Skip to main content

Signal Processing for Optical and Cordless Transmission

Objective

This project was originally set up to provide assistance to the CPN and CAC projects in the areas of signal processing for transmission. During its initial phase, the main objectives were to study and assess the effects of several signal processing operations upon the transmission performance of optical and cordless links, used in an integrated broadband customer premises network for IBC.

More recently, special attention has been devoted to those signal processing techniques offering the higher prospects for economical deployment of IBC services. One such technique is sub-carrier multiplexing (SCM). The main objective of the work is to specify, design, simulate and contribute towards the optimisation of sub-carrier multiplexing systems. These systems are intended for use in the customer access connection as currently developed by R1030-ACCESS.
The main objectives of the research were to study and assess the effects of several signal processing operations upon the transmission performance of optical and cordless links, used in an integrated broadband customer premises network for integrated broadband communications (IBC). Special attention has also been devoted to those signal processing techniques offering higher prospects for economical deployment of IBC services. One such technique is subcarrier multiplexing (SCM). The main objective of the work was to specify, design, simulate and contribute towards the optimization of subcarrier multiplexing systems.

The research has resulted in the following achievements:
the development of analytical and software tools for the simulation of digital transmission channels, incorporating (in a user definable manner), the effects of scrambling and/or line coding, channel degradations, bandwidth limitations, direct current (DC) wandering, equalization behaviour, etc;
the development of analytical and software tools for the assessment of the effects of channel length variation on transmission system behaviour;
the development of analytical and computational tools to support the specification, design, simulation and optimization of subcarrier multiplexing systems for the customer access connection network.
Technical Approach

The methods and procedures adopted to achieve the above objectives are basically the following:

. Collection and elaboration of relevant information available in the literature. Data is interpreted and combined into conclusions meaningful to the project.
. Analysis of technical options by careful estimation, calculation and experimental testing.
. Modelling and simulation. Where appropriate models exist (or can be created), simulation techniques are used to obtain the characteristics of components, sub-systems or techniques.
. Experimental research and development of new techniques.

Following an initial phase when the project was mostly addressing the CPN environment, for the last two . years attention has turned to the customer access connection (CAC) as defined by project R1030 (ACCESS). A collaboration agreement was established between R1030 and R1052 with the support of RCO, to reinforce and facilitate articulation between the two projects. R1052 has devoted increased attention to some of the issues associated with the analogue technique of sub- carrier multiplexing, being the central architecture under consideration within ACCESS. Particular care is devoted to the implications of receiver reproducibility and cost.

The results of R1052 can be made available to other relevant RACE projects, on request.

Key Issues
Signal processing, in the context of this project, has been used with two quite different meanings:

. In the CPN environment it referred to such operations as equalisation, detection, line coding and/or scrambling, packetisation (eg STM or ATM).
. In the CAC environment it has been referring mainly to the operations associated with sub-carrier multiplexing systems (SCM).

Achievements
. Development of analytical and software tools for the simulation of digital transmission channels, incorporating (in a user definable manner), the effects of scrambling and/or line coding, channel degradations, bandwidth limitations, DC wandering, equalisation behaviour, etc. This also has the possibility of quantifying such aspects as eye diagram penalties, jitter, etc.
. Development of analytical and software tools for the assessment of the effects of channel length variation on transmission system behaviour. For a certain line code or framing structure (eg STM), this is capable of optimising the receiver equaliser, given the limits of variation of the channel length.
. Development of analytical and computational tools to support the specification, design, simulation and optimisation of sub-carrier multiplexing systems for the customer access connection network.

Expected Impact
The provision of cost-effective solutions for IBC requires that the cost of both the customer connection and the distribution network within customer premises should be as low as possible. Signal processing techniques can have a major impact on the cost and efficiency of transmission systems by overcoming some of the media limitations and allowing the use of simple and robust equipment at a low-cost level.

Coordinator

University of Aveiro
Address
Campus Universitario
3800 Aveiro
Portugal