Sharif Digital Repository

Generalized Frequency Division Multiplexing (GFDM) is a cyclic filtered multicarrier modulation that may be employed for many new wireless applications. However, due to its non-orthogonal structure, a trade-off between the complexity and error performance should be considered in the design of GFDM receivers. This study proposes an orthogonal cyclic filtered multicarrier modulation called Generalized Orthogonal Frequency Division Multiplexing (GOFDM), which is based on the cyclic Perfect Reconstruction-Quadrature Mirror Filter (PR-QMF) bank. We first derive the frequency domain matrix descriptions for GOFDM linear receivers based on which, the impact of PR-QMF bank on the GOFDM error... 

Generalized frequency division multiplexing (GFDM) is one of the multicarrier modulation candidates proposed for the 5th generation of wireless networks. Among GFDM linear receivers, GFDM MMSE receiver achieves the best error performance for multipath fading channels at the cost of high numerical complexity. Hence, the combination of GFDM match filter (MF) receiver and double-side successive interference cancellation (DSIC) method is used instead. However, there is a significant gap between the error performance of GFDM MMSE and DSIC/MF receivers for the case of employing modern channel coding. Recently, we have proposed a new multicarrier scheme based on GFDM architecture called generalized... 

We study the problem of optimizing the symbol error probability (SEP) performance of cluster-based cooperative wireless sensor networks (WSNs). It is shown in the literature that an efficient relay selection protocol based on simple geographical information of the nodes to execute the cooperative diversity transmission, can significantly improve the SEP performance at the destination of such networks. Also, a similar analysis on the optimal power allocation for the source and the relay exists in the literature. However, we propose that to achieve the minimum SEP at the destination, a joint optimization of power allocation and relay selection should be accomplished. To this aim, we... 

Security in mobile ad hoc networks (MANETs) is an active research topic. Bulks of prior work focused on key management and secure routing without addressing an important pre-requisite: network access control, the problem of admission and revocation of ad hoc nodes. In this paper, we present ID-NAC, identity-based network access control for MANETs. In ID-NAC each node in the network maintains a profile table, which contains information about the behavior of the nodes in the MANET. It is used to assign a quantitative value for the trustworthiness of a node. Since, there is no observation about the behaviors of prospective members at first; they are admitted to the network tentatively. Then,... 

The vision of advanced long-term evolution (LTE-A) project is set to ultimate increase of network capacity in heterogeneous networks (HetNets). In HetNets with small cell configuration, a considerable majority of user devices is eventually connected to the macrocell base station (MBS), while small base stations (BSs), such as femtocell access points (FAPs), are still without any user. This results in unbalanced load and reduces the data rate of macrocell user equipment (MUE). In this paper, a method is proposed for load balancing among FAPs, while desired throughput is achieved. The proposed method uses the estimated received signal strength from different BSs and adjusted pilot signals.... 

Motivated by the statistical correspondence between phases of the transmitted and received vectors, we present a fast decoding method for quasi-orthogonal space-time block codes (QOSTBCs) in this paper. The proposed decoder selects proper candidates from precomputed and sorted sets by focusing on the phase of a specific entry of the combined and decoupled vector. The ML metric of the most probable candidates is first evaluated, and then, the remaining candidates are assessed based on the similarity between the phases. The new algorithm can work with any type of constellation such as QAM and PSK and supports generalized block-diagonal QOSTBCs. Theoretical results backed by simulation tests... 

DG application has received increasing attention during recent years. The impact of DG on various aspects of distribution system operation, such as reliability and energy loss, depend highly on DG location in distribution feeder. Optimal DG placement is an important subject which has not been fully discussed yet. This paper presents an optimization method to determine optimal DG placement, based on a cost/worth analysis approach. This method considers technical and economical factors such as energy loss, load point reliability indices and DG costs, and particularly, portability of DG. The proposed method is applied to a test system and the impacts of different parameters such as load growth... 

combination of smart antenna techniques and OFDM could be considered as a promising solution for improving the performance and enhancing the data rates of next generation wireless communication systems operating in frequency selective fading environments. There are different design parameters which could affect the application of adaptive arrays in OFDM-based systems. Various beam-forming methods in frequency or time domain, different array architectures and various number of array elements are important factors which are able to change the performance and complexity of the system. These parameters may show different effects in different channel conditions. In this paper we implemented a new... 

In this paper, a hierarchical routing protocol for wireless sensor networks is introduced that aims at reducing the energy imbalance among sensor nodes by integrating the distance of the nodes from the base station into clustering policies. Moreover, the proposed routing protocol does not need any centralized support from a certain node which is at odds with aiming to establish a scalable routing protocol. Mobility management is a salient feature of this protocol that guarantees reliable communications between mobile and static nodes. A simulator was developed in the MATLAB environment to evaluate the performance of this protocol. Simulations on two different network configurations are used... 

we study the uplink performance of wireless infrared code-division multiple access (CDMA) networks using OOK with optical orthogonal codes (OOC's). The analysis is performed in two cases assuming a cellular network architecture, in which all users are uniformly distributed in the cell's area. The first case is when all users transmit with the same power and no power control mechanism is used. Then, the system that deploys power control mechanism is analyzed and the performance improvements are demonstrated. The impact of imperfect power control which is caused by errors in channel estimation is also analyzed and the analytical and numerical results for all cases are included. The results... 

