Wireless Body Area Networks (WBANs) as one of the most important applications of the Internet, make their way towards smart health-care domain. These networks consist of a few number of wireless nodes placed on/inside the human body, which are supposed to measure vital body information such as blood pressure, body temperature and blood oxygen levels, and send it to a medical facility. These networks have serious constraints with respect to energy consumption, transmission range, and node size. The protocol used in the Medium Access Control (MAC) layer of these networks will have a considerable impact on their performance. The IEEE 802.15.4 standard has always been one of the prominent technologies for these networks due to its functional features. But this standard suffers from the other wireless technologies such as Wi-Fi and Bluetooth operating in the same frequency. Time Slotted Channel Hopping (TSCH) is one of the operational modes of this standard that is developed for industrial and noisy environments. This standard utilizes both frequency hopping and Time Division Multiple Access (TDMA) characteristics, and effectively overcomes the effects of cross-technology interference and multi-path fading. This standard can be a good option for use in WBANs. The contribution of this thesis is two-folded. The first contribution is an experimental study of the performance of TSCH in WBANs. In this part, several wireless nodes are installed on a human body and several experiments are performed. Experiments are conducted in a variety of environments without interference, with controlled interference, and the office environment with different transmitting powers and different body posture. These experiments are repeated once again for the IEEE 802.15.4 standard. The purpose of these tests is to demonstrate the performance of the TSCH standard compared to the base IEEE 802.15.4 with respect to the effects of multi-path fading and interference. The second contribution of this research is investigating the impact of interference between TSCH networks. First, the chance of collision between two TSCH networks in the same frequency is analyzed. This part shows that such two TSCH networks do not necessarily interfere with each other. Then, the Probability Mass Function (PMF) of collided channels is obtained for the different number of TSCH networks. The results of these analyses contain very important information for the TSCH network designers, which indicate the probability of the worst and best cases for collided channels for a certain number of TSCH networks. Moreover , an interference simulator for TSCH networks is implemented in MATLAB. This simulator is able to simulate interference of any number of TSCH networks in both synchronized and asynchronized modes. Key Words : 1-Wireless Body Area Networks , 2-IEEE 802.15.4 Standard , 3-TSCH Protocol, 4-Interference