LTE Channel Research Articles

Iterative Interference Cancellation for Multi-Carrier Modulation in MIMO-DWT Downlink Transmission

The Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) scheme represents the dominant radio interface for broadband multicarrier communication systems. However, with insufficient Cyclic Prefixes (CP), Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) occur due to the time-varying multipath channel. This means that the performance of the system will be degraded. In this paper, we investigate the interference problem for a MIMO Discrete Wavelet Transform (MIMO-DWT) system under the effect of the downlink LTE channel. A Low-Density Parity-Check (LDPC) decoder is used to estimate the decoded signal. The proposed iterative algorithm uses the estimated decoded signal to compute the components required for ICI/ISI interference reduction. In this paper, Iterative Interference Cancellation (IIC) is employed to mitigate the effects of interference that contaminates the received signal due to multiple antenna transmission and a multipath channel. An equalizer with minimum mean square error is considered. We compare the performance of our proposed algorithm with the traditional MIMO-OFDM scheme in terms of bit error probability under insufficient CP. Simulation results verify that significant improvements are achieved by using IIC and MIMO-IIC for both systems.

GaRuDa: A Blockchain-Based Delivery Scheme Using Drones for Healthcare 5.0 Applications

Over the years, the healthcare industry has transformed from being hospital-centric to patient-centric. This shift is mainly due to the convergence of emergent technologies such as Internet of Things (IoT)-based healthcare, fifth generation (5G)-assisted networking, and data-driven analytics through artificial intelligence. The convergence, referred to as Healthcare 5.0, has improved healthcare services to support real-time analytics, user mobility, remote monitoring, and personalized user experience through decentralized applications. However, the medical supply chain systems and delivery operations among healthcare stakeholders suffer from limitations of harsh environmental conditions due to restricted zones, rough terrains, war-prone areas, poor road conditions, congested traffic, and remote locations. Thus, the Internet of Drones (IoD) is deployed in Healthcare 5.0 supply chains to streamline and expedite the medical delivery process through open channels (i.e. the Internet). However, the Internet is an open channel that is prone to malicious activities which can violate the privacy and confidentiality of patient data. Blockchain is a promising technology that can handle the security and reliability of drone delivery among untrusted open channels. Motivated by the aforementioned facts, we propose GaRuDa, a blockchain-based drone delivery scheme for Healthcare 5.0 applications. The proposed scheme integrates IoD and blockchain through 5G-enabled tactile Internet to facilitate low-latency responsive delivery of medical supplies that can be chronologically monitored and tracked among different stakeholders. We compared the proposed scheme with the traditional medical delivery scheme with payment gateways to demonstrate its effectiveness in terms of data storage, computation, and communication costs. The simulation results obtained show that the average transaction cost has been reduced by ≈ 44.56 percent, and 5G tactile Internet has a reduced latency of 0.051 ms compared to 18.3 ms in 4G LTE service. The average communication overheads have reduced by ≈ 67.34 percent compared to traditional 4G LTE and orthogonal frequency-division multiplexing channels, which indicates the scheme's viability.

Optimized artificial neural network assisted trade-off between transmission and delay in LTE networks

The quality of data transmitted via LTE channels is often affected with the trade-off between the delay and network throughput. It often affects the performance of video transmitted with data rate distortion. In this paper, Lagrange dual multiplier with Artificial Neural Network (ANN) is used to solve the NP-hard problem and incorporates the Lagrange approach to achieve an optimum solution for higher network rating by reducing resource allocation. The way to find the optimal radio resource block (RRB) assignment strategy is iterated many times. Lagrange Dual Multiplier will also be used and implemented in this solution and this will help to achieve a closed form solution for any RRB assignment and further simulations to assess the efficiency of the process proposed. The experimental verification shows the efficacy of the model over existing state-of-art mechanism in terms of transmission errors and delay.

