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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 performance, particularly TCP performance. When the uplink interface is congested, TCP ACK packets are delayed by TCP data packets on the uplink, causing considerable TCP retransmissions on the downlink channel. Thus, downlink bandwidth cannot be fully utilized, which results in significantly degraded downlink throughput. To resolve this problem, this paper proposes a feedback scheme, network traffic chunk regulator (NCR). We analyzed the aforementioned problem through the empirical study, and we designed and implemented NCR based on the analysis. NCR adaptively controls TCP according to the degree of link usage asymmetry. We evaluate NCR performance through simulations and experiments with real devices. We verify that the proposed scheme allows the downlink traffic to not interfere with the aggressive uplink traffic. Thus, NCR increases total link utilization and aggregated throughput significantly, without imposing additional overhead on base or mobile stations.
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Jiang, Jian-feng, and Hui-jie Ding. "Uplink Spectrum Overlay Coverage Enhancement Algorithm in 5G Network." Mathematical Problems in Engineering 2021 (December 22, 2021): 1–8. http://dx.doi.org/10.1155/2021/9724623.
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The imbalance between the uplink and downlink rates and coverage of the 5G network has led to limited vertical industry services. Aiming at breaking the imbalance between the uplink and downlink rates and improving the coverage of 5G network, a uplink coverage enhancement algorithm is designed from the aspects of networking mode, bandwidth, uplink and downlink subframe ratio, etc. It uses high- and low-frequency time-frequency joint scheduling to enable uplink full-time slot scheduling, thereby improving uplink coverage and rate. According to the actual test on the live network, the results show that the super-uplink algorithm can increase the near-point uplink rate by 15% to 30%, increase the uplink rate for indoor midpoint scenarios by 40% to 80%, and increase the uplink rate for outdoor and indoor weak spot scenarios by 100% to 400%.
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Liu, Qingli, Jiaxu Sun, and Peiling Wang. "Uplink Assisted MIMO Channel Feedback Method Based on Deep Learning." Entropy 25, no. 8 (July 27, 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 encoder reduces the network depth and uses multi-resolution convolution to increase the accuracy of channel state information extraction while reducing the number of computations relating to user equipment. Afterward, the channel state information is compressed to reduce feedback overhead in the channel. At the decoder, with the help of the reciprocity of the uplink and downlink, the feature extraction of the uplink’s magnitudes is carried out, and the downlink channel state information is integrated into a channel state information feature matrix, which is restored to its original size. The simulation results show that compared with CSINet, CRNet, CLNet, and DCRNet, indoor reconstruction precision was improved by an average of 16.4%, and outside reconstruction accuracy was improved by an average of 21.2% under all compressions.
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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 (October 2, 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 transmission delay-based uplink multi-user scheduling method. The proposed method consists of two steps. In the first step, the proposed method makcreateses station clusters so that stations in each cluster have similar expected transmission delays. The transmission delay-based station clustering increases the ues of uplink data channels during the uplink multi-user transmission scenario specified in IEEE 802.11ax. In the second step, the proposed method selects cluster for uplink multi-user transmissions. The cluster selection can be performed with a proportional fair-based approach. With the highly channel-efficient station cluster, the proposed scheduling method increases network throughput performance. Through the IEEE 802.11ax standard compliant simulations, we verify the network throughput performance of the proposed uplink scheduling method.
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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 intercell interference, to verify the downlink-uplink channel asymmetry. Based on these results, we propose an enhanced handoff scheme that exploits both the uplink and downlink channel qualities to reduce the handoff-call dropping probability and the service interruption time. The simulation results show that the proposed handoff scheme reduces the handoff-call dropping probability about 30% and increases the satisfaction of the service interruption time requirement about 7% under high-offered load, compared to conventional mobile-assisted handoff. Especially, the proposed handoff scheme is more efficient when the uplink QoS requirement is much stricter than the downlink QoS requirement or uplink channel quality is worse than downlink channel quality.
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Wieser, Vladimir, and Tomas Marek. "UMTS uplink simulator." Communications - Scientific letters of the University of Zilina 6, no. 4 (December 31, 2004): 58–62. http://dx.doi.org/10.26552/com.c.2004.4.58-62.
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Zhang, Lan, Weili Nie, Gang Feng, Fu-Chun Zheng, and Shuang Qin. "Uplink Performance Improvement by Decoupling Uplink/Downlink Access in HetNets." IEEE Transactions on Vehicular Technology 66, no. 8 (August 2017): 6862–76. http://dx.doi.org/10.1109/tvt.2017.2653799.
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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 (July 11, 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 transmitted simultaneously at the same frequency. The transmission processes of the proposed method above are divided into three phases, including pilot phase, estimation phase, and data phase, in chronological order. When the uplink is in pilot phase, the corresponding downlink is in data phase and vice versa. After the channel state information estimation, both uplinks and downlinks are in data phase. The maximum ratio combination (MRC) receiver and the maximum ratio transmission (MRT) precoding are adopted in the uplink and downlink. The closed-form expressions are derived based on large-scale random matrix theory. We compared our asymptotic results with practical results in simulation, and find that they are well matched. Moreover, the proposed method is superior to the normal time-division duplex (TDD) system.
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Haider, Amir, and Seung-Hoon Hwang. "Maximum Transmit Power for UE in an LTE Small Cell Uplink." Electronics 8, no. 7 (July 16, 2019): 796. http://dx.doi.org/10.3390/electronics8070796.
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To furnish the network with small cells, it is vital to consider parameters like cell size, interference in the network, and deployment strategies to maximize the network’s performance gains expected from small cells. With a small cell network, it is critical to analyze the impact of the uplink power control parameters on the network’s performance. In particular, the maximum transmit power (Pmax) for user equipment (UE) needs to be revisited for small cells, since it is a major contributor towards interference. In this work, the network performance was evaluated for different Pmax values for the small cell uplink. Various deployment scenarios for furnishing the existing macro layer in LTE networks with small cells were considered. The Pmax limit for a small cell uplink was evaluated for both homogenous small cell and heterogeneous networks (HetNet). The numerical results showed that it would be appropriate to adopt Pmax = 18 dBm in uniformly distributed small cells rather than Pmax = 23 dBm, as in macro environments. The choice of Pmax = 18 dBm was further validated for three HetNet deployment scenarios. A decrease of 0.52 dBm and an increase of 0.03 dBm and 3.29 dBm in the proposed Pmax = 18 dBm were observed for the three HetNet deployments, respectively. Furthermore, we propose that the fractional power control mode can be employed instead of the full compensation mode in small cell uplinks.
