Interference Distribution in the Nakagami Fading Wireless CDMA Ad Hoc Networks with Multi-code Multi-packet Transmission (MCMPT) PDF Download
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Languages : en
Pages : 7
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In this paper, we derive the distribution of multiple access interference (MAI) power for wireless code division multiple access (CDMA) ad hoc networks operating in a general Nakagami-m fading channel model. Furthermore, we propose a multi-code multi-packet transmission (MCMPT) scheme for it to increase the performance, in terms of the expected forward progress. Based on the instantaneous good channel conditions in a Nakagami-m fading channel, a node can initiate flexible number of parallel transmission of multiple packets on multiple codes. Numerical results show that adaptive MCMPT considering varying channel conditions not only outperforms the nonadaptive conventional packet transmission (CPT), but also achieves better progress improvement with the increasing values of parameter m in a slowly-varying Nakagami-m fading channel.
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Languages : en
Pages : 7
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Book Description
In this paper, we derive the distribution of multiple access interference (MAI) power for wireless code division multiple access (CDMA) ad hoc networks operating in a general Nakagami-m fading channel model. Furthermore, we propose a multi-code multi-packet transmission (MCMPT) scheme for it to increase the performance, in terms of the expected forward progress. Based on the instantaneous good channel conditions in a Nakagami-m fading channel, a node can initiate flexible number of parallel transmission of multiple packets on multiple codes. Numerical results show that adaptive MCMPT considering varying channel conditions not only outperforms the nonadaptive conventional packet transmission (CPT), but also achieves better progress improvement with the increasing values of parameter m in a slowly-varying Nakagami-m fading channel.
Author: Ali Moftah Ali Mehemed
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Category :
Languages : en
Pages :
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Author: Stefan Panic
Publisher: CRC Press
ISBN: 1466508426
Category : Computers
Languages : en
Pages : 263
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Book Description
Fading and Interference Mitigation in Wireless Communications will help readers stay up to date with recent developments in the performance analysis of space diversity reception over fading channels in the presence of cochannel interference. It presents a unified method for computing the performance of digital communication systems characterized by a variety of modulation and detection types and channel models. The book includes coverage of multichannel reception in various fading environments, influence of cochannel interference, and macrodiversity reception when channels are simultaneously affected by various types of fading and shadowing.
Author: Ariel Sacramento
Publisher:
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Category :
Languages : en
Pages : 0
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With applications such as video conferencing, extensive web browsing and live video streaming, future wireless systems become extremely demanding in terms of high data rates and improved signal quality. In this thesis the performance of a space-time spreading transmit diversity scheme is examined over a frequency-flat Nakagami- m fading channel. The Nakagami- m channel model is considered as it is well known for modeling signal fading conditions ranging from severe to moderate, to light fading or no fading, through its parameter m. We also propose in this thesis a coded transmit diversity scheme which is based on a combination of a convolutional code with a space-time transmit diversity scheme that uses direct-sequence code division multiple access (DS-CDMA) for multiuser access. Our focus will be on the uplink of the communication system. The space-time scheme employs N = 2 and N r antennas at the mobile station (MS) side and at the base station (BS) side respectively. DS-CDMA is used to support many users and a linear decorrelator detector is used to combat the effect of multiuser interference. We study the performance of both the uncoded and coded transmit diversity schemes over slow fading and fast fading channels. In all cases, the investigations start by determining the probability density function (PDF) of the signal to interference and noise ratio at the output of the space-time combiner at the BS receiver side. Using this PDF we derive a closed-form (or an approximation) expression for the bit error rate (BER) of the system under consideration. The accuracy of the PDF and BER expressions are verified when compared to simulation results for different values of the fading figure m and for different combinations of transmit and receive antennas. In the case of the coded space-time transmit diversity scheme, the pairwise error probability and the corresponding BER upper bounds are obtained for fast and slow fading channels. The derived error bounds, when compared to system simulations, are shown to be tight at high signal-to-noise ratios. Furthermore, our analytical results explicitly show the achieved system diversity in terms of the number of transmit and receive antennas and the fading figure m. When the coded space-time scheme is considered, its diversity is shown to be a function of the minimum free distance d free of the convolutional code used. Furthermore we show that the diversity of the different schemes considered is always independent of the system load.
