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The safety of telecommunications workers has always been an important issue, particularly in the areas of external plant and power. Some of the more notable dangers that exist include asphyxiation in underground plant, especially manholes; falls from overhead plant, such as poles; traffic in the vicinity of work on underground or overhead plant in or near the road; and electrocution from a variety of power sources. All these, and many more, risks must be managed proactively in a telecommunications company. An example of risk management in the pole stock with a methodology for a risk assessment based prioritization is given in Risk and safety in the access network, BT Technology Journal, Vol 16, No4.
This is a process of reading and recording the values of an analogue signal at precisely spaced intervals of time. It is the first stage in Pulse Code Modulation (PCM) where the signal is sampled at slightly more than twice the highest frequency to be encountered (sampling rate) to allow the next stage of encoding to take place. PCM allows an analogue signal to be converted into digital form.
Satellites have been used for long-distance inter-continental commercial civil telecommunications since 1995. This followed from the Telstar 1 satellite in 1962 that demonstrated that it was technically feasible between the USA (Andover, Maine) and France (Pleumeur Bodou, Brittany) and the UK (Goonhilly, Cornwall). Prior to that the first transatlantic telephone cable had only been inaugurated in 1956 to deal with the heavy demand for long-distance telephony that followed the second world war and which had hitherto been handled by HF radio. The demonstration of television signals across the Atlantic broadcast by the BBC, also using Telstar 1, excited great public interest in the use of satellites.
Telstar 1 was launched in a relatively low elliptical orbit with an orbital period of about 3 hours but this meant it was only visible from both sides of the atlantic for about 30 minutes on each pass and this involved complex tracking equipment. Subsequent experience and the solving of some technical problems led to the use of a geostationary earth orbit GEO) whereby the satellites appear to stand still in the sky. A Geostationary orbit is a circular equatorial orbit about 36,000 km high. The resulting transmission time of 260ms is very high by terrestrial standards. In the early days when there were few long-distance submarine cables the delay was acceptable but as the cost of submarine cable channels reduced and the available channels rose hugely with the advent of optical fibres they became dominant compared to satellite channels. Nevertheless, satellite technology still plays an important role as shown in the following two papers.
An overview of satellite access networks, BTTJ, Vol 18, No 3.
The use of satellite for multimedia communications, BTTJ, Vol 21 No 3.
For Wireless Security see Wireless security, BTTJ, Vol 19, No 3.
A main element of the electro-mechanical Strowger telephone exchange.
Uniselector
Group selector
Final selector
A small device that responds to a physical stimulus, such as electrical, magnetic, electromagnetic, light, sound, temperature, pressure, or motion and produces an electrical output. Sensors provide outputs that can be processed and communicated. Sometimes the output is processed locally before communication and sometimes it is communicated before processing. Examples of the use of sensors include building environmental management and alarms. See also military communications, motes and smart dust.
A computing resource, such as a database, that can be accessed over a network by another computer called a client. See client/server.
An agrement, sometimes contractual, between the provider and user of a service or network capability with specified metrics that represent the agreed service level. These metrics might typically cover technical performance measures and response times for fault restoration.
A retail company, with its own OSS, that sells products and services based on a network provided by a wholesaler (which may be a part of the same company separated by regulation). See also Virtual Service Provider.
Service providers are often qualified with a preceding letter such as ISP (Internet service provider), ASP (applications service provider) and SSP (storage service provider).
Customers will contact the service provider to order services. The handling of these services will often require the retail system to interface (via a Business-to-Business gateway) to a wholesale operator to get the service provisioned. From the wholesaler’s viewpoint, the retailer is a customer raising an order for a service, and when the wholesaler has fulfilled the order a response will be returned to indicate completion (successful or not) of the order. Any changes to the products and services which the customer has must be reflected to the billing system. Problems with the service will also be raised by customers contacting the retailer (see also CRM), which the latter must handle by interfacing to the wholesale system. The result of a fault report (or other service management events) may be that a credit or debit should be applied to the customer’s bill. As the customer uses the service so usage records are generated from the network or service platform which need to be relayed for bill generation.
