<p>This dissertation studies a state-of-the-art bandwidth-efficient coded modulation technique, known as bit interleaved coded modulation with iterative decoding (BICM-ID), together with various diversity techniques to dramatically improve the performance of digital communication systems over wireless channels.</p> <p>For BICM-ID over a single-antenna frequency non-selective fading channel, the problem of mapping over multiple symbols, i.e., multi-dimensional (multi-D) mapping, with 8-PSK constellation is investigated. An explicit algorithm to construct a good multi-D mapping of 8-PSK to improve the asymptotic performance of BICM-ID systems is introduced. By comparing the performance of the proposed mapping with an unachievable lower bound, it is conjectured that the proposed mapping is the global optimal mapping. The superiority of the proposed mapping over the best conventional (1-dimensional complex) mapping and the multi-D mapping found previously by computer search is thoroughly demonstrated.</p> <p>In addition to the mapping issue in single-antenna BICM-ID systems, the use of signal space diversity (SSD), also known as linear constellation precoding (LCP), is considered in BICM-ID over frequency non-selective fading channels. The performance analysis of BICM-ID and complex N-dimensional signal space diversity is carried out to study its performance limitation, the choice of the rotation matrix and the design of a low-complexity receiver. Based on the design criterion obtained from a tight error bound, the optimality of the rotation matrix is established. It is shown that using the class of optimal rotation matrices, the performance of BICM-ID systems over a frequency non-selective Rayleigh fading channel approaches that of the BICM-ID systems over an additive white Gaussian noise (AWGN) channel when the dimension of the signal constellation increases. Furthermore, by exploiting the sigma mapping for any M-ary quadrature amplitude modulation (QAM) constellation, a very simple sub-optimal, yet effective iterative receiver structure suitable for signal constellations with large dimensions is proposed. Simulation results in various cases and conditions indicate that the proposed receiver can achieve the analytical performance bounds with low complexity.</p> <p>The application of BICM-ID with SSD is then extended to the case of cascaded Rayleigh fading, which is more suitable to model mobile-to-mobile communication channels. By deriving the error bound on the asymptotic performance, it is first illustrated that for a small modulation constellation, a cascaded Rayleigh fading causes a much more severe performance degradation than a conventional Rayleigh fading. However, BICM-ID employing SSD with a sufficiently large constellation can close the performance gap between the Rayleigh and cascaded Rayleigh fading channels, and their performance can closely approach that over an AWGN channel.</p> <p>In the next step, the use of SSD in BICM-ID over frequency selective Rayleigh fading channels employing a multi-carrier modulation technique known as orthogonal frequency division multiplexing (OFDM) is studied. Under the assumption of correlated fading over subcarriers, a tight bound on the asymptotic error performance for the general case of applying SSD over all N subcarriers is derived and used to establish the best achievable asymptotic performance by SSD. It is then shown that precoding over subgroups of at least L subcarriers per group, where L is the number of channel taps, is sufficient to obtain this best asymptotic error performance, while significantly reducing the receiver complexity. The optimal joint subcarrier grouping and rotation matrix design is subsequently determined by solving the Vandermonde linear system. Illustrative examples show a good agreement between various analytical and simulation results.</p> <p>Further, by combining the ideas of multi-D mapping and subcarrier grouping, a novel power and bandwidth-efficient bit-interleaved coded modulation with OFDM and iterative decoding (BI-COFDM-ID) in which multi-D mapping is performed over a group of subcarriers for broadband transmission in a frequency selective fading environment is proposed. A tight bound on the asymptotic error performance is developed, which shows that subcarrier mapping and grouping have independent impacts on the overall error performance, and hence they can be independently optimized. Specifically, it is demonstrated that the optimal subcarrier mapping is similar to the optimal multi-D mapping for BICM-ID in frequency non-selective Rayleigh fading environment, whereas the optimal subcarrier grouping is the same with that of OFDM with SSD. Furthermore, analytical and simulation results show that the proposed system with the combined optimal subcarrier mapping and grouping can achieve the full channel diversity without using SSD and provide significant coding gains as compared to the previously studied BI-COFDM-ID with the same power, bandwidth and receiver complexity.