Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-30T14:18:27Z No. of bitstreams: 1 luamoloisefernandesdasilveira.pdf: 589211 bytes, checksum: e51494b1c23ff74fa1fc26264147a6a1 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-30T15:36:08Z (GMT) No. of bitstreams: 1 luamoloisefernandesdasilveira.pdf: 589211 bytes, checksum: e51494b1c23ff74fa1fc26264147a6a1 (MD5) / Made available in DSpace on 2017-05-30T15:36:08Z (GMT). No. of bitstreams: 1 luamoloisefernandesdasilveira.pdf: 589211 bytes, checksum: e51494b1c23ff74fa1fc26264147a6a1 (MD5) Previous issue date: 2016-08-19 / Recentemente, Power Line Communication (PLC) tem atraído o interesse de pesquisadores de todo mundo. Contudo, sistemas PLC enfrentam diversos desafios em termos da degradação da qualidade de comunicação de dados. Para superar tais problemas, propomos o CodePLC, um protocolo MAC para PLC que utiliza network coding. Utilizamos um nó intermediário para intermediar a comunicação, armazenar e repassar uma combinação linear de pacotes PLC. Avaliamos o desempenho do CodePLC através da simulação de uma topologia comum em um sistema PLC baseado no esquema Orthogonal Frequency Division Multiplexing whith Time Domain Multiple Access (TDMA-OFDM), sob uma ampla gama de cenários. Em suma, os resultados mostram que, para transmissões do tipo broadcast, o uso de network coding melhora desempenho geral do sistema PLC baseado no TDMA-ODFM. De fato, quando comparado a um sistema que utiliza uma camada MAC PLC multihop stop&wait tradicional, podemos observar um pico de aumento de 110% no valor de pico do goodput. Além disso, nosso protocolo reduz em até 71,4% a ocupação dos buffers da rede. Finalmente, CodePLC pode reduz a latência média em até quatro vezes. / Recently, power line communication (PLC) has attracted interest of worldwide researchers. However, PLC systems face several challenges which degrade data communication quality. To overcome such issues, we propose CodePLC, a network coding PLC MAC protocol. We use a single relay node to intermediate communication, storing and forwarding linear combinations of PLC data packets. We evaluate CodePLC performance through simulations of a common topology for a PLC system based in Orthogonal Frequency Division Multiplexing whith Time Domain Multiple Access (TDMA-OFDM) under a wide range of scenarios. In summary, our results show that in a broadcast like transmission, the use of network coding enhances overall system performance. In fact, when compared to a traditional PLC system using multihop stop&wait MAC layer protocol, we have observed an peak of 110% goodput increase. Moreover, our protocol reduces in 71,4% network occupancy buffers. Finally, CodePLC reduces mean latency by four times.

Abstract Multicarrier and multiple input–multiple output (MIMO) techniques have become popular in wireless communications over multipath fading channels in recent years. This thesis firstly considers the characterization and simulation of fading mobile radio channels for MIMO multicarrier systems. Secondly, the performance of spread-spectrum multicarrier (MC) code-division multiple-access (CDMA) with multirate transmission is analyzed. Thirdly, the analysis is applied to ultra-wideband (UWB) orthogonal frequency-division multiplexing (OFDM) systems enhanced with frequency-domain code-division multiplexing (CDM). The response of a small-scale fading channel is derived as a function of time, transmit and receive antenna positions, and subcarrier frequency, which leads to a tapped delay-line model with time-, space-, and frequency-selective taps. The taps are modeled as a sum of a deterministic line-of-sight or dominant scattered path and a zero-mean Gaussian part composed of a number of unresolvable scattered paths and, therefore, are Rice fading. The Gaussian parts have the desired temporal and spatiospectral correlations generated by time-correlation shaping filtering and a space-frequency correlation transformation, respectively. The simulator achieves a good accuracy while retaining a reasonable computational complexity. The generic performance analysis of MC-CDMA includes both the multicode and variable spreading factor (VSF) multirate schemes that are inherent for CDMA and capable of providing efficient support for services of different required data rates. The analysis also takes into account the intersymbol interference caused by the multipath delay components exceeding a guard interval, which is commonly omitted in the literature by assuming the guard interval to be longer than the maximum delay spread. Results comparing and pointing out notable differences in the error rate performance of the two multirate schemes in conjunction with six different combining techniques are presented for a synchronous downlink and both a synchronous and asynchronous uplink. The analysis of CDM-enhanced OFDM-UWB involves first a single piconet with different combinations of the VSF and multicode schemes. Frequency-domain spreading is found to improve the performance remarkably when a sufficient spreading factor and a suitable subcarrier combining method are used. Subsequently, CDMA of simultaneously operating piconets (SOPs) with either the VSF or multicode scheme is considered. While both multirate schemes result in a similar performance when the number of SOPs is large, notable differences arise when there are only a few SOPs.

