Esquemas distribuídos para seleção de múltiplas antenas em redes com retransmissores do tipo amplifica-e-encaminha

Orientador: José Cândido Silveira Santos FilhoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A seleção de antena na transmissão tem sido apresentada como uma estratégia promissora para explorar os benefícios do uso de múltiplas antenas em sistemas de comunicações com retransmissores. No entanto, essa abordagem pode exigir um montante considerável de estimações de canal, transmissões de realimentação e atraso, dado que a sua implementação ótima e centralizada requer o monitoramento do estado do canal de todos os enlaces. Para aliviar essas deficiências, este trabalho propõe e analisa um conjunto de esquemas subótimos de seleção de antena na transmissão para sistemas com retransmissores do tipo amplifica-e-encaminha, os quais podem ser implementados de uma forma distribuída. Nos esquemas propostos, a antena é selecionada com base na informação local do estado de canal que está disponível na fonte, requerendo, portanto, um atraso e uma carga de realimentação pequenos e constantes. Tal abordagem é considerada em uso conjunto com diferentes técnicas, incluindo métodos de combinação de diversidade (combinação por máxima razão e combinação por seleção) no destino, protocolos de ganho fixo ou variável no relay, e transceptores com múltiplas antenas no relay. Além disso, para o caso particular em que o retransmissor tem ganho fixo e uma única antena, considera-se também o uso de um mecanismo de seleção de enlace na fonte. Para cada caso, o desempenho do sistema é avaliado em termos de probabilidade de outage, eficiência espectral e/ou vazão. O foco principal é direcionado à probabilidade de outage, para a qual são deduzidas expressões exatas e limitantes de desempenho. Uma análise assintótica é também efetuada para enriquecer a compreensão do comportamento do sistema quando operando sob alta relação sinal-ruído. Finalmente, como contribuição isolada, uma estratégia subótima e simples de alocação de potência é elaborada para um sistema com múltiplos retransmissores do tipo decodifica-e-encaminha, considerando-se enlaces com erros e codificação de fonte distribuídaAbstract: Transmit-antenna selection has been presented as a promising strategy for exploiting the benefits of multiple antennas in relaying communication systems. However, this approach may demand a considerable amount of channel estimations, feedback transmissions, and delay, since its optimal centralized implementation requires monitoring the channel state of all links. To alleviate those impairments, this work proposes and analyzes a set of suboptimal transmit-antenna selection schemes for amplify-and-forward relaying systems, which can be implemented in a distributed manner. In the proposed schemes, the antenna is selected based on the local channel-state information that is available at the source, thus requiring a low and constant delay/feedback overhead. Such an approach is considered along with different techniques, including diversity combining methods (maximal-ratio combining and selection combining) at the destination, fixed- and variable-gain protocols at the relay, and multi-antenna transceivers at the relay. A link-selection mechanism at the source is also considered for the special case of a single-antenna fixed-gain relay. For each case, the system performance is assessed in terms of outage probability, spectral efficiency, and/or throughput. The main focus is placed on the outage probability, for which exact or bound expressions are derived. An asymptotic analysis is also performed to provide further insights into the system behavior at high signal-to-noise ratio. Finally, as an isolated contribution, a simple suboptimal power allocation strategy is designed for a decode-and-forward multi-relay system with lossy intra-links and distributed source codingDoutoradoTelecomunicações e TelemáticaDoutora em Engenharia ElétricaCAPE

Diversity techniques for broadband wireless communications: performance enhancement and analysis

The diversity techniques have been proven to be effective for next generation broadband wireless communications, and are the focus of this thesis. The diversity techniques can be broadly categorized into three types: Space, Time, and Frequency. In this thesis, we are mainly concerned with frequency and space diversity techniques. Orthogonal Frequency Division Multiplexing (OFDM) is a frequency diversity technique which offers several benefits such as easier digital implementation, immunity to multipath channels, low complexity channel equalization, etc. Despite these desirable features, there are few inherent problems in OFDM such as high peak-to-average power ratio (PAPR). High PAPR demands large dynamic range in the transmitted chain such as digital to analog converter (DAC) and power amplifier (PA). Unless pre-processed, the transmitted signal gets distorted due to quantization errors and inter-modulation. In the initial stage of PhD candidature, the author focused on PAPR reduction techniques. A simple modification on conventional iterative clipping and filtering (ICF) technique was proposed which has less computational complexity. The power savings achievable from clipping and filtering method was considered next. Furthermore the ICF is compared with another distortion-less PAPR reduction technique called Selective Mapping (SLM) based on power savings. Finally, impact of clipping and filtering on the channel estimation was analyzed. Space diversity seeks to exploit the multi-path characteristics of wireless channels to improve the performance. The simplest form of the space diversity is the receive diversity where two or more antennas with sufficient spacing collect independent copies of the same transmitted signal, which contributes to better signal reception. In this thesis new analytical expressions for spectral efficiency, capacity, and error rates were presented for adaptive systems with channel estimation error. Beamforming (steering signal towards desired receiver) is another useful technique in multiple-antenna systems to further improve the system performance. MRT (Maximal Ratio Transmission) or MIMO-MRC is such system where the transmitter, based on channel feedback from the receiver, uses weighting factors to steer the transmitted signal. Closed form expressions for symbol error rates were derived for MRT system with channel estimation error. The results were extended to evaluate closed form expressions of error rates for Rectangular QAM. Antenna correlation was considered in another contribution on MRC systems. Relay and Cooperative networks represent another form of spatial diversity and have recently attracted significant research attention. These networks rely on intermediate nodes called "relays" to establish communication between the source and the destination. In addition to coverage extension, the relay networks have shown to offer cooperative diversity when there is a direct link or multiple relays. The first contribution is to analyze a dual-hop amplify-forward relay networks with dissimilar fading scenarios. Next error rates of Rectangular QAM for decode-forward selection relay system are derived. Multiple antenna at relay is included to analyze the benefits of dual spatial diversity over Rayleigh and Nakagami fading channels. Antenna selection is a cost-effective way to exploit the antenna diversity. General Order Antenna Selection (GOAS), based on Ordered Statistics, is used to evaluate signal statistics for a MIMO relay network

