Low power, low cost, and security-conscious wireless sensor networks are becoming increasingly pervasive in the internet of things (IoT). In these networks, receiver-assigned code division multiple access (RA-CDMA) offers benefits over existing multiple access techniques. RA-CDMA networks are asynchronous, robust against multipath interference, and offer resilience against collision. A lightweight medium access control (MAC) protocol is needed to facilitate communication in RA-CDMA networks between low power sensor nodes and access points. This article provides an overview of RA-CDMA and proposes elements of a new MAC protocol that could improve performance of certain wireless sensor networks. Key features of the proposed MAC design are introduced and compared to those of existing protocols, highlighting its simple and lightweight design. Through its compatibility with RA-CDMA, the MAC design eliminates significant overhead and complexity while meeting requirements for low power networks, which enables the implementation of dense IoT sensor networks.