abstract: Dynamic channel selection in cognitive radio consists of two main phases. The first phase is spectrum sensing, during which the channels that are occupied by the primary users are detected. The second phase is channel selection, during which the state of the channel to be used by the secondary user is estimated. The existing cognitive radio channel selection literature assumes perfect spectrum sensing. However, this assumption becomes problematic as the noise in the channels increases, resulting in high probability of false alarm and high probability of missed detection. This thesis proposes a solution to this problem by incorporating the estimated state of channel occupancy into a selection cost function. The problem of optimal single-channel selection in cognitive radio is considered. A unique approach to the channel selection problem is proposed which consists of first using a particle filter to estimate the state of channel occupancy and then using the estimated state with a cost function to select a single channel for transmission. The selection cost function provides a means of assessing the various combinations of unoccupied channels in terms of desirability. By minimizing the expected selection cost function over all possible channel occupancy combinations, the optimal hypothesis which identifies the optimal single channel is obtained. Several variations of the proposed cost-based channel selection approach are discussed and simulated in a variety of environments, ranging from low to high number of primary user channels, low to high levels of signal-to-noise ratios, and low to high levels of primary user traffic. / Dissertation/Thesis / M.S. Electrical Engineering 2014

Understanding speech in noisy environments is a challenge for normal-hearing and impaired-hearing listeners alike. However, it has been shown that speech intelligibility can be improved in these situations using a strategy called the ideal binary mask. Because this approach requires knowledge of the speech and noise signals separately though, it is ill-suited for practical applications. To address this, many algorithms are being designed to approximate the ideal binary mask strategy. Inevitably though, these algorithms make errors, and the implications of these errors are not well-understood. The main contributions of this thesis are to introduce a new framework for investigating binary masking algorithms and to present listener studies that use this framework to illustrate how certain types of algorithm errors can affect speech recognition outcomes with both normal-hearing listeners and cochlear implant recipients.

The IEEE 802.11/802.16 standards conformant wireless communication stations have multi-homing transmission capability. To achieve greater communication efficiency, multi-homing capable stations use handover mechanism to select appropriate transmission channel according to variations in the channel quality. This thesis presents three internal-linked handover schemes, (1) Interface Selection Protocol (ISP), belonging to Wireless Local Area Network (WLAN)- Worldwide Interoperability for Microwave Access (WiMAX) environment (2) Fast Channel Scanning (FCS) and (3) Traffic Manager (TM), (2) and (3) belonging to WiMAX Environment. The proposed schemes in this thesis use a novel mechanism of providing a reliable communication route. This solution is based on a cross-layer communication framework, where the interface selection module uses various network related parameters from Medium Access Control (MAC) sub-layer/Physical Layer (PHY) across the protocol suite for decision making at the Network layer. The proposed solutions are highly responsive when compared with existing multi-homed schemes; responsiveness is one of the key factors in the design of such protocols. Selected route under these schemes is based on the most up to date link-layer information. Therefore, such a route is not only reliable in terms of route optimization but it also fulfils the application demands in terms of throughput and delay. Design of ISP protocol use probing frames during the route discovery process. The 802.11 mandates the use of different rates for data transmission frames. The ISP-metric can be incorporated into various routing aspects and its applicability is determined by the possibility of provision of MAC dependent parameters that are used to determine the best path metric values. In many cases, higher device density, interference and mobility cause variable medium access delays. It causes creation of ‘unreachable zones’, where destination is marked as unreachable. However, by use of the best path metric, the destination has been made reachable, anytime and anywhere, because of the intelligent use of the probing frames and interface selection algorithm implemented. The IEEE 802.16e introduces several MAC level queues for different access categories, maintaining service requirement within these queues; which imply that frames from a higher priority queue, i.e. video frames, are serviced more frequently than those belonging to lower priority queues. Such an enhancement at the MAC sub-layer introduces uneven queuing delays. Conventional routing protocols are unaware of such MAC specific constraints and as a result, these factors are not considered which result in channel performance degradation. To meet such challenges, the thesis presents FCS and TM schemes for WiMAX. For FCS, Its solution is to improve the mobile WiMAX handover and address the scanning latency. Since minimum scanning time is the most important issue in the handover process. This handover scheme aims to utilize the channel efficiently and apply such a procedure to reduce the time it takes to scan the neighboring access stations. TM uses MAC and physical layer (PHY) specific information in the interface metric and maintains a separate path to destination by applying an alternative interface operation. Simulation tests and comparisons with existing multi-homed protocols and handover schemes demonstrate the effectiveness of incorporating the medium dependent parameters. Moreover, show that suggested schemes, have shown better performance in terms of end-to-end delay and throughput, with efficiency up to 40% in specific test scenarios.