A service provisioning system receives customer orders from a CRM system and supports the complex functionality required to manage those orders through to completion. The process of fulfilling a telecommunications service order may involve steps such as:
- Assigning unique resource identities (such as telephone numbers, SIM cards, etc).
- Interfacing to network provisioning systems to activate or deactivate services on the network components.
- Interfacing to work management functionality to organise engineers’ visits to customer premises or work within the network.
- Interfacing to other systems supporting direct fulfillment to the customer – eg sending out CPE or literature for the customer.
The system must handle the complexities of error recovery (when one step fails) or cancellation of the order part way through the process, as well as linked-type orders such as upgrades (seamlessly from one service to another) and takeovers (such as a new customer taking over an existing telephone line).
A session is a communication between terminal devices or an application over a data network. It is the connectionless data equivalent of a circuit switched call.
Session Initiation Protocol (SIP)
The Session Initiation Protocol, is a session set-up protocol for use in applications such as Internet conferencing, telephony, presence, events notification and instant messaging. SIP was developed within the IETF MMUSIC (Multiparty Multimedia Session Control) working group as part of the proposed Internet Multimedia conferencing architecture, with work proceeding since September 1999 in the IETF SIP working group and more recently in the SIPPING working group which focuses on application specific uses of SIP.
See also SIP and conversational Internet applications, D Wisely, BT Technology Journal, Vol 19, No 2
A standard for sending and receiving short alphanumeric messages to and from mobile handsets on a cellular mobile network. Each message is limited to 160 characters.
Signalling is the exchange of information between involved points in the network, or users of the network, that sets up, controls and terminates sessions. A session can be a relationship between resources in the network or between users of the network.
An examples of a signalling protocol in the PSTN is the signalling system number 7 (SS7), previously known as CCITT No. 7 or C7, and in IP networks examples are RSVP and SIP.Signalling can be subdivided into the purposes of signalling:
- Call control
- Bearer control
- Addressing
Processing signals, such as coding, compressing, converting, detecting, filtering, retiming and shaping, that results in their transformation into other forms. Can be performed in analogue or digital form. Digital signal processing (DSP) is a huge area of electronics and systems design that is largely outside the scope of this encyclopedia which concentrates more on end systems that make use of DSP. As a discipline it has its own publications, University specialisms and societies. See for example the IEEE Signal Processing Society web-page for further references: http://www.ieee.org/organizations/society/sp/
The subscriber identity module first introduced into GSM networks.
A circuit that allows transmission in both directions but only one way at a time. Sometimes used to refer to a circuit over which messages can only be sent in one direction (more properly uni-directional) in which case the users of the term refer to simplex as half-duplex. See also duplex.
The sinusoid (a waveform with the shape of a sine-wave) is the most common waveshape in analogue electronics. If voltages and currents in a circuit are sinusoidal then Ohm's Law is applicable as long as complex numbers are used to represent voltage, current and impedance. Where waveshapes are not sinusoidal, including square waves, they can be reduced to sinusoids - see harmonics - thus making sinusoid theory applicable to any waveform. A sinusoid is described by its amplitude, frequency and phase and each of these parameters may be modulated - see amplitude modulation, frequency modulation and phase modulation.
The shape of a sinusoid can be described by a point on a rotating circle moving along a line. The sine wave is the plot of a point moving around a unit circle as a function of time. Look for some neat inter-active Java-based demonstrations of this on the web. A full sinusoid is described as 360 degrees. The point at 180 degrees where the wave crosses the axis is sometimes called the zero crossing point.
A form of propagation where the energy reaching the receiving antenna arrives as a result of a bending of the wave path introduced by the ionisation in the upper atmosphere. This ionised region, termed the ionosphere, extends from about 50km to about 400km above the earth's surface, and accounts for practically all very long-distance HF (3 to 30 MHz) radio communications. It has a number of layers with slightly different effects at different frequencies. These layers are affected by the Sun and especially sun-spot activity.
