Feasibility of In-band Full-Duplex Radio Transceivers with Imperfect RF Components: Analysis and Enhanced Cancellation Algorithms

In this paper we provide an overview regarding the feasibility of in-band full-duplex transceivers under imperfect RF components. We utilize results and findings from the recent research on full-duplex communications, while introducing also transmitter-induced thermal noise into the analysis. This means that the model of the RF impairments used in this paper is the most comprehensive thus far. By assuming realistic parameter values for the different transceiver components, it is shown that IQ imaging and transmitter-induced nonlinearities are the most significant sources of distortion in in-band full-duplex transceivers, in addition to linear self-interference. Motivated by this, we propose a novel augmented nonlinear digital self-interference canceller that is able to model and hence suppress all the essential transmitter imperfections jointly. This is also verified and demonstrated by extensive waveform simulations.Comment: 7 pages, presented in the CROWNCOM 2014 conferenc

Reference Receiver Based Digital Self-Interference Cancellation in MIMO Full-Duplex Transceivers

In this paper we propose and analyze a novel self-interference cancellation structure for in-band MIMO full-duplex transceivers. The proposed structure utilizes reference receiver chains to obtain reference signals for digital self-interference cancellation, which means that all the transmitter-induced nonidealities will be included in the digital cancellation signal. To the best of our knowledge, this type of a structure has not been discussed before in the context of full-duplex transceivers. First, we will analyze the overall achievable performance of the proposed cancellation scheme, while also providing some insight into the possible bottlenecks. We also provide a detailed formulation of the actual cancellation procedure, and perform an analysis into the effect of the received signal of interest on self-interference coupling channel estimation. The achieved performance of the proposed reference receiver based digital cancellation procedure is then assessed and verified with full waveform simulations. The analysis and waveform simulation results show that under practical transmitter RF/analog impairment levels, the proposed reference receiver based cancellation architecture can provide substantially better self-interference suppression than any existing solution, despite deploying only low-complexity linear digital processing.Comment: 7 pages, 4 figures. To be presented in the 2014 IEEE Broadband Wireless Access Worksho

Cancellation of Power Amplifier Induced Nonlinear Self-Interference in Full-Duplex Transceivers

Recently, full-duplex (FD) communications with simultaneous transmission and reception on the same channel has been proposed. The FD receiver, however, suffers from inevitable self-interference (SI) from the much more powerful transmit signal. Analogue radio-frequency (RF) and baseband, as well as digital baseband, cancellation techniques have been proposed for suppressing the SI, but so far most of the studies have failed to take into account the inherent nonlinearities of the transmitter and receiver front-ends. To fill this gap, this article proposes a novel digital nonlinear interference cancellation technique to mitigate the power amplifier (PA) induced nonlinear SI in a FD transceiver. The technique is based on modeling the nonlinear SI channel, which is comprised of the nonlinear PA, the linear multipath SI channel, and the RF SI canceller, with a parallel Hammerstein nonlinearity. Stemming from the modeling, and appropriate parameter estimation, the known transmit data is then processed with the developed nonlinear parallel Hammerstein structure and suppressed from the receiver path at digital baseband. The results illustrate that with a given IIP3 figure for the PA, the proposed technique enables higher transmit power to be used compared to existing linear SI cancellation methods. Alternatively, for a given maximum transmit power level, a lower-quality PA (i.e., lower IIP3) can be used.Comment: To appear in proceedings of the 2013 Asilomar Conference on Signals, Systems & Computer

Downlink Coverage and Rate Analysis of Low Earth Orbit Satellite Constellations Using Stochastic Geometry

As low Earth orbit (LEO) satellite communication systems are gaining increasing popularity, new theoretical methodologies are required to investigate such networks' performance at large. This is because deterministic and location-based models that have previously been applied to analyze satellite systems are typically restricted to support simulations only. In this paper, we derive analytical expressions for the downlink coverage probability and average data rate of generic LEO networks, regardless of the actual satellites' locality and their service area geometry. Our solution stems from stochastic geometry, which abstracts the generic networks into uniform binomial point processes. Applying the proposed model, we then study the performance of the networks as a function of key constellation design parameters. Finally, to fit the theoretical modeling more precisely to real deterministic constellations, we introduce the effective number of satellites as a parameter to compensate for the practical uneven distribution of satellites on different latitudes. In addition to deriving exact network performance metrics, the study reveals several guidelines for selecting the design parameters for future massive LEO constellations, e.g., the number of frequency channels and altitude.Comment: Accepted for publication in the IEEE Transactions on Communications in April 202

