Showing papers in "Electronics & Communication Engineering Journal in 1993"

Co-occurrence matrices for image analysis

Abstract: The authors present a range of techniques for image segmentation and edge detection based on co-occurrence matrices. Co-occurrence matrices are described and transforms are defined which adapt to global image characteristics and emphasise the differences between typical and atypical image features using co-occurrence matrices as look-up tables. The techniques are extended by analysing the matrices and labelling them, with the result that a labelled matrix can be used to segment the regions of an image and to simultaneously detect prominent edges. Examples are given for a variety of images: synthetic, infrared, multispectral and temporal. It is also shown that the techniques presented can be integrated easily with a variety of postprocessing techniques such as hysteresis and relaxation labelling for enhanced performance.

TOBI, a vehicle for deep ocean survey

Abstract: TOBI is an instrumented vehicle which is towed close to the bottom of the deep ocean from a ship, and uses sound to form detailed images of the sea floor. The authors describe the mechanical design of this vehicle and its instrument package. The way in which sonar images are formed is discussed and the acoustic design parameters are considered. Signals are frequency multiplexed on to 10 km of armoured coaxial towing cable, which also provides the power to the vehicle and a two-way communication link. At the ship these signals are separated, displayed and logged onto magneto-optical cartridges. Examples of results are shown and some future developments are identified.

Navstar GPS and GLONASS: global satellite navigation systems

Abstract: Both the Navstar GPS and GLONASS satellite navigation systems, developed respectively by the United States and the Soviet Union (now the Commonwealth of Independent States), are now planned to become operational by the year 1994/95. Both systems are capable of providing the civil community with high-precision position-fixes and/or timing references on a continuous, world-wide basis. For many years both systems have had satellites in orbit in order for pre-operational testing to be conducted. The paper discusses (a) the widely-differing launch histories of both systems, (b) developments in the planned use of orbits, (c) the deliberate degradation of accuracy by the use of selective availability and (d) progress in plans to provide a joint Navstar GPS/GLONASS civil satellite navigation system, possibly integrated with other satellite ranging systems.

Simplified matched filter receiver designs for spread spectrum communications applications

Abstract: The design of receiver architectures for use in direct sequence spread spectrum systems is reviewed. As it is difficult to construct the long matched filters for these systems, the authors propose a programmable receiver architecture which achieves the required high processing gain while, at the same time, simplifying the filter hardware requirements. Results are presented for a prototype receiver, based on digital signal processing (DSP) components, which can be reprogrammed for serial, serial-parallel or fully parallel operation while offering minimal degradation from theoretical performance.

Digital-to-analogue conversion using pulse width modulation

Abstract: Pulse width modulation (PWM) has found application in various situations where efficient delivery of high power is required. In this paper its use in the conversion of signals from digital to analogue representations is addressed, i.e. as a digital-to-analogue converter (DAC), and it is shown that there are many advantages in using PWM over conventional DAC methods and that high resolution and accuracy can be achieved. One advantage is that, provided a suitable output stage can be provided, a complete, high-power, high-resolution digital-to-analogue power converter can be constructed. Because this work was motivated by the author's interest in digital audio, such a device has come to be known as a digital (power) amplifier. The article describes PWM, particularly in its digital forms, and shows how to make it practical for use as a DAC. This involves various digital signal processing stages prior to the final modulator. Results are presented from simulations and from demonstrator hardware.

Functional models of UMTS and integration into future networks

Abstract: The universal mobile telecommunication system (UMTS) will implement terminal mobility and a form of personal mobility limited to UMTS. The most essential procedures to provide this are related to user registration, location management, handover and security. These mobility procedures are specified using specific functional models. In these models, the required functions are identified and the distribution of the functions in the network is anticipated. In a next step, the specific models are mapped onto a generic functional model. This generic model can be considered as the integration and unification of the specific models. Its structure reflects two important implementation aspects. First, the integration of UMTS into future networks for fixed telecommunications is anticipated. Secondly, the application of the intelligent network architecture for the implementation of the UMTS mobility procedures and service provision is assumed.