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Zhang, De Ming, Sheng Yao, and Xiao Wen Li. "Research and Implementation of Uplink Synchronization in TD-LTE." Advanced Materials Research 756-759 (September 2013): 846–50. http://dx.doi.org/10.4028/www.scientific.net/amr.756-759.846.
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To make sure a good communication between the terminal and the base station, synchronization is needed between them. The Uplink Time Alignment has been provided in the long term evolution system (TD-LTE), by which uplink synchronization can be maintained in terminals. In this letter, the concrete implementation of the Uplink Time Alignment in MAC sub-layer of terminals and independently adjustment of uplink timing were designed with research of the Uplink Time Alignment and detailed analysis of the specific applications of Timing Advance Command in the terminal. The proposed implementation can be applied for the development of test instrumentation and TD-LTE ratio frequency conformance.
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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 (June 23, 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 link-level co-operative simulator has been developed using MatlabTM and SimulinkTM software, where an indoor-to-outdoor scenario and mmWave transceiver with off-the shelf components are considered. The main novelty of this link-level co-operative simulator and the implemented relay nodes is the usage of signals with 5G NR features, such as UL-SCH transport channel coding and PUSCH generation, which are the other main contributions of this article. Based on the numerical results in terms of the achievable Bit Error Rate (BER) and throughput, we show that the two-hop uplink co-operative network substantially improves the performance in the communications between the NR-User Equipment (NR-UE) and the logical 5G Radio Node (gNodeB). For example, the results from using uplink mmWave NR-D&F protocols far exceed those achieved with the uplink mmWave NR-A&F algorithm; in the case of the 64-QAM modulation scheme for the SISO technique, an improvement of 6.5 Mbps was achieved using the D&F PCE protocol, taking into account that the 256-QAM constellation is higher by 4.05 Mbps. On the other hand, an average throughput enhancement of 28.77 Mbps was achieved when an uplink mmWave (2 × 4 × 4) D&F PCE strategy was used versus an uplink mmWave SISO D&F LS protocol for a Signal-to-Noise Ratio (SNR) = 20 dB and 64-QAM signal. However, an improvement of 56.42 Mbps was reached when a 256-QAM modulation scheme was employed. Furthermore, this paper introduces the first study to develop an uplink mmWave MIMO 5G co-operative network platform through a Software Defined Radio (SDR) from a practical implementation point of view.
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Ari Ujianto. "Pengorganisasian Komunitas Paska Bencana Studi Kasus: Pengorganisasian Komunitas yang dilakukan UPC/UPLINK di Aceh Paska Bencana Tsunami Tahun 2004." Talenta Conference Series: Local Wisdom, Social, and Arts (LWSA) 2, no. 1 (November 20, 2019): 1–9. http://dx.doi.org/10.32734/lwsa.v2i1.587.
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AbstractThis paper examines community organizing by the Urban Poor Consortium (UPC) / UPLINK in carrying out reconstruction in Aceh after the 2004 earthquake and tsunami disaster. The unprecedented magnitude of the disaster has prompted the Indonesian government to declare it as a national disaster and request for assistance from international agencies. As a response, many organizations at the national and international levels came to assist in the reconstruction of Aceh, with various program focuses and approaches. UPC / UPLINK also took part in the reconstruction stage, but rather with a distinct participatory approach. This paper aims to elaborate the approach UPC/UPLINK has taken in carrying out its post-disaster reconstruction programs in Aceh. This research mostly uses secondary data, namely from documents owned by UPC / UPLINK and data obtained through the internet, as well as primary data with deep interviews with UPC / UPLINK activists. This study found that appropriate approach, strategies, and method of community organizing, taken by UPC/UPLINK are important elements in which the survivors are able stand back on their feet and take ownership of in the post-disaster reconstruction process.
Makalah ini mengkaji pengorganisasian komunitas (community organizing) yang dilakukan Urban Poor Consortium (UPC)/UPLINK dalam melakukan rekonstruksi di Aceh paska bencana gempa dan Tsunami tahun 2004. Bencana gempa dan tsunami yang meluluhlantakkan Aceh pada tahun akhir 2004 telah mendorong pemerintah Indonesia menetapkannya sebagai bencana nasional dan meminta bantuan internasional dalam penanganannya. Setelah itu banyak organisasi di tingkat nasional maupun internasional datang membantu dalam rehabilitasi dan rekonstruksi Aceh, dengan berbagai fokus program dan pendekatan. UPC/UPLINK juga melaksanakan program rekonstruksi dengan pendekatan yang partisipatif dan komprehensif. Makalah ini menawarkan konsep pengorganisaian komunitas yang progresif untuk menganalisis pendekatan dan strategi yang digunakan UPC/UPLINK dalam melakukan program rekonstruksi Aceh paska bencana. Penelitian ini sebagian besar menggunakan data-data sekunder, yakni dari dokumen-dokumen yang dimiliki UPC/UPLINK maupun data yang diperoleh melalui internet, serta data primer dengan wawancara langsung dengan beberapa aktivivis UPC/UPLINK yang terlibat dalam program rekonstruksi paska tsunami di Aceh. Penelitian ini menemukan bahwa melalui strategi dan metode pengorganisasian komunitas yang tepat, proses rekonstruksi paska bencana di Aceh yang dilakukan oleh UPC/UPLINK bisa berjalan secara efisien, efektif, dan mencapai hasil yang mempunyai kualitas tinggi. Penelitian juga menyimpulkan bahwa dalam proses rekonstruksi paska bencana, amatlah penting mendudukkan masyarakat lokal (penyintas) sebagai subyek yang memimpin atau tulang punggung dalam proses rekonstruksi.
