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The primary function of the Dynamic MF-TDMA Multi-carrier Demodulator (MCD) is the generation of the demodulated, decoded ATM or MPEG compatible traffic cells and associated overhead signalling information received on the satellite up-link that employs a MF-TDMA type primary access scheme. The MCD also performs parametric measurements on each uplink carrier for uplink carrier power control, burst position and Signal Quality (Es/No) estimation purposes. In general terms, the MCD can be defined as a real-time, Digital Signal Processor.
The input to an MCD Module consists of the QPKS modulated carrier signals that constitute the FDM composite signal at the L-Band level. The FDM composite signal consists of a maximum of 96 active QPSK modulated carriers. For any given frequency plan, the actual number of carriers is a dependent upon the uplink carrier information rate and the required processing MCD Module Demultiplexer processing bandwidth. The output of the MCD Module consists of the following recovered data fields: - The demodulated, decoded, base-band ATM compatible or MPEG traffic cells,
- The overhead signalling information (In-Band Requests, Out-of-Band Requests, Terminal Information, etc.) contained in the SYNC, TRF and CSC SAC data fields,
- The parametric measurements performed on each uplink carrier processed by the MCD
Module The MCD consists of the following signal processing functions: - MIF (L-Band to Base-band Frequency Down Converter),
- Frequency Demultiplexer,
- Format Converter,
- Burst Mode Demodulator,
- MCD Controller,
- Dynamic Scheduler.
The project plan consists of the development of hardware, software and the validation of the resulting product.
- A maximum aggregated information rate of 24 Mbps,
- Support up to 96 uplink carriers,
- Variable channel spacing between adjacent carriers,
- Uplink carrier information rates are from 32 Kbps to 4 Mbps,
- Each timeslot that composes the MF-TDMA frame map can be assigned any of the four slot types (TRF, SYNC, CSC and ACQ),
- The type format, the number of timeslots and timeslot assignment can be unique for each uplink carrier,
- Each uplink carrier can be assigned a unique coding rate, information rate and Payload Traffic format,
- The supported Payload are: one, two or four ATM Cells per Traffic Slot or one MPEG Packet per TRF Slot.
- Higher throughput,
- More flexibility,
- Lower over-all system cost (by reducing the number of MCD boards in the RLSS system).
Functional and performance tests were finalized in December and a Final Design Review meeting was held on December 14th 2005. The MCD product has met or exceeded specifications during a series of validation tests held in January. EMS is now in the process of product commercialisation; new MCD boards have been built and are in the process of validation, MIF boards, the RF front end of the MCD, are being assembled by the subcontractor and the first customers are expecting to receive their first MIF/MCD units shortly. The Dynamic MCD follows on from the highly successful Release 1 MCD and the current Release 1.5/1.6 MCD. The design of this Release 2.0 MCD utilises a software-based DSP architecture that allows much more flexibility in the frame formatting than the current product. It also introduces greater frequency plan flexibility, by means of a sophisticated multicarrier de-multiplexer, and covers a greater total bandwidth. In summary, the major new features are: - Improved traffic burst flexibility,
- More programmability in the area of traffic vs. overhead assignments,
- Carrier rates down to 64 Kbps and up to 8 Mbps,
- Mixed carrier rates in the same MCD,
- An increase from 32 to 96 maximum carriers per MCD,
- Wider total bandwidth, an increase from total capacity of 8Mbps to 24Mbps,
- Tighter carrier spacing, carrier spacing is programmable from 1.25 to 1.5 of the carrier bandwidth (1.25Rs to 1.5Rs),
- Supports future developments towards alternative modulation schemes and on-the-fly changes to burst and frame formats,
- DSP structure accommodates coding, modulation, symbol rate and burst length programmability.
These features will provide the EMS Return Link Sub System (RLSS) with significantly improved implementations of Rain Fade Countermeasures by Rate Reduction and other systems flexibility that is considered mandatory for all market segments. The Dynamic MCD project is now concluded. Overall, EMS is extremely satisfied with the resulting product that will undoubtedly strengthen EMS position as a leader in the supply of DVB-RCS Gateways, Terminals and Systems to Satellite Operators and Enterprise customers worldwide. EMS would like to express its gratitude to the Canadian Space Agency and European Space Agency who have played a key role in supporting the development of the Dynamic MCD.
Last Update: 30 May 2006
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