Mobile broadband system (MBS): trends and impact on 60 GHz band MMIC development

Abstract: The RACE mobile broadband system (MBS) project aims to extend the broadband integrated services digital network (B-ISDN) to mobile users. To meet the future demand for broadband wireless picocell networks, frequencies have been allocated in the 62-63 and 65-66 GHz bands. However, for the use of a mobile broadband system to become widespread it is necessary to develop relatively low cost transceivers based on millimetre wave GaAs P-HEMT MMICs. A transceiver architecture and elementary building blocks have been defined. 60 GHz transistor models have been refined and circuit design, layout and simulation achieved. Future cost decrease is a function of the MMIC manufacturing yield, since a high yield allows a higher layout density and consequently fewer MMICs per transceiver, and of the improvement in packaging techniques above 60 GHz.

Modern data encryption

Abstract: Communications security is increasing in importance as a result of the use of electronic communications in more and more business activities. Cryptography is the only practical means to provide security services in many applications. Research into cryptography has exploded in the last 18 years and a variety of cryptographic algorithms and techniques have emerged.Cryptographic algorithms may be classified as either symmetric, if the same key is shared by the sender and receiver, or asymmetric, if they use different keys. Symmetric algorithms have been dominated by the Data Encryption Standard since 1976, but a number of replacements are now being proposed. Asymmetric, or public key, algorithms allow provision of new security services such as digital signatures. The RSA algorithm is the most widely known of these, but a recently proposed standard for digital signatures is also of intense current interest.

Electronic odour sensing systems

Abstract: An odour sensing instrument has been developed and used to classify many different materials, including beers, spirits and alcohols. The next stage in development is to begin to relate subjective odour descriptors (e.g. fruity, minty) to quantitative sensor array measurements. This task is being approached using both neural network and multivariate statistical techniques. The ultimate goal is to provide a measurement standard for odours. This exciting prospect requires the integration of sensor technology, signal conditioning, data acquisition and pattern recognition.

Third generation PCN and the intelligent multimode mobile portable

Abstract: The radio interfaces required for a third generation personal communications network (PCN), and the attributes of an intelligent multimode portable to operate within the PCN are speculated upon. After discussing key factors in determining spectral efficiency in PCNs, multiple access methods are considered for radio interfaces associated with high-capacity network nodes, microcellular networks, macrocellular networks, megacells, satellite mobile and private mobile radio. Modulation issues are then addressed, followed by source and channel coding. Some elements of a third generation PCN are considered next. Finally the authors present their views on an intelligent multimode mobile portable that will function in many different geographical environments and, in any one, be adaptive in changing its subsystems to variations in the channel conditions and local teletraffic loading.

Digital modulation techniques for mobile and personal communication systems

Abstract: The paper describes in detail various digital modulation techniques for mobile and personal communication systems. Among others, these include pi /4-shift quadrature phase-shift keying (QPSK), used in the second generation digital cellular mobile systems in North America and Japan, and Gaussian minimum-shift keying (GMSK), employed in the GSM system in Europe. It then briefly discusses the current research activities in modulation schemes for future systems.< >

A reservation based access mechanism for 3rd generation cellular systems

Abstract: The paper reports on initial investigations in RACE project 2084, ATDMA, into the mapping of reservation access mechanisms onto an adaptive TDMA structure. This work is a natural extension of studies in RACE 1043, on packet access mechanisms, and considers the influence of some practical constraints on system performance. The paper presents realistic burst and frame structures for reservation mode access and gives some capacity estimates for macrocells in which reservation mode access is employed. The results are derived from a Medium Access Control simulation module which is being designed as part of a simulated testbed for the ATDMA project.

Wideband propagation measurements of short range millimetric radio channels

Abstract: There is an increasing emphasis to extend the services available on fixed telecommunication networks to the mobile user. One area of the RACE 1043 project examined the possibility of universal mobile services within future integrated broadband communications networks. Essential to the feasibility of such a scheme is an understanding of the wideband characteristics of the radio channel. The article describes the results of a wideband channel sounding programme conducted at 39 and 60 GHz, together with a channel-modelling exercise based on these measurements, aimed at producing a statistical model of the wide band millimetric channel.

