Abstract
Local multipoint distribution systems (LMDS), which are
operating worldwide in the frequency range of 26 to 43 GHz,
have large bandwidths of 0.1 up to 2 GHz but a limited area
coverage of a few kilometers only. This is due to line-of-sight
(LOS) constraints for reliable point-to-multipoint links as well
as due to large propagation losses. The size of the macrocells
illuminated by the base stations, where LOS exists, is
approximately 1 to 5 km. As suggested in the CRABS report
(1999), the maximal spectral efficiency can be
obtained with a dual frequency and polarization reuse plan. This
frequency and polarization reuse leads to interference. In this
paper, we report a new technique that uses trellis-coded
modulation (TCM) for increasing the capacity of LMDS networks.
Analytical expressions have been derived for pairwise error
probability for both high and low SNR scenarios. Numerical
simulations have shown that using the proposed TCM schemes in
cochannel cells have resulted in a large decrease in
interference, thereby allowing us to reduce the frequency reuse
distance. In this paper, we present the strategy using two TCM
schemes that allow the frequency reuse factor of unity, without
compromising on the QoS caused by increased interference. Design
rules for constructing TCM schemes are also proposed in this
paper.