Battery-powered beacon devices introduce high maintenance costs due to the finite operation time dictated by the fixed capacity of their batteries. To tackle this problem we propose FreeBLE: an indoor beacon system aimed at operating perpetually without batteries. We propose three methods to increase the utilization efficiency of harvested Radio Frequency (RF) energy in the beacon system, by which the energy consumption level becomes low enough to fit within the energy harvesting budget. We implement FreeBLE using off-the-shelf Bluetooth Low Energy (BLE) and RF energy harvesting devices, and test FreeBLE in a laboratory environment. Our results show that FreeBLE enables perpetual operation in an indoor deployment of RF-powered BLE beacon devices.

We present a simulation-based assessment of the performance potential of distributed MIMO (D-MIMO), multi-user MIMO (MU-MIMO) and particularly the combined D/MU-MIMO operation, for which we extend previously published scheduling and beamforming principles. The assessment study reveals that, when optimizing average user throughput performance, D-MIMO, while fruitless when used in isolation, is very effective when intelligently combined with MU-MIMO. Alternatively, when optimizing the cell edge performance, MU-MIMO, while also shown to be ineffective when used in isolation, is in fact very valuable when accompanied by a suitable configuration of D-MIMO. As an illustrative example, when using a jointly optimised configuration of D/MU-MIMO in a highly loaded urban deployment scenario, a 121% cell edge performance gain can be attained over a scenario using only D-MIMO, and even a demonstrated 153% gain over a scenario where only the MU-MIMO feature is available.