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Kim, Yonggang, and Yohan Kim. "Lyapunov Drift-Plus-Penalty-Based Cooperative Uplink Scheduling in Dense Wi-Fi Networks." Sensors 24, no. 8 (April 9, 2024): 2399. http://dx.doi.org/10.3390/s24082399.
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In high-density network environments with multiple access points (APs) and stations, individual uplink scheduling by each AP can severely interfere with the uplink transmissions of neighboring APs and their associated stations. In congested areas where concurrent uplink transmissions may lead to significant interference, it would be beneficial to deploy a cooperative scheduler or a central coordinating entity responsible for orchestrating cooperative uplink scheduling by assigning several neighboring APs to support the uplink transmission of a single station within a proximate service area to alleviate the excessive interference. Cooperative uplink scheduling facilitated by cooperative information sharing and management is poised to improve the likelihood of successful uplink transmissions in areas with a high concentration of APs and stations. Nonetheless, it is crucial to account for the queue stability of the stations and the potential delays arising from information exchange and the decision-making process in uplink scheduling to maintain the overall effectiveness of the cooperative approach. In this paper, we propose a Lyapunov drift-plus-penalty framework-based cooperative uplink scheduling method for densely populated Wi-Fi networks. The cooperative scheduler aggregates information, such as signal-to-interference-plus-noise ratio (SINR) and queue status. During the aggregation procedure, propagation delays are also estimated and utilized as a value of expected cooperation delays in scheduling decisions. Upon aggregating the information, the cooperative scheduler calculates the Lyapunov drift-plus-penalty value, incorporating a predefined model parameter to adjust the system accordingly. Among the possible scheduling candidates, the proposed method proceeds to make uplink decisions that aim to reduce the upper bound of the Lyapunov drift-plus-penalty value, thereby improving the network performance and stability without a severe increase in cooperation delay in highly congested areas. Through comprehensive performance evaluations, the proposed method effectively enhances network performance with an appropriate model parameter. The performance improvement is particularly notable in highly congested areas and is achieved without a severe increase in cooperation delays.
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Kurda, Reben. "Heterogeneous networks: Fair power allocation in LTE-A uplink scenarios." PLOS ONE 16, no. 6 (June 21, 2021): e0252421. http://dx.doi.org/10.1371/journal.pone.0252421.
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Effective management of radio resources and service quality assurance are two of the essential aspects to furnish high-quality service in Long Term Evolution (LTE) networks. Despite the base station involving several ingenious scheduling schemes for resource allocation, the intended outcome might be influenced by the interference, especially in heterogeneous scenarios, where many kinds of small cells can be deployed under the coverage of macrocell area. To develop the network of small cells, it is essential to take into account such boundaries, in particular, mobility, interference and resources scheduling a strategy which assist getting a higher spectral efficiency in anticipate small cells. Another challenge with small cellular network deployment is further analyzing the impact of power control techniques in the uplink direction for the network performance. With that being said, this article investigates the problem of interference in LTE-advanced heterogeneous networks. The proposed scheme allows mitigation inter-cell interference through fractional self-powered control performed at each femtocell user. This study analyzes a scheme with optimum power value that provides a compromise between the served uplink signal within unwanted interference plus noise ratio to enhance spectral efficiency in terms of throughput. In particular, the maximum transmit power for user equipment in uplink direction should be reviewed for small cells as a major contributor to the interference. The simulation results showed that the proposed fractional power control approach can outperform the traditional power control employed as a full compensation mode in small cell uplinks.
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Backfrieder, Christian, and Gerald Ostermayer. "Analysis of an Adaptive Switching Point for LTE TDD by Dynamic System-Level Simulations." International Journal of Electronics and Telecommunications 61, no. 2 (June 1, 2015): 171–78. http://dx.doi.org/10.1515/eletel-2015-0022.
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Abstract This paper introduces an LTE system level simulator and presents investigations of scenarios with differently balanced traffic emergence between uplink and downlink as well as inhomogeneous distribution of link direction asymmetry. In the TDD mode of LTE, duplexing is implemented via sharing the time domain between uplink and downlink users. This is done by different switching configurations, which offer varying capacity distributions between downlink and uplink, from a downlink-heavy configuration with 90 percent of the capacity in downlink direction to uplink heavy configurations with 60 percent uplink. We utilize the available capacity perfectly by adjusting the link configuration appropriately to traffic emergence. Performance gains when selecting a configuration appropriate to the arising traffic compared to usage of a static configuration with equally distributed capacity are investigated. In case of different configurations, additional interference can occur in neighbored cells due to distinct communication direction at the same time. We clarify the differences between these scenarios and quantify the gains and losses when the switching point between uplink and downlink is variable.
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Plets, D., W. Joseph, K. Vanhecke, G. Vermeeren, J. Wiart, S. Aerts, N. Varsier, and L. Martens. "Joint Minimization of Uplink and Downlink Whole-Body Exposure Dose in Indoor Wireless Networks." BioMed Research International 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/943415.
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The total whole-body exposure dose in indoor wireless networks is minimized. For the first time, indoor wireless networks are designed and simulated for a minimal exposure dose, where both uplink and downlink are considered. The impact of the minimization is numerically assessed for four scenarios: two WiFi configurations with different throughputs, a Universal Mobile Telecommunications System (UMTS) configuration for phone call traffic, and a Long-Term Evolution (LTE) configuration with a high data rate. Also, the influence of the uplink usage on the total absorbed dose is characterized. Downlink dose reductions of at least 75% are observed when adding more base stations with a lower transmit power. Total dose reductions decrease with increasing uplink usage for WiFi due to the lack of uplink power control but are maintained for LTE and UMTS. Uplink doses become dominant over downlink doses for usages of only a few seconds for WiFi. For UMTS and LTE, an almost continuous uplink usage is required to have a significant effect on the total dose, thanks to the power control mechanism.
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Gustavson, R. P., D. N. Page, and L. J. Miller. "Low cost uplink concepts." Acta Astronautica 35 (1995): 455–64. http://dx.doi.org/10.1016/0094-5765(94)00212-5.
