Coverage extension — repetitions and CE levels 0/1/2

The Repetition Trick

NB-IoT (and LTE-M) achieve their extreme coverage targets not through higher transmit power but through repetition of transmissions. The same data block is sent multiple times across consecutive subframes, and the receiver coherently combines the repetitions to extract the signal from below the noise floor. Sixteen repetitions provide roughly twelve decibels of processing gain. One hundred and twenty-eight repetitions provide roughly twenty-one decibels. Two thousand and forty-eight repetitions, the maximum for some channels, push beyond thirty decibels. The trade-off is direct: more…