Image Transmission Using SC-FDMA System Over mmWave Measured Channel at 29.5 GHz

Aims: This paper presents an investigation of image transmission using SC-FDMA system over wireless fading channels. Background: A comparison is performed between the performance of the wireless transmitted image over 3GPP LTE channel (vehicular and pederstain) and mmWaves measured channel at 29.5 GHz. Objective: One of the important benefits of this work is the real measurement obtained at 29.5 GHz under NLOS scenario using an original sounder based on the ensuring of phase coherence between the transmitter and the receiver. Methods: Cameraman image has been transmitted over the SC-FDMA with different subcarriers mapping schemes. PSNR and MSE are the metrics used to evaluate the performance of the image transmitted under Matlab simulation where their values of the received image are calculated for different SNR values. Results and Conclusion: : The simulation results show that the image transmission over mmWaves channel works and the best values of PSNR are attained beyond 12 dB and 14 dB for LSC-FDMA and ISC-FDMA respectively.

Instrumental assessment of mobile communication base station electromagnetic field exposure

Introduction. Monitoring and ensuring safe operating conditions of modern base stations for occupational and general public exposure is relevant with the use of methods for measuring electromagnetic fields, which allow to assess the contribution of different sources to the overall level of the electromagnetic background, taking into account the dynamic features of base stations and the spectral electromagnetic characteristics. The aim of study is the levels of electromagnetic fields assessment from modern base stations using broadband and selective measurement methods, as well as the possibility of predicting the worst exposure conditions. Materials and methods. The levels of electromagnetic fields from base stations according to the LTE2600 standard were evaluated at the maximum transmission traffic (laboratory mearements) and at real variable traffic (field measurements). For broadband measurements, the power density (PD) was estimated, for selective measurements, the PD level in the LTE frequency channel (frequency-selective measurements) and the PD level of the reference signal (code-selective measurements) were evaluated. The theoretical maximum PD level was calculated from the maximum value of the reference signal. Results. When simulating the maximum intensity of data traffic, the PD level in the LTE channel was 94.51-101.39% of the calculated maximum value. According to field measurements, the values of electromagnetic field levels obtained from frequency-selective measurements in the LTE frequency channel were less than the corresponding values estimated from the results of broadband measurements, and were no more than 25% of the theoretical maximum. Conclusions. The use of selective approach and measurement methods made it possible to estimate the maximum possible contribution of a single source to the overall level of the electromagnetic background and to predict the worst conditions for human exposure.

An Efficient Performance Analysis of Rake Receiver in Spatial Modulation OFDM on a LTE Channel

An Efficient Performance Analysis of Rake Receiver in Spatial Modulation OFDM on a LTE Channel

Enhancing Carrier Aggregation: Design of BAW Quadplexer With Ultrahigh Cross-Band Isolation

Carrier aggregation (CA) is a technology first introduced in LTE-Advanced (LTE-A) to increase the peak data rate of 4G networks (for example, the maximum available speed) [1]. The mobile network operator can increase the total available bandwidth for a single user by aggregating multiple channels together, thereby increasing the user data rate as well as the spectrum utilization efficiency and resource allocation flexibility of the entire network. Before LTE-A, mobile network operators could allocate the spectral resource only to a particular user within a single designated frequency band, limiting the maximum channel capacity. The realization of CA allows network operators to create larger channels from nonadjacent spectrum blocks. For example, operators can use a 10-MHz carrier from the 2,100-MHz band and combine it with another 5-MHz carrier from the 700-MHz band to create a 15-MHz LTE channel. The LTE-A standard specifies that each of the component carriers (CCs) of the communication signal is limited to 20 MHz of bandwidth. Aggregation of up to five CCs allows a maximum of 100 MHz of total signal bandwidth, as depicted in Figure 1. This leads to a fivefold increase in channel capacity and data speed [2]. It is projected that CA technology will continue to be widely and intensively used in future-generation communications, such as 5G.

