A new class of Wireless Sensor Networks (WSNs) is emerging within the Internet of Things (IoT) that features extremely high node density, low data rates per node, and high network dependability. Applications such as industrial IoT, factory automation, vehicular networks, aviation, spacecraft and others will soon feature hundreds of low power, low data rate (1-15 kbps) wireless sensor nodes within a limited spatial environment. Existing Medium Access Control (MAC) layer protocols, namely IEEE 802.15.4, may not be suitable for highly dense, low rate networks. A new MAC protocol has been proposed that supports a Receiver-Assigned Code Division Multiple Access (RA-CDMA) physical (PHY) layer multiple access technique, which may enable higher network scalability while maintaining performance and contributing additional robustness. This thesis presents a comparison of the contention mechanisms of IEEE 802.15.4 non- beacon enabled mode and RA-CDMA along with a Matlab simulation framework used for end-to-end simulations of the protocols. Simulations suggest that IEEE 802.15.4 networks begin to break down in terms of throughput, latency, and delivery ratio at a relatively low overall traffic rate compared to RA-CDMA networks. Results show that networks using the proposed RA-CDMA multiple access can support node densities on the order of two to three times higher than IEEE 802.15.4 within the same bandwidth. Furthermore, features of a new MAC layer protocol are proposed that is optimized for RA-CDMA, which could further improve network performance over IEEE 802.15.4. The protocol's simple and lightweight design eliminates significant overhead compared to other protocols while meeting performance requirements, and could further enable the deployment of RA-CDMA WSNs. / Master of Science / Factories, automobiles, planes, spacecraft and other systems in the future will require hundreds of sensors within a relatively small area for data gathering purposes. The sensors, which form Wireless Sensor Networks (WSNs), must have some method of wireless communication that allows each of them to transmit information when needed without obstructing other sensors’ transmissions. Wireless communication protocols provide a method for doing so. Some recognizable examples of wireless communication protocols include Bluetooth, WiFi, 3G and LTE. For WSNs in the future, the industry’s leading candidate protocol is called IEEE 802.15.4, but it may not be most suitable because it is known to break down as large amounts of sensors are added to its networks. Because of this, a new protocol has been proposed around a channel sharing technique called Receiver-Assigned Code Division Multiple Access (RACDMA), which uses a different strategy to efficiently distribute network resources among sensors. This work analyzes the differences between IEEE 802.15.4 and RA-CDMA, focusing specifically on how each protocol allows sensors to transmit without conflicting with one another. A simulation framework is introduced for complete simulations of each protocol. The result of the simulations shows that IEEE 802.15.4 breaks down in dense sensor networks. RACDMA, however, is able to support very large networks, on the order of two to three times the size of IEEE 802.15.4. This result could be an enabling technology for large wireless sensor networks in the future. Additionally, a new protocol optimized for RA-CDMA is presented. Its simple design could further enable the deployment of RA-CDMA WSNs.