Subcarrier Nulling Algorithms for Channel Shortening in Uplink OFDMA Systems

Miyajima, Teruyuki; Ding, Zhi

doi:10.1109/tsp.2012.2185230

Cited by 10 publications

(8 citation statements)

References 31 publications

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“…Before transmission, we can easily find the codes and target channel that satisfy the above condition of the rank of (20). Note that the condition does not depend on the physical channel h (k) [m].…”

Section: Performance Analysismentioning

confidence: 99%

“…Under this assumption, perfect channel shortening, i.e., perfect IBI removal, has been accomplished [10], [13]- [17], [22]. For multiuser systems, a method for single-carrier interleaved frequency-division multiple access (SC-IFDMA) [19] requires transmitted samples to be uncorrelated, and a method for orthogonal frequency division multiple access (OFDMA) [20] requires a sufficient number of null subcarriers to completely eliminate IBI. On the other hand, in multiuser MC-CDMA systems, transmitted samples are highly correlated and there are no sufficient null subcarriers.…”

Section: Introductionmentioning

confidence: 99%

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Blind Channel Shortening for MC-CDMA Systems by Restoring the Orthogonality of Spreading Codes

Miyajima

Kotake

2015

IEEE Trans. Commun.

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This study considers blind channel shortening to mitigate the effects of inter-block interference and multiple-access interference in both uplink and downlink multicarrier code-division multiple-access systems. We derive the blind channel shortening methods by extending the blind channel equalization method previously proposed by Djebbar, Abed-Meraim, and Djebbari. The basic idea is to restore, at the frequency-domain equalizer output, the orthogonality of spreading codes, which is destroyed when interference is present. We show that the extended methods can perfectly shorten the channels and that the resulting effective channel is identical to the predetermined target channel thus avoiding channel estimation. Computer simulation results illustrate the effectiveness of the proposed methods.

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Section: Performance Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Blind Channel Shortening for MC-CDMA Systems by Restoring the Orthogonality of Spreading Codes

Miyajima

Kotake

2015

IEEE Trans. Commun.

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“…is assumed to be tall [4]. Subcarriers in the resulting effective channel c can be in a deep fading.…”

Section: Channel Shorteningmentioning

confidence: 99%

“…A bandwidth efficient way to mitigate the effect of IBI is blind channel shortening using a timedomain equalizer (TEQ) [1], such as carrier nulling algorithm (CNA) [2] and MERRY algorithm [3]. It has been proven that these blind channel shortening methods can perfectly suppress IBI by shortening the impulse response of the overall effective channel consisting of a physical channel and a TEQ to within the CP length [4], [5]. It should be noted, however, that the resulting effective channel is still frequency selective.…”

Section: Introductionmentioning

confidence: 99%

A Max-Min Approach to Channel Shortening in OFDM Systems

Takahashi

Miyajima

2013

IEICE Trans. Fundamentals

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In OFDM systems, residual inter-block interference can be suppressed by a time-domain equalizer that blindly shortens the effective length of a channel impulse response. To further improve the performance of blind equalizers, we propose a channel shortening method that attempts to maximize the minimum FFT output power over data subcarriers. Simulation results indicate that the max-min strategy has performance improvement over a conventional channel shortening method.

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“…Traditional method is to insert pilot in the transmitting data [1]. In order to improve frequency spectrum efficiency, blind channel estimation has become hot topic in recent years [2]~ [7]. Among those blind algorithm, subspace based algorithm receives great attention because of its better accuracy performance [8].…”

Section: Introductionmentioning

confidence: 99%

Semi-blind Channel Estimation for MIMO-OFDM Systems Based on Received Signal Reconstruction

Cui¹,

Zhou²

2015

Advances in Intelligent Systems Research

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Abstract. Blind channel estimation for MIMO-OFDM systems was discussed, and a subspace based blind channel estimation algorithm by re-constructing the received signal and its simplified one were proposed. The algorithm changed the channel matrix of the transfer function into a block Toeplitz high matrix exploiting OFDM cyclic prefix, and the channel estimation characteristic equation was obtained with the orthogonality between the signal subspace and the noise subspace of the reconstructed signal. In order to eliminate the influence of virtual carriers, the singular value decomposition of the equivalent transmit signal was imported. The simplified algorithm exploited a QR decomposition and Gram-Schmidt orthogonalization process aiming at reducing the complexity of obtaining the noise subspace. Simulation results illustrate the performance of the proposed algorithm via numerical experiments compared with the other one, and it's insensitive to overestimates of the true channel order.

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Subcarrier Nulling Algorithms for Channel Shortening in Uplink OFDMA Systems

Cited by 10 publications

References 31 publications

Blind Channel Shortening for MC-CDMA Systems by Restoring the Orthogonality of Spreading Codes

Blind Channel Shortening for MC-CDMA Systems by Restoring the Orthogonality of Spreading Codes

A Max-Min Approach to Channel Shortening in OFDM Systems

Semi-blind Channel Estimation for MIMO-OFDM Systems Based on Received Signal Reconstruction

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