360 research outputs found
Soft Sphere Detection with Bounded Search for High-Throughput MIMO Receivers
We propose a soft sphere detection algorithm where search-bounds are determined based on the distribution of candidates found inside the sphere for different search levels. Detection accuracy of unbounded search is preserved while
significant saving of memory space and reduction of latency is achieved. This probabilistic search algorithm provides significantly better frame-error rate performance than the soft K-best solution and has comparable performance and smaller computational complexity than the bounded depth-first search method.
Techniques for efficient and flexible architecture design of soft sphere detectors are also presented. The estimated hardware cost is lower than the hardware cost of other soft sphere detectors from the literature, while high detection throughput per channel use is achieved
Probabilistically Bounded Soft Sphere Detection for MIMO-OFDM Receivers: Algorithm and System Architecture
Iterative soft detection and channel decoding for MIMO OFDM downlink receivers is studied in this work. Proposed inner soft sphere detection employs a variable upper bound for number of candidates per transmit antenna and utilizes the breath-first candidate-search algorithm. Upper bounds are based on probability distribution of the number of candidates found inside the spherical region formed around the received symbol-vector. Detection accuracy of unbounded breadth-first candidate search is preserved while significant reduction of the search latency and area cost is achieved. This probabilistically bounded candidate-search algorithm improves error-rate performance of non-probabilistically bounded soft sphere detection algorithms,
while providing smaller detection latency with same hardware resources. Prototype architecture of soft sphere detector is synthesized on Xilinx FPGA and for an ASIC design. Using area-cost of a single soft sphere detector, a level of processing parallelism required to achieve targeted high data rates for future wireless systems (for example, 1 Gbps data rate) is determined.NokiaNational Science Foundatio
A General Hardware/Software Co-design Methodology for Embedded Signal Processing and Multimedia Workloads
This paper presents a hardware/software co-design methodology for partitioning real-time embedded multimedia applications between software programmable DSPs and hardware based FPGA coprocessors. By following a strict set of guidelines, the input application is partitioned between software executing on a programmable DSP and hardware based FPGA implementation to alleviate computational bottlenecks in modern VLIW style DSP architectures used in embedded systems. This methodology is applied to channel estimation firmware in 3.5G wireless receivers, as well as software based H.263 video decoders. As much as an 11x improvement in runtime performance can be achieved by partitioning performance critical software kernels in these workloads into a hardware based FPGA implementation executing in tandem with the existing host DSP.Nokia Inc.Texas InstrumentsNational Science Foundatio
Architecture and Algorithm for a Stochastic Soft-output MIMO Detector
In this paper, we propose a novel architecture for a
soft-output stochastic detector in multiple-input, multiple-output
(MIMO) systems. The stochastic properties of this detector
are studied and derived in this work, and several complexity
reduction techniques are proposed to significantly reduce its
cost from an architecture-implementation perspective. We also
propose an efficient architecture to implement this detector.
Finally, this detector is incorporated into an iterative detectiondecoding
structure, and through simulations, it is shown that
the overall frame error rate (FER) performance and complexity
is of the same order as that of the conventional K-best sphere
detector.Nokia CorporationXilinx Inc.National Science Foundatio
Hardware/Software Co-design Methodology and DSP/FPGA Partitioning: A Case Study for Meeting Real-Time Processing Deadlines in 3.5G Mobile Receivers
This paper presents a DSP/FPGA hardware/software partitioning methodology for signal processing workloads. The example workload is the channel equalization and user-detection in HSDPA wireless standard for 3.5G mobile handsets. Channel equalization and user-detection is a major component of receiver baseband processing and requires strict adherence to real time deadlines. By intelligently exploring the embedded design space, this paper presents a hardware/software system-on-chip partitionings that utilizes both DSP and FPGA based coprocessors to meet and exceed the real time data rates determined
by the HSDPA standard. Hardware and software partitioning strategies
are discussed with respect to real time processing deadlines, while an
SOC simulation toolset is presented as vehicle for prototyping embedded
architectures.Nokia Inc.Texas InstrumentsNational Science Foundatio
QRD-QLD searching based sphere detection for emerging MIMO downlink OFDM receivers
In this paper, a detection algorithm with parallel partial candidate-search algorithm is presented. Two fully independent partial search processes are simultaneously employed for two groups of transmit antennas based on QR
and QL decompositions of the channel matrix. Proposed QRDQLD detection algorithm is compared with well-known QRD-M scheme adopted for several emerging wireless standards. Latency of the QRD-QLD candidate search is about twice as small
