実観測に基づく電波環境データベースを用いた空間的周波数共用に関する研究

The growth in demand for mobile communication systems has exponentially increased data traffic during the last decade. Because this exponential growth consumes finite spectrum resources, traditional spectrum utilization policies with exclusive resource allocation faces a limit. In order to develop novel spectrum resources, many researchers have shown an interest in spectrum sharing with cognitive radio (CR). This method allows secondary users (SUs) to share spectrum bands with primary users (PUs) under interference constraints for PUs. SUs are required to take into consideration the interference margin to the estimated interference temperature at PUs in order to protect communication quality of PUs. On the other hand, an excess interference margin decreases the spectrum sharing opportunity; therefore, it is important to manage the interference power properly. Spectrum estimation techniques in spectrum sharing can be categorized into two methods: spectrum sensing and spectrum database. Spectrum sensing uses the detection of PU signals to characterize radio environments. To provide good protection, signal detection must be performed under the (strict) condition that the PU signal strength be below the noise floor, even under low signal-to-noise ratios (SNRs) and fading conditions. These fluctuations make it difficult for the SUs to achieve stable detection; thus, it is very challenging to accurately estimate the actual activity of the PU. The second method is based on storing information about spectrum availabilities of each location in spectrum databases. In this method, afterSUs query the database before they utilize the spectrum, the database provides spectrum information to the SUs. Current databases usually evaluate white space (WS) based on empirical propagation models. However, it is well known that empirical propagation models cannot take into account all of the indeterminacies of radio environments, such as shadowing effects. Because SUs must not interfere toward PUs, the conventional database requires the SUs to set large margins to ensure no interference with PUs.In this dissertation, we propose and comprehensively study a measurement-based spectrum database for highly efficient spectrum management. The proposed database is a hybrid system, combining spectrum sensing and a spectrum database. The spectrum database consists of radio environment information measured by mobile terminals. After enough data are gathered, the database estimates the radio environment characteristics by statistical processing with the large datasets. Using the accurate knowledge of the received PU signal power, spectrum sharing based on PU signal quality metrics such as the signal-to-interference power ratio (SIR) can be implemented.We first introduce the proposed database architecture. After we briefly discuss a theoretical performance of the proposed database, we present experimental results for the database construction using actual TV broadcast signals. The experimental results show that the proposed database reduces the estimation error of the radio environment. Next, we propose a transmission power control method with a radio environment map (REM) for secondary networks. The REM stores the spatial distribution of the average received signal power. We can optimize the accuracy of the measurement-based REM using the Kriging interpolation. Although several researchers have maintained a continuous interest in improving the accuracy of the REM, sufficient study has not been done to actually explore the interference constraint considering the estimation error. The proposed method uses ordinary Kriging for the spectrum cartography. According to the predicted distribution of the estimation error, the allowable interference power to the PU is approximately formulated. Numerical results show that the proposed method can achieve the probabilistic interference constraint asymptotically, and an increase in the number of measurement datasets improves the spectrum sharing capability. After that, we extend the proposed database to the radio propagation estimation in distributed wireless links in order to accurately estimate interference characteristics from SUs to PUs. Although current wireless distributed networks have to rely on an empirical model to estimate the radio environment, in the spectrum sharing networks, such a path loss-based interference prediction decreases the spectrum sharing opportunity because of the requirement for the interference margin. The proposed method focuses on the spatial-correlation of radio propagation characteristics between different wireless links. Using Kriging-based shadowing estimation, the radio propagation of the wireless link that has arbitrary location relationship can be predicted. Numerical results show that the proposed method achieves higher estimation accuracy than path loss-based estimation methods. The methods discussed in this thesis can develop more spatial WSs in existing allocated bandwidth such as TVWS, and can provide these WSs to new wireless systems expected to appear in the future. Additionally, these results will contribute not only to such spectrum sharing but also to improvement of the spectrum management in existing systems. For example, in heterogeneous networks (HetNets), a suitable inter-cell interference management enables transmitters to reuse the frequency efficiently and the user equipment can select the optimum base station. We anticipate that this dissertation strongly contributes to improvingthe spectrum utilization efficiency of the whole wireless systems.電気通信大学201

The methods of using the sword of Shinkage-ryu-kenjutsu and the Contemporary Kendo: The techniques of the body for manipulating a bamboo sword

[EN] Nowadays the Japan Kendo Federation guides practitioners to develop mind and body through competing ..

In vitro 代謝試験系およびヒト肝細胞キメラマウスを用いたフェルバメートの反応性代謝物生成メカニズムの解析

広島大学(Hiroshima University)博士(医薬学)Doctor of Philosophy in Medical Biosciencedoctora

Insights into motor learning from a viewpoint of transcranial magnetic stimulation

Several protocols of non-invasive transcranial magnetic stimulation have been developed in the past decades. Single-and paired-pulse transcranial magnetic stimulation are painless, and noninvasive tools to evaluate cortical and corticospinal excitability in cerebral cortex compared with transcranial electric stimulation. Motor evoked potential induced by paired-pulse transcranial magnetic stimulation can particularly assess changes of the cortical excitability after motor learning, such as motor skill and motor practice in sports and functional recovery in rehabilitation. However, the effect of electric current in transcranial magnetic stimulation on pyramidal neuron and interneuron in gray and white matters is not actually understood well yet in the field of sports and rehabilitation sciences. Here, we show the important basic knowledge of neurophysiology and transcranial magnetic stimulation and introduce some studies of cortical plasticity and motor learning by using transcranial magnetic stimulation

Relationships of Posterior Condylar Offset Change to Condylar Length and Pre/Postoperative Range of Motion in Total Knee Arthroplasty

This study investigated the relationships of pre- to postoperative changes in posterior condylar offset（PCO）to differences in condylar length and range of motion in posterior stabilized（PS）-type total knee arthroplasty（TKA）. Subjects and Methods: We studied 40 knees of 40 patients（10 males and 30 females）treated by PS-type TKA. Slide calipers were used to measure condyle lengths intraoperatively and PCO was measured by standard X-ray. The patients were divided into two groups based on a pre- to postoperative change in PCO of ≥ 3mm or＜3mm, with the differences in both condylar length and range of motion compared between groups. The mean differences in condyle lengths were 2.6mm（33 knees）and 4.3mm（7 knees）in cases with PCO changes of＜3mm and ≥ 3mm, respectively. The means in the respective groups were −6° and −7° for preoperative extension, 116° and 118° for preoperative flexion, −3° and −4° for postoperative extension, and 131° and 129° for postoperative flexion. There was no significant difference in the range of motion between the groups. Cases with a large difference in condylar lengths were likely to have a small PCO postoperatively; however, the postoperative range of knee flexion was not significantly related to a small postoperative PCO. These findings suggested that preoperative range of knee motion, age, and type of TKA could influence both the postoperative range of motion and PCO