Hebat-Allah M. Mourad

Reducing ICI in OFDM Systems Using a Proposed Pulse Shape

A novel pulse shape is suggested to decrease the Inter-Carrier Interference (ICI) in an Orthogonal Frequency Multiplexing System (OFDM) due to frequency offset. Furthermore several Nyquist- I pulses recently found are also used for the same purpose. Simulation results are compared for the average ICI and for the signal to interference ratio (SIR) for the pulses under consideration. The sensitivity of the ICI to the used pulse shape and the effectiveness of the proposed pulse shape are reported.

Composite Macroscopic and Microscopic Diversity of Sectorized Macrocellular and Microcellular Mobile Radio SystemsEmploying RAKE Receiver over Nakagami Fading Plus Lognormal Shadowing Channel

This paper presents a generalized model of binary phase shift keying (BPSK) direct sequence code division multiple access (DS/CDMA) macrocellular and microcellular sectorized mobile radio systems over Nakagami fading plus lognormal shadowing channels. RAKE receiver, perfect and imperfect sectorization, voice activity monitoring, microscopic and composite microscopic plus macroscopic diversity are considered. The interrelationships among the number of interfering cells, sectorization degree, sectorization imperfection, voice activity factor, fading parameter, microscopic diversity degree, microscopic plus macroscopic diversity degree and the number of users are considered. Numerical results show that voice activity monitoring and sectorization can reduce multiple access interference (MAI). Furthermore, composite microscopic plus macroscopic diversity system can counteract the fast and slow fading components simultaneously.

Multi-User MIMO Mobile CDMA Uplink System Employing Turbo Coding and Joint Detection Through a Multipath Rayleigh Fading Channel

In this paper, a generalized multiple-input multiple-output (MIMO) antenna system that can be fitted to the uplink of a wireless communication system is considered for the general case of multi-user. At the transmitter, the information bits are Turbo coded, then interleaved and passed through a serial-to-parallel converter. The channel is assumed bad urban suffering from multipath Rayleigh fading resulting in inter-symbol and multiple access interferences (ISI and MAI). At the front-end of the receiver, a number of receiving antennas are used followed by a joint multi-user estimator based on the Minimum Mean Square Error Block Linear Equalizer (MMSE-BLE).Computer simulations demonstrate a significant performance improvement in both single user and multi-user cases.

Capacity of the alpha-mu fading channel with SC diversity under adaptive transmission techniques

Motivated by the generalization of the α-μ distribution in describing the small-scale fading over wireless channels, in this paper, closed-form expressions for the Shannon capacity of the α-μ fading channel operating under three adaptive transmission strategies are derived. These expressions are derived for the case of no diversity as well as for selection combining diversity with independent and identically distributed branches. The obtained expressions reduce to those previously derived in the literature for the Weibull as well as the Rayleigh fading cases, which are both special cases of the α-μ channel. Numerical results are presented for the capacity under the three adaptive transmission strategies and the effect of the fading parameter as well as the number of diversity branches is studied.

Outage Probability Analysis of Cooperative Diversity Networks Over Weibull and Weibull-Lognormal Channels

This paper presents the analysis of outage probability for a cooperative diversity wireless network using amplify-and-forward relays over independent non-identical distributed Weibull and Weibull-lognormal fading channels for single as well as multiple relays. To reach that end, a closed-from expression for the moment-generating function of the total signal-to-noise-ratio (SNR) at the destination is derived in terms of the tabulated Meijer’s G-function. Since it is hard to determine the exact probability distribution function of the SNR, a tight lower bound approximation is proposed. Simulation results are presented that show that the outage probability lower bound tends to be tight at high SNR values thus verifying the analytical results. The results also show the potential gain of relaying on the outage probability.

Closed-Form Exact and Asymptotic Expressions for the Symbol Error Rate and Capacity of the

In this paper, we derive closed-form exact and asymptotic expressions for the symbol error rate (SER) and channel capacity when communicating over Foxs H-function fading channel. The SER expressions are obtained for numerous practically employed modulation schemes in case of single-branch and three multiple-branch diversity receivers: maximal ratio combining (MRC), equal gain combining (EGC), and selection combining (SC). The derived exact expressions are given in terms of the univariate and multivariate Foxs H-functions for which we provide a portable and efficient Python code. Since Foxs H-function fading channel represents the most generalized fading model ever presented in the literature, the derived expressions subsume most of those previously presented for all the known simple and composite fading models. Moreover, easy-to-compute asymptotic expansions are provided to easily study the behavior of the SER and channel capacity at high values of the average signal-to-noise ratio (SNR). The asymptotic expansions are also useful in comparing different modulation schemes and receiver diversity combiners. Numerical and simulation results are also provided to support the mathematical analysis and prove the validity of the obtained expressions.

H

CDMA mobile radio systems suffer from intersymbol interference (ISI) and multiple access interference (MAI) which can be combated by using joint detection (JD) techniques. Furthermore, the time variation of the radio channels leads to degradations of the receiver performance due to fading. These degradations can be reduced by applying diversity techniques. Three suboptimum detection techniques based on matched filters (MF), zero forcing (ZF) and minimum mean square-error (MMSE) equalization are considered. For further improvements, switched and equal gain diversity techniques are employed to combat fading. The performance is depicted in terms of the average bit error probability versus the average SNR per bit in a single cell environment showing an appreciable improvement over the non diversity situation. Theoretical results for the SNR at the front end of the receiver and the BER for ideal channel are obtained and compared with the simulation results.

-Function Fading Channel

In this paper, we consider a switch-and-examine combining (SEC) diversity scheme operating over independent and identically distributed (i.i.d) branches assuming an α-μ fading channel. We derive expressions for the average symbol error rate (ASER) for a class of coherent modulation techniques considering this fading model as well as expressions for the ergodic capacity under the same assumptions. The results for the ASER and the ergodic capacity are shown to reduce to those previously reported in the literature for other channel models such as the Weibull model as a special case, which confirms the validity of the obtained expressions. Different aspects are studied including the effect of fading severity, the number of branches and the modulation scheme used. Also, insights on the optimal choice of the switching threshold are provided.

Joint Detection and Diversity Techniques in CDMA Mobile Radio Systems

Although Constant Modulus Algorithm (CMA) is effective to equalize non-minimum phase channels blindly, it suffers from residual intersymbol interference (ISI) and large Mean Square Error (MSE) when applied to higher order constellations (QAM). Methods based on cost function matched to the signal constellation namely alphabet matched algorithm (AMA) were previously reported and proves its superiority on CMA concerning the MSE. Thus dual mode algorithms between CMA and AMA were introduced. A hybrid technique combining CMA and AMA using a cosine square function as a constellation matched error (CME) was lately reported. In this paper two different CME functions are introduced. The MSE of the proposed algorithms are calculated using Matlab simulation under multipath slow fading channels for different signal to noise ratios (SNR) and different levels of QAM constellations. A comparison is established among them. Depicted results show the effectiveness of the two proposed CME functions.

Average symbol error rate and ergodic capacity of switch-and-examine combining diversity receivers over the α-μ fading channel

In this paper, a multi-carrier code division multiple access (MC-CDMA) downlink mobile communication system employing pre-rake and dual transmit diversity is proposed. It combines high spectral efficiency with an immunity to channel dispersion and fading. It also ensures small size, cost and power consumption of the terminal. Theoretical and simulation results for the system under consideration are obtained. Depicted results show appreciable improvements of the proposed system over those previously known.