A signal from a transmitter will be reflected by the ionosphere under certain conditions, as shown below. The reflected wave will return to the earth some distance away - called the skip distance. Multiple skips can occur, allowing signals to reach around the world in some conditions. At some frequency, dependent on time of day and atmospheric and sun-spot conditions, the signal will not be reflected and will be lost to outer space. The frequency at which this occurs is called the maximum usable frequency (MUF).
See also ground waves, space waves and troposphere. Fading
Slip occurs periodically in a digital system in which there is a mismatch between input and output line frequencies and when some bytes in a digital signal are deleted or lost, probably due to a buffer overflow. Slips can be uncontrolled, and hence unpredictable in their effect, or controlled. A controlled slip is predictable and can be accommodated to cause minimum disruption. It is usual for controlled slips to be in units of one frame, known as frame slip. Satisfactory, acceptable and unacceptable slip rates are apportioned in ITU standards (G822). The causes of slip can be many and varied and include imperfect clocks, transmission delay variation including wander and jitter, and re-timing caused by automatic re-routing.
Adaptive antennas are able to enhance received signals and may be used to form beam patterns for transmission. Their coverage pattern can change dynamically to adjust for noise, interference and multi-path effects. A simpler approach with reduced functionality, called switched beams, uses several fixed beams with the receiver selecting the greatest signal enhancement and interference reduction. Another approach is to make use of the multi-path effects by establishing parallel paths by using multiple antenna elements at both ends of the radio link. This is called multiple input/multiple output or MIMO. It is an extension of traditional diversity techniques usually only employed at one end. Collectively these are called array processing techniques or smart antennas and they improve spectral efficiency and increase range and coverage.
Some of the techniques, notably beam forming, are already used for base stations but not yet for portable terminals outside military use. The wider frequency ranges implied by smart spectrum suggest that smart antennas will find a wider role and there is much ongoing research in this area.
A card with an embedded chip - typically of credit card size for banking and many other markets or of another form factor, such as is used for GSM mobile phone SIM cards. In many applications they have replaced simpler magnetic strip cards. They are widely used for phone cards and payment and credit cards as well as for SIM cards. They are developing to embrace retail loyalty cards and, in conjunction with biometrics, for security and ID applications as well as for multi-purpose applications.
The chips contain storage (memory) and may have processing capability. Phone cards use principally memory chips whereas mobile networks and banking use microprocessors and memory. The storage capability is being developed over time as the costs come down and the application requirements go up. The early low-end cards of 8k and 16k are already being replaced by 32k, 64k and 128k cards including Java cards. Technical innovation in this area is likely to continue. Early chips required metallic contact to be made but there is increasing interest in contactless technologies. These are already used for physical access systems and there is further interest in them for transactions where speed and convenience are important including the possibility of biometric passports. Contactless technologies require a reader in close proximity and use wireless technologies similar to RFID tags.
Many applications making use of smart cards are Government based: examples include national ID cards in Hong Kong, Italy, Japan, Malaysia, South Africa and the UAE; health cards in Taiwan; driving licences in India; military ID cards in the USA. In general these applications provide easy identification, with future extensibility to biometrics, and result in decreased fraud with extra benefits such as the potential for the future integration of applications.
Massively distributed sensor networks. Nodes will be completely autonomous and small. Each will contain a sensor, electronics, power supply and a communications capability. A network may contain hundreds or many thousands of nodes. Eventually each node may be contained in a cubic millimetre using various nanotechnologies but initially they may are the size of a bar of soap reducing to the size of a coin. They have military and civilian applications. Also see motes.
Smart networks
Another name for intelligent networks.
Smart radios embrace several concepts but all imply software re-configurability. This can apply at all the communications layers of the terminal and has impact on the core network as well. For example, the air interface physical link, the coding and multiplexing requirements can be changed by software to adapt to different standards (e.g. to switch between 3G and WLAN). Or it can apply at the applications level to provide new services and applications which in turn imply matching capabilities in the core network and at the service provider. Some military radios and some base stations already adopt this approach to some extent but the potential lies in re-configurability of hand-held terminals as processing capabilities and chip design evolves. The software can be configured at the outset or by, for example, using a smart-card which may itself be re-configured over a fixed connection or perhaps the ultimate aspiration, being re-configured over the air.
