Wireless Access Systems Research Articles

On Identifying Threats and Quantifying Cybersecurity Risks of Mnos Deploying Heterogeneous Rats

Wireless networks constitute a significant attack vector for adversaries due to their wide usage in our everyday life. As the fifth generation of wireless networks reaches maturity, several vulnerabilities affecting earlier generations have been resolved. Nevertheless the coexistence of legacy wireless technologies is giving rise to the risk of allowing adversaries to perform downgrade attacks, thus bypassing the improved security of the state-of-the-art communication networks. Vulnerabilities due to the trade-off between security and usability could also exist in the latest wireless networking technologies; hence mobile network operators need to be aware of the risks related to both protocol vulnerabilities and configuration defects. This paper proposes a methodology for the systematic identification of vulnerabilities associated with wireless access protocols and systems and the quantitative evaluation of the resulting risks for mobile operators using attack trees, while considering the current legislative frameworks. The proposed methodology has been designed to aid both, mobile operators towards planning more effective cybersecurity strategies and adopting efficient defences to minimise the probability of an attack and predict its impact on the operational, market and business aspects of mobile network operators. The proposed risk assessment analysis is evaluated over three distinct vertical scenarios, namely an emergency call, a high-speed train commute and a massive public event, with the most relevant threats and their impact being measured and discussed. The evaluation of the model revealed significant results for mobile network operators that are deploying a mix of legacy and state of the art cellular technologies.

ABOUT RELATIONSHIP BETWEEN THE SIGNAL POWER, NUMBER OF M-QAM POSITIONS AND NOISE IMMUNITY IN BROADBAND WIRELESS ACCESS SYSTEMS

Is studied the effect of measurement error on the accuracy of selecting the modulation type in the transmitter of the base station. The article discusses changes in the statistical characteristics of the measured signal as it passes through the stage of the feedback loop of the system of the LMDS type. Probabilistic characteristics of pilot-signal are determined at the output of this loop. The aim of the work was to find a compromise between the type of modulation and the power of the BS transmitter to maintain the transmission faithfulness within the given limits in the forward channel of an interactive wireless broadband radio access system of the LMDS. In this system a transition is made from one type of modulation to another in order to maintain the noise immunity of the system within the admissible limits. An adaptive controlling method of modulation type makes it possible to obtain an energy gain in the forward channel of the system. It is useful to determine the type of modulation by measuring the current value of the signal-to-interference ratio at the base station (BS) receiver. For this purpose a pilot signal is transmitted on the reverse channel of the system. This signal, passing through the turbulent medium, undergoes attenuation, and therefore at the input of the BS receiver we have a random process. Moreover, the distribution law of this process can be different and is determined by the communication channel model. The problem consisted in determining the necessary probabilistic characteristics of the output process by using the system parameters and probabilistic characteristics of the input random process. For this purpose the cumulants of the input random process and the random process at the output of the linear inertial system are determined. An expression for the probability density of the random process at the output of a linear inertial system is obtained. The graphics of the error probability on the energy parameter at 16-QAM and 64-QAM type of modulation are constructed. The influence of the measurement error on the accuracy of the choice of the modulation type in the transmitter of the BS is studied. The limits of the change in the energy parameter are defined graphically, under which the modulation type changes to ensure a given error probability. It is determined, that the system is more critical to the measurement error at high admissible error probability, i.e. at high error probabilities, small errors in the measurement of the signal-to-noise ratio make it necessary to transition to a more noise-immune modulation mode.

Моделирование амплитудной характеристики радиотракта с кодовым разделением каналов

In CDMA radio access systems, amplitude distortions in a nonlinear amplifier (NA) of a group signal lead to bit errors at the outputs of subscriber channels. To assess the permissible distortion limits and their influence on the transmission quality of subscriber signals, an electronic model of the amplitude characteristic (AC) and analytical relations are needed that relate the probability of an error when registering the output signal of the communication channel with the nonlinearity of the AC NA and other destabilizing factors. The article compares alternative mathematical models of AC NA. In contrast to traditional methods of analysis, usually limited to the choice of models with fixed parameters, a method for variably determining the parameters of AC is considered. The results are: a comparison of known methods for approximating the AC of broadband nonlinear power amplifiers of radio signals is given, an algorithm for selecting model parameters for CDMA systems with QAM using the Rapp model is proposed.

