Reuse Factor Research Articles

Intelligent Transition Mechanisms in 5G DSA: A Logistic Regression Approach to Reuse Factor Adaptation

This research work use Dynamic Spectrum Allocation (DSA) embedded in 5G technology and logistic regression as Machine learning tool to alter the reuse factor of assigned telecommunication frequency to a more robust and reliable frequency. The switch from a frequency reuse of 3 (FR3) to a frequency reuse of 7 (FR7) was considered. Historical data generated from a Telecommunications Company in Nigeria was utilised. This data consist of User throughput and the number of user equipment to assess traffic load and congestion from user equipment (UE).The ideal was meant to determine the probability at which a switch or transition between reuse factors will occur. With a resolution threshold of 50 users which was set to commence the shift from reuse factor of 3 when the number of users have reached its threshold of 50 to reuse factor of 7 when the number of users exceeds 50 and above. The objective of this combination is to increase spectrum utilisation efficiency and network flexibility, by optimising spectrum resources in densely populated urban areas. This study explains the mechanisms and also demonstrate how logistic regression with DSA will enhance network capacity of wireless communication systems. The logistic regression model proved effective in making intelligent decisions regarding the transition from reuse factor 3 to reuse factor 7 as it was able to accommodate up to 79 users as against the threshold value of 50 users when running under the reuse factor of 3. With a high accuracy of 91.9% and balanced precision-recall values, it showcased its ability to optimize spectral efficiency.

Analysis of 5G Capacity in Line-Of-Sight Condition of Urban Macro (UMa) Using 3.5 GHz Frequency

This study is projected to be the initial design for the implementation of 5G technology, particularly in the Urban Macro (UMa) scenario, with a frequency of 3.5GHz and a bandwidth of 100 MHz. 3GPP (3rd Generation Partnership Project) TR 38.901 recommends performing performance analysis with line-of-sight (LOS) situations using the propagation model urban macro (uMa). In this study, 100 users are distributed at random distances to examine system capacity using the frequency reuse factors K = 1/3 and K = 1/7. According to the calculation results, this study demonstrates that system capacity is dependent on user distribution arrangement and the frequency reuse factor approach used. A high frequency reuse factor increases bandwidth efficiency and yields more optimum capacity. Furthermore, distributing users near the base station will boost capacity.

Turning Data Center Waste Heat into Energy: A Guide to Organic Rankine Cycle System Design and Performance Evaluation

This study delves into the adoption of the organic Rankine cycle (ORC) for recovering waste heat from data centers (DCs). Through a literature review, it examines energy reuse with a focus on electric power generation, the selection of working fluids, and system design principles. The objective is to develop a thorough framework for system design and analysis, beginning with a quantity and quality investigation of waste heat available. Air cooling systems, chosen often for their simplicity, account for about 70% of used cooling methods. Water cooling demonstrates greater effectiveness, albeit less commonly adopted. This study pays close attention to the selection of potential working fluids, meticulously considering the limitations presented by the available sources of heat and cold for vaporization and condensation, respectively. It reviews an ORC-based system setup, incorporating fluid streams for internal processes. The research includes a conceptual case study where the system is designed and simulations are conducted in the DWSIM environment. The simulation model considers hot air or hot liquid water returning from the data center cooling system for ORC working fluid evaporation. Ambient water serves for condensing, with pentane and isopentane identified as suitable organic fluids. Pentane assures ORC net electric efficiencies ranging between 3.1 and 7.1% when operating pressure ratios increase from 2.8 to 6.4. Isopentane systems, meanwhile, achieve efficiencies of 3.6–7.0% across pressure ratios of 2.7–6.0. Furthermore, the investigation provides key performance indicators for a reference data center in terms of power usage effectiveness (PUE), energy reuse factor (ERF), energy reuse effectiveness (ERE), and greenhouse gas (GHG) savings. This study concludes with guidelines for system analysis, including exergy considerations, and details the sizing process for evaporators and condensers.

