Fading Channel

This letter finds the relation between different parameters that characterize the reverberation chamber as a channel emulator for over-the-air (OTA) testing of wireless devices and components. It is shown experimentally for the first time that the coherence bandwidth is proportional to the average mode bandwidth of the chamber. Both coherence bandwidth and average mode bandwidth increase when the chamber is loaded with absorbing objects, and thereby, the reverberation chamber can be controlled to emulate many different real-life environments. The relationship between RMS delay spread and coherence bandwidth are found from the measured channel response and are equal to the theoretical relation for isotropic multipath environments, being within previously published fundamental limits.

Modern wireless communication demands reliable data communication at high throughput in severe channel conditions like narrowband interference, frequency selective fading due to multipath and attenuation of high frequencies. Traditional single carrier systems address this set of problems by the use of complex, computationally intensive equalization filters. The Orthogonal Frequency Division Multiplexing (OFDM) based system, as opposed to single-carrier systems, is considered to be the future of the wireless communication and is being used to achieve high data rate by overcoming severe channel conditions without the use of these complex filters. This paper discusses the problem of Adaptive Modulation scheme selection through an OFDM based system over parallel frequency selective fading channels. An adaptive coding scheme is proposed by using Generalized Concatenated Codes (GCC), which have simple structure and are designed in such a way that they are best suited for fading channels. GCC are based on binary cyclic codes. The criterion of the proposed research is to optimize the throughput of a wireless system. Depending on the quality of sub-channels an adaptive modulation selection scheme and code assigning method is proposed. The proposed research combats against channel impairments better than those used in conventional systems by exploiting individual sub-channel condition. Results show better performance in terms of higher throughput by minimizing the bit error rate.

We present closed-form expressions for the average bit error probability (ABEP) of BPSK, QPSK and M -QAM of an amplify-and-forward average power scaling dual-hop relay transmission, over non-identical Nakagami-m fading channels, with integer values of m. Additionally, we evaluate in closedform the ABEP under sufficiently large signal-to-noise ratio for the source-relay link, valid for arbitrary m. Numerical and simulation results show the validity of the proposed mathematical analysis and point out the effect of the two hops unbalanced fading conditions on the error performance.

The increasing need of high data rate transmissions over time or frequency selective fading channels has drawn attention to modulation schemes with high spectral efficiency such as QAM. With the aim of increasing the 'diversity order' of the signal set we consider the multidimensional rotated QAM constellations. Very high diversity orders can be achieved and this results in an almost Gaussian performance over the fading channel. This multidimensional modulation scheme is essentially uncoded and enables to trade diversity for system complexity, at no expense of power or bandwidth.

In this work, we study coding over a class of two-user broadcast channels (BCs) with additive white Gaussian noise and multiplicative fading known at the receivers only. Joint decoding of low-density paritycheck (LDPC) codes is analyzed. The message update rule at the mapping node linking the users' codes is derived and is found to exhibit an interesting soft interference cancellation property. High performance codes are found using the differential evolution optimization technique and extrinsic information transfer analysis adapted to our multiuser setting. The optimized codes have rates very close to the boundary of the achievable region for binary constrained input for both faded and unfaded channels. Simulation results for moderate block lengths show that our codes operate within less than 1 dB of their respective threshold.

A statistical discrete-time model is proposed for simulating wideband multiple-input multiple-output (MIMO) fading channels which are triply selective due to angle spread, Doppler spread, and delay spread. The new discrete-time MIMO channel model includes the combined effects of the transmit filter, physical MIMO multipath channel fading, and receive filter, and it has the same sampling period as that of the MIMO receiver. This leads to very efficient simulation of physical continuous-time MIMO channels. A new method is also presented to efficiently generate the MIMO channel stochastic coefficients. The statistical accuracy of the discrete-time MIMO channel model is rigorously verified through theoretical analysis and extensive simulations in different conditions. The high computational efficiency of the discrete-time MIMO channel model is illustrated by comparing it to that of the continuous-time MIMO channel model. The new model is further employed to evaluate the channel capacity of MIMO systems in a triply selective Rayleigh fading environment. The simulation results reveal some interesting effects of spatial correlations, multipaths, and number of antennas on the MIMO channel capacity. Index Terms-Discrete-time channel model, multiple-input multiple-output (MIMO) channel, multiple-input multiple-output multipath channel capacity, Rayleigh fading, triply selective fading, wide-sense stationary uncorrelated scattering (WSSUS) multipath channel. I. INTRODUCTION T HE multiple-input multiple-output (MIMO) communication architecture has recently emerged as a new paradigm for high data rate wireless cellular communications in rich multipath environments. Using multiple-element antenna arrays at both the transmitter and receiver, which effectively exploits the spatial dimension in addition to time and frequency dimensions, this architecture shows channel capacity potential far beyond that of traditional techniques. In quasi-static, independent and identically distributed (i.i.d.) frequency flat Rayleigh fading channels, the MIMO capacity scales linearly with the number of antennas under some conditions [1], [2]. However, in practice,

