  In this paper, we propose a new technique for the future fifth generation
cellular network wireless backhauling. We show that hundreds of bits per second
per Hertz (bits per second per Hz) of spectral efficiency can be attained at a
high carrier frequency (such as 26 GHz) between large antenna arrays deployed
along structures (such as lamp posts) that are close and roughly parallel to
each other. Hundreds of data streams are spatially multiplexed through a short
range and line of sight massive multiple input massive multiple output
propagation channel thanks to a new low complexity spatial multiplexing scheme,
called block discrete Fourier transform based spatial multiplexing with maximum
ratio transmission. Its performance in real and existing environments is
assessed using accurate ray-tracing tools and antenna models. In the best
simulated scenario, 1.6 kbits per second per Hz of spectral efficiency is
attained, corresponding to 80% of Singular Value Decomposition performance,
with a transmitter and a receiver that are 200 and 10,000 times less complex,
respectively.
