Waveform Design Considerations for 5G Wireless Networks

In this chapter, we first introduce new requirements of 5G wireless network and its differences from past generations. The question “Why do we need new waveforms?” is answered in these respects. In the following sections, time‐frequency (TF) lattice structure, pulse shaping, and multicarrier schemes are discussed in detail. TF lattice structures give information about TF localization of the pulse shape of employed filters. The structures are examined for multicarrier, single‐carrier, time‐division, and frequency‐division multiplexing schemes, comparatively. Dispersion on time and frequency response of these filters may cause interference among symbols and carriers. Thus, effects of different pulse shapes, their corresponding transceiver structures, and trade‐offs are given. Finally, performance evaluations of the selected waveform structures for 5G wireless communication systems are discussed

Channel estimation techniques for filter bank multicarrier based transceivers for next generation of wireless networks

A dissertation submitted to Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering (Electrical and Information Engineering), August 2017The fourth generation (4G) of wireless communication system is designed based on the principles of cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) where the cyclic prefix (CP) is used to combat inter-symbol interference (ISI) and inter-carrier interference (ICI) in order to achieve higher data rates in comparison to the previous generations of wireless networks. Various filter bank multicarrier systems have been considered as potential waveforms for the fast emerging next generation (xG) of wireless networks (especially the fifth generation (5G) networks). Some examples of the considered waveforms are orthogonal frequency division multiplexing with offset quadrature amplitude modulation based filter bank, universal filtered multicarrier (UFMC), bi-orthogonal frequency division multiplexing (BFDM) and generalized frequency division multiplexing (GFDM). In perfect reconstruction (PR) or near perfect reconstruction (NPR) filter bank designs, these aforementioned FBMC waveforms adopt the use of well-designed prototype filters (which are used for designing the synthesis and analysis filter banks) so as to either replace or minimize the CP usage of the 4G networks in order to provide higher spectral efficiencies for the overall increment in data rates. The accurate designing of the FIR low-pass prototype filter in NPR filter banks results in minimal signal distortions thus, making the analysis filter bank a time-reversed version of the corresponding synthesis filter bank. However, in non-perfect reconstruction (Non-PR) the analysis filter bank is not directly a time-reversed version of the corresponding synthesis filter bank as the prototype filter impulse response for this system is formulated (in this dissertation) by the introduction of randomly generated errors. Hence, aliasing and amplitude distortions are more prominent for Non-PR. Channel estimation (CE) is used to predict the behaviour of the frequency selective channel and is usually adopted to ensure excellent reconstruction of the transmitted symbols. These techniques can be broadly classified as pilot based, semi-blind and blind channel estimation schemes. In this dissertation, two linear pilot based CE techniques namely the least square (LS) and linear minimum mean square error (LMMSE), and three adaptive channel estimation schemes namely least mean square (LMS), normalized least mean square (NLMS) and recursive least square (RLS) are presented, analyzed and documented. These are implemented while exploiting the near orthogonality properties of offset quadrature amplitude modulation (OQAM) to mitigate the effects of interference for two filter bank waveforms (i.e. OFDM/OQAM and GFDM/OQAM) for the next generation of wireless networks assuming conditions of both NPR and Non-PR in slow and fast frequency selective Rayleigh fading channel. Results obtained from the computer simulations carried out showed that the channel estimation schemes performed better in an NPR filter bank system as compared with Non-PR filter banks. The low performance of Non-PR system is due to the amplitude distortion and aliasing introduced from the random errors generated in the system that is used to design its prototype filters. It can be concluded that RLS, NLMS, LMS, LMMSE and LS channel estimation schemes offered the best normalized mean square error (NMSE) and bit error rate (BER) performances (in decreasing order) for both waveforms assuming both NPR and Non-PR filter banks. Keywords: Channel estimation, Filter bank, OFDM/OQAM, GFDM/OQAM, NPR, Non-PR, 5G, Frequency selective channel.CK201

