Abstract
The Internet of Things (IoT), describing the Machine Type Communications (MTC), is in the center of many new technical studies and industrial projects. It is also a central topic for the future 5G technologies standardization. Pending the new generation of cellular networks, the 3rd Generation Partnership Project (3GPP) has already standardized in May 2016, an evolution of the 2G and 4G networks to include IoT features. EC-GSM-IoT, the standard for the 2G technologies including the MTC, uses several technical evolutions to obtain a 20 dB improvement of the legacy Maximum Coupling Loss (MCL) of GPRS. One of them is the use of blind repetitions, and of combination techniques in the receiver. In a previous work [1], the Bit Error Rate (BER) performance of several time diversity combining mechanisms in a classical GSM receiver were studied in simulation. The present paper focuses on two of these combination techniques and leads a novel analytical study of their performances under a time variant multipath Rayleigh fading channel. The impact of the time correlation of the channels on the average Signal to Noise and Interference Ratio (SINR) is enlightened. Simulation results are compared to the theoretical curves and confirm the analytical work. This analytical investigation allows us to foresee the consequences on the final BER of the system. To the best of our knowledge, this is the first analytical study of the performance of such time diversity combining mechanisms under time variant multipath Rayleigh fading channels.