Optimum rake Processing for Multipath Fading in Direct-Sequence Spread-Spectrum Communication Systems 


Vol. 28,  No. 10, pp. 995-1006, Oct.  2003


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  Abstract

It is well known that in the wireless communication system the transmitted signals can suffer from multipath fading due to the wave propagation characteristics and the obstacles over the paths, resulting in serious reduction in the power of the received signals. However, it is possible to take advantage of the inherent diversity imposed in the multipath reception if the underlying channel can be properly estimated. One of the diversity reception methods in this case Rake processing. In this paper we study the Rake receivers for the direct-sequence spread-spectrum communication systems utilizing PN (pseudo noise) sequences to achieve spread spectrum, A conventional Rake receiver can use the finite-duration impulse (FIR) filter followed by the PN sequences demodulator, where the FIR filter coefficients are the reverse ordered complex conjugate values of the fading channel impulse response estimates, Here, we propose a new Rake processing method by replacing the aforementioned PN code sequence with a new set of optimum demodulator coefficients. More specifically, the concept of the new optimum Rake processing is first introduced and then the optimum demodulator coefficients are theoretically derived. The performance obtained using the new optimum Rake processing is also calculated. The analytical results are verified by computer simulation. As a result, it is shown that the new optimum Rake processing method improves the MSE performance more than 10 dB over the conventional one using the fixed PN sequence demodulator, It is also shown that the new optimum Rake processing method improves the MSE, performance about 10 dB over the Adaptive correlator that performs the combining of the multipath components and PN demodulation concurrently. And finally, the MSE performance of the optimum Rake demodualtor is very close to the MSE performance of QPSK demodulator under the AWGN channel.

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  Cite this article

[IEEE Style]

W. Jang and J. Lee, "Optimum rake Processing for Multipath Fading in Direct-Sequence Spread-Spectrum Communication Systems," The Journal of Korean Institute of Communications and Information Sciences, vol. 28, no. 10, pp. 995-1006, 2003. DOI: .

[ACM Style]

Won-Suk Jang and Jae-Chon Lee. 2003. Optimum rake Processing for Multipath Fading in Direct-Sequence Spread-Spectrum Communication Systems. The Journal of Korean Institute of Communications and Information Sciences, 28, 10, (2003), 995-1006. DOI: .

[KICS Style]

Won-Suk Jang and Jae-Chon Lee, "Optimum rake Processing for Multipath Fading in Direct-Sequence Spread-Spectrum Communication Systems," The Journal of Korean Institute of Communications and Information Sciences, vol. 28, no. 10, pp. 995-1006, 10. 2003.

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pISSN : 1226 - 4717
eISSN : 2287 - 3880