PERFORMANCE ANALYSIS OF DIFFERENT SCHEMES FOR TRANSMISSION OF WATERMARKED MEDICAL IMAGES OVER FADING CHANNELS

ABSTRACT Performance Analysis of Different Schemes for Transmission of Watermarked Medical images over Fading Channels Praveen Kumar Korrai In this thesis, we investigate different types of robust schemes for transmission of medical images with concealed patient information as a watermark. In these schemes, spatial domain digital watermarking technique is adapted to embed the patient information as a watermark into the lower order bits of the medical images to reduce the storage and transmission overheads. The watermark, which comprises text data, is encrypted to prevent unauthorized access of data. To enhance the robustness of the embedded information, the encrypted watermark is coded by concatenation of Reed Solomon (RS) and low density parity check (LDPC) codes. A robust scheme for transmission of watermarked images over impulsive noisy wireless channels is first proposed and its performance analyzed. In this scheme, the bursty wireless channel is simulated by adding impulse noise to the watermark embedded image. Furthermore, turbo channel coding is used to correct the transmission errors over impulsive noisy wireless channels. However, single input single output (SISO) channel capacity is not enough to provide modern wireless services such as data and multimedia messaging services. Further, it is not reliable due to multipath fading. To overcome these problems, a multiple-input multiple-output (MIMO) transmission scheme in which multiple antennas are used at both the transmitter and the receiver has emerged as one of the most significant technical breakthroughs in modern wireless communications. MIMO can improve the channel capacity and provide diversity gain. Hence, a scheme with a MIMO channel is proposed for the transmission of watermarked medical images over Rayleigh flat fading channels and its performance analyzed using MIMO maximum likelihood detector at the receiver. We present another scheme, namely, MIMO space frequency block coded OFDM (MIMO SFBC OFDM) in this thesis for transmission of watermarked medical images over Rayleigh fading channels to mitigate the detrimental effects due to frequency selective fading. The performance of this MIMO SFBC OFDM scheme is analyzed and compared with that of SISO-OFDM using minimum mean square error V-BLAST- based detection at the receiver. The efficacy of the different proposed schemes is illustrated through implementation results on watermarked medical images

Sistemas MIMO com STBC e correcção de erros em comunicações móveis de alto débito

Dissertação apresentada à Escola Superior de Tecnologia do Instituto Politécnico de Castelo Branco para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Comunicações Móveis.Esta dissertação tem como objectivo apresentar soluções eficientes para melhorar a eficiência de potência, recorrendo à implementação de sistemas MIMO (Multiple-Input Multiple-Output), com códigos de correcção de erros. Graças à união destas duas técnicas, é possível obter uma baixa probabilidade de erros com um baixo consumo de energia. Nos sistemas MIMO, a diversidade na transmissão é obtida com a codificação STBC (Space-Time Block Codes) e, na recepção com a combinação MRC (Maximum Ratio Combining). Na codificação STBC recorre-se à matriz de Alamouti [1] e às propostas por Tarokh et al [2]. Nos códigos de correcção de erros são usados algoritmos com saída branda (MAP, log-MAP e max-log-MAP) para o TC (Turbo-Código), conforme está descrito no 3G-LTE (3G-Long Term Evolution) [3]. Os resultados das simulações de desempenho, apresentados nesta dissertação, são obtidos em MATLAB, com uma modulação 4QAM (Quadrature Amplitude Modulation), num canal Rayleigh.ABSTRACT: This dissertation aims to present effective solutions to improve the efficiency of power, using the implementation of MIMO systems (Multiple-Input Multiple-Output), with error correction codes. Thanks to the union of these two techniques, is possible to obtain a low probability of errors with low power consumption. In MIMO systems, diversity in the transmission is obtained by STBC encoding (Space-Time Block Codes) and, in the reception with MRC (Maximum Ratio Combining). In STBC encoding are used the Alamouti [1] and proposed by Tarokh et al [2] matrixes. In the error correction codes are used algorithms with soft output ( MAP, log-MAP and max-log-MAP) for the TC (Turbo-Code), as described in 3G-LTE (3G-Long Term Evolution) [3]. The simulation results of performance, presented in this dissertation, are obtained in MATLAB, with 4QAM (Quadrature Amplitude Modulation) modulation, in a Rayleigh fading channel

