  We consider single-antenna interference networks where M sources, each with
an average transmit power of P/M, communicate with M destinations over
frequency-selective channels (with L taps each) and each destination has
perfect knowledge of its channels from each of the sources. Assuming that there
exist error-free non-interfering broadcast feedback links from each destination
to all the nodes (i.e., sources and destinations) in the network, we show that
naive interference alignment, in conjunction with vector quantization of the
impulse response coefficients according to the scheme proposed in Mukkavilli et
al., IEEE Trans. IT, 2003, achieves full spatial multiplexing gain of M/2,
provided that the number of feedback bits broadcast by each destination is at
least M(L-1) log P.