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Jung, Bang, Sung Cho, and Dan Sung. "Uplink capacity improvement through orthogonal code hopping in uplink-synchronized CDMA systems." IEEE Transactions on Wireless Communications 8, no. 11 (November 2009): 5404–10. http://dx.doi.org/10.1109/twc.2009.081355.
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Gao, Ji Ke, De Min Zhang, and Fa Tang Chen. "Research on Uplink Semi-Persistent Scheduling in LTE System." Advanced Materials Research 791-793 (September 2013): 1952–56. http://dx.doi.org/10.4028/www.scientific.net/amr.791-793.1952.
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In LTE(Long Term Evolution) system, scheduling plays an important role in the process of allocating resource. LTE system puts forward semi-persistent scheduling (SPS) for new applications such as VoIP(Voice on Internet Protocol) and online games. Considering the problem of resource collision in SPS HARQ(Hybrid Automatic Repeat reQuest) process, we explore the relationship between uplink semi-persistent scheduling period and the number of semi-persistent transmissions, and propose two novel solutions. One is choosing specific uplink semi-persistent period for different uplink/downlink (UL/DL) configurations and the number of transmissions. The other is delaying collision processes for the configuration of small uplink period. The analysis proves that the two solutions can reduce the collision probability and improve the stability of LTE system.
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Matalatala, Michel, Margot Deruyck, Sergei Shikhantsov, Emmeric Tanghe, David Plets, Sotirios Goudos, Kostas E. Psannis, Luc Martens, and Wout Joseph. "Multi-Objective Optimization of Massive MIMO 5G Wireless Networks towards Power Consumption, Uplink and Downlink Exposure." Applied Sciences 9, no. 22 (November 19, 2019): 4974. http://dx.doi.org/10.3390/app9224974.
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The rapid development of the number of wireless broadband devices requires that the induced uplink exposure be addressed during the design of the future wireless networks, in addition to the downlink exposure due to the transmission of the base stations. In this paper, the positions and power levels of massive MIMO-LTE (Multiple Input Multiple Output-Long Term Evolution) base stations are optimized towards low power consumption, low downlink and uplink electromagnetic exposure and maximal user coverage. A suburban area in Ghent, Belgium has been considered. The results show that the higher the number of BS antenna elements, the fewer number of BSs the massive MIMO network requires. This leads to a decrease of the downlink exposure (−12% for the electric field and −32% for the downlink dose) and an increase of the uplink exposure (+70% for the uplink dose), whereas both downlink and uplink exposure increase with the number of simultaneous served users (+174% for the electric field and +22% for the uplink SAR). The optimal massive MIMO network presenting the better trade-off between the power consumption, the total dose and the user coverage has been obtained with 37 64-antenna BSs. Moreover, the level of the downlink electromagnetic exposure (electric field) of the massive MIMO network is 5 times lower than the 4G reference scenario.
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Larasati, Solichah Larasati, Khoirun Ni'amah, and Zein Hanni Pradana. "Analysis of 5G Network Performance in Line-of-Sight Conditions Using 3.3 GHz Frequency at Sawahan, Surabaya." Journal of Information Technology and Its Utilization 5, no. 2 (December 28, 2022): 31–40. http://dx.doi.org/10.56873/jitu.5.2.4892.
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This research is expected to be the beginning of the initial design for the implementation of 5G technology in Indonesia especially in Area Sawahan, Surabaya based on the coverage area with the frequency of 3.3 GHz. Performance analysis with line-of-sight (LOS) conditions using propagation model urban macro (uMa) according to the recommendation of 3GPP (3rd Generation Partnership Project) TR 38.901. This research based on four scenarios, outdoor-to-outdoor (O2O) for downlink and uplink, and outdoor-to-indoor (O2I) scenario for uplink and downlink. Performance of 5G network simulated using Atoll 3.4 and shown the pathloss values of 105.405 dB for uplink and 101.405 dB for downlink. The performance results in the O2O scenario for the uplink direction require 5 gNodeB and 8 gNodeB in the downlink direction. In the O2I scenario, the uplink direction requires as many as 6 gNodeB and the downlink direction as much as 9 gNodeB. The simulation parameters analyzed in this research are based on the signal strength received by the user (SS-RSRP) and signal quality (SS-SINR). The best result of SS-RSRP in the O2I uplink scenario is -89 dBm and the SS-SINR parameter in the O2O scenario is 0.93 dBm. These results show that in the city of Sawahan a 5G system can be applied.
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Liu, Jichao, Xu Zhao, Yubo Wang, Hao Liu, Yubing Zhang, Xin Wang, Jie Gan, and Dejian Li. "A Resource Optimization for Two-Step Random Access in 5G New Radio." Journal of Physics: Conference Series 2625, no. 1 (October 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 scheduling resource efficiency in cases of some RO unoccupied. To achieve higher utilization efficiency, this paper studies the reusing of the PUSCH slots and occasions fixed to RACH in MsgA. By detecting the preambles in RO before the corresponding PUSCH slots, the network acquires the occupancy of the RO. Then the PUSCH occasion (PO) in reserved PUSCH can be released, which conforms to the RO detection result. The release of the previously reserved PUSCH occasions can be rescheduled and reused by the user equipment (UE) for uplink data transmission. Hence more wireless resources can be scheduled in contrast to the existing allocation of uplink share channel in 2-step type random access. It suggests that using the method improves the efficiency of resource utilization.
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Yu, Bencheng, Zihui Ren, and Shoufeng Tang. "CSI-Impaired Beamforming Optimization for Dense MIMO Communication Networks." Electronics 11, no. 19 (October 8, 2022): 3225. http://dx.doi.org/10.3390/electronics11193225.
