where hRU,i,j ∈ C1×Nt represents the MUI channel vector between
relay j and user i for j 6= i, and the i-th access channel
vector between relay i and user i for j = i, respectively. nU,i
is AWGN with nU,i ∼ CN(0, 2n
). Assume that the channel
between each relay-user pair is time-invariant within a block of
end-to-end transmissions [16]. The achievable rate on access link i is given by