Rayleigh fading channel

For the practical simulation and performance evaluation of mobile‐to‐mobile (M2M) communication systems, it is desirable to develop accurate M2M channel simulation models for more realistic scenarios of non‐isotropic scattering. In this paper, by using a ‘double‐ring’ concept to describe M2M non‐isotropic scattering environments, we propose new deterministic and stochastic sum‐of‐sinusoids (SoS) based simulation models. The proposed simulation models extensively consider the distributions of the angle of arrival (AoA) and the angle of departure (AoD), and thus provide a good approximation to the desired statistical properties of the reference model. Copyright © 2009 John Wiley & Sons, Ltd.

In this paper, an expression for the channel capacity (CC) of the combined L-branch (SC) selection receiver is derived in the presence of Rayleigh small fading and co-channel interference (CCI) also by Rayleigh distribution. Rayleigh fading occurs when there is a large number of objects between the transmitter and receiver on which the signal scatters. Analytical results for CC will be performed in closed form and then graphed for channel capacity. In addition, a machine learning approach based on ChatGPT is introduced to recognize the type of fading based on channel capacity measurements, which is further leveraged for quality of service (QoS) adjustment tuning the corresponding parameters on receiver's side.

We study iterative receivers for joint decoding and channel-state estimation for transmission on block-fading channels of root-LDPC-coded signals. Root-LDPC codes are known to be most performant codes for block-fading channels, as their spacial "root" structure allows to get the full-diversity property. This property ensures a good error decoding performance of root LDPC codes, especially in contrast with the performance standard LDPC codes (having the maximum diversity equal to 1). However, as any channel code, root-LDPC codes also suffer from the diversity loss when the channel state information is not known at the receiver. In this work we propose a joint channel estimation-decoding scheme for root-LDPC codes that helps to overcome this problem and still to have the full-diversity. V 0 . 1 1 Joint decoding and channel state estimation block-fading channels EB

In this study, we propose two hybrids concatenated Super-Orthogonal Space-Time Trellis Codes (SOSTTC) applying iterative decoding in Orthogonal Frequency Division Multiplexing (OFDM) over frequency selective fading channels. The coding scheme is based on the concatenation of convolution coding, interleaving and space-time coding along multiple-transmitter/multiple-receiver diversity systems. The Pair wise Error Probability (PEP) for the two proposed concatenated schemes is derived and their performance is evaluated using computer simulation with Maximum a Posteriori (MAP) iterative decoding algorithm. Simulation results based on the iterative decoding process show a significant improvement in the achieved error rate performance of the concatenated scheme over existing concatenated designs.

This study designs space-time codes in analog network coding for asynchronous two-way relay networks, where asynchronous transmissions can cause diversity loss. We propose a novel code, called zero-padded interleave reversal Alamouti code (ZP-IR AC) to achieve full diversity with fast maximum likelihood decoding. Specifically, to combat symbol misalignment caused by asynchronous transmissions, the two terminals insert zero padding when transmitting to relays. Thereafter, the second relay performs an interleave reversal procedure to retain full diversity at each terminal. A salient feature of ZP-IR AC is that it can be decoupled into several independent parts that facilitate fast maximum likelihood decoding. Simulations of ZP-IR AC show full diversity gain. The bit error rate performance of ZP-IR AC is comparable to that of the synchronized Alamouti code and outperforms those of some recent schemes.

The codeword error rate (WER) performance of noncoherent FSK with soft decision decoding of block codes using Chase's second algorithm is investigated in a Rayleigh fading channel. The received signal envelope is sampled and used as channel measurement information. The theoretical upper and lower bounds of the WER are derived assuming independent Rayleigh envelope samples in a received block. When the Golay (23, 12, 7) code is used, soft decision decoding with 6-bit error correction capability (3-bit error and 3-bit erasure) requires an average signal-to-noise power ratio about 5 dB lower than that for minimum distance decoding with 3-bit error correction to obtain a WER = lo-'. The effects of bit interleaving on the WER performance when fading envelope variations is slow compared to the bit rate are investigated through computer simulations. When 23 x M , bit interleaving is used for transmitting M , Golay codewords, the simulation results show that M, = 0.2 x (bit rate/fading maximum Doppler frequency) is sufficient to obtain the full advantages of soft decision decoding. The theoretical analysis was supported by laboratory experiments.

