626 research outputs found
Channel, Phase Noise, and Frequency Offset in OFDM Systems: Joint Estimation, Data Detection, and Hybrid Cramer-Rao Lower Bound
Oscillator phase noise (PHN) and carrier frequency offset (CFO) can adversely
impact the performance of orthogonal frequency division multiplexing (OFDM)
systems, since they can result in inter carrier interference and rotation of
the signal constellation. In this paper, we propose an expectation conditional
maximization (ECM) based algorithm for joint estimation of channel, PHN, and
CFO in OFDM systems. We present the signal model for the estimation problem and
derive the hybrid Cramer-Rao lower bound (HCRB) for the joint estimation
problem. Next, we propose an iterative receiver based on an extended Kalman
filter for joint data detection and PHN tracking. Numerical results show that,
compared to existing algorithms, the performance of the proposed ECM-based
estimator is closer to the derived HCRB and outperforms the existing estimation
algorithms at moderate-to-high signal-to-noise ratio (SNR). In addition, the
combined estimation algorithm and iterative receiver are more computationally
efficient than existing algorithms and result in improved average uncoded and
coded bit error rate (BER) performance
Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years
Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions
Channel, Phase Noise, and Frequency Offset in OFDM Systems: Joint Estimation, Data Detection, and Hybrid Cramer-Rao Lower Bound
Oscillator phase noise (PHN) and carrier frequency offset (CFO) can adversely
impact the performance of orthogonal frequency division multiplexing (OFDM)
systems, since they can result in inter carrier interference and rotation of
the signal constellation. In this paper, we propose an expectation conditional
maximization (ECM) based algorithm for joint estimation of channel, PHN, and
CFO in OFDM systems. We present the signal model for the estimation problem and
derive the hybrid Cramer-Rao lower bound (HCRB) for the joint estimation
problem. Next, we propose an iterative receiver based on an extended Kalman
filter for joint data detection and PHN tracking. Numerical results show that,
compared to existing algorithms, the performance of the proposed ECM-based
estimator is closer to the derived HCRB and outperforms the existing estimation
algorithms at moderate-to-high signal-to-noise ratio (SNR). In addition, the
combined estimation algorithm and iterative receiver are more computationally
efficient than existing algorithms and result in improved average uncoded and
coded bit error rate (BER) performance.ARC Discovery Projects Grant DP14010113
Signal Detection for OFDM-Based Virtual MIMO Systems under Unknown Doubly Selective Channels, Multiple Interferences and Phase Noises
In this paper, the challenging problem of signal detection under severe communication environment that plagued by unknown doubly selective channels (DSCs), multiple narrowband interferences (NBIs) and phase noises (PNs) is investigated for orthogonal frequency division multiplexing based virtual multiple-input multiple-output (OFDM-V-MIMO) systems. Based on the Variational Bayesian Inference framework, a novel iterative algorithm for joint signal detection, DSC, NBI and PN estimations is proposed. Simulation results demonstrate quick convergence of the proposed algorithm, and after convergence, the bit-error-rate performance of the proposed signal detection algorithm is very close to that of the ideal case which assumes perfect channel state information, no PN, and known positions and powers of NBIs plus additive white Gaussian noise. Furthermore, simulation results show that the proposed signal detection algorithm outperforms other state-of-the-art methods.published_or_final_versio
Network-Wide Distributed Carrier Frequency Offsets Estimation and Compensation via Belief Propagation
In this paper, we propose a fully distributed algorithm for frequency offsets estimation in decentralized systems. The idea is based on belief propagation, resulting in that each node estimates its own frequency offsets by local computations and limited exchange of information with its direct neighbors. Such algorithm does not require any centralized information processing or knowledge of global network topology, thus is scalable with network size. It is shown analytically that the proposed algorithm always converges to the optimal estimates regardless of network topology. Simulation results demonstrate the fast convergence of the algorithm and show that estimation mean-squared-error at each node approaches the centralized Craḿer-Rao bound within a few iterations of message exchange.published_or_final_versio
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