Analysis of PAPR Reduction in 5G communication

The goal of this thesis is to analyze PAPR reduction performance in 5G communication. 5G communication technology is beyond 4G and LTE technology and expected to be employed around 2020. Research is going on for standardization of 5G technology. One of the key objective of 5G technology is to achieve high data rate (10Gbps). For this a large bandwidth is needed. Since limited frequency resources are available, the frequency spectrum should be efficiently utilized to obtain high data rate. Also to utilize white space, cognitive radio networks are needed. In cognitive radio network very low out of band radiation is desired. OFDM is used in 4G communication but it has the drawback of low spectral efficiency and high out of band radiation, which makes it a poor choice for 5G communication. So for 5G communication new waveform is required. FBMC, UFMC, GFDM are some of the waveform candidates for 5G communication. FBMC is a potential candidate for 5G communication and it is used in many 5G projects around the world. In this thesis FBMC is used as a waveform candidate for 5G communication. High PAPR is always a problem in multicarrier communication system. FBMC is also a multicarrier communication system, so it also suffers from high PAPR problem. To reduce the PAPR several PAPR reduction techniques have been proposed over the last few decades. Tone injection and companding are two promising techniques, which are used in PAPR reduction of multicarrier communication system. In this thesis a combined scheme of tone injection and companding is used, which gives significant performance improvement compared to the tone injection and companding techniques taken separately. Simulation is performed to analyses the PAPR and BER performance of FBMC-FMT and FBMC-SMT system. Also a new clipping based PAPR reduction scheme is proposed in this thesis. For this scheme simulation is performed to analyze the PAPR performance of FBMC-FMT, FBMC-SMT and FBMC-CMT system. All the simulations are performed in MATLAB

Future 5G wireless communication systems: A new multicarrier shemes

Current wireless communication networks and technologies are being pushed to their limits by the massive growth in demands for mobile wireless data services. We now stand at a turning point in the wireless communication domain where the technologies are being driven by applications and expected use cases. This paper presents an overview on the drivers behind the 5G evolution and presents the new waveforms candidates for future generation network; the FBMC for filter bank multicarrier and UFMC for Universal filtered multi carrier are a potential concept for 5G and replacing the famous multicarrier modulation OFDM used in different technologies 4G. So there is a new way for the 5G transition expected beyond 2020

Filtered Multicarrier Transmission

Orthogonal frequency‐division multiplexing (OFDM) has been adopted as the waveform of choice in the existing and emerging broadband wireless communication systems for a number of advantages it can offer. Nevertheless, investigations of more advanced multicarrier transmission schemes have continued with the aim of eliminating or mitigating its essential limitations. This article discusses multicarrier schemes with enhanced spectrum localization, which manage to reduce the spectral sidelobes of plain OFDM that are problematic in various advanced communication scenarios. These include schemes for enhancing the OFDM waveform characteristics through additional signal processing as well as filter‐bank multicarrier (FBMC) waveforms utilizing frequency‐selective filter banks instead of plain (inverse) discrete Fourier transform processing for waveform generation and demodulation.acceptedVersionPeer reviewe

Efficient implementation of filter bank multicarrier systems using circular fast convolution

In this paper, filter bank-based multicarrier systems using a fast convolution approach are investigated. We show that exploiting offset quadrature amplitude modulation enables us to perform FFT/IFFT-based convolution without overlapped processing, and the circular distortion can be discarded as a part of orthogonal interference terms. This property has two advantages. First, it leads to spectral efficiency enhancement in the system by removing the prototype filter transients. Second, the complexity of the system is significantly reduced as the result of using efficient FFT algorithms for convolution. The new scheme is compared with the conventional waveforms in terms of out-of-band radiation, orthogonality, spectral efficiency, and complexity. The performance of the receiver and the equalization methods are investigated and compared with other waveforms through simulations. Moreover, based on the time variant nature of the filter response of the proposed scheme, a pilot-based channel estimation technique with controlled transmit power is developed and analyzed through lower-bound derivations. The proposed transceiver is shown to be a competitive solution for future wireless networks

Multitone NB-IoT optimization based on filtered OFDM waveform

Narrowband Internet of Things (NB-IoT) is standardized by 3GPP as a novel radio-access scheme for next-generation IoT technology. In-band operation mode, as one of its deployment methods, shares the spectrum of LTE. To avoid interference leakage on adjacent resource blocks (RBs), the spectrum sharing system needs a spectrally well-localized waveform. In this thesis, we investigate filtered-OFDM waveform for NB-IoT in-band system. This is achieved by designing and exploiting optimized filter for each sub-band. Specifically, the optimum filter needs a suitable length, a relatively narrowed transition band, and adequate stopband attenuation, which efficiently reduces the required guard-band, minimizing the related overhead in resource usage. In the experiments, we simplify the system model by shifting the NB-IoT RB to the center of the LTE spectrum. Firstly, we test potential filter types with various transition bands, selecting suitable filter configurations with acceptable performance when the system operates under carrier frequency offset (CFO) of half subcarrier spacing. Then, we define two different power level test cases, which are based on the minimum SNR for 1% uncoded bit-error rate (BER), for examining NB-IoT and LTE error tolerance in asynchronous cases, when NB-IoT system fails to synchronize to the time-frequency alignment of LTE. Finally, the system performance in a multipath channel is evaluated. With filtered-OFDM, the out-of-band emission is suppressed effectively and the tolerance to time and frequency offset is significantly improved, which makes the proposed scheme suitable for supporting asynchronous NB-IoT operation

