Unlicensed Frequency Bands Research Articles

Network Coding-Based D2D Transmission for Public Safety Networks over LTE HetNets and 5G Networks

Device to Device (D2D) communications appear like an emergency solution for the Public Safety Network (PSN) when the LTE cell range is limited. D2D networks can use the unlicensed frequency bands, as this makes their transmissions cheaper and easier to deploy. Therefore, the development of this technology must deal with the security challenge. On the one hand, it is important to know how to design a secure D2D solution within the small cells, and on the other hand, the new scheme needs to deal with the problem of radio resources limit, since it will be used during emergency situations. This paper develops a new algorithm, named Generalized Secure Network Coding-based Data splitting algorithm (G-SNCDS), to ensure a secure data transmission for Public Safety D2D communications over LTE Heterogeneous Networks (HetNets) and 5G networks, without using additional radio resources. Our approach consists of performing Network Coding (NC) data packets transmissions based on a new Data Splitting (DS) technique, which we developed, based on a constructed butterfly effect that uses a new Butterfly network algorithm that we propose. Our solution enhances the security without affecting the level of Quality of Service (QoS). Thus, it is more suitable when network resources are limited. The simulation results show that our approach provides a secure D2D communication without increasing the overhead in the network.

ДОСЛІДЖЕННЯ ЗАДАЧ ПОБУДОВИ БЕЗДРОТОВИХ СЕНСОРНИХ МЕРЕЖ

The research of problems of construction of wireless sensor networks is carried out in the work, the main stage of their decision is development of models of the description of a sensor network and the corresponding methods, technologies of maintenance of necessary parameters of quality of functioning of a sensor network. The study involves the consideration of basic technologies and standards in which there is an opportunity to implement the creation of wireless sensor networks. The basis of wireless sensor networks are communication channels organized between network elements using appropriate wireless technology. The main tasks of building wireless sensor networks: determining traffic parameters; determining the list of services; development or selection of a network model; determination of network functioning indicators; solving the problem of compromise between the quality of operation, traffic and resources. A number of wireless networking technologies are widespread in corporate networks, use an unlicensed frequency band, and in private networks, which allows their use in a number of tasks, due to the density of devices that support them and the availability of technology. A number of technologies do not support the functions of self-organization of the communication network. Such mechanisms can be implemented using software and related protocols at the network level. Existing technologies have the ability to organize communication from tens to tens of thousands of meters. For specific applications, it is one of the essential factors in choosing the appropriate technology. The probability of connectivity in wireless sensor networks depends on the structure and parameters that determine the network: characteristics of the service area (volume, flat, configuration, geometric dimensions), number of network nodes, characteristics of communication capabilities of network elements, antenna patterns, standards and protocols, communication range, transmitter power), features of the involved routing protocols. Features of providing connectivity in wireless sensor networks lie in the possibility of using gateways built using various technologies, which can significantly expand the capabilities of wireless networks in increasing the likelihood of connectivity. A feature of the construction of wireless sensor networks are significant differences in traffic servicing in the networks of different technologies used. Indicators of the quality of wireless networks, such as bandwidth, delay, probability of loss are interdependent and show how effectively the sensor network works. When you change one of the performance indicators of wireless sensor networks, it affects other quality indicators.

Performance Analysis and Throughput Enhancement of the STET Technique for WLAN IEEE 802.11ad

