학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 김성철.In this dissertation, the effects of human body on Ultra Wideband (UWB) channel in indoor environments are represented. Unlike previous communication system, UWB system has a large bandwidth. This leads to interference to the other communication systems in the same frequency bands. This feature makes UWB system deployable in line-of-sight (LOS) and slightly cluttered non-line-of-sight (NLOS) environment in which the signal undergoes less attenuation. In these environments, the UWB channel largely depends on surroundings of a transmitter (Tx) and receiver (Rx) antennas. In indoor environments, a human body is a major factor that changes channel characteristics. This dissertation dealt with the effect of human body on the UWB channel in indoor environments.
First, this dissertation addresses UWB channel variation depending on the number of people in indoor LOS environments. To assess variation of UWB channels, four environments which have different room sizes and wall structures are considered. During measurements, people did not move around, but were just sitting on their chair with small motion if necessary. Because the UWB system operates in a wide bandwidth compared to previous communication systems, it is necessary to understand the frequency correlation characteristics of UWB channels. We found the correlation coefficients between two frequency tones with an interval of 10MHz are smaller than about 0.5. In the dissertation, we deal with a distance-dependent path-loss model, a frequency-dependent path-loss model, and time dispersion parameters. To provide a general channel model, we obtained the linear regression model with population density for each parameter.
Next, the dissertation considered a situation where either LOS path is not blocked or slightly blocked by human bodies as a Rx is shifted by small-scale (1λ) distance while a Tx is fixed. In this situation, we measure the small-scale amplitude statistics in the absence and presence of human bodies and propose a statistical model of the small-scale fading distribution. From the measurement data, we found the best fitted channel model among several typical theoretical distribution models such as Lognormal, Nakagami, and Weibull distributions, showing good agreement with the empirical channel data.
In the last part of dissertation, we dealt with the performance analysis of impulse radio (IR) UWB system based on the proposed small-scale fading distribution and also compare the performance with the existing channel model. Due to the fine time resolution of UWB system, the system mainly uses a rake receiver which consists of a number of correlators that are sampled at the delays related to specific number of multipath components. The dissertation considers two types of rake receiver, selective combining (SC) and partial combing (PC) rake receiver. The standard channel model, IEEE 802.15.4a, shows the best bit-error-rate (BER) performance. But this model does not include the effect of human body. When the effect of human body is included on 802.15.4a model, the BER performance is deteriorated.Chapter 1 Introduction.............................................................1
1.1 UWB system................................................................................1
1.2 UWB channel standard model.....................................................2
1.2.1 IEEE 802.15.3a……....................................................................2
1.2.2 IEEE 802.15.4a……....................................................................2
1.3 Motivation……....................................................................................3
1.4 Dissertation Outline............................................................................5
Chapter 2 Modeling of UWB channel with Population density in indoor LOS Environments................... ...............................6
2.1 Introduction..................................................................................6
2.2 Measurement Methodology ........................................................8
2.2.1 Measurement System...................................................................8
2.2.2 Measurement Scenario.................................................................9
2.3 Frequency Correlation Coefficient of the Measured Channel Gains ................................................................................................12
2.4 Path-Loss Characteristics……………………………………..15
2.4.1 Empirical distance-dependent path-loss model.........................15
2.4.2 Empirical frequency-dependent path-loss model......................18
2.5 Time-Dispersion Parameters.....................................................22
2.6 Conclusion...………..................................................................26
Chapter 3 Human body Affected Small-Scale Fading for indoor UWB channel…….....................................................27
3.1 Introduction................................................................................27
3.2 Measurement Campaign………………………………………28
3.2.1 Measurement System………………………………................28
3.2.2 Measurement Scenario…...........................................................28
3.3 Statistical Modeling of Small-Scale Fading ………….…………35
3.4 Small-Scale Fading Distribution by Body………….…………37
3.5 Conclusions................................................................................48
Chapter 4 Performance Analysis of Rake receiver in IR-UWB system………………………………………………………49
4.1 Introduction................................................................................49
4.2 UWB Rake receiver…....….......................................................51
4.2.1 UWB Rake receiver structure... ………………........................51
4.2.2 Rake Receiver Type... ………………………..........................54
4.3 Channel models…………………………….............................56
4.3.1 801.15.4a UWB channel model ……………….......................56
4.3.2 People Shadowing Effect on UWB Channels...........................58
4.4 BER performance analysis.........................................................60
4.5 Conclusion..................................................................................66
Bibliography..........................................................................67
Abstract in Korean.................................................................70Docto
