Detection algorithms and FPGA implementations for SC-FDMA uplink receivers

Abstract The demand in mobile broadband communications is increasing dramatically. It is expected that 1000 times more mobile-network capacity will be needed within 10 years. Multiple-input, multiple-output (MIMO) antenna configuration and spatial multiplexing are among the essential techniques for reaching the targets. This creates motivation for study of advanced receivers for combating inter-antenna interference (IAI) and inter-symbol interference (ISI). While various receiver structures have been extensively considered for MIMO receivers, the emphasis has been on those operating in downlink orthogonal frequency-division multiple access (OFDM) systems, wherein ISI is not a problem. Advanced receiver structures for single-carrier frequency-division multiple access (SC-FDMA) uplink systems were studied and analysed. Various receivers were compared via MATLAB simulations, with the objective being to gain solid understanding of how they perform in different channel environments. An efficient combination of IAI and ISI equalisation for SC-FDMA receivers is proposed. The proposed receiver architecture is shown to be a considerable improvement over the conventional linear minimum mean-square error (LMMSE) receiver. Several MIMO detector algorithms and their performance–complexity characteristics are presented. The K-best algorithm with a list size of 8 is shown to be the best option for practical MIMO detector implementation of this receiver in the 4x4 MIMO 64-level quadrature amplitude modulation (QAM) scenario. The second objective involved examining the implementation aspects of the 8-best receiver to achieve good understanding of the complexity of various implementation architectures. It emerged that avoiding the sorting operation in the 8-best list sphere detector (LSD) tree-search algorithm implementation is not recommendable in the 4x4 MIMO 64-QAM scenario. Several field-programmable gate array (FPGA) implementations were carried out, with a range of high-level synthesis (HLS) tools. It is shown that HLS tools have improved significantly and are especially favourable for prototyping of large designs. Additionally, the importance of FPGA technology selection is addressed. Smaller silicon technology should be exploited if base-station baseband processing power consumption is to be minimised. The potential performance or complexity-related gain with the latest FPGAs should be taken into account in comparison of the performance–complexity characteristics of the algorithms. Differences of a few tens of per cent in estimated complexity or performance between two algorithms are often below the threshold of what can be gained or lost in the practical implementation process.Tiivistelmä Tiheään asuttujen kaupunkien uudet langattomat palvelut tarvitsevat tietoliikenneverkkoja, jotka mahdollistavat suuremman tiedonsiirtonopeuden ja kapasiteetin kuin sen, jonka nykyiset mobiiliverkot voivat tarjota. On arveltu, että mobiiliverkkojen kapasiteetin tarve tuhatkertaistuu seuraavan kymmenen vuoden aikana. Tuhatkertainen kapasiteetti on arvioitu saavutettavan kasvattamalla kolmea eri osa-aluetta kymmenkertaiseksi: taajuusspektrin määrä, spektrin käytön tehokkuus sekä tukiasematiheys. Tämä väitöskirja keskittyy spektrin käytön tehokkuuden kasvattamiseen. Moniantennitoteutus (multiple-input multiple-output, MIMO) on siinä välttämätön. MIMO-tekniikkaa hyödyntävien solukkojärjestelmien tukiasemavastaanottimissa tarvitaan melko monimutkainen kanavakorjain sekä ilmaisin, joiden algoritmien optimointi ja toteutus ymmärretään vielä sangen puutteellisesti. Väitöskirjatutkimuksen päätavoitteena on tutkia edistyksellisiä vastaanotinrakenteita, joilla saavutetaan LTE-A-standardin tavoitetiedonsiirtonopeus kohtuullisella kompleksisuudella. Työssä keskitytään ns. nousevaan siirtosuuntaan (uplink) eli päätelaitteesta tukiasemaan tapahtuvaan tiedonsiirtoon, jossa käytetään yhden kantoaallon taajuusjakomonikäyttötekniikkaa (single-carrier frequency-division multiple-access, SC-FDMA) ortognaalisen taajuusjakomonikäytön (orthogonal frequency division multiple access, OFDMA) sijaan. Eri vastaanotinrakenteita ja näiden ilmaisinalgoritmeja vertaillaan tietokonesimuloinnein MATLAB-ympäristössä. Väitöskirjassa ehdotetaan kaksiosaista vastaanotinrakennetta, jossa antennien välinen keskinäishäiriö (inter antenna interference, IAI) ja symbolien välinen keskinäisvaikutus (intersymbol interference, ISI) poistetaan kahdessa eri vaiheessa. Tietokoneimulaatiot osoittavat ko. rakenteen parantavan suorituskykyä huomattavasti perinteiseen lineaariseen keskineliövirheen minimoivaan (linear minimum mean square error, LMMSE) vastaanottimeen verrattuna. Nk. K parasta polkua valitsevan MIMO-ilmaisinalgoritmin listan koolla kahdeksan todetaan tarjoavan 4x4 MIMO 64-tasoisen kvadratuuriamplitudimodulaation (quadrature amplitude modulation, QAM) ympäristössä parhaan kompromissin suorituskyvyn ja kompleksisuuden suhteen. Käytännön toteutettavuuden kannalta keskitytään ohjelmoitavaan digitaalipiiritoteutukseen (field-programmable gate array, FGPA) ja ns. korkean tason synteesi (high-level synthesis, HLS) -työkalujen käyttöön vastaanottimen suunnittelussa. K parasta polkua valitsevan MIMO-ilmaisinalgoritmin arkkitehtuurivertailut osoittavat, että sinänsä vaativaa lajittelualgoritmia ei aina kannata yrittää välttää kirjallisuudessa aikaisemmin ehdotetulla ratkaisulla. Useita eri HLS työkaluja käytetään FPGA toteutuksissa ja todetaan että työkalut ovat kehittyneet huomattavasti viimeisen kahdeksan vuoden aikana. Lisäksi todetaan, että 16 nm viivanleveyden piireillä voidaan saavuttaa noin 15 % suurempi ilmaisunopeus ja 60 % pienempi tehonkulutus verrattuna 28 nm viivanleveyttä käyttäviin piireihin. Erityisesti potentiaali tehonkulutuksen minimoiseksi kannattaa hyödyntää, mikäli signaalinkäsittely näyttelee merkittävää roolia vastaanottimen kokonaistehonkulutuksessa. Kokonaisuutena todetaan, että toteutukseen liittyvät valinnat sekä vaikutus lopputulokseen, tulisi ottaa huomioon jo algoritmien valinnassa. Pieni ero kahden eri algoritmin suorituskyvyn välillä häviää helposti toteutusvaiheen ratkaisujen vaikutusten alle

