Cellular Frequency Bands Research Articles

A complete artificial intelligence pipeline for radio frequency energy prediction in cellular bands for energy harvesting systems

Radio Frequency (RF) energy harvesting has been used to power wireless and low-powered devices. However, RF energy harvesting has limitations in terms of the amount of power that can be collected based on signal availability. Hence, energy prediction is essential to improve energy harvesting circuits' performance. Previous research has mainly focused on improving power harvesting policies or theoretically estimating the harvested energy. Very few works have considered the prediction of the RF signal as time series data using real RF measurements. Moreover, challenges such as the power consumed by the circuit's harvesting decisions and the impact of outliers on the model performance haven't been addressed yet. This paper presents a complete pipeline for developing the best predictive model for RF energy in cellular frequency bands. Real-time measurements are taken in different frequency bands using software-defined radio technology. We use four artificial intelligence techniques to model the RF energy signal. Additionally, we propose an optimized model with an enhanced loss function, which makes the model more resilient to anomalies, saving computational power and time consumed in cleaning the data. The four algorithms are investigated, and their prediction accuracies are compared. The average power of a period of 5 min is accurately forecasted. Numerical results in the 1960 MHz band show that long short-term memory has the best performance, followed by the DeepAR algorithm with prediction accuracies of 95.76% and 95.02%, respectively. Moreover, the proposed optimized model showed a 32.2% lower prediction error than the traditional models.

Resource Allocation for RIS-Assisted Device-to-Device Communications in Heterogeneous Cellular Networks

In recent years, with the explosive growth of data traffic, communication base stations (BSs) need to serve more and more users. Offloading traffic from BSs has become an efficient way to reduce the burden on BSs. Device-to-Device (D2D) communications have emerged to improve spectrum utilization by reusing the frequency spectrum of the cellular frequency band. In the general environment, Heterogeneous Cellular Networks (HCNs) including millimeter wave (mm-wave) have appeared. Since the D2D link allows to share of spectrum resources with the cellular user, it will bring potential interference to the cellular user. Fortunately, an emerging technology called Reconfigurable Intelligent Surface (RIS) can mitigate the severe interference caused by D2D links by shaping the incident beam and improving the multipath phase shift. In this paper, we study the resource allocation scheme to maximize the system sum rate, in the RIS-assisted single-cell heterogeneous D2D communication scenario. To solve the Block Coordinate Descent (BCD) problem, the problem of maximizing the sum rate is decomposed into three sub-problems. The resource allocation sub-problem is solved by a coalitional game method based on the game theory. The power allocation problem of the coalition converts the concave function into a convex optimization by mathematical transformation. The problem is solved by the gradient descent method. The local search method is adopted to find the optimum for the phase conversion problem. Then iterate until the difference of sum rate is less than the threshold. The simulation results show that the designed algorithm is superior to other benchmark schemes in the literature.

Simulation of the Earth’s radio-leakage from mobile towers as seen from selected nearby stellar systems

ABSTRACT Mobile communication towers represent a relatively new but growing contributor to the total radio-leakage associated with planet Earth. We investigate the overall power contribution of mobile communication towers to the Earth’s radio leakage budget, as seen from a selection of different nearby stellar systems. We created a model of this leakage using publicly available data of mobile tower locations. The model grids the surface of the planet into small, computationally manageable regions, assuming a simple integrated transmission pattern for the mobile antennas. In this model, these mobile tower regions rise and set as the Earth rotates. In this way, a dynamic power spectrum of the Earth was determined, summed over all cellular frequency bands. We calculated this dynamic power spectrum from three different viewing points – HD 95735, Barnard’s star, and Alpha Centauri A. Our preliminary results demonstrate that the peak power leaking into space from mobile towers is ∼4GW. This is associated with Long Term Evolution (LTE) mobile tower technology emanating from the East Coast of China as viewed from HD 95735. We demonstrate that the mobile tower leakage is periodic, direction dependent, and could not currently be detected by a nearby civilization located within 10 light-years of the Earth, using instrumentation with a sensitivity similar to the Green Bank Telescope. We plan to extend our model to include more powerful 5G mobile systems, radar installations, ground based up-links (including the Deep Space Network), and various types of satellite services, including low-Earth orbit constellations, such as Starlink and OneWeb.

