The Internet of Wearable Things (IoWT) is a revolutionary technology of Wireless Body Area Networks (WBAN). IoWT applications are widely employed in diverse sectors including medical, civil, and military domains. In these emerging applications, human bodies are equipped with wearable and interconnected sensors, which can be used on, inside, or around the human body. However, the deployment of these devices in close proximity of the human body faces several electromagnetic factors such as channel fading due to several reasons like energy absorption, reflection, multipath, and shadowing by the body. These electromagnetic phenomena can degrade the quality of the communication link budget between wearable sensor systems in WBAN. Therefore, investigation in channel modeling between wearable sensors has become a major challenge in Wireless Body Area Networks (WBAN), especially when using these devices for real-time monitoring and remote control of vital signs and physiological data of patients in medical applications. This paper presents a novel approach of a rigorous and effective mathematical voxel-based channel model for channel modeling between wearable wireless antenna sensors in free space and human body environments. Also, this work presents a design flow and performance analysis of the proposed 3D-voxel human body model and the designed wearable antenna at 2.4 GHz. Moreover, a performance evaluation studies between IEEE 802.15.6 CM3 channel model based on the proposed analytical voxel based-human body at 2.4 GHz for various distances between the coordinator and the on-body wearable antenna sensors are presented. These studies reveal a good agreement between IEEE 802.15.6 CM3A and our model.