Nearby Base Stations Research Articles

A compact triple‐band metamaterial‐inspired antenna for wearable applications

AbstractA low‐profile (28 mm × 32 mm × 0.394 mm), metamaterial‐inspired antenna employing an array of 3 × 5 Hilbert‐shaped unit radiators printed on the upper side of a flexible dielectric substrate while the lower side contains a partial‐ground plane and the rest consists of a periodic square‐slotted ground plane is presented for wearable wireless devices covering Long‐Term Evolution (LTE), Long Term Evolution‐Advanced (LTE‐A), Wireless Local Area Network (WLAN), and Worldwide Interoperability for Microwave Access (WiMAX) bands. The antenna provides steerable radiation patterns for frequencies ranging from 3.3 to 3.9 GHz and a directive end‐fire radiation in the 5.8 GHz band. At 2.45 GHz, the antenna allows short‐range communications between a wearable sensor and handheld wireless device or a nearby base station. Two prototypes are fabricated; the first using traditional wet etching with copper; the second using inkjet printing with silver nano‐particles (SNPs) as the conducting material. We provide a systematic design procedure and a new physical insight into the operation of the antenna, in particular the end‐fire radiation patterns, which is based on the anisotropic dispersion characteristics of the radiating structure along the length axis leading to different effective electrical length to width ratios within the stopband. The realized gain varies from 0 to 2.5 dBi for frequencies ranging from 3.3 to 3.9 GHz where the 3‐dB beamwidth varies from 110° to 140° and the boresight is steered from 0° to 80°. The maximum realized gain varies from 4.75 to 4.5 dBi over the frequency range from 4.4 to 6 GHz, with slight change in the beamwidth and main lobe direction. Experimental measurements for the SNP prototype are reported in air and on a standard phantom model.

Radiofrequency radiation from nearby mobile phone base stations-a case comparison of one low and one high exposure apartment.

Radiofrequency (RF) radiation in the frequency range of 30–300 GHz has, since 2011, been classified as a ‘possible’ human carcinogen by Group 2B, International Agency for Research on Cancer (IARC) at WHO. This was based on a number of human epidemiology studies on increased risk for glioma and acoustic neuroma. Based on further human epidemiology studies and animal studies, the evidence on RF radiation carcinogenesis has increased since 2011. In previous measurement studies, it has been indicated that high environmental RF radiation levels are present in certain areas of Stockholm Sweden, including in one apartment. Field spatial distribution measurements were performed in the previously measured apartment in Stockholm, which exhibited high RF radiation from nearby base stations. Based on the RF broadband analyzer spot measurements, the maximum indoor E-field topped at 3 V m−1 in the bedroom at the 7th floor. The maximum outdoor exposure level of 6 V m−1 was encountered at the 8th floor balcony, located at the same elevation and only 6.16 m away from the base station antennas. For comparison, a measurement was made in a low exposure apartment in Stockholm. Here, the maximum indoor field 0.52 V m−1 was measured at the corner window, with direct line of sight to the neighboring house with mobile phone base station antennas. The maximum outdoor field of 0.75 V m−1 was measured at the balcony facing the same next-door building with mobile phone base station antennas. The minimum field of 0.10 V m−1 was registered on the apartment area closest to the center of the building, demonstrating the shielding effects of the indoor walls. Good mobile phone reception was achieved in both apartments. Therefore, installation of base stations to risky places cannot be justified using the good reception requirement argument.

Interference cancelation for high-density fifth-generation relaying network using stochastic geometrical approach

In order to resolve the issue of coverage limitation for the future fifth-generation network, deploying a relay node within a cell is one of the most capable and cost-effective solution, which not only enhances the coverage but also improves the spectral efficiency. However, this solution leads to the undesired interferences from nearby base station and relay nodes that affects user’s signal-to-interference-plus-noise ratio and can cause the ambiguous received signal at the user end. In this article, we have analyzed a relay-based interference-limited network at millimeter wave frequency and proposed a Poisson point process–based model using a stochastic geometrical approach. The results for the proposed Poisson point process model have been evaluated in terms of success probability, network ergodic capacity, and outage probability, compared with the ideal grid model and conventional multiple-antenna ultra-dense network model. The results proved that the success probability and ergodic capacity for the proposed model are 3.5% and 2.3% higher as compared to the most commonly used model for the high-density network, respectively. Furthermore, the results have been analyzed at different multiple-input-multiple-output antenna configuration, which validates the model in the improvement of overall network performance even for higher number of antennas.

