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

Subband filtered multi-carrier systems for multi-service wireless communications

Flexibly supporting multiple services, each with different communication requirements and frame structure, has been identified as one of the most significant and promising characteristics of next generation and beyond wireless communication systems. However, integrating multiple frame structures with different subcarrier spacing in one radio carrier may result in significant inter-service-band-interference (ISBI). In this paper, a framework for multi-service (MS) systems is established based on a subband filtered multi-carrier system. The subband filtering implementations and both asynchronous and generalized synchronous (GS) MS subband filtered multi-carrier (SFMC) systems have been proposed. Based on the GS-MS-SFMC system, the system model with ISBI is derived and a number of properties on ISBI are given. In addition, low-complexity ISBI cancelation algorithms are proposed by precoding the information symbols at the transmitter. For asynchronous MS-SFMC system in the presence of transceiver imperfections, including carrier frequency offset, timing offset, and phase noise, a complete analytical system model is established in terms of desired signal, inter-symbol-interference, inter-carrier-interference, ISBI, and noise. Thereafter, new channel equalization algorithms are proposed by considering the errors and imperfections. Numerical analysis shows that the analytical results match the simulation results, and the proposed ISBI cancelation and equalization algorithms can significantly improve the system performance in comparison with the existing algorithms

Channel Equalization in Fast-Convolution Filter Bank based Receivers for Professional Mobile Radio

Abstract-Fast convolution processing has recently been proposed as an efficient approach for implementing filter bank multicarrier systems with good spectral containment and high flexibility in adjusting the subchannel bandwidths and center frequencies. These features make fast convolution filter banks (FC-FBs) a particularly interesting choice for multicarrier transmission in challenging radio scenarios like dynamic spectrum access, cognitive radio, and fragmented spectrum use. In this contribution, the target is to compare the performance of the time-domain equalizer with the frequency-domain equalizer implemented through subcarrier processing in LTE-like multicarrier systems. It is shown that integrating the equalization functions with the FC-FB processing leads to an efficient overall implementation in terms of performance and computational complexity

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

Generalized Fast-Convolution-based Filtered-OFDM: Techniques and Application to 5G New Radio

This paper proposes a generalized model and methods for fast-convolution (FC)-based waveform generation and processing with specific applications to fifth generation new radio (5G-NR). Following the progress of 5G-NR standardization in 3rd generation partnership project (3GPP), the main focus is on subband-filtered cyclic prefix (CP) orthogonal frequency-division multiplexing (OFDM) processing with specific emphasis on spectrally well localized transmitter processing. Subband filtering is able to suppress the interference leakage between adjacent subbands, thus supporting different numerologies for so-called bandwidth parts as well as asynchronous multiple access. The proposed generalized FC scheme effectively combines overlapped block processing with time- and frequency-domain windowing to provide highly selective subband filtering with very low intrinsic interference level. Jointly optimized multi-window designs with different allocation sizes and design parameters are compared in terms of interference levels and implementation complexity. The proposed methods are shown to clearly outperform the existing state-of-the-art windowing and filtering-based methods.Comment: To appear in IEEE Transactions on Signal Processin

Nopeaan konvolutioon perustuva suodatettu OFDM ja ikkunoitu OFDM aaltomuotojen suorituskykyvertailussa 5G fyysiselle kerrokselle

Nykyisten mobiiliverkkojen vaatimukset kasvavat jatkuvasti, mikä johtuu pitkälti uusien mobiililaitteiden ja -palveluiden suosion kasvusta. Lisäksi matkapuhelinverkkoja on alettu käyttämään pääasiallisena internetyhteytenä, sillä nykyteknologialla on mahdollista saavuttaa kiinteään laajakaistayhteyksiin verrattavia käyttäjäkokemuksia useimmissa sovelluksissa. Nykyiset Long Term Evolution (LTE) ja LTE-Advanced ovat neljännen sukupolven (4G) teknologioita, jotka tarjoavat jo hyvin suuria tiedonsiirtonopeuksia. Tulevaisuuden palvelut vaativat kuitenkin uusia ominaisuuksia verkolta ja tämän takia uusia teknlogioita tutkitaan jatkuvasti lisää. Viidennen sukupolven (5G) teknologia pyrkii kasvattamaan tiedonsiirtonopeuksia entisestään. Lisäksi on ennustettu, että tulevaisuuden teknologiat vaativat tukea myös pienille ja viivekriittisille lähetyksille, kuten Internet of Things (IoT) ja Machineto-Machine (M2M) -tyyppisille palveluille. Tämä tarkoittaa, että verkkoon yhdistettyjen laitteiden määrä tulee kasvamaan räjähdysmäisesti. Verkossa ovat jatkossa esimerkiksi älykkäät autot, kodinkoneet, sensorit ja monet muut älykkäät laitteet, mikä vaatii mobiiliverkoilta merkittävästi suurta kapasiteettia ja joustavuutta. Tässä diplomityössä tutkitaan kahden uuden aaltomuodon soveltuvuutta 5G aaltomuodoksi: ikkunoitu CP-OFDM ja nopeaan konvoluutioon perustuva suodatettu CP-OFDM. Referenssinä on käytetty LTE-tyylistä kanavasuodatettua CP-OFDM aaltomuotoa vertaillen alltomuotojen spektraalista tehokkuutta ja vuototehoa. Aaltomuotojen suorituskykyä vertaillaan lopuksi kokonaisen tietoliikennelinkin yli. Tulosten perusteella kanavan käyttötehokkuus kasvaa uusilla aaltomuodoilla niin laaja- kuin kapeakaistalähetyksissä, mahdollistaen suurempia tiedonsiirtonopeuksia samassa kanavassa. Parannusta on havaittavissa erityisesti kapeakaistaisten lähetysten vuototehossa. Tämä sallii taajudessa lähekkäin olevien eri alikantoaaltoväliä, eri mittaisia syklisiä etuliitteitä tai eri aikasynkronisuusvaatimuksia käyytävien signaalien lähettämisen samanaikaisesti, häiritsemättä merkittävästi muita lähetyksiä.The demands for modern wireless cellular networks are increasing constantly due to the introduction of new mobile devices and services. Additionally, mobile networks are being used as a primary Internet connection as the current wireless networks are able to achieve similar user experiences than with wired connections in most applications. Long Term Evolution (LTE) and LTE-Advanced are current 4G technologies already allowing very high peak data rates. However, additional features are needed from network to satisfy traffic demands of the future and suitable technologies are in high interest in nowadays research. The fifth generation (5G) wireless system targets to increase data transmission rates further. In addition, it has been forecast that the traffic trends of the future becomes more delay-critical and small bursts communication has a bigger role. These type of services are e.g. Internet of Things (IoT) and Machine-to-Machine (M2M) communications. These increases dramatically the number of devices connected to Internet, for example smart cars, domestic appliances, sensors and other smart devices, which will require significantly improved capacity and flexibility from the forthcoming mobile communication networks. In this thesis, two waveform candidates for 5G are evaluated and compared: Windowed CP-OFDM and Fast Convolution based Filtered CP-OFDM. LTE-like channel filtered CP-OFDM is used as a reference in spectral efficiency, power leakage and overall link performance comparisons of the waveforms. It will be shown that the spectral utilization is improved with proposed waveforms in broadband and narrowband transmissions, which allows higher data rates inside the same bandwidth. The most significant improvement is observed in narrowband power leakage evaluations. Reduced power leakage allows to transmit several narrowband signals with different subcarrier spacings, cyclic prefix lengths, or different timing accuracy with tight frequency spacing without significant interference levels