The Telikom Public Switched Telephone Network (PSTN) is now predominantly digital. Alcatel System 12 digital exchanges and the Telrad DMS series of digital exchanges are now installed at all urban and major traffic centres throughout the country. Small stand-alone digital exchanges, remote switching units and digital line concentrators are also installed at some of the smaller or remote centres. As at March 2001, the network comprised more than 40 digital exchanges and remote units with total installed capacity of about 85,000 lines out of which about 62,200 are connected. About 50% of installed lines and connected subscribers are in the Southern Region.

This includes the Port Moresby Area in the National Capital District (NCD) where almost ninety per cent of the regional telephone lines and subscribers are installed.The NCD is presently served by three local exchanges at Boroko, Ela Beach and Gerehu. These exchanges are interconnected and integrated into the national network by an intra-city optical fibre transmission network. The three exchanges and their dependant remote switching units have a combined installed capacity of about 40,000 lines and connect about 30,000 subscribers. The other main regional transit and local exchanges that account for the remaining fifty percent installed lines and subscribers include Lae, Mt. Hagen, Tomavatur, Goroka and Madang. The others are Alotau, Wewak, Tabubil, Kimbe, Kokopo, Rabaul and Kavieng.

Telephone exchanges at Lae, Goroka, Hagen and Alotau are presently connected to the national network via digital microwave radio and satellite links while the others are connected via digital satellite links and analogue radio. Digital radio transmission is expected to be extended to Madang and Wewak during 2001, and to Kimbe, Tomavatur, Kokopo and Rabaul in 2002.

The National Transmission Network

The national transmission network comprises of a nationwide microwave trunk radio system that links all urban and major traffic centres. The trunk network also subtends to other towns and villages via small/medium capacity microwave radios. The terrestrial radio network is complemented by a domestic satellite system that provides alternate transmission to the major urban and provincial centres. Some regional or district networks also consist of intra-city optical fibre and/or PCM line transmission systems.

The Microwave Radio Trunk Network

The Telikom backbone microwave transmission network comprises a microwave radio ring linking four major network nodes and fifteen repeaters. The primary path of the transmission ring is a PDH microwave radio system linking Port Moresby, Lae, Goroka and Hagen. The secondary path on the ring network links Boroko with Hagen over a different transmission path. The analogue radio on this path is now being replaced with SDH radio that will soon be commissioned. This provides supplemental capacity as well as route diversity for the main path.

Each of the four major nodes on the radio ring network also constitutes points of interconnection for linear microwave trunk bearers that link other regional and provincial centres. These include the seven-hop Port Moresby-Alotau SDH radio link and the five-hop Hagen-Wewak analogue bearer. The latter is being replaced with SDH radio which will be commissioned before 2002. The other regional links are the Goroka-Madang and the Lae-Tomavatur bearers. Both bearers are still analogue but are now being replaced with digital systems. Other remote network nodes subtend from the backbone transmission network via low/medium-capacity analogue or digital radio spurs.

The Domestic Satellite Network

Domestic satellite service (DOMSAT) was introduced into the PNG national network with the establishment of a thin-route network in 1992. The interim DOMSAT, as it was then called, comprised of a master station in Port Moresby and eight VSAT-type earth stations located mainly at the operations sites of mining and exploration companies.With subsequent expansion, the network now consists of an 11-metre hub linking 26 remote terminals nationwide with antenna sizes raging from 1.8m to 4.5m. The network currently operates via the Palapa B4 (118^oE) satellite and comprises of three sub-networks as follows:

• Pre Assigned Multiple Access/Multiple Channel Per Carrier (PAMA/MCPC)

• Demand Assigned Multiple Access (DAMA)

• Time Division Multiple Access

These provide small capacity private leased lines for commercial banks and the mining and exploration companies. It is also used to provide subscriber lines in rural as well as in remote and isolated locations. The basic transmission rates are 64Kbit/s and 128Kbit/s.

Following the successful implementation of the interim DOMSAT system, a full DOMSAT network was established and put into service in 1995. The network initially comprised of a master station at the Gerehu Earth Station in Port Moresby and eleven remote terminals nationwide. The network has since been upgraded and now comprises of an 18 metre hub and twenty 7.0 metre remote terminals which are located at Telikom’s network nodes and terminals throughout the country. The network operates via a 72 MHz leased transponder on the Intelsat satellite IS 701 (180^oE) and provides IDR bearers with transmission rates from 512 Kbit/s to 2 Mbit/s. The network now provides supplemental transmission for the terrestrial microwave radio trunk network and restoration capacities for provincial and district centers. The terminals at Daru and Lorengau also replaced the obsolete troposcatter systems at these locations.

