1,721,003 research outputs found
Spectrum Monitoring Based on the VITA 49 Standard and a General-Purpose RF Platform
No full textSpectrum monitoring has become a topic of interest in the recent decades due to the increase of wireless communication systems. Traditional methods for spectrum monitoring use a spectrum analyzer to capture and analyze signals. Furthermore, these traditional methods rely on a human observer and largely consider the RF environment constant. As a result, they are not only high cost, but also inefficient. The objective of this research is building a scalable and a low-cost wideband spectrum monitoring system. A unique feature of the system is due to the use of VME bus International Trade Association (VITA) 49 standard. The proposed system is more appropriate for a dynamic RF spectrum environment and is built using off-the-shelf computer hardware and the low-cost Software-Defined Radio (SDR) R820T to collect spectral and temporal data of the spectrum around the city of Fort Wayne
A generalized prefix for multi-carrier modulation
No full textWireless communication systems are pervasive today. There is an ever increasing need to increase throughput and to make more efficient use of the available spectrum for data transmission (i.e. the wireless channel). Orthogonal Frequency Division Multiplexing is a modulation technique that assists in achieving these goals. This technique allows multiple information symbols to be transmitted on orthogonal sub-carrier frequencies and then recombines them to recover the transmitted information at the receiver. To separate the OFDM information symbols at the receiver and avoid Inter-Symbol Interference (ISI), one approach is to add an information buffer or prefix before each OFDM symbol. In most practical wireless systems, a cyclic prefix is used for this purpose. Although the cyclic prefix prevents ISI, it does not prevent loss of data in frequency-selective fading channels. In such a channel with spectral nulls or deep fades, data transmitted along affected frequencies is lost and the bit error rate (BER) has an error floor. In this research, a generalized prefix is advanced which prevents ISI as well as transforms frequency-selective fading channels into channels without spectral nulls thus obliterating the error floor which constrains systems using the conventional cyclic prefix. The proposed system is comparable in complexity to systems implementing the cyclic prefix and as such has similar associated cost and power requirements while offering significant improvements in BER performance in frequency-selective fading channels. This is the case because the generalized prefix repairs any available channel with spectral nulls in a Single-Input Single-Output (SISO) system and transforms the existing channel into one allowing lower BER. This research also investigates the impact of the generalized prefix on communication systems which already exploit diversity gain techniques. The diversity technique to be examined is spatial or antenna diversity in which multiple antennas are used to mitigate the effects of a poor channel by providing alternate paths to the receiver. In examination of this technique, Space-Time Block Coding (STBC) will be employed to encode and decode data in a wireless system. The generalized prefix approach, therefore, produces a wireless system that is of comparable complexity with the cyclic prefix scheme and offers significantly better BER performance in channels with spectral nulls or deep fades. In addition, with similar complexity to the conventional approach, the generalized prefix method offers a practical alternative to existing systems
A Software Defined Radio Testbed for Research in Dynamic Spectrum Access
Get PDFWith the rapidly-increasing amount of high data rate wireless devices, technologies and services appearing on the market today, there is an increasing demand for the wireless spectrum. Current wireless networks are characterized by a static spectrum allocation policy, where governmental agencies assign wireless spectrum to license holders on a long-term basis for large geographical regions. Recently, because of the increase in spectrum demand, this policy faces spectrum scarcity in particular spectrum bands. Dynamic spectrum access (DSA) shows promise to increase spectral efficiency. DSA aims at dynamically sharing spectrum that is licensed to primary users (PUs) with non-licensed secondary users (SUs). In order to effectively share spectrum the SUs must be sure to access the spectrum only when the PUs are not utilizing it, otherwise the SUs could cause interference to the PUs. One method to determine when a PU is accessing the spectrum is for a SU to identify if the spectrum is occupied or not through spectrum sensing. Spectrum probing is a key component in spectrum sensing and defines the policy for when the SU will perform a channel scan of the spectrum to collect spectral data to be used for spectrum sensing.
