| 1. |
- Özdogan, Özgecan, et al.
(author)
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Cell-Free Massive MIMO with Rician Fading : Estimation Schemes and Spectral Efficiency
- 2018
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In: 2018 CONFERENCE RECORD OF 52ND ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS, AND COMPUTERS. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538692189 ; , s. 975-979
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Conference paper (peer-reviewed)abstract
- As the cell sizes in cellular networks shrink, the inter-cell interference becomes more of an issue. Instead of operating each cell autonomously, we can connect all the access points (APs) together to form a cell-free massive MIMO (multiple-input multiple-output) system that can alleviate interference by spatial processing. Previous studies have focused on Rayleigh fading channels, but in densely deployed systems, it is likely that some of the users will have line-of-sight (LoS) propagation to some of the APs. In this paper, we model this by arbitrarily distributed Rician fading channels. Two types of channel estimators are considered: a classical least-square (LS) estimator and a Bayesian minimum mean square error (MMSE) estimator. We derive closed-form spectral efficiency (SE) expressions for the uplink (UL) and downlink (DL) when using each of these estimators for maximum ratio (MR) processing. The performance difference is evaluated numerically to figure out under which conditions it is beneficial to know the channel statistics when estimating a channel.
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| 2. |
- Özdogan, Özgecan, et al.
(author)
-
Uplink Spectral Efficiency of Massive MIMO with Spatially Correlated Rician Fading
- 2018
-
In: 2018 IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538635124 ; , s. 216-220
-
Conference paper (peer-reviewed)abstract
- This paper considers the uplink (UL) of a multicell Massive MIMO (multiple-input multiple-output) system with spatially correlated Rician fading channels. The channel model is composed of a deterministic line-of-sight (LoS) path and a stochastic non-line-of-sight (NLoS) component describing a spatially correlated multipath environment. We derive the statistical properties of the minimum mean squared error (MMSE) and least-square (LS) channel estimates for this model. Using these estimates for maximum ratio (MR) combining, rigorous closed-form UL spectral efficiency (SE) expressions are derived. Numerical results show that the SE is higher when using the MMSE estimator than the LS estimator, and the performance gap increases with the number of antennas. Moreover, Rician fading provides higher achievable SEs than Rayleigh fading since the LoS path improves the sum SE.
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