Maximum likelihood multipath channel estimation for synchronous-CDM systems

Franchi, A.; Elia, C.; Colzi, E.

doi:10.1109/glocom.1994.513314

Cited by 15 publications

(3 citation statements)

References 3 publications

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“…It is noted that in a typical application most of the time there will be active users, therefore the result in this paper can be considered as more pessimistic than typical operating conditions. We assume that the channel impulse response and the carrier phase are known, and in a practical system they can be estimated from a pilot sequence or some other channel estimator [13]. Our tests and the case of [2] indicate that a multiuser detector is not very sensitive to parameters variation.…”

Section: Introductionmentioning

confidence: 88%

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Suboptimal maximum-likelihood multiuser detection of synchronous CDMA on frequency-selective multipath channels

Raphaeli

2000

IEEE Trans. Commun.

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Abstract-We propose a signal processing technique, based on the estimate-maximize algorithm, in order to perform multiuser code-division multiple-access (CDMA) detection. This algorithm iteratively seeks for the maximum-likelihood solution. The resulting structure is a successive interference cancellation scheme which can be applied to both synchronous and asynchronous CDMA. Higher performance than similar methods is obtained from using deterministic annealing and multiple stages. A soft output is defined, and the signal-to-noise ratio in the soft output of the detector is measured for predicting performance with an outer code with soft input decoder. The new receiver is applied to the problem whereby in a synchronous CDMA system the orthogonality of the codes is destroyed by a frequency-selective channel, caused by multipath fading. This nonlinear technique is shown to perform much better than the minimum mean-square-error linear solution and several other algorithms. The algorithm lends itself to an efficient DSP or VLSI implementation. We evaluate the performance by simulations with coherent quadrature phase-shift keying modulation, known channel and long random Rayleigh multipath. In most cases, we set the number of users equal to the processing gain for maximal throughput. The results are also presented in the form of outage probabilities for random Rayleigh multipath against required fading margin.

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Section: Introductionmentioning

confidence: 88%

“…Let be the th element of the matrix and is given by (13) If the codes are fixed, then are precomputed and stored in memory. Then, after some algebra (14) Note that computations of are also needed for the MMSE linear detector, if used (for ).…”

Section: A Reduced Complexity Direct Implementation Of the Algorithmmentioning

confidence: 99%

Suboptimal maximum-likelihood multiuser detection of synchronous CDMA on frequency-selective multipath channels

Raphaeli

2000

IEEE Trans. Commun.

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“…Others have been investigating signature waveform estimation techniques [2]. All these methods require a periodic transmission of the training sequence.…”

Section: Introductionmentioning

confidence: 99%

A subspace method for signature waveform estimation in synchronous CDMA systems

Liu

Proceedings of 6th International Symposium on Personal, Indoor and Mobile Radio Communications

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Synchronous-CDMA techniques possess intrinsic protection against co-channel interference due to orthogonal codes employed and thus allow multiple users to operate within the same frequency band. In the presence of multipath, however, each signal is subject to frequency-selective fading and the code orthogonality condition does not hold leading to increased cross correlation. In these scenarios, multiuser detection techniques need to be employed to suppress interference and recover the message symbols. To implement these algorithms, explicit knowledge of the (nonorthogonal) signature waveforms of all users is required. Here, we propose a blind estimation scheme that provides a closed-form solution to the estimation of signature waveforms by exploiting the structure information of the data output. In particular, we show that the subspace of the data matrix contains sufficient information of the signature waveforms. Based on this observation, a MUSIC-like [9] algorithm which can accomplish blind estimation using a minimum number of data samples is derived.

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Channel estimation in TDD mode

Zhang

2006

The Journal of China Universities of Posts and Telecommunicatio

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Maximum likelihood multipath channel estimation for synchronous-CDM systems

Cited by 15 publications

References 3 publications

Suboptimal maximum-likelihood multiuser detection of synchronous CDMA on frequency-selective multipath channels

Suboptimal maximum-likelihood multiuser detection of synchronous CDMA on frequency-selective multipath channels

A subspace method for signature waveform estimation in synchronous CDMA systems

Channel estimation in TDD mode

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