This work describes the development of a software defined radio (SDR) testbed based on the Universal Software Radio Peripheral (USRP) for research in DSA with a focus in spectrum probing methods. Spectrum probing methodology is an often overlooked component of spectrum sensing. Theoretical analysis and simulation results for comparing different spectrum probing methods are presented in [1]. This work expands on the work in [1] by using the developed SDR testbed to collect experimental data and compare the results. Different spectrum probing methods are implemented for the case of an independent SU and for the case of a cooperative network of SUs. Experimental results are compared to theoretical analysis and simulated results. The experimental findings further support the conclusions based on simulation in [1]. In particular, in the independent sensing scenario, periodic probing indeed achieves the smallest probing delay; however, in the cooperative sensing scenario randomization can drastically reduce the probing delay
Data Transfer Performance Analysis From Programmable Logic to Processing System of ZYNQ 7000
No full textField-Programmable Gate Arrays (FPGAs) were invented in the 1980s. Since then the use of FPGAs in many fields has been growing rapidly. Due to the inherent reconfigurability and relatively low development cost FPGA technology has become one of the important components in data processing and communication systems.The recent development of computing technology affects not only the software but also requires integrating and utilizing a custom logic design on a dedicated hardware platform.In this context, this research work analyses and compares on-chip interfaces for hardware/software communications in the Zynq-7000 all programmable SoC-based platform. Several experiments were carried out to evaluate the performance of data communication between the processing system and the programmable logic through general-purpose (GP), highperformance ports (HP), and accelerator coherency port (ACP); the experiments were conducted for bare-metal standalone applications. The results identified the most effective interfaces for transferring data from the PL to PS and store the data to DRAM memory. The Xilinx Software Development Kit (SDK) and Vivado Design Suite together provide hardware/software development platform to evaluate their performance.One conclusion of this work is that the selection of suitable ports depends on application requirements. For low-bandwidth applications the GP port is appropriate. For high-speed applications, the High Performance (HP) port and Accelerator Coherence Port (ACP) are suitable and work better. The results of this thesis are useful in high-performance embedded systems design
Efficient Implementation Of Sobel Edge Detection With ZYNQ-7000
No full textEdge detection is one of the most important application in image processing. Field-Programmable Gate Arrays (FPGAs) have become popular computing platforms for signal and image processing. The Zynq-7000 System on Chip (SOC) is a dual-processor platform with shared memory. The thesis describes a novel and fast implementation of Sobel edge detection using the Zynq-7000 SoC. Our implementation is a combination of software and hardware using the Vivado HLS and Zynq (SoC). As a result our implementation is fast. We make a comparison with other conventional edge detection techniques and show that the speed of operation of this design is much faster
Enhancing the performance of ad hoc networking by lower layer design
Get PDFAbstractThe research of early ad hoc-like networks, namely multi-hop packet radio networks, was mainly concentrated on lower layers (below network layer). Interestingly, the research of modern ad hoc networks has been mainly restricted to routing protocols. This is understandable, since routing is very challenging in such dynamic networks, but the drawback is that the lower layer models used in the studies are often highly simplified, giving inaccurate or even incorrect results. In addition, modern ad hoc network solutions are usually suboptimal because lower layers, not designed especially for ad hoc networking, are used. Thus, ad hoc networking performance, in general, can be notably enhanced by considering also the design of lower layers. The simple deployment and robustness make wireless ad hoc networks attractive for several applications (e.g., military, public authority, peer-to-peer civilian, and sensor networking), but the performance of the current solutions is typically not adequate.The focus of this work is on the effects of lower layer functionalities on the performance of ad hoc networks, while also taking into account the effects of upper layers (e.g., the effect of application traffic models). A CDMA (Code Division Multiple Access) based dual channel flat ad hoc network solution, incorporating cross-layering between all three lowest layers, is proposed and analyzed. The main element of this is the Bi-Code Channel Access (BCCA) method, in which a common code channel is used for broadcast information (e.g., route discovery), while a receiver-specific code channel is used for