Vertical Handover Analysis Using Modified MADM Method in LTE

Ubiquitous Communication is being a trend in this era. It is possible anywhere anytime with the sustenance and by the agreement of different service providers of Mobile technology. A mobile node which is attached to its base station relinquishes its connection while continuous mobility causes a fluctuation of signal strength. To overcome this issue, heterogeneous networks provision is obligatory. Normally Base stations serve several mobile nodes. Whenever a base station cannot handle a mobile terminal, it will assign its node to nearby available base station for service. The process of assignment of mobile nodes to another base station is termed as Heterogeneous handover. This type of Handover is needed for seamless integration of networks. LTE has proved promising outcomes in providing successful handover, Since it uses eNodeB infrastructure. In this work, Received signal strength is taken as main measure and analysed. Received Power acts as the building block for making possible handover across heterogeneous Radio Access Technologies. Proposed method suggests a vertical handover based on various signal measures. Enhanced Weighted Sum Method is incorporated for Handover decision making. Several criteria also utilized.

Compressive Initial Access and Beamforming Training for Millimeter-Wave Cellular Systems

Initial access (IA) is a fundamental physical layer procedure in cellular systems where user equipment (UE) detects nearby base station (BS) as well as acquire synchronization. Due to the necessity of using antenna array in millimeter-wave (mmW) IA, the channel spatial information can also be inferred. The state-of-the-art directional IA (DIA) uses sector sounding beams with limited angular resolution, and thus requires additional dedicated radio resources, access latency and overhead for refined beam training. To remedy the problem of access latency and overhead in DIA, this work proposes to use a quasi-omni pseudorandom sounding beam for IA, and develops a novel algorithm for joint initial access and fine resolution initial beam training without requiring extra radio resources. We provide the analysis of the proposed algorithm miss detection rate under synchronization error, and further derive Cram\'er-Rao lower bound of angular estimation under frequency offset. Using QuaDRiGa simulator with mmMAGIC model at 28 GHz, the numerical results show that the proposed approach is advantageous to DIA with hierarchical beam training. The proposed algorithm offers up to two order of magnitude access latency saving compared to DIA, when the same discovery, post training SNR, and overhead performance are targeted. This conclusion holds true in various propagation environments and 3D locations of a mmW pico-cell with up to 140m radius.

Dual-Mode User-Centric Open-Loop Cooperative Caching for Backhaul-Limited Small-Cell Wireless Networks

The spectral efficiency of small-cell wireless networks is limited by the backhaul capacity of the base stations (BSs) as well as the severe interference from the neighboring BSs. One promising approach to improve the spectral efficiency of small-cell wireless networks is cache-aided cooperative transmission, where caching at the BSs can alleviate the high-speed backhaul capacity requirement and cooperative transmission can enhance the signal-to-interference-plus-noise ratio. A key issue is that the cached content may not be located at the nearest BS, which means that to access such content, a user needs to overcome strong interference from the nearby BSs. We propose an interference-aware dual-mode caching and user-centric open-loop cooperative transmission scheme that embraces spatial caching diversity and user-centric open-loop cooperative transmission, and alleviate the interference issue in the system. Based on the proposed scheme, we derive a tractable expression of the average successful transmission probability (STP) in terms of key system parameters. We then design a low-complexity algorithm to optimize the average STP with respect to the bandwidth and the cache storage capacity allocation. Simulations show that the proposed scheme achieves a higher average STP than the existing caching schemes.

