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This paper proposes a new channel estimation scheme for two-path relaying networks where two amplify-and-forward (AF) half-duplex relay nodes alternatively transmit the signals received from a source node. The channel estimation and interference cancellation would be mutually conditional in two-path relaying networks. To overcome such a difficulty, we design new training sequences and propose precoding matrices for use at the source and relays. Deriving the Cramer-Rao lower bound (CRLB), it is shown that the proposed estimator is efficient, i.e., the proposed channel estimation scheme achieves the CRLB. The performance of the proposed channel estimation is evaluated through the computer simulations where the validity of the theoretical analysis is also demonstrated.

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In this paper, an analytical formula for the net gain of singleinput single-output single frequency network (SISO-SFN) is derived. In order to formulate the net SISO-SFN gain (SISO-SFNG), we derive the average signal to noise ratio, where the SFN gain is calculated by the aggregate power sum as a function of the power imbalance, whereas the SFN loss is calculated by a two-term exponential model from a curve fitting as a function of the erasure probability, modulation order, and code rate. The accuracy and effectiveness of the derived formula are verified by comparing the measurement results with the analytical results. The derived formula helps to rationalize why the net gain is positive or negative under a given condition, e.g., a negative net gain is obtained if the power imbalance exceeds the erasure-free limit. The formula would be very useful to predict more realistic and accurate service coverage of SISO-SFN for various system configurations.Index Terms-Single frequency network (SFN), erasure effect, power imbalance, calibrated coverage prediction.