Author: Martin Haenggi
Publisher: Now Publishers Inc
ISBN: 1601982984
Category : Wireless communication systems
Languages : en
Pages : 136
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Book Description
Since interference is the main performance-limiting factor in most wireless networks, it is crucial to characterize the interference statistics. The main two determinants of the interference are the network geometry (spatial distribution of concurrently transmitting nodes) and the path loss law (signal attenuation with distance). For certain classes of node distributions, most notably Poisson point processes, and attenuation laws, closed-form results are available, for both the interference itself as well as the signal-to-interference ratios, which determine the network performance. This monograph presents an overview of these results and gives an introduction to the analytical techniques used in their derivation. The node distribution models range from lattices to homogeneous and clustered Poisson models to general motion-invariant ones. The analysis of the more general models requires the use of Palm theory, in particular conditional probability generating functionals, which are briefly introduced in the appendix.
Author: Ramesh Annavajjala
Publisher:
ISBN:
Category :
Languages : en
Pages : 145
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Some of the challenges in the design of next generation wireless systems are providing high data rate multimedia services, increasing user capacity, improving reliability and range, terminal mobility, robustness to interference, limited spectrum availability, and transmission power constraints. The approaches that we take in this dissertation to address some of the aforementioned issues are cross-layer design and user cooperation. In the first part of the dissertation, on a wideband CDMA channel with a finite transmission bandwidth constraint, we consider the problem of optimal bandwidth allocation for source coding, channel coding and spread-spectrum modulation. For analytical tractability, we assume a memoryless Gaussian source with an optimum quantizer, a convolutional encoder with a soft-decision decoder, and a spread spectrum modulator with random spreading codes and a RAKE receiver. In the presence of both multiple access interference (MAI) and narrowband interference (NBI), for frequency-selective Nakagami fading channels, we derive upper and lower bounds on the end-to-end average source distortion. Since an exact expression for the average distortion is difficult to derive, we seek to obtain the three-tuple (i.e., source coding rate, channel coding rate, and spreading factor) that optimizes the upper and lower bounds on the average distortion. Under various channel conditions and interference levels, we numerically computed the optimum three-tuple, and verify the accuracy with system-level simulations. For small values of spreading factor, we show that the system performance is hurt by the self-interference of the user-of-interest, thus cautioning against aggressive channel coding. Since a multi-carrier DS-CDMA (or, simply MC-CDMA) system is more robust to NBI, we propose to employ an MC-CDMA system to improve the distortion performance on channels with severe NBI. For a fixed channel code rate, we then quantify the tradeoff between source coding and spreading for an MC-CDMA system. In the second part of the dissertation, we consider a parallel relay channel wherein the relay nodes help the source transmissions to provide improved reliability at the destination. With multiple relay nodes, we design and analyze robust noncoherent amplify-and forward receivers for use on rapidly varying Rayleigh fading channels with unknown instantaneous channel knowledge. Next, with a sum power constraint, we consider the problem of optimal transmit power allocation when only statistical knowledge, in terms of the average fading power, of the channel is available at the transmitting nodes. We quantify the improvements in both outage probability performance and asymptotic cooperation gain of various relaying protocols with optimal power allocation.
Author: Haichang Sui
Publisher:
ISBN:
Category :
Languages : en
Pages : 188
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In this dissertation, interference suppression techniques and applications will be presented for cellular networks with direct-sequence (DS) CDMA and mobile ad hoc networks with frequency-hopped (FH) CDMA. The first part of the dissertation focuses on three novel finger placement designs that effectively equalize the DS-CDMA multi- path downlink channel to restore code orthogonality and consequently suppress multiple-access interference. For typical multipath channel models, the proposed schemes may significantly outperform the uniformly spaced tapped-delay-line equalizer with much less fingers/taps. In addition, analytic insight into the effect of the finger number and the smoothness of the chip pulse are obtained. The second part of the dissertation considers mobile ad hoc networks with FH-CDMA, where error-correcting codes are employed with differential unitary space-time modulation. The use of multiple transmit antennas in FH-CDMA systems, to the best knowledge of the author, has not been proposed in previous literature. The proposed receiver performs decision-feedback demodulation, decision-aided adaptive estimation, and erasure-insertion decoding jointly to suppress arbitrary unknown interference without channel state information. The third part of the dissertation presents network performance analysis for FH-CDMA networks with the proposed transceiver. Information efficiency and transmission range optimization is investigated under realistic time-varying channel models, which extends previous studies based on static channels and/or simplistic physical layer models. Impacts of various design parameters and channel properties on the network performance are revealed. The results also provide guidance on optimizing the modulation and coding scheme from a network perspective.
Author: Rodolfo Javier Fuentes González
Publisher:
ISBN:
Category : Acceso múltiple de división de código
Languages : en
Pages : 55
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Author: Manjunath Krishnam
Publisher:
ISBN:
Category : Code division multiple access
Languages : en
Pages : 184
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