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Author: Yu Zhang Publisher: ISBN: Category : MIMO systems Languages : en Pages : 188
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: Yu Zhang Publisher: ISBN: Category : MIMO systems Languages : en Pages : 188
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: Mohamed Jalloh Publisher: ISBN: Category : Languages : en Pages : 197
Book Description
The age of wireless technologies and the associated convenience that portable wireless products and services provide, continues to drive the need for more advanced products and broadband wireless services that demand carefully selected spectrally efficient modulation schemes to support the desired higher data rates. The development of multicarrier systems has paved the way to meeting the system requirements and fulfilling these needs. Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation technique that has provided effective means for achieving high data rates and spectral efficiency requirements in wireless communication systems, while making use of relatively simple receiver designs. In wireless communications, one of the major implementation challenges is system sensitivity to synchronization issues, which is even more pronounced in multicarrier systems such as OFDM. The use of OFDM with a high number of subcarriers, to achieve the high data rates it provides, makes it more susceptible to these non-idealities such as phase noise. Another critically limiting factor of system performance is the introduction of channel estimation errors as a consequence of imperfect channel estimation at the receiver. Accurate channel estimates are very essential in ensuring correct detection of the transmitted signal at the receiver. A thorough understanding of system operation therefore requires a detailed analysis of the effects of all the impairments. This dissertation addresses these system impairments by investigating the effects analytically on OFDM systems, deriving bit error rate (BER) expressions for systems that employ a single antenna at both the transmitter and receiver. The investigation is extended to also include OFDM systems that employ multi-antenna configurations at the receiver followed by a similar multi-antenna configuration at the transmitter. The impact of these negative effects is further investigated when applied to a practical system, comparing the analytical results with simulations that makes use of system parameters of the IEEE 802.16 standards.
Author: Aditya Awasthi Publisher: ISBN: Category : Noise control Languages : en Pages : 150
Book Description
Performance of orthogonal frequency division multiplexing (OFDM)-based wireless communication system is severely degraded by the presence of phase noise. Phase noise can reduce the effective signal-to-noise ratio (SNR) at the receiver, and consequently, limit the bit error rate (BER) and data rate of the wireless system.
Author: Tim Schenk Publisher: Springer Science & Business Media ISBN: 1402069030 Category : Technology & Engineering Languages : en Pages : 323
Book Description
This is one of the first books on the emerging research topic of digital compensation of RF imperfections. The book presents a new multidisciplinary vision on the design of wireless communication systems. In this approach the imperfections of the RF front-ends are accepted and digital signal processing algorithms are designed to suppress their impact on system performance. The book focuses on multiple-antenna orthogonal frequency division multiplexing (MIMO OFDM).
Author: Rangaraj Veeraraghavan Garudapuram Publisher: LAP Lambert Academic Publishing ISBN: 9783659139307 Category : Languages : en Pages : 128
Book Description
OFDM is a computationally efficient scheme to send high bit rate data through multipath wireless channels. The combination of OFDM with multiple transmit and/or receive antennas can not only exploit space diversity, but also the inherent multipath diversity in OFDM. Multiple antennas with considerable separation are known to provide diversity in wireless systems to overcome fading. Spatial correlation is introduced when antennas are not well separated, and it often leads to performance degradation in flat fading environment. However, in frequency selective environment with OFDM, there is rich multipath diversity which helps in overcoming this performance degradation. This is due to transformation of a highly spatially correlated channel impulse response to less spatial correlated channel frequency response inherently by an OFDM system in the presence of rich multipath diversity. This is illustrated for a simple receive diversity OFDM system and the concept of space sampling at the receiver where antennas are placed relatively close to each other is introduced. The minimum separation required between the antennas is also analytically derived under such circumstances.
Author: Nor Kamariah Noordin Publisher: ISBN: Category : Languages : en Pages : 268
Book Description
In this thesis, issues such as link adaptation that include adaptive spatial mode in the context of orthogonal frequency division multiplexing (OFDM) is addressed, particularly in a multiple-input single-input (MISO) configuration suitable for mobile communications. The performances of ST- and SF-OFDM incorporating channel coding are extensively investigated in the presence of channel fading and noise. Realizing that ST and SF behave differently in different enviroments, a new adaptive spatial mode (ASM)-OFDM is proposed. This scheme selects the mode of transmission based on the instantenous signal noise ratio (SNR) for a 2 x 1 MISO system. A new adaptive multiple antenna selection (AdMAS) using second-order moment of the channel impulse response between multiple transmitting antennas and a single receiver MISO-OFDM configuration os also proposed a major contributio. This scheme employs a 4 x 1 space-time-frequency coding with a symbol rate of 3/4, using orthogonal signals, to avoid high complexity in detection. In the proposed AdMAS scheme the worst faded channel(s) in (are) adaptively turned off based on the calculated second-order moment of the channel impulse response. Findings show that the proposed scheme outperforms other multiple antenna schemes such as the one based on the mean of the channel impulse response, especially at higher order modulation. Throughout the simulation, channel state information (CSI) is assumed to be known both by the transmitter and the receiver which may be achieved via a dedicated feedback channel or through the reciprocity of the channel such as that found in time division duplex (TDD) system. Minor contribution of this thesis includes a simplified sphere decoding algorithm for MIMO that forms part of the detection scheme at the receiver. A maximum achievable diversity order of the 4 x 1 MISO-OFDM has also been derived analytically and proved through simulation. A diversity gain of more than 10 dB can be achieved with Binary Phase Shift Keying modulation when compared to Almouti's Space-Time Block Code (STBC) at a bit error rate (BER) of 10-3. This makes the proposed scheme a potential scheme to be considered for the future high data rate communication. The proposed schemes are tested through simulations in different types of practical channels such as Wireless Local Area Network (WLAN) IEEE 802.11, Rayleigh fading with various delay spreads, as well as the most recent Fixed Broadband Wireless Access (FBWA) IEEE 802.16 Standford University Interim Channels, or better known as the WiMAX channels.
Author: Ahmet Y. Erdogan Publisher: ISBN: 9781423515111 Category : Languages : en Pages : 151
Book Description
Orthogonal frequency division multiplexing (OFDM) is being successfully used in numerous applications. It was chosen for IEEE 802.1 la wireless local area network (WLAN) standard, and it is being considered for the fourth- generation mobile communication systems. Along with its many attractive features, OFDM has some principal draw-backs. Sensitivity to frequency errors is the most dominant of these drawbacks. In this thesis, the frequency offset and phase noise effects on OFDM based communication systems are investigated under a variety of channel conditions covering both indoor and outdoor environments. The simulation performance results of the OFDM system for these channels are presented.
Author: David Tse Publisher: Cambridge University Press ISBN: 9780521845274 Category : Computers Languages : en Pages : 598
Book Description
This textbook takes a unified view of the fundamentals of wireless communication and explains cutting-edge concepts in a simple and intuitive way. An abundant supply of exercises make it ideal for graduate courses in electrical and computer engineering and it will also be of great interest to practising engineers.
Author: Yu Zhang
Author: Yu Zhang
Author: Mohamed Jalloh
Author: 
Author: Aditya Awasthi
Author: Tim Schenk
Author: Rangaraj Veeraraghavan Garudapuram
Author: Nor Kamariah Noordin
Author: Ahmet Y. Erdogan
Author: Arogyaswami Paulraj
Author: David Tse