In this work, we present a framework analysis of millimeter waves (mmWaves) vehicular communications systems. Communications between vehicles take place through a cooperative relay which acts as an intermediary base station (BS). The relay is equipped with multiple transmit and receive antennas and it employs decode-and-forward (DF) to process the signal. Also, the relay applies maximal ratio combining (MRC), and maximal ratio transmission (MRT), respectively, to receive and forward the signal. As the vehicles' speeds are relatively high, the channel experiences a fast fading and this time variation is modeled following the Jakes' autocorrelation model. We also assume narrowband fading channel. Closed-form expressions of the reliability metrics such as the outage probability, the probability of error and the channel capacity are derived. Capitalizing on these performances, we derive the low and high power regimes for the capacity, and the high signal-to-interference-plus-noise-ratio (SINR) asymptotes for the outage and error probability to get full insights into the system gains such as the diversity and coding gains.

This letter studies the effect of quantized channel state information (CSI) feedback on the average rate of correlated channels. Demonstrating the general rate optimization problem, the results are obtained for both delayed and delay-free feedback conditions under different short-and long-term power allocation strategies. We also evaluate the effect of adaptive CSI quantization on the channel average rate. Analytical and numerical results show that exploiting the channel memory not only increases the forward channel data transmission efficiency but also can lead to dramatic feedback rate reduction.

This paper addresses the problem of wireless transmission of a captured scene from multiple cameras, which do not communicate among each other, to a joint decoder. Correlation among different camera views calls for distributed source coding for efficient multiview image compression. The fact that cameras are placed within a short range of each other results in a high level of interference, multipath fading, and noise effects during communications. We develop a novel two-camera system, that employs multiterminal source coding and complete complementary data spreading, so that while the former technique exploits the statistical correlation between camera views, and performs joint compression to reduce transmission rates, the spreading technique will protect transmitted data by mitigating the effects of wireless fading channels. Our results indicate that the proposed system is competitive when compared to two independently JPEG encoded streams at low to medium transmission rates.

Ionospheric scintillation induces distortion onto RF
communication and radar signals that propagate through the
ionospheric medium. Unless properly accounted for, this
scintillation may greatly impact the performance of military and
commercial satellite signals. Accurate verification of satellite
systems and associated ground equipment is achievable through
the use of hardware-in-the-loop (HWIL) scintillation simulators.
Test results of a scintillation simulator are presented and
compared with theoretical performance of Rayleigh, Rician, and
Nakagami-m fading.

In this work, we study the performance of free space optical links with fading statistics modelled by the negative exponential distribution which describes channels under strong atmospheric turbulence conditions. We investigate the availability and the practical channel capacity's bounds, for links with fast and slow fading statistics, with line of sight architecture and intensity modulation with direct detection, through the evaluation of the outage probability and the outage and average capacity. Moreover, the average error probability, for on-off keying cases, is estimated. For these, very significant, magnitudes we extract closed form mathematical expressions for, practically valuation of link's performance.

Secrecy capacity is a fundamental informationtheoretic performance metric to predict the maximum data rate
of reliable communication, while the intended message is not
revealed to the eavesdropper. Motivated by this consideration,
in this paper a unified communication-theoretic framework for
the analysis of the probability of non-zero secrecy capacity, the
secrecy outage probability and the secrecy capacity of multipleantenna systems over fading channels is proposed. Specifically,
a powerful frequency-domain approach is first developed, in
which the integrals involved in the evaluation of the probability
of non-zero secrecy capacity and secrecy outage probability are
transformed into the frequency domain, by employing Parseval’s
theorem. A generic approach for the evaluation of the asymptotic
secrecy outage probability at high signal-to-noise ratio (SNR)
region is also introduced, thus providing useful insight as to the
parameters affecting the secrecy performance. Finally, a unified
numerical approach for computing the average secrecy capacity
of multiple-antenna systems under arbitrary fading environments is developed. The proposed framework is general enough
to accommodate any well-known multi-antenna transmission
technique and fading model. Finally, the secrecy performance
of several multiple-antenna system setups is assessed, in the
presence of generalized fading conditions and arbitrary antenna
correlation, while various numerical and computer simulation
results are shown and compared to substantiate the proposed
mathematical analysis

