Rateless TLRCM for IoT Uplink Transmission

It is critical to lower the power consumption of battery powered nodes in Internet-of-Things (IoT) applications while maintaining a high transmission throughput. In this article, a novel turbo coded lightweight rate compatible modulation (TLRCM) with a simple weight set {±1} is proposed for IoT uplink transmission. Unlike narrowband IoT (NB-IoT) standard where the whole data block will be retransmitted repeatedly until the data are recovered successfully, the proposed TLRCM works in a rateless manner and can achieve a smooth rate adaptation to channel variations, reducing the number of symbols to be retransmitted. Thus, TLRCM can significantly reduce the power consumption of IoT device and improve transmission throughput. To reduce computational complexity, a 1-b subtraction and memory reading algorithm, which can be easily implemented in limited computing capability IoT devices, is proposed for the generation of TLRCM symbols. In addition, an iterative algorithm with significantly reduced complexity is proposed for TLRCM demodulation. Moreover, the reliable soft information from the output of TLRCM demodulator enables a fast convergence of Turbo codes decoding. The simulation results show that compared with the repetition transmission scheme in NB-IoT standard, the proposed TLRCM can reduce by over 37% the average transmission power consumption while maintaining a high throughput of transmission in both Gaussian channels and fading channels. The uniqueness of low-power consumption, high throughput transmission, and low-complexity implementation enables the proposed TLRCM to be a potential technique for IoT applications.