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Recent research has shown that multiple-input multiple-output (MIMO) systems provide high spectral efficiencies and error performance gains. However, the use of multiple antennas in mobile terminals may not be very practical. Certainly there is limited space and other implementation issues which make this a challenging problem. Therefore, to harness the diversity gains afforded by MIMO transmitter diversity techniques, while maintaining a minimal number of antennas on each handset, cooperative diversity techniques have been proposed. In addition, attention has also been given to combining wireless relaying systems with MIMO techniques to improve capacity, coverage, and obtain better diversity at the expense of increased node complexity. This thesis considers the design and analysis of cooperative diversity systems and MIMO amplify-and-forward relaying systems. In particular, we investigate adaptive time- and frequency-domain equalization techniques for cooperative diversity systems using space-time block codes (STBC). For MIMO relaying systems, we analyze the ergodic capacity of various systems and compare different amplify-and-forward methods in terms of system capacity performance. We propose a new block time-domain adaptive equalization structure for time reversal-space time block coding (TR-STBC) systems, which eliminates the separate decoder and also the need for explicit channel state information (CSI) estimation at the receiver. Our simulation results show that the time-domain adaptive block equalizer performs better than the frequency-domain counterpart but at the cost of increased complexity. Then, we extend this time-domain adaptive equalization scheme to distributed TR-STBC systems. We also develop a frequency-domain counterpart for the distributed systems. Our simulation results show that the adaptive algorithms work well for Protocols I and III proposed by Nabar et al. The time-domain adaptive algorithms perform better than the frequency-domain algorithms, and overall the Protocol I receivers outperform the Protocol III receivers. We also show that, if only the Protocol III receiver is used, it can be susceptible to noise amplification due to a weaker source-to-relay link compared to the relay-to-destination link. This problem can be mitigated by using the Protocol I receivers with some extra complexity but much superior diversity performance. We also present an ergodic capacity analysis of an amplify-and-forward (AF) MIMO two-hop system including the direct link and validate the analysis with simulations. We show that having the direct link improves the capacity due to diversity and quantify this improvement. We also present an ergodic capacity analysis of an AF MIMO two-hop, two relay system. Our results verify the capacity gain of relaying systems with two relays due to the extra diversity compared to a single relaying system. However, the results also show that when one of the source-to-relay links has a markedly higher SNR compared to the other, a single relay system has better capacity than a two relay system. Finally, we compare three types of relay amplification methods: a) average amplification, b) instantaneous channel amplification, and c) instantaneous power amplification. The instantaneous power amplification method has a higher mean capacity but with a higher variance. Also, it requires additional information at the destination and would create enormous overheads compared to the other methods. We also find that the instantaneous channel amplification method has almost no advantage in terms of the mean capacity but its capacity is less variable than the average amplification method. On the other hand, the average amplification method is simpler to implement as it does not require channel estimation at the relaying terminal.

This thesis describes the use of adaptive equalization techniques to compensate for the intersymbol interference (ISI) that results when digital data is transmitted over a multipath radio channel. The equalization structures covered in this work are the linear transversal equalizer (LTE), the fractionally spaced equalizer (FSE), the decision-feedback equalizer (DFE), and the maximum-likelihood sequence estimation (MLSE) equalizer. This work also covers adaptive algorithms for equalization including both the least mean squares (LMS) and the recursive least squares (RLS) algorithm. All these equalizer structures and algorithms will be modeled using various simulation modules. Equalization for both stationary and mobile radio channels is considered. Stationary channels are modeled with a simple exponentially decaying profile. The mobile radio channel is represented using a two-ray Rayleigh fading model for an outdoor environment. The SIRCIM channel modeling tool is used to create channel profiles for an indoor mobile radio channel. Adaptive arrays and their similarities to linear equalizers are also studied in this thesis. The properties and performance of simple adaptive array systems using the LMS and RLS algorithms are examined through simulation. This thesis concludes with an in-depth study of the use of adaptive equalization for high-speed data systems operating in an indoor environment. Both stationary and slowly varying radio channels are examined. Simulations of DFE and MLSE equalizers operating in such a system show that both equalizer structures provide better BER performance over a system with no equalization. These simulation results also show that the MLSE equalizer provides better performance than the DFE in almost all cases, but requires a great deal more computations. / Master of Science

ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NV / The US Army Yuma Proving Ground (YPG) utilizes telemetry in several critical ways. Data, video, and voice from test aircraft provides YPG the information necessary to effectively execute missions. This information must be displayed real-time for efficient use of available flight time, making a robust telemetry link vital. In seeking an increased telemetry downlink capability, YPG considered three new technologies: Space Time Coding (STC), Adaptive Equalization (EQ), and Low Density Parity Check (LDPC). These technologies have shown reduced multipath and increased datalink reliability on fixed-wing aircraft; however, YPG's concern was the technology's benefits on rotary wing aircraft tested here. To assess potential benefits of these technologies, YPG conducted flight tests using representative flight profiles and vendor-supplied equipment to collect quantitative and qualitative data.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / It is widely recognized that telemetry channels, particularly airborne channels, are afflicted by multipath propagation effects. It has also been shown that adaptive equalization can be highly effective in mitigating these effects. However, numerous other factors influence the behavior of adaptive equalization, and the type of modulation employed is certainly one of these factors. This is particularly true on modulations which exhibit different operating bandwidths. In this paper, we will examine the effect multipath and adaptive equalization for three modulation techniques which are either already in use, or have been proposed, for airborne telemetry.

The new released 4G standard wireless communication reminds us that higher transmission data rate and more reliable service are required urgently. However, to fulfill the demand can face problems in a complex environment like mines. In this thesis, characterization of underground tunnel mines with the idea of combating intersymbol interference effect is presented.            Ray tracing simulation method is applied to characterize channel impulse response in different positions of an underground tunnel. From this channel impulse response, we can obtain how intersymbol interference affects different wireless systems. Intersymbol interference occurs due to multipath propagation of time dispersion channel.           Adaptive Equalization is the most effective way to compensate intersymbol interference. Adaptive filter adapts filter coefficients to compensate the channel so that the combination of the filter and channel offers a flat frequency response and linear phase. The bit error rate performance without using adaptive equalization is compared with using equalizer. Moreover, adaptive equalization approaches using RLS and LMS algorithms are compared with each other. The tradeoff between convergence rate, computation cost instability and ensemble averaged minimum squared errors are analyzed to determine how to select the optimum adaptive equalizer.

This thesis presents the design, implementation, and fabrication of a pattern-guided equalizer in a 65nm CMOS process. By counting the occurrence of 6 out of 16 4-bit patterns in the received data and utilizing their spectral content, the signal is equalized separately at fN and fN/2, where fN is half the bit rate. The design was packaged using a 64 pin Quad Flat No leads (QFN) package. Two different channels were used and the equalizer was able to open the eye for both 13dB and 17dB of attenuation at the Nyquist frequency. The adaptation performance was determined by measuring the vertical and horizontal eye openings for all possible equalizer coefficients. Measured results at 6Gb/s confirm that the adaptation engine opens a closed eye to within 2.6% of optimal vertical opening and 7% of optimal horizontal eye opening while consuming 16.8mW from a 1.2V supply.

This thesis presents the design, implementation, and fabrication of a pattern-guided equalizer in a 65nm CMOS process. By counting the occurrence of 6 out of 16 4-bit patterns in the received data and utilizing their spectral content, the signal is equalized separately at fN and fN/2, where fN is half the bit rate. The design was packaged using a 64 pin Quad Flat No leads (QFN) package. Two different channels were used and the equalizer was able to open the eye for both 13dB and 17dB of attenuation at the Nyquist frequency. The adaptation performance was determined by measuring the vertical and horizontal eye openings for all possible equalizer coefficients. Measured results at 6Gb/s confirm that the adaptation engine opens a closed eye to within 2.6% of optimal vertical opening and 7% of optimal horizontal eye opening while consuming 16.8mW from a 1.2V supply.

Space-time block coding (STBC) has added a new dimension to broadband wireless communication systems. Applications such as wireless Internet access and multimedia require the transmission of high data rates over frequency selective fading channels. The reliability of the wireless communication system can be increased by using diversity techniques combined with an equalizer at the receiver to eliminate the inter-symbol interference caused by multipath propagation. Generalizing Alamouti's famous STBC method to frequency selective channels, Time Reversal-Space Time Block Coding (TR-STBC) was first introduced in [1] and has since been shown to be an effective transmit diversity scheme [2, 3, 4]. TR-STBC-based schemes are considered promising candidates for indoor transmission [5] as well as for the enhanced data rates of the global evolution (EDGE) system [2, 3]. The optimal equalizer for a TR-STBC-based transceiver is the Maximum Likelihood Sequence Estimator (MSLE), realized using the Viterbi algorithm. Unfortunately, a Viterbi equalizer is difficult to implement in real-time due its exponential increase in complexity with the number of antennas and the length of the channel impulse response. Thus, we consider an adaptive algorithm-based Decision Feedback Equalizer (DFE). Such a DFE requires only linear processing complexity while maintaining good performance. Theoretically, the two output streams of a 2 x 1 TR-STBC decoder are uncoupled in terms of the input signal statistics and uncorrelated in terms of the channel noise statistics. The standard approach to removing the inter-symbol interference from these streams is to use either two parallel independently-adapted Single-Input Single-Output (SISO) equalizers or to use a single Multiple-Input Multiple-Output (MIMO) equalizer. By exploiting the common second-order statistics of the two output streams, we proposea novel hybrid equalizer structure which shares the statistical information between two SISO equalizers while constraining them to have common tap weights. To accommodate various levels of performance versus computational complexity, we propose novel Least Mean Square (LMS), Normalized Least Mean Square (NLMS), and Recursive Least Squares (RLS)-based adaptive algorithms for this new equalizer architecture. We use both statistical analysis and Monte Carlo simulations to characterize the dynamic convergence of these algorithms and to compare our new structure with the conventional uncoupled SISO equalizers and fully-coupled MIMO equalizer. We show that our new equalizer outperforms the other two equalizers using a reduced computational complexity similar to the uncoupled SISO equalizers. As expected, with increasing complexity, we find that the novel RLS-based algorithms converge the fastest followed by the novel NLMS- and LMS-based algorithms. We also consider alternative packet structures and kick-start methods to increase the convergence speed and reliability of the equalizer at realistic complexity. Finally, adding multiple receiver antennas to our system, we extend our equalizer structures and algorithms to the 2 x NR case. Using analysis and simulations, we demonstrate that the added receiver diversity in this case yields even greater reliability.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / This paper will present the results of experiments to characterize the performance of a blind, adaptive constant modulus algorithm (CMA) equalizer in simulated telemetry multipath environments. The variables included modulation method, bit rate, received signal-to-noise ratio, delay of the indirect path relative to the direct path, amplitude of the indirect path relative to the direct path, and fade rate. The main measured parameter was bit error probability (BEP). The tests showed that the equalizer usually improved the data quality in the presence of multipath.