Evolved Universal Terrestrial Radio Access Research Articles

Performance Evaluation of LTE Network using Maximum Flow Algorithm

In this paper, we propose a new traffic flow model of the Long Term Evaluation (LTE) network for the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). Here only one Evolve Node B (eNB) nearest to the Mobility Management Entity (MME) and Serving Gateway (S-GW) will use the S1 link to bridge the E-UTRAN and Evolved Packet Core (EPC). All the eNBs of a tracking area will be connected to each other by the X2 link. Determination of capacity of a links of such a network is a challenging job since each node offers its own traffic and at the same time conveys traffic of other nodes. In this paper, we apply maximum flow algorithm including superposition theorem to solve the traffic flow of radio network. Using the total flow per subcarrier, a new traffic model is also developed in the paper. The relation among the traffic parameters: ‘blocking probability’, ‘offered traffic’, ‘instantaneous capacity’, ‘average holding time’, and ‘number of users’ are shown graphically under both QPSK and 16-QAM. The concept of the network will be helpful to improve the SINR of the received signal ofeNBslocated long distance relative to MME/S-GW.

An Optimal Security Management Framework for Backhaul-aware 5G-Vehicle to Everything (V2X)

Cellular (C) setups facilitate the connectivity amongst the devices with better provisioning of services to its users. Vehicular networks are one of the representative setups that aim at expanding their functionalities by using the available cellular systems like Long Term Evolution (LTE)-based Evolved Universal Terrestrial Radio Access Network (E-UTRAN) as well as the upcoming Fifth Generation (5G)-based functional architecture. The vehicular networks include Vehicle to Vehicle (V2V), Vehicle to Infrastructure (V2I), Vehicle to Pedestrian (V2P) and Vehicle to Network (V2N), all of which are referred to as Vehicle to Everything (V2X). 5G has dominated the vehicular network and most of the upcoming research is motivated towards the fully functional utilization of 5G-V2X. Despite that, credential management and edge-initiated security are yet to be resolved under 5G-V2X. To further understand the issue, this paper presents security management as a principle of sustainability and key-management. The performance tradeoff is evaluated with the key-updates required to maintain a secure connection between the vehicles and the 5G-terminals. The proposed approach aims at the utilization of high-speed mmWave-based backhaul for enhancing the security operations between the core and the sub-divided functions at the edge of the network through a dual security management framework. The evaluations are conducted using numerical simulations, which help to understand the impact on the sustainability of connections as well as identification of the fail-safe points for secure and fast operations. Furthermore, the evaluations help to follow the multiple tradeoffs of security and performance based on the metrics like mandatory key updates, the range of operations and the probability of connectivity.

Real Time- Optimized Scheduler Using Earliest Due Date Mechanism in LTE Downlink System

Long Term Evolution (LTE) is standardized by the Third Generation Partnership Project (3GPP) as the most recent standard in the mobile network technology tree with flat architecture in order to conduct a new model aiming to offer higher-data-rate, lower-latency, and packet-optimized radio access technology called Evolved Universal Terrestrial Radio Access Network (E-UTRAN). However, the schedulers aiming to deal with the Real Time (RT) and the Non-Real Time (NRT) traffic have not defined by the 3GPP specifications. Accordingly, it is very important to design and implement optimum scheduling schemes for achieving the required Quality of Service (QoS) prerequisites such as packet delay and Packet Loss Rate (PLR) of RT multimedia services in E-UTRAN. Thus, the proposed scheduler is presented in this paper as well as the performance of the new scheduling strategy which is based on the Earliest Due Date (EDD) approach. The new proposed scheduler provides better results as compared with the conventional scheduling strategies, especially for multimedia applications in downlink framework of LTE system. The proposed scheduler achieves the highest good-put as well as the lowest PLR especially for the video users.

A linear LTE‐advanced CMOS RF power amplifier with integrated phase linearizer

ABSTRACTIn this work, a linear CMOS RF power amplifier (RF PA) to support 40‐MHz BW long‐term evolution‐advanced (LTE‐A) application is developed. The AM–PM distortion of the CMOS RF PA is compensated by the proposed wideband phase linearizer, which generates asymmetric triangular current waveform to provide pre‐distorted current to the RF PA. The fabricated PA is tested with 40‐MHz BW LTE‐A signal at 0.837 GHz carrier frequency and showing 30.3% overall system power‐added efficiency (PAE) and −36.1 dBc carrier aggregation (CA) evolved universal terrestrial radio access (E‐UTRA) adjacent channel leakage ratio (ACLR) at 24 dBm output power. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1119–1122, 2017

