Outage probability of unequal block-based OFDM Amplify-and-Forward relay protocol over wideband channels

In this paper, we consider a dual-hop multiple-relay network with orthogonal frequency division multiplexing (OFDM) based Amplify-and-Forward (AF) relay protocol over frequency-selective channels. In practice, subcarriers suffered that suffer deep fade in one relay may have good channels available for another relay. Therefore, each relay can support a different number of subcarriers. We propose an unequal block-based OFDM-AF relaying scheme. In our scheme, an OFDM symbol is divided into unequal blocks of subcarriers at its destination. The destination assigns each relay a corresponding number of subcarriers depending on the signal-to-noise ratio (SNR) of the signals. We derive a closed form expression of the probability of outage and this gives the general expression for our protocol and selective OFDM, OFDMA, and block-OFDM schemes. results show that the scheme achieves a better performance for a given number of blocks than the selective block-OFDM protocol.