The information-theoretic capacity of multiple antenna systems was shown to be significantly higher than that of single antenna systems in Rayleigh-fading channels. In an attempt to realize this capacity, Foschini proposed the layered space-time architecture. This scheme was argued to asymptotically achieve a lower bound on the capacity. Another line of work has focused on the design of channel codes that exploit the spatial diversity provided by multiple transmit antennas [2], [3]. In this paper, we take a fresh look at the problem of designing multiple-input-multiple-output (MIMO) wireless systems. First, we develop a generalized framework for the design of layered space-time systems. Then, we present a novel layered architecture that combines efficient algebraic code design with iterative signal processing techniques. This novel layered system is referred to as the threaded space-time (TST) architecture. The TST architecture provides more flexibility in the tradeoff between power efficiency, bandwidth efficiency, and receiver complexity. It also allows for exploiting the temporal diversity provided by time-varying fading channels. Simulation results are provided for the various techniques that demonstrate the superiority of the proposed TST architecture over both the diagonal layered space-time architecture in [1] and the recently proposed multilayering approach [4].

In wireless communication system, Doppler induced inter-carrier interference (ICI) degrades the system performances severely. In this thesis, a theoretical analysis is presented to find the performance of an orthogonal frequency division multiplexing (OFDM) system, considering the channel characterized by frequency selective and Rayleigh fading environment. The analysis includes the effect of ICI due to frequency offset caused by Doppler frequency shift. Analysis is carried out to find the expression of the signal to noise plus interference ratio (SNIR) conditioned on a given value of ICI which is considered to be Gaussian in a PSK OFDM system. We extend the analysis for a single input multiple output (SIMO) OFDM and multiple input multiple output (MIMO) OFDM. Data is encoded using a quasi-orthogonal space-time block code (QOSTBC), and the encoded data is split into N s streams which are simultaneously transmitted using N t transmit antennas. The received signal at each receive antenna is a linear superposition of the N t transmitted signals perturbed by noise. Maximal ratio combining (MRC) reception is a simple way for decoupling of the signals transmitted from different antennas by multiple receive antenna. The result are presented in terms of bit error rate (BER), power penalty, BER-floor for different values of fading, number of sub-carriers, symbol duration and different number of antennas for QPSK modulation schemes. It is noticed that the system suffers significantly due to ICI and it has been shown that quality of service can be improved by employing diversity scheme. Analytical results show that performance of a MIMO-OFDM system can be significantly improved by increasing the number of antennas.

In this paper, the performance of the Unpunctured Turbo Trellis-Coded Modulation (UTTCM) over Additive White Gaussian Noise (AWGN) channel is analyzed using the non-binary extrinsic information transfer (EXIT) chart. The exchange of the extrinsic information between the decoder components is tracked, allowing the generation of an EXIT chart, which is a powerful tool for analyzing the convergence behavior of iterative decoding and prediction of convergence position. The Simulation results are compared with the turbo cliff positions on the BER curves.

Transmission of multimedia, especially transmission of image/video information, requires high reliability and high digital transmission speed. But, in case of mobile communication systems, since transmission reliability is degraded by multipath fading also the frequency bandwidth is severely limited, it is difficult to realize the multimedia transmission without applying techniques to overcome these limitations. For achieving a high quality and high speed in digital image transmission in a band-limited fading channel, Hierarchical modulation is a better method. This method is also constellation is used to give different degrees of error protection for the most important information of the image content. A higher order i.e. 256-HQAM where non-uniform signal constellation with hierarchical oriented OFDM modulator has been proposed. Proposed method is used to provide lesser BER and Bandwidth efficiency in the compressed image data at lower channel Signal to Noise Ratio (SNR). An information theoretical approach is applied to analyze the performance of proposed technique. Using the approach, it is quantitatively evaluated how much the proposed technique outperforms. BER and PSNR of reconstructed image of proposed methodology, which include uniform and non-uniform constellations, over AWGN environments, have been calculated to analyze the performance. The performance of proposed and existing technique has been evaluated by doing simulation using MATLAB 7.6 (R2008a).

In this study, the performance of a synchronous fast frequency-hopped multiple-access (MA) M-ary frequency-shiftkeying system employing maximum-likelihood (ML) method over either frequency-selective Rician-or Rayleigh-fading channels is investigated. The ML receiver structures are derived and analysed. It is assumed that all the signals arrive at a receiver with the same power strength and all the users operating in the system undergo independent frequency-selective fading. The performance of the ML receivers is compared with that of the linear-combining and the product-combining receivers. The bit-error rate results of the two conventional receivers are obtained via simulation. The proposed analysis, validated by simulation results, shows that the proposed ML receivers can suppress the MA interference more effectively than other existing receivers under different fading conditions. Moreover, the proposed ML receivers are shown to be robust against the inaccuracy in estimation of the required side information.

