Modems and codecs
ITR has a significant history of design and implementation of a wide range of modems and codecs, including:
- numerous projects with UK-based Inmarsat in the development of air interfaces and specifications for numerous prospective services. This includes aspects of the ICO system design over 12 years ago, as well as Inmarsat C, D, M and BGAN work
- high performance modems for Intelsat (US) services. This includes modems and codecs from 64 kbit/s to 155 Mbit/s
- earth resource satellite demodulators up to 1 Gbit/s
- dual-mode CDMA/GSM terminals for field trials (UK client)
- CDMA Wireless Local Loop System for PT.INTI, Indonesia
- bandwidth efficient microwave modems to 34 Mbit/s.
Project examples
Turbo-coded modem for VSAT applications
The application is a full mesh interconnected VSAT network system that uses MF-TDMA along with SCPC overlay for on demand or reconfigurable high speed data links, and this work was carried out for a US client. The EPG team has designed the new generation of modems which incorporate advanced coding technology. Broadly, the product has a built-in drop and insert capability, plus an IP port supporting SIP protocol. The modulation and coding rate can be configured in real time for every on-demand link to meet the instantaneous throughput requirements using the available satellite capacity.Bandwidth efficient modems
ITR has worked on a number of R&D projects in the area of bandwidth efficient communications over nonlinear satellite channels. One project investigated predistortion techniques that allow 16QAM turbo coded systems to operate close to the saturation point of a nonlinear amplifier. The proposed schemes achieve a more efficient utilisation of the space segment. The outcome was proof-of-concept hardware, the Iterative Satellite Transceiver. This hardware also implements the latest turbo-like coding technology, developed at ITR, that allows quasi-error free communication at less than 1 dB from channel capacity.
The work extended previous research to more complex techniques such as iterative demapping and decoding, centroid estimation and turbo equalisation of 16QAM signalling over nonlinear satellite channels. In conjunction with predistortion techniques, the schemes investigated achieve the best performance described to date in the published literature.