Technology Aspects of the Digital Divide

Introduction

There has been much recent discussion of the extent to which socio-economic factors, cultural background, skills and other issues may limit the ability of some people to take full advantage of online information systems, in particular the Internet. This phenomenon is often referred to as the digital divide. Limitations on access due to geographic location and the quality and capacity of the telecommunications infrastructure are also aspects of the digital divide issue.

This paper briefly backgrounds the technical issues underlying geographic aspects of the digital divide. Although the paper is concerned with access to the Internet, much of the discussion focuses on access to quality of telephone service since this is the principle means of Internet connection available in most areas.

The paper also looks at developing technologies and the roles that they may fill, and at the conclusions drawn in the report of the telecommunications enquiry.

Some Definitions of Technical Terms

Bandwidth describes the data throughput capacity of a particular communications technology or link. It is closely analogous to the carrying capacity of a water pipe. It is usually measured as the number of bits of information per second that can be transferred, a bit being a single binary digit (either '0' or '1'). A single alphanumeric character is usually represented by a string of eight bits (a byte). Allowing for overheads, the rate at which characters can be transferred over a particular link is roughly one tenth of the specified bit transfer rate. So, for example, at a relatively low transfer rate of 14,400 bits per second (14.4 Kbps) a page of text of say 2,500 characters (approximately 20,000 bits) would take nearly 2 seconds.

A full colour picture (image) could require 100 Kbits to represent a 25x25 mm2 area. Usually images are compressed using a system such as JPEG (for Joint Photographic Experts Group) which can reduce this by a factor of 10 to 100, depending on the richness of the visual information. A video clip, with sound and pictures, is similar to a series of pictures and a 60 second segment using a small frame (75x50 mm2) and a low quality compression system can take up 4 Mbits (500 Kbytes), which would take almost five minutes to download using a 14.4 Kbps line running at full capacity. On the other hand, a full screen broadcast quality image with 720x480 resolution using MPEG-2 (for Moving Pictures Experts Group), such as is used for DVD movies, requires up to 15 Mbps of bandwidth. The various rates are compared in Table 1.

Table 1: Comparative download times for different types of content

Bandwidth	Content Type	Page of text(20 Kbits)	Video - 60 sec 75x50 mm2 compressed(4 Mbits)	DVD quality video - 60 sec compressed(900 Mbits)
14.4 Kbps	Low	2 sec	4.6 min	17.4 hours
56 Kbps	Low	0.5 sec	71 sec	4.5 hours
128 Kbps	High	0.2 sec	31 sec	2 hours
2 Mbps	Broadband	-	2 sec	7.5 min
15 Mbps	Broadband	-	0.3 sec	60 sec

Low bandwidth (or low speed) links are anything below 100,000 bits per second (represented as 100 Kbps). High bandwidth or high speed links are in the range 100 Kbps to 2,000 Kbps which is usually presented as 2 Mbps.

Broadband commonly refers to a data throughput capacity of more than 2 Mbps. The term reflects the ability of such links to handle many different types of information up to and including full motion video and other services requiring very large throughput capability.

Analogue vs Digital. Analogue information is based on signals where some feature of the signal, usually amplitude or phase, varies continuously with time. Digital information (a 1 or 0), on the other hand, is represented by just one of two possible states: high/low (voltage), on/off (signal) etc. Computers deal with digital information. It is often necessary to convert the digital information used in the computers into analogue signals in order for it to be transmitted over a communications link and then convert it back to digital form when received. A modem (modulator/demodulator) is used to carry out the analogue to digital conversion, and its reverse.

The upper limit of data carrying capacity over a normal telephone line for analogue communications is 56 Kbps (and this only under favourable conditions) whereas digital communications can range up to several megabits per second (1 Mbps plus). In general, analogue signals are better over long distances and noisy lines.

Cable modems, which connect to co-axial cable networks, can carry data at speeds up to 2 Mbps. Digital signals can be used for higher data speeds but require high line quality and can usually be sent only over relatively short distances.

Fibre optic cables always transmit digital signals and under appropriate conditions can reach into the Gigabit range (1,000 Mbps plus). Fibre is widely used for the high volume inter city telecommunications, backbone and international links but is only slowly being deployed for business and domestic use.

Connection Infrastructure

Infrastructure refers to the physical telecommunications network itself. Figure 1 shows the relationships between some of the key entities which make up the connection infrastructure.

Figure 1: Some elements of the telecommunications/Internet infrastructure

Local loop: This includes the copper wire pairs that link terminals (commonly telephones) to their nearest exchange but may also in some rural areas include multi-access radio technology.

Internet Service Provider (ISP): The ISP is integral to connection to the Internet. It is the ISP who provides the Internet Protocol (IP) linking services which allow messages to be routed throughout the Internet 'cloud'. Most ISPs will have one or more broadband or high bandwidth connections to the telecommunications backbone which both allows users to connect to the ISP and links the ISP to other IP service providers on the Internet.

Telephone Exchange: Internet connection capacity is normally dependent on the capacity of the link between a user and their local telephone exchange, which will in turn depend on the location and the age and quality of the exchange's equipment. Many Telecom NZ exchanges in rural and congested urban areas were upgraded in the early 1980s and continue to provide good standard telephone services but are not able to provide services and access speeds which are available through a modern exchange.

Backbone: The telecommunications backbone is the network which links exchanges to each other and includes both transmission and circuit switching elements. The transmission elements may include copper and optical fibre cabling, and microwave links. The international circuits also include satellite links. Parts of the existing domestic backbone between some provincial centres may require upgrading to support greater digital data flows.

