Universal Filtered Multi-Carrier System Research Articles

Análisis de la técnica UFMC en un canal multitrayecto y usando estimación de canal

UFMC (Universal Filtered Multi-Carrier) is a novel multi-carrier transmission technique that aims to replace the OFDM (Orthogonal Frequency Division Multiplexing) modulation technique for fifth generation (5G) wireless communication systems. UFMC, being a generalization of OFDM and FBMC (Filter Bank Multicarrier), combines the advantages of these systems and at the same time avoids their main disadvantages. Using a Matlab simulation, this article presents an analysis of the robustness of UFMC against fading effects of multipath channels without using a CP (cyclic prefix). The behavior of the UFMC system is analyzed in terms of the PSD (Power Spectral Density), BER (Bit Error Rate) and MSE (Mean Square Error). The results show that UFMC reduces the out-band side lobes produced in the PSD of the processed signal. Also, it is shown that the pilot-assisted channel estimation method applied in OFDM systems can also be applied in UFMC systems.

Reduced OoB Emission and PAPR Using Partial-OSLM technique in 5G UFMC Systems

Universal-filtered multi-carrier (UFMC) waveformis considered as a potential candidate for next generation wirelesssystems due to its robustness against inter-carrier interference(ICI) and the low latency required in 5G systems. In this paper, apulse shaping approaches in UFMC technique is studied to reducethe spectral leakage into nearby sub-bands. The performance ofvarious types of window functions such as Chebychev, Hamming,Hanning and Blackman with UFMC are compared. This leadsto different coefficients and attenuation shapes, that enabledto choose the proper window function. Finally, a new selectivemapping (SLM) peak to average power ratio (PAPR) reductiontechnique is proposed to enhance the UFMC system performance.Results show that the BER performance of UFMC with allwindows functions are the same. However, Blackman windowfunction has a higher attenuation for sidebands compared withothers.

A Hardware-Efficient and Reconfigurable UFMC Transmitter Architecture With its FPGA Prototype

Universal-filtered multicarrier (UFMC) is one of the potential candidates for 5G multicarrier waveforms due to its several attractive features such as suppressed out-of-band radiation to the nearby sub-band. However, the hardware realization of UFMC systems is limited by a large number of arithmetic units for inverse fast Fourier transform (IFFT) and pulse shaping filters. In this letter, we propose an architecture that presents a refreshing approach toward designing a low-complexity architecture for the baseband UFMC transmitter with Dolph–Chebyshev filter. Compared to the read-only-memory (ROM)-based state-of-the-art, the proposed architecture requires less number of ROM locations and has the flexibility to externally select the inverse discrete Fourier transform (IDFT)-size, number of sub-bands, and number of subcarriers in a sub-band. Moreover, we implement the proposed architecture on a commercially available Virtex-5 field-programmable gate array (FPGA) device for testing and analyzing the baseband UFMC signal. Finally, the XILINX post-route results are found comparable with MATLAB simulations.

UFMC and f-OFDM: Contender Waveforms of 5G Wireless Communication System

Because of the increased demand for high data rates, looking for using new technologies that meet these requirements are considered a necessary. Hence, Fifth Generation (5G) is expected to be impressive in offering these requirements and implement around 2020. Orthogonal Frequency Division Multiplexing (OFDM) is considered a main technology of LTE wireless communication standards. Due to its suffering from high Bit Error Rate (BER) and Peak Average Power Ratio (PAPR), OFDM doesn't consider as charming solution for future wireless communications and several emerging applications of 5G. Moreover, high Out of Band Emission (OOBE) and inability of supporting the flexible numerology are other demerits of OFDM systems. Thus, looking for alternative waveforms which have the ability of solving OFDM disadvantages are necessary to introduce it as contender candidate for 5G wireless communication systems. In this paper, both of Filtered-OFDM (f-OFDM) and Universal Filtered Multi carrier (UFMC) systems have been discussed for 5G wireless communication systems and compared to OFDM system. The results showed that f-OFDM system is better than both OFDM and UFMC systems and could be introducing as competitive candidate for 5G wireless communication systems because of its ability of reducing OOBE and enhancing BER performance.

