Given nodes [v.sub.1], [v.sub.2], ..., [v.sub.m] and [u.sub.1], [u.sub.2], ..., [u.sub.k] residing at different blocks and connected to a common articulation point [v.sub.a], the task of constructing a CC-link by selecting appropriate helper set [H.sub.v,u] [not subset] N([v.sub.i])(1 [less than or equal to] i [less than or equal to] m) and [H.sub.u,v] [not subset] N([v.sub.j]) (1 [less than or equal to] j [greater than or equal to] n) can be computed by CARCC in O([DELTA] (G) x log [DELTA] (G)) time using O([DELTA] (G)) messages.
Note that, whenever possible, CARCC creates bidirectional CC-links among distinct blocks connected to an articulation point.
To assess the goodness of the Connectivity Autorecovering via Cooperative Communication (CARCC) protocol, we have implemented it and other prominent alternatives in Matlab .
To verify goodness of the selected backup nodes in terms of power consumption and connectivity, CARCC is compared to the following: (i) a centralized solution in which global topology information is available and (ii) a localized solution in which k-hop node distance information is known beforehand.
In what follows, the transmission power with and without employing Algorithm 3 is denoted as "CARCC" and "CARCC_PwOpt," respectively.
This fact can be observed in results shown in Figure 5, where CARCC without optimization is able to cut the transmission power in approximately 50% when comparing lower ([N.sub.d] = 4.0 x [10.sup.-4]) and higher node density ([N.sub.d] = 12.0 x [10.sup.-4]).
In fact, the transmission power used by CARCC with power optimization is similar to that obtained when precise node location at 2 hops is used.
As can be observed, nodes participating in a CC-link require [W.sub.CC] ([H.sub.i,j]) [approximately equal to] [P.sub.MAX] in case of CARCC without optimization.
The transmission power required by the optimized CARCC is about 10.35% higher than the best global CC-link and about 5.42% compared to the best local CC-link.
With node density d = 12.0 x [10.sup.-4], the CARCC expands at most 14% more transmission power than a direct link computed using global topological information and at most 9.2% using 2-hop local information.
CARCC without optimization requires a higher number of helper nodes due to higher estimated distance of the CC-links.