  We present the design and implementation of WaveFlex, the first smart surface
that enhances Private LTE/5G networks operating under the shared-license
framework in the Citizens Broadband Radio Service frequency band. WaveFlex
works in the presence of frequency diversity: multiple nearby base stations
operating on different frequencies, as dictated by a Spectrum Access System
coordinator. It also handles time dynamism: due to the dynamic sharing rules of
the band, base stations occasionally switch channels, especially when priority
users enter the network. Finally, WaveFlex operates independently of the
network itself, not requiring access to nor modification of the base station or
mobile users, yet it remain compliant with and effective on prevailing cellular
protocols. We have designed and fabricated WaveFlex on a custom multi-layer
PCB, software defined radio-based network monitor, and supporting control
software and hardware. Our experimental evaluation benchmarks an operational
Private LTE network running at full line rate. Results demonstrate an 8.50 dB
average SNR gain, and an average throughput gain of 4.36 Mbps for a single
small cell, and 3.19 Mbps for four small cells, in a realistic indoor office
scenario.
