Opportunistic Multiple Antenna Systems: Channel Estimation and Experimental Results

Kecicioglu, Balkan; Özdemir, Özgür; Torlak, Murat

doi:10.1109/icc.2006.255277

Cited by 4 publications

(3 citation statements)

References 5 publications

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“…The SNR expression on can be written as :

γ_{k, n} = {boldq}_{n}^{H} {boldh}_{k, n} {boldh}_{k, n}^{H} {boldq}_{n} = {boldc}_{n}^{H} {boldf}_{k, n}

where

{boldc}_{n} = {({boldq}_{n}^{T} \otimes {boldq}_{n}^{H})}^{H}

is an L 2 ×1 vector,

\otimes

symbolises Kronecker product,

{boldf}_{k, n} = vec ({boldh}_{k, n} {boldh}_{k, n}^{H})

and ‘vec’ is vector operation that stacks the columns of L × L matrix into a L 2 ×1 vector.…”

Section: The Proposed Channel Estimation Methodsmentioning

confidence: 99%

“…In this method, the channel estimation is performed starting at the N ‐th time slot where SNR feedbacks are sent N times from each user. In , a method similar to the direct channel estimation method (direct method) exists where NSNR feedback is used instead of SNR. Note that the NSNR scheduling in our case is still possible because of the channel estimation.…”

Section: The Proposed Channel Estimation Methodsmentioning

confidence: 99%

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Opportunistic vector channel estimation based on scalar feedback

Kakşi

Özdemir

Torlak

2016

Trans. Emerging Tel. Tech.

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Multi‐user diversity exploits channel fluctuations by favouring the user with the best channel. In slow fading environments, channel fluctuations are artificially created by the use of random beamforming at the transmitter, a technique called opportunistic beamforming. One drawback of opportunistic beamforming is that, it needs large number of users to achieve the capacity of a true beamforming system. On the other hand, if partial channel state information is available at the transmitter, this can be used to reduce the necessary number of users to reach this capacity. Opportunistic beamforming systems require scalar feedback from users in the system instead of the complete channel vector to reduce the feedback load. In conventional systems, these feedback values are used for scheduling only. In this letter, we propose three channel estimation methods that solely rely on the scalar feedback already available at the transmitter. We also propose an accompanying scheduling method where these estimates are used to form the beamforming vectors. Although we use the same information available in a conventional opportunistic beamforming system, the proposed scheduling scheme in conjunction with channel estimation is able to achieve higher throughput and also achieve better fairness which is verified by simulations. Copyright © 2016 John Wiley & Sons, Ltd.

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“…The SNR expression on can be written as :

γ_{k, n} = {boldq}_{n}^{H} {boldh}_{k, n} {boldh}_{k, n}^{H} {boldq}_{n} = {boldc}_{n}^{H} {boldf}_{k, n}

where

{boldc}_{n} = {({boldq}_{n}^{T} \otimes {boldq}_{n}^{H})}^{H}

is an L 2 ×1 vector,

\otimes

symbolises Kronecker product,

{boldf}_{k, n} = vec ({boldh}_{k, n} {boldh}_{k, n}^{H})

and ‘vec’ is vector operation that stacks the columns of L × L matrix into a L 2 ×1 vector.…”

Section: The Proposed Channel Estimation Methodsmentioning

confidence: 99%

Section: The Proposed Channel Estimation Methodsmentioning

confidence: 99%

Opportunistic vector channel estimation based on scalar feedback

Kakşi

Özdemir

Torlak

2016

Trans. Emerging Tel. Tech.

Self Cite

View full text Add to dashboard Cite

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“…The Gaussianity of the estimation errors are observed in [5] where channel estimation is performed using training sequences or in [6] where the channel estimation is performed in the presence of feedback delay. We have recently shown that it is even possible to estimate the channel vector from the SNR feedback values [10].…”

Section: Introductionmentioning

confidence: 99%

Opportunistic Beamforming over Rayleigh Channels with Partial Side Information

Özdemir

Torlak

2008

IEEE Trans. Wireless Commun.

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In recent years, diversity techniques have evolved into highly attractive technology for wireless communications in different forms. For instance, the channel fluctuations of the users in a network are exploited as multiuser diversity by scheduling the user with the best signal-to-noise ratio (SNR). When fading is slow, beamforming at a multiple antenna transmitter is used to induce artificial channel fluctuations to ensure multiuser diversity in the network. Such a beamforming scheme is called opportunistic beamforming since the transmitter uses random beamforming to artificially induce opportunism in the network [1]. Opportunism requires a large number of users in the system in order to reach the performance of the true beamforming that uses perfect channel state information (CSI). In this paper we investigate the benefit of having partial CSI at an opportunistic transmitter. In the investigation, we focus on the maximum normalized SNR scheduling where user's feedback consists of SNR relative to its channel gain. We show that opportunism can be beneficially used to increase the average throughput of the system. Simulations support the analytical average throughput results obtained as the amount of CSI and the number of users vary.

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