28 GHz CAP-MIMO Prototype


May 4, 2016 marked a major milestone for the CAP-MIMO project: A live real-time demonstration of the Gen 2 CAP-MIMO prototype link operating at 28GHz. The link connects one CAP-MIMO access point (AP) with two single antenna mobile stations (MSs). The image on the left shows the picture of the point-to-multipoint (P2MP) link. The image on the right is a picture from the live demonstration.

This is the first mm-wave MIMO prototype capable of multi-beam data multiplexing from a single antenna aperture: that is, multiplexing data simultaneously over multiple distinct beams (in this case two). All existing prototypes, including those from major companies (Samsung, Qualcomm, Nokia, Ericsson, Intel, e.g.) can only steer a single beam using a phased array antenna. In contrast, the CAP-MIMO transceiver enables the critical functionality of electronic multi-beam steering and data multiplexing (MBDM) through the lens-array based front-end antenna. Click here for a comparison of three key mm-wave MIMO transceiver architectures.

The prototype link enables real-time communication and has the following key characteristics:

  • The AP has a 6″ lens antenna driven by a 16-feed antenna array. The coverage area is spanned by the 16 beams and the MSs can be anywhere in the coverage area.
  • The prototype enables simultaneous real-time communication from the two MSs to the AP.
  • The frame structure enables the following key tasks: MS discovery and beam selection (BS) – selecting the 4 most dominant beams out of the 16 that carry most of the MSs signal power; beam-frequency channel estimation for the two MSs for the selected beams; space-frequency interference suppression and channel equalization, using the channel estimate; and data detection (coherent or differential).
  • The prototype enables the key operational functionality of electronic MBDM for  mobile access – the location of the MSs can be tracked  anywhere in the coverage area.

We will be sharing some of these exiting recent results at the upcoming meeting for the NSF PFI: AIR-TT program in Atlanta and at the TIA 2016 in Dallas (5G densification and enabling technologies session).

 We gratefully acknowledge the support of many companies that facilitated this effort, including Reactel, MiWave, Sigatek, and especially Analog Devices.