Performance analysis of massive MIMO using various transmit precoding schemes for a wireless network

SummaryAn evaluation of various transmit precoding schemes is proposed in this thesis on basis of spectral efficiency (SE) of massive MIMO (m‐MIMO) system in 2 GHz spectrum. The present generation of wireless networks must be rethought due to the rapidly rising user base, huge volume data transfer, wide coverage requirement, and exponential rise in data rate. 5G mobile network includes a multi‐fold increase in network capacity, energy conservation, decreased latency, higher coverage probability, and a seamless connection. m‐MIMO has provided good solution for enhancing the data rate with the coverage, overcoming the effects of multipath fading and has also increased diversity of the system. Massiveness of MIMO system along with 5G network is the key technology to address the issue of SE, throughput, improvement of QoS (quality of service), coverage probability, power delay profile, diversity simulation, energy efficiency, and improvement in bit error rate. Parameters such as SE, throughput, and coverage probability are important for any communication system, and their improvement can increase overall capacity of cellular network system and could meet the requirement of upcoming demand for mobile network. The research paper is focused on performance analysis of m‐MIMO with reference to the SE of various transmit precoding schemes. Simulation results show that SE provided by M‐MMSE (multi‐cell minimum mean‐squared error) technique of precoding ranks highest for the same number of antennas and pilot reuse factor as compared to other schemes.

Optimum Base Station Antenna Tilt Angle for Inter-Cell Interference Limited Mobile Cellular System

This paper investigates the effect of base station (BS) antenna tilt angle on the performance of LTE-Advanced physical layer downlink channel in Inter-Cell Interference (ICI) limited scenario for five cell ranges, two carrier frequencies, and two BS antenna heights. The cellular system is deployed following the 3GPP hexagonal grid with a frequency reuse factor of one and three sectors per site. An urban based 3D ray-tracing tool is used to model the wireless channel for many BS and user equipment (UE) links. System performance is evaluated in terms of Signal power to Interference plus Noise power Ratio (SINR), received signal power, received interference power, achievable throughput (THR), Average Spectrum Efficiency (ASE) and UEs outage probability. The objective is to find the BS antenna tilt angle that provides the maximum ASE, minimum UEs outage probability, or optimum ASE and UE outage probability. The obtained simulation results unveil that the maximum ASE occurs at a tilt angle where the mean of the SINR is maximum and the mean of rms delay spread is minimum, while the minimum UEs outage occurs at a tilt angle where the received signal power is maximum. This is an important finding to facilitate the planning and the deployment of cellular system in the presence of ICI. Moreover it is found that the optimum tilt angles decrease as the cell range increase and BS antenna height decrease. The results also show that these optimum tilt angles are independent of the carrier frequency.

Innovative Approach of Spectral Efficiency Optimization over Various Pilot Reuse Factors

The Massive MIMO with TDD is breakthrough technology for spectral efficiency gains. The CSI is essential for spectral efficiency gains and CSI can be obtained by channel estimation methods. The channel estimation methods employ known pilot s sequences to estimate the channel before actual data transmission. However, the channel coherence is time and frequency limited, which reflects the trade-off between the resources available for pilots and those available for data in coherent block for transmission. The pilot sequences reuse in other cells can reduce pilot overhead, called pilot reuse. However potential interference is introduced, by pilot reuse, in the channel estimation phase, called pilot contamination. The aim is to determine optimum pilot reuse factor for better SE using low computational complexity estimation method. The sum averaged SE has been obtained for pilot reuse factor 1, 2, 4, 8 and 16 using MMSE, EW-MMSE and LS channel estimation methods. The obtained results reveals that the difference between values of SEs for f=1 to f=2 to f=4 is very low and performance difference between estimators decreases as pilot reuse factor increases, which allows to use LS estimator to get performance almost equal to MMSE with less computational complexity. Also, the pilot reuse factor f=4 found optimum among all for given constraint.

Optimal Coverage of Full Frequency Reuse in FFR Networks in Relation to Power Scaling of a Base Station.

