Remodulation Relaying Method Combined with Decode and Forward
Original Publication Date: 2008-Mar-26
Included in the Prior Art Database: 2008-Mar-26
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In cellular networks different types of RNs (Relay Nodes) exist, which either utilize an A&F (Amplify and Forward) or a D&F (Decode and Forward) scheme. In case of A&F the relays are devices of low complexity, which do not process the data but only transmit the signal received from the BS (Base Station). This leads to noise enhancement, especially if the first link provides low SNR (Signal to Noise Ratio). Furthermore, on the first and second hop the same MCS (Modulation and Coding Scheme) is required, i.e. the MCS requested for the second hop has to be used at the first hop as well. As the first hop often outperforms the second hop, the first hop is not used efficiently, i.e. with a smaller MCS as possible. This reduces the data rate at the first hop while the performance of relay systems depends on the data rate of the first hops. The D&F scheme is more complex because the received signal is demodulated and decoded in the baseband before retransmission. On the one hand this allows the detection and correction of bit errors on the first hop, but on the other hand introduces a higher delay as decoding has to be done on the minimum packet size for error correction. In both cases the received data is stored for at least one OFDM (Orthogonal Frequency Division Multiplexing) symbol length, which avoids simultaneous receive and transmit operation on the air.