Robust communication against femtocell access failures

A single macrocell serving a number of outdoor users, overlaid with a femtocell which includes several home users, is studied. The home users in the femtocell are served by a home base station (HBS) that is connected to the macrocell base station (BS) via an unreliable connection (e.g., DSL). The unreliable link may take several possible capacity values. Robust communications strategies for the home users are investigated accounting for the facts that: (a) the home users (served by the HBS) may not be aware of the current state of the HBS-BS link; and that (b) the performance of the outdoor users (served directly by the BS) should not be disrupted by possible outages on the HBS-BS link. The problem is formulated in information-theoretic terms and inner and outer bounds are given to achievable sum-rates for outdoor and home users. Expected sum-rates with respect to the distribution over the HBS-BS link states are studied as well, and conditions are identified under which the proposed schemes are optimal.