Active antennas (AAs), also called Smart antennas, are a major advance over legacy base station antennas (BSAs). AAs are designed to support a myriad of wireless use cases that are evolving with next generation cellular service. AAs promise performance improvements of more than 2-3X over conventional BSAs in roughly the same form factor and at comparable costs.
So, what’s the difference? Conventional BSAs are connected to a remote radio unit (RRU) via coaxial cable and essentially blast high-power RF energy from high on a tower over a wide coverage area in horizontal beamwidths up to 120 degrees per sector. For 360-degree coverage, BSAs are installed in 3-sector arrays with one or more antennas per sector depending on the area and the number of active users. In high-density applications, carriers use mechanical gear to point antennas downward to deliver more RF energy to a smaller coverage area on the ground. A single BSA can operate on one frequency band or on multiple bands in a single shroud. Multiband operation reduces the number of discrete antennas needed at a cell site.
By contrast, AAs incorporate the RF source, basically a radio-on-a-chip, that connects to an array of small antennas all mounted in the same shroud. Power and fiber optic cables connect directly to the AA, eliminating the RRU. With integrated radios and antenna arrays under software control, AAs dynamically deliver high-speed signals wherever needed in a coverage area to enable a range of new customer-driven applications not feasible before now. With multiband operation, AAs can support new high-speed, low latency 5G use cases across many vertical public and private markets. This diversity of applications is creating a bandwidth-on-demand scenario that exceeds the limits of conventional BSAs but that AAs can handle.
AAs designs achieve these capabilities with Massive MIMO and dynamic beamforming. Multiple in/multiple out (MIMO) improves RF transmission through multiple transmit and receive paths that improve connections between mobile devices and the antennas. With advances in RF semiconductor technology, Massive MIMO, also called Large Scale Antenna Systems, uses many miniature, individually controlled antennas that perform rapid multiplexing/demultiplexing for all active users. Massive MIMO is scalable to dozens of service antennas in the same shroud to deliver vastly improved spectral efficiency, increased throughput, reduced interference, and uniform service throughout the cell.
Beamforming, at its basics, involves a fixed antenna designed with a narrow beamwidth directing RF energy at a small targeted area. Directed beams improve signal levels, reduce interference and increase throughput capacity. With adaptive systems and greater processing power, AAs can automatically adjust beam size and direction to meet dynamically changing network traffic and performance demands. Typical phased array systems switch between pre-defined patterns according to the direction required, whereas adaptive array systems (AAS) utilize adaptive beamforming to produce an infinite number of patterns where the beam is directed in the exact direction needed, in real time.
Santa Clara, CA-based start-up, Blue Danube Systems offers a Coherent Massive MIMO AA solution that brings real-time beamforming to 5G networks, significantly increasing network capacity and enhancing end user experience.
“The sweet spot of our active antenna is between 1.7 and 4.2 GHz for FDD and TDD. In the US, given the EIRP limitations for CBRS 3.5 GHz and considering the tradeoff around speed and range, deployed 2 GHz mid-band spectrum will continue to remain the work horse and prime spectrum where wireless carriers will realize the biggest payoff for 5G applications,” says Sesh Krishnamoorthy, Blue Danube’s Product Management Lead. “We’ve demonstrated in live domestic and international field deployments that mobile network operators can realize 2-3X network capacity increases in the 2 GHz range.”
Blue Danube’s software-driven solution is the only commercially proven system to deliver true 3D beamforming for sub-6 GHz FDD and TDD bands, realizing 2-3X capacity gain in multiple live networks. That’s equivalent to an operator doubling or tripling their existing radio spectrum. That’s huge!
by John Celentano, Business Editor, Inside Towers