all directed transmissions. In addition, a new MAC (Medium Access Control) solution designed for BCCA is presented. Moreover, a novel network layer spreading code distribution (NSCD) method is presented. The advantage of these methods is that they are designed especially to be used in ad hoc networks.With an extensive set of case studies, it is shown that the presented methods outperform the typically used ad hoc network solutions (based on IEEE 802.11) in different kind of scenarios, environments, modeling concepts, and with different parameters. Detailed simulations are carried out in order to analyze the effects of different features at the lower layers, finding also interesting phenomena and dependencies between different layers. It is also shown that close attention should be paid to lower layer modeling even though the overall network performance would be in focus. In addition, various interesting features and behavior models regarding ad hoc networking are brought up.TiivistelmäEnsimmäiset tutkimukset rakenteettomista (ad hoc) verkoista esiintyivät nimellä monihyppypakettiradioverkot, ja ne koskivat pääasiassa verkkokerroksen alapuolella olevia tietoliikennekerroksia, mutta nykyiset tutkimukset ovat kuitenkin keskittyneet pääasiassa reititysprotokolliin. Tämä on sikäli ymmärrettävää, että reititys on hyvin haasteellista tämän tyyppisissä dynaamisissa verkoissa, mutta ongelma on, että käytetyt alempien kerrosten mallit ovat usein hyvinkin yksinkertaistettuja, mikä voi johtaa epätarkkoihin tai jopa vääriin tuloksiin. Tämän lisäksi nykyiset ehdotetut rakenteettomien verkkojen ratkaisut ovat usein tehottomia, sillä käytettyjä alempien kerrosten ratkaisuja ei ole tarkoitettu tällaisiin verkkoihin. Niinpä rakenteettomien verkkojen suorituskykyä voidaan parantaa huomattavasti kiinnittämällä huomiota alempien kerrosten suunnitteluun. Verkkojen rakenteettomuus on ajatuksena houkutteleva useissa käyttökohteissa (esimerkiksi sotilasympäristössä, viranomaiskäytössä, käyttäjien välisissä suorissa yhteyksissä ja sensoriverkoissa), mutta suorituskyky ei useinkaan ole riittävällä tasolla käytännön sovelluksiin.Työssä tutkitaan pääasiassa alempien kerrosten toiminnallisuuden vaikutusta rakenteettomien verkkojen suorituskykyyn ottaen huomioon myös ylemmät kerrokset, kuten sovellustason mallit. Työssä esitellään ja analysoidaan koodijakomonikäyttöön (CDMA, Code Division Multiple Access) perustuva kaksikanavainen tasaisen rakenteettoman verkon ratkaisu, jossa hyödynnetään kaikkien kolmen alimman kerroksen välistä keskinäistä viestintää. Ratkaisun ydin on BCCA-menetelmä (Bi-Code Channel Access), jossa käytetään kahta kanavaa tiedonsiirtoon. Yksi kanava on tarkoitettu kaikille yhteiseksi kontrollikanavaksi (esimerkiksi reitinmuodostus voi käyttää tätä kanavaa), kun taas toinen kanava on käyttäjäkohtainen kanava, jota käytetään suoraan viestittämiseen kyseiselle käyttäjälle (varsinainen data yms.). Tämän lisäksi esitellään myös BCCA-menetelmää varten suunniteltu kanavakontrollimenetelmä sekä verkkotasolla toimiva hajotuskooditiedon jakamiseen tarkoitettu menetelmä. Näiden uusien menetelmien etu on se, että ne on suunniteltu nimenomaan rakenteettomiin verkkoihin.Kattavan testivalikoiman avulla osoitetaan, että esitetty uusi ratkaisu peittoaa tyypilliset IEEE 802.11 -standardiin pohjautuvat rakenteettomien verkkojen ratkaisut. Testeissä käytetään erityyppisiä verkkorakenteita, ympäristöjä, mallinnusmenetelmiä ja parametreja. Yksityiskohtaisissa simuloinneissa ajetaan eri testitapauksia ja selvitetään, miten alempien kerrosten eri menetelmät missäkin tapauksessa vaikuttavat suorituskykyyn. Alempien kerrosten mallinnuksessa on syytä olla tarkkana, sillä työssä käy ilmi, että mallinnusvirheillä voi olla suurikin vaikutus myös ylempien kerrosten suorituskykyyn. Työ myös paljastaa useita mielenkiintoisia ilmiöitä ja vuorovaikutussuhteita, jotka liittyvät tutkittujen menetelmien ja yleisesti rakenteettomien verkkojen toimintaan. Academic dissertation to be presented, with the assent of the Faculty of Technology of the University of Oulu, for public defence in Auditorium IT116, Linnanmaa, on December 5th, 2008, at 12 noonAbstract
The research of early ad hoc-like networks, namely multi-hop packet radio networks, was mainly concentrated on lower layers (below network layer). Interestingly, the research of modern ad hoc networks has been mainly restricted to routing protocols. This is understandable, since routing is very challenging in such dynamic networks, but the drawback is that the lower layer models used in the studies are often highly simplified, giving inaccurate or even incorrect results. In addition, modern ad hoc network solutions are usually suboptimal because lower layers, not designed especially for ad hoc networking, are used. Thus, ad hoc networking performance, in general, can be notably enhanced by considering also the design of lower layers. The simple deployment and robustness make wireless ad hoc networks attractive for several applications (e.g., military, public authority, peer-to-peer civilian, and sensor networking), but the performance of the current solutions is typically not adequate.
