54 research outputs found
BASEBAND RADIO MODEM DESIGN USING GRAPHICS PROCESSING UNITS
A modern radio or wireless communications transceiver is programmed via
software and firmware to change its functionalities at the baseband. However, the
actual implementation of the radio circuits relies on dedicated hardware, and the
design and implementation of such devices are time consuming and challenging. Due
to the need for real-time operation, dedicated hardware is preferred in order to meet
stringent requirements on throughput and latency. With increasing need for higher
throughput and shorter latency, while supporting increasing bandwidth across a
fragmented spectrum, dedicated subsystems are developed in order to service individual
frequency bands and specifications. Such a dedicated-hardware-intensive
approach leads to high resource costs, including costs due to multiple instantiations
of mixers, filters, and samplers. Such increases in hardware requirements in turn
increases device size, power consumption, weight, and financial cost.
If it can meet the required real-time constraints, a more flexible and reconfigurable
design approach, such as a software-based solution, is often more desirable
over a dedicated hardware solution. However, significant challenges must be
overcome in order to meet constraints on throughput and latency while servicing
different frequency bands and bandwidths. Graphics processing unit (GPU) technology
provides a promising class of platforms for addressing these challenges. GPUs,
which were originally designed for rendering images and video sequences, have been
adapted as general purpose high-throughput computation engines for a wide variety
of application areas beyond their original target domains. Linear algebra and signal
processing acceleration are examples of such application areas.
In this thesis, we apply GPUs as software-based, baseband radios and demonstrate
novel, software-based implementations of key subsystems in modern wireless
transceivers. In our work, we develop novel implementation techniques that allow
communication system designers to use GPUs as accelerators for baseband processing
functions, including real-time filtering and signal transformations. More
specifically, we apply GPUs to accelerate several computationally-intensive, frontend
radio subsystems, including filtering, signal mixing, sample rate conversion,
and synchronization. These are critical subsystems that must operate in real-time
to reliably receive waveforms.
The contributions of this thesis can be broadly organized into 3 major areas:
(1) channelization, (2) arbitrary resampling, and (3) synchronization.
1. Channelization: a wideband signal is shared between different users and
channels, and a channelizer is used to separate the components of the shared signal
in the different channels. A channelizer is often used as a pre-processing step in
selecting a specific channel-of-interest. A typical channelization process involves signal
conversion, resampling, and filtering to reject adjacent channels. We investigate
GPU acceleration for a particularly efficient form of channelizer called a polyphase
filterbank channelizer, and demonstrate a real-time implementation of our novel
channelizer design.
2. Arbitrary resampling: following a channelization process, a signal is often
resampled to at least twice the data rate in order to further condition the signal.
Since different communication standards require different resampling ratios, it is
desirable for a resampling subsystem to support a variety of different ratios. We
investigate optimized, GPU-based methods for resampling using polyphase filter
structures that are mapped efficiently into GPU hardware. We investigate these
GPU implementation techniques in the context of interpolation (integer-factor increases
in sampling rate), decimation (integer-factor decreases in sampling rate),
and rational resampling. Finally, we demonstrate an efficient implementation of arbitrary
resampling using GPUs. This implementation exploits specialized hardware
units within the GPU to enable efficient and accurate resampling processes involving
arbitrary changes in sample rate.