In this work, a channel estimation technique based on Artificial Neural Networks (ANN) has been proposed as an alternative to pilot based channel estimation technique for Space-Time Block Coded Multiple-Input Multiple-Output (STBC-MIMO) systems over Rayleigh fading channels. ANNs, due to their high degree of adaptability, can be used for modelling the nonlinear phenomenon of channel estimation and for decoding the degraded symbols over severely faded channel. Two different ANN structures, namely Multilayer Perceptron (MLP) and Recurrent Neural Networks (RNN) have been trained and tested extensively for estimating the channel in STBC-MIMO systems with Binary Phase Shift Keying (BPSK) modulation scheme. Simulated results in terms of Bit Error Rates (BER) vs. Signal to Noise Ratio (SNR) have been used to compare the effectiveness of the learning capability of the two ANN structures over wireless fading channel. RNN structures are found to outperform the MLP, both in terms of training performance and BER results and thus proving its nonlinear dynamic adaptive behaviour.

In this work, a channel estimation technique based on Artificial Neural Networks (ANN) has been proposed as an alternative to pilot based channel estimation technique for Space-Time Block Coded Multiple-Input Multiple-Output (STBC- MIMO) systems over Rayleigh fading channels. ANNs, due to their high degree of adaptability, can be used for modelling the nonlinear phenomenon of channel estimation and for decoding the degraded symbols over severely faded channel. Two different ANN structures, namely Multilayer Perceptron (MLP) and Recurrent Neural Networks (RNN) have been trained and tested extensively for estimating the channel in STBC- MIMO systems with Binary Phase Shift Keying (BPSK) modulation scheme. Simulated results in terms of Bit Error Rates (BER) vs. Signal to Noise Ratio (SNR) have been used to compare the effectiveness of the learning capability of the two ANN structures over wireless fading channel. RNN structures are found to outperform the MLP, both in terms of training...

We study the problem of communication reliability and diversity in multi-hop wireless networks. Our aim is to develop a new network model that better takes into account the fading nature of the wireless physical layer. To that end, we use the outage probability model for a fading channel to develop a probabilistic model for a wireless link. This model establishes a relationship between the link reliability, the distance between communicating nodes and the transmission power. Applying this probabilistic model to a multi-hop network setting, we define and analyze the end-to-end route reliability and develop algorithms for finding the optimal route between a pair of nodes. The relationship between the reliability of the optimal route and the consumed power is studied. The idea of route diversity is introduced as a way to improve the end-to-end route reliability by taking advantage of the wireless broadcast property, the independence of fade state between different pairs of nodes, and the space diversity created by multiple relay nodes along the route. We give analytical results for the improvements due to route diversity in some simple network topologies. Our results suggest that route diversity can fundamentally change the trade off between reliability and power in a multi-hop network.

When the mechanisms of fading channels were first modeled in the 1950s and 1960s, the ideas were primarily applied to over-the-horizon communications covering a wide range of frequency bands. The 3-30 MHz high-frequency (HF) band is used for ionospheric communications, and the 300 MHz-3 GHz ultra-high-frequency (UHF) and 3-30 GHz super-high-frequency (SHF) bands are used for tropospheric scatter. Although the fading effects in a mobile radio system are somewhat different than those in ionospheric and tropospheric channels, the early models are still quite useful to help characterize fading effects in mobile digital communication systems. This tutorial addresses Rayleigh fading primarily in the UHF band. That affects mobile systems such as cellular and personal communication systems (PCS). Part I of the tutorial itemizes the fundamental fading manifestations and types of degradation

Achieving optimal performance is a paramount concern in wireless networks. One of the strategies is to use wireless empirical models to predict wireless link quality factors such as path loss and the received power in any given transmission domain with irregular terrain. Measurement results of signal strength in UHF band obtained in Idanre Town of Ondo State Nigeria were validated against theoretical estimations. Okumura-Hata model, COST231-Hata model and Egli model applicable for path loss prediction in area with high hill were examined. These models predictions were compared with predictions from measurements taken in Idanre to determine the path loss prediction error for each model. Consequently, modified COST231-Hata model was developed for path loss prediction in the hilly areas. The model developed has 6.02% error which made it applicable for hilly areas (Idanre).

