  In this paper, we develop a partner selection protocol for enhancing the
network lifetime in cooperative wireless networks. The case-study is the
cooperative relayed transmission from fixed indoor nodes to a common outdoor
access point. A stochastic bivariate model for the spatial distribution of the
fading parameters that govern the link performance, namely the Rician K-factor
and the path-loss, is proposed and validated by means of real channel
measurements. The partner selection protocol is based on the real-time
estimation of a function of these fading parameters, i.e., the coding gain. To
reduce the complexity of the link quality assessment, a Bayesian approach is
proposed that uses the site-specific bivariate model as a-priori information
for the coding gain estimation. This link quality estimator allows network
lifetime gains almost as if all K-factor values were known. Furthermore, it
suits IEEE 802.15.4 compliant networks as it efficiently exploits the
information acquired from the receiver signal strength indicator. Extensive
numerical results highlight the trade-off between complexity, robustness to
model mismatches and network lifetime performance. We show for instance that
infrequent updates of the site-specific model through K-factor estimation over
a subset of links are sufficient to at least double the network lifetime with
respect to existing algorithms based on path loss information only.
