Ph.D. Dissertations
Mohammad Heidari, Dynamic Behavior and Detection of Direct Path for Indoor Geolocation, 2008
Nayef Alsindi, Indoor Cooperative Localization for Ultra Wideband Wireless Sensor Networks, 2008
Muzaffer Kanaan, Node Density and Quality of Estimation for Infrastructure-based Indoor Geolocation Using Time of Arrival, 2008
Ahmad Hatami, Application of Channel Modeling for Indoor Localization Using TOA and RSS, 2006
Bardia Alavi, Distance Measurement Error Modeling for Time-of-Arrival Based Indoor Geolocation, 2006
Mika Ylianttila, Vertical Handoff and Mobility, Vertical Handoff and Mobility - System Architecture and Transition Analysis, University of Oulu, Finland, 2005.
Xinrong Li, Super-resolution TOA estimation with diversity for indoor geolocation, 2003
Sastri Kota, Broadband Satellite Internet - Quality of Service, Technology, and Services, University of Oulu, Finland, 2003.
Licentiate Degree Theses
M.Sc. Theses
Analysis
and Modeling of the Wideband Radio Channel for Indoor Geolocation Applications
Prashant
Krishnamurthy, Ph. D, 1999
Advisor:
Prof. Kaveh Pahlavan
Indoor radio propagation
studies in recent years have been motivated by wireless telecommunications
applications such as PCS, Wireless LANs, wireless PBX, etc. and their focus
has been towards characterizing the signal coverage and RMS multipath delay
spread that influence system infrastructure and transceiver design. Emerging
position location (geolocation) applications, (civilian, such as E-911
services, and military) require a significantly different characterization
of the radio channel. The parameters of importance in this case are the
probability of detecting the direct line-of-sight path and the distribution
of range error when it is not detected.
Measurements, simulation,
analysis, and modeling of the indoor radio channel are considered with
geolocation applications in view. Qualitative and quantitative frameworks
are developed incorporating the parameters of importance for geolocation
applications. The drawbacks of existing wideband channel models (for e.g.
the JTC models for indoor PCS applications) are illustrated. New radio
channel models are proposed for geolocation applications and techniques
for a generalized model that is suitable for both telecommunications and
geolocation applications are suggested.
Site-specific statistical modeling for indoor radio channel using the results of the ray-tracing (RT) simulation is presented in this thesis. The motivation of this study are to yield (1) a more accurate statistical propagation model than the ad-hoc standard statistical models such as JTC [JTC94], (2) a less expensive statistical model than the measurement based site-specific statistical models such as those developed in [Gan91][How91], (3) a less computationally complex model than the brute force RT [Yan94]. The time domain statistics of arrival times and path amplitudes of the third floor of the Atwater Kent laboratories at WPI obtained from results of RT are compared with the statistical results obtained from empirical data. A fifth order autoregressive (AR) model is adopted to characterize the channel response in the frequency domain. The poles obtained from the RT channel response are compared to the poles obtained from measurements. A new statistical model for site-specific modeling of indoor radio propagation is proposed to replace the use of the brute forec RT method. This model relates power prediction directly to the floor plan and the material used in the construction of the building. The predictions using the new model in a typical office environment are checked against the results of RT prediction and measurements.
This dissertation provides analytical frameworks for evaluating the performance of a WLAN for different patterns of traffic. First, the performance of the WLAN with ALOHA and CSMA access methods for voice and data traffic is analyzed. In this system, TCP is used for the data packets to guarantee accuracy of information and UDP for the voice packets to handle the delay requirement. Then the capacity of a WLAN access point is related to the type of applications such as web access, email processing, Telnet, FTP, and data base access. The behavior of the two way traffic for each application is modeled with a statistical ratio of the up-link to down-link traffic. Using empirical data from HP Open View, WLRL benchmark tool, and MS Internet Explorer the statistics of the network parameters are measured. The statistical information from the empirical data is used in the analytical framework to obtain the number of users per AP for different applications. The analytical framework introduces the effects of natural hidden terminal in the overall throughput of a WLAN and also includes the effects of capture caused by the near-far problem.