This paper addresses the design of low-order Kalman filters to estimate radio channels with Rayleigh fading. Rayleigh fading cannot be perfectly modelled with any finite order auto-regressive (AR) process. Previously, only first and second order Kalman filters were used for channel estimation since higher order Kalman filters were found to not significantly improve accuracy. This is due to mismatches in the statistics of the AR models of the Kalman filters and the true Rayleigh fading. In this paper, the coefficients of the AR models for the Kalman filter are calculated by solving for the minimum square error solutions of an over-determined linear systems. The AR models generated have statistics closely matching the Rayleigh fading process. The Kalman filter using these AR models can accurately estimate the Rayleigh fading process. The accuracy of the new Kalman filters is demonstrated in the tracking of simulated Rayleigh fading processes of different bandwidths.

Multi-user detection allows for the efficient use of bandwidth in Code-Division Multiple-Access (CDMA) channels through mitigation of near-far effects and multiple-access noise limitations. Due to its inherent noise and multipath immunity, CDMA multi-access is being considered as a platform for personal communication systems (PCS). As CDMA based digital communication networks proliferate, the need to determine the presence of a new user and integrate knowledge of this new user into the detection scheme becomes more important. The decorrelafing detector is a linear multi-user detector that is asymptotically optimal in terms of near far resistance; however, in the presence of a new unknown user, performance of the decorrelator is severely degraded. Adaptive decorrelators are constructed which adaptively augment an existing conventional decorrelator to demodulate a new active user in addition to existing users. Several likelihood ratio based schemes are employed. Both synchronous and asynchronous communication are investigated.

Channel estimation and equalization is explored in the context of Direct-Sequence/Code-Division Multiple-Access signals transmitted through multipath channels. The focus is on adaptive and recursive methods which exploit pilot symbols or pilot signals, resulting in algorithms which are alternatively appropriate for the uplink or the downlink. Moderate complexity, linear estimators and receivers are investigated which optimize the minimum-mean squared error or a w eighted least-squares criterion, respectively. Di erent w eight estimators are thus investigated. The proposed algorithms are explored via Monte Carlo simulations and are shown to be robust and o er near-optimal performance in certain scenarios. Fast convergence is also achieved. In addition, the channel estimation algorithms do not require coordination amongst the active users in terms of the transmission of pilots. Finally, the e ects of mismatch in synchronization data are explored and methods to compensate for such errors are examined. Keywords| CDMA, adaptive algorithms, multiuser receivers, frequency selective fading channels.

Multi-user detection allows for the efficient use of bandwidth in Code-Division Multiple-Access (CDMA) channels through mitigation of near-far effects and multiple-access noise limitations. Due to its inherent noise and multipath immunity, CDMA multi-access is being considered as a platform for personal communication systems (PCS). As CDMA based digital communication networks proliferate, the need to determine the presence of a new user and integrate knowledge of this new user into the detection scheme becomes more important. The decorrelafing detector is a linear multi-user detector that is asymptotically optimal in terms of near far resistance; however, in the presence of a new unknown user, performance of the decorrelator is severely degraded. Adaptive decorrelators are constructed which adaptively augment an existing conventional decorrelator to demodulate a new active user in addition to existing users. Several likelihood ratio based schemes are employed. Both synchronous and asynchronous communication are investigated.

I Certify that this thesis submitted for the degree of Master is the result of my own research, except where otherwise acknowledged, and that this thesis (or any part of the same) has not been submitted for a higher degree to any other university or institution.

The problem of linear tracking of fast Rayleigh-faded MIMO channels is considered. Due to computational complexity limitations, Kalman filters based on low-order autoregressive (AR) models are often used although realistic Rayleigh-faded channels cannot be properly approximated by low-order AR models. By increasing the order of the AR model, the channel tracking performance is considerably improved, but the resulting computational complexity may become large. In this paper, the filters used to track the channel are restricted to have a recursive structure, based on the previous estimate and new observation. The knowledge of the autocorrelation function of the channel taps is used to derive filters that are significantly less complex than high-order AR model based Kalman filters at the price of only a minor degradation in performance.

In this contribution, we propose an adaptive Turbo Trellis Coded Modulation (TTCM) aided Distributed Space-Time Trellis Coding (STTC) scheme for cooperative communication over quasi-static Rayleigh fading channels. An adaptive TTCM (ATTCM) scheme is employed by the source node during the first transmission period for reliably conveying the source bits to N number of relay nodes by appropriately adjusting the coderate and modulation mode according to the near-instantaneous channel condition. The TTCM switching thresholds are chosen to ensure that the Bit Error Ratio (BER) at each relay node becomes lower than 10 -6 in order to minimise the potential error propagation imposed by the relay nodes. During the second transmission period, an N -antenna assisted Distributed STTC (DSTTC) scheme is created with the aid of the aforementioned N single-antenna relay nodes. More specifically, the N relay nodes are utilised to form STTC codewords based on the re-encoded TTCM symbols of the relays for transmission to the destination node. At the destination node, iterative extrinsic information exchange is performed between the STTC and TTCM decoders for recovering the original source bits. It is shown that the proposed ATTCM-DSTTC scheme requires 12 dBs less transmission power in comparison to a standard TTCM scheme when aiming for a frame error ratio of 10 -3 .

