22 research outputs found
A General Framework for Analyzing, Characterizing, and Implementing Spectrally Modulated, Spectrally Encoded Signals
Fourth generation (4G) communications will support many capabilities while providing universal, high speed access. One potential enabler for these capabilities is software defined radio (SDR). When controlled by cognitive radio (CR) principles, the required waveform diversity is achieved via a synergistic union called CR-based SDR. Research is rapidly progressing in SDR hardware and software venues, but current CR-based SDR research lacks the theoretical foundation and analytic framework to permit efficient implementation. This limitation is addressed here by introducing a general framework for analyzing, characterizing, and implementing spectrally modulated, spectrally encoded (SMSE) signals within CR-based SDR architectures. Given orthogonal frequency division multiplexing (OFDM) is a 4G candidate signal, OFDM-based signals are collectively classified as SMSE since modulation and encoding are spectrally applied. The proposed framework provides analytic commonality and unification of SMSE signals. Applicability is first shown for candidate 4G signals, and resultant analytic expressions agree with published results. Implementability is then demonstrated in multiple coexistence scenarios via modeling and simulation to reinforce practical utility
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Ultra-wideband systems exploiting orthonormal waveforms
textElectrical and Computer Engineerin
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Intelligent genetic algorithms for next-generation broadband multi-carrier CDMA wireless networks
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This dissertation proposes a novel intelligent system architecture for next-generation broadband multi-carrier CDMA wireless networks. In our system, two novel and similar intelligent genetic algorithms, namely Minimum Distance guided GAs (MDGAs) are invented for both peak-to-average power ratio (PAPR) reduction at the transmitter side and multi-user detection (MUD) at the receiver side. Meanwhile, we derive a theoretical BER performance analysis for the proposed MC-CDMA system in A WGN channel. Our analytical results show that the theoretical BER performance of synchronized MC-CDMA system is the same as that of the synchronized DS-CDMA system which is also used as a theoretical guidance of our novel MUD receiver design. In contrast to traditional GAs, our MDGAs start with a balanced ratio of exploration and exploitation which is maintained throughout the process. In our algorithms, a new replacement strategy is designed which increases significantly the convergence rate
and reduces dramatically computational complexity as compared to the conventional GAs. The simulation results demonstrate that, if compared to those schemes using exhaustive search and traditional GAs, (1) our MDGA-based P APR reduction scheme achieves 99.52% and 50+% reductions in computational complexity, respectively; (2)
our MDGA-based MUD scheme achieves 99.54% and 50+% reductions in computational complexity, respectively. The use of one core MDGA solution for both issues can ease the hardware design and dramatically reduce the implementation cost in practice
Performance study of air interface for broadband wireless packet access
Ph.DDOCTOR OF PHILOSOPH
Intelligent genetic algorithms for next-generation broadband multi-carrier CDMA wireless networks
This dissertation proposes a novel intelligent system architecture for next-generation broadband multi-carrier CDMA wireless networks. In our system, two novel and similar intelligent genetic algorithms, namely Minimum Distance guided GAs (MDGAs) are invented for both peak-to-average power ratio (PAPR) reduction at the transmitter side and multi-user detection (MUD) at the receiver side. Meanwhile, we derive a theoretical BER performance analysis for the proposed MC-CDMA system in A WGN channel. Our analytical results show that the theoretical BER performance of synchronized MC-CDMA system is the same as that of the synchronized DS-CDMA system which is also used as a theoretical guidance of our novel MUD receiver design. In contrast to traditional GAs, our MDGAs start with a balanced ratio of exploration and exploitation which is maintained throughout the process. In our algorithms, a new replacement strategy is designed which increases significantly the convergence rate and reduces dramatically computational complexity as compared to the conventional GAs. The simulation results demonstrate that, if compared to those schemes using exhaustive search and traditional GAs, (1) our MDGA-based P APR reduction scheme achieves 99.52% and 50+% reductions in computational complexity, respectively; (2) our MDGA-based MUD scheme achieves 99.54% and 50+% reductions in computational complexity, respectively. The use of one core MDGA solution for both issues can ease the hardware design and dramatically reduce the implementation cost in practice.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Identification of Technologies for Provision of Future Aeronautical Communications
