List decoding for arbitrarily varying multiple access channels with conferencing encoders

Research activities reveal a trend from an exclusive to a shared use of certain frequency bands. Then, uncoordinated interference will be unavoidable resulting in a channel that may vary in an arbitrary and unknown manner from channel use to channel use. This is the arbitrarily varying channel (AVC), for which it has been shown that the classical deterministic approaches with pre-specified encoder and decoder fail if the AVC is symmetrizable. This necessitates more sophisticated strategies such as common randomness (CR) assisted strategies or list decoding which are capable to resolve the ambiguity induced by symmetrizable AVCs. Here, we study the arbitrarily varying multiple access channel (AVMAC) with conferencing encoders, which is motivated by cooperating base stations or access points in future communication systems. The capacity region of the AVMAC with conferencing encoders is established and it is shown that list decoding allows for reliable communication also for symmetrizable AVMACs. The list capacity region equals the CR-assisted capacity region for large enough list size. Finally, for fixed probability of decoding error the amount of resources, i.e., CR or list size, is shown to be finite.