192 research outputs found
A Test Methodology for Evaluating Cognitive Radio Systems
The cognitive radio field currently lacks a standardized test methodology that is repeatable, flexible, and effective across multiple cognitive radio architectures. Furthermore, the cognitive radio field lacks a suitable framework that allows testing of an integrated cognitive radio system and not solely specific components. This research presents a cognitive radio test methodology, known as CRATM, to address these issues. CRATM proposes to use behavior-based testing, in which cognition may be measured by evaluating both primary user and secondary user performance. Data on behavior based testing is collected and evaluated. Additionally, a unique means of measuring secondary user interference to the primary user is employed by direct measurement of primary user performance. A secondary user pair and primary user radio pair are implemented using the Wireless Open-Access Research platform and WARPLab software running in MATLAB. The primary user is used to create five distinct radio frequency environments utilizing narrowband, wideband, and non-contiguous waveforms. The secondary user response to the primary user created environments is measured. The secondary user implements a simple cognitive engine that incorporates energy-detection spectrum sensing. The effect of the cognitive engine on both secondary user and primary user performance is measured and evaluated
An FPGA implementation of OFDM transceiver for LTE applications
The paper presents a real-time transceiver using an
Orthogonal Frequency-Division Multiplexing (OFDM)
signaling scheme. The transceiver is implemented on a
Field-
Programmable Gate Array (FPGA) through Xilinx System
Generator for DSP and includes all the blocks needed
for the
transmission path of OFDM. The transmitter frame can be
reconfigured for different pilot and data schemes. In the
receiver, time-domain synchronization is achieved thr
ough a
joint maximum likelihood (ML) symbol arrival-time and
carrier frequency offset (CFO) estimator through the
redundant information contained in the cyclic prefix (CP).
A
least-squares channel estimation retrieves the channel
state
information and a simple zero-forcing scheme has been
implemented for channel equalization. Results show that a
rough implementation of the signal path can be impleme
nted
by using only Xilinx System Generator for DSP
Space-Based Reconfigurable Software Defined Radio Test Bed Aboard International Space Station
The National Aeronautical and Space Administration (NASA) recently launched a new software defined radio research test bed to the International Space Station. The test bed, sponsored by the Space Communications and Navigation (SCaN) Office within NASA is referred to as the SCaN Testbed. The SCaN Testbed is a highly capable communications system, composed of three software defined radios, integrated into a flight system, and mounted to the truss of the International Space Station. Software defined radios offer the future promise of in-flight reconfigurability, autonomy, and eventually cognitive operation. The adoption of software defined radios offers space missions a new way to develop and operate space transceivers for communications and navigation. Reconfigurable or software defined radios with communications and navigation functions implemented in software or VHDL (Very High Speed Hardware Description Language) provide the capability to change the functionality of the radio during development or after launch. The ability to change the operating characteristics of a radio through software once deployed to space offers the flexibility to adapt to new science opportunities, recover from anomalies within the science payload or communication system, and potentially reduce development cost and risk by adapting generic space platforms to meet specific mission requirements. The software defined radios on the SCaN Testbed are each compliant to NASA's Space Telecommunications Radio System (STRS) Architecture. The STRS Architecture is an open, non-proprietary architecture that defines interfaces for the connections between radio components. It provides an operating environment to abstract the communication waveform application from the underlying platform specific hardware such as digital-to-analog converters, analog-to-digital converters, oscillators, RF attenuators, automatic gain control circuits, FPGAs, general-purpose processors, etc. and the interconnections among different radio components
Deep Reinforcement Learning for Power Control in Next-Generation WiFi Network Systems
This paper presents a deep reinforcement learning (DRL) solution for power
control in wireless communications, describes its embedded implementation with
WiFi transceivers for a WiFi network system, and evaluates the performance with
high-fidelity emulation tests. In a multi-hop wireless network, each mobile
node measures its link quality and signal strength, and controls its transmit
power. As a model-free solution, reinforcement learning allows nodes to adapt
their actions by observing the states and maximize their cumulative rewards
over time. For each node, the state consists of transmit power, link quality
and signal strength; the action adjusts the transmit power; and the reward
combines energy efficiency (throughput normalized by energy consumption) and
penalty of changing the transmit power. As the state space is large, Q-learning
is hard to implement on embedded platforms with limited memory and processing
power. By approximating the Q-values with a DQN, DRL is implemented for the
embedded platform of each node combining an ARM processor and a WiFi
transceiver for 802.11n. Controllable and repeatable emulation tests are
performed by inducing realistic channel effects on RF signals. Performance
comparison with benchmark schemes of fixed and myopic power allocations shows
that power control with DRL provides major improvements to energy efficiency
and throughput in WiFi network systems.Comment: 5 pages, 6 figures, 1 tabl
- …