Abstract
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.
Highlights
At present, various services for massively connected IoT devices, such as Machine Type Communications (MTC), narrowband (NB)-IoT, and so on, are being developed actively [1]
To solve the inter-user interference (IUI) problem under the constraints of low cost and low complexity, we propose a simple interference cancellation method for the massive Machine Type Communications (mMTC) devices
PROPOSED IUI CANCELLATION METHOD To design a simple IUI cancellation method for mMTC devices, a part of the repetition signals can be exploited for measuring the IUI term in (4) and interference cancellation can be performed by subtracting the measured interference from the received signal
Summary
Various services for massively connected IoT devices, such as Machine Type Communications (MTC), narrowband (NB)-IoT, and so on, are being developed actively [1]. The desired quality of service (QoS) cannot be achieved when the MTC device is fixed at a place where channel gain is low despite the base station (BS) transmitting downlink signals with the maximum power. To overcome this problem, the BS transmits the same data symbols repeatedly, and the MTC devices combine the repetition signals to increase the strength of the desired signal [2]. S. Lim et al.: Low Complexity Interference Cancellation Method for mMTC Devices interference, and the desired mMTC device eliminates IUI by combining the received repetition signals. B and M are the number of co-scheduled mMTC devices and the number of interference combining groups, respectively
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