Land Mobile Satellite Systems (LMSS) generally differ from other terrestrial wireless systems. The LMSS exhibit unique characteristics with regard to the physical layer, interference scenarios, channel impairements, propagation delay, link characteristics, service coverage, user and satellite mobility etc. Terrestrial wireless systems have employed the spatial diversity or MIMO (Multiple Input Multiple Output) technique in addressing the problem of providing uninterrupted service delivery to all mobile users especially in places where non-Line-of-Sight (NLoS) condition is prevalent (e.g. urban and suburban environments). For the LMSS, cooperative diversity has been proposed as a valuable alternative to the spatial diversity technique since it does not require the deployment of additional antennas in order to mitigate the fading effects. The basis of cooperative diversity is to have a group of mobile terminals sharing their antennas in order to generate a “virtual” multiple antenna, thus obtaining the same effects as the conventional MIMO system. However, the available cooperative diversity schemes as employed are based on outdated channel quality information (CQI) which is impracticable for LMSS due to its peculiar characteristics and its particularly long propagation delay. The key objective of this work is therefore to develop a cooperative diversity technology model which is most appropriate for LMSS and also adequately mitigates the outdated CQI challenge. To achieve the objective, the feasibility of cooperative diversity for LMSS was first analyzed by employing an appropriate LMSS channel model. Then, a novel Predictive Relay Selection (PRS) cooperative diversity scheme for LMSS was developed which adequately captured the LMSS architecture. The PRS cooperative scheme developed employed prediction algorithms, namely linear prediction and pattern-matching prediction algorithms in determining the future CQI of the available relay terminals before choosing the most appropriate relay for cooperation. The performance of the PRS cooperative diversity scheme in terms of average output SNR, outage probability, average channel capacity and bit error probability were simulated, then numerically analyzed. The results of the PRS cooperative diversity model for LMSS developed not only showed the gains resulting from introducing cooperative techniques in satellite communications but also showed improvement over other cooperative techniques that based their relay selection cooperation on channels with outdated quality information (CQI). Finally, a comparison between the results obtained from the various predictive models considered was carried out and the best prediction model was recommended for the PRS cooperation. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2013.

With the development of modern technology, mobile communications are changing people’s life and making their day to day life activities easier. The aim of this thesis work is to address one of the modern technology solution that simplifies and act as an HMI solution between a pump drive and a operator based on smart phones.   Xylem provides a wide range of pump control units, serving several advanced features includes condition monitoring, cleaning sequence, flow calculation, energy optimizer, sump cleaning and so on. Smart run is a pump control unit, whose parameters installed at wastewater pump stations are possible to monitor and configure physically using keypad or remotely using extension communication  gateway, which is a costly solution for installations and maintenance. So, a simple working prototype HMI solution based on smart phones is interested to see how smart phone can relay information between a pump control and an operator in the vicinity of the pump.    For this approach a thorough study has been done on different types of smart phones, their trends and different possible wireless communication solutions between  operator’s smart phone  and the pump. An interactive design process with a focus on usability and data representation  on a smart phone application was developed to support their needs and provide a cost effective solution. The result showed that this approach has many benefits includes serving as cost effective HMI solution, data monitoring, better alarm monitoring with additional information, enhanced display over Smart Run’s OLED displays, multilingual support, provides easier support services and also useful as a receiver unit for dewatering pumps hardware developed in parallel with this thesis. This thesis work is carried out in Xylem Water Solutions AB[1], Stockholm, Sweden in collaboration with Mittuniversitetet[2], Sundsvall, Department of Electronics Design.  This report can be used as groundwork for future development of smart phone applications for Xylem products [1]  http://www.xyleminc.com [2]  http://www.miun.se

