LTE System Research Articles

NB-IoT Uplink Receiver Design and Performance Study

LTE Narrowband Internet of Things (NB-IoT) is a 3GPP defined cellular technology that is designed to enable connectivity to many low-cost and low power/throughput IoT devices running delay-tolerant applications. NB-IoT can coexist within LTE spectrum either in a standalone mode, in-band with LTE or in guard-band of LTE. With NB-IoT designed to operate in very low signal to noise power ratios, the uplink receiver design presents several challenges. In this paper the design and performance of a NB-IoT uplink receiver is studied in detail. First, receiver design for NB-IoT uplink channels, with corresponding mathematical analysis, is presented. Specifically, it is shown how the time/frequency structure of signals can be exploited to enhance the receiver performance. Second, the performance of each channel is characterized with both link level simulations and implementation on a commercially deployed Qualcomm(registered) FSM(Trade Mark) platform [1]. Comparisons against the 3GPP defined Radio Performance and Protocol aspect requirements are also provided. Finally, implementation details are addressed and discussions on proposed enhancements to NB-IoT in 3GPP Release 15 are provided. It is shown how the proposed receiver algorithms can be adopted to Release 15 enhancements with minor or no modifications. The work in this paper is of significance to system designers looking to implement efficient NB-IoT uplink receiver to coexist with legacy LTE systems.

Research on Scheduling Algorithms in Uplink of LTE System

Downlink scheduling of LTE packet scheduling has been widely studied, while uplink scheduling is rarely studied. Aiming at the problem that uplink scheduling can not guarantee the transmission of real-time traffic packets within the delay period, a new uplink scheduling algorithm is proposed, we establish the target integer linear programming model by the delay constraints of real-time traffic. And aiming at the problem that the bandwidth of low priority traffic is insufficient and the overall QoS is affected when multi-class traffic is processed, a new scheduling algorithm for multi-class traffic is proposed, which includes multi-class traffic scheduling algorithm for eNodeB and priority adjustment algorithm for UE. Through our algorithm, emergency UE is always scheduled first, the algorithm can also maximize MAC throughput and satisfy the minimum QoS constraints. It can also improve the problem that the bandwidth of low priority traffic is insufficient. The experimental results show that the proposed algorithm can significantly improve LTE uplink performance.

Performance Analysis of Scheduling with Combined Unicast and Multicast Services in Downlink LTE System

Multicasting is an efficient solution for transmitting data to a group of users, which leads to the minimal network requirements. However, in real scenario both type of users (unicast and multicast) will exist in the network. Therefore, an appropriate resource allocation method is necessary to satisfy the Quality of Service (QoS) requirements of each user using these services. This paper proposes a resource allocation method to improve the performance of real time service users in spite of their transmission mode is unicast or multicast. If the user is in unicast transmission, the transmission rate is chosen based on the feedback from the user and if the user is in multicast transmission, then the resource allocation is done by subgrouping and adopting different transmission rates. Genetic algorithm is performed on subgroup formation such that the overall rate of the group should be maximized. From the simulation results, it is inferred that there is 46% increase in the average throughput and 10% reduction in delay for the real time users when compared to conventional resource allocation method.

Performance Optimal for Deploying Relays in Urban Micro Cells on LTE-Advanced Technology

Cooperative Relay is a promising enhancement to modern radio technologies which has been considered in LTE-Advanced and IEEE 802.16m technologies. Cooperative Relay is one of the technologies that used to improve coverage in downlink mobile network. The work is done by designing numerous environments for LTE-Advanced networks involving relays, whereby using vertical distributions of relays for both AAF & DAF techniques as well as comparison between the performances optimal of both techniques on urban micro cell for LTE-Advanced Technologies, Insertion the channel model from WINNER project. The performances optimal of non-Cooperative Relay and Cooperative Relay are evaluated in terms of Symbol Error Rate (SER) and Signal-to Noise-Ratio (SNR). The simulation results show that relay technologies can effectively improve system performance. On the other hand, 10-Relay in vertical distributions clearly shows outperforms on other environments and, when the relay put near, middle and far from Evolved Node B (eNB), the result shows at SER of 10-3 the system that employs AAF technique outperforms on the system that employs DAF technique in LTE-A system by about 6.5 dB, 2.5 dB and 2 dB sequent.