In this thesis, we propose a low voltage low power wide-tuning 4th-order butterworth low-pass OTA-C channel selection filter. It is implemented by using TSMC 0.35£gm 2P4M CMOS technology. The drain voltage of triode-biased input transistors of the OTA is regulated through an active-cascode loop for low power and wide-tuning range. The Gm-C channel selection filter can be programmed from 0.5 to 12MHz. The OTA also employs a circuit to reduce the OTA output current in a high transconductance mode and the total power consumption of filter is suppressed below 3mW.

The P300 Speller brain-computer interface (BCI) allows a user to communicate without muscle activity by reading electrical signals on the scalp via electroencephalogram. Modern BCI systems use multiple electrodes ("channels") to collect data, which has been shown to improve speller accuracy; however, system cost and setup time can increase substantially with the number of channels in use, so it is in the user's interest to use a channel set of modest size. This constraint increases the importance of using an effective channel set, but current systems typically utilize the same channel montage for each user. We examine the effect of active channel selection for individuals on speller performance, using generalized standard feature-selection methods, and present a new channel selection method, termed jumpwise regression, that extends the Stepwise Linear Discriminant Analysis classifier. Simulating the selections of each method on real P300 Speller data, we obtain results demonstrating that active channel selection can improve speller accuracy for most users relative to a standard channel set, with particular benefit for users who experience low performance using the standard set. Of the methods tested, jumpwise regression offers accuracy gains similar to the best-performing feature-selection methods, and is robust enough for online use.

No description available.

In this thesis, we investigate several radio resourcemanagement (RRM) techniques and concepts in an indoorenvironment with a dense infrastructure. Future wireless indoorcommunication networks will very likely be implemented atplaces where the user concentration is very high. At these hotspots, the radio resources must be used efficiently. The goalis to identify efficient RRM techniques and concepts that aresuitable for implementation in an indoor environment. Handling the high level of co-channel interference is shownto be of paramount importance. Several investigations in thethesis point this out to be the key problem in an indoorenvironment with a dense infrastructure. We show that a locallycentralized radio resource management concept, the bunchconcept, can give a very high performance compared to othercommonly used RRM concepts. Comparisons are made withdistributed systems and systems using channel selection schemeslike CSMA/CA. The comparisons are primarily made by capacityand throughput analysis which are made by system levelsimulations. Results show that the centralized concept can give85 percent higher capacity and 70 percent higher throughputthan any of the compared systems. We investigate several RRM techniques to deal with thechannel interference problem and show that beamforming cangreatly reduce the interference and improve the systemperformance. Beamforming, especially sector antennas, alsoreduce the transmitter powers and the necessary dynamic range.A comparison is made between the use of TD/CDMA and pure TDMAwhich clearly shows the performance benefits of usingorthogonal channels that separates the users and reduces theco-channel interference. Different channel selection strategiesare studied and evaluated along with various methods to improvethe capability of system co-existence. We also investigate several practical measures to facilitatesystem implementation. Centralized RRM is suitable forguaranteeing QoS but is often considered too complex. With thestudied centralized concept the computational complexity can bereduced by splitting the coverage area into smaller pieces andcover them with one centralized system each. This reduces thecomplexity at the prize of lost capacity due to theuncontrolled interference that the different systems produce.Our investigations show that sector antennas can be used toregain this capacity loss while maintaining high reduction incomplexity. Without capacity loss, the computational complexitycan be reduced by a factor of 40 with sectoring. Theimplementation aspects also include installation sensitivity ofthe indoor architecture and the effect of measurement errors inthe link gains. The robustness against installation errors ishigh but the bunch concept is quite sensitive to largemeasurement errors in the studied indoor environment. Thiseffect can be reduced by additional SIR-margins of the radiolinks. The studied bunch concept is shown to be promising for usein future wireless indoor communication systems. It provideshigh performance and is feasible to implement. Keywords:Radio resource management, indoorcommunication, the bunch concept, centralized RRM, dynamicchannel allocation, channel selection, co-channel interference,power control, feasibility check, capacity, throughput, qualityof service, beamforming, downtilting, sector antennas,co-existence, computational complexity, sensitivity analysis,measurement errors, infrastructure, system implementation,WLAN, HiperLAN/2, IEEE 802.11.

Recently, with advances in CMOS process, the RF receiver which is integrated into the SOC chip can effectively reduce production costs. When designing the wireless receiver, one of the most important technologies is to design channel-selection filter. Typically, the design of the channel-selection filter in multi-standard high-frequency will take up a large chip area and higher power consumption. Therefore, in order to reduce the area and power consumption, this thesis designed a low-power OTA and low-pass filter. This thesis presents a multi-mode wireless communication application in the receiver channel selection filter. This filter is designed to use the fifth-order Butterworth low pass filter, the filter range can be used in Bluetooth, cdma2000, wideband CDMA, and IEEE 802.11a/b/g/n wireless LAN. Using floating transistor architecture in the input stage of OTA can effectively increase the THD performance. Using MOS transistors operating in triode region and combined with current multiplier can achieve the voltage-to-current conversion. Using the trans-linear loop can reach a wide tunable range, and the OTA operating in weak inversion region can significantly reduce the transconductance. Implementation is to use the TSMC 0.18£gm CMOS process. Simulation results show that the successful operation of this filter can be between 650 kHz ~ 22MHz frequency range. The filter may have compatibility in different wireless communication applications. 14.5mW to 17.5mW, respectively, is the smallest to the largest power consumption. The supply voltage is 1.2 volts.