As a strategy to coordinate inter-cell interference in cellular networks, a fractional frequency reuse (FFR) system is proposed, in which the frequency bandwidth is split into two orthogonal bands; users staying near the center of a FFR cell use the band with a frequency reuse (FR) factor of one (i.e., full FR), and users located close to the cell edge utilize the band with a FR factor greater than one (i.e., partial FR). Full FR coverage, which identifies full FR and partial FR regions (that is, near-center and near-edge regions) within a FFR cell, has a crucial effect on system performance. Some of the authors of this paper recently investigated the optimization of full FR coverage to maximize system throughput. They analytically showed that under the constraint of satisfying a specified target outage probability, the optimal full FR coverage is a non-increasing function of base station power when all base station powers in the cellular network are scaled at an equal rate. Interestingly, in this paper, it is proven that as the power of a single base station is scaled, the optimal full FR coverage in that cell is a non-decreasing function of base station power. Our results provide useful insight into the design of full FR coverage in relation to the transmit power of a base station. It gives a deeper understanding of the intricate relationship between important FFR system parameters of base station power and full FR coverage.

A realistic view on heat reuse from direct free air-cooled data centres

This paper examines the opportunities to reuse excess heat from direct free air-cooled data centres without incorporating heat pumps to upgrade the heat. The operation of a data centre in northern Sweden, Luleå, was simulated for a year. It was established that heat losses through the thermal envelope and from the humidification of the cooling airflow influenced the momentary energy reuse factor, iERF, with up to 7%. However, for the annual energy reuse factor, ERF, the heat losses could be neglected since they annually contributed to an error of less than 1%.It was shown that the ideal heat reuse temperature in Luleå was 13, 17, and 18 °C with an exhaust temperature of 30, 40 and 50 °C. The resulting ERF was 0.50, 0.59 and 0.66, meaning that a higher exhaust temperature resulted in potentially higher heat reuse. It could also be seen that raising the exhaust temperature lowered the power usage effectiveness, PUE, due to more efficient cooling.Using heat reuse applications with different heat reuse temperatures closer to the monthly average instead of an ideal heat reuse temperature for the whole year improved the ERF further. The improvement was 11–31% where a lower exhaust temperature meant a higher relative improvement.

Impact of Circuit Power on the Energy Efficiency of Massive Multiple-Input Multiple-Output (MIMO) Cellular Systems

Massive multiple-input multiple-output (MIMO) systems are designed to increase data capacity systems. However, there are growing social and economic concerns in developing these communication technologies. Energy efficient systems are desirable for these systems considering the costs and minimizing resources. Thus, the optimization of these approaches is significant in the advancement of green communication. This paper converges on the circuit power in modelling massive MIMO systems. Specifically, to apply various power consumption of the transceiver chains, to determine the desired power of the base station value for maximum energy efficiency, and to define the effects of a realistic circuit power consumption model in Massive MIMO systems. Mathematical models were developed, and the corresponding codes were simulated using MATLAB. Different processing schemes were also studied, namely, maximum ratio transmission/maximum ratio combining, and zero forcing for the perfect and imperfect single-cells scenario. In contrast, multiple cells consider different re-use factors. As observed, a low power wattage consumption of transceiver chains and base stations is desired to produce a more remarkable relative change in energy efficiency. Local oscillators' power usage is also recommended to be low wattage. Low-power systems utilize low energy consumption but not disregarding higher energy efficiency. Other factors in data throughput – bandwidth, transmit power, noise power spectral density, and path loss, can be studied to optimize energy-efficient massive MIMO systems.

Energy consumption reduction in OFDMA wireless sensor networks in existence of interference hazards