Analysis of electromagnetic compatibility of groups of radio-electronic means in mobile communication networks during radio frequency spectrum refarming

The article analyzes the EMC during refarming using the criterion of energy equivalence. The analysis allows us to determine the conditions for maintaining the energy equivalence of the GSM network in the frequency band of the corresponding width, which was planned to create the LTE network during refarming, namely: calculate the allowable number of LTE transmitters at each GSM site when planning sectors and MIMO configurations on them; еstimate (if necessary) the limitation of the radiation power of the LTE transmitters. The dependences of the energy equivalence index on the number of frequencies that are not repeated in the receiver band of the RES for various LTE channel widths are obtained. The obtained dependences show a decrease in the energy equivalence indicator with an increase in the number of frequencies that are not repeated. The dependences of the energy equivalence index on the degree of possible limitation of the power of LTE transmitters for various LTE channel widths are obtained. These dependencies show a decrease in the energy equivalence rate while increasing the degree of possible power limitation of LTE transmitters. The dependences of the energy equivalence index on the number of LTE transmitters are obtained for various LTE channel widths, which show an increase in the energy equivalence index with an increase in the number of LTE transmitters. The dependences of the permissible number of LTE transmitters on the LTE channel width are obtained for various values of the number of frequencies that are not repeated in the receiver band of the RES. The analysis showed that it is possible to increase the allowable number of LTE transmitters and observe EMC conditions by increasing the LTE channel width and by increasing the number of frequencies that are not repeated in the receiver band of the RES. The above results allow us to evaluate and plan the possible architecture of the created LTE radio network in specific situations. For example, if for some conditions the allowable number of transmitters on the LTE site is calculated to be insufficient, it can be increased due to some reduction (limitation) of the radiation power of these transmitters, while maintaining energy equivalence.

Technical and economic analysis of transport telecommunication infrastructure

By reviewing solutions for data transmitting infrastructure applicable to vehicle needs with direct LTE channel and expanded two-rank communication channel LTE and Wi-Fi, it is important to understand which option is technically and economically reasonable. The chosen option of communication solution in this work is justified with evaluation of technical parameters like goodput and response time, as well as efficiency indicators, such as costs and offloading parameter. By evaluating technical parameters in two-rank system a Machine repairmen model is used, where the performance of processing node μ is determined experimentally. The reviewed solutions of vehicle communications are suitable to providing commercial communication channels, for example, in such areas like entertainment, trucking and navigation.

Optical Multilevel Pulse Width Modulation for Analog Mobile Fronthaul

The evolution of radio access networks is towards a centralized architecture (C-RAN), with massive antenna deployments and large radio-frequency bandwidths. In the next future, traditional optical transport technologies based on digital radio over fiber will no longer be able to support the mobile fronthaul traffic connecting antennas hosted at remote radio units and centralized baseband units. Analog radio over fiber can be selected to support the mobile fronthaul (MFH) network and, in particular, pulse width modulation (PWM) is a viable alternative for analog signal transport. In order to increase the MFH spectral efficiency, we propose to exploit multilevel PWM (M-PWM) in a wavelength division multiplexing-passive optical network (WDM-PON) network, comparing its performance with a conventional 2-level PWM solution. Experimental results show successful transmission over 7.5-km standard single mode fiber (SSMF) of up to 16 aggregated LTE-like 20-MHz signals with 64-QAM on each subcarrier, while up to eight aggregated LTE-like 20-MHz signals with 256-QAM could be supported. M-PWM thus allows either using higher order modulation formats or aggregating a higher number of LTE channels.

A Software-Defined Frequency-Reconfigurable Meandered Printed Monopole

In this letter, a frequency-reconfigurable printed meandered monopole structure is presented. The antenna structure is composed of three radiating parts that are connected through two integrated PIN diodes. Such integration allows the antenna to reconfigure its operation within four frequency bands that correspond to various LTE, UMTS, and GSM channels. A graphical user interface (GUI) using Java is employed to control the states of the switches. The interface allows the control of a microcontroller to supply appropriate current to each of the two diodes. The GUI also simulates a cognitive radio environment where the activation of the corresponding PIN diodes is determined by the users’ activities. A prototype is fabricated and tested as a proof of concept where measured results agree with simulated data.