This report provides a comprehensive profile of Dr. Vasileios Papamichail, a distinguished Electrical and Computer Engineer. His academic journey, rooted at the University of Patras, has fostered a deep specialization in wireless communication systems, with a particular focus on multi-port antenna design, Multiple-Input Multiple-Output (MIMO) systems, and diversity techniques. Currently operating as an independent researcher and the President and CEO of Wi.S.Per. (Wireless System Performance), Dr. Papamichail has made significant contributions to the field through his extensive publications. His pioneering work encompasses advanced simulation methods for wireless systems, novel antenna designs, and sophisticated capacity evaluation techniques. Notably, his recent research explores the interplay between radiation entropy and wireless capacity, aiming to redefine spectral efficiency for next-generation networks. This report exclusively details the professional and academic contributions of the Vasileios Papamichail whose primary expertise is in wireless communications and antenna systems, distinguishing him from other individuals with similar names found in the research material who specialize in fields such as public health, plasma physics, or general business leadership. Dr. Vasileios Papamichail is a prominent Electrical and Computer Engineer whose work has significantly advanced the understanding and performance of wireless communication systems. His expertise is primarily centered on the intricate aspects of multi-element antenna design, their integration into user equipment, and the characterization of wireless channels. His academic and professional trajectory consistently reflects a dedication to pushing the boundaries of wireless technology. It is important to clarify that this report focuses exclusively on the Vasileios Papamichail who is an Electrical and Computer Engineer, born in Patras, Greece, and who received his diploma and PhD from the Electrical and Computer Engineering Department at the Polytechnic School of the University of Patras. His core research interests unequivocally lie in electromagnetic-circuit modeling of compact multi-port antenna systems, performance evaluation of MIMO and Diversity user equipment devices, and wireless channel modeling and characterization. This distinction is crucial because the available information includes references to other individuals with similar names involved in disparate fields, such as public health , dentistry , medical research , business consulting in Romania , or even sports. Furthermore, another individual named Vasileios Papamichail, also with an Electrical Engineering background from Patras, is noted for a PhD in Plasma Physics from a French university and holds patents related to computational mechanics and plasma technology. The consistent thematic alignment across the majority of the provided information confirms the focus of this profile on the wireless communications and antenna systems expert. The need for such careful disambiguation underscores a common challenge in profiling individuals with common names, particularly in academic and professional contexts where multiple experts might share identical or similar

Due to its increasing applications in personal communications systems, body-centric wireless communications has become a major field of interest for researchers. Fading and interference are the two concerns that affect the reliability and quality of service of wireless links. Diversity has been used to overcome these two problems. This thesis looks into the use of receive diversity for on-body channels. Space, pattern, and polarization diversity performance is analyzed and quantified by actual measurements in real environments. Significant diversity gains of up to 10 dB are achieved for most of the on-body channels. The on-body diversity channels have also been characterized by performing the statistical and spectral analyses. The fast fading envelope best fits the Rician distribution, with moderate K-factor values, and the slow fading envelope best fits the Log-normal distribution. Diversity has been found effective in the BAN-BAN interference rejection and significant rejection gain values are achieved. A new algorithm for BAN-BAN interference rejection has been proposed and compared with the conventional adaptive algorithms. The use of multiple antennas at both the transmitter and receiver end, i.e., MIMO has been investigated for on-body applications. It has been noticed that MIMO provides significant capacity increase for these channels despite the line-of-sight. Yuriy I. Nechayev, who has been very supportive and generous in sharing his knowledge. I am very grateful to Mr. Alan Yates for providing all the technical support in using the equipment and making the antennas. Special thanks to my other brilliant colleagues and very nice friends,

