Clustered OFDM with channel estimation for high rate wireless data

Li, Y.G.; Sollenberger, N.R.

doi:10.1109/26.974252

Cited by 51 publications

(12 citation statements)

References 13 publications

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“…As it was observed in (22) and (24), a prerequisite for determining the different users' vectors of optimum CIR-related tap predictor coefficients is the knowledge of the users' space-time 6 Recall that the representation of the jth user's estimation MSE was valid only when assuming that the unitary transform matrixŨ [f ] has elements of unity magnitude, which is the case, for example, for the DFT matrix W. However, in the more general scenario of employing an arbitrary unitary transform matrix, which could be, for example, one of the robust transforms proposed in [23], this condition is not fulfilled. In this case, the matrix R ∆Ĥ (j) apr…”

Section: Channel Statisticsmentioning

confidence: 99%

Parallel-interference-cancellation-assisted decision-directed channel estimation for OFDM systems using multiple transmit antennas

Münster

Hanzo

2005

IEEE Trans. Wireless Commun.

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Section: Channel Statisticsmentioning

confidence: 99%

Parallel-interference-cancellation-assisted decision-directed channel estimation for OFDM systems using multiple transmit antennas

Münster

Hanzo

2005

IEEE Trans. Wireless Commun.

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“…CFO correction for OFDMA uplink with a subband-based subcarrier assignment scheme was investigated in [6] and [18]. However, the proposed algorithms in [6] and [18] are not applicable to a variety of other subcarrier assignment schemes, such as block-random assignment [13], interleaved assignment [14], random assignment [19], and clustered assignment [20], [21]. In [22], an iterative interference cancelation scheme is proposed for OFDMA uplink with the assumption that CFO is small compared with subcarrier spacing.…”

Section: Introductionmentioning

confidence: 99%

Low-Complexity Orthogonal Spectral Signal Construction for Generalized OFDMA Uplink With Frequency Synchronization Errors

Cao

Tureli

Yao

2007

IEEE Trans. Veh. Technol.

116

138

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Abstract-In orthogonal frequency-division multiplexing, the total spectral resource is partitioned into multiple orthogonal subcarriers. These subcarriers are assigned to different users for simultaneous transmission in orthogonal frequency-division multiple access (OFDMA). In an unsynchronized OFDMA uplink, each user has a different carrier frequency offset (CFO) relative to the common uplink receiver, which results in the loss of orthogonality among subcarriers and thereby multiple access interference. Hence, OFDMA is very sensitive to frequency synchronization errors. In this paper, we construct the received signals in frequency domain that would have been received if all users were frequency synchronized. A generalized OFDMA framework for arbitrary subcarrier assignments is proposed. The interference in the generalized OFDMA uplink due to frequency synchronization errors is characterized in a multiuser signal model. Least squares and minimum mean square error criteria are proposed to construct the orthogonal spectral signals from one OFDMA block contaminated with interference that was caused by the CFOs of multiple users. For OFDMA with a large number of subcarriers, a low-complexity implementation of the proposed algorithms is developed based on a banded matrix approximation. Numerical results illustrate that the proposed algorithms improve the system performance significantly and are computationally affordable using the banded system implementation.Index Terms-Banded matrix, carrier frequency offset (CFO), least squares (LS), minimum mean-square error (MMSE), multiple access, orthogonal frequency-division multiplexing (OFDM), synchronization.

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“…OFDM signaling has been adopted for use in digital audio broadcasting (DAB) [1] and terrestrial digital video broadcasting (DVB-T) [2] systems, as well as in wireless local area network (W-LAN) standards, such as the IEEE 802.11a [3], IEEE 802.11g [4], and Hiperlan II [5]. OFDM has also been proposed for packet data systems [6].…”

Section: Introductionmentioning

confidence: 99%

Diversity Combining Options and Low-Complexity MMSE Equalization for Spread Spectrum OFDM Systems in Frequency Selective Fading Channels

Novak

Krzymien

2006

Wireless Pers Commun

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This paper compares diversity combining schemes for the downlink of spread spectrum orthogonal frequency division multiplexing (SS-OFDM) systems in frequency selective fading channels. In particular, symbollevel combining after despreading is compared to chip-level combining under maximal ratio combining (MRC) of signals from different diversity branches and minimum mean-square error (MMSE) equalization of spreading sequences. Symbol-level combining takes place after the operations of MMSE equalization and despreading, whereas the operations of equalization and despreading occur after MRC if chip-level combining is used. Chip-level combining combines diversity samples in an efficient manner while reducing inter-code interference (self-interference) that results from the loss of orthogonality of spreading sequences due to a frequency selective channel. This method is shown to be superior to symbol-level combining when the diversity branches are uncorrelated, and when the branches differ only due to subcarrier interleaving. An MMSE equalization method with significantly reduced complexity for partially loaded systems is also presented, based on the premise of chip-level combining. Novel expressions for the bit error rate (BER) of the two methods, as well as the extension of the analysis to partially loaded systems are given. The extensions of chip-level combining and low-complexity equalization of a partially loaded system to an OFDM system with 2-dimensional spreading are also presented. The results are relevant to antenna diversity as well as temporal diversity achieved though re-transmission within an ARQ scheme.

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Clustered OFDM with channel estimation for high rate wireless data

Cited by 51 publications

References 13 publications

Parallel-interference-cancellation-assisted decision-directed channel estimation for OFDM systems using multiple transmit antennas

Parallel-interference-cancellation-assisted decision-directed channel estimation for OFDM systems using multiple transmit antennas

Low-Complexity Orthogonal Spectral Signal Construction for Generalized OFDMA Uplink With Frequency Synchronization Errors

Diversity Combining Options and Low-Complexity MMSE Equalization for Spread Spectrum OFDM Systems in Frequency Selective Fading Channels

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