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Power optimization of LTE-800 and coexistence with DVB-T services

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Publication date: Available online 1 May 2018
Source:Physical Communication
Author(s): Marija Denkovska, Daniel Denkovski, Vladimir Atanasovski, Liljana Gavrilovska
The emergence of cognitive radio technologies and the reallocation of the upper Ultra High Frequency (UHF) band ( 790 862 MHz) for broadband services has led to interference concerns for the DVB-T (Digital Video Broadcasting - Terrestrial) services. The DVB-T receivers need to be protected from aggregate interference coming from in-band and out-of-band transmissions, especially from the LTE-800 (Long-Term Evolution at 800 MHz) networks due to the operation in near spectral and location proximity. Although operating in different, but neighboring bands, the LTE-800 networks can be a serious threat to the DVB-T services due to excessive aggregate out-of-band interference caused to the DVB-T receivers. The regulators have assessed and defined the protection criteria for these cases. The power optimization of the LTE cellular networks, operating in near one spectral reuse factor, also remains an open issue due to the non-convex optimization problems. This paper proposes a novel algorithm for LTE-800 power allocation algorithm for capacity maximization of an LTE-800 network under DVB-T protection criteria. The algorithm uses k-means clustering to find the most critical geographical areas based on the DVB-T receivers protection ratios. It also adapts a local D.C. (Difference of two Convex functions/sets) programming approach to make the power optimization problem convex and perform the LTE-800 coverage and capacity optimization. The simulation analysis of the algorithm include realistic data for DVB-T modeling and Poisson Point Process for LTE-800 base stations (BS) spatial modeling. The proposed algorithm is compared to two extreme approaches, i.e. the max LTE BS power approach totally ignoring the DVB-T protection and the uniform power scaling approach that certainly protects the DVB-T service. The results prove the performance increase introduced by the proposed algorithm in terms of spatial capacity and coverage and DVB-T service protection.


Non-renewable energy efficiency optimization in energy harvesting relay-assisted system

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Publication date: Available online 3 May 2018
Source:Physical Communication
Author(s): Ming Zhao, Dan Deng, Wuyang Zhou, Lisheng Fan
In this paper, we consider a scenario where the source node powered by the conventional power grid transmits data with the assistance of some energy harvesting (EH) decode-and-forward (DF) relay nodes. Unlike EH providing renewable energy, most power grids are supported by the non-renewable fossil fuels. So our goal is to maximize the non-renewable energy efficiency (EE) of the non-EH source throughout multiple timeslots. To deal with the randomness of energy arrivals and non-ideal circuit power, we formulate the EE optimization problem of the relaying system by combining the power allocation and the sleep mode in both the source and the relay. We firstly deal with this problem in a special case with just one timeslot and then solve it in a multi-timeslot scenario with dynamic programming (DP) approach. We also propose a heuristic algorithm with a complexity lower than the DP algorithm. We compare the performance of the two algorithms with a baseline scheme. Simulation results show that the heuristic algorithm provides close EE with the DP algorithm, and a significant EE gain over the baseline scheme.

SINR balancing technique for robust beamforming in V2X-SWIPT system based on a non-linear EH model

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Publication date: Available online 3 May 2018
Source:Physical Communication
Author(s): Shidang Li, Chunguo Li, Shi Jin, Mingsheng Wei, Luxi Yang
Vehicle to everything (V2X) is emerging as a promising application scenario of next generation mobile communications. In V2X systems, a series of applications (information transmission, in-car entertainment, etc.) rely on the limited vehicle battery. However, most prior work limits to the automatic piloting, channel measurement/estimation and high speed transmissions, seldom study has been done on the battery-limited for V2X. In light of this, here we investigate the problem of the downlink beamforming design for signal-to-interference ratio balancing in a V2X-SWIPT environment with imperfectly estimated channels at the base station, where a practical non-linear energy harvesting model is considered. The problem is further transformed into a two-layer optimization problem, where we solve the inner-level problem by exploiting S-Procedure, and the outer-level problem through bisection approach. Finally, simulation results are carried out to confirm that the proposed robust beamforming design obtains a favorable result in applications of practical interest.

