Extended GFDM Framework: OTFS and GFDM Comparison

Orthogonal time frequency space modulation (OTFS) has been recently proposed to achieve time and frequency diversity, especially in linear time-variant (LTV) channels with large Doppler frequencies. The idea is based on the precoding of the data symbols using symplectic finite Fourier transform (SFFT) then transmitting them by mean of orthogonal frequency division multiplexing (OFDM) waveform. Consequently, the demodulator and channel equalization can be coupled in one processing step. As a distinguished feature, the demodulated data symbols have roughly equal gain independent of the channel selectivity. On the other hand, generalized frequency division multiplexing (GFDM) modulation also employs the spreading over the time and frequency domains using circular filtering. Accordingly, the data symbols are implicitly precoded in a similar way as applying SFFT in OTFS. In this paper, we present an extended representation of GFDM which shows that OTFS can be processed as a GFDM signal with simple permutation. Nevertheless, this permutation is the key factor behind the outstanding performance of OTFS in LTV channels, as demonstrated in this work. Furthermore, the representation of OTFS in the GFDM framework provides an efficient implementation, that has been intensively investigated for GFDM, and facilitates the understanding of the OTFS distinct features.Comment: Accepted in IEEE Global Communications Conference 9-13 December 2018 Abu Dhabi, UA

Subcarrier Filtering For Spectrally Efficient Multicarrier Modulation Schemes and Its Impact on PAPR: A Unified Approach

Multicarrier modulation (MCM) based schemes have been a major contributing factor in revolutionizing cellular networks due to their ability to overcome fading. One of the popular scheme orthogonal frequency division multiple access (OFDMA), having been part of 4G, is also adapted as part of 5G enhanced mobile broadband (eMBB).  Though it has several advantages, spectral efficiency (SE) and peak to average power ratio (PAPR) have been two major concerns which have attracted lot of attention resulting in proposals of several other MCM schemes.  But most of these studies have treated the two issues independently. This paper in particular studies the subcarrier filtering approach to improve the spectral efficiency of MCM scheme and its impact on the overall PAPR of such schemes. The analysis shows that the PAPR improvement is also achieved by such filters meant for spectral confinement and the simulation results validate the same provoking a unified research direction less explored till now

Subcarrier Filtering For Spectrally Efficient Multicarrier Modulation Schemes and Its Impact on PAPR: A Unified Approach

Multicarrier modulation (MCM) based schemes have been a major contributing factor in revolutionizing cellular networks due to their ability to overcome fading. One of the popular scheme orthogonal frequency division multiple access (OFDMA), having been part of 4G, is also adapted as part of 5G enhanced mobile broadband (eMBB).  Though it has several advantages, spectral efficiency (SE) and peak to average power ratio (PAPR) have been two major concerns which have attracted lot of attention resulting in proposals of several other MCM schemes.  But most of these studies have treated the two issues independently. This paper in particular studies the subcarrier filtering approach to improve the spectral efficiency of MCM scheme and its impact on the overall PAPR of such schemes. The analysis shows that the PAPR improvement is also achieved by such filters meant for spectral confinement and the simulation results validate the same provoking a unified research direction less explored till now

Reducción del PAPR mediante técnicas de Clipping y Peak Windowing en sistemas multiportadoras FBMC

A comparison of the classical clipping technique with the peak window technique for hamming, hanning and kaiser windows to reduce PAPR in an FBMC signal over an AWGN channel is presented. The techniques are probabilistically analyzed by showing that the classic clipping technique reduces PAPR more than the kaiser peak windowing technique for a length of 4 which is the one that reduces the most among the peak window techniques. So, their performances through BER were evaluated over an AWGN channel. Showing the classic clipping technique has better performance than peak windowing techniques.Una comparación de la técnica de recorte clásico con la técnica de ventana pico para las ventanas de hamming, hanning y kaiser para reducir el PAPR en una señal FBMC sobre un canal AWGN es presentada. Las técnicas son analizadas probabilísticamente mostrando que la técnica de recorte clásico reduce el PAPR más que la técnica de ventana pico kaiser para una longitud de 4 que es la que más reduce de las técnicas de ventana pico. Entonces, sus desempeños mediante el BER fueron evaluados sobre un canal AWGN, mostrando la técnica de recorte clásico tiene un mejor desempeño que las técnicas de ventana pico

UNIVERSAL FILTER MULTICARRIER MODULATION SYSTEM WITH VARIED PARAMETERS & IMPACT ON PAPR

One of the main objectives of multicarrier modulation is to provide multiple accesses for wireless communication systems with higher data rates while having minimum out of band radiation, high spectral efficiency and less complexity. Orthogonal frequency division multiplexing (OFDM), Universal filter multicarrier (UFMC), Filter bank multicarrier (FBMC) and Generalized frequency division multiplexing (GFDM) modulation techniques have been developed to support fourth generation and beyond 4G wireless systems. Demand of high data rate in fourth generation wireless communication systems has been fulfilled by OFDM techniques but it suffers from the limitation of less spectral efficiency and high PAPR (Peak to average power ratio). Thus to support next generation wireless systems other waveform models are getting attention. Among the techniques available, UFMC seems to be attractive due to high spectral efficiency and less complexity. It has not explored much so in this paper, performance of UFMC have been evaluated with different design factors such as number of sub bands, FFT (Fast Fourier Transform) size, filter characteristics and modulation under the light of PAPR

Performance Assessment of Dual-Polarized 5G Waveforms and Beyond in Directly Modulated DFB-Laser using Volterra Equalizer

International audienceWe investigate the performance of 25-Gbps dual-polarized orthogonal frequency division multiplexing (OFDM)-based modulation in a directly modulated distributed feedback (DFB)-laser over 25 km of single-mode fiber. A Volterra equalizer is used to compensate for the nonlinear effects of the optical fiber. The results show that FBMC-OQAM modulation outperforms OFDM, universal filtered multicarrier (UFMC), and generalized frequency division multiplexing (GFDM) waveforms. Indeed, a target bit error rate of similar to 3.8 x 10(-3) [forward error correction (FEC) limit] for FBMC, UFMC, OFDM, and GFDM can be achieved at -30.5, -26, -16, and -14.9 dBm, respectively. The effect of the DFB laser is also investigated for UFMC, OFDM, and GFDM, and they undergo a Q penalty of 2.44, 2.77, and 4.14 dB, respectively, at their FEC limit points. For FBMC-OQAM, the signal is perfectly recovered when excluding the DFB laser at -30.5 dBm. (C) 2020 Society of Photo-Optical Instrumentation Engineers (SPIE