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Journal articles on the topic 'MIMO-OFDM, wireless communications, indoor wireless transmissions'
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Panta, Jariya, Poompat Saengudomlert, and Keattisak Sripimanwat. "Performance Improvement of ACO-OFDM Indoor Optical Wireless Transmissions Using Partial Pre-Equalization." ECTI Transactions on Electrical Engineering, Electronics, and Communications 14, no. 1 (September 11, 2015): 1–11. http://dx.doi.org/10.37936/ecti-eec.2016141.171081.
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This paper analyzes the performances and presents the benets of partial pre-equalization for indoor optical wireless transmissions based on asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) with intensity modulation and direct detection (IM/DD). In particular, for diffuse indoor optical wireless channels, partial pre-equalization can reduce the optical transmit power over post-equalization at the same target bit error rate (BER) for point-to-point transmissions even with imperfect channel knowledge. To further im-prove its performance, bit loading is considered to minimize the optical transmit power of ACO-OFDM while maintaining a constant target BER. In addition, broadcast transmissions to multiple users with possibly dierent channel qualities are considered, where pre-equalization is not applicable. Finally, we specify an appropriate channel estimate at the transmitter for such broadcast transmissions.
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Azhar, Ahmad Helmi, Tuan-Anh Tran, and Dominic O'Brien. "A Gigabit/s Indoor Wireless Transmission Using MIMO-OFDM Visible-Light Communications." IEEE Photonics Technology Letters 25, no. 2 (January 2013): 171–74. http://dx.doi.org/10.1109/lpt.2012.2231857.
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Lizeaga, Aitor, Pedro M. Rodríguez, Iñaki Val, and Mikel Mendicute. "Evaluation of 5G Modulation Candidates WCP-COQAM, GFDM-OQAM, and FBMC-OQAM in Low-Band Highly Dispersive Wireless Channels." Journal of Computer Networks and Communications 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/2398701.
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We analyse some of the candidates for modulations for 5G: FBMC-OQAM, GFDM-OQAM, and WCP-COQAM. Unlike most of the related bibliographies, which are oriented to mobile communications, our research is focused on 5G in cognitive radio based industrial wireless communications. According to the ultrareliability and low-latency requirements of industrial communications, we simulate the aforementioned modulations in low-band transmissions (carrier frequencies below 6 GHz and a bandwidth narrower than 100 MHz) through large indoor spaces and severe multipath channels that emulate industrial halls. Moreover, we give detailed information about WCP-COQAM and how the windowing affects the protection against multipath effect and reduces spectral efficiency compared to GFDM-OQAM. We also compare the aforementioned filtered multicarrier techniques and OFDM in terms of robustness against multipath channels, power spectral density, and spectral efficiency. Based on these results, we aim at providing an approximate idea about the suitability of 5G MCM candidates for industrial wireless communications based on CR.
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Pavia, João Pedro, Vasco Velez, Nuno Souto, Marco Ribeiro, Pedro Sebastião, and Américo Correia. "System-Level Assessment of Low Complexity Hybrid Precoding Designs for Massive MIMO Downlink Transmissions in Beyond 5G Networks." Applied Sciences 12, no. 6 (March 9, 2022): 2812. http://dx.doi.org/10.3390/app12062812.
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The fast growth experienced by the telecommunications field during the last few decades has been motivating the academy and the industry to invest in the design, testing and deployment of new evolutions of wireless communication systems. Terahertz (THz) communication represents one of the possible technologies to explore in order to achieve the desired achievable rates above 100 Gbps and the extremely low latency required in many envisioned applications. Despite the potentialities, it requires proper system design, since working in the THz band brings a set of challenges, such as the reflection and scattering losses through the transmission path, the high dependency with distance and the severe hardware constraints. One key approach for overcoming some of these challenges relies on the use of massive/ultramassive antenna arrays combined with hybrid precoders based on fully connected phase-shifter architectures or partially connected architectures, such as arrays of subarrays (AoSAs) or dynamic AoSAs (DAoSAs). Through this strategy, it is possible to obtain very high-performance gains while drastically simplifying the practical implementation and reducing the overall power consumption of the system when compared to a fully digital approach. Although these types of solutions have been previously proposed to address some of the limitations of mmWave/THz communications, a lack between link-level and system-level analysis is commonly verified. In this paper, we present a thorough system-level assessment of a cloud radio access network (C-RAN) for beyond 5G (B5G) systems where the access points (APs) operate in the mmWave/THz bands, supporting multi-user MIMO (MU-MIMO) transmission with massive/ultra-massive antenna arrays combined with low-complexity hybrid precoding architectures. Results showed that the C-RAN deployments in two indoor office scenarios for the THz were capable of achieving good throughput and coverage performances, with only a small compromise in terms of gains when adopting reduced complexity hybrid precoders. Furthermore, we observed that the indoor-mixed office scenario can provide higher throughput and coverage performances independently of the cluster size when compared to the indoor-open office scenario.
