Precoding for MIMO systems in line-of-sight (LOS) environment

Kenichi Kobayashi, Tomoaki Ohtsuki, Toshinobu Kaneko

Research output: Chapter in Book/Report/Conference proceedingConference contribution

11 Citations (Scopus)


In line-of-sight (LOS) environments, the signal detection of Multiple-Input Multiple-Output (MIMO) systems becomes difficult because the correlation among channels becomes higher when the phase differences of direct paths are close to each other. In this paper, we propose a MIMO system with precoding to maximize the minimum distance (denoted hereafter as Maxdmin precoding) to improve the performance of MIMO systems in LOS environments. Max-dmin precoding can improve the detection performance of maximum likelihood detection (MLD) by maximizing the minimum Euclidean distance between symbol points at the receiver side, but the design becomes complicated as the number of substreams increases. The design of our proposed Max-dmin precoding is easy by using the property that the first eigenvalue of channel matrix becomes dominant in LOS environments even when the number of substreams is large. We use long-term average channel state information (CSI) instead of instantaneous CSI for precoding. Moreover, we propose a reduced-complexity MLD that uses the ordered reliability of symbols that results from Max-dmin precoding. From the results of computer simulation, we show that our proposed scheme with reduced-complexity MLD can achieve low complexity and good bit error rate (BER) performance in LOS environments with Rician factor K = 5 dB.

Original languageEnglish
Title of host publicationIEEE GLOBECOM 2007 - 2007 IEEE Global Telecommunications Conference, Proceedings
Number of pages5
Publication statusPublished - 2007
Event50th Annual IEEE Global Telecommunications Conference, GLOBECOM 2007 - Washington, DC, United States
Duration: 2007 Nov 262007 Nov 30

Publication series

NameGLOBECOM - IEEE Global Telecommunications Conference


Other50th Annual IEEE Global Telecommunications Conference, GLOBECOM 2007
Country/TerritoryUnited States
CityWashington, DC

ASJC Scopus subject areas

  • General Engineering


Dive into the research topics of 'Precoding for MIMO systems in line-of-sight (LOS) environment'. Together they form a unique fingerprint.

Cite this