Linear MMSE detection technique for MC-CDMA

Hélard, Jean-François; Baudais, Jean-Yves; Citerne, J.

doi:10.1049/el:20000532

Cited by 65 publications

(34 citation statements)

References 3 publications

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“…Moreover, a new lattice model for the MC-CDMA system is introduced, which avoids any whitening process. We evaluate the proposed detection scheme in a high frequencyselective channel and compare SD with some sub-optimal methods such as Equal Gain Combining (EGC), Minimum Mean-Squared Error (MMSE), and Minimum Mean-Squared Error per User (MMSE-U) [16], [17], [18] in full and nonSection II the MC-CDMA transmission system is described. Complex sphere decoding is investigated in Section III.…”

Section: Introductionmentioning

confidence: 99%

Efficient Complex Sphere Decoding for MC-CDMA Systems

Mozos

García

2006

IEEE Trans. Wireless Commun.

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Abstract-Maximum Likelihood (ML) joint detection of MultiCarrier Code Division Multiple Access (MC-CDMA) systems can be effi iently implemented with a Sphere Decoding (SD) algorithm. In this paper, we examine the application of complex instead of real SD to detect MC-CDMA, which solves many problems in a more elegant manner and extends SD adaptability to any constellation. We f rst propose a new complex SD algorithm whose effi iency is based on not requiring an estimate of the initial search radius but selecting the Babai Point as the initial sphere radius instead; also, effi ient strategies regarding sorting the list of possible lattice points are applied. Indeed, complex SD allows complex matrix operations which are faster than real counterparts in double dimension. Next, a novel lattice representation for the MC-CDMA system is introduced, which allows optimum multiuser detection directly from the received signal. This avoids noise whitening operation, and also despreading and equalization procedures are not required further at the receiver side.Index Terms-Multi carrier code division multiple access, maximum likelihood decoding, sphere decoding, multiuser detection.

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Section: Introductionmentioning

confidence: 99%

Efficient Complex Sphere Decoding for MC-CDMA Systems

Mozos

García

2006

IEEE Trans. Wireless Commun.

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“…In the coherent case, several detection schemes, such as per-carrier minimum mean square error (MMSE) and EGC schemes have been widely studied in the literature, mostly with BPSK or QPSK modulation, and ideal channel estimation [1,9]. Here, a simple training symbol based equalizer with real (non-ideal) channel estimation is considered in these coherent cases, in order to show the effect of errors induced by the imperfect channel estimation and equalization.…”

Section: Introductionmentioning

confidence: 99%

The performance analysis of a multi-carrier CDMA system in mobile environment

Xing

Renfors

2005

Eur. Trans. Telecomm.

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SUMMARYIn this paper, several detection schemes are studied for a multi-carrier code division multiple access (MC-CDMA) system in the downlink case. Both analytical methods and system simulations are used to examine the performance of those detection schemes. The inter-symbol interference (ISI) can be absorbed by guard intervals, so the data in each subcarrier can be well equalized in slowly fading environment in case of coherent detection. Since each individual subcarrier of an MC-CDMA system is flat fading, it is possible to apply differential modulation schemes with non-coherent reception at subcarrier level. In the ideal case, the non-coherent reception provides worse performance than the coherent reception. However, the performance gap between coherent and differential reception reduces with increasing channel estimation and equalization errors. In the extreme cases, in fast-fading environment, the performance of differential detection may even exceed that of a coherent receiver with practical channel estimation methods. This is proved by the simulation results when a simple coherent detection scheme and a differential phase detection scheme are compared. It is also shown in this paper that with a simple equalizer, an MC-CDMA system can provide good performance in multi-user and multipath fading environments.

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“…Multiuser detection deals with the problem of the reliable demodulation of the user's bits in such a scenario. Various detectors, such as MRC, ERC and MMSE [2] have already been proposed for the downlink case. Traditionally, adaptive filtering in communications has been developed based on the Mean Square Error (MSE) criterion [4].…”

Section: Introductionmentioning

confidence: 99%

Minimum probability of error demodulation for MC-CDMA

Dayap

Mahanta

Desai³

2004

Proceedings of the IEEE 6th Circuits and Systems Symposium on Emerging Technologies: Frontiers of Mobile and Wireless Communica

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Abstruct-Multi-Carrier Code Division Multiple Access (MC-CDMA) is an attractive choice for high speed wireless communication as it mitigates the problem of Intersymbol Interference (ISI) and also exploits frequency diversity. The data stream in MC-CDMA is spread using a user specific spreading sequence in the frequency domain and every chip travels on a different sub-carrier. At the receiver, the different sub-carriers have to be combined properly to form the decision variable. Minimum Mean Square Error (MMSE) detector is a popular choice for this, but as it tries to minimize the Mean Square Error (MSE) and not the Bit Error Rate (BER), the BER it attains is not optimum. In this paper, we propose a Minimum Probability of Error (MPOE) based linear multiuser detector, which tries to minimize the probability of error, by exploiting the probability density function (pdf) of the filter output. Theoretical and simulation results are 1 presented for the MPOE detector and it can be seen that the W O E detector outperforms the MMSE detector.Index Terms-WOE, MMSE, MC-CDMA, Multiuser Detection I. INTRODUCTION Multi-Carrier Code Division Multiple Access (MC-CDMA) is a fairly recent multiple access technique that has attracted much research during the past decade. A combination of Orthogonal Frequency Division Multiplexing (OFDM) and CDMA [l], MC-CDMA combines the advantages of both the schemes. Like OFDM, MC-CDMA signals have attractive spectral characteristics. Their spectral energy is confined almost to the allocated bandwidth. Owing to this and other spectral characteristics, MC-CDMA allows for easier system coexislence. Moreover, by transmitting the same data bit over different sub-carriers, MC-CDMA exploits frequency diversity better than OFDM and also reduces the symbol rate on each of the sub-carrier. Due to this reduced symbol rate, the effect of Intersymbol Interference (ISI) on the transmitted signals is also reduced. The residual IS1 can be eliminated using sufficient guard interval. The data bits of the different users are spread using a user specific spreading waveform in the frequency domain.This paper focuses on the downlink scenario, where the base station communicates with the mobile sets. Each user receives his own signal corrupted by noise and Multiple Access Interference: (MAI) from the other users. Multiuser detection deals with the problem of the reliable demodulation of the user's bits in such a scenario. Various detectors, such as MRC, ERC and

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Linear MMSE detection technique for MC-CDMA

Cited by 65 publications

References 3 publications

Efficient Complex Sphere Decoding for MC-CDMA Systems

Efficient Complex Sphere Decoding for MC-CDMA Systems

The performance analysis of a multi-carrier CDMA system in mobile environment

Minimum probability of error demodulation for MC-CDMA

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