Download or read book Real time Sub carrier Adaptive Modulation and Coding in Wideband Orthogonal Frequency Division Multiplexing Wireless Systems written by Farinaz Edalat and published by . This book was released on 2008 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: The increasing demand for high speed wireless connectivity at low cost proposes new challenges for communication systems designers to implement solutions that increase the data rate by utilizing the limited radio resources more efficiently at a low additional complexity. Sub-carrier Adaptive Modulation and Coding (AMC) exploits the high frequency diversity in wideband Orthogonal Frequency Division Multiplexing (OFDM) channels to obtain higher data rates. While prior work has discussed the value of sub-carrier AMC from a theoretical perspective, this work presents the design and performance of a real-time sub-carrier AMC system. We describe our OFDM transceiver prototype, which implements real-time subcarrier AMC for a wideband wireless channel. We discuss how our design achieves accurate and consistent Signal-to-Noise Ratio (SNR) estimates, which are critical for the success of AMC. We compare the performance of sub-carrier AMC with a non-adaptive scheme that assigns the same modulation and channel coding to all sub-carriers that can support that modulation and coding for the target Bit Error Rate (BER). For a conservative comparison, we compare against the uniform modulation/coding assignment that achieves the highest data rate. Our experiments over the wireless channel show that for a target coded BER of 10-5, our system achieves average data rates of 308.3 and 237.1 Mbps across a variety of Line-of-Sight (LOS) and Non Line-of-Sight (NLOS) locations respectively, which result in 34% and 40% gain over the best non-adaptive scheme. Equivalently, such data rate gain from AMC translates to an SNR improvement of 3 dB. Finally, our implementation of AMC incurs a low overhead of 1.1% of the data rate, and a reasonable complexity, occupying 9.95% of the total transceiver gates on the Field Programmable Gate Array (FPGA).

Download or read book Sub Carrier Adaptive Modulation and Coding in Ofdm written by Farinaz Edalat and published by LAP Lambert Academic Publishing. This book was released on 2010-04 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive Modulation and Coding (AMC) technique exploits the high frequency diversity in wideband OFDM channels to obtain higher data rates. While prior work has discussed the value of AMC from a theoretical perspective, this work presents the design and performance of a real-time sub-carrier AMC system. The measurements from this AMC scheme implemented on an OFDM transceiver prototype indicate how this design achieves accurate and consistent Signal-to-Noise estimates, which are critical for the success of AMC. The performance of this design is compared with a uniform-adaptation scheme that assigns the same modulation and coding to all sub-carriers. The experiments over the wireless channel shows that for a target coded BER of 10 DEGREES-5, this technique achieves average data rates of 308.3 Mbps and 237.1 Mbps across a variety of line-of-sight (LOS) and non-LOS locations respectively, which result in 34% and 40% gain over the best uniform-adaptation scheme. Finally, the implementation of this AMC incurs a low overhead of 1.1% of the data rate, and a reasonable complexity, occupying 9.95% of the total transceiver gates on the Field Programmable Gate Array.

Download or read book Orthogonal Frequency Division Multiplexing for Wireless Communications written by Ye Geoffrey Li and published by Springer Science & Business Media. This book was released on 2006-05-31 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal Frequency Division Multiplexing for Wireless Communications is an edited volume with contributions by leading authorities in the subject of OFDM. Its coverage consists of principles, important wireless topics (e.g. Synchronization, channel estimation, etc.) and techniques. Included is information for advancing wireless communication in a multipath environment with an emphasis on implementation of OFDM in base stations. Orthogonal Frequency Division Multiplexing for Wireless Communications provides a comprehensive introduction of the theory and practice of OFDM. To facilitate the readers, extensive subject indices and references are given at the end of the book. Even though each chapter is written by different experts, symbols and notations in all chapters of the book are consistent.

