Systems of wireless relays under imperfect-and-outdated-CSI severity

Relay networks typically experience channel-state-information impairments in practice, which has been known to severely impact their effectiveness. Despite their practical importance, research on CSI impairments has appeared to be scarce in the existing literature. In this work, assuming that relays operate under independent-and-identically-distributed Rayleigh fading, this paper studies the impact of imperfect-channel-state-information (iCSI), and outdated-CSI (oCSI) conditions by deriving functions of relay instantaneous signal-to-noise ratio (SNR). Impact of iCSI and oCSI severity on system performance is then assessed. To improve fading combat capability, selection combining (SC) is also deployed. To facilitate derivation of the new results, a conditional function of relay instantaneous SNR under iCSI, and oCSI (i-oCSI) severity given the best-relay's SNR is first derived, from which the distribution of Rayleigh fading for SC deployment under i-oCSI conditions can be derived. An end-to-end analysis in the presence of a Source-Destination link is also performed, which helps improve this work's practicality and robustness. Ergodic channel capacity and average bit error rates of the non-coherent binary phase-shift keying (NCBPSK) modulation scheme are then computed under i-oCSI, and oCSI conditions, from which the impact of their severity on the system performance is thoroughly examined. Monte Carlo simulation is employed to validate the proposed theoretical predictions. The new functions can be employed for performance assessment of wireless networks under relay CSI outdatedness, and imperfection conditions