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This paper studied the robust beamforming for dense transmission systems with imperfect channel state information (CSI). The objective was to maximize the minimum signal to interference plus noise ratio (SINR) in the constraint of the per base station (BS) power. By performing the uplink–downlink duality theory, the referred non-convex optimization problem can be changed into the equivalent uplink decoupling optimization problem. Then, we proposed the instantaneous updating uplink–downlink power algorithm, which relies on instantaneous CSI for the finite system. For the massive MIMO system, to obtain the solution to the problem required for power to instantaneously update, we proposed the updating uplink–downlink power algorithm, which only requires statistical CSI, by applying the random matrix theory. The simulation results show the feasibility and effectiveness of our proposed algorithms.
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Kuo, Nai-Chung, and Ali M. Niknejad. "RF-Powered-Tag Intermodulation Uplink With Three-Tone Transmitter for Enhanced Uplink Power." IEEE Journal of Radio Frequency Identification 3, no. 2 (June 2019): 56–66. http://dx.doi.org/10.1109/jrfid.2019.2892939.
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Wang, Sheng, Xiao Yan Xue, Kai Xun Wang, and Shi Lei Zhu. "An Adaptive User Grouping Algorithm in Uplink CoMP System." Applied Mechanics and Materials 687-691 (November 2014): 3950–55. http://dx.doi.org/10.4028/www.scientific.net/amm.687-691.3950.
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Aiming at improving the uplink sum capacity of the CoMP (Cooperated Multiple Point) system, an adaptive user grouping algorithm is proposed based on the properties of users, in which the uplink CoMP system is regarded as a virtual MIMO system. The proposed algorithm firstly finds out the count of the groups that the users should be divided into, then divides the users into groups by their quantitative properties. Simulation results show that the proposed algorithm increases the sum capacity of uplink, and also proves the algorithm’s effectiveness.
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Park, Jaehyoung, Yonggang Kim, Gyungmin Kim, and Hyuk Lim. "Majority Voting-Based MAC Protocol for Exploiting Link-Layer Diversity in Wireless Networks." Sensors 21, no. 8 (April 12, 2021): 2706. http://dx.doi.org/10.3390/s21082706.
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In wireless local area networks (WLANs), the effect of interference signals between neighboring nodes increases as the number of wireless nodes using limited radio frequency resources in a limited space increases, which can significantly degrade the reliability of data transmission. In high-density WLANs, there can be several neighboring access points (APs) that can receive uplink transmission from a station. In conventional medium access control (MAC) protocols, uplink data frames containing errors or transmitted from a non-associated station are discarded at APs. Alternatively, we propose a MAC protocol using redundant wireless links between neighboring APs and the non-associated stations. In the proposed MAC protocol, we consider a centralized WLAN with a control node that performs error corrections of erroneous uplink data frames via a majority voting algorithm-based link-layer diversity scheme using uplink data received from multiple APs to increase the reliability of data transmission. In addition, we propose an adaptive carrier sensing ranging mechanism to improve the uplink network throughput in the proposed centralized WLAN system. Further, we conduct simulation studies and software-defined radio-based experiments to evaluate the performance of the proposed MAC protocol in various WLAN scenarios.
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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 (December 18, 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. Measuring and analyzing network performance to determine throughput using several supporting software, namely Tems Investigation, Tems Discovery and Gnet Track. There was an increase in the downlink throughput and uplink throughput values due to the implementation of CA compared to not using CA. The maximum Downlink Throughput value in the CA combination is greater than the Uplink Throughput. The maximum Downlink throughput value on CA 20+20Mhz is 9427kbps, while the Uplink value is 1133.28kbps. The maximum downlink throughput value on CA 20+15Mhz is 8272.24kbps, and the maximum uplink throughput value is 745kbps.
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Tan, Zhenkun, Jiao Wang, Yingxiu Kong, Sichen Lei, and Pengfei Wu. "An Effective Method for Enhancing Heterodyne Efficiency by Comparing the Effect of Degree of Polarization on an Uplink Path and a Downlink Path." Photonics 9, no. 11 (October 25, 2022): 798. http://dx.doi.org/10.3390/photonics9110798.
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By analyzing the effect of the degree of polarization (DoP) of the partially coherent Gaussian Schell-model (GSM) beam on a heterodyne system of an uplink path and a downlink path, we developed an innovative and noteworthy theory according to which σsy (signal beam waist radius in the y direction component) and δSyy (coherence length of the signal beam in the yy direction component) had a more significant impact on heterodyne efficiency and DoP than the turbulence term on uplink and downlink paths. Namely, the DoP and heterodyne efficiency of an uplink path are higher than that of a downlink path when σsy > 0.02 m or δSyy ≥ 0.03 m. This innovative rule provides an efficient way for increasing the heterodyne efficiency of a signal beam propagating along an uplink or a downlink path channel in satellite-ground communication links in free-space optical heterodyne detection communication.
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An, Zuoyu, Shaohua Wu, Tiange Liu, Jian Jiao, and Qinyu Zhang. "Scheduling Strategy Design Framework for Cyber–Physical System with Non-Negligible Propagation Delay." Entropy 23, no. 6 (June 4, 2021): 714. http://dx.doi.org/10.3390/e23060714.
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Cyber–physical systems (CPS) have been widely employed as wireless control networks. There is a special type of CPS which is developed from the wireless networked control systems (WNCS). They usually include two communication links: Uplink transmission and downlink transmission. Those two links form a closed-loop. When such CPS are deployed for time-sensitive applications such as remote control, the uplink and downlink propagation delay are non-negligible. However, existing studies on CPS/WNCS usually ignore the propagation delay of the uplink and downlink channels. In order to achieve the best balance between uplink and downlink transmissions under such circumstances, we propose a heuristic framework to obtain the optimal scheduling strategy that can minimize the long-term average control cost. We model the optimization problem as a Markov decision process (MDP), and then give the sufficient conditions for the existence of the optimal scheduling strategy. We propose the semi-predictive framework to eliminate the impact of the coupling characteristic between the uplink and downlink data packets. Then we obtain the lookup table-based optimal offline strategy and the neural network-based suboptimal online strategy. Numerical simulation shows that the scheduling strategies obtained by this framework can bring significant performance improvements over the existing strategies.
