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Eskom Telecommunications

Assignment

• Use Wikipedia to lookup the following terms:• SDH systems• PDS systems

• Power line communication

Core ActivitiesProvide Support to Eskom’s Core Activities• Teleprotection• Telecontrol• Data: Frame Relay / P-to-P / X.25• Voice Services: Direct / Switched• Area Coverage

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What is X.21?X.21 is the electrical specification interface recommended by the CCITT in 1976.

It is defined as a digital signalling interface between customers (DTE) equipment and carrier's equipment (DCE). And thus primarally used for telecom equipment.

All signals are balanced. Meaning there is always a pair (+/-) for each signal, like used in RS422.

Electrally the X.21 signals are the same as RS422, so please refer to RS422 for the exact details.

Core Activities

What is X.25?

X.25 was used for permanent virtual circuits (PVCs) to connect two host computers in a dedicated link.

This was common for applications using dumb terminals to connect to host computers.

Speeds from 2400bit/s up to 2 Mbit/s, although speeds above 64 kbit/s were uncommon.

What Is Frame Relay?Frame relay consists of an efficient data transmission technique used to send digital information quickly and cheaply in a relay of frames to one or many destinations from one or many end-points.

Network providers commonly implement frame relay for voice and data as an encapsulation technique, used between local area networks (LANs) over a wide area network (WAN).

Each end-user gets a private line (or leased line) to a frame-relay node. The frame-relay network handles the transmission over a frequently-changing path transparent to all end-users.

What is P-to-PA?Peer to peer (or "P2P") networks use diverse connectivity between participants in a network and the cumulative bandwidth of network participants rather than conventional centralized resources where a relatively low number of servers provide the core value to a service or application.

Peer-to-peer networks are typically used for connecting nodes via largely ad hoc connections. Such networks are useful for many purposes. Sharing content files such as FTP containing audio, video, data or anything in digital format is very common, and realtime data, such as telephony traffic, is also passed using P2P technology

Provides Telecoms services to:

• System Operations & Planning• Transmission Group• Distribution Group• Generation Group

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SDH Backbone

• SDH (Synchronous Digital Hierarchy) Backbone Network• 622 Mbit/s Fibre Optic - 5 links - 95 kms (Gauteng area)• 155 Mbit/s Fibre Optic / Radio - 100 links• 51 Mbit/s Radio - 57 links

Synchronous networking uses exact timing to transport the data and is tightly synchronized across the entire network, using atomic clocks.

This synchronization system allows entire inter-country networks to operate synchronously, greatly reducing the amount of buffering required between elements in the network.

SDH networks are configured to be highly redundant, with fibre optic networks providing backup. The optimum network topology is a ring.

Data Flow155 Mbit/s

Add / Drop Multiplexer: allows the insertion (add) or removal (drop) of the required bandwidth from an SDH signal passing through the multiplexer.

1 x 155 Mbit/s + monitoring has 62 x E1 circuits running at 2M/Sec

Add / Drop Multiplexers

1 x 2Mbit/s circuit has 30 x 64 Kbit/s circuits + monitoring

155 Mbit/s

9600 Kbit/s

155 Mbit/s

RTU TEMSE

9600 Kbit/s

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PDH Systems

• PDH Systems• 34 / 16 / 8 / 4 / 2 Mbit/s Radio links - 443• 8 / 4 / 2 Mbit/s Fibre Optic links - 142• Used to connect between sites or from a site to a backbone site• Fibre optic typically used shorter distances• Diverse fibre routes on campus environments

PDH SystemsThe Plesiochronous Digital Hierarchy (PDH)

• A technology used to transport large quantities of data over digital transport equipment such as fibre optic and microwave radio systems.

• The term plesiochronous is derived from Greek plesio, meaning near, and chronos, time, and refers to the fact that PDH networks run in a state where different parts of the network are nearly, but not quite perfectly, synchronised.

