PAGE CONTENTS
Objectives
The project has designed and demonstrated a protocol for VSAT communication with significantly higher performance for the return link than achievable with DVB-RCS (ETSI EN 301 790). Also transmission modes for lower SNR have been included. Parts of the new design have been accepted in the current DVB-RCS2 (ETSI EN 301 545-2) specification and all of the design is included in a pending revision of the current DVB-RCS2 standard. Demonstrations with the implemented prototype confirms that the performance expected from the simulations can be achieved in an implementation, and that ACM can be effectuated to dynamically select the transmission mode that fits best with the instantaneous channel conditions, both with respect to maximizing the bandwidth efficiency and minimizing the packet loss. This has been demonstrated for different fading conditions. Different burst size combinations have been investigated and the final set of new transmission modes includes alternative transmission burst durations allowing a dynamic trade-off between QoS and bandwidth efficiency.
Additionally, methods for estimating signal compression due to insufficient OBO at the remote SSPA have been investigated, and methods for combining UPC, ACM and ACS (DRA) have been investigated.
Challenges
The key issue is the opportunity to do ACM on the return link for each VSAT, complementing ACM on the forward link. Further, the physical layer is new with customized burst constructions using less overhead, a state-of-the art 16-state Turbo FEC and support for different orders of modulation with 16QAM, 8PSK, QPSK and BPSK available. Work has been done on the physical layer framing and preamble/pilot design to maximize the burst demodulator performance. New FEC codes have been designed (derived from the former Turbo-Phi FEC through optimization for the new frame sizes). The ACM capabilities are integrated with ACS (DRA) to extend the operational range of the system. The burst constructions are designed to fit into a unified slot grid allowing the space to be utilized by different burst sizes at just-in-time decision. This flexibility is useful to sustain the burst payload size when changing transmission mode and also to adapt the burst payload size when the level of traffic vary and QoS requirements vary. An adaptive user packet encapsulation scheme has been developed to enhance the efficiency in the utilization of a varying burst payload size.
Plan
The following main activities were planned:
- Design protocols and simulate modem performance
- mplement demonstrator and verify the performance of the design
- Test-bed Specification Review
- Preliminary Design Review
- Critical Design Review
- Test Readiness Review
- Acceptance Review (Final Review)
