Abstract-In order to approach the theoretical limit of the decode-and-forward strategy for the half-duplex relay channel, distributed LDPC coding schemes have been proposed. In these schemes, the code applied at the source should be decodable at the relay to yield correct parity bits. With the help of the parity bits the destination should also be able to estimate the transmitted information correctly. For successful decoding the distributed coding scheme has to be designed jointly, requiring a high design complexity. As an alternative a distributed LDPC scheme based on puncturing is investigated, which requires only the design of one mother code. In this paper we compare three different approaches for designing distributed LDPC codes with respect to their performance and their design complexity.

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Abstract-In this paper physical layer network coding (PLNC) in two-phase two-way relaying networks using coded orthogonal frequency division multiplexing (OFDM) transmission is investigated. After receiving the superimposed signal from both sources, the relay estimates the XOR-based network coded signal, which is broadcast back to the sources. Assuming that the relay is equipped with multiple antennas, the uplink transmission forms a multiple-input multiple-output (MIMO) system, which allows the application of MIMO detection technologies. To this end, the impact of employing multiple antennas at the relay on different detection and decoding schemes under investigations is studied and compared with respect to mutual information (MI). Numerical simulations verify our theoretical analysis.

Abstract-In this paper we develop a power allocation scheme for single-relay systems applying Decode-and-Forward (DF) based on the resulting bit error rate (BER) at the destination. First, an analytical expression for the BER of M -QAM modulation considering estimation errors at the relay is derived. Based on this expression, the total transmit power is optimally assigned to the source and the relay in order to minimize the probability of errors at the destination. The preciseness of the derived closed form expression as well as the superior performance of the proposed DF-based relaying system are demonstrated by simulation results.

Abstract-In this paper, power allocation schemes are proposed for the total transmit power of the source and the relay in a triplet relaying system based on Bit Error Rate (BER) analysis. Considering Amplify-and-Forward (AF), Decode-and-Forward (DF) for relaying systems and direct transmission (DT) without relay, we perform a fair comparison with respect to their power consumption in order to achieve the same target BER at the destination. For coded systems, the relationship between the input and the output BERs of the decoder for specific channel codes is modeled by polynomials to facilitate the BER analysis. Additionally, the Feasible Relay Region (FRR) is investigated, which determines geographically when AF or DF outperforms DT.