Blind index coding over wireless channels: the value of repetition coding

We introduce an index coding problem over wireless channels where a transmitter broadcasts to multiple receivers through an erasure channel, and receivers have access to some side-information unknown to the transmitter. Such scenarios can arise naturally, for example, in caching networks where users locally store popular files as side-information or in relay networks where users opportunistically overhear transmissions from multiple relays. For this problem, we present a coding scheme based on repetition coding combined with random linear coding, that allows us to send a message to one receiver while blindly exploiting side-information to control interference at the other. Within this class of coding schemes, we identify a tension between number of repetitions and random linear coding, characterize the achievable rate region, and compare the performance of our scheme against that of conventional methods.