Accurate analysis of a high data rate UWB-DTR system in dense multipath fading channels

2010 ◽  
Vol 3 (2) ◽  
pp. 67-72 ◽  
Author(s):  
Hassan Khani ◽  
Paeiz Azmi
Author(s):  
Pratima Manhas ◽  
M.K. Soni

<p>The nature of future wireless applications requires high data rates and for this OFDM technique is used. OFDM stands for orthogonal frequency division multiplexing and is a type of multi-carrier transmission where all the subcarriers are orthogonal to each other. At high data rates, the channel distortion to the data is very important and it is somewhat impossible to recover the transmitted data with a simple receiver. So a complex receiver structure is needed which uses computationally expensive equalization and channel estimation algorithms to estimate the channel. These estimations can be used within the received data to recover the originally transmitted data. OFDM can simplify the equalization problem by changing the frequency-selective channel into a flat channel. The radio channels in mobile radio systems are usually multipath fading channels that results in intersymbol interference (ISI) in the received signal. To remove ISI from the signal, many kind of equalizers can be used. The need for equalizers arises from the fact that the channel has amplitude and phase dispersion which results in the interference of the transmitted signals with one another which is known as ISI .So, to solve this problem equalizers are designed. Equalizer is intend to work in such a way that Bit Error Rate (BER) should be low and Signal-to-Noise Ratio (SNR) should be high. An equalizer within a receiver compensates for the average range of expected channel amplitude and delay characteristics. This paper deals with the various equalization techniques (LMS, RLS and CMA) used for OFDM system .A comparative analysis of different equalization technique in terms of BER is done using MATLAB Simulink.</p>


Author(s):  
Karthik Kumar Vaigandla, Allanki Sanyasi Rao and Kallepelli Srikanth

Communications systems concerted over wireless channels depend on the environment. Communications system can be more reliable and efficient by properly analyzing wireless channels. Today's most important features are a high data rate and reliable performance to exploiting viable networks during this new information age. The channel is not time-invariant in wireless communication, so the received signal exhibits amplitude, phase, and angle variations due to multipath fading. Increasing data rates and reducing bandwidth make Orthogonal Frequency Division Multiplexing (OFDM) an important component of wireless communication systems. The OFDM technique uses many carriers very efficiently. With this scheme, interference is robustly reduced, and fading scenarios are easily accommodated. Analyzing digital modulation schemes requires evaluating link performance with fading channels. The paper compares channel performance over varying fading environments using a variety of modulation schemes. We study the BER and SNR properties of the AWGN, Rician fading and Rayleigh fading channels modulated with BPSK, QPSK, and M-ary QAM.


Author(s):  
Fadhil Sahib Hasan ◽  
Hayder Fadhil Fahad

In this paper, a new non-coherent <span class="il">chaos</span>-<span class="il">based</span> communication that combined <span class="il">Orthogonal</span> <span class="il">Multilevel</span> <span class="il">Code</span>-<span class="il">Shifted</span> <span class="il">Differential</span> <span class="il">Chaos</span> <span class="il">Shift</span> <span class="il">Keying</span> with <span class="il">orthogonal</span> frequency division multiplexing named (<span class="il">OFDM</span>-OMCS-DCSK) modulation system. New <span class="il">orthogonal</span> chaotic signal sets are generated by hybrid Gram-Schmidt algorithm <span class="il">and</span> Walsh <span class="il">code</span> function <span class="il">and</span> used it to carry high data rate in the same time slot. The Bandwidth efficiency <span class="il">of</span> the <span class="il">OFDM</span>-OMCS-DCSK system is comparing with conventional system. Also, the BER analytic expressions are derived under (AWGN) <span class="il">and</span> multipath Rayleigh fading channels <span class="il">and</span> comparing with the simulation results. Furthermore, the BER performance is compared with <span class="il">OFDM</span>-DCSK to found that the proposed system has the best BER performance with high data rate feature.


1998 ◽  
Author(s):  
Robert Kerczewski ◽  
Duc Ngo ◽  
Diepchi Tran ◽  
Quang Tran ◽  
Brian Kachmar

Author(s):  
John D. Terry ◽  
Juha Heiskala ◽  
Victor Stolpman ◽  
Majid Fozunbal

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