Multi-antenna relay beamforming is a promising candidate in the next generation wireless communication systems. The assumption of sum power constraint at the relay in previous work is often unrealistic in practice, since each antenna of the relay is limited by its own front-end power amplifier and thus has its own individual power constraint. In this thesis, given per-antenna power constraints, we obtain the semi-closed form solution for the optimal relay beamforming design in the two-hop amplify-and-forward relay beamforming and establish its duality with the point-to-point single-input multiple-output (SIMO) beamforming system. Simulation results show that the per-antenna power constraint case has much lower per-antenna peak power and much smaller variance of per-antenna power usage than the sum-power constraint case. A heuristic iterative algorithm to minimize the total power of relay network is proposed.

Multi-antenna relay beamforming is a promising candidate in the next generation wireless communication systems. The assumption of sum power constraint at the relay in previous work is often unrealistic in practice, since each antenna of the relay is limited by its own front-end power amplifier and thus has its own individual power constraint. In this thesis, given per-antenna power constraints, we obtain the semi-closed form solution for the optimal relay beamforming design in the two-hop amplify-and-forward relay beamforming and establish its duality with the point-to-point single-input multiple-output (SIMO) beamforming system. Simulation results show that the per-antenna power constraint case has much lower per-antenna peak power and much smaller variance of per-antenna power usage than the sum-power constraint case. A heuristic iterative algorithm to minimize the total power of relay network is proposed.

Employment of the multiple-antenna transmitters/receivers in communication systems is known as a promising solution to provide high-data-rate wireless links. In the multi-user environments, the problems of signaling and fairness for multi-antenna systems have emerged as challenging problems. This dissertation deals with these problems in several multi-antenna multi-user scenarios. In part one, a simple signaling method for the multi-antenna broadcast channels is proposed. This method reduces the MIMO broadcast system to a set of parallel channels. The proposed scheme has several desirable features in terms of: (i) accommodating users with different number of receive antennas, (ii) exploiting multi-user diversity, and (iii) requiring low feedback rate. The simulation results and analytical evaluations indicate that the achieved sum-rate is close to the sum-capacity of the underlying broadcast channel. In part two, for multiple-antenna systems with two transmitters and two receivers, a new non-cooperative scenario of data communication is studied in which each receiver receives data from both transmitters. For such a scenario, a signaling scheme is proposed which decomposes the system into two broadcast or two multi-access sub-channels. Using the decomposition scheme, it is shown that this signaling scenario outperforms the other known non-cooperative schemes in terms of the achievable multiplexing gain. In particular for some special cases, the achieved multiplexing gain is the same as the multiplexing gain of the system, where the full cooperation is provided between the transmitters and/or between the receivers. Part three investigates the problem of fairness for a class of systems for which a subset of the capacity region, which includes the sum-capacity facets, forms a polymatroid structure. The main purpose is to find a point on the sum-capacity facet which satisfies a notion of fairness among active users. This problem is addressed in the cases where the complexity of achieving interior points is not feasible, and where the complexity of achieving interior points is feasible. In part four, $K$-user memoryless interference channels are considered; where each receiver sequentially decodes the data of a subset of transmitters before it decodes the data of the designated transmitter. A greedy algorithm is developed to find the users which are decoded at each receiver and the corresponding decoding order such that the minimum rate of the users is maximized. It is proven that the proposed algorithm is optimal. The results of the parts three and four are presented for general channels which include the multiple-antenna systems as special cases.

The Vehicular Ad-hoc Network (VANET) has been studied in many fields since it has the ability to provide a variety of services, such as detecting oncoming collisions and providing warning signals to alert the driver. The services provided by VANET are often based on collaboration among vehicles that are equipped with relatively simple motion sensors and GPS units. Awareness of its precise location is vital to every vehicle in VANET so that it can provide accurate data to its peers. Currently, typical localization techniques integrate GPS receiver data and measurements of the vehicle’s motion. However, when the vehicle passes through an environment that creates a multipath effect, these techniques fail to produce the high localization accuracy that they attain in open environments. Unfortunately, vehicles often travel in environments that cause a multipath effect, such as areas with high buildings, trees, or tunnels. The goal of this research is to minimize the multipath effect with respect to the localization accuracy of vehicles in VANET. The proposed technique first detects whether there is a noise in the vehicle location estimate that is caused by the multipath effect using neural network technique. It next takes advantage of the communications among the VANET vehicles in order to obtain more information from the vehicle’s neighbours, such as distances from target vehicle and their location estimates. The proposed technique integrates all these pieces of information with the vehicle’s own data and applies optimization techniques in order to minimize the location estimate error. The new techniques presented in this thesis decrease the error in the location estimate by 53% in the best cases, and in the worst case produce almost the same error in the location estimate as the traditional technique. Moreover, the simulation results show that 60% of the vehicles in VANET decrease the error in their location estimates by more than 13.8%.