The IEEE 802.11ad innovation has enabled the impact of remote devices in unauthorized 60 GHz unlicensed frequency band at Giga bits per second information transfer rate in speed concentrated 5G applications. We have presented an innovative work that deals with the upgradation of the ability of IEEE 802.11ad wireless LAN to make it suitable for wireless applications. An exact examination on the IEEE 802.11ad analysis has been carried out in this work to achieve the greatest throughput. This has pulled attraction in broad consideration for accomplishing the pinnacle transmission rate of 8 Gbit/s. IEEE 802.11ad is a convention utilized for extremely high information rates (around 8 Gbit/s) and for short range remote correspondence of around 1 to 10 meters. The Multi-layer with Multi-User Multiple Input Multiple-Output (MLMU-MIMO) innovation has enabled transmission of multiple information packets all the while from the WLAN IEEE 802.11 ad Access Point (AP) to various receivers by means of different wireless applications. To help the MLMU-MIMO innovation at Medium Access Control (MAC), a new method called Simultaneous Transmission for Enhanced Throughput (STET) has been presented for enhancement of the transmission rate of the wireless standard. A mathematical model has been used for the evaluation of the performance of an IEEE 802.11ad AP empowering the STET allocation technique. This STET model can help determination of the throughput improvement of a STET technique, for example, audio information, images, good quality and foundation impact. The main goal of this work is to analyze the improvement of the STET allocation technique in regard to the usage of rare frequency band, when obtaining spectrum access between the various access points. The theoretical and simulation outcomes are also confirmed by Riverbed modeler 17.5 simulation tool.

Dynamic spectrum management using frequency selection at licensed and unlicensed bands for efficient vehicle-to-vehicle communication

Background: The exponential increase in pattern of vehicles on the roads demands a need to develop a vehicular infrastructure that may not only ease congestions and provide a better experience but also pivot the levels of safety among users. The development of wireless technology has made it convenient for machines, devices and vehicles to interact with one another. The efficacy of this wireless communications relies on utilising current and available technology to enable information to be shared efficiently. In the wake of the available advancement in wireless technology, a new dynamic spectrum management (DSM) in vehicle-to-vehicle (V2V) communication that coexists with the existing Long-Term Evolution (LTE) network to increase the throughput in V2V communication is proposed. This will provide some solutions to enable a more efficient vehicular infrastructure. Methods: This paper focuses on the utilization of DSM in V2V communications by selecting an appropriate frequency band through the selection of available licensed and unlicensed frequency bands for vehicles. Further investigations are done to identify the effect of interference in the dynamic spectrum by observing the path loss, SINR, and the throughput with various interfering users. Results: The results show that the performance of the proposed DSM augments a significant improvement in the overall throughput and the signal-to-interference-plus-noise ratio (SINR) value is reduced by up to 60% when compared to the fixed spectrum allocation. Conclusions: Although the dynamic spectrum is still affected by the interference from the existing cellular users, the throughput of the dynamic spectrum remains sufficient to transmit the information to other vehicles.

Energy-efficient and self-organizing Internet of Things networks for soil monitoring in smart farming

Nowadays, we are witnessing a massive deployment of connected objects via the Internet of Things (IoT) in numerous fields. IoT can lead to a highly effective and significant contribution to the agricultural sector’s improvement. Once these IoT sensors are placed beneath the surface for water content and salinity measurements, they will need to communicate with the mobile operator’s base stations. However, electromagnetic propagation through soil is very different from propagation through the air because of the soil’s permittivity and electrical conductivity. This study relates more precisely to low consumption and large-scale deployment purposes. The simulations will be carried out for unlicensed frequency bands to assess the theoretical approach studied. We also outline the recent IoT applications in agriculture, the various protocols, and energy harvesting techniques for IoT that can be used in agricultural monitoring systems.

Joint Time and Power Allocation for 5G NR Unlicensed Systems

The fifth-generation (5G) and beyond networks are designed to efficiently utilize the spectrum resources to meet various quality of service (QoS) requirements. The unlicensed frequency bands used by WiFi are mainly deployed for indoor applications and are not always fully occupied. The cellular industry has been working to enable cellular and WiFi coexistence. In particular, 5G New Radio in unlicensed channel spectrum (NR-U) supports the uplink and downlink transmission on the maximum channel occupation time (MCOT) duration. In this paper, we consider maximizing the total throughput of both downlink and uplink in NR-U by jointly optimizing the time and power allocation during MCOT while ensuring fair coexistence with WiFi. Fairness is guaranteed in two steps: 1) tuning the access related parameters of NR-U to achieve proportional fairness, and 2) including 3GPP fairness from the throughput perspective as a constraint in NR-U throughput maximization. Numerical analysis and simulation have demonstrated the superior performance of the proposed resource allocation algorithm compared to conventional deployment strategies.