In this paper, the problem of joint Carrier Frequency Offset (CFO) and channel estimation for OFDM systems over the fast time-varying frequency-selective channel is explored within the framework of the expectation-maximization (EM) algorithm and parametric channel model. Assuming that the path delays are known, a novel iterative pilot-aided algorithm for joint estimation of the multi-path Rayleigh channel Complex Gains (CG) and the Carrier Frequency Offset (CFO) is introduced. Each CG time-variation, within one OFDM symbol, is approximated by a Basis Expansion Model (BEM) representation. An auto-regressive (AR) model is built to statistically characterize the variations of the BEM coefficients across the OFDM blocks. In addition to the algorithm, the derivation of the Hybrid Cramér-Rao Bound (HCRB) for CFO and CGs estimation in our context of very high mobility is provided. We show that the proposed EM has a lower computational complexity than the optimum maximum a posteriori estimator and yet incurs only an insignificant loss in performance. of CFO and channel response in a static context. In , the authors derived the CRB of path CGs in the presence of high mobility. We propose to extend this bound to the case of joint CFO and CGs estimation. Depending on the prior knowledge available on parameters, the CRB has different expressions. The hybrid CRB (HCRB) is considered in the case of a hybrid vector containing deterministic and random parameters. We provide the derivation of the HCRB for joint estimation of CFO and the fast time-varying CGs in the OFDM context. To sum up, the main contributions for the work presented in this paper are the following:

The design of efficient rateless coding schemes for multicast applications in wireless environments is investigated. First, the digital fountain paradigm for non-ergodic channels is introduced by making use of the dynamic-decoding nature of rateless codes that allows them to adapt opportunistically the code rate to the channel realization (assumed unknown at the transmitter). The information theoretical limits of such codes can be interpreted in terms of the notion of outage capacity. Then, we consider a quasi-static Rayleigh-fading channel with perfect and imperfect channel state information (CSI) at the receiver. We show that the optimal consistent measure of information for decoding with imperfect CSI, is given by the log-likelihood ratio (LLR) of the received bits via a composite (more noisy) channel. The optimization of Raptor codes, which depends on the delay requirements of decoding, is obtained by using Information content evolution under Gaussian approximation. Simulation results show that optimized Raptor codes can operate very close to the theoretical limits on a wide range of delay requirements.

The idea of combining RS (Reed-Solomon) codes with multiphase signaling schemes on fading channels is introduced. The performance of these schemes over a Rayleigh fading channel is evaluated for different decoding strategies, Le., errors- on&, errors-and-erasures, and softdecision decoding techniques. Both analytical and simulation results show that substantial coding gains are obtained compared to the uncoded reference system.

Cutoff rates for (perfect) coordinate interleaving over flat Rayleigh fading channels are computed for some representative two-dimensional (2-D) and four-dimensional (4-D) quadrature amplitude modulation (QAM) schemes and compared to the standard symbol interleaved approaches. It is shown that for optimized coordinate interleaving [Le., using optimum rotation parameters that maximize the cutoff rate for a given signal-to-noise ratio (SNR)], coding gains can be achieved visa-vis symbol interleaving that increases with the dimensionality of the signal constellation. Perfect coherent detection, as well as perfect channel state information are assumed.

The principle of coding in the signal space follows directly from Shannon's analysis of waveform Gaussian channels subject to an input constraint. The early design of communication systems focused separately on modulation, namely signal design and detection, and error correcting codes, which deal with errors introduced at the demodulator of the underlying waveform channel. The correct perspective of signalspace coding, although never out of sight of information theorists, was brought back into the focus of coding theorists and system designers by Imai's and Ungerböck's pioneering work on coded modulation. More recently, powerful families of binary codes with a good tradeoff between performance and decoding complexity have been (re-) discovered. Bit-Interleaved Coded Modulation (BICM) is a pragmatic approach combining the best out of both worlds: it takes advantage of the signal-space coding perspective, whilst allowing for the use of powerful families of binary codes with virtually any modulation format. n w the essence of knowledge BICM avoids the need for the complicated and somewhat less flexible design typical of coded modulation. As a matter of fact, most of today's systems that achieve high spectral efficiency such as DSL, Wireless LANs, WiMax and evolutions thereof, as well as systems based on low spectral efficiency orthogonal modulation, feature BICM, making BICM the de-facto general coding technique for waveform channels. The theoretical characterization of BICM is at the basis of efficient coding design techniques and also of improved BICM decoders, e.g., those based on the belief propagation iterative algorithm and approximations thereof. In this monograph, we review the theoretical foundations of BICM under the unified framework of error exponents for mismatched decoding. This framework allows an accurate analysis without any particular assumptions on the length of the interleaver or independence between the multiple bits in a symbol. We further consider the sensitivity of the BICM capacity with respect to the signal-to-noise ratio (SNR), and obtain a wideband regime (or low-SNR regime) characterization. We review efficient tools for the error probability analysis of BICM that go beyond the standard approach of considering infinite interleaving and take into consideration the dependency of the coded bit observations introduced by the modulation. We also present bounds that improve upon the union bound in the region beyond the cutoff rate, and are essential to characterize the performance of modern randomlike codes used in concatenation with BICM. Finally, we turn our attention to BICM with iterative decoding, we review extrinsic information transfer charts, the area theorem and code design via curve fitting. We conclude with an overview of some applications of BICM beyond the classical coherent Gaussian channel.

