scholarly journals ANALISIS MIMO UNTUK PENINGKATAN KAPASITAS SISTEM SELULER 4G LTE PADA SISTEM KOMUNIKASI HIGH ALTITUDE PLATFORM STATION

2017 ◽  
Vol 8 (2) ◽  
pp. 111
Author(s):  
Catur Budi Waluyo
Keyword(s):  
Channel Estimation ◽  
High Altitude ◽  
Orthogonal Frequency Division Multiplexing ◽  
Low Cost ◽  
Elevation Angle ◽  
Multipath Fading ◽  
Satellite Communications ◽  
Ergodic Capacity ◽  
Coverage Area ◽  
K Factor

The development of technology has opened up a new wireless infrastructure to complement the satellite and terrestrial networks. High Altitude Platforms (HAPs) is a communications infrastructure that uses air balloon as a solution between terrestrial and satellite communications systems with medium coverage and low cost o f launching and maintenance. HAPs can be joined with a Long Term Evolution (LTE) technology standardized by the Third Generation Partnership Project (3GPP). LTE uses orthogonal frequency division multiplexing (OFDM) technology for downlink. OFDM technology is a technology that uses multicarrier and bring the data in parallel and the bandwidth is divided into several subcarrier. To improve the performance of LTE in an increase in capacity, coverage, and speed of data, then it can use MIMO techniques. MIMO is a technique using multiple antenna transmitter and receiver antennas that are used to overcome the problem of multipath fading and increase the capacity of the system to be serviced. MIMO support the achievement of high transmission speed. In the simulation, signals generated by the modified jakes model into a ricean channel using the K factor 1.41, 1.99, 2.33, 2.66, 4.61, 6.35, 9.21, 12.15, 16.77 dB with elevation angle of 1 0 ° to 90°. The larger the K factor, the smaller the shift doppler at each speed. Elevation angle have a relationship to the coverage area of HAPs, the smaller the elevation angle of the wider the coverage area, and the higher the position, the wider HAPs coverage area too. In ergodic capacity, the smaller the K factor, the smaller the elevation angle so that the capacity is also greater. System without estimation for the K factor o f 1.41dB and K 9.21dB is necessary for channel estimation and the Bit Error Rate (BER) o f the same system that made channel estimation has a better performance compared with the existing channel without estimation with the SNR improvement o f about 18 dB.

scholarly journals ANALISIS PENINGKATAN KAPASITAS SISTEM SELULER 4G LTE PADA SISTEM KOMUNIKASI HIGH ALTITUDE PLATFORM STATION

2017 ◽  
Vol 9 (1) ◽  
pp. 31
Author(s):  
Catur Budi Waluyo ◽  
Yenni Astuti
Keyword(s):  
High Altitude ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Elevation Angle ◽  
Coverage Area ◽  
Data Services ◽  
High Altitude Platform ◽  
High Speed Data ◽  
4G Lte ◽  
High Altitude Platform Station

In the development o f wireless communications, to provide high-speed data services and wide bandwidth become a challenge. One technique to make it happen is by using Multicarrier Orthogonal Frequency Division Multiplexing (OFDM) modulation, where in OFDM, frequency selective fading channel effect will be perceived flat fading by each subcarrier. One communication system that supports OFDM technology is Long Term Evolution (LTE) with various types of bandwidth configurations provided. To improve LTE performance in capacity building, coverage area and data rate, it can use multi antenna technique both in receiver and sender, and integrate with High altitude platform station (HAPs) system. In this study the estimation used is Linear Minimum Mean Square (LMMSE). The relationship o f the elevation angle and the K factor is directly proportional, but the elevation angle value is inversely proportional to the diameter o f the HAPs coverage area. In addition, the more the number o f used antennas, the greater the capacity served. Based on the simulation results, the system with estimation can be used to expand the coverage area to 215.77 km which is from 0.032 km in QPSK modulation, speed 60 kmpj with 2x2 antennas.

scholarly journals Comparison of solar power measurements in alpine areas using a mobile dual-axis tracking system

