Geosphere: Consistently turning MIMO capacity into throughput

Konstantinos Nikitopoulos, Juan Zhou, Ben Congdon, Kyle Jamieson

Research output: Contribution to journalConference article

10 Scopus citations

Abstract

This paper presents the design and implementation of Geosphere, a physical- and link-layer design for access point-based MIMO wireless networks that consistently improves network throughput. To send multiple streams of data in a MIMO system, prior designs rely on a technique called zero-forcing, a way of "nulling" the interference between data streams by mathematically inverting the wireless channel matrix. In general, zero-forcing is highly effective, significantly improving throughput. But in certain physical situations, the MIMO channel matrix can become "poorly conditioned," harming performance. With these situations in mind, Geosphere uses sphere decoding, a more computationally demanding technique that can achieve higher throughput in such channels. To overcome the sphere decoder's computational complexity when sending dense wireless constellations at a high rate, Geosphere introduces search and pruning techniques that incorporate novel geometric reasoning about the wireless constellation. These techniques reduce computational complexity of 256-QAM systems by almost one order of magnitude, bringing computational demands in line with current 16- and 64-QAM systems already realized in ASIC. Geosphere thus makes the sphere decoder practical for the first time in a 4 × 4 MIMO, 256-QAM system. Results from our WARP testbed show that Geosphere achieves throughput gains over multi-user MIMO of 2× in 4 × 4 systems and 47% in 2 × 2 MIMO systems.

Original languageEnglish (US)
Pages (from-to)631-642
Number of pages12
JournalComputer Communication Review
Volume44
Issue number4
DOIs
StatePublished - Feb 25 2015
Externally publishedYes
EventACM SIGCOMM 2014 Conference - Chicago, United States
Duration: Aug 17 2014Aug 22 2014

All Science Journal Classification (ASJC) codes

  • Software
  • Computer Networks and Communications

Keywords

  • Distributed MIMO
  • MIMO
  • Sphere decoder

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