Direction prediction assisted handover using the multilayer perception neural network to reduce the handover time delays in LTE networks

Nowadays, the rapid increase in the development of the wireless communication, the Evolved Universal Terrestrial Radio Access (E-UTRA) of the Long Term Evolution (LTE) is more improved and modern technology compared with the WiMAX technology. The researchers discussed the accurate and fast handover in the LTE in the recent years. Moreover, the researchers of the evolved Node B(eNB) proposed the history of the UE visited base stations and the use of their information just to consider the target in the case of handover. While the identification of the cell and their times were kept inside the cell of the base station. In this paper, an advanced technique using the historical information to reduce the handover time delay as much as possible depending on the packet loss, the time required for the base station to reply and the region domain as much as the time domain. In conclusion, the angle of the situated target base station is computed and the distance to that base station is taken into consideration for cutting down more and more real-time of the handover procedure in the LTE system. The simulation results showed that the proposed model is more efficacious in decreasing the handover time delay by skipping unwanted base station according to their angles.

Linear X‐band GaN HEMT transformer‐based Doherty power amplifier

An X-band gallium-nitride high electron mobility transistor (GaN HEMT) transformer-based Doherty power amplifier (TBD PA) module with a phase lineariser has been developed. The TBD PA uses Cree's 6 W GaN HEMT bare die and realised in seven-layer PCB. The proposed lineariser is employed before the TBD PA to compensate the phase distortion during the Doherty operation. The implemented TBD PA with 9.56 GHz continuous wave test shows a 38.5% power-added efficiency at 39.6 dBm output power. Linearity characterisation is also performed using 40 MHz bandwidth, two carriers aggregated long-term evolution-advanced signal and shows −35.4 dBc carrier aggregation evolved-universal terrestrial radio access adjacent channel leakage power ratio which is 7 dB enhanced after phase compensation.

Dynamic Stack-Controlled CMOS RF Power Amplifier for Wideband Envelope Tracking

In this paper, a dynamic stack-controlled CMOS FET RF power amplifier (PA) is developed to enhance the efficiency of the envelope tracking power amplifier (ET PA) system for low-voltage operation. The power cell used in the two-stage PA is a quadruple-stacked FET structure with dynamic stacking controller to reconfigure the power cell into the quasi-triple or quasi-double stacks according to the magnitude of the input envelope signal. The proposed power cell boosts the peak efficiency in the low V DD region by bypassing the stack entering the triode region and reoptimizing the load impedance so that all the FETs operate under the saturation and the optimum load conditions. A detailed analysis is presented to understand the gain and phase step discontinuities at the stack switching points, and the circuit techniques to equalize the gain and phase between the adjacent stack configurations are developed. The proposed two-stage stack-controlled PA is fabricated with a 0.32-μm silicon-on-insulator (SOI) CMOS process together with the envelope amplifier (EA). Full long-term evolution (LTE) characterization is performed using LTE signals with a peak-to-average power ratio (PAPR) of 6.7 dB and signal bandwidths (BW) of 10 and 20 MHz. With 10-MHz signals, dynamic stacking provides 3.5% power added efficiency (PAE) improvement over the static stack at 25.7 dBm, resulting in 47.5% PAE with 26.6-dB gain. A 20-MHz LTE test shows an overall PAE of 45.9% with an evolved universal terrestrial radio access (E-UTRA) adjacent channel leakage ratio (ACLR) of -33 dBc with memoryless digital predistortion. Even with the lower efficiency of the EA compared with the state-of-the-art results, the measured overall system efficiency with 3.4 V maximum voltage is comparable with those reported using GaAs HBT's with 5 V supplies, which clearly demonstrates the advantages of the proposed dynamic stack control.

Protection Ratio and Antenna Separation for DVB—T/LTE Coexistence Issues

This paper concerns the analysis of adjacent channel interference of the 3GPP Long Term Evolution (LTE) E-UTRA (Evolved Universal Terrestrial Radio Access) mobile systems into Digital Video Broadcasting - Terrestrial (DVB-T) systems. The simulated performance of both systems allows us to define recommendations for minimizing the interference effects. The subjective quality of the received TV signal has been evaluated experimentally in terms of picture failure (PF). We also investigated the importance of the selection of suitable Spectral Emission Masks (SEMs) of the LTE downlink transmission. Results show that, by using the ECC 148 SEM, both the protection ratio and the minimum distance between LTE towers and DVB-T receivers can be significantly decreased.