In this paper, we consider signal reception in multicarrier code-division multiple-access (MC-CDMA) systems. A blind adaptive algorithm is proposed to determine a weight vector which optimally combines the desired signal contributions from different carriers while suppressing noise and interference. No knowledge of the channel conditions (fading coefficients, signature sequences and timing of interferers, statistics of other noises, etc.) nor any training sequence is required. The performance is examined for Rayleigh fading channels. Results show that the proposed algorithm performs well and is robust to the near-far problem. Hence, the results show that MC-CDMA systems are attractive candidates for future CDMA systems.

We derive power adaptation strategies optimizing the error rates of broadband bit-interleaved coded OFDM systems performing hard-decisions after the demodulation and ideal interleaving. The adaptive subchannel power allocation is based on either perfect or outdated channel state information in a time-division duplex transmission. We find that for an average bit error rate level of 10-6 a gain of up to 4 dB can be achieved by the proposed adaptation in Rayleigh fading channels.

A simple serially concatenated turbo code using differen- tial 8PSK modulation as the inner code and a (3,2,2) parity code as the outer code is studied. This inner code allows for noncoherent operation, but is decoded coherently accord- ing to turbo principles with iterative exchange of extrinsic probabilities. Results show a turbo cliff at 4.4 dB, about 1.5 dB away

Current 'economies of scale' in global agribusiness -across space, time, genetics and organizational structure -constitute an insurmountable barrier to public health efforts at control of pandemic disease. A relatively elementary model of noise-induced stabilization suggests that sufficient and properly designed and monitored disruption of global agricartels -breakup -would act as a de-facto sterilizing temperature to prevent pathogen emergence.

Multi-Carrier Code Division Multiple Access (MC-CDMA) is one of the recent technologies to support multiple users with high speed data communications in advanced wireless systems. This paper specially analyzes the BER performance under Rayleigh and Rician fading channel conditions of MC-CDMA in presence of AWGN (Additive White Gaussian Noise) using BPSK modulation using MATLAB program, and finally the paper also presents a comparison between simulated results, which shows the reduction in BER performance. Keywords— MCCDMA, CDMA, OFDM, Rayleigh Fading, Rician Fading.

In cooperative communications, estimation and compensation of multiple carrier frequency offsets is an important implementation issue that needs to be addressed in practice. This paper proposes an efficient maximum likelihood estimator (MLE) using alternating projection technique, for the joint estimation of Rayleigh fading channels and multiple carrier frequency offsets (MCFO) in cooperative communication systems. Our proposed equalizer incorporates these channel and MCFO estimates and uses matrix inverse technique to decode the transmitted symbols. Unlike existing schemes for equalizer design, the proposed design does not assume any perfect MCFO and/or channel estimate knowledge at the receiver or code redundancy or delay diversity and works for the full range (±0.5 cycles/sec) of the normalized frequency offsets. We present simulation results to illustrate that the Mean Square Error (MSE) of MCFO achieves the Cramér Rao Bound (CRB) above 7 dB signal-to-noise ratio (SNR) while the MSE of channel estimation achieves the CRB for all SNR values. In addition, the Bit Error Rate (BER) performance shows that our proposed equalizer can achieve the full spatial diversity gain of space-time block codes.

Wireless Relaying is one of the promising solutions to overcome the channel impairments and provide high data rate coverage that appears for beyond 3G mobile communications. In this paper we present an end to end BER performance analysis of dual hop wireless communication systems equipped with multiple Decode and Forward relays over the Rayleigh fading channel with relay selection. We select the best relay based on end to end channel conditions. We apply Orthogonal Space Time Block coding (OSTBC) at source, and also present how the multiple antennas at the source terminal affects the end to end BER performance. This intermediate relay technique will cover long distance where destination is out of reach from source. Keywords-Bit error rate (BER), amplify and forward (AF), multiple input multiple output (MIMO), decodeand-forward (DF),probability density function (PDF).

In this work, the performance of turbo codes over the Rice multiplicative fading channel is evaluated through analysis and simulation. The analysis is conducted through improved upper bounds on bit error probabilities in conjunction with both the fully interleaved channel and the correlated Rice slow fading channel. The analytical expression of the improved bound is obtained by extending the results presented in [1] to the Rice multiplicative fading channel case. Simulation results are obtained and presented also for intermediate fading rates, ranging between the two extreme multipath fading rates considered in the analysis. Simulations are performed using the improved Jakes' channel simulator presented in [2] to simulate Rayleigh fading channels, and extended to adequately model the multipath Rice fading propagation environment.