3. Synchronization: incoming signals in a wireless communications transceiver
must be synchronized in order to recover the transmitted data properly from complex
channel effects such as thermal noise, fading, and multipath propagation. We investigate
timing recovery in GPUs to accelerate the most computationally intensive
part of the synchronization process, and correctly align the incoming data symbols
in the receiver. Furthermore, we implement fully-parallel timing error detection to
accelerate maximum likelihood estimation
Circuit Techniques for Multiple and Wideband Beamforming
University of Minnesota Ph.D. dissertation.June 2018. Major: Electrical Engineering. Advisor: Ramesh Harjani. 1 computer file (PDF); x, 102 pages.This thesis presents different architectures with regard to multiple beamforming and wideband phased array transceiver. Three different designs are implemented in TSMC 65nm RF CMOS to demonstrate different solutions. The design in this thesis have included major RF blocks in state-of-art wireless transceiver: RF receiver, local oscillator, and RF transmitter. First, a RF/analog FFT based four-channel four-beam receiver with progressive partial spatial ltering is proposed. This architecture is particularly well suited for MIMO systems where multiple beams are used to increase throughput. Like the FFT, the proposed architecture reuses computations for multi-beam systems. In particular, the proposed architecture redistributes the computations so as to maximize the reuse of the structure that already exist in a receiver chain. In many fashions the architecture is quite similar to a Butler matrix but unlike the Butler matrix it does not use large passive components at RF. Further, we exploit the normally occurring quadrature down-conversion process to implement the tap weights. In comparison to traditional MIMO architectures, that effectively duplicate each path, the distributed computations of this architecture provide partial spatial ltering before the final stage, improving interference rejection for the blocks between the LNA and the ADC. Additionally, because of the spatial ltering prior to the ADC, a single interferer only jams a single beam allowing for continued operation though at a lower combined throughput. The four-beam receiver core prototype in 65nm CMOS implements the basic FFT based architecture but does not include an LNA or extensive IF stages. This four-channel design consumes 56mW power and occupies an active area of 0:65mm2 excluding pads and test circuits. Second, a wideband phased array receiver architecture with simultaneous spectral and spatial filtering by sub-harmonic injection oscillators is presented. The design avoids using expensive delay elements by many conventional wideband phased array. Different from prior art of channelization which cannot solve beam-squinting issue among the sub-channels, we use sub-harmonic injection locking scheme, which make the center frequencies of all sub-channels point to the same spatial direction to overcome beam-squinting issue. The low frequency, low power and narrowband phase shifters are placed at LO in comparison to conventional way of placing delay elements or phase shifters in the signal path. This avoids receiver performance degradation from delay elements or phase shifters. The simultaneous spectral and spatial ltering dictates less ADC dynamic range requirement and further reduces power. The injection locking scheme reduces the phase noise contribution from the oscillators. The two-band prototype design realized in 65nm GP CMOS is centered at 9GHz, provides 4GHz instantaneous bandwidth, reduces beam-squinting by half, consumes 31.75mW/antenna and occupies 2.7mm2 of chip area. In the third work, a steerable RF/analog FFT based four-beam transmitter architecture is presented. This work is based on the idea of FFT based multiple beamforming in 1st work, but extended to the transmitter and make the all beams steerable. Due to the reciprocity between receiver and transmitter, decimation-in-frequency (DIF) FFT is utilized in the transmitter. All the beams are steered simultaneously by front-end phase shifters, while keep each of the beams is independent of the others. The steerability of FFT based multiple beamforming scheme makes this proposed prototype could tackle more complicated portable wireless environment. The first and second proposed architecture have been silicon veried, and the design of the third has been finished and ready for tapeout
A Primer on Software Defined Radios
The commercial success of cellular phone systems during the late 1980s and early 1990 years heralded the wireless revolution that became apparent at the turn of the 21st century and has led the modern society to a highly interconnected world where ubiquitous connectivity and mobility are enabled by powerful wireless terminals. Software defined radio (SDR) technology has played a major role in accelerating the pace at which wireless capabilities have advanced, in particular over the past 15 years, and SDRs are now at the core of modern wireless communication systems. In this paper we give an overview of SDRs that includes a discussion of drivers and technologies that have contributed to their continuous advancement, and presents the theory needed to understand the architecture and operation of current SDRs. We also review the choices for SDR platforms and the programming options that are currently available for SDR research, development, and teaching, and present case studies illustrating SDR use. Our hope is that the paper will be useful as a reference to wireless researchers and developers working in the industry or in academic settings on further advancing and refining the capabilities of wireless systems
Characterization of the John A. Galt telescope for radio holography with CHIME
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) will measure the
21 cm emission of astrophysical neutral hydrogen to probe large scale structure
at redshifts z=0.8-2.5. However, detecting the 21 cm signal beneath
substantially brighter foregrounds remains a key challenge. Due to the high
dynamic range between 21 cm and foreground emission, an exquisite calibration
of instrument systematics, notably the telescope beam, is required to
successfully filter out the foregrounds. One technique being used to achieve a
high fidelity measurement of the CHIME beam is radio holography, wherein
signals from each of CHIME's analog inputs are correlated with the signal from
a co-located reference antenna, the 26 m John A. Galt telescope, as the 26 m
Galt telescope tracks a bright point source transiting over CHIME. In this work
we present an analysis of several of the Galt telescope's properties. We employ
driftscan measurements of several bright sources, along with background
