  Recent work has characterized the sum capacity of
time-varying/frequency-selective wireless interference networks and $X$
networks within $o(\log({SNR}))$, i.e., with an accuracy approaching 100% at
high SNR (signal to noise power ratio). In this paper, we seek similar capacity
characterizations for wireless networks with relays, feedback, full duplex
operation, and transmitter/receiver cooperation through noisy channels. First,
we consider a network with $S$ source nodes, $R$ relay nodes and $D$
destination nodes with random time-varying/frequency-selective channel
coefficients and global channel knowledge at all nodes. We allow full-duplex
operation at all nodes, as well as causal noise-free feedback of all received
signals to all source and relay nodes. The sum capacity of this network is
characterized as $\frac{SD}{S+D-1}\log({SNR})+o(\log({SNR}))$. The implication
of the result is that the capacity benefits of relays, causal feedback,
transmitter/receiver cooperation through physical channels and full duplex
operation become a negligible fraction of the network capacity at high SNR.
Some exceptions to this result are also pointed out in the paper. Second, we
consider a network with $K$ full duplex nodes with an independent message from
every node to every other node in the network. We find that the sum capacity of
this network is bounded below by $\frac{K(K-1)}{2K-2}+o(\log({SNR}))$ and
bounded above by $\frac{K(K-1)}{2K-3}+o(\log({SNR}))$.