Employment of the multiple-antenna transmitters/receivers in communication systems is known as a promising solution to provide high-data-rate wireless links. In the multi-user environments, the problems of signaling and fairness for multi-antenna systems have emerged as challenging problems. This dissertation deals with these problems in several multi-antenna multi-user scenarios. In part one, a simple signaling method for the multi-antenna broadcast channels is proposed. This method reduces the MIMO broadcast system to a set of parallel channels. The proposed scheme has several desirable features in terms of: (i) accommodating users with different number of receive antennas, (ii) exploiting multi-user diversity, and (iii) requiring low feedback rate. The simulation results and analytical evaluations indicate that the achieved sum-rate is close to the sum-capacity of the underlying broadcast channel. In part two, for multiple-antenna systems with two transmitters and two receivers, a new non-cooperative scenario of data communication is studied in which each receiver receives data from both transmitters. For such a scenario, a signaling scheme is proposed which decomposes the system into two broadcast or two multi-access sub-channels. Using the decomposition scheme, it is shown that this signaling scenario outperforms the other known non-cooperative schemes in terms of the achievable multiplexing gain. In particular for some special cases, the achieved multiplexing gain is the same as the multiplexing gain of the system, where the full cooperation is provided between the transmitters and/or between the receivers. Part three investigates the problem of fairness for a class of systems for which a subset of the capacity region, which includes the sum-capacity facets, forms a polymatroid structure. The main purpose is to find a point on the sum-capacity facet which satisfies a notion of fairness among active users. This problem is addressed in the cases where the complexity of achieving interior points is not feasible, and where the complexity of achieving interior points is feasible. In part four, $K$-user memoryless interference channels are considered; where each receiver sequentially decodes the data of a subset of transmitters before it decodes the data of the designated transmitter. A greedy algorithm is developed to find the users which are decoded at each receiver and the corresponding decoding order such that the minimum rate of the users is maximized. It is proven that the proposed algorithm is optimal. The results of the parts three and four are presented for general channels which include the multiple-antenna systems as special cases.

The Vehicular Ad-hoc Network (VANET) has been studied in many fields since it has the ability to provide a variety of services, such as detecting oncoming collisions and providing warning signals to alert the driver. The services provided by VANET are often based on collaboration among vehicles that are equipped with relatively simple motion sensors and GPS units. Awareness of its precise location is vital to every vehicle in VANET so that it can provide accurate data to its peers. Currently, typical localization techniques integrate GPS receiver data and measurements of the vehicle’s motion. However, when the vehicle passes through an environment that creates a multipath effect, these techniques fail to produce the high localization accuracy that they attain in open environments. Unfortunately, vehicles often travel in environments that cause a multipath effect, such as areas with high buildings, trees, or tunnels. The goal of this research is to minimize the multipath effect with respect to the localization accuracy of vehicles in VANET. The proposed technique first detects whether there is a noise in the vehicle location estimate that is caused by the multipath effect using neural network technique. It next takes advantage of the communications among the VANET vehicles in order to obtain more information from the vehicle’s neighbours, such as distances from target vehicle and their location estimates. The proposed technique integrates all these pieces of information with the vehicle’s own data and applies optimization techniques in order to minimize the location estimate error. The new techniques presented in this thesis decrease the error in the location estimate by 53% in the best cases, and in the worst case produce almost the same error in the location estimate as the traditional technique. Moreover, the simulation results show that 60% of the vehicles in VANET decrease the error in their location estimates by more than 13.8%.

A fully integrated, fast-locking fractional-N frequency synthesizer is proposed and demonstrated in this work. In this design, to eliminate the need for large, inaccurate capacitors and resistors in a loop filter, an analog continuous-time loop filter whose performance is sensitive to process and temperature variations and aging has been replaced with a programmable digital Finite Impulse Response (FIR) filter. In addition, using the adaptive loop gain control proportional to the frequency difference, the frequency-locking time has been reduced. Also, the phase noise and spurs have been reduced by a Multi-stAge noise SHaping (MASH) controlled Fractional Frequency Detector (FFD) that generates a digital output corresponding directly to the frequency difference. The proposed frequency synthesizer provides many benefits in terms of high integration ability, technological robustness, fast locking time, low noise level, and multimode flexibility. To prove performance of the proposed frequency synthesizer, the frequency synthesizers analysis, design, and simulation have been carried out at both the system and the circuit levels. Then, the performance was also verified after fabrication and packaging.

