Although the Almost Blank Subframes (ABSF) proposed in heterogeneous cellular networks can enhance the performance of the Cell Range Expansion (CRE) User Equipments (UEs), it significantly degrades macro-cell total throughput. To address this problem, the Low Power Subframes (LPSF) are encouraged to be applied in macro-cell center region by the Further-enhanced Inter-cell Interference Coordination (FeICIC). However, the residual power of the LPSF which interferes the CRE UEs, and the proportion of the LPSF affect the downlink throughput together. To achieve a better rate coverage probability, appropriate LPSF power and proportion are required. In this paper, the analytical results of the overall Signal to Interference and Noise Ratio (SINR) coverage probability and the rate coverage probability are derived under the stochastic geometric framework. The optimal region bias ranges for maximizing the rate coverage probability are also analysed. The results show that the ABSF still outperform the LPSF in terms of rate with the optimal range expansion bias, but lead to a heavier burden on the back-haul of the pico-cell. However, with a static range expansion bias, the LPSF provide better rate coverage than the ABSF. Also, in a low range expansion scenario, the reduced power of the LPSF has negligible effect on the rate coverage with the optimal resource partitioning.