Research on satellite communications and network protocols is carried out to extend terrestrial network infrastructure to the battlefield and bring Command, Control and Intelligence information, such as moving plans, operation orders, and logistic information, to the deployed area for timely response. Quality of Service (QoS) mechanisms, satellite resource management techniques, and transmission reliability protocols are being analyzed.

A computer-based modeling tool is used to design, develop, simulate and analyze the performance of potential improvements to current satcom services and equipment when used for multi-media network applications. Various deployment scenarios, medium access control techniques, satellite communications and network protocols are modeled, simulated and assessed against parameters such as quality of service, bandwidth requirements, and congestion levels. The techniques developed are also assessed against civilian network topologies such as remote and rural communities.

This project is co-sponsored by DND/PTO PMSC, DND/DRDC under the Defence Communications Program and by CRC. The group also collaborates with industry and university to expand its workforce and facilitate technology transfer.

The group is developing a module, called the Satellite Capacity Optimization and Performance Enhancement (SCOPE), to be included between the terrestrial network and the satellite terminal to improve multi-media services over satcom link. The two main features of the module are: TCP enhancements for satellite links Dynamic Bandwidth Allocation mechanism

TCP enhancements

It is well known that due to long delays and high bit error rates encountered over a satellite link, the congestion control and packet acknowledgment mechanisms of conventional TCP RENO fails to deliver adequate performance for multi-media applications. A number of proposals have been made to improve the performance of TCP and various proprietary implementations have been put in place. However, because of compatibility issues, the standard TCP RENO stack remains the most widely spread stack. The Transport protocol of the Satellite Communications Protocol Standard (SCPS-TP) is a replacement for the conventional TCP stack based on the RENO protocol. SCPS-TP is an open architecture protocol, standardized by the CCSDS, the military and ISO.

The group is developing an OPNET version of the SCPS-TP protocol. Additional features to improve the protocol for multi-media applications are being investigated. To be able to make use of SCPS-TP without modifying end-user stacks, a SCPS proxy is also developed to convert TCP into SCPS-TP and vice versa.

Dynamic Bandwidth Allocation

For deployed operations, and for many remote or rural civilian communities, satellite is the only mean of communication between dispersed entities. Because of the characteristics of multi-media traffic, which can be extremely bursty, conventional static channel reservation mechanism is not cost efficient. For optimum performance, a single user performing a mix of web browsing, email and ftp transfer requires channel bandwidth between 20 to 100 times its average throughput. Novel protocols are being developed to dynamically allocate the precious satellite bandwidth to the various ground terminals, depending on their current needs. A more efficient use of the resource can translate in better application performance, lower bandwidth requirements, or higher traffic volume.

Publications:

1. Claude Bélisle, Peter Andreadis, Steve Bernier, François Lévesque, and Michel Barbeau, "Bandwidth Allocation for IP Traffic Over Satellite Links", International Conference on Advances in Infrastructure for Electronic Business, Science, and Education on the Internet, L'Aquila, Italy, August 2000.

2. P. Andreadis, C. Bélisle, C. Auger, and M. Delorey, "Performance Analysis of Multimedia Networks over Satellite Links", OPNETWORK 2001, August 27th - 31st, 2001, Washington D.C.

3. J.Peng, P. Andreadis, C. Bélisle, and M. Barbeau, "Improving TCP Performance over Long Delay Satellite Links", OPNETWORK 2001, August 27th - 31st, 2001, Washington D.C.

4. C. Auger, P. Andreadis, C. Bélisle, and S. Bernier, "Bandwidth Allocation and Management for Multimedia Networks Over Satellite Links", OPNETWORK 2001, August 27th - 31st, 2001, Washington D.C.

5. P. Andreadis and J. Peng, "TCP Over Satellite - A Review of TCP Over Satellite Links: Problems and Suggested Solutions", CRC Technical Note No. CRC-TN-2001-01,Ottawa, April 2001

6. C. Bélisle, P. Andreadis, S. Bernier, C. Auger, M. Phisel, Maj. M. Delorey, D. Simmerlink, A. Howell, "AEHF Network Performance Analysis", TTCP 2001, Boston, USA, April 2001

7. C. Bélisle, P. Andreadis, D. Simmelink, A. Howell, S. Bernier, C. Auger, M. Phisel "Protected MilSatCom Network Performance Analysis - AEHF Baseline Network Evaluation", Contract Report DND \ PMSC, May 2001.

8. J.Peng, M.Phisel, W.Chen, C.Bélisle, "TCP Performance Enhancing Proxies (PEPs) for Internet over Satellite", Opnetworks 2002, Washington DC, August 2002

9. M.Phisel, J. Peng, W.Chen, C.Bélisle, "Performance of SCPS-TP over Satellite Links", Opnetworks 2002, Washington DC, August 2002

10. C.Bélisle, C.Auger, J.Peng, M.Phisel, M.Delorey, "Bandwidth Management of MilSatCom Links for Multimedia Network Traffic", Milcom 2002, San Diego, USA.