Reducing Energy of Baseband Processor for IoT Terminals with Long Range Wireless Communications

In this paper, we propose a new baseband architecture for Internet of Things (IoT) terminals that support long range communications such as those based on Orthogonal Frequency-Division Multiple Access (OFDMA) and spread spectrum technologies. We analyze the workload profiles of both systems and find that the frame detection unit has by far the highest computational load. Based on this analysis, we propose a simple architecture that uses only a scalar datapath. To optimize for low energy consumption, we introduce application specific instructions that minimize register accesses and include address generation units for streamlined memory access. Next, we derive energy-optimal operation settings for different channel conditions. We find that if target signal detection probability is greater than 0.9 and false alarm probability is less than 0.1, then for both good and bad channel conditions, our baseband processor has the lowest energy when the frame detection algorithm uses the longest correlation window and the highest detection threshold value.