Showing papers by "Yanxiang Jiang published in 2009"
01 Sep 2009
TL;DR: A new preamble structure is proposed, and the corresponding timing and frequency synchronization algorithms are also presented for the cooperative relay systems and the performance of the proposed algorithms is evaluated by simulations.
Abstract: In the cooperative relay system, different frames from different relays are not aligned in the time domain, and have different carrier frequency offsets (CFOs). Estimation of these time offsets and multiple CFOs is a crucial and challenging task. In this contribution, a new preamble structure is proposed, and the corresponding timing and frequency synchronization algorithms are also presented for the cooperative relay systems. CAZAC sequence is utilized in the preamble design regarding of its correlation properties. The performance of the proposed algorithms is evaluated by simulations. The simulation results show that the proposed preamble structure and synchronization algorithms have a satisfactory performance in cooperative relay systems. (7), a time and CFO estimation of a new user is presented, for the situation where all other users have been synchronized. Pun et al. (8) gave a joint CFO and channel estimation based on the maximum-likelihood (ML) principle. The method needs a multidimensional optimization, which is very complicated. In (9) and (10), specially designed pilot symbols are proposed to turn the multi-dimensional optimization problem into independent 1-dimensional optimization problems. In this paper, we consider using one pilot OFDM symbol for the timing synchronization and two repeated pilot symbols for CFOs estimation in cooperative relay systems. The corresponding timing and CFO estimation algorithms are proposed. Coarse timing acquisition is realized by utilizing unequal period synchronization basic sequence (SBS), and then, the received samples are correlated with the transmitted sequence to implement fine time acquisition. Based on the specially designed preamble, the method in (3) for P2P OFDM is extended for cooperative relay systems. Utilizing the correlation properties of preamble sequence, the range of the estimated CFOs can be extended to integral frequency offsets. CAZAC sequence has been used to generate the preamble for its perfect correlation properties. The rest of the paper is organized as follows: Section Ⅱ presents the signal model for a cooperative relay system. The preamble structure and the proposed synchronization algorithms are described in Section Ⅲ, and our simulation results are discussed in Section Ⅳ. Finally, Section Ⅴ gives the conclusion.
19 citations
01 Sep 2009
TL;DR: It is shown that the SNR is very sensitive to CFO and the sensitivity of SNR to C FO is mainly determined by the power of the corresponding link channel and gain factor.
Abstract: In this paper, we analyze signal-to-noise ratio (SNR) performance of amplify-and-forward (AF) relay system in the presence of carrier frequency offset (CFO) for fading channels. The expression for the average SNR is derived under one-relay-node scenario, and is further extended to multiple-relay-node scenario. It is shown that the SNR is very sensitive to CFO and the sensitivity of SNR to CFO is mainly determined by the power of the corresponding link channel and gain factor. The analytical results are validated through Monte Carlo simulations for both flat and frequency-selective fading channels. Keywords—SNR, CFO, amplify-and-forward, OFDM
3 citations