The focus of this work is on the effects of lower layer functionalities on the performance of ad hoc networks, while also taking into account the effects of upper layers (e.g., the effect of application traffic models). A CDMA (Code Division Multiple Access) based dual channel flat ad hoc network solution, incorporating cross-layering between all three lowest layers, is proposed and analyzed. The main element of this is the Bi-Code Channel Access (BCCA) method, in which a common code channel is used for broadcast information (e.g., route discovery), while a receiver-specific code channel is used for all directed transmissions. In addition, a new MAC (Medium Access Control) solution designed for BCCA is presented. Moreover, a novel network layer spreading code distribution (NSCD) method is presented. The advantage of these methods is that they are designed especially to be used in ad hoc networks.
With an extensive set of case studies, it is shown that the presented methods outperform the typically used ad hoc network solutions (based on IEEE 802.11) in different kind of scenarios, environments, modeling concepts, and with different parameters. Detailed simulations are carried out in order to analyze the effects of different features at the lower layers, finding also interesting phenomena and dependencies between different layers. It is also shown that close attention should be paid to lower layer modeling even though the overall network performance would be in focus. In addition, various interesting features and behavior models regarding ad hoc networking are brought up.Tiivistelmä
Ensimmäiset tutkimukset rakenteettomista (ad hoc) verkoista esiintyivät nimellä monihyppypakettiradioverkot, ja ne koskivat pääasiassa verkkokerroksen alapuolella olevia tietoliikennekerroksia, mutta nykyiset tutkimukset ovat kuitenkin keskittyneet pääasiassa reititysprotokolliin. Tämä on sikäli ymmärrettävää, että reititys on hyvin haasteellista tämän tyyppisissä dynaamisissa verkoissa, mutta ongelma on, että käytetyt alempien kerrosten mallit ovat usein hyvinkin yksinkertaistettuja, mikä voi johtaa epätarkkoihin tai jopa vääriin tuloksiin. Tämän lisäksi nykyiset ehdotetut rakenteettomien verkkojen ratkaisut ovat usein tehottomia, sillä käytettyjä alempien kerrosten ratkaisuja ei ole tarkoitettu tällaisiin verkkoihin. Niinpä rakenteettomien verkkojen suorituskykyä voidaan parantaa huomattavasti kiinnittämällä huomiota alempien kerrosten suunnitteluun. Verkkojen rakenteettomuus on ajatuksena houkutteleva useissa käyttökohteissa (esimerkiksi sotilasympäristössä, viranomaiskäytössä, käyttäjien välisissä suorissa yhteyksissä ja sensoriverkoissa), mutta suorituskyky ei useinkaan ole riittävällä tasolla käytännön sovelluksiin.
