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- An Interpolation-Based Frequency-Synchronization Scheme for OFDM Systems
- The mismatch of the oscillators in the transmitter and receiver, or Doppler shift, introduces an offset in the expected carrier frequency. In orthogonal frequency-division multiplexing OFDM systems, this frequency offset causes large errors in the signal values and therefore it is important to minimize this offset. This paper proposes an...
- Tags: Helsinki University, Offset, OFDM, Wireless
- White papers 2005-04-28
- Joint Time-Domain Tracking of Channel and Frequency Offset for OFDM Systems
- This paper addresses the problem of joint channel and frequency offset estimation and tracking for OFDM systems. The proposed method is based on Extended Kalman filtering. The channel taps and the frequency offset are estimated in time-domain while equalization is performed in frequency domain. Simulation results demonstrate accurate tracking capability...
- Tags: Frequency, Channel, Method, OFDM, Wireless
- White papers 2006-03-21
- Optimal Training Signals for MIMO OFDM Channel Estimation in the Presence of Frequency Offset and Phase Noise
- The authors develop robust Mean-Square Error MSE-optimal training signal designs for multiple-input multiple-output orthogonal frequency-division multiplexing channel estimation with frequency offset and Phase Noise PN, and present analytical and simulation results for the frequency-offset and PN effects on channel estimation. The proposed designs are more advantageous for moderate-to-high values of...
- Tags: Frequency, Training, MIMO-OFDM, Channel Estimation, OFDM, Workforce Management, Wireless, Human Resources
- White papers 2006-10-01
- Experimental Studies on a OFDM Carrier Frequency Offset Estimator
- In OFDM carrier frequency offset must be estimated and compensated at the receiver to maintain orthogonality. OFDM carrier frequency synchronization performance can be improved by using diversity. This paper examines the sensitivity of the carrier frequency estimator against key system parameters in a practical implementation using real data obtained on...
- Tags: OFDM, Wireless
- White papers
- Blind Estimation of the Carrier Frequency Offset in OFDM Systems
- This paper presents a novel approach for carrier frequency offset estimation in OFDM systems. Before they enter the OFDM system, the information bearing symbols are segmented into blocks so that each even indexed block shares one common symbol with the previous block. This redundancy allows for the frequency offset estimation...
- Tags: Estimation, OFDM, Wireless
- White papers
- A Blind Frequency Offset Estimator for OFDM/OQAM Systems
- Like other OFDM-like systems, OFDM/OQAM systems are very sensitive to carrier frequency offset. A new blind carrier frequency estimator is introduced herein for OFDM- /OQAM systems by exploiting the non-circularity of the received signal. Since the received signal exhibits conjugate cyclic frequencies at twice the carrier frequency offset, a frequency...
- Tags: Frequency, Texas A&M University, OFDM, Wireless
- White papers
- Estimation of Carrier-Frequency Offset and Frequency-Selective Channels in MIMO OFDM Systems Using a Common Training Signal
- This paper presents a common training signal design and corresponding estimation methods for carrier frequency offset and frequency-selective channels in MIMO OFDM systems. In designing the common training signal, a training signal structure which yields low complexity estimation methods is developed while the optimality of the training signal is maintained....
- Tags: Estimation, Training, MIMO-OFDM, Estimation Method, Workforce Management, Human Resources
- White papers 2004-09-13
- Joint Compensation of OFDM Transmitter and Receiver IQ Imbalance in the Presence of Carrier Frequency Offset
- Zero-IF based OFDM transmitters and receivers are gaining a lot of interest because of their potential to enable low-cost, low-power and less bulky terminals. However these systems suffer from In-phase/Quadrature-phase IQ imbalances in the front-end analog processing which may have a huge impact on the performance. The paper also considers...
- Tags: Compensation, Imbalance, Carrier Frequency, OFDM, Wireless
- White papers 2006-02-03
- Hopping Pilots for Estimation of Frequency-Offset and Multiantenna Channels in MIMO-OFDM
- Orthogonal frequency-division multiplexing OFDM has been widely adopted by many standards (e.g., IEEE802.11a, IEEE802.11g in the U.S., and digital audio/video broadcasting (DAB/DVB), HiperLAN/2 in Europe), because it offers the possibility for high data rates at low decoding complexity. In this paper a pilot-symbol-assisted modulation for carrier frequency offset CFO and...
- Tags: MIMO-OFDM, OFDM, Wireless
- White papers 2005-01-01
- Performance of an Adaptive Multiuser OFDM Uplink With Carrier Frequency Offsets
- Using an OFDM based uplink for the future cellular network has been controversial issue due to difficulties in time and frequency synchronization and high Peak-to-Average Power Ratio PAPR. In this paper, a model is provided to quantify the effects of carrier frequency offsets in a multiuser OFDM uplink. The paper...
