Mobile communication systems

One of the biggest factors in the quest to better wireless communication is cellular
call handoff, which in tum, is a function of geographic location. In this thesis, our
fundamental goal was to demonstrate the value addition brought forth by spatial data
visualization techniques for the analysis of geo-referenced data from two different
location tracking technologies: GPS and cellular systems. Through our efforts, we
unearthed some valuable and surprising insights from the data being analyzed that led to
interesting observations about the data itself as opposed to the entity, or entities, that the
data is supposed to describe. In doing so, we underscored the value addition brought forth
by spatial data visualization techniques even in the incipient stages of analysis of georeferenced
data from cellular networks. We also demonstrated the value of visualization
techniques as a verification tool to verify the results of analysis done through other
methods, such as statistical analysis.

Channel assignment in multi-radio networks is a topic of great importance because
the use of multiple channels and multiple radios reduces interference and increases the
network throughput. The goal of our research is to design algorithms that maximize the
use of available resources while providing robustness to primary users that could reclaim
one or more channels. Our algorithms could be used in ad hoc networks, mesh networks,
and sensor networks where nodes are equipped with multiple radios. We design
algorithms for channel assignment which provide robustness to primary users without
assuming an accurate primary user behavior model. We also compute bounds for capacity
in grid networks and discuss how the capacity of a network changes when multiple
channels are available. Since preserving energy is very important in wireless networks,
we focus on algorithms that do not require powerful resources and which use a reduced
number of messages.

In current mobile system environment there is a large gap in the use of smart phones for
personal and enterprise use due to required enterprise security policies, privacy concerns
as well as freedom of use. In the current environment, data-plans on mobile systems have
become so wide spread that the rate of adaptation of data plans for every day customers
has far outpaced the ability for enterprises to keep up with existing secure enterprise
infrastructures. Most of the enterprises require/provide the access of emails and other
official information on smart platforms which presents a big challenge for the enterprise
in securing their systems. Therefore due to the security issues and policies imposed by
the enterprise in using the same device for dual purpose (personal and enterprise), the
consumers often lose their individual freedom and convenience at the cost of security.
Few solutions have been successful addressing this challenge. One effective way is to
partition the mobile device such that the enterprise system access and its information are completely separated from the personal information. Several approaches are described
and presented for mobile virtualization that creates a secure and secluded environment for
enterprise information while allowing the user to access their personal information. A
reference architecture is then presented that allows for integration with existing enterprise
mobile device management systems and at the same time providing a light weight
solution for containerizing mobile applications. This solution is then benchmarked with
several of the existing mobile virtualization solutions.

In this present computer age, cellular technology and portable computers are becoming an integral part of day to day life. Each computer user wants to access the computing resources, irrespective of the location. Because of this need the computing paradigm "Mobile Computing" has assumed a primary role in modern computer communication technology. There are different Internet protocols proposed for Mobile Computing. In the present research, we study the Internet Engineering Task Force (IETF) Mobile IPv6 (new version of current IPv4 protocol). We have developed simulation program using Scientific and Engineering Software (SES/workbench) and studied three mobility patterns namely Travelling Salesman, Pop-Up and Boring Professor for the performance study of Mobile IPv6. Performance of Mobile IPv6 is measured in terms of utilization and overhead and compared with Mobile IPv4 and Basic Triangular Routing (BTR). It has been observed that Mobile IPv6 scheme has better route optimization than the other schemes when Mobile node's movement from one network to another network is less frequent. But, when the movement of the Mobile node is more frequent then Basic Triangular Routing scheme outperformed the Mobile IPv6 scheme.

This thesis is concerned with the performance analysis of mobile cellular systems under various distributions of portable users. The performance measure used is the average outage probability. Performance analysis is performed for macrocellular as well as microcellular systems, for different distributions of mobile users such as uniform, ring, and bell distribution. The outage probability is evaluated for systems with hexagonal, triangular, and square grid layouts. The effect of macroscopic diversity on system performance is also considered. Finally, computer simulations are used to verify the evaluated results.

Indexed Resource Auction Multiple Access (I-RAMA), a new medium access protocol for wireless cellular networks based on Resource Auction Multiple Access (RAMA) is presented. I-RAMA relies in variable length resource auctions, whose length depends on the time it takes the Base Station to uniquely identify the Mobile Station. This identification is done by using dynamic Base Station information about the users present in the cell at any moment. I-RAMA effectively reduces the amount of time spent in the resource auctions without introducing contention or excessive complexity at the Base Station. The effects of introducing data users in the system are investigated using a simulation, and it is shown that I-RAMA guarantees Quality of Service for isochronous users while maintaining a bounded delay for data users at much higher loads than RAMA.

IP address autoconfiguration poses a challenge for mobile ad-hoc networks (MANETs) because it has to be done to ensure correct routing. An IP autoconfiguration protocol that is based on quorum voting is proposed. Nodes are distributed configured when a write quorum can be collected. Making the compromise between message overhead and data consistency, quorum voting enforces data consistency by ensuring fresh read on every access so that each node is configured with a unique IP address. The protocol is scalable since the configuration information is maintained locally and no central server is involved. Extensive experiments are carried out comparing the configuration latency, message overhead and address reclamation cost between our protocol and existing stateful protocols. The simulation results show that nodes are configured in lower latency and the message overhead for maintaining the network is fairly low. Moreover, the proposed protocol greatly enhances the address availability by keeping proper redundancy.

This thesis presents the simulation based performance evaluation on the transmission of multimedia services (H.264/AVC video streaming) to a mobile user over a packet-switched wireless network based on the WCDMA standard. The H.264/AVC refers to the codec, which is used as the main tool for video compression. It enables the transport of high bandwidth video data over Third Generation (3G) wireless systems by offering a high video compression rate, adaptability to the channel, and error resilience. It is transported using the RTP/UDP/IP protocol stack over the 3G wireless system. The WCDMA technology is simulated with special emphasis on the upper layers of the wireless channel. The performance of the WCDMA system is studied when transporting RTP/UDP/IP packets of H.264/AVC compressed video data under diverse configuration scenarios, namely, ARQ schemes and variable length of the transmitted frame at the link layer. These components of a packet-switched streaming service are integrated into a software simulation model, which is used to evaluate the end-to-end H.264/AVC video quality in a WCDMA wireless network.

This thesis is an effort to present the performance analysis of the RLP in cdma2000, which uses the NAK based ARQ scheme for Random Error Channels. The performance analyses is done in terms of throughput and mean extra delay, which are calculated analytically and are compared with the results generated from the simulations. As the demand for higher data rates increases over the wireless channels, this thesis studies the effect of the random errors over the different types of RLP frame formats and also the performance of the NAK based ARQ mechanism used in these conditions. The simulation provides with the overall characteristics of the throughput and the mean extra delay in terms of realistic environment parameters like Eb/No and probability of packet error (Pe), based on the channel conditions.

Location management in a mobile network provides functions to locate, identify, and validate a terminal or user. The purpose of this thesis is to describe a scheme that would be useful in a wireless network for managing the location of mobile users. This thesis presents a new, distributed location management strategy for mobile systems. Its features are fast location update and query, load balancing among location servers, and scalability. The strategy employs dynamic hashing techniques and quorums to manage location update and query operations. Location information of a mobile host is replicated at a subset of location servers.