Time-frequency based channel estimation for high-mobility OFDM systems—Part II: Cooperative relaying case (original) (raw)

Time-frequency based channel estimation for high-mobility OFDM systems

Multiple-input multiple-output (MIMO) systems hold the potential to drastically improve the spectral efficiency and link reliability in future wireless communications systems. A particularly promising candidate for next-generation fixed and mobile wireless systems is the combination of MIMO technology with Orthogonal Frequency Division Multiplexing (OFDM). OFDM has become the standard method because of its advantages over single carrier modulation schemes on multipath, frequency selective fading channels. Doppler frequency shifts are expected in fast-moving environments, causing the channel to vary in time, that degrades the performance of OFDM systems. In this paper, we present a time-varying channel modeling and estimation method based on the Discrete Evolutionary Transform to obtain a complete characterization of MIMO-OFDM channels. Performance of the proposed method is evaluated and compared on different levels of channel noise and Doppler frequency shifts.

Channel Estimation for Fast-Varying Mimo-Ofdm Systems

Multiple input-multiple output (MIMO) systems hold the potential to drastically improve the spectral efficiency and link reliability in future wireless communications systems. A particularly promising candidate for next-generation fixed and mobile wireless systems is the combination of MIMO technology with Orthogonal Frequency Division Multiplexing (OFDM). OFDM has become the standard method because of its advantages over single carrier modulation schemes on multi-path, frequency selective fading channels. Doppler frequency shifts are expected in fast-moving environments, causing the channel to vary in time, that degrades the performance of OFDM systems. In this paper, we present a time-varying channel modelling and estimation method based on the Discrete Evolutionary Transform to obtain a complete characterization of MIMO-OFDM channels. Performance of the proposed method is evaluated and compared on different levels of channel noise.

Time-frequency modeling and estimation of wireless OFDM channels

Orthogonal Frequency Division Multiplexing (OFDM) has become a very popular method for high data rate wireless communications because of its advantages over single carrier modulation schemes on multi-path, frequency selective fading channels. However, inter-carrier interference due to Doppler frequency shifts, and multipath fading severely degrades the performance of OFDM systems. Estimation of channel parameters is required at the receiver. In this paper, we present a channel modeling and estimation method based on time-frequency representation of the received signal. The Discrete Evolutionary Transform provides a time-frequency procedure to obtain a complete characterization of the multi-path, fading and frequency selective channel. Performance of the proposed method is tested on different levels of channel noise, Doppler frequency shifts, and jamming interference powers.

Modeling and estimation of wireless OFDM channels by using time-frequency analysis

Orthogonal Frequency Division Multiplexing (OFDM) has become a very popular method for high data rate wireless communications because of its advantages over single carrier modulation schemes on multi-path, frequency selective fading channels. However, inter-carrier interference due to Doppler frequency shifts, and multipath fading severely degrades the performance of OFDM systems. Estimation of channel parameters is required at the receiver. In this paper, we present a channel modeling and estimation method based on time-frequency representation of the received signal. The Discrete Evolutionary Transform provides a time-frequency procedure to obtain a complete characterization of the multi-path, fading and frequency selective channel. Performance of the proposed method is tested on different levels of channel noise, Doppler frequency shifts, and jamming interference powers.

Channel Estimation for Wireless OFDM Communications

Orthogonal Frequency Division Multiplexing (OFDM) has become a very popular method for high data rate wireless communications because of its advantages over single carrier modulation schemes on multi-path, frequency selective fading channels. However, inter-carrier interference due to Doppler frequency shifts, and multipath fading severely degrades the performance of OFDM systems. Estimation of channel parameters is required at the receiver. In this paper, we present a channel modeling and estimation method based on time-frequency representation of the received signal. The Discrete Evolutionary Transform provides a time-frequency procedure to obtain a complete characterization of the multi-path, fading and frequency selective channel. Performance of the proposed method is tested on different levels of channel noise, Doppler frequency shifts, and jamming interference powers.

