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.

scholarly journals On the Practical Implementation of VFDM-based Opportunistic Systems: Issues and Challenges

2012 ◽  
Vol 2 (1-2) ◽  
Author(s):  
Marco Maso ◽  
Leonardo S. Cardoso ◽  
Ejder Bastug ◽  
Nguyen Linh-Trung ◽  
Mérouane Debbah ◽  
...  
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Null Space ◽  
Delay Spread ◽  
Practical Implementation ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Test Bed ◽  
Short Root ◽  
The Impact ◽  
Secondary Link

Vandermonde-subspace frequency division multiplexing (VFDM) is a physical layer technique for cognitive two-tiered networks, allowing for the coexistence of an orthogonal frequency division multiplexing (OFDM) legacy system and a cognitive secondary system in a time division duplex mode. It consists of a linear null-space precoder used by the secondary transmitter to effectively cancel the interference towards one or more primary receivers, while guaranteeing a non-negligible rate to a served secondary receiver. In this work, we propose an implementation of an experimental test-bed using the new SDR4All platform developed at the Alcatel-Lucent Chair on Flexible Radio (SUPELEC) to take a step towards a proof of concept of a VFDM-based system. We focus on the secondary link, where an opportunistic transmitter/receiver pair communicates over moderately frequency selective channels, characterized by very short root mean square (r.m.s.) delay spreads and non uniform power delay profiles (PDP). The obtained results show the practical feasibility of a VFDM transmission over a secondary link. However, a significant bit error rate (BER) loss with respect to the previously shown achievable theoretical performance is evident. A thorough analysis of the structure of the VFDM precoder is carried out and the impact of the channel characteristics on the performance of the opportunistic system is discussed. Numerical findings demonstrate that the potential BER drop can be addressed by designing a suitable flexible receiver able to deal with the effect induced by non uniform PDP and short r.m.s. delay spread channels.

scholarly journals Experimental Studies on the Effect of Antenna Orientations to the Performance of OFDM-based System

2018 ◽  
Vol 8 (4) ◽  
pp. 2588
Author(s):  
J. Muslimin ◽  
A. L. Asnawi ◽  
A. F. Ismail ◽  
A. Z. Jusoh ◽  
N. A. Malek ◽  
...  
Keyword(s):  
System Performance ◽  
Software Defined Radio ◽  
Orthogonal Frequency Division Multiplexing ◽  
Development Process ◽  
Low Cost ◽  
Experimental Studies ◽  
Empirical Evaluation ◽  
Packet Error Rate ◽  
Frequency Division ◽  
Transmission Technique

<span>Software-defined radio (SDR) is an emerging and promising high re-configurable platform for rapid prototyping inreal environment applications. It offers both flexibility and low cost to facilitate the development process of agile communication system, such as Orthogonal Frequency Division Multiplexing (OFDM). Other than modulation and transmission technique like OFDM, antenna orientations play a significant importance in wireless communication. The availabililty of SDR platform like USRP has enabled the empirical evaluation of antenna orientation to the system performance. The performance has been evaluated in terms of throughput and packet error rate. The findings show the antenna orientation affect the system performance significantly.</span>

scholarly journals KINERJA SISTEM COFDM (CODED ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING) PADA KANAL RADIO MOBILE

2016 ◽  
Vol 8 (2) ◽  
Author(s):  
Hendra Winata ◽  
Heroe Wijanto ◽  
Suyatno Suyatno
Keyword(s):  
Wireless Lan ◽  
Orthogonal Frequency Division Multiplexing ◽  
Delay Spread ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Coding Gain ◽  
Video Broadcasting ◽  
Forward Error ◽  
Inter Symbol Interference

Komunikasi data berkecepatan tinggi memerlukan teknik modulasi yang dapat mengatasi terjadinya ISI (Inter-Symbol Interference) dan respons frekuensi kanal yang tidak rata. OFDM (Orthogonal Frequency Division Multiplexing) merupakan teknik transmisi multicarrier dengan periode simbol relatif lebih lebar dibandingkan nilai delay spread kanal. Dengan subcarrier spektral yang lebih sempit dari lebar-pita frekuensi koheren, OFDM diharapkan memiliki ketahanan terhadap gangguan kanal yang tidak rata. FEC (Forward Error Correcting) masih dibutuhkan untuk meminimumkan efek kesalahan akibat dari beberapa subcarrier yang mengalami fading lebih kuat dibandingkan lainnya. FEC dengan teknik pengkodean konvolusional dan interleaver banyak dipakai pada standar OFDM seperti Wireless LAN 802.11a dan Direct Video Broadcasting. Hasil simulasi menunjukkan pengkodean konvolusional [133 171] memberikan nilai coding gain maksimal 6 dB untuk modulasi subcarrier QPSK dan 7 dB untuk 16-QAM. Pada kanal radio mobile dengan frekuensi doppler 0, 9, 56 dan 130 Hz, diperoleh coding gain 7 dB. Penggunaan matriks interleaver 32?18 (IS�95) bekerja kurang optimal dengan perbaikan daya kurang dari 1dB. Ketika frekuensi doppler 130 Hz, matriks interleaver 100?96 mampu memperbaiki kinerja sistem secara siginifikan, BER di sekitar 10-6 dicapai pada SNR = 16 dB.Kata kunci: OFDM, interleaver, delay spread, frekuensi doppler, coding gain, IFFT-FFT