</p> <p>Finally, the investigation is extended to the application of BICM-ID over a multiple-input multiple-output (MIMO) system equipped with multiple antennas at both the transmitter and the receiver to exploit both time and spatial diversities, where neither the transmitter nor the receiver knows the channel fading coefficients. The concentration is on the class of unitary constellation, due to its advantages in terms of both information-theoretic capacity and error probability. The tight error bound with respect to the asymptotic performance is also derived for any given unitary constellation and mapping rule. Design criteria regarding the choice of unitary constellation and mapping are then established. Furthermore, by using the unitary constellation obtained from orthogonal design with quadrature phase-shift keying (QPSK or 4-PSK) and 8-PSK, two different mapping rules are proposed. The first mapping rule gives the most suitable mapping for systems that do not implement iterative processing, which is similar to a Gray mapping in coherent channels. The second mapping rule yields the best mapping for systems with iterative decoding. Analytical and simulation results show that with the proposed mappings of the unitary constellations obtained from orthogonal designs, the asymptotic error performance of the iterative systems can closely approach a lower bound which is applicable to any unitary constellation and mapping.</p>

This dissertation investigates the use of advanced acoustical communication techniques for wireless downhole telemetry systems. Using acoustic waves for downhole telemetry systems is investigated in order to replace the wired communication systems currently being used in oil and gas wells. While the acoustic technology offers great benefits, a clear understanding of its propagation aspects inside the wells is lacking. This dissertation describes a testbed that was designed to study the propagation of acoustic waves over production pipes. The wireless communication system was built using an acoustic transmitter, five connected segments of seven inch production pipes, and an acoustic receiver. The propagation experiments that were conducted on this testbed in order to characterize the channel behavior are explained as well. Moreover, the large scale statistics of the acoustic waves along the pipe string are described. Results of this work indicate that acoustic waves experience a frequency- dependent attenuation and dispersion over the pipe string. In addition, the testbed was modified by encasing one pipe segment in concrete in order to study the effect of concrete on wave propagation. The concrete was found to filter out many of the signal harmonics; accordingly, the acoustic waves experienced extra attenuation and dispersion. Signal processing techniques are also investigated to address the effects of multipaths and attenuation in the acoustic channel; results show great enhancements in signal qualities and the usefulness of these algorithms for downhole communication systems. Furthermore, to explore an alternative to vibrating the body of a cemented pipe string, a testbed was designed to investigate the propagation aspects of sound waves inside the interior of the production pipes. Results indicate that some low-frequency sound waves can travel for thousands of feet inside a cemented pipe string and can still be detected reliably.

Computation problems, such as network coding and averaging consen- sus, have become increasingly central to the study of wireless networks. Network coding, in which intermediate terminals compute and forward functions of others’ messages, is instrumental in establishing the capacity of multicast networks. Averaging consensus, in which terminals compute the mean of others’ measurements, is a canonical building block of dis- tributed estimation over sensor networks. Both problems, however, are typically studied over graphical networks, which abstract away the broad- cast and superposition properties fundamental to wireless propagation. The performance of computation in realistic wireless environments, there- fore, remains unclear. In this thesis, I seek after near-optimal computation strategies under realistic wireless models. For both network coding and averaging con- sensus, cooperative communications plays a key role. For network cod- ing, I consider two topologies: a single-layer network in which users may signal cooperatively, and a two-transmitter, two-receiver network aided by a dedicated relay. In the former topology, I develop a decode-and- forward scheme based on a linear decomposition of nested lattice codes. For a network having two transmitters and a single receiver, the proposed scheme is optimal in the diversity-multiplexing tradeo↵; otherwise it pro- vides significant rate gains over existing non-cooperative approaches. In the latter topology, I show that an amplify-and-forward relay strategy is optimal almost everywhere in the degrees-of-freedom. Furthermore, for symmetric channels, amplify-and-forward achieves rates near capacity for a non-trivial set of channel gains. For averaging consensus, I consider large networks of randomly-placed nodes. Under a path-loss wireless model, I characterize the resource de- mands of consensus with respect to three metrics: energy expended, time elapsed, and time-bandwidth product consumed. I show that existing con- sensus strategies, such as gossip algorithms, are nearly order optimal in the energy expended but strictly suboptimal in the other metrics. I propose a new consensus strategy, tailored to the wireless medium and cooperative in nature, termed hierarchical averaging. Hierarchical averaging is nearly order optimal in all three metrics for a wide range of path-loss exponents. Finally, I examine consensus under a simple quantization model, show- ing that hierarchical averaging achieves a nearly order-optimal tradeo↵ between resource consumption and estimation accuracy.

