Análisis de eficiencia espectral en la banda LTE para la inclusión de señales 5G usando GFDM

El presente artículo tiene como finalidad el análisis del espectro en la banda LTE del Ecuador para determinar qué espacios de frecuencias no están siendo utilizados e introducir algunas señales con características 5G (alta velocidad y baja latencia), mediante la técnica de acceso al medio GFDM (Multiplexación por División de Frecuencia Generalizado) usando un USRP 2944R (radio definido por software) y LabVIEW Communications System Design. En primera instancia se realizó un estado del arte y se comprendió cuáles son los parámetros establecidos por la UIT (Unión Internacional de Telecomunicaciones) para las NGN (Redes de Nueva Generación), y las configuraciones necesarias para un funcionamiento correcto del transceptor en la frecuencia libre de los 2.16GHz perteneciente al bloque K´ del espectro radioeléctrico asignado por la ARCOTEL. Se transmitió video MP4 vía UDP hacia LabVIEW implementando varias velocidades de Tx y diferentes calidades de video, llegando hasta los 3 Gbps como velocidad máxima. Los mejores resultados se obtuvieron implementando una velocidad de 925,2 Mbps con una resolución de 1920x1080 pixeles; es decir, a una calidad de 1080p y un BW de 10 MHz, obteniendo así un valor del BER en el orden de 10^-3.The purpose of this article is to analyze the spectrum in the LTE band of Ecuador to determine which frequency spaces are not being used and to introduce some 5G characteristic signals (high speed and low latency), through the GFDM medium access technique (Multiplexing by Generalized Frequency Division) using a USRP 2944R (software defined radio) and LabVIEW Communications System Design. In the first instance a state of the art was made and it was understood what are the parameters established by the ITU (International Telecommunication Union) for the NGN (New Generation Networks), and the necessary configurations for a correct functioning of the transceiver in the free frequency 2.16GHz belonging to the K' block of the radio spectrum assigned by the ARCOTEL. MP4 video was transmitted via UDP to LabVIEW implementing various Tx speeds and different video qualities, reaching up to 3 Gbps as maximum speed, the best results were obtained by implementing a speed of 925.2 Mbps with a resolution of 1920x1080 pixels, that is, at a quality of 1080p and a BW of 10 MHz, thus obtaining a BER value in the order of 10^-3

Waveform Advancements and Synchronization Techniques for Generalized Frequency Division Multiplexing

To enable a new level of connectivity among machines as well as between people and machines, future wireless applications will demand higher requirements on data rates, response time, and reliability from the communication system. This will lead to a different system design, comprising a wide range of deployment scenarios. One important aspect is the evolution of physical layer (PHY), specifically the waveform modulation. The novel generalized frequency division multiplexing (GFDM) technique is a prominent proposal for a flexible block filtered multicarrier modulation. This thesis introduces an advanced GFDM concept that enables the emulation of other prominent waveform candidates in scenarios where they perform best. Hence, a unique modulation framework is presented that is capable of addressing a wide range of scenarios and to upgrade the PHY for 5G networks. In particular, for a subset of system parameters of the modulation framework, the problem of symbol time offset (STO) and carrier frequency offset (CFO) estimation is investigated and synchronization approaches, which can operate in burst and continuous transmissions, are designed. The first part of this work presents the modulation principles of prominent 5G candidate waveforms and then focuses on the GFDM basic and advanced attributes. The GFDM concept is extended towards the use of OQAM, introducing the novel frequency-shift OQAM-GFDM, and a new low complexity model based on signal processing carried out in the time domain. A new prototype filter proposal highlights the benefits obtained in terms of a reduced out-of-band (OOB) radiation and more attractive hardware implementation cost. With proper parameterization of the advanced GFDM, the achieved gains are applicable to other filtered OFDM waveforms. In the second part, a search approach for estimating STO and CFO in GFDM is evaluated. A self-interference metric is proposed to quantify the effective SNR penalty caused by the residual time and frequency misalignment or intrinsic inter-symbol interference (ISI) and inter-carrier interference (ICI) for arbitrary pulse shape design in GFDM. In particular, the ICI can be used as a non-data aided approach for frequency estimation. Then, GFDM training sequences, defined either as an isolated preamble or embedded as a midamble or pseudo-circular pre/post-amble, are designed. Simulations show better OOB emission and good estimation results, either comparable or superior, to state-of-the-art OFDM system in wireless channels