Abstract Iterative receiver techniques, multiple-input – multiple-output (MIMO) processing, and orthogonal frequency division multiplexing (OFDM) are amongst the key physical layer technologies when aiming at higher spectral efficiency for a wireless communication system. Special focus is put on iterative detection, decoding, and channel estimation for a MIMO-OFDM system. After designing separately efficient algorithms for the detection, channel decoding, and channel estimation, the objective is to optimize them to work together through optimizing the activation schedules for soft-in soft-out (SfISfO) components. A list parallel interference cancellation (PIC) detector is derived to approximate an a posteriori probability (APP) algorithm with reduced complexity and minimal loss of performance. It is shown that the list PIC detector with good initialization outperforms the K-best list sphere detector (LSD) in the case of small list sizes, whereas the complexities of the algorithms are of the same order. The convergence of the iterative detection and decoding is improved by using a priori information to also recalculate the candidate list, aside from the log-likelihood ratios (LLRs) of the coded bits. Unlike in pilot based channel estimation, the least-squares (LS) channel estimator based on symbol decisions requires a matrix inversion in MIMO-OFDM. The frequency domain (FD) space-alternating generalized expectation-maximization (SAGE) channel estimator calculates the LS estimate iteratively, avoiding the matrix inversion with constant envelope modulation. The performance and computational complexity of the FD-SAGE channel estimator are compared to those of pilot based LS channel estimation with minimum mean square error (MMSE) post-processing exploiting the time correlation of the channel. A time domain (TD) SAGE channel estimator is derived to avoid the matrix inversion in channel estimation based on symbol decisions for MIMO-OFDM systems also with non-constant envelope modulation. An obvious problem, with more than two blocks in an iterative receiver, is to find the optimal activation schedule of the different blocks. It is proposed to use extrinsic information transfer (EXIT) charts to characterize the behavior of the receiver blocks and to find out the optimal activation schedule for them. A semi-analytical expression of the EXIT function is derived for the LS channel estimator. An algorithm is proposed to generate the EXIT function of the APP algorithm as a function of the channel estimate’s mutual information (MI). Surface fitting is used to get closed form expressions for the EXIT functions of the APP algorithm and the channel decoder. Trellis search algorithms are shown to find the convergence with the lowest possible complexity using the EXIT functions. With the proposed concept, the activation scheduling can be adapted to prevailing channel circumstances and unnecessary iterations will be avoided.