Sizing up the microcell for mobile radio communications

Abstract: Within cellular mobile radio communication systems large cells have been widely deployed, with cell sizes decreasing as the number of subscribers increase. This has lead to the possibility of using very small cells, or microcells. However, the term microcell has been used to mean different things to different organisations. With much work being performed on propagation within microcells and on infrastructure issues for microcells there is now a sufficient base of knowledge to allow the introduction of these small cells. The paper defines the microcell, examines propagation modelling methods and tools, and looks at problematic areas such handover and the complexity of the infrastructure required. Finally, the future of microcells for mobile radio use is considered.

Power limitation and high-power amplifier nonlinearities in on-board satellite communications systems

Abstract: The authors discuss the problem of power limitation in on-board satellite communications systems. They consider the nonlinear characteristics of on-board high-power amplifiers and corresponding linearisation techniques. It is shown that, with the recent development of solid-state high-power amplifier designs and linearisation techniques for travelling wave-tube amplifiers, it is now possible to operate on-board amplifiers near to saturation without increasing their nonlinear effects.

Heading towards an advanced signalling system for multimedia, multiparty services in broadband ISDN

Abstract: Introduction of the broadband integrated services digital network (B-ISDN) will enable network users to make use of advanced multimedia, multiparty services. With this aim in view, RACE II project R2044, MAGIC, is investigating long-term signalling requirements, architecture and protocols for B-ISDN. New service concepts are being developed in MAGIC which will provide more flexibility when compared to narrowband ISDN (N-ISDN). The service requirements and other signalling requirements, such as the separation between call and associated connections at the network–node interface (NNI), are used to determine the distribution of functions over the network. The signalling protocols which are used to exchange the signalling information are subsequently developed. These signalling protocols will be simulated to prove the performance and the feasibility of call handling concepts.

High-bit-rate digital subscriber lines

Abstract: High-bit-rate digital subscriber line (HDSL) technology provides a simple, cost-effective solution for the rapid provision of new digital telecommunication services direct to a customer's premises over existing twisted copper pair telephone lines. It makes full use of the existing network infrastructure and hence removes the need for the costly replacement of copper twisted pairs by alternative transmission media.

Resolving revolutions : imaging and mapping by modern radar

Abstract: High-performance synthetic aperture radars (SARs) for mapping demand massive digital signal processing powers. The fall in the cost of computing devices has recently passed the point at which such processors can be afforded and SARs are now being used in a range of applications. The analogous inverse synthetic aperture radar (ISAR), which enables moving targets to be imaged by stationary or moving radars, is also becoming widely used. The unifying principle underlying SARs and ISARs is presented and the common parameters defining the performances of both types of radar are derived. A novel technique is described which enables the radar to measure the random angular spin of a ship at sea, thereby permitting it to be imaged deterministically by ISAR. Results are presented from a representative selection of ISARs and SARs ranging from the imaging of model targets by ISARs operating at scaled-up frequencies through to the mapping of the surface of Venus by a satellite SAR. The paper concludes with a review of likely future developments of these types of radar and suggests that further major advances are possible.

Block versus trellis: an introduction to coded modulation

Abstract: Coded modulation has had a very significant impact on the communications scene in the decade or so since its introduction, finding practical applications from voice-band modems for telephone lines to deep-space communications. The paper introduces the principles of coded modulation and describes the two main schemes: block coded modulation (BCM) and trellis coded modulation (TCM). In particular it considers the argument between the proponents of BCM and TCM, and points out some pitfalls in the use of performance measures such as asymptotic coding gain for these schemes. It concludes that in terms of performance versus decoder complexity the schemes seem to be quite close, and the choice of the system designer may be determined by other factors.