- Tags: Performance, Carrier Frequency Offset, Frequency Division Duplex, OFDM, Wireless
- White papers
- Blind Carrier Frequency Offset Estimation in SISO, MIMO, and Multiuser OFDM Systems
- Relying on a kurtosis-type criterion, a low-complexity blind carrier frequency offset CFO estimator is developed for orthogonal frequency-division multiplexing OFDM systems. The paper demonstrates analytically how identifiability and performance of this blind CFO estimator depend on the channel's frequency selectivity and the input distribution. The paper shows that this approach...
- Tags: MIMO, OFDM, Wireless
- White papers 2005-01-01
- Orthogonal Frequency Division Multiplexing Based on Offset QAM
- One of the factors determining the performance of wireless Orthogonal Frequency Division Multiplexing OFDM systems is time-frequency localization of the transmitter and receiver pulse shaping filters. OFDM based on offset quadrature amplitude modulation (OFDM/OQAM) bypasses a major disadvantage of OFDM based on ordinary QAM, namely the fact that time-frequency well-localized...
- Tags: ETH Zurich, OFDM, Wireless
- White papers
- Joint Estimation of Channel Response, Frequency Offset, and Phase Noise in OFDM
- Accurate channel estimates are needed in Orthogonal Frequency-Division Multiplexing OFDM, and easily obtained under the assumption of perfect phase and frequency synchronization. However, the practical receiver encounters nonnegligible PHase Noise PHN and Carrier Frequency Offset CFO, which create substantial intercarrier interference that a conventional OFDM channel estimator cannot account for....
- Tags: OFDM, Wireless
- White papers 2006-09-01
- Multiuser Interference Cancellation for OFDM Systems With Frequency Offset
- This paper proposes a method to counteract the effect of different frequency offsets of the users in a OFDMA uplink system with frequency selective Rayleigh fading channel. The multiple access interference is reduced by reconstructing and removing the interfering signals. This is done by accomplish Successive or Selective Cancellation. The...
- Tags: Frequency, Access Interference, OFDM, Wireless
- White papers 2003-07-15
- A Combined Timing and Frequency Synchronization and Channel Estimation for OFDM
- This paper addresses training signal based combined timing and frequency synchronization and channel estimation for OFDM systems. The proposed scheme consists of two stages. At the first stage, coarse timing and frequency offset estimates are obtained. Based on these estimates, a coarse channel response estimate is obtained. The timing and...
- Tags: IEEE, Channel Estimation, OFDM, Wireless
- White papers 2005-08-30
- Maximum-Likelihood Carrier Frequency Offset Estimation for OFDM Systems in Fading Channels
- Carrier Frequency Offset CFO is a major contributor to the inter-carrier - interference in OFDM systems. This effect becomes more sever when compounded by the presence of Doppler fading in wireless channels. This paper presents two maximum-likelihood CFO estimation schemes, one in frequency domain and another in time-domain, both under...
- Tags: Carrier Frequency Offset, OFDM, Wi-Fi, Wireless
- White papers 2006-03-09
- Design of Robust Pulses to Carrier Frequency Offset for OFDM/OQAM System
- The high sensitivity to carrier frequency offset of OFDM systems compared to single carrier systems is well known. This paper studies how this can be remedied for OFDM/OQAM systems by appropriate pulse shaping. Building on earlier methods for minimizing out-of-band energy, a procedure for pulse shape design is derived. The...
- Tags: Pulse, OFDM, Wireless
- White papers 2005-07-12
- Joint Channel and Frequency Offset Estimation for OFDM Systems
- In this paper, a joint channel and frequency o set estimation algorithm is proposed. The time variation of the effective Channel Impulse Response CIR due to frequency o set is tracked using a channel tracker. This variation is used to estimate the frequency o set as well as the actual...
- Tags: Algorithm, Frequency, OFDM, Engineering, Productivity, Wireless
- White papers
- A Reduced Complexity, Improved Frequency Offset Estimation for OFDM-Based WLANs
- This paper presents a reduced complexity frequency offset estimation method as a modification to the nonlinear least square NLS method. The complexity reduction is achieved by utilizing the Chirp-Z transform. At similar complexity, the estimation performance gain, de-fined as the mean square error ratio between the NLS method and the...
- Tags: Method, WLAN, University Of Texas, Training, Complexity Reduction, Workforce Management, OFDM, Wireless LANs, Wireless, Human Resources
- White papers
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