PAPR Reduction in UFMC for 5G Cellular Systems

Universal filtered multi-carrier (UFMC) is a potential multi-carrier system for future cellular networks. UFMC provides low latency, frequency offset robustness, and reduced out-of-band (OOB) emission that results in better spectral efficiency. However, UFMC suffers from the problem of high peak-to-average power ratio (PAPR), which might impact the function of high power amplifiers causing a nonlinear distortion. We propose a comparative probabilistic PAPR reduction technique, called the decomposed selective mapping approach, to alleviate PAPR in UFMC systems. The concept of this proposal depends on decomposing the complex symbol into real and imaginary parts, and then converting each part to a number of different phase vectors prior to the inverse fast Fourier transform (IFFT) operation. The IFFT copy, which introduces the lowest PAPR, is considered for transmission. Results obtained using theoretical analysis and simulations show that the proposed approach can significantly enhance the performance of the UFMC system in terms of PAPR reduction. Besides, it maintains the OOB emission with candidate bit error rate and error vector magnitude performances.

An optimal nonlinear companding transform with clipping scheme for universal filtered multicarrier systems

SummaryIn this article, an exponential companding (EC) scheme, which can reduce PAPR without raising the average output power level, is proposed for universal filtered multi carrier (UFMC) signals. However, EC scheme degrades the BER performance. Therefore, an optimal nonlinear companding transform named as “modified exponential companding” (MEC), which can use two companding levels based on a threshold value, is proposed. The proposed MEC scheme shows enhanced PAPR and BER performances than EC scheme. Moreover, the MEC provides more design flexibility and freedom with an unchanged average output power level. Furthermore, a hybrid scheme is also proposed to improve PAPR performance, where clipping operation is employed on MEC signal based on an appropriate clipping threshold. Simulation results illustrate that proposed MEC scheme offers improved system performance with a net gain of 7.22 dB than conventional EC and μ‐law techniques. Besides, the proposed hybrid scheme with clipping ratio 1.3 proffers enhanced PAPR reduction of 8.85 dB and improved net gain of 7.95 dB. Also, the proposed EC, MEC, and hybrid schemes can provide lesser spectrum side‐lobe levels than μ‐law. Finally, the UFMC system with the proposed hybrid scheme is verified by employing wireless open‐access research platform (WARP) as hardware over real‐time channel.

UFMC system performance improvement using RS codes for 5G communication system

Fifth generation (5G) mobile communication is expected to be deployed in several countries by 2020. Where, the data consumptions are expected to be increased to 30% thus, it cannot be supported by the present technologies 3G and 4G. In contrast, looking for new alternative modulation techniques of orthogonal frequency division modulation (OFDM) system which is suffering from high Peak to Average Power Ratio (PAPR) and out of band (OOB) side lobes are needed to use in 5G communication system. Hence, Universal Filtered Multi-Carrier (UFMC) is considered as alternative waveform to overcome of OFDM disadvantages. In communication systems, channel coding is considered vital part, where error correction codes (ECC) are used to detect and correct the errors which is occurring in channel noise. In this paper, RS codes are suggested with UFMC system to achieve the reliability of information transmission over noisy channels. The results showed that although, the values of PAPR levels for using RS codes in UFMC increased to 8.8653dB against 6.9735 dB for OFDM system. However, there are significant improvements in BER performance owing to use RS codes against uncoded-UFMC system. Furthermore, the values of OOB in UFMC system was lower than OFDM system.

Low-Complexity SLM PAPR Reduction Approach for UFMC Systems

The universal filtered multicarrier (UFMC) system is one of the novel candidate waveforms for 5G systems. UFMC is expected to achieve low latency, robustness against frequency offset, and reduce out-of-band (OoB) radiation that leads to a higher spectral efficiency. Although, the UFMC system offers many advantages as mentioned before, but being a multicarrier transmission technology, it suffers from high peak-to-average power ratio (PAPR). In this paper, a modified selected mapping (SLM) approach with low-complexity is proposed for reducing PAPR in UFMC systems. The main idea of the proposed modified SLM (P-SLM) approach is to utilize the linearity property of the UFMC modulator. The P-SLM approach generates U w alternative UFMC waveforms using U m UFMC modulators, where U m is the square-root of U w . Therefore, the computational complexity of the P-SLM approach is reduced compared to the existing SLM based PAPR reduction approaches for UFMC systems. The P-SLM approach is compared to the other approaches found in the literature in terms of PAPR reduction ability, bit error rate (BER) performance, and the computational complexity.

