Technologies Explained
The term broadband refers to a range of access technologies that allow
subscribers to enjoy high-speed, reliable Internet access. But just what
are those technologies?
In this section, we will highlight the main technologies in use today.
xDSL
Digital Subscriber LineThe x refers to the fact that there are several different types of DSL technologies, such as ADSL (Asynchronous DSL), HDSL (High-Speed DSL), and RADSL (Rate Adaptive DSL). The majority of DSL services use existing telephone lines to carry both voice and data signals, The most common services being offered by the leading service providers to businesses and resident alike are ADSL and RADSL.Both these services make use of standard telephone lines. All the work to provide these services is carried out at the telephone exchange, meaning that no time, money or disruption is incurred. At the consumer end, a filter must be installed on the line. This filter separates the voice signals from the data signals so that telephone calls and Internet or fax calls can be made over the same line.
xDSL provides one of the most cost effective and efficient ways to use a broadband connection to access the Internet. However, its availability is limited due to operators’ reluctance to invest large sums of money in infrastructure and services for which there may not yet be a market.
In addition, xDSL technologies are distance restricted. For ADSL, one of the more widespread xDSL technologies, consumers must be located no more than 5.5km (3.4 miles) from an ADSL enabled exchange to be able to subscribe to the service. Nevertheless, the technologies are improving all the time, with the distance limitation being extended in recent months.
One last consideration for some xDSL services, including ADSL and RADSL, is contention. These are contended services meaning that the amount of bandwidth a subscriber can use during an online session can be affected by the number of other users, so during very busy or peak usage times, a users bandwidth can be contended by up to 50:1. The contention ratio should always be stated with the package.
Cable
Cable operators use their own network infrastructure to set and receive voice and data signals. To connect to a cable modem service, you must be living in an area where a cable operator has infrastructure. In Northern Ireland, this is limited, while in Derry City, non-existent.A cable modem is a device that enables you to connect your PC to a local cable TV line and receive data at up to 1.5 Mbps.
A cable modem can be added to or integrated with a set-top box to provide your TV set with channels for Internet access. In most cases, cable modems are furnished as part of the cable access service and are not purchased directly or installed by the subscriber.
This access technology is aimed primarily at the residential market, although cable operators have since been offering packages aimed at the business market.
Leased Lines
If a standard dial up connection over a telephone line is the Lada of Internet access technologies, then a leased line connection is the Rolls Royce.A leased line is a permanent telephone connection between two points set up by a telecommunications carrier. Typically, leased lines are used by businesses to connect geographically distant offices, or simply to provide very high-speed dedicated Internet access.
Unlike normal dial-up connections, a leased line is always active, with the fee for the connection based on a fixed monthly rate. The primary factors affecting the monthly fee are the distance between the end points and the speed of the circuit. Because the connection does not carry anyone else's communications, the carrier can ensure a given level of quality. However, cost is a critical factor when considering this technology, and indeed pricing may be based on distance between the user equipment and the carrier’s backbone.
Satellite
Using low earth orbit (LEO) satellites, satellite Broadband Internet service providers are able to provide service to subscribers in remote regions all over the world. Two pieces of hardware are required at the subscriber’s site – a satellite dish in direct line with the orbiting satellites, and a transceiver taking information from the satellite and translating it into the end user device (more than likely to be a PC).Satellite is an excellent potential solution for remote or rural areas that ordinarily would not have access to Broadband communications, however it is prone to a number of quality-diminishing factors.
Fixed Wireless
Fixed wireless (or the wireless local loop, WLL) refers to wireless devices or systems situated in fixed locations, such as an office or home, as opposed to mobile devices, such as cell phones and PDAs. Fixed wireless devices normally derive their electrical power from utility mains, as opposed to portable wireless devices which normally derive their power from batteries.Point-to-point signal transmissions occur through the air over a terrestrial microwave platform rather than through copper or fibre cables; therefore, fixed wireless does not require satellite feeds or local phone service. The advantages of fixed wireless include the ability to connect users in remote areas without the need for laying new cables and a capacity for broad bandwidth that is not impeded by fibre or cable capacities. Satellite telecommunications may be categorised as being wireless.
It should be noted that there are a number of methods of deploying wireless technology and a number of frequency spectrums that are offered. For example:
- Conventional fixed wireless networks rely on one of two models:
- a single base station transmitting to a single receiver (point
to point)
or
- a single base station transmitting to many receivers (point to
multipoint).
- a single base station transmitting to a single receiver (point
to point)
- With a mesh network, a base station transmits to another base station, but then the signal 'hops' to the next station in a relay (point to point to point). This allows for a quick and relatively cheap rollout of technology.
3G
3G is short for 3rd Generation wireless, and encompasses the latest, and near future developments in personal and business wireless technology, especially mobile telecommunications. The technology is expected to include capabilities and features such as enhanced multimedia, usability on popular models, Broadband access (up to 2mbps fixed, 384kbps slow moving, and 128kbps fast moving), routing flexibility, and worldwide roaming capabilities.3G is built on the older technologies of 1G (1st Generation), based on analogue voice signalling, and 2G (2nd Generation), featuring digital voice encoding. 2G has been widely developed since the 90s, with the current state in use today being referred to as 2.5G (GPRS).
3G networks are yet to be fully rolled out in the UK. The plans for Northern Ireland with regard 3G networks have been put on hold.
FTTH/O
Fibre To The Home/OfficeWith FTTH, fibre deployment is carried the whole way to the customer’s home. A wide range of signal services (for example, telephony, Internet access, satellite and digital TV services) is combined onto a single fibre at the telecommunication operator’s central office (CO). This signal is split about 2.5 miles from the CO, and delivered a further half mile to a maximum of 32 homes over a single fibre.
With FTTH, end users are able to receive complete bundle of pay services, including, circuit-switched telephony, high-speed data, and broadcast video services. Central to the development of the technology is the need, and subsequent evolution of Voice Over (Vo) technologies, such as VoIP, VoDSL and VoATM. It is a very reliable passive network, with no active components, thus minimising network maintenance cost and requirements, and eliminating DC power.
Rather than using the copper wire-based system of branching out transmissions, which can lead to bottlenecks and dramatic slowdown of transfer rates for each subscriber, FTTH delivers gigabit capacity to each subscriber over their own optical fibre. It is a full-duplex communications solutions so that each user on the network is guaranteed capacity, while multicasting is used to ensure that bandwidth not being used is opened up to other services.
Fibre to the curb (FTTC) on the other hand, provide the fibre optic transmission to within 0.2 miles of the home, with the connection being completed by coaxial cable.This is still a relatively new technology and is currently being piloted in Sweden, Japan and Canada.