Academic literature on the topic 'Maximal Ratio Combining (MRC)'

Different diversity techniques such as Maximal-Ratio Combining (MRC), Equal-Gain Combining (EGC) and Selection Combining (SC) are described and analyzed. Two branches (N=2) diversity systems that are used for pre-detection combining have been investigated and computed. The statistics of carrier to noise ratio (CNR) and carrier to interference ratio (CIR) without diversity assuming Rayleigh fading model have been examined and then measured for diversity systems. The probability of error (p_e) vs CNR and (p_e) versus CIR have also been obtained. The fading dynamic range of the instantaneous CNR and CIR is reduced remarkably when diversity systems are used [1]. For a certain average probability of error, a higher valued average CNR and CIR is in need for non-diversity systems [1]. But a smaller valued of CNR and CIR are compared to diversity systems. The overall conclusion is that maximal-ratio combining (MRC) achieves the best performance improvement compared to other combining methods. Diversity techniques are very useful to improve the performance of high speed wireless channel to transmit data and information. The problems which considered in this thesis are not new but I have tried to organize, prove and analyze in new ways.

Multi-user MIMO (MIMO-MU) communication techniques make use of available channel state information at the transmitter to mitigate the inter-user interference. The goal of these techniques is to provide the least interference at the mobile stations by applying a precoding operation. In this thesis a comparison of available techniques in the literature such as Channel Decomposition, SINR Balancing, Joint-MMSE optimization is presented. Novel techniques for the MIMO multi-user downlink communication systems, where a single stream is transmitted to each user are proposed. The proposed methods, different from the other methods in the literature, use a simple receiver to combat the interference. It has been shown that MRC based receivers are as good as more complicated joint MMSE receivers.

Steadily-increasing user demand for a wide range of high-quality video services delivered via satellite has driven broadcasters to move into the Ka-band and higher frequency spectrum in order to accommodate the necessary data rates. However, a major issue at these frequencies is the effect of severe rain-induced fading on link reliability, which requires that the system must be designed to implement mitigation techniques in order to achieve an acceptable quality-of-service. These techniques generally involve the use of adaptive modulation and data rates, together with various forms of diversity, switching or combining. In this thesis, we analyse and quantify the benefits of adding Time Diversity (TD) and Maximal Ratio Combining (MRC) to the widely-used DVB-S2 standard. Our results, which are based on i) 3 years of satellite beacon propagation measurements from 2 UK sites; ii) high-fidelity computer simulations; and iii) our new TD / MRC technology, indicate that substantial improvements in data throughput and significant reductions in outage time are readily achievable. Accurate knowledge of the statistical distribution of rain attenuation is necessary for the proper design of a Fade Mitigation Technique (FMT) to operate with the required level of service availability. Therefore, since July 2010, the University of South Wales and the Science and Technology Facilities Council have undertaken a programme of simultaneous satellite beacon measurements at the University campus in Pontypridd, Wales, and at the STFC Chilbolton Observatory, in Southern England, respectively. Transmissions from the Eutelsat Hotbird l3A (previously Hotbird 6) satellite at 19.7 GHz were recorded, together with meteorological measurements, at both sites. These data enabled reliable estimation of the instantaneous propagation conditions and carrier-to-noise ratio on the Ku-band beacon downlinks. Using standard ITU-R recommendations, the resulting data-set of measured 19.7 GHz attenuations was also frequency- scaled to yield a predicted data-set of 29.5 GHz attenuations. Thereby, the performance of an operationally-representative, hypothetical DVB-S2 communications link, with uplink at 30 GHz (from Chilbolton to the satellite), and downlink at 20 GHz (from the satellite to Pontypridd), was analysed based on l-year's data. The DVB-S2 transmission and reception signal processing architecture has been faithfully implemented in the MATLAB simulation environment with reference to the appropriate technical standards documents. Extensive testing has been conducted to verify that the bit error rate performance of the MATLAB simulation closely matches that defined in the DVB-S2 standard for all combinations of modulation schemes and coding rates. Inputs to the simulator comprise a test data stream (which can be a real HDTV signal), together with the uplink and downlink attenuation time- series data for the fading event being studied. Outputs consist of the bit error rate statistics and modulation scheme / coding rate configuration as a function of time, the total data throughput over the event duration, and the demodulated baseband signal. A novel feature of this work is the extension of the existing DVB-S2 standard to include TD and MRC. During periods of fading, TD is enabled, such that the transmitted data is duplicated into 2 parallel streams with a suitably-chosen time offset between them. In the receiver, MRC is employed in order to obtain a greater SNR improvement than could be achieved by the more traditional switched-combining method. We have designated this extended version of the DVB-S2 standard, incorporating the twin techniques of TO and MRC, as DVB-S2-TD. It provides the potential to continue delivering services at SNRs significantly below the currently acceptable threshold for DVB-S2, such as would be experienced under the propagation impairments associated with severe weather conditions. In this thesis, we describe the experimental systems used to collect the satellite beacon and meteorological measurements. The implementation of the MATLAB simulator for DVB-S2 is then discussed, together with the enhancements for TD and MRC. Finally, we compare the performance of DVB-S2 and DVB-S2-TD, so as to demonstrate the operational benefits of our new techniques.