estimates derived from the 408 MHz Haslam map, to estimate the Galt system
temperature. To determine the Galt telescope's beam shape, we perform and
analyze a raster scan of the bright radio source Cassiopeia A. Finally, we use
early holographic measurements to measure the Galt telescope's geometry with
respect to CHIME for the holographic analysis of the CHIME and Galt
interferometric data set
Real-time stream processing in radio astronomy
A major challenge in modern radio astronomy is dealing with the massive data
volumes generated by wide-bandwidth receivers. Such massive data rates are
often too great for a single device to cope, and so processing must be split
across multiple devices working in parallel. These devices must work in unison
to process incoming data in real time, reduce the data volume to a manageable
size, and output a science-ready data product. The aim of this chapter is to
give a broad overview of how digital systems for radio telescopes are commonly
implemented, with a focus on real-time stream processing over multiple compute
devices.Comment: Chapter to appear in "Big Data in Radio Astronomy: Scientific Data
Processing for Advanced Radio Telescopes
A Primer on Software Defined Radios
The commercial success of cellular phone systems during the late 1980s and early 1990 years heralded the wireless revolution that became apparent at the turn of the 21st century and has led the modern society to a highly interconnected world where ubiquitous connectivity and mobility are enabled by powerful wireless terminals. Software defined radio (SDR) technology has played a major role in accelerating the pace at which wireless capabilities have advanced, in particular over the past 15 years, and SDRs are now at the core of modern wireless communication systems. In this paper we give an overview of SDRs that includes a discussion of drivers and technologies that have contributed to their continuous advancement, and presents the theory needed to understand the architecture and operation of current SDRs. We also review the choices for SDR platforms and the programming options that are currently available for SDR research, development, and teaching, and present case studies illustrating SDR use. Our hope is that the paper will be useful as a reference to wireless researchers and developers working in the industry or in academic settings on further advancing and refining the capabilities of wireless systems
Real-Time Localization Using Software Defined Radio
Service providers make use of cost-effective wireless solutions to identify, localize, and possibly track users using their carried MDs to support added services, such as geo-advertisement, security, and management. Indoor and outdoor hotspot areas play a significant role for such services. However, GPS does not work in many of these areas. To solve this problem, service providers leverage available indoor radio technologies, such as WiFi, GSM, and LTE, to identify and localize users. We focus our research on passive services provided by third parties, which are responsible for (i) data acquisition and (ii) processing, and network-based services, where (i) and (ii) are done inside the serving network. For better understanding of parameters that affect indoor localization, we investigate several factors that affect indoor signal propagation for both Bluetooth and WiFi technologies. For GSM-based passive services, we developed first a data acquisition module: a GSM receiver that can overhear GSM uplink messages transmitted by MDs while being invisible. A set of optimizations were made for the receiver components to support wideband capturing of the GSM spectrum while operating in real-time. Processing the wide-spectrum of the GSM is possible using a proposed distributed processing approach over an IP network. Then, to overcome the lack of information about tracked devices’ radio settings, we developed two novel localization algorithms that rely on proximity-based solutions to estimate in real environments devices’ locations. Given the challenging indoor environment on radio signals, such as NLOS reception and multipath propagation, we developed an original algorithm to detect and remove contaminated radio signals before being fed to the localization algorithm. To improve the localization algorithm, we extended our work with a hybrid based approach that uses both WiFi and GSM interfaces to localize users. For network-based services, we used a software implementation of a LTE base station to develop our algorithms, which characterize the indoor environment before applying the localization algorithm. Experiments were conducted without any special hardware, any prior knowledge of the indoor layout or any offline calibration of the system
C-Band Airport Surface Communications System Standards Development. Phase II Final Report. Volume 2: Test Bed Performance Evaluation and Final AeroMACS Recommendations
This report is provided as part of ITT s NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: New ATM Requirements-Future Communications, C-Band and L-Band Communications Standard Development and was based on direction provided by FAA project-level agreements for New ATM Requirements-Future Communications. Task 7 included two subtasks. Subtask 7-1 addressed C-band (5091- to 5150-MHz) airport surface data communications standards development, systems engineering, test bed and prototype development, and tests and demonstrations to establish operational capability for the Aeronautical Mobile Airport Communications System (AeroMACS). Subtask 7-2 focused on systems engineering and development support of the L-band digital aeronautical communications system (L-DACS). Subtask 7-1 consisted of two phases. Phase I included development of AeroMACS concepts of use, requirements, architecture, and initial high-level safety risk assessment. Phase II builds on Phase I results and is presented in two volumes. Volume I is devoted to concepts of use, system requirements, and architecture, including AeroMACS design considerations. Volume II (this document) describes an AeroMACS prototype evaluation and presents final AeroMACS recommendations. This report also describes airport categorization and channelization methodologies. The purposes of the airport categorization task were (1) to facilitate initial AeroMACS architecture designs and enable budgetary projections by creating a set of airport categories based on common airport characteristics and design objectives, and (2) to offer high-level guidance to potential AeroMACS technology and policy development sponsors and service providers. A channelization plan methodology was developed because a common global methodology is needed to assure seamless interoperability among diverse AeroMACS services potentially supplied by multiple service providers
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