Technologies Available and in Use

Aside from dedicated fibre-optic and coaxial cable networks, which are available at present only to people in Wellington suburbs and the Wellington CBD, and wireless connections in use in Auckland, Wellington and some other areas, access to the Internet is generally only available over the telephone network. Even for those with satellite connections, the return path from the user to the ISP relies on the telephone network. Thus, in practice for the overwhelming majority of New Zealanders, technologies available for Internet connection are limited to those capable of using the copper wire local loop.

Technologies available over the local loop

V90 Modem: This is presently the 'domestic standard' for achieving a data rate of up to 56 Kbps over a standard telephone line. It requires only an inexpensive modem connecting a personal computer to a telephone line, and will support slow-motion video. There are limiting factors, however. A connection speed of 56 Kbps cannot be realised if there is more than one analogue-to-digital conversion in the connection to the ISP and is usually limited to a maximum line length between subscribers and the nearest exchange of 3 to 5 kilometres. In practice this means that for many users access speeds are less than the theoretical maximum. Typically in urban areas 33 Kbps is available but in many rural areas line quality is such that speeds fall well below this. For example, many rural areas are served with multi-access radio technology, which was introduced over ten years ago to eliminate party lines, and can only handle data transfer rates of 9.6 Kbps.

ADSL (Asynchronous Digital Subscriber Line): This is one of a family of technologies referred to collectively as xDSL, a term covering different types of Digital Subscriber Lines. xDSL technologies use sophisticated modulation schemes to pack digital data onto copper wires. xDSL is similar to ISDN (see below) inasmuch as both operate over existing copper telephone lines, but requires short runs to a central telephone exchange (about 2 kilometres). Potentially, xDSL offers broadband level speeds - up to 32 Mbps for downstream traffic, and from 32 kbps to over 1 Mbps for upstream traffic.

ADSL is offered by Telecom NZ to subscribers as JetStream. It is capable of speeds of up to (but generally much less than ) 6 Mbps in one direction and a much lesser speed in the other. It is currently available only in the main centres but is slated to be rolled out progressively throughout the country and is displacing ISDN (see below). However, this may be slow (after almost 20 years, ISDN still does not reach into most of rural New Zealand). Given that even inner city suburbs in areas such as Wellington cannot presently be serviced with ADSL, some further technology development will be required before ADSL can provide a widespread solution to bandwidth limitations, especially in rural areas.

ISDN (Integrated Services Digital Network): Telecom provides ISDN in all the main centres as well as many of the smaller centres, however, with one or two exceptions it is not generally available in rural areas. The technology supports data transfer rates of from 64 Kbps to 2 Mbps. Basic Rate ISDN installations provide the equivalent of two standard telephone lines. One can be used for voice and the other for data, or both lines can be used to achieve data rates of 128 Kbps. This is just adequate for two-way video applications such as distance learning and video-conferencing. Multiple ISDN lines can be used to obtain higher quality connections, for example, three ISDN lines provide a connection speed of 384 Kbps and this is typically used where video quality is critical, for example for tele-medicine applications. Telecom NZ has demonstrated a reluctance to make further investment in its ISDN infrastructure, promoting ADSL services as a preferred alternative.

Frame Relay: This is available from 64 Kbps and is easily scalable up to 2 Mbps. Frame relay is generally used as a dedicated point-to-point service or as a virtual private network and has the advantage of fixed price tariffs (no usage charges). The technology is specially suited to applications where guaranteed bandwidth is required such as for voice and video applications.

Asynchronous Transfer Mode (ATM): This technology offers very high bandwidth, up to 150 Mbps and is typically used for linking corporate networks.

IP Networking: This is a new family of services being piloted by Telecom NZ which is specially suitable for Internet connections where dedicated bandwidth is not critical. The focus is on flexibility and interconnectivity between a variety of connection services, such as dial-up telephone, ISDN and frame relay.

Rural issues with the local loop

While in some urban areas high bandwidth and even broadband access speeds are available, telephone subscribers more than 3 to 5 kilometres from an exchange are limited to access rates of 33 Kbps or less. In addition there are major problems with line quality reported for rural subscribers. A recent survey conducted for MAF reported 54% of rural subscribers as having problems affecting telephone lines including noise, electric fences (often a problem of poor fence installation by the farmer) and exchange overload. Telecom NZ reports that only 5% percent of local loop lines are not capable of maintaining a reliable data speed of 14.4 Kbps. The overwhelming majority of these would be in rural areas and thus this figure represents a large proportion of rural subscribers.

An indicator of insufficient infrastructure capacity is the number of reported problems with obtaining a second or third telephone line (an obvious way of trying to bypass the data rate bottleneck). Over one third of survey respondents who indicated that they had attempted to get a second line failed to do so.

Alternative terrestrial technologies

Wellington is currently the only area in New Zealand where there are alternative wire/cable options to the Telecom NZ local loop.

Telstra/Saturn has installed co-axial cabling in many Wellington, Hutt Valley and Kapiti suburbs and now has up to 25% of the Wellington domestic telecommunications market. It provides a cable modem service (Chello) for Internet access at speeds of 0.5 to 2 Mbps. Expansion is planned to the Auckland and Christchurch urban areas but it is unlikely to be extended to provincial centres for several years and is unlikely to ever be extended to rural areas.

CityLink is a fibre optic network covering much of the Wellington CBD. It uniquely offers a choice of 'dark fibre' or 'serviced IP' options. Dark fibre service is essentially the rental of a fibre optic pair available for the user to use in any way they like. For example, it is available for switched Ethernet at speeds of up to 1,000 Mbps. Serviced IP provides Ethernet connections of up to 10 Mbps. There are plans to install CityLink-type networks in the Auckland and Christchurch CBDs and a similar service is being discussed for introduction in some provincial areas such as Southland, Otago, New Plymouth and the Far North using mainly wireless technologies.