Pilot multiplexing OFDM system frequency offset estimation method

The algorithm proposed in this Article is intended for estimated accuracy and network throughput, two indexes of LTE channel, to design an approach for improvement of algorithm, and linear least square algorithm by using of weighted multilayer time-frequency domain LTE-OFDM resource model, for estimation of weighting parameters and the 2D spread spectrum power normalization algorithm. The results of simulation comparison on standard model database show that, while improving estimated accuracy, algorithm proposed in this Article can also remain network throughput at a high level, which verifies efficiency of the algorithm. Practicability of the algorithm is verified in laboratory and the results of comparison on simulation example shows a better effect of channel estimation with the proposed algorithm than standard 2D spread spectrum algorithm and the linear least square algorithm.

Error-rate analysis of MIMO MC-IDMA system for frequency-selective channels

In this treatise, we study the error-rate results of turbo coded multi-carrier interleave division multiple access (MC-IDMA) using multiple-input multiple-output (MIMO) system for up-link (UL) communications. In a multi-user system, users experience multi user interference (MUI), multi-path effects and inter antenna interference (IAI). Further, the antenna correlation reflects in the system performance. We consider sub-optimal multi-user detection techniques based on zero-forcing maximum-a-posteriori probability (MAP) Multi-user detection (MUD) and minimum mean square error (MMSE) MAP MUD in order to mitigate the effects of above mentioned interferences for our system. Further, we realize multi-carrier modulation to obviate the effects of multi-path propagations. Specifically we analyze the effects of four types of delay-spread distributions pertaining to LTE and SUI channel models in the UL MIMO MC-IDMA. Our computer simulation reveals that coded MC-IDMA with the non-linear MMSE-MAP algorithm obtain better error-rate results performance with fewer signals to noise ratio by mitigating MUI and multi-path propagations.

Transmission Experiment of Bandwidth Compressed Carrier Aggregation in a Realistic Fading Channel

In this paper, an experimental testbed is designed to evaluate the performance of a bandwidth compressed multicarrier technique, termed spectrally efficient frequency division multiplexing (SEFDM) in a carrier aggregation (CA) scenario. Unlike orthogonal frequency division multiplexing (OFDM), SEFDM is a nonorthogonal waveform which, relative to OFDM, packs more subcarriers in a given bandwidth, thereby improving spectral efficiency. CA is a long-term evolution-advanced (LTE-Advanced) featured technique that offers a higher throughput by aggregating multiple legacy radio bands. Considering the scarcity of the radio spectrum, SEFDM signals can be utilized to enhance CA performance. The combination of the two techniques results in a larger number of aggregated component carriers (CCs) and, therefore, increased data rate in a given bandwidth with no additional spectral allocation. It is experimentally shown that CA-SEFDM can aggregate up to seven CCs in a limited bandwidth, while CA-OFDM can only put five CCs in the same bandwidth. In this paper, LTE-like framed CA-SEFDM signals are generated and delivered through a realistic LTE channel. A complete experimental setup is described, together with error performance and effective spectral efficiency comparisons. Experimental results show that the measured bit error rate performance for CA-SEFDM is very close to CA-OFDM and that the effective spectral efficiency of CA-SEFDM can be substantially higher than that of CA-OFDM.

OFDM Channel Estimation Algorithms based on Discrete Fourier Transform

In allusion to such problem as unsatisfactory accuracy of the traditional laser communication LTE channel estimation algorithm, an LTE-OFDM multi-layer channel estimation algorithm based on least square 2D spread spectrum is proposed in this paper. Firstly, 2D spread spectrum estimation is adopted to design the weighted 2D spread spectrum estimation algorithm framework under multi-layer time-frequency domain LTE-OFDM resource model; secondly, in order to improve the accuracy of 2D spread spectrum estimation, the linear least square algorithm is adopted for weight parameter estimation and 2D spread spectrum power normalization; finally, through the comparison in the simulation calculation example, it is indicated that the proposed algorithm is superior to the standard 2D spread spectrum algorithm and the linear least square algorithm in the aspect of channel estimation effect.

