November 01, 2017

Massive MIMO with Max-Min Power Control in Line-of-Sight Propagation Environment

  • Marzetta T.
  • Yang H.

A key component for the success of Massive MIMO is the asymptotic orthogonality of channel vectors. With M service antennas, the expected correlation between a pair of channel vectors in line-of-sight (LoS) propagation environment decreases at least as fast as log(M)/M while its counterpart in independent and identically distributed (iid) Rayleigh fading propagation environment decreases much slower at 1/sqrt(M), but the variance is higher in LoS. This signifies that most likely channel vectors are more nearly orthogonal in LoS than in iid Rayleigh, but in the worst case they can be highly correlated in LoS. Massive MIMO with max-min power control performs comparably in LoS and iid Rayleigh when a simple algorithm is applied to drop a few users with high channel vector correlation from service in LoS.

View Original Article

Recent Publications

January 01, 2019

Friendly, appealing or both? Characterising user experience in sponsored search landing pages

  • Bron M.
  • Chute M.
  • Evans H.
  • Lalmas M.
  • Redi M.
  • Silvestri F.

© 2017 International World Wide Web Conference Committee (IW3C2), published under Creative Commons CC BY 4.0 License. Many of today's websites have recognised the importance of mobile friendly pages to keep users engaged and to provide a satisfying user experience. However, next to the experience provided by the sites themselves, ...

January 01, 2019

Analyzing uber's ride-sharing economy

  • Aiello L.
  • Djuric N.
  • Grbovic M.
  • Kooti F.
  • Lerman K.
  • Radosavljevic V.

© 2017 International World Wide Web Conference Committee (IW3C2), published under Creative Commons CC BY 4.0 License. Uber is a popular ride-sharing application that matches people who need a ride (or riders) with drivers who are willing to provide it using their personal vehicles. Despite its growing popularity, there exist ...

January 01, 2019

The paradigm-shift of social spambots: Evidence, theories, and tools for the arms race

  • Cresci S.
  • Petrocchi M.
  • Pietro R.
  • Spognardi A.
  • Tesconi M.

© 2017 International World Wide Web Conference Committee (IW3C2), published under Creative Commons CC BY 4.0 License. Recent studies in social media spam and automation provide anecdotal argumentation of the rise of a new generation of spambots, so-called social spambots. Here, for the first time, we extensively study this novel ...