Técnicas de processamento MIMO para sistemas 4G

Mestrado em Engenharia Eletrónica e TelecomunicaçõesThe theme of this dissertation work is focused in one of the key technologies specified in the last 4G cellular standards, which are the MIMO systems. In this context, the MIMO (Multiple Input Multiple Output) acronym is used to define a communication system where multiple antennas are used, therefore using this type of systems jointly with specific signal processing techniques, we can use the spatial dimension in order to generate multiplexing, diversity and beamforming gains. The aim of this work is to show the type of signal processing techniques that must be applied in order to achieve the gains referenced above, as well the optimal channel conditions in which these gains are maximized.Therefore, beyond the presentation of the theoretical background related with these type of techniques, we will present the MIMO transmission modes specified on 4G-LTE, having not only the aiming of show the type of practical constraints verified in a practical implementation, but also present the solutions used to solve that kind of constraints. In the last part of this work is presented a simulation platform implemented for one of the spatial multiplexing modes specified on LTE, which is the mode 4. The numerical results obtained allowed to see the advantage in the use of SIC (Successive Interference Cancelation) equalizers for multi-layer transmission modes, as well as the performance limitations related with the transmission through a channel where high spatial correlation conditions are verified. With the use of multiple precoding matrices, we understand the importance of perform a correct precoding selection in order to improve the transmission through a channel with this type of conditions.Beyond the observations referred above, we also saw the diversity cost related with the increase of spatial multiplexing gain.O tema deste trabalho de dissertação visa uma das tecnologias chave especificada nos últimos standards 4G para o sector das comunicações móveis, que são os sistemas MIMO. Neste contexto, o acrónimo MIMO é usado para referenciar um sistema de comunicação que faz uso de múltiplas antenas, assim, usando este tipo de sistemas conjuntamente com técnicas de processamento de sinal apropriadas, podemos usar a dimensão espacial de forma a gerar ganhos de multiplexagem, diversidade e beamforming. O objetivo deste trabalho é mostrar que tipo de processamento de sinal deve ser feito de forma a gerar cada um dos ganhos acima referidos, assim como as condições de canal em que estes podem ser maximizados. Para além da apresentação dos fundamentos teóricos relacionados com este tipo de técnicas, iremos apresentar os modos de transmissão MIMO especificados para o 4GLTE, tendo não só como objectivo observar o tipo de constrangimentos prácticos inerentes a uma implementação real, mas também observar o tipo de soluções usadas para fazer face a esses mesmos constrangimentos. Na parte final do trabalho é apresentada uma plataforma de simulação implementada para um dos modos de multiplexagem espacial especificados no LTE, ou seja o modo 4. Os resultados numéricos obtidos permitiram constatar a vantagem em usar equalizadores SIC em modos de transmissão multi-camada, assim como também nos permitiu observar as limitações de performance inerentes á transmissão através de um canal com elevada correlação espacial. Usando várias matrizes de pré-codificação especificadas no LTE para este modo, conseguimos perceber a importância que a escolha de uma correcta précodificação tem no melhoramento de desempenho da transmissão neste tipo de canais. Para além das observações referidas acima, também podemos verificar o custo em termos de diversidade inerente ao aumento do ganho de multiplexagem

Self-interference cancellation for full-duplex MIMO transceivers

PhD ThesisIn recent years, there has been enormous interest in utilizing the full-duplex (FD) technique with multiple-input multiple-output (MIMO) systems to complement the evolution of fifth generation technologies. Transmission and reception using FD-MIMO occur simultaneously over the same frequency band and multiple antennas are employed in both sides. The motivation for employing FD-MIMO is the rapidly increasing demand on frequency resources, and also FD has the ability to improve spectral efficiency and channel capacity by a factor of two compared to the conventional half-duplex technique. Additionally, MIMO can enhance the diversity gain and enable FD to acquire further degrees of freedom in mitigating the self-interference (SI). The latter is one of the key challenges degrading the performance of systems operating in FD mode due to local transmission which involves larger power level than the signals of interest coming from distance sources that are significantly more attenuated due to path loss propagation phenomena. Various approaches can be used for self-interference cancellation (SIC) to tackle SI by combining passive suppression with the analogue and digital cancellation techniques. Moreover, active SIC techniques using special domain suppression based on zero-forcing and null-space projection (NSP) can be exploited for this purpose too. The main contributions of this thesis can be summarized as follows. Maximum-ratio combining with NSP are jointly exploited in order to increase the signal-to-noise ratio (SNR) of the desired path and mitigate the undesired loop path, respectively, for an equalize-and-forward (EF) relay using FD-MIMO. Additionally, an end-to-end performance analysis of the proposed system is obtained in the presence of imperfect channel state information by formulating mathematically the exact closed-form solutions for the signal-to-interference-plus-noise ratio (SINR) distribution, outage probability, and average symbol-error rate for uncoded M-ary phase-shift keying over Rayleigh fading channels and in the presence of additive white Gaussian noise (AWGN). The coefficients of the EF-relay are designed to attain the minimum mean-square error (MMSE) between the transmission symbols. Comparison of the results obtained with relevant state-of-the-art techniques suggests significant improvements in the SINR figures and system capacity. Furthermore, iterative detection and decoding (IDD) are proposed to mitigate the residual self-interference (SI) remaining after applying passive suppression along with two stages of SI cancellation (SIC) filters in the analogue and digital domains for coded FD bi-directional transceiver based multiple antennas. IDD comprises an adaptive MMSE filter with log-likelihood ratio demapping, while the soft-in soft-out decoder utilizes the maximum a posteriori (MAP) algorithm. The proposed system’s performance is evaluated in the presence of AWGN over non-selective (flat) Rayleigh fading single-input multiple-output (SIMO) and MIMO channels. However, the results of the analyses can be applied to multi-path channels if orthogonal frequency division multiplexing is utilised with a proper length of cyclic prefix in order to tackle the channels’ frequency-selectivity and delay spread. Simulation results are presented to demonstrate the bit-error rate (BER) performance as a function of the SNR, revealing a close match to the SI-free case for the proposed system. Furthermore, the results are validated by deriving a tight upper bound on the performance of rate-1=2 convolutional codes for FD-SIMO and FD-MIMO systems for different modulation schemes under the same conditions, which asymptotically exhibits close agreement with the simulated BER performance.Ministry of Higher Education and Scientific Research (MoHESR), and the University of Mosul and to the Iraqi Cultural Attache in London for providing financial support for my PhD scholarship

