This thesis has investigated radioclimatological study in a clear-air environment as applicable to terrestrial line of sight link design problems. Radioclimatological phenomena are adequately reviewed both for the precipitation effect and clear-air effect. The research focuses more on the clear-air effect of radioclimatological studies. Two Southern African countries chosen for case study in the report are Botswana and South Africa. To this end, radiosonde data gathered in Maun, Botswana and Durban, South Africa are used for model formulation and verification. The data used in the thesis ranges from three years to ten years in these two stations. Three to ten years of refractivity data gathered in Botswana and South Africa is used for the model formulation. On the other hand, eight months signal level measurement data recorded from the terrestrial line of sight link set up between Howard College and Westville Campuses of the University of KwaZulu-Natal, Durban South Africa is used for model verification. Though various radioclimatic parameters could affect radio signal propagation in the clear-air environment, this report focuses on two of these parameters. These two parameters are the geoclimatic factor and effective earth radius factor (k-factor). The first parameter is useful for multipath fading determination while the second parameter is very important for diffraction fading, modeling and characterization. The two countries chosen have different terrain and topographical structures; thus further underlying the choice for these two parameters. While Maun in Botswana is a gentle flat terrain, Durban in South Africa is characterized by hilly and mountainous terrain structure, which thus affects radioclimatological modeling in the two countries. Two analytical models have been proposed to solve clear-air radioclimatic problems in Southern Africa in the thesis. The first model is the fourth order polynomial analytical expression while the second model is the parabolic equation. The fourth order polynomial model was proposed after an extensive analysis of the eight month signal level measurement data gathered in Durban, South Africa. This model is able to predict the fade exceedance probabilities as a function of fade depth level. The result from the fourth order polynomial model is found to be comparable with other established multipath propagation model reviewed in the thesis. Availability of more measurement data in more location will be necessary in future to further refine this model. The second model proposed to solve clear-air propagation problem in the thesis is the modified parabolic equation. We chose this technique because of its strength and its simplistic adaptation to terrestrial line of sight link design problem. This adaptation is possible because, the parabolic equation can be modified to incorporate clear-air parameters. Hence this modification of the parabolic equation allows the possibility of a hybrid technique that incorporates both the statistical and mathematical procedures perfectly into one single process. As a result of this, most of the very important phenomena in clear-air propagation such as duct occurrence probabilities, diffraction fading and multipath fading is captured by this technique. The standard parabolic equation (SPE) is the unmodified parabolic equation which only accounts for free space propagation, while the modified parabolic equation (MPE) is the modified version of the parabolic equation. The MPE is classified into two in the thesis: the first modified parabolic equation (MPE1) and second modified parabolic equation (MPE2). The MPE1 is designed to incorporate the geoclimatic factor which is intended to study the multipath fading effect in the location of study. On the other hand, MPE2 is the modified parabolic equation designed to incorporate the effective earth radius factor (k-factor) intended to study the diffraction fading in the location of study. The results and analysis of the results after these modifications confirm our expectation. This result shows that signal loss is due primarily to diffraction fading in Durban while in Botswana, signal loss is due primarily to multipath. This confirms our expectation since a flatter terrain attracts signal loss due to multipath while hilly terrain attracts signal loss due to diffraction fading. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2010.