Information flow in a telecommunication network is accomplished through the interaction of mechanisms at various design layers with the end goal of supporting the information exchange needs of the applications. In wireless networks in particular, the different layers interact in a nontrivial manner in order to support information transfer. In this text we will present abstract models that capture the cross-layer interaction from the physical to transport layer in wireless network architectures including cellular, ad-hoc and sensor networks as well as hybrid wireless-wireline. The model allows for arbitrary network topologies as well as traffic forwarding modes, including datagrams and virtual circuits. Furthermore the time varying nature of a wireless network, due either to fading channels or to changing connectivity due to mobility, is adequately captured in our model to allow for state dependent network control policies. Quantitative performance measures that capture the quality of service requirements in these systems depending on the supported applications are discussed, including throughput maximization, energy consumption minimization, rate utility function maximization as well as general performance functionals. Cross-layer control algorithms with optimal or suboptimal performance with respect to the above measures are presented and analyzed. A detailed exposition of the related analysis and design techniques is provided.

Ascertaining on the suitability of the Weibull distribution to model fading channels, a theoretical framework for a class of multivariate Weibull distributions, originated from Gaussian random processes, is introduced and analyzed. Novel analytical expressions for the joint probability density function (pdf), moment-generating function (mgf), and cumulative distribution function (cdf) are derived for the bivariate distribution of this class with not necessarily identical fading parameters and average powers. Two specific distributions with arbitrary number of correlated variates are considered and studied: with exponential and with constant correlation where their pdfs are introduced. Both cases assume equal average fading powers, but not necessarily identical fading parameters. For the multivariate Weibull distribution with exponential correlation, useful corresponding formulas, as for the bivariate case, are derived. The presented theoretical results are applied to analyze the performance of several diversity receivers employed with selection, equal-gain, and maximal-ratio combining (MRC) techniques operating over correlated Weibull fading channels. For these diversity receivers, several useful performance criteria such as the moments of the output signal-to-noise ratio (SNR) (including average output SNR and amount of fading) and outage probability are analytically derived. Moreover, the average symbol error probability for several coherent and noncoherent modulation schemes is studied using the mgf approach. The proposed mathematical analysis is complemented by various evaluation results, showing the effects of the fading severity as well as the fading correlation on the diversity receivers performance.

Radio waves or radio signals propagate through the atmosphere in wireless communication. They are affected mostly by variability in radio refractivity which leads to a decrease in their speed or rate of propagation which eventually cause propagation delay or attenuation in the troposphere.The hourly averages of radio refractivity for dry particulates during dry season (January) were calculated from the data obtained from the Nigeria Meteorological Agency (NIMET) when UHF broadcast signal measurement was also taken for each hour throughout the whole day in Akure, Ondo state, Nigeria. However, the statistical correlation (with a correlation coefficient of -0.97) reveals that at different points when the refractivity was high (most especially at night and in the morning when the humidity was high) the signal strength was low and at the points when the refractivity was low (most especially during the day when the humidity was low due to high temperature) the signal strength was higher. Therefore, the higher the refractivity the lesser the signal strength at the point of observation in the troposphere i.e. they are inversely proportional to each other.

Diversity methods provide the receiver with independently faded copies of the transmitted signal with the expectation that at least one of these replicas will be received correctly. There are ranges of techniques available through which these faded copies can be recovered and used as part of arrangements for better reception. This paper proposes a method based on Space-Time Block Coding (STBC) with Multiple-Input Single-Output (MISO) and Multiple-Input Multiple-Output (MIMO) set-up for use in wireless channels. A special version of STBC called Alamouti code is used for exploiting the performance of MISO and MIMO in frequency-selective fading environment. Performance differences are observed with and without STBC in frequency selective faded channels. A comparison is made between the diversity gain of MISO and MIMO systems in terms of BER for two specific modulation schemes, namely BPSK and QPSK. The obtained results demonstrate that spatial diversity along with the power of STBC significantly improves the error performance in frequency selective wireless fading channels.

