Fundamentals of statistical signal processing: estimation theory
Fundamentals of statistical signal processing: estimation theory
The effect of imperfect carrier frequency offset estimation on an OFDMA uplink
IEEE Transactions on Communications
High accuracy frequency offset correction with adjustable acquisition range in OFDM systems
IEEE Transactions on Wireless Communications
Time and Frequency Synchronization for OFDMA Uplink System using the SAGE Algorithm
IEEE Transactions on Wireless Communications
Cooperative Communications with Outage-Optimal Opportunistic Relaying
IEEE Transactions on Wireless Communications
MIMO-OFDM Channel Estimation in the Presence of Frequency Offsets
IEEE Transactions on Wireless Communications
Cooperative diversity in wireless networks: Efficient protocols and outage behavior
IEEE Transactions on Information Theory
Fading relay channels: performance limits and space-time signal design
IEEE Journal on Selected Areas in Communications
Joint optimization of relay strategies and resource allocations in cooperative cellular networks
IEEE Journal on Selected Areas in Communications
IEEE Journal on Selected Areas in Communications
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Frequency offset estimation for an Orthogonal Frequency-Division Multiple Access (OFDMA) uplink for amplify-and-forward (AF) relays and a new type of relay (R) called decode-and-compensate-and-forward (DcF) relays are studied. Multiple relays are considered, and the relay with the best S → R channel is chosen to perform re-transmission, where S and R represent the source and relay nodes, respectively. Frequency offsets due to the mismatches between the transmitter and receiver oscillators are considered, and without considering the effect of Doppler Shift, both S → D and S → R → D links have the same frequency offset, where D represents the destination. Thus, by using these two transmissions, D generates two frequency offset estimates, which are combined to minimize the mean square error (MSE). Power allocation between S and R can be adaptively adjusted to optimize the cooperative scheme in terms of frequency offset error variance. When channel state information (CSI) is available at each mobile node, a scheme where the relays adaptively switch between the cooperative and conventional (no relaying) transmissions is proposed to optimize the frequency offset estimation. Although the frequency offset estimation accuracy in the DcF mode is somewhat worse than the AF mode, both modes outperform the conventional transmission. However, DcF (or decode-and-forward (DF)) relays outperform AF relays in terms of channel capacity and bit error rate (BER).