Interference Voltage Estimation for Implantable Cardiac Pacemaker Electromagnetic Interference at Fourth-Generation (4G) and Fifth-Generation (5G) Sub-6 GHz Cellular Frequency Bands

Interference Voltage Estimation for Implantable Cardiac Pacemaker Electromagnetic Interference at Fourth-Generation (4G) and Fifth-Generation (5G) Sub-6 GHz Cellular Frequency Bands

Design of a 5G Sub-6 GHz Vehicular Cellular Antenna Element with Consistent Radiation Pattern Using Characteristic Mode Analysis.

A cellular 5G sub-6 GHz vehicle antenna design with a consistent radiation pattern across the frequency bands in 0.617-5 GHz is demonstrated via characteristic mode analysis. The design focuses on maintaining monopole first-order mode radiation pattern over cellular frequency bands and avoiding higher-order modes out of the operational frequency bands to provide optimal performance for automotive requirements. Rather than using an empirical design method, the design procedure in this paper uses the calculated modal significance, characteristic current, modal radiation pattern, and reflection coefficient to define the antenna structure dimensions. The proposed design was simulated, a prototype was measured, and the performance was evaluated on a 1-m ground plane. The antenna has perfect omnidirectionality with a high and stable gain across the frequency range in the 30° area above the horizon.

A 3-Dimensional Multiband Antenna for Vehicular 5G Sub-6 GHz/GNSS/V2X Applications

A compact multiband monopole antenna is proposed for vehicular roof top shark-fin applications. The proposed multiband antenna covers 5G sub-6 GHz and LTE bands starting at 617 MHz to 5000 MHz and the higher GNSS band from 1559 to 1606 MHz as well as the V2X band at 5900 MHz. The presented antenna is a three-dimensional monopole antenna with two branches to cover the required bands with compact size to fit inside a roof top shark-fin. The long antenna branch covers the lower cellular frequency band from 617 to 960 MHz, while the short branch covers the higher frequency band from 1559 to 6000 MHz. The presented antenna is mounted on a double-sided FR4 PCB and is feeded through a short cable. The proposed antenna covers multiple frequency bands with compact size (H x L x W) of 58 × 37 × 17 mm3. The antenna is simulated and optimized, and then, a prototype is fabricated, and its radiation characteristics are measured when mounted on one-meter ground plane and on a vehicle’s roof. The maximum measured linear average gain is 3 dBi at 1900 MHz, and the maximum measured efficiency is 88% at 787 MHz. The active GNSS antenna gain is measured using an LNA with good isolation. A good agreement is achieved between the simulated and measured results when compared in terms of voltage standing wave ratio (VSWR), radiation patterns, linear average gain (LAG), and antenna efficiency.

Ultra-Compact mm-Wave Monolithic IC Doherty Power Amplifier for Mobile Handsets

This work develops a novel dynamic load modulation Power Amplifier (PA) circuity that can provide an optimum compromise between linearity and efficiency while covering multiple cellular frequency bands. Exploiting monolithic microwave integrated circuits (MMIC) technology, a fully integrated 1W Doherty PA architecture is proposed based on 0.1 μm AlGaAs/InGaAs Depletion-Mode (D-Mode) technology provided by the WIN Semiconductors foundry. The proposed wideband DPA incorporates the harmonic tuning Class-J mode of operation, which aims to engineer the voltage waveform via second harmonic capacitive load termination. Moreover, the applied post-matching technique not only reduces the impedance transformation ratio of the conventional DPA, but also restores its proper load modulation. The simulation results indicate that the monolithic drive load modulation PA at 4 V operation voltage delivers 44% PAE at the maximum output power of 30 dBm at the 1 dB compression point, and 34% power-added efficiency (PAE) at 6 dB power back-off (PBO). A power gain flatness of around 14 ± 0.5 dB was achieved over the frequency band of 23 GHz to 27 GHz. The compact MMIC load modulation technique developed for the 5G mobile handset occupies the die area of 3.2 mm2.

