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Nhiều giao thức truy cập đối với truyền thông di động P2
CELLULAR MOBILE COMMUNICATION SYSTEMS: FROM 1G TO 4G The basic principles of cellular communications were explained in the introductory chapter, and terms such as cluster size and reuse efficiency introduced. In the following, some more considerations on the advantages and limitations of the cellular concept will be made before reviewing first generation (1G) and second generation (2G) cellular communication systems. Moving on to 3G, we will first discuss the initial requirements according to which 3G systems were designed, and then to what extent they are likely to be satisfied by first releases of ‘true’ 3G systems on the one hand, and...
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Nhiều giao thức truy cập đối với truyền thông di động P3
MULTIPLE ACCESS IN CELLULAR COMMUNICATION SYSTEMS To examine the problem of multiple access in cellular communications, first the relevant OSI layers need to be identified, which is not necessarily straightforward. A split into basic multiple access schemes such as CDMA, TDMA, and FDMA, associated with the physical layer, and multiple access protocols, situated at the medium access control layer, is adopted here. After a discussion of basic multiple access schemes, approaches chosen for medium access control in 2G cellular communication systems are briefly reviewed....
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Nhiều giao thức truy cập đối với truyền thông di động P4
MULTIPLE ACCESS IN GSM AND (E)GPRS This chapter discusses features of the GSM air interface from phase 1 recommendations through to the specifications released in 1999. This entails GSM voice, circuit-switched data, and High Speed Circuit-Switched Data (HSCSD) services. A key topic is the matter of radio resource utilisation, hence on top of summarising the relevant system features, we present also some research results dealing with resource utilisation under heterogeneous GSM and HSCSD traffic load....
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Nhiều giao thức truy cập đối với truyền thông di động P5
MODELS FOR THE PHYSICAL LAYER AND FOR USER TRAFFIC GENERATION In general, sophisticated communication systems are designed according to the concept of layering, often adhering to the OSI layering approach. The designer of a certain layer can then consider other layers as black boxes, which provide certain services defined in terms of functional relations between their respective inputs and outputs. She does not have to worry about the details of implementation of the next lower layer, but must only be aware of the services it provides....
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Nhiều giao thức truy cập đối với truyền thông di động P6
MULTIDIMENSIONAL PRMA The PRMA protocol extended for operation on a hybrid CDMA/TDMA air interface is defined in the following. This extended version of PRMA is referred to as multidimensional PRMA or MD PRMA. First, the basic protocol suitable for frequency-division duplexing is described. Then, the implications of different approaches to time-division duplexing on the protocol operation will be discussed. Finally, the two investigated approaches to access control, namely load-based access control and backlog-based access control, will be introduced....
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Nhiều giao thức truy cập đối với truyền thông di động P7
MD PRMA WITH LOAD-BASED ACCESS CONTROL Chapter 5 provided descriptions of channel and traffic models used for investigations on the MD PRMA protocol, which was defined in detail in Chapter 6. Starting with this chapter, and continuing in Chapters 8 and 9, the outcomes of our research efforts on MD PRMA will be discussed. In this chapter, the focus is on load-based access control (for MD PRMA), a technique adopted to protect reservation-mode users from multiple access interference generated by contending users. Only voice traffic is considered...
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Nhiều giao thức truy cập đối với truyền thông di động P8
MD PRMA ON CODE-TIME-SLOTS This chapter is concerned with MD PRMA on perfect-collision code-time-slot channels. The simple and abstract channel model used, representative for a blocking-limited system, allows one to consider an arbitrary number of code-slots E per time-slot, without having to worry about the spreading factor required to meet a certain packet erasure performance. In this framework, the scope of investigations can conveniently be extended to two extreme cases, namely only one code-slot per time-slot, but numerous time-slots N per TDMA frame, and only one time-slot per frame carrying numerous code-slots....
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Nhiều giao thức truy cập đối với truyền thông di động P9
MD PRMA WITH PRIORITISED BAYESIAN BROADCAST This last of the three chapters dealing exclusively with MD PRMA-related research results finally treats scenarios that are not limited to voice traffic only. To assess the performance of the prioritised Bayesian broadcast algorithm proposed in the following, a simulation study for different mixtures of voice and data traffic is conducted, where the latter consists either of Web traffic, email traffic, or a combination of the two.
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Nhiều giao thức truy cập đối với truyền thông di động P10
PACKET ACCESS IN UTRA FDD AND UTRA TDD In this chapter, first a brief introduction to UMTS Terrestrial Radio Access (UTRA) matters is provided, such as fundamental radio access network concepts, basics of, for example, the physical and the MAC layer, and the types of channels defined (namely logical, transport and physical channels). This is followed by a discussion of certain UTRA FDD features, such as soft handover, fast power control and compressed mode operation.
