Outage Performance of Space-Time Network Coding With Overhearing AF Relays

This letter investigates the outage performance of overhearing amplify-and-forward (AF) cooperative relaying system, where multiple sources transmit information symbols to a destination through multiple helping overhearing AF relays with space-time network coding (STNC) employed. First, by introducing the overhearing among the relays of STNC, a new transmission protocol, i.e., the STNC-based cooperative relaying with overhearing AF relays (STNC-OHAF), is presented. Then, the instantaneous end-to-end SNR expression of STNC-OHAF is analyzed. Based on this, an explicit expression of the outage probability for STNC-OHAF over independent but not necessarily identically distributed (i.n.i.d) Rayleigh fading channels is theoretically derived and the ability of STNC-OHAF to achieve full diversity order is proved. Numerical results validate our theoretical analysis and show that by introducing overhearing among relays, the outage performance of the STNC-based AF relaying system can be greatly improved. Besides, it is also shown that there is a trade-off between the normalized sum efficient system transmission rate and the number of sources.