  This paper investigates information freshness of multichannel access in
information update systems. Age of information (AoI) is a fundamentally
important metric to characterize information freshness, defined as the time
elapsed since the generation of the last successfully received update. When
multiple devices share the same wireless channel to send updates to a common
receiver, an interesting question is whether dividing the whole channel into
several subchannels will lead to better AoI performance. Given the same
frequency band, dividing it into different numbers of subchannels lead to
different transmission times and packet error rates (PER) of short update
packets, thus affecting information freshness. We focus on a multichannel
access system where different devices take turns to transmit with a cyclic
schedule repeated over time. We first derive the average AoI by estimating the
PERs of short packets. Then we examine bounded AoI, for which the instantaneous
AoI is required to be below a threshold a large percentage of the time.
Simulation results indicate that multichannel access can provide low average
AoI and uniform bounded AoI simultaneously across different received powers.
Overall, our investigations provide insights into practical designs of
multichannel access systems with AoI requirements.
