Joint CFO and channel estimation for CP-OFDM modulated two-way relay networks

In this paper, we study the problem of joint carrier frequency offset (CFO) and channel estimation for amplify-andforward (AF) two-way relay network (TWRN) that comprises two source terminals and one relay node. Both the system design and the estimation problem become more challenging when CFO is non-zero in a frequency-selective environment, as compared to the conventional point-to-point communication systems. By introducing some redundancy, we propose a cyclic prefix (CP) based OFDM modulation for TWRN that is capable of maintaining the advantage of using multi-carrier transmission and at the same time facilitates the system initialization, e.g., synchronization and channel estimation. We then apply a least square (LS) approach to solve the estimation problem. The approximated Cramér-Rao Bound (CRB) has been derived as the performance benchmark of the proposed estimator. Finally, simulations are provided to corroborate the theoretical studies. ©2010 IEEE.published_or_final_versionThe IEEE International Conference on Communications (ICC 2010), Cape Town, South Africa, 23-27 May 2010. In Proceedings of the IEEE International Conference on Communications, 2010, p. 1-

Frequency Offset Tracking for OFDM Systems via Scattered Pilots and Virtual Carriers

In this paper, we propose a new carrier frequency offset (CFO) tracking algorithm for orthogonal frequency division multiplexing (OFDM) systems. Assuming that the channel remains constant during two consecutive OFDM blocks, a CFO estimation algorithm is proposed based on the limited number of pilots in each OFDM block. Identifiability of this pilot based algorithm is fully discussed under the noise free environment. A weighted algorithm is then developed by considering both pilot carriers and virtual carriers. The asymptotic mean square error (MSE) of the proposed algorithm is provided, and simulation results clearly show the performance improvement of the proposed algorithm over the existing methods

Scattered Pilots and Virtual Carriers Based Frequency Offset Tracking for OFDM Systems: Algorithms, Identifiability, and Performance Analysis

In this paper, we propose a novel carrier frequency offset (CFO) tracking algorithm for orthogonal frequency division multiplexing (OFDM) systems by exploiting scattered pilot carriers and virtual carriers embedded in the existing OFDM standards. Assuming that the channel remains constant during two consecutive OFDM blocks and perfect timing, a CFO tracking algorithm is proposed using the limited number of pilot carriers in each OFDM block. Identifiability of this pilot based algorithm is fully discussed under the noise free environment, and a constellation rotation strategy is proposed to eliminate the c-ambiguity for arbitrary constellations. A weighted algorithm is then proposed by considering both scattered pilots and virtual carriers. We find that, the pilots increase the performance accuracy of the algorithm, while the virtual carriers reduce the chance of CFO outlier. Therefore, the proposed tracking algorithm is able to achieve full range CFO estimation, can be used before channel estimation, and could provide improved performance compared to existing algorithms. The asymptotic mean square error (MSE) of the proposed algorithm is derived and simulation results agree with the theoretical analysis

Blind maximum likelihood CFO estimation for OFDM systems via polynomial rooting

10.1109/LSP.2005.861583IEEE Signal Processing Letters13273-76ISPL

A comment on "Blind maximum likelihood CFO estimation for OFDM systems via polynomial rooting"

10.1109/LSP.2006.887785IEEE Signal Processing Letters144291-ISPL