MIMO detector for LTE/LTE-A uplink receiver

Abstract We propose a carefully selected receiver structure, detector and detector implementation architecture for multiple-input multiple-output (MIMO) uplink base station receiver for fourth generation (4G) wireless cellular systems. First, we compare different receiver algorithms and structures for single-carrier frequency-division multiple access (SC-FDMA) uplink transmission to get a good understanding of the performance and complexity of these algorithms and their suitability for practical realization. One of those structures, namely the frequency domain MMSE equalization with sphere detection (SD), is proposed for implementation. The receiver consists of separate stages for inter-symbol interference (ISI) and inter-antenna interference (IAI) mitigation in frequency selective MIMO channels. Frame error rate (FER) performance is studied via simulations in realistic wireless channels and practical system parameters. K-best SD is selected as a detector algorithm for this receiver. There are several publications proposing a sort-free architecture for tree search type of detectors. Both a conventional K-best architecture and a sort-free architecture are implemented on a Xilinx Virtex-6 field-programmable gate array (FPGA) using High Level Synthesis (HLS) tool. Both architectures support 4 × 4 MIMO with 64-level modulation (64-QAM). Complexity results confirm that avoiding the sorter is not always recommended. The benefit of sort-free architecture depends on the system parameters

Base station MIMO detector algorithm implementations

Abstract In this paper, we implement a high throughput multiple-input multiple-output (MIMO) detector for single-carrier frequency-division multiple access (SC-FDMA) base station. High-level Synthesis (HLS) tool is used for implementing the algorithm on Xilinx Virtex and Zynq FPGAs. First, we compare the throughput performance and power consumption results of the different implementations. Second, we evaluate the quality of the results by comparing the HLS results to handwritten register-transfer level (RTL) implementations. In conclusion, the HLS tools have evolved into applicable implementation tools. Furthermore, the possible slight losses in the performance or design complexity with the HLS design method could be counteracted by choosing a higher category FPGA

