  Age of information (AoI) has been proposed as a more suitable metric for
characterizing the freshness of information than traditional metrics like delay
and throughput. However, the calculation of AoI requires complex analysis and
strict end-to-end synchronization. Most existential AoI-related works have
assumed that the statistical characterizations of the arrival process and the
service process are known. In fact, due to the randomness of the sources and
the channel noises, these processes are often unavailable in reality. To this
end, we propose a method to estimate the average AoI on a point-to-point
wireless Rayleigh channel, which uses the available finite order statistical
moments of the arrival process. Based on this method, we explicitly present the
upper and lower bounds on the average AoI of the system. Our results show that
1) with the increase of the traffic intensity, the absolute error of the
estimated average AoI bounds is first increasing and then decreasing, while the
average AoI is monotonically increasing; 2) the average AoI can be effectively
approximated by using the first two order moment estimation bounds, especially
when traffic intensity is small or approaches unity; 3) tighter bounds can be
obtained by using more moments.
