A MAC Level Scheduling Protocol in Multi-User MIMO Wireless Systems for Improved Transmission and Reliability

Computing & Wireless : Wireless and Communications

Available for non-exclusive licensing


  • Robert Heath, Jr., Ph.D. , Electrical and Computer Engineering
  • Sunghyun Cho , Samsung Advanced Institute of Technology
  • Manish Airy , Electrical and Computer Engineering
  • Jae-Hak Chung, Ph.D. , Samsung Advanced Institute of Technology
  • Won-Hyoung Park , Samsung Advanced Institute of Technology

Background/unmet need

Multiple-input multiple-output (MIMO) wireless systems provide high quality and capacity by exploiting multiple transmit and multiple receive antennas. MlMO technology allows high-data-rate transmission to a single user or lower-rate transmissions to multiple users. To achieve optimal performance in a MlMO system, a MAC (medium access and control) protocol is needed that schedules (or maps) multiple users onto the MlMO channel to fully utilize the spatial element of the channel.

Invention Description

A MIMO wireless data system that schedules multiple users to the same resource (i.e., in the same time slot, using the same frequency, and using the same transmit antenna) every scheduling instant requires a MAC structure that supports such simultaneous transmission to multiple users. This invention allows multi-user transmission scheduling in multi-antenna systems by implementing a mobile subscriber pre-MAC processor, a feedback formatter, a MlMO scheduler at the base transceiver station, and logical control channels.

The base transceiver is equipped with the scheduler that coordinates transmission. The scheduler allocates time-slots, frequency blocks, and antennas. In addition to selecting the appropriate one or more users for transmission, the scheduler may also configure the transmit precoding block. Essentially, the transmit precoding block maps the users to the antennas to achieve the required performance metric. The mobile subscribers are equipped with MAC preprocessors that provide feedback information to the base transceiver to support the MlMO scheduling operation.


  • Significant advantages in rate and reliability over single-antenna systems
  • A flexible multi-user scheduler
  • The Pre-MAC Processor relieves the base transceiver station of the task of channel monitoring
  • No other MAC protocols for multi-user MlMO systems exist
  • Allows multi-user performance gains to be realized


  • The scheduler works at both the MAC and physical layers and thus it makes use of partial information about the forward link channel obtained via feedback from the mobile subscriber.
  • Logical control channels are used on both the forward link (to inform the subscriber of the results of the scheduling algorithm) and the reverse link (to inform the base of the partial channel information generated by the MAC preprocessor).

Market potential/applications

MIMO cellular systems, wireless LAN systems, wireless packet data centers

Development Stage

Proof of concept