Low Complexity Implementation of Universal Filtered Multi-Carrier Transmitter

Universal Filtered Multi-Carrier (UFMC) is a promising multi-carrier modulation scheme. It can be considered as the combine of filtered OFDM and Filter Bank Multi-Carrier (FBMC) modulations. The difference among them is that filtered OFDM filters the entire band and FBMC filters the single subcarrier, while UFMC filters groups of subcarriers. It is evaluated their performance for the new conditions. While UFMC offers superior advantages, such as higher spectral efficiency, lower overhead, more robustness and less out-of-band (OOB) emission, the introduction of filters and the application of FFTs for the subband increase the implementation complexity of the transmitter. In terms of complexity, based on the analysis of UFMC transceiver structure, few low complexity implementation methods for UFMC systems are recently put forward. The low complexity solutions need to be found. In this paper, the computational complexity of different UFMC implementation methods based on lightweight structure which combines with the FIR filter and the poly-phase filter is evaluated. It is shown that the computational complexity of the UFMC transmitter can be reduced to be similar to OFDM, which is a promising solution for the advanced waveform. In addition, we analyze the effect of the filter on the power spectral density (PSD) of the proposed structure. Analysis shows that the system can be implemented with better performance by adjusting the filter parameters.

Universal Filtered Multi-Carrier System Based on Selective Mapping

Internet of things (IoT) and machine-to-machine (M2M) communication are characterized by short periods and bursts. Traditional orthogonal frequency division multiplexing (OFDM) has not meet the demand for such traffic, while IoT and M2M communication will play an important role in the next fifth generation (5G) communication, so it is particularly urgent to study the small packet and low-latency wireless transmission technologies that satisfy IoT and M2M communication. Universal filter multi-carrier (UFMC) is a new kind of filtered wireless transmission mechanism that meets this requirement, but it faces a higher peak-to-average power ratio (PAPR) than OFDM, which affects the energy efficiency of UFMC. Based on the PAPR performance evaluation of several multi-carrier transmission technologies, a universal filtered multi-carrier based on selective mapping (SLM-UFMC) system is proposed, and the relationship between the number of candidate sub-bands and the performance or between the number of carriers and the performance is carried out. The simulation results show that SLM-UFMC can effectively reduce the PAPR of UFMC system, and the PAPR performance is improved by 1.8 dB comparing with the traditional UFMC. It also further indicates that SLM-UFMC is more suitable for IoT and M2M communication in 5G communication.

Complexity-Reduced Receiver for Universal Filtered Multicarrier Systems

In this letter, a low complexity least squares-based receiver is proposed for universal filtered multicarrier systems. Specifically, the coarse estimate of the transmitted symbol is first obtained by one-tap equalization using the even components of the frequency-domain received signal. The inter-block interference is then removed from the received signal, and the out-of-subband data are punctured. Finally, a complexity-reduced approach is designed to obtain performance improvement based on the overall pre-processed data. A closed-form mean-square error expression and computational complexity analysis are derived to quantify the achievable advantages. Simulation study confirms the effectiveness of the proposed receiver.

Channel Estimation Techniques for OFDM and UFMC Systems for 5G Communications

In this paper, pilot-assisted techniques for channel estimation (CE) are simulated for Universal Filtered Multi-Carrier (UFMC) modulation scheme. UFMC aims at replacing orthogonal frequency division multiplexing (OFDM) and improves performance and robustness in the case of timefrequency misalignment. These techniques efficiently support Internet of Things (IoT) and massive machine type communications (mMTC), which are identified as challenges for 5G wireless communication systems (WCS). Pilot-aided techniques are adopted and applied to OFDM and UFMC. Simulation results are supplemented to compare the performance of UFMC systems with conventional CP-OFDM systems.