Distributed Suboptimal Schemes For Tas/sc And Tas/ls In Fixed-gain Af Relaying Systems

We design and analyze two distributed suboptimal schemes for transmit-antenna selection and link selection in a dual-hop, fixed-gain, amplify-and-forward relaying system, composed by one multi-antenna source, one single-antenna destination, and one single-antenna relay. The proposed schemes share the same antenna-selection policy, but differ from each other in the way the direct or relaying link is selected for communication. In a first scheme, the link is selected after transmission, at the destination; in a second scheme, it is selected before transmission, at the source. A great advantage of the proposed schemes over the optimal centralized solution is their low and constant delay/feedback overhead, regardless of the number of transmit antennas. In addition, the second scheme brings an improved spectral efficiency, once it saves one time slot when selecting the direct link. We derive analytical lower and upper bounds for the outage probability of the first scheme, in single-fold integral form, and exact closed-form expressions for the outage probability and mean spectral efficiency of the second scheme. We also perform an asymptotic analysis, showing that the first scheme achieves full diversity order, whereas the second scheme achieves full diversity order minus one, as a penalty for its improved spectral efficiency.131160416053Li, E., Yang, S., Wu, H., A source-relay selection scheme in two-way amplify-and-forward relaying networks (2012) IEEE Commun. Lett, 16 (10), pp. 1564-1567. , OctBao, V.N.Q., Phuong, B.P.L., Thanh, T.T., Performance analysis of TAS/SC-based MIMO decode-and-forward relaying for multi-hop transmission over Rayleigh fading channels (2012) Proc. ICCE, Santander, Spain, pp. 150-155. , Jul. 1-6Yeoh, P., Elkashlan, M., Yang, N., Da Costa, D.B., Duong, T., MIMO multi-relay networks with TAS/MRC and TAS/SC inWeibull fading channels (2012) Proc. IEEE Int. Symp. PIMRC, pp. 2314-2318. , Sydney, Australia, Sep. 9-12Suraweera, H., Smith, P., Nallanathan, A., Thompson, J., Amplify-andforward relaying with optimal and suboptimal transmit antenna selection (2011) IEEE Trans. Wireless Commun, 10 (6), pp. 1874-1885. , JunDing, H., Ge, J., Da Costa, D.B., Tsiftsis, T., A novel distributed antenna selection scheme for fixed-gain amplify-and-forward relaying systems (2012) IEEE Trans. Veh. Technol, 61 (6), pp. 2836-2842. , JulAmarasuriya, G., Tellambura, C., Ardakani, M., Performance analysis framework for transmit antenna selection strategies of cooperative MIMO AF relay networks (2011) IEEE Trans. Veh. Technol, 60 (7), pp. 3030-3044. , SepChen, Z., Yuan, J., Vucetic, B., Analysis of transmit antenna selection/maximal-ratio combining in Rayleigh fading channels (2005) IEEE Trans. Veh. Technol, 54 (4), pp. 1312-1321. , JulSimon, M.K., Alouini, M., (2000) Digital Communication over Fading Channels: A Unified Approach to Performance Analysis, , New York NY USA: WileyKaraevli, I.L., Altunbas, I., Karabulut Kurt, G., Performance analysis of cooperative relaying scheme applying TAS/SC (2010) Proc. ISCC, Riccione, pp. 127-132. , Italy, Jun 2-25Karaevli, I.L., Karabulut Kurt, G., Altunbas, I., Analysis of cooperative MIMO transmission system with transmit antenna selection and selection combining (2012) Wireless Commun. Mobile Comput, 12 (14), pp. 1266-1275. , OctYilmaz, A., Kucur, O., Performance of joint transmit and receive antenna selection in dual hop amplify-and-forward relay network over Nakagami-m fading channels (2014) Wireless Commun. Mobile Comput, 14 (1), pp. 103-114. , JanYilmaz, A., Kucur, O., End-to-end performance of transmit antenna selection and generalized selection combining in dual-hop amplify-andforward relay network in the presence of feedback errors (2014) Wireless Commun. Mobile Comput, 14 (7), pp. 689-703. , MaySanayei, S., Nosratinia, A., Antenna selection in MIMO systems (2004) IEEE Commun. Mag, 42 (10), pp. 68-73. , OctYeoh, P.L., Elkashlan, M., Collings, I., Selection relaying with transmit beamforming: A comparison of fixed and variable gain relaying (2011) IEEE Trans. Commun, 59 (6), pp. 1720-1730. , JunDing, H., Ge, J., Da Costa, D.B., Jiang, Z., Link selection schemes for selection relaying systems with transmit beamforming: New and efficient proposals from a distributed concept (2012) IEEE Trans. Veh. Technol, 61 (2), pp. 533-552. , FebDing, H., Ge, J., Da Costa, D.B., Jiang, Z., Diversity and coding gains of fixed-gain amplify-and-forward with partial relay selection in Nakagami-m fading (2010) IEEE Commun. Lett, 14 (8), pp. 734-736. , AugXu, F., Lau, F., Yue, D.-W., Diversity order for amplify-and-forward dual-hop systems with fixed-gain relay under Nakagami fading channels (2010) IEEE Trans. Wireless Commun, 9 (1), pp. 92-98. , JanGradshteyn, I.S., Ryzhik, M.I., (2007) Table of Integrals, Series, Products, , 7th ed San Diego, CA, USA: Academi