In this dissertation, routing protocols, load-balancing protocols, and efficient evaluation techniques for multi-hop mobile wireless networks are explored. With the advancements made in wireless communication and computer technologies, a new type of mobile wireless network, known as a mobile ad hoc network (MANET), has drawn constant attention. In recent years, several routing protocols for MANETs have been proposed. However, there still remains the need for mechanisms for better scalability support with respect to network size, traffic volume, and mobility. To address this issue, a new method for multi-hop routing in MANETs called Dynamic NIx-Vector Routing (DNVR) is proposed. DNVR has several distinct features compared to other existing on-demand routing protocols, which lead to more stable routes and better scalability. Currently, ad hoc routing protocols lack load-balancing capabilities. Therefore they often fail to provide good service quality, especially in the presence of a large volume of network traffic since the network load concentrates on some nodes, resulting in a highly congested environment. To address this issue, a novel load-balancing technique for ad hoc on-demand routing protocols is proposed. The new method is simple but very effective in achieving load balance and congestion alleviation. In addition, it operates in a completely distributed fashion. To evaluate and verify wireless network protocols effectively, especially to test their scalability properties, scalable and efficient network simulation methods are required. Usually simulation of such large-scale wireless networks needs a long execution time and requires a large amount of computing resources such as powerful CPUs and memory. Traditionally, to cope with this problem, parallel network simulation techniques with parallel computing capabilities have been considered. This dissertation explores a different type of method, which is efficient and can be achieved with a sequential simulation, as well as a parallel and distributed technique for large-scale mobile wireless networks.

Technological progress in the field of wireless communications over the past few years has only been matched by the increasing demand for sophisticated services at lower costs. A significant breakthrough was achieved in the design of efficient wireless communication systems with the advent of the diversity concept. Spatial diversity exploits the availability of multiple spatial paths between the transmitter and receiver by placing antenna arrays at either end. In addition to improving the reliability of communication by creating redundant copies of the transmitted information at the receiver, wireless transceivers with multiple antennas exploit the spatial degrees of freedom to multiplex multiple streams of data and achieve significant gains in spectral efficiencies. In this thesis, we design spatial diversity techniques for slow-fading wireless channels. There are two parts to this thesis: In Part I we propose spatial diversity techniques for point-to-point single-user wireless systems, while in Part II we propose multiuser cooperative diversity techniques for multiuser wireless communication systems. In the first part, we propose a set of new wireless communication techniques for multiple-input, multiple-output (MIMO) channels over Rayleigh slow-fading wireless channels. We introduce MIMO transceivers that achieve high data rates and low error rates using a class of MIMO systems known as layered space-time (ST) architectures, which use low complexity, suboptimal decoders such as successive cancellation (SC) decoders. We propose a set of improved layered space-time architectures and show that it is possible to achieve near-optimal error performance over MIMO channels while requiring just SC decoding at the receiver. We show that these architectures achieve high rate and diversity gains. We also show that some of the proposed layered space-time architectures could find applications in multiple-access communications as low-complexity solutions for achieving near-optimum performance. In the second part of this thesis, we propose novel techniques for cooperative communication between terminals in multiuser wireless communication systems. Cooperative communication is a concept where neighboring terminals share their antennas and signal processing resources to create a virtual transmit array . In addition to transmitting their own information, users in a cooperative communication system listen to transmission from other users and relay this information to the destination, thus creating multiple paths between transmitter and receiver. This form of diversity, known as cooperative diversity, helps improve the overall reliability of all the users in a network. We start with a simple three node multiple-access system where two users are communicating with a common destination. We propose new high-rate cooperation strategies which achieve the full diversity gain offered by the cooperative channel for this simple system. We propose a new framework to address the tradeoff between cooperation and independent transmission over a multiple access channel and determine the conditions under which each idea is better than the other. Finally, we propose a high rate cooperation protocol which achieves the maximum diversity over a multiple access system with an arbitrary number of users and achieves high rates which scale favorably as the number of users increases.

Information exchange in wireless communication without being blocked by terrain or infrastructure is easier and simpler than that in the traditional wired communication environments. Due to the transmission type, anonymity is urgently required in wireless communications for concealing the footprint of mobile users. Additionally, the mobility of a mobile device may incur possible threats to the past encrypted transmitted data, where the past session keys for the encryptions of wireless communications may be derived by the long-term secret stored the mobile device if it is lost. In this thesis, we propose an efficient solution by using symmetry-based cryptosystems for forward secrecy and anonymity in the standards of mobile networks, such as GSM, UMTS, and LTE, without losing the compatibility. By adopting secret chain (SC) based mechanism, the generation of every session key involves a short-term secret, changed in every session, to achieve forward secrecy and anonymity. Furthermore, synchronization mechanism required for the SC-protocol is also proposed. For more advanced security requirements of truly non-repudiation and strong anonymity, which is additionally anonymous to systems, certificateless signatures and group signatures are applied in the authentication protocols for UMTS and VANETs. Certificateless signatures can eliminate the overhead of using public-key infrastructure (PKI) in wireless communications. Our work proposed a certificateless signature scheme achieving the same security level of non-repudiation as that in the PKI-based signature scheme, that most of the proposed certificateless signatures cannot fulfill. Group signatures practice the privacy of the participants of the authentication protocol by originating the group signatures belonging to their group. However, directly applying group signatures in wireless communications results in inefficiency of computation when a group has a large amount of members. Therefore, we aim at reducing the computation costs of membership revocation on the proposed group signature scheme to constant without being influenced by the amount of members and then apply the scheme to VANETs and UMTS. Eventually, all the proposed schemes in the thesis are theoretically proven secure under the standard reduction.