Spectrum Occupancy Measurements in Cellular Frequency Band in Samsun

In this study, available spectrum parts in GSM900, LTE800, LTE900, GSM1800, LTE1800, UMTS2100 and LTE2600 were determined. The measurement campaigns were performed at 115 different locations in Samsun city center at the most active time of a day using RF Explorer 6G Combo analyzer device. The spectrum utilization rates were determined using energy detection technique (EDT), and average spectrum occupancy technique (ASOT). The thresholds were chosen manually as -40, -45, -50, -55, -60, -65, -70, -75 dBm, and as 10-dB above the noise floor, as recommended by International Telecommunication Union (ITU), and spectrum utilization was evaluated through EDT and ASOT. Obtained results show that at most of the measurement locations spectrum occupancy percentages calculated via EDT and ASOT very close to each other. Based on the results UMTS2100 band showed the highest average spectrum occupancy i.e. 33.91% and the overall average spectrum occupancy rate was found to 22.72%. Additionally, at 50% of the measurement locations occupancy percentage was below 33% for all services. The average occupancy over GSM900 band was between 0,87% - 66.61% according to the predetermined threshold. It was also found that the bands LTE1800 and LTE2600 were mostly occupied for the thresholds below -60 dBm whereas the measured spectrum was mostly vacant for -40 dBm. This led us to infer that there is a great potential for share some of UHF band for cognitive radio applications and future 5G systems.

Multiband Patch Antenna Design Using Nature-Inspired Optimization Method

Radio frequency energy harvesting has attracted considerable interest as a technique of enabling self-powered wireless networks. This technique faces several challenges, such as the receiving and the rectifying modules of a rectenna system. Multiband antennas provide several comparative advantages against the goal of maximizing the amount of energy harvesting. In this work, we present a multiband microstrip patch antenna with three slits operating in the LoRaWAN (Long Range Wide Area Network) and the cellular (GSM-1800 and UMTS) communication frequency bands. A feasible solution of the antenna is obtained by the application of a recently introduced nature-inspired optimization technique, namely the Coyote Optimization Algorithm. The proposed antenna operates satisfactorily in the LoRaWAN (Long Range Wide Area Network) and the cellular (GSM-1800 and UMTS) communication frequency bands. Measured results of the proposed antenna exhibit an acceptable performance (multiband frequency operation, maximum gain of 3.94 dBi, broadside operation) and demonstrate features of operation, which make it a strong candidate for various RF energy harvesting applications.

Towards Reliable UAV Swarm Communication in D2D-Enhanced Cellular Networks

In the existing cellular networks, it remains a challenging problem to communicate with and control an unmanned aerial vehicle (UAV) swarm with both high reliability and low latency. Due to the UAV swarm’s high working altitude and strong ground-to-air channels, it is generally exposed to multiple ground base stations (GBSs), while the GBSs that are serving ground users (occupied GBSs) can generate strong interference to the UAV swarm. To tackle this issue, we propose a novel two-phase transmission protocol by exploiting cellular plus device-to-device (D2D) communication for the UAV swarm. In Phase I, one swarm head is chosen for ground-to-air channel estimation, and all the GBSs that are not serving ground users (available GBSs) transmit a common control message to the UAV swarm simultaneously, using the same cellular frequency band. Both the swarm head and other swarm members can utilize the high power gain from multiple available GBSs’ transmission, to combat the strong interference from occupied GBSs, while some UAVs may fail to decode the message due to uncorrelated ground-to-air channels. In Phase II, all the UAVs that have decoded the message in Phase I further relay it to the other UAVs in the swarm via D2D communication, by exploiting the less interfered D2D frequency band and the proximity among UAVs. In this paper, we aim to characterize the reliability performance of the above two-phase transmission protocol, i.e., the expected percentage of UAVs in the swarm that can decode the common control message, which is a non-trivial problem due to the complex system setup and the intricate coupling between the two transmission phases. Nevertheless, we manage to obtain an approximated expression of the reliability performance of interest, under reasonable assumptions and with the aid of the Pearson distributions. Numerical results validate the accuracy of our analytical results and show the effectiveness of our proposed protocol over other benchmark protocols. We also study the effect of key system parameters on the reliability performance, to reveal useful insights on the practical design of cellular-connected UAV swarm communication.

Ultralow Profile, Low Passive Intermodulation, and Super-Wideband Ceiling Mount Antennas for Cellular and Public Safety Distributed Antenna Systems.

This paper presents an ultralow profile, low passive intermodulation (PIM), and super-wideband in-building ceiling mount antenna that covers both the cellular and public safety ultra high frequency (UHF) band for distributed antenna system (DAS) applications. The proposed antenna design utilizes a modified 2-D planar discone design concept that is miniaturized to fit into a small disc-shaped radome. The 2-D planar discone has an elliptical-shaped disc monopole and a bell-shaped ground plane, a stub at the shorting path, with asymmetrical structure and an additional proximity coupling patch to maximize the available electrical path to support the 350 MHz band range. The proposed design maximizes the radome area with a reduction of about 62% compared to similar concept type antennas. Besides, the proposed design exhibits an improved radiation pattern with null reduction compared to a typical dipole/monopole when lies at the horizontal plane. A prototype was manufactured to demonstrate the antenna performance. The VSWR and radiation pattern results agreed with the simulated results. The proposed antenna achieves a band ratio of 28.57:1 while covering a frequency range of 350–10000 MHz. The measured passive intermodulation levels are better than −150 dBc (2 × 20 Watts) for 350, 700 and 1920 MHz bands.

