Low Complexity Tree Searching-Based Iterative Precoding Techniques for Multiuser MIMO Broadcast Channel

Jongsub CHA
Kyungho PARK
Joonhyuk KANG
Hyuncheol PARK

IEICE TRANSACTIONS on Communications   Vol.E91-B    No.6    pp.2045-2048
Publication Date: 2008/06/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e91-b.6.2045
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Wireless Communication Technologies
precoding,  vector perturbation,  broadcast channel,  MIMO,  lattice reduction,  

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In this letter, we propose two computationally efficient precoding algorithms that achieve near-ML performance for multiuser MIMO downlink. The proposed algorithms perform tree expansion after lattice reduction. The first full expansion is tried by selecting the first level node with a minimum metric, constituting a reference metric. To find an optimal sequence, they iteratively visit each node and terminate the expansion by comparing node metrics with the calculated reference metric. By doing this, they significantly reduce the number of undesirable node visit. Monte-Carlo simulations show that both proposed algorithms yield near-ML performance with considerable reduction in complexity compared with that of the conventional schemes such as sphere encoding.