Electromagnetic Radiation Exposure from Nearby Cellular Base Stations in the Gaza Strip, Palestine: A Concern for Public Health

The widespread mobile station’s antennas and the continued increase in the number of mobile phones users throughout the Gaza strip causing great panic in the population relating the debate overexposure to electromagnetic radiation EMR emitted from the antennas of mobile base stations. Therefore, this study was conducted to measure the levels of electromagnetic radiation emitted from the antennas of cellular base stations in Gaza governorate as well as to evaluate the citizen’s awareness and practices regarding potential health risks and mitigation methods of exposure to electromagnetic radiation emitted from cellular base stations, respectively. Fifty cellular base stations out of 197 stations were selected depending on the criteria of selecting one site per kilometer using Global Positioning System (GPS). Electromagnetic power density, electric field strength, and the magnetic field strength emitted from cellular base stations were measured using Narda-550. Assessment tool for observation was used to collect operational information of each station. A structured questionnaire with four-level Likert rating scale was used to survey 384 mobile phone users from the areas surrounding the selected cellular base stations. The results showed that the electromagnetic radiation levels of all stations were low and less than the national and international acceptable limits. Furthermore, the awareness of participant about health risks that could result from exposure to electromagnetic radiation emitted from cellular base stations and mobile phones was low. Nevertheless, the participant’s practices in mitigating the adverse impacts of electromagnetic radiation emitted from cellular base stations and mobile phones on their health were good.

Design and Analysis of Satellite Based Automatic Identification System in VHF Band for Maritime Applications

This paper is introducing analyses of new design of the Automatic Identification System (AIS) ships antenna that will serve for both VHF-band Radio and Satellite tracking and identification system for maritime applications. The current AIS network is an automatic tracking system used by ships of Vessel Traffic Service (VTS) for identification and location of vessels by electronically exchanging data between nearby ships and on-shore base station. In the AIS system for the electronic data exchange, the Very High Frequency (VHF) range is used. Utilizing of the VHF range makes the AIS as short-range communication, identification and collision avoidance system between AIS equipped ships and base station is possible in the antennas Line-of-Sight (LOS). In order to widen the range of the AIS from short range up to long or global range should be used AIS communication via a satellite. In order to provide communication via satellite as well should be designed multifunctional antenna for both Radio AIS (R-AIS) and Satellite AIS (S-AIS) communication antenna. The analyses and design of a new multifunctional antenna, calculation and development, including implementation and testing of helical VHF antenna for R-AIS and S-AIS equipment are discussed.

Coverage Probability Analysis for mmWave Communication Network With ABSF-Based Interference Management by Stochastic Geometry

Millimeter wave (mmWave) communication technology has been widely discussed as a promising part to be used in 5th Generation (5G) fig: interference networks. However, mmWave signals are sensitive to blockage compared with traditional spectrums used for cellular networks, which proposes new challenges. In addition, 5G networks will support Time-Division Duplex (TDD) mode, which is able to provide flexible and dynamic uplink-downlink (UL-DL) configurations. However, dynamic adjustment will then introduce UL-DL interference and will further influence system performance. This paper will focus on the coverage probability of mmWave communication network with dynamic TDD configuration based on stochastic geometry analysis. Both the Line-of-Sight (LoS) link and Non-Line-of-Sight (NLoS) link are modeled, since the transmissions of mmWave signals will be greatly influenced by different link types. Coverage probabilities for downlink and uplink are analyzed, respectively. Furthermore, in order to mitigate the UL-DL interference introduced by dynamic TDD, the Almost-Blank-SubFrame (ABSF) scheme is studied in this work. In ABSF scheme, a base station with DL transmission will mute temporarily to avoid severe DL-UL interference to nearby base stations with LoS links and UL transmissions. Possible improvement after introducing ABSF is studied by updating downlink and uplink coverage probability expressions. Numerical results under different configurations are obtained and discussed. It is shown that uplink coverage probability is greatly influenced by downlink interference, which provides basis for applying ABSF. Improvements by ABSF are validated by corresponding results.