Smart radios are variously known as re-configurable radios, software radios, software based radios (SBR) and software defined radio (SDR). They hold out the promise of a single re-configurable multi-mode, multi-band terminal capable of operating in several or all of the different wireless access environments. They may thus overcome the Achilles Heel of wireless – too many standards – and facilitate even wider implementations.
Spectrum is finite and the demands for it are increasing but any part of the spectrum that is not used at any place or time is effectively wasted. This may remain true for remote areas and oceans but an alternative to static band-allocation exists for more populous regions. The traditional approach has been to re-use frequencies by limiting power outputs (the basis of the cellular concept) but it will be possible for radios to dynamically find unused spectrum and then use it. Such an approach will need regulatory changes for dynamic spectrum allocation based on international agreements but such changes are already under consideration in some countries. Radio terminals must develop in their processing capability to handle the changes needed not just at the physical air-interface but at higher levels as well.
Smart spectrum is also known as dynamic spectrum assignment or free spectrum. In this case free means vacant not free of cost.
An application programming interface (API) developed as part of TCP/IP (the basic protocols of the Internet, standing for transmission control protocol and internet protocol) that allows applications to access the communications protocols.
A switching system realised in software and operating on a server. It provides the call-control, switching, signalling and intelligence for telephony calls over IP networks (voice over IP), including interfacing to traditional circuit-switched telephony networks. A softswitch can be a PBX or be part of a public switching system.
The definition of a softswitch and its architecture is not tightly defined but it generally assumes that the interface to the IP network is via gateways which in turn interface to the call servers. The call servers provide the call-control and the intelligence and like IN the call server software analogous to the operating system of a computer. Further back-end servers provide service management capabilities and links to established operational support systems (OSS). Some definitions of softswitch only embrace the call servers. An important function of a softswitch is to handle interconnection with the existing circuit-switched network through the use of signalling system number 7 (SS7). Other key protocols are the service initiation protocol (SIP) and H323.
This is a technology to provide reconfigurable mobile communications systems. These will have a key role in seamless network convergence, at least across different types of wireless networks and possibly across all networks as untethered terminals become more widespread. This is because a major assumption in the concept is for a single re-configurable multi-mode multi-band terminal. This would be capable of operating in several or all of the different wireless access environments and support a wide range of applications. More broadly, the aim is to provide a common platform for running software, updated by software downloads, which will enable reconfigurable radio protocol stacks thereby increasing the capabilities and versatility of the network and terminals. With the proliferation of open APIs, software from different vendors will be able to run on proprietary hardware platforms. On such platforms the air interface protocols as well as the applications will be executed under the control of a common software environment. Software defined radio therefore concerns all communication layers of the radio interface, from the physical layer to the application layer, and impacts both the mobile terminal and the network.
During the definition stage of project management a solution design, or high level design, can be undertaken. It follows an architecture and sets the scene for detailed design activities. A solution design includes the costs to be used in a business case, normally authorised before detailed design commences.
A form of propagation where the energy reaching the receiving antenna arrives through the earth's troposphere, i.e. the portion of the earth's atmosphere in the first 15km adjacent to the earth's surface. At frequencies above about 20 - 30 MHz (dependent on the sun-spot cycle) the ionosphere is not able to refract energy to earth. The energy comprises two elements, a direct ray travelling between the transmitting and receiving antennas and a path involving a reflection from the ground. The latter is affected by the curvature of the earth and is less important at ultra high frequencies (see radio waves) and above, leading to the need for line-of-sight propagation. See also ground waves, ionosphere and sky waves.