Проблематика построения систем широкополосного радиодоступа мобильной радиосвязи

The article is focused on the problem of degrading the signals of broadband 3G / 4G mobile radio access systems in places of subscribers clustering and in so-called “dead zones”. The analysis of the actual principles of building mobile networks has been carried out, the main disadvantages of the approaches to the development of cellular networks have been identified. The current trend of building macro cells in the urban environment has lost its effectiveness due to the increasing frequencies used; it has to be replaced by a fundamentally new way of planning mobile networks. A new principle of providing access to mobile communications “from inside to outside” is proposed, which takes into account the needs of a large number of subscribers in the premises. It is based on setting the maximum number of internal base stations fully meeting the needs of internal network users. Such a distinction will positively affect all subscribers and improve the experience from using the high-quality services of the mobile operators, which will result in increasing the economic performance

ELECTROMAGNETIC CONDITIONS HYGIENIC ASSESSMENT AT WORKPLACES WITH PERSONAL COMPUTERS: HISTORY AND PRESENT STATUS

Introduction. Currently, in force hygienic normative-methodical documents (SanPiN 2.2.2/2.4.1340-03, SanPiN 2.2.2/2.4.2620-10, SanPiN 2.2.4.3359-16) do not allow to objectively estimating EMF on modern workplaces of personal computers (PCs) users by and other means of information and communication technologies (ICT). Aim of the study is scientific substantiation of improvement of normative-methodical documentation on hygienic regulation and evaluation of EMF in computerized workplaces using modern ICT. Material and methods. The analytical method of evaluation of modern normative-methodical documentation regulating hygienic norms and methods of evaluation of EMF in the workplace of PC users is used. More than 11 thousand measurements of EMF levels were carried out. Results. A critical analysis of the current hygienic regulations of EMF in the workplace of PC users and other means of ICT in Russia showed they to be not scientifically justified, and the existing methodology does not allow an adequate hygienic assessing of the electromagnetic environment (EME). The main sources forming EME on modern workplaces of PC users are both PCs, and switching power supplies, network support devices (UPS), cable lines, wiring, broadband wireless access systems (base stations, Wi-Fi routers, access points, external and built-in laptops USB modems), cell phones, lamps of local and general lighting. EMFs on a workplace of PC users are characterized by complex amplitude-frequency composition: electric and magnetic fields at frequencies of 30 Hz - 300 kHz, EMF at frequencies above 300 MHz, electrostatic fields, hypogeomagnetic fields. New EMF hygienic standards at workplaces of PC users and other means of ICT are scientifically proved. Conclusion. The introduction of new regulations will ensure an adequate hygienic assessment of EMF in the workplaces of PC users in each normalized frequency band in total from all sources and will eliminate the current contradictions and shortcomings. The introduction of new EMF hygienic standards in the practice of sanitary and epidemiological supervision will preserve the health of the PC users and other ICT facilities.

Method of Principal Informative Components in Problems of Statistical Measurements of Signal Parameters (Systematic Review)

The method of Principal Informative Components (PIC) is presented for problems of statistical measurements, where the signal to be measured cannot be directly observed. Such situations include image reconstruction, system identification, communication channel reversal, media tomography, etc. The common feature of such problems, usually, is instability of their solutions to small variations of initial data that generally require the attraction of special methods of regularization. The basic principle of PIC method consists in employing decomposition of signals in special bases that were formed from eigenvectors of Fischer’s information operator. These bases are related to the method of Principal Components Analysis (PCA), which is well known in statistics, however, they have a somewhat different meaning as compared to the PCA method. The review indicates that by using the special procedures for selecting coordinate vectors, it is possible, first, to guarantee the signal estimation stability to unpredictable factors of problem and, second, to ensure a significant reduction of total measurement error as compared to the “direct” signal estimation, i.e., without the use of basis notions. The review presents a substantiation of PIC method application for problems of linear and nonlinear estimation. The composite technique of coordinate basis optimization is also considered that combines advantages of the physical approach (obviousness and effectiveness) with advantages of statistically informative approach (minimization of statistical errors). The specified technique is based on projecting the arbitrary coordinate basis on PIC subspace. As a result, the range of possible fluctuations of signal estimation is reduced and the upper bound of statistical error of signal measurement is lowered. Some numerical estimates of the PIC method efficiency are given using the example of problem of medium acoustic tomography that confirms the general theoretical conclusions. The review includes the analysis of some information technologies, where the ideas of PIC method hold a good promise for practical application. In particular, it is suggested that one of such promising fields can be MIMO systems that play an important part in 5G wireless access systems.