Energy-Efficient MTC Data Offloading in Wireless Networks Based on K-Means Grouping Technique

Machine-type communication (MTC) devices provide a broad range of data collection especially on the massive data generated environments such as urban, industrials and event-enabled areas. In dense deployments, the data collected at the closest locations between the MTC devices are spatially correlated. In this paper, we propose a k-means grouping technique to combine all MTC devices based on spatially correlated. The MTC devices collect the data on the event-based area and then transmit to the centralized aggregator for processing and computing. With the limitation of computational resources at the centralized aggregator, some grouped MTC devices data offloaded to the nearby base station collocated with the mobile edge-computing server. As a sensing capability adopted on MTC devices, we use a power exponential function model to compute a correlation coefficient existing between the MTC devices. Based on this framework, we compare the energy consumption when all data processed locally at centralized aggregator or offloaded at mobile edge computing server with optimal solution obtained by the brute force method. Then, the simulation results revealed that the proposed k-means grouping technique reduce the energy consumption at centralized aggregator while satisfying the required completion time.

Wireless-Powered Device-to-Device-Assisted Offloading in Cellular Networks

Offloading cellular traffic to device-to-device (D2D) communications has been proposed to improve the network capacity and to alleviate the traffic burden on base stations (BSs). However, as mobile devices are powered by limited battery energy, there is no obligation for D2D transmitters (D2D-Txs) to offload cellular traffic through D2D content sharing. In this paper, we model and analyze the wireless-powered D2D-assisted offloading (WPDO) in cellular networks, where the D2D-Txs can harvest radio frequency energy from nearby BSs and utilize the harvested energy to share popular contents with nearby user equipments. Stochastic geometry is used to characterize the intrinsic relationship between the wireless power transfer (WPT) and the information transmission. Based on the proposed model, we derive the average transmit power at D2D-Tx, the expected minimum transmit power at BS, the D2D outage probability, and the cellular downlink outage probability. We also investigate the energy efficiency of the WPDO network from a system-level perspective. Simulation and numerical results show that the energy efficiency of the WPDO network can be maximized by optimizing the fraction of time allocated for WPT and it can be further improved by using massive antenna arrays at each BS and by sharing more popular contents between devices.

Simless GSM positioning for navigation in GPS-denied environments

PurposeUntil now, air navigation systems have mainly relied on global navigation satellite systems (GNSS) on the worldwide spread global positioning system. However, the so-called GNSS-denied environments open a new research line which pursues the development of alternative technologies which will cover this gap in positioning systems’ services.Design/methodology/approachThis paper presents the possibility of using positioning systems based on global system for mobile communications (GSM) signal. This approach developed in a standalone device will provide real-time information. The presented algorithm pursues a new methodology for providing useful information.FindingsAmong all the different technologies aimed at giving a navigation solution in the absence of any kind of GNSS in which this paper is based, it advocates for the use of the signals of opportunity, particularly the usage of GSM.Practical implicationsTechnology is currently immersed in an era of continuous progress and expansion of navigation systems. These are evolving toward high performance systems, offering precise, efficient and safe air navigation. In addition, the growing demand for unmanned aerial vehicles increases the level of exigency on this activity even more. Therefore, in the context of the development of unmanned navigation technologies, the aim is to implement positioning systems that will allow high precision even in though environments.Originality/valueReferencing the SIMless concept, a SIM-free system is described in this paper. The SIM-free system is supported by open data bases and permits the positioning based on the information sniffed from the signals broadcast by a set of several nearby base station of the GSM network. Hence, it provides same and in some cases even better accuracies than the already developed techniques, not being necessary to synchronize the link between the mobile terminal and the base station transceiver (BTS).