scholarly journals Analysis of the Ordinary and Extraordinary Ionospheric Modes for NVIS Digital Communications Channels

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2210
Author(s):  
Jordi Male ◽  
Joaquim Porte ◽  
Tomas Gonzalez ◽  
Josep M. Maso ◽  
Joan L. Pijoan ◽  
...  
Keyword(s):  
Low Cost ◽  
Satellite Communications ◽  
Frequency Instability ◽  
Mean Value ◽  
Single Frequency ◽  
Delay Spread ◽  
Noise Power ◽  
Ordinary Wave ◽  
Polarization Diversity ◽  
Noise Power Spectral Density

Sensor networks have become more popular in recent years, now featuring plenty of options and capabilities. Notwithstanding this, remote locations present many difficulties for their study and monitoring. High-frequency (HF) communications are presented as an alternative to satellite communications, being a low-cost and easy-to-deploy solution. Near vertical incidence skywave (NVIS) technology provides a coverage of approximately 250 km (depending on the frequency being used and the ionospheric conditions) without a line of sight using the ionosphere as a communication channel. This paper centers on the study of the ionosphere and its characteristic waves as two independent channels in order to improve any NVIS link, increasing its robustness or decreasing the size of the node antennas through the appliance of specific techniques. We studied the channel sounding of both the ordinary and extraordinary waves and their respective channels, analyzing parameters such as the delay spread and the channel’s availability for each wave. The frequency instability of the hardware used was also measured. Furthermore, the correlation coefficient of the impulse response between both signals was studied. Finally, we applied polarization diversity and two different combining techniques. These measurements were performed on a single frequency link, tuned to 5.4 MHz. An improvement on the mean bit energy-to-noise power spectral density (Eb/N0) was received and the bit error rate (BER) was achieved. The results obtained showed that the extraordinary mode had a higher availability throughout the day (15% more availability), but a delayed spread (approximately 0.3 ms mean value), similar to those of the ordinary wave. Furthermore, an improvement of up to 4 dB was achieved with the usage of polarization diversity, thus reducing transmission errors.

scholarly journals Desain dan Implementasi Real-Time Visible Light Communication System Berbasis BPSK

2019 ◽  
Vol 3 (2) ◽  
pp. 1-9 ◽  
Author(s):  
Trio Adiono ◽  
Syifaul Fuada
Keyword(s):  
Bit Error Rate ◽  
Orthogonal Frequency Division Multiplexing ◽  
Low Cost ◽  
Visible Light Communication ◽  
Pulse Time ◽  
Proof Of Concept ◽  
Frequency Division ◽  
Transfer Data ◽  
Time Modulation ◽  
Shift Keying

Salah satu teknik multiplexing yang saat ini populer digunakan untuk aplikasi akses komunikasi cepat berbasis cahaya tampak adalah Orthogonal Frequency Division Multiplexing (OFDM). Meskipun lebih kompleks dibandingkan modulasi berbasis Pulse Time Modulation (PTM), teknik OFDM disinyalir dapat lebih menghemat bandwidth komunikasi karena membagi bandwidth lebar menjadi spektrum yang sempit (sub-carrier) dan saling overlap. Sebagai akibat, transfer data akan lebih cepat dibandingkan PTM. Pada penelitian sebelumnya, penulis telah berhasil mendesain sistem low-cost VLC dengan modulasi digital 1-PWM (3,3 kbps) dan 2-PWM (6,2 kbps). Motivasi dari penelitian ini adalah menigkatkan laju data dengan menggunakan OFDM. Modulasi binary shift-keying modulation (BPSK) dipilih sebagai Mapper. Adapun hardware sistem VLC, penulis memanfaatkan penelitian yang sebelumnya sehingga penelitian ini sebatas proof-of-concept (POC) untuk membuktikan bahwa modulasi BPSK lebih cepat daripada 1-PWM dan 2-PWM. Hasil pengujian menunjukkan bahwa modulasi BPSK memiliki kecepatan dua kali lipat dibandingkan 2-PWM, yakni 13.4 kbps. Pengujian lain yang dilakukan adalah pengukuran Bit-error-rate (BER) dengan variasi jarak kanal optik dan sudut penerimaan.

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.

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