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Nhiều giao thức truy cập đối với truyền thông di động P11
TOWARDS ‘ALL IP’ AND SOME CONCLUDING REMARKS This concluding chapter provides first an introduction to some of the planned release 5 enhancements to UMTS and the GPRS/EDGE RAN (GERAN). These can be seen as the first step towards ‘all IP’. The challenges when having to deliver real-time IP services over an air interface, in particular voice over IP services, are summarised and possible solutions to achieve spectrum efficiencies similar to those of optimised cellular voice services are outlined. Unlike the UTRA modes, the GSM/GPRS air interface was not designed to handle real-time packet-data traffic. Further enhancements are required to support real-time...
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Multisensor thiết bị đo đạc thiết kế 6o (P1)
PROCESS, QUANTUM, AND ANALYTICAL SENSORS INTRODUCTION Automatic test systems, manufacturing process control, analytical instrumentation, and aerospace electronic systems all would have diminished capabilities without the availability of contemporary computer integrated data systems with multisensor information structures. This text develops supporting quantitative error models that enable a unified performance evaluation for the design and analysis of linear and digital instrumentation systems with the goal of compatibility of integration with other enterprise quality representations....
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Multisensor thiết bị đo đạc thiết kế 6o (P2)
INSTRUMENTATION AMPLIFIERS AND PARAMETER ERRORS This chapter is concerned with the devices and circuits that comprise the electronic amplifiers of linear systems utilized in instrumentation applications. This development begins with the temperature limitations of semiconductor devices, and is then extended to differential amplifiers and an analysis of their parameters for understanding operational amplifiers from the perspective of their internal stages.
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Multisensor thiết bị đo đạc thiết kế 6o (P3)
ACTIVE FILTER DESIGN WITH NOMINAL ERROR Although electric wave filters have been used for over a century since Marconi’s radio experiments, the identification of stable and ideally terminated filter networks has occurred only during the past 35 years. Filtering at the lower instrumentation frequencies has always been a problem with passive filters because the required L and C values are larger and inductor losses appreciable. The band-limiting of measurement signals in instrumentation applications imposes the additional concern of filter error additive to these measurement signals when accurate signal conditioning is required. ...
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Multisensor thiết bị đo đạc thiết kế 6o (P4)
LINEAR SIGNAL CONDITIONING TO SIX-SIGMA CONFIDENCE INTRODUCTION Economic considerations are imposing increased accountability on the design of analog I/O systems to provide performance at the required accuracy for computerintegrated measurement and control instrumentation without the costs of overdesign. Within that context, this chapter provides the development of signal acquisition and conditioning circuits, and derives a unified method for representing and upgrading the quality of instrumentation signals between sensors and data-conversion systems....
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Multisensor thiết bị đo đạc thiết kế 6o (P5)
DATA CONVERSION DEVICES AND ERRORS Data conversion devices provide the interfacing components between continuoustime signals representing the parameters of physical processes and their discrete-time digital equivalent. Recent emphasis on computer systems for automated manufacturing and the growing interest in using personal computers for data acquisition and control have increased the need for improved understanding of the design requirements of real-time computer I/O systems.
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Multisensor thiết bị đo đạc thiết kế 6o (P6)
SAMPLING AND RECONSTRUCTION WITH INTERSAMPLE ERROR A fundamental requirement of sampled-data systems is the sampling of continuoustime signals to obtain a representative set of numbers that can be used by a digital computer. The primary goal of this chapter is to provide an understanding of this process. The first section explores theoretical aspects of sampling and the formal considerations of signal recovery, including ideal Wiener filtering in signal interpolation. Aliasing of signal and noise are considered next in a detailed development involving a heterodyne basis of evaluation. ...
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Multisensor thiết bị đo đạc thiết kế 6o (P7)
MEASUREMENT AND CONTROL INSTRUMENTATION ERROR ANALYSIS Systems engineering considerations increasingly require that real-time I/O systems fully achieve necessary data accuracy without overdesign and its associated costs. In pursuit of those goals, this chapter assembles the error models derived in previous chapters for computer interfacing system functions into a unified instrumentation analysis suite, including the capability for evaluating alternate designs in overall system optimization. This is especially of value in high-performance applications for appraising alternative I/O products. ...
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Multisensor thiết bị đo đạc thiết kế 6o (P8)
MULTISENSOR ARCHITECTURES AND ERROR PROPAGATION The purpose of this chapter is to extend the data acquisition error analysis of the preceding chapters to provide understanding about how errors originating in multisensor architectures combine and propagate in algorithmic computations. This development is focused on the wider applications of sensor integration for improving data characterization rather than the narrower applications of sensor fusion employed for data ambiguity reduction. Three diverse multisensor instrumentation architectures are analyzed to explore error propagation influences....
