  Using a connected dominating set (CDS) to serve as the virtual backbone of a
wireless sensor network (WSN) is an effective way to save energy and reduce the
impact of broadcasting storms. Since nodes may fail due to accidental damage or
energy depletion, it is desirable that the virtual backbone is fault tolerant.
This could be modeled as a k-connected, m-fold dominating set ((k,m)-CDS).
Given a virtual undirected network G=(V,E), a subset C\subset V is a (k,m)-CDS
of G if (i) G[C], the subgraph of G induced by C is k-connected, and (ii) each
node in V\C has at least m neighbors in C. We present a two-phase greedy
algorithm for computing a (2,2)-CDS that achieves an asymptotic approximation
factor of $(3+\ln(\Delta+2))$, where $\Delta$ is the maximum degree of G. This
result improves on the previous best known performance factor of
$(4+\ln\Delta+2\ln(2+\ln\Delta))$ for this problem.
