  In order to understand the key merits of multiuser diversity techniques in
relay-assisted cellular multihop networks, this paper analyzes the spectral
efficiency of opportunistic (i.e., channel-aware) scheduling algorithms over a
fading multiuser relay channel with $K$ users in the asymptotic regime of large
(but finite) number of users. Using tools from extreme-value theory, we
characterize the limiting distribution of spectral efficiency focusing on Type
I convergence and utilize it in investigating the large system behavior of the
multiuser relay channel as a function of the number of users and physical
channel signal-to-noise ratios (SNRs). Our analysis results in very accurate
formulas in the large (but finite) $K$ regime, provides insights on the
potential performance enhancements from multihop routing and spectrum reuse
policies in the presence of multiuser diversity gains from opportunistic
scheduling and helps to identify the regimes and conditions in which
relay-assisted multiuser communication provides a clear advantage over direct
multiuser communication.
