  In this paper, we consider distributive subband, power and rate allocation
for a two-hop transmission in an orthogonal frequency-division multiple-access
(OFDMA) cellular system with fixed relays which operate in decode-and-forward
strategy. We take into account of system fairness by considering weighted sum
goodput as our optimization objective. Based on the cluster-based architecture,
we obtain a fast-converging distributive solution with only local imperfect
CSIT by using decomposition of the optimization problem. To further reduce the
signaling overhead and computational complexity, we propose a reduced feedback
distributive solution, which can achieve asymptotically optimal performance for
large number of users with arbitrarily small feedback overhead per user. We
also derive asymptotic average system throughput for the relay-assisted OFDMA
system so as to obtain useful design insights.