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Wang, Xin, Hai Dong Chi, Tao Zheng, and Wen Li Cheng. "One Data Transmission System for the Indoor Wireless Communications." Advanced Materials Research 760-762 (September 2013): 582–86. http://dx.doi.org/10.4028/www.scientific.net/amr.760-762.582.
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The indoor communications is a new market in the future. This Article introduces one data transmission system based with OFDM signals. The overview of the communication system and synchronization theory background will be introduced. The simulation results shown in this article implies that this OFDM system achieves excellent performance for indoor wireless communication.
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Subramani, Prabu, Ganesh Babu Rajendran, Jewel Sengupta, Rocío Pérez de Prado, and Parameshachari Bidare Divakarachari. "A Block Bi-Diagonalization-Based Pre-Coding for Indoor Multiple-Input-Multiple-Output-Visible Light Communication System." Energies 13, no. 13 (July 4, 2020): 3466. http://dx.doi.org/10.3390/en13133466.
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Visible Light Communication (VLC) is a promising field in optical wireless communications, which uses the illumination infrastructure for data transmission. The important features of VLC are electromagnetic interference-free, license-free, etc. Additionally, Multiple-Input-Multiple-Output (MIMO) techniques are enabled in the VLC for enhancing the limited modulation bandwidth by its spectral efficiency. The data transmission through the MIMO-VLC system is corrupted by different interferences, namely thermal noise, shot noise and phase noise, which are caused by the traditional fluorescent light. In this paper, an effective precoding technique, namely Block Bi-Diagonalization (BBD), is enabled to mitigate the interference occurring in the indoor MIMO-VLC communications. Besides, a Quadrature Amplitude Modulation (QAM) is used to modulate the signal before transmission. Here, the indoor MIMO-VLC system is developed to analyze the communication performance under noise constraints. The performance of the proposed system is analyzed in terms of Bit Error Rate (BER) and throughput. Furthermore, the performances are compared with three different existing methods such as OAP, FBM and NRZ-OOK-LOS. The BER value of the proposed system of scenario 1 is 0.0501 at 10 dB, which is less than that of the FBM technique.
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Sharma, Preeti, Rakesh N. Tiwari, Prabhakar Singh, Pradeep Kumar, and Binod K. Kanaujia. "MIMO Antennas: Design Approaches, Techniques and Applications." Sensors 22, no. 20 (October 14, 2022): 7813. http://dx.doi.org/10.3390/s22207813.
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The excessive use of digital platforms with rapidly increasing users in the wireless domain enforces communication systems to provide information with high data rates, high reliability and strong transmission connection quality. Wireless systems with single antenna elements are not able to accomplish the desired needs. Therefore, multiple-input multiple-output (MIMO) antennas are getting more attention in modern high-speed communication systems and play an essential part in the current generation of wireless technology. However, along with their ability to significantly increase channel capacity, it is a challenge to achieve an optimal isolation in a compact size for fifth-generation (5G) terminals. Portable devices, automobiles, handheld gadgets, smart phones, wireless sensors, radio frequency identification and other applications use MIMO antenna systems. In this review paper, the fundamentals of MIMO antennas, the performance parameters of MIMO antennas, and different design approaches and methodologies are discussed to realize the three most commonly used MIMO antennas, i.e., ultra-wideband (UWB), dual-band and circularly polarized antennas. The recent MIMO antenna design approaches with UWB, dual band and circularly polarized characteristics are compared in terms of their isolation techniques, gain, efficiency, envelope correlation coefficient (ECC) and channel capacity loss (CCL). This paper is very helpful to design suitable MIMO antennas applicable in UWB systems, satellite communication systems, GSM, Bluetooth, WiMAX, WLAN and many more. The issues with MIMO antenna systems in the indoor environment along with possible solutions to improve their performance are discussed. The paper also focuses on the applications of MIMO characteristics for future sixth-generation (6G) technology.