First and Second-Order Semi-Hidden Fritchman Markov models for a multi-carrier based indoor narrowband power line communication system

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Publication date: Available online 4 May 2018
Source:Physical Communication
Author(s): Ayokunle Damilola Familua, Ling Cheng
The realization of a Semi-Hidden Fritchman Markov models (SHFMMs) for power line communication (PLC) channel is only practicable if combined with efficient algorithms for learning and inference. This article thus reports First and Second-Order SHFMMs for the bit error pattern at the output of an Orthogonal Frequency Division Multiplexing based system for in-home narrowband PLC applications. Accurate SHFMMs have been derived for a residential and laboratory environment using the efficient iterative Baum-Welch algorithm. The log-likelihood ratio plots, the error-free run distribution plots, the mean square error and Chi-Square ( χ 2 ) test validates the accuracy of the derived models. The reliability and accuracy of resulting models are confirmed by a close match between the measured bit error sequences and the model generated bit error sequences. The estimated Second-Order SHFMMs have been validated to be superior to the First-Order models, although at the expense of more computational complexity. Resulting models assist designers to speed up and facilitate the process of designing and evaluating novelties for PLC systems.

Performance of a frequency-domain OFDM-frame detector

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Publication date: Available online 5 May 2018
Source:Physical Communication
Author(s): Chantri Polprasert, Tanee Demeechai
A frequency-domain algorithm for orthogonal frequency-division multiplexing (OFDM)-frame detection is considered useful when the OFDM system is to operate in a known narrowband interference (NBI) channel, e.g., in a cognitive radio OFDM-based overlay system. While frame detection algorithm based on state-of-the-art time-domain correlation perform poorly in such a channel, we propose a frame detection algorithm based on energy detection in frequency domain. By exploiting the NBI band information obtained during sensing period, the proposed algorithm exhibits strong performance and outperforms other existing frequency-domain OFDM frame detection alternatives even at the signal-to-interference ratio (SIR) below 0 dB. Moreover, simulation results are confirmed by the analytical performance presented as a linear combination of the incomplete gamma function. The weight of each component is a function of the eigenvalues of the matrix associated with the detection metric and the number of summation is proportional to the number of non-zero eigenvalues of the matrix associated with the detection metric.

A novel bandwidth and power allocation scheme for power efficient hybrid RF/VLC indoor systems

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Publication date: Available online 7 May 2018
Source:Physical Communication
Author(s): Mai Kafafy, Yasmine Fahmy, Mohamed Abdallah, Mohamed Khairy
Indoor Visible Light Communication (VLC) uses the illumination power of indoor LED luminaries for data transmission. Deploying RF communication alongside VLC is preferable as it improves the coverage and the reliability of the system. This paper studies the power efficiency of hybrid RF/VLC indoor systems. The power efficiency is defined as the system’s total rate per unit power consumed, and the paper considers a hybrid system consisting of a single RF access point and multiple interfering VLC access points. We develop a joint power and bandwidth allocation scheme that iteratively optimizes the power and bandwidth allocated by the access points to their associated users to maximize the system’s power efficiency. We compare the power efficiency of the hybrid system for different layouts of the VLC access points, and we show through simulations that deploying VLC alongside RF communication improves the power efficiency of the hybrid system, especially when users receive low RF signal due to walls.

