  The analysis of signal-to-interference ratios (SIRs) in wireless networks is
instrumental to derive important performance metrics, including reliability,
throughput, and delay. While a host of results on SIR distributions are now
available, they are often not straightforwards to interpret, bound, visualize,
and compare. In this letter, we offer an alternative path towards the analysis
and visualization of the SIR distribution. The quantity at the core of this
approach is the signal fraction (SF), which is the ratio of the signal power to
the total received power. A key advantage is that the SF is constrained to
[0,1]. We exemplify the benefits of the SF-based approach by reviewing known
results for Poisson cellular networks. In the process, we derive new
approximation and bounding techniques that are generally applicable.
