A Performance Analysis of MIMO-OFDM/TDM in a Peak-limited Multipath Fading Channel PDF Download

Author: Amir Ligata
Publisher:
ISBN:
Category :
Languages : en
Pages : 6

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Author: G.KRISHNA REDDY
Publisher: Archers & Elevators Publishing House
ISBN: 8119385861
Category : Antiques & Collectibles
Languages : en
Pages : 86

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Author: Gunjan Manik
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659108389
Category :
Languages : de
Pages : 76

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High spectral efficiency and high transmission data rate are the challenging requirements of wireless broadband communications. The MIMO technology has rapidly gained in popularity due to its powerful performance-enhancing capabilities. Spatial diversity can be obtained by using multiple antennas and space-time codes. For future wireless broadband systems, OFDM is discussed as access scheme. OFDM provides an essentially flat fading channel for each subcarrier by insertion of a cyclic guard interval at each antenna. Therefore, space-time block codes are well suited to be applied in OFDM. We investigate SFBC for OFDM systems with multiple transmit antennas, where coding is applied in the frequency domain rather than in the time domain. In this thesis, performance of two coding techniques STBC and SFBC is analyzed in OFDM. In order to appreciate the performances offered by coding through space and frequency, different simulation scenarios have been proposed where variation of the modulation order , channel fading, antenna selection technique, receiver diversity and effect of power conditions have been considered.

Author: Kishor Gannamaneni
Publisher:
ISBN: 9781321549799
Category : Multiplexing
Languages : en
Pages : 71

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Book Description
Orthogonal frequency division multiplexing (OFDM) is an advanced 3G/4G scheme which achieves high data rate and combats multipath fading. However, OFDM systems suffer from nonlinear peak to average power ratio (PAPR) and carrier frequency offsets (CFO). These two factors lead to degraded performance and thereby reducing the system efficiency. OFDM with multiple antennas both at transmitter and receiver and space-time block coding is used to increase the channel capacity and receiver diversity. Space-time block coding is used to increase data rate and for reliable communications. With space-time block coding we can take advantage of both space and time. It is also possible to implement spatial multiplexing using space-time block coding. However, MIMO-OFDM also suffers from high PAPR value. Many methods have been proposed to reduce the PAPR problem in OFDM. Distortion techniques, coding techniques and scrambling techniques are some of those methods. These methods can be extended to MIMO-OFDM. Distortion techniques can reduce the PAPR, but in turn it increases bit error rate. Coding techniques have limitations with number of subcarriers. Scrambling techniques can reduce the PAPR effectively. In this paper we used SLM and PTS methods to reduce the PAPR problem in MIMO-OFDM. The bit error rate performance for each method is plotted and compared with each other. BER performance of MIMO is compared with SIMO and MISO.

Author: Bannour Ahmed
Publisher: Springer
ISBN: 3319191535
Category : Technology & Engineering
Languages : en
Pages : 99

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Book Description
This book introduces the reader to the MIMO-OFDM system, in Rayleigh frequency selective-channels. Orthogonal frequency division multiplexing (OFDM) has been adopted in the wireless local-area network standards IEEE 802.11a due to its high spectral efficiency and ability to deal with frequency selective fading. The combination of OFDM with spectral efficient multiple antenna techniques makes the OFDM a good candidate to overcome the frequency selective problems.

Author: Fabien Delestre
Publisher:
ISBN:
Category :
Languages : en
Pages :

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This thesis is concerned with channel estimation and data detection of MIMO-OFDM communication systems using Space-Time Block Coding (STBC) and Space-Frequency Block Coding (SFBC) under frequency selective channels. A new iterative joint channel estimation and signal detection technique for both STBC-OFDM and SFBC-OFDM systems is proposed. The proposed algorithm is based on a processive sequence of events for space time and space frequency coding schemes where pilot subcarriers are used for channel estimation in the first time instant, and then in the second time instant, the estimated channel is used to decode the data symbols in the adjacent data subcarriers. Once data symbols are recovered, the system recursively performs a new channel estimation using the decoded data symbols as pilots. The iterative process is repeated until all MIMO-OFDM symbols are recovered. In addition, the proposed channel estimation technique is based on the maximum likelihood (ML) approach which offers linearity and simplicity of implementation. Due to the orthogonality of STBC and SFBC, high computation efficiency is achieved since the method does not require any matrix inversion for estimation and detection at the receiver. Another major novel contribution of the thesis is the proposal of a new group decoding method that reduces the processing time significantly via the use of sub-carrier grouping for transmitted data recovery. The OFDM symbols are divided into groups to which a set of pilot subcarriers are assigned and used to initiate the channel estimation process. Designated data symbols contained within each group of the OFDM symbols are decoded simultaneously in order to improve the decoding duration. Finally, a new mixed STBC and SFBC channel estimation and data detection technique with a joint iterative scheme and a group decoding method is proposed. In this technique, STBC and SFBC are used for pilot and data subcarriers alternatively, forming the different combinations of STBC/SFBC and SFBC/STBC. All channel estimation and data detection methods for different MIMO-OFDM systems proposed in the thesis have been simulated extensively in many different scenarios and their performances have been verified fully.

