Before revision:  Our results show that the throughput of Geometric Retransmission is unstable for large n  while the throughput  of Exponential Backoff still exists for n -> infinity .
After revision:  Our results show that the throughput of Geometric Retransmission is unstable for large n since its stable throughput region vanishes as the number of nodes n -> infinity; while the throughput of Exponential Backoff still exists for n -> infinity .