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Li, Hai Yan. "Bit and Power Allocation Algorithm for OFDM UWB Systems." Advanced Materials Research 760-762 (September 2013): 472–77. http://dx.doi.org/10.4028/www.scientific.net/amr.760-762.472.
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Ultra-wide-band (UWB) is a promising short-range indoor wireless communication technology for large communication capacity, high transmission rate, low power consumption, etc. Multi-band orthogonal frequency-division multiplexing ultra-wide-band (MB-OFDM UWB) system can achieve much higher anti-noise capability and flexibility. However, the transmission power of UWB systems is strictly restricted for avoiding the interference with other wireless communication systems existing in the same frequency spectrum range. It is necessary that adequately utilizes channel estimation to allocate bit and power effectively. According to the change of channel gain, UWB systems modify the allocation factor to optimize the performance of systems and reduce power allocation remainder. Simulation shows modified bit-power allocation algorithm can enhance power allocation efficiency. Furthermore, it is found that the power remainder of modified allocation factor algorithm is less influenced by the bit error rate.
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Yang, Jiyeong, Wonjae Ryoo, Wonjin Sung, Jeong-Ho Kim, and Jonghyun Park. "3D Antenna Structures Using Uniform Triangular Arrays for Efficient Full-Directional Multiuser Transmission." International Journal of Antennas and Propagation 2019 (November 5, 2019): 1–12. http://dx.doi.org/10.1155/2019/4150378.
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In order to increase the system capacity of the 5G mobile communication system, multiple-input multiple-output (MIMO) transmission techniques using a large-scale array over the millimeter-wave band have attracted a great amount of attention. To cope with various types of receivers expected in 5G communications such as user equipment (UE) in small cells, indoor Internet-of-Things (IoT) devices at diverse locations, and drones performing aerial navigation, newer types of antenna arrays require all-directional transmission capability. Existing antenna structures with typical panel arrays, however, have restrictions on their transmission angles in both horizontal and vertical directions. In this paper, we propose to employ three-dimensional (3D) array structures composed of multiple triangular panels for efficient massive MIMO transmission of the next-generation wireless systems. We analyze beamforming characteristics of a uniform triangular array (UTA) suitable for such 3D array configurations and present a basic codebook applicable to UTAs. Using antenna structures with multiple UTA panels, multiuser transmission performance is evaluated to demonstrate the effectiveness of the proposal.
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Sure, Pallaviram, and Chandra Mohan Bhuma. "On the Comparison of Various Overhead Arrangements for Massive MIMO-OFDM Channel Estimation." International Journal of Electronics and Telecommunications 60, no. 2 (June 1, 2014): 173–79. http://dx.doi.org/10.2478/eletel-2014-0021.
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Abstract Massive multi input multi output (MIMO) systems incorporate orthogonal frequency division multiplexing (OFDM) technology to render high data rate services for future wireless communication applications. The channel estimator (CE) employed by a reliable massive MIMO-OFDM system requires huge amount of overhead in the form of known and null data transmissions, hence limiting the system spectral efficiency (SE). Often, CE design is a tradeoff between SE and system reliability. In this paper, CE with three different overhead arrangements, namely time domain synchronous (TDS), comb type with cyclic prefix (CTCP), 2D grid type with cyclic prefix (GTCP) are investigated and a GTCP based CE is proposed which offers both high SE and improved system reliability. The proposed CE uses autocorrelation based denoising threshold for channel impulse response (CIR) estimation and does not require any knowledge of channel statistics (KCS). A 4 x 16 MIMO-OFDM system is simulated in a rayleigh fading channel environment with U-shaped doppler spectrum. From the bit error rate (BER) performance results inWiMax SUI-4, Advanced Television Technology Center (ATTC) and Brazil A channel environments, it is verified that the proposed CE with GTCP overhead and proposed denoising scheme, indeed improves both SE and system reliability. Hence it is suitable for application in all massive MIMO-OFDM systems.
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Bao, Jingjing, Qiang Mai, Zhangwen Fang, and Xiaowen Mao. "ARM-Based Indoor RGB-LED Visible Light Communication System." Scientific Programming 2022 (June 18, 2022): 1–10. http://dx.doi.org/10.1155/2022/8290106.
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As a new green solid-state light source, semiconductor light-emitting diodes (LEDs) have the advantages of low power consumption, small size, long life, short response time, and good modulation performance. At the same time, the frequency band to which LED light sources belong does not require regulatory registration, thus alleviating the current problem of spectrum scarcity for wireless communications. However, white LED-based visible light communication (VLC) systems suffer from limited bandwidth and low energy efficiency. Therefore, an ARM-based indoor RGB-LED VLC system is proposed. Firstly, the three RGB colours are mixed into white light, thus obtaining a larger modulation bandwidth than normal white LEDs while illuminating normally. Secondly, the S3C6410 processor is used to modulate and demodulate the RGB-LEDs with biased light OFDM, thus obtaining a high spectrum utilisation while ensuring system transmission stability. Then, according to the characteristics of the light source of the VLC system, the leading and window functions used in the optical network transceiver module are designed to improve the communication energy efficiency of the system. Finally, functional tests were carried out on an ARM development board. The experimental results show that with a single RGB-LED light source, the maximum transmission distance is 5 cm, the maximum average delay is 68 ms, the maximum throughput is 25 Mbps, and the BER is controlled below 3.2 × 10−3, which meets the basic communication requirements.
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Xiao, Ye, Yi-Jun Zhu, and Zheng-Guo Sun. "Linear Precoding Designs for MIMO VLC Using Multi-Color LEDs under Multiple Lighting Constraints." Crystals 8, no. 11 (October 30, 2018): 408. http://dx.doi.org/10.3390/cryst8110408.
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Multiple-input multiple-output (MIMO) technology as an efficient approach to improve the transmission rate in visible light communication (VLC) has been well studied in recent years. In this paper, we focus on the MIMO VLC system using multi-color LEDs in the typical indoor scenario. Besides the correlation of the MIMO channel, the multi-color crosstalk interference and quadrangle chromaticity region are also considered to increase the practicality of this system. With the constraints of power, amplitude and chromaticity, an iterative algorithm to minimize mean-squared-error (MSE) is proposed to jointly design the precoder and equalizer. Our proposed algorithm provides an effective method to get the optimal precoder by updating optimization variables iteratively. As the equalizer matrix is fixed at each iteration, the main non-convex precoding design problem is transformed into a convex optimization problem and then solved. With the utilization of multi-color LEDs, our proposed precoding method would be promising to promote the practical applications of high-speed indoor optical wireless communication. Simulation results show that our proposed method owns better performance than conventional chromaticity-fixed schemes and zero-forcing precoding designs.
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Sadat, Hesham, Mohamed Abaza, Ali Mansour, and Ayman Alfalou. "A Survey of NOMA for VLC Systems: Research Challenges and Future Trends." Sensors 22, no. 4 (February 11, 2022): 1395. http://dx.doi.org/10.3390/s22041395.
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Visible light communication (VLC) has become a promising technology for high data rate communications and an attractive complementary to conventional radio frequency (RF) communication. VLC is a secure, energy efficient and cost-effective technology that exploits the existing infrastructure, particularly in indoor environments, for wireless data transmission. Nevertheless, the main limitation of developing high data rate VLC links is the narrow modulation bandwidth of light-emitting diodes (LEDs), which is in the megahertz range. The power domain nonorthogonal multiple access (PD-NOMA) scheme is envisioned to address several challenges in VLC systems. In this paper, we present a detailed overview of PD-NOMA based VLC systems. Moreover, we introduce insights on some PD-NOMA VLC system constraints and challenges such as power allocation, clipping effect, MIMO and security. Finally, we provide open research problems as well as possible directions for future research to pave the way for the implementation of PD-NOMA VLC systems.
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Tsai, Pei-Yun, Po-Cheng Lo, Fong-Jay Shih, Wen-Ji Jau, Meng-Yuan Huang, and Zheng-Yu Huang. "A 4 $\times$ 4 MIMO-OFDM Baseband Receiver With 160 MHz Bandwidth for Indoor Gigabit Wireless Communications." IEEE Transactions on Circuits and Systems I: Regular Papers 62, no. 12 (December 2015): 2929–39. http://dx.doi.org/10.1109/tcsi.2015.2495740.
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Wang, Qi, Xuefeng Yin, Jingxiang Hong, and Guangzheng Jing. "Propagation Channel Characterization for 6–14 GHz Bands Based on Large Array Measurement for Indoor Scenarios." Electronics 11, no. 22 (November 10, 2022): 3675. http://dx.doi.org/10.3390/electronics11223675.
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The demand for wideband data transmission in the “next-generation” mobile communication system is growing rapidly. As the frequency band around 10 GHz could be the option for 6th-generation (6G) wireless communication systems. In this paper, a recently conducted measurement campaign in the 6–14 GHz radio wave propagation channel using a large antenna array with 1024 elements is introduced. In order to investigate the behavior of the wideband channel, we have analyzed the channel characteristics with respect to different carrier frequencies, bandwidths, the locations of antenna elements, and user locations, aiming at exploring the spatio-frequency variability of channels in the massive multiple-input multiple-output (MIMO) scenarios. Moreover, the sparsity of the channel in frequency and spatial domains is evaluated through the degree of freedom (DoF) analysis, and statistical models are established.
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Wang, Youqing, Kun Zhao, and Zhengqi Zheng. "A 3D Indoor Positioning Method of Wireless Network with Single Base Station in Multipath Environment." Wireless Communications and Mobile Computing 2022 (April 14, 2022): 1–13. http://dx.doi.org/10.1155/2022/3144509.
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The proliferation of indoor location-based services has increased the demand of indoor positioning technology. Severe multipath and coherence effects are the difference between signal propagation indoors and outdoors. Most existing indoor localization methods build their models in 2-dimensional space and try to avoid the influence of multipath. We propose a method to realize 3-dimensional indoor positioning with single base station by using multipath channel. The angles of multipath coherent signals are estimated by MIMO antenna and the delays are estimated by OFDM signal. To avoid the complicated calculation in joint estimation of angles and delays in 3-dimensional space, the angles and delays are estimated separately and matched by the proposed algorithm. The line-of-sight channel is differentiated by time delay, and the reflection paths for non-line-of-sight channels are established with angle information and indoor maps. Finally, combine the angle information of the reflection paths and the line-of-sight path to obtain the target position in 3-dimensional indoor space. We verified the method through simulation in an indoor space of 6 m × 8 m × 4.5 m . The positioning errors are submeter level in 95 % cases and less than 0.4m in 60 % cases. The proposed method requires only one base station and can be applied in most wireless networks. Compared with existing indoor localization methods, it has lower computational complexity and higher application potential.
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Verdecia-Peña, Randy, and José I. Alonso. "Design and Synchronization Procedures of a D&F Co-Operative 5G Network Based on SDR Hardware Interface: Performance Analysis." Sensors 22, no. 3 (January 25, 2022): 913. http://dx.doi.org/10.3390/s22030913.
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Software defined radio (SDR) is a commonly used platform for its ease of operation and cost-effectiveness for the development and testing of real wireless communication systems. By supporting high transmission rates and enabling fast and cost-effective deployments, mainly in millimeter-wave (mmWave), the co-operative 5G network has been standardized by 3GPP Release 16. In this paper, a decode-and-forward (D&F) co-operative hardware network is proposed as one of the key technologies for future 5G/6G wireless networks. The proposed system consists of an emulated base station processing unit (gnodeB), a D&F protocol and the user equipment (UE). In particular, the design of the D&F relay node is based on an MIMO layer 2 relay technology. A testbed based on an SDR platform and MatlabTM software, in which the physical broadcast channel (PBCH) transmission, physical downlink control channel (PDCCH), physical downlink shared channel (PDSCH), and downlink shared channel (DL-SCH) for transport channel coding, according to the 3GPP standardized 5G downlink signal, has been designed. The key performance indicators (KPIs), namely EVM, BER, and throughput, were measured for 5G signals with 64-QAM and 256-QAM modulation schemes. The obtained results show that the D&F co-operative 5G network achieves substantially improved KPIs in the communication between the gnodeB and the UE in an outdoor-to-indoor scenario. Furthermore, it has been demonstrated that the D&F protocol presents a good performance and behavior being compared to one commercial equipment.
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Zhong, Xin, Chen Chen, Shu Fu, Zhihong Zeng, and Min Liu. "DeepGOMIMO: Deep Learning-Aided Generalized Optical MIMO with CSI-Free Detection." Photonics 9, no. 12 (December 5, 2022): 940. http://dx.doi.org/10.3390/photonics9120940.
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Generalized optical multiple-input multiple-output (GOMIMO) techniques have been recently shown to be promising for high-speed optical wireless communication (OWC) systems. In this paper, we propose a novel deep learning-aided GOMIMO (DeepGOMIMO) framework for GOMIMO systems, wherein channel state information (CSI)-free detection can be enabled by employing a specially designed deep neural network (DNN)-based MIMO detector. The CSI-free DNN detector mainly consists of two modules: one is the preprocessing module, which is designed to address both the path loss and channel crosstalk issues caused by MIMO transmission, and the other is the feedforward DNN module, which is used for joint detection of spatial and constellation information by learning the statistics of both the input signal and the additive noise. Our simulation results clearly verify that, in a typical indoor 4 × 4 MIMO-OWC system using both generalized optical spatial modulation (GOSM) and generalized optical spatial multiplexing (GOSMP) with unipolar nonzero 4-level pulse-amplitude modulation (4-PAM) modulation, the proposed CSI-free DNN detector achieves near the same bit error rate (BER) performance as the optimal joint maximum-likelihood (ML) detector, but with much-reduced computational complexity. Moreover, because the CSI-free DNN detector does not require instantaneous channel estimation to obtain accurate CSI, it enjoys the unique advantages of improved achievable data rate and reduced communication time delay in comparison to the CSI-based zero-forcing DNN (ZF-DNN) detector.
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He, Bingyan, Tao Sun, Chuanmu Li, and Xingwang Huang. "Secrecy Capacity of Time Reversal Beamforming for Multi-User MIMO System under Spatial Correlation." Security and Communication Networks 2021 (December 18, 2021): 1–14. http://dx.doi.org/10.1155/2021/3670101.
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In this paper, for strengthening the security of wireless transmission system, the time reversal (TR) beamforming method is proposed for the downlink of multi-user MIMO system with multiple users who potentially act as eavesdroppers. We develop a multi-input, single-output, multi-eavesdropper (MISOME) wiretap channel model in which Rayleigh fading and spatial correlation are taken into account. Using the proposed model, we further analyze the confidentiality provided by TR beamforming and we use achievable secrecy rates as our performance metrics. In particular, we derive novel closed-formed expressions for the average secrecy-SINR and the mean secrecy sum-rate in order to characterize the influences of propagation conditions on network secrecy metrics. These expressions provide deeper insights into the impact of network interference on communication confidentiality. We find that TR beamforming can deliver the maximum secrecy capacity potential in uncorrelated Rayleigh channels and achieve perfect confidential communication without any extra secrecy cost. On the other hand, even weak inter-user correlation may cause a significant loss of achievable secrecy sum-rate and therefore result in high secrecy cost. But benefiting more from larger signal bandwidth and rich-scattering environment, the TR beamforming technique is still an attractive and cost-effective solution for low-power indoor applications.
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Kim, Jeong Gon, and Ho Kyung Yu. "Analysis of Pulse Modulation in LC Based Typical Indoor Environment." Journal of Communications, 2020, 702–7. http://dx.doi.org/10.12720/jcm.15.9.702-707.
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The 4th industrial revolution is affecting to medical and other industry. Recently, secure and reliable communication are required in medical or factory data transmission since ISM band is used and it occurs a lot of EMI Problems in existing RF communication. We use LC (Light Communication) to solve this problem in typical wireless environment. We use LED on the ceiling as the transmitter and PD in mobile device as the receiver for that. In this paper, we consider single carrier modulation for the connection between server and patients. We can also extend to Multi carrier Modulation such as DCO-OFDM for the high rate support. Based on the CIR model of the hospital or factory environment, the simulation is performed using OOK, 4-PAM, and 8-PAM to obtain link level performance. BER and the throughput are analyzed and compared in order to evaluate the potential use of VLC to the hospital ward or factory wirelss. It is shown that OOK can be applied to more secure cases and 8PAM can be better in considering the tradeoff between BER and throughput when the same transmitting power is used for that.