In this paper, we consider signal reception in multicarrier code-division multiple-access (MC-CDMA) systems. A blind adaptive algorithm is proposed to determine a weight vector which optimally combines the desired signal contributions from different carriers while suppressing noise and interference. No knowledge of the channel conditions (fading coefficients, signature sequences and timing of interferers, statistics of other noises, etc.) nor any training sequence is required. The performance is examined for Rayleigh fading channels. Results show that the proposed algorithm performs well and is robust to the near-far problem. Hence, the results show that MC-CDMA systems are attractive candidates for future CDMA systems.

Bandwidth efficient parallel-concatenated Turbo Trellis Coded Modulation (TTCM) schemes were designed for communicating over uncorrelated Rayleigh fading channels. A symbol-based union bound was derived for analysing the error floor of the proposed TTCM schemes. A pair of In-phase (I) and Quadrature-phase (Q) interleavers were employed for interleaving the I and Q components of the TTCM coded symbols, in order to attain an increased diversity gain. The decoding convergence of the IQ-TTCM schemes was analysed using symbolbased EXtrinsic Information Transfer (EXIT) charts. The best TTCM component codes were selected with the aid of both the symbol-based union bound and non-binary EXIT charts for the sake of designing capacity-approaching IQ-TTCM schemes in the context of 8PSK, 16QAM and 32QAM signal sets. It will be shown that our TTCM design is capable of approaching the channel capacity within 0.5 dB at a throughput of 4 bit/s/Hz, when communicating over uncorrelated Rayleigh fading channels using 32QAM.

We study an incremental redundancy (IR) cooperative coding scheme for wireless networks. To exploit the distributed spatial diversity benefit we propose a cluster-based collaborating strategy for a quasi-static Rayleigh fading channel model. Our scheme allows for enhancing the reliability performance of a direct communication over a single hop. The collaborative cluster consists of M -1 nodes between the sender and the destination. The transmitted message is encoded using a mother code which is partitioned into M blocks each assigned to one of M transmission slots. In the first slot, the sender broadcasts its information by transmitting the first block, and its helpers attempt to relay this message. In the remaining slots, each of left-over M -1 blocks is sent either through a helper which has successfully decoded the message or directly by the sender where a dynamic schedule is based on the ACK-based feedback from the cluster. By employing powerful good codes including turbo, low-density parity-check, and repeat-accumulate codes, our approach illustrates the benefit of collaboration through not only a cooperation diversity gain but also a coding advantage. The basis of our error rate performance analysis is the threshold behavior of good codes. We derive a new simple code threshold for the Bhattacharyya distance based on the modified Shulman-Feder bound and the relationship between the Bhattacharyya parameter and the channel capacity for an arbitrary binary-input symmetric-output memoryless channel. The study of the diversity and the coding gain of the proposed scheme is based on this new threshold. An average frame-error rate (FER) upper bound and its asymptotic (in SNR) version are derived as a function of the average fading channel SNRs and the code threshold. Based on the asymptotic bound, we investigate both the diversity, the coding, and the transmission energy gain in the high and moderate SNR regimes for three different scenarios: transmitter clustering, receiver clustering, and cluster hopping. Furthermore, given a geometric distance profile of the network, we have observed that the energy saving of the IR cooperative coding scheme is universal for all good code families.

Abstract—Space Time Trellis codes provided maximum diversity advantage using simple decoding techniques. However, space-time block codes did not provide coding gain, and nonfullrate space-time block codes introduced bandwidth expansion. In this paper we ...

The 60 GHz band is of much interest since this is the band in which a massive amount of spectral space (5 GHz) has been allocated unlicensed worldwide for dense wireless local communications. Orthogonal frequency division multiplexing (OFDM) has gained much popularity in the field of wireless communication because of its ability to transfer the data at higher rate, high bandwidth efficiency and its robustness with regard to multipath and delay. In this paper we consider a discrete cosine transform (DCT)-based OFDM system for calculating bit error rate with additive white Gaussian noise (AWGN) channel and Saleh-Valenzuela (SV) channel model at 60 GHz. The BER is calculated for signaling formats BPSK and the performance of DCT based OFDM is analyzed at 60 GHz. The results indicate that DCT-OFDM performs better than FFT-OFDM system with AWGN channel. DCT based OFDM system outshines FFT based OFDM scheme at 60GHz.

In this paper, the performance of the proposed fuzzy logic parallel interference cancellation (FLPIC) multiuser detector is evaluated for frequency-selective fading channels in wireless CDMA communication systems. A modified fuzzy logic system (FLS) with an adequate scaling factor (SF) is proposed to infer adequate partial factors (PFs) for the PIC scheme. Simulation results show that the proposed FLS can adapt to the large variations of users' fading effects; the FLPIC thus outperforms the conventional PIC (CPIC) and constant-weight PIC (CWPIC) over two-path and three-path time-varying frequency-selective fading channels, especially at heavy system load in DS-CDMA systems.

