Blind Symbol Timing and CFO Estimation for OFDM/OQAM Systems

Abstract

The paper deals with the problem of blind synchronization for OFDM/OQAM systems. Specifically, by exploiting the approximate conjugate-symmetry property of the beginning of a burst of OFDM/OQAM symbols, due to the presence of the time offset, a new procedure for blind symbol timing and CFO estimation is proposed. The performance of the derived blind estimators is analyzed by computer simulations; the results show that the proposed methods may provide acceptable performance for reasonable values of the signal-to-noise ratio

Joint frequency offset, time offset, and channel estimation for OFDM/OQAM systems

“…This simple equalization scheme inverts the channel at the center frequency of the corresponding subcarrier and it works well in mildly selective channels as long as the number of subcarriers is sufficiently large [36]. 7 This is only valid for the PHYDYAS filter. There are other prototype filter functions in discussion for OFDM/OQAM systems which may require a different value for β [34].…”

“…In spite of these advantages, accurate carrier frequency and timing synchronization along with channel estimation (for the purpose of equalization) remain of There exist three main categories of synchronization and channel estimation methods for OFDM/OQAM systems: blind, semi-blind and pilot-based methods. While blind methods, e.g., [4][5][6][7], provide higher spectral efficiency by avoiding the overhead of training sequences, the requirement of a longer observation window for accurate estimation limits their tracking ability, rendering them less popular in most practical applications. In contrast, the semi-blind methods only require the transmission of a small number of parameters to resolve an estimation ambiguity, e.g., [8] and as such, they offer a useful tradeoff between spectral efficiency and estimation accuracy.…”

New Integer Normalized Carrier Frequency Offset Estimators

“…Their estimators use the following correlation between two received OFDM symbols: (14) where 1) Existing PAE: Three existing PAEs will be briefly described. DT's PAE in [22] reads as (15) where is the pilot-based metric calculated as (16) and is the data-based metric calculated as (17) where and mean the real part and the imaginary part of the enclosed quantity, respectively. In practical OFDM systems (e.g., [23], [24]), the power of a pilot subcarrier is set times larger than the average power of a data subcarrier in order to aid reliable synchronization.…”

“…Separate algorithms are used to estimate and correct the fractional and the integer normalized CFO (FCFO and ICFO). Some of the existing works incorporate practical issues/scenarios, e.g., pilot-aided FCFO estimation jointly with channel and phase noise [14], in the pres- ence of I/O imbalance [15], blind FCFO estimation with timing synchronization [16], with noise power and SNR estimation [17] and with multi-antenna channel estimation [18]. However, these existing works overlook that when a CFO occurs, the receiver filter's spectrum becomes misaligned with the received signal.…”

Performance analysis of some timing offset equalizers for FBMC/OQAM systems

“…Specific schemes have been recently proposed for synchronization [4][5][6] and some performance analysis and comparison has been carried out in the asynchronous context [7]. In spite of these efforts, no development and deployment of real FBMC systems have taken place so far.…”