Psychometric properties of the Neuropsychiatric Inventory: a review

Neuropsychiatric symptoms (NPSs) cause a significant burden to individuals with memory disorders and their families. Insights into the clinical associations, neurobiology, and treatment of NPSs are largely dependent on informant questionnaires, such as the commonly used Neuropsychiatric Inventory (NPI). Like any scale, the utility of the NPI relies on its psychometric properties, but unlike many scales, the NPI faces unique challenges related to its skip-question and scoring formats. We examined and reviewed the psychometric properties of the NPI in a framework including psychometric properties pertinent for construct validation, and health-related outcome measurement in general. We found that aspects such as test-retest and inter-rater reliability are major strengths of the NPI in addition to its flexible and relatively quick administration. These properties are desired in clinical trials. However, it seems that the reported properties cover only some of the generally examined psychometric properties, representing perhaps necessary but not sufficient reliability and validity evidence for the NPI. There appear to be significant gaps in psychometric data, at least partially owing to small sample sizes in the studies that preclude more comprehensive analyses. Regarding construct validity, only one study examined structural validity with the NPI subquestions. Measurement error was not assessed in the reviewed studies. For future validation, we recommend using data from all subquestions, collecting larger samples, paying specific attention to construct validity and formulating hypotheses a priori. As the NPI is an outcome measure of interest in clinical trials, examining measurement error could be of practical importance

Delivery capability in rapid productisation

Abstract Rapid productisation introduces a strategic approach to company management, which will help companies focus their productisation efforts in order to increase their return on development and become more competitive. Rapid productization is a mode of operation which creates a field for faster response for a customer demand than with “a standard” productization is able to achieve. On the other hand rapid productisation process creates disruption into an organisation. Rapid productisation as a framework is a way to fix the portfolio shortage whatever the reason behind for it is. Use of rapid productisation framework is not needed if predefined offering (a portfolio) match in sales situation to the customer’s demand. During a business case analysis phase a company need to decide whether there is possibilities to response or not to the customer’s demand and make a rapid offer for a new product or service. Business case analysis is a key stage and it is not fast if the rapid productisation process requires a data collecting far too detail level. One way to speed up the analysis is 1) limiting a number of used interfaces’ 2) do less unnecessary paper work and 3) throw away routine meetings. This will boost the rapid productisation start up and streamline running of whole process. Rapid productisation is an exception and it a company need to differ from an approach they normally use. If rapid productisation process will be handled like a basic productisation process there are no possibilities to get any improvements like faster throughput. One important target of rapid productisation process is to use less or minimal engineering work (manpower) and have predictable delivery than most of productisation cases in general. That advantage will be losing if the process itself is not steamed compare to basic productisation process. Main point in rapid productisation is to ensure that all necessary sales and R&D interfaces will get the information. In other words make sure that only absolutely needed organisations units and roles will be involved and those got information of new productised product. In minimum decision to start a rapid productisation should be able to make within minimum participant from sales, R&D and company’s management team. A goal of rapid productisation process is to define whether a business exists and at the same time delivery capability can be achieved in able to make rapid offering. As a result of this study, fast track frame was formed. This study provides guidance for the managers considering rapid productisation as an option to serve customers better and improve agility within organisations. Rapid productisation seeks to add value to a company in sales negotiation.Tiivistelmä Tämän Nopea tuotteistaminen on yrityksen johdolle strategisen työkalun, jonka avulla yrityksellä on mahdollisuus reagoida nopeasti myyntitilanteessa esiin tuleviin uusiin asiakasvaatimuksiin. Nopea tuotteistaminen auttaa keskittämään tekemistä oikeisiin asioihin ja näin ollen savuttamaan paremman tuottavuuden. Toimintamallina nopea tuotteistaminen antaa mahdollisuuden vastata nopeammin asiakkaan vaatimuksiin, kuin mitä olisi mahdollista perinteisen tuotteistamisen avulla. Toisaalta nopea tuotteistaminen saa aikaan häiriötilan yrityksen toiminnassa. Nopea tuotteistaminen mahdollistaa portfolion puutteiden nopean korjaamisen myyntitilanteen aikana. Mikäli myyntitilanteessa tuote- tai palvelutarjonta vastaa asiakaan toiveita on selvää, ettei nopeaa tuotteistamista tarvitse käynnistää. Lähtökohtaisesti asiakkaan vaatimus pitäisi olla toteutettavissa kannattavasti. Nopean tuotteistamisen kohdalla myös muut perusteet voivat tulla kysymykseen. Kannattavuuslaskennan onnistuminen nopealla aikataululla on koko hankeen tärkeimpiä vaiheita. Nopeus ei toteudu, jos tietoa joudutaan keräämään liian perusteellisesti. Kannattavuusanalyysiä voidaan nopeuttaa, jos 1) rajoitetaan hankkeeseen osallistuvien lukumäärää, 2) vältetään ”turhaa” paperien kierrätystä ja 3) poiketaan totutuista rutiini prosesseista. Näin menetellen nopea tuotteistus saa nopean alun ja se vauhdittaa koko prosessin etenemistä. On tärkeää muistaa, että nopean tuotteistamisen prosessi on poikkeus tila ja sen käyttäminen vaatii kykyä hylätä tutut käytännöt. Tutkimuksessa on selvinnyt, ettei nopea tuotteistaminen ole mahdollista turvautumalla pelkästään perinteisiin tuotteistamisen menetelmiin. Nopean tuotteistamisen tavoitteena on käyttää mahdollisimman vähän perinteistä insinöörityötä ja ennustaa tarkasti toimitusaika mikä ei ole itsestään selvää perinteisiä tuotteistamistapoja käytettäessä. Nämä edut menetetään myös nopeassa tuotteistamisessa, jos käytössä on vain perinteiset hyväksi havaitut menetelmät. Erityisen tärkeää nopeassa tuotteistamisessa on varmistaa, että myynti ja tuotekehitysorganisaatiot saava käyttöön kaiken tarvittavan tiedon. Nopean päätöksenteon edellytys on rajata hankkeeseen osallistuvien lukumäärää. Tämä tarkoittaa, että hankkeeseen osallistuu pieni joukko myynnistä, tuotekehityksestä ja yrityksen johdosta. Nopean tuotteistamisen tavoitteena on selvittää hankkeen liiketaloudellisuus ja se, että tuotte tai palvelu on mahdollista toteuttaa asiakkaan toiveiden mukaan halutussa aikataulussa ennen lopullisen tarjouksen tekoa. Tässä tutkimuksessa on kehitetty nopean tuotteistamisen toimintamalli. Yritykselle tämä tarjoaa mahdollisuuden lisäarvon luomiseen myyntineuvottelujen aikana ja samalla kehittää organisaation toimintaa

