In this paper, we propose and model an enhanced IEEE 802.15.4 MAC for sensor nodes operating in multi-hop scenarios. Existing IEEE 802.15.4 MAC, when adapted to multi-hop networks may not perform efficiently due to lack of knowledge about the instantaneous state of local gateway. We therefore ameliorate the channel access mechanism by introducing a new Active-Tx state, which aids in identifying the state of local gateway along with traditionally existing Sleep and CSMA/CA states. A 3D Markov chain based model is developed for analysing the performance of proposed MAC framework under different configurations of network. Upon considering reliability, energy and delay as the key performance metrics the analysis shows that the model captures behaviour of the sensor node most accurately with 95% confidence level. In addition performance is also analysed using real time deployment and found to be in good accordance with analytical and simulation outcomes. © 2016 IEEE.