iosr-JECE   Volume-2 ~ Issue-2

Abstract : The Improved DFT-based Channel Estimation Algorithm for MIMO-OFDM System uses the symmetric property to extend the LS estimate in frequency domain, and calculates the changing rate of the leakage energy, and selects useful paths by the changing rate.
The Discrete Fourier Transform (DFT) is used for spectral analysis, the sequence usually represents a finite set of uniformly-spaced time-samples of some signal , where t represents time. The conversion from a very long (or infinite) sequence to a manageable size entails a type of distortion called leakage, which is manifested as a loss of detail in the DTFT. Choice of an appropriate sub-sequence length is the primary key to minimizing that effect. When the available data (and time to process it) is more than the amount needed to attain the desired frequency resolution, a standard technique is to perform multiple DFTs. Multiple Input Multiple Output (MIMO) - Orthogonal Frequency Division Multiplexing (OFDM) can not only effectively enhance the transmission rate and capacity of the wireless communication system but also effectively combat multipath fading and inter-symbol interference (ISI). MIMO-OFDM technology has become one of the most promising solutions in the high data rate wireless channel transmission. In the OFDM system with transmit diversity, when the receiver knows the channel information better, the space-time codes can be decoded effectively. In order to enhance frequency efficiency, the receiver also needs to know the channel information for coherent demodulation. So channel estimation is directly related to the system performance. Least squares (LS) approach is the simplest channel estimation. This algorithm has lower complexity. However, it has larger mean square error (MSE) and easily influenced by noise and intercarrier interference. Another approach is also proposed by extending the LS estimate with a symmetric signal of its own. Based on these two methods, we propose a new method to solve the problem of energy leakage.
Keywords - Channel Estimation, Energy Leakage, DFT- Discrete Fourier transform, MIMO- Multiple Input Multiple Output, OFDM-Orthogonal Frequency Division Multiplexing.

[1] G.L. Stuber, J.R. Barry, S.W. McLaughlin, Ye Li, M.A. Ingram and T.G. Pratt, "Broadband MIMO-OFDM wireless communications," Proceedings of the IEEE, vol. 92, No. 2, pp. 271-294, February. 2004. [2] Jan-Jaap van de Beek, O.Edfors, and M.Sandell, "On channel estimation in OFDM systems," Presented at in proceedings of Vehicular Technology, Chicago, pp. 815-819, 1995. [3] B.Song, L.Gui, and W.Zhang, "Comb type pilot aided channel estimation in OFDM systems with transmit diversity," IEEE Trans. Broadcast., vol. 52, pp. 50-57, March. 2006. [4] Noh. M., Lee. Y. , and Park. H. "A low complexity LMMSE channel estimation for OFDM," IEE Proc. Commum., vol. 153, No. 5, pp. 645-650, 2006. [5] M. K. Özdemir, H. Arslan, E. Arvas. "Towards Real–Time Adaptive Low–Rank Lmmse Channel Estimation of MIMO–OFDM Systems," IEEE Trans. Wireless Commun., vol. 5, no. 10, pp. 2675–2678, October.2006. [6] I. Tolochko, M. Faulkner. "Real Time Lmmse Channel Estimation for Wireless OFDM Systems with Transmitter Diversity," Proc. IEEE Vehic. Tech. Conf. vol. 3, Vancouver, Canada, pp. 1555-1559. September.2002. [7] O. Edfors, M. Sandell, J.-J. van de Beek, S. K. Wilson, and P. O.Börjesson, "Analysis of DFT-based channel estimators for OFDM," Wireless Personal Commun, vol. 12, pp. 55-70, January. 2000. [8] Li Li, Wang ke, and Han li. "Channel Estimation Based on DFT for OFDM Systems on Non-sample Spaced Channel," Journal of Wuhan University of Technology, vol. 33, No. 6, pp. 1195-1198, December.2009.
[9] Y. Wang, L. Li, P. Zhang and Z. Liu, "Channel estimation for OFDM systems in non-sample-spaced multipath channels," Electronics Letters, vol. 45, January. 2009.

