<p>Internet has gained much popularity among the public since the mid 1990's and is now an integrated part of our society. A large range of high-speedbroadband providers and the development of new and more efficient Internet applications increase the possibilities to watch movies and live TV, use IP-telephony and share files over the Internet. Such applications demand high data transmission rates, which in turn consume network bandwidth. Since several users must share the common bandwidth capacity on the Internet, there will be locations in the network where the demand is higher than the capacity. This causes network congestion, which has negative impact on both the data transmission rate and transmission quality.</p><p>This thesis is about methods for measuring the available bandwidth of a network path between two computers. The available bandwidth can be interpreted as the maximum transfer rate possible without causing congestion. By deploying the methods studied in this thesis the available bandwidth can be measured without previous knowledge of the network topology. When an estimate of the available bandwidth is obtained, the transfer rate when sending messages between computers can be set to the measured value in order to avoid congestion.</p><p>In the thesis an active end-to-end available bandwidth measurement method called "Bandwidth Available in Real Time" (BART for short) is evaluated. BART measures the available bandwidth by injecting probe packets into the network at a given rate and then analysing how this rate has changed on the receiving side. A Kalman filter is used to update the current estimate of the available bandwidth using the new measurement sample.</p><p>The focus of the thesis is on how methods, such as BART, function in wireless 802.11 networks, which are very popular in work as well as in home environments. Wireless networks have a different construction compared to many other types of networks and this can affect the accuracy of the measurement methods discussed in this thesis. The effects must be analyzed and understood in order to obtain accurate available bandwidth estimates. Since wireless links are often parts of the network path between a sender and a receiver on the Internet, it is important to study how these links affect the estimates of the available bandwidth.</p>

<p>This is a thesis report done as part of the Master of Science in Electronics Design Engineering given at Linköping University, Campus Norrköping. The thesis work is done at Ericsson AB in the spring of 2005. The thesis describes a method of removing variations in the tuning sensitivity of voltage-controlled crystal oscillators due to different manufacturing processes. These variations results in unwanted variations in the modulation bandwidth of the phase-locked loop the oscillator is used in. Through examination of the theory of phase-locked loops it is found that the bandwidth of the loop is dependent on the tuning sensitivity of the oscillator.</p><p>A method of correcting the oscillator-sensitivity by amplifying or attenuating the control-voltage of the oscillator is developed. The size of the correction depends on the difference in oscillator-sensitivity compared to that of an ideal oscillator. This error is measured and the correct correction constant calculated.</p><p>To facilitate the measurements and correction extra circuits are developed and inserted in the loop. The circuits are both analog and digital. The analog circuits are mounted on an extra circuit board and the digital circuits are implemented in VHDL in an external FPGA.</p><p>Tests and theoretical calculations show that the method is valid and able to correct both positive and negative variations in oscillator-sensitivity of up to a factor ±2.5 times. The bandwidth of the loop can be adjusted between 2 to 15 Hz (up to ±8 dB, relative an unmodified loop).</p>

Internet has gained much popularity among the public since the mid 1990's and is now an integrated part of our society. A large range of high-speedbroadband providers and the development of new and more efficient Internet applications increase the possibilities to watch movies and live TV, use IP-telephony and share files over the Internet. Such applications demand high data transmission rates, which in turn consume network bandwidth. Since several users must share the common bandwidth capacity on the Internet, there will be locations in the network where the demand is higher than the capacity. This causes network congestion, which has negative impact on both the data transmission rate and transmission quality. This thesis is about methods for measuring the available bandwidth of a network path between two computers. The available bandwidth can be interpreted as the maximum transfer rate possible without causing congestion. By deploying the methods studied in this thesis the available bandwidth can be measured without previous knowledge of the network topology. When an estimate of the available bandwidth is obtained, the transfer rate when sending messages between computers can be set to the measured value in order to avoid congestion. In the thesis an active end-to-end available bandwidth measurement method called "Bandwidth Available in Real Time" (BART for short) is evaluated. BART measures the available bandwidth by injecting probe packets into the network at a given rate and then analysing how this rate has changed on the receiving side. A Kalman filter is used to update the current estimate of the available bandwidth using the new measurement sample. The focus of the thesis is on how methods, such as BART, function in wireless 802.11 networks, which are very popular in work as well as in home environments. Wireless networks have a different construction compared to many other types of networks and this can affect the accuracy of the measurement methods discussed in this thesis. The effects must be analyzed and understood in order to obtain accurate available bandwidth estimates. Since wireless links are often parts of the network path between a sender and a receiver on the Internet, it is important to study how these links affect the estimates of the available bandwidth.