The mobile wireless communication systems has been growing fast and continuously over the past two decades. Therefore, in order to fulfill the demand for this rapid growth, the standardization bodies along with wireless researchers and mobile operators around the world have been constantly working on new technical specifications.An important problem in modern communication is known as NP complete problem in the Maximum Likelihood (ML) detection of signals transmitting over Multiple Input Multiple Output channel of the OFDM transceiver system. Development of the Sphere Decoder (SD) as a result of the rapid advancement in signal processing techniques provides ML detection for MIMO channels at polynomial time complexity average case. There are weaknesses in the existing SDs. The sphere decoder performance is very sensitive for the most current proposals in order to choose the search radius parameter. At high spectral efficiencies SNR is low or as the problem dimension is high and the complexity coefficient can become very large too. Digital communications of detecting a vector of symbols has importance as, is encountered in several different applications. These symbols are as the finite alphabet and transmitted over a multiple-input multiple-output (MIMO) channel with Gaussian noise. There are no limitation to the detection of symbols spatially multiplexed over a multiple-antenna channel and the multi user detection problem. Efficient algorithms are considered for the detection problems and have recognized well. The algorithm of sphere decoder, orders has optimal performance considering the error probability and this has proved extremely efficient in terms of computational complexity for moderately sized problems in case of signal to noise ratio. At high SNR the algorithm has a polynomial average complexity and it is understood the algorithm has an exponential worst case complexity. The efficiency of the algorithm is ordered the exponential rate derivation of growth. Complexity is positive for the finite SNR and small in the high SNR. To achieve the sphere decoding solution applying Schnorr-Euchner by Maximum likelihood method , Depth-first Stack-based Sequential decoding is used. This thesis focuses on the receiver part of the transceiver system and takes a good look at the near optimal algorithm for sphere detection of a vector of symbols transmitted over MIMO channel. The analysis and algorithms are general in nature. / Cell:+8801553448014

WLAN/n är en attraktiv teknik då det ökar data genomströmningen och räckvidden med ökad effektivitet som ger mer bits per sekund. Utvecklingen inom 802.11n har ökat data raten och prestanda till högre nivåer. En teknik är att använda multipla antenner för sändare och mottagare för att sända multipla data strömmar genom MIMO system för n standarden. Mobila enheter i en cell kanske inte har fixerade positioner i cellen så utveckling av mer avancerade algoritmer som OFDM har också utvecklats och presenteras i den här rapporten. Interference för signalen är ett dilemma då den beräknade mängden av data tillverkare av wlan produkter har i sina specifikationer knappast stämmer med verkligheten när man mäter data genomströmning. Resultat från experimenten visar att störningar i vissa fall kan anses vara ett problem. Målet med den här rapporten är att besvara frågeställning kring olika tekniker inom WLAN teknologin och vilka typer av störningar och utveckling det finns för en stabilare och högre data genomströmning. Experimenten inkluderar WLAN nät i naturlig miljö med accesspunkt och laptop med nätverkskort.

3GPP LTE (Long Term Evolution) is a project of the Third Generation Partnership Project to improve the UMTS (Universal Mobile Telecommunications System) mobile phone standard to cope with future technology evolutions. Two duplex schemes FDD and TDD are investigated in this thesis. Several computational intensive components of the baseband processing for LTE uplink such as synchronization, channel estimation, equalization, soft demapping, turbo decoding is analyzed. Cost analysis is hardware independent so that only computational complexity is considered in this thesis. Hardware dependent discussion for LTE baseband SDR platform is given according the analysis results.

Constantly increasing demand for wireless communications in various applications has always led to new ways of modulating the radio frequency (RF) carrier signal by advancing waveform structure throughout generations. Although communication data rates are limited by the theoretical capacity, specific signaling designs for the signal that experiences natural and artificial effects in the transmission medium such as multipath fading channel, hardware impairments and multiuser environment promised better solutions in providing improved wireless access to various type of users and networks. Besides communication capacity, broadcasting nature of radio signals poses the information security as another main concern in wireless communications. In this dissertation, new advanced methods for improving signal statistics in multiple domains are studied. Instead of focusing on a single aspect, the waveform design approaches studied in this dissertation tackle with improving the orthogonal frequency-division multiplexing (OFDM)-based signaling in multiple perspectives such as out-of-band (OOB) emission reduction, peak-to-average-power ratio (PAPR) reduction, and secure transmission with minimum or no eect at the receiver side. Various concepts are coherently exploited while achieving aforementioned goals with minimal cost such as unexplored spaces in the signal space like (CP), guard band, multipath fading; multivariate nature of the multicarrier signals; time spreading and location uniqueness of the wireless channels. The proposed techniques are analyzed theoretically and performance results are presented including related previous works in the literature. It is worth noting that the methods presented in the dissertation can be easily applicable to conventional OFDM systems thanks to having no or minimal change in the receiver structure.