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Multisensor thiết bị đo đạc thiết kế 6o (P9)
INSTRUMENTATION SYSTEM INTEGRATION AND INTERFACES Technical evolution and economic influences have combined to define the integration of contemporary multisensor instrumentation systems relative to a delineation of applications. A hierarchical instrumentation taxonomy is accordingly described as illustrated by discrete automatic test equipment, remote measurement environments, automation system virtual instruments, and analytical instrumentation for aiding sensed-feature understanding. The integration of each of these instrumentation categories is also defined by bus and network structures appropriate for meeting application performance requirements....
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Mạng và viễn thông P1
Znformation and its Lonveyance The world about us brims with information. the time our ears, All eyes, fingers, mouths and noses sense theenvironmentaround us, continuallyincreasing our ‘awareness’,‘intelligence’ and ‘instructive knowledge’. Indeed these last two phrases are the heart of the Oxford Dictionary’s at definition of thewordinformation.
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Mạng và viễn thông P2
Introduction to Signal Transmission and the Basic Line Circuit To make it suitable for carriage over most telecommunications networks, information must first be encoded in an electrical manner, as anelectrical signal. Only such signalscan be conveyed over the wires and exchanges that comprise ‘transport the mechanism’ of telecommunications networks.Overtheyears,avarietyofdifferentmethodshave been developed forencoding different types of information.
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Mạng và viễn thông P3
Long-haul . Communication None of the circuits that we have so far discussed are suitable as they stand for long haul communication. To get us anywhere with long haulwe need to address ourselves to the following inescapably pertinent topics:
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Mạng và viễn thông P4
Data and the Binary Code System ‘Data’, a plural noun, the term used to describe information which is storedand processed by is in computers. It is essential to know how such data are represented electronically before we can begin to understand how it can be communicated between computers, communication devices (e.g. facsimile machines) other data storage or devices. As a necessary introduction to the concept of ‘digital’ transmission, this chapter is devoted to a description of tha method of representing textual and numeric information which is called the ‘binary code’. ...
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Mạng và viễn thông P5
Digital Transmission and Pulse Code Modulation Following trials in the196Os, digital telecommunications systems were first widely deployed in the 1970s. Since then, the miniaturization and large scale integration of electronic components and the rapid advancein computer technology have made digital technology the obvious for all choice newtelecommunicationstransmissionandswitchingsystems.Now,inthenetworks of most countries and with world wider international satellite and submarine networks, digital transmission has no rivals. ...
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Mạng và viễn thông P6
In this chapter we deal with the mechanics of the switching process, describing the sequence of functionsnecessary to establishconnectionsacross a telecommunicationsnetwork.Weshall cover the principles of circuit switching (as would be used in voice or circuit data networks) as well as the statisticalmultiplexing switching techniques of packet and cell switching. In addition, we describe in outline some of the better known types of switch technology.
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Mạng và viễn thông P7
Setting Up and Clearing Connections The establishment of a physical connection across a connection-oriented network relies not only on the availability of an appropriate topology of exchanges and transmission links between the twoend-pointsbutalso on thecorrectfunctioning of alogical call set-upand ‘cleardown’ procedure. This is the logical sequence of events for establishing calls
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Mạng và viễn thông P8
The basic line transmission theory that we have considered so far, together with theprinciples of analogue and digital signal transmission over pairs of electrical wires, is quite suitable for short range conveyance of a small number of circuits. However, it is not always practical or economic to use many multiple numbers of physical ‘pairs’ between exchanges, so we have recourse to frequency division and time division multiplexing reduce the numberof physical pairs of wires to needed to convey a large number of long haul circuits between common end-points....
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Mạng và viễn thông P9
Data Network Principles and Protocols We have described the binary form in which data are held by computer systems, and how such data are conveyed over digital line transmission systems, but we shall need to know more than this before we can design the sort ofdevices which can communicatesensibly with one another in somethingequivalent to human conversation.Inthischapter we shalldiscuss indetailthe networks required, the and so-called conveyance of data between computer systems, the ‘protocols’ they will need to ensure that they are communicating properly....
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Mạng và viễn thông P10
Zntegrated Services Digital Network (ISDN) Most public telecommunication operators throughout the world have now at least commenced the modernization of their networks by introducing digital transmission and digital switching into the public switched telephone network (PSTN). Simultaneously many operators are converting their networks to integrated services digital networks (ISDN) which will allow customers access to a variety of services while reducing the cost of provision of these services both to the administration and to the customer....
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Mạng và viễn thông P11
Intelligent Networks and Services By storing a massive ‘memory’ of customer and service information ina network, andreferring to it while setting up calls, and as a historical record of network use, a phenomenal new range of services becomes possible. The effect is almost as if the network had some degree of ‘intelligent’ power of thought
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