Delay CoMP of LoRa Modulation in Wireless Tree Topology Network

Abstract

The rapid development of Internet of Things (IoT) puts forward much requirements for wireless communication technology. Low Power Wide Area Networks (LPWAN) are designed for low bandwidth, low power, long range and large number of connected IoT applications. As one of the LPWAN, Low Power Long Range Transceiver (LoRa) described as a Frequency Shift Chirp Modulation (FSCM), is widely concerned and studied. In this paper, the signal reception of LoRa modulation in the wireless tree topology is analyzed, and the multi-user interference analysis proves that the multi-user interference has a great impact on the system performance. At the same time, we proposed Delay Coordinated Multiple Points Transmission (DCoMP). Multiple nodes close to each other send the same data to the target node. Due to the inaccuracy of synchronization between nodes, there will be a certain timing offset when sending signals to the same target node. After combining signals of multiple nodes according to different timing offset, the receiver performance of signals can be improved. The coordinated nodes can also actively adjust the signal sending timing according to the path time delay and processing delay, so as to improve the receiving performance of the signal merging algorithm of the receiver node. LoRa modulation improves the signal reception performance by adopting DCoMP transmission, thus improving the overall throughput of the system.