2-Port DL-MIMO Antenna Design for LTE-Enabled USB Dongles

A geometrically symmetric 2-port downlink (DL)- multiple-input-multiple-output (MIMO) antenna for Universal Serial Bus (USB) dongles is described. The design makes use of a center-tapped inductance to independently excite both the common mode and the differential mode. The solution allows for separate, mutually independent, common-mode and differential- mode matching networks. So as to maximize bandwidth and efficiency of the differential mode, the antenna physical structure is designed for maximum occupation of the very small available volume using two symmetric elements each comprising a helix loaded at its end with a capacitive plate. Fabricated prototype of the antenna features higher than 7 dB return loss (RL) and higher than 17 dB isolation in Evolved Universal Terrestrial Radio Access (E-UTRA) band class (BC) 13 and BC 17 and total efficiency higher than 50%.

Survey of Adaptive Modulation Scheme in MIMO Transmission

Adaptive modulation (AM) technique may make more promote in the execution of wireless communication systems through adaptively conformity transmitter parameters to fading channels; therefore, it has been taken as one of the key physical techniques in 3GPP Evolved Universal Terrestrial Radio Access (E-UTRA). This paper offers a general overview of the adaptive modulation scheme in wireless multiple-input multiple-output (MIMO) systems. Study a set of properties by which adaptive modulation systems are evaluated, and then apply this valuation method to survey a number of existing systems, also, discuss modulation schemes and channel modeling in detail since it is utilized in most current system or solutions, as well survey some MIMO models which are included in adaptive modulation activities in order to reproduce and corresponding MIMO system ratings. Comprehensive execution comparisons including, BER analysis, average spectral efficiency (ASE), modulation schemes, and channel model are presented.

An Uniform Handover Authentication between E-UTRAN and Non-3GPP Access Networks

To achieve seamless handovers between the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and other access networks is a challenging task as it requires comprehensive real-time interconnectivity in the LTE networks. The third Generation Partnership Project (3GPP) has suggested support the mobility between the E-UTRAN and non-3GPP access networks, which requires full access authentication procedures and distinct procedures for different mobility scenarios, which will bring a lot of message exchanges and increase the system complexity. Besides, the existing handover schemes for other wireless networks are not suitable for the mobility scenarios in the LTE networks due to their inherent vulnerabilities. In this paper, we propose a fast and secure handover authentication scheme to fit in with all of the mobility scenarios in the LTE networks. Compared with other handover schemes, our scheme cannot only provide strong security guarantees including Perfect Forward Secrecy (PFS) and Master Key Forward Secrecy (MKFS) and user anonymity, but also achieve a simple authentication process with robust efficiency in terms of communication cost, storage cost and computational cost. The experimental results and formal verification by using the TLA+ and TLC show that the proposed scheme is secure against various malicious attacks.

Resource Reduction Method for the LTE-Advanced Uplink ACK/NACK Signal and SR

SUMMARY Advanced Evolved Universal Terrestrial Radio Access (Advanced E-UTRA), called LTE-Advanced, has been standardized in the 3rd Generation Partnership Project (3GPP) as a candidate for IMTAdvanced. LTE-Advanced supports spatial orthogonal-resource transmit diversity (SORTD) [1], [2] for ACK/NACK signals and scheduling requests (SRs), which are used to control downlink hybrid automatic repeat requests (HARQs) and manage uplink radio resources based on uplink data traffic, respectively. Both ACK/NACK signals and SRs are carried via a physical uplink control channel (PUCCH) [3], and a common PUCCH format is used for both ACK/NACK signals and SRs. If SORTD is used, the base station assigns mutually orthogonal resources to each antenna included in the user equipment (UE) for ACK/NACK signals and SRs; hence, the number of required resources increases with the number of transmitting antennas in the UE. In this paper, we study the resource reduction method for ACK/NACK signal and SR in case of SORTD using the concept of common resource. In addition, we investigate a phase rotation scheme for com

Effects of a Phase Rotation Scheme on the DTX Detection Performance for the E-UTRA Uplink ACK/NACK Signals