This dissertation uses the results of ray tracing in a typical indoor environment to compare the performance of five radio transmission techniques that are under consideration as the air interface by standards bodies. The performance of direct sequence and frequency hopping spread spectrum are compared with the performance of multi-carrier modems, as well as modems using decision feedback equalization and sectored antenna systems. Validity of using ray tracing for performance evaluation is examined by comparing the results with the results of performance evaluation obtained from the empirical wideband measurement of the channel characteristics. Using the definition of the JTC air interface standard for indoor office environments, it is shown that the test area qualifies as a typical office environment with low to moderate delay spread. Based on the maximum achievable data rate and minimum power requirement, operation of all modems in bandlimited applications are discussed and compared.
The design and layout
of PCS or WLLANs requires accurate characterization of radio channels.
A 3D universal ray tracing model for indoor and outdoor microcellular radio
propagation is presented. The model is developed for the multipath propagation
based on ray optics and the Uniform Geometrical Theory of Diffraction (UTD).
Propagation mechanisms for specular reflection, specular transmission,
diffraction and diffuse scattering are included in the model. The accuracy
of predictions is examined with measurement results obtained in an indoor
and an urban radio environment. These results include propagation loss,
statistics of RMS delay spread, effects of antenna pattern and polarization.
The accuracy and suitability of the model allows us to use it to characterize
a typical indoor environment for performance evaluation of various high
speed wireless data systems. This thesis presents a comprehensive investigation
of various performance enhancing techniques to increase maximum data rates
of systems.
Using the ray tracing
model, the thesis first examines the outage probabilities of BPSK and BPSK/DFE
radio modems with omnidirectional and six-sector antennas. The effects
of room size, data rate, transmitted power and sector antenna patterns
on the systems are analyzed. Comparative performance evaluation of DFEs
and sector antennas provides a comprehensive understanding of the behavior
of sector antennas. The thesis also evaluates the performance of multicarrier
BPSK and QPSK radio modems with and without Reed Solomon coding schemes in the
same typical office environment. The effects of key parameters such as number of
carriers, bandwidth efficiency, roll-off factor of filters and adjacent channel
interference are analyzed.
Performance
of M-ARY CDMA Over Modelled and Measured Indoor Radio Channels
M.
Chase, Ph.D., 1993
Advisor:
Prof. Kaveh Pahlavan
Multipath propagation measurements performed in various indoor environments are analyzed to develop a time domain statistical model for the wideband characteristics of the indoor radio channel. The measurements are broadly classified as local, spatial, and partitioned. The local measurements are performed to analyze the effects of movement of personnel near the transmitting or receiving antennas and/or local movements of the terminals around a given location on the channel characteristics. The spatial measurements are analyzed to determine and compare the channel characteristics in two different environments: manufacturing floors and college office areas. Five manufacturing floor areas and three college office areas are used as measurement sites. The partitioned measurements involve dividing the cite into three partitions on the basis of building architecture and number of walls between transmitter and receiver. Channel characteristics are studied and compared for the partitions. The spatial and partitioned measuremens are used to develop a statistical model for the impulse response, suitable for computer simulation of multipath profiles in each environment. To evaluate the performance of this simulation model, the distribution of the rms delay spreads from the simulated profiles is compared with that obtained from the measured profiles.
A new statistical autoregressive model for the frequency selective behavior of the indoor radio channel is presented. The model was derived for frequency domain measurements that were performed as paret of this research. The measurements were made in the 0.9-1.1 GHz band. It is the first known use of a frequency domain system, which is relatively simpler than other measurement systems, to characterize and model the indoor radio channel. A two pole autoregressive model is shown to regenerate channel frequency responses that have the same characteristics as those observed in the actualy measurements. Compared to existing models used for computer simulation of the indoor radio channel, the model uses fewere parameters (random variables). To examine the accuracy of the model, the peroformance f a BPSK modem (with and without decision feedback equalization) is presented as derived from actual time domain measurements of the indoor radio channel, a time domain simulation of the channel, the frequency domain measurements of the channel, and the proposed frequency domain model of the channel. The closeness of the results from the frequency domain measurements and the proposed model reveals the accuracy of the model. All the results are consistent and show similar performance.
