ARQ schemes for data transmission in mobile radio systems

An important problem in land mobile radio communications is how to provide reliable data communications to the largest number of users. To explore this problem, several existing ARQ protocols are examined which have application to the land mobile radio channel, as well as some new protocol combinations. All protocols are analyzed for several key system performance measures which are verified by experimental means for static as well as fading channels. Finally, a conclusion is reached regarding a new protocol combination which is found to offer significant advantages over all other protocols explored.     

Linear unbiased data estimation in mobile radio systems applyingCDMA

Data estimation in the uplink of a synchronous mobile radio system applying code-division multiple access (CDMA) is considered. In mobile radio systems applying CDMA, multipath propagation leads to intersymbol interference (ISI) and together with time variance, to cross interference between the signals of different users regardless of whether the user codes are chosen orthogonal or not. A linear unbiased data estimation algorithm is presented that eliminates both ISI and cross interference perfectly by jointly detecting the different user signals, leading to unbiased estimates of the transmitted data symbols. By theoretical analysis and simulation, the performance of the linear unbiased data estimation algorithm is examined under the assumption that the radio channel impulse responses are known at the receiver. The price to be paid for the interference elimination are SNR degradations, which are calculated for typical mobile radio situations in urban areas. The resulting average uncoded bit error probabilities lead to the conclusion that systems applying the linear unbiased data estimation algorithm are well suited for mobile radio applications     

The role of Internet technology in future mobile data systems

Mobile telephony and the Internet are the fastest growing businesses in the telecommunications market. This is why most operators and service providers are looking after the development of new services in both sectors, and newcomers are expected to enter the arena. The mobile operators foresee an increasing share of their revenues coming from new data services, while Internet service providers are attracted to wireless technology and mobility services both to reduce costs within the last-mile segment and to enrich their market share, providing ubiquitous access to the Internet and corporate intranets. In this scenario several wireless overlay networks will coexist, and their interworking will be a challenging objective. The employment of Internet technology, with its novel mobility and security extensions, seems to be the most attractive option for achieving that goal. In addition, the migration to a full IP network architecture, even within each specific wireless domain, will be another promising opportunity, already under consideration within several technical and standardization bodies. The envisioned role of Internet technology makes it worthwhile to undertake significant research efforts on the development of innovative IP-based mobile data systems, and opens promising opportunities for both telcos and Internet service providers.     

Ensuring strong data guarantees in highly mobile ad hoc networks via quorum systems

Ensuring the consistency and the availability of replicated data in highly mobile ad hoc networks is a challenging task because of the lack of a backbone infrastructure. Previous work provides strong data guarantees by limiting the motion and the speed of the mobile nodes during the entire system lifetime, and by relying on assumptions that are not realistic for most mobile applications. We provide a small set of mobility constraints that are sufficient to ensure strong data guarantees and that can be applied when nodes move along unknown paths and speed, and are sparsely distributed.

In the second part of the paper, we analyze the problem of conserving energy while ensuring strong data guarantees, using quorum system techniques. We devise a condition necessary for a quorum system to guarantee data consistency and data availability under our mobility model. This condition shows the unsuitability of previous quorum systems and is the basis for a novel class of quorum systems suitable for highly mobile networks, called mobile dissemination quorum (MDQ) systems. We also show a MDQ system that is provably optimal in terms of communication cost by proposing an efficient implementation of a read/write atomic shared memory.

The suitability of our mobility model and MDQ systems is validated through simulations using the random waypoint model and the restricted random waypoint on a city section. Finally, we apply our results to assist routing and coordinate the low duty cycle of mobile nodes while maintaining network connectivity.     

Performance analysis of session oriented data communications for mobile computing in cellular systems

Future cellular communication systems must seamlessly support services for a wide range of user needs, including voice, data, video and multi‐media. It is envisioned that mobile users may do much computer processing in an off‐line mode but must occasionally connect to a network in order to exchange data and/or files. For this purpose a communication session is initiated. During the session the user has access to network resources, although this access may be shared with others. Owing to the mobile environment, the user's connection to the network during a session may be severed. Since the mobile user can act semi‐autonomously, such disconnections can be transparent. That is, the mobile user can continue to function in an off‐line mode while the system will begin transparent automatic reconnection attempts to reestablish a link to the network. Only after a fixed (given) number of such attempts to reconnect have failed, is the session deemed to have failed. The issue is complicated by the hostile mobile radio environment and by user mobility. We consider session‐oriented communications and develop a tractable analytical model for traffic performance based on multi‐dimensional birth–death processes. The approach allows consideration of various platform types, such as pedestrians, automobiles, and buses, which may have very different mobility characteristics. Performance characteristics, such as: blocking, forced session termination, carried traffic, the average time per suspension, and the average number of suspensions per session, are calculated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Small-cell mobile phone systems