Analog Imperfections in Wireless Full-Duplex Transceivers

Käytössä olevien taajuusalueiden ruuhkautumisen vuoksi langattoman tiedonsiirron spektritehokkuuden lisääminen on tullut yhä tärkeämmäksi. Vastauksena tähän, useat viimeaikaiset tutkimukset osoittavat, että on itse asiassa mahdollista lähettää ja vastaanottaa radiosignaaleja langattomasti käyttäen vain yhtä keskitaajuutta. Nämä niinkutsutut full-duplex lähetin/vastaanottimet voivat teoriassa jopa kaksinkertaistaa spektritehokkuuden, koska ne eivät tarvitse erillisiä taajuuskaistoja lähetetyille ja vastaanotetuille signaaleille. Haasteena tällaisessa tiedonsiirrossa on kuitenkin se, että lähetetty signaali on vastaanottimen näkökulmasta voimakas häiriölähde, sillä se kytkeytyy lähettimestä suoraan vastaanottimeen. Tämä itse-interferenssi on suurin käytännön este full-duplex lähetin/vastaanottimen toteutukselle, joten on erittäin tärkeää pystyä jollakin keinolla vaimentamaan sitä. Tässä työssä tutkitaan itse-interferenssin vaikutusta tyypilliseen full-duplex lähetin/vastaanottimeen, kun itse-interferenssiä vaimennetaan sekä analogisesti että digitaalisesti. Lisäksi työssä esitetään analogiselle vaimennukselle kaksi vaihtoehtoista toteutustapaa. Kaiken kaikkiaan, työn tuloksena saadaan tietoa full-duplex lähetin/ vastaanottimessa esiintyvien eri epäideaalisuuksien voimakkuuksista. Varsinainen analyysi perustuu yksinkertaistettuihin malleihin, joilla pyritään mallintamaan yksittäisten komponenttien synnyttämiä analogisia häiriöitä. Näiden mallien avulla johdetaan lausekkeet eri signaalikomponenttien tehoille, joilla saadaan laskettua lopullinen signaali-kohina-interferenssi suhde. Tämän lisäksi johdetuilla lausekkeilla lasketaan lukuisia esimerkkituloksia käyttäen todenmukaisia parametreja. Saadut tulokset osoittavat, että analogia-digitaalimuunnoksessa vaaditaan runsaasti bittejä, tai vaihtoehtoisesti, että itse-interferenssiä täytyy vaimentaa analogisesti huomattava määrä. Lisäksi havaittiin, että tietyt analogiset häiriöt, etenkin tehovahvistimen aiheuttama epälineaarinen vääristymä, sekä mahdollisesti myös vastaanottimen epälineaarisuus, täytyy ottaa huomioon vaimennettaessa itse-interferenssiä digitaalisesti. Saadut tulokset ovat yhtäpitäviä aaltomuotosimulaatioilla saatujen tulosten kanssa, mikä vahvistaa niiden luotettavuuden

Modeling and Efficient Cancellation of Nonlinear Self-Interference in MIMO Full-Duplex Transceivers

This paper addresses the modeling and digital cancellation of self-interference in in-band full-duplex (FD) transceivers with multiple transmit and receive antennas. The self-interference modeling and the proposed nonlinear spatio-temporal digital canceller structure takes into account, by design, the effects of I/Q modulator imbalances and power amplifier (PA) nonlinearities with memory, in addition to the multipath self-interference propagation channels and the analog RF cancellation stage. The proposed solution is the first cancellation technique in the literature which can handle such a self-interference scenario. It is shown by comprehensive simulations with realistic RF component parameters and with two different PA models to clearly outperform the current state-of-the-art digital self-interference cancellers, and to clearly extend the usable transmit power range.Comment: 7 pages, 5 figures. To be presented in the 2014 International Workshop on Emerging Technologies for 5G Wireless Cellular Network