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.

No description available.

Symbol timing recovery is an important function of any digital receiver. In the wireless mobile data field the task of establishing accurate symbol timing at the receiver is complicated by the time varying channel. This time varying channel also makes the use of coherent modulation schemes significantly more difficult. This is one of the major reasons that almost all existing mobile wireless digital standards utilise some form of differential modulation and detection. This thesis takes a primarily practical approach to the investigation of timing and phase estimation problems. The main focus of the work is on the comparison of three existing all digital timing synchronisation algorithms, two of which were originally designed for the AWGN channel, and the third was designed from ML principles for the Rayleigh fading channel. In order to test these sub-systems in the wider context of receiver performance, a pilot symbol assisted (PSAM) receiver was simulated to compare the effects of the different synchronisers on receiver steady state performance. Finally, because the real time implementation aspects of software radio are of considerable interest to the author, some attempt has been made to migrate the MATLAB synchronisation simulations to a real time DSP platform, specifically the TMS320C6701 Texas Instruments floating point device.

Demand for capacity in wireless communication systems has been rapidly growing world- wide. This has been driven by increasing data rate requirements of cellular mobile systems, and demand for wireless Internet and multimedia services. As the available radio spec- trum is limited, higher data rates can only be achieved by designing more efficient signaling techniques. In this thesis, we propose a new transmission scheme, which benefits from the advantages of conventional space-time trellis codes (CSTTCs) but does not have the disadvantages, especially for larger signal constellations. We achieve this by developing a new class of codes, called Multilevel Space-Time Trellis Codes (IMLSTTC). The new scheme provides a scalable and promising alternative to CSTTCs, by providing the system designer with the flexibility to choose any desired balance between code performance, complexity and throughput. The proposed scheme outperforms layered schemes at high SNRs, using a smaller number of antennas.

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

Techn. University, Diss., 2007--Darmstadt.

Zugl.: Dresden, Techn. University, Diss., 2006.

Zugl.: Erlangen, Nürnberg, Univ., Diss., 2008

abstract: During attempted fixation, the eyes are not still but continue to produce so called "fixational eye movements", which include microsaccades, drift, and tremor. Microsaccades are thought to help prevent and restore vision loss during fixation, and to correct fixation errors, but how they contribute to these functions remains a matter of debate. This dissertation presents the results of four experiments conducted to address current controversies concerning the role of microsaccades in visibility and oculomotor control. The first two experiments set out to correlate microsaccade production with the visibility of foveal and peripheral targets of varied spatial frequencies, during attempted fixation. The results indicate that microsaccades restore the visibility of both peripheral targets and targets presented entirely within the fovea, as a function of their spatial frequency characteristics. The last two experiments set out to determine the role of microsaccades and drifts on the correction of gaze-position errors due to blinks in human and non-human primates, and to characterize microsaccades forming square-wave jerks (SWJs) in non-human primates. The results showed that microsaccades, but not drifts, correct gaze-position errors due to blinks, and that SWJ production and dynamic properties are equivalent in human and non-human primates. These combined findings suggest that microsaccades, like saccades, serve multiple and non-exclusive functional roles in vision and oculomotor control, as opposed to having a single specialized function. / Dissertation/Thesis / Doctoral Dissertation Neuroscience 2014

Abstract Broadband single-carrier modulated signals experience severe multipath distortion when propagating through the physical medium. Correcting the distortion with channel equalization is the foremost task of the detector. Prior information about the transmitted signals in the form of channel decoder feedback can significantly enhance equalization accuracy. An algorithm that iteratively performs channel decoding and equalization with prior information is generally denoted a turbo equalizer. This thesis focuses on turbo equalization with prior information using the principle of interference cancellation followed by minimum mean squared error (MMSE) filtering. Receiver algorithms, receiver convergence, and coding and modulation in the context of MMSE turbo equalization are studied. Computationally efficient versions of the receiver algorithm through approximate time-average filtering, matched filtering, square-root time-variant filtering and frequency-domain filtering are studied. The frequency-domain turbo equalizer (FDTE) is found to exhibit both superior convergence and low computational complexity among the compared equalizer algorithms. Multi-dimensional extrinsic information transfer (EXIT) charts are introduced for the purpose of tracking the convergence of the turbo equalization of layered MIMO transmissions. Generic properties of the equalizer EXIT functions defining the equalizer convergence are analyzed. The principles for detector ordering, maximum sum-rate code design and maximum rate symmetric design are derived from the properties of the multidimensional EXIT functions. Semi-analytical EXIT charts are developed for the convergence analysis of the FDTE. The effects of channel parameters and the channel code are analyzed with semi-analytical methods. A new approach for the design of irregular low-density parity-check (LDPC) codes using a convergence outage principle is proposed. A performance gain is demonstrated in a single-input multiple output (SIMO) channel over non-optimized regular LDPC codes and irregular LDPC codes optimized for the AWGN channel. The outage convergence based design, which takes advantage of the semi-analytical convergence analysis method, is also extended to layered MIMO transmissions. Quadrature amplitude modulation using multilevel bit-interleaved coded modulation (MLBICM) is studied as an alternative to regular bit-interleaved coded modulation (BICM) for highly bandwidth-efficient transmission in MMSE turbo equalized systems. A linear bit-to-symbol mapping is introduced that enables the use of a computationally efficient MMSE turbo equalizer at the receiver. The proposed coded modulation is compared with BICM in channel measurement data based simulations and found to exhibit superior robustness against changes in spatial channel parameters. An automatic repeat request (ARQ) configuration using one ARQ controller for each equally performing group of code levels is proposed. The configuration takes advantage of the unequal error protection (UEP) property of the coded modulation. The semi-analytical convergence analysis is extended to the multilevel modulated case and applied in a channel measurement based convergence evaluation. The construction of the MLBICM is found to have an inherently better convergence behavior than BICM. Finally, the outage convergence based channel code design is extended to the layered MIMO multilevel signalling case.