Rapid productization – empirical study on preconditions and challenges

Abstract Rapid productization is a new concept originating from the practical challenges of case companies. The purpose of this paper is to provide tangible examples of what are rapid productization preconditions and challenges in high-tech companies in sales situations. This study seeks to answer to the following research questions: what is rapid productization and what are preconditions and challenges for rapid productization? The research approach of this study follows constructivism and utilizes qualitative research to empirical observation based on interviews done to target enterprises and specialists. The need to quickly respond to new customer preferences addresses new structure to companies in changing business environment. Rapid productisation offers a framework for companies a new way how to solve a lack of offering in existing portfolio or service. Limitation of this study is that productization and rapid productization is not yet a stable concept in academic research. As a result of this study, a sales and rapid productization frame was formed. This study provides guidance for the managers considering rapid productisation as an option to serve customers better and improve agility within organisations. Rapid productization seeks to add value to a company in sales negotiation.Tiivistelmä Nopea tuotteistaminen on uusi käsite, joka perustuu tutkittujen yrityksen käytännön haasteisiin. Tämän tutkimuksen tavoitteena on luoda konkreettisia esimerkkejä siitä, mitä ovat myyntitilanteessa korkean teknologian yritysten nopean tuotteistamisen edellytykset ja haasteet. Tässä tutkimuksessa vastataan seuraaviin kysymyksiin: mitä nopea tuotteistaminen on ja mitkä ovat nopean tuotteistamisen ennakkoehdot ja haasteet? Tutkimusmenetelmänä on laadullinen yrityshaastattelututkimus. Tutkimuksessa esitetään malli miten vastata nopeasti myyntitilanteessa asiakkaan esittämiin uusiin vaatimuksiin ja pyrkiä näin ratkaisemaan tuote- ja palvelutarjonnassa oleva puutteet. Mallin hyödyntäminen mahdollistaa yritykselle uuden nopeamman tavan tuotteistaa haluttu lopputulos. Yritykselle tämä tarjoaa mahdollisuuden lisäarvon luomiseen myyntineuvottelujen aikana. Yritysjohtajille tämä tutkimus antaa esimerkin tuotteistamisesta, jonka avulla on mahdollista palvella asiakkaita paremmin ja samalla nopeuttaa organisaation toimintaa