This dissertation investigates the capacity required by an internet application in tandem with the network connection type (dial-up or broadband). An internet user’s experience in accessing various types of applications with either high bandwidth or low bandwidth is examined in a consumer choice model of broadband adoption. A consumer implicitly values the time-saving benefits derived from a higher speed internet connection used to access a particular internet application, and compares those utility benefits to the higher price of high speed connection services in making the decision to shift to broadband or remain with a dial-up connection. We find that using broadband rather than dial-up to run bandwidth intensive applications presents considerable gains in the implicit value of time saved. Assuming that internet users are rational utility maximizing agents, a logit model is used to calculate the likelihood of broadband adoption as a function primarily of the nature/type of the internet applications (“elastic or inelastic”). While the empirical results are generally consistent with our hypothesis that consumers are more likely to subscribe to broadband if they regularly run applications that are bandwidth intensive, the results vary somewhat by model specification, and are potentially sensitive to controlling for endogeneity. Correcting for endogeneity remains the major challenge in extending this research. Research Question: What is the relationship between consumer valuation of the net benefits of using bandwidth intensive applications and the adoption of broadband internet? Hypothesis: The less a consumer requires bandwidth intensive applications; the lower is the likelihood of switching from a low level bandwidth internet service like dial-up to a high level bandwidth internet type like broadband. While this relationship may appear obvious, it has not been systematically investigated or measured, nor has its importance in affecting lags in broadband adoption been adequately appreciated.

The variable gain amplifier (VGA) is utilized in various applications of remote sensing and communication equipments. Applications of the variable gain amplifier (VGA) include radar, ultrasound, wireless communication and even speech analysis. These applications use the variable gain amplifier (VGA) to enhance dynamic performance. The purpose of the thesis work is to implement a high linearity and low noise variable gain amplifier in 150 nm CMOS technology, for an analog-front-end of a transceiver. Two different amplifier architectures are designed and compared. First architecture is an amplifier with diode connected load and second architecture is a source degenerative amplifier. The performance of the amplifier with diode connected load is lower than the source degenerative amplifier in terms of gain, power, linearity, noise and bandwidth. So, the source degenerative amplifier is selected for implementation. The three stage variable gain differential amplifier is implemented with selected architecture. The implemented three stage variable gain differential amplifier have gain range of -541.5 mdB to 22.46 dB with step size of approximately 0.3 dB and total gain steps are 78. The -3 dB bandwidth achieved is 953.3 MHz. The third harmonic distortion (HD3) is -45 dBc at 250 mV and the power is 35 mW at 1.8 V supply source.

This is a thesis report done as part of the Master of Science in Electronics Design Engineering given at Linköping University, Campus Norrköping. The thesis work is done at Ericsson AB in the spring of 2005. The thesis describes a method of removing variations in the tuning sensitivity of voltage-controlled crystal oscillators due to different manufacturing processes. These variations results in unwanted variations in the modulation bandwidth of the phase-locked loop the oscillator is used in. Through examination of the theory of phase-locked loops it is found that the bandwidth of the loop is dependent on the tuning sensitivity of the oscillator. A method of correcting the oscillator-sensitivity by amplifying or attenuating the control-voltage of the oscillator is developed. The size of the correction depends on the difference in oscillator-sensitivity compared to that of an ideal oscillator. This error is measured and the correct correction constant calculated. To facilitate the measurements and correction extra circuits are developed and inserted in the loop. The circuits are both analog and digital. The analog circuits are mounted on an extra circuit board and the digital circuits are implemented in VHDL in an external FPGA. Tests and theoretical calculations show that the method is valid and able to correct both positive and negative variations in oscillator-sensitivity of up to a factor ±2.5 times. The bandwidth of the loop can be adjusted between 2 to 15 Hz (up to ±8 dB, relative an unmodified loop).

