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Keysight Technologies
Solutions for Creating and Analyzing
Custom OFDM Waveforms for
Software-Defined Radio (SDR)



Application Brief
02 | Keysight | Solutions for Creating and Analyzing Custom OFDM Waveforms for Software-Defined Radio (SDR) - Application Brief




Many of today's commercial wireless standards are based on a highly versatile
transmission scheme: orthogonal frequency-division multiplexing (OFDM).
Additionally, a method to enable multiple users on the same OFDM spectral channel is
employed called orthogonal frequency-division multiple-access (OFDMA). Examples
include 802.11a/g/n, 802.11ac/ad, 802.16e WiMAX, FDD-LTE, TDD-LTE and
LTE-Advanced.

OFDM and OFDMA technologies provide important advantages in four areas: data
throughput, spectral efficiency and scalability, data integrity, and waveform
robustness in the presence of multipath fading. In addition, both technologies have
the potential to be customized to suit the needs of proprietary applications.

For these reasons and more, OFDM and OFDMA are viewed as viable technologies for
the development of communications systems including software-defined radio (SDR)
and cognitive radio. The more successfully these technologies can be deployed, the
easier it will be to achieve seamless communication and coordination between diverse
public-safety agencies or military forces.

Because OFDM and OFDMA technologies are complex, they pose many challenges
in the development process. Fortunately, development can be accelerated by design
and test tools that simplify the creation, simulation, generation and analysis of
standard or proprietary OFDM and OFDMA waveforms.

For device testing, waveforms can be created using the Keysight Technologies, Inc.
SystemVue electronic system level (ESL) design software and downloaded to an
Keysight high-precision arbitrary waveform generator (AWG). Vector signal
generators such as the Keysight MXG offers an internal AWG with modulation
bandwidth to 160 MHz that can be used to produce gigahertz-range carrier signals
modulated with custom or standardized waveforms. On the analysis side, single-
input/single-output (SISO) and multiple-input/multiple-output (MIMO) measurements
are possible. For example, SISO measurements of custom OFDM waveforms can be
made with an Keysight X-Series RF signal analyzer or an Infiniium 90000 X-Series
high-performance digital oscilloscope coupled with the Keysight 89600 vector signal
analysis (VSA) software. Additionally the oscilloscope and VSA software can be used
for MIMO measurements of OFDMA standard waveforms like LTE or WiMAX.

This application note outlines the complexities of generating and analyzing
standardized and custom waveforms, proposes solutions that address these
problems, and presents the results of the suggested approaches. For those interested
in deeper background about OFDM and OFDMA, a list of related information is
included at the end of the note.
03 | Keysight | Solutions for Creating and Analyzing Custom OFDM Waveforms for Software-Defined Radio (SDR) - Application Brief



Problem
The use of custom OFDM waveforms presents several key and the entire array has been filled with those values
challenges in both design and test. First, simulation plus four bins that contain "pilot" signals.
environments need custom OFDM baseband simulation