Use Ultra-Wideband Discone Rectenna for Broadband RF Energy Harvesting Applications

In this study, a broadband Radio Frequency (RF) energy harvester implementation is presented. The system uses a broadband discone antenna, which can operate efficiently in a broad frequency spectrum, including LTE, DCS 1800 and UMTS 2100 cellular frequency bands. The system is able to harvest energy from various electromagnetic field sources, thus has the potential to efficiently charge a storage energy element in a short time. The prototype broadband RF energy harvester was tested in the laboratory and also in a typical urban environment.

Energy Minimization of Multi-Cell Cognitive Capacity Harvesting Networks With Neighbor Resource Sharing

In this paper, we investigate the energy minimization problem for a cognitive capacity harvesting network (CCHN), where secondary users (SUs) without cognitive radio (CR) capability communicate with CR routers via device-to-device (D2D) transmissions, and CR routers connect with base stations (BSs) via CR links. Different from traditional D2D networks that D2D transmissions share the resource of cellular transmissions in the same cell, we consider the scenario that D2D transmissions share the uplink cellular frequency bands (CFBs) of neighbor cells. To ensure that the transmissions from SUs do not affect the transmissions for the cellular users (CUs) in the neighbor cells, an inter-cell handshake process is proposed. We formulate the energy minimization problem for SUs as a mixed integer non-linear programming (MINLP). To solve this problem, we decompose it into two nested subproblems: a transmit power optimization subproblem and a CR router and uplink CFB selection subproblem. For the first subproblem, it is proved to be convex, and thus can be efficiently solved. For the second subproblem, we propose a two-level nested game theoretic approach to finding its solution. Simulation results show that the proposed algorithms can significantly improve the performance. With the help of CR routers/the neighbor resource sharing, the energy consumption for SUs can be saved around 30%-37% on average.

Implementation of 5G in Guided and Unguided Optical Communication System with Cellular Frequency Bands

Implementation of 5G in Guided and Unguided Optical Communication System with Cellular Frequency Bands

A voltage-mode RF DAC for massive MIMO system-on-chip digital transmitters

As the number of antenna elements increases in massive multiple-input multiple-output-based radios such as fifth generation mobile technology (5G), designing true multi-band base-station transmitter, with efficient physical size, power consumption and cost in emerging cellular frequency bands up to 10 GHz, is becoming a challenge. This demands a hard integration of radio components, particularly the radio’s digital application-specific integrated circuits (ASIC) with high performance multi-band data converters. In this work, a novel radio frequency digital-to-analog converter (RF DAC) solution is presented, that is also capable of monolithic integration into today’s digital ASIC due to its digital-in-nature architecture. A voltage-mode conversion method is used as output stage, and configurable mixing logic is employed in the data path to create a higher frequency lobe and utilize the output signal in the first or the second Nyquist zone. This 12-bit RF DAC is designed in a 22 nm FDSOI CMOS process, and shows excellent linearity performance for output frequencies up to 10 GHz, with no calibration and no trimming techniques. The achieved linearity performance is able to fulfill the high requirements of 5G base-station transmitters. Extensive Monte-Carlo analysis is performed to demonstrate the performance reliability over mismatch and process variation in the chosen technology.

Small Cell Cluster-Based Resource Allocation for Wireless Backhaul in Two-Tier Heterogeneous Networks With Massive MIMO

In this paper, we investigate the resource allocation problem in two-tier heterogenous networks (HetNets) with massive MIMO, where two frequency bands, cellular frequency band and millimeter wave frequency band, are used for wireless backhaul links. To coordinate the interference among small cells (SCs), SCs are grouped into multiple SC clusters (SCCs), where SC users are jointly served by SC base stations (BSs) (SBSs) belonging to the same SCC. To eliminate the multi-user and inter-tier interference, we propose a block diagonalization based precoding scheme at macro-BS and each SCC, where the transmit precoding matrix for users is projected onto the null space of interference channels. Following this, we formulate a power allocation optimization problem to maximize the downlink sum rate of the system subject to per-SCC power and users’ quality of service requirements. Since the formulated problem is nonconvex, we transform it into a convex one by appropriate approximation, and a constrained concave convex procedure based iterative algorithm is proposed to obtain the solution. Furthermore, we prove that the obtained solution converges to the local optimum. Meanwhile, according to the structure of the original formulated problem, we divide it into multiple subproblems and propose an optimal iterative water-filling algorithm. Next, we extend the original problem with per-SBS power constraint, which results in that the precoding of each SCC has to be redesigned. On this basis, we propose an iterative water-filling algorithm to obtain the optimal power allocation and precoding. Numerical results are presented to verify the performance of our proposed algorithms.