This thesis discusses channel access protocols and voice/data integration methods used for digital wireless local area networks. The network is assumed to have a star configuration witha fixed central station. The performance of demand assignment and contention based protocols are related to the propagation characteristics of the radio channel. A mathematical model for the calculation of the probability of capture in contention based access protocol for fading channels is introduced. This model relates the performance to the modulation and coding of the system, distance power relation of the indoor radio channel, length of the packets and the distribution of the terminals. The performance of slotted ALOHA and Carrier Sense Multiple Access (CSMA) protocols are analyzed using this capture model. Then, a high speed integrated voice/data system using framed polling and movable boundary scheme is proposed and analyzed. This system uses multiple antenna diversity and double rate transmission to achieve a channel througput in the order of megabits per second to comply with the current data rates used in the wired LANs.
Modeling of the indoor radio channel for the purpose of predicting data rate limitations is discussed. The channel is considered to be frequency selective and fading. The performance of equalized and conventional modems is found using continuous and discrete channel models. A channel model having a finite number of channel paths at Poisson distributed delays is found to have the same form, in the limit, as a model continuous in dleay. The importance of path population as the distinguishing feature between the models is analyzed. The sensitivity of the performance to the shape of the delay power spectrum, the shape of the envelope delay power spectrum, and the arrival rate of the paths is discussed. The probability of outage for a decision feedback equalizer is derived and evaluated. It is determined that, for both conventional and equalized modems, the shape of the delay power spectrum or delay power spectrum envelope is irrelevant in determining peformance for useful data rates. This is verified for the equalized modem by comparing performance results based on exhaustive channel simulation and results based on the probability density of the delay spread only. For continuous channel modeling, the delay spread of the delay power spectrum determines performance. For discrete channel modeling, knowledge of two parameters is required: the delay spread of the delay power spectrum envelope as well as the mean arrival rate of the paths.
Next
Generation Wireless Networks - A Case Study of Voice over IP and Vertical
Mobility
Mika
Ylianttila, University of Oulu, 2001
Advisor:
Prof. Kaveh Pahlavan
The evolutionary convergence of the wireless networks has opened the road for many new applications. There is an obvious trend towards interoperability and convergence among various wireless networks, as well as a tendency towards IP based solutions. The most challenging task for the designers of these emerging networks is to provide means to deliver time sensitive information such as voice over the heterogeneous IP-based Internet that is shifting towards a new version (IPv6). An important area for traffic optimization in these next generation wireless networks is to manage the delay and throughput in handoff process in heterogeneous networks. Geolocation information may provide new possibilities to help this process. A comparative evaluation of alternative protocols for an efficient delivery of voice over heterogeneous wireless access to Internet is discussed in this thesis.
This thesis provides a case study of wireless voice over Internet and vertical mobility in the emerging heterogeneous integrated wireless networks. The focus of the thesis is on three areas related to the analysis of the performance of these networks at architectural, protocol and algorithm levels. This thesis identifies the importance of integration between telecommunication and geolocation networks, the complexity of vertical handoff in heterogeneous networks, and impacts of IPv6 on emerging voice over IP applications as three technical issues to be studied in the rest of the thesis. First, an overview of the key concepts in the emergence of the next generation heterogeneous wireless networks is provided. Then, architectural issues related to integration of geolocation with the emerging heterogeneous telecommunication networks is addressed. Next, the efficiency of vertical handoff between 802.11 WLAN and GPRS networks is analyzed. Thesis analyzes the effects of handoff latency, user population, dwell-timer and other important parameters for vertical handoff performance. Handoff smoothing with a dwell-timer is discussed as one potential scheme for optimizing vertical handoff. Lastly, the impact of IPv6 on evolving VoIP applications has been analyzed, by comparing the performance of VoIPv6 and VoIPv4 in a wireless LAN testbed. Comparisons have been made with both varying ICMP payload and with actual VoIP application using three different codecs.
Keywords: IPv6, VoIP, Wireless LAN, GPRS, Mobility
Currently, RF Channel Characterization and System Deployment are major issues in the development of Standards for Personal Communication Systems (PCS). This thesis presents work done to develop a block-oriented software to simulate the air interface recommended by the Joint Technical Committee (JTC). The algorithm, which is based on the JTC recommendation for statistical modelling of the radio channel in the time domain, is presented and discussed. The model gives channel profiles that represent general circumstances for PCS applications. The goal of the channel modelling is to provide an accurate mathematical description of radio propagation to be used in radio link and systems simulation. The thesis also provides an alternate approach to modelling the air-link equivalent to the time-domain model. The model is a frequency auto-regressive (AR) process that requires fewer parameters and exemplifies less computational expense. The accuracy of the frequency domain model is examined by comparing the CDF of the RMS delay spread of simulations in the frequency domain with that of the time domain JTC model. Both models are simulated in Signal Processing WorkSystem (SPW) software. Several applications in the SPW system development software are given that explain the properties of the channel model and provide a visual understanding of the statistical process occurring in the radio channel.
