SAR codes

Hochwald, Bertrand M.; Love, David J.; Yan, Su; Jin, Jian‐Ming

doi:10.1109/ita.2013.6502942

Cited by 26 publications

(19 citation statements)

References 21 publications

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“…Detailed derivation and verification of the proposed SAR model can be found in [11], [12]. More SAR simulation results for two and three antennas are also available in [12].…”

Section: B Impact Of Multiple Antennas On Sarmentioning

confidence: 99%

“…This work developed a framework for modeling SAR as a quadratic function of the transmitted signals [7]. Under the same SAR model, the SAR reduction problem is addressed from a coding perspective that gives rise to the design of SAR codes in [11], [12]. The proposed SAR codes outperform the popular Alamouti space-time code by 2.5 dB in probability of error on a SAR-constrained channel.…”

Section: Introductionmentioning

confidence: 99%

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Closed-Loop Precoding and Capacity Analysis for Multiple-Antenna Wireless Systems With User Radiation Exposure Constraints

Ying

Love

Hochwald

2015

IEEE Trans. Wireless Commun.

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Mobile handsets, classified as portable devices, are regulated on the amount of user electromagnetic exposure. The widely accepted exposure measurement is the specific absorption rate (SAR). Despite the prevalence of SAR constraints throughout the world, there has been barely any work on the design and analysis of communication signals for SAR-constrained wireless systems. In this paper, we show that multiple antenna systems greatly reduce the SAR measurements when proper precoders are used. 5G and beyond cellular systems will be expected to support high rate uplinks, making multiple transmit antennas on user equipment a necessity. Our proposed SAR-aware transmission for multi-antenna systems can be applied in 5G handsets to reduce the SAR and increase the rate. Assuming that channel knowledge is available at the transmitter and the receiver, we perform capacity analysis for multiple antenna systems under both transmit power and SAR constraints. Analytical and numerical results demonstrate substantial performance improvements over schemes that ignore the SAR constraint. Our work shows that SAR-constrained precoders have structures similar to precoders designed for spatially correlated channels.Index Terms-Multiple antenna array, specific absorption rate, precoding optimization 1536-1276 (c)

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“…Detailed derivation and verification of the proposed SAR model can be found in [11], [12]. More SAR simulation results for two and three antennas are also available in [12].…”

Section: B Impact Of Multiple Antennas On Sarmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Closed-Loop Precoding and Capacity Analysis for Multiple-Antenna Wireless Systems With User Radiation Exposure Constraints

Ying

Love

Hochwald

2015

IEEE Trans. Wireless Commun.

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“…The relative phase angle between MIMO antennas has also been identified as a parameter affecting the SAR [13], [14], [15]. More precisely, it has been shown in [13] and [14] that the SAR of a two antenna UT could be significantly reduced by using a suitable relative phase angle between the two antenna elements and [14] proposed a signal processing scheme to implement this finding.…”

Section: Introductionmentioning

confidence: 99%

Dual Antenna Coupling Manipulation for Low SAR Smartphone Terminals in Talk Position

Jamshed

Brown

Héliot

2022

IEEE Trans. Antennas Propagat.

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A rigorous analysis of the concept of coupling manipulation utilizing two antennas suited to modern smartphone devices in talk position for voice calls is presented. By using the optimum relative phase between the elements, they can substantially reduce the specific absorption rate (SAR) but still maintain efficiency due to the splitting of power between them and by exploiting a suitable level of inter element coupling. The same antenna elements can still be used for multiple input multiple output (MIMO) when not in talk position without heavily degrading their fundamental capacity limit but this is of secondary importance. The concept could be applied to frequency ranges used in mobile communications from 1.8 to 6 GHz where the ground plane has sufficient form factor. Extensive simulations using two planar inverted-F antennas (PIFAs) operating at 2.4 GHz are carried out to demonstrate conceptually how two antennas can be optimized to reduce SAR by over 50% compared to a single antenna element. SAR reduction is maintained regardless of the user's head composition and how they are handling the device in talk position. Antenna prototypes are measured and compared to verify the capacity when the handset is used away from the body with two MIMO terminal antennas.

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“…Some current approaches in [2] [3], consider a hardware based approach where antennas are designed in conjunction with phase splitters to steer a null towards the user. In [4], a signal processing approach, referred to as SAR codes, is proposed based on the idea that a portable device placed in a 'talk position', i.e. placed at the user's skull, can reduce its userimparted power by setting a phase offset of π 3 between the transmit spatial samples.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast to the CST software approach of [4], an experimental approach is considered here and unlike the hardware solution described in [2] [3], a low complexity baseband precoding technique is proposed. …”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of precoding for EM exposure reduction

Chambers

Brown

2014

The 8th European Conference on Antennas and Propagation (EuCAP 2014)

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Abstract-Reduction of human exposure to electromagnetic (EM) radiation from communications devices without compromising link quality is of importance as people spend more and more time using devices with wireless connectivity. This paper considers the idea of designing a low complexity baseband precoder to reduce user EM exposure for the user scenario of a laptop making an uplink connection to an access point terminal in a picocell environment. The design of the precoder is supported by channel sounding measurements and a ten-fold reduction in user exposure is indicated.

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SAR codes

Cited by 26 publications

References 21 publications

Closed-Loop Precoding and Capacity Analysis for Multiple-Antenna Wireless Systems With User Radiation Exposure Constraints

Closed-Loop Precoding and Capacity Analysis for Multiple-Antenna Wireless Systems With User Radiation Exposure Constraints

Dual Antenna Coupling Manipulation for Low SAR Smartphone Terminals in Talk Position

Experimental investigation of precoding for EM exposure reduction

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