Dissertations / Theses 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)
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
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.
Master of Science

Approved for public release; distribution is unlimited.
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.
Major, Republic of Singapore Airforce

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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.
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.

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.

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.
Master of Science

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, Dec. 2004.
Thesis advisor(s): Murali Tummala, Roberto Cristi. Includes bibliographical references (p. 69-71). Also available online.

Thesis (M.S. in Electrical Engineering and M.S. in Applied Physics)--Naval Postgraduate School, June 2004.
Thesis advisor(s): Tri T. Ha, Brett H. Borden. Includes bibliographical references (p. 107-109). Also available online.

碩士
大葉大學
電信工程學系碩士在職專班
93
The Nakagami fading distribution is assumed in this thesis for investigating the outage performance of digital communication with MRC (maximal ratio combining) diversity technique. Besides, the phenomena of CCI (co-channel interference), frequency selective channel, and the random communication branch are also considered in here. In this thesis some new formulae of outage performance are proposed. The numerical results obviously show that not only the characteristics parameters of the channel model, but the number of branch also affect the performance of wireless radio systems over CCI environments.

碩士
義守大學
電機工程學系碩士班
95
In this thesis, the performances of a QAM scheme in the TAS/MRC (Transmit Antenna Selection/ Maximal-Ratio Combining) on Nakagani-m fading channels are analyzed. The use of QAM scheme is considered since it offers an attractive solution to current bandwidth restrictions in mobile communications. By the way, the TAS/MRC diversity scheme draws considerable attention because it provides a good trade-off between hardware complexity and diversity benefits. The quotation of Nakagami model lies in its general physical description for both severe and weak fading. Closed-form expressions are derived for SNR, cumulative distribution function (CDF) of instantaneous SNR, and BER for the integer values of Nakagami fading parameter. On the other hands, the above-mentioned performances can be simple to evaluate by single integral expressions for the non-integer Nakagami fading parameters. Analytical results deduce that the advantage of TAS/MRC scheme may be gained apparently in a severe fading channel, in other words, in the Nakagami channel with a small fading parameter. The results are helpful to evaluate the performances for the TAS/MRC scheme over Nakagami-m fading channels with a wide range of fading conditions. All the analytical results are verified by Monte Carlo simulations.

碩士
國立臺灣大學
資訊管理學研究所
95
Recently, broadband wireless networks have become greatly popular and among these, IEEE 802.16j, which is a developing standard, is attracting considerable interests. The concept of adopting relays, which is the main focus of 802.16j, has two major advantages. Firstly, relays can serve as inter-mediums between base stations (BSs) and mobile stations (MSs) to repeat signals on both directions for the purpose of coverage extensions. Secondly, cooperatively relaying techniques are exploited in 802.16j to achieve superior reliabilities of communications using gain combining approaches like maximal ratio combining (MRC). In this thesis, we propose a solution for decisions on where and how many relays should be deployed in a design of 802.16j wireless network to minimize the total development cost. During the procedure, we derive a multicast tree routing algorithm to fulfill the QoS and throughput requirements on both down-link (DL) and up-link (UL) communications. The solution approach is based on Lagrangean relaxation in conjunction with novel optimization-based heuristics. With the exceptional properties of Lagrangean relaxation we expect to efficiently and effectively solve this complicated optimization problem. Computational experiments will be conducted to evaluate the performance of the proposed algorithm.

Please read the abstract in the section 00front of this document
Dissertation (M Eng (Electronic Engineering))--University of Pretoria, 2005.
Electrical, Electronic and Computer Engineering
unrestricted

