Orthogonal frequency division multiplexing (OFDM) systems have attracted attention as the fourth generation mobile communication systems. In OFDM systems, the impact of a fading is identified by using the channel estimation (CE). However, a large number of pilot symbols is required to identify an accurate channel state information (CSI) in the conventional OFDM systems. To reduce this problem, a time frequency interferometry (TFI) for OFDM has been proposed. Under the fast fading environment, since the channel is rapidly changed, many errors are occurred. Therefore, we have proposed the fast fading compensation method by using the decision direct and linear prediction methods. However, this method has several problems. To overcome these problems, in this paper, we propose the nonlinear prediction method based on the weighted channel variance.

In recent years, cooperative communications are widely studied. Cooperative communications can obtain the space diversity as multiple-input multiple-output (MIMO) systems. In cooperative communications, the relay method is important as decode-and-forward (DF) and decode-amplify-forward (DAF). The multi-relay cooperative communications can improve the system performance. In the multi-relay cooperative communications, the optimum packet splitting method is effective. Moreover, the multi-relay cooperative communications can more improve the system performance by using the power allocation (PA). However, the PA method requires large feedback information (FBI). To solve this problem, in this article, we propose the optimum packet splitting method based on the time domain channel state information (CSI) in the multi-relay cooperative communication with DF and DAF.

Cross-linkable 7-deaza-6-vinylguanosine (ADVP) and 7-propynyl-7-deaza-6-vinylguanosine (ADpVP) derivatives were synthesized and successfully incorporated into 2'-OMe-RNA oligonucleotides by solid-phase oligonucleotide synthesis. Analysis of their cross-link properties revealed that the 7-propynyl substituent on ADpVP induces a significant enhancement of the cross-link kinetics of the proximal 6-vinyl group to the complementary uracil base in the target RNA compared to that of ADVP. In addition, the 2'-OMe-RNA oligonucleotide containing ADpVP exhibited a higher antisense effect on luciferase production in the cell lysate than that of ADVP. These results suggested that the 7-substituted 7-deaza-6-vinylguanosine derivatives can be used as potent cross-linkers to target mRNA inside of cells.