Low Complexity Interference Cancellation Method for mMTC Devices

For the massive Machine Type Communications (mMTC) service, a large number of devices can be connected simultaneously and the repetition signals that contain the same data can be transmitted to increase the received signal strength. Therefore, a multi-user transmission is required because the BS supports many devices by using limited radio resources. To manage inter-user interference (IUI) by multi-user transmission, a low-cost receiver that can cancel IUI is required because conventional MTC devices are low cost and low complexity. In this paper, a simple IUI cancellation method for the mMTC devices is proposed. The proposed method can measure IUI by using blank resources that are the parts of repetition signals, and it cancels IUI by subtracting the measured IUI at a signal-level. After canceling IUI, the mMTC device combines the signals to increase the signal-to-noise ratio (SNR). The block error rate (BLER) performances are investigated in a time-invariant channel and a time-varying channel, and the simulation results show that the proposed method can manage IUI successfully.