Simultaneous cooperative spectrum sensing and wireless power transfer in multi-antenna cognitive radio

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Publication date: Available online 7 May 2018
Source:Physical Communication
Author(s): Zhiqun Song, Zhongzhao Zhang, Xin Liu, Yutao Liu, Lisheng Fan
In multi-antenna cognitive radio (CR), the sensing performance of detecting the presence of primary user (PU) in fading channel can be improved through multi-antenna cooperative spectrum sensing. However, the CR may consume more stored energy due to the cooperative spectrum sensing and thus decrease its transmission performance. In this paper, to guarantee the transmission performance, a simultaneous cooperative spectrum sensing and wireless power transfer (SCSSWPT) scheme has been proposed, which can harvest the radio frequency (RF) energy of the PU signal to supply the consumed energy of spectrum sensing. Time splitting model, power splitting and antenna splitting model are proposed to implement cooperative spectrum sensing, energy harvesting and data transmission simultaneously. Three optimization problems have been formulated to maximize spectrum efficiency of the CR in the three SCSSWPT models, respectively, subject to the constraints of detection probability and harvested energy. The simulation results have shown that there is an optimal number of sensing antennas to maximize the spectrum efficiency of the CR, and the time splitting model can achieve higher spectrum efficiency.

Joint optimization of power splitting and allocation for SWIPT in interference alignment networks

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Publication date: August 2018
Source:Physical Communication, Volume 29
Author(s): Nan Zhao, Bingcai Chen
Interference alignment (IA) is a promising solution for interference management in wireless networks. On the other hand, simultaneous wireless information and power transfer (SWIPT) has become an emerging technique. Although some works have been done on IA and SWIPT, these two important areas have traditionally been addressed separately in the literature. In this paper, we propose to use a common framework to jointly study IA and SWIPT with perfect channel state information (CSI). We analyze the performance of SWIPT in IA networks. Specifically, we derive the upper bound of the power that can be harvested in IA networks. In addition, we show that, to improve the performance of wireless power transfer and information transmission, users should be dynamically selected as energy harvesting (EH) or information decoding (ID) terminals. Furthermore, we design two easy-implemented SWIPT-user selection (SWIPT-US) algorithms in IA networks based on the assumption of perfect CSI. To optimize the ID and EH performance of SWIPT in IA networks, a power-splitting optimization (PSO) algorithm is proposed when power splitters are available, and its closed-form optimal solutions are derived. Power allocation in the PSO algorithm is also studied to further optimize the performance. Simulation results are presented to show the effectiveness of the proposed algorithms.


Editorial Board

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Publication date: June 2018
Source:Physical Communication, Volume 28



Experimental measurement of the atmospheric turbulence effects and their influence on performance of fully photonic wireless communication receiver

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Publication date: Available online 9 May 2018
Source:Physical Communication
Author(s): P. Barcik, O. Wilfert, A. Dobesch, Z. Kolka, L. Hudcova, M. Novak, E. Leitgeb
The new generation of Free-Space Optical systems utilizes photonic components used in optical fiber communications which demand high precision and complexity of the system. We present an analysis of the laser beam propagation in the context of fully photonic free space optical links. The experimental data is presented and used for the estimation of single-mode (SM) fiber coupling loss.

An investigation of S-DF cooperative communication protocol over keyhole fading channel

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Publication date: Available online 15 May 2018
Source:Physical Communication
Author(s): R.S. Tripathi, Ritesh Kumar Mishra
This paper investigates the keyhole or pinhole effect on the pairwise error probability (PEP) performance of the multiple-input multiple-output (MIMO) space–time block-code (STBC) based selective decode and forward (S-DF) protocol. The closed form PEP expressions are derived for several configurations in terms of number of hops, phases, and relays over Nakagami-m fading channel, with perfect and imperfect channel state information (CSI), and with and without the keyhole condition. Further, a framework is developed for deriving the diversity order (DO) for each configuration. It demonstrates that full DO for cooperation protocol can be achieved when there is a knowledge of perfect CSI. A convex optimization framework is formulated for obtaining the optimal source-relay power allocation factors which significantly improve the end-to-end reliability of the system under power constraint scenarios. Monte Carlo simulations are performed for both equal and optimal power allocation factors and results show the substantial improvement in PEP performance with an increase in the value of the shape parameter and relay to destination (RD) link channel variance. Results show an improved PEP performance by increasing the RD link channel variance in comparison to increasing the source to relay (SR) link channel variance. Also PEP performance degrades for keyhole Nakagami-m fading channel as compared to Nakagami-m fading channel. Simulation results are in close agreement with the analytical results at high signal to noise ratio (SNR) regimes.