2019 ◽  
Vol 2 (S1) ◽  
Author(s):  
Jelenko Karpić ◽  
Ekanki Sharma ◽  
Tamer Khatib ◽  
Wilfried Elmenreich
Keyword(s):  
High Altitude ◽  
Peak Power ◽  
Power Plants ◽  
Low Cost ◽  
Elevation Angle ◽  
Test Site ◽  
Maximum Power ◽  
Maximum Power Point ◽  
Photovoltaic Power ◽  
Power Point

Abstract The rising demand for sustainable energy requires to identify the sites for photovoltaic systems with the best performance. This paper tackles the question of feasibility of photovoltaic power plants at high altitude. A direct comparison between an alpine and an urban area site is conducted in the south of Austria. Two low-cost automatic photovoltaic power measurement devices with dual-axis sun tracking and maximum power point tracking are deployed at two test sites. The system periodically performs a scan over the southern semihemisphere and executes maximum power point adjustment in order to assess the performance for a given direction. The gathered data shows a higher photovoltaic power yield in the higher altitude test site. Furthermore, the high altitude photovoltaic power as a function of azimuth and elevation angle appears to be not only higher but also more flat than in lower altitudes. This indicates a lower power loss in case of deviation from the optimal solar angles. The results show that even on low-cost hardware a difference in photovoltaic power can be observed, even though in this experiment it amounts to less than 5% increase of peak power in higher altitudes. However, the measured peak powers on the mountain are more stable and therefore closer to a constant level than the heavily fluctuating peak power values at the low altitude site. Additionally, a slight shift in optimal elevation angles between altitudes can be observed, as the optimum angle turns out to be lower on the high altitude site. This angle shift could be caused by snow reflections on the mountainous test site.

scholarly journals Iterative Channel Estimation Scheme for the WLAN Systems with the Multiple-Antenna Receivers

2012 ◽  
Vol 6-7 ◽  
pp. 871-875
Author(s):  
Zi Wei Zheng
Keyword(s):  
Fourier Transform ◽  
Channel Estimation ◽  
Fast Fourier Transform ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Fading ◽  
Spectrum Efficiency ◽  
Frequency Division Multiplexing ◽  
Multiple Antenna ◽  
Frequency Division ◽  
Estimation Scheme

Alleviate the multipath delay spread and suitable for broadband transmission efficiency, orthogonal frequency division multiplexing wireless local area network (WLAN) is widely used to assist inverse fast Fourier transform and fast Fourier transform operation domain. Orthogonal frequency division multiplexing is a blow to the broadcast channel multipath fading and high data throughput, transmission, wireless fading channel method, which is widely used to support high performance bandwidth-efficient wireless multimedia services. Several times in the transmitter and receiver antenna technology allows data transfer rate and spectrum efficiency and the use of multiple transmit antennas and multiple receive antennas through spatial processing. High-precision channel estimation scheme is very important wideband multi-carrier orthogonal frequency complex WLAN systems use multiple antenna receiver based division of labor and the overall multi-carrier orthogonal frequency multiplexing division of performance-based WLAN system is to crucial antenna to receive the symbol error rate. In this article, the iterative channel estimation scheme proposed multi-carrier orthogonal frequency division multiplexed using multiple antennas receiver-based WLAN system.

scholarly journals Iterative Channel Estimation for the Chinese Digital Television Terrestrial Broadcasting Systems with the Multiple-Antenna Receivers

2012 ◽  
Vol 6-7 ◽  
pp. 439-444
Author(s):  
Zi Wei Zheng
Keyword(s):  
Fourier Transform ◽  
Channel Estimation ◽  
Fast Fourier Transform ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Fading ◽  
Wireless Channel ◽  
Digital Television ◽  
Frequency Division Multiplexing ◽  
Multiple Antenna ◽  
Frequency Division