Cooperation for Spreading Factor Assignment in a Multioperator LoRaWAN Deployment

Faced with the limitations of the Aloha random access scheme and spread spectrum techniques, LoRaWAN is yet to realize its potential as the flagship technology for large-scale Internet-of-Things applications. LoRaWAN allows for low power and long range communications. Nonetheless, concurrent transmissions on the same spreading factors (SFs), increased with the inevitable densification of device deployment, will lead to collisions and degradation in performance. The problem is further amplified due to the shortage in radio resources, with multiple operators utilizing the same unlicensed frequency bands. In this article, we investigate different interoperator cooperation schemes and devise multiple algorithms for SF assignment in a multioperator LoRaWAN deployment scenario. We start by proposing a proportional fair optimal formulation for the assignment with the objective of maximizing the logarithmic sum of the normalized throughput per SF. Under the assumption of partial operator cooperation, we propose a gradient ascent-based iterative algorithm for solving the SF assignment problem, and a game theory-based approach, wherein each network operator seeks to maximize its own normalized throughput. Finally, and with cooperation between different operators bound to be limited, we use recurrent neural networks to enable the prediction of the success rate per SF. This prediction allows the different operators to assign SFs with minimum cooperation. We simulate our proposals and compare them to the legacy LoRaWAN approach as well as others in the state of the art, highlighting the gains they produce in terms of total normalized throughput and packet delivery ratios.

A comprehensive hybrid bit-level and packet-level LoRa-LPWAN simulation model

LoRa is a rising LPWAN technology designed to use a simple Aloha-like medium access mechanism exploiting free ISM frequency bands. This makes LoRa packets inevitably exposed to the threat of the same LoRa network interference (intra-system interference). Additionally, they are also exposed to disturbances caused by packets from other networks using the license-free spectrum (inter-system interference). LoRa-LPWAN is actively being deployed in the literature state-of-the-art. The capture effect essentially reflects the joint relation between the physical layer capabilities of LoRa modulation in relation to the LoRaWAN Aloha-based MAC operation. Moreover, most efforts adopted in the literature have ignored the impact of inter-system ISM interference signals on LoRa-LPWAN transmissions. This paper devises a new paradigm for modeling LoRa modulation performance that incorporates the joint impact of SNR and SIR in order to represent the intra- system interference behavior during LoRAWAN operation. The physical layer abstractions are then combined with comprehensive implementation of the LoRaWAN MAC protocol standard in an OMNeT++ module, delivering a hybrid bit-level and packet-level simulation model. The devised LoRa simulation model framework also introduces a representative abstraction for LoRa reception capabilities under ISM interference in accordance with the IEEE 802.15.4 interference model [1] that has been recently introduced in the literature of long-range, low-power communication. The developed OMNeT++ Simulation model acts as a reliable platform to test different potential bottlenecks in LoRa-LPWAN operating in the free, unlicensed frequency bands. The proposed simulation framework has the potential to support high accuracy of error performance prediction in a realistic LoRa-LPWAN deployment.

Enhanced network sensitive access control scheme for LTE–LAA/WiFi coexistence: Modeling and performance analysis

Implementation of 5G and beyond networks is looking to expand the operation of licensed systems into unlicensed frequency bands through technologies such as license assisted access (LAA) and New Radio Unlicensed (NR-U). LAA aggregates licensed and unlicensed bands for long term evolution (LTE) implementation to address the ever-increasing demand for cellular data traffic and shortage of licensed spectrum. Spectrum-efficient resource-sharing schemes are, however, critical for the harmonious coexistence of LTE–LAA with incumbent systems on the unlicensed band, especially WiFi, while opportunistically improving LTE throughput and enhancing spectrum utilization of the unlicensed band. In this paper, we present a listen before talk (LBT) based clear channel assessment (CCA) mechanism for LAA eNodeBs (eNBs) to improve the coexistence performance of LTE–LAA with WiFi. Particularly, we propose an adaptive exponential backoff scheme for LTE eNB that dynamically updates the contention window (CW) size and transmission opportunity (TXOP) parameters according to network load variations. A three-dimensional discrete Markov model is developed to describe the LBT procedure of LAA eNB, and a performance model is further derived to evaluate steady-state channel access, transmission, and failure probabilities. The proposed scheme’s performance is evaluated in terms of successful transmission probability, throughput, and delay according to the 3GPP and WiFi guidelines. The results are compared with the traditional schemes proposed in literature considering fixed and adaptive CW size for LAA eNB.