This report describes the process, findings, and recommendations of the second of three phases of the Future Communications Study (FCS) technology investigation conducted by NASA Glenn Research Center and ITT Advanced Engineering & Sciences Division for the Federal Aviation Administration (FAA). The FCS is a collaborative research effort between the FAA and Eurocontrol to address frequency congestion and spectrum depletion for safety critical airground communications. The goal of the technology investigation is to identify technologies that can support the longterm aeronautical mobile communication operating concept. A derived set of evaluation criteria traceable to the operating concept document is presented. An adaptation of the analytical hierarchy process is described and recommended for selecting candidates for detailed evaluation. Evaluations of a subset of technologies brought forward from the prescreening process are provided. Five of those are identified as candidates with the highest potential for continental airspace solutions in L-band (P-34, W-CDMA, LDL, B-VHF, and E-TDMA). Additional technologies are identified as best performers in the unique environments of remote/oceanic airspace in the satellite bands (Inmarsat SBB and a custom satellite solution) and the airport flight domain in C-band (802.16e). Details of the evaluation criteria, channel models, and the technology evaluations are provided in appendixes
Multiuser MIMO-OFDM for Next-Generation Wireless Systems
This overview portrays the 40-year evolution of orthogonal frequency division multiplexing (OFDM) research. The amelioration of powerful multicarrier OFDM arrangements with multiple-input multiple-output (MIMO) systems has numerous benefits, which are detailed in this treatise. We continue by highlighting the limitations of conventional detection and channel estimation techniques designed for multiuser MIMO OFDM systems in the so-called rank-deficient scenarios, where the number of users supported or the number of transmit antennas employed exceeds the number of receiver antennas. This is often encountered in practice, unless we limit the number of users granted access in the base station’s or radio port’s coverage area. Following a historical perspective on the associated design problems and their state-of-the-art solutions, the second half of this treatise details a range of classic multiuser detectors (MUDs) designed for MIMO-OFDM systems and characterizes their achievable performance. A further section aims for identifying novel cutting-edge genetic algorithm (GA)-aided detector solutions, which have found numerous applications in wireless communications in recent years. In an effort to stimulate the cross pollination of ideas across the machine learning, optimization, signal processing, and wireless communications research communities, we will review the broadly applicable principles of various GA-assisted optimization techniques, which were recently proposed also for employment inmultiuser MIMO OFDM. In order to stimulate new research, we demonstrate that the family of GA-aided MUDs is capable of achieving a near-optimum performance at the cost of a significantly lower computational complexity than that imposed by their optimum maximum-likelihood (ML) MUD aided counterparts. The paper is concluded by outlining a range of future research options that may find their way into next-generation wireless systems
Técnicas de processamento com múltiplas antenas para o sistema LTE
Mestrado em Engenharia Electrónica e TelecomunicaçõesPerformance, mobilidade e partilha podem ser consideras como as três
palavras-chave nas comunicações móveis de hoje em dia. Uma das necessidades
fundamentais do ser humano é a partilha de experiencias e informação.
Com a evolução ao nível do hardware móvel, a crescente popularidade de
smartphones, tablets e outros dispositivos moveis, fez com que a exigência
em termos de capacidade e taxa de transferência por parte das redes móveis
não parasse de crescer.
As limitações das redes 3G fizeram com que não conseguissem corresponder
a tais exigências e como tal, a transição para uma tecnologia mais robusta e
eficiente passou a ser inevitável. A resposta escolhida como solução a longo
prazo é a rede designada por LTE, desenvolvida pela organização 3GPP é
assumido que será a rede de telecomunicações predominante no futuro. As
vantagens mais sonantes são, naturalmente, elevadas taxas de transmissão,
maior eficiência espectral, redução da latência e de custos de operação. As
principais tecnologias em que o LTE se baseia, são o OFDM e sua variante
para múltiplo acesso, OFDMA, usado para o downlink e o SC-FDMA para
o uplink. Além disso, usa sistemas com múltiplas antenas para impulsionar
a eficiência espectral. Apesar de já implementado em alguns países por
diversas operadoras, constantes pesquisas continuam a ser realizadas com
o intuito de melhorar a sua performance.
Nesta dissertação é proposto um esquema duplo de codificação na frequência
e no espaço (D-SFBC) para um cenário baseado em OFDM com 4
antenas de transmissão e duas antenas de recepção (4 × 2 D-SFBC) para
o downlink. No cenário considerado, 4 símbolos de dados são transmitidos
utilizando unicamente 2 sub-portadoras, fazendo com que, este sistema seja
limitado pela interferência. Para de forma eficiente descodificar os símbolos
de dados transmitidos, foi desenvolvido um equalizador iterativo no domínio
da frequência. Duas abordagens são consideradas: cancelamento da interferência
em paralelo (PIC) e sucessivo cancelamento de interferência (SIC).
Uma vez que apenas 2 sub-portadoras são usadas para transmitir quatro
símbolos de dados em paralelo, o esquema desenvolvido duplica a taxa de
dados quando comparado com o esquema 2 × 2 SFBC, especificado no
standard do LTE.
