  Irregular repetition slotted aloha (IRSA) is a massive random access protocol
in which users transmit several replicas of their packet over a frame to a base
station. Existing studies have analyzed IRSA in the single-cell (SC) setup,
which does not extend to the more practically relevant multi-cell (MC) setup
due to the inter-cell interference. In this work, we analyze MC IRSA,
accounting for pilot contamination and multiuser interference. Via numerical
simulations, we illustrate that, in practical settings, MC IRSA can have a
drastic loss of throughput, up to $70\%$, compared to SC IRSA. Further, MC IRSA
requires a significantly higher training length (about 4-5x compared to SC
IRSA), in order to support the same user density and achieve the same
throughput. We also provide insights into the impact of the pilot length,
number of antennas, and signal to noise ratio on the performance of MC IRSA.