for similar error-rate performance and for identical hardware resources. Total detection latency of QRD-QLD algorithm that also includes computation of soft information for outer decoder is also substantially smaller.Nokia CorporationNational Science Foundatio
Parallel Searching-Based Sphere Detector for MIMO Downlink OFDM Systems
In this paper, implementation of a detector with parallel partial candidate-search algorithm is described. Two fully independent partial candidate search processes are simultaneously employed for two groups of transmit antennas based
on QR decomposition (QRD) and QL decomposition (QLD) of a multiple-input multiple-output (MIMO) channel matrix. By using separate simultaneous candidate searching processes, the proposed implementation of QRD-QLD searching-based sphere detector provides a smaller latency and a lower computational complexity
than the original QRD-M detector for similar error-rate performance in wireless communications systems employing four transmit and four receive antennas with 16-QAM or 64-QAM constellation size. It is shown that in coded MIMO orthogonal
frequency division multiplexing (MIMO OFDM) systems, the detection latency and computational complexity of a receiver can be substantially reduced by using the proposed QRD-QLD detector implementation. The QRD-QLD-based sphere detector is also implemented using Field Programmable Gate Array (FPGA) and application specific integrated circuit (ASIC), and its hardware design complexity is compared with that of other sphere detectors reported in the literature.Nokia Renesas MobileTexas InstrumentsXilinxNational Science Foundatio
Reconfigurable Architectures for Wireless Systems: Design Exploration and Integration Challenges
Mobile devices are severely power and area limited due to battery capacity
and system size. In many of these example systems, advanced features require
computationally complex signal processing on high-speed data streams for enhanced networking capabilities. Thus, mapping high-level communication and networking algorithms to system architectures is a complex and challenging procedure. An important challenge is to characterize the area, time, and power requirements of these embedded system modules and to use this information effectively to determine the architecture of programmable, reconfigurable, and fixed-function modules. In this paper, we will focus on application examples in wireless networking which highlight these challenges in reconfigurable systems integration.Nokia CorporationTexas Instruments IncorporatedNational Science Foundatio
Electronic Devices Based on Purified Carbon Nanotubes Grown By High Pressure Decomposition of Carbon Monoxide
The excellent properties of transistors, wires, and sensors made from
single-walled carbon nanotubes (SWNTs) make them promising candidates for use
in advanced nanoelectronic systems. Gas-phase growth procedures such as the
high pressure decomposition of carbon monoxide (HiPCO) method yield large
quantities of small diameter semiconducting SWNTs, which are ideal for use in
nanoelectronic circuits. As-grown HiPCO material, however, commonly contains a
large fraction of carbonaceous impurities that degrade properties of SWNT
devices. Here we demonstrate a purification, deposition, and fabrication
process that yields devices consisting of metallic and semiconducting nanotubes
with electronic characteristics vastly superior to those of circuits made from
raw HiPCO. Source-drain current measurements on the circuits as a function of
temperature and backgate voltage are used to quantify the energy gap of
semiconducting nanotubes in a field effect transistor geometry. This work
demonstrates significant progress towards the goal of producing complex
integrated circuits from bulk-grown SWNT material.Comment: 6 pages, 4 figures, to appear in Nature Material
Phylogeographic structure of common sage (Salvia officinalis L.) reveals microrefugia throughout the Balkans and colonizations of the Apennines
Studying the population-genetic and phylogeographic structures of a representative species of a particular geographical region can not only provide us with information regarding its evolutionary history, but also improve our understanding of the evolutionary processes underlying the patterns of species diversity in that area. By analysing eight highly polymorphic microsatellite loci and two chloroplast DNA regions, we have investigated the influence of Pleistocene climate fluctuations on the evolutionary history of Salvia officinalis L. (common sage). The populations with the highest genetic diversity were located in the central parts of the Balkan distribution range. A large group of closely related haplotypes was distributed throughout the Balkans and the central Apennines, while the private lineage occupied the southern Apennines. In addition, two highly differentiated lineages were scattered only over the Balkans. The results suggest that a single refugium of the studied species from the last glacial period was located in the central part of the range in the Balkans. Numerous microrefugia, probably spanning several glaciation cycles, were scattered across the Balkans, while colonisation of the Apennines from the Balkans occurred at least on two occasions
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