Intelligent Trajectory Inference Through Cellular Signaling Data

As cellular networks get widely deployed, mobiles generate enormous amount of signaling data during every call and session. These signaling data contains rich location information. If at the network side, we can accurately locate large amounts of users using the signaling data, this will present opportunities for many novel applications, e.g., assisting wireless operators to troubleshoot the network performance, and providing location assisted service. However, it is challenging to accurately locate a user using only the signaling data due to its relatively high noise. Most existing solutions are based on fingerprint approaches, which apply supervised learning and are costly to build the fingerprint map. In this paper, we propose LTETrack, a novel trajectory tracking system using LTE signaling data. LTETrack only uses data that is already available in current LTE system and does not require any special hardware/software. LTETrack first makes a key observation that the Timing Advance (TA) data is suitable for trajectory tracking. TA value corresponds to the length of time that a signal takes to reach the cell tower from a mobile phone, which is required in cellular communication standard. LTETrack incorporates novel filtering techniques to identify the most accurate TAs, and then runs a map-matching algorithm to locate a user. We have evaluated LTETrack using traces collected in our city covering more than 800km. The results show that LTETrack achieves a high trajectory matching accuracy in metropolitan area.

A quad-band slot antenna with spiral stub and interdigital CPW Feed

This paper proposes a quad-band slot antenna with spiral stub and interdigital CPW feed. The antenna has a compact size and can be used for four frequency bands of 1.8 GHz, 2.45 GHz, 3.7 GHz and 5.2 GHz applicable for LTE, WiMAX and WLAN systems. The important technique designs of the proposed antenna are divided into 2 parts. The first part includes the stepped slot antenna added with square-shaped spiral stub. As a result, the resonance frequencies of the third and fourth harmonics can be controlled as desired. For the second part, the technique of interdigital capacitive CPW is employed at the feeding line, resulting in length reduction from λ/4 of the conventional one to λ/8, which is caused by the slow-wave effect. Moreover, with this technique the resonance frequency of the second harmonic can be independently controlled. The optimized antenna has good performances for all frequency bands with bandwidths of 190 MHz (1.72 GHz-2GHz) at 1.8 GHz band, 280 MHz (2.34GHz-2.53GHz) at 2.45 GHz band, 410 MHz (3.54 GHz-3.95 GHz) at 3.7 GHz band and 220 MHz (5.10 GHz-5.32 GHz) at 5.2 GHz band, respectively.

Energy Efficiency Improvement in Mobile Communication System by Reducing the PAPR

Peak to average power ratio (PAPR) is a great issue in multicarrier systems especially in the LTE/LTEA communication system, so there is still a wide range that handles the PAPR problem. Orthogonal frequency division multiple access (OFDMA) technique is used in the downlink LTE system as it has many advantages over multipath propagation system. On the other side it suffers from a high PAPR that will affect the energy efficiency. In this paper, a new hybrid scheme is proposed in the downlink mobile communication system to overcome this issue. Besides reducing the PAPR, the proposed scheme did not have a significant increase in the system complexity but also it had nearly the same bit error rate (BER) system performance as OFDM system. Also we introduce a combination of different pre-coding techniques in OFDM system that improve the BER such as (Discrete Hartley Transform, Discrete Cosine Transform and Discrete Sine Transform) with the companding techniques that have a good ability in reducing the PAPR with a little increase in system complexity such as (Absolute exponential, Tangent rooting and Logarithmic) companding techniques. We tested the system performance for different techniques combination, and according to the analysis and the simulations done, it was found that the hybrid technique that is composed from the Discrete Hartley transform pre-coding technique and the Logarithmic companding technique in the downlink system outperforms all other hybrid techniques combinations.

