Abstract
We consider the downlink of Cell-Free Massive MIMO systems, where a very large number of distributed access points (APs) simultaneously serve a much smaller number of users. Each AP uses local channel estimates obtained from received uplink pilots and applies conjugate beamforming to transmit data to the users. We derive a closed-form expression for the achievable rate. This expression enables us to design an optimal max-min power control scheme that gives equal quality of service to all users. We further compare the performance of the Cell-Free Massive MIMO system to that of a conventional small-cell network and show that the throughput of the Cell-Free system is much more concentrated around its median compared to that of the small cell system. The Cell-Free Massive MIMO system can provide an almost 20-fold increase in 95%-likely per-user throughput, compared with the small-cell system. Furthermore, Cell-Free systems are more robust to shadow fading correlation than smallcell systems.
| Original language | English |
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| Title of host publication | IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) |
| Publisher | Institute of Electrical and Electronics Engineers Inc. |
| ISBN (Electronic) | 978-1-4799-1931-4 |
| ISBN (Print) | 978-1-4799-1932-1 |
| DOIs | |
| Publication status | Published - 31 Aug 2015 |