SBT (Sense Before Transmit) Based LTE Licenced Assisted Access for 5\xa0GHz Unlicensed Spectrum

Utilization of unlicensed spectrum under licensed assisted access ensuring fair co-existence with Wi-Fi networks is a good solution to address immense usage of mobile data. Radio communication operation of LTE in unlicensed frequency band is referred as LTE-unlicensed (LTE-U) or LTE-licensed assisted access. In this paper, we consider a HGNW in which coverage area of Wireless-Fidelity (Wi-Fi)’s Access Point is integrated within the LTE-U small base station’s cellular network coverage area. To overcome the disadvantages of existing LTE-U technics like carrier sense adaptive transmission and listen before talk, we proposed a new methodology i.e., sense before transmit in this paper by adopting a transmit power control mechanisms using reciprocity theorem based on the channel state information to assign the secondary carriers in the uplink as well as in the downlink directions in the unlicensed spectrum to carry the traffic. In our proposal, LTE-U users are allowed to use the unlicensed spectrum provided that the interference produced at Wi-Fi users due to LTE-U activities is remained below a certain threshold. We evaluated the performance of proposed network model in terms of outage probability and achievable throughputs.

CR-LBT: Listen-Before-Talk With Collision Resolution for 5G NR-U Networks

To achieve higher throughputs in cellular networks, 3GPP proposes to use unlicensed frequency bands and develops technologies — the latest one is NR-U — allowing a cellular base station to transmit in unlicensed bands, which are already occupied by Wi-Fi networks. To enable fair channel sharing between two technologies, the base station uses a sort of CSMA/CA with binary exponential backoff similar to Wi-Fi. However, the base station can start data transmission only at strictly periodic time moments. Many papers propose sending a reservation signal between the end of the backoff procedure and such a moment to prevent nearby devices from accessing the channel. However, this approach significantly reduces Wi-Fi performance. The paper proposes a novel method CR-LBT of transmitting a reservation signal that greatly decreases channel resource waste caused by collisions and improves channel resource sharing fairness. With developed analytical models and simulations, it is shown that CR-LBT may simultaneously increase the throughput of both NR-U and Wi-Fi networks. The effect is more noticeable for the Wi-Fi network, the throughput of which may rise three times compared with the traditional method of sending the reservation signal. Finally, the influence of various factors on CR-LBT performance is studied.

RETRACTED: Research on Indoor Environment Design Based on VR Technology and Wireless Sensor Network

Integration of indoor environmental issues of sustainable buildings, overall the construction of environmental performance, requires a scientific evaluation. The quality of the indoor environment, must be evaluated in the context of the impact on the overall building performance and overall indoor environment. Indoor Environment Quality (IEQ) and well-being of its residents affect the comfort, is an important field. Comfort of IEQ occupant and the complexity of the relationship between happiness parameters, these parameters are worse due to the relationship that they have each other in the same way. Virtual reality (VR) device, a multi-user environment VR and user experience of wireless connection, should be considered as the next generation of VR device. Wireless Sensor Networks (WSN) is a wireless communication device is a popular consumer electronic device for use in high throughput and unlicensed frequency bands and low cost. Effective multi-user wireless communications VR architecture and communication scheme for VR. The proposed architecture utilizes a plurality of WSN standard, because it is based on the characteristics of each group of VR traffic, the proposed scheme, a large amount of effective uplink data generated by the plurality of VR devices to enable the delivery, and sufficient to provide video frame rate and control the frame rate is a high-quality VR services.