Hybrid automatic repeat request (HARQ) is employed for the Evolved Universal Terrestrial Radio Access (E-UTRA) downlink. The base station not only decodes the ACK/NACK signals from the user equipment (UE), but also detects a termination of the transmission (DTX) of the ACK/NACK signals caused by the mis-detection of the downlink control information (DCI) at the UE side. Since ACK/NACK signals from UEs are multiplexed by CDMA, there are sometimes severe inter-code interference (ICI) effects, which significantly degrade the performance of ACK/NACK signals. In order to mitigate such ICI effects, in [1],[2], we proposed a novel phase rotation scheme on the constellations of the uplink ACK/NACK signals, and confirmed the effects on the ACK/NACK bit error rate performance; however, the previous paper did not analyze the effects of the phase rotation on the DTX detection performance. Hence, in this paper, we further analyze the effects of the phase rotation for the ACK/NACK signals in conjunction with a new DTX detection scheme which utilizes equalizer outputs, and investigate the performance of the proposed scheme by means of computer simulations.

Performance study for HARQ–ARQ interaction of LTE

AbstractThe 3GPP working group proposes the Long‐Term Evolution (LTE) system as the 4G mobile communications technology. To reduce the transmission latency in the radio access network, Evolved Universal Terrestrial Radio Access Network (E‐UTRAN), of LTE, the base station and radio network controller are merged into a single network node, namely eNB. In E‐UTRAN, the Stop‐And‐Wait Hybrid ARQ (SAW‐HARQ) protocol in the Media Access Control (MAC) layer deals with transmission errors without the need to engage the ARQ protocol in the Radio Link Control (RLC) layer. The HARQ and ARQ protocols interact only in case of dealing HARQ residual errors. In this paper, we propose an analytical model to model the behavior of the HARQ–ARQ Interaction. Our analytical model is validated against the simulation experiments that provide more performance metrics (which cannot be obtained through our analytical model). Finally, we investigate the impacts of the HARQ–ARQ Interaction on the Protocol Data Unit (PDU) transmission delay based on our simulation experiments. Copyright © 2009 John Wiley & Sons, Ltd.

LTE, the radio technology path towards 4G

Evolved Universal Terrestrial Radio Access (EUTRA), known as the Long Term Evolution (LTE) technology, brings cellular communication to the fourth generation (4G) era. In this article, we discuss the most important characteristics of LTE; its simplified network architecture which allows ultimate means for adaptation of the radio transmission to the Internet packet traffic flows and to the varying channel states. LTE radio resource management is based on time–frequency scheduling, fast feedback between the transmitter and receiver, and nearly optimal adaptation of transport formats. Yet, the radio system is simple and cost efficient to manage from the evolved packet core network, having a server architecture with IP tunnels. The mobility states and resource allocation allow power save operation of the User Equipment when not actively communicating. In addition, we brief the key results on the LTE baseline performance for paired and unpaired frequency bands, i.e. the two duplex modes.

Adaptive CQI Update and Feedback for Codebook Based MU-MIMO in E-UTRA

Codebook based multiple-input multiple-output (MIMO) precoding can significantly improve the system spectral efficiency with limited feedback and has been accepted as one of the most promising techniques for the Evolved UTRA (E-UTRA). Compared with single-user (SU) MIMO, multi-user (MU) MIMO can further improve the system spectral efficiency due to increased multi-user diversity gain. MU-MIMO is preferred for the case of a large number of users, when the total feedback overhead will become a problem. In order to reduce the feedback overhead, feedback of single channel quality indicator (CQI), e.g. rank 1 CQI, is required in E-UTRA currently. The main challenge is how to obtain CQIs of other ranks at Node B for rank adaptation with single CQI feedback. In this paper, an adaptive CQI update scheme at Node B based on statistical characteristics of CQI of various ranks is proposed. To further increase the accuracy of CQI at Node B for data transmission, an adaptive CQI feedback scheme is then proposed in which single CQI with the rank same as previously scheduled is fed back. Simulation results show that our proposed CQI update scheme can achieve 2.5-5% gain compared with the conventional method with fixed backoff. Moreover, with the proposed adaptive feedback scheme, 20-40% performance gain can be obtained and the performance can approach the upper bound.

