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Search Results: 1 - 10 of 112015 matches for " Mazen O. Hasna "
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Joint Optimization of Area Spectral Efficiency and Delay Over PPP Interfered Ad-hoc Networks
Young Jin Chun,Aymen Omri,Mazen O. Hasna
Mathematics , 2015,
Abstract: Due to the increasing demand on user data rates, future wireless communication networks require higher spectral efficiency. To reach higher spectral efficiencies, wireless network technologies collaborate and construct a seamless interconnection between multiple tiers of architectures at the cost of increased co-channel interference. To evaluate the performance of the co-channel transmission based communication, we propose a new metric for area spectral efficiency (ASE) of interference limited Ad-hoc network by assuming that the nodes are randomly distributed according to a Poisson point processes (PPP). We introduce a utility function, U = ASE/delay and derive the optimal ALOHA transmission probability p and the SIR threshold \tau that jointly maximize the ASE and minimize the local delay. Finally numerical results has been conducted to confirm that the joint optimization based on the U metric achieves a significant performance gain compared to conventional systems.
Generalized Area Spectral Efficiency: An Effective Performance Metric for Green Wireless Communications
Lei Zhang,Hong-Chuan Yang,Mazen O. Hasna
Computer Science , 2014,
Abstract: Area spectral efficiency (ASE) was introduced as a metric to quantify the spectral utilization efficiency of cellular systems. Unlike other performance metrics, ASE takes into account the spatial property of cellular systems. In this paper, we generalize the concept of ASE to study arbitrary wireless transmissions. Specifically, we introduce the notion of affected area to characterize the spatial property of arbitrary wireless transmissions. Based on the definition of affected area, we define the performance metric, generalized area spectral efficiency (GASE), to quantify the spatial spectral utilization efficiency as well as the greenness of wireless transmissions. After illustrating its evaluation for point-to-point transmission, we analyze the GASE performance of several different transmission scenarios, including dual-hop relay transmission, three-node cooperative relay transmission and underlay cognitive radio transmission. We derive closed-form expressions for the GASE metric of each transmission scenario under Rayleigh fading environment whenever possible. Through mathematical analysis and numerical examples, we show that the GASE metric provides a new perspective on the design and optimization of wireless transmissions, especially on the transmitting power selection. We also show that introducing relay nodes can greatly improve the spatial utilization efficiency of wireless systems. We illustrate that the GASE metric can help optimize the deployment of underlay cognitive radio systems.
A Novel Spectrally-Efficient Scheme for Physical Layer Network Coding
Ahmed G. Helmy,Tamer Khattab,Mazen O. Hasna
Computer Science , 2014,
Abstract: In this paper, we propose a novel three-time-slot transmission scheme combined with an efficient embedded linear channel equalization (ELCE) technique for the Physical layer Network Coding (PNC). Our transmission scheme, we achieve about 33% increase in the spectral efficiency over the conventional two-time-slot scheme while maintaining the same end-toend BER performance.We derive an exact expression for the endto- end BER of the proposed three-time-slot transmission scheme combined with the proposed ELCE technique for BPSK transmission. Numerical results demonstrate that the exact expression for the end-to-end BER is consistent with the BER simulation results.
A Stochastic Geometry Based Approach to Modeling Interference Correlation in Cooperative Relay Networks
Young Jin Chun,Simon L. Cotton,Mazen O. Hasna,Ali Ghrayeb
Mathematics , 2015,
Abstract: Future wireless networks are expected to be a convergence of many diverse network technologies and architectures, such as cellular networks, wireless local area networks, sensor networks, and device to device communications. Through cooperation between dissimilar wireless devices, this new combined network topology promises to unlock ever larger data rates and provide truly ubiquitous coverage for end users, as well as enabling higher spectral efficiency. However, it also increases the risk of co-channel interference and introduces the possibility of correlation in the aggregated interference that not only impacts the communication performance, but also makes the associated mathematical analysis much more complex. To address this problem and evaluate the communication performance of cooperative relay networks, we adopt a stochastic geometry based approach by assuming that the interfering nodes are randomly distributed according to a Poisson point process (PPP). We also use a random medium access protocol to counteract the effects of interference correlation. Using this approach, we derive novel closed-form expressions for the successful transmission probability and local delay of a relay network with correlated interference. As well as this, we find the optimal transmission probability $p$ that jointly maximizes the successful transmission probability and minimizes the local delay. Finally numerical results are provided to confirm that the proposed joint optimization strategy achieves a significant performance gain compared to a conventional scheme.