The presented research paper aims to
analyze the channel capacity of a MIMO System in
Rayleigh fading channel with different antenna nodes and
spacing. It is argued that an implementable model is not
readily available in the evaluated reference papers. As
such a model is developed for simulating spatially
correlated MIMO system in Rayleigh fading channel. To
verify the developed model, a MATLAB code is devised to
simulate the capacity of MIMO system for different
numbers of antenna nodes and that is depicted in the
comparative result MIMO systems have collected
extensive attention in the new millennium due to its
promise for a considerable increase in capacity, which is
commonly considered to be a viable means for satisfying
the ever-increasing demand for a higher data rate. The
ground-breaking work by Telatar [1], Foschini and Gans
[2] toward the end of last millennium not only provided
some exciting results on capacity of multiple-antenna
Gaussian channels but also stimulated a huge wave of
enthusiasm toward various topics involving MIMO
systems, including MIMO channel capacity, MIMO
channel coding, space-time coding, etc. Among all lot of
research and analysis is done in the area of channel
capacity by modeling various channels and developing
various algorithm.

This letter addresses the problem of energy detection of an unknown signal over a multipath channel. It starts with the no-diversity case, and presents some alternative closed-form expressions for the probability of detection to those recently reported in the literature. Detection capability is boosted by implementing both square-law combining and square-law selection diversity schemes.

In emerging cognitive radio (CR) networks, the first cognitive task preceding any dynamic spectrum management is the sensing and identification of spectrum holes in wireless environments. This paper develops a distributed compressed spectrum sensing approach for (ultra-)wideband CR networks. First, compressive sampling is performed at local CRs to scan the very wide spectrum at practical signal-acquisition complexity. Then, measurements or states from multiple CR detectors are fused to collect spatial diversity gain, which improves the detection quality especially under fading channels. Distributed fusion algorithms are derived to effect collaborative fusion at low communication and computation load scalable to the network size. Multiple performance metrics are identified to evaluate the proposed spectrum sensing techniques, as well as to assess those performance-determining factors in system design. Computer simulations corroborate the effectiveness of the proposed techniques in id...

In orthogonal frequency division multiplexing (OFDM) systems over fast-varying fading channels, channel estimation and tracking is generally carried out by transmitting known pilot symbols in given positions of the frequency-time grid. The traditional approach consists of two steps. First, the least-squares (LS) estimate is obtained over the pilot subcarriers. Then, this preliminary estimate is interpolated/smoothed over the entire frequency-time grid. In this paper, we propose to add an intermediate step, whose purpose is to increase the accuracy of the estimate over the pilot subcarriers. The presented techniques are based on the observation that the wireless radio channel can be parametrized as a combination of paths, each characterized by a delay and a complex amplitude. The amplitudes show fast temporal variations due to the mobility of terminals while the delays (and their associated delay-subspace) are almost constant over a large number of OFDM symbols. We propose to track the delay-subspace by a subspace tracking algorithm and the amplitudes by the least mean square algorithm (or modifications of the latter). The approach can be extended to multiple input multiple output OFDM or multicarrier code-division multiple-access systems. Analytical results and simulations prove the relevant benefits of the novel structure.

In a companion paper, we showed the existence of decoding thresholds for maximum-likelihood (ML) decoding of a serial concatenated trellis-coded modulation (SCTCM) system with one or more inner accumulate codes. In this paper, we compute the decoding thresholds for an iterative, non-ML decoder by density evolution (DE), assuming infinite blocklengths. We also derive a stability condition for the particular case of an outer paritycheck code and a single inner accumulate code. We show that, for equiprobable signaling, the bit-wise log-likelihood ratio densities for higher order constellations are symmetric. Furthermore, when used in DE, these densities can be averaged without significantly affecting the resulting threshold values. For an outer single paritycheck code, the lowest decoding thresholds are achieved with two inner accumulate codes. For an outer repeat code, a single inner accumulate code gives the lowest thresholds. At code rates 2 3, the decoding thresholds for the SCTCM system are within 1 dB of the constellation-constrained channel capacity for additive white Gaussian noise channels, and within 1.5 dB for independent, identically distributed Rayleigh channels. Simulation results verify the computed thresholds.