Gender inclusiveness in the adoption and use of home energy technologies

Abstract Home energy technologies, such as smart home energy management systems (SHEMS), are important in reducing energy-related emissions and empowering energy users. However, there are concerns on gender inclusiveness of the adoption and use of SHEMS. So far, information systems research has failed to address this significant challenge. This study examines factors shaping gendered adoption and use of smart home technologies, particularly SHEMS, and the implications this has for sustainability and energy equality. Applying a critical lens, we examine findings from a sensory ethnographic study on the adoption of SHEMS in households. The findings underline the need for more inclusive energy technology design, more understanding of diversity of households and more variety in the approaches for increasing awareness on and facilitating the adoption of energy technologies. We contribute to research on gender and home energy technologies, and to the larger discussion of gender and energy

MIMO detector implementations using high-level synthesis tools from different generations

Abstract In 2011, we proposed a new receiver structure called Frequency domain linear MMSE filter with sphere detection for single-carrier frequency-division multiple access (SC-FDMA) uplink transmission. Frame error rate simulations and complexity estimations were used to define the most practical sphere detector algorithm for this receiver. High-level Synthesis (HLS) tools were used for comparing different architectures for the sphere detector. After 2011, the HLS design approach has gained more popularity and the tools have evolved. In this paper, HLS tools from different generations were used for implementing the same K-best list sphere detector. The results were compared and the overall experience of the optimization process and the evolution of the HLS tools was discussed. Additionally, the evolution of FPGA technology was discussed. In conclusion, the HLS tools have evolved into practical implementation tools even for high complex wireless communication algorithms. Moreover, 25% increase in throughput and 58% lower resource usage was achieved with the latest generation FPGA

Data collection from LoRaWAN sensor network by UAV gateway:design, empirical results and dataset

Abstract Collecting data from Internet-of-Things (IoT) devices, especially the variety of sensors dispersed in the environment, is an increasingly important and difficult task. Several long-range radio-access technologies, such as low-power wide-area networks (LPWAN) and specifically LoRaWAN, have been proposed to address this challenge. However, until now, the key focus of the related studies has been on static terrestrial LPWAN deployments. In this study, we depart from this vision and investigate the practical feasibility and performance of a LoRaWAN gateway (GW) on a flying platform, specifically — an unmanned aerial vehicle (UAV). The key contributions of this study are (i) the design and field-testing of a packet-sniffer-based mobile LoRaWAN GW prototype, allowing collection of the data from LoRaWAN networks, including the already deployed ones; (ii) the open-publication of the data collected during our experimental campaign in the 426 LoRaWAN sensor node network of the University of Oulu illustrating the performance of different drone trajectories; (iii) the initial results of the system’s performance analysis, revealing some interesting trends and setting goals for further studies, and pinpointing the lessons learned during the experimental campaign. Our empirical findings suggest that the Travelling Salesman Problem (TSP) trajectory is the most effective moving trajectory for the number of packets collected and the average energy consumed per packet collected

Improving LoRaWAN performance by randomizing network access for data and on-air activation

Abstract During the past years, the LoRaWAN technology took a prominent position among the wireless connectivity solutions for the Internet of Things (IoT) and has attracted substantial attention. The LoRaWAN technology has become popular for collecting the data from the sensors, which traditionally have periodic communication patterns. Meanwhile, recent studies have shown that the LoRaWAN procedures, such as the over-the-air activation, may also compromise the uniformity of data traffic distribution. Therefore, in this study, we investigate how the communication pattern of LoRaWAN devices during activation and data communication affects the overall network performance with respect to speed of activation and overall packet delivery probability. We show that the periodic communication patterns, widely employed by commercial LoRaWAN devices today, are less efficient than the patterns featuring random delays between the packets. Also, we find that introduction of a random delay between uplink data packets helps randomizing the channel access and enables network performance boost both for the application data transfer and during the activation. Finally, we show that implementation of the suggested communication patterns modification is feasible for the state-of-the-art LoRaWAN transceivers with no hardware modifications