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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 stressing the importance of emulating full bidirectional channel and proposing possible directions to implement uplink channels in the literature. Nevertheless, there is no currently published work reporting an experimental validation of such concepts. In this paper, a general framework to emulate bidirectional channels for time division duplexing (TDD) and frequency division duplexing (FDD) communication systems is proposed. The proposed technique works for MPAC setups with arbitrary uplink and downlink probe configurations, that is, possibly different probe configurations (e.g., number of probes or their configurations) in the uplink and downlink. The simulation results are further supported by measurements in a practical MPAC setup. The proposed algorithm is shown to be a valid method to emulate bidirectional spatial channel models.
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Liu, Chun-Tai, and Jen-Yi Pan. "Optimal Beamwidth for Maximizing Uplink Coverage Probability in Quasi Earth-Fixed LEO Satellite Communication System." Electronics 13, no. 7 (April 3, 2024): 1349. http://dx.doi.org/10.3390/electronics13071349.
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Satellite communication is proposed to fulfill the ubiquitous coverage for next-generation wireless networks. Considering the propagation delay and path loss, low-earth orbit (LEO) satellites are widely adopted. However, since the beam boresight directions become close in quasi-earth-fixed cells (QEFC) scenarios at low elevation angles, the interference increases and causes low communication quality. This paper introduces the optimal beamwidth maximizing uplink coverage probability scheme for quasi-earth-fixed cells in LEO satellite communication systems. The proposed scheme dynamically adjusts the beamwidth to achieve max uplink coverage probability at different elevation angles. The simulation results show that the proposed scheme matches the exhaustive search method in different scenarios and target signal-to-interference-plus-noise ratios. Furthermore, the proposed scheme significantly mitigates interference and improves the uplink coverage probability. Compared with the 3GPP setting, the proposed scheme improves the uplink coverage probability by 0.93 at time 100 s, and compared with the three-color frequency reuse, the proposed scheme improves the uplink coverage probability by 0.195 at time 100 s. The dynamic beamwidth and boresight direction adjustments enable the satellite to maintain seamless and reliable communication services across a wide range of operating conditions, ultimately realizing the goal of ubiquitous communications in the QEFC LEO satellite system.
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Maejima, Hironori, Susumu Sasaki, Chiho Akagi, Harunobu Kobayashi, and Yoshiaki Ohkami. "Uplink Radio Frequency Signal Fluctuations." Journal of Spacecraft and Rockets 50, no. 2 (March 2013): 352–57. http://dx.doi.org/10.2514/1.a32185.
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Pan, Zhipeng, Junshan Luo, Jing Lei, Lei Wen, and Chaojing Tang. "Uplink Spatial Modulation SCMA System." IEEE Communications Letters 23, no. 1 (January 2019): 184–87. http://dx.doi.org/10.1109/lcomm.2018.2882813.
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Dias, José, and António Grilo. "LoRaWAN multi-hop uplink extension." Procedia Computer Science 130 (2018): 424–31. http://dx.doi.org/10.1016/j.procs.2018.04.063.
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Rim, Minjoong, and Chung Kang. "Uplink Non-Orthogonal Multiple Access with Channel Estimation Errors for Internet of Things Applications." Sensors 19, no. 4 (February 21, 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 errors, assuming that quadrature phase shift keying (QPSK) modulation is used. When pilot signals are superimposed onto the shared resources and a large number of devices perform random accesses concurrently to a single resource of the base station, the channels might not be accurately estimated even in high SNR environments. In this paper, we propose an uplink NOMA scheme, which can alleviate the performance degradation due to channel estimation errors.
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Sulaeman, Enceng, Yaya Sulaeman, and Asep Yudi Hercuadi. "Desain dan Implementasi Duplekser dengan Metoda Pseudo-Interdigital untuk Uplink dan Downlink LTE." Jurnal Elektronika dan Telekomunikasi 13, no. 2 (June 29, 2016): 73. http://dx.doi.org/10.14203/jet.v13.73-80.
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Duplekser merupakan perangkat yang dapat mengisolasi receiver dari transmitter saat keduanya saling berbagi antena yang sama, digunakan agar komunikasi bisa berjalan secara full duplex. Ada dua metode transmisi duplex yaitu frequency division duplex (FDD) dan time division duplex (TDD). FDD merupakan teknik duplex yang menggunakan dua frekuensi yang berbeda untuk melakukan komunikasi dalam dua arah, sedangkan TDD menggunakan frekuensi tunggal dan frekuensi tersebut digunakan oleh semua kanal untuk melakukan pengiriman dan penerimaan data. Gabungan dua bandpass filter dengan metoda pseudo-interdigital untuk aplikasi LTE (long term evolution). Metode ini lebih unggul dibandingkan duplekser dengan metoda hybrid. Duplekser bekerja pada FDD LTE band ke-7 yaitu frekuensi uplink 2500-2570 MHz dan downlink 2620-2690 MHz. Dari hasil pengukuran diperoleh sebagai berikut: nilai frekuensi center pada uplink 2639 MHz dan pada downlink 2659 MHz, insertion loss pada uplink 1,561 dB dan downlink 1,74 dB, bandwidth ±70 MHz, isolasi 23,03 dB, serta nilai return loss 23,5 dB pada uplink dan downlink 23,45 dB.
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Chen, Da Jiang, Zhen Qin, Rui Jing Wang, and Zhi Guang Qin. "Scaling Wireless Uplink Capacity with Multi-User Beamforming." Applied Mechanics and Materials 577 (July 2014): 961–64. http://dx.doi.org/10.4028/www.scientific.net/amm.577.961.
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Due to the fact that the wireless spectrum is limited but the wireless demand can grow unlimited, how to improve the wireless capacity becomes one of the hot topics in wireless network field. In this paper, we focus on the scenario of busy wireless environment, and present a protocol with multiple user beamforming. The protocol enables a network to scale its uplink throughput with the number of access points. Theoretical and experimental results show that our protocol have higher uplink throughput compared with 802.11. Moreover, our protocol is the first method that shows that linear scaling of uplink throughput with the number of access points is possible.
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Ferreira, Marcus V. G., and Flávio Henrique Teles Vieira. "Delay minimization based uplink resource allocation for device-to-device communications considering mmWave propagation." PeerJ Computer Science 7 (April 8, 2021): e462. http://dx.doi.org/10.7717/peerj-cs.462.
