrier 2 dimensional (2D) spreading systems based on a...
Based on the high peak to average power ratio of orthogonal frequency division multiplexing systems, several methods of reducing the peak to average power ratio were analyzed. Then a method based on Golay complementary sequences was proposed to realize the low peak to average power ratio. The high peak to average power ratio sequences were encoded into Golay complementary sequences, peak to average...
In this paper, we develop and present a DFT-SOFDM system (operating in both distributed and localized FDMA modes) for transmission and reception through a frequency-selective, slow fading channel. This system allows us to use well-known linear receiver techniques such as the zero-forcing (ZF) and minimum mean-squared error (MMSE) equalization. More importantly, we proposed using a sphere decoding...
We propose the combination of orthogonal frequency division multiplexing (OFDM) and turbo decodulation (TDeC) - a multiple turbo process consisting of iterative demodulation and iterative source-channel decoding - for transmission of correlated source codec parameters over wireless frequency-selective broadband fading channels. As OFDM systems split up frequency-selective fading channels into orthogonal...
The performance of super-orthogonal space time trellis coded orthogonal frequency division multiplexing (SOTTC-OFDM) systems relies on accurate channel state information at the receiver for proper decoding. In this paper, we propose a channel estimation algorithm that takes advantage of the super-orthogonal properties of the super-orthogonal space time trellis code. The algorithm is tested via a Monte...
This paper proposes joint maximum a posteriori (MAP) detection and spatial filtering for MIMO-OFDM mobile communications, which can maintain excellent receiver performance even over interference-limited channels. The proposed joint processor consists of a log likelihood generator and a MAP equalizer. The log likelihood generator suppresses cochannel interference by spatially filtering received signals...
In this paper, we present a floating-point model for OFDM part of the IEEE 802.16a standard. This part has been assigned as the mandatory structure for WiMax. Next, we present a bit-true model for Viterbi decoder and encoder of it with the constraint of having less than 0.5 dB degradation in the performance of the system while minimizing the hardware cost of it. Since the most sensitive modulation...
In this paper we investigate the performance of array codes and in particular generalised array codes (GAC) and row and column array codes (RAC) as coding schemes in the power line communications (PLC) environment. We apply different code rates and modulation techniques and we examine how these codes perform in the hostile channel of power lines in terms of BER (bit error rate) versus Eb / N0 (signal...
For MIMO OFDM data detection, maximum-likelihood detection (MLD) has the best performance of all the detection algorithms. However, the involved computational complexity is prohibitively high for practical applications. In this paper, by optimizing trade-off between BER performance and computational complexity, we propose a combined detection scheme for MIMO OFDM systems. The combined method comprises...
Among new technologies, ultra wideband (UWB) is gathering interests as a short-reach transmission system. At present, as one of the prevailing UWB systems, the multiband-orthogonal frequency division multiplexing (MB-OFDM) system has attracted much attention where convolutional code (CC) is used. The main contribution of this paper is to evaluate the bit error rate (BER) and decoding complexity performances...
In this paper we study how power line communications are affected by different coding techniques. We investigate the case of LDPC coding scheme and its application to the PLC channel. The modulation method applied is BPSK while the transmission technique used is OFDM. We study regular LDPC codes, which is the worst case scenario concerning the performance of LDPC codes. The OFDM symbol size is initially...
In this paper, we develop a signal model for the transmission of discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-SOFDM) in a frequency selective channel. Although maximum likelihood (ML) estimation of the transmitted signal in the DFT-SOFDM system gives the optimum bit-error rate (BER) performance, it incurs exponential complexity due to its exhaustive search implementation...
We consider the decoding of bit interleaved coded modulation (BICM) applied to multiband OFDM for practical scenarios where only a noisy (possibly very bad) estimate of the channel is available at the receiver. First, a decoding metric based on the channel a posteriori probability density, conditioned on the channel estimate is derived and used for decoding BICM multiband OFDM. Then, we characterize...
A model of turbo code based on OFDM-CDMA (orthogonal frequency division multiplexing and code division multiple access) is proposed in this paper. The model consists of three parts, channel code, extending frequency and the modulation of the multicarrier, which has prominent advantages that making full use of the frequency spectrum, overcoming ISI (inter symbol interference), high reliability and...
This article presents a new method for the selection of the spreading parameters for the downlink of two dimensional (2D) OFDM-CDMA systems in the presence of channel coding. This new approach allows the determination of the spreading factor values in time (ST) and in frequency (SF) directions in order to find the most reliable 2D transmission scheme. The method is based on the exponential effective...
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