Despite the growing number of mobile devices equipped with multiple networking interfaces, they are not using multiple available networks in parallel. The simple network selection techniques only allow for single network to be used at a time and switching between different networks interrupts all existing connections. This work presents system that improves network connectivity in presence of multiple network adapters, not only through better network handovers, smarter network selection and failure detection, but also through increased bandwidth offered to the device over aggregated channels. The biggest challenge such a system has to face is the heterogeneity of networks in mobile environment. Different wireless technologies, and even different networks of the same type offer inconsistent link parameters like available bandwidth, latency or packet loss. The wireless nature of these networks also means, that most of the parameters fluctuate in unpredictable way. Given the intended practicality of designed system, all that complexity has to be hidden from both client-side applications and from the remote servers. These factors combined make the task of designing and implementing an efficient solution difficult. The system incorporates client-side software, as well as network proxy that assists in splitting data traffic, tunnelling it over a number of available network interfaces, and reassembling it on the remote side. These operations are transparent to both applications running on the client, as well as any network servers those applications communicate with. This property allows the system to meet one of the most important requirements, which is the practicality of the solution, and being able to deploy it in real life scenarios, using network protocols available today and on existing devices. This work also studies the most critical cost associated with increased data processing and parallel interface usage - the increase in energy usage, which needs to remain within reasonable values for this kind of solution being usable on mobile devices with limited battery life. The properties of designed and deployed system are evaluated using multiple experiments in different scenarios. Collected results confirm that our approach can provide applications with increased bandwidth when multiple networks are available. We also discover that even though per-second energy usage increases when multiple interfaces are used in parallel, the use of multi-interface connectivity can actually reduce the total energy cost associated with performing specific tasks - effectively saving energy.

Speech enhancement has been an active research problem for decades and continues to be an important problem. This is made even more true by the proliferation of portable devices having audio input capabilities. In the presence of noise, both the quality and intelligibility of speech signals have been significantly deteriorated. The proposed research are the frameworks for improving the quality/intelligibility of the degraded speech: 1) a single-channel noise suppression system based on perceptual speech detection 2) multi-sensor noise suppression system for acoustic harsh environments based on non-air conductive sensors 3) a speech bandwidth extension system for telephone speech Significant improvement in both speech intelligibility and quality from the proposed frameworks are indicated from extensive experiments, inlcuding MOS, DRT, speech recognition task, and log spectral distortion.

In recent years, the miniaturization of cell phones and computers has led to a requirement for antennas to be small and lightweight. Antennas, desired to operate in the WLAN frequency range, often possess physical sizes that are too large for integration with radio-frequency (RF) devices. When integrating antennas into three-dimensional (3D) system-on-package (SOP) transceivers, the maintenance of a compact size also provides isolation from other devices, hence, surface wave propagation or high dielectric constant materials such as low temperature cofired ceramics (LTCC) does not affect nearby components of the transceiver such as filters, baluns, and other embedded passives. Therefore, the application of design methods is necessary for realizing compact antennas in the wireless community that can be integrated to RF packages. Furthermore, it is essential that these compact antennas maintain acceptable performance characteristics, such as impedance bandwidth, low cross-polarization, and high efficiency. In addition, the analysis of circuit modeling techniques that could be used to obtain a better understanding of the physical phenomena of the antenna is quite necessary as modules become more and more complex. Based on these requirements, the focus of this research is to improve the design of compact antennas for wireless communications, wireless local area networks (WLAN), and millimeter-wave applications by using time-domain electromagnetic and circuit modeling techniques and optimizations. These compact antenna designs are applied to practical wireless communications systems such as global system of mobile communications (GSM), Bluetooth Industrial-Scientific-Medical (ISM) devices, IEEE802.11a WLAN, and Local Multipoint Distribution Systems (LMDS) applications. Parametric analyses are conducted to study critical parameters that may affect the antenna designs. Moreover, optimizations are performed to optimize the structures, and measured results are presented to validate design techniques.

¡@¡@In this Thesis, we proposed a new SVC Layer Scheduling Algorithm (CSDB, Chunk Scheduling with Delay-trend and Bandwidth-monitoring) in SVC-P2P Video Streaming by using RTT Probing and Bandwidth Monitoring mechanisms to measure RTT/2 and historic bandwidth between peers simultaneously. When transmission delay (TD) dominates in the end-to-end delay and when instantaneous bandwidth increases, peer will quickly increase the downloading layers of video segment (VS). On the other hand, when instantaneous bandwidth decreases, peer will decrease the number of layer chunks (LCs) not in time according to RTT/2 and historic bandwidth. When queuing delay (QD) and propagation delay (PD) dominate in the end-to-end delay, peer will assume RTT/2 is accurate because every LC is in time. In this case, peer will quickly increase the downloading layers; otherwise, peer assumes there is a big difference between RTT/2 and one-way delay (OWD) such that it will decrease the downloading layers to half. When peer cannot grab VS in time according to measured RTT/2 but every LC grabbed is in time, peer will assume there is a big difference between measured RTT/2 and OWD. In this case, peer will keep no change in downloading layers; otherwise, peer will assume measured RTT/2 is close to OWD, and it will decrease the downloading layers to half. ¡@¡@In order to demonstrate the advantages of CSDB, we designed a simulator written in C++. In the simulation, we consider two scenarios: 1) When TD dominates. 2) When QD and PD dominate. Simulation results show that peer can achieve high quality SVC video by balancing the number of received layers and the number of LCs not it time.