The three major small-cell mobile phone systems now entering commercial use are described. These are the Bell system in the greater Chicago area, the Motorola system in the Baltimore/Washington area, and the Japanese system in the Tokyo area. The Bell system is described in some detail, including its procedure when reducing cell size, and the steps in setting up and in handing off a talking circuit. The major differences in the other systems are stated.     

Land mobile satellite systems

The general advantages and potential operating characteristics of the mobile satellite service (MSS) are described, and distinctions are made between radio telephone, which is interconnected to the public switched telephone network, and private mobile radio systems. Mobile satellite service offers voice, data, position location, and paging services, interconnection to the public switched telephone network, and the possibility of private networks. Performance and cost characteristics are given along with summaries of market needs and market demands. The space and ground systems of the MSS are described     

European third-generation mobile systems

Vast importance is being placed in Europe on the development of third-generation mobile telecommunications systems, since it is expected that mobile and personal communications will become a key driver for growth and innovation in the next millenium as well as being a necessary building block of the wireless information society. Significant progress has been made since 1988 by a number of European Union funded R&D projects working toward the development of future generations of mobile communication concepts, systems, and networks. The ACTS (Advanced Communications Technologies and Services) program will offer, in the period 1995-1998, service providers, communications operators, and equipment manufacturers greater opportunities to master and trial mobile and personal communications services and technologies. From the user's perspective the ACTS program will strive to ensure that current mobile services are extended to include multimedia and broadband services, that access to services are made without regard to the underlying networks, and that convenient, lightweight, compact, and power-efficient terminals adapt automatically to whatever air-interface parameters are appropriate to the user's location and desired services     

Emerging mobile and personal communication systems

The market demand for wireless communications has been demonstrated by the rapid growth of different second-generation wireless technologies that are optimized for particular applications and environments. Obvious examples include: digital cellular systems like GSM, ADC, PDC,and DCS1800 for widespread vehicular and pedestrian services, and cordless telecommunication systems based on CT2, DECT, and PHS standards for residential, business, and public cordless access applications. Efforts are also underway to consolidate the various radio environments and applications under a single standard for third generation wireless, i.e., FPLMTS. In the area of personal mobility, with the recent availability of “personal” numbers in various countries (e.g., 500 numbers in the United States), many fixed network operators are starting to offer such personal mobility services as “personal number service” and “number portability”. These services represent initial stages of full personal mobility that will be provided by UPT in both wireline as well as wireless environments. The expected heavy demand for PCS in the United States and the underlying market/regulatory forces are driving the standardization and business activity. A number of air interface standards for the 1900 MHZ PCS band are being considered, which are based on TDMA, CDMA, and FDMA technologies singly or in combination. Many are variations of existing digital cellular and cordless telecommunications technologies. PCS networking standards are also being developed; both for standalone systems and for systems that will utilize public switched network capabilities     

Network awareness and mobile agent systems

Most current computer applications are insensitive to changing network conditions. With the growing demand for wireless, satellite, and other highly volatile computer communications networks, however, applications that are robust in the presence of network volatility must be designed and built. Network-robust applications are of great interest in military situations today, and we expect that interest to grow in industrial and eventually consumer environments as well. Mobile agents are one way to realize such applications, especially when used in a wireless environment. This article discusses issues and results related to the problem of making computer applications network-aware and reactive to changing network conditions. It contains a short overview of our work on mobile agents as well as a tutorial on network sensing from the agent perspective. Some prototypes of network sensing systems and network aware mobile-agent applications are presented     

An access protocol for speech/data/video integration in TDMA-basedadvanced mobile systems

One key requirement in the radio access design of advanced, third-generation mobile systems is the ability to accommodate a variety of service types via flexible and efficient multiple-access protocols. This paper introduces a multiple-access protocol, SIR++ (service integration for radio access), which has the potential for meeting the service requirements of speech, video, and bursty data traffic in an efficient way. SLR++ is evolved from and generalizes a former protocol, SIR, which only considered the requirements of speech and data. The paper also evaluates the buffer occupancy distribution associated with an (H.263) video connection by solving a worst case model of the system     

