  Due to its longevity and enormous information density, DNA is an attractive
medium for archival storage. In this work, we study the fundamental limits and
tradeoffs of DNA-based storage systems under a simple model, motivated by
current technological constraints on DNA synthesis and sequencing. Our model
captures two key distinctive aspects of DNA storage systems: (1) the data is
written onto many short DNA molecules that are stored in an unordered way and
(2) the data is read by randomly sampling from this DNA pool. Under this model,
we characterize the storage capacity, and show that a simple index-based coding
scheme is optimal.