Analisis Kinerja Teknik Linear Precoding Block Diagonalization Pada Sistem Multi User Mimo-Gfdm Menggunakan Detektor Mmse

Penerapan sistem MIMO untuk layanan ke banyak pengguna (dikenal dengan Multi User-MIMO) diperlukan untuk sistem komunikasi 5G. Generalized Frequency Division Multiplexing (GFDM) adalah transmisi multi-carrier fleksibel dengan bentuk gelombang non-orthogonal dan penggunaan subcarrier lebih sedikit mampu mengatasi kelemahan OFDM, yaitu tingginya PAPR dan emisi out-of-band (OOB). Adanya MU-MIMO menimbulkan interferensi antar pengguna yang dapat diatasi dengan teknik linear precoding Block Diagonalization (BD). Interferensi antar antena pada setiap pengguna dapat dimitigasi dengan teknik detektor. Pada paper ini, kami menganalisis kinerja gabungan BD precoding di sisi pengirim dan detektor Minimum Mean Square Error (MMSE) di sisi penerima pada sistem MU MIMO-GFDM. Hasil simulasi menunjukkan kinerja sistem MU MIMO-GFDM pada skema 2x2 dan 2 pengguna dengan RRC pulse lebih baik ±0.35dB dari MU MIMO-OFDM dan MU MIMO-GFDM dengan rectangular pulse. Pada pengamatan CCDF =10-2, nilai PAPR sistem MU MIMO-GFDM lebih rendah ±0.502dB dari MU MIMO-OFDM. Radiasi OOB sistem MU MIMO-GFDM dengan RRC pulse bernilai ±4.5dB dibawah MU MIMO-GFDM dan MU MIMO-OFDM dengan rectangular pulse. Disamping itu juga dilakukan analisa BD precoding pada sistem MU MIMO-GFDM. Kinerja sistem MU MIMO-GFDM antena 2x2 dengan 2 pengguna lebih baik ±2dB dari 4 pengguna, lebih baik ±3dB dari 7 pengguna, dan lebih baik ±8dB dari 9 pengguna. Kinerja sistem MU MIMO-GFDM dengan spatial multiplexing pada 2 pengguna menunjukkan antena 2x2 lebih baik ±4dB dari antena 4x4. Sedangkan kinerja sistem MU MIMO-GFDM pada MIMO 2x2 dan 4 pengguna menggunakan detektor MMSE lebih baik ±4.07dB dari ZF. ========================================================================================================= The implementation of the MIMO system for services to multiple users (known as Multi User-MIMO) is required for 5G communication systems. Generalized Frequency Division Multiplexing (GFDM) is a flexible multi-carrier transmission with non-orthogonal waveforms and fewer subcarriers are able to overcome OFDM weaknesses, namely high PAPR and out-of-band (OOB) emissions. The existence of MU-MIMO cause interference among users that can be overcome with Block Diagonalization (BD) linear precoding technique. Inter-antenna interference (IAI) resulted by each user can be mitigated by detector techniques. In this paper, we analyze the combined performance of BD precoding on the transmitter and the Minimum Mean Square Error (MMSE) detector on the receiver of the MU MIMO-GFDM system. The simulation results show the performance of MU MIMO-GFDM system use 2x2 antenna scheme in two users with RRC pulse is better ±0.35dB than MU MIMO-OFDM and MU MIMO-GFDM with rectangular pulse. In the observation of CCDF=〖10〗^(-2), PAPR MU MIMO-GFDM is lower ±0.502dB than MU MIMO-OFDM. OOB radiation in MU MIMO-GFDM system using RRC pulse is lower ±4.5dB than MU MIMO-GFDM dan MU MIMO-OFDM using rectangular pulse. Besides, BD precoding has been analyzed on the MU MIMO-GFDM system. The performance of MU MIMO-GFDM system use 2x2 antenna with 2 users is better ±2dB than 4 users, better ±3dB than 7 users, and better ±8dB than 9 users. The performance of MU MIMO-GFDM system with spatial multiplexing in two users shows 2x2 antenna is ±4dB better than 4x4 antenna. While the performance of MU MIMO-GFDM system to mitigate IAI use 2x2 antenna and 4 users shows MMSE detector is better ±4.07dB than ZF detector