A group-based data-driven approach for data synchronization in unstructured mobile P2P systems

This paper addresses the problem of data consistency on mobile peer-to-peer (MP2P) systems (or MP2P networks). The considered MP2P system is based on a mobile ad-hoc network, where the energy and connectivity on the mobile devices are limited. Since different mobile nodes may store copies of shared information, data synchronization on an MP2P system becomes crucial and challenging due to frequent disconnection and change on network topology caused by node mobility. We propose an effective approach to improving the performance of data synchronization with a dynamic inverted data indexing structure and group-based data-driven consistency management. The proposed approach can effectively synchronize the data items without using a central cache node in each group (or cluster) and perform well in terms of the coverage of successfully synchronized nodes and the number of redundant messages. Last, the proposed approach is validated through extensive simulation experiments.     

A bandwidth reservation protocol for speech/data integration in TDMA-based advanced mobile systems

The traffic performance of third-generation mobile systems is greatly influenced by the multiple access protocols used in the radio access subsystem. The paper introduces an access protocol, SIR (Service Integration Radio Access), which has the potential for accommodating the requirements of speech and bursty data traffic in an efficient way. SIR is evolved from a protocol (PRMA ++) studied in the framework of a TDMA-based version of the European Universal Mobile Telecommunication System (UMTS) and uses dedicated mechanisms for data bandwidth request collection and servicing.     

Limited-lifetime shared-access in mobile systems

In this paper, we propose a simple access protocol to shared information in a mobile environment. The objective of the proposed scheme is to allow a specified set of users access toshared information and protect the confidentiality of the information from users outside this set. The set of users may be updated from time to time. In particular, the duration during which a user is allowed access to the shared information may be restricted. Furthermore, the information itself has limited lifetime and the confidentiality of the information has to be preserved during this lifetime only. The proposed access protocol is in particular suited to the mobile environment, because of the loose binding of the communicating entities.     

Satellite land mobile communication systems

The emergence of satellite land mobile services over the last 10 to 15 years is described together with future trends. The difficulties of providing a commercially viable voice service are discussed and alternatives, such as inclined orbit systems and satellites with very large antennas, are suggested as ways in which the initial disadvantages might be overcome. Data services for satellite land mobile traffic and the possibilities of including radio determination of vehicle location as part of these data services are also considered. Future systems, which could have their architecture strongly influenced by the use of onboard processing, are discussed     

Optimal relayed mobile communication systems

Recently, D.T. Chiang and R.F. Chiang (1986) considered a relayed mobile communication system with evenly spaced mobile relay stations (spacecraft) moving at the same speed from an origin towards a destination. Such a system can be considered as a consecutive-k-out-of-n line. They gave equations for computing the mean number of stations needed for a successful relay and studied the optimal choice of k to minimize the mean number. In the present work, the authors show that it is always better to replace a consecutive-k-out-of-n line by a consecutive-1-out-of- n line, but with k redundancy. The problem of choosing an optimal k still has no closed-form solution, but it is much more tractable than the original problem studied by Chiang and Chiang. Exact solutions are provided for a wide range of parameters     

Admission control and buffer management of wireless communication systems with mobile stations and integrated voice and data services

This study presents models for management of voice and data traffic and new algorithms, which use call admission control as well as buffer management to optimise the performance of single channel systems such as wireless local area networks in the presence of mobile stations. Unlike existing studies, the new approach queues incoming voice packets as well as data packets, and uses a new pre-emption algorithm in order to keep the response time of voice requests at certain levels while the blocking of data requests is minimised. A new performance metric is introduced to provide uncorrelated handling of integrated services. Queueing related issues such as overall queue capacity, individual capacities for voice and data requests, the probability of blocking, and effects of waiting time on overall quality of service are considered in detail. Analytical models are presented and the results obtained from the analytical models were validated using discrete event simulations.     