Performance enhancement of LEO-to-ground FSO systems using All-optical HAP-based relaying

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Publication date: Available online 16 May 2018
Source:Physical Communication
Author(s): Minh Q. Vu, Nga T.T. Nguyen, Hien T.T. Pham, Ngoc T. Dang
In this paper, we propose to use all-optical high altitude platform (HAP)-based relaying technique to improve the performance of the free-space optical communication (FSO) system from a low-earth orbit (LEO) satellite to the ground station. Two all-optical relaying techniques are applied to HAP-based relay node including optical amplify-and-forward (OAF) and optical detect-amplify-and-forward (ODAF). A closed-form expression for bit error rate (BER) of the proposed relay-assisted LEO-to-ground FSO system under the effects of free space loss, path loss, and atmospheric turbulence is derived. We also carry out Monte-Carlo (M-C) simulation to verify the theoretical results in terms of BER and the quality of image transmission. The numerical results show that 28 dB power gain at BER of 1 0 9 can be achieved thanks to the use of HAP-based relaying. Also, lower BER that results in better quality of restored images at the ground station is demonstrated in this paper.

Reduced complexity Kalman filtering for phase recovery in XPIC systems

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Publication date: August 2018
Source:Physical Communication, Volume 29
Author(s): Farzana Kulsoom, Anna Vizziello, Roberta Borra, Pietro Savazzi
Reduced-complexity Kalman-based algorithms are proposed to recover the phase of cross-polar interference cancellation (XPIC) receivers in microwave radio relay links. In particular, two completely independent radio frequency (RF) transceiver chains are considered for the two different polarizations, in order to have the maximum flexibility to connect different single carrier transceivers to dual-polarized antennas. A one-state Kalman model is proposed, which is of low complexity and thus suitable for a modern higher data rates M-ary quadrature amplitude modulation (M-QAM) receiver. Moreover, a further reduced complexity version is developed that uses a lower amount of information to recover the phase at the receiver, as well as a downsampling procedure to speed up the Kalman algorithm, and an alternative error computation that is essential to ease the Kalman implementation. It is worth noting that the three last simplifications are general and can be applied not only to a one-state Kalman model. Simulation results compare the proposed simplified Kalman solutions to typical phase-locked loop (PLL) algorithms proving their comparable performance with the benefit of lower complexity. Finally, the relationships between the Extended Kalman and the PLL approaches are investigated. The obtained relation is essential for the cross-polar phase recovery, since, as far as the authors know, there are not closed-form solutions for the PLL parameter optimization in cross schemes.

Performance analysis of hybrid PAPR reduction technique for LTE uplink communications

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Publication date: August 2018
Source:Physical Communication, Volume 29
Author(s): Shri Ramtej Kondamuri, Anuradha Sundru
Long Term Evolution standard implemented Single Carrier Frequency Division Multiple Access (SC-FDMA) in the uplink communications due to its low peak to average power ratio (PAPR). But for higher order modulations, there is a need for further reduction of PAPR in SC-FDMA systems. There are numerous techniques to decrease PAPR, but clipping and companding techniques are very simple to implement without any side information. μ law companding provides good PAPR reduction but increases the average power of companded signal. In this paper, the distribution of SC-FDMA signal is approximated, and a companding technique is proposed to transform the approximated distribution into a uniform distribution, which reduces PAPR without increasing average power of the signal. For further improvement in PAPR, a hybrid technique is also proposed where the companded signal is clipped to a specific threshold value. Simulation results show that PAPR reduction achieved by the proposed companding technique is better than that of μ law companding with a slight degradation in bit error rate (BER) performance. The proposed companding technique with no decompanding operation has better BER performance when compared to that with approximated decompanding operation. The hybrid technique further reduces PAPR with similar BER performance as that of proposed companding technique by carefully choosing the clipping ratio.

