REV Journal on Electronics and Communications
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230 research outputs found
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Design and Simulation of Measurement-Based Correlation Models for Shadow Fading
Get PDFThis paper deals with the design of measurement-based correlation models for shadow fading. Based on the correlation model, we design a simulation model using the sum-of-sinusoids (SOS) method to enable the simulation of spatial lognormal processes characterizing real-world shadow fading scenarios. The model parameters of the simulation model are computed by applying the Lp-norm method (LPNM). This method facilitates an excellent fitting of the simulation model’s autocorrelation function (ACF) to that of measured channels. Our study includes an evaluation of all important statistical quantities of the proposed measurement-based simulation model, such as the probability density function (PDF), spatial ACF, decorrelation and coherence distance, as well as the level-crossing rate (LCR) and the average duration of fades (ADF). A comparison with the Gudmundson correlation model shows that the developed measurement-based correlation model outperforms the former one by far in terms of the goodness of fit to the measured data. The proposed measurement-based simulation model allows to study the effects of long-term fading on the performance of mobile communication systems under real-world shadow fading conditions
Improving the Behavior of an Electro-Optic Modulator by Controlling Its Temperature
Get PDFThe purpose of this paper is to present the improvement of the stability of an electro-optic modulator obtained from its temperature control. A digital system based on PSOC microcontroller and a small power amplifier has been developed. The behavior of the modulator can be observed by the way of its nonlinear properties. Thanks to the improved thermal stability, it is possible to reduce significantly the drift of the electro-optic modulator
Dual Band-Notched UWB Antenna based on Electromagnetic Band Gap Structures
Get PDFA printed ultra-wideband (UWB) antenna with dual band-notched characteristics based on electromagnetic band-gap (EBG) structure is presented. To produce dual-band rejection, the microstrip feed line is placed between two pairs of EBG cells which are designed to act as stop-band filters. The final design of the antenna satisfies the voltage standing wave ratio (VSWR) requirement of less than 2.0 in a bandwidth spreading from 2.275 GHz to 10.835 GHz, which entirely covers UWB frequency band allocated from 3.1 to 10.6 GHz. The antenna also shows dual band-notched performance at the frequency bands of 3.375 − 3.875 GHz for WiMAX and 5.325 − 6.150 GHz for WLAN, while possessing omni-directional characteristic in the whole operating frequency band. The results show good agreement between simulation and measurement
An Efficient Architecture of Forward Transforms and Quantization for H.264/AVC Codecs
Get PDFThanks to many novel coding tools, H.264/AVC has become the most efficient video compression standard providing much better performance than previous standards. However, this standard comes with an extraordinary computational complexity and a huge memory access requirement, which make the hardware architecture design much more difficult and costly, especially for realtime applications. In the framework of H.264 codec hardware architecture project, this paper presents an efficient architecture of Forward Transform and Quantization (FTQ) for H.264/AVC codecs in mobile applications. To reduce the hardware implementation overhead, the proposed design uses only one unified architecture of 1-D transform engine to perform all required transform processes, including discrete cosine transform and Walsh Hadamard transform. This design also enables to share the common parts among multipliers that have the same multiplicands. The performance of the design is taken into consideration and improved by using a fast architecture of the multiplier in the quantizer, the most critical component in the design. Experimental results show that our architecture can completely finish transform and quantization processes for a 4:2:0 macroblock in 228 clock cycles and the achieved throughput is 445Msamples/s at 250MHz operating frequency while the area overhead is very small, 147755μm2 (approximate 15KGates), with the 130nm TSMC CMOS technology
Minimalist Self-Organization in Wireless Networks
Get PDFMany fields of human endeavour, such as biology and the theory of complex systems, are now embracing the concept of self-organization based on local actions leading to a desirable global emergent behavior. While many examples, both natural and artificial, can be found of such self-organized systems, the relationship between the local rules and the global behavior remains elusive and no systematic procedure is known to engineer a specific global result. Given the increasing pervasiveness of wireless networks of all sorts, including ad hoc networks competing within narrow unlicensed bands and wireless sensor networks, self-organization could constitute the next defining paradigm in wireless communications. It can be shown that a set of heuristic principles can be leveraged to engineer a self-organized connection-oriented wireless network with minimal complexity. Such a system requires no centralization of information, yet achieves a nearly optimal global state with only a modest amount of local signaling. It will naturally and jointly balance the many parameters related to radio resource management, exhibiting great adaptability, fault tolerance and scalability
A Scalable Wi-Fi Based Localization Algorithm
Get PDFThis paper proposes an applicable and scalable approach which allows deploying the fingerprint Wi-Fi localization algorithm for different mobile devices. The original fingerprint localization algorithm performs accurately when the mobile device used in the deployment phase is the same as the mobile device used in the training phase. However, when a different mobile device is used in the deployment phase, a time-consuming re-training step (in the order of hours or days) is required to achieve the equivalent degree of accuracy. Our proposed approach replaces this re-training step by a short period of calibration (in the order of a few minutes), which can be done transparently to the user. To validate our approach, we did an analysis on collected data from a large scale experiment (14 laptops and 2 smartphones with 224-hour of collected data) and evaluated the performance on the real devices
Bit-Interleaved Coded Modulation Systems with Iterative Decoding and Partial Reusing QAM Signal Points
Get PDFA new method of reusing a subset of an M-QAM signal constellation is presented for Bit-Interleaved Coded Modulation systems with Iterative Decoding (BICM-ID). In addition to the remapping of high-energy signals to low-energy signals in order to save the average signal energy as a shaping technique known so far, a new scheme of remapping low-energy signals to high-energy signals is proposed in order to gain the equivalent distance when decoding bits, often called the Squared Euclidean Weights (SEW). Numerical analysis and simulation results show that the partial reuse of the signals in the BICM-ID system with 16-QAM can improve the system performance in terms of lowering the bit error rate in the error floor region
Theoretical Foundations of Mobile Flexible Networks
Get PDFThe general framework of Mobile Flexible Networks (MFN) is to design dense self-organizing, self-healing and self-energy harvesting secure networks where terminals and base stations interact and self-adapt in an intelligent manner without the need of a central controller or with the right amount of regulation to let the agents in the network exploit fully the degrees of freedom. The design depends mainly on the mobility pattern as in highly mobile environments, intelligence at the terminal reduces the cost of signaling whereas for fixedling whereas for fixed (non-mobile) networks, all the intelligence can be put on the network side. One of the big challenges is to find how to optimally split the intelligence between cognitive terminals and cognitive networks. In this paper, we discuss the challenges ahead and provide some research directions to develop the theoretical foundations of these networks