The imminent inception of third-generation (3G) mobile communication networks offers an unprecedented opportunity for the development of video streaming applications through wireless Internet access. Different design challenges exist in implementing video streaming connections spanning both wired and wireless domains. A split-domain TCP-friendly streaming video transmission protocol is presented based on adaptive rate encoding in the MPEG-4 video format. Network simulations are conducted to demonstrate the benefits and viability of such a video streaming scheme over existing options. Further feature enhancements and refinements are necessary for the proposed protocol to achieve its full potential.

Next generation wireless communication systems are expected to provide a variety of services including voice, data and video. The rapidly growing demand for these services needs high data rate wireless communication systems with reliability and high user capacity. Recently, it has been shown that reliability and achievable data rate of wireless communication systems increases dramatically by employing multiple transmit and receive antennas. Transmit diversity is a powerful technique for combating multipath fading in wireless communications. However, employing multiple antennas in a mobile terminal to achieve the transmit diversity in the uplink is not feasible due to the limited size of the mobile unit. In order to overcome this problem, a new mode of transmit diversity called cooperative diversity (CD) based on user cooperation, was proposed very recently. By user cooperation, it is meant that the sender transmits to the destination and copies to other users, called partners, for relaying to the destination. The antennas of the sender and the partners together form a multiple antenna situation. CD systems are immuned not only against small scale channel fading but also against large scale channel fading. On the other hand, CD systems are more sensitive to interuser (between sender and partner) transmission errors and user mobility. In this dissertation, we propose a bandwidth and power efficient CD system which could be accommodated with minimal modifications in the currently available direct or point-to-point communication systems. The proposed CD system is based on quadrature signaling (QS). With quadrature signaling, both sender’s and partners’ information symbols are transmitted simultaneously in his/her multiple access channels. It also reduces the synchronization as well as the interference problems that occur in the schemes reported in the literature. The performance of the proposed QS-CD system is analyzed at different layers. First, we study the bit error probability (BEP) of the QS-CD system for both fixed and adaptive relaying at the partner. It is shown from the BEP performance that the QS-CD system can achieve diversity order of two. Then, a cross-layer communication system is developed by combing the proposed QS-CD system at the physical layer and the truncated stop-and- wait automatic repeat request (ARQ) at the data link layer. The performance of the cross-layer system is analyzed and compared with existing schemes in the literature for performance metrics at the data link layer and upper layers, i.e., frame error rate, packet loss rate, average packet delay, throughput, etc. In addition, the studies show that the proposed QS-CD-ARQ system outperforms existing schemes when it has a good partner. In this respect, the proposed system is fully utilizing the communication channel and less complex in terms of implementation when compared with the existing systems. Since the partner selection gives significant impact on the performance of the CD systems, partner selection algorithms (PSAs) are extensively analyzed for both static and mobile user network. In this case, each individual user would like to take advantage of cooperation by choosing a suitable partner. The objective of an individual user may conflict with the objective of the network. In this regard, we would like to introduce a PSA which tries to balance both users and network objectives by taking user mobility into consideration. The proposed PSA referred to as worst link first (WLF), to choose the best partner in cooperative communication systems. The WLF algorithm gives priority to the worst link user to choose its partner and to maximize the energy gain of the radio cell. It is easy to implement not only in centralized networks but also in distributed networks with or without the global knowledge of users in the network. The proposed WLF matching algorithm, being less complex than the optimal maximum weighted (MW) matching and the heuristic based Greedy matching algorithms, yields performance characteristics close to those of MW matching algorithm and better than the Greedy matching algorithm in both static and mobile user networks. Furthermore, the proposed matching algorithm provides around 10dB energy gain with optimal power allocation over a non-cooperative system which is equivalent to prolonging the cell phone battery recharge time by about ten times.