Downlink capacity of OFDMA-CR based 5G femtocell networks

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Publication date: Available online 18 May 2018
Source:Physical Communication
Author(s): Joydev Ghosh, Dushantha Nalin K. Jayakody, Marwa Qaraqe
This research work explores small cell densification as a key technique for next generation wireless network (NGWN). Small cell densification comprises space (i.e, dense deployment of femtocells) and spectrum (i.e., utilization of frequency band at large). The usage of femtocells not only improves the spectral efficiency (SE) of the Heterogeneous two-tier networks against conventional approach, but also it alleviates outage probability and enhances the achievable capacity. We yield an analytical framework to establish the density of the femto base station (FBS) to a monotonically increasing or decreasing function of distance or radius, respectively. This ensures the enhanced performance in spectrum sharing Orthogonal Frequency Division Multiple Access (OFDMA) femtocell network models. We also illustrate the influence of active Femto users (i.e., users in femtocells, and they are usually low mobility and located closer to the cell center with less fading), cluster size (i.e., a group of adjacent macrocells which use all of the systems frequency assignments) via simulation results.


Advanced verification system using a smart card for smart city users

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Publication date: Available online 21 May 2018
Source:Physical Communication
Author(s): Trupil Limbasiya, Mihir Garg, Shivam Shandil
In this rapidly growing IoT (Internet of Things) environment, people avail various facilities for different intentions with the help of the Internet generally. There are many application systems, in which both (server and user) are located at separate locations. Normally, a user requests for availing diverse facilities and a server is available to provide legal services precisely. But, a server cannot grant a right of entry to any user without verifying genuinely else an adversary has many opportunities to exploit the system or users. Hence, there is a need of well-established mutual authentication framework, which can permit legal customers to access provisions and the system can be protected against multiple security attacks. In this paper, we identified that a scheme suggested by Madhusudhan et al. cannot withstand against session key disclosure, smart card lost, and includes a security flaw regarding password update. Therefore, we suggest a new authentication protocol, which can resist upon numerous security vulnerabilities and can perform the verification process within a less time period. Furthermore, the proposed protocol performs effectively in communication, storage, and energy consumption rather than other relevant authentications mechanisms.

Trellis coded quadrature spatial modulation

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Publication date: Available online 22 May 2018
Source:Physical Communication
Author(s): Zehra Yigit, Ertugrul Basar, Raed Mesleh
In this paper, a novel multiple-input multiple-output (MIMO) transmission scheme called trellis coded quadrature spatial modulation (TC-QSM), is proposed. In the proposed scheme, trellis coded modulation (TCM) principle is applied to the emerging quadrature spatial modulation (QSM) scheme, and a trellis encoder and a QSM mapper are jointly designed to benefit from both coding and multiplexing gains. At the receiver side, a soft-decision Viterbi decoder is used along with a QSM decoder to obtain the optimum error performance. Considering our design criterion, TC-QSM schemes are designed for different number of trellis states, transmit antennas and spectral efficiencies. The pairwise error probability (PEP) of the TC-QSM scheme is derived over quasi-static Nakagami- m , Rician and Rayleigh fading channels and an upper bound on the average bit error probability (BEP) is obtained. Through comprehensive Monte Carlo simulations, the effect of signal and spatial bits on uncoded and trellis coded SM and QSM schemes over Nakagami- m andRician fading channels are investigated for different fading parameters. Moreover, the error performance of the TC-QSM and SM with trellis coding (SM-TC) schemes are compared for different spectral efficiency values, where it is revealed that the proposed TC-QSM scheme provides an interesting trade-off between performance and implementation cost, and achieves an improved error performance over reference schemes including SM, QSM and SM-TC.