The bit error rate (BER) performance of DS-CDMA in a frequency-selective fading channel can be significantly improved by the use of frequency-domain equalization (FDE). Accurate estimation of the channel transfer function is necessary for FDE. Direct application of pilot-assisted channel estimation (CE) degrades the BER performance, since the frequency spectrum of the pilot chip sequence is not constant over the spreading bandwidth. In this paper, we propose a pilot-assisted frequency-domain CE based on minimum mean square error (MMSE) criterion. The BER performance with MMSE-CE in a frequency-selective Rayleigh fading channel is evaluated by computer simulation. It is found that MMSE-CE always provides a good BER performance irrespective of the choice of pilot chip sequence. For a spreading factor SF of 16, the E b /N 0 degradation with MMSE-CE from the ideal CE case is as small as 0.4 dB at BER=10 -4 (a 0.28 dB loss due to the pilot insertion is included).

Recently, we have proposed an adaptive channel estimation (CE) scheme using one-tap recursive least square (RLS) algorithm (adaptive RLS-CE), where the forgetting factor is adapted to the changing channel condition by the least mean square (LMS) algorithm, for direct sequence-code division multiple access (DS-CDMA) with frequency-domain equalization (FDE). However, the tracking ability for adaptive RLS-CE is limited since the channel estimate obtained from the previously received block is used. In this paper, we introduce the polynomial prediction to improve the tracking ability. We evaluate the bit error rate (BER) performance of DS-CDMA using polynomial prediction RLS-CE in a frequency-selective fast Rayleigh fading channel by computer simulation.

Broadband wireless packet access will be the core technology of the next generation mobile communication systems. For very high-speed and high-quality packet transmissions in a limited bandwidth, the joint use of multipleinput multiple-output (MIMO) multiplexing and hybrid ARQ (HARQ) is an effective method. However, if single-carrier (SC) transmission is used, the transmission performance significantly degrades due to a large inter-symbol interference (ISI) resulting from a severe frequency-selective fading. In this paper, we propose an iterative frequency-domain successive interference cancellation (SIC) with two dimensional (2D) MMSE-FDE. At each iteration stage, the successive signal detection/cancellation is performed according to the descending order of the signal reliability. However, since the interference from the other transmit antennas can be only partially cancelled by performing SIC, the residual interference is present at the output of SIC. In this paper, we propose to update the 2D MMSE-FDE weights at each signal detection in order to suppress simultaneously the ISI and the interference from other antennas while obtaining antenna and frequency diversity gain. However, since a single use of SIC with 2D MMSE-FDE is insufficient, it is repeated a sufficient number of times. The bit error rate (BER) and HARQ throughput performance in a frequency-selective Rayleigh fading channel are evaluated by computer simulation.

Recently, multi-carrier code division multiple access (MC-CDMA) has been attracting much attention for the next generation mobile communication systems. The insertion of the guard interval (GI) is necessary to avoid the inter-block interference (IBI), resulting in the transmission efficiency loss. In this paper, an overlap frequency-domain equalization (overlap FDE) technique, which requires no GI insertion, is presented for MC-CDMA signal transmission. The received MC-CDMA signal is divided into a sequence of M-sample signal blocks, where M is smaller than the number Nc of MC-CDMA subcarriers and then each block is equalized by using the overlap MMSE-FDE with Nc-sample FFT. Setting the block size M to be smaller than the FFT block size Nc, the IBI can be sufficiently reduced. The achievable BER performance with overlap MMSE-FDE in a frequency- selective Rayleigh fading channel is evaluated by computer simulation.

In mobile communications, the channel consists of many resolvable paths with different time delays, resulting in a severely frequency-selective fading channel. The frequency-domain equalization (FDE) can take advantage of the channel selectivity and improve the bit error rate (BER) performance of the single-carrier (SC) transmission. Recently, multi-input multi-output (MIMO) multiplexing is gaining much attention for achieving very high speed data transmissions with the limited bandwidth. Eigenbeam space division multiplexing (E-SDM) is known as one of MIMO multiplexing techniques. In this paper, we propose frequency-domain SC E-SDM for SC transmission. In frequency-domain SC E-SDM, the orthogonal transmission channels to transmit different data in parallel are constructed at each orthogonal frequency. At a receiver, FDE is used to suppress the inter-symbol interference (ISI). In this paper, the transmit power allocation and adaptive modulation based on the equivalent channel gains after performing FDE are applied. The BER performance of the frequency-domain SC E-SDM in a severe frequency-selective Rayleigh fading channel is evaluated by computer simulation.