Basic properties and new design principles of ultra wideband Vivaldi antennas are presentedand discussed in this paper. The focus will be on the modeling of Vivaldi antenna design curves, by which it is constructed; its simulation results, realization and the measurements. According to the aim of this research the discussion starts with the review of the previous researches done for Vivaldi antennas. Introductory part of the report also contains the problem description for the current project and the classification of the goals to be achieved. As a theoretical review, the discussion initiates with the definitions anddescription of basic parameters of the antennas and covers a short presentation of UWBpulse-based radar system. The attention will be focused on UWB signals behavior and characterization, their propagation principles and basic troubles stands nowadays. As anapplication the wall penetrating Radar systems will be considered. The major part of thereport holds on the investigation of the design principles of Vivaldi Antenna andoptimization of the key parameters for achieving the best performance for radar. Theending part of the report shows the simulations and measurement results and theircomparisons following with conclusions/discussions. The report will be supportive for the antenna designers, who work for UWB systems andparticularly for Vivaldi antennas, as long as there are showing up detailed descriptions ofVivaldi antenna characteristics depending on its shape and substrate properties. The modelfor designing Vivaldi antennas, given in this project, can successfully be applied for almostall the cases used in practice nowadays.

The imminent inception of third-generation (3G) mobile communication networks offers an unprecedented opportunity for the development of video streaming applications through wireless Internet access. Different design challenges exist in implementing video streaming connections spanning both wired and wireless domains. A split-domain TCP-friendly streaming video transmission protocol is presented based on adaptive rate encoding in the MPEG-4 video format. Network simulations are conducted to demonstrate the benefits and viability of such a video streaming scheme over existing options. Further feature enhancements and refinements are necessary for the proposed protocol to achieve its full potential.

Next generation wireless communication systems are expected to provide a variety of services including voice, data and video. The rapidly growing demand for these services needs high data rate wireless communication systems with reliability and high user capacity. Recently, it has been shown that reliability and achievable data rate of wireless communication systems increases dramatically by employing multiple transmit and receive antennas. Transmit diversity is a powerful technique for combating multipath fading in wireless communications. However, employing multiple antennas in a mobile terminal to achieve the transmit diversity in the uplink is not feasible due to the limited size of the mobile unit. In order to overcome this problem, a new mode of transmit diversity called cooperative diversity (CD) based on user cooperation, was proposed very recently. By user cooperation, it is meant that the sender transmits to the destination and copies to other users, called partners, for relaying to the destination. The antennas of the sender and the partners together form a multiple antenna situation. CD systems are immuned not only against small scale channel fading but also against large scale channel fading. On the other hand, CD systems are more sensitive to interuser (between sender and partner) transmission errors and user mobility. In this dissertation, we propose a bandwidth and power efficient CD system which could be accommodated with minimal modifications in the currently available direct or point-to-point communication systems. The proposed CD system is based on quadrature signaling (QS). With quadrature signaling, both sender’s and partners’ information symbols are transmitted simultaneously in his/her multiple access channels. It also reduces the synchronization as well as the interference problems that occur in the schemes reported in the literature. The performance of the proposed QS-CD system is analyzed at different layers. First, we study the bit error probability (BEP) of the QS-CD system for both fixed and adaptive relaying at the partner. It is shown from the BEP performance that the QS-CD system can achieve diversity order of two. Then, a cross-layer communication system is developed by combing the proposed QS-CD system at the physical layer and the truncated stop-and- wait automatic repeat request (ARQ) at the data link layer. The performance of the cross-layer system is analyzed and compared with existing schemes in the literature for performance metrics at the data link layer and upper layers, i.e., frame error rate, packet loss rate, average packet delay, throughput, etc. In addition, the studies show that the proposed QS-CD-ARQ system outperforms existing schemes when it has a good partner. In this respect, the proposed system is fully utilizing the communication channel and less complex in terms of implementation when compared with the existing systems. Since the partner selection gives significant impact on the performance of the CD systems, partner selection algorithms (PSAs) are extensively analyzed for both static and mobile user network. In this case, each individual user would like to take advantage of cooperation by choosing a suitable partner. The objective of an individual user may conflict with the objective of the network. In this regard, we would like to introduce a PSA which tries to balance both users and network objectives by taking user mobility into consideration. The proposed PSA referred to as worst link first (WLF), to choose the best partner in cooperative communication systems. The WLF algorithm gives priority to the worst link user to choose its partner and to maximize the energy gain of the radio cell. It is easy to implement not only in centralized networks but also in distributed networks with or without the global knowledge of users in the network. The proposed WLF matching algorithm, being less complex than the optimal maximum weighted (MW) matching and the heuristic based Greedy matching algorithms, yields performance characteristics close to those of MW matching algorithm and better than the Greedy matching algorithm in both static and mobile user networks. Furthermore, the proposed matching algorithm provides around 10dB energy gain with optimal power allocation over a non-cooperative system which is equivalent to prolonging the cell phone battery recharge time by about ten times.

