Dissertation (MSc Telecommunications Engineering)Magnetic induction (MI) is a physical layer technology that is effective for underground wireless communications. The underground communications involve three major communication links, namely underground to underground (UG2UG), underground to aboveground (UG2AG), and aboveground to underground (AG2UG). AG2UG and UG2AG links are special in a sense that they cross two different media, which are soil and free space. While this is the case, the soil electrical conductivity (EC) is proved to be among the factors that affect MI underground communication. Therefore, this study looked at the impact of the changes in soil EC on UG2AG and AG2UG links. Channel models were reviewed and the model for communication between underground and aboveground devices that included the attenuation factor of soil EC was proposed. Experiments were also done in four different fields; at Agricultural Research Institute – Uyole, The University of Dodoma, Tanzania Research and Career Development Institute and Gairo area. These fields were used as they had different soil types and varying soil ECs. Experiments were done using GNU radio, HackRF One transceivers, MI coils and soil EC tester. The results of the experiments were analyzed using MATLAB software. The results showed that the AG2UG and UG2AG had a similar performance in terms of power received. Also, the increase in soil EC value increases the rate of attenuation of magnetic field signal. However, changes in EC were seen to have more impact on higher frequency (433.92 MHz) than on lower frequency (13.56 MHz) due to skin effect. Thus, 13.56 MHz can provide a preferable performance for UG2AG and AG2UG communications. Based on the results of the experiments, a hybrid MI and electromagnetic waves architecture for underground wireless networks was proposed.