5G network is geared towards massive deployment of Internet-of- Things (IoTs) with requirements of low end-to-end latency, low control overhead and low power transmissions. Current 4G network is optimized for large bandwidth applications and inefficient to handle short sporadic IoT messages. This paper focuses on low power underlay CDMA access for IoT devices considering eventdriven and latency sensitive traffic profile, thus will significantly reduce the access time. We propose a PHY/MAC layer design for CDMA based communication for IoT devices. We evaluate coexisting operation of CDMA based IoT network in presence of the exiting LTE network. Our proposed protocol will integrate IoT traffic with legacy system by minimal modification at the edge network, essentially eNodeB. We show that the underlay CDMA IoT network meets IoT data traffic requirements with minimal degradation (∼ 3%) to the LTE throughput. We also implement the proposed design using Software Defined Radios and show the viability of the proposal under different network scenarios.