Orthogonal frequency division multiplexing is an effective against multipath fading and high data throughput wireless channel transmission technology. Assistance with the inverse fast Fourier transform and fast Fourier transform operation, orthogonal frequency division multiplexing modulation and demodulation operations of the system convenient and convenient hardware implementation, orthogonal frequency division multiplexing, so in the modern digital television terrestrial broadcasting the system is widely used to support high performance bandwidth-efficient multimedia services. Broadband multi-carrier orthogonal frequency division multiplexing with multi-antenna and multi-antenna receiving system, to increase the diversity gain and improve the capacity of the system in different multipath fading channel. Accurate channel estimation in a simple channel equalization and decoding of broadband multi-carrier orthogonal frequency division multiple-antenna receiver and channel estimation accuracy and multiplexing system is very important, is the key to the performance of the overall broadband multi-carrier orthogonal frequency division multiplexing system in the multi-antenna receiver bit error rate. In this paper, iterative channel estimation to plan for digital terrestrial television broadcasting broadband multi-carrier orthogonal frequency division multiple antenna receiver multiplexing system proposal.

scholarly journals Channel Estimation in DCT-Based OFDM

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Yulin Wang ◽  
Gengxin Zhang ◽  
Zhidong Xie ◽  
Jing Hu
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Fading ◽  
Wireless Channel ◽  
Least Square ◽  
System Throughput ◽  
Multipath Fading Channel ◽  
Channel Response ◽  
Coherent Demodulation ◽  
And Performance

This paper derives the channel estimation of a discrete cosine transform- (DCT-) based orthogonal frequency-division multiplexing (OFDM) system over a frequency-selective multipath fading channel. Channel estimation has been proved to improve system throughput and performance by allowing for coherent demodulation. Pilot-aided methods are traditionally used to learn the channel response. Least square (LS) and mean square error estimators (MMSE) are investigated. We also study a compressed sensing (CS) based channel estimation, which takes the sparse property of wireless channel into account. Simulation results have shown that the CS based channel estimation is expected to have better performance than LS. However MMSE can achieve optimal performance because of prior knowledge of the channel statistic.

scholarly journals An Algorithm Combining Synchronization and Channel Estimation for OFDM Systems

2009 ◽  
Author(s):  
Pham Hong Lien ◽  
Nguyen Duy Lai
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Multipath Fading ◽  
Frequency Offset ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Clock Frequency ◽  
Close Relationship ◽  
Ofdm Signals

OFDM (Orthogonal Frequency Division Multiplexing) is more and more popular in applications of digital communications because of the effective spectrum and less impacts  of multipath fading. However, beside these advantages, OFDM signals are destroyed easily by errors such as CFO (Carrier Frequency Offset), SFO (Sampling Clock Frequency Offset). Thus, it’s necessaryto have robustly offset algorithms to overcome these disadvantages. Studies about OFDM we just examined channel estimation with assumptions that synchronization is perfect, and vice versa. However, they have a close relationship, channel estimation can be restricted if synchronization is bad, and vice versa. This paper presents an algorithm combining synchronization and channel estimation in OFDM systems. The algorithm is compared with other proposed algorithms by simulation. The simulation result of the algorithm combining synchronization and channel estimation is close to that of ideal conditions: perfect channel estimation and synchronization.

scholarly journals A Summative Comparison of Blind Channel Estimation Techniques for Orthogonal Frequency Division Multiplexing Systems

2018 ◽  
Vol 8 (5) ◽  
pp. 2744
Author(s):  
Vivek Kumar Gupta ◽  
Sadip Vijay
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Fading ◽  
Blind Channel Estimation ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Subspace Iteration ◽  
Blind Channel ◽  
Improved Performance

The OFDM techniquei.e. Orthogonal frequency division multiplexing has become prominent in wireless communication since its instruction in 1950’s due to its feature of combating the multipath fading and other losses. In an OFDM system, a large number of orthogonal, overlapping, narrow band subchannels or subcarriers, transmitted in parallel, divide the available transmission bandwidth. The separation of the subcarriers is theoretically optimal such that there is a very compact spectral utilization. This paper reviewed the possible approaches for blind channel estimation in the light of the improved performance in terms of speed of convergence and complexity. There were various researches which adopted the ways for channel estimation for Blind, Semi Blind and trained channel estimators and detectors. Various ways of channel estimation such as Subspace, iteration based, LMSE or MSE based (using statistical methods), SDR, Maximum likelihood approach, cyclostationarity, Redundancy and Cyclic prefix based. The paper reviewed all the above approaches in order to summarize the outcomes of approaches aimed at optimum performance for channel estimation in OFDM systems

