5,714 research outputs found
Vanishing integrals for Hall-Littlewood polynomials
It is well known that if one integrates a Schur function indexed by a
partition over the symplectic (resp. orthogonal) group, the integral
vanishes unless all parts of have even multiplicity (resp. all parts
of are even). In a recent paper of Rains and Vazirani, Macdonald
polynomial generalizations of these identities and several others were
developed and proved using Hecke algebra techniques. However at (the
Hall-Littlewood level), these approaches do not work, although one can obtain
the results by taking the appropriate limit. In this paper, we develop a direct
approach for dealing with this special case. This technique allows us to prove
some identities that were not amenable to the Hecke algebra approach, as well
as to explicitly control the nonzero values. Moreover, we are able to
generalize some of the identities by introducing extra parameters. This leads
us to a finite-dimensional analog of a recent result of Warnaar, which uses the
Rogers-Szeg\"o polynomials to unify some existing summation type formulas for
Hall-Littlewood functions.Comment: 31 page
Hybrid Analog and Digital Precoding: From Practical RF System Models to Information Theoretic Bounds
Hybrid analog-digital precoding is a key millimeter wave access technology,
where an antenna array with reduced number of radio frequency (RF) chains is
used with an RF precoding matrix to increase antenna gain at a reasonable cost.
However, digital and RF precoder algorithms must be accompa- nied by a detailed
system model of the RF precoder. In this work, we provide fundamental RF system
models for these precoders, and show their impact on achievable rates. We show
that hybrid precoding systems suffer from significant degradation, once the
limitations of RF precoding network are accounted. We subsequently quantify
this performance degradation, and use it as a reference for comparing the
performance of different precoding methods. These results indicate that hybrid
precoders must be redesigned (and their rates recomputed) to account for
practical factors.Comment: Accepted in Globecom 16 W
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