Long-term evolution (LTE) is aimed to achieve the peak data rates in excess of 300 Mb/s for the next-generation wireless communication systems. Turbo codes, the specified channel-coding scheme in LTE, suffer from a low-decoding throughput due to its iterative decoding algorithm. One efficient approach to achieve a promising throughput is to use multiple maximum a posteriori (MAP) cores in parallel, resulting in a large area overhead. The two computationally challenging units in an MAP core are α and β recursion units. Although several methods have been proposed to shorten the critical path of these recursion units, their area-efficient architecture with minimum silicon area is still missing.... 

Long term evolution (LTE)-advanced aims the peak data rates in excess of 3 Gbps for the next generation wireless communication systems. Turbo codes, the specified channel coding scheme in LTE, suffers from a low-decoding throughput due to its iterative decoding algorithm. One efficient approach to achieve a promising throughput is to use multiple Maximum a Posteriori (MAP) cores in parallel, resulting in a large area overhead, a big drawback. The scaled Max-log MAP algorithm is a common approach to implement the MAP algorithm due to its efficient architecture with its acceptable performance. Although many works have been reported to reduce the area of the MAP unit, an efficient VLSI... 

In this paper, a "Game Theory" approach for finding an optimal path in a "Wireless Sensor Network" is discussed. WSN is one of the most interesting research fields in the communication networks, and is the center of attention in recent years. In our model, a pricing and payment technique is presented to obtain an optimal path in a WSN by considering reliability, energy and traffic load. The proposed algorithm is able to find a path which improves network lifetime, load distribution and path reliability  

In diffusive molecular communication (DMC), the transmitter has to be able to control the release of signaling molecules for modulation of the information bits. In natural cells, pumping ions is an important control mechanism for releasing molecules which is carried out by ion pumps embedded in the membrane. The activity of the ion pumps is controlled by a driving parameter. In particular, light driven pumps are controlled by light intensity and enable a high degree of spatial and temporal control for modulation functionality. In this paper, a modulator based on ion pumps is proposed for DMC which controls the release rate of the molecules from the transmitter by modulating a light intensity... 

With the evolution and significant growth in wireless technology and the development of mobile commerce, businesses can achieve superior performance through the implementation of platforms for mobile payment. However, there are several platforms for mobile payment to choose from which makes the selection of an appropriate platform for specific applications a challenging task. In response to this challenge, the most common mobile payment platforms recorded in the literature have been reviewed. This paper presents the result of this review describing the advantages and disadvantages of each system and offers ranking of the technologies considered. MCDM method is used for assessing and... 

Nowadays, wireless sensor networks are known as a new challenge in network science. New features of these networks have made it impossible to use the traditional routing protocols. The most important challenge of these networks is the limited energy of nodes. In this paper, we will introduce MEHR as a multi-hop location-unaware hierarchical routing protocol to decrease the energy consumption in nodes, and to increase the network lifetime, we also apply MEHR to reach to a scalable routing. We will introduce a new factor to select candidate nodes and to send intra-cluster messages. We will use place-advertisement messages of sink, and a limiting parameter and also overhearing concept to create... 

Cooperation of nodes for routing and packet forwarding is inevitable in a mobile ad hoc network. Selfishness in such networks is a significant challenge and can cause network performance to noticeably degrade. In this paper, we propose some new selfishness models elicited from psychological behavior of human beings. We also evaluate performance of MANET in the presence of different percentages of selfish nodes that act based on our selfishness models. Results show that energy-based selfishness is a serious problem that could affect performance depends on mobility of nodes, density of network, and time of simulation. This kind of selfishness needs a comprehensive mechanism to cope with and we... 

A simulation tool, based on Ray Tracing method, has been developed and validated for millimeter-wave band. This tool helps for predicting the signal level as well as the delay characteristics of a propagation channel. Since the resultant of the received replicas of the transmitted signal at receiver point can experience a deep fade and consequently the quality degradation, a proper diversity method can effectively alleviate this drawback. Using this simulation tool and extracting the received wave characteristics in a street scenario, an analytical expression for predicting the space diversity gain for the Selection Combining technique and Maximal-Ratio Combining technique has been proposed  

In this paper an enhanced ETSI-Hata propagation model tuning is presented. The three-dimensional (3D) digital terrain map (DTM) was included in the simulation process. For the enhancement of the model tuning process and precision verification of ETSI-Hata model, the real 3D map of the buildings of the simulated area was incorporated over the DTM. Multiple knife edge diffraction method and the antenna effective height method were used to calculate the diffraction loss. This method was applied for a real urban scenario. For every sector in the coverage area, a tuned model was exploited. Using a genetic algorithm, frequency planning for the entire urban area was performed, which resulted in an... 

This paper considers a two-level supply chain consisting of one warehouse and one retailer. In this model we determine the optimal ordering policy according to inventory and transportation costs. We assume that the demand rate by the retailer is known. Shortages are allowed neither at the retailer nor at the warehouse. We study this model in two cases; decentralized and centralized. In the decentralized case the retailer and the warehouse independently minimize their own costs; while in the centralized case the warehouse and the retailer are considered as a whole firm. We propose an algorithm to find economic order quantities for both the retailer and the warehouse which minimize the total...