Providing guarantees in the Quality of Service (QoS) has become essential to the transmission of multimedia traffic over wireless links with fading channels. However this poses significant challenges due to the variable nature of such channels and the diverse QoS requirements of different applications including voice, video and data. The benefits of dynamic adaptation to system and channel conditions have been accepted, but the true potential of optimized adaptation is lost if the layers operate independently, ignoring possible interdependencies between them. Cross-layer design mechanisms exploit such interdependencies to provide QoS guarantees for the transmission of multimedia traffic over fading channels. Channel adaptive M-QAM schemes are examples of some of the earliest works in the area of cross-layer design. However, many of the original schemes use the assumption that thresholds designed for AWGN channels can be directly applied to slow-fading channels. The thresholds are calculated with a commonly used approximation bit error rate (BER) expression and the first objective of the thesis was to study the accuracy of this commonly used expression in fading channels. It is shown that that the inaccuracy of the expression makes it unsuitable for use in the calculation of the threshold points for an adaptive M-QAM system over fading channels. An alternative BER expression is then derived which is shown to be far more accurate than the previous one. The improved accuracy is verified through simulations of the system over Nakagami-m fading channels. Many of the cross-layer adaptation mechanisms that address the QoS provisioning problem only use the lower layers (physical and data link) and few explore the possibility of using higher layers. As a result, restrictions are placed on the system which introduces functional limitations such as the inability to insert more than one class of traffic in a physical layer frame. The second objective in this thesis was to design a physical and application layer cross-layer adaptation mechanism which overcomes this limitation. The performance results of the scheme in both AWGN and fading channels show that the cross-layer mechanism can be efficiently utilized for the purposes of providing error rate QoS guarantees for multimedia traffic transmissions over wireless links. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2009.

Small mobile devices which have an ability to access the world wide web (WWW) wirelessly are in demand of late. This demand is attributed to the fact that video and audio streaming are cost effectively accessible via the WWW through wireless fidelity (Wi-Fi). This high demand for cheap real-time multimedia access via Wi-Fi makes it imperative for researchers to develop a wireless local area network (WLAN) standard, such as IEEE (802.11n), that has high data throughput and/or link reliability. The current drawback with the IEEE (802.11n) standard is that it is not power efficient for battery powered small mobile devices because of the high complexity multiple-input-multiple-output (MIMO) scheme implemented within the standard. Spatial modulation (SM) is a recently proposed low complexity MIMO scheme that can achieve high data throughput with good link reliability whilst being power efficient for small mobile devices. This study is aimed at further improving data throughputs of SM and also determining the bit error rate (BER) performance of SM in a city centre environment. Conventional spatial modulation has been investigated in literature with most research efforts geared towards improving the BER performance and minimizing receiver complexity of the scheme over non-cascaded fading channels. We propose adaptive M-ary quadrature amplitude spatial modulation (A-QASM) as a scheme that will improve the average throughput in comparison to conventional spatial modulation given a target BER constraint. The analytical BER lower bound is derived for this proposed scheme and validated by the Monte Carlo simulation results. The simulation results also prove that the average throughput of the proposed scheme (A-QASM) outperforms that of conventional spatial modulation. The definition for the received SNR of the A-QASM scheme is also proposed. In research literature, conventional spatial modulation has been discussed in depth in non-cascaded wireless fading channels. The performance analysis derived in literature in non-cascaded wireless fading channels; does not apply in predicting the BER performance of a mobile device, using conventional spatial modulation, in an environment where there is signal diffraction (i.e city centre or a forest) which makes the signal susceptible to independent cascaded fading. This study contributes by developing an analytical framework for the BER lower bound of conventional spatial modulation over cascaded fading channels. Simulation results closely agree with the derived theoretical framework. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