АЛГОРИТМ ОЦЕНКИ И КОРРЕКЦИИ ПАРАМЕТРОВ МНОГОЛУЧЕВОГО КАНАЛА ПРИ ДЕМОДУЛЯЦИИ СИГНАЛОВ OFDM

OFDM signals form the basis of the radio interface of 4G mobile networks. Among the most well-known systems using OFDM signals, the LTE / LTE-Advanced, IEEE 802.11, IEEE 802.16 family, as well as DVB-T, DVB-T2 digital television standards, should be noted. Due to the high spectral efficiency and noise immunity in channels with multipath propagation of radio waves, OFDM signals are also used in other systems under development. Radio systems with OFDM signals have two significant drawbacks: the high peak factor (PAPR), which reduces the efficiency of the radio transmitter, and the high sensitivity of the demodulator to frequency synchronization errors. Because of them, in the LTE system in the Up lines (from a subscriber - mobile station – MS - to the base station - BS), the SC-OFDM transmission method is used instead of the classical OFDM, which reduces the spectral efficiency. High-speed user movement in an environment with many diffusers characteristic of dense urban development leads to frequency dispersion, when a Doppler spectrum occurs near each subcarrier of the OFDM signal. In addition, in any radio communication system, there are random fluctuations in the phase of the radio signal caused by the instability of the generators of the radio receiver and radio transmitter. As a result, the orthogonality of the subcarriers is violated and mutual interference between them (ICI - inter-carrier interference) occurs. This can significantly impair the noise immunity of the transmission system. Therefore, an integral part of the demodulator processing the OFDM signal is the channel parameter estimation and correction unit (adaptive equalizer). There are two categories of equalizers that determine the parameters of the channel – in the frequency domain and in the time domain. Since the OFDM signal demodulators use the fast Fourier transform at the subcarrier separation stage, as well as the pilot subcarriers being contained in the signal structure, it is advisable to consider equalizers that calculate the channel parameters in the frequency domain for efficient hardware implementation and good performance. Such an equalizer joins in with a demodulator after the stage of fast Fourier transformation. Traditionally for OFDM signals, an adaptive equalizer is built based on approximation of frequency description of channel by averaging of results obtained on the pilot subcarrier. Frequency dependence of total phase change of multibeam signal is not considered in such methods. Accordingly, good results can be expected at the dense location of the pilot subcarrier that reduces frequency efficiency in turn. An offered method allows considering a frequency-dependent phase change and interference losses, arising due to addition of copies of the signal from the different ways of distribution. It is special topically in systems with a small number of the pilot subcarriers.

An Omnidirectional Multiband Antenna for Railway Application

In this letter, we propose a top-mounted train antenna to work for GSM, LTE, and Wi-Fi communication systems. The antenna has a double-sided planar dipole configuration with a single port. An additional feeding structure has also been designed. To achieve multiband, an asymmetrically folded branch was loaded, whereas slits were etched on the rectangular patch. The structure was then optimized considering the roof and coupling effects. Simulated results show that the antenna can operate in the bands of 825–960 MHz, 1.7–2.7 GHz, and 5.7–5.9 GHz with a return loss better than 10 dB. The dimensions of the antenna are 116 mm × 40 mm × 1.6 mm. A gain of 4.27–9.82 dBi with omnidirectional (horizontal) coverage is realized to ensure reliable mobile communication. The antenna can be integrated with a global navigation satellite system (GNSS) antenna in a compact radome. It has the advantages of low cost and easy fabrication. Good agreements are observed between measured and simulated results. Furthermore, the proposed dipole is compared with a commercial antenna for similar applications in terms of impedance matching, isolation, and radiation characteristics.

A Cloud-Based Wireless Radio Intensity Recording System

In recent years, many wireless communication services have become indispensable for our daily life, such as voice telephoning and the internet surfing. However, these applications also cause lots of concerns related to the health issues. Many people think that the risk of illness will be increased if they are exposed at the electromagnetic field long termly. Therefore, lots of conflicts occurred between the residents and the system operators. Nevertheless, the correlation relation between the electromagnetic field and the specific disease is still unclear. In this paper, we setup a cloud-based measurement system that can measure and record simultaneously the radio intensity of our daily access wireless communication systems, such as the IEEE 802.11 Wi-Fi and 3GPP LTE systems. The system adopts the spectrum analyzer to measure the power of the electromagnetic wave in the considered areas and spectrums. The measured data can be uploaded to the remote database via the internet. Combining the open data sources from the government or the authorities, the quantitative analysis between the radio intensity of wireless communications and the related diseases can be further analyzed.

A broadband 23.1 ∼ 27.2 GHz doherty power amplifier with peak output power of 24.3 dBm

Purpose This paper aims to implement a new high output power fully integrated 23.1 to 27.2 GHz gallium arsenide heterojunction bipolar transistor power amplifier (PA) to meet the stringent linearity requirements of LTE systems. Design/methodology/approach The direct input power dividing technique is used on the chip. Broadband input and output matching techniques are used for broadband Doherty operation. Findings The PA achieves a small-signal gain of 22.8 dB at 25.1 GHz and a saturated output power of 24.3 dBm at 25.1 GHz with a maximum power added efficiency of 31.7%. The PA occupies 1.56 mm2 (including pads) and consumes a maximum current of 79.91 mA from a 9 V supply. Originality/value In this paper, the author proposed a novel direct input dividing technique with broadband matching circuits using a low Q output matching technique, and demonstrated a fully-integrated Doherty PA across frequencies of 23.1∼27.2 GHz for long term evolution-license auxiliary access (LTE-LAA) handset applications.