Download or read book An Adaptive Orthological Frequency Division Miltiplexing Baseband Modem for Wideband Wireless Communication written by Jit Ken Tan and published by . This book was released on 2006 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis shows the design of an Orthogonal Frequency Division Multiplexing base-band modem with Frequency Adaptive Modulation protocol for a wideband indoor wireless channel. The baseband modem is implemented on a Field Programmable Gate Array and uses 294,939 2-input NAND gates with a clock frequency of 128 MHz. The Frequency Adaptive Modulation algorithm is 6% of the entire baseband modem which means that it is of low complexity. The baseband modem is then integrated with a RF Front End. The maximum transmit power of the RF Front End is 7.5 dBm. This prototype takes 128 MHz of bandwidth and divides it into 128 1-MHz bins. The carrier frequency is at 5.25 GHz. Measurements are taken with this prototype to investigate the concept of Frequency Adaptive Modulation. With a target uncoded Bit Error Rate of 10-3, it is found at distances of 1.0m to 10.8m, the data rate varies from 355 Mbps to 10 Mbps. The average data rate of this system is 2.57 times the average data rate without Frequency Adaptive Modulation. The fact that a Rayleigh channel is decomposed into Gaussian sub-channels through Frequency Adaptive Modulation is also verified.

Download or read book Orthogonal Frequency Division Multiplexing with Diversity for Future Wireless Systems written by Khoa N. Le and published by Bentham Science Publishers. This book was released on 2012 with total page 621 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The book examines several aspects of Orthogonal Frequency Division Multiplexing (OFDM) employing linear diversity techniques such as inter-carrier interference, bit error rate, peak to average power and inter-block interference. It should be a useful refe"

Download or read book Multi Carrier and Spread Spectrum Systems written by K. Fazel and published by John Wiley & Sons. This book was released on 2004-02-06 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Frequency spectrum is a limited and valuable resource for wireless communications. A good example can be observed among network operators in Europe for the prices to pay for UMTS-frequency bands. Therefore, the first goal when designing future wireless communication systems (e.g. 4G - fourth generation) has to be the increase in spectral efficiency. The development in digital communications in the past years has enabled efficient modulation and coding techniques for robust and spectral efficient data, speech, audio and video transmission. These are the multi-carrier modulation (e.g. OFDM) and the spread spectrum technique (e.g. DS-CDMA), where OFDM was chosen for broadcast applications (DVB, DAB) as well as for broadband wireless indoor standards (ETSI HIPERLAN-II, IEEE-802.11) and the DS-CDMA was selected in mobile communications (IS-95, third generation mobile radio systems world wide, UMTS/IMT 2000). Since 1993 various combinations of multi-carrier (MC) modulation and the spread spectrum (SS) technique have been introduced and the field of MC-SS communications has become an independent and important research topic with increasing activities. New application fields have been proposed such as high rate cellular mobile, high rate wireless indoor and LMDS. It has been shown that MC-SS offers the high spectral efficiency, robustness and flexibility that is required for the next generation systems. Meanwhile, different alternative hybrid schemes such as OFDM/OFDMA, MC-TDMA, etc. have been deeply analysed and adopted in different international standards (ETSI-BRAN, IEEE-802 & MMAC). Multi-Carrier & Spread-Spectrum: Analysis of Hybrid Air Interfaces draws together all of the above mentioned hybrid schemes therefore providing a greatly needed resource for system engineers, telecommunication designers and researchers in order to enable them to develop, build and deploy several schemes based on MC-transmission for the next generation systems (which will be an integration of broadband multimedia services covering both 4G mobile and fixed wireless systems). * Offers a complete treatment of multi-carrier, spread-spectrum (SS) and time division multiplexing (TDM) techniques * Provides an in-depth insight into hybrid multiple access techniques based on multi-carrier (MC) transmission * Presents numerous hybrid multiple access and air interface architectures including OFDM/CDMA, MC-CDMA, MC-DS-CDMA and MT-CDMA * Covers new techniques such as space-time coding and software radio Telecommunications engineers, hardware & software system designers and researchers as well as students, lecturers and technicians will all find this an invaluable addition to their bookshelf.

