GSM Cell

The number of cells in any geographic area is determined by the number of MS

subscribers who will be operating in that area, and the geographic layout of the area

(hills, lakes, buildings etc).

The maximum cell size for GSM is approximately 70 km in diameter, but this is

dependent on the terrain the cell is covering and the power class of the MS. In GSM, the

MS can be transmitting anything up to 8 Watts; obviously, the higher the power output of

the MS the larger the cell size. If the cell site is on top of a hill, with no obstructions for

miles, then the radio waves will travel much further than if the cell site was in the middle

of a city, with many high-rise buildings blocking the path of the radio waves.

Generally large cells are employed in:

_ Remote areas.

_ Coastal regions.

_ Areas with few subscribers.

_ Large areas which need to be covered with the minimum number of cell sites.

Small cells are used where there is a requirement to support a large number of MSs, in a

small geographic region, or where a low transmission power may be required to reduce

the effects of interference. Small cells currently cover 200 m and upwards.

Typical uses of small cells:

_ Urban areas.

_ Low transmission power required.

_ High number of MSs.

There is no right answer when choosing the type of cell to use. Network providers would

like to use large cells to reduce installation and maintenance cost, but realize that to

provide a quality service to their customers, they have to consider many factors, such as

terrain, transmission power required, number of MSs etc. This inevitably leads to a

mixture of both large and small cells.

 

 

Frequency Re-use

Standard GSM has a total of 124 frequencies available for use in a network. Most

network providers are unlikely to be able to use all of these frequencies and are generally

allocated a small subset of the 124.

We will take an example here suppose a network provider has been allocated 48 frequencies to provide coverage over a large area, let us take for example Great Britain.As we have already seen, the maximum cell size is approximately 70 km in diameter,thus our 48 frequencies would not be able to cover the whole of Britain.

To overcome this limitation the network provider must re-use the same frequencies over and over again, in what is termed a “frequency re-use pattern”. When planning the frequency re-use pattern the network planner must take into account how often to use the same frequencies and determine how close together the cells are, otherwise co-channel and/or adjacent channel interference may occur. The network provider will also take into account the nature of the area to be covered. This may range from a densely populated city (high frequency re-use, small cells, high capacity) to a sparsely populated rural expanse (large omni cells, low re-use, low capacity).

Principles of Cellular Telecommunications

A cellular telephone system links mobile station (MS) subscribers into the public

Telephone system or to another cellular system’s MS subscriber.

Information sent between the MS subscriber and the cellular network uses radio

Communication. This removes the necessity for the fixed wiring used in a traditional

telephone installation. Due to this, the MS subscriber is able to move around and become fully mobile, perhaps traveling  in a vehicle or on foot.

Cellular networks have many advantages over the existing “land” telephone networks.There are advantages for the network provider as well as the mobile subscriber.

Network Components :

GSM networks are made up of Mobile services Switching Centres (MSC), Base Station Systems (BSS)and Mobile Stations (MS). These three entities can be broken down further into smaller entities; such as, within the BSS we have Base Station Controllers, Base Transceiver Stations and Transcoders. These smaller network elements, as they are referred to, will be discussed later in the course. For now we will use the three major

entities. With the MSC, BSS and MS we can make calls, receive calls, perform billing etc, as any normal PSTN network would be able to do. The only problem for the MS is that all the calls made or received are from other MSs. Therefore, it is also necessary to connect the GSM network to the PSTN. Mobile Stations within the cellular network are located in “cells”, these cells are provided by the BSSs. Each BSS can provide one or more cells, dependent on the manufacturers equipment.The cells are normally drawn as hexagonal, but in practice they are irregularly shaped, this is as a result of the influence of the surrounding terrain, or of design by the network

planners.

Frequency Spectrum :

The frequency spectrum is very congested, with only narrow slots of bandwidth allocated for cellular communications. The list opposite shows the number of frequencies and spectrum allocated for GSM, Extended GSM 900 (EGSM), GSM 1800 (DCS1800) and PCS1900. A single Absolute Radio Frequency Channel Number (ARFCN) or RF carrier is actually a pair of frequencies, one used in each direction (transmit and receive). This allows information to be passed in both directions. For GSM900 and EGSM900 the paired frequencies are separated by 45 MHz, for DCS1800 the separation is 95 MHz and for PCS1900 separation is 80 MHz. For each cell in a GSM network at least one ARFCN must be allocated, and more may be allocated to provide greater capacity. The RF carrier in GSM can support up to eight Time Division Multiple Access (TDMA) timeslots. That is, in theory, each RF carrier is capable of supporting up to eight simultaneous telephone calls, but as we will see later in this course although this is possible, network signalling and messaging may reduce the overall number  from eight timeslots per RF carrier to six or seven timeslots per RF carrier, therefore reducing the number of mobiles that can be supported. Unlike a PSTN network, where every telephone is linked to the land network by a air of fixed wires, each MS only connects to the network over the radio interface when required. Therefore, it is possible for a single RF carrier to support many more mobile stations than its eight TDMA timeslots would lead us to believe. Using statistics, it has been found that a typical RF carrier can support up to 15, 20 or even 25 MSs. Obviously, not all of these MS subscribers could make a call at the same time, but it is also unlikely that all the MS subscribers would want to make a call at the same time. Therefore, without knowing it, MSs share the same physical resources, but at different times.