Optimization of out-of-band emission using kaiser-bessel filter for UFMC in 5G cellular communications

Across the world, we are currently witnessing the deployments of 4G LTE-Advanced and the 5G research is reaching its peak point. The 5G research mainly concentrates on addressing some of the existing OFDM based LTE problems along with use of non-contiguous fragmented spectrum. Universal Filtered Multi Carrier (UFMC) has been considered as one of the candidate waveform for the 5G communications because it provides robustness against the Inter Symbol Interference (ISI), and Inter Carrier Interference (ICI) and is suitable for low latency scenarios. In this paper, a novel approach is proposed to use Kaiser-Bessel filter based pulse shaping instead of standard Dolph-Chebyshev filter for UFMC based waveform to reduce the spectral leakage into nearby sub-bands. In this paper, UFMC system is simulated using MATLAB software, a comparative study for Dolph-Chebyshev and Kaiser-Bessel filters are performed and the results are also presented in terms of power spectrum density (PSD) analysis, Complementary Cumulative Distribution Function (CCDF) analysis, and Adjacent Channel Power Ratio (ACPR) analysis. The simulated results show a better power spectral density and lower sidebands for UFMC (Kaiser Based window), when compared with UFMC (Dolph-Chebyshev) and conventional OFDM.

Low‐complexity carrier frequency offset estimation for UFMC systems

In this Letter, the authors propose a simple carrier frequency offset estimation for universal filtered multicarrier (UFMC) systems, which not only greatly reduces the computational complexity but also promises excellent performance. First, based on the concept of the bisection method, a low-complexity selection criterion is designed to iteratively narrow the frequency range of interest. Then, the carrier frequency offset is effectively estimated using a closed-form expression derived from the Taylor series expansion technique. Computer simulations indicate that the proposed scheme can achieve performance comparable to the least squares-based estimator using high-complexity exhaustive search.

Performance Analysis of the Universal Filtered Multi-Carrier (UFMC) Waveform for 5G System

In the 5th generation mobile communication (5G) system, it is required to provide three different types of services, including enhanced Mobile Broadband (eMBB), massive machine-type communication (mMTC), and ultra-reliable and low-latency communication (URLLC).To meet all those demand in 5G, the waveform is crucial. Although the CP-OFDM waveform has been wildly used in 4G, it is hardly to satisfy the requirements of 5G.A lot of candidate waveforms are discussed for 5G system, including UFMC, FBMC, F-OFDM etc. In this paper, the UFMC waveform is discussed, the different filters and different frequency width of the subband in UFMC system are studied and appropriate parameters for the system are recommended.

Performance Analysis of Hybrid Peak to Average Power Ratio Reduction Techniques in 5G UFMC Systems

The universal filtered multi-carrier (UFMC) technique has been proposed as a prominent waveform candidate for fifth generation (5G) communication techniques. However, UFMC systems exhibit a high peak-to-average power ratio (PAPR), which causes serious degradation in the performance of the system. Therefore, this paper puts forward an effective hybrid PAPR reduction method to reduce the high PAPR of the UFMC system. The proposed hybrid scheme consists of a combination of precoding and non-linear companding techniques (NLCTs). A comparative analysis of the performance of different precoding methods, NLCTs, and hybrid methods are investigated in terms of the cumulative distribution function of the PAPR and the bit error rate (BER). The simulation results show that the proposed hybrid UFMC system has better PAPR reduction performance compared to conventional NLC and precoded UFMC systems. Moreover, the BER analysis of the UFMC system verifies that the proposed hybrid technique shows better BER performance compared to conventional companding techniques.

Optimal Filter Length and Zero Padding Length Design for Universal Filtered Multi-Carrier (UFMC) System

