Volume 13, Issue 2, April 2012

Performance of a DS-UWB system with a Wiener timing offset [Full Text] 

K. Ben Hamida El Abri and A. Bouallegue

Abstract—Ultra-wideband (UWB) systems impose a stringent requirement on the alignment between transmitter and receiver clocks because of the short pulse duration which requires a fast synchronization algorithm. Until now, only the effect of Gaussian timing offset has been considered in the literature. However, practical clocks commonly exhibit a wiener distribution. In this paper, we investigate the effect of this offset model on the performance of a DS UWB system using the Code Block Synchronization Algorithm (CBSA) to synchronize the clock. Simulation results show the good performance of the proposed scheme with a phase noise following wiener model. 


Design and Simulation of an Easy Structure Multiband Printed Ring Slot Antenna [Full Text]

M.H. Amini and H.R. Hassani

Abstract— An easy structure printed slot antenna providing multi frequency is designed and simulated. The antenna operates over UMTS/WLAN/MMDS and WIMAX bands. The multiband antenna consists of four ring slots and a single microstrip feed line. To match the input impedance of the antenna to the 50 ohm SMA connector, the width of three slots become narrow in their feeding places. By choosing the appropreate value for angle of page1image6192, good impedance match can be achieved. The fourth slot also is matched through the conventional stub length. The reflection coefficient of the proposed structure is simulated and good result is achieved at each bands through this design. The antenna also has a symmetrical far field radiation patterns suitable for wireless communication networks. 


Node Failure Aware Tree-Clustered Routing Algorithm In WSN [Full Text]

Deepthi Kulkarni, B. P. Patil and M. D. Goudar

Abstract—Wireless Sensor Networks consist of thousands of tiny nodes having the capability of sensing, computation, and wireless communications. Many routing, power management and data dissemination protocols have been specifically designed, where energy consumption is an essential design issues. Since wireless sensor network protocols are application specific, so the focus has been given to the routing protocols that might differ depending on the application and network architecture. The study of various routing protocols for sensor networks presents a classification for the various approaches pursued. This paper have reviewed and compared protocols like Direct, Pegasis, Leach, TCDGP and an improved node failure aware tree cluster routing algorithm is suggested. This routing scheme has the common objective of trying to get better throughput, end to end delay and to extend the lifetime of the sensor network.The improvements have been obtained in the simulations done using NS2. 


A survey on scheduling algorithms in LTE [Full Text] 

Mohammad Reza Amini, Mostafa Rezaei and Morteza Bayat

Abstract— This paper contains recent related works to scheduling algorithms proposed in Long Term Evolution (LTE). Different criteria and utility (objective) functions are stated; furthermore some scheduling problem definitions with different constraints and their solution algorithms are mentioned. The differences between downlink and uplink in scheduling and Multiple Input and Multiple Output (MIMO) and Single Input and Single Output (SISO) models are discussed.


Low Flicker Noise CMOS Sub threshold Mixer for 2.4 Ghz Application [Full Text]

M. Safari, S. Toofan and A. Jalilvand 

Abstract— This paper presents a low flicker noise, 2.4 GHz down conversion 0.18μm-CMOS subthreshold mixer based on double balanced Gilbert cell. The flicker noise is a strong factor of mixer noise figure. In order to reduce its noise figure, all transistors are biased in subthreshold region at this work. Also, a static current injection circuit (current bleeding circuit) is used to improve its noise performance. Simulation results of designed mixer show 21.1 dB conversion gain and 6.32 dB average noise figure at 1 GHz - 6 GHz. Moreover, these demonstrate that using current bleeding circuit has low noise figure. Its consumption power is 10.6 mW at 1.8V supply voltage. 


A new approach to annotate web images and how to search for the personal images [Full Text]

M. Yasrebi

Abstract—These Now a day we are facing the increase in the quantity of digital photos in the web further more numerous web sites hosting various images of individuals & groups, as an illustration we can point to the most popular ones like FlickrTM & the FaceBookTM. But the drawback we are encountering is annotation of those photos which is done based on visual features of the issue.In this article we are proposing a new approach to use the existing images in Photo sharing & social networking web sites originated from human annotation which makes us capable of searching family member’s pictures in the most possible efficient trend.The offered algorithm is based on the familial ties which make it possible to access distant members of an individual’s family via his/her close relatives regarding the fact that the applicant must run his /her search through the cannel of close family members.Our empirical evaluation highlighted the fact that this approach can be considered as another step forward to help people in their search for their beloved ones.