Download or read book Adaptive Wireless Transceivers written by Lajos Hanzo and published by Wiley-IEEE Press. This book was released on 2002-04-03 with total page 760 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive Wireless Transceivers provides the reader with a broad overview of near-instantaneously adaptive transceivers in the context of TDMA, CDMA and OFDM systems. The adaptive transceivers examined employ powerful turbo codecs, turbo equalisers and space-time codecs, equipping the reader with a future-proof technological road map. It demonstrates that adaptive transceivers are capable of mitigating the channel quality fluctuations of the wireless channel as a lower-complexity alternative to space-time coding. By contrast, if the higher complexity of multiple transmitters and multiple receiver-assisted systems is deemed acceptable, the advantages of adaptability erode. Provides an in-depth introduction to channel equalisers and Kalman filtering and discusses the associated complexity versus performance trade-offs Introduces wideband near-instantaneously adaptive transceivers and studies their performance both with and without turbo channel coding Describes how to optimise adaptive modulation mode switching and highlights a range of practical considerations Introduces neural network based channel equalisers and discusses Radial Basis Function (RBF) assisted equalisers embedded into adaptive modems supported by turbo channel coding and turbo channel equalisation Employs the above adaptive principles also in the context of CDMA and OFDM transceivers and discusses the pros and cons of space-time coding versus adaptive modulation Researchers, advanced students and practising development engineers working in wireless communications will all find this valuable text an informative read.

Download or read book Self Organized Radio Resource Management in OFDM Based Cellular Systems written by Ting Chen and published by Cuvillier Verlag. This book was released on 2010-12-14 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: The OFDM transmission technique brings high efficiency in future wideband mobile communication systems. With self-organized radio resource management, an OFDM based cellular system can reach full flexibility, especially in a network with hotspots. Each base station allocates resources on demand, based on real-time measurements of signal and interference. Neither a central controller nor direct communication between base stations is needed. Additional schemes can be applied to reduce call interruptions due to unpredictable new interference after resource allocation. Future mobile communication systems require higher data rate and more flexibility. The OFDM, as a multi-carrier transmission technique, achieves high efficiency by subdividing the bandwidth into narrow and orthogonal subcarriers with specific spectrums. The consequent long symbol duration enables also a simple receiver structure in a multi-path propagation environment. Moreover, each subcarrier can use independently individual transmission parameters. In this thesis, a scheme of self-organized radio resource management is proposed for an OFDM based cellular system. All base stations in a cellular network are operating in the same central carrier frequency, but with different radio resources. A resource can be defined as a timeslot, a subcarrier, or any frequency-time block. All resources are accessible at any cell in the cellular network. Neither central controllers nor direct communication between base stations is needed. Each base station allocates radio resources and selects transmission parameters independently in accordance with the requirement and the measured real-time network condition. The powers of signal and interference are measured at both base stations and mobile terminals. To have an interference free measurement, a dedicated signal measurement timeslot is designed in the uplink. A resource quality function is defined to predict the transmission result in a time variant channel, applying both adaptive modulation and coding, and link adaptation. Those resources with highest possible data rates are allocated. In this way, an adaptive and up-to-date resource reuse can be realized. To reduce the amount of droppings due to unpredictable new interference after allocation, a security margin is introduced, which reserves a priori a space for new interference. A suitable margin brings 13% capacity increase. More efficiently, a reallocation procedure can be triggered when service degradation is observed for certain duration. This method can even bring about two times more capacity. The SO-RRM shows its high flexibility in a cellular network with non-uniform or fast changing user distribution. Hotspot cells can declare more resources, while the cells with few users use only much less resources. Furthermore, the multi-user diversity enables in the downlink adaptive resource rearrangement. Resources used inside a cell is exchanged based on instantaneous channel condition. Three different algorithms are compared. They can bring about 80% spectrum higher efficiency. Further information: - Tsinghua University (Chinese) - Tsinghua University (English) - Ruijie Networks Co., Ltd (Chinese) - Ruijie Networks Co., Ltd (English)