Efficient integration of isochronous and data bursty traffics in low earth orbit‐mobile satellite systems

This paper focuses on the radio resource management in low earth orbit‐mobile satellite systems (LEO‐MSSs) based on a time division multiple access (TDMA) air interface. A novel demand–assignment medium access control (MAC) protocol, named DRAMA+ (dynamic resource assignment multiple access—enhanced version), is proposed, where voice and Web traffic sources obtain transmission slots through requests sent by means of a random access phase. The round‐trip propagation delay (RTD) of LEO‐MSSs prevents an immediate feedback for each transmission attempt. Therefore, the main concern of the DRAMA+ scheme is to realize an efficient access phase. All the transmission requests successfully received at the satellite are managed by an on board scheduler. We have shown that DRAMA+ outperforms other techniques appeared in the literature in terms of voice quality, transmission delays for bursty data traffics and resource utilization. Moreover, a performance analysis of an ideal version of the DRAMA+ scheme has permitted us to prove the potentialities of the proposed DRAMA+ technique. Stability issues have been addressed as well as the impact on the DRAMA+ performance of the LEO satellite constellation RTD value. Copyright © 2002 John Wiley & Sons, Ltd.     

Context-aware platform for mobile data management

Interaction design is a major issue for mobile information systems in terms of not only the choice of input/output channels and presentation of information, but also the application of context-awareness. To support experimentation with these factors, we have developed platforms to support the rapid prototyping of multi-channel, multi-modal, context-aware applications. The Java-based platform presented here is based on an integration of a cross-media link server and an object-oriented framework for advanced content publishing, along with a Client Controller and Context Engine. We also describe how this platform was used to develop a mobile tourist information system for an international arts festival where interaction was based on a combination of interactive paper and speech output. Moira C. Norrie is a Professor at ETH Zurich where she is head of the Institute for Information Systems and leads the Global Information Systems research group. Her research interests include object-oriented models and systems for data management, web engineering, mobile and personal information systems and interactive paper as a medium for integrating printed and digital information. Beat Signer is a Post-Doctoral researcher in the Global Information Systems research group at ETH Zurich. He received a Ph.D. from ETH Zurich in 2005 for his work investigating fundamental concepts for interactive paper and cross-media information management. His research interests include interactive paper, cross-media information management, object-oriented technologies and software engineering. Michael Grossniklaus is a research assistant in the Global Information Systems research group at ETH Zurich. He received a Diploma (M.Sc.) in Computer Science from ETH Zurich in 2001 and is currently completing his Ph.D. His main research interest is empowering information systems for context-aware data management and delivery in the domain of web engineering and mobile computing. Rudi Belotti was a research assistant in the Global Information Systems research group at ETH Zurich from 2004–2006. He received a Diploma (M.Sc.) in Computer Science from ETH Zurich in 2004. In his research, he developed a general model and engine for the management of context information in mobile information systems. He is currently working for an e-business services company in Ticino, Switzerland. Corsin Decurtins is a research assistant in the Global Information Systems research group at ETH Zurich. He received a Diploma (M.Sc.) in Computer Science from ETH Zurich in 2002. His research focusses on model-based approaches and infrastructure for ubiquitous and mobile information environments. In addition to his Ph.D. Corsin also works part-time as a senior software engineer at the software company Netcetera. Nadir Weibel is a research assistant in the Global Information Systems research group at ETH Zurich. He received a Diploma (M.Sc.) in Computer Science from ETH Zurich in 2003 and is currently working on his Ph.D. His research is in the area of interactive paper, particularly on the authoring and publishing infrastructure for interactive documents as well as issues of human computer interaction and mobile environments.     

LEO/MEO systems – Global mobile communication systems

LEO/MEO systems are moving from a dream to a reality, their global reach is becoming apparent with the launch of the first LEO satellites. The global mobility offered by these systems is expected to have a profound effect on the way that organizations and individuals operate. Billions of dollars are invested in the research and development of LEO/MEO based communication systems, and larger amounts will be needed for their ongoing operation and use. Many global satellite based systems have been announced over the last decade, Ellipsat, Globalstar, ICO, Iridium, M‐Star, Odyssey, Orbcomm, and Teledesic, are just a few of the many systems in deployment or under development. Being such a risky venture, limited experience exists in developing and managing large scale civilian satellite based mobile communication systems. Many interesting and challenging research issues are faced by the designers and operators of such systems. This paper presents the different approaches to the configuration of the various LEO and MEO based communication systems. It compares their advantages and disadvantages, and analyzes their economic viability. Based on the analysis, it is possible to identify the specific roles that each type will play in the global communication market. The paper presents and discusses some of the important research areas involved in their development, configuration, maintenance, operation and management. In particular, it introduces the problem of gateway placement in LEO/MEO systems and presents a mathematical formulation of the problem. This revised version was published online in June 2006 with corrections to the Cover Date.