Serial Genetic Algorithm Decoder for Low Density Parity Check Codes  [PDF]
Hasna Chaibi
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2015, DOI: 10.4236/ijcns.2015.89034
Abstract: Genetic algorithms are successfully used for decoding some classes of error correcting codes, and offer very good performances for solving large optimization problems. This article proposes a new decoder based on Serial Genetic Algorithm Decoder (SGAD) for decoding Low Density Parity Check (LDPC) codes. The results show that the proposed algorithm gives large gains over sum-product decoder, which proves its efficiency.
Sensing/Decision-Based Cooperative Relaying Schemes With Multi-Access Transmission: Stability Region And Average Delay Characterization
Mohamed Salman,Amr El-Keyi,Mohammed Nafie,Mazen Omar Hasna
Mathematics , 2015,
Abstract: We consider a cooperative relaying system which consists of a number of source terminals, one shared relay, and a common destination with multi-packet reception (MPR) capability. In this paper, we study the stability and delay analysis for two cooperative relaying schemes; the sensing-based cooperative (SBC) scheme and the decision-based cooperative (DBC) scheme. In the SBC scheme, the relay senses the channel at the beginning of each time slot. In the idle time slots, the relay transmits the packet at the head of its queue, while in the busy one, the relay decides either to transmit simultaneously with the source terminal or to listen to the source transmission. The SBC scheme is a novel paradigm that utilizes the spectrum more efficiently than the other cooperative schemes because the relay not only exploits the idle time slots, but also has the capability to mildly interfere with the source terminal. On the other hand, in the DBC scheme, the relay does not sense the channel and it decides either to transmit or to listen according to certain probabilities. Numerical results reveal that the two proposed schemes outperform existing cooperative schemes that restrict the relay to send only in the idle time slots. Moreover, we show how the MPR capability at the destination can compensate for the sensing need at the relay, i.e., the DBC scheme achieves almost the same stability region as that of the SBC scheme. Furthermore, we derive the condition under which the two proposed schemes achieve the same maximum stable throughput.
On Modeling Heterogeneous Wireless Networks Using Non-Poisson Point Processes
Young Jin Chun,Mazen Omar Hasna,Ali Ghrayeb,Marco Di Renzo
Computer Science , 2015,
Abstract: Future wireless networks are required to support 1000 times higher data rate, than the current LTE standard. In order to meet the ever increasing demand, it is inevitable that, future wireless networks will have to develop seamless interconnection between multiple technologies. A manifestation of this idea is the collaboration among different types of network tiers such as macro and small cells, leading to the so-called heterogeneous networks (HetNets). Researchers have used stochastic geometry to analyze such networks and understand their real potential. Unsurprisingly, it has been revealed that interference has a detrimental effect on performance, especially if not modeled properly. Interference can be correlated in space and/or time, which has been overlooked in the past. For instance, it is normally assumed that the nodes are located completely independent of each other and follow a homogeneous Poisson point process (PPP), which is not necessarily true in real networks since the node locations are spatially dependent. In addition, the interference correlation created by correlated stochastic processes has mostly been ignored. To this end, we take a different approach in modeling the interference where we use non-PPP, as well as we study the impact of spatial and temporal correlation on the performance of HetNets. To illustrate the impact of correlation on performance, we consider three case studies from real-life scenarios. Specifically, we use massive multiple-input multiple-output (MIMO) to understand the impact of spatial correlation; we use the random medium access protocol to examine the temporal correlation; and we use cooperative relay networks to illustrate the spatial-temporal correlation. We present several numerical examples through which we demonstrate the impact of various correlation types on the performance of HetNets.