Channel Estimation for Wireless OFDM Communication Systems

2006

Orthogonal Frequency Division Multiplexing (OFDM) has become a very popular method for high data rate wireless communications because of its advantages over single carrier modulation schemes on multi-path, frequency selective fading channels. However, inter-carrier interference due to Doppler frequency shifts, and multipath fading severely degrades the performance of OFDM systems. Estimation of channel parameters is required at the receiver. In this paper, we present a channel modeling and estimation method based on time-frequency representation of the received signal. The Discrete Evolutionary Transform provides a time-frequency procedure to obtain a complete characterization of the multi-path, fading and frequency selective channel. Performance of the proposed method is tested on different levels of channel noise, Doppler frequency shifts, and jamming interference powers.

Time-Varying Channel Estimation for MIMO OFDM Systems

2007 International Conference on Wireless Communications, Networking and Mobile Computing, 2007

Channel estimation for multiple-input multiple-output/orthogonal frequency-division multiplexing (MIMO/ OFDM) systems in linearly time-varying (LTV) wireless channels using superimposed training (ST) is considered. The LTV channel is modeled by truncated discrete Fourier bases. Based on this model, a two-step approach is adopted to estimate the LTV channel over multiple OFDM symbols. We also present a performance analysis of the channel estimation and derive a closed-form expression for the channel estimation variances. It is shown that the estimation variances, unlike that of the conventional ST-based schemes, approach to a fixed lowerbound as the training length increases, which is directly proportional to information-pilot power ratios. To further enhance the channel estimation performance with a limited pilot power, an interference cancellation procedure is introduced to iteratively mitigate the information sequence interference to channel estimation. Simulation results show that the proposed algorithm outperforms frequency-division multiplexed trainings schemes.

Time-Varying Channel Estimation for OFDM Systems

2007 IEEE International Conference on Acoustics, Speech and Signal Processing - ICASSP '07, 2007

Channel estimation for multiple-input multiple-output/orthogonal frequency-division multiplexing (MIMO/ OFDM) systems in linearly time-varying (LTV) wireless channels using superimposed training (ST) is considered. The LTV channel is modeled by truncated discrete Fourier bases. Based on this model, a two-step approach is adopted to estimate the LTV channel over multiple OFDM symbols. We also present a performance analysis of the channel estimation and derive a closed-form expression for the channel estimation variances. It is shown that the estimation variances, unlike that of the conventional ST-based schemes, approach to a fixed lowerbound as the training length increases, which is directly proportional to information-pilot power ratios. To further enhance the channel estimation performance with a limited pilot power, an interference cancellation procedure is introduced to iteratively mitigate the information sequence interference to channel estimation. Simulation results show that the proposed algorithm outperforms frequency-division multiplexed trainings schemes.

Channel estimation for MIMO-OFDM systems in Fast Time-Varying Environments

2010 4th International Symposium on Communications, Control and Signal Processing (ISCCSP), 2010

A channel estimation algorithm for MIMO-OFDM systems in Fast Time-Varying Environments is proposed. The channel estimation function is based on the equivalent discretetime channel taps or on the physical propagation channel parameters. To handle rapid variations of channels within a transmission block, we approximate the channel by a basis expansion model (BEM). Based on the Jakes process, an auto-regressive (AR) model of the BEM coefficients dynamics is built, making it possible to estimate and track the BEM coefficients using Kalman filter . Hence, the channel matrix is easily computed, and the data symbol is detected with free ICI . Our claims are supported by theoretical analysis and simulation results, which are obtained considering Jakes' channels with high Doppler spreads.

Channel Estimation In MIMO -OFDM Wireless Communication Systems

The global explosion in the use of wireless (handheld) devices-that rely heavily on wireless infrastructures/systems for their functioning-necessitates the need for robust and efficient wireless communication systems. MIMO-OFDM wireless systems have been shown to improve spectral efficiency and reliability among other advantages. However, their deployment in mobile time-varying environments requires very accurate estimation of the channel characteristics. This paper reviews channel estimation in MIMO-OFDM wireless communication systems and their suitability for mobile time-varying channel environments.