Spectrum-Agile Massive MIMO System and Capacity Adaptation Between Uplink and Downlink

Massive MIMO is a potential candidate for next-generation wireless communication, such as for 5G. Massive MIMO uses a large number of base station (BS) antennas to potentially allow for orders of magnitude improvement in spectral and energy efficiency. Existing Massive MIMO literature views that such technology with large number of beams (large number of simultaneous users) is not compatible with systems using frequency division duplexing (FDD) due to prohibitively large overhead required to obtain channel knowledge.

The practical need for enabling massive MIMO technology for FDD systems with larger number of simultaneous users remains evident as companies continue to test FDD Massive MIMO with a limited number of beams; this technology enables FDD with a reasonable overhead cost. Three techniques are proposed, including transreceiver designs, for reducing channel state information (CSI) overhead for FDD and time division duplexing (TDD) systems by using alternate frame structures and resource adaptation algorithms within the frame structures.

Technical Summary:

This novel method for resource adaptation between uplink (UL) and downlink (DL) for wireless systems with non-contiguous bands provides significant potential for performance enhancement. The method considers massive MIMO in non-contiguous bands with frequency-selective channels and time-varying asymmetric traffics. In multi-cell environments, not to cause additional intercell interferences, adjacent cells should adopt the same resource adaptation between UL and DL which can be determined by a mobile switching center which those cells are connected to.

Three schemes:

Rotating FDD (RFDD) – Used for FDD by alternating UL and DL frequency between the 2 bands and using CSI of UL in one subframe for DL of the subsequent subframe.

Synchronous TDD (STDD) – Uses reciprocity in TDD to dual bands synchronously.

Asynchronous TDD (ATDD) – Similar to STDD but the 2 bands need not be synchronized in time, enabling better use of resources for asymmetric demand for resources.

Value Proposition:

Provides a method for capacity adaptation between uplink and downlink for systems with non-contiguous bands, enabling massive MIMO with FDD systems for large numbers of beams at a reasonable overhead cost.

Key Benefits:

Novel Technique – Enables FDD Massive MIMO with a reasonable overhead cost; provides method for resource adaptation between UL/DL for systems with non-contiguous bands
5G Standard – Highly desirable for running efficient 5G wireless networks by minimizing energetic costs, an essential for leading the 5G revolution
Decreased Overhead – reduces cost of obtaining channel state information in FDD systems
Increased Beams – Maximizes the tolerated number of simultaneous users on the same time and frequency resource

Applications: