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Journal articles on the topic 'Uplink channel'

Author: Grafiati

Published: 4 June 2025

Last updated: 1 August 2025

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1

Cho, Sunghyun, Ji-Su Kim, and Jae-Hyun Kim. "Enhanced Handoff Scheme for Downlink-Uplink Asymmetric Channels in Cellular Systems." Scientific World Journal 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/241483.

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In the latest cellular networks, data services like SNS and UCC can create asymmetric packet generation rates over the downlink and uplink channels. This asymmetry can lead to a downlink-uplink asymmetric channel condition being experienced by cell edge users. This paper proposes a handoff scheme to cope effectively with downlink-uplink asymmetric channels. The proposed handoff scheme exploits the uplink channel quality as well as the downlink channel quality to determine the appropriate timing and direction of handoff. We first introduce downlink and uplink channel models that consider the in

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2

Fan, Wei, Pekka Kyösti, Jesper Ø. Nielsen, Lassi Hentilä, and Gert F. Pedersen. "Emulating Realistic Bidirectional Spatial Channels for MIMO OTA Testing." International Journal of Antennas and Propagation 2015 (2015): 1–13. http://dx.doi.org/10.1155/2015/289843.

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This paper discusses over the air (OTA) testing for multiple input multiple output (MIMO) capable terminals with emphasis on modeling bidirectional spatial channel models in multiprobe anechoic chamber (MPAC) setups. In the literature, work on this topic has been mainly focused on how to emulate downlink channel models, whereas uplink channel is often modeled as free space line-of-sight channel without fading. Modeling realistic bidirectional (i.e., both uplink and downlink) propagation environments is essential to evaluate any bidirectional communication systems. There have been works stressi

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3

Liu, Qingli, Jiaxu Sun, and Peiling Wang. "Uplink Assisted MIMO Channel Feedback Method Based on Deep Learning." Entropy 25, no. 8 (2023): 1131. http://dx.doi.org/10.3390/e25081131.

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In order to solve the problem wherein too many base station antennas are deployed in a massive multiple-input–multiple-output system, resulting in high overhead for downlink channel state information feedback, this paper proposes an uplink-assisted channel feedback method based on deep learning. The method applies the reciprocity of the uplink and downlink, uses uplink channel state information in the base station to help users give feedback on unknown downlink information, and compresses and restores the channel state information. First, an encoder–decoder structure is established. The encode

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4

Mengesha, Befekadu, Pablo Torres-Ferrera, and Roberto Gaudino. "Analysis of 5G New Radio Uplink Signals on an Analogue-RoF System Based on DSP-Assisted Channel Aggregation." Applied Sciences 9, no. 1 (2018): 47. http://dx.doi.org/10.3390/app9010047.

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The 3rd Generation Partnership Project (3GPP) is in the process of developing 5th generation (5G) radio access technology, the so-called new radio (NR). The aim is to achieve the performance requirements forIMT-2020 radio interface technology. In this paper, we focus on the analysis of the transmission of 5G NR uplink physical channels, such as physical uplink shared channel (PUSCH) and physical uplink control channel (PUCCH), dedicated for data and control channels, respectively, as specified in the 3GPP standard, using digital signal processing (DSP)-assisted frequency division multiple acce

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Oyerinde, Olutayo Oyeyemi, Adam Flizikowski, Tomasz Marciniak, Dmitry Zelenchuk, and Telex Magloire Nkouatchah Ngatched. "Compressive Sensing-Based Channel Estimation for Uplink and Downlink Reconfigurable Intelligent Surface-Aided Millimeter Wave Massive MIMO Systems." Electronics 13, no. 15 (2024): 2909. http://dx.doi.org/10.3390/electronics13152909.

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This paper investigates single-user uplink and two-user downlink channel estimation in reconfigurable intelligent surface (RIS)-aided millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) wireless communication systems. Because of the difficulty associated with the estimation of channels in RIS-aided wireless communication systems, channel state information (CSI) is assumed to be known at the receiver in some previous works in the literature. By assuming that prior knowledge of the line-of-sight (LoS) channel between the RIS and the base station (BS) is known, two compressive

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6

Rim, Minjoong, and Chung Kang. "Uplink Non-Orthogonal Multiple Access with Channel Estimation Errors for Internet of Things Applications." Sensors 19, no. 4 (2019): 912. http://dx.doi.org/10.3390/s19040912.

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One of the key requirements for next generation wireless or cellular communication systems is to efficiently support a large number of connections for Internet of Things (IoT) applications, and uplink non-orthogonal multiple access (NOMA) schemes can be used for this purpose. In uplink NOMA systems, pilot symbols, as well as data symbols can be superimposed onto shared resources. The error rate performance can be severely degraded due to channel estimation errors, especially when the number of superimposed packets is large. In this paper, we discuss uplink NOMA schemes with channel estimation

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7

Zhangyong, Li. "Millimeter Wave Multi-mode OAM-MIMO Channel Capacity Study." Journal of Big Data and Computing 2, no. 2 (2024): 35–45. http://dx.doi.org/10.62517/jbdc.202401206.

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This study examines the theoretical aspects of channel capacity for millimeter wave multi-mode Orbital Angular Momentum (OAM) Multiple Input Multiple Output (MIMO) systems. It begins with a theoretical analysis of these channels, highlighting their importance and potential applications in wireless communications. A Sparse Bayesian Learning (SBL) based Joint Uplink and Downlink Channel Estimation (JUDCE) approach is then employed to estimate the downlink channel using uplink training signals, while accounting for inactive receiving antennas. Exploiting the sparsity of millimeter wave channels,

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8

Zhao, Bai-Shan, Peng-Fei Lv, and Yan-Qing Hong. "Channel Correlation-Based Adaptive Power Transmission for Free-Space Optical Communications." Photonics 11, no. 9 (2024): 859. http://dx.doi.org/10.3390/photonics11090859.

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Free-space optical (FSO) communication has received widespread attention as a high-bandwidth, low-latency communication technique. However, the scintillation effect caused by atmospheric turbulence leads to intensity fluctuations of the transmission signal, which, in turn, affects the performance of the FSO communication system. This paper proposes a channel correlation-based adaptive power transmission for FSO communications. Based on the correlation between uplink and downlink turbulence channels, the power of the reverse transmission signal is adjusted by the fluctuation strength of the rec

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9

Yalavarthy, Srinivasa Rao. "Optimizing Uplink Scheduling in IEEE 802.11bn UHR Networks with NPCA Primary Channel Access." European Journal of Computer Science and Information Technology 13, no. 49 (2025): 117–30. https://doi.org/10.37745/ejcsit.2013/vol13n49117130.

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This article explores uplink scheduling optimization in IEEE 802.11bn Ultra High Reliability (UHR) networks utilizing Non-Primary Channel Access (NPCA) functionality. NPCA enhances network resilience by enabling devices to switch to alternative channels when the primary channel experiences congestion, but introduces challenges in uplink scheduling efficiency and fairness. Traditional Enhanced Distributed Channel Access (EDCA) mechanisms prove inadequate in time-constrained NPCA scenarios due to collision probability and fairness concerns. The proposed solution implements a trigger-based uplink

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10

Syed Ameer Abbas, S., M. Venisubha, S. Siva Gayathri, and S. J. Thiruvengadam. "Realization of LTE physical layer baseband processing architecture for narrowband IOT." International Journal of Engineering & Technology 7, no. 2.31 (2018): 56. http://dx.doi.org/10.14419/ijet.v7i2.31.13397.

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The 3GPP Long Term Evolution represents the major innovation in cellular technology. NB-IoT is the 3GPP standard for machine to machine communication finalized within LTE Release13. NB-IoT technology occupies frequency band of 180 kHz bandwidth which corresponds to one resource block in LTE transmission. The Long Term Evolution (LTE) supports higher data rates, higher bandwidth, Low latency, good Quality of Service whereas objective of Narrow Band Internet of Things (NB - IOT) is to achieve extended coverage, to support massive number of smart devices and have multi - year long battery life. S

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Maharjan, Nilesh, Nikesh Devkota, and Byung Wook Kim. "Atmospheric Effects on Satellite–Ground Free Space Uplink and Downlink Optical Transmissions." Applied Sciences 12, no. 21 (2022): 10944. http://dx.doi.org/10.3390/app122110944.

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Free space optical (FSO) communications have the potential to be one of the most essential technologies for solving the high-bandwidth demands of communications between satellites and ground stations. In this study, we examine the impact of the atmosphere on satellite–ground FSO uplink and downlink communications. To consider diverse atmospheric conditions on both uplink and downlink, we derive FSO channel elements such as the fog attenuation coefficient, refractive index parameter, coherence length, turbulence model, and angle-of-arrival fluctuation. Unlike conventional work, we provide FSO c

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12

Yang, Rong, and Aiqun Hu. "Secure transmission technology based on direct modulation with random channel characteristics." Security and Safety 1 (2022): 2022006. http://dx.doi.org/10.1051/sands/2022006.

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Aiming at the problem of insufficient security in the existing wireless data transmission, a security transmission technology based on direct modulation with random channel characteristics is proposed. The method first estimates channel characteristics using the preamble in the communication frame, and then embeds channel characteristics into the I/Q modulator. After that, the modulated constellation diagram undergoes random hopping of the constellation position compared with the original constellation diagram, thus achieving the effect of secure transmission. Due to the reciprocity of the upl

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13

Kim, Yonggang, Gyungmin Kim, Youngwoo Oh, and Wooyeol Choi. "Transmission Delay-Based Uplink Multi-User Scheduling in IEEE 802.11ax Networks." Applied Sciences 11, no. 19 (2021): 9196. http://dx.doi.org/10.3390/app11199196.

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As the demands for uplink traffic increase, improving the uplink throughput has attracted research attention in IEEE 802.11 networks. To avoid excessive competition among stations and enhance the uplink throughput performance, the IEEE 802.11ax standard supports uplink multi-user transmission scenarios, in which AP triggers certain stations in a network to transmit uplink data simultaneously. The performance of uplink multi-user transmissions highly depends on the scheduler, and station scheduling is still an open research area in IEEE-802.11ax-based networks. In this paper, we propose a trans

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14

Ma, Tao, Yanfeng Hu, Zhenqi Fan, Xinjiang Xia, and Dongming Wang. "Performance Analysis of Cell-Free Massive MIMO System with Network-Assisted Full-Duplex under Time-Shifting Pilot Scheme." Electronics 11, no. 14 (2022): 2171. http://dx.doi.org/10.3390/electronics11142171.

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A network-assisted full-duplex (NAFD) system based on a cell-free (CF) massive multiple-input, multiple-output (MIMO) framework has been proposed to satisfy the demands of higher data transmission rates and efficient communication. However, pilot contamination may occur due to the reuse of pilot sequences in a massive MIMO. With this consideration, we raise an asynchronous channel estimation method based on an uplink and downlink time-shifting pilot-sending scheme, which is able to avoid pilot sequence reuse when obtaining channel state information (CSI), while the data signals could be transm

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15

Honda, Kazuhiro. "A Method of Implementing a 4 × 4 Correlation Matrix for Evaluating the Uplink Channel Properties of MIMO Over-the-Air Apparatus." Sensors 21, no. 18 (2021): 6184. http://dx.doi.org/10.3390/s21186184.

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This paper presents a method of implementing a 4 × 4 correlation matrix for evaluating the uplink channel properties of multiple-input multiple-output (MIMO) antennas using an over-the-air measurement system. First, the implementation model used to determine the correlation coefficients between the signals received at the base station (BS) antennas via the uplink channel is described. Then, a methodology is introduced to achieve a 4 × 4 correlation matrix for a BS MIMO antenna based on Jakes’ model by setting the initial phases of the secondary wave sources in the two-dimensional channel model

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16

Yusnita, Sri, Khalidia Igna Fillah, Popy Maria, Widya Andriani, and Yulia Jihan SY. "Analysis of the Application of Carrier Aggregation Combinations on the Existing LTE Network." International Journal of Advanced Science Computing and Engineering 5, no. 3 (2023): 220–24. http://dx.doi.org/10.62527/ijasce.5.3.179.

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The implementation of Carrier Aggregation makes it possible to expand spectrum use by combining several bandwidth channels that work like a single spectrum. The LTE network is deployed on several bandwidth channels, namely 1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz and 20MHz. Each bandwidth channel that is correlated with the implementation of carrier aggregation will occupy a different and non-adjacent frequency band, namely 900MHz, 1800MHz, 2100MHz and 2300MHz. In this research, we tested the effect of a combination of CAs that occupy non-adjacent frequency bands on uplink and downlink performance. Me

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17

Mansoor, Babar, Moazzam Islam Tiwana, Syed Junaid Nawaz, Abrar Ahmed, Abdul Haseeb, and Ataul Aziz Ikram. "Data Ridden Pilots Based Estimation of Sparse Multipath Massive MIMO Channels Using Orthogonal Matching Pursuit." Elektronika ir Elektrotechnika 25, no. 4 (2019): 81–87. http://dx.doi.org/10.5755/j01.eie.25.4.23975.

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Massive Multiple-Input Multiple-Output (MIMO) is envisioned to be a strong candidate technology for the upcoming 5th generation (5G) of wireless communication networks. This research work presents a novel Compressed Sensing (CS) and Superimposed Training (SiT) based technique for estimating the sparse uplink channels in massive MIMO systems. The proposed technique involves arithmetic addition of a periodic, but low powered training sequence with each user’s information sequence. Consequently, separately dedicated resources for the pilot symbols are not needed. Moreover, to attain the estimates

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18

Hayajneh, Mohammad Suleiman, and Chaouki Abdallah. "Game Theoretic Distributed Power Control Algorithms for Uplink Wireless Data in Flat Fading Channels." International Journal of Computers Communications & Control 10, no. 4 (2015): 520. http://dx.doi.org/10.15837/ijccc.2015.4.380.

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<p>In this paper we present a game-theoretic power control algorithms for wireless data in CDMA cellular systems under two realistic channels: (a1) Fast flat fading channel and (a2) Slow flat fading channel. The fading coefficients under both (a1) and (a2) are studied for three appropriate small scale channel models that are used in the CDMA cellular systems: Rayleigh channel, Rician channel and Nakagami channel. This work is inspired by the results presented by [1] under nonfading channels. In other words, we study the impact of the realistic channel models on the findings in [1] throug

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19

Beyene, Yihenew, Kalle Ruttik, and Riku Jäntti. "Angular Domain Data-Assisted Channel Estimation for Pilot Decontamination in Massive MIMO." Mobile Information Systems 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/2785948.

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Massive Multiple-Input-Multiple-Output (M-MIMO) system is a promising technology that offers to mobile networks substantial increase in throughput. In Time-Division Duplexing (TDD), the uplink training allows a Base Station (BS) to acquire Channel State Information (CSI) for both uplink reception and downlink transmission. This is essential for M-MIMO systems where downlink training pilots would consume large portion of the bandwidth. In densely populated areas, pilot symbols are reused among neighboring cells. Pilot contamination is the fundamental bottleneck on the performance of M-MIMO syst

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20

Liu, Jichao, Xu Zhao, Yubo Wang, et al. "A Resource Optimization for Two-Step Random Access in 5G New Radio." Journal of Physics: Conference Series 2625, no. 1 (2023): 012063. http://dx.doi.org/10.1088/1742-6596/2625/1/012063.

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Abstract This paper presents a resource optimization method for the 2-step random access (RA) procedure in the 5th generation new radio (5G NR). In 2-step RA, the MsgA includes a sequence as a preamble on the physical random access channel (PRACH) and uplink payload on the physical uplink shared channel (PUSCH). The mapping between PRACH slots and PUSCH slots is specified by system configuration parameters. The network reserves the corresponding PUSCH resource fixedly, regardless of the random access occasion (RO) occupancy rate and the uplink data traffic request. It deprives the uplink sched

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21

Sun, Peng, Jing Yang, Ya Jie Chen, and Chun Zhou. "The Realization of Receiving and Reporting the HARQ-ACK Information in LTE System." Advanced Materials Research 989-994 (July 2014): 4132–35. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.4132.

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A brief introduction of hybrid automatic repeat request (HARQ) is given first, and then a description of physical uplink shared channel (PUCCH) or physical uplink shared channel (PUSCH) receiving and reporting the HARQ-ACK information in bundling mode or multiplexing mode is made in detail. Based on the principle, a scheme is designed to solve the problem of receiving and reporting the HARQ-ACK information.

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22

Tuzlukov, Vyacheslav. "Employment of Generalized Receiver for Group-Blind Intersymbol Detection in Downlink CDMA over Fading Multipath Channels." WSEAS TRANSACTIONS ON SYSTEMS AND CONTROL 16 (November 3, 2021): 541–59. http://dx.doi.org/10.37394/23203.2021.16.51.

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Group-blind multiuser detectors for uplink code-division multiple-access (CDMA) were developed by Wang and Host-Madsen. These detectors make use of the spreading sequences of known users to construct a group constraint to suppress the intracell interference. However, such techniques demand the estimation of the multipath channels and the delays of the known users. In the present paper, the blind generalized receiver is de-veloped for CDMA in fading multipath channels. The proposed generalized receiver utilizes the correlation in-formation between consecutively received signals to generate the

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23

He, Fugui, Congcong Wang, Yao Nie, Xianglin Fan, Chensitian Zhang, and Yang Yang. "Task-Based Quantizer for CSI Feedback in Multi-User MISO VLC/RF Systems." Electronics 14, no. 11 (2025): 2277. https://doi.org/10.3390/electronics14112277.

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The performance of multiple-input single-output (MISO) transmission is highly dependent on the accuracy of the channel state information (CSI) at the base station (BS), which necessitates precise CSI estimation and reliable feedback from the user equipment. However, the overhead of the CSI feedback occupies substantial uplink bandwidth resources. To alleviate the overhead, this paper proposes a novel task-based quantizer for uplink MISO visible light communication (VLC) systems. In particular, a hybrid radio frequency (RF)/VLC system is considered, where VLC links are mainly used for large-vol

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Verdecia-Peña, Randy, and José I. Alonso. "Performance Analysis of Two-Hop mmWave Relay Nodes over the 5G NR Uplink Signal." Applied Sciences 11, no. 13 (2021): 5828. http://dx.doi.org/10.3390/app11135828.

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In this paper, the uplink in a two-hop 5G new radio co-operative system using Relay Nodes (RNs) in millimeter bands has been simulated and studied. We focus on an uplink Amplify-and-Forward Relay Node (A&F RN) and Decode-and-Forward Relay Node (D&F RN) with an mmWave-band transceiver chain (Tx/Rx). We study two uplink mmWave MIMO D&F relaying protocols assuming, firstly, the complete knowledge of the uplink channel and, secondly, the uplink channel estimation through a Least Square (LS) algorithm. To verify the benefits of the proposed uplink mmWave MIMO co-operative network, a lin

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Adamu, Mohammed Jajere, Li Qiang, Rabiu Sale Zakariyya, Charles Okanda Nyatega, Halima Bello Kawuwa, and Ayesha Younis. "An Efficient Turbo Decoding and Frequency Domain Turbo Equalization for LTE Based Narrowband Internet of Things (NB-IoT) Systems." Sensors 21, no. 16 (2021): 5351. http://dx.doi.org/10.3390/s21165351.

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This paper addresses the main crucial aspects of physical (PHY) layer channel coding in uplink NB-IoT systems. In uplink NB-IoT systems, various channel coding algorithms are deployed due to the nature of the adopted Long-Term Evolution (LTE) channel coding which presents a great challenge at the expense of high decoding complexity, power consumption, error floor phenomena, while experiencing performance degradation for short block lengths. For this reason, such a design considerably increases the overall system complexity, which is difficult to implement. Therefore, the existing LTE turbo cod

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26

Shen, Yushi, Pamela C. Cosman, Laurence B. Milstein, and Eduardo F. Martinez. "On Uplink Channel Estimation in WiMAX Systems." International Journal of Mobile Computing and Multimedia Communications 2, no. 2 (2010): 67–77. http://dx.doi.org/10.4018/jmcmc.2010040105.

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In this paper, channel estimation algorithms are proposed and compared for uplink WiMAX systems, which are OFDMA based. These algorithms are investigated based on a dynamic resource allocation scheme, and it is shown that each of them is suitable to specific system scenarios. For example, for a system with a bandwidth of 10MHz operating in the low frequency region (2-11GHz), a two-dimensional averaging algorithm outperforms other algorithms, such as a bilinear interpolation algorithm, because the correlations between the pilots and signals are sufficiently high in both the frequency and the ti

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Yu, Ya-Ju, Yu-Hsiang Huang, and Yuan-Yao Shih. "Cross-Cycled Uplink Resource Allocation over NB-IoT." Sensors 21, no. 23 (2021): 7948. http://dx.doi.org/10.3390/s21237948.

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Before each user equipment (UE) can send data using the narrowband physical uplink shared channel (NPUSCH), each UE should periodically monitor a search space in the narrowband physical downlink control channel (NPDCCH) to decode a downlink control indicator (DCI) over narrowband Internet of Things (NB-IoT). This monitoring period, called the NPDCCH period in NB-IoT, can be flexibly adjusted for UEs with different channel qualities. However, because low-cost NB-IoT UEs operate in the half-duplex mode, they cannot monitor search spaces in NPDCCHs and transmit data in the NPUSCH simultaneously.

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YANG, QINGHAI, and KYUNG SUP KWAK. "PILOT-AIDED MULTIUSER CHANNEL ESTIMATION AND TRACKING IN MIMO-OFDM SYSTEMS." Journal of Circuits, Systems and Computers 16, no. 03 (2007): 319–35. http://dx.doi.org/10.1142/s0218126607003691.

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This paper addresses the pilot-aided multiuser least square (LS) channel estimation for the uplink of multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. The systems under consideration allow all users use all available subcarriers independently and thus involve multiuser interference in the frequency domain. Direct application of the known pilot-aided single-user channel estimation methods to these systems is prohibited, requiring much more new investigations. The decentralized and centralized channel estimation algorithms are developed according t

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Kanagasabai, Aswin, and Amiya Nayak. "Channel Aware Scheduling Algorithm for LTE Uplink and Downlink." Network Protocols and Algorithms 7, no. 3 (2015): 111. http://dx.doi.org/10.5296/npa.v7i3.8229.

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In the past two decades, there has been a drastic increase in the mobile traffic, which is caused by the improved user experience with smart phones and its applications. In LTE system, the packet scheduler plays a vital role in the effective utilization of the resources. This field is not standardized and has immense scope of improvement, allowing vendor-specific implementation. LTE scheduling can be categorized into two extremes, namely, Opportunistic scheduling and Fairness scheduling. The Best Channel Quality Indicator (BCQI) algorithm falls under the former category while Proportional Fair

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Abebaw, Yibeltal, Rajeev K. Shakya, Demissie Jobir Gelmecha, and Eshetu Tessema Ware. "Spectral Efficiency Analysis for Uplink Multicell Massive MIMO Cellular Communication System under Fading Channels." Journal of Electrical and Computer Engineering 2023 (October 16, 2023): 1–16. http://dx.doi.org/10.1155/2023/6623938.

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In multicell massive MIMO system, the maximum limit on area throughput can be achieved by improving spectral efficiency and cell density, as well as bandwidth. In order to evaluate the area throughput for such scenarios, the spectral efficiency (SE) that utilizes the linear zero forcing uplink combining scheme, can be modeled under the Rician fading channel and the BS in case of up-links, is responsible to estimate the channel. Different from existing work, the proposed model incorporates various estimators such as minimum mean square error (MMSE), element-wise minimum mean square error estima

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Xue, Jian Bin, and Song Bai Li. "An SC-FDMA Channel Estimation Algorithm Research Based on Pilot Signals." Applied Mechanics and Materials 347-350 (August 2013): 1682–87. http://dx.doi.org/10.4028/www.scientific.net/amm.347-350.1682.

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SC-FDMA as LTE uplink main technology has been widely studied,at the same time, channel estimation around such technology is becoming hot,In order to research and increase channel estimation accuracy of LTE uplink system,an algorithm based on pilot is proposed in this paper,this algorithms main idea is,by setting a certain bit error rate,choosing some proper data after channel estimation done under R-LS and M-MMSE, combining the chosen data and former block pilot and increasing pilot number to do channel estimation again, system bit error rate and mean square error results can be got by simula

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Kim, Hwangnam, Woonghee Lee, Hyunsoon Kim, Hwantae Kim, and Jaehyeuk Michael Yang. "Protecting Download Traffic from Upload Traffic over Asymmetric Wireless Links." Wireless Communications and Mobile Computing 2018 (July 12, 2018): 1–15. http://dx.doi.org/10.1155/2018/1283420.

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Many varied mobile device networks have been developed with the advancement of communication and network technologies. Cellular data networks are currently the most widely used, and the number of cellular network subscriptions has increased steadily. Most recent wireless access technologies employ asymmetric uplinks and downlinks because mobile subscribers usually download contents from the Internet. Therefore, most cellular network service providers allocate more bandwidth to downlinks than uplinks for mobile subscribers. However, this asymmetry can have unexpected influence on network perfor

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Lee, Kyu-haeng, and Daehee Kim. "CFX: Contention-Free Channel Access for IEEE 802.11ax." Sensors 22, no. 23 (2022): 9114. http://dx.doi.org/10.3390/s22239114.

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Orthogonal frequency-division multiple access (OFDMA) has attracted great attention as a key technology for uplink enhancement for Wi-Fi, since it can effectively reduce network congestion and channel access delay. Unfortunately, the traditional random access protocol of Wi-Fi seldom allows these benefits to be achieved, especially in dense network environments, as the access point (AP) rarely gains the channel access needed to trigger OFDMA uplink transmissions due to severe frame collisions. To address this problem, we propose a new channel access scheme called Contention-Free Channel Access

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Al Rabee, Faeik T., and Richard D. Gitlin. "Uplink Power-Domain Non-Orthogonal Multiple Access (NOMA)." International Journal of Interdisciplinary Telecommunications and Networking 12, no. 4 (2020): 65–73. http://dx.doi.org/10.4018/ijitn.2020100105.

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Non-orthogonal multiple access (NOMA) has been proposed as a promising multiple access (MA) technique in order to meet the requirements for fifth generation (5G) communications and to enhance the performance in internet of things (IoT) networks by enabling massive connectivity, high throughput, and low latency. This paper investigates the bit error rate (BER) performance of two-user uplink power-domain NOMA with a successive interference cancellation (SIC) receiver and taking into account channel estimation errors. The analysis considers two scenarios: perfect (ideal) channel estimation and a

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Hou, Shuai, Yafeng Wang, and Chao Li. "Uplink Sparse Channel Estimation for Hybrid Millimeter Wave Massive MIMO Systems by UTAMP-SBL." Sensors 21, no. 14 (2021): 4760. http://dx.doi.org/10.3390/s21144760.

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The compressive sensing (CS)-based sparse channel estimator is recognized as the most effective solution to the excessive pilot overhead in massive MIMO systems. However, due to the complex signal processing in the wireless communication systems, the measurement matrix in the CS-based channel estimation is sometimes “unfriendly” to the channel recovery. To overcome this problem, in this paper, the state-of-the-art sparse Bayesian learning using approximate message passing with unitary transformation (UTAMP-SBL), which is robust to various measurement matrices, is leveraged to address the multi

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Zheng, Zhi Hua. "An Efficient Power Control Algorithm with Dynamic Channel Allocation for TDD/CDMA Systems." Advanced Materials Research 562-564 (August 2012): 2049–52. http://dx.doi.org/10.4028/www.scientific.net/amr.562-564.2049.

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Asymmetrical traffic service requirements between uplink (UL) and downlink (DL) will cause serious inter-cell interference in TDD/CDMA system. In this paper, an efficient power control algorithm with dynamic channel allocation (PC/DCA) is investigated, which is based on the average power control algorithms. In the uplink and downlink, PC/DCA scheme is addressed with channel reservation to resolve the interference between base-stations. Simulation results show that the performance of the PC/DCA scheme is improved 20% than that of the traditional DCA schemes for asymmetrical traffic service.

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Qi, Chenhao, and Lenan Wu. "Uplink channel estimation for massive MIMO systems exploring joint channel sparsity." Electronics Letters 50, no. 23 (2014): 1770–72. http://dx.doi.org/10.1049/el.2014.2769.

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Flizikowski, Adam, Mateusz Półcienniczak, Maciej Rybicki, Witold Hołubowicz, and Maciej Podyma. "Assessing Capabilities of Commercial WiMAX Networks for Deliverling Real-Time Surveillance Video Traffic in Uplink." Image Processing & Communications 20, no. 1 (2015): 33–44. http://dx.doi.org/10.1515/ipc-2015-0028.

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Abstract Streaming video in uplink is an interesting opportunity for network operators for capitalizing unused part of bandwidth (due to Internet asymmetry). The uplink seems not optimized nowadays due to lack of business cases. The main challenge however is bursty and unpredictable nature of wireless channel observed especially as mobility comes into play in current broadband networks. That is why in this paper, we have approached the diagnosis of commercial mobile WiMAX network towards the capabilities of assuring real-time video in uplink direction. We present results of drive tests showing

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Song, Xin, Xiuwei Han, Yue Ni, Li Dong, and Lei Qin. "Joint Uplink and Downlink Resource Allocation for D2D Communications System." Future Internet 11, no. 1 (2019): 12. http://dx.doi.org/10.3390/fi11010012.

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In cellular networks, device-to-device communications can increase the spectrum efficiency, but some conventional schemes only consider uplink or downlink resource allocation. In this paper, we propose the joint uplink and downlink resource allocation scheme which maximizes the system capacity and guarantees the signal-to-noise-and-interference ratio of both cellular users and device-to-device pairs. The optimization problem is formulated as a mixed integer nonlinear problem that is usually NP hard. To achieve the reasonable resource allocation, the optimization problem is divided into two sub

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Viet Tuan, Pham, Pham Ngoc Son, Tran Trung Duy, et al. "Optimizing a Secure Two-Way Network with Non-Linear SWIPT, Channel Uncertainty, and a Hidden Eavesdropper." Electronics 9, no. 8 (2020): 1222. http://dx.doi.org/10.3390/electronics9081222.

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In this paper, the optimization of downlink beamforming vectors, uplink transmission power, and power-splitting factors is investigated for a secure two-way SWIPT network in the presence of a hidden eavesdropper and non-linear energy harvesting circuits over both perfect and imperfect channels. The eavesdropper is inactive, so its channel information is not available at the base stations (BSs). The purpose of artificial noise is to create downlink interference with the hidden eavesdropper as much as possible, while satisfying the quality of service for two-way communications. For perfect downl

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Zohdy, Maha, Ali Tajer, and Shlomo Shamai (Shitz). "Broadcast Approach to Uplink NOMA: Queuing Delay Analysis." Entropy 24, no. 12 (2022): 1757. http://dx.doi.org/10.3390/e24121757.

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Emerging wireless technologies are envisioned to support a variety of applications that require simultaneously maintaining low latency and high reliability. Non-orthogonal multiple access techniques constitute one candidate for grant-free transmission alleviating the signaling requirements for uplink transmissions. In open-loop transmissions over fading channels, in which the transmitters do not have access to the channel state information, the existing approaches are prone to facing frequent outage events. Such outage events lead to repeated re-transmissions of the duplicate information packe

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Nguyen, Tung T., Brian Berscheid, Ha H. Nguyen, and J. Eric Salt. "A Novel Iterative OFDMA Channel Estimation Technique for DOCSIS 3.1 Uplink Channels." IEEE Transactions on Broadcasting 63, no. 2 (2017): 361–75. http://dx.doi.org/10.1109/tbc.2016.2636738.

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Wu, Liang, Zaichen Zhang, Jian Dang, Jiangzhou Wang, Huaping Liu, and Yongpeng Wu. "Channel Estimation for Multicell Multiuser Massive MIMO Uplink Over Rician Fading Channels." IEEE Transactions on Vehicular Technology 66, no. 10 (2017): 8872–82. http://dx.doi.org/10.1109/tvt.2017.2698833.

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Chang, Rui, Chaowei Yuan, and Jianhe Du. "PARAFAC-Based Multiuser Channel Parameter Estimation for MmWave Massive MIMO Systems over Frequency Selective Fading Channels." Electronics 10, no. 23 (2021): 2983. http://dx.doi.org/10.3390/electronics10232983.

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Channel estimation is crucial in millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems, especially with a few training sequences. To solve the problem of uplink channel estimation in mmWave massive MIMO systems, a PARAFAC-based algorithm is proposed for joint estimation of multiuser channels. The orthogonal frequency divisional multiplexing (OFDM) technique is exploited to combat the frequency selective fading channels. In this paper, the received signal at the base station (BS) is formulated as a third-order parallel factor (PARAFAC) tensor, and then a low-complexity

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Amirsaidov, Ulugbek, and Azamat Qodirov. "Cross-Layer Model of Dynamic Distribution of Radio Resources and Data Flow Service in LTE Networks." International journal of electrical and computer engineering systems 14, no. 1 (2023): 13–19. http://dx.doi.org/10.32985/ijeces.14.1.2.

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In this article, the results of the development of a mathematical model for the time-frequency resource allocation of the uplink channel and flow service in LTE (Long Term Evolution) networks are given. The proposed model is aimed at ensuring the maximum performance of the radio channel and the guaranteed quality of service for data flows of wireless network users. A comparative analysis of the proposed model with the existing methods of the time-frequency resource allocation of the LTE technology is carried out in terms of ensuring the overall performance of the uplink and allocating the requ

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Vidal-Beltrán, Sergio, and José Luis López-Bonilla. "Improving Spectral Efficiency in the SCMA Uplink Channel." Mathematics 9, no. 6 (2021): 651. http://dx.doi.org/10.3390/math9060651.

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The Third Generation Partnership Project (3GPP) and the International Telecommunication Union (ITU) identified the technical requirements that the fifth generation of mobile communications networks (5G) had to meet; within these parameters are the following: an improved data rate and a greater number of users connected simultaneously. 5G uses non-orthogonal multiple access (NOMA) to increase the number of simultaneously connected users, and by encoding data it is possible to increase the spectral efficiency (SE). In this work, eight codewords are used to transmit three bits simultaneously usin

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YAMASAKI, Takeo, Osamu TAKYU, and Yohtaro UMEDA. "Scattered Pilot Assisted Channel Estimation for IFDMA Uplink." IEICE Transactions on Communications E92-B, no. 12 (2009): 3803–14. http://dx.doi.org/10.1587/transcom.e92.b.3803.

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Jung, Young-Ho, and Hongsun Park. "Pilot sharing method for uplink OFDMA channel estimation." IEICE Electronics Express 6, no. 14 (2009): 1051–56. http://dx.doi.org/10.1587/elex.6.1051.

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Zeng, Zhao Hua, Li Jun Xue, and Qian Zhao. "An Improved Channel Estimation Method for LTE Uplink." Advanced Materials Research 433-440 (January 2012): 3847–51. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.3847.

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As users of the increasing demand for multimedia services, 3GPP long term evolution system proposed the Long Term Evolution, LTE. LTE is the most important improvements with a new air interface technology to provide users with higher peak rates. Accurate channel estimation is to ensure the transmission quality of LTE system and the key to its advantages. In pursuit of lower bit error rate (BER), this paper based on pilot signals TDD LTE system on the uplink channel estimation algorithm. Use LS algorithm, MMSE algorithm and svd algorithm. Based on these three improved svd algorithm, it gave the

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Hoydis, Jakob, Mari Kobayashi, and Mérouane Debbah. "Optimal Channel Training in Uplink Network MIMO Systems." IEEE Transactions on Signal Processing 59, no. 6 (2011): 2824–33. http://dx.doi.org/10.1109/tsp.2011.2129513.

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