Design Considerations for Radios for Cellular Infrastructure

The emergence of 4G and 5G radio access networks and the explosion in demand for wireless data has driven radical changes in cellular base stations over the past decade, including dramatic increases in the number and bandwidth of frequency bands, over an order of magnitude increase in radio channel count due to the deployment of Massive-MIMO, and the proliferation of small cells. These changes have put huge pressure on the cost, power, and performance of the base station radio, and driven the requirement for frequency agile, wideband, multi-standard radios. This tutorial presents an overview of base station architecture and some important base station performance requirements. It will show how these standards-based requirements translate to radio requirements, and the calibrations and algorithms used to meet them with a focus on sub-6GHz zero-IF radios. It will cover topics such as radio impairments and how they impact important performance metrics, wideband quadrature error correction and LO feedthrough/DC offset cancellation, power amplifier digital pre-distortion (DPD), passive intermodulation cancellation (PIM), and compare and contrast the advantages and disadvantages of RF sampling and zero-IF radios.