Estudo e simulação dos algoritmos SIC, DSIC e PIC para cancelamento de interferência em sistemas multiportadora baseados em GFDM

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2017.A variedade de especificações exigidas da forma de onda para a quinta geração de telefonia (5G) abriu espaço para um sistema flexível, como o GFDM (Generalized Frequency Division Mul- tiplexing). No entanto, essa flexibilidade veio ao custo da ortogonalidade de suas subportado- ras, causando perda de desempenho. Neste trabalho, serão apresentados os conceitos básicos de comunicações digitais, assim como os conceitos do sistema OFDM (Orthogonal Frequency Di- vision Multiplexing), amplamente adotado em sistemas de comunicação digital. A partir dessa base, apresenta-se o GFDM e técnicas de cancelamento de interferência, visando a mitigação das perdas menciondas.The variety of waveform specifications required for fifth-generation telephony (5G) has made room for a flexible system, such as GFDM (Generalized Frequency Division Multiplexing). Howe- ver, this flexibility has come at the cost of the orthogonality of its subcarriers, causing loss of performance. In this document, we will present the basic concepts of digital communications, as well as the concepts of the OFDM (Orthogonal Frequency Division Multiplexing) system, widely adopted in digital communication systems. From this foundation, the GFDM and interference cancellation techniques are presented, aiming at mitigating the mentioned losses

Perbaikan Kinerja Sistem Generalized Frequency Division Multiplexing dengan menggunakan Offset Quadrature Amplitude Modulation

Generalized Frequency Division Multiplexing (GFDM) merupakan kandidat yang menjanjikan untuk bentuk gelombang dari generasi kelima (5G) pada komunikasi nirkabel. GFDM adalah teknik pengiriman data dengan blok berbasis teknik filtered-multicarrier non-orthogonal di mana masing-masing subcarrier dibentuk dengan bentuk pulsa non-rectangular filter. Penggunaan modulasi QAM pada GFDM sudah cukup baik untuk dapat meningkatkan efisiensi spektral, namun disisi lain QAM memiliki kelemahan yaitu kompleksitas implementasi yang tinggi dan masih terdapat ICI (Intercarrier Interference). Salah satu peluang untuk mengatasi hal tersebut adalah dengan cara menerapkan modulasi Offset QAM. Dengan skema OQAM, spektrum kanal yang berdekatan terjadi overlap tanpa mengakibatkan crosstalk antar subcarrier yang dikarenakan penundaan setengah simbol waktu antara komponen inphase dan quadrature sinyal pada setiap subcarrier. Hal ini akan mengurangi efek dari ICI (Intercarrier Interference) karena terjadi pengurangan jarak kanal yang berdekatan pada subcarrier. Guna melihat kinerja modulasi OQAM, maka pada penelitian ini dibandingkan dua skema antara sistem GFDM menggunakan modulasi OQAM dan modulasi QAM dengan dilakukan analisa dalam hal performa bit error rate (BER) pada kasus kanal AWGN dan Rayleigh Fading. Dari hasil simulasi dapat diketahui bahwa sistem GFDM/OQAM memiliki kinerja lebih baik dibandingkan GFDM/QAM. Hal itu terlihat pada saat hasil simulasi untuk SNR 25dB mengalami penurunan nilai BER dari modulasi QAM ke modulasi OQAM mencapai 99,56% pada kanal AWGN dan 23,61% pada kanal Rayleigh Fading. =============================================================================================== Generalized Frequency Division Multiplexing (GFDM) is one of the candidate for the fifth generation (5G) wireless communications. GFDM is a block based on filtered-multicarrier non-orthogonal technique in which each subcarrier is formed with a non-rectangular filter pulse shape. The use of QAM modulation in GFDM has been good enough to increase spectral efficiency, but on the other hand QAM has some susceptibilities, the complexity of high implementation and ICI (Intercarrier Interference) included. One of the opportunities to overcome the susceptibilities is by applying the Offset QAM modulation. By using the OQAM scheme, the adjacent channels spectrum are overlaps without causing crosstalk between subcarriers due to a delay of half time symbol between the inphase component and the quadrature signal on each subcarrier. It reduces the effect of ICI due to the reduction of adjacent channels distance on the subcarriers. In order to observe the performance of OQAM modulation, this study compared two schemes between the GFDM system using OQAM modulation and QAM modulation by analyzing the performance of bit error rate (BER) in the AWGN and Rayleigh Fading channels’ cases. From the simulation results show that the GFDM/OQAM system has better performance than GFDM/OQAM system. It is seen that the simulation result of SNR 25dB decreased the BER value in QAM modulation to OQAM modulation achieving 99.56% on AWGN channel and 23.61% on Rayleigh Fading channel