Composition of low-voltage systems

Structured cabling systems greatly simplify and optimize the management of various cable systems, since the installation of SCS allows you to combine them into a single information space. SCS include information, telephone, security and fire protection and so on. network, various switchgears, cables, control panels, necessary equipment, etc.
Design by SCS at the stage of construction. This requirement will create a literate project distribution of communications and connectivity for all cable systems to a single hardware node - the control center structured cabling system.
Local-area networks provide the following: resource sharing networks (modems, printers, files, and so on.) Reserve funds and storage of different information, the ability to quickly access the necessary information in the network information is protected from hacking, to work with modern means of enhancing the effectiveness of working process (electronic document management system, receiving and sending faxes, online databases, uninterrupted Internet access).

Automatic telephone stations are used to create a rapid and reliable telephone communications between departments and offices of the company. On the design and installation of ATS should also be approached intelligently. You must select a telephone station, to carry out programming and configuration of equipment and trained personnel to use the telephone station.

The system-clockwise and radio include: basic elements - the master clock and the secondary clock (interior, street, etc.); tuner - radio receiver, the receiver wire broadcasting, switching (jumper) equipment, aerial devices, line equipment.
This system provides indexing lap, Moscow and Greenwich Time; indication of the number, day of week, month and year, the alarm went off at the scheduled time, input signals a single time in a synchronized hardware. System indexes the level of background radiation.
World total time is measured ultra-precise atomic clocks that transmit signals to a satellite global positioning system (GPS), where the radio signal is received which were in connection with the master clock. Master clock, in turn, combined with the secondary clock (digital, switch, etc.), making the whole system shows the exact time.
Thus, low-voltage systems are designed to satisfy the most diverse aspects of modern life. Thanks slabotochke, our lives become more convenient, comfortable and safe. Home and office we are doing chores, relax and socialize, do not hesitate to organize the points needed to optimize the residential and commercial spheres of human activity. Modern equipment running smoothly, thanks to low-voltage systems, controls the situation in the home or office. And all that is required of us - is to learn to use new, accessible to every opportunity for his own benefit.

Designing low-power networks

The problem of designing "slabotochki" should be approached with understanding of its special importance, because the low-voltage systems will operate without problems only if well-designed project of installation. Ask for help is a professional design engineers. The project should be conceived not only in terms of literacy to accommodate objects of different sites (low-current flap, sockets, switches and so on.) Wire harnesses on the risers, but in accordance with established norms and standards, which are governed by SNIP 083-98.

Total regulatory documentation to be followed is as follows: GOST 21.101-97 "Basic requirements for design and documentation; RD 78.36.002-99" Technical means of security objects. Graphical symbols of system elements; SEP 7, "Electrical Code"; RD 78.145-93 "systems and systems security, fire and burglar alarms. Rules of production and acceptance of work; SNIP 3.05.06-85 "Building Regulations. Electrical devices; NPB 105-03 "Determination of categories of rooms, buildings and outdoor facilities for the explosion and fire hazard."

Of course, do not forget about the designer design room, where all the attributes of low-voltage systems must seamlessly fit.

To compile the project engineer to the Terms of Reference, which reflected the following aspects: the technical conditions for connection, the plan of the building design project facilities, the plan adjacent protected areas. Also need to pre-departure of the expert on the subject.

New Event Explains Polymer Production Efficiency

Four UK polymer companies will hold a new one-day conference entitled 'Improvement in Production Efficiency', which is aimed at increasing performance and efficiency in the processing of plastics. GandA Moulding Technology, a plastics consultancy and training provider, will host the event at its Peterborough facility on 13 April 2010 and will repeat it the following day. This is in conjunction with machinery supplier Premier Moulding Machinery (PMM), polymer distributor Velox (UK) and Triton Technology.