Joint Frequency Reuse and Cache Optimization in Backhaul-Limited Small-Cell Wireless Networks

Caching at base stations (BSs) is a promising approach for supporting the tremendous traffic growth of content delivery over future small-cell wireless networks with limited backhaul. This paper considers exploiting spatial caching diversity (i.e., caching different subsets of popular content files at neighboring BSs) that can greatly improve the cache hit probability, thereby leading to better overall system performance. A key issue in exploiting spatial caching diversity is that the cached content may not be located at the nearest BS, which means that to access such content, a user needs to overcome strong interference from the nearby BSs; this significantly limits the gain of spatial caching diversity. In this paper, we consider a joint design of frequency reuse and caching, such that the benefit of an improved cache hit probability induced by spatial caching diversity and the benefit of interference coordination induced by frequency reuse can be achieved simultaneously. We obtain a closed-form characterization of the approximate successful transmission probability for the proposed scheme and analyze the impact of key operating parameters on the performance. We design a low-complexity algorithm to optimize the frequency reuse factor and the cache storage allocation. Simulations show that the proposed scheme achieves a higher successful transmission probability than existing caching schemes.

IoT Communications Network for Wireless Power Transfer System State Estimation and Stabilization

Wireless energy harvesting has emerged as an appealing solution to prolong the lifespan of energy-constrained wireless networks and been regarded as a main functional unit for almost all perpetual communications. This paper proposes a channel coding-based Internet of Things communication network, and state estimation as well as stabilization algorithms for wireless power transfer systems. After modeling the energy harvesting module like wireless energy transfer systems as a state-space framework, Web-enabled smart sensors are deployed to obtain measurements. The sensing information is transmitted to the nearby base station for collection and digital communication under the condition of packet losses. A recursive systematic convolutional code is used to add redundancy into the quantize system states. After digital modulation, the signal is transmitted to a control center for system state estimation and stabilization. The optimal gain of the state estimation scheme is determined after minimizing the mean squared errors. Afterward, a stabilization algorithm is designed considering packet losses in the communication networks using the semidefinite programming approach. Furthermore, the convergence of the developed estimation algorithm is proved. Numerical simulation results demonstrate, considering packet loss, sensor faults, disturbances, and delay into account, that the proposed algorithms can estimate and stabilize the system states within a short period of time.

Performance Analysis of Energy-Efficient Cellular Networking on Urban and Rural Environments

Each base station in both rural and urban areas produces significant amount of carbon dioxide toxins in the surrounding environment. The volume of these toxins is proportional to the energy consumption of the base stations (BSs). In this paper, a Greedy methodology is proposed to reduce the energy consumption of the BS. The energy consumption of the BS can be achieved through the greedy algorithm in the following ways. The low traffic BS can transfer their traffic to the nearby BS, which reduces the energy consumption of the low traffic BS. The high traffic BS suffers the link failure due to its overloaded traffic in BS, which increases the energy consumption. The proposed energy efficient greedy methodology reduces the energy consumption of the BS in both criteria, by measuring traffic levels on BS and switches the modes of base stations based on their traffic levels.

Identifying the Fake Base Station: A Location Based Approach

Fake base station (FBS) attack is a great security challenge to wireless user equipment (UE). During the cell selection stage, the UE receives multiple synchronization signals (SSs) from multiple nearby base stations (BSs) and then synchronizes itself with the strongest SS. An FBS also can transmit an SS with sufficient power to confuse the UE, which makes the UE connect to the FBS, and may lead to the leakage of private information. In this letter, countermeasure to the FBS attack by utilizing the location information is investigated. Two location awareness based FBS-resistance schemes are proposed by checking the received signal strength according to the position of the UE and a legitimate BS map. The successful cheating rate (SCR) defined as the probability that the UE will connect to the FBS is investigated. Numeric results show that with the two proposed schemes, the SCR can be greatly reduced especially when the transmit power of the FBS is large. Beyond that, a cooperation-aided method is further proposed to improve the performance, and we show that the cooperation-aided method can further suppress the SCR when the signal strength from the FBS is similar to that from the legitimate BS.