Os esquemas desenvolvidos foram avaliados sob as especificações para LTE
e usando codificação de canal. Os resultados mostram que os esquemas
implementados neste trabalho utilizando um equalizador iterativo supera os
convencionais equalizadores lineares na eliminação da interferência adicional
introduzida, em apenas 2 ou 3 iterações.Performance, mobility and sharing can be assumed as the three keywords
in the mobile communications nowadays. One of the fundamental needs of
human beings is to share experiences and information. With the evolution of
mobile hardware level, the growing popularity of smartphones, tablets and
other mobile devices, has made that the demand in terms of capacity and
throughput by mobile networks did not stop growing.
Thus, the limitations of 3G stops it of being the answer of such demand, and
a transition to a powerful technology has become unavoidable. The answer
chosen is LTE, developed by the 3GPP organization is assumed to be the
predominant telecommunications network in the future. The most relevant
advantages are high transmission rates, higher spectral efficiency, reducing
latency and operating costs. The key technologies in which LTE is based,
are OFDM and its variant schemes for multiple access, OFDMA, used for
downlink, and SC-FDMA for the uplink. It also uses multiple antennas systems
in order to improve spectral efficiency. Although already implemented
in some countries by several operators, continuous research is conducted in
order to improve their performance.
In this dissertation it is proposed a double space-frequency block coding
(D-SFBC) scheme for an OFDM based scenario with 4 transmit antennas
and 2 receive antennas (4×2 D-SFBC) for the downlink. In the considered
scenario, 4 data symbols are transmitted by using only 2 subcarriers and thus
the system is interference limited. To efficiently decode the transmitted data
symbols an iterative equalizer designed in frequency domain is developed.
Two approaches are considered: parallel interference cancellation (PIC) and
successive interference cancellation (SIC). Since only 2 subcarriers are used
to transmit 4 data symbols in parallel the developed scheme achieve the
double data rate when compared with the 2×2 SFBC, specified in the LTE
standard.
The developed schemes were evaluated under the main LTE specifications
and using channel coding. The results have show that the schemes implemented
in this work using an interactive equalizer outperforms the conventional
linear equalizers in the interference removal, just by using 2 or 3
iterations
Characterisation of MIMO radio propagation channels
Due to the incessant requirement for higher performance radio systems, wireless designers have been constantly seeking ways to improve spectrum efficiency, link reliability, service quality, and radio network coverage. During the past few years, space-time technology which employs multiple antennas along with suitable signalling schemes and receiver architectures has been seen as a powerful tool for the implementation of the aforementioned requirements. In particular, the concept of communications via Multiple-Input Multiple-Output (MIMO) links has emerged as one of the major contending ideas for next generation ad-hoc and cellular systems. This is inherently due to the capacities expected when multiple antennas are employed at both ends of the radio link. Such a mobile radio propagation channel constitutes a MIMO system. Multiple antenna technologies and in particular MIMO signalling are envisaged for a number of standards such as the next generation of Wireless Local Area Network (WLAN) technology known as 802.1 ln and the development of the Worldwide Interoperability for Microwave Access (WiMAX) project, such as the 802.16e. For the efficient design, performance evaluation and deployment of such multiple antenna (space-time) systems, it becomes increasingly important to understand the characteristics of the spatial radio channel. This criterion has led to the development of new sounding systems, which can measure both spatial and temporal channel information. In this thesis, a novel semi-sequential wideband MIMO sounder is presented, which is suitable for high-resolution radio channel measurements. The sounder produces a frequency modulated continuous wave (FMCW) or chirp signal with variable bandwidth, centre frequency and waveform repetition rate. It has programmable bandwidth up to 300 MHz and waveform repetition rates up to 300 Hz, and could be used to measure conventional high- resolution delay/Doppler information as well as spatial channel information such as Direction of Arrival (DOA) and Direction of Departure (DOD). Notably the knowledge of the angular information at the link ends could be used to properly design and develop systems such as smart antennas. This thesis examines the theory of multiple antenna propagation channels, the sounding architecture required for the measurement of such spatial channel information and the signal processing which is used to quantify and analyse such measurement data. Over 700 measurement files were collected corresponding to over 175,000 impulse responses with different sounder and antenna array configurations. These included measurements in the Universal Mobile Telecommunication Systems Frequency Division Duplex (UMTS-FDD) uplink band, the 2.25 GHz and 5.8 GHz bands allocated for studio broadcast MIMO video links, and the 2.4 GHz and 5.8 GHz ISM bands allocated for Wireless Local Area Network (WLAN) activity as well as for a wide range of future systems defined in the WiMAX project. The measurements were collected predominantly for indoor and some outdoor multiple antenna channels using sounding signals with 60 MHz, 96 MHz and 240 MHz bandwidth. A wide range of different MIMO antenna array configurations are examined in this thesis with varying space, time and frequency resolutions. Measurements can be generally subdivided into three main categories, namely measurements at different locations in the environment (static), measurements while moving at regular intervals step by step (spatial), and measurements while the receiver (or transmitter) is on the move (dynamic). High-scattering as well as time-varying MIMO channels are examined for different antenna array structures