SMART-Navigation over Pilot LTE-Maritime: Deployment and Coexistence with PS-LTE

The SMART-Navigation project aims to develop a next-generation maritime safety integrated management system based on the e-Navigation concept of the IMO. The purpose of the pilot LTE-Maritime project is to construct test zones and establish effective LTE-Maritime plans based on the pilot test results. The spectrum band for LTE-Maritime system is the licensed public radio frequency band over 718-728 MHz for UL and 773-783 MHz for DL, but this band is shared with the Public Safety LTE (PS-LTE) and LTE-Railway (LTE-R) systems. Because these systems share the same spectrum band, CCI from PS-LTE and LTE-R arises during the Pilot LTE-Maritime test. To resolve this issue, we perform a test on the East Sea (around the city of Gangneung) in Korea with the proposed radio access network RAN-Sharing technique. In addition to the proposed RAN-Sharing technique, this article addresses the system architecture, requirements, test environment, and results of the LTE-Maritime system.

An Efficient Load Balanced Strategy for LTE-WLAN

With each very little cell LTE and Wi-Fi systems accessible as selections for causing in unauthorised teams (quite five GHz), the examination regarding their concurrence could be a theme of dynamic intrigue, primarily determined by business gatherings. 3GPP has as lately institutionalized LTE authorized assisted Access (LTE-LAA) that tries to form LTE a lot of conjunction unthreatening with Wi-Fi by fusing comparative detective work and back-off highlights. Regardless, the outcomes displayed by business bunches provide very little accord on important problems like separate system parameter settings that advance "reasonable access" PRN by 3GPP. Answers to such key framework causing angles, thusly, need valid diagnostic models, on that there has been very little advancement so far. In like manner, in one in every of the most work of its type, we have a tendency to build up another system for assessing the outturn of Wi-Fi and LTELAA in concurrence things by means that of affordable changes to the discovered Bianchi [1] model.

Toward Cost-Effective Mobile Video Streaming through Environment-Aware Watching State Prediction.

Mobile video applications are becoming increasingly prevalent and enriching the way people learn and are entertained. However, on mobile terminals with inherently limited resources, mobile video streaming services consume too much energy and bandwidth, which is an urgent problem to solve. At present, research on cost-effective mobile video streaming typically focuses on the management of data transmission. Among such studies, some new approaches consider the user’s behavior to further optimize data transmission. However, these studies have not adequately discussed the specific impact of the physical environment on user behavior. Therefore, this paper takes into account the environment-aware watching state and proposes a cost-effective mobile video streaming scheme to reduce power consumption and mobile data usage. First, the watching state is predicted by machine learning based on user behavior and the physical environment during a given time window. Second, based on the resulting prediction, a downloading algorithm is introduced based on the user equipment (UE) running mode in the LTE system and the VLC player. Finally, according to the corresponding experimental results obtained in a real-world environment, the proposed approach, compared to its benchmarks, effectively reduces the data usage (14.4% lower than that of energy-aware, on average) and power consumption (about 19% when there are screen touches) of mobile devices.

Adaptive beamformers using 2D-novel ULA for cellular communication

This paper presents the use of a novel two dimensional (2D) uniform linear array for adaptive beamforming algorithms. We used this novel antenna configuration to study the popular adaptive beamforming algorithms, namely, least mean square algorithm (LMS) and least normalized mean square algorithm (NLMS) and also proposed a variable step-size NLMS (VSSNLMS) algorithm. These beamformers are named as 2D-LMS, 2D-NLMS and 2D-VSSNLMS algorithms respectively. These algorithms not only improve the convergence rate but also mitigates the effect of interference by producing deep nulls in the interference directions. These algorithms are suitable for low-power, low-cost, anti-interference MIMO-WLAN, WiMAX, 4G LTE and other advanced communication systems.

Optimal Resource Scheduler for LTE A Based Networks

Long Term Evolution (LTE) may be a commonplace for prime rate radio transmission for cellular telephone and knowledge terminal. It is a complex technology that provides an accumulated network capability and speed by employing a totally special wireless interface beside the counter work enhancements. In the proposed method we deal with the setback of bandwidth administration in LTE-A systems and suggest valuable and profitable solutions to improve the quality of support in these networks. This paper presents an Optimal Resource Schedule which enhances the system throughput of LTE A based networks.