Single Carrier Frequency Division Multiple Access (SC-FDMA) is a multiple access transmission scheme that has been adopted in the 4th generation 3GPP Long Term Evolution (LTE) of cellular systems. In fact, its relatively low peak-to-average power ratio (PAPR) makes it ideal for the uplink transmission where the transmit power efficiency is of paramount importance. Multiple access among users is made possible by assigning different users to different sets of non-overlapping subcarriers. With the current LTE specifications, if an SC-FDMA system is operating at its full capacity and a new user requests channel access, the system redistributes the subcarriers in such a way that it can accommodate all of the users. Having less subcarriers for transmission, every user has to increase its modulation order (for example from QPSK to 16QAM) in order to keep the same transmission rate. However, increasing the modulation order is not always possible in practice and may introduce considerable complexity to the system. The technique presented in this thesis report describes a new way of adding more users to an SC-FDMA system by assigning the same sets of subcarriers to different users. The main advantage of this technique is that it allows the system to accommodate more users than conventional SC-FDMA and this corresponds to increasing the spectral efficiency without requiring a higher modulation order or using more bandwidth. During this work, special attentions wee paid to the cases where two and three source signals are being transmitted on the same set of subcarriers, which leads respectively to doubling and tripling the spectral efficiency. Simulation results show that by using the proposed technique, it is possible to add more users to any SC-FDMA system without increasing the bandwidth or the modulation order while keeping the same performance in terms of bit error rate (BER) as the conventional SC-FDMA. This is realized by slightly increasing the energy per bit to noise power spectral density ratio (Eb/N0) at the transmitters.

Master of Engineering (Research)<br>The latest wireless communication techniques such as highspeed wireless internet application demand higher data rates and better quality of service (QoS). However, transmission reliability is still degraded by harsh propagation channels. Multiple-input multiple-output (MIMO) systems can increase the system capacity and improve transmission reliability. By transmitting multiple copies of data, a MIMO system can effectively combat the effects of fading. Due to the high hardware cost of a MIMO system, antenna selection techniques have been applied in MIMO system design to reduce the system complexity and cost. The Nakagami-m distribution has been considered for MIMO channel modeling since a wide range of fading channels, from severe to moderate, can be modeled by using Nakagami-m distribution. The Rayleigh distribution is a special case of the Nakagami-m distribution. In this thesis, we analyze the error performance of two MIMO schemes: maximal-ratio combining with transmit antenna selection (the TAS/MRC scheme) and space-time block codes with transmit antenna selection (the TAS/STBC scheme) over Nakagami-m fading channels. In the TAS/MRC scheme, one of multiple transmit antennas, which maximizes the total received signal-to-noise ratio (SNR), is selected for uncoded data transmission. First we use a moment generating function based (MGF-based) approach to derive the bit error rate (BER) expressions for binary phase shift keying (BPSK), the symbol error rate (SER) expressions for M-ray phase shift keying (MPSK) and M-ray quadrature amplitude modulation (MQAM) of the TAS/MRC scheme over Nakagami-m fading channels with arbitrary and integer fading parameters m. The asymptotic performance is also investigated. It is revealed that the asymptotic diversity order is equal to the product of the Nakagami fading parameter m, the number of transmit antenna Lt and the number of receive antenna Lr as if all transmit antenna were used. Then a Gaussian Q-functions approach is used to investigate the error performance of the TAS/STBC scheme over Nakagami-m fading channels. In the TAS/STBC scheme, two transmit antennas, which maximize the output SNR, are selected for transmission. The exact and asymptotic BER expressions for BPSK are obtained for the TAS/STBC schemes with three and four transmit antennas. It is shown that the TAS/STBC scheme can provide a full diversity order of mLtLr.

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California<br>This work explores aeronautical telemetry communication performance with the SOQPSK- TG ARTM waveforms when frequency-selective multipath corrupts received information symbols. A multi-antenna equalization scheme is presented where each antenna's unique multipath channel is equalized using a pilot-aided optimal linear minimum mean-square error filter. Following independent channel equalization, a maximal ratio combining technique is used to generate a single receiver output for detection. This multi-antenna equalization process is shown to improve detection performance over maximal ratio combining alone.