The NCD Fibre Optic Transmission Network

The first fibre optic cable was laid in November 1991 to provide intra-city communications links in Port Moresby. The major traffic nodes in the National Capital District (NCD) are now interconnected by the NCD intra-city optical fibre transmission network which is essentially a PDH star network that provide point-to-point transmission between Boroko and the other nodes. The primary links on the network are currently being upgraded from linear PDH links to higher capacity SDH self-healing rings with capabilities for automatic restoration of failed circuits. The upgrade is also to include the expansion and modernisation of the customer access network in the National Capital District. This, together with nodal switches and terminal equipment will culminate in the implementation of a Metropolitan Area Network.

Data Network

The Telikom Data Network presently comprises of three subnetworks – Digital Data Network, Packet Switched Data Network and Frame Relay Network.

Digital Data Network  

The Digital Data Network is based on the Telettra 513 MX 2Mbit/s Flexible Multiplexers and currently comprises of 29 nodes nationwide. It provides point-to-point leased line services offering data rates 2.4kbit/s – 64kbit/s with capability for nx64kbit/s. The network has a bandwidth of 2Mbit/s and maximum node capacity of 8Mbit/s. Inter-nodal trunk interconnection and subrack interconnection is at 2Mbit/s. The network is managed by a proprietary text based Circuit Management Operations Systems that provides fault, configuration, performance, and security management functions.

Packet Switched Data Network     

The Packet Switched Data Network is based on the Sprint 4900 series network equipment and consists of nine switches that are deployed throughout the country.The network supports X.25, X.75, X.28 and X.32 data transmission mode at data rate 2.4 – 64 Kbit/s for synchronous access. Although not implemented, the network can optionally support Frame Relay. Trunk lines (inter nodal) are duplicated for redundancy and can be up to 256 Kbit/s if provided with high-speed interface. Each node can support up to 96 ports.

The Network Control Centre for the NMS supports software module management, accounting, remote diagnostics, events and statistics reporting and dynamic updates of network elements/nodes tables. These functions enable the proprietary TP4850 NMS to initially obtain and load access information about every TP4900 node in the PSDN network and to remotely control the node. The NMS is mirrored with redundant links to two different TP4900 nodes (Boroko and Ela Beach)

Frame Relay Network

The Frame Relay Network consists of three Netrix switches at Boroko, Lae and Hagen. The switches initially operated as packed data switches before being re-commissioned in 1997 to operate as Frame Relay switches. The network is linked via the ATM switches at the same node locations and supports low speed V.24 and high speed V.35 circuits. The NMS application runs on HP Apollo hardware (Unix) and manages the network end-to-end.

International Links  

Two international gateway telephone exchanges diversely located in Port Moresby and Lae provide international connection to the rest of the world on digital circuits via satellite and submarine cable. Majority of these connections terminate or transit through Australia via the Telstra and the Optus networks. Most of the traffic to Telstra is routed via the Australia-PNG submarine cable which was enhanced with the addition of digital modems in the mid 1990s. Other Telstra circuits are routed via the Intelsat satellite. International connections terminating or transiting on the Optus network are routed via satellite. Earth station facilities at Gerehu and Lae provide direct digital connections to the Optus network via the Optus A2 satellite. This arrangement enables international calls to or through Australia to be routed via the Telstra or the Optus network. Telikom also has direct digital links with other major international traffic destinations via the Intelsat satellite.

Rural Telecommunications  

Rural telecommunications services to the rural areas are presently provided through high frequency radio service, thin-route satellite systems, point-to-point and point-to-multipoint radio systems, wireless local loop etc. In addition, several institutions including health centres, mining companies, plantations, among others, operate private high frequency radio links to their respective headquarter offices.This high frequency (HF) communication system now covers the whole country and is capable of providing modest services to rural dwellers at any location nationwide. The HF network is now complemented by point-to-point radio system, multi-access point-to-multipoint systems, trunked radio and wireless local loop.

HF radio remains a very important medium for Telikom as it provides an effective communication link to outstations in rural areas beyond the reach of the microwave and VHF network. For these isolated communities, HF is their only communication link with the outside world. It is also vital for safety of life at sea. Telikom is committed as part of its community service obligations to provide for humanitarian, national security, natural disasters and development reasons. The recent introduction of the Automatic HF Telephone Interconnect System enables HF outstations access to the national telephone network via radio direct dialling. The present High Frequency Interconnect system has access to the national network via one trunk channel, which is shared by approximately 300 rural and remote subscribers for communications between the PSTN and the remote subscriber. The system will soon be upgraded to interconnect the national network via four trunk channels to facilitate communications for approximately 1,000 remote subscribers. The system presently operates on eight frequency pairs.

Coastal Radio and High Frequency Outstation Services

Telikom also provides a Coastal Radio Service that alerts seamen of imminent dangers. The CRS transmits weather forecasts, strong wind and cyclone warnings, receiving distress signals from ships and people at sea, testing of ships radios and connecting calls from people at sea to subscribers on land. Although Coastal Radio Service is now being superseded by new technologies, the system still plays a vital role in maritime services.