فهرست مطالب

  • Volume:8 Issue: 4, 2016
  • تاریخ انتشار: 1395/09/30
  • تعداد عناوین: 7
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  • Ali Golestani, Ali H. Bastami, Kamal Mohamed-Pour Pages 1-10
    In this paper, the spatial interference alignment (IA) is investigated in the downlink (DL) of a relay-assisted multi-cell multi-user network. The transmission from the base station (BS) to the mobile station (MS) takes place in two phases with the help of the selected relay station (RS). The closed-form IA algorithms are employed in both the BS to RS and RS to MS links. The performance of this cooperative scheme is analyzed in terms of the sum rate and the sum degrees of freedom (DoF) for the amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes. The simulation results of the sum rate show that the DF scheme significantly outperforms the noncooperative minleakage and max-SINR iterative algorithms over the entire range of SNR, and the AF scheme performs very close to the min-leakage algorithm. Moreover, the DF scheme outperforms the noncooperative closed-form IA algorithm in the low and medium-SNR regimes.
    Keywords: Cellular network, degrees of freedom, interference alignment, relay, sum rate
  • Hamed Alizadeh Ghazijahani, Milad Abdollahzadeh, Hadi Seyedarabi, Mir Javad Musevi Niya Pages 19-27
    Recently, Visible Light Communication (VLC) has got increasing attention in the field of indoor wireless communications. Color Shift Keying (CSK) is a VLC modulation scheme proposed by IEEE 802.15.7 task group. In this method diffused light wavelengths are symbol points so that their combination provides an overall white sensation. Modulation depth in CSK influences Bit Error Rate (BER) as determines transmission rate. In the case of video streaming over VLC network, video encoding rate should be compatible with the transmission rate, consequently, affects video quality. We have proposed an adaptive modulation scheme for video transmission over VLC network considering the dependency of encoded video quality and modulation BER to modulation. This algorithm jointly minimizes BER and encoded video distortion via adaptive selection of CSK modulation depth to decline frame loss besides desirable video quality protection.
    Keywords: bit error rate, color shift keying, modulation, video streaming, visible light communication
  • Mehrdad Taki, Reza Mahin Zaeem Pages 29-34
    Complexity issues and limited feedback rate strictly constrain the number of transmission modes in discrete link adaptation. A new algorithm is designed for selecting an optimum set of modes out of all the possible transmission modes based on the link’s characteristics and the constraints, meanwhile, imperfect channel state information (CSI) is available. The design goal is to maximize the average spectral efficiency and the selection is done using a combination of nonlinear quantization and integer programming. As numerical evaluations for adaptive LDPC or convolutional coded, QAM modulated transmission show, performance of the proposed scheme is considerably improved in comparison with the benchmark schemes.
    Keywords: component, Link Adaptation, Adaptive Modulation, Coding, Integer programming
  • Nasrin Dastranj, Kolsoom Abbasi Shahkooh, Tahereh Mirsaeedghazi, Mahmood Kharrat Pages 35-43
    Technology roadmapping is a tool for decision-makers to identify, assess and choose between different strategic options to achieve technological objectives and help companies and industries create better understanding of their market and technological choices. In this research, a technology roadmap for planning and developing e-services in rural and least developed areas is designed. Along with development of communication infrastructure and providing access all over the country, it is necessary to create a comprehensive plan to develop e-services in rural and least developed areas. This roadmap provides a platform for participation of stakeholders from all sectors and also provides access to high quality and effective services. By using technology roadmap approach, e-services have been defined in different categories including agriculture, education, health, finance and banking, tourism, public facilities, employment and entrepreneurship, registration, environment, police and judiciary; and then characteristics and requirements of services are clarified. After specific steps to extract the required content of the roadmap, the content is mapped to the structure of the roadmap in layers of drivers, services, requirements and strategies.
    Keywords: e, services, technology roadmap, rural, least developed areas, USO
  • Sajjad Salehi, Fattaneh Taghiyareh Pages 45-54
    Opinion leaders are individuals who have specific personal features that enable them to impact opinions of other agents named followers. In this paper we are going to introduce an agent based opinion formation model to investigate the impact of structural position of agents on their ability to navigate the opinion of social network. For each agent, this ability is defined based on the judgment of his neighbors about his status. The status of each agent is estimated based on status theory. In proposed model, we suppose each agent can modify the opinion of his neighbors with lower status. By applying this model on two complete and scale free graphs, we have investigated the effect of agents’ position on opinion leadership ability. Also the effect of leaders to navigate the opinion of agents is studied. The results of our work can be applicable in competitive environments that different parties try to change the social opinion.
    Keywords: opinion formation, social network, leader, follower, agent
  • Leila Mansourifar, Nasser Mozayani Pages 55-64
    Efficient data transfer in broadband networks is the anchor point of digital economy in modern era. One of the most challenging issues for providing different services in broadband is the bandwidth allocation. That is a realtime multi-dimensional problem solving requiring to satisfy QoS and SLA constraints at the same time. This problem is economically defined as a utility optimization issue aiming to maximize user profits. In this paper, we present an adaptive framework for the problem of optimal utility optimization of bandwidth allocation to broadband services. We used first an online optimization for the allocation based on user preferences and Network Utility Maximization. Our second solution is a particle swarm optimization method in order to consider both parameters at the same time to find an optimal allocation pattern. Simulation results showed satisfactory bandwidth allocation patterns in different scenarios according to the network utility and user preferences in SLA.
    Keywords: component, Digital Economy, Utility Optimizatioin, Network Utility Maximization (NUM), Bandwidth Allocation, QoS, Broadband Services, PSO
  • Page 65
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