This thesis focuses on one of the key development areas of Beyond IMT-2000 or Beyond 3rd Generation (B3G) systems recommended by ITU-R M.1645, that is, new radio access systems that provide significantly higher performance for different deployment scenarios which may encompass different access technologies while maintaining seamless access and mobility from the user's perspective. Our objective is to develop various Medium Access Control (MAC) solutions for this new B3G access system. We introduce a novel B3G multi-mode access system framework based on heterogeneous physical layer (PL) modes or configurations, anchored by a common layer 2 and layer 3 protocol stack. Such a system can support a wide variety of physical layer multiple access technologies to target different deployment scenarios and performance targets. The anchor or common layer 2/3 protocols enable seamless handoff and dynamic radio resource/load/spectrum management across the different PL modes to achieve optimum spectrum efficiency and Quality of Service (QoS) support. As a basic form of the proposed B3G multi-mode access system and the first evolution step from the existing 3rd Generation (3G) cellular systems, we propose the multi-carrier expansion of Direct Spread Code Division Multiple Access, i.e. MC DS-CDMA. MC DS-CDMA supports concurrent transmissions on multiple DS-CDMA carriers anchored by a common layer 2/3 protocol stack. The common layer 2/3 protocol stack supports fully asymmetrical and dynamic Forward Link (FL) and Reverse Link (RL) carrier(s) allocation based on QoS requirements and Service Level Agreement (SLA). MC DS¬CDMA also provides backward compatibility to existing single carrier DS-CDMA systems, thus allowing for overlay of legacy and new systems while the network deployment migrates towards B3G broadband support. We further investigate load balancing schemes across multiple PL modes sharing the same spectrum resource in Time Division Multiplex (TDM), Frequency Division Multiplex (FDM) or Code Division Multiplex (CDM) fashions. For TDM and FDM cases, we propose a new Integrated Load Balancing and Scheduling (ILBS) scheme that maximizes the system capacity while meeting users' QoS and SLA. For the CDM case, we propose a dynamic Walsh code and Base Station (BS) transmit power sharing scheme between power-controlled dedicated traffic channels and rate-controlled packet data channels across multiple CDMA carriers. An important aspect of MAC for wireless mobile systems is the MAC states management. We develop a universal MAC state machine concept that anchors the heterogeneous PL modes so that when a user switches from one PL mode to another, the MAC state and the associated context information of the MS can be retained. to minimize packet loss and PL mode switching/handoff latency. We further look into the decision criteria used to transition a user from one MAC state to another. It is an important part of MAC for both the existing 3G systems and the B3G systems. The decision criteria should aim to maximize system capacity while meeting users' QoS and SLA requirements, while at the same time achieving power-saving. We propose a novel priority based state transition algorithm that achieves these objectives. Overall, our research provides key solutions to the challenges of next generation wireless systems envisioned to encompass heterogeneous characteristics and performance targets.

Demand for Wireless Local Area Networking (WLAN) has grown significantly during the past several years. WLAN systems need to support varying data rate applications and consume low amount of energy. This work presents a reconfigurable WLAN transceiver architecture that has the following key features: Four-stage pipeline struc¬ture to increase throughput and reduce dynamic power consumption; Multiple adjustable clocks to avoid excessive handshaking and buffering between pipeline stages, Dynamic reconfigurability to support different modes of operation; and Low reconfiguration cost, in terms of energy consumption and delay, to allow for efficient frame-by-frame adaptation. We have chosen the IEEE 802.11a standard as the demonstration platform, how-ever our ideas are extendable to other WLAN standards that are based on similar communication principles. For example, the popular IEEE 802.11g standard uses the same Orthogonal Frequency Division Multiplexing (OFDM) scheme as 802.11a. Consequently, both standards require somewhat similar data processing; i.e., our design techniques remain applicable. Our proposed architecture is prototyped on Xilinx FPGA, and simulations show a relatively low power consumption in comparison with other 802.11a baseband processors.

Wireless systems that have traditionally been designed using a layered approach have seen a recent paradigm shift to a cross-layered approach where the interactions between two or more layers are considered explicitly in an integrated framework. This dissertation presents new methodologies that aim to improve the performance of wireless systems through consideration of cross-layer based design. The physical (PHY) and the medium access control (MAC) layers are the primary layers responsible for data transmission and user selection/control, respectively, in wireless systems. This dissertation begins with an analysis illustrating the use of multiple antennas and antenna arrays at. the PHY layer. A framework combining space-time block coding and beamforming for uplink in a wireless systems is con¬sidered for studying the trade-offs between antennas and antenna arrays at the receiver. Results indicate that in high noise environments the diversity achieved by using a large number of antennas combats bit error rate (BER) more efficiently than beamforming. On the other hand, in low noise environments beamforming plays an important role in reducing BER by minimizing the effect of interference from other co-channel users. Two approaches of cross-layer design that are currently available are the bottom-up and top-down approaches. The bottom-up approach uses the PHY laver infor¬mation at the MAC and higher layers to make decisions that affect the system performance. Following a bottom-up approach, a new scheduling algorithm is designed that uses the channel state information and direction of arrival information of mobile users to efficiently schedule users for service. Both semi-analytical (based on the probability density and cumulative distribution functions) and numerical frameworks are used to compare the performance of this algorithm with the traditional round-robin and greedy scheduling algorithms. Both the numerical and semi-analytical frameworks which are shown to be consistent with each other yield improved system capacity for the proposed algorithm compared to the traditional algorithms. This is the result of explicitly considering the angular location of mobile users around the base station that results into the reduced interference between simultaneously served users on one other. The effect of channel availability on the scheduling algorithms is also investigated within a queuing framework and the results indicated that the system performance is also dependent on channel availability and traffic conditions. A top-down approach is based on modifying the PHY layer to support the require¬ments or protocols used at the MAC layer to improve system throughput. Following a top-down approach, a new methodology is presented that reduces null depths of a given beam to address the hidden beam problem in IEEE 802.11 systems. The hidden beam problem occurs in carrier sensing multiple access (CSMA) systems when mobile users lying in deep nulls are unable to sense an ongoing downlink transmission and start transmitting data in an uplink. The modified beam with reduced null depths is compared with the original beam in terms of reducing the hidden beam problem when used in non-persistent CSMA systems. The modified beam is shown to improve the throughput of a slotted non-persistent CSMA system significantly when compared to original beam with relatively small changes to directivity and half power beamwidth. The bottom-up and top-down approaches used in this dissertation illustrate that by jointly addressing the PHY and MAC layer issues in an integrated cross-layer framework the performance of wireless systems can be significantly improved.