This paper presents the results of a performance evaluation of a wireless LAN (WLLAN) in an indoor environment. The LAN operates in the ISM bands using spread spectrum technology. Hardware specific parameters such as bit error rate vs. signal to noise ratio (BER vs. SNR), maximum transmission rate, and platform software overhead are measured experimentally for a single node. This empirical data, in combination with manufacturer specifications, was then used as a basis for deriving a network simulation model. A ray trace algorithm is employed to obtain the indoor channel characteristics for point to point transmissions within a test room. The network simulation employs the measured BER vs. SNR, node and hardware specifications, and the ray trace channel characteristics to model the behavior of a multiple node network in a wireless environment. The network simulation model developed was used as a general purpose tool to predict the performance of CSMA type WLLANs in different working environments.
This thesis concerns the development of software tools for performance evaluation of wireless communication systems. Two statistical indoor radio propagation models were written in the C programming language and then incorporated into the Comdisco Signal Processing WorkSystem (SPW) software platform as custom coded blocks. Treating the statiscitcal channel model as a single object significantly simplifies communication system simulation. Linked to each block is a parameter screen that pops up when selected by the user. The parameter screen enables easy modification of model parameters. One block is a time domain model whose statistics match those of the measurements taken in office areas and manufacturing floors. The path arrival times form a modified Poisson process; the amplitudes are lognormal, Nakagami, Rayleigh, Suzuki, or Weibull. Items such as areas and pdf are selectable through the parameter screen. The other block is a frequency domain model in which the frequency response of the channel is modeled as a statistical autoregressive (AR) process. The statistics ofthe parameters used in the AR model are taken from the results of local and spatially distributed measurements in the office environment. The time response is generated by taking the invers Fourier transform of the output of the AR model.
This thesis presents a graphical user interface program that uses a two dimensional ray tracing algorithm to predict the radio propagation in the indoor radio channel from the layout of the floor plan. Modeling the indoor radio channel is extremely difficult due to the effects of multipath propagation. Current statistical models of multipath propagation in the indoor environment cannot take into account the many variations in building layout and materials and only general conclusions about the channel can be made. Another approach to this channel modeling problem is to use deterministic models (ray tracing) which take into account the details of the environment (walls, doors, etc.). The graphical interface program allows the user to interactively specify the location of the walls in the floor plan, the type of material in the construction, and the location of the radio transmitter and receiver. The ray tracing algorithm determines the magnitude, phase, time of arrival, and direction of every signal path between the specified radio transmitter and receiver when an RF pulse is transmitted. The accuracy of the model for a small shielded cage is examined by comparing the results of simulations with those obtained from empirical measurements. Comparisons are also made between the simulation and the results of measurements in a more complex laboratory environment in the Atwater Kent Laboratories at Worcester Polytechnic Institute. This area represents a typical indoor environment for using a wireless LAN since it includes both line-of-sight (LOS) and off-line-of-sight (OLOS) areas. The effects of the various parameters of the ray tracing algorithm on the received power and RMS delay spread are discussed as well.
In local area ALOHA systems, the capture effect has been found to greatly improve the system performance. This improvement is shared by all the users in the system, not just the ones with the strongest received signals. However, the retransmission problem, in these multipel access systems having the capture effect, has thus far not been fully investigated. There have been attempts to mathematically relate the retransmission probability to the capture parameter, but the analysis fails to predict accurate results even at the boundaries. This report, shows results which relate the retransmission probability and the effects of capture to the throughput and delay characteristics of a network, suited for wireless local area communications. The optimum retransmission probability for the system is found to vary with the capture parameter at the receiver. To find the performance of a system which has a capture parameter between that of perfect capture and no capture, computer simulations were done and the results are presented in this work.