Short Blocklength Priority-Based Coding for Unequal Error Protection in the AWGN Channel

This work introduces a priority-based coding scheme for unequal error protection in the AWGN channel using short messages. The scheme simultaneously encodes two messages, one with high and one with low priority, both requiring short blocklengths. The code structure allows the transmission of the higher priority message with higher reliability even at a shorter blocklength. This allows a high- priority, urgent message to be sent at high reliability without interrupting a lower priority message that may have been in transmission. We derive tight analytical upper bounds on the error probabilities of these messages. Numerical results confirm better reliability and delay performance for the high priority message, and also verify the tightness of the analytical upper bound especially as the SNR increases even with very short blocklengths. The scheme is applicable to ultra-reliable and ultra-low latency communication in 5G systems as well as prioritized and delay-sensitive applications such as emergency and vehicular safety communications.