SC-FDMA LTE Performance Through High Altitude Platforms Communications Channel

It is known that HAPS is one of the promising wireless infrastructures in the years to come. HAPS exploit many advantages from cellular satellite system as well as from cellular terrestrial system. Therefore, HAPS is envisaged as a novel technology for communication. This paper aims at evaluating the performance of a pilot-based channel estimation for uplink LTE using SC-FDMA over Ricean HAPS communication channel. Pilot-based channel estimation is used to estimate an uplink channel of LTE users who transmit the data to HAPS as a base transceiver station (BTS). Analysis is performed to determine the effect of users elevation angle with respect to user position inside HAPS coverage, LTE channel bandwidth, modulation type, and the Doppler frequency shift effect. We found that user’s elevation angle contribute major effect to the pilot-based channel estimation of LTE SC-FDMA performance. System capability to overcome fading effect that users with low elevation angle would be needed to increase the performance. In particular to keep an acceptable performance, in this paper we compensate the channel bandwidth, changing modulation type, and limit the Doppler effect through vehicle speed limitation.

Timely Delivery Versus Bandwidth Allocation for DASH-Based Video Streaming Over LTE

We study HTTP video streaming over a wireless access cell, such as LTE. We derive a closed form expression for the probability of timely delivery of the streamed video packets as a function of the bandwidth allocated to the user. The probability expression uses application, transport, and physical layer parameters relating to the employed video stream rate and to the quality of the communications channel. We validate the analytical results via numerical simulations based on the execution of real video traces and with LTE channel quality index trace modeling. The attained results allow the system designer, scheduler, and manager to calculate the bandwidth level that should be allocated to maintain acceptable system performance, expressed by two quality-of-experience (QoE) metrics, namely the video rate and the probability of timely delivery of video packets. The model provides a rationale and tools for performing admission procedures, bandwidth pricing policies, and cell dimensioning designs.

Performance and Complexity Evaluation of Iterative Receiver for Coded MIMO-OFDM Systems

Multiple-input multiple-output (MIMO) technology in combination with channel coding technique is a promising solution for reliable high data rate transmission in future wireless communication systems. However, these technologies pose significant challenges for the design of an iterative receiver. In this paper, an efficient receiver combining soft-input soft-output (SISO) detection based on low-complexity K-Best (LC-K-Best) decoder with various forward error correction codes, namely, LTE turbo decoder and LDPC decoder, is investigated. We first investigate the convergence behaviors of the iterative MIMO receivers to determine the required inner and outer iterations. Consequently, the performance of LC-K-Best based receiver is evaluated in various LTE channel environments and compared with other MIMO detection schemes. Moreover, the computational complexity of the iterative receiver with different channel coding techniques is evaluated and compared with different modulation orders and coding rates. Simulation results show that LC-K-Best based receiver achieves satisfactory performance-complexity trade-offs.

Performance of SISID Algorithm for LTE Channel Models

Performance of SISID Algorithm for LTE Channel Models

A joint multicast/D2D learning-based approach to LTE traffic offloading

Multicast is the obvious choice for disseminating popular data on cellular networks. In spite of having better spectral efficiency than unicast, its performance is bounded by the user with the worst channel in the cell. To overcome this limitation, we propose to combine multicast with device-to-device (D2D) communications over an orthogonal channel. Such a strategy improves the efficiency of the dissemination process while saving resources at the base station. It is quite challenging, however, to decide which users should be served through multicast transmissions and which ones should receive the content via D2D communications. The progress of content dissemination through D2D communications depends on how users meet while on the move. The optimal decision for each content depends both on the status of the LTE channel (when the multicast transmission is executed) and on the evolution of the mobility process of the nodes from there on. We propose a learning solution based on a multi-armed bandit algorithm that dynamically selects the best allocation of users between multicast and D2D to guarantee the timely delivery of data. Numerical evaluations are performed to compare our proposal with the state-of-the-art scheme and an optimal but unfeasible strategy. We confirm that a proper mix of multicast and D2D helps operators save resources at the base station and that the learning algorithm can autonomously find a near-optimal configuration in a reasonable time.