A Novel Phase Rotation Scheme on the Constellations for the E-UTRA Uplink ACK/NACK Signals

Hybrid automatic repeat request (HARQ) is employed for the Evolved Universal Terrestrial Radio Access (E-UTRA) downlink. The ACK/NACK signals from each user equipment (UE) are multiplexed by code division multiple access (CDMA) and transmitted via a physical uplink control channel (PUCCH). The ACK/NACK signals are code spread by the cyclic shift (CS) sequences made from zero auto-correlation (ZAC) sequences; however, the orthogonality of these sequences is not guaranteed depending on the propagation channels; moreover, the amount of inter-code interference (ICI) depends on the delay spread of the channel and the transmitting timing control error of each UE. In the conventional PUCCH structure, ICI between two ACK signals does not degrade their detection performance, whereas ICI between an ACK signal and a NACK signal degrades the detection performance. This causes a serious gap between the detection performances of ACK and NACK signals, because generally in a PUCCH, there are more ACK signals than NACK signals. In this paper, we propose a novel phase rotation scheme on the constellations of ACK/NACK signals that can resolve this issue, and the simulation evaluation results confirm the benefits of the proposed phase rotation scheme.

A Novel Spreading Code Design for E-UTRA Uplink Control Channel and Its Performance

Hybrid automatic repeat request (HARQ) is employed for the Evolved Universal Terrestrial Radio Access (E-UTRA) downlink. Each user equipment (UE) sends its ACK/NACK corresponding to the downlink data reception to the base station via a physical uplink control channel (PUCCH). The ACK/NACK signals from the UE are first code spread by the cyclic shift (CS) sequences, and then code spread again by the orthogonal cover (OC) sequences. The ACK/NACK signals from each UE are multiplexed by means of code division multiple access (CDMA), however, it is difficult for the conventional PUCCH code design to satisfy the required bit error rate (BER) of 10-3 [1] in fast-fading environments because of inter-code interference (ICI) among the OC sequences. Therefore, resource management of PUCCH is required depending on the mobility of the UEs to maximize the performance of the ACK/NACK signals and the capacity of PUCCH simultaneously. In this paper, we propose a novel code design for PUCCH, which can suppress the effects of ICI among the OC sequences, and thus can simplify the resource management of PUCCH. The simulation evaluations confirm that the proposed code design can significantly improve the performance of the ACK/NACK signals via PUCCH in fast-fading environments, and any complicated resource management based on the mobility of the UEs are not necessary.

Performance Comparison between Turbo Code and Rate-Compatible LDPC Code for Evolved UTRA Downlink OFDM Radio Access

This paper compares the turbo code and rate-compatible low-density parity-check (LDPC) codes based on the block error rate (BLER) performance and decoding complexity in order to clarify which channel coding scheme is most appropriate for the channel coding scheme in the OFDM based Evolved UTRA (E-UTRA) downlink. Simulation results and the decoding complexity analysis show that although the Rate-Compatible/Quasi-Cyclic (RC/QC)-LDPC code employing an offset layered belief propagation (BP) method can reduce the computational complexity by approximately 30% for the channel coding rate of R ≥ 1/2, the required average received signal energy per bit-to-noise power spectrum density ratio (Eb/N0) is degraded by approximately 0.2-0.3dB for R=1/3, 1/2 and 3/4 compared to that for the turbo code. Moreover, the decoding complexity level of the RC/QC-LDPC code with the δ-min algorithm is almost the same or higher than that for the turbo code with a slight degradation in the required received Eb/N0. Although the decoding complexity level of the ZigZag code is lower than that of the turbo code, the code brings about a distinct loss in the required average received Eb/N0 of approximately 0.4dB. Finally, the turbo Single Parity Check (SPC) code improves the BLER performance compared to the ZigZag code, i.e., achieves almost the same BLER performance as that for the turbo code, at the cost of a two-fold increase in the decoding complexity. As a result, we conclude that the turbo code with a contention free interleaver is more promising than the LDPC codes for prioritizing the achievable performance over complexity and as the channel coding scheme for the shared data channel in the E-UTRA.

Field and Indoor Experimental Results of E-UTRA Uplink

This paper investigates the uplink throughput performance and the interference power to other cells using an Evolved UTRA (E-UTRA) laboratory and field experimental system. In E-UTRA uplink, the near-far problem is not an issue since the orthgonality among the users within the target cell is maintained. Therefore, the fractional transmission power control (TPC), in which the target level of TPC is adjusted according to the path loss level, can be adopted. Thus, it is expected the high cell throughput and the large coverage area by combining fractional TPC, adaptive modulation and channel coding (AMC), and variable resource block (RB) allocation. The indoor and field experimental results show that the peak throughput of approximately 45Mbps is achieved by allocating a wider bandwidth and setting higher target level for the UE located near the cell site while keeping the adjacent cell interference level almost the constant. We also showed that the system capacity can be improved by 50% in simple cell model by applying the AMC and the fractional TPC.