Age of Information Analysis of Short Packet Communications in Cellular Networks

Abstract

Compared to conventional communications, as the real-time application that requires the low latency and the high reliability has been introduced, the ultra reliable low latency communications (URLLC) is considered as a one of possible scenarios. However, since the packet size becomes small to reduce the latency, the decoding error probability is newly considered. The thesis analyzes the effect of the finite blocklength on the latency in the downlink cellular network considering the retransmission scheme. Hence, the thesis derive the closed form expression of the average Age of Information (AoI) and the AoI violation probability. This thesis then derive the average decoding error probability and present the upper bound of the average decoding error probability to obtain the average AoI and the AoI violation probability efficiently. After discussing the impacts of parameters on the average AoI and AoI violation probability, we finally show the existence of the optimal blocklength that minimizes the average AoI and AoI violation probability for different values of the resource reuse factor and some network parameters. Furthermore, we show the optimal blocklength increases as the maximum number of retransmissions decreases or the age threshold increases.