Architecture Design and Implementation of the Metric First List Sphere Detector Algorithm

Soft-output detection of a multiple-input–multiple-output (MIMO) signal pose a significant challenge in future wireless systems. In this paper, we introduce a soft-output modified metric first (MMF)-LSD algorithm for MIMO detection. We design a scalable architecture and address a method to decrease memory requirements. We provide implementation results for a spatial multiplexing (SM) system with four transmitted streams and with 16- and 64-quadrature amplitude modulation (QAM) on a 0.18- m CMOS application specific integrated circuit (ASIC) technology. The MFF-LSD implementation is more efficient than the depth first (DF) -LSD in the crucial low signal-to-noise rate (SNR)region and the detection rate of the 64-QAM implementation is 39.2 Mbps@26 db with 48.2 kGEs complexity

ARCHITECTURE DESIGN AND IMPLEMENTATION OF THE INCREASING RADIUS - LIST SPHERE DETECTOR ALGORITHM

A list sphere detector (LSD) is an enhancement of a sphere detector (SD) that can be used to approximate the optimal MAP detector. In this paper, we introduce a novel architecture for the increasing radius (IR)-LSD algorithm, which is based on the Dijkstra’s algorithm. The parallelism possibilities are introduced in the presented architecture, which is also scalable for different multiple-input multiple-output (MIMO) systems. The novel architecture is implemented on a Virtex-IV field programmable gate array (FPGA) chip using high-level ANSI C++ language based Catapult C Synthesis tool from Mentor Graphics. The used word lengths, the latency of the design, and the required resources are presented and analyzed for 4 x 4 MIMO system with 16- quadrature amplitude modulation (QAM). The detector implementation achieves a maximum throughput of 12.1Mbps at high signal-to-noise ratio (SNR)

ASIC Implementation Comparison of SIC and LSD Receivers for MIMO-OFDM

MIMO-OFDM receivers with horizontal encoding are considered in this paper. The successive interference cancellation (SIC) algorithm is compared to the K-best list sphere detector (LSD). A modification to the K-best LSD algorithm is introduced. The SIC and K-best LSD receivers are designed for a 2 x 2 antenna system with 64-quadrature amplitude modulation (QAM). The ASIC implementation results for both architectures are presented. The K-best LSD outperforms the SIC receiver in bad channel conditions but the SIC receiver performs better in channels with less correlated MIMO streams. The latency of the K-best LSD is large due to the high modulation order and list size. The throughput of the SIC receiver is more than 6 times higher than that of the K-best LSD.TekesFinnish Funding Agency for Technology and InnovationNokiaTexas InstrumentsNokia Siemens Networks (NSN)Elekrobi

COMPARISON OF TWO NOVEL LIST SPHERE DETECTOR ALGORITHMS FOR MIMO-OFDM SYSTEMS

In this paper, the complexity and performance of two novel list sphere detector (LSD) algorithms are studied and evaluated in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system. The LSDs are based on the K-best and the Schnorr-Euchner enumeration (SEE) algorithms. The required list sizes for LSD algorithms are determined for a 2×2 system with 4- quadrature amplitude modulation (QAM), 16-QAM, and 64-QAM. The complexity of the algorithms is compared by studying the number of visited nodes per received symbol vector by the algorithm in computer simulations. The SEE based LSD algorithm is found to be a less complex and a feasible choice for implementation compared to the K-best based LSD algorithm.ElekrobitNokiaTexas InstrumentsFinnish Funding Agency for Technology and InnovationTeke

The Effect of Preprocessing to the Complexity of List Sphere Detector Algorithms

A list sphere detector (LSD) is an enhancement of a sphere detector (SD) that can be used to approximate the soft output MAP detector used in the detection of the multiple-input multiple-output (MIMO) signals. The LSD algorithm executes a tree search on the given lattice and returns a candidate list. The LSD algorithm complexity, i.e., the number of visited nodes in the search tree, can be decreased by applying proper ordering of the transmitted spatial streams in the detection. In this paper, we study the effect of two sophisticated preprocessing methods, the channel matrix column ordering based on Euclidean norm and the sorted QR decomposition (SQRD), to the performance and complexity of the LSD algorithms and compare them to the traditional QR decomposition (QRD). We show that the SQRD preprocessing is a simple way to decrease complexity of the LSD and it decreases the number of visited nodes approximately 20 - 30% compared to the QRD which results in significant number of saved arithmetic operations in the LSD. We also show that the plain channel matrix column ordering is not feasible preprocessing method to be used with LSD in highly correlated channel realization.ElekrobitNokiaNokia Siemens Networks (NSN)Texas InstrumentsFinnish Funding Agency for Technology and InnovationTeke