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Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 84-89). / Also available by subscription via World Wide Web / xi, 89 leaves, bound ill. 29 cm

This work presents a study of the adaptive equalization techniques designed to improve the bit error rates of digital transmissions degraded by intersymbol interference in radio communication. This thesis considers the following structures: the linear transversal equalizer (LTE), the decision feedback equalizer (DFE), the lattice equalizer, and the maximum likelihood sequence estimation (MLSE) equalizer. Least mean square (LMS) and recursive least squares (RLS) algorithms are used as the adaptive algorithms for these equalizers. Lattice-DFE, DFE, and MLSE with an RLS algorithm are recommended to be implemented in mobile systems because of their better performances. A two-ray Rayleigh fading channel model is used to simulate the mobile channels. The results show that adaptive equalization can significantly improve the performance of mobile communications if the channel does not change too fast. The simulation shows that if the delay (T) of the second ray is too small, the adaptive equalization will degrade the BER performance, and the value of T at which the adaptive equalizer can improve the BER is determined by the speed of the mobile channel variation. Also, simulation results obtained by using SIRCIM, a real world indoor channel simulator, shows that adaptive equalization has good performance in slowly varying channels. An equalizer working in indoor high data rate systems has a BER less than 10-3 at 15 dB Eb/Noâ ¢ The SMRCIM urban channel model is also developed and implemented for equalization simulation. Finally, equalization structures for differential modulation techniques are proposed. / Master of Science

by Kin Kwong Leung. / Thesis submitted in: November 1999. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 67-[70]). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Code Division Multiple Access (CDMA) --- p.1 / Chapter 1.1.1 --- The Cellular Concept --- p.2 / Chapter 1.2 --- Fading and Power Control --- p.3 / Chapter 1.2.1 --- Large Scale Fading --- p.3 / Chapter 1.2.2 --- Small Scale Fading --- p.4 / Chapter 1.2.3 --- Power Control --- p.5 / Chapter 1.2.4 --- Standard Interference Function --- p.5 / Chapter 1.3 --- Previous Work --- p.6 / Chapter 1.3.1 --- Power Control --- p.6 / Chapter 1.3.2 --- Convergence Analysis --- p.8 / Chapter 1.4 --- Scope of this Thesis --- p.8 / Chapter 1.5 --- Organization of the Thesis --- p.9 / Chapter 2 --- System Model --- p.10 / Chapter 2.1 --- System and Definitions --- p.10 / Chapter 2.2 --- Varying Link Gains Model --- p.11 / Chapter 2.3 --- SIR model in CDMA System --- p.13 / Chapter 2.4 --- Simulation Model --- p.14 / Chapter 3 --- Fade Margin --- p.17 / Chapter 3.1 --- Introduction --- p.17 / Chapter 3.2 --- Fixed-step Power Control Algorithm --- p.18 / Chapter 3.3 --- Definitions and Feasibility of SIR --- p.19 / Chapter 3.3.1 --- Definition --- p.19 / Chapter 3.3.2 --- Feasibility --- p.20 / Chapter 3.4 --- Performance Analysis on Fading Channel --- p.22 / Chapter 3.4.1 --- Single-User --- p.22 / Chapter 3.4.2 --- Multiple-User --- p.24 / Chapter 4 --- Generalized Step Power Control Algorithm --- p.28 / Chapter 4.1 --- Introduction --- p.28 / Chapter 4.2 --- Generalized Fixed Step Power Control Algorithm --- p.29 / Chapter 4.3 --- Existence of the Solution --- p.30 / Chapter 4.4 --- Parameter Optimization --- p.31 / Chapter 4.4.1 --- Single-User --- p.34 / Chapter 4.4.2 --- Multiple-User --- p.37 / Chapter 4.5 --- Performance Analysis --- p.41 / Chapter 4.5.1 --- Single-User --- p.41 / Chapter 4.5.2 --- Multiple-User --- p.42 / Chapter 4.6 --- Hybrid Scheme --- p.47 / Chapter 5 --- Convergence Analysis --- p.49 / Chapter 5.1 --- Introduction --- p.49 / Chapter 5.2 --- Totally Asynchronous Models --- p.50 / Chapter 5.3 --- Normalized Interference Function --- p.52 / Chapter 5.4 --- Existence of Quantized Solution --- p.53 / Chapter 5.5 --- Convergence Theorem --- p.55 / Chapter 6 --- Conclusion and Future Work --- p.64 / Chapter 6.1 --- Conclusion --- p.64 / Chapter 6.2 --- Future Works --- p.65 / Bibliography --- p.67