Abstrac :The focus of this Paper is the actual implementation of Network Router and verifies the functionality of the five port router for network on chip using the latest verification methodologies, Hardware Verification Languages and EDA tools and qualifies the Design for Synthesis and implementation. This Router design contains Four output ports and one input port, it is packet based Protocol. This Design consists of Registers, FSM and FIFO's. For larger networks, where a direct-mapped approach is not feasible due to FPGA resource limitations, a virtualized time multiplexed approach was used. Compared to the provided software reference implementation, our direct-mapped approach achieves three orders of magnitude speedup, while our virtualized time multiplexed approach achieves one to two orders of magnitude speedup, depending on the network and router configuration.
Keywords- FIFO, FSM, Network-On-Chip, Register blocks, and Router Simulation.

[1] D. Chiou, "MEMOCODE2011Hardware/SoftwareCoDesignContest", https://ramp.ece.utexas.edu/ redmine / Attachments/ DesignContest.pdf
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[5] "Application Note: Using the Router Interface to Communicate Motorola, ANN91/D Rev. 1, 01/2001.
[6] Cisco Router OSPF: Design& Implementation Guide, Publisher: McGraw-Hill
[7] "Nortel Secure Router 4134", Nortel Networks Pvt. Ltd.
[8] "LRM", IEEE Standard Hardware Description Language Based on the Verilog Hardware Description Language – IEEE STD 1364-1995.
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Abstract: This paper presents a new approach to design the dielectric resonator antenna (DRA) for wideband applications, which has a stepped construction the hexagon shaped upper resonator and triangle shaped lower resonator. The DRA is excited by a conformal inverted-trapezoidal patch connected to a microstrip line. The wider bandwidth is achieved, because of three factors: compact honeycomb and triangle shaped dielectric resonator, a conformal inverted-trapezoid patch as a feed mechanism, and a copper-clad substrate as a baseboard. A 76.25% matching bandwidth (S11<10 dB) is achieved with broadside radiation patterns where the impedance bandwidth covers a frequency range from 5.1 to 11.1 GHz. Based on the proposed structure, a four-element array is designed, and the degree of the directivity increases largely.
Keywords: dielectric resonator antenna, hexagonal upper resonator, triangle shaped lower resonator , inverted trapezoidal patch, DRA

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Abstract:The spectrum sensing problem has gained new aspects with cognitive radio and opportunistic spectrum access concepts. It is one of the most challenging issues in cognitive radio systems. In cognitive radio networks, the secondary (unlicensed) users need to find idle channels via spectrum sensing for their transmission. Adaptive spectrum sensing (ASS) is a promising technology in spectrum sensing with an admirable performance. In ASS, multiple secondary users individually sense the idle channels and send their decisions to the network center, and then the center will do a final decision. Spectrum sensing, which aims at detecting spectrum holes, is the precondition for the implementation of cognitive radio (CR). In this work we formed an information table at MSC (main switching center) which consists of channel information and according to the requirement any primary or secondary user can fetch that channel and utilize without any interference. The experiment is conducted on static as well as adaptive environment to check the throughput, route delay of the conventional as well as proposed method.
Keywords: cognitive radio, cognitive radio network, MANets, spectrum sensing, wireless sensor networks

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Abstarct: Wireless communication deals with data transmission over air as interfacing medium between the transmitting and receiving stations posing data security as biggest challenge. Although, technologies other than wireless introduced earlier pay significant service to users, the broadband wireless, with mobility is the first choice of people all over. In this, WiMAX 802.16e is one possibly technology supporting data security. It uses different authentication and authorization protocols between the client and agent. This paper describes strategy of WiMAX and security mechanisms used in it. Keywords: WiMAX, DSN, AAA, WWAN, WBA

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[9]. Prashant Sharma (2009), Facts about WiMAX.

Abstract: An ad hoc network is a collection of mobile nodes that dynamically form a temporary network. Routing in a MANET is challenging because of the dynamic topology and the lack of an existing fixed infrastructure. In such a scenario a mobile host can act as both a host and a router forwarding packets for other mobile nodes in the network. Routing protocols used in mobile ad hoc networks (MANET) must adapt to frequent or continual changes of topology, while simultaneously limiting the impact of tracking these changes on wireless resources. In his paper investigation has been done on the effect of change in number of nodes, node speed and pause time on packet delivery ratio (PDR) of MANET reactive routing protocols. Here, it has been analyzed and compared the performance of MANET routing protocols AODV and DSR based on both CBR and TCP based traffic patterns. The NS-2 simulator is used for performing various simulations and used awk scripts for analyzing the results. AODV in the simulation experiment shows the overall best performance. It has an improvement over DSR.
Keywords: Aodv, Cbr , Dsr, Manet, Ns2, Tcp,