Download or read book Adaptive Modulation and Coding Using Signal to noise Ration Switching Threshold written by Faezah Jasman and published by . This book was released on 2009 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) is one of the key enabling technologies for fourth generation (4G) wireless system. It offers high data rate transmission with high spectral efficiency, immunity to multipath fading and simple implementation using fast Fourier transform (FFT). However inefficient utilization of the channel will result when OFDM system is designed for worst-case channel conditions. Thus adaptive transmission scheme that can be adjusted to channel conditions is one of the techniques to improve the performance of OFDM systems. In this thesis, three types of subband adaptive transmission scheme namely adaptive modulation (AM), adaptive coding (AC) and adaptive modulation and coding (AMC) based on SNR switching threshold are investigated. The performances of these systems are evaluated using an efficient adaptation algorithm. The efficient adaptation algorithm is based on the average value of the SNR of the subcarriers in the subband. First the performance of adaptive modulation using quadrature amplitude modulation (QAM) and phase shift keying (PSK) system are evaluated. The results obtained showed that a significant improvements in terms of bit error rate (BER), spectral efficiency and throughput can be achieved. To further enhance the system, convolutional coding is employed. However convolutional coding causes the maximum throughput to be limited. To solve this problem adaptive coding schemes which provides another area of flexibility is investigated. Finally the combination of adaptive modulation and adaptive coding is examined. Simulations results have shown that the performance of adaptive transmission schemes are superior compared to fixed (nonadaptive) transmission schemes. A high throughput performance can be achieved without scarifying the BER. The performance comparisons of the proposed system with the conservative system showed that the proposed scheme is able to meet the BER target of 10-3 with a slightly better throughput performance around 0.3 Bps/Hz.

Download or read book Orthogonal Frequency Division Multiple Access Fundamentals and Applications written by Tao Jiang and published by CRC Press. This book was released on 2010-04-21 with total page 640 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supported by the expert-level advice of pioneering researchers, Orthogonal Frequency Division Multiple Access Fundamentals and Applications provides a comprehensive and accessible introduction to the foundations and applications of one of the most promising access technologies for current and future wireless networks. It includes authoritative cove

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 906 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Block Transceivers written by Paulo Diniz and published by Springer Nature. This book was released on 2022-05-31 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: The demand for data traffic over mobile communication networks has substantially increased during the last decade. As a result, these mobile broadband devices spend the available spectrum fiercely, requiring the search for new technologies. In transmissions where the channel presents a frequency-selective behavior, multicarrier modulation (MCM) schemes have proven to be more efficient, in terms of spectral usage, than conventional modulations and spread spectrum techniques. The orthogonal frequency-division multiplexing (OFDM) is the most popular MCM method, since it not only increases spectral efficiency but also yields simple transceivers. All OFDM-based systems, including the single-carrier with frequency-division equalization (SC-FD), transmit redundancy in order to cope with the problem of interference among symbols. This book presents OFDM-inspired systems that are able to, at most, halve the amount of redundancy used by OFDM systems while keeping the computational complexity comparable. Such systems, herein called memoryless linear time-invariant (LTI) transceivers with reduced redundancy, require low-complexity arithmetical operations and fast algorithms. In addition, whenever the block transmitter and receiver have memory and/or are linear time-varying (LTV), it is possible to reduce the redundancy in the transmission even further, as also discussed in this book. For the transceivers with memory it is possible to eliminate the redundancy at the cost of making the channel equalization more difficult. Moreover, when time-varying block transceivers are also employed, then the amount of redundancy can be as low as a single symbol per block, regardless of the size of the channel memory. With the techniques presented in the book it is possible to address what lies beyond the use of OFDM-related solutions in broadband transmissions. Table of Contents: The Big Picture / Transmultiplexers / OFDM / Memoryless LTI Transceivers with Reduced Redundancy / FIR LTV Transceivers with Reduced Redundancy