Author: Raghu Mysore Rao
Publisher:
ISBN:
Category :
Languages : en
Pages : 440

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Author: Muhammad Rehan Khalid
Publisher: LAP Lambert Academic Publishing
ISBN: 9783848488377
Category :
Languages : de
Pages : 108

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Book Description
The new generation of wireless devices support higher data rates. Most of the new standards like HSPA utilize the spatial multiplexing of MIMO channels to achieve higher data rates, and exploit the diversity of MIMO channels to provide better performance. Hence there is an increased interest in the analysis of MIMO communication systems. The eventual objective is to achieve higher data rates in MIMO systems under the constraints of limited bandwidth and power. The radio spectrum is a scarce resource, and very expensive to license. Hence improved and efficient channel utilization techniques are requisite, that exploit the radio spectrum more proficiently. The multipath characteristics of the environment cause the MIMO channels to be frequency selective. For frequency selective deep fading, MIMO system remains ineffective. OFDM, a multicarrier transmission scheme, is well recognized for its potential for attaining high rate transmission over frequency selective channels. It can transform such a frequency selective MIMO channel into a set of parallel frequency-flat channels. Implementing space resources based on OFDM i.e., MIMO-OFDM provides higher data rate.

Author: Yu Zhang
Publisher:
ISBN:
Category : MIMO systems
Languages : en
Pages : 188

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Book Description
Orthogonal frequency division multiplexing (OFDM), which has been very attractive for future high rate wireless communications, is very robust to channel multipath fading effect while providing high transmission data rate with high spectral efficiency. Multiple antennas can be combined with OFDM to increase diversity gain and to improve spectral efficiency through spatial multiplexing and space-time coding (STC). This dissertation focuses on performance analysis and detection schemes of multi-antenna OFDM systems in the presence of phase noise and doubly-selective fading where channel is both time-selective and frequency-selective. In space-time coded OFDM (ST-OFDM), channel time variations cause not only intercarrier interference (ICI) among different subcarriers in one OFDM symbol, but also intertransmit-antenna interference (ITAI). We quantify the impact of time-selective fading on the performance of quasi-orthogonal ST-OFDM systems by deriving, via an analytical approach, the expressions of carrier-to-interference ratio (CIR) and signal-to-interference-plus-noise ratio (SINR). We also evaluate the performance of five different detection schemes and show that all these schemes suffer from an irreducible error floor. Multiple-input multiple-output (MIMO) antennas combined with OFDM are very attractive for high-data-rate communications. However, MIMO-OFDM systems are very vulnerable to time-selective fading. We apply frequency-domain correlative coding in MIMO-OFDM systems over doubly-selective fading channels and derive the analytical expression of CIR to demonstrate the effectiveness of correlative coding in mitigating ICI. When applied in fast fading channels, common ST-OFDM receivers usually suffer from an irreducible error floor. We apply frequency-domain correlative coding combined with a modified decision-feedback (DF) detection scheme with low complexity to effectively suppress the error floor of quasi-orthogonal ST-OFDM over fast fading channels. Similar to single-antenna OFDM, MIMO-OFDM suffers from significant performance degradation due to phase noise and time-selective fading. After characterizing the common phase error (CPE) caused by phase noise and ICI caused by phase noise as well as time-selective fading, we derive a minimum mean-squared error (MMSE)- based scheme to mitigate the effect of both phase noise and Doppler frequency shift. We also evaluate and compare the performance of various detection schemes combined with the proposed CPE mitigation scheme. Throughout the dissertation, theoretical performance analysis is always presented along with corroborating simulations.

Author: P. Mukunthan
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659553806
Category :
Languages : en
Pages : 140

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Book Description
The present wireless systems aim for two conflicting goals, viz., providing quality of service such as delay, fairness to users, and maximizing the throughput of the system. Several techniques have been developed for increasing bandwidth with high data rate. Among these techniques, Orthogonal Frequency Division Multiplexing (OFDM) is a special form of multicarrier technique where all the subcarriers are orthogonal to each other. OFDM offers higher data rate and high immunity to the multipath fading channel without degrading the Bit Error Rate (BER) performance. It has gained popularity for broadband communication system because of its high spectral efficiency and capacity to combat multipath fading. At the same time, it has some limitations such as Inter-Symbol Interference (ISI), Inter-Carrier Interference (ICI) and high Peak-to-Average Power Ratio (PAPR). This book contain seven chapters and an attempt has been made in this research work to enhance the power amplifier efficiency and reduce the high PAPR of the OFDM and MIMO-OFDM systems through modified PTS approach combined with some PAPR reduction techniques.