Internet of Things network is managed by battery operated devices and low power radio links since they are referred to low power networks. In present communication era, many research works are concentrating on low power wireless network. Cross layer design is one of the acclaimed technique that decidedly improves the network performance. In this article, we come up with the cross-layer model that satisfies distinct network requirements and prolongs network lifetime. It integrates physical layer, data link layer (Media Access Control) and network layer in the protocol stack. In our model, a threshold value called ETRT (Expected Transmission Range Threshold) is introduced, which is computed with the help of routing information. Later, MAC based power control technique utilizes the ETRT value and assigns optimum transmission range for every node. The idea at the heels of proposed cross layer model is estimating the capability (ETRT value) of the particular node and assigning the suitable transmission power for every node, based on its capability (ETRT value). Hence, assigning optimum transmission power based on ETRT information prolongs the network lifetime with better reliability and Quality of Service(QoS). From our results, it is noticed that the ETRT based cross layer model performs twice better than the standard model.