Efficient Fast-Convolution-Based Waveform Processing for 5G Physical Layer

This paper investigates the application of fast-convolution (FC) filtering schemes for flexible and effective waveform generation and processing in the fifth generation (5G) systems. FC-based filtering is presented as a generic multimode waveform processing engine while, following the progress of 5G new radio standardization in the Third-Generation Partnership Project, the main focus is on efficient generation and processing of subband-filtered cyclic prefix orthogonal frequency-division multiplexing (CP-OFDM) signals. First, a matrix model for analyzing FC filter processing responses is presented and used for designing optimized multiplexing of filtered groups of CP-OFDM physical resource blocks (PRBs) in a spectrally well-localized manner, i.e., with narrow guardbands. Subband filtering is able to suppress interference leakage between adjacent subbands, thus supporting independent waveform parametrization and different numerologies for different groups of PRBs, as well as asynchronous multiuser operation in uplink. These are central ingredients in the 5G waveform developments, particularly at sub-6-GHz bands. The FC filter optimization criterion is passband error vector magnitude minimization subject to a given subband band-limitation constraint. Optimized designs with different guardband widths, PRB group sizes, and essential design parameters are compared in terms of interference levels and implementation complexity. Finally, extensive coded 5G radio link simulation results are presented to compare the proposed approach with other subband-filtered CP-OFDM schemes and time-domain windowing methods, considering cases with different numerologies or asynchronous transmissions in adjacent subbands. Also the feasibility of using independent transmitter and receiver processing for CP-OFDM spectrum control is demonstrated

Design and implementation of a bi-directional visible light communication testbed

Abstract. This work defines a bi-directional visible light communication (VLC) testbed design and implementation process using Universal Software Radio Peripheral (USRP) software defined radios (SDR) and open-source software. The visible light communication design uses LED light sources for wireless communications purposes. The testbed combines light, infrared and radio frequencies as wireless media to be utilized in a hybrid wireless communication system. Bi-directional communication at 12.5 Mbps bit rate was successfully achieved and only limited by a sample rate of the USRP system. The achieved communication distance was in the range of 0.5 to 7 meters depending on the used optics. A TCP-IP communication and access to the Internet was also established by using light and infrared communication links. The Internet connection was also established by using power line communication for providing data to the lighting through the existing power line cables. The results in the work were obtained by using a GMSK modulation. Also, GFSK, QPSK, 8-PSK, 16-QAM and OFDM modulation were initially tested for future study.Kaksisuuntaisen näkyvän valon tiedonsiirtotestialustan suunnittelu ja toteutus. Tiivistelmä. Työssä suunnitellaan ja rakennetaan kaksisuuntainen kokeiluympäristö valon käyttöön langattomassa tiedonsiirrossa käyttäen ohjelmistoradioita ja avoimen lähdekoodin ohjelmistoja. Kokeiluympäristössä voidaan tutkia ja käyttää valon, Infrapunan ja radioaaltojen taajuusalueita tiedonsiirtoon. Valon tiedonsiirrossa käytetään valaistuskäyttöön suunniteltuja LED valaisimia sekä valaistukseen että tiedonsiirtoon. Työssä saavuttiin laitteiston näytteistystaajuuden rajoittama kaksisuuntainen 12,5 Mb/s tiedonsiirtonopeus ja käytetyn optiikan ominaisuuksista sekä tiedonsiirtonopeudesta riippuvainen tiedonsiirtoetäisyys 0,5–7 metriä. Järjestelmään ohjelmoitiin valo- ja infrapunalinkin avulla toimiva TCP-IP yhteys Internetiin. Internet yhteys valaisimelle onnistuttiin siirtämään myös käyttäen sähköverkon valmiita kaapelointeja. Työn tulokset saavuttiin käyttäen GMSK moduloitua signaalia. Myös GFSK, QPSK, 8-PSK, 16-QAM ja OFDM modulaatioiden toimivuus testattiin tutkimuksen jatkoa varten