The demand of different multimedia services and different internet supported applications on mobile devices requires a high speed data rate and good service of quality. This can be obtained by implementing multiple Antenna technology on both stations i.e. User terminal and base station with an appropriate coding technique, and on the other hand MIMO can fulfill 3G & 4G demand and standard with a combination of other techniques. The MIMO diversity and MIMO multiplexing are the key factors to discuss and matter of concern is to achieve and support high speed data rate. MIMO multiplexing is a way to gain robustness and achievement in speed of data information. This thesis work describes a brief overview of WiMAX technology and MIMO-OFDM system and it also discusses the simplest Space time block code (STBC) known as Alamouti Space Time Code. The research approach is a literary survey to have theoretical understanding of the MIMO-OFDM system and WiMAX. The system‘s error performance is analyzed through simulation which showed the simulated results of Multi-Rate Resource Control (MRRC) scheme and Alamouti scheme are identical. And also the Bit Error Rate (BER) were checked for different MIMO systems, the simulation results shows that the BER improved to agreeable value also gains maximum diversity when the number of antennas increased on the receiver side. By improving the BER, we will get the better QoS. Matlab simulation has been performed, and presented the results, which shows the considerable error free transmission (FEC) for MIMO systems in WiMAX technology.

The goal of this thesis was to implement a DVB-T receiver on Coresonic’s DSP-processor and attempt to evaluate how to design a receiver that is robust against very strong echoes with a long delay. Long delayed echoes is very common in Single Frequency Networks (SFN) which is why focus was put on finding algorithms that work well in SFN.The thesis involved analyzing different algorithms involved in making a DVB-T receiver where the focus was to find a good channel estimation algorithm. The thesis also included programming the DSP-processor and making some smaller modifications to their hardware solution to integrate their error correction hardware. After finding relevant articles with promising algorithms a small transmitter, channel and receiver was modeled in Matlab in order to try the different algorithms. After testing the different algorithms some of the simpler ones were first implemented to quickly get a working receiver. The implementation was however time consuming and all of the most appropriate algorithms to better avert the effects of long and strong echoes where not implemented. This means some algorithms where only analyzed and discussed.The receiver performance is tested and simulated in Coresonic’s DSP simulator. The receiver does not fully meet the requirements set by NorDig when it comes to handling long delay spread echoes with a magnitude of 0db when tested in the DSP processor simulator. The receiver is however able to handle the Ricean channel at a SNR of 19 Db and Rayleigh channel at an SNR of 24 Db.This report is the result of the final thesis of a Master of Science in Computer Engineering at Linköpings Tekniska Högskola. The thesis was performed at Coresonic AB in Mjärdevi Linköping.

Wireless Sensor Network is an emerging technology that has applicationsin Wireless Actuators, remote controlling, distribution of softwareupdates and distribution of parameters to sensor nodes. This projectwork basically covers the concept of macro-diversity. This is a situationin which several transmitters are used for transferring the same signal (inmulti-hop sensor networks) to check the increase in connected nodes orin network coverage. Transmitter macro-diversity increases the receivedsignal strength and thus increases the signal-to-noise ratio which resultsin a lower outage probability. To accomplish this task three differentstrategies have been simulated using thirteen different cases. Broadcastingis used when forming SFN of size one (strategy one) and uni-castingis used for forming SFNs of size two (strategy two) and size three (strategythree).In this project reference material has been gathered frombooks, journals and web sources; and MATLAB has been used as thesimulation tool in which codes are written in the M programming language.The algorithm works firstly by discovering all the nodes that areconnected directly with the Base Station through multi-hoping, afterwhich the second algorithm is applied to check how many more nodescan be reached by forming SFNs. A gain of up to 79% was observedusing strategy one and strategy two and up to 83% in strategy three.The results shows that strategy one (Forming SFNs using BroadcastingTechnique) is the best as more nodes can be reached (for different cases)than for the other two strategies (forming SFNs using uni-casting technique).