Signal processing for future MIMO-OFDM wireless communication systems

The combination of multiple-input multiple-output (MIMO) technology and orthogonal frequency division multiplexing (OFDM) is likely to provide the air-interface solution for future broadband wireless systems. A major challenge for MIMO-OFDM systems is the problem of multi-access interference (MAI) induced by the presence of multiple users transmitting over the same bandwidth. Novel signal processing techniques are therefore required to mitigate MAI and thereby increase link performance. A background review of space-time block codes (STBCs) to lever age diversity gain in MIMO systems is provided together with an introduction to OFDM. The link performance of an OFDM system is also shown to be sensitive to time-variation of the channel. Iterative minimum mean square error (MMSE) receivers are therefore proposed to overcome such time-variation. In the context of synchronous uplink transmission, a new two-step hard-decision interference cancellation receiver for STBC MIMO-OFDM is shown to have robust performance and relatively low complexity. Further improvement is obtained through employing error control coding methods and iterative algorithms. A soft output multiuser detector based on MMSE interference suppression and error correction coding at the first stage is shown by frame error rate simulations to provide significant performance improvement over the classical linear scheme. Finally, building on the "turbo principle", a low-complexity iterative interference cancellation and detection scheme is designed to provide a good compromise between the exponential computational complexity of the soft interference cancellation linear MMSE algorithm and the near-capacity performance of a scheme which uses iterative turbo processing for soft interference suppression in combination with multiuser detection.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Signal processing for future MIMO-OFDM wireless communication systems

The combination of multiple-input multiple-output (MIMO) technology and orthogonal frequency division multiplexing (OFDM) is likely to provide the air-interface solution for future broadband wireless systems. A major challenge for MIMO-OFDM systems is the problem of multi-access interference (MAI) induced by the presence of multiple users transmitting over the same bandwidth. Novel signal processing techniques are therefore required to mitigate MAI and thereby increase link performance. A background review of space-time block codes (STBCs) to lever age diversity gain in MIMO systems is provided together with an introduction to OFDM. The link performance of an OFDM system is also shown to be sensitive to time-variation of the channel. Iterative minimum mean square error (MMSE) receivers are therefore proposed to overcome such time-variation. In the context of synchronous uplink transmission, a new two-step hard-decision interference cancellation receiver for STBC MIMO-OFDM is shown to have robust performance and relatively low complexity. Further improvement is obtained through employing error control coding methods and iterative algorithms. A soft output multiuser detector based on MMSE interference suppression and error correction coding at the first stage is shown by frame error rate simulations to provide significant performance improvement over the classical linear scheme. Finally, building on the "turbo principle", a low-complexity iterative interference cancellation and detection scheme is designed to provide a good compromise between the exponential computational complexity of the soft interference cancellation linear MMSE algorithm and the near-capacity performance of a scheme which uses iterative turbo processing for soft interference suppression in combination with multiuser detection

Space-time coded cooperation in Wireless Networks

Nowadays, the concept of spatial diversity and cooperative networks attract a lot of interest because they improve the reliability of transmission in wireless networks. Spatial diversity is achieved when multiple antennas are at the transmitter. With great growth and demand for high speed high data rate wireless communication, more and more antennas are required. In order to achieve maximum diversity, these antennas should be well separated so that the fading on each link is uncorrelated. This condition makes it difficult to have more than two antennas on a mobile terminal. The relay's cooperation helps increase the diversity order without extra hardware cost. However, its main inconvenience is the use of multiple time slots compared to the direct link transmission. In this thesis, we develop a cooperation model which is composed of three terminals: source, relay and destination. The transmitters (source and relay) are composed of 2 antennas at the transmitter and the receivers (relay and destination) have 4 antennas. In the first proposed model, transmitters and decoders are composed of an Alamouti encoder and decoder respectively. In the second model, we also add a turbo encoder at transmitters and iterative decoding takes place at receivers. In both cases, the transmission cycle is composed of two time slots and the decode and forward (DF) protocol is applied. Multiple scenarios are considered by changing the environment of the transmission, such as line of sight (LOS) or non line of sight (NLOS) or by modifying the location of the relay between the source and destination. We also simulate an uplink and a downlink communication. All the scenarios show a coding gain with the turbo coded space-time cooperation