6. Applicable Technologies
6.1 Switching Systems Network
Small switches and RLUs provide telephone service. Very small switches have mostly been replaced by Customer Transmission Systems in cabinets.
Switching Systems are a part of the rural telephone access network. In the New Zealand network switches have been consolidated and reduced in number, with more economical Remote Line Units (RLUs) hosted on to a larger parent switch replacing small switches. RLUs have replaced many small individual switches above 500 lines in size. Some "stand alone" capability is lost if the link to the parent switch is broken. The switches are connected into the backbone network with fibre optic transmission systems, or via high capacity digital microwave radio.
For smaller, more remote clusters of customers, the use of Customer Transmission Systems using Pulse Code Modulation (PCM) multiplex systems in roadside cabinets is more economic. They are now serving clusters of customers in the 120 to 480 line size ranges. The PCM cabinets are integrated with the RLU or switch via fibre or copper cable bearer systems.
This part of the Telecom network infrastructure is now optimised in terms of the balance of capital and operational costs between the various network elements.
6.2 Copper Cable Based Technology
Copper cables connect most customers to their switch or PCM cabinet. Loop lengths are limited. ISDN switched services are available, mostly in cities. Various types of Digital Subscriber Line (DSL) systems can be used to deliver data services for Internet access over copper cable. The lower speed versions are suitable for rural areas.
Copper Cable continues to be the most economic technology of choice for local loops of limited lengths up to 5 - 7 km, providing a physical link from the switch or PCM cabinet to the customer. Longer loops need to be reduced in length to improve transmission performance. The major impediment to high quality speech and data transmission is believed to be in the poor signal to noise ratio performance of ageing copper cables; with unbalance, water ingress and declining maintenance practices. These result in increasing interference from power supply systems, electric fences, farm electrical systems etc - a particular problem in rural areas.
Integrated Services Digital Network (ISDN) switched services, at speeds up to 128 kbps, are available from many Telecom city area exchanges, but generally not outside the cities. Telecom is not promoting expansion of the ISDN network.
Digital Subscriber Line (DSL) systems can be deployed only on copper cable loops, with various configurations (symmetrical, asymmetrical) and speeds. The variants are known collectively as "xDSL" systems. The major system variants include:
| Type | Data Rate Downstream | Data Rate Upstream | Range | Typical Application |
|---|
| HDSL (High Speed) | 2 Mbps | 2 Mbps | 5 km | E1 dedicated connections to switches, cell sites, customers. Range to 12 km with repeaters. |
| SDSL (Symmetrical) | 192 kbps to 2.32 Mbps | 192 kbps to 2.32 Mbps | 6 km | ISP, data, videoconference access to customers. Replaces ISDN. |
| ADSL (Asymmetrical) | Up to 8 Mbps | Up to 768 kbps | 2 km | Internet access, video on demand. Greater range at lower speeds - typically to 4 - 5 km at 2 Mbps. |
| ADSL Lite | Up to 2 Mbps | Up to 384 kbps | 6 km | Fast Internet access, with lower speed and longer range than ADSL |
| VDSL (Very High Speed) | Up to 60 Mbps | Up to 60 Mbps | 300m to 1.5 km | High-speed data access for business, symmetric or asymmetric. |
The longer cables typical of rural areas are less likely to be capable of carrying high-speed xDSL systems. Most applicable are the lower speed SDSL, ADSL and ADSL Lite families that have longer reach. They can be deployed in rural applications, but the volumes will be relatively low and the costs high (up to two or three times urban applications).
As noted above, remote clusters of customers are often more economically served by Customer Transmission Systems using PCM multiplex systems in roadside cabinets. The cabinets have customer capacities in the 120 to 480 line size ranges. The early generation systems (1981 - 1990) were connected to the switch by PCM over copper cable bearer systems that cannot easily be expanded to provide extra broadband data service capacity. Later generation systems have used fibre optic cable bearers that have better capability for expansion to provide broadband capacity. However, in nearly all installations the roadside cabinets have little spare space for additional equipment, so costs will escalate if extra cabinets have to be installed to contain broadband data services equipment, xDSL or additional fibre optic bearer equipment.
6.3 Optical Cable Based Technology
Fibre optic cables are replacing copper cables, and have inherently much higher transmission capacity. New high speed and IP enabling technologies have been developed - mostly for business users prepared to pay a premium.
Fibre optic cable and transmission systems have been increasing deployed in the "feeder" part of the cable local loop, connecting the switch to the cabinet. This trend will continue. The end distribution copper cables to the customer are then much shorter, overall loss is reduced, and performance improved. The fibre optic cables are immune to electrical interference. This also provides the possibility of installing xDSL systems over the distribution cables, and transporting the high-speed data signals back over the fibre cable from interfaces in the electronics cabinet.
In some installations space will be at a premium in the cabinets, limiting simple and economic solutions. Developments of "fibre to the home" using active and passive optical networks have been based on high-density suburban environments to date, and are not economic in rural areas.