Analisis Aplikasi Predistorter Untuk Mitigasi Nonlinier HPA Pada Sistem GFDM

Sistem GFDM (Generalized Frequency Division Multiplexing) adalah sistem komunikasi multi-carrier yang dikembangkan untuk memenuhi kebutuhan teknologi seluler generasi kelima (5G). Sistem GFDM dikembangkan untuk menjadi alternatif dari sistem OFDM. Modulasi OQAM digunakan pada sistem GFDM dikarenakan beberapa kelebihan yakni memiliki sifat mendekati orthogonal sehingga sistem GFDM lebih tahan terhadap ISI dan ICI. High power amplifier (HPA) merupakan perangkat yang esensial dalam sistem komunikasi. Namun HPA memiliki titik saturasi yang dapat mengakibatkan penguatan tidak linier atau nonlinier, sehingga berujung dengan munculnya distorsi pada sinyal yang dikirimkan. Salah satu cara untuk memitigasi efek nonlinier HPA adalah dengan menggunakan teknik predistorsi. Sehingga dalam penelitian ini akan dibandingkan dua skema antara sistem GFDM-OQAM sebelum dan sesudah penggunaan predistorter dengan menganalisis kinerja BER untuk nilai IBO yang berbeda serta meneliti distorsi residu setelah aplikasi predistorter pada sistem. Dari hasil simulasi dapat diketahui bahwa dengan menggunakan predistorter, kinerja sistem GFDM-OQAM menjadi lebih baik. Hal ini dapat diketahui dari kinerja BER dimana sebelum aplikasi predistorter untuk mencapai nilai BER 10-3 dibutuhkan IBO atau redaman sebesar 15 dB. Sedangkan setelah aplikasi predistorter untuk mencapai nilai BER yang sama dibutuhkan IBO atau redaman sebesar 3 dB. Kemudian untuk mengetahui distorsi residu dapat diketahui dari nilai EVM mengalami penurunan drastis dimana sebelum aplikasi predistorter untuk mencapai nilai EVM 15%, dibutuhkan IBO atau redaman sebesar 15 dB. Sedangkan setelah aplikasi predistorter untuk mencapai nilai EVM yang sama dibutuhkan IBO atau redaman sebesar 3 dB. Apabila pada kanal diberikan noise berupa AWGN maka diperlukan kompensasi yakni penambahan IBO atau redaman dari 6 dB menjadi 8 dB sehingga dicapai kinerja BER 10-5. ================================================================================================================================ Generalized Frequency Division Multiplexing (GFDM) is a multi carrier communication system developed to fulfill the need of Fifth Generation (5G) cellular technology. GFDM is meant to become the alternate system after OFDM. Offset QAM (OQAM) is being used in GFDM with many benefits such as near orthogonality properties which decrease GFDM suceptibility against ISI and ICI. High power amplifier (HPA) is a device essential in communication system. As essential as it is, HPA has a saturation operating point which lead to nonlinear amplifying causing nonlinear distortion on the output signal. One way to mitigate this effect is using predistortion technique. In order to observe the effect of using predistorter, this study compared two schemes between before and after usage of predistorter on GFDM-OQAM system by analyzing the perfomance of BER with different IBO and the distortion’s residue after using predistorter. From the results of the simulation, it shows that by using predistorter the GFDM-OQAM system’s performance would be better. From BER performance perspective, to reach 10-3 the system which doesn’t apply predistorter need 15 dB of IBO while after applying predistorter the system only need 3 dB of IBO to reach the same value of BER. Also to identify the distortion’s residue, EVM value could be use as identifier. For the system to reach 15% of EVM value without using predistorter, the system need 15 dB of IBO while the system after using predistorter only need 3 dB of IBO to reach the same value of EVM. If AWGN noise are to be added into the signal through the ideal channel, then to get a better system’s performance the IBO needed to reach 10-5 of BER performance increase from 6 dB into 8 dB