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Mobile Users (mobile + user)

Distribution by Scientific Domains

Engineering	83%

Selected Abstracts

Simulation and analysis of Awerbuch,Peleg and GSM schemes for location tracking of mobile users

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 1 2001
Ishan P. Weerakoon
Abstract Mobile users are increasingly demanding full access to networked communications while they are on the move. Several studies have shown that the overhead incurred by the network to keep track of the current location of mobile users is considerably high. The methods currently used for location tracking incur heavy unnecessary costs by requiring that users update locations in their home networks after each move regardless of the distance at which the move occurs, and that all search attempts for a mobile user are first routed to that user's home network. The Awerbuch,Peleg scheme presents a formal model for location tracking which attempts to minimize the cost of local operations,both move and find operations,through the construction of a regional hierarchy. In this paper we present a performance evaluation of the Awerbuch,Peleg scheme. We also compare its performance to that of the GSM-based location tracking scheme. It is found that the Awerbuch,Peleg scheme in general results in higher costs than the GSM scheme. The reason for this is found to be some unexpected properties of the read and write sets which are key components of the Awerbuch,Peleg scheme. Copyright © 2001 John Wiley & Sons, Ltd. [source]

A new privacy and authentication protocol for end-to-end mobile users

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2003
Cheng-Chi Lee
Abstract In this papecr, we propose a new privacy and authentication scheme for end-to-end mobile users. There are three goals in our scheme. The first allows two end-to-end mobile users to communicate privately each other. The second allows two end-to-end mobile users to distribute a session key simply. The third allows two end-to-end mobile users to mutually authenticate. Copyright © 2003 John Wiley & Sons, Ltd. [source]

A multiple access protocol with explicit and implicit reservation

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2001
F. Davoli
Abstract A new version of a MAC-level protocol is introduced and investigated, operating in a cellular environment, where a base station co-ordinates mobile users within each cell. The channel multiplexing structure is based on time division, and the slots in each frame are dynamically assigned to the users and their service classes by the cell base station. Decisions are taken on the basis of binary channel feedback information (collision/no collision), by assuming independence in the presence of packets at the mobile stations, and aim at maximizing the one-step throughput in the current frame. The frame is divided into two periods: the first (short) one contains a number of minislots, equal to the number of ,real' slots (i.e. those capable of containing a fixed size packet) of the second part. At the beginning of the frame, the access rights are computed and broadcast to the users; the enabled stations that have a packet to transmit respond, by sending a short burst that contains their ID in a minislot. This most recent feedback is used at the base station to update the parameters of the decision algorithm, which is then re-applied to yield the final access rights for the second part of the frame. The performance of the scheme is analysed by simulation in the presence of mixed voice and data traffic, and compared with those of a reservation random access protocol using the same algorithm in a single-phase fashion (RRA-ISA) and PRMA. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Simulation and analysis of Awerbuch,Peleg and GSM schemes for location tracking of mobile users

Mobile IPv6 network: implementation and application

INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 1 2006
Jiann-Liang Chen
Recently, the world has become increasingly mobile, and people have started communicating by wireless networking. Mobile IPv6 enables mobile users to communicate with each other while moving. In this study, a mobile IPv6 network was implemented by the IEEE 802.11 specification, and its performance was analyzed using TCP and UDP applications. The experimental results indicate that throughput stabilized for UDP applications after about 6,14 seconds. However, TCP applications were found to stabilize throughput in 10,20 seconds. The evaluation results reveal that TCP applications perform less well in mobile IPv6 networking than UDP applications. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Mobility prediction and routing in ad hoc wireless networks

INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 1 2001
William Su
By exploiting non-random behaviors for the mobility patterns that mobile users exhibit, we can predict the future state of network topology and perform route reconstruction proactively in a timely manner. Moreover, by using the predicted information on the network topology, we can eliminate transmissions of control packets otherwise needed to reconstruct the route and thus reduce overhead. In this paper, we propose various schemes to improve routing protocol performances by using mobility prediction. We then evaluate the effectiveness of using mobility prediction via simulation. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Overview of DVB-RCS+M and its development

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3-4 2010
Harald Skinnemoen
Abstract The use of DVB-S and DVB-RCS for conducting two-way communications from small satellite terminals has become well established in Europe and elsewhere. During the development of DVB-RCS the possibility of limited use for satellite terminals that were moving was considered in January 2004 and incorporated into the Guideline document associated with the Standard in April 2005. It was noted, however, that this matter could be addressed further as a future development. This paper addresses the steps that have been taken since then to realize this objective. During the last few years, it has been shown that the DVB-S2/DVB-RCS specifications are good candidate baselines for the efficient implementation of broadband services to mobile users. Results of these studies were gathered in a study mission report from the TM-RCS ad hoc group. It was demonstrated that both forward and return channel waveforms are impacted by the mobile usage, and should be addressed in the scope of an update of the DVB-RCS standard. Technical analysis identified that DVB-RCS, as it had been originally designed for fixed satellite services, provided most of the features required by mobile applications above 5,GHz, and could be turned into a competitive solution with a few carefully crafted modifications. Subsequent activities within the TM-RCS Group have led to an efficient and robust standard that incorporates mobility more definitely into version 1.5.1 of the DVB-RCS specifications, along with appropriate detailed ,Guidelines' documentation giving expanded description of the standard and its use and application. Copyright © 2009 John Wiley & Sons, Ltd. [source]

A survey on mobile satellite systems

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2010
Paolo Chini
Abstract Satellite systems represent a significant solution to provide communication services to mobile users in under-populated regions, in emergency areas, on planes, trains, and ships. In all these cases, satellite systems have unique capabilities in terms of robustness, wide area coverage, and broadcast/multicast capabilities. This paper surveys current mobile satellite networks and services from different standpoints, encompassing research issues, recent standardization advances (e.g. mobile extension for DVB-S2/-RCS, DVB-SH) and some operational systems (e.g. Globalstar, Inmarsat BGAN, Iridium, and Thuraya). The last part of this paper is devoted to qualitative and quantitative comparisons of the different mobile satellite systems to understand their characteristics in terms of services, capacity, resource utilization efficiency, and user mobility degree.Copyright © 2009 John Wiley & Sons, Ltd. [source]

Fade correlation and diversity effects in satellite broadcasting to mobile users in S-band

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2008
Albert Heuberger
Abstract In this paper, we present measurement results for fade correlation in time and space of signals from two satellites in geostationary orbit with 30° separation. Fade data for urban, residential and rural environments are analyzed. In addition to fade cumulative distribution function, rice factor and coherence length of individual fade signals, also the joint probability density function and the cross-correlation for the fade from the two satellites are presented. The coherence length of single satellite fades extends to about 18,m in the urban area and is around 2,m in the rural area. The correlation coefficient of dual satellite fades is below 0.3 in the residential and rural area. In the urban area larger correlations around 0.7 occur. Based on the measured fade data the diversity gain for various network configurations are determined by simulation for a forward error correction scheme using concatenated codes in combination with random interleavers. Network configurations of interest are single-satellite space diversity, two-satellite space diversity, one-satellite time diversity and two-satellite space and time diversity. For short interleavers of 5,m the diversity gain is in the residential area of 2.3,dB for the two-satellite space diversity, 0.3,dB for one-satellite time diversity and 4.1,dB for two-satellite space and time diversity. Copyright © 2008 John Wiley & Sons, Ltd. [source]