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(2006)ThesisThis thesis proposes an idea to selectively detect the code bits in an iterative soft interference cancellation multiuser receiver. It is of a great interest to reduce the complexity of the multiuser detectors in order to achieve faster multiuser communication systems. Although the suboptimum detector has much less complexity than the optimum, the detections are made on each code bit of all users through-out every iteration. Selective detection greatly reduces the amount of calculation by re-detecting only the unreliably detected code bits from the second iteration. Simulation results show that the number of detections is significantly reduced, while the performance is maintained. Necessary background information to understand the working principles of the iterative soft cancellation receiver is presented as well. Selective detection may also be used in any other receiver structures with iterative procedures to provide much less complexity. Hence, it is able to handle much more complicated receiver structures, or implement the system to a mobile device where the computational ability is much less than at the base station.
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(2006)ThesisThis thesis addresses the problem of classifying an audio stream as either speech or music, an issue which is beginning to receive increasing attention due to its wide range of applications. Various techniques have been presented in last decade to discriminate between speech and music. However, their accuracy is still not sufficient since music can refer to a very broad class of signals due to the large number of musical instruments found in audio data. Performance can also be further compromised in noisy conditions, which are unavoidable in some practical situations. This thesis presents an analysis of feature extraction techniques and classifiers currently being used, followed by the proposal and evaluation of new features for improved classification. These include two novel cepstral features, delta cepstral energy and power spectrum deviation, along with amplitude and frequency modulation features. The modified group delay feature, initially proposed for speech recognition, is also investigated for speech and music discrimination. Experiments were performed using different sets of features, compared among themselves and with conventional MFCCs using error rate criteria and Detection Error Trade-off curves. It is shown that the proposed cepstral and modulation features result in an increase in the accuracy of the conventional MFCC based system. However, the modified group delay feature which has been shown to improve accuracy for speech classification problems, does not contribute much to the problem of speech and music discrimination. Among the ones presented here the optimum feature configuration, both modulation features with MFCC, resulted in overall error rate of 6.57% as compared to 7.43% for MFCC alone.
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(2006)ThesisMultiple-input multiple-output (MIMO) wireless technology is an emerging cost-effective approach to offer multiple-fold capacity improvement relative to the conventional single-antenna systems. To achieve the capacities of MIMO channels, MIMO bit-interleaved-coded-modulation (BICM) systems with iterative detection and decoding (IDD) are studied in this thesis. The research for this dissertation is conducted based on the iterative receivers with convolutional codes and turbo codes. A variety of MIMO detectors, such as a maximum a posteriori probability (MAP) detector, a list sphere detector (LSD) and a parallel interference canceller (PIC) together with a decision statistic combiner (DSC), are studied. The performance of these iterative receivers is investigated via bounding techniques or Monte-Carlos simulations. Moreover, the computational complexities of the components are quantified and compared. The convergence behaviors of the iterative receivers are analyzed via variance transfer (VTR) functions and variance exchange graphs (VEGs). The analysis of convergence behavior facilitates the finding of components with good matching. For a fast fading channel, we show that the "waterfall region" of an iterative receiver can be predicted by VEG. For a slow fading channel, it is shown that the performance of an iterative receiver is essentially limited by the early interception ratio (ECR) which is obtained via simulations. After the transfer properties of the detectors are unveiled, a detection switching (DSW) methodology is proposed and the switching criterion based on cross entropy (CE) is derived. By employing DSW, the performance of an iterative receiver with a list sphere detector (LSD) of a small list size is considerably improved. It is shown that the iterative receiver achieves a performance very close to that with a maximum a posteriori probability (MAP) detector but with a significantly reduced complexity. For an iterative receiver with more than two components, various iteration schedules are explored. The schedules are applied in an iterative receiver with PIC-DSC. It is shown that the iterative receiver with a periodic scheduling outperforms that with the conventional scheduling at the same level of complexity.
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(2006)ThesisDue to terminal mobility and change of service area, efficient IP mobility support is an important aspect in UMTS networks in order to provide mobile users negligible packet loss rate and low handover latency, and thus some level of guaranteed quality-ofservice (QoS) to support real-time applications. 3G/UMTS has been specified and implemented as an end-to-end mobile communications system. The underlying WCDMA access systems manage radio access handover (layer 1) and provide linklayer mobility (layer 2) in terms of connection setup and resource management. For the UMTS nodes to have seamless connectivity with the Internet, the UMTS core networks need to be able to support continuous and no network service session handover (layer 3 and above). A long IP handover latency results in high packet loss rate and severely degrades its end-to-end transport level performance. Network-layer handover latency has therefore been regarded as one of the fundamental limitations in IP-based UMTS networks. Therefore, it is crucial to provide efficient network-layer mobility management in UMTS/WCDMA networks for seamless end-to-end TCP connection with the global Internet. Mobility of UMTS nodes necessitates extra functionalities such as user location tracking, address registration and handover related mechanisms. The challenge to provide seamless mobility in UMTS requires localised location management and efficient IP handover management. Mobile IPv6 protocol offers a better mobility support as the extended IPv6 features with mobility mechanism are integrated to the mobile nodes. To mitigate the effect of lengthy IP handover latency, two well-known handover reducing mechanisms based on Mobile IPv6 support have been proposed in the literature. They are designed with hierarchical network management and address pre-configuration mechanism. Hierarchical management aims to reduce the network registration time, and fast-handover attempts to minimise the address resolution delay. S-MIP (Seamless Mobile IP) integrates the key benefits of the above IP mobility mechanisms coupled with local retransmission scheme to achieve packet lossless and extremely low handover latency, operating in WLAN environments. In this thesis, we explore the possible Mobile IP solutions and various IP handover optimisation schemes in IPv6 to provide seamless mobility in UMTS with the global Internet. It aims at developing an optimised handover scheme that encompasses the packet lossless and extremely low handover latency scheme in S-MIP, and applying it into the UMTS/WCDMA packet data domain. Therefore, the hybrid UMTS-SMIP architecture is able to meet the requirements of delay sensitive real-time applications requiring strict delay bound, packet lossless and low handover latency performance for end-to-end TCP connection during a UMTS IP-based handover. The overall seamless handover architecture in UMTS facilitates integrated, scalable and flexible global IP handover solution enabling new services, assuring service quality and meeting the user s expectations in future all-IP UMTS deployment. The viability of the seamless mobility scheme in UMTS is reflected through and validated in our design model, network protocol implementation, and service architecture. We illustrate the performance gained in QoS parameters, as a result of converged UMTS-SMIP framework compared to other Mobile IPv6 variants. The simulation results show such a viable and promising seamless handover scheme in UMTS on IP handover latency reduction on its end-to-end TCP connection.