Deployment of mesh network in an indoor scenario for application in IoT communications

The need for digital transformation in the industry and the related development of the Internet of Things (IoT) has led to the rapid development of various communication technologies and approaches for the implementation of flexible and intelligent communication networks. The main direction is wireless technologies, which make it possible to accelerate the wide range of new applications and services related to smart cities, industry, e-government and others. The possibilities are wide - use of different licensed or unlicensed frequency bands, channel bandwidths, modulation formats, power efficiency, reliability and security. Different network topologies could be applied for the access and collection of data from the sensor networks - star topology, mesh topology, tree topology, each of which has different advantages and disadvantages. This paper discusses the possibilities for deploying low-power mesh networks in an indoor scenario based on IQRF technology. Important communication parameters, approach advantages, and technological limitations will be highlighted. As an example, a study of network behaviour and efficiency in an indoor scenario will be considered.

Coexistence Analysis of D2D‐Unlicensed and Wi‐Fi Communications

By enabling direct communications between nearby user equipment (UE), device‐to‐device (D2D) communication has become one of the key technologies in 5th generation (5G) mobile networks. D2D communication brings new communication opportunities for mobile devices, especially in a highly dense network. In this paper, D2D communication in the unlicensed spectrum, namely, D2D‐Unlicensed (D2D‐U), is discussed. The use of unlicensed frequency bands can ease the shortage of spectrum resources and improve network performance. However, the D2D‐U in 5G has significant effects on the network performance of existing unlicensed networks sharing the same frequency bands, such as Wi‐Fi and Bluetooth. Therefore, it is necessary to design a fair coexistence scheme for D2D‐U. To understand the coexistence problem, in this paper, we first formulate the network performance of D2D‐U and Wi‐Fi under two different coexistence schemes, namely, listen before talk (LBT) and duty cycle mechanism (DCM). Then, we use computer simulations to investigate a mode selection scheme that switches between these two schemes and point out the best possible solution for the coexistence between D2D‐U and Wi‐Fi.

Resource Allocation for 5G-Enabled Vehicular Networks in Unlicensed Frequency Bands

In this paper, a resource allocation problem is formulated to maximize the throughput of vehicular user equipments (VUEs) in both licensed, and unlicensed frequency bands under constraints of reliability, and latency for vehicular communications as well as the Quality of Service (QoS) for WiFi network based on a network system with coexisting VUEs, and WiFi user equipments (WUEs). In the system, the VUEs are able to access to the unlicensed frequency bands, and the interference among the VUEs, and WUEs are mitigated by the listen-before-talk (LBT) scheme or the duty cycle scheme. Due to the mixed integer nonlinear programming (MINLP) objective in the optimization problem, the problem is hard to be solved directly. Instead, we solve the problem by two steps. The number of VUEs offloaded to unlicensed frequency bands as well as the time factor for duty cycle scheme is firstly determined, and then, the optimization problem is converted into a convex optimization problem, which is solved by the proposed Lagrange Duality Method (LDM). Numerical results show the efficiency of our proposed application scenario compared to case with only LTE system or only WiFi system. Moreover, compared to traditional Greedy algorithm, the proposed algorithm performs better in terms of throughput with a guaranteed QoS of WUEs.

An Overview of Current and Future Vehicular Communication Technologies

The present paper provides a technical overview about the most relevant vehicular communication technologies including IEEE 802.11p, IEEE 802.11bd, LTEV2X and NRV2X. IEEE 802.11p is the most matured one Wi-Fi based technology, and its successor, the IEEE 802.11bd is expected to be released in 2021. As CV2X (Cellular Vehicle to Everything) technologies, LTEV2X (Long Term Evolution V2X) and NRV2X (New Radio V2X) are discussed in this paper. The former one is already available, while the latter one’s final specification will be finalized in 2020 by the 3GPP (Third Generation Partnership Project). These four technologies also motivate the already started transformation of vehicle industry by enabling basic safety features and more efficient traffic management, as well as cooperative maneuver execution towards high-level automated driving. The comparison of these technologies is essential to clarify their benefits completely. These technologies are considered as competitors, however, it is expected that they will coexist in the same geographical region. Thus, they will share on the same unlicensed frequency bands in 5.9 GHz domain. Therefore, different coexistence scenarios are also discussed in the paper to see how their advantages could be utilized.