Energy consumption reduces Wireless Sensor Network’s (WSN’s) lifetime. Hence, this paper addresses energy saving problematic in cooperative Orthogonal Frequency Division Multiplexing Access (OFDMA) systems for WSNs (COFDMA-WSN). Analytical handlings are implemented. The performance improvement of COFDMA-WSNs is executed by considering two different COFDMA-WSNs schemes. These schemes represent classical COFDMA-WSNs and Relay Supported (R-S) COFDMA-WSNs. Additionally, there are different pondered configurations due to these schemes. These configurations denote classical OFDMA network with classical WSN, R-S OFDMA network with classical WSN, classical OFDMA network with R-S WSN, and R-S OFDMA network with R-S WSN. Moreover, each configuration is applied with four different fractional frequency reuse (FrFR) techniques. These techniques represent strict (St) FrFR technique with Frequency Reuse Factor (FReF) = 3, St FrFR technique with FReF = 4, sectored (Sc) FrFR technique and soft frequency reuse (SoFR) technique. Consequently, there are sixteen different patterns of COFDMA-WSNs are considered. Moreover, closed-form terms (CFTs) for cluster-head’s (C-H’s) signal to interference ratio (SIR) and sensor node’s (SN’s) SIR are presented. Additionally, different metrics are evaluated to contrast the performance of altered patterns using the obtained CFTs. The outcomes demonstrate, that St FrRF4 system outperforms other systems in prime and ensuing links. The cause of this outcome can be credited, to the frequency reuse process decrement due to FReF increment. As a result, the interference sources decrease. Hence, the interfering signals drop. Consequently, St FrRF4 system achieves the highest values of SIR. Moreover, St FrRF3 technique has the second usage priority in the prime link. But, it losses this preference in the ensuing link and SoFR technique that applied in the fourth configuration takes this significance. The work outcomes attain much higher C-H's and SN’s SIR improvements. Accordingly, the packet transmission and protocol behaviour are enhanced. So, the energy consumption is reduced. Consequently, WSN’s lifetime is maximized.

The Effect of Pilot Reuse Factor on Massive MIMO Spectral Efficiency

Due to their much increased spatial resolution and array gain, large-scale antenna arrays have the potential to significantly enhance the spectral efficiency of wireless systems. Recent research in the area of massive Multiple-Input Multiple-Output (MIMO) antennas shows that user channels are enhanced as the number of antennas at the Base Stations (BSs) rises, allowing achieving high signal improvement with minimum inter-user interference. The combined effects of the pilot reuse factor and the BS number of antennas on average overall spectral efficiency in huge MIMO antennas will be investigated. To examine the SE of these receivers, several channel estimators will be utilized, including LMMSE, ZF, and MR methods. Theoretically, BS could offer a substantially higher average total SE if it had more antennas.

Performance analysis of downlink massive MIMO system with precoding techniques and pilot reuse factor

Performance analysis of downlink massive MIMO system with precoding techniques and pilot reuse factor

User perspectives on reuse of construction products in Norway: Results of a national survey

Construction industry is one of the main contributors to the world's emissions and material footprints. Reuse of construction products is one way to lower the sector's embodied emissions and increase resource utilisation. The aim of this study is to identify the main drivers and challenges affecting reuse of construction products as well as assess success factors, reuse potential, and potential measures which should be considered to overcome these obstacles. An online national survey was conducted on reuse of construction products among actors from the Norwegian construction industry. The valid responses obtained from 260 participants show ‘emission reduction’ as the most important driver for reuse of construction products by all user groups. Even if regulatory and economic components were listed under drivers in the survey questions, they were considered as barriers rather than drivers by some of the respondents. All user groups, except suppliers of reused products, rated ‘lack of documentation’ as the most important barrier, and ‘good planning’ as the most important success factor. Suppliers of reused products rated ‘high cost’ and ‘good planning’ as the most challenging and the most important success factor for reuse, respectively. The findings also reveal different perceptions and levels of optimism among actors. Most respondents were optimistic about availability of reusable products (within less than 5 y), but least optimistic about finding cheaper reusable products in the near future (assuming it might take 9 to 17 y). Laws and regulations, testing, documentation and certification, and economic subsidies are mentioned as the top three measures to address the current barriers. Concerning the definition of the term ‘Reuse’, the findings indicate a lack of common understanding – and the need to create a clear description and a harmonised definition. The findings from the study show the need to take several actions to address the current challenges of reuse.

A Proposed Analytical Inter-Cell Interference Model for Mobile Cellular Systems with Isotropic Antenna

4G and beyond cellular systems intend to use a frequency reuse factor of one with three sectors per BS site. This configuration leads to an increase in inter-cell interference (ICI). Thus, ICI modeling is very necessary to design and analyze any cellular system. The impact of ICI is modeled analytically in this paper. The effect of six interfering BS sites surrounding the serving BS is examined. The ICI is first mathematically modeled as a function of BS-UE distance for several environments based on pathloss exponent and then validated using an explicit simulation model. Secondly, the results obtained from the proposed model and the explicit simulation model are compared. The comparisons showed good agreement between the results of the proposed model and the simulation model. The mathematical model is convenient to the standardized ITU-R model and has the flexibility to apply any antenna patterns that is compatible with these international models. Furthermore, this model enables ICI estimation by deploying the serving BS cell only without the need to deploy the surrounding nine interfering cell. This has positive impact on reducing the time required for system level simulation.

