A research team at NUI Galway is developing high-speed Internet access which could generate considerable savings for commercial and eventually home users. One of the key attractions of the technology for business users will be rapid two-way transfer of information over existing copper wire phone lines.
The £50,000 project funded by Toucan Technology and Forbairt will further refine a high-speed two megabits per second modem Toucan plans to launch in December.
Internet service providers generally provide high-speed commercial Internet access via leased, ISDN or fibre optic lines, which are costly and beyond the budget of home users. The Galway research team is extending the capabilities of the original telephone copper wire network using HDSL (high bit rate digital subscriber line) technology.
The aim is to overcome existing problems with low-speed communications over the "local loop" between users and their local telephone exchange. By passing the cost of laying down fibre optic cables, and technical support for installation and maintenance of lines, HDSL tries to squeeze as much capacity as possible out of existing copper phone lines to increase the data rate available to Internet users.
The outcome of the project will form the basis of a new generation of DSL modems delivering digital data at more than two megabits per second in both directions. Modems allow computers to send and receive information over telephone lines. Until recently the fastest rate achieved was 56 kilobits per second the equivalent of receiving up to 14 pages of single-spaced text per second.
Installed at the user base and the local telephone exchange, the HDSL modems can provide data transfer speeds over 40 times greater than currently provided by voice-band modems. This is enough to carry 32 simultaneous phone calls or six video-conferencing channels from a remote office. This will support the growing trend towards teleworking and network computing. Using HDSL, staff located in branch offices or on the road will be able to gain high-speed access to centrally located computer databases.
According to Dr Edward Jones, head of the project at the Department of Electronic Engineering, NUI Galway: "HDSL focuses on symmetric rates of data transfer unlike ADSL (asymmetric digital subscriber line). These are better suited to the business user because files can be uploaded as quickly as they are downloaded. Being an overlay network HDSL will also remove a lot of pressure from the voice network."
The first family of HDSL modems will operate over two twisted copper wire telephone lines, but the real thrust of NUI Galway's research is to provide the transmission rate for the next generation of these modems over a single twisted copper line - single pair HDSL. This greatly opens up the market for its deployment on a grand scale.
Dr Jones says: "The installed base of telephone wires is a finite and valuable resource, and given that the single biggest cost of providing new telephone lines is the cost of digging up the streets to lay cable, telephone companies are anxious to maximise the use of lines already in the ground. If the same service can be provided using half the resources, then twice the number of customers can be served."
The Galway research team is using advanced DSP (Digital Signal Processing) techniques to achieve single pair HDSL. A number of companies worldwide are hoping to come on-stream with it over the next year. While it is currently possible, one of the biggest problems the Galway team has encountered is distortion on the copper wire at the high speeds required by HDSL.
Much of the work centres on "cleaning" the signal of noise and crosstalk from other signals in neighbouring wires, to enable reliable communications at high rates. Progress is also very much dependent on achieving interoperability standards with other telecommunications vendors' products.
The NUI Galway team will develop the DSP algorithms and architecture, and its industrial partner, Toucan Technology, will work to turn the design concepts into a working product. According to Mr Pat Sheehan, chief executive officer of Toucan Technology, if the project succeeds, the two pair HDSL modem, due for release later this year, will be readily replaceable with the single pair HDSL modem once it is developed.