Työssä tutkitaan pääasiassa alempien kerrosten toiminnallisuuden vaikutusta rakenteettomien verkkojen suorituskykyyn ottaen huomioon myös ylemmät kerrokset, kuten sovellustason mallit. Työssä esitellään ja analysoidaan koodijakomonikäyttöön (CDMA, Code Division Multiple Access) perustuva kaksikanavainen tasaisen rakenteettoman verkon ratkaisu, jossa hyödynnetään kaikkien kolmen alimman kerroksen välistä keskinäistä viestintää. Ratkaisun ydin on BCCA-menetelmä (Bi-Code Channel Access), jossa käytetään kahta kanavaa tiedonsiirtoon. Yksi kanava on tarkoitettu kaikille yhteiseksi kontrollikanavaksi (esimerkiksi reitinmuodostus voi käyttää tätä kanavaa), kun taas toinen kanava on käyttäjäkohtainen kanava, jota käytetään suoraan viestittämiseen kyseiselle käyttäjälle (varsinainen data yms.). Tämän lisäksi esitellään myös BCCA-menetelmää varten suunniteltu kanavakontrollimenetelmä sekä verkkotasolla toimiva hajotuskooditiedon jakamiseen tarkoitettu menetelmä. Näiden uusien menetelmien etu on se, että ne on suunniteltu nimenomaan rakenteettomiin verkkoihin.
Kattavan testivalikoiman avulla osoitetaan, että esitetty uusi ratkaisu peittoaa tyypilliset IEEE 802.11 -standardiin pohjautuvat rakenteettomien verkkojen ratkaisut. Testeissä käytetään erityyppisiä verkkorakenteita, ympäristöjä, mallinnusmenetelmiä ja parametreja. Yksityiskohtaisissa simuloinneissa ajetaan eri testitapauksia ja selvitetään, miten alempien kerrosten eri menetelmät missäkin tapauksessa vaikuttavat suorituskykyyn. Alempien kerrosten mallinnuksessa on syytä olla tarkkana, sillä työssä käy ilmi, että mallinnusvirheillä voi olla suurikin vaikutus myös ylempien kerrosten suorituskykyyn. Työ myös paljastaa useita mielenkiintoisia ilmiöitä ja vuorovaikutussuhteita, jotka liittyvät tutkittujen menetelmien ja yleisesti rakenteettomien verkkojen toimintaan
Engineering standards and engineering education
No full textThe role of standards is increasing, and as a result the role of education about standards should also increase. At the same time, there are a set of requirements—accreditation criteria—toward engineering programs. The close relationships between the accreditation criteria and standards education is not fully recognized, even by accreditation bodies and educators. The goal of this article is to uncover these relationships. Furthermore, the article establishes connections between other components of engineering education such as ethics, engineering design, labs, and integrated courses, on one hand and standards education on another. The conclusion from these relationships is that standards education is more important than previously realized. The article also discusses how standards education can be incorporated in engineering and technical curricula
The VITA 49 RF-digital interface
No full textOver the last several years, the interface between the digital and analog RF subsystems of a radio (the analog RF-digital interface) has become increasingly important. this article first discusses the different technology alternatives that exist for this interface and the rationale behind them. the emergence of cognitive radio technology is identified as a trend that increases the importance of the analog RF-digital interface. then the article discusses in detail the VmE bus International trade association (VIta) 49 standard. VIta 49 is a packet-based protocol to convey digitized signal data and metadata (or context data) pertaining to different reference points within a radio receiver. the metadata includes analog front-end parameters such as RF center frequency, bandwidth, If center frequency, sampling rate, gain, location, etc. this standard allows all information about the spectrum as seen by a radio at its antenna to be described, stored, and transported to other systems. VIta 49 is identified as a hierarchical radio description language that is a new paradigm for radio architectures
Wireless communication standards a study of IEEE 802.11, 802.15, and 802.16
No full textWireless Communications Standards: A Study of IEEE 802.11, 802.15, and 802, is one of the latest books in the IEEE Standards Wireless Networks Series, and it is the only book of its kind that covers all of the current 802 wireless standards! Presented in a clear style, by Dr. Todor Cooklev of San Francisco State University, the book is accessible to a wide audience. It is aimed at engineers, computer scientists, managers, and marketing specialists. It can also be used as the primary textbook for a one-semester advanced undergraduate/graduate level course on wireless communication standards, or as a complementary textbook for a course in wireless communication
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