Ultra-wideband (UWB) wireless systems rely on signals spanning very wide bandwidths, typically several gigahertz, for information transmission. The distinguishing feature of UWB communications technology is the unrivalled data-rates it provides, with other benefits such as fade resistance and spectral reusability. These characteristics render UWB the technology of choice for a gamut of modern wireless communications applications, including multimedia transmission, personal- and body-area networks, imaging devices, and sensor networks. The use of wide bandwidth signals, however, leads to many complications that necessitate specialised design considerations. The propagation channel and system components acquire frequency-selective characteristics, and their nonlinear and dispersive nature, usually innocuous in a conventional setting, causes signal distortion and erroneous detection. This thesis analyses various aspects of the indoor channel and the distortion to a UWB signal propagating through it. The performance of transmitter and receiver sub-systems is evaluated, with an emphasis on the challenges posed by the large operating bandwidth. The significance of incorporating this knowledge into the system design process is demonstrated, and a novel framework for optimising the performance-complexity tradeoff is presented. • The following are the contributions of this thesis to the state of the art in UWB communications. • Experimental characterisation of the indoor UWB channel spanning the FCC band (3.1-10.6 GHz) • Demonstration of the variability of propagation characteristics in the spectral sub-bands • Assessment of frequency-dependent pathless and the consequent signal waveform distortion • Polarimetric analysis of the temporal, spectral and angular channel evolution • Evaluation of rake receiver performance and its dependence on various channel conditions • Investigation of the effect of antenna angular-spectral distortion on signal propagation • A technique for the normalisation of UWB link aberration due to antennas • Performance evaluation of diversity and spatial multiplexing with multiple-antenna systems • Design of gigabit wireless links for high data-rate applications or high user density scenarios • A novel holistic framework for the design of an optimal UWB communications system.

Lattice-Reduction has become a popular way of improving the performance of MIMO detectors. However, developing an efficient high-throughput VLSI implementation of LR has been a major challenge in the literature. This thesis proposes a hardware-optimized version of the popular LLL algorithm that reduces its complexity by 70% and achieves a fixed runtime while maintaining ML diversity. The proposed algorithm is implemented for 4x4 MIMO systems and uses a novel pipelined architecture that achieves a fixed low processing latency of 40 cycles, resulting in a fixed throughput that is independent of the channel correlation. The proposed LR core, fabricated in 0.13um CMOS, is the first fabricated and tested LR ASIC implementation in the literature. Test results show that the LR core achieves a maximum clock rate of 204 MHz, yielding a throughput of 510 Mbps, thus satisfying the aggressive throughput requirements of emerging 4G wireless standards, such as IEEE-802.16m and LTE-Advanced.

Lattice-Reduction has become a popular way of improving the performance of MIMO detectors. However, developing an efficient high-throughput VLSI implementation of LR has been a major challenge in the literature. This thesis proposes a hardware-optimized version of the popular LLL algorithm that reduces its complexity by 70% and achieves a fixed runtime while maintaining ML diversity. The proposed algorithm is implemented for 4x4 MIMO systems and uses a novel pipelined architecture that achieves a fixed low processing latency of 40 cycles, resulting in a fixed throughput that is independent of the channel correlation. The proposed LR core, fabricated in 0.13um CMOS, is the first fabricated and tested LR ASIC implementation in the literature. Test results show that the LR core achieves a maximum clock rate of 204 MHz, yielding a throughput of 510 Mbps, thus satisfying the aggressive throughput requirements of emerging 4G wireless standards, such as IEEE-802.16m and LTE-Advanced.

Thesis (M.S.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references. / vi, 62 leaves, bound ill. 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 94-96). / xv, 96 leaves, bound ill. 29 cm