• PDH is now being replaced by Synchronous Digital Hierarchy (SDH) equipment.

• PDH allows transmission of data streams that are nominally running at the same rate, but allowing some variation on the speed around a nominal rate.

• By analogy, any two watches are nominally running at the same rate, clocking up 60 seconds every minute. However, there is no link between watches to guarantee they run at exactly the same rate, and it is highly likely that one is running slightly faster than the other

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2 Channel Radio Links

• 248 Links• Mainly connect Area Coverage repeaters back to a higher-capacity link• Operate in the 406 / 416 MHz and 450 / 460 MHz bands

Power Line Carriers

• Primary function is Teleprotection• Single Channel• Audio 300 to 2 700 Hz• Super Audio 2 900 to 3 400 Hz• Only used for voice in exceptional circumstances

• All power line communications systems operate by impressing a modulated carrier signal on the wiring system.

• The propagation problem is a limiting factor for each type of power line communications

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Line Trap

Power Line Carriers

• A power line carrier is communication equipment that operates at radio-frequencies, generally below 600 kilohertz, to transmit information over electric power transmission lines.

• A high frequency signal is superimposed on the normal voltage on a power circuit.

• The power line carrier is usually coupled to the power line by means of a coupling capacitor in conjunction with a line trap.

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Network Design Philosophy

Network Design Philosophy• SDH Extended “Rings”• Centrally Managed• Largely influenced by the power network• Criticality “A” : 3 Diverse routes / 2 technologies• Criticality “B” : 2 Diverse routes• Criticality “C” : Single route; repair time better than 8 hours

Eskom Telecommunications

Radio Link

Fibre Optic

51 Mbit/s

622 Mbit/s

155 Mbit/s

8 Mbit/s

Simmerpan (A)Jupiter (B)

Eiger (B)

Rigi (C)

Glockner (B)

Lethabo (B) Brakfontein

Simmerpan

Megawatt Park (A)

ErmeloVaalkop

To Natal

Alpha

Elandsfontein

Duvha /Standby NCC

Pluto (B)

To NatalTo Cape

Fontana

Vulcan (B)

Majuba PS

Hekpoort

Midas (C)

Driehoek

Apollo (B)Minerva (B)To Nth Province

EloffSunnyridge

Witbank

Kendal PS (B)

To Nth Province

Croydon (C)

Northrand (C)

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Questions

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SDH Frame

The first 9 columns contain the overhead and the pointers. For the sake of simplicity, the frame is shown as a rectangular structure of 270 columns and 9 rows, but the protocol does not transmit the bytes in this order in practice

For the sake of simplicity, the frame is shown as a rectangular structure of 270 columns and 9 rows.

The first 3 rows and 9 columns contain Regenerator Section Overhead (RSOH) and the last 5 rows and 9 columns contain Multiplex Section Overhead (MSOH. The 4th row from the top contains pointers

STM-1 Frame

The STM-1 (Synchronous Transport Module level - 1) frame is the basic transmission format for SDH.

The STS-1 frame transmitted in exactly 125 microseconds.

Therefore, there are 8000 frames per second on a fiber-optic circuit designated OC-1 (optical carrier one).

The STM-1 frame consists of overhead plus a virtual container capacity.

The first 9 columns of each frame make up the Section Overhead, and the last 261 columns make up the Virtual Container (VC) capacity.

The VC plus the pointers (H1, H2, H3 bytes) is called the AU (Administrative Unit).

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STM-1 FrameCarried within the VC capacity, which has its own frame structure of nine rows and 261 columns, is the Path Overhead and the Container .

The first column is for Path Overhead; it’s followed by the payload container, which can itself carry other containers. Virtual Containers can have any phase alignment within the Administrative Unit, and this alignment is indicated by the Pointer in row four,

The Section overhead of an STM-1 signal (SOH) is divided into two parts: the Regenerator Section Overhead (RSOH) and the Multiplex Section Overhead (MSOH).