This thesis deals with wireless channels in uncorrelated block fading environment with Rayleigh distribution. All nodes are assumed to be oblivious to their forward channel gains; however, they have perfect information about their backward channel gains. We also assume a stringent decoding delay constraint of one fading block that makes the definition of ergodic (Shannon) capacity meaningless. In this thesis, we focus on two different systems. In each case, the throughput and expected-rate are analyzed. First, the point-to-point multiple-antenna channel is investigated in chapter 2. We prove that in multiple-input single-output (MISO) channels, the optimum transmission strategy maximizing the throughput is to use all available antennas and perform equal power allocation with uncorrelated signals. Furthermore, to increase the expected-rate, multilayer coding (the broadcast approach) is applied. Analogously, we establish that sending uncorrelated signals and performing equal power allocation across all available antennas at each layer is optimum. A closed form expression for the maximum continuous-layer expected-rate of MISO channels is also obtained. Moreover, we investigate multiple-input multiple-output (MIMO) channels, and formulate the maximum throughput in the asymptotically low and high SNR regimes and also asymptotically large number of transmit or receive antennas by obtaining the optimum transmit covariance matrix. Furthermore, a distributed antenna system, wherein two single-antenna transmitters want to transmit a common message to a single-antenna receiver, is considered. It is shown that this system has the same outage probability and hence, throughput and expected-rate, as a point-to-point 2x1 MISO channel. In chapter 3, the problem of dual-hop transmission from a single-antenna source to a single-antenna destination via two parallel full-duplex single-antenna relays under the above assumptions is investigated. The focus of this chapter is on simple, efficient, and practical relaying schemes to increase the throughput and expected-rate at the destination. For this purpose, various combinations of relaying protocols and multi-layer coding are proposed. For the decode-forward (DF) relaying, the maximum finite-layer expected-rate as well as two upper-bounds on the continuous-layer expected-rate are obtained. The main feature of the proposed DF scheme is that the layers being decoded at both relays are added coherently at the destination although each relay has no information about the number of layers being successfully decoded by the other relay. It is proved that the optimum coding scheme is transmitting uncorrelated signals via the relays. Next, the maximum expected-rate of ON/OFF based amplify-forward (AF) relaying is analytically formulated. For further performance improvement, a hybrid decode-amplify-forward (DAF) relaying strategy, adopting multi-layer coding at the source and relays, is proposed and its maximum throughput and finite-layer expected-rate are presented. Moreover, the maximum throughput and expected-rate in the compress-forward (CF) relaying adopting multi-layer coding, using optimal quantizers and Wyner-Ziv compression at the relays, are fully derived. All theoretical results are illustrated by numerical simulations. As it turns out from the results, when the ratio of the relay power to the source power is high, the CF relaying outperforms DAF (and hence outperforms both DF and AF relaying); otherwise, DAF scheme is superior.