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This paper addresses the resource allocation problem in multi-sharing uplink for device-to-device (D2D) communication, one aspect of 5G communication networks. The main advantage and motivation in relation to the use of D2D communication is the significant improvement in the spectral efficiency of the system when exploiting the proximity of communication pairs and reusing idle resources of the network, mainly in the uplink mode, where there are more idle available resources. An approach is proposed for allocating resources to D2D and cellular user equipments (CUE) users in the uplink of a 5G based network which considers the estimation of delay bound value. The proposed algorithm considers minimization of total delay for users in the uplink and solves the problem by forming conflict graph and by finding the maximal weight independent set. For the user delay estimation, an approach is proposed that considers the multifractal traffic envelope process and service curve for the uplink. The performance of the algorithm is evaluated through computer simulations in comparison with those of other algorithms in the literature in terms of throughput, delay, fairness and computational complexity in a scenario with channel modeling that describes the propagation of millimeter waves at frequencies above 6 GHz. Simulation results show that the proposed allocation algorithm outperforms other algorithms in the literature, being highly efficient to 5G systems.
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Li, Ting. "The Effects of RB Usage on Single User Rate in TD-LTE." Advanced Materials Research 981 (July 2014): 478–81. http://dx.doi.org/10.4028/www.scientific.net/amr.981.478.
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Resource Block (RB) allocation effects network coverage and throughput. The impact principles are analyzed in theory. Exist TD-LTE network data is collected, organized and analyzed. The results show that the effects of RB allocation on user rate in downlink is greater than uplink and uplink RB usage is more stable.
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Chen, Hua-Min, Siyu Huang, Peng Wang, Tao Chen, Chao Fang, Shaofu Lin, and Fan Li. "A Joint Positioning Algorithm in Industrial IoT Environments with mm-Wave Communications." Symmetry 14, no. 7 (June 28, 2022): 1335. http://dx.doi.org/10.3390/sym14071335.
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With the real restriction of packet size and transmission power, a joint UL-AoA (Uplink Angle of Arrival) and UL-TDOA (Uplink Time Difference of Arrival) positioning method is discussed for the Industrial Internet of Things (IIoT), which demands high accuracy of position information. One motivation of the UL positioning method of IIoT is an asymmetric network and uplink traffic is dominant in most identified scenarios. Further, IIoT sensors are power limited for low cost, compared to the transmission power of base stations and other normal user equipment. This paper considers an environment of a 5G-enabled IIoT network with massive Multiple input multiple output (MIMO) antennas, beamforming and millimeter operating bands. After reviewing downlink positioning reference signal (PRS) and uplink sounding reference signal for positioning (SRS-Pos), a general system model and a theoretical localization problem is derived under the joint positioning method. The provided simulation results help to investigate the impact of system configurations on positioning measurements. Further, through the test in this paper, it is proved that joint positioning outperforms that of the time only or angle only method.
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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 (September 15, 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. The performance of the uplink channel for a four-element MIMO terminal array antenna is evaluated using a two-dimensional bidirectional fading emulator. The results show that the measured correlation coefficients between the signals received via the uplink channel at the BS antennas using the proposed method are in good agreement with the BS correlation characteristics calculated using Monte Carlo simulation and the theoretical formula, thereby confirming the effectiveness of the proposed method.
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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 (March 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 that delay in WiMAX networks for LOS-NLOS (Line of sight - No n line of sight) mobile conditions is largely contributed by uplink direction (60-90% of RTT (Round trip time)) whereas downlink directions hardly ever exceeds 40ms. We show that enabling MIMO-A(Multiple Input Multiple Output) can decrease delays by 100ms in NLOS conditions and decrease delay variation by up to 90%. For each of tests we have presented exact probabilities of particular modulations involved based on channel realizations.
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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 (January 6, 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-problems including power allocation and channel assignment. It is proved that the objective function of power control is a convex function, in which the optimal transmission power can be obtained. The Hungarian algorithm is developed to achieve joint uplink and downlink channel assignment. The proposed scheme can improve the system capacity performance and increase the spectrum efficiency. Numerical results reveal that the performance of the proposed scheme of jointly uplink and downlink is better than that of the schemes for independent allocation.
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Saleh, Salah, and Martin Fleury. "Options for WiMAX Uplink Media Streaming." International Journal of Mobile Computing and Multimedia Communications 2, no. 2 (April 2010): 49–66. http://dx.doi.org/10.4018/jmcmc.2010040104.
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IEEE 802.16e (mobile WiMAX) uplink behavior is a relatively neglected area of investigation, but emerging interactive media services have highlighted the need for closer investigation of uplink issues. In this simulation study of uplink queue management, the authors found that media streaming by TCP-Friendly Rate Control (TFRC) has advantages. However, temporal behavior of the queuing disciplines exhibits oscillations in buffer occupancy with build-up of delay during video streaming. This paper suggests a possible remedy lies in the choice of the more complex H.264/AVC Main profile, but this will impact upon mobile devices. It was also found that WiMAX video delivery is sensitive to choice of transmission frame size.
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Martinez, Noelia. "Atmospheric Pre-Compensation of Ground-to-Space Communications with Adaptive Optics: Past, Present and Future—A Field Review." Photonics 10, no. 7 (July 24, 2023): 858. http://dx.doi.org/10.3390/photonics10070858.
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Conventionally used in astronomy, adaptive optics (AO) systems measure and correct for turbulence and, therefore, have the capability to mitigate the impact of the atmosphere on the ground-to-space communication links. Historically, there have been two main streams, respectively, advocating to use or not use adaptive optics on optical communications. This paper aims to present a comprehensive review of the field of AO-based uplink pre-compensation. It will cover the technical challenges associated with uplink correction, provide an overview of the state-of-the-art research and demonstrations from the early days to the present, and discuss the future prospects of AO-based uplink pre-compensation and potential trade-offs between performance, cost, and operational considerations.