Design and analysis of triple band circular patch antenna

This paper presents a circular slotted patch antenna resonating at three frequencies namely 1.8 GHz, 2.4 GHz and 5.4 GHz. The antenna is fabricated using Roger RT Duroid 5870 substrate having a thickness of 1.5 mm. The multiband behavior is achieved by etching slots on the patch. The measured antenna gains at the three frequencies are 5.5 dBi, 7.8 dBi and 7.9 dBi respectively. This paper extends its contribution by incorporating and discussing the resonation using the higher order modes. The designed antenna is suitable to be used for Global System for Mobile communication (GSM), Wi-Fi applications, Bluetooth, WLAN, Radio Local Area Network (RLAN) and Fixed Wireless Access systems (FWAS).

Evaluating the interference from fixed wireless access TDMA systems into HAPS systems: a probabilistic approach

This study presents a probabilistic model to assess the co-channel interference produced by multiple transmitters of a fixed wireless access network into a high altitude platform stations (HAPS) victim receiver. The authors propose an alternative probabilistic approach that avoids the worst case assumptions usually considered in traditional interference calculation methods, by considering the random modelling of some of the technical parameters involved. More specifically, the geographic positions of fixed wireless access system transmitters are modelled by a two-dimensional point process and their antenna gains in the sidelobe region are modelled as gamma distributed random variables. The proposed method is validated by comparing the minimal operating distance resulting from the traditional deterministic interference calculation methods and that obtained with th proposed approach. Results corresponding to the four possible interfering scenarios indicate that the proposed probabilistic approach leads to a reduction in coordination distances.

Quasi-Incoherent Filtration Algorithm for Linear Recurrent Sequences

Abstract—This paper considers the problem of synchronization in information transmission systems that use noiselike signals based on linear recurrent sequences (LRSs). For a model of a sequence of characters we use an approach associated with the representation of an LRS as a Markov chain. Radio access systems use synchronization for pilot sequences based on LRSs, which can be received using the algorithms described in this paper. The paper is devoted to the synthesis of quasi-incoherent recurrent LRS-filtration algorithms; the results of their statistical simulation are presented.

On Performance Analysis of Underlay Cognitive Radio-Aware Hybrid OMA/NOMA Networks with Imperfect CSI

This study considers the outage and throughput performance of downlink in the secondary network of cognitive radio assisted non-orthogonal multiple access (NOMA) systems. Both orthogonal multiple access (OMA) mode and NOMA mode are investigated with respect to status of decoding operation of each user. Depending on the transmit signal-to-noise ratio (SNR) at the primary source and interference constraint from the primary network, the closed-form expressions of the outage probability for two users are obtained and compared in terms of performance. To obtain further insights, an asymptotic analysis of the outage probability in the high SNR regime is presented. Optimal throughput also provides insight in the computation of the power allocation factor. Furthermore, power allocation factor, target rates, and transmit SNR are evaluated to obtain reasonable outage performance. Monte Carlo simulations are conducted to confirm the analytical results.

5G-U: Conceptualizing Integrated Utilization of Licensed and Unlicensed Spectrum for Future IoT

IoT applications constitute one of the fastest developing areas in today's technology and at the same time pose the most demanding challenges for the respective radio access network design. While the initial studies in IoT were focused primarily on scaling the existing radio solutions for higher numbers of small-data and low-cost sensors, the current developments aim at supporting wearable augmented/virtual reality platforms, moving industrial robots, driving (semi-)autonomous vehicles, and flying drones, which produce large amounts of data. To satisfy these rapidly growing performance demands, the 5G-grade IoT is envisioned to increasingly employ millimeter-wave (mmWave) spectrum, where wider bandwidths promise to enable higher data rates and low-latency communication. While the mainstream trend in mmWave-based IoT is to rely on licensed bands around 28 GHz or leverage unlicensed bands at 60 GHz, in this work we introduce a conceptual vision for the integrated use of these frequencies within a single radio access system named 5G over unlicensed spectrum or 5G-U. We study the performance of 5G-U in supporting stringent IoT use cases, discuss and compare the alternative strategies for spectrum management in 5G-U, and demonstrate that a harmonized utilization of licensed and unlicensed bands provides notable performance improvements in both device-centric and network-centric metrics. Finally, we offer useful guidelines for future implementations of 5G-U and detail its potential applications in the area of advanced IoT services.