<p>This dissertation studies a state-of-the-art bandwidth-efficient coded modulation technique, known as bit interleaved coded modulation with iterative decoding (BICM-ID), together with various diversity techniques to dramatically improve the performance of digital communication systems over wireless channels.</p> <p>For BICM-ID over a single-antenna frequency non-selective fading channel, the problem of mapping over multiple symbols, i.e., multi-dimensional (multi-D) mapping, with 8-PSK constellation is investigated. An explicit algorithm to construct a good multi-D mapping of 8-PSK to improve the asymptotic performance of BICM-ID systems is introduced. By comparing the performance of the proposed mapping with an unachievable lower bound, it is conjectured that the proposed mapping is the global optimal mapping. The superiority of the proposed mapping over the best conventional (1-dimensional complex) mapping and the multi-D mapping found previously by computer search is thoroughly demonstrated.</p> <p>In addition to the mapping issue in single-antenna BICM-ID systems, the use of signal space diversity (SSD), also known as linear constellation precoding (LCP), is considered in BICM-ID over frequency non-selective fading channels. The performance analysis of BICM-ID and complex N-dimensional signal space diversity is carried out to study its performance limitation, the choice of the rotation matrix and the design of a low-complexity receiver. Based on the design criterion obtained from a tight error bound, the optimality of the rotation matrix is established. It is shown that using the class of optimal rotation matrices, the performance of BICM-ID systems over a frequency non-selective Rayleigh fading channel approaches that of the BICM-ID systems over an additive white Gaussian noise (AWGN) channel when the dimension of the signal constellation increases. Furthermore, by exploiting the sigma mapping for any M-ary quadrature amplitude modulation (QAM) constellation, a very simple sub-optimal, yet effective iterative receiver structure suitable for signal constellations with large dimensions is proposed. Simulation results in various cases and conditions indicate that the proposed receiver can achieve the analytical performance bounds with low complexity.</p> <p>The application of BICM-ID with SSD is then extended to the case of cascaded Rayleigh fading, which is more suitable to model mobile-to-mobile communication channels. By deriving the error bound on the asymptotic performance, it is first illustrated that for a small modulation constellation, a cascaded Rayleigh fading causes a much more severe performance degradation than a conventional Rayleigh fading. However, BICM-ID employing SSD with a sufficiently large constellation can close the performance gap between the Rayleigh and cascaded Rayleigh fading channels, and their performance can closely approach that over an AWGN channel.</p> <p>In the next step, the use of SSD in BICM-ID over frequency selective Rayleigh fading channels employing a multi-carrier modulation technique known as orthogonal frequency division multiplexing (OFDM) is studied. Under the assumption of correlated fading over subcarriers, a tight bound on the asymptotic error performance for the general case of applying SSD over all N subcarriers is derived and used to establish the best achievable asymptotic performance by SSD. It is then shown that precoding over subgroups of at least L subcarriers per group, where L is the number of channel taps, is sufficient to obtain this best asymptotic error performance, while significantly reducing the receiver complexity. The optimal joint subcarrier grouping and rotation matrix design is subsequently determined by solving the Vandermonde linear system. Illustrative examples show a good agreement between various analytical and simulation results.</p> <p>Further, by combining the ideas of multi-D mapping and subcarrier grouping, a novel power and bandwidth-efficient bit-interleaved coded modulation with OFDM and iterative decoding (BI-COFDM-ID) in which multi-D mapping is performed over a group of subcarriers for broadband transmission in a frequency selective fading environment is proposed. A tight bound on the asymptotic error performance is developed, which shows that subcarrier mapping and grouping have independent impacts on the overall error performance, and hence they can be independently optimized. Specifically, it is demonstrated that the optimal subcarrier mapping is similar to the optimal multi-D mapping for BICM-ID in frequency non-selective Rayleigh fading environment, whereas the optimal subcarrier grouping is the same with that of OFDM with SSD. Furthermore, analytical and simulation results show that the proposed system with the combined optimal subcarrier mapping and grouping can achieve the full channel diversity without using SSD and provide significant coding gains as compared to the previously studied BI-COFDM-ID with the same power, bandwidth and receiver complexity.</p> <p>Finally, the investigation is extended to the application of BICM-ID over a multiple-input multiple-output (MIMO) system equipped with multiple antennas at both the transmitter and the receiver to exploit both time and spatial diversities, where neither the transmitter nor the receiver knows the channel fading coefficients. The concentration is on the class of unitary constellation, due to its advantages in terms of both information-theoretic capacity and error probability. The tight error bound with respect to the asymptotic performance is also derived for any given unitary constellation and mapping rule. Design criteria regarding the choice of unitary constellation and mapping are then established. Furthermore, by using the unitary constellation obtained from orthogonal design with quadrature phase-shift keying (QPSK or 4-PSK) and 8-PSK, two different mapping rules are proposed. The first mapping rule gives the most suitable mapping for systems that do not implement iterative processing, which is similar to a Gray mapping in coherent channels. The second mapping rule yields the best mapping for systems with iterative decoding. Analytical and simulation results show that with the proposed mappings of the unitary constellations obtained from orthogonal designs, the asymptotic error performance of the iterative systems can closely approach a lower bound which is applicable to any unitary constellation and mapping.</p>