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Pugh, Christopher J., Jean-Francois Lavigne, Jean-Philippe Bourgoin, Brendon L. Higgins, and Thomas Jennewein. "Adaptive optics benefit for quantum key distribution uplink from ground to a satellite." Advanced Optical Technologies 9, no. 5 (November 26, 2020): 263–73. http://dx.doi.org/10.1515/aot-2020-0017.
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AbstractFor quantum communications, the use of Earth-orbiting satellites to extend distances has gained significant attention in recent years, exemplified in particular by the launch of the Micius satellite in 2016. The performance of applied protocols such as quantum key distribution (QKD) depends significantly on the transmission efficiency through the turbulent atmosphere, which is especially challenging for ground-to-satellite uplink scenarios. Adaptive optics (AO) techniques have been used in astronomical, communication, and other applications to reduce the detrimental effects of turbulence for many years, but their applicability to quantum protocols, and their requirements specifically in the uplink scenario, is not well established. Here, we model the effect of the atmosphere on link efficiency between an Earth station and a satellite using an optical uplink and how AO can help recover from loss due to turbulence. Examining both low Earth orbit and geostationary uplink scenarios, we find that a modest link transmissivity improvement of about 3 dB can be obtained in the case of a coaligned downward beacon, while the link can be dramatically improved, up to 7 dB, using an offset beacon, such as a laser guide star. AO coupled with a laser guide star would thus deliver a significant increase in the secret key generation rate of the QKD ground-to-space uplink system, especially as reductions of channel loss have a favourably nonlinear key-rate response within this high-loss regime.
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Han, Shujun, Xiaodong Xu, Litong Zhao, and Xiaofeng Tao. "Joint time and power allocation for uplink cooperative non-orthogonal multiple access based massive machine-type communication Network." International Journal of Distributed Sensor Networks 14, no. 5 (May 2018): 155014771877821. http://dx.doi.org/10.1177/1550147718778215.
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Non-orthogonal multiple access is an essential promising solution to support large-scale connectivity required by massive machine-type communication scenario defined in the fifth generation (5G) mobile communication system. In this article, we study the problem of energy minimization in non-orthogonal multiple access–based massive machine-type communication network. Focusing on the massive machine-type communication scenario and assisted by grouping method, we propose an uplink cooperative non-orthogonal multiple access scheme with two phases, transmission phase and cooperation phase, for one uplink cooperative transmission period. Based on uplink cooperative non-orthogonal multiple access, the machine-type communication device with better channel condition and more residual energy will be selected as a group head, which acts as a relay assisting other machine-type communication devices to communicate. In the transmission phase, machine-type communication devices transmit data to the group head. Then, the group head transmits the received data with its own data to base station in the cooperation phase. Because the massive machine-type communication devices are low-cost dominant with limited battery, based on uplink cooperative non-orthogonal multiple access, we propose a joint time and power allocation algorithm to minimize the system energy consumption. Furthermore, the proposed joint time and power allocation algorithm includes dynamic group head selection and fractional transmit time allocation algorithms. Simulation results show that the proposed solution for uplink cooperative non-orthogonal multiple access–based massive machine-type communication network outperforms other schemes.
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Ullah, Arif, Ziaul Haq Abbas, Fazal Muhammad, Ghulam Abbas, and Sunghwan Kim. "Uplink Performance Analysis of User- Centric Small Cell Aided Dense HCNets With Uplink-Downlink Decoupling." IEEE Access 8 (2020): 148460–74. http://dx.doi.org/10.1109/access.2020.3015915.
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Zhang, Bing, Ze Hua Gao, Feng Gao, and Da Hsiung Hsu. "An Adaptive Optimization Scheme for IEEE 802.11 DCF to Achieve Fairness Between Uplink and Downlink Flows." Applied Mechanics and Materials 198-199 (September 2012): 567–71. http://dx.doi.org/10.4028/www.scientific.net/amm.198-199.567.
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The data traffic needed to be transferred by APs is much more than the other STAs in the IEEE802.11 DCF networks. However, APs access the wireless link with the same priority as STAs, and thus the throughput between uplink and downlink is of great injustice. In this paper, an adaptive optimization scheme is proposed to achieve fairness between uplink and downlink flows. APs monitor the growing real-time data traffic, and when the network system is in heavy traffic, APs could adaptively adjust the contention window to achieve fairness. Detailed simulation results show that the scheme can effectively adapt to various networks different in data flow numbers and packet size, and consequently achieve fairness between uplink and downlink flows with the total throughput increased.
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N. Sirhan, Najem, and Manel Martinez-Ramon. "LTE Cellular Networks Packet Scheduling Algorithms in Downlink and Uplink Transmission: A Survey." International Journal of Wireless & Mobile Networks 14, no. 2 (April 30, 2022): 1–15. http://dx.doi.org/10.5121/ijwmn.2022.14201.
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This survey paper provides a detailed explanation of Long Term Evolution (LTE) cellular network’s packet scheduling algorithms in both downlink and uplink directions. It starts by explaining the difference between Orthogonal Frequency Division Multiple Access (OFDMA) that is used in downlink transmission, and Single Carrier – Frequency Division Multiple Access (SC-FDMA) is used in uplink. Then, it explains the difference between the LTE scheduling process in the donwlink and uplink through explaining the interaction between users and the scheduler. Then, it explains the most commonly used downlink and uplink scheduling algorithms through analyzing their formulas, characteristics, most suitable conditions for them to work in, and the main differences among them. This explanation covers the Max Carrier-toInterference (C/I), Round Robin (RR), Proportional Fair (PF), Earliest Deadline First (EDF), Modified EDF-PF, Modified-Largest Weighted Delay First (M-LWDF), Exponential Proportional Fairness (EXPPF), Token Queues Mechanism, Packet Loss Ratio (PLR), Quality Guaranteed (QG), Opportunistic Packet Loss Fair (OPLF), Low Complexity (LC), LC-Delay, PF-Delay, Maximum Throughput (MT), First Maximum Expansion (FME), and Adaptive Resource Allocation Based Packet Scheduling (ARABPS). Lastly, it provides some concluding remarks.