Naso Alveolar Cleft Reconstruction: Does Patients’ Age Play a Factor in Postoperative Complication Rate?  [PDF]
Almasri Mazen
Surgical Science (SS) , 2013, DOI: 10.4236/ss.2013.41016

Purpose: The purpose of this report is to compare the outcome of unilateral alveolar cleft reconstruction (ACR) in patients aged 6 - 8 years versus older more comprehending patients aged 9 - 12 years. Materials and Methods: A chart review (from March 2006 to June 2010) was conducted of patients who had alveolar cleft reconstruction using anterior iliac crest bone graft. All the cases included are non syndromic healthy patients whom had unilateral alveolar cleft and were operated for the first time. A total of 49 healthy patients were included in the study. Twenty-four had their surgery between the age of 6 and 8 (Group A), and twenty-five had theirs between 9 and 12 (Group B). The postoperative recovery and complications were compared between the two groups. Results: In group A, 16% (n = 4) showed minimal wound dehiscence while 8% (n = 2) had a minor wound infection due to food particles wedged in the wound. In Group B, 20% (n = 5) of the patients presented with minimal wound dehiscence, while 12% (n = 3) had minor wound infection due to food particles wedged in the wound. No significant difference was found between the two groups using Fishers exact test, two-tailed p-value >0.05. Conclusion: Age factor was not found to be a factor contributing to ACR complication rate.

Does Immediate Reconstruction of Postextraction Lost Buccal Plate Reduce the Chances of Implant Surface Exposure after Crown Placement?  [PDF]
Mazen Almasri
Surgical Science (SS) , 2013, DOI: 10.4236/ss.2013.41020

Objective: To investigate if immediate reconstruction of fresh extraction sockets lost buccal wall would reduce the possibilities of implant surface exposure and improve the treatment predictability. Materials and Methods: A retrospective chart review of Healthy patients harboring periodontally compromised anterior teeth that were planned for extraction and subsequent implant therapy were the target of our study. All the sockets included witnessed loss of the buccal bone plate. Seventy-two anterior sockets were grafted with xenogenic grafts to reconstruct such defects immediately after the extractions. 9 to 13 months later, the alveolar ridges were surgically exposed and implants were placed. Results: All the surgical sites did not show any labial plate thinning, dehiscence, or fenestration at the time of implant placement. Moreover, no gingival recession and implant metal show was noticed up to 39 months post crown placement. Conclusion: Immediate reconstructions of lost buccal plate in fresh extraction sockets reduces the chances of implant surface exposure up to two years post crown placement.

Selecting the Six Sigma Project: A Multi Data Envelopment Analysis Unified Scoring Framework  [PDF]
Mazen Arafah
American Journal of Operations Research (AJOR) , 2015, DOI: 10.4236/ajor.2015.53011
Abstract: The importance of the project selection phase in any six sigma initiative cannot be emphasized enough. The successfulness of the six sigma initiative is affected by successful project selection. Recently, Data Envelopment Analysis (DEA) has been proposed as a six sigma project selection tool. However, there exist a number of different DEA formulations which may affect the selection process and the wining project being selected. This work initially applies nine different DEA formulations to several case studies and concludes that different DEA formulations select different wining projects. Also in this work, a Multi-DEA Unified Scoring Framework is proposed to overcome this problem. This framework is applied to several case studies and proved to successfully select the six sigma project with the best performance. The framework is also successful in filtering out some of the projects that have “selective” excellent performance, i.e. projects with excellent performance in some of the DEA formulations and worse performance in others. It is also successful in selecting stable projects; these are projects that perform well in the majority of the DEA formulations, even if it has not been selected as a wining project by any of the DEA formulations.
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