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
[2] Blue spec Inc, http://www.bluespec.com
[3]Xilinx,"ML605HardwareUserGuide",http://www.xilinx.com/support/documentation/boardsandits/ug534.pdf [4] Xilinx,"LogiCOREIPProcessor Local Bus (PLB) v4.6", http://www.xilinx.com/support/documentation/ip documentation/plb v46.pdf
[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.
Books:
[9]. Chris Spears SYSTEMVERILOG FOR VERIFICATION, Publisher: Springer. [10]. Bhaskar. J, A Verilog HDL Primer, Publisher: Syndicate Publications.

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

[1] Kishk A.A., Zhou G., and Glisson A.W., "Analysis of dielectric-resonator antennas with emphasis on hemispherical structures," IEEE Antennas Propagation Magazine, 36(2), 1994, 20–31.
[2] Kishk A.A., "Wide-band truncated tetrahedron dielectric resonator antenna excited by a coaxial probe," IEEE Trans. Antennas Propagation, 51(10), 2003, 2913–2917.
[3] Kishk A.A., Yan Y., and Glisson A.W., "Conical dielectric resonator antennas for wide-band applications," IEEE Trans. Antennas Propagation, 2002, 50(4), 469–474.
[4] Junker G.P., Kishk A.A., and Glisson A.W., "Input impedance of dielectric resonator antennas excited by coaxial probe," IEEE Trans. Antennas Propagation, 1994, 42, 960–966.
[5] Leung K.W., and Ng H.K., "The slot-coupled hemispherical dielectric resonator antenna with a parasitic patch: Applications to the circularly polarized antenna and wideband antenna," IEEE Trans. Antennas Propagation, 2005, 53(5), 1762–1769.
[6] Al Salameh M.S., Antar Y.M.M., and Seguin G.,"Coplanar-waveguide-fed slot-coupled rectangular dielectric resonator antenna," IEEE Trans. Antennas Propagation, 2002, 50(10), 1415–1419.
[7] Kishk A.A., Ahn B., and Kajfez D., "Broadband stacked dielectric resonator antennas," IEEE Electron. Lett., 1989, 25(18), 1231–1233.
[8] Petosa A., Simons N., Siushansian R., Ittipiboon A., and Cuhaci,M., "Design and analysis of multisegment dielectric resonator antennas," IEEE Trans. Antennas Propagation, 2000, 48(5), 738–742.