  We analyze different aspects of multiparty communication over quantum
memoryless channels and generalize some of key results known from bipartite
channels to that of multiparty scenario. In particular, we introduce multiparty
versions of minimal subspace transmission fidelity and entanglement
transmission fidelity. We also provide alternative, local, versions of
fidelities and show their equivalence to the global ones in context of capacity
regions defined. The equivalence of two different capacity notions with respect
to two types of the fidelities is proven. In analogy to bipartite case it is
shown, via sufficiency of isometric encoding theorem, that additional classical
forward side channel does not increase capacity region of any quantum channel
with $k$ senders and $m$ receivers which represents a compact unit of general
quantum networks theory. The result proves that recently provided capacity
region of multiple access channel ([M. Horodecki et al, Nature {\bf 436} 673
(2005)], [J.Yard et al, quant-ph/0501045]) is optimal also in the scenario of
additional support of forward classical communication.