Mobile arrays employing diversity combining and adaptive beamforming techniques overcome multipath fading, improve coverage, and increase capacity in wireless communications systems. In this thesis, diversity combining and adaptive beamforming performance of different four element arrays for mobile (vehicular speed) and portable (pedestrian speed) terminals is investigated. The performance of four element arrays with different configurations and with different element patterns is compared using the square array of four half-wave dipole elements as the baseline. Results from diversity and beamforming measurements, performed in urban and suburban environments for both line-of-sight (LOS) and obstructed multipath channels are used to analyze and compare the performances of different four element arrays. At cumulative probabilities of 10%, 1% and 0.1%, diversity gain and improvement in signal-to-interference-plus-noise-ratio (SINR) are calculated from the diversity combining measurements and interference rejection measurements respectively. Experimental results illustrating the dependence of diversity gain on power imbalance, envelope correlation and diversity-combining scheme are presented. Measurements were performed at 2.05 GHz using the handheld antenna array testbed (HAAT). Low profile linear arrays are shown to provide diversity gain values of 5 to 8 dB and 11 to 16 dB, respectively for switched and maximal ratio combining at the 99% reliability level in non-line-of-sight urban channel. Interference cancellation of 24 to 28 dB was recorded in urban and suburban line-of-sight (LOS) channels for the sectorized square array. Results of vehicular measurements with the arrays mounted on a ground plane supported above the vehicle roof are also reported.<br>Master of Science

Approved for public release; distribution is unlimited.<br>In military operations, covertness of operation is of paramount importance. The transmission power of the data link must be kept to the minimum to maintain a low probability of detection (LPD) from the adversary. However, a reduction in the transmitted power implies a reduction in the operating range, though the detection range by the enemy is also reduced. Therefore, to reduce the enemy’s detection range while maintaining operating distance, this thesis explores strategies to discriminate gain against an adversary’s sensor. The strategies involve using processing gain, directional antennas, polarization and the natural environment as a transmission shield. The processing gain strategy analyzed in this thesis uses a diversity technique called Maximal Ratio Combining (MRC) applied to an IEEE 802.16a link. Sinclair D. Smith carried out a study on the possible processing gain derivable from this technique and this thesis will bring his results to practical applications via link analyses. In the event that the link is detected and the enemy decides to carry out jamming, the thesis explores a possible anti-jamming (AJ) strategy by using MRC and a directional antenna. Daniel P. Zastrow carried out a study on the AJ capability of MRC and this thesis brings his results to practical applications via link analyses.<br>Major, Republic of Singapore Airforce

Made available in DSpace on 2016-03-15T19:37:57Z (GMT). No. of bitstreams: 1 RICHARD JOHN LINTULAHTI OLANDIM.pdf: 2276167 bytes, checksum: 0d3c0536034c612074740ab02558a1be (MD5) Previous issue date: 2015-06-25<br>In Brazil, the broadcasting system for television content in high definition is the ISDB-Tb. Although robust, the content transmission in this system, like in any radio frequency propagation, can suffer from external attenuating factors, such as distortion by multipath propagation. One of the techniques used in radio communications for minimizing the effects of this type of distortion is the spatial diversity reception, which uses multiple antennas connected to a single receiver. The signals, received by different antennas, are combined, in a technique known as MRC or Maximal Ratio Combiner, so that the output signal-to-noise ratio is greater than the individual signal-to-noise ratios, allowing the successfully decoding of the received content, even though the individual signal in each antenna does not have sufficient quality to be decoded independently. This study aims to establish a method of spatial diversity in receiving television signals in ISDB-Tb, pondering between the advantages and disadvantages of their use in edge regions of coverage, where the reception of the Brazilian digital TV system is not yet total.<br>No Brasil, o sistema de radiodifusão para conteúdos televisivos em alta definição é o ISDB-Tb. Apesar de robusto, a transmissão de conteúdos neste sistema, como qualquer propagação em radiofrequência, pode sofrer com fatores externos atenuantes, como por exemplo a distorção por propagação em multi-percurso. Uma das técnicas utilizadas em radiocomunicação para que se minimizem os efeitos deste tipo de distorção é a diversidade espacial na recepção, que utiliza múltiplas antenas conectadas a um mesmo receptor. Os sinais, recebidos pelas diferentes antenas, são trabalhados em uma técnica conhecida como MRC ou Combinação de Máxima Razão, de modo que a relação sinal-ruído de saída seja maior do que as relações sinal-ruído individuais, permitindo a decodificação do conteúdo com sucesso, mesmo que os sinais individuais em cada antena não tenham qualidade suficiente para serem decodificados independentemente. Este estudo tem como objetivo propor um método de diversidade espacial na recepção de sinais televisivos no padrão brasileiro ISDB-Tb, ponderando entre as vantagens e desvantagens de sua utilização em regiões de borda de cobertura, onde a recepção do sistema brasileiro de TV digital ainda não é total.

Recently multiple antenna systems have received significant attention from researchers as a means to improve the energy and spectral efficiency of wireless systems. Among many classes of schemes, Space-Time Block codes (STBC) and Space-Time Trellis codes (STTC) have been the subject of many investigations.<p> Both techniques provide a means for combatting the effects of multipath fading without adding much complexity to the receiver. This is especially useful in the downlink of wireless systems. In this thesis we investigate the impact of channel estimation error on the performance of both STBC and STTC.<p> Channel estimation is especially important to consider in multiple antenna systems since (A) for coherent systems there are more channels to estimate due to multiple antennas and (B) the decoupling of data streams relies on correct channel estimation. The latter effect is due to the intentional cross-talk introduced into STBC.<br>Master of Science