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Adaptive bit-loading algorithms can improve the performance of OFDM systems significantly. The tradeoff between the algorithms performance (optimum solution) and the computational complexity is essential for implementation of loading algorithms. In this paper, we present a low complexity non-iterative discrete bit-loading algorithm to maximize the data rate subject to specified target BER and uniform...
This work proposes an adaptive frequency-domain equalizer (FDE) for single carrier and OFDM indoor over Gbps data rate wireless receiver. System simulation and specifications are based on the IEEE 802.15.3c standard. The proposed LS-LMS FDE uses low computational complexity Least-Mean-Square (LMS) algorithm with Least-Square (LS) channel estimation to accelerate the convergence speed. The FDE can...
Nonorthogonal Frequency Division Multiplexing (NOFDM) is a digital modulation technique that promises to provide extremely high spectral efficiencies. However, this modulation scheme is seldom used in practice due to the high computational complexity involved in decoding the received signal in the presence of noise. The basic aim of this paper is to reduce this decoding complexity. Here, we propose...
A bit loading algorithm is presented for orthogonal frequency division multiplexing (OFDM) systems to minimize bit error rate (BER), where quadrature amplitude modulation (QAM) is employed. The target data bits are loaded onto selected subcarriers that have largest remaining signal-to-noise ratio (SNRrem) values on a group-by-group basis. The number of iterations is determined by the maximum size...
The channel estimation algorithms are employed in 3GPP Long Term Evolution (LTE) downlink system to assist the coherent demodulation of Orthogonal Frequency Division Multiplexing (OFDM) symbols. Based on the comparison of several exiting different channel estimation algorithms, we propose a joint time-frequency two-dimensional iterative Wiener filter (IWF) channel estimation algorithm for 3GPP LTE...
In this paper, we propose a blind SLM scheme using cyclic shift (BSLM-CS) in STBC MIMO-OFDM. After an OFDM signal sequence in each transmit antenna is cyclically shifted, alternative signal sequences in the proposed scheme are generated by linearly combining OFDM signal sequences using addition and subtraction without the need of the additional IFFT. Therefore, the proposed BSLM-CS scheme has low...
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...
For single-carrier systems with frequency domain equalization, decision feedback equalization (DFE) performs better than linear equalization, and has a lower complexity and computational costs than optimum equalizers. The main challenge in DFE is the feedback symbol selection rule. In this paper, we give a theoretical framework for a simple, sparsity based thresholding algorithm. We feedback multiple...
In this paper, a new SLM scheme for peak to average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems is proposed. This scheme is special case of selected mapping (SLM) scheme. The proposed SLM scheme generates alternative OFDM signal sequences by exploiting the intermediate OFDM signal sequence in inverse fast Fourier transform (IFFT). By using this technique,...
Multi-user multi-input multi-output (multi-user MIMO) can increase the number of users simultaneously accessing the same base station (BS) without increasing the signal bandwidth. MIMO signal detection which can provide better bit error rate (BER) performance than linear detection with less computational complexity is indispensable in order to enhance the uplink cellular capacity of multi-user MIMO...
Traditional detection algorithms for frequency selective Orthogonal Frequency Division Multiplexing Vertical-Bell Labs Layered Space-Time system (OFDM-V-BLAST) suffer from high computational complexity. So it's necessary to develop a detection algorithm to minimize the computational complexity and improve BER performance. This paper presents a new reduced-rank detection algorithm based on MMSE Sorted...
Adaptive HF OFDM system can improve the transmission performance by bit and power loading based on the characteristic of subchannel. Greedy algorithm is the optimal method for finite granularity bit allocation, but it has high computational complexity. A new improved bit and power loading algorithm is proposed for HF OFDM systems in this paper, some bits is pre-allocated to some subchannels based...
Multi-user cognitive orthogonal frequency division multiplexing (C-OFDM) is an extremely promising technique for achieving high transmission capacity in the next generation cellular and wireless local area network (WLAN) systems with limited spectrum resources. And a proportional fairness subcarriers allocation algorithm based on the margin adaptive (MA) principle is used to meet the rate fairness...
We propose two practical schemes for the cancellation of nonlinear distortions caused by the power amplifiers (PA) in Orthogonal Frequency Division Multiplexing (OFDM) systems. The algorithms are iterative and located at the receiver. They utilize a soft channel decoder to improve the capabilities of the distortion estimation and relay all the computational complexity to the receiver. Simulation results...
Adaptive coded modulation (ACM) is a key technique to increase spectral as well as power efficiency for orthogonal frequency division multiplexing (OFDM) systems. In this paper, an efficient rate adaptive low density parity check (LDPC) coded modulation (RALCM) algorithm is proposed, which maximizes the payload rate for OFDM systems under the constraint of the given transmit power and the target bit...
This paper introduces a new multicarrier system that uses a low computational complexity transform developed by Boussakta to combine the Walsh-Hadamard Transform (WHT) and Discrete Fourier Transform (DFT) into a single orthogonal transform or as a transition from one transform domain to another. The proposed transform is used in a new orthogonal frequency division multiplexing (T-OFDM) system, across...
This paper introduces a novel multicarrier system called the BPSK modulated parallel combinatory / half-symbol multicarrier modulation (PC/HS-MCM) system by combining the BPSK modulated HS-MCM system and the parallel combinatory code. The proposed system can achieve twice bandwidth efficiency (BWE) than that of the BPSK modulated PC-OFDM system by sending a half time-domain BPSK-modulated PC-OFDM...
This paper proposes a bit loading algorithm for orthogonal frequency division multiplexing (OFDM) systems. With the restrictions of available transmit power and required bit-error-rate (BER) performance, the algorithm aims at achieving the maximal data rate. Although the proposed algorithm is based on the Hughes-hartogs algorithm, the computational complexity is only O(k × M), where k denotes the...
In this paper, a new transmit waveform design algorithm for MIMO-OFDM systems is proposed. The algorithm is based on a geometric channel model consisting of different paths, where the geometric channel parameters are assumed to be known. Using the spatial channel information at the transmitter, the frequency selective MIMO channel is transformed into a number of uncoupled flat-fading SISO channels...
Multiple-Input Multiple-Output (MIMO) antennas and Multi-Carrier Code Division Multiple Access (MC-CDMA) are very promising candidates for simultaneous utilize in 4G systems, since they attain robustness, high spectral efficiency, and high data rates in rich scattering environments. This paper proposes an efficient hybrid detection algorithm for downlink MC-CDMA system based on Orthogonal Frequency...
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