scholarly journals NVIS Multicarrier Modulations for Remote-Sensor Applications

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6232
Author(s):  
Josep M. Maso ◽  
Tomas Gonzalez ◽  
Jordi Male ◽  
Joaquim Porte ◽  
Joan L. Pijoan ◽  
...  
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Low Cost ◽  
Coverage Area ◽  
Sensor Applications ◽  
Remote Sensors ◽  
Remote Sensor ◽  
Communication Method ◽  
Large Growth ◽  
Data Volume ◽  
Iot Devices

The number of Internet of Things (IoT) devices has experienced a large growth during the last decade, as well as the data volume gathered from remote sensors. Satellites are still a suitable communication method and may be preferable for a remote ubiquitous sensor network (USN), which sometimes are located in places without much communications infrastructure where coverage is the principal drawback. Alternatively, the proposed solution for this article aims at a near-vertical incidence skywave (NVIS) channel for high frequencies (HF) with a low-cost platform, allowing a low-power transmissions coverage area up to 250 km for USN. The HF standards are focused on generic communication channels not being robust for NVIS communications. In this article we study and test an alternative based on orthogonal frequency-division multiplexing (OFDM) modulations to make them more robust and less dependent on the channel NVIS communications. For that purpose, we test the HF standard modulations and a designed OFDM modulation to prove the robustness of each. This study has been tested between Barcelona and Tarragona, using different transmission power levels and modulation orders.

Improved Channel Estimation for OFDM Systems by Exploiting Ordered Space

2012 ◽  
Vol 271-272 ◽  
pp. 1317-1322
Author(s):  
Yu Ying Zhou
Keyword(s):  
Channel Estimation ◽  
Fading Channels ◽  
Orthogonal Frequency Division Multiplexing ◽  
Minimum Description Length ◽  
Estimation Method ◽  
Multipath Fading ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Multipath Fading Channels ◽  
Ordered Space

In this paper, we propose an improved channel estimation method for orthogonal frequency division multiplexing (OFDM) systems in sparse multipath fading channels. The proposed method transforms the channel estimates into an ordered space and uses the minimum description length (MDL) criterion to estimate the number of paths and the path positions. Simulation results demonstrated that an improved channel estimation performance is obtained due to the reduction of signal space.

scholarly journals Study of NVIS Channel for USN Protocol Definition in Antarctica

Electronics ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1037
Author(s):  
Josep M. Maso ◽  
Joaquim Porte ◽  
Joan L. Pijoan ◽  
David Badia
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Low Cost ◽  
Satellite Communications ◽  
Doppler Spread ◽  
Line Of Sight ◽  
Delay Spread ◽  
Frequency Division ◽  
High Frequencies ◽  
Ubiquitous Sensor Networks ◽  
Hf Communications

Every year, the number of ubiquitous sensor networks (USN) is increasing and the need for remote USN communications is emerging in some scenarios. As an alternative to satellite communications, more interests are focused on high frequencies (HF) communications as a low-cost option to reach links of more than 250 km without a line of sight. The HF standards are designed for generic communication channels being not robust for near vertical incidence skywave (NVIS) USN. In this article, we propose a new protocol for USN in remote places based on NVIS communications. For that purpose, we study the main characteristics of the NVIS channel with the presence of groundwaves, particularly in Antarctica. We analyze the availability of the channel, the height of the layers, the delay spread, and the Doppler spread. On the basis of the results obtained, we propose two protocols based on an OFDM (orthogonal frequency division multiplexing) modulation depending on the presence of the groundwave at the receiver. Finally, we make a simulation of the two OFDM configurations and we compare it with real tested standard modulations. The results show a better performance of the new protocol compared to the current HF standards.

Sign in / Sign up

Export Citation Format

Share Document