[1] C. E. Perkins and E. M. Royer. "The ad hoc on-demand distance vector protocol," Ad Hoc Networking, Addison-Wesley, pp. 173-219, 2001.
[2] D. B. Johnson, D. A. Maltz, and J. Broch, "DSR: the dynamic source routing protocol for multi-hop wireless ad hoc networks," in Ad Hoc Networking, Addison-Wesley, 2001, pp. 139-172.
[3] Johnson, D. B., Maltz, D. A., Hu, Y. C. and Jetcheva, J. G. 2002. "The dynamic source routing protocol for mobile ad hoc networks (DSR)". Draft-ietf-manet-dsr-07.txt.
[4] Perkins, C. E., Royer, E. M. and Das, S. R. 1999. "Ad Hoc On-Demand Distance Vector Routing". IETF Internet Draft. http://www.ietf.org/internet-drafts/draft-ietf-manetaodv-03.txt.
[5] Anuj K. Gupta, Dr. Harsh Sadawarti, Dr. Anil K. Verma, "Performance analysis of AODV, DSR and TORA Routing Protocols", International Journal of Engineering & Technology (IJET), ISSN: 1793-8236, Article No. 125, Vol.2 No.2, April 2010, pp. – 226-231.
[6] Narendran Sivakumar, Satish Kumar Jaiswal, "Comparison of DYMO protocol with respect to various quantitative performance metrics", ircse 2009.
[7] NS-2, The ns Manual (formally known as NS Documentation) available at http://www.isi.edu/nsnam/ns/doc.NAM
[8] http://www.isi.edu/nsnam/nam/
[9] C. E. Perkins and P. Bhagwat, "Highly Dynamic Destination- Sequenced Distance-Vector Routing (DSDV) for Mobile Computers," SIGCOMM, London, UK, August 1994, pp. 234-244.
[10] Vincent D. Park and M.Scott Corson. "A highly adaptive distributed routing algorithm for mobile wireless networks".In Proceedings of INFOCOM 1997, 1997.

Abstract: In this paper, a broadband rectangular microstrip patch antenna fed by coplanar waveguide feed with two slots in the ground plane is proposed. Investigations are carried out using coplanar waveguide feed with slotting in the ground plane to optimize the broadband operation. A sensitivity analysis shows the variation of return loss with different antenna parameters. This design of broadband antenna is obtained by properly choosing the suitable shape of slots in ground plane and selecting proper shape and size of the radiating patch. The designed antenna gives a return loss of -61dB and impedance bandwidth of 1.02GHz. The simulated results for return loss, bandwidth, VSWR and radiation pattern are studied.
Keywords: Broadband, bandwidth, CPW-feed, microstrip patch antenna, return loss,

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[3]. P. Jearapraditkul, W. Kueathaweekun, N. Anantrasirichai, O Sangaroon and T. Wakabayashit, Bandwidth Enhancement of CPW-Fed Slot Antenna with Inset Tuning Stub,International Symposium on Communications and Information Technologies, 2008.
[4]. D. Mitra, D. Das and S. R. Bhadra Chaudhuri, Bandwidth enhancement of microstrip line and CPW-fed asymmetrical slot antennas, Progress In Electromagnetics Research Letters, 2012, 69–79.
[5]. L. Varshney, V. R. Gupta, H. Kumar, P. Suraj, CPW-Fed Broadband Microstrip Patch Antenna, International journal of advanced engineering and application, 2011
[6]. C.A. Balanis, Antenna Theory Analysis and Design (John Wiley & Sons, Inc., 1997).

Abstract: A comparative study of the effects of electrostatic discharge (ESD) on digital and analog circuits is carried out. Direct and Indirect discharge is performed on the circuit having both analog and digital circuitry. First the Indirect discharge on the ground plane is done for different voltages and distances. Then the direct air discharge is performed near the digital and discreet analog circuitry. These results are compared and the effect of electrostatic discharge over digital and analog circuits is summarized from the experimental results.
Keywords:- Electrostatic Discharge; Indirect discharge; Direct air discharge; Analog circuit; Digital circuit; ESD simulator; Electromagnetic Interference

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