Other possibilities also now exist to deliver high capacity data services over optical cables - Synchronous Digital Hierarchy (SDH), Asynchronous Transfer Mode (ATM) and Internet Protocol (IP)/Ethernet based technologies can be used. However, most solutions to date using these technologies have been developed for high capacity business users that will pay a premium for high speeds, advanced services and connectivity. Mass deployment in low capacity, low-density environments have not yet proved economic.
6.4 Fixed Wireless and Radio Access Technologies
Multi-Access Radio serves about 10,000 individual Telecom rural customers at the very edge of the network. Data capability is very limited and upgrading will be very costly. Wireless Local Loop systems are being used to provide businesses with Internet access in metropolitan areas. Deployment costs in rural areas could be two or three times higher, making services costly and hard to afford.
Multi-Access Radio (MAR), that shares system resources over a group of customers, have been specifically designed for rural customers in very remote areas. They are economic in specific geographic conditions where cable laying is not possible. They serve individual customers located well beyond the definition of "Rural Town" adopted earlier. Over 10,000 individual Telecom customers in New Zealand are served by these systems. The systems are capable of good voice performance, especially when integrated to the switching system with 2 Mbps digital links. Fax and data transmission at 14.4 kbps is generally possible. Sharing of internal trunks in the system limits their traffic capacity, and Internet access demands are resulting in overloads. Many of the MAR systems now need to be upgraded or de-loaded, which is costly ($1,000 to $5,000 or more per customer). The MAR systems are not capable of delivering 128 kbps data services.
Wireless Local Loop (WLL) systems, generally based on adaptations of cellular technology, have not been used in New Zealand in rural areas for voice and data access. Their data capability is often limited.
Wireless access is, however, increasingly being used in metropolitan areas for data transmission to provide high speed Internet access from businesses to Internet Service Providers (ISPs). These dedicated systems could be deployed in rural areas, but at higher cost than in urban areas. Costs are high due to the low customer densities, and the long distances to back haul the data traffic to the ISP - with costs probably two to three times higher than in city and urban areas. Since they would overlay the existing local access loop plant, the customers would need to pay for the new infrastructure costs in some way. Some of the high capacity microwave radio data systems (e.g.. Local Multipoint Distribution Service (LMDS), Multichannel Multipoint Distribution Systems (MMDS)) have limited range due to the high microwave frequencies that have to be used to transport the high data rates. Such networks need the microwave radio base stations to be located near to the customers, and require expensive high capacity backhaul links into the core network. They are unlikely to be economic or affordable in the short term in rural areas. High capacity data service provision is not covered by the Kiwi Share Obligation (KSO).
6.5 Cellular Systems
The cellular radio networks are developing more capability and higher speeds for data access. However, coverage is aimed at business users in cities and suburban residential customers. Rural coverage is incidental. Costs will be high.
Cellular Mobile Radio systems can be used to provide service to rural areas. However, the cellular operators are focused on their business and suburban customer base, and are not required to provide rural coverage or to meet the KSO.
Most rural coverage is fortuitous, along major highways, or around provincial towns. The truly rural areas will not be specifically served, and are unlikely to be, without special measures being taken. Cellular connections therefore can supplement the PSTN cable-based network, but not replace it. Costs are high to link remote cellular base stations back into the core cellular network.
New enhancements being presently made to the Groupe Speciale Mobile (GSM) cellular systems, and Code Division Multiple Access (CDMA) cellular systems are being implemented. This gives them the capability for data transmission at 64 - 144 kbps. However, such capability is mostly intended for business users prepared to pay a premium for specific services. Coverage and enhanced capacity in the early stages is limited mostly to city areas. Third generation (3G) cellular will provide even more data capability and services in one or two years time, with capacity up to 2 Mbps becoming possible to stationary (but portable) customer terminals. Again, these enhanced services will be provided to business users in the cities in the first instance.
6.6 Satellite Systems
Satellite systems provide an option for access, with limitations. Capital and operating costs are high.
Services from commercial satellite systems are available (e.g. from Inmarsat), although the signal footprint over New Zealand may need large antennas for high data rates. Capital costs for a portable terminal are about $6,000, and operating costs are high at about $5 per minute. Such systems have been used in a very limited way in rural areas, for those few users who are prepared to pay for the service, and where no link is available via terrestrial transmission systems. Data transmission rates are typically up to 56 kbps.
IHUG offer a satellite based network for Internet access to their ISP, with a high speed incoming path from the satellite of up to 400 kbps at off peak times, and a much slower return path at up to 56 kbps via a dial up modem over the PSTN. This provides an asymmetric service. In the long term their satellite capacity may be a limiting factor with a lot of users. They also have a terrestrial wireless access system serving central Auckland. The satellite service costs of the order of $650 to install, with monthly fees starting at $60 per month for up to 2 Gb of data.
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