Complexity Analysis of MMSE Detector Architectures for MIMO OFDM Systems

In this paper, a field programmable gate array (FPGA) implementation of a linear minimum mean square error (LMMSE) detector is considered for MIMO-OFDM systems. Two square root free algorithms based on QR decomposition (QRD) are introduced for the implementation of LMMSE detector. Both algorithms are based on QRD via Givens rotations, namely coordinate rotation digital computer (CORDIC) and squared Givens rotation (SGR) algorithms. Linear and triangular shaped array architectures are considered to exploit the parallelism in the computations. An FPGA hardware implementation is presented and computational complexity of each implementation is evaluated and compared.ElekrobitNokiaTexas InstrumentsNational Technology Agency of FinlandTeke

Implementation aspects of list sphere decoder algorithms for MIMO-OFDM systems

A list sphere decoder (LSD) can be used to approximate the optimal maximum a posteriori (MAP) detector for the detection of multiple-input multiple-output (MIMO) signals. In this paper, we consider two LSD algorithms with different search methods and study some algorithm design choices which relate to the performance and computational complexity of the algorithm. We show that by limiting the dynamic range of log-likelihood ratio, the required LSD list size can be lowered, and, thus, the complexity of the LSD algorithm is decreased. We compare the real and the complex-valued signal models and their impact on the complexity of the algorithms. We show that the real-valued signal model is clearly the less complex choice and a better alternative for implementation. We also show the complexity of the sequential search LSD algorithm can be reduced by limiting the maximum number of checked nodes without sacrificing the performance of the system. Finally, we study the complexity and performance of an iterative receiver, analyze the tradeoff choices between complexity and performance, and show that the additional computational cost in LSD is justified to get better soft-output approximation.TekesFinnish Funding Agency for Technology and InnovationNokiaNokia Siemens Networks (NSN)ElekrobitUninor

Pikselitaide ja sen käyttö peleissä

Tämän opinnäytetyön aiheena on pikselitaiteen tutkiminen ilmiönä ja taiteenmuotona. Opinnäytetyössä perehdytään hyväksi havaittuihin pikselitaide tekniikoihin ja hyödynnetään opittua tietoa grafiikan tekemisessä. Opinnäytetyötä ei ole tehty yrityksen toimesta, vaan tavoitteena on henkilökohtainen oppiminen ja uusien tekniikoiden kokeilu Lähteinä käytettiin pääosin internet lähteitä. Kirjalähteitä on hyödynnetty animaation tutkimisessa. Työn alussa esitellään mitä pikselitaide on ja tämän jälkeen esitellään erilaisia tekniikoita pikselitaiteen tekemiseen. Työssä käydään myös läpi animoidun hahmon graafinen toteutus ja pikselitaiteen hyödyntäminen peligrafiikassa. Työn lopussa pohditaan pikseligrafiikan kannattavuutta kolmiulotteisen grafiikan aikakautena ja arvioidaan omaa suoritusta ja oppimista. Työn produktiivinen osa koostuu digitaalisessa muodossa olevasta spritesheetistä, hahmografiikasta ja animaatiotestistä.The aim of this thesis was to study pixel art as an art form and phenomenon. In this thesis new pixel art techniques were learned and utilised in making graphics. This thesis was not made for any company, because the goal of this work was to learn new techniques. Majority of the sources are from the internet sources. Book sources are used when studying animation. What pixel art is and what kind of techniques are used commonly are discussed at the beginning of this thesis. Also, making an animated character and using pixel art graphics for game are discussed. At the end of this thesis it is pondered if the pixel art style is still valid in times of three dimensional graphics. Also, personal learning and the results of this thesis were evaluated. Productive part of this work consist of digital sprite sheet, character graphics and animation test

Detection algorithms and architectures for wireless spatial multiplexing in MIMO-OFDM systems