Further Research on Frequency Allocation (19-Cell System) Method based on IFR and FFR

Many of the most advanced technology has a basic need for efficient telecommunication. In order to achieve this goal, the team should allocate those frequency channels in an intelligent way so that the interference can be reduced to the maximum extent. Here the team introduced a new method based on IFR3&IFR1 (Integer frequency reuse) in a 19-cell network, but also apply the FFR (fractional frequency reuse) method to reduce the interference ulteriorly. In the pure IFR situation, the integer frequency reuse factor and the cellular network specification collectively decide the network capacity. While in FFR only a fraction of the whole bandwidth is used by the users in the edge. By contrast, the users near the BS can make use of the total bandwidth. The cell is divided into an outer and an inner part in this effective way. Fractional Frequency Reuse (FFR) and its derivative method are accepted widely in the downlink (DL) inter-cell interference coordination(ICIC) schemes. The team also optimized the FFR method by measuring the distance in a more precise way. The team utilized Matlab to make a simulation of the system applying the new method and come to a couple of reasonable conclusions by comparing the FFR+IFR3 with FFR+IFR3. FFR+IFR3 has a better performance against FFR+IFR1 in a system whose distance between each cell is with more accuracy. While the average number of users per cell and transmission power for cell edge have little impact on average capacity. When the SNR increases, the network capacity starts steep but later flattens. Our method is more intelligent and can minish interference efficiently.

Comparison of FFR+IFR and IFR Models with Different Frequency Reuse Factors in Cellular Networks

With the development of information network transmission, how to efficiently complete frequency reuse has been studied by many scholars. Frequency reuse refers to reusing the same frequency in a digital cellular system. Generally, limited frequencies are divided into several groups. As we all know, fractional frequency reuse (FFR) and integer frequency reuse (IFR) are classical frequency reuse methods in cellular networks. The combination of FFR method and IFR method to find the best model has attracted the attention of researchers at home and abroad. Therefore, through the fusion and combination of the four models, this paper will first introduce two frequency reuse methods, IFR and FFR, as well as the combination of these two methods and the calculation methods of these two methods. Through Matlab software modeling and simulation, according to the average capacity results, study the impact of different user numbers on the average capacity of the central area and the edge area. The experimental results provide a new idea for future practical applications.

Hybrid NOMA/OFDMA visible light communication system with coordinated multiple point transmission.

In this study, a hybrid non-orthogonal multiple access / orthogonal frequency division multiple access (NOMA/OFDMA) scheme is proposed for multi-cell multi-user visible light communication (VLC) systems. Each cell is divided into several sub-cells that are multiplexed using OFDMA. Users within the same sub-cell are multiplexed by NOMA. Thus, the hybrid NOMA/OFDMA scheme takes advantage of both NOMA and OFDMA, which not only improves the spectral efficiency of OFDMA but also avoids the co-channel interference of NOMA. Moreover, coordinated multiple-point transmission based on repeated coding is introduced to eliminate multiuser interference, which also improves the received signal-to-noise ratio of edge users. In this manner, spectrum resources are fully utilized, where the frequency reuse factor is equal to 1. Furthermore, we propose a two-dimensional power-allocation algorithm for the proposed hybrid NOMA/OFDMA VLC system. Based on the fixed power allocation strategy, power is allocated jointly among sub-cells and users within sub-cells to minimize the average symbol error rate (SER). The performance of the proposed system was investigated in detail by simulation, where the SERs were evaluated under different power ratios. Simulation results also show that the SER performance of the proposed hybrid NOMA/OFDMA VLC system is significantly improved compared to the traditional NOMA and OFDMA VLC systems in different VLC networks. Finally, the proof-of-concept experiment was set up, clearly validating the superiority of the proposed system further.