The conference will consist of a series of papers and practical demonstrations intended to be of interest to polymer processors that are seeking to boost their own production efficiency. At the event, GandA will present its Pro-Op process-optimisation software, which allows users to optimise their processing in a step-wise and logical approach, with an emphasis on process consistency and component quality and, as a consequence, a fall in energy costs through the reduction of scrap and downtime.

PMM will present the Venus series of all-electric injection-moulding machines from Zhafir Plastics Machinery. The Venus series can result in 20 to 70 per cent less energy consumption compared with hydraulic machines and a 10 per cent lower consumption than other general servo machines. PMM will hold a live demonstration of the Asaclean purging compound and mould cleaner for extrusion and injection-moulding equipment. Triton Technology will show its Identipol QA, which uses Dynamic Mechanical Analysis (DMA) and Differential Scanning Calorimetry (DSC) to provide simple and cost-effective quality-assurance testing of mouldable thermoplastics.

It can help prevent the loss of time and money on sub-standard materials. Beyond practical demonstrations of the equipment and systems mentioned above, there will be talks on the advantages of injection-moulding technology training and the savings to be made by investing in power-efficient equipment.

ISD860 Drives Gives High Servo Performance Control

Based on Technosoft Motionchip DSP technology, ISD860 is a flexible intelligent drive. It has been developed for motion applications that require cost-optimised design, embedded intelligence, networking possibilities and high servo performance control. It is able to drive 12A continuous and 31A peak currents at a supply voltage ranging from 12 to 72V DC, with a PWM of 20 kHz frequency. Embedding motion controller, drive and PLC functionality in one 136 x 84 x 26mm unit, ISD860 controls brushless, DC or linear motors up to 860W continuous/2.2kW peak voltage.

Due to its advanced motion-control algorithms, a precise control of position, speed or torque over a range of dynamic conditions can be achieved. ISD860 works in single-axis, multi-axis or standalone configurations. The drive setup, tuning and motion programming are made simple with Easymotion Studio and Technosoft Motion Language (TML), according to the company. With ISD860, motion programming can be done from a CAN master, via PC/PLC, using the appropriate motion library, or directly at drive level through its built-in motion controller.

The embedded Technosoft Motion Language includes a high-level command protocol, which can be used by the host through the onboard RS232/CAN serial interfaces. A CANopen version of the ISD860 drive, supporting DS-301 and DSP-402 profiles, is also available. In standalone operation, ISD860 can be managed with programmable I/Os or analogue inputs. Using the TML language, multiple operations can be performed with ISD860: setting of various motion modes (profiles, PVT, PT, electronic gearing or camming, etc), change of motion modes and/or parameters, execution of homing sequences or program flow control.

At the same time, IDS860 can handle digital I/O and analogue input signals, execute arithmetic and logic operations, and transfer data between axes. The drive is able to control other axes via motion commands. ISD860 can send commands to a group of axes, or synchronise all the axes from a network. Flexibility and easy implementation make ISD860 suitable for higher-power motion axis-control using modern distributed intelligence architecture. The drive is suitable for cost-sensitive applications, from medical to factory automation, requiring high servo performance and enhanced compactness.

Esab Introduces Origo Tech 9-13 Welding Helmets

Esab's Origo Tech 9-13 range of welding helmets, masks and screens offer superior face, head, ear and neck protection. They are available in striking high-gloss colours and feature the Esab comfort headgear with a lightweight shell. Since they offer higher levels of security for the wearer, it is possible to use the Origo Tech 9-13 to weld in all positions. The Esab variable-shade ADF is screwed into a slightly curved cradle designed to seal out dangerous levels of light.

The front spatter lens is also curved for extra strength and security. The external shade-adjustment varies between DIN 9 and 13, which can be adjusted from inside the helmet. The helmet is suitable for MIG/MAF, MMA and TIG (more than 20A) welding. The 0700 000 296 model is primarily black and the 0700 000 298 helmet is mostly yellow. The Origo Tech 9-13 comes in an Esab display box, fully assembled and ready to use.

Also available from Esab is a comfortable, lightweight and durable battery-powered respiratory unit designed to snugly fit the Origo Tech welding helmets. This offers the welder clean, filtered air in some of the most challenging welding conditions, resulting in increased comfort and safety for the welder. The Origo Air comes with an eight-hour battery, P3 filter, comfort pad, waist belt and an air hose with a fitted Proban hose cover.

Every Origo Air comes with an intelligent charger to ensure prolonged battery life and reduce the risk of over-charging. The battery-powered air filter is also equipped with a low-flow alarm that makes a noise when it is blocked or the battery is running low.