The overheads contain information from the system itself, which is used for a wide range of management functions, such as monitoring transmission quality, detecting failures, managing alarms, data communication channels, service channels, etc.

The STM frame is continuous and is transmitted in a serial fashion, byte-by-byte, row-by-row.

STM–1 frame contains

• Total content : 9 x 270 bytes = 2430 bytes

• overhead : 9 rows x 9 bytes

• payload : 9 rows x 261 bytes

• Period : 125 µsec

• Bitrate : 155,520 Mbit/s (2430 x 8 bits x 8000 frames/sec )

Equipment Types• Alcatel : SDH Radios / ADMs / Element Manager R2L & R1.5 PDH Radio Links• Alcatel (Newbridge): 28 of 3645s / 290 of 3600s / 574 of 3630s / 85 FRE / Dual

5620 E M • DMC: 15 / 23 GHz PDH Radio Links• Plessey: PDR 23 PDH Radio Links• Timeplex: Synchronisation equipment

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Fibre Optic Technologies on Power Lines

• OPGW (Optical Fibre in Ground Wire) > 132 kV• ADSS (All Dielectric Self Supporting) < 132 kV• GWWOP (Ground Wire Wrapped Optical Fibre)• Add Lash

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Network Expansions

• 155 Mbit/s SDH Fibre Optic to Windhoek• 622 Mbit/s SDH Fibre Optic to Swaziland / Maputo• Under Investigation:

– Fibre Optic cable Ellisras / Selibwe Pikwe (Botswana) / Bulawayo (Zimbabwe)

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Second Network Operator

Second Network Operator• Eskom Telecommunications allocated 15%• Rolled out - 4600 Km fibre optic cable• NOC established• Equipment containers being commissioned• (n+1) 2.5 Gbit/s backbone• POPs established• R1 Billion spent so far

Both SONET (Synchronous Optical Network) and SDH can be used to encapsulate earlier digital transmission standards, such as the PDH standard, or used directly to support either ATM or so-called Packet over SONET/SDH (POS) networking.

As such, it is inaccurate to think of SDH or SONET as communications protocols in and of themselves, but rather as generic and all-purpose transport containers for moving both voice and data.

The basic format of an SDH signal allows it to carry many different services in its Virtual Container (VC) because it is bandwidth-flexible.

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Long Distance Fibre Optic Backbone

George

Namibia

Bethlehem

Botswana

Klerksdorp

Mozambique

Poseidon

Swaziland

Umtata

Kenhardt

Maputo

ManziniErmelo

Gaberone

Ellisras

Welkom

LadybrandLesotho

Copperton

Rustenburg

Mosselbay

Stellenbosch

Potchefstroom

Cape Peninsula

Tongaat

New Castle

Alice

BritsZeerust

Leeudoringstad

Rhodes

Aggeneys

Vereeniging

Saldanha

Pietersburg

Beit Bridge

Business Opportunities

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Network Management• Network Management Control Centre Operates 24x7• Provides full FCAPS capability• SLA Management• Fault Centre• Spares Management

Operations and Field Services

• Technical Staff - Approx. 270 (NTD / B.Sc) • Main Centres - E. Cape, W. Cape, KZN, Witbank, Bloemfontein and Gauteng.• Satellite Centres - Pietersberg, Rustenberg, Pietermaritsberg, Kimberly,

Klerksdorp and Nelspruit

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Service Level AgreementsAvailabilities (real time)• Platinum 99.9% (max - 4 hrs per incident, 8hrs 46 mins per annum, total

window).• Gold 99.6%• Silver 99.2%• Bronze 98%

Business Diversity• Eskom - Gx, Tx, Dx and System Operations transmission services• Arivia.kom - IT and internet services• ATNS - bandwidth and services• Caledon Casino CT - Siemens EMS601 mntce• Logitel - Agency • Cell Direct - Agency

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Questions