Hub station and communication control products (Broadband Return Link System)

Objectives

The project aims at:

• Developing a generic Return Link Subsystem (RLS) platform, possible to use as an integral component in virtually any satellite gateway that includes a return channel.
• Particular emphasis on a TDMA on the Return Link Subsystem supporting high user rate (1 - 2Mbps), giving full support of the "DVB-Return Channel over Satellite" specification. This will be a component within the HUB Station in an interactive DVB system shown above.

Nera RLS platform

Features

The Return Link Subsystem

The modem platform is implemented in a subrack supporting a configurable number of simultaneous TDMA carriers, depending on the board configuration. The function modules shown in the figure "RLS Hardware Architecture" is briefly described in the following paragraphs.

RLS Hardware Architecture

MUX + I/O

This module will perform control and supervision functions for all receiver chains. Additionally, the module will reassemble received TDMA bursts and transmit the packets over the network interface.

Decoder

This module performs RS/Viterbi or Turbo decoding, and descrambling, depending on the configuration.

Demodulator

The demodulator performs TDMA burst detection and demodulation

A/D + Filtering

This module samples the analog signal. This stage is followed by decimation and matched filtering before the signal is interpolated to the desired output rate.

Mixing

The mixing stage performs channel selection and converts the incoming signal from L-band to a low IF.

Project Plan

The following main activities are included in the plan;

• Designing and producing HW to support the receiver chains.
• Writing a complete set of software drivers for the new/changed HW.
• Redesigning the application SW to support a tenfold plus increase in symbol rates.
• Integrate and test the system

Challenges

The key issues is to move from low user rates (128 kbits/sec) to high user rates (1-2 Mbits/sec) and to move from prototype development to a more commercially finished product.

Benefits

The main benefits is expected to be;

• A fully flexible and configurable Return Link Subsystem with open industry-standard interfaces, making it possible to be used as a main component in any satellite system solution.
• A TDMA Return Link Subsystem with flexible user rates included in Nera's DVB-Return Channel Satellite gateway.

Current Status (dated: 06 Apr 2001)

Hardware: Hardware test in progress. Integration of hardware and driver software soon finished. New models in progress.

Driver software: Main part of test finished. Integration of hardware and driver software soon finished.

Application software: Integration in progress. Optimisation in progress.