Capacity improvements using adaptive nullsteering antennas in IS-95 cellular CDMA systems

In this thesis, the effect of adaptive nullsteering on the system capacity of an IS-95 system is investigated. Adaptive nullsteering is a Spatial Division Multiple Access (SDMA) technology which can be used to increase the system capacity by exploiting a new spatial dimension. By using this SDMA smart antenna with Code Division Multiple Access (CDMA), the system capacity can be increased significantly. In order to simulate and compare the performance of adaptive algorithms in the IS-95 receivers, both IS-95 uplink and downlink are simulated at chip level. Classical adaptive algorithms such as Direct Matrix Inversion (DMI), Least Mean Square (LMS) and Recursive Least Square (RLS) are modified accordingly to conform to this IS-95 receiver architecture. With this receiver structure, performances between different adaptive nullsteering algorithms and that without smart antenna are compared in terms of Signal-to- Interference Ratio (SIR) and their convergence rate to the steady-state SIR. Based on these performance results, a power method is proposed which can be used to estimate the IS-95 system capacity efficiently in a multiple-cell scenario without performing Monte-Carlo simulation. Realistic urban multipath models are used in the simulation to obtain accurate system capacity results. From these results, the advantages of adaptive nullsteering over that without smart antenna are presented. In addition, the performances of adaptive nullsteering and beamforming are also compared in terms of IS-95 system capacity. It is shown that both adaptive nullsteering and beamforming have their own advantages in different urban environments.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat

Striatal dopamine D_2/3receptors in medication-naïve schizophrenia:An [¹²³I] IBZM SPECT study

BACKGROUND: The hyper-function of the striatal dopamine system has been suggested to underlie key pathophysiological mechanisms in schizophrenia. Moreover, patients have been observed to present a significant elevation of dopamine receptor availability compared to healthy controls. Although it is difficult to measure dopamine levels directly in humans, neurochemical imaging techniques such as single-photon emission computed tomography (SPECT) provide indirect indices of in vivo dopamine synthesis and release, and putative synaptic levels. METHODS: We focused on the role of dopamine postsynaptic regulation using [(123)I] iodobenzamide (IBZM) SPECT. We compared D(2/3) receptor availability between 53 healthy controls and 21 medication-naive patients with recent-onset schizophrenia. RESULT: The mean specific striatal binding showed no significant difference between patients and controls (estimated difference = 0.001; 95% CI −0.11 to 0.11; F = 0.00, df = 1, 69; p = 0.99). There was a highly significant effect of age whereby IBZM binding declined with advancing age [estimated change per decade of age = −0.01(binding ratio); 95% CI −0.01 to −0.004; F = 11.5, df = 1, 69; p = 0.001]. No significant correlations were found between the mean specific striatal binding and psychopathological or cognitive rating scores. CONCLUSIONS: Medication-naïve patients with recent-onset schizophrenia have similar D(2/3) receptor availability to healthy controls. We suggest that, rather than focusing exclusively on postsynaptic receptors, future treatments should target the presynaptic control of dopamine synthesis and release

Intense Arm Rehabilitation Therapy Improves the Modified Rankin Scale Score: Association Between Gains in Impairment and Function

Objective To evaluate the effect of intensive rehabilitation on the modified Rankin Scale (mRS), a measure of activities limitation commonly used in acute stroke studies, and to define the specific changes in body structure/function (motor impairment) most related to mRS gains. Methods Patients were enrolled \u3e90 days poststroke. Each was evaluated before and 30 days after a 6-week course of daily rehabilitation targeting the arm. Activity gains, measured using the mRS, were examined and compared to body structure/function gains, measured using the Fugl-Meyer (FM) motor scale. Additional analyses examined whether activity gains were more strongly related to specific body structure/function gains. Results At baseline (160 ± 48 days poststroke), patients (n = 77) had median mRS score of 3 (interquartile range, 2–3), decreasing to 2 [2–3] 30 days posttherapy (p \u3c 0.0001). Similarly, the proportion of patients with mRS score ≤2 increased from 46.8% at baseline to 66.2% at 30 days posttherapy (p = 0.015). These findings were accounted for by the mRS score decreasing in 24 (31.2%) patients. Patients with a treatment-related mRS score improvement, compared to those without, had similar overall motor gains (change in total FM score, p = 0.63). In exploratory analysis, improvement in several specific motor impairments, such as finger flexion and wrist circumduction, was significantly associated with higher likelihood of mRS decrease. Conclusions Intensive arm motor therapy is associated with improved mRS in a substantial fraction (31.2%) of patients. Exploratory analysis suggests specific motor impairments that might underlie this finding and may be optimal targets for rehabilitation therapies that aim to reduce activities limitations

Efficacy of Home-Based Telerehabilitation vs In-Clinic Therapy for Adults After Stroke: A Randomized Clinical Trial.

ImportanceMany patients receive suboptimal rehabilitation therapy doses after stroke owing to limited access to therapists and difficulty with transportation, and their knowledge about stroke is often limited. Telehealth can potentially address these issues.ObjectivesTo determine whether treatment targeting arm movement delivered via a home-based telerehabilitation (TR) system has comparable efficacy with dose-matched, intensity-matched therapy delivered in a traditional in-clinic (IC) setting, and to examine whether this system has comparable efficacy for providing stroke education.Design, setting, and participantsIn this randomized, assessor-blinded, noninferiority trial across 11 US sites, 124 patients who had experienced stroke 4 to 36 weeks prior and had arm motor deficits (Fugl-Meyer [FM] score, 22-56 of 66) were enrolled between September 18, 2015, and December 28, 2017, to receive telerehabilitation therapy in the home (TR group) or therapy at an outpatient rehabilitation therapy clinic (IC group). Primary efficacy analysis used the intent-to-treat population.InterventionsParticipants received 36 sessions (70 minutes each) of arm motor therapy plus stroke education, with therapy intensity, duration, and frequency matched across groups.Main outcomes and measuresChange in FM score from baseline to 4 weeks after end of therapy and change in stroke knowledge from baseline to end of therapy.ResultsA total of 124 participants (34 women and 90 men) had a mean (SD) age of 61 (14) years, a mean (SD) baseline FM score of 43 (8) points, and were enrolled a mean (SD) of 18.7 (8.9) weeks after experiencing a stroke. Among those treated, patients in the IC group were adherent to 33.6 of the 36 therapy sessions (93.3%) and patients in the TR group were adherent to 35.4 of the 36 assigned therapy sessions (98.3%). Patients in the IC group had a mean (SD) FM score change of 8.36 (7.04) points from baseline to 30 days after therapy (P < .001), while those in the TR group had a mean (SD) change of 7.86 (6.68) points (P < .001). The covariate-adjusted mean FM score change was 0.06 (95% CI, -2.14 to 2.26) points higher in the TR group (P = .96). The noninferiority margin was 2.47 and fell outside the 95% CI, indicating that TR is not inferior to IC therapy. Motor gains remained significant when patients enrolled early (<90 days) or late (≥90 days) after stroke were examined separately.Conclusions and relevanceActivity-based training produced substantial gains in arm motor function regardless of whether it was provided via home-based telerehabilitation or traditional in-clinic rehabilitation. The findings of this study suggest that telerehabilitation has the potential to substantially increase access to rehabilitation therapy on a large scale.Trial registrationClinicalTrials.gov identifier: NCT02360488