Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 6 Articles
Relaying is standardized in 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE)-Advanced\r\nRelease 10 as a promising cost-efficient enhancement to existing radio access networks. Relay deployments\r\npromise to alleviate the limitations of conventional macrocell-only networks such as poor indoor penetration\r\nand coverage holes. However, to fully exploit the benefits of relaying, power control (PC) in the uplink should\r\nbe readdressed. In this context, PC optimization should jointly be performed on all links, i.e., on the\r\ndonor-evolved Node B (DeNB)-relay node (RN), the DeNB-user equipment (UE) link, and the RNââ?¬â??UE link. This\r\nensures proper management of interference in the network besides attaining a receiver dynamic range which\r\nensures the orthogonality of the single-carrier frequency-division multiple access (SC-FDMA) system. In this\r\narticle, we propose an automated PC optimization scheme which jointly tunes PC parameters in relay\r\ndeployments. The automated PC optimization can be based on either Taguchiââ?¬â?¢s method or a meta-heuristic\r\noptimization technique such as simulated annealing. To attain a more homogeneous user experience, the\r\nautomated PC optimization scheme applies novel performance metrics which can be adapted according to the\r\noperatorââ?¬â?¢s requirements. Moreover, the performance of the proposed scheme is compared with a reference\r\nstudy that assumes a scenario-specific manual learn-by-experience optimization. The evaluation of the\r\noptimization methods within the LTE-Advanced uplink framework is carried out in 3GPP-defined urban and\r\nsuburban propagation scenarios by applying the standardized LTE Release 8 PC scheme. Comprehensive results\r\nshow that the proposed automated PC optimization can provide similar performance compared to the\r\nreference manual optimization without requiring direct human intervention during the optimization process.\r\nFurthermore, various trade-offs can easily be achieved; thanks to the new performance metrics....
In this contribution, we investigate the concept of time division duplexing (TDD) mode as an alternative to underlay\r\nshort-range femtocells on the uplink of legacy macrocell deployments. To mitigate the resulting co-channel\r\ninterference, the underlaid femtocell tier uses a distributed mechanism which is based on regular busy tones and\r\nrelies on minimal signaling exchange. Stochastic geometry is used to model practical scenarios by capturing network\r\ndynamics and channel variations. The impact of the fading correlation on the performance of the coordination\r\nmechanism is examined as well. Higher-order statistics through the cumulants concept are used to recover the\r\ndistribution of the co-channel interference and evaluate the system performance in terms of the outage probability\r\nand average channel capacity. We observe that our analytical framework matches well with numerical results\r\nobtained using Monte Carlo simulations. In contrast to the uncoordinated frequency division duplexing mode, the\r\ncoordinated TDD-underlay solution shows a reduction in the outage probability of nearly 80%, while the average\r\nspectral efficiency increases by approximately 90% in high loads....
In the 21st century it is vital to control & fetch the necessary information from every corner of the world. Robot is a machine which has the potential to do such types of works very accurately & timely, especially where human entry may prove costly. Despite of many methods have developed, the use of mobile phone for the robotic control can overcome the limitations of limited frequency range & limited control. In addition to this the mobile controlled robot provides the advantage of no interference with other devices. This robot can be operated via two ways: either by making a call to another mobile stacked in the robot or through the wireless communication module with interfacing the mobile. This method for robotic control involves three distinct phases: perception, processing & action. Here, the preceptors are the sensors & cameras mounted on the robot, processing is done by the micro-controller & the action is performed by the DC motors....
Wireless sensor network always face challenges from point of view of application and proper utilization of resources like energy source provided in sensor node. This paper propose new hierarchical routing protocol for application of wireless sensor network merge with more than one task and to utilize energy source efficiently. Proposed protocol deal with both stationary and dynamic or moving sensor nodes. To balance the load of main cluster head, concept of virtual cluster head is use. Where virtual cluster head come in existence only when load of main cluster head exceed the threshold. Performance of proposed protocol is analyze with the help of life time of system by comparing it with LEACH protocol....
In this article, a tool for simulating the channel impulse response for indoor visible light communications using 3D\r\ncomputer-aided design (CAD) models is presented. The simulation tool is based on a previous Monte Carlo\r\nray-tracing algorithm for indoor infrared channel estimation, but including wavelength response evaluation. The 3D\r\nscene, or the simulation environment, can be defined using any CAD software in which the user specifies, in\r\naddition to the setting geometry, the reflection characteristics of the surface materials as well as the structures of\r\nthe emitters and receivers involved in the simulation. Also, in an effort to improve the computational efficiency, two\r\noptimizations are proposed. The first one consists of dividing the setting into cubic regions of equal size, which\r\noffers a calculation improvement of approximately 50% compared to not dividing the 3D scene into sub-regions.\r\nThe second one involves the parallelization of the simulation algorithm, which provides a computational speed-up\r\nproportional to the number of processors used....
Sensing-throughput tradeoff has widely been investigated in cognitive radio networks. Detection probability and\r\ninterference ratio are usually considered the main constraints to the protection of primary signals. However, the\r\ndetection probability defined during a sensing duration does not fully capture the goal of primary protection\r\nbecause two important factors are not taken into consideration. Neither the detection latency during the detection\r\nof the primary signal nor the unavoidable misdetection of the primary signal due to its ability to only occupy the\r\nchannel between two consecutive sensing durations are considered. Motivated by these problems, we propose a\r\nnew detection probability called the time-constrained detection probability (TDP) and investigate the effect of the\r\nsensing interval on the TDP. This sensing interval consists of a sensing duration and a transmission duration.\r\nMoreover, both an optimal sensing duration and an optimal sensing interval are proposed, which not only satisfy\r\nboth the TDP and the interference ratio constraints for primary protection, but also maximize the achievable\r\nthroughput for secondary users. Numerical analyses show the relationship between the sensing interval and the\r\nTDP and the optimal sensing parameters consisting of the optimal sensing duration and the optimal sensing\r\ninterval....
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