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"A Novel Transceiver Model for Polar Transform Optical (PTO-) OFDM for Visible Light Communication (VLC) Based on Peak to Average Power Ratio Reduction using Precoding." Regular 9, no. 10 (August 10, 2020): 307–15. http://dx.doi.org/10.35940/ijitee.e9914.0891020.
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Indoor visible light communication (VLC) has the potential of providing high data rates for short-range wireless communication with a relative spatial elevated security in contrast to a radiofrequency wireless one. To support that high data stream, Orthogonal Frequency Division Multiplexing (OFDM) is used; however, due to the limited operational bandwidth of the commercial white light-emitting diode (LED), signal processing techniques are used to increase the efficiency of the OFDM and to adapt OFDM to VLC systems. As a major concern, the intensity modulation direct detection necessary for VLC requires positive real signal, this is dealt with by imposing Hermitian pre-possessing or Cartesian to polar conversion post-processing to the OFDM. The use of the Cartesian to polar converter allows the transmission of complex OFDM symbols through the intensity modulation channel. A polar transform optical (PTO-) OFDM presented here as an improvement and simplification of previous polar optical OFDM schemes gives an efficient transceiver architecture. Nevertheless, both OFDM transmission techniques for Visible optical links, similar to radiofrequency (RF), suffer greatly from irregular excessive Peak-to-Average power ratio (PAPR). Higher PAPR reduces the power efficiency of the On-Off Keying (OOK) based on pulse amplitude modulation (PAM). Furthermore, it also is recommendable to reduce the PAPR for conformity with eye safety. A precoding technique is proposed to reduce the PAPR of intensity-modulated for direct detectability of the OFDM signal destined for the wireless optical link using Cartesian-to-Polar conversion. Based on the enhanced processing at the front ends and using MATLAB simulation, it is proven that the presented model can improve the link parameters including the bit error rate (BER) and signal to noise ratio (SNR) and bandwidth efficient compared to Hermitian modified ones.
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Hardan, Saad M., Ayad A. Abdulkafi, Saadi Hamad Thalij, and Sherine S. Jumaah. "Mobility aware of WDM-based CMO OFDM communication system." Journal of Optical Communications, July 29, 2021. http://dx.doi.org/10.1515/joc-2021-0103.
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Abstract The continued increase in several mobile applications forces to replace existing limited spectrum indoor radio frequency wireless connections with high-speed ones. Visible light communications (VLC) technology has gained prominence in the development of high data rate transmission for fifth-generation networks. In optical wireless communications, light-emitting diode (LED) transmitters are used in applications that desire mobility as LED divergence enables larger coverage. Since each VLC access point covers a small area, handovers of mobile users are inevitable. Wavelength division multiplexing (WDM) can be used in VLC systems to tackle the above issue and to meet the increasing demand for indoor connectivity with high bit rates. In this paper, a new system architecture for WDM with coded modulated optical in orthogonal frequency division multiplexing (OFDM) VLC system in conjunction with red, green, blue, and yellow (RGBY) LEDs is proposed to reduce the impact of random receiver orientation of indoor mobile users over VLC downlink channels and improves the system’s bit-error-rate (BER) performance. Simulation results show that the proposed method is not affected by the user’s mobility and hence it performs better than other approaches, in terms of BER for all scenarios and at all positions. This study reveals that using WDM-OFDM-VLC with RGBY LEDs to construct a VLC system is very promising.
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Kaur, Simarpreet, Mahendra Kumar, and Ashu Verma. "An Integrated High-Speed Full Duplex Coherent OFDM-PON and Visible-Light Communication System." Journal of Optical Communications, January 29, 2019. http://dx.doi.org/10.1515/joc-2018-0236.
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AbstractWe demonstrated a full duplex hybrid passive optical network and indoor optical wireless system employing coherent optical frequency division multiplexing. To accomplish reliable transmission in passive optical networks integrated visible-light communication (VLC), yellow light-emitting diode and infrared LED is used in downstream and upstream, respectively, for intra building network. In order to support high data rate, pulse-width reduction scheme based on dispersion compensation fiber is incorporated and system successfully covered the distance of 50 km. A data stream at the rate of 30 Gb/s is transmitted for each user out of eight users. VLC-supported users are catered with the bit rate of 1.87 Gb/s over 150 cm and in order to realize a low-cost system, visible and infrared LEDs are used in downlink and uplink, respectively.