Subcarrier allocation based Simultaneous Wireless Information and Power Transfer algorithm in 5G cooperative OFDM communication systems

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Publication date: Available online 23 May 2018
Source:Physical Communication
Author(s): Zhenyu Na, Yuyao Wang, Xiaotong Li, Junjuan Xia, Xin Liu, Mudi Xiong, Weidang Lu
Self-sustainable communications are highly vital for large amounts of mobile terminals in the Fifth Generation (5G) communication systems. Simultaneous Wireless Information and Power Transfer (SWIPT) makes it possible that terminal transfers information while prolonging battery life by harvesting Radio Frequency (RF) energy. Though the traditional sub-carrier allocation based SWIPT algorithm in OFDM communication systems can optimize resource allocation, the receiver often cannot achieve higher information decoding rate when the channel condition of direct transmission deteriorates. In view of this situation, a sub-carrier allocation based SWIPT algorithm in 5G cooperative OFDM communication systems is proposed in this paper. The amplify-and-forward protocol is adopted by relay node which transmits information from source node to destination node by using a part of its sub-carriers. The remaining sub-carriers are used for energy harvesting. On the premise of minimum threshold of harvested energy, the sub-carrier and power allocations at relay node are optimized by establishing and solving the corresponding optimization model. Simulation results reveal that the proposed algorithm not only achieves the optimal sub-carrier and power allocations, but also improves information decoding rate with fast converging speed.

Energy-efficient self-backhauling in heterogeneous wireless networks: A game-theoretic approach

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Publication date: Available online 26 May 2018
Source:Physical Communication
Author(s): Maryam Lashgari, Behrouz Maham, Hamed Kebriaei
Heterogeneous wireless networks are seen as the most promising approach to improve coverage and capacity in wireless networks. However, one key challenge is the presence of wireless backhaul links whose resources must be jointly allocated with those of the radio access network. In this paper, a novel approach for energy-efficient joint backhaul and radio resource allocation in a two tier small cell network is proposed. The problem is formulated as a Stackelberg game, in which the macro base station (MBS) acts as the leader and the overlaid pico base stations (PBSs) act as followers. In this game, the MBS maximizes its sum-rate transmission by properly allocating the subcarriers over the backhaul links and the PBSs seek to maximize their energy efficiency by allocating the resources under maximum allowable transmit power constraint. A self-backhauling model, in which the access and the backhaul links share the same wireless channel is adopted. An orthogonal frequency allocation between the backhaul and the access links is used, in which the subcarrier allocation over the backhaul and the access links are modeled in the leader’s and followers’ optimization problems, respectively. Furthermore, the optimal transmission power of the PBSs derived for the followers’ game. The energy efficiency improvement problem in the followers’ side is transformed to a subtractive form, which enables the derivation of an efficient iterative subcarrier and power allocation algorithm. Furthermore, the uniqueness of the strategies and convergence of iterative power update algorithm to the Stackelberg equilibrium point are investigated. Simulation results show that the proposed game-theoretic approach yields up to 147% and 125 . 9 % energy efficiency improvement.

Optimal selection of spatial dimensions of signal subspace for relay constellation decoding

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Publication date: Available online 26 May 2018
Source:Physical Communication
Author(s): Xiyuan Wang, Yong Wang
The dimension of the right null space is only one for traditional signal space alignment with the minimum configuration of antennas. Then, the direction of a pair of alignment signal space is fixed and cannot be flexibly adjusted. Although the different alignment directions are mutually independent to facilitate relay decoding, the minimum Euclidean distance between modulated signals code words is small, which affects the decoding accuracy. In this paper, we design a novel alignment signal transmission scheme using degrees of freedom of null space generated by redundant antennas. The scheme selects the mutually orthogonal space dimension in the redundant null space as the signal alignment direction. It optimizes the minimum Euclidean distance in the system by maximizing the minimum constellation point distance. Simulation results show that the distances between the constellation points of different code symbols become significantly larger. The larger constellation distance of different coded symbols can improve the decoding accuracy. By optimizing the distance between the minimum constellation points, the transmission performance of each link is balanced and the whole system performance is improved.

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