An optimal bandwidth allocation algorithm for improving QoS in WiMAX

In the last few years, the term “quality of service” has become increasingly synonymous with digital cellular networks and has greatly influenced the way we manage network traffic. The IEEE 802.16 standard is a broadband wireless access system that enables high speed data transfer over large distances. It is one of the standards that meet the IMT-Advanced specifications. It also incorporates a quality of service framework to provide quality of service to both realtime and non-realtime multimedia applications. One of the critical contributions of a QoS framework is efficient scheduling of network traffic. This paper dilates on a two-level scheduling algorithm for base station uplink scheduler to provide quality of service to various classes of traffic. The proposed algorithm ensures efficient and fair multimedia transmission. We also deliberated on a video transmission framework based on the proposed algorithm. The performance of two-level scheduling algorithm has been extensively analyzed through simulations and the results have effectively established the efficacy of the proposed algorithm. The results reveal that the the proposed algorithm is able to fairly and efficiently schedule network traffic while ensuring quality of service for all classes of traffic.

W-band CMOS direct injection-locked frequency divider with 23.5-GHz locking range using distributed LC network and power matching and body bias techniques

A low power and wide locking-range W-band (75–110 GHz) divide-by-2 direct injection-locked frequency-divider (DILFD) using standard 90 nm CMOS technology is reported. To enhance the operation frequency, distributed LC network is used as the load of the crossed-coupled transistors. To improve the input sensitivity, a power matching network is included at the injection terminal of the switch transistor. In addition, to enhance the frequency locking range, body bias technique (i.e. a body resistor in conjunction with a zero body-source bias) is adopted in the switch transistor to reduce its threshold voltage. The result shows that a wide locking-range of 23.5 GHz [from 69.5 to 93 GHz (28.9%)], covering the 77–81-GHz-band for short range automotive radar system and 81–86-GHz-band for high-speed point-to-point wireless communication access system, was achieved. The DILFD can be operated at a low input power of − 35 dBm, one of the best input sensitivity ever reported for a W-band CMOS divider. The power consumption of the DILFD was only 3 mW from a 0.7 V power supply. The chip area was only 0.76 × 0.66 mm2 excluding the test pads.

Cell search and synchronization in 5G NR

An overview of the physical signals foreseen by the 3GPP 5G New Radio specification for frame synchronization and cell search in fifth- generation wireless broadband access systems is presented in the paper. The frame synchronization algorithm and the cell initialization procedure are demonstrated. An estimate of probability of error detection of a physical identifier by the signals of the primary and secondary synchronization is obtained. The comparison of the successful synchronization in AWGN channel for 4G LTE and 5G NR is shown.

SmartWAZ: Design and Implementation of a Smart WiFi Access System Assisted by Zigbee

Recently, WiFi networks have witnessed an unprecedented deployment, and WiFi APs are ubiquitous around the world. On one hand, the WiFi clients have to actively discover new WiFi access points (APs), and try to access to them, even though most of the APs are privately owned, which wastes the precious energy of mobile devices due to excessive listening and scanning operations of WiFi network interface cards. On the other hand, many wireless technologies coexist in overlapping channels (e.g., 2.4 GHz ISM bands). It provides a new opportunity of cross-technology communication (CTC) that utilizes these overlapping frequencies to share information among different technologies. This paper deeply investigates the application of wireless CTC into smart and energy-effective WiFi access with the assistance of low-power radio. Specifically, we design a smart WiFi access system assisted by Zigbee, SmartWAZ, for mobile terminals with both WiFi and Zigbee interfaces. The most prominent feature of this system is that the different WiFi beacon periods are intentionally used to distinguish publicly accessible and privately owned WiFi APs. Then, the folding algorithm is applied by the Zigbee module in clients to detect the specific WiFi beacon period used by public APs, and then the WiFi interface will be waked only when a public WiFi AP is detected. From the system design viewpoint, we investigate the influence of the beacon period of the sender (i.e., WiFi AP) and the judgment threshold of the mobile client on a false positive and false negative, and provide the basic rule to appropriately set those system parameters. Compared to the traditional WiFi access methods, the SmartWAZ significantly saves the energy consumption of continuous WiFi scanning; compared to other low-power radio assisted WiFi access systems, SmartWAZ avoids waking WiFi interface when private WiFi APs appear. The experiment results show that the SmartWAZ averagely consumes only 36% of the energy of traditional WiFi access schemes and achieves reliable detection with an error rate of less than 1%.