Download or read book Multi Carrier Spread Spectrum Related Topics written by Khaled Fazel and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: Khaled Fazel Stefan Kaiser Digital Microwave Systems German Aerospace Center (DLR) Bosch Telecom GmbH Institute for Communications Technology D-71522 Backnang, Germany D-82234 Wessling, Germany In this last decade of this millennium the technique of multi-carrier transmission for wireless broadband multimedia applications has been receiving wide interests. Its first great success was in 1990 as it was selected in the European Digital Audio Broadcasting (DAB) standard. Its further prominent successes were in 1995 and 1998 as it was selected as modulation scheme in the European Digital Video Broadcasting (DVB-T) and in three broadband wireless indoor standards, namely ETSI-Hiperlan-II, American IEEE-802. 11 and Japanese MMAC, respectively. The benefits and success of multi-carrier (MC) modulation in one side and the flexibility offered by spread spectrum (SS) technique in other hand motivated many researchers to investigate the combination of both techniques, known as multi-carrier spread-spectrum (MC-SS). This combination benefits from the main advantages of both systems and offers high flexibility, high spectral efficiency, simple detection strategies, narrow band interference rejection capability, etc. . The basic principle of this combination is straightforward: The spreading is performed as direct SS (DS-SS) but instead of transmitting the chips over a single sequence carrier, several sub-carriers could be employed. As depicted in Figure 1, after spreading with assigned user specific code of processing gain G the frequency mapping and multi-carrier modulation is applied. In the receiver side after multi-carrier demodulation and frequency de-mapping, the corresponding detection algorithm will be performed.

Download or read book Space time Coding and Orthogonal Frequency Division Multiplexing in Cooperative Wireless Relays written by Yan Mei and published by . This book was released on 2006 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advanced Wireless Communications written by Savo G. Glisic and published by John Wiley & Sons. This book was released on 2007-06-13 with total page 890 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fully revised and updated version of the successful "AdvancedWireless Communications" Wireless communications continue to attract the attention ofboth research community and industry. Since the first edition waspublished significant research and industry activities have broughtthe fourth generation (4G) of wireless communications systemscloser to implementation and standardization. "Advanced Wireless Communications" continues to provide acomparative study of enabling technologies for 4G. This secondedition has been revised and updated and now includes additionalinformation on the components of common air interface, includingthe area of space time coding , multicarrier modulation especiallyOFDM, MIMO, cognitive radio and cooperative transmission. Ideal for students and engineers in research and development inthe field of wireless communications, the second edition ofAdvanced Wireless Communications also gives an understanding tocurrent approaches for engineers in telecomm operators, governmentand regulatory institutions. New features include: Brand new chapter covering linear precoding in MIMO channelsbased on convex optimization theory. Material based on game theory modelling encompassing problemsof adjacent cell interference, flexible spectra sharing andcooperation between the nodes in ad hoc networks. Presents and discusses the latest schemes for interferencesuppression in ultra wide band (UWB) cognitive systems. Discusses the cooperative transmission and more details onpositioning.

Download or read book Carrier Frequency Offset Estimation for Orthogonal Frequency Division Multiplexing Systems written by Xiangnian Zeng and published by . This book was released on 2008 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modulation and Coding Techniques in Wireless Communications written by Evgenii Krouk and published by John Wiley & Sons. This book was released on 2011-01-19 with total page 731 pages. Available in PDF, EPUB and Kindle. Book excerpt: The high level of technical detail included in standards specifications can make it difficult to find the correlation between the standard specifications and the theoretical results. This book aims to cover both of these elements to give accessible information and support to readers. It explains the current and future trends on communication theory and shows how these developments are implemented in contemporary wireless communication standards. Examining modulation, coding and multiple access techniques, the book is divided into two major sections to cover these functions. The two-stage approach first treats the basics of modulation and coding theory before highlighting how these concepts are defined and implemented in modern wireless communication systems. Part 1 is devoted to the presentation of main L1 procedures and methods including modulation, coding, channel equalization and multiple access techniques. In Part 2, the uses of these procedures and methods in the wide range of wireless communication standards including WLAN, WiMax, WCDMA, HSPA, LTE and cdma2000 are considered. An essential study of the implementation of modulation and coding techniques in modern standards of wireless communication Bridges the gap between the modulation coding theory and the wireless communications standards material Divided into two parts to systematically tackle the topic - the first part develops techniques which are then applied and tailored to real world systems in the second part Covers special aspects of coding theory and how these can be effectively applied to improve the performance of wireless communications systems