Cognitive Radio Systems

Cognitive radio is a hot research area for future wireless communications in the recent years. In order to increase the spectrum utilization, cognitive radio makes it possible for unlicensed users to access the spectrum unoccupied by licensed users. Cognitive radio let the equipments more intelligent to communicate with each other in a spectrum-aware manner and provide a new approach for the co-existence of multiple wireless systems. The goal of this book is to provide highlights of the current research topics in the field of cognitive radio systems. The book consists of 17 chapters, addressing various problems in cognitive radio systems

Journal of Telecommunications and Information Technology, 2022, nr 3

kwartalni

Self organization in 3GPP long term evolution networks

Mobiele en breedbandige internettoegang is realiteit. De internetgeneratie vindt het immers normaal om overal breedbandige internettoegang te hebben. Vandaag zijn er al 5,9 miljard mobiele abonnees ( 87% van de wereldbevolking) en 20% daarvan hebben toegang tot een mobiele breedbandige internetverbinding. Dit wordt aangeboden door 3G (derde generatie) technologieën zoals HSPA (High Speed Packet Access) en 4G (vierde generatie) technologieën zoals LTE (Long Term Evolution). De vraag naar hoogkwalitatieve diensten stelt de mobiele netwerkoperatoren en de verkopers van telecommunicatieapparatuur voor nieuwe uitdagingen: zij moeten nieuwe oplossingen vinden om hun diensten steeds sneller en met een hogere kwaliteit aan te bieden. De nieuwe LTE-standaard brengt niet alleen hogere pieksnelheden en kleinere vertragingen. Het heeft daarnaast ook nieuwe functionaliteiten in petto die zeer aantrekkelijk zijn voor de mobiele netwerkoperator: de integratie van zelfregelende functies die kunnen ingezet worden bij de planning van het netwerk, het uitrollen van een netwerk en het controleren van allerhande netwerkmechanismen (o.a. handover, spreiding van de belasting over de cellen). Dit proefschrift optimaliseert enkele van deze zelfregelende functies waardoor de optimalisatie van een mobiel netwerk snel en automatisch kan gebeuren. Hierdoor verwacht men lagere kosten voor de mobiele operator en een hogere kwaliteit van de aangeboden diensten

Potentzia domeinuko NOMA 5G sareetarako eta haratago

Tesis inglés 268 p. -- Tesis euskera 274 p.During the last decade, the amount of data carried over wireless networks has grown exponentially. Several reasons have led to this situation, but the most influential ones are the massive deployment of devices connected to the network and the constant evolution in the services offered. In this context, 5G targets the correct implementation of every application integrated into the use cases. Nevertheless, the biggest challenge to make ITU-R defined cases (eMBB, URLLC and mMTC) a reality is the improvement in spectral efficiency. Therefore, in this thesis, a combination of two mechanisms is proposed to improve spectral efficiency: Non-Orthogonal Multiple Access (NOMA) techniques and Radio Resource Management (RRM) schemes. Specifically, NOMA transmits simultaneously several layered data flows so that the whole bandwidth is used throughout the entire time to deliver more than one service simultaneously. Then, RRM schemes provide efficient management and distribution of radio resources among network users. Although NOMA techniques and RRM schemes can be very advantageous in all use cases, this thesis focuses on making contributions in eMBB and URLLC environments and proposing solutions to communications that are expected to be relevant in 6G

LIPIcs, Volume 261, ICALP 2023, Complete Volume

LIPIcs, Volume 261, ICALP 2023, Complete Volum