Optimal Hierarchical Radio Resource Management for HetNets With Flexible Backhaul

Providing backhaul connectivity for macro and pico base stations (BSs) constitutes a significant share of infrastructure costs in future heterogeneous networks (HetNets). To address this issue, the emerging idea of flexible backhaul is proposed. Under this architecture, not all the pico BSs are connected to the backhaul, resulting in a significant reduction in the infrastructure costs. In this regard, pico BSs without backhaul connectivity need to communicate with their nearby BSs in order to have indirect accessibility to the backhaul. This makes the radio resource management (RRM) in such networks more complex and challenging. In this paper, we address the problem of cross-layer RRM in HetNets with flexible backhaul. We formulate this problem as a two-timescale non-convex stochastic optimization which jointly optimizes flow control, routing, interference mitigation and link scheduling in order to maximize a generic network utility. By exploiting a hidden convexity of this non-convex problem, we propose an iterative algorithm which converges to the global optimal solution. The proposed algorithm benefits from low complexity and low signalling, which makes it scalable. Moreover, due to the proposed two-timescale design, it is robust to the backhaul signalling latency as well. Simulation results demonstrate the significant performance gain of the proposed solution over various baselines.

Fast Content Delivery via Distributed Caching and Small Cell Cooperation

The demand for higher and higher wireless data rates is driven by the popularity of mobile video content delivery through wireless devices such as tablets and smartphones. To achieve unprecedented mobile content delivery speeds while reducing backhaul cost and delay, in this paper we propose a new system architecture that combines two recent ideas, distributed caching of content in small cells (FemtoCaching), and, cooperative transmissions from nearby base stations (Coordinated Multi-Point). A key characteristic of the proposed architecture is the interdependence between the caching strategy and the physical layer coordination. Specifically, the caching strategy may cache different content in nearby base stations (BSs) to maximize the cache hit ratio, or cache the same content in multiple nearby BSs such that the corresponding BSs can transmit concurrently, e.g., to multiple users using zero-forcing beamforming, and achieve multiplexing gains. Such interdependency allows a joint cross-layer optimization. Given the popularity distribution of the content, the available cache size, and the network topology, we devise near-optimal strategies of caching such that the system throughput is maximized or the system delay is minimized. Under realistic scenarios and assumptions, our analytical and simulation results show that our system yields significantly faster content delivery, which can be one order of magnitude faster than that of legacy systems.

Radiofrequency radiation from nearby base stations gives high levels in an apartment in Stockholm, Sweden: A case report.

Exposure to radiofrequency (RF) radiation was classified in 2011 as a possible human carcinogen, Group 2B, by the International Agency for Research on Cancer of the World Health Organisation. Evidence of the risk of cancer risk has since strengthened. Exposure is changing due to the rapid development of technology resulting in increased ambient radiation. RF radiation of sufficient intensity heats tissues, but the energy is insufficient to cause ionization, hence it is called non-ionizing radiation. These non-thermal exposure levels have resulted in biological effects in humans, animals and cells, including an increased cancer risk. In the present study, the levels of RF radiation were measured in an apartment close to two groups of mobile phone base stations on the roof. A total of 74,531 measurements were made corresponding to ~83 h of recording. The total mean RF radiation level was 3,811 µW/m2 (range 15.2–112,318 µW/m2) for the measurement of the whole apartment, including balconies. Particularly high levels were measured on three balconies and 3 of 4 bedrooms. The total mean RF radiation level decreased by 98% when the measured down-links from the base stations for 2, 3 and 4 G were disregarded. The results are discussed in relation to the detrimental health effects of non-thermal RF radiation. Due to the current high RF radiation, the apartment is not suitable for long-term living, particularly for children who may be more sensitive than adults. For a definitive conclusion regarding the effect of RF radiation from nearby base stations, one option would be to turn them off and repeat the measurements. However, the simplest and safest solution would be to turn them off and dismantle them.

The effect of living nearby telecommunication base station: From the residents’ feeling

The effect of living nearby telecommunication base station: From the residents’ feeling