Universal filtered multi-carrier (UFMC) systems offer a flexibility of filtering arbitrary number of subcarriers to suppress out of band (OoB) emission, while keeping the orthogonality between subcarriers and robustness to transceiver imperfections. Such properties enable it as a promising candidate waveform for Internet of Things (IoT) communications. However, subband filtering may affect system performance and capacity in a number of ways. In this paper, we first propose the conditions for interference-free one-tap equalization and corresponding signal model in the frequency domain for UFMC system. The impact of subband filtering on the system performance is analyzed in terms of average signal-to-noise ratio (SNR), capacity and bit error rate (BER) and compared with the orthogonal frequency division multiplexing (OFDM) system. This is followed by filter length selection strategies to provide guidelines for system design. Next, by taking carrier frequency offset (CFO), timing offset (TO), insufficient guard interval between symbols and filter tail cutting (TC) into consideration, an analytical system model is established. In addition, a set of optimization criteria in terms of filter length and guard interval/filter TC length subject to various constraints is formulated to maximize the system capacity. Numerical results show that the analytical and corresponding optimal approaches match the simulation results, and the proposed equalization algorithms can significantly improve the BER performance.

Adaptive Modulation and Filter Configuration in Universal Filtered Multi-Carrier Systems

Universal filtered multi-carrier (UFMC) is a potential waveform technology, which can efficiently combat different carrier frequency offsets (CFOs) of multiple users. First, adaptive modulation and power allocation are applied for each subcarrier to meet a preset bit error rate (BER) requirement by ignoring CFOs. Then, we prove that different CFOs will cause different interference variances to adjacent users, which results in performance degradation in UFMC systems. To reduce the interference caused by CFOs and improve achievable rate, a novel adaptive filter configuration algorithm is proposed to adaptively design the parameters of the finite impulse response filters. Specifically, the proposed algorithm is available for the UFMC systems, where the user equipments are allocated with different bandwidths. Finally, simulation results show that the proposed adaptive filter configuration algorithm can dramatically eliminate the interference caused by different CFOs, and achieve better BER performance and a higher achievable rate than the conventional scheme.

Design of Waveform Shaping Filter in the UFMC System

The universal filtered multi-carrier (UFMC) has been taken as a promising candidate for future wireless communication, where a finite impulse response filter is employed to shape the waveform and enhance its resistance to inter-carrier interference. In previous studies, the Dolph–Chebyshev filter had been used due to its low-sidelobe levels, but at the cost of low flexibility to filter the performance control. Hence, this paper puts forward an effective scheme to design an anti-interference filter for UFMC system, where the Nyquist condition (or sampling inter-symbol interference equivalently), the in-band distortion, and the out-of-band emission are taken into consideration. First, this paper models the filter design as a constrained minimax optimization concerning above-mentioned filter performance indexes. Then, the original nonconvex constraints on Nyquist condition are approximately transformed to a linear matrix inequation and two linear inequations. Finally, the optimization problem is solved by semi-definite programming. The numerical examples explicitly demonstrate the flexible performance tradeoff of the proposed method, in which the included filter performance indexes can be effectively controlled. Moreover, the bit-error-rate (BER) tests of the UFMC system confirms the effectiveness of our study, where the designed filters show BER advantages over filters of the previous literature. Therefore, the proposed waveform shaping filters can benefit variant applications of UFMC for its flexible performance tradeoffs as well as the improved anti-interference performance.

Design and Performance Comparison of W-OFDM Under the Nonlinear HPA Environment

Recently, the spectral efficiency improvement of wireless and cellular communications is very important. Several waveforms have been proposed in order to satisfy key performance indicators of the 5th generation (5G) cellular communication. Universal filtered multi-carrier (UFMC) and filter bank multi-carrier (FBMC) and the filtered orthogonal frequency division multiplexing are typical candidate for 5G waveform, but they have some advantages and problems as well. In this paper, a weighted orthogonal frequency division multiplexing (W-OFDM) is considered since W-OFDM has pretty low complexity and comparable merits. In this paper, at first, we describe the system model and operation principle about UFMC, FBMC, and W-OFDM system. Next, we evaluate the out-of-band (OOB) power spectrum and bit error rate (BER) performance of these systems in the linear or nonlinear HPA. Simulation results show that OOB power spectrum and BER performance of UFMC, FBMC, and W-OFDM are similar in the linear operation. From the implementation point of view, if these performance and characteristics are similar, low-complexity is very decisive for the communication processing speed that is very important to the low latency and ultra-fast processing in the receiver. Additionally, under the nonlinear HPA environment, W-OFDM system is more advantageous because W-OFDM system uses a simple time-domain windowing technique in order to reduce OOB power.