Rate region and power considerations in a simple 2×2 interference channel

We study the rate region of a simplified wireless network for a given degree of interference, considered as noise, and power constrains. The network nodes use a specific modulation scheme with a specific bit error rate and a constant bandwidth. We define the necessary conditions that maximize the system´s sum rate for a 2-link interference channel and provide criteria under which simultaneous link operation outperforms timesharing. We identify critical points in the rate region where higher sum rates can be achieved in practical band limited channels at the expense of higher power expenditure. In case of light interference the relation between the maximum achieved rate and power is shown to be almost linear, but in case of strong interference, there is need for disproportionally high total power. Finally, for higher order modulations, we give the condition on the maximum individual transmission power for switching to the next higher modulation level in order to achieve higher aggregate rate.