# Presentation: 246670

## Architecture Study of Space-Based Satellite Networks for NASA Missions 

**Will Ivancic**
**wivancic@grc.nasa.gov**
**216-433-3494**

## Traditional NASA Mission

- Stovepipe Architecture – Mission Specific
- Optimized from application to RF
- Efficient, but not flexible
- Ground Infrastructure
- Dedicated or
- Highly Scheduled
- Store and Forward
- Onboard Storage
- High Space to Ground Transmission
- Relay Satellite (TDRSS)
- Highly Scheduled

## Future NASA 

- Network Centric Architectures and Operation
- Interoperability between mission
- Support of multiple missions
- New Architecture Concepts
- Shared Satellite Resources
- Shared Ground Infrastructure
- Direct to PI Data Distribution
- Remote Control of Experiments
- Coordinated Science
- Emerging Technologies
- Software Radios
- Phased Array Antennas
- Media Access
- Authentication, Authorization and Accounting
- Encryption

## Design  Philosophy

- Volume Production
- Iridium and Globalstar
- Willing to trade optimization for flexibility and interoperability
- Use existing techniques and technologies available in the communication and computing industries
- Examples
- COTS intellectual property
- Standard Interfaces
- Commodity protocols
- Results
- Reduced time to deploy
- Reduced cost
- Reduced risk

## Myriad of Ground Stations

- Feasibility
- Technically, Economically and Politically
- Volume Production of Satellite and Earth Stations
- Shared Infrastructure = Shared Cost
- Evolve and Grow
- Scalable
- Allows for greater flexibility in choice of orbits

## Myriad of Ground Stations

## Fully Meshed Sensor Web

- Evolving Web
- Flexible must be built in
- Unable to optimize for the unknown
- Pre-engineering not possible
- Communication paths will vary
- Time delays will vary
- Available bandwidth will vary
- Link Characteristics will change instantaneously
- Utilizes all of the emerging technologies

## Fully Meshed Sensor Web

**Notes:**
Our vision is to leverage the explosive growth of the telecommunications industry through industry’s impressive technology advancements and potential new commercial satellite systems to provide global, interoperable,seamless  connectivity to NASA missions.  These technology products will leverage commercially provided capabilities to support inter-orbital, inter-satellite links with commercial space networks, intra-network links within science spacecraft constellations, while operating with terrestrial networks  AS much as possible, future communications systems architectures will draw on existing and planned commercial satellite constellations and ground based infrastructures to meet NASA's needs.  Using future NASA systems in conjunction with anticipated commercial space networks at higher frequencies  will provide higher rate capability and enable reduction in component size, thereby reducing NASA mission development and operational costs.

## Key Technologies for Sensor Webs

- Standard Media Access Techniques
- Starting point for communication
- What antennas, frequencies, modulations schemes
- Where am I and where will I be (if possible)
- Orbits are deterministic (ephemerous data)
- Aircraft and balloon tracks are not.
- AAA
- Programmable modems or software defined radios
- Directional tracking antennas
- Routing Techniques
- Secure networking over shared infrastructure

## Formation Flying Constellations

- Entire constellation performs and one unit
- Tendency to be more mission specific
- Less flexibility, lose volume production gains except for common parts.
- Some science may not be possible by single spacecraft
- Multiple spacecraft may reduce risk
- Provides redundancy
- Reduced launch costs
- No single point of failure – depending on architecture
- Except ---- the mother ship (reach back in ad hoc networks)

## Formation Flying Constellations

## Key Technologies for Formation Flying Constellations

- Overall architecture and distribution of processing
- Mother ship (hub-spoke) or peer-to-peer?
- Self-healing, self configuring?
- Types of communication that needs to take place between spacecraft
- Command, Control, Timing and Positioning
- Science data
- Media Access Technology
- Can one architect the constellation design so at to reused existing media access techniques and radio technologies?

## Reconfigurable Radios

- Utopian Solution
- Single radio sends and receives multiple waveforms at any data rate and any frequency
- Modulation and coding scheme automatically sense and adapt to link characteristics.
- Need starting point, restarting point and protocol for adaptation
- Manual Reconfiguration
- Not practical in large dynamic sensor web
- Reality
- Multiple links will probably have their own radio
- Greatly eases securing links
- Data rates and frequency limit the degree of reconfigurability that is possible and practical.

## AAA and Encryption

- Authentication
- Are You who you say you are?
- Authorization
- What resources are you permitted access to?
- Use of the network?
- Command and control?
- Access to experimental data?
- Accounting
- How much of the resources did you use?    $$$
- Encryption
- Secures Data (used for security and/or privacy)
- Possible to hide (somewhat) the secure network
- Does not replace AAA
- How does one validate certificates and load and manage keys in space-based networks – particularly when isolated from the ground infrastructure?

## Routing in Mobile Network

- Routing Protocols
- Convergence time
- Will one ever be allowed to inject routes into another’s network?
- Mobile-IP and Networks in Motion (NEMO)
- Allows entire networks to roam
- Can be nested (reduces bandwidth utilization)
- Security and route optimization do not mix well
- Ad hoc Networking
- Self Configuring and dynamically reconfigurable
- Most space based networks are not truly ad hoc
- Orbits are deterministic
- Reach back implies structure
- Need development of layer-2 radio and media access to support ad hoc networking.

## Shared Network Infrastructure

## Autotuning Reliable Transport Protocols

- Desire to fully utilize available links
- Maintain Fairness
- Observe and support Quality of Service
- End-to-End Link due to mobility and crossing networks
- Instantaneous path delay
- Instantaneous bandwidth variation
- Instantaneous BER variation
- Need and End-to-End solution due to End-to-End Encryption

## Conclusions/Recommendations

- Many pieces are in place to begin deploying a space-base network that can support multiple science endeavors and share network infrastructure
- Mobile-IP, Software Radios, AAA, Directional Tracking Antennas
- Start now.
- Keep it simple and flexible.
- Learn as we go.
- Address the political issues and policies through demonstration and deployment.
- The sensor web networks will evolve with as technology evolves and we learn.
- The same technologies and techniques that apply to space-based networks apply to the military and aeronautical networks.

## NSSA

**Crosslink Magazine - Future U.S. Military Satellite Communication Systems**
**Glen Elfers and Stephen B. Miller**
- http://www.aero.org/publications/crosslink/winter2002/08.html