Time-Modulated Antenna Array With Beam-Steering for Low-Power Wide-Area Network Receivers

The Internet of Things (IoT) denotes a concept of connected devices that communicate seamlessly over the Internet. The wireless connectivity between IoT nodes and the Internet gateways can be realized in unlicensed frequency bands upon the low-power wide-area network (LPWAN). It is foreseen that due to a massive introduction of IoT devices the unlicensed bands will experience an increased interference level which will negatively affect the communication performance. Therefore, adaptive solutions should be considered to obtain robustness. This letter presents a time-modulated antenna array (TMAA) for LPWAN receivers and demonstrates its interoperability with a commercial of-the-shelf LoRa device. According to the conducted experimental investigation, whereby the beam-steering is obtained over the sidebands inherently generated by the TMAA, both the received signal strength and the signal-to-noise ratio (SNR) are improved by means of the progressive delay applied to the time modulation functions.

Survey on Wireless Networks Coexistence: Resource Sharing in the 5G Era

The next generation of mobile-enabled wireless networks, known as 5G networks, is announced to be deployed by 2020. In the 5G framework, access technologies are one of the main features that would allow users to seamlessly connect to the Internet using any of the available technologies. These technologies are going to coexist in the same physical environment. This coexistence has the advantage of offering the user multiple options for establishing communications. On the other hand, existing and upcoming wireless standards have not given this coexistence enough attention. In this paper, we survey existing communication protocols, techniques and mechanisms, as well as features of the 5G communication standards that allow technology to cope well with coexistence. We focus on access layer solutions that can be used in unlicensed frequency bands. We also argue that resource sharing should be extended not only to manage the available spectrum but also the available physical systems. We argue in this paper that resource sharing mechanisms would have a positive impact on the 5G infrastructure for better spectrum efficiency.

Automatic Detection of Wireless Transmissions

The current understanding of activity in the wireless spectrum is limited to mostly punctual studies of aggregated energy values. However, there is a need and increasing technological means for a better understanding of spectrum usage by automatically detecting and recognizing wireless transmissions in an unlicensed or shared frequency band. In this paper we propose, implement and evaluate a framework for automatic detection of wireless transmissions. Our framework includes a manual component as our assessment suggests manual labor has a paramount impact on tuning and maintaining good performance of an automatic transmission detection system. However, a considerable problem in this aspect is represented by the disagreement amongst human annotations which is a universally recognized issue. To this end, we discuss and evaluate challenges in generating labeled datasets that can then be used as ground truth for evaluating and possibly training automatic transmission detection systems. We also propose two methods for automatic transmission detection that are not based on machine learning and therefore do not need training data and evaluate their performance against each other and manually labeled data. Our results show that generating human-labeled ground truth data is an expensive and imperfect process. Humans on average require 90 minutes to label 56 minutes of unlicensed European narrowband spectrum. The experts that generate the ground truth sometimes only agree on as little as 40.18% of the labeled cases.

Mathematical Modeling of Joint Operation of Wireless Local Area Networlss and Fifth Generation Cellular Networks

To improve the performance of LTE cellular networks operating in the licensed frequency spectrum, a new LTE-LAA technology has been developed that allows LTE devices to transmit data in unlicensed frequency bands already used by Wi-Fi devices. The channel access method in LTE-LAA networks, as well as in Wi-Fi networks, is based on the mechanism of carrier sense with collision avoidance; however, LTE-LAA transmission can only begin at the boundary of licensed slots. In this work, we develop a mathematical model for the joint operation of LTE-LAA and Wi-Fi networks, which allows to assess the fairness of the distribution of channel resources between LTE-LAA stations and Wi-Fi stations depending on the duration of the licensed slot, the regulation of which will become possible as part of the New Radio technology of fifth generation cellular networks.