Effective capacity of URLLC over parallel fading channels with imperfect channel state information

This paper investigates the effective capacity of a point-to-point ultra-reliable low latency communication (URLLC) transmission over multiple parallel sub-channels at finite blocklength (FBL) with imperfect channel state information (CSI). Based on reasonable assumptions and approximations, we derive the effective capacity as a function of the pilot length, decoding error probability, transmit power and the sub-channel number. Then we reveal significant impact of the above parameters on the effective capacity. A closed-form lower bound of the effective capacity is derived and an alternating optimization based algorithm is proposed to find the optimal pilot length and decoding error probability. Simulation results validate our theoretical analysis and show that the closed-form lower bound is very tight. In addition, through the simulations of the optimized effective capacity, insights for pilot length and decoding error probability optimization are provided to evaluate the optimal parameters in realistic systems.