Combination for Modulation: Toward Enhancing LoRa Link Capacity

In recent years, Long Range (LoRa) modulation has attracted much attention from both academia and industry because of its capability to offer long-distance, low-power communication through the use of chirp spread spectrum (CSS) modulation at the physical layer. However, LoRa is slow in link speed, reaching a maximum data rate of 50 kbps, and unable to deliver adequate data rates. We present Combination-Encoded CSS (CE-CSS), which is compatible to the legacy LoRa. At the physical layer, CE-CSS can transmit multiple concurrent symbols in a single chirp period to increase link capacity, while avoiding the need for complex demodulation processes. The core of CE-CSS is a combination-encoded mechanism that focuses on encoding combinations of all concurrent symbols, rather than only modulating individual symbols. CE-CSS enables standard LoRa demodulation to extract out the concurrent symbols by only one pass of Fast Fourier Transform, without requiring any complex processes or customized hardware deployed at the gateway. The simulation-based experiments show the effectiveness and efficiency of our design.