<p>In this thesis, we investigate several radio resourcemanagement (RRM) techniques and concepts in an indoorenvironment with a dense infrastructure. Future wireless indoorcommunication networks will very likely be implemented atplaces where the user concentration is very high. At these hotspots, the radio resources must be used efficiently. The goalis to identify efficient RRM techniques and concepts that aresuitable for implementation in an indoor environment.</p><p>Handling the high level of co-channel interference is shownto be of paramount importance. Several investigations in thethesis point this out to be the key problem in an indoorenvironment with a dense infrastructure. We show that a locallycentralized radio resource management concept, the bunchconcept, can give a very high performance compared to othercommonly used RRM concepts. Comparisons are made withdistributed systems and systems using channel selection schemeslike CSMA/CA. The comparisons are primarily made by capacityand throughput analysis which are made by system levelsimulations. Results show that the centralized concept can give85 percent higher capacity and 70 percent higher throughputthan any of the compared systems.</p><p>We investigate several RRM techniques to deal with thechannel interference problem and show that beamforming cangreatly reduce the interference and improve the systemperformance. Beamforming, especially sector antennas, alsoreduce the transmitter powers and the necessary dynamic range.A comparison is made between the use of TD/CDMA and pure TDMAwhich clearly shows the performance benefits of usingorthogonal channels that separates the users and reduces theco-channel interference. Different channel selection strategiesare studied and evaluated along with various methods to improvethe capability of system co-existence.</p><p>We also investigate several practical measures to facilitatesystem implementation. Centralized RRM is suitable forguaranteeing QoS but is often considered too complex. With thestudied centralized concept the computational complexity can bereduced by splitting the coverage area into smaller pieces andcover them with one centralized system each. This reduces thecomplexity at the prize of lost capacity due to theuncontrolled interference that the different systems produce.Our investigations show that sector antennas can be used toregain this capacity loss while maintaining high reduction incomplexity. Without capacity loss, the computational complexitycan be reduced by a factor of 40 with sectoring. Theimplementation aspects also include installation sensitivity ofthe indoor architecture and the effect of measurement errors inthe link gains. The robustness against installation errors ishigh but the bunch concept is quite sensitive to largemeasurement errors in the studied indoor environment. Thiseffect can be reduced by additional SIR-margins of the radiolinks.</p><p>The studied bunch concept is shown to be promising for usein future wireless indoor communication systems. It provideshigh performance and is feasible to implement.</p><p><b>Keywords:</b>Radio resource management, indoorcommunication, the bunch concept, centralized RRM, dynamicchannel allocation, channel selection, co-channel interference,power control, feasibility check, capacity, throughput, qualityof service, beamforming, downtilting, sector antennas,co-existence, computational complexity, sensitivity analysis,measurement errors, infrastructure, system implementation,WLAN, HiperLAN/2, IEEE 802.11.</p>

The Infrared Atmospheric Sounding Interferometer (IASI) provides atmospheric observations with high spectral resolution and its data have been shown to have a significant positive impact on global Numerical Weather Prediction (NWP) and trace gas retrievals. A fundamental component of the retrieval of atmospheric composition is the radiative transfer model used to simulate the observations. An accurate representation of the expected emission spectrum measured by the satellite is essential given that differences in the reproduced atmospheric spectra propagate through a retrieval procedure and produce an altered estimate of the atmospheric state. The importance of the assumptions within the forward model are discussed and it is established that in the simulation of spectra from satellite-borne instruments the choice of the model parameters can have a large impact upon the resulting output. These assumptions are explored in the context of the Reference Forward Model (RFM), which is further configured to optimise its output for simulating the IASI spectrum in the troposphere. In order to ascertain the consistency of different radiative transfer models, comparisons are carried out between the RFM and the Radiative Transfer model for TOVS (RTTOV) in order to quantify any discrepancies in the reproduction of IASI measurements. Good agreement is shown across the majority of the spectrum, with exceptions caused by CO₂ line mixing effects and the H₂O continuum. Alongside model comparisons, the RFM is validated against real IASI measurements. Being a Fourier Transform Spectrometer, there are a large number of channels available from the IASI instrument, which leads to a very large quantity of data. However, this can lead to problems within retrievals and data assimilation. Choosing an optimal subset of the channels is an established method to reduce the amount of data; maintaining the information contained within it whilst eliminating spectral regions with large uncertainties. The method currently used at the UK Met Office to select their spectral channels is re-assessed and a modified method is presented that improves upon the modelling of spectrally correlated errors.