Abstract The development of wireless telecommunication systems has been rapid during the last two decades and the data rates as well as the quality of service (QoS) requirements are continuously growing. Multiple-input multiple-output (MIMO) techniques in combination with orthogonal frequency-division multiplexing (MIMO–OFDM) have been identified as a promising approach for high spectral efficiency wideband systems. The optimal detection method for a coded MIMO–OFDM system with spatial multiplexing (SM) is the maximum a posteriori (MAP) detector, which is often too complex for systems with high order modulation. Suboptimal linear detectors, such as the linear minimum mean square error (LMMSE) criterion based detection, offer low complexity solutions, but have poor performance in correlated fading channels. A list sphere detector (LSD) is a tree search based soft output detector that can be used to approximate the MAP detector with a lower computational complexity. The benefits of the more advanced detectors can be realized especially in a low SNR environment by, e.g., increasing the cell coverage. In this thesis, we consider the linear minimum mean square error (LMMSE) criterion based detectors and more advanced LSDs for detection of SM transmission. The LSD algorithms are not as such feasible for hardware implementation. Therefore, we identify the design choices that relate to the performance and implementation complexity of the LSD algorithms. We give guidelines to the LSD algorithm design and propose the proper trade-off solutions for practical wireless systems. The more stringent requirements call for further research on architectures and implementation. In particular, it is important to address the parallelism and pipelining factors in the architecture design to enable an optimal trade-off between used resources and operating speed. We design pipelined systolic array architecture for LMMSE detector algorithms and efficient architectures with given algorithm properties for the LSD algorithms. We consider the VLSI implementation of the algorithms to study the true performance and complexity. The designed architectures are implemented on a field programmable gate array (FPGA) chip and CMOS application specific integrated circuit (ASIC) technology. Finally, we present some measurement results with a hardware testbed to verify the performance of the considered algorithms.Tiivistelmä Langattoman tietoliikenteen kehitys on ollut nopeaa viimeisien vuosikymmenien aikana ja järjestelmiltä vaaditaan yhä suurempia datanopeuksia ja luotettavuutta. Multiple-input multiple-output (MIMO) tekniikka yhdistettynä monikantoaaltomodulointiin (MIMO-OFDM) on tunnistettu lupaavaksi järjestelmäksi, joka mahdollistaa tehokkaan taajuusalueen hyödyntämisen. Optimaalinen ilmaisumenetelmä tilakanavoituun (SM) ja koodattuun MIMO-OFDM järjestelmään on maximum a posteriori (MAP) ilmaisin, joka on tyypillisesti liian kompleksinen toteuttaa laajakaistajärjestelmissä, joissa käytetään korkean asteen modulointia. Alioptimaaliset lineaariset ilmaisimet, kuten pienimpään keskineliövirheeseen (LMMSE) perustuvat ilmaisimet, ovat suhteellisen yksinkertaisia toteuttaa nykyteknologialla, mutta niiden suorituskyky on varsin heikko korreloivassa radiokanavassa. Listapalloilmaisin (LSD) on puuhakualgoritmiin perustuva pehmeän ulostulon ilmaisin, joka pystyy jäljittelemään MAP ilmaisinta sitä pienemmällä kompleksisuudella. Kehittyneemmät ilmaisimet, kuten LSD, voivat parantaa langattoman verkon suorituskykyä erityisesti ympäristössä, jossa on matala signaalikohinasuhde, esimerkiksi mahdollistamalla suuremman toiminta-alueen. Tässä väitöskirjassa on tutkittu kahta LMMSE ilmaisinta ja kolmea LSD ilmaisinta SM lähetyksen ilmaisuun. Yleisesti LSD algoritmit eivät ole sellaisenaan toteutuskelpoisia kaupallisiin järjestelmiin. Väitöskirjassa on tämän vuoksi tutkittu LSD:n toteutukseen liittyviä haasteita ja toteutusmenetelmiä ja annetaan suosituksia LSD algorithmien suunnitteluun sekä ehdotetaan sopivia toteutuskompromisseja käytännön langattomiin järjestelmiin. Haastavammat suorituskyky- ja latenssivaatimukset edellyttävät lisätutkimuksia toteutusarkkitehtuureihin ja toteutuksiin. Erityisesti rinnakkaisten resurssien käyttö ja liukuhihnatekniikka toteutusarkkitehtuureissa mahdollistavat optimaalisen kompromissin löytämisen toteutuksessa käytettyjen resurssien ja laskentanopeuden väliltä. Väitöskirjassa suunnitellaan tehokkaat arkkitehtuurit tutkituille LMMSE ja LSD algoritmeille ottaen huomioon niiden ominaisuudet. Väitöskirjassa tutkitaan algoritmien toteutusta VLSI tekniikalla ja pyritään saamaan realistinen arvio algoritmien kompleksisuudesta ja suorituskyvystä. Algoritmeille suunnitellut arkkitehtuurit on toteutettu sekä FPGA piirille että erillisenä toteutuksena ASIC teknologialla. Väitöskirjassa esitetään myös testilaitteistolla tehtyjä mittaustuloksia ja varmistetaan toteutettujen algoritmien suorituskyky

Implementation and complexity analysis of list sphere detector for MIMO-OFDM systems

A list sphere detector (LSD) is an enhancement of a sphere detector (SD) that can be used to approximate the soft output maximum a posteriori probability (MAP) detector used in the detection of the multiple-input multiple-output (MIMO) signals. The LSD consists of three different parts: the preprocessing unit, the LSD algorithm unit and the log-likelihood ratio (LLR) calculation unit. Architecture design is the key point to enable an efficient implementation of the LSD. In this paper, we design the architecture for the whole detector structure and exploit the parallelism and pipelining possibilities of the presented architecture units. The designed architecture is implemented in a field programmable gate array (FPGA) using Mentor Graphics Catapult C tool. We show that a scalable architecture can be designed for the LSD. The LSD is also shown to be feasible for practical implementation, and the implementation complexity and latency results are presented.ElekrobitNokiaNokia Siemens Networks (NSN)Texas InstrumentsFinnish Funding Agency for Technology and InnovationTeke