I'll be seeing you: Multimedia communications in the 21st century

Abstract: The world's telecommunications network is not yet 120 years old and is the largest man-made machine of all time. The paper outlines some of the key technologies which have underpinned its development and argues that rapid technological advance, coupled with a convergence of technologies and markets in the IT sector, will create a highly competitive multimedia environment characterised by revolutionary, rather than evolutionary, change. The paper argues that a full multimedia capability, with integrated voice, text and fixed and moving image capabilities, will create major market opportunities and have a pervasive impact on all aspects of commerce and social life. Examples of multimedia services are provided and the importance of a national broadband network infrastructure to deliver them is stressed.

Packet access mechanisms for cellular radio

Abstract: The paper reviews the findings of work completed in RACE Mobile Telecommunications Project 1043 on the suitability of packet access mechanisms for mixed services in the Universal Mobile Telecommunication System A first order comparison of random and scheduled access is provided and conditions under which these mechanisms provide an attractive alternative to channel allocation for call duration are specified It is concluded that packet reservation multiple access (PRMA) is an attractive candidate for mixed services over a range of cell sizes as it can accommodate fixed channel access, reserved channel access and random channel access

Integrated broadband communications development and implementation strategies

Abstract: The paper summarises the consolidated results of the collaborative research within Project RACE 1044 ‘IBC development and implementation strategies’. It is aimed at giving a comprehensive view of R1044 activities and achievements. The results of the activities of the five R1044 workpackages are summarised; more details will be provided in further papers. This paper provides a description of the role that R1044 played in phase I of the European Communities’ ‘Research and development in Advanced Communications Technologies in Europe’ (RACE) programme, and describes the general objectives, organisation, and results achieved by the project.

Optical telecommunications : future prospects

Abstract: Optical technology is already the dominant carrier of global information. It is also central to the realisation of future networks which have the capabilities demanded by society. For example, essentially unlimited bandwidth to convey services of any kind, full transparency that allows terminal-only upgrades in capacity, and flexible routeing of channels are some of the key features that cannot be provided by alternative technologies. In the main, all of the necessary elements for such networks already exist in experimental form, and rapid progress is being made towards a field deployment capability. This will bring about a paradigm change in the whole nature of telecommunications as we move into the third millennium.

Digital signal processing. Part 2: Spectral analysis

Abstract: This is the second of two papers introducing the main topics in digital signal processing The subject of this paper is the estimation of the spectra of signals and both classical estimation methods and modern model-based methods are discussed These techniques are compared and results are presented which demonstrate the superior resolution which is obtained with modern autoregressive spectral analysis methods Examples are given of the application of these techniques in the areas of speech processing and biomedical signal analysis

Fractals and image representation

Abstract: For some years now, ‘fractals’ have provided spectacular displays (which have seemingly hypnotised both the popular technical press and the ‘media’) on computer workstations equipped with high-power graphics processors, and also provoked much controversy with regard to their potential for mimicking real-world imagery. In this paper the authors briefly describe the theoretical background of fractal representations and investigate in more detail the validity of such an approach for applications in natural scene portrayal and coding.

UMTS mobility management

Abstract: The characteristics of first, second and third generation mobile communication systems are first described. The state of standardisation of the universal mobile telecommunication system (UMTS) is then outlined and the system concept is introduced. A mobility management platform which will provide uniform access to mobility functions for every user or network entity independent of the actual location of the requested function in the network is described. The mobility management platform is based on the intelligent network concept. Mobility management aims to share the processing load in the distributed UMTS environment. >

Ocean-going ship support using multimedia teleconferencing via satellite

Abstract: The opportunities offered by advances in shore-based communication networks, satellites and ship-board equipment may be significant for the future operating practices of the marine industry. The use of advanced telecommunications, such as high data-rate land networks and satellite links, allows the transmission of digitised moving video, voice and computer data, to support applications such as multimedia conferencing and computer interworking. These facilities can be used for the remote support of ships' crews from land-based agencies. A series of experiments conducted within a large-scale project on the use of advanced communications in the marine industry demonstrated multimedia conferencing between a specially equipped ship and shore-based organisations. In the case of a serious technical problem on the ship, it was shown how experts at the shipping company and other locations could use such facilities for remote inspection, problem diagnosis, advice, co-operative decision-making and supervision of the repair procedure.