In Situ Measurement of Acoustic Filters on RF Transceiver Modules

In cellular communications certain frequency bands are licensed to specific applications guaranteeing predictability and reliability of service quality. Undesirable interference from these bands have to be removed by high-quality passive filters. This paper introduces a novel measurement method to determine the frequency response of a cellular system related to these passive filters. The method is based on in situ BER measurements and does not require access to the components of the transceiver hardware or knowledge about components and implementation. It is nondestructive and can be applied as in situ measurement of any wireless modem during normal operation. The results are successfully verified against direct S -parameter measurements of the SMT components.

Double-negative metamaterial for mobile phone application

In this paper, a new design and analysis of metamaterial and its applications to modern handset are presented. The proposed metamaterial unit-cell design consists of two connected square spiral structures, which leads to increase the effective media ratio. The finite instigation technique based on Computer Simulation Technology Microwave Studio is utilized in this investigation, and the measurement is taken in an anechoic chamber. A good agreement is observed among simulated and measured results. The results indicate that the proposed metamaterial can successfully cover cellular phone frequency bands. Moreover, the uses of proposed metamaterial in modern handset antennas are also analyzed. The results reveal that the proposed metamaterial attachment significantly reduces specific absorption rate values without reducing the antenna performances.

Modeling and inferring the attenuation induced by vegetation barriers at 2G/3G/4G cellular bands using Artificial Neural Networks

Modeling vegetation is a recurrent problem for wireless communications industry. The raising number of available frequency bands increases this issue, since most of the existing methods nowadays rely on measurement campaigns. The presence of vegetation in urban areas (such as parks or gardens) is bothersome for radio planners, which have to deal with an in-excess attenuation difficult to predict due to the large number of different cases (i.e. vegetation species, topologies of vegetation volumes, frequencies…). Usually, these vegetation formations appear in the form of forests or barriers, emphasizing the problem, since their impact in the transmitted power is not negligible. This paper proposes the use of Artificial Neural Networks as powerful tools to model and infer the excess attenuation induced by vegetation formations. The study is held at cellular frequency bands (2G/3G/4G) for different vegetation species and barrier configurations, where a multilayer perceptron has been trained over existing experimental data at 2G/3G frequencies. We demonstrate the efficiency of the model to predict accurately the attenuation in the frequencies for which it has been trained for, and to infer and extend the model obtained to new frequencies, e.g. 4G, while maintaining an overall low median error. The proposed framework, which is sought to be a powerful tool for radio planners to predict attenuation due to a vegetation formation, has been validated against measurements conducted in controlled environments at several mobile radio frequencies, but it could be easily extended to other radio frequencies, such as WiFi, WiMax or 5G frequency bands, as long as a proper training is performed, to include different propagation effects at such bands.

Design and performance analysis of pattern reconfigurable MIMO antennas for mobile smartphones

ABSTRACTThis paper presents compact pattern reconfigurable antennas for mobile handsets in MIMO configuration. Each antenna of the MIMO configuration being coupled fed monopole in meandered form is capable of covering several cellular frequency bands in the range of 1.75–2.67 GHz including 4G‐LTE, 2G‐GSM, 3G‐UMTS, and WLAN. The MIMO antennas are printed diagonally at the left and right no‐ground portions on the top layer of the substrate to enhance the isolation performance. The substrate used is FR‐4 with relative permittivity of 4.35 and loss tangent of 0.02. The volume of the substrate is 120 × 65 × 1.6 mm3 with each antenna occupying an area of 26.5 × 14.5 mm2. The pattern reconfigurability is achieved by connecting and disconnecting a 4.5 × 2 mm2 metallic strip using the p‐i‐n diode switch. The antennas are pattern reconfigurable in the frequency range of 1.9–2.1 GHz. The isolation achieved is better than 16 dB over all the frequency bands covered by each antenna. A prototype has been fabricated and tested. The simulated and measured results show a good performance of the MIMO antennas. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:148–156, 2017