Fibre radio atm network and services
Summary : The design and development of the CDMA (Code Division Multiple Access) tranceiver is used in order to transmitt and receive data with safety since the spreading code used is 63Mchips/s wide. This system is using state of the art QPSK direct modulation for the transmitter case where for the receiver case a simple superheterodyne technique is used.This system can be used in telecommunication services where high security is needed or low jamming interception is needed. It is easily upgradeable to higher frequencies if requested.
Summary : For LETI, the main result is the ASIC CESSIUM, designed in the frame of the project, this component processes all the digital base band functions required by both a direct sequence spread spectrum transmitter and receiver. Moreover, the transmitter of the circuit could be used also as an interference generator, therefore by arranging several circuits a parallel interference cancellation receiver for asynchronous CDMA applications could be implemented
Summary : The IAF has developed customized MMICs to be used in the antenna unit (AU) and the customer premises equipment (CPE) used in the FRANS project. According to the system specifications 2stage and 3stage low noise amplifer MMICs, used as drivers for mixer and power amplifier, a resistive mixer and a high power amplifier in the frequency range of 28-30 GHz have been developed. The major issue was the development of a high power amplifier with a saturated output power of more than 26 dBm (400 mW). This high output power was required, to be able to operate in the linear region of the power amplifier (6 dB lower than Psat) and to be able to feed the antenna with at least 100 mW signal power. With the improvement of our in-house process, an output power of 28 dBm (Psat) was achieved. With further investigation and improved design, this power amplifier offers the possibility to reach high output power at 30 GHz up to 1 W.
The project is concerned with the specification, development and establishment of field trials demonstrating an optically supported millimetre wave link as a final drop to the subscriber, to provide rapid and flexible deployment of broadband interactive services. It merges existing passive optical networks with a photonic technique for generation, modulation and transmission of information bearing millimetre wave signals to a hybrid fibre-radio customer access system. Two trials are proposed, working at different bit rates and based on different multiple access techniques in the uplink. Achievements so far include: system concept and specification, including specification of interfaces to trial platform; realisation of first components, design of subsystem; QPSK transmission experiment (27.98 GHz, 25 Mb/s) over 12 km standard single mode fibre and 1:8 splitting; carrying out of a first hybrid fibre-radio field experiment over a 46.2 km installed standard single mode fibre loop between Stuttgart and Ludwigsburg in Germany (using fibre cable of Deutsche Telekom) using a 60 GHz carrier frequency and 140 Mb/s data rate.
Summary : Original research has been done to provide media streaming between DIANE server and the client, both for recording and for multimedia presentation. The Java Media API has been used, although standardized capture and recording capability of the API will be available in3Q1999. The result will be further used in R&D projects with the intention to evaluate and build an OS independent service platform for distributed multimedia.
Two-user two-stage RAKE-receiver for joint data detection and channel parameter estimation for a DS-CDMA uplink
Summary : A two-stage RAKE-receiver for joint data detection and channel parameter estimation based on interference cancellation has been developed for the uplink of a two-user direct sequence code-division multiple access (DS-CDMA) system. As software simulations have shown, this advanced receiver scheme outperforms conventional schemes in terms of bit-error rate (BER) by far and is robust against the effects of multiple access interference. To validate the scheme under real conditions, a laboratory demonstrator has been realized consisting of two DS-CDMA transmitters and a two-user base station receiver. The latter comprises a front-end for the down-conversion and baseband processing (A/D conversion, correlation) of the users' incoming signals and a DSP-board on which the detection and estimation algorithms, based on the correlator outputs, are implemented in software. Currently, the system is in the debugging phase. A study for the feasibility of an ASIC implementation of the scheme has come to the conclusion that such a realization is feasible with today's technology. The integration of the developed scheme into a base station receiver of a mobile communications system adopting CDMA as access technique would considerably reduce the requirements a power control scheme must meet. For that, further developments have to be done, especially in the extension of the number of users in the system.