Selection of optimal SINR threshold in fractional frequency reuse by comparing Otsu's and entropy method

Interference is a major challenge in cellular networks and has been mitigated by introducing a frequency re-use factor to alternate the frequency used by adjacent cells. Fractional Frequency Re-use is an approach that is utilized in handling interferences which occur between cells, particularly in cellular networks using long-term evolution and leads to better bandwidth utilization. The basic cell structure is split into two regions, a partial re-use region and a full re-use region. The full re-use region uses the same frequency for all the cells while the partial re-use regions adopt a re-use factor to mitigate interference with neighboring cells. The Signal-to-Interference-plus-Noise-Ratio threshold is a vital parameter to be set in Fractional Frequency re-use since it sets the basis of determining the subscribers that will fall within the full re-use region and those that will fall in the partial re-use region. The bandwidth is then allocated proportionately based on the number of subscribers in respective regions using a frequency partitioning ratio. The focus of this paper develop a dynamic thresholding technique by testing the performance of two thresholding techniques which are mostly used in image processing and include Otsu's, and entropy methods The results are validated by comparing the performance metrics of throughput and fairness with a dynamic thresholding technique from literature called centralized dynamic frequency allocation technique. The cell Signal-to-Interference-plus-Noise-Ratio value obtained from subscribers in the network are used to set threshold which is periodically updated as the subscribers continuously report their signal values. Simulation results show that Otsu's method outperforms entropy method in terms of throughput averagely by 29% and 23.3% in terms of fairness. Otsu outperforms centralized dynamic frequency allocation technique averagely by 39% in throughput and 32.9% in fairness.

Intelligent Network Solution for Improved Efficiency in 6G-Enabled Expanded IoT Network

The fast-moving world relies on intelligent connected networks to support the numerous applications of the expanded Internet-of-Things (IoT). The evolving communication requirements of this connected world require a new sixth generation (6G) radio to enable intelligent interaction with the massive number of connected objects. The energy management of billions of connected devices supporting massive Internet-of-Things (IoT) applications is the main challenge. These IoT devices and connected nodes are energy limited, and hence, energy-aware solutions are needed to enable seamless information flow between these communicating nodes. This paper presents an intelligent network solution for improved energy efficiency in a 6G-enabled expanded IoT network. A cell-free massive multiple input multiple output (mMIMO) technology is utilized for maximum energy efficiency with optimum network resource allocation. A practical power consumption model is proposed for the designed network topology which contains all the power components related to data transmission and circuit power. The proposed scheme aims to achieve maximum energy efficiency by the optimal allocation of pilot reuse factor and access point (AP) density for a given number of antennas at each AP and number of users. It is observed that the maximum energy efficiency of 5.2362 Mbit/Joule is achieved at the AP density of 29 and pilot reuse factor of 4 with PMMSE receive combining. In the end, the role of energy efficiency and area throughput tradeoff on the system performance is also evaluated, which suggests that both the energy efficiency and area throughput can be jointly increased until maximum energy efficiency is reached at a point.

Fractional Frequency Reuse Optimal SINR Threshold Selection Using NIR and ISODATA

A vital part of cellular network evolution has been long-term evolution networks. In these networks, it is important to mitigate inter-cell interference. Fractional frequency re-use has been proposed to address this. The method involves the division of cells into two regions based on a signal-to-interference-plus-noise-ratio threshold value. The inner region adopts a frequency re-use of one (1), while the outer region uses a higher frequency re-use factor. Setting the threshold value is a critical problem addressed in this paper. The proposed approach adapts techniques used in image processing called global-thresholding techniques. The approaches considered are iterative self-organizing data analysis and native integral ratio. Mobile stations in a cell continuously report their signal-to-interference-plus-noise-ratio values to the base station. These reported values are used to determine a threshold which dictates which subscribers fall in the inner and outer regions. The threshold value is periodically updated based on the new reported values over time. Simulations are used to assess the performance using throughput and fairness metrics. By setting the threshold optimally, better throughputs and fairness are then achieved. We concluded that native integral ratio marginally outperformed the iterative self-organizing data analysis method, and it significantly outperformed static fractional frequency reuse techniques.