Unwanted and unsolicited e-mail, or message posted in chat room or on a news group. Most frequently it is untargeted commercial e-mail from sources that disguise or conceal their identity, make fraudulent claims, purvey goods or services that are illegal or provide no genuine 'opt-out' provision. Sometimes an off-topic message in a news group. Spamming is the act of sending it. A spammer is the person or machine sending it.
The radio spectrum is a part of the electromagnetic spectrum, ranging from very low frequencies (3 kHz) to extremely high frequencies (300 Ghz) and then on to 3000 Ghz. There are many users of radio spectrum not just telecommunications - radio and television broadcasters, radar and military applications are just some of the better known examples. To ensure that the world can share the resources on a fair and equitable basis the ITU-R has developed radio regulations for spectrum allocation through the World Radio Conferences (WRC) held every few years. As the number of devices communicating by wireless grow so the need for greater efficiencies in the use of spectrum grows. Spectrum that is not being used at any place or time is being wasted and dynamic spectrum allocation, assignment and utilisation is seen as a possible way forward as the hardware and software in terminal devices is better able to handle the issues involved - see smart spectrum.
Further information on spectrum management can be found in the following papers.
Radio spectrum management for tetherless communications, BTTJ, Vol 21, No3.
Radio spectrum for mobile networks, BTTJ Vol 14, No 3.
Speech is the easiest, most expressive and most natural form of human communication. It not only conveys words or ideas it also conveys gender and the essence of emotion, moods and personality including clues to approximate age, educational background and so on. Despite the rise of digital data there is no doubt that transmitting voice remains one of the core activities of telecommunications companies. The technologies associated with the transmission of speech are to be found throughout this encyclopedia. Other technologies, such as speech synthesis (machine generation of speech) and speech recognition are covered in the following paper.
Speech technology for telecommunications, BTTJ, Vol 14, No 1.
Generally used to refer to the bit rate of a digital transmission path and is the digital equivalent of bandwidth.
A program that interrogates web resources (web pages, files etc) and collects information which it deposits into a database. Spiders provide useful information such as that used by search engines but can also be used to collect benign information, such as e-mail addresses used for spam.
Alternative names for a joint/jointing, i.e the activity associated with joining together two separate lengths of cable by connecting each conductor or fibre separately and then sealing the end result.
Spread-spectrum is one of many military technologies to break through to the civilian sector. It originated as a means of making interception of radio traffic difficult or impossible. The aim was either to spread the signal out over a large defined bandwidth or to make use of a large bandwidth by constantly hopping between different frequencies in the defined band of operation. This leads to the two main types of spread-spectrum signals: DSSS (direct sequence spread spectrum) and FHSS (frequency hopping spread spectrum). The frequency hopping version came first. The techniques are now used widely in telecommunications. Wireless LANs using the IEEE 802.11 standard make use of DSSS whereas Bluetooth makes use of FHSS. CDMA as used in cellular radio systems is a form of DSSS.
A shortened form of the ITU-T Signalling System No 7. See also signalling and C7.
In the telecommunications world there has been a long history of trying to avoid proprietary solutions built on protected intellectual property. This has been driven by a need for interworking on a global scale and for competitive purchasing policies with second and third suppliers to give continuity of supply and competitive prices together with minimum costs of integration. This has led to a need for internationally agreed standards of which the ITU recommendations are the most important.
Standards are vital, but not glamorous. There is a huge amount of work involving high levels of expertise and ‘politics’ to get them into place that is little understood by the many who subsequently apply them. Standards are created by leaders in their field many of whom are world renowned but once in place standards are taken for granted and forgotten but last for many years. Without them there is mayhem.
Standing Wave/Standing Wave Ratio (SWR)
A term used in transmission-line theory which is of more practical relevance at radio frequencies. A single frequency signal transmitted into a pair of wires or a co-axial cable will consist of a wave travelling from the source to the destination, or load, called an incident wave and a wave travelling back towards the source reflected by the load called a reflected wave (see reflection). The nature of the reflected wave will depend on the degree of matching of the impedance of the load to the impedance of the transmission line. A perfectly matched load will not result in any reflections but this is very hard to produce in practice. At any instant along the transmission line, therefore, the voltage and current can conveniently be expressed as the sum of the voltages and currents of the incident wave and the reflected wave and this resultant is referred to as a standing wave. The standing wave ratio (SWR) is a measure of the ratio of the reflected to the incident wave. This is useful because it is easy to measure and provides information about the extent of standing waves and helps us measure impedance. An SWR of unity indicates the absence of a reflection and hence perfectly matched transmission line and load impedances. A very high SWR indicates problems because a theoretically lossless line with an open or short circuit would produce an infinite SWR.
