The development of in-vivo communications and networking systems has the potential for improving the healthcare delivery while also enabling the creation of new services and applications. In-vivo communications provide wireless networked cyber-physical systems of the embedded devices that enable accurate, quick, and cost-effective responses under a variety of circumstances. Also, it is focused upon modeling and characterizing in-vivo wireless channel, as well as contrasting it to other well-known channels. In this paper, channel coding is also mentioned because it improves data rates and performance gain. This work also discusses present problems and potential research topics for in-vivo communications. This article aims to show the researchers how the orthogonal frequency multiple access (OFDMA) technique improved the performance of in-vivo channel and how it is outperformed compared to the other techniques (TDM, TDMA, CDMA and OFDM) also how the OFDMA outperformed equalizers and channel coding in terms of bit error rate with giving a significant improvement of data transmitting and avoiding inter symbol interference. However, when it comes to the in-vivo communications, the modeling of in-vivo wireless channel is vital.Understanding the features of the in-vivo channel is critical for achieving optimal processing and designing successful procedures that allow WBANs to be arranged inside the human body.