RESULTS AND TOOLS FOR EVALUATING THE EFFECTIVENESS OF FOCUSING SYSTEMS TO IMPROVE ACCESSIBILITY IN WIRELESS NETWORKS

The widespread use of wireless technologies leads to an ever-increasing number of users and permanently functioning devices. However, the growth of the number of wireless users in a limited space and a limited frequency range leads to an increase in their mutual influence, which ultimately affects the throughput of wireless channels and even the performance of the system as a whole. The article presents the statistics and tendencies of the distribution of wireless networks of the IEEE 802.11 standard systems, as well as analyzes the main problems that arise during the expansion of their use. Substantiation and choice of ways to overcome these difficulties largely depends on the objective control of radiation parameters of access points and subscriber funds in a particular environment. The review of the state control facilities provided by the developers of the equipment is presented, and author's variants of experimental measuring complexes are offered, allowing to control signal and information parameters of Wi-Fi systems. The experimental results obtained with the use of the indicated means, obtained using the accelerating metal-plate lens as an additional autonomous element for focusing the field, including for MIMO systems, the effect of the accelerating metal-plate lens on the spatial distribution of the field, on the spectral structure of the signal are presented. In addition, polarization effects were investigated. Possible ways to further increase the availability, integrity of information and energy efficiency of wireless access systems are discussed. The authors propose simpler and less costly options for increasing the direction of radiation on the basis of an accelerating metal-plate lens, experimentally tested, as well as the use of zone zoning on the path of the computer.

Dynamic Bandwidth Allocation in Small-Cell Networks: An Economics Approach

We propose and experimentally demonstrate a bandwidth allocation method based on the comparative advantage of spectral efficiency among users in a multi-tone small-cell radio access system with frequency-selective fading channels. The method allocates frequency resources by ranking the comparative advantage of the spectrum measured at the receivers ends. It improves the overall spectral efficiency of the access system with low implementation complexity and independently of power loading. In a two-user wireless transmission experiment, we observe up to 23.1% average capacity improvement by using the proposed method.

Discontinuous Reception for Multiple-Beam Communication

Discontinuous reception (DRX) techniques have successfully been proposed for energy savings in 4G radio access systems, which are deployed on legacy 2GHz spectrum bands with signal features of omni ...

BLEDoorGuard: A Device-Free Person Identification Framework Using Bluetooth Signals for Door Access

Recently, door access control with Internet of Things has become increasingly popular in the field of security. However, conventional approaches such as video-based or biological information-based cannot satisfy the requirements of personal privacy protection in the modern society. Hence, a wireless signal-based technique which does not need users to carry any devices, called device-free have been introduced in recent years to detect and identify persons. In this paper, we present BLEDoorGuard, a wireless, invisible, and robust door access system which leverages received signal strength indicator from Bluetooth low energy (BLE) beacons to recognize a person who accesses a door. We evaluated BLEDoorGuard in two real-world scenarios: the first is an office with a key lock, and the second is a meeting room with swipe card access. We exploit the characteristics of use of BLE for person identification and propose a two-step algorithm with multiple classifiers. We demonstrate that BLEDoorGuard is capable of identifying the actual user during door access with an accuracy of 69% and 62% among groups of 6 and 10 people, respectively.

Predictive Bandwidth Allocation Scheme With Traffic Pattern and Fluctuation Tracking for TDM-PON-Based Mobile Fronthaul

In future radio access systems, since the number of mobile base stations will increase to cope with the increasing mobile traffic, the number of mobile fronthaul (MFH) links will also have to increase. To reduce the MFH link cost, MFH networking has been attracting attention. In particular, the use of a time-division multiplexed passive optical network (TDM-PON) makes the MFH link cost effective. On the other hand, a TDM-PON has a huge latency when forwarding uplink traffic. In a typical dynamic bandwidth allocation (DBA) scheme, an optical network unit (ONU) has a very long transmission waiting time, e.g., several milliseconds. This transmission waiting time in the ONU is a critical problem since the latency requirement for the MFH link is very strict, e.g., less than 250 μs defined by the Third Generation Partnership Project. In this paper, we propose a novel statistical DBA scheme taking high-speed traffic fluctuation to reduce the transmission waiting time. Our proposed scheme allocates bandwidth based on the only ratio of the data amount of each distributed unit and detects the pattern of the transmission interval of the burst signal. We show the feasibility with a numerical simulation and experiments.