One of the basic forms of networks.
Current storage networking solutions no longer require directly attached storage-to-server connections, which makes for a more flexible and cost effective storage solution. This overcomes one of the main drawbacks to the traditional storage approach - that storage traffic can degrade the performance of the LAN/WAN as client-server transactions are implemented. Deployment of a SAN provides a significant benefit as storage traffic flows are isolated from the LAN/WAN and hence the end user. The key elements of the storage network include the SAN switch, directors, servers and storage subsystems/storage devices. See also Storage area networking - an introduction and future development trends, BTTJ, Vol 20, No 4.
Another name for a computer controlled switching system. In the early days of switching a manual operator controlled all calls, switching each one in turn, a form of centralised call-control. The mechanisation of switching led to step-by-step (Strowger) and crossbar systems with distributed but hard-wired logic for call-control. Telephony circuit-switching moved to computerised call-control in the USA Bell system with the introduction of the No 1 ESS switch in 1965. This used the computer for centralised call-control functions and became known as stored programme control (SPC) after the programmes stored on the computer. The later introduction of microprocessors meant that even SPC moved to being distributed throughout the exchange but still under the overall control of a central processor.
A means of transmitting voice and/or video over packet networks such as the Internet. The signal can be received to all intents and purposes as it is sent rather than having to send the whole content before listening/viewing, as with a file. In practice it is buffered for a short period at the receiving end to equalise any inconsistencies of packet arrival. It is widely used for recorded and live radio over the Internet and to a lesser extent, until the ubiquitous availability of broadband links, to video.
An electro-mechanical switching system named after an undertaker who invented an automatic switching system to stop his business being diverted to a competitor by telephone operators.
A cabling system for telecommunications services in a building that allows for changes and expansion.
An archaic term for customer and dating back to the very early days of telephony when people subscribed a fixed sum for telephone service. With the passage of time and the proliferation of services and charging mechanisms the term customer has largely taken over but the old usage persists, notably in mobile networks with the subscriber identity module (SIM card).
See Group
Generally associated with ISDN, they are services that have no purpose on their own as they have to be used in conjunction with a bearer service (such as a speech or data channel) to which they add supplementary value. An example is ring back when free.
Generally taken to mean surfing the web, meaning going from page to page following the hot links (URLs) on the pages, using the browser 'back' button and also listed favourites. Sometimes with a specific goal in view but sometimes aimlessly in the hope of finding something of interest.
The essence of switching is to be able to connect one telecommunications terminal (e.g. a telephone) to any other of a similar type, in a number of stages. In connection-oriented mode and translating this into an individual switch matrix, it is to connect n inlets to n-1 outlets (the "minus 1" arising because it does not want to connect to itself) and to do it reliably, economically and with good transmission performance. Achieving this has resulted in an evolution of switching types and principles over more than 100 years. They are still evolving, and probably always will.
You should also be aware of the concepts of connection-oriented and connectionless.
The more detailed section on switching describes switching systems in more detail including circuit switching, message switching, packet switching, frame switching, cell switching, label switching and softswitching. Packet switching is closely allied to routing. Business systems also have their own variations, for example PBXs for circuit switched voice and Ethernet and FDDI for data.
A software licencing company, owned by companies in the wireless field, that is developing an operating system for data-enabled mobile devices, including mobile phones.
A term for ad-hoc networks implying a close symbiosis between nodes. This term implies that any negative effects of ad-hoc networking between nodes of different ownership, such as resource sharing, are overcome. See Symbiotic Networks, BTTJ Vol 21, No 3.