Design of Multi-Carrier LBT for LAA&WiFi Coexistence in Unlicensed Spectrum

To relieve the shortage problem of licensed spectrum, the aggregation of licensed and unlicensed carriers has emerged as an attractive solution for opportunistically increasing the throughput of LTE systems while enhancing the utilization of unlicensed spectrum. As one of the representative aggregation technologies, LAA is in favor of the harmonious coexistence with WiFi systems by leveraging the LBT mechanism and different pre-defined access priorities. In this article, we present a general overview of the attractive benefits and technical challenges for aggregating licensed carriers with unlicensed carriers. We then introduce some fundamental features of the LBT based LAA, including transmission modes, ED threshold, random backoff within the contention window, and access priority classes. Under multiple unlicensed channels, we propose two novel multi-carrier LBT mechanisms to improve the transmission behavior and coexistence performance of LAA and WiFi. It is verified in terms of successful transmission probability and carrier utilization rate that two proposed multi-carrier LBT mechanisms can achieve much better performance than the conventional counterpart using random carrier selection.

A dual threshold listen-before-talk for unlicensed LTE systems

The insufficient wireless frequency bands are likely to arise with the increase in mobile traffic demand. Many mobile operators suffer from a high annual increase in the cost of licensed wireless bands. Unlicensed bands present a potential opportunity for mobile operators. A single 5-GHz band with a large bandwidth provides faster transmission for each user. However, interference caused by existing wireless transmissions, such as Wi-Fi in unlicensed bands, is a serious issue in the effective utilization of unlicensed bands by mobile operators. The Listen-Before-Talk (LBT) was proposed as a promising method to ensure the coexistence of Wi-Fi and commercial mobile services such as LTE. We focus on effective control of the contention window (CW) size to maximize the operability of LBT. Control of the CW size depends on the repetition of extended clear channel assessment (ECCA). We introduce a dual threshold system that counts the repetition of ECCA. The newly developed NS-3-based unlicensed band network simulator shows the effectiveness of the proposed control mechanism. The results indicated that the advantage of the proposed method improves 4.3–7.6% than traditional LBT method. We develop a composite metric of throughput and fairness to evaluate the performance of LTE-LAA access.

EFFECT OF CHANGI NG DFT PROCESS SI ZE ON DATA RATE I N LTE UPLI NK LAYER

This paper deals with Matlab simulation of Long Term Evolution system (Lte) to show data rate of the uplink layer from user equipment toward the tower with respect to the size of Desecrate Fourier Transform process (DFT) which will be increased from 2 to the size of Inverse Desecrate Fourier Transform process (IDFT). Also it shows the way of using Cyclic Prefix technique (CP) in Lte system and its types which effect on the data rate for uplink layer. Finally the results will show the value of Lte system data rate for different types of modulation and Cyclic Prefix which will be for many types of system bandwidth individually, and it will show the minimum and maximum values of (DFT) process size with the midpoint which is the best one.

Multi-IF-Over-Fiber System With Adaptive Frequency Transmit Diversity for High Capacity Mobile Fronthaul

In this paper, we present and experimentally demonstrate a broadband intermediate frequency-over-fiber (IFoF) system with adaptive frequency transmit diversity for the next generation mobile fronthaul (MFH) applications. We propose to employ an integrated dual-parallel Mach-Zehnder Modulator (DPMZM) with adaptive dc-bias voltage setting for a simplified, efficient, and flexible IFoF communication system. The DPMZM is utilized to compensate the chromatic dispersion (CD) induced deep RF power fading impact, by taking advantage of the frequency transmit diversity of the two parallel modulators and optical paths. Using probe signals and the supervised machine learning (ML) technique, an accurate frequency response of the system is generated and utilized to design a dynamic allocation of IF channels to each DPMZM port. This ML-based link frequency response can capture the accumulated CD-induced power fading frequency region, as well as the random degradation caused by the used RF and optical devices characteristics and bandwidth limitation. Applying our proposed system, we successfully transmitted 15 IF channels with 1.2 GHz bandwidth and 64-QAM-OFDM modulated signals over 20-km fiber length, leading to about 1.18 Tbps CPRI-equivalent data rate. If we assume the maximum spectral efficiency of the LTE-A systems (i.e., 3.75 bit/s/Hz), the user throughput can be higher than 67 Gb/s. The obtained results show the potentials of DPMZM-based multi-IFoF system to satisfy the high capacity requirement of 5G mobile network and beyond.