In recent years, energy optimization is one of the the major concern for research community while designing an Self Sustainable Energy Efficient Wireless Sensor Networks. In this paper, we review the different cross-layer architectures based on cross layer design and the available RF energy-harvesting mechanisms. In the cross-layer design, different parameters are exchanged between the adjacent layers to ensure efficient use of energy. Energy scavenging is the process of harvesting energy from the ambient sources (e.g., solar power, RF energy ,thermal energy, wind energy, salinity gradients), stored in storage devices like batteries, and is used to power up small wireless electronic devices and wireless sensor networks.