Is Unequal Error Protection useful?

When transmitting source-encoded data, not all information bits are equally important, due to the different sensitivity of the source decoder to errors. Unequal Error Protection (UEP) consists of allocating coding redundancy depending on the importance of the information bits. We consider progressive transmission of source-encoded data under three different packet formats where either number of source bits per packet is fixed (fixed-k approach), or packet block length is fixed (fixed-n approach) or both parameters allowed to vary for each block (variable-(n, k) approach). Most existing results are based on some chosen family of channel codes and consider a single-user setting. Thanks to the recent finite length error probability results by Polyanskiy et al., in this work we investigate the UEP concept using the new finite-length random coding bounds. In the single-user case, we show that when codes meeting Polyanskiy achievability bounds are used, UEP does not obtain significant advantages over Equal-Error Protection (EEP) (advantages disappear for the variable-(n, k) case). Based on these results, a low complexity optimization algorithm is proposed for the multiuser (multicast) scenario.