In digital transmission it is the basic unit of a signal and the symbol rate is the number of changes of state per second. The number of symbols per second is the Baud rate which is not necessarily the same as the bit rate, although it is in a two state system. With complex line codes (more than two states: ternary, quaternary, N-ary) the bit rate can be many times the symbol rate. Such codes allow a larger bit-rate to be accommodated than the line would support using simple binary codes. Intersymbol interference (ISI) occurs when a symbol in one time interval becomes distorted and overlaps the time interval of another symbol.
A symbol can also be a representation of something else: such as Z for impedance.
Synchronisation is of fundamental importance to the performance of digital networks. The effects of poor timing on the information being transported are often largely ignored. Synchronisation distributes information about time and frequency across a network of clocks over a wide geographical area. The goal is to align (i.e. synchronise) the time and frequency scales of all clocks by using the communications capacity of their interconnecting links. See Synchronisation in data networks, BTTJ, Vol 16, No 1.
Two signals are said to be synchronous when they are isochronous digital signals whose respective timing signals have the same frequency and have a controlled phase relationship. See also isochronous, mesochronous, plesiochronous and heterochronous.
Synchronous Digital Hierarchy (SDH)
This is the name given by the ITU-T to the world standards covering synchronous transmission, principally used in core networks for long-distance transmission, although it has made some progress in fibre access systems serving large customers. It was an evolution at the time from plesiochronous multiplexing systems which required much more equipment. Its benefits therefore included reduced equipment cost; lower maintenance costs including lower spares holdings and power standby equipment; increased reliability; and modular upgrades. More information on SDH and its relationship to the earlier plesiochronous hierarchy is given in Broadband transport - the synchronous digital hierarchy, BTTJ, Vol 16, No 1 and in its relationship to optical networks in Evolution of optical core networks, BTTJ, Vol 20, No 4.
Synchronous Optical Network (SONET)
This is the name given to the USA-based equivalent of SDH. Although the two standards are not directly compatible they were evolved at the same time with allowances made for interworking between the two.
A very general term with many nuances when used on its own. A source of misunderstanding where one person means something different to another and where the difference is not even apparent in face-to-face conversation. At its most general it can refer to organised collections of equipment, networks, software, people or procedures. It is generally safer to qualify it with an associated word or words, e.g. systems design. It is also often used as a shorthand version of Operational Support Systems meaning all the software support systems needed to control and run a network, hence an often frequently used coupling of "networks and systems". As a network that cannot be managed is of little use and management systems on their own of no use then the coupling is tautological and system may as well be used on its own.
An activity at the beginning of a computerisation project where the requirements are deduced by an analysis of the existing processes. The person carrying out the activity is called a systems analyst.
A high level design which determines all the sub-systems and component parts of the system to meet the requirement.
Systems Engineering is an all-embracing term that covers the whole process of creating effective solutions to problems and managing the complexity of the resulting technical developments. It covers everything from customer needs, requirements capture, feasibility and definition (possibly including modelling), architectural principles, systems design, development, prototyping, integration testing, trials/pilots, installation, implementation and ongoing support. The whole process is invariably so complex that formal project management techniques are required to achieve successful implementation.
Book: Systems Engineering - coping with complexity. Richard Stevens, Peter Brook, Ken Jackson, Stuart Arnold. Pub: Prentice Hall, 1998. ISBN 0-13-095085-8.
As explained under integration there is a continuum of integration activity from component level to system level. System integration in telecommunications operating companies is concerned with the integration of large elements of networks and, usually, with the network and its operational support systems (OSS) as well. It is aimed at verifying end-to-end service capabilities across the diverse parts of the system that make up those services or of verifying that a new element (such as a telephone exchange or OSS software upgrade) does not adversely affect existing services and capabilities.
The paper Systems integration throughout the early life cycle describes various methodologies and approaches for performing systems integration and testing.
See also and testing including the related paper Automated testing as an aid to systems integration, BTTJ, Vol 15, No 3.
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