In this article, we derive six distinct series representations of the generalized Nuttall Q-function. Interestingly, some of these expressions generalise some of the recent results on series representation of the Marcum Q-function since the Marcum Q-function is a special case of the Nuttall Qfunction. To the best of our knowledge, five of these representations are novel and the other one is included for the completeness of the article. The performances of these representations are compared using the magnitude of the truncation error which gives a measure of the accuracy and rate of convergence and allow us to show the strength of each representation. We then discussed the area of applications of our result. We showed that our Nuttall Q-function representations and their corresponding special case (Marcum Q-function) (though not limited to only these), can be used in (i) the computation of outage probability of wireless communication system with co-channel interferers, (ii) the evaluation of detection probability of energy detector over generalized fading channels in cognitive radio system, and (iii) the computation of cumulative distribution of selection diversity combining in correlated Nakagami-m fading channel. In all these areas of application, our solution has no restriction on any parameter of interest.

A sensitivity analysis of two distortionless beamformers is presented in this paper 1 . Specifically, two well-known variants, namely the minimum power distortionless response (MPDR) and minimum variance distortionless response (MVDR) beamformers, are considered. In our scenario, which is typical to many modern communications systems, waves emitted by multiple point sources are received by an antenna array. An analytical expression for the signal to interference and noise ratio (SINR) improvement obtained by both beamformers under steering errors is derived. These expression are experimentally evaluated and compared with the robust Capon beamformer (RCB), a robust variant of the MPDR beamformer. We show that the MVDR beamformer, which uses the noise correlation matrix in its minimization criterion, is more robust to steering errors than its counterparts, that use the received signal correlation matrix. Furthermore, even if the noise correlation matrix is erroneously estimated due to steering errors in the interference direction, the MVDR advantage is still maintained for reasonable range of steering errors. These conclusions conform with Cox [1] findings. Only line of sight propagation regime is considered in the current contribution. Ongoing research extends this work to fading channels.

Aperture extension (interferometry baseline extension) is achieved in this novel ESPRIT-based two-dimensional (2-D) arrival angle estimation scheme using a sparse (a.k.a., thin or thinned) uniform rectangular array of electromagnetic vector sensors spaced much farther apart than a half-wavelength. An electromagnetic vector sensor is composed of six spatially co-located, orthogonally oriented, diversely polarized antennas, distinctly measuring all six electromagnetic-field components of an incident multisource wavefield. Each incident source's direction of arrival (DOA) is estimated from the source's electromagnetic-field vector component and serves as a coarse reference to disambiguate the cyclic phase ambiguities in ESPRIT's eigenvalues when the intervector sensor spacing exceeds a half wavelength. Simulations demonstrate the significant performance gain realizable by this method for radar and wireless mobile fading-channel communications.

A technique intended to increase the diversity order of Bit-Interleaved Coded Modulations (BICM) over non Gaussian channels is presented. It introduces simple modifications to the mapper and to the corresponding demapper. They consist of a constellation rotation coupled with signal space component interleaving. Iterative processing at the receiver side can provide additional improvement to the BICM performance. This method has been shown to perform well over fading channels with or without erasures. It has been adopted for the 4-, 16-, 64-and 256-QAM constellations considered in the DVB-T2 standard. Resulting gains can vary from 0.2 dB to several dBs depending on the order of the constellation, the coding rate and the channel model.

We consider the design of channel codes for improving the data rate and/or the reliability of communications over fading channels using multiple transmit antennas. Data is encoded by a channel code and the encoded data is split into n streams that are simultaneously transmitted using n transmit antennas. The received signal at each receive antenna is a linear superposition of the n transmitted signals perturbed by noise. We derive performance criteria for designing such codes under the assumption that the fading is slow and frequency nonselective. Performance is shown to be determined by matrices constructed from pairs of distinct code sequences. The minimum rank among these matrices quantifies the diversity gain, while the minimum determinant of these matrices quantifies the coding gain. The results are then extended to fast fading channels. The design criteria are used to design trellis codes for high data rate wireless communication. The encoding/decoding complexity of these codes is comparable to trellis codes employed in practice over Gaussian channels. The codes constructed here provide the best tradeoff between data rate, diversity advantage, and trellis complexity. Simulation results are provided for 4 and 8 PSK signal sets with data rates of 2 and 3 bits/symbol, demonstrating excellent performance that is within 2-3 dB of the outage capacity for these channels using only 64 state encoders.

