Full Diversity Unitary Precoded Integer-Forcing

TL;DR

This paper introduces a novel MIMO transmission scheme called UPIF that employs unitary precoding with integer-forcing receivers to achieve full diversity and improve high-rate performance.

Contribution

It proposes the UPIF scheme with two design types, providing new criteria for full-diversity MIMO communication with lattice coding and integer-forcing detection.

Findings

UPIF achieves full diversity under specific lattice-based constraints.

Type II UPIF outperforms MIMO X-codes at high data rates.

Simulation results confirm the effectiveness of UPIF in 2x2 and 4x4 MIMO systems.

Abstract

We consider a point-to-point flat-fading MIMO channel with channel state information known both at transmitter and receiver. At the transmitter side, a lattice coding scheme is employed at each antenna to map information symbols to independent lattice codewords drawn from the same codebook. Each lattice codeword is then multiplied by a unitary precoding matrix ${\bf P}$ and sent through the channel. At the receiver side, an integer-forcing (IF) linear receiver is employed. We denote this scheme as unitary precoded integer-forcing (UPIF). We show that UPIF can achieve full-diversity under a constraint based on the shortest vector of a lattice generated by the precoding matrix ${\bf P}$. This constraint and a simpler version of that provide design criteria for two types of full-diversity UPIF. Type I uses a unitary precoder that adapts at each channel realization. Type II uses a unitary precoder, which remains fixed for all channel realizations. We then verify our results by computer simulations in $2\times2$, and $4\times 4$ MIMO using different QAM constellations. We finally show that the proposed Type II UPIF outperform the MIMO precoding X-codes at high data rates.