Background: Prenatal alcohol exposure causes behavioural, growth and central nervous system deficits in the offspring, termed Fetal Alcohol Spectrum Disorder (FASD). Our lab has previously shown that structured saccadic eye movement tasks probe executive functioning and can be used to measure cognitive dysfunction in children with an FASD, because performance of these tasks reflects the structural integrity of brain areas shown to be vulnerable to prenatal alcohol exposure. Recently developed portable electroencephalographic (EEG) devices record brain activity using a single dry-sensor electrode. Our objectives were: 1) to assess attention and working memory via a delayed memory-guided saccadic eye movement task of varying mnemonic load and 2) to explore the use of a portable single-channel EEG recording device in measuring differences in frontal lobe activity in children with FASD during the performance of this eye movement task. Methods: A total of 18 children with an FASD diagnosis and 19 typically developing control children performed a memory-guided saccadic eye movement task with one, two or three target stimuli. During the task, frontal lobe EEG was recorded using the Neurosky Mindwave Mobile® portable recording device. Results: In the delayed, memory-guided task when two or three target stimuli were required to be held in working memory, children with an FASD performed the task correctly less often than children in the control group. During task performance, children with FASD exhibited a reduction in theta frequency band power, and in alpha frequency band power only at higher mnemonic loads, suggesting that children with FASD recruited more cognitive resources to complete the task. Conclusion: The results of this study suggest that a portable EEG recording device can be used to assist in the recognition of underlying neural mechanisms of executive functioning deficits in children with FASD. Portable devices offer greater user comfort than typical EEG recording equipment as well as flexibility for use outside the laboratory. This could greatly facilitate the study of children with FASD, and other groups who may be less tolerant of typical laboratory environments. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2013-08-14 20:22:10.995

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Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier transmission scheme used in most of the existing wireless standards such as LTE, WiFi and WiMAX. The popularity of OFDM stems from the multitude of benefits it offers in terms of providing high data rate transmission, robustness against multipath fading and ease of implementation. Additionally, OFDM signals are agile in the sense that any subcarrier can be switched on or off to fit the available transmission bandwidth, which makes it well suited for systems with dynamic spectrum access such as cognitive radio systems. Nonetheless, and despite all the aforementioned advantages, OFDM signals have high spectral sidelobes outside the designated band of transmission, that can create severe interference to users in adjacent transmission bands, particularly when there is no synchronization between users. The focus of this dissertation is to propose baseband solutions at the Physical Layer (PHY) of the communications system to address the interference resulting from the high out-of-band (OOB) emissions of OFDM. In the first part of this dissertation, we propose a precoder capable of generating mask compliant OFDM signals with low OOB emissions that are always contained under a given spectrum emission mask (SEM) specified by the OFDM standard. The proposed precoder generates transmitted signals with bit error rate (BER) performance similar to that of classical OFDM and does not reduce the spectral efficiency of the system. In the second part of this dissertation, we introduce a novel and elegant approach, called suppressing alignment (SA), to jointly reduce the OOB interference and peak-to-average power ratio (PAPR) of OFDM systems. SA exploits the unavoidable redundancy provided by the CP as well as the wireless communications channel to generate an OOB/PAPR suppressing signal at the OFDM transmitter. Furthermore, after passing through the wireless channel, the suppressing signal is aligned with the CP duration at the OFDM receiver, essentially causing no interference to the data portion of the OFDM symbol. The proposed approach improves the PAPR of the transmitted OFDM signal and reduces the OOB interference by tens of decibels. Additionally, the proposed approach maintains an error performance similar to that of plain OFDM without requiring any change in the receiver structure of legacy OFDM. In order to reduce the spectral emissions of OFDM, additional blocks, such as linear precoders, are usually introduced in the transmitter leading to a transmitted signal that is drastically different than that of a classical OFDM signal. This distortion is typically quantified by the error vector magnitude (EVM), a widely used metric specified by the wireless standard and is directly related to the BER performance of the system. The receiver can usually decode the information data with acceptable error probabilities if the distortion introduced to the transmitted signal is below the EVM values specified in the OFDM standard. Linear precoders, while capable of achieving significant reduction in the OOB interference, they typically introduce large distortion to the transmitted signal. As such, the receiver needs to know the precoding done at the transmitter to be able to recover the data which usually entails sending large amount of side information that can greatly reduce the spectral efficiency of the system. In the last part of this dissertation, we target the design of precoders for the purpose reducing the OOB interference, in a transparent manner where the receiver does not need to know the changes introduced in the transmitter. We present two precoders capable of significantly reducing the OOB emissions while producing transmitted signals with EVM values below those specified by the wireless standard, thereby guaranteeing acceptable error performance.

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