M. Dohler is with CTTC, Parc Mediterrani de la Tecnologia, Av. Canal Olimpic S/N, Abstract This letter addresses the problem of finding a tractable expression for the symbol error outage (SEO) in flat Nakagami-m fading and shadowing channels. We deal with M-ary phase shift keying (M-PSK) and quadrature amplitude modulation (M-QAM) which extends our previous results on BPSK signaling. We propose a new tight approximation of the symbol error probability (SEP) holding for M-PSK and M-QAM signals which is accurate over all signal to noise ratios (SNRs) of interest. We derive a new generic expression for the inverse SEP which facilitates the derivation of a tight approximation of the SEO in a lognormal shadowing environment. Index Terms Mobile Communications, Symbol Error Probability, Symbol Error Outage, Shadowing, Fast Fading Channel, M-PSK, M-QAM. √ m + 1, where k mod is a constant depending on m and the modulation order M . However, for the considered values of P * s (E), i.e. P * s (E) ≤ 10 −1 , the condition holds.

The combination of space-time coding (STC) and smart antenna technology promises an enhanced performance in terms of power and spectral efficiency. However, with STC transmit diversity, each co-channel interferer (CCI) will produce more than one interference signal that appears independent to the smart antenna receiver, and thus reducing the interference's suppression ability of the system. Furthermore, when combined with STC, the conventional smart antenna should be redesigned to form multibeams toward the same desired user. In this paper, we propose an effective smart antenna system that can mitigate CCI while taking into account the STC transmit diversity. The performance of the proposed approach is evaluated in term of bit error rate and array pattern for flat fading channels as well as for frequency selective channels.

This paper investigates the impact of residual transceiver hardware impairments (RTHIs) on cooperative non-orthogonal multiple access (NOMA) networks, where generic α − µ fading channel is considered. To be practical, imperfect channel state information (CSI) and imperfect successive interference cancellation (SIC) are taken into account. More particularly, two representative NOMA scenarios are proposed, namely non-cooperative NOMA and cooperative NOMA. For the non-cooperative NOMA, the base station (BS) directly performs NOMA with all users. For the cooperative NOMA, the BS communicates with NOMA users with the aid of an amplify-and-forward (AF) relay, and the direct links between BS and users are existent. To characterize the performance of the proposed networks, new closed-form and asymptotic expressions for the outage probability (OP), ergodic capacity (EC) and energy efficiency (EE) are derived, respectively. Specifically, we also design the relay location optimization algorithms from the perspectives of minimize the asymptotic OP. For non-cooperative NOMA, it is proved that the OP at high signal-to-noise ratios (SNRs) is a function of threshold, distortion noises, estimation errors and fading parameters, which results in 0 diversity order. In addition, high SNR slopes and high SNR power offsets achieved by users are studied. It is shown that there are rate ceilings for the EC at high SNRs due to estimation error and distortion noise, which cause 0 high SNR slopes and ∞ high SNR power offsets. For cooperative NOMA, similar results can be obtained, and it also demonstrates that the outage performance of cooperative NOMA scenario exceeds the non-cooperative NOMA scenario in the high SNR regime.

We investigate the performance and design of free-space optical (FSO) communication links over slow fading channels from an information theory perspective. A statistical model for the optical intensity fluctuation at the receiver due to the combined effects of atmospheric turbulence and pointing errors is derived. Unlike earlier work, our model considers the effect of beam width, detector size, and jitter variance explicitly. Expressions for the outage probability are derived for a variety of atmospheric conditions. For given weather and misalignment conditions, the beam width is optimized to maximize the channel capacity subject to outage. Large gains in achievable rate are realized versus using a nominal beam width. In light fog, by optimizing the beam width, the achievable rate is increased by 80% over the nominal beam width at an outage probability of 10 −5 . Well-known error control codes are then applied to the channel and shown to realize much of the achievable gains.

We obtain the (Shannon) optimal power and rate allocation strategies for the uplink on single cell systems. For an N user system, we show that successive decoding which is independent of channel state is optimal in the Shannon sense. Using this result, we,frame a simple N dimensional convex optimization problem, which is solved to obtain optimum power and rate allocation as explicit functions of the channel state.