A Software-defined Radio Testbed for MIMO-OFDM Communications

Authors

• Chaz G. Maschman, University of Nebraska-LincolnFollow

First Advisor

Yi Qian

Committee Members

Hamid Sharif, Andrew Harms

Date of this Version

4-2026

Document Type

Thesis

Citation

Presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Telecommunications Engineering

Under the supervision of Professor Yi Qian

Lincoln, Nebraska, April 2026

Comments

Copyright 2026, Chaz G. Maschman. Used by permission

Abstract

In this thesis, we implement a testbed for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems via GNU Radio. Specifically, we implement a configurable framework for the construction of MIMO-OFDM software-defined radio (SDR) systems as a GNU Radio module. The GNU Radio MIMO-OFDM module consists of multiple algorithmic blocks necessary for implementation of a MIMO-OFDM system. This includes a library for the generation of orthogonal or pseudo-random pilot sequences, amendments to the Schmidl-Cox protocol for MIMO synchronization, and the creation of click-and-drag GNU Radio blocks implementing the conversion of arbitrary data sent via external programs to MIMO-OFDM frames, the initial synchronization and detection of MIMO-OFDM frames, channel equalization and demultiplexing, and statistics collection for the received signals. This module and its features are then used to construct two separate GNU Radio programs, implementing both a transmitter and receiver, respectively, for MIMO-OFDM communications, which is then used in a span of possible configurations to verify the framework’s behavior. After validating the transmitter and receiver program behavior, these are then used for the physical implementation of a real-world testbed via software-defined radios. The accuracy and performance of the system in a real-world setting is then observed, and the differences in performance between some different configurations are compared.

The configurable framework allows for an arbitrary number of transmitter andreceiver antennas, as well as an arbitrary subcarrier quantity. The number of symbols per OFDM frame can also be configured, as well as the specific signal constellation each subcarrier shall use. The presence of null carriers, pilot carriers, and both of these item’s locations in a frame are fully user-definable, as well as the signal values used for each pilot. To enable this variability, multiple configurable equalization strategies were implemented using an external linear algebra library optimized for large matrix operations were used to allow the testbed to scale to an arbitrary number of antennas. Three separate decomposition methods of the sample matrices into separate receiver matrices were constructed and implemented to allow configurable equalizer functionality.

By providing a highly-configurable testbed, we hope to enable further performance and stability measurements using a variety of changeable parameters for MIMO-OFDM systems.

Advisor: Yi Qian