NB-IoT Uplink Receiver Design and Performance Study

Long-term evolution (LTE) narrowband Internet of Things (NB-IoT) is a Third Generation Partnership Project 3GPP defined cellular technology that is designed to enable connectivity to many low-cost and low-power/throughput IoT devices running delay-tolerant applications. NB-IoT can coexist within the LTE spectrum either in a standalone mode, in-band with LTE or in guard-band of LTE. With NB-IoT designed to operate in very low signal-to-noise power ratios, the uplink receiver design presents several challenges. In this article, the design and performance of an NB-IoT uplink receiver are studied in detail. First, receiver design for NB-IoT uplink channels, with corresponding mathematical analysis, is presented. Specifically, it is shown how the time/frequency structure of signals can be exploited to enhance the receiver performance. Second, the performance of each channel is characterized with both link-level simulations and implementation on a commercially deployed Qualcomm FSM platform. Comparisons against the 3GPP defined radio performance and protocol aspect requirements are also provided. Finally, the implementation details are addressed and discussions on proposed enhancements to NB-IoT in 3GPP Release 15 are provided. It is shown how the proposed receiver algorithms can be adopted to Release 15 enhancements with minor or no modifications. The work in this article is of significance to system designers looking to implement efficient NB-IoT uplink receiver to coexist with legacy LTE systems.