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Inter-carrier interference (ICI) caused by time-variant multi-path channels degrades the performance of orthogonal frequency division multiplexing (OFDM) based digital terrestrial television broadcasting systems, especially for large number of sub-carriers and high speed mobile reception. In this paper, we propose an minimum mean square error (MMSE) based equalization and ICI mitigation scheme for...
In this paper, the impact of interferers that are not synchronized in frequency is investigated in multi-antenna OFDM systems. Exact closed-form expressions for the outage probabilities are derived for two spatial linear receivers: the matched-filter (MF) receiver and the linear minimum-mean-square-error (LMMSE) receiver, assuming correlated frequency-selective Rayleigh fading channels and carrier...
This paper presents a theoretical analysis of the performance of a filter bank-based multicarrier spread spectrum (FB-MC-SS) system. In FB-MC-SS, each data symbol is spread across multiple subcarriers, but — contrary to some other systems — there is no spreading in time. The results of this system are then compared with those of the well-known direct sequence spread spectrum (DS-SS) system with a...
Recent advances in microwave technology and signal processing have unveiled the potential of the so-called wireless power transfer (WPT) from one device to the other. This has resulted in reducing the need of a local power source at the wireless devices. In this paper, we target a popular physical layer technology, namely the orthogonal frequency division multiplexing (OFDM) and propose a novel approach...
Wideband spectrum sensing (SS) allows cognitive radios (CRs) to reach, by monitoring large portions of spectrum, a better awareness of the surrounding radio environment. In this paper, we formulate wideband SS as a model order selection problem. This approach consists in the adoption of information theoretic criteria (ITC) to identify the occupied frequency components in a frequency domain representation...
This paper considers the coded OFDM system and instead of discarding the cyclic prefix (CP) at the receiver, we utilize the CP observation for joint detection, decoding and channel estimation. In particular, detection and decoding are performed iteratively between an equalizer and a soft-input soft-output (SISO) decoder based on the turbo principle, and the expectation-maximization (EM) algorithm...
Compared with standard cyclic prefix OFDM (CP-OFDM), time domain synchronous OFDM (TDS-OFDM) can achieve a higher spectrum efficiency by using the known training sequence instead of CP as the guard interval. However, TDS-OFDM suffers from reduced energy efficiency and performance loss due to the existing mutual inferences. In this paper, based on the newly emerging theory of structured compressive...
In this paper, equalization of multihop relaying orthogonal frequency division multiplexing (OFDM) signal is investigated under time-varying channel with unknown noise powers, channel orders and Doppler frequencies. An iterative algorithm is developed under variational expectation maximization (EM) framework. The proposed algorithm iteratively estimates the channel, learns the channel and noise statistical...
In this paper, we consider the application scenario where multiple Base Stations (BSs) cooperate to transmit signals to a mobile terminal in the same frequency and any of the cooperative BSs is allowed to enter into sleeping mode to save energy. The mobile terminal employs the Joint Maximum Likelihood Sequence Estimation (JMLSE) based Joint Signal Detection (JSD) to simultaneously detect multiple...
Due to the high cost and power consumption of radio frequency (RF) chains, millimeter wave (mm-wave) communication systems equipped with large antenna arrays typically employ less RF chains than the antenna elements. This leads to the use of a hybrid MIMO processor consisting of a RF beamformer and a baseband MIMO processor in mm-wave communications. In this paper, we consider amplify-and-forward...
We propose a low-complexity frequency synchronization approach for semi-blind independent component analysis (ICA) based coordinated multi-point (CoMP) orthogonal frequency division multiplexing (OFDM) systems, with multiple carrier frequency offsets (CFOs). The key idea is to introduce a short pilot for both multi-CFO estimation and ambiguity elimination in the ICA equalized signals. First, by minimizing...
Cooperative communication systems employ cooperation among nodes in a wireless network to increase data throughput and robustness to signal fading. However, such advantages are only possible if there exist perfect synchronization among all nodes. Impairments like channel multipath, time varying phase noise (PHN) and carrier frequency offset (CFO) result in the loss of synchronization and diversity...
Energy efficiency has currently become one of the central topics in today's wireless communication industry. In this paper, we focus on the energy-efficient design in downlink multi-user MIMO-OFDM systems, so as to optimize the energy efficiency with users' quality of service (QoS) guarantees. Particularly, an optimization problem concerning power allocation is formulated, where the objective is the...
In this paper, we present a sparse channel estimation method for orthogonal frequency division multiplexing (OFDM) based two-way relay networks (TWRN). Conventional channel estimation methods, such as least squares (LS), have been proposed to obtain channel state information (CSI) at the cost of the training resource, which reduce spectrum efficiency. However, physical measurements have verified that...
In what follows signal-code constructions employing block and convolutional nonbinary inner codes that can perform under severe jamming are proposed. Robustness of the proposed signal-code constructions to jamming is verified by means of simulation.
Collision resolution via interference cancellation (IC) in packet-based random multiple access (RMA) systems is a promising technique to decrease number of retransmissions and increase overall throughput. This paper proposes novel iterative algorithm of IC in OFDM systems for the case when one of the interfering packets is known to the receiver. Comparing to well-known successive interference cancellation...
This paper is concerned with a challenging problem of channel estimation for amplify-and-forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in the presence of sparse underwater acoustic channels and of the correlative non-Gaussian noise. We exploit the sparse structure of the channel impulse response to improve the performance of the channel estimation algorithm,...
Motivated by dual use of OFDM signal format for communications and radar in ever-worsening Electromagnetic (EM) coexistence environments, this paper deals with transmit waveform design problem considering multiple design objectives. Spectral nulling is a typical way for friendly coexistence with narrow band systems. However, a Non-Contiguous Orthogonal Frequency-Division Multiplexing (NC-OFDM) waveform...
Orthogonal frequency division multiplexing (OFDM) radar is highly appropriate in applications where communication and radar functionalities are intended simultaneously. The same waveform and the same infrastructure are used, reducing hardware complexity. In this paper, we focus on the radar processing of a pulsed waveform, where the pulses are composed of several OFDM symbols. We derive a novel signal...
Wireless communication systems based on multiple input-multiple output (MIMO) in combination with orthogonal frequency division multiple access (OFDMA) and space division multiple access (SDMA) are flexible, spectrally efficient and of high capacity. These systems can allocate frequency, time, and space resources adaptively among mobile stations (MSs). In order to perform an effective resource allocation...
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