However, the proposed receiver and channel selection scheme still suffer from the mismatches picked up during RF-to-IF conversion. Therefore, a system called phase and amplitude mismatch cancellers is adopted to deal with the problem. Existing implementations neglected several critical behaviors of the cancellers, and provide image rejection ratios (IRR) ranging from 50dB to 65dB only. These behaviors include (i) arithmetic underflow, (ii) angular obscurity and (iii) spurious intermodulation products (IMD) produced by cancellers. We analyzed them and established several design rules, by which a far better IRR of at least 82.5dB was achieved. The system makes the proposed receiver and channel selection method feasible. / In traditional receivers involving intermediate frequency (IF), two different RF channels, Signal and Image, are converted to the same IF and overlap with each other. The Signal is always wanted with the Image eliminated, so each RF LO frequency can only select one RF channel. By digital low-IF, the IF-to-baseband conversion can be configured so that either channel can be selected, then each RF LO frequency can select two RF channels. This enhanced channel selection scheme can effectively reduce the number of LO frequency locations by half as well as the requirements of RF PLL frequency synthesizer. An existing approach makes use of configurable sampling scheme to achieve the same aim, but its use of analog sampling circuits results in phase and amplitude mismatches, from which the performance of image rejection suffers. Digital low-IF does not have this problem, since no mismatches are introduced to the signals after digitization. / The proposed digital low-IF Weaver receiver, together with the enhanced channel selection scheme and the phase and amplitude mismatch cancellers, are demonstrated to be feasible by a multi-band multi-mode receiver prototype supporting GSM900 and WCDMA. / The receiver architecture proposed in this thesis makes use of Weaver architecture with digital low-IF. Its flexibility allows for any operations to be performed on the digitized signals, as well as the enhanced channel selection scheme proposed in this thesis. / Chan Pak Kee. / "September 2007." / Adviser: Chiu Sing Choy. / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4924. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 152-162). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Kin Kwong Leung. / "August 15, 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 77-[82]). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Yau Chin Hang Herman. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 90-92). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- To A Localization --- p.10 / Chapter 2.1 --- Linear Estimator --- p.13 / Chapter 2.2 --- The Approximate Maximum Likelihood (AML) estimator --- p.14 / Chapter 2.3 --- Estimator for Linear BS --- p.18 / Chapter 3 --- TDoA Localization --- p.22 / Chapter 3.1 --- AML in TDoA localization --- p.27 / Chapter 4 --- Discussions of Application Considerations --- p.32 / Chapter 4.1 --- The Non-Line-of-Sight Problem --- p.33 / Chapter 4.2 --- Multipath Propagation --- p.34 / Chapter 4.3 --- Optimum placement of 4 sensors --- p.35 / Chapter 5 --- Simulation Studies --- p.44 / Chapter 5.1 --- Measures of Accuracy --- p.45 / Chapter 5.2 --- Simulations for non-linear array BSs --- p.47 / Chapter 5.2.1 --- Simulation 1: MS locating inside the enclosed area formed by 3BSs --- p.48 / Chapter 5.2.2 --- Simulation 2: The MS is outside the enclosed area formed by 3 BSs --- p.52 / Chapter 5.2.3 --- Simulation 3: The MS is inside the enclosed area formed by 6 BSs --- p.55 / Chapter 5.2.4 --- Simulation 4: The MS locates outside the enclosed area formed by 6 BSs --- p.58 / Chapter 5.3 --- ML estimator for linear array --- p.62 / Chapter 5.3.1 --- Simulation 5: Three BSs with equal spacing --- p.62 / Chapter 5.3.2 --- Simulation 6: Three BSs with non-equal spacing --- p.64 / Chapter 5.4 --- TDOA localization simulations --- p.66 / Chapter 5.4.1 --- Simulation 7: TDOA localization with 4 equal spacing microphones and the speaker is inside the enclosed area --- p.66 / Chapter 5.5 --- To see the performance of optimum placement --- p.69 / Chapter 5.5.1 --- Simulation 8: Optimum placement of the 4th microphone if the other three are fixed --- p.70 / Chapter 5.5.2 --- Simulation 9: Fixing 2 microphone and find the optimum placement of the other two microphones --- p.74 / Chapter 5.5.3 --- Simulation 10: The optimum placement of microphones without constraint --- p.78 / Chapter 6 --- Conclusions and Suggestions for future work --- p.81 / Chapter 6.1 --- Conclusions --- p.81 / Chapter 6.2 --- Suggestion for future work --- p.83 / Appendices --- p.85 / Chapter A --- The relationship between range variance and range difference variance --- p.85 / Chapter B --- The Cramer-Rao Lower Bound (CRLB) for TDoA and ToA cases --- p.87