Before revision:  Modeling the interference field as a Poisson point process (PPP) , we derive the exact distribution of the signal-to-interference ratio (SIR) for the case of two receive antennas  and upper and lower bounds for the general case.
After revision:  Modeling the interference field as a Poisson point process (PPP) , we derive the exact distribution of the signal-to-interference ratio (SIR) for the case of two receive antennas , and upper and lower bounds for the general case.