Objective
Main Objective
The main objective of FLEXIMACS is to investigate and develop a synchronous code division multiple access (S-CDMA) technique, which allows flexible bitrate assignment and quality of service for the individual user in an ATM based multipoint to point access network supporting both high capacitance and high robustness against interference and noise. The project will identify applicable S-CDMA flexibilization schemes and investigate appropriate solutions for the minimisation of multiple access interference (MAI) and for media access control (MAC) protocols regarding their efficiency, delay and flexibility. Based on the identified and defined alternative approaches and algorithms, a preferred overall system solution will be selected in terms of granularity, complexity, flexibility, performance and cost.
Technical Approach
Broadband access systems of the immediate future will have to use existing wired networks, such as cable television (CATV) networks, or emerging wireless techniques, e.g. microwave and mm-wave radio, to bridge the last mile to the user and offer rapid, flexible and economical access to new services. ATM is an appropriate transport technique to integrate services of different bitrate and quality requirements onto a single digital access link and to provide interoperability of technologies as different as wireline and wireless final drop on a single access node.
An access system with a shared medium, such as a hybrid fiber coax (HFC) cluster or a radio cell, needs a multiple access scheme in the upstream direction to manage the traffic of a number of simultaneous users. Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA) as well as hybrids of these are being considered. Both frequency and time division multiplexing are mature telecommunication technologies, but are sensitive to ingress noise and interference. CDMA on the other hand is based on spread spectrum technology, which has been used in military communication for decades because of its resistance to jamming and eavesdropping, and has distinct advantages in media subject to ingress noise. In a coax system within the designated uplink band of 5-40 MHz, the ingress consists mainly of impulse noise, narrow band signals such as short wave and amateur radio. In a cellular radio system, intercell interference and co-located systems are the dominant sources. In addition, CDMA offers a certain degree of privacy through individual user individual codes and provides flexibility for system evolution as the demand for capacity and services grows.
A CDMA system has two possible operational modes. In asynchronous mode, the spreading sequences of different channels are arbitrary in phase. Here, the spreading gain is partly consumed by multiple access interference, since the codes are not exactly orthogonal, and the system capacity is limited. In synchronous mode, the spreading sequences of different channels have fixed mutual phase relations due to transmitter-receiver closed loop controls. Appropriate selection of codes allows the MAI to be minimised and offers a significant increase in system capacity.
CDMA in its classical form provides continuous transmission at the same fixed data rate for all users, whereas ATM data streams are bursty packet oriented signals with constant or variable bitrate. Based on a set of alternative flexibility schemes, FLEXIMACS will develop an S-CDMA functional specification and reference system configuration.
Appropriate solutions for MAI minimisation will be investigated. This will include the identification and specification of code families with correlation properties suitable for S-CDMA and advanced MAI cancellation strategies in the receiver. Physical layer control as well as a MAC protocol will be developed to map the ATM flexibility requirements onto the S-CDMA physical layer capabilities. They will be designed according to efficiency, delay and flexibility criteria taking existing TDMA standards into consideration. The evaluation and comparison of the alternative approaches will be done via modelling and a combined approach of simulation and hardware feasibility experiments. Finally, a preferred solution in terms of granularity, complexity, flexibility, performance and cost will be specified.
Summary of Trial
Since FLEXIMACS is developing a preferred concept and system specification for an S-CDMA upstream communication system for a shared medium fixed access network environment, no field trials are envisaged during the project. However the technical solutions and the overall system concept will be evaluated by means of simulations and hardware feasibility experiments.
Expected Achievements
The main expected achievement will be the development of new S-CDMA concepts that merge the inherent advantages of CDMA and ATM to provide a flexible, robust and cost effective broadband access network infrastructure based on existing CATV infrastructure or wireless access techniques. A preferred overall system solution will be specified that is capable of transporting ATM traffic efficiently.
Expected Impact
Affordable, universal and uncensored access to broadcast information is an accepted fact in developed democratic countries. The provision of a return channel on a broadband system will make it possible for users to actively select multimedia information, to give feedback, to compose information of their own, to disseminate that information and make use of their freedom of opinion. The provision of cost-competitive robust equipment for broadband access to a wide range of multimedia services for residential and business areas is therefore of enormous significance.
FLEXIMACS will develop, evaluate and improve robust return channel technologies for bi-directional broadband access networks. The project therefore supports the rapid and flexible deployment of new services by enabling an increase of interaction channel capacity, by efficient multiplexing of various services and efficient use of the available uplink spectrum.
Main contributions to the programme objectives:
Main deliverables
Evaluation of synchronous CDMA system for an advanced transmission system. Specification of the optimum solution for integration on a chip.
Contribution to the programme
Definition of a transmission platform for interactive services in fixed access networks providing improved capacity, bitrate flexibility, multiple access capabilities and Quality-of-Service.
Key Issues
The following key issues will be tackled:
-Identification and definition of alternative S-CDMA flexibilization schemes
-Development and specification of an S-CDMA MAC protocol taking existing TDMA standards into consideration
-Elaboration of an MAI optimised system design with respect to code families suitable for S-CDMA and MAI cancellation techniques
-Evaluation of system properties and performance by means of simulation and hardware feasibility experiments
-Specification of a preferred overall system solution
Fields of science (EuroSciVoc)
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques.
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques.
- engineering and technologymaterials engineeringfibers
- natural sciencescomputer and information sciencescomputer securityaccess control
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Topic(s)
Call for proposal
Data not availableFunding Scheme
CSC - Cost-sharing contractsCoordinator
D-70499 Stuttgart
Germany