In a two tier cellular network consisting of conventional
macro cells underlaid with home user-deployed femtocells,
cross tier interference significantly reduces the average sum
throughput of the system. This work considers the downlink
cross tier interference problem in Orthogonal Frequency Division
Multiple Access (OFDMA) based heterogeneous systems. We
analytically derive a frequency reuse pattern for femtocells
deployed in macrocells (employing soft frequency reuse scheme)
such that the cross tier interference is minimized. The impact of
power control factor1 on cross tier interference is also analyzed
and system simulation results are presented to ascertain the
veracity of the analysis.