Στην παρούσα διπλωματική εργασία μελετάμε τα πλεονεκτήματα που επιφέρει η χρήση πολλαπλών κεραιών στον πομπό και στον δέκτη, κατά την μετάδοση, με στόχο την βελτίωση των παρεχομένων υπηρεσιών στο χρήστη. Στο Κεφάλαιο 1, γίνεται μια ιστορική αναδρομή των ασύρματων επικοινωνιών καθώς των σύγχρονων ασύρματων τεχνολογιών και κεραιών που χρησιμοποιούνται. Στη συνέχεια γίνεται μια αναφορά στις έννοιες του διαφορισμού, του κέρδους διάταξης και της χωρικής πολυπλεξίας οι οποίες συνδέονται άρρηκτα με τα συστήματα MIMO. Στο Κεφάλαιο 2, αναφερόμαστε σε όλα εκείνα τα χαρακτηριστικά που περιγράφουν το ασύρματο κανάλι και εξάγουμε την γραμμική σχέση εισόδου-εξόδου του ασύρματου καναλιού. Στην συνέχεια γίνεται μια ανάλυση των στοχαστικών μοντέλων περιγραφής του ασύρματου διαύλου διαλείψεων και πιο συγκεκριμένα των μοντέλων Rayleigh και Rice. Στο Κεφάλαιο 3 εξετάζουμε την αξιοπιστία διαφόρων τύπων κεραιοσυστημάτων, ως προς τον ρυθμό των ρυθμό των λανθασμένων συμβόλων στον δέκτη. Πιο συγκεκριμένα εξετάζεται η τεχνική Maximal Ratio Combining για τα συστήματα SIMO καθώς και του σχήματος Alamouti για τα συστήματα ΜISO. Συνεχίζοντας στα MIMO συστήματα αναλύουμε τις μεθόδους ισοστάθμισης για την ανάκτηση των δεδομένων, και πιο συγκεκριμένα τις τεχνικές Zero Forcing, Minimum Mean Square Error,V-Blast και καθώς και την βέλτιστη τεχνική Maximum Likelihood. Στο τελευταίο μέρος της εργασίας αναλύουμε τα πλεονεκτήματα των MIMO συστημάτων, ως προς την χωρητικότητα που προσφέρουν, σε στοχαστικά κανάλια διαλείψεων.Στη συνέχεια, γίνεται αναφορά στην μέθοδο SVD και στην αναπαράσταση του MIMO καναλιού από έναν αριθμό ανεξάρτητων SISO διαύλων. Κλείνοντας αναφέρουμε την μέθοδο βέλτιστης κατανομής ισχύος στις κεραίες του πομπού Water-filling, και στην περαιτέρω αύξηση της χωρητικότητας του διαύλου που προσφέρει.
In this diploma thesis we are investigating the benefits of using Multiple Input and Multiple Output antennas in information transmission, with final goal to improve Quality of Service. The first Chapter, includes a historical background of the wireless communications but also is a reference to the modern wireless and antenna technologies. Moreover, we introduce the definition of new concepts, such as diversity and array gain and also spatial multiplexing, which are closely connected with MIMO technology. In the second chapter, we introduce the characteristics which they are describe the wireless channel, while simultaneously we mention the linear input-output relationship of the wireless channel. Additionally, we analyze the stochastic wireless channel models, namely the Rayleigh and the Rician fading models. In the third chapter, we investigate the reliability of different types of antenna topologies, regarding the pace of the invalid symbols in the transmitter. More specifically, we examine the Maximal Ratio Combining and Alamouti technique, for SIMO and MISO systems respectively. The next step is to analyze the equalization methods, which are used in MIMO antennas, and more specifically are, Zero Forcing, Minimum Mean Square Error and V-Blast receivers, but also the optimal Maximum Likelihood equalizer. In the last part of this Thesis, we investigate the benefits of MIMO systems regarding the Capacity, in random channels. Also, a reference to the SVD method has been made,which we use to analyze the MIMO channel, in a number of parallel SISO channels. Lastly, we use the water-filling method to allocate, with the optimal way, the given power in the transmit antennas, a fact that leads to even greater Capacity gain.

The importance of cooperative relaying communication in substituting for, or complementing, multiantenna systems is described, and a brief literature review is presented. Amplify-and-forward (AF) and decode-and-forward (DF) relaying are investigated and compared for a dual-hop relay channel. The optimal strategy, source and relay optimal power allocation, and maximum cooperative gain are determined for the relay channel. It is shown that while DF relaying is preferable to AF relaying for strong source-relay links, AF relaying leads to more gain for strong source-destination or relay-destination links. Superimposed and selection AF relaying are investigated for multirelay, dual-hop relaying. Selection AF relaying is shown to be globally strictly outage suboptimal. A necessary condition for the selection AF outage optimality, and an upper bound on the probability of this optimality are obtained. A near-optimal power allocation scheme is derived for superimposed AF relaying. The maximum instantaneous rates, outage probabilities, and average capacities of multirelay, dual-hop relaying schemes are obtained for superimposed, selection, and orthogonal DF relaying, each with parallel channel cooperation (PCC) or repetition-based cooperation (RC). It is observed that the PCC over RC gain can be as much as 4 dB for the outage probabilities and 8.5 dB for the average capacities. Increasing the number of relays deteriorates the capacity performance of orthogonal relaying, but improves the performances of the other schemes. The application of rateless codes to DF relaying networks is studied by investigating three single-relay protocols, one of which is new, and three novel, low complexity multirelay protocols for dual-hop networks. The maximum rate and minimum energy per bit and per symbol are derived for the single-relay protocols under a peak power and an average power constraint. The long-term average rate and energy per bit, and relay-to-source usage ratio (RSUR), a new performance measure, are evaluated for the single-relay and multirelay protocols. The new single-relay protocol is the most energy efficient single-relay scheme in most cases. All the multirelay protocols exhibit near-optimal rate performances, but are vastly different in the RSUR. Several future research directions for fixed-rate and rateless coded cooperative systems, and frameworks for comparing these systems, are suggested.
Communications